Patent Publication Number: US-2017351336-A1

Title: Time of flight based gesture control devices, systems and methods

Description:
BACKGROUND 
     Technical Field 
     The present disclosure relates generally to gesture control of electronic devices such as smartphones, and more specifically to time of flight based gesture detection and control. 
     Description of the Related Art 
     In mobile devices such as smart phones a touch screen or touch panel is utilized to control the operation of the mobile device, along with buttons typically contained on the mobile device. Similarly, wearable devices are typically controlled through a touch panel, and may also include buttons on the device. In some situations, the utilization of a touch panel may be problematic. For example, a wearable device may have a relatively small display requiring a correspondingly small touch panel, making it difficult for at least some persons to easily control the device by touching desired portions of the touch panel. Similarly, in mobile devices such as smart phones, when taking a selfie (i.e., extending the phone away from one&#39;s face and taking a picture of oneself) it may be difficult for the person taking the selfie to control the operation of the smart phone to take the picture. For example, the button on the touch panel may make it difficult for some users to hold the smart phone in one hand and press the button with a finger of that same hand. As a result, the person may need to use their second hand to take the picture, which can undesirably bring the phone closer to the person&#39;s face making it more difficult to take the desired selfie picture. There is a need for improved control of mobile devices like as smart phones as well as other types of electronic devices such as wearable devices. 
     BRIEF SUMMARY 
     In one embodiment of the present disclosure, a device includes a time-of-flight sensor configured to transmit an optical pulse signal and to receive a return optical pulse signal corresponding to a portion of the transmitted optical pulse signal that has reflected off an object within a field of view of the time-of-flight sensor. The time-of-flight generates a range estimation signal including an estimated distance to the object and a signal amplitude indicating an amplitude of the return optical pulse signal. A controller is coupled to the time of flight sensor and is configured to process the range estimation signal over time to detect an input gesture based upon the signal amplitude and estimated distance. In an embodiment, the device includes a front side and a back side opposite the front side, and the time-of-flight sensor is positioned on the back side to detect input gestures provided on the back side of the device. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       The foregoing and other features and advantages will become apparent from the following detailed description of embodiments, given by way of illustration and not limitation with reference to the accompanying drawings, in which: 
         FIG. 1  is a functional block diagram of an electronic device including a time-of-flight sensor for detecting input gestures to control operation of the electronic device according to one embodiment of the present disclosure. 
         FIG. 2  is a functional diagram illustrating the operation of the time-of-flight sensor of  FIG. 1 . 
         FIG. 3  is a functional block diagram illustrating in more detail one embodiment of the time-of-flight sensor of  FIGS. 1 and 2 . 
         FIGS. 4A and 4B  show the time-of-flight sensor of  FIG. 1  positioned on the back side and along a front edge of electronic devices according to embodiments of the present disclosure. 
         FIGS. 5A and 5B  illustrate a finger of a user providing an input gesture to the time-of-flight sensors in the embodiments of  FIGS. 4A and 4B , respectively. 
         FIG. 6A  is a perspective view of an electronic device illustrating a frame of reference relative to a time-of-flight sensor contained in the device. 
         FIG. 6B  illustrates how the range estimation signal provided by the time-of-flight sensor of  FIGS. 1-3  enables the sensing of different types of input gestures according to embodiments of the present disclosure. 
         FIGS. 7A-7D  illustrate the concept of multiple fields of view or zones utilized in some embodiment of the time-of-flight sensor of  FIGS. 1-3  to sense some of types of input gestures. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  is a functional block diagram of an electronic device  100  including a touch/gesture controller  102  and a time-of-flight sensor  104  operable to detect input gestures and to control the electronic device based on the detected input gestures according to one embodiment of the present disclosure. The time-of-flight sensor  104  utilizes time-of-flight based sensing to transmit an optical pulse that is then reflected off an object within a field of view of the sensor and a portion of which returns to the sensor in the form a return optical pulse. A time-to-digital converter, time-to-analog converter or other suitable circuitry in the time-of-flight sensor  104  detects a time-of-flight of the optical pulse and in this way determines a distance to the object, as will be appreciated by those skilled in the art and as will be described in more detail below. 
     The time-of-flight sensor  104  generates a range estimation signal RE that provides a sensed distance D TOF  to an object as well as providing signal strength or amplitude SA information for the return optical pulse. Based on the signal amplitude SA and sensed distance D TOF  information provided by the range estimation signal RE signal over time, the touch/gesture controller  102  detects various types of input gestures provided to the electronic device  100  by a user (not shown), and the electronic device is controlled in response to these detected input gestures, as will be described in more detail below. 
     In the present description, certain details are set forth in conjunction with the described embodiments to provide a sufficient understanding of the present disclosure. One skilled in the art will appreciate, however, that the other embodiments may be practiced without these particular details. Furthermore, one skilled in the art will appreciate that the example embodiments described below do not limit the scope of the present disclosure, and will also understand that various modifications, equivalents, and combinations of the disclosed embodiments and components of such embodiments are within the scope of the present disclosure. Embodiments including fewer than all the components of any of the respective described embodiments may also be within the scope of the present disclosure although not expressly described in detail below. Finally, the operation of well-known components and/or processes has not been shown or described in detail below to avoid unnecessarily obscuring the present disclosure. 
