Transcutaneous muscle oxygen saturation detection device

Abstract

This device for detecting oxygen saturation of percutaneous muscle comprises a light source for causing light to enter the body, and a first light detector and a second light detector for detecting reflected light reflected in the body. The second light detector is positionally shifted, in the circumferential direction about the light source, from a first imaginary line linking the light source and the first light detector.

Description

Technical Field

[0001] The present disclosure relates to a transcutaneous muscle oxygen saturation detection device.

Background Art

[0002] The oxygen saturation in blood (hereinafter referred to as blood oxygen saturation (SpO2)) is the ratio of the amount of oxygen actually bound to hemoglobin to the total amount of oxygen assuming that all of the hemoglobin in the blood is bound to oxygen. As a method for detecting such blood oxygen saturation (SpO2), first, there is a method of collecting arterial blood and measuring the amount of oxygen. Second, there is a method of using a detection device to detect blood oxygen saturation (SpO2) based on light that is incident from the skin into the body and transmitted or reflected by arteries. Since the second detection method passes through the skin, the detection device may be referred to as a transcutaneous oxygen saturation detection device. In addition, the transcutaneous oxygen saturation detection device of the following patent document includes one light source that irradiates light into the body and two light detection units that receive the reflected light reflected inside the body.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In recent years, the oxygen saturation of athletes' muscle tissues (hereinafter referred to as muscle oxygen saturation (SmO2)) has been detected. The detection method is the same as the detection of blood oxygen saturation (SpO2), in which light is incident from the skin into the body, and muscle oxygen saturation (SmO2) is detected based on the light transmitted or reflected by the capillaries in the muscle tissue. However, when the light transmitted or reflected by the capillaries in the muscle tissue further passes through the artery, the light contains information on the blood oxygen saturation (SpO2) of the artery. Therefore, accurate muscle oxygen saturation (SmO2) cannot be detected.

[0005] In the patent document, the transcutaneous oxygen saturation detection device has one light source and two photodetectors aligned in a straight line. With this arrangement, if one light source and one photodetector overlap with an artery, the other photodetector may also overlap with the artery. In other words, although it has two photodetectors, it may not be possible to obtain accurate muscle oxygen saturation (SmO2). And if accurate muscle oxygen saturation (SmO2) cannot be obtained, the cumbersome process of reattaching the transcutaneous oxygen saturation detection device to a different location and performing detection again is required. For these reasons, there is a need for the development of a convenient transcutaneous muscle oxygen saturation detection device that can avoid the cumbersome process (reattachment).

[0006] This disclosure aims to provide a highly convenient transcutaneous muscle oxygen saturation detection device. [Means for solving the problem]

[0007] A transcutaneous muscle oxygen saturation detection device according to one aspect of the present disclosure comprises a light source that causes light to be incident inside the body, and a first light detection unit and a second light detection unit that detect reflected light reflected inside the body. The second light detection unit is circumferentially offset from a first imaginary line connecting the light source and the first light detection unit, with respect to the light source. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a schematic plan view showing the transcutaneous muscle oxygen saturation detection device of Embodiment 1. [Figure 2] Figure 2 shows the path of light when light is incident inside the body of a subject. [Figure 3] Figure 3 shows the absorption coefficients of red and infrared light. [Figure 4] Figure 4 shows the subject with a transcutaneous muscle oxygen saturation detection device attached to their right leg. [Figure 5] Figure 5 is a schematic plan view showing the transcutaneous muscle oxygen saturation detection device of Embodiment 2. [Figure 6]Figure 6 is a schematic plan view showing the transcutaneous muscle oxygen saturation detection device of Embodiment 3. [Figure 7] Figure 7 is a cross-sectional view taken along the line VII-VII in Figure 6. [Figure 8] Figure 8 is a schematic plan view showing the transcutaneous muscle oxygen saturation detection device of Embodiment 4. [Figure 9] Figure 9 is a cross-sectional view taken along the line IX-IX in Figure 8. [Figure 10] Figure 10 is a schematic plan view showing the transcutaneous muscle oxygen saturation detection device of Embodiment 5. [Figure 11] Figure 11 is a schematic plan view showing the transcutaneous muscle oxygen saturation detection device of Embodiment 6. [Figure 12] Figure 12 is a schematic plan view showing the transcutaneous muscle oxygen saturation detection device of Embodiment 7. [Figure 13] Figure 13 is a schematic plan view of the transcutaneous muscle oxygen saturation detection device of Embodiment 8, and further shows the range of the photodetector that is driven during the first to third illumination. [Figure 14] Figure 14 is a plan view showing the range of the photodetector that is driven during the fourth to sixth illumination in the transcutaneous muscle oxygen saturation detection device of Embodiment 8. [Modes for carrying out the invention]

[0009] Embodiments for implementing this disclosure will be described in detail with reference to the drawings. This disclosure is not limited to the embodiments described below. Furthermore, the components described below include those that can be easily conceived by a person skilled in the art, and those that are substantially the same. In addition, the components described below can be combined as appropriate. Note that this disclosure is merely an example, and any modifications that can be easily conceived by a person skilled in the art while maintaining the spirit of the invention are naturally included within the scope of this disclosure. Furthermore, in order to make the explanation clearer, the drawings may schematically represent the width, thickness, shape, etc. of each part compared to the actual embodiment, but these are merely examples and do not limit the interpretation of this disclosure. Furthermore, in this specification and each drawing, elements similar to those described above with respect to previously shown drawings are denoted by the same reference numerals, and detailed explanations may be omitted as appropriate.

