JP2008073072A - Impedance detector, impedance detection method, living body recognition apparatus and fingerprint authentication apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To highly precisely detect an impedance of a subject by suppressing the deterioration of a detection precision due to a process fluctuation or the like with a simple circuit constitution. <P>SOLUTION: A waveform information detection section 4 is provided with a reply signal conversion circuit 41 and a digital phase comparison circuit 43, the reply signal conversion circuit 41 converts a reply signal 3S from a reply signal generation section 3 into a comparison object signal 41S consisting of a digital signal indicating a voltage change of the reply signal 3S and outputs it, the digital phase comparison circuit 43 compares the phases of a rectangular-wave digital criterion signal 42S synchronized with a feed signal 2S from a feed signal generation section 2 and the comparison object signal 41S to detect a phase difference between the comparison object signal 41S and the feed signal 2S as waveform information, and generates a detection signal 4S consisting of the digital signal having the pulse width according to the phase difference. <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. 24 is a block diagram showing a configuration of a conventional biometric recognition apparatus. This biological recognition apparatus includes a detection element 1, a supply signal generation unit 2, a response signal generation unit 3, a waveform information detection unit 4X, and a biological recognition unit 5 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 detector 4X.

The waveform information detection unit 4X 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 4X, 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. The phase difference or amplitude of the response signal 3S is detected by the waveform information detection unit 4X, and a detection signal 4S including information indicating these detection results 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 4X 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. 25, 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. 25 is a block diagram showing a specific configuration of a conventional impedance detection apparatus for detecting a phase difference, and the same or equivalent parts as those in FIG.

In FIG. 25, 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 4X is provided with an offset correction circuit 41X, a reference signal generation circuit 42X, and a phase comparison circuit 43X. 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 having a predetermined frequency, and the waveform shaping circuit 22 generates and outputs a supply signal 2 </ b> S composed of a sine wave or the like based on the clock signal from the frequency generation circuit 21. .

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

The operation of the impedance detection apparatus of FIG. 25 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 and amplitude of the current flowing through the subject 10 changes according to the impedance inherent to the subject 10, and these changes are output as a response signal 3S converted into a voltage.

  FIG. 26 is a signal waveform example 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 potential 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 41X is level-shifted so that the center voltage of the response signal 3S matches the reference potential VB used in the phase comparison circuit 43X, and outputs the compared signal 41XS with the offset potential corrected. The phase comparison circuit 43X outputs a waveform having a pulse width corresponding to the phase difference between the signal to be compared 41XS and the reference signal 42XS as the detection signal 4S. This pulse width includes waveform information as a phase difference.

International Publication No. 05/016146 Pamphlet

  However, in such a conventional technique, when detecting the phase difference according to the impedance of the subject, the phase of the comparison signal made of an analog signal and the phase of the reference signal are compared. This causes a decrease in detection accuracy due to fluctuations, and there is a problem in that an impedance detection apparatus that can detect the impedance of a subject with high accuracy with a simple circuit configuration cannot be realized.

That is, in the prior art, when detecting a phase difference according to the impedance of the subject in the waveform information detection unit, an analog circuit that corrects and detects an analog potential is used to compare the phase of the signal to be compared and the reference signal made up of analog signals. Are comparing. For this reason, when trying to increase the detection accuracy of the impedance of the subject, the analog circuit becomes complicated and the circuit scale increases.
In addition, when an analog circuit is configured by an integrated circuit using semiconductor process technology, its characteristics fluctuate due to factors such as process fluctuations. Therefore, in an analog circuit that corrects and detects an analog potential, waveform information of phase difference and amplitude Detection accuracy is reduced.

  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. 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 problems, and with a simple circuit configuration, it is possible to suppress deterioration in detection accuracy due to factors such as process fluctuations, and to detect an impedance of a subject with high accuracy and An object of the present invention is to provide an impedance detection method, a biometric recognition device that can obtain high recognition accuracy, and a fingerprint authentication device that can obtain 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 Response signal generation connected to the element to apply an applied signal corresponding to the supply signal to the subject, and to generate and output an alternating response signal that changes depending on the current flowing through the subject in accordance with the applied signal A waveform information detection unit that detects waveform information indicating characteristics of the waveform of the response signal from the response signal, and generates and outputs a detection signal according to the impedance of the subject based on the waveform information, The waveform information detection unit includes a response signal conversion circuit that converts the response signal into a signal to be compared that is a digital signal indicating a voltage change of the response signal, and a rectangular wave digital base synchronized with the supply signal. By comparing the phase of the signal and the signal to be compared, the phase difference between the signal to be compared and the supply signal is detected as waveform information, and the first detection signal composed of a digital signal having a pulse width corresponding to the phase difference is detected. And a digital phase comparison circuit that generates and outputs a detection signal.

  At this time, the supply signal generation unit is supplied with a frequency generation circuit that generates and outputs a clock signal having a predetermined frequency, and a sine wave, a triangular wave, or a trapezoidal wave synchronized with the clock signal based on the clock signal. A waveform shaping circuit that generates and outputs as a supply signal may be provided.

  The response signal conversion circuit may be composed of a limiter amplifier that amplifies the response signal to convert it into a digital signal and outputs it as a signal to be compared. You may comprise from the threshold circuit which converts into a signal and outputs as a signal to be compared.

  Further, the digital phase comparison circuit may be composed of an exclusive OR circuit that outputs an exclusive OR of the signal to be compared and the digital reference signal as a detection signal.

  The waveform information detection unit may use the clock signal as a digital reference signal.

  Further, the waveform information detection unit may be provided with a digital reference signal generation circuit including a threshold circuit that converts a supply signal into a digital signal by comparing it with a predetermined threshold voltage and outputs the digital signal as a digital reference signal.

  In addition, the waveform information detector converts the reference signal to a digital signal by comparing the reference signal with a predetermined threshold voltage and outputs the digital signal as a digital reference signal. A digital reference signal generation circuit comprising a threshold circuit may be provided.

  Further, the waveform information detection unit detects a voltage change of the response signal as the waveform information, and based on the voltage change, the response signal is a second detection signal composed of a digital signal having a pulse width corresponding to the magnitude of the response signal. There may be further provided a pulse conversion circuit which converts the signal into a detection signal and outputs it as a detection signal.

  The pulse conversion circuit may be configured by a threshold circuit that compares the response signal with a predetermined threshold voltage and outputs a digital signal corresponding to the comparison result as the second detection signal.

  In addition, the threshold signal has a pulse width corresponding to the voltage change of the response signal that changes according to the impedance of the subject. 2 may be output as a detection signal.

  Further, the waveform information detection unit may be further provided with a low-pass filter that removes high-frequency components contained in the response signal, and the response signal conversion circuit may convert the response signal output from the low-pass filter into a signal to be compared. .

  In addition, the first detection electrode that is in electrical contact with the subject and connected to a predetermined common potential is connected to the detection element, and the applied signal from the response signal generation unit is subjected to electrical contact with the subject. A second detection electrode applied to the specimen may be provided.

  The response signal generation unit includes a resistance element connected between the supply signal generation unit and the detection element, and a current-voltage conversion circuit that outputs a response signal from a connection node between the resistance element and the detection element. It may be configured.

  The response signal generation unit includes a resistance element connected between the supply signal generation unit and the detection element, and a differential amplifier that generates and outputs a response signal by differentially amplifying the voltage across the resistance element. You may comprise from the current-voltage conversion circuit which has.

  Alternatively, the response signal generation unit includes a first resistance element having one end connected to the supply signal generation unit, and a second resistance element connected between the other end of the first resistance element and the detection element. A current-voltage conversion circuit having a differential amplifier that generates and outputs a response signal by differentially amplifying the voltage across the second resistor element may be used.

  In addition, the impedance detection method according to the present invention applies an applied signal corresponding to an AC supply signal to a subject that is in electrical contact with the detection element, and a current that flows through the subject in accordance with the applied signal. A response signal generating step for generating and outputting a response signal that varies depending on the waveform, and detecting waveform information indicating the characteristics of the waveform of the response signal from the response signal, and detecting signals corresponding to the impedance of the subject based on the waveform information A waveform information detection step for generating and outputting the response information, wherein the waveform information detection step converts the response signal into a signal to be compared consisting of a digital signal indicating a voltage change of the response signal, and outputs a response signal conversion step; By comparing the phase of the digital reference signal with the rectangular wave synchronized with the supply signal and the phase of the signal to be compared, The detected, and a digital phase step of outputting as a first generation detecting signal a detection signal composed of a digital signal having a pulse width corresponding to the phase difference.

