JP7655609B2 - Smart Ring and Smart Ring System - Google Patents

Description

The present invention relates to a smart ring and a smart ring system.

Photoplethysmography is a method that uses a volume pulse wave sensor consisting of an LED light source and a photodetector to detect changes in the volume of blood in capillaries caused by perfusion. The light source used is an LED that emits light in the visible to near-infrared range. It is possible to detect volume pulse waves from changes in absorbance that accompany changes in the amount of hemoglobin in the blood vessels. Light from the LED light source is irradiated onto the skin, and the diffuse reflected light or transmitted light is measured.

By analyzing the volume pulse waves detected by the photoplethysmography method, it is possible to estimate pulse rate and blood oxygen saturation. In addition, in recent years, research has been reported that it is also possible to estimate blood pressure and blood sugar levels.

Pulse wave sensors are made of inexpensive elements and are non-invasive. For this reason, they are used in many consumer products such as smartphones, smart watches, and wearable devices (e.g., Patent Document 1). Many of these devices calculate the pulse rate from the pulse wave detected using a light source with a wavelength of 500 nm to 600 nm.

Pulse wave sensors are also used in medical devices such as blood oxygen concentration meters. Blood oxygen concentration meters use two wavelength light sources, 630-690 nm and 810-990 nm, to calculate the blood oxygen saturation level from the ratio of absorbance at each wavelength of oxygenated hemoglobin and deoxygenated hemoglobin.

A method has also been proposed for detecting the concentration of glycated hemoglobin in blood using a volume sensor. Using a light source with three or four wavelengths in the wavelength range of 600 nm to 990 nm, the concentration of glycated hemoglobin in blood is calculated from the absorbance ratio of oxyhemoglobin, deoxyhemoglobin, and glycated hemoglobin.

There are two main methods of photoplethysmography: the reflective diffuse method and the transmissive method. In the reflective diffuse method, light from an LED light source is irradiated onto the skin, and the reflected and diffused light from the skin is detected by a photodetector. Therefore, with the reflective diffuse method, the volume pulse wave sensor can be applied anywhere on the body, such as the wrist or forehead. In the transmissive method, light is emitted from an LED light source, and the light that passes through the biological tissue is detected by a photodetector on the skin surface on the back side of the emission surface. Therefore, it is used in places where the tissue is relatively thin, such as the fingertips. Attempts have also been made to use it on the earlobe.

The reflective diffusion method is more susceptible to external disturbances than the through-transmission method. The reflective diffusion method detects the absorbance of hemoglobin in blood from terminal arterioles with diameters of 17 to 26 microns that exist in the papillary dermis, and from arterioles with diameters of 150 to 242 microns that exist at the junction of the dermis and subcutaneous tissue. The blood flow velocity and shear rate of these terminal arterioles are relatively easily reduced by external pressure, so the volume pulse wave shape changes with external pressure. On the other hand, the through-transmission method is less susceptible to external pressure because it measures the absorbance of hemoglobin in blood from relatively large arterioles with diameters of around 1 mm that are located deep in the subcutaneous tissue.

Given the above theoretical background, in order to measure volume pulse waves more accurately using photoplethysmography, a transmission method that can access large arterioles is desirable. In recent years, in addition to medical devices that measure fingertips, there are also consumer products equipped with volume pulse wave sensors that target the base of the finger or the earlobe.

U.S. Patent No. 10,893,833 (U.S. Patent Application Publication No. 2018/0103902)

For example, in the device described in Patent Document 1, an appropriate light-emitting element or light-receiving element is selected depending on the distance between the sensor module and the part of the body worn by the user. However, after the light-emitting element or light-receiving element is selected, the distance between the device and the part of the body worn by the user may change due to the user's movement, etc., and the selected light-emitting element or light-receiving element may no longer be appropriate.

Therefore, the object of the present invention is to provide a smart ring and a smart ring system that can accurately measure volume pulse waves.

In order to achieve the above object, a smart ring according to a first aspect of the present invention comprises:
a first light source that irradiates a finger via a first optical element; a first photodetector that receives light emitted from the first light source or another light source via a second optical element and acquires a volume pulse wave; and a housing through which the finger is inserted;
The first and second optical elements are arranged to surround the first light source and the first photodetector, respectively, and protrude from a main surface of the housing on the side where the finger is inserted, toward the finger.

In addition, it is preferable that a first angle formed between the position where the first light source is located, the center point of the ring hole, and the position where the first photodetector is located is greater than 60° and less than 105°.

a second photodetector that receives the light emitted from the first light source or another light source via a third optical element;
the third optical element is disposed to surround the second photodetector,
a second angle formed by a position where the first light source is disposed, the center point, and a position where the second photodetector is disposed is greater than 60° and less than 105°;
It is advisable to select the signal obtained from the photodetector with the highest received light intensity to obtain the volume pulse wave.

The first, second and third optical elements may include aspherical mirrors that focus the light.

In addition, the first, second and third optical elements may further include at least one of a lens, a filter and a prism that focus the light.

A first central angle formed by a predetermined base point on the inner surface of the smart ring, the center point, and the position where the first light source is located is greater than a second central angle formed by the base point, the center point, and the position where the first photodetector is located, and is smaller than a third central angle formed by the base point, the center point, and the position where the second photodetector is located.

the first light source is an LED array light source composed of a plurality of LEDs having different peak wavelengths;
The first and second photodetectors may have different peak wavelengths within their wavelength ranges of light sensitivity.

The plurality of LEDs may include one or more LEDs having a peak wavelength in the range of 500-550 nm, two or more LEDs having a peak wavelength in the range of 600-800 nm, and one or more LEDs having a peak wavelength in the range of 900-1000 nm.

After each specified time, the signal obtained from the photodetector with the highest received light intensity is selected to obtain the volume pulse wave.

The aspherical mirror may be a parabolic mirror in which the end of the parabolic curved surface on the side where the light enters or exits coincides with the starting point of the parabolic curved surface of the mirror.

a second light source that illuminates the finger through a fourth optical element;
A fourth central angle formed by the base point, the center point, and the position where the second light source is disposed is greater than a first angle obtained by adding a fifth central angle formed by the first light source, the center point, and the position where the first photodetector is disposed to the second central angle, and is greater than a second angle obtained by adding a sixth central angle formed by the position where the second light source is disposed, the center point, and the position where the second photodetector is disposed to the second central angle.

