Biological signal measurement system

Abstract

The present invention comprises a first device (100a) and a second device (100b). The first device (100a) is, for example, a wearable device used by being worn on a human body (150). The second device (100b) is, for example, a non-wearable device that is not worn on the human body (150). The first device (100a) is provided with a measurement unit (101a), and the measurement unit (101a) is provided with an electrode (102a), a reception circuit (103a), an amplification circuit (104a), and a transmission circuit (105a). The second device (100b) is provided with a measurement unit (101b), and the measurement unit (101b) is provided with an electrode (102b), a reception circuit (103b), an amplification circuit (104b), and a transmission circuit (105b).

Description

Biological signal measurement system

[0001] The present invention relates to a biological signal measurement system.

[0002] In order to acquire weak signals (biological signals) derived from a living body, wearable devices are worn on a plurality of parts of the body, the bioelectrical potentials obtained from each wearable device are transmitted to the other device, and the bioelectrical potentials are differentially amplified using the received potential information. A technology has been proposed (Non-Patent Document 1).

[0003] Kento Watanabe et al., "Examination of a Wiringless Electrocardiogram Measurement Circuit Using the Human Body as an Inter-Element Wiring," IEICE General Conference, B-19-04, 2024.

[0004] However, in the prior art, instead of eliminating the sense of restraint during measurement associated with physical wiring or device wearing and not interfering with daily activities, it is necessary to wear a plurality of wearable devices, so there is a problem that it takes time and effort to wear them according to the use case.

[0005] The present invention has been made to solve the above problems, and an object thereof is to reduce the trouble of wearing and enable measurement of biological signals.

[0006] The biological signal measurement system according to the present invention includes a plurality of devices each having a measurement unit that measures a biological signal. The measurement unit includes an electrode that measures a biological signal in a target human body, a reception circuit that receives a biological signal transmitted from another device by body communication, an amplification circuit that differentially amplifies the measured biological signal and the biological signal transmitted from another device and received, and a transmission circuit that transmits the biological signal differentially amplified by the amplification circuit to another device by body communication. At least one device is worn on the human body, at least one device is not worn on the human body, and the amplification circuit of the measurement unit of at least one device outputs the differentially amplified amplified signal outside the measurement unit.

[0007] As described above, according to the present invention, among the devices each having a measurement unit that measures a biological signal, at least one is worn on the human body and at least one is not worn on the human body, so the trouble of wearing is reduced and biological signals can be measured.

[0008] Figure 1 is a configuration diagram showing the configuration of a biosignal measurement system according to an embodiment of the present invention. Figure 2 is a configuration diagram showing a partial configuration of a biosignal measurement system according to an embodiment of the present invention. Figure 3 is a configuration diagram showing a partial configuration of a biosignal measurement system according to an embodiment of the present invention. Figure 4 is a configuration diagram showing a partial configuration of a biosignal measurement system according to an embodiment of the present invention. Figure 5 is a configuration diagram showing a partial configuration of a biosignal measurement system according to an embodiment of the present invention. Figure 6 is a configuration diagram showing the configuration of another biosignal measurement system according to an embodiment of the present invention. Figure 7 is a flowchart for explaining an example of operation of the first device 100a by the detection circuit 107a. Figure 8 is a configuration diagram showing the configuration of another biosignal measurement system according to an embodiment of the present invention. Figure 9 is an explanatory diagram showing the transmission of signals between the first device and the second device, which is initiated by trigger generation by the trigger generation circuit 108. Figure 10 is a configuration diagram showing the configuration of another biosignal measurement system according to an embodiment of the present invention. Figure 11A is a configuration diagram showing the configuration used for simulating the effect of the GND electrode. Figure 11B is a characteristic diagram showing the simulation results of the effect of the GND electrode. Figure 12 is a configuration diagram showing a part of the biosignal measurement system according to an embodiment of the present invention. Figure 13 is a configuration diagram showing a part of the biosignal measurement system according to an embodiment of the present invention. Figure 14 is a configuration diagram showing a part of the biosignal measurement system according to an embodiment of the present invention. Figure 15 is a configuration diagram showing a part of the biosignal measurement system according to an embodiment of the present invention.

