Patent Publication Number: US-8994693-B2

Title: Locating method of optical touch device and optical touch device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based upon and claims the benefit of priority from the prior Taiwanese Patent Application No. 098138898, filed Nov. 16, 2009, the entire contents of which are incorporated herein by reference. 
     BACKGROUND 
     1. Field of the Invention 
     The present invention relates to a touch device, and particularly to a locating method of an optical touch device and an optical touch device that is suitable for using the locating method. 
     2. Description of the Related Art 
     Nowadays, a touch function has been one of necessary functions of many electronic devices. A touch device is an important component to achieve the touch function. Generally, a familiar type of the touch device is, for example, a resistive touch device, a capacitive touch device or an optical touch device. The electronic devices can be equipped with various touch devices in accordance with the various demands. 
       FIG. 1  is a schematic view of a conventional optical touch device. Referring to  FIG. 1 , the conventional optical touch device  100  includes a light guide module  110 , a light source module  120  and an image detecting module  130 . The light guide module  110  includes three light reflecting bars  112   a ,  112   b  and  112   c  arranged along three sides of a rectangle. The light reflecting bar  112   a  faces to the light reflecting bar  112   c  and the light reflecting bar  112   b  is connected between the light guide bar  112   a  and the light reflecting bar  112   c . The area in the rectangle defines a detecting area  114 . The light source module  120  includes two light emitting components  122   a  and  122   b . The light emitting component  122   a  is disposed at an end of the light guide bar  112   a  far away from the light guide bar  112   b , and the light emitting component  122   b  is disposed at an end of the light guide bar  112   c  far away from the light guide bar  112   b . The light source module  120  is configured for emitting light to the three light reflecting bars  112   a ,  112   b  and  112   c . The three light reflecting bars  112   a ,  112   b  and  112   c  are configured for reflecting the light from the light source module  120  to irradiate the detecting area  114 . The image detecting module  130  includes two image detecting components  132   a  and  132   b . The image detecting component  132   a  is disposed at the end of the light reflecting bar  112   a  far away from the light reflecting bar  112   b , and the image detecting component  132   b  is disposed at the end of the light reflecting bar  112   c  far away from the light reflecting bar  112   b . Each of the two image detecting components  132   a  and  132   b  includes a number of pixels  135  arranged in a straight line. The pixels  135  are configured for detecting a light blocking object (i.e., a touch point) in the detecting area  114 , thereby calculating a position (i.e., coordinates) of the light blocking object in accordance with the information detected by the pixels  135 . 
     In detail, a field of view (FOV) of the image detecting component  132   a  covers the light reflecting bars  112   b  and  112   c . That is, the pixels  135  of the image detecting component  132   a  are configured for detecting the light reflecting bars  112   b  and  112   c . When the light blocking object is located in the detecting area  114  and a dark point caused by the light blocking object is located at the light reflecting bar  112   b , the light reflecting bar  112   c , or a connecting portion of the light reflecting bar  112   b  and the light reflecting bar  112   c , the dark point can be detected by some pixels  135  of the image detecting component  132   a . Similarly, a field of view of the image detecting component  132   b  covers the light reflecting bars  112   a  and  112   b . That is, the pixels  135  of the image detecting component  132   a  are configured for detecting the light reflecting bars  112   a  and  112   b . When the light blocking object is located in the detecting area  114  and a dark point caused by the light blocking object is located at the light reflecting bar  112   a , the light reflecting bar  112   b , or a connecting portion of the light reflecting bar  112   a  and the light reflecting bar  112   b , the dark point can be detected by some pixels  135  of the image detecting component  132   b.    
