Low pressing force notification device

Abstract

A finger-mounted device is configured to be worn on a finger. A computer-readable program is stored in a storage medium. The finger-mounted device has a first optical sensor, a second optical sensor, and a control unit. Each of a first optical sensor and a second optical sensor includes a light-emitting unit that emits light toward the inside of the finger on which the finger-mounted device is worn, and a light-receiving unit that receives the light irregularly reflected inside the finger. The distance from the light-emitting unit to the light-receiving unit of the first optical sensor is shorter than the distance from the light-emitting unit to the light-receiving unit of the second optical sensor. The control unit operates the first optical sensor and the second optical sensor to collect light reception level measurement values. The storage medium stores a program with which, if it is detected that the pressing force at which the inner circumferential surface of the finger-mounted device is pressing the surface of the finger is lower than an appropriate range, a computer is caused to realize a low pressing force notification function for notifying a user that the pressing force is lower than the appropriate range.

Description

Low pressure notification device

[0001] The present invention relates to a low pressure force notification device that is applied to a finger-worn device.

[0002] Finger-worn devices that are worn on a finger to collect biometric information such as photoplethysmographic information are known. To collect effective photoplethysmographic information, it is preferable to keep the pressure applied by the inner circumferential surface of the finger-worn device within an appropriate range. A pulse wave signal processing device with a function for determining whether this pressure falls within the appropriate range is known (see Patent Document 1). This pulse wave signal processing device determines whether the pressure falls within the appropriate range based on a feature related to the steepness of the rising edge of the pulse wave.

[0003] International Publication No. 2023 / 233901

[0004] Conventional pressure force determination methods can detect excessive pressure, but cannot accurately detect pressure that falls below the appropriate range. When pressure falls below the appropriate range, collection of biometric information, such as photoplethysmographic information, becomes unstable. The object of the present invention is to provide a low pressure force notification device that enables stable collection of biometric information using a finger-worn device.

[0005] According to one aspect of the present invention, there is provided a low pressure force notification device comprising: a finger wearable device configured to be worn on a finger; and a storage medium storing a computer-readable program, wherein the finger wearable device has a first optical sensor, a second optical sensor, and a control unit, each of the first optical sensor and the second optical sensor including a light-emitting unit that emits light toward the inside of the finger on which the finger wearable device is worn and a light-receiving unit that receives light diffused inside the finger, wherein the distance from the light-emitting unit to the light-receiving unit of the first optical sensor is shorter than the distance from the light-emitting unit to the light-receiving unit of the second optical sensor, and the control unit operates the first optical sensor and the second optical sensor to collect light reception level measurement values, and the storage medium stores a program that causes a computer to implement a low pressure force notification function that notifies a user that the pressure force is lower than the appropriate range when it is detected that the pressure force applied by the inner surface of the finger wearable device to the surface of the finger is lower than the appropriate range.

[0006] When the user is notified that the pressure applied is lower than the appropriate range, they can take appropriate measures to adjust the pressure. By taking appropriate measures, it becomes possible to stably collect biometric information.

[0007] Fig. 1 is a block diagram of a low pressure notification device according to a first embodiment. Fig. 2A is a cross-sectional view of an internal member 20 disposed inside a finger-worn device 10 to maintain the annular shape of the finger-worn device. Fig. 2B is a cross-sectional view of several components disposed along the outer periphery of the internal member 20. Fig. 2C is a cross-sectional view of the finger-worn device 10. Fig. 3A is a graph showing the amplitude of photoplethysmograms obtained by the first optical sensor 11 and the second optical sensor 12. Fig. 3B is a graph showing the ratio of the amplitude of the photoplethysmogram obtained by the second optical sensor 12 to the amplitude of the photoplethysmogram obtained by the first optical sensor 11. Fig. 4A is a graph showing the DC components of the photoplethysmograms obtained by the first optical sensor 11 and the second optical sensor 12. Fig. 4B is a graph showing the ratio of the DC component of the photoplethysmogram obtained by the second optical sensor 12 to the DC component of the photoplethysmogram obtained by the first optical sensor 11. FIG. 5A is a graph showing temporal changes in the first amplitude and second amplitude of a photoelectric pulse wave in a low-pressure state. FIG. 5B is a graph showing temporal changes in the first DC component and second DC component of a photoelectric pulse wave in a low-pressure state. FIG. 6A is a graph showing the coefficient of variation of the first amplitude and the coefficient of variation of the second amplitude. FIG. 6B is a graph showing the ratio of the second amplitude variation coefficient to the first amplitude variation coefficient. FIG. 7A is a graph showing the coefficient of variation of the first DC component and the coefficient of variation of the second DC component. FIG. 7B is a graph showing the ratio of the second DC component variation coefficient to the first DC component variation coefficient. FIG. 8 is a flowchart showing processing procedures executed by the control unit 14 of the finger wearable device 10 ( FIG. 1 ), the processing unit 51 of the control terminal 50 ( FIG. 1 ), and the processing unit 101 of the cloud 100. FIG. 9 is a flowchart showing processing procedures executed by the control unit 14 of the finger wearable device 10 ( FIG. 1 ), the processing unit 51 of the control terminal 50 ( FIG. 1 ), and the processing unit 101 of the cloud 100. Fig. 10 is a block diagram of a low pressing force notification device according to a second embodiment. Figs. 11A and 11B are graphs showing the time change in the light receiving level measured by light receiving units 11B and 12B (Figs. 2B and 2C). Figs. 12A and 12B are graphs showing the time change in the light receiving level measured by light receiving units 11B and 12B (Figs. 2B and 2C). Figs. 13A and 13B are graphs showing the time change in the light receiving level measured by light receiving units 11B and 12B (Figs. 2B and 2C).FIG. 14 is a block diagram of a low pressure notifying device according to the third embodiment.

[0008] [First Embodiment] A low pressure force notification device according to a first embodiment will be described with reference to Figures 1 to 9. Figure 1 is a block diagram of the low pressure force notification device according to the first embodiment. The low pressure force notification device according to the first embodiment includes a finger wearable device 10, a control terminal 50, and a cloud 100.

[0009] The control terminal 50 includes a processing unit 51, an input / output unit 52, a storage medium 60, and a second communication unit 55. The processing unit 51 includes a microcontroller unit (MCU) and realizes various functions by executing programs stored in the storage medium 60. The storage medium 60 includes a non-volatile memory in which programs and the like are stored, and a volatile memory for temporarily storing various data and programs. The control terminal 50 may be, for example, a smartphone, a smartwatch, a tablet terminal, or a personal computer.

