JP2018161250A - Biological information sensor and wear determination method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a biological information sensor capable of accurately determining wear/non-wear thereof on a living body.SOLUTION: A biological information sensor 1 includes: an optical sensor part 11 having a light emitting part 11A and a light receiving part 11B; an acceleration sensor part 18; and a wear determination part for determining the wear using the optical sensor part and the acceleration sensor part. The wear determination part sequentially performs, in a stepwise manner: motion state determination processing of determining whether or not the acceleration sensor part detects acceleration; ambient light determination processing of determining whether or not the light receiving part does not detect the ambient light; proximity determination processing of determining whether or not reflected light is detected by the receiving part, when the light emitting part exits light; and biological information determination processing of determining whether or not biological information is acquired from the light detected by the receiving part, when the light emitting part exits light. When it is determined to be yes in all the determination processing, the biological information sensor determined that it is OK to wear.SELECTED DRAWING: Figure 3

Description

  The invention disclosed in the present specification relates to a biological information sensor and a method for determining attachment thereof.

  In recent years, a photoelectric type that irradiates a living body (such as a subject's arm or finger) with light from a light emitting unit and detects various biological information (such as pulse wave information) based on the intensity of light returning from the living body to the light receiving unit. This biological information sensor has been put into practical use.

  Moreover, as a conventional method for determining whether or not the biological information sensor is correctly attached to the living body, for example, a method (Patent Document 1 to Patent Document 3) for determining the presence or absence of the subject's body movement, There is a technique for determining the presence or absence of detection (Patent Document 4 by the applicant of the present application).

JP, 2006-123473, A JP2013-202289A Japanese Patent Laid-Open No. 2006-16203 International Publication No. 2015/166990

  However, in the above-described conventional method, there is room for further improvement with respect to the mounting determination accuracy of the biological information sensor.

  In view of the above-mentioned problems found by the inventors of the present application, the invention disclosed in the present specification provides a biological information sensor that can accurately determine whether or not a living body is mounted. With the goal.

  The biological information sensor disclosed in the present specification includes an optical sensor unit including a light emitting unit and a light receiving unit, an acceleration sensor unit, and a mounting determination that performs mounting determination using the optical sensor unit and the acceleration sensor unit. A movement state determination process for determining whether or not acceleration is detected by the acceleration sensor unit, and whether or not ambient light is not detected by the light receiving unit. Ambient light determination processing, proximity determination processing for determining whether or not reflected light is detected by the light receiving portion when light is emitted from the light emitting portion, and light reception when light is emitted from the light emitting portion. And biological information determination processing for determining whether biological information has been acquired from the light detected by the unit in a step-by-step manner, and when yes determination is made in all of the above determination processing, it is determined that the mounting is OK Configuration (first configuration)

  In the biological information sensor having the first configuration, the wearing determination unit shifts to the ambient light determination process when a positive determination is made in the exercise state determination process, and the negative determination is determined in the ambient light determination process. The process proceeds to the proximity determination process when it is performed, shifts to the biological information determination process when a yes determination is made in the proximity determination process, and is attached when the yes determination is made in the biological information determination process. And the transition to the normal operation of continuously acquiring the biological information is permitted, and when no determination is made in any one of the determination processes, it is determined as wearing NG and the process returns to the exercise state determination process. A configuration (second configuration) is preferable.

  In the biological information sensor having the second configuration, the current consumption during the motion state determination process is smaller than that during the ambient light determination process, and the current consumption during the ambient light determination process is equal to that during the proximity determination process. The current consumption during the proximity determination process is preferably smaller than that during the biometric information determination process (third configuration).

  In the biometric information sensor having the second or third configuration, the mounting determination unit performs the biometric information determination process even after shifting to the normal operation, and when no determination is made in the determination process, the mounting determination unit A configuration (fourth configuration) for determining and returning to the exercise state determination process may be used.

  The biological information sensor having any one of the second to fourth configurations further includes a pulse driving unit that intermittently turns on and off the light emitting unit during the normal operation, and the mounting determination unit shifts to the normal operation. After that, when the light emitting unit is turned off, the light receiving unit performs a light-off ambient light determination process for determining whether or not ambient light is not detected, and when the determination process is negative, it is determined as wearing NG. Thus, the configuration (fifth configuration) may be returned to the exercise state determination process.

  In the biological information sensor having any one of the first to fifth configurations, the wearing determination unit outputs an output signal of the light receiving unit over at least one of the ambient light determination process and the proximity determination process over a predetermined determination period. It is preferable to adopt a configuration (sixth configuration) in which measurement is repeatedly performed at a predetermined measurement cycle.

  The biological information sensor having any one of the first to sixth configurations may have a configuration (seventh configuration) further including a notification unit that notifies the determination result of the mounting determination unit.

  In the biological information sensor having any one of the first to seventh configurations, a plurality of the light emitting units may be configured around the light receiving unit (eighth configuration).

  In the biological information sensor having any one of the first to eighth configurations, the output wavelength of the light emitting unit may be configured to belong to a visible light region of 600 nm or less (ninth configuration).

  In addition, the mounting determination method disclosed in the present specification determines whether or not a biological information sensor having an optical sensor unit including a light emitting unit and a light receiving unit and an acceleration sensor unit is correctly mounted on a living body. A determination method for determining whether or not acceleration is detected by the acceleration sensor unit, and determining whether or not ambient light is not detected by the light receiving unit Processing, proximity determination processing for determining whether reflected light is detected by the light receiving unit when light is emitted from the light emitting unit, and detection by the light receiving unit when light is emitted from the light emitting unit. The biometric information determination process for determining whether or not the biometric information has been acquired from the light to be attached is sequentially performed step by step, and when a yes determination is made in all the above determination processes, the configuration is determined to be OK (10th Composition).

