Contact impedance measurement system and contact impedance measurement method

Abstract

The present invention is capable of measuring the values of the contact impedance to a living body of both a detection electrode and a bias electrode which contact and are attached to a living body.　This contact impedance measurement system measures the contact impedance relative to a living body of a first electrode capable of contacting a living body, and of a second electrode for applying a reference potential to the living body. This contact impedance measurement system has: a first current source that causes a first measurement current to flow from a first electrode along a current path that passes through a living body and reaches a second electrode; a first voltage detector that detects a first voltage of the first electrode relative to the reference potential; a second voltage detector that detects a second voltage of a third electrode which contacts the living body relative to the reference potential; and a calculation unit that calculates the contact impedance relative to the living body of each of the first electrode and the second electrode, on the basis of the values of the first measurement current, and the first voltage and second voltage when the first measurement current flows.

Description

Contact impedance measurement system and contact impedance measurement method

[0001] The present invention relates to a contact impedance measurement system and a contact impedance measurement method.

[0002] Patent Document 1 discloses an active electrode that includes a detection electrode that contacts a living body, a first current source that passes a first current from the detection electrode to the living body to measure the contact impedance between the living body and the detection electrode, and a second current source that passes a second current that provides an electrical stimulus to the living body.

[0003] International Publication No. 2020 / 026880

[0004] When acquiring a biological signal, a bias electrode that applies a reference potential to the living body and a detection electrode that acquires the biological signal are attached in contact with the skin of the living body. When evaluating the contact impedance between the detection electrode and the living body, a measurement current is passed through a current path from the detection electrode through the living body to the bias electrode. Then, the voltage of the detection electrode relative to the reference potential is measured, and the contact impedance is calculated as a value obtained by dividing the measured voltage by the measurement current.

[0005] However, the contact impedance calculated as described above is a composite impedance value including the contact impedance of the detection electrode and the contact impedance of the bias electrode, and it is not possible to evaluate the contact impedance of the detection electrode and the bias electrode individually. Therefore, even if there is an abnormality in the contact impedance value calculated as described above, it is not possible to determine which of the detection electrode and the bias electrode has the abnormality.

[0006] An object of the present invention is to make it possible to measure the value of the contact impedance of each of the detection electrodes and bias electrodes attached in contact with the living body.

[0007] One aspect of the present invention is a contact impedance measurement system that measures the contact impedance of a first electrode that can contact a living organism and a second electrode that applies a reference potential to the living organism, the contact impedance measurement system comprising: a first current source that flows a first measurement current through a current path that runs from the first electrode through the living organism to the second electrode; a first voltage detector that detects a first voltage of the first electrode relative to the reference potential; a second voltage detector that detects a second voltage of a third electrode that contacts the living organism relative to the reference potential; and a calculation unit that calculates the contact impedance of each of the first electrode and the second electrode with the living organism, wherein the calculation unit calculates the contact impedance of each of the first electrode and the second electrode with the living organism from the first measurement current and the first voltage and the second voltage when the first measurement current is passed through. Another aspect of the present invention is a contact impedance measurement system that measures the contact impedance of a first electrode that can contact a living body and a second electrode that applies a reference potential to the living body, the contact impedance measurement system comprising: a first current source that flows a first measurement current through a current path that runs from the first electrode through the living body to the second electrode; a first voltage detector that detects a first voltage of the first electrode relative to the reference potential; a second current source that supplies a second measurement current to a current path that runs from a third electrode that contacts the living body through the living body to the second electrode; and a calculation unit that calculates the contact impedance of each of the first electrode and the second electrode with the living body, wherein the calculation unit calculates the contact impedance of each of the first electrode and the second electrode with the living body from the first measurement current, the second measurement current, the first voltage when the first measurement current is passed, and the first voltage when the second measurement current is passed.Another aspect of the present invention is a contact impedance measurement method executed by a computer for measuring the contact impedance of a first electrode that can contact a living body and a second electrode that applies a reference potential to the living body, the contact impedance measurement method comprising: a current passing step of passing a first measurement current from a first current source through a current path from the first electrode through the living body to the second electrode; a first voltage detection step of detecting a first voltage of the first electrode relative to the reference potential; a second voltage detection step of detecting a second voltage of a third electrode in contact with the living body relative to the reference potential; and a calculation step of calculating the contact impedance of each of the first electrode and the second electrode with the living body, wherein in the calculation step, the contact impedance of each of the first electrode and the second electrode with the living body is calculated from the first measurement current and the first voltage and the second voltage when the first measurement current is passed. Another aspect of the present invention is a contact impedance measurement method executed by a computer for measuring the contact impedance of a first electrode that can contact a living body and a second electrode that applies a reference potential to the living body, the contact impedance measurement method comprising: a first current flow step of passing a first measurement current from a first current source through a current path from the first electrode through the living body to the second electrode; a first voltage detection step of detecting a first voltage of the first electrode relative to the reference potential; a second current flow step of passing a second measurement current from a second current source through a current path from a third electrode in contact with the living body through the living body to the second electrode; and a calculation step of calculating the contact impedance of each of the first electrode and the second electrode with the living body, wherein in the calculation step, the contact impedance of each of the first electrode and the second electrode with the living body is calculated from the first measurement current, the second measurement current, the first voltage when the first measurement current is passed, and the first voltage when the second measurement current is passed.Another aspect of the present invention is a program executed by a computer for measuring the contact impedance of a first electrode that can contact a living body and a second electrode that applies a reference potential to the living body, the program causing the computer to execute the following steps: a current flow step of flowing a first measurement current from a first current source through a current path from the first electrode through the living body to the second electrode; a first voltage detection step of detecting a first voltage of the first electrode relative to the reference potential; a second voltage detection step of detecting a second voltage of a third electrode in contact with the living body relative to the reference potential; and a calculation step of calculating the contact impedance of each of the first electrode and the second electrode with the living body, wherein in the calculation step, the program calculates the contact impedance of each of the first electrode and the second electrode with the living body from the first measurement current and the first voltage and the second voltage when the first measurement current is passed. Yet another aspect of the present invention is a program executed by a computer for measuring the contact impedance of a first electrode that can contact a living body and a second electrode that applies a reference potential to the living body, the program causing the computer to execute the following steps: a first current flow step of passing a first measurement current from a first current source through a current path from the first electrode through the living body to the second electrode; a first voltage detection step of detecting a first voltage of the first electrode relative to the reference potential; a second current flow step of passing a second measurement current from a second current source through a current path from a third electrode in contact with the living body through the living body to the second electrode; and a calculation step of calculating the contact impedance of each of the first electrode and the second electrode with the living body, wherein in the calculation step, the program calculates the contact impedance of each of the first electrode and the second electrode with the living body from the first measurement current, the second measurement current, the first voltage when the first measurement current is passed, and the first voltage when the second measurement current is passed. This specification includes the entire contents of Japanese Patent Application No. 2024-069890, filed on April 23, 2024.

[0008] According to the present invention, it is possible to measure the value of the contact impedance of each of the detection electrode and bias electrode attached in contact with the living body.

