Biological information measurement device

Abstract

Provided is a more accurate biological information measurement device.　According to the present invention, a biological information measurement device that measures biological information comprises a light projection unit that emits light, a light projection light guide unit that projects the light emitted by the light projection unit onto a living body, a light reception light guide unit that receives light that has been scattered inside the living body, a filter unit that has wavelength filters that are struck by light emitted from the light reception light guide unit, and a light detection unit that detects light that has been transmitted by the wavelength filters. The filter unit has a first wavelength filter that transmits light within a first wavelength range but reflects light within a second wavelength range and a second wavelength filter that transmits light within the second wavelength range but reflects light within the first wavelength range, and the light detection unit has a first light reception element that receives light transmitted by the first wavelength filter and a second light reception element that receives light transmitted by the second wavelength filter.

Description

Biological information measuring device

[0001] This invention relates to a biological information measuring device.

[0002] Techniques for measuring the concentration of a specific substance present in a living body by optical sensing are known (Patent Documents 1 and 2). By using this technique, the concentration of a specific substance present in a living body can be measured without sampling blood.

[0003] Patent No. 3303831 Patent No. 5499748

[0004] In the technologies disclosed in Patent Documents 1 and 2, light is projected onto a living body and light in two wavelength ranges is received. The concentration of a specific substance present in the living body is measured based on the relationship between the amounts of light received. To receive light in the two wavelength ranges, an absorption-type color filter is used, which transmits light in a specific wavelength range and absorbs light of other wavelengths. However, because absorption-type color filters depend on the light absorption characteristics of the constituent materials themselves, it is difficult to freely set the transmission band optimal for measurement. As a result, there is room for improvement in the accuracy of the measurement.

[0005] An object of the present disclosure to solve is to provide a biological information measuring device with improved accuracy.

[0006] In order to solve the above problems, the present disclosure provides a biological information measuring device for measuring biological information, comprising: a light-projecting unit that emits light; a light-projecting light-guiding unit that projects the light emitted by the light-projecting unit onto a living organism; a light-receiving light-guiding unit that receives light scattered inside the living organism; a filter unit having a wavelength filter into which the light emitted from the light-receiving light-guiding unit is incident; and a light-detecting unit that detects light that has passed through the wavelength filter, wherein the filter unit has: a first wavelength filter that transmits light in a first wavelength range and reflects light in a second wavelength range; and a second wavelength filter that transmits light in the second wavelength range and reflects light in the first wavelength range, and the light-detecting unit has: a first light-receiving element that receives light that has passed through the first wavelength filter; and a second light-receiving element that receives light that has passed through the second wavelength filter.

[0007] A second aspect of the present invention is the first aspect of the present invention, wherein an incident surface onto which light of the first wavelength filter is incident and an incident surface onto which light of the second wavelength filter is incident are arranged parallel to each other.

[0008] A third aspect of the present invention is the optical fiber optical system according to the first or second aspect, wherein the wavelength filter is a dielectric multilayer filter.

[0009] The invention described in claim 4 is the invention described in claim 1 or 2, which has an aperture section that limits the amount of light that passes through the wavelength filter, and the aperture section has a first opening that limits the amount of light received by the first light receiving element and a second opening that limits the amount of light received by the second light receiving element, and the aperture section absorbs light in at least the first wavelength range and the second wavelength range.

[0010] The invention described in claim 5 is the invention described in claim 4, wherein the distance between the area centers of the opening surfaces of the first opening and the second opening is longer than the distance between the area centers of the light receiving surfaces of the first light receiving element and the second light receiving element.

[0011] A sixth aspect of the present invention is directed to the fourth aspect of the present invention, wherein the shapes of the opening surfaces of the first opening and the second opening include arcs and straight lines.

[0012] A seventh aspect of the present invention is the fourth aspect of the present invention, wherein an area of ​​an opening surface of the first opening is larger than an area of ​​an opening surface of the second opening.