[0010] The input / output unit 52 is used to input various commands and information from the user and to notify the user of various information, and includes, for example, a touch panel, a microphone, a speaker, a vibrator, and the like.

[0011] The storage medium 60 stores a program that causes a computer to implement an input / output function 61 and a second communication function 62 .

[0012] The input / output function 61 is a function that controls the input of commands and information from the input / output unit 52 and the output of various information to the input / output unit 52. The second communication function 62 is a function that controls the second communication unit 55 to perform data communication with the finger wearable device 10 and the cloud 100. For data communication between the finger wearable device 10 and the control terminal 50, wireless communication standards such as BLE (Bluetooth Low Energy), NFC (Near Field Communication), and WiFi (Wireless Fidelity) are used. Data communication between the cloud 100 and the control terminal 50 is performed via a communication network 90, for example.

[0013] The second communication function 62 adds user information and time information to the various data received from the finger wearable device 10 and transmits the data to the cloud 100. The cloud 100 analyzes the data and transmits the analysis results to the control terminal 50. The control terminal 50, which has received the analysis results, executes the input / output function 61 to notify the user of the analysis results.

[0014] The finger wearable device 10 includes a first optical sensor 11, a second optical sensor 12, a first temperature sensor 13A, a second temperature sensor 13B, a control unit 14, a storage medium 15, a notifier 16, a battery 17, an acceleration gyro sensor 19, and a first communication unit 18. Each of the first optical sensor 11 and the second optical sensor 12 includes a light-emitting unit that emits light toward the inside of the finger on which the finger wearable device 10 is worn, and a light-receiving unit that receives light diffused and reflected inside the finger. Note that, as will be described later with reference to FIG. 2B , one light-receiving unit may be shared by the first optical sensor 11 and the second optical sensor 12.

[0015] The first temperature sensor 13A mainly measures the temperature of the finger on which the finger-worn device 10 is worn, and the second temperature sensor 13B mainly measures the temperature outside the finger-worn device 10.

[0016] The control unit 14 controls various components mounted on the finger wearable device 10 and controls communication with the control terminal 50. The control unit 14 includes a microcontroller unit (MCU) and realizes various functions by executing programs stored in the storage medium 15. The storage medium 15 includes a non-volatile memory for saving programs and the like, and a volatile memory for temporarily storing various data, programs, and the like. Note that at least a portion of these storage media may be built into the MCU.

[0017] For example, the control unit 14 has a function of operating the first optical sensor 11 and the second optical sensor 12 to collect the measured light reception level. Furthermore, the control unit 14 has a function of controlling the first communication unit 18 to transmit the measured light reception level to the control terminal 50. When a wireless communication link with the control terminal 50 is not established, the control unit 14 stores the measured light reception level in the storage medium 15. Additionally, the control unit 14 has a function of collecting measured values ​​of the finger temperature and the external temperature from the first temperature sensor 13A and the second temperature sensor 13B, a function of collecting measured values ​​of acceleration and angular velocity from the acceleration gyro sensor 19, and a function of operating the notifier 16 to notify the user of various information. For example, a light-emitting element is used as the notifier 16. The light-emitting unit of the first optical sensor 11 or the second optical sensor 12 may be used as the notifier 16.

[0018] The cloud 100 includes a processing unit 101, a storage medium 110, and a third communication unit 102. Various functions are realized by the processing unit 101 executing programs stored in the storage medium 110. The storage medium 110 stores programs that cause a computer to realize a low pressure force detection function 111, a low blood flow state detection function 112, and an attachment determination function 113. The third communication unit 102 provides data communication with the control terminal 50.

[0019] The low pressure detection function 111 is a function that detects whether the pressure with which the inner circumferential surface of the finger wearable device 10 presses the surface of the finger is lower than an appropriate range. This detection is performed based on the light reception level measurement values ​​by the first optical sensor 11 and the second optical sensor 12 received from the finger wearable device 10 via the control terminal 50. A specific example of the detection method will be described later.

[0020] When the low pressure detection function 111 detects that the pressure is lower than the appropriate range, the processing unit 51 of the control terminal 50 executes the input / output function 61 to notify the user that the pressure is low. The input / output function 61 and the low pressure detection function 111 implement the low pressure notification function 200. That is, the processing unit 101 of the cloud 100 and the processing unit 51 of the control terminal 50 execute the low pressure notification function 200 to notify the user that the pressure is lower than the appropriate range.

[0021] The low blood flow state detection function 112 is a function that detects whether the location where the finger wearable device 10 is worn is in a low blood flow state. This detection is performed based on the light reception level measurement values ​​by the first optical sensor 11 and the second optical sensor 12 received from the finger wearable device 10 via the control terminal 50. A specific example of the detection method will be described later.

[0022] When the low blood flow state detection function 112 detects a low blood flow state, the processing unit 51 of the control terminal 50 executes the input / output function 61 to notify the user that a low blood flow state exists. The input / output function 61 and the low blood flow state detection function 112 implement a low blood flow state notification function 201. That is, the processing unit 101 of the cloud 100 and the processing unit 51 of the control terminal 50 execute the low blood flow state notification function 201 to notify the user that a low blood flow state exists.

[0023] Next, the structure of the finger-worn device 10 will be described with reference to Figures 2A, 2B, and 2C. Figure 2A is a cross-sectional view of an internal member 20 that is placed inside the finger-worn device 10 and maintains the annular shape of the finger-worn device. The internal member 20 has an annular shape that follows a substantial circumference. The internal member 20 is made of, for example, a non-transparent resin such as ABS or polycarbonate. The internal member 20 is produced by injection molding.

[0024] The first opening 20A and the second opening 20B are provided at different positions in the circumferential direction of the internal member 20. The internal member 20 may have a shape that follows the outer periphery of an ellipse, or a shape that follows a closed curve without an inflection point, in addition to a circular shape. For example, a shape that follows the outer periphery of the cross-sectional shape of a human finger is preferable. The internal member 20 may also have a partially open C-shape.

[0025] 2B is a cross-sectional view of multiple components arranged along the outer periphery of internal member 20 (FIG. 2A). A wiring board consisting of rigid portions 21, 22, and 23 and flexible portions 24, 25, and 26, and battery 17 are arranged along the outer periphery of internal member 20 (FIG. 2A). Battery 17 and rigid portion 21 are connected by flexible portion 24, rigid portions 21 and 22 are connected by flexible portion 25, and rigid portions 22 and 23 are connected by flexible portion 26.

