JPWO2013021414A1 - Capacitance type input detection method - Google Patents

Abstract

An electrostatic capacity type input detection method for detecting an input operation of an input operation body with respect to a detection electrode from a capacitance between the input operation body and a detection electrode is provided. Signal detection means for detecting a reception level of an AC detection signal appearing on a detection electrode via a capacitance between the detection electrode and an input operation body converts the AC detection signal appearing on the detection electrode from an AC detection signal cycle. It has an integration circuit that integrates and outputs during a sufficiently long integration operation period, detects the reception level of the AC detection signal from the slope of the output of the integration circuit, and detects the distance between the detection electrode and the input operating body. Ask. [Selection] Figure 1

Description

  The present invention relates to a capacitance type input detection method for detecting an input operation position of an input operation body from an arrangement position of a detection electrode where an input operation body such as a finger approaches and the capacitance increases.

  2. Description of the Related Art A capacitive touch panel that detects an input operation and an input operation position by a capacitive input detection method is known as a pointing device that inputs an instruction displayed on a display of an electronic device. This capacitance type input detection method pays attention to the fact that the floating capacitance (capacitance between the input operation body and the detection electrode) of the detection electrode approaching the input operation body to be input increases. The input operation itself and the input operation position of the input operation body are detected from the position of the detection electrode where the capacitance changes.

  However, the capacitance between the input operation body and the detection electrode is extremely small, for example, about 50 fF at an input operation position 10 cm away from the detection electrode, assuming that the input operation body is a finger, and directly from the capacitance. It was difficult to detect the approach of the input operation body. Therefore, in the conventional input detection method, a large number of X-side detection electrodes and Y-side detection electrodes are formed in a matrix shape so as to intersect each other on the front and back of the insulating substrate, and the input operation body is in either position. The X-side detection electrode and the Y-side detection electrode are close to each other, and the input operation position is detected by relatively comparing the change in capacitance of each detection electrode (Patent Document 1).

  In this conventional input detection method, it is necessary to arrange a large number of X-side detection electrodes and Y-side detection electrodes along the input operation surface, and it is necessary to form a transparent body so that the display on the back side can be seen, which is expensive. In addition, in order to increase the detection resolution of the input operation position, it is necessary to arrange a larger number of X-side detection electrodes and Y-side detection electrodes densely, and a scanning time for detecting a change in capacitance for all the detection electrodes. The input position could not be detected in a short time.

  Therefore, the detection electrode is arranged only around the input operation surface, and a dielectric having a high dielectric constant is interposed between the input operation body and the detection electrode, so that the capacitance changes between the input operation body and the detection electrode. An electrostatic capacitance type input detection method for detecting an input position from the above has been proposed (Patent Document 2). In the capacitance type input detection method described in Patent Document 2, a touch-sensitive member made of a dielectric material having a high dielectric constant is arranged along the input operation surface, and the capacitance between the input operation position and the detection electrode is determined. The input operation position on the input operation surface is detected from a change in capacitance that is enlarged by a touch member having a higher dielectric constant than in the air.

  In addition, an integration circuit is connected to each detection electrode for multiple detection electrodes, the detection electrode that the input operating body contacts is detected based on the gradient of the output of the integration circuit, and the input operation position is detected from the position of the detection electrode. A position detecting device is also known (Patent Document 3). In this conventional position detection device, the output of the integration circuit changes according to the time constant obtained by multiplying the resistance value of the detection electrode and the floating capacitance of the detection electrode, and the floating capacitance of the detection electrode that the input operating body contacts increases. Therefore, the input operation position is detected from the arrangement position of the detection electrode, using the detection electrode whose output from the integration circuit becomes a predetermined value or less after a certain time as the detection electrode with which the input operation body is in contact.

  Input operation positions in a direction orthogonal to the arrangement direction of the plurality of detection electrodes are detected by connecting integration circuits to both ends of each detection electrode and comparing the outputs of the integration circuits. The detection electrode is configured such that the resistance value is proportional to the distance along the longitudinal direction, and the resistance of the detection electrode is proportional to the distance from the input operation position (contact position) of the input operation body to each end. Yes. As a result, the output of each integration circuit also rises gently according to the distance from one end of the detection electrode to which the integration circuit is connected to the input operation position. The input operation position along the longitudinal direction is detected.

JP 2005-337773 A JP-A-8-171449 Japanese Patent No. 3861333

  In the capacitance-type input detection method disclosed in Patent Document 1, in order to increase the detection accuracy of the input operation position, it is necessary to arrange a large number of detection electrodes on the input operation surface at a narrow pitch, and a large number of detections. Since it is necessary to scan the electrodes, detection time is required, and when the display is arranged on the back side, even if it is formed of a transparent conductive material, it is not a complete transparent body. There is a problem that it is difficult.

  In order to solve the above problem, even in the capacitance type input detection method disclosed in Patent Document 2 in which the detection electrode is not arranged on the input operation surface, a high dielectric constant feel parallel to the input operation surface Since the members are arranged, the problem of the decrease in transmittance cannot be solved.

  In addition, if the input operation body such as a finger is not touched with the touch member and the input operation is not performed, the capacitance between the input operation body and the detection electrode changes significantly. Therefore, it is necessary to perform the input operation by touching the touch member. Yes, it is limited to the detection of a two-dimensional input operation position parallel to the input operation surface. Further, since the input operation is performed by touching the touch member, there is a problem that the operability is impaired, the touch member made transparent by the input operation body is soiled, the aesthetic appearance is impaired, and the transmittance is lowered.

  The capacitance type input detection method described in Patent Document 3 expands the change in the resistance value and stray capacitance of the detection electrode due to the input operation of the input operation body to the output of the integration circuit, and detects the input operation position from the output. However, the input to the integration circuit, which rises due to a transient phenomenon, is not proportional to the stray capacitance or resistance value of the detection electrode, and does not directly obtain the stray capacitance or resistance value of the detection electrode from the output of the integration circuit. The operation position cannot be detected with high accuracy. Therefore, when the input operation position is detected from the change in the stray capacitance of the detection electrode, the input operation position is detected from the arrangement position of the specific detection electrode by relatively comparing the change in the stray capacitance of many detection electrodes. As in Patent Document 1, it is necessary to arrange a large number of detection electrodes along the detection direction.

  In addition, since the electrostatic capacitance between the non-contact input operation body and the detection electrode is extremely small as described above, the capacitance detection method described in Patent Document 3 has a stray capacitance for the detection electrode. The capacitance between the input operating body and the ground potential assuming that the input operating body is in contact with the detection electrode without comparing the detection potential is compared as the stray capacitance of the detection electrode. Only the input operation to contact can be detected.

