Abstract:
In a gesture detection method for a capacitive touchpad, various gesture operations are determined by detecting the touching on the touchpad, leaving from the touchpad, and moving on the touchpad.

Description:
RELATED APPLICATIONS 
     This Application claims foreign application priority upon Taiwan Application No. 094137356, filed 25 Oct. 2005. 
     FIELD OF THE INVENTION 
     The present invention is related generally to 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  shows 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 values (to the capacitances of the traces in the touchpad  100 ) on the touched position will vary, and the control circuit connected to the touchpad  100  can convert the sensed capacitive variation 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 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 noise, which will cause erroneous determination and accordingly operation that is not desired or predicted. Moreover, the operation of drag gesture on the touchpad  100  is determined based on the time relationship when an object operates to fall down to 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 of the user might not be so definite that the touchpad  100  will detect thereto incorrectly and cause inconvenient use. In addition, with the trend of reducing the size of electronic products, the size of the touchpad  100  also needs to reduce. It results in inconvenience that the drag is often over the range of the touchpad  100  and thus the user needs to repeat the operation several times for a wide drag range. 
     Therefore, it is desired 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 with. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide a gesture detection method for a touchpad to prevent the operation of the touchpad from noise interference. 
     In a gesture detection method for a touchpad, according to the present invention, a gesture for operation is determined by detecting if an object touches the touchpad, leaves from the touchpad, and moves 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 in the sensed value on the touchpad shown in  FIG. 1 ; 
         FIG. 4  shows a variation in the cumulative sensed value on the touchpad shown in  FIG. 1 ; 
         FIG. 5  shows a variation in 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 in 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 in 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 drag gesture; and 
         FIG. 14  shows a detected signal and an output signal of another embodiment in a drag gesture; and 
         FIGS. 15A-15D  show an operation to illustrate the embodiment shown in  FIG. 13 . 
     
    
    
