JP2005091139A - Capacity detecting sensor, fingerprint sensor, and capacity detecting method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a capacity detecting sensor, a fingerprint sensor and a capacity detecting method capable of reducing a noise picked up in a sensor part and a noise transmitted from a human body to the sensor part, and capable of enhancing an S/N ratio. <P>SOLUTION: A capacity change in an intersection of a drive line with a detection line is detected in the sensor part 5, using an impressed signal wave multiplied with a modulated wave to the drive signal. The capacity change is converted into a voltage in a CV conversion part 6. A phase of the modulated wave is conformed with a phase of the voltage-converted impressed signal wave output from the CV conversion part 6, in a phase regulation part 8, and the modulated wave is multiplied with the impressed signal wave in the a multiplier 7 to pick out a frequency component of the drive signal, in a filter part 9. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a capacitance detection sensor, a fingerprint sensor, and a capacitance detection method.

In the fingerprint sensor part which is most promising among biometrics, an area type fingerprint sensor for detecting the shape of fingerprint ridges and valleys is required. As an example, column wiring (drive lines) and row wiring (detection lines) are formed on the surface of two films at a predetermined interval, and a necessary insulating film is added to face each other with a predetermined interval. An area-type capacitance detection sensor arranged in this manner can be considered. In this area-type sensor unit, when the finger is placed, the film surface is deformed following the shape of the fingerprint. Therefore, the distance between the column wiring and the row wiring changes depending on the location, and is detected as a minute capacitance change. Functions as a pressure sensor.
In this area type sensor unit, it is necessary to detect a minute change in capacitance that is less than several tens of femto farads in a matrix at each point where the column wiring and the row wiring intersect. For this reason, since the capacitance change in the detection circuit is minute, it is required not only to have high sensitivity but also to be resistant to noise transmitted from the human body and circuit system noise.
In addition to this pressure-sensitive sensor, the capacitance change of this electrode is detected according to the change in the lines of electric force from the electrode due to the proximity of a conductor such as a finger or a dielectric to the electrode connected to the column wiring and row wiring. A method for detecting a fingerprint shape has also been proposed. Similarly, the detection circuit is required not only to have high sensitivity because the capacitance change is minute, but also to remove noise transmitted from the human body or the like.

As a conventional technique applicable to this capacitance detection, for example, as described in Patent Document 1, there is a detection circuit that converts a change in capacitance value into an electrical signal by a switched capacitor unit. This is a switched capacitor circuit in which a sensor capacitive element that is driven by a first sensor drive signal and detects a change in capacitance of a detection target and a reference capacitive element that is driven by a second sensor drive signal and serves as a detection circuit reference capacitor. After the first and second sample and hold units connected to each other and having an output signal having a phase difference of 90 degrees sample each signal, a detection signal can be obtained by obtaining a difference between the sampling results.
In this detection circuit, in a common switched capacitor circuit, the capacitance Cs to be detected can be stably detected in inverse proportion to the feedback capacitance Cf, and is stored in the gate electrode of the reset switch (feedback control switch) of the switched capacitor circuit. The influence of the charged charge Qd, that is, the influence of the feedthrough capacity is offset. Further, it is expected that the low-frequency noise included in the offset component of the reference potential of the switched capacitor circuit or the input signal can be removed to some extent by obtaining the difference between the two sampling results.
Further, as disclosed in FIG. 4 of the third embodiment of Patent Document 1, noise can be removed by inserting a high-pass filter, a low-pass filter, and a band-pass filter after the switched capacitor.
Japanese Patent No. 2561040

However, the noise that can be removed by the above-described configuration is noise that occurs after the switched capacitor and is difficult to remove with respect to noise mixed before the switched capacitor or cannot be removed at all.
This is because the input current is accumulated and the voltage corresponding to the charge amount is output regardless of the signal and noise while the switched capacitor unit opens the reset switch. Therefore, even if this voltage is simply filtered at a later stage, there is a problem that noise picked up by the sensor unit and noise conducted from the human body to the sensor unit are difficult to remove or cannot be removed at all.