  The present invention has been made in consideration of such conventional problems, and is a capacitance type input that detects an input operation of the input operation body with respect to the detection electrode from the capacitance between the input operation body and the detection electrode. The purpose is to provide a detection method.

  It is another object of the present invention to provide a capacitance type input detection method capable of detecting an input operation position of a non-contact input operation that only approaches the input operation surface.

  In order to achieve the above-mentioned object, the capacitance type input detection system according to claim 1 transmits a detection electrode arranged in an insulating case and an AC detection signal for changing a relative potential between the input operation body and the detection electrode. A transmission means, and a signal detection means for detecting the reception level of the AC detection signal appearing on the detection electrode via the capacitance between the detection electrode and the input operation body, from the reception level of the AC detection signal appearing on the detection electrode, A capacitance type input detection method for obtaining a distance between a detection electrode and an input operation body and detecting an input operation by the input operation body, wherein the signal detection means converts an AC detection signal appearing on the detection electrode to an AC detection signal. An integration circuit that integrates and outputs during an integration operation period sufficiently longer than the cycle is provided, and the reception level of the AC detection signal is detected from the slope of the output of the integration circuit.

  The reception level of the AC detection signal appearing on the detection electrode is proportional to the capacitance Cm between the detection electrode and the input operating body, and the integration circuit converts the AC detection signal into an integration operation period sufficiently longer than the cycle of the AC detection signal. Since the signal is integrated and output, the reception level proportional to the minute capacitance Cm between the detection electrode and the input operation body is expanded and expressed in the inclination of the output of the integration circuit.

  The capacitance Cm between the detection electrode and the input operation body is expressed as follows. The distance between the detection electrode and the input operation body is d, the dielectric constant of vacuum is ε0, the relative dielectric constant ε of air is about 1, and the input operation body and the detection electrode are Since the opposed area is s, it is expressed by Cm = ε0 · s / d, and is inversely proportional to the distance d between them, so that the input position detecting means is based on the reception level Vi of the AC detection signal expressed by the slope of the output of the integrating circuit. A distance d between the detection electrode and the input operation body is obtained, and an input operation for bringing the input operation body closer to the detection electrode and its input operation position can be detected.

  In the capacitance type input detection system according to claim 2, the integrating circuit has an integrating resistor connected to the output side of the detecting electrode and an integrating resistor connected from the detecting electrode to the first reference voltage of the non-inverting input terminal. An integration operational amplifier that outputs a difference from the input voltage of the AC detection signal that is input to the inverting input terminal via, and an integration capacitor connected between the inverting input terminal and the output terminal of the integration operational amplifier, The signal detection means further applies an offset adjustment voltage that cancels an offset voltage generated between the inverting input terminal and the non-inverting input terminal of the integrating operational amplifier to the inverting input terminal or the non-inverting input terminal of the integrating operational amplifier. It is characterized by having.

  In the signal detection means, the offset voltage generated between the inverting input terminal and the non-inverting input terminal of the integrating operational amplifier is canceled by the offset adjustment voltage, so that the offset voltage is integrated into the output signal output from the integrating operational amplifier. Is not included, and only the AC detection signal representing a minute capacitance between the detection electrode and the input operation body can be integrated and output as an expanded reception level from the integrating operational amplifier.

  The capacitance type input detection method according to claim 3 is characterized in that the offset adjusting means has a non-inverting input terminal connected to the input side of the integrating resistor which is set as the second reference voltage during the predetermined offset adjusting period, and the integrating operational amplifier. The inverting input terminal is connected to the output of the non-inverting input terminal during the offset adjustment period, and the difference between the output voltage of the feedback operational amplifier input to the inverting input terminal and the second reference voltage of the non-inverting input terminal is output. An operational amplifier, a switch that is connected between the output of the feedback operational amplifier and the non-inverting input terminal of the integrating operational amplifier, operates to close during the offset adjustment period, and opens during the integrating operation period, and the non-inverting input terminal of the integrating operational amplifier To the non-inverting input terminal of the integrating operational amplifier during the integration operation period. Characterized in that comprising a hold capacitor to be added to.

  During the offset adjustment period, the difference between the second reference voltage and the output voltage output from the integrating operational amplifier immediately before is input to the non-inverting input terminal of the integrating operational amplifier, and the second reference voltage is input to the inverting input terminal. Is done. The output voltage output from the integrating operational amplifier is the integrated value of the difference between the input voltage at the non-inverting input terminal and the input voltage at the inverting input terminal plus the offset voltage. By negative feedback to the terminal, the output voltage converges to the offset voltage and becomes a constant voltage. At this time, the output voltage of the feedback operational amplifier is stabilized by the offset adjustment voltage that adds the offset voltage and the difference in the input voltage between the non-inverting input terminal and the inverting input terminal of the integrating operational amplifier becomes 0, and the holding capacitor is charged. The voltage is an offset adjustment voltage.

  During the integration operation period, the output of the feedback operational amplifier and the non-inverting input terminal of the integrating operational amplifier are disconnected, and an offset adjustment voltage is applied from the holding capacitor to the non-inverting input terminal of the integrating operational amplifier. As a result, during the integration operation period, the offset voltage is not included in the output of the integrating operational amplifier, and only the reception level of the AC detection signal is integrated and expanded.

  According to a fourth aspect of the present invention, there is provided a capacitance type input detection method comprising: a plurality of detection electrodes arranged in an insulating case insulated from each other; and a switching means for selectively switching and connecting each of the plurality of detection electrodes to the signal detection means. The input operation position of the input operation body is detected from the reception level of the AC detection signal detected by the signal detection means for each detection electrode and the arrangement position of each detection electrode.

  Since the distance between each detection electrode and the input operation body is obtained from the reception level of the AC detection signal detected for each of the plurality of detection electrodes, even in a non-contact input operation in which the input operation body is separated from the detection electrode, The input operation position can be detected.

  According to the first aspect of the present invention, it is possible to detect a minute change in electrostatic capacitance when an input operation body such as a finger is brought close to the input operation surface. The operation position can be detected.

  In addition, since the distance between the detection electrode and the input operation body can be obtained from the capacitance, the two-dimensional or three-dimensional input operation position can be detected with a small number of detection electrodes.

  According to the second aspect of the present invention, the reception level of the AC detection signal proportional to a small capacitance of about several tens of fF between the input operation body and the detection electrode can be expanded and detected, and a high dielectric constant contact member is interposed. The distance to the input operation body that approaches the detection electrode in a non-contact manner can be detected without causing the contact to occur.

