Detection device

Abstract

Provided is a detection device capable of improving detection sensitivity. This detection device comprises: a sensor body having a detection region; a plurality of sensor electrodes arranged in a matrix on the detection region; a dielectric cover member disposed on the sensor body; and a conductive rod to which a predetermined reference potential is supplied. The cover member has a conductive rod embedded at the position corresponding to the sensor electrode.

Description

Detection device

[0001] The present disclosure relates to a detection device.

[0002] A capacitance-based detection device that detects the proximity of an object by detecting a change in capacitance is known (see, for example, Patent Document 1). Such a detection device having a so-called hover detection (proximity detection) function is provided with a plurality of detection electrodes and a shield electrode that is arranged around a detection area where the plurality of detection electrodes are provided, and an electrical signal is applied to the shield electrode.

[0003] U.S. Patent No. 9,151,792

[0004] However, in a capacitance-type detection device, if a thick insulator is placed in a position overlapping the detection area, the detection sensitivity may decrease, making it difficult to detect an object to be detected that is on the insulator.

[0005] An object of the present disclosure is to provide a detection device that can improve detection sensitivity.

[0006] A detection device according to one aspect of the present disclosure comprises a sensor body having a detection area, a plurality of sensor electrodes arranged in a matrix on the detection area, a dielectric cover member placed on the sensor body, and a conductive rod to which a predetermined reference potential is supplied, the conductive rod being embedded in the cover member at a position corresponding to the sensor electrode.

[0007] FIG. 1 is a perspective view showing a schematic configuration of a detection device according to an embodiment. FIG. 2 is a diagram showing the main components of a detection device according to an embodiment. FIG. 3 is a plan view showing a schematic configuration of a detection device according to embodiment 1. FIG. 4 is a schematic cross-sectional view showing an example of a schematic configuration of a detection device according to embodiment 1. FIG. 5 is a plan view showing an example of an arrangement of conductive rods according to embodiment 1. FIG. 6 is a schematic diagram showing an example of a connection between a sensor main body and a processing device of a detection device according to an embodiment. FIG. 7 is a diagram showing an example of a block configuration of a detection device according to an embodiment. FIG. 8 is a diagram showing an example of a configuration of a drive signal generation circuit according to embodiment 1. FIG. 9 is a diagram showing an example of a functional circuit block configuration of a detection device according to embodiment 1. FIG. 10 is a schematic diagram showing the flow of electricity in an electric field generated when the potential of a peripheral electrode is higher than the potential of a sensor electrode. FIG. 11 is a schematic diagram showing the flow of electricity in an electric field generated when the potential of a peripheral electrode is lower than the potential of a sensor electrode. FIG. 12 is a main flowchart showing an example of a detection process in the detection device. FIG. 13 is a sub-flowchart showing an example of a baseline setting process. FIG. 14 is a sub-flowchart showing an example of a detection mode determination process. FIG. 15 is an explanatory diagram illustrating the relationship between the distance from the end of the surface side of the conductive rod to the surface of the cover member and the SNR when the conductive rod is a spacer. FIG. 16 is an explanatory diagram illustrating the relationship between the distance from the end of the surface side of the conductive rod to the surface of the cover member and the SNR when the conductive rod is an M3 screw. FIG. 17 is an explanatory diagram illustrating the relationship between the distance from the end of the surface side of the conductive rod to the surface of the cover member and the SNR when the conductive rod is a nail. FIG. 18 is a schematic cross-sectional view showing an example of the overall configuration of a detection device according to a modified example of the first embodiment. FIG. 19 is a plan view showing an example of the arrangement of conductive rods according to the second embodiment. FIG. 20 is a schematic cross-sectional view showing an example of the arrangement of conductive rods according to a comparative example. FIG. 21 is an explanatory diagram illustrating the relationship between the area ratio of the conductive rod to the sensor electrode and the signal value.

[0008] Modes (embodiments) for carrying out the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the contents described in the following embodiments. Furthermore, the components described below include those that can be easily imagined by a person skilled in the art and those that are substantially identical. Furthermore, the components described below can be combined as appropriate. Furthermore, the disclosure is merely an example, and appropriate modifications that a person skilled in the art can easily conceive while maintaining the gist of the invention are naturally included within the scope of the present invention. Furthermore, for clarity of explanation, the drawings may show the width, thickness, shape, etc. of each part schematically compared to the actual embodiment. However, these are merely examples and are not intended to limit the interpretation of the present invention. Furthermore, in this specification and each figure, elements similar to those described above with reference to the previous figures may be designated by the same reference numerals, and detailed descriptions may be omitted as appropriate.

[0009] In this specification and claims, when expressing an aspect of placing another structure on top of a certain structure, the term "on top" is used, unless otherwise specified, to include both a case in which another structure is placed directly on top of a certain structure so as to be in contact with the certain structure, and a case in which another structure is placed above a certain structure via yet another structure.

[0010] 1 is a perspective view showing a schematic configuration of a detection device according to an embodiment. As shown in Fig. 1, the detection device 1 includes a cover member 270 and a sensor main body 40 provided on the back surface of the cover member 270.

[0011] The cover member 270 is disposed on the plurality of sensor electrodes 42 shown in FIG. 2. The cover member 270 is a dielectric, plate-shaped protective panel that protects the front surface of the detection device 1. The cover member 270 may be made of, for example, wood, acrylic resin, or the like. The thicker the cover member 270, the lower the detection sensitivity of the sensor main body 40 for the object to be detected 101.

[0012] The object to be detected 101 is, for example, floating metal, wood, a hand, marble, glass, etc. In this embodiment, the object to be detected 101 is described as floating metal. Wood has anisotropy, in which detection sensitivity varies depending on the direction of the wood grain. The relative dielectric constant of wood is 2.0 or more and 6.0 or less.

[0013] 2 is a diagram showing the main configuration of the detection device 1 according to the embodiment. As shown in FIG. 2, the detection device 1 includes a sensor main body 40 and a detection circuit 2.