[0009] FIG. 1 is a diagram showing an example of a biosignal measurement system to which a contact impedance measurement system according to the present invention is applied. FIG. 2 is a diagram showing the configuration of a headset in which the contact impedance measurement system according to the first embodiment is realized. FIG. 3 is a diagram showing the configuration of the contact impedance measurement system according to the first embodiment. FIG. 4 is a flowchart of a contact impedance measurement method in the contact impedance measurement system according to the first embodiment. FIG. 5 is a diagram showing the configuration of a contact impedance measurement system according to the second embodiment. FIG. 6 is a flowchart of a contact impedance measurement method in the contact impedance measurement system according to the second embodiment. FIG. 7 is a diagram showing the configuration of a headset in which a contact impedance measurement system according to the third embodiment is realized. FIG. 8 is a diagram showing the configuration of a contact impedance measurement system according to the third embodiment. FIG. 9 is a flowchart of a contact impedance measurement method in the contact impedance measurement system according to the third embodiment.

[0010] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A contact impedance measuring system according to an embodiment of the present invention will be described below with reference to the accompanying drawings. As an example, the contact impedance measuring system according to the present invention is used as a biosignal measuring system such as an electroencephalogram measuring system.

[0011] In electroencephalogram (EEG) measurements, the electroencephalogram signals measured as biosignals have a voltage on the order of several μV, which is three orders of magnitude smaller than electrocardiogram and electromyogram signals, which are detected on the order of several mV. Therefore, in an electroencephalogram (EEG) measurement system, the results of the EEG measurement can be significantly affected if the electrodes are not attached in a state where they are in better contact with the skin of the subject P (i.e., where the contact impedance is smaller) compared to systems that perform electrocardiogram and electromyogram measurements.

[0012] When trying to achieve such better contact between the electrodes and the skin, it is particularly important to quickly identify, among the multiple electrodes attached to the skin, those electrodes that require the above-mentioned treatment, so as not to increase the number of times the electrodes have to be reattached to the skin, which would cause stress to the subject.

[0013] However, when a composite impedance including the contact impedance of the detection electrode and the contact impedance of the bias electrode is measured as in the above-mentioned conventional technology, it is impossible to determine which of the detection electrode and the bias electrode is in inappropriate contact with the living body, and therefore it may be necessary to repeatedly reattach the detection electrode and the bias electrode to the living body until the composite impedance reaches an appropriate value.

[0014] Therefore, the contact impedance measuring system according to the present invention is configured to be able to measure the respective values ​​of the contact impedance of the detection electrode and bias electrode attached to the skin of the subject with respect to the living body.

[0015] [1. First Embodiment] First, a first embodiment of the present invention will be described. [1.1. Overall Configuration] Fig. 1 is a diagram showing an example of the configuration of a biosignal measurement system 2 in which a contact impedance measurement system 1 according to a first embodiment of the present invention is used. The biosignal measurement system 2 is, for example, an electroencephalogram (EEG) measurement system that measures electroencephalograms as biosignals of a subject P. The biosignal measurement system 2 includes, for example, a headset 3 that is worn on the ears of the subject P to acquire the electroencephalogram signal of the subject P, and a processing device 4. The term "biological organism" refers to a part or the whole of the body of the subject P, and the term "biological signal" refers to an electrical signal generated by the body of the subject P.

[0016] The processing device 4 performs signal processing on the EEG signal output from the headset 3 and performs EEG analysis on the processed EEG signal. The signal processing includes, for example, filtering, averaging, noise reduction, etc. on the EEG signal, and these signal processing processes improve the signal quality of the EEG signal. These signal processing processes may be performed in the headset 3. The processing device 4 may be, for example, a desktop PC or a mobile PC such as a notebook PC or tablet PC. The results of the EEG analysis by the processing device 4 are output to, for example, an output device such as a display device provided in the processing device 4.

[0017] In this embodiment, the contact impedance measurement system 1 is realized, for example, as a part of the headset 3. As a preliminary step to acquiring a biological signal in the headset 3, the contact impedance measurement system 1 measures the contact impedance between the detection electrodes 5 and bias electrodes 6 of the headset 3, which will be described later, and the living body after the detection electrodes 5 and bias electrodes 6 are attached to the skin of the subject P.

[0018] The measured contact impedance is used to determine whether the detection electrode 5 and the bias electrode 6 are properly attached to the skin of the living body. For example, the measured contact impedance value is sent to the processing device 4 and displayed on the display device of the processing device 4.

[0019] [1.2. Configuration of the Contact Impedance Measuring System] In the present embodiment, as an example, the contact impedance measuring system 1 is realized inside the headset 3. However, the components of the contact impedance measuring system 1 described below can also be provided separately in the headset 3 and the processing device 4.

[0020] Fig. 2 is a diagram showing an example of the configuration of a headset 3 including the contact impedance measuring system 1 according to this embodiment. Fig. 3 is a diagram showing an example of the configuration of the contact impedance measuring system 1.

[0021] 2 , the headset 3 includes a plurality of electrodes attached to the subject P in contact with the skin. The electrodes include a detection electrode 5 and a bias electrode 6 that applies a reference potential to the living body. In this embodiment, one of the electrodes attached to the subject P is used as an auxiliary electrode 7 to measure the contact impedance between the detection electrode 5 and the bias electrode 6 and the skin of the subject P. Here, the detection electrode 5 and the bias electrode 6, whose contact impedance is measured, correspond to the first electrode and the second electrode, respectively, in the present disclosure. Furthermore, the auxiliary electrode 7 corresponds to the third electrode in the present disclosure. Note that, although the headset 3 includes one detection electrode 5 in this embodiment, it may include a plurality of detection electrodes 5.

[0022] The headset 3 includes a control device 8. The detection electrode 5 and the auxiliary electrode 7 are connected to the control device 8 via a detection electrode circuit 50 and an auxiliary electrode circuit 70, respectively. The configurations of the detection electrode circuit 50 and the auxiliary electrode circuit 70 will be described later.

[0023] 3 , the control device 8 includes a power supply circuit 9, a reference voltage generation circuit 10, a communication device 11, a memory 12, and a processor 13. The power supply circuit 9 may include, for example, a battery and a power supply monitoring IC that monitors the output of the battery. The reference voltage generation circuit 10 receives power supply from the power supply circuit 9 and generates a reference potential Vr to be applied to the bias electrode 6.

[0024] The communication device 11 includes a transceiver for the headset 3 to perform wireless or wired communication with the processing device 4. In this embodiment, the communication device 11 includes, for example, a wireless transceiver for performing wireless communication with the processing device 4 in accordance with the Bluetooth (registered trademark) communication standard.

[0025] The memory 12 is a volatile and / or non-volatile storage device, and may be configured, for example, as a semiconductor memory. The memory 12 stores the program 22 executed by the processor 13 and / or various parameters used in the execution of the processes. The memory 12 may also temporarily store data generated during the execution of the processes.

[0026] The processor 13 is a computer including, for example, a CPU, an MPU, or an MCU. The processor 13 may include a ROM in which a program is written, a RAM for temporarily storing data, etc. The processor 13 includes a calculation unit 20 and an acquisition unit 21 as functional elements or units.