  According to the third aspect of the present invention, the reception level of the AC detection signal can be expanded and expressed in the slope of the output voltage waveform without being affected by the offset voltage of the integrating amplifier.

  According to the fourth aspect of the present invention, since the distance between each detection electrode and the input operation body can be obtained from the reception level of the AC detection signal detected for each of the plurality of detection electrodes, a limited number of detection electrodes are on the plane. Alternatively, it is possible to detect a three-dimensional input operation position.

It is a circuit diagram which shows the electrostatic capacitance type input detection system 1 which concerns on 1st Embodiment of this invention. 3 is a plan view of an instruction input device 50. FIG. It is the sectional view on the AA line of FIG. It is a block diagram of the instruction | indication input device 50 using the electrostatic capacitance type input detection system. 3 is an equivalent circuit diagram of a power supply circuit of the instruction input device 50. FIG. It is an equivalent circuit diagram around the detection electrode 11 through which the AC detection signal SG flows. FIG. 6 is a block diagram showing an operation of the integration processing circuit 14 during an offset adjustment period. It is explanatory drawing which shows the calculated value of offset voltage (DELTA) V in the offset period, and the output voltage Vf of the operational amplifier 26 for feedback. It is a voltage waveform diagram of each part shown in (a) (b) (c) of Drawing 1. It is a block diagram which shows the integration process circuit 40 of the electrostatic capacitance type input detection system which concerns on 2nd Embodiment of this invention.

  Hereinafter, the capacitance type input detection method 1 according to the first embodiment of the present invention will be described with reference to FIGS. 1 to 9. The input detection method 1 according to the present embodiment detects the input operation position of the input operation body 30 serving as input operation data, and outputs the operation data including the detected input operation position to the host processing device for display. It is used for the instruction input device 50 that controls the movement of the displayed cursor.

  As shown in FIG. 2, the input operation unit of the instruction input device 50 has a horizontally long rectangular window hole 21 formed inside the rectangular frame-shaped insulating case 20, and the opening surface of the window hole 21 is a finger as an operating body. An input operation surface 21a is used for performing an input operation with 30 being approached. As shown in FIG. 3, the inner edge 20 a of the insulating case 20 adjacent to the window hole 21 is an inclined surface that is inclined downward toward the center of the window hole 21, and the surfaces of the four inner edges 20 a that are orthogonal to each other. In addition, a pair of detection electrodes X0, Y1 that face each other in the X direction and a pair of detection electrodes Y0, Y1 that face each other in the Y direction are integrally attached.

  Each of the detection electrodes 11 (X0, X1, Y0, Y1) is formed in an elongated strip shape, and is disposed almost entirely along the inner edge 20a to be attached. As a result, the finger 30 faces all the detection electrodes 11 regardless of the position of the finger 30 at any position on the input operation surface 21a. Here, by arranging each detection electrode 11 along the inner edge 20a inclined upward, when the finger 30 is arranged above the input operation surface 21a, the area facing the finger 30 is maximized, which will be described later. The capacitance Cm is set to a large value.

  As shown in FIG. 4, the main circuit components constituting the input detection method 1 including the detection electrodes 11 are separately mounted on two types of the non-vibration side circuit board 2 and the vibration side circuit board 3. The non-vibration circuit board 2 is provided with a reference power supply circuit 4 including a low-voltage reference power supply line GND and a high-voltage reference power supply line VCC that are set to the ground potential, and a DC voltage Vcc between the low-voltage reference power supply line GND and the high-voltage reference power supply line VCC. Is connected to a DC power source 5. Thereby, each circuit component such as the interface circuit 6 mounted on the non-vibration circuit board 2 is connected to the reference power supply circuit 4 and driven by the output voltage Vcc of the DC power supply 5.

  Further, the vibration side circuit board 3 is provided with a vibration power circuit 7 including a low voltage vibration power line SGND and a high voltage vibration power line SVCC. The low-voltage vibration power supply line SGND is connected to the low-voltage reference power supply line GND, and the high-voltage vibration power supply line SVCC is connected to the high-voltage reference power supply line VCC via the coils 8 and 9, respectively. The inductances of the coil 8 and the coil 9 are both set to values having high impedance with respect to an AC detection signal SG having a natural frequency f described later. Here, the coils 8 and 9 having the same inductance L are used.

  An oscillation circuit 15 serving as a transmission means for transmitting the natural frequency f of the AC detection signal SG is mounted on the vibration side circuit board 3 and is branched into two branches via capacitors 17 and 18 having a capacitance C ′ that cuts off the DC voltage. The AC detection signal SG is connected to the low-voltage reference power line GND and the high-voltage reference power line VCC of the reference power circuit 4. As a result, as shown in FIG. 4, when the AC detection signal SG having the natural frequency f is output to the low voltage reference power line GND and the high voltage reference power line VCC of the reference power circuit 4 in synchronization with each other, the low voltage reference of the reference power circuit 4 is output. Since the power supply line GND is grounded and at a stable potential, the potentials of the low-voltage vibration power supply line SGND and the high-voltage vibration power supply line SVCC of the vibration power supply circuit 7 fluctuate synchronously with the natural frequency f. The DC output voltage Vcc is the same as that of the power supply circuit 4. The natural frequency f of the AC detection signal SG can be arbitrarily adjusted. Here, the AC detection signal SG having a natural oscillation frequency of 187 kHz is output.

  When the AC detection signal SG having the natural frequency f flows in the reference power supply circuit 4 and the vibration power supply circuit 7, the low-voltage reference power supply line GND and the high-voltage reference power supply line VCC and the low-voltage vibration power supply line SGND and the high-voltage vibration power supply line SVCC are close to each other. If the power supply lines are short-circuited in the band of the natural frequency f, the reference power supply circuit 4 and the vibration power supply circuit 7 are shown in the equivalent circuit diagram of FIG.

  As shown in FIG. 5, since capacitors 17 and 18 having a capacitance C ′ are connected in parallel between the output of the oscillation circuit 15 on the vibration power supply circuit 7 side and the reference power supply circuit 4, the combined capacitance is 2C. In addition, the combined inductance of the coils 8 and 9 connected in parallel between the reference power supply circuit 4 and the vibration power supply circuit 7 is L / 2. These capacitors and inductors are connected in series in a closed circuit in which an AC detection signal SG having a natural frequency f flows, and the amplitude (level) of the AC detection signal SG is Vsg, the reference power supply circuit 4 at both ends of the coils 8 and 9 and the vibration power supply. If the voltage between the circuits 7 is Vs, and the angular velocity represented by 2πf is ω (rad / sec),

It is represented by
Here, the circuit shown in FIG. 4 resonates in series at ω ² LC ′ = 1, and the frequency f _{0 at} that time is

It becomes.

