JP2020032105A - Biological measurement device, biological measurement system, control method, and computer program - Google Patents

Abstract

To provide a novel technique for accurately measuring biological information on a user in a non-contact manner.SOLUTION: A biological measurement device to be used in a system comprising a seat whose position and/or angle are/is variable, a seat sensor for outputting a first signal representing the position and/or the angle of the seat, and a biological measurement device, comprises: a light source for emitting light with which a subject part of a user sitting on the seat is to be irradiated; a photo detector for detecting at least part of light that is emitted from the light source and returns from the subject part to output a second signal; a control circuit for controlling the light source and the photo detector; and a signal processing circuit for generating and outputting a third signal representing a state of the user's brain activity on the basis of the second signal. On the basis of a variation of the first signal, the control circuit varies a time difference until the photo detector being made to detect the light after the light source being made to emit the light.SELECTED DRAWING: Figure 1A

Description

The present disclosure relates to a biological measurement device, a biological measurement system, a control method, and a computer program.

  Conventionally, a method of measuring a change in biological information by light irradiation has been known. For example, Patent Literature 1 discloses a biological light measurement device that arranges a light irradiation unit and a light receiving unit on the head of a subject and measures a change in blood flow dynamics of the brain. Patent Literature 2 discloses a biological information acquisition device that mounts an infrared light unit on a headrest of a driver's seat and acquires information on a blood flow distribution or a blood flow amount of a driver's head. Patent Literature 3 discloses a life activity measurement device that irradiates a subject with light and non-contactly measures information indicating a life activity of the subject. The same applies to Patent Document 4.

JP-A-09-019408 JP 2008-284165 A JP 2003-337102 A JP-A-2017-001984

  The present disclosure provides a new technique for measuring biological information of a user in a non-contact and accurate manner.

  A living body measurement device according to an aspect of the present disclosure includes a seat capable of changing a position and / or an angle, a seat sensor that outputs a first signal indicating the position and / or the angle of the seat, and a living body. And a measurement device, which is a biological measurement device used in a system including: a light source that emits light to be irradiated on a test portion of a user sitting on the seat; and a light source that emits light from the light source and returns from the test portion. A light detector that detects at least a part of the received light and outputs a second signal, a control circuit that controls the light source and the light detector, and, based on the second signal, biometric information of the user. And a signal processing circuit that generates and outputs a third signal as shown in the figure, wherein the control circuit causes the light source to emit the light based on a change in the first signal, and then causes the light detector to emit the light. Until it is detected Changing the time difference.

  According to the technology of the present disclosure, biological information of a user can be accurately measured without contact.

FIG. 1A is a diagram schematically illustrating an example of a biological measurement system. FIG. 1B is a diagram illustrating an example of a temporal change in the intensity of light reaching the photodetector. FIG. 1C is a diagram in which the width of the input pulse light is represented on the horizontal axis, and the light amount detected by the photodetector is represented on the vertical axis. FIG. 1D is a diagram illustrating an example of a schematic configuration of one pixel of the photodetector. FIG. 1E is a diagram illustrating an example of a configuration of a photodetector. FIG. 1F is a diagram illustrating an example of an operation in one frame. FIG. 1G is a flowchart schematically showing the operation of the control circuit. FIG. 2 is a diagram for explaining a method of detecting an internal scattering component of pulsed light. FIG. 3A is a diagram schematically illustrating an example of a timing chart when a surface reflection component is detected. FIG. 3B is a diagram schematically illustrating an example of a timing chart when an internal scattering component is detected. FIG. 4A is a flowchart illustrating an operation of recording a candidate for an initial value of a time difference between the emission timing and the detection timing. FIG. 4B is a flowchart of the operation of the control circuit during normal use. FIG. 5 is a diagram schematically illustrating a modified example of the biological measurement system. FIG. 6A is a flowchart illustrating an example of an operation in the embodiment in which personal authentication is performed. FIG. 6B is a flowchart illustrating an example of an operation during normal use in the embodiment in which personal authentication is performed. FIG. 7A is a diagram schematically illustrating a seat and a user sitting on the seat before and after adjustment of the position and / or angle of the seat. FIG. 7B is a diagram schematically illustrating a relationship between the seat and the photodetector before adjustment of the position and / or angle of the seat illustrated in FIG. 7A. FIG. 8A is a diagram schematically illustrating a user's face image acquired from a signal output from the photodetector. FIG. 8B is a diagram schematically illustrating the relationship between the user and the photodetector when the position of the seat changes in the horizontal direction. FIG. 8C is a diagram schematically illustrating the relationship between the user and the photodetector when the position of the seat changes in the vertical direction. FIG. 8D is a diagram schematically illustrating a face image of the user when the test section of the user does not face the photodetector. FIG. 9A is a diagram schematically illustrating an example in which a user sits on a seat during a hospital diagnosis or meditation training. FIG. 9B is a diagram schematically illustrating an example in which a user sits on a seat in an automobile.

(History leading to one embodiment of the present disclosure)
In the device described in Patent Literature 1, a change in blood flow dynamics of the brain is measured in a state where the light irradiation unit and the light receiving unit are in contact with the head of the subject. In the device described in Patent Literature 2, the blood flow distribution or blood flow of the driver's head is acquired in a state where the infrared light unit is close to the driver's head. In any of the devices, the subject or the driver may feel stress due to the sense of restraint in the above-described state.

  On the other hand, the devices described in Patent Literature 3 and Patent Literature 4 emit light from a light source toward a user's test section, and detect reflected light from the test section using a photodetector, thereby reducing the user's demand. The information inside the living body can be measured in a non-contact manner. In the non-contact measurement, no stress is caused by the sense of restraint. However, in the non-contact measurement, when the distance between the user's test section and the photodetector changes, the time during which the reflected light from the test section enters the photodetector changes. Therefore, if the measurement is performed without considering the change in the time, the measurement accuracy may be reduced.

  The present inventor has conceived the biological measuring device described in the following items based on the above study.

[Item 1]
A biometric device according to a first item includes a seat capable of changing a position and / or an angle, a seat sensor that outputs a first signal indicating the position and / or the angle of the seat, and a biometric device. A biological measurement device used in a system comprising: a light source that emits light to be applied to a test portion of a user sitting on the seat; and a light source that emits light from the light source and returns from the test portion. A light detector that detects at least a part of the emitted light and outputs a second signal, a control circuit that controls the light source and the light detector, and indicates biological information of the user based on the second signal. A signal processing circuit that generates and outputs a third signal, wherein the control circuit causes the light source to emit the light based on a change in the first signal, and then outputs the light to the photodetector. Time to detect Changing the difference.

[Item 2]
In the biological measurement device according to the first item, the control circuit sets an initial value of the time difference with reference to data indicating a relationship between the position and / or the angle of the seat and the time difference. Is also good.

[Item 3]
The biometric device according to the first item, further includes an authentication sensor for authenticating the user, wherein the control circuit is configured to determine the position and / or the angle of the seat based on an authentication result by the authentication sensor; An initial value of the time difference may be set.

[Item 4]
In the biological measurement device according to any one of the first to third items, the photodetector can change a posture according to an instruction from the control circuit, and the control circuit responds to the first signal. After determining the attitude of the photodetector based on the determination, a measurement operation using the light source and the photodetector may be started.

[Item 5]
In the living body measurement device according to any one of the first to fourth items, the test portion of the user is a forehead of the user, and the control circuit emits one or more pulse lights to the light source. The photodetector, by detecting a component included in a period from the start of the intensity of each pulse light to the end of the decrease in the intensity of each pulse light among the respective pulse lights returned from the test portion. The obtained signal may be output as the second signal, and the signal processing circuit may generate a signal indicating a state of the brain activity of the user as the third signal based on the second signal.

[Item 6]
A biological measurement system according to a sixth item includes the biological measurement device according to any of the first to fourth items, the seat, and the seat sensor.

[Item 7]
The control method according to the seventh item includes causing the light source to emit light to be irradiated on a test portion of a user sitting on a seat capable of changing a position and / or an angle, and causing a light detector to: Detecting at least a part of the light emitted from the light source and returning from the test portion, obtaining a first signal indicating the position and / or the angle of the seat, and detecting the first signal. Changing the time difference from when the light source emits the light to when the light detector detects the light based on the change.

[Item 8]
The computer program according to the eighth item is a computer program executed on a computer, wherein the computer program includes a light source, a test part of a user who sits on a seat capable of changing a position and / or an angle. Emitting light irradiated to the light source; and causing the photodetector to detect at least a part of light emitted from the light source and returned from the test portion; and detecting the position of the seat and / or the light. Obtaining a first signal indicating an angle, and changing a time difference between emitting the light from the light source and detecting the light by the photodetector based on a change in the first signal. And let it run.

  Each of the embodiments described below shows a comprehensive or specific example. Numerical values, shapes, materials, components, arrangement positions of components, and the like shown in the following embodiments are merely examples, and do not limit the technology of the present disclosure. In addition, among the components in the following embodiments, components not described in the independent claims indicating the highest concept are described as arbitrary components.

  In this disclosure, all or a part of a circuit, a unit, an apparatus, a member, or a part, or all or a part of a functional block in a block diagram is, for example, a semiconductor device, a semiconductor integrated circuit (IC), or an LSI (large scale integration). ) May be performed by one or more electronic circuits. The LSI or IC may be integrated on one chip, or may be configured by combining a plurality of chips. For example, functional blocks other than the storage element may be integrated on one chip. Here, the term is referred to as an LSI or an IC, but the term varies depending on the degree of integration, and may be referred to as a system LSI, VLSI (very large scale integration), or ULSI (ultra large scale integration). A Field Programmable Gate Array (FPGA), which is programmed after the manufacture of the LSI, or a reconfigurable logic device capable of reconfiguring a bonding relationship inside the LSI or setting up a circuit section inside the LSI can also be used for the same purpose.

