PATENT DOCUMENT

Publication Number: US-11036318-B2
Application Number: US-201615275323-A
Country: US
Kind Code: B2

Title: Capacitive touch or proximity detection for crown

Abstract:
An electronic device is disclosed. In some examples, the electronic device comprises a rotatable mechanical input mechanism. In some examples, the electronic device comprises sense electrode positioned proximate to the mechanical input mechanism. In some examples, the electronic device comprises a capacitive sense circuit comprising drive circuity operatively coupled to the mechanical input mechanism and configured for driving a drive signal onto the mechanical input mechanism. In some examples, the electronic device comprises a capacitive sense circuit comprising sense circuitry operatively coupled to the sense electrode and configured to measure an amount of coupling between the rotatable mechanical input mechanism and the sense electrode. In some examples, the electronic device comprises a housing, wherein the sense electrode is included in a gasket for connecting a display to the housing.

Claims:
What is claimed is: 
     
       1. A wearable electronic device comprising:
 a cover substrate forming an outer surface of the wearable electronic device; 
 a display disposed beneath the cover substrate; 
 a housing; 
 a mechanical input mechanism comprising a shaft and a crown, the mechanical input mechanism configured to be rotated; 
 a sense electrode positioned proximate to the mechanical input mechanism, wherein the sense electrode is disposed in a gasket connecting the display and cover substrate to the housing, wherein the shaft is separated from the gasket by the housing; and 
 a capacitive sense circuit comprising:
 drive circuitry operatively coupled to a conductive portion of the mechanical input mechanism and configured to drive a drive signal onto the conductive portion of the mechanical input mechanism; and 
 sense circuitry operatively coupled to the sense electrode and configured to measure an amount of capacitive coupling in response to driving the drive signal onto the conductive portion of the mechanical input mechanism. 
 
 
     
     
       2. The electronic device of  claim 1 , wherein:
 the mechanical input mechanism comprises a plurality of conductive segments; 
 in a first rotational orientation of the mechanical input mechanism, the drive circuitry is coupled to a first conductive segment of the plurality of conductive segments via an internal electrical contact; and 
 in a second rotational orientation of the mechanical input mechanism, different from the first rotational orientation, the drive circuitry is coupled to a second conductive segment of the plurality of conductive segments, different from the first conductive segment, and decoupled from the first conductive segment, via the internal electrical contact. 
 
     
     
       3. The electronic device of  claim 1 , wherein a change in the amount of capacitive coupling between the conductive portion of the mechanical input mechanism and the sense electrode is indicative of an object contacting or in proximity with the mechanical input mechanism. 
     
     
       4. The electronic device of  claim 1 , the gasket comprising a force sensor configured for detecting an intensity of contact between an object and the cover substrate. 
     
     
       5. The electronic device of  claim 4 , wherein the force sensor and the sense electrode are disposed on different layers of the gasket. 
     
     
       6. The electronic device of  claim 1 , further comprising:
 a shear plate; and 
 a drive electrode, wherein the drive electrode is disposed between the shear plate and the mechanical input mechanism. 
 
     
     
       7. The electronic device of  claim 1 , wherein the conductive portion of the mechanical input mechanism comprises a plurality of conductive pads disposed in the crown and a plurality of routing traces disposed in the shaft, a respective one of the plurality of routing traces corresponding to a respective one of the plurality of conductive pads. 
     
     
       8. The electronic device of  claim 7 , wherein at least one of the plurality of routing traces is disposed internal to the shaft. 
     
     
       9. The electronic device of  claim 7 , wherein at least one of the plurality of routing traces is disposed on an exterior surface of the shaft. 
     
     
       10. The electronic device of  claim 7 , wherein the plurality of routing traces are directly electrically connected. 
     
     
       11. A method comprising:
 driving a conductive portion of a crown of a wearable device with a drive signal; 
 sensing, at a sense electrode proximate to the crown and disposed in a gasket connecting a cover substrate over a display to a housing, the gasket separated from a shaft coupled to the crown by the housing, an amount of capacitive coupling in response to driving the drive signal onto the conductive portion of the crown; and 
 detecting an object touching or in proximity to the crown based on the amount of capacitive coupling. 
 
     
     
       12. The method of  claim 11 , wherein the amount of capacitive coupling comprises a mutual capacitance between the conductive portion of the crown and the sense electrode. 
     
     
       13. The method of  claim 11 , wherein the conductive portion of the crown comprises a plurality of conductive pads, and wherein driving the conductive portion of the crown comprises:
 in a first rotational orientation of the crown, driving a first of the plurality of conductive pads without driving a second of the plurality of conductive pads; and 
 in a second rotational orientation, different from the first rotational orientation, of the crown, driving the second of the plurality of conductive pads without driving the first of the plurality of conductive pads. 
 
     
     
       14. A non-transitory computer readable storage medium, the computer readable storage medium including instructions that, when executed by a processor, cause the processor to perform a method comprising:
 driving a conductive portion of a crown of a wearable device with a drive signal; 
 sensing, at a sense electrode proximate to the crown and disposed in a gasket connecting a cover substrate over a display to a housing, the gasket separated from a shaft coupled to the crown by the housing, an amount of capacitive coupling in response to driving the drive signal onto the conductive portion of the crown; and 
 detecting an object touching or in proximity to the crown based on the amount of capacitive coupling. 
 
     
     
       15. The non-transitory computer readable storage medium of  claim 14 , wherein the amount of capacitive coupling comprises a mutual capacitance between the conductive portion of the crown and the sense electrode. 
     
     
       16. The non-transitory computer readable storage medium of  claim 14 , wherein the conductive portion of the crown comprises a plurality of conductive pads, and wherein driving the conductive portion of the crown comprises:
 in a first rotational orientation of the crown, driving a first of the plurality of conductive pads without driving a second of the plurality of conductive pads; and 
 in a second rotational orientation, different from the first rotational orientation, of the crown, driving the second of the plurality of conductive pads without driving the first of the plurality of conductive pads. 
 
     
     
       17. The electronic device of  claim 1 , wherein the gasket extends around an exterior edge portion of a bottom surface of the display and forms a seal to prevent outside air or a liquid from entering an interior cavity of the housing.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     This application claims the benefit under 35 U.S.C. § 119(e) of U.S. Provisional Patent Application No. 62/235,465, filed Sep. 30, 2015, of U.S. Provisional Patent Application No. 62/235,254, filed Sep. 30, 2015, of U.S. Provisional Patent Application No. 62/235,473, filed Sep. 30, 2015, of U.S. Provisional Patent Application No. 62/235,426, filed Sep. 30, 2015, of U.S. Provisional Patent Application No. 62/297,780, filed Feb. 19, 2016, of U.S. Provisional Patent Application No. 62/304,129, filed Mar. 4, 2016, and of U.S. Provisional Patent Application No. 62/304,135, filed Mar. 4, 2016, the contents of which are incorporated by reference herein in their entirety for all purposes. 
    