That is, if the resonance frequency f ₀ obtained from the relationship of the expression (2) is the natural frequency f of the AC detection signal SG, the level of the AC detection signal SG is theoretically calculated from the expression (1) of the vibration power supply circuit 7. The potential vibrates at infinity, and the potential of each detection electrode 11 connected to the vibration power supply circuit 7 can be vibrated to infinity. In the actual input detection method 1, resonance does not occur at the frequency f ₀ obtained from the equation (2) due to the influence of the inductance and stray capacitance of the reference power supply circuit 4 and the vibration power supply circuit 7. Due to energy loss or the like when the AC detection signal SG flows through the circuit 7, the vibration power supply circuit 7 vibrates with the amplitude Vs expanded to a finite magnification with respect to the level Vsg of the AC detection signal SG.

Furthermore, since a large voltage cannot be applied to each detection electrode 11 that the operator's finger 30 may touch, the natural frequency f of the AC detection signal SG is adjusted in the vicinity of the resonance frequency f ₀ so that each detection electrode 11 The output level Vs of the AC detection signal SG that vibrates relatively can be arbitrarily set. Here, the output level Vs is set to 5V.

  Also, the natural frequency f of the AC detection signal SG can be set to an arbitrary frequency. However, around the commercial AC power supply line, the input operating body 30 is not at a constant potential, but common mode noise at the frequency of the commercial AC power supply is generated. Since it may be superposed, it is necessary to detect the AC detection signal SG of the natural frequency f from each detection electrode 11 as the frequency of the commercial AC power supply, and set the frequency excluding the frequency of the commercial AC power supply and its harmonics. It is preferable.

  Each of the detection electrodes 11 described above is connected to one of the low-voltage vibration power supply line SGND and the high-voltage vibration power supply line SVCC of the vibration power supply circuit 7, here the high-voltage vibration power supply line SVCC. When all the detection electrodes 11 are connected to the high-voltage vibration power supply line SVCC, the operator's finger 30 is vibrated at the natural frequency f at the output level Vs of the AC detection signal SG, while a part such as a foot is grounded. Is a constant potential, a voltage of an output level Vs of the AC detection signal SG is generated between the two, and the detection electrode 11 in which the finger 30 approaches and the capacitance Cm with the finger 30 increases. The AC detection signal SG having the natural frequency f appears from the detection electrode 11 to the finger 30 via the capacitance Cm. If this is seen from the vibration power supply circuit 7 that vibrates at the natural frequency f, the finger 30 as the input operating body vibrates at the natural frequency f of the AC detection signal SG with respect to the constant potential detection electrode 11.

  The electrostatic capacitance Cm between each detection electrode 11 and the input operation body 30 is such that the distance between the detection electrode and the input operation body is d, the dielectric constant of vacuum is ε0, the relative dielectric constant ε of air is about 1, and the input operation body 30 And the detection electrode 11 is represented by Cm = ε0 · εr · s / d, and the reactance Xc of the capacitance Cm with respect to the AC detection signal is f because the natural frequency of the AC detection signal is f.

から、

From

It is represented by

  FIG. 6 is an equivalent circuit diagram of the entire signal detection circuit unit for detecting the reception level Vi of the AC detection signal SG appearing on the detection electrode 11, where Cp is a floating between the detection electrode 11 and the low-voltage vibration power supply line SGND. Capacitance, rp is the internal resistance value of the detection electrode 11, and R4 is the resistance value of the output resistance. In the equivalent circuit diagram in the figure,

From the equations (3) to (6),

The relationship is obtained.

  If the internal resistance rp is set to 0 and R4 is connected to an integration operational amplifier A / D25, which will be described later, via the multiplexer 12 and the signal processing circuit 13, it is assumed that it is infinite.

Since the electrostatic capacitance Cm is extremely small, such as several tens of fF, compared to the stray capacitance Cp of several tens of pF, the equation (7)

The reception level Vi is proportional to the capacitance Cm.

  As described above, Cm of the input operation body 30 and the detection electrode 11 is

If it is transformed by substituting this into equation (8),

となり、入力操作中に指３０と検出電極１１との対向面積ｓがほぼ変化しないものとして、（９）式中の（ε０・εｒ・ｓ／Ｃｐ）は、定数であるので、これを１／ｋとおけば、検出電極１１に表れる交流検出信号ＳＧの受信レベルＶｉは、

Assuming that the facing area s between the finger 30 and the detection electrode 11 does not substantially change during the input operation, (ε0 · εr · s / Cp) in the equation (9) is a constant, so If k, the reception level Vi of the AC detection signal SG appearing on the detection electrode 11 is

As the detection electrode 11 is closer to the finger 30 and the distance d is closer to the finger 30, the reception level Vi becomes a larger value that approaches the output level Vs of the AC detection signal SG. However, when the finger 30 is close to the detection electrode 11 and the electrostatic capacitance Cm therebetween becomes so large that it cannot be ignored compared to the stray capacitance Cp of several tens of pF, the equation (10) cannot be applied and the reception level Vi. Becomes a maximum output level Vs.

  If the expression (10) is used, the reception level Vi of the AC detection signal appearing on each of the plurality of detection electrodes 11 can be compared, and the distance between the finger 30 and each detection electrode 11 can be compared. In this embodiment, The input in the XY direction parallel to the input operation surface 21a is determined from the arrangement position of each detection electrode 11 (X0, X1, Y0, Y1) and the reception level Vi of each detection electrode 11 (X0, X1, Y0, Y1). A three-dimensional input operation position between the operation position (x, y) and the input operation position z in the Z direction orthogonal to the input operation surface 21a is detected.

The capacitance Cm between the finger 30 and the detection electrode 11 when the input operation is performed on the finger 30 that is the input operation body to a position 10 cm away from the detection electrode 11 is the facing area s between the finger 30 and the detection electrode 11. Is 5 · 10 ⁻⁴ (m ² ), the dielectric constant ε0 of vacuum is 8.854 · 10 ⁻¹² (F / m), and the relative dielectric constant ε of air is about 1, and about 44.27 · 10 ^−15. F, that is, a very small value of 44.27 fF.

