Measurement device and method

Abstract

The present technology relates to a measurement device and method whereby pulse wave information can be inexpensively obtained even in a non-contact state. This measurement device comprises: a light-receiving unit that receives reflected light of light irradiated onto a body; and a control unit that, on the basis of the received amounts of light of two or more mutually different wavelengths in the reflected light, estimates pulse wave information by estimating a temporal change in the spectral shape of the reflected light. The present technology can be applied to a measurement module.

Description

Measurement device and method

[0001] The present technology relates to a measurement device and method, and more particularly to a measurement device and method that enable pulse wave information to be obtained inexpensively even in a non-contact state.

[0002] Conventionally, various manufacturers have provided various services that detect heart rate using photoplethysmographic sensors incorporated into wearable devices such as wristwatches and rings, and that use indicators based on the measured heart rate (see, for example, Non-Patent Document 1 and Patent Document 1).

[0003] On the other hand, because ear shape varies greatly from person to person, the areas that can be used to detect heart rate using PPG (Photoplethysmography) are limited in earphone shape, and heart rate detection is not possible with headphones.

[0004] This is because the PPG element is not in contact with the skin, and the light reflected from the skin surface enters the photodetector as a noise component, causing the amount of received reflected light to change aperiodically.In this way, when the PPG element is in a non-contact state, heart rate detection is possible when the patient is at rest, but stable heart rate detection is difficult when the patient moves around in everyday life.

[0005] Furthermore, as a technique for detecting heartbeats, a non-contact heartbeat detection method using a laser Doppler blood flow meter or the like has also been proposed (see, for example, Patent Document 2).

[0006] International Publication No. 2017 / 199597 International Publication No. 2020 / 026612

[0007] Int. J. Biosens. Bioelectron. 2018, 4, p.195. “A review on wearable photoplethysmography sensors and their potential future applications in health care”

[0008] However, heart rate detection methods using laser Doppler blood flow meters and the like are not only expensive, but also lack sufficient resistance to body movement noise, making it impossible to perform detection with sufficient accuracy when used in daily life.

[0009] In order to make it possible to provide users with a variety of services in more situations based on estimated heart rate, respiratory rate, and emotional state obtained from pulse wave information, it is desirable to be able to inexpensively detect the wearer's pulse wave information using a worn device even in a non-contact state.

[0010] The present technology has been developed in view of such circumstances, and makes it possible to obtain pulse wave information inexpensively even in a non-contact state.

[0011] A measuring device according to one aspect of the present technology includes a light receiving unit that receives reflected light of light irradiated onto a body, and a control unit that estimates pulse wave information by estimating the change over time in the spectral shape of the reflected light based on the amount of light received of two or more different wavelengths of the reflected light.

[0012] A measurement method according to one aspect of the present technology includes a measurement device receiving reflected light of light irradiated onto a body, and estimating pulse wave information by estimating a change over time in the spectral shape of the reflected light based on the amount of light received of two or more different wavelengths of the reflected light.

[0013] In one aspect of the present technology, light is irradiated onto a body and reflected light is received, and pulse wave information is estimated by estimating the change over time in the spectral shape of the reflected light based on the amount of light received that has two or more different wavelengths in the reflected light.

[0014] FIG. 1 is a diagram illustrating an application example of the present technology. FIG. 2 is a diagram illustrating an example configuration of a measurement module. FIG. 3 is a diagram illustrating measurement of pulse wave information. FIG. 4 is a diagram illustrating an example measurement result of pulse wave information. FIG. 5 is a diagram illustrating a more specific configuration example of a measurement module. FIG. 6 is a diagram illustrating a more specific configuration example of a measurement module. FIG. 7 is a flowchart illustrating measurement processing. FIG. 8 is a diagram illustrating measurement of pulse wave information. FIG. 9 is a diagram illustrating measurement of pulse wave information. FIG. 10 is a diagram illustrating an example configuration of a computer.

[0015] Hereinafter, embodiments to which the present technology is applied will be described with reference to the drawings.

[0016] First Embodiment Example of Measurement Module Configuration The present technology enables pulse wave information to be optically detected in a non-contact state over a relatively short distance, such as a few centimeters, using a simple, i.e., inexpensive, device.

[0017] This technology focuses on the time-series changes in the spectral shape of reflected light, which essentially cancels stray light reflections such as surface reflections, the biggest factor in reducing detection accuracy in photoplethysmography, enabling measurements to be performed with sufficient accuracy even in a non-contact state. This technology also makes it possible to repurpose existing devices, meaning that sufficiently accurate measurements can be achieved with inexpensive devices.

[0018] FIG. 1 shows an example in which the present technology is applied to headphones, which are an example of a wearable device.

[0019] In this example, headphones 11 are worn on the user's head. A measurement module 12 is provided inside a housing portion of the headphones 11 that comes into contact with the user's ears. The measurement module 12 is a measurement device to which the present technology is applied, and measures pulse wave information. The pulse wave information is information indicating a pulse wave (pulse wave signal) accompanying the user's heartbeat.

[0020] For example, when a user wears headphones 11 on their head, measurement module 12 is basically out of contact with the user's head, more specifically, the user's ears. Measurement module 12 measures the user's pulse wave information by irradiating the user's ears with light while out of contact with the user's ears.

[0021] The pulse wave information obtained by the measurement module 12 is used to estimate heart rate and heart rate variability, and further to estimate emotions and stress based on these estimation results. Furthermore, the estimation results of heart rate, emotions, stress, etc. are used to provide various services.

[0022] This technology can achieve sufficient measurement accuracy even in a non-contact state using an inexpensive device, making it possible to provide users with stable, high-quality services using headphones 11, regardless of individual differences in the shape of the ears, etc.