The first and second light sources may have opposite pulse-on and pulse-off times.

A smart ring system according to a second aspect of the present invention comprises:
The smart ring;
and an electronic device that receives the volume pulse wave from the smart ring via wireless communication.

According to the present invention, volume pulse waves can be measured with high accuracy.

FIG. 1 is a perspective view of a smart ring according to an embodiment of the present invention. 1 is a side cross-sectional view of a smart ring according to an embodiment of the present invention. 1 is a front cross-sectional view of a smart ring according to an embodiment of the present invention, with the inner housing omitted when the smart ring is worn on a finger. FIG. FIG. 1 is a block diagram of a smart ring system according to an embodiment of the present invention. 1 is a perspective view of an optical element according to an embodiment of the present invention. 1 is a longitudinal sectional view of an optical element according to an embodiment of the present invention. 1 is a cross-sectional view of an optical element according to an embodiment of the present invention taken along an XY plane, with the right half indicated by a dashed dotted line. 2 is a cross-sectional view of an optical element according to an embodiment of the present invention taken along a ZY plane, with the right half indicated by a dashed dotted line. 1 is a front cross-sectional view of a smart ring according to a first embodiment, in which an optical element is omitted. FIG. FIG. 2 is a side view of the smart ring according to the first embodiment, in which the optical element is omitted. 1 is a flowchart of a signal acquisition process 1 performed in a smart ring according to a first embodiment. FIG. 11 is a front cross-sectional view of a smart ring according to a second embodiment, in which the optical element is omitted. FIG. 11 is a side view of a smart ring according to a second embodiment, in which the optical element is omitted. 13A and 13B are diagrams illustrating drive timings of the PD and the light source of the smart ring according to the second embodiment. 13 is a flowchart of a signal acquisition process 2 performed in a smart ring according to a second embodiment. FIG. 11 is a front cross-sectional view of a smart ring according to a third embodiment, in which the optical element is omitted. FIG. 11 is a side view of a smart ring according to a third embodiment, in which the optical element is omitted. 13A and 13B are diagrams illustrating drive timings of the PD and the light source of the smart ring according to the third embodiment. 13 is a flowchart of a signal acquisition process 3 performed in a smart ring according to the third embodiment. 13 is a side cross-sectional view of a smart ring according to a modified example of the present invention. 13 is a side cross-sectional view of a smart ring according to another modified example of the present invention. FIG. FIG. 13 is a diagram showing the radiation distribution of a light source of a smart ring when no optical element is attached to the light source. 13 is a diagram showing the radiation distribution of a light source when an optical element is attached to the light source of a smart ring. 11A and 11B are diagrams illustrating the received light intensity of a PD depending on the positional relationship between the PD and a light source. 11 is a diagram showing the AC/DC ratio of light received by a PD depending on the positional relationship between the PD and a light source. FIG.

The smart ring system according to an embodiment of the present invention will be described below with reference to the attached drawings. Note that the x, y and z directions in the description follow the arrows in each figure. Also, the same reference numerals are used for the same or equivalent parts.

As shown in Figures 1A, 1B, 2, etc., the smart ring system 1 of an embodiment of the present invention non-invasively measures a user's heart rate, blood oxygen concentration, body surface temperature, etc. by a smart ring 10 inserted on the user's finger 200.

[First embodiment]
As shown in FIG. 2 and FIG. 3, the smart ring system 1 according to the first embodiment of the present invention includes a smart ring 10 inserted into a user's finger 200, and a host device 300 that receives data on the user's volume pulse wave acquired by the smart ring 10 via wireless communication. The smart ring 10 acquires a volume pulse wave acquired from a photodetector (hereinafter referred to as PD (Photo Detector)) 40, 41 that receives light from a light source 30 that emits light of multiple wavelengths toward the user's finger 200 inserted into the smart ring 10, and calculates the user's heart rate, blood oxygen concentration, body surface temperature, etc. with high accuracy from the acquired volume pulse wave. Since the user lives a daily life while wearing the smart ring 10, the smart ring 10 may rotate in the circumferential direction of the finger 200 when the user works, does housework, exercises, etc., and the positions of the light source 30 and the PDs 40, 41 may move to positions that are not suitable for measuring the volume pulse wave. To prevent this, as shown in Figures 1A, 1B, and 2, the optical elements 50 and 51 of the smart ring 10, which are arranged to surround the light source 30 and the PD 40 and 41, respectively, protrude from the main surface 24 of the inner housing 22 on the side where the user's finger 200 is inserted toward the user's finger 200. Here, the main surface 24 refers to a portion that corresponds to the part or surface (including a curved surface) on the side where the user's finger 200 is inserted in a normal ring that does not have the light source 30, the PD 40 and 41, or the optical elements 50 and 51. Since the optical elements 50 and 51 protrude from the main surface 24, by pressing the user's finger 200, the optical elements 50 and 51 can be closely attached to the user's finger 200, and the smart ring 10 can be maintained in a fixed state at a predetermined position on the user's finger 200, making it difficult for the smart ring 10 to slip off. Note that the optical element 51 actually protrudes from the main surface 24, but in Figure 2, it is depicted as not protruding in order to make the figure easier to see. In addition, in the cross-sectional views of the smart ring 10 (or 11, 12) from FIG. 6A onwards, the optical elements 50, 51 themselves are omitted for ease of understanding and to make the drawings easier to see.

(Configuration of smart ring 10)
Externally, the smart ring 10 comprises a housing 20 that houses a light source 30 and PDs 40 and 41, a light source 30 that emits light having multiple peak wavelengths, PDs 40 and 41 that receive the light emitted by the light source 30, optical elements 50 and 51 that collect the light emitted by the light source 30, and a substrate 60 on which various electronic components are mounted.