  According to the invention disclosed in the present specification, it is possible to provide a biological information sensor that can accurately determine whether or not a living body is mounted.

Schematic diagram for explaining the principle of pulse wave measurement at the wrist Waveform diagram showing how the attenuation (absorbance) of light in a living body changes over time The block diagram which shows the example of 1 structure of the biometric information sensor 1 The circuit diagram which shows one structural example of the optical sensor part 11 and the pulse drive part 17 The block diagram which shows the example of 1 structure of the filter part 12. Circuit diagram showing one configuration example of the transimpedance amplifier 121 The block diagram which shows the example of 1 structure of the control part 13. The flowchart which shows 1st Example of a mounting | wearing determination process. The flowchart which shows 2nd Example of mounting | wearing determination processing. Signal waveform diagram for explaining the principle of ambient light judgment processing when the light is off

<Principle of pulse wave measurement>
FIG. 1 is a schematic diagram for explaining the principle of pulse wave measurement at the wrist, and FIG. 2 is a waveform diagram showing how the attenuation (absorbance) of light in the living body changes with time.

In the pulse wave measurement by the volume pulse wave method, for example, as shown in FIG. 1, a light emitting unit (LED [light emitting diode] or the like) is directed toward a part of a living body (wrist in FIG. 1) pressed against the measurement window. ), And the intensity of the light transmitted through the body and coming out of the body is detected by a light receiving unit (a photodiode, a phototransistor, or the like). Here, as shown in FIG. 2, the attenuation (absorbance) of light due to living tissue and venous blood (deoxygenated hemoglobin Hb) is constant, but the attenuation of light due to arterial blood (oxygenated hemoglobin HbO ₂ ). (Absorbance) varies with time due to pulsation. Therefore, by utilizing the “biological window” (wavelength range where light is easily transmitted through the living body) from the visible region to the near-infrared region, the change in the absorbance of the peripheral artery is measured, so that the volume pulse wave can be generated non-invasively. Can be measured.

  In FIG. 1, for convenience of illustration, a state in which the biological information sensor (light emitting unit and light receiving unit) is mounted on the back side (outside) of the wrist is depicted, but the mounting position of the biological information sensor is described here. It is not limited and may be on the ventral side (inside) of the wrist, or other part (fingertip, between the interphalangeal joint and proximal interphalangeal joint of the finger, forehead, between the eyebrows, and the tip of the nose , Cheeks, under eyes, temples, ear lobes, etc.).

<What you can understand from the pulse wave>
Note that the pulse wave under the control of the heart and the independent nerve does not always exhibit a constant behavior, but causes various changes (fluctuations) depending on the condition of the subject. Accordingly, various body information of the subject can be obtained by analyzing the change (fluctuation) of the pulse wave. For example, from the heart rate, it is possible to know the exercise ability, the degree of tension, and the like of the subject, and from the heart rate variability, it is possible to know the fatigue level, the degree of sleep, the magnitude of stress, and the like. Further, from the acceleration pulse wave obtained by differentiating the pulse wave twice with respect to the time axis, the blood vessel age, arteriosclerosis degree, etc. of the subject can be known.

<Biological information sensor>
FIG. 3 is a block diagram illustrating a configuration example of the biological information sensor. The biological information sensor 1 of the present configuration example has a bracelet structure (watch-type structure) including a head unit 10 and a band unit 20 that is wound around the living body 2 (for example, a wrist of a subject) while holding the head unit 10. It is said that. In addition, as a material for forming the band portion 20, leather, metal, resin, or the like can be used.

  The head unit 10 (= main unit) includes an optical sensor unit 11, a filter unit 12, a control unit 13, a display unit 14, a communication unit 15, a power supply unit 16, a pulse driving unit 17, and an acceleration sensor unit. 18. However, this configuration is merely an example, and some or all of the above-described components may be provided in the band unit 20. Further, the head unit 10 and the band unit 20 can be integrated without being distinguished.

  The optical sensor unit 11 is provided on the back surface of the head unit 10 (= the surface on the side facing the living body 2). The light sensor 11 irradiates the living body 2 with light from the light emitting unit 11A and receives the reflected light from the living body 2 as the light receiving unit 11B. By detecting the current signal, a current signal corresponding to the received light intensity is generated. In the biological information sensor 1 of this configuration example, the optical sensor unit 11 has a configuration in which a light emitting unit 11A and a light receiving unit 11B are provided on opposite sides of the living body 2 (so-called transmission type, see broken line arrows in FIG. 1). Instead, the light emitting unit 11A and the light receiving unit 11B are both provided on the same side with respect to the living body 2 (so-called reflection type, see solid line arrow in FIG. 1). The inventors of the present application have actually confirmed through experiments that biological information (for example, pulse wave information) can be sufficiently obtained from the wrist. Further, in the example of this figure, the light sensor unit 11 is provided with one light emitting unit 11A and one light receiving unit 11B. However, for example, a plurality of light emitting units 11A may be provided so as to surround the light receiving unit 11B. I do not care.

  The filter unit 12 performs various signal processing (current / voltage conversion processing, detection processing, filter processing, and amplification processing) on the current signal input from the optical sensor unit 11 and outputs the processed signal to the control unit 13. A specific configuration of the filter unit 12 will be described later in detail.

