Finger-worn device

Abstract

This finger-worn device comprises an annular structure configured to be worn on a finger. A first light source and a second light source held by the annular structure emit light of mutually different wavelengths to a space surrounded by the annular structure. A light receiver held by the annular structure receives light which is emitted from the first light source and the second light source and then reflected or scattered. A control unit performs control to cause the first light source and the second light source to emit light intermittently, and determines whether or not the annular structure is worn on a finger on the basis of light reception levels measured by the light receiver. The distance from the light receiver to the second light source is longer than the distance from the light receiver to the first light source. The control unit performs worn state determination processing for determining that the annular structure is worn on a finger if a first light reception level measured by the light receiver when the first light source is caused to emit light is greater than a first threshold value and a second light reception level measured by the light receiver when the second light source is caused to emit light is greater than a second threshold value. The control unit further performs biological information measurement processing for obtaining biological information on the basis of at least one of the first light reception level and the second light reception level.

Description

Finger-worn device

[0001] The present invention relates to a finger-worn device.

[0002] A biometric sensor equipped with a light-emitting unit and a light-receiving unit is known (see Patent Document 1). The biometric sensor disclosed in Patent Document 1 is worn on the wrist and has a function of determining whether it is worn correctly. This determination process includes a proximity determination process that determines whether reflected light is detected by the light-receiving unit when light is emitted from the light-emitting unit. When the biometric sensor is worn on the wrist, the light-receiving unit detects the reflected light from the wrist. If the biometric sensor is not worn on the wrist, the reflected light does not return to the light-receiving unit. Therefore, it is possible to determine whether the biometric sensor is worn correctly on the wrist from the detection result by the light-receiving unit.

[0003] JP 2018-161250 A

[0004] In a finger-worn device, a light-emitting unit and a light-receiving unit are arranged on the inner circumferential surface of an annular structure that is worn on a finger. A portion of the light emitted from the light-emitting unit is reflected by the inner circumferential surface of the annular structure and received by the light-receiving unit. As such, even when the device is not worn on a finger, some light is incident on the light-receiving unit. Therefore, a method of determining whether the device is worn on a finger based on whether or not the light-receiving unit receives light reduces the accuracy of the determination.

[0005] An object of the present invention is to provide a finger wearable device that can improve the accuracy of determining whether or not the device is worn on a finger.

[0006] According to one aspect of the present invention, there is provided an annular structure configured to be wearable on a finger; a first light source and a second light source held by the annular structure and emitting light of mutually different wavelengths into a space surrounded by the annular structure; a light receiver held by the annular structure and receiving light emitted from the first light source and the second light source and reflected or scattered; and a control unit that controls the first light source and the second light source to emit light intermittently and determines whether the annular structure is worn on a finger based on a light reception level measured by the light receiver, wherein the distance from the light receiver to the second light source is longer than the distance from the light receiver to the first light source, and the control unit has a function of performing a wearing state determination process to determine that the annular structure is worn on a finger when a first light reception level by the light receiver when the first light source is caused to emit light exceeds a first threshold and a second light reception level by the light receiver when the second light source is caused to emit light exceeds a second threshold; and performing a biological information measurement process to obtain biological information based on at least one of the first received light level and the second received light level.

[0007] The accuracy of the determination can be improved by determining the wearing state using both the first light reception level when the first light source is illuminated and the second light reception level when the second light source is illuminated.

[0008] FIG. 1A is a schematic perspective view of a finger wearing device according to a first embodiment, and FIG. 1B is a cross-sectional view of the finger wearing device according to the first embodiment, taken perpendicular to the insertion / removal direction. FIG. 2 is a block diagram for explaining the function of the finger wearing device according to the first embodiment. FIGS. 3A and 3B are graphs showing changes over time in the level of received light measured by the light receiver. FIGS. 4A and 4B are graphs showing changes over time in the level of received light measured by the light receiver. FIGS. 5A and 5B are graphs showing changes over time in the level of received light measured by the light receiver. FIG. 6 is a flowchart showing the procedure for a wearing state determination process performed by a control unit of the finger wearing device according to the first embodiment when biometric information is not being measured. FIG. 7 is a flowchart showing the procedure for a wearing state determination process performed by a control unit of the finger wearing device according to the first embodiment when biometric information is being measured. FIG. 8 is a cross-sectional view of a finger wearing device according to a second embodiment. FIG. 9 is a block diagram for explaining the function of the finger wearing device according to the second embodiment. FIG. 10 is a flowchart showing the procedure for a wearing state determination process performed by a control unit of the finger wearing device according to the second embodiment when biometric information is not being measured. FIG. 11 is a cross-sectional view schematically illustrating a finger wearing device according to a third embodiment. FIG. 12 is a block diagram for explaining the function of the finger wearing device according to the third embodiment. FIG. 13 is a schematic view of the inner circumferential surface of a finger wearing device according to a fourth embodiment, viewed from the direction of insertion and removal of a finger. FIG. 14 is a cross-sectional view of a finger wearing device according to a fifth embodiment worn on a finger. FIG. 15 is a block diagram of a finger wearing device according to a sixth embodiment and external equipment related to the operation of the finger wearing device. FIG. 16 is a flowchart illustrating the procedure for a wearing state determination process executed by a control unit of a finger wearing device according to a seventh embodiment when biological information is not being measured. FIG. 17 is a cross-sectional view schematically illustrating a finger wearing device according to an eighth embodiment. FIG. 18 is a graph illustrating the change over time in temperature measured by the first temperature sensor and the second temperature sensor of the finger wearing device according to the eighth embodiment, and the standard deviation of the temperature within a predetermined period. FIG. 19 is a flowchart illustrating the procedure for a wearing state determination process executed by a control unit of a finger wearing device according to the eighth embodiment when biological information is being measured.

[0009] 1A to 7, a finger wearable device according to a first embodiment will be described. FIG. 1A is a schematic perspective view of a finger wearable device 10 according to the first embodiment. The finger wearable device 10 has an annular shape. The finger wearable device 10 is worn on a finger by inserting the finger into the hollow portion of the annular finger wearable device 10. The finger wearable device 10 acquires biometric information such as a photoplethysmogram while worn on the finger. An xyz Cartesian coordinate system is defined, with the z direction being the direction in which the finger is inserted and removed when the finger wearable device 10 is worn on the finger.

[0010] 1B is a cross-sectional view perpendicular to the z-axis of the finger-worn device 10 according to the first embodiment. The finger-worn device 10 includes an annular structure 20 along a circular or elliptical outer periphery, and a sensor module 30 held by the annular structure 20. The annular structure 20 includes an annular inner member 20A and an outer member 20B that surrounds the outer periphery of the inner member 20A.

[0011] The inner member 20A has an opening that penetrates from its inner peripheral surface to its outer peripheral surface. The sensor module 30 is fitted into this opening. The sensor module 30 is fixed to the inner member 20A with an adhesive or adhesive tape.

[0012] The sensor module 30 includes two rigid substrates 31 and 32 and a flexible substrate 33 connecting the two rigid substrates. For example, a rigid-flexible substrate that integrates a rigid substrate and a flexible substrate is used as the two rigid substrates 31 and 32 and the flexible substrate 33. The two rigid substrates 31 and 32 are arranged at different positions in the circumferential direction.

[0013] The first light source 21 and the light receiver 23 are mounted at different positions in the circumferential direction on the inner surface (the surface facing the space surrounded by the annular structure 20) of one rigid substrate 31. The second light source 22 is mounted on the inner surface of the other rigid substrate 32. The light receiver 23, the first light source 21, and the second light source 22 are arranged in this order in the circumferential direction. The distance from the light receiver 23 to the second light source 22 is longer than the distance from the light receiver 23 to the first light source 21.

[0014] The distance from the light receiver 23 to the first light source 21 is, for example, 1 mm or more and 3 mm or less, and the distance from the light receiver 23 to the second light source 22 is, for example, 5 mm or more and 20 mm or less. For example, the center points of active regions such as the light-emitting region and the light-receiving region can be used as reference points for specifying the relative positions of the first light source 21, the second light source 22, and the light receiver 23. A resin member 25 is arranged so as to cover the inner surfaces of the first light source 21, the second light source 22, the light receiver 23, the rigid substrates 31 and 32, and the flexible substrate 33.

[0015] The first light source 21 and the second light source 22 emit light in different wavelength ranges into the space surrounded by the annular structure 20. When the finger wearable device 10 is worn on a finger, the first light source 21 and the second light source 22 emit light toward the finger. For example, a vertical cavity surface emitting laser (VCSEL), a light emitting diode (LED), or the like is used as the first light source 21 and the second light source 22. For example, a photodiode, a phototransistor, or the like is used as the light receiver 23. For example, a resin such as epoxy, silicone, acrylic, polycarbonate, urethane, polyethylene terephthalate, polypropylene, PET, or ABS is used as the resin member 25.

[0016] When the finger wearable device 10 is not worn on a finger, a portion of the light emitted from the first light source 21 and the second light source 22 is reflected by the inner circumferential surface of the annular structure 20 and enters the light receiver 23. When the finger wearable device 10 is worn on a finger, the light emitted from the first light source 21 and the second light source 22 is scattered inside the finger (inside the living body), and the scattered light enters the light receiver 23.

