BIOLOGICAL INFORMATION MEASUREMENT DEVICE AND BIOLOGICAL INFORMATION MEASUREMENT SYSTEM

Abstract

Provided is a technology capable of accurately measuring biological information with a simple structure. Provided is a biological information measurement device including: a light emitting element that irradiates a living body with light; and a plurality of light receiving elements that receives light scattered in the living body, in which at least one light receiving element has a different area from an area of another light receiving element. Further, provided is a biological information measurement system including: a biological information measurement device including a light emitting element that irradiates a living body with light, and a plurality of light receiving elements that receives light scattered in the living body, in which at least one light receiving element has a different area from an area of another light receiving element; and an analysis device that analyzes biological information on the basis of signals obtained from the light receiving elements.

Claims

1. A biological information measurement device comprising: a light emitting element that irradiates a living body with light; and a plurality of light receiving elements that receives light scattered in the living body, wherein at least one light receiving element has a different area from an area of another light receiving element.

2. The biological information measurement device according to claim 1, comprising: a first light receiving element having an area of 1 mm.sup.2 or less; and a second light receiving element having an area exceeding 1 mm.sup.2.

3. The biological information measurement device according to claim 2, comprising a plurality of the first light receiving elements.

4. The biological information measurement device according to claim 2, comprising: the one first light receiving element; and the one second light receiving element.

5. The biological information measurement device according to claim 1, wherein distances from the light emitting element to the plurality of light receiving elements are substantially the same.

6. The biological information measurement device according to according to claim 2, further comprising an analysis unit that analyzes biological information on a basis of signals obtained from the light receiving elements.

7. The biological information measurement device according to claim 6, wherein the analysis unit analyzes the biological information by referring to a signal obtained from the second light receiving element.

8. The biological information measurement device according to claim 7, wherein the analysis unit analyzes the biological information by referring to the signals obtained from the respective plurality of light receiving elements with each other.

9. The biological information measurement device according to claim 6, wherein the analysis unit analyzes information derived from a blood vessel on a basis of a signal obtained from the first light receiving element.

10. The biological information measurement device according to claim 6, wherein the analysis unit analyzes information derived from a heart on a basis of a signal obtained from the second light receiving element.

11. The biological information measurement device according to claim 1, further comprising a control unit that controls driving of each of the plurality of light receiving elements.

12. A biological information measurement system comprising: a biological information measurement device including a light emitting element that irradiates a living body with light, and a plurality of light receiving elements that receives light scattered in the living body, in which at least one light receiving element has a different area from an area of another light receiving element; and an analysis device that analyzes biological information on a basis of signals obtained from the light receiving elements.

13. The biological information measurement system according to claim 12, wherein the biological information measurement device and the analysis device are connected via a network.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0017] FIG. 1 is a graph schematically showing a phenomenon in which, in a case where no stress is loaded, almost all blood vessels move in a uniform manner, and thus light receivers have a high correlation, whereas, when stress is loaded, physiological indices such as a blood flow rate change according to constriction force of each blood vessel, and thus the correlation between the light receivers decreases.

[0018] FIG. 2 is a schematic diagram of an arrangement example 1.

[0019] FIG. 3 is a schematic diagram of an arrangement example 2.

[0020] FIG. 4 is a block diagram of a configuration example of a processing unit 100.

MODE FOR CARRYING OUT THE INVENTION

[0021] Hereinafter, preferred modes for carrying out the present technology will be described with reference to the drawings. Embodiments described below show examples of representative embodiments of the present technology, and the scope of the present technology is not limitedly interpreted by the embodiments. Note that description will be provided in the following order.

[0022] 1. Biological information measurement device 10 according to present technology

[0023] 1-1. Configuration of biological information measurement device 10

[0024] 1-2. Arrangement example 1

[0025] 1-3. Arrangement example 2

[0026] 1-4. Processing unit 100

[0027] 2. Biological information measurement system according to present technology

[0028] 1. Biological Information Measurement Device 10 According to Present Technology

[0029] Hereinafter, a configuration of a biological information measurement device 10 according to the present embodiment will be described. Note that the embodiment shows a suitable example of the present technology, but the biological information measurement device 10 according to the present technology is not limited to this configuration.

[0030] 1-1. Configuration of Biological Information Measurement Device 10

[0031] The biological information measurement device 10 according to the present embodiment includes a light emitting element 11 that irradiates a living body with light and a plurality of light receiving elements 12 that receives light scattered in the living body, and at least one light receiving element 12 has a different area from that of another light receiving element 12. Further, the biological information measurement device may include a processing unit 100 including an analysis unit 103 and a control unit 104 as necessary.

