Abstract:
A single-layer multi-touch sensing electrode group of a touch panel includes a plurality of first electrodes, and a plurality of second electrodes including a plurality of first sub-electrodes and a plurality of second sub-electrodes that are alternately arranged. Each of the first sub-electrodes includes a first body and a first extension portion. A first accommodating space is formed between the first body and the first extension portion. Each of the second sub-electrodes includes a second body and a plurality of second extension portions. At least one second accommodating space is formed among the second extension portions. Each of first accommodating spaces accommodates one of the second extension portions, and the second accommodating spaces accommodate the first bodies. A plurality of mutual capacitance changes between the first electrodes and the second electrodes are for calculating a position of a touch event.

Description:
This application claims the benefit of Taiwan application Serial No. 104108604, filed Mar. 18, 2015, the subject matter of which is incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The invention relates in general to a single-layer multi-touch sensing electrode group, and more particularly to a single-layer multi-touch sensing electrode group of a touch panel for enhancing linearity and accuracy of the touch panel. 
     Description of the Related Art 
       FIG. 1  shows a conventional single-layer multi-touch sensing electrode group. The sensing electrode group can be divided into two kinds—transmitting electrodes and receiving electrodes. As shown in  FIG. 1 , the transmitting electrodes include a sensing electrode  105 , a sensing electrode  110 , a sensing electrode  120  and a sensing electrode  130 ; the receiving electrodes include a sensing electrode  140 , a sensing electrode  150 , a sensing electrode  160  and a sensing electrode  170 . In general, the transmitting electrodes are equal in size. That is, the sensing electrode  105 , the sensing electrode  110 , the sensing electrode  120  and the sensing electrode  130  have equal areas. Further, the receiving electrodes are also equal in size. That is, the sensing electrode  140 , the sensing electrode  150 , the sensing electrode  160  and the sensing electrode  170  have equal areas. The sensing electrode  105 , the sensing electrode  110 , the sensing electrode  120  and the sensing electrode  130  are directly connected to a control unit (not shown) by connecting lines. The receiving electrodes may further be divided into two types—a first type (an electrode denoted R 1  in  FIG. 1 ), including the sensing electrode  140  and the sensing electrode  160  connected by a connecting line  115 , and a second type (an electrode denoted R 2  in  FIG. 1 ), including the sensing electrode  150  and the sensing electrode  170  connected by a connecting line  125 . It should be noted that, the number of electrodes of a touch panel is not limited to the exemplary values in the diagram, and both of the transmitting electrodes and the receiving electrodes may be further extended towards the lower part of the diagram to include more electrodes. The receiving electrodes of the first type are connected to the control unit from the sensing electrode  140  via the connecting lines, and the receiving electrodes of the second type are similarly connected to the control unit from the sensing electrode  150  via the connecting lines. 
     When the touch panel detects a touch event, the control unit transmits a signal to the transmitting electrodes (the sensing electrode  105 , the sensing electrode  110 , the sensing electrode  120  and the sensing electrode  130 ), and the position of the touch event is calculated according to the capacitance changes detected between the receiving electrodes and the transmitting electrodes. For example, when a touch event  180  occurs in a region among the sensing electrode  110 , the sensing electrode  140  and the sensing electrode  150  (assuming that the position of the touch event  180  in the y direction is between the sensing electrode  140  and the sensing electrode  150 ), the sensing electrode  140  and the sensing electrode  150  theoretically sense capacitance changes having equal values. Thus, the control unit may calculate the position of the touch event. However, the proximity of the touch event further includes the connecting line  115  in addition to the sensing electrode  140  and the sensing electrode  150 . The connecting line  115  affects the distribution of electric charge and further affects mutual capacitance changes between the sensing electrode  110  and the sensing electrode  140  as well between the sensing electrode  110  and the sensing electrode  150 . More specifically, as the connecting line  115  is connected to the sensing electrode  140 , the connecting line  115  may be regarded as an extension of the sensing region of the sensing electrode  140 . As such, the sensing electrode  140  not only reacts more sensitively to the touch event  180  but also hinders the sensing electrode  150  from sensing the touch event  180  to certain extent. As a result, the touch position of the touch event  180  determined by the control unit is higher than (closer to the sensing electrode  140 ) the actual position, hence affecting the linearity and accuracy of the touch panel. 
     SUMMARY OF THE INVENTION 
     The invention is directed to a pattern of sensing electrode group of a touch panel to improve the linearity and accuracy of the touch panel. 