At this time, the reception level Vi of the AC detection signal SG appearing on the detection electrode 11 is 1 when the stray capacitance Cp is 50 pF because the proportionality constant k is Cp / (ε0 · εr · s) in the equation (10). .13 - 10 ^4, and the output level Vs to 5V AC detection signal SG, when a d ^{10 -1,} represented by a very small voltage change of about 4.4MV.

  Therefore, the minute input level Vi is enlarged by the capacitance type input detection method 1, and the distance d between each detection electrode 11 and the finger 30 is obtained from the enlarged reception level Vout, and the input operation position ( x, y, z) are detected.

  The vibration side circuit board 3 includes an analog multiplexer 12, a signal processing circuit 13, an integration processing circuit 14, an A / D converter 19, and an MPU (microprocessor unit) 10 constituting the capacitance type input detection method 1 shown in FIG. Each of the circuit elements of the oscillation circuit 15 and the oscillation circuit 15 are mounted and connected to the low-voltage oscillation power supply line SGND and the high-voltage oscillation power supply line SVCC of the oscillation power supply circuit 7 and operate by receiving the output voltage Vcc from the DC power supply 5.

  The analog multiplexer 12 switches and connects each detection electrode 11 to the signal processing circuit 13 at a constant period, here, every 200 msec by switching control from the MPU 10, and sequentially processes the AC detection signal SG appearing on each detection electrode 11. It is output to the circuit 13.

  The signal processing circuit 13 includes a resonance circuit 23 that passes a signal in a frequency band centered on the natural frequency f of the AC detection signal, an amplifier circuit 24 for impedance conversion, and a first analog connected in series therebetween. The switch ASW1. The resonance circuit 23 cuts low-frequency components such as a DC signal and high-frequency noise such as common mode noise from the signal appearing on the detection electrode 11 connected via the analog multiplexer 12, and converts the AC detection signal SG into a subsequent amplification circuit 24. Output to. The amplifier circuit 24 is an impedance conversion element having an input impedance close to infinity and an output impedance of a minute value. Even if the weak AC detection signal SG appears on the detection electrode 11, an integration process connected to the output side of the amplification circuit 24. The circuit 14 is made to operate.

  The first analog switch ASW1 is controlled to be opened and closed by the MPU 10, and connects the resonance circuit 23 and the amplifier circuit 24 during an integration operation period (Tint) in which the integration processing circuit 14 performs an integration operation described later, thereby adjusting an offset described later. Cut off during period (Tset). This prevents the AC detection signal SG from being output to the integration processing circuit 14 during the offset adjustment period (Tset).

  As shown in FIG. 1, the integration processing circuit 14 includes an integration operational amplifier 25, an integration resistor R 1 connected between the output of the signal processing circuit 14 and the inverting input terminal of the integration operational amplifier 25, and the integration operational amplifier 25. An integrating capacitor C1 connected between the inverting input terminal and the output terminal, and a second analog switch ASW2 connected in parallel to the integrating capacitor C1 and controlled to be opened and closed by the MPU 10 are provided.

  The voltage of the AC detection signal input to the integrating resistor R connected to the inverting input terminal of the integrating operational amplifier 25 is Vin, the voltage output from the output terminal of the integrating operational amplifier 25 is Vout, and the resistance value of the integrating resistor R1 is R, if the capacitance of the integrating capacitor C1 is C,

The voltage Vout obtained by integrating the input voltage Vin is output from the output terminal of the integrating operational amplifier 25.

  The second analog switch ASW2 is controlled to be closed by the MPU 10 for a short time after the start of the offset adjustment period (Tset), so that the charge accumulated in the integrating capacitor C1 can be quickly transferred during the integration operation period (Tint) of the integration processing circuit 14. The charging voltage charged in the integration capacitor C1 during the immediately preceding integration operation period (Tint) does not affect the offset operation during the offset adjustment period (Tset) of the integration processing circuit 14 to be described later. .

  There is a DC component error between the inverting input terminal and the non-inverting input terminal of the integrating operational amplifier 25 due to the offset voltage of the integrating operational amplifier 25 and other factors, and the combined error voltage is represented by the offset voltage Δv. , (11)

Since the offset voltage Δv is a DC component, the equation (12) is

As time t elapses, the error due to the offset voltage Δv in the output voltage Vout increases in proportion to the integration time.

  Therefore, in the present embodiment, the integration processing circuit 14 is further provided with a feedback circuit section serving as an offset adjusting means in order to substantially eliminate the influence of the offset voltage Δv. As shown in FIG. 1, the feedback circuit section includes a feedback operational amplifier 26, a third analog switch ASW3 connected between the output of the feedback operational amplifier 26 and the non-inverting input terminal of the integrating operational amplifier 25, and an integrating operational amplifier. 25. A hold capacitor 27 connected between the 25 non-inverting input terminals and the ground and charged by the output voltage of the feedback operational amplifier 26.

  The non-inverting input terminal of the feedback operational amplifier 26 is connected to the output of the integrating operational amplifier 25 via the resistor R2, and the inverting input terminal is connected to the input side of the integrating resistor R1. The resistance values of the resistor R3 and the resistor R2 connected between the inverting input terminal and the output terminal of the feedback operational amplifier 26 are equal. Therefore, the feedback operational amplifier 26 is used for integration while the third analog switch ASW3 is closed and controlled. The potential on the input side of the integrating resistor R connected to the inverting input terminal of the operational amplifier 25 is set as the input voltage Vin, and the difference of the output voltage Vout of the integrating operational amplifier 25 with respect to the input voltage Vin is amplified by gain −1. It acts to return to the non-inverting input terminal.

  During the offset adjustment period (Tset) controlled by the MPU 10, the third analog switch ASW3 is closed and controlled, and the input of the integrating resistor R1 and each detection electrode 11 are shut off by the first analog switch ASW1 controlled to open. Therefore, the AC detection signal SG is not input to the input side of the integrating resistor R1, and the potential of the inverting input terminal of the integrating operational amplifier 25 is maintained at the input voltage Vin that is a constant reference voltage. .

  The feedback circuit unit during the offset adjustment period (Tset) in which the first analog switch ASW1 is controlled to open and the third analog switch ASW3 is controlled to close is shown in the block diagram of FIG. In FIG. 7, Vi (s), Vo (s), and Vf (s) indicate the elapsed time of the input voltage Vin of the integrating operational amplifier 25, the output voltage Vout of the integrating operational amplifier 25, and the output voltage Vf of the feedback operational amplifier 26, respectively. The Laplace transform values G (s) and H (s) expressed by the functions Vi (t), Vo (t), and Vf (t) of t are the values of each block including the integrating operational amplifier 25 and the feedback operational amplifier 26. It is a transfer function. Note that s is a Laplace operator.

