Capacitive sensor, sensor sheet, sensor unit, detection circuit, and capacitance detection device

Abstract

This capacitive sensor comprises: a base material; a detection electrode disposed on one surface of the base material; and a back shield electrode disposed on the other surface of the base material so as to face the detection electrode with the base material interposed therebetween. A first AC drive voltage is applied to the detection electrode, and a second AC drive voltage having the same frequency and the same phase as the first AC drive voltage is applied to the back shield electrode. The capacitive sensor further comprises an output amplification reverse phase electrode which is arranged side by side with the detection electrode on the one surface of the base material and to which is applied a third AC drive voltage that has the same frequency as the second AC drive voltage and that is opposite in phase to the second AC drive voltage.

Description

Capacitive sensor, sensor sheet, sensor unit, detection circuit, and capacitance detection device

[0001] The present invention relates to a capacitance sensor, a sensor sheet, a sensor unit, a detection circuit, and a capacitance detection device.

[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] Furthermore, Patent Documents 2 and 3 listed below disclose a technique for adjusting a second AC voltage in a capacitance detection device having a shield electrode arranged on the back side of the detection electrode so that the drive current of the detection electrode becomes zero when there is no object close to the detection electrode.

[0004] Furthermore, Patent Document 3 listed below discloses a technique for adjusting a second AC voltage in a capacitance detection device having a shield electrode arranged on the back side of the detection electrode, so that the amplitude of an operational amplifier is smaller than the amplitude of a first AC voltage supplied to the shield electrode.

[0005] International Publication No. 2009 / 044920 International Publication No. 2018 / 116706 International Publication No. 2021 / 090636

[0006] However, in the techniques of Patent Documents 1 to 3, if the conductivity or dielectric constant of the object to be detected is low, the capacitance of the object to be detected by the detection electrode becomes small, and therefore the object to be detected cannot be detected with high sensitivity.

[0007] A capacitance-type sensor according to one embodiment comprises a substrate, a detection electrode disposed on one surface of the substrate, and a back shield electrode disposed on the other surface of the substrate opposite the detection electrode via the substrate, 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 back shield electrode, and the capacitance-type sensor further comprises an output amplification antiphase electrode disposed on one surface of the substrate in parallel with the detection electrode and to which a third AC drive voltage having the same frequency and antiphase as the second AC drive voltage is applied.

[0008] According to the capacitance type sensor of one embodiment, it is possible to detect a detection target having a low conductivity or dielectric constant with high sensitivity.

[0009] FIG. 1 is a plan view of a capacitance type sensor according to a first embodiment; FIG. 2 is a cross-sectional view of a capacitance type sensor according to a first embodiment; FIG. 3 is a diagram showing a circuit model of a capacitance detection device according to a first embodiment (when a detection target is not present on the capacitance type sensor); FIG. 4 is a diagram showing a circuit model of a capacitance detection device according to a first embodiment (when a detection target is present on the capacitance type sensor); FIG. 5 is a diagram showing an example of a drive waveform of each AC drive voltage applied to the capacitance type sensor according to the first embodiment; FIG. 6 is a diagram showing an example of a circuit configuration of a capacitance detection unit included in the capacitance detection device according to the first embodiment;

[0010] 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.

[0011] First Embodiment (Configuration of Capacitive Sensor 100) Fig. 1 is a plan view of a capacitive sensor 100 according to a first embodiment. Fig. 2 is a cross-sectional view of the capacitive sensor 100 according to the first embodiment.

[0012] As shown in FIGS. 1 and 2, the capacitance type sensor 100 according to the first embodiment includes a substrate 101, a detection electrode 102, an output amplification antiphase electrode 104, and a back shield electrode 106.

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

[0014] The detection electrode 102 is a thin-film electrode made of a conductive material such as metal, inorganic conductive oxide, or conductive resin, and provided on the upper surface 101A (an example of "one surface") of the substrate 101. The detection electrode 102 has a strip shape that extends linearly in the front-to-rear direction (Y-axis direction) on the upper surface 101A of the substrate 101.

[0015] Output amplification antiphase electrode 104 is a thin-film electrode made of a conductive material such as metal, inorganic conductive oxide, or conductive resin, provided on upper surface 101A of substrate 101. Output amplification antiphase electrode 104 has a strip shape that extends linearly in the front-to-rear direction (Y-axis direction) on upper surface 101A of substrate 101. Output amplification antiphase electrode 104 is provided in parallel with detection electrode 102 on the left side of detection electrode 102 (negative side of the X-axis).

