Capacitive sensor, detection circuit, and detection method

Abstract

The present invention comprises: a first insulating layer; a detection electrode that extends in a first direction on a surface of the first insulating layer; a side shield electrode that is provided in parallel with the detection electrode on the surface of the first insulating layer; a side ground electrode that is provided in parallel with the detection electrode and the side shield electrode on the surface of the first insulating layer, and is connected to a ground potential; and a first back shield electrode that is disposed on the other surface of the first insulating layer and faces the detection electrode with the first insulating layer interposed therebetween. A first alternating-current drive voltage is applied to the detection electrode. A second alternating-current drive voltage having the same frequency and the same phase as the first alternating-current drive voltage is applied to the side shield electrode and the first back shield electrode. The detection electrode comprises a plurality of individual electrodes provided in parallel with each other at intervals in the first direction. The side shield electrode is provided between the detection electrode and the side ground electrode.

Description

Capacitive sensor, detection circuit, and detection method

[0001] The present invention relates to a capacitive sensor, a detection circuit, and a detection method.

[0002] The following Patent Document 1 discloses a technology for applying a potential equivalent to that of the sensor electrode to the auxiliary electrode and the shield electrode in a capacitive proximity sensor having a sensor electrode, an auxiliary electrode arranged near the sensor electrode, and a shield electrode arranged on the back side of the sensor electrode.

[0003] WO 2009 / 044920

[0004] However, while the technology of Patent Document 1 above can detect an increase or decrease in the number of objects to be detected placed on the capacitance-type proximity sensor, the amount of change in capacitance per object to be detected is not constant, so it is not possible to determine with high accuracy the number of objects to be detected placed on the capacitance-type proximity sensor.

[0005] A capacitance-type sensor according to one embodiment includes a first insulating layer, a detection electrode extending in a first direction on a surface of the first insulating layer, a side shield electrode arranged parallel to the detection electrode on the surface of the first insulating layer, a side ground electrode arranged parallel to the detection electrode and the side shield electrode on the surface of the first insulating layer and connected to ground potential, and a first back shield electrode arranged on the other surface of the first insulating layer and facing the detection electrode via the first insulating layer, wherein a first AC drive voltage is applied to the detection electrode, and a second AC drive voltage having the same frequency and phase as the first AC drive voltage is applied to the side shield electrode and the first back shield electrode, the detection electrode has a plurality of individual electrodes arranged parallel to each other at intervals in the first direction, and the side shield electrode is arranged parallel to the detection electrode and the side ground electrode.

[0006] According to the capacitance sensor of one embodiment, the number of detection targets placed on the capacitance sensor can be determined with high accuracy.

[0007] FIG. 1 is a plan view of a capacitance type sensor according to an embodiment; FIG. 2 is a cross-sectional view of a capacitance type sensor according to an embodiment, taken along the line A-A; FIG. 3 is a cross-sectional view of a capacitance type sensor according to an embodiment, taken along the line B-B; FIG. 4 is an exploded plan view of a capacitance type sensor according to an embodiment; FIG. 5 is a circuit model of a capacitance type sensor according to an embodiment (when a detection target is present on the capacitance type sensor); FIG. 6 is a circuit configuration example of a capacitance detection unit included in a capacitance type sensor according to an embodiment;

[0008] An embodiment will be described below with reference to the drawings. For convenience, in the following description, the X-axis direction will be referred to as the left-right direction, the Y-axis direction as the front-rear direction, and the Z-axis direction as the up-down direction. However, the positive X-axis direction will be referred to as the rightward direction, the positive Y-axis direction as the forward direction, and the positive Z-axis direction as the upward direction. These directions indicate relative positional relationships within the device and do not limit the installation direction or operation direction of the device. Any devices that have the same relative positional relationships within the device, even if they have different installation directions or operation directions, are all within the scope of the present invention.

[0009] (Configuration of Capacitive Sensor 100) FIG. 1 is a plan view of the capacitive sensor 100 according to one embodiment. FIG. 2 is a cross-sectional view of the capacitive sensor 100 according to one embodiment taken along the A-A cross-sectional line (see FIG. 1). FIG. 3 is a cross-sectional view of the capacitive sensor 100 according to one embodiment taken along the B-B cross-sectional line (see FIG. 1). FIG. 4 is an exploded plan view of the capacitive sensor 100 according to one embodiment. Note that FIG. 4 shows a plan view of each of the electrode layer L1, bridge wiring layer L2, wiring layer L3, and back shield layer L4 of the capacitive sensor 100 as viewed from above (positive direction of the Z axis).

[0010] As shown in Figures 1 to 4, a capacitance sensor 100 according to one embodiment includes a detection circuit 120, a first insulating layer 101, two detection electrodes 102, two side shield electrodes 103, a side ground electrode 104, and a first back shield electrode 106.

[0011] As shown in FIGS. 1 and 4 , the detection circuit 120 is provided on the electrode layer L1 on the surface 101A side of the first insulating layer 101 and is disposed at the front end (positive side of the Y axis) of the surface 101A of the first insulating layer 101. The detection circuit 120 is connected to each of the plurality of individual electrodes 102A of the detection electrode 102 via the wiring group 110. The detection circuit 120 can detect changes in the capacitance of each of the plurality of individual electrodes 102A by applying a first AC drive voltage V1 to each of the plurality of individual electrodes 102A via the wiring group 110. The detection circuit 120 can also apply a second AC drive voltage V2 having the same frequency and phase as the first AC drive voltage V1 to each of the side shield electrode 103, the first back shield electrode 106, the second back shield electrode 109, and the third back shield electrode 112.

[0012] In this embodiment, the detection circuit 120 is configured to be integral with the capacitance sensor 100 (surface 101A of the first insulating layer 101), but this is not limiting, and for example, the detection circuit 120 may be configured to be provided separately from the capacitance sensor 100 and electrically connected to the capacitance sensor 100 by a wiring member (for example, a cable, an FPC, etc.). Furthermore, the detection circuit 120 may be provided on the back side of the capacitance sensor 100.

[0013] The first insulating layer 101 is a layer formed of an insulating material. The first insulating layer 101 supports each electrode (the detection electrode 102, the side ground electrode 104, the side shield electrode 103, and the first back shield electrode 106). When viewed from above (the positive direction of the Z axis), the first insulating layer 101 has a rectangular shape with a constant width in the left-right direction (the X axis) and a constant length in the front-back direction (the Y axis). The first insulating layer 101 is formed using, for example, an insulating resin such as PET (polyethylene terephthalate) or PMMA (polymethyl methacrylate), glass, glass epoxy resin, glass polyimide resin, paper epoxy resin, paper phenolic resin, or the like.

[0014] The side ground electrode 104 is provided on the electrode layer L1 on the surface 101A side of the first insulating layer 101. It is a thin-film electrode made of a conductive material such as metal, inorganic conductive oxide, or conductive resin, and is arranged in the center of the surface 101A of the first insulating layer 101 in the left-right direction (X-axis direction). The side ground electrode 104 has a strip shape that extends linearly in the front-rear direction (Y-axis direction). The side ground electrode 104 is arranged side by side between the two detection electrodes 102 on the surface 101A of the first insulating layer 101. The side ground electrode 104 is connected to a ground potential.