The housing 20 has an outer housing 21 that forms the outside of the smart ring 10, and an inner housing 22 that forms the inside of the smart ring 10. The outer housing 21 is a ring made of metal, for example titanium, with a substantially U-shaped cross section, and is integrated with the inner housing 22 to form the outer shape of the smart ring 10. A decorative part 23 is formed on a part of the outside of the outer housing 21. The decorative part 23 is located on the back of the hand when the user inserts the smart ring 10 onto the finger 200, enhancing the decorativeness of the smart ring 10 and making it easier for the user to place the smart ring 10 in a position suitable for measuring the volume pulse wave. The inner housing 22 is made of a transparent resin that has a high transmittance of light with a wavelength of 400-1000 nm. The inner housing 22 is formed inside the outer housing 21 with the light source 30, the light receiving elements 40, 41, the optical elements 50, 51, and the substrate 60 arranged in predetermined positions within the outer housing 21. The inner housing 22 protrudes toward the center point C of the ring hole so as to cover the optical elements 50, 51, but the center of the protruding portion may be recessed or flat, or there may be a mixture of protruding and non-protruding portions.

The light source 30 is an LED (Light Emitting Device) and is surface mounted on the substrate 60. The light source 30 has a peak wavelength between 400-1000 nm. The light source 30 is also one of the components of the multi-wavelength PPG (Photoplethysmography) sensor 141 described below. The light source 30 is arranged in a position that is point-symmetric with respect to the base point BP at the +y direction end inside the housing 20 and the -y direction end inside the housing 20, with the ring hole center point C as the reference point.

The photodetectors 40 and 41 are light receiving elements that receive light emitted from the light source 30 and transmitted and diffusely reflected by the soft tissue of the user's finger 200. In this embodiment, the photodetectors 40 and 41 are PIN type photodiodes. The photodetectors 40 and 41 have light receiving sensitivity in a wavelength range that includes the peak wavelength of the light emitted by the light source 30. The photodetectors 40 and 41 are one of the components of the multi-wavelength PPG sensor 141 described later, and are mounted on the substrate 60.

The optical elements 50 and 51 are parabolic mirrors, which are one of aspheric mirrors, arranged on the substrate 60 so as to surround the light source 30 and the PDs 40 and 41. The optical elements 50 and 51 have a parabolic curved surface 54, at which the light is incident or emitted, and an end of the light condensing surface 54 coincides with a starting point 55 of the parabolic curved surface of the mirror. When the light source 30 and the PDs 40 and 41 are in a predetermined positional relationship described later, the optical elements 50 and 51 condense the light emitted by the light source 30, improving the accuracy of acquiring the volume pulse wave. In this embodiment, the optical element 50 protrudes more toward the user's finger 200 inserted into the ring hole than the optical element 51. As shown in FIG. 4A and FIG. 4B, the optical elements 50 and 51 have a main body 52, an attachment 53, a condensing surface 54, and a starting point 55. A hole penetrates the center of the main body 52, and a mounting portion 53 is formed on one side of the hole, and a light collecting surface 54 is formed on the other side of the hole. Either the light source 30 or the PD 40, 41 is attached to the mounting portion 53. The light collecting surface 54 is adjusted by translating a parabolic surface function x ² = 4·0.4·(y-0.4) in each axial direction, and has a focal length f = 0.4 mm. As shown in Figures 5A and 5B, the starting point 55 is set on the main body 52 so that the parabolic surface obtained by extending the light collecting surface 54 in each of the XY plane and the ZY plane passes as close as possible to the light emitting portion 35 of the light source 30, thereby forming the light collecting surface 54, and the dimension of the optical elements 50, 51 in the Y direction is kept small.

The board 60 is installed across both ends of the approximately U-shaped portion of the outer housing 21. On the inner housing 22 side of the board 60, the light source 30, the PDs 40 and 41, the optical elements 50 and 51, and a charging IC (Integrated Circuit) 61 (described later) are arranged. On the inside of the recess in the approximately U-shaped portion of the board 60, the MCU (Micro Computer Unit) 100 (described later), various sensor ICs, various sensor elements, and a power management IC 62 are mounted.

As shown in Figure 3, in addition to the above configuration, the smart ring 10 has a sensor unit 140, an alarm unit 150, and a power supply unit 160. The MCU 100 also has a control unit 110, a memory unit 120, and a communication unit 130.

The MCU 100 is a microprocessor-based controller IC. The MCU 100 is equipped with a microprocessor, inputs and outputs required for controlling the smart ring 10, and memory for storing programs and data.

The control unit 110 is composed of a CPU (Central Processing Unit) etc., and by executing a program stored in the memory unit 120, realizes the functions of each unit described below (light source control unit 111, PD control unit 112, measurement unit 113, selection/collection unit 114).

The memory unit 120 is composed of a ROM (Read Only Memory), a RAM (Random Access Memory), etc., and includes a setting memory unit 121 and a measurement result memory unit 122. The ROM stores programs executed by the CPU of the control unit 110 and data required in advance to execute the programs. The RAM stores data that is created or changed during program execution.

The setting memory unit 121 stores various settings (e.g., a light receiving intensity measurement period for measuring the light receiving intensity of the PD, a signal collection period for acquiring measurement values from a selected PD, etc.) described below.

The measurement result memory unit 122 stores the measurement results measured using the various sensors included in the sensor unit 140. The stored measurement results are transmitted to the host device 300 by wireless communication via the communication unit 130.

The communication unit 130 is a module for wireless communication with the host device 300. The communication device 131 performs wireless communication with the host device 300 based on, for example, Bluetooth (registered trademark).

The sensor unit 140 has a multi-wavelength PPG sensor 141, a gyro sensor 142, an acceleration sensor 143, a temperature sensor 144, a millimeter wave sensor 145, a microwave sensor 146, and an optical sensor 147. The multi-wavelength PPG sensor 141 detects the user's volume pulse wave using the light source 30 as a light source and the photodetectors 40 and 41 as light receiving elements. The gyro sensor 142 measures the inclination and measures the user's exercise amount. The acceleration sensor 143 is used, for example, to calculate the pace when running. The temperature sensor 144 measures the user's body temperature, outside temperature, etc. The millimeter wave sensor 145 is used for motion detection and distance measurement functions. The microwave sensor 146 is used to measure the user's breathing, heart rate, body movement, etc. The optical sensor 147 is used for the (long-distance) distance measurement function.