    
     FIELD OF THE DISCLOSURE 
     This relates generally to user inputs, such as mechanical inputs, and more particularly, to providing touch and proximity sensing for such inputs. 
     BACKGROUND OF THE DISCLOSURE 
     Many types of input devices are presently available for performing operations in a computing system, such as buttons or keys, mice, trackballs, joysticks, touch sensor panels, touch screens and the like. Touch screens, in particular, are becoming increasingly popular because of their ease and versatility of operation as well as their declining price. Touch screens can include a touch sensor panel, which can be a clear panel with a touch-sensitive surface, and a display device such as a liquid crystal display (LCD) that can be positioned partially or fully behind the panel so that the touch-sensitive surface can cover at least a portion of the viewable area of the display device. Touch screens can allow a user to perform various functions by touching the touch sensor panel using a finger, stylus or other object at a location often dictated by a user interface (UI) being displayed by the display device. In general, touch screens can recognize a touch and the position of the touch on the touch sensor panel, and the computing system can then interpret the touch in accordance with the display appearing at the time of the touch, and thereafter can perform one or more actions based on the touch. In the case of some touch sensing systems, a physical touch on the display is not needed to detect a touch. For example, in some capacitive-type touch sensing systems, fringing electrical fields used to detect touch can extend beyond the surface of the display, and objects approaching near the surface may be detected near the surface without actually touching the surface. However, devices that accept non-mechanical inputs, such as capacitive touch input, often do not provide tactile feedback to a user. Therefore, in addition to touch panels/touch screens, many electronic devices may also have mechanical inputs, such as buttons, switches, and/or knobs. These mechanical inputs can control power (i.e., on/off) and volume for the electronic devices, among other functions. 
     The examples described herein refer to detection of an object (e.g., a finger of a user) touching a mechanical input (e.g., a crown) of a device (e.g., a wearable device such as a watch) having a touch screen. In some examples, the detection of an object touching (but not pressing or rotating) the crown can be useful to alert the device that the user is interacting (or is about to interact) with the crown or display. In some configurations, the crown can be touch-sensitive, for example, using capacitive touch technologies that can detect contact with the crown. In some cases, devices in these configurations can only detect objects that can modulate capacitance. It can be beneficial to detect the presence (and in some cases, characteristics of) objects touching the crown on a device. 
     SUMMARY OF THE DISCLOSURE 
     In addition to touch panels/touch screens, many electronic devices may also have mechanical inputs, such as buttons, switches, and/or knobs. These mechanical inputs can control power (i.e., on/off) and volume for the electronic devices, among other functions. The examples described herein refer to detection of an object (e.g., a finger of a user) touching a mechanical input (e.g., a crown) of a device (e.g., a wearable device such as a watch) having a touch screen. In some examples, the detection of an object touching (but not pressing or rotating) the crown can be useful to alert the device that the user is interacting (or is about to interact) with the crown or display. In some configurations, the crown can be touch-sensitive, for example, using capacitive touch technologies that can detect contact with the crown. However, in some cases, devices in these configurations can only detect objects that can modulate capacitance. Therefore, it can be beneficial to detect the presence (and in some cases, characteristics) of objects touching the crown on a device. 
     In some examples, a device can use acoustic touch sensors to determine the presence (and in some examples, characteristics of) objects touching the crown on a device. In some configurations, an acoustic touch sensor can use one or more acoustic waves emitted from an emitter (e.g., a transducer) into the crown or crown shaft. In these examples, the emitted acoustic wave can travel from an acoustic emitter at the near end of a crown shaft (i.e., the end distal to the crown), through the crown shaft, reflect off the far end (i.e., the end proximate to the crown) and return back to the near end, where it is received by an acoustic receiver. The received wave&#39;s strength and characteristics will depend on the material properties of the material (e.g., air, skin, fabric) at the crown. Thus, the received wave can be analyzed in order to determine the presence and, in some cases, the characteristics of any objects in contact with the crown. In addition, in some examples, the acoustic waves can be channeled through one or more acoustic channels in the crown shaft and/or crown. In some examples, the crown itself can be divided into acoustically isolated segments, each forming a portion of a touch sensor. Acoustic waves can be sent on each segment and analyzed to determine the presence and/or characteristics of an object touching a respective segment. In some examples, an acoustic touch sensor can use acoustic resonance to determine the presence and/or characteristics of an object touching the crown. In these configurations, a resonator can be operatively coupled to the crown or crown shaft, and the resonator can be configured to vibrate the crown or crown shaft. A sensor can detect the parameters of the vibration and detect the presence and/or characteristics of an object based on the parameters of the vibration (e.g., based on the amount of damping caused by the touching object.) In some configurations, the sensor can be coupled to the crown shaft or crown (e.g., when an accelerometer operates as a sensor) or not coupled to the crown shaft or crown (e.g., when a proximity sensor operates as a sensor). The acoustic touch sensors described herein can be useful to alert the device that the user is interacting (or is about to interact) with the crown or display, and in some cases, can cause the device to exit a rest state. 
     In some cases, the proximity sensor can be mounted such that the cover substrate (e.g., glass) refracts a field of view of the proximity detector. As a result, the proximity detector can detect the presence of an object to the side of the wearable device (i.e., adjacent to the device in a direction parallel to the plane of the display), even if the proximity sensor is not mounted normal to the side of the wearable device. For example, the proximity sensor can be mounted to an inner surface of the cover substrate, normal to a first angle with respect to the plane of the display. The field of view can refract through the cover substrate such that the field of view extending beyond the cover substrate is centered about a second angle, different than the first, with respect to the plane of the display. Consequently, the field of view of proximity sensor can include areas adjacent to the wearable device in a direction parallel to the plane of the display. This can be beneficial, for example, in detecting the presence of an object near a crown of the wearable device. In some examples, methods for detecting the presence of an object are described, including examples where the proximity sensor in the wearable device utilizes one or more light-pulsing schemes, including schemes where the light-pulse frequency can change during the operation of the proximity sensor. In some examples, the wearable device can perform one or more operations if the wearable device detects the presence of an object. In some examples, the wearable device can distinguish between the presence of an object which is touching the wearable device (e.g., touching the crown of the wearable device), and the presence of an object that is not touching the wearable device. In some configurations, the wearable device can wake from a power saving mode when a non-touching object is detected, and can perform a touch operation when a touching object is detected. 
     In some examples discussed herein, a proximity sensor can use an array of light detectors to detect the presence of objects. In some examples, the proximity sensor can determine the location of a centroid of light detected by the array of light detectors. Due to parallax in the imaging path of the array of light detectors, the position of the centroid detected by the array of light detectors can change as a function of the distance of the object to the proximity sensor. In some examples, the array of light detectors can be one or two-dimensional. In addition, in some examples, the size and/or shape of the light detected by the array of light detectors can be used to determine the distance and/or characteristics of an object. In some examples, the wearable device can perform one or more operations if the wearable device detects the presence of an object. 
     In some examples discussed herein, a proximity sensor can use multiple channels to detect the presence of objects. In some examples, the proximity sensor can have two or more light emitters located at different distances from a light detector. In this configuration, the proximity sensor can use a ratio of light received from the first emitter to light received from a second emitter to determine whether an object is proximate to the proximity sensor. In other examples, a proximity sensor can have two or more light detectors located at different distances from a light emitter. In these configurations, the proximity sensor can use a ratio of light detected by the first detector and light detected by the second detector to determine whether an object is proximate to the proximity sensor. In some examples, the wearable device can perform one or more operations if the wearable device detects the presence of an object. 
     A device can inject electromagnetic energy into the crown to detect objects touching or proximate to the crown of a device. In some examples, a touch and/or proximity sensor can include a transmit circuit operatively coupled to a rotational input element (e.g., crown) and configured to inject electromagnetic energy via inductive coupling into the rotational input element, and a monitoring circuit operatively coupled to the rotational input element and configured to measure one or more parameters (e.g., resonant frequency). The one or more parameters can be indicative of an object touching or in proximity to the rotational input element. One or more touch or hover events can be detected based on the one or more parameters measured by the monitoring circuit. In some examples, the proximity sensor can include a transmit circuit and a receive circuit. The transmit circuit can include a first inductive element and one or more first capacitive elements and can oscillate at a first resonant frequency. The receive circuit can be operatively coupled to or formed as part of the rotational input element. The receive circuit can include a second inductive element and one or more second capacitive elements, and can oscillate at a second resonant frequency. The inductive elements of the transmit circuit and the receive circuit can be coupled transmit energy therebetween. In some examples, the resonant frequencies of the transmit circuit and receive circuit can be designed or turned to be the same frequency. In some examples, the touch and/or proximity sensor can measure changes in resonant frequency of the transmit circuit to detect touch and/or hover events. n some examples, a touch and/or proximity sensor can include a transmit circuit operatively coupled to a rotational input element (e.g., crown) and configured to inject electromagnetic energy into the rotational input element, and a monitoring circuit operatively coupled to the rotational input element and configured to measure one or more parameters (e.g., resonant frequency). The one or more parameters can be indicative of an object touching or in proximity to the rotational input element. One or more touch or hover events can be detected based on the one or more parameters measured by the monitoring circuit. In some examples, the touch and/or proximity sensor can measure changes in resonant frequency of an oscillating circuit (e.g., an LC tank circuit). In some examples, the touch and/or proximity sensor can measure detuning of an antenna (e.g., the crown acting as an antenna). 
     In some examples, a device can drive the crown with a drive signal to detect objects in contact or in proximity of the crown of the device. In some examples, a contact and/or proximity sensor can include a drive circuit operatively coupled to a rotational input element (e.g., crown) and configured to drive the drive signal onto the rotational input element, and a sense circuit for sensing capacitive coupling to an object (e.g., a finger) based on capacitive coupling between the finger and the contact and/or proximity sensor. The capacitive coupling can be indicative of an object contacting or in proximity to the rotational input element. One or more touch or hover events can be detected based on the signals measured by the sense circuit. In some examples, the contact and/or proximity sensor can detect an object by performing a self-capacitance measurement. In some examples, the contact and/or proximity sensor can detect an object by performing a mutual capacitance measurement. In some examples, the contact and/or proximity sensor can switch between performing self-capacitance measurements and performing mutual capacitance measurements. In some examples, to assist in the detection of objects in contact or in proximity of the crown of the device, one or more gasket sensor electrodes can be added proximate to the crown. In some examples, the gasket sensor electrodes can form a mutual capacitance with the rotational input element for performing a mutual capacitance measurement. In some examples, the gasket sensor electrode can be used for performing a self-capacitance measurement. Due to the proximity of the gasket sensor electrode to the crown, measurements indicative of contact or proximity of the object and the gasket sensor electrode can also indicate that the object is in contact or proximity of the crown. The additional touch detection capabilities provided by the driven crown and/or gasket sensor electrodes of the disclosure can be used to provide new interactions with user interface elements displayed on the electronic device. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates an exemplary personal electronic device including a crown according to examples of the disclosure. 
         FIG. 2  illustrates an exemplary block diagram of components within an exemplary device according to examples of the disclosure. 
         FIGS. 3A-3B  illustrate exemplary processes for processing mechanical events and touch events detected at the crown according to examples of the disclosure. 
         FIG. 4  illustrates a simplified cross-sectional view of wearable device according to examples of the disclosure. 
         FIG. 5A  illustrates a magnified cross-sectional view of an exemplary acoustic touch detector according to examples of the disclosure. 
         FIG. 5B  illustrates a magnified cross-sectional view of another exemplary acoustic touch detector according to examples of the disclosure. 
         FIGS. 6A-6F  illustrate a simplified example of an acoustic wave touch detection process according to examples of the disclosure. 
         FIG. 7  illustrates a conceptual circuit of an acoustic wave touch detector according to examples of the disclosure. 
         FIGS. 8A-8D  illustrate different scenarios of the touch detector according to examples of the disclosure. 
         FIGS. 8E-8H  illustrate waveforms corresponding to the scenarios shown in  FIGS. 8A-8D , respectively according to examples of the disclosure. 
         FIG. 9  illustrates an exemplary process for detecting the presence of a capacitive or non-capacitive object touching crown according to examples of the disclosure. 
         FIGS. 10A-10B  illustrate an example configuration in which crown shaft and crown can include an acoustic channel according to examples of the disclosure. 
         FIGS. 11A-11B  illustrate an example configuration in which the crown includes two or more touch sensors according to examples of the disclosure. 
         FIGS. 12A-12B  illustrate another example configuration in which the crown includes two or more touch sensors according to examples of the disclosure. 
         FIG. 13  illustrates a magnified cross-sectional view of an exemplary acoustic touch detector which uses acoustic resonance according to examples of the disclosure. 
         FIG. 14  illustrates an exemplary process for detecting the presence of a capacitive or non-capacitive object touching the crown according to examples of the disclosure. 
         FIG. 15  illustrates a magnified cross-sectional view of an exemplary acoustic touch detector which uses acoustic resonance and a proximity sensor according to examples of the disclosure. 
         FIGS. 16A-16B  illustrate an exemplary acoustic touch detector which includes two or more touch sensors according to examples of the disclosure. 
         FIGS. 17A and 17B  illustrate an exemplary optical proximity sensor according to examples of this disclosure 
         FIG. 18  illustrates a simplified cross-sectional diagram of an exemplary wearable device having an integrated optical proximity sensor according to examples of this disclosure. 
         FIG. 19  illustrates a magnified view of the curved portion of a cover substrate of an exemplary wearable device according to examples of this disclosure. 
         FIGS. 20A and 20B  illustrate an optical filtering structure including an optical mask and optical filter according to examples of this disclosure. 
         FIG. 21  illustrates a simplified block diagram of an exemplary wearable device according to examples of this disclosure. 
         FIG. 22  illustrates an exemplary process for detecting the presence of an object proximate to the device according to examples of this disclosure. 
         FIG. 23  illustrates an exemplary process for performing operations according to examples of this disclosure. 
         FIG. 24  shows an exemplary optical proximity sensor integrated in a wearable device according to examples of this disclosure. 
         FIG. 25  illustrates a graph relating to proximity detection using a single-channel amplitude-based optical proximity sensor according to examples of this disclosure. 
         FIGS. 26A-26C  illustrate an example configuration of a parallax-based proximity sensor including an array of light detectors according to examples of this disclosure. 
         FIGS. 27A-27H  illustrate an example operation of a parallax-based proximity sensor including an array of light detectors according to examples of this disclosure. 
         FIG. 28  illustrates a graph relating to proximity detection of a parallax-based proximity sensor including an array of light detectors according to examples of this disclosure. 
         FIG. 29  illustrates an exemplary process for proximity detection using a parallax-based proximity sensor including an array of light detectors according to examples of this disclosure. 
         FIGS. 30A-30C  illustrate an example configuration of a parallax-based proximity sensor including a two-dimensional array of light detectors according to examples of this disclosure. 
         FIGS. 31A-31D  illustrate an example operation of a parallax-based proximity sensor including a two-dimensional array of light detectors according to examples of this disclosure. 
         FIGS. 32A and 32B  illustrate an optical filtering structure configured to preferentially pass light to and from a proximity sensor according to examples of this disclosure. 
         FIG. 33  shows an exemplary optical proximity sensor integrated in a wearable device according to examples of this disclosure. 
         FIG. 34  illustrates a graph relating to proximity detection using a single-channel amplitude-based optical proximity sensor according to examples of this disclosure. 
         FIGS. 35A-35B  illustrate an example configuration of a dual-channel proximity sensor including multiple light emitters according to examples of this disclosure. 
         FIGS. 36A-36B  illustrate an example operation of a dual channel proximity sensor including multiple light emitters according to examples of this disclosure. 
         FIG. 37  illustrates a graph relating to proximity detection of a dual channel proximity sensor including multiple light emitters according to examples of this disclosure. 
         FIG. 38  illustrates an exemplary process for proximity detection using a dual channel proximity sensor including multiple light detectors according to examples of this disclosure. 
         FIGS. 39A-39B  illustrate an example configuration of a multiple-channel proximity sensor including multiple light detectors according to examples of this disclosure. 
         FIGS. 40A-40B  illustrate an example operation of a dual channel proximity sensor including multiple light detectors according to examples of this disclosure. 
         FIG. 41  illustrates a graph relating to proximity detection of a dual channel proximity sensor including multiple light detectors according to examples of this disclosure. 
         FIG. 42  illustrates an exemplary process for proximity detection using a dual channel proximity sensor including multiple light detectors according to examples of this disclosure. 
         FIGS. 43A and 43B  illustrate an optical filtering structure configured to preferentially pass light to and from a proximity sensor according to examples of this disclosure. 
         FIGS. 44A and 44B  illustrate exemplary processes for processing touch and hover events detected at the crown according to examples of the disclosure. 
         FIG. 44C  illustrates examples of touch and hover events that can be reported based on the estimated distance between an object and a crown according to examples of the disclosure. 
         FIG. 45A  illustrates a circuit diagram of an exemplary touch and/or proximity sensor according to examples of the disclosure. 
         FIG. 45B  illustrates an example object in proximity to an example crown according to examples of the disclosure. 
         FIG. 45C  illustrates an example touch and/or proximity sensor using a crown according to examples of the disclosure. 
         FIG. 46  illustrates an example contact between a crown/shaft and transmit circuit according to examples of the disclosure. 
         FIGS. 47A and 47B  illustrate circuit diagrams of an exemplary touch and/or proximity sensor using inductive coupling according to examples of the disclosure. 
         FIG. 48  illustrates an example object in proximity to an example crown according to examples of the disclosure. 
         FIG. 49A  illustrates an example touch and/or proximity sensor using a crown according to examples of the disclosure. 
         FIG. 49B  illustrates a circuit diagram corresponding to the example touch and/or proximity sensor of  FIG. 49A . 
         FIG. 49C  illustrates a view of crown electrodes for the example touch and/or proximity sensor of  FIG. 49A . 
         FIG. 50A  illustrates another example touch and/or proximity sensor using a crown according to examples of the disclosure. 
         FIG. 50B  illustrates a circuit diagram corresponding to the example touch and/or proximity sensor of  FIG. 50A . 
         FIG. 50C  illustrates a view of crown electrodes for the example touch and/or proximity sensor of  FIG. 50A  according to examples of the disclosure. 
         FIGS. 51A-51D  illustrate example touch and/or proximity sensors using four crown electrodes according to examples of the disclosure. 
         FIG. 52  illustrates an exemplary process for detecting objects touching and/or proximate to the crown of a device according to examples of the disclosure. 
         FIG. 53  illustrates an exemplary process for detecting objects touching and/or proximate to the crown of a device according to examples of the disclosure. 
         FIG. 54A  illustrates an example circuit diagram of an exemplary touch and/or proximity sensor using antenna detuning according to examples of the disclosure. 
         FIG. 54B  illustrates an exemplary touch and/or proximity sensor using antenna detuning according to examples of the disclosure. 
         FIG. 55  illustrates another exemplary process for detecting objects touching and/or proximate to a crown of a device according to examples of the disclosure. 
         FIG. 56A  illustrates an example shaft and crown formed of one or more conducting materials according to examples of the disclosure. 
         FIG. 56B  illustrates an example shaft and/or crown formed of conducting and non-conducting materials according to examples of the disclosure. 
         FIGS. 56C and 56D  illustrate an example crown including two conducting electrodes according to examples of the disclosure. 
         FIG. 57  illustrates an example contact between a crown shaft and transmit circuit according to examples of the disclosure. 
         FIG. 58  illustrates an example device including an existing antenna that can be used for touch and/or proximity detection according to examples of the disclosure. 
         FIG. 59  illustrates a block diagram of components within an exemplary device according to examples of the disclosure. 
         FIG. 60  illustrates a diagram of various components of an optical encoder that may be used to receive crown position information according examples of the disclosure. 
         FIG. 61  illustrates an exemplary device including an exemplary mechanical input assembly according to examples of the disclosure. 
         FIGS. 62A-62C  illustrate variations of an exemplary device that can be used to detect proximity or contact with an object using mutual capacitance sensing between the crown and one or more touch screen electrodes according to examples of the disclosure. 
         FIGS. 63A-63B  illustrate variations of an exemplary device that can be used to detect proximity or contact of an object to the mechanical input assembly by utilizing a gasket sensor electrode that can be included in a gasket of the device. 
         FIGS. 64A-64B  illustrate exemplary control circuitry configurations for coordinating operations of a gasket sensor electrode and a force electrode included in the gasket according to examples of the disclosure. 
         FIGS. 65A-65B  illustrate exemplary variations of electrode configurations for a mechanical input assembly according to examples of the disclosure. 
         FIG. 66  illustrates exemplary capacitive couplings between a crown and an object in contact or proximity with the crown according to examples of the disclosure. 
         FIGS. 67A-67B  illustrate exemplary performance of self-capacitance and mutual capacitance measurements for detecting an object in proximity or contact with a crown according to examples of the disclosure. 
         FIG. 68  illustrates an exemplary process for performing a proximity or contact measurement utilizing self-capacitance and mutual capacitance measurements according to examples of the disclosure. 
         FIG. 69  illustrates an example computing system for implementing finger-on-crown detection according to examples of the disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     In the following description of the disclosure and examples, reference is made to the accompanying drawings in which it is shown by way of illustration specific examples that can be practiced. It is to be understood that other examples can be practiced and structural changes can be made without departing from the scope of the disclosure. 
       FIG. 1  illustrates exemplary personal electronic device  100  including a crown according to examples of the disclosure. In the illustrated example, device  100  is a watch that generally includes housing  102  and strap  104  for affixing device  100  to the housing of a user. That is, device  100  is a wearable device. Housing  102  can be designed to couple to straps  104 . Device  100  can have touch-sensitive display screen  106  (hereafter display) and crown  108 . Device  100  can also have buttons  112  and  114 . Though device  100  is illustrated as a watch, it is understood that the examples of the disclosure can be implemented in devices other than watches, such as tablet computers, mobile phones, or any other wearable or non-wearable electronic device that can include a rotary input such as a crown. 
     Conventionally, the term ‘crown,’ in the context of a watch, can refer to the cap atop a stem or shaft for winding the watch. In the context of a personal electronic device  100 , the crown can be a physical component of the electronic device, rather than a virtual crown on a touch-sensitive display. Crown  108  can be mechanical, meaning that it can be connected to a sensor for converting physical movement of the crown into electrical signals. Crown  108  can rotate in two directions of rotation (e.g., forward and backward, or clockwise and counter-clockwise). Crown  108  can also be pushed in towards the housing  102  of device  100  (i.e., like a button) and/or be pulled away from the device. Inputs that require physical movement of crown  108  (e.g., crown rotation or crown press) can be referred to as “mechanical inputs,” and the events associated with these inputs can be referred to as “mechanical events.” Crown  108  can be touch-sensitive, for example, using capacitive touch technologies (e.g., self-capacitance, mutual capacitance) or other suitable technologies as described herein that can detect whether a user is touching the crown. In some examples, crown  108  can also be used as part of a sensor to detect touch and/or proximity of an object (e.g., a finger) to the crown. Crown  108  can further be configured, in some examples, to tilt in one or more directions or slide along a track at least partially around a perimeter of housing  102 . In some examples, more than one crown  108  can be included in device  100 . The visual appearance of crown  108  can, but need not, resemble crowns of conventional watches. Buttons  112  and  114 , if included, can each be a physical or a touch-sensitive button. The buttons may be, for example, physical buttons actuated by physical movement or capacitive buttons actuated by sensing a change in capacitance due to an object (e.g., a finger) touching a touch-sensitive surface corresponding to the capacitive buttons. Further, housing  102 , which can include a bezel, may have predetermined regions on the bezel that can act as buttons. 
     Display  106  can include a display device, such as a liquid crystal display (LCD), light-emitting diode (LED) display, organic light-emitting diode (OLED) display, or the like, positioned partially or fully behind or in front of a touch sensor panel implemented using any desired touch sensing technology, such as mutual-capacitance touch sensing, self-capacitance touch sensing, resistive touch sensing, projection scan touch sensing, or the like. Display  106  can allow a user to perform various functions by touching or hovering near the touch sensor panel using one or more fingers or other objects. The electrodes can be coupled to conductive traces, where one set of conductive traces can form drive lines to drive the electrodes with drive signals from drive circuitry and another set of conductive traces can form sense lines to transmit touch or sense signals, indicative of a touch proximate to the display  106 , from the electrodes to sense circuitry. In some examples, additional electrodes can be added near an edge of housing  116  proximate to crown  108 , and can be used to indicate the touch or proximity of an object at the edge of the housing. One type of touch panel for display  106  can have a row-column electrode pattern. Another type of touch panel for display  106  can have a pixelated electrode pattern. Display  106  can allow a user to perform various functions by touching or hovering near the touch sensor panel using one or more fingers or other objects. 
     In some examples, device  100  can further include one or more force or pressure sensors (not shown) for detecting an amount of force or pressure applied to the display  106 . The amount of force or pressure applied to display  106  can be used as an input to device  100  to perform any desired operation, such as making a selection, entering or exiting a menu, causing the display of additional options/actions, or the like. In some examples, different operations can be performed based on the amount of force or pressure being applied to display  106 . The one or more pressure sensors can further be used to determine a position of the force that is being applied to display  106 . 
     The examples described herein refer to detection of an object (e.g., a finger) proximate to or touching crown  108 . In some examples, the detection of an object proximate to crown  108  or touching crown  108  can alert device  100  that a user is about to interact with crown  108  or display  106  (e.g., wake the device from a power-saving mode). In some examples, crown  108  can be touch-sensitive, for example, using capacitive touch technologies that can detect contact with the crown. 
     Although examples described herein primarily involve touch sensors used to detect objects touching or near the crown of a watch, it should be understood that the touch sensors described herein can be implemented for any rotary input or button input for wearable devices and portable or non-portable electronic devices. 
     In addition to touch panels/touch screens, many electronic devices may also have mechanical inputs, such as buttons, switches, and/or knobs. These mechanical inputs can control power (i.e., on/off) and volume for the electronic devices, among other functions. The examples described herein refer to detection of an object (e.g., a finger of a user) touching a mechanical input (e.g., a crown) of a device (e.g., a wearable device such as a watch) having a touch screen. In some examples, the detection of an object touching (but not pressing or rotating) the crown can be useful to alert the device that the user is interacting (or is about to interact) with the crown or display. In some configurations, the crown can be touch-sensitive, for example, using capacitive touch technologies that can detect contact with the crown. However, in some cases, devices in these configurations can only detect objects that can modulate capacitance. Therefore, it can be beneficial to detect the presence (and in some cases, characteristics of) objects touching the crown on a device. 
     In some examples, a device can use acoustic touch sensors to determine the presence (and in some examples, characteristics of) objects touching the crown on a device. In some configurations, an acoustic touch sensor can use one or more acoustic waves emitted from an emitter (e.g., a transducer) into the crown or crown shaft. In these examples, the emitted acoustic wave can travel from an acoustic emitter at the near end of a crown shaft (i.e., the end distal to the crown), through the crown shaft, reflect off the far end (i.e., the end proximate to the crown) and return back to the near end, where it is received by an acoustic receiver. The received wave&#39;s strength and characteristics will depend on the material properties of the material (e.g., air, skin, fabric) at the crown. Thus, the received wave can be analyzed in order to determine the presence and, in some cases, the characteristics of any objects in contact with the crown. In addition, in some examples, the acoustic waves can be channeled through one or more acoustic channels in the crown shaft and/or crown. In some examples, the crown itself can be divided into acoustically isolated segments, each forming a portion of a touch sensor. Acoustic waves can be sent on each segment and analyzed to determine the presence and/or characteristics of an object touching a respective segment. In some examples, an acoustic touch sensor can use acoustic resonance to determine the presence and/or characteristics of an object touching the crown. In these configurations, a resonator can be operatively coupled to the crown or crown shaft, and the resonator can be configured to vibrate the crown or crown shaft. A sensor can detect the parameters of the vibration and detect the presence and/or characteristics of an object based on the parameters of the vibration (e.g., based on the amount of damping caused by the touching object.) In some configurations, the sensor can be coupled to the crown shaft or crown (e.g., when an accelerometer operates as a sensor) or not coupled to the crown shaft or crown (e.g., when a proximity sensor operates as a sensor). The acoustic touch sensors described herein can be useful to alert the device that the user is interacting (or is about to interact) with the crown or display, and in some cases, can cause the device to exit a rest state. 
     In some cases, the proximity sensor can be mounted such that the cover substrate (e.g., glass) refracts a field of view of the proximity detector. As a result, the proximity detector can detect the presence of an object to the side of the wearable device (i.e., adjacent to the device in a direction parallel to the plane of the display), even if the proximity sensor is not mounted normal to the side of the wearable device. For example, the proximity sensor can be mounted to an inner surface of the cover substrate, normal to a first angle with respect to the plane of the display. The field of view can refract through the cover substrate such that the field of view extending beyond the cover substrate is centered about a second angle, different than the first, with respect to the plane of the display. Consequently, the field of view of proximity sensor can include areas adjacent to the wearable device in a direction parallel to the plane of the display. This can be beneficial, for example, in detecting the presence of an object near a crown of the wearable device. In some examples, methods for detecting the presence of an object are described, including examples where the proximity sensor in the wearable device utilizes one or more light-pulsing schemes, including schemes where the light-pulse frequency can change during the operation of the proximity sensor. In some examples, the wearable device can perform one or more operations if the wearable device detects the presence of an object. In some examples, the wearable device can distinguish between the presence of an object which is touching the wearable device (e.g., touching the crown of the wearable device), and the presence of an object that is not touching the wearable device. In some configurations, the wearable device can wake from a power saving mode when a non-touching object is detected, and can perform a touch operation when a touching object is detected. 
     In some examples discussed herein, a proximity sensor can use an array of light detectors to detect the presence of objects. In some examples, the proximity sensor can determine the location of a centroid of light detected by the array of light detectors. Due to parallax in the imaging path of the array of light detectors, the position of the centroid detected by the array of light detectors can change as a function of the distance of the object to the proximity sensor. In some examples, the array of light detectors can be one or two-dimensional. In addition, in some examples, the size and/or shape of the light detected by the array of light detectors can be used to determine the distance and/or characteristics of an object. In some examples, the wearable device can perform one or more operations if the wearable device detects the presence of an object. 
     In some examples discussed herein, a proximity sensor can use multiple channels to detect the presence of objects. In some examples, the proximity sensor can have two or more light emitters located at different distances from a light detector. In this configuration, the proximity sensor can use a ratio of light received from the first emitter to light received from a second emitter to determine whether an object is proximate to the proximity sensor. In other examples, a proximity sensor can have two or more light detectors located at different distances from a light emitter. In these configurations, the proximity sensor can use a ratio of light detected by the first detector and light detected by the second detector to determine whether an object is proximate to the proximity sensor. In some examples, the wearable device can perform one or more operations if the wearable device detects the presence of an object. 
     A device can inject electromagnetic energy into the crown to detect objects touching or proximate to the crown of a device. In some examples, a touch and/or proximity sensor can include a transmit circuit operatively coupled to a rotational input element (e.g., crown) and configured to inject electromagnetic energy via inductive coupling into the rotational input element, and a monitoring circuit operatively coupled to the rotational input element and configured to measure one or more parameters (e.g., resonant frequency). The one or more parameters can be indicative of an object touching or in proximity to the rotational input element. One or more touch or hover events can be detected based on the one or more parameters measured by the monitoring circuit. In some examples, the proximity sensor can include a transmit circuit and a receive circuit. The transmit circuit can include a first inductive element and one or more first capacitive elements and can oscillate at a first resonant frequency. The receive circuit can be operatively coupled to or formed as part of the rotational input element. The receive circuit can include a second inductive element and one or more second capacitive elements, and can oscillate at a second resonant frequency. The inductive elements of the transmit circuit and the receive circuit can be coupled transmit energy therebetween. In some examples, the resonant frequencies of the transmit circuit and receive circuit can be designed or turned to be the same frequency. In some examples, the touch and/or proximity sensor can measure changes in resonant frequency of the transmit circuit to detect touch and/or hover events. n some examples, a touch and/or proximity sensor can include a transmit circuit operatively coupled to a rotational input element (e.g., crown) and configured to inject electromagnetic energy into the rotational input element, and a monitoring circuit operatively coupled to the rotational input element and configured to measure one or more parameters (e.g., resonant frequency). The one or more parameters can be indicative of an object touching or in proximity to the rotational input element. One or more touch or hover events can be detected based on the one or more parameters measured by the monitoring circuit. In some examples, the touch and/or proximity sensor can measure changes in resonant frequency of an oscillating circuit (e.g., an LC tank circuit). In some examples, the touch and/or proximity sensor can measure detuning of an antenna (e.g., the crown acting as an antenna). 
     In some examples, a device can drive the crown with a drive signal to detect objects in contact or in proximity of the crown of the device. In some examples, a contact and/or proximity sensor can include a drive circuit operatively coupled to a rotational input element (e.g., crown) and configured to drive the drive signal onto the rotational input element, and a sense circuit for sensing capacitive coupling to an object (e.g., a finger) based on capacitive coupling between the finger and the contact and/or proximity sensor. The capacitive coupling can be indicative of an object contacting or in proximity to the rotational input element. One or more touch or hover events can be detected based on the signals measured by the sense circuit. In some examples, the contact and/or proximity sensor can detect an object by performing a self-capacitance measurement. In some examples, the contact and/or proximity sensor can detect an object by performing a mutual capacitance measurement. In some examples, the contact and/or proximity sensor can switch between performing self-capacitance measurements and performing mutual capacitance measurements. In some examples, to assist in the detection of objects in contact or in proximity of the crown of the device, one or more gasket sensor electrodes can be added proximate to the crown. In some examples, the gasket sensor electrodes can form a mutual capacitance with the rotational input element for performing a mutual capacitance measurement. In some examples, the gasket sensor electrode can be used for performing a self-capacitance measurement. Due to the proximity of the gasket sensor electrode to the crown, measurements indicative of contact or proximity of the object and the gasket sensor electrode can also indicate that the object is in contact or proximity of the crown. The additional touch detection capabilities provided by the driven crown and/or gasket sensor electrodes of the disclosure can be used to provide new interactions with user interface elements displayed on the electronic device. 
       FIG. 2  illustrates an exemplary block diagram of components within an exemplary device (e.g., wearable device  200 ) according to examples of the disclosure. As illustrated, the wearable device  200  can include a processor  202  configured to execute instructions and to carry out operations associated with the wearable device  200 . For example, using instructions retrieved from, for example, memory, the processor  202  may control the reception and manipulation of input and output data between components of the wearable device  200 . The processor  202  can be a single-chip processor or can be implemented with multiple components. 
     In some examples, the processor  202  together with an operating system can operate to execute computer code and produce and use data. The computer code and data may reside within a program storage block  204  that can be operatively coupled to the processor  202 . Program storage block  204  can generally provide a place to store data used by the wearable device  200 . By way of example, the program storage block may include Read-Only Memory (ROM)  206 , Random-Access Memory (RAM)  208 , hard disk drive  210  and/or the like. The computer code and data can also reside on a removable storage medium that can be loaded or installed onto the computer system when needed. Removable storage mediums can include, for example, CD-ROM, PC-CARD, floppy disk, magnetic tape, a network component, and the like. 
     The wearable device  200  can also include an input/output (I/O) controller  212  that can be operatively coupled to the processor  202 . The I/O controller  212  may be integrated with the processor  202  or it may be one or more separate components. The I/O controller  212  can be configured to control interactions with one or more I/O devices. The I/O controller  212  can operate by exchanging data between the processor  202  and the I/O devices that desire to communicate with the processor. The I/O devices and the I/O controller can communicate through one or more data links  214 . The one or more data links  214  may include data links that have a one way link or two way (bidirectional) link. In some examples, the I/O devices may be coupled to I/O controller  212  through wired connections. In other examples, the I/O devices may be wirelessly coupled to I/O controller  212 . By way of example, the one or more data links  214  can correspond to one or more of PS/2, USB, Firewire, IR, RF, BLUETOOTH™ or the like. 
     Wearable device  200  can also include a display device  220  that can be operatively coupled to the processor  202 . For example, as illustrated in  FIG. 2 , display device  220  can be coupled to a display controller  222 , and display controller  222  can be coupled to I/O controller  212 . In other examples, the functionality of display controller  222  can be implemented in I/O controller  212  or processor  202 , and display device  220  can be coupled to I/O controller  212  or directly to processor  202 . Display device  220  can be a separate component (peripheral device) or it can be integrated with the processor and/or program storage in a single device. Display device  220  can be configured to display a graphical user interface (GUI) including, for example, a pointer or cursor or other information to the user. 
     Wearable device  200  can also include a touch screen  230  that can be operatively coupled to processor  202 . Touch screen  230  can include a transparent or semi-transparent touch sensor panel  234  that can be positioned, for example, in front of the display device  220 . Touch sensor panel  234  may be integrated with the display device  220  (e.g., touch sensing circuit elements of the touch sensing system can be integrated into the display pixel stack-ups of the display) or it may be a separate component. Touch screen  230 /touch sensor panel  234  can be configured to receive input from an object  260  (e.g., a finger) touching or proximate to touch screen  230 /touch sensor panel  234  and to send this information (e.g., presence of touch and/or magnitude of touch signals) to processor  202 . Touch screen  230  can report the touch information to processor  202 , and processor  202  can process the touch information in accordance with its programming. For example, processor  202  may initiate a task in accordance with a particular touch event. 
     In some examples, touch screen  230  can track one or more objects (e.g., object  260 ), which hover over, rest on, tap on, or move across the touch-sensitive surface of touch screen  230 . The objects can be conductive objects including, but not limited to, fingers, palms, and styli. Touch screen  230  can include a sensing device, such as touch sensor panel  234 , configured to detect an object touching or in close proximity thereto and/or the force or pressure exerted thereon. 
     Touch sensor panel  234  can be based on a wide variety of technologies including self-capacitance, mutual capacitance, resistive and/or other touch sensing technologies. In some examples, touch sensor panel  234  can include a matrix of small plates of conductive material (e.g., ITO) that can be referred to as sensing points, nodes or regions  236 . For example, a touch sensor panel  234  can include a plurality of individual sensing nodes, each sensing node identifying or representing a unique location on the touch screen at which touch or proximity (hovering) (i.e., a touch or proximity event) is to be sensed, and each sensing node being electrically isolated from the other sensing nodes in the touch screen/sensor panel. Such a touch sensor panel/screen can be referred to as a pixelated touch sensor panel/screen. During self-capacitance operation of the pixelated touch screen, for example, a sensing node can be stimulated with an AC waveform, and the self-capacitance of the sensing node can be measured. As an object approaches the sensing node, the self-capacitance to ground of the sensing node can change. This change in the self-capacitance of the touch node can be detected and measured by the touch sensing system to determine the positions of one or more objects when they touch, or come in proximity to, the pixelated touch screen. 
     The number and configuration of the sensing points  236  may be widely varied. The number of sensing points  236  can, for example, be a tradeoff between the desired sensitivity (resolution) and the desired transparency of the touch screen. More nodes or sensing points can generally increase sensitivity, but can also, in some examples, reduce transparency (and vice versa). With regards to the configuration, the sensing points  236  can map the touch screen plane into a coordinate system such as a Cartesian coordinate system, a Polar coordinate system, or some other coordinate system. When a Cartesian coordinate system is used (as shown), the sensing points  236  can correspond to x and y coordinates. When a Polar coordinate system is used, the sensing points  236  can correspond to radial (r) and angular coordinates (φ). 
     Although touch sensor panel  234  is illustrated and described with reference to  FIG. 2  as a pixelated touch sensor panel, in other examples, the touch sensor panel can be formed from rows and columns of conductive material (row-column touch sensor panel), and changes in the self-capacitance to ground of the rows and columns can be detected. Additionally or alternatively, in some examples, the pixelated touch sensor panel or row-column touch sensor panel can be configured to sense changes in mutual capacitance at sensing nodes measuring capacitive coupling between two electrodes (e.g., at the intersection of a drive and a sense electrode). In some examples, a touch screen can be multi-touch, single touch, projection scan, full-imaging multi-touch, capacitive touch, etc. 
     Touch screen  230  can include and/or be operatively coupled to a touch controller  232  that can perform touch sensing scans and acquire the touch data from touch sensor panel  234  and that can supply the acquired data to processor  202 . For example, as illustrated in  FIG. 2 , touch screen  230  can be coupled to touch controller  232 , and touch controller  232  can be coupled to I/O controller  212 . In other examples, the functionality of touch controller  232  can be implemented in I/O controller  212  or processor  202 , and touch screen  230  can be coupled to I/O controller  212  or directly to processor  202 . The touch screen  230  can be a separate component (peripheral device) or it can be integrated with the processor and/or program storage in a single device. 
     In some examples, touch controller  232  can be configured to send raw touch data to processor  202 , and processor  202  can process the raw touch data. For example, processor  202  can receive data representative at touch measured at sensing points  234 , process the data to identify touch events, and then take actions based on the identified touch events. The touch data may include the coordinates of each sensing point  234  and/or the force measured at each sensing point  234 . In some examples, touch controller  232  can be configured to process the raw data and then transmit identified touch events and location information to processor  202 . Touch controller  232  can include a plurality of sense channels, logic and/or other processing circuitry (not shown) that may perform optimization and/or touch detection operations. Optimization operations can be implemented to reduce a busy data stream and reduce the load on processor  202 . In some examples, processor  202  can perform at least some of the optimization operations. The touch detection operations can include, acquiring raw data (e.g., scanning the touch sensor panel), adjust the raw data (e.g., compensating the touch image), performing centroid calculations, identifying touch events, etc. before sending or reporting information to processor  202 . 
     Touch screen  230  and touch controller  232  can be referred to as the touch sensing system. Touch controller  232  can include or be coupled to one or more touch processors (not shown) to perform some of the processing functions described herein. Touch controller  232  can include circuitry and/or logic configured to sense touch inputs on touch screen  230  as described herein. In some examples, touch controller  232  and the one or more touch processors can be integrated into a single application specific integrated circuit (ASIC). 
     The wearable device  200  can also include one or more buttons  240  (e.g., corresponding to buttons  110 ,  112  and  114 ) that can be operatively coupled to processor  202 . For example, as illustrated in  FIG. 2 , buttons  240  can be coupled to a button controller  242 , and button controller  242  can be coupled to I/O controller  212 . In other examples, the functionality of button controller  242  can be implemented in I/O controller  212  or processor  202 , and buttons  240  can be coupled to I/O controller  212  or directly to processor  202 . 
     The wearable device  200  can also include crown  250  (e.g., corresponding to crown  108 ) or other rotary input that can be operatively coupled to processor  202 . For example, as illustrated in  FIG. 2 , crown  250  can be coupled to a crown controller  252 , and crown controller  252  can be coupled to I/O controller  212 . In other examples, the functionality of crown controller  252  can be implemented in I/O controller  212  or processor  202 , and crown  250  can be coupled to I/O controller  212  or directly to processor  202 . 
     Crown controller  252  can include an encoder (not shown), which can be configured to monitor a physical state or change of physical state of crown  250  (e.g., the position of the crown), convert it to an electrical signal (e.g., convert it to an analog or digital signal representation of the position or change in position of crown  250 ), and provide the signal to processor  202 . In some examples, the encoder can be configured to sense the absolute rotational position (e.g., an angle between 0-360°) of crown  250  and output an analog or digital representation of this position to processor  202 . Alternatively, in other examples, the encoder can be configured to sense a change in rotational position (e.g., a change in rotational angle) of crown  250  over some sampling period and to output an analog or digital representation of the sensed change to processor  202 . In these examples, the crown position information can further indicate a direction of rotation of the crown (e.g., a positive value can correspond to one direction and a negative value can correspond to the other). In yet other examples, the encoder can be configured to detect a rotation of crown  250  in any desired manner (e.g., velocity, acceleration, or the like) and can provide the crown rotational information to processor  202 . The rotational velocity can be expressed in numerous ways. For example, the rotational velocity can be expressed in a direction and a speed of rotation, such as hertz, as rotations per unit of time, as rotations per frame, as revolutions per unit of time, as revolutions per frame, as a change in angle per unit of time, and the like. In some examples, instead of providing information to processor  202 , this information can be provided to other components of device. The rotational position of crown  250  can be used, for example, to control scrolling or scaling of a view in the GUI displayed on display device  220 , though the rotational input of the crown can be used for other purposes. 
     Additionally, it should be appreciated that any other physical state of crown  250  can be used as an input (e.g., pressing the crown when the crown includes a button). In some examples, the physical state of the crown  250  can control physical attributes of display device  220 . For example, if crown  250  is in a particular position (e.g., rotated forward), display device  220  can have limited z-axis traversal ability. In other words, the physical state of the crown can represent physical modal functionality of display device  220 . In some examples, a temporal attribute of the physical state of crown  250  can be used as an input to wearable device  200 . For example, a fast change in physical state can be interpreted differently than a slow change in physical state. Additionally or alternatively, crown controller  252  can include circuitry configured to transfer energy to the crown to enable detection of touch events at the surface of the crown and/or proximity events of an object proximate to the crown. 
     In some examples, processor  202  can be a host processor for receiving outputs from various I/O devices and performing actions based on the outputs. Processor  202  can be connected to program storage block  204 . For example, processor  202  can be operably coupled to receive signals from touch sensor panel  234 , buttons  240  and crown  250 . Processor  202  can be configured to interpret these input signals and output appropriate display signals to cause an image to be produced by touch-sensitive display  220 . The inputs, individually or in combination, can also be used to perform other functions for wearable device  200 . For example, processor  202  can contribute to generating an image on touch screen  230  (e.g., by controlling a display controller to display an image of a user interface (UI) on the touch screen), and can use touch controller  232  to detect one or more touches on or near touch screen  230 . Processor  202  can also contribute to sensing and/or processing mechanical inputs from buttons  240  and crown  250 . The inputs from touch screen  230  and/or mechanical inputs can be used by computer programs stored in program storage block  204  to perform actions in response to the touch and/or mechanical inputs. For example, touch inputs can be used by computer programs stored in program storage block  204  to perform actions that can include moving an object such as a cursor or pointer, scrolling or panning, adjusting control settings, opening a file or document, viewing a menu, making a selection, executing instructions, operating a peripheral device connected to the host device, answering a telephone call, placing a telephone call, and other actions that can be performed in response to touch inputs. Mechanical inputs can be used by computer programs stored in program storage block  204  to perform actions that can include changing a volume level, locking the touch screen, turning on the touch screen, taking a picture, and other actions that can be performed in response to mechanical inputs. Processor  202  can also perform additional functions that may not be related to touch and/or mechanical input processing. 
     Note that one or more of the functions described above can be performed by firmware stored in memory in wearable device  200  and executed by touch processor in touch controller  232 , or stored in program storage block  204  and executed by processor  202 . The firmware can also be stored and/or transported within any non-transitory computer-readable storage medium for use by or in connection with an instruction execution system, apparatus, or device, such as a computer-based system, processor-containing system, or other system that can fetch the instructions from the instruction execution system, apparatus, or device and execute the instructions. In the context of this document, a “non-transitory computer-readable storage medium” can be any medium (excluding signals) that can contain or store the program for use by or in connection with the instruction execution system, apparatus, or device. The computer-readable storage medium can include, but is not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus or device, a portable computer diskette (magnetic), a random access memory (RAM) (magnetic), a read-only memory (ROM) (magnetic), an erasable programmable read-only memory (EPROM) (magnetic), a portable optical disc such a CD, CD-R, CD-RW, DVD, DVD-R, or DVD-RW, or flash memory such as compact flash cards, secured digital cards, USB memory devices, memory sticks, and the like. 
     The firmware can also be propagated within any transport medium for use by or in connection with an instruction execution system, apparatus, or device, such as a computer-based system, processor-containing system, or other system that can fetch the instructions from the instruction execution system, apparatus, or device and execute the instructions. In the context of this document, a “transport medium” can be any medium that can communicate, propagate or transport the program for use by or in connection with the instruction execution system, apparatus, or device. The transport medium can include, but is not limited to, an electronic, magnetic, optical, electromagnetic or infrared wired or wireless propagation medium. 
     Acoustic Detection Apparatus and Methods 
       FIGS. 3A and 3B  illustrate exemplary processes for processing mechanical and touch inputs detected at the crown according to examples of the disclosure.  FIG. 3A  illustrates an example process using touch events at the crown to transition between two modes of operation. At block  300 , the device can be in a rest mode. The rest mode may correspond, for example, to a low-power mode. In some examples, the display device (e.g., display device  220 ) can be powered down or enter a low-power state in the rest mode. Additionally or alternatively, in some examples, the touch sensing system (e.g., touch sensor panel  234  and touch controller  232 ) can be powered down or enter a low-power state in the rest mode. Additionally or alternatively, in some examples, one or more processors, I/O devices and/or other circuitry can be powered down or enter a low-power state in the rest mode. 
     At block  305 , the device (e.g., a processor or state machine) can receive input from a touch sensor of the crown. In some examples, the touch sensor can be implemented using the crown and/or the crown shaft as part of the sensor. At block  310 , the device (e.g., the processor or state machine) can determine from the received input whether a touch event is detected. If a touch event is detected, processing can proceed to block  315 , where processing can wake up the device, and the device can enter a ready mode. Waking up the device can including powering up one or more processors, I/O devices and/or other circuitry that were powered down or placed in a low-power state during rest mode, resuming touch sensing operations, and/or resuming display operations. 
     In some examples, the device can exit the rest mode and enter the ready mode in response to detecting a mechanical event (e.g., a rotation or press of the crown), rather than a touch event. In some examples, the device can wake up and enter the ready mode in response to detecting either of a touch or mechanical event. 
     Although not illustrated, the device can return to the rest mode under various conditions. For example, the device can return to rest mode manually when user input is detected causing the device to enter a rest mode (e.g., covering the touch screen, rotating the touch screen away from the user, or in response to selection of UI element by touch, button, or crown input) or automatically in response to detecting no inputs for a threshold period of time (e.g., no touch, button or crown inputs). In some examples, as long as a touch event is detected at the crown, the device cannot return to the rest mode. 
     In some examples, mechanical events and/or touch events at the crown can be used as additional inputs to the device.  FIG. 3B  illustrates an example process using touch (touch) events and/or mechanical events as additional inputs. At block  320 , the device can be in a ready mode. At block  325 , the device can receive input from a mechanical input and/or touch sensor at the crown. In some examples, the touch sensor can be implemented using the crown and/or the crown shaft as part of the sensor. At block  330 , the device (e.g., the processor or state machine) can determine from the received input whether a mechanical event is detected. If a mechanical event is detected, processing can proceed to block  335 , where a mechanical event can be reported. The reported mechanical event can be used by the device to perform one or more functions (e.g., changing the UI or selecting a UI element) corresponding to a mechanical event at the crown, and processing can return to block  320  (i.e., the device can remain in ready mode). If no mechanical event is detected at block  330 , processing can proceed to block  340 , and the device (e.g., the processor or state machine) can determine from the received input whether a touch event is detected. If a touch event is detected, processing can proceed to block  345 , where a touch event can be reported. The reported touch event can be used by device to perform one or more functions (e.g., changing the UI or selecting a UI element) corresponding to a touch event at the crown, and processing can return to block  320  (i.e., the device can remain in ready mode). If no touch event is detected at block  340 , processing can proceed to block  320  (i.e., the device can remain in ready mode). In some examples, if no mechanical event or touch event is detected, the device can exit ready mode and return to rest mode (e.g., for example if no other inputs are detected in addition to detecting no mechanical event or touch event at the crown). 
     Although discussed in the context of a crown for a wearable device, the exemplary processes of  FIGS. 3A and 3B  can be applied to a mechanical event and/or touch sensor implemented to detect mechanical events or touch events for other rotary input devices, button inputs, or other inputs. 
     Although the touch event is described above as a binary event (i.e., touch event or no touch event), in some examples, different types of touch events can be reported. For example, as will be described in more detail with reference to  FIGS. 6A-6F  below, in some examples of “acoustic wave touch detection,” the touch sensor can estimate characteristics of a touch object based on the loss of amplitude of an acoustic wave as it travels through the crown shaft and crown and reflects off a boundary between the crown and touch object. Thus, in these examples, a touch event threshold may correspond to a difference in amplitude between two or more waveforms. Other acoustic touch sensors may operate using acoustic resonance touch detection, as will be described in more detail with reference to  FIGS. 13-14  below. In acoustic resonance touch detection, the touch sensor can estimate characteristics of a touch object based on the amount of damping a touch object applies to the crown shaft and crown when vibrating. Thus, in these examples, a touch event threshold may correspond, for example, to a difference in vibration amplitude when an object is applied to the crown. It should be noted, however, that in both acoustic wave touch detection and acoustic resonance touch detection, other parameters may correspond to touch event thresholds. 
     As described herein, in some examples, the touch sensor can be implemented using the crown and/or crown shaft as part of the sensor. For example, as will be described in more detail with reference to  FIGS. 5-9  below, in some examples, the touch sensor can detect the presence of (and in some cases, estimate characteristics of) a touch object based on the loss of amplitude of an acoustic wave as it travels through the crown shaft and crown and reflects off a boundary between the crown and touch object. In other examples, as will be described in more detail with reference to  FIGS. 13-15  below, the touch sensor can detect the presence of (and in some cases, estimate characteristics of) a touch object based on the amount of damping a touch object applies to the crown shaft and crown when vibrating. 
       FIG. 4  illustrates a simplified cross-sectional view of wearable device  100  including a housing  102 , a crown shaft  410 , and a crown  108  mounted on the crown shaft according to examples of the disclosure. In some configurations, wearable device  100  can include at least one acoustic transmitter  412  and at least one acoustic receiver  414 , illustrated in  FIG. 4  as boxes for simplicity. Also for simplicity, other elements of device  100 , including transmitter and receiver circuitry, are omitted. Example configurations of the acoustic transmitter and acoustic receiver will be discussed in more detail with reference to  FIGS. 5A-5B  below, however, it should be noted here that the configuration of these components can differ from the simplified examples shown in  FIG. 4 . 
       FIG. 5A  illustrates a magnified cross-sectional view of an exemplary acoustic touch detector  501  according to examples of the disclosure. Some configurations can include a crown  108 , crown shaft  410 , an transmit transducer  514  operating as an acoustic emitter, an acoustic transmit circuit  516  coupled to the acoustic emitter, a receiver transducer  512  operating as an acoustic receiver, and an acoustic receiver circuitry  518  coupled to the receiver transducer. Both the transmit transducer  514  and the receiver transducer  512  can encircle crown shaft  410 . In some configurations, the emitter or receiver transducer can be contact coupled to crown shaft  410 , and can thus emit and receive acoustic signals via contact coupling. For example, in configurations where transducers  512 ,  514  are contact coupled to crown shaft  410 , the emitter or receiver transducer can be a piezoelectric transducer. In other configurations, the emitter transducer can be non-contact coupled to crown shaft  410 . In these configurations, acoustic signals can be emitted without physical contact between the transducer and crown shaft, for example, using electromagnetic waves to vibrate the area of crown shaft encircled by transmit transducer  514 . The operation of the acoustic touch detector according to some configurations will now be discussed. 
       FIG. 5B  illustrates a magnified cross-sectional view of another exemplary acoustic touch detector  502  according to examples of the disclosure. In the configuration shown in  FIG. 5B , a single transducer  522  can encircle the crown shaft  110 . In some configurations, a switching circuitry  520  can be included to selectively couple transducer  516  to transmit circuit  516  and receiver circuit  518 . Thus, in some examples, single transducer  522  can operate both as the acoustic emitter and acoustic receiver. The operation of the example configuration shown in  FIG. 5B  are discussed in more detail below. 
     In some configurations, an acoustic touch detector can utilize time-domain reflectometry (TDR), specifically acoustic TDR, in order to detect one or more objects (e.g., one or more fingers) touching the crown. In short, an acoustic wave can travel from an acoustic emitter at the near end of a crown shaft (i.e., the end distal to the crown), through the crown shaft, reflect off the far end (i.e., the end proximate to the crown) and return back to the near end, where it is received by an acoustic receiver. The received wave&#39;s strength and characteristics will depend on the material properties of the material (e.g., air, skin, fabric) at the crown. Thus, the received wave can be analyzed in order to determine the presence and, in some cases, the characteristics of any objects in contact with the crown. In some examples, acoustic wave is an ultrasonic pulse. 
       FIGS. 6A-6F  illustrate a simplified example of an acoustic wave touch detection process according to examples of the disclosure. For simplicity, other elements, including wiring and mounting elements are omitted. A transmitter  633  (shown as box “TX”) can represent, for example, a transmit transducer and transmit circuit. A receiver  631  (shown as box “RX”) can represent, for example, a receiver transducer and receiver circuit. An acoustic wave is shown in  FIGS. 6A-6F  symbolically ( 641 ,  643 ,  645 ,  647 ,  649 ), though it should be understood that the waveforms are merely an example provided for ease of explanation, and may not represent the actual waveform of an acoustic wave. 
       FIGS. 6A-6C  illustrate the operation of an acoustic touch detector when no object is touching crown  108 . As shown in  FIG. 6A , transmitter  633  can couple emitted acoustic wave having a waveform  641  to the near end of the shaft. Next, as shown in  FIG. 6B , acoustic wave  643  can reflect off the crown  108  at the border between crown  108  and air. As shown, the amplitude and phase of corresponding waveform  643  of acoustic wave is largely retained after the reflection off the crown boundary. Next, as shown in  FIG. 6C , reflected acoustic wave can travel back toward the near end of crown shaft  110  where it is detected by receiver  631 . As shown, the amplitude and phase of corresponding waveform  645  of received acoustic wave can be similar to that of waveform  641  corresponding to emitted acoustic wave. 
     In contrast,  FIGS. 6D-6F  illustrate the operation of an acoustic touch detector when an object (e.g., a finger  653 ) is touching crown  108 . As similarly shown in  FIG. 6A , transmitter  633  can couple emitted acoustic wave having a waveform  647  to the near end of crown shaft  110 . However, in this example, acoustic wave reflects off the crown  108  at a border between crown  108  and finger  653 . Because finger  653  absorbs more of the acoustic wave at the boundary than air, waveform  649  of reflected acoustic wave is slightly decreased in amplitude. That is, less of the acoustic wave is reflected back to the near end of crown shaft  110 . The reflected acoustic wave is received at the receiver  631  where the waveform  651  and its parameters can be analyzed to determine that finger  653  is touching crown  108 . Specific examples of waveforms and waveform characteristics will be discussed in more detail with reference to  FIGS. 8A-8H  below. 
     In configurations such as the configuration shown in  FIG. 5B , acoustic touch detection with acoustic waves can be performed using a process as similarly described with respect to  FIGS. 6A-6F , but between the time that acoustic wave is emitted (e.g., as in  FIG. 6A ) and the time that reflected acoustic wave  645  is received (e.g., as in  FIG. 6C ), switching circuitry can change the transducer coupling from the transmitter  633  to the receiver  631 . 
     As discussed above, acoustic touch detection with acoustic waves can be used to detect the presence of objects at the crown of a wearable device. In some configurations, the characteristics of reflected acoustic waveforms can indicate that an object is touching the crown. In some examples, the characteristics of the touching object or objects (e.g., location of touch, number of objects touching, density of object) can be determined or estimated based on the characteristics of the reflected acoustic waveforms. In analyzing reflected acoustic waveforms, it can be helpful to conceptualize the process of acoustic touch detection with acoustic waves in terms of a conceptual circuit as shown in  FIG. 7 . 
       FIG. 7  illustrates a conceptual circuit of an acoustic wave touch detector according to examples of the disclosure. For simplicity, other elements, including wiring and mounting elements are omitted. A transmitter  733  (shown as box “TX”) can represent, for example, an emitter transducer and transmitter circuit. A receiver  731  (shown as box “RX”) can represent, for example, a receiver transducer and receiver circuit. As similarly discussed with reference to  FIGS. 6A-6F , transmitter  733  can couple an acoustic wave (such as an ultrasonic pulse) onto the near end of crown shaft  110  which travels down the length of the crown shaft, reflects off crown  108 , travels back down the length of the crown shaft toward the near end, and be received by receiver  731 . As the acoustic wave travels down the length of the crown shaft, the acoustic wave will experience some loss in amplitude, depending on the characteristics of the crown shaft and crown material or materials. As indicated in  FIG. 7 , this path of the acoustic wave from the emitter to the crown can be conceptually represented as a first impedance Z1. When the acoustic wave is reflected at the boundary of the crown, the amplitude of the acoustic wave can decrease as only some of the wave is reflected back toward the near end of crown shaft  110 , while another portion of the acoustic wave is absorbed by the material (e.g., air or an object) at the end of crown shaft  110 . As indicated in  FIG. 7 , this reflection of the acoustic wave off of the boundary between crown and material in contact with the crown (e.g., skin, air, etc.) can be conceptually represented as a resistance divider including a second impedance Z2 and a third impedance Z3. Conceptually speaking, the higher that impedance Z3 is in comparison to impedance Z2, the less the amplitude will decrease after the acoustic wave is reflected off of the boundary. As the acoustic wave travels back from the reflection toward receiver  731 , the wave can experience more loss depending on the properties of the crown material. This loss can be conceptually represented as a fourth impedance Z4, as indicated in  FIG. 7 . It should be noted that the path of an acoustic wave illustrated in  FIG. 7  has been simplified for ease of explanation. In reality, acoustic waves traveling through crown shaft  110  and crown  108  can take a variety of paths and encounter a variety of losses. 
       FIGS. 8A-8D  illustrate different scenarios of the touch detector (e.g., whether an object or objects are touching crown  108 ), while  FIGS. 8E-8H  illustrate waveforms corresponding to the scenarios shown in  FIGS. 8A-8D , respectively according to examples of the disclosure.  FIGS. 8E-8H  show examples of emitted and received acoustic waveforms in an acoustic touch detector according to examples of the disclosure. For ease of comparison and illustration, each of the waveforms shown in  FIGS. 8E-8H  is assumed to be a pulse waveform of the same duration and amplitude, though it should be understood that these waveforms are exemplary only, and the actual acoustic pulse waveforms may differ from those shown here. In each of  FIGS. 8E-8H , the emitted pulse is represented in solid line, while the reflected pulse detected at the receiver is shown in dashed line. In each of  FIGS. 8E-8H , the y axis represents the amplitude of the waveforms, while the x axis represents time. 
       FIG. 8A  illustrates a scenario in which no objects are touching crown  108  such that the material at the boundary at the far end of crown  108  is air.  FIG. 8E  illustrates a corresponding example pulse waveforms  841 ,  851  for the scenario shown in  FIG. 8E . In all  FIGS. 8E-8H , the difference between the time t1 of the rising edge of the emitted waveform  841  and the time t2 of the rising edge of received waveform  851  is represented as Δ1. Because Δ1 corresponds to the time it takes the acoustic wave to travel down the length of the crown shaft and back to the receiver, the distance from the receiver to the reflective boundary (in this case, the boundary between crown  108  and the air) can be calculated. Moreover, although only one received waveform  851  is illustrated in each of  FIGS. 8E-8H , it should be understood that multiple reflected waveforms can be detected at the receiver if the acoustic wave reflects off of more than one boundary. For example, if crown  108  was formed of a second material different from a first material of the crown shaft  110 , two acoustic waveforms may be received at the receiver, including a first waveform representing the wave reflection at the boundary between the first material and second material, and a second waveform representing the wave reflection at the boundary between the second material and the air. However, in the example shown in  FIG. 8E , only one received waveform  851  is present, representing the reflection of the acoustic wave at the boundary between the crown and air. Referring back to  FIG. 7 , air can be conceptually thought of as representing a high impedance Z3 in comparison to the impedance Z2 of crown  108  at the boundary, such that most of the acoustic waveform is reflected back down crown shaft  110  to receiver (not shown). As a result, the difference Δ1 between the amplitude A1 of the emitted wave (represented as waveform  841 ) and the amplitude A2 of the received wave (represented as waveform  851 ) is relatively small. In some examples, device  100  (e.g., processor  202  or crown controller  252 ) can analyze the received waveform to determine that no object is touching crown  108 . 
       FIG. 8B  illustrates a scenario in which a single bare finger  831  is touching crown  108  such that the material at the boundary of crown  108  is skin.  FIG. 8F  illustrates a corresponding example emitted waveform  842  and received waveform  852  for the scenario shown in  FIG. 8B . Here, some of the emitted acoustic wave is absorbed by finger  831 , with the remainder reflecting back down crown shaft  110  to receiver (not shown). As a result, the amplitude A2 of the received wave  852  is considerably smaller than the amplitude A1 of the emitted wave  842 , resulting in a large difference Δ1. In some examples, device  100  (e.g., processor  202  or crown controller  252 ) can analyze the received waveform to determine that an object is touching the crown, and in some examples, determine that finger  831  is touching crown  108 . 
       FIG. 8C  illustrates a scenario in which two bare fingers  831  and  832  are touching crown  108  such that the material at the boundary of crown  108  is skin, but with a larger area of contact than the scenario illustrated in  FIG. 8B .  FIG. 8G  illustrates a corresponding example emitted waveform  843  and received waveform  853  for the scenario shown in  FIG. 8C . Here, some of the emitted acoustic wave is absorbed by finger  831 , with the remainder reflecting back down crown shaft  110  to receiver (not shown). Here, unlike in the scenario described with reference to  FIGS. 8B and 8F , the additional finger  831  provides an additional path for the acoustic wave to be absorbed by. Consequently, the difference in amplitude Δ1 is even larger than in the examples shown in  FIGS. 8E and 8F . In some examples, device  100  (e.g., processor  202  or crown controller  252 ) can analyze the characteristics of the received waveform to determine that an object is touching the crown, and in some examples, determine that two fingers are touching crown  108 . 
       FIG. 8D  illustrates a scenario in which a gloved finger  833  is touching crown  108  such that the material at the boundary of crown  108  is fabric.  FIG. 8H  illustrates a corresponding example waveform for the scenario shown in  FIG. 8D . Here, a small amount of the emitted acoustic wave is absorbed by gloved finger  833 , with the remainder reflecting back down crown shaft  110  to receiver (not shown). Here, unlike in the scenario described with reference to  FIGS. 8B and 8F , the gloved finger  833  does not absorb as much of the acoustic wave. Consequently, the difference in amplitude Δ1 is larger than in the example shown in  FIG. 8E  (i.e., where no object is touching crown), but is less than the examples shown in  FIGS. 8B-8C  (i.e., where one or more bare fingers are touching the crown). In some examples, device  100  (e.g., processor  202  or crown controller  252 ) can analyze the characteristics of the received waveform to determine that an object is touching the crown, and in some examples, more specifically determine that a gloved finger is touching crown  108 . 
     Although example scenarios are discussed with reference to  FIGS. 8A-8D  above, the scope of the disclosure includes other scenarios in which wearable device  100  can analyze the characteristics of a waveform to determine the presence (and in some configurations, the characteristics) of an object touching crown  108 . For example, in some configurations, wearable device  100  can determine that a user&#39;s wrist is touching the crown (e.g., an unintentional touch). In other examples, wearable device  100  can use the techniques described herein to determine the amount of force applied to the crown by an object (e.g., how hard a finger is pressed against crown  108 ). 
       FIG. 9  illustrates an exemplary process  900  for detecting the presence of a capacitive or non-capacitive object touching the crown according to examples of the disclosure. The device can apply an acoustic wave to at least the crown shaft and crown of the device ( 901 ). For example, as discussed above with regard to  FIGS. 5A-5B  for example, a transmit circuit can include a transducer operatively coupled to the crown shaft or crown. The device can measure changes in one or more parameters (e.g., characteristics of the waveform) of the acoustic wave after it travels through the crown shaft and crown and reflects off of the crown ( 902 ). For example, a receiver circuit or element can detect changes in amplitude, frequency, phase, and/or slew rate of the reflected acoustic wave. The device can detect touch and/or characteristics of an object at the crown ( 903 ). For example, based on the measured one or more parameters, the device (e.g., processor  202  or crown controller  252 ) can detect that an object is touching the crown (e.g., based on comparing the one or more parameters in the reflected wave to known parameters or parameters in the emitted wave). In some examples, the characteristics of a touching object can be estimated by comparing the one or more parameters to values in a look-up table (LUT). In some examples, the system can exit a rest state (as described, for example, with respect to  FIG. 3A ) in response to detecting a threshold level of contact between the object and the crown. 
     In some examples, wearable device  100  can perform acoustic wave touch detection using a range of emitted acoustic pulses, including pulses of varying duration, amplitude, and waveform shape. In some examples, acoustic wave touch detection can be performed using varying emitted acoustic pulses having different characteristics, and the characteristics of each waveform corresponding to a respective emitted acoustic pulse can be analyzed. Certain materials (e.g., fabric, skin, etc.) can have a “signature” reflected acoustic wave, which, in some examples, can be stored by device  100  (e.g., stored by processor  202  or crown controller  252  in a LUT) and used to determine that the specific material is touching the crown. It should be noted that the waveform shape of the emitted acoustic wave need not be a pulse shape, but can include any waveform shape beneficial to performing acoustic wave touch detection, including, but not limited to, sinusoidal waveforms. It should also be noted that the characteristics of reflected waveforms analyzed by device (e.g., by processor  202  or crown controller  252 ) are not limited to those discussed here. It should further be understood that, in these configurations, the processor may utilize multiple thresholds, and that the thresholds may vary dynamically. 
     In some examples, the characteristics (e.g., acoustic conductivity) of crown  108  and crown shaft  110  can be selected to facilitate object detection using acoustic property changes. For example, the one or more materials forming crown  108  and crown shaft  110  can be selected such that an acoustic wave can effectively travel longitudinally along the length of the crown shaft and crown. In some examples, portions of the crown or crown shaft can be formed of a metal material.  FIGS. 10A-10B  illustrate an example configuration in which crown shaft  110  and crown  108  can include an acoustic channel  1040  according to examples of the disclosure. In some examples, an acoustic channel can guide the emitted and reflected acoustic waves from transmitter  1031 , down the crown shaft  110  to the boundary at the far end of crown  108 , and back to receiver  1032 . As shown in the configuration illustrated in  FIG. 10A-10B , in some examples, a single acoustic channel can operate as an acoustic channel for both emitted and reflected acoustic waves. In other configurations not shown, crown  108  and crown shaft  110  can include separate channels for emitted acoustic waves and reflected acoustic waves. In some examples, acoustic channels can be formed using a step gradient density, wherein the material with the highest density forms the channel, while one or more materials having a lower density form the boundaries of the channel. For example,  FIG. 10B  illustrates a cross sectional view of crown shaft  110  including acoustic channel  1040  at a reference plane P1 as indicated in  FIG. 10A . As shown, the innermost (e.g., center) portion of crown shaft  110  can be formed of a first material M1 having a first acoustic conductivity. In some examples, the first material M1 can form an acoustic channel. The next portion of crown shaft  110  extending outwardly from the center can be formed of a second material M2 having a second acoustic conductivity. The second material M2 can form the boundary  1042  of the acoustic channel. The outermost portion of crown shaft  110  can be formed of a third material. In some examples, the difference in characteristics (e.g., acoustic conductivity) between the acoustic channel  1040  and acoustic channel boundary  1042  can confine the emitted acoustic wave such that more energy moves longitudinally along the length of the crown and is reflected back to the receiver. 
     In some examples, wearable device  100  can use acoustic waves to detect touching objects in specific areas of crown  108 . This can be beneficial, for example, to distinguish objects touching the top of crown  108  (e.g., intentional touches from a user&#39;s finger) from objects touching the bottom of crown  108  (e.g., unintentional touches from a user&#39;s wrist). In some configurations, crown shaft  110  and crown  108  can include a plurality of acoustic channels, like those discussed with reference to  FIGS. 9A-9B  above  FIGS. 11A-11B  illustrate a side cross sectional view and front cross-sectional view, respectively, of a crown shaft  110  and crown  108  including two acoustic channels  1140  and  1144  according to examples of the disclosure. The cross-sectional view of  FIG. 11B  is at a cross-sectional plane P2, as shown in  FIG. 11A . Each of the plurality of acoustic channels can terminate at a particular area of crown  108  (e.g., one acoustic channel terminates to an area on a first half of crown  108 , while another acoustic channel terminates to an area on a second half of crown  108 ). In these configurations, each acoustic channel can have a dedicated emitter and receiver (e.g.,  1131 - 1132  and  1133 - 1134 ), though in other configurations, the plurality of acoustic channels can share the same emitter and receiver through time multiplexing and switching networks. 
       FIGS. 12A-12B  illustrates a side cross-sectional view and perspective view, respectively, of another example configuration in which crown  108  includes two or more touch sensors according to examples of the disclosure. In the example shown, crown shaft  110  and crown  108  can be collectively divided lengthwise, forming a first half  1240  and second half  1242 . In some configurations, first half  1240  and second half  1242  can be separated by an acoustically isolating material  1244 . In some configurations, as shown in  FIGS. 12A-12B , first half  1240  and second half  1242  can each be coupled to a respective emitter and receiver (e.g.,  1231 - 1232  and  1233 - 1234 ), though in other examples, each half may share an emitter and receiver using, for example, switching networks and time multiplexing. 
       FIG. 13  illustrates a magnified cross-sectional view of another exemplary acoustic touch detector according to examples of the disclosure. The configuration shown in  FIG. 13  uses acoustic resonance according to examples of the disclosure. As in the configuration described with reference to  FIGS. 5A-5B  above, in some configurations, wearable device  100  can include a crown shaft  110 , and a crown  108  supported by the crown shaft. In some examples, wearable device  100  can also include a resonator  1340  coupled to a transmit circuit  1348  and a sensor  1342  coupled to a receiver circuit  1350 . In some configurations, crown shaft  110  can be supported by mounts  1344  which can be integrated with (or coupled to) housing  102  of the wearable device (not shown). In some examples, one or more flexible supports  1346  (for example, rubber bushings) can be positioned between mounts  1344  and crown shaft  110 . In some examples resonator  1340  can be configured to resonate the crown shaft  110  and crown  108 . Sensor  1342  can be configured to sense any damping of the resonation, thereby detecting when an object is touching crown  108 . 
       FIG. 14  illustrates an exemplary process  1400  for detecting the presence of a capacitive or non-capacitive object touching the crown according to examples of the disclosure. The device can apply a vibration to at least the crown shaft and crown of the device ( 1401 ). As will be discussed in more detail below, a resonator can include, for examples, a transducer, a vibrating mass, an electromagnet or a mechanical hammer operatively coupled to the crown shaft or crown. The resonator can be configured such that, if no object is touching crown, the crown shaft and crown will vibrate at the set frequency (e.g., the resonant frequency of the crown shaft and crown) with a set of known parameters. As an object comes in contact with the crown, the actual vibration will be dampened, resulting in a change in vibration characteristics (e.g., vibration amplitude or frequency). Therefore, while the resonator vibrates the crown shaft and crown, the device can measure one or more parameters of the actual vibration on the crown shaft and crown ( 1402 ). For example, a receiver circuit coupled to a sensor can detect amplitude, frequency, phase, of the vibration. As will be discussed in more detail below, the sensor can include, for example, and accelerometer, or an optical proximity sensor. The device can detect touch and/or characteristics of an object at the crown ( 1403 ). For example, based on the measured one or more parameters, the device (e.g., processor  202  or crown controller  252 ) can detect that an object is touching the crown (e.g., based on determining the amount of damping by comparing the one or more parameters in the vibration to known parameters). In some examples, the characteristics of an object touching the crown can be determined by comparing the one or more parameters to values in a look-up table (LUT). In some examples, the system can exit a rest state (as described, for example, with respect to  FIG. 3A ) in response to detecting a threshold level of proximity between the object and the crown. 
     As discussed, in some examples, wearable device  100  can determine whether an object is touching the crown based on whether a change in vibration parameters exceeds one or more preselected thresholds. Similar to the examples discussed above with reference to  FIGS. 8A-8D , in some examples, the change in vibration characteristics (e.g., frequency and amplitude) can be unique for different scenarios of object interaction with the crown. For example, a single bare finger in contact with the crown can change the vibration characteristics differently than when two fingers, a gloved finger, or a wrist are in contact with the crown. In other words, each of these scenarios can have a unique vibration characteristic “signature” (though it should be noted that possible scenarios and signatures are not limited to these examples only). In some examples, detected vibration characteristics can be compared against stored vibration characteristic signatures (e.g., vibration characteristic signatures stored in an LUT) and determine that a corresponding scenario (e.g., a finger touching crown) is occurring when the vibration character signature is detected. In some examples, vibration characteristic signatures can be learned during operation (e.g., learning that a signature represents a finger touch if crown is mechanically pressed thereafter), or predetermined. In some examples, the resonator can operate in a plurality of frequencies. For example, the resonator can perform a frequency sweep wherein crown shaft and crown are vibrated at a range of frequencies, and sensor can detect changes in the vibration characteristics at each of these frequencies. In these configurations, a single scenario (e.g., a finger touching crown) can have multiple vibration characteristic signatures corresponding to multiple vibration frequencies, which can be beneficial in distinguishing scenarios one from another. 
     Examples of resonators in an acoustic resonance touch detection configuration will now be discussed. Returning to  FIG. 13 , in some examples, resonator  1340  can be contact coupled to crown shaft  110  in order to vibrate the crown shaft  110  and crown  108  at a frequency (e.g., a resonant frequency). In some configurations, resonator  1340  can comprise a spinning mass (e.g., an off-balance mass on a motor) configured to vibrate crown shaft  110  and crown  108 . In these configurations, the revolution speed of the spinning mass can be tuned in order to optimize the resonance of the crown shaft  110  and crown  108 . In some examples, a haptic feedback device of wearable device  100  can be coupled to crown shaft  110  and crown  108  and can be configured to operate as a resonator  1340  for the crown shaft and crown (e.g., by being configured to run at a different frequency when operating as a resonator). In other examples, crown shaft  110  and crown  108  can vibrate and resonate as a result of being struck by a mechanical hammer (e.g., a solenoid) within the housing of wearable device  100 , that is, the mechanical hammer can operate as resonator  1340 . In still other examples, the crown shaft  110  and crown  108  can be vibrated by magnetomechanical effects. For example, in some configurations, resonator  1340  can comprise an electromagnet configured to provide electromagnetic pulses which can vibrate crown shaft  110  and crown  108 . In these configurations, resonator  1340  need not be contact coupled to crown shaft  110  or crown  108  in order to vibrate and resonate these elements. It should be noted that, although the resonator illustrated in  FIG. 13  is mounted at a base of crown shaft  110 , resonator can be mounted anywhere on the crown shaft  110  or crown  108  (or, in the case of electromagnetic coupling, mounted in proximity to the crown shaft or crown). In still other examples, the resonator may not be directly coupled to the crown shaft or crown, but can be indirectly coupled to the crown shaft or crown (e.g., coupled to a mount which is, in turn, coupled to the crown shaft). It should also be understood that some configurations may include multiple resonators and/or multiple sensors. 
     Examples of sensors in an acoustic resonance touch detection configuration will now be discussed. In some examples, the sensor can comprise an accelerometer coupled to the crown shaft or crown. For example, referring again to  FIG. 13 , sensor  1342  can comprise an accelerometer coupled to the crown shaft  110  or crown  108 , which can detect the movement (i.e., vibration characteristics) of the crown shaft  110  or crown  108 . Additionally or alternatively, in some configurations, the sensor can include a proximity detector. For example,  FIG. 15  illustrates a magnified cross-sectional view of an exemplary acoustic touch detector which uses acoustic resonance and a proximity sensor according to examples of the disclosure. In the example illustrated in  FIG. 15 , sensor  1542  can comprise a proximity detector, which is not coupled to the crown shaft or crown, but is configured to detect a distance D1 between sensor  1542  and crown shaft  110  or crown  108 . As shown in  FIG. 15 , in some configurations, crown shaft  110  can be supported by one or more mounts  1344 . In some examples, one or more flexible supports  1346  (for example, rubber bushings) can be positioned between mounts  1344  and crown shaft  110 . The flexibility of flexible supports  1346  can allow crown shaft  110  to move and rotate about the fulcrum of mounts  1344 . Thus, in some examples, resonator  1340  can be configured to vibrate crown shaft  110  and crown  108  such that crown shaft  110  moves about the fulcrum of mounts  1344  as indicated by the directional arrows in  FIG. 15 . As sensor  1542  can be configured to measure a distance D1 between the optical sensor and crown shaft  110  over time, the frequency with which crown shaft  110  returns to a position (i.e., the frequency of the vibration) and the range in detected distance D1 (i.e., the amplitude of the vibration) can be determined. In some configuration, sensor  1542  can be an optical sensor configured to operate using any appropriate optical distance-detection techniques including, but not limited to, time of flight, coincidence, or stereoscopic distance calculation). In some examples, sensor  1542  can also operate as an optical encoder to register mechanical rotation of crown  108 , as discussed with reference to  FIG. 2  above. 
     As similarly discussed with reference to the examples shown in  FIGS. 12A-12B  above, crown shaft  110  and crown  108  can be configured to detect touching objects in specific areas of crown  108 . This can be beneficial, for example, to distinguish objects touching the top of crown  108  (e.g., intentional touches from a user&#39;s finger) from objects touching the bottom of crown  108  (e.g., unintentional touches from a user&#39;s wrist).  FIGS. 16A-16B  illustrate an example configuration in which crown  108  includes two or more touch sensors according to examples of the disclosure. In the example shown, crown shaft  110  and crown  108  can be collectively divided lengthwise, forming a first half  1640  and second half  1642 . In some configurations, first half  1640  and second half  1642  can be separated by an acoustically isolating material  1644 . In some configurations, as shown in  FIG. 16 , first half  1640  and second half  1642  can each be coupled to a respective resonator and sensors (e.g.,  1635 - 1636  and  1637 - 1638 ) and respective transmit circuits and receiver circuits (e.g.,  1631 - 1632  and  1633 - 1634 ) (though in other examples not shown, each half may share a resonator and sensor and circuitry via time multiplexing). 
     Although examples described herein primarily involve acoustic touch sensors used to detect objects touching the crown of a watch, it should be understood that the sensors described herein can be used to detect the presence of objects on any component of a device that can be resonated. For example, referring back to  FIG. 1 , buttons  112  and  114  can be configured as described in this disclosure in order to detect objects that are touching (but not necessarily pressing) a button. In some of these configurations, touch sensors can be used in conjunction with a display of a device to ready the device (e.g., touchscreen) for a button-press operation based on a detected touch on the button, as similarly described with reference to the process illustrated in  3 A- 3 B above. Similarly, although the examples discussed herein focus primarily on wearable devices, it should be noted that the examples discussed herein can be used in other electronic devices including, but not limited to, cellular phones, laptops, or tablet devices. 
     Optical Detection Apparatus and Methods 
     In some examples, it can be beneficial to detect the presence of both conductive and non-conductive objects (e.g., an ungloved or gloved finger) at specific areas proximate to a crown (e.g.,  108  in  FIG. 1  above) with improved accuracy. In addition, it can be beneficial to detect objects at a greater range than possible with capacitive touch technologies. Moreover, when a device is a watch, it can be beneficial to have proximity sensors be unobtrusive, and in some examples, positioned within the housing of the watch beneath the cover substrate of the watch. 
     Some examples described herein refer to an optical proximity sensor. The configurations described herein can be used to detect the presence and/or distance of an object. For example, proximity sensors can be used to detect user interaction with an electronic device by sensing the presence and/or distance of an object such as a stylus or a user&#39;s finger. In these configurations, near-field proximity sensing can be used to detect when an object is touching or approaching the electronic device. In some cases, different objects interacting with an electronic device can have different levels of optical reflectivity (e.g., a gloved finger, a non-gloved finger, or a finger with lotion), and some conventional amplitude-based optical proximity sensors can have difficulty reliably detecting the proximity of objects having different levels of optical reflectivity. Moreover, while some time-of-flight (i.e., not amplitude-based) optical sensors can more reliably detect objects of varying levels of reflectivity, these sensors can be less suited for near-field proximity sensing. Therefore, it can be beneficial to detect the presence and/or distance of objects near an electronic device with improved accuracy, better range, and with more consistency between objects having different reflective characteristics. The examples herein discuss proximity sensors in the context of a wearable device; however, it should be understood that the examples herein can be used in any appropriate application which requires proximity or contact sensing. 
       FIG. 17A  shows an exemplary optical proximity sensor  1720  integrated in a wearable device  1700  (which can correspond to device  100  above) according to examples of the disclosure.  FIG. 17B  shows a magnified simplified drawing of the optical proximity sensor according to examples of the disclosure. As shown, proximity sensor  1720  can comprise a photo emitter  1722  and photodetector  1724 , though in some cases, proximity sensor can include multiple emitters and/or detectors. Proximity sensor  1720  can determine the presence and/or range of object  1730  (e.g., a user finger) using any appropriate method. For example, emitter  1722  can emit a beam of electromagnetic radiation (e.g., Infra-Red (IR) light), and the presence and/or range of object  1730  can be detected based on the amount of radiation received back at detector  1724 . In some examples, the beam of electromagnetic radiation emitted from emitter  1722  can be emitted through a cover substrate  1712  of the device (e.g., a cover glass). In some examples, a higher amount of radiation (e.g., light) received back at the detector can correspond to an object at a closer distance, while a lower amount of radiation received back at the detector can correspond to an object at a further distance. In some examples, proximity sensor  1720  can detect objects at a distance from the wearable device  1700  ranging from 0 mm (i.e., when an object is touching the wearable device) to 100 mm. 
     In other examples, other methods can be used to detect the presence and/or range of the object such as, for example, time of flight calculations. It should be noted that the scope of the disclosure is not limited to the proximity sensors described herein, but can include any optical proximity sensor capable of detecting the presence and/or range of an object according to examples of the disclosure. For example, emitter  1722  can, in some examples, emit light of other wavelengths including visible light and ultraviolet light, or can selectively emit light from other wavelengths according to environmental conditions (e.g., characteristics of approaching object, ambient light level, etc.). 
     In some examples, the proximity sensor can be positioned beneath the cover substrate of the wearable device  1800  (which can correspond to device  100  above).  FIG. 18  illustrates a simplified cross-sectional diagram of wearable device  1800  having a crown  1808  (which can correspond to crown  108  above) and integrated optical proximity sensor according to examples of the disclosure. Cover substrate  1812  (which can correspond to cover substrate  1712  above) can have an outer surface  1832  and an inner surface  1834 . In some examples, display  1806  (which can correspond to display  106  above) can be positioned behind the cover substrate  1812 . In some examples, the field of view of proximity sensor  1720  (that is, the path of light emitted and received by the proximity sensor) can be refracted using cover substrate  1812  and the cover substrate can provide a protective barrier for the display  1806 . In some examples, the characteristics of proximity sensor  1720  and cover substrate  1812  can be selected such that the field of view is focused to a particular region about the wearable device  1800  such as the area above crown  1808 . 
     In general, the path of a light wave passing across a boundary between two media (e.g., through air and cover substrate  1812 ) can be determined using Snell&#39;s law of refraction, shown in Equation (1) below:
 