  Furthermore, all or some of the functions or operations of the circuits, units, devices, members, or units can be executed by software processing. In this case, the software is recorded on one or more non-transitory recording media such as a ROM, an optical disk, a hard disk drive, etc., and when the software is executed by a processor, a function specified by the software is executed. It is performed by a processor and peripheral devices. The system or apparatus may include one or more non-transitory storage media on which the software is recorded, a processor, and any required hardware devices, such as an interface.

  Hereinafter, embodiments will be specifically described with reference to the drawings. In the following description, the same or similar components are denoted by the same reference numerals.

(Embodiment)
[1. Biological measuring device 100]
With reference to FIGS. 1A to 3B, a configuration of the biological measurement device 100 according to an exemplary embodiment of the present disclosure will be described.

  FIG. 1A is a diagram schematically illustrating an example of a biological measurement system 100S according to the present embodiment. In the example shown in FIG. 1A, the horizontal direction is defined as the X direction, and the vertical direction is defined as the Y direction. The biological measurement system 100S can be provided inside, for example, an automobile. The biological measurement system 100S includes a seat 12, a seat sensor 14, and a biological measurement device 100.

  The seat 12 includes a seat portion 12s and a backrest portion 12b. The position and / or angle of the seat 12 can be changed by a user operation. The position of the seat 12 may vary horizontally and / or vertically. The angle of the seat 12 is the inclination angle of the backrest 12b of the seat 12. In the present embodiment, the backrest 12b also includes a headrest with which the head of the user 10 contacts. The seat sensor 14 may include, for example, a position sensor such as a linear potentiometer and / or an angle sensor such as a rotary position sensor. The seat sensor 14 detects the position and / or angle of the seat 12 with these sensors. The seat sensor 14 outputs a signal 16 indicating the position and / or angle of the seat 12. The signal 16 is called a "first signal." The biological measurement device 100 includes a light source 20, a photodetector 30, a control circuit 60, and a signal processing circuit 70. The photodetector 30 in the present embodiment is an image sensor that acquires a two-dimensional image. The photodetector 30 is not limited to an image sensor that acquires a two-dimensional image, and may be an image sensor that acquires a one-dimensional image. Depending on the application, the photodetector 30 may be a sensor including a single photoelectric conversion element.

  The light source 20 emits pulsed light that is applied to the test portion 10t of the user 10 who is sitting on the seat 12. The photodetector 30 detects at least a part of the pulse light returned from the test section 10t of the user 10. The control circuit 60 controls the light source 20 and the light detector 30. The signal processing circuit 70 processes the signal output from the photodetector 30.

  In the present embodiment, the control circuit 60 includes a light source control unit 61 that controls the light source 20 and a sensor control unit 62 that controls the photodetector 30. The light source control unit 61 controls the intensity, pulse width, emission timing, and / or wavelength of the pulse light emitted from the light source 20. The sensor control unit 62 controls the timing of signal accumulation in each pixel of the photodetector 30.

  In the present specification, “biological information” means a measurable amount of a living body. Biological information includes, for example, blood flow, blood pressure, heart rate, pulse rate, respiratory rate, body temperature, brain waves, oxygenated hemoglobin concentration in blood, deoxygenated hemoglobin concentration in blood, blood oxygen saturation, Various quantities are included, such as the reflection spectrum. A part of the biological information may be called a vital sign. Hereinafter, each component of the biological measurement device 100 will be described.

[1-1. Light source 20]
The light source 20 emits light toward the test portion 10t of the user 10. The subject 10 t of the user 10 is, for example, the amount of the user 10. When the brain activity information is not used, the subject 10t of the user 10 may be, for example, an arm, a torso, or a foot. The light emitted from the light source 20 and reaching the user 10 is divided into a component I1 reflected on the surface of the user 10 and a component I2 scattered inside the user 10. In the following description, the component I1 reflected on the surface is referred to as “surface reflection component I1”, and the component scattered inside is referred to as “internal scatter component I2”. The internal scatter component I2 is a component that is reflected or scattered once inside the living body, or multiple scattered. When light is emitted toward the forehead of the user 10, the internal scattering component I2 indicates a component that reaches a position about 8 mm to 16 mm deep from the surface of the forehead, for example, the brain, and returns to the biological measurement device 100 again. The surface reflection component I1 includes three components: a direct reflection component, a diffuse reflection component, and a scatter reflection component. The direct reflection component is a reflection component whose incident angle and reflection angle are equal. The diffuse reflection component is a component that is diffused and reflected by the uneven shape of the surface. The scattered reflection component is a component that is scattered and reflected by the internal tissue near the surface. When light is emitted toward the forehead of the user 10, the scattered reflection component is a component that is scattered and reflected inside the epidermis. Hereinafter, in the present embodiment, the surface reflection component I1 reflected on the surface of the user 10 includes these three components. The traveling direction of the surface reflection component I1 and the internal scattering component I2 changes due to reflection or scattering, and a part of the traveling direction reaches the photodetector 30.

  First, a method for obtaining the internal scattering component I2 will be described. The light source 20 repeatedly emits the pulsed light a plurality of times at a predetermined time interval or a predetermined timing in accordance with an instruction from the control circuit 60. The pulse light emitted from the light source 20 may be, for example, a rectangular wave whose falling period is close to zero. In this specification, the “falling period” is a period from when the intensity of the pulsed light starts to decrease until the decrease ends. In general, light that has entered the user 10 propagates through the user 10 along various paths and exits from the surface of the user 10 with a time difference. For this reason, the rear end of the internal scattering component I2 of the pulsed light has a spread. When the test portion 10t of the user 10 is a forehead, the extension of the rear end of the internal scattering component I2 is about 4 ns. In consideration of this, the falling period of the pulsed light can be set to, for example, 2 ns or less, which is half or less thereof. The fall period may be 1 ns or less, which is a half thereof. The rising period of the pulse light emitted from the light source 20 is arbitrary. In the present specification, the “rising period” is a period from when the intensity of the pulsed light starts to increase to when the increase ends. This is because the falling portion of the pulse light is used in the detection of the internal scattering component I2 in the present embodiment, and the rising portion is not used. The rising portion of the pulse light can be used for detecting the surface reflection component I1. The light source 20 can be, for example, a laser such as an LD. Light emitted from the laser has a steep time response characteristic in which the falling part of the pulse light is substantially perpendicular to the time axis.

The wavelength of the light emitted from the light source 20 may be any wavelength included in a wavelength range of, for example, 650 nm or more and 950 nm or less. This wavelength range is included in the wavelength range from red to near infrared rays. In this specification, the term “light” is used not only for visible light but also for infrared light. The above-mentioned wavelength range is called a “window of a living body” and has a property that it is relatively hard to be absorbed by water and skin in a living body. When a living body is to be detected, the detection sensitivity can be increased by using light in the above wavelength range. When detecting a change in blood flow in the skin and brain of the user 10 as in the present embodiment, the light used is mainly absorbed by oxygenated hemoglobin (HbO ₂ ) and deoxygenated hemoglobin (Hb). Conceivable. The wavelength dependence of light absorption differs between oxygenated hemoglobin and deoxygenated hemoglobin. In general, changes in blood flow change the concentration of oxygenated and deoxygenated hemoglobin. With this change, the degree of light absorption also changes. Therefore, when the blood flow changes, the amount of light detected also changes with time.

  The light source 20 may emit light of two or more wavelengths included in the above wavelength range. Such a plurality of wavelengths of light may be respectively emitted from a plurality of light sources.

  In the biological measurement device 100 according to the present embodiment, the light source 20 designed in consideration of the influence on the retina may be used in order to measure the user 10 without contact. For example, a light source 20 that satisfies Class 1 of the laser safety standards established in each country may be used. When class 1 is satisfied, the user 10 is irradiated with light having low illuminance such that the atomic emission limit (AEL) is less than 1 mW. Note that the light source 20 itself does not have to satisfy Class 1. For example, class 1 of the laser safety standard may be satisfied by installing a diffusion plate or an ND filter in front of the light source 20 to diffuse or attenuate the light.

  Conventionally, a streak camera has been used to distinguish and detect information such as an absorption coefficient or a scattering coefficient at different places in a depth direction inside a living body. For example, Japanese Patent Laid-Open No. 4-189349 discloses an example of such a streak camera. In these streak cameras, ultra-short pulse light with a pulse width of femtoseconds or picoseconds has been used in order to measure at a desired spatial resolution.

  On the other hand, the biological measurement device 100 according to the present embodiment can detect the surface reflection component I1 and the internal scattering component I2 separately. Therefore, the pulse light emitted from the light source 20 does not need to be ultra-short pulse light, and the pulse width can be arbitrarily selected.

  When irradiating the forehead with light to measure cerebral blood flow, the light amount of the internal scattering component I2 becomes a very small value of about one thousandth to several tens of thousands of the light amount of the surface reflection component I1. obtain. Further, in consideration of laser safety standards, the amount of light that can be irradiated is extremely small. Therefore, it becomes very difficult to detect the internal scattering component I2. Even in such a case, if the light source 20 emits pulsed light having a relatively large pulse width, the integrated amount of the internal scattering component I2 with a time delay can be increased. Thereby, the amount of detected light can be increased, and the SN ratio can be improved.