The notification unit 150 is used to notify the user when the rechargeable battery 162 of the smart ring 10 falls below a predetermined remaining charge. The notification device 151 emits an alarm to notify the user when the rechargeable battery 162 falls below a predetermined remaining charge.

The power supply unit 160 has a power supply monitoring unit 161, a rechargeable battery 162, and a charging receiver 163. The power supply unit 160 charges the smart ring 10 from the charging device 400, for example, by NFC (Near Field Communication) wireless charging. The rechargeable battery 162 is a lithium polymer battery arranged inside the recess in the approximately U-shaped portion of the outer housing 21. The rechargeable battery 162 is wirelessly powered from the charging transmitter 401 of the charging device 400 via the power supply monitoring unit 161 and the charging receiver 163.

Next, the functions of the control unit 110 will be described. The control unit 110 includes a light source control unit 111, a PD control unit 112, a measurement unit 113, and a selection and collection unit 114, and executes signal acquisition processes 1-3 and the like, which will be described later.

The light source control unit 111 controls the ON/OFF of the light sources 30 and 31 (light source 31 will be described in the third embodiment). When the smart ring 10 (10, 11, 12) is inserted on the user's finger 200, the light source control unit 111 causes the light source 30 (31) to emit light. The light source control unit 111 also stops one of the light sources 30 and 31 for a certain period of time.

The PD control unit 112 controls ON/OFF of the PDs 40 and 41 (in the second embodiment, PDs _{40 1} , 40 ₂ , ..., 40 _N-1 , and 40 _N ). When the smart ring 10 is inserted on the user's finger 200, the PD control unit 112 drives the PDs 40 and 41 (in the second embodiment, PDs _{40 1} , 40 ₂ , ..., 40 _N-1 , and 40 _N ). In addition, the PD control unit 112 stops one of the light sources 30 and 31 (in the second embodiment, among PDs _{40 1} , 40 ₂ , ..., 40 _N-1 , and 40 _N , other than the PD that received the maximum amount of light) for a certain period of time.

The measurement unit 113 uses various sensors of the sensor unit 140 to measure the user's volume pulse wave, blood oxygen saturation, blood glycated hemoglobin concentration, etc., and stores the measurement results in the measurement result memory unit 122.

The selection and collection unit 114 selects which PD to use for the measurement based on the measurement results stored in the measurement result memory unit 122, and collects the measurement results from the selected PD.

(Other configurations)
In this embodiment, the host device 300 is a smartphone. By downloading a dedicated app or the like, the volume pulse wave data received from the smart ring 10 can be viewed, analyzed, etc. The host device may be an electronic device such as a tablet, a PC (Personal Computer), a router, etc.

The charging device 400 is a device for wirelessly charging the smart ring 10. The smart ring 10 can be charged by abutting the charging receiver 163 against the charging transmitter 401.

(Structure of smart ring 10)
As shown in Figures 6A and 6B, the smart ring 10 has a light source 30 disposed on the inner housing 22 opposite to the base point BP, passing through the ring hole center point C from the base point BP on the inner housing 22 side of the circumferential center of the decorative part 23 of the smart ring 10. Here, the angle formed by the line segment connecting the base point BP, the ring hole center point C, and the PD40 (front view, clockwise, the same for subsequent angles) is θ1, the angle formed by the line segment connecting the base point BP, the ring hole center point C, and the light source 30 is θ2 (= 180 °), and the angle formed by the line segment connecting the base point BP, the ring hole center point C, and the PD41 is θ3. The PD40 is disposed so that the angle θ2-θ1 formed by the line segment connecting the light source 30, the ring hole center point C, and the PD40 is a predetermined value in the range of 60 ° < θ2-θ1 < 105 °. PD41 is disposed so that the angle θ3-θ2 formed by the line segment connecting the light source 30, the ring hole center point C, and PD41 is a predetermined value in the range of 60°<θ3-θ2<105°. θ2-θ1=θ3-θ2. The basis for 60°<θ2-θ1<105° and 60°<θ3-θ2<105° will be explained in the examples described later.

(Method of acquiring volume pulse wave using smart ring 10)
Signal acquisition process 1, which is executed by the smart ring 10 of the smart ring system 1 to acquire the user's volume pulse wave with high accuracy, will be described with reference to FIG.

The smart ring 10 is inserted onto the user's finger 200, and the light source control unit 111 causes the light source 30 to emit light having a predetermined wavelength, in this embodiment a peak wavelength between 400-1000 nm (step S1).

In synchronization with the driving of the light source 30, the PD control unit 112 drives the PDs 40 and 41. The light emitted from the light source 30 is transmitted and diffusely reflected by the soft tissue of the user's finger 200 and is received by the PDs 40 and 41. The measurement unit 113 measures the light intensity T1 at the PD 40 during the light intensity measurement period (step S2), and also measures the light intensity T2 at the PD 41 during the light intensity measurement period (step S3).

The selection and collection unit 114 determines whether the received light intensity T1 is greater than the received light intensity T2 (step S4), and if T1>T2 (step S4; Yes), collects a signal from PD40 during the signal collection period (step S5) and transmits it to the host device 300, and if T1>T2 is not true (step S4; No), collects a signal from PD41 during the signal collection period (step S6) and transmits it to the host device 300.

Proceed to step S7. If the user removes the smart ring 10 from the finger 200 or the remaining charge of the rechargeable battery 162 is insufficient, terminate the signal acquisition process 1 (step S7; Yes); if not (step S7; No), return to step S1.

As described above, in the smart ring 10 used in the smart ring system 1, the angle formed by the light source 30, the ring hole center point C, and each of the PDs 40 and 41 is in a position that is greater than 60° and less than 105°, so that the AC (Alternate Current)/DC (Direct Current) ratio can be improved. In addition, the optical elements 50 and 51 arranged to surround the light source 30 and the PDs 40 and 41 protrude so as to press against the user's finger 200, so that the smart ring 10 can be prevented from rotating in the ring circumferential direction even when the user is working, doing housework, exercising, etc. Furthermore, in the smart ring system 1, the signal of the PD that has a higher light reception intensity from the light source 30 out of the two PDs is collected at regular intervals, so that the volume pulse wave can be accurately measured even if the smart ring 10 rotates in the ring circumferential direction on the user's finger 200 as the user works, does housework, exercises, etc.