[0016] The back shield electrode 106 is a thin-film electrode provided on the lower surface 101B (an example of the "other surface") of the substrate 101 and made of a conductive material such as metal, inorganic conductive oxide, or conductive resin. The back shield electrode 106 has the same shape (i.e., rectangular) as the lower surface 101B of the substrate 101 when viewed from above (positive direction of the Z axis) in a plan view so as to cover the entire lower surface 101B of the substrate 101 or at least the detection electrode 102. The back shield electrode 106 is disposed opposite the detection electrode 102 across the substrate 101.

[0017] (Circuit Model of Capacitance Detection Device 10) Fig. 3 is a diagram showing a circuit model of the capacitance detection device 10 according to the first embodiment (when the detection object 20 is not present on the capacitance sensor 100). Fig. 4 is a diagram showing a circuit model of the capacitance detection device 10 according to the first embodiment (when the detection object 20 is present on the capacitance sensor 100).

[0018] As shown in FIGS. 3 and 4, the capacitance detection device 10 includes a capacitance sensor 100 and a detection circuit 120.

[0019] As shown in FIGS. 3 and 4, the detection circuit 120 includes a capacitance detection unit 121, a processing unit 122, an I / F (interface) 124, and a phase inversion circuit 125.

[0020] The capacitance detection unit 121 is electrically connected to the detection electrode 102 and the back shield electrode 106. The capacitance detection unit 121 includes a first drive / detection circuit 121A, a second drive circuit 121B, and a phase inversion circuit 125.

[0021] The first drive and detection circuit 121A generates a first AC drive voltage V1 and applies the first AC drive voltage V1 to the detection electrode 102. The first drive and 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.

[0022] 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 back shield electrode 106.

[0023] The phase inversion circuit 125 has an input electrically connected between the second drive circuit 121B and the back shield electrode 106, and an output electrically connected to the output amplification anti-phase electrode 104. The phase inversion circuit 125 inverts the phase of the second AC drive voltage V2 generated by the second drive circuit 121B to generate a third AC drive voltage V3 having the same frequency and an opposite phase to the first AC drive voltage V1, and applies the third AC drive voltage V3 to the output amplification anti-phase electrode 104.

[0024] 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.

[0025] 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.

[0026] (Parasitic Capacitance Generated in Capacitive Sensor 100) As shown in FIGS. 3 and 4, the following parasitic capacitances are generated in the capacitive sensor 100 according to the first embodiment.

[0027] Parasitic capacitance between the detection electrode 102 and the ground potential: Crgl(a) Parasitic capacitance between the detection electrode 102 and the output amplification anti-phase electrode 104: Crgl(b) Parasitic capacitance between the detection electrode 102 and the back shield electrode 106: Crs(a) Parasitic capacitance between the output amplification anti-phase electrode 104 and the back shield electrode 106: Csg(a)

[0028] (Driving Waveforms of Each AC Driving Voltage) FIG. 5 is a diagram showing an example of the driving waveforms of each AC driving voltage applied to the capacitance sensor 100 according to the first embodiment.

[0029] The first AC drive voltage V1 shown in Fig. 5 is a sine wave applied from the detection circuit 120 to the detection electrode 102. The second AC drive voltage V2 shown in Fig. 5 is a sine wave applied from the detection circuit 120 to the back shield electrode 106. The third AC drive voltage V3 shown in Fig. 5 is a sine wave applied from the detection circuit 120 to the output amplification anti-phase electrode 104.

[0030] 5, the second AC drive voltage V2 has the same frequency and phase as the first AC drive voltage V1. On the other hand, the third AC drive voltage V3 is obtained by inverting the phase of the second AC drive voltage V2 by the phase inversion circuit 125. That is, the third AC drive voltage V3 has the same frequency and the opposite phase as the first AC drive voltage V1.

[0031] 5 shows a case where the amplitude of the second AC drive voltage V2 is set larger than the amplitude of the first AC drive voltage V1. Therefore, the voltage difference between the first AC drive voltage V1 applied to the detection electrode 102 and the third AC drive voltage V3 applied to the output amplification anti-phase electrode 104 is approximately twice or more the voltage difference between the first AC drive voltage V1 and ground potential. Therefore, the capacitance-type sensor 100 according to the first embodiment can approximately double the current flowing through the capacitance (Crg+Crg') of the detection object 20 detected by the detection electrode 102, compared to a case where the output amplification anti-phase electrode 104 is connected to ground potential without being connected to the phase inversion circuit 125.

[0032] 6 is a diagram showing an example of the circuit configuration of the capacitance detection unit 121 included in the capacitance detection device 10 according to the first 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.

[0033] The first drive / detection circuit 121A is electrically connected to the detection electrode 102 via the lead wiring 11A-1. 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.