[0013] The invention described in claim 8 is the invention described in claim 4, further comprising a diffusion section that diffuses light emitted from the light receiving guide section, the diaphragm section being arranged between the diffusion section and the wavelength filter, and the diffusion surface of the diffusion section, the incident surface of the wavelength filter, and the opening surface of the diaphragm section being arranged in parallel.

[0014] The invention described in claim 9 is the invention described in claim 1 or 2, wherein the first wavelength range is a light absorption band of the substance to be measured, the second wavelength range is a light non-absorption band of the substance to be measured, and the first wavelength range is narrower than the second wavelength range.

[0015] The invention described in claim 10 is the invention described in claim 1 or 2, wherein the biological information is a concentration of bilirubin in the living body.

[0016] According to the present disclosure, the accuracy of a biological information measuring device can be improved.

[0017] 1 is a perspective view showing the appearance of the biological information measuring device 20 of the present embodiment; FIG. 2 is a perspective view schematically showing the internal configuration of the biological information measuring device 20 of the present embodiment; FIG. 3 is an optical cross-sectional view for explaining changes in the effective optical path length; FIG. 4 is a schematic view of the filter section 5 as seen from the direction in which the detection light L is incident; FIG. 5 is a perspective view of the light receiving and guiding section 3, the diffusion section 4, the filter section 5, and the light detection section 6 as seen from above; FIG. 6 is a schematic cross-sectional view of an example of a dielectric multilayer film filter 8; FIG. 7 is a schematic view of the filter section 5, the light detection section 6, and the diaphragm section 7 as seen from the direction in which the detection light L is incident when the filter section 5 is composed of four wavelength filters; FIG. 8 is a schematic view of the filter section 5, the light detection section 6, and the diaphragm section 7 as seen from the direction in which the detection light L is incident when the filter section 5 is composed of two wavelength filters; FIG. 9 is an explanatory diagram of the arrangement of the diaphragm section 7; FIG. 10 is an explanatory diagram of the arrangement of the diaphragm section 7; FIG. 11 is a graph showing the light absorption characteristics of bilirubin; and FIG. 12 is a graph showing the light transmission characteristics of examples of a first wavelength filter 51 and a second wavelength filter 52.

[0018] One or more embodiments of the present disclosure will be described below with reference to the drawings, however, the scope of the present disclosure is not limited to the disclosed embodiments.

[0019] [Configuration of Biological Information Measurement Device 20] Fig. 1 is a perspective view showing the appearance of the biological information measurement device 20 of this embodiment. However, this embodiment is not limited to this. As shown in Fig. 1, the biological information measurement device 20 includes, for example, a tip unit AS and a display unit 22. The person measuring the biological information measures the concentration (biological information) of a specific substance by contacting the tip unit AS with the skin of the subject. The display unit 22 displays, for example, a measured value.

[0020] 2 is a perspective view schematically showing the internal configuration of a biological information measuring device 20 according to this embodiment. The biological information measuring device 20 includes a light projecting unit 1, a light projecting and receiving system 11, diffusion units 4A and 4B, filter units 5A and 5B, light detecting units 6A and 6B, a control unit 21, and a display unit 22. The light projecting and receiving system 11 includes a light projecting and guiding unit 2 and light receiving and guiding units 3A and 3B. Note that the diffusion units 4A and 4B are not necessarily included.

[0021] The light projecting unit 1 is configured with a long, linear light source, for example, a xenon tube. The light projecting unit 1 emits illumination light (white light) toward the light projecting and guiding unit 2. The illumination light LW includes light in at least a first wavelength range and a second wavelength range. Note that instead of a xenon tube, the light projecting unit 1 may be configured with a plurality of light sources (for example, LEDs) arranged in one direction.

[0022] The light projecting and guiding unit 2 guides the illumination light (white light) LW emitted from the light projecting unit 1 from an entrance 2p to an exit 2q, and emits the illumination light LW toward the living body 9 that is the measurement target. The entrance 2p of the light projecting and guiding unit 2 has a linearly long rectangular surface shape that corresponds to the shape of the light projecting unit 1. An optical lens or a mirror may be used to focus the illumination light LW emitted from the light projecting unit 1 onto the entrance 2p. The exit 2q of the light projecting and guiding unit 2 is ring-shaped.