[0014] The sensor main body 40 has a plurality of sensor electrodes (first electrodes) 42 and peripheral electrodes (second electrodes) 41 provided on a sensor substrate 15. The detection device 1 is a hover detection device that detects the position and movement of a detected object 101 (hereinafter also referred to as "hover detection") without contacting the detection surface of the sensor main body 40. In this embodiment, the detection device 1 performs hover detection using a self-capacitance method. The detection device 1 can be used, for example, in an educational toy that, when the detected object 101 is placed on a mark MA on a cover member 270, makes a sound in response to the sensor electrodes 42 overlapping the mark MA.

[0015] The sensor body 40 has a detection area SA and a peripheral area BE outside the detection area SA. The detection area SA is an area where the sensor electrodes 42 are provided and is an area for detecting an object to be detected that is close to the detection surface. The peripheral area BE is an area outside the detection area SA where the sensor electrodes 42 are not provided and where the peripheral electrodes 41 are provided along the four sides of the detection area SA.

[0016] In the following description, the first direction Dx is a direction in a plane parallel to the sensor substrate 15. The second direction Dy is a direction in a plane parallel to the sensor substrate 15, and is a direction perpendicular to the first direction Dx. The second direction Dy may intersect the first direction Dx without being perpendicular to it. The third direction Dz is a direction perpendicular to the first direction Dx and the second direction Dy, and is a normal direction to the main surface of the sensor substrate 15. Furthermore, "planar view" refers to the positional relationship when viewed from a direction perpendicular to the sensor substrate 15.

[0017] The plurality of sensor electrodes 42 are arranged in a matrix on the detection area SA of the sensor substrate 15. In other words, the plurality of sensor electrodes 42 are arranged side by side in the first direction Dx and the second direction Dy. The plurality of sensor electrodes 42 are each electrically connected to the AFE circuit 16 via wiring (not shown). In this embodiment, the size of the sensor electrode 42 is a square with each side measuring 32 mm.

[0018] The peripheral electrode 41 is disposed to surround the plurality of sensor electrodes 42 provided in the detection area SA.

[0019] A detection circuit 2 is connected to the sensor main body 40. The detection circuit 2 drives the sensor electrodes 42 and detects capacitance. The detection circuit 2 includes an AFE circuit 16 that performs hover detection based on the output of the sensor main body 40, and a control circuit 60 that controls the hover detection operation in the AFE circuit 16. The AFE circuit 16 is, for example, an analog front end (AFE). The control circuit 60 includes, for example, an MCU (Micro Control Unit).

[0020] A processing device (external processing device) 110 is connected to the detection circuit 2. The processing device 110 functions as a host computer (HOST) of the detection device 1 according to the embodiment. The processing device 110 is, for example, a point of sale (POS) cash register terminal, but is not limited thereto and may be any terminal capable of accepting a hover operation in the detection device 1.

[0021] Fig. 3 is a plan view showing a schematic configuration of the detection device according to embodiment 1. Fig. 4 is a schematic cross-sectional view showing an example of the schematic configuration of the detection device according to embodiment 1. Fig. 5 is a plan view showing an example of the arrangement of conductive rods according to embodiment 1.

[0022] 3 and 4, the detection device 1 includes a conductive rod 102. A plurality of markers MA corresponding to each sensor electrode 42 are provided on the surface of the cover member 270, overlapping the conductive rods 102. The surface of the cover member 270 excluding the markers MA does not overlap the conductive rods 102. The markers MA are arranged to overlap the sensor electrodes 42, overlapping the centers of the sensor electrodes 42, and a detectable object 101 can be provided on each of the markers MA. The markers MA are, for example, a button that reacts to the detectable object 101, or a recess in which the detectable object 101 can be placed or a slidable recess.

[0023] As shown in FIG. 4 , the detection device 1 includes a shield layer 14 , a sensor substrate 15 , a peripheral electrode 41 , a sensor electrode 42 , and a cover member 270 .

[0024] The sensor substrate 15 is a light-transmitting substrate made of glass, resin, etc. The sensor substrate 15 may be a flexible printed circuit (FPC) or a rigid substrate.

[0025] Furthermore, a plurality of sensor electrodes 42 are formed on the sensor substrate 15, and the peripheral electrodes 41 and the sensor electrodes 42 are covered with a protective layer OC, thereby flattening the surface and protecting the peripheral electrodes 41 and the sensor electrodes 42.

[0026] The protective layer OC is a light-transmitting resin, such as an acrylic resin. The protective layer OC may be made of an inorganic resin, an organic resin, or a laminate of an organic resin and an inorganic resin.

[0027] The shield layer 14 is laminated on the detection device 1. The shield layer 14 is a conductive layer of a metallic film that has a metallic luster and is translucent. The material of the shield layer 14 is a metallic material such as Al, Ag, or Mo. The shield layer 14 can block electromagnetic waves that reach the detection device 1 from the rear surface of the detection device 1. The shield layer 14 also overlaps with the detection area AA of the sensor main body 40 in the third direction Dz and has the same area as the detection area AA. Therefore, the shield layer 14 has a larger area than the sensor electrode 42. The shield layer 14 may also have a larger area than the detection area AA.

[0028] The cover member 270 is laminated with the sensor substrate 15 in a third direction Dz perpendicular to the surface of the cover member 270. The sensor substrate 15 is fixed to the cover member 270 via an adhesive layer AT. The adhesive layer AT is a light-transmitting adhesive called an OCA (Optical Clear Adhesive). The adhesive layer AT may be a light-transmitting film with double-sided adhesive properties. The surface SF of the cover member 270 is a detection surface for hover detection.

[0029] The peripheral electrodes 41 and the sensor electrodes 42 are provided on the same sensor substrate 15. The sensor substrate 15 is a film-like or plate-like member made of an insulating material, such as a resin film or a glass substrate. The peripheral electrodes 41 and the sensor electrodes 42 are not limited to being provided on the same layer of the sensor substrate 15, but may be provided on different layers of the sensor substrate 15. The sensor electrode 42 is formed of a translucent conductive material such as ITO (indium tin oxide) or IZO (indium zinc oxide). The peripheral electrode 41 may be formed of the same material as the sensor electrode 42, or may be formed of a different metal material from the sensor electrode 42.

[0030] As shown in FIG. 4, the thickness of the cover member 270 is not less than 10 mm and not more than 40 mm.