     Generally, the conventional optical touch device  100  calculates the position of the dark point caused by the light blocking object using either a medium center calculating method or a gravity center calculating method, thereby determining the position of the light blocking object. However, positions of the dark points caused by all light blocking objects in the detecting area  114  can not be calculated accurately using either the medium center calculating method or the gravity center calculating method. For example, in the case of using the medium center calculating method to calculate the position of the dark point, the detecting area  114  of conventional optical touch device  100  has an insensitive area  114   a . If the light blocking object is just located in the insensitive area  114   a , the calculated position of the dark point will generate an inaccuracy due to a large offset angle of the light. In addition, if the position of the dark point is calculated using the gravity center calculating method and the dark point caused by the light blocking object is just located at the connecting portion of two neighboring light reflecting bars, the calculated position of the dark point will generate an inaccuracy. 
     Referring to  FIG. 2 , the medium center calculating method is described in detail by using the image detecting component  132   b  as an example. A light blocking object A is located in the insensitive area  114   a , and the image detecting component  132   b  is configured for detecting a dark point A 1  caused by the light blocking object A. The dark point A 1  is located at the light reflecting bar  112   a . During a process of detecting the dark point A 1 , the dark point A 1  can be detected by some pixels  135 , for example, from the n-th pixel  135   n  to the r-th pixel  135   r , of the image detecting component  132   b . The calculated center position of the dark point A 1  using the medium center calculating method is equal to (n+r)/2. That is, the center of the dark point A 1  corresponds to the (n+r)/2-th pixel  135   m . But, in fact, a straight line L passing through the center of the light blocking object A and the center of the dark point A 1  is connected to the pixel  135   m ′. In other words, the accurate center of the dark point A 1  should correspond to the pixel  135   m ′ rather than the pixel  135   m . Similarly, the image detecting component  132   a  has the above-mentioned problem. Therefore, when the position of the dark point caused by the light blocking object in the insensitive area  114   a  is calculated using the medium center calculating method, the calculated position of the dark point will generate an inaccuracy. 
     Referring to  FIG. 3 , the gravity center calculating method is described in detail by using the image detecting component  132   a  as an example. A light blocking object B is located in the detecting area  114 , and the image detecting component  132   a  is configured for detecting a dark point B 1  caused by the light blocking object B. The dark point B 1  is located at the connecting portion of the light reflecting bar  112   b  and the light reflecting bar  112   c . During a process of detecting the dark point B 1 , the dark point B 1  can be detected by some pixels  135 , for example, from the x-th pixel  135   x  to the y-th pixel  135   y , of the image detecting component  132   a . A calculating formula of the gravity center calculating method is as follow: 
     
       
         
           
             Cg 
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     In the formula, w represents the w-th pixel, bg[w] represents a background brightness of the w-th pixel, img[w] represents an image brightness of the image detected by the w-th pixel, and Cg represents the calculated gravity center position of the dark point B 1  caused by the light blocking object B. However, the conventional optical touch device  100  has poor light irradiation at the connecting portion of the light reflecting bar  112   b  and the light reflecting bar  112   c . When the dark point B 1  is located at the connecting portion of the light reflecting bar  112   b  and the light reflecting bar  112   c  as shown in  FIG. 3 , the background brightness and the image brightness detected by the pixels  135  of the image detecting components  132   a  are inaccurate. Therefore, a large error between the calculated position of the dark point B 1  and the actual position of the dark point B 1  will generate. 
     As mentioned above, the conventional locating method can not accurately calculate the position of the dark point caused by the light blocking object located in any area of the detecting area  114 . Thus, the conventional optical touch device  100  can not determine the position of the light blocking object accurately. 
     BRIEF SUMMARY 
     The present invention provides a locating method of an optical touch device so as to determine a position of a light blocking object accurately. 
     The present invention also provides an optical touch device to so as to determine a position of a light blocking object accurately. 
     To achieve the above-mentioned advantages, the present invention provides a locating method of an optical touch device. The locating method is suitable for an optical touch device to calculate a position of a light blocking object. The optical touch device includes a number of image detecting components. Each of the image detecting components includes a number of pixels arranged in a straight line. In the locating method, the pixels of each of the image detecting components are at least divided into a first group and a second group. When the first group detects a dark point caused by the light blocking object, a position of the dark point is calculated using a first calculating method. When the second group detects the dark point caused by the light blocking object, the position of the dark point is calculated using a second calculating method. 
