Pulse wave detection device

Abstract

This pulse wave detection device is provided with: a sensor substrate that has a mounting surface and a rear surface; a light-receiving element that is arranged on the mounting surface of the sensor substrate; a light-emitting element that is arranged on the mounting surface so as to be apart from the light-receiving element; and an optical guide unit that has, on the mounting surface side of the sensor substrate, a first opening surrounding the light-receiving unit, a second opening corresponding to the first opening and arranged in a top part of a curved surface or in the vicinity of the top part, a third opening surrounding the light-emitting unit, a fourth opening corresponding to the third opening and arranged in the curved surface, a first optical guide path having a reflection surface connecting the first opening and the second opening to each other, and a second optical guide path having a reflection surface connecting the third opening and the fourth opening to each other.

Description

Pulse wave detector

[0001] The present embodiment relates to a pulse wave detecting device.

[0002] One type of pulse wave detection device known is a photoplethysmographic sensor. A photoplethysmographic sensor irradiates light emitted by a light-emitting element onto the surface of the human body and receives the transmitted or reflected light. The wavelength of the light used is selected from a wavelength range (e.g., from green to near-infrared) that is easily absorbed by hemoglobin in the blood. A photoplethysmographic sensor detects pulse waves by utilizing the fact that changes in the amount of received light correspond to vascular volume pulse waves.

[0003] JP 2013-63203 A JP 2015-16194 A

[0004] In recent years, photoplethysmographic sensors have been installed in wearable devices such as smartwatches, and in such cases, it is desirable to detect pulse waves with high sensitivity and stability.

[0005] An object of the present invention is to provide a pulse wave detecting device that is capable of detecting pulse waves with high sensitivity and stability.

[0006] According to the present invention, a pulse wave detection device includes a sensor substrate having a mounting surface and a back surface, a light receiving element provided on the mounting surface of the sensor substrate, a light emitting element provided on the mounting surface at a distance from the light receiving element, and a light guiding section having a first opening on the mounting surface side of the sensor substrate surrounding the light receiving element, a second opening corresponding to the first opening and provided at or near the top of the curved surface, a third opening surrounding the light emitting element, a fourth opening corresponding to the third opening and provided on the curved surface, a first light guiding path having a reflective surface connecting the first opening and the second opening, and a second light guiding path having a reflective surface connecting the third opening and the fourth opening.

[0007] The present invention has the effect of providing a pulse wave detecting device that can detect pulse waves with high sensitivity and stability.

[0008] FIG. 1 shows a conventional sensor and is a diagram illustrating the optical path of light for pulse wave detection. FIG. 2 shows a conventional sensor and is a diagram illustrating the optical path of light for pulse wave detection. FIG. 3 is a diagram illustrating a method for wearing a wearable device equipped with a pulse wave detection device of an embodiment. FIG. 4 is a cross-sectional view of the wearable device of the embodiment worn on the arm, taken along the YZ plane. FIG. 5 is a cross-sectional view of the sensor of the embodiment, taken along the YZ plane. FIG. 6 is a cross-sectional view of the sensor of the embodiment, taken along the XZ plane. FIG. 7 is a view of the sensor of the embodiment as seen from the negative side in the Z axis direction. FIG. 8 is a perspective view of the light guide unit of the embodiment, taken along the YZ plane. FIG. 9 is a block diagram illustrating a circuit mounted on a sensor substrate of the embodiment. FIG. 10 is a diagram illustrating the optical path of light emitted from a light-emitting element in the sensor of the embodiment when the wearable device is worn so that the second surface is in close contact with the skin. FIG. 11 is a diagram illustrating the optical path of light emitted from a light-emitting element in the sensor of the embodiment when a gap is formed between the second surface and the skin. FIG. 12 is a diagram illustrating contact between the light guide unit and skin according to an embodiment when the contact direction is tilted around the X axis. FIG. 13 is a diagram illustrating contact between the light guide unit and skin according to an embodiment when the contact direction is tilted around the Y axis. FIG. 14 is a diagram illustrating the S / N ratio when a user wearing a wearable device equipped with a sensor according to an embodiment in which the second surface is configured as a curved surface swings their arm in various directions. FIG. 15 is a diagram illustrating an adjustment mechanism according to a modified embodiment. FIG. 16 is a diagram illustrating an example of the shape of a sponge serving as the elastic portion according to a modified embodiment. FIG. 17 is a diagram illustrating another example of the shape of a sponge serving as the elastic portion according to a modified embodiment. FIG. 18 is a diagram illustrating yet another example of the shape of a sponge serving as the elastic portion according to a modified embodiment.

