PATENT DOCUMENT

Publication Number: US-9323398-B2
Application Number: US-50138209-A
Country: US
Kind Code: B2

Title: Touch and hover sensing

Abstract:
Improved capacitive touch and hover sensing with a sensor array is provided. An AC ground shield positioned behind the sensor array and stimulated with signals of the same waveform as the signals driving the sensor array may concentrate the electric field extending from the sensor array and enhance hover sensing capability. The hover position and/or height of an object that is nearby, but not directly above, a touch surface of the sensor array, e.g., in the border area at the end of a touch screen, may be determined using capacitive measurements of sensors near the end of the sensor array by fitting the measurements to a model. Other improvements relate to the joint operation of touch and hover sensing, such as determining when and how to perform touch sensing, hover sensing, both touch and hover sensing, or neither.

Claims:
What is claimed is: 
     
       1. A capacitive touch sensing apparatus comprising:
 a cover surface; 
 a sensor array substantially adjacent to the cover surface; 
 a touch control system configured to transmit a first alternating current (AC) signal to the sensor array and measure a capacitance of the sensor array resulting from the first AC signal; and 
 switching circuitry capable of switching the sensor array from a mutual capacitance detection configuration to a self capacitance detection configuration, the sensor array configured to operate in the mutual capacitance detection configuration during a first detection mode, and in the self capacitance detection configuration during a second detection mode, 
 wherein the touch control system is further configured to:
 perform a first self capacitance measurement at the sensor array; 
 in accordance with a determination that the first self capacitance measurement is indicative of activity of an object on the sensor array, independent of a distance of the object from the sensor array, cause the switching circuitry to alternate the sensor array between the mutual capacitance detection configuration and the self capacitance detection configuration; and 
 in accordance with a determination that the first self capacitance measurement is not indicative of activity on the sensor array, perform a second self capacitance measurement at the sensor array. 
 
 
     
     
       2. The capacitive touch sensing apparatus of  claim 1 , wherein the sensor array includes an electrode including a substantially transparent conductor. 
     
     
       3. The capacitive touch sensing apparatus of  claim 1 , further comprising:
 an AC shield, wherein the sensor array is positioned substantially between the AC shield and the cover surface; and 
 an AC shield driving system that transmits a second AC signal to the AC shield such that a first voltage of the sensor array is substantially the same as a second voltage of the AC shield. 
 
     
     
       4. The capacitive touch sensing apparatus of  claim 3 , wherein the AC shield is electrically isolated from the sensor array. 
     
     
       5. The capacitive touch sensing apparatus of  claim 3 , wherein the AC shield includes an electrode including a non-transparent conductor. 
     
     
       6. The capacitive touch sensing apparatus of  claim 3 , further comprising:
 a second AC shield substantially surrounding at least a portion of a transmission line connecting the touch control system and the sensor array, the first AC signal being transmitted on the transmission line. 
 
     
     
       7. The capacitive touch sensing apparatus of  claim 3 , wherein the first AC signal has a waveform and the second AC signal is generated from a buffered copy of the waveform. 
     
     
       8. A touch screen including the capacitive touch sensing apparatus of  claim 3 , wherein the touch screen further comprises:
 a display, wherein the touch control system and the AC shield are substantially collocated with the display, the display including display circuitry, and the AC shield is positioned substantially between the display circuitry and the sensor array. 
 
     
     
       9. The capacitive touch sensing apparatus of  claim 1 , wherein the switching circuitry comprises a switch. 
     
     
       10. The capacitive touch sensing apparatus of  claim 1 , further comprising a switching system to control the switching circuitry. 
     
     
       11. The capacitive touch sensing apparatus of  claim 1 , wherein the activity on the sensor array comprises touch or hover activity on the sensor array. 
     
     
       12. A method of detecting a hover position of an object near a distal end of a sensor array and outside of a space directly above the sensor array, the method comprising:
 obtaining a set of capacitance measurements of a plurality of sensors of the sensor array in a range of sensor positions near the distal end of the sensor array, the capacitance measurements being caused by the object; 
 fitting the set of capacitance measurements to a model that defines a curve including a local maximum with a position outside of the range of sensor positions; and 
 determining the hover position based on the position of the local maximum. 
 
     
     
       13. The method of  claim 12 , wherein the model is based on a previous set of capacitance measurements of the object, wherein the previous set includes a local maximum. 
     
     
       14. The method of  claim 12 , wherein the model includes a Gaussian curve. 
     
     
       15. The method of  claim 12 , wherein the fitting includes determining a maximum likelihood estimate of parameters of the model. 
     
     
       16. The method of  claim 15 , wherein the parameters include at least one of object conductivity and object size. 
     
     
       17. The method of  claim 15 , wherein the fitting includes estimating a number of objects and parameters of each object. 
     
     
       18. The method of  claim 12 , wherein the fitting includes determining a closest match between the capacitance measurement of a first sensor of the plurality of sensors and one of plurality of stored capacitance measurements of the sensor array. 
     
     
       19. A method of detecting a user input, including the method of detecting a hover position of  claim 12 , the method further comprising:
 detecting a plurality of hover positions of the object near the distal end of a sensor array and outside of the space directly above the sensor array; 
 determining a motion of the object corresponding to the plurality of detected hover positions; and 
 detecting the user input based on the determined motion of the object. 
 
     
     
       20. The method of  claim 19 , further comprising:
 controlling a graphical user interface (GUI) based on the detected user input. 
 
     
     
       21. A method of controlling a motion of a graphical user interface (GUI) item including the method of detecting a hover position of  claim 12 , the method further comprising:
 moving the GUI item in correspondence with a motion of the object inside of the space directly above the sensor array; and 
 continuing the motion of the GUI item when the motion of the object is detected to stop at a hover position near the distal end of the sensor array and outside of the space directly above the sensor array. 
 