[0010] Furthermore, in this specification and the claims, when describing a manner in which one structure is placed on top of another structure, unless otherwise specified, the term "on top of" includes both cases: when one structure is placed directly on top of another structure so as to be in contact with it, and when another structure is placed above another structure via yet another structure.

[0011] (Embodiment 1) Figure 1 is a schematic plan view of the transcutaneous muscle oxygen saturation detection device of Embodiment 1. Embodiment 1 describes the transcutaneous muscle oxygen saturation detection device 1 equipped with a basic configuration. As shown in Figure 1, the transcutaneous muscle oxygen saturation detection device 1 of Embodiment 1 comprises a sheet 2, one light source 3, and two light detection units (a first light detection unit 4 and a second light detection unit 5). The direction parallel to the normal to the sheet 2 will be referred to as the "orthogonal direction" below. Also, "plan view" below refers to a view from the orthogonal direction.

[0012] Sheet 2 is a support plate for supporting the light source 3 and the light detection units (the first light detection unit 4 and the second light detection unit 5). Sheet 2 has a rectangular shape in plan view. The surface 2a of sheet 2 is the surface that is attached facing the arm or leg of the subject (see Fig. 4). The light source 3, the first light detection unit 4, and the second light detection unit 5 are attached to the surface 2a.

[0013] Sheet 2 is made of a flexible material. Therefore, when sheet 2 is attached to the subject, sheet 2 is deformed into a shape along the outer surface of the arm or leg. Therefore, the light source 3, the first light detection unit 4, and the second light detection unit 5 fixed to the surface 2a of sheet 2 are in a state of contacting the body 100 (see Fig. 2).

[0014] A flexible printed circuit board 7 is provided on one side of sheet 2. Terminals 7a are provided at the ends of the flexible printed circuit board 7. The flexible printed circuit board 7 is fixed to sheet 2 such that the terminals 7a project outside sheet 2 from one side of sheet 2. Various wirings are provided on sheet 2. One end of each of the various wirings is connected to any one of the light source 3, the first light detection unit 4, and the second light detection unit 5, and the other end extends to the terminal 7a of the flexible printed circuit board 7. And the terminal 7a of the flexible printed circuit board 7 is inserted into the connector of the control device 8. Thereby, the light source 3, the first light detection unit 4, and the second light detection unit 5 receive various signals from the control device 8 or send signals (detection results) to the control device 8.

[0015] The light source 3 is fixed to sheet 2 so as to irradiate light in a direction orthogonal to the surface 2a of sheet 2. The light source 3 emits light of two wavelengths. One of the two wavelengths of light is light having a wavelength of 600 nm or more and less than 800 nm. The light having a wavelength of 600 nm or more and less than 800 nm is red visible light, and may be hereinafter referred to as "red light" or "R". The other of the two wavelengths of light is light having a wavelength of 800 nm or more and less than 1000 nm. The light having a wavelength of 800 or more and less than 1000 nm is infrared light, and may be hereinafter referred to as "infrared light" or "IR (infrared)".

[0016] Although not particularly shown, the light source 3 of the present embodiment includes a first light emitting element that emits red light and a second light emitting element that emits infrared light. In the present embodiment, LEDs (Light Emitting Diodes) are used for the first light emitting element and the second light emitting element. The first light emitting element of the embodiment mainly emits red light with a wavelength of 665 nm. The second light emitting element mainly irradiates infrared light with a wavelength of 880 nm. Then, by alternately lighting the first light emitting element and the second light emitting element in a time-sharing manner, the light source 3 alternately emits light of two wavelengths.

[0017] Note that the light source of the present disclosure only needs to be able to irradiate light of two wavelengths, red light and infrared light, and does not necessarily need to include two light emitting elements. Further, the oxygen saturation detection device of the present disclosure is not limited to alternately emitting red light (R) and infrared light (IR) in a time-sharing manner, and may alternately emit red light and infrared light in sequence, or emit them simultaneously.

[0018] FIG. 2 is a diagram showing the optical path when light is incident on the inside of the subject's body. As shown in FIG. 2, when detecting the muscle oxygen saturation (SmO2), the light source 3 emits light toward the epidermis 101 of the body 100. Thereby, light is incident on the inside of the body 100.

[0019] Note that the tissues of the body 100 are arranged in the order of the epidermis 101, dermis 102, subcutaneous tissue 103, and muscle tissue 104 from the outside. Also, in FIG. 2, the epidermis 101 and the dermis 102 are shown integrally. Blood (capillaries) flows through the dermis 102, subcutaneous tissue 103, and muscle tissue 104. Hereinafter, the direction in which the muscle tissue 104 is present as viewed from the epidermis 101 is referred to as the depth direction.

[0020] The light emitted from the light source 3 penetrates the epidermis 101 and enters in the depth direction. As the light enters, it is reflected by some part of the body 100 and emitted outside the body 100 as reflected light. Of the reflected light, the light that reaches the muscle tissue 104 and passes through the blood flowing through the muscle tissue 104 (reflected light) comes to contain information about muscle oxygen saturation (SmO2). On the other hand, the light that only reaches the subcutaneous tissue 103 and passes through the blood flowing through the subcutaneous tissue 103 (reflected light) does not contain information about muscle oxygen saturation (SmO2).

[0021] In addition, light is attenuated as it passes through each part of the body 100. Therefore, in order to ensure sufficient light intensity, it is preferable that the light source 3 has a narrow beam of light, or in other words, high directivity. Also, the transmittance inside the body 100 is higher for infrared light (IR) than for red light (R). Therefore, it is preferable that the intensity of red light (R) is higher than the intensity of infrared light (IR). Next, the light detection unit will be described.