     The present invention discloses a single-layer multi-touch sensing electrode group of a touch panel. The single-layer multi-touch sensing electrode group includes a plurality of first electrodes, and a plurality of second electrodes including a plurality of first sub-electrodes and a plurality of second sub-electrodes. The first sub-electrodes and the second sub-electrodes are alternately arranged. The first sub-electrodes are connected to one another, and the second sub-electrodes are connected to one another. Each of the first sub-electrodes includes a body and a first extension portion. A first accommodating space is formed between the first body and the first extension portion. Each of the second sub-electrodes includes a second body and a plurality of second extension portions. At least one second accommodating space is formed between the second extension portions. Each of the first accommodating spaces accommodates one of the second extension portions. The second accommodating spaces accommodate the first bodies. A plurality of mutual capacitance changes between the first electrodes and the second electrodes are for calculating a position of a touch event. 
     The present invention further discloses a single-layer multi-touch sensing electrode group of a touch panel. The single-layer multi-touch sensing electrode group includes a plurality of first electrodes, and a plurality of second electrodes including a plurality of first sub-electrodes and a plurality of second sub-electrodes. The first sub-electrodes and the second sub-electrodes are alternately arranged. Each of the first sub-electrodes includes a body and a first extension portion. An accommodating space is formed between the first body and the first extension portion. Each of the second sub-electrodes includes a second body ad a plurality of second extension portions. The accommodating spaces accommodate the second extension portions. A plurality of mutual capacitance changes between the first electrodes and the second electrodes are for calculating a position of a touch event. 
     The present invention further discloses a single-layer multi-touch sensing electrode group of a touch panel. The single-layer multi-touch sensing electrode group includes: a plurality of first electrodes, arranged along a distribution direction; a plurality of second electrodes, arranged parallel to the distribution direction, including a plurality of first sub-electrodes and a plurality of second sub-electrodes, the first sub-electrodes and the second sub-electrodes being alternately arrange, the first sub-electrodes connected to one another, the second sub-electrodes connected to one another; a plurality of first connecting lines, located between the first sub-electrodes and the second sub-electrodes, connecting the first sub-electrodes; a plurality of second connecting lines, connecting the second sub-electrodes; and a plurality of unit electrodes, unapplied by any electric potential, located between the first sub-electrodes and the second sub-electrodes. The area of each of the first sub-electrodes is smaller than the area of each of the second sub-electrodes. A plurality of mutual capacitance changes between the first electrodes and the second electrodes are for calculating a position of a touch event. 
     In the single-layer multi-touch sensing electrode group of a touch panel of the present invention, by changing the shape of sensing electrode, the sensing electrode is allowed to extend to main sensing regions of adjacent sensing electrodes to expand the sensing range. Compared to a conventional touch panel, the touch panel of the present invention provides better linearity and accuracy. 
     The above and other aspects of the invention will become better understood with regard to the following detailed description of the preferred but non-limiting embodiments. The following description is made with reference to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a conventional single-layer multi-touch sensing electrode group of a touch panel; 
         FIG. 2  shows a single-layer multi-touch sensing electrode group of a touch panel according to an embodiment of the present invention; 
         FIG. 3A  and  FIG. 3B  are enlarged views of the sensing electrodes of the embodiment in  FIG. 2  of the present invention; 
         FIG. 4  is a partial enlarged view of the sensing electrode group of the embodiment in  FIG. 2  of the present invention; 
         FIG. 5  shows a single-layer multi-touch sensing electrode group of a touch panel according to another embodiment of the present invention; 
         FIG. 6A  and  FIG. 6B  are enlarged views of the sensing electrodes of the embodiment in  FIG. 5  of the present invention; 
         FIG. 7  shows a single-layer multi-touch sensing electrode group of a touch panel according to yet another embodiment of the present invention; 
         FIG. 8  shows a partial view of the sensing electrode group and a curve diagram of touch sensing values corresponding to the embodiment in  FIG. 2  of the present invention; 
         FIG. 9  shows a partial view of the sensing electrode group and a curve diagram of touch sensing values corresponding to the embodiment in  FIG. 7  of the present invention; and 
         FIG. 10  shows a single-layer multi-touch sensing electrode group of a touch panel according to yet another embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The disclosure of the present invention includes a sensing electrode group of a touch panel for enhancing the accuracy and linearity of the touch panel. In possible implementation, one skilled person in the art may choose equivalent elements to implement the present invention based on the disclosure of the application. That is, the implementation of the present invention is not limited by the embodiments described in the disclosure. 