[0032] In the present technology, because the plurality of light receiving elements 12 has different areas as described above, it is possible to calculate biological information with high accuracy even with a simple structure.

[0033] The biological information measurement device 10 according to the present embodiment is worn on, for example, a part of skin of the living body (e.g. human body) and may have various forms such as, for example, a wristband type, earring type, ring type, necklace type, attachment type, and supporter type.

[0034] In the present specification, the word “biological information” means various kinds of information regarding the living body. The living body includes, for example, a human body and also includes bodies of animals and the like other than a human. In the present technology, the biological information can be preferably a state of the autonomic nerve serving as an index of stress or tension.

[0035] The light emitting element 11 irradiates the living body with light. In the present embodiment, at least one light emitting element 11 is provided.

[0036] Examples of the light emitting element include laser light sources such as a light emitting diode (LED), an edge emitting laser (LD), and a surface emitting laser (VCSEL).

[0037] Further, for example, in a case where the light emitting element is a laser light source that emits coherent light, the light emitting element can be used for measuring biological information such as a plethysmogram and a blood flow rate. Further, for example, in a case where the light emitting element is an LED that emits non-coherent light, the light emitting element can be used for measuring biological information such as a plethysmogram. In the present technology, light emitted from the light emitting element may be visible light or non-visible light (e.g. infrared light).

[0038] It is possible to use, for example, a wavelength in a visible region, a near-infrared region, or an infrared region as a wavelength of the light emitting element.

[0039] The light receiving elements 12 receive light scattered at a plurality of measurement sites in the living body. In the present embodiment, at least two light receiving elements 12 are provided.

[0040] The light receiving element includes, for example, a photodiode (PD), a phototransistor, and the like.

[0041] Specifically, as the light receiving element, it is possible to adopt, for example, a multi-divided PD having a plurality of light receiving regions arranged one-dimensionally or two-dimensionally, a line sensor in which pixels including a PD are one-dimensionally arranged, an image sensor in which pixels including a PD are two-dimensionally arranged, or the like.

[0042] Note that, in general, in a case of a photoplethysmography (PPG) sensor that detects a heart rate, an LED is used as the light emitting element, and a PD is used as the light receiving element. A blood flow flowing through a human body pulsates, and thus a density of red blood cells under the skin is partially high and partially low. Therefore, when light having a wavelength absorbed by red blood cells is emitted and an amount of returned light is observed, the amount of light slightly changes. A heart rate monitor calculates the heart rate by using the fact that the change in the amount of light is equal to a beat of a heart.

[0043] Further, in general, in a case of a laser Doppler flowmeter (LDF), an LD is used as the light emitting element, and a PD is used as the light receiving element. When the skin is irradiated with light, part of the light is scattered by red blood cells in blood under the skin. At this time, when the red blood cells are moving, the scattered light causes the Doppler shift, and a wavelength thereof slightly changes. Meanwhile, light reflected by a non-moving tissue does not cause the Doppler shift. The light is laser light and thus has high coherence, and, as a result, a beat signal corresponding to a wavelength difference of the Doppler shift is generated in a light receiver. An LDF sensor calculates the blood flow rate by analyzing the beat signal.

[0044] In the present embodiment, the plurality of light receiving elements 12 includes a first light receiving element 121 and a second light receiving element 122.

[0045] Here, in general, many sympathetic nerves are distributed in arterioles, and it is considered that, when the sympathetic nerves are subjected to stress stimulation, norepinephrine (NE) that is a neurotransmitter is released from nerve terminals and acts on al receptors of vascular smooth muscle cells to cause vasoconstriction. Meanwhile, it is known that smooth muscle cells in the arterioles are sparsely distributed and that the arterioles lead to capillaries while a density of the smooth muscle cells gradually decreases toward a periphery.

[0046] Therefore, it is considered that constriction of the arterioles caused by stress depends on the density of the smooth muscle cells of each blood vessel, and thus each blood vessel shows different responses. That is, when stress is loaded, the arterioles in which many smooth muscles are distributed strongly constrict, and an amount of constriction decreases in a blood vessel near capillaries, i.e., a blood vessel in which smooth muscle is sparse. By using this fact to observe each blood vessel, it is possible to sense a stress response of a human body. For example, there is a phenomenon in which, in a case where no stress is loaded, almost all blood vessels move in a uniform manner, and thus the light receivers have a high correlation, whereas, when stress is loaded, physiological indices such as a blood flow rate change according to constriction force of each blood vessel, and thus the correlation between the light receivers decreases.