[0023] Note that an example in which the measurement module 12 is provided in headphones 11 has been shown here. However, the present invention is not limited to this, and the measurement module 12 can be provided in various wearable devices (wearable equipment) worn on the user's body, such as earphones, head-mounted displays (HMDs) used for augmented reality (AR) / virtual reality (VR), and smart glasses. Furthermore, although the following description will be given of a case in which the subject of measurement of pulse wave information is a human being, the subject of measurement of pulse wave information may also be an animal other than a human being.

[0024] FIG. 2 is a diagram showing an example of the configuration of the measurement module 12. As shown in FIG.

[0025] The measurement module 12 shown in FIG. 2 includes a light emitting unit 51 , a light receiving unit 52 , and a control unit 53 .

[0026] The light emitting unit 51 has one or more light sources, and, under the control of the control unit 53, irradiates light (hereinafter also referred to as irradiated light) onto the skin of the user (human body) whose pulse wave information is to be measured.

[0027] The irradiated light is composed of light of multiple wavelengths (colors). For example, the irradiated light may include at least one of red light, green light, blue light, and infrared light. In particular, when irradiating the skin, it is known that depending on the skin color, it is effective for the irradiated light to include an infrared component (approximately 820 to 950 nm). Furthermore, when measuring information related to blood flow, it is known that it is effective for the irradiated light to include a green component (approximately 505 to 555 nm).

[0028] For example, each of the multiple light sources constituting the light-emitting unit 51 may be configured to emit light of different wavelengths, or one light source constituting the light-emitting unit 51 may be configured to emit light of multiple different wavelengths, i.e., illumination light containing multiple wavelength components.

[0029] Furthermore, when the light-emitting unit 51 is provided with a plurality of light sources that emit light of different wavelengths, the plurality of light sources may emit light simultaneously or at different times. For example, the plurality of light sources may emit light in sequence, that is, may emit light in sequence.

[0030] When the light-emitting unit 51 irradiates the skin portion of the user (human body), the irradiated light is reflected from the skin portion, more specifically, the surface of the skin, the surface of blood vessels inside the skin, the inside of blood vessels, etc., to become reflected light, and the reflected light enters the light-receiving unit 52. Hereinafter, the light (irradiated light) reflected from the skin portion and entering the light-receiving unit 52 will be specifically referred to as reflected light.

[0031] The light receiving unit 52 has one or more photoelectric conversion elements, i.e., photodetectors (light receivers), that function as photoelectric conversion units, receives reflected light of light (irradiated light) irradiated onto the skin of the user (human body), and detects the amount of received light (amount of received light). Specifically, the light receiving unit 52 receives the reflected light incident from the skin and performs photoelectric conversion, and outputs a signal indicating the amount of received light of each wavelength component of the reflected light obtained as a result to the control unit 53.

[0032] In the light receiving unit 52, signals indicating the amount of received light of different wavelengths (wavelength components) may be obtained by each of multiple photodetectors (photoelectric conversion units) having sensitivity peaks in different wavelength bands, or signals indicating the amount of received light of each of multiple wavelengths may be obtained by a single photodetector.

[0033] Furthermore, for example, the light receiving unit 52 is placed in a non-contact state with respect to the part of the user that is the target of measurement of pulse wave information.

[0034] As a specific example, the light sources constituting light-emitting unit 51 and the photodetectors constituting light-receiving unit 52 are arranged on the same plane, with the distance from that plane to the surface of the user's skin being 5 cm or less. In other words, light-emitting unit 51 and light-receiving unit 52 are arranged so as not to be in contact with the human body, and pulse wave information is measured in a non-contact state.

[0035] Furthermore, verification has confirmed that pulse wave information can be measured with sufficiently high accuracy when the distance between the light-emitting unit 51 and the light-receiving unit 52 and the skin surface is 5 cm or less. Pulse wave information may also be measured in a contact state.

[0036] The control unit 53 controls the overall operation of the measurement module 12. For example, the control unit 53 controls the emission of light by the light-emitting unit 51, i.e., the light emission of the light source, and estimates (calculates) pulse wave information based on signals supplied from the light-receiving unit 52. For example, the control unit 53 estimates the spectral shape of the reflected light based on signals supplied from the light-receiving unit 52 that indicate the amount of received light of light (wavelength components) of two or more different wavelengths in the reflected light, and obtains pulse wave information by estimating the change over time (time-series change) of the spectral shape, i.e., the change over time.

[0037] The control unit 53 may be realized by an analog circuit, or may be realized by a digital circuit such as a processor, or may be realized by a combination of an analog circuit and a digital circuit.

[0038] <About the Present Technology> A specific example of measurement of pulse wave information by the measurement module 12 will be described.

[0039] For example, as shown in FIG. 3, the light-emitting unit 51 is provided with one LED (Light Emitting Diode) 81 as a light source, and the light-receiving unit 52 is provided with two photodetectors, 82-1 and 82-2, as photoelectric conversion units.

[0040] In this example, the LED 81 is a white light source that emits white light as the illumination light. Furthermore, the photodetector 82-1 outputs a signal indicating the amount of red light received from the reflected light, and the photodetector 82-2 outputs a signal indicating the amount of green light received from the reflected light. Hereinafter, when there is no need to distinguish between the photodetectors 82-1 and 82-2, they will also be simply referred to as the photodetectors 82.

[0041] First, the LED 81 attached to a wearable device such as the headphones 11 irradiates white light onto the surface of the human body, that is, the skin portion, which is the object of measurement of pulse wave information.

[0042] In addition, when irradiating the irradiation light, only one type of light source may be used, or in order to irradiate light in a wider wavelength band, multiple light sources that output light with different wavelength bands may be used in combination.