  The control unit 13 comprehensively controls the operation of the entire biological information sensor 1 and performs various signal processing on the output signal of the filter unit 12 to thereby provide the biological information of the subject (pulse wave fluctuation, heart rate, heart rate). Fluctuation, acceleration pulse wave, etc.). As the control unit 13, a CPU [central processing unit] or the like can be preferably used. The control unit 13 also has a function as a mounting determination unit that determines whether the biological information sensor 1 is mounted or not using the optical sensor unit 11 and the acceleration sensor 18. This function will be described in detail later.

  The display unit 14 is provided on the surface of the head unit 10 (the surface on the side not facing the living body 2), and displays predetermined display information (including information related to date and time as well as measurement results of biological information). Output. That is, the display unit 14 corresponds to a dial face of a wristwatch. The display unit 14 also has a function as a notification unit that notifies the subject of the result of the attachment determination. In addition, as the display part 14, a liquid crystal display panel etc. can be used suitably.

  The communication unit 15 transmits the measurement data of the biological information sensor 1 to an external device (such as a personal computer or a mobile phone) wirelessly or by wire. In particular, if the configuration is such that the measurement data of the biological information sensor 1 is transmitted to an external device wirelessly, it is not necessary to connect the biological information sensor 1 and the external device with a wire, so that, for example, without restricting the behavior of the subject Measurement data can be transmitted in real time. Further, when the biological information sensor 1 has a waterproof structure, it is desirable to adopt a wireless transmission method as an external transmission method of measurement data from the viewpoint of completely eliminating external terminals. Note that when the wireless transmission method is employed, a Bluetooth (registered trademark) wireless communication module IC or the like can be suitably used as the communication unit 15.

  The power supply unit 16 includes a battery and a DC / DC converter, converts an input voltage from the battery into a desired output voltage, and supplies the output voltage to each unit of the biological information sensor 1. In this way, with the battery-driven biometric information sensor 1, it is not necessary to connect an external power supply cable when measuring biometric information, and thus biometric information can be measured without restricting the behavior of the subject. It becomes possible. In addition, as said battery, it is desirable to use the secondary battery (A lithium ion secondary battery, an electric double layer capacitor, etc.) which can be charged repeatedly. Thus, if it is the structure which uses a secondary battery as a battery, since the troublesome battery replacement | work operation | work will become unnecessary, the convenience of the biometric information sensor 1 can be improved. Further, as a power supply method from the outside during battery charging, a contact power supply method using a USB [universal serial bus] cable or the like may be used, or an electromagnetic induction method, an electric field coupling method, a magnetic field resonance method, or the like may be used. A non-contact power feeding method may be used. However, when the biological information sensor 1 has a waterproof structure, it is desirable to employ a non-contact power feeding method as an external power supply method from the viewpoint of completely eliminating external terminals.

  In the normal operation for continuously acquiring biological information, the pulse driving unit 17 causes the light emitting unit 11A of the optical sensor unit 11 to have a predetermined frame frequency f (for example, 50 to 1000 Hz) and a duty D (1/8 to 1). / 200) to intermittently turn on and off.

  The acceleration sensor 18 generates an acceleration signal corresponding to the acceleration applied to itself (= body motion of the subject, etc.) and outputs it to the control unit 13. As the acceleration sensor 18, for example, a MEMS (micro electro mechanical systems) type triaxial that can detect acceleration in each of three directions (X-axis direction, Y-axis direction, and Z-axis direction) with one device. An acceleration sensor can be suitably used.

  As described above, if the biological information sensor 1 has a bracelet structure, the biological information sensor 1 is dropped from the wrist of the subject during measurement of the biological information unless the subject intentionally removes the biological information sensor 1 from the wrist. There is almost no fear of it. Therefore, it is possible to measure biological information without restricting the behavior of the subject.

  In addition, the biological information sensor 1 having a bracelet structure does not need to be so conscious that the subject is wearing the biological information sensor 1, and thus continues for a long period (several days to several months). Even when biological information is measured, it is not necessary to apply excessive stress to the subject.

  In particular, in the case of the biological information sensor 1 (= the biological information sensor 1 having a wristwatch structure) provided with the display unit 14 that can display not only the measurement result of biological information but also date and time information, the subject is the biological information sensor 1. Can be worn on a daily basis as a wristwatch, so that the resistance to wearing of the biological information sensor 1 can be further wiped away, which in turn can contribute to the development of new user groups.

  Moreover, it is desirable that the biological information sensor 1 has a waterproof structure. By adopting such a configuration, it is possible to measure biological information without failure even when wet with water (rain) or sweat. Further, when the biometric information sensor 1 is shared by a large number of people (for example, when used for lending in a gym), the biometric information sensor 1 can be kept clean by washing the entire biometric information sensor 1 with water. It becomes possible.

<Optical sensor unit and pulse drive unit>
FIG. 4 is a circuit diagram illustrating a configuration example of the optical sensor unit 11 and the pulse driving unit 17. The optical sensor unit 11 of this configuration example includes a light emitting diode (corresponding to a light emitting unit) 11A and a phototransistor (corresponding to a light receiving unit) 11B. Further, the pulse driving unit 17 of this configuration example includes a switch 171 and a current source 172.

  The anode of the light emitting diode 11A is connected to the application terminal of the power supply voltage AVDD via the switch 171. The cathode of the light emitting diode 11 </ b> A is connected to the ground terminal via the current source 172. The switch 171 is turned on / off according to the pulse drive signal S171. The current source 172 generates a constant current IA according to the brightness control signal S172. In order to accurately measure pulse waves during exercise or outdoors, it is desirable that the light emitting diode 11A is pulse-driven with a higher brightness than external light.

