PATENT DOCUMENT

Publication Number: US-10963095-B1
Application Number: US-202016778796-A
Country: US
Kind Code: B1

Title: Glove touch detection

Abstract:
An electronic device including a touch screen or touch sensor panel can operate in a bare finger touch detection mode or a glove touch detection mode. While operating in the bare finger touch detection mode, in response to detecting a signal density slope corresponding to a gloved object touching the panel and lifting off without re-approaching the panel within a predetermined time or in response to detecting a signal density slope corresponding to a gloved object touching the panel continuously for a predetermined period of time, the electronic device can transition from the bare finger mode to the glove touch mode, for example. While in the glove touch detection mode, the electronic device can transition to the bare finger touch detection mode in response to detecting a touch signal density that exceeds a predetermined threshold or in response to detecting a touch signal that exceeds a predetermined threshold.

Claims:
The invention claimed is: 
     
       1. A method comprising:
 at an electronic device comprising a touch screen and one or more processors:
 sensing, in a first proximity sensing mode, signals indicative of a proximate object during multiple touch frames; 
 
 calculating signal densities associated with the proximate object corresponding to the multiple touch frames;
 in accordance with a determination that the signal densities meet a plurality of criteria, transitioning from sensing the signal in the first proximity sensing mode to sensing the signal in a second proximity sensing mode, wherein the plurality of criteria comprise:
 a first criterion that is satisfied when the slope of the signal densities, calculated from the signal densities corresponding to the multiple touch frames, is indicative of the proximate object approaching the surface of the touch screen; and 
 a second criterion that is satisfied when the slope of the signal densities is indicative of the proximate object indirectly contacting the touch screen at a distance from the touch screen that deviates less than a predetermined amount from being constant; and 
 a third criterion that is satisfied when the slope of the signal densities is indicative of the proximate object moving away from the surface of the touch screen. 
 
 
 
     
     
       2. The method of  claim 1 , wherein:
 satisfying the first criterion includes detecting that the slope of the signal densities, calculated from the signal densities corresponding to the multiple touch frames, exceeds a first threshold at a first time, 
 satisfying the second criterion includes detecting that the slope of the signal densities is less than a second threshold and greater than a third threshold for a first threshold duration of time after the first time, the second threshold less than the first threshold, and the third threshold less than the second threshold, and 
 satisfying the third criterion includes detecting that the slope of the signal densities is less than a fourth threshold at a second time after the threshold duration of time, the fourth threshold less than the third threshold. 
 
     
     
       3. The method of  claim 2 , wherein the plurality of criteria further include a fourth criterion that is satisfied in accordance with a determination that, from the second time to a third time after the third time, the signal densities are less than a fifth threshold greater than the second threshold. 
     
     
       4. The method of  claim 2 , further comprising:
 in accordance with a determination that, at any time from the first time to the second time, a signal density of the signal densities exceeds a fifth threshold:
 forgoing transitioning from sensing the signal in the first proximity sensing mode to sensing the signal in the second proximity sensing mode; and 
 continuing to sense the signal in the first proximity sensing mode. 
 
 
     
     
       5. The method of  claim 2 , further comprising:
 while sensing the signal in the first proximity sensing mode, comparing the signal densities to a fifth threshold to determine whether or not the proximate object is touching the touch screen; and 
 while sensing the signal in the second proximity sensing mode, comparing the signal densities to a sixth threshold to determine whether or not the proximate object is touching the touch screen, the sixth threshold less than the fifth threshold. 
 
     
     
       6. The method of  claim 2 , wherein:
 the first threshold and second threshold are positive, and 
 the third threshold and fourth threshold are negative. 
 
     
     
       7. The method of  claim 2 , wherein calculating the slope of the signal densities comprises:
 identifying a first region of the touch screen corresponding to the proximate object at a first respective time; 
 calculating a signal density of the first region of the touch screen at the first respective time; 
 identifying a second region of the touch screen corresponding to the proximate object at a second respective time; 
 calculating a signal density of the second region of the touch screen at the second respective time; and 
 calculating the rate of change between the signal density of the first region at the first respective time to the signal density of the second region at the second respective time, 
 wherein calculating a respective signal density at a respective time includes:
 computing a sum of the one or more respective signals indicative of the proximate object, each respective signal of the one or more respective signals associated with a touch node included in a respective region of the touch screen; and 
 dividing the sum of the one or more respective signals by the number of touch nodes included in the respective region of the touch screen. 
 
 
     
     
       8. The method of  claim 2 , wherein:
 the third criterion is satisfied when the slope of the signal densities is less than a fourth threshold at a second time after the threshold duration of time, the fourth threshold less than the third threshold or the slope of the signal densities is less than the second threshold and greater than the third threshold for a second threshold duration of time after the first time, the second threshold duration of time greater than the first threshold duration of time. 
 
     
     
       9. An electronic device, comprising:
 a touch screen; 
 sense circuitry operatively coupled to the touch screen; and 
 one or more processors storing instructions that, when executed, cause the electronic device to perform a method comprising:
 sensing, in a first proximity sensing mode, signals indicative of a proximate object during multiple touch frames; 
 calculating signal densities associated with the proximate object corresponding to the multiple touch frames; 
 in accordance with a determination that the signal densities meet a plurality of criteria, transitioning from sensing the signal in the first proximity sensing mode to sensing the signal in a second proximity sensing mode, wherein the plurality of criteria comprise:
 a first criterion that is satisfied when the slope of the signal densities, 
 calculated from the signal densities corresponding to the multiple touch frames, is indicative of the proximate object approaching the surface of the touch screen; and 
 a second criterion that is satisfied when the slope of the signal densities is indicative of the proximate object indirectly contacting the touch screen at a distance from the touch screen that deviates less than a predetermined amount from being constant; and 
 a third criterion that is satisfied when the slope of the signal densities is indicative of the proximate object moving away from the surface of the touch screen. 
 
 
 
     
     
       10. The electronic device of  claim 9 , wherein:
 satisfying the first criterion includes detecting that the slope of the signal densities, calculated from the signal densities corresponding to the multiple touch frames, exceeds a first threshold at a first time, 
 satisfying the second criterion includes detecting that the slope of the signal densities is less than a second threshold and greater than a third threshold for a first threshold duration of time after the first time, the second threshold less than the first threshold, and the third threshold less than the second threshold, and 
 satisfying the third criterion includes detecting that the slope of the signal densities is less than a fourth threshold at a second time after the threshold duration of time, the fourth threshold less than the third threshold. 
 
     
     
       11. The electronic device of  claim 10 , wherein the plurality of criteria further include a fourth criterion that is satisfied in accordance with a determination that, from the second time to a third time after the third time, the signal densities are less than a fifth threshold greater than the second threshold. 
     
     
       12. The electronic device of  claim 10 , wherein the method further comprises:
 while sensing the signal in the first proximity sensing mode, comparing the signal densities to a fifth threshold to determine whether or not the proximate object is touching the touch screen; and 
 while sensing the signal in the second proximity sensing mode, comparing the signal densities to a sixth threshold to determine whether or not the proximate object is touching the touch screen, the sixth threshold less than the fifth threshold. 
 
     
     
       13. The electronic device of  claim 10 , wherein calculating the slope of the signal densities comprises:
 identifying a first region of the touch screen corresponding to the proximate object at a first respective time; 
 calculating a signal density of the first region of the touch screen at the first respective time; 
 identifying a second region of the touch screen corresponding to the proximate object at a second respective time; 
 calculating a signal density of the second region of the touch screen at the second respective time; and 
 calculating the rate of change between the signal density of the first region at the first respective time to the signal density of the second region at the second respective time, 
 wherein calculating a respective signal density at a respective time includes:
 computing a sum of the one or more respective signals indicative of the proximate object, each respective signal of the one or more respective signals associated with a touch node included in a respective region of the touch screen; and 
 dividing the sum of the one or more respective signals by the number of touch nodes included in the respective region of the touch screen. 
 
 
     
     
       14. The electronic device of  claim 10 , wherein:
 the third criterion is satisfied when the slope of the signal densities is less than a fourth threshold at a second time after the threshold duration of time, the fourth threshold less than the third threshold or the slope of the signal densities is less than the second threshold and greater than the third threshold for a second threshold duration of time after the first time, the second threshold duration of time greater than the first threshold duration of time. 
 
     
     
       15. A non-transitory computer-readable medium comprising instructions that, when executed by one or more processors of an electronic device comprising a touch screen, cause the electronic device to:
 sense, in a first proximity sensing mode, signals indicative of a proximate object during multiple touch frames; 
 calculate signal densities associated with the proximate object corresponding to the multiple touch frames; 
 in accordance with a determination that the signal densities meet a plurality of criteria, transition from sensing the signal in the first proximity sensing mode to sensing the signal in a second proximity sensing mode, wherein the plurality of criteria comprise:
 a first criterion that is satisfied when the slope of the signal densities, calculated from the signal densities corresponding to the multiple touch frames, is indicative of the proximate object approaching the surface of the touch screen; and 
 a second criterion that is satisfied when the slope of the signal densities is indicative of the proximate object indirectly contacting the touch screen at a distance from the touch screen that deviates less than a predetermined amount from being constant; and 
 a third criterion that is satisfied when the slope of the signal densities is indicative of the proximate object moving away from the surface of the touch screen. 
 
 
     
     
       16. The non-transitory computer-readable medium of  claim 15 , wherein:
 satisfying the first criterion includes detecting that the slope of the signal densities, calculated from the signal densities corresponding to the multiple touch frames, exceeds a first threshold at a first time, 
 satisfying the second criterion includes detecting that the slope of the signal densities is less than a second threshold and greater than a third threshold for a first threshold duration of time after the first time, the second threshold less than the first threshold, and the third threshold less than the second threshold, and 
 satisfying the third criterion includes detecting that the slope of the signal densities is less than a fourth threshold at a second time after the threshold duration of time, the fourth threshold less than the third threshold. 
 
     
     
       17. The non-transitory computer-readable medium of  claim 16 , wherein the plurality of criteria further include a fourth criterion that is satisfied in accordance with a determination that, from the second time to a third time after the third time, the signal densities are less than a fifth threshold greater than the second threshold. 
     
     
       18. The non-transitory computer-readable medium of  claim 16 , wherein the instructions further cause the electronic device to:
 while sensing the signal in the first proximity sensing mode, compare the signal densities to a fifth threshold to determine whether or not the proximate object is touching the touch screen; and 
 while sensing the signal in the second proximity sensing mode, compare the signal densities to a sixth threshold to determine whether or not the proximate object is touching the touch screen, the sixth threshold less than the fifth threshold. 
 