[0026] The flexible portions 24, 25, and 26 have flexibility that allows them to deform along the outer circumferential surface of the internal member 20. The rigid portions 21, 22, and 23 have higher rigidity than the flexible portions 24, 25, and 26 and do not deform easily. As a wiring board including the rigid portions 21, 22, and 23 and the flexible portions 24, 25, and 26, for example, a rigid-flexible board can be used.

[0027] Rigid portions 22 and 23 are disposed at the positions of the first opening 20A and the second opening 20B ( FIG. 2A ), respectively. A first optical sensor 11 and a second optical sensor 12 ( FIG. 1 ) are mounted on the inner peripheral surfaces of the rigid portions 22 and 23. The first optical sensor 11 includes a light-emitting portion 11A and a light-receiving portion 11B, and the second optical sensor 12 includes a light-emitting portion 12A and a light-receiving portion 12B. The light-receiving portion 12B of the second optical sensor 12 is shared with the light-receiving portion 11B of the first optical sensor 11.

[0028] The light-emitting unit 11A and the light-receiving unit 11B of the first optical sensor 11 are mounted on a rigid part 22, and the light-emitting unit 12A of the second optical sensor 12 is mounted on another rigid part 23. The distance from the light-emitting unit 11A to the light-receiving unit 11B of the first optical sensor 11 is shorter than the distance from the light-emitting unit 12A to the light-receiving unit 12B of the second optical sensor 12.

[0029] A first temperature sensor 13A and a second temperature sensor 13B are mounted on the inner peripheral surface of rigid portion 23 and the outer peripheral surface of rigid portion 21, respectively. Surface-mounted thermistors may be used as first temperature sensor 13A and second temperature sensor 13B. A control unit 14 and an acceleration gyro sensor 19 are mounted on the outer peripheral surface of rigid portion 23. Although not shown in the cross section shown in FIG. 2B , storage medium 15 and first communication unit 18 ( FIG. 1 ) are mounted on either rigid portions 21, 22, 23 or flexible portions 24, 25, 26.

[0030] 2C is a cross-sectional view of the finger wearable device 10. A wiring board consisting of rigid portions 21, 22, and 23 and flexible portions 24, 25, and 26, and a battery 17 are arranged along the outer circumferential surface of the internal member 20 and fixed to the internal member 20. The light-emitting portion 11A and the light-receiving portions 11B and 12B are arranged in the first opening 20A, and the light-emitting portion 12A and the first temperature sensor 13A are arranged in the second opening 20B. Because the internal member 20 is made of a non-translucent material, it is possible to prevent ambient light, such as illumination light or sunlight, from unintentionally entering the light-receiving portions 11B and 12B.

[0031] The internal member 20, the battery 17, and the multiple components mounted on the wiring board are covered with a transparent resin member 30. For example, epoxy resin, silicone resin, urethane resin, polycarbonate, etc. can be used as the transparent resin member 30. The inner peripheral surface of the transparent resin member 30 forms the inner peripheral surface of the finger wearable device 10. An annular outer member 31 is in close contact with the outer peripheral surface of the transparent resin member 30.

[0032] It is preferable to form raised portions 30A and 30B that are raised relative to the surrounding inner circumferential surface at positions on the inner circumferential surface of the finger wearable device 10 corresponding to the positions where the light-emitting units 11A and 12A are arranged. This improves the adhesion between the inner circumferential surface of the area where the light-emitting units 11A and 12A are arranged and the surface of the body. Furthermore, raised portions may be arranged on the inner circumferential surface at positions corresponding to the positions where the light-receiving units 11B and 12B are arranged.

[0033] Although not shown in Fig. 2C, a light-shielding wall may be disposed between the light-emitting unit 11A and the light-receiving unit 11B. By disposing the light-shielding wall, it is possible to suppress light emitted from the light-emitting unit 11A from directly entering the light-receiving unit 11B without passing through the living body. This light-shielding wall is preferably black.

[0034] The outer member 31 may be made of, for example, metal, ceramic, resin, etc. Preferably, the metal material is biocompatible and less likely to cause allergies. Examples of metal materials include stainless steel, titanium, titanium alloy, cobalt-chromium alloy, tantalum, magnesium alloy, gold, silver, platinum, etc. Examples of ceramic materials include zirconia (zirconium dioxide), aluminum nitride, aluminum oxide, silicon carbide, silicon nitride, etc. Examples of resin materials include ABS, polycarbonate, etc.

[0035] Light emitted from the light-emitting unit 11A of the first optical sensor 11 is diffused inside the finger, and a portion of the diffused light is received by the light-receiving unit 11B. Similarly, light emitted from the light-emitting unit 12A of the second optical sensor 12 is diffused inside the finger, and a portion of the diffused light is received by the light-receiving unit 12B. The change over time in the measured light reception level collected by operating the first optical sensor 11 and the second optical sensor 12 is called a photoplethysmogram. The low pressure force notifying device according to the first embodiment collects photoplethysmogram information as biological information.

[0036] The light-emitting unit 11A of the first optical sensor 11 emits light in a wavelength range from blue to near yellow-green (e.g., a wavelength range of 500 nm to 550 nm), while the light-emitting unit 12A of the second optical sensor 12 emits light in a wavelength range near red (e.g., a wavelength range of 650 nm to 700 nm) or near-infrared wavelength range (e.g., a wavelength range of 850 nm to 950 nm). These light-emitting units 11A and 12A may be, for example, light-emitting diodes (LEDs) or vertical-cavity surface-emitting lasers (VCSELs). The light-receiving units 11B and 12B may be, for example, photodiodes or phototransistors.

[0037] Since light in the wavelength range from blue to yellow-green is highly absorbed by living bodies, it is preferable to set the distance between the light-emitting unit 11A and the light-receiving unit 11B to 1 mm or more and 3 mm or less. Since light in the wavelength range around red and near-infrared light is less absorbed by living bodies, it is preferable to set the distance between the light-emitting unit 12A and the light-receiving unit 12B to 5 mm or more and 20 mm or less.

