JP2008073073A - Impedance detector, impedance detection method, living body recognition apparatus and fingerprint authentication apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To stably detect an impedance without deteriorating a detection precision even if the impedance of a subject used in a living body recognition apparatus and a fingerprint authentication apparatus is distributed over a wide range. <P>SOLUTION: A drive circuit 31 of a reply signal generation section 3 applies an application signal 1S according to a drive signal to a subject 20 via a detection element 1, detects and outputs a current information signal 31S according to a current flowing the subject 10 with the application signal 1S, a current-voltage conversion circuit 32 of the reply signal generation section 3 outputs a drive signal 32S for acquiring the application signal 1S equal to the feed signal 2S to the drive circuit 31 based on the current information signal 31S, and converts the current flowing the subject 10 into a replay signal consisting of the voltage signal based on the current information signal 31S and outputs it to a waveform information detection section 4. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an impedance detection technique, and in particular, an impedance detection technique for applying a predetermined signal to a living body as a subject and detecting the impedance of the living body based on the obtained response signal, and the impedance detection technique. The present invention relates to a technique for performing biometric recognition, and further relates to a fingerprint authentication technique for performing fingerprint authentication using this biometric recognition technique.

  Along with the progress of the information society, technology for maintaining confidentiality of information processing systems has been developed. For example, an ID card has been conventionally used for entrance / exit management of a computer room or the like, but there is a high possibility that the ID card is lost or stolen. For this reason, a personal recognition system is being introduced in which fingerprints of individual persons are registered in advance instead of ID cards and collated when entering a room. In some cases, such a personal recognition system can pass a test if a replica of a registered fingerprint or the like is created. Therefore, the personal recognition system needs to recognize not only the fingerprint verification but also that the subject is a living body.

Conventionally, as a technique for detecting that a subject is a living body, a technique using an impedance detection technique that applies a predetermined signal to the subject and detects the impedance of the subject based on the obtained response signal. It has been proposed (see, for example, Patent Document 1).
FIG. 23 is a block diagram showing a configuration of a conventional biometric recognition apparatus. In this biological recognition device, a detection element 1, a supply signal generation unit 2, a response signal generation unit 3, a waveform information detection unit 4, and a biological recognition unit 5 are provided as main functional units.

  The detection element 1 is in electrical contact with the subject 10 via the detection electrode 12 and connects the reactance component and resistance component of the impedance Zf of the subject 10 to the response signal generation unit 3. When the subject 10 is a living body, the reactance component (imaginary component) of the impedance Zf of the subject 10 is mainly composed of a capacitive component. In the following description, it is assumed that the reactance component of the specimen 10 is a capacitive component.

The supply signal generation unit 2 generates a supply signal including a sine wave having a predetermined frequency and outputs the supply signal to the response signal generation unit.
The response signal generation unit 3 includes a resistance element Rs connected between the supply signal generation unit 2 and the detection element 1, and the supply signal 2S from the supply signal generation unit 2 is applied as an application signal via the resistance element Rs. 1S is applied to the detection element 1 from one end of the resistance element Rs, that is, the connection point between the resistance element Rs and the detection element 1, depending on the impedance Zf of the detection element 1, here the capacitance component and resistance component of the impedance of the subject 10 The changing response signal 3S is output to the waveform information detection unit 4.

The waveform information detection unit 4 detects a phase difference or amplitude from the supply signal 2S from the waveform indicated by the response signal 3S from the response signal generation unit 3, and a detection signal 4S including waveform information indicating the phase difference or amplitude. Is output to the biometric recognition unit 5.
The living body recognition unit 5 recognizes and determines whether or not the subject 10 is a living body based on the waveform information included in the detection signal 4S from the waveform information detection unit 4, and outputs the recognition result 5S.

The operation of the biological recognition apparatus is as follows.
First, when the subject 10 comes into contact with the detection element 1, the applied signal 1S applied to the detection element 1 based on the supply signal 2S from the supply signal generation unit 2 is an impedance characteristic, that is, a capacitance inherent to the subject 10. This varies depending on the component and the resistance component, and this is output from the response signal generator 3 as the response signal 3S. A phase difference or amplitude of the response signal 3S is detected by the waveform information detection unit 4, and a detection signal 4S including information indicating the detection result is output to the living body recognition unit 5.

In the living body recognition unit 5, whether or not the subject 10 is a living body is determined based on whether or not the waveform information included in the detection signal 4S from the waveform information detection unit 4 is within the reference range of the legitimate living body waveform information. Is recognized and the recognition result 5S is output.
Note that the magnitude of the reactance component and resistance component of the impedance of the subject may be calculated from these phase differences and amplitudes and compared with the reference range of the reactance component and resistance component of a legitimate living body. In this case, the impedance of the subject in contact with the detection element is detected.

  Next, with reference to FIG. 24, a specific method for detecting a phase difference will be described as a conventional technique for detecting impedance information of a subject in a living body recognition apparatus. FIG. 24 is a block diagram showing a specific configuration of a conventional impedance detection device for detecting a phase difference, and the same or equivalent parts as those in FIG.

In FIG. 24, the detection element 1 is provided with a detection electrode 11 and a detection electrode 12 for making electrical contact with the subject 10.
The supply signal generation unit 2 is provided with a frequency generation circuit 21 and a waveform shaping circuit 22. The response signal generation unit 3 is provided with a current-voltage conversion circuit 32. The waveform information detection unit 4A is provided with an offset correction circuit 41, a reference signal generation circuit 42, and a phase comparison circuit 43. The biometric recognition unit 5 (not shown) is provided with a signal conversion circuit and a determination circuit.

  In the detection element 1, the detection electrode 11 is connected to a common potential such as a ground potential, and the detection electrode 12 is connected to the output stage of the current-voltage conversion circuit 32 of the response signal generation unit 3. In the supply signal generation unit 2, the frequency generation circuit 21 generates a clock signal 21S having a predetermined frequency, and the waveform shaping circuit 22 generates a supply signal 2S composed of a sine wave or the like based on the clock signal 21S from the frequency generation circuit 21. Output.

  The current-voltage conversion circuit 32 of the response signal generation unit 3 includes a resistance element Rs connected between the supply signal generation unit 2 and the detection element 10, and has a predetermined output impedance that is sufficiently lower than the impedance of the living body. The supply signal 2S is applied to the subject 10 as the application signal 1S, and the current flowing through the subject 10 via the detection element 1 at that time is converted into a voltage and output as a response signal 3S.

  The offset correction circuit 41 of the waveform information detection unit 4A corrects an offset generated in the response signal according to the resistance component of the subject 10, that is, a potential difference between the center voltage of the response signal 3S and the reference potential, and performs phase comparison as a signal to be compared 41S. Output to the circuit 43. The reference signal generation circuit 42 outputs a reference signal 42S synchronized with the supply signal 2S to the phase comparison circuit 43. The phase comparison circuit 43 compares the phase of the signal to be compared 41S and the reference signal 42S, thereby detecting the impedance characteristic unique to the subject 10, in this case, the phase difference corresponding to the reactance component, as waveform information, and the waveform A detection signal 4AS including information is output.

The operation of the impedance detection apparatus of FIG. 24 is as follows.
First, the subject 10 is connected to the output stage of the current-voltage conversion circuit 32 via the detection electrode 11 and the detection electrode 12 of the detection element 1. Here, the impedance inherent to the subject 10 can be represented by a reactance component (mainly a capacitive component) and a resistance component connected between the detection electrode 11 and the detection electrode 12 of the detection element 1. Therefore, the applied signal 1S applied with a predetermined output impedance from the current-voltage conversion circuit 32 is divided by the output impedance of the current-voltage conversion circuit 32 and the impedance unique to the subject 10. Then, the phase or amplitude of the current flowing through the subject 10 changes according to the impedance inherent to each subject 10, and the change is output as a response signal 3S converted into a voltage.

  FIG. 25 is an example of a signal waveform in each part of the impedance detection apparatus of FIG. In the waveform shaping circuit 22 of the supply signal generation unit 2, a supply signal 2S having a center voltage VA that is a substantially intermediate potential between the operation power supply potential VDD and the ground potential (0V = GND) of the circuit is generated, and the subject 10 is used as the application signal 1S. To be applied. The response signal 3S is a signal including an offset due to the resistance component of the subject 10. For example, when the resistance component is larger than a predetermined value, VB2 higher than the reference potential VB becomes the center voltage, and when the resistance component is smaller than the predetermined value, VB1 lower than the reference potential VB becomes the center voltage. At this time, the offset correction circuit 41 is level-shifted so that the center voltage of the response signal 3S matches the reference potential VB used in the phase comparison circuit 43, and outputs the compared signal 41S with the offset corrected. The phase comparison circuit 43 outputs a waveform having a pulse width corresponding to the phase difference between the signal to be compared 41S and the reference signal 42S as the detection signal 4S. This pulse width includes waveform information as a phase difference.

Next, with reference to FIG. 26, a specific method for detecting amplitude will be described as another technique for detecting impedance information of a subject in the living body recognition apparatus. FIG. 26 is a block diagram showing a specific configuration of a conventional impedance detection apparatus for detecting amplitude, and the same or equivalent parts as those in FIG. 23 are given the same names.
The configurations of the detection element 1, the supply signal generation unit 2, and the response signal generation unit 3 in FIG. 26 are the same as those in FIG. 23 described above, and a detailed description thereof is omitted here.

  The waveform information detection unit 4 detects the amplitude of the response signal 3S by comparing the peak voltage value of the response signal 3S with the center voltage value. The waveform information detection unit 4 includes a peak voltage detection circuit 44, a center voltage detection circuit 45, and a voltage comparison circuit 46. The peak voltage detection circuit 44 detects the peak voltage value 44S from the response signal 3S. The center voltage detection circuit 45 detects the center voltage value 45S from the response signal 3S. The voltage comparison circuit 46 detects the amplitude of the response signal 3S from the voltage difference by comparing the peak voltage value 44S and the center voltage value 45S, and outputs a detection signal 4BS including the amplitude as waveform information.

  FIG. 27 is an example of a signal waveform in each part of the impedance detection apparatus of FIG. In the waveform shaping circuit 22 of the supply signal generation unit 2, a supply signal 2 </ b> S having a center voltage VA that is a substantially intermediate potential between the circuit operating power supply potential VDD and the ground potential (0V = GND) is generated and output to the subject 10. Applied. The response signal 3S is a signal including an offset due to the resistance component of the subject 10. A peak voltage value 44S and a center voltage value 45S (VB) of the response signal 3S are detected and compared by the voltage comparison circuit 46, thereby outputting a voltage value corresponding to the amplitude of the response signal 3S as the detection signal 4BS. . This voltage value includes waveform information as amplitude. The peak voltage value 44S may be the maximum voltage value or the minimum voltage value of the response signal 3S.

International Publication No. 05/016146 Pamphlet

  However, in such a conventional technique, it is difficult to stably detect the phase difference and amplitude of the response signal with high accuracy from the case where the impedance of the subject is small to the case where the impedance is large, and the input dynamic range as the impedance detection device is small. There was a problem of being small.

24 and 26 described above, for example, when the impedance of the subject 10 is very small, the applied signal 1S applied with a predetermined output impedance from the current-voltage conversion circuit 32 is the output impedance of the current-voltage conversion circuit 32. And the impedance of the subject 10, the potential of the response signal 3S becomes very low, making it difficult to detect the phase difference and amplitude of the response signal 3S.
On the other hand, in order to prevent this, when the output impedance of the current-voltage conversion circuit 32 is set small, when the impedance of the subject 10 is large, the potential of the response signal 3S is almost equal to the supply signal 2S. Thus, it becomes difficult to detect the phase difference and amplitude of the response signal 3S.

  Further, when the conventional technique is used for the impedance detection means of the biological recognition apparatus, there is a problem that the recognition accuracy cannot be increased for the reason described above when the inherent impedance of the biological body is distributed over a wide range. Further, when such a biometric recognition device is mounted on a personal recognition system using a fingerprint authentication device, there is a problem that the security performance of the entire system cannot be improved.

  The present invention is for solving such a problem, and even when the impedance of a subject used in a biometric recognition device, a fingerprint authentication device, or the like is distributed over a wide range, the impedance detection accuracy is stable without deteriorating. It is an object of the present invention to provide an impedance detection device and an impedance detection method that can detect impedance, and to provide a biometric recognition device that provides high recognition accuracy, and a fingerprint authentication device that provides high security performance.

  In order to achieve such an object, an impedance detection device according to the present invention includes a detection element that is in electrical contact with a subject, a supply signal generation unit that generates an alternating supply signal, a supply signal generation unit, and a detection A response signal generating unit connected between the device and applying an applied signal corresponding to the supply signal to the subject, and generating and outputting a response signal that changes according to the current flowing through the subject in accordance with the applied signal; A waveform information detection unit that detects waveform information indicating the characteristics of the waveform of the response signal from the response signal and outputs a detection signal indicating the impedance of the subject based on the waveform information, and the response signal generation unit includes: A drive circuit that applies an applied signal corresponding to a predetermined drive signal to the subject via the detection element and detects and outputs a current information signal corresponding to a current flowing through the subject in accordance with the applied signal; and a current Outputs a drive signal for obtaining an applied signal equal to the supply signal based on the report signal to the drive circuit, and converts the current flowing through the subject into a response signal composed of a voltage signal based on the current information signal to detect waveform information And a current-voltage conversion circuit for outputting to the unit.