       FIG. 2  shows a single-layer multi-touch sensing electrode group of a touch panel according to an embodiment of the present invention. The touch panel includes at least one single-layer multi-touch sensing electrode group, and may further include other electrodes for some purposes, such as electrode at the fringe of the touch panel for fringe calibration. A sensing electrode  105 , a sensing electrode  110 , a sensing electrode  120  and a sensing electrode  130  are transmitting electrodes, and are rectangular in shape and arranged along the y direction shown in the diagram to become connected via connecting lines or connected directly to a control unit (not shown). A sensing electrode  240 , a sensing electrode  250 , a sensing electrode  260  and a sensing electrode  270  are receiving electrodes, which are similarly arranged along the y direction and are parallel to the arrangement direction of the transmitting electrodes. The receiving electrodes may be further divided into two types of sensing electrodes, which are respectively denoted as sensing electrodes R 1  and sensing electrodes R 2 . The sensing electrodes R 1  and the sensing electrodes R 2  are alternately arranged. The sensing electrodes R 1  are connected to one another, and are connected to the control unit. Similarly, the sensing electrodes R 2  are connected to one another, and are connected to the control unit.  FIG. 3A  and  FIG. 3B  show enlarged views of the sensing electrodes of the embodiment in  FIG. 2  of the present invention. A sensing electrode  301  in  FIG. 3A  shows an enlarged view of the sensing electrode R 1  in  FIG. 2 , and includes a body  310 , a connecting portion  320  and an extension portion  330 . The connecting portion  320  connects the body  310  and the extension portion  330 . An accommodating space  340  is formed between the body  310  and the extension portion  330 . In the embodiment, the body  310  and the extension portion  330  are both rectangular, and have parallel long sides. The extension portion  330  connects to the extension portion  330  of other adjacent sensing electrodes R 1  (except for a particular sensing electrode R 1  in  FIG. 2 , which has its extension portion directly connected to the control unit or connected to the control unit via the connecting line). Thus, given that a distance between centers of two adjacent electrodes R 1  in  FIG. 2  is d 1 , the length of the extension portion  330  is also d 1 . On the other hand, a sensing electrode  302  shown in  FIG. 3B  is an enlarged view of the sensing electrode R 2  in  FIG. 2 , and includes a body  350 , an extension portion  360 , an extension portion  370 , an extension portion  380  and an extension portion  390 . In this embodiment, the body  350  is rectangular, the extension portion  360  and the extension portion  370  are extended outwards along one of the long sides, and the extension portion  380  and the extension portion  390  are extended outwards along the other long side. An accommodating space  395  is formed among the extension portions. The extension portion  380  and the extension portion  390  connect to the extension portion  390  or the extension portion  380  of other adjacent sensing electrodes R 2  (except for a particular sensing electrode R 2  in  FIG. 2 , which has its extension portion directly connected to the control unit or connected to the control unit via the connecting line). Thus, given that a distance between centers of two adjacent electrodes R 2  in  FIG. 2  is d 2 , a sum of the length of the extension portion  380 , the length of the extension portion  390  and the length of the body  350  is also d 2 . In one preferred embodiment, the sensing electrode  302  is horizontally symmetrical. More specifically, regarding an axis passing through the center of the body  350  and parallel to the short sides as an axis of symmetry, the lengths of the extension portion  380  and the extension portion  390  are equal, which is to say that, the sum of twice the length of length of the extension portion  380  (also the extension portion  390 ) and the length of the body  350  is d 2 . In one preferred embodiment, respective gaps between the sensing electrode R 1  and the sensing electrode R 2  are equal, i.e., d 1  is equal to d 2 . 