  The light source 20 emits pulsed light having a pulse width of 3 ns or more, for example. Generally, the temporal spread of light scattered in a living tissue such as the brain is about 4 ns. FIG. 1B is a diagram illustrating an example of a temporal change in the intensity of light reaching the photodetector 30. In the example shown in FIG. 1B, the width of the input pulse light emitted from the light source 20 is 0 ns, 3 ns, and 10 ns. As shown in FIG. 1B, as the width of the pulse light from the light source 20 is increased, the amount of the internal scattering component I2 that appears at the rear end of the pulse light returned from the user 10 increases. FIG. 1C is a diagram in which the width of the input pulse light is represented on the horizontal axis, and the light amount detected by the photodetector 30 is represented on the vertical axis. The light detector 30 includes an electronic shutter. 1C was obtained under the condition that the electronic shutter was opened 1 ns after the time when the rear end of the pulsed light was reflected on the surface of the user 10 and reached the photodetector 30. The reason for selecting this condition is that the ratio of the surface reflection component I1 is higher immediately after the rear end of the pulsed light arrives than the internal scattering component I2. As shown in FIG. 1C, when the pulse width of the pulse light emitted from the light source 20 is 3 ns or more, the detected light amount can be maximized.

  The light source 20 may emit pulsed light having a pulse width of 5 ns or more, and further, 10 ns or more. On the other hand, even if the pulse width is too large, unused light increases and is wasted. Therefore, the light source 20 emits pulsed light having a pulse width of 50 ns or less, for example. Alternatively, the light source 20 may emit pulsed light having a pulse width of 30 ns or less, or even 20 ns or less.

  The irradiation pattern of the light source 20 may be, for example, a pattern having a uniform intensity distribution in the irradiation area. In this respect, the present embodiment is different from the conventional living body measuring device disclosed in, for example, Japanese Patent Application Laid-Open No. 11-164826. In the device disclosed in JP-A-11-164826, the detector and the light source are separated by about 3 cm, and the surface reflection component is spatially separated from the internal scattering component. For this reason, discrete light irradiation must be performed. On the other hand, the biological measurement device 100 according to the present embodiment can temporally separate the surface reflection component I1 from the internal scattering component I2 and reduce it. Therefore, the light source 20 having an irradiation pattern having a uniform intensity distribution can be used. The irradiation pattern having a uniform intensity distribution may be formed by diffusing light emitted from the light source 20 with a diffusion plate.

  In the present embodiment, unlike the related art, the internal scattering component I2 can be detected even immediately below the irradiation point of the user 10. By irradiating the user 10 with light over a wide spatial range, the measurement resolution can be increased.

[1-2. Photodetector 30]
The light detector 30 detects at least a part of the light emitted from the light source 20 and returned from the test portion 10t of the user 10, and outputs a signal. The signal is, for example, a signal corresponding to the intensity included in at least a part of the rising period or the signal corresponding to the intensity included in at least a part of the falling period in the reflected pulse light. This signal is referred to as a “second signal”.

  The photodetector 30 includes a plurality of photoelectric conversion elements 32 and a plurality of charge storage units 34. Specifically, the light detector 30 includes a plurality of light detection cells arranged two-dimensionally, and acquires the two-dimensional information of the user 10 at one time. In this specification, the light detection cell is also referred to as a “pixel”. The light detector 30 is an arbitrary image sensor such as a CCD image sensor or a CMOS image sensor. More generally, the photodetector 30 includes at least one photoelectric conversion element 32 and at least one charge storage unit 34.

  The light detector 30 includes an electronic shutter. The electronic shutter is a circuit that controls the timing of imaging. In the present embodiment, the sensor control unit 62 in the control circuit 60 has a function of an electronic shutter. The electronic shutter controls one signal accumulation period in which received light is converted into a valid electric signal and accumulated, and a period in which signal accumulation is stopped. The signal accumulation period can also be referred to as an “exposure period” or an “imaging period”. In the following description, the width of the exposure period may be referred to as “shutter width”. The time from the end of one exposure period to the start of the next exposure period may be referred to as a “non-exposure period”. Hereinafter, the state in which exposure is performed may be referred to as “OPEN”, and the state in which exposure is stopped may be referred to as “CLOSE”.

  The photodetector 30 can adjust the exposure period and the non-exposure period by the electronic shutter in sub-nanoseconds, for example, in the range of 30 ps to 1 ns. A conventional TOF camera whose purpose is distance measurement detects all the light emitted from the light source 20 and reflected by the subject and returned to correct the effect of the brightness of the subject. Therefore, in the conventional TOF camera, the shutter width needs to be larger than the pulse width of light. On the other hand, in the biological measurement device 100 according to the present embodiment, it is not necessary to correct the light amount of the subject. Therefore, the shutter width does not need to be larger than the pulse width. Therefore, the shutter width can be set to, for example, a value of 1 ns or more and 30 ns or less. According to the living body measurement device 100 of the present embodiment, since the shutter width can be reduced, the influence of the dark current included in the detection signal can be reduced.

  When illuminating the forehead of the user 10 with light to detect information such as cerebral blood flow, the internal light attenuation rate is very large. For example, the outgoing light may be attenuated to about one millionth of the incident light. For this reason, in order to detect the internal scatter component I2, the amount of light may be insufficient with only one pulse irradiation. In the case of irradiation in class 1 of the laser safety standard, the amount of light is particularly weak. In this case, the light source 20 emits the pulsed light a plurality of times, and the photodetector 30 is also exposed multiple times by the electronic shutter in response to the pulsed light, whereby the detection signals can be integrated and the sensitivity can be improved.

  Hereinafter, a configuration example of the photodetector 30 will be described.

  The photodetector 30 may include a plurality of pixels two-dimensionally arranged on the imaging surface. Each pixel may include a photoelectric conversion element such as a photodiode, for example, and one or more charge storage units. Hereinafter, a photoelectric conversion element in which each pixel generates a signal charge according to the amount of received light by photoelectric conversion, a charge storage unit that stores the signal charge generated by the surface reflection component I1 of the pulse light, and an internal scattering component of the pulse light An example including a charge storage unit that stores the signal charges generated by I2 will be described. In the following example, the control circuit 60 causes the photodetector 30 to detect a portion of the pulse light returned from the head of the user 1 before the start of falling, thereby detecting the surface reflection component I1. The control circuit 60 also causes the photodetector 30 to detect a portion of the pulse light returned from the head of the user 1 after the start of falling, thereby detecting the internal scattering component I2. The light source 20 emits light of two wavelengths.

  FIG. 1D is a diagram illustrating an example of a schematic configuration of one pixel 201 of the photodetector 30. FIG. 1D schematically illustrates a configuration of one pixel 201, and does not necessarily reflect an actual structure. The pixel 201 in this example includes a photodiode 203 that performs photoelectric conversion, a first floating diffusion (FD) 204 that is a charge storage unit, a second floating diffusion layer 205, and a third floating diffusion layer 206. , And a fourth floating diffusion layer 207 and a drain 202 for discharging signal charges.

  Photons that have entered each pixel due to one pulsed light emission are converted by the photodiode 203 into signal electrons that are signal charges. The converted signal electrons are discharged to the drain 202 or distributed to any one of the first floating diffusion layer 204 and the fourth floating diffusion layer 207 according to a control signal input from the control circuit 60.

  The emission of the pulse light from the light source 20, the first floating diffusion layer (FD1) 204, the second floating diffusion layer (FD2) 205, the third floating diffusion layer (FD3) 206, and the fourth floating diffusion layer The accumulation of the signal charge in the (FD4) 207 and the discharge of the signal charge to the drain 202 are repeatedly performed in this order. This repetition operation is fast, and can be repeated, for example, tens of thousands to hundreds of millions of times within one frame of a moving image. The time of one frame is, for example, about 1/30 second. The pixel 201 finally generates and outputs four image signals from the first floating diffusion layer 204 based on the signal charges stored in the fourth floating diffusion layer 207.

  The control circuit 60 in this example causes the light source 20 to repeatedly emit a first pulsed light having a first wavelength and a second pulsed light having a second wavelength in order. By selecting two wavelengths having different absorptances in the internal tissue of the user 10 as the first wavelength and the second wavelength, the state of the user 10 can be analyzed. For example, a wavelength longer than 805 nm may be selected as the first wavelength, and a wavelength shorter than 805 nm may be selected as the second wavelength. This makes it possible to detect changes in the oxygenated hemoglobin concentration and the deoxygenated hemoglobin concentration in the blood of the user 10.

  The control circuit 60 first causes the light source 20 to emit the first pulse light. The control circuit 60 causes the first floating diffusion layer 204 to store signal charges during the first period in which the surface reflection component I1 of the first pulse light is incident on the photodiode 203. Subsequently, the control circuit 60 causes the second floating diffusion layer 205 to store signal charges during the second period in which the internal scattering component I2 of the first pulse light is incident on the photodiode 203. Next, the control circuit 60 causes the light source 20 to emit the second pulse light. The control circuit 60 causes the third floating diffusion layer 206 to accumulate signal charges during the third period in which the surface reflection component I1 of the second pulse light is incident on the photodiode 203. Subsequently, the control circuit 60 causes the fourth floating diffusion layer 207 to accumulate signal charges during the fourth period in which the internal scattering component I2 of the second pulsed light is incident on the photodiode 203.

  As described above, after starting emission of the first pulsed light, the control circuit 60 sends the first floating diffusion layer 204 and the second floating diffusion layer 205 to the first floating diffusion layer 204 and the second floating diffusion layer 205 with a predetermined time difference. The signal charges are sequentially accumulated. Thereafter, after starting emission of the second pulse light, the control circuit 60 sends the signal from the photodiode 203 to the third floating diffusion layer 206 and the fourth floating diffusion layer 207 at the above-described predetermined time interval. Charges are sequentially accumulated. The above operation is repeated a plurality of times. In order to estimate the amount of disturbance light and ambient light, a period for accumulating signal charges in another floating diffusion layer (not shown) may be provided with the light source 20 turned off. By subtracting the signal charge amount of the other floating diffusion layer from the signal charge amount of the fourth floating diffusion layer 207 from the first floating diffusion layer 204, it is possible to obtain a signal from which disturbance light and environmental light components have been removed. it can.