Hereinafter, this problem will be described with reference to the drawings. 9, 10, and 11 are respectively a waveform diagram, an equivalent circuit diagram showing a noise mixing path conducted from the human body to the sensor, and an explanatory diagram showing a noise mixing path conducted from the human body to the sensor.
In FIG. 9, the detection current is a detection current flowing through the negative input terminal line of the operational amplifier.
As an example that is difficult to remove with a filter, if there is a noise indicated by a dotted line, such as the detection current N1, an operational amplifier output such as a CV output voltage N1 is obtained. Such a noise component is difficult to remove because it is limited.
Similarly, as an example in which noise cannot be completely eliminated by the filter, when the noise indicated by the dotted line simultaneously with the true value overlaps like the detection current N2, the operational amplifier output becomes the dotted line of the CV output voltage N2. Since no current fluctuation appears at all in the current output, naturally noise cannot be removed even if a filter is provided in the subsequent stage.

Furthermore, as shown in FIG. 11, the pressure-sensitive sensor is insulated with a film, and even when the impedance of the circuit that drives the wiring is low, there is wiring resistance. , Wiring ”, that is, capacitors of fingers (electrodes), films (dielectrics), and wirings (electrodes) are formed, and noise generated by the human body is coupled to the wiring. Noise generated is superimposed.
In addition, sensors that detect changes in the capacitance of electrodes in response to changes in the lines of electric force from the electrodes due to the proximity of conductors or dielectrics such as fingers to the electrodes connected to the column wiring and row wiring, electromagnetic waves received from the outside, etc. Thus, when the potential of a conductor such as a finger or the dielectric varies, the lines of electric force naturally also vary, so noise is superimposed on the output current of the sensor.
As described above, in the conventional example, the switched capacitor is charged with the feedback capacitor in a state including the superimposed noise current. Therefore, the noise reduction effect is small or cannot be reduced at all by simply providing a filter in the subsequent stage. There was a problem.

  The present invention has been made in view of such circumstances, and its purpose is to detect capacitance picked up by the sensor unit and noise transmitted from the human body to the sensor unit and to improve the S / N ratio. It is to provide a sensor, a fingerprint sensor, and a capacity detection method.

  The present invention has been made to solve the above-described problems. The present invention provides a drive signal generation unit that outputs a drive signal, a modulation wave generation unit that outputs a modulation wave that modulates the drive signal, and the drive signal. And a first multiplier that outputs an applied signal wave obtained by multiplying the modulated wave by the modulation wave, and a change in capacitance at the intersection of the drive line and the detection line, using the applied signal wave input from the first multiplier as a drive signal. A sensor unit for detection, a CV conversion unit for converting a capacitance change input from the sensor unit into a voltage, and a phase of the modulation wave input from the modulation wave generation unit are voltage-converted by the CV conversion unit. A phase adjustment unit that matches the phase of the applied signal wave, a second multiplier that multiplies the modulated wave input from the phase adjustment unit, and the applied signal wave input from the CV conversion unit, and the second multiplication. Of the signals input from the instrument Characterized by comprising a filter unit for taking out a frequency component of the driving signal generated by the drive signal generating unit.

  In the invention, it is preferable that the sensor unit is an area type sensor in which a plurality of detection lines are arranged in a matrix for a plurality of drive lines.

  In the invention, it is preferable that the sensor unit is a line type sensor in which one detection line is formed for a plurality of drive lines.

  Further, the present invention is characterized in that the capacitance detection sensor is used as a fingerprint sensor.

  In the present invention, the drive signal generation unit outputs the drive signal, the modulation wave generation unit outputs the modulation wave that modulates the drive signal, and the first multiplier includes the drive signal and the modulation wave. And the sensor unit detects a change in capacitance at the intersection of the drive line and the detection line using the applied signal wave input from the first multiplier as a drive signal, and a CV conversion unit Converts the capacitance change input from the sensor unit into a voltage, and the phase adjustment unit converts the phase of the modulation wave input from the modulation wave generation unit into a voltage-converted applied signal wave output from the CV conversion unit. And the second multiplier multiplies the modulation wave input from the phase adjustment unit by the applied signal wave input from the CV conversion unit, and the filter unit from the second multiplier. Of the input signals, generated by the drive signal generator And wherein the retrieving the frequency component of the driving signal.