[0009] First, the problems with conventional photoplethysmographic sensors will be described. Conventional photoplethysmographic sensors will be referred to as P sensor 200, with the prefix "prior" added. In this specification, "returned light" refers to light used for pulse wave detection that is irradiated onto and returned from the human body. This specification also describes the case where the P sensor 200 and a pulse wave detection device (also referred to as a sensor) of the embodiment are mounted in a wristwatch-type wearable device (e.g., a smartwatch).

[0010] 1 and 2 show the P sensor 200 and are diagrams for explaining the optical path of the light for detecting the pulse wave.

[0011] 1 shows arm skin 401 and blood vessels 402 beneath the skin 401. The P sensor 200 includes a sensor substrate 201, two light-emitting elements 202, and a light-receiving element 203. The two light-emitting elements 202 and the light-receiving element 203 are mounted on the surface of the sensor substrate 201. The sensor surface is disposed so as to be in close contact with the skin 401.

[0012] The light received by the light receiving element 203 is mainly light 301 that is emitted from the light emitting element 202, penetrates under the skin 401, and is reflected or scattered by the subcutaneous tissue before returning. Because blood vessels 402 are present under the skin, some of the light 301 increases or decreases due to the influence of the volume pulse wave of the blood vessels 402. Oxygenated hemoglobin is present in arterial blood in particular, and has the property of absorbing incident light. Therefore, a pulse wave signal can be measured by sensing the blood flow rate (change in blood vessel volume) that changes in accordance with the pulsation of the heart in a time series.

[0013] Therefore, the P sensor 200 can detect the pulse wave based on the change in the amount of light 301.

[0014] However, when the P sensor 200 is mounted on a wristwatch-type wearable device, depending on the method of wearing the device on the arm and the shape of the wearer's arm, it may be difficult to bring the sensor surface into close contact with the skin 401. Furthermore, due to the wearer's body movements, it may be difficult to maintain the sensor surface in close contact with the skin 401 for the entire period during which the pulse wave is detected. In these cases, a gap may be created between the sensor surface of the P sensor 200 and the skin 401.

[0015] FIG. 2 shows the case where a gap occurs between the skin 401 and the sensor surface, and illustrates the optical path at that time.

[0016] As shown in Fig. 2, light receiving element 203 receives not only light 301 that penetrates beneath skin 401 and returns after being reflected or scattered at a site where blood vessels 402 are present, but also light 302 that is directly incident on light receiving element 203 from light emitting element 202 and light 303 that is reflected or scattered at the surface of skin 401. Light 302 and light 303 are not affected by the volume pulse wave of blood vessels 402. In the case shown in Fig. 2, the proportion of components unrelated to the pulse wave, such as light 302 and light 303, is higher than in the case shown in Fig. 1, which deteriorates the S (signal) / N (noise) ratio of the pulse waveform obtained by calculation and makes it difficult to detect the pulse wave.

[0017] The pulse wave detecting device of the embodiment uses a light guide section to prevent light 302 and light 303 from entering the light receiving element, thereby enabling highly accurate and stable pulse wave detection.

[0018] The pulse wave detection device of the embodiment will be described in detail below. However, the present invention is not limited to this embodiment. As described above, the pulse wave detection device of the embodiment will be described as being mounted on a wristwatch-type wearable device. The pulse wave detection device of the embodiment may also be mounted on wearable devices other than wristwatch-type devices. For example, the pulse wave detection device of the embodiment may be mounted on wearable devices such as smart glasses, smart rings, or wireless earphones. In the case of smart glasses, the sensor surface may be provided on nose pads or ear hooks. The pulse wave detection device of the embodiment may also be mounted on any stationary device. For example, it may be implemented in an examination device that measures CAVI (Cardio-Ankle Vascular Index) or ABI (Ankle-Brachial Pressure Index), or an FMD (Flow Mediated Dilation) examination device.