[0027] These functional elements of the processor 13 are realized, for example, by the processor 13, which is a computer, executing the program 22. The program 22 can be stored in any computer-readable storage medium. Alternatively, all or part of the functional elements of the processor 13 can be configured by hardware, each of which includes one or more electronic circuit components.

[0028] The calculation unit 20 controls the detection electrode circuit 50 and the auxiliary electrode circuit 70 to calculate the contact impedance between the detection electrode 5 and the bias electrode 6 and the living body. For example, when the calculation unit 20 receives an instruction to measure the contact impedance from the processing device 4, it calculates the contact impedance of each of the detection electrode 5 and the bias electrode 6 and transmits the calculated values ​​of the contact impedance of each of the detection electrode 5 and the bias electrode 6 to the processing device 4. The calculation process of the contact impedance in the calculation unit 20 will be described later.

[0029] The acquiring unit 21 acquires the biosignals of the subject P from the detection electrodes 5 and the bias electrodes 6 according to conventional technology. For example, after the calculation of the contact impedance in the calculating unit 20 is completed, when the acquiring unit 21 receives a signal acquisition instruction from the processing device 4, the acquiring unit 21 acquires the biosignals from the detection electrodes 5 and the bias electrodes 6 and transmits the acquired biosignals to the processing device 4.

[0030] In the above configuration, the contact impedance measuring system 1 is made up of the parts of the headset 3 excluding the acquisition unit 21 of the control device 8 (the part indicated by the two-dot chain line in FIG. 3 ). The parts of the contact impedance measuring system 1 excluding the auxiliary electrode 7, the auxiliary electrode circuit 70, and the calculation unit 20 of the control device 8 are also used as components for the acquisition unit 21 to acquire biosignals.

[0031] FIG. 3 shows a detection electrode 5, a bias electrode 6, and an auxiliary electrode 7 attached so as to be in contact with the skin SK (shown as a dashed line) of the living body LB of the subject P.

[0032] The bias electrode 6 is connected to the output line of the reference voltage generating circuit 10, and its potential is maintained at the reference potential Vr.

[0033] The output line of the reference voltage generating circuit 10 applies a reference potential Vr to the circuit ground (or signal ground) lines of the detection electrode circuit 50 and the auxiliary electrode circuit 70. The detection electrode circuit 50 and the auxiliary electrode circuit 70 operate using the reference potential Vr as the ground potential in their circuit operation. In the following description, unless otherwise specified, the term "voltage" refers to a voltage relative to the reference potential Vr (i.e., a potential difference from the reference potential Vr).

[0034] The detection electrode circuit 50 connected to the detection electrode 5 includes an ADC (A / D converter) 51 that converts the voltage of the skin SK acquired from the detection electrode 5 into digital data. Here, in the contact impedance measurement system 1, the voltage of the skin SK acquired from the detection electrode 5 and the ADC 51 correspond to the first voltage and the first voltage detector in the present disclosure, respectively.

[0035] The input line of the ADC 51 is provided with a buffer amplifier 52 having an impedance conversion function, located immediately adjacent to the ADC 51. The buffer amplifier 52 has a high input impedance and hardly any input current flows through it. The ADC 51 repeatedly samples the voltage of the skin SK obtained from the detection electrode 5 at predetermined time intervals and outputs the digital value of the sampled voltage to the control device 8.

[0036] The predetermined time interval is set to a value equal to or less than the measurement current I (to be described later) so that the voltage waveform of the skin SK obtained from the detection electrode 5 can be grasped. １ The clock signal that defines the sampling time interval can be provided by, for example, a clock circuit and / or a frequency divider circuit (both not shown) that the control device 8 includes.

[0037] The detection electrode circuit 50 further supplies a measurement current I for contact impedance measurement to a current path from the detection electrode 5 through the living body LB to the bias electrode 6. １ The current source 53 supplies a measurement current I to the detection electrode 5. １The current flow is turned on and off by a switching circuit 54. The switching circuit 54 may be configured using, for example, a field effect transistor (FET) as a switching element. １ and current source 53 correspond to the first measured current and first current source in this disclosure.

[0038] The on / off operation of the switching circuit 54 is controlled by the control device 8. The measured current I １ may be an alternating current. The measured current I １ The frequency of the measurement current I is preferably set to a frequency within the frequency band of the biosignal that the acquisition unit 21 acquires using the detection electrode 5. This is because the contact impedance also has frequency characteristics, and therefore it is possible to calculate the contact impedance in the same frequency band as the biosignal that is to be acquired. １ can also be a direct current.

[0039] The auxiliary electrode circuit 70 connected to the auxiliary electrode 7 includes an ADC 71 that converts the voltage of the skin SK acquired from the auxiliary electrode 7 into digital data. Here, in the contact impedance measurement system 1, the voltage of the skin SK acquired from the auxiliary electrode 7 and the ADC 71 correspond to the second voltage and the second voltage detector in the present disclosure, respectively.

[0040] The input line of the ADC 71 is equipped with a buffer amplifier 72 having an impedance conversion function. The buffer amplifier 72 has a high input impedance and almost no input current flows. The ADC 71 samples the voltage of the skin SK obtained from the auxiliary electrode 7 at a predetermined time interval and outputs the digital value of the sampled voltage to the control device 8. The predetermined time interval is preferably the same as the sampling time interval in the ADC 51 described above.

[0041] Calculation process of contact impedance] Next, the calculation process of contact impedance performed by the calculation unit 20 of the control device 8 will be described with reference to the flowcharts shown in Fig. 3 and Fig. 4. Fig. 4 is a flowchart showing the procedure of the process of the contact impedance measurement method performed by the processor 13, which is a computer provided in the contact impedance measurement system 1.

[0042] The process shown in FIG. 4 starts, for example, when the detection electrode 5, bias electrode 6, and auxiliary electrode 7 are attached so as to contact the skin SK of the living body LB of the subject P, the headset 3 is turned on, and the control device 8 receives an instruction to measure the contact impedance from the processing device 4.

[0043] When the process starts, the calculation unit 20 first turns on the switching circuit 54 of the detection electrode circuit 50, and supplies a measurement current I to the current path from the detection electrode 5 through the living body LB to the bias electrode 6. １ The calculation unit 20 calculates the measured current I １ The voltage V of the skin SK detected by the detection electrode 5 when the current is applied to the living body LB ＥＥＧ１ is acquired by the ADC 51 of the detection electrode circuit 50 (S102). ＥＥＧ１ is the measurement current I, which is, for example, an AC current. １ By calculating the average value, the voltage V of the skin SK obtained from the detection electrode 5 is removed from the noise component, and the voltage V is calculated as V ＥＥＧ１ can be measured.

[0044] The calculation unit 20 also calculates the measured current I １ The voltage V of the skin SK detected from the auxiliary electrode 7 when current is applied to the living body LB. ＩＭＰ is acquired by the ADC 71 of the auxiliary electrode circuit 70 (S104). Next, the calculation unit 20 turns off the switching circuit 54, and the measurement current I １ The power supply to the motor is stopped (S106).

[0045] V measured in step S104 ＩＭＰ is, for example, the above-mentioned VＥＥＧ１ As with the measurement of １ It can be an average value of the peak voltage of the voltage V obtained from the auxiliary electrode 7 during the time length of 10 periods.