     The electronic device  100  further includes a touch screen  106  containing a touch display  108 , such as a liquid crystal display, and a touch panel including a number of touch sensors  110  positioned on the touch display to detect touch points P(X,Y,Z), with only three touch sensors being shown merely by way of example and to simplify the figure. There are typically many more touch sensors  110 . These touch sensors  110  are usually contained in a transparent sensor array that is then mounted on a surface of the touch display  108 . The number and locations of the touch sensors  110  can vary as can the particular technology or type of sensor, with typical sensors being resistive, vibration, capacitive, or ultrasonic sensors. In the embodiments described herein, the sensors are considered to be capacitive sensors by way of example. In operation of the touch screen  106 , a user generates a touch point P(X,Y,Z) through a suitable interface input, such as a touch event, hover event, or gesture event. In response to a touch point P(X,Y,Z), the sensors  110  generate respective signals that are provided to the gesture controller  102  which, in turn, processes these signals to generate touch information for the corresponding touch point. Thus, in the example embodiment of  FIG. 1  the touch/gesture controller  102  processes signals from touch sensors  110  to sense touch, hover and gesture events through the touch screen  106  and also processes the range estimation signal RE to detect input gestures through the time-of-flight sensor  104 . 
     The electronic device  100  also includes processing circuitry  112  coupled to the touch/gesture controller  102  to receive from the touch/gesture controller  102  the generated touch information, including the location of the touch point P(X,Y,Z) and the corresponding type of detected interface input (e.g., touch event, hover event, or gesture event) associated with the touch point. The touch/gesture controller  102  also provides to the processing circuitry  112  gesture information for input gestures sensed through the time-of-flight sensor  104 , as described in more detail below. The processing circuitry  112  executes applications or “apps”  114  that control the electronic device  100  to implement desired functions or perform desired tasks. These apps  114  executing on the processing circuitry  112  interface with a user of electronic device  110  through the controller  102  and touch screen  106 , allowing a user to start execution of or “open” one of the apps  114  and thereafter interface with the app through the touch display  108  or through the time-of-flight sensor  104 . 
     The processing circuitry  112  generally represents different types of circuitry that may be contained in the electronic device  100 . For example, where the electronic device  100  is a mobile device such as a smart phone, the processing circuitry  112  would typically include communications circuitry like mobile telecommunications circuitry and Wi-Fi circuitry, along with power management circuitry, input/output circuitry, and so on. Image capture circuitry  116 , which would typically include a digital camera to capture still and video images, is shown as being part of the processing circuitry  112  in the embodiment of  FIG. 1 . This image capture circuitry  116  includes an autofocus subsystem AF that can use the estimated distance D TOF  sensed by the time-of-flight sensor  104  to an object being imaged to focus the image capture circuitry on the object. Where the electronic device  100  is a smart phone, the image capture circuitry  116  is typically able to capture images from a front side of the smart phone, which is the side on which the touch screen  106  positioned, as well as from the back side of the smart phone, as will be discussed in more detail below with reference to the embodiment of  FIGS. 4A and 5A . 
     In one embodiment, the time-of-flight sensor  104  is an existing sensor contained in the electronic device  100  that is utilized by the autofocus subsystem AF when the image capture circuitry is active (i.e., being used to capture still or video images). When the image capture circuitry  116  is inactive (i.e., not being used to capture still or video images) the time-of-flight sensor  104  in conventional electronic devices is typically deactivated. In the electronic device  100 , when the image capture circuitry  116  is inactive the time-of-flight sensor  104  is used for detecting input gestures, as will be described in more detail below. 
     The time-of-flight sensor  104  is positioned on the electronic device  104  to detect a particular type or types of input gestures provided to the electronic device  100 . For example, in one embodiment the electronic device  100  is a smart phone and the time-of-flight sensor  104  is positioned on a back side of the smart phone opposite a front side containing the touch screen  106 . Thus, in addition to detecting touch events on the touch screen  106 , the touch/gesture controller  102  processes the range estimation signal RE from the time-of-flight sensor  104  over time to detect input gestures provided by a user on a back side of the electronic device  100 . The touch/gesture controller  102  then provides information about the input gesture detected through the range estimation signal RE in the information provided to the processing circuitry  112  which, in turn, controls the operation of the electronic device  100  based on the detected input gestures, as will be described in more detail below. 
     Although the time-of-flight sensor  104  is shown as being coupled to the touch/gesture controller  102 , the time-of-flight sensor could alternatively be coupled directly to the processing circuitry  112 , as indicated through the dashed line in  FIG. 1 . In this situation, the processing circuitry  112  would process the range estimation signal RE over time to generate detected input gestures as described above for the touch/gesture controller  102 . Thus, control circuitry for processing the range estimation signal RE or signals from the time-of-flight sensor  104  over time may be contained or implemented in either the touch/gesture controller  102  or the processing circuitry  112 , or in both. 