[0043] When white light is irradiated onto the skin of a human body (user), the light is reflected by the skin and becomes reflected light, which enters the photodetectors 82. That is, the reflected light is received by each photodetector 82.

[0044] In this example, the two photodetectors 82 are light receivers having sensitivity peaks in different wavelength bands.

[0045] For example, the photodetector 82-1 is composed of a silicon photodiode and a red color filter placed in front of the light-receiving surface of the photodiode, and receives and photoelectrically converts incident reflected light, particularly light in the red wavelength band of the reflected light. The photodiode is a photoelectric conversion element that photoelectrically converts incident light and outputs (generates) a current corresponding to the amount of incident light.

[0046] In contrast, photodetector 82-2 consists of a photodiode made of silicon and a green color filter placed in front of the light receiving surface of the photodiode, and receives light in the green wavelength band from the incident reflected light and performs photoelectric conversion.

[0047] In addition, as a method for making the sensitivity peaks of each photodetector 82 different, in addition to using color filters of different colors, any method can be used, such as providing different types of photoelectric conversion elements for each photodetector 82.

[0048] Each photodetector 82 supplies the control unit 53 with a signal indicating the amount of incident light obtained by photoelectric conversion in the photodetector 82, more specifically, a signal indicating the amount of current generated in accordance with the amount of incident light (amount of received light).

[0049] The control unit 53 calculates a one-dimensional index S that reflects the spectral shape of the reflected light based on the signal supplied from each photodetector 82, i.e., the amount of current (amount of received light) obtained by photoelectric conversion in the photodetector 82.

[0050] This index S is information that represents (indicates) the spectral shape of the reflected light, i.e., information whose value is determined according to the spectral shape, and is, for example, the ratio of different chromaticity components based on the reflected light. The chromaticity components here refer to the components on the axes (chromaticity axes) of an arbitrary chromaticity coordinate system.

[0051] As an example, the control unit 53 calculates an index S shown in the following formula (1): Formula (1) shows a representative example of the index S in the example of FIG.

[0052]

[0053] In equation (1), i is the number of photodetectors 82, more specifically, an index indicating the photodetector 82, and in this example, index i=1, 2. i indicates the magnitude of the signal output from the photodetector 82 indicated by index i, i.e., the amount of current (current amount) obtained by photoelectric conversion in the photodetector 82 according to the amount of received reflected light.

[0054] Furthermore, in equation (1), α i and β i is the amount of current I for the photodetector 82 indicated by the index i, which is determined for each chromaticity component. iFor example, the coefficient α i is a coefficient for determining a predetermined chromaticity component, and the coefficient β i is a coefficient for determining a chromaticity component other than the predetermined chromaticity component.

[0055] In particular, each coefficient α i is determined in advance to satisfy the following equation (2), and similarly, each coefficient β i are also determined in advance to satisfy the following equation (3): That is, the sum (sum) of coefficient α1 and coefficient α2 is set to 1, and the sum (sum) of coefficient β1 and coefficient β2 is also set to 1.

[0056]

[0057]

[0058] In equation (1), Σα i I i The chromaticity component obtained by the calculation of Σβ i I i The ratio of the chromaticity component obtained by the calculation of the above is calculated as a one-dimensional index S.

[0059] For example, the simplest example of the index S is when the number of photodetectors 82 is 2 and α i = (1,0) and β i = (0,1), that is, α1 = 1, α2 = 0, β1 = 0, β2 = 1.

[0060] In this case, the index S is equivalent to the ratio of the amount of current detected (generated) by the photodetector 82-1, i.e., the amount of red light received, to the amount of current detected by the photodetector 82-2, i.e., the amount of green light received.

[0061] The ratio of the photoelectric current amounts of light of different colors (wavelengths) may be calculated by AD (Analog to Digital) converting the amount of current generated by each photodetector 82 (photoelectric conversion element) and inputting it into a processor, or may be calculated by an analog circuit based on the amount of current. For example, it is possible to calculate the ratio of the photoelectric current amounts by using an analog division circuit.

[0062] Through the above processing, the value of the index S corresponding to the spectral shape of the reflected light is obtained.

[0063] The spectral shape of the reflected light from the light irradiated onto the skin changes in accordance with changes in blood flow caused by the heartbeat of the human body (user). Therefore, the change over time (time-series change) in the value of index S can be used to estimate the change over time in blood flow in the human body, i.e., pulse wave information, which is information related to the heartbeat.

[0064] The biggest difference between this technology's pulse wave information measurement method and conventional photoplethysmography (PPG) is that it can estimate heart rate (pulse wave information) without being affected by the intensity of light reflected from the skin surface.

[0065] Generally, PPG estimates heart rate from information on the intensity of reflected light, so it is easily affected by changes in the intensity of surface reflected light, especially in non-contact conditions, and even slight body movement can cause noise that is much larger than the heart rate fluctuation component to be superimposed, making heart rate estimation difficult.

[0066] On the other hand, the method of the present technology estimates the heart rate using an index S that reflects the spectral shape of the reflected light, rather than the intensity of the reflected light. More specifically, pulse wave information is estimated, and the heart rate and other parameters are estimated from the pulse wave information. Therefore, the method of the present technology is less susceptible to changes in the amount of reflected light due to body movement, and enables stable heart rate estimation even in daily life.

[0067] FIG. 4 shows the measurement results of a general photoplethysmography (PPG) and the measurement results of pulse wave information (heart rate) using this technology.

[0068] 4, the horizontal axis represents time, and the vertical axis represents heart rate, i.e., the frequency component of reflected light. The shading in the figure indicates the magnitude of the frequency component (heart rate) at each time.

[0069] In Figure 4, the left side shows the measurement results using a general PPG, and the right side shows the measurement results using this technology. The left side of each measurement result shows the measurement results when the subject is at rest, and the right side shows the measurement results when the subject is running.