[0038] The photoelectric pulse wave information collected by operating the first optical sensor 11 contains a larger proportion of information from a region shallower than the skin, while the photoelectric pulse wave information collected by operating the second optical sensor 12 contains a larger proportion of information from a region deeper than the skin. In this way, by differentiating the wavelength of light emitted by the first optical sensor 11 and the second optical sensor 12 and the distance between the light-emitting unit and the light-receiving unit, it is possible to collect information from both a region shallower than the skin and a region deeper than the skin. Red or near-infrared light can also be used to measure oxygen saturation by utilizing the difference in absorption spectra between oxygenated hemoglobin and deoxygenated hemoglobin.

[0039] The measurement of the light reception level by the first optical sensor 11 and the measurement of the light reception level by the second optical sensor 12 are performed in a time-division manner. For example, the first optical sensor 11 and the second optical sensor 12 are alternately operated at a sampling rate in the range of 50 Hz to 1000 Hz to measure the light reception level.

[0040] To reduce power consumption, it is preferable that the first optical sensor 11 and the second optical sensor 12 collect photoplethysmographic information intermittently. Furthermore, since photoplethysmographic information is significantly affected by body movement, it is preferable that the first optical sensor 11 and the second optical sensor 12 operate when the subject is in a resting state while awake or in a sleeping state. The resting state or sleeping state can be detected based on the measurement value of the acceleration gyro sensor 19.

[0041] Next, the characteristics of photoplethysmograms collected under various conditions will be described with reference to FIGS. 3A to 7B.

[0042] Fig. 3A is a graph showing the amplitude of the photoelectric pulse wave obtained by the first optical sensor 11 and the second optical sensor 12 (Fig. 1), and Fig. 3B is a graph showing the ratio of the amplitude of the photoelectric pulse wave obtained by the second optical sensor 12 (hereinafter referred to as the second amplitude) to the amplitude of the photoelectric pulse wave obtained by the first optical sensor 11 (hereinafter referred to as the first amplitude). Fig. 4A is a graph showing the DC components of the photoelectric pulse wave obtained by the first optical sensor 11 and the second optical sensor 12, and Fig. 4B is a graph showing the ratio of the DC component of the photoelectric pulse wave obtained by the second optical sensor 12 (hereinafter referred to as the second DC component) to the DC component of the photoelectric pulse wave obtained by the first optical sensor 11 (hereinafter referred to as the first DC component).

[0043] Each column on the horizontal axis of each graph corresponds to the pressure state when photoplethysmographic information was collected, and from the left column to the right column, the pressure states applied by the inner circumferential surface of the finger wearable device 10 to the finger surface correspond to high pressure, normal pressure, and low pressure. The rightmost column corresponds to low blood flow at the location where the finger wearable device 10 is worn when the pressure state is normal.

[0044] The high pressure state was achieved by strongly bending the finger wearing the finger-worn device 10. The low pressure state was achieved by wearing a finger-worn device 10 that was larger than the finger's thickness. The low blood flow state was achieved by compressing the artery (radial artery) upstream of the finger wearing the finger-worn device 10.

[0045] The vertical axis of the graph in Figure 3A represents the amplitude of the photoplethysmogram in arbitrary units. The amplitude in this graph is the beat-by-beat amplitude of the photoplethysmogram averaged over 10 beats. The thick solid line with circles indicates the first amplitude. The thin solid line with squares and the dashed line with triangles indicate the second amplitude collected by the second optical sensor 12 using near-infrared light and the second optical sensor 12 using red light, respectively.

[0046] The vertical axis of the graph in Fig. 3B represents the ratio of the amplitudes of the photoplethysmogram. The solid line with square symbols in the graph represents the ratio of the second amplitude to the first amplitude when near-infrared light is used in the second optical sensor 12, and the dashed line with triangle symbols represents the ratio of the second amplitude to the first amplitude when red light is used in the second optical sensor 12.

[0047] The vertical axis of the graph in Figure 4A represents the DC component of the photoplethysmogram in arbitrary units. The DC component in this graph is the DC amplitude for each beat of the photoplethysmogram averaged over 10 beats. The thick solid line with circles indicates the DC component (hereinafter referred to as the first DC component) calculated based on the photoplethysmogram collected by the first optical sensor 11. The thin solid line with squares and the dashed line with triangles indicate the DC components (hereinafter referred to as the second DC component) calculated based on the photoplethysmogram collected by the second optical sensor 12 using near-infrared light and the second optical sensor 12 using red light, respectively.

[0048] 4B represents the ratio of the DC component of the photoplethysmographic wave. The solid line with square symbols in the graph represents the ratio of the second DC component to the first DC component when near-infrared light is used in the second optical sensor 12, and the dashed line with triangle symbols represents the ratio of the second DC component to the first DC component when red light is used in the second optical sensor 12.

[0049] As shown in Figure 4A, when the pressure state is low, the second DC component increases and the first DC component decreases compared to when the pressure state is high or normal. That is, as shown in Figure 4B, the ratio of the second DC component to the first DC component increases. Next, the reason for this change in the DC component of the photoplethysmogram will be explained.

[0050] When the pressure state becomes low, a gap is generated between the first optical sensor 11 or the second optical sensor 12 and the skin. When the distance from the light-receiving unit 12B to the light-emitting unit 12A is long, as in the case of the second optical sensor 12 (FIG. 2C), a larger proportion of the light emitted from the light-emitting unit 12A reaches the light-receiving unit 12B without penetrating the finger. This increases the DC component of the photoplethysmographic wave. In contrast, when the distance from the light-receiving unit 11B to the light-emitting unit 11A is short, as in the case of the first optical sensor 11 (FIG. 2C), the longer the distance from the light-emitting unit 11A and the light-receiving unit 11B to the surface of the finger, the greater the impact of the decrease in the light reception level, resulting in a decrease in the DC component of the photoplethysmographic wave.

[0051] A low pressure state can be detected based on the difference in the DC component of the photoplethysmogram between a high pressure state or a normal pressure state and a low pressure state. For example, a low pressure state can be detected when the ratio of the second DC component to the first DC component exceeds a threshold value. As can be seen from the measurement results shown in FIG. 4B, this threshold value can be set to "0.5." This function of detecting a low pressure state is realized by the low pressure detection function 111 (FIG. 1).

