Patent Publication Number: US-7710404-B2

Title: Method for gesture detection on a touchpad

Description:
FIELD OF THE INVENTION 
   The present invention is generally related to a detection method for a touchpad and, more particularly, to a method for gesture detection on a capacitive touchpad. 
   BACKGROUND OF THE INVENTION 
   Capacitive touchpad is an input device that allows user to slide his finger on a smooth panel thereof for cursor movement control. Because of its very small thickness, capacitive touchpad can be designed in slim notebooks, keyboards, digital media players and other devices, and moreover, due to its non-mechanical design it is virtually maintenance free. 
     FIG. 1  is a cross-sectional view of a conventional two-dimensional capacitive touchpad  100 , which comprises a panel  102 , a Y-axial sensing layer  104 , an insulating layer  106 , an X-axial sensing layer  108 , and a bottom plate  110 . When a finger  112  touches on the panel  102 , the sensed value (in capacitance) on the touched position will varies, and the control circuit connected to the touchpad  100  can convert the capacitance on the touchpad  100  to a sensed value as shown in  FIG. 2 , by which the position where the finger  112  touches and the moving distance and the moving direction of the finger  112  can be determined. Conventionally, there are two methods to determine whether an object touches on the touchpad  100 . In the first method, the sensed value on the touchpad  100  is used to determine if an object touches on the touchpad  100  by the way as shown in  FIG. 3 . When the sensed value is greater than a threshold th, it is determined that an object touches on the touchpad  100 , and on the contrary, when the sensed value is less than the threshold th, it is determined that the object leaves the touchpad  100  or no object touches on the touchpad  100 . In the second method, the cumulative sensed value on the touchpad  100  is used to determine if an object touches on the touchpad  100  by the way as shown in  FIG. 4 , by which, if the cumulative sensed value is greater than a threshold th, it is determined that an object touches on the touchpad  100 , otherwise it is determined that the object leaves the touchpad  100  or no object touches on the touchpad  100 . However, these two detection methods might be interfered by external noises, which will cause erroneous determination and accordingly operation that is not desired or predicted. Moreover, the operations of tap, drag, double tap and other gestures on the touchpad  100  are determined based on the time relationship when an object is operated to touch on the touchpad  100 , leave from the touchpad  100 , and move on the touchpad  100 , and thus, for a user using the touchpad  100  first time or being unfamiliar with operating the touchpad  100 , the action might not be so definite that the touchpad  100  will detect thereto incorrectly and cause inconvenient use. 
   Therefore, there is a need of a detection method for a touchpad that will avoid noise to interfere the operation of the touchpad and have the touchpad to be easy to operate therewith. 
   SUMMARY OF THE INVENTION 
   An object of the present invention is to provide a gesture detection method for a touchpad for preventing the operation of the touchpad from noise interference. 
   In a gesture detection method for a touchpad, according to the present invention, various gestures such as tap, drag and double tap are determined by operating an object to touch on the touchpad, leave from the touchpad, and move on the touchpad. 

   
     BRIEF DESCRIPTION OF DRAWINGS 
       FIG. 1  is a cross-sectional view of a conventional two-dimensional capacitive touchpad; 
       FIG. 2  shows a relationship between the sensed value and the touched position of the touchpad shown in  FIG. 1 ; 
       FIG. 3  shows a variation of the sensed value on the touchpad shown in  FIG. 1 ; 
       FIG. 4  shows a variation of the cumulative sensed value on the touchpad shown in  FIG. 1 ; 
       FIG. 5  shows a variation of the sensed value on the touchpad shown in  FIG. 1  when the sensed value becomes greater than a down threshold; 
       FIG. 6  shows a difference between two sensed values shown in  FIG. 5 ; 
       FIG. 7  shows a detected signal; 
       FIG. 8  shows a variation of the sensed value on the touchpad shown in  FIG. 1  when the sensed value becomes less than a lift threshold; 
       FIG. 9  shows a difference between two sensed values shown in  FIG. 8 ; 
       FIG. 10  shows a detected signal; 
       FIG. 11  shows a variation of the sensed value on the touchpad shown in  FIG. 1  when an object moves from still to left side; 
       FIG. 12  shows a difference between two sensed values shown in  FIG. 11 ; 
       FIG. 13  shows a detected signal and an output signal of an embodiment in a tap gesture; 
       FIG. 14  shows a detected signal and an output signal of an embodiment in a drag gesture; and 
       FIG. 15  shows a detected signal and an output signal of an embodiment in a double tap gesture. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   In a detection method for a capacitive touchpad according to the present invention, the noise resistive capability of the touchpad is enhanced without any improvement on the hardware detection circuit of the touchpad, and several gestures for operations on the touchpad can be distinguished by such method. 