[0022] As shown in Figure 1, the first photodetector 4 and the second photodetector 5 are each photodiodes. The back surfaces of the first photodetector 4 and the second photodetector 5, opposite to the light-receiving surface, are fixed to the surface 2a of the sheet 2. In other words, the light-receiving surfaces of the first photodetector 4 and the second photodetector 5 face the same direction as the surface 2a of the sheet 2. The first photodetector 4 and the second photodetector 5 each receive reflected light emitted to the outside of the body 100. The first photodetector 4 and the second photodetector 5 transmit an electrical signal corresponding to the amount of light received to the control device 8. The reflected light received by the first photodetector 4 and the second photodetector 5 includes both red light emitted from the first light-emitting element and infrared light emitted from the second light-emitting element.

[0023] The first photodetector 4 and the second photodetector 5 are located at a distance of approximately 10 mm or more from the light source 3. The reason for this will be explained with reference to Figure 2. Note that the arrows in Figure 2 indicate light entering the interior of the body 100. As shown in Figure 2, the direction of light propagation changes as it enters the interior of the body 100. In other words, if the optical path inside the body 100 is long (as shown by arrows A3 and A4 in Figure 2, reaching the muscle tissue 104 deep inside the body 100), the distance away from the light source 3 in the radial direction (away from the light source 3) is also large (see arrows A5 and A6 in Figure 2). Therefore, the light that reaches the muscle tissue 104 (reflected light) is dispersed to positions near or far from the light source 3 and emitted outside the body 100. On the other hand, if the optical path inside the body 100 is short (for example, if reflected by the dermis 102 as shown by arrows A7 and A8 in Figure 2), the distance away from the light source 3 becomes relatively small. In other words, the light is emitted outside the body 100 near the light source 3. Therefore, the first light detection unit 4 and the second light detection unit 5 are positioned at a distance that allows them to receive reflected light that has reached the muscle tissue 104 while avoiding the reception of reflected light that has not reached the muscle tissue 104.

[0024] Therefore, the first photodetector 4 receives a relatively large amount of light (including both R and IR) that has been transmitted through the portion of the muscle tissue 104 located between the light source 3 and the first photodetector 4 (see the area enclosed by the dashed line A1 in Figures 1 and 2). Similarly, the second photodetector 5 receives a relatively large amount of light (including both R and IR) that has been transmitted through the portion of the muscle tissue 104 located between the light source 3 and the second photodetector 5 (see the area enclosed by the dashed line A2 in Figures 1 and 2).

[0025] Furthermore, as shown in Figure 1, the first light detection unit 4 and the second light detection unit 5 of Embodiment 1 are at the same distance from the light source 3. The first light detection unit 4 and the second light detection unit 5 are positioned at a 90° angle to the light source 3 in a plan view. In other words, the first virtual line L1 connecting the center O3 of the light source 3 and the center O4 of the first light detection unit 4, and the second virtual line L2 connecting the center O3 of the light source 3 and the center O5 of the second light detection unit 5 intersect at the center O3 of the light source 3. The angle at which the first virtual line L1 and the second virtual line L2 intersect at the intersection point is 90°. From the above, the second light detection unit 5 is circumferentially offset from the first virtual line L1 connecting the light source 3 and the first light detection unit 4, with the light source 3 as the center. Note that the first virtual line L1 and the second virtual line L2 in Figure 1 are shown extended beyond the centers O3, O4, and O5 for clarity.

[0026] The control device 8 calculates oxygen saturation based on the amount of light received from the first photodetector 4 and the second photodetector 5. The method for calculating oxygen saturation will be briefly explained below with reference to Figure 3.

[0027] Figure 3 shows the absorption coefficients for red and infrared light. The absorption coefficient on the vertical axis of Figure 3 indicates that a higher value means the light is absorbed more easily. In Figure 3, Hb represents hemoglobin in an unbound state. In Figure 3, HbO2 represents hemoglobin in an oxygen-bound state.

[0028] Red blood cells, which are contained in blood, contain hemoglobin. Hemoglobin is dark red when it is not bound to oxygen, and becomes bright red when it is bound to oxygen. For this reason, the absorption coefficient of red light differs between hemoglobin bound to oxygen (HbO2) and hemoglobin not bound to oxygen (Hb). Specifically, as shown in Figure 3, hemoglobin not bound to oxygen (Hb) has a higher absorption coefficient of red light (R) than hemoglobin bound to oxygen (HbO2). Therefore, when red light (R) passes through blood, if there is a lot of hemoglobin bound to oxygen (HbO2), there will be a lot of transmitted (reflected) red light (R). On the other hand, if there is a lot of hemoglobin not bound to oxygen (Hb), there will be less transmitted (reflected) red light. Based on the above, the amount of hemoglobin (HbO2) bound to oxygen can be relatively determined based on the amount of reflected light (red light with a wavelength of 665 nm) from the first light-emitting element received by the first light-detecting unit 4 and the second light-detecting unit 5.

[0029] On the other hand, as shown in Figure 3, the extinction coefficient of infrared light (IR) does not differ significantly between hemoglobin (Hb) that is not bound to oxygen and hemoglobin (HbO2) that is bound to oxygen. In other words, the amount of infrared light (IR) decreases in proportion to the total amount of hemoglobin transmitted. Therefore, the total amount of hemoglobin can be determined based on the amount of reflected light (infrared light with a wavelength of 880 nm) from the second light-emitting element received by the first photodetector 4 and the second photodetector 5. Then, by comparing the amount of red light (R) received with the amount of infrared light (IR) received (R / IR), the muscle oxygen saturation (SmO2) can be calculated.