     Where the electronic device  100  is a smart phone or other mobile electronic device, the time-of-flight sensor  104  may already be contained in the smart phone for use in performing auto focus operations for image capture circuitry  116  contained in the electronic device, and thus an existing time-of-flight sensor already contained in the smart may be used in embodiments of the present disclosure. Existing time-of-flight sensors contained in image capture circuitry  116  of electronic devices are only activated and utilized when this image capture circuitry is being utilized. As a result, these existing time-of-flight sensors may be utilized for input gesture recognition according to embodiments of the present disclosure when the sensor is not being utilized to perform autofocusing of the image capture circuitry  116  or not performing other distance related sense functions. The existing time-of-flight sensor could also be utilized in situations where the image capture circuitry  116  is being utilized but the time-of-flight sensor is not being utilized to perform autofocusing, such as where the image capture circuitry is being used to take a selfie of the user. Some image capture systems include a rear facing camera and a front facing camera to accommodate taking a variety of images. 
       FIG. 2  is a functional diagram illustrating components and operation of the time-of-flight sensor  104  of  FIG. 1 . The time-of-flight sensor  104  may be a single chip that includes a light source  200  and a return and reference array of photodiodes  214 ,  210 . Alternatively, these components may be incorporated within a camera module or other chip within the electronic device  100 . The light source  200  and the return and reference arrays  214 ,  210  are on a substrate  211 . In one embodiment, the touch/gesture controller  102  only includes circuitry for generating the range estimation signal RE and the time-of-flight sensor  102  and controller are contained in the same chip or package, and may be formed in the same integrated circuit within this package. 
     The light source  200  transmits optical pulse signals having a transmission field of view FOV TR  to irradiate objects within the field of view. A transmitted optical pulse signal  202  is illustrated in  FIG. 2  as a dashed line and irradiates an object  204  within the transmission field of view FOV TR  of the light source  200 . In addition, a reflected portion  208  of the transmitted optical pulse signal  202  reflects off an integrated panel, which may be within a package  213  or may be on a cover  206  of the electronic device. The reflected portion  208  of the transmitted pulse is illustrated as reflecting off the cover  206 , however, it may be reflected internally within the package  213 . 
     The cover  206  maybe be glass, such as on a front of a mobile device associated with a touch panel or the cover may be metal or another material that forms a back cover of the electronic device. The cover will include openings to allow the transmitted and return signals to be transmitted and received through the cover if not a transparent material. 
     The reference array  210  of light sensors detects this reflected portion  208  to thereby sense transmission of the optical pulse signal  208 . A portion of the transmitted optical pulse signal  202  reflects off the object  204  as a return optical pulse signal  212  that propagates back to the time-of-flight sensor  104 . More specifically, the time-of-flight sensor  104  includes a return array  214  of light sensors having a receiving field of view FOV REC  that detects the return optical pulse signal  212 . The time-of-flight sensor  104  then determines a distance D TOF  ( FIG. 3 ) between the time-of-flight sensor and the object  204  based upon the time between the reference array  210  sensing transmission of the optical pulse signal  202  and the return array  214  sensing the return optical pulse signal  212 . 
     Before describing further embodiments of the present disclosure, the time-of-flight sensor  104  will first be discussed with reference to  FIG. 3 , which is a more detailed functional block diagram of the time-of-flight sensor of  FIGS. 1 and 2  according to one embodiment of the present disclosure. In the embodiment of  FIG. 3 , the time-of-flight sensor  104  includes a light source  300 , which is, for example, a laser diode such as a vertical-cavity surface-emitting laser (VCSEL) for generating the transmitted optical pulse signal designated as  302  in  FIG. 3 . The transmitted optical pulse signal  302  is transmitted in the transmission field of view FOV TR  of the light source  300  as discussed above with reference to  FIG. 2 . In the embodiment of  FIG. 3 , the transmitted optical pulse signal  302  is transmitted through a projection lens  304  to focus the transmitted optical pulse signals  302  so as to provide the desired field of view FOV TR . The projection lens  304  can be used to control the transmitted field of view FOV TR  of the sensor  104  and is an optional component, with some embodiments of the sensor not including the projection lens. 
     The reflected or return optical pulse signal is designated as  306  in the figure and corresponds to a portion of the transmitted optical pulse signal  302  that is reflected off an object, which is a hand  308  in  FIG. 3 . The return optical pulse signal  306  propagates back to the time-of-flight sensor  104  and is received through a return lens  309  that provides a desired return or receiving field of view FOV REC  for the sensor  104 , as described above with reference to  FIG. 2 . The return lens  309  in this way is used to control the field of view FOV REC  of the sensor  104 . The return lens  309  directs the return optical pulse signal  306  to range estimation circuitry  310  for estimating the imaging distance D TOF  between time-of-flight sensor  104  and the hand  308 . The return lens  309  is an optional component and thus some embodiments of the time-of-flight sensor  104  do not include the return lens. 
     In the embodiment of  FIG. 3 , the range estimation circuitry  310  includes a return single-photon avalanche diode (SPAD) array  312 , which receives the returned optical pulse signal  306  via the lens  309 . The SPAD array  312  corresponds to the return array  214  of  FIG. 2  and typically includes a large number of SPAD cells (not shown), each cell including a SPAD for sensing a photon of the return optical pulse signal  306 . In some embodiments of the time-of-flight sensor  104 , the lens  309  directs reflected optical pulse signals  306  from separate spatial zones within the field of view FOV REC  of the sensor to certain groups of SPAD cells or zones of SPAD cells in the return SPAD array  312 , as will be described in more detail below. 