[0031] A conductive rod 102 is embedded in the cover member 270 from the rear surface to the front surface at a position corresponding to the sensor electrode 42. The conductive rod 102 is, for example, a floating metal. The conductive rod 102 is formed from a conductive material, and for example, a hexagonal spacer, an M3 screw, a nail, or the like is used. Note that the conductive rod 102 may also be an insulating rod coated with a conductive material.

[0032] Furthermore, the end 102x of the conductive rod 102 closest to the surface SF of the cover member 270 is arranged so as to be parallel to the surface SF.

[0033] 4 and 5 , the area of ​​the end 102x of one conductive rod 102 closest to the front surface SF of the cover member 270 is smaller in plan view than the area of ​​the sensor electrode 42. In the first embodiment, the area of ​​the surface of the conductive rod 102 is 0.1% or more and 1.8% or less of the area of ​​the sensor electrode 42 in plan view.

[0034] This makes it possible to improve the detection sensitivity when the object to be detected 101 is placed at the position of the mark MA.

[0035] When the object to be detected 101 is a hand, the fist becomes difficult to see, and therefore, false detections and malfunctions can be suppressed when detecting the coordinates of the object to be detected 101 .

[0036] FIG. 6 is a schematic diagram showing an example of connection between the sensor body and the processing device of the detection device according to the embodiment.

[0037] In the so-called on-cell type device configuration shown in Fig. 6, the detection device 1 includes an FPC (Flexible Printed Circuits) 70. The FPC 70 is connected to a PCB (Printed Circuit Board) 46. Various circuits that constitute the detection circuit 2 are mounted on the PCB 46. Fig. 6 illustrates circuits 46a and 46b as examples of the various circuits that constitute the detection circuit 2. The circuits 46a and 46b function as, for example, the AFE circuit 16 and the control circuit 60.

[0038] The PCB 46 is connected to the processing device 110 via a cable 470. The cable 470 has a function of transmitting signals generated between the detection device 1 and the processing device 110. An example of the cable 470 is a USB (Universal Serial Bus) cable.

[0039] FIG. 7 is a diagram illustrating an example of a block configuration of a detection device according to an embodiment.

[0040] As shown in FIG. 7, the detection device 1 includes, in addition to the sensor body 40, the AFE circuit 16, and the control circuit 60 described above, a first power supply circuit 11 (POW1), an isolated DC-DC converter 12, a second power supply circuit 13 (POW2), a drive signal generation circuit 20, a first isolator 51, and a second isolator 52.

[0041] The plurality of sensor electrodes 42 are each connected to the AFE circuit 16. The peripheral electrode 41 and the shield layer 14 function as an active shield whose potential periodically fluctuates in response to changes in the second reference potential GND2 provided by the drive signal generation circuit 20. The AFE circuit 16 acquires, as a detection signal Rx, an electrical signal corresponding to the self-capacitance generated in each sensor electrode 42.

[0042] The magnitude of the detection signal Rx obtained from each sensor electrode 42 changes depending on the distance between each sensor electrode 42 and a nearby object. Based on the detection signal Rx obtained from each sensor electrode 42, the AFE circuit 16 generates sensing data according to the distance between each sensor electrode 42 and a nearby object, and outputs the sensing data to the control circuit 60.

[0043] The processing device 110, the control circuit 60, the first power supply circuit 11, and the drive signal generation circuit 20 are included in a first reference potential block 3. In the present disclosure, the second power supply circuit 13, the AFE circuit 16, and the sensor main body 40 are included in a second reference potential block 4. The processing device 110, the control circuit 60, the first power supply circuit 11, and the drive signal generation circuit 20 included in the first reference potential block 3 operate using a first reference potential GND1, which is a fixed potential, as a ground potential. The second power supply circuit 13, the AFE circuit 16, and the sensor main body 40 included in the second reference potential block 4 operate using a second reference potential GND2 generated by the drive signal generation circuit 20 as a ground potential.

[0044] The first power supply circuit 11 converts the voltage of the power supplied via the power line VBUS of the USB cable and supplies the converted voltage to the control circuit 60 and the drive signal generation circuit 20 .

[0045] The insulated DC-DC converter 12 provides insulation and power transmission between the processing device 110 and the second power supply circuit 13. The insulated DC-DC converter 12 performs power transmission using a magnetic insulation method.

[0046] In the isolated DC-DC converter 12, power is supplied to the coil on the first reference potential block 3 side via the power line VBUS of the USB cable, causing the coil to generate a magnetic field. The coil on the second reference potential block 4 side is provided within the range of influence of the magnetic field generated by the coil on the first reference potential block 3 side.

[0047] An induced electromotive force is generated in the coil on the second reference potential block 4 side according to the magnetic field generated by the coil on the first reference potential block 3 side. The power generated in the coil on the second reference potential block 4 side is supplied to the second power supply circuit 13.

[0048] The second power supply circuit 13 converts the voltage of the power supplied from the isolated DC-DC converter 12 and supplies the converted voltage to the AFE circuit 16 .

[0049] The AFE circuit 16 generates a rectangular wave signal Tx as a periodically varying potential having a periodic potential variation pattern. The rectangular wave signal Tx includes a fundamental frequency component and harmonic components of a drive signal to be supplied to the peripheral electrode 41 of the sensor body 40 and the shield layer 14.

[0050] In addition, the AFE circuit 16 acquires sensing data from the plurality of sensor electrodes 42 and outputs it to the control circuit 60 via the first isolator 51 .

[0051] In the present disclosure, signals between the AFE circuit 16 and the control circuit 60 are transmitted via a serial peripheral interface (SPI), which is a clock-synchronized serial interface. Note that the serial interface for transmitting signals between the AFE circuit 16 and the control circuit 60 is not limited to the SPI.

[0052] The first isolator 51 provides insulation and transmits signals between the control circuit 60 and the AFE circuit 16. Electrical signals input and output via the first isolator 51 are synchronized between the control circuit 60 and the AFE circuit 16.

[0053] The second isolator 52 provides insulation between the AFE circuit 16 and the drive signal generation circuit 20 and transmits the rectangular wave signal Tx. The rectangular wave signal Tx input / output via the second isolator 52 is synchronized between the AFE circuit 16 and the drive signal generation circuit 20.