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

  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, the response signal conversion circuit of the waveform information detection unit converts the response signal from the response signal generation unit into a signal to be compared that is composed of a digital signal indicating a voltage change of the response signal, and outputs the waveform information. The phase of the digital reference signal of the rectangular wave synchronized with the supply signal from the supply signal generation unit and the signal to be compared are compared by the digital phase comparison circuit of the detection unit, and the phase difference between the signal to be compared and the supply signal is obtained as waveform information. Detection is performed, and a detection signal composed of a digital signal having a pulse width corresponding to the waveform information is generated and output.
Thereby, without complicating the analog circuit, it is possible to suppress deterioration in detection accuracy due to factors such as process fluctuations with a simple circuit configuration, and to detect the impedance of the subject with high accuracy.

  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, the waveform information detection unit 4 is provided with a response signal conversion circuit 41 and a digital phase comparison circuit 43, and the response signal conversion circuit 41 converts the response signal 3S from the response signal generation unit 3 into the response signal 3S. The signal is converted into a signal to be compared 41S composed of a digital signal indicating a voltage change of the signal, and is compared with the digital reference signal 42S of a rectangular wave synchronized with the supply signal 2S from the supply signal generator 2 by the digital phase comparison circuit 43. By comparing the phase with the signal 41S, a phase difference between the signal to be compared 41S and the supply signal 2S is detected as waveform information, and a detection signal (first detection signal) having a pulse width corresponding to the phase difference is detected. Signal) 4S is generated and output.

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 is in electrical contact with the subject 10 through the detection electrodes 11 and 12 and has a function of connecting the reactance component and the resistance component of the impedance of the subject 10 to the response signal generation unit 3. .

  The detection electrode (first detection electrode) 11 is connected to a common potential such as a ground potential, and the detection electrode (second detection electrode) 12 is connected to the output stage of the current-voltage conversion circuit 32 of the response signal generator 3. Has been. 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. 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 includes a frequency generation circuit 21 and a waveform shaping circuit 22, and 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 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.

  The response signal generation unit 3 includes a current-voltage conversion circuit 32, applies an application signal 1S corresponding to the supply signal 2S from the supply signal generation unit 2 to the detection element 1, and detects the detection element along with the application signal 1S. 1 has a function of generating a response signal 3S that changes in accordance with the output impedance of 1, that is, the capacitance component and resistance component of the impedance of the subject 10 and outputting the response signal 3S to the waveform information detection unit 4. The current-voltage conversion circuit 32 has a function of converting a current flowing through the subject 10 into a response signal 3S composed of a voltage signal based on the applied signal 1S and outputting the response signal 3S to the waveform information detection unit 4.

  The waveform information detection unit 4 includes a response signal conversion circuit 41, a digital reference signal generation circuit 42, and a digital phase comparison circuit 43. The waveform information detection unit 4 converts the response signal 3S from the response signal generation unit 3 into the impedance of the subject 10. A function for detecting the phase difference between the response signal 3S and the supply signal 2S and a detection signal 4S indicating the impedance of the subject 10 based on the waveform information consisting of these phase differences are output as waveform information indicating the characteristics of the corresponding waveform. It has the function to do.

  The response signal conversion circuit 41 has a function of converting the response signal 3S from the response signal generation unit 3 into a signal to be compared 41S composed of a digital signal indicating a voltage change of the response signal 3S and outputting it. The digital reference signal generation circuit 42 has a function of generating a rectangular digital reference signal 42S synchronized with the supply signal 2S from the supply signal generator 2. The digital phase comparison circuit 43 compares the phase of the signal to be compared 41S from the response signal conversion circuit 41 with the phase of the digital reference signal 42S from the digital reference signal generation circuit 42 by digital signal processing. It has a function of detecting a phase difference between 41S and the supply signal 2S, and generating and outputting a detection signal (first detection signal) 4S composed of a digital signal having a pulse width corresponding to the phase difference.

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 generation unit 3 is applied to the detection element 1 as the application signal 1S via the current-voltage conversion circuit 32.
The current-voltage conversion circuit 32 applies an applied signal 1S to the impedance of the subject 10 via the detection element 1 to cause the current to flow to the subject 10 and at the same time converts the current flowing to the subject 10 into a voltage and responds. Output as signal 3S.

The waveform information detector 4 detects the phase information included in the response signal 3S and outputs a detection signal 4S including this phase information.
At this time, the response signal conversion circuit 41 of the waveform information detection unit 4 converts the response signal 3S from the response signal generation unit 3 into a signal to be compared 41S composed of a digital signal indicating a voltage change of the response signal 3S and outputs it. . The digital phase comparison circuit 43 compares the phase of the signal to be compared 41S from the response signal conversion circuit 41 with the phase of the digital reference signal 42S from the digital reference signal generation circuit 42 by digital signal processing. A phase difference between 41S and the supply signal 2S is detected, and a detection signal 4S composed of a digital signal having a pulse width corresponding to the phase difference is generated and output.

  Thus, in the present embodiment, the waveform information detection unit 4 is provided with the response signal conversion circuit 41 and the digital phase comparison circuit 43, and the response signal conversion circuit 41 receives the response signal 3S from the response signal generation unit 3. A digital reference signal of a rectangular wave synchronized with the supply signal 2S from the supply signal generation unit 2 by the digital phase comparison circuit 43 after being converted into a signal to be compared 41S composed of a digital signal indicating the voltage change of the response signal 3S. By comparing the phase of 42S and the signal to be compared 41S, a phase difference between the signal to be compared 41S and the supply signal 2S is detected as waveform information, and a detection signal 4S comprising a digital signal having a pulse width corresponding to the phase difference is detected. Because the analog circuit is generated and output, the degradation of detection accuracy due to factors such as process fluctuations can be suppressed with a simple circuit configuration without complicating the analog circuit. Can, it is possible to detect the impedance of the object with high precision.

In the present embodiment, the supply signal generation unit generates a clock signal having a predetermined frequency and outputs it, and a sine wave, a triangular wave, or a trapezoidal wave synchronized with the clock signal based on the clock signal. Since it comprises the waveform shaping circuit that generates any one and outputs it as a supply signal, it is possible to generate a supply signal having an arbitrary waveform with a predetermined frequency with a very simple circuit configuration.
Further, in the present embodiment, the detection element is electrically contacted with the subject and connected to a predetermined common potential, and the response signal generator is electrically contacted with the subject. Since the second detection electrode for applying the signal applied to the subject is applied to the subject, a current can be applied to the subject with a very simple configuration, and a current change corresponding to the impedance of the subject can be detected.

[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 a specific configuration example of the impedance detection apparatus according to the first embodiment, in the waveform information detection section 4, the response signal conversion circuit 41 is configured by a limiter amplifier 41A, and a digital reference signal generation circuit 42 is provided. Will be described as comprising a reference signal generating circuit 42A and a threshold circuit 42B, and a digital phase comparison circuit 43 comprising an XOR circuit. Here, a case where a sine wave is used as the supply signal 2S will be described as an example.

  In FIG. 2, a limiter amplifier 41A of the waveform information detection unit 4 is an amplifier having a sufficient amplification factor, and the response signal 3S composed of an analog voltage signal is set to a high level (power supply potential VDD) with a peak value based on the center voltage. ) And Low level (ground potential GND), and has a function of converting to a full amplitude digital signal and outputting it as a signal to be compared 41S. The limiter amplifier does not require a unique configuration in the present embodiment, and a general known circuit may be used.

  The digital reference signal generation circuit 42 includes a reference signal generation circuit 42A and a threshold circuit 42B. The reference signal generation circuit 42A has a function of outputting a reference signal composed of, for example, a sine wave synchronized with the supply signal 2S. The threshold circuit 42B is realized by a buffer circuit combined with an inverter circuit (inverted logic circuit) or the like, and converts the reference signal from the reference signal generation circuit 42A into a digital signal by comparing it with a predetermined threshold voltage Vt1. And has a function of outputting as a digital reference signal 42S. The threshold circuit is not required to have a unique configuration in this embodiment, and a generally known circuit may be used.

  The digital phase comparison circuit 43 has an XOR circuit 43A. The XOR circuit 43A calculates the exclusive OR of the signal 41S to be compared from the response signal conversion circuit 41 and the digital reference signal 42S from the digital reference signal generation circuit 42, thereby digitally processing the phases of both. It has a function to compare. As a result, the XOR circuit 43A detects the phase difference between the signal to be compared 41S and the supply signal 2S as waveform information, and the detection signal 4S is generated and output based on the phase difference.

  The current-voltage conversion circuit 31 of the response signal generation unit 3 includes a resistance element (first resistance element) Rs connected between the supply signal generation unit 2 and the detection element 1, and the resistance element Rs is interposed therebetween. Based on the function of applying the supply signal 2S from the supply signal generator 2 to the detection element 1 as the application signal 1S and the current change of the applied signal 1S that changes depending on the impedance of the detection element 1, that is, the impedance of the subject 10. The phase information of the current flowing through the subject 10 is converted into a voltage signal and output as a response signal 3S.

