Patent Publication Number: US-2010117992-A1

Title: Touch System and Method for Obtaining Position of Pointer Thereof

Description:
BACKGROUND 
     1. Technical Field 
     The present invention generally relates to the field of touch technology and, more particularly, to a touch system and a method for obtaining a position of a pointer thereof. 
     2. Description of the Related Art 
     Referring to  FIG. 1 , a conventional touch system is shown. The touch system  100  includes a panel  110 , image sensing apparatuses  120 ,  130  and a processing circuit  140 . The panel  110  has a touch surface  112  and a shape of the touch surface  112  is a rectangle. The image sensing apparatuses  120  and  130  both are located at a same boundary of the touch surface  112  and disposed at different comers of the touch surface  112 , so that sensing areas of the two image sensing apparatuses cooperatively cover the touch surface  112 . In addition, the image sensing apparatuses  120  and  130  both are coupled to the processing circuit  140 . 
     When a pointer  150  touches (or approaches) the touch surface  112 , the image sensing apparatuses  120  and  130  can sense the pointer  150  respectively along the sensing lines  162  and  164  and transmit acquired images to the processing circuits  140 . Subsequently, the processing circuit  140  finds out the sensing lines  162  and  164  according to the received images and calculate a coordinate value of the pointer  150  according to the two sensing lines. Thus, the detection of the coordinate value of the pointer  150  is realized. 
     However, since the processing circuit  140  detects the coordinate value of the pointer  150  only from the images acquired by the image sensing apparatuses  120  and  130 , the detected coordinate value has a relative large error, resulting in the coordinate positioning for the touch system  100  is not accurate. 
     BRIEF SUMMARY 
     The present invention relates to a touch system can achieve a relatively accurate coordinate positioning. 
     The present invention further relates to a method for obtaining a position of a pointer, adapted for a touch system having at least three image sensing apparatuses. 
     The present invention provides a touch system. The touch system includes a touch surface, at least three image sensing apparatuses and a processing circuit. A shape of the touch surface is a quadrilateral. The image sensing apparatuses are disposed at different corners of the touch surface and sensing areas of the image sensing apparatuses cooperatively cover the touch surface. The processing circuit is coupled to each of the image sensing apparatuses. When a pointer approaches the touch surface, the processing circuit takes each two of the image sensing apparatuses as one pair and detects a coordinate value of the pointer from images acquired by each pair of image sensing apparatuses, and after at least two coordinate values have been detected, the processing circuit calculates a mean value of coordinate values of the pointer according to the detected coordinate values. 
     The present invention further provides a method for obtaining a position of a pointer. The method is adapted for a touch system including a quadrilateral touch surface and at least three image sensing apparatuses. The image sensing apparatuses are disposed at different corners of the touch surface and sensing areas of the image sensing apparatuses cooperatively cover the touch surface. In this method, when a pointer approaches the touch surface, taking each two of the image sensing apparatuses as one pair and detecting a coordinate value of the pointer from images acquired by each pair of image sensing apparatuses. Subsequently, after at least two coordinate values have been detected, calculating the mean value of coordinate values of the pointer according to the detected coordinate values. 
     In one embodiment, the approach of calculating the mean value of coordinate values of the pointer is by way of performing arithmetic, geometric or harmonic means. 
     In one embodiment, the mean value of coordinate values of the pointer is calculated according to N coordinate values after the N coordinate values have been detected, the N is the amount of all possible pairs each of which is constituted by two of the image sensing apparatuses. 
     The present invention configures at least three image sensing apparatuses in a touch system, takes each two of the image sensing apparatuses as one pair and detects a coordinate value of a pointer from images acquired by each pair of image sensing apparatuses; and after at least two coordinate values have been detected, calculates the mean value of coordinate values of the pointer according to the detected coordinate values. Accordingly, compared with the prior art, the touch system in accordance with the present invention can achieve more accurate coordinate positioning. 