  When the switch 171 is turned on, the current path through which the constant current IA flows is conducted, so that the light emitting diode 11A is turned on and the living body 2 is irradiated with light. At this time, a current signal IB corresponding to the received light intensity of the reflected light returning from the living body 2 flows between the collector and the emitter of the phototransistor 11B. On the other hand, when the switch 171 is off, the current path through which the constant current IA flows is interrupted, and thus the light emitting diode 11A is turned off.

<Filter section>
FIG. 5 is a block diagram illustrating a configuration example of the filter unit 12. The filter unit 12 of this configuration example includes a transimpedance amplifier 121 (hereinafter abbreviated as TIA [transimpedance amplifier] 121), a buffer circuit 122, a detection circuit 123, a band-pass filter circuit 124, an amplifier circuit 125, And a reference voltage generation circuit 126.

  The TIA 121 is a type of current / voltage conversion circuit that converts the current signal IB into a voltage signal Sa and outputs the voltage signal Sa to the subsequent buffer circuit 122 and the control unit 13.

  The buffer circuit 122 is a voltage follower that transmits the voltage signal Sa as a buffer signal Sb to the subsequent stage.

  The detection circuit 123 generates the detection signal Sc by extracting only the envelope from the pulse-driven voltage signal Sb, and outputs this to the subsequent stage. As the detection circuit 123, a half-wave rectification detection circuit, a full-wave rectification detection circuit, or the like can be used.

  The bandpass filter circuit 124 generates a filter signal Sd by removing both the low frequency component and the high frequency component superimposed on the detection signal Sc, and outputs this to the subsequent stage. Note that the pass frequency band of the bandpass filter circuit 124 is preferably set to about 0.6 to 4.0 Hz.

  The amplifying circuit 125 amplifies the filter signal Sd with a predetermined gain to generate a light reception signal Se and outputs it to the control unit 13 at the subsequent stage.

  The reference voltage generation circuit 126 generates a reference voltage VREF (= AVDD / 2) by dividing the power supply voltage AVDD by ½, and supplies this to each part of the filter unit 12.

  Since the subject's body movement noise can be appropriately removed with the filter unit 12 of this configuration example, not only the biological information when the subject is at rest, but also when the subject is exercising (walking, jogging, or running) It is also possible to detect biological information at a higher accuracy.

  In the filter unit 12 of this configuration example, the TIA 121, the buffer circuit 122, the detection circuit 123, the band-pass filter circuit 124, and the amplifier circuit 125 all operate with the reference voltage VREF (= AVDD / 2) as the center value. Therefore, the light reception signal Se output from the filter unit 12 has a waveform whose amplitude varies up and down with respect to the reference voltage VREF. Therefore, with the filter unit 12 of this configuration example, saturation of the light reception signal Se (sticking to the power supply voltage AVDD and the ground voltage GND) can be prevented, and biological information can be detected correctly.

<TIA>
FIG. 6 is a circuit diagram showing a configuration example of the TIA 121. The TIA 121 of this configuration example includes an operational amplifier AMP1, a resistor R1, and a capacitor C1. The non-inverting input terminal (+) of the operational amplifier AMP1 is connected to the application terminal of the reference voltage VREF (= AVDD / 2). The inverting input terminal (−) of the operational amplifier AMP1 is connected to the emitter of the photodiode 11B. The collector of the photodiode 11B is connected to the application end of the power supply voltage AVDD. The output terminal of the operational amplifier AMP1 corresponds to the output terminal of the voltage signal Sa. The resistor R1 and the capacitor C1 are respectively connected in parallel between the inverting input terminal (−) and the output terminal of the operational amplifier AMP1.

  In the TIA 121 of this configuration example, the current signal IB flows through a current path from the inverting input terminal (−) of the operational amplifier AMP1 to the output terminal of the voltage signal Sa through the resistor R1. Therefore, a voltage (= Sa + IB × R1) obtained by adding the voltage across the resistor R1 to the voltage signal Sa is applied to the inverting input terminal (−) of the operational amplifier AMP1. On the other hand, the operational amplifier AMP1 generates the voltage signal Sa so that the non-inverting input terminal (+) and the inverting input terminal (−) are imaginarily short-circuited. Therefore, the voltage signal Sa generated by the TIA 121 has a voltage value (VREF−IB × R1) obtained by subtracting the voltage across the resistor R1 from the reference voltage VREF.

  That is, the voltage signal Sa decreases as the current signal IB flowing through the resistor R1 (corresponding to the amount of light received by the phototransistor 11B) increases, and conversely, the voltage signal Sa increases as the current signal IB decreases. Note that the gain of the TIA 121 can be arbitrarily adjusted by changing the resistance value of the resistor R1.

<Control unit (mounting determination unit)>
FIG. 7 is a block diagram illustrating a configuration example of the control unit 13. The control unit 13 of this configuration example includes a main control circuit 131 and a sub control circuit 132.

  The main control circuit 131 is a main body that mainly controls a display operation using the display unit 14 and a communication operation using the communication unit 15.

  The sub-control circuit 132 mainly controls the measurement operation of the biological information using the optical sensor unit 11 and also controls the wearing determination operation using the optical sensor unit 11 and the acceleration sensor unit 18, and is an A / D converter. 132a, a digital signal processing unit 132b, a serial data communication port 132c, and a general-purpose input / output port 132d.