[0030] Furthermore, the control device 8 detects muscle oxygen saturation (SmO2) separately for each photodetector. The transcutaneous muscle oxygen saturation detection device 1 of Embodiment 1 is equipped with two photodetectors: a first photodetector 4 and a second photodetector 5. Therefore, the control device 8 calculates the muscle oxygen saturation (SmO2) of the portion of the muscle tissue 104 located between the light source 3 and the first photodetector 4 (see the area enclosed by the dashed line A1 in Figures 1 and 2) based on the amount of red light (R) and infrared light (IR) received from the first photodetector 4. Similarly, the control device 8 calculates the muscle oxygen saturation (SmO2) of the portion of the muscle tissue located between the light source 3 and the second photodetector 5 (see the area enclosed by the dashed line A2 in Figures 1 and 2) based on the amount of red light (R) and infrared light (IR) received from the second photodetector 5.

[0031] Furthermore, the control device 8 determines whether or not information on arterial oxygen saturation is included based on the detection results of the first photodetector 4 and the second photodetector 5. Arteries pulsate, and the amount of hemoglobin bound to oxygen (HbO2) and the total amount of hemoglobin changes in a short period of time. Therefore, when light passes through an artery, the amount of red light (R) and infrared light (IR) received by the photodetector also changes over time. Thus, if the amount of light received by the photodetector changes in a short period of time, the control device 8 determines that the accuracy of the detected muscle oxygen saturation (SmO2) is low because it includes information on arterial blood oxygen saturation (SpO2).

[0032] Figure 4 shows the transcutaneous muscle oxygen saturation detection device attached to the subject's right leg. Next, the method of attaching the transcutaneous muscle oxygen saturation detection device 1 of Embodiment 1 will be described. As shown in Figure 4, the transcutaneous muscle oxygen saturation detection device 1 is attached to the area where muscle oxygen saturation (SmO2) is to be detected (in this embodiment, the calf of the right leg) with the surface 2a of the sheet 2 facing the area. Then, the sheet 2 is secured with a supporter or elastic band (not shown) to prevent it from shifting.

[0033] Furthermore, regarding the orientation of the transcutaneous muscle oxygen saturation detection device 1, the direction in which the light source 3 and the first photodetector 4 are aligned (the direction of extension of the first imaginary line L1) is aligned parallel to the longitudinal direction of the measurement site (the direction in which the arm extends in the case of the arm, and the direction in which the leg extends in the case of the leg). Note that arteries extend in the longitudinal direction. As a result, the first photodetector 4 and the second photodetector 5 are not aligned in the longitudinal direction of the measurement site. In other words, both detection sites (areas enclosed by dashed lines A1 and A2) do not overlap with arteries. Therefore, as shown in Figure 4, even if an artery 9 overlaps between the light source 3 and the second photodetector 5 (area enclosed by dashed line A2), an artery 9 does not overlap between the light source 3 and the first photodetector 4 (area enclosed by dashed line A1). Consequently, there is a high probability that accurate muscle oxygen saturation (SmO2) can be detected from the detection results of the first photodetector 4.

[0034] As described above, the transcutaneous muscle oxygen saturation detection device 1 of Embodiment 1 has a high probability of detecting muscle oxygen saturation (SmO2). Therefore, the troublesome task of reattaching sheet 2 and performing detection again can be avoided, making it highly convenient.

[0035] In Embodiment 1, the first virtual line L1 and the second virtual line L2 intersect at an angle of 90°, but this disclosure is not limited to this. It is sufficient that the first light detection unit 4 and the second light detection unit 5 are not aligned in the longitudinal direction of the measurement area, i.e., the intersection angle is 5° or more. Next, other embodiments will be described. In the following description, the same reference numerals are used for the same components as those described in Embodiment 1, and redundant explanations are omitted.

[0036] (Embodiment 2) Figure 5 is a schematic plan view of the transcutaneous muscle oxygen saturation detection device of Embodiment 2. As shown in Figure 5, the transcutaneous muscle oxygen saturation detection device 1A of Embodiment 2 differs from the transcutaneous muscle oxygen saturation detection device 1 of Embodiment 1 in that it is equipped with four optical detection devices 10. The differences will be explained below.

[0037] The photodetector 10 comprises a substrate 11 and a plurality of photodetectors 12 provided on the substrate 11. The substrate 11 is equipped with TFTs (Thin Film Transistors) such as switching elements and various wiring, and is called a backplane or array substrate.

[0038] When the light detection device 10 is viewed from above, the frame-shaped edges of the light detection device 10 constitute a non-detection region. A scan line drive circuit 16 and a signal line processing circuit 17 are provided in this non-detection region. The region surrounded by the non-detection region is a detection region where multiple light detection units 12 are arranged. The multiple light detection units 12 are arranged in a matrix within the detection region, aligned in a first direction Dx and a second direction Dy.

[0039] The first direction Dx described above is parallel to the substrate 11. The second direction Dy is parallel to the substrate 11 and intersects with the first direction Dx. In this embodiment, the second direction Dy is perpendicular to the first direction Dx. The direction perpendicular to both the first direction Dx and the second direction Dy is referred to as the third direction Dz. The view from the third direction Dz is referred to as a plan view, as in Embodiment 1.

[0040] The scan line drive circuit 16 is a circuit that drives multiple scan lines based on various control signals from the control device 8 (see Figure 1). The scan line drive circuit 16 sequentially or simultaneously selects multiple scan lines and supplies drive signals to the selected scan lines. The signal line processing circuit 17 is a circuit that sequentially or simultaneously selects multiple output signal lines and connects the selected signal lines to the control device 8 (see Figure 1). The signal line processing circuit 17 also processes analog signals sent to the control device 8 (see Figure 1) via the output signal lines into digital signals. As a result, the control device 8 receives the detection results from multiple photodetectors 12 provided in each of the four photodetectors 10.