    
    
     
       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 touch system. 
         FIG. 2  is a schematic view of a touch system in accordance with an embodiment of the present invention. 
         FIG. 3  shows the pointer is situated on a diagonal line of the touch surface in accordance with the embodiment of the present invention. 
         FIG. 4  is a schematic view of a touch system in accordance with another embodiment of the present invention. 
         FIG. 5  is a trimetric view of a touch system in accordance with still another embodiment of the present invention. 
         FIG. 6  shows an image sensing apparatus adapted for matching with the reflector of  FIG. 5  in use. 
         FIG. 7  is a schematic view of an image acquired by the image sensing apparatus of  FIG. 5 . 
         FIG. 8  shows primary steps of a method for obtaining a position of a pointer, in accordance with an embodiment of the present invention. 
         FIG. 9  is a schematic diagram of a touch system detecting a coordinate value of a pointer. 
         FIG. 10  is a schematic diagram of obtaining a linear equation of a sensing line. 
         FIG. 11  is a schematic diagram of obtaining a linear equation of a sensing line. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIG. 2 , a touch system in accordance with an embodiment of the present invention is shown. The touch system  200  includes a panel  210 , image sensing apparatuses  220 ,  230 ,  240  and  250  and a processing circuit  260 . The panel  210  has a touch surface  212  of which a shape is a quadrilateral. In this embodiment, the shape of the touch surface  212  is a rectangle. The image sensing apparatuses  220 ,  230 ,  240  and  250  are disposed at different corners of the touch surface  212 , so that sensing areas of the four image sensing apparatuses  220 ,  230 ,  240  and  250  cooperatively cover the touch surface  212 . In addition, the image sensing apparatuses  220 ,  230 ,  240  and  250  all are coupled to the processing circuit  260 . 
     When a pointer  270  touches (or approaches) the touch surface  212  and the image sensing apparatuses  220 ,  230 ,  240  and  250  can sense the pointer  270 , the four image sensing apparatuses respectively transmit images acquired by themselves to the processing circuit  260 . Subsequently, the processing circuit  260  takes each two of the image sensing apparatuses  220 ,  230 ,  240  and  250  as one pair and detects a coordinate value of the pointer  270  from the images acquired by each pair of image sensing apparatuses. After six coordinate values of the pointer  270  have been detected, the mean value of coordinate values of the pointer  270  is calculated according to the six detected coordinate values. The mean value is determined as the coordinate value of the pointer position. The above-mentioned amount of six is the amount of all possible pairs each of which is constituted by two of the four image sensing apparatuses, and detailed description will be described as follows. 
     Assuming that the coordinate value of the pointer  270  detected by the processing circuit  260  from the images acquired by the image sensing apparatuses  220  and  230  is (x 1 , y 1 ), the coordinate value of the pointer  270  detected by the processing circuit  260  from the images acquired by the image sensing apparatuses  230  and  250  is (x 2 , y 2 ), the coordinate value of the pointer  270  detected by the processing circuit  260  from the images acquired by the image sensing apparatuses  250  and  240  is (x 3 , y 3 ), the coordinate value of the pointer  270  detected by the processing circuit  260  from the images acquired by the image sensing apparatuses  240  and  220  is (x 4 , y 4 ), the coordinate value of the pointer  270  detected by the processing circuit  260  from the images acquired by the image sensing apparatuses  220  and  250  is (x 5 , y 5 ), and the coordinate value of the pointer  270  detected by the processing circuit  260  from the images acquired by the image sensing apparatuses  230  and  240  is (x 6 , y 6 ), the processing circuit  260  will calculate the mean value of coordinate values of the pointer  270  according to the six detected coordinate values. 