[0034] 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 .

[0035] The inverting input terminal (−) of the operational amplifier 30 is connected to the detection electrode 102 via the lead wire 11A-1, 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.

[0036] 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 back shield electrode 106 via the lead wiring 11A-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.

[0037] (Configuration Example of Phase Inversion Circuit 125) FIG. 7 is a diagram showing a configuration example of the phase inversion circuit 125 included in the electrostatic capacitance detection device 10 according to the first embodiment. For example, as shown in FIG. 7, the phase inversion circuit 125 has an operational amplifier 125A. The second AC drive voltage V2 generated by the second AC voltage circuit 70 is input to the inverting input terminal (−) of the operational amplifier 125A. The non-inverting input terminal (+) of the operational amplifier 125A is connected to ground potential. A feedback resistor 125B is connected in parallel between the output terminal of the second AC drive voltage V2 and the inverting input terminal (−) to apply negative feedback. This allows the phase inversion circuit 125 to output a third AC drive voltage V3 having the same frequency as but opposite in phase to the second AC drive voltage V2 from the output terminal of the operational amplifier 30.

[0038] The phase inversion circuit 125 may further include a configuration for amplifying the amplitude of the third AC drive voltage V3 or a configuration for adjusting the amplitude of the third AC drive voltage V3. As a result, for example, by making the amplitude of the third AC drive voltage V3 larger than the amplitude of the first AC drive voltage V1, the voltage difference between the first AC drive voltage V1 and the third AC drive voltage V3 can be made two or more times larger, and therefore the current flowing through the capacitance (Crg+Crg') of the detection object 20 detected by the detection electrode 102 can be amplified by two or more times.

[0039] (Detection Operation of Capacitive Sensor 100) In the capacitive sensor 100 according to the first embodiment configured as described above, the detection electrode 102 is driven by a first AC drive voltage V1 supplied from the detection circuit 120. As a result, in the capacitive sensor 100 according to the first embodiment, when the placement state of the detection object 20 on the capacitive sensor 100 changes, the capacitance (Crg+Crg') of the detection object 20 detected by the detection electrode 102 changes. Therefore, the detection circuit 120 according to the first embodiment can determine the placement state of the detection object 20 on the capacitive 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 electrode 102.

[0040] Here, the capacitance-type sensor 100 according to the first embodiment has a back shield electrode 106 provided on the lower surface 101B of the substrate 101 so as to face the detection electrode 102, and the back shield electrode 106 is driven by a second AC drive voltage V2 having the same frequency and phase as the first AC drive voltage V1 applied to the detection electrode 102. The amplitude of the second AC drive voltage V2 is set to be larger than the amplitude of the first AC drive voltage V1.

[0041] As a result, in the capacitance sensor 100 of the first embodiment, as shown in Figures 3 and 4, the sum of the current Irgl(b) flowing through the parasitic capacitance Crgl(b) between the detection electrode 102 and the output amplification antiphase electrode 104 and the current Irgl(a) flowing through the parasitic capacitance Crgl(a) between the detection electrode 102 and ground potential is canceled out by the current Irs-b flowing through the parasitic capacitance Crs(a) between the back shield electrode 106 and the detection electrode 102. This is because the capacitance detection unit 121 appropriately adjusts the amplitude of the first AC drive voltage V1 applied to the detection electrode 102 and the amplitude of the second AC drive voltage V2 applied to the back shield electrode 106 so that the current Irs-b flowing from the back shield electrode 106, to which the second AC drive voltage V2 is applied, to the detection electrode 102 is equal to the sum of the current Irgl(a) and current Irgl(b) flowing out of the detection electrode 102.

[0042] Therefore, in the capacitance type sensor 100 of the first embodiment, the sum of the parasitic capacitance Crgl(b) between the detection electrode 102 and the output amplification antiphase electrode 104 and the parasitic capacitance Crgl(a) between the detection electrode 102 and the ground potential can be offset by the parasitic capacitance Crs(a) between the back shield electrode 106 and the detection electrode 102.

[0043] As described above, in the capacitance sensor 100 according to the first embodiment, when no detection object 20 is present on the capacitance sensor 100 as shown in FIG. 3 , the parasitic capacitance Crgl (Crgl(a) + Crgl(b)) occurring between the detection electrode 102 and the ground potential / output amplification anti-phase electrode 104 can be offset by the parasitic capacitance Crs(a) of the back shield electrode 106. Therefore, as shown in FIG. 4 , when a detection object 20 is present on the capacitance sensor 100, the capacitance detected by the detection electrode 102 is the capacitance (Crg + Crg') of the detection object 20, with the parasitic capacitance Crgl eliminated. Therefore, the capacitance sensor 100 according to the first embodiment can improve the detection accuracy of the detection object 20 by the detection electrode 102. The capacitance (Crg+Crg') of the detection object 20 detected by the detection electrode 102 is detected by the first drive and detection circuit 121A as a change Ie in the current Is.