[0019] FIG. 3 is a diagram for explaining a method of wearing the wearable device 1000 equipped with the pulse wave detection device of the embodiment.

[0020] The wearable device 1000 comprises a flat housing 1001, a display device 1002, and a band 1003. The housing 1001 is made up of a top surface, a bottom surface, and side surfaces connecting the periphery of the top surface and the periphery of the bottom surface. In the figure, the housing is made up of a roughly rectangular parallelepiped and has four side surfaces.

[0021] The sensor 100 is provided in the housing 1001. Bands 1003 are attached to one side and the other side of the housing 1001. The band 1003 is wrapped around the wearer's arm 400, thereby fixing the bottom surface of the housing 1001 to the arm 400. A display device 1002 is provided on the surface (top surface) of the housing 1001 opposite to the surface facing the arm 400, and the wearable device 1000 outputs various types of image information to the display device 1002. The wearer can visually confirm the various types of image information output to the display device 1002.

[0022] In the following description, the direction corresponding to the extension of the arm will be referred to as the positive direction of the X axis, the direction from the bottom to the top of the two surfaces of the housing 1001 will be referred to as the positive direction of the Z axis, and the axis perpendicular to both the X axis and the Z axis will be referred to as the Y axis.

[0023] FIG. 4 is a cross-sectional view of the wearable device 1000 and the arm 400 in FIG. 3 taken along the YZ plane.

[0024] A radius 411 and an ulna 412 extend in the X-axis direction inside the arm 400. A radial artery 413 runs below the radius 411, and an ulnar artery 414 runs below the ulna 412. A tendon 415 runs subcutaneously at the lowest part of the cross section of the arm 400.

[0025] A sensor 100, which is a pulse wave measuring device according to an embodiment, is provided on the underside of the housing 1001. The sensor 100 includes a sensor substrate 110 and a light guide unit 120.

[0026] 5 and 6 show the sensor 100 of FIG. 4 in its original orientation.

[0027] Two light-emitting elements 111 (not shown in FIG. 4 ) and a light-receiving element 112 are provided on the surface of the sensor substrate 110 on the negative side in the Z axis direction, i.e., on an element mounting surface 113. A light-guiding section 120 is provided on the mounting surface 113 of the sensor substrate 110 so as to encompass and cover the elements 111 and 112. The mounting surface 113 of the sensor substrate 110 is an example of a first surface (the first surface 113 described below). The surface of the sensor substrate 110 opposite the mounting surface 113 is referred to as the back surface.

[0028] 4, the width of light guiding unit 120 in the Y-axis direction is sufficiently narrower than the width of arm 400 in the Y-axis direction. Furthermore, light guiding unit 120 protrudes from the mounting surface of housing 1001 toward the arm. This protruding surface actually has a shape like a cut sphere or a rugby ball, as shown in FIG. 8, and its cross section describes a curved surface, as shown in FIGS. 5 and 6.

[0029] Therefore, when wearable device 1000 is worn on arm 400, a portion of light guiding unit 120 digs into arm 400 depending on the tightness of band 1003, and the curved surface of light guiding unit 120 comes into close contact with the skin. Note that the curved surface of light guiding unit 120 is an example of a second surface (second surface 121 described later).

[0030] The light guide unit 120 may be made of an elastic material. The elastic material is made of a material that can stretch when a force is applied. The elastic material may be, for example, silicone or rubber, but is not limited to these. Furthermore, it is desirable that the elastic material constituting the light guide unit 120 be made of a material that is soft to the touch, does not cause irritation, provides a comfortable fit, is highly durable, and is resistant to deformation and tearing, similar to the rubber band of a smartwatch.