     The processing circuit  260  calculates the mean value of coordinate values of the pointer  270  by way of performing arithmetic, geometric, harmonic means or other algorithm. In terms of the arithmetic means, the mean value of the six coordinate values on X-axis direction and the mean value of the six coordinate values on Y-axis direction respectively are expressed by the following equations (1) and (2): 
         x   e =( x   1   +x   2   +x   3   +x   4   +x   5   +x   6 )/6   (1) 
         y   e =( y   1   +y   2   +y   3   +y   4   +y   5   +y   6 )/6   (2) 
     where: x e  and y e  respectively are the mean value on X-axis direction and the mean value on Y-axis direction, and the mean value of coordinate values of the pointer  270  is (x e , y e ) correspondingly. In addition, in terms of the geometric means, the mean value on X-axis direction and the mean value on Y-axis direction of the six coordinate values respectively are expressed by the following equations (3) and (4): 
         x   g = 6 √{square root over ( x   1   ×x   2   ×x   3   ×x   4   ×x   5   ×x   6 )}  (3) 
         y   g = 6 √{square root over ( y   i   ×y   2   ×y   3   ×y   4   ×y   5   ×y   6 )}  (4) 
     where: x g  and y g  respectively are the mean value on X-axis direction and the mean value on Y-axis direction, and the mean value of coordinate values of the pointer  270  is (x g , y g ) correspondingly. Moreover, in terms of the harmonic means, the mean value on X-axis direction and the mean value on Y-axis direction of the six coordinate values are respectively expressed by the following equations (5) and (6): 
         x   h =6/((1 /x   1 )+(1 /x   2 )+(1 /x   3 )+(1 /x   4 )+(1 x   5 )+(1 /x   6 ))   (5) 
         y   h =6/((1 /y   1 )+(1 /y   2 )+(1 /y   3 )+(1 /y   4 )+(1 /y   5 )+(1 y/   6 ))   (6) 
     where: x h  and y h  respectively are the mean value on X-axis direction and the mean value on Y-axis direction, and the mean value of coordinate values of the pointer  270  is (x h , y h ) correspondingly. 
     Accordingly, since the processing circuit  260  can detect six coordinate values of the pointer  270  from the image acquired by the six pairs of image sensing apparatuses and calculates out the mean value of the six coordinate values, so that the positioning of the pointer  270  exists a relatively small error, the coordinate positioning for the present touch system is more accurate with respect to that of the prior art. 
     Although in the above-mentioned embodiment, the effect of reducing positioning error is achieved by detecting six coordinate values of the pointer  270  from the images acquired by six pairs of image sensing apparatuses and then calculating the mean value of the six coordinate values, a similar effect also can be achieved by detecting at least two coordinate values of the pointer  270  and then calculating the mean value of the at least two coordinate values. Moreover, the amount of the image sensing apparatuses is not limited to four, as long as the touch system  200  has at least three image sensing apparatuses, the mean value of coordinate values of the pointer  270  still can be calculated. 
     It is noted that, in the framework as illustrated in  FIG. 2 , when the approach of the processing circuit  260  detecting a coordinate value of the pointer  270  from images acquired by one pair of image sensing apparatuses is by way of calculating an intersection point of two sensing lines of the pair of image sensing apparatuses, the situation illustrated in  FIG. 3  ought to be taken in consideration.  FIG. 3  shows the pointer  270  situates on a diagonal line of the touch surface  212 . As illustrated in  FIG. 3 , in this situation, the sensing line  282  of the image sensing apparatus  220  and the sensing lines  284  of the image sensing apparatus  250  have no intersection point. Accordingly, when the processing circuit  260  calculates the mean value of coordinate values of the pointer  270 , the images acquired by the pair of image sensing apparatuses  220 ,  250  would be excluded. 
     Likewise, if the pointer  270  illustrated in  FIG. 3  not only situates on the diagonal line between the image sensing apparatuses  220  and  250 , but also the diagonal line between the image sensing apparatuses  230  and  240 , when the processing circuit  260  calculates the mean values of coordinate values of the pointer  270 , the images acquired by the two pairs of image sensing apparatuses would be excluded correspondingly. In a similar way, even if the touch system  200  only has three image sensing apparatuses or has more than four image sensing apparatuses, the above-mentioned exceptional situation also ought to be taken in consideration. 