  In FIG.

as well as

So
The transfer function Vo (s) / Vi (s) of the entire feedback circuit unit is
From equations (14) and (15)

It becomes.

Here, the transfer function G (s) is expressed by G (s) = − 1 / sCR from the equation (11).
Since the transfer function H (s) is the gain Af of the feedback operational amplifier 26, the equation (16) is

If the pole Af / CR of the transfer function becomes negative from the system stability theorem, the control system of the entire feedback circuit section is stabilized.

  Assuming that the input voltage Vin, which is a constant reference voltage during the offset adjustment period (Tset), is 0 V, and the offset voltage ΔV generated by the integrating operational amplifier 25 is input to this control system, the offset voltage ΔV (t) is Since it is a step function, Laplace transform

When this is substituted as Vi (s) in equation (17),

It becomes.

  When this is expanded into partial fractions,

Therefore, when the inverse plus transformation is performed, Vo (t) becomes

It becomes.

  Here, for example, the resistance value R of the integrating resistor R1 is 10 kΩ, the capacitance C of the integrating capacitor C1 is 1000 pF, the offset voltage ΔV of the integrating operational amplifier 25 is 100 mV, and the gain Af of the feedback operational amplifier 26 is −1. When the output voltage Vout of the integrating operational amplifier 25 and the output voltage Vf of the feedback operational amplifier 26 are calculated for the elapsed time t after the start of the offset adjustment period (Tset) using the equations (15) and (21), FIG. As shown, the output Vout of the integrating operational amplifier 25 converges to a voltage having a polarity opposite to that of the offset voltage Δv after about 30 μs and stabilizes. In this state, the output voltage Vf of the feedback operational amplifier 26, that is, the input voltage of the inverting input terminal of the integrating operational amplifier 25 becomes equal to the potential obtained by adding the offset voltage Δv to the input voltage Vin of the non-inverting input terminal. A value obtained by integrating the offset voltage Δv with the output voltage Vout of 25 does not appear.

  Equation (21) shows that the elapsed time t until convergence becomes faster as the gain Af of the feedback operational amplifier 26 increases. However, when the gain Af is increased, the time due to the integration resistor R1 and the integration capacitor C1 is increased. The time until convergence from the constant RC is significantly shortened, and the delay time of the integrating operational amplifier 25 itself cannot be ignored.

  Therefore, the offset adjustment period (Tset) takes into account the gain Af of the feedback operational amplifier 26, the resistance value R of the integrating resistor R1, and the capacitance C of the integrating capacitor C1, until the output voltage Vout converges stably. Set a period sufficiently longer than the elapsed time.

  During the offset adjustment period (Tset), the hold capacitor 27 is charged with the output voltage Vf of the feedback operational amplifier 26, and the charge voltage of the hold capacitor 27 when the output Vout of the integrating operational amplifier 25 is stabilized is the feedback at that time. This is an offset adjustment voltage that makes the difference voltage between the non-inverting input terminal and the inverting input terminal zero, including the influence of the output voltage Vf of the operational amplifier 26, that is, the offset voltage Δv. Therefore, as the hold capacitor 27, a capacitor that is at least saturated when the output Vout of the integrating operational amplifier 25 converges stably is used.

  After the elapse of the offset adjustment period (Tset), the MPU 10 controls to close the first analog switch ASW1, and controls to open the third analog switch ASW3, and shifts to the integration operation period (Tint). In the integration operation period (Tint), the first analog switch ASW1 is closed and controlled, so that the AC detection signal SG appearing on the detection electrode 11 selectively connected by the analog multiplexer 12 is input to the inverting input terminal of the integration operational amplifier 25. . In addition, since the third analog switch ASW3 is controlled to open, the offset adjustment voltage charged in the hold capacitor 27 is input to the non-inverting input terminal of the integrating operational amplifier 25 during the offset adjustment period (Tset). The difference voltage between the non-inverting input terminal and the inverting input terminal of the integrating operational amplifier 25 including the voltage Δv becomes 0, and an error −Δv · that is obtained by integrating the offset voltage Δv shown in the equation (13) into the output Vout of the integrating operational amplifier 25. t / CR is not included.

  As a result, only the voltage Vin of the minute AC detection signal SG is integrated and expanded, and appears as the output Vout of the integrating operational amplifier 25. The MPU 10 is at the determination time t1 after the elapsed time that is the same elapsed time for each detection electrode 11 from the start of the integration operation period (Tint) and immediately before the end of the integration operation period (Tint). The output Vout is output to the A / D converter 19 connected in the subsequent stage, and the A / D converter 19 quantizes the output Vout of the integrating operational amplifier 25 at the determination time t1 for each detection electrode 11 and outputs it to the MPU 10.

  The quantized data output from the A / D converter 19 is proportional to the reception level Vi of the AC detection signal SG appearing on the detection electrode 11 selectively connected by the analog multiplexer 12 during the integration operation period (Tint). The MPU 10 acting as detection means uses the quantized data output from the A / D converter 19 as the reception level Vi of the AC detection signal SG appearing on the detection electrode 11 and obtains the distance d between the detection electrode 11 and the finger 30. Further, since the reception level Vi of the AC detection signal SG is amplified to n times the reception level Vi through the signal processing circuit 13 and the integration circuit 14, the MPU 10 receives the quantum output from the A / D converter 19. The distance d between the detection electrode 11 and the finger 30 may be obtained by setting the digitized data to 1 / n and the reception level Vi of the AC detection signal SG.

  Hereinafter, the reception level Vx0, Vx1, Vy0, Vy1 of the AC detection signal SG for each of the detection electrodes X0, X1, Y0, Y1 is detected by the input detection method 1 described above, and the input operation position (x, y) of the finger 30 is detected. , Z) will be described.

  While detecting the input operation position, the MPU 19 switches and controls the connection of the analog multiplexer 12 at a cycle of about 200 msec shown in FIG. 9, and sets the detection electrodes 11 in the order of the detection electrodes X0, X1, Y0, and Y1 to the signal processing circuit 13. And one cycle of individually switching and connecting all the detection electrodes X0, X1, Y0, and Y1 is repeated. One period connected to the signal processing circuit 13 for each detection electrode 11 is composed of the above-described offset adjustment period Tset and integration operation period Tint. The MPU 19 performs the second analog switch for a certain period immediately after the start of the offset adjustment period Tset. The ASW 2 is closed and controlled, and the charge accumulated in the integrating capacitor C 1 during the immediately preceding integration operation period Tint is discharged.