[0070] For example, because a typical PPG uses the change in intensity of one color (monochromatic) light detected by a photodetector, the measurement results contain a large amount of non-periodic noise components in situations where a lot of noise is superimposed due to body movement, such as when running. Therefore, as shown on the left side of the figure, while it is possible to extract the heart rate component when at rest, there is a lot of noise when running, making it impossible to extract the heart rate component.

[0071] In contrast, with the measurement method of this technology, for example, the method of calculating the ratio of the amount of received light of the two colors mentioned above, the non-periodic noise component during running is significantly reduced, as shown on the right side of the figure. Therefore, it can be seen that the frequency peak corresponding to the heart rate component can be clearly confirmed not only when at rest but also when running. In this example, the part indicated by arrow A11 is the heart rate component, and it can be seen that the user's heart rate gradually increases over time from when at rest.

[0072] The control unit 53 can be realized by using either an analog circuit or a digital circuit.

[0073] FIG. 5 shows an example in which at least a part of the control unit 53 is realized by an analog circuit.

[0074] 5, the light-emitting unit 51 is realized by a white LED 111 and a resistor 112 connected to the LED 111. When a voltage is applied to the LED 111 via the resistor 112, the LED 111 emits light, and the white light emitted (output) from the LED 111 is irradiated as irradiation light onto the skin of the user (human body) that is the measurement target.

[0075] In this example, the light receiving section 52 is provided with photodiodes 113-1 and 113-2, color filters 114-1 and 114-2, operational amplifiers 115-1 and 115-2, resistors 116-1 and 116-2, and capacitors 117-1 and 117-2.

[0076] Furthermore, in this example, a division circuit 118 and an estimation circuit 119 are provided as circuits constituting the control unit 53. Here, for example, the division circuit 118 is configured by an analog circuit. Note that the estimation circuit 119 may be configured by a digital circuit or an analog circuit.

[0077] A red color filter 114-1, for example, is disposed directly above the light receiving surface of the photodiode 113-1, which is a photoelectric conversion element, and reflected light output from the LED 111 is incident on the photodiode 113-1 via the color filter 114-1. Here, the photodiode 113-1 and the color filter 114-1 form one photodetector.

[0078] The positive terminal (non-inverting input terminal) of the operational amplifier 115-1 is connected to the anode of the photodiode 113-1 and the ground.

[0079] The negative terminal (inverting input terminal) of the operational amplifier 115-1 is connected to the output terminal of the operational amplifier 115-1 via a resistor 116-1.

[0080] The output terminal of the operational amplifier 115-1 is connected not only to the inverting input terminal of the operational amplifier 115-1 via a resistor 116-1 but also to the cathode of the photodiode 113-1 via a capacitor 117-1. Furthermore, the output terminal of the operational amplifier 115-1 is also connected to a division circuit 118.

[0081] An amplifier circuit is formed by the operational amplifier 115-1 and the resistor 116-1.

[0082] When the photodiode 113-1 receives light (reflected light) through the color filter 114-1, a current (photoelectric current) indicating the amount of reflected light that is received flows through the photodiode 113-1. That is, a photoelectric current corresponding to the amount of reflected light that is received is generated.

[0083] Then, a voltage signal corresponding to the amount of photoelectric current, i.e., indicating the amount of current, is input to the non-inverting input terminal of the operational amplifier 115-1, and the input voltage signal is amplified by the operational amplifier 115-1 (amplification circuit) and output from the output terminal of the operational amplifier 115-1 to the division circuit 118. Here, a signal (voltage signal) indicating voltage V1 is supplied from the operational amplifier 115-1 to the division circuit 118. This voltage signal of voltage V1 can be said to be a signal indicating the amount of reflected light received by the photodiode 113-1, or in other words, the amount of photoelectric current generated in the photodiode 113-1.

[0084] A green color filter 114-2, for example, is disposed directly above the light receiving surface of the photodiode 113-2, which is a photoelectric conversion element, and reflected light output from the LED 111 is incident on the photodiode 113-2 via the color filter 114-2. Here, the photodiode 113-2 and the color filter 114-2 form one photodetector.

[0085] The non-inverting input terminal (positive terminal) of the operational amplifier 115-2 is connected to the anode of the photodiode 113-2 and the ground.

[0086] The output terminal of the operational amplifier 115-2 is connected to the inverting input terminal (negative terminal) of the operational amplifier 115-2 via a resistor 116-2, and is also connected to the cathode of the photodiode 113-2 via a capacitor 117-2. Furthermore, the output terminal of the operational amplifier 115-2 is also connected to a division circuit 118.

[0087] An amplifier circuit is formed by the operational amplifier 115-2 and resistor 116-2. As in the case of the photodiode 113-1, a voltage signal corresponding to the photoelectric current in the photodiode 113-2 is amplified by the amplifier circuit and input to the division circuit 118. That is, a signal (voltage signal) indicating a voltage V2 corresponding to the photoelectric current generated in the photodiode 113-2 is supplied from the operational amplifier 115-2 to the division circuit 118.

[0088] The division circuit 118 performs division based on the voltage V1 supplied from the operational amplifier 115-1 and the voltage V2 supplied from the operational amplifier 115-2, and supplies a signal (voltage signal) indicating the voltage Vout, which is the result of the calculation (division result), to the estimation circuit 119. Here, for example, an operation is performed to divide the voltage V1 by the voltage V2, and the result of the calculation is set as the voltage Vout. This voltage Vout corresponds to the index S at a given time calculated by the above-mentioned equation (1).

[0089] The estimation circuit 119 sequentially estimates pulse wave information based on the index S at each time supplied from the division circuit 118, and also estimates heart rate, heart rate variability, emotion, stress, etc. as necessary based on the estimation results.