[0031] Because light guide 120 is made of an elastic material, it can expand and contract when a force is applied to light guide 120. This improves the adhesion between the curved surface of light guide 120 (i.e., second surface 121) and the skin of arm 400. Even if the wearing position of sensor 100 shifts in the X-axis, Y-axis, or Z-axis directions or shifts slightly in the rotational direction around these axes due to the wearer's body movement or wearing method, these shifts can be absorbed by the elastic deformation of light guide 120, and the adhesion between the curved surface of light guide 120 (i.e., second surface 121) and the skin can be maintained.

[0032] Although the description of tight contact is given, if the band 1003 is not tight enough, the device will not be tight. When the band is fastened to the arm, if the device 1000 is worn with a part of the protruding part in contact with or sinking into the skin, it will be possible to take in reflected light from the light guide unit 120 even if the device 1000 is shifted to some extent. Details will be described later.

[0033] Fig. 5 is a cross-sectional view of the light receiving element 112 in Fig. 7 cut along the YZ plane. Fig. 6 is a cross-sectional view of the light emitting element 111 and the light receiving element 112 in Fig. 7 cut along the XZ plane. Fig. 7 is a plan view of the sensor 100 of the embodiment, seen from the negative side in the Z axis direction. Fig. 8 is a perspective view of the light guiding unit 120 of the embodiment cut along the YZ plane.

[0034] 5 to 7 , two light-emitting elements 111 and a light-receiving element 112 are provided spaced apart in the X direction (long side direction) on the mounting surface 113 of the rectangular sensor substrate 110, i.e., the surface 113 facing the skin 401. Furthermore, one light-receiving element 112 is provided between the two light-emitting elements 111 on the surface 113. Hereinafter, the surface 113 will be referred to as the first surface 113.

[0035] Each light-emitting element 111 emits light in a wavelength band that is easily absorbed by hemoglobin. For example, this is a wavelength band from green to near-infrared. The two light-emitting elements 111 may emit light of the same wavelength, or may emit light of different wavelengths. Each light-emitting element 111 is, for example, a light-emitting diode. Note that each light-emitting element 111 does not have to be a light-emitting diode.

[0036] The light receiving element 112 outputs a signal according to the amount of light received. The light receiving element 112 is, for example, a photodiode. However, the light receiving element 112 does not have to be a photodiode.

[0037] The curved surface 121 of the light guiding section 120 has two first openings 122 for the light emitting elements and one second opening 123 for the light receiving element.

[0038] As shown in FIG. 10, the light guide section 120 has two first light guide paths 124 for the light emitting element and one second light guide path 125 for the light receiving element.

[0039] As shown in FIGS. 7 and 8, the light guide section 120 is a dome-shaped resin molded body, and has a curved surface 121 and a flat contact surface on the sensor substrate 110 side.

[0040] 7, the plane of the contact surface is rectangular (rectangular in this case) and curves from the inside to the outside of the outer shape. Since it curves and protrudes so as to surround the two light-emitting elements 111 and the light-receiving element 112 together, the curved portion appears elliptical when viewed in plan.

[0041] The contact surface is provided with openings 122A surrounding the two light emitting elements 111 respectively, and an opening 123A surrounding the light receiving element 112.

[0042] The outer periphery of each opening 122A forms a megaphone-shaped reflecting surface that connects the outer peripheries of the corresponding first openings 122, and the inside of the reflecting surface forms a space.

[0043] A portion of the light emitted from the light emitting element 111 travels straight through the space of the first light guide path 124 and is emitted to the outside (skin). A portion of the light is emitted to the outside while reflecting off the reflective surface of the first light guide path. On the other hand, a portion of the light that enters the second opening 123 of the second light guide path heads directly toward the light receiving element, and a portion of the light is reflected off the reflective surface of the second light guide path 125 and heads toward the light receiving element.

[0044] The sensor substrate 110 is a printed circuit board made of resin or ceramic, and has a conductive pattern made of electrodes and wiring on the mounting surface, with the light-emitting element and light-receiving element mounted and electrically connected to the electrodes. For insulation, the light-guiding section 120 is made of an insulator, and the surface of the printed circuit board is covered with solder resist. Therefore, the contact surface of the light-guiding section 120 can contact the printed circuit board.