     Each SPAD cell in the return SPAD array  312  provides an output pulse or SPAD event when a photon in the form of the return optical pulse signal  306  is detected by that cell in the return SPAD array. A delay detection circuit  314  in the range estimation circuitry  310  determines a delay time between transmission of the transmitted optical pulse signal  302  as sensed by a reference SPAD array  316  and a SPAD event detected by the return SPAD array  312 . The reference SPAD array  316  is discussed in more detail below. The SPAD event detected by the return SPAD array  312  corresponds to receipt of the return optical pulse signal  306  at the return SPAD array. In this way, by detecting these SPAD events, the delay detection circuit  314  estimates an arrival time of the return optical pulse signal  306 . The delay detection circuit  314  then determines the time of flight TOF based upon the difference between the transmission time of the transmitted optical pulse signal  302  and the arrival time of the return optical pulse signal  306  as sensed by the SPAD array  312 . From the determined time of flight TOF, the delay detection circuit  314  generates the range estimation signal RE ( FIG. 1 ) indicating the detected distance D TOF  between the hand  308  and the time-of-flight sensor  104 . 
     The reference SPAD array  316  senses the transmission of the transmitted optical pulse signal  302  generated by the light source  300  and generates a transmission signal TR indicating detection of transmission of the transmitted optical pulse signal. The reference SPAD array  316  receives an internal reflection  318  from the lens  304  of a portion of the transmitted optical pulse signal  302  upon transmission of the transmitted optical pulse signal from the light source  300 , as discussed for the reference array  210  of  FIG. 2 . The lenses  304  and  309  in the embodiment of  FIG. 3  may be considered to be part of the glass cover  206  or may be internal to the package  213  of  FIG. 2 . The reference SPAD array  316  effectively receives the internal reflection  318  of the transmitted optical pulse signal  302  at the same time the transmitted optical pulse signal is transmitted. In response to this received internal reflection  318 , the reference SPAD array  316  generates a corresponding SPAD event and in response thereto the transmission signal TR indicating the transmission of the transmitted optical pulse signal  302 . 
     The delay detection circuit  314  includes suitable circuitry, such as time-to-digital converters or time-to-analog converters, to determine the time-of-flight TOF between the transmission of the transmitted optical pulse signal  302  and receipt of the reflected or return optical pulse signal  308 . The delay detection circuit  314  then utilizes this determined time-of-flight TOF to determine the distance D TOF  between the hand  308  and the time-of-flight sensor  104 . The range estimation circuitry  310  further includes a laser modulation circuit  320  that drives the light source  300 . The delay detection circuit  314  generates a laser control signal LC that is applied to the laser modulation circuit  320  to control activation of the laser  300  and thereby control transmission of the transmitted optical pulse signal  302 . The range estimation circuitry  310  also determines the signal amplitude SA based upon the SPAD events detected by the return SPAD array  312 . The signal amplitude SA is related to the number of photons of the return optical pulse signal  306  received by the return SPAD array  312 . The closer the object  308  is to the TOF ranging sensor  104  the greater the sensed signal amplitude SA, and, conversely, the farther away the object the smaller the sensed signal amplitude. 
       FIG. 4A  illustrates the time-of-flight sensor  104  of  FIG. 1  positioned on the back side of the electronic device  100  according to one embodiment of the present disclosure. In this embodiment, the electronic device  100  is a smart phone and the time-of-flight sensor  104  is positioned on a back surface or side of the smart phone as shown in the figure. The back side is opposite the front side of the device, which is the side on which the touch screen  106  is positioned. In the embodiment of  FIG. 4A , the time-of-flight sensor  104  is positioned proximate other components of the image capture circuitry  116  contained in the smart phone  100 . For example, an aperture  400  of a digital camera is shown proximate the time-of-flight sensor  104  and a flash device  402  of the camera is also shown. Some smart phones and other types of mobile devices containing digital or video cameras may already include a time-of-flight sensor for use in an auto focusing system of these cameras. In this situation, the existing time-of-flight sensor  104  may also be used to detect input gestures according to embodiments of the present disclosure, as will be described in more detail below. 
     In one embodiment, the time-of-flight sensor  104  is used as a virtual button to allow the user to control the mobile device. If the mobile device includes a digital camera, the rear facing time-of-flight sensor can be used to activate a front facing camera to capture selfie images. For example, where the user is taking a selfie the user extends his or her arm away from themselves and then performs an up/down or tap input gesture by placing his or her finger at a distance over the sensor  104  and then moving the finger downward to touch the sensor, and then back upward again. The touch/gesture controller  102  ( FIG. 1 ) processes the range estimation signal RE generated by the time-of-flight sensor  104  in response to the tap input gesture to thereby detect the tap input gesture. The touch/gesture controller  102  then provides information indicating the detection of a tap input gesture to the processing circuitry  112  which, in turn, controls the image capture circuitry  116  to capture an image. 