  At this time, the drive circuit is constituted by a first driver circuit that amplifies the drive signal input to the input terminal and outputs the applied signal and the current information signal from the output terminal. A differential that is input to the first input terminal, is input to the second input terminal having a polarity opposite to that of the first input terminal so that the current information signal is negatively fed, and outputs a drive signal and a response signal from the output terminal. You may comprise from an amplifier.

  The drive circuit includes a first driver circuit that inputs a drive signal to an input terminal and outputs an application signal and a current information signal from an output terminal. The supply signal is a first input terminal. And a differential amplifier that outputs a drive signal from the output terminal and is input to the input terminal so that the current information signal is negatively fed back so that the current information signal is negatively fed back. The second driver circuit may amplify the drive signal and output a response signal from the output terminal.

  The detection element is provided with a first detection electrode that is in electrical contact with the subject and connected to a predetermined common potential, and a second detection electrode that is in electrical contact with the subject, and a response signal In the generation unit, the drive circuit applies an application signal to the second detection electrode, and detects a current information signal including a phase change of the current flowing through the second detection electrode according to the impedance of the subject. A response signal including a phase change is output to the waveform information detection unit based on the current information signal by the current-voltage conversion circuit, and the waveform information detection unit compares the phases of the predetermined reference signal and the response signal. The phase difference may be detected as waveform information of the response signal.

  The detection element is provided with a first detection electrode that is in electrical contact with the subject and connected to a predetermined common potential, and a second detection electrode that is in electrical contact with the subject, and a response signal In the generation unit, the drive circuit applies an applied signal to the second detection electrode, and detects a current information signal including a change in amplitude of the current flowing through the second detection electrode according to the impedance of the subject. A response signal including an amplitude change is output to the waveform information detection unit based on the current information signal by the current-voltage conversion circuit, and the waveform information detection unit detects the amplitude of the response signal as the waveform information of the response signal. Also good.

  In addition, the supply signal generating unit generates a frequency generation circuit that generates and outputs a clock signal having a predetermined frequency, and generates one of a sine wave, a triangular wave, and a trapezoidal wave synchronized with the clock signal based on the clock signal. And a waveform shaping circuit for outputting as a supply signal.

  In addition, the impedance detection method according to the present invention applies an application signal corresponding to an AC supply signal to a subject that is in electrical contact with the detection element, and responds to the subject along with the application signal. A response signal generating step for generating and outputting a response signal that changes according to the flowing current, and detecting waveform information indicating the waveform characteristics of the response signal from the response signal, and indicating the impedance of the subject based on the waveform information A waveform information detection step for outputting a detection signal, and the response signal generation step applies an application signal corresponding to a predetermined drive signal to the subject via the detection element and flows to the subject along with the application signal. A drive step for detecting and outputting a current information signal corresponding to the current, and a drive step for obtaining an applied signal equal to the supply signal based on the current information signal Outputs, current outputs and converts the current flowing through the object based on the current information signal in the response signal comprising a voltage signal to the waveform information detection step - and a voltage conversion step.

  The living body recognition apparatus according to the present invention includes any one of the above-described impedance detection apparatuses that outputs a detection signal corresponding to the impedance of the subject, and the subject is a living body based on the detection signal output from the impedance detection apparatus. A biometric recognition unit for determining whether or not.

  The fingerprint authentication apparatus according to the present invention includes the biometric recognition apparatus that determines whether or not the subject is a living body based on a detection signal corresponding to the impedance of the subject, and fingerprint data indicating the unevenness of the fingerprint from the subject. A fingerprint detection device that detects fingerprints, a fingerprint authentication unit that compares fingerprint data and pre-registered verification data, and performs user fingerprint authentication based on the verification result, and a biometric determination output from the biometric recognition device An authentication determination unit that determines whether the user has succeeded in fingerprint authentication based on the result and the fingerprint authentication result output from the fingerprint authentication unit;

  According to the present invention, an application signal corresponding to a predetermined drive signal is applied to the subject via the detection element by the drive circuit provided in the response signal generation unit, and the subject is accompanied by the application signal. A current information signal corresponding to the flowing current is detected and output, and a drive signal for obtaining an applied signal equal to the supply signal based on the current information signal is supplied to the drive circuit by the current-voltage conversion circuit provided in the response signal generation unit. At the same time, the current flowing through the subject is converted into a response signal composed of a voltage signal based on the current information signal, and is output to the waveform information detector.

  As a result, compared to the conventional technique in which impedance information is extracted by dividing the output impedance of the current-voltage conversion circuit and the impedance inherent to each subject, the subject The impedance information can be extracted stably. Thereby, the input dynamic range of the detectable impedance can be greatly expanded.

  Further, not only a sine wave but also a triangular wave or a trapezoidal wave can be used as a supply signal, and the detection accuracy can be improved while simplifying the circuit configuration. In particular, when the impedance detection device is used as the impedance detection means of the living body recognition device, there is an effect of improving the recognition accuracy when the impedance inherent in the living body is distributed over a wide range. In addition, if such a biometric recognition device is installed in a personal recognition system using a fingerprint authentication device, the security performance of the entire system can be improved, which is very effective.

Next, embodiments of the present invention will be described with reference to the drawings.
[First Embodiment]
First, with reference to FIG. 1, an impedance detection apparatus according to a first embodiment of the present invention will be described. FIG. 1 is a block diagram showing the configuration of the impedance detection apparatus according to the first embodiment of the present invention. The same or equivalent parts as those in FIG.

  The impedance detection device 100 is a device that applies a predetermined signal to the subject and detects the impedance of the subject based on the obtained response signal. The impedance detection apparatus 100 includes a detection element 1, a supply signal generation unit 2, a response signal generation unit 3, and a waveform information detection unit 4 as main functional units. These functional units have a configuration common to the impedance detection apparatuses according to the embodiments described later.

  In the present embodiment, a drive circuit 31 and a current-voltage conversion circuit 32 are provided in the response signal generation unit 3, and an application signal 1S corresponding to the drive signal 32S from the current-voltage conversion circuit 32 is supplied by the drive circuit 31. In addition to being applied to the subject 10 via the detection element 1, a current information signal 31S corresponding to the current flowing through the subject 10 in accordance with the applied signal 1S is detected and output, and the current-voltage conversion circuit 32 supplies the supply signal 2S. A drive signal 32S for obtaining an applied signal 1S equal to the supply signal 2S based on the current information signal 31S and the current information signal 31S is output to the drive circuit 31, and flows to the subject 10 based on the supply signal 2S and the current information signal 31S. The current is converted into a response signal 3S made up of a voltage signal and output to the waveform information detector 4.

Hereafter, with reference to FIG. 1, each function part of the impedance detection apparatus concerning the 1st Embodiment of this invention is demonstrated in detail.
The detection element 1 has a function of making electrical contact with the subject 10 through the detection electrode and connecting the impedance reactance component and resistance component of the subject 10 to the response signal generation unit 3. When the subject 10 is a living body, the reactance component (imaginary component) of the impedance Zf of the subject 10 is mainly composed of a capacitive component. In the following description, it is assumed that the reactance component of the specimen 10 is composed of a capacitive component for easy understanding, but in reality, a reactance component including an inductance component is detected as phase information.

The supply signal generation unit 2 has a function of generating a supply signal 2 </ b> S composed of a sine wave having a predetermined frequency and outputting it to the response signal generation unit 3.
The response signal generation unit 3 applies an application signal 1S corresponding to the supply signal 2S from the supply signal generation unit 2 to the detection element 1, and the output impedance of the detection element 1, that is, the subject 10 has the application signal 1S. It has a function of generating a response signal 3S that changes depending on the capacitance component and resistance component of the impedance and outputting the response signal 3S to the waveform information detection unit 4.
The response signal generation unit 3 includes a drive circuit 31 and a current-voltage conversion circuit 32 as main circuit units.

The drive circuit 31 has a function of applying an application signal 1S corresponding to the drive signal 32S from the current-voltage conversion circuit 32 to the subject 10 via the detection element 1, and flows to the subject 10 along with the application signal 1S. It has a function of detecting the current information signal 31S corresponding to the phase and amplitude of the current and outputting it to the current-voltage conversion circuit 32.
The current-voltage conversion circuit 32 outputs a drive signal 32S for obtaining an applied signal 1S equal to the supply signal 2S to the drive circuit 31 based on the current information signal 31S from the drive circuit 31, and the current information signal 31S. Based on this, it has a function of converting the current flowing through the subject 10 into a response signal 3S composed of a voltage signal and outputting the response signal 3S to the waveform information detection unit 4.

  The waveform information detection unit 4 uses the waveform indicated by the response signal 3S from the response signal generation unit 3 as the waveform information indicating the characteristics of the waveform according to the impedance of the subject 10, and the phase difference between the response signal 3S and the supply signal 2S. Or it has the function to detect an amplitude, and the function to output the detection signal 4S which shows the impedance of the subject 10 based on the waveform information which consists of these phase differences or amplitude.

Next, the operation of the impedance detection apparatus according to the first embodiment of the present invention will be described with reference to FIG.
The supply signal 2S input to the response signal generator 3 is transmitted as a drive signal 32S to the drive circuit 31 via the current-voltage conversion circuit 32, and is applied to the detection element 1 as the application signal 1S from the drive circuit 31.
The drive circuit 31 applies an applied signal 1S to the impedance of the subject 10 to cause a current to flow to the subject 10, and at the same time, detects information on the current flowing to the subject 10 and serves as a current information signal 31S as a current-voltage conversion circuit. 32.

The current-voltage conversion circuit 32 adjusts the drive signal 32S based on the current information signal 31S and the supply signal 2S, so that regardless of the magnitude of the current flowing through the impedance of the subject 10, that is, the magnitude of the impedance of the subject 10. Regardless, the application signal 1S is controlled to be equal to the supply signal 2S.
At this time, the fact that the phase or amplitude of the current flowing through the subject 10 has changed according to the impedance inherent to the subject 10 is also transmitted to the current-voltage conversion circuit 32 by the current information signal 31S.

Based on the current change notified by the current information signal 31S, the current-voltage conversion circuit 32 converts the phase information or amplitude information of the current flowing through the impedance of the subject 10 into a voltage signal and outputs it as a response signal 3S. To do.
Thereafter, the waveform information detector 4 detects phase information or amplitude information included in the response signal 3S, and outputs a detection signal 4S including the phase information or amplitude information.

  As described above, in the present embodiment, the response signal generator 3 applies the application signal 1S to the subject 10 and the response signal 3S corresponding to the impedance of the subject 10 from the current flowing through the subject 10. Is separately provided. Therefore, according to the present embodiment, the impedance of the subject is compared with the conventional technique in which the impedance information is extracted by dividing the output impedance of the current-voltage conversion circuit and the impedance inherent to each subject. Regardless of the size, the impedance information of the subject can be stably extracted. Thereby, the input dynamic range of the detectable impedance can be greatly expanded.

[Second Embodiment]
Next, an impedance detection apparatus according to a second embodiment of the present invention will be described with reference to FIG. FIG. 2 is a block diagram showing the configuration of the impedance detection apparatus according to the second embodiment of the present invention, and the same or equivalent parts as those in FIG.

In the present embodiment, as an example, the response signal generation unit 3 configured by the drive circuit 31 and the current-voltage conversion circuit 32 of the first embodiment is used to detect and output the impedance of the subject as phase information. A configuration example of the impedance detection device will be described in detail.
In the impedance detection apparatus 100 according to the present embodiment, the waveform information detection unit 4A detects the phase difference between the reference signal 42S synchronized with the original supply signal 2S and the response signal 3S as waveform information, and includes the waveform information. The detection signal 4AS is output. Compared to the conventional example of FIG. 24 described above, the difference is that the response signal generation unit 3 includes a drive circuit 31 and a current-voltage conversion circuit 32.

  In FIG. 2, the detection element 1 is provided with a detection electrode 11 and a detection electrode 12 for making electrical contact with the subject 10. The supply signal generation unit 2 is provided with a frequency generation circuit 21 and a waveform shaping circuit 22. The response signal generation unit 3 is provided with a drive circuit 31 and a current-voltage conversion circuit 32. The waveform information detection unit 4A is provided with an offset correction circuit 41, a reference signal generation circuit 42, and a phase comparison circuit 43.

  In the detection element 1, the detection electrode 11 is connected to a common potential such as a ground potential, and the detection electrode 12 is connected to the output stage of the current-voltage conversion circuit 32 of the response signal generation unit 3. This common potential is supplied at a constant potential (low impedance) from a predetermined supply circuit unit (not shown) such as a power supply circuit.

  In the supply signal generation unit 2, the frequency generation circuit 21 has a function of generating a clock signal 21S composed of a rectangular wave having a predetermined frequency. The waveform shaping circuit 22 has a function of generating an AC supply signal 2S having a repetitive waveform such as a sine wave or a triangular wave based on the clock signal 21S from the frequency generation circuit 21, and outputting the generated signal to the response signal generation unit 3. . The supply signal 2S may be supplied from an external waveform generation device instead of the supply signal generation unit 2.