[0054] The second isolator 52 performs optically isolated signal transmission using, for example, a photocoupler. The signal transmission method between the control circuit 60 and the AFE circuit 16 in the first isolator 51 may be the same as or a different method from that of the second isolator 52. In other words, the first isolator 51 may be, for example, an optically isolated photocoupler or a magnetically isolated digital isolator similar to the isolated DC-DC converter 12.

[0055] The first isolator 51 is capable of bidirectional signal transmission, i.e., signal transmission from the control circuit 60 to the AFE circuit 16 and signal transmission from the AFE circuit 16 to the control circuit 60. In a configuration in which an optically isolated photocoupler is used as the first isolator 51, a photocoupler that transmits signals from the control circuit 60 to the AFE circuit 16 and a photocoupler that transmits signals from the AFE circuit 16 to the control circuit 60 are connected in parallel.

[0056] The control circuit 60 transmits signals such as various information related to sensing data and control commands to and from the processing device 110 .

[0057] Furthermore, based on reference information (DP control reference data) indicating the correspondence between the fundamental frequency of the rectangular wave signal Tx output from the AFE circuit 16 and the electrical resistance value of the digital potentiometer 22 described below, the control circuit 60 outputs an electrical resistance value setting command to the digital potentiometer 22 to set the electrical resistance value of the digital potentiometer 22 to an electrical resistance value corresponding to the fundamental frequency of the rectangular wave signal Tx output from the AFE circuit 16. As a result, the electrical resistance value of the digital potentiometer 22 is controlled to an electrical resistance value corresponding to the fundamental frequency of the rectangular wave signal Tx.

[0058] The digital potentiometer 22 is a digital potentiometer circuit that can adjust the electrical resistance value in response to a command from the control circuit 60. The digital potentiometer 22 is provided on the output transmission path of the rectangular wave signal Tx output from the AFE circuit 16 via the second isolator 52. Hereinafter, the digital potentiometer 22 will also be referred to as the "DP circuit 22."

[0059] The control circuit 60 also performs noise determination processing on the sensing data and position determination (coordinate calculation processing) of the detectable object based on the sensing data. The noise determination processing is processing performed to determine the amount of noise components contained in the sensing data. The coordinate calculation processing is processing performed to determine the position of the detectable object adjacent to the sensor main body 40. Specifically, the coordinate calculation processing can derive, for example, the position of the detectable object adjacent to the sensor main body 40 in the first direction Dx, the second direction Dy, and the third direction Dz (see FIG. 1 ). The details of the noise determination processing and the coordinate calculation processing are similar to those well known, and therefore will not be described in detail here.

[0060] In the present disclosure, signals between the control circuit 60 and the processing device 110 are transmitted via a USB serial interface. Specifically, signals between the control circuit 60 and the processing device 110 are transmitted via signal lines D+ and D- of a USB cable. Note that the serial interface for transmitting signals between the control circuit 60 and the processing device 110 is not limited to USB.

[0061] In the above-described configuration, the first reference potential block 3, which includes the processing device 110, the control circuit 60, the first power supply circuit 11, and the drive signal generating circuit 20, and the second reference potential block 4, which includes the second power supply circuit 13, the AFE circuit 16, and the sensor main body 40, are electrically insulated via the insulated DC-DC converter 12, the first isolator 51, and the second isolator 52.

[0062] The first reference potential GND1 provided as a ground potential to the first reference potential block 3 is a fixed potential maintained by a large electrode such as a solid electrode, while the second reference potential GND2 provided as a ground potential to the second reference potential block 4 is a periodically varying potential generated by the drive signal generation circuit 20.

[0063] In the detection device 1 according to the present disclosure, the fluctuation period of the periodically fluctuating potential (second reference potential GND2) is the same as the generation period (the rectangular wave period of the rectangular wave signal Tx) of the rectangular wave generated by the AFE circuit 16. In other words, the second reference potential GND2 is a potential that periodically fluctuates in synchronization with the rectangular wave signal Tx generated by the AFE circuit 16.

[0064] 8 is a diagram showing an example of the configuration of a drive signal generation circuit according to embodiment 1. In the configuration according to embodiment 1, a drive signal generation circuit 20 includes an LPF circuit 21, an active filter circuit 23, and an amplifier circuit 24.

[0065] The LPF circuit 21 is provided with a resistive element R instead of the DP circuit 22. The LPF circuit 21 functions as a low-pass filter by an RC circuit configured with the resistive element R and a capacitive element C in the subsequent stage. An intermediate wave signal that has been impedance-converted by a voltage follower circuit connected in the subsequent stage of the RC circuit is output to the active filter circuit 23.

[0066] The amplifier circuit 24 includes a DP circuit 22 as an input resistor of an inverting amplifier circuit including a negative feedback resistor Rf. The output Vout of the amplifier circuit 24 is expressed by the following equation (1), where the input of the amplifier circuit 24 is Vin. Note that a configuration may also be adopted in which a capacitance element Cf for phase compensation is connected in parallel with the negative feedback resistor Rf.

[0067] Vout=-(Rf / Rdp)×Vin...(1)

[0068] The sine wave signal inverted and amplified by the amplifier circuit 24 undergoes impedance conversion by a voltage follower circuit connected downstream of the inverting amplifier circuit, and is supplied as a drive signal to the peripheral electrode 41 and shield layer 14 of the sensor body 40, and is also given as a second reference potential GND2, which is the ground potential of the second reference potential block 4. Depending on the polarity of the sine wave signal, the amplifier circuit 24 may not invert the polarity.

[0069] In the configuration of the drive signal generation circuit 20 according to the first embodiment described above, when the amplitude value Vpp of the drive signal is changed by changing the electrical resistance value of the DP circuit 22, no change in phase occurs in the LPF circuit 21. Therefore, it is possible to suppress a decrease in detection sensitivity caused by a difference in the timing of acquiring sensing data.

[0070] FIG. 9 is a diagram illustrating an example of a functional circuit block configuration of the detection device according to the first embodiment.