     The time-of-flight sensor  104  could of course be used to detect other types of input gestures to activate the image capture circuitry  116  to capture a selfie or standard digital image. The touch/gesture controller  102  processes the range estimation signal RE from the time-of-flight sensor  104  to detect the desired type of input gestures, as described in more detail below. As mentioned above, the control circuitry for processing the range estimation signal RE or signals from the time-of-flight sensor  104  over time may be contained or implemented in either the touch/gesture controller  102  or the processing circuitry  112 , or in both. 
       FIG. 4B  illustrates the time-of-flight sensor  104  positioned along an edge on a front surface of the electronic device  100  where the electronic device is a wearable device, such as a smart watch. Wearable devices may have relatively small displays, making utilization of a touch screen with the small display impractical or difficult for a user. The use of the time-of-flight sensor  104  allows a user to provide input gestures to control the wearable device  100  without a conventional capacitive, resistive or other type of touch screen. In addition, the utilization of the time-of-flight sensor  104  also enables a user to provide input gestures to the wearable device  100  while wearing a glove, which is not available for conventional capacitive based touchscreens without incorporating a special feature in the glove. 
       FIGS. 5A and 5B  illustrate a user&#39;s hand  500  and a finger  502  of the hand providing an input gesture to the time-of-flight sensor  104  in the embodiments of  FIGS. 4A and 4B , respectively. In this way, the user utilizes his or her finger  502  to provide input gestures to control the operation of the corresponding electronic device  100 . The time-of-flight sensor  104  could also be positioned in locations of the electronic device  100  other than those illustrated in  FIGS. 4A, 4B, 5A and 5B . For example, the time-of-flight sensor  104  could be positioned on an edge of the electronic device  110 , where an edge is a surface of the device extending between the front and back sides of the device. An example of the time-of-flight sensor  104  positioned on a side edge of the electronic device  100  is shown in dashed lines in  FIG. 4A , and other locations on edges as well as on the front and back sides device may be utilized. 
       FIG. 6A  is a perspective view of an electronic device  600  including the time-of-flight sensor  104  and illustrating a frame of reference relative to the time-of-flight sensor. The electronic device  600  if one embodiment of the electronic device  100  of  FIG. 1  and is a smart phone in the example of  FIG. 6A . The time-of-flight sensor  104  is positioned on a back side or surface  602  of the electronic device  600 . A Cartesian coordinate system is shown where the back surface  602  is in the XY-plane and the Z-axis accordingly extends orthogonal to the back surface. A top edge  603 , a bottom edge  605 , a left edge  607  and a right edge  609  of the device  600  are shown. Input gesture movement from left-to-right or right-to-left is movement between the left and right edges  607 ,  609  parallel to the X-axis. Input gesture movement to top-to-bottom or bottom-to-top is movement between the top and bottom edges  603  and  605  parallel to the Y-axis. Finally, input gestures movement parallel to the Z-axis (i.e., orthogonal to the back surface  602 ) is movement “down” or towards the back surface and movement “up” or away from the back surface parallel to the Z-axis. The time-of-flight sensor  104  may be utilized to detect a variety of different types of input gestures, as will now be described in more detail with reference to this Cartesian coordinate system and  FIG. 6A  and with reference to  FIG. 6B . 
       FIG. 6B  is an array of subfigures or representations illustrating input gestures and the range estimation signal RE provided by the time-of-flight sensor  104  in one embodiment of the present disclosure. More specifically, the figure shows the range estimation signal RE generated by the time-of-flight sensor  104  in response to an up/down input gesture and in response to a swipe input gesture, and also shows the signals generated by a conventional infrared (IR) sensor, which may be used to detect distance, in response to the same up/down and swipe input gestures. 
     The upper leftmost column of  FIG. 6B  includes a representation  601  of an up/down input gesture. The representation  601  is a side view along the X-axis of the back surface  602  of the electronic device  600  on which the time-of-flight sensor is located. To perform an up/down input gesture, a hand  604  of a user is initially positioned over or spaced away from the back surface  602  and within the field of view FOV of the sensor  104  positioned on the back surface. The field of view FOV represents the overall field of view of the time-of-flight sensor  104  and thus includes the transmitting field of view FOV TR  and receiving field of view FOV REC  discussed above with reference to  FIG. 2 . An up/down input gesture involves the user initially positioning his or her hand  604  at a relatively large distance d over the surface  602  as shown in the leftmost figure of the representation  601 . The back surface  602  is in the XY-plane and thus the hand  604  is positioned at the distance d along an axis parallel to the Z-axis extending orthogonal to the surface  602 . 
     A complete up/down input gesture is movement parallel to the Z-axis down or towards the surface  602  from the distance d to some minimum distance and then movement up or away from the back surface and again parallel to the Z-axis. Thus, after the user has positioned his or her hand at the distance d over the back surface  602 , the user then moves his or her hand down from the distance d parallel to the Z-axis towards the back surface  602  as indicated by an arrow  606 . The distance d of the hand  604  from the back surface  602  accordingly becomes smaller until the distance reaches some minimum value. The user then moves his or her hand  604  up from the minimum distance parallel to the Z-axis and away from the back surface  602  as indicated by an arrow  608  so that the distance d of the hand from the surface increases. This upward movement of the hand  604  completes the up/down input gesture. 