     
     
       19. The non-transitory computer-readable medium of  claim 16 , wherein calculating the slope of the signal densities comprises:
 identifying a first region of the touch screen corresponding to the proximate object at a first respective time; 
 calculating a signal density of the first region of the touch screen at the first respective time; 
 identifying a second region of the touch screen corresponding to the proximate object at a second respective time; 
 calculating a signal density of the second region of the touch screen at the second respective time; and 
 calculating the rate of change between the signal density of the first region at the first respective time to the signal density of the second region at the second respective time, 
 wherein calculating a respective signal density at a respective time includes:
 computing a sum of the one or more respective signals indicative of the proximate object, each respective signal of the one or more respective signals associated with a touch node included in a respective region of the touch screen; and 
 dividing the sum of the one or more respective signals by the number of touch nodes included in the respective region of the touch screen. 
 
 
     
     
       20. The non-transitory computer-readable medium of  claim 16 , wherein:
 the third criterion is satisfied when the slope of the signal densities is less than a fourth threshold at a second time after the threshold duration of time, the fourth threshold less than the third threshold or the slope of the signal densities is less than the second threshold and greater than the third threshold for a second threshold duration of time after the first time, the second threshold duration of time greater than the first threshold duration of time.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of U.S. Provisional Application No. 62/907,046, filed Sep. 27, 2019, which is hereby incorporated by reference in its entirety for all purposes. 
    
    
     FIELD OF THE DISCLOSURE 
     This relates generally to a touch sensor panel or touch screen and, more specifically, to an electronic device that transitions between touch detection modes based on one or more criteria related to the detected touch data. 
     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 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), light emitting diode (LED) display or organic light emitting diode (OLED) display 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. 
     Capacitive touch sensor panels can be formed by a matrix of transparent, semi-transparent or non-transparent conductive plates made of materials such as Indium Tin Oxide (ITO). In some examples, the conductive plates can be formed from other materials including conductive polymers, metal mesh, graphene, nanowires (e.g., silver nanowires) or nanotubes (e.g., carbon nanotubes). In some implementations, due in part to their substantial transparency, some capacitive touch sensor panels can be overlaid on a display to form a touch screen, as described above. Some touch screens can be formed by at least partially integrating touch sensing circuitry into a display pixel stackup (i.e., the stacked material layers forming the display pixels). 
     In some examples, an electronic device compares sensed touch data to a touch threshold to determine whether or not a proximate object touches the touch screen. In some situations, users interact with touch screens with a barrier between their fingers and the touch screen. For example, a user may be wearing gloves while operating an electronic device with a touch screen. The electronic device may not be able to detect a gloved finger touching the touch screen because the touch signal generated in response to the touching gloved finger may not reach the tuned touch detection threshold of the electronic device. 
     BRIEF SUMMARY OF THE DISCLOSURE 
     This relates generally to a touch sensor panel or touch screen and, more specifically, to an electronic device that transitions between touch detection modes based on one or more criteria related to the detected touch data. In some examples, the electronic device is able to detect touch in a bare finger touch mode with an associated bare finger touch detection threshold or in a glove touch mode with an associated glove touch detection threshold that is lower than the bare finger touch detection threshold. Detecting touch can include sensing touch signals of an input patch corresponding to a proximate object (e.g., a conductive object such as a finger or stylus), for example. In some examples, the electronic device can calculate the slope of the signal density over time. While operating in the bare finger touch detection mode, in response to detecting a touch signal density slope that satisfies a plurality of predetermined criteria, the electronic device can transition from the bare finger touch detection mode to the glove touch detection mode. 
     In some examples, the predetermined criteria are satisfied in response to detecting a slope of a signal density that corresponds to a gloved finger touching the panel and lifting off from the panel without re-approaching the panel within a predetermined period of time. In some examples, the predetermined criteria are satisfied in response to detecting a slope of a signal density that corresponds to a gloved finger continuously touching the panel for a predetermined period of time. The electronic device can evaluate the predetermined criteria by comparing the slope of the signal density to one or more predetermined thresholds according to a finite state machine, for example. While in the glove touch detection mode, the electronic device can transition to the bare finger touch detection mode in response to detecting a touch signal density that exceeds a bare finger touch threshold or in response to detecting a touch signal that exceeds a predetermined threshold. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1A-1F  illustrate example systems that can use glove touch detection techniques according to examples of the disclosure. 
         FIG. 2  illustrates an example computing system including a touch screen that can use glove touch detection techniques according to examples of the disclosure. 
         FIG. 3A  illustrates an exemplary touch sensor circuit corresponding to a self-capacitance measurement of a touch node electrode and sensing circuit according to examples of the disclosure. 
         FIG. 3B  illustrates an exemplary touch sensor circuit corresponding to a mutual-capacitance drive line and sense line and sensing circuit according to examples of the disclosure. 
         FIG. 4A  illustrates touch screen with touch electrodes arranged in rows and columns according to examples of the disclosure. 
         FIG. 4B  illustrates touch screen with touch node electrodes arranged in a pixelated touch node electrode configuration according to examples of the disclosure. 
         FIG. 5A  illustrates an exemplary image of touch according to examples of the disclosure. 
         FIG. 5B  illustrates an exemplary representation indicative of an object that moves along the surface of the touch screen according to some examples of the disclosure. 
         FIG. 6A  illustrates an exemplary signal density diagram for an object touching and lifting off a touch sensor panel according to examples of the disclosure. 
         FIG. 6B  illustrates the Zdensity slope of a representative curve of an object touching down on and lifting off from a touch screen according to some examples of the disclosure. 
         FIG. 7  illustrates an exemplary finite state machine for transitioning a touch screen between two modes of operation according to some examples of the disclosure. 
         FIG. 8A  illustrates exemplary Zdensity and Zdensity slope profiles associated with detecting a gloved touch according to some examples of the disclosure. 
         FIG. 8B  illustrates exemplary Zdensity and Zdensity slope profiles associated with detecting a gloved touch according to some examples of the disclosure. 
         FIG. 9  illustrates an exemplary process of transitioning the electronic device between two different touch detection modes according to some examples of the disclosure. 
     
    
    