[0071] 9, the AFE circuit 16 includes a readout circuit 161, an ADC (Analog Digital Converter) circuit 162, and a DSP (Digital Signal Processor) circuit 163. Each circuit element of the AFE circuit 16 operates using a second reference potential GND2, which is a periodically varying potential generated by the drive signal generation circuit 20, as the ground potential.

[0072] The readout circuit 161 acquires the detection signal Rx from each of the sensor electrodes 42 .

[0073] The ADC circuit 162 converts the detection signal Rx acquired by the readout circuit 161 from an analog signal to a digital signal.

[0074] The DSP circuit 163 performs digital filtering on the digital data converted by the ADC circuit 162 to generate a detection signal Rx.

[0075] The AFE circuit 16 outputs the sensing data generated by the DSP circuit 163 to the control circuit 60 via the first isolator 51 .

[0076] The control circuit 60 includes a read circuit 61, a noise determination circuit 62, a coordinate calculation circuit 63, and a memory circuit 64. Each circuit element of the control circuit 60 operates with a first reference potential GND1, which is a fixed potential, as the ground potential.

[0077] The readout circuit 61 acquires the sensing data output from the AFE circuit 16 via the first isolator 51 .

[0078] The noise determination circuit 62 performs the above-described noise determination process based on the sensing data acquired by the readout circuit 61 .

[0079] The coordinate calculation circuit 63 performs the above-mentioned coordinate calculation process based on the sensing data acquired by the readout circuit 61 .

[0080] The memory circuit 64 stores in advance DP control reference data that indicates the correspondence between the fundamental frequency of the rectangular wave signal Tx output from the AFE circuit 16 and the electrical resistance value of the DP circuit 22. The DP control reference data is, for example, data in the form of a table in which the fundamental frequency of the rectangular wave signal Tx output from the AFE circuit 16 and the electrical resistance value of the DP circuit 22 are associated one-to-one.

[0081] In addition, in the present disclosure, it is assumed that the memory circuitry 64 stores in advance a threshold value used for determining the detection mode in the detection mode setting process described below.

[0082] The control circuit 60 refers to the DP control reference data stored in the memory circuit 64 and outputs an electrical resistance value setting command to set the electrical resistance value of the DP circuit 22 so that the electrical resistance value corresponds to the fundamental frequency of the rectangular wave signal Tx output from the AFE circuit 16.

[0083] The control circuit 60 also has a function of changing the fundamental frequency of the rectangular wave signal Tx output from the AFE circuit 16. When the fundamental frequency of the rectangular wave signal Tx output from the AFE circuit 16 is changed, the control circuit 60 resets the electrical resistance value of the DP circuit 22 in accordance with the changed fundamental frequency of the rectangular wave signal Tx.

[0084] In the present disclosure, the control circuit 60 has a function of changing the fundamental frequency of the square wave signal Tx output from the AFE circuit 16. In the present disclosure, the drive frequency in the self-capacitance hover detection, i.e., the fundamental frequency of the square wave signal Tx output from the AFE circuit 16, can be changed. This makes it possible to suppress the effects of noise. Hereinafter, changing the fundamental frequency of the square wave signal Tx is also referred to as "frequency hopping."

[0085] 10 and 11 are schematic diagrams showing the flow of electricity in an electric field that occurs when the potential of the peripheral electrode is higher than that of the sensor electrode, respectively.

[0086] Fig. 10 is a schematic diagram showing the flow of electricity in an electric field that occurs when the potential of the peripheral electrode 41 is higher than the potential of the sensor electrode 42. Fig. 11 is a schematic diagram showing the flow of electricity in an electric field that occurs when the potential of the peripheral electrode 41 is lower than the potential of the sensor electrode 42. The strength of the detection signals obtained from each of the sensor electrodes 42a, 42b, and 42c changes depending on whether an object in proximity to the sensor main body 40 is at position P1 or at position P2.

[0087] 12 is a main flowchart illustrating an example of a detection process in the detection device 1. The detection device 1 performs sensing operation by dynamically switching between a hover detection mode (first detection mode) and a touch detection mode (second detection mode) depending on the maximum value of sensing data acquired in the detection area SA.

[0088] When the sensing operation by the detection device 1 starts (step S1), the detection device 1 sets baselines in both the hover detection mode and the touch detection mode (step S2). Fig. 13 is a sub-flowchart illustrating an example of the baseline setting process.

[0089] In the baseline setting process (step S2), first, the control circuit 60 sets an electrical resistance value for hover detection in the DP circuit 22 (step S21). The electrical resistance value for hover detection is set to, for example, a value that makes the amplitude value Vpp of the drive signal 6.8 V.

[0090] The AFE circuit 16 acquires detection signals Rx from each sensor electrode 42 when no object to be detected is in proximity to the sensor main body 40, and generates baseline data for hover detection based on the detection signals Rx (step S22).

[0091] Next, the control circuit 60 sets an electrical resistance value for touch detection in the DP circuit 22 (step S23). The electrical resistance value for touch detection is set to, for example, a value that makes the amplitude value Vpp of the drive signal 2.5V.

[0092] The AFE circuit 16 acquires the detection signals Rx from the sensor electrodes 42 when no object to be detected is in proximity to the sensor main body 40, and generates baseline data for touch detection based on the detection signals Rx (step S24).

[0093] After the baseline setting process (step S2) is executed, the process returns to the main flow of the detection process shown in Fig. 12, where the AFE circuit 16 acquires the detection signals Rx from each sensor electrode 42, generates sensing data, and transmits it to the control circuit 60. The control circuit 60 sets the detection mode based on the sensing data transmitted from the AFE circuit 16 (step S3). Fig. 14 is a sub-flowchart showing an example of the detection mode determination process.

[0094] In the detection mode setting process (step S3), the control circuit 60 first determines whether the current detection mode is the hover detection mode or the touch detection mode. More specifically, the control circuit 60 determines whether the current detection mode is the hover detection mode (step S31).

[0095] If the hover detection mode is selected (Step S31: Yes), the control circuit 60 determines whether the maximum value RDHmax of the sensing data (RDH(n), where n is a natural number from 1 to N and N is the number of sensor electrodes in the detection area SA) in the detection area SA is equal to or greater than a predetermined threshold value RDHth (RDHmax≧RDHth, Step S32). The threshold value RDHth is pre-stored in the memory circuit 64.