 n 1 sin(α)= n 2 sin(β)  (1)
 
where n1 is the refractive index of the first medium, n2 is the refractive index of the second medium, a is the angle of incidence (i.e., the entrance angle) of the light, and β is the angle of refraction (i.e., the exit angle) of the light. Although the examples herein describe a path of light being emitted from the proximity sensor  1720  through the cover substrate  1812  and toward an object (e.g., finger  1730  above), it should be understood that light received at the proximity sensor can follow a similar path. Both the light path of the light emitted by the proximity sensor and light received by the proximity sensor can be described generally as the field of view of the proximity sensor. As shown in  FIG. 18 , the field of view can be represented as having an upper bound  1824  and lower bound  1826  (both shown in dashed line). In some examples, the field of view can be centered about a center line, where the center line is refracted through the cover substrate at an angle in the range of 10 and 60 degrees.
 
       FIG. 19  illustrates a magnified view of the curved portion of cover substrate  1912  (which can correspond to cover substrate  1812  above) including an inner surface  1834 , outer surface  1832 , and proximity sensor  1720  (which can correspond to proximity sensor  1720  above) mounted to the inner surface of the cover substrate  1912  (e.g., glass) according to examples of the disclosure. In other examples, proximity sensor  1720  need not be mounted to cover substrate  1912 , but can be mounted to some other component within the housing and cover substrate  1912  of the device. The initial field of view of proximity sensor  1720  (e.g., the field of view beneath the inner surface of cover substrate  1912 ) shown in  FIG. 19  is defined by an upper bound beneath the cover substrate having an angle θ 1  and a lower bound beneath the cover substrate having an angle θ 2 . As shown in  FIG. 19 , angles θ 1  and θ 2  are expressed with respect to normal lines  1942  and  1944  (shown in dotted line) perpendicular to the boundary at the inner surface. The characteristics of proximity sensor  1720  (such as focal length and lens shape), can be selected to produce desired angles θ 1  and θ 2 . As shown, the light path of the upper bound beneath the cover substrate and lower bound beneath the cover substrate can change as the light path enters the cover substrate  1912  at the boundary of the inner surface  1834 . In  FIG. 19  the angles of the light path as it enters the cover substrate are represented for the upper and lower bounds as θ 1 ′ and θ 2 ′ respectively. As indicated in Equation (1), the refractive index n of cover substrate  1912  can define, at least in part, angles θ 1 ′ and θ 2 ′. Using Equation (1) to solve for β and substituting variables for those at hand, θ′ (e.g., θ 1 ′ or θ 2 ′ as illustrated in  FIG. 4  can be represented as shown in Equation (2) below: 
     
       
         
           
             
               
                 
                   
                     θ 
                     ′ 
                   
                   = 
                   
                     
                       sin 
                       
                         - 
                         1 
                       
                     
                     ⁡ 
                     
                       ( 
                       
                         
                           
                             n 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             AIR 
                           
                           
                             n 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             GLASS 
                           
                         
                         ⨯ 
                         
                           sin 
                           ⁡ 
                           
                             ( 
                             θ 
                             ) 
                           
                         
                       
                       ) 
                     
                   
                 
               
               
                 
                   ( 
                   2 
                   ) 
                 
               
             
           
         
       
     
     One skilled in the art would understand that the refractive index n GLASS  of the cover substrate (which could also be made of other transparent materials such as plastic) and the distance and angle at which proximity sensor  1720  is positioned with respect to the inner surface of cover substrate  1912  can be selected to achieve a desired light path within cover substrate  1912 . In some examples, angles θ and  0 ′ can be the same, that is, the upper and lower bounds can be symmetric within the cover substrate. For example, the upper and lower bounds may be symmetric when the proximity sensor  1720  is mounted parallel to the inner surface  1834 . 
     The light path of the upper bound  1824  and lower bound  1826  within cover substrate  1912  can be refracted at the boundary between the outer surface of the cover substrate  1912  and air. As shown in  FIG. 19 , angles β 1  and β 2  can represent the exit angles where the upper and lower bounds of the light path ( 1824  and  1826 ) exit cover substrate  1912 . As shown, angles β 1  and β 2  are expressed with respect to the normal lines  1946  and  1948  perpendicular to the boundary at the upper and lower bounds  1824  and  1826 , respectively. As indicated in Equation (1), the refractive index n GLASS  of cover substrate  1912  can define, at least in part, angles β 1  and β 2 . Using Equation (1) to solve for β and substituting variables for those at hand, β 1  or β 2  as illustrated in  FIG. 19  can be represented as shown in Equation (3) below: 
     
       
         
           
             
               
                 
                   β 
                   = 
                   
                     
                       sin 
                       
                         - 
                         1 
                       
                     
                     ⁡ 
                     
                       ( 
                       
                         
                           
                             n 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             GLASS 
                           
                           
                             n 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             AIR 
                           
                         
                         ⨯ 
                         
                           sin 
                           ⁡ 
                           
                             ( 
                             α 
                             ) 
                           
                         
                       
                       ) 
                     
                   
                 
               
               
                 
                   ( 
                   3 
                   ) 
                 
               
             
           
         
       
     