[0044] Furthermore, in the capacitance sensor 100 according to the first embodiment, the output amplification anti-phase electrode 104 is disposed juxtaposed to the detection electrode 102 on the upper surface 101A of the substrate 101. Therefore, in the capacitance sensor 100 according to the first embodiment, as shown in FIG. 4 , when a detection object 20 is present, 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 output amplification anti-phase electrode 104. Therefore, in the capacitance sensor 100 according to the first embodiment, when a detection object 20 is present, the capacitance of the detection object 20 detected by the detection electrode 102 is 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.

[0045] In particular, in the capacitance sensor 100 according to the first embodiment, the output amplification anti-phase electrode 104 is driven by a third AC drive voltage V3 having the same frequency and anti-phase as the first AC drive voltage V1 applied to the detection electrode 102. As shown in Fig. 5 , the voltage difference between the first AC drive voltage V1 and the third AC drive voltage V3 is V, which is approximately twice or more the voltage difference between the first AC drive voltage V1 and the ground potential. As a result, as shown in Fig. 4 , the capacitance sensor 100 according to the first embodiment can amplify the current flowing through the capacitance (Crg+Crg') of the detection object 20 detected by the detection electrode 102 when the detection object 20 is present. Specifically, the capacitance sensor 100 according to the first embodiment can approximately double the current flowing through the capacitance (Crg+Crg') of the detection object 20 compared to when the output amplification anti-phase electrode 104 is connected to ground potential. Therefore, the capacitance sensor 100 according to the first embodiment can further improve the detection accuracy of the detection electrode 102 for the detection object 20.

[0046] As described above, the capacitance-type sensor 100 according to the first embodiment includes a substrate 101, a detection electrode 102 arranged on one surface of the substrate 101, and a back shield electrode 106 arranged on the other surface of the substrate 101 so as to face the detection electrode 102 with the substrate 101 interposed therebetween. A first AC drive voltage V1 is applied to the detection electrode 102, and a second AC drive voltage V2 having the same frequency and the same phase as the first AC drive voltage V1 is applied to the back shield electrode 106. The capacitance-type sensor 100 further includes an output amplification antiphase electrode 104 arranged in parallel with the detection electrode 102 on one surface of the substrate 101, and to which a third AC drive voltage V3 having the same frequency and the opposite phase as the second AC drive voltage V2 is applied.

[0047] As a result, by applying the third AC drive voltage V3 to the output amplification anti-phase electrode 104, the capacitance type sensor 100 according to the first embodiment can amplify the capacitance of the detection object 20 detected by the detection electrode 102 to approximately twice the sum of the capacitance between the detection electrode 102 and the detection object 20 and the capacitance between the detection object 20 and the output amplification anti-phase electrode 104. Therefore, the capacitance type sensor 100 according to the first embodiment can detect the detection object 20 having a low conductivity or dielectric constant with high sensitivity.

[0048] In the capacitance sensor 100 according to the first embodiment, the detection circuit 120 may make the amplitude of the second AC drive voltage V2 applied from the second drive circuit 121B to the back shield electrode 106 larger than the amplitude of the first AC drive voltage V1 applied from the first drive / detection circuit 121A to the detection electrode 102.

[0049] In this case, the capacitance type sensor 100 according to the first embodiment can efficiently cancel out the parasitic capacitance Crgl (Crgl(a)+Crgl(b)) between the detection electrode 102 and the ground potential and between the detection electrode 102 and the output amplification anti-phase electrode 104 by the parasitic capacitance (Crs(a)) between the detection electrode 102 and the 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.

[0050] Second Embodiment (Configuration of Capacitive Sensor 100-2) Fig. 8 is a plan view of a capacitive sensor 100-2 according to a second embodiment. Fig. 9 is a cross-sectional view of the capacitive sensor 100-2 according to the second embodiment.

[0051] As shown in FIGS. 8 and 9, the capacitance sensor 100-2 according to the second embodiment differs from the capacitance sensor 100 according to the first embodiment in that it further includes a first side shield electrode 103.