[0023] The light receiving light guides 3A and 3B guide the detection light LA ​​and LB scattered inside the living body 9 from the entrances 3pA and 3pB to the exits 3qA and 3qB, respectively, and emit the light to the diffusion sections 4A and 4B on the light detection side. The entrance 3pA of the light receiving light guide 3A is circular and is located inside the ring of the exit 2q of the light projecting light guide 2. The entrance 3pB of the light receiving light guide 3B is ring-shaped and is located outside the ring of the exit 2q. Therefore, the exit 2q of the light projecting light guide 2 and the entrances 3pA and 3pB of the light receiving light guides 3A and 3B are located concentrically.

[0024] The light projecting and receiving light guides 2 and 3A and 3B are both light guide members including a plurality of optical fibers, and light is incident and emitted at the end faces of the fiber bundles. Since the space between the light projecting and receiving light guides 2 and 3A and 3B is light-shielded, light does not travel between the fiber bundles without passing through the living body 9.

[0025] The light output port 2q of the light projecting / guiding unit 2 and the light input ports 3pA and 3pB of the light receiving / guiding units 3A and 3B are located at the tip AS of the probe of the biological information measuring device 20. The subject presses the tip AS of the probe of the biological information measuring device 20 against the living body 9. If the biological information measuring device 20 is a jaundice meter, the tip AS of the probe may be pressed against, for example, the forehead or chest of the newborn. Jaundice meters will be described in detail later. When the subject starts measurement, the light projecting unit 1 emits light, and illumination light LW emitted from the light projecting unit 1 enters the light projecting / guiding unit 2 through the entrance port 2p. The illumination light LW is then guided from the entrance port 2p to the exit port 2q and emitted from the exit port 2q in a ring shape toward the living body 9.

[0026] 3 is an optical cross-sectional view illustrating changes in the effective optical path length. Illumination light LW incident on a living body 9 through the epidermis 9a passes through the dermis 9b and is scattered by subcutaneous tissue 9c. The backscattered illumination light LW is emitted outside the living body 9. This emitted light is referred to as detection light LA ​​and LB. As shown in FIG. 2, the detection light LA ​​and LB that have passed through the living body 9 are guided from entrances 3pA and 3pB of the light-receiving guide units 3A and 3B to circular exits 3qA and 3qB, respectively, and are emitted from the exits 3qA and 3qB.

[0027] The diffusion units 4A and 4B diffuse the detection light LA ​​and LB emitted from the exit ports 3qA and 3qB of the light receiving and guiding units 3A and 3B, eliminating brightness unevenness. The shape of the diffusion units 4A and 4B is not particularly limited, but a plate shape is preferable. The detection light LA ​​and LB diffused by the diffusion units 4A and 4B enter the filter units 5A and 5B, respectively.

[0028] The filter units 5A and 5B have two types of wavelength filters that transmit light with different wavelength ranges. The detection lights LA and LB that pass through the filter units 5A and 5B are detected by the light detection units 6A and 6B, respectively. The filter units 5A and 5B will be described in detail later.

[0029] The light detection units 6A and 6B have a first light receiving element 61 and a second light receiving element 62, which are photoelectric conversion elements that convert the detection light LA ​​and LB that have passed through the filter units 5A and 5B into electricity. Examples of the light receiving elements include photodiodes. The electrical signals photoelectrically converted by the light detection units 6A and 6B are converted into digital signals and then output to the control unit 21 as detection signals.

[0030] The control unit 21 calculates the concentration of the substance to be measured or a value correlated to the concentration from the detection signals input from the light detection units 6A and 6B. The control unit 21 displays the calculated concentration of the substance to be measured on the display unit 22. The display unit 22 includes, for example, a liquid crystal display screen, and displays the concentration of the substance to be measured output from the control unit 21 on the liquid crystal display screen.