     The accommodating space  340  of the sensing electrode R 1  (i.e., the sensing electrode  301 ) may be used to accommodate the extension portion of the adjacent sensing electrode R 2  (i.e., the sensing electrode  302 ) of the other type. More specifically, the accommodating space  340  is for accommodating the extension portion  360  or the extension portion  370  of the sensing electrode  302 . The extension portion  360  or the extension portion  370  accommodated in the accommodating space  340  is close to the connecting portion  320  of the sensing electrode  301 , and a closest distance in between is the technological limit of electrode fabrication, e.g., 0.075 mm. However, gaps between other lines are also restrained by technological limits. Further, the line width of the sensing electrodes is also restrained by the technological limit. For example, the width of the extension portion  360  or the connecting line is greater than or equal to 0.125 mm in one preferred embodiment. It is known from  FIG. 2  that, the sum of twice the length of the extension portion  360  (also the extension portion  370 ) and the length of the body  350  is smaller than the distance d 2 . The difference between the two is equal to the sum of the length of the connecting portion  320  of the sensing electrode  301  and twice the gap in the y direction. Thus, as far as the sensing electrode  302  is concerned, the lengths of the extension portions (the extension portion  380  and the  390 ) that are not accommodated in the accommodating spaces are greater than the lengths of the extension portions (the extension portion  360  and the extension portion  370 ) that are accommodated in the accommodating spaces. On the other hand, the accommodating space  395  of the sensing electrode R 2  (i.e., the sensing electrode  302 ) may accommodate the body of the adjacent sensing electrode R 1  (i.e., the sensing electrode  301 ) of the other type, i.e., the body  310  of the sensing electrode  301 . In one preferred embodiment, the body  310  of the sensing electrode  301  and the body  350  of the sensing electrode  302  are rectangular, and have equal long sides. 
     Referring to  FIG. 1  and  FIG. 2 , it is discovered by comparing the sensing electrodes of the present invention with conventional sensing electrodes that, the area of the body of the sensing electrode R 1  is reduced, and the area of the sensing electrode R 2  is increased by the additional extension portion. That is to say, the area of the sensing electrode R 1  corresponding to any transmitting electrode is reduced, while the area of the corresponding sensing electrode R 2  is increased. As one is reduced and the other is increased, for the touch event  180  in  FIG. 2 , compared to the conventional sensing electrodes in  FIG. 1 , the capacitance change detected by the sensing electrode R 1  becomes smaller, whereas the capacitance change detected by the sensing electrode R 2  becomes larger, thereby significantly improving the unsatisfactory accuracy of conventional sensing electrodes of a touch panel. 
       FIG. 4  shows a partial enlarged view of the sensing electrode group in  FIG. 2 . In  FIG. 4 , a sensing electrode T 0 , a sensing electrode R 1  and a sensing electrode R 2  are depicted. When a touch event  410  occurs in a region A, a larger touch sensing value exists between the sensing electrode T 0  and the sensing electrode R 2 , whereas a smaller touch sensing value exists between the sensing electrode T 0  and the sensing electrode R 1 . The two touch sensing values are 13.266 pf/meter and 4.475 pf/meter, respectively. On the other hand, when the touch event  410  occurs in a region B, a larger touch sensing value exists between the sensing electrode T 0  and the sensing electrode R 1 , whereas a smaller touch sensing value exists between the sensing electrode T 0  and the sensing electrode R 2 . The two touch sensing values are 13.228 pm/meter and 3.97 pf/meter, respectively. It is discovered that, the touch sensing value between the sensing electrode T 0  and the sensing electrode R 2  in the region A is close to the touch sensing value between the sensing electrode T 0  and the sensing electrode R 1  in the region B. That is to say, by adjusting the sensing electrodes, the present invention helps to balance the touch sensing values of the sensing electrode R 1  and sensing electrode R 2 , hence enhancing the accuracy of the touch panel. 