     A representation  610  in the upper row and middle column of  FIG. 6B  shows the amplitude of a signal S generated as a function of time by a conventional IR sensor in response to the up/down input gesture. The signal S is shown as starting at a time T 0 , which corresponds to the initial situation in representation  601  where the hand is positioned an orthogonal distance d from the back surface  602 . The signal S then starts increasing as the hand  604  moves downward parallel to the Z-axis and towards the back surface  602  as indicated by arrow  606  in representation  601 . The signal S reaches a peak at which point the hand  604  is at a minimum distance from the surface  602 . The signal S then decreases from the peak value as the hand  604  starts moving upward parallel to Z-axis and away from the back surface  602  as indicated by arrow  608  in the representation  601 . The distance d of the hand  604  from the back surface  602  is inversely proportional to the amplitude of the signal S in the representation  610 , as will be appreciated by those skilled in the art. 
     A representation  612  in the upper row and rightmost column of  FIG. 6B  shows the range estimation signal RE generated by the time-of-flight sensor  104  over time in response to the up/down input gesture of representation  601 . The range estimation signal RE includes the signal amplitude SA indicating the amplitude of the return optical pulse signal  306  ( FIG. 3 ) and the detected distance D TOF  between time-of-flight sensor  104  and the hand  604  in response to the up/down input gesture. The range estimation signal RE again starts at a time T 0  and the detected signal amplitude SA and distance D TOF  vary as shown over time in response to the up/down input gesture. Again, as the hand  604  moves from the distance d down towards the surface  602  and then back upward the signal amplitude SA has a similar shape to the signal S generated by the conventional IR sensor as shown in representation  610 . The signal amplitude SA is related to the number of photons of the return optical pulse signal  306  ( FIG. 3 ) received by the time-of-flight sensor  104 , and thus the closer the hand  604  to the back surface  602  (i.e., the smaller the distance d along the Z axis) the larger the sensed signal amplitude SA. This is also seen in the value of the sensed distance D TOF  detected by the sensor  104 , with the signal amplitude SA having the maximum value when the sensed distance has a minimum value. In comparing representation  612  to representation  610 , the signal amplitudes S and SA have similar shapes or patterns over time for the conventional IR sensor and time-of-flight sensor  104 , but the time-of-flight sensor also provides the sensed distance D TOF  over time, which is used to distinguish between up/down input gestures and swipe input gestures, as will be explained more detail below. 
     The bottom row in the leftmost column of  FIG. 6B  includes a representation  614  showing a top view of a swipe input gesture. The representation  614  is a top view shown looking down on the back surface  602  along the Z-axis (see  FIG. 6A ). Thus, in the representation  614 , the back surface  602  containing the time-of-flight sensor  104  is below the user&#39;s hand  604  positioned over or spaced away from this surface at a distance d from the surface. To perform a swipe input gesture, the user positions his or her hand at a distance d over or spaced away from the back surface  602  on which the sensor  104  is positioned, and within the field of view FOV of the sensor. The user then moves his or her hand  604  either to the left as indicated by an arrow  616  or to the right as indicated by an arrow  618  through the field of view FOV. During this movement, the user maintains the hand  604  over or spaced away from and at a relatively constant distance d from the back surface  602 . Thus, the user moves his or her hand  604  parallel to the X-axis in either the positive direction (i.e., to the right as indicated by arrow  618 ) or in the negative direction (i.e., to the left as indicated by arrow  616 ) to perform a swipe gesture. The hand  604  passes through the field of view FOV of the sensor  104  positioned on the surface  602  as the hand is moved to the left  616  or to the right  618 . The swipe input gesture could alternatively be performed by movement of the user&#39;s hand  604  along the Y-axis instead of the X-axis. Where the time-of-flight sensor  104  is a multiple zone sensor, a swipe input gesture along the X-axis or the Y-axis may be distinguished, as will be described in more detail with reference to  FIG. 7 . 
     A representation  616  in the lower row and middle column shows the amplitude of the signal S generated as a function of time by a conventional IR sensor in response to the swipe input gesture of the representation  614 . The signal S in representation  616  is the same as the signal S in representation  610  generated in response to the up/down input gesture. More specifically, the signal S again starts at a time T 0  and starts increasing as the hand  604  moves leftward over the surface  602  as indicated by arrow  616  and passes through the field of view of the sensor. The signal S reaches a peak at which point the hand  604  is directly over the field of view of the sensor and then decreases from the peak value as the hand moves out of the field of view of the sensor. In comparing representation  616  to representation  610 , it is seen that the signal S generated by a conventional IR sensor is the same for both the up/down input gesture and the swipe input gesture. Thus, these two input gestures cannot be distinguished with a conventional IR sensor. 