As described above, according to the present invention, the drive signal generation unit outputs the drive signal, the modulation wave generation unit outputs the modulation wave that modulates the drive signal, and the first multiplier outputs the drive signal. And an applied signal wave obtained by multiplying the modulated wave by the sensor unit, the sensor unit detects a change in capacitance at the intersection of the drive line and the detection line using the applied signal wave input from the first multiplier as a drive signal, and CV The conversion unit converts the capacitance change input from the sensor unit into a voltage, the phase adjustment unit converts the phase of the modulation wave input from the modulation wave generation unit, and the phase of the voltage-converted applied signal wave output from the CV conversion unit And the second multiplier multiplies the modulated wave input from the phase adjustment unit by the applied signal wave input from the CV conversion unit, and the filter unit out of the signals input from the second multiplier The frequency component of the drive signal generated by the drive signal generator It is.
Therefore, it is possible to reduce the noise picked up by the sensor unit and the noise transmitted from the human body to the sensor unit, and to improve the SN ratio.

Further, according to the present invention, the sensor unit is constituted by an area type sensor in which a plurality of detection lines are arranged in a matrix with respect to a plurality of drive lines.
Accordingly, since an area type sensor in which drive lines and detection lines are arranged in a matrix can be configured, noise picked up by the sensor unit and noise transmitted from the human body to the sensor unit can be reduced, and the SN ratio can be improved. The effect which can improve the operativity of is acquired.

Further, according to the present invention, the sensor unit is configured by a line type sensor in which one detection line is formed for a plurality of drive lines.
Therefore, since a line type sensor having only one row of drive lines can be configured, noise picked up by the sensor unit and noise transmitted from the human body to the sensor unit can be reduced, the SN ratio can be improved, and the circuit can be downsized. The effect that a cost reduction can be aimed at is acquired.

  Hereinafter, the best mode for carrying out the present invention will be described.

Hereinafter, an embodiment of a capacitance detection sensor of the present invention will be described with reference to the drawings. FIG. 1 is a configuration diagram of a capacitance detection sensor according to the present embodiment.
The capacitance detection sensor according to the present embodiment includes a drive signal generation unit 1, a modulation wave generation unit 2, a multiplier 3, a switching unit 4, a sensor unit 5, a CV conversion unit 6, a multiplier 7, and a phase. The adjustment unit 8, the filter unit 9, the amplitude detection unit 10, the selector unit 16, and the AD conversion unit 11 are mainly configured.
The drive signal generation unit 1 generates a drive signal supplied to the sensor unit 5 and outputs it to the multiplier 3. Now, this drive signal is defined as A cos ω _c t.
The modulated wave generator 2 generates a modulated wave that modulates the drive signal generated by the drive signal generator 1 and outputs the modulated wave to the multiplier 3 and the phase adjuster 8. Similarly, this modulated wave is defined as B cos ω _m t.
The multiplier 3 switches the applied signal wave Acos ω _c t · B cos ω _m t obtained by multiplying the drive signal A cos ω _c t input from the drive signal generation unit 1 by the modulation wave B cos ω _m t input from the modulation wave generation unit 2 to the switching unit 4. Output to.