[0015] The two detection electrodes 102 are provided on the electrode layer L1 on the surface 101A side of the first insulating layer 101. They are thin-film electrodes made of a conductive material such as metal, inorganic conductive oxide, or conductive resin, and are arranged on the surface 101A of the first insulating layer 101. Each of the two detection electrodes 102 has an overall strip shape extending linearly in the front-to-rear direction (Y-axis direction). The two detection electrodes 102 are arranged side by side on the surface 101A of the first insulating layer 101, on both outer sides of the side ground electrode 104 in the left-to-right direction (X-axis direction). Each of the two detection electrodes 102 is driven by application of a first AC drive voltage V1 from a first drive / detection circuit 121A of the detection circuit 120.

[0016] In the capacitance sensor 100 according to one embodiment, when the placement state of the detection object 20 on the capacitance sensor 100 changes, the capacitance (Crg+Crg') (see FIG. 5 ) of the detection object 20 detected by the detection electrodes 102 changes. Therefore, the detection circuit 120 according to one embodiment can determine the placement state of the detection object 20 on the capacitance sensor 100 (presence or absence of the detection object 20, the number of the detection objects 20, etc.) based on the capacitance (Crg+Crg') of the detection object 20 detected by the detection electrodes 102.

[0017] In particular, the capacitance sensor 100 according to one embodiment has a side ground electrode 104 disposed in parallel with the detection electrode 102 on the surface 101A of the first insulating layer 101. Therefore, in the capacitance sensor 100 according to one embodiment, when the detection object 20 is present on the capacitance sensor 100, a capacitance Crg is generated between the detection electrode 102 and the detection object 20, and a capacitance Crg' is generated between the detection object 20 and the side ground electrode 104 (see FIG. 5 ). Therefore, in the capacitance sensor 100 according to one embodiment, when the detection object 20 is present on the capacitance sensor 100, the capacitance of the detection object 20 detected by the detection electrode 102 is amplified to the sum of the capacitance Crg and the capacitance Crg', thereby improving the detection accuracy of the detection object 20 by the detection electrode 102.

[0018] The two side shield electrodes 103 are provided on the electrode layer L1 on the surface 101A side of the first insulating layer 101. They are thin-film electrodes made of a conductive material, such as a metal, an inorganic conductive oxide, or a conductive resin, and are arranged on the surface 101A of the first insulating layer 101. The two side shield electrodes 103 are arranged side by side on the surface 101A of the first insulating layer 101, on both outer sides of the side ground electrode 104 in the left-right direction (X-axis direction). Each of the two side shield electrodes 103 has a rectangular frame shape surrounding the detection electrode 102 in a plan view from above (positive Z-axis direction). The side shield electrodes 103 are driven by application of a second AC drive voltage V2 from a second drive circuit 121B of the detection circuit 120. In this embodiment, as an example, two side shield electrodes 103 are integrally formed on the surface 101A of the first insulating layer 101 (i.e., connected on the surface 101A), but the two side shield electrodes 103 may be formed separately and driven individually and simultaneously by the second drive circuit 121B of the detection circuit 120.

[0019] As shown in Figures 1 to 3, the side shield electrode 103 has a pair of left and right straight portions 103A that extend in the front-to-rear direction (X-axis direction) and are parallel to each other, and the detection electrode 102 is arranged between the pair of left and right straight portions 103A.

[0020] One of the pair of left and right linear portions 103A is disposed between the detection electrode 102 and the side ground electrode 104, thereby reducing the parasitic capacitance between the detection electrode 102 and the side ground electrode 104. Therefore, the capacitance-type sensor 100 according to one embodiment can detect the detection object 20 having a low conductivity or dielectric constant with even higher sensitivity.

[0021] Note that providing a pair of left and right linear portions 103A is synonymous with providing a pair of left and right two side shield electrodes 103. In other words, providing the detection electrode 102 between the pair of left and right linear portions 103A is synonymous with providing the detection electrode 102 between the pair of left and right two side shield electrodes 103.

[0022] The other straight line portion 103A of the pair of left and right straight line portions 103A is disposed outside the detection electrode 102 (on the positive side of the X-axis), thereby preventing external noise from outside the detection electrode 102 from flowing into the detection electrode 102. Therefore, the capacitance sensor 100 according to one embodiment can improve resistance to external noise and improve the stability of the high S / N ratio of the detection signal.

[0023] The first back shield electrode 106 is provided on the bridge wiring layer L2 on the rear surface 101B side of the first insulating layer 101. It is a thin-film electrode made of a conductive material, such as a metal, an inorganic conductive oxide, or a conductive resin, and is disposed on the rear surface 101B of the first insulating layer 101. The first back shield electrode 106 has a rectangular shape with its longitudinal direction extending in the front-to-rear direction (Y-axis direction) when viewed from above (positive Z-axis direction) so as to cover the entire rear surface 101B of the first insulating layer 101. The first back shield electrode 106 is disposed opposite the detection electrode 102 across the first insulating layer 101. The first back shield electrode 106 is driven by application of a second AC drive voltage V2 from a second drive circuit 121B of the detection circuit 120. A rectangular opening 106A extending in the front-to-rear direction (Y-axis direction) when viewed from above (positive Z-axis direction) is formed in the center of the first back shield electrode 106 in the left-to-right direction (X-axis direction). The rectangular opening 106A extends in the front-to-rear direction (Y-axis direction) when viewed from above (positive Z-axis direction).

[0024] By including the first back shield electrode 106, the capacitance sensor 100 according to one embodiment can reduce the parasitic capacitance occurring between the detection electrode 102 and the side ground electrode 104 and the ground potential by the parasitic capacitance Crs(c) (see FIG. 5 ) of the first back shield electrode 106. Therefore, when a detection target 20 is present on the capacitance sensor 100, the capacitance detected by the detection electrode 102 is the capacitance (Crg+Crg') of the detection target 20, with the parasitic capacitance Crgl eliminated. Therefore, the capacitance sensor 100 according to one embodiment can improve the detection accuracy of the detection target 20 by the detection electrode 102.

[0025] 1, each of the two detection electrodes 102 provided on the surface 101A of the first insulating layer 101 has a plurality of individual electrodes 102A arranged side by side at intervals in the front-rear direction (Y-axis direction) (an example of the "first direction"). That is, in the capacitance sensor 100 according to one embodiment, a plurality of pairs of left and right individual electrodes 102A (hereinafter referred to as "individual electrode pairs") are arranged side by side at intervals in the front-rear direction (Y-axis direction) (an example of the "first direction").

[0026] In each individual electrode pair, one of the individual electrodes 102A is connected to the detection circuit 120 via a wiring group 110 described later, and is driven by individually applying a first AC drive voltage V1 from the first drive / detection circuit 121A of the detection circuit 120.

[0027] In each pair of individual electrodes, the other individual electrode 102A is electrically connected to one of the individual electrodes 102A by a connecting member 102B provided in the bridge wiring layer L2 within the opening 106A of the first back shield electrode 106. As a result, the other individual electrode 102A is integrated with the one of the individual electrodes 102A and is driven simultaneously with the one of the individual electrodes 102A.