[0052] As shown in FIG. 3B , the ratio of the second amplitude to the first amplitude is larger in the low-pressure state than in the high-pressure state or the normal-pressure state. The low-pressure state can be detected based on the difference in the ratio of the photoelectric pulse wave amplitudes between the high-pressure state, the normal-pressure state, and the low-pressure state. For example, if the ratio of the second amplitude to the first amplitude exceeds a determination threshold, the low-pressure state can be determined. As can be seen from the measurement results shown in FIG. 3B , this determination threshold can be set to, for example, "2." Furthermore, if the second optical sensor 12 uses near-infrared light, this determination threshold can be set to approximately "3." The function of detecting the low-pressure state is realized by the low-pressure detection function 111 ( FIG. 1 ).

[0053] As shown in Fig. 3A, when the blood flow becomes low under normal pressure, both the first and second amplitudes become smaller. However, as shown in Fig. 4A, even when the blood flow becomes low, the first and second DC components hardly change.

[0054] This characteristic can be used to detect a low blood flow state. In particular, the decrease in the first amplitude is large. Therefore, when the first amplitude falls below the determination threshold, it can be determined that a low blood flow state exists. For example, under the condition that the low pressure state is not present, a determination threshold of "5" can be used when the arbitrary units shown on the vertical axis of FIG. 3A are used. Note that when a determination of whether or not a low pressure state is present is not performed, it is recommended to use a determination threshold of "1.5."

[0055] Furthermore, when the second amplitude is below a determination threshold, it may be determined that the blood flow is low. When the second amplitude is used for the determination, for example, a determination threshold of "1.5" may be used when the arbitrary unit shown on the vertical axis of FIG. 3A is used.

[0056] FIG. 5A is a graph showing the time change of the first amplitude and the time change of the second amplitude in a low pressure state. Near-infrared light was used to measure the second amplitude. The horizontal axis represents time in units of seconds, and the vertical axis represents the amplitude of the photoplethysmogram in arbitrary units. The thick and thin solid lines in FIG. 5A represent the first and second amplitudes, respectively. In FIG. 5A, the amplitude of the photoplethysmogram is calculated for each beat, and the calculated values ​​are plotted.

[0057] FIG. 5B is a graph showing the time variation of the first DC component and the time variation of the second DC component in a low pressure state. Near-infrared light was used to measure the second DC component. The horizontal axis represents time in units of seconds, and the vertical axis represents the DC component of the photoplethysmographic wave in arbitrary units. The thick and thin solid lines in FIG. 5B represent the first and second DC components, respectively. In FIG. 5B, the DC component of the photoplethysmographic wave is calculated for each beat, and the calculated values ​​are plotted.

[0058] The measurement results shown in Figure 5A indicate that the time variation of the second amplitude is larger than that of the first amplitude. The measurement results shown in Figure 5B indicate that the time variation of the second DC component is larger than that of the first DC component. The reason for this difference in time variation is considered as follows.

[0059] When a low pressure state occurs and a gap is generated between the inner circumferential surface of the finger wearable device 10 and the surface of the finger, fluctuations occur in the amount of light incident on the skin of the finger. Since the influence of fluctuations in the amount of light increases as the distance from the light receiving unit to the light emitting unit increases, it is considered that the fluctuations in the second amplitude and the second DC component become larger than the time fluctuations of the first amplitude and the first DC component.

[0060] Fig. 6A is a graph showing the coefficient of variation of the first amplitude (hereinafter referred to as the first amplitude variation coefficient) and the coefficient of variation of the second amplitude (hereinafter referred to as the second amplitude variation coefficient), Fig. 6B is a graph showing the ratio of the second amplitude variation coefficient to the first amplitude variation coefficient, Fig. 7A is a graph showing the coefficient of variation of the first DC component (hereinafter referred to as the first DC component variation coefficient) and the coefficient of variation of the second DC component (hereinafter referred to as the second DC component variation coefficient), Fig. 7B is a graph showing the ratio of the second DC component variation coefficient to the first DC component variation coefficient, where the coefficient of variation is the standard deviation divided by the average value.

[0061] The horizontal columns of the graphs shown in Figures 6A to 7B correspond to high pressure, normal pressure, and low pressure, respectively, from the left to the right, in the same way as the graphs shown in Figures 3A to 4B. The rightmost column corresponds to low blood flow at the location where the finger-worn device 10 is worn when the normal pressure is applied.

[0062] 6A represents the coefficient of variation of the amplitude of the photoplethysmogram in units of %. The thick solid line with circles indicates the first coefficient of variation of the amplitude, the thin solid line with squares indicates the second coefficient of variation of the amplitude when near-infrared light is used by the second optical sensor 12, and the dashed line with triangles indicates the second coefficient of variation of the amplitude when red light is used by the second optical sensor 12.

[0063] 6B represents the ratio of the second amplitude variation coefficient to the first amplitude variation coefficient. The solid line with square symbols represents the ratio of the second amplitude variation coefficient to the first amplitude variation coefficient when near-infrared light is used in the second optical sensor 12, and the dashed line with triangle symbols represents the ratio of the second amplitude variation coefficient to the first amplitude variation coefficient when red light is used in the second optical sensor 12.

[0064] 7A represents the coefficient of variation of the DC component of the photoplethysmographic wave in units of %. The thick solid line with circles indicates the first DC component coefficient of variation, the thin solid line with squares indicates the second DC component coefficient of variation when near-infrared light is used by the second optical sensor 12, and the dashed line with triangles indicates the second DC component coefficient of variation when red light is used by the second optical sensor 12.

[0065] 7B represents the ratio of the second DC component variation coefficient to the first DC component variation coefficient. The solid line with square symbols represents the ratio of the second DC component variation coefficient to the first DC component variation coefficient when near-infrared light is used in second optical sensor 12, and the dashed line with triangle symbols represents the ratio of the second DC component variation coefficient to the first DC component variation coefficient when red light is used in second optical sensor 12.

[0066] As shown in Fig. 6A, in the low pressure state, the second amplitude variation coefficient is larger than the first amplitude variation coefficient. Also, as shown in Fig. 6B, in the low pressure state, the ratio of the second amplitude variation coefficient to the first amplitude variation coefficient is larger than in the high pressure state or the normal pressure state.

[0067] As shown in Fig. 7A, in the low pressure state, the second DC component variation coefficient is larger than the first DC component variation coefficient, and as shown in Fig. 7B, in the low pressure state, the ratio of the second DC component variation coefficient to the first DC component variation coefficient is larger than in the normal pressure state.