  During the offset adjustment period Tset, the first analog switch ASW1 is controlled to be opened, and the third analog switch ASW3 is controlled to be closed. As a result, the output voltage Vo (c) of the integrating operational amplifier 25 is controlled so that the ASW1 is opened and is constant. At the end of the offset adjustment period Tset that converges and stabilizes at the potential difference between the input voltage (a) of the inverting input terminal and the offset voltage Δv, and the charging voltage of the hold capacitor 27 is The offset adjustment voltage cancels the offset voltage Δv of the integrating operational amplifier 25.

  Subsequently, the MPU 19 closes the first analog switch ASW1, controls the third analog switch ASW3, and shifts to the integration operation period Tint. When the first analog switch ASW1 is closed and controlled, the AC detection signal SG appearing on the detection electrode 11 connected via the analog multiplexer 12 is input from the signal processing circuit 13 to the integration processing circuit 14 within that period. Further, when the third analog switch ASW3 is controlled to be opened, the output of the feedback operational amplifier 26 is disconnected from the non-inverting input terminal of the integrating operational amplifier 25, and the charging voltage of the holding capacitor 27 is added to the offset voltage Δv. The difference voltage between the non-inverting input terminal and the inverting input terminal to which is added is zero.

  As shown in FIG. 9, during the integration operation period Tint, the offset adjustment voltage (b) of the hold capacitor 27 that cancels the offset voltage Δv from the difference voltage from the inverting input terminal is applied to the non-inverting input terminal of the integrating operational amplifier 25. Only the input voltage Vi (a) of the AC detection signal SG having a natural frequency of 187 kHz input to the inverting input terminal is integrated at the elapsed time t, inverted and output from the integrating operational amplifier 25 (c). In the figure, the AC detection signal SG input to the inverting input terminal has a larger slope of the output waveform of the integrating operational amplifier 25 that appears in a staircase pattern as the input voltage Vi increases.

  In the present embodiment, a determination time t1 is set immediately before the end of the integration operation period Tint, and the elapsed time Tc from the start of the integration operation period Tint is the same for each detection electrode 11, and this determination time t1 The output Vout of the integrating operational amplifier 25 is output to the A / D converter 19 as reception levels Vx0, Vx1, Vy0, and Vy1 of the AC detection signal SG appearing at the connected detection electrode 11.

  After the end of the integration operation period Tint, the MPU 10 switches and controls the analog multiplexer 12 so that the next detection electrode 11 is connected to the signal processing circuit 13, and the offset adjustment period Tset and the integration operation period are similarly detected for the detection electrode 11. Repeat Tint control. Since the output voltage Vout input from the A / D converter 19 is obtained by enlarging the reception level Vi of the AC detection signal SG appearing at each detection electrode at the same magnification, the MPU 10 has all the detection electrodes X0, X1, Y0, Y1. After the elapse of one cycle, the output voltage Vout input from the A / D converter 19 for each detection electrode 11 is used as the reception level Vi of the AC detection signal SG for the detection electrode 11 and the two-dimensional of the finger 30 An input operation position (x, y) or a three-dimensional input operation position (x, y, z) is detected.

When the analog multiplexer 12 connects the detection electrodes X0 and X1, the reception level Vi of the AC detection signal SG output from the A / D converter 19 is set to a pair of detection electrodes X0 and Vx that face each other in the Vx0, Vx1, and X directions. If the distance between X1 is Lx and the finger 30 is at the input operation position P (x, z) shown in FIG.
About the detection electrode X0,

And for the detection electrode X1,

Since k, Lx, and Vs are known values, the detected Vx0 and Vx1 are substituted into the equations (22) and (23), and the condition that Lx−x and z are not negative is
A position x in the X direction from the detection electrode X0 and a position z in the Z direction orthogonal to the input operation surface 21a are obtained.

  When it is difficult to detect the output level Vs of the AC detection signal SG, for example, reception of the AC detection signal SG for the detection electrode X1 at the input operation position (x (0), z (0)) of the detection electrode X0. Detect level Vx1 (0, 0) and substitute it into equation (10)

May be obtained from

Similarly, in the Y direction, when the analog multiplexer 12 connects the detection electrodes Y0 and Y1, the reception level Vi of the AC detection signal SG output from the A / D converter 19 is opposed in the Vy0, Vy1, and Y directions, respectively. If the distance between the set of detection electrodes Y0 and Y1 is Ly and the finger 30 is at the input operation position P (y, z),
For the detection electrode Y0,

And for the detection electrode Y1,

Substituting the detected Vy0 and Vy1 into the equations (24) and (25), and assuming that Ly-y and z are not negative, the position y in the Y direction from the detection electrode Y0 and the input operation A position z in the Z direction perpendicular to the surface 21a is obtained.

  Since each of the detection electrodes X0, X1, Y0, Y1 is arranged over the entire inner edge of the rectangular window hole 21, the finger that has performed an input operation at least in the vertical direction of the input operation surface 21a. 30 faces the detection electrodes X0 and X1 in the X direction and the detection electrodes Y0 and Y1 in the Y direction, and therefore the three-dimensional input operation position (x, y) of the finger 30 from the equations (22) to (25). Z) can be detected.

  In particular, in the case of the input detection method 1 for detecting the two-dimensional input operation position (x, y) only for the input operation on the input operation surface 21a, the equation (22) is set to z = 0 in the X direction. From equation (23), if the output level Vs is deleted, from 0 ≦ x ≦ Lx

And solving equation (26) for x,

It becomes.

  Similarly, from the formulas (24) and (25) in the Y direction,

The input position (x, y) in the XY direction on the input operation surface 21a can be easily obtained from Vx0, Vx1, Vy0, Vy1.

The input operation data including the input operation position (x, y, z) detected by the MPU 10 is output to the interface circuit 6 mounted on the non-vibration circuit board 2 via the signal line 16 in which the direct current is insulated. The data is output from the circuit 6 to a host device that uses input operation data by USB communication, I ² C communication, or the like.

  FIG. 10 is a block diagram of an integration processing circuit 40 according to the second embodiment in which the feedback circuit unit of the above-described integration processing circuit 14 has another configuration. Hereinafter, in the other embodiments shown in FIG. Since only the configuration of the feedback circuit section is different, the configuration common to the first embodiment in the figure is given the same number, and the description thereof is omitted.