[0041] The four light detection devices 10 are fixed to the sheet 2 in two rows each in the first direction Dx and the second direction Dy. The light source 3 is fixed to the sheet 2 so as to be located in the center of the four light detection devices 10.

[0042] The dashed line 13 in Figure 5 represents a boundary line approximately 10 mm away from the light source 3. In each of the four photodetectors 10, some of the multiple photodetectors 12 are located in a nearby region 14, within approximately 10 mm of the light source 3. The remaining photodetectors 12 are located in a separated region 15, at a distance of approximately 10 mm or more from the light source 3. The photodetectors 12A and 12B located in the separated region 15 correspond to the first photodetector 4 and second photodetector 5 described in Embodiment 1. In other words, the first virtual line L1 passing through the light source 3 and the photodetector 12A, and the second virtual line L2 passing through the light source 3 and the photodetector 12B intersect at the center O3 of the light source 3. Therefore, the multiple photodetectors 12 include the first photodetector 4 and the second photodetector 5.

[0043] According to the transcutaneous muscle oxygen saturation detection device 1A of this embodiment 2, reflected light is received by each of the multiple light detection units 12 arranged in the first direction Dx and the second direction Dy. Therefore, the muscle oxygen saturation (SmO2) can be detected for each region of the muscle tissue 104 divided in the first direction Dx and the second direction Dy. Thus, detailed muscle oxygen saturation (SmO2) can be obtained.

[0044] Furthermore, the transcutaneous muscle oxygen saturation detection device 1A of Embodiment 2 is equipped with four optical detection devices 10, and its detection range is expanded compared to the transcutaneous muscle oxygen saturation detection device 1 of Embodiment 1. In other words, the probability of accurately detecting muscle oxygen saturation (SmO2) without overlapping with arteries 9 is extremely high. Therefore, the troublesome task of reattaching the sheet 2 and performing detection again can be avoided, resulting in superior convenience.

[0045] Furthermore, the reflected light received by the photodetector 12 located in the separation region 15 passes through the dermis 102 and subcutaneous tissue 103 both from the epidermis 101 to the muscle tissue 104 and from the muscle tissue 104 to the epidermis 101. Therefore, it contains information (noise) about the oxygen saturation of blood vessels flowing through the dermis 102 and subcutaneous tissue 103. On the other hand, the photodetector 12 located in the proximity region 14 receives a large amount of reflected light that penetrates shallowly into the depth direction of the body 100. Therefore, information (noise) about the oxygen saturation of blood vessels flowing through the dermis 102 and subcutaneous tissue 103 can be obtained from the detection results of the photodetector 12 located in the proximity region 14. From the above, in order to calibrate the muscle oxygen saturation (SmO2) calculated from the detection results of the photodetector 12 located in the separation region 15, the detection results of the photodetector 12 located in the proximity region 14 can be utilized to obtain a more accurate muscle oxygen saturation (SmO2).

[0046] (Embodiment 3) Figure 6 is a schematic plan view of the transcutaneous muscle oxygen saturation detection device of Embodiment 3. Figure 7 is a cross-sectional view taken along the line VII-VII in Figure 6. As shown in Figure 6, the transcutaneous muscle oxygen saturation detection device 1B of Embodiment 3 differs from the transcutaneous muscle oxygen saturation detection device 1A of Embodiment 2 in that it is equipped with a filter 18. The filter 18 will be described below.

[0047] The filter 18 is positioned between the light detection device 10 and the body 100 to define (limit) the angle of reflected light incident on the light detection unit 12. A filter 18 is provided for each light detection device 10. In Embodiment 3, the filter 18 is a louver 19 equipped with a plurality of first vanes 22.

[0048] As shown in Figure 7, the louver 19 is a flat resin layer 20 fixed to the light-receiving surface of the light detection device 10. The light-receiving surface of the light detection device 10 is the surface on which the light detection unit 12 is located and onto which reflected light is incident. The resin layer 20 comprises a plurality of transmissive parts 21 and a plurality of first vanes 22 which are made of black resin. The transmissive parts 21 are transparent resin parts that allow light to pass through. On the other hand, the first vanes 22 are made of black resin and are designed to absorb light. The details of the first vanes 22 will be described below.

[0049] The first vane plate 22 extends in the thickness direction of the resin layer 20 and is plate-shaped. As shown in Figure 6, the first vane plate 22 extends perpendicular to a virtual line L3 that extends in the direction away from the light source 3 in a plan view. The multiple transmissive sections 21 and the multiple first vane plates 22 are arranged alternately in the direction in which the virtual line L3 extends. In addition, each light detection section 12 is arranged to overlap with the transmissive section 21. The virtual line L3 intersects the first direction Dx and the second direction Dy at 45° angles.

[0050] The first vane plate 22 comprises a first inclined plate 23, a second inclined plate 24, and a third inclined plate 25, arranged in order from the one closest to the light source 3. In other words, the multiple first vane plates 22 include a first inclined plate 23 positioned near the light source 3, a second inclined plate 24 positioned further from the light source 3 than the first inclined plate 23, and a third inclined plate 25 positioned further from the light source 3 than the second inclined plate 24. In this embodiment, there are four of each of the first inclined plate 23, the second inclined plate 24, and the third inclined plate 25.

[0051] The first inclined plate 23 overlaps with the neighboring region 14. Therefore, the first inclined plate 23 limits the angle of reflected light incident on the light detection unit 12 located in the neighboring region 14. The spaces between the second inclined plates 24 and the spaces between the third inclined plates 25 overlap with the separation region 15. Therefore, the second inclined plate 24 and the third inclined plate 25 limit the angle of reflected light incident on the light detection unit 12 located in the separation region 15.