In the response signal generation unit 3, the drive circuit 31 has a function of applying the application signal 1 S corresponding to the drive signal 32 S from the current-voltage conversion circuit 32 to the subject 10 via the detection element 1, and the application signal 1 S. Accordingly, the current information signal 31S corresponding to the current flowing through the subject 10 is detected and output to the current-voltage conversion circuit 32.
The current-voltage conversion circuit 32 outputs a drive signal 32S for obtaining an applied signal 1S equal to the supply signal 2S to the drive circuit 31 based on the current information signal 31S from the drive circuit 31, and the current information signal 31S. Based on this, it has a function of converting the current flowing through the subject 10 into a response signal 3S composed of a voltage signal and outputting the response signal 3S to the waveform information detector 4A.

In the waveform information detection unit 4A, the offset correction circuit 41 corrects the direct current bias of the entire signal so that the predetermined reference potential becomes the center voltage, and the phase of the response signal 3S having the common potential as the center voltage becomes the compared signal 41S. A function of outputting to the comparison circuit 43 is provided.
The reference signal generation circuit 42 has a function of outputting a reference signal 42S synchronized with the supply signal 2S to the phase comparison circuit 43.

The phase comparison circuit 43 has a function of comparing the phase of the signal to be compared 41S and the reference signal 42S, and a waveform composed of impedance characteristics unique to the subject 10 based on the comparison result, here, a phase difference corresponding to a capacitance component. It has a function of detecting as information and outputting a detection signal 4AS including the waveform information. At this time, the supply signal 2S may be used as the reference signal 42S.
The offset correction circuit 41, the reference signal generation circuit 42, and the phase comparison circuit 43 may be configured by general known circuits.

Next, the operation of the impedance detection apparatus according to the second embodiment of the present invention will be described with reference to FIG.
The supply signal 2S output from the waveform shaping circuit 22 and input to the response signal generation unit 3 is transmitted as a drive signal 32S to the drive circuit 31 via the current-voltage conversion circuit 32, and is applied as an application signal 1S from the drive circuit 31. Applied to the detection element 1.
The drive circuit 31 applies an applied signal 1S to the impedance of the subject 10 to cause a current to flow to the subject 10, and at the same time, detects information on the current flowing to the subject 10 and serves as a current information signal 31S as a current-voltage conversion circuit. 32.

  The current-voltage conversion circuit 32 adjusts the drive signal 32S based on the current information signal 31S and the supply signal 2S, so that regardless of the magnitude of the current flowing through the impedance of the subject 10, that is, the magnitude of the impedance of the subject 10. Regardless, the application signal 1S is controlled to be equal to the supply signal 2S.

At this time, the fact that the phase of the current flowing through the subject 10 has changed according to the impedance inherent to the subject 10 is also transmitted to the current-voltage conversion circuit 32 by the current information signal 31S.
Based on the current change notified by the current information signal 31S, the current-voltage conversion circuit 32 converts the phase information of the current flowing through the impedance of the subject 10 into a voltage signal and outputs it as a response signal 3S.

Thereafter, the waveform information detection unit 4 corrects the direct current bias of the entire signal so that the predetermined reference potential becomes the center voltage by using the offset correction circuit 41 so that the response signal 3S having the common potential as the center voltage is obtained. 41S is output to the phase comparison circuit 43.
The phase comparison circuit 43 compares the phase of the comparison signal 41S with the reference signal 42S from the reference signal generation circuit 42 synchronized with the supply signal 2S, and based on the comparison result, the impedance characteristic unique to the subject 10, here Then, waveform information including a phase difference corresponding to the capacitive component is detected, and a detection signal 4AS including the waveform information is output.

  As described above, in the present embodiment, in addition to the first embodiment, the response signal generator 3 applies the application signal 1S to the detection electrode 12 by the drive circuit 31 and receives the signal via the detection electrode 12. A current information signal 31S including a phase change of the current flowing according to the impedance of the specimen 10 is detected, and a response signal 3S including the phase change is detected by the current-voltage conversion circuit 32 based on the current information signal 31S as a waveform information detection unit. 4A, the waveform information detector 4A compares the phases of the reference signal 42S and the response signal 3S, and detects the phase difference as the waveform information of the response signal 3S. It is possible to stably detect information indicating reactance components in a wide input dynamic range regardless of the impedance of the subject. To become.

[Third Embodiment]
Next, an impedance detection apparatus according to a third embodiment of the present invention will be described with reference to FIG. FIG. 3 is a block diagram showing the configuration of the impedance detection apparatus according to the third embodiment of the present invention, and the same or equivalent parts as those in FIG.

In this embodiment, an example is described in which the response signal generation unit 3 configured by the drive circuit 31 and the current-voltage conversion circuit 32 of the first embodiment is used to detect and output the impedance of the subject 10 as amplitude information. The configuration example of the impedance detection device will be described in detail.
In the impedance detection device 100 according to the present embodiment, the waveform information detection unit 4B detects the amplitude of the response signal 3S as waveform information and outputs a detection signal 4BS including the waveform information. 26 is different from the conventional example of FIG. 26 described above in that the response signal generation unit 3 includes a drive circuit 31 and a current-voltage conversion circuit 32.

  In FIG. 3, the detection element 1 is provided with a detection electrode 11 and a detection electrode 12 for making electrical contact with the subject 10. The supply signal generation unit 2 is provided with a frequency generation circuit 21 and a waveform shaping circuit 22. The response signal generation unit 3 is provided with a drive circuit 31 and a current-voltage conversion circuit 32. The waveform information detection unit 4B is provided with a peak voltage detection circuit 44, a center voltage detection circuit 45, and a voltage comparison circuit 46.

  In the detection element 1, the detection electrode 11 is connected to a common potential such as a ground potential, and the detection electrode 12 is connected to the output stage of the current-voltage conversion circuit 32 of the response signal generation unit 3. This common potential is supplied at a constant potential (low impedance) from a predetermined supply circuit unit (not shown) such as a power supply circuit.

  In the supply signal generation unit 2, the frequency generation circuit 21 has a function of generating a clock signal 21S having a predetermined frequency. The waveform shaping circuit 22 has a function of generating an AC supply signal 2S having a repetitive waveform such as a sine wave or a triangular wave based on the clock signal 21S from the frequency generation circuit 21, and outputting the generated signal to the response signal generation unit 3. . The supply signal 2S may be supplied from an external waveform generation device instead of the supply signal generation unit 2.

In the response signal generation unit 3, the drive circuit 31 has a function of applying the application signal 1 S corresponding to the drive signal 32 S from the current-voltage conversion circuit 32 to the subject 10 via the detection element 1, and the application signal 1 S. Accordingly, the current information signal 31S corresponding to the current flowing through the subject 10 is detected and output to the current-voltage conversion circuit 32.
The current-voltage conversion circuit 32 outputs a drive signal 32S for obtaining an applied signal 1S equal to the supply signal 2S to the drive circuit 31 based on the current information signal 31S from the drive circuit 31, and the current information signal 31S. Based on this, it has a function of converting the current flowing through the subject 10 into a response signal 3S composed of a voltage signal and outputting the response signal 3S to the waveform information detector 4B.

In the waveform information detection unit 4B, the peak voltage detection circuit 44 has a function of detecting the maximum voltage value or the minimum voltage value of the response signal 3S and outputting the peak voltage value 44S.
The center voltage detection circuit 45 has a function of detecting the center voltage of the response signal 3S and outputting it as a center voltage value 45S.

The voltage comparison circuit 46 has a function of comparing the voltage of the peak voltage value 44S and the center voltage value 45S, and a waveform composed of an impedance characteristic unique to the subject 10, based on the comparison result, here, an amplitude value corresponding to the resistance component. It has a function of detecting as information and outputting a detection signal 4BS including the waveform information.
The peak voltage detection circuit 44, the center voltage detection circuit 45, and the voltage comparison circuit 46 may be configured by general known circuits.

Next, the operation of the impedance detection apparatus according to the third embodiment of the present invention will be described with reference to FIG.
The supply signal 2S output from the waveform shaping circuit 22 and input to the response signal generation unit 3 is transmitted as a drive signal 32S to the drive circuit 31 via the current-voltage conversion circuit 32, and is applied as an application signal 1S from the drive circuit 31. Applied to the detection element 1.
The drive circuit 31 applies an applied signal 1S to the impedance of the subject 10 to cause a current to flow to the subject 10, and at the same time, detects information on the current flowing to the subject 10 and serves as a current information signal 31S as a current-voltage conversion circuit. 32.

  The current-voltage conversion circuit 32 adjusts the drive signal 32S based on the current information signal 31S and the supply signal 2S, so that regardless of the magnitude of the current flowing through the impedance of the subject 10, that is, the magnitude of the impedance of the subject 10. Regardless, the application signal 1S is controlled to be equal to the supply signal 2S.

At this time, the fact that the amplitude of the current flowing through the subject 10 has changed according to the impedance inherent to the subject 10 is also transmitted to the current-voltage conversion circuit 32 by the current information signal 31S.
Based on the current change notified by the current information signal 31S, the current-voltage conversion circuit 32 converts the amplitude information of the current flowing through the impedance of the subject 10 into a voltage signal and outputs it as a response signal 3S.

Thereafter, the waveform information detection unit 4 detects the maximum voltage value or the minimum voltage value of the response signal 3S by the peak voltage detection circuit 44, and outputs it to the voltage comparison circuit 46 as the peak voltage value 44S. Further, the center voltage detection circuit 45 detects the center voltage of the response signal 3S and outputs it as a center voltage value 45S.
The voltage comparison circuit 46 compares the peak voltage value 44S and the center voltage value 45S, and detects the waveform information including the impedance characteristic unique to the subject 10, here, the amplitude value corresponding to the resistance component, based on the comparison result. The detection signal 4BS including the waveform information is output.

  As described above, in the present embodiment, in addition to the first embodiment, the response signal generator 3 applies the application signal 1S to the detection electrode 12 by the drive circuit 31 and receives the signal via the detection electrode 12. A current information signal 31S including a phase change of the current flowing according to the impedance of the specimen 10 is detected, and a response signal 3S including the phase change is detected by the current-voltage conversion circuit 32 based on the current information signal 31S as a waveform information detection unit. 4B, and the waveform information detection unit 4B detects the amplitude value of the response signal 3S as the waveform information of the response signal 3S. Therefore, information indicating the resistance component of the impedance inherent to the subject 10 is received. Regardless of the impedance of the specimen, it is possible to detect stably with a wide input dynamic range.

[Fourth Embodiment]
Next, an impedance detection apparatus according to a fourth embodiment of the present invention will be described with reference to FIG. FIG. 4 is a block diagram showing the configuration of the impedance detection apparatus according to the fourth embodiment of the present invention, and the same or equivalent parts as those in FIG.

In the second embodiment, a case where the response signal generation unit 3 configured by the drive circuit 31 and the current-voltage conversion circuit 32 of the first embodiment is used to detect and output the impedance of the subject as phase information is used. Described as an example.
In the present embodiment, a case will be described in which, in the second embodiment, the drive circuit 31 of the response signal generation unit 3 is configured by a driver circuit 31A, and the current-voltage conversion circuit 32 is configured by a differential amplifier 32A.

  In FIG. 4, the driver circuit 31A has an input terminal connected to the output terminal of the differential amplifier 32A, and an output terminal connected to the detection electrode 12 of the detection element 1 and the positive input terminal of the differential amplifier 32A. The driver circuit 31A has a function of amplifying the drive signal 32S input to the input terminal and outputting the applied signal 1S and the current information signal 31S from the output terminal with low impedance.

  The differential amplifier 32A has a positive input terminal connected to the output of the supply signal generator 2, a reverse polarity input terminal connected to the output terminal of the driver circuit 31A and the detection electrode 12, and an output terminal input to the driver circuit 31A. And connected to the input of the waveform information detector 4A. The differential amplifier 32A differentially amplifies the supply signal 2S input to the positive input terminal and the current information signal 31S input to the reverse polarity input terminal, and outputs the drive signal 32S and the response signal 3S from the output terminal. It has a function to output.

The sine wave generation circuit 22A is a specific example of the waveform shaping circuit 22 of FIG. 2, and generates an alternating supply signal 2S composed of a sine wave based on the clock signal 21S from the frequency generation circuit 21 and supplies it to the response signal generation unit 3. It has a function to output. As a specific example of the sine wave generation circuit 22A, a known circuit may be used, such as a generation using a D / A converter or a generation of a triangular wave waveform blunted using a diode element.
The configuration other than the response signal generation unit 3 and the sine wave generation circuit 22A is the same as that of the second embodiment, and detailed description thereof is omitted here.

Next, the operation of the impedance detection apparatus according to the fourth embodiment of the present invention will be described with reference to FIG.
The supply signal 2S composed of a sine wave output from the sine wave generation circuit 22A and input to the response signal generator 3 is input to the positive input terminal of the differential amplifier 32A. The differential amplifier 32A outputs a drive signal 32S as an input of the driver circuit 31A. The driver circuit 31A generates an application signal 1S based on the drive signal 32S and applies it to the detection element 1. Thereby, a current flows through the impedance of the subject 10.

The output terminal of the driver circuit 31A is connected to the reverse polarity input terminal of the differential amplifier 32A so that negative feedback is applied. Thereby, information on the current flowing through the impedance of the subject 10 is transmitted to the differential amplifier 32A as the current information signal 31S.
The differential amplifier 32A detects the difference between the potential of the output terminal of the driver circuit 31A and the potential of the supply signal 2S and adjusts the drive signal 32S, that is, regardless of the magnitude of the current flowing through the impedance of the subject 10, that is, the subject. The applied signal 1S is controlled to be equal to the supply signal 2S regardless of the magnitude of the impedance.