  In the present embodiment, the number of charge storage units is four, but it may be designed to be two or more according to the purpose. For example, when only one type of wavelength is used, the number of charge storage units may be two. Further, in a case where only one wavelength is used and the surface reflection component I1 is not detected, the number of charge storage units for each pixel may be one. Further, even when two or more wavelengths are used, the number of charge storage units may be one if imaging using each wavelength is performed in another frame. Further, as will be described later, if the detection of the surface reflection component I1 and the detection of the internal scattering component I2 are performed in different frames, the number of charge storage units may be one.

  FIG. 1E is a diagram illustrating an example of the configuration of the photodetector 30. In FIG. 1E, a region surrounded by a two-dot chain line frame corresponds to one pixel 201. The pixel 201 includes one photodiode. Although FIG. 1E shows only four pixels arranged in two rows and two columns, more pixels may actually be arranged. The pixel 201 includes four from the first floating diffusion layer 204 to the fourth floating diffusion layer 207. The signals stored in four of the first floating diffusion layer 204 to the fourth floating diffusion layer 207 are treated as if they were signals of four pixels of a general CMOS image sensor, and output from the photodetector 30. You.

  Each pixel 201 has four signal detection circuits. Each signal detection circuit includes a source follower transistor 309, a row selection transistor 308, and a reset transistor 310. In this example, the reset transistor 310 corresponds to the drain 202 shown in FIG. 1D, and the pulse input to the gate of the reset transistor 310 corresponds to the aforementioned drain discharge pulse. Each transistor is, for example, a field effect transistor formed on a semiconductor substrate, but is not limited to this. As illustrated, one of the input terminal and the output terminal of the source follower transistor 309 is connected to one of the input terminal and the output terminal of the row selection transistor 308. The one of the input terminal and the output terminal of the source follower transistor 309 is typically a source. The one of the input terminal and the output terminal of the row selection transistor 308 is typically a drain. A gate, which is a control terminal of the source follower transistor 309, is connected to the photodiode 203. The hole or electron signal charges generated by the photodiode 203 are stored in a floating diffusion layer which is a charge storage portion between the photodiode 203 and the source follower transistor 309.

  Although not shown in FIG. 1E, the first to fourth floating diffusion layers 204 to 207 are connected to the photodiode 203. A switch may be provided between the photodiode 203 and each of the first to fourth floating diffusion layers 204 to 207. This switch switches the conduction state between the photodiode 203 and each of the first floating diffusion layer 204 to the fourth floating diffusion layer 207 according to a signal accumulation pulse from the control circuit 60. Thus, the start and stop of the accumulation of the signal charges from the first floating diffusion layer 204 to each of the fourth floating diffusion layers 207 are controlled. The electronic shutter according to the present embodiment has a mechanism for such exposure control.

  The signal charges stored in the first floating diffusion layer 204 to the fourth floating diffusion layer 207 are read out when the gate of the row selection transistor 308 is turned on by the row selection circuit 302. At this time, the current flowing from the source follower power supply 305 to the source follower transistor 309 and the source follower load 306 is amplified according to the signal potentials of the first floating diffusion layer 204 to the fourth floating diffusion layer 207. An analog signal based on this current read from the vertical signal line 304 is converted into digital signal data by an analog-digital (AD) conversion circuit 307 connected for each column. The digital signal data is read for each column by the column selection circuit 303 and output from the photodetector 30. The row selection circuit 302 and the column selection circuit 303 read out one row, then read out the next row, and similarly read out information on signal charges in the floating diffusion layers in all rows. After reading out all the signal charges, the control circuit 60 turns on the gate of the reset transistor 310 to reset all the floating diffusion layers. Thereby, the imaging of one frame is completed. Hereinafter, similarly, by repeating high-speed imaging of a frame, imaging of a series of frames by the photodetector 30 is completed.

  In this embodiment, the example of the CMOS photodetector 30 has been described, but the photodetector 30 may be another type of image sensor. The photodetector 30 may be, for example, a CCD type, a single photon counting type element, or an amplification type image sensor such as an EMCCD or an ICCD.

  FIG. 1F is a diagram illustrating an example of an operation within one frame according to the present embodiment. As shown in FIG. 1F, the emission of the first pulse light and the emission of the second pulse light may be alternately switched a plurality of times within one frame. In this way, the time difference between the acquisition timings of the detected images based on the two wavelengths can be reduced, and even the user 10 that is moving can shoot with the first pulse light and the second pulse light almost simultaneously. .

  In the present embodiment, the photodetector 30 can detect the surface reflection component I1 and / or the internal scattering component I2 of the pulse light. The first biological information of the user 10 can be obtained from the temporal or spatial change of the surface reflection component I1. The first biological information may be, for example, the pulse of the user 10. On the other hand, the brain activity information as the second biological information of the user 10 can be obtained from the temporal or spatial change of the internal scattering component I2.

  The first biological information may be obtained by a method different from the method of detecting the surface reflection component I1. For example, the first biological information may be obtained by using another type of detector different from the photodetector 30. In that case, the photodetector 30 detects only the internal scatter component I2. Other types of detectors may be, for example, radar or thermography. The first biological information may be, for example, at least one selected from the group consisting of the pulse, sweating, respiration, and body temperature of the user 10. The first biological information is biological information other than brain activity information obtained by detecting the internal scatter component I2 of the pulse light applied to the head of the user 10. Here, “other than brain activity information” does not mean that the first biological information does not include any information due to brain activity. The first biological information includes biological information resulting from a biological activity different from the brain activity. The first biological information is, for example, biological information resulting from an autonomous or reflexive biological activity.

[1-3. Control circuit 60 and signal processing circuit 70]
The control circuit 60 adjusts the time difference between the emission timing of the pulse light from the light source 20 and the shutter timing of the photodetector 30. The “emission timing” of the light source 20 is a timing at which pulse light emitted from the light source 20 starts rising. “Shutter timing” is a timing at which exposure starts. The control circuit 60 may adjust the time difference by changing the emission timing, or may adjust the time difference by changing the shutter timing.

  The control circuit 60 may be configured to remove an offset component from a signal detected by each pixel of the photodetector 30. The offset component is a signal component due to ambient light such as sunlight or fluorescent light, or disturbance light. By detecting the signal with the photodetector 30 in a state where the driving of the light source 20 is turned off and no light is emitted from the light source 20, an offset component due to environmental light or disturbance light can be estimated.

  The control circuit 60 may be, for example, an integrated circuit such as a combination of a processor and a memory, or a microcontroller containing the processor and the memory. The control circuit 60 performs, for example, adjustment of the emission timing and shutter timing, estimation of the offset component, and removal of the offset component, for example, by the processor executing a program recorded in the memory.

  The signal processing circuit 70 is a circuit that processes the image signal output from the photodetector 30. The signal processing circuit 70 performs arithmetic processing such as image processing. The signal processing circuit 70 includes, for example, a digital signal processor (DSP), a programmable logic device (PLD) such as a field programmable gate array (FPGA), or a central processing unit (CPU) or an image processing processor (GPU) and a computer program. Can be realized by a combination of Note that the control circuit 60 and the signal processing circuit 70 may be one integrated circuit, or may be separated individual circuits. The signal processing circuit 70 may be a component of an external device such as a server provided at a remote place. In this case, an external device such as a server transmits and receives data to and from the light source 20, the photodetector 30, and the control circuit 60 by wireless communication or wired communication.

  The signal processing circuit 70 in the present embodiment can generate moving image data indicating a temporal change of the blood flow on the skin surface and the cerebral blood flow based on the signal output from the photodetector 30. The signal processing circuit 70 is not limited to such moving image data, and may generate other information. For example, biological information such as blood flow in the brain, blood pressure, blood oxygen saturation, or heart rate may be generated by synchronizing with another device.

  It is known that there is a close relationship between changes in blood components such as cerebral blood flow or hemoglobin and human neural activity. For example, cerebral blood flow or a component in blood changes as the activity of nerve cells changes in response to changes in human emotions. Therefore, if biological information such as changes in cerebral blood flow or blood components can be measured, the psychological state of the user 10 can be estimated. The psychological state of the user 10 means, for example, a mood, an emotion, a health state, or a sense of temperature. The mood is, for example, pleasant or unpleasant. The emotion is, for example, relief, anxiety, sadness, or anger. The health condition is, for example, well or fatigue. The temperature sensation is, for example, hot, cold, or sultry. In addition, the psychological state also includes an index indicating the degree of brain activity, for example, a skill level, a skill level, and a concentration level. The signal processing circuit 70 may estimate a mental state such as the degree of concentration of the user 10 based on a change in the cerebral blood flow rate or the like, and may output a signal indicating the estimation result.

  FIG. 1G is a flowchart showing an outline of the operation of the control circuit 60 regarding the light source 20 and the photodetector 30. The control circuit 60 roughly performs the operation shown in FIG. 1G. Here, the operation when only the internal scattering component I2 is detected will be described. In step S101, the control circuit 60 first causes the light source 20 to emit pulsed light for a predetermined time. At this time, the electronic shutter of the photodetector 30 has stopped exposure. The control circuit 60 causes the electronic shutter to stop exposing until a period in which a part of the pulsed light is reflected on the surface of the user 10 and reaches the photodetector 30 is completed. Next, in step S102, the control circuit 60 causes the electronic shutter to start exposure at a timing when another part of the pulsed light scatters inside the user 10 and reaches the photodetector 30. After the elapse of the predetermined time, in step S103, the control circuit 60 causes the electronic shutter to stop exposing. Subsequently, in step S104, the control circuit 60 determines whether or not the number of times of executing the signal accumulation has reached a predetermined number. If the determination in step S104 is No, steps S101 to S103 are repeated until the determination is Yes. If the determination in step S104 is Yes, in step S105, the control circuit 60 causes the photodetector 30 to generate and output a signal indicating an image based on the signal charges accumulated in each floating diffusion layer.