[0046] Here, if the current flowing into the buffer amplifiers 52 and 72 is negligibly small, the measurement current I supplied from the current source 53 is １ can be considered to flow only in the path from the detection electrode 5 to the bias electrode 6. ＥＥＧ１ and V ＩＭＰ are expressed by the following equations (1) and (2), respectively.

[0047] In formulas (1) and (2), R ＥＥＧ is the contact impedance between the detection electrode 5 and the skin SK, R ＢＩＡＳ is the contact impedance between the bias electrode 6 and the skin SK, I Ｐ１ is the measured current I １ The peak current is the measured current I １ Peak current I Ｐ１ can be stored in advance in the memory 12 as characteristic information of the current source 53 .

[0048] From equations (1) and (2), the contact impedance R of the bias electrode 6 is ＢＩＡＳ and the contact impedance R of the detection electrode 5 ＥＥＧ are given by the following equations (3) and (4), respectively.

[0049] Therefore, the calculation unit 20 calculates V using equation (3). ＩＭＰ from the contact impedance R of the bias electrode 6 ＢＩＡＳ is calculated (S108), and then (V ＥＥＧ１ -V ＩＭＰ ) to the contact impedance R of the detection electrode 5 ＥＥＧ Then, the calculation unit 20 calculates the contact impedance R of the detection electrode 5 calculated above (S110). ＥＥＧ and the bias electrode 6 contact impedance R ＢＩＡＳ is transmitted to the processing device 4 (S112), and the process ends.

[0050] As described above, in the contact impedance measurement system 1 of this embodiment, the auxiliary electrode 7 is provided, so that the contact impedance R ＢＩＡＳ The voltage V represents the voltage drop at ＩＭＰ As a result, in the contact impedance measurement system 1, the values ​​R of the contact impedances of the detection electrode 5 and the bias electrode 6 attached in contact with the living body LB to the living body LB are obtained. ＥＥＧ and R ＢＩＡＳ It should be noted that the impedance inside the human body, which forms the current path between the bias electrode 6 and the detection electrode 5, is negligibly small compared to the contact impedance, so the bias electrode 6 and the detection electrode 5 are not limited to being arranged as shown in FIG. 1 and may be arranged at positions separated from each other.

[0051] [2. Second Embodiment] Next, a second embodiment of the present invention will be described. [2.1. Configuration of Contact Impedance Measurement System] Fig. 5 is a diagram showing the configuration of a contact impedance measurement system 1A according to a second embodiment of the present invention, and corresponds to Fig. 3 showing the contact impedance measurement system 1 according to the first embodiment. In Fig. 5, the same components as those in the contact impedance measurement system 1 shown in Fig. 3 are designated by the same reference numerals as in Fig. 3, and the above description of each component is applicable.

[0052] The contact impedance measuring system 1A can be realized as a part of a headset 3A. The headset 3A can be used in the biosignal measuring system 2 in place of the headset 3.

[0053] The contact impedance measurement system 1A differs from the contact impedance measurement system 1 in that it includes a control device 8A instead of the control device 8. The control device 8A has the same configuration as the control device 8, but differs in that it includes a processor 13A instead of the processor 13. The processor 13A has the same configuration as the processor 13, but differs in that it includes a calculation unit 20A instead of the calculation unit 20. The operation or processing content of the calculation unit 20A is different from that of the calculation unit 20. The operation of the calculation unit 20A will be described later.

[0054] The calculation unit 20A is a functional element or functional unit included in the processor 13A. The calculation unit 20A is realized, for example, by the processor 13A, which is a computer, executing a program 22A stored in the memory 12. The program 22A can be stored in any computer-readable storage medium. Alternatively, the calculation unit 20A can be configured as hardware including one or more electronic circuit components.

[0055] The contact impedance measuring system 1A also differs from the contact impedance measuring system 1 in that it includes an auxiliary electrode circuit 70A instead of the auxiliary electrode circuit 70. Unlike the auxiliary electrode circuit 70, the auxiliary electrode circuit 70A does not include an ADC 71 and a buffer amplifier 72, and a measurement current I is applied to the current path from the auxiliary electrode 7 through the living body LB to the bias electrode 6. ２ The auxiliary electrode circuit 70A also includes a current source 73 that supplies a measurement current I to the auxiliary electrode 7. ２ The switching circuit 74 is configured to turn on and off the power supply to the power supply 1. The switching circuit 74 may be configured using, for example, an FET as a switching element. The on / off operation of the switching circuit 74 is controlled by the control device 8A.

[0056] Measuring current I ２ may be an alternating current. The measured current I ２ The frequency of the measured current I １ It is preferable that the frequency of the measurement current I ２ is the measured current I １ When a direct current is used as the current, it can be regarded as a direct current.

[0057] Here, in the contact impedance measurement system 1A, the voltage acquired from the detection electrode 5 and the ADC 51 correspond to the first voltage and the first voltage detector in the present disclosure, respectively. １ In the contact impedance measurement system 1A, the current source 73 provided in the auxiliary electrode circuit 70A and the measurement current I supplied by the current source 73 correspond to the first measurement current and the first current source in the present disclosure. ２ correspond to the second current source and the second measurement current in the present disclosure, respectively.

[0058] [2.2. Contact Impedance Calculation Process] Next, the contact impedance calculation process performed by the calculation unit 20A of the control device 8A will be described with reference to the flowcharts shown in Fig. 6 and Fig. 7. Fig. 7 is a flowchart showing the procedure of the process of the contact impedance measurement method performed by the processor 13A, which is a computer included in the contact impedance measurement system 1A.

[0059] The process shown in FIG. 7 starts, for example, when the detection electrode 5, bias electrode 6, and auxiliary electrode 7 are attached so as to contact the skin SK of the living body LB of the subject P, the headset 3A is turned on, and the control device 8A receives an instruction to measure the contact impedance from the processing device 4.

[0060] When the process starts, the calculation unit 20A first turns on the switching circuit 54 of the detection electrode circuit 50, and causes the current source 53 to supply a measurement current I to a current path from the detection electrode 5 through the living body LB to the bias electrode 6. １ The calculation unit 20A calculates the measured current I １ When current is applied to the living body LB, the voltage V of the skin SK detected by the detection electrode 5 is ＥＥＧ１ Then, the calculation unit 20A turns off the switching circuit 54 and acquires the measurement current I １ The power supply to the motor is stopped (S204).

[0061] V measured in step S202 ＥＥＧ１For example, V can be the average value of the peak voltage of the voltage V of the skin SK acquired from the detection electrode 5 over a time length of 10 cycles of the measurement current I1, which is an AC current. By calculating the average value, V can be obtained as a voltage value from which noise has been removed. ＥＥＧ１ can be measured.

[0062] Next, the calculation unit 20A turns on the switching circuit 74 of the auxiliary electrode circuit 70A, and the current source 73 supplies a measurement current I to the current path from the auxiliary electrode 7 through the living body LB to the bias electrode 6. ２ The calculation unit 20A calculates the measured current I ２ When current is applied to the living body LB, the voltage V of the skin SK detected by the detection electrode 5 is ＥＥＧ２ Then, the calculation unit 20A turns off the switching circuit 74, and the measurement current I ２ The power supply to the motor is stopped (S210).