  The feedback circuit unit of the integration processing circuit 40 has a non-inverting input terminal as an output of the integrating operational amplifier 25, a feedback operational amplifier 41 having an inverting input terminal as a reference potential (here, ground potential), and one side as a reference potential. The holding capacitor 42 having the other side connected to the output of the feedback operational amplifier 41 via the fourth analog switch ASW4, and the voltage connecting the connection point of the holding capacitor 42 and the fourth analog switch ASW4 to the non-inverting input terminal The follower 43 includes a second integration resistor R5 connected between the output of the voltage follower 43 and the inverting input terminal of the integration operational amplifier 25.

  That is, in the integration processing circuit 40 according to the second embodiment, the output of the feedback circuit unit is fed back to the inverting input terminal side of the integration operational amplifier 25 via the second integration resistor R5. 2 A voltage follower 43 having an output impedance of approximately 0 is interposed so that the integrating operational amplifier 25 operates stably with the output of the feedback operational amplifier 41 flowing through the integrating resistor R5.

  When the first analog switch ASW1 is controlled to be opened and the fourth analog switch ASW4 is controlled to be closed during the offset adjustment period Tset, the output of the feedback operational amplifier 41 is set to Vf, the resistance value of the integrating resistor R5 is set to R, and the integrating operational amplifier 25 The output voltage Vout of

The integrating operational amplifier 25 operates so as to output a voltage Vout obtained by integrating the input voltage Vf. As a result, the output voltage Vout of the integrating operational amplifier 25 converges and stabilizes at the input voltage of the inverting input terminal, that is, the output voltage Vf of the feedback operational amplifier 41, and at the end of the offset adjustment period Tset when the output voltage Vout is stable. The charging voltage of the holding capacitor 42 becomes an offset adjustment voltage that cancels the offset voltage Δv of the integrating operational amplifier 25.

  When the first analog switch ASW1 is controlled to be closed and the fourth analog switch ASW4 is controlled to be opened and the integration operation period (Tint) is started, the offset adjustment that offsets the offset voltage Δv to the AC detection signal SG that appears on the detection electrode 11 A voltage is applied from the holding capacitor 42 and input to the inverting input terminal of the integrating operational amplifier 25. Therefore, the difference voltage from the reference voltage (ground potential) of the non-inverting input terminal does not include the offset voltage Δv, and only the output voltage Vout obtained by integrating the input voltage Vin of the AC detection signal SG is output.

  In the above-described embodiment, the detection electrode 11 is vibrated at the output level Vs of the AC detection signal SG with respect to the input operating body 30, and the relative potential of the output level Vs is generated between them. May be set to a constant potential, and the potential of the input operating body 30 may be varied with the output level Vs of the AC detection signal SG.

  Moreover, although the input operation body 30 was demonstrated with the finger | toe 30 which an operator performs input operation, you may be an operation body different from an operator, such as a dedicated input pen which an operator holds.

  As a method for obtaining the reception level Vi of the AC detection signal from the slope of the output voltage Vout of the integration circuit, the reception level Vi is obtained from the output voltage Vout when a certain integration time has elapsed in the above-described embodiment. The reception level Vi may be obtained from the integration time until the output voltage Vout becomes a constant value.

  In the above-described embodiment, the example in which the input operation position of the input operation body 30 is detected by comparing the reception levels Vi for the plurality of detection electrodes 11 has been described. However, the reception level Vi for the specific detection electrode 11 is described. Since this exceeds a certain level, it can also be used for detecting an input operation in which the input operating body 30 is brought close to the detection electrode 11.

  The present invention is suitable for an input detection method used for a capacitive touch panel that detects an input operation without contact.

1 Capacitance type input detection method 10 MPU
11 detection electrode 14 integration processing circuit (signal detection means)
15 Oscillator circuit (transmitting means)
30 fingers (input operation body)
Cm Capacitance SG AC detection signal Vs Output level of AC detection signal Vi Reception level of AC detection signal

Claims (4)

A sensing electrode disposed in an insulating case;
Transmitting means for transmitting an AC detection signal for changing the relative potential between the input operation body and the detection electrode;
Signal detecting means for detecting the reception level of the AC detection signal appearing on the detection electrode via the capacitance between the detection electrode and the input operation body,
From the reception level of the AC detection signal appearing on the detection electrode, the distance between the detection electrode and the input operation body is obtained, and the capacitance type input detection method for detecting the input operation by the input operation body,
The signal detection means has an integration circuit that integrates and outputs the AC detection signal appearing on the detection electrode during an integration operation period sufficiently longer than the cycle of the AC detection signal, and the AC detection signal is obtained from the slope of the output of the integration circuit. Capacitance type input detection method characterized by detecting the reception level. The integration circuit is configured to detect the AC detection input from the detection electrode to the inverting input terminal via the integration resistor with respect to the integration resistor connected to the output side of the detection electrode and the first reference voltage of the non-inverting input terminal. It consists of an integration operational amplifier that outputs the difference from the signal input voltage, and an integration capacitor connected between the inverting input terminal and the output terminal of the integration operational amplifier.
The signal detection means further applies an offset adjustment voltage that cancels an offset voltage generated between the inverting input terminal and the non-inverting input terminal of the integrating operational amplifier to the inverting input terminal or the non-inverting input terminal of the integrating operational amplifier. The electrostatic capacitance type input detection system according to claim 1, wherein: The offset adjusting means has a non-inverting input terminal connected to the input side of the integrating resistor used as the second reference voltage during a predetermined offset adjusting period, and an inverting input terminal connected to the output of the integrating operational amplifier. A feedback operational amplifier that outputs a difference between the output voltage of the feedback operational amplifier input to the inverting input terminal with respect to the second reference voltage of the non-inverting input terminal, and the output of the feedback operational amplifier and the integrating operational amplifier. Connected between the non-inverting input terminals, closed during the offset adjustment period, opened during the integration operation period, and connected to the non-inverting input terminal of the integrating operational amplifier, and fed back to the feedback operational amplifier during the offset adjustment period. From the hold capacitor that applies the offset adjustment voltage charged by the output voltage to the non-inverting input terminal of the integration operational amplifier during the integration operation period Capacitive input detection method according to claim 2, characterized in Rukoto. A plurality of detection electrodes arranged insulated from each other in an insulating case;
Switching means for selectively switching and connecting each of the plurality of detection electrodes to the signal detection means,
The input operation position of the input operation body is detected from the reception level of the AC detection signal detected by the signal detection means for each detection electrode and the arrangement position of each detection electrode. The capacitance-type input detection method according to any one of the above.

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