[0090] In the following description, we will assume that the measurement module 12 (control unit 53) has the function of estimating heart rate, emotions, stress, etc. based on pulse wave information, but this function may also be provided in a subsequent stage of the measurement module 12.

[0091] FIG. 6 shows an example in which the control unit 53 is realized by a digital circuit.

[0092] In this example, the measurement module 12 includes an LED 141 , a photodetector 142 - 1 , a photodetector 142 - 2 , an AD conversion unit 143 - 1 , an AD conversion unit 143 - 2 , and a processor 144 .

[0093] The LED 141 functions as the light-emitting unit 51 and emits light under the control of the processor 144. That is, under the control of the processor 144, the LED 141 irradiates white light, which serves as irradiation light, onto the skin of the user (human body) that is the measurement target.

[0094] In the example of FIG. 6, the light receiving unit 52 is configured by, for example, the photodetector 142-1, the photodetector 142-2, the AD conversion unit 143-1, and the AD conversion unit 143-2, and the processor 144 functions as the control unit 53.

[0095] The photodetector 142-1 and the photodetector 142-2 correspond to, for example, the photodiode 113-1 and the color filter 114-1, and the photodiode 113-2 and the color filter 114-2 shown in FIG.

[0096] The photodetectors 142-1 and 142-2 receive the reflected light of the light output from the LED 141, perform photoelectric conversion, and supply the resulting signal indicating the amount of received reflected light, i.e., photoelectric current, to the AD conversion units 143-1 and 143-2.

[0097] For example, photodetector 142-1 receives only the red component of the reflected light and performs photoelectric conversion, and photodetector 142-2 receives only the green component of the reflected light and performs photoelectric conversion, and photodetector 142-1 and photodetector 142-2 output signals indicating the amount of light received of different wavelength components.

[0098] The AD conversion units 143-1 and 143-2 AD convert the signals indicating the amount of received reflected light supplied from the photodetectors 142-1 and 142-2, and supply the resulting digital signals to the processor 144.

[0099] Processor 144 calculates index S based on the signals supplied from AD conversion units 143-1 and 143-2, estimates pulse wave information based on index S at each time, and estimates the heart rate and the like based on the pulse wave information. Processor 144 also controls the light emission of LED 141, more specifically, controls the turning on and off of LED 141 and controls the amount of light when it is emitting light (light emission intensity control).

[0100] <Description of Measurement Processing> Next, a description will be given of the operation of the measurement module 12. That is, the measurement processing by the measurement module 12 will be described below with reference to the flowchart of FIG.

[0101] In step S11, the control unit 53 controls the light emitting unit 51 to irradiate the skin of the user (human body) with light that will become irradiation light.

[0102] The light-emitting unit 51 emits light from one or more light sources thereof under the control of the control unit 53, thereby irradiating the skin portion of the human body with the light. The light irradiated onto the skin portion is reflected by the skin portion and becomes reflected light, and the reflected light enters the light-receiving unit 52.

[0103] In step S12 , the light receiving unit 52 receives the incident reflected light, performs photoelectric conversion, and supplies the resulting signal indicating the amount of received reflected light to the control unit 53 .

[0104] It should be noted that several methods are possible for emitting (irradiating) the irradiating light and receiving the reflected light in steps S11 and S12.

[0105] As an example, as described with reference to Fig. 3, it is conceivable to output illumination light containing multiple wavelength components (color components) from a single light source and simultaneously receive reflected light of the illumination light using multiple photodetectors, each of which outputs a signal indicating the amount of received light of a different wavelength component (color component).

[0106] It is also possible to simultaneously emit light from multiple light sources that output light of different wavelength components (color components), and simultaneously receive the light for each wavelength component using one or more photodetectors (photoelectric conversion elements).

[0107] Alternatively, for example, a plurality of light sources outputting light of different wavelength components may be caused to emit light in sequence at a predetermined cycle, and the light of each wavelength component may be received by a photodetector at the timing when the light of each wavelength component is irradiated. In this case, a photodetector may be provided for each wavelength component, or a single photodetector that is sensitive to all wavelength components may be provided.

[0108] In step S13, the control unit 53 calculates an index S for one time period based on the signals supplied from the light receiving unit 52 that indicate the amounts of received light of different wavelength components in the reflected light.

[0109] For example, the control unit 53 calculates the index S representing the spectral shape of the reflected light by calculating the above-mentioned formula (1).

[0110] In step S14, the control unit 53 estimates pulse wave information based on the index S at each of the multiple times obtained up to that point, that is, the time-series change of the index S.

[0111] For example, in step S14, pulse wave information is calculated (estimated) by peak analysis, periodicity analysis, etc. based on the index S at each time. Furthermore, the control unit 53 estimates the heart rate and heart rate variability from the pulse wave information as needed, and further estimates emotions and stress from the results of the heart rate and other estimations.

[0112] In step S15, control unit 53 determines whether or not to terminate the process of measuring pulse wave information. For example, in step S15, it is determined that the process should be terminated when the power is turned off or when the user issues an instruction to terminate measurement.

[0113] If it is determined in step S15 that the process should not be ended, the process then returns to step S11, and the above-described process is repeated.

[0114] On the other hand, if it is determined in step S15 that the process is to be ended, the control unit 53 stops the processes of the respective parts of the measurement module 12, and the measurement process ends.

[0115] In this way, the measurement module 12 calculates an index S that represents the spectral shape of the reflected light based on the amount of light received of multiple wavelength components of the reflected light, and obtains pulse wave information from the time-series changes in the index S.