     Returning again to  FIG. 18 , the characteristics of proximity sensor  1720  and cover substrate  1812  can be selected such that the field of view is focused to a particular region about the wearable device  1800  such as the area above crown  1808 . As discussed above, the refractivity of the cover substrate material can be selected in order to achieve desired angles θ 1 ′, θ 2 ′, β 1  and β 2  as shown in  FIG. 19 . In addition, the curvature of the inner surface  1834  of cover substrate  1812  can be selected to achieve desired angles θ 1 ′ and θ 2 ′ Likewise, the curvature of the outer surface  1832  of cover substrate  1812  can be also selected to achieve desired angles β 1  and β 2 . In addition, the thickness of cover substrate  1812  can be selected to produce desired results. Although the cover substrate has been described herein as comprising a single material for convenience, it should be understood that cover substrate  1812  can comprise multiple materials, including configurations wherein cover substrate comprises layers of materials. In such configurations, the light path of proximity sensor  1720  can undergo multiple refractions at the boundaries between each material. Accordingly, in configurations where cover substrate  1812  comprises multiple layers of materials, the refraction index of one or more of the materials can be selected to achieve a desired field of view for the proximity sensor. It should be noted that, in addition to the above-mentioned approaches, the field of view of proximity sensor  1820  can be further defined using other well-known techniques including, but not limited to, utilizing additional lenses, prisms, or mirrors. 
     As illustrated in  FIG. 18 , in some examples, the field of view defined by bounds  1824 - 1826  of proximity sensor  1720  can extend to an area not normal to the proximity sensor. In some cases, the field of view of proximity sensor  1720  can extend to next to the device  1800 . That is, the field of view can include an area adjacent to the device in a direction parallel to the plane of the display  1806  (which can correspond to display  106  above). In some examples, the field of view can extend to an area next to crown  1808  (which can correspond to crown  108  above) in a direction parallel to the plane of touch sensor panel  1836 . In some examples, the field of view can include an area proximate to device  1800  at an angle with respect to the plane of touch sensor pane  1836 , wherein the angle can be in a range of 10 to 80 degrees. 
     In some examples, a wearable device according to examples of the disclosure can include optical filtering structures.  FIGS. 20A and 20B  illustrate an optical filtering structure in a device  2000  (which can correspond to device  100  above) including an optical opaque mask  2042  configured to preferentially pass light to and from proximity sensor  1720  and optical filter  2044  according to examples of the disclosure. As shown in  FIG. 20A , proximity sensor  1720  can include an opaque mask  2042  (shown in double cross-hatching) which blocks light from entering the proximity sensor at respective areas surrounding the light emitter  1722  and photodetector  1724  of proximity sensor. As shown in  FIG. 20B , in some examples, opaque mask  2042  can include respective apertures (e.g., circular openings) in front of light emitter  1722  and photodetector  1724  to allow light to pass through this portion. In some examples, the apertures in front of light emitter  1722  and photodetector  1724  can include an optical filter  2044  formed of a material which is permeable to light of specific wavelengths (e.g., IR wavelengths) and blocks other light (e.g., visible light). In these examples, one or both of the opaque mask  2042  and optical filter  2044  can be formed by depositing opaque or filtering material on the inner surface of cover substrate  2012  (which can correspond to cover substrate  1812  above).  FIG. 20B  illustrates a top view of the proximity sensor configuration of  FIG. 20A  in which the area surrounding proximity sensor  1720  includes opaque mask  2042  which can be deposited, for example, on the inner surface of cover substrate  2012 . As shown, optical filter  2044  can also be deposited on the inner surface of cover substrate  2012  at locations where light is emitted and received by proximity sensor  1720 . In addition, other optical filtering structures not described here are contemplated within the scope of the disclosure including, for example, optical coatings configured to alter the reflection or transmission of light within device  2000 . 
       FIG. 21  illustrates a simplified block diagram  2100  of wearable device  2100  (which can correspond to device  100  above) according to examples of the disclosure. As shown, device  2100  can include input mechanisms  2101 , which can include one or more buttons and crown (e.g., buttons  110 ,  112 ,  114 , and crown  108  above). Device  2100  may also include a touchscreen  2105 , a proximity sensor  2104 , and an analog-to-digital converter (ADC)  2103 . A processor  2102  may also be included in the wearable device  2100  and be configured to execute algorithms for carrying out the various methods described herein and control the reception and manipulation of input and output data between components of wearable device, e.g., the buttons, crown, display, and emitters and receivers of proximity sensor  2104 . The processor can be a single-chip processor or can be implemented with multiple components. It should be understood that the scope of the disclosure is not limited to the components and configuration of  FIG. 21 , but can include other or additional components in multiple configurations. 
     Methods for detecting the presence of an object proximate to the crown of a watch are further disclosed herein. In some variations, the methods generally include detecting the presence of a conductive or non-conductive object proximate to the device. In some configurations, the device can detect objects as far as 100 mm from the wearable device. In some configurations, the device can execute one or more operations based on the detection of the presence of an object. 
       FIG. 22  illustrates an exemplary process  2200  for detecting the presence of a capacitive or non-capacitive object proximate to the device according to examples of the disclosure. At block  2201 , the device can emit light from a light emitter. At block  2202 , the light can be refracted through a cover substrate as described above with reference to  FIGS. 18-19 . At block  2203  a photodetector can detect the amount of the emitted light which is reflected back from the emitted light. This amount can be represented as a value. At block  2204 , the presence (and in some examples, the distance) of an object can be detected based on the value representing the amount of emitted light which is reflected back. In some examples, a processor can be configured to operate the proximity sensor according to various light-pulsing (i.e., luminous modulation) schemes. For example, referring back to  FIG. 21 , in some configurations, the processor  2102  can be configured in conjunction with proximity sensor  2104  to pulse and detect light at a frequency less likely to match to the pulse frequency of ambient light (e.g., 120 Hz, which matches the flicker of conventional fluorescent lamps). In some configurations, processor  2102  can be configured in conjunction with proximity sensor  2104  to emit and detect light at changing pulse frequencies, i.e., according to a pulse-frequency hopping scheme. 
     In some configurations, the device can execute one or more operations based on the detection of the presence of an object. Referring back to  FIG. 17 , in some examples, device  1700  can determine the distance between object  1730  and crown  1708 , including determining when the object is touching the crown (i.e., when the distance between the object and device is zero). Moreover, in some configurations, device  1700  can determine when object  1730  is approaching crown  1708  (i.e., when the distance between object and crown decreases during two successive times) and when object  1730  is traveling away from crown  1708  (i.e., when the distance between object and crown decreases during two successive times). In some examples, different operations can be performed based on whether the object is not touching the crown (e.g., approaching the crown or distancing itself from the crown) or touching the crown. In some configurations, the determination can be performed in conjunction with a touch-sensor on crown  1708  itself (e.g., a capacitive touch sensor). 
       FIG. 23  illustrates an exemplary process  2300  for performing the operations described above according to examples of the disclosure. At block  2301 , the device can be in a rest mode. This may correspond, for example, to a power-saving mode in which the device display is powered down. In other examples, the rest mode can correspond to a device mode where the display is operative, but the device is not performing an operation (e.g., a touch or hover operation). At block  2302 , device can obtain crown input from, for example, the proximity sensor. If the input represents a crown touch, processing proceeds to block  2306 . At block  2306 , a touch operation can be performed. The touch operation can correspond, for example, to a display of a contextual message on the device display, the selection of an icon on a screen, etc. During the performance of the touch operation at block  2306 , the device can again obtain crown input, as shown in block  2307 . If a touch is still detected, then the touch operation can continue to be performed in block  2306 . If a touch is no longer detected, processing can determine whether a hover input (i.e., an object proximate to, but not touching, the crown) is detected). If, however, a hover is not detected, processing can return the device to rest mode shown in block  2301 . If a hover input is detected, processing can set the device to ready mode as shown in block  2304 . Ready mode will be described in more detail shortly. Returning again to block  2302 , if the crown input obtained is a hover input, processing can proceed to block  2303 , where processing can wake the device, and next configure the device to be in ready mode as indicated in block  2304 . Ready mode can correspond, for example, to a mode where the device is preparing to receive a touch input. During the ready mode at block  2304 , the device can again obtain crown input, as shown in block  2305 . If a touch is detected, then processing can proceed to block  2306  to perform a touch operation. After performing a touch operation at block  2306 , process  2300  can obtain an input at block  2307 . If a touch is not detected at block  2304  or block  2307 , processing can determine whether a hover input is still detected. If a hover is still detected, processing can return to block  2304  where the device continues to operate in ready mode. If, however, hover is no longer detected, then processing can return to rest mode in block  2301 . 
       FIG. 24  shows an alternative exemplary optical proximity sensor  2410  integrated in a wearable device  2400  (which can correspond to device  100  above) according to examples of the disclosure. As shown, proximity sensor  2410  can determine the presence and/or range of object  2411  (e.g., a user finger) using any appropriate method. In some configurations, proximity sensors can operate by emitting light and detecting light reflected off of an object. In some examples, the light can be emitted through a cover substrate  2412  (which can correspond to cover substrate  1812  above). In some examples, proximity sensor can have a field of view  2440 , which can include an area above crown  2408  (which can correspond to crown  108  above). In some examples, proximity sensor  2410  can detect objects at a distance ranging from 0 mm (i.e., when an object is touching the device) to 100 mm. In some examples, device  2400  can have a corresponding block diagram as illustrated in  FIG. 21 . 
     As described above, in some cases, it can be beneficial to detect the proximity of objects having different levels of optical reflectivity, where each object may interact with a device. For example, a gloved finger, a bare finger, a dry finger, or a finger has lotion on the skin may all have different levels of optical reflectivity. It can be beneficial for a device to determine the presence of objects such as these at a range of distances from the device. For instance, it can be beneficial to detect whether an object is present at a “trigger distance,” at which the proximity sensor determines that an object is proximate to the proximity sensor (e.g., a finger is proximate to a crown of a wearable device). Similarly, it can be beneficial to detect whether an object is present at a “release distance,” at which, if the object is not detected, the proximity sensor determines than an object is not proximate to the proximity sensor (e.g., a finger is not proximate to the crown of the wearable device). 
       FIG. 25  illustrates a graph relating to proximity detection using a single-channel amplitude-based optical proximity sensor according to examples of the disclosure. The x-axis  2554  can represent the distance of an object (e.g., object  2411  in  FIG. 24 ) from the single-channel proximity sensor in units of millimeters. The y-axis  2555  can represent the detected amplitude of light received by a single light detector originating from a single emitter in units of nanowatts (nW). Also shown is a trigger distance, T1, and release distance, R1. As discussed above, trigger distance T1 can represent a point at which the proximity sensor determines that an object is proximate to the proximity sensor. Likewise, release distance R1 can represent a point at which the proximity sensor determines than an object is not proximate to the proximity sensor. In some examples, trigger distance T1 can be 3 mm from the proximity sensor, and release distance R1 can be 6 mm from the proximity sensor.  FIG. 25  illustrates two curves  2541  and  2551 . First curve  2541  can represent light detected by the single light detector which is emitted by a single light emitter and reflected off of an object having a Lambertian (matte or diffusely reflecting) surface. This may correlate, for example, to a scenario in which light is reflected from the emitter off of a dry finger. Second curve  2551  represents light received by the single detector which is emitted by the single light emitter and reflected off of an object having a more specular (more reflective) surface. This may correlate, for example, to a scenario in which light is reflected from the emitter off of an oily surface of a finger (e.g., a finger having a coating of hand lotion). As shown, at trigger distance T1, curve  2541  (corresponding to an object having a Lambertian surface) can have a first value (in this example about 70 nW of optical power). In contrast, at trigger distance T1, curve  2551  (corresponding to an object having a more specular surface) can have a second value significantly lower than the value of curve  2541  (in this example, about 3 nW of optical power). Likewise, as shown, curve  2551  can have a value significantly lower than that of curve  341  at release distance R1. Accordingly, in some examples, a single-channel proximity sensor cannot unambiguously detect the presence of an object at trigger distance T1, or at release distance R1. 
     In some examples, a proximity sensor (e.g., proximity sensor  2410  shown in  FIG. 24 ) can utilize an array of light detectors to perform parallax-based proximity sensing.  FIGS. 26A-26C  illustrate an example configuration of a parallax-based proximity sensor including an array of light detectors according to examples of the disclosure. In the example configuration shown here, proximity sensor  2610  uses a light emitter  2621  (e.g., a light-emitting diode (LED)) and an array of light detectors  2630  (e.g., an array of photodetectors).  FIG. 26A  illustrates a cross-sectional side view of proximity sensor  2610 , while  FIG. 26B  illustrates a top view.  FIG. 26C  illustrates a detailed view of detector array  2630 , which includes detectors 1-8 labeled accordingly, though it should be understood that detector array  2630  can include any number of detectors according to examples of the disclosure. 
     As shown, in some examples, emitter  2621  and detector array  2630  can be aligned in a direction parallel to the cover substrate  2612  (which can correspond to cover substrate  1812  above). Detector array  2630  can have a length L1 from end-to-end which can be, for example, in the range of 1 mm to 1.8 mm. Detector array  2630  can also have a width W1, which can be, for example, in the range of 0.3 mm to 1 mm. As shown, light emitter  2621  and detector array  2630  can each be positioned within respective cavities  2641  and  2645 . As shown in  FIG. 26A , in some examples, each of light emitter  2621  and detector array  2630  can correspond to respective imaging lenses  2651  and  2655 , which can direct emitted light or (in the case of detector array  2630 ) received light so as to form a desired field of view, which can correspond, for example, to the field of view  2440  shown in  FIG. 24 . In some examples, imaging lens  2655  corresponding to detector array  2630  can be positioned off-center with respect to the length of detector array  2630 . For example, as shown in  FIGS. 26A and 26C , imaging lens  2655  can be positioned above the detectors 2 and 3 of array  2630  which is nearer to emitter  2621  than the center point along the length of detector array  2630  between detectors 4 and 5. In some configurations, the individual field of view of each of the detectors in detector array can overlap such that, for example, light seen by one detector can also be seen by an adjacent detector. 
     In some examples, proximity sensor  2610  can be positioned such that emitted and reflected light passes through a cover substrate  2612  of a device (which can correspond to cover substrate  1812  above). In some examples, proximity sensor  2610  can be positioned such that an air gap  2647  exists between the imaging lenses  2651 ,  2655  and cover substrate  2612 . For ease of illustration, cover substrate  2612 , air gap  2647 , and imaging lenses  2651 ,  2655  are not shown in  FIG. 26B . As shown, in some examples, light emitter  2621  can be separated from detector 1 of detector array  2630  by a first center-to-center distance D1, while detector 8 can be separated from emitter  2621  by a second center-to-center distance D2, which is greater than distance D1. 
     The operation of the example proximity sensor  2610  illustrated in  FIGS. 26A-26C  will now be discussed with reference to the examples shown in  FIGS. 27A-27H  below.  FIGS. 27A-27H  illustrate an example operation of a parallax-based proximity sensor  2610  described with reference to  FIGS. 26A-26C , according to examples of the disclosure.  FIGS. 27A-27C and 27E-27G  relate to a scenario in which an object  2711  has a first optical reflectivity level, and  FIGS. 27D and 27H  relate to a scenario in which a different object  2713  has a second reflectivity level lower than that of object  2711 . 
     In these examples, proximity sensor  2610  can operate by detecting the centroid (and in some examples the size and shape) of the light received by detector array  2630  (labeled here as  2630 A,  2630 B,  2630 C, and  2630 D for ease of reference). As shown, light can be emitted by emitter  2621 , pass through lens  2651  (e.g., a collimating lens), reflect off of an object (object  2711  in  FIGS. 27A-27C , object  2713  in  FIG. 27D ), pass through lens  2655  (e.g., a converging lens), and be received by one or more of detectors 1-8 of detector array  2630 . As shown, emitter  2621  and detector array  2630  can be aligned in a first direction, which can be parallel to cover substrate  2612 . Detectors 1-8 of detector array  2630  can also be aligned in the first direction as to have a collective length L1 from one end to the other as shown in  FIGS. 27E-27H . As will be explained, due to parallax in the imaging path, the detected light received by detector array  2630  can move across the detector array in the first direction as a function of the distance of the object to proximity sensor  2610 , the distance measured in a direction orthogonal to the first direction. It should be understood that, while 8 detectors are shown here, detector arrays can include any number of detectors. Moreover, as will be explained further with reference to  FIGS. 30A-30B  below, in some configurations, detector arrays may be two-dimensional. 
       FIG. 27A  illustrates a first scenario where an object  2711  (corresponding, for example, to finger  2411  shown in  FIG. 24 ) is positioned at a distance D3 from proximity sensor  2610 .  FIG. 27E  illustrates a representation of the amplitude of light received at each of detectors 1-8 in detector array  2630 A (so labeled for ease of reference) shown in  FIG. 27A , with darker areas indicating a higher amplitude of light. In  FIG. 27A , the light path  2741 A is represented symbolically as lines with arrows indicating direction. As shown in  FIGS. 27A and 27E , when object  2711  is positioned at relatively far distance D3, light passing through lens  2655  can be directed primarily to detector 3 of detector array  2630 A, with lesser parts of the light directed equally to adjacent detectors 2 and 4. In some examples, the one-dimensional centroid of the received light from light path  2651 A can be calculated using the respective amplitudes detected by detectors 1-8 of detector array  2630 . In some examples, the determined centroid can be determined only in terms of which detector the centroid is located. For example, in the scenario shown in  FIG. 27E , the centroid can be calculated merely to be in the area of detector 3. In these examples, the centroid can be estimated to be in the center of the detector (i.e., in the center of detector 3 in this example). In other configurations, interpolation can be used to more precisely determine the centroid. For example, in this scenario, the amplitude detected by detector 3 and the equal amplitude detected by detectors 2 and 4 can be used to determine that the centroid is located at a distance D7, measured from a point A to point B, where point A is located at the end of detector array nearest to emitter  2621  and point B can be located midway between the border of detectors 2 and 3 and the border of detectors 2 and 4. In some examples, the centroid of the light received by detector array  2630  can be used to determine that object  2711  is at a distance D3 from the proximity sensor. 
       FIG. 27B  illustrates a second scenario where object  2711  is at a distance D4 from proximity sensor  2610 , where distance D4 is less than distance D3.  FIG. 27F  illustrates a representation of the amplitude of light received at each of detectors 1-8 in detector array  2630 B (so labeled for ease of reference), with darker areas indicating a higher amplitude of light. The light path  2741 B is represented symbolically as lines with arrows indicating direction. As shown, due to parallax in the imaging path, the light path can be directed to a different position on the detector array  2630  than in the scenario described with reference to  FIGS. 27A and 27E . Here, when object  2711  is positioned at a distance D4, smaller than D3, light passing through lens  2655  can be directed primarily to detector 4 of detector array  2630 B, with a lesser part directed to adjacent detector 5 and an even lesser part directed to adjacent detector 3. Therefore, in the scenario shown in  FIG. 27F , the centroid can be calculated to be in the area of detector 4, or if interpolation is used, the centroid can be calculated to be a distance D8, greater than D7, where D8 is measured from point A to a point C in the area of detector 4, but nearer to detector 5 than detector 3. The centroid of the light received by detector array  2630  can be used to determine that object  2711  is at a distance D4 from the proximity sensor. 
       FIG. 27C  illustrates a third scenario where object  2711  is at a distance D5 from proximity sensor  2610 , where distance D5 is less than distance D4.  FIG. 27F  illustrates a representation of the amplitude of light received at each of detectors 1-8 in detector array  2630 C with darker areas indicating a higher amplitude of light. In  FIG. 27C , the light path  2741 C is represented symbolically as lines with arrows indicating direction. As shown, the light path can be directed to a different position on the detector array  2630  than in the scenarios described above with reference to  FIGS. 27A and 27B . Here, when object  2711  is positioned at a distance D5, smaller than D4, light passing through lens  2655  can be directed primarily to detector 6 of detector array  2630 C, with a lesser part light directed to adjacent detector 5 and an even lesser part directed to adjacent detector 7. Therefore, in the scenario shown in  FIG. 27G , the centroid can be calculated to be in the area of detector 6, or if interpolation is used, the centroid can be more specifically calculated to be at a distance D9, greater than D8, where D9 is measured from point A to a point D located in the area of detector 6 and nearer to detector 5 than detector 7. The centroid of the light received by detector array  2630 C can be used to determine that object  2711  is at a distance D4 from the proximity sensor. 
       FIG. 27D  illustrates a fourth scenario where a different object  2713  is at the distance D5 from proximity sensor  2610 , as similarly shown with reference to object  2711  in  FIG. 27C . As similarly shown in  FIG. 27C ,  FIG. 27D  illustrates that light can be emitted and reflected off of object  2713  and follow a light path  2741 D. However, unlike  FIG. 27C , in  FIG. 27D , object  2713  can be less optically reflective than object  2711 . Therefore, though the same amount of light can be emitted from emitter  2621 , less light is reflected back to detector array  2630 D (so labeled for ease of reference). Despite this, light path  2741 D follows substantially the same path as  2741 C shown in  FIG. 27C . Thus, as in  FIG. 27G ,  FIG. 27H  illustrates that when object  2711  is positioned at a distance D5, light passing through lens  2655  can be directed primarily to detector 6 of detector array  2630 D, with a lesser part directed to adjacent detector 5 and an even lesser part directed to adjacent detector 7. Although the magnitude of light to each of detectors 1-8 in detector array  2630 D is less than those shown in detectors 1-8, respectively, of detector  2630 C, the location of the centroid will still be in the area of detector 6, and more specifically at distance D9 if interpolation is utilized. Consequently, the centroid of the light received by detector array  2630 D can be used to determine that object  2713  (having a second level of reflectivity) is at a distance D4 from the proximity sensor, just as object  2711  (having a first level of reflectivity) was at the distance D4 in the scenario of  FIG. 27C . 
     In addition to detecting the centroid of light detected at detector array  2630 , in some examples, detector array  2630  can also detect the one-dimensional shape and/or size of the detected light, which can also change as a function of the distance of the object to the proximity sensor. For example, in some configurations, as a distance between an object and proximity sensor decreases, a detected size of a spot created by the detected light may increase. Moreover, in some examples the detected shape and/or size of the detected light can be used in conjunction with the detected centroid to determine optical reflectance characteristics of an object. 
     As discussed above with reference to  FIG. 25 , the detected optical power at a detector can vary greatly depending on the reflectance of an object. Therefore, it can be difficult to unambiguously detect the presence of an object at both the trigger distance T1 and release distance R1 using a single-channel amplitude-based proximity sensor. More generally, it can be beneficial to unambiguously detect the presence of objects having different reflective characteristics at a range of distances from the proximity sensor. Therefore, based on the above, it can be beneficial to unambiguously detect the presence of objects having different reflective characteristics at both the trigger distance T1 and release distance R2 using a parallax-based proximity sensor, such as the sensor  2610  discussed above with reference to  FIGS. 26A-26B . This is illustrated and explained below with reference to the graph shown in  FIG. 28 . 
       FIG. 28  illustrates a graph relating to proximity detection of the proximity sensor  410  described above with reference to  FIGS. 26A-26B and 27A-27H  according to examples of the disclosure.  FIG. 28  relates to proximity detection using the position of a centroid of light detected by an array of light detectors (e.g., detector array  2630 ). The x-axis  2854  in  FIG. 28  can represent the distance of an object to a proximity sensor in units of millimeters. This distance can correspond, for example, to distances D3, D4, or D5 from proximity sensor  2610  to object  2711  or  2713  as shown in  FIGS. 27A-2D . The y-axis  656  represents the centroid position of light detected by the array of light detectors with respect to the length of the array of light detectors, L1. L1 can correspond, for example, to the length L1 shown in  FIGS. 5E-5H  above. Also shown is a trigger distance, T1, and release distance, R1, which can be similar to the trigger distance T1 and R1 explained above with reference to  FIG. 3 . In some examples, trigger distance T1 can be 3 mm from the proximity sensor, and release distance R1 can be 6 mm from the proximity sensor. 
       FIG. 28  illustrates two curves  2843  and  2853 . First curve  2843  can represent a scenario in which respective light is received by a detector array (e.g., detector array  430 ) which is emitted by the light emitter (e.g., light emitter  2621  above) and reflected off of an object having a Lambertian (matte or diffusely reflecting) surface. This can correspond, for example, to the scenario set forth above with reference to curve  2541  of  FIG. 25 . Second curve  2853  can represent a scenario in which light is received by a detector array which is emitted by the light emitter and reflected off of an object having a more specular (more reflective) surface. This can correspond, for example, to the scenario set forth above with reference to curve  2551  of  FIG. 25 . However, unlike the graph shown in  FIG. 25 , in which curves  2541  and  2551  represent the amount of detected optical power by a single emitter and detector, here, curves  2843  and  2853  represent the position of the centroid of the received light with respect to the length (L1) of the detector array as a function of the distance of an object from the proximity sensor. As shown, unlike the curves in  FIG. 25 , here, at both trigger distance T1 and release distance R1, curves  2843  and  2853  are sufficiently close to one another (i.e., the centroid positions are sufficiently close to one another) such that the presence of objects having both Lambertian and specular surfaces can be reliably detected at distances T1 and R1. 
       FIG. 29  illustrates an exemplary process  2900  for proximity detection using a parallax-based proximity sensor including an array of light detectors, such as detector array  2630  described with reference to  FIGS. 26A-26C and 27A-27H  above, according to examples of the disclosure. At block  2901 , the device can emit light from a light emitter. At block  2902  a plurality of light detectors, such as a detector array, can detect respective amplitudes of light received at each detector originating from the light emitter. At block  2903 , a centroid of the light received at the detector array is determined. In some configurations, the centroid can be determined only to be within the area of a detector. In some configurations, interpolation can be used to more precisely determine a location of the centroid within a detector based, at least in part, on the amplitudes of adjacent cells. In still other examples, the position of a light path (e.g., the position of the centroid) can be estimated based on which of the detectors in the detector array receive a maximum amplitude of light. At block  2904 , the presence (and in some examples, the distance) of an object can be detected based on the determined position of the centroid. In some examples, the proximity sensor can be configured to determine a continuous range of distances of an object. In other examples, the proximity sensor can be configured to detect the presence of an object at only one or more discrete distances (e.g., the threshold and release distances T1 and R1 discussed above with reference to  FIG. 28 ). 
     In some examples, a processor can be configured to operate the proximity sensor according to various light-pulsing (i.e., luminous modulation) schemes. For example, referring back to  FIG. 24 , in some configurations, a processor (e.g., processor  2102  above) can be configured in conjunction with proximity sensor  2410  to pulse and detect light at a frequency less likely to match to the pulse frequency of ambient light (e.g., 120 Hz, which matches the flicker of conventional fluorescent lamps). In some configurations, processor  2102  shown in  FIG. 21  can be configured in conjunction with proximity sensor  2410  to emit and detect light at changing pulse frequencies, i.e., according to a pulse-frequency hopping scheme. 
     As shown in the examples explained above with reference to  FIGS. 26-28 , a proximity sensor can utilize a one-dimensional detector array to determine the distance of an object using the one-dimensional centroid of the light detected by the detector array. In addition or alternatively to the above-discussed examples, in some configurations, a proximity sensor (e.g., the proximity sensor  2410  shown in  FIG. 24 ) can include a two-dimensional detector array. In these configurations, the characteristics of light detected by the two-dimensional detector array can be used to detect the presence of objects having different reflective characteristics at a range of distances from the proximity sensor. 
       FIGS. 30A-30C  illustrate an example configuration of a parallax-based proximity sensor which uses a two-dimensional detector array according to examples of the disclosure. In the example configuration shown here, proximity sensor  3010  uses a two-dimensional detector array  3030  and a single light emitter  3021  (e.g., an LED).  FIG. 30A  illustrates a cross-sectional side view of proximity sensor  3010 , while  FIG. 30B  illustrates a top view.  FIG. 30C  illustrates a detailed view of detector array  3030 , which includes detectors 1-24 labeled accordingly, though it should be understood that detector array  3030  can include any number of detectors according to examples of the disclosure. Detector array  3030  can have a length L2 from end-to-end which can be, for example, in the range of 1 mm to 1.8 mm. Detector array  3030  can also have a width W2, which can be, for example, in the range of 0.3 mm to 1 mm. In some configurations, W2 and L2 can correspond, for example, to the width and length W1 and L1 described above with reference to  FIG. 26C  above. As shown, in some examples, emitter  3021  and detector array  3030  can be aligned in a direction parallel to the cover substrate  3012  (which can correspond to cover substrate  1812  above). 
     As in the examples described above with reference to  FIGS. 26A-26B , light emitter  3021  and detector array  3030  can each be positioned within respective cavities  3041  and  3045 , and proximity sensor  3030  can include lenses  3051  (e.g., a collimating lens) and  3055  (e.g., a converging lens), where imaging lens  3055  corresponding to detector array  3030  can be positioned off-center with respect to the length of detector array  3030 . Moreover, as in  FIGS. 26A-26B , emitted and reflected light can pass through a cover substrate  3012  of a device, and proximity sensor  3010  can be positioned such that an air gap  3047  exists between the imaging lenses  3051 ,  3055  and cover substrate  3012 . For ease of illustration, cover substrate  3012 , air gap  3047 , and imaging lenses  3051 ,  3055  are not shown in  FIG. 30B . As shown, in some examples, light emitter  3021  can be separated from a first column of detectors (i.e., detectors 1, 9, 17) of detector array  3030  by a first center-to-center distance D10, while the light emitter can be separated from an eighth column of detectors (i.e., detectors 8, 16, 24) by a second center-to-center distance D11, which can be greater than distance D10. 
     The operation of the example proximity sensor  3010  illustrated in  FIGS. 30A-30C  will now be discussed with reference to the examples shown in  FIGS. 31A-31D  below.  FIGS. 31A-31D  illustrate an example operation of a proximity sensor including a two-dimensional detector array  3030  described with reference to  FIGS. 30A-30C , according to examples of the disclosure.  FIGS. 31A-31C  relate to a scenario in which an object has a first optical reflectivity level, and  FIG. 31D  relates to a scenario in which an object has a second reflectivity level lower than the first reflectivity level. In each of the detector arrays depicted in  FIGS. 30A-30D , the amplitude of light received by each of detectors 1-24 is represented symbolically by shading within respective detectors, a darker shade indicating a higher amplitude of light received. 
     The scenarios reflected in  FIGS. 31A-31D  can correspond to scenarios similar to those depicted in  FIGS. 27A-27D , respectively.  FIG. 31A  illustrates detector array  3030 A when an object  2711  is at a distance, D11 from proximity sensor  3010 .  FIG. 31B  illustrates detector array  3030 B when object  2711  is a distance D12 from proximity sensor  3010  (D12 being less than D13).  FIG. 31C  illustrates detector array  3030 C when object  2711  is a distance D13 from the proximity sensor  3010  (D13 being less than D12).  FIG. 31D  illustrates detector array  3030  when a different object  2713 , having a lower optical reflectivity than object  2711 , is the distance D13 from the proximity sensor  3010 . 
     In these examples, proximity sensor  3010  can operate by detecting the centroid (and in some examples the size and shape) of the light received by detector array  3030  (labeled here as  3030 A,  3030 B,  3030 C and  3030 D for ease of reference). As in the examples explained with reference to  FIGS. 27A-27H  above, due to parallax in the imaging path, the detected light received by detector array  3030  moves along the length of the detector array as a function of the distance of the object to proximity sensor  3030 . In addition, in some examples, the two-dimensional detector array  3030  can also detect the shape and size of the detected light, which can also change as a function of the distance of the object to proximity sensor. X and Y coordinates  3170  are shown only for ease of explanation, and should not be understood to imply any specific orientation of the detector arrays shown. 
       FIG. 31A  illustrates a representation of the amplitude of light received at each of detectors 1-24 in detector array  3030 A (so labeled for ease of reference) in a scenario where an object  2711  is at a distance D11 from the proximity sensor  3010  (which can correspond to proximity sensor  2610  above). As shown in  FIG. 31A , when object  3111  is positioned at relatively far distance D11, light can be directed primarily to detector 11 of detector array  3030 A, with a lesser part of the light directed to adjacent detectors 18-20, and an even lesser part directed to detectors 2-4,  10 ,  12 . In some examples, the two-dimensional centroid of the received light can be calculated using the respective amplitudes detected by detectors 1-24 of detector array  3030 A. In some configurations, the centroid can be calculated only to be in the area of detector 11. In other configurations, interpolation can be used to more precisely determine the centroid in both X and Y coordinates. For example, in this scenario, the amplitude detected by detector 11, the lesser amplitudes detected by detectors 18-20, and the even lesser amplitudes detected by detectors 2-4, 10, 12 can be used to determine that the centroid is located at a point E as shown. Point E can be a distance D14 in an X-direction from point A, where point A is at the end of the detector array nearest to emitter  3021 , and point E is midway between the borders of detectors 10 and 11 and detectors 11 and 12 in the X-direction. In the Y-direction, point E can be a distance D15 measured from point D to point E, where point E can be in the area of detector 11 nearest to detector 19 in the Y-direction. In some examples, the centroid of the light received by detector array  3030  can be used to determine that object  3111  is at a distance D11 from the proximity sensor. In addition, in some examples, the shape and size can be used to determine characteristics of the object  3111 . For example, here, the comparatively high amplitude detected by detectors 18-20 and the comparatively low amplitude detected by detectors 2-4, 10, 12 can indicate that the portion of light reflecting off of object  3111  onto detectors 2-4, 10, 12 may be further from the proximity sensor than the portion of light reflecting off of the object and onto detectors 18-20. In some examples, the proximity sensor can use this information to determine the shape or other characteristics of object  3111 . 
       FIG. 31B  illustrates a representation of the amplitude of light received at each of detectors 1-24 in detector array  3030 B (so labeled for ease of reference) in a second scenario where the object  3111  is at a distance D12 from the proximity sensor  3010  (not shown), where D12 is smaller than D11. As shown in  FIG. 31B , when object  3111  is positioned at nearer distance D12, the light path can be directed to a different position on the detector array  3030 B than in the scenarios described above with reference to  FIG. 31A  due to parallax in the imaging path. As shown, light can be directed primarily to detector 12 of detector array  3030 B, with a lesser part of the light directed to adjacent detectors 19-21, an even lesser part directed to adjacent detectors 5, 13, and an even lesser part to detectors 3, 4, 11. As similarly described with reference to  FIG. 31A , in some configurations, the centroid can be calculated only to be generally in the area of detector 12, or more precisely determined to be at a point F on detector array  3030 B. Point F can be measured from point A in the X-direction to be at a distance D16 located in the area of detector 12 near detector 13 in the X-direction. In the Y-direction, point F can be measured from point A to be a distance D17, which is located in the area of detector 12 and near detector 20 in the Y-direction. In some examples, the centroid of the light received by detector array  3030  can be used to determine that object  3111  is at a distance D12 from the proximity sensor. 
       FIG. 31C  illustrates a representation of the amplitude of light received at each of detectors 1-24 in detector array  3030 C (so labeled for ease of reference) in a third scenario where the object  3111  is at a distance D13 from the proximity sensor  3010  (not shown), where D13 is smaller than D12. As shown in  FIG. 31C , when object  3111  is positioned at nearer distance D13, the light path can be directed to a different position on the detector array  3030 C than in the scenarios described above with reference to  FIGS. 31A and 31B  due to parallax in the imaging path. As shown, light can be directed primarily to detector 14 of detector array  3030 C, with a lesser part of the light directed to adjacent detector 21-23, an even lesser part directed to adjacent detectors 5, 13, and an even lesser part to detectors 6, 7, 15. As similarly described with reference to  FIGS. 31A and 31B , in some configurations, the centroid can be calculated only to be generally in the area of detector 14, or more precisely determined to be at a point G on detector array  3030 C. Point G can be measured from point A in the X-direction to be at a distance D18 located in the area of detector 14 near detector 13 in the X-direction. In the Y-direction, point G can be measured from point A to be a distance D19, which can be located in the area of detector 14 and near detector 22 in the Y-direction. In some examples, the centroid of the light received by detector array  3030 C can be used to determine that object  3111  is at a distance D13 from the proximity sensor. 
       FIG. 31D  illustrates a representation of the amplitude of light received at each of detectors 1-24 in detector array  3030 D in a fourth scenario where a different object  2713  is at the distance D13 from proximity sensor  3010  (not shown), as similarly described above with reference to object  3111  in  FIG. 31C . As in the example of  FIG. 31C , light can be emitted and reflected off of object  3112 , however, unlike  FIG. 31C , in  FIG. 31D , object  3112  can be less optically reflective than object  3111 . Therefore, though the same amount of light can be emitted from emitter  3021  (not shown), less light is reflected back to detector array  3030 D (so labeled for ease of reference). Despite this,  FIG. 31D  illustrates that when object  3112  is positioned at a distance D13, light can still be directed primarily to detector 14 of detector array  3030 C, with a lesser part of the light directed to adjacent detector 21-23, an even lesser part directed to adjacent detectors 5, 13, and an even lesser part to detectors 6, 7, 15. Although the amplitude of light detected by each of detectors 1-24 in detector array  3030 D is less than those shown in corresponding detectors 1-24 of detector  3030 C, the location of the centroid can still be in the area of detector 14, and more specifically at the point G if interpolation is used. Therefore, as in the scenario of  FIG. 31C , the centroid of the light received by detector array  3030 D can be used to determine that object  2713  (having a second level of reflectivity) is at the distance D13 from the proximity sensor, just as object  3111  (having a first level of reflectivity) was determined to be at distance D13 in the scenario of  FIG. 31C . In some configurations, the size and/or shape of the detected light can be used in conjunction with the centroid information to determine characteristics of the object. For example, object  2713  in the scenario of  FIG. 31D  could be determined to be of a lower reflectivity than objection  3111  due to the difference in amplitude detected by the detector array  3030 . 
     In some configurations, the device can execute one or more operations based on the detection of the presence (and in some examples, the distance) of an object. Referring back to  FIG. 24 , in some examples, device  2400  can determine the distance between object  2411  and crown  2408 , including determining when the object is touching the crown (i.e., when the distance between the object and crown is zero). Moreover, in some configurations, device  2400  can determine when object  2411  is approaching crown  2408  (i.e., when the distance between object and crown decreases during two successive times) and when object  2411  is traveling away from crown  2408  (i.e., when the distance between object and crown decreases during two successive times). In some examples, different operations can be performed based on whether the object is not touching the crown (e.g., approaching the crown or distancing itself from the crown) or touching the crown. In some configurations, the determination can be performed in conjunction with a touch-sensor on crown  2408  itself (e.g., a capacitive touch sensor). 
     In some examples, wearable device  3200  (which can correspond to device  100  above) can include optical filtering structures.  FIGS. 32A-32B  illustrate an optical filtering structure configured to preferentially pass light to and from proximity sensor  3210  (which can correspond to proximity detector  2610  or  3010  above) according to examples of the disclosure. As shown in  FIG. 32A , device  3200  can include an opaque mask  3242  (shown in double cross-hatching) which blocks light from entering the proximity sensor at respective areas surrounding the light emitter or emitters and light detector or light detectors of proximity sensor  3210 . As shown in  FIG. 32B , in some examples, opaque mask  3242  can include respective apertures (e.g., circular openings) in front of a light emitter  3222  (which can correspond, for example to emitters  2621  and  3021  in  FIGS. 26A-26B and 30A-30B ) and light detector  3224  (which can correspond, for example, to detector arrays  2630  and  3030  in  FIGS. 26A-26B and 30A-30B ) to allow light to pass through this portion. Though not shown, opaque mask  3242  can include additional apertures for additional light emitters or light detectors. In some examples, the apertures in front of light emitter  3222  and light detector  3224  can include an optical filter  3244  formed of a material which is permeable to light of specific wavelengths (e.g., IR wavelengths) and blocks other light (e.g., visible light). In these examples, one or both of the opaque mask  3242  and optical filter  3244  can be formed by depositing opaque or filtering material on the inner surface of cover substrate  112 .  FIG. 32B  illustrates a top view of the proximity sensor configuration of  FIG. 32A  in which the area surrounding proximity sensor  3210  includes opaque mask  3242  which can be deposited, for example, on the inner surface of cover substrate  3212  (which can correspond to cover substrate  1812  above). As shown, optical filter  3244  can also be deposited on the inner surface of cover substrate  3212  at locations where light is emitted and received by proximity sensor  3210 . In addition, other optical filtering structures not described here are contemplated within the scope of the disclosure including, for example, optical coatings configured to alter the reflection or transmission of light within device  3200 . 
       FIG. 33  shows an exemplary optical proximity sensor  3310  integrated in a wearable device  3300  (which can correspond to device  100  above) according to examples of this disclosure. As shown, proximity sensor  3310  can determine the presence and/or range of object  3311  (e.g., a user&#39;s finger) using any appropriate method. In some configurations, an optical amplitude-based proximity sensor operates by emitting light and detecting the amount of emitted light reflected off of an object. In some examples, proximity sensor can have a field of view  3340 , which can include an area above crown  108 . In some examples, proximity sensor  3310  can detect objects at a distance ranging from 0 mm (i.e., when an object is touching the wearable device) to 100 mm. 
     In some cases, it can be beneficial to detect the proximity of objects having different levels of optical reflectivity, where each object may interact with a device. For example, a gloved finger, a bare finger, a dry finger, or a finger has lotion on the skin may all have different levels of optical reflectivity. It can be beneficial for a device to determine the presence of objects such as these at a range of distances from the device. For instance, it can be beneficial to detect whether an object is present at a “trigger distance,” at which the proximity sensor determines that an object is proximate to the proximity sensor (e.g., a finger is proximate to a crown of a wearable device). Similarly, it can be beneficial to detect whether an object is present at a “release distance,” at which, if the object is not detected, the proximity sensor determines than an object is not proximate to the proximity sensor (e.g., a finger is not proximate to the crown of the wearable device). 
       FIG. 34  illustrates a graph relating to proximity detection using a single-channel amplitude-based optical proximity sensor according to examples of the disclosure. The x-axis  3454  represents the distance of an object (e.g., object  211  in  FIG. 2B ) from the single-channel proximity sensor in units of millimeters. The y-axis  3455  represents the detected amplitude of light received by a single light detector originating from a single emitter in units of nanowatts (nW). Also shown is a trigger distance, T1, and release distance, R1. As discussed above, trigger distance T1 can represent a point at which the proximity sensor determines that an object is proximate to the proximity sensor. Likewise, release distance R1 can represent a point at which the proximity sensor determines than an object is not proximate to the proximity sensor. In some examples, trigger distance T1 can be 3 mm from the proximity sensor, and release distance R1 can be 6 mm from the proximity sensor.  FIG. 34  illustrates two curves  3441  and  3451 . First curve  3441  can represent light detected by the single light detector which is emitted by a single light emitter and reflected off of an object having a Lambertian (matte or diffusely reflecting) surface. This may correlate, for example, to a scenario in which light is reflected from the emitter off of a dry finger. Second curve  3451  represents light received by the single detector which is emitted by the single light emitter and reflected off of an object having a more specular (more reflective) surface. This may correlate, for example, to a scenario in which light is reflected from the emitter off of an oily surface of a finger (e.g., a finger having a coating of hand lotion). As shown, at trigger distance T1, curve  3441  (corresponding to an object having a Lambertian surface) can have a first value (in this example about 70 nW of optical power). In contrast, at trigger distance T1, curve  3451  (corresponding to an object having a more specular surface) can have a second value significantly lower than the value of curve  3441  (in this example, about 3 nW of optical power). Likewise, as shown, curve  3451  can have a value significantly lower than that of curve  3441  at release distance R1. Accordingly, in some examples, a single-channel proximity sensor cannot unambiguously detect the presence of an object at trigger distance T1, or at release distance R1. 
     In some examples, a proximity sensor (e.g., proximity sensor  3310  shown in  FIG. 33 ) can utilize multiple channels for proximity sensing.  FIGS. 35A-35B  illustrate an example configuration of a dual-channel proximity sensor including multiple light emitters according to examples of the disclosure. In the example configuration shown here, proximity sensor  3510  uses dual light emitters  3521  and  3523  (e.g., light-emitting diode (LED) emitters) and a single light detector  3530  (e.g., a photodetector). For ease of reference, first light emitter  3521  is referred to hereinafter as “LED1” and light emitter  3523  is hereinafter referred to as “LED2,” though it should be understood that the scope of the disclosure can include light emitters which are not LEDs. Furthermore, the terms “LED1” and “LED2” should be not be understood to signify any difference in the characteristics of the light emitters, as LED1 and LED2 can be the same or different, as will be discussed in more detail below. 
       FIG. 35A  illustrates a cross-sectional side view of proximity sensor  3510 , while  FIG. 35B  illustrates a top view. As shown, LED1  3521 , LED2  3523 , and detector  3530  can each be positioned within respective cavities  3541 ,  3543 , and  3545 . As shown in  FIG. 35A , in some examples, each of LED1  3521 , LED2, and detector  3530  can correspond to respective imaging lenses  3553 ,  3551 , and  3555 , which can direct emitted light or (in the case of detector  3530 ) received light so as to form a desired field of view, which can correspond, for example to the field of view  3340  shown in  FIG. 33 . In some examples, proximity sensor  3510  can be positioned such that emitted and reflected light passes through cover substrate  3512  of a device (which can correspond to cover substrate  1812  above). In some examples, proximity sensor  3510  can be positioned such that an air gap  3547  exists between the imaging lenses  3551 ,  3553 ,  3555  and cover substrate  3512 . For ease of illustration, cover substrate  3512   
     As shown, in some examples, LED1  3521 , LED2  3523 , and detector  3530  can all be aligned in a direction parallel to the cover substrate  3512 . LED1  3521  can be separated from detector  3530  by a first center-to-center distance D1, while LED2  3523  can be separated from detector  3530  by a second center-to-center distance D2, which is greater than distance D1. LED1 can be separated from LED2 by a center-to-center distance D3, which can be greater than distance D2 separating LED1 from detector  3530 . 
     The operation of the example proximity sensor  3510  illustrated in  FIGS. 35A-35B  will now be discussed with reference to the examples shown in  FIGS. 36A-36B  below.  FIGS. 36A-36B  illustrate an example operation of a dual channel proximity sensor  3510  described with reference to  FIGS. 35A-35B , according to examples of the disclosure. For clarity of illustration, some elements such as imaging lenses are omitted.  FIG. 36A  illustrates a first scenario where an object  3611  (corresponding, for example, to object  3311  shown in  FIG. 33 ) is positioned at a distance D4 from detector  3530 .  FIG. 36B  illustrates a second scenario where object  3611  is at a distance D5 from detector  3530 , where distance D5 is less than distance D4. 
     In these examples, proximity sensor  3510  can operate by calculating the ratio between light received by detector  3530  from LED1  3521  and light received by LED2  3523 , and determining the distance of object  3611  from proximity sensor  3510  using this ratio. As explained, LED1  3521 , LED2  3523 , and detector  3530  can all be aligned in a first direction parallel to the cover substrate  3512 , and the distance of object  3611  to proximity sensor  3510  can be measured in a second direction orthogonal to the first direction. As shown, LED I can emit light having a light path  3641 A or  3641 B (shown symbolically as arrows having dotted lines) and LED2 can emit light having a light path  3643 A or  3643 B (shown symbolically as arrows having solid lines). Both light paths  3643  and  3641  can reflect off of object  3611 , and some of the reflected light of both paths can be directed to detector  3530 . As indicated symbolically by the number of arrows which reflect back to detector  3530 , some of the light emitted by LED1  3521  and LED2  3523  is scattered in the air, reflected off of object  3611  in a different direction, or absorbed by object  3611 . 
       FIG. 36A  illustrates a scenario where object  3611  is separated from proximity sensor  3510  by a relatively far distance D4. As shown in  FIG. 36A , when object  3611  is relatively far from detector  3530 , the amount of reflected light received from LED1  3521  can be comparable to the amount of reflected light received from LED2  3523 . In the example here, an approximate ratio of 2:2 of LED1 to LED2 light is represented symbolically by two dotted arrows of light path  3641 A being received by detector  3530  and two solid arrows of light path  3643 A received by the detector, though it should be understood that these values are illustrative only. The ratio 2:2 representing a comparable amount of light reflected back to detector  3530  by both emitters can be due, at least in part, to the similar distance traveled by light paths  3643 A and  3641 A. 
     In contrast, as shown in  FIG. 36B , when object  3611  is separated by a relatively near distance D5 (less than distance D4), the amount of reflected light received from LED1  3521  can be significantly greater than the amount of light received from LED2  3523 . In the example here, an approximate ratio of 3:2 of LED1 light to LED2 light is represented symbolically by three dotted arrows of light path  3641 B received by detector  3530  and two solid arrows of light path  3643 B received by the detector, though it should be understood that these numbers are illustrative only. Because object  3611  is at a distance D5 which is shorter than distance D4, the difference in respective distances of light paths  3641 B and  3643 B can be comparatively greater than the difference in respective distances of  3641 A and  3643 A. Accordingly, the ratio 3:2 representing a greater difference between the amount of light reflected back to detector  3530  by LED1  3521  and LED2  3523  can be due, at least in part, to the greater difference in distance traveled by light paths  3643 B and  3641 B. 
     As discussed, proximity sensor  3510  can operate by calculating the ratio between light received by detector  3530  from LED1  3521  and light received by LED2  3523  and determining the distance of object  3611  using the ratio. In some examples, light emitted from LED1  3521  can be distinguishable from light emitted from LED2  3523 . For example, light emitted from both sources can be of different wavelength (e.g., different color) or pulsed at different frequencies. In such configurations, detector  3530  can simultaneously receive light from both LED1  3521  and LED2  3523 . In other configurations, light emissions from LED1  3521  and LED2  3523  can be time-multiplexed such that detector  3530  receives light from one emitter at a time (e.g., light is emitted sequentially from the multiple emitters). 
     As discussed above with reference to  FIG. 34 , the detected optical power at a detector can vary greatly depending on the reflectance of an object. Therefore, it can be difficult to unambiguously detect the presence of an object at both the trigger distance T1 and release distance R1 using a single-channel proximity sensor. More generally, it can be beneficial to unambiguously detect the presence of objects having different reflective characteristics at a range of distances from the proximity sensor. Therefore, based on the above, it can be beneficial to unambiguously detect the presence of objects having different reflective characteristics at both the trigger distance T1 and release distance R2 using a dual-channel proximity sensor, such as the sensor  3510  discussed above with reference to  FIG. 35 . This is illustrated and explained below with reference to the graph shown in  FIG. 37 . 
       FIG. 37  illustrates a graph relating to proximity detection of the proximity sensor  3510  described above with reference to  FIGS. 35A-35B and 36A-36B  according to examples of the disclosure.  FIG. 37  relates to proximity detection using a ratio of the amount of light received from a second emitter (e.g., LED2  3523 ) to the amount of light received from a first emitter (e.g., LED1  3521 ). The x-axis  3754  in  FIG. 37  can represent the distance of an object to a proximity sensor in units of millimeters. This distance can correspond, for example, to distances D4 or D5 from proximity sensor  3510  to object  3611  as shown in  FIGS. 36A-36B . The y-axis  3756  represents the ratio of the light received from the second emitter to the light received from the first emitter. Also shown in each of the graphs is a trigger distance, T1, and release distance, R1, which can be similar to the trigger distance T1 and R1 explained above with reference to  FIG. 35 . In some examples, trigger distance T1 can be 3 mm from the proximity sensor, and release distance R1 can be 6 mm from the proximity sensor. 
       FIG. 37  illustrates two curves  3743  and  3753 . First curve  3743  can represent a scenario in which respective light is received by a detector (e.g., detector  3530 ) which is emitted by the first and second light emitter (e.g., LED1  3521  and LED2  3523 ) and reflected off of an object having a Lambertian (matte or diffusely reflecting) surface. This can correspond, for example, to the scenario set forth above with reference to curve  3741  of  FIG. 37 . Second curve  3753  can represent a scenario in which light is received by the detector which is emitted by the first and second light emitter and reflected off of an object having a more specular (more reflective) surface. This can correspond, for example, to the scenario set forth above with reference to curve  3751  of  FIG. 37 . However, unlike the graph shown in  FIG. 37 , in which curves  3741  and  3751  represent the amount of detected optical power by a single emitter and detector, here, curves  3743  and  3753  represent a ratio of the light detected from two emitters. Specifically, curves  3743  and  3753  represent a ratio of light detected from the second emitter by the detector to the light detected from the first emitter by the detector. As shown, unlike the curves shown in  FIG. 37 , here, at both trigger distance T1 and release distance R1, curves  3743  and  3753  are sufficiently close to one another (i.e., the ratios at these points are sufficiently similar) such that the presence of objects having both Lambertian and specular surfaces can be reliably detected at distances T1 and R1. 
       FIG. 38  illustrates an exemplary process  3800  for proximity detection using a dual channel proximity sensor including multiple light emitters, such as proximity sensor  3530  described with reference to  FIGS. 35A-35B and 36A-36B , according to examples of the disclosure. At block  3801 , the device can emit light from a first light emitter. At block  3802  a light detector can detect a first amount of the emitted light from the first light emitter which is reflected back from the first light emitter. This amount can be represented as a first value. At block  3803 , the device can emit light from a second light emitter. At block  3804  a light detector can detect a second amount of emitted light which is reflected back from the second light emitter. This amount can be represented as a second value. In some examples, the same light detector can detect both the first and second amounts of light. At block  3805 , the presence (and in some examples, the distance) of an object can be detected based on a ratio of the second value to the first value. In some examples, a processor can be configured to operate the proximity sensor according to various light-pulsing (i.e., luminous modulation) schemes. For example, referring back to  FIGS. 21 and 33 , in some configurations, a processor (e.g., processor  2102  above) can be configured in conjunction with proximity sensor  3310  to pulse and detect light at a frequency less likely to match to the pulse frequency of ambient light (e.g., 120 Hz, which matches the flicker of conventional fluorescent lamps). In some configurations, processor  2102  can be configured in conjunction with proximity sensor  3310  to emit and detect light at changing pulse frequencies, i.e., according to a pulse-frequency hopping scheme. Similarly, in some configurations, processor  2102  can be configured in conjunction with the proximity sensor to emit and detect light at one or more pulse frequencies for the first light emitter and one or more different pulse frequencies for the second light emitter, thus allowing the proximity sensor to distinguish between emitted light received from the first emitter and emitted light received from the second emitter. 
     As shown in the examples explained above with reference to  FIGS. 35-37 , a proximity sensor can utilize multiple channels by using multiple light emitters. In addition or alternatively to the above-discussed examples, in some configurations, a proximity sensor can utilize multiple channels by using multiple light detectors. 
       FIGS. 39A-39B  illustrate an example configuration of a multiple-channel proximity sensor which uses multiple light detectors according to examples of the disclosure. In the example configuration shown here, proximity sensor  3910  uses dual light detectors  3921  and  3923  (e.g., photodetectors) and a single light emitter  3930  (e.g., an LED). For ease of reference, first light detector  3921  is referred to hereinafter as “detector1” and light detector  3923  is hereinafter referred to as “detector2,” though it should be understood that the terms “detector1” and “detector2” should be not be understood to signify any difference in the characteristics of the light detectors; detector 1 and detector2 can be the same or different, as will be discussed in more detail below. Similarly, the light emitter  3930  is hereinafter referred to as “LED,” though it should be understood that the scope of the disclosure can include light emitters which are not LEDs. 
       FIG. 39A  illustrates a cross-sectional side view of proximity sensor  3910 , while  FIG. 39B  illustrates a top view. As shown, detector1  3921 , detector2  3923 , and LED  3930  can each be positioned within respective cavities  3941 ,  3943 , and  3945 . As shown in  FIG. 39A , in some examples, each of detector1  3921 , detector2  3923 , and LED  3930  can correspond to respective imaging lenses  3951 ,  3953 , and  3955 , which can direct emitted light or (in the case of detectors  3921  and  3923 ) received light so as to form a desired field of view, which can correspond, for example to the field of view  3340  shown in  FIG. 33 . As in the example illustrated in  FIGS. 35A-35B , in some examples, proximity sensor  3910  can be positioned such that emitted and reflected light passes through a cover substrate  3912  (which can correspond to cover substrate  1812  above) of a device. Likewise, in some examples, proximity sensor  3930  can be positioned such that an air gap  3947  exists between the imaging lenses  3951 ,  3953 ,  3955  and cover substrate  3912 . For ease of illustration, cover substrate  3912 , air gap  3947  and imaging lenses  3951 ,  3953 , and  3955  are not shown in  FIG. 39B . 