[0009] Hereinafter, a biosignal measurement system according to an embodiment of the present invention will be described with reference to Figure 1. This biosignal measurement system comprises multiple devices, each equipped with a measurement unit for measuring biosignals. At least one device is attached to the human body, and at least one device is not attached to the human body.

[0010] In this example, the system comprises a first device 100a and a second device 100b. The first device 100a is, for example, a wearable device used by being attached to a human body 150. The second device 100b is, for example, a non-wearable device that is not attached to the human body 150. Note that there is not limited to one second device 100b, but multiple devices can be provided.

[0011] The first device 100a includes a measuring unit 101a, which includes an electrode 102a, a receiving circuit 103a, an amplification circuit 104a, and a transmitting circuit 105a.

[0012] Electrode 102a measures the biological signals in the target human body 150. Receiving circuit 103a receives the biological signals transmitted from the other device (second device 100b) via human body communication. Amplifying circuit 104a differentially amplifies the measured biological signals and the biological signals transmitted from the other device (second device 100b) and received. Transmitting circuit 105a transmits the biological signals differentially amplified by amplification circuit 104a to the other device (second device 100b) via human body communication. Although not shown, the first device 100a may be equipped with a power source such as a secondary battery to supply power to the measurement unit 101a, etc.

[0013] The second device 100b includes a measurement unit 101b, which includes an electrode 102b, a receiving circuit 103b, an amplification circuit 104b, and a transmitting circuit 105b.

[0014] Electrode 102b measures the biological signal in the target human body 150. Receiving circuit 103b receives the biological signal transmitted from the other device (first device 100a) via human body communication. Amplifying circuit 104b differentially amplifies the measured biological signal and the biological signal transmitted from the other device (first device 100a) and received. Transmitting circuit 105b transmits the biological signal differentially amplified by amplification circuit 104b to the other device (first device 100a) via human body communication. Although not shown, the second device 100b may be equipped with a power source such as a secondary battery to supply power to the measurement unit 101b, etc.

[0015] Furthermore, the amplification circuits 104a and 104b of the measurement units 101a and 101b of at least one device output the differentially amplified signal to the outside of the measurement units 101a and 101b. In this example, the amplification circuit 104b of the measurement unit 101b of the second device 100b, which is a non-wearable device, outputs the differentially amplified signal, which is output by the output unit 106, to the outside of the measurement unit 101b.

[0016] Non-patent document 1 describes a measurement system that eliminates physical wiring, enabling the measurement of biosignals without restricting the user's movement. However, this requires the user to wear multiple wearable devices to measure biosignals. According to this embodiment, the system comprises a wearable device that the user attaches to their body 150 and a non-wearable device that the user touches during use. According to this embodiment, the effort required to attach multiple devices is reduced.

[0017] Furthermore, according to this embodiment, as will be described later, the system is configured to acquire biosignals only when the user touches a non-wearable device. Conventional technology had the problem of constantly consuming power to differentially amplify the biopotential using the received potential information, but according to this embodiment, biosignals are measured only when necessary, enabling long-term operation.

[0018] Wearable devices can take any form, such as smartwatches, bands, ankle bands, adhesive devices, or clothing, while non-wearable devices can be computer-related equipment such as mice and keyboards, mobile phones such as smartphones, remote controls, and mat-like items such as weighing scales—anything that comes into direct contact with the body.

[0019] Figure 2 shows an example using a mat-type second device 100b, such as a weighing scale, as a non-wearable device. The user wears the first device 100a as a wearable device on their wrist, for example. By stepping onto the second device 100b, which is in the form of a weighing scale, the user's feet come into contact with electrodes 102b provided on the top surface. This allows biosignals to be transmitted through the body using the wrist and sole of the foot as interfaces, and biosignals can be acquired.

[0020] For example, the biosignal measurement system illustrated in Figure 2 can measure electrocardiograms and obtain electrocardiogram waveforms. Obesity and metabolic syndrome are known to cause changes in heart rate and its variability. By determining heart rate from electrocardiogram waveforms (ECG) along with weight and body fat percentage, it becomes possible to monitor the risks associated with obesity and metabolic syndrome in more detail.