  The A / D converter 132a receives the light reception signal Se and the voltage signal Sa input from the filter unit 12 and the acceleration signal Sf input from the acceleration sensor 18 in a time division manner, and digitally converts each of them to a digital signal processing unit. Sequentially output to 132b. In place of the multi-input type A / D converter 132a, a plurality of single-input type A / D converters that receive each input of the light receiving signal Se, the voltage signal Sa, and the acceleration signal Sf may be provided in parallel. I do not care.

  The digital signal processor 132b performs various digital signal processing on the output of the A / D converter 132a. The digital signal processing here includes waveform shaping processing and analysis processing of measurement data based on the light reception signal Se, and monitoring processing (mounting determination processing) for each of the voltage signal Sa, the light reception signal Se, and the acceleration signal Sf. It is. That is, the digital signal processing unit 132b functions as an attachment determination unit for determining whether or not the biological information sensor 1 is correctly attached to the living body 2. Details of the attachment determination process will be described later.

The serial data communication port 132 c is a port for performing serial data communication between the main control circuit 131 and the sub control circuit 132. For example, the digital signal processing unit 132b transmits the biological information acquired by the sub control circuit 132 to the main control circuit 131 via the serial data communication port 132c. The main control circuit 131 displays the biological information transmitted from the sub control circuit 132 on the display unit 14 or transfers it from the communication unit 15 to an external device. As the serial data communication port 132c, an I ² C port or the like can be preferably used.

  The general-purpose input / output port 132d is a port for inputting / outputting a 1-bit signal (binary signal). For example, the digital signal processing unit 132b outputs a mounting determination flag (corresponding to a result of mounting determination) to the general-purpose input / output port 132d. Specifically, when the digital signal processing unit 132b determines that the biological information sensor 1 is correctly attached to the living body 2, the general-purpose input / output port 132d is set to a high level, while the biological information sensor 1 is connected to the living body 2. The general-purpose input / output port 132d is set to the low level when it is determined that the general-purpose input / output port 132 is not correctly mounted. The main control circuit 131 monitors the output logic level of the general-purpose input / output port 132d, and displays the monitoring result on the display unit 14 or transfers it from the communication unit 15 to an external device. As the general-purpose input / output port 132d, a GPIO (general purpose input / output) port or the like can be preferably used.

  In addition, the digital signal processing unit 132b can transmit the wearing determination result of the biological information sensor 1 from the serial data communication port 132c to the main control circuit 131. For example, a request signal is periodically transmitted from the main control circuit 131 via the serial data communication port 132c, and the attachment determination result of the biological information sensor 1 is transmitted from the sub control circuit 132 that has received the request signal via the serial data communication port 132c. A sequence for confirming mounting may be set up so as to reply. In this case, the general-purpose input / output port 132d may be omitted.

<Wearing determination process>
FIG. 8 is a flowchart showing a first embodiment of the mounting determination process by the control unit 13 (particularly, the digital signal processing unit 132b). When the flow is started, first, in step S1, the acceleration sensor unit 18 determines whether or not acceleration of a predetermined value or more (or a predetermined pattern indicating a movement state such as a walking state or a jogging state) is detected. Judgment processing is performed. The acceleration measurement cycle may be set to several tens of Hz (for example, 32 to 50 Hz).

  If the determination in step S1 is YES, there is a high possibility that the biological information sensor 1 is attached to the living body 2 (= the wrist of the subject in motion), and the flow proceeds to step S2 where the flow continues. On the other hand, when a negative determination is made in step S1, it is determined as wearing NG, the flow is returned to step S1, and the above-described motion state determination process is repeated. In addition, as a situation where no determination is made in step S1, for example, a case where the biological information sensor 1 is placed on a desk or the like can be cited.

  In step S1, only the minimum necessary circuit units (such as the control unit 13 and the acceleration sensor 18) are driven to perform the exercise state determination process, and other circuit units (such as the optical sensor unit 11) are Both have been stopped. Therefore, the current consumption (eg, several μA) during the exercise state determination process in step S1 may be smaller than the current consumption (eg, 10 μA) during the ambient light determination process in step S2 (described later).

  If a YES determination is made in step S1, ambient light determination is performed in subsequent step S2 to determine whether or not ambient light is not detected by the light receiving unit 11B (= whether or not the periphery of the optical sensor unit 11 is dark). Processing is performed. In the ambient light determination process, the output signal of the light receiving unit 11B (specifically, the voltage signal Sa output from the TIA 121) is used for a predetermined determination period (for example, 1 to 10 s) while the light emitting unit 11A is turned off. The measurement may be repeated at a predetermined measurement period (for example, 1 to 8 Hz). For example, when the determination period is 10 seconds and the measurement cycle is 1 Hz, ambient light measurement is performed 10 times in total (= 10 seconds × 1 Hz) in step S2.

  Here, in a state where the biological information sensor 1 is correctly attached to the living body 2 (= a state in which the optical sensor unit 11 is in close contact with the living body 2 and incidence of ambient light on the light receiving unit 11B is appropriately blocked). Unless the light emitting unit 11A is turned on, the light receiving intensity at the light receiving unit 11B is substantially zero. At this time, since the current signal IB hardly flows through the resistor R1, the voltage signal Sa ideally matches the reference voltage VREF. Therefore, by comparing the voltage signal Sa and the predetermined threshold voltage Vth, it can be determined whether or not ambient light is not detected.