     In one embodiment provided by the present invention, the first calculating method is a gravity center calculating method, and the second calculating method is a medium center calculating method. 
     In one embodiment provided by the present invention, the optical touch device includes a detecting area, a field of view of the second group of each of the image detecting components covers a corner area of the detecting area, and the corner area faces to the corresponding image detecting component. 
     In one embodiment provided by the present invention, the pixels of each of the image detecting components are divided into the first group, the second group and a third group. The third group is located between the first group and the second group. When the third group detects the dark point caused by the light blocking object, the position of the dark point is calculated using a third calculating method. 
     In one embodiment provided by the present invention, the third calculating method includes the steps of: calculating the position of the dark point caused by the light blocking object using the first calculating method and the second calculating method respectively to obtain a first value and a second value; multiplying the first value with a first weight a (0&lt;α&lt;1) to obtain a third value and multiplying the second value with a second weight (1−α) to obtain a fourth value; and adding the third value and the fourth value together. 
     In one embodiment provided by the present invention, when the pixels of the third group detecting the dark point caused by the light blocking object becomes closer to the first group, the first weight a becomes lager correspondingly. 
     In one embodiment provided by the present invention, the pixels of each of the image detecting components are divided into the first group, the second group, the third group and a fourth group. The second group is located between the third group and the fourth group. When the fourth group detects the dark point caused by the light blocking object, the position of the dark point is calculated using either the first calculating method or the third calculating method. 
     To achieve the above-mentioned advantages, the present invention also provides an optical touch device including a frame, a light source module, a first image detecting component and a second image detecting component. The frame includes a first sidewall, a second sidewall, a third sidewall and a fourth sidewall. The first sidewall faces to the third sidewall and the second sidewall faces to the fourth sidewall. The frame defines a detecting area therein. The light source module is configured for providing light to the detecting area. The first image detecting component is disposed between two neighboring ends of the first sidewall and the second sidewall. A field of view of the first image detecting component covers the third sidewall and the fourth sidewall. The second image detecting component is disposed between two neighboring ends of the second sidewall and the third sidewall. A field of view of the second image detecting component covers the first sidewall and the fourth sidewall. Each of the first image detecting component and the second image detecting component includes a number of pixels arranged in a straight line. The pixels of each of the first image detecting component and the second image detecting component are at least divided into a first group and a second group. When the first group detects a dark point caused by a light blocking object, a position of the dark point is calculated using a first calculating method. When the second group detects the dark point caused by the light blocking object, the position of the dark point is calculated using a second calculating method. 
     In one embodiment provided by the present invention, the third sidewall includes a first section connected to the second sidewall and a second section connected to the fourth sidewall. The first group of the first image detecting component is configured for detecting the first section, and the second group of the first image detecting component is configured for detecting the second section and the fourth sidewall. The first sidewall includes a third section connected to the second sidewall and a fourth section connected to the fourth sidewall. The first group of the second image detecting component is configured for detecting the third section, and the second group of the second image detecting component is configured for detecting the fourth section and the fourth sidewall. 
     In one embodiment provided by the present invention, a portion of the pixels of each of the first image detecting component and the second image detecting component are further divided into a third group. The third group is located between the first group and the second group. When the third group detects the dark point caused by the light blocking object, the position of the dark point is calculated using a third calculating method. 
     In one embodiment provided by the present invention, the third sidewall includes a first section connected to the second sidewall, a second section connected to the fourth sidewall and a fifth section connected between the first section and the second section. The first group of the first image detecting component is configured for detecting the first section, the second group of the first image detecting component is configured for detecting the second section and the fourth sidewall, and the third group of the first image detecting component is configured for detecting the fifth section. The first sidewall includes a third section connected to the second sidewall, a fourth section connected to the fourth sidewall and a sixth section connected between the third section and the fourth section. The first group of the second image detecting component is configured for detecting the third section, the second group of the second image detecting component is configured for detecting the fourth section and the fourth sidewall, and the third group of the second image detecting component is configured for detecting the sixth section. 