Switching unit 4 is connected to the driving line side of the sensor unit 5, based on the control signal input of the applied signal wave Acosω _{c t} · Bcosω _{m t} input from multiplier 3 from a control unit (not shown) Output to one selected drive line. Note that the switching unit 4 is configured so that all unselected outputs (that is, other than the selected one) are connected to a constant DC voltage, for example, ground.
The sensor unit 5 is an area type in which a plurality of detection lines 13 are arranged in a matrix on the CV conversion unit 6 side or a plurality of drivings on the switching unit 4 side with respect to the plurality of driving lines 12 on the switching unit 4 side. A line-type capacitive detection type fingerprint sensor in which one detection line 13 is formed on the CV conversion unit 6 side with respect to the line 12, and an applied signal wave input from the multiplier 7 is used as a drive signal as a drive line. Capacitance change at the intersection of 12 and the detection line 13 is detected. Specifically, as shown in FIG. 2, at the intersection of the drive line 12 and the detection line 13, a capacitor provided between the vicinity point on the drive line 12 and the vicinity point on the detection line 13. An applied signal wave proportional to the capacity is output from the detection line 13.

For example, the CV conversion unit 6 is configured as shown in FIG. 3, and changes the capacitance input from the detection line 13 of the sensor unit 5, that is, applies an applied signal wave kAcosω _c t · Bcosω _m t proportional to the capacitance of the capacitor to a voltage. And output to the multiplier 7. However, k shows a proportionality constant. The configuration example shown in FIG. 3 is appropriately selected by those skilled in the art depending on the implementation, and design changes and the like that do not change the gist of the present invention are included in the present invention.
Here, let us consider the noise mixing which is a problem in the present invention. If the noise mixed before the CV conversion unit 6 is Ccos ω _n t, when noise is mixed, the output of the CV conversion unit 6 is kA cos ω _c t · B cos ω _m t + C cos ω _n t. Hereinafter, the applied signal wave in consideration of the noise mixture is referred to as a detection wave.
The phase adjustment unit 8 matches the phase of the modulation wave input from the modulation wave generation unit 2 with the phase of the detection wave output from the CV conversion unit 6. Specifically, the phase adjustment unit 8 delays the phase of the modulation wave so that the phase of the detection wave and the phase of the modulation wave delayed from the sensor unit 5 by the CV conversion unit 6 are equal to each other. Output. The output of the phase adjustment unit 8 is defined as Dcos ω _m t.

The multiplier 7 multiplies the modulation wave input from the phase adjustment unit 8 and the detection wave input from the CV conversion unit 6 and outputs the result to the filter unit 9 (described later).
The filter unit 9 extracts the frequency component of the drive signal generated by the drive signal generation unit 1 from the signal input from the multiplier 7.
For example, the amplitude detection unit 10 includes a peak hold circuit as shown in FIG. 4, detects the amplitude of the frequency component of the drive signal extracted by the filter unit 9, and outputs a DC level equal to this amplitude. The configuration example shown in FIG. 4 is appropriately selected by those skilled in the art according to the implementation, and design changes and the like that do not change the gist of the present invention are included in the present invention.
Note that a plurality of sets of multipliers 7, filters 9, and amplitude detectors 10 subsequent to the CV converter 6 are provided corresponding to the number of detection lines.
The selector unit 16 selects the amplitude output of the amplitude detection unit 10 and outputs it to the AD conversion unit 11.
The AD conversion unit 11 performs AD conversion on the amplitude output from the selector unit 16 and extracts a digital output proportional to the fingerprint shape.

Next, the operation of the capacitance detection sensor of this embodiment will be described with reference to the drawings. FIG. 5 is a waveform diagram of each block of the capacitance detection sensor of the present embodiment.
As shown in FIG. 5, first, the drive signal generation unit 1 generates the drive signal Acos ω _c t, and the modulation wave generation unit 2 generates the modulation wave B cos ω _m t. The drive signal Acos ω _c t and the modulated wave B cos ω _m t are multiplied by the multiplier 3, and the applied signal wave A cos ω _c t · B cos ω _m t is output to the switching unit 4.
In the switching unit 4, the plurality of drive lines 12 and corresponding detection lines 13 are sequentially scanned based on a control signal from the control unit. At this time, the applied signal wave is sequentially supplied to the selected j-th drive line 12 and a signal (detection wave) proportional to the capacitance of the capacitor provided at the intersection is output from the corresponding detection line 13.