The supply signal generation unit 2 is provided with a sine wave generation circuit 22 </ b> A as the waveform shaping circuit 22. The sine wave generation circuit 22A is a specific example of the waveform shaping circuit 22 in FIG. 1, 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.
In the impedance detection apparatus according to the present embodiment, configurations other than the waveform information detection unit 4, the current-voltage conversion circuit 31, and the sine wave generation circuit 22A are the same as those in the first embodiment, and here The detailed description in is omitted.

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 AC sine wave supply signal 2S output from the waveform shaping circuit 22 and input to the response signal generation unit 3 is applied to the detection element 1 as the application signal 1S via the current-voltage conversion circuit 31 including the resistance element Rs. The The current-voltage conversion circuit 31 converts the phase information of the current flowing through the subject 10 into a voltage signal based on the current change of the applied signal 1S, and outputs it as a response signal 3S.

  The waveform information detection unit 4 amplifies the response signal 3S with reference to the center voltage by the limiter amplifier 41A, thereby converting the response signal 3S into a signal to be compared 41S composed of a digital signal indicating the voltage change of the response signal 3S. The comparison circuit 43 compares the phase of the signal to be compared 41S from the response signal conversion circuit 41 and the phase of the digital reference signal 42S from the digital reference signal generation circuit 42 by digital signal processing, thereby comparing the signal to be compared 41S as waveform information. The phase difference of the supply signal 2S is detected, and a detection signal 4S composed of a digital signal having a pulse width corresponding to the phase difference is generated and output.

FIG. 3 is a signal waveform diagram showing an operation of the impedance detection device according to the second exemplary embodiment of the present invention. Here, a case where the supply signal 2S is a sine wave will be described as an example.
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 central voltage VA, which is a substantially intermediate potential VA between the circuit operation power supply potential VDD and the ground potential (0V = GND). It is output to the response signal generator 3.

When the supply signal 2S is applied to the subject 10 via the resistance element Rs of the response signal generation unit 3, the phase and amplitude of the current flowing through the subject 10 become impedance inherent to the subject 10. Will change accordingly. In the response signal generator 3, this current change is converted into a voltage signal and output as a response signal 3S.
The response signal 3S is a signal including an offset potential 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.

The response signal 3S including the offset potential is amplified by the limiter amplifier 41A of the response signal conversion circuit 41 and converted into a signal to be compared 41S formed of a rectangular wave digital signal not including the offset potential.
Further, the reference signal from the reference signal generating circuit 42A is compared with the threshold voltage Vt1 which is the center voltage of the reference signal by the threshold circuit 42B and converted into the digital reference signal 42S.
The signal to be compared 41S and the digital reference signal 42S are input to the XOR circuit 43A of the digital phase comparison circuit 43 to detect a phase difference, and a detection signal 4S having a signal waveform having a pulse width corresponding to the phase difference is output. The

  Thus, in this embodiment, the response signal conversion circuit 41 is realized by the limiter amplifier 41A that converts the response signal 3S into a digital signal by amplifying the response signal 3S and outputs it as the signal to be compared 41S. The response signal 3S of an analog signal having an amplitude corresponding to the above and including a DC offset potential can be converted to a digital signal to be compared 41S with a very simple circuit configuration.

  Further, in this embodiment, the digital phase comparison circuit 43 is realized by the XOR circuit 43A that outputs the exclusive OR of the signal to be compared 41S and the digital reference signal 42S as the detection signal 4S. The detection signal 4S having a pulse width corresponding to the reactance component can be detected and output by an extremely simple circuit.

In the present embodiment, the case where the digital reference signal generation circuit 42 generates the digital reference signal 42S separately from the supply signal 2S has been described as an example. However, the digital reference signal 42S is generated based on the supply signal 2S. May be.
FIG. 4 is a block diagram showing another configuration of the impedance detection device according to the second exemplary embodiment of the present invention. Compared with FIG. 2, the digital reference signal generation circuit 42 includes a threshold circuit 42C. It is different in the configuration.

The threshold circuit 42C of FIG. 4 is realized by a buffer circuit combined with an inverter circuit (inverted logic circuit) or the like, and by comparing the supply signal 2S from the supply signal generator 2 with a predetermined threshold voltage Vt1. It has a function of converting it into a digital signal and outputting it as a digital reference signal 42S. The threshold circuit is not required to have a unique configuration in this embodiment, and a generally known circuit may be used.
As a result, in the digital reference signal generation circuit 42, it is possible to omit the highly accurate reference signal generation circuit 42A that generates a reference signal synchronized with the frequency generation circuit 21 of the supply signal generation unit 2, thereby simplifying the circuit and reducing the cost. Can be realized.

In addition, as shown in FIG. 5, a clock signal 21S output from the frequency generation circuit 21 of the supply signal generation unit 2 may be used as the digital reference signal 42S. FIG. 5 is a block diagram showing another configuration of the impedance detection device according to the second exemplary embodiment of the present invention, which is output from the frequency generation circuit 21 of the supply signal generation unit 2 as compared with FIG. The clock signal 21S is directly input to the digital phase comparison circuit 43 as the digital reference signal 42S.
Thereby, in the waveform information detection unit 4, the digital reference signal generation circuit 42 itself can be omitted, and the circuit can be simplified and the cost can be reduced.

[Third Embodiment]
Next, an impedance detection apparatus according to a third embodiment of the present invention will be described with reference to FIG. FIG. 6 is a block diagram showing a configuration of an impedance detection device according to the third exemplary embodiment of the present invention. The same or equivalent parts as those in FIG. 4 described above are denoted by the same reference numerals.

In the second embodiment, the case where the current-voltage conversion circuit 31 of the response signal generation unit 3 is configured by the resistance element Rs has been described as an example.
In the present embodiment, a case where the current-voltage conversion circuit 31 is configured by a resistance element Rs and a differential amplifier 31A will be described as an example.

In FIG. 6, the current-voltage conversion circuit 31 of the response signal generation unit 3 is provided with a resistance element (first resistance element) Rs and a differential amplifier 31A.
The resistance element Rs is a resistance element connected between the supply signal generation unit 2 and the detection element 1. The differential amplifier 31A has a positive input terminal connected to the output of the supply signal generation unit 2, a reverse polarity input terminal connected to the detection electrode 12, and an output terminal connected to the input of the waveform information detection unit 4A. This differential amplifier 31A has a function of differentially amplifying the supply signal 2S input to the positive input terminal and the applied signal 1S input to the reverse polarity input terminal and outputting the response signal 3S from the output terminal. is doing.

  In the impedance detection apparatus according to the present embodiment, the configuration other than the current-voltage conversion circuit 31 is the same as that in FIG. 4 of the second embodiment, and detailed description thereof is omitted here.

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 AC sine wave supply signal 2S input to the response signal generator 3 is applied to the detection element 1 as the application signal 1S via the resistance element Rs of the current-voltage conversion circuit 31. At this time, the current of the applied signal 1S changes according to the impedance of the subject 10, and the current change occurs at both ends of the resistance element Rs. The differential amplifier 31A differentially amplifies the potential difference between both ends of the resistance element Rs, thereby converting the phase information of the current flowing through the subject 10 into a voltage signal and outputting it as a response signal 3S.

  The waveform information detection unit 4 amplifies the response signal 3S with reference to the center voltage by the limiter amplifier 41A, thereby converting the response signal 3S into a signal to be compared 41S composed of a digital signal indicating the voltage change of the response signal 3S. The comparison circuit 43 compares the phase of the signal to be compared 41S from the response signal conversion circuit 41 and the phase of the digital reference signal 42S from the digital reference signal generation circuit 42 by digital signal processing, thereby comparing the signal to be compared 41S as waveform information. The phase difference of the supply signal 2S is detected, and a detection signal 4S composed of a digital signal having a pulse width corresponding to the phase difference is generated and output.

FIG. 7 is a signal waveform diagram showing the operation of the impedance detection device according to the third 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 central voltage VA, which is a substantially intermediate potential VA between the circuit operation power supply potential VDD and the ground potential (0V = GND). It is output to the response signal generator 3.

When the supply signal 2S is applied to the subject 10 via the resistance element Rs of the response signal generation unit 3, the phase and amplitude of the current flowing through the subject 10 become impedance inherent to the subject 10. Will change accordingly. In the response signal generation unit 3, these changes appearing in the resistance element Rs are amplified by the differential amplifier 31A, converted into a voltage signal, and output as a response signal 3S.
At this time, if the current flowing through the subject 10 is If, the current flowing through the resistance element Rs is also If. As a result, the voltage difference between the two input terminals of the differential amplifier 31A is Rs · If. Therefore, when the amplification factor of the differential amplifier 31A is A, the output voltage is obtained by V = A · Rs · If, and the current flowing through the subject 10 can be directly converted into a response signal 3S composed of a voltage signal. it can.