     As shown in  FIG. 39B , in some examples, LED  3930 , detector1  3921 , and detector3  3923  can all be aligned in a direction parallel to the cover substrate  3912 . Detector1  3921  can be separated from emitter  3930  by a first center-to-center distance D6, while detector2  3923  can be separated from emitter  3930  by a second center-to-center distance D7, which can be greater than distance D6. Detector1 can be separated from detector2 by a center-to-center distance D8, which can be greater than distance D6 separating detector1 from LED  3930 . 
     The operation of the example proximity sensor  3910  illustrated in  FIGS. 39A-39B  will now be discussed with reference to the examples shown in  FIGS. 40A-40B  below.  FIGS. 40A-40B  illustrate an example operation of a dual channel proximity sensor  3910  described with reference to  FIGS. 39A-39B , according to examples of the disclosure. For clarity of illustration, some elements such as imaging lenses are omitted.  FIG. 40A  illustrates a first scenario where an object  4011  (corresponding, for example, to object  3311  shown in  FIG. 33 ) is positioned at a distance D9 from LED  3930 .  FIG. 40B  illustrates a second scenario where object  4011  is at a distance D10 from LED  3930 , where distance D10 is less than distance D9. 
     Similar to the operation of the example discussed with reference to  FIGS. 36A-36B , in these examples, proximity sensor  3910  can operate by calculating the ratio between light detected by detector1  3921  from LED  3930  and light detected by detector2  3923  from LED  3930  and determining the distance of object  4011  from proximity sensor  3910  using this ratio. As explained, LED  3930 , detector1  3921 , and detector3  3923  can all be aligned in a first direction parallel to the cover substrate  3912 , and the distance of object  4011  to proximity sensor  3910  can be measured in a second direction orthogonal to the first direction. As shown, detector1 can receive a certain amount of light from LED  3930 , the light having a first light path  4041  and detector2 can receive a certain amount of light from LED  3930 , the light having a second light path  4043 . Light paths  4041  and  4043  are represented symbolically as arrows. Light paths  4043  and  4041  can reflect off of object  4011 , and some of the reflected light can be directed to detector1  3921  and detector2  3923 . As indicated symbolically by the number of arrows which reflect back to detectors  3921  and  3923 , some of the light emitted LED  3930  is scattered by the air, reflected off of object  4011  in a different direction than toward the detectors, or absorbed by object  4011 . 
       FIG. 40A  illustrates a scenario where object  4011  is separated from proximity sensor  3910  by a relatively far distance D9. As shown in  FIG. 40A , when object  4011  is relatively far from detectors  3921  and  3923 , the amount of reflected light received by detector1  3921  from the light emitter can be comparable to the amount of reflected light received by detector2  3923  from the light emitter. In the example here, an approximate ratio of 2:2 of light detected by detector1 to light detected by detector2 is represented symbolically by two arrows being received by detector1  3921  and two arrows received by the detector2  3923 , though it should be understood that these values are illustrative only. The ratio 2:2 representing a comparable amount of light detected by both detectors can be due, at least in part, to the similar distance traveled by light paths  4043 A and  4041 A. 
     In contrast, as shown in  FIG. 40B , when object  4011  is separated by a relatively near distance D10 (less than distance D9), the amount of reflected light detected by detector1  3921  can be significantly greater than the amount of light detected by detector2  3923 . In this example, an approximate ratio of 4:3 of detector1 light to detector2 light is represented symbolically by four arrows received by detector2  3923  and three arrows received by detector1  3921 , though it should be understood that these numbers are illustrative only. Because object is at a distance D10 (which is shorter than distance D9), the differences in distances of light paths  4041 B and  4043 B is comparatively greater than the difference in distances between  4041 A and  4043 A. Accordingly, the ratio 4:3 between light detected by detector2 and detector1 can be due, at least in part, to the greater difference in distance traveled by light paths  4043 B and  4041 B. 
     As discussed, proximity sensor  3910  can operate by calculating the ratio between light detected by detector1  3921  and light detected by detector2  3923  and determining the distance of object  4011  using the ratio. Because multiple detectors (rather than multiple emitters) are used in the configuration discussed above, both channels of the proximity sensor can be used at the same time. This is in contrast to some configurations discussed above with reference to  FIGS. 35A-35B and 36A-36B  above, wherein the detection of light in the multiple channels can be time-multiplexed so that the single detector  3530  can distinguish between light emitted from LED1  3921  and light emitted from LED2  3923 . Accordingly, the examples discussed above with reference to  FIGS. 39A-39B and 40A-40B  can perform proximity detection faster than configurations in which a single detector is used. In addition, in some examples, detectors such as detectors  3921  and  3923  can require less power than light emitters (e.g., LEDs). Accordingly, in some cases, the configurations discussed above with reference to  FIGS. 39A-39B and 40A-40B  can be more power efficient than configurations which use multiple light emitters. 
       FIG. 41  illustrates a graph relating to proximity detection of the proximity sensor  3910  described above with reference to  FIGS. 39A-39B and 40A-40B  according to examples of the disclosure.  FIG. 41  relates to proximity detection using a ratio of the light detected by a second detector (e.g., detector2  3923 ) to the light detected by the first detector (e.g., detector1  3921 ), both of which originate from a light emitter (e.g., LED  3930 ). As in  FIG. 37 , the x-axis  4154  in  FIG. 41  can represent the distance of an object to a proximity sensor in units of millimeters. This distance can correspond, for example, to distances D9 or D10 from proximity sensor  3910  to object  4011  as shown in  FIGS. 36A-36B . The y-axis  4156  can represent the ratio of the light received from the second emitter to the light received from the first emitter. Also shown in each of the graphs is a trigger distance, T1, and release distance, R1, which can be similar to the trigger distance T1 and R1 explained above with reference to  FIG. 34 . In some examples, trigger distance T1 can be 3 mm from the proximity sensor, and release distance R1 can be 6 mm from the proximity sensor. 
       FIG. 41  illustrates two curves  4143  and  4153 . First curve  4143  can represent a ratio of light received by two detectors (e.g., detector1  3921  and detector2  3923 ) which can originate from a light emitter (e.g., LED  3930 ) and reflected off of an object having a Lambertian surface. This can correspond, for example, to the scenario set forth above with reference to curve  3441  of  FIG. 34 . Second curve  4153  can represent a ratio of light received by the two detectors which is reflected off of an object having a more specular surface. This can correspond, for example, to the scenario set forth above with reference to curve  3451  of  FIG. 34 . As shown, unlike the curves shown in  FIG. 34 , here, at both trigger distance T1 and release distance R1, curves  4143  and  4153  are sufficiently close to one another (i.e., the ratios at these points are sufficiently similar) such that the presence of objects having both Lambertian and specular surfaces can be reliably detected at distances T1 and R1. 
       FIG. 42  illustrates an exemplary process for proximity detection using a dual channel proximity sensor such as proximity sensor  3930  described with reference to  FIGS. 39A-39B and 40A-40B  according to examples of the disclosure. At block  4201 , the device can emit light from a light emitter. At block  4202 , the device can detect a first amount of light reflected back from the light emitter to a first detector and a second amount of light reflected back to a second detector. These first and second amounts can be represented as first and second values, respectively. At block  4203  a light detector can detect the amount of the emitted light which is reflected back to the second light emitter. This amount can be represented as a second value. At block  4204 , the presence (and in some examples, the distance) of an object can be detected based on a ratio of the second value to the first value. In some configurations the first and second amounts of light can be detected simultaneously. As in the example operation discussed above with reference to  FIG. 38 , in some examples, a processor can be configured to operate the proximity sensor according to various light-pulsing (i.e., luminous modulation) schemes. For example, referring back to  FIGS. 21 and 33 , in some configurations, the processor  2102  can be configured in conjunction with proximity sensor  3310  to pulse and detect light at a frequency less likely to match to the pulse frequency of ambient light (e.g., 120 Hz, which matches the flicker of conventional fluorescent lamps). In some configurations, processor  2102  can be configured in conjunction with proximity sensor  3310  to emit and detect light at changing pulse frequencies, i.e., according to a pulse-frequency hopping scheme. 
     In some configurations, the device can execute one or more operations based on the detection of the presence (and in some examples, the distance) of an object. Referring back to  FIG. 33 , in some examples, device  3310  can determine the distance between object  3311  and crown  3308 , including determining when the object is touching the crown (i.e., when the distance between the object and crown is zero). Moreover, in some configurations, device  3300  (which can correspond to device  100  above) can determine when object  3311  is approaching crown  3308  (i.e., when the distance between object and crown decreases during two successive times) and when object  3311  is traveling away from crown  3308  (i.e., when the distance between object and crown decreases during two successive times). In some examples, different operations can be performed based on whether the object is not touching the crown (e.g., approaching the crown or distancing itself from the crown) or touching the crown. In some configurations, the determination can be performed in conjunction with a touch-sensor on crown  3308  itself (e.g., a capacitive touch sensor). 
     In some examples, wearable device  4300  (which can correspond to device  100  above) can include optical filtering structures.  FIGS. 43A and 43B  illustrate an optical filtering structure configured to preferentially pass light to and from proximity sensor  4310  according to examples of the disclosure. As shown in  FIG. 43A , proximity sensor  4310  can include an opaque mask  4342  (shown in double cross-hatching) which blocks light from entering the proximity sensor at respective areas surrounding the light emitter or emitters and light detector or light detectors of proximity sensor  4310 . As shown in  FIG. 43B , in some examples, opaque mask  4342  can include respective apertures (e.g., circular openings) in front of a light emitter  4322  (which can correspond, for example to LED1  3921  in  FIGS. 39A-39B ) and light detector  4324  (which can correspond, for example, to detector  3930  in  FIGS. 39A-39B ) to allow light to pass through this portion. Though not shown, opaque mask  4342  can include additional apertures for additional light emitters or light detectors (such as LED2  3923  in  FIGS. 39A-39B ). In some examples, the apertures in front of light emitter  4322  and light detector  4324  can include an optical filter  4344  formed of a material which is permeable to light of specific wavelengths (e.g., IR wavelengths) and blocks other light (e.g., visible light). In these examples, one or both of the opaque mask  4342  and optical filter  4344  can be formed by depositing opaque or filtering material on the inner surface of cover substrate  4312  (which can correspond to cover substrate  1812  above).  FIG. 43B  illustrates a top view of the proximity sensor configuration of  FIG. 43A  in which the area surrounding proximity sensor  4310  includes opaque mask  4342  which can be deposited, for example, on the inner surface of cover substrate  4312 . As shown, optical filter  4344  can also be deposited on the inner surface of cover substrate  4312  at locations where light is emitted and received by proximity sensor  4310 . In addition, other optical filtering structures not described here are contemplated within the scope of the disclosure including, for example, optical coatings configured to alter the reflection or transmission of light within device  4300 . 
     Radio Frequency Detection Apparatus and Methods 
     Some examples of the disclosure relate to a device that can inject electromagnetic energy into the crown (e.g., crown  108  of device  100  above) to detect objects touching or proximate to the crown of a device. In some examples, a touch and/or proximity sensor can include a transmit circuit operatively coupled to a rotational input element (e.g., crown) and configured to inject electromagnetic energy via inductive coupling into the rotational input element, and a monitoring circuit operatively coupled to the rotational input element and configured to measure one or more parameters (e.g., resonant frequency). The one or more parameters can be indicative of an object touching or in proximity to the rotational input element. One or more touch or hover events can be detected based on the one or more parameters measured by the monitoring circuit. In some examples, the proximity sensor can include a transmit circuit and a receive circuit. The transmit circuit can include a first inductive element and one or more first capacitive elements and can oscillate at a first resonant frequency. The receive circuit can be operatively coupled to or formed as part of the rotational input element. The receive circuit can include a second inductive element and one or more second capacitive elements, and can oscillate at a second resonant frequency. The inductive elements of the transmit circuit and the receive circuit can be coupled transmit energy therebetween. In some examples, the resonant frequencies of the transmit circuit and receive circuit can be designed or turned to be the same frequency. In some examples, the touch and/or proximity sensor can measure changes in resonant frequency of the transmit circuit to detect touch and/or hover events. 
       FIGS. 44A and 44B  illustrate exemplary processes for processing touch and hover events detected at the crown according to examples of the disclosure.  FIG. 44A  illustrates an example process using proximity (hover) events and/or touch events at the crown to transition between two modes of operation. At block  4400 , the device can be in a rest mode. The rest mode may correspond, for example, to a low-power mode. In some examples, referring back to  FIG. 2 , the display device (e.g., display device  220 ) can be powered down or enter a low-power state in the rest mode. Additionally or alternatively, in some examples, the touch sensing system (e.g., touch sensor panel  234  and touch controller  232 ) can be powered down or enter a low-power state in the rest mode. Additionally or alternative, in some examples, one or more processors, I/O devices and/or other circuitry can be powered down or enter a low-power state in the rest mode. 
     At block  4405 , the device (e.g., a processor or state machine) can receive input from a touch and/or proximity sensor detecting touch or proximity events for the crown. In some examples, the touch and/or proximity sensor can be implemented using the crown and/or the crown shaft as part of the sensor. At block  4410 , the device (e.g., the processor or state machine) can determine from the received input whether a touch event or proximity (hover) event is detected. If a proximity (hover) event is detected, processing can proceed to block  4415 , where processing can wake up the device, and the device can enter a ready mode. For example, a proximity event can be reported when the touch and/or proximity sensor detects an object within a first threshold distance of the crown (e.g., within 1 cm of the crown). Waking up the device can including powering up one or more processors, I/O devices and/or other circuitry that were powered down or placed in a low-power state during rest mode, resuming touch sensing operations, and/or resuming display operations. 
     In some examples, the device can exit the rest mode and enter the ready mode in response to detecting a touch event, rather than a proximity event. For example, a touch event can be reported when the touch and/or proximity sensor detects an object within a second threshold distance of the crown. In some examples, the second threshold can be set such that the distance between the crown at the object is zero (direct contact). In some examples, the device can wake up and enter the ready mode in response to detecting either of a touch or hover event. 
     Although not illustrated, the device can return to the rest mode under various conditions. For example, the device can return to rest mode manually when user input is detected causing the device to enter a rest mode (e.g., covering the touch screen, rotating the touch screen away from the user, or in response to selection of UI element by touch, button, or crown input) or automatically in response to detecting no inputs for a threshold period of time (e.g., no touch, button or crown inputs). In some examples, as long as a touch or hover event is detected at the crown, the device cannot return to the rest mode. 
     In some examples, touch and/or hover events at the crown can be used as additional inputs to the device.  FIG. 44B  illustrates an example process using proximity (hover) events and/or touch input events as additional inputs. At block  4420 , the device can be in a ready mode. At block  4425 , the device can receive input from a touch and/or proximity sensor detecting touch or proximity events at the crown. In some examples, the touch and/or proximity sensor can be implemented using the crown and/or the crown shaft as part of the sensor. At block  4430 , the device (e.g., the processor or state machine) can determine from the received input whether a touch event is detected (e.g., using a first threshold). If a touch event is detected, processing can proceed to block  4435 , where a touch event can be reported. The reported touch event can be used by the device to perform one or more functions (e.g., changing the UI or selecting a UI element) corresponding to a touch event at the crown, and processing can return to block  4420  (i.e., the device can remain in ready mode). If no touch event is detected at block  4430 , processing can proceed to block  4440 , and the device (e.g., the processor or state machine) can determine from the received input whether a hover event is detected (e.g., using a second threshold). If a hover event is detected, processing can proceed to block  4445 , where a hover event can be reported. The reported hover event can be used by device to perform one or more functions (e.g., changing the UI or selecting a UI element) corresponding to a hover event at the crown, and processing can return to block  4420  (i.e., the device can remain in ready mode). If no hover event is detected at block  4440 , processing can proceed to block  4420  (i.e., the device can remain in ready mode). In some examples, if no touch or hover event is detected, the device can exit ready mode and return to rest mode (e.g., for example if no other inputs are detected in addition to detecting no touch or hover event at the crown). 
     The first thresholds used to detect touch events in the example processes of  FIGS. 44A and 44B  can be the same or different. The second thresholds used to detect hover events in the example processes of  FIGS. 44A and 44B  can be the same or different. Although discussed in the context of a crown for a wearable device, the exemplary processes of  FIGS. 44A and 44B  can be applied to a touch and/or proximity sensor implemented to detect touch or hover events for other rotary input devices, button inputs, or other inputs). 
     Although the hover event is described above as a binary event (i.e., hover event or no hover event), in some examples, different types of hover events can be reported. For example, the touch and/or proximity sensor can estimate a distance between the object and the crown. Depending on the distance, different types of hover events can be reported.  FIG. 44C  illustrates examples of touch and hover events that can be reported based on the estimated distance between an object and a crown according to examples of the disclosure. As described herein, the touch and/or proximity sensor can estimate a distance between the object and the crown. In some examples, a touch event threshold  4450  can be set at an estimated distance of zero (or within a threshold distance of zero, such as 5%, 10%, etc.). When the estimated distance is zero or less than zero (i.e., or otherwise meets touch detection threshold  4450 ), a touch event can be reported. 
     In some examples, a first proximity event threshold  4455  can be set at a maximum estimated distance (d max ) that can be detected by the sensor (or within a threshold distance of d max , such as 5%, 10%, etc.) When the estimated distance is between the first proximity event threshold  4455  and the touch event threshold  4450 , a proximity (hover) event can be reported. In some examples, one or more additional proximity event thresholds can be used to provide one or more additional proximity/hover event inputs. For example,  FIG. 44C  illustrates a second proximity event threshold  4460  and a third proximity event threshold  4465 , which can allow reporting a first, second or third proximity/hover events. It should be understood that fewer or more proximity detection thresholds than illustrated in  FIG. 44C  can be used to generate a different number of proximity/hover events. 
     Returning to  FIG. 44A , in some examples, detecting a proximity event that triggers waking up the device can be a proximity event meeting the first proximity event threshold of  FIG. 44C  (e.g., at least within the maximum detectable distance). In other examples, in order to wake up the device, the proximity event must meet a different proximity event threshold (i.e. the distance of the object is closer that the maximum detectable distance of the sensor). 
     As described herein, in some examples, the touch and/or proximity sensor can be implemented using the crown and/or crown shaft as part of the sensor. For example, a device including a crown can include a circuit to inject electromagnetic energy into the shaft and/or crown and monitor electrical effects due to an object touching or proximate to the crown. The monitored electrical effects can be used to detect a touch or hover event at the crown. 
       FIG. 45A  illustrates a circuit diagram of an exemplary touch and/or proximity sensor according to examples of the disclosure.  FIG. 45A  illustrates a circuit  4500  including a current source  4502 , inductor  4504  and capacitance  4506 . Circuit  4500  can be referred to as a resonant circuit or tank circuit that can oscillate with a resonant frequency f. Although circuit  4500  is illustrated as including a current source  4502 , it is understood that current source  4502  can be replaced with any suitable driving source (e.g., a voltage source, etc.) When an object, modeled by ground  4508 , is proximate to or contacting node  4510 , a variable capacitance  4512  can be formed between the object and circuit  4500 . The variable capacitance  4512  can cause a change in the operation of circuit  4500 . For example, the resonant frequency of circuit  4500  can shift to f+Δf, where f can represent the resonant frequency without a proximate object and Δf can represent the shift in resonant frequency due to the variable capacitance introduced by a proximate object. The shift in frequency can be monitored and used to determine the presence of an object touching or proximate to circuit  4500 . Additionally, the shift in frequency can be used to estimate the distance between the object and circuit  4500  based on the amount of shift in frequency, as the capacitance value associated with variable capacitance  4512  can be a function of the distance between the object and circuit  4500 . It should be understood that the example circuit  4500  in  FIG. 45A  is exemplary only and fewer or additional components can be added in the same or a different configuration. 
     Although discussed above as monitoring a shift in frequency, the sensor can be configured to measure other parameters that can be used to determine touch and/or proximity events. For example, the dynamics of the circuit that can be measured can include changes in the amplitude or phase of the signals produced by the driving source (e.g., current source  4502 ). Depending on the signal dynamics to be measured, a suitable monitoring circuit or element (not shown) can be used to measure the parameter(s), which can be used to detect the presence of an object proximate to the crown and can be used to estimate the distance between the object and the crown from the parameter. For example, when the measured shift in frequency from the resonant frequency meets a first threshold, but not a second threshold, the object can be estimated to be proximate to the crown, but not touching the crown. The distance between the object and crown can be estimated as a function of the shift in frequency. When the object meets the second threshold, the object can be estimated to be touching the crown. In some examples, the first threshold can represent the maximum distance (e.g., d=d max ) between the object and the crown that can be detected by the sensor (e.g., above a noise threshold), and the second threshold can represent the minimum distance between the object and the crown (e.g., d=0). In some examples, detecting an object touching or proximate to the crown (and estimating its distance) can be based on measuring more than one of the parameters. In some examples, each of the one or more parameters can be compared to one or more thresholds to determine a touch and/or hover event. 
     In some examples, the touch and/or proximity sensor can include processing circuitry to process measured parameters and detect the presence of a touch or hover event and/or estimate the distance between an object and the crown. In other examples, the raw or partially processed data can be processed by other processing circuitry external to the sensor (e.g., by processor  202 ). 
     The detection range of the touch and/or proximity sensor can be a function of the sensitivity of the sensor to detect changes in capacitance between the object and the crown. As described herein, the capacitance can be a function of the surface area of the crown, the surface area of the object proximate to the crown, and the distance between the object and the crown. As a result, the maximum detectable distance of the sensor can be function of the surface area of the crown and the surface area of the finger. 
     Additionally or in the alternative, in some examples, rather than comparing one or more measured parameters to one or more thresholds to detect a touch and/or proximity event, a signature of an approaching object can be detected based on a multiple (e.g., a sequence) of measurements by the touch and/or proximity sensor. For example, an object approaching the crown can be sensed to have a signature of increasing shifts in resonant frequency that can be used to trigger a touch/proximity event. In some examples, the rate of change of the shifts in resonant frequency can be used to determine if the rate of change corresponds to the signature of an object approaching and/or contacting the crown. 
     The example circuit of  FIG. 45A  can be implemented in a device with a crown to detect touch and/or proximity between an object and the crown.  FIG. 45B  illustrates an example object in proximity to an example crown according to examples of the disclosure.  FIG. 45B  illustrates an example device  4520  (e.g., a wearable device) including a housing  4522 . Shaft  4523  can extend from the housing  4522  and can be coupled to crown  4524 . Transmit circuit  4525  can be operatively coupled to shaft  4523  and can correspond, for example, to the circuit  4500  illustrated in  FIG. 45A . Transmit circuit  4525  can inject electromagnetic energy into shaft  4523  and crown  4524 . An object, such as finger  4526  (which can be considered to be coupled to ground through C body    4528 ) approaching crown  4524  can cause a capacitance to form between the crown  4524  and ground  4529 . The capacitance formed between the finger and crown can be a function of the distance  4530  (labeled “d”) between the crown  4524  and the finger  4526 . This capacitance can cause dynamic changes in the transmit circuit  4525  that can be measured by a monitoring circuit (not shown) to detect the presence of an object proximate to or touching the crown based, for example, on the estimated distance  4530 . 
       FIG. 45C  illustrates an example touch and/or proximity sensor using a crown according to examples of the disclosure.  FIG. 45C  illustrates an example device  4540  (e.g., a wearable device) including a housing  4542 , shaft  4544  and crown  4546 . Shaft  4544  and crown  4540  can be modeled by a parasitic capacitance  4550 . Transmit circuit  4548  (e.g., corresponding to the circuit  4500  illustrated in  FIG. 45A ) can be operatively coupled to shaft  4544  and crown  4546 . In some examples, the parasitic capacitance  4550  of the shaft and crown can replace the capacitor  4506  in  FIG. 45A . In other examples, the parasitic capacitance can add to capacitor  4506  forming an equivalent capacitance for the transmit circuit  4548 . The circuit elements of transmit circuit  4548  can be selected to cause transmit circuit to resonate at a desired frequency using the effective capacitance of parasitic capacitance  4550  and additional capacitance from transmit circuit  4548  (if any) and the inductor from transmit circuit  4548 . In some examples, transmit circuit  4548  can include an adjustable capacitance to allow for tuning the resonant frequency of transmit circuit  4548 . 
     Transmit circuit  4548  can inject electromagnetic energy into shaft  4544  and crown  4546  as discussed above. An object, represented by node  4552  (which can be considered to be coupled to ground) can form an additional capacitance between the crown, represented by a first parallel plate  4554 , and the object, represented by a second parallel plate  4556  in  FIG. 45C . The capacitance formed between parallel plates  4554  and  4556  can correspond to the variable capacitance illustrated in  FIG. 45A . This variable capacitance can cause dynamic changes in the operation of transmit circuit  4548  that can be measured by a monitoring circuit (not shown) to detect the presence of the object proximate to or touching the crown  4546 . 
     In the examples described above, the transmit circuit is illustrated as injecting energy into the shaft and/or crown. In some examples, an electrical contact can be added to couple the transmit circuit to the crown. The electrical contact can be a single point contact. In some examples, a bearing and/or slip ring (or other contact mechanisms) can be used to couple the shaft to transmit circuitry.  FIG. 46  illustrates an example contact between a crown/shaft and transmit circuit according to examples of the disclosure.  FIG. 46  illustrates device  4600  including a housing  4602 , crown  4604  and shaft  4606 . Shaft  4606  can be coupled to a mounting  4608  that can allow rotational movement by crown  4604  and shaft  4606 . The proximal (rear) portion of shaft  4606  can be formed, at least in part, from a conducting material that can contact dome switch  4610 . In some examples, the portion of dome switch  4610  contacting shaft  4606  can be conducting as well. Transmit circuit  4612  can be coupled (e.g., via wired pathway  4614 ) to the conductive portion of dome switch  4610 , such that the transmit circuit can inject energy into the crown via the existing point of contact between the dome switch  4610  and shaft  4606  (i.e., without adding an additional point of contact to the shaft). 
     In some examples, rather than using a physical contact to the shaft and/or crown, which can be difficult (e.g., because of the rotational movement of the crown), a wireless coupling can be used. In some examples, energy can be injected into the shaft and/or crown via capacitive coupling. For example, the transmit circuit  4612  can be disposed proximate to the shaft (or crown) such that energy in the transmit circuit can capacitively couple (e.g., via capacitive pathway  4616 ) to the shaft and/or crown. Transmitting energy via capacitive coupling, however, can consume significant power in order to transfer enough energy to the crown for proper touch and/or proximity sensing. 
     In some examples, energy can be injected into the shaft and/or crown via inductive coupling (e.g., a transformer). Inductive coupling can, in some examples, provide for relatively efficient energy transfer to the shaft and/or crown (as compared with capacitive coupling described above) and without requiring reliable contact with the shaft and/or crown.  FIGS. 47A and 47B  illustrate circuit diagrams of an exemplary touch and/or proximity sensor using inductive coupling according to examples of the disclosure.  FIG. 47A  illustrates a circuit  4700  including a transmit (Tx) stage  4720  and a receive (Rx) stage  4730 . Tx stage  4720  can include a voltage source  4702 , inductor  4704  and capacitor  4706 . Tx stage  4720  can be referred to as a resonant circuit or tank circuit that can oscillate with a resonant frequency f 1  (e.g., based on the inductance of inductor  4704  and the capacitance of capacitor  4706 ). Although Tx stage  4720  is illustrated as including a voltage source  4702 , it is understood that voltage source  4702  can be replaced with any suitable driving source (e.g., a current source, etc.) Rx stage  4730  can include inductor  4708  and capacitor  4710 . Rx stage  4730  can also be referred to as a resonant circuit or tank circuit that can oscillate with a resonant frequency f 2  (e.g., based on the inductance of inductor  4708  and the capacitance of capacitor  4710 ). Inductors  4704  and  4708  together can form a transformer  4712  to inductively couple energy between the Tx stage  4720  and Rx stage  4730 . 
       FIG. 47B  illustrates example circuit  4700  when an object is touching or proximate to the Rx stage  4720 . When an object is proximate to or contacting node  4714  of Rx stage  4730 , for example, a variable capacitance  4716  can be formed between the object and circuit Rx stage  4730 . The variable capacitance  4716  can cause a change in the operation (detuning) of Rx stage  4730  (e.g., due to energy dissipated through the finger). For example, the resonant frequency of Rx stage  4730  can shift to f 2 +Δf, where f 2  can represent the resonant frequency without a proximate object and Δf can represent the shift in resonant frequency due to the variable capacitance introduced by a proximate object. The shift in frequency in Rx stage  4730  can cause a shift in frequency of Tx stage  4720  (detuning), which can be monitored and used to determine the presence of an object touching or proximate to circuit  4700 . Additionally, the shift in frequency can be used to estimate the distance between the object and circuit  4700  based on the amount of shift in frequency, as the capacitance value associated with variable capacitance  4716  can be a function of the distance between the object and circuit  4700 . It should be understood that the example circuit  4700  in  FIGS. 47A and 47B  is exemplary only and fewer or additional components can be added in the same or a different configuration. 
     In some examples, Tx stage  4720  and Rx stage  4730  can be designed to have the same resonant frequency (i.e., f 1 =f 2 ), though in some examples, Tx stage  4720  and Rx stage  4730  can be designed to have different resonant frequencies. Using a common resonant frequency for Tx stage  4720  and Rx stage  4730  can increase (and, in some examples, maximize) the power transfer between the two stages. In some examples, capacitor  4506  and/or capacitor  4510  can be adjustable such that the resonant frequency can be turned for Tx stage  4720  and/or Rx stage  4730 . Additionally, improving the coupling between inductors  4704  and  4708  can improve the energy transfer between the two stages. 
     Although discussed above as monitoring a shift in frequency, the sensor can be configured to measure other parameters that can be used to determine touch and/or proximity events. For example, the dynamics of the circuit that can be measured can include changes in the amplitude or phase of the signals produced by the driving source (e.g., voltage source  4702 ). Additionally, in some examples, the dynamics can be detuning of the Tx stage measured, for example, by power loss or standing wave ratio. Depending on the signal dynamics to be measured, a suitable monitoring circuit or element (not shown) can be used to measure the parameter(s), which can be used to detect the presence of an object proximate to the crown and can be used to estimate the distance between the object and the crown from the parameter. For example, when the measured shift in frequency from the resonant frequency meets a first threshold, but not a second threshold, the object can be estimated to be proximate to the crown, but not touching the crown. The distance between the object and crown can be estimated as a function of the shift in frequency. When the object meets the second threshold, the object can be estimated to be touching the crown. In some examples, the first threshold can represent the maximum distance (e.g., d=d max ) between the object and the crown that can be detected by the sensor (e.g., above a noise threshold), and the second threshold can represent the minimum distance between the object and the crown (e.g., d=0). In some examples, detecting an object touching or proximate to the crown (and estimating its distance) can be based on measuring more than one of the parameters. In some examples, each of the one or more parameters can be compared to one or more thresholds to determine a touch and/or hover event. 
     In some examples, the touch and/or proximity sensor can include processing circuitry to process measured parameters and detect the presence of a touch or hover event and/or estimate the distance between an object and the crown. In other examples, the raw or partially processed data can be processed by other processing circuitry external to the sensor (e.g., by processor  202 ). 
     The detection range of the touch and/or proximity sensor can be a function of the sensitivity of the sensor to detect changes in capacitance between the object and the crown. As described herein, the capacitance can be a function of the surface area of the crown, the surface area of the object proximate to the crown, and the distance between the object and the crown. As a result, the maximum detectable distance of the sensor can be function of the surface area of the crown and the surface area of the finger. 
     Additionally or alternative, in some examples, rather than comparing one or more measured parameters to one or more thresholds to detect a touch and/or proximity event, a signature of an approaching object can be detected based on a multiple (e.g., a sequence) of measurements by the touch and/or proximity sensor. For example, an object approaching the crown can be sensed to have a signature of increasing shifts in resonant frequency that can be used to trigger a touch/proximity event. In some examples, the rate of change of the shifts in resonant frequency can be used to determine if the rate of change corresponds to the signature of an object approaching and/or contacting the crown. 
     The example circuit of  FIGS. 47A and 47B  can be implemented in a device with a crown to detect touch and/or proximity between an object and the crown.  FIG. 48  illustrates an example object in proximity to an example crown according to examples of the disclosure.  FIG. 48  illustrates an example device  4800  (e.g., a wearable device) including a housing  4802 . Shaft  4804  can extend from the housing  4802  and can be coupled to crown  4806 . The primary winding  4810  and secondary winding  4812  can be inductively coupled (e.g., forming a transformer that can correspond to transformer  4712 ) of the crown touch and/or proximity sensor. The transformer formed by primary winding  4810  and secondary winding  4812  can operatively couple a Tx stage (including primary winding  4810 ) to an Rx stage formed from shaft  4804  and/or crown  4806  (including secondary winding  4812 ). The transformer can inject electromagnetic energy from the Tx stage into the Rx stage formed from shaft  4804  and/or crown  4806  without a physical connection between the Tx stage and Rx stage. An object, such as finger  4808  (which can be considered to be effectively shorted to ground through C body ) approaching crown  4806  can cause a capacitance to form between the crown  4806  and ground. The capacitance formed between the finger and crown can be a function of the distance  4814  (labeled “d”) between the crown  4806  and the finger  4808 . This capacitance can cause dynamic changes in the Rx stage that can in turn cause to the Tx stage. The dynamic changes in the Tx stage can be measured by a monitoring circuit (not shown) to detect the presence of an object proximate to or touching the crown based, for example, on the estimated distance  4814 . 
       FIG. 49A  illustrates an example touch and/or proximity sensor using a crown according to examples of the disclosure.  FIG. 49A  illustrates an example shaft  4900  and crown  4902 , which can form an Rx stage. Shaft  4900  can have a cylindrical shape, for example, and can include inductor  4904  forming the secondary winding of a transformer (coupled inductors). Inductor  4904  can be coupled to two electrodes  4906  and  4908  disposed in the crown. Each electrode can be coupled to one terminal of inductor  4904 . Inductor  4910 , forming the primary winding of the transformer, can envelope shaft  4900  including some or all of inductor  4904  (without contacting secondary winding of inductor  4904 ). In other words the inductor  4904  and inductor  4908  can form a solenoid within a solenoid that can provide inductive coupling to transfer energy between the Tx stage and Rx stage. Inductor  4910  can correspond to the inductor of the Tx stage, the remainder of which is not shown for ease of illustration and brevity of description. When an object, such as finger  4912 , is proximate to or contacts crown  4906 , a capacitance can be formed between each of electrodes  4906  and  4908 . The capacitances can detune the Rx stage and thereby detune the Tx stage (via inductive coupling). 
     It should be understood that the sensor in  FIG. 49A  is exemplary only and fewer or additional components can be added in the same or a different configuration. For example, the shaft and/or crown can include one or more additional capacitors (including a variable capacitor, for example) to tune the Rx stage to a desired resonant frequency. Additionally or alternatively, the Tx stage can include one or more additional capacitors (including a variable capacitor, for example) to tune the Tx stage resonant frequency to match the resonant frequency of the Rx stage. 
       FIG. 49B  illustrates a circuit diagram corresponding to the example touch and/or proximity sensor of  FIG. 49A . As illustrated in  FIG. 49B , inductor  4910  of the Tx stage can inductively couple with inductor  4904  of the Rx stage. The shaft  4900  and/or crown  4902  can form a parasitic capacitance  4920 . Inductor  4904  and parasitic capacitance  4920  can form the resonant circuit of the Rx stage. Additionally, electrodes  4906  and  4908  disposed in the crown  4902  can each be modeled as one plate of a variable capacitors  4922  and  4924 . An object, such as finger  4912 , proximate to crown  4902  can be modeled as a second plate of the variable capacitors  4922  and  4924 . 
     In some examples, inductor  4904  can be wire wrapped around an outer surface of the shaft  4900 . In some examples, inductor  4904  can be incorporated, at least in part, into shaft  4900 . In some examples, inductor  4910  can be a wire wrapped around shaft  4900 . In some examples, inductor  4910  can be incorporated, at least in part, into the shaft mounting (e.g., formed internally to the mounting or wrapped around a surface of the shaft mounting facing the shaft). The amount of coupling between inductor  4904  and inductor  4908  can be a design parameter for the touch and/or proximity sensor. The placement of inductor  4904  and inductor  4910  can impact the coupling between the Rx stage and the Tx stage. In some examples, to increase inductive coupling, inductor  4904  and inductor  4908  can be disposed such that the electromagnetic field lines of inductor  4908  can be captured by inductor  4904 . When inductor  4904  is located closer to the outside surface of the shaft, more field lines of inductor  4908  can be captured (increased coupling). When inductor  4904  is located closer to the center of the shaft, fewer field lines of inductor  4908  can be captured (decreased coupling). 
     In some examples, one or more of the inductors can be implemented using non-ferrous, air core inductors (e.g., with a high quality factor). In some examples, the electric field can be concentrated to improve efficiency of power transfer between the inductors. For example, rather than an air core, one or more of the inductors can be implemented using a ferrous core (e.g., soft iron, steel, alloy, etc.). In some examples, the inductors can be cut into sheets to prevent current losses. 
       FIG. 49C  illustrates a view of crown electrodes for the example touch and/or proximity sensor of  FIG. 49A  according to examples of the disclosure.  FIG. 49C  illustrates shaft  4900  with crown  4902  at its distal end. Electrodes  4906  and  4908  can be disposed in crown  4902 , and can be electrically isolated (e.g., separated from one another by an insulator). Although electrodes  4906  and  4908  are illustrated in  FIG. 49C  as having a semi-circular shape (i.e., in the plane of the crown face), in other examples, the electrodes can have a different shape. For example, the electrodes can have a polygonal or square shape, for example. Additionally, the electrodes can also have different orientations. For example, the electrodes can have an orientation as illustrated and described below with reference to  FIG. 50C . 
     Referring back to  FIG. 49A , the crown electrodes (and, in some examples, portions of the feeding traces/electrodes in the shaft) can be formed of one or more conducting materials (e.g., metal, semi-conductor, alloy, conducting plastic or composites, etc.). In some examples, the conducting portions of the shaft and/or crown can be formed of the same materials. In some examples, the conducting portions of the shaft and/or crown can be formed of different conducting materials. 
     In some examples, the dimensions of the crown electrodes can be selected to ensure sufficient coupling with an object touching or proximate to the crown to enable touch and/or proximity detection. Increasing the size of the crown electrodes can increase capacitive coupling and can thereby increase the sensitivity of the sensor. 
     The two crown electrodes  4906  and  4908  can be coupled to remaining sensor circuitry (e.g., of the Rx stage) through traces/electrodes in shaft  4900 . The electrodes in shaft  4900  can be separated by an insulating material. In some examples, the electrodes in shaft  4900  can have a coaxial structure including one shaft electrode in the center of shaft  4900  coupling to one of electrodes  4906  and  4908  and a second shaft electrode away from the center of shaft  4900  coupling to a second electrode of electrodes  4906  and  4908 , for example. The electrodes in shaft  4900  can be separated by a dielectric material. 
       FIG. 50A  illustrates another example touch and/or proximity sensor using a crown according to examples of the disclosure.  FIG. 50A  illustrates an example shaft  5000  and crown  5002 , which can form an Rx stage. Shaft  5000  can include inductor  5004  forming the secondary winding of a transformer. Inductor  5004  can be coupled to two electrodes  5006  and  5008  that can be disposed in the crown. Inductor  5010 , forming the primary winding of the transformer, can envelope shaft  5000  including some or all of inductor  5004  (without contacting secondary winding of inductor  5004 ). Unlike the electrodes in the sensor of  FIG. 49A , the electrodes in the sensor of  FIG. 50A  can be disposed in the crown such that electrode  5006  can be disposed in the center of the crown  5002  and electrode  5008  can be disposed away from the center of crown  5002  (e.g., around the circumference of a cylindrical portion of the crown). It should be understood that the sensor in  FIG. 50A  is exemplary only and fewer or additional components can be added in the same or a different configuration. 
       FIG. 50B  illustrates a circuit diagram corresponding to the example touch and/or proximity sensor of  FIG. 50A . As illustrated in  FIG. 50B , inductor  5010  of the Tx stage can inductively couple with inductor  5004  of the Rx stage. The shaft  5000  and/or crown  5002  can form a parasitic capacitance  5020  (i.e., mutual capacitance between electrodes  5006  and  5008 ). Inductor  5004  and parasitic capacitance  5020  can form the resonant circuit of the Rx stage. When an object is proximate to or contacts crown  5006 , the object can interfere with the electric field between electrodes  5006  and  5008  that can cause a change in the mutual capacitance (modeled by the variable capacitance of capacitor  5020 ). The change in mutual capacitance can detune the Rx stage and thereby detune the Tx stage (via inductive coupling). 
       FIG. 50C  illustrates a view of crown electrodes for the example touch and/or proximity sensor of  FIG. 50A  according to examples of the disclosure.  FIG. 50C  illustrates shaft  5000  with crown  5002  at its distal end. Electrodes  5006  and  5008  can be disposed in crown  5002 , and can be separated from one another by an insulator so as to form mutual capacitance therebetween. Although electrodes  5006  and  5008  are illustrated in  FIG. 50C  as having a circular shape (in the plane of the crown face), in other examples, the electrodes can have a different shape. For example, the electrodes can have a polygonal, semi-circular or square shape. Additionally, the electrodes can also have different orientations. For example, the electrodes can have an orientation as illustrated and described with reference to  FIG. 49C . 
     In some examples, rather the two electrodes, the crown can have a different number of electrodes (e.g., one or more).  FIGS. 51A-51D  illustrate example touch and/or proximity sensors using four crown electrodes according to examples of the disclosure.  FIG. 51A  illustrates an example shaft  5100  and crown  5102 , which can form an Rx stage. Shaft  5100  can include two inductors  5104 A and  5104 B forming the secondary windings of transformers for two Rx stages. Inductors  5104 A and  5100 B can be coupled to four electrodes  5106 - 5109  that can be disposed in the crown. Inductor  5110 , forming the primary winding of the transformer can envelope shaft  5100  including some or all of the inductors  5104 A and  5104 B (without contacting the secondary windings). It should be understood that the sensor in  FIG. 51A  is exemplary only and fewer or additional components can be added in the same or a different configuration. 
       FIG. 51B  illustrates a circuit diagram corresponding to the example touch and/or proximity sensor of  FIG. 51A . As illustrated in  FIG. 51B , inductor  5110  of the Tx stage can inductively couple with the two inductors  5104 A and  5104 B of the two Rx stages. The shaft  5100  and/or crown  5102  can form a parasitic capacitance. The inductor  5104 A and the parasitic capacitance can form the resonant circuit of the first Rx stage and the inductor  5104 B and the parasitic capacitance can form the resonant circuit of the second Rx stage. The resonant frequency of the first and second Rx stages can be different (by changing inductance or capacitance for the respective circuits) so as to distinguish between the two Rx stages as described herein. When an object, such as a finger, is proximate to or contacts crown  5106 , capacitances  5122 ,  5124 ,  5126  and  5128  can be formed between each of electrodes  5106 - 5109  and the object. In some examples, system can measure a change in mutual capacitance between pairs of electrodes  5106 - 5109  (as discussed, for example, with reference to  FIG. 50B ). The capacitances can detune the corresponding Rx stage and thereby detune the Tx stage (via inductive coupling). 
     The Tx stage can include, in addition to inductor  5106 , a current source  5112  (or some other driving source) and an adjustable capacitor  5114 , for example. The Tx stage can be tuned to two different resonant frequencies f A  and f B  to match the corresponding resonant frequencies for the two Rx stages. By switching the tuning of the Tx stage (e.g., alternating between two different capacitance values for adjustable capacitor  5114  when the sensor is active), the sensor can measure the detuning due to objects proximate to the electrodes for each Rx stage. 
     Using two different Rx stages for proximity/touch detection at the crown can allow, for example, for improved differentiation of touch and/or proximity events due to person&#39;s wrist (undesired) and due to an object such as a finger (desired). For example, the device may want to wake up (from a rest mode) when touch and/or proximity is detected at the crown by a person&#39;s finger (intentional use) and not by accidental proximity or touch by a person&#39;s wrist. Improving differentiation of finger and wrist input, for example, can reduce the number of false positive touch and/or proximity events reported. Additionally, two or more Rx stages can allow, for example, for touch and/or proximity information for different parts of the crown (that can be used, for example, as additional touch and/or proximity inputs for the crown). 
     In some examples, the touch and/or proximity information for the outer electrodes (e.g., electrode  5106  and  5109 ) can be used as a first input that can represent touch and/or proximity events around the circumference of the crown. The touch and/or proximity information for the inner electrodes (e.g.,  5107  and  5108 ) can be used as a second input that can represent touch and/or proximity events at the face of the crown. In some examples, the touch and/or proximity information from each crown electrode (or group of crown electrodes) can be used to distinguish between undesired touch and/or proximity from person&#39;s wrist and desired touch and/or proximity from a finger or other object, which can reduce false positives due to undesired contact by a user&#39;s wrist. For example, a ratio of the touch and/or proximity information can be compared to a threshold to predict whether the object is a finger or wrist. In other examples, the touch and/or proximity information from each electrode (or group of electrodes) can be compared with a threshold, and the touch and/or proximity event can be reported only when the thresholds are met for each electrode (or group of electrodes). 
       FIGS. 51C and 51D  illustrate views of crown electrodes for the example touch and/or proximity sensor of  FIG. 51A  according to examples of the disclosure.  FIGS. 51C and 10D  illustrate shaft  5100  with crown  5102  at its distal end. Electrodes  5106 - 5109  can be disposed in crown  5102 . In  FIG. 51C , the electrodes  5107  and  5108  can have a semi-circular shape (in the plane of the crown face). Electrodes  5106  and  5109  can have a semi-disk shape (in the plane of the crown face). In  FIG. 51D , the electrodes  5106 - 5109  can have a wedge shape (in the plane of the crown face). In other examples, the electrodes can have different shapes and/or orientations than illustrated in  FIGS. 51C and 51D . 
       FIG. 52  illustrates an exemplary process for detecting objects touching and/or proximate to the crown of a device according to examples of the disclosure. The device can apply electromagnetic energy to a first circuit ( 5200 ). For example, the first circuit can be the LC circuit of the Tx stage energized by the driving source of the Tx stage. The device can couple the energy from the first circuit to the second circuit, which can include the shaft and crown of the device ( 5205 ). For example, the second circuit can be the LC circuit of the Rx stage. Coupling can occur between the inductive elements of the Tx stage and Rx stage so as to transfer/inject electromagnetic energy into the shaft and crown of the device. The device can measure changes in one or more parameters (e.g., electromagnetic dynamics) of the first circuit ( 5210 ). For example, a monitoring circuit or element can detect changes in frequency, phase and/or amplitude (or other parameters) of the Tx stage. In some examples, a shift in resonant frequency of the Tx stage LC circuit can be measured. The device can detect touch and/or proximity of an object at the crown ( 5215 ). For example, based on the measured one or more parameters, the device (e.g., processor  202  or crown controller  252 ) can sense a capacitance formed between the crown and an object (e.g., a finger) proximate to the crown. The one or more parameters (e.g., the sensed capacitance) can be used to detect whether the object is touching or proximate to the crown (e.g., based on comparing the one or more parameters to one or more detection thresholds). Additionally or alternatively, the device can estimate the distance between the object and the crown based on the one or more measured parameters. In some examples, the distance can be estimated by comparing the one or more parameters to values in a look-up table (LUT). In some examples, the system can exit a rest state (as described, for example, with respect to  FIG. 44A ) in response to detecting a threshold level of proximity between the object and the crown. In some examples, the estimated distance can be compared with multiple thresholds that can be used for reporting one or more touch/hover events (as described, for example, with respect to  FIGS. 44B and 44C ). 
     The resonant frequency used by Tx stage and Rx stage can be selected to avoid or reduce interference with external objects or other elements of the device. For example, the stages can operate in a different frequency range than a WiFi® and/or BLUETOOTH™ antenna in the device. Additionally, the frequency can be selected to reduce interference and susceptibility to detecting conducing objects like buttons or cufflinks that a person might be wearing proximate to the crown. In some examples, the Tx stage and/or Rx stage can include a variable capacitor that can be used to tune the resonant frequencies to avoid or reduce interference. In some examples, the tuning can be performed during factory calibration. In some examples, the tuning can be performed dynamically in response, for example, to detecting noise in the operating environment. 
     In some examples, the crown touch and/or proximity detection described herein can be performed continuously (e.g., 100% duty cycle) or periodically (e.g., at a fixed duty cycle, such as a 50% duty cycle). In some examples, the crown touch and/or proximity detection can be performed intermittently or can be performed based on device conditions. For example, if touch and/or proximity detection is used only to wake up the device (e.g., as described with respect to  FIG. 44A ), the crown touch and/or proximity detection can be performed (e.g., continuously or periodically) when the device is in the rest mode, and stopped or performed less frequently during the ready mode. Additionally or alternatively, when touch/hover event inputs can be accepted as inputs by the UI, the crown touch and/or proximity detection can be performed (e.g., continuously or periodically). When touch/hover event inputs cannot be accepted as inputs by the UI, the crown touch and/or proximity detection can be stopped or performed less frequently. 
     In some additional examples of the disclosure, a device can inject electromagnetic energy into the crown to detect objects touching or proximate to the crown of a device. In some examples, a touch and/or proximity sensor can include a transmit circuit operatively coupled to a rotational input element (e.g., crown) and configured to inject electromagnetic energy into the rotational input element, and a monitoring circuit operatively coupled to the rotational input element and configured to measure one or more parameters (e.g., resonant frequency). The one or more parameters can be indicative of an object touching or in proximity to the rotational input element. One or more touch or hover events can be detected based on the one or more parameters measured by the monitoring circuit. In some examples, the touch and/or proximity sensor can measure changes in resonant frequency of an oscillating circuit (e.g., an LC tank circuit). In some examples, the touch and/or proximity sensor can measure detuning of an antenna (e.g., the crown acting as an antenna). 
       FIG. 53  illustrates an exemplary process for detecting objects touching and/or proximate to the crown of a device according to examples of the disclosure. The device can apply electromagnetic energy to a circuit including the shaft and crown of the device ( 5300 ). For example, as discussed above with regard to  FIGS. 45A-45C  for example, a transmit circuit can form an LC resonant tank circuit that can inject electromagnetic energy into the shaft and crown of the device. The device can measure changes in one or more parameters (e.g., electromagnetic dynamics) of the circuit ( 5305 ). For example, a monitoring circuit or element can detect changes in frequency, phase and/or amplitude of the LC resonant tank circuit. In some examples, a shift in resonant frequency of the LC resonant tank circuit can be measured. The device can detect touch and/or proximity of an object at the crown ( 5310 ). For example, referring back to  FIG. 2 , based on the measured one or more parameters, the device (e.g., with processor  202  or crown controller  252 ) can sense a capacitance formed between the crown and an object (e.g., a finger) proximate to the crown. The one or more parameters (e.g., the sensed capacitance) can be used to detect whether the object is touching or proximate to the crown (e.g., based on comparing the one or more parameters to one or more detection thresholds). Additionally or alternatively, the device can estimate the distance between the object and the crown based on the one or more measured parameters. In some examples, the distance can be estimated by comparing the one or more parameters to values in a look-up table (LUT). In some examples, the system can exit a rest state (as described, for example, with respect to  FIG. 44A ) in response to detecting a threshold level of proximity between the object and the crown. In some examples, the estimated distance can be compared with multiple thresholds that can be used for reporting one or more touch/hover events (as described, for example, with respect to  FIGS. 44B and 44C  above). 
     In some examples, touch and/or proximity events at the crown can be detected using the shaft and/or crown as an antenna. Radio frequency energy can be injected into the shaft and crown and detuning of the antenna (e.g., formed of the shaft and crown), caused by an object proximate to or touching the crown, can be measured and used to detect touch and/or proximity of the object.  FIG. 54A  illustrates an example circuit diagram of an exemplary touch and/or proximity sensor using antenna detuning according to examples of the disclosure.  FIG. 54A  illustrates a touch and/or proximity sensor circuit  5400  including a radio frequency transmit circuit  5402  (RF Tx) to radiate electromagnetic energy to an antenna  5410 , and a monitoring circuit, such as power meter  5412 , to measure detuning of antenna  5410 . The antenna  5410  can be formed of some or all of shaft  5406  and/or some or all of crown  5408 . In other words, the portions of shaft  5406  and crown  5408  radiating the RF energy can be modeled by antenna  5410 . The radio frequency transmit circuit  5402  and power meter  5412  can be operatively coupled to the shaft and/or crown by a duplexer circuit  5404  (circulator circuit). The duplexer circuit  5404  can include three ports (labeled  1 ,  2  and  3  in  FIG. 54A ) that can allow the RF energy to pass to the antenna  5410  from port  1  to port  2 , and that can allow reflected RF energy to return from the antenna  5410  from port  2  to port  3 . The touch and/or proximity sensor circuit  5400  can be designed to tune the performance of antenna  5410  to a baseline performance. When an object, such as finger  5414  approaches or touches crown  5408 , the capacitance C sense    5416  (variable capacitance) formed between crown  5408  and finger  5414  can detune the antenna  5410 , and the detuning can be used to detect touch and/or proximity events and to estimate the distance between the object and the crown (e.g., based on how different the performance of the detuned antenna is from the baseline performance). 
     In some examples, the monitoring circuit can measure detuning using a standing wave ratio, such as a voltage standing wave ratio (VSWR) or a power standing wave ratio (PSWR). The standing wave ratio can be used to measure the impedance matching between the impedance of radio frequency transmit circuit  5402  (Z Tx ) with the impedance of antenna  5410  (Z ANT ). An object proximate to the crown can introduce a variable capacitance that can change Z ANT  (resulting in an impedance discontinuity). The change in the standing wave ratio can be compared with a baseline standing wave ratio (i.e., the standing wave ration when no object is touching or proximate to the crown) to detect touch and/or proximity events. In some examples, the touch and/or proximity sensor circuit  5400  can be tuned to match the impedance of radio frequency transmit circuit  5402  (Z Tx ) with the impedance of antenna  5410  (Z ANT ), such that the baseline standing wave ratio is 1:1. In some examples, rather than using a standing wave ratio, the monitoring circuit can use a reflection coefficient (F) or return loss to measure detuning due to an object proximate to or touching the crown. Other metrics or parameters can be used to detect touch and/or hover events at the crown. In some examples, the metrics described above can be generated (e.g., calculated) based on other parameters (e.g., voltage/current, amplitude/phase/frequency) measured by the monitoring circuit. 
     The one or more parameters/metrics measured by the monitoring circuit can be compared with one or more thresholds to determine a touch and/or one or more different hover events (as with the measured parameters from the resonant tank circuit discussed above). The metrics can also be used to estimate the distance between a hovering object and the crown. For brevity, the discussion of various thresholds, resulting touch and/or hover events, and corresponding operations is omitted here. 
       FIG. 54B  illustrates an exemplary touch and/or proximity sensor using antenna detuning according to examples of the disclosure.  FIG. 54B  illustrates a touch and/or proximity sensor circuit  5420  including a radio frequency transmit circuit  5422  (RF Tx) implemented with an LC resonant tank circuit. The RF transmit circuit  5422  can radiate electromagnetic energy (at the resonant frequency f LC ) through an antenna formed by shaft  5426  and crown  5428 .  FIG. 54B  illustrates a monitoring circuit, implemented by frequency counter circuit  5424 , that can measure detuning of the antenna due to variable capacitance  5432  formed between crown  5428  and proximate object  5430  (e.g., finger). The frequency counter circuit  5424  (or other monitoring circuit) can be used to detect a shift in frequency of the LC resonant tank circuit due to antenna detuning, and the shift in frequency can be used to detect touch/hover events and estimate the distance between the crown and the object as discussed herein. 
     In some examples, the shaft and crown together can form the antenna. In other examples, the shaft can be designed as a transmission line between the transmit circuit and the antenna formed of the crown. In some examples a portion of the shaft and/or a portion of the crown can form the antenna and there remaining portions can be designed as a transmission line. In some examples, the shaft and/or crown portions acting as a transmission line can be implemented with a coaxial structure to improve the transmission line characteristics. 