     
     
       22. A capacitive touch sensing apparatus comprising:
 a sensor array; 
 a sensor control system including a first control system configured to, during a mutual capacitance measurement mode, transmit a first alternating current (AC) signal to the sensor array and measure a mutual capacitance of the sensor array resulting from the first AC signal, and a second control system configured to, during a self capacitance measurement mode, transmit a second alternating current (AC) signal to the sensor array and measure a self capacitance of the sensor array resulting from the second AC signal; and 
 a switching system configured to switch the sensor control system between the mutual capacitance measurement mode and the self capacitance measurement mode, 
 wherein the sensor control system is configured to:
 perform a first self capacitance measurement at the sensor array; 
 in accordance with a determination that the first self capacitance measurement is indicative of activity of an object on the sensor array, independent of a distance of the object from the sensor array, alternate between the mutual capacitance measurement mode and the self capacitance measurement mode; and 
 in accordance with a determination that the first self capacitance measurement is not indicative of activity on the sensor array, perform a second self capacitance measurement at the sensor array. 
 
 
     
     
       23. The capacitive touch sensing apparatus of  claim 22 , wherein the sensor array includes common circuitry that operates in both the mutual capacitance measurement mode and the self capacitance measurement mode. 
     
     
       24. The capacitive touch sensing apparatus of  claim 22 , wherein the first control system includes first control system circuitry, and the second control system includes second control system circuitry, and the switching system includes a physical switch that alternatively connects the first control system circuitry to the sensor array or connects the second control system circuitry to the sensor array during the mutual capacitance measurement mode and the self capacitance measurement mode, respectively. 
     
     
       25. The capacitive touch sensing apparatus of  claim 22 , wherein the switching system includes a low-leakage analog switch. 
     
     
       26. A method for detecting a touch event on or near a touch sensing apparatus, the method comprising:
 performing a first self capacitance measurement at a sensor array of the apparatus; 
 in accordance with a determination that the first self capacitance measurement is indicative of activity of an object at the sensor array, independent of a distance of the object from the sensor array:
 transmitting a first alternating current (AC) signal to the sensor array, and measuring a mutual capacitance of the sensor array resulting from the first AC signal; 
 detecting a first touch event based on the mutual capacitance; 
 transmitting a second alternating current (AC) signal to the sensor array and measuring a self capacitance of the sensor array resulting from the second AC signal; and 
 detecting a second touch event based on the self capacitance; and 
 
 in accordance with a determination that the first self capacitance measurement is not indicative of activity on the sensor array, performing a second self capacitance measurement at the sensor array. 
 
     
     
       27. The method of  claim 26 , wherein the first AC signal and the second AC signal are transmitted concurrently through one of frequency multiplexing and code division multiplexing. 
     
     
       28. The method of  claim 26 , wherein the first AC signal and the second AC signal are transmitted concurrently through space multiplexing, in which the first AC signal is transmitted to a first group of sensors of the sensor array, and the second AC signal is transmitted to a second group of sensors of the sensor array. 
     
     
       29. The method of  claim 26 , wherein the first AC signal is transmitted during a first sensing phase and the second AC signal is transmitted during a second sensing phase that is non-overlapping with the first sensing phase, the method further comprising:
 setting the apparatus to operate in one of a plurality of operational phases including the first sensing phase and the second sensing phase. 
 
     
     
       30. The method of  claim 29 , wherein setting the apparatus to operate in one of the plurality of operational phases is based on at least one of a predetermined schedule, a request from an external computer process, a current number and positions of objects detected, and a distance of an object from the sensor array. 
     
     
       31. A touch sensing device comprising:
 a touch sensing panel having multiple sensors, each sensor capable of detecting one or more objects proximate to the panel, wherein the objects touch the panel to cause a touch event, hover over the panel to cause a hover event, or touch and hover concurrently to cause touch and hover events; and 
 a touch control system configured to:
 perform a first self capacitance measurement at the touch sensing panel; 
 in accordance with a determination that the first self capacitance measurement is indicative of activity of an object on the touch sensing panel, independent of a distance of the object from the sensor array, operate the sensors in a mutual capacitance detection configuration and a self capacitance detection configuration; and 
 in accordance with a determination that the first self capacitance measurement is not indicative of activity on the touch sensing panel, perform a second self capacitance measurement at the touch sensing panel. 
 
 
     
     
       32. The device of  claim 31 , wherein the touch control system is further configured to switch a portion of the sensors to the self capacitance detection configuration and another portion of the sensors to the mutual capacitance detection configuration so as to partition the panel to concurrently detect mutual capacitance and self capacitance. 
     
     
       33. The device of  claim 31 , further comprising a display configured to display graphical information to select in response to the touch and hover events. 
     
     
       34. The device of  claim 31  incorporated into at least one of a mobile phone, a digital media player, or a computer. 
     
     
       35. A capacitive touch sensing apparatus comprising:
 a cover surface; 
 a sensor array substantially adjacent to the cover surface; and 
 a touch control system configured to:
 perform a first self capacitance measurement at the sensor array; 
 in accordance with a determination that the first self capacitance measurement is indicative of activity of an object on the sensor array, independent of a distance of the object from the sensor array:
 transmit a first alternating current (AC) signal concurrently with a second alternating current (AC) signal to the sensor array, and 
 measure a self capacitance of the sensor array resulting from the first AC signal concurrently with a mutual capacitance of the sensor array resulting from the second AC signal; and 
 
 in accordance with a determination that the first self capacitance measurement is not indicative of activity on the sensor array, perform a second self capacitance measurement at the sensor array. 
 