  Further, since the differential amplifier 31A is used in the current-voltage conversion circuit 31, unlike the second embodiment, the reference potential VB of the response signal 3S is the circuit operating power supply potential VDD and the ground potential (0 V = In contrast to the second embodiment, when the resistance component of the subject 10 is larger than a predetermined value, VB2 lower than the reference potential VB becomes the center potential, and the resistance component is the above-described potential. When it is smaller than the predetermined value, VB1 higher than the reference potential VB becomes the center voltage.

The response signal 3S is amplified by the limiter amplifier 41A of the response signal conversion circuit 41 and converted into a signal to be compared 41S composed of a rectangular wave digital signal not including an offset potential.
When the limiter amplifier 41A of the response signal conversion circuit 41 amplifies the response signal 3S and converts it into a signal to be compared 41S composed of a digital signal, the reference potential VB of the response signal 3S is grounded with the operating power supply potential VDD of the circuit as described above. Since the potential is almost in the middle of the potential (0V = GND), the input range of the limiter amplifier 41A, here, the allowable fluctuation range of the center voltage when the response signal 3S is amplified is made smaller than in the second embodiment. Can do.

  In this way, the compared signal 41S and the digital reference signal 42S having the same signal waveform as in FIG. 3 are generated and input to the XOR circuit 43A of the digital phase comparison circuit 43, and the pulse width corresponding to these phase differences A detection signal 4S having a signal waveform having

  As described above, in the present embodiment, the current-voltage conversion circuit 31 of the response signal generation unit 3 includes the resistance element Rs connected between the supply signal generation unit 2 and the detection element 1, and the resistance element Rs. Since the differential amplifier 31A that generates and outputs the response signal 3S by differentially amplifying the voltage at both ends, the current flowing through the subject 10 can be directly converted into the voltage response signal 3S. Further, the input range of the limiter amplifier 41A can be made relatively small, and the circuit configuration of the limiter amplifier can be simplified.

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

In the third embodiment, the case where the current-voltage conversion circuit 31 includes the resistance element Rs and the differential amplifier 31A has been described as an example.
In the present embodiment, a case where a resistance element Rr is added between the resistance element Rs and the supply signal generation unit 2 in the current-voltage conversion circuit 31 of the third embodiment will be described as an example.

In FIG. 8, the current-voltage conversion circuit 31 of the response signal generator 3 is provided with a resistance element (first resistance element) Rs, a resistance element (second resistance element) Rr, and a differential amplifier 31A. Yes.
The resistance element Rs and the resistance element Rr are connected in series between the supply signal generation unit 2 and the detection element 1, and supply signal 2S input to the positive polarity input terminal and application input to the reverse polarity input terminal The signal 1S is differentially amplified and a response signal 3S is output from the output terminal.

When the resistance element Rr is provided between the resistance element Rs and the supply signal generation unit 2, the potentials at the nodes of Rs and Rr vary according to the impedance of the subject 10. As a result, the potential fluctuation of the two input terminals of the differential amplifier 31A, which occurs according to the impedance of the subject 10, can be canceled, and the offset fluctuation of the response signal can be reduced.
In the impedance detection apparatus according to the present embodiment, the configuration other than the resistance element Rr of the current-voltage conversion circuit 31 is the same as that of the third embodiment, and detailed description thereof is omitted here.

Next, with reference to FIG. 8, operation | movement of the impedance detection apparatus concerning the 4th Embodiment of this invention is demonstrated.
The AC sine wave supply signal 2S input to the response signal generator 3 is applied to the detection element 1 as the application signal 1S via the resistance elements Rr and Rs of the current-voltage conversion circuit 31. At this time, the current of the applied signal 1S changes according to the impedance of the subject 10, and the current change occurs at both ends of the resistance element Rs. The differential amplifier 31A differentially amplifies the potential difference between both ends of the resistance element Rs, thereby converting the phase information of the current flowing through the subject 10 into a voltage signal and outputting it as a response signal 3S.

  The waveform information detection unit 4 amplifies the response signal 3S with reference to the center voltage by the limiter amplifier 41A, thereby converting the response signal 3S into a signal to be compared 41S composed of a digital signal indicating the voltage change of the response signal 3S. The comparison circuit 43 compares the phase of the signal to be compared 41S from the response signal conversion circuit 41 and the phase of the digital reference signal 42S from the digital reference signal generation circuit 42 by digital signal processing, thereby comparing the signal to be compared 41S as waveform information. The phase difference of the supply signal 2S is detected, and a detection signal 4S composed of a digital signal having a pulse width corresponding to the phase difference is generated and output.

FIG. 9 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 central voltage VA, which is a substantially intermediate potential VA between the circuit operation power supply potential VDD and the ground potential (0V = GND). It is output to the response signal generator 3.

When the supply signal 2S is applied to the subject 10 via the resistance element Rs of the response signal generation unit 3, the phase and amplitude of the current flowing through the subject 10 become impedance inherent to the subject 10. Will change accordingly. In the response signal generator 3, this current change is converted into a voltage signal and output as a response signal 3S.
At this time, since the current flowing through the subject 10 changes according to the impedance of the subject 10, the potentials at the nodes of Rs and Rr vary. As a result, the potential fluctuation of the two input terminals of the differential amplifier 31A, which occurs according to the impedance of the subject 10, is canceled, and the offset fluctuation of the response signal 3S is suppressed to be small.

The response signal 3S is amplified by the limiter amplifier 41A of the waveform information detection unit 4 and converted into a signal to be compared 41S composed of a rectangular wave digital signal not including an offset potential.
In this way, the compared signal 41S and the digital reference signal 42S having the same signal waveform as in FIG. 3 are generated and input to the XOR circuit 43A of the digital phase comparison circuit 43, and the pulse width corresponding to these phase differences A detection signal 4S having a signal waveform having

  As described above, in the present embodiment, the current-voltage conversion circuit 31 of the response signal generation unit 3 is changed between the resistance element Rr, one end of which is connected to the supply signal generation unit 2, and the resistance element Rr and the detection element 1. And the differential amplifier 31A that generates and outputs the response signal 3S by differentially amplifying the voltage across the resistor element Rs, so that the current flowing through the subject 10 is directly The voltage response signal 3S can be converted. Further, the input range of the limiter amplifier 41A can be made relatively small, and the circuit configuration of the limiter amplifier can be simplified. Further, it is possible to cancel the potential fluctuation of the two input terminals of the differential amplifier 31A, which occurs according to the impedance of the subject 10, and to suppress the offset fluctuation of the response signal 3S to improve the detection accuracy. Become.

[Fifth Embodiment]
Next, an impedance detection apparatus according to a fifth embodiment of the present invention will be described with reference to FIG. FIG. 10 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 second to fourth embodiments, the case where the response signal conversion circuit 41 is configured by the limiter amplifier 41A has been described as an example.
In the present embodiment, a case where the response signal conversion circuit 41 is configured by a threshold circuit 41B will be described as an example.

In FIG. 10, the response signal conversion circuit 41 of the waveform information detection unit 4 is provided with a threshold circuit 41B.
The threshold circuit 41B is realized by a buffer circuit combined with an inverter circuit (inverted logic circuit) or the like, and compares the response signal 3S from the response signal generation unit 3 with a predetermined threshold voltage Vt2 to generate a digital signal. It has a function of converting and outputting as a compared signal 41S. The threshold circuit is not required to have a unique configuration in this embodiment, and a generally known circuit may be used.
In the impedance detection apparatus according to the present embodiment, the configuration other than the threshold circuit 41B is the same as that of the fourth embodiment, and detailed description thereof is omitted here.

Next, with reference to FIG. 10, an operation of the impedance detection apparatus according to the fifth exemplary embodiment of the present invention will be described.
The AC sine wave supply signal 2S input to the response signal generator 3 is applied to the detection element 1 as the application signal 1S via the resistance elements Rr and Rs of the current-voltage conversion circuit 31. At this time, the current of the applied signal 1S changes according to the impedance of the subject 10, and the current change occurs at both ends of the resistance element Rs. The differential amplifier 31A differentially amplifies the potential difference between both ends of the resistance element Rs, thereby converting the phase information of the current flowing through the subject 10 into a voltage signal and outputting it as a response signal 3S.