[Second embodiment]
8A and 8B, in the second embodiment, instead of the two PDs 41 and 42 in the first embodiment, N PDs _{40 1} , 40 ₂ , ..., 40 _N-1 , and 40 _N are arranged in the smart ring 11, and all the PDs are driven simultaneously to receive light. Another difference from the first embodiment is that the light source 31 is an LED array light source.

The light source 31 comprises a number of LEDs with different peak wavelengths λ ₁ , λ ₂ , . . . , λ _n , at least between 500-550 nm, between 600-800 nm, and between 900-1000 nm.

For PDs _{40 1} , 40 ₂ , ..., 40 _N-1 , 40 _N , the angles formed by the base point BP, the ring hole center point C, and each PD are θ ₁ , θ ₂ , ..., θ _N-1 , and θ _N. For light source 31, the angle formed by the base point BP, the ring hole center point C, and light source 31 is θ _L. Furthermore, θ ₁ < θ ₂ < ... < θ _L < ... < ... < θ _N-1 , < θ _N. In the smart ring 11, the absolute values of θL- _θ1 , _θL - _θ2 , _θL - _{θ2 ,} ..., _θL - _θN-1 , _θL - _θN are each greater than 60° and less than 105° (note that in Figs. 8A and 8B, light sources 31 and PDs are also placed at positions less than 60° and greater than 105° to make the drawings easier to see). The other configurations are the same as those in the first embodiment.

As shown in Figure 9, the signal acquisition process 2 executed by the smart ring 11 differs from the first embodiment in that, during the signal collection period, PDs other than the PD that showed the maximum light receiving intensity during the light receiving intensity measurement period are stopped.

(Method of acquiring volume pulse wave using smart ring 11)
The signal acquisition process 2 executed by the smart ring 11 of the smart ring system 1 will be described with reference to FIG.

The smart ring 11 is inserted on the user's finger 200, and the light source control unit 111 causes the light source 31 to emit light having predetermined wavelengths, in this embodiment, different peak wavelengths λ ₁ , λ ₂ , ..., λ _n having peak wavelengths at least between 500-550 nm, 600-800 nm, and 900-1000 nm (step S11).

In accordance with the driving of the light source 31, the PD control unit 112 simultaneously drives all of the PDs _{40 1} , 40 ₂ , ..., 40 _N-1 , and 40 _N. The light emitted from the light source 31 is transmitted and diffusely reflected by the soft tissue of the user's finger 200 and is received by the PDs _{40 1} , 40 ₂ , ..., 40 _N-1 , and 40 _N. The measurement unit 113 measures the received light intensities T ₁ , T ₂ , ..., T _{N-1 ,} and T _N at the PDs 40 ₁ , 40 2 , ..., 40 _N-1 , and 40 _N during a received light intensity measurement period (step S12).

The selection and collection unit 114 compares T ₁ , T ₂ , ..., T _N-1 , T _N to select PD _MAX showing the maximum received light intensity (step S13), and collects a signal of PD _MAX during the signal collection period and transmits it to the host device 300. In addition, it stops the PDs other than the PD showing the maximum received light intensity during the received light intensity measurement period (step S14).

Proceed to step S15. If the user removes the smart ring 11 from the finger 200 or the remaining charge of the rechargeable battery 162 is insufficient, terminate the signal acquisition process 2 (step S15; Yes); if not (step S15; No), return to step S11.

As described above, in the smart ring system 1 of the second embodiment, the angle formed by the light source 31, the ring hole center point C, and the PDs _{40 1} , 40 ₂ , ..., 40 _N-1 , 40 _N is greater than 60° and less than 105°, so that the AC/DC ratio can be improved. In addition, the optical elements 50 and 51 arranged to surround the light source 31 and the PDs _{40 1} , 40 ₂ , ..., 40 _N-1 , 40 _N protrude so as to press the user's finger 200, so that the smart ring 11 can be prevented from rotating in the ring circumferential direction even when the user is working, doing housework, exercising, etc. Furthermore, in the smart ring system 1, the signal of the PD that has the highest light reception intensity from the light source 31 among the N PDs is collected at regular intervals, so that the volume pulse wave can be measured with even greater accuracy even if the smart ring 11 rotates in the ring circumferential direction on the user's finger 200 as the user works, does housework, exercises, etc. In addition, during the signal collection period, PDs other than the PD that showed the maximum light receiving intensity during the light receiving intensity measurement period are stopped, thereby saving power consumption and suppressing the decrease in the charge of the rechargeable battery 162 of the smart ring 11.

[Third embodiment]
As shown in Figures 11A and 11B, in the third embodiment, the smart ring 12 has a sensor unit 15 including a light source 31 and a PD 40, and a sensor unit 16 including a light source 32 and a PD 41. The light sources 31 and 32 are LED array light sources and have a plurality of LEDs with different peak wavelengths λ ₁ , λ ₂ , ..., λ _n , including at least one LED having a peak wavelength between 500-550 nm, two LEDs having peak wavelengths between 600-800 nm, and one LED having a peak wavelength between 900-1000 nm. As shown in Figure 12, the light sources 31 and 32 are pulse-driven and controlled so that the pulse-on time and the pulse-off time are reversed, and the light sources 31 and 32 emit light alternately.

11A and 11B, in the sensor unit 15, the angle _Φ1 formed by the base point BP, the ring hole center point C, and the PD40 plus the angle _ΦL1 formed by the light source 31, the ring hole center point C, and the PD40 is less than the angle _Φ2 formed by the base point BP, the ring hole center point C, and the light source 32. _ΦL2 is the angle formed by the light source 32, the ring hole center point C, and the PD41. In addition, 60°< _ΦL1 = _ΦL2 <105°. The other configurations are the same as those in the first embodiment.

In addition, in the signal acquisition process 3 executed by the smart ring 12, as shown in FIG. 12, during the signal collection period, the _PDL and the light source on the side other than the _PDH with the larger received light intensity during the received light intensity measurement period are stopped.