[0063] V measured in step S206 ＥＥＧ２ is, for example, the measured current I ２ It can be an average value of the peak voltage of the voltage V obtained from the detection electrode 5 over a time length of 10 periods.

[0064] Here, if the current flowing into the buffer amplifier 52 is negligibly small, V ＥＥＧ１ and V ＥＥＧ２ is expressed by the following equations (5) and (6).

[0065] In formula (6), I Ｐ２ is the measured current I ２ The peak current is the measured current I ２ Peak current I Ｐ２ can be stored in advance in the memory 12 as characteristic information of the current source 73 .

[0066] From equations (5) and (6), the contact impedance R of the bias electrode 6 is ＢＩＡＳ and the contact impedance R of the detection electrode 5 ＥＥＧ are given by the following equations (7) and (8), respectively.

[0067] The calculation unit 20A calculates V using equation (7). ＥＥＧ２ from the contact impedance R of the bias electrode 6 ＢＩＡＳ is calculated (S212), and V is calculated using equation (8). ＥＥＧ１ and the above calculated R ＢＩＡＳ from the contact impedance R of the detection electrode 5 ＥＥＧ Then, the calculation unit 20 calculates the contact impedance R of the detection electrode 5 calculated above (S214). ＥＥＧ and the bias electrode 6 contact impedance R ＢＩＡＳ is transmitted to the processing device 4 (S216), and the process ends.

[0068] As described above, in the contact impedance measurement system 1A of this embodiment, the auxiliary electrode 7 is provided in the same manner as in the contact impedance measurement system 1, and the measurement current I2 is passed from the auxiliary electrode 7 to the bias electrode 6, thereby obtaining the contact impedance R of the bias electrode 6 as additional information. ＢＩＡＳ The voltage drop at the detection electrode 5 is V ＥＥＧ２ As a result, in the contact impedance measurement system 1, the values ​​R of the contact impedance of the detection electrode 5 and the bias electrode 6 attached in contact with the living body LB with respect to the living body LB can be obtained. ＥＥＧ and R ＢＩＡＳ In this embodiment, the ADC 71 is not necessary, as compared with the first embodiment, and it is possible to reduce costs and make the contact impedance measuring system 1A smaller.

[0069] [3. Third Embodiment] Next, a third embodiment of the present invention will be described. [3.1. Configuration of Contact Impedance Measurement System] Fig. 7 is a diagram showing an example of the configuration of a headset 3B including a contact impedance measurement system 1B according to a third embodiment of the present invention, and corresponds to Fig. 2 showing the contact impedance measurement system 1 according to the first embodiment. In Fig. 7, the same components as those in the headset 3 shown in Fig. 2 are indicated by the same reference numerals as those in Fig. 2, and the above description of each component is applicable.

[0070] 2 , but differs in that it does not include the auxiliary electrode 7 and includes multiple detection electrodes 5 instead of one. The headset 3B also differs from the headset 3 in that it includes a control device 8B instead of the control device 8. The contact impedance measuring system 1B can be configured as part of the headset 3B. The headset 3B can be used in the biosignal measuring system 2 in place of the headset 3.

[0071] The contact impedance measurement system 1B can operate with a combination of any two of the multiple detection electrodes 5. Hereinafter, the two detection electrodes 5 constituting the combination will be referred to as detection electrodes 5A and 5B. The contact impedance measurement system 1B uses one of the detection electrodes 5 (for example, detection electrode 5B) as the auxiliary electrode 7.

[0072] Specifically, the contact impedance measurement system 1B operates in the same manner as the contact impedance measurement system 1 according to the first embodiment described above, using the detection electrode 5B as the auxiliary electrode 7 to obtain additional information and measure the contact impedance of each of the detection electrode 5A and the bias electrode 6. Thereafter, the contact impedance measurement system 1B passes a measurement current from the detection electrode 5B to the bias electrode 6, and measures the contact impedance of the detection electrode 5B used as the auxiliary electrode 7 from the voltage at the detection electrode 5B and the contact impedance of the bias electrode 6.

[0073] Fig. 8 is a diagram showing the configuration of a contact impedance measuring system 1B according to the third embodiment, and corresponds to Fig. 3 showing the contact impedance measuring system 1 according to the first embodiment. In Fig. 8, the same components as those in the contact impedance measuring system 1 shown in Fig. 3 are denoted by the same reference numerals as in Fig. 3, and the above description of each component is applicable.

[0074] The control device 8B has a similar configuration to the control device 8, but differs in that it includes a processor 13B instead of the processor 13. The processor 13B has a similar configuration to the processor 13, but differs in that it includes a calculation unit 20B instead of the calculation unit 20. The operation or processing content of the calculation unit 20B differs from that of the calculation unit 20. The operation of the calculation unit 20B will be described later.

[0075] The calculation unit 20B is a functional element or functional unit included in the processor 13B. The calculation unit 20B is realized, for example, by the processor 13B, which is a computer, executing a program 22B stored in the memory 12. The program 22B can be stored in any computer-readable storage medium. Alternatively, the calculation unit 20B can be configured as hardware including one or more electronic circuit components.

[0076] 8 shows a state in which two detection electrodes 5, namely, detection electrodes 5A and 5B, and a bias electrode 6, are attached so as to contact the skin SK (shown as a dashed line) of a living body LB of a subject P. The detection electrodes 5A and 5B are connected to a control device 8B via detection electrode circuits 50A and 50B, which are detection electrode circuits 50, respectively. That is, the detection electrode circuits 50A and 50B are configured in the same manner as the detection electrode circuit 50. The letters "A" and "B" added to the reference numerals of the components in the detection electrode circuits 50A and 50B shown in FIG. 8 are added simply to distinguish them as components in the detection electrode circuits 50A and 50B, respectively, and do not indicate any difference between the components.

[0077] That is, the detection electrode circuit 50A includes an ADC 51A, a buffer amplifier 52A, a current source 53A, and a switching circuit 54A, which are similar to the ADC 51, the buffer amplifier 52, the current source 53, and the switching circuit 54 of the detection electrode circuit 50. The detection electrode circuit 50B includes an ADC 51B, a buffer amplifier 52B, a current source 53B, and a switching circuit 54B, which are similar to the ADC 51, the buffer amplifier 52, the current source 53, and the switching circuit 54 of the detection electrode circuit 50.

[0078] As described above, in this embodiment, the detection electrode 5B is used as the auxiliary electrode 7. Here, in the contact impedance measurement system 1B, the detection electrode 5B used as the auxiliary electrode 7 corresponds to the third electrode in the present disclosure. The voltage detected from the skin SK by the detection electrode 5B as the third electrode, the ADC 51B of the detection electrode circuit 50B, the current source 53B, and the measurement current I supplied by the current source 53B are used as the voltage. １Ｂ correspond to the second voltage, the second voltage detector, the second current source, and the second current in the present disclosure, respectively.