 
     
     
       36. The capacitive touch sensing apparatus of  claim 35 , wherein the touch control system is further configured to combine the first AC signal and the second AC signal using frequency multiplexing before transmitting the combined signal to the sensor array. 
     
     
       37. The capacitive touch sensing apparatus of  claim 35 , wherein the touch control system is further configured to combine the first AC signal and the second AC signal using code division multiplexing before transmitted the combined signal to the sensor array. 
     
     
       38. The capacitive touch sensing apparatus of  claim 35 , wherein the first AC signal has a first frequency, and the second AC signal has a second frequency, the second frequency being different than the first frequency.

Description:
FIELD 
     This relates generally to touch and hover sensing, and in particular, to improved capacitive touch and hover sensing. 
     BACKGROUND 
     Many types of input devices are presently available for performing operations in a computing system, such as buttons or keys, mice, trackballs, joysticks, touch sensor panels, touch screens and the like. Touch screens, in particular, are becoming increasingly popular because of their ease and versatility of operation as well as their declining price. Touch screens can include a transparent touch sensor panel positioned in front of a display device such as a liquid crystal display (LCD), or an integrated touch screen in which touch sensing circuitry is partially or fully integrated into a display, etc. Touch screens can allow a user to perform various functions by touching the touch screen using a finger, stylus or other object at a location that may be dictated by a user interface (UI) being displayed by the display device. In general, touch screens can recognize a touch event and the position of the touch event on the touch sensor panel, and the computing system can then interpret the touch event in accordance with the display appearing at the time of the touch event, and thereafter can perform one or more actions based on the touch event. 
     Mutual capacitance touch sensor panels can be formed from a matrix of drive and sense lines of a substantially transparent conductive material such as Indium Tin Oxide (ITO), often arranged in rows and columns in horizontal and vertical directions on a substantially transparent substrate. Drive signals can be transmitted through the drive lines, which can make it possible to measure the static mutual capacitance at the crossover points or adjacent areas (sensing pixels) of the drive lines and the sense lines. The static mutual capacitance, and any changes to the static mutual capacitance due to a touch event, can be determined from sense signals that can be generated in the sense lines due to the drive signals. 
     While some touch sensors can also detect a hover event, i.e., an object near but not touching the touch sensor, typical hover detection information may be of limited practical use due to, for example, limited hover detection range, inefficient gathering of hover information, etc. 
     SUMMARY 
     This relates to improved capacitive touch and hover sensing. A capacitive sensor array can be driven with electrical signals, such as alternating current (AC) signals, to generate electric fields that extend outward from the sensor array through a touch surface to detect a touch on the touch surface or an object hovering over the touch surface of a touch screen device, for example. The electric field can also extend behind the sensor array in the opposite direction from the touch surface, which is typically an internal space of the touch screen device. An AC ground shield may be used to enhance the hover sensing capability of the sensor array. The AC ground shield can be positioned behind the sensor array and can be stimulated with signals having the same waveform as the signals driving the sensor array. As a result, the electric field extending outward from the sensor array can be concentrated. In this way, for example, the hover sensing capability of the sensor array may be improved. 
     Hover sensing may also be improved using methods to detect a hover position of an object outside of a space directly above the touch surface. In particular, the hover position and/or height of an object that is nearby, but not directly above, the touch surface (in other words, an object outside of the space directly above the touch surface), e.g., in the border area at the end of a touch screen, may be determined using measurements of sensors near the end of the touch screen by fitting the measurements to a model. Other improvements relate to the joint operation of touch and hover sensing, such as determining when and how to perform touch sensing, hover sensing, both touch and hover sensing, or neither. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present disclosure, in accordance with one or more various embodiments, is described in detail with reference to the following figures. The drawings are provided for purposes of illustration only and merely depict example embodiments of the disclosure. These drawings are provided to facilitate the reader&#39;s understanding of the disclosure and should not be considered limiting of the breadth, scope, or applicability of the disclosure. It should be noted that for clarity and ease of illustration these drawings are not necessarily made to scale. 
         FIGS. 1A-1B  illustrate an example sensor array and AC ground shield according to embodiments of the disclosure. 
         FIGS. 2A-2B  illustrate example sensor array configurations with and without an AC ground shield according to embodiments of the disclosure. 
         FIG. 3  illustrates an example touch screen according to embodiments of the disclosure. 
         FIG. 4  illustrates an object directly above an example touch screen according to embodiments of the disclosure. 
         FIG. 5  illustrates an object outside of a space directly above an example touch screen according to embodiments of the disclosure. 
         FIG. 6  illustrates example capacitance measurements according to embodiments of the disclosure. 
         FIG. 7  is a flowchart of an example method of determining a hover position/height according to embodiments of the disclosure. 
         FIG. 8  illustrates an example touch and hover sensing system according to embodiments of the disclosure. 
         FIG. 9  illustrates an example touch and hover sensing system according to embodiments of the disclosure. 
         FIG. 10  is a flowchart of an example method of detecting touch and hover events according to embodiments of the disclosure. 
         FIG. 11  is a flowchart of an example method of operating a touch and hover sensing system according to embodiments of the disclosure. 
         FIG. 12A  illustrates an example mobile telephone that can include improved capacitive touch and hover sensing according to embodiments of the disclosure. 
         FIG. 12B  illustrates an example digital media player that can include improved capacitive touch and hover sensing according to embodiments of the disclosure. 
         FIG. 12C  illustrates an example personal computer that can include improved capacitive touch and hover sensing according to embodiments of the disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     In the following description of embodiments, reference is made to the accompanying drawings which form a part hereof, and in which it is shown by way of illustration specific embodiments that can be practiced. It is to be understood that other embodiments can be used and structural changes can be made without departing from the scope of the disclosed embodiments. 