[0017] The first light source 21 emits light in a wavelength range from blue to yellow-green, for example, and the second light source 22 emits light in a wavelength range from red to near-infrared. Light in the red to near-infrared wavelength range is less absorbed by the body than light in the blue to yellow-green wavelength range, and therefore penetrates deeper into the body. Therefore, biological information of a relatively shallow region is obtained from the measurement result of the light reception level when the first light source 21 is operated (hereinafter referred to as the first light reception level), and biological information of a relatively deep region is obtained from the measurement result of the light reception level when the second light source 22 is operated (hereinafter referred to as the second light reception level).

[0018] 2 is a block diagram for explaining the function of the finger wearable device 10 according to the first embodiment. The finger wearable device 10 according to the first embodiment includes a control unit 50. The control unit 50 is configured, for example, with one or more integrated circuits, and is held by the annular structure 20. For example, the control unit 50 is mounted on rigid substrates 31, 32, etc.

[0019] The control unit 50 includes a light emission control unit 51, a light reception level acquisition unit 52, a determination processing unit 53, a biological information measurement unit 54, and a calibration unit 55. Power is supplied to the control unit 50 from a battery 41. The battery 41 is connected to the finger wearable device 10 via a power cable. Note that the finger wearable device 10 may have a built-in battery 41.

[0020] The light emission control unit 51 controls the light emission of the first light source 21 and the second light source 22. For example, the light emission control unit 51 causes the first light source 21 and the second light source 22 to emit light intermittently at different timings. The light reception level acquisition unit 52 acquires a signal indicating the light reception level of light received by the light receiver 23. The determination processing unit 53 determines whether or not the finger wearable device 10 is worn on a finger. Details of the processing performed by the determination processing unit 53 will be described later with reference to FIGS. 6 and 7.

[0021] The biological information measurement unit 54 performs biological information measurement processing to obtain biological information such as photoplethysmography, pulse rate, oxygen saturation, autonomic nerve and respiratory state, sleep state (sleep or wakefulness, sleep quality, etc.), blood pressure, blood glucose level, blood flow, and vascular resistance based on the light reception level and its change over time by the light receiver 23. The calibration unit 55 calibrates threshold values ​​referenced when the determination processing unit 53 determines the wearing state. Details of the processing by the calibration unit 55 will be described later.

[0022] Next, with reference to Figures 3A to 5B, the change over time in the light reception level measured by the light receiver 23 will be described. Figures 3A to 5B are graphs showing the change over time in the light reception level measured by the light receiver 23. The horizontal axis of these graphs represents time in units of seconds, and the vertical axis represents the light reception level in arbitrary units. The graphs of Figures 3B, 4B, and 5B are enlarged versions of the vertical axes of the graphs of Figures 3A, 4A, and 5A, respectively. In addition, the solid lines in these graphs indicate the first light reception level when the first light source 21 emitting light in the green wavelength range is operated, and the dashed lines indicate the second light reception level when the second light source 22 emitting light in the near-infrared wavelength range is operated.

[0023] 3A and 3B show the light reception level when the inner circumferential surface of the finger-worn device 10 is white, and the graphs from FIG. 4A to FIG. 5B show the light reception level when the inner circumferential surface of the finger-worn device 10 is black.

[0024] The graphs in Figures 3A to 4B show the change over time in the light reception level when a black cloth is inserted into the finger wearable device 10 (black cloth inserted state), when nothing is inserted (hollow state), and when a finger is inserted (worn state). The graphs in Figures 5A and 5B show the change over time in the light reception level when a white cloth is inserted into the finger wearable device 10 (white cloth inserted state), when it is hollow, and when it is worn.

[0025] As shown in Figures 3A, 4A, and 5A, the first light-receiving level in the attached state is higher than the first light-receiving level in the hollow state. Therefore, by measuring the first light-receiving level, it is possible to distinguish between the hollow state and the attached state. For example, by comparing the first light-receiving level with a first threshold value Th1, it is possible to distinguish between the hollow state and the attached state. By setting the first threshold value Th1 to "4" in the arbitrary units of the vertical axis shown in Figures 3A, 4A, and 5A, it is possible to distinguish between the hollow state and the lazy state with sufficiently high accuracy.

[0026] However, as shown in Figure 5A, the first light reception level in the wearing state is almost the same as or slightly lower than the first light reception level in the white cloth insertion state. This is because the intensity of the light scattered by the white cloth is equal to or stronger than the intensity of the light scattered by the finger. Therefore, it is not possible to distinguish between the white cloth insertion state and the wearing state by measuring only the first light reception level.

[0027] As shown in Figure 5B, the second light reception level indicated by the dashed line differs between the white cloth insertion state and the worn state, with the second light reception level in the worn state being higher than the second light reception level in the white cloth insertion state. In the graph shown in Figure 5B, for example, by comparing the second light reception level with a second threshold value Th2, the white cloth insertion state and the worn state can be distinguished. As an example, by setting the second threshold value Th2 to "0.15," if the second light reception level is equal to or greater than the second threshold value Th2, it can be determined that the state is worn or the hollow state, rather than the white cloth insertion state. Note that in the graphs shown in Figures 3B and 4B, the second light reception level in the worn state and the hollow state is equal to or greater than the second threshold value Th2.

[0028] Based on these findings, when the first light reception level is equal to or greater than the first threshold value Th1 and the second light reception level is equal to or greater than the second threshold value Th2, it can be determined that the finger wearable device 10 is not in a hollow state, a black cloth inserted state, or a white cloth inserted state, but is in a worn state. While the drawings from Figures 3A to 5B show cases where the inner surface of the finger wearable device 10 is white or black and the inserted cloth is white or black, if the cloth is any other color, the first light reception level and the second light reception level will be intermediate values ​​between black and white. Therefore, it is possible to determine the worn state even if the colors are other than black or white.

[0029] Next, the procedure of the wearing state determination process performed by the control unit 50 (FIG. 2) while biological information is not being measured will be described with reference to Fig. 6. Fig. 6 is a flowchart showing the procedure of the wearing state determination process performed by the control unit 50 of the finger wearing device 10 according to the first embodiment while biological information is not being measured.

[0030] First, the first light source 21 is activated to emit light and a first light reception level is measured (step SA1). It is determined whether the first light reception level is equal to or greater than a first threshold value Th1 (step SA2). If the first light reception level is equal to or greater than the first threshold value Th1, the second light source 22 is activated to emit light and a second light reception level is measured (step SA3). It is determined whether the second light reception level is equal to or greater than a second threshold value Th2 (step SA4). If the second light reception level is equal to or greater than the second threshold value Th2, it is determined that the finger wearable device 10 ( FIG. 1 ) is in a worn state (step SA5). Then, a biometric information measurement process is initiated (step SA6).

[0031] If it is determined in step SA2 that the first light-receiving level is less than the first threshold value Th1, the procedure from step SA1 is repeated. Similarly, if it is determined in step SA4 that the second light-receiving level is less than the second threshold value Th2, the procedure from step SA1 is repeated.

[0032] When the biological information measurement process is started in step SA6, the control unit 50 alternately and intermittently causes the first light source 21 and the second light source 22 to emit light and acquires temporal changes in the first and second light reception levels. Various biological information can be acquired based on these temporal changes. During biological information measurement, the first light source 21 and the second light source 22 emit light at a frequency sufficient to acquire a photoplethysmographic waveform, for example, a frequency of 100 Hz or higher. Note that, as long as a photoplethysmographic waveform can be acquired with sufficient accuracy, it is not necessary to increase the frequency more than necessary. For example, the first light source 21 and the second light source 22 may emit light at a frequency of 1000 Hz or lower. Note that, when high measurement accuracy is not required or when measuring oxygen saturation, the emission frequency of the first light source 21 and the second light source 22 may be reduced to approximately 50 Hz or higher and 100 Hz or lower.

[0033] When biological information is not being measured, there is no need to observe the waveform of the photoplethysmogram, and therefore there is no need to increase the light emission frequency of the first light source 21 and the second light source 22. For example, the light emission frequency when performing the attachment state determination process when biological information is not being measured may be set to 0.1 Hz or more and 50 Hz or less.

[0034] From the viewpoint of reducing power consumption, it is preferable to have a short pulse width when emitting light from the first light source 21 and the second light source 22. However, if the pulse width is too short, noise resistance will decrease. As an example, it is preferable to set the pulse width to be 1 μs or more and 100 μs or less.

[0035] Next, the wearing state measurement process during biological information measurement will be described with reference to Fig. 7. Fig. 7 is a flowchart showing the procedure of the wearing state determination process performed by the control unit 50 (Fig. 1) during biological information measurement.