[0052] The first side shield electrode 103 is a thin-film electrode provided on the upper surface 101A of the substrate 101 and made of a conductive material such as metal, inorganic conductive oxide, or conductive resin. The first side shield electrode 103 has a strip shape that extends linearly in the front-to-rear direction (Y-axis direction). The first side shield electrode 103 is arranged in parallel between the detection electrode 102 and the output amplification anti-phase electrode 104. The first side shield electrode 103 is electrically connected to the back shield electrode 106. As a result, the first side shield electrode 103, together with the back shield electrode 106, is driven by application of a second AC drive voltage V2 from a first drive / detection circuit 121A of the detection circuit 120.

[0053] Although not shown, the circuit model of the capacitance detection device 10 according to the second embodiment differs from the circuit model of the capacitance detection device 10 according to the first embodiment shown in Figures 3 and 4 in that a capacitance sensor 100-2 is provided instead of the capacitance sensor 100, and in that in the capacitance sensor 100-2, the first side shield electrode 103 is electrically connected to the back shield electrode 106.

[0054] The capacitance sensor 100-2 according to the second embodiment can reduce the parasitic capacitance between the detection electrode 102 and the output amplification anti-phase electrode 104 by juxtaposing the first side shield electrode 103 between the detection electrode 102 and the output amplification anti-phase electrode 104 and applying the second AC drive voltage V2 to the first side shield electrode 103. Therefore, the capacitance sensor 100-2 according to the second embodiment can detect the detection object 20 having a low conductivity or dielectric constant with even higher sensitivity.

[0055] Third Embodiment (Configuration of Capacitive Sensor 100-3) Fig. 10 is a plan view of a capacitive sensor 100-3 according to a third embodiment. Fig. 11 is a cross-sectional view of the capacitive sensor 100-3 according to the third embodiment.

[0056] As shown in FIGS. 10 and 11, the capacitance sensor 100-3 according to the third embodiment differs from the capacitance sensor 100-2 according to the second embodiment in that it further includes a second side shield electrode 105.

[0057] The second side shield electrode 105 is a thin-film electrode provided on the upper surface 101A of the substrate 101 and made of a conductive material such as metal, inorganic conductive oxide, or conductive resin. The second side shield electrode 105 has a strip shape that extends linearly in the front-to-rear direction (Y-axis direction). The second side shield electrode 105 is arranged parallel to the detection electrode 102 on the right side (positive side of the X-axis) of the detection electrode 102. As a result, the detection electrode 102 is arranged parallel to the first side shield electrode 103 and the second side shield electrode 105. The second side shield electrode 105 is electrically connected to the back shield electrode 106. As a result, the second side shield electrode 105, together with the back shield electrode 106 and the first side shield electrode 103, is driven by application of a second AC drive voltage V2 from the first drive / detection circuit 121A of the detection circuit 120.

[0058] Although not shown, the circuit model of the capacitance detection device 10 according to the third embodiment differs from the circuit model of the capacitance detection device 10 according to the first embodiment shown in FIGS. 3 and 4 in that a capacitance sensor 100-3 is provided instead of the capacitance sensor 100, and in that in the capacitance sensor 100-3, the first side shield electrode 103 and the second side shield electrode 105 are each electrically connected to the back shield electrode 106.

[0059] In the capacitance sensor 100-3 according to the third embodiment, the second side shield electrode 105 is provided in parallel with the outer side (positive side of the X-axis) of the detection electrode 102, and thus the second side shield electrode 105 to which the second AC drive voltage V2 is applied can prevent external noise from flowing into the detection electrode 102 from the outer side in the width direction of the capacitance sensor 100-2 (positive side of the X-axis). This allows the capacitance sensor 100-3 according to the third embodiment to have improved resistance to external noise. Therefore, the capacitance sensor 100-3 according to the third embodiment can improve the stability of the high S / N ratio of the detection signal compared to the capacitance sensor 100 according to the first embodiment and the capacitance sensor 100-2 according to the second embodiment.

[0060] <Experimental Example> Fig. 12 is a table showing the products used in the experimental example, and Fig. 13 is a table showing a list of the detection results of the experimental example.

[0061] In the experimental example, the following five capacitance sensors (1) to (5) were used to detect changes in capacitance (changes in detection signal strength) associated with changes in the display state of product A on the shelves of a product shelf, as shown in Fig. 12. Specifically, the changes in capacitance (changes in detection signal strength) were detected when product A on the first shelf was placed and removed, when product A on the second shelf was placed and removed, and when product A on the third shelf was placed and removed.

[0062] Product A: Packaged sweets (chocolate, laid flat, stacked three layers)

[0063] (1) Capacitive sensor 100 according to the first embodiment (with output amplification reverse phase electrode 104) (2) Comparative Example 1: The output amplification reverse phase electrode 104 of the capacitive sensor 100 is not connected to the phase inversion circuit 125, but functions as a side ground electrode connected to the ground potential of the detection circuit 120.