[0031] (Filter section) Hereinafter, there will be no distinction between light receiving systems A and B, and the reference symbols A and B will be omitted. Fig. 4 is a schematic diagram of the filter section 5 as viewed from the direction in which the detection light L is incident. The filter section 5 has two types of wavelength filters that transmit light in different wavelength ranges. The number of types of wavelength filters that transmit light in different wavelength ranges in the filter section 5 may be three or more.

[0032] In Fig. 4, two first wavelength filters 51 and two second wavelength filters 52 are arranged in a grid pattern so that they are not adjacent to each other, but the arrangement of the wavelength filters is not limited to this. For example, one first wavelength filter 51 and one second wavelength filter 52 may be arranged. In Fig. 4, the first wavelength filters 51 and the second wavelength filters 52 are all arranged on the same plane, but they do not necessarily have to be on the same plane. Furthermore, wavelength filters that transmit light in different wavelength ranges may be arranged.

[0033] Fig. 5 is a perspective view of the light receiving guide 3, diffusion section 4, filter section 5, and light detection section 6 as viewed from above. That is, Fig. 5 is a perspective view of the light receiving guide 3, diffusion section 4, filter section 5, and light detection section 6 as viewed from top to bottom in the direction of the arrow in the S direction in Fig. 2. Note that Fig. 5 omits the first wavelength filter 51 and second wavelength filter 52 at the bottom of the filter section 5 and the corresponding first light receiving element 61 and second light receiving element 62.

[0034] The detection light L guided by the light receiving and guiding unit 3 is emitted from the emission port 3q. The emitted detection light L is diffused by the diffusion unit 4 and enters the first wavelength filter 51 or the second wavelength filter 52 in the filter unit 5. The detection light L transmitted through the first wavelength filter 51 or the second wavelength filter 52 is received by the first light receiving element 61 or the second light receiving element 62, respectively.

[0035] The detection light L emitted from the exit port 3q of the light receiving and guiding unit 3 is received by the light detecting unit 6, which is composed of four light receiving elements. This makes it possible to reduce the influence of slight misalignment of the light receiving elements during the manufacturing process. Furthermore, it is possible to reduce the influence of uneven brightness within the exit end face of the exit port 3q of the light receiving and guiding unit 3. As a result, it is possible to reduce variation in measurement accuracy between manufactured biological information measuring devices 20.

[0036] The first wavelength filter 51 transmits light in a first wavelength range and reflects light in a second wavelength range. The second wavelength filter 52 transmits light in the second wavelength range and reflects light in the first wavelength range. In other words, light in the wavelength range transmitted by the first wavelength filter 51 is reflected by the second wavelength filter 52, and light in the wavelength range transmitted by the second wavelength filter 52 is reflected by the first wavelength filter 51.

[0037] In this embodiment, the term "wavelength range" refers to the full width at half maximum of the maximum peak in the transmission spectrum of the wavelength filter. The full width at half maximum is defined as the bandwidth on the long wavelength side and the short wavelength side of the maximum peak, which is 50% (half maximum) of the maximum transmittance.

[0038] When the biological information measurement device 20 is a jaundice meter, the first wavelength range is the bilirubin light absorption band (near 450 nm), and the second wavelength range is the bilirubin light non-absorption band (near 550 nm).

[0039] In the transmission spectrum of the first wavelength filter 51, the maximum transmittance in the first wavelength range is preferably 80% or more, and more preferably 85% or more. In the transmission spectrum of the first wavelength filter 51, the average transmittance in the second wavelength range is preferably 1% or less, and more preferably 0.1% or less. In the first wavelength filter 51, most of the light in the second wavelength range other than the transmitted light, for example, 95% or more, is reflected. The remaining small amount of light other than the transmitted light and reflected light is absorbed or scattered by the constituent material of the first wavelength filter 51.

[0040] In the transmission spectrum of the second wavelength filter 52, the maximum transmittance in the second wavelength range is preferably 80% or more, and more preferably 85% or more. In the transmission spectrum of the second wavelength filter 52, the average transmittance in the first wavelength range is preferably 1% or less, and more preferably 0.1% or less. In the second wavelength filter 52, most of the light other than the transmitted light in the first wavelength range, for example, 95% or more, is reflected. The remaining small amount of light other than the transmitted light and reflected light is absorbed or scattered by the constituent material of the second wavelength filter 52.