   &lt;Detection for Verifying an Object Down&gt; 
   In  FIG. 5 , it is shown a variation of the sensed value on the touchpad  100  of  FIG. 1  when the sensed value becomes greater than a down threshold th, in which curve  200  represents the sensed value at this time and curve  202  represents the sensed value at the last time.  FIG. 6  shows the difference between the sensed values  200  and  202  of  FIG. 5 , and  FIG. 7  shows a detected signal  204 . In a detection of the sensed value on the touchpad  100 , when the sensed value is detected greater than the down threshold th as shown in  FIG. 5 , the detected signal  204  will transit from low to high as shown in  FIG. 7 , and then, within a reference time interval T DownDetect , the sensed value on the touchpad  100  is continuously detected and the differential sensed value dV is calculated by subtracting each current sensed value  202  by the last sensed value  200  as shown in  FIG. 6 . If the differential sensed value dV within the reference time interval T DownDetect  maintains positive, it is determined that an object touches down to the touchpad  100 . 
   &lt;Detection for Verifying an Object Lift&gt; 
     FIG. 8  shows a variation of the sensed value on the touchpad  100  of  FIG. 1  when the sensed value becomes less than a lift threshold th, in which curve  210  represents the sensed value at this time and curve  212  represents the sensed value at the last time,  FIG. 9  shows the difference between the sensed values  210  and  212  of  FIG. 8 , and  FIG. 10  shows a detected signal  214 . After an object has touched on the touchpad  100 , once the sensed value is detected less than the lift threshold th as shown in  FIG. 8 , the detected signal  214  will transit from high to low as shown in  FIG. 10 , and then, within a reference time interval T LiftDetect , the sensed value on the touchpad  100  is continuously detected and the differential sensed value dV is calculated by subtracting each current sensed value  210  by the last sensed value  212  as shown in  FIG. 9 . If the differential sensed value dV within the reference time interval T LiftDetect  maintains negative, it is determined that the object leaves from the touchpad  100 . 
   &lt;Detection for Verifying an Object Moving&gt; 
   The variation of an object on the touchpad  100  from still to move is verified to avoid noise or slight vibration of the object to cause a misjudgment on the object position which will result in the corresponding cursor to have wrong action.  FIG. 11  shows a variation of the sensed value on the touchpad  100  shown in  FIG. 1  when an object on the touchpad  100  moves from still to left side, in which curve  220  represents the sensed value at this time and curve  222  represents the sensed value at the last time, and  FIG. 12  shows the difference between the sensed values  220  and  222  shown in  FIG. 11 . After an object is verified to touch on the touchpad  100 , the sensed value on the touchpad  100  is continuously detected and the differential sensed value dV is calculated by subtracting each current sensed value  220  by the last sensed value  222 . Within a reference time interval T MovingDetect , if the left side of the object is detected to have the differential sensed value dV in an increasing trend and the right side of the object is detected to have the differential sensed value dV in a decreasing trend as shown in  FIGS. 11 and 12 , the object is determined to move from still to left side. On the contrary, within the reference time interval T MovingDetect , if the left side of the object is detected to have the differential sensed value dV in a decreasing trend and the right side of the object is detected to have the differential sensed value dV in an increasing trend, the object is determined to move from still to right side. 
   &lt;Detection for a Tap Gesture&gt; 
     FIG. 13  shows a detected signal  310  and an output signal  320  in a tap gesture, and the output signal  320  includes a gesture signal  322 . In response to an object touching down to the touchpad  100 , the detected signal  310  transits from low to high. If the detection for verifying an object down confirms that the object indeed touches down to the touchpad  100 , the object is further determined whether or not to move on the touchpad  100  according to the detection for verifying an object moving. If the object is determined to move on the touchpad  100 , a moving gesture is determined; otherwise the detected signal  310  will transit from high to low thereafter when the object is determined to leave the touchpad  100  and then, if the detection for verifying an object lift confirms that the object indeed leaves the touchpad  100 , the gesture signal  322  is initiated and the departure time is counted for the object to leave the touchpad  100 . When the departure time reaches a reference time interval T Tap , the gesture signal  322  is terminated. The gesture signal  322  includes a key signal, and it is in a key-press state when the detection for verifying an object lift confirms that the object indeed leaves the touchpad  100  and it is initiated, and then in a key-release state when the departure time reaches the reference time interval T Tap  and it is terminated. In another embodiment, the gesture signal  322  is a voltage level signal that transits from an initial level to another level (e.g., from low to high) when the detection for verifying an object lift confirms that the object indeed leaves the touchpad  100 , and then comes back to the initial level when the departure time reaches the reference time interval T Tap . 