[0028] The connecting member 102B is a thin-film electrode that extends in the left-right direction (X-axis direction) in the bridge wiring layer L2 and is made of a conductive material such as metal, inorganic conductive oxide, conductive resin, etc. As shown in Fig. 2, the left end (negative side of the X-axis) of the connecting member 102B is connected to the left (negative side of the X-axis) piece electrode 102A by a second through-hole 115 that penetrates the first insulating layer 101, and the right end (positive side of the X-axis) of the connecting member 102B is connected to the right (positive side of the X-axis) piece electrode 102A by a second through-hole 115 that penetrates the first insulating layer 101.

[0029] Since the connection member 102B is provided for each individual electrode pair, as shown in FIG. 4, in the bridge wiring layer L2, a plurality of connection members 102B, the same number as the number of individual electrode pairs, are arranged side by side in the front-to-back direction (Y-axis direction) within the opening 106A of the first back shield electrode 106.

[0030] In addition, in the present embodiment, as a preferred example, the connecting member 102B is provided on the bridge wiring layer L2, but this is not limiting, and the connecting member 102B may be provided in a layer below the bridge wiring layer L2. For example, the connecting member 102B may be provided on the wiring layer L3, and the pair of left and right individual electrodes 102A may be connected to the connecting member 102B by second through-holes 115 that penetrate the first insulating layer 101, the first back shield electrode 106, and the second insulating layer 107.

[0031] In this way, the capacitance sensor 100 according to one embodiment has a plurality of individual electrode pairs in which the detection electrodes 102 are arranged side by side in the front-to-back direction (Y-axis direction), and the plurality of individual electrode pairs can be individually driven by the detection circuit 120. Therefore, when the placement state of the detection object 20 on the capacitance sensor 100 changes, the capacitance detection values ​​of some of the individual electrode pairs that are provided at positions that overlap the detection object 20 in a plan view from above (positive Z-axis direction) change significantly, and therefore the capacitance sensor 100 according to one embodiment can identify with high accuracy the position and range of change in the placement state of the detection object 20 in the front-to-back direction (Y-axis direction).

[0032] Furthermore, in one embodiment of the capacitance sensor 100, the number B of individual electrodes 102A required to detect one detection object 20 is determined in advance, and by counting the number A of individual electrodes 102A whose capacitance has changed, the number of detection objects 20 placed on the capacitance sensor 100 can be easily calculated using the formula (A÷B).

[0033] Furthermore, in one embodiment of the capacitance sensor 100, even when multiple detection objects 20 are arranged spaced apart in the front-to-back direction (Y-axis direction), the capacitance detection value of the individual electrode pairs located at positions overlapping each detection object 20 when viewed in a planar view from above (positive Z-axis direction) changes significantly, making it possible to individually identify the placement position of each detection object 20 with high accuracy.

[0034] As shown in Figures 2 and 3, the capacitance sensor 100 according to one embodiment includes a second insulating layer 107 provided on the back side of the first back shield electrode 106 (i.e., the bridge wiring layer L2), a wiring layer L3 provided on the back side of the second insulating layer 107, and a third insulating layer 108 provided on the back side of the wiring layer L3.

[0035] Similar to the first insulating layer 101, the second insulating layer 107 and the third insulating layer 108 are layers formed from an insulating material.

[0036] As shown in Figures 2 to 4, the wiring layer L3 has a second back shield electrode 109 covering the back surface of the second insulating layer 107, and a wiring group 110 arranged within a cutout portion 109A formed in the second back shield electrode 109.

[0037] Like the first back shield electrode 106, the second back shield electrode 109 is a thin-film electrode made of a conductive material such as metal, inorganic conductive oxide, or conductive resin. The second back shield electrode 109 has a rectangular shape with its longitudinal direction extending in the front-to-rear direction (Y-axis direction) when viewed from above, so as to cover the entire back surface of the second insulating layer 107. Like the first back shield electrode 106, the second back shield electrode 109 is driven by application of a second AC drive voltage V2 from a second drive circuit 121B of the detection circuit 120.

[0038] The wiring group 110 is configured to have a plurality of wirings 110A, one for each individual electrode 102A. The wiring group 110 extends in the front-to-rear direction (Y-axis direction) within the cutout 109A of the second back shield electrode 109. One end (the end on the Y-axis positive side) of the wiring group 110 is connected to the detection circuit 120, and the other end (the end on the Y-axis negative side) is connected to each of the plurality of individual electrodes 102A via first through-holes 111 that penetrate the first insulating layer 101, the first back shield electrode 106, and the second insulating layer 107.

[0039] In this way, in the capacitance sensor 100 according to one embodiment, the wiring group 110 for applying the first AC drive voltage V1 to the plurality of individual electrodes 102A is provided on the wiring layer L3 on the back side of the first back shield electrode 106 and connected to each of the plurality of individual electrodes 102A via the first through holes 111, thereby reducing the capacitive coupling and parasitic capacitance between the wiring group 110 and the object to be detected 20 and improving the signal-to-noise ratio of the detection signal.

[0040] Furthermore, in the capacitance sensor 100 according to one embodiment, the wiring group 110 is provided within the notch 109A of the second back shield electrode 109 (i.e., the area surrounded by the second back shield electrode 109), and by applying the second AC drive voltage V2 to the second back shield electrode 109, the parasitic capacitance of the wiring group 110 is reduced and superimposition of external noise on the wiring group 110 can be prevented, thereby further improving the signal-to-noise ratio of the detection signal.

[0041] 2 to 4, the second back shield electrode 109 has two notches 109A formed on the left and right sides, and a wiring group 110 is arranged in each of the two notches 109A. This is because, in this embodiment, the number of individual electrodes 102A and the number of wirings 110A are relatively large, and therefore the two notches 109A are provided so that the large number of wirings 110A can be accommodated.

[0042] 4 , each of the two notches 109A has a shape cut out along the overall shape of the wiring group 110 in a plan view from above (positive direction of the Z axis). The wiring group 110 arranged in the left (negative side of the X axis) notch 109A connects the left (negative side of the X axis) piece electrodes 102A of some of the plurality of piece electrode pairs to the detection circuit 120, and a plurality of wirings 110A extending in the front-rear direction (positive direction of the Y axis) are arranged in parallel. The wiring group 110 arranged in the right (positive side of the X axis) notch 109A connects the right (positive side of the X axis) piece electrodes 102A of some of the remaining plurality of piece electrode pairs to the detection circuit 120, and a plurality of wirings 110A extending in the front-rear direction (positive direction of the Y axis) are arranged in parallel.

[0043] 4, each of the plurality of wirings 110A in the wiring group 110 has a length that reaches the individual electrode 102A to be connected, and therefore the lengths of the wirings 110A in the front-rear direction (Y-axis direction) are different. In the example shown in FIG. 4, each wiring group 110 has a plurality of wirings 110A of different lengths arranged side by side so that the lengths of the wirings 110A gradually decrease toward the inside of the capacitance sensor 100 (i.e., the side ground electrode 104).