となる。 On the other hand, when the modulation wave is input in the phase adjustment unit 8, the phase of the modulation wave is delayed so that the phase of the detection wave delayed from the sensor unit 5 by the CV conversion unit 6 is equal to the phase of the modulation wave. , And output to the multiplier 7.
In the multiplier 7, the modulated wave D cosω _m t input from the phase adjustment unit 8 is multiplied by the detection wave (kA cosω _c t · B cosω _m t + C cosω _n t) input from the CV conversion unit 6.
That is,

It becomes.

Here, the first term is only the same frequency component as the signal generated by the drive signal generator 1. The second term is a component separated by ± ω _n of the noise frequency around the frequency 2ω _m that is twice the signal generated by the modulated wave generator 2. That is, as shown in FIG. 6, the frequency component of the noise moves to the vicinity of the frequency omega _m of the signal generated by the modulation wave generator 2.
Here, by configuring the filter unit 9 to extract only the first term, it is possible to extract a sine wave having an amplitude corresponding to a change in the capacitance of the sensor unit 5. If necessary, the selector unit 16 can select the amplitude output of the amplitude detection unit 10 and pass the AD conversion unit 11 to extract a desired signal.
That is, it is possible to suppress noise mixed before the CV converter 6 from the above. In the present embodiment, for simplification of description, the noise frequency has been described as ω _m . However, the above description holds even when there are a plurality of noise frequencies by the superposition theorem. It is clear.

As described above, according to the capacitance detection sensor of the present embodiment, the drive signal generation unit 1 outputs a drive signal, the modulation wave generation unit 2 outputs a modulation wave that modulates the drive signal, and a multiplier. 3 outputs an applied signal wave obtained by multiplying the drive signal and the modulated wave, and the sensor unit 5 uses the applied signal wave input from the multiplier 3 as a drive signal to change the capacitance at the intersection of the drive line and the detection line. Then, the CV conversion unit 6 converts the capacitance change input from the sensor unit 5 into a voltage, and the phase adjustment unit 8 outputs the phase of the modulation wave input from the modulation wave generation unit 2. The multiplier 7 matches the phase of the voltage-converted applied signal wave, the multiplier 7 multiplies the modulated wave input from the phase adjustment unit 8 and the applied signal wave input from the CV conversion unit 6, and the filter unit 9 multiplies. Of the signals input from the device 7, the signal is generated by the drive signal generator 1. Retrieve the frequency component of the driving signal.
Therefore, it is possible to reduce the noise picked up by the sensor unit and the noise transmitted from the human body to the sensor unit, and to improve the SN ratio.

Hereinafter, a second embodiment of the capacitance detection sensor of the present invention will be described with reference to the drawings. FIG. 7 is a configuration diagram of the capacitance detection sensor of the present embodiment.
The capacity detection sensor of the present embodiment is different from the first embodiment in that a switching unit 15 that switches the outputs of a plurality of CV conversion units 6 is provided, and a multiplier 7, a filter 9, and an amplitude subsequent to the CV conversion unit 6 are provided. This is a point in which one set of the detection unit 10 is provided.
That is, the sensor unit 5 is sequentially scanned as in the first embodiment, and detection waves are output to the plurality of CV conversion units 6. Each CV conversion unit 6 performs CV conversion on the detected wave and outputs it to the switching unit 15. The switching unit 15 switches the outputs of the plurality of CV conversion units 6 in the scan order and outputs the input detection wave to the multiplier 7.
The multiplier 7, the phase adjustment unit 8, the filter unit 9, and the amplitude detection unit 10 operate in the same manner as in the first embodiment, and extract the frequency component of the drive signal generated by the drive signal generation unit 1.