[0041] The light incident surface of the first wavelength filter 51 and the light incident surface of the second wavelength filter 52 are preferably arranged parallel to each other. This allows a large amount of light to be incident on the filter unit 5.

[0042] It is preferable that the diffusion surface that diffuses light of the diffusion unit 4 and the incident surface onto which light of the wavelength filter of the filter unit 5 is incident are arranged parallel to each other. This allows a large amount of light to be incident on the filter unit 5, and a large amount of light to be received by the light detection unit 6. Increasing the amount of light received by the light detection unit 6 can improve the accuracy of measurement. From the same perspective, it is preferable that the incident surface onto which light of the wavelength filter of the filter unit 5 is incident and the surface of the light receiving element of the light detection unit 6 that receives light are arranged parallel to each other.

[0043] The wavelength filter is not particularly limited as long as it satisfies the above optical characteristics. An interference filter that transmits light in a specific wavelength range and reflects light of other wavelengths can easily set the optimum transmission band for detecting light in the wavelength band that is absorbed or not absorbed by the substance to be measured, thereby improving the accuracy of concentration measurement.

[0044] Among them, the interference type wavelength filter is preferably a dielectric multilayer filter. Fig. 6 is a cross-sectional view of an example of a dielectric multilayer filter 8. The dielectric multilayer filter 8 has a high refractive index layer 81 (for example, TiO ２ ), and a low refractive index layer 82 (e.g., SiO ２ ) are alternately stacked in a multilayer film. This configuration makes it easier to freely set the optimum transmission band, improving the accuracy of concentration measurement. In addition, the refractive index difference within the film can be increased, reducing the incidence angle dependency of the wavelength filter.

[0045] The material of the high refractive index layer 81 is TiO ２ , Ta ２ O ５ , AlO, ZrO ２ , HfO ２ The low refractive index layer 82 may be made of, for example, SiO ２ , MgF ２Examples of the material for the transparent substrate 83 include resin, glass, etc. The method for forming the dielectric multilayer filter 8 is not particularly limited, and examples thereof include electron beam deposition, resistance heating deposition, ion-assisted deposition, ion plating, and sputtering.

[0046] When the first wavelength filter 51 also transmits light in a third wavelength range other than the first wavelength range, it is preferable to use a first cut filter that absorbs or reflects light in the third wavelength range in combination. When the second wavelength filter 52 also transmits light in a fourth wavelength range other than the second wavelength range, it is preferable to use a second cut filter that absorbs or reflects light in the fourth wavelength range in combination. This makes it possible to reduce the amount of light in the third or fourth wavelength range detected by the light detection unit 6, thereby improving the accuracy of measurement.

[0047] The first cut filter may be located between the first wavelength filter 51 and the light exit 3q of the light receiving guide 3 or between the diffusion section 4 and the first wavelength filter 51, or between the first wavelength filter 51 and the first light receiving element 61. The second cut filter may be located between the second wavelength filter 52 and the light exit 3q of the light receiving guide 3 or between the diffusion section 4 and the second wavelength filter 52, or between the second wavelength filter 52 and the second light receiving element 62. The first cut filter and the second cut filter may be separate or may be integrated.

[0048] When the biological information measuring device 20 is a jaundice meter, an example of the filter used in combination is an infrared cut filter. The infrared cut filter absorbs or reflects infrared light and transmits visible light, and therefore can be used as a filter in which the first cut filter and the second cut filter are integrated.

[0049] (Aperture Section) The biological information measurement device 20 preferably includes an aperture section 7 that limits the amount of light passing through the wavelength filters. The aperture section 7 reduces the amount of light reflected by a wavelength filter from entering other wavelength filters as stray light, thereby improving measurement accuracy. In particular, when the biological information measurement device 20 includes a diffusion section 4, light reflected by a wavelength filter is more likely to be diffused, resulting in stray light. However, the aperture section 7 reduces the amount of stray light from entering other wavelength filters, thereby improving measurement accuracy. This allows different types of wavelength filters to be arranged closely together, thereby reducing the size of the device. Furthermore, this allows the light-receiving elements corresponding to each wavelength filter to be arranged closely together, thereby shortening the distance from the light-receiving guide section 3 to the light detection section 6. As a result, the amount of light received by the light detection section 6 can be increased, improving measurement accuracy.