[0021] Figure 3 shows an example of a non-wearable device, where the second device 100b is in the form of a thermometer. Electrodes are provided on the temperature measurement unit 111 or the housing, and, as in the previous example, the user places the thermometer under their armpit to establish human body transmission and measure biological signals. Since heart rate increases with rising body temperature, measuring electrocardiogram in addition to body temperature is expected to reduce errors in health assessment due to temperature errors caused by the external environment or misidentification of normal body temperature.

[0022] Figures 4 and 5 show an example in which a mobile terminal 120, such as a smartphone, is used as a non-wearable device (second device 100b). By providing electrodes 102b on the sides and back of the mobile terminal 120 that come into contact when it is held, good biosignal measurement can be performed. It is said that the mobile terminal 120 is used for about 20 hours a week, and it is possible to expect long-term biosignal measurement in accordance with the user's activities without interfering with daily activities. The mobile terminal 120 is a computer device equipped with a CPU (Central Processing Unit), main memory, external memory, network connection device, etc., and the above functions are realized when the CPU operates (executes the program) based on the program deployed in the main memory.

[0023] Regarding the positional relationship between wearable and non-wearable devices, it is desirable that the non-wearable device touches a part of the body that is not wearing the wearable device. For example, when measuring electrocardiogram (ECG) with a wearable device attached to the left wrist, if the non-wearable device is placed on the right hand, left or right foot, or torso, the amplitude of the ECG can be captured, allowing for stable and reliable measurements. This is not the case when measuring electromyography (EMG), in which case the two devices can be positioned around the muscle to be measured.

[0024] The specific operation will be explained using electrocardiogram (ECG) measurement as an example. The user wears a wearable device and touches the electrodes of a non-wearable device. This establishes a communication channel between the wearable device and the non-wearable device via the human body, which acts as a dielectric. Each device acquires a weak ECG component of 1 mV or less from its own biosignal detection electrode and performs differential amplification in an amplification circuit. An operational amplifier circuit configuration, similar to that used in instrumentation amplifiers, can be employed for differential amplification.

[0025] In the differential amplifier circuit, the inputs are the electrocardiogram measured by electrodes and the received signal demodulated from the transmitted signal from the other device. The signal output from the amplifier circuit is modulated and transmitted from the electrodes to the other device via the human body, thereby constructing a circuit system capable of mutual signal exchange. This fulfills the function of a differential amplifier circuit without direct wiring, including GND and signal lines, between the devices. The human body is a dielectric material and is particularly suitable for transmission up to about 100 MHz, so simultaneous bidirectional transmission is possible by performing frequency division multiplexing in the frequency range below 100 MHz.

[0026] In this embodiment, the biosignal measurement system can be configured so that measurement is only performed when the user touches a non-wearable device. For example, intermittent operation can be performed by the wearable device recognizing that the user has touched a non-wearable device. This configuration increases the available time per charge of the power supply, improving usability by reducing the number of times the device is attached and detached and the number of times it is charged.

[0027] Generally, non-wearable devices have larger battery capacities than wearable devices, allowing for longer operating times. Therefore, signals are repeatedly transmitted from the transmission circuit of the non-wearable device. The wearable device can detect contact with the non-wearable device by receiving the signals transmitted from it. Specifically, the first device 100a, which is a wearable device, can be further equipped with a detection circuit 107a that detects contact and communication (Figure 6).

[0028] The detection circuit 107a activates its self-measurement unit when the signal level received by the receiving circuit 103a exceeds a set value. The detection circuit 107a rectifies the signal input to the receiving circuit 103a, evaluates the amplitude level, and determines whether it is at a level that can be demodulated. If it is determined that it is at a level that can be demodulated, the detection circuit 107a activates the measurement unit 101a. A comparator or a digital value converted by an AD converter can be used to evaluate the amplitude level.

[0029] Figure 7 shows the operation flow of the first device 100a by the detection circuit 107a described above. To reduce power consumption, only the receiving circuit 103a is activated in the measurement unit 101a of the first device 100a (first step S101), and the signal level to the receiving circuit 103a is evaluated (second step S102). If the user touches the non-wearable device (second device 100b) and the signal input to the receiving circuit 103a exceeds a threshold, for example, a level that can be demodulated back to the original signal (yes in second step S102), the amplification circuit 104a and the transmission circuit 105a are also activated (third step S103), and measurement begins. On the other hand, if it falls below a certain level (yes in fourth step S104), it is assumed that the user has moved away from the non-wearable device, and the device enters a sleep state (fifth step S105), thereby achieving low power consumption.