     DETAILED DESCRIPTION OF THE DISCLOSURE 
     In the following description of examples, reference is made to the accompanying drawings which form a part hereof, and 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 used and structural changes can be made without departing from the scope of the disclosed examples. 
     This relates generally to a touch sensor panel or touch screen and, more specifically, to an electronic device that transitions between touch detection modes based on one or more criteria related to the detected touch data. In some examples, the electronic device is able to detect touch in a bare finger touch mode with an associated bare finger touch detection threshold or in a glove touch mode with an associated glove touch detection threshold that is lower than the bare finger touch detection threshold. Detecting touch can include sensing touch signals of an input patch corresponding to a proximate object (e.g., a conductive object such as a finger or stylus), for example. In some examples, the electronic device can calculate the slope of the signal density over time. While operating in the bare finger touch detection mode, in response to detecting a touch signal density slope that satisfies a plurality of predetermined criteria, the electronic device can transition from the bare finger touch detection mode to the glove touch detection mode. 
     In some examples, the predetermined criteria are satisfied in response to detecting a slope of a signal density that corresponds to a gloved finger touching the panel and lifting off from the panel without re-approaching the panel within a predetermined period of time. In some examples, the predetermined criteria are satisfied in response to detecting a slope of a signal density that corresponds to a gloved finger continuously touching the panel for a predetermined period of time. The electronic device can evaluate the predetermined criteria by comparing the slope of the signal density to one or more predetermined thresholds according to a finite state machine, for example. While in the glove touch detection mode, the electronic device can transition to the bare finger touch detection mode in response to detecting a touch signal density that exceeds a bare finger touch threshold or in response to detecting a touch signal that exceeds a predetermined threshold. 
       FIGS. 1A-1F  illustrate example systems that can use glove touch detection techniques according to examples of the disclosure.  FIG. 1A  illustrates an example mobile telephone  136  that includes a touch screen  124  that can use glove touch detection techniques according to examples of the disclosure.  FIG. 1B  illustrates an example digital media player  140  that includes a touch screen  126  that can use glove touch detection techniques according to examples of the disclosure.  FIG. 1C  illustrates an example personal computer  144  that includes a touch screen  128  and a touch sensor panel  134  (e.g., a trackpad) that can use glove touch detection techniques according to examples of the disclosure.  FIG. 1D  illustrates an example tablet computing device  148  that includes a touch screen  130  that can use glove touch detection techniques according to examples of the disclosure.  FIG. 1E  illustrates an example wearable device  150  that includes a touch screen  132  and can be attached to a user using a strap  152  and that can use glove touch detection techniques according to examples of the disclosure.  FIG. 1F  illustrates an example remote control device  154  that includes a touch sensor panel  138  that can use glove touch detecting techniques according to examples of the disclosure. It is understood that a touch screen and glove touch detection techniques can be implemented in other devices, including future devices not yet in the marketplace. Additionally it should be understood that although the disclosure herein primarily focuses on touch screens, the disclosure of glove touch detection techniques can be implemented for devices including touch sensor panels (and displays) that may not be implemented as a touch screen. 
     In some examples, touch screens  124 ,  126 ,  128 ,  130  and  132  and touch sensor panels  134  and  138  can be based on self-capacitance. A self-capacitance based touch system can include a matrix of small, individual plates of conductive material or groups of individual plates of conductive material forming larger conductive regions that can be referred to as touch electrodes or as touch node electrodes (as described below with reference to  FIG. 4B ). For example, a touch screen can include a plurality of individual touch electrodes, each touch electrode identifying or representing a unique location (e.g., a touch node) on the touch screen at which touch or proximity is to be sensed, and each touch node electrode being electrically isolated from the other touch node electrodes in the touch screen/panel. Such a touch screen can be referred to as a pixelated self-capacitance touch screen, though it is understood that in some examples, the touch node electrodes on the touch screen can be used to perform scans other than self-capacitance scans on the touch screen (e.g., mutual capacitance scans). During operation, a touch node electrode can be stimulated with an alternating current (AC) waveform, and the self-capacitance to ground of the touch node electrode can be measured. As an object approaches the touch node electrode, the self-capacitance to ground of the touch node electrode can change (e.g., increase). This change in the self-capacitance of the touch node electrode can be detected and measured by the touch sensing system to determine the positions of multiple objects when they touch, or come in proximity to, the touch screen. In some examples, the touch node electrodes of a self-capacitance based touch system can be formed from rows and columns of conductive material, and changes in the self-capacitance to ground of the rows and columns can be detected, similar to above. In some examples, a touch screen can be multi-touch, single touch, projection scan, full-imaging multi-touch, capacitive touch, etc. 
     In some examples, touch screens  124 ,  126 ,  128 ,  130  and  132  and touch sensor panels  134  and  138  can be based on mutual capacitance. A mutual capacitance based touch system can include electrodes arranged as drive and sense lines (e.g., as described below with reference to  FIG. 4A ) that may cross over each other on different layers (in a double-sided configuration), or may be adjacent to each other on the same layer. The crossing or adjacent locations can form touch nodes. During operation, the drive line can be stimulated with an AC waveform and the mutual capacitance of the touch node can be measured. As an object approaches the touch node, the mutual capacitance of the touch node can change (e.g., decrease). This change in the mutual capacitance of the touch node can be detected and measured by the touch sensing system to determine the positions of multiple objects when they touch, or come in proximity to, the touch screen. As described herein, in some examples, a mutual capacitance based touch system can form touch nodes from a matrix of small, individual plates of conductive material. 
     In some examples, touch screens  124 ,  126 ,  128 ,  130  and  132  and touch sensor panels  134  and  138  can be based on mutual capacitance and/or self-capacitance. The electrodes can be arrange as a matrix of small, individual plates of conductive material (e.g., as in touch node electrodes  408  in touch screen  402  in  FIG. 4B ) or as drive lines and sense lines (e.g., as in row touch electrodes  404  and column touch electrodes  406  in touch screen  400  in  FIG. 4A ), or in another pattern. The electrodes can be configurable for mutual capacitance or self-capacitance sensing or a combination of mutual and self-capacitance sensing. For example, in one mode of operation electrodes can be configured to sense mutual capacitance between electrodes and in a different mode of operation electrodes can be configured to sense self-capacitance of electrodes. In some examples, some of the electrodes can be configured to sense mutual capacitance therebetween and some of the electrodes can be configured to sense self-capacitance thereof. 
       FIG. 2  illustrates an example computing system including a touch screen that can use glove touch detection techniques according to examples of the disclosure. Computing system  200  can be included in, for example, a mobile phone, tablet, touchpad, portable or desktop computer, portable media player, wearable device or any mobile or non-mobile computing device that includes a touch screen or touch sensor panel. Computing system  200  can include a touch sensing system including one or more touch processors  202 , peripherals  204 , a touch controller  206 , and touch sensing circuitry (described in more detail below). Peripherals  204  can include, but are not limited to, random access memory (RAM) or other types of memory or storage, watchdog timers, co-processor(s) and the like. Touch controller  206  can include, but is not limited to, one or more sense channels  208 , channel scan logic  210  and driver logic  214 . Channel scan logic  210  can access RAM  212 , autonomously read data from the sense channels and provide control for the sense channels. In addition, channel scan logic  210  can control driver logic  214  to generate stimulation signals  216  at various frequencies and/or phases that can be selectively applied to drive regions of the touch sensing circuitry of touch screen  220 , as described in more detail below. In some examples, touch controller  206 , touch processor  202  and peripherals  204  can be integrated into a single application specific integrated circuit (ASIC), and in some examples can be integrated with touch screen  220  itself. 
     It should be apparent that the architecture shown in  FIG. 2  is only one example architecture of computing system  200 , and that the system could have more or fewer components than shown, or a different configuration of components. The various components shown in  FIG. 2  can be implemented in hardware, software, firmware or any combination thereof, including one or more signal processing and/or application specific integrated circuits. 
     Computing system  200  can include a host processor  228  for receiving outputs from touch processor  202  and performing actions based on the outputs. For example, host processor  228  can be connected to program storage  232  and a display controller/driver  234  (e.g., a Liquid-Crystal Display (LCD) driver). It is understood that although some examples of the disclosure may described with reference to LCD displays, the scope of the disclosure is not so limited and can extend to other types of displays, such as Light-Emitting Diode (LED) displays, including Organic LED (OLED), Active-Matrix Organic LED (AMOLED) and Passive-Matrix Organic LED (PMOLED) displays. Display driver  234  can provide voltages on select (e.g., gate) lines to each pixel transistor and can provide data signals along data lines to these same transistors to control the pixel display image. 
     Host processor  228  can use display driver  234  to generate a display image on touch screen  220 , such as a display image of a user interface (UI), and can use touch processor  202  and touch controller  206  to detect a touch on or near touch screen  220 , such as a touch input to the displayed UI. The touch input can be used by computer programs stored in program storage  232  to perform actions that can include, but are not limited to, 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, terminating a telephone call, changing the volume or audio settings, storing information related to telephone communications such as addresses, frequently dialed numbers, received calls, missed calls, logging onto a computer or a computer network, permitting authorized individuals access to restricted areas of the computer or computer network, loading a user profile associated with a user&#39;s preferred arrangement of the computer desktop, permitting access to web content, launching a particular program, encrypting or decoding a message, capturing an image with a camera in communication with the electronic device, exiting an idle/sleep state of the electronic device, and/or the like. Host processor  228  can also perform additional functions that may not be related to touch processing. 
     Note that one or more of the functions described herein, including the configuration of switches, can be performed by firmware stored in memory (e.g., one of the peripherals  204  in  FIG. 2 ) and executed by touch processor  202 , or stored in program storage  232  and executed by host processor  228 . 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. In some examples, RAM  212  or program storage  232  (or both) can be a non-transitory computer readable storage medium. One or both of RAM  212  and program storage  232  can have stored therein instructions, which when executed by touch processor  202  or host processor  228  or both, can cause the device including computing system  200  to perform one or more functions and methods of one or more examples of this disclosure. 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. 
     Touch screen  220  can be used to derive touch information at multiple discrete locations of the touch screen, referred to herein as touch nodes. Touch screen  220  can include touch sensing circuitry that can include a capacitive sensing medium having a plurality of drive lines  222  and a plurality of sense lines  223 . It should be noted that the term “lines” is sometimes used herein to mean simply conductive pathways, as one skilled in the art will readily understand, and is not limited to elements that are strictly linear, but includes pathways that change direction, and includes pathways of different size, shape, materials, etc. Drive lines  222  can be driven by stimulation signals  216  from driver logic  214  through a drive interface  224 , and resulting sense signals  217  generated in sense lines  223  can be transmitted through a sense interface  225  to sense channels  208  in touch controller  206 . In this way, drive lines and sense lines can be part of the touch sensing circuitry that can interact to form capacitive sensing nodes, which can be thought of as touch picture elements (touch pixels) and referred to herein as touch nodes, such as touch nodes  226  and  227 . This way of understanding can be particularly useful when touch screen  220  is viewed as capturing an “image” of touch (“touch image”). In other words, after touch controller  206  has determined whether a touch has been detected at each touch nodes in the touch screen, the pattern of touch nodes in the touch screen at which a touch occurred can be thought of as an “image” of touch (e.g., a pattern of fingers touching the touch screen). As used herein, an electrical component “coupled to” or “connected to” another electrical component encompasses a direct or indirect connection providing electrical path for communication or operation between the coupled components. Thus, for example, drive lines  222  may be directly connected to driver logic  214  or indirectly connected to drive logic  214  via drive interface  224  and sense lines  223  may be directly connected to sense channels  208  or indirectly connected to sense channels  208  via sense interface  225 . In either case an electrical path for driving and/or sensing the touch nodes can be provided. 