[0079] The detection electrode 5A and the bias electrode 6, whose contact impedance is measured using the detection electrode 5B as the auxiliary electrode 7, correspond to the first electrode and the second electrode in the present disclosure, respectively. The voltage detected from the skin SK by the detection electrode 5A, which is the first electrode, the ADC 51A of the detection electrode circuit 50A, the current source 53A, and the measurement current I supplied by the current source 53A are used as the detection electrode circuit 50A. １Ａ correspond to the first voltage, the first voltage detector, the first current source, and the first measured current, respectively, in the present disclosure.

[0080] Calculation process of contact impedance] Next, the calculation process of contact impedance performed by the calculation unit 20 of the control device 8B will be described with reference to the flowcharts shown in Fig. 8 and Fig. 9. Fig. 9 is a flowchart showing the procedure of the process of the contact impedance measurement method performed by the processor 13B, which is a computer included in the contact impedance measurement system 1B.

[0081] The process shown in FIG. 7 starts, for example, when a plurality of detection electrodes 5 and a bias electrode 6 are attached so as to contact the skin SK of the living body LB of the subject P, the headset 3B is turned on, and the control device 8B receives an instruction to measure the contact impedance from the processing device 4.

[0082] When the process starts, the calculation unit 20B first turns on the switching circuit 54A of one of the detection electrode circuits 50A, and supplies a measurement current I to the current path from the detection electrode 5A through the living body LB to the bias electrode 6. １Ａ The calculation unit 20B calculates the measured current I １ＡWhen current is applied to the living body LB, the voltage V of the skin SK detected by the detection electrode 5A is ＥＥＧ１ＡＡ and the voltage V of the skin SK detected by the detection electrode 5B. ＥＥＧ１ＡＢ (S302). ＥＥＧ１ＡＡ and voltage V ＥＥＧ１ＡＢ are acquired by the ADC 51A of the detection electrode circuit 50A and the ADC 51B of the detection electrode circuit 50B, respectively.

[0083] Voltage V ＥＥＧ１ＡＡ and voltage V ＥＥＧ１ＡＢ and the measured current I, which is, for example, an AC current. １Ａ It can be an average value of the peak voltages of the voltage V of the skin SK acquired from the detection electrodes 5A and 5B over a time length of 10 periods.

[0084] Next, the calculation unit 20B turns off the switching circuit 54A of the detection electrode circuit 50A, and the measurement current I １Ａ Next, the calculation unit 20B turns on the switching circuit 54B of the other detection electrode circuit 50B, and supplies the measurement current I to the current path from the detection electrode 5B through the living body LB to the bias electrode 6 (S304). １Ｂ is energized (S306).

[0085] Then, the calculation unit 20B calculates the measured current I １Ｂ When current is applied to the living body LB, the voltage V of the skin SK detected by the detection electrode 5B is ＥＥＧ１ＢＢ is acquired by the ADC 51B of the detection electrode circuit 50B (S308). Subsequently, the calculation unit 20B turns off the switching circuit 54B of the detection electrode circuit 50B, and the measurement current I １Ｂ The power supply to the voltage V is stopped (S310). ＥＥＧ１ＢＢ is the measured current I, which is an AC current １Ｂ The voltage V may be an average value of the peak voltages of the voltage V obtained from the detection electrode 5B over a time length corresponding to 10 periods.

[0086] Here, if the current flowing into the buffer amplifiers 52A and 52B is negligibly small, the voltage V obtained as described above ＥＥＧ１ＡＡ , V ＥＥＧ１ＡＢ , and voltage V ＥＥＧ１ＢＢare expressed by the following equations (9), (10), and (11), respectively.

[0087] In formulas (9), (10), and (11), R ＥＥＧＡ is the contact impedance between the detection electrode 5A and the skin SK, R ＥＥＧＢ is the contact impedance between the detection electrode 5B and the skin SK, R ＢＩＡＳ is the contact impedance between the bias electrode 6 and the skin SK, I Ｐ１Ａ is the measured current I1 Ａ Peak current, I Ｐ１Ｂ is the measured current I １Ｂ The peak current is the measured current I １Ａ Peak current I Ｐ１Ａ and the measured current I １Ｂ Peak current I Ｐ１Ｂ can be stored in advance in the memory 12 as characteristic information of the current sources 53A and 53B.

[0088] From equations (9), (10), and (11), the contact impedance R of the bias electrode 6 is ＢＩＡＳ , the contact impedance R of the detection electrode 5A ＥＥＧＡ , and the contact impedance R of the detection electrode 5B ＥＥＧＢ are given by the following equations (12), (13), and (14), respectively.

[0089] The calculation unit 20B calculates V using equation (12). ＥＥＧ１ＡＢ from the contact impedance R of the bias electrode 6 ＢＩＡＳ is calculated (S312), and V is calculated using equation (13). ＥＥＧ１ＡＡ and the calculated R ＢＩＡＳ from the contact impedance R of the detection electrode 5A ＥＥＧＡ (S314). In addition, the calculation unit 20B calculates V ＥＥＧ１ＢＢ and the calculated R ＢＩＡＳ from the contact impedance R of the detection electrode 5B ＥＥＧＢ The calculation unit 20B calculates the contact impedance R of the detection electrodes 5A and 5B calculated above (S316). ＥＥＧＡ and R ＥＥＧＢ , and the bias electrode 6 contact impedance RＢＩＡＳ is transmitted to the processing device 4 (S318), and the process ends.

[0090] As described above, the contact impedance measurement system 1B of this embodiment operates with any two of the detection electrodes 5A and 5B among the plurality of detection electrodes 5. In the contact impedance measurement system 1B, additional information is obtained by using one of the detection electrodes 5B as the auxiliary electrode 7, and the contact impedance R of the other detection electrode 5A and the bias electrode 6 is calculated. ＥＥＧＡ and R ＢＩＡＳ In the contact impedance measurement system 1B, the measurement current I is further measured from the detection electrode 5B used as the auxiliary electrode 7. １Ｂ By passing the voltage V ＥＥＧ１ＢＢ and the contact impedance R of the bias electrode 6 measured above. ＢＩＡＳ From this, the contact impedance R of the detection electrode 5B ＥＥＧＢ Also measure.

[0091] Furthermore, the contact impedance R of the bias electrode 6 is ＢＩＡＳ is measured, the calculation unit 20B can then measure the contact impedances of all the other detection electrodes 5 other than the detection electrodes 5A and 5B. That is, the calculation unit 20B sequentially instructs the detection electrode circuit 50 to flow a measurement current from the detection electrode 5 to measure the voltage of the detection electrode 5, and calculates the relationship between the measured voltage and the contact impedance R of the bias electrode 6. ＢＩＡＳ From this, it is possible to measure the contact impedance of the detection electrode 5. When EEG measurement is performed using multiple electrodes, by adopting this embodiment, it is possible to measure the contact impedance of all electrodes used in EEG measurement without placing any extra auxiliary electrodes.

[0092] 4. Other Embodiments

[0093] In the above-described embodiments, the contact impedance measurement systems 1, 1A, and 1B measure the contact impedance R ＢＩＡＳ , R ＥＥＧThe contact impedance R ＢＩＡＳ , R ＥＥＧ The measurement and transmission of the above may be repeated at predetermined time intervals. In this case, the processing device 4 can display the real-time contact impedance of the detection electrodes 5, bias electrodes 6, etc. on the display device. This allows the user to properly attach these electrodes to the subject P while checking the real-time contact impedance of the detection electrodes 5, bias electrodes 6, etc.