  With the above operation, the light component scattered inside the measurement target can be detected with high sensitivity. Note that light emission and exposure a plurality of times are not essential, and are performed as necessary.

[1-4. Others]
The biological measurement device 100 may include an imaging optical system that forms a two-dimensional image of the user 10 on the light receiving surface of the photodetector 30. The optical axis of the imaging optical system is substantially orthogonal to the light receiving surface of the photodetector 30. The imaging optical system may include a zoom lens. When the position of the zoom lens changes, the magnification of the two-dimensional image of the user 10 changes, and the resolution of the two-dimensional image on the photodetector 30 changes. Therefore, even if the distance to the user 10 is long, a desired measurement area can be enlarged and observed in detail.

  In addition, the biometric device 100 may include a band-pass filter between the user 10 and the photodetector 30 that passes only light in the wavelength band emitted from the light source 20 or light near the wavelength band. Thereby, the influence of disturbance components such as ambient light can be reduced. The band-pass filter is constituted by a multilayer filter or an absorption filter. In consideration of the temperature of the light source 20 and a band shift accompanying oblique incidence on the filter, the band width of the band-pass filter may have a width of about 20 to 100 nm.

  Further, the biological measurement device 100 may include a polarizing plate between the light source 20 and the user 10 and between the light detector 30 and the user 10. In this case, the polarization directions of the polarizing plate disposed on the light source 20 side and the polarizing plate disposed on the photodetector 30 side are in a crossed Nicols relationship. Accordingly, it is possible to prevent the regular reflection component, that is, the component having the same incident angle and the reflection angle, of the surface reflection component I1 of the user 10 from reaching the photodetector 30. That is, the amount of light that the surface reflection component I1 reaches the photodetector 30 can be reduced.

[2. Operation of light source and photodetector]
The biological measurement device 100 according to the present embodiment can detect the surface reflection component I1 and the internal scattering component I2 separately. When the test portion 10t of the user 10 is set to the forehead, the signal intensity due to the internal scatter component I2 to be detected becomes very small. As mentioned above, in addition to irradiating a very small amount of light that meets the laser safety standards, the scalp, cerebrospinal fluid, skull, gray matter, white matter, and light scattering and absorption by the bloodstream are large. . Furthermore, a change in signal intensity due to a change in blood flow or a component in blood flow during brain activity is very small, equivalent to a magnitude of several tenths. Therefore, in the present embodiment, at the time of imaging, the surface reflection component I1, which is several thousand times to tens of thousands times the signal component to be detected, is removed as much as possible.

  Hereinafter, an example of the operation of the light source 20 and the photodetector 30 in the biological measurement device 100 according to the present embodiment will be described.

  As shown in FIG. 1A, when the light source 20 irradiates the user 10 with pulsed light, a surface reflection component I1 and an internal scattering component I2 are generated. Part of the surface reflection component I1 and the internal scattering component I2 reach the photodetector 30. The internal scattering component I2 is emitted from the light source 20 and passes through the user 10 before reaching the photodetector 30. Therefore, the optical path length of the internal scattering component I2 is longer than the optical path length of the surface reflection component I1. Therefore, the time when the internal scattering component I2 reaches the photodetector 30 is on average delayed from the time when the surface reflection component I1 reaches the photodetector 30.

  FIG. 2 is a diagram illustrating an optical signal in which rectangular pulse light is emitted from the light source 20 and light returned from the user 10 reaches the photodetector 30. The horizontal axis represents time (t) in (a) to (d). The vertical axis represents the intensity in (a) to (c) and the open or closed state of the electronic shutter in (d). (A) shows the surface reflection component I1. (B) shows the internal scattering component I2. (C) shows the total component of the surface reflection component I1 shown in (a) and the internal scattering component I2 shown in (b). As shown in (a), the surface reflection component I1 maintains a rectangle. On the other hand, as shown in (b), the internal scattering component I2 is the sum of light having passed through various optical path lengths. For this reason, (b) shows a characteristic in which the trailing end of the pulsed light trails. In other words, the falling period of the internal scattering component I2 is longer than the falling period of the surface reflection component I1. In order to increase and extract the ratio of the internal scattering component I2 from the optical signal of (c), the exposure of the electronic shutter is started after the rear end of the surface reflection component I1, as shown in (d). The term “after the rear end” means when or after the surface reflection component I1 has fallen. This shutter timing is adjusted by the control circuit 60. As described above, the biological measurement device 100 of the present disclosure distinguishes and detects the surface reflection component I1 and the internal scattering component I2 that has reached the deep part of the target. For this reason, the emission pulse width and the shutter width are arbitrary. Therefore, unlike a method using a conventional streak camera, the cost can be significantly reduced by a simple configuration.

  In FIG. 2A, the rear end of the surface reflection component I1 falls vertically. In other words, the time from the start of the fall of the surface reflection component I1 to the end thereof is zero. However, in reality, when the pulsed light itself emitted from the light source 20 is not perfectly vertical, when the surface of the user 10 has fine irregularities, the rear end of the surface reflection component I1 becomes vertically due to scattering in the epidermis. May not fall. Further, since the user 10 is an opaque object, the light amount of the surface reflection component I1 is much larger than the light amount of the internal scattering component I2. Therefore, even when the rear end of the surface reflection component I1 slightly protrudes from the vertical falling position, the internal scattering component I2 may be buried. Further, during the readout period of the electronic shutter, a time delay due to the electron movement may occur. Therefore, an ideal binary readout as shown in FIG. 2D may not be realized. Therefore, the control circuit 60 may slightly delay the shutter timing of the electronic shutter from immediately after the fall of the surface reflection component I1. For example, the delay may be about 0.5 ns to 5 ns. Instead of adjusting the shutter timing of the electronic shutter, the control circuit 60 may adjust the emission timing of the light source 20. The control circuit 60 adjusts the time difference between the shutter timing of the electronic shutter and the emission timing of the light source 20. When measuring a change in blood flow or a component in a blood flow during non-contact brain activity, if the shutter timing is too late, the originally small internal scatter component I2 is further reduced. For this reason, the shutter timing may be kept near the rear end of the surface reflection component I1. The time delay due to the scattering of the user 10 is 4 ns. Therefore, the maximum delay amount of the shut timing is about 4 ns.

  Each of the plurality of pulsed lights emitted from the light source 101 may be exposed at the same time difference in shutter timing. Thereby, the detected light amount of the internal scattering component I2 is amplified.

  Instead of, or in addition to, disposing a band-pass filter between the user 10 and the photodetector 30, the control circuit 60 may perform imaging with the same exposure time in a state where the light source 20 does not emit light. May be used to estimate the offset component. The estimated offset component is subtracted from the signal detected by each pixel of the photodetector 30. Thereby, the dark current component generated on the photodetector 30 can be removed.

  The internal scattering component I2 includes internal characteristic information of the user 10, for example, cerebral blood flow information. The amount of light absorbed by the blood changes according to the temporal fluctuation of the cerebral blood flow of the user 10. As a result, the amount of light detected by the photodetector 30 increases or decreases accordingly. Therefore, by monitoring the internal scatter component I2, it becomes possible to estimate a brain activity state from a change in the cerebral blood flow of the user 10.

  Next, an example of a method for detecting the surface reflection component I1 will be described. The surface reflection component I1 includes surface characteristic information of the user 10, for example, blood flow information of the face and the scalp. The photodetector 30 detects the surface reflection component I1 of the optical signal in which the pulse light emitted from the light source 20 reaches the user 10 and returns to the photodetector 30 again.

  FIG. 3A is a diagram schematically illustrating an example of a timing chart when the surface reflection component I1 is detected. To detect the surface reflection component I1, for example, as shown in FIG. 3A, the shutter is opened before the pulse light reaches the photodetector 30, and the shutter is opened before the rear end of the pulse light arrives. It may be CLOSE. By controlling the shutter in this way, the mixing of the internal scattering component I2 can be reduced. As a result, the ratio of light that has passed near the surface of the user 10 can be increased. The shutter CLOSE may be performed immediately after the light reaches the photodetector 30. As a result, signal detection with an increased ratio of the surface reflection component I1 having a relatively short optical path length can be performed. By acquiring the signal of the surface reflection component I1, it is also possible to detect the pulse of the user 10 or the degree of oxygenation of the face blood flow. As another method of acquiring the surface reflection component I1, the photodetector 30 may acquire the entire pulsed light or may detect continuous light emitted from the light source 20.

  FIG. 3B is a diagram schematically illustrating an example of a timing chart when the internal scattering component I2 is detected. The signal of the internal scattering component I2 can be obtained by setting the shutter to OPEN during the period when the rear end portion of the pulse reaches the photodetector 30.

  To summarize the operation shown in FIG. 3B, the control circuit 60 performs the following operation. The control circuit 60 causes the light source 20 to emit one or more pulse lights. The control circuit 60 causes the photodetector 30 to detect a component included in the falling period of each pulse light among the pulse lights returned from the test section 10t of the user 10. The component includes an internal scattering component I2. The control circuit 60 causes the photodetector 30 to output a signal obtained by the detection. The signal processing circuit 70 generates a signal indicating the state of the brain activity of the user 10 based on the signal.