  The waveform information detection unit 4 compares the response signal 3S with a predetermined threshold voltage Vt1 by the threshold circuit 41B, thereby converting the response signal 3S into a signal to be compared 41S composed of a digital signal indicating the voltage change of the response signal 3S. Then, the digital phase comparison circuit 43 compares the phase of the signal to be compared 41S from the response signal conversion circuit 41 with the phase of the digital reference signal 42S from the digital reference signal generation circuit 42 by digital signal processing. A phase difference between the comparison signal 41S and the supply signal 2S is detected, and a detection signal 4S composed of a digital signal having a pulse width corresponding to the phase difference is generated and output.

FIG. 11 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 central voltage VA, which is a substantially intermediate potential VA between the circuit operation power supply potential VDD and the ground potential (0V = GND). It is output to the response signal generator 3.

  When the application signal 1S is applied from the response signal generator 3 to the subject 10 based on the supply signal 2S, the phase and amplitude of the current flowing through the subject 10 change according to the impedance inherent in the subject 10. . In the response signal generation unit 3, these changes appearing in the resistance element Rs are amplified by the differential amplifier 31A, converted into a voltage signal, and output as a response signal 3S.

The response signal 3S is compared with a predetermined threshold voltage Vt2 by the threshold circuit 41B of the response signal conversion circuit 41, and is converted into a signal to be compared 41S composed of a rectangular wave digital signal not including an offset potential.
In this way, the compared signal 41S and the digital reference signal 42S having the same signal waveform as in FIG. 3 are generated and input to the XOR circuit 43A of the digital phase comparison circuit 43, and the pulse width corresponding to these phase differences A detection signal 4S having a signal waveform having

  Here, when the compared signal 41S and the digital reference signal 42S are compared by the XOR circuit 43A, as shown in FIG. 11, two pulses of the detection signal 4S are generated within a period corresponding to one cycle of the supply signal 2S. To do. Further, the pulse width of these pulses varies depending on the selection of the threshold voltage Vt2 used in the threshold circuit 41B and the threshold voltage Vt1 used in the generation of the digital reference signal 42S in the threshold circuit 42C. However, these pulses include waveform information as a phase difference, and the phase difference between the compared signal 41S and the digital reference signal 42S can be detected. The reason will be described below.

The phase difference φ between the signal to be compared 41S and the digital reference signal 42S is expressed by the difference in the timing of the fall or rise of each pulse, but the center timing A of the pulse of the signal to be compared 41S and the pulse of the digital reference signal 42S. It can also be expressed by the difference in the center timing B.
Here, if the width of each pulse of the detection signal 4S is Ta and Tb, φ = (Ta−Tb) / 2. Therefore, the phase difference φ between the compared signal 41S and the digital reference signal 42S can be obtained by extracting the pulse widths Ta and Tb of the detection signal 4S.
Therefore, it is not necessary to use the center voltage of the response signal 3S as Vt2 used in the threshold circuit 41B. Further, it is not necessary to use the center voltage of the supply signal 2S as the threshold voltage Vt1 used for generating the digital reference signal 42S in the threshold circuit 42C.

  As described above, in the present embodiment, the response signal conversion circuit 41 converts the response signal 3S into the digital signal by comparing the response signal 3S with the predetermined threshold voltage Vt1, and outputs the digital signal as the compared signal 41S. Thus, the analog signal response signal 3S having a phase corresponding to the impedance of the subject 10 and including a DC offset potential can be converted into a digital signal comparison signal 41S with a very simple circuit configuration.

Further, in the detection signal 4S, the phase difference between the signal to be compared 41S and the digital reference signal 42S can be detected based on the difference between the center timings of two pulses generated within a period corresponding to one cycle of the supply signal 2S. Therefore, the threshold voltage Vt2 used in the threshold circuit 41B and the threshold voltage Vt1 used in the generation of the digital reference signal 42S in the threshold circuit 42C can be freely selected.
Therefore, even if these threshold voltages fluctuate due to process fluctuations, it is possible to accurately detect phase information corresponding to the phase difference between the signal to be compared 41S and the digital reference signal 42S, that is, the reactance component of the impedance of the subject 10. It becomes possible.

[Sixth Embodiment]
Next, with reference to FIG. 12, an impedance detection apparatus according to a sixth 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 sixth embodiment of the present invention, and the same or equivalent parts as those in FIG.

In the first to fifth embodiments, the waveform information detection unit 4 detects phase information indicating the reactance component of the impedance of the subject 10 based on the response signal 3S from the response signal generation unit 3 as an example. As explained.
In the present embodiment, the waveform information detection unit 4 detects both the phase information indicating the reactance component of the impedance of the subject 10 and the amplitude information indicating the resistance component based on the response signal 3S from the response signal generation unit 3. An example of the case will be described.

In FIG. 12, the waveform information detection unit 4 is provided with a pulse conversion circuit 44 including a threshold circuit 44A.
The threshold value circuit 44A of the pulse conversion circuit 44 detects the voltage change of the response signal 3S as waveform information from the response signal 3S by comparing the response signal 3S with a predetermined threshold voltage Vt3. Based on this, the detection signal (second detection signal) 4SB having a pulse width corresponding to the magnitude of the response signal 3S, that is, the resistance component of the impedance of the subject 10, is generated and output. Yes. The threshold circuit is not required to have a unique configuration in this embodiment, and a generally known circuit may be used.
In the impedance detection apparatus according to the present embodiment, the configuration other than the pulse conversion circuit 44 is the same as that of the fifth embodiment, and 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 AC sine wave supply signal 2S input to the response signal generator 3 is applied to the detection element 1 as the application signal 1S via the resistance elements Rr and Rs of the current-voltage conversion circuit 31. At this time, the current of the applied signal 1S changes according to the impedance of the subject 10, and the current change occurs at both ends of the resistance element Rs. The differential amplifier 31A differentially amplifies the potential difference between both ends of the resistance element Rs, thereby converting the phase information of the current flowing through the subject 10 into a voltage signal and outputting it as a response signal 3S.

  The waveform information detection unit 4 compares the response signal 3S with a predetermined threshold voltage Vt2 by the threshold circuit 41B, thereby converting the response signal 3S into a compared signal 41S composed of a digital signal indicating the voltage change of the response signal 3S. Then, the digital phase comparison circuit 43 compares the phase of the signal to be compared 41S from the response signal conversion circuit 41 with the phase of the digital reference signal 42S from the digital reference signal generation circuit 42 by digital signal processing. A phase difference between the comparison signal 41S and the supply signal 2S is detected, and a detection signal 4SA composed of a digital signal having a pulse width corresponding to the phase difference is generated and output.

  Further, the waveform information detection unit 4 compares the response signal 3S with a predetermined threshold voltage Vt3 by the threshold circuit 44A, and as a voltage change of the response signal 3S as waveform information, the signal voltage of the response signal 3S. And the threshold voltage Vt3 are detected, and a detection signal 4SB composed of a digital signal having a pulse width corresponding to the magnitude of the response signal 3S is generated and output based on the voltage change, here the magnitude relationship.

FIG. 13: is a signal waveform diagram which shows operation | movement of the impedance detection apparatus concerning the 6th Embodiment of this invention. Note that the signal to be compared 41S, the digital reference signal 42S, and the detection signal 4SA are the same as in FIG. 11, and a detailed description thereof is omitted here.
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 central voltage VA, which is a substantially intermediate potential VA between the circuit operation power supply potential VDD and the ground potential (0V = GND). It is output to the response signal generator 3.

  When the application signal 1S is applied from the response signal generator 3 to the subject 10 based on the supply signal 2S, the phase and amplitude of the current flowing through the subject 10 change according to the impedance inherent in the subject 10. . In the response signal generation unit 3, these changes appearing in the resistance element Rs are amplified by the differential amplifier 31A, converted into a voltage signal, and output as a response signal 3S.

At this time, if the current flowing through the subject 10 is If, the current flowing through the resistance element Rs is also If. As a result, the voltage difference between the two input terminals of the differential amplifier 31A is Rs · If. Therefore, when the amplification factor of the differential amplifier 31A is A, the output voltage is obtained by V = A · Rs · If, and the current flowing through the subject 10 is directly obtained. The response signal 3S can be converted to a voltage signal.
In addition, since the differential amplifier 31A is used for the current-voltage conversion circuit 31, the reference potential of the response signal 3S is an intermediate potential between the circuit operation power supply potential VDD and the ground potential (0V = GND). When the resistance component of the subject 10 is larger than a predetermined value, the potential is lower than the intermediate potential, and when the resistance component is smaller than the predetermined value, the potential is higher than the intermediate potential.

