PATENT DOCUMENT

Publication Number: US-10606418-B2
Application Number: US-201815923967-A
Country: US
Kind Code: B2

Title: Ultrasonic touch detection on stylus

Abstract:
An input device outfitted with one or more ultrasonic transducers can determine the location of one or more objects in contact with the input device. For example, the input device can include one or more transducers disposed in a ring around the circumference of the input device or in an array of rings along the length of the input device. The ultrasonic transducers can be used to detect the position of the one or more touching objects in at least one dimension, for example. In some examples, the one or more ultrasonic transducers can produce directional ultrasonic waves.

Claims:
The invention claimed is: 
     
       1. A stylus comprising:
 a shaft; 
 a tip coupled to an end of the shaft; 
 one or more ultrasonic transducers coupled to the shaft, the one or more ultrasonic transducers configured to transmit one or more transmitted ultrasonic waves and to sense one or more sensed ultrasonic waves; and 
 a touch controller operatively coupled to the one or more ultrasonic transducers, the touch controller configured to generate the one or more transmitted ultrasonic waves and determine a position in at least one dimension of an object touching an exterior surface of the shaft based on one or more characteristics of the one or more sensed ultrasonic waves. 
 
     
     
       2. The stylus of  claim 1 , wherein:
 the shaft extends along an axis, and 
 the one or more ultrasonic transducers comprises a plurality of ultrasonic transducers arranged in one or more rows, the one or more rows parallel to the first axis. 
 
     
     
       3. The stylus of  claim 2 , wherein:
 the shaft includes a plurality of cross-sectional areas orthogonal to the axis, 
 the one or more rows comprise a first row and a second row, 
 one or more of the plurality of cross-sectional areas each comprise a first ultrasonic transducer included in the first row and a second ultrasonic transducer included in the second row, 
 the first ultrasonic transducer is configured to transmit the one or more transmitted ultrasonic waves, and 
 the second ultrasonic transducer is configured to sense the one or more sensed ultrasonic waves. 
 
     
     
       4. The stylus of  claim 1 , wherein:
 the shaft extends along an axis, 
 the stylus shaft includes a plurality of cross-sectional areas orthogonal to the axis, 
 the one or more ultrasonic transducers comprises a plurality of ultrasonic transducers arranged around the circumference of one of the plurality of cross-sectional areas. 
 
     
     
       5. The stylus of  claim 1 , wherein:
 the shaft extends along an axis, 
 the shaft includes a plurality of cross-sectional areas orthogonal to the axis, 
 an ultrasonic transducer of the one or more ultrasonic transducers is disposed at a distal end opposite the tip around the circumference of one of the plurality of cross-sectional areas, 
 the ultrasonic transducer is configured to:
 at a first time, generate one of the one or more transmitted ultrasonic waves, the transmitted ultrasonic wave propagating along the axis; and 
 at a second time after the first time, sense one of the one or more sensed ultrasonic waves, and 
 
 the touch controller determines the position of the object based on the second time. 
 
     
     
       6. The stylus of  claim 1 , wherein the one or more characteristics of the reflected wave comprise one or more of time of arrival and magnitude. 
     
     
       7. The stylus of  claim 1 , further comprising:
 a plurality of ultrasonic barriers configured to reflect the ultrasonic wave. 
 
     
     
       8. The stylus of  claim 7 , wherein the ultrasonic barriers are coupled to the shaft or etched or embedded in the shaft. 
     
     
       9. The stylus of  claim 1 , wherein the one or more ultrasonic transducers comprise a plurality of ultrasonic transducers configured to:
 at a first time, transmit a first of the one or more transmitted ultrasonic waves using a first ultrasonic transducer; and 
 after a delay of a predetermined duration after the first time, transmit a second of the one or more transmitted ultrasonic waves using a second ultrasonic transducer disposed proximate to the first ultrasonic transducer, wherein the first transmitted ultrasonic wave and the second transmitted ultrasonic wave produce a directional ultrasonic wave including coherent contributions from the first transmitted ultrasonic wave and the second transmitted ultrasonic wave. 
 
     
     
       10. The stylus of  claim 1 , further comprising:
 a wedge coupled to the interior surface of the shaft, wherein at least one of the one or more ultrasonic transducers are mounted to the wedge, and the one or more transmitted ultrasonic waves generated by the one or more ultrasonic transducers is coupled to the surface of the shaft via the wedge. 
 
     
     
       11. A method for determining a location of an object touching an outside of a stylus comprising a tip and a shaft, the method comprising:
 transmitting, with one or more ultrasonic transducers coupled to the shaft, one or more transmitted ultrasonic waves; 
 receiving, with the one or more ultrasonic transducers, one or more received ultrasonic waves; and 
 determining, with a touch controller operatively coupled to the plurality of one or more ultrasonic transducers, the position in at least one dimension of the object touching the outside of the stylus based on one or more characteristics of the one or more received ultrasonic waves. 
 
     
     
       12. The method of  claim 11 , wherein:
 the shaft extends along an axis, and 
 the one or more ultrasonic transducers comprises a plurality of ultrasonic transducers arranged in one or more rows, the one or more rows parallel to the first axis. 
 
     
     
       13. The method of  claim 12 , wherein:
 the shaft includes a plurality of cross-sectional areas orthogonal to the axis, 
 the one or more rows comprise a first row and a second row, 
 one or more of the plurality of cross-sectional areas each comprise a first ultrasonic transducer included in the first row and a second ultrasonic transducer included in the second row, and 
 the method further comprises:
 transmitting, with the first ultrasonic transducer, the one or more transmitted ultrasonic waves, and 
 sensing, with the second ultrasonic transducer the one or more received ultrasonic waves. 
 
 
     
     
       14. The method of  claim 11 , wherein:
 the shaft extends along an axis, 
 the shaft includes a plurality of cross-sectional areas orthogonal to the axis, 
 the one or more ultrasonic transducers comprises a plurality of ultrasonic transducers arranged around the circumference of one of the plurality of cross-sectional areas. 
 
     
     
       15. The method of  claim 11 , wherein:
 the shaft extends along an axis, 
 the shaft includes a plurality of cross-sectional areas orthogonal to the axis, 
 an ultrasonic transducer of the one or more ultrasonic transducers is disposed at a distal end opposite the tip of the stylus around the circumference of one of the plurality of cross-sectional areas, and 
 the method further comprises:
 at a first time, generate one of the one or more transmitted ultrasonic waves with the ultrasonic transducer of the one or more ultrasonic transducers, the transmitted ultrasonic wave propagating along the axis; 
 at a second time after the first time, sense one of the one or more sensed ultrasonic waves with the ultrasonic transducer of the one or more ultrasonic transducers; and 
 determining, with the touch controller, the position of the object based on the second time. 
 
 
     
     
       16. The method of  claim 11 , wherein the one or more characteristics of the one or more sensed ultrasonic waves comprise time of arrival and magnitude. 
     
     
       17. The method of  claim 11 , further comprising:
 reflecting, with a plurality of ultrasonic barriers, the one or more transmitted ultrasonic waves. 
 
     
     
       18. The method of  claim 17 , wherein the plurality of ultrasonic barriers are coupled to the shaft or etched or embedded in the shaft. 
     
     
       19. The method of  claim 11 , wherein the one or more ultrasonic transducers comprise a plurality of ultrasonic transducers, and the method further comprises:
 transmitting, at a first time, a first of the one or more transmitted ultrasonic waves using a first ultrasonic transducer; and 
 after a delay of a predetermined duration after the first time, transmitting a second of the one or more transmitted ultrasonic waves using a second ultrasonic transducer disposed proximate to the first ultrasonic transducer, wherein the first ultrasonic wave and the second ultrasonic wave produce a directional wave including coherent contributions from the first transmitted ultrasonic wave and the second transmitted ultrasonic wave. 
 
     
     
       20. The method of  claim 11 , wherein the stylus further comprises a wedge coupled to the interior surface of the shaft, wherein at least one of the one or more ultrasonic transducers are mounted to the wedge, and the one or more transmitted ultrasonic waves generated by the one or more ultrasonic transducers is coupled to the surface of the shaft via the wedge.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims benefit of U.S. Provisional Patent Application No. 62/480,174, filed Mar. 31, 2017, which is hereby incorporated by reference in its entirety. 
    