     This relates generally to touch and hover sensing, and more particularly, to improved capacitive touch and hover sensing. For example, an alternating current (AC) ground shield may be used to enhance the hover sensing capability of a sensor array, such as a capacitive touch sensor array. Electrical signals, such as AC signals, transmitted to a capacitive touch sensor array in a touch screen can generate electric fields that extend outward from the sensor array through a touch surface to detect a touch on the touch surface or an object hovering over the touch surface. The electric field can also extend behind the sensor array in the opposite direction from the touch surface, which is typically an internal space of the touch screen device. An AC ground shield can be positioned behind the sensor array, and the AC ground shield can be stimulated with signals having the same waveform as the AC signals, for example. As a result, the electric field extending outward from the sensor array can be concentrated, as described in more detail below. In this way, for example, the hover sensing capability of the sensor array may be improved. 
     Hover sensing may also be improved using methods to detect a hover position of an object outside of a space directly above the touch surface. In particular, the hover position and/or height of an object that is nearby, but not directly above, the touch surface (in other words, an object outside of the space directly above the touch surface), e.g., in the border area at the end of a touch screen, may be determined using measurements of sensors near the end of the touch screen by fitting the measurements to a model, as described in more detail below. Other improvements relate to the joint operation of touch and hover sensing, such as determining when and how to perform touch sensing, hover sensing, both touch and hover sensing, or neither, as described in more detail below. 
       FIGS. 1A and 1B  show an example embodiment of a capacitive touch and hover sensing apparatus that includes an AC ground shield (also referred to as a “driven shield”). 
       FIG. 1A  shows a portion of a touch and hover sensing apparatus  100  with a sensor array  101  that includes an array of horizontal lines  103  and vertical lines  105 . Horizontal lines  103  and vertical lines  105  can be, for example, electrically conductive lines in a self capacitive sensing system. In other embodiments, other types of sensing schemes may be used, such as mutual capacitive, optical, ultrasonic, etc. In some embodiments, such as touch screens, for example, lines  103  and/or  105  can be formed of substantially transparent conductive materials. In some embodiments, such as trackpads, for example, lines  103  and/or  105  may be formed of a non-transparent conductive material. 
     Touch and hover sensing apparatus  100  also includes a touch and hover control system  107  that can drive sensor array  101  with electrical signals, e.g., AC signals, applied to horizontal lines  103  and/or vertical lines  105 . The AC signals transmitted to sensor array  101  create electric fields extending from the sensor array, which can be used to detect objects near the sensor array. For example, an object placed in the electric field near sensor array  101  can cause a change in the self capacitance of the sensor array, which can be measured by various techniques. Touch and hover control system  107  can measure the self capacitance of each of the horizontal and vertical lines to detect touch events and hover events on or near sensor array  101 . 
     The maximum range of detection can depend on a variety of factors, including the strength of the electric field generated by sensor array  101 , which can depend on the voltage, i.e., amplitude, of the AC signals used for detection. However, the AC signal voltage may be limited by a variety of design factors, such as power limitations, impedance limitations, etc. In some applications, such as consumer electronics in general and portable electronics in particular, the limited maximum voltage of the AC signals may make it more difficult to design touch and hover sensing systems with acceptable detection ranges. 
     In this regard,  FIG. 1B  shows an AC ground shield system that can be used with sensor array  101 . The AC ground shield system includes an AC ground shield  201  and an AC shield driving system  203 . AC ground shield  201  can be positioned substantially behind sensor array  101 , that is, on the side of sensor array  101  opposite to the touch and hover detection side of the sensor array. AC shield driving system  203  can transmit AC signals to AC ground shield  201  to create an electric field that can help concentrate the electric field generated by sensor array  101  in a detection space above sensor array  101  (shown as the z-direction in  FIG. 1B ). 
       FIGS. 2A and 2B  illustrate an example of how the electric field generated by sensor array  101  may be concentrated by AC ground shield  201 .  FIG. 2A  shows a stimulated horizontal conductive line  103  of sensor array  101  in a configuration without AC ground shield  201 . An electric field  250  extends substantially radially from horizontal conductive line  103  in all directions.  FIG. 2B  illustrates how including AC ground shield  201  with the configuration of  FIG. 2A  can concentrate electric field of conductive line  103  into a different electric field  253 . In  FIG. 2B , horizontal conductive line  103  of sensor array  101  is stimulated in the same way as in  FIG. 2A , and AC ground shield  201  is stimulated in a substantially similar way as conductive line  103 . For example, the AC signals transmitted to AC ground shield  201  can have substantially the same waveform as the AC signals transmitted to sensor array  101 , such that the voltage of the AC ground shield can be substantially the same as the voltage of sensor array  101  at any particular time. The stimulation of AC ground shield generates an electric field  255 .  FIG. 2B  shows electric field  253  concentrated above (in the z-direction) horizontal conductive line  103  due to the operation of AC ground shield  201 . In this way, for example, the addition of AC ground shield  201  can help boost the detection range of sensor array  101 . 
     In addition, AC ground shield  201  can reduce or eliminate the electric field between sensor array  101  and AC ground shield  201 . More particularly, even though the voltages on sensor array  101  and AC ground shield  201  may be changing over time, the change can be substantially in unison so that the voltage difference, i.e., electric potential, between the sensor array and the AC ground shield can remain zero or substantially zero. Therefore, little or no electric fields may be created between sensor array  101  and AC ground shield  201 .  FIG. 2B , for example, shows that the space between horizontal conductive line  103  and AC ground shield  201  is substantially free of electric fields in the example configuration. 