       FIG. 3A  illustrates an exemplary touch sensor circuit  300  corresponding to a self-capacitance measurement of a touch node electrode  302  and sensing circuit  314  (e.g., corresponding to a sense channel  208 ) according to examples of the disclosure. Touch node electrode  302  can correspond to a touch electrode  404  or  406  of touch screen  400  or a touch node electrode  408  of touch screen  402 . Touch node electrode  302  can have an inherent self-capacitance to ground associated with it, and also an additional self-capacitance to ground that is formed when an object, such as finger  305 , is in proximity to or touching the electrode. The total self-capacitance to ground of touch node electrode  302  can be illustrated as capacitance  304 . Touch node electrode  302  can be coupled to sensing circuit  314 . Sensing circuit  314  can include an operational amplifier  308 , feedback resistor  312  and feedback capacitor  310 , although other configurations can be employed. For example, feedback resistor  312  can be replaced by a switched capacitor resistor in order to minimize a parasitic capacitance effect that can be caused by a variable feedback resistor. Touch node electrode  302  can be coupled to the inverting input (−) of operational amplifier  308 . An AC voltage source  306  (V ac ) can be coupled to the non-inverting input (+) of operational amplifier  308 . Touch sensor circuit  300  can be configured to sense changes (e.g., increases) in the total self-capacitance  304  of the touch node electrode  302  induced by a finger or object either touching or in proximity to the touch sensor panel. Output  320  can be used by a processor to determine the presence of a proximity or touch event, or the output can be inputted into a discrete logic network to determine the presence of a proximity or touch event. 
       FIG. 3B  illustrates an exemplary touch sensor circuit  350  corresponding to a mutual-capacitance drive line  322  and sense line  326  and sensing circuit  314  (e.g., corresponding to a sense channel  208 ) according to examples of the disclosure. Drive line  322  can be stimulated by stimulation signal  306  (e.g., an AC voltage signal). Stimulation signal  306  can be capacitively coupled to sense line  326  through mutual capacitance  324  between drive line  322  and the sense line. When a finger or object  305  approaches the touch node created by the intersection of drive line  322  and sense line  326 , mutual capacitance  324  can change (e.g., decrease). This change in mutual capacitance  324  can be detected to indicate a touch or proximity event at the touch node, as described herein. The sense signal coupled onto sense line  326  can be received by sensing circuit  314 . Sensing circuit  314  can include operational amplifier  308  and at least one of a feedback resistor  312  and a feedback capacitor  310 .  FIG. 3B  illustrates a general case in which both resistive and capacitive feedback elements are utilized. The sense signal (referred to as V in ) can be inputted into the inverting input of operational amplifier  308 , and the non-inverting input of the operational amplifier can be coupled to a reference voltage V ref . Operational amplifier  308  can drive its output to voltage V o  to keep yin substantially equal to V ref , and can therefore maintain V in  constant or virtually grounded. A person of skill in the art would understand that in this context, equal can include deviations of up to 15%. Therefore, the gain of sensing circuit  314  can be mostly a function of the ratio of mutual capacitance  324  and the feedback impedance, comprised of resistor  312  and/or capacitor  310 . The output of sensing circuit  314  Vo can be filtered and heterodyned or homodyned by being fed into multiplier  328 , where Vo can be multiplied with local oscillator  330  to produce V detect . V detect  can be inputted into filter  332 . One skilled in the art will recognize that the placement of filter  332  can be varied; thus, the filter can be placed after multiplier  328 , as illustrated, or two filters can be employed: one before the multiplier and one after the multiplier. In some examples, there can be no filter at all. The direct current (DC) portion of V detect  can be used to determine if a touch or proximity event has occurred. 
     Referring back to  FIG. 2 , in some examples, touch screen  220  can be an integrated touch screen in which touch sensing circuit elements of the touch sensing system can be integrated into the display pixel stack-ups of a display. The circuit elements in touch screen  220  can include, for example, elements that can exist in LCD or other displays (LED display, OLED display, etc.), such as one or more pixel transistors (e.g., thin film transistors (TFTs)), gate lines, data lines, pixel electrodes and common electrodes. In a given display pixel, a voltage between a pixel electrode and a common electrode can control a luminance of the display pixel. The voltage on the pixel electrode can be supplied by a data line through a pixel transistor, which can be controlled by a gate line. It is noted that circuit elements are not limited to whole circuit components, such as a whole capacitor, a whole transistor, etc., but can include portions of circuitry, such as only one of the two plates of a parallel plate capacitor. 
       FIG. 4A  illustrates touch screen  400  with touch electrodes  404  and  406  arranged in rows and columns according to examples of the disclosure. Specifically, touch screen  400  can include a plurality of touch electrodes  404  disposed as rows, and a plurality of touch electrodes  406  disposed as columns. Touch electrodes  404  and touch electrodes  406  can be on the same or different material layers on touch screen  400 , and can intersect with each other, as illustrated in  FIG. 4A . In some examples, the electrodes can be formed on opposite sides of a transparent (partially or fully) substrate and from a transparent (partially or fully) semiconductor material, such as ITO, though other materials are possible. Electrodes displayed on layers on different sides of the substrate can be referred to herein as a double-sided sensor. In some examples, touch screen  400  can sense the self-capacitance of touch electrodes  404  and  406  to detect touch and/or proximity activity on touch screen  400 , and in some examples, touch screen  400  can sense the mutual capacitance between touch electrodes  404  and  406  to detect touch and/or proximity activity on touch screen  400 . Although the touch electrodes  404  and  406  are illustrated as being rectangularly-shaped, it should be understood that other electrode shapes and structures (e.g., diamond-, square-, stripe- or circle-shaped electrodes connected by jumpers or vias) are possible. 
       FIG. 4B  illustrates touch screen  402  with touch node electrodes  408  arranged in a pixelated touch node electrode configuration according to examples of the disclosure. Specifically, touch screen  402  can include a plurality of individual touch node electrodes  408 , each touch node electrode identifying or representing a unique location on the touch screen at which touch or proximity (i.e., a touch or proximity event) is to be sensed, and each touch node electrode being electrically isolated from the other touch node electrodes in the touch screen/panel, as previously described. Touch node electrodes  408  can be on the same or different material layers on touch screen  402 . In some examples, touch screen  402  can sense the self-capacitance of touch node electrodes  408  to detect touch and/or proximity activity on touch screen  402 , and in some examples, touch screen  402  can sense the mutual capacitance between touch node electrodes  408  to detect touch and/or proximity activity on touch screen  402 . Although touch node electrodes  408  are illustrated as having rectangular shapes, it should be understood that other electrode shapes (e.g., diamonds, circles, stripes etc.) and structures are possible. 
     As discussed above, signals generated at the touch nodes of touch screen  124 ,  220 ,  400 , or  402  can be viewed as an image of the touch.  FIG. 5A  illustrates an exemplary image of touch according to examples of the disclosure. Touch screen  500  can include a plurality of touch nodes  502 . As described above, with reference to  FIGS. 1-4 , each touch node  502  can be the intersection of touch electrodes  404  and  406  arranged as row electrodes and column electrodes that function as drive electrodes and sense electrodes, such as in touch screen  400  illustrated in  FIG. 4A . In some examples, as described above with reference to  FIGS. 1-4 , each touch node  502  can be at a location of a touch node electrode  408 , such as in touch screen  402  described above with reference to  FIG. 4B . In some examples, an image of touch can be generated by a touch screen  500  in response to detecting a proximate conductive object (e.g., a finger, a stylus, etc.). 
     Each object touching or hovering over the touch screen  500  (i.e., proximate to the touch screen) can be represented by an input patch  510  in the touch image that includes touch nodes with a touch signal above a threshold in an area corresponding to the location at which the object is in contact with or proximity to the touch screen and, in some examples, that includes one or more additional touch nodes proximate to the location at which the object is in contact with or proximity to the touch screen. For example, one or more touch nodes  502  of the input patch  510  located at locations overlapping a location of the touch or proximity of an object can produce signals with one or more first magnitudes and one or more touch nodes of the input patch  510  at locations adjacent to or otherwise proximate to the location of the touch or proximity of an object can produce signals with one or more second magnitudes that are less than the first magnitude. Thus, signals from proximate touch nodes  502  can be grouped together to form input patches  510 . Thus, the input patch  510  can be a region within the image of touch corresponding to touch nodes  502  having signal values produced by an object touching or hovering over the touch screen  500  (e.g., those with signal greater than a threshold). 
     In some situations, a proximate object can change the location at which the proximate object is in contact with (or proximate to) the touch screen  500 . For example, a user may perform a gesture at (or over) the touch screen, such as a swipe or other movement, or the user&#39;s hand may move involuntarily.  FIG. 5B  illustrates an exemplary representation indicative of an object that moves along the surface of the touch screen according to some examples of the disclosure. As shown in  FIG. 5B , input patch  510  can initially be detected in a first touch image (e.g., when the user initially touches the touch screen) and input patch  512  can be detected at a time after input patch  510  was detected in a second, subsequent touch image. Although not shown in  FIG. 5B , an input patch can be detected during additional touch images between those including input patches  510  and  512 . For example, the proximate object being detected by input patches  510  and  512  can move along the surface of the touch screen  500 , such as by a user moving their finger along the surface of touch screen  500 . The electronic device is able to detect the image of touch across several frames, determine that input patches  510  and  512  correspond to the same object and track the movement of the object based on the corresponding input patches  510  and  512 . Although the location, shape, and size of input patches  510  and  512  is not necessarily the same, the electronic device is able to track the movement of the proximate object by determining that the input patches  510  and  512  have continuity (e.g., several frames of input patches indicative of movement of a continuous contact can be detected). Thus, characteristics of the input patches  510  and  512 , such as z-density, which will be described below, can be tracked over time and associated with one proximate object. 
     For example, input patches from a corresponding object captured across multiple touch images can be assigned to a corresponding path. Assigning input patches to paths can allow for tracking gesture inputs (e.g., swipe, pinch, etc.). In some examples, the path can track the input contact from an initial touchdown on the touch screen through a liftoff from the touch screen. In some examples, the input patches of a path can be analyzed to identify movement of the input patch across one or more touch images and thereby track movement of an object corresponding to the input patches. Although a path can be used to identify movement, some paths may not include movement (e.g., when the input patch remains in the same position from touchdown to liftoff, such as in a tap). The tracking can include tracking position, velocities, and/or geometries (e.g., shape, number of touch nodes) of the input patches from various touch images corresponding to a path. 
     Various characteristics can be computed for each input patch (e.g., input patches  510  and  512 , and any input patches in between) that can be used for further processing. For example, each input patch (e.g., input patches  510  and  512 , and any input patches in between for a given path) can be represented by an ellipse defined by a centroid, major and minor axis lengths and a major axis (and/or minor axis) orientation (or alternatively an x-axis radius and a y-axis radius). In some examples, a maximum signal and/or a minimum signal can be measured for each input patch. Additionally, the total signal, the number of touch nodes, and signal density for each input patch (e.g., input patches  510  and  512 , and any input patches in between) can be computed. As described herein, in some examples, a slope across time of the signal density can be derived from the signal densities of input patches associated with the path. For example, an input patch&#39;s total signal can be calculated by summing the square of the signal value at each touch node in the input patch (e.g., input patches  510  and  512 , and any input patches in between). Thus, total signal for an input patch (e.g., input patches  510  and  512 , and any input patches in between) can be expressed mathematically as in Equation (1): 
     