     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 a gesture for operation on the touchpad can be detected 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 Drag Gesture&gt; 
       FIG. 13  shows a detected signal  310  and an output signal  320  in a drag gesture, and the output signal  320  includes gesture signals  322 ,  324 ,  326  and  328 . When an object is detected to touch down to the touchpad  100  first time, the detected signal  310  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  310  will transit from high to low thereafter when the object is detected 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  (e.g., a key-press signal or a key-press and zero-displacement signal) is initialized and the departure time T 1  is counted after the object leaves the touchpad  100 . Further, if the touchpad  100  is detected to be touched again before the departure time T 1  reaches a reference time interval T A , the detected signal  310  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, the gesture signal  322  is maintained, and the position information is sent out by the gesture signal  324  (e.g., a combined signal of a key-press signal and the position information). Until the object is detected to leave the touchpad  100  again, the detected signal  310  transits from high to low again, and after the detection for verifying an object lift confirms that the object indeed leaves the touchpad  100 , the gesture signal  324  is terminated and the departure time T 2  is counted after the object leaves the touchpad  100 . Further, if the touchpad  100  is detected to be touched again before the departure time T 2  reaches a reference time interval T B , the detected signal  310  transits from low to high again. After 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 indeed to move on the touchpad  100 , the position information of the object is calculated, the gesture signal  322  is maintained, and the position information is sent out by the gesture signal  326  (e.g., a combined signal of a key-press signal and the position information). When the object is detected to leave the touchpad  100  again, the detected signal  310  transits from high to low, and after the detection for verifying an object lift confirms that the object indeed leaves the touchpad  100 , the gesture signal  326  is terminated. The foregoing steps are repeated until the detection for verifying an object down confirms that the touchpad  100  is touched by an object, and the detection for verifying an object moving confirms that the object doesn&#39;t move on the touchpad  100 , and then, the detected signal  310  transits from high to low when the object is detected to leave the touchpad  100 , and the gesture signal  328  (e.g., a key-release signal) is produced to terminate the gesture signal  322  after the detection for verifying an object lift confirms that the object indeed leaves the touchpad  100 . 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. 
       FIG. 14  shows a detected signal  330  and an output signal  340  in another embodiment, and the output signal  340  includes gesture signals  342 ,  344 ,  346 ,  348 , and  350 . 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 detected 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  (e.g., a key-press signal or a key-press and zero-displacement signal) is initialized and the departure time T 3  is counted after the object leaves the touchpad  100 . Further, if the touchpad  100  is detected to be touched again before the departure time T 3  reaches a reference time interval T C , 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, the gesture signal  342  is maintained, and the position information is sent out by the gesture signal  344  (e.g., a combined signal of a key-press signal and the position information). When the object is detected to leave the touchpad  100  again, the detected signal  330  transits from high to low again, and after the detection for verifying an object lift confirms that the object indeed leaves the touchpad  100 , the gesture signal  344  is terminated and the departure time T 4  is counted after the object leaves the touchpad  100 . Further, if the touchpad  100  is detected to be touched again before the departure time T 4  reaches a reference time interval T D , the detected signal  330  transits from low to high again. After 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 indeed to move on the touchpad  100 , the position information of the object is calculated, the gesture signal  342  is maintained, and the position information is sent out by the gesture signal  346  (e.g., a combined signal of a key-press signal and the position information). When the object is detected to leave the touchpad  100  again, the detected signal  330  transits from high to low, and after the detection for verifying an object lift confirms that the object indeed leaves the touchpad  100 , the gesture signal  346  is terminated. The foregoing steps are repeated until the object is detected to leave the touchpad  100 , the detected signal  330  transits from high to low accordingly, the detection for verifying an object lift confirms that the object indeed leaves the touchpad  100 , and the gesture signal  348  (e.g., a combined signal of a key-press signal and the position information) is terminated, and then, if the touchpad is detected not to be touched within a reference time interval T D  after the object leaves the touchpad  100 , the gesture signal  350  (e.g., a key-release signal) is produced to terminate the gesture signal  342 . Likewise, 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. 
       FIGS. 15A-15D  show an operation to illustrate the embodiment shown in  FIG. 13 . In  FIG. 15A , an object  410  touches and then leaves a touchpad  420 . During this period, the object  410  doesn&#39;t move on the touchpad  420 , an initial signal is sent out by the touchpad  420 , and the cursor  440  on the monitor  430  is constantly located at a position A. In  FIG. 15B , the object  410  touches the touchpad  420  again within a reference time interval after the last time the object leaves the touchpad  420 , and then leaves the touchpad  420  again. During this period, the object  410  moves on the touchpad  420 , and therefore, the position information of the object  410  is calculated, the initial signal is maintained, and the position information is sent out by the touchpad  420 . In response thereto, the cursor  440  on the monitor  430  moves in the same direction as the moving direction of the object  410 , for example from the position A to a position B. In  FIG. 15C , the object  410  touches the touchpad  420  again within the reference time interval after the last time the object leaves the touchpad  420 , and then leaves the touchpad  420  again. During this period, the object  410  moves on the touchpad  420 , and therefore, the position information of the object  410  is calculated, the initial signal is maintained, and the position information is sent out by the touchpad  420 . In response thereto, the cursor  440  on the monitor  430  moves in the same direction as the moving direction of the object  410 , for example from the position B to a position C. In  FIG. 15D , the object  410  touches the touchpad  420  again within the reference time interval after the last time the object leaves the touchpad  420 , and then leaves the touchpad  420  again. During this period, however, the object  410  doesn&#39;t move on the touchpad  420 . Therefore, a terminal signal is sent out by the touchpad  420  to terminate the initial signal, and the cursor  440  on the monitor  430  stays at the position C. The steps shown in  FIGS. 15B and 15C  can be repeated until the cursor  440  moves to the desired position, and then the initial signal is terminated as shown in  FIG. 15D . The operation with the touchpad  420  thus becomes more convenient. 
     As shown in the above embodiments, a gesture for operating on a touchpad is confirmed with the variation of the sensed value and by determining whether or not the object moves on the touchpad. Therefore, in addition to avoid noise to interfere the operations of the touchpad and to avoid the touchpad to fail to identify the operation of indefinite actions, the cursor can be operated to a continuous movement, and the convenience of use is thus 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.