  When a positive determination is made in step S2, there is a high possibility that the biological information sensor 1 is correctly attached to the living body 2, and therefore the flow proceeds to step S3 where the flow continues. On the other hand, when a negative determination is made in step S2, it is determined as wearing NG, the flow is returned to step S1, and the exercise state determination process described above is repeated. In addition, although a yes determination is made in step S1, a situation in which a no determination is made in step S2 is, for example, a subject walking in the day with the biological information sensor 1 in his hand. Cases can be mentioned.

  In step S2, since the optical sensor unit 11 is used as ambient light detection means, it is not necessary to turn on the light emitting unit 11A. Therefore, the current consumption (for example, 10 μA) during the ambient light determination process in step S2 may be smaller than the current consumption (for example, 75 μA) during the proximity determination process in step S3 (described later).

  If the determination in step S2 is YES, in the subsequent step S3, whether or not the reflected light is detected by the light receiving unit 11B when light is emitted from the light emitting unit 11A (= light is emitted in the vicinity of the optical sensor unit 11). Proximity determination processing for determining whether there is a reflecting object (= whether or not the living body 2) exists. In the proximity determination process described above, the output signal of the light receiving unit 11B (more specifically, the voltage signal Sa output from the TIA 121) is used for a predetermined determination period (for example, 1 to 10 seconds) while the light emitting unit 11A is turned on. ) Over a predetermined measurement cycle (for example, 1 to 8 Hz). For example, when the determination period is 10 seconds and the measurement cycle is 1 Hz, reflected light measurement is performed 10 times (= 10 seconds × 1 Hz) in total in step S2.

  When a positive determination is made in step S3, there is a high possibility that the biological information sensor 1 is correctly attached to the living body 2, and therefore the flow proceeds to step S4 where the flow continues. On the other hand, when a negative determination is made in step S3, it is determined as wearing NG and the flow is returned to step S1, and the exercise state determination process described above is repeated. In addition, as a situation where a negative determination is made in step S3 even though a negative determination is made in both steps S1 and S2, for example, the subject walks at night while holding the biological information sensor 1 in his / her hand. The case can be mentioned.

  Further, in step S3, since it is only necessary to detect the presence or absence of reflected light, the light emission intensity of the light emitting unit 11A can be lowered as compared with the measurement of biological information. Therefore, the current consumption (for example, 75 μA) during the proximity determination process in step S3 may be smaller than the current consumption (for example, 0.74 mA) during the biological information determination process in step S4 (described later).

  In step S3, the optical sensor unit 11 is used not only as a biological information acquisition unit but also as a proximity sensor. Therefore, the proximity determination process can be performed without increasing the cost or size of the biological information sensor 1.

  When a positive determination is made in step S3, in subsequent step S4, biological information for determining whether or not desired biological information has been acquired from the light detected by the light receiving unit 11B when light is emitted from the light emitting unit 11A. Judgment processing is performed. As the biological information determination process, for example, the amplitude (= difference between the maximum signal value and the minimum signal value) of the voltage signal Sa obtained when the light emitting unit 11A is turned on is read, and the read amplitude exceeds a predetermined threshold value. What is necessary is just to determine whether it exists. In addition, the measurement period of biological information may be set to several tens of Hz (for example, 32 Hz).

  When a positive determination is made in step S4, it is determined that the attachment is OK, the shift to step S5 is permitted, and a normal operation for continuously acquiring biometric information is started. On the other hand, when a negative determination is made in step S4, it is determined as wearing NG and the flow is returned to step S1, and the exercise state determination process described above is repeated. In addition, although the yes determination is made in all of steps S1 to S3, the situation where the no determination is made in step S4 is, for example, the case where the optical sensor unit 11 is floating from the wrist of the subject. Can do.

  As described above, in the wearing determination process of this embodiment, the exercise state determination process (step S1), the ambient light determination process (step S2), the proximity determination process (step S3), and the biological information determination process (step S4). Are determined step by step, and it is determined as wearing OK when a positive determination is made in all of the above determination processes, while it is determined as wearing NG when a negative determination is made in any of the above determination processes. Thus, the flow is returned to the exercise state determination process (step S1). According to such mounting determination processing, mounting / non-mounting of the biological information sensor 1 is determined through four stages of determination processing, so that it is possible to improve the mounting determination accuracy of the biological information sensor 1.

  Moreover, according to said mounting | wearing determination process, unless mounting | wearing of the biometric information sensor 1 is confirmed, transfer to a normal operation | movement (step S5) is not permitted, but the determination process of steps S1-S4 (= optical sensor part 11 or The intermittent driving of the acceleration sensor unit 18) is repeated. In particular, in the determination process of steps S1 to S4, the current consumption is reduced as the previous step. Therefore, it is possible to realize a reasonable power saving when the biological information sensor 1 is not attached.

  Further, in the mounting determination process of the present embodiment, the flow is periodically returned to step S4 after the transition to the normal operation (step S5), and the above-described biological information determination process is performed. When a negative determination is made in the determination process, it is determined as wearing NG as in the previous case, and the above-described exercise state determination process is repeated. In addition, although the transition to the normal operation is once permitted, a case where the determination is made again in step S4 is, for example, the case where the biological information sensor 1 is removed from the wrist of the subject. it can. Thus, it can be said that it is desirable to repeat the above-described series of mounting determination processes periodically even during measurement of biological information.

  Moreover, when a negative determination is made in any of steps S1 to S4, the subject may be notified using the display unit 14 or the like that the biological information sensor 1 is not correctly attached. By performing such notification, it is possible to prompt the subject to correctly wear the biological information sensor 1.

  In addition, when performing the luminance adjustment processing (calibration processing) of the light emitting unit 11A, first, the above-described mounting determination processing is performed, and after confirming that the biological information sensor 1 is correctly mounted on the living body 2, It is desirable to start the brightness adjustment process.