     In one embodiment provided by the present invention, a portion of the pixels of each of the first image detecting component and the second image detecting component are further divided into a third group and a fourth group. The third group is located between the first group and the second group. The second group is located between the third group and the fourth group. When the third group detects the dark point caused by the light blocking object, the position of the dark point is calculated using a third calculating method. When the fourth group detects the dark point caused by the light blocking object, the position of the dark point is calculated using either the first calculating method or the third calculating method. 
     In one embodiment provided by the present invention, the third sidewall includes a first section connected to the second sidewall, a second section connected to the fourth sidewall and a fifth section connected between the first section and the second section. The first group of the first image detecting component is configured for detecting the first section, the second group of the first image detecting component is configured for detecting the second section and a section of the fourth sidewall that is adjacent to the third sidewall, the third group of the first image detecting component is configured for detecting the fifth section, and the fourth group of the first image detecting component is configured for detecting a section of the fourth sidewall that is adjacent to the first sidewall. The first sidewall includes a third section connected to the second sidewall, a fourth section connected to the fourth sidewall and a sixth section connected between the third section and the fourth section. The first group of the second image detecting component is configured for detecting the third section, the second group of the second image detecting component is configured for detecting the fourth section and a section of the fourth sidewall that is adjacent to the first sidewall, the third group of the second image detecting component is configured for detecting the sixth section, and the fourth group of the second image detecting component is configured for detecting a section of the fourth sidewall that is adjacent to the third sidewall. 
     In one embodiment provided by the present invention, the optical touch device further includes a number of light guide components, and the light guide components are at least disposed on the first sidewall, the third sidewall and the fourth sidewall. 
     In the locating method and the optical touch device of the present invention, the pixels of each of the image components are divided into a number of groups. When the pixels of one of the groups detect the dark point caused by the light blocking object, a suitable calculating method is used to calculate the position of the dark point. Thus, the accurate position of the dark point can be calculated, thereby improving the accuracy of locating the light blocking object. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other features and advantages of the various embodiments disclosed herein will be better understood with respect to the following description and drawings, in which like numbers refer to like parts throughout, and in which: 
         FIG. 1  is a schematic view of a conventional optical touch device. 
         FIG. 2  is a schematic view of using a medium center calculating method to calculate a dark point caused by a light blocking object in an insensitive area shown in  FIG. 1 . 
         FIG. 3  is a schematic view of using a gravity center calculating method to calculate a dark point caused by a light blocking object in a detecting area shown in  FIG. 1 . 
         FIG. 4  is a schematic view of a locating method of an optical touch device applied to an optical touch device in accordance with an embodiment of the present invention. 
         FIG. 5  is a schematic view of a locating method of an optical touch device applied to an optical touch device in accordance with another embodiment of the present invention. 
         FIG. 6  is a schematic view of a locating method of an optical touch device applied to an optical touch device in accordance with further another embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 4  is a schematic view of a locating method of an optical touch device applied to an optical touch device in accordance with an embodiment of the present invention. Referring to  FIG. 4 , the locating method applied to an optical touch device  200  will be described here. It is noted that the locating method can be, but not limited to, applied to the optical touch device  200 . The locating method also can be applied to the other optical touch devices. 
     The optical touch device  200  includes a frame  210 , a light source module  220  and a first image detecting component  232   a  and a second image detecting component  232   b . In the present embodiment, the frame  210  is, for example, a rectangular frame. The frame  210  includes a first sidewall  201 , a second sidewall  202 , a third sidewall  203  and a fourth sidewall  204 . The first sidewall  201  faces to the third sidewall  203  and the second sidewall  202  faces to the fourth sidewall  204 . The frame  210  defines a detecting area  214  therein. In other words, the first sidewall  201 , the second sidewall  202 , the third sidewall  203  and the fourth sidewall  204  defines the detecting area  214  therebetween. The detecting area  214  is, for example, a rectangular area. The light source module  220  is configured for providing light to the detecting area  214 . The first image detecting component  232   a  and the second image detecting component  232   b  are configured for detecting the optical information of a light blocking object in the detecting area  214 . 