[0116] This allows pulse wave information to be obtained stably and with high accuracy even in a non-contact state. Furthermore, this technology can measure pulse wave information using inexpensive devices such as common light sources such as LEDs and photoelectric conversion elements such as photodiodes. In other words, this technology can keep device costs lower than laser Doppler blood flowmeters and the like.

[0117] <First Example of Measurement of Pulse Wave Information> Another specific example of measurement of pulse wave information by the measurement module 12 will be described.

[0118] In the example shown in FIG. 8, for example, the measurement module 12 is placed inside the enclosure of a headphone.

[0119] The light-emitting unit 51 is provided with one white LED 171. The light-receiving unit 52 is further provided with a photodetector 172-1 that receives (detects) red light, a photodetector 172-2 that receives green light, and a photodetector 172-3 that receives blue light. That is, each of the photodetectors 172-1 to 172-3 has a red, green, or blue color filter provided in front of the light-receiving surface.

[0120] When measuring pulse wave information, first, the LED 171 disposed inside the headphone enclosure irradiates white light onto the ear where the headphones are worn. The white light irradiation continues for, for example, 100 μs.

[0121] When white light is irradiated onto the ear, photodetectors 172-1 to 172-3 receive red, green, and blue components of the light reflected from the white light, and obtain signals indicating the amount of received light.

[0122] Here, the amount of red light received by photodetector 172-1 will be denoted as R, the amount of green light received by photodetector 172-2 will be denoted as G, and the amount of blue light received by photodetector 172-3 will be denoted as B.

[0123] In the measurement module 12, the amounts of red, green, and blue light received by the photodetectors 172-1 to 172-3 may be detected in advance when white light (illumination light) is not being emitted by the LED 171. In this way, it is possible to obtain only the reflected light component of the illumination light (white light) output from the LED 171.

[0124] For example, let R' be the amount of received red light detected by photodetector 172-1 in advance when white light (irradiation light) is not being irradiated. In this case, the amount of received light (R-R') obtained by subtracting the amount of received light R' from the amount of received light R described above is the final amount of received red light, i.e., the value of the final amount of received light R. Subtractions are similarly performed for the other amounts of received light G and B.

[0125] By doing this, components (noise) other than the reflected light of the irradiated light (white light) can be removed, and pure, i.e., more accurate, components of each color of the reflected light of the irradiated light (white light) can be obtained as the received light amounts R, G, and B.

[0126] When the control unit 53 obtains the light reception amounts R, G, and B of each color component (wavelength component), it calculates an index S representing the spectral shape of the reflected light by calculating the following equation (4) based on these light reception amounts.

[0127]

[0128] In equation (4), X and Y respectively represent the X and Y components (chromaticity components) of the CIE XYZ color system, which is a chromaticity coordinate system, in other words, the magnitude of the projection vector of the amount of reflected light received onto the X and Y axes. In equation (4), the ratio of the X and Y components, which are different chromaticity axis components of the chromaticity coordinate system (chromaticity space), is obtained as index S.

[0129] When measuring pulse wave information, the above process is repeated at a cycle of 128 Hz, and as a result, the time series change in index S, that is, the index S at each time, is obtained.

[0130] The control unit 53 estimates the heart rate and heart rate variability by peak analysis, periodicity analysis, etc. of the time-series change in the index S. More specifically, pulse wave information is obtained from the time-series change in the index S, and the heart rate and heart rate variability are estimated from the pulse wave information.

[0131] The method for calculating the index S from the R (red), G (green), and B (blue) color components of the reflected light is not limited to the calculation of equation (4), and any other method may be used.

[0132] For example, the control unit 53 may estimate the skin color of the human body being measured from the intensity of the reflected light incident on the photodetectors 172-1 to 172-3, i.e., the amount of light received, and calculate the index S using a coefficient determined for the estimated result.

[0133] In such a case, for example, for each skin color, an index S that is highly sensitive to that skin color, that is, that exhibits large time-series changes in relation to blood flow, is determined in advance, and a coefficient for determining the index S is prepared. The coefficient here is, for example, the coefficient α in Equation (1), i and coefficient β i is.

[0134] The control unit 53 stores in advance a table in which skin color is associated with a coefficient for calculating an index S prepared (predetermined) for that skin color. When measuring pulse wave information, the control unit 53 estimates the skin color from the amounts of received light R, G, and B, reads out the coefficient associated with the estimated skin color from the table, and calculates the index S based on the read coefficient and the amounts of received light R, G, and B.

[0135] It is also possible to calculate the optimal coefficient for skin color online. In such a case, for example, the control unit 53 transmits the estimated results of the received light amounts R, G, and B or skin color to a server connected via a network, and receives the coefficient for calculating the index S transmitted from the server in response to the transmission.

[0136] Alternatively, the number of types of photodetectors provided in the light-receiving unit 52 may be any number, such as four or more types, as long as they correspond to the light sources provided in the light-emitting unit 51. In other words, for example, photodetectors that receive (detect) light of four or more different wavelength components may be provided in the light-receiving unit 52.

[0137] Furthermore, the light-emitting unit 51 may be provided with a plurality of light sources that output light in different wavelength bands, and these light sources may be used in parallel. That is, irradiation light may be output from the plurality of light sources simultaneously. In this way, the width of the wavelength band of light used for measurement can be made wider.

[0138] <Pulse Wave Information Measurement Example 2> FIG. 9 shows another specific example of pulse wave information measurement.

[0139] In the example shown in FIG. 9, the measurement module 12 is provided in an earphone, for example.

[0140] The light-emitting unit 51 is provided with an LED 201-1 that outputs infrared light (IR) and an LED 201-2 that outputs green light. For example, infrared light has a wavelength component of approximately 820 to 950 nm, and green light has a wavelength component of approximately 505 to 555 nm. The light-receiving unit 52 is further provided with a photodetector 202 that can detect both infrared light and green light.