[0052] As shown in Figure 7, the first inclined plate 23, the second inclined plate 24, and the third inclined plate 25 are inclined toward the light source 3 as they move away from the light-receiving surface. Specifically, the inclination angle θ11 of the first inclined plate 23 relative to the light detection device 10 is 50°. The inclination angle θ12 of the second inclined plate 24 relative to the light detection device 10 is 65°. Therefore, the inclination angle θ11 of the first inclined plate 23 is greater than the inclination angle θ12 of the second inclined plate 24. Also, the inclination angle θ13 of the third inclined plate 25 relative to the light detection device 10 is 80°. From the above, the inclination angle of the first vane 22 relative to the light detection device 10 increases as it moves away from the light source 3.

[0053] Next, the effects of Embodiment 3 will be described. Reflected light irradiated outside the body 100 and near the light source 3 passes through the transmissive portion 21 between the first inclined plates 23 only if it is significantly inclined with respect to the normal direction of the light-receiving surface of the photodetector 10. Therefore, reflected light that penetrates shallowly into the depth direction of the body 100 (light reflected by the dermis 102 and subcutaneous tissue 103; see arrow B1 in Figure 7) passes through the first inclined plates 23. On the other hand, reflected light that penetrates deeply into the depth direction of the body 100 (light transmitted through muscle tissue 104; see arrows B2 and B3 in Figure 7) is not significantly inclined with respect to the normal direction of the light-receiving surface of the photodetector 10 and does not pass through the transmissive portion 21 between the first inclined plates 23. From the above, the photodetector 12 located in the nearby region 14 receives only reflected light that penetrates shallowly into the depth direction of the body 100. As a result, the accuracy of the oxygen saturation (noise) information of the dermis 102 and subcutaneous tissue 103, calculated from the detection results of the photodetector 12 located in the nearby region 14, is improved.

[0054] On the other hand, reflected light that is outside the body 100 and irradiated away from the light source 3 passes through the transmission section 21 between the second inclined plates 24 or between the third inclined plates 25 only if it is slightly inclined with respect to the normal direction of the light-receiving surface of the light detection device 10. Therefore, reflected light that penetrates deeply into the depth direction of the body 100 (see arrows B4 and B6 in Figure 7) passes through the space between the second inclined plates 24 or between the third inclined plates 25. On the other hand, reflected light that penetrates shallowly into the depth direction of the body 100 (see arrow B5 in Figure 7) is significantly inclined with respect to the normal direction of the light-receiving surface of the light detection device 10 and does not pass through the transmission section 21 between the second inclined plates 24 and between the third inclined plates 25. Therefore, the light detection unit 12 located in the separation region 15 receives only reflected light that penetrates deeply into the depth direction of the body 100. As a result, the accuracy of the muscle oxygen saturation (SmO2) calculated from the detection results of the photodetector 12 located in the separation region 15 is improved.

[0055] As described above, according to Embodiment 3, the filter 18 (louvers 19) separates the light that has passed through the dermis 102 and subcutaneous tissue 103 from the light that has passed through the muscle tissue 104, allowing the light detection unit 12 to receive them. In other words, the resolution of each light detection unit 12 is improved, and accurate muscle oxygen saturation (SmO2) can be detected.

[0056] Note that the inclination angles θ11, θ12, and θ13 of the first inclined plate 23, second inclined plate 24, and third inclined plate 25 in Embodiment 3 are illustrative examples and may differ from the angles exemplified in the embodiments. Also, while Embodiment 3 has three first vane plates 22 with different inclination angles (first inclined plate 23, second inclined plate 24, and third inclined plate 25), it may have two or four or more, and is not particularly limited.

[0057] (Embodiment 4) Figure 8 is a schematic plan view of the transcutaneous muscle oxygen saturation detection device of Embodiment 4. Figure 9 is a cross-sectional view taken along the line IX-IX in Figure 8. As shown in Figure 8, the transcutaneous muscle oxygen saturation detection device 1C of Embodiment 4 differs from the transcutaneous muscle oxygen saturation detection device 1B of Embodiment 3 in that the louvers 19 are equipped with a plurality of second blades 26. The second blades 26 will be described below.

[0058] The second vane plate 26 is part of the resin layer 20 and is a plate-shaped, black light-absorbing portion that extends in the thickness direction. In other words, like the first vane plate 22, the second vane plate 26 has a black outer surface and absorbs reflected light incident on its outer surface. As shown in Figure 8, the second vane plate 26 extends in a direction perpendicular to the first vane plate 22. Multiple second vane plates 26 are arranged at equal intervals in the direction in which the first vane plate 22 extends. A transmissive portion 21 is positioned between the second vane plates 26. As shown in Figure 9, the second vane plate 26 is interposed between the first vane plate 22 and the light detection device 10. The transmissive portion 21 and the light detection unit 12 located between the second vane plates 26 are positioned to overlap. The inclination angle of the second vane plate 26 with respect to the light detection device 10 is 90°.

[0059] As described above, according to the transcutaneous muscle oxygen saturation detection device 1C of Embodiment 4, reflected light irradiated to the outside of the body 100 passes between the first vane plates 22 and then between the second vane plates 26 before entering the photodetector 12. Furthermore, among the reflected light irradiated to the outside of the body 100, reflected light that is significantly tilted in the direction in which the first vane plates 22 extend (see arrows B7, B8, and B9 in Figure 9) comes into contact with the second vane plates 26 and does not enter the photodetector 12. Therefore, each photodetector 12 receives only the reflected light from the corresponding region among the regions divided into first and second directions of the muscle tissue 104. Consequently, the resolution of each photodetector 12 is improved, and accurate muscle oxygen saturation (SmO2) can be detected.