[0050] FIG. 7 is a schematic diagram of the filter unit 5, photodetector unit 6, and aperture unit 7 when the filter unit 5 is composed of four wavelength filters, viewed from the direction in which the detection light L is incident. The filter unit 5 here is the same as the filter unit 5 shown in FIG. 4 . The filter unit 5 is disposed between the photodetector unit 6 and aperture unit 7 or in front of the aperture unit 7. The filter unit 5 is composed of two first wavelength filters 51 and two second wavelength filters 52. The photodetector unit 6 is composed of two first light-receiving elements 61 and two second light-receiving elements 62. The aperture unit 7 is composed of two first apertures 71 and two second apertures 72. The dotted lines in FIG. 7 indicate the peripheries of the first wavelength filters 51 and second wavelength filters 52 when the filter unit 5 is disposed.

[0051] The aperture that limits the amount of light that passes through the first wavelength filter 51 and enters the first light receiving element 61 is referred to as the first aperture 71. The aperture that limits the amount of light that passes through the second wavelength filter 52 and enters the second light receiving element 62 is referred to as the second aperture 72. The dotted line in Fig. 7 also indicates the boundary between the first aperture 71 and the second aperture 72. The first aperture 71 and the second aperture 72 may be separate or may be integrated.

[0052] The first diaphragm 71 has a first opening 711. The first opening 711 limits the amount of light that passes through the first wavelength filter 51 and enters the first light receiving element 61 by adjusting the area, shape, etc. of the opening surface. The "opening surface" refers to the surface of the opening onto which the detection light L enters.

[0053] It is preferable that the first diaphragm 71 absorbs the light reflected by the second wavelength filter 52 so that the light reflected by the second wavelength filter 52 is not received by the first light receiving element 61. On the other hand, from the viewpoint of measurement accuracy, it is preferable to increase the S / N ratio, and in order to increase the S / N ratio, it is preferable to increase the amount of light received by the light detection unit 6. The S / N ratio refers to the ratio of the peak signal of the measurement object to the noise.

[0054] From these perspectives, the opening surface of the first opening 711 preferably has a shape obtained by cutting a portion of a circle with two straight lines, i.e., a shape including an arc and a straight line, as shown in FIG. 7 . The periphery of the first opening 711 is preferably narrowed on the two sides where the first wavelength filter 51 and the second wavelength filter 52 are adjacent, forming a linear shape parallel to the sides of the light-receiving surface of each light-receiving element. The periphery of the first opening 711 is preferably widened on the two sides where the first wavelength filter 51 and the second wavelength filter 52 are not adjacent, forming a circular shape. Generally, wavelength filters have incident angle dependency, and at high incident angles, the characteristics tend to deteriorate in the transmission band and non-transmission band (forbidden band). Therefore, it is preferable to limit the maximum incident angle to a certain value or less. By making part of the shape of the first opening 711 circular, the maximum incident angle can be limited to a certain value or less. Furthermore, the circular shape allows for efficient light collection, thereby increasing the signal-to-noise ratio.

[0055] It is preferable that the first aperture center 712 is shifted toward the side where the first wavelength filter 51 and the second wavelength filter 52 are not adjacent, compared to the first light receiving element center 611. The first aperture center 712 is the center of area (center of gravity) of the opening surface of the first opening 711, and the first light receiving element center 611 is the center of area (center of gravity) of the light receiving surface of the first light receiving element 61.

[0056] The shape of the second opening 721 is also preferably the same as that of the first opening 711. Furthermore, the positional relationship between the second opening center 722 and the second light receiving element center 621 is also preferably the same as that of the first opening 711. For this reason, it is preferable that the distance between the first opening center 712 and the second opening center 722 is longer than the distance between the first light receiving element center 611 and the second light receiving element center 621.