       
         
           
             
               
                 
                   
                     Z 
                     p 
                   
                   = 
                   
                     
                       ∑ 
                       
                         i 
                         , 
                         
                           j 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           in 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           P 
                         
                       
                     
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     
                       [ 
                       
                         V 
                         
                           
                             [ 
                             i 
                             ] 
                           
                           ⁡ 
                           
                             [ 
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                   ( 
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     where Z P  can represent the total signal for an input patch (e.g., input patches  510  and  512 , and any input patches in between), V can represent the signal value at a touch node and i, j can represent the row and column coordinate of each touch node. In some examples, the signal value at each touch node can be calibrated before computing the total signal. 
     An input patch&#39;s signal density can be computed based on the input patch&#39;s total signal. In some examples, an input patch&#39;s signal density can be calculated by dividing the total signal for an input patch (e.g., input patches  510  and  512 , and any input patches in between) by the geometric mean radius of the input patch. In other examples, the input patch&#39;s signal density can be calculated by dividing the total signal for an input patch (e.g., input patches  510  and  512 , and any input patches in between) by the number of touch nodes in the input patch. Thus, signal density for an input patch (e.g., input patches  510  and  512 , and any input patches in between) can be expressed mathematically, for example, as in Equations (2) or (3): 
     
       
         
           
             
               
                 
                   
                     Z 
                     
                       density 
                       , 
                       p 
                     
                   
                   = 
                   
                     
                       Z 
                       p 
                     
                     
                       geometric 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       mean 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       radius 
                       ⁢ 
                       
                           
                       
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                       of 
                       ⁢ 
                       
                           
                       
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                   ( 
                   2 
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                     Z 
                     
                       density 
                       , 
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                   = 
                   
                     
                       Z 
                       p 
                     
                     
                       number 
                       ⁢ 
                       
                           
                       
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                       of 
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                       touch 
                       ⁢ 
                       