       FIG. 4  is a schematic view of a touch system in accordance with another embodiment of the present invention. A difference of the touch system  400  as illustrated in  FIG. 4  with respect to the touch system  200  as illustrated in  FIG. 2  is that the touch system  400  further includes four subsidiary processing circuits having an amount identical with that of the image sensing apparatuses  220 ,  230 ,  240  and  250  and respectively labeled by  402 ,  404 ,  406  and  408 . Each of the subsidiary processing circuits  402 ,  404 ,  406  and  408  is coupled between one of the image sensing apparatuses and the processing circuit  260  and for preprocessing the image data acquired by the image sensing apparatus, to facilitate the processing circuit  260  to detect the coordinate value of the pointer  270  according to the preprocessed image data from the subsidiary processing circuit. 
       FIG. 5  is a trimetric view of a touch system in accordance with still another embodiment of the present invention. Referring to  FIG. 5 , the touch system  500  has a structural configuration similar to that of the touch system  200  as illustrated in  FIG. 2  and further includes a reflector  502 . The reflector  502  is disposed on the touch surface  212  and surrounds the touch surface  212 . An inner margin of the reflector  502  has a reflective material  504 , e.g., a retro-reflective material. 
       FIG. 6  illustrates an image sensing apparatus adapted for matching with the reflector  502  of  FIG. 5  in use. Referring to  FIG. 6 , the image sensing apparatus  600  includes an infrared illumination device  602 , an infrared filtering device  604  only allowing infrared light to pass therethrough, and a photosensor  606 . The photosensor  606  acquires an image of the touch surface through the infrared filtering device  604 . In addition, the infrared illumination device  602  can include an infrared light emitting diode (LED), and the infrared filtering device  604  can be an infrared-pass (IR-pass) filter. 
     Assuming that the image sensing apparatus  240  of  FIG. 5  uses the structural configuration of the image sensing apparatus  600  in  FIG. 6  and the infrared illumination device normally operates, an image acquired by the image sensing apparatus  240  is the same as illustrated in  FIG. 7 .  FIG. 7  is a schematic view of the image acquired by the image sensing apparatus  240  of the  FIG. 5 . In  FIG. 7 , the label  700  represents an image sensing window of the image sensing apparatus  240 . The label  702  represents a bright zone which has a relatively high brightness and is formed on the image by the rays reflected by the reflective material  504  of the reflector  502 , and the bright zone  702  is a main sensing area. The label  704  represents a black strip caused by the pointer  270 . Therefore, the reflective material  504  is used as a main background of the pointer  270  when the image sensing apparatus  240  acquires the image of the touch surface  212 , so as to highlight the position of the pointer  270 . 
     According to the teachings of the above-mentioned embodiments, as illustrated in  FIG. 8 , a method for obtaining a position of a pointer can be extracted therefrom.  FIG. 8  illustrates primary steps of a method for obtaining a position of a pointer in accordance with an embodiment of the present invention. The present method is adapted for a touch system having a quadrilateral touch surface and at least three image sensing apparatuses. The image sensing apparatuses are disposed at different comers of the touch surface and sensing areas of the image sensing apparatuses cooperatively cover the touch surface. In the present method, when a pointer approaches the touch surface, each two of the image sensing apparatuses are taken as one pair and a coordinate value of the pointer is detected from images acquired by each pair of image sensing apparatuses (as shown in step S 802 ). Subsequently, after at least two coordinate values have been detected, the mean value of coordinate values of the pointer is calculated according to the detected coordinate values (as shown in step S 802 ). 