[0064] (3) Second embodiment: Capacitive sensor 100-2 according to the second embodiment (with output amplification anti-phase electrode 104 and first side shield electrode 103) (4) Comparative example 2: The output amplification anti-phase electrode 104 of the capacitive sensor 100-2 is not connected to the phase inversion circuit 125, but functions as a side ground electrode connected to the ground potential of the detection circuit 120.

[0065] (5) Prior art: A side shield electrode is provided in place of the output amplification antiphase electrode 104 of the capacitance type sensor 100. Here, the side shield electrode is electrically connected to the back shield electrode 106, and a second AC drive voltage V2 is applied to the side shield electrode.

[0066] As shown in Figure 13, in the experimental example, for each of the capacitance sensors (1) to (4), a sufficient change in detection signal strength and a sufficient S / N ratio (20 dB or more) were obtained when product A was placed and removed from the first tier, when product A was placed and removed from the second tier, and when product A was placed and removed from the third tier.

[0067] In this way, in the experimental example, both capacitance type sensors (1) and (3) have an output amplification inverted phase electrode 104, and both capacitance type sensors (2) and (4) have a side ground electrode, so that changes in the display state of product A (changes in the detection signal strength) could be detected with high sensitivity.

[0068] As shown in FIG. 13, in the experimental example, the capacitance sensor (1) was able to obtain a change in detection signal strength that was more than twice as large as that obtained by the capacitance sensor (2) when product A was placed on and removed from the first tier, when product A was placed on and removed from the second tier, and when product A was placed on and removed from the third tier.

[0069] This is because in the capacitance type sensor (1), a third AC drive voltage V3 is applied to the output amplification antiphase electrode 104, whereas in the capacitance type sensor (2), the output amplification antiphase electrode 104 functions as a side ground electrode connected to the ground potential.

[0070] Similarly, as shown in Figure 13, in the experimental example, the capacitance sensor (3) was able to obtain more than twice the change in detection signal strength compared to the capacitance sensor (4) when product A was placed on and removed from the first tier, when product A was placed on and removed from the second tier, and when product A was placed on and removed from the third tier.

[0071] This is because, in the capacitance type sensor (3), a third AC drive voltage V3 is applied to the output amplification antiphase electrode 104, whereas in the capacitance type sensor (4), the output amplification antiphase electrode 104 functions as a side ground electrode connected to the ground potential.

[0072] Furthermore, as shown in FIG. 13, in the experimental example, the capacitance sensor (3) was able to obtain a larger change in the detection signal strength when placing and removing product A on the second tier and when placing and removing product A on the third tier, compared to the capacitance sensor (1).

[0073] This is because the first side shield electrode 103 is provided in parallel between the detection electrode 102 and the output amplification anti-phase electrode 104, and a second AC drive voltage V2 is applied to the first side shield electrode 103, thereby reducing the parasitic capacitance between the detection electrode 102 and the output amplification anti-phase electrode 104 more than the capacitance sensor (1), making it more advantageous for detecting when a product A is placed or removed from the second or third row, which are higher in position. Note that, as shown in Figure 13, the capacitance sensor (3) is able to ensure a sufficient change in detection signal strength even when a product A is placed or removed from the first row.

[0074] As shown in Figure 13, in the experimental example, when product A was placed on and removed from the first tier, when product A was placed on and removed from the second tier, and when product A was placed on and removed from the third tier, the capacitance sensor (5) was unable to obtain a sufficient change in detection signal strength, and product A could not be detected.

[0075] 14 is a plan view of a capacitance detection device 10 according to a first embodiment. As shown in Fig. 14, the capacitance detection device 10 according to the first embodiment includes a sensor sheet 12. The sensor sheet 12 has a plurality of capacitance sensors 100 (three capacitance sensors 100 in the example shown in Fig. 14) arranged side by side in the left-right direction (X-axis direction).

[0076] Each capacitance sensor 100 provided on the sensor sheet 12 is a sheet-like sensor that extends linearly in the front-to-rear direction (Y-axis direction). Each capacitance sensor 100 provided on the sensor sheet 12 is configured to be able to detect a detection target 20 placed on the capacitance sensor 100 by a self-capacitance method. The sensor sheet 12 is entirely covered by a cover 107.