[0141] When measuring pulse wave information, first, infrared light is emitted from the LED 201-1 provided on the earphone to the ear where the earphone is worn. The infrared light is emitted continuously for, for example, 100 μs.

[0142] Then, the photodetector 202 receives the reflected light generated by the irradiation of the infrared light, and obtains a signal indicating the amount of received light IR.

[0143] After the infrared light irradiation and reception are completed, the LED 201-2 provided on the earphone emits green light onto the ear where the earphone is worn. The green light irradiation also continues for, for example, 100 μs, the same as the infrared light irradiation. While the green light irradiation is ongoing, the infrared light irradiation is not carried out.

[0144] The photodetector 202 receives the reflected light generated by the irradiation of the green light, and obtains a signal indicating the amount G of the received light.

[0145] Therefore, in this example, irradiation with light is performed in a time-division (alternate) manner for each wavelength band.

[0146] The control unit 53 calculates an index S based on the thus obtained amounts of received light IR and G. For example, the ratio of the amounts of received light G and IR is calculated as index S=G / IR.

[0147] When measuring pulse wave information, the above process is repeated at a cycle of 128 Hz, and as a result, the time series change in index S, that is, the index S at each time, is obtained.

[0148] The control unit 53 estimates the heart rate and heart rate variability by peak analysis, periodicity analysis, etc. of the time-series change of the index S, in the same manner as in the example of FIG.

[0149] In this example, the control unit 53 can also control the light emission intensity, i.e., the light emission amount, of LED 201-1 and LED 201-2 based on the intensity of the reflected light obtained immediately after the start of measurement of the pulse wave information, i.e., the received light amount IR and the received light amount G.

[0150] Specifically, at any timing, for example, immediately after the start of measurement, the received light amount IR (reflected light intensity) of reflected light corresponding to the infrared light output from LED 201-1 and the received light amount G of reflected light corresponding to the green light output from LED 201-2 are measured.

[0151] The control unit 53 adjusts the emission intensity (emission amount) of infrared light from the LED 201-1 and the emission intensity of green light from the LED 201-2 so that the received light amount IR and the received light amount G are values ​​within an appropriate range that is approximately the same. This makes it possible to perform measurements with higher reliability.

[0152] As an example, the emission intensities of the infrared light and the green light are controlled (adjusted) so that the following two conditions are satisfied.

[0153] That is, the first condition is that the amount of current indicating the amount of received light (amount of received light IR, G) obtained by photoelectric conversion in the photodetector 202 falls within a preset range.

[0154] The second condition is that the ratio of the amount of received light IR to the amount of received light G, i.e., the ratio of the amounts of current indicating the amounts of received light IR and G, is within three times each other, i.e., both IR / G and G / IR are equal to or less than 3. This second condition is that the ratio of the amount of received light of light (components) of different wavelengths in the reflected light is equal to or less than a predetermined value such as 3.

[0155] Based on these first and second conditions, the amount of irradiated light (emission intensity) is adjusted so that the amount of photoelectric current for each wavelength is within an appropriate range and is approximately the same.

[0156] Note that, in this example, the number of types of light sources constituting the light-emitting unit 51 does not need to be two; three or more types of light sources may be used. Furthermore, two or more types of photoelectric conversion elements (photodetectors) may be used depending on the light sources. Furthermore, only two types of invisible light may be used as the irradiated light, rather than visible light. For example, if invisible light is used as the irradiated light when the measurement module 12 is mounted in an HMD, even if some of the irradiated light is irradiated as stray light on the screen presented to the user, the stray light will not be visible to the user, and the user will not find the stray light disturbing.

[0157] <Example of Computer Configuration> The above-described series of processes can be executed by hardware or software. When the series of processes is executed by software, the programs that constitute the software are installed on a computer. Here, the computer includes a computer built into dedicated hardware, and a general-purpose computer, for example, that can execute various functions by installing various programs.

[0158] FIG. 10 is a block diagram showing an example of the hardware configuration of a computer that executes the above-described series of processes by a program.

[0159] In the computer, a CPU (Central Processing Unit) 501, a ROM (Read Only Memory) 502, and a RAM (Random Access Memory) 503 are interconnected by a bus 504.

[0160] An input / output interface 505 is further connected to the bus 504. An input unit 506, an output unit 507, a recording unit 508, a communication unit 509, and a drive 510 are connected to the input / output interface 505.

[0161] The input unit 506 includes switches, buttons, a microphone, an image sensor, etc. The output unit 507 includes a display, a speaker, a light source, etc. The recording unit 508 includes a hard disk, a non-volatile memory, etc. The communication unit 509 includes a network interface, etc. The drive 510 drives a removable recording medium 511 such as a semiconductor memory.

[0162] In a computer configured as described above, the CPU 501 loads, for example, a program recorded in the recording unit 508 into the RAM 503 via the input / output interface 505 and the bus 504, and executes the program, thereby performing the above-described series of processes.

[0163] The program executed by the computer (CPU 501) can be provided by being recorded on a removable recording medium 511 such as a package medium, for example. The program can also be provided via a wired or wireless transmission medium such as a local area network, the Internet, or digital satellite broadcasting.

[0164] In a computer, a program can be installed in the recording unit 508 via the input / output interface 505 by inserting a removable recording medium 511 into the drive 510. The program can also be received by the communication unit 509 via a wired or wireless transmission medium and installed in the recording unit 508. Alternatively, the program can be installed in the ROM 502 or the recording unit 508 in advance.

[0165] The program executed by the computer may be a program that processes in chronological order according to the order described in this specification, or may be a program that processes in parallel or at the required timing, such as when called.

[0166] Furthermore, the embodiments of the present technology are not limited to the above-described embodiments, and various modifications are possible within the scope of the gist of the present technology.