    
     FIELD OF THE DISCLOSURE 
     This relates generally to an input device, and more specifically, to an input device outfitted with one or more ultrasonic transducers configured to determine the location of one or more objects in contact with the input device. 
     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 panels, touch screens and the like. Touch-sensitive devices, and touch screens in particular, are quite popular because of their ease and versatility of operation as well as their affordable prices. A touch-sensitive device can include a touch panel, which can be a clear panel with a touch-sensitive surface, and a display device such as a liquid crystal display (LCD) that can be positioned partially or fully behind the panel so that the touch-sensitive surface can cover at least a portion of the viewable area of the display device. The touch-sensitive device can allow a user to perform various functions by touching or hovering over the touch 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, the touch-sensitive device can recognize a touch or hover event and the position of the event on the touch panel, and the computing system can then interpret the event in accordance with the display appearing at the time of the event, and thereafter can perform one or more actions based on the event. 
     Styli have become popular input devices for touch-sensitive devices. In particular, use of an active stylus capable of generating stylus stimulation signals that can be sensed by the touch-sensitive device can improve the precision and control of the stylus. In some instances it may be desirable for input devices, such as styli, to be able to transfer data, in addition to a stimulation signal used to identify touch location, to the touch screen. For example, data from the input devices (such as touch, force, orientation, tilt, or the like) may be communicated to the touch screen, which may use that data to change an output of the display or perform some other operation. 
     SUMMARY OF THE DISCLOSURE 
     This relates generally to an input device, and more specifically, to an input device outfitted with one or more ultrasonic transducers configured to determine the location of one or more objects in contact with the input device. In some examples, the input device can include an array of ultrasonic transducers in rows along the length of the input device. In this configuration, the location along the length of the input device of an object touching the input device can be determined based on which ultrasonic transducer(s) detect(s) the object. In some examples, the ultrasonic transducers can also be used to determine the position around the circumference of the input device of an object touching the input device and the location, for example. 
     In some examples, one or more ultrasonic transducers can be disposed at one end of the input device. A single ultrasonic transducer can determine the location along the length of the input device of an object touching the input device, for example. In some examples, multiple ultrasonic transducers disposed in a ring around one end of the input device can determine the position of the touching object both along the length of the input device and around the circumference of the input device (i.e., in two dimensions). 
     Some examples of the disclosure relate to generating a directional ultrasonic wave with one or more ultrasonic transducers. For example, one or more ultrasonic transducers can be attached to the input device by way of a wedge. The ultrasonic waves generated by the one or more transducers mounted by way of the wedge can be guided along the surface of the input device based on material properties and/or an angle of the wedge, for example. In some examples, a plurality of ultrasonic transducers can be disposed in an array to produce a guided wave using constructive interference in the direction of wave travel and destructive interference to decrease wave magnitude in the opposite direction. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1A-1D  illustrate examples of systems with touch screens that can accept input from an active stylus according to examples of the disclosure. 
         FIG. 2  illustrates a block diagram of an example computing system that can receive input from an active stylus according to examples of the disclosure. 
         FIG. 3  illustrates an exemplary intelligent stylus for use with a touch sensitive device according to various embodiments. 
         FIG. 4  illustrates an exemplary stylus outfitted with a touch sensitive area along the stylus shaft according to examples of the disclosure. 
         FIG. 5  illustrates an exemplary stylus and touch images according to some examples of the disclosure. 
         FIG. 6A  illustrates a stylus outfitted with a plurality of ultrasonic transducers according to examples of the disclosure. 
         FIG. 6B  illustrates an exemplary cross-section of a stylus outfitted with a plurality of ultrasonic transducers according to examples of the disclosure. 
         FIG. 6C  illustrates an exemplary cross-section of a stylus outfitted with a plurality of ultrasonic transducers according to examples of the disclosure. 
         FIG. 7  illustrates an exemplary cross-section of a stylus outfitted with a plurality of ultrasonic transducers detecting touch according to examples of the disclosure. 
         FIG. 8  illustrates an exemplary cross-section of a touch sensitive stylus including ultrasonic transducers and barriers according to examples of the disclosure. 
         FIG. 9  illustrates an exemplary stylus including an ultrasonic transducer at its end according to examples of the disclosure. 
         FIG. 10A  illustrates an exemplary stylus including ultrasonic transducers disposed in a ring formation at an end of the stylus configured to perform a “passive search” according to examples of the disclosure. 
         FIG. 10B  illustrates an exemplary stylus including ultrasonic transducers disposed in a ring formation at an end of the stylus configured to perform an “active search” according to examples of the disclosure. 
         FIG. 11  illustrates an exemplary ultrasonic transducer configured to transmit a guided wave according to examples of the disclosure. 
         FIG. 12  illustrates an exemplary stylus outfitted with ultrasonic transducers configured to produce a directional ultrasonic wave. 
     
    
    