[0047] FIG. 1 is a graph schematically showing the phenomenon. With a time 0 as a boundary, a negative time is a rest time, and a positive time is a time when a stress load is applied. A vertical axis represents, for example, a blood flow rate. In this case, at the rest time, each blood vessel pulsates at a blood flow rate specific to the blood vessel (which is determined by, for example, an inner diameter or the like). When stress is applied, a blood vessel represented by γ is less likely to constrict because the amount of smooth muscle is small. Thus, the blood flow rate does not greatly change. Meanwhile, a line represented by α with a high density of smooth muscles indicates a blood vessel in which there are many smooth muscles, and the blood flow rate greatly increases due to the stress. As a result, for example, a correlation represented in the order of γ-β-α at the rest time is replaced with a correlation of α-β-γ when the stress is applied. Thus, it is possible to determine whether or not the stress is loaded.

[0048] By the way, as to how to distinguish each blood vessel, the arterioles generally have a diameter of 100 to 200 μm, and thus, if a light receiver larger than the diameter is used, a plurality of blood vessels is simultaneously measured. This makes it difficult to observe individual blood vessels to identify stress as described above. Therefore, an area of the light receiver is preferably as small as possible.

[0049] In the present embodiment, the first light receiving element 121 preferably has an area of 1 mm.sup.2 or less, and more preferably 0.1 mm.sup.2 or less.

[0050] By the way, it is widely known that a reaction derived from the heart, such as an increase in heart rate or an increase in blood pressure, is also simultaneously observed when a stress load is applied. This phenomenon is widely known, and thus many wearable devices and the like provided with a PPG sensor are commercially available as a device for displaying a stress state. In this case, it is required to prolong a life of a battery, and thus a photodiode having a relatively large area is used to improve light utilization efficiency.

[0051] In the present embodiment, the second light receiving element 122 preferably has an area exceeding 1 mm.sup.2, and more preferably has an area exceeding 2 mm.sup.2.

[0052] 1-2. Arrangement Example 1

[0053] FIG. 2 illustrates an arrangement example of the plurality of light receiving elements 12 in the present embodiment.

[0054] In the arrangement example of FIG. 2, a plurality of first light receiving elements 121 and one second light receiving element 122 are provided so as to surround one light emitting element 11. As described above, a biological reaction when stress is applied includes two physiological phenomena, i.e., a physiological phenomenon derived from a blood vessel and a physiological phenomenon derived from the heart. By using both the physiological phenomena, it is possible to acquire the presence or absence of stress or tension with high accuracy. Therefore, by using the first light receiving elements 121 and the second light receiving element 122 as described above, it is possible to accurately calculate an index of the stress or tension.

[0055] In this case, in order to equalize an amount of light received by each light receiving element 12 and facilitate adjustment of an amplification factor in an amplifier, it is preferable that distances from the light emitting element 11 to each light receiving element 12 be substantially the same.

[0056] 1-3. Arrangement Example 2

[0057] FIG. 3 illustrates an arrangement example of the light receiving elements 12 different from that in FIG. 2.

[0058] In the arrangement example of FIG. 3, one first light receiving element 121 and one second light receiving element 122 are arranged adjacent to one light emitting element 11. In the present technology, as described above, one first light receiving element 121 and one second light receiving element 122 may be provided. Even in a case where the number of the first light receiving elements 121 is reduced, biological information can be measured with high accuracy as long as a correlation with the second light receiving element 122 can be established.

[0059] 1-4. Processing Unit 100

[0060] FIG. 4 is a block diagram of a configuration example of the processing unit 100.

[0061] The processing unit 100 analyzes biological information (e.g. a state of the autonomic nerve serving as a stress or tension index) on the basis of output from the light receiving elements 12.

[0062] The processing unit 100 can include, for example, an extraction unit 101, a recording unit 102, and the analysis unit 103. Further, the processing unit 100 may include the control unit 104 as necessary.

[0063] The processing unit 100 may be directly connected to the plurality of light receiving elements 12 or may be connected to the plurality of light receiving elements 12 in a wired or wireless manner.

[0064] The extraction unit 101 extracts information from the output of the light receiving elements 12. The extraction unit 101 is achieved by, for example, a low-pass filter.

[0065] The low-pass filter is connected to an output end of each light receiving element 12, cuts a high-frequency component (noise component) of a signal output from the light receiving element 12, and outputs the signal in which the high-frequency component has been cut. The signal that has passed through the low-pass filter is transmitted to the recording unit 102 and the analysis unit 103 described later. Note that the low-pass filter may be provided for each light receiving element 12.