Thereafter, the response signal 3S is compared with a predetermined threshold voltage Vt3 by the threshold circuit 44A of the pulse conversion circuit 44, and a detection signal 4S having a signal waveform having a pulse width corresponding to the amplitude value of the response signal 3S. Is obtained.
Therefore, when the resistance component of the subject 10 is smaller than the predetermined value, the pulse width TA corresponding to the magnitude of the response signal 3S, here, the amplitude A from the upper peak voltage of the response signal 3S to the ground potential (0V = GND). A detection signal 4S is generated. When the resistance component of the subject 10 is larger than a predetermined value, the pulse width TB corresponding to the magnitude of the response signal 3S, here, the amplitude B from the upper peak voltage of the response signal 3S to the ground potential (0V = GND). A detection signal 4S is generated.

As described above, in this embodiment, the waveform information detector 4 is provided with the pulse conversion circuit 44 including the threshold circuit 44A, and the response signal 3 is compared with the predetermined threshold voltage Vt3. A detection signal composed of a digital signal having a pulse width corresponding to the magnitude of the response signal 3S, that is, the resistance component of the impedance of the subject 10 based on the voltage change. Since 4SB is generated and output, when the resistance component and reactance component of the impedance of the subject 10 are detected, the detection element 1, the supply signal generation unit 2, and the response signal generation unit 3 can be combined. The resistance component and reactance component of the impedance of the subject 10 can be detected with an extremely simple circuit configuration.
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.

  In the present embodiment, since the threshold circuit 44A is used as the pulse conversion circuit 44, even if Vt3 varies due to process variations, the correspondence between the amplitude of the response signal 3S and the pulse width of the detection signal 4S is Since it does not change, amplitude information, that is, a resistance component can be detected with high accuracy.

  In the present embodiment, the current-voltage conversion circuit 31 is provided with a resistance element Rr between the resistance element Rs and the supply signal generation unit 2, and a response is obtained by amplifying the voltage across the resistance element Rs with the differential amplifier 31A. Since the signal 3S is generated, the potential fluctuation of the two input terminals of the differential amplifier 31A, which occurs according to the impedance of the subject 10, can be canceled, and the offset fluctuation of the response signal can be reduced. Thereby, even if the impedance of the subject 10 changes, the response signal 3S can always be adjusted to a voltage range that intersects the threshold voltage Vt3.

  In the present embodiment, the waveform information detection unit 4 is provided with a pulse conversion circuit 44 including a threshold circuit 44A to generate a detection signal 4SB having a pulse width corresponding to the resistance component of the impedance of the subject 10. However, the threshold value circuit 41B may be regarded as the pulse conversion circuit 44, and the compared signal 41S from the threshold value circuit 41B may be output as the detection signal 4SB.

FIG. 14 is a block diagram showing another configuration of the impedance detection device according to the sixth exemplary embodiment of the present invention. Compared with FIG. 12, the threshold circuit 44A is also used as the threshold circuit 41B. Is different.
As described in the fifth embodiment, the threshold circuit 41B has a function equivalent to that of the threshold circuit 44A, and the signal to be compared 41S corresponds to the resistance component of the impedance of the subject 10. It can be regarded as a rectangular wave having a pulse width.
Therefore, the threshold circuit 44A can be omitted only by providing a wiring and an output terminal for outputting the output of the threshold circuit 41B as the detection signal 4SB, and the impedance resistance of the subject 10 can be reduced with a simple circuit configuration. Components and reactance components can be detected.

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

In the fifth embodiment, the current-voltage conversion circuit 31 is configured by the resistance element Rs, the resistance element Rr, and the differential amplifier 31A, and the case where a sine wave having a predetermined frequency is used as the supply signal 2S has been described as an example. .
In the present embodiment, a case where a triangular wave is used as the supply signal 2S in the fifth embodiment will be described as an example.

In FIG. 15, the supply signal generation unit 2 is provided with a triangular wave generation circuit 22 </ b> B as the waveform shaping circuit 22. The triangular wave generation circuit 22B is a specific example of the waveform shaping circuit 22 in FIG. 1, and generates an alternating supply signal 2S composed of a triangular wave based on the clock signal 21S from the frequency generation circuit 21 and outputs it to the response signal generation unit 3. It has a function. Usually, the sine wave is generated using, for example, a D / A converter, or the waveform of a triangular wave is generated using a diode element or the like. Therefore, the generation of the triangular wave can simplify the circuit configuration more than the generation of the sine wave. As a specific example of the triangular wave generation circuit 22B, a known circuit may be used.
In the impedance detection apparatus according to the present embodiment, the configuration other than the triangular wave generation circuit 22B is the same as that of the fifth embodiment, and detailed description thereof is omitted here.

Next, the operation of the impedance detection apparatus according to the seventh embodiment of the present invention will be described with reference to FIG.
The AC triangular wave supply signal 2S output from the triangular wave generation circuit 22B and input to the response signal generation unit 3 is applied to the detection element 1 as the applied signal 1S via the resistance elements Rr and Rs of the current-voltage conversion circuit 31. Is done. At this time, the current of the applied signal 1S changes according to the impedance of the subject 10, and the current change occurs at both ends of the resistance element Rs. The differential amplifier 31A differentially amplifies the potential difference between both ends of the resistance element Rs, thereby converting the phase information of the current flowing through the subject 10 into a voltage signal and outputting it as a response signal 3S.

  The waveform information detection unit 4 compares the response signal 3S with a predetermined threshold voltage Vt2 by the threshold circuit 41B, thereby converting the response signal 3S into a compared signal 41S composed of a digital signal indicating the voltage change of the response signal 3S. Then, the digital phase comparison circuit 43 compares the phase of the signal to be compared 41S from the response signal conversion circuit 41 with the phase of the digital reference signal 42S from the digital reference signal generation circuit 42 by digital signal processing. A phase difference between the comparison signal 41S and the supply signal 2S is detected, and a detection signal 4S composed of a digital signal having a pulse width corresponding to the phase difference is generated and output.

FIG. 16 is a signal waveform diagram showing an operation of the impedance detection device according to the seventh exemplary embodiment of the present invention. FIG. 17 is a signal waveform diagram showing an operation of the impedance detection device according to the seventh exemplary embodiment of the present invention. Here, a case where the supply signal 2S is a triangular wave will be described as an example.
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 approximately in the middle of the circuit operation power supply potential VDD and the ground potential (0V = GND) as a center voltage. It is output to the generation unit 3.

Here, as shown in FIG. 16, when the impedance of the subject 10 is only a capacitive component, when a supply signal 2S consisting of a triangular wave is input to the subject 10, the current flowing through the impedance becomes a differential response waveform of the 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.

As shown in FIG. 17, when the application signal 1S is applied to the subject 10, the magnitude of the amplitude of the response signal 3S changes according to the capacitance component of the impedance of the subject 10. That is, when the capacitance component is large, the current flowing through the impedance increases and the amplitude of the response signal 3S increases. When the capacitance component is small, the current flowing through the impedance decreases and the amplitude of the response signal 3S decreases.
The response signal 3S is compared with a predetermined threshold voltage Vt2 by the threshold circuit 41B of the response signal conversion circuit 41, and is compared to a signal 41S to be compared which is a digital signal having a pulse width corresponding to the amplitude. Converted.

Further, the supply signal 2S is compared with the threshold voltage Vt1 by the threshold circuit 42C and converted into the digital reference signal 42S.
The signal to be compared 41S and the digital reference signal 42S are input to the XOR circuit 43A of the digital phase comparison circuit 43 to detect a phase difference, and a detection signal 4S having a signal waveform having a pulse width corresponding to the phase difference is output. The

  Here, when the compared signal 41S and the digital reference signal 42S are compared by the XOR circuit 43A, as shown in FIG. 17, two pulses of the detection signal 4S are generated within a period corresponding to one cycle of the supply signal 2S. To do. Further, the pulse width of these pulses varies depending on the selection of the threshold voltage Vt2 used in the threshold circuit 41B and the threshold voltage Vt1 used in the generation of the digital reference signal 42S in the threshold circuit 42C. However, these pulses include waveform information as a phase difference, and the phase difference between the compared signal 41S and the digital reference signal 42S can be detected. The reason will be described below.

The phase difference φ between the signal to be compared 41S and the digital reference signal 42S is expressed by the difference in the timing of the fall or rise of each pulse, but the center timing A of the pulse of the signal to be compared 41S and the pulse of the digital reference signal 42S. It can also be expressed by the difference in the center timing B.
Here, if the width of each pulse of the detection signal 4S is Ta and Tb, φ = (Ta−Tb) / 2. Therefore, the phase difference φ between the compared signal 41S and the digital reference signal 42S can be obtained by extracting the pulse widths Ta and Tb of the detection signal 4S.