     DETAILED DESCRIPTION 
     In the following description of examples, reference is made to the accompanying drawings in which it is shown by way of illustration specific examples that can be practiced. It is to be understood that other examples can be used and structural changes can be made without departing from the scope of the various examples. 
       FIGS. 1A-1D  illustrate examples of systems with touch screens that can accept input from an active stylus according to examples of the disclosure.  FIG. 1A  illustrates an exemplary mobile telephone  136  that includes a touch screen  124  that can accept input from an active stylus according to examples of the disclosure.  FIG. 1B  illustrates an example digital media player  140  that includes a touch screen  126  that can accept input from an active stylus according to examples of the disclosure.  FIG. 1C  illustrates an example personal computer  144  that includes a touch screen  128  that can accept input from an active stylus according to examples of the disclosure. In some examples, a personal computer  144  can include a trackpad that can accept input from an active stylus according to examples of the disclosure. Although generally described herein with regard to touch screens, active stylus input can be received by touch-sensitive surfaces without a display.  FIG. 1D  illustrates an example tablet computing device  148  that includes a touch screen  130  that can accept input from an active stylus according to examples of the disclosure. Other devices, including wearable devices, can accept input from an active stylus according to examples of the disclosure. 
     Touch screens  124 ,  126 ,  128  and  130  can be based on, for example, self-capacitance or mutual capacitance sensing technology, or another touch sensing technology. For example, in a self-capacitance based touch system, an individual electrode with a self-capacitance to ground can be used to form a touch pixel (touch node) for detecting touch. As an object approaches the touch pixel, an additional capacitance to ground can be formed between the object and the touch pixel. The additional capacitance to ground can result in a net increase in the self-capacitance seen by the touch pixel. This increase in self-capacitance can be detected and measured by a touch sensing system to determine the positions of multiple objects when they touch the touch screen. 
     A mutual capacitance based touch system can include, for example, drive regions and sense regions, such as drive lines and sense lines. For example, drive lines can be formed in rows while sense lines can be formed in columns (i.e., orthogonal). Touch pixels (touch nodes) can be formed at the intersections or adjacencies (in single layer configurations) of the rows and columns. During operation, the rows can be stimulated with an alternating current (AC) waveform and a mutual capacitance can be formed between the row and the column of the touch pixel. As an object approaches the touch pixel, some of the charge being coupled between the row and column of the touch pixel can instead be coupled onto the object. This reduction in charge coupling across the touch pixel can result in a net decrease in the mutual capacitance between the row and the column and a reduction in the AC waveform being coupled across the touch pixel. This reduction in the charge-coupled AC waveform can be detected and measured by the touch sensing system to determine the positions of multiple objects when they touch the touch screen. In some examples, a touch screen can be multi-touch, single touch, projection scan, full-imaging multi-touch, or any capacitive touch. 
     In some examples, one or more touch sensors can detect signals from a powered stylus via mutual capacitance. Rather than generating a stimulation signal, the touch sensors can be used to receive coupled charge indicative of the stylus&#39; stimulation signals. As the stylus approaches a touch sensor, charge coupling can occur between a conductive tip of the stylus (which can be driven by the stylus stimulation signal) and the touch sensor. This charge coupling can be received as an AC waveform indicative of stylus presence. In some examples, stylus stimulation signals can be sampled, analyzed, and decoded to receive data encoded in the stylus signal. 
       FIG. 2  illustrates a block diagram of an example computing system  200  that can receive input from an active stylus according to examples of the disclosure. Computing system  200  could be included in, for example, mobile telephone  136 , digital media player  140 , personal computer  144 , tablet computing device  148 , wearable device, or any mobile or non-mobile computing device that includes a touch screen. Computing system  200  can include an integrated touch screen  220  to display images and to detect touch and/or proximity (e.g., hover) events from an object (e.g., finger  203  or active or passive stylus  205 ) at or proximate to the surface of the touch screen  220 . Computing system  200  can also include an application specific integrated circuit (“ASIC”) illustrated as touch ASIC  201  to perform touch and/or stylus sensing operations. Touch ASIC  201  can include one or more touch processors  202 , peripherals  204 , and touch controller  206 . Touch ASIC  201  can be coupled to touch sensing circuitry of touch screen  220  to perform touch and/or stylus sensing operations (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 and the like. Touch controller  206  can include, but is not limited to, one or more sense channels in receive circuitry  208 , panel scan engine  210  (which can include channel scan logic) and transmit circuitry  214  (which can include analog or digital driver logic). In some examples, the transmit circuitry  214  and receive circuitry  208  can be reconfigurable by the panel scan engine  210  based the scan event to be executed (e.g., mutual capacitance row-column scan, mutual capacitance row-row scan, mutual capacitance column-column scan, row self-capacitance scan, column self-capacitance scan, pixelated sensor array scan, stylus data scan, stylus location scan, etc.). Panel scan engine  210  can access RAM  212 , autonomously read data from the sense channels and provide control for the sense channels. The touch controller  206  can also include a scan plan (e.g., stored in RAM  212 ) which can define a sequence of scan events to be performed at the touch screen. The scan plan can include information necessary for configuring or reconfiguring the transmit circuitry and receive circuitry for the specific scan event to be performed. Results (e.g., touch/stylus signals or touch/stylus data) from the various scans can also be stored in RAM  212 . In addition, panel scan engine  210  can provide control for transmit circuitry  214  to generate stimulation signals at various frequencies and/or phases that can be selectively applied to drive regions of the touch sensing circuitry of touch screen  220 . Although illustrated in  FIG. 2  as a single ASIC, the various components and/or functionality of the touch ASIC  201  can be implemented with multiple circuits, elements, chips, and/or discrete components. 
     Computing system  200  can also include an application specific integrated circuit illustrated as display ASIC  216  to perform display operations. Display ASIC  216  can include hardware to process one or more still images and/or one or more video sequences for display on touch screen  220 . Display ASIC  216  can be configured to generate read memory operations to read the data representing the frame/video sequence from a memory (not shown) through a memory controller (not shown), for example. Display ASIC  216  can be configured to perform various processing on the image data (e.g., still images, video sequences, etc.). In some examples, display ASIC  216  can be configured to scale still images and to dither, scale and/or perform color space conversion on the frames of a video sequence. Display ASIC  216  can be configured to blend the still image frames and the video sequence frames to produce output frames for display. Display ASIC  216  can also be more generally referred to as a display controller, display pipe, display control unit, or display pipeline. The display control unit can be generally any hardware and/or firmware configured to prepare a frame for display from one or more sources (e.g., still images and/or video sequences). More particularly, display ASIC  216  can be configured to retrieve source frames from one or more source buffers stored in memory, composite frames from the source buffers, and display the resulting frames on touch screen  220 . Accordingly, display ASIC  216  can be configured to read one or more source buffers and composite the image data to generate the output frame. 
     Display ASIC  216  can provide various control and data signals to the display, including timing signals (e.g., one or more clock signals) and/or vertical blanking period and horizontal blanking interval controls. The timing signals can include a pixel clock that can indicate transmission of a pixel. The data signals can include color signals (e.g., red, green, blue). The display ASIC  216  can control the touch screen  220  in real-time, providing the data indicating the pixels to be displayed as the touch screen is displaying the image indicated by the frame. The interface to such a touch screen  220  can be, for example, a video graphics array (VGA) interface, a high definition multimedia interface (HDMI), a digital video interface (DVI), a LCD interface, a plasma interface, or any other suitable interface. 
     In some examples, handoff circuitry  218  can also be included in computing system  200 . Handoff circuitry  218  can be coupled to the touch ASIC  201 , display ASIC  216 , and touch screen  220 , and can be configured to interface the touch ASIC  201  and display ASIC  216  with touch screen  220 . The handoff circuitry  218  can appropriately operate the touch screen  220  according to the scanning/sensing and display instructions from the touch ASIC  201  and the display ASIC  216 . In other examples, the display ASIC  216  can be coupled to display circuitry of touch screen  220  and touch ASIC  201  can be coupled to touch sensing circuitry of touch screen  220  without handoff circuitry  218 . 