(Method of acquiring volume pulse wave using smart ring 12)
The signal acquisition process 3 executed by the smart ring 12 of the smart ring system 1 will be described with reference to FIG.

The smart ring 12 is inserted on the user's finger 200, and the light source control unit 111 interleaves pulse trains for the light source 31 of the sensor unit 15 and the light source 32 of the sensor unit 16 to emit light having different peak wavelengths λ ₁ , λ ₂ , ..., λ _n having predetermined wavelengths, in this embodiment, peak wavelengths at least between 500-550 nm, 600-800 nm, and 900-1000 nm (step S21).

In accordance with the driving of light sources 31 and 32, PD control unit 112 drives PDs 40 and 41. The light emitted from light sources 31 and 32 is transmitted and diffusely reflected by the soft tissue of the user's finger 200 and received by PDs 40 and 41. Measurement unit 113 measures the received light intensities T3 and T4 at PDs 40 and 41 during the received light intensity measurement period (step S22).

The selection and collection unit 114 compares T3 and T4 to select the _PDH with the greater received light intensity (step S23), stops the sensor unit having the other _PDL during the signal collection period, collects the signal of the _PDH with the greater received light intensity (step S24), and transmits it to the host device 300.

Proceed to step S25. If the user removes the smart ring 12 from the finger 200 or the remaining charge of the rechargeable battery 162 is insufficient, terminate the signal acquisition process 3 (step S25; Yes); if not (step S25; No), return to step S21.

As described above, in the smart ring system 1 of the third embodiment, the angle Φ _L1 formed by the light source 31, the ring hole center point C, and the PD 40, and the angle Φ L2 formed by the light source 31, the ring hole center point C, and the PD ₄₀ are greater than 60° and less than 105°, so that the AC/DC ratio can be improved. In addition, the optical elements 50 and 51 arranged to surround the light sources 31 and 32 and the PDs 40 and 41 protrude so as to press the user's finger 200, so that the smart ring 12 can be prevented from rotating in the ring circumferential direction even when the user is working, doing housework, exercising, etc. Furthermore, in the smart ring system 1, the signal of the PD _H , whichever has the greater light receiving intensity from the light source 31 or the light source 32, is collected at regular intervals, so that the volume pulse wave can be measured with high accuracy even if the smart ring 12 rotates in the ring circumferential direction on the user's finger 200 as the user works, does housework, exercises, etc. In addition, during the signal collection period, the sensor units having the PD _L other than the PD with the larger received light intensity during the received light intensity measurement period are stopped, so that power consumption can be saved and the consumption of the rechargeable battery 162 of the smart ring 12 can be suppressed.

[Modification]
In each of the above embodiments, the outer housing 21 is made of titanium, but may be made of other metals such as surgical stainless steel, or may be made of ceramic, resin, wood, etc. The inner housing 22 is made of resin, but may be made of metal or ceramic.

In each of the above embodiments, the light source 30 was an LED having multiple peak wavelengths, but it may also be an LED array light source composed of multiple LEDs having different peak wavelengths, or it may be any other light source as long as it is capable of emitting light having different peak wavelengths.

In each of the above embodiments, the photodetectors 40 and 41 were PIN type photodiodes, but they may also be PN type photodiodes or avalanche photodiodes, or photoconductive elements such as CdS or PbS.

In addition, in each of the above embodiments, the optical elements 50 and 51 are parabolic mirrors, but they may be aspheric mirrors with a parabolic, hyperbolic or elliptical surface. They may also be lenses, filters, prisms, or combinations of these.

In each of the above embodiments, the optical element 50 arranged to surround the light source 30 protrudes more toward the user's finger 200 inserted into the ring hole than the optical element 51 arranged to surround the PDs 40, 41, but the protrusion amounts of all optical elements may be the same, or the optical element arranged to surround the PD may protrude more.

In each of the above embodiments, the power supply unit 160 performs NFC wireless charging, and the charging device 400 is a lithium polymer battery, but it may be a lithium ion battery or other rechargeable battery. Alternatively, it may be configured to use a non-rechargeable small battery.

In each of the above embodiments, the MCU 100 has a control unit 110, a memory unit 120, and a communication unit 130, but the configuration of the MCU may be different from this, or a control unit, memory unit, and communication unit may be provided without using an MCU.

In addition, in each of the above embodiments, the communication device 131 performs wireless communication based on Bluetooth, but it may also perform wireless communication based on Wi-Fi (registered trademark), LoRaWAN (registered trademark), or other standards.

In each of the above embodiments, the sensor unit 140 has a multi-wavelength PPG sensor 141, a gyro sensor 142, an acceleration sensor 143, a temperature sensor 144, a millimeter wave sensor 145, a microwave sensor 146, and an optical sensor 147, but may have other sensors or may not have some sensors other than the multi-wavelength PPG sensor 141.

In the first embodiment described above, the angle formed by the light source 30, PDs 41 and 42, and the center point C of the ring hole was θ2-θ1=θ3-θ2, but θ2-θ1 and θ3-θ2 may be different as long as the angles are greater than 60° and less than 105°.

In each of the above embodiments, the optical elements 50, 51 protrude from the main surface 24 of the inner housing 22, but as shown in Fig. 14, the optical elements 50, 51 may be arranged in a recess 25 formed in the inner housing 22 so as to protrude from the recess 25, and a sealant 56 made of a transparent resin similar to that of the inner housing 22 may be filled to cover the optical elements 50, 51. Alternatively, as shown in Fig. 15, the optical elements 50, 51 may be arranged in a hole 65 of the substrate 60 and a recess in the outer housing 21. A lens, a prism, or the like may be used instead of the sealant 56.

In addition, in the above third embodiment, the smart ring 12 was equipped with two sensor units, but it may be equipped with three or more sensor units.

Below are experimental results regarding the light intensity of the PD versus the angle formed by the light source, the center point C of the ring hole, and the PD. Below are the results of four simulation patterns, with and without optical elements arranged to surround the light source and PD, respectively.