  The surface reflection component I1 may be detected by a device other than the biological measurement device 100 that acquires the internal scattering component I2. An apparatus different from the apparatus for acquiring the internal scatter component I2, or another device such as a pulse wave meter or a Doppler blood flow meter may be used. In that case, the separate device is used in consideration of timing synchronization between devices, light interference, and matching of a detection position. If time-division imaging is performed by the same camera or the same sensor as in the present embodiment, a temporal and spatial shift hardly occurs. When signals of both the surface reflection component I1 and the internal scattering component I2 are acquired by the same sensor, the components acquired for each frame may be switched as shown in FIGS. 3A and 3B. Alternatively, as described with reference to FIGS. 1D to 1F, the components acquired at high speed may be alternately switched within one frame. In that case, the detection time difference between the surface reflection component I1 and the internal scattering component I2 can be reduced.

  Further, the signals of the surface reflection component I1 and the internal scattering component I2 may be acquired using light of two wavelengths. For example, pulsed light having two wavelengths of 750 nm and 850 nm may be used. Thereby, the change in the concentration of oxygenated hemoglobin and the change in the concentration of deoxygenated hemoglobin can be calculated from the change in the detected light amount at each wavelength. When the surface reflection component I1 and the internal scattering component I2 are acquired at two wavelengths, for example, as described with reference to FIGS. 1D to 1F, a method of rapidly switching four types of charge accumulation in one frame is used. Can be done. With such a method, the time lag of the detection signal can be reduced.

  The biological measurement device 100 emits pulsed near-infrared light or visible light toward the forehead of the user 10, and detects a change in the amount of oxygenated hemoglobin or a pulse of the scalp or face from a temporal change of the surface reflection component I1. Can be detected. The light source 20 emits near-infrared light or visible light to obtain the surface reflection component I1. Near-infrared light can be measured day and night. When measuring the pulse, visible light with higher sensitivity may be used. In the daytime, sunlight or indoor light, which is disturbance light, may be used instead of lighting. If the amount of light is insufficient, it may be reinforced with a dedicated light source. The internal scattering component I2 includes a light component that has reached the brain. By measuring the time change of the internal scattering component I2, it is possible to measure the temporal increase or decrease of the cerebral blood flow.

  Light that reaches the brain also passes through the scalp and face surface. For this reason, fluctuations in blood flow of the scalp and face are also detected in a superimposed manner. In order to remove or reduce the influence, the signal processing circuit 70 may perform a process of subtracting the surface reflection component I1 from the internal scatter component I2 detected by the photodetector 30. Thus, pure cerebral blood flow information excluding scalp and face blood flow information can be obtained. As the subtraction method, for example, a method of subtracting a value obtained by multiplying the signal of the surface reflection component I1 by one or more coefficients determined in consideration of the optical path length difference from the signal of the internal scattering component I2 may be used. This coefficient can be calculated by simulation or experiment, for example, based on the average value of the optical constants of the general human head. Such a subtraction process can be easily performed when the same camera or sensor performs measurement using light of the same wavelength. This is because the temporal and spatial deviations are easily reduced, and the scalp blood flow component included in the internal scattering component I2 and the characteristics of the surface reflection component I1 are easily matched.

  There is a skull between the brain and the scalp. Therefore, the two-dimensional distribution of cerebral blood flow and the two-dimensional distribution of scalp and facial blood flow are independent. Therefore, based on the signal detected by the photodetector 30, the two-dimensional distribution of the internal scattering component I2 and the two-dimensional distribution of the surface reflection component I1 are separated using a statistical method such as independent component analysis or principal component analysis. May be.

[3. Determination of time difference during measurement operation]
In the example illustrated in FIG. 1A, if the user 10 adjusts the position and / or angle of the seat 12 during the measurement operation, the distance between the test section 10t of the user 10 and the photodetector 30 may change. In the following description, the distance between the center of the test portion 10t of the user 10 and the center of the light receiving surface of the photodetector 30 is referred to as “measurement distance”. If the measurement is performed without considering the change in the measurement distance, the measurement accuracy of the surface reflection component I1 and the internal scattering component I2 may decrease.

  In the following, in order to prevent a decrease in measurement accuracy, a time difference until light emitted from the light source 20 is reflected by the test portion 10t of the user 10 during the measurement operation and the light detector 30 detects the reflected light is described. An example of a determination method will be described.

  In the present embodiment, before normal use of the biological measurement device 100, the control circuit 60 records a candidate for an initial value of the time difference in a memory (not shown).

  FIG. 4A is a flowchart illustrating an operation of recording a candidate for an initial value of a time difference.

  In step S201, the user 10 sits on the seat 12.

  In step S202, the user 10 adjusts the optimal position and / or angle of the seat 12. In this specification, the position and / or angle of the seat 12 may be referred to as “seat setting”. When measuring the degree of tension, the optimal position and / or angle is a position and / or angle at which the user 10 can relax and sit without feeling cramped. When measuring the degree of concentration during some work, the optimum position and / or angle is a position and / or angle at which the user 10 is easy to work.

  In step S203, the control circuit 60 records the optimal position and / or angle of the seat 12 as a reference position and / or reference angle in a memory (not shown) provided in the control circuit 60. In this specification, the reference position and / or the reference angle of the seat 12 may be referred to as “reference seat setting”. The seat sensor 14 detects the position and / or angle of the seat 12 by the position sensor and / or the angle sensor, and outputs a signal 16 indicating the position and / or angle of the seat 12 to the control circuit 60 by wireless communication or wired communication. Output to the illustrated memory.

In step S204, the control circuit 60 determines the time difference from when the light emitted from the light source 20 is reflected by the test section 10t of the user 10 to the time when the light enters the photodetector 30 as a reference time difference. Record in memory. The reference time difference is calculated as follows. The measurement distance between the test portion 10t of the user 10 and the photodetector 30 is obtained as a reference measurement distance by a known TOF technique. The reference time difference is calculated by dividing the reciprocating distance, which is twice the reference measurement distance, by the speed of light in air c = 3.0 × 10 ⁸ [m / sec]. Note that the reference time difference may be a time difference adjusted so that the photodetector 30 can acquire the surface reflection component I1 or the internal scattering component I2. In this case, the detection is performed a plurality of times while changing the shutter timing of the photodetector 30, and the shutter timing is adjusted so that the photodetector 30 can acquire the rising portion or the falling portion of the pulse light. The time difference from the emission of the pulse light to the shutter timing is defined as a reference time difference. In a memory (not shown) of the control circuit 60, back data indicating an association between the reference position and / or the reference angle of the seat 12 and the reference time difference is recorded. Table 1 shows an example of the back data. The back data includes a reference position and / or a reference angle of the seat 12, a reference measurement distance, and a reference time difference. For example, shown in Table _{1 (X a, Y a;} β a) is the inclination angle of the backrest 12b of the horizontal position X _a, the vertical direction of the seat 12 position Y _a, and the seat 12 of the seat 12 to be described later It represents the reference seat settings including beta _a. The plurality of reference time differences shown in Table 1 are candidates for the initial value of the time difference when the measurement operation is started.

  FIG. 4B is a flowchart of the operation of the control circuit 60 during normal use.

  In step S301, the user 10 sits on the seat 12. The user 10 adjusts the position and / or angle of the seat 12 to the reference position and / or the reference angle. The seat 12 may have a function of adjusting the position and / or angle of the seat 12 to a reference position and / or a reference angle according to an input from the user 10.

  In step S302, the seat sensor 14 outputs the signal 16 and inputs data on the reference position and / or reference angle of the seat 12 to the control circuit 60. The biological measurement device 100 may include an input device (not shown). In this case, the user 10 inputs the reference position and / or the reference angle of the seat 12 to the input device.

  In step S303, the control circuit 60 refers to the input reference position and / or reference angle of the seat 12 and the above-mentioned back data previously recorded in a memory (not shown) to determine the recorded reference time difference, Set as the initial value of the time difference. Thus, the control circuit 60 sets the initial value of the time difference with reference to the previously recorded back data as shown in Table 1 before executing the measurement operation.

  In step S304, the control circuit 60 starts a measurement operation.

  In step S305, the control circuit 60 causes the light source 20 to emit pulse light, and causes the photodetector 30 to detect reflected pulse light. This operation may be repeated multiple times, as shown in FIGS. 3A and 3B.

  In step S306, the control circuit 60 causes the photodetector 30 to output a signal. The signal processing circuit 70 generates and outputs a signal indicating biological information of the user 10 based on the signal output from the photodetector 30. The signal generated and output by the signal processing circuit 70 is referred to as a “third signal”. The biological information of the user 10 is the first biological information and / or the second biological information described above.

  In step S307, control circuit 60 determines whether or not user 10 has adjusted the position and / or angle of seat 12 based on signal 16 output from seat sensor 14.

  In step S308, if the determination in step S307 is Yes, the control circuit 60 determines whether the difference Δd between the measured distance and the reference measured distance is within an allowable range. The measured distance is calculated by an operation using the signal 16 output from the seat sensor 14. The calculation method will be described later. When the minimum unit in which the time difference can be adjusted is 200 [picoseconds], the allowable range is | Δd | <3 [cm]. This is because, when | Δd | = 3 [cm], the value obtained by dividing the reciprocating distance of 2 | Δd | = 6 [cm] by the speed of light in air is 200 [picoseconds]. When Δd> 0, the test portion 10t of the user 10 moves away from the photodetector 30. Therefore, the time during which the reflected light pulse enters the photodetector 30 is delayed. When Δd <0, the subject 10 t of the user 10 approaches the photodetector 30. Therefore, the time during which the reflected light pulse enters the photodetector 30 is shortened.