     Finally, a representation  618  in the lower rightmost column of  FIG. 6B  shows the range estimation signal RE generated by the time-of-flight sensor  104  over time in response to the swipe input gesture. The range estimation signal RE again starts at a time T 0  and the detected signal amplitude SA and distance D TOF  vary as shown over time in response to the swipe input gesture. In comparing representation  618  to representation  616 , the signal amplitudes S and SA have the same pattern over time for the conventional IR sensor and time-of-flight sensor  104 , but the time-of-flight sensor also provides the sensed distance D TOF  which is used to distinguish between a swipe input gesture and an up/down input gesture, as will now be explained in more detail. 
     To detect whether an input gesture is an up/down input gesture or a swipe input gesture, the touch/gesture controller  102  ( FIG. 1 ) determines whether the range estimation signal RE has the pattern of representation  612  or the pattern of representation  618 . More specifically, when the signal amplitude SA of the range estimation signal RE has the pattern of representations  612  and  618 , the controller determines whether the sensed distance D TOF  is relatively constant as in representation  618  or varies as shown in representation  612 . If the sensed distance D TOF  is relatively constant, the touch/gesture controller  102  determines the input gesture is a swipe input gesture since the patterns of the signal amplitude SA and sensed distance D TOF  correspond to representation  618 . Conversely, if the sensed distance D TOF  varies as shown in representation  612 , the touch/gesture controller  102  determines the input gesture is an up/down input gesture since the patterns of the signal amplitude SA and sensed distance D TOF  correspond to representation  612 . In this way, the utilization of the time-of-flight sensor  104  and the range estimation signal RE generated by that sensor enables the touch/gesture controller  102  two distinguish between up/down and swipe input gestures, which is not possible with conventional IR sensors. 
       FIGS. 7A-7D  illustrates the concept of multiple fields of view FOV or multiple zones utilized in some embodiment of the time-of-flight sensor  104  of  FIGS. 1-3  to sense some of types of input gestures. In  FIGS. 7A-7D , the overall large square represents the receiving field-of-view FOV REC  of the time-of-flight sensor  104  as discussed above with reference to  FIG. 2 . Where the time-of-flight sensor  104  is a multiple zone sensor as illustrated in  FIGS. 7A-7B , however, the receiving field of view FOV REC  includes a number of separate spatial zones or independent subfields of view within the receiving field of view. In the example of  FIGS. 7A-7D , the receiving field of view FOV REC  includes sixteen separate spatial zones or subfields of view. The time-of-flight sensor  104  may include different numbers of subfields of view FOV in other embodiments, such as four zones, nine zones, or any number of zones more than two. 
     When the time-of-flight sensor  104  senses objects in multiple independent zones or fields of view as shown in  FIG. 7 , the lens  309  ( FIG. 3 ) is formed to direct reflected optical pulse signals  306  from separate spatial zones within the field of view FOV REC  of the sensor  104  to corresponding groups or zones of SPAD cells in the return SPAD array  312 . Alternatively, multiple lenses and multiple return SPAD arrays  312  could be utilized. Each group or zone of SPAD cells in the return SPAD array  312  generates a corresponding range estimation signal RE and thus the multi zone time-of-flight sensor  104  generates multiple range estimation signals. 
     Referring to  FIGS. 2, 3 and 7 , the overall operation of such a multiple zone time-of-flight sensor  104  will now be described in more detail. In operation, the light source  200  illuminates or transmits the transmitted optical pulse signal  302  into the transmission field of view FOV TR  and return optical pulse signals  306  corresponding to portions of the transmitted optical pulse signal reflect off an object within the transmission field of view and are back to the sensor  104 . The return optical pulse signals  306  within the receiving field of view FOV REC  are received by the return SPAD array  316 . More specifically, return optical pulse signals  306  within each of the sixteen subfields of view are received by corresponding groups or zones of SPAD cells in the return SPAD array  316 . The outputs provided by SPAD cells in the different regions of the return SPAD array  312  each generate a corresponding range estimation signal RE for the associated subfield of view FOV of the multi zone time-of-flight sensor  104 . The multiple range estimation signals RE thus indicate where a user&#39;s hand is in relation to each field of view. The touch/gesture controller  102  utilizes the range estimation signals RE provided from all the regions or zones of the return SPAD array  312 , taken at successive points in time, to determine the course of the hand or other object passing through the multiple subfields of view. This is illustrated in  FIGS. 7A-7D . In each of these figures, each of the subfields of view or zones has either a zero (0) or a three (3) inserted in that zone. These numbers represent the range estimation signal RE generated for each zone. A zero for the range estimation signal RE in a given zone indicates no object is detected in that zone. Conversely, the number three for the range estimation signal RE indicates an object has been detected for that zone, with the magnitude of the range estimation signal indicating a distance of the detected object within the zone. 
     The example of  FIGS. 7A-7D  illustrates an example of a swipe input gesture moving from left to right across the zones over time starting in  FIG. 7A  and ending in  FIG. 7D . In this description, the rows of zones are referred to as rows 1-4 from the top to bottom and the columns referred to as columns 1-4 from left to right in these figures. In  FIG. 7A , the user&#39;s hand is first detected at a first point in time within the zones in column 1, rows 2-4. As a result, the zones in column 1, rows 2-4 include a 3 for the range estimation signal RE.  FIG. 7B  shows the sensed values for the range estimation signals RE for each of the zones at a later point in time. In this example, the user&#39;s hand has continued moving from left to right through the zones so that now the range estimation signals for the zones in both columns 1 and 2 and rows 2-4 have values of 3. A swipe gesture occurs at a relatively constant distance from the time-of-flight sensor  104  (see representation  618  in  FIG. 6B ) and thus the magnitudes for all zones in which the user&#39;s hand is detected have values of 3. 