[0096] If the maximum value RDHmax of the sensing data is less than the threshold value RDHth (step S32; No), the control circuit 60 maintains the hover detection mode. If the maximum value RDHmax of the sensing data is equal to or greater than the threshold value RDHth (step S32; Yes), the control circuit 60 changes the detection mode from the hover detection mode to the touch detection mode.

[0097] If the touch detection mode is selected (Step S31: No), the control circuit 60 determines whether the maximum value RDTmax of each piece of sensing data (RDT(n), n is a natural number ranging from 1 to N, and N is the number of sensor electrodes in the detection area SA) in the detection area SA is less than a predetermined threshold value RDTth (RDTmax<RDTth, Step S34). The threshold value RDTth is stored in advance in the memory circuit 64.

[0098] If the maximum value RDTmax of the sensing data is equal to or greater than the threshold value RDTth (step S34; No), the control circuit 60 enters the touch detection mode. If the maximum value RDTmax of the sensing data is less than the threshold value RDTth (step S34; Yes), the control circuit 60 changes the detection mode from the touch detection mode to the hover detection mode.

[0099] As described above, when the detectable object 101 is in contact with the detection surface of the sensor main body 40, the sensing data becomes prominently large at the position where the detectable object 101 is in contact with the detection surface of the sensor main body 40. Therefore, by performing a threshold judgment on the maximum value of the sensing data, it can be determined whether or not the detectable object 101 has come into contact (touched) with the detection surface of the sensor main body 40.

[0100] The control circuit 60 sets the electrical resistance value of the DP circuit 22 so that the amplitude value Vpp of the drive signal is a value corresponding to the detection mode set in the detection mode setting process (step S3). Specifically, when the hover detection mode is set in the detection mode setting process (step S3), the control circuit 60 sets the electrical resistance value of the DP circuit 22 so that the amplitude value Vpp of the drive signal is a first amplitude value (e.g., 6.8 V). When the touch detection mode is set in the detection mode setting process (step S3), the control circuit 60 sets the electrical resistance value of the DP circuit 22 so that the amplitude value Vpp of the drive signal is a second amplitude value (e.g., 2.5 V) smaller than the first amplitude value.

[0101] After executing the detection mode setting process (step S3), the process returns to the main flow of the detection process shown in Fig. 12, and the detection device 1 executes a normal sensing operation (step S4). The AFE circuit 16 acquires the detection signals Rx from each sensor electrode 42, generates sensing data, and transmits it to the control circuit 60. The noise determination circuit 62 of the control circuit 60 executes the above-mentioned noise determination process based on the sensing data transmitted from the AFE circuit 16 (step S5).

[0102] Furthermore, the coordinate calculation circuit 63 executes coordinate calculation processing (step S6) based on the difference between the baseline data acquired in the baseline setting processing (step S2) and the sensing data.

[0103] Although FIG. 12 shows an example in which the coordinate calculation process (step S6) is executed after the noise determination process (step S5), the noise determination process (step S5) may be executed after the coordinate calculation process (step S6), or the noise determination process (step S5) and the coordinate calculation process (step S6) may be executed in parallel.

[0104] Next, the control circuit 60 determines whether or not the above-described conditions for performing frequency hopping (hereinafter also simply referred to as "frequency hopping conditions") are met (step S7).

[0105] If the frequency hopping condition is not met (step S7; No), the process proceeds to step S10.

[0106] If the frequency hopping condition is met (step S7; Yes), the control circuit 60 sets the electrical resistance of the DP circuit 22 to a value corresponding to the frequency of the rectangular wave signal Tx after frequency hopping (step S8).The control circuit 60 also sets the fundamental frequency of the rectangular wave signal Tx output from the AFE circuit 16 to the drive frequency after frequency hopping (step S9).

[0107] In addition, in Figure 12, an example is shown in which the drive frequency is set after the electrical resistance value of the DP circuit 22 is set, but it is also possible to have a configuration in which the electrical resistance value of the DP circuit 22 is set after the drive frequency is set, or a configuration in which the setting of the electrical resistance value of the DP circuit 22 and the setting of the drive frequency are performed in parallel.

[0108] When setting the electrical resistance value of the DP circuit 22 in step S8, the control circuit 60 references, for example, the DP control reference data described above to set the electrical resistance value of the DP circuit 22 corresponding to the frequency of the rectangular wave signal Tx after frequency hopping. This controls the electrical resistance value of the DP circuit 22 to an electrical resistance value corresponding to the rectangular wave signal Tx after frequency hopping. More specifically, when the detection mode is the hover detection mode, the control circuit 60 sets the electrical resistance value of the DP circuit 22 so that, for example, the amplitude value Vpp of the drive signal is 6.8 V. When the detection mode is the touch detection mode, the control circuit 60 sets the electrical resistance value of the DP circuit 22 so that, for example, the amplitude value Vpp of the drive signal is 2.5 V.

[0109] When the sensing operation of the detection device 1 is completed (Step S10; Yes), the detection device 1 ends the sensing operation. Examples of cases in which the sensing operation ends include when the power supply to the detection device 1 is stopped, or when a command to end the sensing operation is output from the processing device 110 to the detection device 1. When the sensing operation of the detection device 1 is not completed (Step S10; No), the operations from Step S3 onwards are repeatedly executed.

[0110] In the configuration of the above-described first embodiment, the control circuit 60 controls the amplitude value Vpp of the drive signal supplied from the drive signal generation circuit 20 to the peripheral electrode 41 and the shield layer 14 in accordance with the sensing data output from the AFE circuit 16.

[0111] More specifically, in the detection mode setting process (step S3), when the current detection mode is the hover detection mode (first detection mode), the control circuit 60 switches to the hover detection mode (first detection mode) if the maximum value RDHmax of the sensing data RDH(n) of the multiple sensor electrodes 42 is less than a predetermined threshold value RDHth, and switches to the touch detection mode (second detection mode) if the maximum value RDHmax is equal to or greater than the threshold value RDHth.