       FIG. 55  illustrates another exemplary process for detecting objects touching and/or proximate to a crown of a device according to examples of the disclosure. The device can apply electromagnetic energy (e.g., in the form of a radio frequency signal) to a circuit including the shaft and crown of the device ( 5500 ). For example, as discussed above with regard to  FIGS. 54A and 54B , for example, an RF transmit circuit can inject electromagnetic energy into the shaft and crown of the device which can form an antenna. The device can measure changes in one or more parameters (e.g., electromagnetic dynamics) of the circuit corresponding to detuning of the antenna ( 5505 ). For example, a monitoring circuit or element can detect changes in a standing wave ratio, return loss or reflection coefficient. Additionally or alternatively, the monitoring circuit or element can detect changes of frequency, phase and/or amplitude of the transmit circuit. The device can detect the touch and/or proximity of an object at the crown ( 5510 ). For example, based on the measured one or more parameters, the device (e.g., processor  202  or crown controller  252 ) can sense a capacitance formed between the crown and an object (e.g., a finger) proximate to the crown. The one or more parameters (or the sensed capacitance) can be used to detect whether the object is touching or proximate to the crown (e.g., based on comparing the one or more parameters to one or more detection thresholds). Additionally or alternatively, the device can estimate the distance between the object and the crown based on the one or more measured parameters. In some examples, the distance can be estimated by comparing the one or more parameters to values in a look-up table (LUT). In some examples, the system can exit a rest state (as described, for example, with respect to  FIG. 44A ) in response to detecting a threshold level of proximity between the object and the crown. In some examples, the estimated distance can be compared with multiple thresholds that can be used for reporting one or more touch/hover events (as described, for example, with respect to  FIGS. 44B and 44C ). 
     As described above, touch and/or proximity to the crown can be detected by capacitively coupling between the crown (and/or shaft) and an object. In some examples, the crown and/or shaft can be formed of one or more conducting materials (e.g., metal, semi-conductor, alloy, conducting plastic or composites, etc.).  FIG. 56A  illustrates an example shaft and crown formed of one or more conducting materials according to examples of the disclosure.  FIG. 56A  illustrates a shaft  5600  and crown  5602  formed of one or more conducting materials. In some examples, the shaft and/or crown can be solid. In some examples, the shaft and/or crown can include a hollow. In some examples, the shaft and/or crown can be formed of the same materials. In some examples, the shaft and/or crown can be formed of different materials. 
     In some examples, the shaft and/or crown can be formed of conducting and non-conducting materials.  FIG. 56B  illustrates an example shaft and/or crown formed of conducting and non-conducting materials according to examples of the disclosure.  FIG. 56B  illustrates a shaft  5610  including a conducting portion  5614  and a non-conducting portion  5615 , and crown  5612  including a conducting portion  5616  and a non-conducting portion  5617 . The conducting portions  5614  and  5616  can be coupled together and can be coupled to transmit circuitry (e.g., at the proximal end of the shaft). The conducting portions  5614  and  5616  can also capacitively couple to an object proximate to or touching the crown. 
     In some examples, the dimensions of the conducting portions  5614  and  5616  can be selected to ensure sufficient coupling with an object touching or proximate to the crown  5612  to enable touch and/or proximity detection. Increasing the size of the conducting portions can increase capacitive coupling and can thereby increase the sensitivity of the sensor. In some examples, the shaft  5610  can include a conducting portion  5614  and a non-conducting portion  5615 , and the crown can be entirely a conductor. In some examples, the crown  5612  can include a conducting portion  5616  and a non-conducting portion  5617 , and the shaft can be entirely a conductor. In some examples, the shaft and/or crown can also include a hollow. In some examples, the conducting and/or non-conducting portions of the shaft and/or crown can be formed of the same materials. In some examples, the conducting and/or non-conducting portions of the shaft and/or crown can be formed of different materials. 
     In some examples, the crown and/or shaft can include two or more conducting portions (electrodes). Using two or more conducting electrodes for proximity/touch detection at the crown can allow, for example, for improved differentiation of touch and/or proximity events due to person&#39;s wrist (undesired) and due to an object such as a finger (desired). For example, the device may want to wake up (from a rest mode) when touch and/or proximity is detected at the crown by a person&#39;s finger (intentional use) and not by accidental proximity or touch by a person&#39;s wrist. Improving differentiation of finger and wrist input, for example, can reduce the number of false positive touch and/or proximity events reported. Additionally, two or more conducting electrodes can allow, for example, for touch and/or proximity information for different parts of the crown (that can be used, for example, as additional touch and/or proximity inputs for the crown). 
       FIGS. 56C and 56D  illustrate a crown including two conducting electrodes according to examples of the disclosure.  FIG. 56C  illustrates a cross-sectional view of shaft  5620  and crown  5622  (along a plane symmetrically dividing the shaft and crown).  FIG. 56D  illustrates a cross sectional view of the crown face (along a plane orthogonal to the plane of  FIG. 56C ). Crown  5622  can include two electrodes  5624  and  5626  that can be separated by an insulating layer  5628 . As illustrated in  FIG. 56D , the inner electrode  5624  can have a circular cross-sectional shape and be disposed in the center of the circular crown face, and the outer electrode  5626  can have a circular cross-sectional shape and be disposed around the inner electrode  5624  and away from the center of the circular crown face. As illustrated in  FIG. 56C , for example, the outer electrode  5626  can have a cylindrical shape wrapping around crown  5622 . Although illustrated in  FIGS. 56C and 56D  as having circular/cylindrical shapes, inner and outer electrodes  5624  and  5626  can have different shapes (e.g., polygonal, square, conic, etc.). The two electrodes  5624  and  5626  in the crown can be coupled to remaining sensor circuitry through electrodes in shaft  5620 . The electrodes in shaft  5620  can be separated by an insulating layer as well. In some examples, the electrodes in shaft  5620  can have a coaxial structure with one electrode in the center of shaft  5620  and one electrode away from the center of shaft  5620 . The electrodes in shaft  5620  can be separated by a dielectric material. 
     In some examples, each crown electrode in  FIGS. 56C and 56D  can be coupled to a different transmit circuit (and one or more monitoring circuits). For example as described herein, each crown electrode can be coupled to an RF transmit circuit (e.g., each tuned to a different frequency) and a corresponding monitoring circuit, and each crown electrode can act as an antenna. The detuning of each antenna can be measured to generate touch and/or proximity information for each crown electrode. Alternatively, each crown electrode can be coupled to a resonant tank LC circuit (e.g., each tuned to a different frequency) and a corresponding monitoring circuit. The shift in resonant frequencies of each resonant tank LC circuit can be measured to generate touch and/or proximity information for each crown electrode. 
     In some examples, the touch and/or proximity information for the outer electrode can be used as a first input that can represent touch and/or proximity events around the circumference of the crown. The touch and/or proximity information for the inner electrode can be used as a second input that can represent touch and/or proximity events at the face of the crown. In some examples, the touch and/or proximity information from each crown electrode can be used to distinguish between undesired touch and/or proximity from person&#39;s wrist and desired touch and/or proximity from a finger or other object, which can reduce false positives due to undesired contact by a user&#39;s wrist. For example, a ratio of the touch and/or proximity information can be compared to a threshold to predict whether the object is a finger or wrist. In other examples, the touch and/or proximity information from each electrode can be compared with a threshold, and the touch and/or proximity event can be reported only when the thresholds are met for both electrodes. 
     In some examples, rather than measuring touch and/or proximity information for each crown electrode with two transmit circuits, the touch and/or proximity sensor can be configured to measure changes mutual capacitance the between the two crown electrodes. For example, referring back to  FIG. 45C , rather than modeling the crown as a parasitic capacitance to ground, one crown electrode can be coupled to one node of the circuit (e.g., to the node at one terminal of the inductor) and the second crown electrode can be coupled to a second node of the circuit (e.g., to the node at a second terminal of the inductor). The sensor can measure the coupling between the two electrodes to differentiate between a finger and a wrist. For example, when a finger is contacting the crown, the mutual capacitance coupling between the two electrodes can be more reduced in comparison with a wrist contacting the crown. 
     In the examples described above, the transmit circuit is illustrated as injecting energy into the shaft and/or crown. In some examples, an electrical contact can be added to couple the transmit circuit to the crown. The electrical contact can be a single point contact. In some examples, a bearing and/or slip ring (or other contact mechanisms) can be used to couple the shaft to transmit circuitry.  FIG. 57  illustrates an example contact between a crown/shaft and transmit circuit according to examples of the disclosure.  FIG. 57  illustrates device  5700  including a housing  5702 , crown  5704  and shaft  5706 . Shaft  5706  can be coupled to a mounting  5708  that can allow rotational movement by crown  5704  and shaft  5706 . The proximal (rear) portion of shaft  5706  can be formed, at least in part, from a conducting material that can contact dome switch  5710 . In some examples, the portion of dome switch  5710  contacting shaft  5706  can be conducting as well. Transmit circuit  5712  can be coupled (e.g., via wired pathway  5714 ) to the conductive portion of dome switch  5710 , such that the transmit circuit can inject energy into the crown via the existing point of contact between the dome switch  5710  and shaft  5706  (i.e., without adding an additional point of contact to the shaft). 
     In some examples, rather than using a physical contact, energy can be injected into the shaft and/or crown via capacitive coupling. For example, the transmit circuit  5712  can be disposed proximate to the shaft (or crown) such that energy in the transmit circuit can capacitively couple (e.g., via capacitive pathway  5716 ) to the shaft and/or crown. Transmitting energy via capacitive coupling, however, can consume significant power in order to transfer enough energy to the crown for proper touch and/or proximity sensing. 
     In some examples, rather than adding additional transmit circuitry, existing transmit circuits in the device that generate oscillating signals can be coupled to the crown to perform touch and/or proximity sensing described herein. For example, the device can include a WiFi® and/or BLUETOOTH™ antenna, which can be coupled to the shaft and/or crown. Detuning of the existing antenna (WiFi® and/or BLUETOOTH™ antenna) can be measured to detect touch and/or proximity events without adding additional transmit circuits to the device. In some examples, a point of contact connection between the existing antenna can result in a shared ground between the existing antenna the crown acting as an extension of the antenna. The touch and/or proximity of an object to the crown can detune the antenna formed of the existing antenna and the crown. In some examples, the existing antenna can be capacitively coupled to the shaft and/or crown using a capacitive pathway as discussed above. 
       FIG. 58  illustrates an example device including an existing antenna that can be used for touch and/or proximity detection according to examples of the disclosure.  FIG. 58  illustrates a device  5800  including housing  5801 , cover substrate  5802 , shaft  5803  and crown  5804 . Device  5800  can also include one or more existing antennas (e.g., WiFi®, BLUETOOTH™, etc.). In some examples, the existing antenna can include an element  5806  (e.g., a plastic element) acting as an antenna carrier, with an antenna trace  5808  disposed on the surface of element  5806  (e.g., using laser direct structuring technology). The existing antenna can be positioned in a groove in the cover substrate, and the antenna trace  5808  can be positioned over the top portion of element  5806  to enable WiFi® and/or BLUETOOTH™ signals to be efficiently transmitted out and away from the device. In some examples, the ground for the existing antenna can be shared with the crown via a physical connection (e.g., a wire). 
     In some examples, the existing antenna can be proximate to shaft  5803  such that energy can be injected from the existing antenna to the shaft via a capacitive pathway. In such examples, a trace  5809  can be added on the surface of element  5806  proximate to shaft  5803  to allow capacitive coupling between the existing antenna and the shaft  5803 . An object touching and/or proximate to the crown  5804  can then be detected based on how it detunes the antenna. 
     In some examples, rather than coupling the existing transmit circuits in the device to the crown, the existing antenna itself can act as a touch and/or proximity sensor without coupling to the crown. For example, the existing antenna can be disposed within the device, proximate to the crown (for example as illustrated in  FIG. 58 ). When a finger or other object comes into proximity with the crown, it also can come into proximity with antenna trace  5808  and can cause some detuning of the existing antenna. This antenna detuning can be measured to detect touch and/or proximity of an object. 
     In some examples, the transmit circuit can be implemented using element  5806  of the existing antenna. For example, referring to  FIG. 58 , an additional antenna trace  5810  can be added to element  5806 . Antenna trace  5810  can be coupled to different transmit circuitry than is coupled to antenna trace  5808 . Antenna trace  5810  can also be coupled on a different portion of element  5806  that can be more proximate to and/or facing the crown  5804 . Antenna trace  5810  can be coupled to shaft  5803  and crown  5804 , for example, via a wired connection or capacitive coupling (not shown). This second antenna structure can be operated in a manner than can allow for touch and/or proximity detection as described herein. 
     The RF frequency or resonant frequency used by transmit circuit can be selected to avoid or reduce interference with external objects or other elements of the device. For example, the transmit circuit can operate in a different frequency range than a WiFi® and/or BLUETOOTH™ antenna in the device. Additionally, the frequency can be selected to reduce interference and susceptibility to detecting conducing objects like buttons or cufflinks that a person might be wearing proximate to the crown. In some examples, the transmit circuit can include a variable capacitor that can be used to tune the RF or resonant frequency to avoid or reduce interference. In some examples, the tuning can be performed during factory calibration. In some examples, the tuning can be performed dynamically in response, for example, to detecting noise in the operating environment. 
     In some examples, the crown touch and/or proximity detection described herein can be performed continuously (e.g., 100% duty cycle) or periodically (e.g., at a fixed duty cycle, such as a 50% duty cycle). In some examples, the crown touch and/or proximity detection can be performed intermittently or can be performed based on device conditions. For example, if touch and/or proximity detection is used only to wake up the device (e.g., as described with respect to  FIG. 3A ), the crown touch and/or proximity detection can be performed (e.g., continuously or periodically) when the device is in the rest mode, and stopped or performed less frequently during the ready mode. Additionally or alternatively, when touch/hover event inputs can be accepted as inputs by the UI, the crown touch and/or proximity detection can be performed (e.g., continuously or periodically). When touch/hover event inputs cannot be accepted as inputs by the UI, the crown touch and/or proximity detection can be stopped or performed less frequently. 
     Capacitive Detection Apparatus and Methods 
     In some examples, a device (e.g., device  100  above) can drive the crown with a drive signal to capacitively detect objects in contact or in proximity of the crown of the device. In some examples, a contact and/or proximity sensor can include a drive circuit operatively coupled to a rotational input element (e.g., crown) and configured to drive the drive signal onto the rotational input element, and a sense circuit for sensing capacitive coupling to an object (e.g., a finger) based on capacitive coupling between the object and the contact and/or proximity sensor. The capacitive coupling can be indicative of an object contacting or in proximity to the rotational input element. One or more touch or hover events can be detected based on the signals measured by the sense circuit. In some examples, the contact and/or proximity sensor can detect an object by performing a self-capacitance measurement. In some examples, the contact and/or proximity sensor can detect an object by performing a mutual capacitance measurement. In some examples, the contact and/or proximity sensor can switch between performing self-capacitance measurements and performing mutual capacitance measurements. 
     To assist in the detection of objects in contact or in proximity of the crown of the device, one or more gasket sensor electrodes can be added proximate to the crown. In some examples, the gasket sensor electrodes can form a mutual capacitance with the rotational input element for performing a mutual capacitance measurement. In some examples, the gasket sensor electrode can be used for performing a self-capacitance measurement. Due to the proximity of the gasket sensor electrode to the crown, measurements indicative of contact or proximity of the object and the gasket sensor electrode can also indicate that the object is in contact or proximity of the crown. The additional touch detection capabilities provided by the driven crown and/or gasket sensor electrodes of the disclosure can be used to provide new interactions with user interface elements displayed on the electronic device. 
     It should be noted that the terms “poorly grounded,” “ungrounded,” “not grounded,” “partially grounded,” “not well grounded,” “improperly grounded,” “isolated,” and “floating” can be used interchangeably to refer to poor grounding conditions that can exist when an object is not making a low impedance electrical coupling to the ground of the device. 
     It should be further noted that the terms “grounded,” “properly grounded,” and “well grounded” can be used interchangeably to refer to good grounding conditions that can exist when an object is making a low impedance electrical coupling to the ground of the device. 
       FIG. 59  illustrates an exemplary block diagram of components within an exemplary device  5900  according to examples of the disclosure. In some examples, crown  5908  (which can correspond to crown  108  described above) can be coupled to encoder  5904 , which can be configured to monitor a physical state or change of physical state of the crown (e.g., the position and/or rotational state of the crown), convert it to an electrical signal (e.g., convert it to an analog or digital signal representation of the position or change in position of the crown), and provide the signal to processor  5902 . For instance, in some examples, encoder  5904  can be configured to sense the absolute rotational position (e.g., an angle between 0-360°) of crown  5908  and output an analog or digital representation of this position to processor  5902 . Alternatively, in other examples, encoder  5904  can be configured to sense a change in rotational position (e.g., a change in rotational angle) of crown  5908  over some sampling period and to output an analog or digital representation of the sensed change to processor  5902 . In these examples, the crown position information can further indicate a direction of rotation of the crown  5908  (e.g., a positive value can correspond to one direction and a negative value can correspond to the other). In yet other examples, encoder  5904  can be configured to detect a rotation of crown  5908  in any desired manner (e.g., velocity, acceleration, or the like) and can provide the crown rotational information to processor  5902 . The rotational velocity can be expressed in numerous ways. For example, the rotational velocity can be expressed as a direction and a speed of rotation, such as hertz, as rotations per unit of time, as rotations per frame, as revolutions per unit of time, as revolutions per frame, as a change in angle per unit of time, and the like. In alternative examples, instead of providing information to processor  5902 , this information can be provided to other components of device  5900 , such as, for example, a state machine. While the examples described herein refer to the use of rotational position of crown  5908  to control scrolling or scaling of a view, it should be appreciated that any other physical state of the crown can be used to control appropriate actions. 
     In some examples, the state of the display  5906  (which can correspond to display  106  described above) can control physical attributes of crown  5908 . For example, if display  5906  shows a cursor at the end of a scrollable list, crown  5908  can have limited motion (e.g., cannot be rotated forward). In other words, the physical attributes of the crown  5908  can be conformed to a state of a user interface that is displayed on display  5906 . The mechanisms for controlling the physical attributes of the crown are described in further detail below. In some examples, a temporal attribute of the physical state of crown  5908  can be used as an input to device  5900 . For example, a fast change in physical state can be interpreted differently than a slow change in physical state. These temporal attributes can also be used as inputs to control physical attributes of the crown. 
     Processor  5902  can be further coupled to receive input signals from buttons  5910 ,  5912 , and  5914  (which can correspond to buttons  110 ,  112 , and  114 , above respectively), along with touch signals from touch-sensitive display  5906 . Processor  5902  can be configured to interpret these input signals and output appropriate display signals to cause an image to be produced by touch-sensitive display  5906 . While a single processor  5902  is shown, it should be appreciated that any number of processors or other computational devices can be used to perform the functions described above. 
       FIG. 60  illustrates an exemplary block diagram of various components of an optical encoder  6004  that can be used to receive crown position information according to examples of the disclosure. The optical encoder  6004  shown in  FIG. 60  may correspond to the encoder  5904  described above, or may be used in conjunction with the encoder  5904  described above. In various electronic devices, rotational and/or axial movement of a component (e.g., a crown) of the electronic device may need to be determined (e.g., the user interface scrolling operations described above for  FIG. 1 ). In such instances, an optical encoder  6004  may be used to detect the rotational movement and the axial movement of the component. For example, an optical encoder  6004  according to examples of the disclosure can include a light source  6018  that shines on a wheel  6016  (also referred to as an encoder wheel) or a shaft of the optical encoder. The wheel  6016  (or shaft) may include an encoding pattern, such as, for example, a collection of light and dark lines that are arranged in a particular sequence or in a particular pattern. In some examples, the wheel  6016  may be integrated with or attached by a shaft to the crown  108  described above. 
     When light from the light source  6018  hits the encoding pattern, the encoding pattern can modulate the light and reflect it onto one or more sensors  6020  associated with the optical encoder. In certain examples, the one or more sensors  6020  may be an array of photodiodes (PD). As light from the light source  6018  is reflected off the wheel  6016 , one or more photodiodes of the photodiode array  6020  can produce a voltage measurement associated with an amount of light received at a given sample time. Once the light is received by the photodiode array  6020  at a given time period, an analog-to-digital circuit  6010  can convert the analog signal received from the photodiode array to a digital signal. The corresponding digital signals can be processed, and a determination may be made as to the direction, speed and/or movement (rotational and/or axial) of the wheel. 
       FIG. 61  illustrates exemplary device  6100  (which can correspond to device  100  above) including an exemplary mechanical input assembly  6108  according to examples of the disclosure. In some examples, device  6100  can include a housing  6102  (which can correspond to housing  116  above). In some examples, a display screen  6104  (which can correspond to display screen  106  above) can be attached to housing  6102  by a gasket  6106 . In some examples, display screen  6104  can be disposed on a cover substrate (which can correspond to cover substrate  1812  above), and the cover substrate can be attached to the housing  6102  by the gasket  6106 . In some examples, gasket  6106  can attach around an exterior edge portion of a bottom surface of the display screen  6104 . In some examples, the gasket  6106  can form a seal for preventing outside air and/or liquid from entering an interior cavity of the housing  6102 . In some examples, gasket  6106  can be a compressible material. In some examples, the gasket  6106  can also be used to perform additional functions. Some of the possible additional functions for gasket  6106  will be described in further detail below. In some examples, a mechanical input assembly  6108  can be physically coupled to the housing  6102  such that a shaft  6112  of the mechanical input assembly passes through the housing and can rotate within the housing. In some examples, a crown  6110  (which can correspond to crown  108  above) portion of the mechanical input assembly  6108  can protrude outside of the housing and provide a user with a mechanical input to device  6100  as described in detail above in  FIGS. 1 and 59-60 . In some examples, the shaft  6112  can be attached to an encoder wheel  6114  (which can correspond to wheel  6016  above) inside of the housing. In some examples, a portion of the encoder wheel  6114  or a protrusion on the encoder wheel can contact a shear plate  6116 . In some examples, the shear plate  6116  can be held in a stationary position within the housing. In some examples, shear plate  6116  can be disposed between mechanical input assembly  6108  and a depressible switch (not shown) for providing an additional input mechanism for the mechanical input assembly. In some examples, the shear plate  6116  can be constructed from a durable material capable of withstanding prolonged friction from rotation of the mechanical input assembly  6108 . In some examples, debris, oils, moisture, or sweat can penetrate spaces between the crown  6110  and the housing  6102 , which can create a conductive connection between the crown and housing. In some examples, a portion of the mechanical input assembly  6108  (e.g., crown  6110 ) can be coated with an insulating material to prevent conductive contact or bridging between conductive portions of the housing  6102  and the mechanical input assembly  6108 . 
     In some examples, device  6100  can be configured to detect the presence of an object (e.g., a finger) touching or hovering near mechanical input assembly  6108  by measuring a self-capacitance with the mechanical input assembly as an electrode. In some examples, an internal electrical contact  6118  can be disposed on the shear plate  6116  such that a conductive portion of the mechanical input assembly  6108  can contact the internal electrical contact. In some examples, the internal electrical contact  6118  can be coupled to a capacitive sense controller  6120 . In some examples, contact between the internal electrical contact  6118  and the mechanical input assembly  6108  can cause some or all of the mechanical input assembly (e.g., conductive portions) to behave as a drive and/or sense electrode. Specifically, the internal electrical contact  6118  can act as a fixed contact point for connecting the mechanical input assembly  6108  (which can be rotated by a user) to drive and/or sense circuitry in the capacitive sense controller  6120  for detecting contact or proximity of an object with the crown  6110 . In some examples, the capacitive sense controller  6120  can also be a controller that can be used to control capacitive touch sensing operations for a touch sensitive display (e.g., touch sensitive display  106  described above). In other examples, the capacitive sense controller  6120  can be a separate controller for controlling capacitive touch sensing operations. In some examples, the capacitive sense controller  6120  can be configured to drive the internal electrical contact  6118  with a drive signal. In some examples, the mechanical input assembly  6108  can be made from a conductive material such that the drive signal couples from the internal electrical contact  6118  to the entire mechanical input assembly. In some examples, portions of the mechanical input assembly  6108  can be conductive while other portions of the mechanical input assembly can be non-conductive. In some examples, portions of the mechanical input assembly  6108  that form a conductive path from the internal electrical contact  6118  can be driven with the drive signal while portions of the mechanical input assembly that do not form a conductive path from the internal electrical contact can be undriven. In some examples, an exterior surface of a non-conductive mechanical input assembly  6108  can be coated with a conductive layer to form the electrode on the mechanical input assembly such that the entire mechanical input assembly can be driven with the drive signal despite the underlying material being non-conductive. Such an approach can reduce the drive signal strength required relative to a mechanical input assembly that is entirely made of metal, for example. In some examples, the internal electrical contact  6118  can also be used to receive sensed signals from the mechanical input assembly  6108  (e.g., self-capacitance sensing using the mechanical input assembly as a contact or proximity sensing electrode or mutual capacitance sensing using the crown  6110  as a sense electrode). In some examples, capacitive sense controller  6120  can detect proximity of an object or contact by an object with crown  6110  based on signals present on internal electrical contact  6118 . 
     In some examples, device  6100  can be a wearable device worn, for example, on a user&#39;s wrist (not shown). In some examples, crown  6110  can be in close proximity to the user&#39;s wrist such that movement of the crown relative to the user&#39;s wrist can be detected by the internal electrical contact  6118 . In some examples, changes in the user&#39;s wrist position relative to crown  6110  (including contact between the user&#39;s wrist and the crown) can generate a self-capacitance signal that can interfere with detection of proximity or contact by other objects, such as a user&#39;s finger. 
     While the above examples describe the internal electrical contact  6118  being disposed on a shear plate  6116 , it is understood that the internal electrical contact can be placed in a different location, as long as the internal electrical contact can be positioned to make electrical contact with a portion of the mechanical input assembly  6108 . In some examples, the internal electrical contact  6118  can be operatively coupled to the mechanical input assembly  6108  without direct electrical contact. For example, the internal electrical contact  6118  can be capacitively coupled to the mechanical input assembly  6108 . In such an arrangement, the capacitance formed between the internal electrical contact  6118  and the mechanical input assembly  6108  can be in series with a capacitance between the mechanical input assembly and an object (e.g., a user&#39;s finger). In some examples, internal electrical contact  6118  can be configured to maintain a consistent spacing with mechanical input assembly  6108  so that the capacitance between the mechanical input assembly and the internal electrical contact remains stable, as changes in the capacitance can modulate the signal driven onto the mechanical input assembly. In some examples, such a non-contact based configuration for driving the mechanical input assembly can improve reliability by reducing both mechanical wear and electromigration of conductive material between the internal electrical contact  6118  and the mechanical input assembly  6108 . 
     In the examples below, where figure components or elements are labeled with the reference numerals  6102 - 6120 , it is understood that the labeled components or elements in the figure being discussed can correspond to components/elements  6102 - 6120  described in  FIG. 61 . More generally, where descriptions of figures below refer to components or elements with reference numerals used in the descriptions of preceding examples of the disclosure, it is understood that the labeled components or elements in the figure being discussed can correspond to the previously discussed components having the same reference numeral and/or variations thereof. 
       FIGS. 62A-62C  illustrate variations of exemplary device  6200  (which can correspond to device  6100  above), that can be used to detect proximity or contact with an object using mutual capacitance sensing between the crown  6110  and one or more touch screen electrodes  6222  according to examples of the disclosure. 
       FIG. 62A  illustrates a cross sectional view of an exemplary device  6200  that can be used to detect proximity or contact of an object to the mechanical input assembly  6108  by utilizing a mutual capacitance touch sensing measurement. In some examples, display screen  6104  can be a touch sensitive display screen and can include touch screen electrodes  6222 . In some examples, touch screen electrodes  6222  can be configured to detect proximity or contact of an object (e.g., a finger or stylus) near or at a display area of display screen  6104 . As described above, the mechanical input assembly  6108  can be configured as an electrode. In some examples, touch screen electrodes  6222  can be further configured in conjunction with the mechanical input assembly  6108  to detect proximity or contact of an object near the crown  6110 . In some examples, a mutual capacitance can be formed between a touch screen electrode  6222  and the crown  6110  portion of the mechanical input assembly  6108  (CSIG_TSC). In some examples, CSIG_TSC can be considered to represent coupling between the mechanical input assembly  6108  and the touch screen electrode  6223  at the edge of display screen  6104  nearest to crown  6110  corresponding to the region located between the touch screen electrode and the crown itself. In some examples, an additional mutual capacitance CSIG_TSE can be considered to represent coupling between the encoder wheel  6114  (which can correspond to wheel  6016  above) and the touch screen electrode  6223 .  FIG. 62B  illustrates an exemplary top view of device  6200  depicting a possible location for touch screen electrode  6223  near the crown. It should be understood that although a 3×3 array of touch screen electrodes  6222  is illustrated, different touch screen electrode arrangements are within the scope of the present disclosure. In addition, although the discussion above describes only a single capacitive coupling (CSIG_TSC) between crown  6110  and screen electrode  6223 , it should be understood that a capacitive coupling can exist between crown  6110  and additional touch screen electrodes  6222 . Similarly, a capacitive coupling can exist between encoder wheel  6114  and additional touch screen electrodes  6222 . In some examples, measuring capacitive coupling values with multiple touch screen electrodes  6222  (and/or  6223 ) can provide additional information about a proximity and/or position of an object relative to the crown  6110  by, for example, comparing relative signal strength received at each of the touch screen electrodes. 
     Returning to  FIG. 62A , in some examples, housing  6102  can be configured to shield electric fields between the encoder wheel  6114  and the touch screen such that only CSIG_TSC is measured. In some examples, touch screen electrode  6223  can be driven with a drive signal and the mechanical input assembly  6108  can be a sense electrode (as described above in  FIG. 61 ). In some examples, internal electrical contact  6118  can transfer the sensed signal from the mechanical input assembly  6108  to capacitive sense controller  6120 . In other examples, the mechanical input assembly  6108  can be driven with a drive signal, and touch screen electrode  6223  can be a sense electrode. In some examples, various control schemes can be utilized to prevent interference between contact and proximity detection for the display screen  6104  and contact and proximity detection for the crown  6110 . In some examples, a single controller can be used to control display screen  6104  and crown  6110  detection operations. In some examples, interference can be prevented by assigning different time slots for contact or proximity detection at the display screen  6104  and the crown  6110 . In some examples, different frequencies can be used to prevent interference. For example, a first frequency can be used for contact and proximity detection for the display screen  6104  and a second frequency can be used for contact and proximity detection for the crown  6110 . In some examples, different pseudo-random noise drive signals can be used to prevent interference between the two types of detection. 
       FIG. 62C  illustrates a top view of a variation of exemplary device  6200  according to examples of the disclosure. In some examples one or more touch screen electrodes  6223  of the display screen  6104  can be divided into multiple sub-electrodes. It should be understood that while the illustration depicts a single electrode  6223  divided into four sub-electrodes in a rectangular pattern, other variations are possible. In some examples, a single electrode can be divided into two sub-electrodes, three sub-electrodes, or more than four sub-electrodes. In some examples, the sub-electrodes can have a non-rectangular shape, including non-uniform sub-electrode shapes. In some examples, multiple electrodes can be divided into sub-electrodes: for example, all electrodes along the side of the device nearest to crown  6110  could be divided into sub-electrodes. In some examples, dividing the electrode  6223  into sub-electrodes can allow additional information about a position of an object relative to the crown  6110  by, for example, comparing relative signal strength received at each of the sub-electrodes. In some examples, it can be advantageous to use sub-electrodes of electrode  6223  because such an arrangement can result in more unique electrode elements in proximity to the crown  6110 . Since the required drive strength of a drive signal on crown  6110  for detecting proximity of an object (e.g., a user&#39;s finger) can depend on the distance between the sense electrodes and the crown, placing additional sense electrodes near the crown can reduce the required drive strength of the drive signal (e.g., relative to measurements using multiple touch screen electrodes  6222 / 6223  described above). Such a reduction of drive strength can have advantages in many design aspects including, but not limited to, reduced power consumption, reduced interference with nearby circuitry, and improved reliability due to lower current densities. 
       FIGS. 63A-63B  illustrate variations of exemplary device  6300  (which can correspond to device  6100  above) that can be used to detect proximity or contact of an object with the mechanical input assembly  6108  by utilizing a gasket sensor electrode  6328  that can be included in a gasket  6106  of the device.  FIG. 63A  illustrates a cross-sectional view of exemplary device  6300  that can include a gasket sensor electrode  6328  in the gasket  6106 . In some examples, the gasket  6106  can include one or more force sensors  6326  that can detect intensity of one or more contacts with display screen  6104 . For example, force sensors  6326  can be used to determine an amount of force applied by a finger to the display screen  6104 . In some examples, the gasket  6106  can include multiple force sensors  6326  (as discussed further below) around the perimeter of the display screen  6104 . In some examples, gasket sensor electrode  6328  can be disposed in gasket  6106  above a portion of the force sensor  6326  near crown  6110 . In some examples, gasket sensor electrode  6328  can be stacked above the force sensors  6326  in the gasket. In some examples, the gasket sensor electrode  6328  can be used for self-capacitance measurement for detecting contact or proximity of an object with the crown  6110 . In some examples, gasket sensor electrode  6328  can be used for mutual capacitance sensing together with mechanical input assembly  6108  analogously to the mutual capacitance sensing with touch sensor electrode  6223  described above in FIGS.  62 A- 62 C. In addition, techniques for avoiding conflicts between touch sensing for display screen  6104  and contact or proximity sensing for crown  6110  described above in  FIGS. 62A-62C  can similarly be applied. 
       FIG. 63B  illustrates a top view of a variation of device  6300  that can include a gasket  6106  that can include four force sensors  6326 A- 6326 D (i.e., one sensor per side of the touch sensitive display screen  6104 ) to detect intensity of a contact and/or multiple simultaneous contacts (e.g., detecting different amounts of force corresponding to each of two fingers contacting the display screen  6104 ). In some examples, gasket  6106  can include multiple force sensors per side of the display screen  6104 . In some examples, gasket sensor electrode  6328  can replace a portion of force sensor  6326 A (i.e., the sensor nearest to crown  6110  of mechanical input assembly  6108 ). In some examples, gasket sensor electrode  6328  can be divided into multiple electrodes to provide a multi-dimensional representation of proximity or contact by an object (as described in reference to  FIG. 62C  above). In some examples, the multi-dimensional representation can include two or more of object proximity, x-axis position, and y-axis position. In some examples, replacing a portion of force sensor  6326 A with gasket sensor electrode  6328  can reduce an effective sense area of force sensor  6326 A. In some examples, a sampling or integration time of force sensor  6326 A can be increased relative to sample or integration times for force sensors  6326 B- 6326 D to compensate for the reduction in area of force sensor  6326 A. In some examples, a signal can be driven onto crown  6110  (as described above) and sense electrode  6328  and can be used as a sense electrode for a mutual capacitance measurement (e.g., a measurement of capacitance CSIG_GSC). In this example, mutual capacitance between crown  6110  and gasket sensor electrode  6328  can be used to detect proximity or contact of an object near the crown  6110  (analogous to the mutual capacitance measurements described above regarding  FIGS. 62A-62C ). In some examples, gasket sensor electrode  6328  can be closer to the crown  6110  than touch screen electrodes  6222  and  6223  on the display panel  6104  (see  FIG. 62 ), and the signal drive strength on crown necessary for mutual capacitance detection of proximity or contact of an object near the crown can be significantly reduced. Such a reduction of drive strength can improve power performance, as well as reducing corrosive effects (e.g., electromigration) of driving a larger (e.g., higher current) signal to drive the mechanical input assembly  6108  with the drive signal. In some examples, drive and sense electrodes can be reversed such that gasket sensor electrode  6328  can be driven with a drive signal while crown  6110  can be a sense electrode. In some examples, a self-capacitance measurement can be performed with gasket sensor electrode  6328  acting as the self-capacitance electrode. A self-capacitance measurement of gasket sensor electrode  6328  can be less susceptible to proximity of a user&#39;s wrist compared to the self-capacitance measurement using crown  6110  as the electrode (described in  FIG. 61  above). This reduced susceptibility to the user&#39;s wrist can be due to a larger distance between the gasket sensor electrode  6328  and the user&#39;s wrist relative to the distance between a user&#39;s wrist and the crown  6110  and/or shielding due to the housing  6102  between the wrist and the gasket sensor electrode. 
       FIGS. 64A-64B  illustrate exemplary control circuitry configurations for coordinating operations of a gasket sensor electrode  6328  and force sensors  6326  included in the gasket  6106  according to examples of the disclosure.  FIG. 64A  illustrates one variation of a control circuitry configuration for coordinating operations of gasket sensor electrode  6328  and force sensors  6326 . In some examples, gasket sensor electrode  6328  and force sensors  6326  can be operated by independent controllers. For example, gasket sensor electrode  6328  can be controlled by a capacitive sense controller  6430  and force sensors  6326  can be controlled by a force controller  6432 . In some examples, capacitive sense controller  6330  can control gasket sensor electrode  6328  and mechanical input assembly  6108  to perform any of the measurements described above in  FIGS. 61-63 . 
       FIG. 64B  illustrates another variation of a control scheme for coordinating operations of gasket sensor electrode  6328  and force sensors  6326 . In some examples, a single force and capacitance sense controller  6434  can be used to control operation of two or more of the force sensors  6326 , the gasket sensor electrode  6328 , and the mechanical input assembly  6108 . In some examples, demultiplexer  6436  can be connected to a drive output of the force and capacitance sense controller  6434  for distributing drive signals to the various circuits. In some examples, control line (CTRL) can be used to connect an output of demultiplexer  6436  connected to the drive signal from the force and capacitance sense controller  6434 . In some examples, an additional buffer amplifier  6438  can be connected to one or more of the demultiplexer  6436  outputs. In some examples, demultiplexer  6436  outputs connected to particularly large loads can be connected to the buffer amplifier  6438 . In some examples, the mechanical input assembly  6108  can present a particularly load, and accordingly the buffer  6438  is illustrated connected to the internal electrical contact  6118  for driving the mechanical input assembly  6108 . Variations of the mechanical input assembly  6108  that can reduce the load of the assembly are discussed below. These reduced load variations of the mechanical input assembly  6108  can potentially be driven without need for the buffer amplifier  6438 . In some examples, separate drive connections can be provided for driving each of the gasket sensor electrode  6328 , force sensors  6326 , and mechanical input assembly  6108  (not shown). In some examples, providing separate drive connections between force and capacitance sense controller  6434  and each element can allow for more flexibility in control how each of the force sensors  6326 , the gasket sensor electrode  6328 , and the mechanical input assembly  6108  can be driven. In some examples, some of the drive connections can have separate connections, while others can be driven by the demultiplexer  6436 . In some examples, the force sensors can be grounded during capacitive sensing operations, and the drive electrode can be grounded during force sensing operations. In addition to the drive signal connections described above, sense connections connected to the force and capacitance sense controller  6434  can be included for sensing outputs of the sensors and electrodes described above. In some examples, force and capacitance sense controller  6434  can control gasket sensor electrode  6328  and mechanical input assembly  6108  to perform any of the contact or proximity measurements described above in  FIGS. 61-63 . Similarly, in some examples, techniques for avoiding conflict between measurements described above in  FIGS. 61-63  can analogously be applied to avoid conflicts between force sensing and contact or proximity sensing. 
       FIGS. 65A-65B  illustrate exemplary variations of electrode configurations for mechanical input assembly  6108  according to examples of the disclosure. As described above in connection with  FIG. 61 , in some examples, mechanical input assembly  6108  can be formed completely from a conductive material, or can have a non-conductive core with an exterior surface completely surrounded or plated with a conductive material.  FIG. 65A  illustrates a side view of an exemplary mechanical input assembly  6108  configuration wherein a reduced portion of the surface of the mechanical input assembly can be covered by a conductive material. The conductive material can include routing traces  6507  (e.g.,  6507 A- 6507 C) and conductive pads  6509  (e.g.,  6509 A- 6509 C). It is understood that one or more additional routing traces  6507  and conductive pads  6509  can be disposed on the far side of the mechanical input assembly  6108  as well. In some examples (as illustrated), the routing traces can be routed along an exterior surface of the mechanical input assembly  6108 , following any contours of the mechanical input assembly surface, and can provide routing from a first distal end of the mechanical input assembly near the shear plate  6116  toward the conductive pads  6509  located at an opposite distal end of the mechanical input assembly at crown  6110 . In some examples, the routing traces can be routed through the interior of mechanical input assembly  6108 . In some examples, the conductive pads  6509 A- 6509 C can be disposed around a perimeter of crown  6110  at a top side, near side, and bottom side, respectively. In some examples, routing traces  6507 A- 6507 C can be electrically connected together near the shear plate  6116  such that conductive pads  6509 A- 6509 C can also be electrically connected together. In some examples, reducing the amount of conductive material on the mechanical input assembly  6108  (compared to a solid metal or fully metal plated mechanical input assembly) can reduce an amount of current required to drive a correspondingly smaller load. In some examples, a high current between internal electrical contact  6118  and the mechanical input assembly  6108  can result in electromigration of conductive material between the internal electrical contact and the mechanical input assembly. Since internal electrical contact  6118  can experience significant mechanical stresses due to friction of rotation caused by contact with mechanical input assembly  6108 , reducing the electromigration of conductive material can be useful in extending device life. In addition, in some examples, reducing an amount of conductive material on the mechanical input assembly  6108  can reduce manufacturing costs. As explained above, coupling of a drive signal between internal electrical contact  6118  and conductive pads  6509  on crown  6110  can be achieved through conductive (e.g., direct contact) or non-conductive (e.g., capacitive) coupling. In some examples, the exterior of the crown  6110 , including conductive pads  6509 , can be coated with a non-conductive material to shield the conductive pads from the user and the environment. 
       FIG. 65B  illustrates a side view of a further variation of electrode configurations for mechanical input assembly  6108  according to examples of the disclosure. In some examples, conductive material can be disposed on the mechanical input assembly surface to form multiple conductive pads  6511  (e.g., conductive pads  6511 A-C) that can be electrically isolated from each other. For example, routing traces  6507 A- 6507 C (which can correspond to routing traces  6507 A- 6507 C in  FIG. 65A ) can provide routing between the conductive pads  6511 A-C on the crown  6110  and the opposite distal end of the mechanical input assembly  6108  near the shear plate  6116 . In some examples, routing traces  6507  can be routed along an exterior surface of the mechanical input assembly  6108 , and in some examples, routing traces can be routed internally to the mechanical input assembly. As illustrated, the traces  6507 A- 6507 C can be electrically isolated from one another by physically separating the traces. In some examples, internal electrical contact  6118  can be positioned on shear plate  6116  such that the internal electrical contact only couples to a subset of the routing traces  6507 A- 6507 C at any time, and consequently only couples to the subset of corresponding conductive pads  6511 A-C on the crown  6110 . In some examples, portions of the shear plate  6116  can be coated with a non-conductive material to avoid conductively connecting routing traces  6507 A- 6507 C together. The conductive pads  6511 A-C can be disposed around a perimeter of crown  6110  at a top side, near side, and bottom side, respectively. In the illustrated example, routing trace  6507 A is shown proximate to internal electrical contact  6118 , and in this position conductive pad  6511 A can be operatively coupled to the internal electrical contact. In some examples, a pad (not shown) can also be placed at the end of the routing traces  6507  near the shear plate  6116  to increase the area for coupling with the internal electrical contact  6118 . As the crown is rotated, the routing traces  6507  can be arranged such that one or more conductive pads  6511  are always coupled to the internal electrical contact  6118 . For example, rotation of the crown could move the routing trace  6507 A in the illustration away from the internal electrical contact  6118 , and instead bring the routing trace  6507 B proximate to the internal electrical contact, thus coupling conductive pad  6511 B to the internal electrical contact and uncoupling conductive pad  6511 A. In this configuration, the conductive pad (or pads)  6511  coupled to the internal electrical contact  6118  can be driven with a drive signal from the capacitive sense controller  6430  and/or can be coupled to sense circuitry for detecting contact or proximity of an object to the mechanical input assembly as described above in  FIGS. 61-63 . 
     As explained above, coupling of a signal between internal electrical contact  6118  and routing traces  6507  (and corresponding conductive pads  6511  on crown  6110 ) can be achieved through conductive (e.g., direct contact) or non-conductive (e.g., capacitive) coupling. In some examples, the routing traces  6507  can be shielded to reduce stray capacitances and maintain a consistent capacitance of the routing traces (and corresponding conductive pads  6511 ) coupled to the internal electrical contact  6118  as the crown rotates. In some examples, the shielding for routing trace  6507  can be a grounded shield. In some examples, a portion of shear plate  6116  that contacts the mechanical input assembly can provide a ground connection to the mechanical input assembly. In some examples, a portion of mechanical input assembly  6108  (e.g. the central shaft) can be coupled to a device chassis (e.g., housing  116  of device  100  above) for providing a ground connection. In some examples, routing traces  6507  can be disposed with a small area (e.g, by providing narrow traces) to minimize an amount of stray capacitive coupling affecting signals coupled onto the routing traces. 
     In some examples, the variation of the electrode configuration described above can be utilized to perform self-capacitance sensing (as described in  FIG. 61  above). In some examples, the driven conductive pads  6511  can be configured such that only the conductive pads positioned away from the user&#39;s wrist will be activate (as described above). This configuration can reduce sensitivity of a self-capacitance measurement to proximity or contact of a user&#39;s wrist which can interfere with detection of contact or proximity of an object with the crown  6110 . As noted above, in some examples, the exterior of the crown  6110 , including conductive pads  6511 , can be coated with a non-conductive material to shield the conductive pads from the user and the environment. 
       FIG. 66  illustrates exemplary capacitive couplings between crown  6110  of device  6600  (which can correspond to device  6300 ) and an object in contact or in proximity with crown  6110  according to examples of the disclosure. In some examples, a mutual capacitance CSIG can form between a crown  6110  and gasket sensor electrode  6328 . In some examples, the crown  6110  can be a drive electrode, and the gasket sensor electrode  6328  can be a sense electrode. In some examples, the crown  6110  can be the sense electrode and the gasket sensor electrode  6328  can be the drive electrode. In some examples, a finger-to-sense capacitance (CFS) can form between a finger  6640  and the sense electrode. In some examples, a finger-to-drive capacitance (CFD) can form between the finger  6640  and the drive electrode. In some examples, mutual capacitance touch detection is performed by driving the drive electrode with a stimulation (or drive) signal, and measuring a resulting sense signal at the sense electrode due to the capacitive coupling between the drive and sense electrode. In some examples, when there are no objects in proximity or contact with the device  6600 , the capacitive coupling between drive and sense electrodes can be expressed as a capacitance CSIG. In some examples, when a grounded object (such as finger  6640  of a grounded user) is in proximity or contact with the crown  6110 , a portion of the coupling electric field between the drive and sense electrodes can be disrupted (i.e., reduced), and the reduction can be represented by a capacitance change ΔCSIG. This capacitance change ΔCSIG can be caused by current or charge from the electric field lines being shunted through the touching finger to ground. As a result, the proximity or contact of finger  6640  can reduce an amount of coupling between the drive and sense electrode, and accordingly reduce the resulting measured signal. In other words, proximity or contact of an object can be indicated by an apparent reduction in CSIG. Touch signals representative of the capacitance change ΔCSIG can be transmitted by the sense lines  102  to sense circuitry for processing. 
     In some examples, when an ungrounded user&#39;s finger  6640  (or other ungrounded object) is in proximity or contact with the crown  6110 , current or charge from the electric field lines coupling from the drive electrode can be transmitted by the finger to the sense electrode rather than being shunted to ground. As illustrated in  FIG. 9 , capacitors CFS and CFD can form a signal path through the finger  6640  between the drive electrode and sense electrode. The drive signal transmission to the sense electrode through this signal path can be represented as capacitance Cneg. Thus, in some examples, proximity or contact of ungrounded finger  6640  can reduce CSIG by an amount ΔCSIG−Cneg. In some examples, the capacitance Cneg can result in erroneous touch signals representative of the capacitance change corresponding to the proximity or contact of the finger  6640  with the crown  6110 . In some examples, CSIG can be larger than Cneg, and the sensed signals can still generally indicate proximity or contact by the finger  6640 . In some examples, Cneg can be greater than or equal to ΔCSIG, and the sensed signals can indicate no change or even an apparent increase in the capacitance CSIG (i.e., an apparent increase in the coupling capacitance between the drive and sense electrodes). In some examples, the sensed signals may indicate no touch or a negative touch despite the finger  6640  being positioned close to the crown  6110 . Such a result can occur when the ungrounded finger  6640  is located between the drive and sense electrodes, and in close proximity and/or contact with the drive and sense electrodes. When the poorly grounded finger  6640  is in close proximity and/or contact with the drive and sense electrodes, both CFS and CFD can be large, and Cneg can correspondingly also be large. As a result, touch signals indicative of sensed capacitance can appear to increase, rather than decrease as described in the example above for grounded finger  6640 , and thus indicate a “negative pixel” condition. Device  6600  can be configured to address this potential “negative pixel” condition as will be described in more detail below. 
       FIGS. 67A and 67B  illustrate exemplary operation of self-capacitance and mutual capacitance measurements for detecting an object in proximity or contact with a crown  6110  of device  6700  (which can correspond to device  6100  above) according to examples of the disclosure.  FIG. 67A  illustrates an exemplary coordinate system for relating position of an object such as a user&#39;s finger  6640  relative to the device  6700 . As illustrated, an exemplary x=0 position can run vertically through the center of crown  6110  (which can be a portion of mechanical input assembly  6108  described above) protruding from one side of the device  6700 . Positive x values can represent positions to the right of the center of crown  6110  while negative x values can represent positions to the left of the center of the crown. In some examples, gasket sensor electrode  6328 , which can be located at a negative x position, can be used for performing self-capacitance measurements and for performing mutual capacitance measurements with the crown  6110  as described above. 
       FIG. 67B  illustrates exemplary signal to noise ratio (SNR) values for different object positions along the x-direction that can result from self-capacitance and mutual capacitance sensing as described above regarding  FIG. 67B . The x-axis is presented on a dimensionless scale as the particular dimensions and measurement values can vary among various implementations of the present disclosure. It should be understood that the graphs presented in  FIG. 67B  are merely exemplary and for the purpose of illustration. The dashed line (labeled Target SNR) can represent a threshold SNR that can be used to detect a proximity or contact of an object with a crown (e.g., crown  6110  above). While a single target SNR threshold is illustrated, it should be understood that different SNR thresholds can be used for each of mutual capacitance sensing and self-capacitance sensing. In some examples, the illustrated dotted line can represent a SNR for mutual capacitance sensing relative to a position of an object along the x-axis (e.g., finger  6640  above). In some examples, as the finger  6640  approaches device  6700  from a positive value of x&gt;5, the SNR value can gradually increase as the finger begins to disrupt fringing electric fields between drive and sense electrodes, resulting in a signal ΔCSIG as described above in  FIG. 66 . In some examples, if the finger  6640  is ungrounded or poorly grounded, as the finger nears the crown, a negative pixel condition can occur as described above in  FIG. 66 . In the example graph, the SNR of the mutual capacitance measurement reaches a maximum SNR value at approximately x=2. In some examples, as the finger  6640  continues to move in the negative x-axis direction, the negative pixel condition can gradually become larger such that the SNR can become zero and eventually become increasingly negative for x&lt;0. Accordingly, when finger  6640  is poorly grounded, a mutual capacitance measurement may only be able to detect presence of the finger for positions x&gt;1.1 (i.e., where the dotted line crosses the target SNR). 
     In some examples, the solid line can represent a SNR for self-capacitance sensing (e.g., as described in  FIGS. 61 and 63 ). In some examples, as the finger or object  6640  approaches the device  6700  from the positive x-axis direction, the self-capacitance measurement SNR can slowly climb, until eventually reaching the target SNR for detecting the finger at an x-axis position of approximately 0.8. In some examples, as the finger  6640  continues to move in the negative x-axis direction, the SNR of the self-capacitance measurement can continue to increase, in contrast to the mutual capacitance measurement described above. In some examples, this self-capacitance measurement profile can be present even if the finger  6640  is poorly grounded. Thus, the self-capacitance measurement in the exemplary graph can detect the presence of the poorly grounded finger  6640  in locations where the mutual capacitance measurement is unable to detect the poorly grounded finger due to a negative pixel condition. Accordingly, a person of ordinary skill can recognize that a measurement technique that includes a mutual capacitance measurement and self-capacitance measurement can potentially detect presence of a poorly grounded finger  6640  for a larger range of finger positions along the x-axis. 
     It should be noted, as further illustrated in the exemplary graphs, there can be a region of x values between the detection range of the self-capacitance measurement (i.e., x&lt;0.8) and the detection range of the mutual capacitance measurement (i.e., 1.1&lt;x&lt;3) that can be considered a “dead-zone” for detection of the poorly grounded finger (i.e., dead zone 0.8&lt;x&lt;1.1). In some examples, the dead-zone can be eliminated by lowering the target SNR to the SNR value where the SNR of the mutual capacitance measurement and the SNR of the self-capacitance measurement intersect (i.e., x=1). In some examples, a similar effect can be achieved by increasing the SNR of either of the mutual capacitance measurement, the self-capacitance measurement, or both. 
       FIG. 68  illustrates an exemplary process for performing proximity or contact measurement utilizing self-capacitance and mutual capacitance measurements according to examples of the disclosure. It should be noted that any of the exemplary devices or configurations above or any number of variations of or alternatives to the devices or configurations above that are capable of performing a mutual capacitance measurement and a self-capacitance measurement to determine a proximity or contact of a proximate object can be suitable for implementing process  6800 . At step  6802 , process  6800  can perform a mutual capacitance measurement for sensing proximity or contact of a proximate object to a rotatable mechanical input of a device (e.g., mutual capacitance sensing described in  FIGS. 62-63 ). At step  6804 , process  6800  can determine whether an object was detected by the mutual capacitance measurement. As described above, in some examples, a negative pixel condition can result in no object being detected. If it is determined that an object was not detected during the mutual capacitance measurement, process  6800  can proceed to step  6806 . At step  6806 , process  6806  can perform a self-capacitance measurement (e.g., a self-capacitance measurement of mechanical input assembly  6118  or a self-capacitance measurement of a gasket sensor electrode  6328  as described above in  FIGS. 61 and 63 ). At step  6808 , process  6800  can determine whether an object was detected by the self-capacitance measurement. If an object is detected at either step  6804  or step  6808 , process  6800  can report that an object was detected and return to step  6802 . In some examples, if an object is detected at step  6808 , process  6800  can further report that the object is potentially a poorly grounded object, and that a negative pixel condition may be present as described in greater detail above. 
       FIG. 69  illustrates an example computing system  6900  (which can correspond to one or more components of device  200  illustrated in  FIG. 2  above) for implementing detection of proximity or contact of an object with a crown of a device according to examples of the disclosure. Computing system  6900  can be included in, for example, device  100  above or any mobile or non-mobile computing device and/or wearable or non-wearable device that includes a rotary input (e.g., crown  6110  described above). Computing system  6900  can include a touch sensing system including one or more touch processors  6902 , touch controller  6906  and touch screen  6904 . Touch screen  6904  can be a touch screen adapted to sense touch inputs, as described in the disclosure. Touch controller  6906  can include circuitry and/or logic configured to sense touch inputs on touch screen  6904 . In some examples, touch controller  6906  and touch processor  6902  can be integrated into a single application specific integrated circuit (ASIC). 