  In step S309, if the determination in step S308 is No, the control circuit 60 changes the time difference. For example, if 3 [cm] ≦ | Δd | <6 [cm], the control circuit 60 delays the light detection timing by 200 picoseconds when Δd> 0, and only 200 picoseconds when Δd <0. Hasten. When 6 [cm] ≦ | Δd | <9 [cm], the control circuit 60 delays the light detection timing by 400 [picoseconds] when Δd> 0, and by 400 [picoseconds] when Δd <0. Hasten.

Adjustable minimum unit of the time difference is represented as t _m, when the upper limit of the allowable range (ct _m) / 2 = represented as d _m, the natural numbers represented as _{n, nd m ≦ | Δd |} <(n + 1 ) in d _m, the control circuit 60, a time difference, delaying nt _m when [Delta] d> 0, advancing only nt _m when [Delta] d <0.

  In step S310, control circuit 60 determines whether or not to end the measurement. If the determination in step S310 is No, the above operation is repeated again. This operation is repeated as many times as the number of frames to be measured.

  If the determination in step S307 is Yes, before the determination in step S310, or after the determination in step S310 is No, the control circuit 60 sets the reference measurement distance to the position and / or angle of the seat 12. May be changed to the measurement distance after the adjustment. This is because the posture of the user 10 can change over time.

  The operation of the control circuit 60 described above is summarized as follows. The control circuit 60 changes the time difference based on a change in the signal 16 output from the seat sensor 14 of the seat 12. More specifically, the control circuit 60 repeats the measurement operation of causing the light source 20 to emit pulse light and causing the photodetector 30 to output a signal. The control circuit 60 changes the time difference when detecting a change in the signal 16 output from the seat sensor 14 of the seat 12 during the measurement operation.

  Next, a modified example of the biological measurement device 100 according to the present embodiment will be described.

  FIG. 5 is a diagram schematically illustrating a modified example of the biological measurement system 100S according to the present embodiment. In the example illustrated in FIG. 5, unlike the example illustrated in FIG. 1A, the biometric device 100 further includes an authentication sensor 40 that authenticates the user 10. The control circuit 60 further includes an authentication control unit 63 that controls the authentication sensor 40. The authentication sensor 40 may include, for example, an image sensor that captures a user's face, and a processing circuit that processes data of the face image acquired by the image sensor. When the light detector 30 includes an image sensor, the image sensor may be used as a part of the authentication sensor 40. The authentication sensor 40 may authenticate the user based on information other than the face image. For example, a user may be authenticated based on a fingerprint, a vein pattern, and / or an input user ID.

  FIG. 6A is a flowchart illustrating an example of an operation in the embodiment in which personal authentication is performed.

  The operations of step S401 and steps S403 to S404 shown in FIG. 6A are the same as the operations of steps S201 to S203 shown in FIG. 4A, respectively.

  In step S402, the authentication sensor 40 acquires data necessary for personal authentication of the user 10, for example. Data required for personal authentication may be, for example, a user ID, a face image, a fingerprint, and / or a vein pattern.

  In step S405, the control circuit 60 determines the time difference from when the light emitted from the light source 20 is reflected by the test portion 10t of the user 10 to the time when the light enters the photodetector 30 as a reference time difference. Record in memory. Note that the reference time difference may be a time difference adjusted so that the photodetector 30 can acquire the surface reflection component I1 or the internal scattering component I2. In a memory (not shown) of the control circuit 60, back data indicating an association between the user 10, the reference position and / or the reference angle of the seat 12, and the reference time difference is recorded. Table 2 shows an example of the back data. The back data includes back data necessary for personal authentication, a reference position and / or a reference angle of the seat 12, a reference measurement distance, and a reference time difference. In Table 2, each user is associated with a reference position and / or reference angle of one seat 12, one reference measurement distance, and one reference time difference. On the other hand, a reference position and / or a reference angle of the plurality of seats 12, a plurality of reference measurement distances, and a plurality of reference time differences may be associated with each user.

  FIG. 6B is a flowchart illustrating an example of an operation during normal use in the embodiment in which personal authentication is performed.

  The operations of step S501 and steps S504 to S510 shown in FIG. 6B are the same as the operations of step S301 and steps S304 to S310 shown in FIG. 4B, respectively.

  In step S502, the control circuit 60 specifies the user 10 based on the result of the personal authentication by the authentication sensor 40.

  In step 503, the control circuit 60 automatically sets the reference time difference as an initial value of the time difference with reference to the specified user 10 and the recorded back data. Similarly, the control circuit 60 can automatically set the reference position and / or the reference angle of the seat 12. As described above, the control circuit 60 sets the reference position and / or the reference angle of the seat 12 and the initial value of the time difference based on the authentication result by the authentication sensor 40 before executing the measurement operation.

  In the example illustrated in FIG. 6B, personal authentication is performed after the user 10 sits on the seat 12, but is not limited thereto. Before the user 10 sits on the seat 12, the user 10 may be recorded and authenticated, for example, by a vein pattern. For example, when the present system is used in a hospital, the biometric device may identify the user 10 by recognizing a user ID input by a doctor, a nurse, or the user himself.

[4. Calculation of measurement distance during measurement operation]
Next, an example of a method of calculating the measurement distance in step S308 illustrated in FIG. 4B and step S508 illustrated in FIG. 6B will be described.

  FIG. 7A is a diagram schematically illustrating the seat 12 and the user 10 sitting on the seat 12 before and after adjustment of the position and / or angle of the seat 12. The solid line represents the position and / or angle of the seat 12 before adjustment. The dashed line represents the position and / or angle of the seat 12 after the adjustment.

  In the example illustrated in FIG. 7A, it is assumed that the distance between the uppermost portion 12t of the seat 12 and the photodetector 30 is substantially equal to the distance between the subject 10t of the user 10 and the photodetector 30. The rotation fulcrum 12f of the backrest 12b of the seat 12 is different from the rotation fulcrum 10f of the upper body of the user 10. Further, the height of the backrest 12 b of the seat 12 is different from the sitting height of the user 10. Due to these differences, when the inclination of the backrest 12b of the seat 12 changes, the change in the distance between the uppermost portion 12t of the seat 12 and the photodetector 30 depends on the distance between the subject 10t and the photodetector 30 of the user 10. Not the same as a change in distance.

Strictly, information on the physique of the user 10 is also taken into account in calculating the change in the distance between the subject 10 t of the user 10 and the photodetector 30. However, here, for simplicity, the following three conditions are assumed.
(1) The inclination angle of the backrest 12b of the seat 12 is the same as the inclination angle of the upper body of the user 10.
(2) The rotation fulcrum 10f of the upper body of the user 10 is closer to the photodetector 30 than the rotation fulcrum 12f of the backrest 12b of the seat 12.
(3) When the backrest portion 12b of the seat 12 is made vertical, the height of the uppermost portion 12t of the seat 12 is higher than or equal to the height of the test portion 10t of the user 10.

  Under the above conditions, when the inclination of the backrest portion 12b of the seat 12 changes, the change in the distance between the uppermost portion 12t of the seat 12 and the photodetector 30 depends on the test portion 10t and the photodetector 30 of the user 10. Is larger than the change Δd in the distance. However, for the sake of simplicity, the difference between the changes is ignored here. That is, it is assumed that when a change in the distance between the uppermost portion 12t of the seat 12 and the photodetector 30 occurs, a similar change also occurs in the distance between the subject 10t of the user 10 and the photodetector 30. The control circuit 60 determines whether to change the phase based on the amount of change in the distance between the uppermost portion 12t of the seat 12 and the photodetector 30.

FIG. 7B is a diagram schematically illustrating a relationship between the seat 12 and the photodetector 30 before adjustment of the position and / or angle of the seat 12 illustrated in FIG. 7A. For simplicity, the back portion 12b of the seat 12 is treated as a single plate. X ₀ represents a distance between the fulcrum 12f of the backrest 12b of the seat 12 and the photodetector 30 in the horizontal direction. Y ₀ represents the distance between the fulcrum 12 f of the backrest 12 b of the seat 12 and the photodetector 30 in the vertical direction. L represents the distance between the uppermost part 12t of the seat 12 and the fulcrum 12f. β ₀ represents the inclination angle of the backrest 12b of the seat 12. The inclination angle is an angle formed by the backrest 12b of the seat 12 and a line parallel to the Y direction.

The distance d between the uppermost portion 12t of the seat 12 and the photodetector 30 before the adjustment of the position and / or the angle of the seat 12 is represented by the following equation (1).

When the position and / or angle of the seat 12 is adjusted, X ₀ changes to X ₀ + ΔX, Y ₀ changes to Y ₀ + ΔY, and β ₀ changes to β ₀ + Δβ. In this case, the distance between the uppermost portion 12t of the seat 12 and the photodetector 30 after the adjustment of the position and / or the angle of the seat 12 is represented by the following equation (2).

From Expressions (1) and (2), the change amount d′−d of the distance between the top 12t of the seat 12 and the photodetector 30 before and after the adjustment of the position and / or angle of the seat 12 is obtained. Is represented by the following equation (3).

Here, the reference measurement distance between the test portion 10t and the light detector 30 of the user 10 in the front adjustment of the position and / or angle of the seat 12 is represented as d _0, the position and / or angle of the seat 12 the distance between the test portion 10t and the light detector 30 of the user 10 after adjustment is represented as d _1. d ₁ is approximated by the following equation (4) using the equation (3).

From the above, the difference Δd = d ₁ −d ₀ between the measured distance d ₁ and the reference measured distance d _{0 in} step S308 shown in FIG. 4B and step S508 shown in FIG. 6B is calculated from equation (3). . However, L used for the calculation is recorded in a memory (not shown) of the control circuit 60 before normal use. L may be recorded together with the back data shown in Tables 1 and 2. Alternatively, L may be recorded in a memory (not shown) of the control circuit 60 before recording the back data.