[0060] (Embodiment 5) Figure 10 is a schematic plan view of the transcutaneous muscle oxygen saturation detection device of Embodiment 5. As shown in Figure 10, the transcutaneous muscle oxygen saturation detection device 1D of Embodiment 5 differs from the other embodiments in that each component is arranged in a circular shape with the light source 3 at the center.

[0061] In detail, the sheet 2 and the light detection device 10 are circular in shape with the light source 3 at the center. The light source 3 is fixed to the center of the light detection device 10. The first louvers 19 have three first louvers 22, which are annular in shape with the light source 3 at the center. There are three first louvers 22. The three first louvers 22 are the first inclined plate 23, the second inclined plate 24, and the third inclined plate 25, with different inclination angles from the inner circumference. The second louvers 26 extend radially from the light source 3. The light detection units (not shown) of the light detection device 10 are provided one in each region separated by the first louvers 22 (first inclined plate 23, second inclined plate 24, third inclined plate 25) and the second louvers 26.

[0062] In this embodiment 5 of the transcutaneous muscle oxygen saturation detection device 1D, the same effects as in embodiment 4 can be obtained. In addition, in the optical detection device of this disclosure, multiple optical detection units may be arranged in each region separated by the first vane 22 and the second vane 26.

[0063] In Embodiments 1 to 5 described above, transcutaneous muscle oxygen saturation detection devices 1, 1A, 1B, 1C, and 1D, which have only one light source 3, were described. However, the transcutaneous muscle oxygen saturation detection devices of this disclosure may have two or more light sources. Hereinafter, transcutaneous muscle oxygen saturation detection devices equipped with multiple light sources will be described.

[0064] (Embodiment 6) Figure 11 is a schematic plan view of the transcutaneous muscle oxygen saturation detection device of Embodiment 6. The transcutaneous muscle oxygen saturation detection device 1E of Embodiment 6 comprises one sheet 2, two light sources 3A and 3B, four light detection devices 10A and 10B, and four louvers 19.

[0065] Light sources 3A and 3B are fixed to the center of sheet 2 in the first direction Dx. Light sources 3A and 3B are separated from each other in the second direction Dy. Two photodetectors 10A are fixed to sheet 2 so as to sandwich light source 3A from both sides in the first direction Dx. Two photodetectors 10B are fixed to sheet 2 so as to sandwich light source 3B from both sides in the first direction Dx.

[0066] The louvers 19 are provided on each of the light detection devices 10A and 10B. The first vanes 22 extend in the second direction Dy and the third direction Dz. The first vanes 22 are arranged in the first direction Dx. Furthermore, as the distance from the light sources 3A and 3B increases, the inclination angle of the first vanes 22 with respect to the light detection devices 10A and 10B increases (becoming perpendicular to the light detection devices 10A and 10B).

[0067] As described above, according to the transcutaneous muscle oxygen saturation detection device 1D of Embodiment 6, two photodetectors 10A receive light (reflected light) emitted from light source 3A. Photodetector 10B receives light (reflected light) emitted from light source 3B. Therefore, a wider range of muscle oxygen saturation (SmO2) can be obtained. In addition, because louvers 19 are provided, reflected light that penetrates shallowly into the depth direction of the body 100 is incident on the photodetectors near light sources 3A and 3B, and reflected light that penetrates deeply into the depth direction of the body 100 is incident on the photodetectors far from light sources 3A and 3B. Therefore, the resolution of the photodetectors is high. Note that the two light sources 3A and 3B can be lit simultaneously or sequentially.

[0068] (Embodiment 7) Figure 12 is a schematic plan view of the transcutaneous muscle oxygen saturation detection device of Embodiment 7. As shown in Figure 12, the transcutaneous muscle oxygen saturation detection device 1F of Embodiment 7 comprises one sheet 2, five light sources 3C, 3D, 3E, 3F, and 3G, two light detection devices 10C, and two louvers 19.

[0069] Light sources 3C, 3D, 3E, 3F, and 3G are fixed to the center of sheet 2 in the first direction Dx. Light sources 3C, 3D, 3E, 3F, and 3G are also arranged in the second direction Dy, spaced apart from each other. Two light detection devices 10C are positioned to sandwich light sources 3C, 3D, 3E, 3F, and 3G from both sides in the first direction Dx. The first vane 22 of the louver 19 is designed so that its inclination angle with respect to the light detection devices 10C increases as the distance from light sources 3C, 3D, 3E, 3F, and 3G increases.

[0070] In Embodiment 6, the transcutaneous muscle oxygen saturation detection device 1F is illuminated in the order of light sources 3C, 3D, 3E, 3F, and 3G, as indicated by arrow E in Figure 12. The light detection devices 10C on both sides then sequentially receive the light (reflected light) emitted from light sources 3C, 3D, 3E, 3F, and 3G. Therefore, the light detection device 10C is shared among multiple light sources. As a result, the transcutaneous muscle oxygen saturation detection device 1F of Embodiment 6 can obtain a wider range of muscle oxygen saturation (SmO2). Furthermore, it is equipped with louvers 19, and the resolution of the light detection unit is high.

[0071] (Embodiment 8) Figure 13 is a schematic plan view of the transcutaneous muscle oxygen saturation detection device of Embodiment 8, and further shows the range of the photodetectors that are driven during the first to third illumination. Figure 14 is a plan view showing the range of the photodetectors that are driven during the fourth to sixth illumination in the transcutaneous muscle oxygen saturation detection device of Embodiment 8. As shown in Figure 13, the transcutaneous muscle oxygen saturation detection device 1G of Embodiment 8 comprises a sheet 2, six light sources 3, and twelve photodetectors 10.