     Of course, as illustrated in the foregoing embodiments, the approach for calculating the mean value of the coordinate values is by way of performing arithmetic, geometric or harmonic means. In addition, the mean value of the coordinate values is calculated after N coordinate values of the pointer have been detected and according to the N coordinate values. The N is the amount of all possible pairs each of which is constituted by two of all the image sensing apparatuses. 
     It is indicated that, there are various different methods can be used to detect a coordinate value of the pointer according to images acquired by two image sensing apparatuses, for example, the method is proposed by U.S. Pat. No. 4,782,328. Furthermore, another method will be described as follows so as to give the system designer much more choices. Referring to  FIG. 9 , being a schematic diagram of the touch system detecting a coordinate value of the pointer. As illustrated in  FIG. 9 , the labels  220  and  230  represent image sensing apparatuses, the label  212  represents a quadrilateral touch surface, and the label  270  represents a pointer. The image sensing apparatuses  220  and  230  sense the pointer  270  respectively along sensing lines  902  and  904 . Accordingly, as long as linear equations of the two sensing lines are obtained, an intersection point of the two sensing lines can be obtained as the coordinate value of the pointer  270 . More detailed description will be described with reference to  FIGS. 10 and 11 . 
       FIG. 10  is a schematic diagram of obtaining the linear equation of the sensing line  902 . As illustrated in  FIG. 10 , in order to obtain the linear equation of the sensing line  902 , coordinate values of points A and A′ are needed to be firstly acquired. Since the size of the touch surface  212  is fixed, the coordinate values of the points A, B, C and D are known while the X-axis coordinate value of point A′ is unknown. Therefore, an imaginary line  906  can be provided between the points B and D, and an intersection point of the sensing line  902  with the imaginary line  906  is point Z. Accordingly, line sections  AB ,  BZ  and  ZA  constitute a triangle, and line sections  DA′ ,  A′Z  and  ZD  constitute another triangle. The two triangles are similar triangles and have a proportional relationship. Subsequently, since a resolution of the image sensing apparatus  220  is known, a length ratio of the line sections  BZ  and  ZD  of the imaginary line  906  can be acquired according to the pixel amounts of the respective line sections  BZ  and  ZD . Since the line sections  AB  and  DA′  have the same length ratio with respect to the length ratio of the line sections  BZ  and  ZD , and the length of the line section  AB  is known, so that the length of the line section  DA′  can be worked out and the X-axis coordinate value of the point A′ is obtained correspondingly. Finally, the linear equation of the sensing line  902  can be obtained according to the coordinate values of the points A and A′. 
     Likewise, as illustrated in  FIG. 11 , the linear equation of the sensing line  904  can be obtained by using a similar method as above described.  FIG. 11  is a schematic diagram of obtaining the linear equation of the sensing line  904 . Referring to  FIG. 11 , the label  908  represents an imaginary line, point Z′ is the intersection point of the sensing line  904  and the imaginary line  908 . Therefore, line sections  AB ,  BZ′  and  Z′A  constitute a triangle, and line sections  B′C ,  CZ′  and  Z′B′  constitute another triangle. The two triangles also are similar triangles and have a proportional relationship. Subsequently, a length ratio of the line sections  CZ′  and  Z′A  is acquired, a length of the line section  B′C  then can be worked out and correspondingly the X-axis coordinate value of the point B′ is obtained. Accordingly, the linear equation of the sensing line  904  can be obtained according to the coordinate values of points B and B′. After the linear equations of the sensing lines  902  and  904  are obtained, the intersection point of the sensing lines  902  and  904  can be acquired. 
     In summary, the present invention configures at least three image sensing apparatuses in a touch system, takes each two of the image sensing apparatuses as one pair and detects a coordinate value of the pointer from images acquired by each pair of image sensing apparatuses; after at least two coordinate values have been detected, calculates the mean value of coordinate values of the pointer according to the detected coordinate values. Accordingly, compared with the prior art, the touch system in accordance with the present invention can achieve more actuate coordinate positioning. 
     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.