[0112] In addition, when the current detection mode is the touch detection mode (second detection mode), the control circuit 60 enters the touch detection mode (second detection mode) if the maximum value RDTmax of the sensing data RDT(n) of the multiple sensor electrodes 42 is equal to or greater than a predetermined threshold value RDTth, and enters the hover detection mode (first detection mode) if the maximum value RDTmax is less than the threshold value RDTth.

[0113] Then, the control circuit 60 sets the electrical resistance value of the DP circuit 22 so that the amplitude value Vpp of the drive signal becomes a value according to the detection mode set in the detection mode setting process (step S3).

[0114] More specifically, when the detection mode set in the detection mode setting process (step S3) is the hover detection mode (first detection mode), the control circuit 60 controls the electrical resistance value of the DP circuit 22 so that the amplitude value Vpp of the drive signal becomes the first amplitude value (e.g., 6.8 V).

[0115] In addition, when the detection mode set in the detection mode setting process (step S3) is the touch detection mode (second detection mode), the control circuit 60 controls the electrical resistance value of the DP circuit 22 so that the amplitude value Vpp of the drive signal becomes a second amplitude value (e.g., 2.5 V) smaller than the first amplitude value.

[0116] In this way, in the hover detection mode (first detection mode), the amplitude value Vpp of the drive signal is controlled to be relatively large, and in the touch detection mode (second detection mode), the amplitude value Vpp of the drive signal is controlled to be relatively small. This makes it possible to suppress saturation of sensing data at the contact position when the object to be detected comes into contact with the detection surface of the sensor main body 40, and to suppress a decrease in position determination accuracy due to sensing data errors caused by capacitive coupling between adjacent sensor electrodes.

[0117] In addition, in a configuration in which a sine wave signal is generated by filtering the square wave signal Tx output from the AFE circuit 16 and the sine wave signal is amplified to generate a drive signal, a DP circuit 22 is connected in series to the input path of the amplifier circuit 24. In addition, the control circuit 60 is capable of setting the fundamental frequency of the square wave signal Tx, and the higher the fundamental frequency of the square wave signal Tx, the smaller the electrical resistance value of the DP circuit 22 becomes, and the lower the fundamental frequency of the square wave signal Tx, the larger the electrical resistance value of the DP circuit 22 becomes.

[0118] This allows the amplitude value Vpp of the drive signal to be kept constant (for example, 6.8 V in hover detection mode and 2.5 V in touch detection mode) even if, for example, the frequency hopping condition is met by the noise determination process and the fundamental frequency of the rectangular wave signal Tx (the frequency of the drive signal) is changed.

[0119] Fig. 15 is an explanatory diagram for explaining the relationship between the distance from the end 102x of the conductive rod on the detection surface side to the surface of the cover member and the SNR. Fig. 16 is an explanatory diagram for explaining the relationship between the distance from the end 102x of the conductive rod on the detection surface side to the surface of the cover member and the SNR. Fig. 17 is an explanatory diagram for explaining the relationship between the distance from the end 102x of the conductive rod on the detection surface side to the surface of the cover member and the SNR.

[0120] 15 to 17 explain how the distance from the end 102x of the conductive rod 102 closest to the surface SF to the surface SF becomes equal to or greater than the target value of 100 when the target value of SNR (Signal to Noise Ratio) is 100, depending on the change in the diameter of the surface of the object to be detected 101. In the following explanation of FIGS. 15 to 17, the height of the object to be detected 101 is constant at 25 mm. The thickness of the cover member is 28 mm.

[0121] 15 is an explanatory diagram of the case where the conductive rod 102 is a spacer. In this case, the area of ​​the end 102x of the conductive rod 102 closest to the front surface SF side is 19.1 mm ２ is constant.

[0122] 15, when the diameter of the surface of the object to be detected 101 is 9 mmφ and the length of the conductive rod 102 is 24 mm or more, the SNR becomes 100 or more. In this case, the distance from the end 102x of the conductive rod 102, which is closest to the surface SF, to the surface SF is 4 mm or less.

[0123] 15, when the diameter of the surface of the object to be detected 101 is 15 mmφ and the length of the conductive rod 102 is 21 mm or more, the SNR becomes 100 or more. In this case, the distance from the end 102x of the conductive rod 102, which is closest to the surface SF, to the surface SF is 7 mm or less.

[0124] 15, when the diameter of the surface of the object to be detected 101 is 22 mmφ and the length of the conductive rod 102 is 15 mm or more, the SNR becomes 100 or more. In this case, the distance from the end 102x of the conductive rod 102, which is closest to the surface SF, to the surface SF is 13 mm or less.

[0125] 16 is an explanatory diagram of the case where the conductive rod 102 is an M3 screw. In this case, the area of ​​the end 102x of the conductive rod 102 closest to the front surface SF side is 7.07 mm ２ is constant.

[0126] 16, when the diameter of the surface of the object to be detected 101 is 9 mmφ and the length of the conductive rod 102 is 26 mm or more, the SNR becomes 100 or more. In this case, the distance from the end 102x of the conductive rod 102, which is closest to the surface SF, to the surface SF is 2 mm or less.

[0127] 16, when the diameter of the surface of the object to be detected 101 is 15 mmφ and the length of the conductive rod 102 is 22 mm or more, the SNR becomes 100 or more. In this case, the distance from the end 102x of the conductive rod 102, which is closest to the surface SF, to the surface SF is 6 mm or less.

[0128] 16, when the diameter of the surface of the object to be detected 101 is 22 mmφ and the length of the conductive rod 102 is 15 mm or more, the SNR becomes 100 or more. In this case, the distance from the end 102x of the conductive rod 102, which is closest to the surface SF, to the surface SF is 13 mm or less.

[0129] 17 is an explanatory diagram of a case where the conductive rod 102 is a nail. In this case, the area of ​​the end 102x of the conductive rod 102 closest to the surface SF side is 2.27 mm ２ is constant.

[0130] As shown in FIG. 17, when the diameter of the surface of the detection object 101 is 9 mmφ, the SNR is 100 or less.

[0131] 17, when the diameter of the surface of the object to be detected 101 is 15 mmφ and the length of the conductive rod 102 is 26 mm or more, the SNR becomes 100 or more. In this case, the distance from the end 102x of the conductive rod 102, which is closest to the surface SF, to the surface SF is 2 mm or less.