       FIG. 7C  shows the sensed values for the range estimation signals RE for each of the zones at a still later point in time. The user&#39;s hand has accordingly continued moving from left to right through the zones so that now the range estimation signals for the zones in columns 1-3 and rows 2-4 have values of 3. The magnitudes for all zones in which the user&#39;s hand is detected have values of 3 for the swipe gesture. Finally, in  FIG. 7D  the user&#39;s hand has continued moving from left to right through the zones so that now the range estimation signals for the zones in columns 2-4 and rows have values of 3. Thus, at this point the user&#39;s hand has move rightward to the extent that the hand is no longer present in the zones column 1. Once again, the magnitudes for all the zones in which the user&#39;s hand is detected have values of 3, which is would be the case for a swipe gesture occurring at a relatively constant distance from the time-of-flight sensor  104 . 
     The touch/gesture controller  102  is configured to process these multiple range estimation signals RE from the multiple zones or subfields of view over time to recognize specific input gestures that may be detected by the time-of-flight sensor  104 , as will be appreciated by those skilled in the art. Such a multi zone time-of-flight sensor  104  may be utilized to detect a variety of different types of input gestures. Also note that as will be evident from the example of  FIGS. 7A-7D , the touch/gesture controller  102  can distinguish between swipe gestures occurring along the X axis or the Y axis as previously discussed with reference to the representation  614  of  FIG. 6B .  FIGS. 7A-7B  illustrate a left-to-right swipe input gesture occurring along the X axis. This left-to-right swipe input gesture along the X axis can be distinguished from a right-to-left swipe input gesture along the X axis based on the range estimation signals RE generated by the time-of-flight sensor  104 . In the right-to-left swipe input gesture along the X axis, the zones in which the hand is detected would be the opposite of that in  FIGS. 7A-7D , with the hand first being detected in column 4, rows 2-4 and then propagating in the same way to column 1. Similarly, a swipe input gesture occurring along the Y axis can be distinguished from swipe input gestures occurring along the X axis. Swipe input gestures along the Y axis would result in the detected object propagating through the rows of zones in a manner analogous to that for propagation thorough the columns of zones illustrated in  FIGS. 7A-7D , as will be understood by those skilled in the art in view of the present description. 
     Some input gestures require the time-of-flight sensor  104  be a multi zone sensor while other input gestures can be detected through a time-of-flight sensor having only a single zone or field of view. In addition to the up/down and swipe input gestures discussed above with reference to  FIG. 6B , other input gestures such as a double swipe gesture may also be detected. A double swipe is where the user&#39;s hand moves from left to right, or right to left, across the fields of view and then back across the fields of view in the opposite direction. In some embodiments, the time-of-flight sensor  104  may be viewed as a “virtual button” on the electronic device  100  containing the sensor. A user could in this situation provide a “block” input gesture where the user places his or her finger on the sensor to cover or “block” all the fields of view of the time-of-flight sensor  104 . In addition to the up/down or “tap” gesture described above with reference to  FIG. 6B , a double tap gesture could also be detected where the up/down movement of the user&#39;s hand in performed twice. Although an up/down input gesture is shown in  FIG. 6B  and described as involving a user&#39;s hand  604 , such an up/down input gesture could alternatively involve only a finger of the user&#39;s hand. In this situation, one of the user&#39;s fingers would perform the motion discussed with reference to the representation  601  of  FIG. 6B . The time-of-flight sensor  104  could again be viewed as a “virtual button” in this situation, with each up/down gesture being performed by a user&#39;s finger to effectively “press” the virtual button, with associated functionality then being performed such as capturing an image in response to the virtual button being pressed. 
     In operation, the touch/gesture controller  102  processes the one or more range estimation signals RE from the time-of-flight sensor  104  to detect the various types of input gestures that may be detected by the electronic device  100 . The touch/gesture controller  102  then provides this detected gesture information to the processing circuitry  112 . The apps  114  executing on the processing circuitry  112  then operate based on functionality assigned to each of the recognized input gestures. For example, the swipe gesture could move from one page in a document to the next, or to a next song or prior song if associated with a music app  114 . The block input gesture could be associated with a pause function or a hold function when the app  114  is a music or video app, while the double tap could be associated with start/stop control within apps. As mentioned above, recognition of some input gestures requires the time-of-flight sensor  104  be a multi zone sensor. For example, to sense swipe input gestures and double swipe input gestures, the time-of-flight sensor  104  must be a multi-zone sensor. 
     The various embodiments described above can be combined to provide further embodiments. These and other changes can be made to the embodiments in light of the above-detailed description. In general, in the following claims, the terms used should not be construed to limit the claims to the specific embodiments disclosed in the specification and the claims, but should be construed to include all possible embodiments along with the full scope of equivalents to which such claims are entitled. Accordingly, the claims are not limited to the present disclosure.