     Touch screen  220  can use liquid crystal display (LCD) technology, light emitting polymer display (LPD) technology, organic LED (OLED) technology, or organic electro luminescence (OEL) technology, although other display technologies can be used in other examples. In some examples, the touch sensing circuitry and display circuitry of touch screen  220  can be stacked on top of one another. For example, a touch sensor panel can cover some or all of a surface of the display (e.g., fabricated one on top of the next in a single stack-up or formed from adhering together a touch sensor panel stack-up with a display stack-up). In other examples, the touch sensing circuitry and display circuitry of touch screen  220  can be partially or wholly integrated with one another. The integration can be structural and/or functional. For example, some or all of the touch sensing circuitry can be structurally in between the substrate layers of the display (e.g., between two substrates of a display pixel cell). Portions of the touch sensing circuitry formed outside of the display pixel cell can be referred to as “on-cell” portions or layers, whereas portions of the touch sensing circuitry formed inside of the display pixel cell can be referred to as “in cell” portions or layers. Additionally, some electronic components can be shared, and used at times as touch sensing circuitry and at other times as display circuitry. For example, in some examples, common electrodes can be used for display functions during active display refresh and can be used to perform touch sensing functions during touch sensing periods. A touch screen stack-up sharing components between sensing functions and display functions can be referred to as an in-cell touch screen. 
     Computing system  200  can also include a host processor  228  coupled to the touch ASIC  201 , and can receive outputs from touch ASIC  201  (e.g., from touch processor  202  via a communication bus, such as an serial peripheral interface (SPI) bus, for example) and perform actions based on the outputs. Host processor  228  can also be connected to program storage  232  and display ASIC  216 . Host processor  228  can, for example, communicate with display ASIC  216  to generate an image on touch screen  220 , such as an image of a user interface (UI), and can use touch ASIC  201  (including 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 a 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, and/or the like. As described herein, host processor  228  can also perform additional functions that may not be related to touch processing. 
     Computing system  200  can include one or more processors, which can execute software or firmware implementing various functions. Specifically, for integrated touch screens which share components between touch and/or stylus sensing and display functions, the touch ASIC and display ASIC can be synchronized so as to properly share the circuitry of the touch sensor panel. The one or more processors can include one or more of the one or more touch processors  202 , a processor in display ASIC  216 , and/or host processor  228 . In some examples, the display ASIC  216  and host processor  228  can be integrated into a single ASIC, though in other examples, the host processor  228  and display ASIC  216  can be separate circuits coupled together. In some examples, host processor  228  can act as a master circuit and can generate synchronization signals that can be used by one or more of the display ASIC  216 , touch ASIC  201  and handoff controller  218  to properly perform sensing and display functions for an in-cell touch screen. The synchronization signals can be communicated directly from the host processor  228  to one or more of the display ASIC  216 , touch ASIC  201  and handoff controller  218 . Alternatively, the synchronization signals can be communicated indirectly (e.g., touch ASIC  201  or handoff controller  218  can receive the synchronization signals via the display ASIC  216 ). 
     Computing system  200  can also include a wireless module (not shown). The wireless module can implement a wireless communication standard such as a WiFi®, BLUETOOTH™ or the like. The wireless module can be coupled to the touch ASIC  201  and/or host processor  228 . The touch ASIC  201  and/or host processor  228  can, for example, transmit scan plan information, timing information, and/or frequency information to the wireless module to enable the wireless module to transmit the information to an active stylus, for example (i.e., a stylus capable generating and injecting a stimulation signal into a touch sensor panel). For example, the computing system  200  can transmit frequency information indicative of one or more low noise frequencies that the stylus can use to generate a stimulation signals. Additionally or alternatively, timing information can be used to synchronize the stylus  205  with the computing system  200 , and the scan plan information can be used to indicate to the stylus  205  when the computing system  200  performs a stylus scan and expects stylus stimulation signals (e.g., to save power by generating a stimulus only during a stylus scan period). In some examples, the wireless module can also receive information from peripheral devices, such as an active stylus  205 , which can be transmitted to the touch ASIC  201  and/or host processor  228 . For example, the active stylus  205  can include one or more sensors and can transmit the sensed data wirelessly. In response to the received data, the computing system can perform an action, such as changing an input mode of the stylus operation. In other examples, the wireless communication functionality can be incorporated in other components of computing system  200 , rather than in a dedicated chip. 
     Note that one or more of the functions described herein can be performed by firmware stored in memory and executed by the touch processor in touch ASIC  201 , or stored in program storage 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 a signal) that can contain or store the program for use by or in connection with the instruction execution system, apparatus, or device. The non-transitory computer readable medium storage 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 readable medium can include, but is not limited to, an electronic, magnetic, optical, electromagnetic or infrared wired or wireless propagation medium. 
     It is to be understood that the computing system  200  is not limited to the components and configuration of  FIG. 2 , but can include other or additional components in multiple configurations according to various examples. Additionally, the components of computing system  200  can be included within a single device, or can be distributed between multiple devices. 
       FIG. 3  illustrates an exemplary intelligent stylus  310  for use with a touch sensitive device  320  according to various embodiments. In the example of  FIG. 3 , touch sensitive device  320  (e.g., corresponding to the systems illustrated in  FIGS. 1A-D ) can include an array of touch nodes  306  formed at the crossing points of conductive rows  301  and columns  302 . Though  FIG. 3  depicts the conductive elements  301 ,  302  in rows and columns, other configurations of conductive elements are also possible according to various embodiments. 
     When stylus  310  touches or hovers over a surface of the touch sensitive device  320 , the stylus can form a capacitance with one or more of the conductive rows  301  and/or columns  302  that can be detected by device sensing circuitry (not shown). The stylus touch can be represented in an image captured at the touch sensitive device  320  and processed for touch input information, e.g., the location on the touch sensitive device that the stylus touched or hovered over. 
     In addition to providing the touch input information when touching or in proximity to a touch sensitive device  320 , the stylus  310  can provide information sensed by the stylus, which can be used by the touch sensitive device  320  to perform some action. In some embodiments, the information can be used by the stylus to perform some action or the information can be communicated to the touch sensitive device  320  to perform some action. The stylus  310  can include one or more sensors configured to detect one or more objects (e.g., fingers) in contact with the surface of the stylus, for example. Based on the sensor data of the one or more sensors, the touch sensitive device  320  or the stylus  310  can perform some action. The stylus&#39; ability to sense a touch on its surface can allow the stylus to perform operations (or cause operations to be performed by another device in communication with the stylus) beyond touch input information. 
       FIG. 4  illustrates an exemplary stylus  400  outfitted with a touch sensitive area  410  along the stylus shaft according to examples of the disclosure. The touch sensitive area  410  can be an “active area” of the stylus shaft, for example. In some examples, stylus  400  can further include tip  420 . In stylus some examples, tip  420  of stylus  400  can include an electrode configured to emit a stimulation signal to be detected by a separate touch-sensitive device (e.g., mobile telephone  136 , digital media player  140 , personal computer  144 , tablet computing device  148 , wearable computing device, etc.), for example. In some examples, tip  420  can be conductive and a conductive path can be formed between the tip  420  and a user&#39;s hand or fingers to allow for detection of the stylus by a touch sensitive device without the need for the stylus to emit a stimulation signal. 
     In some examples, touch sensitive area  410  of stylus  400  can include an array of capacitive touch sensors. For ease of description the touch sensitive area  410  can be “unrolled” and viewed as a two-dimensional plane. Touch sensitive area  410  can include an array of capacitive sensors formed by electrodes in a row-column layout  412 . Row-column layout  412  can include a plurality of conductive rows  414  and a plurality of conductive columns  416 , where the conductive rows and columns can be arranged orthogonally. Touch nodes  418  can be formed at the crossing points of a respective conductive row  414  and a conductive column  416 . In some examples, the rows  414  and columns  416  can detect a touch using mutual capacitance or self-capacitance. In essence, the array of capacitive touch sensors can operate generally as described above in the context of touch screens. 
     In some examples, touch sensitive area  410  can have a pixelated touch electrode layout  432 , for example. Pixelated touch electrode layout  432  can include a plurality of conductive electrodes  435  configured to sense a touch. In some examples, each conductive electrode  435  can act as a touch node. The conductive electrodes  435  can detect a touch using self-capacitance or mutual capacitance. 
