Patent Publication Number: US-2012038574-A1

Title: Detection method and detection circuit for detecting touch event on touch panel by selecting non-adjacent sensing axis as reference axis

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The disclosed embodiments of the present invention relate to touch control technology, and more particularly, to a detection method for detecting a touch event on a touch panel and related detection circuit thereof. 
     2. Description of the Prior Art 
     In modern electronic products, a capacitive touch panel is often used as a man-machine interface due to its intuitive-to-use characteristic, wherein a projective capacitive touch panel has benefits of multi-touch support, higher transmittance and power conservation, and thus is widely used on portable devices such as mobile phones, vehicle navigation devices, etc. However, measurement of the projective capacitive touch panel usually has only several or dozens of sensing electrodes disposed in a direction of a horizontal axis or vertical axis, and the sensing electrodes of the touch panel respectively generate a plurality of sensing signals according to a touch event thereon, and respectively generate a plurality of sensing outputs according to differences of sensing signals generated by each pair of adjacent sensing electrodes. In the prior arts, a calculation of a contact usually employs an interpolation method for estimating a distance between a measured point and a peak value via an estimated peak value determined by the calculated sensing output or a ratio of the calculated sensing output value to an extreme value. Please refer to  FIG. 1 , which is a schematic diagram illustrating an example of detecting a touch event TEa on a conventional touch panel  100 . As shown in  FIG. 1 , the conventional touch panel  100  has 6 sensing axes X 1 ˜X 6  and Y 1 ˜Y 6  on the X axis and Y axis, respectively, and the sensing axes X 1 ˜X 6  and Y 1 ˜Y 6  have corresponding sensing output values SX 1   a ˜SX 6   a  and SY 1   a ˜SY 6   a,  respectively. For example, regarding the sensing axes X 1 ˜X 6 , only the sensing output values SX 3   a ˜SX 5   a  are effective values (i.e., non-zero values). The sensing output value SX 3   a  is obtained by a detection circuit comparing the sensing signal detected by the sensing axis X 3  and the sensing signal detected by the sensing axis X 2 ; similarly, the sensing output value SX 4   a  and the sensing output value SX 5   a  are obtained by the detection circuit comparing the sensing signals detected by the sensing axis X 4 , X 5  and X 5 , X 6 , respectively. Contacts of the touch event TEa can be known to be located between the sensing axis X 3  and X 4  via calculating these effective values with the interpolation method. In the same manner, contacts of the touch event TEa can be known to be located on the sensing axis Y 4  via calculating effective values (i.e. SY 3   a ˜SY 5   a ) corresponding to the sensing axis Y 1 ˜Y 6 . 
     Please refer to  FIG. 2 , which is a schematic diagram illustrating an example of detecting another touch event TEb on the conventional touch panel  100 . Compared to the touch event TEa, contacts of the touch event TEb are smaller, which cannot cover areas of sensing electrodes in the touch panel  100 , and thus a number of effective values decreases. In the example shown in  FIG. 2 , only the sensing output values SX 3   b ˜SX 4   b  and SY 4   b  are effective values, and therefore positions of the contacts cannot be accurately obtained in the following calculation using the interpolation method. Moreover, when the touch event TEb is a contact in motion (e.g., a user uses a touch pen to slide on the touch panel  100 ), a trace of the detected contacts would present non-linear characteristics due to lack of efficient effective values, and thus leads to poorer system performance. 
     Hence, how to increase effective data detected on the touch panel  100  for increasing linearity of detected data is still a problem needed to be solved in the field. 
     SUMMARY OF THE INVENTION 
     In accordance with exemplary embodiments of the present invention, a detection method capable of increasing effective detected data so as to improve linearity of detected data and related detection circuit thereof are proposed to solve the above-mentioned problem. 
     According to one embodiment of the present invention, a detection method for detecting a touch event on a touch panel including a plurality of first sensing axes on a first dimension and a plurality of second sensing axes on a second dimension is disclosed. The detection method includes: regarding each first sensing axis, choosing another first sensing not neighboring with the first sensing axis as a first reference axis, and utilizing the first sensing axis and the first reference axis to derive a first sensing data corresponding to the first sensing axis; utilizing the second axes to derive a second sensing data corresponding to each second sensing axis; and utilizing first sensing data respectively corresponding to the first sensing axes and second sensing data respectively corresponding to the second sensing axes to derive a touch event detection result. 
     According to another embodiment of the present invention, a detection circuit for detecting a touch event on a touch panel including a plurality of first sensing axes on a first dimension and a plurality of second sensing axes on a second dimension is disclosed. The detection circuit includes a scanning element and a determining element. Regarding each of the first sensing axes, the scanning element selects a first sensing axis which is not adjacent to the first sensing axis as a first reference axis, utilizes the first sensing axis and the first reference axis to obtain a first sensing data corresponding to the first sensing axis; and further obtains a second sensing data corresponding to each of the second sensing axis according to the second sensing axes. The determining element is coupled to the scanning element, for obtaining a touch event detection result according to a plurality of first sensing data respectively corresponding to the first sensing axes and a plurality of second sensing data respectively corresponding to the second sensing axes. 
     These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram illustrating an example of detecting a touch event on a conventional touch panel. 