[0044] 2 and 3 , the capacitance-type sensor 100 according to one embodiment also includes a third back shield electrode 112 provided on the back shield layer L4 on the back surface side of the third insulating layer 108. Like the first back shield electrode 106 and the second back shield electrode 109, the third back shield electrode 112 is a thin-film electrode made of a conductive material such as a metal, an inorganic conductive oxide, or a conductive resin. The third back shield electrode 112 has a rectangular shape with its longitudinal direction extending in the front-to-back direction (Y-axis direction) when viewed from above, so as to cover the entire back surface of the third insulating layer 108. Like the first back shield electrode 106 and the second back shield electrode 109, the third back shield electrode 112 is driven by application of a second AC drive voltage V2 from the second drive circuit 121B of the detection circuit 120.

[0045] In this way, in the capacitance sensor 100 according to one embodiment, the third back shield electrode 112 is provided on the back side of the third insulating layer 108 via the third insulating layer 108, and by applying the second AC drive voltage V2 to the third back shield electrode 112, the parasitic capacitance of the wiring group 110 is reduced and superposition of external noise on the wiring group 110 can be prevented, thereby further improving the signal-to-noise ratio of the detection signal.

[0046] As shown in Figures 2 and 3, the capacitance sensor 100 according to one embodiment further includes a background electrode 113 that is provided on the back side of the third back shield electrode 112, spaced apart from and facing the third back shield electrode 112, and is connected to a ground potential.

[0047] As a result, the capacitance sensor 100 of one embodiment can effectively attenuate external electromagnetic noise from the back side of the third back shield electrode 112 and prevent noise from flowing into the detection electrode 102, thereby improving the stability of the high S / N ratio of the detection signal.

[0048] Furthermore, in one embodiment of the capacitance sensor 100, the pair of left and right individual electrodes 102A are connected by a connecting member 102B provided in the bridge wiring layer L2 (the empty space 106A of the first back shield electrode 106), so there is no need to provide a separate wiring member for connecting the pair of left and right individual electrodes 102A, and the capacitance sensor 100 can be made smaller.

[0049] 2 and 3 , the capacitance sensor 100 according to one embodiment further includes a cover 114. The cover 114 is provided on the top surface of the capacitance sensor 100 and is an insulating member that covers the surface 101A of the first insulating layer 101 and the electrodes (the detection electrode 102, the side shield electrode 103, and the side ground electrode 104). The cover 114 has the same shape (i.e., rectangular) as the surface 101A of the first insulating layer 101 when viewed from above (positive Z-axis direction) so as to cover the entire surface 101A of the first insulating layer 101. The cover 114 may be made of, for example, a resin material such as PET (polyethylene terephthalate), PMMA (polymethyl methacrylate), a photosensitive resist such as a novolac resin, or a solder resist, or a glass material.

[0050] (Circuit Model of Capacitive Sensor 100) Fig. 5 is a diagram showing a circuit model of the capacitive sensor 100 according to one embodiment (when the detection target 20 is present on the capacitive sensor 100). This diagram schematically shows approximately half of the right side (positive X-axis direction) including the side ground electrode 104 in Fig. 2, which is the cross section A-A in Fig. 1.

[0051] As shown in FIG. 5, the detection circuit 120 included in the capacitance sensor 100 includes a capacitance detection unit 121, a processing unit 122, and an I / F (interface) .

[0052] The capacitance detection unit 121 is electrically connected to the detection electrode 102, the plurality of wirings 110A, the side shield electrode 103, and the third back shield electrode 112. The capacitance detection unit 121 has a first drive / detection circuit 121A and a second drive circuit 121B.

[0053] The first drive / detection circuit 121A generates a first AC drive voltage V1 and applies the first AC drive voltage V1 to the detection electrodes 102 (i.e., each of the plurality of individual electrodes 102A) via the plurality of wirings 110A. The first drive / detection circuit 121A also detects a change Ie in the current Is flowing through the detection electrode 102 as a change in the capacitance of the detection electrode 102, and outputs a detection signal Ds based on the change Ie in the current Is.

[0054] The second drive circuit 121B generates a second AC drive voltage V2 having the same frequency and phase as the first AC drive voltage V1, and applies the second AC drive voltage V2 to the side shield electrode 103 and the third back shield electrode 112. This enables the second drive circuit 121B to drive the side shield electrode 103 and the third back shield electrode 112, as well as to drive the first back shield electrode 106 electrically connected to the side shield electrode 103 and the second back shield electrode 109 electrically connected to the third back shield electrode 112.

[0055] The processing unit 122 executes various predetermined processes based on the detection signal Ds output from the capacitance detection unit 121. For example, the processing unit 122 executes predetermined processes such as determining whether or not a detection target 20 exists on the capacitance sensor 100, determining the number of detection targets 20 present on the capacitance sensor 100, etc., based on the detection signal Ds. For example, the processing unit 122 is configured with a processing processor (e.g., a CPU (Central Processing Unit)), memory (e.g., a RAM (Random Access Memory)), etc., and executes various predetermined processes by the processing processor executing a program stored in the memory. For example, an integrated circuit (IC) is used as the processing unit 122.

[0056] The I / F 124 outputs data indicating the results of a predetermined process performed by the processing unit 122 (e.g., the presence or absence of a detection target 20 on the capacitance sensor 100, the number of detection targets 20 present on the capacitance sensor 100, etc.) to another device that uses the data.

[0057] As shown in FIG. 5, the following parasitic capacitance occurs in the capacitance sensor 100 according to the embodiment.

[0058] Parasitic capacitance between the side ground electrode 104 and the connecting member 102B: Crgl(a) Parasitic capacitance between the side ground electrode 104 and the side shield electrode 103: Csg(a) Parasitic capacitance between the side shield electrode 103 and the connecting member 102B: Crs(a) Parasitic capacitance between the detection electrode 102 and the side shield electrode 103: Crs(b) Parasitic capacitance between the detection electrode 102 and the first back shield electrode 106: Crs(c) Parasitic capacitance between the connecting member 102B and the second back shield electrode 109: Crs(d) Parasitic capacitance between the third back shield electrode 112 and the background electrode 113: Csg(b) Parasitic capacitance between the wiring 110A and the first back shield electrode 106: Crs'(a) Parasitic capacitance between the wiring 110A and the second back shield electrode 109: Crs'(b) Parasitic capacitance between the wiring 110A and the third back shield electrode 112: Crs′ (c)

[0059] 5 , in the capacitance sensor 100 according to one embodiment, the periphery (above, below, and to the sides) of each wiring 110A is protected by the first back shield electrode 106, the second back shield electrode 109, and the third back shield electrode 112. Therefore, in the capacitance sensor 100 according to one embodiment, the parasitic capacitance of each wiring 110A can be reduced and capacitive coupling between each wiring 110A and the detection electrode 102 can be prevented, thereby improving the signal-to-noise ratio of the detection signal.

[0060] 6 is a diagram showing an example of the circuit configuration of the capacitance detection unit 121 included in the capacitance sensor 100 according to one embodiment. For example, as shown in FIG. 6, the capacitance detection unit 121 has a first drive / detection circuit 121A, a second drive circuit 121B, and an A / D converter 25.

[0061] The first drive / detection circuit 121A is electrically connected to the detection electrode 102 via wiring 110A. The first drive / detection circuit 121A also has an operational amplifier 30, a feedback resistor 40, a feedback capacitor 50, and a first AC voltage circuit 60 which is a first AC power supply.