[0094] In the above-described embodiments, the contact impedance measurement system 1, 1A, 1B is realized as part of a headset 3, 3A, 3B equipped with electrodes that contact a living body, but the calculation unit 20, 20A, or 20B may be provided in a processing device 4, and the contact impedance measurement system 1, 1A, 1B may be realized as part of a biosignal measurement system 2 that includes the processing device 4.

[0095] Furthermore, in the above-described embodiment, the headsets 3, 3A, and 3B are ear-hook types, but they may be any type of device equipped with electrodes that come into contact with the living body, such as a hat type that is worn on the head.

[0096] In the above-described embodiment, the contact impedance measurement systems 1, 1A, and 1B are applied to the biosignal measurement system 2, which is an electroencephalogram (EEG) measurement system, but they may be applied to any biosignal measurement system that uses multiple electrodes that are placed in contact with a living body. Such a biosignal measurement system may be an electrocardiogram measurement system, an electromyogram measurement system, or the like.

[0097] The present invention is not limited to the configurations of the above-described embodiments, and can be implemented in various forms without departing from the spirit of the invention.

[0098] 5. Configurations Supported by the Above-described Embodiments The above-described embodiments support the following configurations.

[0099] (Configuration 1) A contact impedance measurement system for measuring the contact impedance of a first electrode contactable with a living body and a second electrode applying a reference potential to the living body, the system comprising: a first current source for passing a first measurement current through a current path from the first electrode through the living body to the second electrode; a first voltage detector for detecting a first voltage of the first electrode relative to the reference potential; a second voltage detector for detecting a second voltage of a third electrode in contact with the living body relative to the reference potential; and a calculation unit for calculating the contact impedance of each of the first electrode and the second electrode with the living body, the calculation unit calculating the contact impedance of each of the first electrode and the second electrode with the living body from the first measurement current and the first voltage and the second voltage when the first measurement current is passed. According to Configuration 1, the system can measure the contact impedance of each of the first electrode and the second electrode, which is a bias electrode, with the living body, using the third electrode as an auxiliary electrode.

[0100] (Configuration 2) A contact impedance measurement system for measuring the contact impedance of a first electrode that can contact a living body and a second electrode that applies a reference potential to the living body, the system comprising: a first current source that supplies a first measurement current to a current path that runs from the first electrode through the living body to the second electrode; a first voltage detector that detects a first voltage of the first electrode relative to the reference potential; a second current source that supplies a second measurement current to a current path that runs from a third electrode in contact with the living body to the second electrode through the living body; and a calculation unit that calculates the contact impedance of each of the first electrode and the second electrode with the living body from the first measurement current, the second measurement current, the first voltage when the first measurement current is passed, and the first voltage when the second measurement current is passed. According to Configuration 2, the system can measure the contact impedance of each of the first electrode and the second electrode, which is a bias electrode, with the living body, using the third electrode as an auxiliary electrode.

[0101] (Configuration 3) The contact impedance measurement system according to Configuration 2 further includes a second voltage detector that detects a second voltage of the third electrode relative to the reference potential, and the calculation unit measures and calculates the contact impedance of each of the first electrode, the second electrode, and the third electrode with the living body from the first measurement current, the second measurement current, the first voltage and the second voltage when the first measurement current is passed, and the second voltage when the second measurement current is passed. In the contact impedance measurement system of Configuration 3, the third electrode has the same configuration as the first electrode, which includes a voltage detector and a current source, so that the contact impedances of all of the first electrode, the second electrode, and the third electrode can be measured. Furthermore, this allows all of the two or more electrodes in contact with the living body, except for the second electrode, which is a bias electrode, to have the same configuration as the first electrode and the third electrode, so that the contact impedance values ​​of all of the electrodes can be easily measured.

[0102] (Configuration 4) The contact impedance measuring system according to Configuration 1, wherein the first measurement current is an AC current, and the calculation unit calculates the contact impedance of each of the first electrode and the second electrode with the living body from a peak current of the first measurement current, the first voltage, and the peak voltage of the second voltage. The contact impedance measuring system of Configuration 4 can calculate the contact impedance in the same frequency band as the biological signal to be acquired in Configuration 1.

[0103] (Configuration 5) The contact impedance measurement system according to Configuration 2, wherein the first measurement current and the second measurement current are AC, and the calculation unit calculates the contact impedance of each of the first electrode and the second electrode with the living body from a peak current of the first measurement current, a peak current of the second measurement current, and a peak voltage of the first voltage. The contact impedance measurement system of Configuration 5, in Configuration 2, can calculate the contact impedance in the same frequency band as the biological signal to be acquired.

[0104] (Configuration 6) A computer-executed contact impedance measurement method for measuring the contact impedance of a first electrode contactable with a living body and a second electrode that applies a reference potential to the living body, the method comprising: a current passing step of passing a first measurement current from a first current source through a current path from the first electrode through the living body to the second electrode; a first voltage detection step of detecting a first voltage of the first electrode relative to the reference potential; a second voltage detection step of detecting a second voltage of a third electrode in contact with the living body relative to the reference potential; and a calculation step of calculating the contact impedance of each of the first electrode and the second electrode with the living body, wherein the calculation step calculates the contact impedance of each of the first electrode and the second electrode with the living body from the first measurement current and values ​​of the first voltage and the second voltage when the first measurement current is passed. According to Configuration 6, the contact impedance measurement method can measure the respective values ​​of the contact impedance of the first electrode and the second electrode, which is a bias electrode, with the living body, using a third electrode as an auxiliary electrode.

[0105] (Configuration 7) A contact impedance measurement method executed by a computer for measuring the contact impedance of a first electrode that can contact a living body and a second electrode that applies a reference potential to the living body, the contact impedance measurement method comprising: a first current flow step of passing a first measurement current from a first current source through a current path from the first electrode through the living body to the second electrode; a first voltage detection step of detecting a first voltage of the first electrode relative to the reference potential; a second current flow step of passing a second measurement current from a second current source through a current path from a third electrode that contacts the living body through the living body to the second electrode; and a calculation step of calculating the contact impedance of each of the first electrode and the second electrode with the living body, wherein in the calculation step, the contact impedance of each of the first electrode and the second electrode with the living body is calculated from the first measurement current, the second measurement current, the first voltage when the first measurement current is passed, and the first voltage when the second measurement current is passed. According to the seventh aspect, the third electrode is used as an auxiliary electrode, and the contact impedances of the first electrode and the second electrode, which is a bias electrode, with respect to the living body can be measured.

[0106] (Configuration 8) A program executed by a computer for measuring the contact impedance of a first electrode that can contact a living body and a second electrode that applies a reference potential to the living body, the program causing the computer to execute the following steps: a current passing step of passing a first measurement current from a first current source through a current path from the first electrode through the living body to the second electrode; a first voltage detection step of detecting a first voltage of the first electrode relative to the reference potential; a second voltage detection step of detecting a second voltage of a third electrode in contact with the living body relative to the reference potential; and a calculation step of calculating the contact impedance of each of the first electrode and the second electrode with the living body, the calculation step calculating the contact impedance of each of the first electrode and the second electrode with the living body from the first measurement current and values ​​of the first voltage and the second voltage when the first measurement current is passed. Configuration 8 achieves the same effects as the contact impedance measurement system of Configuration 1.