  At this time, the phase of the current flowing through the subject 10 changes according to the reactance component of the impedance inherent to the subject 10. This phase change becomes a change in the potential of the output terminal of the driver circuit 31A, and is transmitted to the differential amplifier 32A as the current information signal 31S. The voltage value of the drive signal 32S is adjusted based on the current information signal 31S by the differential amplifier 32A. As a result, a response signal 3S in which the phase information of the current flowing through the impedance of the subject 10 is converted into a voltage is obtained.

  In the present embodiment, the supply signal 2S is connected to the positive input terminal of the differential amplifier 32A, and the current information signal 31S is connected to the reverse polarity input terminal of the differential amplifier 32A. In the case of an inverting amplifier, the supply signal 2S may be connected to the reverse polarity input terminal of the differential amplifier 32A, and the current information signal 31S may be connected to the positive input terminal of the differential amplifier 32A. That is, the current information signal 31S may be connected to the reverse polarity input terminal of the differential amplifier 32A so that negative feedback is applied. The same applies to the other embodiments described below.

FIG. 5 is a signal waveform diagram showing the operation of the impedance detection device according to the fourth exemplary embodiment of the present invention.
In the sine wave generation circuit 22A of the supply signal generation unit 2, a supply signal 2S composed of a sine wave is generated with a potential VA that is substantially intermediate between the circuit operating power supply potential VDD and the ground potential (0V = GND) as a center voltage. .

When the application signal 1S is applied to the subject 10, the voltage of the application signal 1S drops due to the current flowing through the subject 10, and its phase also changes. This phase change becomes the phase information of the current information signal 31S.
The differential amplifier 32A adjusts and outputs the drive signal 32S so that the supply signal 2S and the current information signal 31S are the same. As a result, with respect to the waveform of the supply signal 2S having the potential VA as the center voltage, the drive signal 32S has a waveform increased by a voltage that compensates for the voltage drop, that is, a waveform having the offset correction potential VA1 as the center voltage.

At this time, the phase of the drive signal 32S also changes based on the phase information of the current information signal 31S, and the drive signal 32S including this phase change is output as the response signal 3S. Therefore, the response signal 3S is a signal including an offset due to the impedance of the subject 10.
The offset correction circuit 41 level-shifts the DC potential so that the center voltage of the response signal 3S matches the reference potential VA used in the phase comparison circuit 43, and outputs the signal 41S to be compared with the offset corrected.

  The phase comparison circuit 43 compares the phase of the signal 41S to be compared with the phase of the reference signal 42S from the reference signal generation circuit 42, and outputs a detection signal 4AS having a signal waveform having a pulse width corresponding to the phase difference. Therefore, a signal including waveform information (phase information) corresponding to the phase difference between the supply signal 2S and the applied signal 1S, that is, the reactance component of the impedance of the subject 10, is obtained as the detection signal 4AS.

As described above, in this embodiment, the drive circuit 31 of the response signal generation unit 3 is configured by the driver circuit 31A and the current-voltage conversion circuit 32 is configured by the differential amplifier 32A in the second embodiment. Therefore, it is possible to stably detect information indicating the reactance component in the impedance inherent to the subject 10 with a very simple circuit in a wide input dynamic range regardless of the magnitude of the impedance of the subject.
In the present embodiment, the case where the waveform information detection unit 4A includes the offset correction circuit 41, the reference signal generation circuit 42, and the phase comparison circuit 43 is shown as an example. However, the present invention is not limited to this. The waveform information detector 4A may be configured by other circuits.

[Fifth Embodiment]
Next, an impedance detection apparatus according to a fifth embodiment of the present invention will be described with reference to FIG. FIG. 6 is a block diagram showing the configuration of the impedance detection apparatus according to the fifth embodiment of the present invention, and the same or equivalent parts as those in FIG.

In the third embodiment, a case where the response signal generation unit 3 configured by the drive circuit 31 and the current-voltage conversion circuit 32 according to the first embodiment is used to detect and output the impedance of the subject as amplitude information is used. Described as an example.
In the present embodiment, a case will be described in which, in the third embodiment, the drive circuit 31 of the response signal generation unit 3 is configured by a driver circuit 31A, and the current-voltage conversion circuit 32 is configured by a differential amplifier 32A.

  In FIG. 6, the driver circuit 31A has an input terminal connected to the output terminal of the differential amplifier 32A, and an output terminal connected to the detection electrode 12 of the detection element 1 and the positive input terminal of the differential amplifier 32A. The driver circuit 31A has a function of amplifying the drive signal 32S input to the input terminal and outputting the applied signal 1S and the current information signal 31S from the output terminal with low impedance.

  The differential amplifier 32A has a positive input terminal connected to the output of the supply signal generator 2, a reverse polarity input terminal connected to the output terminal of the driver circuit 31A and the detection electrode 12, and an output terminal input to the driver circuit 31A. And connected to the input of the waveform information detector 4B. The differential amplifier 32A differentially amplifies the supply signal 2S input to the positive input terminal and the current information signal 31S input to the reverse polarity input terminal, and outputs the drive signal 32S and the response signal 3S from the output terminal. It has a function to output.

The sine wave generation circuit 22A is a specific example of the waveform shaping circuit 22 of FIG. 3, and generates an alternating supply signal 2S composed of a sine wave based on the clock signal 21S from the frequency generation circuit 21 and supplies it to the response signal generation unit 3. It has a function to output.
The configuration other than the response signal generation unit 3 and the sine wave generation circuit 22A is the same as that of the second embodiment, and detailed description thereof is omitted here.

Next, the operation of the impedance detection apparatus according to the fifth embodiment of the present invention will be described with reference to FIG.
The supply signal 2S composed of a sine wave output from the sine wave generation circuit 22A and input to the response signal generator 3 is input to the positive input terminal of the differential amplifier 32A. The differential amplifier 32A outputs a drive signal 32S as an input of the driver circuit 31A. The driver circuit 31A generates an application signal 1S based on the drive signal 32S and applies it to the detection element 1. Thereby, a current flows through the impedance of the subject 10.

The output terminal of the driver circuit 31A is connected to the reverse polarity input terminal of the differential amplifier 32A so that negative feedback is applied. Thereby, information on the current flowing through the impedance of the subject 10 is transmitted to the differential amplifier 32A as the current information signal 31S.
The differential amplifier 32A detects the difference between the potential of the output terminal of the driver circuit 31A and the potential of the supply signal 2S and adjusts the drive signal 32S, that is, regardless of the magnitude of the current flowing through the impedance of the subject 10, that is, the subject. The applied signal 1S is controlled to be equal to the supply signal 2S regardless of the magnitude of the impedance.

  At this time, the amplitude of the current flowing through the subject 10 changes according to the resistance component of the impedance inherent to the subject 10. This amplitude change becomes a change in the potential of the output terminal of the driver circuit 31A, and is transmitted to the differential amplifier 32A as the current information signal 31S. The voltage value of the drive signal 32S is adjusted based on the current information signal 31S by the differential amplifier 32A. As a result, a response signal 3S in which the amplitude information of the current flowing through the impedance of the subject 10 is converted into a voltage is obtained.

FIG. 7 is a signal waveform diagram showing the operation of the impedance detection device according to the fifth exemplary embodiment of the present invention.
In the sine wave generation circuit 22A of the supply signal generation unit 2, a supply signal 2S composed of a sine wave is generated with a potential VA that is substantially intermediate between the circuit operating power supply potential VDD and the ground potential (0V = GND) as a center voltage. .

When the application signal 1S is applied to the subject 10, the voltage of the application signal 1S drops due to the current flowing through the subject 10, and the amplitude thereof also changes. This amplitude change becomes the amplitude information of the current information signal 31S.
The differential amplifier 32A adjusts and outputs the drive signal 32S so that the supply signal 2S and the current information signal 31S are the same. As a result, with respect to the waveform of the supply signal 2S having the potential VA as the center voltage, the drive signal 32S has a waveform increased by a voltage that compensates for the voltage drop, that is, a waveform having the offset correction potential VA1 as the center voltage.

At this time, the amplitude of the drive signal 32S also changes based on the amplitude information of the current information signal 31S, and the drive signal 32S including this amplitude change is output as the response signal 3S. Therefore, the response signal 3S is a signal including an offset potential due to the impedance of the subject 10.
The peak voltage detection circuit 44 detects the maximum voltage value or the minimum voltage value of the response signal 3S and outputs it as the peak voltage value 44S. The center voltage detection circuit 45 detects the center voltage VA1 of the response signal 3S and outputs it as a center voltage value 45S.

  The voltage comparison circuit 46 compares the peak voltage value 44S and the center voltage value 45S, and outputs a detection signal 4BS having a signal waveform having a voltage value corresponding to the difference. At this time, since the voltage comparison circuit 46 compares the peak voltage value 44S with the center voltage value 45S, only the amplitude value not including the offset of the response signal 3S is detected. Therefore, a signal including waveform information (amplitude information) corresponding to the amplitude difference between the supply signal 2S and the applied signal 1S, that is, the resistance component of the impedance of the subject 10, is obtained as the detection signal 4BS.

Thus, in the present embodiment, in the third embodiment, the drive circuit 31 of the response signal generation unit 3 is configured by the driver circuit 31A, and the current-voltage conversion circuit 32 is configured by the differential amplifier 32A. Therefore, it is possible to stably detect information indicating the resistance component of the impedance inherent to the subject 10 with a very simple circuit in a wide input dynamic range regardless of the magnitude of the impedance of the subject.
In the present embodiment, the case where the waveform information detection unit 4B is configured by the peak voltage detection circuit 44, the center voltage detection circuit 45, and the voltage comparison circuit 46 is shown as an example. However, the present invention is not limited to this. The waveform information detector 4B may be configured by other circuits.

[Sixth Embodiment]
Next, with reference to FIG. 8, an impedance detection apparatus according to a sixth embodiment of the present invention will be described. FIG. 8 is a block diagram showing the configuration of the impedance detection apparatus according to the sixth embodiment of the present invention, and the same or equivalent parts as those in FIG.

In the fourth embodiment, in the second embodiment, the drive circuit 31 of the response signal generation unit 3 is configured by a driver circuit 31A, and the current-voltage conversion circuit 32 is configured by a differential amplifier 32A. As explained.
In the present embodiment, the case where the current-voltage conversion circuit 32 is configured by a differential amplifier 32A and a driver circuit 32B in the fourth embodiment will be described.

  In FIG. 8, the driver circuit 31A has an input terminal connected to the output terminal of the differential amplifier 32A, and an output terminal connected to the detection electrode 12 of the detection element 1 and the positive input terminal of the differential amplifier 32A. The driver circuit 31A has a function of amplifying the drive signal 32S input to the input terminal and outputting the applied signal 1S and the current information signal 31S from the output terminal with low impedance.

  The differential amplifier 32A has a positive input terminal connected to the output of the supply signal generator 2, a reverse polarity input terminal connected to the output terminal of the driver circuit 31A and the detection electrode 12, and an output terminal connected to the driver circuit 31A and the driver circuit. It is connected to the input terminal of 32B and the input of the waveform information detector 4A. The differential amplifier 32A differentially amplifies the supply signal 2S input to the positive input terminal and the current information signal 31S input to the reverse polarity input terminal, and outputs the drive signal 32S and the response signal 3S from the output terminal. It has a function to output.

  The driver circuit 32B has an input terminal connected to the output terminal of the differential amplifier 32A, and an output terminal connected to the input of the waveform information detector 4A. The driver circuit 32B has a function of amplifying the drive signal 32S input to the input terminal and outputting the response signal 3S with low impedance from the output terminal.

The sine wave generation circuit 22A is a specific example of the waveform shaping circuit 22 of FIG. 2, and generates an alternating supply signal 2S composed of a sine wave based on the clock signal 21S from the frequency generation circuit 21 and supplies it to the response signal generation unit 3. It has a function to output.
The configuration other than the response signal generation unit 3 and the sine wave generation circuit 22A is the same as that of the fourth embodiment, and a detailed description thereof is omitted here.

Next, the operation of the impedance detection apparatus according to the sixth embodiment of the present invention will be described with reference to FIG.
The supply signal 2S composed of a sine wave output from the sine wave generation circuit 22A and input to the response signal generator 3 is input to the positive input terminal of the differential amplifier 32A. The differential amplifier 32A outputs a drive signal 32S as an input to the driver circuit 31A and the driver circuit 32B. The driver circuit 31A generates an application signal 1S based on the drive signal 32S and applies it to the detection element 1. Thereby, a current flows through the impedance of the subject 10.

The output terminal of the driver circuit 31A is connected to the reverse polarity input terminal of the differential amplifier 32A so that negative feedback is applied. Thereby, information on the current flowing through the impedance of the subject 10 is transmitted to the differential amplifier 32A as the current information signal 31S.
The differential amplifier 32A detects the difference between the potential of the output terminal of the driver circuit 31A and the potential of the supply signal 2S and adjusts the drive signal 32S, that is, regardless of the magnitude of the current flowing through the impedance of the subject 10, that is, the subject. The applied signal 1S is controlled to be equal to the supply signal 2S regardless of the magnitude of the impedance.