[0036] First, the control unit 50 causes the first light source 21 to emit light and measures a first light-receiving level (step SB1). The control unit 50 compares the first light-receiving level with a first threshold Th1 (step SB2). If the first light-receiving level is equal to or greater than the first threshold Th1, the control unit 50 causes the second light source 22 to emit light and measures a second light-receiving level (step SB3). The control unit 50 then compares the second light-receiving level with a second threshold Th2 (step SB4). If the second light-receiving level is equal to or greater than the second threshold Th2, the control unit 50 calculates the degree of temporal fluctuation of the first light-receiving level (step SB5). For example, the control unit 50 calculates the amplitude of the waveform of the first light-receiving level, the standard deviation of the first light-receiving level, etc.

[0037] During the measurement of biological information shown in Fig. 7, the first light source 21 and the second light source 22 are intermittently illuminated at a higher frequency than during the non-measurement of biological information shown in Fig. 6. In this case, it is preferable to thin out the time-series data acquired at a high sampling frequency for measuring the biological information, and collect the data for determining the wearing state shown in Fig. 7. For example, if the sampling frequency for measuring the biological information is 200 Hz, it is preferable to thin out the number of time-series data to 1 / 8 before acquiring them. In this case, the sampling frequency for determining the wearing state is 25 Hz.

[0038] In step SB5, the first light-receiving level measured at a high sampling frequency in the biological information measurement process may be used as the first light-receiving level referenced when calculating the degree of fluctuation in the first light-receiving level, thereby making it possible to detect the presence or absence of a photoplethysmogram.

[0039] The first threshold value Th1 used in step SA2 (FIG. 6) of the process during non-measurement of biological information and the first threshold value Th1 used in step SB2 (FIG. 7) of the process during measurement of biological information do not necessarily have to be the same value. Similarly, the second threshold value Th2 used in step SA4 (FIG. 6) of the process during non-measurement of biological information and the second threshold value Th2 used in step SB4 (FIG. 7) of the process during measurement of biological information do not necessarily have to be the same value.

[0040] When the finger wearable device 10 is worn, the amplitude or standard deviation corresponding to the waveform of the photoplethysmogram is calculated as the amplitude or standard deviation value. When the finger wearable device 10 is not worn on the finger, the photoplethysmogram is not detected, and therefore the amplitude of the waveform of the first light reception level or the standard deviation of the first light reception level is smaller than the value when the finger wearable device 10 is worn.

[0041] The degree of fluctuation in the first light reception level is compared with the third threshold value Th3 (step SB6), and if the degree of fluctuation in the first light reception level is equal to or greater than the third threshold value Th3, it is determined that the finger wearable device 10 is in a worn state (step SB7), and the biometric information measurement process is continued.

[0042] If it is determined in step SB2 that the first light reception level is equal to or less than the first threshold value Th1, if it is determined in step SB4 that the second light reception level is equal to or less than the second threshold value Th2, or if it is determined in step SB6 that the degree of fluctuation in the first light reception level is equal to or less than the third threshold value Th3, the finger wearable device 10 is determined to be in an unworn state, and the biometric information measurement process is stopped (step SB8). After the biometric information measurement process is stopped, the wearing state determination process when biometric information is not being measured, shown in FIG. 6, is started.

[0043] Next, the function of the calibration unit 55 ( FIG. 2 ) of the control unit 50 will be described. The calibration unit 55 measures the first and second received light levels when the finger wearable device 10 is not worn on a finger, and corrects the first and second threshold values ​​Th1 and Th2 based on the measured values. For example, this process is performed when the finger wearable device 10 is completed and before the product is shipped. It is preferable to measure the first and second received light levels in a dark state where there is no ambient light.

[0044] For example, before product shipment, the first and second light reception levels are measured for each of a plurality of finger wearable devices 10 when the device is not being worn. The first threshold value Th1 for an individual having a larger measured first light reception level is set to be higher than the first threshold value Th1 for an individual having a smaller measured first light reception level. Similarly, the second threshold value Th2 for an individual having a larger measured second light reception level is set to be higher than the second threshold value Th2 for an individual having a smaller measured second light reception level.

[0045] Next, the advantageous effects of the first embodiment will be described. In the first embodiment, whether or not the finger wearable device 10 is in the worn state is determined using both the first light reception level when the first light source 21 is illuminated and the second light reception level when the second light source 22 is illuminated. Therefore, as will be described below, it is possible to improve the accuracy of determining whether or not the finger wearable device 10 is in the worn state.

[0046] For example, as shown in Figures 3A and 4A, the magnitude of the first light reception level is significantly different between the black cloth insertion state, the hollow state, and the worn state. This allows for highly accurate discrimination between the black cloth insertion state or the hollow state and the worn state. As shown in Figure 5A, it is difficult to accurately discriminate between the white cloth insertion state and the worn state using only the first light reception level. In the first embodiment, by also using the second light reception level, it is possible to accurately discriminate between the white cloth insertion state and the worn state, as shown in Figure 5B.

[0047] 4B , when the inner peripheral surface of the finger wearable device 10 is black, the difference between the second light reception level in the hollow state and the second light reception level in the worn state is small. Therefore, it is difficult to accurately distinguish between the hollow state and the worn state using only the second light reception level. In the first embodiment, the first light reception level is also used to determine the worn state, so that the hollow state and the worn state can be accurately distinguished.

[0048] In the first embodiment, the light emission frequency of the first light source 21 and the second light source 22 when biological information is not being measured, as shown in Fig. 6, is set lower than the light emission frequency of the first light source 21 and the second light source 22 when biological information is being measured, as shown in Fig. 7. This makes it possible to reduce power consumption when biological information is not being measured.

[0049] Furthermore, in the first embodiment, by shifting the light emission timing between the first light source 21 and the second light source 22, the first light reception level when the first light source 21 emits light and the second light reception level when the second light source 22 emits light are measured by a single light receiver 23. Therefore, the number of light receivers 23 can be reduced compared to a configuration in which a light receiver is provided for each light source.

[0050] If the contact between the light source emitting the measurement light and the finger is poor, the quality of the waveform of the received light level will deteriorate. In the first embodiment, since the first light source 21 and the second light source 22 are installed, even if the contact between one light source and the finger is poor, it is possible to operate the other light source and obtain a waveform of high quality of the received light level.

[0051] In the first embodiment, the first light source 21 and the second light source 22 emit light in different wavelength ranges, so that biological information appropriate for each wavelength can be obtained. For example, like a pulse oximeter, it is possible to determine the amount and concentration of various components in blood by utilizing the absorption spectrum. Furthermore, by utilizing the fact that the penetration depth into the living body varies depending on the wavelength, it is possible to obtain information on regions at different depths.

[0052] In the first embodiment, as shown in FIG. 7 , if the degree of fluctuation in the first received light level during biometric information measurement is less than the third threshold Th3, the finger wearable device 10 is determined to be in an unworn state, and the biometric information measurement is stopped (step SB8). In a method of determining the wearing state based only on the magnitudes of the first and second received light levels, if an erroneous determination that the finger wearable device 10 is in an unworn state occurs, the biometric information measurement process continues in an unworn state, resulting in unnecessary power consumption. In the first embodiment, the biometric information measurement process is stopped when the degree of fluctuation in the first received light level is less than the third threshold Th3 in addition to the magnitudes of the first and second received light levels, thereby reducing unnecessary power consumption.

[0053] Next, the advantageous effect of the calibration unit 55 ( FIG. 2 ) having the function of correcting the first threshold value Th1 and the second threshold value Th2 will be described. When the distance between the first light source 21 and the light receiver 23 is short, a portion of the light emitted from the first light source 21 travels through the resin member 25 while being reflected or scattered, increasing the amount of stray light that enters the light receiver 23. When the amount of stray light increases, the base level of the first light reception level increases. In this case, it is desirable to increase the first threshold value Th1 in accordance with the increase in the base level.

[0054] The calibration unit 55 measures the first received light level when the finger wearable device 10 is not worn on a finger. This measurement value includes a received light level due to stray light. As shown in FIGS. 3B and 4B , there is no significant difference in the first received light level between the black cloth insertion state and the hollow state. Therefore, it is believed that most of the first received light level in the hollow state is due to stray light.

[0055] In the first embodiment, the first threshold value Th1 is corrected based on the first light reception level due to stray light, so that even if there is variation in the first light reception level due to stray light between individuals, the first threshold value Th1 is appropriately set for each individual. This prevents a decrease in the accuracy of the determination of the wearing state. Similarly, even if there is variation in the second light reception level due to stray light between individuals, a decrease in the accuracy of the determination of the wearing state is prevented.

[0056] Next, we will explain the preferred color of the inner circumferential surface of the finger wearable device 10. When the first light reception level is compared with the first threshold value Th1 in step SA2 ( FIG. 6 ) and the second light reception level is compared with the second threshold value Th2 in step SA4 ( FIG. 6 ), a lower light reception level in the hollow state is preferred in order to distinguish between the hollow state and the worn state with high accuracy.

[0057] When the inner circumferential surface of the finger wearable device 10 is white, the first and second light receiving levels in the hollow state are in the range of 0.55 to 0.65, as shown in Fig. 3B. In contrast, when the inner circumferential surface of the finger wearable device 10 is black, the first and second light receiving levels in the hollow state are approximately 0.35, as shown in Fig. 4B and Fig. 5B. For this reason, it is preferable to paint the inner circumferential surface of the finger wearable device 10 black.