[0107] (Configuration 9) A computer-executable program for measuring contact impedances of a first electrode contactable with a living body and a second electrode that applies a reference potential to the living body, the program causing the computer to execute the following steps: a first current flow step of passing a first measurement current from a first current source through a current path from the first electrode through the living body to the second electrode; a first voltage detection step of detecting a first voltage of the first electrode relative to the reference potential; a second current flow step of passing a second measurement current from a second current source through a current path from a third electrode in contact with the living body through the living body to the second electrode; and a calculation step of calculating the contact impedances of the first electrode and the second electrode with the living body, respectively, from the first measurement current, the second measurement current, the first voltage when the first measurement current is passed, and the first voltage when the second measurement current is passed. Configuration 9 achieves the same effects as the contact impedance measurement system of Configuration 2.

[0108] 1...contact impedance measurement system, 2...biological signal measurement system, 3, 3A, 3B...headset, 4...processing device, 5, 5A, 5B...detection electrode, 6...bias electrode, 7, 7A...auxiliary electrode, 8, 8A, 8B...control device, 9...power supply circuit, 10...reference voltage generation circuit, 11...communication device, 12...memory, 13, 13A, 13B...processor, 20, 20A, 20B...calculation unit, 21...acquisition unit, 22, 22A, 22B...program, 50, 50A, 50B...detection electrode circuit, 51, 51A, 51B, 71...ADC, 52, 52A, 52B, 72...buffer amplifier, 53, 53A, 53B, 73...current source, 54, 54A, 54B, 74...switching circuit, 70...auxiliary electrode circuit, LB...living body, P...subject, SK...skin.

Claims

1. A contact impedance measurement system for measuring the contact impedance of a first electrode that can contact a living organism and a second electrode that applies a reference potential to the living organism, comprising: a first current source that flows a first measurement current through a current path that runs from the first electrode through the living organism to the second electrode; a first voltage detector that detects a first voltage of the first electrode relative to the reference potential; a second voltage detector that detects a second voltage of a third electrode that contacts the living organism relative to the reference potential; and a calculation unit that calculates the contact impedance of each of the first electrode and the second electrode with the living organism, wherein the calculation unit calculates the contact impedance of each of the first electrode and the second electrode with the living organism from the first measurement current and the first voltage and the second voltage when the first measurement current is passed.

2. A contact impedance measurement system for measuring the contact impedance of a first electrode that can contact a living body and a second electrode that provides a reference potential to the living body, comprising: a first current source that flows a first measurement current in a current path that runs from the first electrode through the living body to the second electrode; a first voltage detector that detects a first voltage of the first electrode relative to the reference potential; a second current source that supplies a second measurement current in a current path that runs from a third electrode that contacts the living body to the second electrode through the living body; and a calculation unit that calculates the contact impedance of each of the first electrode and the second electrode with the living body from the first measurement current, the second measurement current, the first voltage when the first measurement current is passed, and the first voltage when the second measurement current is passed.

3. A contact impedance measurement system as described in claim 2, further comprising a second voltage detector that detects a second voltage of the third electrode relative to the reference potential, and wherein the calculation unit measures and calculates the contact impedance of each of the first electrode, second electrode, and third electrode with the living body from the first measurement current, the second measurement current, the first voltage and the second voltage when the first measurement current is passed, and the second voltage when the second measurement current is passed.

4. The contact impedance measuring system of claim 1, wherein the first measured current is an alternating current, and the calculation unit calculates the contact impedance of each of the first electrode and the second electrode with the living body from the peak current of the first measured current, the peak voltage of the first voltage, and the peak voltage of the second voltage.

5. The contact impedance measuring system of claim 2, wherein the first measurement current and the second measurement current are alternating currents, and the calculation unit calculates the contact impedance of each of the first electrode and the second electrode with the living body from the peak current of the first measurement current, the peak current of the second measurement current, and the peak voltage of the first voltage.

6. A computer-implemented contact impedance measurement method for measuring the contact impedance of a first electrode that can contact a living body and a second electrode that applies a reference potential to the living body, comprising: a current-passing step of passing a first measurement current from a first current source through a current path from the first electrode through the living body to the second electrode; a first voltage detection step of detecting a first voltage of the first electrode relative to the reference potential; a second voltage detection step of detecting a second voltage of a third electrode in contact with the living body relative to the reference potential; and a calculation step of calculating the contact impedance of each of the first and second electrodes with the living body, wherein in the calculation step, the contact impedance of each of the first and second electrodes with the living body is calculated from the first measurement current and the first and second voltages when the first measurement current is passed.

7. A contact impedance measurement method executed by a computer for measuring the contact impedance of a first electrode that can contact a living body and a second electrode that applies a reference potential to the living body, comprising: a first current-flow step of flowing a first measurement current from a first current source into a current path that runs from the first electrode through the living body to the second electrode; a first voltage detection step of detecting a first voltage of the first electrode relative to the reference potential; a second current-flow step of flowing a second measurement current from a second current source into a current path that runs from a third electrode in contact with the living body to the second electrode through the living body; and a calculation step of calculating the contact impedance of each of the first and second electrodes with the living body, wherein in the calculation step, the contact impedance of each of the first and second electrodes with the living body is calculated from the first measurement current, the second measurement current, the first voltage when the first measurement current is flowed, and the first voltage when the second measurement current is flowed.

8. A program executed by a computer for measuring the contact impedance of a first electrode that can contact a living body and a second electrode that provides a reference potential to the living body, the program causing the computer to execute the following steps: a current flow step of flowing a first measurement current from a first current source through a current path from the first electrode through the living body to the second electrode; a first voltage detection step of detecting a first voltage of the first electrode relative to the reference potential; a second voltage detection step of detecting a second voltage of a third electrode in contact with the living body relative to the reference potential; and a calculation step of calculating the contact impedance of each of the first electrode and the second electrode with the living body, wherein in the calculation step, the contact impedance of each of the first electrode and the second electrode with the living body is calculated from the first measurement current and the first voltage and the second voltage when the first measurement current is passed.

9. A program executed by a computer for measuring the contact impedance of a first electrode that can contact a living body and a second electrode that provides a reference potential to the living body, the program causing the computer to execute the following steps: a first current flow step of flowing a first measurement current from a first current source into a current path that runs from the first electrode through the living body to the second electrode; a first voltage detection step of detecting a first voltage of the first electrode relative to the reference potential; a second current flow step of flowing a second measurement current from a second current source into a current path that runs from a third electrode in contact with the living body to the second electrode through the living body; and a calculation step of calculating the contact impedance of each of the first electrode and the second electrode with the living body, wherein in the calculation step, the program calculates the contact impedance of each of the first electrode and the second electrode with the living body from the first measurement current, the second measurement current, the first voltage when the first measurement current is flowed, and the first voltage when the second measurement current is flowed.

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