                           
                       
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                       nodes 
                       ⁢ 
                       
                           
                       
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                       forming 
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     In some examples, an input patch&#39;s signal density, Zdensity, can be used to discriminate between an object hovering over the surface of a touch sensor panel and an object touching the surface of a touch sensor panel.  FIG. 6A  illustrates an exemplary signal density diagram for an object touching and lifting off a touch sensor panel according to examples of the disclosure. In the example of  FIG. 6A , bare finger touch threshold  606  can be defined as the signal density at which point the touch sensing system can identify an input patch representative of an object directly touching the touch sensor panel when detecting touch in a bare finger touch detection mode, as will be described below. In other words, the bare finger touch threshold  606  can be the signal density at which the system determines that an object is touching the touch sensor panel when detecting touch in a bare finger touch detection mode, as will be described below. In some examples, when the signal density changes from being above the bare finger touch threshold  606  to being below the touch threshold, the touch sensing system can determine that the object has lifted off of the touch screen. In some examples, the liftoff threshold can be a different threshold than the touch threshold. 
     Representative curve  602  illustrates a signal density of an input patch as a function of time (e.g., the signal density measurements for a path) that can correspond to an object, such as a finger or stylus in the following sequence: approaching, touching and lifting off the touch sensor panel. At time t1, Zdensity of the input patch can reach the bare finger touch threshold  606  and the input patch can be identified as touching the touch sensor panel. At time t2, Zdensity of the input patch can decrease and cross the bare finger touch threshold again and the electronic device can determine that the object has lifted off of the touch screen. 
     In some examples, an object touching the surface of the touch sensor panel (e.g., Zdensity of the input patch reaches or exceeds the touch threshold) can be used to interact with a graphical user interface, whereas objects that do not produce an input patch with a Zdensity exceeding the touch threshold can be ignored. Setting inappropriate touch threshold values can cause errors. For example, setting the touch threshold too low can cause the touch sensor circuitry to be oversensitive and mistakenly identify hovering objects as touch events (i.e. false positives). 
     In some cases, a non-conductive barrier between an object and a touch sensor panel can cause the Zdensity of intended touches to fail to reach the bare finger touch threshold. For example, a user can be wearing one or more gloves or have a bandage one or more fingers. Touches through such a barrier (generally, “gloved touches”) can be more distant from touch nodes of the touch screen and thus can have a lower total signal and signal density. As a result, although intended as touches by the user, some gloved touches can fail to reach the touch threshold and can be ignored by the touch sensor circuitry. 
     Referring back to  FIG. 6A , representative curve  612  illustrates the signal density of an input patch that can correspond to a gloved object, such as a gloved finger in the following sequence: approaching, touching and lifting off the touch sensor panel. In the example of  FIG. 6A , Zdensity of a gloved touch patch can fail to reach bare finger touch threshold  606 . Thus, during a gloved touch detection mode, glove touch detection threshold  608 , which is less than bare finger touch detection threshold, can be used to detect such gloved touches. In some situations, lowering the touch threshold can cause the system to be oversensitive to non-touches made by a proximate finger without a barrier (“ungloved touches” or “bare finger touches”). For example, lowering the touch threshold inappropriately can cause the system to falsely identify a hovering ungloved/bare finger as a touch, which can, in turn, can cause the electronic device to perform actions unintended by the user (e.g., activating a user interface element, etc.). 
     Therefore, in some examples, it is advantageous to dynamically change the touch threshold depending on whether the user is interacting with the electronic device while wearing gloves (or having some other barrier, such as a bandages) or interacting with the electronic device with bare fingers. In some examples, the electronic device can operate in one of a “bare finger mode” (e.g., the default mode) and a “glove mode” in which the touch threshold is at a higher value and an appropriate lower value, respectively. For example, the electronic device can compare the Zdensity of input patches to the bare finger touch detection threshold  606  while operating in the bare finger mode and can compare the Zdensity of input patches to the glove touch detection threshold  608  while operating in the glove mode. 
     The electronic device optionally switches between modes by detecting one or more characteristics of one or more input patch that are indicative of “bare finger” operation or “gloved” operation. For example, a “bare finger” touch can be detected when the Zdensity of an input patch exceeds a “bare finger” touch threshold (e.g., the bare finger touch threshold  606  illustrated in  FIG. 6A , which can be the touch threshold when the touch screen is operating in the bare finger mode). A “gloved” touch can be detected, for example, based on the stability of an input patch that has a Zdensity that does not exceed the “bare finger” touch threshold. 
     As shown in  FIG. 6A , representative curve  612  does not reach the bare finger touch threshold  606 , but does reach the glove touch detection threshold  608 . Moreover, representative curve  612  has a relatively stable shape between T1 and T2, unlike a period of time before T1 during which the Zdensity is increasing rapidly (e.g., gloved finger touch down) and a period of time after T2 during which Zdensity is decreasing rapidly (e.g., gloved finger lift off). Likewise, representative curve  606  has a relatively stable section between T1 and T2. 
     As mentioned above, in some examples, the signal density measurements for input patches associated with a path can be used to derive a slope of the signal density for the path.  FIG. 6B  illustrates the Zdensity slope of a representative curve of an object touching down on and lifting off from a touch screen according to some examples of the disclosure. The Zdensity slope  616  illustrated in  FIG. 6B  can be the slope of curve  602  illustrated in  FIG. 6A . In other words, Zdensity slope  616  illustrates the time-based derivative or the rate of change of Zdensity  602  over time. As shown in  FIG. 6B , prior to T1, the Zdensity slope  616  is greater than 0 (positive sign) corresponding to the increase in Zdensity over time before T1 as shown in  FIG. 6A . After time T2, the Zdensity slope  616  illustrated in  FIG. 6B  is less than zero (negative) corresponding to the decrease in Zdensity over time after T2 as shown in  FIG. 6A . Between times T1 and T2, the Zdensity slope  616  is approximately 0 (e.g., within a predetermined threshold value of zero) corresponding to the stability of Zdensity  602  as shown in  FIG. 6A , between times T1 and T2. 
     In some examples, the electronic device is able to detect a gloved touch by detecting an input patch with a Zdensity that is less than a bare finger touch threshold and that has a relatively stable value (e.g., the Zdensity slope is approximately 0) for a predetermined amount of time. In other words, the electronic device can identify input patches as corresponding to a gloved finger when the Zdensity is relatively stable for a period of time. When a user hovers a bare finger above the touch screen, it can be difficult for the user to hover the finger at a stable height. Thus, a hovering bare finger will produce different touch signals than a touching gloved finger; the gloved finger can have a Zdensity that is more stable than the Zdensity of the hovering bare finger. 
     Using the above Zdensity stability criterion described above to detect a gloved touches, however, may result in some false positives. For example, it can be possible for a hovering bare finger to appear to have a stable Zdensity, thus appearing to the electronic device to be a touching gloved finger. For example, when a user is using a soft keyboard (e.g., a virtual keyboard display on the display of the touch screen) to type (e.g., to enter a message, note, etc.), the user may hover one or more fingers above the touch screen between entering characters. For example, if the user&#39;s fingers hover at a stable height (which may be more likely when a user grips the device with two hands and pauses typing), the electronic device can falsely identify the hovering bare fingers as touching gloved fingers and trigger a transition into glove mode. Falsely identifying a bare hovering finger as a touching gloved finger can cause the electronic device to incorrectly lower the touch threshold (e.g., for the purpose of detecting gloved touches). As discussed above, however, incorrectly lowering the touch threshold can lead to errors, such as processing input patches produced by hovering bare fingers as though they were produced by touching gloved fingers, for example. 
     In some examples, rather than using the Zdensity stability criterion alone, additional criteria may be required to transition into glove mode. In some examples, the electronic device transitions from the bare finger mode to the gloved mode in response to detecting, from the touch signals, a sequence of events including detecting the approach of an object, followed by the object remaining a stable distance from the touch screen without having a Zdensity that exceeds the bare finger touch threshold, followed by detecting liftoff of the object without detecting the object re-approaching the touch screen for a predetermined time (e.g., 0 seconds, 0.5 seconds, 1 second, etc.) after liftoff is detected. In some examples, this sequence can be detected based on the values of the Zdensity signal over time (for the path). In some examples, transitions in this sequence can be detected based on the values of the Zdensity slope over time (for the respective path). In some examples, detection of the sequence can be implemented using a finite state machine (e.g., implemented in discrete logic, a programmable logic device (PLD), a field programmable gate array (FPGA) or other circuitry configured or configurable to implement the finite state machine), as described below with reference to  FIG. 7 . In some examples, the finite state machine can be implemented as part of touch controller  206  in  FIG. 2 . 
       FIG. 7  illustrates an exemplary finite state machine  700  for transitioning a touch screen between two modes of operation according to some examples of the disclosure. State machine  700  can be used, for example, to transition between a bare finger touch detection mode  730  and a gloved touch detection mode  740 . In some examples, sensing touch in the bare finger touch detection mode includes using a bare finger touch threshold (e.g., corresponding to bare finger touch threshold  606 ) to identify input patches as touches and sensing touch in the gloved touch detection mode includes using a gloved touch detection threshold (e.g., corresponding to glove touch detection threshold  608 ) to identify input patches as touches. The bare finger touch threshold is higher than the gloved touch threshold, for example. In some examples, while sensing in either mode, the Zdensity of an input patch can be compared to the respective touch threshold to detect a touch. 
     State machine  700  includes a plurality of states  702 ,  704 ,  706 , and  708 . State  702  can correspond to a starting state of the bare finger mode  730  (e.g., default state). State  708  can correspond to the gloved mode of operation  740 . States  704  and  706  can be intermediate states (while the device may continue to operate in the bare finger mode  730 ) used to transition from the bare finger mode  730  to the gloved mode  740 . The transition from state  702  to state  708  via states  704  and  706  can represent a sequence of events (touch down, stability, lift-off without re-approach or touch down followed by sustained stability), that can be determined using Zdensity or Zdensity slope measurements that can be measured for a gloved finger. In some examples, the electronic device senses touch in the bare finger mode  730  with the relatively higher touch threshold while operating in states  702 ,  704 , and  706  and senses touch in the gloved mode  740  with the relatively lower touch threshold while operating in state  708 . The state machine  700  provides exemplary criteria  712 - 728  to transition between states  702 - 708  and thereby transition between the two modes. 
     In some examples, while operating in state  702 , the electronic device senses touch in the bare finger mode. For example, the electronic device compares the Zdensity of input patches to a bare finger touch threshold (e.g., corresponding to bare finger touch threshold  606 ) to determine whether an object is touching the touch screen. In response to detecting an object approaching the touch screen (e.g., criterion  712 ), the electronic device optionally transitions to state  704 . In some examples, detecting the object approaching the touch screen includes comparing the slope of the Zdensity to a positive threshold value. Thus, criterion  712  can be satisfied when the Zdensity slope is greater than the threshold. When criterion  712  is not satisfied (e.g., when the Zdensity slope is less than the threshold), the electronic device can remain in state  702 . 
     In some examples, in state  704 , the electronic device optionally continues to sense touch in the bare finger mode  730 . While in state  704 , in response to detecting an input patch with a Zdensity that exceeds the bare finger touch threshold (e.g., criterion  724 ), the electronic device returns to state  702 , for example. In some examples, a bare finger can be detected in response to detecting an input patch with a maximum touch signal (e.g., a single touch node with the maximum signal in the input patch) greater than a threshold or a total signal for the input patch exceeding a threshold or a signal density greater than a threshold. In some examples, while in state  704 , when the electronic device detects an input patch that has a Zdensity slope within a predetermined range (e.g., within a threshold range of zero) corresponding to a stable Zdensity for a first threshold period of time (e.g., criterion  714 ), the electronic device optionally transitions to state  706 . In some examples, the electronic device determines that the slope of the Zdensity is within the predetermined range by comparing the Zdensity to a negative threshold and a positive threshold that are offset from zero by predetermined amounts. For example, an object that hovers above the touch screen without moving will have a Zdensity slope that is approximately zero. When criterion  714  is not satisfied (e.g., when the Zdensity slope exceeds the threshold in either direction without being stable for a threshold period of time), the electronic device can return to state  702  or remain in state  704 . 
     While operating in state  706 , the electronic device optionally continues to sense touch in the bare finger mode  730 . In response to detecting liftoff of the input patch without detecting the object re-approaching the touch screen within a third predetermined time threshold (e.g., criterion  716 ), the electronic device optionally transitions to state  708 . In some examples, the electronic device detects liftoff by detecting a Zdensity slope that is below a liftoff threshold (comparing the Zdensity slope to a negative threshold value). Thus, criterion  716  can be satisfied when the Zdensity slope is less than the threshold. In some examples, the electronic device detects liftoff by detecting a Zdensity less than a liftoff threshold. In some examples, if, while operating in state  706 , the electronic device continues to detect a stable Zdensity slope for a second predetermined time threshold (e.g., criterion  715 ), the electronic device transitions to state  708  and operates in the glove touch detection mode  740 . 
     In some examples, in response to detecting an input patch with a Zdensity that exceeds the bare finger touch threshold or in response to detecting re-approach of the object (e.g., Zdensity above a positive threshold) within a predetermined amount of time of detecting liftoff (e.g., criteria  726 ), the electronic device returns to state  702 . In some examples, while the Zdensity slope (or Zdensity) is stable in state  706 , the electronic device can remain in state  706 . 
     In some examples, while operating in state  708 , the electronic device detects touch in the glove touch mode  730 , which can include comparing the Zdensity of input patches to a glove touch threshold to detect touch. As described above, the glove touch detection threshold can be lower than the bare finger touch detection threshold because, for example, a gloved finger is not able to directly touch the touch screen (due to the intervening glove) and, therefore, may cause the touch screen to detect a lower Zdensity compared with the Zdensity of a bare finger in contact with the touch screen. The electronic device optionally continues to operate in the glove touch mode until it transitions out of state  708 , such as in response to detecting a Zdensity (or a maximum signal or a total signal) that exceeds the bare finger touch threshold (e.g., criterion  728 ). 
       FIG. 8A  illustrates exemplary Zdensity  802  and Zdensity slope  812  profiles associated with detecting a gloved touch according to some examples of the disclosure. Chart  800  illustrates an exemplary Zdensity curve  802  of a gloved finger approaching, touching, and lifting off of a touch screen, and chart  810  illustrates an exemplary Zdensity slope curve  812  corresponding to Zdensity curve  802 , for example. In this example, when Zdensity  802  is increasing, Zdensity slope  812  is positive; when Zdensity  802  is stable, Zdensity slope  812  is approximately zero; and when Zdensity  802  is decreasing, Zdensity slope  812  is negative. 