[0058] In particular, it is preferable to paint the inner circumferential surface black in the range where the reflected light incident on the light receiver 23 is reflected. For example, when the annular structure 20 is worn on a finger and viewed from the direction in which the finger is inserted and removed (z direction), it is preferable that the point where the perpendicular bisector extending from the midpoint of a line segment having the first light source 21 and the light receiver 23 as its two ends toward the space surrounded by the annular structure 20 intersects with the inner circumferential surface of the annular structure 20 is black.

[0059] It is preferable that the reflectance of the inner circumferential surface of the finger wearable device 10 is 10% or less in the wavelength range emitted from the first light source 21. When the reflectance of the inner circumferential surface is 10% or less in the wavelength range emitted from the first light source 21, the inner circumferential surface can be said to be black.

[0060] Next, the shape of the annular structure 20 will be described. Because the finger wearable device 10 is worn on a finger when used, it is preferable that the annular structure 20 have a shape that reflects the cross-sectional shape of the finger. For example, when viewed from the insertion / removal direction (z direction) of the finger wearable device 10, it is preferable that the inner peripheral surface of the annular structure 20 ( FIG. 1B ) has a shape that follows the outer periphery of a circle or ellipse. Note that in this specification, the term "ellipse" does not necessarily mean a geometrically strict ellipse. In this specification, for example, a closed curve that is shifted a predetermined distance in the radial direction from the outer periphery of an ellipse is also included in the ellipse shape.

[0061] In the cross section of a finger, the axis extending from the pad side to the dorsal side of the finger is shorter than the axis extending from one side of the finger to the other side. The pad portion of the finger has more capillaries and a greater blood flow than the dorsal portion, making it suitable for measuring biometric information. Therefore, it is preferable to wear the finger wearable device 10 so that the sensor module 30 ( FIG. 1B ) contacts the pad of the finger. By positioning the sensor module 30 at the point where the inner surface intersects with the minor axis of the xy cross section, the adhesion between the sensor module 30 and the pad portion of the finger can be improved.

[0062] Next, a finger wearable device according to a modification of the first embodiment will be described. The brightness (intensity of ambient light) around the finger wearable device 10 is not necessarily constant. Because a portion of the ambient light enters the light receiver 23 (FIG. 1B) during and after biometric information measurement, the first and second light reception levels change in response to changes in the intensity of the ambient light. This may result in a decrease in the accuracy of determining the wearing state.

[0063] In this modification, the frequency of the intermittent light emission of the first light source 21 and the second light source 22 ( FIG. 1B ) is set sufficiently higher than the rate of change in the intensity of ambient light. A high-pass filter is applied to the temporal change in the first received light level and the second received light level. The cutoff frequency of the high-pass filter is, for example, in the range of 1 kHz to 1 MHz. By applying the high-pass filter, the influence of gradual changes in the intensity of ambient light can be reduced. [Second Embodiment] Next, a finger wearable device according to a second embodiment will be described with reference to FIGS. 8, 9, and 10. Below, a description of the components common to the finger wearable device according to the first embodiment described with reference to FIGS. 1A to 7 will be omitted.

[0064] 8 is a cross-sectional view of the finger-worn device 10 according to the second embodiment. The finger-worn device 10 according to the second embodiment includes an acceleration sensor 40 in addition to the multiple components of the finger-worn device 10 according to the first embodiment. The acceleration sensor 40 is mounted on, for example, a rigid substrate 32, and measures acceleration in three mutually orthogonal directions.

[0065] 9 is a block diagram illustrating the function of a finger wearable device 10 according to the second embodiment. The control unit 50 of the finger wearable device 10 according to the second embodiment includes an acceleration measurement value acquisition unit 57 in addition to the multiple components of the control unit 50 of the finger wearable device 10 according to the first embodiment. The acceleration measurement value acquisition unit 57 acquires the acceleration measurement value measured by the acceleration sensor 40. In the finger wearable device 10 according to the first embodiment, the determination processing unit 53 determines the wearing state based on the first and second light reception levels. In contrast, in the second embodiment, the wearing state is determined based on the acceleration measurement value in addition to the first and second light reception levels.

[0066] FIG. 10 is a flowchart showing the procedure of the wearing state determination process performed by the control unit 50 (FIG. 9) of the finger wearable device 10 according to the second embodiment while biological information is not being measured.

[0067] First, the acceleration measurement value acquisition unit 57 ( FIG. 9 ) acquires acceleration measurement values ​​from the acceleration sensor 40 ( FIG. 9 ) (step SA10). The acceleration measurement values ​​may be acquired at a sampling frequency of, for example, 10 Hz to 30 Hz. Then, based on the acceleration measurement values, the determination processing unit 53 ( FIG. 9 ) determines whether the finger wearable device 10 is stationary (step SA11). If the finger wearable device 10 is not stationary, the determination processing unit 53 determines whether the wearer of the finger wearable device 10 is exercising (step SA12). If the finger wearable device 10 is stationary or if the wearer is exercising, the procedure from acquiring the acceleration measurement values ​​(step SA10) is repeated.

[0068] When the wearer is not exercising, the control unit 50 of the finger wearable device 10 according to the first embodiment executes steps SA1 to SA6. That is, when the finger wearable device 10 is not stationary and the wearer is not exercising (hereinafter referred to as a non-exercising state), the control unit 50 executes steps SA1 to SA6. Note that when the first light reception level is less than the first threshold value Th1 or the second light reception level is less than the second threshold value Th2, the control unit 50 repeats the steps from obtaining the acceleration measurement value (step SA10).

[0069] For example, in step SA11, if all of the rates of change in the acceleration measurements in the three directions are equal to or less than the first jerk threshold, it is determined that the finger wearable device 10 is in a stationary state. For example, in step SA12, if at least one of the rates of change in the acceleration measurements in the three directions is equal to or greater than the second jerk threshold, it is determined that the wearer is in a moving state. The second jerk threshold is greater than the first jerk threshold. Note that the determination may be made based on the number of times the rate of change in the acceleration measurements exceeds the first jerk threshold within a predetermined period of time.

[0070] In other words, if at least one of the rates of change of the acceleration measurements in the three directions is greater than the first jerk threshold and all of the rates of change of the acceleration measurements in the three directions are less than the second jerk threshold, the wearer is determined to be in a non-exercising state.

[0071] Next, the advantageous effects of the second embodiment will be described. When the finger wearable device 10 is worn by a user, a certain degree of acceleration is measured depending on the user's movements. In the second embodiment, when the finger wearable device 10 is stationary, the first light source 21 and the second light source 22 are not operated. This makes it possible to reduce power consumption during the wear state determination process when biometric information is not being measured.

[0072] Furthermore, when the user is moving with the finger wearable device 10 in a pocket or bag, the acceleration measurement value becomes greater than the first acceleration threshold, and it is determined that the finger wearable device 10 is not stationary. If the wearing state is determined based only on the acceleration measurement value, there is a possibility that a state in which the finger wearable device 10 is moving while in a pocket or bag will be erroneously determined as being worn. In the second embodiment, the wearing state is less likely to be erroneously determined by performing the determination based on the first light reception level and the second light reception level in addition to the acceleration measurement value.

[0073] When walking or typing, which involves vigorous finger movement, blood flow in the measurement unit is disrupted, making it difficult to measure the photoplethysmogram with high accuracy. In the second embodiment, if it is determined in step SA12 that the wearer is in an active state, such as walking or typing, measurement of biological information is not performed. This reduces power consumption. The second acceleration threshold value may be set based on actual measurements of acceleration while the wearer is engaged in various activities that make it difficult to measure the photoplethysmogram with high accuracy.

[0074] Next, a finger wearable device according to a modification of the second embodiment will be described. In the second embodiment, the acceleration measurement value obtained by the acceleration sensor 40 (FIGS. 8 and 9) is used to determine whether the finger wearable device 10 is being worn. However, the acceleration measurement value may also be used to determine what action the wearer is performing (gesture determination). When performing gesture determination, it is preferable that the sampling frequency for acquiring the acceleration measurement value be set to 20 Hz or more and 300 Hz or less, which is higher than the sampling frequency used for wear determination.

[0075] In the second embodiment, the acceleration sensor 40 is mounted on the rigid substrate 32 (FIG. 8) on which the second light source 22 is mounted, but the acceleration sensor 40 may be mounted on another rigid substrate or another location on the annular structure 20. In addition to the acceleration sensor 40, a gyro sensor may be used.

[0076] [Third Example] Next, a finger wearable device according to a third example will be described with reference to Fig. 11 and Fig. 12. Below, a description of the configuration common to the finger wearable device according to the first example described with reference to Figs. 1A to 7 will be omitted.

[0077] 11 is a cross-sectional view schematically illustrating a finger wearable device 10 according to a third embodiment. In the first embodiment (FIGS. 1 and 2), power is supplied to the control unit 50 from an external battery 41 via a power cable, for example, but in the third embodiment, the battery 41 is mounted on the annular structure 20 of the finger wearable device 10.