  At this time, if the capacitance component is large, the center of the signal to be compared 41S changes to the center timing A ', and the phase has advanced by Δφ. For this reason, Tb is shortened, and as a result, the phase difference φ is increased. Therefore, it is possible to detect a change in the phase difference accompanying a change in the capacitance component of the impedance of the subject 10 using the supply signal 2S formed of a triangular wave. Even if the set values of the threshold values Vt1 and Vt2 vary due to semiconductor process fluctuations, the magnitude relationship between the phase information of the detection signal 4S and the impedance of the subject 10 is maintained by using the phase difference φ. Therefore, the change in the capacitance component of the impedance of the subject 10 can be captured by the change in the phase information, that is, the phase difference φ.

  Thus, in this embodiment, since the waveform shaping circuit 22 is configured by the triangular wave generation circuit 22B, the circuit required for generating the supply signal 2S can be simplified as compared with the case where a sine wave is used, and the overall configuration is extremely simple. With a simple circuit, it is possible to suppress deterioration in detection accuracy due to factors such as process fluctuations, and it is possible to detect the impedance of the subject 10 with high accuracy.

[Eighth Embodiment]
Next, with reference to FIG. 18, the impedance detection apparatus concerning the 8th Embodiment of this invention is demonstrated. FIG. 18 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 seventh embodiment, the case where a triangular wave is used as the supply signal 2S in the fifth embodiment has been described as an example.
In the present embodiment, a case where the low-pass filter 45 is provided between the response signal generation unit 3 and the response signal conversion circuit 41 in the seventh embodiment will be described as an example.

In FIG. 18, the waveform information detection unit 4 is provided with a low-pass filter (LPF) 45 between the response signal generation unit 3 and the response signal conversion circuit 41.
The low-pass filter 45 has a function of removing a high-frequency component contained in the response signal 3S composed of a triangular wave. The low-pass filter does not require a unique configuration in the present embodiment, and a general known circuit may be used.
In the impedance detection apparatus according to the present embodiment, the configuration other than the low-pass filter 45 is the same as that of the seventh embodiment, and 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 AC triangular wave supply signal 2S output from the triangular wave generation circuit 22B and input to the response signal generation unit 3 is applied to the detection element 1 as the applied signal 1S via the resistance elements Rr and Rs of the current-voltage conversion circuit 31. Is done. At this time, the current of the applied signal 1S changes according to the impedance of the subject 10, and the current change occurs at both ends of the resistance element Rs. The differential amplifier 31A differentially amplifies the potential difference between both ends of the resistance element Rs, thereby converting the phase information of the current flowing through the subject 10 into a voltage signal and outputting it as a response signal 3S.

  The waveform information detection unit 4 removes a high-frequency component contained in the response signal 3S composed of a triangular wave by the low-pass filter 45, and outputs the response signal 3S from the low-pass filter 45 to a predetermined threshold voltage Vt2 by the threshold circuit 41B. Compare with As a result, the response signal 3S is converted into a compared signal 41S composed of a digital signal indicating a voltage change, and the compared signal 41S from the response signal converting circuit 41 and the digital reference signal generating circuit 42 are converted by the digital phase comparison circuit 43. By comparing the phase with the digital reference signal 42S by digital signal processing, the phase difference between the signal 41S to be compared and the supply signal 2S is detected as waveform information, and the digital signal has a pulse width corresponding to the phase difference. A detection signal 4S is generated and output.

FIG. 19 is a signal waveform diagram showing an 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 approximately in the middle of the circuit operation power supply potential VDD and the ground potential (0V = GND) as a center voltage. It is output to the generation unit 3.

When the application signal 1S is applied from the response signal generator 3 to the subject 10 based on the supply signal 2S, the phase and amplitude of the current flowing through the subject 10 change according to the impedance inherent in the subject 10. . In the response signal generation unit 3, these changes appearing in the resistance element Rs are amplified by the differential amplifier 31A, converted into a voltage signal, and output as a response signal 3S.
Thereafter, the high-frequency component is removed from the response signal 3S by the low-pass filter 45, and then compared with a predetermined threshold voltage Vt3 by the threshold circuit 44A of the pulse conversion circuit 44 to obtain the amplitude value of the response signal 3S. A detection signal 4S having a signal waveform having a corresponding pulse width is obtained.

  As described above, in the present embodiment, the low-pass filter 45 is provided between the response signal generation unit 3 and the response signal conversion circuit 41, and after removing the high-frequency component contained in the response signal 3S composed of a triangular wave, the waveform information is obtained. Since it is made to detect, the detection accuracy of the waveform information in the waveform information detector 4A can be improved.

[Ninth Embodiment]
Next, with reference to FIG. 20, the impedance detection apparatus concerning the 9th Embodiment of this invention is demonstrated. FIG. 20 is a block diagram showing the configuration of the impedance detection apparatus according to the ninth embodiment of the present invention. The same reference numerals are given to the same or equivalent parts as those in FIG.

In the fifth embodiment, the current-voltage conversion circuit 31 is configured by the resistance element Rs, the resistance element Rr, and the differential amplifier 31A, and the case where a sine wave having a predetermined frequency is used as the supply signal 2S has been described as an example. .
In the present embodiment, a case where a trapezoidal wave is used as the supply signal 2S in the fifth embodiment will be described as an example.

In FIG. 20, the supply signal generation unit 2 is provided with a trapezoidal wave generation circuit 22 </ b> C as the waveform shaping circuit 22. The trapezoidal wave generation circuit 22C is a specific example of the waveform shaping circuit 22 of FIG. 1, and generates an alternating supply signal 2S composed of a trapezoidal 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 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.
Note that, in the impedance detection apparatus according to the present embodiment, the configuration other than the trapezoidal wave generation circuit 22C is the same as that of the fifth embodiment, and 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 AC trapezoidal wave supply signal 2S output from the trapezoidal wave generation circuit 22C and input to the response signal generation unit 3 is detected as the applied signal 1S via the resistance elements Rr and Rs of the current-voltage conversion circuit 31. To be applied. At this time, the current of the applied signal 1S changes according to the impedance of the subject 10, and the current change occurs at both ends of the resistance element Rs. The differential amplifier 31A differentially amplifies the potential difference between both ends of the resistance element Rs, thereby converting the phase information of the current flowing through the subject 10 into a voltage signal and outputting it as a response signal 3S.

  The waveform information detection unit 4 compares the response signal 3S with a predetermined threshold voltage Vt2 by the threshold circuit 41B, thereby converting the response signal 3S into a compared signal 41S composed of a digital signal indicating the voltage change of the response signal 3S. Then, the digital phase comparison circuit 43 compares the phase of the signal to be compared 41S from the response signal conversion circuit 41 with the phase of the digital reference signal 42S from the digital reference signal generation circuit 42 by digital signal processing. A phase difference between the comparison signal 41S and the supply signal 2S is detected, and a detection signal 4S composed of a digital signal having a pulse width corresponding to the phase difference is generated and output.

FIG. 21 is a signal waveform diagram showing an operation of the impedance detection device according to the ninth exemplary embodiment of the present invention. FIG. 22 is another signal waveform diagram showing the operation of the impedance detection apparatus according to the ninth exemplary embodiment of the present invention. Here, a case where the supply signal 2S is a trapezoidal wave will be described as an example.
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 central voltage VA which is approximately between the operation power supply potential VDD and the ground potential (0V = GND) of the circuit, It is output to the response signal generator 3.

Here, as shown in FIG. 21, 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.

As shown in FIG. 22, when the application signal 1S is applied to the subject 10, the magnitude of the amplitude of the response signal 3S changes according to the capacitance component of the impedance of the subject 10. That is, when the capacitance component is large, the current flowing through the impedance increases and the amplitude of the response signal 3S increases. When the capacitance component is small, the current flowing through the impedance decreases and the amplitude of the response signal 3S decreases.
The response signal 3S is compared with a predetermined threshold voltage Vt2 by the threshold circuit 41B of the response signal conversion circuit 41, and is compared to a signal 41S to be compared which is a digital signal having a pulse width corresponding to the amplitude. Converted.

Further, the supply signal 2S is compared with the threshold voltage Vt1 by the threshold circuit 42C and converted into the digital reference signal 42S.
The signal to be compared 41S and the digital reference signal 42S are input to the XOR circuit 43A of the digital phase comparison circuit 43 to detect a phase difference, and a detection signal 4S having a signal waveform having a pulse width corresponding to the phase difference is output. The

  Here, when the compared signal 41S and the digital reference signal 42S are compared by the XOR circuit 43A, as shown in FIG. 22, two pulses of the detection signal 4S are generated within a period corresponding to one cycle of the supply signal 2S. To do. Further, the pulse width of these pulses varies depending on the selection of the threshold voltage Vt2 used in the threshold circuit 41B and the threshold voltage Vt1 used in the generation of the digital reference signal 42S in the threshold circuit 42C. However, these pulses include waveform information as a phase difference, and the phase difference between the compared signal 41S and the digital reference signal 42S can be detected. The reason will be described below.