[0167] For example, the present technology can be configured as a cloud computing system in which a single function is shared and processed collaboratively by a plurality of devices via a network.

[0168] Furthermore, each step described in the above flowchart can be executed by one device, or can be shared and executed by a plurality of devices.

[0169] Furthermore, when one step includes multiple processes, the multiple processes included in that one step can be executed by one device or can be shared and executed by multiple devices.

[0170] Furthermore, the present technology can also be configured as follows.

[0171] (1) A measurement device comprising: a light-receiving unit that receives reflected light of light irradiated onto a body; and a control unit that estimates pulse wave information by estimating a time change in the spectral shape of the reflected light based on the received light amount of light of two or more different wavelengths in the reflected light. (2) The measurement device described in (1), further comprising: a light-emitting unit having one or more light sources that irradiate light onto the body, wherein the light-receiving unit receives light irradiated by the light source and reflected by the body as the reflected light. (3) The measurement device described in (1) or (2), wherein the light-receiving unit has a plurality of photoelectric conversion units that receive the reflected light, and each of the plurality of photoelectric conversion units detects the received light amount of light of different wavelengths in the reflected light. (4) The measurement device described in (3), wherein each of the plurality of photoelectric conversion units is provided with a color filter of a different color. (5) The measurement device described in (2), wherein the light-emitting unit has a plurality of light sources that irradiate light of different wavelengths. (6) The measurement device according to (5), wherein the plurality of light sources irradiate the body with light at different timings. (7) The measurement device according to (5) or (6), wherein the control unit controls the light emission amount of each of the light sources so that the ratio of the received light amounts of light of different wavelengths is equal to or less than a predetermined value. (8) The measurement device according to any one of (1) to (7), wherein the control unit calculates a one-dimensional index reflecting the spectral shape based on the received light amount for each wavelength of the reflected light, and estimates the pulse wave information based on a change in the index over time. (9) The measurement device according to (8), wherein the control unit calculates different chromaticity components based on the received light amount of light of each of the plurality of wavelengths, and calculates a ratio of the different chromaticity components as the index. (10) The measurement device according to (9), wherein the control unit is configured with an analog circuit. (11) The measurement device according to any one of (1) to (10), wherein the light receiving unit is disposed so that the distance between the light receiving unit and the skin of the body is 5 cm or less. (12) The measurement device according to (2), wherein the light emitting unit irradiates the body with light including at least one of green light and infrared light.(13) The measurement device according to any one of (1) to (12), wherein the measurement device is provided in a wearable device attached to the body. (14) The measurement device according to (13), wherein the wearable device is attached to the head. (15) The measurement device according to (8) or (9), wherein the control unit calculates the index determined for the skin color of the body. (16) A measurement method including: a measurement device receiving reflected light of light irradiated onto the body; and estimating pulse wave information by estimating a time change in the spectral shape of the reflected light based on the received light amounts of light of two or more different wavelengths in the reflected light.

[0172] REFERENCE SIGNS LIST 11 headphones, 12 measurement module, 51 light emitting unit, 52 light receiving unit, 53 control unit, 111 LED, 113-1, 113-2 photodiode, 118 division circuit, 119 estimation circuit, 141 LED, 142-1, 142-2 photodetector, 144 processor

Claims

1. A measuring device comprising: a light receiving unit that receives reflected light of light irradiated onto the body; and a control unit that estimates pulse wave information by estimating the time change in the spectral shape of the reflected light based on the amount of light received of two or more different wavelengths of the reflected light.

2. The measuring device according to claim 1, further comprising a light emitting unit having one or more light sources that irradiate the body with light, and the light receiving unit receives light that is irradiated by the light sources and reflected by the body as the reflected light.

3. The measuring device according to claim 1, wherein the light receiving unit has a plurality of photoelectric conversion units that receive the reflected light, and each of the plurality of photoelectric conversion units detects the received light amount of light of different wavelengths in the reflected light.

4. The measuring device according to claim 3, wherein each of the plurality of photoelectric conversion sections is provided with a color filter of a different color.

5. The measuring device according to claim 2, wherein the light emitting unit has a plurality of light sources that emit light of different wavelengths.

6. The measurement device according to claim 5, wherein the plurality of light sources irradiate the body with light at different times.

7. The measuring device according to claim 5, wherein the control unit controls the amount of light emitted by each of the light sources so that the ratio of the amount of light received of light of different wavelengths is equal to or less than a predetermined value.

8. The measurement device according to claim 1, wherein the control unit calculates a one-dimensional index that reflects the spectral shape based on the amount of received light for each wavelength of the reflected light, and estimates the pulse wave information based on the change in the index over time.

9. The measurement device according to claim 8, wherein the control unit calculates mutually different chromaticity components based on the amount of light received of each of a plurality of wavelengths, and calculates a ratio of the mutually different chromaticity components as the index.

10. The measuring device according to claim 9, wherein the control unit is configured by an analog circuit.

11. The measurement device according to claim 1, wherein the light receiving unit is positioned so that the distance between the light receiving unit and the skin of the body is 5 cm or less.

12. The measuring device according to claim 2, wherein the light emitting unit irradiates the body with light containing at least one of green light and infrared light.

13. The measuring device according to claim 1, wherein the measuring device is provided in a wearable device that is attached to the body.

14. The measurement apparatus according to claim 13, wherein the wearable device is worn on the head.

15. The measuring device according to claim 8, wherein the control unit calculates the index determined for the skin color of the body.

16. A measurement method including: a measuring device receiving reflected light of light irradiated onto the body; and estimating pulse wave information by estimating the time change in the spectral shape of the reflected light based on the received light amount of light of two or more different wavelengths in the reflected light.

Images