       FIG. 5  shows a single-layer multi-touch sensing electrode group of a touch panel according to another embodiment of the present invention. A sensing electrode  510 , a sensing electrode  520 , a sensing electrode  530  and a sensing electrode are transmitting electrodes, and are arranged along the y direction shown in the diagram to become directly connected or connected via connecting lines to a control unit (not shown). A sensing electrode  140 , a sensing electrode  150 , a sensing electrode  160  and a sensing electrode  170  are receiving electrodes, and are similarly arranged along the y direction and parallel to the arrangement direction of the transmitting electrodes. The transmitting electrodes may be further divided into two types of electrodes, which are denoted as sensing electrodes T 0  and sensing electrodes T 1 , respectively. The sensing electrodes T 0  and the sensing electrodes T 1  are alternately arranged.  FIG. 6A  and  FIG. 6B  show enlarged views of the sensing electrodes of the embodiment in  FIG. 5  of the present invention. A sensing electrode  601  shows an enlarged view of the sensing electrode T 0  in  FIG. 5 , and includes a body  610 , a connecting portion  620  and an extension portion  630 . The connecting portion  620  connects the body  610  and the extension portion  630 . An accommodating space  640  is formed between the body  610  and the extension portion  630 . In the embodiment, the body  610  and the extension portion  630  are rectangular, and have parallel long sides. Thus, given that a distance between centers of two adjacent sensing electrodes T 0  is d 3 , the length of the extension portion  630  is greater than ½ of d 3  and smaller than d 3 . On the other hand, a sensing electrode  602  shows an enlarged view of the sensing electrode T 1  in  FIG. 5 , and includes a body  650 , an extension portion  660  and an extension portion  670 . In the embodiment, the body  650  is rectangular, and the extension portion  660  and the extension portion  670  are extended outwards along one of the long sides. In one preferred embodiment, the sensing electrode  602  is horizontally symmetrical. More specifically, regarding an axis passing through the center of the body  350  and parallel to the short sides as an axis of symmetry, the lengths of the extension portion  660  and the extension portion  670  are equal. Thus, given that a distance between the centers of two adjacent sensing electrodes T 1  in  FIG. 5  is d 4 , the sum of twice the length of the extension portion  660  (also the extension portion  670 ) and the length of the body  650  is greater than ½ of d 4  and smaller than d 4 . In one preferred embodiment, respective gaps between the sensing electrodes T 0  and the sensing electrodes T 1  are equal, i.e., d 3  is equal to d 4 . 
     The accommodating space  640  of the sensing electrode T 0  (i.e., the sensing electrode  601 ) may be used to accommodate the extension portion of the adjacent sensing electrode T 1  (i.e., the sensing electrode  602 ) of the other type. More specifically, the accommodating space  640  is for accommodating the extension portion  660  or the extension portion  670  of the sensing electrode  602 . The extension portion  660  or the extension portion  670  accommodated in the accommodating space  640  is close to the connecting portion  620  of the sensing electrode  601 , and a closest distance in between is the technological limit of electrode fabrication. Similarly, gaps between other lines are also restrained by technological limits. It is seen from  FIG. 5  that, the sum of twice the length of the extension portion  660  (also the extension portion  670 ) and the length of the body  650  is smaller than d 4 . The difference between the two is equal to the sum of the length of the connecting portion  620  of the sensing electrode  601  and twice the gaps in the y direction. 
     Referring to  FIG. 1  and  FIG. 5 , it is discovered by comparing the sensing electrodes of the present invention with convention sensing electrodes that, the area of the body of the sensing electrode T 0  is reduced, and the sensing range of the sensing electrode T 0  is increased through the extension portion to allow the sensing electrode T 0  to correspond to a larger range of receiving electrodes. More specifically, the sensing electrode  120  in  FIG. 1  corresponds to only a lower part of the sensing electrode  150  and an upper part of the sensing electrode  160 , whereas the sensing electrode  530  in  FIG. 5  corresponds to an entire part of the sensing electrode  150  and the entire part of the sensing electrode  160 . Similarly, the area of the body of the sensing electrode T 1  is reduced, and the sensing range of the sensing electrode T 1  is increased through the extension portion to allow the sensing electrode T 1  to correspond to a larger range of receiving electrodes. More specifically, the electrode in  FIG. 1  corresponds to only a lower part of the sensing electrode  140  and an upper part of the sensing electrode  150 , whereas the sensing electrode  520  in  FIG. 5  corresponds to an entire part of the sensing electrode  140  and an entire part of the sensing electrode  150 . One advantage of an increase sensing range of transmitting electrodes is the capability of enhancing the linearity of the touch panel. 