  FIG. 9 is a flowchart showing a second embodiment of the attachment determination processing by the control unit 13 (particularly, the digital signal processing unit 132b). The flowchart of the second embodiment is based on the flowchart of the first embodiment, but there is a difference in the attachment determination process after the transition to the normal operation. Therefore, the same steps as those in the first embodiment are denoted by the same reference numerals as those in FIG. 8, and redundant description is omitted. In the following, characteristic portions of the second embodiment will be mainly described.

  In the flowchart of the second embodiment, after the transition to the normal operation (step S5), the biological information determination process in step S4 is not periodically repeated, but in step S6, the light receiving unit 11B is turned off when the light emitting unit 11A is turned off. An ambient light determination process at the time of turn-off is performed to determine whether or not ambient light is not detected. Note that when a positive determination is made in step S6, the flow is returned to step S5 and the normal operation is continued. On the other hand, when a negative determination is made in step S6, it is determined as wearing NG, and the above-described exercise state determination process is repeated. Hereinafter, the turn-off ambient light determination process in step S6 will be described in detail.

<Ambient light judgment process when extinguished>
FIG. 10 is a signal waveform diagram for explaining the principle of the ambient light determination process at the time of extinction by the control unit 13 (particularly the digital signal processing unit 132b). In the drawing, the signal waveform of the voltage signal Sa and a partially enlarged view thereof are depicted.

  As described above, the voltage signal Sa generated by the TIA 121 has a voltage value (VREF−IB × R1) obtained by subtracting the voltage across the resistor R1 from the reference voltage VREF. Here, the light receiving intensity of the light receiving unit 11B during the lighting period Ton of the light emitting unit 11A (and the current value of the current signal IB) varies with the pulsation of the subject. Therefore, as shown by the point B in the figure, the pulse wave data of the subject (figure of the figure) is obtained by envelope-detecting the voltage signal Sa (ON voltage signal Sa @ B) obtained by the TIA 121 during the lighting period Ton of the light emitting unit 11A. (See thin dashed line in the middle).

  On the other hand, when no light is incident on the light receiving unit 11B and no current signal IB flows through the resistor R1, the voltage signal Sa ideally matches the reference voltage VREF. For example, in a state in which the biological information sensor 1 is correctly attached to the living body 2 (= a state in which the incidence of ambient light on the light receiving unit 11B is appropriately blocked), the light receiving unit 11B in the extinguishing period Toff of the light emitting unit 11A Since the received light intensity is almost zero, the current signal IB hardly flows through the resistor R1. Therefore, as indicated by point A in the figure, the voltage signal Sa (off voltage signal Sa @ A) obtained by the TIA 121 during the extinguishing period Toff of the light emitting unit 11A should substantially match the reference voltage VREF.

  Therefore, in step S6, the off-voltage signal Sa @ A is repeatedly measured at a predetermined measurement period 1 / fs (for example, 1 to 8 Hz) over a predetermined determination period Tj (for example, 1 to 10 s). Sa @ A and the threshold voltage Vth are compared one by one.

  The threshold voltage Vth is set to a voltage value lower than the reference voltage VREF of the TIA 121. For example, when the reference voltage VREF is 1.50 V, it is desirable to set the threshold voltage Vth within a range of 1.40 to 1.49 V (for example, Vth = 1.49 V). As described above, when the biological information sensor 1 is correctly attached to the living body 2, the received light intensity at the light receiving unit 11B during the extinguishing period Toff of the light emitting unit 11A becomes substantially zero, and thus the off-voltage signal Sa @ A should exceed the threshold voltage Vth.

  Therefore, whether or not the biological information sensor 1 is correctly attached to the living body 2 can be determined by comparing the monitored off-voltage Sa @ A and the threshold voltage Vth one by one and comparing the comparison result with a predetermined wearing determination condition. Can be determined.

  Note that, as the above-mentioned mounting determination conditions, (1) all of the monitored off voltages Sa @ A exceed the threshold voltage Vth, (2) almost all (80 to 90%) are the threshold voltage Vth. (3) the majority exceeds the threshold voltage Vth. Speaking of these examples, as a matter of course, (1) is the strictest condition and (3) is the sweetest condition.

  As described above, the living body 2 is not configured to read the amplitude intensity of the voltage signal Sa but to determine whether the biological information sensor 1 is attached based on the light receiving intensity of the light receiving section 11B when the light emitting section 11A that is pulse-driven is turned off. It is possible to quickly and accurately determine whether or not the device is mounted.

<Consideration on output wavelength>
In the experiment, in a so-called reflective biological information sensor, the output wavelength of the light emitting unit is set to λ1 (infrared: 940 nm), λ2 (green: 630 nm), and λ3 (blue: 468 nm), and the output intensity of the light emitting unit (driving) The behavior when the current value was changed to 1 mA, 5 mA, and 10 mA was investigated. As a result, in the visible light region having a wavelength of about 600 nm or less, the absorption coefficient of oxygenated hemoglobin HbO ₂ is increased, and the peak intensity of the measured pulse wave is increased. Therefore, it is relatively easy to acquire the waveform of the pulse wave. I understood.

In the pulse oximeter for detecting the oxygen saturation of arterial blood, the difference between the absorption coefficient (solid line) of oxygenated hemoglobin HbO ₂ and the absorption coefficient (broken line) of deoxygenated hemoglobin Hb is maximized. Although the wavelength (around 700 nm) is widely used as the output wavelength of the light emitting unit, the above experimental results are obtained when considering use as a pulse wave sensor (particularly a so-called reflection type pulse wave sensor). It can be said that it is desirable to use a visible light region having a wavelength of 600 nm or less as the output wavelength of the light emitting unit as shown in FIG.