The structure of the smart ring according to each of the above embodiments was optimized by optical simulation. For the simulation, an optical simulation tool Trace Pro (registered trademark) manufactured by Lambda Research Corporation, USA, was used. As shown in FIG. 2, the optical simulation was performed assuming that the smart ring 10 was inserted into the proximal phalange 204 of the user's finger 200. The model has an outer housing 21, an inner housing 22, a die of the light source 30 (light-emitting area: 0.28 mm x 0.28 mm), a die of the PD 40 (light-receiving area: 1.5 mm x 1.5 mm), an epidermis 201, a dermis 202, a subcutaneous fat 203, a proximal phalange 204, a flexor tendon 205, an artery 206, and a nerve 207. The absorbance, scattering coefficient, and refractive index were defined for each model component, and a simulation was performed as a multiple scattering system. The optical constants of each component were referenced in the following references.

(Reference 1)
V. v. Tuchin, “Light scattering study of tissues”, Phys. -Usp. 40(5), 495-515 (1997).

(Reference 2)
A. N. Bashkatov, D. M. Zhestkov, E. A. Genina, and V. V. Tuchin, “Immersion clearing of human blood in the visible and near-infrared spectral regions”, Opt. Spectrosc. 98(4), 638-646 (2005).

(Reference 3)
O. Zhernovava, V. S. Tuchin, and A. Douplik, “The refractive index of human hemoglobin in the visible range”, Phys. Med. Biol. 56(13), 4013-4021 (2011).

Here, it is assumed that the tissue of the finger 200 is compressed by the inner housing 22 of the smart ring 10 and therefore deforms to conform to the inner housing 22, and in particular, it is assumed that a recess D is formed in the portion pressed against the optical element 50.

Light with a near-infrared wavelength was emitted from the light source 30, and the intensity of the light that was multiple-scattered within the tissue of the finger 200 and reached the PD 40 was analyzed. The positional relationship between the light source 30 and the PD 40 was expressed as the angle θ formed by connecting the light source 30, the ring hole center point C, and the PD 40, using the ring hole center point C, which is the center of the circle when the ring hole of the smart ring 10 is considered as the circumference. Simulations were performed by changing θ from 45° to 105° in increments of 15°.

The light source 30 was analyzed in two cases, with and without the optical element 50, and each of these two cases was analyzed with and without the optical element 51 in the PD 40 (four cases in total). To simplify the model, the analysis was performed assuming that the optical elements 50 and 51 have the same shape. Also, PD 41 was omitted to simplify the model. For reference, the light radiation distribution when the light source 30 does not have the optical element 50 is shown in Figure 16A, and when it does have the optical element 50 is shown in Figure 16B. It can be seen that the light emitted by the light source 30 is focused toward 0° by the optical element 50.

The results of the optical simulation are shown in Figures 17 and 18. The horizontal axis of Figure 17 indicates the angle θ formed between the light source 30, the center point C of the ring hole, and the PD 40, and the vertical axis indicates the intensity of light received by the PD. The graph shown with a solid line is the case where neither the light source 30 nor the PD 40 has an optical element, and the graph shown with a dotted line is the case where only the PD 40 has an optical element. The dashed and dotted line is the case where only the light source 30 has an optical element, and the dashed line is the case where both the light source 30 and the PD 40 have optical elements. It can be seen that in all four cases, the larger θ becomes, the smaller the received light intensity becomes. This is thought to be due to absorption by the skin tissue and subcutaneous tissue of the finger.

18, the horizontal axis represents the angle θ formed between the light source 30, the center point C of the ring hole, and the PD 40, and the vertical axis represents the AC/DC ratio. The AC/DC ratio is defined as follows.
AC/DC=I _artery /I _all

Here, I _artery is the sum of the intensities of the light rays emitted from the light source 30, passed through the artery, and reached the PD 40, and I _all is the sum of the intensities of all the light rays emitted from the light source 30 and reached the PD 40.

The following three points can be seen from Figures 17 and 18.

1. When θ is small (area close to the reflective photoplethysmogram)
It can be said that the smaller θ is, the closer the form is to a reflective photoplethysmogram. From the simulation results, it can be seen that in this case, the intensity of the light reaching the PD 40 is high, but on the other hand, the amount of light reaching the PD 40 via the deep part of the finger tissue where the artery 206 is present is extremely low. Therefore, it can be said that this form is not suitable for the purpose of measuring blood oxygen saturation. It can also be seen that the effect of the optical element in this region is small.

2. When θ is large (area close to the transmitted photoplethysmogram)
It can be said that the larger the θ, the closer the form is to a transmission type photoplethysmogram.

The simulation results show that in this case, a large proportion of the light reaches the PD 40 via the deep part of the finger tissue where the artery 206 is located, making it suitable for measuring blood oxygen saturation. However, the emission intensity needs to be increased, and from the perspective of securing power, it may not be suitable for a smart ring, which is required to be compact. It is also estimated that the benefit of optical elements is small in this region.

3. When θ is between cases 1 and 2 (quasi-transmission type photoplethysmography region)
A form that is neither the reflective type (1) nor the transmissive type (2) is called a quasi-transmissive type. The simulation results show that there is a trade-off between the received light intensity and the AC/DC ratio, so it is important to optimize θ according to the application. It can be confirmed that in the region where 60°<θ<105°, when an optical element is present, the AC/DC ratio is significantly improved. In a quasi-transmissive photoplethysmographic sensor, the AC/DC ratio can be improved by adding an optical element to the light source and PD.

The present invention is capable of various embodiments and modifications without departing from the broad spirit and scope of the present invention. Furthermore, each of the above-described embodiments is intended to explain one example of the present invention and does not limit the scope of the present invention. The above-described embodiments and modifications can be combined in any manner. Furthermore, even if some of the constituent elements of an embodiment are omitted as necessary, the invention will still fall within the scope of the technical idea of the present invention.