       FIG. 3  illustrates an example embodiment in which sensor array  101 , touch and hover control system  107 , AC ground shield  201 , and AC shield driving system  203  are implemented in a touch screen  300 . In this example, horizontal lines  103  and vertical lines  105  can be electrodes formed of a substantially transparent conductor.  FIG. 3  shows a portion of touch screen  300  in which sensor array  101  and AC ground shield  201  can be substantially co-located with display circuitry  317 , and in particular, AC ground shield can be positioned substantially between display circuitry  317  and sensor array  101 . A border  301  holds distal ends  303  of sensor array  101 . The user can view a displayed image through a cover surface  305  and can, for example, touch the cover surface with their fingers and/or hover their fingers near the cover surface in a space  307  directly above sensor array  101  in order to activate corresponding elements of a graphical user interface (GUI) corresponding to the detected touch events and/or hover events. In this example, touch and hover control system  107  transmits AC signals having a waveform  311  on a transmission line  309  that connects the touch and hover control system to sensor array  101 . Touch and hover control system  107  also transmits waveform  311  to a memory  313  for storage. Memory  313  stores a buffered copy  315  of waveform  311 . AC shield driving system  203  reads buffered copy  315  of the waveform from memory  313  and generates corresponding AC signals with waveform  311 , which are then transmitted to AC ground shield  201 . In this example configuration, sensor array  101  can be positioned substantially between AC ground shield  201  and cover surface  305 , and AC ground shield  201  operates as described above to concentrate electric fields in detecting space  307  over cover surface  305 . 
     The configuration of AC ground shield  201  may also help to shield sensor array  101  from other electronics and/or sources of ground, such as from display circuitry  317  which can be driven by a display driver  319  to generate an image viewed through cover surface  305 . In particular, as described above, AC ground shield  201  can help prevent or reduce an electric field emanating from sensor array  101  in the direction of the AC ground shield. In the configuration shown in  FIG. 3 , AC ground shield  201  can be positioned between sensor array  101  and other internal electronics, such as display circuitry  317  and display driver  319 . Therefore, AC ground shield  201  can prevent or reduce an electric field emanating from sensor array  101  that could reach display circuitry  317  and display driver  319 . In this way, AC ground shield  201  may help electrically isolate sensor array  101  from other internal electronics in this example configuration, which may reduce undesirable effects such as noise, stray capacitance, etc. that could interfere with the accurate measuring of capacitance changes caused by objects touching/hovering in detection space  307 . 
     Another type of AC shield, a transmission line AC shield  308 , is shown in  FIG. 3 . Transmission line AC shield  308  substantially surrounds a portion of transmission line  309 . AC shield driving system  203  also uses buffered copy  315  to transmit signals with waveform  311  to transmission line AC shield  308 . This can help to shield transmission line  309  by reducing electric fields emanating from the transmission line. However, in contrast to AC ground shield  201 , transmission line AC shield  308  does not serve to concentrate fields emanating from transmission line  309  to boost a range of detection, for example. 
       FIG. 4  shows a finger  401  hovering in space  307  directly above sensor array  101 . Finger  401  can disturb electric field lines  403  from sensor array  101 . 
       FIG. 5  shows finger  401  near distal end  303  and outside of space  307 . Even though finger  401  is outside of space  307  directly above sensor array  101 , the finger still disturbs some of the field lines  501  emanating from some of the sensors of sensor array  101 . 
       FIG. 6  illustrates capacitance measurements  601  representing measurements from  FIG. 4  and measurements  603  representing measurements from the configuration in  FIG. 5 . Measurements  601  can represent a typical shape of a set of capacitance measurements of sensors of sensor array  101  near a touch object such as finger  401  shown in  FIG. 4 . In particular, measurements closer to the center of finger  401  can be greater than measurements further from the center. Therefore, the shape of measurements  601  can be modeled, for some objects and sensor arrays, with a curve  605 , such as a Gaussian curve, for example. Curve  605  can have a local maximum  607 , which can represent the center of finger  401 , for example. Curve  605  also has tail ends on either side of local maximum  607 .  FIG. 6  also shows measurements  603 , which represent the set of capacitance measurements measured by sensors near distal end  303  of sensor array  101  after finger  401  has traveled outside of space  307 , past distal end  303 . In this case, measurements  603  represent only a tail end  609  of the curve that would be measured if finger  401  were inside of space  307 . In other words, measurements  603  are an incomplete set of measurements, at least as compared to measurements  601 . 
     In typical algorithms used to determine position and/or hover height of an object directly above a sensor array of a touch screen, for example, a full set of measurements such as measurements  601  can provide enough data to determine the position from a determination of local maximum  607 . In this case, the determination of local maximum  607  can be easily made because the set of measurements  601  spans local maximum  607 . In other words, local maximum  607  can be within the range of measurements  601 . On the other hand, measurements  603  represent only tail end  609  portion of a complete curve, which does not include direct information of a local maximum. Thus, while the shape of tail end  609  can be known, the shape of the complete curve that would be measured if sensor array  101  extended beyond distal end  303  can be unknown. 
       FIG. 6  shows one possible estimate of an unknown curve  611  based on a set of unknown measurements  615 . Unknown curve  611  and unknown measurements  615  are not actually measured, but are provided for purposes of illustration to show the general idea of how tail end measurements caused by an object near a distal end of an array of sensors and outside of the space directly above the array may be used to detect a hover position and/or hover height of the object. In particular, it may be recognized that measurements  603  represent a tail end  609  of unknown curve  611  and at that determining the parameters of unknown curve  611 , and consequently determining unknown local maximum  613 , can provide information about the hover position and/or height of the object. Consequently, a hover position of the object outside of the range of sensor positions of sensor array  101  may be determined based on the determined local maximum  613 . 