     Additionally, in the present embodiment, a light guide component (not shown) can be disposed on the first sidewall  210 , the third sidewall  203  and the fourth sidewall  204  of the frame  210  respectively. The light guide component can be either a light guide bar or a light reflecting bar. It is noted that a light guide component can also be disposed on the second sidewall  202 . 
     The light source module  220  includes, for example, a first light emitting component  222   a  and a second light emitting component  222   b . In the present embodiment, the first light emitting component  222   a  is, for example, disposed between two neighboring ends of the first sidewall  201  and the second sidewall  202  of the frame  210 . The second light emitting component  222   b  is, for example, disposed between two neighboring ends of the second sidewall  202  and the third sidewall  203  of the frame  210 . The first light emitting component  222   a  and the second light emitting component  222   b  are configured for emitting light towards the detecting area  214  so as to provide the light to the detecting area  214 . In addition, each of the first light emitting component  222   a  and the second light emitting component  222   b  can be, but not limited to, a light emitting diode. 
     The first image detecting component  232   a  is disposed between two neighboring ends of the first sidewall  201  and the second sidewall  202  of the frame  210 . A field of view of the first image detecting component  232   a  covers the third sidewall  203  and the fourth sidewall  204  of the frame  210 . The second image detecting component  232   b  is disposed between two neighboring ends of the second sidewall  202  and the third sidewall  203  of the frame  210 . A field of view of the second image detecting component  232   b  covers the first sidewall  201  and the fourth sidewall  204  of the frame  210 . Each of the first image detecting component  232   a  and the second image detecting component  232   b  includes a number of pixels  235  arranged in a straight line. In addition, each of the first image detecting component  232   a  and the second image detecting component  232   b  further includes a digital signal processing unit (not shown). The digital signal processing unit is configured for processing a signal detected by the pixels  235  and sending the processed signal to a central processing unit (not shown). Thus, the central processing unit can calculate the position of the light blocking object. The signal detected by the pixels  235  is, for example, a position of a dark point detected by the pixels  235 . 
     A locating method suitable being applied to the optical touch device  200  will be described in detail. 
     The pixels  235  of each of the first image detecting component  232   a  and the second image detecting component  232   b  are divided. The first image detecting component  232   a  is an example to describe the details. The pixels  235  of the first image detecting component  232   a  are divided into a first group G 1  and a second group G 2 . When the first group G 1  detects a dark point caused by a light blocking object in the detecting area  214 , a position of the dark point is calculated using a first calculating method. When the second group G 2  detects the dark point caused by the light blocking object in the detecting area  214 , the position of the dark point is calculated using a second calculating method. 
     Because the pixels  235  of the first image detecting component  232   a  are divided into the first group G 1  and the second group G 2 , the third sidewall  203  is divided into a first section  2031  connected to the second sidewall  202  and a second section  2032  connected to the fourth sidewall  204  correspondingly. The dark point locating at the first section  2031  of the third sidewall  203  can be detected by the first group G 1  of the first image detecting component  232   a . Thus, the position of the dark point can be calculated using the first calculating method, thereby determining the position of the light blocking object. The dark point locating at the fourth sidewall  204  and the second section  2032  of the third sidewall  203  can be detected by the second group G 2  of the first image detecting component  232   a . Thus, the position of the dark point can be calculated using the second calculating method, thereby determining the position of the light blocking object. The connecting portion of the fourth sidewall  204  and the second section  2032  of the third sidewall  203  is a corner area of the detecting area  214 . The corner area faces to the first image detecting component  232   a . In other words, the field of view of the second group G 2  of the first image detecting component  232   a  covers the corner area of the detecting area  214 . In the present embodiment, the first calculating method can be, but not limited to, a gravity center calculating method, and the second calculating method can be, but not limited to, a medium center calculating method. 