[0030] Furthermore, as shown in Figure 8, power reduction can be achieved by equipping the second device 100b, which is a non-wearable device, with a trigger generation circuit 108. The trigger generation circuit 108 intermittently operates the transmission circuit 105a of the first device 100a, which is not attached to the human body 150.

[0031] The trigger generation circuit 108, triggered by a timer or the like, causes the transmission circuit 105b to send a transmission signal at an appropriate period during normal operation. For example, as shown in Figure 9, the trigger generation circuit 108 triggers a signal from the second device 100b to the first device 100a. Upon receiving this signal, the first device 100a confirms receipt and the measurement unit 101a starts operating. As a result, the first device 100a also starts sending a transmission signal. Based on the reception of this signal by the second device 100b, it starts a continuous operation to continuously transmit signals and measure biological signals. This makes it possible to reduce power consumption when not measuring.

[0032] When a timer is used to generate a trigger, it is desirable to control the timer interval according to the configuration of the second device 100b. For example, if user contact confirmation is performed at intervals less than or equal to the time required for a single use of the second device 100b by the user, the biological signal can be measured without missing the timing. For example, if the second device 100b is in the form of a thermometer, the timer interval can be set to 1 to 2 minutes or less, which is the time required to measure body temperature. Also, if the second device 100b is in the form of a weighing scale, the timer interval can be set to 10 to 20 seconds or less.

[0033] Furthermore, the acceleration sensor can be incorporated into the first device 100a, which is a non-wearable device, and configured to activate a timer and start transmitting a signal when the user touches it and causes vibration. Since the power consumption of the transmission circuit tends to be a large proportion of the total power consumption, the above configuration can significantly reduce power consumption when the user does not touch it for a long time.

[0034] Furthermore, as shown in Figure 10, the second device 100b, which is a non-wearable device, can be equipped with a GND electrode 109. The GND electrode 109 is positioned differently from the electrode 102b. The GND electrode 109 capacitively couples with either the human body 150 or the other device, the first device 100a. By providing the GND electrode 109, the capacitive coupling with at least one of the human body 150 or the first device 100a can be strengthened.

[0035] Since the GND electrode 109 does not need to directly touch the human body 150, it can be covered by a device housing or the like without exposing conductive parts such as metal on its surface. Furthermore, since the GND electrode 109 is not worn on the body, it can be positioned away from the second device 100b by physical wiring, without impairing user convenience and without contradicting the objectives of the present invention.

[0036] By strengthening the capacitive coupling between the GNDs of the first device 100a and the second device 100b, the return path loss in signal transmission through the human body 150 is reduced, improving communication stability. Not only is improved communication performance expected, but also improved biopotential measurement performance. If the GND is unstable, the GND potential fluctuates due to biopotential, and the potential difference between the input voltage to electrodes 102a and 102b that measure biosignals and the GND potential becomes small.

[0037] In contrast, by providing a GND electrode 109 and strengthening the coupling between GNDs, fluctuations in the GND potential can be suppressed, and the attenuation of the biopotential input can be reduced. This effect is particularly favorable because the coupling between devices to which the opposite phase potential is input strengthens, causing the fluctuations to pull in opposite directions and cancel each other out. However, this effect can also be achieved by establishing a capacitive coupling between any of the devices and a human body surface away from the electrode contact surface of that device, as this improves the stability of the GND potential.

[0038] The simulation results of the effect of the GND electrode described above will be explained with reference to Figures 11A and 11B. Figure 11A shows the configuration used in the simulation. The first device and the second device each have different GNDs, and a variable capacitance was set assuming that capacitive coupling exists between them. The graph shown in Figure 11B represents the gain at each capacitance value. It can be seen that the gain improves as the capacitance between GNDs increases. Since the design gain of the circuit is not changed, the input attenuation of biopotential is suppressed, and the performance of biopotential measurement is improved.