Therefore, according to the capacitance detection sensor of the present embodiment, the drive signal generator 1 outputs a drive signal, the modulation wave generator 2 outputs a modulation wave that modulates the drive signal, and the multiplier 3 drives the drive. An applied signal wave obtained by multiplying the signal and the modulated wave is output, and the sensor unit 5 detects a change in capacitance at the intersection of the drive line and the detection line using the applied signal wave input from the multiplier 3 as a drive signal, and CV The conversion unit 6 converts the capacitance change input from the sensor unit 5 into a voltage, the switching unit 15 switches the output of the CV conversion unit 6 in the scanning order of the sensor unit 5, and the phase adjustment unit 8 converts the modulation wave generation unit 2. The phase of the modulated wave input from the VV is matched with the phase of the voltage-converted applied signal wave output from the CV conversion unit 6, and the multiplier 7 is selected by the switching unit 15 and the modulated wave input from the phase adjustment unit 8. The applied signal wave is multiplied, and the filter unit 9 Among the signals input from the adder 7, taken out frequency component of the drive signals generated by drive signal generator 1.
Therefore, as in the first embodiment, the noise picked up by the sensor unit and the noise transmitted from the human body to the sensor unit can be reduced, the SN ratio can be improved, and the multiplier 7 to the amplitude detection unit 10 are combined. There is no need to provide a plurality of devices, and the cost can be reduced by sharing the circuit.
In addition, it is good also as a structure which provided multiple switching parts 15 which switch the output of the CV conversion part 6, and reduced the group from the multiplier 7 to the amplitude detection part 10. FIG.

Hereinafter, a third embodiment of the capacitance detection sensor of the present invention will be described with reference to the drawings. FIG. 8 is a configuration diagram of the capacitance detection sensor of the present embodiment.
The capacitance detection sensor of the present embodiment is different from the second embodiment in that one switching unit 14 that switches a plurality of detection lines 13 is provided in the previous stage of the CV conversion unit 6, and the CV conversion unit 6 to the amplitude detection unit 10. It is the point which made the group up to one.
That is, as in the first and second embodiments, the sensor unit 5 is sequentially scanned, and a detection wave is output to the switching unit 14 connected to the plurality of detection lines 13. The switching unit 14 outputs a detection wave input from the selected detection line 13 to the CV conversion unit 6. The CV converter 6 performs CV conversion on the detected wave and outputs the result to the multiplier 7.
The multiplier 7, the phase adjustment unit 8, the filter unit 9, and the amplitude detection unit 10 operate in the same manner as in the first embodiment, and extract the frequency component of the drive signal generated by the drive signal generation unit 1.

Therefore, according to the capacitance detection sensor of the present embodiment, the drive signal generator 1 outputs a drive signal, the modulation wave generator 2 outputs a modulation wave that modulates the drive signal, and the multiplier 3 drives the drive. An applied signal wave obtained by multiplying the signal and the modulated wave is output, and the sensor unit 5 detects a change in capacitance at the intersection of the drive line and the detection line using the applied signal wave input from the multiplier 3 as a drive signal, and switches The unit 14 switches a plurality of detection lines in the scanning order of the sensor unit 5, the CV conversion unit 6 converts the capacitance change input from the sensor unit 5 into a voltage, and the phase adjustment unit 8 inputs from the modulation wave generation unit 2. The phase of the modulated wave to be matched with the phase of the voltage-converted applied signal wave output from the CV converter 6, and the multiplier 7 applies the modulated wave input from the phase adjuster 8 and the application converted by the CV converter 6. The signal wave is multiplied, and the filter unit 9 is a multiplier. Of the input signal from extracts the frequency component of the drive signals generated by drive signal generator 1.
Therefore, as in the first embodiment, noise picked up by the sensor unit and noise transmitted from the human body to the sensor unit can be reduced, the SN ratio can be improved, and the CV conversion unit 6 to the amplitude detection unit 10 can be improved. There is no need to provide a plurality of sets, and the cost can be reduced by sharing the circuit.
In addition, it is good also as a structure which provided multiple switching parts 14 which switch a some detection line, and reduced the group from the CV conversion part 6 to the amplitude detection part 10. FIG.