     For the first image detecting component  232   a , the dark point locating at the first section  2031  of the third sidewall  203  is generally caused by the light blocking object in a region  214   a  (i.e., the conventional insensitive area) of the detecting area  214 . Because the position of the dark point caused by the light blocking object in the region  214   a  is calculated using the gravity center calculating method rather than the medium center calculating method, the accuracy of determining the position of the light blocking object can be improved. Additionally, for the first image detecting component  232   a , the dark point formed on the connecting portion of fourth sidewall  204  and the third sidewall  203  locates at the fourth sidewall  204  and the second section  2032  of the third sidewall  203 . In the present embodiment, because the position of the dark point located at the fourth sidewall  204  and the second section  2032  of the third sidewall  203  is calculated using the medium center calculating method rather than the gravity center calculating method, the accuracy of determining the position of the light blocking object can be improved. 
     Additionally, the dividing method of the pixels  235  of the second image detecting component  232   b  is similar to the dividing method of the pixels  235  of the first image detecting component  232   a  as above-mentioned and is not described here. Correspondingly, the first sidewall  201  includes a third section (not labeled) connected to the second sidewall  202  and a fourth section (not labeled) connected to the fourth sidewall  204 . The first group G 1  of the second image detecting component  232   b  is configured for detecting the third section, and the second group G 2  of the second image detecting component  232   b  is configured for detecting the fourth sidewall  204  and the fourth section of the first sidewall  201 . The calculating method of the position of the dark point detected by the first group G 1  and the second group G 2  of the second image detecting component  232   b  is similar to the calculating method of the first image detecting component  232   a  as above-mentioned and is not described here. 
     As aforesaid description, in the present embodiment, in the locating method of the optical touch device  200 , the pixels  235  of each of the first image detecting component  232   a  and the second image detecting component  232   b  are divided into a number of groups. When the pixels  235  of one of the groups detect the dark point caused by the light blocking object in the detecting area  214 , a suitable calculating method is used to calculate the position of the dark point. Thus, the accurate position of the dark point can be calculated, thereby improving the accuracy of locating the light blocking object. 
       FIG. 5  is a schematic view of a locating method of an optical touch device applied to an optical touch device in accordance with a second embodiment of the present invention. Referring to  FIG. 5 , the locating method is similar to the locating method in the first embodiment except that the pixels  235  of each of the first image detecting component  232   a  and the second image detecting component  232   b  are divided into three groups. The second image detecting component  232   b  is an example here to describe the details. The pixels  235  of the second image detecting component  232   b  are divided into a first group G 1 , a second group G 2  and a third group G 3 . The third group G 3  is located between the first group G 1  and the second group G 2 . 
     Because the pixels  235  of the second image detecting component  232   b  are divided into the first group G 1 , the second group G 2  and the third group G 3 , the first sidewall  201  is divided into a third section  2013  connected to the second sidewall  202 , a fourth section  2014  connected to the fourth sidewall  204  and a sixth section  2016  connected between the third section  2013  and the fourth section  2014  correspondingly. The dark point locating at the third section  2013  of the first sidewall  201  can be detected by the first group G 1  of the second image detecting component  232   ab . The dark point locating at the fourth sidewall  204  and the fourth section  2014  of the first sidewall  201  can be detected by the second group G 2  of the second image detecting component  232   b . The dark point locating at the sixth section  2016  of the first sidewall  201  can be detected by the third group G 3  of the second image detecting component  232   b . The connecting portion of the fourth sidewall  204  and the fourth section  2014  of the first sidewall  201  is a corner area of the detecting area  214 . The corner area faces to the second image detecting component  232   b . In other words, the field of view of the second group G 2  of the second image detecting component  232   b  covers the corner area of the detecting area  214 . 
     Similar to the first embodiment, when the first group G 1  detects the dark point caused by the light blocking object in the detecting area  214 , the position of the dark point is calculated using the first calculating method, thereby determining the position of the light blocking object. When the second group G 2  detects the dark point caused by the light blocking object in the detecting area  214 , the position of the dark point is calculated using the second calculating method, thereby determining the position of the light blocking object. In addition, when the third group G 3  detects the dark point caused by the light blocking object in the detecting area  214 , the position of the dark point is calculated using a third calculating method, thereby determining the position of the light blocking object. 