  However, when both the pulse wave and the blood oxygen saturation are detected using a single optical sensor unit, the wavelength in the near infrared region may be used as before.

<Other variations>
Various configurations of the invention disclosed in the present specification can be variously modified within the scope of the invention, in addition to the embodiment described above. That is, the above-described embodiments are examples in all respects and should not be considered as restrictive, and the technical scope of the present invention is indicated by the claims, and the claims It should be understood that all changes that fall within the meaning and range equivalent to the scope of the above are included.

  Various inventions disclosed in the present specification can be used as a technology for enhancing the convenience of a biological information sensor, and include healthcare support devices, game devices, music devices, pet communication tools, and vehicles. It can be applied to various fields such as a driver's device for preventing falling asleep.

1 Biological information sensor (pulse wave sensor)
2 Living body (wrist etc.)
DESCRIPTION OF SYMBOLS 10 Head part 11 Optical sensor part 11A Light emitting diode (light emission part)
11B Phototransistor (light receiving part)
12 Filter unit 121 Transimpedance amplifier (current / voltage conversion circuit)
122 Buffer Circuit 123 Detection Circuit 124 Band Pass Filter Circuit 125 Amplifier Circuit 126 Reference Voltage Generation Circuit 13 Control Unit (Mounting Function as Mounting Determination Unit)
131 Main Control Circuit 132 Sub Control Circuit 132a A / D Converter 132b Digital Signal Processing Unit 132c Serial Data Communication Port (I ² C Port)
132d General-purpose I / O port (GPIO port)
DESCRIPTION OF SYMBOLS 14 Display part 15 Communication part 16 Power supply part 17 Pulse drive part 171 Switch 172 Current source 18 Acceleration sensor part 20 Band part AMP1 Operational amplifier R1 Resistance C1 Capacitor

Claims (10)

An optical sensor unit including a light emitting unit and a light receiving unit;
An acceleration sensor unit;
A mounting determination unit that performs a mounting determination using the optical sensor unit and the acceleration sensor unit;
Have
The wearing determination unit
An exercise state determination process for determining whether or not acceleration is detected by the acceleration sensor unit;
Ambient light determination processing for determining whether ambient light is not detected by the light receiving unit;
Proximity determination processing for determining whether or not the reflected light is detected by the light receiving unit when light is emitted from the light emitting unit;
A biological information determination process for determining whether biological information is acquired from light detected by the light receiving unit when light is emitted from the light emitting unit;
Are performed step by step,
When it is determined yes in all the above determination processes, it is determined as wearing OK.
A biological information sensor characterized by the above. The wearing determination unit
When a yes determination is made in the exercise state determination process, the process proceeds to the ambient light determination process.
When a yes determination is made in the ambient light determination process, the process proceeds to the proximity determination process.
When a yes determination is made in the proximity determination process, the process proceeds to the biological information determination process.
When a yes determination is made in the biological information determination process, it is determined that the wearing is OK, and a transition to a normal operation of continuously acquiring the biological information is permitted,
When no determination is made in any of the above determination processes, it is determined as wearing NG and the process returns to the exercise state determination process.
The biological information sensor according to claim 1. Current consumption during the exercise state determination process is smaller than that during the ambient light determination process,
The current consumption during the ambient light determination process is smaller than that during the proximity determination process,
Current consumption during the proximity determination process is smaller than that during the biological information determination process,
The living body information sensor according to claim 2 characterized by things. The wearing determination unit performs the biological information determination process even after shifting to the normal operation, and when the determination process is determined to be no, determines that the wearing is NG and returns to the exercise state determination process.
The biological information sensor according to claim 2 or claim 3, wherein A pulse driving unit that intermittently turns on and off the light emitting unit during the normal operation;
The mounting determination unit performs a light-off ambient light determination process that determines whether ambient light is not detected by the light-receiving unit when the light-emitting unit is turned off after the transition to the normal operation. When no determination is made, it is determined as wearing NG and the process returns to the exercise state determination process.
The biological information sensor according to any one of claims 2 to 4, wherein:   The attachment determination unit repeatedly measures an output signal of the light receiving unit at a predetermined measurement period over a predetermined determination period in at least one of the ambient light determination process and the proximity determination process. The biological information sensor according to any one of claims 1 to 5.   The biological information sensor according to any one of claims 1 to 6, further comprising a notification unit that notifies a determination result of the mounting determination unit.   The biological information sensor according to any one of claims 1 to 7, wherein a plurality of the light emitting units are provided around the light receiving unit.   The biological information sensor according to any one of claims 1 to 8, wherein an output wavelength of the light emitting unit belongs to a visible light region of 600 nm or less. A biological information sensor wearing determination method comprising: a light sensor unit including a light emitting unit and a light receiving unit; and an acceleration sensor unit.
An exercise state determination process for determining whether or not acceleration is detected by the acceleration sensor unit;
Ambient light determination processing for determining whether ambient light is not detected by the light receiving unit;
Proximity determination processing for determining whether or not the reflected light is detected by the light receiving unit when light is emitted from the light emitting unit;
A biological information determination process for determining whether biological information is acquired from light detected by the light receiving unit when light is emitted from the light emitting unit;
Are performed step by step,
When it is determined yes in all the above determination processes, it is determined as wearing OK.
A wearing determination method characterized by that.

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