[0077] The capacitance detection device 10 according to the first embodiment also includes a circuit board 11 and a detection circuit 120 provided on the circuit board 11. The detection circuit 120 is connected to each of the multiple capacitance sensors 100 provided on the sensor sheet 12 via lead-out wiring 11A. Each of the multiple capacitance sensors 100 provided on the sensor sheet 12 includes a connection portion 100A with the lead-out wiring 11A provided at an end on the positive side of the Y axis (one end in the first direction). The detection circuit 120 drives each of the multiple capacitance sensors 100 provided on the sensor sheet 12, thereby enabling each of the multiple capacitance sensors 100 provided on the sensor sheet 12 to detect the detection target 20 and enabling the detection result of the detection target 20 to be obtained from each of the multiple capacitance sensors 100 provided on the sensor sheet 12.

[0078] For example, the capacitance detection device 10 according to the first embodiment can be used to detect the display state of products on a shelf 21 of a product shelf in a store that sells a plurality of products. For example, in the example shown in Fig. 14 , the sensor sheet 12 included in the capacitance detection device 10 according to the first embodiment includes a capacitance sensor 100 for each of a plurality of product rows 21A (three product rows 21A in the example shown in Fig. 14 ) on a shelf 21 of the product shelf. This allows the capacitance detection device 10 to detect the display state of products in each of the plurality of product rows 21A (presence or absence of products, number of products, etc.) using the self-capacitance method, using the plurality of capacitance sensors 100 included in the sensor sheet 12.

[0079] In addition, the capacitance detection device 10 of the first embodiment may use any of the capacitance sensor 100 of the first embodiment, the capacitance sensor 100-2 of the second embodiment, and the capacitance sensor 100-3 of the third embodiment for each of the multiple capacitance sensors 100.

[0080] Second Example Fig. 15 is a plan view of a capacitance detection device 10-2 according to a second example. As shown in Fig. 15, the capacitance detection device 10-2 according to the second example includes a sensor unit 13 composed of a plurality of sensor sheets 12 (four sensor sheets 12 in the example shown in Fig. 15) arranged side by side in the left-right direction (X-axis direction). Each of the four sensor sheets 12 included in the sensor unit 13 has a configuration similar to that of the sensor sheet 12 included in the capacitance detection device 10 according to the first example. That is, each of the four sensor sheets 12 included in the sensor unit 13 includes a plurality of capacitance sensors 100 (three capacitance sensors 100 in the example shown in Fig. 15) arranged side by side in the left-right direction (X-axis direction).

[0081] The detection circuit 120 included in the capacitance detection device 10-2 according to the second embodiment is connected to each of the multiple capacitance sensors 100 provided on the multiple sensor sheets 12. For example, in the example shown in FIG. 15 , the detection circuit 120 included in the capacitance detection device 10-2 according to the second embodiment is connected to each of the 12 capacitance sensors 100. As a result, the detection circuit 120 included in the capacitance detection device 10-2 according to the second embodiment drives each of the 12 capacitance sensors 100, thereby enabling each of the 12 capacitance sensors 100 to detect the detection target 20 and enabling the detection results of the detection target 20 to be obtained from each of the 12 capacitance sensors 100.

[0082] The capacitance detection device 10-2 of the second embodiment is equipped with a sensor unit 13 having multiple sensor sheets 12. For example, by placing the sensor unit 13 on a shelf 21 of a product shelf, a larger number of capacitance sensors 100 can be used to detect the display status of products (presence or absence of products, number of products, etc.) in each of a larger number of product rows 21A using the self-capacitance method.

[0083] Third Embodiment Fig. 16 is a plan view of a capacitance detection device 10-3 according to a third embodiment. As shown in Fig. 16, the capacitance detection device 10-3 according to the third embodiment differs from the capacitance detection device 10 according to the first embodiment in that the base material 101 of the sensor sheet 12 is integrally formed with the circuit board 11. The circuit board 11 is formed of an insulating material such as glass epoxy resin, glass polyimide resin, paper epoxy resin, or paper phenolic resin. This makes it possible for the capacitance detection device 10-3 according to the third embodiment to prevent breakage of the sensor sheet 12 due to an impact when the detection target 20 is placed on the sensor sheet 12.

[0084] In addition, the capacitance detection device 10-3 of the third embodiment may use any of the capacitance sensor 100 of the first embodiment, the capacitance sensor 100-2 of the second embodiment, and the capacitance sensor 100-3 of the third embodiment for each of the multiple capacitance sensors 100.

[0085] 17 is a plan view of a capacitance detection device 10-4 according to a fourth embodiment. As shown in FIG. 17, the plan view of the capacitance detection device 10-4 according to the fourth embodiment includes a plurality of capacitance detection devices 10-3 (four capacitance detection devices 10-3 in the example shown in FIG. 16) arranged side by side in the left-right direction (X-axis direction). The capacitance detection device 10-4 according to the fourth embodiment differs from the capacitance detection device 10-2 according to the second embodiment in that each of the plurality of capacitance detection devices 10-3 includes a detection circuit 120.