[0066] The recording unit 102 records the information extracted by the extraction unit 101. The recording unit 102 is achieved by, for example, a central processing unit (CPU), memories such as a read only memory (ROM), a random access memory (RAM), and a flash memory, a hard disk, and the like. The recording unit 102 is connected to an output end of the low-pass filter and holds or updates the signal that has passed through the low-pass filter.

[0067] The analysis unit 103 analyzes the signal obtained from each light receiving element 12 and analyzes biological information on the basis of the analysis result. The analysis unit 103 and the control unit 104 are achieved by, for example, a central processing unit (CPU), a field programmable gate array (FPGA), or the like.

[0068] Specifically, the analysis unit 103 acquires, for example, a correlation between differences of pieces of information of the respective light receiving elements 12 and determines a state of a living body on the basis of the acquisition result. Examples of the “correlation” here include features such as variance, standard deviation, difference, skewness, kurtosis, correlation, quantile, average value, and median value.

[0069] The analysis unit 103 includes, for example, a subtraction unit, a correlation acquisition unit, and a state determination unit.

[0070] The subtraction unit is connected to the output end of the low-pass filter and the recording unit 102. The subtraction unit subtracts the signal (old signal) recorded (held or updated) in the recording unit 102 from a signal (new signal) transmitted through the low-pass filter after a predetermined time from the time of recording and outputs a subtraction result (difference). Note that, in a case where the biological information measurement device 10 according to the present technology includes the plurality of light receiving units 12, the subtraction unit may be provided for each low-pass filter provided in each light receiving unit 12.

[0071] The correlation acquisition unit is connected to an output end of the subtraction unit. The correlation acquisition unit acquires a correlation between subtraction results (differences) in the subtraction unit (calculates the above features) and outputs the acquisition result (calculation result).

[0072] The state determination unit is connected to an output end of the correlation acquisition unit. The state determination unit determines a state of the living body on the basis of the correlation acquired by the correlation acquisition unit.

[0073] Note that the present technology may adopt a method of providing a division unit to acquire a division result, instead of the subtraction unit.

[0074] Alternatively, the correlation may be acquired from signals recorded in the recording unit (the above features may be calculated) without using subtraction or division, and the acquisition result (calculation result) may be output. In this case, the correlation includes a correlation coefficient and the like.

[0075] In the present embodiment, the analysis unit 103 can analyze the biological information by referring to a signal obtained from the second light receiving element 122. Because the second light receiving element 122 has an area exceeding 1 mm.sup.2, the second light receiving element simultaneously measures information derived from a plurality of blood vessels and thus obtains an averaged signal. Therefore, the second light receiving element has a feature that the signal is hardly affected by a difference in an amount of constriction caused by stress of individual blood vessels. Accordingly, by referring to the signal obtained from the second light receiving element 122, it is possible to accurately calculate information corresponding to the heart rate and the blood pressure, without the difference in the constriction of the individual blood vessels becoming noise.

[0076] Further, in this case, the analysis unit 103 can analyze the biological information by referring to the signals obtained from the respective plurality of light receiving elements with each other.

[0077] Specifically, it is possible to calculate a shift from a reference of each first light receiving element 121 by referring to the signal of the second light receiving element 122. For example, in a case where the correlation coefficient between the second light receiving element 122 and the first light receiving elements 121 for the past 30 seconds is high, the living body is determined as being in a resting state, whereas, in a case where the correlation coefficient is low, the living body can be determined as being in a stress-applied state. In a case where a plurality of first light receiving elements 121 is arranged, the correlation coefficient may easily decrease due to an influence of, for example, a slight positional shift. However, by using the stable second light receiving element 122 on one side, stable measurement can be performed with a smaller number of light receiving elements.

[0078] In the present embodiment, the analysis unit 103 can analyze information derived from a blood vessel on the basis of a signal obtained from the first light receiving element 121. The area of the first light receiving element 121 is 1 mm.sup.2 or less, which is substantially the same size as the blood vessel, and thus is suitable for calculating, for example, a stress index derived from the blood vessel.

[0079] Further, the analysis unit 103 can analyze information derived from the heart on the basis of a signal obtained from the second light receiving element 122. Because the area of the second light receiving element 122 exceeds 1 mm.sup.2 and signals of a plurality of blood vessels are averaged, the second light receiving element is suitable for observing a reaction derived from the heart, such as, for example, an increase in heart rate or an increase in blood pressure.