[0045] When the wearable device 1000 is worn on the arm 400, each of the first light guide paths 124 can guide the light emitted from the light emitting element 111 to the arm 400. Furthermore, the second light guide path 125 can guide the returning light from the arm 400 to the light receiving element 112.

[0046] 5 to 8, each of the first light guide paths 124 has a tapered shape in which the cross-sectional area in the XY plane increases from the sensor substrate 110 side toward the first opening 122 side. The second light guide path 125 has a tapered shape in which the cross-sectional area in the XY plane increases from the sensor substrate 110 side toward the second opening 123 side.

[0047] The inner wall 126 of each of the first light guide paths 124 and the inner wall 127 of each of the second light guide paths 125 have a structure that reflects light.

[0048] As described above, the light guide unit 120 is molded using a resin mold. Therefore, the inner surfaces of the mold, which correspond to the reflective surfaces 126 and 127, are gloss-finished. This improves the light reflectivity of the reflective surfaces 126 and 127, preventing unnecessary absorption of energy by the reflective surfaces and improving the sensitivity of the pulse wave detection device. Since epoxy resins, in particular, are molded with a glossy finish, plating or other processes may be used. However, because the resin itself is light-transmitting (to varying degrees depending on the material), the inner walls 126 and 127 may be coated with a light-reflecting material (e.g., a metal) by plating, sputtering, vapor deposition, or other methods.

[0049] The light-reflecting structure of inner wall 126 allows light from light-emitting element 111 to be guided to the outside, thereby increasing the amount of light irradiated onto arm 400. The light-reflecting structure of inner wall 127 allows the oblique light of the returning light from the arm to be guided to light-receiving element 112 by one or more reflections.

[0050] As shown in Figures 5 and 8, the contact surface of the light-guiding section 120 that contacts the sensor substrate 110 has folded sections 128 that extend from the sides corresponding to the two opposing side edges of the sensor substrate toward the back surface of the sensor substrate 110.

[0051] For example, folded portions 128 are provided at both ends of the light guiding unit 120 in the Y-axis direction, and are folded from the side surfaces of the long sides of the sensor substrate 110 to the rear surface 116 (referred to as the third surface 116) of the sensor substrate 110. These folded portions 128 have a contact surface that abuts against the rear surface with a slight width from the outer periphery of the rear surface of the sensor substrate 110. Because the sensor substrate 110 is made of a printed circuit board, it has a certain degree of flatness, and by inserting and fitting the sensor substrate 110 into the space in the folded portions 128 of the light guiding unit 120, the contact surface of the light guiding unit 120 abuts against and is fixed to the mounting surface of the sensor substrate 110.

[0052] 5 to 8, second opening 123 is formed at the top of the curved portion of second surface 121 of light guiding section 120. In other words, second opening 123 is formed by the curved surface at the point where the protrusion height is the highest.

[0053] FIG. 9 is a block diagram for explaining a circuit mounted on the sensor substrate 110 of the embodiment.

[0054] The sensor board 110 includes two light-emitting elements 111 , a light-receiving element 112 , a microcomputer unit 114 , and a gain circuit 115 .

[0055] The gain circuit 115 is a circuit that amplifies the signal from the light receiving element 112 .

[0056] The microcomputer unit 114 is a circuit including a processor and a memory. The processor is, for example, a CPU (Central Processing Unit).

[0057] The microcomputer unit 114 causes the processor to execute a program, thereby turning on the light-emitting element 111 and calculating a pulse wave based on a signal from the light-receiving element 112 that receives light via the gain circuit 115. The microcomputer unit 114 can display the pulse wave obtained by this calculation on the display device 1002.