  At this time, the phase of the current flowing through the subject 10 changes according to the reactance component of the impedance inherent to the subject 10. This phase change becomes a change in the potential of the output terminal of the driver circuit 31A, and is transmitted to the differential amplifier 32A as the current information signal 31S. The voltage value of the drive signal 32S is adjusted based on the current information signal 31S by the differential amplifier 32A. The drive signal 32S is amplified by the driver circuit 32B and output to the waveform information detection unit 4A as the response signal 3S. Therefore, the response signal 3S can be stably output with a desired amplitude. As a result, a response signal 3S in which the phase information of the current flowing through the impedance of the subject 10 is converted into a voltage is obtained.

FIG. 9 is a signal waveform diagram showing the operation of the impedance detection device according to the sixth exemplary embodiment of the present invention.
In the sine wave generation circuit 22A of the supply signal generation unit 2, a supply signal 2S composed of a sine wave is generated with a potential VA that is substantially intermediate between the circuit operating power supply potential VDD and the ground potential (0V = GND) as a center voltage. .

When the application signal 1S is applied to the subject 10, the voltage of the application signal 1S drops due to the current flowing through the subject 10, and its phase also changes. This phase change becomes the phase information of the current information signal 31S.
The differential amplifier 32A adjusts and outputs the drive signal 32S so that the supply signal 2S and the current information signal 31S are the same. As a result, with respect to the waveform of the supply signal 2S having the potential VA as the center voltage, the drive signal 32S has a waveform increased by a voltage that compensates for the voltage drop, that is, a waveform having the offset correction potential VA1 as the center voltage.

At this time, the phase of the drive signal 32S also changes based on the phase information of the current information signal 31S. The drive signal 32S including this phase change is amplified by the driver circuit 32B and then output as the response signal 3S. Therefore, the response signal 3S is a signal including an offset due to the impedance of the subject 10.
The offset correction circuit 41 level-shifts the DC potential so that the center voltage of the response signal 3S matches the reference potential VA used in the phase comparison circuit 43, and outputs the signal 41S to be compared with the offset corrected.

  The phase comparison circuit 43 compares the phase of the signal 41S to be compared with the phase of the reference signal 42S from the reference signal generation circuit 42, and outputs a detection signal 4AS having a signal waveform having a pulse width corresponding to the phase difference. Therefore, a signal including waveform information (phase information) corresponding to the phase difference between the supply signal 2S and the applied signal 1S, that is, the reactance component of the impedance of the subject 10, is obtained as the detection signal 4AS.

  As described above, in the present embodiment, since the current-voltage conversion circuit 32 is configured by the differential amplifier 32A and the driver circuit 32B in the fourth embodiment, it is an extremely simple circuit and is unique to the subject 10. It is possible to stably detect information indicating the reactance component of the impedance of the subject with a wide input dynamic range regardless of the impedance of the subject. Further, the response signal 3S can be amplified and output by the driver circuit 32B, and the detection accuracy of the phase information in the waveform information detection unit 4A can be improved as compared with the fourth embodiment.

  In the present embodiment, the case where the waveform information detection unit 4A includes the offset correction circuit 41, the reference signal generation circuit 42, and the phase comparison circuit 43 is shown as an example. However, the present invention is not limited to this. The waveform information detector 4A may be configured by other circuits.

[Seventh Embodiment]
Next, with reference to FIG. 10, an impedance detection apparatus according to a seventh embodiment of the present invention will be described. FIG. 10 is a block diagram showing a configuration of an impedance detection device according to the seventh exemplary embodiment of the present invention. The same or equivalent parts as those in FIG. 3 described above are denoted by the same reference numerals.

In the fifth embodiment, in the third embodiment, the drive circuit 31 of the response signal generation unit 3 is configured by a driver circuit 31A, and the current-voltage conversion circuit 32 is configured by a differential amplifier 32A. As explained.
In the present embodiment, the case where the current-voltage conversion circuit 32 is configured by a differential amplifier 32A and a driver circuit 32B in the fifth embodiment will be described.

  In FIG. 10, the driver circuit 31A has an input terminal connected to the output terminal of the differential amplifier 32A, and an output terminal connected to the detection electrode 12 of the detection element 1 and the positive input terminal of the differential amplifier 32A. The driver circuit 31A has a function of amplifying the drive signal 32S input to the input terminal and outputting the applied signal 1S and the current information signal 31S from the output terminal with low impedance.

  The differential amplifier 32A has a positive input terminal connected to the output of the supply signal generator 2, a reverse polarity input terminal connected to the output terminal of the driver circuit 31A and the detection electrode 12, and an output terminal connected to the driver circuit 31A and the driver circuit. It is connected to the input terminal of 32B. The differential amplifier 32A differentially amplifies the supply signal 2S input to the positive input terminal and the current information signal 31S input to the reverse polarity input terminal, and outputs the drive signal 32S and the response signal 3S from the output terminal. It has a function to output.

  The driver circuit 32B has an input terminal connected to the output terminal of the differential amplifier 32A, and an output terminal connected to the input of the waveform information detector 4B. The driver circuit 32B has a function of amplifying the drive signal 32S input to the input terminal and outputting the response signal 3S with low impedance from the output terminal.

The sine wave generation circuit 22A is a specific example of the waveform shaping circuit 22 of FIG. 3, and generates an alternating supply signal 2S composed of a sine wave based on the clock signal 21S from the frequency generation circuit 21 and supplies it to the response signal generation unit 3. It has a function to output.
The configuration other than the response signal generation unit 3 and the sine wave generation circuit 22A is the same as that of the third embodiment, and a detailed description thereof is omitted here.

Next, with reference to FIG. 10, an operation of the impedance detection apparatus according to the seventh exemplary embodiment of the present invention will be described.
The supply signal 2S composed of a sine wave output from the sine wave generation circuit 22A and input to the response signal generator 3 is input to the positive input terminal of the differential amplifier 32A. The differential amplifier 32A outputs a drive signal 32S as an input of the driver circuit 31A. The driver circuit 31A generates an application signal 1S based on the drive signal 32S and applies it to the detection element 1. Thereby, a current flows through the impedance of the subject 10.

The output terminal of the driver circuit 31A is connected to the reverse polarity input terminal of the differential amplifier 32A so that negative feedback is applied. Thereby, information on the current flowing through the impedance of the subject 10 is transmitted to the differential amplifier 32A as the current information signal 31S.
The differential amplifier 32A detects the difference between the potential of the output terminal of the driver circuit 31A and the potential of the supply signal 2S and adjusts the drive signal 32S, that is, regardless of the magnitude of the current flowing through the impedance of the subject 10, that is, the subject. The applied signal 1S is controlled to be equal to the supply signal 2S regardless of the magnitude of the impedance.

  At this time, the amplitude of the current flowing through the subject 10 changes according to the resistance component of the impedance inherent to the subject 10. This amplitude change becomes a change in the potential of the output terminal of the driver circuit 31A, and is transmitted to the differential amplifier 32A as the current information signal 31S. The voltage value of the drive signal 32S is adjusted based on the current information signal 31S by the differential amplifier 32A. This drive signal 32S is amplified by the driver circuit 32B, and is output to the waveform information detector 4B as the response signal 3S. Therefore, the response signal 3S can be stably output with a desired amplitude. As a result, a response signal 3S in which the amplitude information of the current flowing through the impedance of the subject 10 is converted into a voltage is obtained.

FIG. 11 is a signal waveform diagram showing an operation of the impedance detection device according to the seventh exemplary embodiment of the present invention.
In the sine wave generation circuit 22A of the supply signal generation unit 2, a supply signal 2S composed of a sine wave is generated with a potential VA that is substantially intermediate between the circuit operating power supply potential VDD and the ground potential (0V = GND) as a center voltage. .

When the application signal 1S is applied to the subject 10, the voltage of the application signal 1S drops due to the current flowing through the subject 10, and the amplitude thereof also changes. This amplitude change becomes the amplitude information of the current information signal 31S.
The differential amplifier 32A adjusts and outputs the drive signal 32S so that the supply signal 2S and the current information signal 31S are the same. As a result, with respect to the waveform of the supply signal 2S having the potential VA as the center voltage, the drive signal 32S has a waveform increased by a voltage that compensates for the voltage drop, that is, a waveform having the offset correction potential VA1 as the center voltage.

At this time, the amplitude of the drive signal 32S also changes based on the amplitude information of the current information signal 31S. The drive signal 32S including this amplitude change is amplified by the driver circuit 32B and then output as the response signal 3S. Therefore, the response signal 3S is a signal including an offset potential due to the impedance of the subject 10.
The peak voltage detection circuit 44 detects the maximum voltage value or the minimum voltage value of the response signal 3S and outputs it as the peak voltage value 44S. The center voltage detection circuit 45 detects the center voltage VA1 of the response signal 3S and outputs it as a center voltage value 45S.

  The voltage comparison circuit 46 compares the peak voltage value 44S and the center voltage value 45S, and outputs a detection signal 4BS having a signal waveform having a voltage value corresponding to the difference. At this time, since the voltage comparison circuit 46 compares the peak voltage value 44S with the center voltage value 45S, only the amplitude value not including the offset of the response signal 3S is detected. Therefore, a signal including waveform information (amplitude information) corresponding to the amplitude difference between the supply signal 2S and the applied signal 1S, that is, the resistance component of the impedance of the subject 10, is obtained as the detection signal 4BS.

  Thus, since the current-voltage conversion circuit 32 is configured by the differential amplifier 32A and the driver circuit 32B in the fifth embodiment, the present embodiment is a very simple circuit and unique to the subject 10. It is possible to stably detect information indicating the resistance component of the impedance in a wide input dynamic range regardless of the magnitude of the impedance of the subject. Further, the response signal 3S can be amplified and output by the driver circuit 32B, and the detection accuracy of the amplitude information in the waveform information detection unit 4B can be improved as compared with the fifth embodiment.

  In the present embodiment, the case where the waveform information detection unit 4B is configured by the peak voltage detection circuit 44, the center voltage detection circuit 45, and the voltage comparison circuit 46 is shown as an example. However, the present invention is not limited to this. The waveform information detector 4B may be configured by other circuits.

[Eighth Embodiment]
Next, with reference to FIG. 12, an impedance detection apparatus according to an eighth embodiment of the present invention will be described. FIG. 12 is a block diagram showing the configuration of the impedance detection apparatus according to the eighth embodiment of the present invention. The same reference numerals are given to the same or equivalent parts as those in FIG.

In the sixth embodiment, in the second embodiment, the drive circuit 31 of the response signal generation unit 3 is configured by a driver circuit 31A, and the current-voltage conversion circuit 32 is configured by a differential amplifier 32A and a driver circuit 32B. The case where the waveform shaping circuit 22 is constituted by the sine wave generation circuit 22A and the impedance of the subject is detected and output as phase information has been described as an example.
In the present embodiment, the case where the waveform shaping circuit 22 is configured by a triangular wave generation circuit 22B in the sixth embodiment will be described.

In FIG. 12, a triangular wave generation circuit 22B is a specific example of the waveform shaping circuit 22 of FIG. 2, and generates an AC supply signal 2S composed of a triangular wave based on the clock signal 21S from the frequency generation circuit 21 to generate a response signal generation unit. 3 is provided. The triangular wave generation circuit 22B may be a general known circuit, and the circuit configuration can be simplified as compared with the sine wave generation circuit.
The configuration other than the triangular wave generation circuit 22B is the same as that of the sixth embodiment, and a detailed description thereof is omitted here.

Next, the operation of the impedance detection apparatus according to the eighth embodiment of the present invention will be described with reference to FIG.
The supply signal 2S composed of a triangular wave output from the triangular wave generation circuit 22B and input to the response signal generation unit 3 is input to the positive input terminal of the differential amplifier 32A. The differential amplifier 32A outputs a drive signal 32S as an input to the driver circuit 31A and the driver circuit 32B. The driver circuit 31A generates an application signal 1S based on the drive signal 32S and applies it to the detection element 1. Thereby, a current flows through the impedance of the subject 10.

The output terminal of the driver circuit 31A is connected to the reverse polarity input terminal of the differential amplifier 32A so that negative feedback is applied. Thereby, information on the current flowing through the impedance of the subject 10 is transmitted to the differential amplifier 32A as the current information signal 31S.
The differential amplifier 32A detects the difference between the potential of the output terminal of the driver circuit 31A and the potential of the supply signal 2S and adjusts the drive signal 32S, that is, regardless of the magnitude of the current flowing through the impedance of the subject 10, that is, the subject. The applied signal 1S is controlled to be equal to the supply signal 2S regardless of the magnitude of the impedance.

  At this time, the phase of the current flowing through the subject 10 changes according to the reactance component of the impedance inherent to the subject 10. This phase change becomes a change in the potential of the output terminal of the driver circuit 31A, and is transmitted to the differential amplifier 32A as the current information signal 31S. The voltage value of the drive signal 32S is adjusted based on the current information signal 31S by the differential amplifier 32A. The drive signal 32S is amplified by the driver circuit 32B and output to the waveform information detection unit 4A as the response signal 3S. Therefore, the response signal 3S can be stably output with a desired amplitude. As a result, a response signal 3S in which the phase information of the current flowing through the impedance of the subject 10 is converted into a voltage is obtained.

FIG. 13 is a signal waveform diagram showing the operation of the impedance detection device according to the eighth exemplary embodiment of the present invention. FIG. 14 is another signal waveform diagram showing the operation of the impedance detection device according to the eighth exemplary embodiment of the present invention.
In the triangular wave generation circuit 22B of the supply signal generation unit 2, a supply signal 2S composed of a triangular wave is generated with a potential VA that is substantially intermediate between the circuit operating power supply potential VDD and the ground potential (0V = GND) as a center voltage.