[0062] The first AC voltage circuit 60 generates a first AC drive voltage V 1 and applies the first AC drive voltage V 1 to the non-inverting input terminal (+) of the operational amplifier 30 .

[0063] The inverting input terminal (−) of the operational amplifier 30 is connected to the detection electrode 102 via wiring 110A, and the first AC voltage circuit 60 is connected to the non-inverting input terminal (+) of the operational amplifier 30. The operational amplifier 30 amplifies the voltage difference between the inverting input terminal (−) connected to the detection electrode 102 and the non-inverting input terminal (+) to which the first AC drive voltage V1 is applied, and outputs an output voltage Vo. A feedback resistor 40 and a feedback capacitor 50 are connected in parallel between the output terminal and the inverting input terminal (−) of the operational amplifier 30, providing negative feedback. The resistance value of the feedback resistor 40 is variable. The capacitance value of the feedback capacitor 50 is adjustable. The operational amplifier 30 outputs a change in the capacitance of the detection electrode 102 as an output voltage Vo based on a change Ie in the current Is flowing through the detection electrode 102. The output voltage Vo is converted into a detection signal Ds by an A / D converter 25.

[0064] The second drive circuit 121B has a second AC voltage circuit 70, which is a second AC power supply. The second AC voltage circuit 70 is electrically connected to the side shield electrode 103 and the third back shield electrode 112 via wiring 110A-2. The second drive circuit 121B uses the second AC voltage circuit 70 to generate a second AC drive voltage V2 that has the same frequency and phase as the first AC drive voltage V1.

[0065] In one embodiment of the capacitance sensor 100, the detection circuit 120 may make the amplitude of the second AC drive voltage V2 applied from the second drive circuit 121B to the side shield electrode 103 and the third back shield electrode 112 larger than the amplitude of the first AC drive voltage V1 applied from the first drive / detection circuit 121A to the detection electrode 102.

[0066] In this case, the capacitance-type sensor 100 according to the embodiment can efficiently cancel the parasitic capacitance between the detection electrode 102 and the ground potential and between the detection electrode 102 and the side ground electrode 104 by the parasitic capacitance Crs(c) between the detection electrode 102 and the first back shield electrode 106, and can obtain a detection signal with a high S / N ratio from the detection electrode 102. Furthermore, saturation of the output voltage Vo of the operational amplifier 30 can be prevented, and the dynamic range of the output voltage Vo can be increased.

[0067] (First Example of Detection Processing by the Detection Circuit 120) FIG. 7 is a flowchart showing a first example of detection processing by the detection circuit 120 included in the capacitance sensor 100 according to one embodiment.

[0068] First, the detection circuit 120 detects the capacitance of each individual electrode 102A (step S201).

[0069] Next, the detection circuit 120 determines whether or not there is any individual electrode 102A whose capacitance exceeds a predetermined threshold value, based on the capacitance of each individual electrode 102A detected in step S201 (step S202).

[0070] In step S202, if it is determined that there is no individual electrode 102A whose capacitance exceeds the predetermined threshold (step S202: NO), the detection circuit 120 returns the process to step S201.

[0071] On the other hand, if it is determined in step S202 that there is an individual electrode 102A whose capacitance exceeds a predetermined threshold (step S202: YES), the detection circuit 120 counts the number of individual electrodes 102A whose capacitance exceeds the predetermined threshold (step S203 (counting process)).

[0072] Then, the detection circuit 120 calculates the number of detection objects 20 placed on the capacitance sensor 100 based on the number of individual electrodes 102A whose capacitance counted in step S202 exceeds a predetermined threshold (step S204 (number of objects placed calculation process)).

[0073] For example, if the number of individual electrodes 102A whose capacitance exceeds a predetermined threshold is A and the number of individual electrodes 102A required to detect one detection object 20 is B, the detection circuit 120 calculates the number of detection objects 20 placed on the capacitance sensor 100 using the formula (A÷B).

[0074] Then, the detection circuit 120 outputs the number of detection targets 20 placed on the capacitance sensor 100 calculated in step S204 (step S205).

[0075] Next, the detection circuit 120 determines whether the number of objects to be detected 20 placed on the capacitance sensor 100 has increased or decreased by comparing the number of objects to be detected 20 calculated in step S204 and the number of objects to be detected 20 that were placed on the capacitance sensor 100 immediately before (step S206).

[0076] In step S206, if it is determined that there is an increase or decrease in the number of detection objects 20 placed on the capacitance sensor 100 (step S206: YES), the detection circuit 120 outputs the increase or decrease in the number of detection objects 20 placed on the capacitance sensor 100 (step S207 (increase or decrease number output process)), and terminates the series of processes shown in Figure 7.

[0077] On the other hand, in step S206, if it is determined that the number of detection objects 20 placed on the capacitance sensor 100 has not increased or decreased (step S206: NO), the detection circuit 120 terminates the series of processes shown in Figure 7.

[0078] (Second Example of Detection Processing by the Detection Circuit 120) FIG. 8 is a flowchart showing a second example of detection processing by the detection circuit 120 included in the capacitance sensor 100 according to an embodiment.

[0079] First, the detection circuit 120 detects the capacitance of each individual electrode 102A (step S301).

[0080] Next, the detection circuit 120 determines whether or not there is any individual electrode 102A whose capacitance exceeds a predetermined threshold value, based on the capacitance of each individual electrode 102A detected in step S301 (step S302).

[0081] In step S302, if it is determined that there is no individual electrode 102A whose capacitance exceeds the predetermined threshold (step S302: NO), the detection circuit 120 returns the process to step S301.

[0082] On the other hand, if it is determined in step S302 that there is an individual electrode 102A whose capacitance exceeds a predetermined threshold (step S302: YES), the continuous portion of individual electrodes 102A whose capacitance exceeds the predetermined threshold is identified as a cell group, and it is determined whether there is a cell group that includes more than a predetermined number of continuous individual electrodes 102A (step S303).

[0083] If it is determined in step S303 that there is no cell group including a predetermined number or more of consecutive individual electrodes 102A (step S303: NO), the detection circuit 120 returns the process to step S301.

[0084] On the other hand, if it is determined in step S303 that there is a cell group that includes a predetermined number or more of consecutive individual electrodes 102A (step S303: YES), the detection circuit 120 calculates the number of detection objects 20 placed on each cell group that includes a predetermined number or more of consecutive individual electrodes 102A based on the number of consecutive individual electrodes 102A included in the cell group (step S304).

[0085] For example, if the number of consecutive individual electrodes 102A included in a cell group is C and the number of individual electrodes 102A required to detect one detection object 20 is B, the detection circuit 120 calculates the number of detection objects 20 placed on the cell group using the formula (C÷B).

[0086] Then, the detection circuit 120 outputs the number of detection targets 20 for each cell group calculated in step S304 (step S305).

[0087] Next, the detection circuit 120 calculates the number of detection objects 20 placed on the capacitance sensor 100 based on the number of detection objects 20 for each cell group calculated in step S304, and determines whether the number of detection objects 20 placed on the capacitance sensor 100 has increased or decreased by comparing the number of detection objects 20 placed on the capacitance sensor 100 with the number of detection objects 20 placed on the capacitance sensor 100 immediately before (step S306).