[0039] For example, as shown in Figure 12, if the second device 100b is a mouse equipped with electrodes 102b on the gripping portion, the palm rest can be used as the GND electrode 109. By providing electrodes 102b on the back of the mouse and having the GND electrode 109 on the surface or inside the palm rest, and connecting the mouse and the palm rest with wiring, a strong capacitive coupling can be formed between the right hand, which is the target of measurement for the second device 100b, and the left hand, to which the first device 100a is attached. In this configuration, if the first device 100a is attached to the left wrist, a capacitive coupling can be formed not only with the human body 150 but also with the first device 100a, resulting in a more advantageous measurement.

[0040] Furthermore, the GND electrode 109 is not limited to the palm rest; it can be provided on the keyboard, and can be attached to or placed on the desk surface on which the second device 100b is placed. In addition, to obtain the effect when the first device 100a is attached to the ankle, a mat-shaped GND electrode 109 can be provided on the floor.

[0041] Furthermore, as shown in Figure 12, if the toilet bowl 121 is the second device 100b, an electrode 102b can be provided on the seat surface of the toilet seat 122. In this case, for example, a GND electrode 109 can be provided on the underside of the lid 123. By doing so, a capacitive coupling can be formed with the user's back. A capacitance of 100 pF or more can be easily secured for the back, which has a large surface area on the human body. In addition, a mat-shaped GND electrode 109 can be provided on the floor surface, and an even stronger coupling can be obtained by using multiple GND electrodes 109 in combination.

[0042] For example, if the user wears the first device 100a on their foot, measurement is possible between the buttocks and the foot. By providing a mat-shaped GND electrode 109 electrically connected to the second device 100b, the GND-to-capacitive coupling between the first device 100a and the second device 100b on the foot can be enhanced, enabling better electrocardiogram measurement. The attachment position of the first device 100a is not limited to the foot, but can be any limb or the back.

[0043] As a general electrocardiograph, there is also a sensor provided with a plurality of biological signal electrodes on the toilet seat 122. However, there are also problems such as not touching all the electrodes depending on the sitting position, or the potential difference of the electrocardiogram being extremely small because the distance between the electrodes is close in the first place.

[0044] Regarding these matters, according to the above-described embodiment, since only a single electrode is required on the seat surface, it is possible to surely secure contact points by expanding the electrode area to the entire seat surface. Also, since the toilet seat surface, which is the second device 100b, and the first device 100a can be separated by a sufficient distance, it is possible to expect to obtain a larger potential difference compared to conventional electrocardiographs.

[0045] Also, when the portable terminal 120 is used as the second device 100b, electrodes for measuring biological signals and GND electrodes may be provided on the side surface or the back surface. However, as shown in FIG. 14, the GND electrode 109 can be arranged using a transparent electrode in the display 124. Also, an electrode (not shown) for measuring biological signals can be formed using a transparent electrode in the display 124. The transparent electrode can be composed of any material such as indium tin oxide or graphene. By doing so, biological signals can be measured well when the user is operating the portable terminal 120.

[0046] Also, as shown in FIG. 15, by using the second device 100b having a presentation function to the user, such as the display (display unit) 124 of the portable terminal 120, and enabling measurement without the user's awareness, it is possible to naturally provide evaluations for various contents obtained from the outside.

[0047] While the user is browsing contents such as images, videos, and text information using the portable terminal 120 or the like, biological signals such as electrocardiograms are measured. Based on the evaluation function provided in the second device 100b and the evaluation function of the server connected to the second device 100b via the network, the emotion towards the content is estimated in real time from the state of the measured biological signal. By these means, an evaluation for the content obtained from the outside can be generated without accompanying additional operations (such as questionnaires or interviews) of the user.

[0048] For example, it is said that the characteristic quantities of electrocardiogram potentials are correlated with human emotions, and it is possible to estimate emotions such as the pleasure or displeasure of the target user from changes in electrocardiogram potentials (electrocardiograms). Specifically, LF (Low Frequency), which is a frequency domain index of heart rate variability analysis and is represented by the power spectrum in the band of 0.004 to 0.15 Hz, HF (Hi Frequency), which is represented by the power spectrum in the band of 0.15 to 0.4 Hz, and in the time domain index, pNN50 (percent of difference between adjacent normal RR intervals greater than 50ms), which is the ratio of the difference between adjacent RR intervals exceeding 50ms, etc.