The phase difference φ between the signal to be compared 41S and the digital reference signal 42S is expressed by the difference in the timing of the fall or rise of each pulse, but the center timing A of the pulse of the signal to be compared 41S and the pulse of the digital reference signal 42S. It can also be expressed by the difference in the center timing B.
Here, if the width of each pulse of the detection signal 4S is Ta and Tb, φ = (Ta−Tb) / 2. Therefore, the phase difference φ between the compared signal 41S and the digital reference signal 42S can be obtained by extracting the pulse widths Ta and Tb of the detection signal 4S.

  At this time, when the capacitance component is large, Tb becomes short, and as a result, the phase difference φ becomes large. Therefore, it is possible to detect a change in the phase difference accompanying a change in the capacitance component of the impedance of the subject 10 using the supply signal 2S formed of a trapezoidal wave. Even if the set values of the threshold values Vt1 and Vt2 vary due to semiconductor process fluctuations, the magnitude relationship between the phase information of the detection signal 4S and the impedance of the subject 10 is maintained by using the phase difference φ. Therefore, the change in the capacitance component of the impedance of the subject 10 can be captured by the change in the phase information, that is, the phase difference φ.

  Thus, in this embodiment, since the waveform shaping circuit 22 is configured by the trapezoidal wave generation circuit 22C, the circuit required for generating the supply signal 2S can be simplified as compared with the case where a sine wave is used. With a simple circuit, deterioration in detection accuracy due to factors such as process variations can be suppressed, and the impedance of the subject can be detected with high accuracy.

[Tenth embodiment]
Next, with reference to FIG. 23, a biometric recognition apparatus and a fingerprint recognition apparatus according to the tenth embodiment of the present invention will be described. FIG. 23 is a block diagram showing configurations of the biometric recognition apparatus and the fingerprint recognition apparatus according to the tenth 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 ninth embodiments of the present invention, applies a predetermined application signal 1S to the subject 10, and 10 has a function of detecting the impedance of the subject based on the current flowing through 10 and outputting a detection signal 4S having waveform information corresponding to the impedance.

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 ninth 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, in order to facilitate understanding of the characteristic configuration of the embodiment, the description has been made based on the embodiment having a similar configuration. However, the overall configuration of the embodiment has not been described. The present invention is not limited to the configuration example described in the embodiment, and may be implemented in any combination with other embodiments.

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 signal waveform diagram which shows operation | movement of the impedance detection apparatus concerning the 2nd Embodiment of this invention. It is a block diagram which shows the other structure of the impedance detection apparatus concerning the 2nd Embodiment of this invention. It is a block diagram which shows the other 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 signal waveform diagram which shows operation | movement 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 other structure 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 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 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 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 biometric recognition apparatus and fingerprint recognition apparatus concerning the 10th 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.

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 ... Current-voltage conversion circuit, 31A ... Differential amplifier, 4 ... Waveform information detection unit, 4S, 4SA, 4SB ... detection signal, 41 ... response signal conversion circuit, 41A ... limiter amplifier, 41B ... threshold circuit, 42 ... digital reference signal generation circuit, 42S ... digital reference signal, 42A ... reference Signal generation circuit, 42B, 42C ... threshold circuit, 43 ... digital phase comparison circuit, 43A ... XOR circuit, 44 ... pulse conversion circuit, 44A ... threshold circuit, DESCRIPTION OF SYMBOLS 5 ... Low pass filter, Zf ... Impedance, 101 ... Biometric recognition part, 110 ... Biometric recognition apparatus, 110S ... Biometric recognition result, 1P ... Surface shape information, 1Z ... Impedance information, 111 ... Fingerprint detection apparatus, 111S ... Fingerprint data, 112 ... fingerprint authentication unit, 112S ... fingerprint recognition result, 113 ... recognition judgment unit, 120 ... fingerprint recognition device, 120S ... judgment result.

Claims (19)

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 generates and outputs a detection signal corresponding to the impedance of the subject based on the waveform information; and
The waveform information detector
A response signal converting circuit that converts the response signal into a signal to be compared that is a digital signal indicating a voltage change of the response signal and outputs the signal to be compared;
A phase difference between the signal to be compared and the supply signal is detected as the waveform information by comparing the phase of the digital reference signal having a rectangular wave synchronized with the supply signal and the signal to be compared, and the phase difference is determined according to the phase difference. And a digital phase comparison circuit that generates a first detection signal composed of a digital signal having a pulse width and outputs the first detection signal as the detection signal. 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. The impedance detection apparatus according to claim 1,
The response signal conversion circuit comprises a limiter amplifier that amplifies the response signal to convert it into a digital signal and outputs it as the signal to be compared. The impedance detection apparatus according to claim 1,
The response signal conversion circuit comprises a threshold circuit that converts the response signal into a digital signal by comparing the response signal with a predetermined threshold voltage and outputs the digital signal as the signal to be compared. The impedance detection apparatus according to claim 1,
The impedance detection apparatus, wherein the digital phase comparison circuit comprises an exclusive OR circuit that outputs an exclusive OR of the signal to be compared and the digital reference signal as the detection signal. The impedance detection apparatus according to claim 2,
The waveform detection unit uses the clock signal as the digital reference signal. The impedance detection apparatus according to claim 1,
The waveform information detection unit includes a digital reference signal generation circuit including a threshold circuit that converts the supply signal to a digital signal by comparing it with a predetermined threshold voltage and outputs the digital signal as the digital reference signal. Impedance detection device. The impedance detection apparatus according to claim 1,
The waveform information detection unit converts a reference signal generation circuit that generates a reference signal synchronized with the supply signal into a digital signal by comparing the reference signal with a predetermined threshold voltage, and outputs the digital signal as the digital reference signal An impedance detection apparatus comprising a digital reference signal generation circuit comprising a threshold circuit for performing the above operation. The impedance detection apparatus according to claim 1,
The waveform information detection unit detects a voltage change of the response signal as the waveform information, and based on the voltage change, the response signal is a second signal composed of a digital signal having a pulse width corresponding to the magnitude of the response signal. An impedance detection device further comprising a pulse conversion circuit that converts the detection signal into a detection signal and outputs the detection signal. The impedance detection device according to claim 9, wherein
The pulse conversion circuit comprises a threshold circuit that compares the response signal with a predetermined threshold voltage and outputs a digital signal corresponding to the comparison result as the second detection signal. Detection device. The impedance detection device according to claim 4, wherein
The threshold circuit compares the response signal obtained by comparing the response signal with a predetermined threshold voltage, and the pulse width corresponding to the voltage change of the response signal that changes according to the impedance of the subject. An impedance detection device that outputs the second detection signal as a second detection signal. The impedance detection apparatus according to claim 1,
The waveform information detection unit further includes a low-pass filter that removes a high-frequency component included in the response signal,
The response detection circuit converts the response signal output from the low-pass filter into the signal to be compared. The impedance detection apparatus according to claim 1,
The detection element includes a first detection electrode that is in electrical contact with the subject and connected to a predetermined common potential; and the application from the response signal generation unit that is in electrical contact with the subject. An impedance detection apparatus comprising: a second detection electrode that applies a signal to the subject. The impedance detection apparatus according to claim 1,
The response signal generation unit includes a resistance element connected between the supply signal generation unit and the detection element, and outputs a response signal from a connection node between the resistance element and the detection element. An impedance detection device comprising a conversion circuit. The impedance detection apparatus according to claim 1,
The response signal generation unit generates and outputs the response signal by differentially amplifying a resistance element connected between the supply signal generation unit and the detection element and a voltage across the resistance element. An impedance detection apparatus comprising a current-voltage conversion circuit having a dynamic amplifier. The impedance detection apparatus according to claim 1,
The response signal generation unit includes a first resistance element having one end connected to the supply signal generation unit, and a second resistance element connected between the other end of the first resistance element and the detection element. And a current-voltage conversion circuit having a differential amplifier that differentially amplifies the voltage across the second resistance element to generate and output the response 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 of detecting waveform information indicating the characteristics of the waveform of the response signal from the response signal, and generating and outputting a detection signal according to the impedance of the subject based on the waveform information, and
The waveform information detection step includes
A response signal conversion step of converting the response signal into a signal to be compared consisting of a digital signal indicating a voltage change of the response signal and outputting the signal to be compared;
A phase difference between the signal to be compared and the supply signal is detected as the waveform information by comparing the phase of the digital reference signal having a rectangular wave synchronized with the supply signal and the signal to be compared, and the phase difference is determined according to the phase difference. And a digital phase comparison step of generating a first detection signal composed of a digital signal having a pulse width and outputting the detection signal as the detection signal. 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 18, wherein it is determined 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.

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