       FIG. 7  shows an example method of detecting a hover position of an object outside of space  307  using measurements  603 . The example method of  FIG. 7 , and other methods described herein, may be performed in, for example, touch and hover control system  107 , a general purpose processor such as a central processing unit (CPU) (not shown), and/or another processor, and results may be stored in, for example, memory  313  and/or another memory (not shown) as one skilled in the art would readily understand in view of the present disclosure. Referring to  FIG. 7 , measurements  603  can be obtained ( 701 ) and fit ( 702 ) to a model including a local maximum outside of space  307 . A variety of models may be used, as well as a variety of fitting methods, to fit measurements  603  to determine the hover position of finger  401 . For example, a Gaussian curve may be used as a model of the type of curve to fit to measurements  603 . In particular, it may be observed from  FIG. 6  that curve  605 , which approximates one set of measurements  601  of finger  401  in one location, appears substantially Gaussian-shaped. Therefore, it may be reasonable to assume that sensor readings made by an object similar to finger  401  will be Gaussian-shaped. In this case, the model selected to fit measurements  603  can be a Gaussian curve. 
     Various methods can be used to fit a Gaussian curve to measurements  603 . For example, one method that may be used is a maximum likelihood estimate method. In this case, for example, parameters of a Gaussian curve, such as maximum height and standard deviation, may be adjusted until differences (errors) between the estimated Gaussian curve and measurements  603  are minimized. The Gaussian curve with the lowest estimated error can be used to determine unknown local maximum  613 , which can represent the position of finger  401  outside of space  307 . 
     In some embodiments, the model used may be another type of curve, for example a modified Gaussian curve, a custom curve determined from previous data, etc. In some embodiments, the model used may not be a curve at all, but may simply be a set of parameters stored in a lookup table (LUT). In this case, individual sensor measurements may be individually fit to the values stored in the lookup table, and once the best match is found, the lookup table can simply return a single value representing the determined hover position of the object. The hover position values in the lookup table can be based on, for example, empirical data of hover positions corresponding to particular sensor measurements, previously calculated curve modeling, etc. 
     In some embodiments, other parameters may be used in the determination of hover position and/or height. For example, if the object&#39;s size, conductivity, etc., are known, these parameters may be included when fitting the measured capacitances to the model. In some embodiments, a model can be based on a previous set of capacitance measurements of the object that includes a local maximum. 
     In some embodiments, information regarding object size, velocity, etc., may be taken into consideration in determining a model to be used in fitting the capacitance measurements. For example,  FIGS. 4-6  illustrate an example situation in which a finger  401  travels from the middle of sensor array  101  toward distal end  303  and then past distal end  303  and outside of space  307 . In this example case, the method could record the set of measurements  601  as the model to which measurements  603  will be fitted. The measurements  601  may be stored directly into a lookup table, for example. In another embodiment, measurements  601  may be interpolated to generate a model curve for use in fitting measurements  603 . 
     In some embodiments, other information about finger  401 , such as the finger&#39;s velocity, may be used when fitting measurements  603 . For example, the velocity of finger  401 , which may be determined by a separate algorithm, may be used as a parameter in the model used during the fitting process. In this way, a curve or representation of measurements  601  may be tracked as finger  401  travels outside of space  307 , such that information regarding the local maximum of the curve can be maintained even though the local maximum may not be directly detected in measurements  603 . 
     In some embodiments, multiple models may be considered during fitting of the measurements. For example, the method may determine that more than one object is causing the particular capacitance measurements near a distal end of the sensor array, and the method may use more than one model and/or fitting method to attempt to fit the capacitance measurements to one or more objects and/or types of objects. For example, the method may determine that the capacitance measurements are caused by multiple objects of the same type, such as “three fingers”, or “two thumbs”, etc. The method may determine that the capacitance measurements are caused by objects of different types, such as “a finger and a thumb”, or “a first and a thumb”, etc. The method may determine that the capacitance measurements are caused by a variety of numbers and types of objects, such as “two fingers and a first”, or “a left thumb, a right finger, and a palm”, etc. The method may fit different models, corresponding to the different number and/or type of objects, to different portions of the capacitance measurements. For example, the method may determine that the capacitance measurements are caused by two objects, e.g., a finger that was previously tracked as it moved off of the sensor array and an unknown object estimated to be a thumb. In this case, the method may attempt to fit the capacitance measurements corresponding to the finger to previously stored data by fitting individual sensor measurements to previously stored values in a LUT and fit the capacitance measurements corresponding to the thumb to a Gaussian curve using a maximum likelihood estimate of parameters associated with a thumb. Thus, some embodiments may estimate the number of objects and the parameters of each object when fitting the capacitance measurements. 
     In some embodiments, the position and/or motion of an object near the distal end of a sensor array and outside of the space directly above the sensor array may be processed as a user input. For example, a position and/or motion of an object may be processed as an input to a graphical user interface (GUI) currently displayed, as an input independent of a GUI, etc. 
     For example, the method described with reference to  FIG. 7  may be used to determine a user input based on the position and/or motion of one or more objects including objects near the distal end of a sensor array and outside of the space directly above the sensor array. The hover position of an object in a border area outside the sensor array may be measured multiple times to determine multiple hover positions. The motion of the object can be determined corresponding to the multiple measured hover positions, and an input can be detected based on the determined motion of the object. For example, a finger detected moving upwards in a border area may be interpreted as a user input to increase the volume of music currently being played. In some embodiments, the user input may control a GUI. For example, a finger detected moving in a border area may control a GUI item, such as an icon, a slider, a text box, a cursor, etc., in correspondence with the motion of the finger. 