     Although stylus  400  can sense a touch at the surface of its shaft at touch sensitive area  410  using either row-column layout  412  or pixelated touch electrode layout  432 , in some examples, capacitive touch sensors can require a large number of channels to operate enough sensors to cover touch sensitive section  410 , thus requiring a complex controller to sense touch. As styluses can be limited in size for ease of user operation, it can be difficult to incorporate a large and/or heavy controller into a stylus. Minimizing the size and complexity of the controller can save weight and space for the controller itself as well as save weight and space for a battery and/or power supply, as a more complicated controller can use more power than a simpler one uses. Additionally, in some examples, the capacitive sensors can detect objects that are proximate to, but not touching, the touch sensitive section  410  of the stylus  400 , making it harder to distinguish the location of multiple touches on the stylus  400 . When a user operates a stylus, the user can grip the stylus with several fingers in close proximity to one another. Further, the parts of the fingers that do not contact the shaft of the stylus can still be in close proximity to the stylus&#39; surface. As a result, fingers that are close together can appear as one larger object in contact with the shaft of the stylus. 
       FIG. 5  illustrates an exemplary stylus  500  and touch images  520  and  530  according to some examples of the disclosure. In some examples, stylus  500  can sense one or more objects, such as fingers  511 ,  513 , and  515  at its surface. If stylus  500  includes capacitive touch sensors, similar to stylus  400  described with respect to  FIG. 4 , the measurements of the capacitive touch sensors can produce touch image  520 , for example. As an example, touch image  520  can include contacts  522  and  525 , which can correspond to locations on the surface of stylus  500  where fingers  511 ,  513 , and  515  are touching or proximate. Contact  522  can correspond to fingers  511  and  513  and contact  525  can correspond to finger  515 , for example. That is to say, although fingers  511  and  513  can contact stylus  500  in two different places, they may be detected together as a single contact, contact  522 , in touch image  520  due to the proximity of the fingers  511  and  513  and due to the fact that portions of fingers  511  and  513  proximate to, but not in contact with, the stylus surface can be detected by the capacitive touch sensors. 
     In some examples, stylus  500  can include one or more ultrasonic transducers, as will be described in more detail below. Unlike capacitive touch sensors, ultrasonic touch sensors can detect objects in contact with the surface of stylus  500 , but may not detect objects proximate to, but not in contact with, the surface of stylus  500 . Stylus  500 , when implemented with ultrasonic touch sensors, can produce touch image  530 . For example, touch image  530  can include contact  531  corresponding to finger  511 , contact  533  corresponding to finger  513 , and contact  535  corresponding to finger  515 . Contacts  531 ,  533 , and  535  can correspond only to locations on stylus  500  where fingers  511 ,  513 , and  513  are touching the surface of stylus  500 . In some examples, one or more algorithms operated by a processor within the stylus or on the host device can detect and/or reject multiple touches as needed. For example, additional contacts that are not consistent with an expected touch image for a user holding the stylus can be identified and/or rejected by such an algorithm. Thus, touch image  530  can more accurately detect and discriminate touches on the surface of stylus  500  than touch image  520 , for example. Ultrasonic touch sensors can also have the advantage of detecting touch even when one or more touching objects are poorly grounded and/or poorly capacitive coupled to the stylus body. For example, ultrasonic touch sensors can detect touch even when the user does not make direct with the stylus (e.g., the user is wearing gloves) or is poorly grounded due to contact with water (e.g., operation with wet or sweaty fingers or in a wet or underwater environment). A similar degree of performance may not be possible using capacitive touch sensors, and even if it is possible, it may require a large number of touch nodes to accurately detect and discriminate touches in close proximity to one another. 
       FIG. 6A  illustrates a stylus  600  outfitted with a plurality of ultrasonic transducers  610  according to examples of the disclosure. Each ultrasonic transducer  610  can be configured to transmit and receive ultrasonic waves, for example. In some examples, stylus  600  can include multiple ultrasonic transducers in the locations indicated by ultrasonic transducers  610  in a configuration described with reference to  FIG. 12 . In some examples, the stylus  600  can include one ultrasonic transducer at each location of ultrasonic transducers  600 . In some examples, ultrasonic transducers  610  can be arranged in a plurality of rows  614  along the length  692  of stylus  600 . Although ultrasonic transducers  610  are arranged in rows  614  that may not completely overlap the surface of stylus  600 , the ultrasonic transducers can still sense a touch at any location around the circumference  694  of the stylus  600  along the length of rows  614 , for example. 
     For ease of description, an area  680  of the stylus  600  shaft can be “unrolled” as shown in a first unrolled area  682  and second unrolled area  684 , for example. In some examples, as shown in the first unrolled area  682 , the ultrasonic transducers  610  can operate in a “pitch-catch” configuration. For example, a first ultrasonic transducer  610   a  can transmit an ultrasonic wave  611  to be received by a second ultrasonic transducer  610   b . The presence of an object touching the stylus  600  along the path of the ultrasonic wave  611  can be determined based on the magnitude of the wave  611  when it is received by the second ultrasonic transducer  610   b , for example. In some examples, the full width of unrolled area  682  can be sensed by operating the second ultrasonic transducer  610   b  as a transmitter to transmit a wave to the right to be received by the first ultrasonic transducer  610   a  or by operating the first ultrasonic transducer  610   a  to transmit an ultrasonic wave to the left. 
     In some examples, as shown in the second unrolled area  684 , the ultrasonic transducers  610  can determine the location around the circumference  694  of the stylus  600  of an object touching the stylus  600  by detecting a reflected wave (e.g., in a “pulse-echo” mode)  613  from the location  620  of touch. For example, a first ultrasonic transducer  610   c  can transmit an ultrasonic wave  611  and receive reflected wave  613  reflected from an object in contact with the stylus  600  at touch location  620 . Based on the time of arrival of the reflected wave  613 , the location  620  of the object along the circumference  694  can be determined. In some examples, a second ultrasonic transducer  610   d  can also be used to detect touch on the remaining part of unrolled area  684  by transmitting an ultrasonic wave to the right. In some examples, both the first ultrasonic transducer  610   c  and the second ultrasonic transducer  610   d  can transmit a wave either to the left or to the right. 
     Whether the ultrasonic transducers  610  are operated as described with respect to the first unrolled area  682  (e.g., in a “pitch-catch” mode) or operated as described with respect to the second unrolled area  684  (e.g., to determine time of arrival in a “pulse-echo” mode), the location along the stylus length  692  of an object touching the stylus  600  can be determined based on which ultrasonic transducers  610  detect the object. In some examples, in either configuration, it can be advantageous to include multiple ultrasonic transducers at each location along the length  692  of the stylus so that a touch anywhere around the stylus  600  circumference  694  can be detected, including a touch directly on top of an ultrasonic transducer  610 . In some examples, an ultrasonic transducer  610  may be unable to detect on object directly on top of it, so providing an additional ultrasonic transducer at the same location along the stylus  600  length  692  can eliminate these “blind spots”. 
     In some examples, providing ultrasonic transducers  610  in rows  614  as shown can reduce the complexity of circuitry necessary to detect a touch compared to a stylus outfitted with sensors overlapping the entirety of its touch sensitive surface (e.g., stylus  400  which includes capacitive touch sensors). Reducing the number of touch sensors in this way can reduce the number of components in stylus  600  and reduce the number of sense channels needed for a touch controller (not shown) included in the stylus  600 , for example. Although  FIG. 6A  illustrates the ultrasonic transducers  610  as being arranged in rows  614 , in some examples, other arrangements are possible. For example, one or more ultrasonic transducers  610  can be staggered with respect to one another. In some examples, the number of ultrasonic transducers at each location along the length  692  of the stylus  600  can be varied to be more dense in some parts of the stylus  600  shaft (e.g., in a location where the user is more likely to grasp, such as towards the tip or in the middle of the stylus shaft) than in other parts of the stylus shaft. 
       FIG. 6B  illustrates an exemplary cross-section of a stylus  600  outfitted with a plurality of ultrasonic transducers  610  according to examples of the disclosure. In some examples, the stylus  600  can include multiple ultrasonic transducers in an array at each location indicated as an ultrasonic transducer  610 . As an example, the ultrasonic transducers  610  can be arranged as described with reference to  FIG. 12 . In some examples, stylus  600  can include two rows  614  of ultrasonic transducers  610 , shown here in a cross-sectional view. Ultrasonic transducers  610  can act as transmitters Tx to transmit one or more ultrasonic waves and receivers Rx to receive one or more ultrasonic waves, for example. 