     As shown in  FIG. 8A , at time T1, Zdensity  802  is increasing and the Zdensity slope  812  exceeds a first threshold  822 , for example. In some examples, the first threshold  822  is associated with detecting an object approaching the touch screen. In response to detecting the Zdensity slope  812  above the first threshold  822 , the electronic device optionally transitions from state  702  to state  704  of state machine  700  illustrated in  FIG. 7 . Thus, detecting the Zdensity slope  812  above the first threshold  822  optionally corresponds to criterion  712 . 
     At time T2, Zdensity  802  is substantially stable and the Zdensity slope  812  is between a second threshold  824  and a third threshold  826 , for example. For example, at time T2, the gloved finger touches down on the touch screen. In some examples, the Zdensity  802  of the gloved finger at time T2 does not reach a bare finger touch threshold (not shown in  FIG. 8A ), such as in a manner similar to how profile  612  is less than bare finger touch threshold  606  in  FIG. 6A . In response to detecting the Zdensity slope  812  between the second threshold  824  and the third threshold  826  for a threshold period of time, the electronic device optionally transitions from state  704  to state  706  of state machine  700  illustrated in  FIG. 7 . Thus, detecting the Zdensity slope  812  between the second threshold  824  and the third threshold  826  optionally corresponds to criterion  714 . 
     At time T3, Zdensity  802  decreases and the Zdensity slope  812  is below a fourth threshold  828 , for example. For example, at time T3, the gloved finger lifts off of the touch screen. From time T3 to time T4, the Zdensity slope  828  is below the first threshold  822 , which can indicate that the object does not re-approach the touch screen between time T3 and time T4. In some examples, time T4 is a predetermined amount of time after T3, such as 0 seconds, 0.5 seconds, 1 second, or another threshold amount of time. In some examples, the threshold to which Zdensity  812  is compared to determine whether or not the object re-approaches the touch screen is different from the first threshold  822  (e.g., second threshold  824 ). In response to detecting the Zdensity slope  812  below the fourth threshold  828  at time T3 without detecting the object re-approaching the touch screen from T3 to T4, the electronic device optionally transitions from operating in the third state  706  to operating in the fourth state  708  of state machine  700  illustrated in  FIG. 7 . Thus, detecting the Zdensity slope  812  below the fourth threshold  828  at time T3 without detecting the object re-approaching the touch screen from T3 to T4 can correspond to criteria  716 . 
     As described above with reference to  FIG. 7 , the electronic device can detect touch in the glove touch mode while operating in state  708 . Thus, in response to detecting the sequence of a Zdensity slope  812  above the first threshold  822 , then between the second threshold  824  and the third threshold  826 , then below the fourth threshold  828  without exceeding a re-approach threshold (e.g., the first threshold  822  or a different threshold) for a predetermined amount of time (e.g., the time between T3 and T4), the electronic device optionally transitions from the bare finger touch detection mode to the glove touch detection mode. 
     If, at a time between T3 and T4, the electronic device were to detect the Zdensity slope  812  above a threshold indicative of the object re-approaching the touch screen, or, if at any time between T1 and T4, the electronic device detects a Zdensity that exceeds the bare finger touch threshold, the electronic device returns to state  702  and continues to operate in the bare finger touch detection mode. 
       FIG. 8B  illustrates exemplary Zdensity  832  and Zdensity slope  842  profiles associated with detecting a gloved touch according to some examples of the disclosure. Chart  830  illustrates an exemplary Zdensity curve  832  of a gloved finger approaching and touching a touch screen, and chart  840  illustrates an exemplary Zdensity slope curve  842  corresponding to Zdensity curve  832 , for example. In this example, when Zdensity  832  is increasing, Zdensity slope  842  is positive; when Zdensity  832  is stable, Zdensity slope  842  is approximately zero; and when Zdensity  832  is decreasing, Zdensity slope  842  is negative. 
     As shown in  FIG. 8B , at time T1, Zdensity  832  is increasing and the Zdensity slope  842  exceeds a first threshold  855 , for example. In some examples, the first threshold  855  is associated with detecting an object approaching the touch screen. In response to detecting the Zdensity slope  842  above the first threshold  855 , the electronic device optionally transitions from state  702  to state  704  of state machine  700  illustrated in  FIG. 7 . Thus, detecting the Zdensity slope  842  above the first threshold  855  optionally corresponds to criterion  712 . 
     At time T2, Zdensity  832  is substantially stable and the Zdensity slope  842  is between a second threshold  854  and a third threshold  856 , for example. For example, at time T2, the gloved finger touches down on the touch screen. In some examples, the Zdensity  832  of the gloved finger at time T2 does not reach a bare finger touch threshold (not shown in  FIG. 8B ), such as in a manner similar to how profile  612  is less than bare finger touch threshold  606  in  FIG. 6A . In response to detecting the Zdensity slope  842  between the second threshold  854  and the third threshold  856  for a first threshold period of time (e.g., 0 seconds, 0.5 seconds, 1 second), the electronic device optionally transitions from state  704  to state  706  of state machine  700  illustrated in  FIG. 7 . Thus, detecting the Zdensity slope  842  between the second threshold  854  and the third threshold  856  optionally corresponds to criterion  714 . 
     At time T3, Zdensity  832  is still substantially stable and the Zdensity slope  842  is still between the second threshold  854  and the third threshold  856 . For example, the time between T2 and T3 is the second predetermined time threshold (e.g., 0 seconds, 0.5 seconds, 1 second) described above with reference to  FIG. 7 . In response to detecting the Zdensity slope  842  between the second threshold  854  and the third threshold  856  for the second predetermined time threshold, the electronic device can transition from state  706  illustrated in  FIG. 7  to state  708  and operate in the glove touch mode  740 . Thus, detecting the stable Zdensity  842  from time T2 to T3 can correspond to criterion  715 . 
       FIG. 9  illustrates an exemplary process  900  of transitioning the electronic device between two different touch detection modes according to some examples of the disclosure. For example, process  900  can be used to transition between detecting touch in a bare finger touch mode using a bare finger touch and to detecting touch in a gloved touch detection mode using a glove touch detection threshold. Process  900  can be performed by touch processor  202 , touch control  206 , host processor  228  or any other processing circuits. In some example, process  900  can be performed by a finite state machine (e.g., corresponding to finite state machine  700 ). 
     At  902 , the electronic device optionally operates in the bare finger touch detection mode to sense one or more proximate objects touching the touch screen. Sensing touch in bare finger mode can include comparing the Zdensity of one or more detected input patches to a bare finger touch detection threshold (e.g., bare finger touch detection threshold  606  illustrated in  FIG. 6 ). 
     At  904 , the electronic device can make a determination whether the detected Zdensity slope is above a first threshold (e.g., whether Zdensity slope  812  is above first threshold  822 ). In accordance with a determination that the Zdensity slope is less than the first threshold, the process  900  can return to  902 . In accordance with a determination that the Zdensity slope is above the first threshold, the method can proceed to  906 . 
     At  906 , the electronic device can make a determination whether the subsequent detected Zdensity slope is between the second threshold and the third threshold for the second predetermined time threshold (e.g., from T2 to T3 illustrated in  FIG. 8B ). If the Zdensity slope is between the second and third threshold for the second predetermined time threshold, the method can proceed to  912  and the electronic device can transition to detecting touch in the glove touch mode, as described above. If the Zdensity slope is not between the second and third threshold for the second predetermined time threshold (e.g., the Zdensity slope is between the second and third threshold for a shorter duration of time, such as the first predetermined time threshold, as described below, or is not between the second and third time threshold), the method proceeds to  907 . 
     At  907 , the electronic device can make a determination whether the Zdensity slope is between the second and third threshold for the first predetermined time threshold (e.g., from T2 to T3 illustrated in  FIG. 8A ). In accordance with a determination that the detected Zdensity slope is not between the second threshold and the third threshold (or is not between the second and third threshold for the first predetermined time threshold), the method can return to  902 . In accordance with a determination that the detected Zdensity slope is between the second threshold and the third threshold for the first threshold period of time, the method can proceed to  908 . 
     At  908 , the electronic device can make a determination whether the subsequently detected Zdensity slope is below the fourth threshold (e.g., whether the Zdensity slope  812  after T3 is below the fourth threshold  828 ). In accordance with a determination that the detected Zdensity slope is above a fifth threshold (not shown) that is positive, such as a threshold having a same or similar value to threshold  822  or threshold  824 , the method can return to  902 . In accordance with a determination that the detected Zdensity slope is below the fourth threshold, the method can proceed to  910 . 
     At  910 , the electronic device can make a determination whether a proximate object is detected approaching the touch screen within a third predetermined time threshold after detecting that the Zdensity slope is below the fourth threshold in  908 . In some examples, the electronic device determines whether an object re-approaches the touch screen by comparing the Z-density slope to a predetermined threshold, such as the first threshold  822  or a different threshold (e.g., second threshold  824 ). In accordance with a determination that the object re-approaches the touch screen within the third predetermined time threshold, the process  900  can return to  902 . In accordance with a determination that the object does not re-approach the touch screen within the third predetermined time threshold, the process  900  can proceed to  912 . 
     At  912 , the electronic device can transition from detecting proximate objects in the bare finger touch detection mode to detecting proximate objects in the glove touch detection mode. Operating in the glove touch detection mode optionally includes comparing the detected Zdensity of one or more input patches to a glove touch detection threshold that is less than the bare finger touch detection threshold (e.g., bare finger touch detection threshold  606 ). 
     After transitioning to the glove touch detection mode, the electronic device optionally determines whether, at any point in time while operating in the glove touch detection mode, the Zdensity exceeds the bare finger touch detection threshold (e.g., touch detection threshold  606 ) or if a touch signal that exceeds a predetermined threshold is detected at one or more touch nodes of the input patch in  914 . In some examples, in accordance with a determination that the Zdensity exceeds the bare finger touch detection threshold, the process  900  can return to  902 . In some examples, while operating in the glove touch detection mode, in accordance with a determination that the detected Zdensity is less than the bare finger touch detection threshold, the method can return to  912  and the electronic device can continue to operate in the glove touch detection mode. After returning to  912 , the process  900  optionally proceeds again to  914  every time an input patch is detected. In other words, every input patch can be compared to the glove touch detection threshold to detect touch and can be compared to the bare finger touch detection threshold to determine whether to return to the bare finger touch detection mode. Although not shown in  FIG. 9 , if, at any point during process  900 , the electronic device detects an input patch with a Zdensity exceeding the bare finger touch detection threshold, the process can return to  902 . In other words, operations  904 - 910  can be executed in order without detecting an input patch with a Zdensity exceeding the bare finger touch detection threshold before transitioning from the bare finger mode to the glove mode. 
     As described above with reference to  FIGS. 1-9 , in some examples, an electronic device can detect touch in one of two touch detection modes. Each touch detection mode can have a unique touch detection threshold. For example, a bare finger touch detection mode can include comparing the detected Zdensity of one or more input patches to a bare finger touch detection threshold and a glove touch detection mode can include comparing the detected Zdensity of one or more input patches to a glove touch detection threshold that is less than the bare finger touch detection threshold. 
     Therefore, according to the above, some examples of the disclosure are directed to a method comprising: at an electronic device comprising a touch screen and one or more processors: sensing, in a first proximity sensing mode, signals indicative of a proximate object during multiple touch frames; calculating signal densities associated with the proximate object corresponding to the multiple touch frames; in accordance with a determination that the signal densities meet a plurality of criteria, transitioning from sensing the signal in the first proximity sensing mode to sensing the signal in the second proximity sensing mode, wherein the plurality of criteria comprise: a first criterion that is satisfied when the slope of the signal densities, calculated from the signal densities corresponding to the multiple touch frames, exceeds a first threshold at a first time; and a second criterion that is satisfied when the slope of the signal densities is less than a second threshold and greater than a third threshold for a first threshold duration of time after the first time, the second threshold less than the first threshold, and the third threshold less than the second threshold; and a third criterion that is satisfied when the slope of the signal densities is less than a fourth threshold at a second time after the threshold duration of time, the fourth threshold less than the third threshold; and in accordance with a determination that the signal densities do not meet the plurality of criteria, continuing to sense the signal in the first proximity sensing mode. Additionally or alternatively, in some examples the first criterion is indicative of the proximate object approaching the surface of the touch screen, the second criterion is indicative of the proximate object indirectly contacting the touch screen at a distance from the touch screen that deviates less than a predetermined amount from being constant, and the third criterion is indicative of the proximate object moving away from the surface of the touch screen. Additionally or alternatively, in some examples the plurality of criteria further include a fourth criterion that is satisfied in accordance with a determination that, from the second time to a third time after the third time, the signal densities are less than a fifth threshold greater than the second threshold. Additionally or alternatively, in some examples the method further includes in accordance with a determination that, at any time from the first time to the second time, a signal density of the signal densities exceeds a fifth threshold: forgoing transitioning from sensing the signal in the first proximity sensing mode to sensing the signal in the second proximity mode; and continuing to sense the signal in the first proximity sensing mode. Additionally or alternatively, in some examples the method includes while sensing the signal in the first proximity sensing mode, comparing the signal densities to a fifth threshold to determine whether or not the proximate object is touching the touch screen; and while sensing the signal in the first proximity sensing mode, comparing the signal densities to a sixth threshold to determine whether or not the proximate object is touching the touch screen, the sixth threshold less than the fifth threshold. Additionally or alternatively, in some examples the first threshold and second threshold are positive, and the third threshold and fourth threshold are negative. Additionally or alternatively, in some examples calculating the slope of the signal densities comprises: identifying a first region of the touch screen corresponding to the proximate object at a first respective time; calculating a signal density of the first region of the touch screen at the first respective time; identifying a second region of the touch screen corresponding to the proximate object at a second respective time; calculating a signal density of the second region of the touch screen at the second respective time; and calculating the rate of change between the signal density of the first region at the first respective time to the signal density of the second region at the second respective time, wherein calculating a respective signal density at a respective time includes: computing a sum of the one or more respective signals indicative of the proximate object, each respective signal of the one or more respective signals associated with a touch node included in a respective region of the touch screen; and dividing the sum of the one or more respective signals by the number of touch nodes included in the respective region of the touch screen. Additionally or alternatively, in some examples the third criterion is satisfied when the slope of the signal densities is less than a fourth threshold at a second time after the threshold duration of time, the fourth threshold less than the third threshold or the slope of the signal densities is less than the second threshold and greater than the third threshold for a second threshold duration of time after the first time, the second threshold duration of time greater than the first threshold duration of time. 