[0058] The sensor 100 described above includes two light-emitting elements 111 and one light-receiving element 112. One light-receiving element 112 is provided approximately at the center of the first surface 113 of the sensor substrate 110, and two light-emitting elements 111 are provided spaced apart on the periphery. Three or more light-emitting elements 111 may be provided around the light-receiving element 112. A light-receiving element 112 may be provided instead of the light-emitting element 111, and in that case, a light-emitting element 111 may be provided instead of the light-receiving element 112. The number of light-emitting elements 111 included in the sensor 100 is not limited to two. The number of light-receiving elements 112 included in the sensor 100 is not limited to one. The light-guiding unit 120 may include first openings 122 and first light guide paths 124 in a number corresponding to the number of light-emitting elements 111, and second openings 123 and second light guide paths 125 in a number corresponding to the number of light-receiving elements 112.

[0059] As described above, according to this embodiment, the sensor 100 includes a sensor substrate 110 and a light guide 120. A light emitting element 111 that emits light and a light receiving element 112 that outputs a signal corresponding to the amount of returned light are provided on a first surface 113, which is a mounting surface of the sensor substrate 110. The light receiving element 112 is provided in the center of the first surface 113 of the substrate 110, and two light emitting elements 111 are provided spaced apart on the periphery. The light guide 120 is provided on the first surface 113. The light guide 120 has a second surface (curved surface) that faces and contacts the human body and has a first opening 122 and a second opening 123. The light guide 120 has a first light guide path 124 that connects the light emitting element 111 to the first opening 122 and a second light guide path 125 that connects the light receiving element 112 to the second opening 123. A microcomputer unit 114 is electrically connected to the sensor board 110. The microcomputer unit 114 calculates the pulse wave based on the signal output from the light receiving element 112.

[0060] FIG. 10, FIG. 12, or FIG. 13 shows the wearable device 1000 when worn so that the second surface (curved surface) 121 is in close contact with the skin.

[0061] Because light-guiding section 120 is configured as a curved section, second opening 123 and its surroundings, particularly the periphery of the top, act as a fulcrum for vertical and horizontal displacement. Therefore, even if light-guiding section 120 is displaced, opening 123 remains in close contact to ensure the optical path. Therefore, most of the light entering opening 123 is made up of returning light.

[0062] The light guide section 120 is provided with a first light guide path 124 that guides the light from the light emitting element 111 and a second light guide path 125 that guides the returning light returning from the human body to the light receiving element 112 .

[0063] Therefore, when second opening 123 is in close contact with skin 401, light enters the skin from light-emitting element 111, and the returning light travels directly to light-receiving element 112. Furthermore, as shown in Figure 2, noise light caused by the gap is blocked. In particular, light reflected by skin 401 and traveling toward light-receiving element 112 is blocked. Therefore, noise components unrelated to the pulse wave can be significantly reduced, enabling highly accurate detection of the pulse wave.

[0064] Fig. 11 shows a case where a gap occurs between the second surface 121 and the skin. However, in general, a gap does not occur because the curved surface is always in contact with the skin as shown in Fig. 12 and Fig. 13. Here, we will explain the case where a gap occurs.

[0065] 11 , even if a gap occurs between second surface 121 and skin 401, light-guiding unit 120 has a certain height due to the curved surface that protrudes toward the skin. This height acts as a barrier to light, preventing the intrusion of light that causes noise.

[0066] Furthermore, according to the embodiment, the light guiding section 120 is made of an elastic body.

[0067] Therefore, even if the wearing position of sensor 100 shifts slightly in the Z-axis direction, Y-axis direction, or around these axes due to the wearer's body movement or wearing method, such shifts can be absorbed by deformation of light-guiding section 120, and close contact between second surface 121 and skin 401 can be maintained. As described above, close contact between second opening 123, which forms the top, and skin 401 can be easily maintained, so that light emitted from light-emitting element 111 and reflected or scattered by skin 401 toward light-receiving element 112 can be blocked. As a result, highly sensitive and stable pulse wave detection is possible.

[0068] Furthermore, since the portion that comes into contact with the wearer's skin is soft, the discomfort felt by the wearer can be reduced compared to when the light guide section 120 is made of a hard material.

[0069] As described above, the light guide section 120 does not necessarily have to be made of an elastic material, but may be made of a hard material.