     During a first period of time T=1, a top ultrasonic transducer  610 - 1  can act as a receiver Rx to receive one or more ultrasonic waves  611  from a bottom ultrasonic transducer  610 - 2 . In some examples, the bottom ultrasonic transducer  610 - 2  can transmit a clockwise ultrasonic wave  611 - 1  during a first time within T=1 and can transmit a counterclockwise ultrasonic wave  611 - 2  during a second time within T=1. Likewise, during a second period of time T=2, the top ultrasonic transducer  610 - 1  can act as a transmitter Tx to transmit one or more ultrasonic waves  611  to the bottom ultrasonic transducer  610 - 2 . In some examples, the top ultrasonic transducer  610 - 1  can transmit a counterclockwise ultrasonic wave  611 - 3  during a first time within T=2 and can transmit a clockwise ultrasonic wave  611 - 4  during a second time within T=2. In some examples, the function of the top ultrasonic transducer  610 - 1  and the bottom ultrasonic transducer  610 - 2  can be fixed—that is, one ultrasonic transducer  610  can always transmit a signal for the other one to receive. In some examples, the top ultrasonic transducer  610 - 1  and the bottom ultrasonic transducer  610 - 2  can alternate between operating as a transmitter and operating as a receiver. It can be advantageous for the ultrasonic transducers  610  to alternate between transmitting and receiving the ultrasonic wave because an ultrasonic transducer acting as a receiver may not be able to detect a touch directly on top of it. By alternating the functionality of the ultrasonic transducers  610 , every touch can be detected because a touch directly on top of one transducer can be detected by the other transducer. 
     As will be described below with reference to  FIG. 7 , a touch can be detected based on the magnitude of the received ultrasonic waves  611  at ultrasonic transducer  610 - 1 . The generation of directional ultrasonic waves  611 - 1 ,  611 - 2 ,  611 - 3 , and  611 - 4  will be described later with reference to  FIGS. 11-12 . Although  FIGS. 6A-6B  illustrate a stylus  600  with two rows  614  of ultrasonic transducers  610 , one row of transducers is possible where the one row of transducers alternates between acting as a transmitter and acting as a receiver. However, it can be advantageous to include at least two rows  614  of ultrasonic transducers because it can allow the stylus  600  to detect a touch directly on top of an ultrasonic transducer  610 . Further, providing additional ultrasonic transducers  610  can increase the resolution of detectable touch locations, as transducers  610  operating in the “pitch-catch” configuration may only be able to detect the presence of an object but not its location around the circumference  694  of the stylus  600  beyond determining which side of each transducer  610  the object is adjacent to. In this way, adding rows  614  of transducers  610  can improve the sensitivity of stylus  600 , for example. In some examples, stylus  600  can include more than two rows  614  of ultrasonic transducers  610 . 
       FIG. 6C  illustrates an exemplary cross-section of a stylus  600  outfitted with a plurality of ultrasonic transducers  610  according to examples of the disclosure. In some examples, stylus  600  can include three rows  614  of ultrasonic transducers  610 , including ultrasonic transducers  610 - 3 ,  610 - 4 , and  610 - 5 . The rows  614  can be evenly spaced or unevenly spaced, for example. Additional rows  614  are possible and can increase the touch sensitivity of stylus  600 , but can also add components and complexity to stylus  600 , creating a tradeoff between sensitivity and simplicity. 
     In some examples, one ultrasonic transducer  610  can act as a transmitter while the others act as receivers. For example, a first ultrasonic transducer  610 - 3  can transmit an ultrasonic wave in both directions to be detected by a second ultrasonic transducer  610 - 4  and a third ultrasonic transducer  610 - 5 . Similarly, the second ultrasonic transducer  610 - 4  and the third ultrasonic transducer  610 - 5  can act as transmitters while the remaining transducers  610  act as receivers. In another example, all three ultrasonic transducers  610  can produce a directional wave in a same direction simultaneously and switch to acting as a receiver to receive the directional waves. The transducers  610  can alternate which direction the wave travels, for example. Other methods of using three or more rows  614  of ultrasonic transducers  610  are possible. 
       FIG. 7  illustrates an exemplary cross-section of a stylus  700  outfitted with a plurality of ultrasonic transducers  710  detecting touch according to examples of the disclosure. In some examples, ultrasonic transducers  710  can be arranged in rows, just as ultrasonic transducers  610  can be arranged in rows  614  along stylus  600  described with reference to  FIGS. 6A-6C . As an example, finger  722  and thumb  724  can touch stylus  700 . Top ultrasonic transducer  710 - 1  can transmit ultrasonic wave  713 , for example. In some examples, finger  722  and thumb  724  can be detected in two ways. 
     First, the magnitude of ultrasonic wave  713  can become attenuated in locations where finger  722  and thumb  724  are touching stylus  700 , allowing the stylus  700  to detect touch using a “pitch-catch” configuration, as described above with reference to  FIGS. 6A-6C . For example, when transmitted, ultrasonic wave  713  can have a first magnitude, shown in wave segment  713 - 1 . At the location of finger  722 , the magnitude of ultrasonic wave  713  can attenuate to a reduced magnitude shown in wave segment  713 - 2 , for example. Likewise, for example, at the location of thumb  724 , the magnitude of ultrasonic wave  713  can attenuate to a further reduced magnitude shown in wave segment  713 - 3 . Bottom ultrasonic transducer  710 - 2  can receive ultrasonic wave  713  and measure its magnitude to determine the presence of an object along the path of ultrasonic wave  713 . However, in some examples, this “pitch-catch” configuration may be unable to resolve the number of objects touching stylus  700  and/or the location(s) of the object(s) around the circumference of the stylus beyond which side of the ultrasonic transducers  710  the object(s) is/are proximate to. 
     Second, ultrasonic wave  713  can be reflected at locations where finger  722  and thumb  724  are touching stylus  700 , allowing the stylus  700  to detect touch based on time of arrival of the reflected wave (e.g., in a “pulse-echo” mode), as described above with reference to  FIGS. 6A-C . For example, finger  722  can cause reflected wave  715  to travel towards top ultrasonic transducer  710 - 1  and thumb  724  can cause reflected wave  717  to travel towards top ultrasonic transducer  710 - 1 . After transmitting ultrasonic wave  713 , the top ultrasonic transducer  710 - 1  can change operation modes to operate as a receiving ultrasonic transducer to receive reflected waves  715  and  717 . The locations of finger  722  and thumb  724  can be resolved based on the times at which the reflected waves  715  and  717  are received. As shown in  FIG. 7 , ultrasonic wave  713  can encounter finger  722  before it encounters thumb  724 , for example. Additionally, wave  713  can travel a shorter distance from finger  722  to the top ultrasonic transducer  710 - 1  than wave  715  can travel from thumb  724  to the top ultrasonic transducer  710 - 1 . Therefore, wave  713  can have a shorter “time of flight” than wave  715  has, allowing the locations of both finger  722  and thumb  724  to be resolved. When no objects are touching stylus  700 , the ultrasonic wave  713  can be received by the first ultrasonic transducer  710 - 1  and/or the second ultrasonic transducer  710 - 2 . The received ultrasonic wave can be unattenuated when no objects are touching the stylus  700 . 
     However, in some examples, finger  722  and/or thumb  724  may not couple to stylus  700  to cause a detectable attenuation or reflection of transmitted ultrasonic wave  713 . Poor coupling can be caused by the material of the surface of stylus  700  (e.g., the material of the stylus  700  is a poor conductor of ultrasonic waves), a characteristic of an object touching stylus  700  (e.g., a user is wearing gloves), one or more defects formed on the surface of stylus  700  over time, or environmental factors (e.g., air pressure and humidity). Accordingly, it can be advantageous in some examples to provide a modified stylus with improved coupling and sensitivity. 
       FIG. 8  illustrates an exemplary cross-section of a touch sensitive stylus  800  including ultrasonic transducers  810  and barriers  830  according to examples of the disclosure. In some examples, ultrasonic transducers  810  can be arranged in rows, just as ultrasonic transducers  610  can be arranged in rows  614  along the length of stylus  600  described with reference to  FIGS. 6A-6C . Stylus  800  can include ultrasonic transducers  810  and barriers  830 , for example. In some examples, barriers  830  can be inside and/or outside of the shaft of stylus  800 . Further, the barriers can be etched into the stylus shaft material or formed of material deposited onto the stylus shaft, for example. As an example, finger  824  can be in contact with the stylus  800 . Top ultrasonic transducer  810 - 1  can act as a transmitter and transmit ultrasonic wave  813  and act as a receiver to receive reflected waves  819 , for example. Additionally, bottom ultrasonic transducer  810 - 2  can also act as a transmitter and receiver simultaneously or sequentially with top ultrasonic transducer  810 - 1 . In some examples, the transmitted ultrasonic wave  813  can reflect off of barriers  830 , generating reflected ultrasonic waves  819 . 
     In some examples, the reflected ultrasonic waves  819  can be received by top ultrasonic transducer  810 - 1 . Based on the magnitudes of the received reflected ultrasonic waves  819 , a location of an object touching stylus  800  can be determined, for example. In some examples, the expected arrival time of each reflected ultrasonic wave  819  can be determined and stored by a touch controller of the stylus  800 . Further, during a calibration procedure, for example, the expected magnitude of each reflected ultrasonic wave  819  can be determined when there are no objects touching the stylus  800 . As an example, finger  824  can touch stylus  800  at a location corresponding to barrier  830 - 1 . Accordingly, reflected wave  819 - 1  can have an attenuated magnitude compared to the magnitude of a wave reflected from barrier  830 - 1  during the calibration procedure (i.e., when no object is touching the stylus  800  at barrier  830 - 1 ), for example. Further, reflected wave  819 - 2  (reflected from barrier  830 - 2 ) and reflected wave  819 - 3  (reflected from barrier  830 - 3 ) can have less attenuation than reflected wave  819 - 1  when there are no objects touching stylus  800  at barriers  830 - 2  and  830 - 3 . In some examples, when an object is touching the stylus  800 , all reflected waves  830  can be somewhat attenuated, even reflected waves  830  from barriers  819  that do not correspond to the location of the touching object. Therefore, in some examples, the touch controller can establish a non-zero attenuation threshold indicative of a location of touch. In some examples, stylus  800  can include multiple rows of ultrasonic transducers  810  so as to detect touch directly on top of the transducers  810 , as described above. Further, it can be advantageous to include multiple transducers  810  at each location along the length of the stylus  800  to increase sensitivity. When the ultrasonic wave  813  reflects off of a barrier  830 , its magnitude can be attenuated, thereby reducing the magnitude of the wave more and more as the wave travels further from the ultrasonic transducer  810 . In some examples, the ultrasonic transducers  810  can alternate which direction the ultrasonic wave  813  is sent in to increase resolution, but this can make the touch detection process slower. Therefore, providing additional ultrasonic transducers  810  can improve sensitivity and speed at the same time. 