[0086] In addition, in the capacitance type sensors 100, 100-2, and 100-3, a background electrode 108 may be further provided on the lower surface 101B side of the substrate 101, spaced apart from and facing the back shield electrode 106, and connected to the ground potential.

[0087] This allows the capacitance sensors 100, 100-2, and 100-3 to effectively attenuate external electromagnetic noise from below (the negative direction of the Z axis). Furthermore, the capacitance sensors 100, 100-2, and 100-3 can improve resistance to external noise, improve the stability of the potential of the output amplification anti-phase electrode 104, and prevent noise from entering the detection electrode 102, thereby improving the stability of the high S / N ratio of the detection signal.

[0088] 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.

[0089] This international application claims priority based on Japanese Patent Application No. 2024-145024, filed on August 26, 2024, the entire contents of which are incorporated herein by reference.

[0090] 10, 10-2, 10-3, 10-4 Capacitance detection device 11 Circuit board 11A Lead wiring 12 Sensor sheet 13 Sensor unit 20 Object to be detected 21 Shelf board 21A Product row 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, 100-3 Capacitance sensor 100A Connection part 101 Base material 101A Upper surface 101B Lower surface 102 Detection electrode 103 First side shield electrode 104 Output amplification anti-phase electrode 105 Second side shield electrode 106 Back shield electrode 107 Cover 108 Background electrode 120 Detection circuit 121 Capacitance detection unit 121A First drive / detection circuit 121B Second driving circuit 122 Processing unit 124 I / F 125 Phase inversion circuit 125A Operational amplifier 125B Feedback resistor Ds Detection signal V1 First AC driving voltage V2 Second AC driving voltage V3 Third AC driving voltage

Claims

1. A capacitance type sensor comprising: a substrate; a detection electrode arranged on one surface of the substrate; and a back shield electrode arranged on the other surface of the substrate so as to face the detection electrode with the substrate interposed therebetween, wherein a first AC drive voltage is applied to the detection electrode and a second AC drive voltage of the same frequency and phase as the first AC drive voltage is applied to the back shield electrode; and further comprising an output amplification antiphase electrode disposed on the one surface of the substrate in parallel with the detection electrode and to which a third AC drive voltage of the same frequency and antiphase as the second AC drive voltage is applied.

2. The capacitance type sensor according to claim 1, further comprising a first side shield electrode arranged in parallel between the detection electrode and the output amplification antiphase electrode on said one surface of the substrate, wherein said first side shield electrode is applied with said second AC drive voltage.

3. The capacitance type sensor according to claim 2, further comprising a second side shield electrode arranged in parallel with the detection electrode on said one surface of the base material, said detection electrode being disposed between said first side shield electrode and said second side shield electrode, and said second side shield electrode being applied with said second AC drive voltage.

4. The capacitance type sensor according to claim 1, further comprising a background electrode provided on the other surface of the substrate, spaced apart from and facing the back shield electrode, and connected to a ground potential.

5. A sensor sheet comprising a plurality of capacitance type sensors according to claim 1, wherein the plurality of capacitance type sensors are arranged side by side and integrally formed.

6. A sensor unit comprising a plurality of sensor sheets according to claim 5, the plurality of sensor sheets being arranged side by side.

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; a second drive circuit that applies the second AC drive voltage to the back shield electrode; and a phase inversion circuit that generates the third AC drive voltage from the second AC drive voltage and applies the third AC drive voltage to the output amplification anti-phase 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 defined in claim 2, 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; a second drive circuit that applies the second AC drive voltage to the back shield electrode and the first side shield electrode; and a phase inversion circuit that generates the third AC drive voltage from the second AC drive voltage and applies the third AC drive voltage to the output amplification anti-phase electrode, wherein the amplitude of the second AC drive voltage is greater than the amplitude of the first AC drive voltage.

9. A detection circuit for a capacitance type sensor as defined 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; a second drive circuit that applies the second AC drive voltage to the back shield electrode, the first side shield electrode, and the second side shield electrode; and a phase inversion circuit that generates the third AC drive voltage from the second AC drive voltage and applies the third AC drive voltage to the output amplification anti-phase electrode, wherein the amplitude of the second AC drive voltage is greater than the amplitude of the first AC drive voltage.

10. A capacitance detection device comprising: the sensor sheet according to claim 5; and a detection circuit connected to each of a plurality of capacitance sensors provided on said sensor sheet.

11. A capacitance detection device comprising: a sensor unit according to claim 6; and a detection circuit connected to each of a plurality of capacitance sensors included in said sensor unit.

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