[0078] An opening 20C is provided in the annular structure 20, penetrating from its inner peripheral surface to its outer peripheral surface. A sensor module 30 is fitted into this opening 20C. A battery 41 is arranged along the outer peripheral surface of the annular structure 20. The battery 41 and the sensor module 30 are connected to each other by a cable 35. The battery 41 and the sensor module 30 may also be connected by a flexible substrate. In this case, it is preferable to use a rigid-flexible substrate in which the rigid substrates 31, 32 (FIG. 8) and the flexible substrate that constitute the sensor module 30 are integrated together.

[0079] 11, the sensor module 30 is shown outside the opening 20C, but after assembly, the sensor module 30 is fitted and fixed in the opening 20C. Also, although a gap is shown between the battery 41 and the cable 35 and the outer peripheral surface of the annular structure 20, after assembly, the battery 41 and the cable 35 are fixed to the outer peripheral surface of the annular structure 20 with an adhesive or adhesive tape.

[0080] 12 is a block diagram illustrating the function of the finger wearable device 10 according to the third embodiment. The control unit 50 of the finger wearable device 10 according to the third embodiment includes a charging control unit 58 in addition to the components of the control unit 50 ( FIG. 2 ) according to the first embodiment. Furthermore, the finger wearable device 10 according to the third embodiment includes a charging circuit 42 that supplies charging power to the battery 41. The charging circuit 42 is controlled by the charging control unit 58, receives a supply of power wirelessly from an external source, and charges the battery 41.

[0081] The determination processing unit 53 receives information indicating the charging state from the charge control unit 58, and determines that the finger wearable device 10 is in an unworn state when the battery 41 is in the charging state. Furthermore, when the battery 41 is in the charging state, the calibration unit 55 causes the first light source 21 and the second light source 22 to emit light at different times, and corrects the first threshold value Th1 used in step SA2 ( FIG. 6 ) and step SB2 ( FIG. 7 ) and the second threshold value Th2 used in step SA4 ( FIG. 6 ) and step SB4 ( FIG. 7 ) based on the first light reception level and the second light reception level at that time.

[0082] Next, the advantageous effects of the third embodiment will be described. In the third embodiment, the battery 41 is mounted on the annular structure 20, so there is no need to connect a power cable to the finger wearable device 10. Therefore, when wearing the device, the wearer can perform various actions without being restricted by the power cable.

[0083] While the battery 41 is being charged, the finger-worn device 10 is removed from the finger and placed on a wireless charger. Since the calibration unit 55 corrects the first threshold value Th1 and the second threshold value Th2 while the battery 41 is being charged, the first threshold value Th1 and the second threshold value Th2 can be corrected in a state where it is almost certain that the finger-worn device 10 is not being worn on the finger. Furthermore, by correcting the first threshold value Th1 and the second threshold value Th2 every time charging is started, the first threshold value Th1 and the second threshold value Th2 can be appropriately corrected according to the amount of stray light at that time, even if the amount of stray light changes over time.

[0084] [Fourth Example] Next, a finger wearable device according to a fourth example will be described with reference to Fig. 13. Below, a description of the configuration common to the finger wearable device according to the first example described with reference to Figs. 1A to 7 will be omitted.

[0085] 13 is a schematic diagram of an inner peripheral surface 20D of a finger wearable device 10 according to a fourth embodiment, as viewed from the direction in which a finger is inserted and removed (z direction). The two-dimensional configuration in the xy cross section will be described below.

[0086] The inner circumferential surface 20D has an elliptical shape that reflects the cross-sectional shape of a finger. The long axis direction of the ellipse is defined as the y-direction, and the short axis direction is defined as the x-direction. The first light source 21, the second light source 22, and the light receiver 23 are arranged near one end of the short axis.

[0087] When viewed from the z direction, a perpendicular bisector L1 extending from the midpoint of the line segment having the first light source 21 and the light receiver 23 at both ends toward the space surrounded by the annular structure 20 intersects with the inner peripheral surface of the annular structure 20, and is denoted as P1. The tangent direction of the xy cross section of the inner peripheral surface of the annular structure 20 at the intersection point P1 is denoted as LT1. The angle θ formed by the perpendicular bisector L1 and the tangent direction LT1 at the intersection point P1 is １ is deviated from 90°. For example, the deviation from 90° is 5° or more. In other words, the angle between the perpendicular bisector L1 and the tangent direction LT1 at the intersection point P1 is 85° or less. By arranging the first light source 21 and the light receiver 23 so as not to have a line-symmetrical positional relationship with respect to either the minor axis or the major axis of the elliptical shape formed by the inner peripheral surface of the annular structure 20, the above-mentioned angle θ １This makes it easier to meet the conditions.

[0088] The distance from the light receiver 23 to the second light source 22 is set to, for example, 5 mm or more.

[0089] Next, the advantageous effects of the fourth embodiment will be described. The angle θ between the perpendicular bisector L1 and the tangent direction LT1 １ is deviated from 90°, the light emitted from the first light source 21 and specularly reflected at the intersection point P1 does not enter the light receiver 23. This reduces the first light reception level in the hollow state shown in FIGS. 3A to 5B. That is, the difference between the first light reception level in the hollow state and the first light reception level in the worn state increases. As a result, the accuracy of determining the worn state can be improved.

[0090] In order to sufficiently reduce the first light reception level in the hollow state, it is preferable to make the inner peripheral surface 20D of the annular structure 20 at the intersection point P1 a mirror surface.

[0091] In addition, in the fourth embodiment, by setting the distance from the light receiver 23 to the second light source 22 to 5 mm or more, the second light reception level is low when an object with low light transmittance (e.g., black cloth or white cloth) is inserted into the finger-worn device. In contrast, the second light reception level is high when the object inserted into the finger-worn device has a relatively high transmittance of light in the red to near-infrared wavelength range, such as a living body. Measuring the second light reception level makes it possible to accurately distinguish between the finger-worn state and the white cloth-inserted state or the black cloth-inserted state.

[0092] Fifth Embodiment Next, a finger wearable device according to a fifth embodiment will be described with reference to Fig. 14. Below, a description of the configuration common to the finger wearable device according to the first embodiment described with reference to Figs. 1A to 7 will be omitted.

[0093] Fig. 14 is a cross-sectional view of the finger wearable device 10 according to the fifth embodiment in a state where it is worn on a finger 80. More specifically, Fig. 14 is a cross-sectional view passing through the first light source 21 and the center of the space surrounded by the inner circumferential surface of the annular structure 20. The sensor module 30 is in close contact with the pad of the finger 80. A cross section perpendicular to the circumferential direction of the annular structure 20 at a portion of the inner circumferential surface of the annular structure 20 facing the first light source 21 is curved in a convex shape toward the space surrounded by the annular structure 20.

[0094] Light emitted from the first light source 21 and incident on the inner circumferential surface facing the first light source 21 is reflected according to the curved shape of the inner circumferential surface of the annular structure 20, and most of the reflected light travels in a direction away from the annular structure 20 in the z direction. Therefore, the amount of light incident on the light receiver 23 is reduced compared to when the inner circumferential surface is substantially flat. In other words, the first light reception level is reduced.

[0095] Next, the excellent effects of the fifth embodiment will be described. In the fifth embodiment, the first light reception level is reduced in the hollow state, and therefore, for example, in the graphs shown in Figures 3A, 4A, and 5A, the difference between the first light reception level in the worn state and the first light reception level in the hollow state becomes large. This increases the accuracy of determining the worn state. In order to enhance the effect of reducing the first light reception level in the hollow state, it is preferable to make the inner peripheral surface of the annular structure 20 facing the first light source 21 a mirror surface.

[0096] Sixth Embodiment Next, a finger wearable device according to a sixth embodiment will be described with reference to Fig. 15. Below, a description of the configuration common to the finger wearable device according to the second embodiment described with reference to Figs.

[0097] 15 is a block diagram of the finger wearable device 10 according to the sixth embodiment and external devices related to the operation of the finger wearable device 10. The finger wearable device 10 according to the sixth embodiment includes an antenna 28 and a charging circuit 42 in addition to the components of the finger wearable device 10 (FIG. 9) according to the second embodiment. The control unit 50 also includes a charging control unit 58 and a communication control unit 59 in addition to the components of the control unit 50 (FIG. 9) of the finger wearable device 10 according to the second embodiment. The functions of the charging control unit 58 and the charging circuit 42 are the same as those of the charging control unit 58 and the charging circuit 42 according to the third embodiment (FIG. 12).

[0098] The control unit 50 communicates data with external devices such as a control terminal 70 via the antenna 28. A smartphone, for example, can be used as the control terminal 70. A control application 71 for controlling the finger wearable device 10 is installed in the control terminal 70. When a user operates the control terminal 70, various commands are given from the control terminal 70 to the finger wearable device 10. Alternatively, various information acquired by the finger wearable device 10 is transferred to the control terminal 70.

[0099] The control terminal 70 communicates data with the server 72 via a network. The server 72 estimates biological information such as pulse rate, blood pressure, blood glucose level, blood flow, vascular resistance, respiratory rate, autonomic nervous state, and sleep state based on the received various information, such as pulse wave waveform information.