[0070] Furthermore, according to the embodiment, the second surface 121 is configured by a curved surface whose protruding height is greatest at the portion of the second opening 123. By configuring the second surface 121 in this way, the following effects can be obtained.

[0071] Depending on the shape of the wearer's arm 400, the wearing method, or the wearer's body movement, skin 401 may come into contact with second surface 121 from a direction other than the Z-axis direction. Fig. 12 is a diagram showing the state of contact between light guide unit 120 and skin 401 when the contact direction is tilted around the X-axis. Fig. 13 is a diagram showing the state of contact between light guide unit 120 and skin 401 when the contact direction is tilted around the Y-axis.

[0072] According to the embodiment, second surface 121 is configured by a curved surface that protrudes the most at second opening 123, and therefore, even if the contact direction is tilted around the X axis or the Y axis, opening 123 (its top and its vicinity) serves as a fulcrum, and close contact between second opening 123 and the skin can be maintained, as shown in Figures 12 and 13. Therefore, it is possible to block light that is emitted from light-emitting element 111, reflected or scattered by skin 401, and directed toward light-receiving element 112, and it is possible to detect a pulse wave without deteriorating detection accuracy.

[0073] FIG. 14 compares the conventional method with the present embodiment, and shows the S / N ratio of the pulse waveform when a user wearing the wearable device 1000 swings the arm 400 in various directions.

[0074] As shown in FIG. 14, in any case, the sensor 100 of the embodiment can obtain a higher S / N ratio than the P sensor 200.

[0075] (Modifications: Regarding the Adjustment Mechanism) Modifications of the embodiment will be described below. As is clear from the explanation so far, it is desirable that the light guide unit 120 be structured so that it always contacts the skin. FIG. 15 explains the adjustment mechanism. It can also be called a pressure adjustment mechanism or height adjustment mechanism for the sensor substrate 110. This mechanism 130 has a housing 131, which is a support member, and a member 132 that can expand and contract under pressure, like a sponge.

[0076] When belt 1003 is tightened, light guide unit 120 is pushed up by the skin, which in turn pushes up sensor substrate 110. As a result, the sponge shrinks in the thickness direction, but at the same time, it pushes sensor substrate 110 towards the skin. Therefore, light guide unit 120 always comes into contact with the skin.

[0077] FIG. 15 is a diagram illustrating the adjustment mechanism 130.

[0078] For example, a support member (here, a housing) having an internal space capable of housing the sensor substrate 110 and the elastic portion 132 is prepared. The housing 131 has a portion opened by an opening, and the periphery of this opening has a step so that the folded portion 128 can fit into it. The light guide portion 120, which is integral with the sensor substrate 110, is fitted into this stepped opening, and the sensor substrate 110 with the fixed light guide portion 120 is provided in the housing 131 so that the first surface 113, which is the mounting surface, faces outward. The rear surface of the sensor substrate 110 exposed from the light guide portion 120 is provided with the adjustment mechanism 130. In the figure, the elastic portion 132 is made of a sponge-like resin. However, the elastic portion may be made of a metal such as a spring.

[0079] Light guide unit 120, to which sensor substrate 100 is fitted, is provided with a very thin gap between it and the inner wall that defines the internal space of the housing, and is provided so as to be movable in the thickness direction of the housing. Therefore, when attached to the arm, it is pushed upward in Figure 15. As a result, sponge 132 contracts. On the other hand, the contraction of the sponge, i.e., its restoring force, presses sensor substrate 110 downward, so that light guide unit 120 always abuts against the skin.

[0080] 15 , the sensor substrate 110 can move from a lower limit position 510 located at the center of the sensor substrate 110 to an upper limit position 520. When the light guide unit 120 is pressed against the skin 401, the elastic portion 132 flexibly deforms and contracts like a spring, moving within the range indicated by the symbol 500. The force that attempts to restore the sensor substrate 110 pushes it in a direction from the third surface 116 toward the first surface 113. Conversely, when the light guide unit 120 is not pressed against the skin 401, the force of the elastic portion 132 pushes the sensor substrate 110 to the lower limit position 510 of the range 500.