Here, as shown in FIG. 13, when the impedance of the subject 10 is only a capacitive component, when a supply signal 2S composed of a triangular wave is input to the subject 10, the current flowing through the impedance becomes a differential response waveform of a triangular wave, and is rectangular. A response signal 3Sc having a waveform close to a wave is obtained.
Further, when the impedance of the subject 10 is only a resistance component, when a supply signal 2S composed of a triangular wave is input to the subject 10, the current flowing through the impedance becomes a response waveform having the same waveform as the triangular wave, and has the original triangular wave waveform. A response signal 3Sr is obtained.

  Therefore, when the impedance of the subject 10 has a capacitance component and a resistance component, when a supply signal 2S consisting of a triangular wave is input to the subject 10, the current flowing through the impedance is combined with the differential response of the triangular wave and the original triangular wave. Waveform. Therefore, the response signal 3S has a waveform obtained by synthesizing the response signal 3Sc and the response signal 3Sr, that is, a signal waveform having a voltage deviation corresponding to the differential response between the rising period and the falling period of the triangular wave.

When the application signal 1S is applied to the subject 10, the voltage of the application signal 1S drops due to the current flowing through the subject 10, and its phase also changes. This phase change becomes the phase information of the current information signal 31S.
As shown in FIG. 14, the differential amplifier 32A adjusts and outputs the drive signal 32S so that the supply signal 2S and the current information signal 31S are the same. As a result, with respect to the waveform of the supply signal 2S having the potential VA as the center voltage, the drive signal 32S has a waveform increased by a voltage that compensates for the voltage drop, that is, a waveform having the offset correction potential VA1 as the center voltage.

At this time, the phase of the drive signal 32S also changes based on the phase information of the current information signal 31S. The drive signal 32S including this phase change is amplified by the driver circuit 32B and then output as the response signal 3S. Therefore, the response signal 3S is a signal including an offset due to the impedance of the subject 10.
The offset correction circuit 41 level-shifts the DC potential so that the center voltage of the response signal 3S matches the reference potential VA used in the phase comparison circuit 43, and outputs the signal 41S to be compared with the offset corrected.

  The phase comparison circuit 43 compares the phase of the signal 41S to be compared with the phase of the reference signal 42S from the reference signal generation circuit 42, and outputs a detection signal 4AS having a signal waveform having a pulse width corresponding to the phase difference. Therefore, a signal including waveform information (phase information) corresponding to the phase difference between the supply signal 2S and the applied signal 1S, that is, the reactance component of the impedance of the subject 10, is obtained as the detection signal 4AS.

  As described above, in this embodiment, the drive circuit 31 of the response signal generation unit 3 is configured by the driver circuit 31A and the current-voltage conversion circuit 32 is replaced with the differential amplifier 32A and the driver circuit in the sixth embodiment. 32B, and further, the waveform shaping circuit 22 is constituted by the triangular wave generation circuit 22B. Therefore, the circuit required for generating the supply signal 2S can be simplified as compared with the case where a sine wave is used. Information indicating the reactance component of the impedance inherent in the subject 10 can be stably detected in a wide input dynamic range regardless of the magnitude of the impedance of the subject.

In the present embodiment, the case where the waveform information detection unit 4A includes the offset correction circuit 41, the reference signal generation circuit 42, and the phase comparison circuit 43 is shown as an example. However, the present invention is not limited to this. The waveform information detector 4A may be configured by other circuits.
In the present embodiment, the case where the response signal generation unit 3 is configured by the driver circuit 31A, the differential amplifier 32A, and the driver circuit 32B has been described as an example. However, the present invention is not limited to this. The response signal generation unit 3 may be configured by other circuits such as the circuit 31A and the differential amplifier 32A.

  Further, in the present embodiment, the case where the response signal 3S from the response signal generation unit 3 is directly input to the waveform information detection unit 4A has been described as an example, but the response signal generation unit 3 and the waveform information detection unit 4A are not affected. A low-pass filter may be provided. Thereby, the high frequency component contained in the response signal 3S which consists of a triangular wave can be removed, and the detection accuracy of the waveform information in the waveform information detection part 4A can be improved. The low-pass filter is provided between the offset correction circuit 41 and the phase comparison circuit 43, and can remove a high-frequency component contained in the signal to be compared 41S formed of a triangular wave. Similarly to the above, the waveform information detection unit 4A The accuracy of detecting waveform information in can be improved.

[Ninth Embodiment]
Next, with reference to FIG. 15, an impedance detection apparatus according to a ninth embodiment of the present invention will be described. FIG. 15 is a block diagram showing the configuration of the impedance detection apparatus according to the ninth embodiment of the present invention. The same or equivalent parts as those in FIG.

In the seventh embodiment, in the third embodiment, the drive circuit 31 of the response signal generation unit 3 is configured by a driver circuit 31A, and the current-voltage conversion circuit 32 is configured by a differential amplifier 32A and a driver circuit 32B. The case where the waveform shaping circuit 22 is constituted by the sine wave generation circuit 22A and the impedance of the subject is detected and output as amplitude information has been described as an example.
In the present embodiment, the case where the waveform shaping circuit 22 is configured by a triangular wave generation circuit 22B in the seventh embodiment will be described.

In FIG. 15, a triangular wave generation circuit 22B is a specific example of the waveform shaping circuit 22 of FIG. 3, and generates an AC supply signal 2S composed of a triangular wave based on the clock signal 21S from the frequency generation circuit 21 to generate a response signal generation unit. 3 is provided. The triangular wave generation circuit 22B may be a general known circuit, and the circuit configuration can be simplified as compared with the sine wave generation circuit.
The configuration other than the triangular wave generation circuit 22B is the same as that of the seventh embodiment, and a detailed description thereof is omitted here.

Next, the operation of the impedance detection apparatus according to the ninth embodiment of the present invention will be described with reference to FIG.
The supply signal 2S composed of a triangular wave output from the triangular wave generation circuit 22B and input to the response signal generation unit 3 is input to the positive input terminal of the differential amplifier 32A. The differential amplifier 32A outputs a drive signal 32S as an input to the driver circuit 31A and the driver circuit 32B. The driver circuit 31A generates an application signal 1S based on the drive signal 32S and applies it to the detection element 1. Thereby, a current flows through the impedance of the subject 10.

The output terminal of the driver circuit 31A is connected to the reverse polarity input terminal of the differential amplifier 32A so that negative feedback is applied. Thereby, information on the current flowing through the impedance of the subject 10 is transmitted to the differential amplifier 32A as the current information signal 31S.
The differential amplifier 32A detects the difference between the potential of the output terminal of the driver circuit 31A and the potential of the supply signal 2S and adjusts the drive signal 32S, that is, regardless of the magnitude of the current flowing through the impedance of the subject 10, that is, the subject. The applied signal 1S is controlled to be equal to the supply signal 2S regardless of the magnitude of the impedance.

  At this time, the amplitude of the current flowing through the subject 10 changes according to the resistance component of the impedance inherent to the subject 10. This amplitude change becomes a change in the potential of the output terminal of the driver circuit 31A, and is transmitted to the differential amplifier 32A as the current information signal 31S. The voltage value of the drive signal 32S is adjusted based on the current information signal 31S by the differential amplifier 32A. This drive signal 32S is amplified by the driver circuit 32B, and is output to the waveform information detector 4B as the response signal 3S. Therefore, the response signal 3S can be stably output with a desired amplitude. As a result, a response signal 3S in which the amplitude information of the current flowing through the impedance of the subject 10 is converted into a voltage is obtained.

FIG. 16 is a signal waveform diagram showing an operation of the impedance detection device according to the ninth exemplary embodiment of the present invention.
In the triangular wave generation circuit 22B of the supply signal generation unit 2, a supply signal 2S composed of a triangular wave is generated with a potential VA that is substantially intermediate between the circuit operating power supply potential VDD and the ground potential (0V = GND) as a center voltage.

  Here, as described with reference to FIG. 13, when the impedance of the subject 10 has a capacitance component and a resistance component, when the supply signal 2 </ b> S composed of a triangular wave is input to the subject 10, the current flowing through the impedance is differentiated from the triangular wave. The response and the original triangular wave are combined. Therefore, the response signal 3S becomes such a composite waveform, that is, a signal waveform having a voltage shift by the differential response between the rising and falling periods of the triangular wave.

When the application signal 1S is applied to the subject 10, the voltage of the application signal 1S drops due to the current flowing through the subject 10, and the amplitude thereof also changes. This amplitude change becomes the amplitude information of the current information signal 31S.
The differential amplifier 32A adjusts and outputs the drive signal 32S so that the supply signal 2S and the current information signal 31S are the same. As a result, with respect to the waveform of the supply signal 2S having the potential VA as the center voltage, the drive signal 32S has a waveform increased by a voltage that compensates for the voltage drop, that is, a waveform having the offset correction potential VA1 as the center voltage.

At this time, the amplitude of the drive signal 32S also changes based on the amplitude information of the current information signal 31S. The drive signal 32S including this amplitude change is amplified by the driver circuit 32B and then output as the response signal 3S. Therefore, the response signal 3S is a signal including an offset potential due to the impedance of the subject 10.
The peak voltage detection circuit 44 detects the maximum voltage value or the minimum voltage value of the response signal 3S and outputs it as the peak voltage value 44S. The center voltage detection circuit 45 detects the center voltage VA1 of the response signal 3S and outputs it as a center voltage value 45S.

  The voltage comparison circuit 46 compares the peak voltage value 44S and the center voltage value 45S, and outputs a detection signal 4BS having a signal waveform having a voltage value corresponding to the difference. At this time, since the voltage comparison circuit 46 compares the peak voltage value 44S with the center voltage value 45S, only the amplitude value not including the offset of the response signal 3S is detected. Therefore, a signal including waveform information (amplitude information) corresponding to the amplitude difference between the supply signal 2S and the applied signal 1S, that is, the resistance component of the impedance of the subject 10, is obtained as the detection signal 4BS.

  Thus, in this embodiment, the drive circuit 31 of the response signal generation unit 3 is configured by the driver circuit 31A and the waveform shaping circuit 22 is configured by the triangular wave generation circuit 22B in the third embodiment. Since the current-voltage conversion circuit 32 is composed of the differential amplifier 32A, the information indicating the resistance component of the impedance inherent to the subject 10 is wide regardless of the magnitude of the impedance of the subject with a very simple circuit. It becomes possible to detect stably in the input dynamic range.

In the present embodiment, the case where the waveform information detection unit 4B is configured by the peak voltage detection circuit 44, the center voltage detection circuit 45, and the voltage comparison circuit 46 is shown as an example. However, the present invention is not limited to this. The waveform information detector 4B may be configured by other circuits.
In the present embodiment, the case where the response signal generation unit 3 is configured by the driver circuit 31A, the differential amplifier 32A, and the driver circuit 32B has been described as an example. However, the present invention is not limited to this. The response signal generation unit 3 may be configured by other circuits such as the circuit 31A and the differential amplifier 32A.

  In the present embodiment, the case where the response signal 3S from the response signal generation unit 3 is directly input to the waveform information detection unit 4B has been described as an example, but the response signal generation unit 3 and the waveform information detection unit 4B A low-pass filter may be provided. Thereby, the high frequency component contained in the response signal 3S which consists of a triangular wave can be removed, and the detection accuracy of the waveform information in the waveform information detection part 4B can be improved.

[Tenth embodiment]
Next, with reference to FIG. 17, an impedance detection apparatus according to a tenth embodiment of the present invention will be described. FIG. 17 is a block diagram showing the configuration of the impedance detection apparatus according to the tenth embodiment of the present invention. The same reference numerals are given to the same or equivalent parts as those in FIG.

In the sixth embodiment, in the second embodiment, the drive circuit 31 of the response signal generation unit 3 is configured by a driver circuit 31A, and the current-voltage conversion circuit 32 is configured by a differential amplifier 32A and a driver circuit 32B. The case where the waveform shaping circuit 22 is constituted by the sine wave generation circuit 22A and the impedance of the subject is detected and output as phase information has been described as an example.
In the present embodiment, the case where the waveform shaping circuit 22 is configured by a trapezoidal wave generation circuit 22C in the sixth embodiment will be described.

17, a trapezoidal wave generation circuit 22C is a specific example of the waveform shaping circuit 22 of FIG. 2, and generates a response signal by generating an alternating supply signal 2S composed of a trapezoidal wave based on a clock signal 21S from the frequency generation circuit 21. It has a function of outputting to the generation unit 3. The trapezoidal wave generating circuit 22C may be a general known circuit, and the circuit configuration can be simplified as compared with the sine wave generating circuit. In addition, according to the trapezoidal waveform, it is possible to generate a waveform with less high-frequency components and close to a sine wave compared to a triangular wave, and the impedance of the subject 10 can be detected more accurately.
The configuration other than the trapezoidal wave generation circuit 22C is the same as that of the sixth embodiment, and a detailed description thereof is omitted here.

Next, the operation of the impedance detection apparatus according to the tenth embodiment of the present invention will be described with reference to FIG.
A supply signal 2S composed of a trapezoidal wave output from the trapezoidal wave generating circuit 22C and input to the response signal generating unit 3 is input to the positive input terminal of the differential amplifier 32A. The differential amplifier 32A outputs a drive signal 32S as an input to the driver circuit 31A and the driver circuit 32B. The driver circuit 31A generates an application signal 1S based on the drive signal 32S and applies it to the detection element 1. Thereby, a current flows through the impedance of the subject 10.