[0100] Next, the advantageous effects of the sixth embodiment will be described. In the sixth embodiment, a user interface is provided by the control terminal 70. Therefore, there is no need to mount a device for providing a user interface on the finger wearable device 10. Furthermore, because data communication between the finger wearable device 10 and the control terminal 70 is performed wirelessly, there is no need to connect a communication cable to the finger wearable device 10. As a result, the wearer is less likely to be restricted in their movements or actions when measuring biometric information.

[0101] Seventh Embodiment Next, a finger wearable device according to a seventh embodiment will be described with reference to Fig. 16. Below, a description of the configuration common to the finger wearable device according to the first embodiment described with reference to Figs. 1A to 7 will be omitted.

[0102] 16 is a flowchart showing the procedure of a wearing state determination process executed by the control unit 50 ( FIG. 2 ) of the finger wearable device 10 according to the seventh embodiment when biometric information is not being measured. In the seventh embodiment, the control unit 50 of the finger wearable device 10 according to the first embodiment measures the light reception level by the light receiver 23 ( FIGS. 1B and 2 ) without operating either the first light source 21 or the second light source 22 ( FIGS. 1B and 2 ) (step SC1) before measuring the first light reception level in step SA1 shown in FIG. 6 . The control unit 50 stores this measured light reception level as a non-operating light reception level. The non-operating light reception level is due to ambient light such as lighting or sunlight.

[0103] The control unit 50 of the finger wearable device 10 according to the seventh embodiment calculates a first light reception level by subtracting the light reception level when the finger wearable device is not worn from the light reception level when the first light source 21 is made to emit light (step SA1a), instead of step SA1 shown in Fig. 6. Similarly, the control unit 50 calculates a second light reception level by subtracting the light reception level when the finger wearable device is not worn from the light reception level when the second light source 22 is made to emit light (step SA3a), instead of step SA3 shown in Fig. 6.

[0104] If it is determined in step SA2 that the first light-receiving level is less than the first threshold value Th1, or if it is determined in step SA4 that the second light-receiving level is less than the second threshold value Th2, the procedure from step SC1 is repeated. Note that the first threshold value Th1 and the second threshold value Th2 are set based on the first light-receiving level and the second light-receiving level in a state where no ambient light is incident on the light receiver 23 (FIGS. 1B and 2).

[0105] The intensity of ambient light may fluctuate while biometric information is not being measured ( FIG. 6 ). For example, the intensity of ambient light fluctuates when a user wearing the finger wearable device 10 goes outdoors, or when the indoor lights are turned on while the finger wearable device 10 is placed on a table. In the seventh embodiment, the non-operating light reception level caused by ambient light is measured, and the wearing state is determined taking the non-operating light reception level into consideration. This reduces the impact of fluctuations in the intensity of ambient light, and prevents a decrease in the accuracy of the wearing state determination.

[0106] Next, a finger wearable device according to a modification of the seventh embodiment will be described. In the seventh embodiment, the non-operating light reception level is taken into consideration in the wearing state determination process performed when biological information is not being measured. Alternatively, the wearing state determination process may be performed while biological information is being measured as shown in FIG. 7, taking into consideration the non-operating light reception level. For example, it is advisable to measure the non-operating light reception level before step SB1 shown in FIG. 7.

[0107] When the non-operating light receiving level exceeds the reference level, the outputs of the first light source 21 and the second light source 22 can be increased to improve the signal-to-noise ratio. Furthermore, when the non-operating light receiving level increases further, processing can be performed to notify the user that the ambient light is too strong.

[0108] Eighth Embodiment Next, a finger wearable device according to an eighth embodiment will be described with reference to Fig. 17, Fig. 18, and Fig. 19. Below, a description of the configuration common to the finger wearable device according to the third embodiment described with reference to Fig. 11 and Fig. 12 will be omitted.

[0109] FIG. 17 is a cross-sectional view schematically illustrating a finger wearable device 10 according to an eighth embodiment. The annular structure 20 includes an inner member 20A and an outer member 20B. While one opening 20C is provided in the inner member 20A in the third embodiment ( FIG. 11 ), two openings 20C and 20E are provided in the inner member 20A in the eighth embodiment. A sensor module 30 is fitted into one opening 20C, and another sensor module 36 is fitted into the other opening 20E. While FIG. 17 illustrates the sensor modules 30 and 36 as being positioned more radially outward than the openings 20C and 20E, in reality, the sensor modules 30 and 36 are fitted into the openings 20C and 20E, respectively.

[0110] One sensor module 30 and the other sensor module 36 are connected to each other by a cable 37 arranged along the outer circumferential surface of the inner member 20A. In Fig. 17, it is shown as if there is a gap between the cables 35, 37 and the outer circumferential surface of the inner member 20A, but in reality, the cables 35, 37 are in almost intimate contact with the outer circumferential surface of the inner member 20A.

[0111] The sensor module 30 of the finger wearable device 10 according to the eighth embodiment includes a first temperature sensor 61 in addition to the components of the sensor module 30 of the finger wearable device 10 according to the first and third embodiments. The first temperature sensor 61 is mounted on the inward-facing surface of the rigid substrate 32. The surface of the first temperature sensor 61 facing the space surrounded by the annular structure 20 is covered with a resin member 25. The first temperature sensor 61 can be a thermistor or a sensor IC with peripheral circuits integrated therein.

[0112] The other sensor module 36 includes a rigid substrate 34, an acceleration sensor 40, and a second temperature sensor 62. The acceleration sensor 40 is mounted on the inward-facing surface of the rigid substrate 34, and the second temperature sensor 62 is mounted on the outward-facing surface. The acceleration sensor 40 is covered with a resin member 26, and the second temperature sensor 62 is covered with a resin member 27. The second temperature sensor 62 can be a thermistor or a sensor IC integrating peripheral circuits.

[0113] The outer member 20B faces the outer peripheral surface of the inner member 20A via the battery 41 and the cables 35 and 37. That is, the battery 41 and the cables 35 and 37 are disposed between the outer peripheral surface of the inner member 20A and the inner peripheral surface of the outer member 20B. A resin (not shown) is filled between the outer peripheral surface of the inner member 20A and the inner peripheral surface of the outer member 20B.

[0114] In this way, the first temperature sensor 61 and the second temperature sensor 62 are held by the annular structure 20. The first temperature sensor 61 is disposed at a position closer to the inner circumferential surface of the annular structure 20 than to the outer circumferential surface, and the second temperature sensor 62 is disposed at a position closer to the outer circumferential surface of the annular structure 20 than to the inner circumferential surface. The second temperature sensor 62 is thermally coupled to the outer member 20B via the resin member 27. When the finger wearable device 10 is worn on a finger, the first temperature sensor 61 is thermally coupled to the finger via the resin member 25.

[0115] The outer member 20B is formed of, for example, metal, ceramic, or the like, and has a higher thermal conductivity than the resin member 25. Examples of metals that can be used for the outer member 20B include stainless steel, titanium, tungsten, silver, gold, and platinum. The first temperature measured by the first temperature sensor 61 tends to reflect the temperature of the finger, and the second temperature measured by the second temperature sensor 62 tends to reflect the environmental temperature.

[0116] 18 is a graph showing the time change of the temperature measured by the first temperature sensor 61 and the second temperature sensor 62 and the standard deviation of the temperature within a predetermined period. The horizontal axis represents elapsed time in units of hours, the left vertical axis represents temperature in units of degrees Celsius, and the right vertical axis represents the standard deviation of the temperature in units of degrees Celsius.

[0117] The solid line T1 and dashed line T2 in the graph indicate the temperature measured by the first temperature sensor 61 (hereinafter referred to as the first temperature) and the temperature measured by the second temperature sensor 62 (hereinafter referred to as the second temperature), respectively. The solid line S1 and dashed line S2 indicate the standard deviation of the first temperature and the second temperature, respectively. The temperature sampling interval was 30 seconds (sampling frequency was 0.033 Hz). The standard deviation was calculated from measurements taken over a 5-minute period.

[0118] The sudden drop in temperature after approximately 3.6 hours is due to the wearer leaving indoors and entering a colder outdoor environment. It can be seen that the first temperature is higher than the second temperature throughout almost the entire measurement period, and the standard deviation of the second temperature is greater than the standard deviation of the first temperature. In other words, the degree of fluctuation of the second temperature is greater than the degree of fluctuation of the first temperature. Note that if the temperature sampling interval is shorter than 30 seconds, the difference in standard deviation between the first and second temperatures will be greater. For example, the sampling interval should be set to a range of 0.05 seconds to 1 second.

[0119] Next, the reason why the standard deviation of the second temperature is larger than the standard deviation of the first temperature will be explained. The second temperature sensor 62 is disposed near the outer circumferential surface of the annular structure 20, and the first temperature sensor 61 is disposed near the inner circumferential surface of the annular structure 20. Therefore, in the worn state, the second temperature is more susceptible to temperature changes in the external environment. In contrast, the first temperature is more susceptible to the temperature of the wearer's finger than the environmental temperature. Because the temperature of the finger is more stable than the environmental temperature, in the worn state, the standard deviation of the second temperature is larger than the standard deviation of the first temperature. Furthermore, in the unworn state, the first temperature and the second temperature are approximately equal, and their standard deviations are also approximately equal. The difference between the standard deviation of the second temperature and the standard deviation of the first temperature can be an indicator for determining whether or not the annular structure 20 is worn.