       FIG. 7  shows a single-layer multi-touch sensing electrode group according to another embodiment of the present invention. The sensing electrode group of the embodiment is a combination of the embodiments in  FIG. 2  and  FIG. 5 . In the embodiment in  FIG. 7 , sensing ranges are remarkably increased for both the transmitting electrodes and the receiving electrodes compared to original sensing electrodes. Further, on a same horizontal height, the two types of transmitting electrodes have overlapping sensing ranges. Similarly, the two types of receiving electrodes also have overlapping sensing ranges. Such electrode arrangement helps enhance the linearity of the touch panel.  FIG. 8  and  FIG. 9  show partial views of the sensing electrode group and curve diagrams of touch sensing values corresponding to the embodiment in  FIG. 2  and the embodiment in  FIG. 7 , respectively. In  FIG. 8 , the left half shows partial view of the sensing electrode group in  FIG. 2 , and the right half shows a curve of touch sensing values (in a unit of pf/meter) corresponding to different partial regions. The partial sensing view on the left side are divided into four regions—a region A, a region B, a region C and a region D. When a touch event  810  occurs in the region C, the sensing electrode T 1  in the region corresponds to the sensing electrode R 1  and the sensing electrodes R 2 , with the sensing electrode R 1  occupying a higher ratio. Thus, the curve at the right side shows that T 1 R 1  between the sensing electrode T 1  and the sensing electrode R 1  (corresponding to the horizontal axis T 1 R 1 ) has the largest touch sensing value, T 1 R 2  between the sensing electrode T 1  and the sensing electrode R 2  has the second largest touch sensing value, and T 0 R 2  between the sensing electrode T 0  and the sensing electrode R 2  as well as T 0 R 1  between the sensing electrode T 0  and the sensing electrode R 1  have touch sensing values in 0.  FIG. 9  corresponds to the sensing electrodes in  FIG. 7 . Similarly, when a touch event  910  occurs in the region C, because the area of the sensing electrode R 1  is greater than the area of the sensing electrodes R 2  in that region, the touch sensing value corresponding to T 1 R 1  has the largest touch sensing value on the right side of the diagram. Further, as the sensing electrode T 0  extends to the region C, touch sensing values also exist at regions between the sensing electrode T 0  and the sensing electrode R 1  as well as between the sensing electrode T 0  and the sensing electrode R 2 . Because the sensing region R 1  in the region C has a greater area, the touch sensing value between the sensing electrode T 0  and the sensing electrode R 1  is larger than the touch sensing value between the sensing electrode T 0  and the sensing electrode R 2 . Comparing  FIG. 8  and  FIG. 9 , it is known that, with a larger extension scope of the transmitting electrodes and hence a broader detectable range, the embodiment in  FIG. 7  has better touch linearity compared to the embodiment in  FIG. 2 . 
       FIG. 10  shows a single-layer multi-touch sensing electrode group according to another embodiment of the present invention. Compared to the conventional sensing electrodes in  FIG. 1 , receiving electrodes are adjusted in this embodiment. The sensing electrode R 1  originally reacts more sensitively to a touch event than the sensing electrode R 2  because of the connecting section  115 . To balance the sensitivities of the sensing electrode R 1  and the sensing electrode R 2  for the touch event, in this embodiment, the area of the sensing electrode R 1  (i.e., a sensing electrode  1010  and a sensing electrode  1030 ) is smaller than the area of the sensing electrode R 2  (i.e., a sensing electrode  150  and a sensing electrode  170 ). In one preferred embodiment, the sensing electrode R 1  and the sensing electrode R 2  are rectangular, and have equal long sides, with however shorter sides of the sensing electrode R 1  being shorter than shorter sides of the sensing electrode R 2 . That is, the sensing electrode R 1  is narrower in order to reduce the area of the electrode to cancel the difference between the sensing sensitivities between the sensing electrode R 1  and the sensing electrode R 2  caused by the connecting line  115 . However, as the sensing electrode R 1  gets narrower than the sensing electrode R 2 , a larger blank region is resulted between the sensing electrode R 1  and the transmitting electrode. To prevent this region from causing uneven brightness levels of an image on a display screen, a dummy electrode  1010  and a dummy electrode  1040  are filled into this blank region. The dummy electrode  1020  and the dummy electrode  140  are made of a same material as the sensing electrode, and are not applied with any electric potential. It should be noted that, although each of the dummy electrode  1020  and the dummy electrode  1040  includes four unit electrodes that are rectangular in this embodiment, the numbers and shapes of the unit electrodes are not limited to the above examples. 
     It should be noted that, the transmitting electrodes and receiving electrodes of the foregoing embodiments may be exchanged. For example, the sensing electrode  510 , the sensing electrode  520 , the sensing electrode  530  and the sensing electrode  540  in  FIG. 7  may serve as receiving electrodes, and the sensing electrode  240 , the sensing electrode  250 , the sensing electrode  260  and the sensing electrode  270  may serve as transmitting electrodes. Such modification may be easily achieved through adjusting signal transmitting and receiving timings of the control unit. 
     While the invention has been described by way of example and in terms of the preferred embodiments, it is to be understood that the invention is not limited thereto. On the contrary, it is intended to cover various modifications and similar arrangements and procedures, and the scope of the appended claims therefore should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements and procedures.