The output terminal of the driver circuit 31A is connected to the reverse polarity input terminal of the differential amplifier 32A so that negative feedback is applied. Thereby, information on the current flowing through the impedance of the subject 10 is transmitted to the differential amplifier 32A as the current information signal 31S.
The differential amplifier 32A detects the difference between the potential of the output terminal of the driver circuit 31A and the potential of the supply signal 2S and adjusts the drive signal 32S, that is, regardless of the magnitude of the current flowing through the impedance of the subject 10, that is, the subject. The applied signal 1S is controlled to be equal to the supply signal 2S regardless of the magnitude of the impedance.

  At this time, the phase of the current flowing through the subject 10 changes according to the reactance component of the impedance inherent to the subject 10. This phase change becomes a change in the potential of the output terminal of the driver circuit 31A, and is transmitted to the differential amplifier 32A as the current information signal 31S. The voltage value of the drive signal 32S is adjusted based on the current information signal 31S by the differential amplifier 32A. The drive signal 32S is amplified by the driver circuit 32B and output to the waveform information detection unit 4A as the response signal 3S. Therefore, the response signal 3S can be stably output with a desired amplitude. As a result, a response signal 3S in which the phase information of the current flowing through the impedance of the subject 10 is converted into a voltage is obtained.

FIG. 18 is a signal waveform diagram showing an operation of the impedance detection device according to the tenth exemplary embodiment of the present invention. FIG. 19 is another signal waveform diagram showing the operation of the impedance detection device according to the tenth exemplary embodiment of the present invention.
In the trapezoidal wave generation circuit 22C of the supply signal generation unit 2, a supply signal 2S composed of a trapezoidal wave is generated with a potential VA that is substantially intermediate between the operation power supply potential VDD and the ground potential (0V = GND) of the circuit as a center voltage. .

Here, as shown in FIG. 18, when the impedance of the subject 10 is only a capacitive component, when a supply signal 2S consisting of a trapezoidal wave is input to the subject 10, the current flowing through the impedance becomes a trapezoidal differential response waveform. A response signal 3Sc having a rectangular staircase waveform is obtained.
Further, when the impedance of the subject 10 is only a resistance component, when a supply signal 2S composed of a trapezoidal wave is input to the subject 10, the current flowing through the impedance becomes a response waveform having the same waveform as the trapezoidal wave, and the original trapezoidal wave A response signal 3Sr having a waveform is obtained.

  Therefore, when the impedance of the subject 10 has a capacitance component and a resistance component, when the supply signal 2S composed of a trapezoidal wave is input to the subject 10, the current flowing through the impedance is changed to the differential response of the trapezoidal wave and the original trapezoidal wave. Becomes a synthesized waveform. Therefore, the response signal 3S has a waveform obtained by synthesizing the response signal 3Sc and the response signal 3Sr, that is, a signal waveform having a voltage deviation corresponding to the differential response in the rising, flat, and falling periods of the trapezoidal wave.

When the application signal 1S is applied to the subject 10, the voltage of the application signal 1S drops due to the current flowing through the subject 10, and its phase also changes. This phase change becomes the phase information of the current information signal 31S.
As shown in FIG. 19, the differential amplifier 32A adjusts and outputs the drive signal 32S so that the supply signal 2S and the current information signal 31S are the same. As a result, with respect to the waveform of the supply signal 2S having the potential VA as the center voltage, the drive signal 32S has a waveform increased by a voltage that compensates for the voltage drop, that is, a waveform having the offset correction potential VA1 as the center voltage.

At this time, the phase of the drive signal 32S also changes based on the phase information of the current information signal 31S. The drive signal 32S including this phase change is amplified by the driver circuit 32B and then output as the response signal 3S. Therefore, the response signal 3S is a signal including an offset due to the impedance of the subject 10.
The offset correction circuit 41 level-shifts the DC potential so that the center voltage of the response signal 3S matches the reference potential VA used in the phase comparison circuit 43, and outputs the signal 41S to be compared with the offset corrected.

  The phase comparison circuit 43 compares the phase of the signal 41S to be compared with the phase of the reference signal 42S from the reference signal generation circuit 42, and outputs a detection signal 4AS having a signal waveform having a pulse width corresponding to the phase difference. Therefore, a signal including waveform information (phase information) corresponding to the phase difference between the supply signal 2S and the applied signal 1S, that is, the reactance component of the impedance of the subject 10, is obtained as the detection signal 4AS.

  As described above, in this embodiment, the drive circuit 31 of the response signal generation unit 3 is configured by the driver circuit 31A and the current-voltage conversion circuit 32 is replaced with the differential amplifier 32A and the driver circuit in the sixth embodiment. 32B, and further, the waveform shaping circuit 22 is constituted by the trapezoidal wave generation circuit 22C. Therefore, the information indicating the reactance component of the impedance inherent in the subject 10 can be set to the magnitude of the subject impedance with a very simple circuit. Regardless, it is possible to detect stably with a wide input dynamic range. Further, since the trapezoidal waveform is used as the supply signal 2S, it is possible to generate a waveform with less high-frequency components and close to a sine wave as compared with the triangular wave, and the impedance of the subject 10 can be detected more accurately.

In the present embodiment, the case where the waveform information detection unit 4A includes the offset correction circuit 41, the reference signal generation circuit 42, and the phase comparison circuit 43 is shown as an example. However, the present invention is not limited to this. The waveform information detector 4A may be configured by other circuits.
In the present embodiment, the case where the response signal generation unit 3 is configured by the driver circuit 31A, the differential amplifier 32A, and the driver circuit 32B has been described as an example. However, the present invention is not limited to this. The response signal generation unit 3 may be configured by other circuits such as the circuit 31A and the differential amplifier 32A.

  In the present embodiment, the case where the response signal 3S from the response signal generation unit 3 is directly input to the waveform information detection unit 4B has been described as an example, but the response signal generation unit 3 and the waveform information detection unit 4B A low-pass filter may be provided. Thereby, the high frequency component contained in the response signal 3S which consists of a trapezoidal wave can be removed, and the detection accuracy of the waveform information in the waveform information detection part 4B can be improved.

[Eleventh embodiment]
Next, with reference to FIG. 20, an impedance detection apparatus according to an eleventh embodiment of the present invention will be described. FIG. 20 is a block diagram showing the configuration of the impedance detection apparatus according to the eleventh embodiment of the present invention. The same reference numerals are given to the same or equivalent parts as those in FIG.

In the seventh embodiment, in the third embodiment, the drive circuit 31 of the response signal generation unit 3 is configured by a driver circuit 31A, and the current-voltage conversion circuit 32 is configured by a differential amplifier 32A and a driver circuit 32B. The case where the waveform shaping circuit 22 is constituted by the sine wave generation circuit 22A and the impedance of the subject is detected and output as amplitude information has been described as an example.
In the present embodiment, the case where the waveform shaping circuit 22 is configured by a trapezoidal wave generation circuit 22C in the seventh embodiment will be described.

In FIG. 20, a trapezoidal wave generation circuit 22C is a specific example of the waveform shaping circuit 22 in FIG. 3, and generates an AC supply signal 2S composed of a trapezoidal wave based on a clock signal 21S from the frequency generation circuit 21 to generate a response signal. It has a function of outputting to the generation unit 3. The trapezoidal wave generating circuit 22C may be a general known circuit, and the circuit configuration can be simplified as compared with the sine wave generating circuit. In addition, according to the trapezoidal waveform, it is possible to generate a waveform with less high-frequency components and close to a sine wave compared to a triangular wave, and the impedance of the subject 10 can be detected more accurately.
The configuration other than the trapezoidal wave generation circuit 22C is the same as that of the seventh embodiment, and a detailed description thereof is omitted here.

Next, the operation of the impedance detection apparatus according to the eleventh embodiment of the present invention will be described with reference to FIG.
A supply signal 2S composed of a trapezoidal wave output from the trapezoidal wave generating circuit 22C and input to the response signal generating unit 3 is input to the positive input terminal of the differential amplifier 32A. The differential amplifier 32A outputs a drive signal 32S as an input to the driver circuit 31A and the driver circuit 32B. The driver circuit 31A generates an application signal 1S based on the drive signal 32S and applies it to the detection element 1. Thereby, a current flows through the impedance of the subject 10.

The output terminal of the driver circuit 31A is connected to the reverse polarity input terminal of the differential amplifier 32A so that negative feedback is applied. Thereby, information on the current flowing through the impedance of the subject 10 is transmitted to the differential amplifier 32A as the current information signal 31S.
The differential amplifier 32A detects the difference between the potential of the output terminal of the driver circuit 31A and the potential of the supply signal 2S and adjusts the drive signal 32S, that is, regardless of the magnitude of the current flowing through the impedance of the subject 10, that is, the subject. The applied signal 1S is controlled to be equal to the supply signal 2S regardless of the magnitude of the impedance.

  At this time, the amplitude of the current flowing through the subject 10 changes according to the resistance component of the impedance inherent to the subject 10. This amplitude change becomes a change in the potential of the output terminal of the driver circuit 31A, and is transmitted to the differential amplifier 32A as the current information signal 31S. The voltage value of the drive signal 32S is adjusted based on the current information signal 31S by the differential amplifier 32A. This drive signal 32S is amplified by the driver circuit 32B, and is output to the waveform information detector 4B as the response signal 3S. Therefore, the response signal 3S can be stably output with a desired amplitude. As a result, a response signal 3S in which the amplitude information of the current flowing through the impedance of the subject 10 is converted into a voltage is obtained.

FIG. 21 is a signal waveform diagram showing an operation of the impedance detection apparatus according to the eleventh embodiment of the present invention.
In the trapezoidal wave generation circuit 22C of the supply signal generation unit 2, a supply signal 2S composed of a triangular wave is generated with a potential VA that is substantially in the middle of the circuit operation power supply potential VDD and the ground potential (0V = GND) as a center voltage.

  Here, as described with reference to FIG. 13, when the impedance of the subject 10 has a capacitance component and a resistance component, when the supply signal 2 </ b> S consisting of a trapezoidal wave is input to the subject 10, the current flowing through the impedance becomes a trapezoidal wave. Is a waveform obtained by synthesizing the differential response and the original trapezoidal wave. Accordingly, the response signal 3S becomes a signal waveform having a voltage deviation corresponding to the differential response in such a composite waveform, a trapezoidal wave rising period, a flat period, and a falling period.

When the application signal 1S is applied to the subject 10, the voltage of the application signal 1S drops due to the current flowing through the subject 10, and the amplitude thereof also changes. This amplitude change becomes the amplitude information of the current information signal 31S.
The differential amplifier 32A adjusts and outputs the drive signal 32S so that the supply signal 2S and the current information signal 31S are the same. As a result, with respect to the waveform of the supply signal 2S having the potential VA as the center voltage, the drive signal 32S has a waveform increased by a voltage that compensates for the voltage drop, that is, a waveform having the offset correction potential VA1 as the center voltage.

At this time, the amplitude of the drive signal 32S also changes based on the amplitude information of the current information signal 31S. The drive signal 32S including this amplitude change is amplified by the driver circuit 32B and then output as the response signal 3S. Therefore, the response signal 3S is a signal including an offset potential due to the impedance of the subject 10.
The peak voltage detection circuit 44 detects the maximum voltage value or the minimum voltage value of the response signal 3S and outputs it as the peak voltage value 44S. The center voltage detection circuit 45 detects the center voltage VA1 of the response signal 3S and outputs it as a center voltage value 45S.

  The voltage comparison circuit 46 compares the peak voltage value 44S and the center voltage value 45S, and outputs a detection signal 4BS having a signal waveform having a voltage value corresponding to the difference. At this time, since the voltage comparison circuit 46 compares the peak voltage value 44S with the center voltage value 45S, only the amplitude value not including the offset of the response signal 3S is detected. Therefore, a signal including waveform information (amplitude information) corresponding to the amplitude difference between the supply signal 2S and the applied signal 1S, that is, the resistance component of the impedance of the subject 10, is obtained as the detection signal 4BS.

  As described above, in this embodiment, the drive circuit 31 of the response signal generation unit 3 is configured by the driver circuit 31A and the waveform shaping circuit 22 is configured by the trapezoidal wave generation circuit 22C in the third embodiment. Therefore, since the current-voltage conversion circuit 32 is composed of the differential amplifier 32A, the information indicating the resistance component of the impedance inherent in the subject 10 can be obtained with a very simple circuit regardless of the magnitude of the impedance of the subject. It becomes possible to detect stably with a wide input dynamic range. Further, since the trapezoidal waveform is used as the supply signal 2S, it is possible to generate a waveform with less high-frequency components and close to a sine wave as compared with the triangular wave, and the impedance of the subject 10 can be detected more accurately.

In the present embodiment, the case where the waveform information detection unit 4B is configured by the peak voltage detection circuit 44, the center voltage detection circuit 45, and the voltage comparison circuit 46 is shown as an example. However, the present invention is not limited to this. The waveform information detector 4B may be configured by other circuits.
In the present embodiment, the case where the response signal generation unit 3 is configured by the driver circuit 31A, the differential amplifier 32A, and the driver circuit 32B has been described as an example. However, the present invention is not limited to this. The response signal generation unit 3 may be configured by other circuits such as the circuit 31A and the differential amplifier 32A.