   &lt;Detection for a Drag Gesture&gt; 
     FIG. 14  shows a detected signal  330  and an output signal  340  in a drag gesture, and the output signal  340  includes a gesture signals  342 . When an object is detected to touch down to the touchpad  100  first time, the detected signal  330  transits from low to high, and if the detection for verifying an object down confirms that the object indeed touches down to the touchpad  100 , the object is further determined whether or not to move on the touchpad  100  according to the detection for verifying an object moving. If the object is determined to move on the touchpad  100 , a moving gesture is determined; otherwise the detected signal  330  will transit from high to low thereafter when the object is determined to leave the touchpad  100  and then, if the detection for verifying an object lift confirms that the object indeed leaves the touchpad  100 , the gesture signal  342  is initialized and the departure time is counted for the object to leave the touchpad  100 . Further, if the touchpad  100  is detected to be touched again before the departure time reaches a reference time interval T Drag , the detected signal  330  transits from low to high again. After the detection for verifying an object down confirms that the touchpad  100  is indeed touched by an object again, the object is determined whether or not to move on the touchpad  100  according to the detection for verifying an object moving. If the object indeed moves on the touchpad  100 , the position information of the object is calculated. Until the object is detected to leave the touchpad  100 , the detected signal  330  transits from high to low again, and the gesture signal  342  is terminated when the detection for verifying an object lift confirms that the object indeed leaves the touchpad  100 . The gesture signal  342  includes a combinational signal of a key-press with the position information. When the first time the detection for verifying an object lift confirms that the object indeed leaves the touchpad  100  and the gesture signal  342  is initialized, the object does not move on the touchpad  100 , so that the position information does not change, and the gesture signal  342  is in a key-press with zero-displacement state. When the object indeed moves on the touchpad  100  after the gesture signal  342  is initiated, the position information of the object is calculated, and the gesture signal  342  is in a key-press and object-moving state. Typically, the position information of an object on the touchpad  100  may have an absolute coordinate, a relative coordinate, or a relative displacement of the object. The absolute coordinate is referred to a coordinate value generated with a fixed position (e.g., the center or a corner of the touchpad  100 ) as the original point, the relative coordinate is referred to a coordinate value generated with a relative position (e.g., the position first touched by the object on the touchpad  100 ) as the original point, and the relative displacement is referred to a displacement relative to the original point. 
   &lt;Detection for a Double Tap Gesture&gt; 
     FIG. 15  shows a detected signal  350  and an output signal  360  in a double tap gesture, and the output signal  360  includes gesture signals  362  and  364 . When an object is detected to touch down to the touchpad  100  first time, the detected signal  350  transits from low to high, and if the detection for verifying an object down confirms that the object indeed touches down to the touchpad  100 , the object is further determined whether or not to move on the touchpad  100  according to the detection for verifying an object moving. If the object is determined to move on the touchpad  100 , a moving gesture is determined; otherwise the detected signal  350  will transit from high to low thereafter when the object is determined to leave the touchpad  100  and then, if the detection for verifying an object lift confirms that the object indeed leaves the touchpad  100 , the gesture signal  362  is initialized and the departure time is counted for the object to leave the touchpad  100 . Further, if the touchpad  100  is detected to be touched again before the departure time reaches a reference time interval T DoubleTap , the detected signal  330  transits from low to high again. After the detection for verifying an object down confirms that the touchpad  100  is indeed touched by an object again, the object is determined whether or not to move on the touchpad  100  according to the detection for verifying an object moving. If the object does not move on the touchpad  100 , the detected signal  350  will transits from high to low again when the object is detected to leave from the touchpad  100  again, and after the detection for verifying an object lift confirms that the object indeed leaves the touchpad  100 , the gesture signal  362  is terminated, followed with the gesture  364 . The gesture signal  362  includes a key signal, and it is in a key-press state when the first time the detection for verifying an object lift confirms that the object indeed leaves the touchpad  100  and it is initiated, and then in a key-release state after the second time the detection for verifying an object lift confirms that the object indeed leaves the touchpad  100  and it is terminated. The gesture signal  364  includes a combinational signal of a key-press and a key-release. In another embodiment, the gesture signals  362  and  364  are voltage level signals that transit from an initial level to another level (e.g., from low to high) when the first time the detection for verifying an object lift confirms that the object indeed leaves the touchpad  100 , comes back to the initial level when the second time the detection for verifying an object lift confirms that the object indeed leaves the touchpad  100 , turns from the initial level to the another level (e.g., from low to high) again, and then comes back to the initial level after a period of time. 
   In the above embodiments, various gestures for operating on the touchpad  100  are confirmed with the variation of the sensed value and by determining whether or not the object moves on the touchpad  100 , and therefore, in addition to avoid noise to interfere the operations of the touchpad  100 , it is also avoided the disadvantage that the touchpad  100  can not determine the operation of indefinite actions, and the convenience of use is improved. 
   While the present invention has been described in conjunction with preferred embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, it is intended to embrace all such alternatives, modifications and variations that fall within the spirit and scope thereof as string forth in the appended claims.