[0081] The elastic portion 132 may be a flat sponge 133 having approximately the same area as the third surface 116, as shown in Fig. 16 . Alternatively, the elastic portion 132 may be a flat sponge 133 with a hole in the center, as shown in Fig. 17 . Alternatively, the elastic portion 132 may be a sponge 133 divided into multiple pieces, as shown in Fig. 18 . Note that in Fig. 18 , the sponge 133 is divided into four pieces and arranged at the four corners of the third surface 116 so that the four corners of the third surface 116 can be pressed. Note that the elastic portion 132 is not limited to the sponge 133. The elastic portion 132 may be composed of one or more springs.

[0082] The first light guide path 124 and the second light guide path 125 may be closed by a light-transmitting member. For example, a member that transmits light emitted by the light-emitting element 111 may close the first opening 122 and the second opening 123, and the first light guide path 124 and the second light guide path 125 may be hollow. Alternatively, the first light guide path 124 and the second light guide path 125 may be filled with a member that transmits light emitted by the light-emitting element 111.

[0083] The first light guide path 124 and the second light guide path 125 are closed with a material that transmits light emitted by the light-emitting element 111, making it possible to prevent dirt from adhering to the light-emitting element 111 or the light-receiving element 112.

[0084] Even if the first light guide path 124 and the second light guide path 125 are not closed with a material that transmits the light emitted by the light emitting element 111, by having a translucent cover that covers the opening 123A or the second opening 123, it is possible to prevent dirt from adhering to the light receiving element 112.

[0085] 100 Sensor, 110 Sensor substrate, 111 Light emitting element, 112 Light receiving element, 113 First surface, 114 Microcomputer unit, 115 Gain circuit, 116 Third surface, 120 Light guide section, 121 Second surface, 122 First opening, 122A Opening, 123 Second opening, 123A Opening, 124 First light guide path, 125 Second light guide path, 126, 127 Inner wall, 128 Folded portion, 130 Height adjustment mechanism, 131 Housing, 132 Elastic portion, 133 Sponge, 200 P sensor, 201 Sensor substrate, 202 Light emitting element, 203 Light receiving element, 301, 302, 303, 310 Light, 400 Arm, 401 Skin, 402 Blood vessel, 411 Radius, 412 Ulna, 413 Radial artery, 414 Ulnar artery, 415 Tendon, 500 Range, 510 Lower limit position, 520 Upper limit position, 1000 Wearable device, 1001 Housing, 1002 Display device, 1003 Band.

Claims

1. a sensor substrate having a mounting surface and a back surface; a light receiving element provided on the mounting surface of the sensor substrate; a light emitting element provided on the mounting surface at a distance from the light receiving element; a light guide section on the mounting surface side of the sensor substrate, the light guide section having a first opening surrounding the light receiving element, a second opening provided on the curved surface corresponding to the first opening, a third opening surrounding the light emitting element, a fourth opening provided on the curved surface corresponding to the third opening, a first light guide path having a reflective surface connecting the first opening and the second opening, and a second light guide path having a reflective surface connecting the third opening and the fourth opening; A pulse wave detection device having the same.

2. a fitting portion is provided on a side of the light guide portion that contacts the sensor substrate, and the light guide portion is fixed to the sensor substrate by the fitting portion; The pulse wave detecting device according to claim 1 .

3. The device further includes a housing having a portion opened by an opening, the sensor substrate to which the light guide unit is fixed is provided in the opening of the housing such that the mounting surface faces outward from the housing; The housing accommodates an elastic portion between a bottom of an internal space of the housing and the sensor substrate. The pulse wave detecting device according to claim 2.

4. The light guide portion is made of an elastic material and is stretchable. The pulse wave detecting device according to any one of claims 1 to 3.

5. the reflective surface of the first light guide path and the reflective surface of the second light guide path are gloss-treated; The pulse wave detecting device according to any one of claims 1 to 3.

6. the first opening or the second opening is covered with a light-transmitting cover; The pulse wave detecting device according to any one of claims 1 to 3.