         FIG. 2  is a schematic diagram illustrating an example of detecting another touch event on the conventional touch panel. 
         FIG. 3  is a schematic diagram of a detection circuit according to one embodiment of the present invention. 
         FIG. 4  is a schematic diagram illustrating detection of a touch event on a touch panel according to one embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Please concurrently refer to  FIG. 3  and  FIG. 4 .  FIG. 3  is a schematic diagram of a detection circuit  300  according to one embodiment of the present invention, and  FIG. 4  is a schematic diagram illustrating detection of a touch event TEc on a touch panel  100  according to one embodiment of the present invention. The touch event TEc in  FIG. 4  and the touch event TEb in  FIG. 2  have contacts with the same contact areas. The detection circuit  300  includes, but not limited to, a scanning element  310  and a determining element  320 . The touch panel  100  includes 6 first sensing axes X 1 ˜X 6  and 6 second sensing axes Y 1 ˜Y 6  on a first dimension (e.g., the X axis) and a second dimension (e.g., the Y axis), respectively. Please note that, the number of the first and second sensing axes is for illustrative purpose only, and is not meant to be a limitation of the present invention. In this embodiment, when the scanning element  310  extracts a sensing output of a specific sensing axis, the scanning element  310  selects a sensing axis which is not adjacent to the specific sensing axis as a reference axis, and utilizes the sensing axis and the reference axis to obtain a sensing data corresponding to the specific sensing axis (i.e., obtain the sensing output corresponding to the specific sensing axis). 
     For example, when the scanning element  310  extracts a sensing output of the first sensing axis X 3 , the scanning element  310  selects a first sensing axis X 1 , which is separated by a first sensing axis X 2 , as a first reference axis, and utilizes the sensing signal corresponding to a first sensing axis X 3  (i.e., the aforementioned specific sensing axis) to be compared with the corresponding first sensing axis X 1  (i.e., the aforementioned reference axis), thereby obtaining a sensing output SX 3   c  corresponding to the first sensing axis X 3  by calculation; similarly, when the scanning element  310  extracts a sensing output of a second sensing axis Y 3 , the scanning element  310  selects a second sensing axis Y 1 , which is separated by a second sensing axis Y 2 , as a second reference axis, and utilizes a sensing signal corresponding to a second sensing axis Y 3  (i.e., the aforementioned specific sensing axis) to be compared with the corresponding first sensing axis Y 1  (i.e., the aforementioned reference axis), thereby obtaining a sensing output SY 3   c  corresponding to the second sensing axis Y 3  by calculation. By the same token, the scanning element  310  processes the first sensing axes X 1 ˜X 6  and second sensing axes Y 1 ˜Y 6  one-by-one, to obtain the sensing outputs SX 1   c ˜SX 6   c  and SY 1   c ˜SY 6   c  corresponding to the first sensing axes X 1 ˜X 6  and the second sensing axes Y 1 ˜Y 6 , respectively. After all the first sensing data and the second sensing data (i.e., sensing outputs SX 1   c ˜SX 6   c  and SY 1   c ˜SY 6   c ) are obtained, the determining element  320  retrieves effective data from the first and second sensing data to determine a detection result of the touch event. 
     Please concurrently refer to  FIG. 2  and  FIG. 4 . As can be known from the figures, effective data shown in  FIG. 4  include the sensing outputs SX 3   c ˜SX 5   c  and SY 3   c ˜SY 5   c,  and the number thereof is greater than the number of effective data (i.e., sensing outputs SX 3   b ˜SX 4   b  and SY 4   b ) in  FIG. 2 . Therefore, the detection circuit  300  can rapidly and precisely identify positions of the contacts corresponding to the touch event TEc according to these effective data. 
     However, the above-mentioned embodiments are for illustrative purpose only, and are not meant to be limitations to the scope of the present invention. For example, when extracting sensing output of the first sensing axis X 3  (or the second sensing axis Y 3 ), the scanning element  310  selects the first sensing axis X 5  (or the second sensing axis Y 5 ) separated by the first sensing axis X 4  (or the second sensing axis Y 4 ) or selects the even farther first sensing axis X 6  (or the second sensing axis Y 6 ) as the first reference axis (or the second reference axis), and obtains the sensing output corresponding to the first sensing axis X 3  (or the second sensing axis Y 3 ) via calculating a difference of sensing signals between the selected first reference axis (or the second reference axis) and the first sensing axis X 3  (or the second sensing axis Y 3 ). In other words, a detection method, including steps of selecting a first sensing axis (or a second sensing axis) which is not adjacent to a first specific sensing axis (or a second specific sensing axis) as the first reference axis (or the second reference sensing axis) and accordingly obtaining a first sensing data (or a second sensing data) corresponding to the first specific sensing axis (or the second specific sensing axis), should fall within the scope of the present invention. 
     To sum up, the present invention provides a detection method capable of increasing effective detected data. When calculating a sensing output of a sensing axis, another sensing axis which is not adjacent to the sensing axis is selected as a reference axis, and the sensing output corresponding to the sensing axis is generated correspondingly. In this way, the present invention can still obtain enough effective detected data even though the contact areas are too small. As the linearity of detected data is enhanced, the accuracy of the final contact detection result/touch event detection result can be improved. 
     Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.