     In the present embodiment, the first calculating method can be, but not limited to, a gravity center calculating method, and the second calculating method can be, but not limited to, a medium center calculating method. In addition, the third calculating method is, for example, a combination of the first calculating method and the second calculating method. In detail, the third calculating method includes the following steps. 
     Firstly, the position of the dark point caused by the light blocking object is calculated using the first calculating method and the second calculating method respectively to obtain a first value and a second value. For example, when the first group G 3  of the second image detecting component  232   b  detects the dark point caused by the light blocking object in the detecting area  214 , the position of the dark point is calculated using the first calculating method (e.g., the gravity center calculating method), thereby obtaining the first value Ci and the position of the dark point is also calculated using the second calculating method (e.g., the medium center calculating method), thereby obtaining the second value Cm. The first value Ci represents a calculated result using the first calculating method, and the second value Cm represents a calculated result using the second calculating method. 
     Next, the first value Ci is multiplied by a first weight a (0&lt;α&lt;1) to obtain a third value Ci′, and the second value Cm is multiplied by a second weight (1−α) to obtain a fourth value Cm′. The first weight a can be a constant. In other words, the first weight α is identical when any of the pixels  235  of the third group G 3  detects the dark point. In another embodiment, the first weight a can be a variable value. That is, when the different pixels  235  of the third group G 3  detect the dark point caused by the light blocking object, the first weight α is different correspondingly. For example, when the pixels  235  of the third group G 3  detecting the dark point caused by the light blocking object become closer to the first group G 1 , the first weight a becomes lager and the second weight (1−α) becomes smaller correspondingly. 
     Then, the third value Ci′ and the fourth value Cm′ are added together to obtain the position of the dark point, thereby determining the position of the light blocking object. 
     In the present embodiment, the dividing method of the pixels  235  of the first image detecting component  232   a  is similar to the dividing method of the pixels  235  of the second image detecting component  232   b  as above-mentioned and is not described here. Correspondingly, the third sidewall  203  includes a first section (not labeled) connected to the second sidewall  202 , a second section (not labeled) connected to the fourth sidewall  204  and a fifth section (not labeled) connected between the first section and the second section. The first group G 1  of the first image detecting component  232   a  is configured for detecting the first section of the third sidewall  203 , the second group G 2  of the first image detecting component  232   a  is configured for detecting the fourth sidewall  204  and the second section of the third sidewall  203  and the third group G 3  of the first image detecting component  232   a  is configured for detecting the fifth section of the third sidewall  203 . The calculating method of the position of the dark point detected by the first group G 1 , the second group G 2  and the third group G 3  of the first image detecting component  232   a  is similar to the calculating method of the second image detecting component  232   b  as above-mentioned and is not described here. 
       FIG. 6  is a schematic view of a locating method of an optical touch device applied to an optical touch device in accordance with a third embodiment of the present invention. Referring to  FIG. 6 , the locating method in the third embodiment is similar to the locating method in the second embodiment except that the pixels  235  of each of the first image detecting component  232   a  and the second image detecting component  232   b  are divided into four groups. The first image detecting component  232   a  is an example here to describe the details. The pixels  235  of the first image detecting component  232   a  are divided into a first group G 1 , a second group G 2 , a third group G 3  and a fourth group G 4 . The third group G 3  is located between the first group G 1  and the second group G 2 , and the second group G 2  is located between the third group G 3  and the fourth group G 4 . 