     Computing system  6900  can also include host processor  6928  for receiving outputs from touch processor  6902  and performing actions based on the outputs. Host processor  6928  can be connected to program storage  6932 . For example, host processor  6928  can contribute to generating an image on touch screen  6904  (e.g., by controlling a display controller to display an image of a user interface (UI) on the touch screen), and can use touch processor  6902  and touch controller  6906  to detect one or more touches on or near touch screen  6904 . Host processor  6928  can also contribute to sensing and/or processing mechanical inputs  6908  (which can correspond to crown  6110  described above) as described in the disclosure. The inputs from touch screen  6904  and/or mechanical inputs  6908  can be used by computer programs stored in program storage  6932  to perform actions in response to the touch and/or mechanical inputs. For example, touch inputs can be used by computer programs stored in program storage  6932  to perform actions that can include moving an object such as a cursor or pointer, scrolling or panning, adjusting control settings, opening a file or document, viewing a menu, making a selection, executing instructions, operating a peripheral device connected to the host device, answering a telephone call, placing a telephone call, waking a device from a screen-off state in response to a user&#39;s contact, turning off touch screen  6904  in response to a user&#39;s palm placed over the screen, and other actions that can be performed in response to touch inputs. Mechanical inputs  6908  can be used by computer programs stored in program storage  6932  to perform actions that can include changing a volume level, locking the touch screen, turning on the touch screen, taking a picture, and other actions that can be performed in response to mechanical inputs. Host processor  6928  can also perform additional functions that may not be related to touch and/or mechanical input processing. In some examples, touch processor  6902  may be connected to separate optional program storage  6934 . In some examples, mechanical inputs  6908  can be connected directly to touch processor  6902 . In some examples, touch processor  6902  can process inputs from touch screen  6904  and/or mechanical inputs  6908  by computer programs stored in program storage  6934  to perform actions in response to the touch and/or mechanical inputs (as described above). In some examples, touch processor  6902  can also perform additional functions that may not be related to touch and/or mechanical input processing. 
     Note that one or more of the functions described above can be performed by firmware stored in memory in computing system  6900  and executed by touch processor  6902 , or stored in program storage  6932  and executed by host processor  6928 . The firmware can also be stored and/or transported within any non-transitory computer-readable storage medium for use by or in connection with an instruction execution system, apparatus, or device, such as a computer-based system, processor-containing system, or other system that can fetch the instructions from the instruction execution system, apparatus, or device and execute the instructions. In the context of this document, a “non-transitory computer-readable storage medium” can be any medium (excluding signals) that can contain or store the program for use by or in connection with the instruction execution system, apparatus, or device. The computer-readable storage medium can include, but is not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus or device, a portable computer diskette (magnetic), a random access memory (RAM) (magnetic), a read-only memory (ROM) (magnetic), an erasable programmable read-only memory (EPROM) (magnetic), a portable optical disc such a CD, CD-R, CD-RW, DVD, DVD-R, or DVD-RW, or flash memory such as compact flash cards, secured digital cards, USB memory devices, memory sticks, and the like. 
     The firmware can also be propagated within any transport medium for use by or in connection with an instruction execution system, apparatus, or device, such as a computer-based system, processor-containing system, or other system that can fetch the instructions from the instruction execution system, apparatus, or device and execute the instructions. In the context of this document, a “transport medium” can be any medium that can communicate, propagate or transport the program for use by or in connection with the instruction execution system, apparatus, or device. The transport medium can include, but is not limited to, an electronic, magnetic, optical, electromagnetic or infrared wired or wireless propagation medium. 
     Thus, according to the above, some examples of the disclosure are directed to an electronic device comprising: a rotational input element having a near end and a far end; a touch sensor, the touch sensor comprising: a transmit circuit operatively coupled to the rotational input element and configured to send an acoustic wave through the rotational input element such that the acoustic wave reflects off of the far end of the rotational input element; a receiver circuit operatively coupled to the rotational input element and configured to measure one or more parameters of the acoustic wave after the acoustic wave has reflected off of the far end of the rotational input element; and a processor operably coupled to the touch sensor and configured to: detect one or more touch events based on the one or more parameters measured by the receiver circuit; and perform an action based on the one or more touch events detected. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the electronic device is a wearable device and the rotational input element is a crown. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the transmit circuit includes an acoustic transducer. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the receiver circuit includes an acoustic transducer. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the transmit circuit includes an acoustic transducer, the receiver circuit includes the same acoustic transducer, and the touch sensor further comprises a switching network configured to selectively couple the acoustic transducer to the transmit circuit and the receiver circuit. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the receiver circuit is operatively coupled to the rotational input element nearer to the near end than the transmit circuit. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the rotational input element is formed of at least a first acoustically conductive material. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the rotational input element includes a first acoustic channel coupled to the transmit circuit and terminating at the far end of the rotational input element, wherein the first acoustic channel comprises: a first material having a first acoustic conductivity; a second material having a second acoustic conductivity encircling the first material along a length of the acoustic channel. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the first acoustic conductivity is greater than the second acoustic conductivity. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the first material of the first acoustic channel has a circular cross-sectional shape and the second material of the first acoustic channel has a hollow cylindrical cross-sectional shape. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the first acoustic channel is coupled to the transmit circuit at the first material. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the first acoustic channel is coupled to the receiver circuit. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the device further comprises: a second acoustic channel, wherein the second acoustic channel is coupled to the receiver circuit. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the device further comprises: a second acoustic channel, wherein the second acoustic channel terminates a different area of the far end of the rotational input element than the first acoustic channel. 
     Additionally or alternatively to one or more of the examples disclosed above, in some examples, the second acoustic channel is coupled to a second transmit circuit. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the rotational input element is divided along a length of the rotational input element into a plurality of segments, wherein each segment is acoustically conductive and each segment is separated from each adjacent segment by an acoustically insulating material. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the device further comprises each segment is coupled to one of a plurality of transmit circuits. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the device further comprises each segment is coupled to one of a plurality of receiver circuits. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the transmit circuit includes a mechanical hammer configured to send the acoustic wave by striking the rotational input element. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the acoustic wave includes a pulse wave. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the parameters of the acoustic wave include an amplitude of the acoustic wave. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the parameters of the acoustic wave include a delay measurement between a first time when the transmit circuit sends the acoustic wave and a second time when the receiver circuit receives the wave. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the transmit circuit is further configured to successively send a plurality of acoustic waves, each having a different frequency, through the rotational input element. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the device further comprises the receiver circuit is further configured to measure one or more parameters of the plurality of acoustic wave and the processor is further configured to detect one of the one or more touch events based on the one or more parameters of more than one of the plurality of acoustic waves. 
     Some examples of the disclosure are directed to a method of detecting one or more touch events on a rotational input element comprising: sending an acoustic wave through the rotational input element such that the acoustic wave reflects off of a far end of the rotational input element; measuring one or more parameters of the acoustic wave after the acoustic wave has reflected off of the far end of the rotational input element; determining whether a touch event has occurred based on the one or more parameters of the acoustic wave. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the rotational input element is a crown. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the acoustic wave is sent through the rotational input element using an acoustic transducer. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the one or more parameters of the acoustic wave are measured using an acoustic transducer. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the acoustic wave is sent through the rotational input element using an acoustic transducer coupled to a transmit circuit, and after sending an acoustic wave through the rotational input element, selectively coupling the acoustic transducer to a receiver circuit, and measuring the one or more parameters of the acoustic wave using the receiver circuit. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the receiver circuit is operatively coupled to the rotational input element nearer to the near end than the transmit circuit. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the acoustic wave reflects off of the far end of the rotational input element at a first area, and the method further comprising: sending a second acoustic wave through the rotational input element such that the acoustic wave reflects off of the far end of the rotational input element at a second location; measuring one or more parameters of the second acoustic wave after the acoustic wave has reflected off of the far end of the rotational input element; determining whether the touch event has occurred at the first area of the rotational input element based on the one or more parameters of the acoustic wave, and determining whether a second touch event has occurred at the second area of the rotational input element based on the one or more parameters of the second acoustic wave. Additionally or alternatively to one or more of the examples disclosed above, in some examples, sending the acoustic wave through the rotational input element includes striking the rotational input element with a mechanical hammer. Additionally or alternatively to one or more of the examples disclosed above, in some examples, measuring the one or more parameters of the acoustic wave includes measuring an amplitude of the acoustic wave. Additionally or alternatively to one or more of the examples disclosed above, in some examples, measuring the one or more parameters of the acoustic wave includes measuring a shape of the acoustic wave. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the method further comprises: successively sending a plurality of acoustic waves, each having a different frequency, through the rotational input element; measuring one or more parameters of the plurality of acoustic waves; and determining one of the one or more touch events based on the one or more parameters of more than one of the plurality of acoustic waves. 
     Some examples of the disclosure are directed to an electronic device comprising: a rotational input element having a near end and a far end; a touch sensor, the touch sensor comprising: a transmit circuit operatively coupled to the rotational input element and configured to cause a vibration of the rotational input element; a receiver circuit operatively coupled to the rotational input element and configured to measure one or more parameters of the vibration; and a processor operably coupled to the touch sensor and configured to: detect one or more touch events based on the one or more parameters measured by the receiver circuit; and perform an action based on the one or more touch events detected. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the electronic device is a wearable device and the rotational input element is a crown. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the transmit circuit includes an acoustic transducer. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the receiver circuit includes an acoustic transducer. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the transmit circuit includes a rotating mass. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the transmit circuit includes an electromagnet configured to emit electromagnetic waves, thereby vibrating the rotational input element. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the receiver circuit comprises an optical sensor. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the receiver circuit comprises an accelerometer. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the rotational input element is divided along a length of the rotational input element into a plurality of segments, wherein each segment is acoustically conductive and each segment is separated from each adjacent segment by an acoustically insulating material. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the device further comprises each segment is coupled to one of a plurality of transmit circuits. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the device further comprises each segment is coupled to one of a plurality of receiver circuits. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the parameters of the vibration include an amplitude and a frequency of the vibration. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the transmit circuit is further configured to cause a plurality of vibrations of the rotational input element, each of the vibrations of the plurality of vibrations having a different frequency. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the device further comprises the receiver circuit is further configured to measure one or more parameters of the plurality of vibrations and the processor is further configured to detect one of the one or more touch events based on the one or more parameters of more than one of the plurality of vibrations. 
     Some examples of the disclosure are directed to a method of detecting one or more touch events on a rotational input element comprising: vibrating the rotational input element at a vibration; measuring one or more parameters of the vibration of the rotational input element; determining whether a touch event has occurred based on the one or more parameters of the vibration. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the rotational input element is a crown. Additionally or alternatively to one or more of the examples disclosed above, in some examples, vibrating the rotational input element includes rotating a mass. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the one or more parameters of the vibration are measured using an acoustic transducer. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the one or more parameters of the vibration are measured using an accelerometer Additionally or alternatively to one or more of the examples disclosed above, in some examples, vibrating the rotational input element includes emitting electromagnetic waves from an electromagnet. Additionally or alternatively to one or more of the examples disclosed above, in some examples, measuring the one or more parameters of the vibration includes using a receiver circuit including an optical sensor. Additionally or alternatively to one or more of the examples disclosed above, in some examples, measuring the one or more parameters of the vibration includes measuring an amplitude of the vibration. Additionally or alternatively to one or more of the examples disclosed above, in some examples, measuring the one or more parameters of the vibration includes measuring a frequency of the vibration. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the method comprises: successively vibrating the rotational input element with a plurality of vibrations, each having a different frequency; measuring one or more parameters of the plurality of vibrations; and detecting one of the one or more touch events based on the one or more parameters of more than one of the plurality of vibrations. 
     Some examples of the disclosure are directed to an apparatus comprising: a housing having a lower surface and a side surface; a cover material coupled to the housing and including an outer surface and an inner surface; and a proximity sensor formed within the housing and the cover material, the proximity sensor and cover material configured for generating a field of view encompassing a first area adjacent to the outer surface of the cover material. Additionally or alternatively to one or more of the examples disclosed above, in some examples, at least a portion of the first area encompassed by the field of view is not directly above the cover material. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the inner surface of the cover material has a flat portion having a plane extending in a first direction. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the first area encompassed by the field of view includes an area adjacent to the side surface in the first direction. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the device further comprises: a crown; wherein the field of view includes an area above the crown in a direction orthogonal to the plane of the flat portion. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the inner surface of the cover material has a curved portion, and wherein the field of view passes through the curved portion. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the proximity sensor is mounted normal to a first angle with respect to the plane of the flat portion, and the field of view of the proximity sensor beyond the outer surface of the cover material is centered about a second angle with respect to the plane of the flat portion, different from the first angle. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the difference between the first angle and the second angle is in a range of 10 degrees and 60 degrees. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the device further comprises: on the inner surface of the cover material, an opaque mask having one or more apertures, wherein the field of view of the proximity sensor passes through the one or more apertures. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the device further comprises: an optical filter configured to pass a first wavelength range of light and block a second wavelength range of light, different from the first wavelength range; wherein the optical filter is positioned, at least in part, in the apertures of the opaque mask and the field of view of the proximity sensor passes through the optical filter. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the device further comprises: a processor capable of receiving data from the proximity sensor; determining whether an object is present in the field of view of the proximity sensor; performing a first operation if the object is not touching the crown; and performing a second operation, different from the first, if the object is touching the crown. Additionally or alternatively to one or more of the examples disclosed above, in some examples, performing the first operation wakes the device from a sleep mode. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the device is a wearable device. 
     Some examples of the disclosure are directed to a device comprising: a cover material; and a proximity sensor including a light emitter, wherein: the proximity sensor is mounted normal to a first angle with respect to a plane, a light path of the light emitter is initially about the first angle and is refracted through the cover material at a second angle, different from the first angle. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the difference between the first angle and the second angle is in a range of 10 degrees and 60 degrees. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the light path passes through an optical filter configured to pass light of a same wavelength as the light path and block light of a different wavelength as the light path. 
     Some examples of the disclosure are directed to a method comprising: emitting a light from a light emitter; refracting the emitted light through a cover material of a device; determining an amount of the emitted light reflected to a photodetector; performing a first operation if the amount of reflected emitted light is a first value; and performing a second operation if the amount of reflected emitted light is a second value different from the first value. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the first value is determined when an object is within a distance of the device, but is not touching the device. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the distance is in a range between 1 mm and 100 mm. Additionally or alternatively to one or more of the examples disclosed above, in some examples, performing the first operation wakes the device from a sleep mode. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the second value is determined when an object is touching the device. Additionally or alternatively to one or more of the examples disclosed above, in some examples, performing the second operation displays a contextual message on a display. Additionally or alternatively to one or more of the examples disclosed above, in some examples, performing the second operation selects an item on a display. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the method further comprises: after performing the first operation, determining an amount of the emitted light reflected to the photodetector; and performing a third operation if the amount of reflected emitted light is a third value. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the method further comprises: if the third value is greater than or equal to the second value, performing the third operation performs the second operation. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the method further comprises: if the third value is less than the second value and greater than or equal to the first value, performing the third operation maintains the device in a ready mode. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the method further comprises: If the third value is less than the first value, the third operation comprises putting the device into a sleep mode. Additionally or alternatively to one or more of the examples disclosed above, in some examples: emitting the light comprises emitted the light at different predetermined pulse frequencies over time; and determining the amount of the emitted light reflected to the photodetector comprises only considering light received at one or more of the predetermined pulse frequencies. 
     Some examples of the disclosure are directed to a non-transitory computer-readable storage medium having computer-executable instructions which, when executed by one or more computer processors, cause the one or more computer processors to: emit a light from a light emitter; determine an amount of the emitted light reflected to a photodetector; perform a first operation if the amount of reflected emitted light is a first value; and perform a second operation if the amount of reflected emitted light is a second value different from the first value; wherein the emitted light is refracted through a cover material of a device. 
     Some examples of the disclosure are directed to a proximity sensor comprising: a light emitter, an emitter lens, a plurality of light detectors each aligned with the light emitter in a first direction, a detector lens, and a processor capable of: determining a centroid location using respective amplitudes detected by one or more of the plurality of light detectors, determining a distance of an object to the proximity sensor in a second direction based on the centroid location, the second direction being orthogonal to the first direction. Additionally or alternatively to one or more of the examples disclosed above, in some examples, two or more light detectors of the plurality of light detectors each have respective fields of view which overlap with one another. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the centroid location is determined based on a particular light detector of the plurality of light detectors which has an amplitude larger than that of any other of the plurality of light detectors. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the centroid location is determined by interpolating the respective amplitudes detected by the one or more of the plurality of light detectors. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the proximity sensor further comprises: a second plurality of light detectors, each of the second plurality of light detectors aligned with one another in the first direction, and the first and second plurality of light detectors collectively forming a two-dimensional array of light detectors. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the centroid location is determined in the first direction and a third direction orthogonal to both the first direction and the second direction. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the processor is further capable of determining a shape of the light detected by the plurality of light detectors. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the distance of the object determined by the processor can be in a range of 0 millimeters to 100 millimeters. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the proximity sensor is in a wearable device including a crown, and the determined distance is from the crown to the object. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the proximity sensor is under a cover of the wearable device. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the proximity sensor further comprises an optical filter configured to pass light of a same wavelength as light emitted by the light emitter and block light of a different wavelength as the light emitted by the light emitter. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the emitter lens is a collimating lens and the detector lens is a converging lens. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the proximity sensor is incorporated into an electronic device. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the processor is further capable of performing an operation based on whether the distance of the object meets a threshold. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the electronic device is a wearable device. 
     Some examples of the disclosure are directed to a method comprising: emitting light from a light emitter through an emitter lens, receiving reflected light originating from the light emitter through a detector lens, detecting respective amplitudes of the received reflected light at each of a plurality of light detectors, determining a centroid location of the received reflected light based on the respective amplitudes of each of the plurality of light detectors, and determining a presence of an object based on the centroid location. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the reflected light is reflected off of the object. Additionally or alternatively to one or more of the examples disclosed above, in some examples, determining the presence of the object based on the centroid location comprises determining a distance of the object from a device. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the presence of the object based on the centroid location further comprises determining that the object is present if the distance meets a first threshold. Additionally or alternatively to one or more of the examples disclosed above, in some examples, determining the presence of the object based on the centroid location further comprises determining that the object is not present if the distance meets a second threshold. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the centroid location is determined based on a light detector of the plurality of light detectors which has an amplitude larger than that of any of the remaining plurality of light detectors. Additionally or alternatively to one or more of the examples disclosed above, in some examples, determining the centroid location comprises interpolating the respective amplitudes detected by the plurality of light detectors. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the centroid location is determined in a first and second direction, where the second direction is orthogonal to the first direction. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the method further comprises: determining a shape based on the respective amplitudes detected by the plurality of light detectors, and determining characteristics of the object based on the determined shape. Additionally or alternatively to one or more of the examples disclosed above, in some examples, emitting light from the light emitter through the emitter lens comprises collimating the light from the light emitter; and detecting light through the detector lens further comprises converging light from the reflected light originating from the light emitter. 
     Some examples of the disclosure are directed to a proximity sensor comprising: a light emitter, a first light detector aligned with the light emitter in a first direction and configured to receive a first amount of light from the light emitter, a second light detector aligned with the light emitter in the first direction and configured to receive a second amount of light from the light emitter, wherein a distance of an object in a second direction is determined using a ratio of the first amount of light and the second amount of light, the second direction being orthogonal to the first direction. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the first light detector is nearer to the light emitter than the second light detector is to the light emitter in the first direction. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the first light detector is nearer to the light emitter than the first light detector is to the second light detector. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the proximity sensor is in a wearable device including a crown, and the determined distance is from the crown to the object. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the proximity sensor is under a cover substrate of the wearable device. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the first amount of light and the second amount of light are received simultaneously. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the first amount of light has a first light path and the second amount of light has a second light path and the first and second light paths pass through an optical filter configured to pass light of a same wavelength as the light paths and block light of a different wavelength as the light paths. 
     Some examples of the disclosure are directed to a proximity sensor comprising: a first light emitter, a second light emitter aligned with the first light emitter in a first direction, and a light detector aligned with the first light emitter and second light emitter in the first direction, the light detector configured to receive a first amount of light originating from the first light emitter and a second amount of light originating from the second light emitter, wherein a distance of an object in a second direction is determined using a ratio of the first amount of light and the second amount of light, the second direction being orthogonal to the first direction. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the first light emitter is nearer to the light detector than the second light emitter is to the light detector in the first direction. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the first light emitter is nearer to the light detector than the first light emitter is to the second light emitter. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the proximity sensor is in a wearable device including a crown, and the determined distance is from the crown to the object. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the proximity sensor is under a cover substrate of the wearable device. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the first amount of light and the second amount of light are received sequentially. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the first amount of light from the first light emitter has a first wavelength, the second amount of light from the second light emitter has a second wavelength, different from the first wavelength, and the first amount of light and the second amount of light are detected by the light detector simultaneously. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the first amount of light from the first emitter is emitted according to a first light pulsing scheme, the second amount of light from the second emitter is emitted according to a second light pulsing scheme, different from the first light pulsing scheme, and the first amount of light and the second amount of light are detected by the light detector at the same time. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the first amount of light has a first light path, the second amount of light has a second light path, and the first and second light paths pass through an optical filter configured to pass light of a same wavelength as the light paths and block light of a different wavelength as the light paths. 
     Some examples of the disclosure are directed to a method comprising: detecting a first amplitude of a first light having a first light path, detecting a second amplitude of a second light having a second light path, determining a ratio of the first amplitude and second amplitude, determining a presence of an object based on the ratio. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the first light path includes a first reflection off of the object and the second light path includes a second reflection off of the object. Additionally or alternatively to one or more of the examples disclosed above, in some examples, determining the presence of the object based on the ratio comprises determining a distance of the object from a device. Additionally or alternatively to one or more of the examples disclosed above, in some examples, determining the presence of the object based on the ratio further comprises determining that the object is present if the distance meets a first threshold. Additionally or alternatively to one or more of the examples disclosed above, in some examples, determining the presence of the object based on the ratio further comprises determining that the object is not present if the distance meets a second threshold. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the first light path is configured to travel a first light path distance and the second light path is configured to travel a second light path distance, and the distance of the object from the device is a function of a difference between the first and second light path distances. Additionally or alternatively to one or more of the examples disclosed above, in some examples, detecting the first amplitude of the first light having the first light path comprises: emitting light from a first light emitter, and detecting, at a light detector, the light from the first light emitter; and detecting the second amplitude of the second light having the second light path comprises: emitting light from a second light emitter, and detecting, at the light detector, the light from the second light emitter. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the first light emitter is aligned with the light detector in a first direction, the second light emitter is aligned with the light detector in the first direction, and the first light emitter is nearer to the light detector than the second light emitter is to the light detector in the first direction. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the first light emitter is nearer to the light detector than to the second light emitter. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the light from the first light emitter and the light from the second emitter are emitted sequentially. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the light from the first light emitter has a first wavelength, the light from the second light emitter has a second wavelength, different from the first wavelength, and the light from the first emitter and the light from the second emitter are detected by the light detector simultaneously. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the light from the first emitter is emitted according to a first light pulsing scheme, the light from the second emitter is emitted according to a second light pulsing scheme, different from the first light pulsing scheme, and the light from the first emitter and the light from the second emitter are detected by the light detector at the same time. Additionally or alternatively to one or more of the examples disclosed above, in some examples, detecting the first amplitude of the first light having the first light path comprises: emitting light from a light emitter, and detecting, at a first light detector, the light from the light emitter, and detecting the second amplitude of the second light having the second light path comprises: emitting light from the light emitter, and detecting, at a second light detector, the light from the light emitter. Additionally or alternatively to one or more of the examples disclosed above, in some examples, detecting at the first light detector the light from the light emitter and detecting at the second light detector the light from the emitter occurs simultaneously. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the first light detector is aligned with the light emitter in a first direction, the second light detector is aligned with the light emitter in the first direction, and the first light detector is nearer to the light emitter than the second light detector is to the light emitter in the first direction. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the first light detector is nearer to the light emitter than to the second light detector. Additionally or alternatively to one or more of the examples disclosed above, in some examples, performing an operation based on whether the presence of the object is detected. 
     Some examples of the disclosure are directed to a device comprising a proximity sensor including: a first light emitter, a second light emitter aligned with the first light emitter in a first direction, and a light detector aligned with the first light emitter and second light emitter in the first direction, the light detector configured to receive a first amount of light originating from the first light emitter and a second amount of light originating from the second light emitter, and a processor capable of determining a distance of an object in a second direction using a ratio of the first amount of light and the second amount of light, the second direction being orthogonal to the first direction. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the determined distance is from the crown to the object. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the processor is configured to perform an operation based on whether the distance of the object meets a threshold. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the device is a wearable device. 
     Some examples of the disclosure are directed to a device comprising a proximity sensor including: a light emitter, a first light detector aligned with the light emitter in a first direction and configured to receive a first amount of light from the light emitter, a second light detector aligned with the light emitter in the first direction and configured to receive a second amount of light from the light emitter, and a processor capable of determining a distance of an object in a second direction using a ratio of the first amount of light to the second amount of light, the second direction being orthogonal to the first direction. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the determined distance is from the crown to the object. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the processor is configured to perform an operation based on whether the distance of the object meets a threshold. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the device is a wearable device. 
     Therefore, according to the above, some examples of the disclosure are directed to an electronic device. The electronic device can comprise a rotational input element, a proximity sensor, and a processor. The proximity sensor can comprise a transmit circuit that can be operatively coupled to the rotational input element and can be configured to inject electromagnetic energy via inductive coupling into the rotational input element, and a monitoring circuit that can be operatively coupled to the rotational input element and can be configured to measure one or more parameters. The one or more parameters can be indicative of an object touching or in proximity to the rotational input element. The processor can be operatively coupled to the proximity sensor and can be capable detecting one or more touch or hover events based on the one or more parameters measured by the monitoring circuit. Additionally or alternatively to one or more of the examples disclosed above, the processor can be further capable of performing an action based on the one or more touch or hover events detected. Additionally or alternatively to one or more of the examples disclosed above, the electronic device can be a wearable device. Additionally or alternatively to one or more of the examples disclosed above, the rotational input element can be a crown. Additionally or alternatively to one or more of the examples disclosed above, the monitoring circuit can detect a shift in a resonant frequency of the transmit circuit. Additionally or alternatively to one or more of the examples disclosed above, the transmit circuit can comprise a first inductive element and one or more first capacitive elements. The transmit circuit can oscillate at a first resonant frequency. The first resonant frequency can be a function of the first inductive element and the one or more first capacitive elements. Additionally or alternatively to one or more of the examples disclosed above, the transmit circuit can comprise at least one adjustable capacitor such that the first resonant frequency can be tunable. Additionally or alternatively to one or more of the examples disclosed above, the proximity sensor can further comprise a receive circuit operatively coupled to or formed as part of the rotational input element, the receive circuit including a second inductive element and one or more second capacitive elements. The receive circuit can oscillate at a second resonant frequency. The second resonant frequency can be a function of the second inductive element and the one or more second capacitive elements. Additionally or alternatively to one or more of the examples disclosed above, the first resonant frequency and the second resonant frequency can be the same. Additionally or alternatively to one or more of the examples disclosed above, the second inductive element can comprise a coil wrapped around at least a portion of rotational input element. Additionally or alternatively to one or more of the examples disclosed above, the second inductive element can be formed, at least in part, within the rotational input element. Additionally or alternatively to one or more of the examples disclosed above, the rotational input element can comprise one or more electrodes formed from a conducting material and coupled to the second inductive element. Additionally or alternatively to one or more of the examples disclosed above, the proximity sensor can further comprise a second receive circuit that can be operatively coupled to or formed as part of the rotational input element. The second receive circuit can include a third inductive element and one or more third capacitive elements. The second receive circuit can oscillate at a third resonant frequency. The third resonant frequency can be a function of the third inductive element and the one or more third capacitive elements. Additionally or alternatively to one or more of the examples disclosed above, the transmit circuit can be configured to tune, during a first time period, the first resonant frequency to match the second resonant frequency of the first receive circuit and to tune, during a second time period, the first resonant frequency to match the third resonant frequency of the second receive circuit. Additionally or alternatively to one or more of the examples disclosed above, detecting the one or more touch or hover events can comprise comparing the one or more parameters measured by the monitoring circuit to one or more thresholds. Additionally or alternatively to one or more of the examples disclosed above, the action can be transitioning one or more components of the device out of a rest state. Additionally or alternatively to one or more of the examples disclosed above, the processor can be further capable of estimating a distance between the rotational input element and the object touching or in proximity to the rotational input element. Additionally or alternatively to one or more of the examples disclosed above, detecting the one or more touch or hover events can comprise identifying a signature from the one or more parameters measured by the monitoring circuit. 
     Some examples of the disclosure are directed to a method of detecting one or more touch or proximity events on a rotational input element. The method can comprise applying electromagnetic energy to a first circuit, coupling the electromagnetic energy to one or more second circuits including the rotational input element, measuring one or more parameters, the one or more parameters indicative of an object touching or in proximity to the rotational input element, and detecting the one or more touch or proximity events based on the one or more parameters. Additionally or alternatively to one or more of the examples disclosed above, the method can further comprise performing an action based on the one or more touch or proximity events detected. Additionally or alternatively to one or more of the examples disclosed above, the action can be transitioning one or more components out of a rest state. Additionally or alternatively to one or more of the examples disclosed above, detecting the one or more touch or proximity events can comprise comparing the one or more parameters to one or more thresholds. Additionally or alternatively to one or more of the examples disclosed above, the method can further comprise estimating a distance between the rotational input element and an object touching or in proximity to the rotational input element. Additionally or alternatively to one or more of the examples disclosed above, detecting the one or more touch or proximity events can comprise identifying a signature from the one or more parameters. Additionally or alternatively to one or more of the examples disclosed above, the rotational input element can be a crown. Additionally or alternatively to one or more of the examples disclosed above, the one or more parameters can include a shift in a resonant frequency of the first circuit. Additionally or alternatively to one or more of the examples disclosed above, the first circuit can comprise a first inductive element and one or more first capacitive elements. The first circuit can oscillate at a first resonant frequency. The first resonant frequency can be a function of the first inductive element and the one or more first capacitive elements. Additionally or alternatively to one or more of the examples disclosed above, the first circuit can comprise at least one adjustable capacitor such that the first resonant frequency can be tunable. Additionally or alternatively to one or more of the examples disclosed above, the one or more second circuits can comprise a first receive circuit including a second inductive element and one or more second capacitive elements. The first receive circuit can oscillate at a second resonant frequency. The second resonant frequency can be a function of the second inductive element and the one or more second capacitive elements. Additionally or alternatively to one or more of the examples disclosed above, the method can further comprise tuning the first resonant frequency to match the second resonant frequency. Additionally or alternatively to one or more of the examples disclosed above, the one or more second circuits can comprise a second receive circuit including a third inductive element and one or more third capacitive elements. The second receive circuit can oscillate at a third resonant frequency. The third resonant frequency can be a function of the third inductive element and the one or more third capacitive elements. Additionally or alternatively to one or more of the examples disclosed above, the method can further comprise tuning, during a first time period, the first resonant frequency of the first circuit to match the second resonant frequency of the first receive circuit, and tuning, during a second time period, the first resonant frequency to match the third resonant frequency of the second receive circuit. Some examples of the disclosure are directed to a non-transitory computer readable storage medium, the computer readable medium containing instructions that, when executed by a processor, can perform any of the above methods. 
     Some examples of the disclosure are directed to a touch and/or proximity sensor. The proximity sensor can comprise a transmit circuit that can be operatively coupled to a rotational input element and can be configured to inject electromagnetic energy via inductive coupling into the rotational input element, and a monitoring circuit that can be operatively coupled to the rotational input element and can be configured to measure one or more parameters. The one or more parameters can be indicative of an object touching or in proximity to the rotational input element. Additionally or alternatively to one or more of the examples disclosed above, the proximity sensor can further comprise one or more receive circuits that can be operatively coupled to or formed, at least in part, as part of the rotational input element. Each of the one or more receive circuits can include a second inductive element and one or more second capacitive elements. Additionally or alternatively to one or more of the examples disclosed above, the one or more receive circuits can oscillate at different resonant frequencies. 
     Therefore, according to the above, some examples of the disclosure are directed to an electronic device. The electronic device can comprise a rotational input element, a proximity sensor, and a processor. The proximity sensor can comprise a transmit circuit operatively coupled to the rotational input element and a monitoring circuit operatively coupled to the rotational input element. The transmit circuit can be configured to inject electromagnetic energy into the rotational input element. The monitoring circuit can be configured to measure one or more parameters. The one or more parameters can be indicative of an object touching or in proximity to the rotational input element. The processor can be operatively coupled to the proximity sensor and can be capable detecting one or more touch or hover events based on the one or more parameters measured by the monitoring circuit. Additionally or alternatively to one or more of the examples disclosed above, the processor can be further capable of performing an action based on the one or more touch or hover events detected. Additionally or alternatively to one or more of the examples disclosed above, the electronic device can be a wearable device. Additionally or alternatively to one or more of the examples disclosed above, the rotational input element can be a crown. Additionally or alternatively to one or more of the examples disclosed above, the transmit circuit can comprise an inductive element and one or more capacitive elements oscillating at a resonant frequency. The resonant frequency can be a function of the inductive element and the one or more capacitive elements. Additionally or alternatively to one or more of the examples disclosed above, the transmit circuit can comprise a radio frequency transmitter. Additionally or alternatively to one or more of the examples disclosed above, the transmit circuit can be coupled to the rotational input element via a duplexer circuit and the monitoring circuit can be coupled to the rotational input element via the duplexer circuit. Additionally or alternatively to one or more of the examples disclosed above, the monitoring circuit can comprise a power meter. Additionally or alternatively to one or more of the examples disclosed above, the monitoring circuit can comprises a frequency counter. Additionally or alternatively to one or more of the examples disclosed above, the monitoring circuit can detect a shift in a resonant frequency of the transmit circuit. Additionally or alternatively to one or more of the examples disclosed above, the monitoring circuit can detect detuning of the rotational input device acting as an antenna. Additionally or alternatively to one or more of the examples disclosed above, the rotational input device can be formed from a conductive material. Additionally or alternatively to one or more of the examples disclosed above, the rotational input element can comprise a non-conducting outer surface and a conducting material within the rotational input element. Additionally or alternatively to one or more of the examples disclosed above, the rotational input element can comprise a first electrode and a second electrode. Additionally or alternatively to one or more of the examples disclosed above, the first electrode can be coupled to a first transmit circuit to measure one or more first parameters indicative of the object touching or in proximity to the first electrode and the second electrode can be coupled to a second transmit circuit to measure one or more second parameters indicative of the object touching or in proximity to the second electrode. Additionally or alternatively to one or more of the examples disclosed above, the one or more parameters can include a capacitance coupling between the first electrode and the second electrode. Additionally or alternatively to one or more of the examples disclosed above, the device can further comprise a switch including a conductive surface. The conductive surface can coupled to the transmit circuit and the conductive surface can contact the rotational input element so as to form a conductive pathway to inject electromagnetic energy into the rotational input element. Additionally or alternatively to one or more of the examples disclosed above, the transmit circuit can be operatively coupled to the rotational input element via a capacitive coupling. Additionally or alternatively to one or more of the examples disclosed above, the transmit circuit can be a wireless communication device. Additionally or alternatively to one or more of the examples disclosed above, detecting the one or more touch or hover events can comprise comparing the one or more parameters measured by the monitoring circuit to one or more thresholds. Additionally or alternatively to one or more of the examples disclosed above, the action can be transitioning one or more components of the device out of a rest state. Additionally or alternatively to one or more of the examples disclosed above, the processor can be further capable of estimating a distance between the rotational input element and the object touching or in proximity to the rotational input element. Additionally or alternatively to one or more of the examples disclosed above, detecting the one or more touch or hover events can comprise identifying a signature from the one or more parameters measured by the monitoring circuit. 
     Some examples of the disclosure are directed to a method of detecting one or more touch or proximity events on a rotational input element. The method can comprise applying electromagnetic energy to a circuit including the rotational input element, measuring one or more parameters, the one or more parameters indicative of an object touching or in proximity to the rotational input element, and detecting the one or more touch or proximity events based on the one or more parameters. Additionally or alternatively to one or more of the examples disclosed above, the method can further comprise performing an action based on the one or more touch or proximity events detected. Additionally or alternatively to one or more of the examples disclosed above, the action can be transitioning one or more components of the device out of a rest state. Additionally or alternatively to one or more of the examples disclosed above, detecting the one or more touch or proximity events can comprise comparing the one or more parameters to one or more thresholds. Additionally or alternatively to one or more of the examples disclosed above, the method can further comprise estimating a distance between the rotational input element and an object touching or in proximity to the rotational input element. Additionally or alternatively to one or more of the examples disclosed above, detecting the one or more touch or proximity events can comprise identifying a signature from the one or more parameters. Additionally or alternatively to one or more of the examples disclosed above, the rotational input element can be a crown. Additionally or alternatively to one or more of the examples disclosed above, the circuit can comprise an inductive element and one or more capacitive elements oscillating at a resonant frequency. The resonant frequency can be a function of the inductive element and the one or more capacitive elements. Additionally or alternatively to one or more of the examples disclosed above, the circuit can comprise a radio frequency transmitter. Additionally or alternatively to one or more of the examples disclosed above, the circuit can be coupled to the rotational input element via a duplexer circuit and the one or more parameters are measured by a monitoring circuit that can be coupled to the rotational input element via the duplexer circuit. Additionally or alternatively to one or more of the examples disclosed above, the one or more parameters can be measured by a power meter. Additionally or alternatively to one or more of the examples disclosed above, the one or more parameters can be measured by a frequency counter. Additionally or alternatively to one or more of the examples disclosed above, the one or more parameters can include a shift in a resonant frequency of the circuit. Additionally or alternatively to one or more of the examples disclosed above, measuring the one or more parameters can comprise detecting detuning of the rotational input device acting as an antenna. Additionally or alternatively to one or more of the examples disclosed above, the rotational input element can comprise a first electrode and a second electrode. Additionally or alternatively to one or more of the examples disclosed above, the method can further comprise applying electromagnetic energy to a first circuit to measure one or more first parameters indicative of the object touching or in proximity to the first electrode and applying electromagnetic energy to a second circuit to measure one or more second parameters indicative of the object touching or in proximity to the second electrode. Additionally or alternatively to one or more of the examples disclosed above, the one or more parameters can include a capacitance coupling between the first electrode and the second electrode. Additionally or alternatively to one or more of the examples disclosed above, the circuit can comprises a wireless communication device. Some examples of the disclosure are directed to a non-transitory computer readable storage medium, the computer readable medium containing instructions that, when executed by a processor, can perform any of the above methods. 
     Therefore, according to the above, some examples of the disclosure are directed to an electronic device comprising: a rotatable mechanical input mechanism; a sense electrode positioned proximate to the mechanical input mechanism; and a capacitive sense circuit comprising: drive circuitry operatively coupled to the mechanical input mechanism and configured for driving a drive signal onto the mechanical input mechanism; and sense circuitry operatively coupled to the sense electrode and configured to measure an amount of coupling between the rotatable mechanical input mechanism and the sense electrode. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the sense circuitry is operatively coupled to the mechanical input mechanism, the sense circuitry configured to measure an amount of self-capacitance coupling between the mechanical input mechanism and an object proximate to the mechanical input mechanism. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the mechanical input circuitry comprises a plurality of conductive segments; and in a first rotational orientation of the mechanical input mechanism, the drive circuitry is coupled to a first conductive segment of the plurality of conductive segments; and in a second rotational orientation of the mechanical input mechanism, different from the first rotational orientation, the drive circuitry is coupled to a second conductive segment of the plurality of conductive segments, different from the first conductive segment. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the drive circuitry is operatively coupled to drive the sense electrode, and the sense circuitry is configured to measure an amount of self-capacitance coupling between the sense electrode and an object proximate to the mechanical input mechanism. Additionally or alternatively to one or more of the examples disclosed above, in some examples, a change in the amount of coupling between the rotatable mechanical input mechanism and the sense electrode is indicative of an object contacting or in proximity with the mechanical input mechanism. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the electronic device further comprises: a display; and a housing, wherein the sense electrode is included in a gasket for connecting the display to the housing. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the electronic device further comprises a force sensor included in the gasket, the force sensor configured for detecting an intensity of contact between an object and the display. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the force sensor and the sense electrode are included on different layers of the gasket. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the electronic device further comprises a touch sensitive display, wherein the sense electrode is an electrode included in the touch sensitive display. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the electronic device is a wearable device and the mechanical input mechanism is a crown. 
     Some examples of the disclosure are directed to a method comprising: driving a drive signal onto a rotatable mechanical input mechanism of a device; performing a mutual capacitance measurement for detecting a proximity or contact of an object with the mechanical input mechanism; determining whether the object was detected by the mutual capacitance measurement; in accordance with a determination that the object was detected by the mutual capacitance measurement, reporting a touch or proximity event; and in accordance with a determination that the object was not detected by the mutual capacitance measurement, performing a self-capacitance measurement for detecting the proximity or contact of the object with the mechanical input mechanism. Additionally or alternatively to one or more of the examples disclosed above, in some examples, determining whether the object was detected by the mutual capacitance measurement comprises comparing the measurement with a first threshold value. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the first threshold value is a threshold signal-to-noise ratio (SNR). Additionally or alternatively to one or more of the examples disclosed above, in some examples, the method further comprises: determining whether the object was detected by the self-capacitance measurement, wherein the determination comprises comparing the self-capacitance measurement with a second threshold value, wherein the second threshold value is a threshold SNR. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the first threshold value and the second threshold value are a same value. 
     Some examples of the disclosure are directed to a non-transitory computer readable storage medium having stored thereon a set of instructions, that when executed by a processor causes the processor to: transmit a drive signal onto a rotatable mechanical input mechanism of a device; perform a mutual capacitance measurement for detecting a proximity or contact of an object with the mechanical input mechanism; in accordance with a determination that the object was detected by the mutual capacitance measurement, report a touch or proximity event; and in accordance with a determination that the object was not detected by the mutual capacitance measurement, perform a self-capacitance measurement for detecting the proximity or contact of the object with the mechanical input mechanism. Additionally or alternatively to one or more of the examples disclosed above, in some examples, determining whether the object was detected by the mutual capacitance measurement comprises comparing the measurement with a first threshold value. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the first threshold value is a threshold signal-to-noise ratio (SNR). Additionally or alternatively to one or more of the examples disclosed above, in some examples, the instructions further cause the processor to: determine whether the object was detected by the self-capacitance measurement, wherein the determination comprises comparing the self-capacitance measurement with a second threshold value, wherein the second threshold value is a threshold SNR. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the first threshold value and the second threshold value are a same value. 
     Some examples of the disclosure are directed to an electronic device comprising: a touch sensor panel disposed on a cover substrate; a housing; a rotatable mechanical input mechanism configured for rotating with respect to the housing; a gasket configured to couple the cover substrate to the housing at a first edge of the cover substrate proximate to the mechanical input mechanism; a force sensor for detecting intensity of contact by an object contacting the cover substrate; a capacitive sense electrode for detecting a proximity or contact by the object with the mechanical input mechanism; and a control circuit for controlling operation of the force sensor and the capacitive sense electrode; wherein the force sensor and the capacitive sense electrode are included in the gasket. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the control circuit is configured to selectively drive one of the force sensor and the capacitive sense electrode with a drive signal. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the electronic device further comprises a demultiplexer, wherein the demultiplexer is selectively configurable for driving one of the force sensor and the capacitive sensed electrode comprises comparing the self-capacitance measurement with a second threshold value, wherein the second threshold value is a threshold SNR. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the control circuit is selectively configurable for driving the force sensor with a ground signal while the capacitive sense electrode is driven with a drive signal. 
     Although some examples described herein involve proximity sensors used to detect objects near the crown of a watch, it should be understood that the proximity sensors described herein can be used in other electronic devices which utilize proximity sensing including, but not limited to, cellular phones, laptops, or tablet devices. 
     Although this disclosure and examples have been fully described with reference to the accompanying figures, it is to be noted that various changes and modifications will become apparent to those skilled in the art. Such changes and modifications are to be understood as being included within the scope of the disclosure and examples as defined by the appended claims.