[0072] The six light sources 3 (31, 32, 33, 34, 35, 36) are arranged in a matrix with two rows in the first direction Dx and three rows in the second direction Dy. The twelve photodetectors 10 (41, 42, 43, 44, 45, 45, 46, 47, 48, 49, 50, 51, 52) are also arranged in a matrix with three rows in the first direction Dx and four rows in the second direction Dy. Each of the four photodetectors 10 is positioned in the center of each light source 3. Therefore, when one light source 3 emits light, the four photodetectors 10 receive the reflected light.

[0073] In this transcutaneous muscle oxygen saturation detection device 1G, the light sources 3 are lit in the following order: first light source 31, second light source 32, third light source 33, fourth light source 34, fifth light source 35, and sixth light source 36. Therefore, when the first light source 31 is lit for the first time, the light detection devices 41, 42, 44, and 45 enclosed by the dashed line M1 in Figure 13 receive light (reflected light). When the second light source 32 is lit for the second time, the light detection devices 42, 43, 45, and 46 enclosed by the dashed line M2 in Figure 13 receive light (reflected light). When the third light source 33 is lit for the third time, the light detection devices 44, 45, 47, and 48 enclosed by the dashed line M3 in Figure 13 receive light (reflected light).

[0074] When the fourth light source 34 is turned on for the fourth time, the light detection devices 45, 46, 48, and 49 enclosed by the dashed line M4 in Figure 14 receive the light (reflected light). When the fifth light source 35 is turned on for the fifth time, the light detection devices 47, 48, 50, and 51 enclosed by the dashed line M5 in Figure 14 receive the light (reflected light). When the sixth light source 36 is turned on for the sixth time, the light detection devices 48, 49, 51, and 52 enclosed by the dashed line M6 in Figure 14 receive the light (reflected light).

[0075] As described above, the transcutaneous muscle oxygen saturation detection device 1G of Embodiment 8 can obtain a wide range of muscle oxygen saturation (SmO2). Furthermore, the photodetector 10 can be shared, and the number of photodetectors 10 can be reduced.

[0076] Although embodiments 1 to 8 have been described above, the transcutaneous muscle oxygen saturation detection device of this disclosure is not limited to the examples described in the embodiments. For example, with respect to the transcutaneous muscle oxygen saturation detection device 1C of Embodiment 4, instead of the second vane 26 perpendicular to the first vane 22, a radial second vane 26 as described in Embodiment 5 may be provided. Also, although the louver 19 in the embodiments is made of a resin layer 20, the louver of this disclosure may be made of a material other than resin. Alternatively, the louver 19 may be provided in the transcutaneous muscle oxygen saturation detection device 1 of Embodiment 1. Furthermore, although an example using the louver 19 as a filter 18 has been given, a combination of a pinhole or microlens may also be used as a filter. In addition, the oxygen saturation detection device of this disclosure may be attached to the forehead to measure the time-dependent change in oxygen saturation of the frontal lobe and monitor the activity of brain cells, in addition to muscle tissue such as the arms and legs. [Explanation of Symbols]

[0077] 1, 1A, 1B, 1C, 1D, 1E, 1F, 1G Transcutaneous muscle oxygen saturation detection device 2 sheets 3, 3A, 3B, 3C, 3D, 3E, 3F, 3G light source 4. First light detection unit 5. Second light detection unit 10, 10A, 10B, 10C Photodetector 18 filters 19 Louvers 20 resin layer 21 Transparent part 22 First blade 23 1st inclined plate 24 2nd inclined plate 25 Third inclined plate 26. Second wing plate 103 Subcutaneous tissue 104 Muscle tissue

Claims

1. A light source that causes light to enter the inside of the body, The body comprises a first light detection unit and a second light detection unit for detecting reflected light reflected from within the body, The second light detection unit is positioned circumferentially around the light source, away from a first imaginary line connecting the light source and the first light detection unit. The device includes a light detection device in which multiple light detection units are provided on a substrate, The plurality of light detection units include the first light detection unit and the second light detection unit, The body is positioned between the light detection device and the body and includes a filter that defines the angle of the reflected light that is emitted from inside the body and incident on the light detection unit, The filter has louvers, The light detection device has a light-receiving surface to which the reflected light is incident, The louver has a plurality of first blades that divide the light-receiving surface in a direction that separates it from the light source, Each of the multiple first vanes includes a first inclined plate positioned near the light source and a second inclined plate positioned further from the light source than the first inclined plate. The first and second inclined plates are inclined toward the light source as they move away from the light-receiving surface. The inclination angle of the first inclined plate is greater than the inclination angle of the second inclined plate. Transcutaneous muscle oxygen saturation detection device.

2. The light source emits red light and infrared light. The transcutaneous muscle oxygen saturation detection device according to claim 1.

3. The intersection angle between the second virtual line connecting the light source and the second light detection unit and the first virtual line is at least 5°. A transcutaneous muscle oxygen saturation detection device according to claim 1 or claim 2.

4. The system includes multiple of the aforementioned light detection devices. The transcutaneous muscle oxygen saturation detection device according to claim 1.

5. The light source comprises multiple such light sources, Multiple detection devices sequentially detect the reflected light emitted from multiple light sources. The transcutaneous muscle oxygen saturation detection device according to claim 1.

6. The percutaneous muscle oxygen saturation detection device according to claim 1, wherein the louver has a plurality of second blades extending in a direction intersecting the first blade.

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