  In the present embodiment, the case where the response signal 3S from the response signal generation unit 3 is directly input to the waveform information detection unit 4B has been described as an example, but the response signal generation unit 3 and the waveform information detection unit 4B A low-pass filter may be provided. Thereby, the high frequency component contained in the response signal 3S which consists of a trapezoidal wave can be removed, and the detection accuracy of the waveform information in the waveform information detection part 4B can be improved.

[Twelfth embodiment]
Next, with reference to FIG. 22, the biometric recognition apparatus and fingerprint recognition apparatus concerning the 12th Embodiment of this invention are demonstrated. FIG. 22 is a block diagram showing configurations of the biometric recognition apparatus and the fingerprint recognition apparatus according to the twelfth embodiment of the present invention.

The biological recognition device 110 is a device that recognizes whether or not the subject 10 is a living body, and includes an impedance detection device 100 and a biological recognition unit 101.
The impedance detection apparatus 100 includes any one of the impedance detection apparatuses described in the first to eleventh embodiments of the present invention, applies a predetermined application signal to the subject 10, and the subject 10 The impedance information 1Z of the subject is detected based on the current flowing through the sensor, and a detection signal 4S having waveform information corresponding to the impedance is output.

The living body recognition unit 101 determines whether or not the waveform information of the detection signal 4S from the impedance detection device 100 is within the reference range indicating the legitimate living body impedance characteristics, thereby determining whether or not the living body is the living body with respect to the subject 10. It has a function of performing recognition determination and outputting a biometric recognition result 110S for the subject 10. The biometric authentication unit 102 may be configured from a dedicated circuit or may be configured using an arithmetic processing unit such as a CPU.
As described above, since any one of the impedance detection devices described in the embodiments of the present invention is used as the impedance detection device 100, the impedance of the subject can be detected with high accuracy, and the living body recognition accuracy for the subject is improved. be able to.

The fingerprint recognition device 120 is a device that authenticates a user based on fingerprint data 1F detected from a subject 10 made of a finger. The biometric recognition device 110, the fingerprint detection device 111, the fingerprint authentication unit 112, and the authentication The determination unit 113 is configured.
As described above, the living body recognition apparatus 110 has a function of recognizing whether or not the subject 10 is a living body using any one of the impedance detection apparatuses described in the first to eleventh embodiments of the present invention. ing.

The fingerprint detection device 111 has a function of detecting fingerprint data 111S corresponding to the surface shape information 1P indicating the fingerprint irregularities from the subject 10.
The fingerprint authentication unit 112 compares the fingerprint data 111S output from the fingerprint detection device 111 with verification data indicating a legitimate fingerprint registered in advance, and performs user fingerprint authentication based on the verification result have.
The authentication determination unit 113 determines whether the user has succeeded in fingerprint authentication based on the biometric recognition result 110S output from the biometric recognition device 110 and the fingerprint authentication result 112S output from the fingerprint authentication unit 112, and outputs the determination result 120S. It has a function to do.
The fingerprint detection device 111, the fingerprint authentication unit 112, and the authentication determination unit 113 may be configured by a dedicated circuit or may be configured by using an arithmetic processing unit such as a CPU.

  As described above, since the biometric recognition device 110 using any one of the impedance detection devices described in the embodiments of the present invention is used as the impedance detection device 100, the impedance of the subject can be detected with high accuracy, The biometric recognition accuracy for the specimen can be increased. Accordingly, fingerprint authentication of the user can be performed with high accuracy. If such a fingerprint authentication device is installed in a personal recognition system, the security performance of the entire system can be improved.

[Extended embodiment]
In each of the above embodiments, the case where the waveform information detection unit 4 (4A, 4B) detects either the phase difference or the amplitude has been described as an example, but both the phase difference and the amplitude are detected in parallel. Then, based on the respective detection signals, the living body recognition unit 5 may determine whether or not the subject 10 is a living body. This makes it extremely difficult to select the material or material of the subject and individually adjust the resistance component and the reactance component, and high security is obtained against fraud recognition by an artificial finger.

It is a block diagram which shows the structure of the impedance detection apparatus concerning the 1st Embodiment of this invention. It is a block diagram which shows the structure of the impedance detection apparatus concerning the 2nd Embodiment of this invention. It is a block diagram which shows the structure of the impedance detection apparatus concerning the 3rd Embodiment of this invention. It is a block diagram which shows the structure of the impedance detection apparatus concerning the 4th Embodiment of this invention. It is a signal waveform diagram which shows operation | movement of the impedance detection apparatus concerning the 4th Embodiment of this invention. It is a block diagram which shows the structure of the impedance detection apparatus concerning the 5th Embodiment of this invention. It is a signal waveform diagram which shows operation | movement of the impedance detection apparatus concerning the 5th Embodiment of this invention. It is a block diagram which shows the structure of the impedance detection apparatus concerning the 6th Embodiment of this invention. It is a signal waveform diagram which shows operation | movement of the impedance detection apparatus concerning the 6th Embodiment of this invention. It is a block diagram which shows the structure of the impedance detection apparatus concerning the 7th Embodiment of this invention. It is a signal waveform diagram which shows operation | movement of the impedance detection apparatus concerning the 7th Embodiment of this invention. It is a block diagram which shows the structure of the impedance detection apparatus concerning the 8th Embodiment of this invention. It is a signal waveform diagram which shows operation | movement of the impedance detection apparatus concerning the 8th Embodiment of this invention. It is another signal waveform diagram which shows operation | movement of the impedance detection apparatus concerning the 8th Embodiment of this invention. It is a block diagram which shows the structure of the impedance detection apparatus concerning the 9th Embodiment of this invention. It is a signal waveform diagram which shows operation | movement of the impedance detection apparatus concerning the 9th Embodiment of this invention. It is a block diagram which shows the structure of the impedance detection apparatus concerning the 10th Embodiment of this invention. It is a signal waveform diagram which shows operation | movement of the impedance detection apparatus concerning the 10th Embodiment of this invention. It is another signal waveform diagram which shows operation | movement of the impedance detection apparatus concerning the 10th Embodiment of this invention. It is a block diagram which shows the structure of the impedance detection apparatus concerning the 11th Embodiment of this invention. It is a signal waveform diagram which shows operation | movement of the impedance detection apparatus concerning the 11th Embodiment of this invention. It is a block diagram which shows the structure of the biometric recognition apparatus and fingerprint recognition apparatus concerning the 12th Embodiment of this invention. It is a block diagram which shows the structure of the conventional biometric recognition apparatus. It is a block diagram which shows the specific structure of the conventional impedance detection apparatus which detects a phase difference. It is an example of a signal waveform in each part of the impedance detection apparatus of FIG. It is the block diagram which showed the specific structure of the conventional impedance detection apparatus which detects an amplitude. It is an example of a signal waveform in each part of the impedance detection apparatus of FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 100 ... Impedance detection apparatus, 1S ... Applied signal, 1 ... Detection element, 11, 12 ... Detection electrode, 2 ... Supply signal generation part, 21 ... Frequency generation circuit, 21S ... Clock signal, 22 ... Waveform shaping circuit, 22A ... Sine Wave generation circuit, 22B ... Triangular wave generation circuit, 22C ... Trapezoid wave generation circuit, 2S ... Supply signal, 3 ... Response signal generation unit, 3S ... Response signal, 31 ... Drive circuit, 31A ... Driver circuit, 31S ... Current information signal, 32 ... current-voltage conversion circuit, 32A ... differential amplifier, 32B ... driver circuit, 32S ... drive signal, 4, 4A, 4B ... waveform information detector, 4S, 4AS, 4BS ... detection signal, 41 ... offset correction circuit, 42 ... reference signal generation circuit, 43 ... phase comparison circuit, 44 ... peak voltage detection circuit, 44S ... peak voltage value, 45 ... center voltage detection circuit, 45S ... center voltage value, 4 DESCRIPTION OF SYMBOLS Voltage comparison circuit, Zf ... Impedance, 101 ... Biometric recognition unit, 110 ... Biometric recognition device, 110S ... Biometric recognition result, 1P ... Surface shape information, 1Z ... Impedance information, 111 ... Fingerprint detection device, 111S ... Fingerprint data, 112 ... fingerprint authentication unit, 112S ... fingerprint recognition result, 113 ... recognition judgment unit, 120 ... fingerprint recognition device, 120S ... judgment result.

Claims (9)

A sensing element in electrical contact with the subject;
A supply signal generator for generating an alternating supply signal;
An AC that is connected between the supply signal generation unit and the detection element, applies an application signal corresponding to the supply signal to the subject, and changes according to a current flowing through the subject in accordance with the application signal. A response signal generator for generating and outputting a response signal of
A waveform information detection unit that detects waveform information indicating the characteristics of the waveform of the response signal from the response signal, and outputs a detection signal indicating the impedance of the subject based on the waveform information; and
The response signal generator is
A drive circuit that applies an application signal corresponding to a predetermined drive signal to the subject via the detection element, and detects and outputs a current information signal corresponding to a current flowing through the subject in accordance with the application signal;
The drive signal for obtaining the applied signal equal to the supply signal based on the current information signal is output to the drive circuit, and the current flowing through the subject based on the current information signal is a voltage signal. An impedance detection device comprising: a current-voltage conversion circuit that converts the signal into a signal and outputs the signal to the waveform information detection unit. The impedance detection apparatus according to claim 1,
The drive circuit includes a first driver circuit that amplifies the drive signal input to an input terminal and outputs the applied signal and the current information signal from an output terminal;
In the current-voltage conversion circuit, the supply signal is input to a first input terminal, and the current information signal is input to a second input terminal having a polarity opposite to that of the first input terminal so as to be negative feedback. An impedance detection apparatus comprising a differential amplifier that outputs the drive signal and the response signal from an output terminal. The impedance detection apparatus according to claim 1,
The drive circuit includes a first driver circuit that receives the drive signal at an input terminal and outputs the applied signal and the current information signal from an output terminal;
In the current-voltage conversion circuit, the supply signal is input to a first input terminal, and the current information signal is input to a second input terminal having a polarity opposite to that of the first input terminal so as to be negative feedback. An impedance circuit comprising: a differential amplifier that outputs the drive signal from an output terminal; and a second driver circuit that amplifies the drive signal input to an input terminal and outputs the response signal from an output terminal. Detection device. The impedance detection apparatus according to claim 1,
The detection element has a first detection electrode in electrical contact with the subject and connected to a predetermined common potential, and a second detection electrode in electrical contact with the subject,
The response signal generation unit applies the applied signal to the second detection electrode by the drive circuit, and changes the phase of the current flowing through the second detection electrode according to the impedance of the subject. Detecting the current information signal including, and outputting the response signal including the phase change to the waveform information detection unit based on the current information signal by the current-voltage conversion circuit,
The said waveform information detection part compares the phase of a predetermined reference signal and the said response signal, and detects the said phase difference as waveform information of the said response signal, The impedance detection apparatus characterized by the above-mentioned. The impedance detection apparatus according to claim 1,
The detection element has a first detection electrode in electrical contact with the subject and connected to a predetermined common potential, and a second detection electrode in electrical contact with the subject,
The response signal generation unit applies the applied signal to the second detection electrode by the drive circuit, and changes the amplitude of the current flowing through the second detection electrode according to the impedance of the subject. The current information signal is detected, and the current-voltage conversion circuit outputs the response signal including the amplitude change to the waveform information detection unit based on the current information signal.
The said waveform information detection part detects the amplitude of the said response signal as waveform information of the said response signal, The impedance detection apparatus characterized by the above-mentioned. The impedance detection apparatus according to claim 1,
The supply signal generation unit generates a clock signal having a predetermined frequency and generates one of a sine wave, a triangular wave, and a trapezoidal wave synchronized with the clock signal based on the clock signal. And a waveform shaping circuit that outputs the supply signal. An application signal corresponding to an AC supply signal is applied to a subject that is in electrical contact with the detection element, and a response signal that varies depending on the current flowing through the subject is generated along with the application signal. A response signal generation step to output;
A waveform information detecting step for detecting waveform information indicating the characteristics of the waveform of the response signal from the response signal, and outputting a detection signal indicating the impedance of the subject based on the waveform information; and
The response signal generation step includes:
A driving step of applying an application signal corresponding to a predetermined drive signal to the subject via the detection element, and detecting and outputting a current information signal corresponding to a current flowing through the subject in accordance with the application signal;
The drive signal for obtaining the applied signal equal to the supply signal based on the current information signal is output to the drive step, and the current flowing through the subject based on the current information signal is a voltage signal. An impedance detection method comprising: a current-voltage conversion step that converts the signal into a signal and outputs the signal to the waveform information detection step. The impedance detection apparatus according to claim 1, which outputs a detection signal corresponding to the impedance of the subject;
A living body recognition device comprising: a living body recognition unit that determines whether or not the subject is a living body based on a detection signal output from the impedance detection device. The living body recognition apparatus according to claim 8, which determines whether or not the subject is a living body based on a detection signal corresponding to the impedance of the subject;
A fingerprint detection device for detecting fingerprint data indicating irregularities of the fingerprint from the subject;
A fingerprint authentication unit that compares the fingerprint data with previously registered verification data, and performs fingerprint authentication of the user based on the verification result;
An authentication determination unit that determines success or failure of fingerprint authentication of the user based on a biometric determination result output from the biometric recognition device and a fingerprint authentication result output from the fingerprint authentication unit. apparatus.

Images