[0068] Next, we consider the cause of this tendency. When the pressure is low, a gap is created between the inner circumferential surface of the finger wearable device 10 and the surface of the finger. This gap causes fluctuations in the amount of light incident on the skin of the finger. The effect of fluctuations in the amount of light is greater on the photoplethysmogram measured by the second optical sensor, which has a long distance between the light receiving unit and the light emitting unit. This is thought to be why the coefficient of variation of the amplitude of the photoplethysmogram increases when the pressure is low.

[0069] A low pressure state can be detected by utilizing such a change in the variation coefficient. For example, when the ratio of the second amplitude variation coefficient to the first amplitude variation coefficient exceeds a judgment threshold, it can be determined that the low pressure state exists. As can be seen from the measurement results shown in FIG. 6B, this judgment threshold can be set to "3." For example, when the ratio of the second DC component variation coefficient to the first DC component variation coefficient exceeds a judgment threshold, it can be determined that the high pressure state or the low pressure state exists. As can be seen from the measurement results shown in FIG. 7B, this judgment threshold can be set to "3." This function of detecting a low pressure state is realized by the low pressure detection function 111 (FIG. 1).

[0070] When the blood flow at the location where the finger wearable device 10 is worn becomes low, the blood flow becomes unstable, and the coefficient of variation of the amplitude of the photoplethysmogram increases, as shown in Fig. 6A. Green light is more absorbed by blood (hemoglobin) than near-infrared light or red light. Therefore, the first coefficient of variation of amplitude measured with green light becomes larger than the second coefficient of variation of amplitude measured with near-infrared light or red light.

[0071] This change in the coefficient of variation can be used to detect a low blood flow state. For example, if the coefficient of variation of the photoplethysmogram exceeds a predetermined threshold, it can be determined that a low blood flow state exists. As can be seen from the measurement results shown in FIG. 6A, this threshold can be set to "50%." The function of detecting this low pressure state is realized by the low pressure detection function 111 (FIG. 1).

[0072] As described above, the low pressure state can be detected based on various determination indices. For example, as described with reference to FIGS. 4A and 4B , a determination indice can be used that includes the value of the DC component of the time change in the measured light level (photoelectric pulse wave) measured by operating each of the first optical sensor 11 and the second optical sensor 12. As described with reference to FIGS. 7A and 7B , a determination indice can be used that includes the coefficient of variation of the DC component of the time change in the measured light level (photoelectric pulse wave) measured by operating each of the first optical sensor 11 and the second optical sensor 12.

[0073] 5A and 5B, it is possible to use a determination index including the amplitude of the change over time in the measured value of the level of received light (photoelectric pulse wave) measured by operating each of the first optical sensor 11 and the second optical sensor 12. As described with reference to FIGS. 6A and 6B, it is possible to use a determination index including the coefficient of variation of the amplitude of the change over time in the measured value of the level of received light (photoelectric pulse wave) measured by operating each of the first optical sensor 11 and the second optical sensor 12.

[0074] Next, an example of a procedure for detecting a pressure state and a low blood flow state will be described with reference to Fig. 8. Fig. 8 is a flowchart showing a processing procedure executed by the control unit 14 of the finger wearable device 10 (Fig. 1), the processing unit 51 of the control terminal 50 (Fig. 1), and the processing unit 101 of the cloud 100.

[0075] First, the control unit 14 of the finger wearable device 10 operates the first optical sensor 11 and the second optical sensor 12 (FIG. 1) to measure the level of received light (step SA1). By operating them for a certain period of time, photoplethysmographic information is collected. The collected photoplethysmographic information is sent to the cloud via the control terminal 50. The processing unit 101 of the cloud 100 executes the low pressure detection function 111 (FIG. 1) (step SA2).

[0076] For example, based on the photoplethysmographic information, the amplitude and DC component of the photoplethysmographic wave are calculated for each beat. When the amplitude of the photoplethysmographic wave (FIGS. 3A and 3B) is used as the determination index, the amplitude for each beat is averaged over multiple beats. For example, the average is averaged over a beat count of 5 to 20 beats. This average value can be used as the determination index. When the DC component of the photoplethysmographic wave (FIGS. 4A and 4B) is used as the determination index, the DC component for each beat is averaged over multiple beats. For example, the average is averaged over a beat count of 5 to 20 beats. This average value can be used as the determination index. Note that a statistical value other than the average, such as the median, can also be used as the determination index.

[0077] When using the coefficient of variation of the amplitude of the photoplethysmogram ( FIGS. 6A and 6B ) or the coefficient of variation of the DC component of the photoplethysmogram ( FIGS. 7A and 7B ) as a judgment index, it is advisable to calculate the coefficient of variation of the amplitude or DC component for each beat within a predetermined unit period. If this unit period is too short, the calculated value of the coefficient of variation will be unstable, and if this unit period is too long, the measurement will require a long time. This unit period should be, for example, 10 to 30 beats. The unit period may also be set in seconds rather than in beats. For example, the unit period should be set in 10 to 30 seconds. However, if the pulse rate is approximately 40 bpm, setting the unit period to 10 seconds will result in the coefficient of variation being calculated based on approximately 6 beats of the photoplethysmogram, which may result in a somewhat unstable calculated value. Therefore, if the pulse rate is approximately 40 bpm, it is advisable to set the unit period to 15 to 30 seconds.

[0078] As an example, the ratio of the DC components of the photoelectric pulse wave ( FIG. 4B ) may be used as a determination index to determine whether or not the pressure is too low. Furthermore, the coefficient of variation of the amplitude of the photoelectric pulse wave ( FIG. 6B ) may also be used in combination. By combining these two, the accuracy of the determination can be improved. In this way, a combination of multiple determination indexes may be used to detect the low pressure state.

[0079] If a low pressure state is not detected, a determination is made as to whether or not the patient is in a low blood flow state, and the determination result is output (steps SA3 and SA4). The determination as to whether or not the patient is in a low blood flow state is made by the processing unit 101 of the cloud 100 executing the low blood flow state detection function 112. The determination result is output by the processing unit 51 of the control terminal 50 executing the input / output function 61 (FIG. 1). For example, the amplitude of the photoplethysmogram (FIG. 3A) may be used as a determination index for determining whether or not the patient is in a low blood flow state.

[0080] If a low pressure state is detected, the user is notified that the pressure is lower than the appropriate range (steps SA3 and SA5). This notification is made by the processing unit 51 of the control terminal 50 executing the input / output function 61 (FIG. 1).