     In some embodiments, a user input can be based on a combination of information including the position and/or motion of an object directly above the sensor array and the position and/or motion of an object near the distal end of the sensor array and outside of the space directly above the sensor array. Referring to  FIGS. 3-5 , for example, a GUI may be displayed at cover surface  305 . The method described above with reference to  FIG. 7  may be used, for example, to control the motion of a GUI item as finger  401  travels off of the touch screen. For example, finger  401  may initiate an input direct above sensor array  101  to “drag” an icon displayed by the GUI. The icon may be controlled by display driver  319  to move along a path corresponding to the motion of finger  401  inside of space  307 . If finger  401  is detected to move outside of space  307  and to stop at a position near the distal end of sensor array  101 , display driver  319  can control the icon to continue moving along the path of the finger just prior to the finger moving off of the touch screen. Display driver  319  can cease the motion of the icon when finger  401  is detected to move away from its stopped position. This may be helpful to allow dragging and/or pointing actions to be continued even when a finger, for example, moves off of the touch screen. 
       FIGS. 8-11  describe examples of different hardware, software, and firmware embodiments that can perform joint operations of touch sensing and hover sensing. For example, in some embodiments, one set of sensors can be used for hover sensing and another set of sensors can be used for touch sensing. For instance, electrodes configured for self-capacitance measurements can be used for hover sensing, and electrodes configured for mutual capacitance measurements can be used for touch sensing. In these cases, switching between touch sensing and hover sensing may be done to save power, reduce interference, etc. In other embodiments, the same sensors may be shared between hover sensing and touch sensing. In these cases, switching may be necessary in order to utilize shared circuit elements, for example. Software and/or firmware may control the joint operation of touch and hover sensing. For example, depending on the particular configuration, software and/or firmware may determine when to switch between touch sensing and hover sensing, e.g., in single-mode operation, determine when to perform touch and hover sensing concurrently, e.g., in multi-mode operation, activate different portions of a sensor to perform touch and/or hover sensing, etc. 
       FIGS. 8-9  illustrate example embodiments of hardware switching that may be used to switch between touch sensing and hover sensing. 
       FIG. 8  shows an example touch and hover sensing system  800  including a sensor array  801  that includes touch and hover circuitry  803  and touch circuitry  805 . For example, touch and hover circuitry  803  can be a set of multiple conductive lines that can operate as a self-capacitance sensor to sense hover events, and touch circuitry  805  can be another set of multiple conductive lines that can sense touch events when paired with the conductive lines of touch and hover circuitry  803 . Therefore, sensor array  801  includes common circuitry that operates in both the touch sensing phase and the hover sensing phase. A sensor control system  807  can operate sensor array  801  to detect both touch and hover, by transmitting signals corresponding to hover sensing to touch and hover circuitry  803  only, and by transmitting signals corresponding to touch sensing to touch and hover circuitry  803  and touch circuitry  805 . Therefore sensor control system  807  can serve as an integrated touch control system and hover control system, and determine when to switch between touch sensing and hover sensing, as described in more detail below. 
       FIG. 9  shows an example touch and hover sensing system  900  including a sensor array  901  and a sensor control system  903 . Sensor control system  903  includes a switching system  905 , a touch control system  907 , a hover control system  909 , and a low-leakage analog switch  911 . In operation, switching system  905  determines when switching from touch sensing to hover sensing, and vice versa, should occur and operates low-leakage analog switch  911  to switch between touch control system  907  and hover control system  909  accordingly. During a touch sensing phase, touch control system transmits an AC signal to sensor array  901  and measures a capacitance of the sensor array resulting from the AC signal. During a hover sensing phase, hover control system  909  transmits an AC signal to sensor array  901  and measures a capacitance of sensor array  901  resulting from the AC signal. 
       FIGS. 10-11  show example methods of joint touch and hover sensing, which can be implemented, for example, in software, firmware, application-specific integrated circuits (ASICs), etc. 
       FIG. 10  shows an example method for detecting a touch event and a hover event on or near a touch and hover sensing apparatus, such as touch screen  300 . In a touch detection phase, touch and hover control system  107  can transmit ( 1001 ) a first AC signal to sensor array  101 , and can measure ( 1002 ) a first capacitance of the sensor array. Touch and hover control system  107  can detect ( 1003 ) a touch event based on the first capacitance, and store ( 1004 ) touch event data, e.g., position, size, shape, gesture data, etc., in a memory. In a hover detection phase, touch and hover control system  107  can transmit ( 1005 ) a second AC signal to sensor array  101 , and can measure ( 1006 ) a second capacitance of the sensor array. Touch and hover control system  107  can detect ( 1009 ) a hover event based on the second capacitance, and store ( 1010 ) hover event data, such as position, height, size, gesture data, etc. 
     Other operations can be occurring during or in between the touch detection and hover detection phases. For example, display driver  319  may transmit image signals to display circuitry  317  in a display phase that can be in between the touch sensing phase and the hover sensing phase. During the touch and/or hover sensing phases, AC shield driving system  203  may operate as described above to shield transmission line  309  using transmission line AC shield  308 , and to boost the electric field emanating from cover surface  305  using AC shield  201 . The touch detection phase and hover detection phase may occur in any order. 
     Some embodiments may not be able to sense touch and hover concurrently, i.e., only a single mode of sensing (non-overlapping touch/hover sensing) is possible. In this case, in some embodiments touch sensing and hover sensing may be time multiplexed, that is, touch and hover sensing can be performed during different, non-overlapping periods of time. Various methods can be implemented for deciding how to time multiplex the sensing operations, i.e., deciding whether touch sensing or hover sensing (or neither) should be performed at a particular time. 
     In some embodiments, touch and hover sensing can operate concurrently, i.e., multi-mode sensing. Even if a system can perform multi-mode touch and hover sensing, it may be advantageous to perform single mode sensing in some cases. For example, if either touch sensing or hover sensing is not needed at a particular time, switching to single mode sensing to save power may be desirable. 