REFERENCE SIGNS LIST 1 Smart ring system 10, 11, 12 Smart ring 15, 16 Sensor unit 20 Housing 21 Outer housing 22 Inner housing 23 Decorative part 24 Main surface 25 Recess ₃₀ , 31, 32 Light source 35 Light emitting part 40, 40 1 , 40 ₂ , ..., 40 _N , 41 Photodetector 50, 51 Optical element 52 Main body part 53 Mounting part 54 Light collecting surface 55 Starting point 60 Substrate 61 Charging IC
62 Power supply management IC
65 holes 100 MCU
110 Control unit 111 Light source control unit 112 PD control unit 113 Measurement unit 114 Selection and collection unit 120 Memory unit 121 Setting memory unit 122 Measurement result memory unit 130 Communication unit 131 Communication device 140 Sensor unit 141 Multi-wavelength PPG sensor 142 Gyro sensor 143 Acceleration sensor 144 Temperature sensor 145 Millimeter wave sensor 146 Microwave sensor 147 Optical sensor 150 Notification unit 151 Notification device 160 Power supply unit 161 Power supply monitoring unit 162 Rechargeable battery 163 Charging receiver 200 Finger 201 Epidermis 202 Dermis 203 Subcutaneous fat 204 Proximal phalange 205 Flexor tendon 206 Artery 207 Nerve 300 Host device 400 Charging device 401 Charging transmitter BP Base point C Ring hole center point

Claims (13)

a first light source that illuminates a finger through a ring-shaped first optical element; a first photodetector that receives light emitted from the first light source or another light source through a ring-shaped second optical element and acquires a volume pulse wave; a housing through which the finger is inserted; and a transparent resin sealing body that fixes the first and second optical elements to the housing ;
the first light source and the first photodetector are disposed in through holes of the first and second optical elements;
the first and second optical elements are arranged to surround the first light source and the first photodetector, respectively, and protrude from a main surface of the housing on a side through which the finger is inserted toward the finger, the finger is pressed against the sealing body covering the first and second optical elements to bring the sealing body into close contact with the finger, and rotation of the housing relative to the finger is suppressed via the sealing body ;
the first and second optical elements are aspheric mirrors having parabolic curved surfaces formed in the through holes to condense the light;
Smart ring. a first angle formed by a position where the first light source is arranged, a center point of a ring hole through which the finger is inserted, which is formed in the housing, and a position where the first photodetector is arranged is greater than 60° and less than 105°;
The smart ring of claim 1. a second photodetector that receives the light emitted from the first light source or another light source via an annular third optical element;
the third optical element is disposed to surround the second photodetector,
a second angle formed by a position where the first light source is disposed, the center point, and a position where the second photodetector is disposed is greater than 60° and less than 105°;
A signal obtained from the photodetector with the highest light receiving intensity is selected to obtain a volume pulse wave.
The smart ring according to claim 2. The finger-insertion device has a first light source that irradiates a finger through a first annular optical element, a first photodetector that receives light emitted from the first light source or another light source through a second annular optical element and acquires a volume pulse wave, a second photodetector that receives the light emitted from the first light source or another light source through a third annular optical element, and a housing through which the finger is inserted,
the first light source and the first photodetector are disposed in through holes of the first and second optical elements, respectively;
the first and second optical elements are arranged to surround the first light source and the first photodetector, respectively, protrude from a main surface of the housing on a side through which the finger is inserted toward the finger, press against the finger to come into close contact with the finger, and suppress rotation of the housing with respect to the finger;
a first angle formed by a position where the first light source is disposed, a center point of a ring hole through which the finger is inserted, which is formed in the housing, and a position where the first photodetector is disposed is greater than 60° and less than 105°;
the second photodetector is disposed in a through hole of the third optical element;
the third optical element is disposed to surround the second photodetector,
a second angle formed by a position where the first light source is disposed, the center point, and a position where the second photodetector is disposed is greater than 60° and less than 105°;
the first, second and third optical elements are parabolic mirrors, each of which has a parabolic curved surface formed in the through hole, the end of which is on the side where the light is incident or the end of which is on the side where the light is emitted, coinciding with a start point of the parabolic curved surface of the mirror;
Smart ring. The first, second and third optical elements further include at least one of a lens, a filter and a prism that condenses the light.
The smart ring according to claim 3 . a first central angle formed by a predetermined base point on an inner surface of the smart ring, the center point, and a position where the first light source is disposed is larger than a second central angle formed by the base point, the center point, and a position where the first photodetector is disposed, and is smaller than a third central angle formed by the base point, the center point, and a position where the second photodetector is disposed;
The smart ring according to claim 5. the first light source is an LED array light source composed of a plurality of LEDs having different peak wavelengths;
The first and second photodetectors include the different peak wavelengths in their light sensitivity wavelength ranges.
The smart ring according to claim 5. The plurality of LEDs include one or more LEDs having a peak wavelength in the range of 500-550 nm, two or more LEDs having a peak wavelength in the range of 600-800 nm, and one or more LEDs having a peak wavelength in the range of 900-1000 nm.
The smart ring of claim 7. every time a predetermined time has elapsed, a signal obtained from a photodetector having the highest received light intensity is selected to obtain a volume pulse wave;
The smart ring of claim 8. The aspheric mirror is a parabolic mirror whose parabolic curved surface has an end on the side where the light is incident or exits, the end coinciding with the start point of the parabolic curved surface of the mirror.
The smart ring of claim 1 . a second light source that illuminates the finger through an annular fourth optical element;
the second light source is disposed in a through hole of the fourth optical element;
the fourth optical element is disposed to surround the second light source,
the fourth optical element is an aspheric mirror having a parabolic curved surface formed in the through hole for collecting the light,
a fourth central angle formed by the base point, the center point, and the position where the second light source is disposed is larger than a first angle obtained by adding a fifth central angle formed by the first light source, the center point, and the position where the first photodetector is disposed to the second central angle, and is also larger than a second angle obtained by adding a sixth central angle formed by the position where the second light source is disposed, the center point, and the position where the second photodetector is disposed to the second central angle;
A signal obtained from a photodetector having the highest light receiving intensity is selected from a combination of two light sources and two photodetectors to obtain a volume pulse wave.
The smart ring of claim 6. The first and second light sources have opposite pulse-on and pulse-off times.
The smart ring of claim 11. A smart ring according to any one of claims 1 to 12;
and an electronic device that receives the volume pulse wave from the smart ring via wireless communication.
Smart Ring System.