[0081] Next, an example of a procedure for collecting biometric information will be described with reference to Fig. 9. Fig. 9 is a flowchart showing a processing procedure executed by the control unit 14 of the finger wearable device 10 (Fig. 1), the processing unit 51 of the control terminal 50 (Fig. 1), and the processing unit 101 of the cloud 100.

[0082] Steps SB1, SB2, and SB3 are the same as steps SA1, SA2, and SA3 in the procedure shown in Figure 8. If a low pressure state is not detected, biometric information is collected (steps SB3 and SB4). The biometric information is collected by the finger wearable device 10 operating the first optical sensor 11 and the second optical sensor 12 to measure the received light level. The measured light level is transmitted to the cloud 100, where various data analyses are performed.

[0083] If a low pressure state is detected, the user is notified that the pressure is lower than the appropriate range (steps SB3 and SB5). The procedure of step SB5 is the same as the procedure of step SA5 shown in FIG.

[0084] Next, the advantageous effects of the first embodiment will be described. In the first embodiment, it is possible to detect, in a simple manner, whether the pressure is below the appropriate range without installing a dedicated sensor for measuring the pressure on the finger wearable device 10. If the pressure is below the appropriate range, the contact state between the inner circumferential surface of the finger wearable device 10 and the skin of the finger becomes unstable, reducing the stability of the collected photoplethysmographic information. In the first embodiment, as shown in FIG. 9 , biometric information is not collected when the pressure is low, but is collected when the pressure is not low (steps SB3 and SB4), thereby enabling stable collection of biometric information, such as photoplethysmographic information.

[0085] When wearing the finger wearing device 10 for the first time, the appropriate size must be selected. Finger thickness varies greatly from person to person, and for general rings, approximately 30 sizes are specified, with inner circumferences differing by 1 mm. The finger wearing device 10 is also prepared in multiple sizes with different inner circumferences. Even if the appropriate size is selected using a ring gauge, that size does not necessarily mean that it is the appropriate size for the finger wearing device 10.

[0086] In the first embodiment, the pressure state is determined based on various judgment indices obtained from actually collected photoplethysmographic information, so that an appropriate size can be selected with an emphasis on the collection of biometric information.

[0087] The finger wearable device 10 is worn on a finger by passing through a joint. Generally, the portion where the finger wearable device 10 is worn is narrower than the joint. When selecting a size that passes through a joint, when the finger wearable device 10 is worn on the wearing portion, a high pressure state is rarely encountered, and a low pressure state is more likely to occur. The first embodiment is particularly effective when determining the size of the finger wearable device 10 because it can detect a low pressure state.

[0088] Furthermore, when a low pressure state is detected (step SB3), the user is notified that the pressure is lower than the appropriate range (steps SA5 and SB5). This allows the user to adjust the pressure so that it falls within the appropriate range. For example, the user can change the finger on which the finger wearable device 10 is worn to a thicker finger. Alternatively, the user can change the finger wearable device 10 to a smaller size.

[0089] Next, a modified example of the first embodiment will be described. The low pressure notification device according to the first embodiment collects photoplethysmographic information as biometric information, but other biometric information can also be collected. The low pressure notification device according to the first embodiment can be effectively used when it is desirable to keep the pressure between the inner circumferential surface of the finger wearable device 10 and the surface of the finger within an appropriate range when collecting biometric information. For example, the low pressure notification device according to the first embodiment can be effectively used when the finger wearable device 10 is equipped with an oxygen saturation sensor, a laser Doppler blood flow sensor, or the like.

[0090] Second Embodiment Next, a low pressure notification device according to a second embodiment will be described with reference to Figures 10 to 13B. Below, a description of the configuration common to the low pressure notification device according to the first embodiment described with reference to Figures 1 to 9 will be omitted.

[0091] 10 is a block diagram of a low pressure force notification device according to the second embodiment. A storage medium 110 of a cloud 100 of the low pressure force notification device according to the second embodiment stores a program for causing a computer to implement a low pressure force detection function 111 and a low blood flow state detection function 112, as well as a program for causing a computer to implement an attachment determination function 113. The attachment determination function 113 is a function for determining whether or not the finger wearable device 10 is attached to a finger. Next, the attachment determination function 113 will be described with reference to FIGS. 11A to 13B.

[0092] 11A to 13B are graphs showing the change over time in the light receiving level measured by the light receiving units 11B and 12B (FIGS. 2B and 2C). The horizontal axis of these graphs represents time in seconds, and the vertical axis represents the light receiving level in arbitrary units. The graphs of FIGS. 11B, 12B, and 13B are enlarged versions of the vertical axes of the graphs of FIGS. 11A, 12A, and 13A, respectively. In addition, the solid lines in these graphs indicate the first light receiving level when the first optical sensor 11 is operated, and the dashed lines indicate the second light receiving level when the second optical sensor 12, which emits light in the near-infrared wavelength range, is operated.

[0093] 11A and 11B show the light reception level when the inner circumferential surface of the finger-worn device 10 is white, and the graphs from FIG. 12A to FIG. 13B show the light reception level when the inner circumferential surface of the finger-worn device 10 is black.

[0094] 11A to 12B 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 Fig. 13A and 13B 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 the device is empty, and when the device is worn.

[0095] As shown in Figures 11A, 12A, and 13A, 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 11A, 12A, and 13A, it is possible to distinguish between the hollow state and the lazy state with sufficiently high accuracy.

[0096] However, as shown in Figure 13A, 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 inserted state. This is because the intensity of light scattered by the white cloth is equal to or stronger than the intensity of light scattered by a finger. Therefore, it is not possible to distinguish between the white cloth inserted state and the wearing state by measuring only the first light reception level.

[0097] As shown in Figure 13B, 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 13B, 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 11B and 12B, the second light reception level in the worn state and the hollow state is equal to or greater than the second threshold value Th2.

[0098] 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 state in which black cloth is inserted, or a state in which white cloth is inserted, but is in a state in which it is being worn on a finger. While the drawings from Figures 11A to 13B show cases in which the inner circumferential surface of the finger wearable device 10 is white or black and the inserted cloth is white or black, if these colors are other than black or white, 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 wearing state even if these colors are other than black or white.

[0099] In the second embodiment, before executing the procedure for detecting the low pressure state, it is determined whether the finger wearable device 10 is worn on a finger. Only when it is determined that the finger wearable device 10 is worn on a finger, the procedure for detecting the low pressure state is executed.

[0100] Next, the advantageous effects of the second embodiment will be described. In the second embodiment, when the finger wearable device 10 is placed in a bag or pocket, the procedure for detecting a low pressure state is not executed. This improves the accuracy of detecting a low pressure state.