[0088] In step S306, if it is determined that there is an increase or decrease in the number of detection objects 20 placed on the capacitance sensor 100 (step S306: YES), the detection circuit 120 outputs the increase or decrease in the number of detection objects 20 placed on the capacitance sensor 100 (step S307), and ends the series of processes shown in Figure 8.

[0089] On the other hand, in step S306, if it is determined that the number of detection objects 20 placed on the capacitance sensor 100 has not increased or decreased (step S306: NO), the detection circuit 120 terminates the series of processes shown in Figure 8.

[0090] By executing the series of processes shown in Figure 7 or Figure 8, the detection circuit 120 can accurately identify and output the number of detection objects 20 placed on the capacitance sensor 100 and the increase or decrease in the number of detection objects 20.

[0091] In particular, the detection circuit 120 calculates the number of detection objects 20 placed on the capacitance sensor 100 using the above formula (A÷B) or (C÷B), so that even if, for example, multiple detection objects 20 are placed together, the number of detection objects 20 can be accurately calculated without being mistakenly detected as one large detection object 20.

[0092] In addition, the series of processes shown in Figure 7 or Figure 8 may further include a threshold determination process in which, with the object to be detected 20 placed on the capacitance sensor 100, the capacitance of the individual electrode 102A with the smallest capacitance among the multiple individual electrodes 102A located in a position overlapping the object to be detected 20 in a planar view is determined as the above-mentioned predetermined threshold to be used in the judgment process of step S202 or step S302.

[0093] As a result, even if an individual electrode 102A has a small amount of overlap with the object to be detected 20 in a planar view and a small capacitance due to the shape of the object to be detected 20, a positional misalignment of the object to be detected 20, etc., the detection circuit 120 can count the individual electrode 102A as an individual electrode 102A that exceeds a predetermined threshold.

[0094] (Experimental Example) Hereinafter, an experimental example will be described with reference to FIGS.

[0095] <Experimental Conditions> Fig. 9 is a diagram showing the experimental conditions used in the experimental example. In this experimental example, as shown in Fig. 9, the placement state of the detection object 20 on the conveyor 21 was changed, and the change in capacitance accompanying the change in placement state was detected by the capacitance sensor 100 according to one embodiment, which was placed below the conveyor 21 with a gap of 3 mm. That is, in this experimental example, the detection object 20 was placed at a distance from the capacitance sensor 100 (so-called floating placement), which can be said to be a relatively difficult condition for the capacitance sensor 100 to detect the detection object 20. Note that the conveyor 21 was composed of multiple rotatable rollers (diameter: 6 mm) arranged side by side at intervals of 2.2 mm in the direction perpendicular to the paper surface.

[0096] <Products> Fig. 10 is a table showing the products used in the experimental example. In this experimental example, as shown in Fig. 10, product A, product B, and product C were used as examples of the detection target object 20.

[0097] Product A: PET bottled drink (water, placed vertically) - Water: Highly conductive Product B: Boxed snacks (chocolate, placed vertically) - Container: Contains conductive aluminum vapor-deposited bag Product C: Boxed snacks (chocolate, placed vertically) - Container: No conductive material

[0098] <First Experimental Results> Fig. 11 is a table showing the first experimental results of the experimental example, which are obtained when Product A shown in Fig. 10 is used.

[0099] As shown in Figure 11, in the results of the first experiment, for the verification type "increase / decrease," when the number of products A placed on the conveyor 21 was changed by 5, 4, 3, 2, or 1, a sufficient change in the detection signal strength of the individual electrodes and a sufficient S / N ratio (20 dB or more) were obtained.

[0100] Furthermore, as shown in Figure 11, in the results of the first experiment, for the verification type "increase / decrease," when the number of products A placed on the conveyor 21 was changed by 5, 4, 3, 2, or 1, the detection circuit 120 provided in the capacitance sensor 100 performed the detection process shown in Figure 7, and it was possible to accurately determine the number of products A placed on the conveyor 21 based on the count number of individual electrodes 102A whose capacitance was equal to or greater than a predetermined threshold.

[0101] Furthermore, as shown in Figure 11, in the results of the first experiment, when the verification type was "arrangement," five products A were placed on the conveyor 21 in five different arrangement patterns, and in each case, a sufficient change in the detection signal strength and a sufficient S / N ratio (20 dB or more) were obtained.

[0102] Furthermore, as shown in Figure 11, in the results of the first experiment, for the verification type "arrangement," five products A were placed on the conveyor 21 in five different arrangement patterns. In each case, the detection circuit 120 provided in the capacitance sensor 100 performed the detection process shown in Figure 7, and the number of products A placed on the conveyor 21 could be accurately determined based on the count number of individual electrodes 102A whose capacitance was equal to or greater than a predetermined threshold.

[0103] <Second Experimental Results> Fig. 12 is a table showing the second experimental results of the experimental example, which are obtained when Product B shown in Fig. 10 is used.

[0104] As shown in Figure 12, in the results of the second experiment, for the verification type "increase / decrease," when the number of products B placed on the conveyor 21 was changed by four, three, two, or one, a sufficient change in the detection signal strength of the individual electrodes and a sufficient S / N ratio (20 dB or more) were obtained.

[0105] Furthermore, as shown in Figure 12, in the results of the second experiment, for the verification type "increase / decrease," when the number of products B placed on the conveyor 21 was changed by four, three, two, or one, the detection circuit 120 provided in the capacitance sensor 100 executed the detection process shown in Figure 7, and it was possible to accurately determine the number of products B placed on the conveyor 21 based on the count number of individual electrodes 102A whose capacitance was equal to or greater than a predetermined threshold.

[0106] <Results of the Third Experiment> Fig. 13 is a table showing the results of the third experiment of the experimental example, in which the product C shown in Fig. 10 was used.

[0107] As shown in Figure 13, in the results of the third experiment, for the verification type "increase / decrease," when the number of products C placed on the conveyor 21 was changed by 5, 4, 3, 2, or 1, a sufficient change in the detection signal strength of the individual electrodes and an effective S / N ratio were obtained in all cases.

[0108] Furthermore, as shown in Figure 13, in the results of the third experiment, for the verification type "increase / decrease," when the number of products C placed on the conveyor 21 was changed by 5, 4, 3, 2, or 1, the detection circuit 120 provided in the capacitance sensor 100 performed the detection process shown in Figure 7, and it was possible to accurately determine the number of products C placed on the conveyor 21 based on the count number of individual electrodes 102A whose capacitance was equal to or greater than a predetermined threshold.

[0109] As described above, in this experimental example, it was confirmed that the capacitance sensor 100 of one embodiment can accurately determine the quantity of the detection object 20 placed on the conveyor 21, even when not only the detection object 20 (product A) with a high dielectric constant, but also the detection object 20 (product B) with an inner bag coated with conductive aluminum and with a relatively low overall dielectric constant, and the detection object 20 (product C) with no conductive material in the container and a low overall dielectric constant are placed floating on the conveyor 21.

[0110] This is because the capacitance type sensor 100 according to one embodiment has a plurality of detection electrodes 102 102A, and also has a side ground electrode 104 sandwiched between the side shield electrode 103, thereby reducing the parasitic capacitance between the detection electrode 102 and the side ground electrode 104 and improving the S / N ratio, and can detect with high sensitivity even if the capacitance of the object to be detected 20 detected by the detection electrode 102 is minute, and furthermore, by providing each shield electrode 103, 106, 109, 112, the effect of reducing parasitic capacitance and the effect of preventing the intrusion of external noise are obtained.