[0049] In addition, characteristic quantities such as the fluctuations, averages, and variances of the above-mentioned indices can also be used. By using algorithms such as pre-trained support vector machines and regression equations for these characteristic quantities, emotions such as the pleasure or displeasure of the user can be evaluated. Based on the evaluation results of this pleasure or displeasure, it can be linked to the provision of appropriate content for each user and the creation of better content

[0050] According to the above-described embodiment, the measured electrocardiogram potential can calculate the above-mentioned indices with higher accuracy than the pulse wave representing the pulsation of the fingers or blood vessels in the wrist measured by an optical sensor or the like. Therefore, the embodiment capable of measuring the electrocardiogram potential during normal daily activities is extremely excellent in achieving both user-friendliness and accuracy.

[0051] In addition, according to the embodiment, since it is possible to extract and provide content of interest to the user unconsciously, it is possible to expect an enhancement of the recommendation function of video distribution sites and EC (electronic commerce) sites, and an improvement in the click-through rate and conversion rate by appropriate advertisement distribution. Furthermore, since changes in the user's preferences over time can also be grasped by emotion measurement, in the case of an EC site, it is possible to avoid events such as the recommendation of products that have already become unnecessary and a decrease in the willingness to purchase.

[0052] By combining these results with conventional content-based filtering and personalized filtering, it becomes possible to lower the priority of content that would normally be displayed with high priority but is not of interest to the user, and to prioritize and focus on what the user is currently interested in. This benefit is brought about by an embodiment that provides the effect of naturally measuring biosignals during the user's everyday activities. This can be implemented not only on mobile devices such as smartphones, but also on PCs and tablets, and can also be achieved on televisions or smart TVs by evaluating the method using a remote control.

[0053] As described above, according to the embodiment of the present invention, among the devices each equipped with a measuring unit for measuring biological signals, at least one is attached to the human body and at least one is not attached to the human body, thereby reducing the effort required for attachment and enabling the measurement of biological signals.

[0054] It should be noted that the present invention is not limited to the embodiments described above, and it is clear that many modifications and combinations can be implemented within the technical concept of the present invention by those with ordinary skill in the art.

[0055] 100a...First device, 100b...Second device, 101a, 101b...Measurement unit, 102a, 102b...Electrodes, 103a, 103b...Receiving circuit, 104a, 104b...Amplifying circuit, 105a, 105b...Transmitting circuit, 150...Human body.

Claims

1. A biosignal measurement system comprising a plurality of devices, each having a measurement unit for measuring biological signals, wherein the measurement unit comprises electrodes for measuring biological signals in a target human body, a receiving circuit for receiving biological signals transmitted from another device via human body communication, an amplification circuit for differentially amplifying the measured biological signal and the biological signal transmitted from and received from the other device, and a transmitting circuit for transmitting the differentially amplified biological signal from the amplification circuit to the other device via human body communication, wherein at least one of the devices is attached to the human body, at least one of the devices is not attached to the human body, and the amplification circuit of the measurement unit of at least one of the devices outputs the differentially amplified signal to the outside of the measurement unit.

2. A biosignal measurement system according to claim 1, wherein the device further comprises a detection circuit that activates a self-measurement unit when the signal level received by the receiving circuit exceeds a set value.

3. A biosignal measurement system according to claim 1, wherein the device not attached to the human body further comprises a trigger generation circuit that causes the transmission circuit to operate intermittently.

4. A biosignal measurement system according to claim 1, wherein the device not attached to the human body further comprises a GND electrode that capacitively couples with the human body.

5. A biosignal measurement system according to claim 1, wherein the device not attached to the human body further comprises a GND electrode that capacitively couples with the other device.

6. A biosignal measurement system according to claim 1, wherein the device not attached to the human body is comprised of a portable terminal.

7. A biosignal measurement system according to claim 6, wherein the portable terminal comprises an evaluation function that evaluates content obtained from an external source based on the measured biosignal, and a display unit that displays the content and the evaluation results evaluated by the evaluation function.

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