     Some examples of the disclosure are directed to an electronic device, comprising a touch screen; sense circuitry operatively coupled to the touch screen; and one or more processors storing instructions that, when executed, cause the electronic device to perform a method comprising: sensing, with the sense circuitry, in a first proximity sensing mode, signals indicative of a proximate object during multiple touch frames; calculating signal densities associated with the proximate object corresponding to the multiple touch frames; in accordance with a determination that the signal densities meet a plurality of criteria, transitioning from sensing the signal in the first proximity sensing mode to sensing the signal in the second proximity sensing mode, wherein the plurality of criteria comprise: a first criterion that is satisfied when the slope of the signal densities, calculated from the signal densities corresponding to the multiple touch frames, exceeds a first threshold at a first time; a second criterion that is satisfied when the slope of the signal densities is less than a second threshold and greater than a third threshold for a threshold duration of time after the first time, the second threshold less than the first threshold, and the third threshold less than the second threshold; and a third criterion that is satisfied when the slope of the signal densities is less than a fourth threshold at a second time after the threshold duration of time, the fourth threshold less than the third threshold; and in accordance with a determination that the signal densities do not meet the plurality of criteria, continuing to sense the signal in the first proximity sensing mode. Additionally or alternatively, in some examples the first criterion is indicative of the proximate object approaching the surface of the touch screen, the second criterion is indicative of the proximate object indirectly contacting the touch screen at a distance from the touch screen that deviates less than a predetermined amount from being constant, and the third criterion is indicative of the proximate object moving away from the surface of the touch screen. Additionally or alternatively, in some examples the plurality of criteria further include a fourth criterion that is satisfied in accordance with a determination that, from the second time to a third time after the third time, the signal densities are less than a fifth threshold greater than the second threshold. Additionally or alternatively, in some examples the method further comprises: in accordance with a determination that, at any time from the first time to the second time, a signal density of the signal densities exceeds a fifth threshold: forgoing transitioning from sensing the signal in the first proximity sensing mode to sensing the signal in the second proximity mode; and continuing to sense the signal in the first proximity sensing mode. Additionally or alternatively, in some examples the method further comprises: while sensing the signal in the first proximity sensing mode, comparing the signal densities to a fifth threshold to determine whether or not the proximate object is touching the touch screen; and while sensing the signal in the first proximity sensing mode, comparing the signal densities to a sixth threshold to determine whether or not the proximate object is touching the touch screen, the sixth threshold less than the fifth threshold. Additionally or alternatively, in some examples the first threshold and second threshold are positive, and the third threshold and fourth threshold are negative. Additionally or alternatively, in some examples calculating the slope of the signal densities comprises: identifying a first region of the touch screen corresponding to the proximate object at a first respective time; calculating a signal density of the first region of the touch screen at the first respective time; identifying a second region of the touch screen corresponding to the proximate object at a second respective time; calculating a signal density of the second region of the touch screen at the second respective time; and calculating the rate of change between the signal density of the first region at the first respective time to the signal density of the second region at the second respective time, wherein calculating a respective signal density at a respective time includes: computing a sum of the one or more respective signals indicative of the proximate object, each respective signal of the one or more respective signals associated with a touch node included in a respective region of the touch screen; and dividing the sum of the one or more respective signals by the number of touch nodes included in the respective region of the touch screen. Additionally or alternatively, in some examples the third criterion is satisfied when the slope of the signal densities is less than a fourth threshold at a second time after the threshold duration of time, the fourth threshold less than the third threshold or the slope of the signal densities is less than the second threshold and greater than the third threshold for a second threshold duration of time after the first time, the second threshold duration of time greater than the first threshold duration of time. 
     Some examples are directed to a non-transitory computer-readable medium comprising instructions that, when executed by one or more processors of an electronic device comprising a touch screen, cause the electronic device to: sensing, in a first proximity sensing mode, signals indicative of a proximate object during multiple touch frames; calculating signal densities associated with the proximate object corresponding to the multiple touch frames; in accordance with a determination that the signal densities meet a plurality of criteria, transitioning from sensing the signal in the first proximity sensing mode to sensing the signal in the second proximity sensing mode, wherein the plurality of criteria comprise: a first criterion that is satisfied when the slope of the signal densities, calculated from the signal densities corresponding to the multiple touch frames, exceeds a first threshold at a first time; a second criterion that is satisfied when the slope of the signal densities is less than a second threshold and greater than a third threshold for a threshold duration of time after the first time, the second threshold less than the first threshold, and the third threshold less than the second threshold; and a third criterion that is satisfied when the slope of the signal densities is less than a fourth threshold at a second time after the threshold duration of time, the fourth threshold less than the third threshold; and in accordance with a determination that the signal densities do not meet the plurality of criteria, continuing to sense the signal in the first proximity sensing mode. Additionally or alternatively, in some examples the first criterion is indicative of the proximate object approaching the surface of the touch screen, the second criterion is indicative of the proximate object indirectly contacting the touch screen at a distance from the touch screen that deviates less than a predetermined amount from being constant, and the third criterion is indicative of the proximate object moving away from the surface of the touch screen. Additionally or alternatively, in some examples in the plurality of criteria further include a fourth criterion that is satisfied in accordance with a determination that, from the second time to a third time after the third time, the signal densities are less than a fifth threshold greater than the second threshold. Additionally or alternatively, in some examples the instructions further cause the electronic device to: in accordance with a determination that, at any time from the first time to the second time, a signal density of the signal densities exceeds a fifth threshold: forgo transitioning from sensing the signal in the first proximity sensing mode to sensing the signal in the second proximity mode; and continue to sense the signal in the first proximity sensing mode. Additionally or alternatively, in some examples the instructions further cause the electronic device to: while sensing the signal in the first proximity sensing mode, compare the signal densities to a fifth threshold to determine whether or not the proximate object is touching the touch screen; and while sensing the signal in the first proximity sensing mode, compare the signal densities to a sixth threshold to determine whether or not the proximate object is touching the touch screen, the sixth threshold less than the fifth threshold. Additionally or alternatively, in some examples the first threshold and second threshold are positive, and the third threshold and fourth threshold are negative. Additionally or alternatively, in some examples calculating the slope of the signal densities comprises: identifying a first region of the touch screen corresponding to the proximate object at a first respective time; calculating a signal density of the first region of the touch screen at the first respective time; identifying a second region of the touch screen corresponding to the proximate object at a second respective time; calculating a signal density of the second region of the touch screen at the second respective time; and calculating the rate of change between the signal density of the first region at the first respective time to the signal density of the second region at the second respective time, wherein calculating a respective signal density at a respective time includes: computing a sum of the one or more respective signals indicative of the proximate object, each respective signal of the one or more respective signals associated with a touch node included in a respective region of the touch screen; and dividing the sum of the one or more respective signals by the number of touch nodes included in the respective region of the touch screen. Additionally or alternatively, in some examples the third criterion is satisfied when the slope of the signal densities is less than a fourth threshold at a second time after the threshold duration of time, the fourth threshold less than the third threshold or the slope of the signal densities is less than the second threshold and greater than the third threshold for a second threshold duration of time after the first time, the second threshold duration of time greater than the first threshold duration of time. 
     Some examples of the disclosure are directed to a method comprising: at an electronic device comprising a touch screen and one or more processors: sensing, in a first proximity sensing mode, signals indicative of a proximate object during multiple touch frames; calculating signal densities associated with the proximate object corresponding to the multiple touch frames; in accordance with a determination that the signal densities meet a plurality of criteria, transitioning from sensing the signal in the first proximity sensing mode to sensing the signal in the second proximity sensing mode, wherein the plurality of criteria comprise: a first criterion that is satisfied when the slope of the signal densities, calculated from the signal densities corresponding to the multiple touch frames, is indicative of the proximate object approaching the surface of the touch screen; and a second criterion that is satisfied when the slope of the signal densities is indicative of the proximate object indirectly contacting the touch screen at a distance from the touch screen that deviates less than a predetermined amount from being constant; and a third criterion that is satisfied when the slope of the signal densities is indicative of the proximate object moving away from the surface of the touch screen. Additionally or alternatively, in some examples, satisfying the first criterion includes detecting that the slope of the signal densities, calculated from the signal densities corresponding to the multiple touch frames, exceeds a first threshold at a first time, satisfying the second criterion includes detecting that the slope of the signal densities is less than a second threshold and greater than a third threshold for a first threshold duration of time after the first time, the second threshold less than the first threshold, and the third threshold less than the second threshold, and satisfying the third criterion includes detecting that the slope of the signal densities is less than a fourth threshold at a second time after the threshold duration of time, the fourth threshold less than the third threshold. 
     Some examples of the disclosure are directed to an electronic device, comprising: a touch screen; sense circuitry operatively coupled to the touch screen; and one or more processors storing instructions that, when executed, cause the electronic device to perform a method comprising: sensing, in a first proximity sensing mode, signals indicative of a proximate object during multiple touch frames; calculating signal densities associated with the proximate object corresponding to the multiple touch frames; in accordance with a determination that the signal densities meet a plurality of criteria, transitioning from sensing the signal in the first proximity sensing mode to sensing the signal in the second proximity sensing mode, wherein the plurality of criteria comprise: a first criterion that is satisfied when the slope of the signal densities, calculated from the signal densities corresponding to the multiple touch frames, is indicative of the proximate object approaching the surface of the touch screen; and a second criterion that is satisfied when the slope of the signal densities is indicative of the proximate object indirectly contacting the touch screen at a distance from the touch screen that deviates less than a predetermined amount from being constant; and a third criterion that is satisfied when the slope of the signal densities is indicative of the proximate object moving away from the surface of the touch screen. Additionally or alternatively, in some examples, satisfying the first criterion includes detecting that the slope of the signal densities, calculated from the signal densities corresponding to the multiple touch frames, exceeds a first threshold at a first time, satisfying the second criterion includes detecting that the slope of the signal densities is less than a second threshold and greater than a third threshold for a first threshold duration of time after the first time, the second threshold less than the first threshold, and the third threshold less than the second threshold, and satisfying the third criterion includes detecting that the slope of the signal densities is less than a fourth threshold at a second time after the threshold duration of time, the fourth threshold less than the third threshold. 
     Some examples of the disclosure are directed to a non-transitory computer-readable medium comprising instructions that, when executed by one or more processors of an electronic device comprising a touch screen, cause the electronic device to: sense, in a first proximity sensing mode, signals indicative of a proximate object during multiple touch frames; calculate signal densities associated with the proximate object corresponding to the multiple touch frames; in accordance with a determination that the signal densities meet a plurality of criteria, transition from sensing the signal in the first proximity sensing mode to sensing the signal in the second proximity sensing mode, wherein the plurality of criteria comprise: a first criterion that is satisfied when the slope of the signal densities, calculated from the signal densities corresponding to the multiple touch frames, is indicative of the proximate object approaching the surface of the touch screen; and a second criterion that is satisfied when the slope of the signal densities is indicative of the proximate object indirectly contacting the touch screen at a distance from the touch screen that deviates less than a predetermined amount from being constant; and a third criterion that is satisfied when the slope of the signal densities is indicative of the proximate object moving away from the surface of the touch screen. Additionally or alternatively, in some examples, satisfying the first criterion includes detecting that the slope of the signal densities, calculated from the signal densities corresponding to the multiple touch frames, exceeds a first threshold at a first time, satisfying the second criterion includes detecting that the slope of the signal densities is less than a second threshold and greater than a third threshold for a first threshold duration of time after the first time, the second threshold less than the first threshold, and the third threshold less than the second threshold, and satisfying the third criterion includes detecting that the slope of the signal densities is less than a fourth threshold at a second time after the threshold duration of time, the fourth threshold less than the third threshold. 
     Although the disclosed examples have been fully described with reference to the accompanying drawings, 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 disclosed examples as defined by the appended claims.

Metadata:
Filing Date: 20200131
Publication Date: 20210330
Grant Date: 20210330
Priority Date: 20190927
Inventors: DEDHIA, SIDDHARTH
ZHOU, XIAOQI
Assignee: APPLE INC
CPC Classifications: [{"code": "G06F2203/04108", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F3/04166", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F3/0446", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F2203/04108", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F3/04166", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F3/0446", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/0446", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/04166", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F2203/04108", "inventive": false, "first": false, "tree": "[]"}]
Family ID: 75164436