[0111] Although one embodiment of the present invention has been described in detail above, the present invention is not limited to these embodiments, and various modifications and changes are possible within the scope of the gist of the present invention described in the claims.

[0112] For example, in the capacitance sensor 100 of this embodiment, a pair of left and right detection electrodes 102 and a pair of left and right side shield electrodes 103 are provided on the surface 101A of the first insulating layer 101, but this is not limiting, and for example, as in a modified example described below, a single detection electrode 102 may be provided on the surface 101A of the first insulating layer 101. In this case, a single rectangular frame-shaped side shield electrode 103 (i.e., a side shield electrode 103 having two linear portions 103A) surrounding a single detection electrode 102 may be provided on the surface 101A of the first insulating layer 101, or two linear side shield electrodes 103 may be provided to sandwich a single detection electrode 102.

[0113] In addition, in the capacitance sensor 100 of this embodiment, all of the shield electrodes 109, 112 and the background electrode 113 are provided, but this is not limited to this, and any of the shield electrodes 109, 112 and the background electrode 113 may not be provided.

[0114] (Modifications) Fig. 14 is a plan view of a capacitance sensor 100-2 according to a modification of the embodiment. Fig. 15 is a cross-sectional view of the capacitance sensor 100-2 according to a modification of the embodiment taken along the line A-A (see Fig. 14). Fig. 16 is an exploded plan view of the capacitance sensor 100-2 according to a modification of the embodiment. Fig. 17 is a diagram showing a circuit model of the capacitance sensor 100-2 according to the embodiment (when the detection target 20 is present on the capacitance sensor 100-2).

[0115] As shown in Figures 14 to 17, a capacitance sensor 100-2 according to one modified example differs from capacitance sensor 100 in that the surface 101A of the first insulating layer 101 is provided with one detection electrode 102, two linear side shield electrodes 103 sandwiching the detection electrode 102, and one side ground electrode 104 arranged in parallel with the detection electrode 102.

[0116] As shown in Figure 14, the detection electrode 102 provided in one modified example of the capacitance sensor 100-2 is similar to the detection electrode 102 provided in the capacitance sensor 100 in that multiple individual electrodes 102A are arranged side by side in the front-to-back direction (Y-axis direction).

[0117] In addition, in one modified example of the capacitance sensor 100-2, each of the multiple individual electrodes 102A is electrically connected to a corresponding one of the wirings 110A included in the wiring group 110 provided in the wiring layer L3 (within the cutout portion 109A) via a corresponding one of the first through holes 111 (see Figure 15).

[0118] Therefore, similar to the capacitance sensor 100, the capacitance sensor 100-2 according to one modified example can detect changes in the capacitance of each of the plurality of individual electrodes 102A by applying a first AC driving voltage V1 to each of the plurality of individual electrodes 102A from the detection circuit 120 (which in this modified example is provided separately from the capacitance sensor 100-2) via the wiring group 110.

[0119] Furthermore, the capacitance sensor 100-2 according to one variant, like the capacitance sensor 100, can accurately identify the area on the capacitance sensor 100 on which the object to be detected 20 is placed based on the change in the capacitance of each of the plurality of individual electrodes 102A, and further, by performing processing such as that shown in Figure 7 or Figure 8 using the detection circuit 120, can easily and accurately calculate the number of objects to be detected 20 placed on the capacitance sensor 100.

[0120] In addition, since the capacitance sensor 100-2 according to one modified example has one detection electrode 102, as shown in Figures 14 to 17, the bridge wiring layer L2 does not have a connecting member 102B for connecting the pair of left and right individual electrodes 102A to each other.

[0121] In addition, in one modified example, the capacitance sensor 100-2 has two linear side shield electrodes 103 sandwiching one detection electrode 102 on the surface 101A of the first insulating layer 101, but the two linear side shield electrodes 103 are driven by the first AC drive voltage V1 applied simultaneously from the detection circuit 120, and therefore function in the same way as the single rectangular frame-shaped side shield electrode 103 (a pair of left and right linear portions 103A) provided in the capacitance sensor 100.

[0122] In addition, the capacitance sensor 100-2 according to one variant has, like the capacitance sensor 100, a side ground electrode 104, a side shield electrode 103, a first back shield electrode 106, a second back shield electrode 109, a third back shield electrode 112, and a background ground electrode 113, and these electrodes can provide the same effects as the capacitance sensor 100 (such as amplifying the capacitance of the object to be detected 20, reducing parasitic capacitance, and preventing the superposition of external noise).

[0123] This international application claims priority based on Japanese Patent Application No. 2024-145025, filed on August 26, 2024, the entire contents of which are incorporated herein by reference.

[0124] 20 Object to be detected 21 Conveyor 25 A / D converter 30 Operational amplifier 40 Feedback resistor 50 Feedback capacitor 60 First AC voltage circuit 70 Second AC voltage circuit 100, 100-2 Capacitive sensor 101 First insulating layer 101A Front surface 101B Back surface 102 Detection electrode 102A Individual electrode 102B Connecting member 103 Side shield electrode 103A Straight portion 104 Side ground electrode 106 First back shield electrode 106A Opening 107 Second insulating layer 108 Third insulating layer 109 Second back shield electrode 109A Notch 110 Wiring group 110A, 110A-2 Wiring 111 First through hole 112 Third back shield electrode 113 Background ground electrode 114 Cover 115 Second through-hole 120 Detection circuit 121 Capacitance detection unit 121A First drive / detection circuit 121B Second drive circuit 122 Processing unit 124 I / F Ds Detection signal L1 Electrode layer L2 Bridge wiring layer L3 Wiring layer L4 Back shield layer V1 First AC drive voltage V2 Second AC drive voltage

Claims

a first insulating layer; a detection electrode extending in a first direction on a surface of the first insulating layer; a side shield electrode arranged in parallel to the detection electrode on the surface of the first insulating layer; a side ground electrode arranged in parallel to the detection electrode and the side shield electrode on the surface of the first insulating layer and connected to ground potential; and a first back shield electrode arranged on the other surface of the first insulating layer and facing the detection electrode via the first insulating layer, wherein a first AC drive voltage is applied to the detection electrode, and a second AC drive voltage having the same frequency and phase as the first AC drive voltage is applied to the side shield electrode and the first back shield electrode, wherein the detection electrode has a plurality of individual electrodes arranged in parallel at intervals in the first direction, and the side shield electrode is arranged in parallel between the detection electrode and the side ground electrode.

2. A capacitance type sensor as described in claim 1, characterized in that it comprises a second insulating layer provided on the back side of the first back shield electrode, a wiring layer provided on the back side of the second insulating layer, and a third insulating layer provided on the back side of the wiring layer, wherein the wiring layer has a second back shield electrode provided so as to cover the back side of the second insulating layer, and a group of wirings arranged within a cutout formed in the second back shield electrode, one end connected to a detection circuit and the other end connected to each of the plurality of individual electrodes via through holes that penetrate the first insulating layer, the first back shield electrode, and the second insulating layer.