Metadata:
Filing Date: 20160923
Publication Date: 20210615
Grant Date: 20210615
Priority Date: 20150930
Inventors: BOKMA, LOUIS W.
HOLENARSIPUR, PRASHANTH
KUBOYAMA, YUTA
HUANG, MENGSHU
Assignee: APPLE INC
CPC Classifications: [{"code": "G04C3/001", "inventive": true, "first": false, "tree": "[]"}, {"code": "G04C3/007", "inventive": true, "first": false, "tree": "[]"}, {"code": "G04G21/08", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F2203/04105", "inventive": false, "first": false, "tree": "[]"}, {"code": "H03K2217/96003", "inventive": false, "first": false, "tree": "[]"}, {"code": "H03K17/962", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/0304", "inventive": true, "first": false, "tree": "[]"}, {"code": "G04C3/005", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F2203/04108", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F3/03547", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F1/163", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/0433", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/0433", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/0362", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F1/163", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/038", "inventive": true, "first": true, "tree": "[]"}, {"code": "G04C3/001", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/044", "inventive": true, "first": false, "tree": "[]"}, {"code": "H03K17/962", "inventive": true, "first": false, "tree": "[]"}, {"code": "G04C3/007", "inventive": true, "first": false, "tree": "[]"}, {"code": "H03K2217/96003", "inventive": false, "first": false, "tree": "[]"}, {"code": "G04C3/005", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F2203/04105", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F3/0304", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/0362", "inventive": true, "first": false, "tree": "[]"}, {"code": "G04G21/08", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/044", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F3/03547", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/038", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F2203/04108", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F3/0362", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/0304", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/038", "inventive": true, "first": true, "tree": "[]"}, {"code": "G04C3/005", "inventive": true, "first": false, "tree": "[]"}, {"code": "H03K2217/96003", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F3/044", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/0433", "inventive": true, "first": false, "tree": "[]"}, {"code": "H03K17/962", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F2203/04108", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F1/163", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F2203/04105", "inventive": false, "first": false, "tree": "[]"}, {"code": "G04C3/007", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/03547", "inventive": true, "first": false, "tree": "[]"}, {"code": "G04C3/001", "inventive": true, "first": false, "tree": "[]"}, {"code": "G04G21/08", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 58407135