  As described above, in the biological measurement device 100 according to the present embodiment, the difference Δd between the measurement distance and the reference measurement distance is obtained without using the TOF technology, so that even if the time of one frame is short, the time difference can be easily and easily determined. Can be changed appropriately. As a result, even when the user 10 adjusts the position and / or angle of the seat 12 during the measurement operation, the biological information of the user 10 can be accurately measured.

  When adjusting the position of the seat 12 without adjusting the angle of the seat 12, the measurement distance between the test portion 10t of the user 10 and the photodetector 30 can also be calculated as follows.

  FIG. 8A is a diagram schematically illustrating a face image of the user 10 acquired from a signal output from the photodetector 30. FIG. In the biological measurement device 100 according to the present embodiment, the posture of the photodetector 30 may be changed according to an instruction from the control circuit 60. Thereby, before starting the measurement operation in step S304 shown in FIG. 4B and step S504 shown in FIG. 5B, the posture of the photodetector 30 is set to the position of the subject 10t of the user 10 as shown in FIG. 8A. The center 10c is adjusted so as to be located at the center of the acquired image. At this time, it can be said that the subject 10 t of the user 10 and the photodetector 30 face each other.

FIG. 8B is a diagram schematically illustrating a relationship between the user 10 and the photodetector 30 when the position of the seat 12 changes in the horizontal direction. α represents the installation angle of the photodetector 30 before the adjustment of the position of the seat 12 when the photodetector 30 faces the test section 10t of the user 10 directly. α is an angle formed between the light receiving surface of the photodetector 30 and a line parallel to the Y direction. α is also an angle formed by a line perpendicular to the light receiving surface of the photodetector 30 and passing through the center 10c of the subject 10t of the user 10 and a line parallel to the X direction. The reference measurement distance d ₀ between the subject 10 t of the user 10 and the photodetector 30 when the subject 10 t of the user 10 faces the photodetector 30 is known by the TOF technique.

When the position of the seat 12 approaches the photodetector 30 by ΔX in the horizontal direction, from the example shown in FIG. 8B, the measurement distance d ₂ between the subject 10 t of the user 10 and the photodetector 30 is represented by the following equation. It is represented by (5).

On the other hand, when the position of the seat 12 is separated from the light detector 30 by ΔX in the horizontal direction, from the example shown in FIG. 8B, the measured distance d ₃ between the subject 10 t of the user 10, the light detector 30, and It is represented by (6).

  FIG. 8C is a diagram schematically illustrating a relationship between the test portion 10 t of the user 10 and the photodetector 30 when the position of the seat 12 changes in the vertical direction.

When the position of the seat 12 rises in the vertical direction by ΔY ₁ and ΔY ₁ is smaller than d ₀ · sin α, the measured distance d between the test portion 10 t of the user 10 and the photodetector 30 is obtained from the example shown in FIG. ₄ is represented by the following equation (7).

Rose to the vertical position of the seat 12 by [Delta] Y _2, when [Delta] Y ₂ is greater than d ₀ · sinα, measuring the distance from the example shown in FIG. 8C, the test portion 10t and the light detector 30 of the user 10 d ₅ is represented by the following equation (8).

When the position of the seat 12 is lowered by ΔY _{1 in the} vertical direction, from the example shown in FIG. 8C, the measurement distance d ₆ between the test portion 10t of the user 10 and the photodetector 30 is calculated by the following equation (9). expressed.

From the above, the measurement distance d _{i (i} = 2 to 6) at step S508 shown in step S308, and 6B is shown in FIG. 4B, the difference [Delta] d between the reference measurement distance _{d 0, Δd = d i -d} 0 May be calculated. Thus, by obtaining the difference Δd between the measurement distance and the reference measurement distance without using the TOF technique, the time difference can be easily and appropriately changed even if the time of one frame is short. As a result, even if the user 10 adjusts the position and / or angle of the seat 12 during the measurement operation, the biological information of the user 10 can be accurately measured.

  Next, an example in which the subject 10 t of the user 10 does not face the photodetector 30 will be described.

  FIG. 8D is a diagram schematically illustrating a face image of the user 10 when the subject 10 t of the user 10 does not face the photodetector 30. FIG. 8D shows, for example, a face image of the user 10 when the position of the seat 12 is lowered in the vertical direction. After the measurement operation is interrupted and the user 10 adjusts the position and / or the angle of the seat 12 and before the measurement operation is started, the control circuit 60 transmits the test object 10 t of the user 10, the light detector 30, May be determined so as to face directly. The attitude of the photodetector 30 can be determined by adjusting the installation angle α of the photodetector 30. Thereafter, the control circuit 60 may start a measurement operation using the light source 20 and the photodetector 30.

[5. Application example]
Next, an application example of the biological measurement device 100 according to the present embodiment will be described.

  FIG. 9A is a diagram schematically illustrating an example in which the user 10 sits on the seat 12 during diagnosis or meditation training at a hospital. In the example illustrated in FIG. 9A, the first biological information and / or the second biological information of the user 10 are measured during the diagnosis in the hospital or the meditation training. Even if the user 10 adjusts the position and / or angle of the seat 12 during a diagnosis in a hospital or during meditation training, the biological information of the user 10 can be accurately measured by the biometric device 100 in the present embodiment.

  FIG. 9B is a diagram schematically illustrating an example in which the user 10 sits on the seat 12 in the automobile. In the example illustrated in FIG. 9B, the first biometric information and / or the second biometric information of the user 10 are measured while driving the automobile. For example, by measuring the second biological information indicating the brain activity information, it is possible to check whether the user 10 is in a drunken state or has a possibility of causing an accident. Even if the user 10 adjusts the position and / or angle of the seat 12 while driving the car, the biological information of the user 10 can be accurately measured by the biological measurement device 100 in the present embodiment.

  The present disclosure also includes an operation method and a program executed by the control circuit 60.

  The biometric device according to the present embodiment can be used for diagnosing a mental state such as a degree of concentration during work when a specific user performs a specific work at a specific place. In addition, the biological measurement device according to the present embodiment includes, for example, periodic diagnosis of a mental illness in a hospital, diagnosis of a mental condition in a brain training gym, detection of concentration or task difficulty during desk work, or during operation of the device. Can be applied to the prediction of errors or the detection of a lazy state.

10: user 10f: fulcrum 10t: subject 12: seat 12s: seat 12b: backrest 12f: fulcrum 12t: uppermost part 14: seat sensor 16: signal 20: light source 30: light detector 60: control circuit 62: Light source controller 63: Sensor controller 70: Signal processing circuit 100: Biological measuring device 100S: Biological measuring system 101: Light source 201: Pixel 202: Drain 203: Photodiode 204, 205, 206, 207: Floating diffusion layer 302: Row Selection circuit 303: Column selection circuit 304: Vertical signal line 305: Source follower power supply 306: Source follower load 307: Conversion circuit 308: Row selection transistor 309: Source follower transistor 310: Reset transistor

Claims (8)

A seat whose position and / or angle can be changed,
A seat sensor that outputs a first signal indicating the position and / or the angle of the seat;
A biological measurement device;
A biometric device used in a system comprising:
A light source that emits light that is irradiated on a test portion of a user sitting on the seat;
A photodetector that emits a second signal by detecting at least a part of the light emitted from the light source and returned from the test section;
A control circuit for controlling the light source and the photodetector,
A signal processing circuit that generates and outputs a third signal indicating the biological information of the user based on the second signal;
With
The control circuit, based on the change of the first signal, to change the time difference from emitting the light to the light source until the light detector to detect the light,
Biological measurement device. The control circuit sets an initial value of the time difference with reference to data indicating the relationship between the position and / or the angle of the seat and the time difference,
The biological measurement device according to claim 1. Further comprising an authentication sensor for authenticating the user,
The control circuit sets the position and / or the angle of the seat and an initial value of the time difference based on an authentication result by the authentication sensor.
The biological measurement device according to claim 1. The photodetector is capable of changing a posture according to an instruction from the control circuit,
The control circuit, based on the first signal, after determining the attitude of the photodetector, starts a measurement operation using the light source and the photodetector,
The biological measurement device according to claim 1. The test portion of the user is the amount of the user,
The control circuit includes:
Causing the light source to emit one or more pulsed lights;
The photodetector is obtained by detecting a component included in a period from the time when the intensity of each pulse light starts to decrease to the time when the decrease ends, among the pulse lights returned from the test section. Outputting a signal as the second signal;
The signal processing circuit generates a signal indicating a state of brain activity of the user as the third signal based on the second signal.
The biological measurement device according to claim 1. A biological measurement device according to any one of claims 1 to 4,
Said seat,
Said seat sensor;
A biological measurement system comprising: Causing the light source to emit light to be irradiated on a test portion of a user sitting on a seat capable of changing a position and / or an angle;
Causing the photodetector to detect at least a portion of the light emitted from the light source and returned from the test portion;
Obtaining a first signal indicating the position and / or the angle of the seat;
Based on the change of the first signal, to change the time difference between the time when the light source emits the light and the time when the light detector detects the light,
And a control method. A computer program executed on a computer,
The computer program comprises:
Causing the light source to emit light to be irradiated on a test portion of a user sitting on a seat capable of changing a position and / or an angle;
Causing the photodetector to detect at least a portion of the light emitted from the light source and returned from the test portion;
Obtaining a first signal indicating the position and / or the angle of the seat;
Based on the change of the first signal, to change the time difference between the time when the light source emits the light and the time when the light detector detects the light,
A computer program that runs

Images