Further, in the configuration described above, the two input signals of the multiplier 7 may be AD-converted, and the capacitance change may be calculated by digital calculation in the multiplier 7, the filter unit 9, and the amplitude detection unit 10.
In this case, the capacitance detection sensor may have a configuration having a programmable logic circuit or a hard logic circuit, but may have a configuration having a computer system therein.
In the case of a configuration having a computer system, the above-described calculation process after AD conversion is stored in a computer-readable recording medium in the form of a program, and the computer reads and executes the program. Thus, the above processing is performed.
Further, the data after the above-described AD conversion may be sent to an external device such as a host computer and the device side may perform arithmetic processing in hardware or software.
That is, in the capacity detection sensor, each processing means and processing unit is configured such that a central processing unit such as a CPU reads the above program into a main storage device such as a ROM or RAM and executes information processing / calculation processing. It is realized.
Here, the computer-readable recording medium means a magnetic disk, a magneto-optical disk, a CD-ROM, a DVD-ROM, a semiconductor memory, or the like. Alternatively, the computer program may be distributed to the computer via a communication line, and the computer that has received the distribution may execute the program.

The block diagram of a 1st Example. Explanatory drawing which shows the structure and scanning method of the sensor part 5. FIG. FIG. 3 is a circuit diagram of a CV conversion unit 6. FIG. 2 is a circuit diagram of an amplitude detector 10. The waveform diagram of each block. The output spectrum figure of the multipliers 3 and 7. FIG. The block diagram of the 2nd Example. The block diagram of a 3rd Example. The wave form diagram of a prior art example. The equivalent circuit diagram which shows the noise mixing path | route conducted from a human body to a sensor. Explanatory drawing which shows the noise mixing path | route conducted from a human body to a sensor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Drive signal generation part 2 ... Modulation wave generation part 3, 7 ... Multiplier 4, 14, 15 ... Switching part 5 ... Sensor part 6 ... CV conversion part 8 ... Phase adjustment part 9 ... Filter part 10 ... Amplitude detection part 11 ... AD converter 12 ... Drive line 13 ... Detection line 16 ... Selector part

Claims (5)

A drive signal generator for outputting a drive signal;
A modulated wave generator for outputting a modulated wave for modulating the drive signal;
A first multiplier that outputs an applied signal wave obtained by multiplying the drive signal and the modulated wave;
A sensor unit that detects a change in capacitance at the intersection of the drive line and the detection line using the applied signal wave input from the first multiplier as a drive signal;
A CV conversion unit that converts a capacitance change input from the sensor unit into a voltage;
A phase adjusting unit that matches the phase of the modulated wave input from the modulated wave generating unit with the phase of the voltage-converted applied signal wave output from the CV converting unit;
A second multiplier that multiplies the modulated wave input from the phase adjustment unit by the applied signal wave input from the CV conversion unit;
A capacitance detection sensor comprising: a filter unit that extracts a frequency component of a drive signal generated by the drive signal generation unit from a signal input from the second multiplier. The capacitance detection sensor according to claim 1, wherein the sensor unit is an area type sensor in which a plurality of detection lines are arranged in a matrix for a plurality of drive lines. The capacitance detection sensor according to claim 1, wherein the sensor unit is a line type sensor in which one detection line is formed for a plurality of drive lines. A capacitance sensor according to any one of claims 1 to 3 is used. A fingerprint sensor. The drive signal generator outputs a drive signal,
The modulated wave generator outputs a modulated wave that modulates the drive signal,
A first multiplier outputs an applied signal wave obtained by multiplying the drive signal and the modulated wave;
The sensor unit detects the change in capacitance at the intersection of the drive line and the detection line using the applied signal wave input from the first multiplier as a drive signal,
The CV conversion unit converts the capacitance change input from the sensor unit into a voltage,
The phase adjustment unit matches the phase of the modulation wave input from the modulation wave generation unit with the phase of the voltage-converted applied signal wave output from the CV conversion unit,
A second multiplier multiplies the modulated wave input from the phase adjustment unit by the applied signal wave input from the CV conversion unit;
The capacitance detection method, wherein the filter unit extracts a frequency component of the drive signal generated by the drive signal generation unit from the signal input from the second multiplier.

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