3. The capacitance type sensor according to claim 2, wherein the second AC drive voltage is applied to the second back shield electrode.

4. The capacitance type sensor according to claim 3, further comprising a third back shield electrode provided on the back surface side of the third insulating layer, wherein the second AC drive voltage is applied to the third back shield electrode.

5. The capacitance type sensor according to claim 4, further comprising a background electrode provided on the back side of the third back shield electrode, spaced apart from and facing the third back shield electrode, and connected to a ground potential.

6. The capacitance type sensor according to claim 1, wherein the side shield electrode has two straight portions parallel to each other, and the detection electrode is disposed between the two straight portions.

7. A detection circuit for a capacitance type sensor as defined in claim 1, comprising: a first drive / detection circuit that applies the first AC drive voltage to the detection electrode and detects changes in the current flowing through the detection electrode; and a second drive circuit that applies a second AC drive voltage to the first back shield electrode and the side shield electrode, wherein the amplitude of the second AC drive voltage is greater than the amplitude of the first AC drive voltage.

8. A detection circuit for a capacitance type sensor as claimed in claim 3, comprising: a first drive / detection circuit that applies the first AC drive voltage to the detection electrode and detects changes in the current flowing through the detection electrode; and a second drive circuit that applies the second AC drive voltage to the first back shield electrode, the side shield electrode and the second back shield electrode, wherein the amplitude of the second AC drive voltage is greater than the amplitude of the first AC drive voltage.

9. A capacitance type sensor comprising: a first insulating layer; a side ground electrode disposed on the surface of the first insulating layer and connected to a ground potential; a pair of detection electrodes arranged on both sides of the side ground electrode on the surface of the first insulating layer, a pair of side shield electrodes arranged on the surface of the first insulating layer, each of the pair of detection electrodes, and a first back shield electrode arranged on the other surface of the first insulating layer and facing the detection electrode via the first insulating layer; wherein a first AC drive voltage is applied to the pair of detection electrodes, and a second AC drive voltage having the same frequency and phase as the first AC drive voltage is applied to the pair of side shield electrodes and the first back shield electrode, each of the pair of detection electrodes having a plurality of individual electrodes arranged side by side at intervals in a first direction, and the pair of side shield electrodes are arranged side by side between each of the pair of detection electrodes and the side ground electrode.

10. A capacitance type sensor as described in claim 9, characterized in that it has a plurality of individual electrode pairs, each consisting of one of the individual electrodes of one of the detection electrodes and one of the individual electrodes of the other of the detection electrodes, the plurality of individual electrode pairs being arranged in parallel with a gap in the first direction, and each of the plurality of individual electrode pairs being connected by a bridge wiring layer via the first insulating layer to the one of the individual electrodes of the other of the detection electrodes.

11. A capacitance type sensor as described in claim 10, characterized in that each of the plurality of individual electrode pairs is connected between one of the individual electrodes of one of the detection electrodes and one of the individual electrodes of the other of the detection electrodes by a connecting member provided in the bridge wiring layer via a through hole that penetrates the first insulating layer, and the first back shield electrodes are provided on both outsides of the connecting member in the bridge wiring layer.

12. The capacitance type sensor according to claim 11, further comprising a second insulating layer provided on the rear surface side of the first back shield electrode and a second back shield electrode provided so as to cover the rear surface of the second insulating layer.

13. A capacitance type sensor as described in claim 9, characterized in that it comprises a second insulating layer provided on the back side of the first back shield electrode and a wiring layer provided on the back side of the second insulating layer, the wiring layer having a group of wires whose one end is connected to a detection circuit and whose other end is connected to each of the plurality of individual electrodes via through holes that penetrate the first insulating layer, the first back shield electrode, and the second insulating layer.

14. The capacitance type sensor described in claim 13, characterized in that the wiring layer has a second back shield electrode arranged to cover the back surface of the second insulating layer, and the wiring group is arranged within a cutout formed in the second back shield electrode.

15. The capacitance type sensor described in claim 14, further comprising: a third insulating layer provided on the back side of the wiring layer; and a third back shield electrode provided on the back side of the third insulating layer, wherein the second AC drive voltage is applied to the third back shield electrode.

16. The capacitance type sensor according to claim 15, further comprising a background electrode provided on the back surface side of the third back shield electrode, spaced apart from and facing the third back shield electrode, and connected to a ground potential.

17. The capacitance type sensor according to claim 9, wherein each of the pair of side shield electrodes has two straight portions parallel to each other, and each of the pair of detection electrodes is disposed between the two straight portions.

18. A detection circuit for a capacitance type sensor as described in claim 9, comprising: a first drive / detection circuit that applies the first AC drive voltage to the detection electrode and detects changes in the current flowing through the detection electrode; and a second drive circuit that applies the second AC drive voltage to the side shield electrode and the first back shield electrode, wherein the amplitude of the second AC drive voltage is greater than the amplitude of the first AC drive voltage.

19. A detection circuit for a capacitance type sensor as described in claim 15, comprising: a first drive / detection circuit that applies the first AC drive voltage to the detection electrode and detects changes in the current flowing through the detection electrode; and a second drive circuit that applies the second AC drive voltage to the side shield electrode, the first back shield electrode, the second back shield electrode, and the third back shield electrode, wherein the amplitude of the second AC drive voltage is greater than the amplitude of the first AC drive voltage.

20. A capacitance type sensor as described in claim 17, characterized in that it comprises a second insulating layer provided on the back side of the first back shield electrode and a wiring layer provided on the back side of the second insulating layer, the wiring layer having a group of wires each having one end connected to a detection circuit and the other end connected to each of the plurality of individual electrodes via through holes that penetrate the first insulating layer, the first back shield electrode, and the second insulating layer.

21. The capacitance type sensor described in claim 20, characterized in that the wiring layer is provided so as to cover the back surface of the second insulating layer and has a second back shield electrode to which the second AC driving voltage is applied, and the wiring group is arranged within a cutout formed in the second back shield electrode.

22. The capacitance type sensor described in claim 21, further comprising: a third insulating layer provided on the back side of the wiring layer; and a third back shield electrode provided on the back side of the third insulating layer, wherein the second AC drive voltage is applied to the third back shield electrode.

23. The capacitance type sensor according to claim 22, further comprising a background electrode provided on the back surface side of the third back shield electrode, spaced apart from and facing the third back shield electrode, and connected to a ground potential.

24. A detection method using a detection circuit provided in the capacitance sensor of claim 1, comprising: a counting step of counting the number of the individual electrodes whose capacitance exceeds a predetermined threshold; a placement number calculation step of calculating the number of detection objects placed on the capacitance sensor by dividing the number of the individual electrodes counted in the counting step by the number of the individual electrodes corresponding to one detection object; and an increase / decrease number output step of outputting an increase / decrease number in the number of detection objects placed on the capacitance sensor by comparing the number of detection objects calculated immediately before in the placement number calculation step with the latest number of detection objects calculated in the placement number calculation step.

25. The detection method described in claim 24, further comprising a threshold determination step of determining, as the predetermined threshold value, the capacitance of the individual electrode having the smallest capacitance among the plurality of individual electrodes arranged in a position overlapping the object to be detected in a planar view when the object to be detected is placed on the capacitance type sensor.

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