[0080] Furthermore, when body motion occurs, the analysis unit 103 can ignore a signal from the first light receiving element 121. Because the first light receiving element 121 has substantially the same size as a blood vessel, a measurement value greatly changes only when an installation position is slightly shifted and thus cannot be considered as a continuous measurement value. Therefore, the first light receiving element 121 has a feature of being vulnerable to body motion. Meanwhile, the second light receiving element 122 averages the signals of the plurality of blood vessels and thus can be continuously used even when some body motion occurs. Therefore, in a case where body motion occurs, it is possible to reduce power and a load of calculation processing by stopping the use of the first light receiving element 121.

[0081] The control unit 104 controls driving of each of the plurality of light receiving elements 12. Further, the control unit can integrally control the extraction unit 101, the recording unit 102, and the analysis unit 103 described above.

[0082] Specifically, the control unit 104 controls driving of the light receiving elements 12 on the basis of signals obtained from the light receiving elements 12. For example, when the above body motion occurs, it is possible to detect occurrence of the body motion on the basis of the plurality of light receiving elements 12 and stop driving of the first light receiving element 121. This makes it possible to reduce power and the load of calculation processing. Further, in a case where it is desired to calculate a stress value with high accuracy, it is possible to drive only the first light receiving element 121. Furthermore, for example, only the second light receiving element may be used to reduce an amount of light emission of the light source for long battery life.

[0083] 2. Biological Information Measurement System According to Present Technology

[0084] The biological information measurement system according to the present technology includes the above biological information measurement device 10 and an analysis device that analyzes biological information on the basis of signals obtained from the light receiving elements.

[0085] Because the biological information measurement device 10 is similar to that described above, the description thereof is omitted here.

[0086] Further, the analysis device may have a function similar to that of the analysis unit 103 described above, for example. Because the analysis unit 103 is similar to that described above, the description thereof is omitted here.

[0087] In the present technology, the biological information measurement device 10 and/or the analysis device can also be provided in a cloud environment and be connected to each other via a network. In this case, various types of information analyzed by the analysis device on the cloud can also be shared among a plurality of users.

[0088] Note that the present technology can also adopt the following configurations.

[1]

[0089] A biological information measurement device including:

[0090] a light emitting element that irradiates a living body with light; and

[0091] a plurality of light receiving elements that receives light scattered in the living body, in which

[0092] at least one light receiving element has a different area from an area of another light receiving element.

[2]

[0093] The biological information measurement device according to [1], including:

[0094] a first light receiving element having an area of 1 mm.sup.2 or less; and

[0095] a second light receiving element having an area exceeding 1 mm.sup.2.

[3]

[0096] The biological information measurement device according to [2], including a plurality of the first light receiving elements.

[4]

[0097] The biological information measurement device according to [2], including:

[0098] the one first light receiving element; and

[0099] the one second light receiving element.

[5]

[0100] The biological information measurement device according to any one of [1] to [4], in which distances from the light emitting element to the plurality of light receiving elements are substantially the same.

[6]

[0101] The biological information measurement device according to any one of [2] to [5], further including an analysis unit that analyzes biological information on the basis of signals obtained from the light receiving elements.

[7]

[0102] The biological information measurement device according to [6], in which the analysis unit analyzes the biological information by referring to a signal obtained from the second light receiving element.

[8]

[0103] The biological information measurement device according to [7], in which the analysis unit analyzes the biological information by referring to the signals obtained from the respective plurality of light receiving elements with each other.

[9]

[0104] The biological information measurement device according to [6], in which the analysis unit analyzes information derived from a blood vessel on the basis of a signal obtained from the first light receiving element.

[10]

[0105] The biological information measurement device according to [6], in which the analysis unit analyzes information derived from a heart on the basis of a signal obtained from the second light receiving element.

[11]

[0106] The biological information measurement device according to any one of [1] to [10], further including a control unit that controls driving of each of the plurality of light receiving elements.

[12]

[0107] A biological information measurement system including:

[0108] a biological information measurement device including

[0109] a light emitting element that irradiates a living body with light, and

[0110] a plurality of light receiving elements that receives light scattered in the living body, in which

[0111] at least one light receiving element has a different area from an area of another light receiving element; and

[0112] an analysis device that analyzes biological information on the basis of signals obtained from the light receiving elements.

[13]

[0113] The biological information measurement system according to [12], in which

[0114] the biological information measurement device and

[0115] the analysis device

[0116] are connected via a network.

REFERENCE SIGNS LIST

[0117] 10 Biological information measurement device [0118] 11 Light emitting element [0119] 12 Light receiving element [0120] 121 First light receiving element [0121] 122 Second light receiving element [0122] 100 Processing unit [0123] 101 Extraction unit [0124] 102 Recording unit [0125] 103 Analysis unit [0126] 104 Control unit