     Although styluses (e.g., stylus  600 , stylus  700 , and stylus  800 ) can sense a touch using ultrasonic transducers (e.g., ultrasonic transducers  610 , ultrasonic transducers  710 , and ultrasonic transducers  810 , respectively), in some examples, further reducing the number of touch sensors in the stylus can be desirable to reduce cost, complexity, and power consumption of the stylus. Accordingly, in some examples, an alternate arrangement of an ultrasonic transducer or ultrasonic transducers can be used. 
       FIG. 9  illustrates an exemplary stylus  900  including an ultrasonic transducer  910  at its end according to examples of the disclosure. As an example, stylus  900  is illustrated as being held by finger  922  and thumb  924 . In some examples, ultrasonic transducer  910  can be used to determine the location(s) along the length of the stylus  900  of one or more objects, such as finger  922  and thumb  924 . Ultrasonic transducer  910  can transmit ultrasonic wave  913  and receive reflected ultrasonic wave  919 , for example. In some examples, a touch controller of the stylus can determine the location of finger  922  and thumb  924  along the length of the stylus  900  based on the time reflected ultrasonic wave  919  is received. Further, touch controller can determine the locations of multiple objects along the length of the stylus  900  if it receives multiple reflected waves in response to one transmitted wave  913 , for example. 
     When stylus  900  includes only one ultrasonic transducer  910  disposed completely around the circumference of the stylus  900 , object location around the circumference of the stylus may not be possible to determine. However, in some examples, detecting only the object location along the length of the stylus  900  can be sufficient. For example, stylus  900  would be able to detect a sliding gesture where the user slides a finger or other object along the length of the stylus. Further, reducing the number of ultrasonic transducers  910  down to one can greatly simplify the circuitry of the stylus  900  including the number of transducers themselves and the number of signals received by a touch controller of the stylus. 
     In some examples, stylus  900  can further include internal channels along the length of the stylus to guide the ultrasonic wave  913 . The internal channels can be positioned at a plurality of radial positions around the circumference of the stylus  900 , for example. In some examples, inclusion of these internal channels can allow stylus  900  to determine the position of an object around the circumference of the stylus by directing ultrasonic waves  913  towards each channel one at a time and receiving reflected waves  919  through channels corresponding to the radial location of the touching object. 
       FIG. 10A  illustrates an exemplary stylus  1000  including ultrasonic transducers  1010  disposed in a ring formation at an end of the stylus  1000  configured to perform a “passive search” according to examples of the disclosure. The ultrasonic transducers  1010  can transmit ultrasonic waves  1013  and receive reflected ultrasonic waves  1019  to determine the location of one or more objects along the length of stylus  1000 . In some examples, the ultrasonic transducers  1010  can transmit ultrasonic waves  1013  one at a time. The location of one or more touch objects along the circumference of the stylus  1000  can be determined from a “passive search” in some examples. That is, the location of the one or more objects along the circumference of the stylus  1000  can be determined based on which ultrasonic transducer  1010  receives the reflected wave. 
     As an example, stylus  1000  can be held by finger  1022  and thumb  1024 . Finger  1022  can contact stylus  1000  along its circumference at a location corresponding to a first ultrasonic transducer  1010 - 1 , while thumb  1024  can contact stylus along its circumference at a location corresponding to a second ultrasonic transducer  1010 - 2 , for example. The first ultrasonic transducer  1010 - 1  can emit a first ultrasonic wave  1013 - 1  and receive a first reflected ultrasonic wave  1019 - 1 . Based on the time that the first reflected ultrasonic wave  1019 - 1  is received, a touch controller of the stylus can also determine the location of finger  1022  along the length of the stylus. Likewise, the second ultrasonic transducer  1010 - 2  can emit a second ultrasonic wave  1013 - 2  and receive a second reflected ultrasonic wave  1019 - 2 . Based on the time that the second reflected ultrasonic wave  1019 - 2  is received, a touch controller of the stylus can also determine the location of thumb  1024  along the length of the stylus. In some examples, the first ultrasonic transducer  1010 - 1  can emit the first ultrasonic wave  1013 - 1  at a first time and the second ultrasonic transducer  1010 - 2  can emit the second ultrasonic wave  1013 - 2  at a second time, and so on. In some examples, multiple ultrasonic transducers  1010  can emit ultrasonic waves concurrently. Further, in some examples where multiple ultrasonic transducers  1010  emit ultrasonic waves concurrently, the ultrasonic waves can be distinguished using frequency or phase differences. In some examples, the “passive search” can determine an object&#39;s location along the length of the stylus and around the circumference of the stylus in one step—that is, operating the transducers  1010  as described above either in series or simultaneously. 
       FIG. 10B  illustrates an exemplary stylus  1000  including ultrasonic transducers  1010  disposed in a ring formation at an end of the stylus  1000  configured to perform an “active search” according to examples of the disclosure. As described above with reference to  FIG. 10A , in a first step, each ultrasonic transducer  1000  can launch an ultrasonic wave  1013  along the length of stylus  1000 . Based on the time at which a reflected wave is received, the location of touch along the length of stylus  1000  can be determined. In some examples, in a second step, to resolve the location of a touch  1020  along the circumference of the stylus  1000 , the ultrasonic transducers  1010  can perform an “active search”. That is, the ultrasonic transducers  1010  can target the ultrasonic waves  1013  at a series of locations around the circumference of the stylus  1000  at a given distance along the length of the stylus  1000  (e.g., along circumferential line  1025 ). In some examples, multiple ultrasonic transducers  1010  can be used to generate directed waves using constructive and/or destructive interference. The ultrasonic transducers  1010  can search along the circumferential line  1025  until the touch location  1020  is determined based on a reflection of the ultrasonic waves  1013  from an object in contact with the stylus  1000  at location  1025 , for example. 
     As discussed above with reference to  FIGS. 6-10 , in some examples, a stylus can include one or more ultrasonic transducers configured to produce ultrasonic waves that travel in one direction (e.g., as opposed to radiating from the ultrasonic transducers in all directions). Various ultrasonic transducer configurations and methods for producing directional ultrasonic waves will now be described. 
       FIG. 11  illustrates an exemplary ultrasonic transducer  1114  configured to transmit a guided wave  1113  according to examples of the disclosure. In some examples, ultrasonic transducer  1114  can be situated on top of wedge  1150 , which can be attached to the surface  1130  of a stylus at an angle θ. In some examples, surface  1130  can be an interior surface of the stylus shaft. In some examples, surface  1130  can be on an exterior surface of the stylus shaft. In some examples, surface  1130  can be embedded within the stylus shaft (e.g., by forming surface  1130 , attaching the wedge  1150  and ultrasonic transducer  114 , and then applying a material on top). The angle θ can correspond to an angle at which the wave  1111  changes paths due to a change in material properties between wedge  1150  and surface  1130 . Ultrasonic transducer can transmit an ultrasonic wave  1111  into the wedge  1114 , which will continue to travel along the surface  1130  as a directional ultrasonic wave  1113 . In some examples, angle θ can be selected based on the material properties of wedge  1150  and surface  1130  and properties of the ultrasonic wave  1111 , such as wavelength and frequency. 
       FIG. 12  illustrates an exemplary stylus  1200  outfitted with ultrasonic transducers  1214  configured to produce a directional ultrasonic wave  1213 . In some examples, the principles of constructive and destructive interference can be applied to create a directional ultrasonic wave  1213  using a plurality of ultrasonic transducers  1214  positioned within stylus  1200 . For example, ultrasonic transducer  1214 - 1  can transmit a first ultrasonic wave at a first time t 0 . After a predetermined time delay Δt, a second ultrasonic transducer  1214 - 2  can transmit a second ultrasonic wave, for example. After a delay of 2Δt, a third ultrasonic transducer  1214 - 3  can transmit a third ultrasonic wave. The resulting directional wave can therefore include coherent contributions from each of the first, second, and third ultrasonic waves, for example. In some examples, additional ultrasonic transducers can be used in this manner. The spacing of the ultrasonic transducers  1214  and the time delay Δt can be selected to create constructive interference in the desired direction of wave travel (e.g., clockwise, as shown in  FIG. 12 ) and destructive interference in the other direction, for example. The constructive interference in the direction of wave travel causes the wave amplitude to increase in one direction (e.g., clockwise). Likewise, the destructive interference in the direction opposite of the desired direction of wave travel causes the wave amplitude to decrease in the other direction (e.g., counterclockwise). As a result, the amplitude in the direction of wave travel can be so large compared to the amplitude in the other direction that the wave effectively travels in one direction. In one or more examples described with reference to  FIGS. 1-11 , a stylus can include ultrasonic transducers arranged as shown in  FIG. 12  in place of any single ultrasonic transducers described, thereby allowing the one or more ultrasonic transducers to produce a directional wave. 