[0101] Next, a low pressure notification device according to a modification of the second embodiment will be described. In the second embodiment, the wearing state was determined based on the light reception level of the first optical sensor 11 and the second optical sensor 12 (FIG. 10). However, other methods may be used to determine the wearing state. For example, the wearing state may be determined based on the temperature measurements by the first temperature sensor 13A and the second temperature sensor 13B. For example, when the finger wearable device 10 is not worn, the temperature measurements by the first temperature sensor 13A and the second temperature sensor 13B are approximately equal. In contrast, when the finger wearable device 10 is worn on a finger, the temperature measurement by the first temperature sensor 13A (FIG. 2C), which faces the finger, tends to reflect the temperature of the finger, while the temperature measurement by the second temperature sensor 13B (FIG. 2C), which faces outward, tends to reflect the outside air temperature. The wearing state can be determined based on the difference between these temperature measurements.

[0102] [Third Example] Next, a low pressure notification device according to a third example will be described with reference to Fig. 14. Below, a description of the configuration common to the low pressure notification device according to the second example described with reference to Figs. 10 to 13B will be omitted.

[0103] 14 is a block diagram of a low pressure notifying device according to the third embodiment. In the second embodiment (FIG. 10), programs for causing a computer to implement the low pressure detection function 111, the low blood flow state detection function 112, and the attachment determination function 113 are stored in the storage medium 110 of the cloud 100. In contrast, in the third embodiment, programs for causing a computer to implement these functions are stored in the storage medium 60 of the control terminal 50. In other words, these functions are implemented by the control terminal 50.

[0104] The third embodiment also provides the same excellent effects as the second embodiment. Note that some of these functions may be implemented by the cloud 100, with the remaining functions implemented by the control terminal 50. In this case, the storage medium 110 of the cloud 100 and the storage medium 60 of the control terminal 50 constitute the storage medium of the low pressure force notification device. Alternatively, some of the functions may be implemented by the finger wearable device 10. In this case, the storage medium 110 of the cloud 100, the storage medium 60 of the control terminal 50, and the storage medium 15 of the finger wearable device 10 constitute the storage medium of the low pressure force notification device.

[0105] 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.

[0106] DESCRIPTION OF SYMBOLS 10 Finger-worn device 11 First optical sensor 11A Light-emitting unit 11B Light-receiving unit 12 Second optical sensor 12A Light-emitting unit 12B Light-receiving unit 13A, 13B Temperature sensor 14 Control unit 15 Storage medium 16 Notifier 17 Battery 18 First communication unit 19 Acceleration gyro sensor 20 Internal member 20A First opening 20B Second opening 21, 22, 23 Rigid part 24, 25, 26 Flexible part 30 Transparent resin member 30A, 30B Protruding part 31 Outer member 50 Control terminal 51 Processing unit 52 Input / output unit 55 Second communication unit 60 Storage medium 61 Input / output function 62 Second communication function 90 Communication network 100 Cloud 101 Processing unit 102 Third communication unit 110 Storage medium 111 Low pressure detection function 112 Low blood flow state detection function 113 Wearing determination function 200 Low pressure notification function 201 Low blood flow state notification function

Claims

1. A low pressure notification device comprising: a finger wearable device configured to be worn on a finger; and a storage medium storing a computer-readable program, wherein the finger wearable device has a first optical sensor, a second optical sensor, and a control unit, wherein each of the first optical sensor and the second optical sensor includes a light-emitting unit that emits light toward the inside of the finger on which the finger wearable device is worn, and a light-receiving unit that receives light diffused inside the finger, wherein the distance from the light-emitting unit to the light-receiving unit of the first optical sensor is shorter than the distance from the light-emitting unit to the light-receiving unit of the second optical sensor, wherein the control unit operates the first optical sensor and the second optical sensor to collect measured light reception level measurements, and wherein the storage medium stores a program that causes a computer to realize a low pressure notification function that notifies the user that the pressure applied by the inner surface of the finger wearable device to the surface of the finger is lower than an appropriate range when it is detected that the pressure applied by the inner surface of the finger wearable device to the surface of the finger is lower than the appropriate range.

2. The low pressure notification device according to claim 1, wherein the light receiving portion of the first optical sensor also serves as the light receiving portion of the second optical sensor.

3. The low pressure notification device of claim 1 or 2, wherein the low pressure notification function includes a function of calculating a judgment index based on the light reception level measurement value measured by operating each of the first optical sensor and the second optical sensor, and detecting that the pressure is lower than the appropriate range based on the judgment index.

4. The low pressure notification device described in claim 3, wherein the judgment index includes a calculated value of a DC component calculated from the change over time in the measured light reception level value measured by operating each of the first optical sensor and the second optical sensor.

5. A low pressure notification device as described in claim 3, wherein the judgment index includes a coefficient of variation of the DC component calculated from the change over time in the measured light reception level value measured by operating each of the first optical sensor and the second optical sensor.

6. A low pressure notification device as described in claim 3, wherein the judgment index includes a calculated value of amplitude calculated from the change over time in the measured light reception level value measured by operating each of the first optical sensor and the second optical sensor.

7. A low pressure notification device as described in claim 3, wherein the judgment index includes an amplitude variation coefficient calculated from the change over time in the light reception level measurement value measured by operating each of the first optical sensor and the second optical sensor.

8. The storage medium further stores a program that causes a computer to implement a low blood flow state notification function that, when the low pressure notification function determines that the pressure is within the appropriate range and the amplitude of the change over time in the light reception level measured by at least one of the first optical sensor and the second optical sensor is equal to or less than a first threshold, determines that the location where the finger-worn device is worn is in a low blood flow state and notifies the user of the determination result. A low pressure force notification device as described in any one of claims 1 to 7.

9. The storage medium stores a program that causes a computer to realize a wear determination function that determines whether the finger wear device is worn on a finger, and if the wear determination function determines that the finger wear device is not worn on a finger, a low pressure force notification function does not make a determination. A low pressure force notification device as described in any one of claims 1 to 8.

10. The control unit has a function of collecting biometric information from the light reception level measurement value measured by operating at least one of the first optical sensor and the second optical sensor, and if the low pressure force notification function detects that the pressure is lower than the appropriate range before starting to collect the biometric information, the low pressure force notification device described in any one of claims 1 to 9 does not collect the biometric information.

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