     Because the pixels  235  of the first image detecting component  232   a  are divided into the first group G 1 , the second group G 2 , the third group G 3  and the fourth group G 4 , the third sidewall  203  is divided into a first section  2031  connected to the second sidewall  202 , a second section  2032  connected to the fourth sidewall  204  and a fifth section  2035  connected between the first section  2031  and the second section  2032  correspondingly. The fourth sidewall  204  is divided into a section  2041  adjacent to the third sidewall  203  and a section  2042  adjacent to the first sidewall  201  correspondingly. The dark point locating at the first section  2031  of the third sidewall  203  can be detected by the first group G 1  of the first image detecting component  232   a . The dark point locating at the second section  2032  of the third sidewall  203  and the section  2041  adjacent to the third sidewall  203  of the fourth sidewall  204  and can be detected by the second group G 2  of the first image detecting component  232   a . The dark point locating at the fifth section  2035  of the third sidewall  203  can be detected by the third group G 3  of the first image detecting component  232   a . The dark point locating at the section  2042  adjacent to the first sidewall  201  of the fourth sidewall  204  and can be detected by the second group G 4  of the first image detecting component  232   a . The connecting portion of the section  2041  adjacent to the third sidewall  203  of the fourth sidewall  204  and the second section  2032  of the third sidewall  203  is a corner area of the detecting area  214 . The corner area faces to the first image detecting component  232   a . In other words, the field of view of the second group G 2  of the first image detecting component  232   a  covers the corner area of the detecting area  214 . 
     Similar to the second embodiment, when the first group G 1  detects the dark point caused by the light blocking object in the detecting area  214 , the position of the dark point is calculated using the first calculating method, thereby determining the position of the light blocking object. When the second group G 2  detects the dark point caused by the light blocking object in the detecting area  214 , the position of the dark point is calculated using the second calculating method, thereby determining the position of the light blocking object. When the third group G 3  detects the dark point caused by the light blocking object in the detecting area  214 , the position of the dark point is calculated using the third calculating method, thereby determining the position of the light blocking object. In addition, when the fourth group G 4  detects the dark point caused by the light blocking object in the detecting area  214 , the position of the dark point is calculated using either the first calculating method or the third calculating method, thereby determining the position of the light blocking object. 
     In the present embodiment, the first calculating method, the second calculating method and the third calculating method are similar to those method described in the second embodiment. The dividing method of the pixels  235  of the second image detecting component  232   b  is similar to the dividing method of the pixels  235  of the first image detecting component  232   a  as above-mentioned and is not described here. Correspondingly, the first sidewall  201  includes a third section (not labeled) connected to the second sidewall  202 , a fourth section (not labeled) connected to the fourth sidewall  204  and a sixth section (not labeled) connected between the third section and the fourth section. The first group G 1  of the second image detecting component  232   b  is configured for detecting the third section, the second group G 2  of the second image detecting component  232   b  is configured for detecting a section adjacent to the first sidewall  201  of the fourth sidewall  204  and the fourth section of the first sidewall  201 , the third group G 3  of the second image detecting component  232   b  is configured for detecting the sixth section, and the fourth group G 4  of the second image detecting component  232   b  is configured for detecting a section adjacent to the third sidewall  203  of the fourth sidewall  204 . The calculating method of the position of the dark point detected by the first group G 1 , the second group G 2 , the third group G 3  and the fourth group G 4  of the second image detecting component  232   b  is similar to the calculating method of the first image detecting component  232   a  as above-mentioned and is not described here. 
     In summary, in the locating method and the optical touch device of the present invention, the pixels of each of the image detecting components are divided into a number of groups. When the pixels of one of the groups detect the dark point caused by the light blocking object, a suitable calculating method is used to calculate the position of the dark point. For example, the position of the dark point caused by the light blocking object in the conventional insensitive area is calculated using the gravity center calculating method. For another example, the position of the dark point located at the connecting portion of two neighboring sidewalls is calculated using the medium center calculating method. Thus, the accurate position of the dark point can be calculated, thereby improving the accuracy of locating the light blocking object. 
     The above description is given by way of example, and not limitation. Given the above disclosure, one skilled in the art could devise variations that are within the scope and spirit of the invention disclosed herein, including configurations ways of the recessed portions and materials and/or designs of the attaching structures. Further, the various features of the embodiments disclosed herein can be used alone, or in varying combinations with each other and are not intended to be limited to the specific combination described herein. Thus, the scope of the claims is not to be limited by the illustrated embodiments.