[0132] 17, when the diameter of the surface of the object to be detected 101 is 22 mmφ and the length of the conductive rod 102 is 20 mm or more, the SNR becomes 100 or more. In this case, the distance from the end 102x of the conductive rod 102, which is closest to the surface SF, to the surface SF is 8 mm or less.

[0133] From the above, when the distance from the end 102x of the conductive rod 102 closest to the surface SF to the surface SF is 2 mm or less, that is, when the length of the conductive rod 102 is 93% or more and 99% or less of the thickness of the cover member 270, the SNR becomes 100 or more, and the detection sensitivity is improved.

[0134] 18 is a schematic cross-sectional view showing an example of the schematic configuration of a detection device according to a modification of embodiment 1. The detection object 101A in the modification of embodiment 1 is wood. In the following description, the same components as those in embodiment 1 are denoted by the same reference numerals, and redundant description will be omitted.

[0135] In the detection device 1A according to the modified example of the first embodiment, the shape of the detection object 101A is, for example, a cube, and the size of the detection object 101 is, for example, 30 mm on a side.

[0136] As shown in FIG. 18, a conductive rod 102A is embedded in the cover member 270 at a position corresponding to the sensor electrode 42, extending from the rear surface of the cover member 270 toward the front surface.

[0137] The conductive rod 102A is, for example, a floating metal. The diameter of the surface of the conductive rod 102A is 22 mmφ, and the height of the conductive rod 102A is 25 mm. The surface area of ​​the conductive rod 102A is 67.2% of the area of ​​the sensor electrode 42 in a plan view.

[0138] The conductive rod 102A is disposed at a position overlapping the mark MA, and is disposed so that the surface of the end 102x of the conductive rod 102A closest to the front surface SF is parallel to the front surface SF.

[0139] This makes it possible to improve the detection sensitivity regardless of the direction of the grain of the object 101A to be detected.

[0140] (Embodiment 2) Fig. 19 is a plan view showing an example of the arrangement of conductive rods according to a comparative example. Fig. 20 is a schematic cross-sectional view showing an example of the arrangement of conductive rods according to embodiment 2. Fig. 21 is an explanatory diagram for explaining the relationship between the area ratio of multiple conductive rods to the sensor electrode and the signal value. In the following explanation, the same components as those in embodiment 1 are assigned the same reference numerals, and redundant explanations will be omitted.

[0141] As shown in Figure 19, in the detection device 1a of the comparative example, the arrangement of the multiple conductive rods 102a is such that multiple conductive rods 102a overlap each other on one sensor electrode 42, and the multiple conductive rods 102a are densely arranged.

[0142] 21 , as the area ratio of the multiple conductive rods 102a to the sensor electrode 42 increases, that is, as the number of conductive rods 102a increases, the signal value increases linearly. Here, when there are 11 conductive rods 102a, the area ratio of the conductive rods 102a to the sensor electrode 42 is 20%. However, when there are 11 or more conductive rods 102a, the outer shape of the parts where the conductive rods do not contact each other approaches the outer shape of the object to be detected 101, and the signal value saturates.

[0143] 20 , in the detection device 1B according to the second embodiment, the conductive rods 102B are arranged so that the conductive rods 102B are overlapped on one sensor electrode 42, and adjacent conductive rods 102B are spaced apart by the material of the cover member 270. The distances between adjacent conductive rods 102B are substantially the same.

[0144] 21 , the total area of ​​the multiple conductive rods 102B overlapping with the sensor electrode 42 is 3% or more of the area of ​​the sensor electrode 42 in a plan view. By arranging adjacent conductive rods 102B to be spaced apart by the material of the cover member 270 on one sensor electrode 42, the conductive rods 102B of the detection device 1B, compared to the conductive rods 102a, increase in the area ratio of the multiple conductive rods 102B to the sensor electrode 42, in other words, increase in the number of conductive rods 102B, and the signal value increases and the detection sensitivity improves.

[0145] Although preferred embodiments of the present disclosure have been described above, the present disclosure is not limited to such embodiments. The contents disclosed in the embodiments are merely examples, and various modifications are possible within the scope of the present disclosure. Appropriate modifications made within the scope of the present disclosure also naturally fall within the technical scope of the present disclosure.

[0146] 1, 1a, 1A, 1B Detecting device 2 Detecting circuit 40 Sensor body 42 Sensor electrode 101 Object to be detected 102, 102a, 102A, 102B Conductive rod 270 Cover member GND1 Reference potential MA Mark SA Detection area

Claims

1. A detection device comprising: a sensor body having a detection area; a plurality of sensor electrodes arranged in a matrix on the detection area; a dielectric cover member placed on the sensor body; and conductive rods to which a predetermined reference potential is supplied, the conductive rods being embedded in the cover member at positions corresponding to the sensor electrodes.

2. The detection device according to claim 1, wherein the area of ​​one of the conductive rods closest to the surface is smaller than the area of ​​the sensor electrode in a plan view.

3. The detection device according to claim 2, wherein a plurality of marks corresponding to each of the sensor electrodes are provided on the surface of the cover member so as to overlap with the conductive rods.

4. The detection device according to claim 3, wherein the surface of the cover member excluding the markings does not overlap with the conductive rod.

5. The detection device according to claim 4, wherein the cover member has a thickness of 10 mm or more.

6. The detection device according to claim 4, wherein the thickness of the cover member is 10 mm or more and 40 mm or less.

7. The detection device according to claim 5 or 6, wherein the length of the conductive rod is 93% or more and 99% or less of the thickness of the cover member.

8. The detection device according to claim 7, wherein a plurality of the conductive rods are superimposed on one of the sensor electrodes.

9. The detection device according to claim 8, wherein adjacent conductive rods are spaced apart by the material of the cover member.

10. The detection device according to claim 9, wherein the distances between adjacent conductive bars are substantially equal to each other.

11. The detection device according to claim 10, wherein the total area of ​​the plurality of conductive rods overlapping with the sensor electrode is 3% or more of the area of ​​the sensor electrode in a plan view.

12. The detection device according to claim 11, further comprising a detection circuit that drives each of the sensor electrodes and detects capacitance.

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