     In some embodiments, the operation of touch sensing and hover sensing can be determined by a fixed schedule. In other embodiments, the time and duration of touch and hover sensing can be varied dynamically, for example, by setting the system to operate in one of a number of operational modes including the touch sensing mode and the hover sensing mode, and possibly other modes, such as a display mode. For instance,  FIG. 11  shows an example method for determining whether to sense touch and/or hover. A touch sensing operation can be performed ( 1101 ), and can determine ( 1102 ) whether a touch is detected. If a touch is detected, the system can perform ( 1103 ) both touch and hover sensing, either by switching between the two, or by performing touch and hover sensing concurrently if the system is capable of multi-mode sensing. Both touch and hover sensing can be performed after a touch is detected because the touch may indicate a period of user activity during which a user may perform hover events and touch events. 
     If a touch is not detected at  1102 , the system can perform ( 1104 ) hover detection, and can determine ( 1105 ) whether a hover is detected. If a hover is detected, the system can perform ( 1103 ) both touch and hover sensing, because the hover may indicate a period of user activity. If a hover is not detected at  1105 , the system can perform ( 1104 ) hover detection again. As long as a hover is not detected, the system may not need to perform touch detection, because any approaching object will cause a hover detection before the object can touch down on the sensing system. 
     Other factors may be used to determine whether to detect touch, hover, both or neither. For example, some embodiments may detect an approaching object during hover sensing and wait until the object gets close to the touch surface to perform touch sensing. In other words, a distance threshold can be used to activate touch sensing. In some embodiments, the touch/hover mode may be determined by a particular software application that may require, for example, touch data but not hover data. In some embodiments, the current number and/or position of touches may be used as a factor. For example, a small mobile touch screen device may alternate between touch sensing and hover sensing until a predetermined number of contacts, e.g., five, touch the touch surface. When five touch contacts are detected, the device can cease detecting hover and can detect only touch because a user is unlikely to use sixth object to perform a hover, for example. 
     Some embodiments may be capable of multi-mode operation, i.e., performing touch sensing and hover sensing concurrently. For example, some embodiments can use frequency multiplexing to combine AC signals used for touch sensing with different frequency AC signals used for hover sensing. In some embodiments, code division multiplexing of the AC signals can be used to perform concurrent touch sensing and hover sensing. 
     Frequency multiplexing and code division multiplexing can allow circuit elements, such as sensing electrodes, to be used to detect touch and hover concurrently. For example, an entire array of sensors may be simultaneously stimulated to detect touch and hover. 
     In some embodiments, touch sensing and hover sensing may be space multiplexed by, e.g., operating one portion of a sensor array for touch sensing and concurrently operating another portion of the sensor array for hover sensing. For example, an AC signal used for touch sensing can be transmitted to a first group of sensors of the sensor array, and an AC signal used for hover sensing can be transmitted to a second group of sensors of the array. The groups of sensors may be changed dynamically, such that touch and hover sensing can be performed by different portions of the sensor array at different times. For example, touch sensing can be activated for portions of the sensor array on which touches are detected, and the remaining sensors may be operated to detect hover. The system can track moving touch objects and adjust the group of sensors sensing touch to follow the moving object. 
       FIG. 12A  illustrates an example mobile telephone  1236  that can include touch sensor panel  1224  and display device  1230 , the touch sensor panel including improved capacitive touch and hover sensing according to one of the various embodiments described herein. 
       FIG. 12B  illustrates an example digital media player  1240  that can include touch sensor panel  1224  and display device  1230 , the touch sensor panel including improved capacitive touch and hover sensing according to one of the various embodiments described herein. 
       FIG. 12C  illustrates an example personal computer  1244  that can include touch sensor panel (trackpad)  1224  and display  1230 , the touch sensor panel and/or display of the personal computer (in embodiments where the display is part of a touch screen) including improved capacitive touch and hover sensing according to the various embodiments described herein. 
     While various embodiments have been described above, it should be understood that they have been presented by way of example only, and not by way of limitation. Likewise, the various diagrams may depict an example architectural or other configuration for the disclosure, which is done to aid in understanding the features and functionality that can be included in the disclosure. The disclosure is not restricted to the illustrated example architectures or configurations, but can be implemented using a variety of alternative architectures and configurations. Additionally, although the disclosure is described above in terms of various example embodiments and implementations, it should be understood that the various features and functionality described in one or more of the individual embodiments are not limited in their applicability to the particular embodiment with which they are described. They instead can be applied alone or in some combination, to one or more of the other embodiments of the disclosure, whether or not such embodiments are described, and whether or not such features are presented as being a part of a described embodiment. Thus the breadth and scope of the present disclosure should not be limited by any of the above-described example embodiments.

Metadata:
Filing Date: 20090710
Publication Date: 20160426
Grant Date: 20160426
Priority Date: 20090710
Inventors: BERNSTEIN JEFFREY TRAER
AMM DAVID T.
LEUNG OMAR
MULLENS CHRISTOPHER TENZIN
KING BRIAN MICHAEL
LAND BRIAN RICHARDS
CUTLER REESE T.
Assignee: APPLE INC
CPC Classifications: [{"code": "G06F3/0486", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F2203/04101", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F3/0416", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/044", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F3/0486", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/041662", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F3/0446", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F2203/04101", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F3/04845", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F2203/04107", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F3/04817", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/041662", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F3/0446", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F2203/04107", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F3/041662", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F3/04845", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F2203/04101", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F3/0446", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F2203/04101", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F3/04817", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F3/0486", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 43427088