[0120] The ventral region of a finger has more capillaries and blood flow than the dorsal region, and therefore has a higher body surface temperature than the dorsal or lateral regions. In order to measure the temperature of the finger with the first temperature sensor 61, it is preferable to thermally couple the first temperature sensor 61 to the ventral region rather than the dorsal or lateral regions. In order to thermally couple the first temperature sensor 61 to the ventral region, it is preferable to arrange the first temperature sensor 61 near a point on the inner circumferential surface of the annular structure 20 where the sensor intersects with the minor axis. For example, it is preferable to arrange the first temperature sensor 61 at a location where the distance to the point where the inner circumferential surface of the annular structure 20 intersects with the minor axis is shorter than the distance to the point where the inner circumferential surface of the annular structure 20 intersects with the major axis.

[0121] In particular, the second temperature sensor 62 is thermally coupled to the outer member 20B (FIG. 17) via the resin member 27. Because the outer member 20B has a higher thermal conductivity than the resin member 25 that covers the first temperature sensor 61, the temperature of the outer member 20B is likely to change with changes in the external temperature. Therefore, the second temperature measured by the second temperature sensor 62 that is thermally coupled to the outer member 20B is likely to change in response to changes in the external temperature.

[0122] Furthermore, the second temperature is likely to change when some object such as a hand, clothing, or water comes into contact with the outer member 20B, when the wearer moves to a place with a different outside temperature, when the outer member 20B is exposed to air conditioning, when the outer member 20B is exposed to direct sunlight, etc. Even in such cases, the first temperature, which is more susceptible to the temperature of the finger than the temperature of the outer member 20B, fluctuates less.

[0123] In contrast, when the finger wearable device 10 is not worn, the first temperature is not affected by the finger temperature, so the first temperature and the second temperature are approximately equal, and the degree of fluctuation of the first temperature and the second temperature are also approximately the same. Therefore, when the finger wearable device 10 is worn, the degree of fluctuation of the second temperature is greater than the degree of fluctuation of the first temperature. When the finger wearable device 10 is not worn, the difference between the degree of fluctuation of the second temperature and the degree of fluctuation of the first temperature is small. Therefore, it is possible to determine the wearing state from the difference between the degree of fluctuation of the first temperature and the degree of fluctuation of the second temperature.

[0124] FIG. 19 is a flowchart showing the procedure of the wearing state determination process executed by the control unit 50 (FIG. 2) of the finger wearable device 10 according to the eighth embodiment during biological information measurement.

[0125] The procedure from step SB1 to step SB7 is the same as the procedure ( FIG. 7 ) performed by the control unit 50 of the finger wearable device 10 according to the first embodiment. In the first embodiment, when any one of the following conditions is satisfied: the first light reception level is less than the first threshold value Th1, the second light reception level is less than the second threshold value Th2, and the degree of fluctuation in the first light reception level is less than the third threshold value, the finger wearable device 10 is determined to be in an unworn state (step SB8 in FIG. 7 ).

[0126] In contrast, in the eighth embodiment, when any one of the following conditions is satisfied: the first light-receiving level is less than the first threshold value Th1, the second light-receiving level is less than the second threshold value Th2, and the degree of fluctuation in the first light-receiving level is less than the third threshold value, the degree of fluctuation (e.g., standard deviation) of the first temperature and the second temperature is calculated (step SB10). Note that the first temperature and the second temperature are measured at regular intervals.

[0127] It is determined whether the difference between the degree of fluctuation of the first temperature and the degree of fluctuation of the second temperature is equal to or greater than a fourth threshold value Th4 (step SB11). Note that, as described with reference to FIG. 18, the degree of fluctuation of the second temperature is usually greater than the degree of fluctuation of the first temperature.

[0128] If the difference between the degree of fluctuation in the first temperature and the degree of fluctuation in the second temperature is equal to or greater than the fourth threshold Th4, the finger wearable device 10 is determined to be in the worn state and continues measuring the biological information (step SB7). If the difference between the degree of fluctuation in the first temperature and the degree of fluctuation in the second temperature is less than the fourth threshold Th4, the finger wearable device 10 is determined to be in the unworn state and stops measuring the biological information (step SB8). The user is then notified that measurement of the biological information has stopped (step SB12). For example, the control terminal 70 shown in FIG. 15 is controlled to display a message on the display screen of the control terminal 70.

[0129] Next, the advantageous effects of the eighth embodiment will be described. In the eighth embodiment, the first temperature and the second temperature are used in addition to the first and second light reception levels to determine whether the device is in an unworn state during biological information measurement. This improves the accuracy of the determination. For example, in the example shown in FIG. 7 , if the determination result in any of steps SB2, SB4, and SB6 is "No" even though the device is in an unworn state, it is erroneously determined that the device is in an unworn state, and measurement of biological information is stopped. In the eighth embodiment, such erroneous determinations are less likely to occur.

[0130] Calculating the degree of temperature fluctuation takes, for example, about one minute. If temperature information is taken into account in the determination process when biological information is not being measured ( FIG. 6 ), it would take about one minute from the time the finger wearable device 10 is worn until measurement of biological information begins. In order to start measurement of biological information immediately after wearing, it is preferable not to take temperature information into account in the determination process of the wearing state when biological information is not being measured.

[0131] The above-described embodiments are merely examples, and it goes without saying that partial substitution or combination of the configurations shown in different embodiments is possible. Similar effects resulting from similar configurations of multiple embodiments will not be mentioned sequentially for each embodiment. Furthermore, the present invention is not limited to the above-described embodiments. For example, it will be obvious to those skilled in the art that various modifications, improvements, combinations, etc. are possible.

[0132] Based on the above-described embodiments described in this specification, the following invention is disclosed: <1> An annular structure configured to be wearable on a finger, a first light source and a second light source held by the annular structure and emitting light of mutually different wavelengths into a space surrounded by the annular structure, a light receiver held by the annular structure and receiving light emitted from the first light source and the second light source and reflected or scattered, and a control unit that controls the first light source and the second light source to emit light intermittently and determines whether the annular structure is worn on a finger based on a light reception level measured by the light receiver, wherein the distance from the light receiver to the second light source is longer than the distance from the light receiver to the first light source, and the control unit has a function of performing a wearing state determination process that determines that the annular structure is worn on a finger when a first light reception level by the light receiver when the first light source is caused to emit light exceeds a first threshold and a second light reception level by the light receiver when the second light source is caused to emit light exceeds a second threshold; and a function of performing a biological information measurement process to obtain biological information based on at least one of the first light reception level and the second light reception level.

[0133] <2> The finger wearing device according to <1>, wherein the control unit starts the biological information measurement process when it determines that the finger is worn in the wearing state determination process when the biological information measurement process is not being performed, and makes the interval between light emissions of the first light source and the second light source longer in the wearing state determination process when the biological information measurement process is not being performed than when the biological information measurement process is being performed.

[0134] <3> The finger wearing device according to <2>, wherein, in the wearing state determination process while the biological information measurement process is being performed, if a degree of fluctuation in the first light reception level within a predetermined period is equal to or greater than a third threshold, the control unit continues the biological information measurement process, and if the degree of fluctuation is less than the third threshold, stops the biological information measurement process.

[0135] <4> The finger wearable device according to any one of <1> to <3>, further comprising an acceleration sensor held by the annular structure, wherein the control unit, when not performing the biometric information measurement process, determines, based on acceleration measurement values ​​measured by the acceleration sensor, whether the finger wearable device is in a stationary state with the smallest acceleration measurement value, a moving state with the largest acceleration measurement value, or a non-moving state with an acceleration measurement value between the stationary state and the moving state, and performs the wearing state determination process when determining the non-moving state.

[0136] <5> The finger wearable device according to any one of <1> to <4>, wherein the control unit has a function of measuring the first light reception level and the second light reception level when the annular structure is not worn on a finger, and correcting the first threshold value and the second threshold value from the measured values ​​of the first light reception level and the second light reception level.

[0137] <6> The finger wearable device according to any one of <1> to <5>, further including: a battery that supplies power to the control unit, the first light source, and the second light source; and a charging circuit that supplies charging power to the battery, wherein the control unit controls the charging circuit to control charging of the battery, and while the battery is charging, the control unit does not operate the first light source and the second light source and determines that the finger wearable device is in an unworn state.

[0138] <7> The finger wearable device according to any one of <1> to <6>, wherein, when viewed from the insertion / removal direction into the annular structure, a point where a perpendicular bisector extending from a midpoint of a line segment having the first light source and the light receiver at both ends toward a space surrounded by the annular structure intersects with an inner surface of the annular structure is black.