     Although several examples of the disclosure have been discussed as they relate to a stylus, in some examples, one or more examples described above can be incorporated into other kinds of input devices. 
     Therefore, according to the above, some examples of the disclosure are directed to a stylus comprising: a shaft; a tip coupled to an end of the shaft; one or more ultrasonic transducers coupled to the shaft, the one or more ultrasonic transducers configured to transmit one or more transmitted ultrasonic waves and to sense one or more sensed ultrasonic waves; and a touch controller operatively coupled to the one or more ultrasonic transducers, the touch controller configured to generate the one or more transmitted ultrasonic waves and determine a position in at least one dimension of an object touching an exterior surface of the shaft based on one or more characteristics of the one or more sensed ultrasonic waves. Additionally or alternatively, in some examples, the shaft extends along an axis, and the one or more ultrasonic transducers comprises a plurality of ultrasonic transducers arranged in one or more rows, the one or more rows parallel to the first axis. Additionally or alternatively, in some examples, the shaft includes a plurality of cross-sectional areas orthogonal to the axis, the one or more rows comprise a first row and a second row, one or more of the plurality of cross-sectional areas each comprise a first ultrasonic transducer included in the first row and a second ultrasonic transducer included in the second row, the first ultrasonic transducer is configured to transmit the one or more transmitted ultrasonic waves, and the second ultrasonic transducer is configured to sense the one or more sensed ultrasonic waves. Additionally or alternatively, in some examples, the shaft extends along an axis, the stylus shaft includes a plurality of cross-sectional areas orthogonal to the axis, the one or more ultrasonic transducers comprises a plurality of ultrasonic transducers arranged around the circumference of one of the plurality of cross-sectional areas. Additionally or alternatively, in some examples, the shaft extends along an axis, the shaft includes a plurality of cross-sectional areas orthogonal to the axis, an ultrasonic transducer of the one or more ultrasonic transducers is disposed at a distal end opposite the tip around the circumference of one of the plurality of cross-sectional areas, the ultrasonic transducer is configured to: at a first time, generate one of the one or more transmitted ultrasonic waves, the transmitted ultrasonic wave propagating along the axis; and at a second time after the first time, sense one of the one or more sensed ultrasonic waves, and the touch controller determines the position of the object based on the second time. Additionally or alternatively, in some examples, the one or more characteristics of the reflected wave comprise one or more of time of arrival and magnitude. Additionally or alternatively, in some examples, the stylus further comprises a plurality of ultrasonic barriers configured to reflect the ultrasonic wave. Additionally or alternatively, in some examples, the ultrasonic barriers are coupled to the shaft or etched or embedded in the shaft. Additionally or alternatively, in some examples, the one or more ultrasonic transducers comprise a plurality of ultrasonic transducers configured to: at a first time, transmit a first of the one or more transmitted ultrasonic waves using a first ultrasonic transducer; and after a delay of a predetermined duration after the first time, transmit a second of the one or more transmitted ultrasonic waves using a second ultrasonic transducer disposed proximate to the first ultrasonic transducer, wherein the first transmitted ultrasonic wave and the second transmitted ultrasonic wave produce a directional ultrasonic wave including coherent contributions from the first transmitted ultrasonic wave and the second transmitted ultrasonic wave. Additionally or alternatively, in some examples, the stylus further comprises a wedge coupled to the interior surface of the shaft, wherein at least one of the one or more ultrasonic transducers are mounted to the wedge, and the one or more transmitted ultrasonic waves generated by the one or more ultrasonic transducers is coupled to the surface of the shaft via the wedge. 
     Some examples of the disclosure are related to a method for determining a location of an object touching an outside of a stylus comprising a tip and a shaft, the method comprising: transmitting, with one or more ultrasonic transducers coupled to the shaft, one or more transmitted ultrasonic waves; receiving, with the one or more ultrasonic transducers, one or more received ultrasonic waves; and determining, with a touch controller operatively coupled to the plurality of ultrasonic transducers, the position in at least one dimension of the object touching the outside of the stylus based on one or more characteristics of the one or more received ultrasonic waves. Additionally or alternatively, in some examples, the shaft extends along an axis, and the one or more ultrasonic transducers comprises a plurality of ultrasonic transducers arranged in one or more rows, the one or more rows parallel to the first axis. Additionally or alternatively, in some examples, the shaft includes a plurality of cross-sectional areas orthogonal to the axis, the one or more rows comprise a first row and a second row, one or more of the plurality of cross-sectional areas each comprise a first ultrasonic transducer included in the first row and a second ultrasonic transducer included in the second row, and the method further comprises: transmitting, with the first ultrasonic transducer, the one or more transmitted ultrasonic waves, and sensing, with the second ultrasonic transducer the one or more received ultrasonic waves. Additionally or alternatively, in some examples, the shaft extends along an axis, the shaft includes a plurality of cross-sectional areas orthogonal to the axis, the one or more ultrasonic transducers comprises a plurality of ultrasonic transducers arranged around the circumference of one of the plurality of cross-sectional areas. Additionally or alternatively, in some examples, the shaft extends along an axis, the shaft includes a plurality of cross-sectional areas orthogonal to the axis, an ultrasonic transducer of the one or more ultrasonic transducers is disposed at a distal end opposite the tip of the stylus around the circumference of one of the plurality of cross-sectional areas, and the method further comprises at a first time, generate one of the one or more transmitted ultrasonic waves with the ultrasonic transducer of the one or more ultrasonic transducers, the transmitted ultrasonic wave propagating along the axis; at a second time after the first time, sense one of the one or more sensed ultrasonic waves with the ultrasonic transducer of the one or more ultrasonic transducers; and determining, with the touch controller, the position of the object based on the second time. Additionally or alternatively, in some examples, the one or more characteristics of the one or more sensed ultrasonic waves comprise time of arrival and magnitude. Additionally or alternatively, in some examples, the method further comprises reflecting, with a plurality of ultrasonic barriers, the one or more transmitted ultrasonic waves. Additionally or alternatively, in some examples, the plurality of ultrasonic barriers are coupled to the shaft or etched or embedded in the shaft. Additionally or alternatively, in some examples, the one or more ultrasonic transducers comprise a plurality of ultrasonic transducers, and the method further comprises: transmitting, at a first time, a first of the one or more transmitted ultrasonic waves using a first ultrasonic transducer; and after a delay of a predetermined duration after the first time, transmitting a second of the one or more transmitted ultrasonic waves using a second ultrasonic transducer disposed proximate to the first ultrasonic transducer, wherein the first ultrasonic wave and the second ultrasonic wave produce a directional wave including coherent contributions from the first transmitted ultrasonic wave and the second transmitted ultrasonic wave. Additionally or alternatively, in some examples, the stylus further comprises a wedge coupled to the interior surface of the shaft, wherein at least one of the one or more ultrasonic transducers are mounted to the wedge, and the one or more transmitted ultrasonic waves generated by the one or more ultrasonic transducers is coupled to the surface of the shaft via the wedge. 
     Although 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 various examples as defined by the appended claims.

Metadata:
Filing Date: 20180316
Publication Date: 20200331
Grant Date: 20200331
Priority Date: 20170331
Inventors: YOUSEFPOR, MARDUKE
TUCKER, AARON SCOTT
KING, BRIAN MICHAEL
KHAJEH, EHSAN
YIP, Marcus
YEKE YAZDANDOOST, MOHAMMAD
ZUBER, Wesley W.
Assignee: APPLE INC
CPC Classifications: [{"code": "G06F3/03545", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/03545", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/0433", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F3/0383", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/0433", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F3/03545", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/0433", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F3/044", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F2203/0339", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F3/0442", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F3/0442", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F2203/0339", "inventive": false, "first": false, "tree": "[]"}]
Family ID: 63672521