[0139] <8> The finger wearable device according to any one of <1> to <7>, wherein, when viewed from the direction in which a finger is inserted into or removed from the annular structure, an angle formed by a tangent direction of the inner circumferential surface of the annular structure at a point where a perpendicular bisector extending from a midpoint of a line segment having both ends, the first light source and the light receiver, toward a space enclosed by the annular structure intersects with the inner circumferential surface of the annular structure and the perpendicular bisector of the line segment having both ends, the first light source and the light receiver, is 85° or less.

[0140] <9> The finger wearable device according to <8>, wherein the annular structure is elliptical when viewed from the direction in which a finger is inserted into or removed from the annular structure.

[0141] <10> The finger wearable device according to <8> or <9>, wherein the inner circumferential surface of the annular structure is a mirror surface.

[0142] <11> The finger wearable device according to any one of <1> to <10>, wherein the distance from the light receiver to the second light source is 5 mm or more.

[0143] <12> The finger wearable device according to any one of <1> to <11>, wherein a cross section perpendicular to the circumferential direction of a portion of an inner circumferential surface of the annular structure that faces the first light source is curved convexly toward a space surrounded by the annular structure.

[0144] <13> The finger wearable device according to any one of <1> to <12>, wherein the light emitted from the first light source includes light in a wavelength range from blue to yellow-green.

[0145] <14> The finger wearable device according to any one of <1> to <13>, wherein the light emitted from the second light source includes light in a wavelength range from red to near-infrared.

[0146] <15> The finger wearable device according to any one of <1> to <14>, further comprising an antenna held by the annular structure, wherein the control unit performs data communication with an external device via the antenna.

[0147] <16> The finger wearing device according to any one of <1> to <15>, wherein the control unit further measures a non-operating light reception level by the light receiver with the first light source and the second light source not in operation, reduces the first light reception level and the second light reception level by a light reception level corresponding to the non-operating light reception level, and performs the wearing state determination process based on the reduced light reception level.

[0148] <17> The finger wearable device according to any one of <1> to <16>, further including a first temperature sensor held by the annular structure and disposed at a position closer to an inner circumferential surface of the annular structure than to an outer circumferential surface of the annular structure.

[0149] <18> The finger wearable device according to <17>, wherein a surface of the first temperature sensor facing the space surrounded by the annular structure is covered with a resin member.

[0150] <19> The finger wearable device according to <17> or <18>, further comprising a second temperature sensor held by the annular structure and positioned closer to an outer circumferential surface of the annular structure than to an inner circumferential surface of the annular structure.

[0151] <20> The finger wearable device according to <19>, wherein the thermal conductivity of a material constituting an outer peripheral surface of the annular structure is higher than the thermal conductivity of a resin member covering the first temperature sensor.

[0152] REFERENCE SIGNS LIST 10 Finger wearable device 20 Annular structure 20A Inner member 20B Outer member 20C Opening 20D Inner peripheral surface 20E Opening 21 First light source 22 Second light source 23 Light receiver 25, 26, 27 Resin member 28 Antenna 30 Sensor module 31, 32 Rigid substrate 33 Flexible substrate 34 Rigid substrate 35 Cable 36 Sensor module 37 Cable 40 Acceleration sensor 41 Battery 42 Charging circuit 50 Control unit 51 Light emission control unit 52 Light reception level acquisition unit 53 Determination processing unit 54 Biometric information measurement unit 55 Calibration unit 57 Acceleration measurement value acquisition unit 58 Charging control unit 59 Communication control unit 61 First temperature sensor 62 Second temperature sensor 70 Control terminal 71 Control application 72 Server 80 Finger

Claims

1. An annular structure configured to be worn on a finger, A first light source and a second light source, which are held in the annular structure and emit light of different wavelengths into the space surrounded by the annular structure, A photodetector held in the annular structure, which receives light emitted from the first light source and the second light source and reflected or scattered light, A control unit that controls the first and second light sources to emit light intermittently, and determines whether or not the annular structure is attached to a finger based on the light reception level measured by the light receiver. Equipped with, The distance from the light receiver to the second light source is longer than the distance from the light receiver to the first light source. The control unit, A function to perform an attachment status determination process that determines that the annular structure is attached to a finger when the first light source is emitted and the first light reception level by the light receiver exceeds a first threshold, and the second light reception level by the light receiver when the second light source is emitted and the second light reception level exceeds a second threshold, A function to perform a biological information measurement process to obtain biological information based on at least one of the first light reception level and the second light reception level. A finger-mounted device having the following features.

2. The control unit, When the wearing state determination process is performed while the biological information measurement process is not being performed, if it is determined that the item is being worn, the biological information measurement process is started. The finger-mounted device according to claim 1, wherein in the mounting state determination process when the biological information measurement process is not being performed, the interval between the emission of light from the first light source and the second light source is longer than when the biological information measurement process is being performed.

3. The finger-mounted device according to claim 2, wherein the control unit, in the mounting state determination process when performing the biological information measurement process, continues the biological information measurement process if the degree of fluctuation of the first light reception level within a predetermined period is greater than or equal to a third threshold, and stops the biological information measurement process if it is less than the third threshold.

4. Furthermore, it is equipped with an acceleration sensor held in the annular structure, The finger-mounted device according to any one of claims 1 to 3, wherein the control unit, when not performing the biological information measurement processing, determines, based on the acceleration measurement value measured by the acceleration sensor, one of the following: a stationary state in which the acceleration measurement value is smallest, a moving state in which the acceleration measurement value is largest, and a non-moving state in which the acceleration measurement value is between the magnitude of the stationary state and the moving state, and when it determines that the state is non-moving, it performs the mounting state determination process.

5. The finger-mounted device according to any one of claims 1 to 3, wherein the control unit has a function of measuring the first light reception level and the second light reception level when the annular structure is not mounted on the finger, and correcting the first threshold and the second threshold from the measured values ​​of the first light reception level and the second light reception level.

6. moreover, The control unit, the first light source, and the battery that supplies power to the second light source, A charging circuit that supplies charging power to the aforementioned battery It is equipped with, The finger-mounted device according to any one of claims 1 to 3, wherein the control unit controls the charging circuit to control the charging of the battery, and during the charging of the battery, the first light source and the second light source are not operated, and the device is determined to be in an unmounted state.

7. The finger-mounting device according to any one of claims 1 to 3, wherein, when viewed from the direction of insertion into or removal from the annular structure, the point where the perpendicular bisector extending from the midpoint of the line segment with the first light source and the light receiver at both ends toward the space enclosed by the annular structure intersects with the inner circumferential surface of the annular structure is black.

8. A finger-wearing device according to any one of claims 1 to 3, wherein, when viewed from the direction of inserting and removing a finger from the annular structure, the angle between the tangential direction of the inner surface of the annular structure at the intersection of the perpendicular bisector extending from the midpoint of the line segment with the first light source and the light receiver at both ends toward the space enclosed by the annular structure and the inner surface of the annular structure and the perpendicular bisector of the line segment with the first light source and the light receiver at both ends and the intersection point of the two, is 85° or less.

9. The finger attachment device according to claim 8, wherein, when viewed from the direction of insertion and removal of a finger into the annular structure, the annular structure follows an ellipse.

10. The finger-wearing device according to claim 8, wherein the inner circumferential surface of the annular structure is mirror-finished.

11. The finger-mounted device according to any one of claims 1 to 3, wherein the distance from the light receiver to the second light source is 5 mm or more.

12. The finger-wearing device according to any one of claims 1 to 3, wherein the cross section of the inner circumferential surface of the annular structure, at the location facing the first light source, perpendicular to the circumferential direction, is curved convexly toward the space enclosed by the annular structure.

13. The finger-mounted device according to any one of claims 1 to 3, wherein the light emitted from the first light source includes light in the wavelength range from blue to yellow-green.

14. The finger-mounted device according to any one of claims 1 to 3, wherein the light emitted from the second light source includes light in the wavelength range from red to near-infrared.

15. Furthermore, it is equipped with an antenna held in the aforementioned annular structure, The finger-mounted device according to any one of claims 1 to 3, wherein the control unit communicates data with an external device via the antenna.

16. The finger attachment device according to any one of claims 1 to 3, wherein the control unit further measures the non-operation light reception level by the light receiver while the first light source and the second light source are not operating, reduces the light reception level from the first light reception level and the second light reception level by an amount corresponding to the non-operation light reception level, and performs the attachment state determination process based on the reduced light reception level.

17. Furthermore, the finger-mounted device according to any one of claims 1 to 3, further comprising a first temperature sensor held by the annular structure and positioned closer to the inner circumferential surface than to the outer circumferential surface of the annular structure.

18. The finger-mounted device according to claim 17, wherein the surface of the first temperature sensor facing the space surrounded by the annular structure is covered with a resin member.

19. Furthermore, the finger-mounted device according to claim 17, further comprising a second temperature sensor held by the annular structure and positioned closer to the outer circumferential surface than to the inner circumferential surface of the annular structure.

20. The finger-mounted device according to claim 19, wherein the thermal conductivity of the material constituting the outer surface of the annular structure is higher than the thermal conductivity of the resin member covering the first temperature sensor.