[0057] The areas of the opening surfaces of the first opening 711 and the second opening 721 may be the same or different depending on the wavelength of the light to be measured.

[0058] 8 is a schematic diagram of the filter unit 5, the light detection unit 6, and the diaphragm unit 7 when the filter unit 5 is composed of two wavelength filters, viewed from the direction in which the detection light L is incident. The filter unit 5 is composed of one first wavelength filter 51 and one second wavelength filter 52.

[0059] In this case, the periphery of the first opening 711 is preferably narrowed to form a straight line parallel to the sides of the wavelength filters on one side where the first wavelength filter 51 and the second wavelength filter 52 are adjacent. The periphery of the first opening 711 is preferably widened to form a circle on three sides where the first wavelength filter 51 and the second wavelength filter 52 are not adjacent. The distance between the first opening center 712 and the second opening center 722 is preferably longer than the distance between the first light receiving element center 611 and the second light receiving element center 621. Note that in this case, the first opening center 712, the second opening center 722, the first light receiving element center 611, and the second light receiving element center 621 are preferably positioned on the same straight line.

[0060] 9 and 10 are explanatory diagrams illustrating the arrangement of the diaphragm unit 7. FIGS. 9 and 10 are perspective views of the light receiving and guiding unit 3, the diffusion unit 4, the filter unit 5, the light detection unit 6, and the diaphragm unit 7, viewed from above. The diaphragm unit 7 may be arranged in the following order, as shown in FIG. 9 , from the direction of incidence of the detection light L: diffusion unit 4, diaphragm unit 7, filter unit 5, and light detection unit 6. Alternatively, the diaphragm unit 7 may be arranged in the following order, as shown in FIG. 10 , from the direction of incidence of the detection light L: diffusion unit 4, filter unit 5, diaphragm unit 7, and light detection unit 6. From the viewpoint of suppressing the generation of reflected light from the filter unit 5, it is preferable that the diaphragm unit 7 be arranged in the following order: diffusion unit 4, diaphragm unit 7, filter unit 5, and light detection unit 6. It is preferable that the diffusion surface of the diffusion unit 4, the incident surface of the wavelength filter of the filter unit 5, and the opening surface of the diaphragm unit 7 are arranged parallel to each other. This allows a large amount of light to be incident on the filter unit 5, and the amount of light transmitted through the wavelength filter can be sufficiently limited by the diaphragm unit 7.

[0061] As shown in FIGS. 9 and 10 , the filter unit 5 may have a boundary portion 53 between the first wavelength filter 51 and the second wavelength filter 52. The shape of the boundary portion 53 is not particularly limited. However, if the boundary portion 53 is extended too far from the shape shown in FIGS. 9 and 10 in a direction approaching the diffusion unit 4, the amount of light incident on each of the first wavelength filter 51 and the second wavelength filter 52 is likely to vary significantly depending on the position of the boundary portion 53. Furthermore, if there is brightness unevenness within the output end surface of the output port 3q of the light receiving and guiding unit 3, the amount of light incident on each of the first wavelength filter 51 and the second wavelength filter 52 is likely to vary even more significantly. Therefore, it is preferable that the boundary portion 53 not be extended too far in a direction approaching the diffusion unit 4.

[0062] [Measurement by Biological Information Measuring Device 20] The following describes measurement of the concentration of a specific substance in a living body performed by the biological information measuring device 20. If the substance has extremely high light absorption characteristics in a specific wavelength range, the concentration can be measured using the biological information measuring device 20. Furthermore, by using the biological information measuring device 20, the concentration of a specific substance in a living body can be measured transcutaneously from the surface of the skin.

[0063] For example, a wavelength range in which the substance to be measured has extremely high light absorption characteristics is defined as a first wavelength range, and a wavelength range in which the substance to be measured has almost no light absorption characteristics is defined as a second wavelength range. Of the light reflected from the substance to be measured, light transmitted through the first wavelength filter 51 and the second wavelength filter 52 is received by the first light receiving element 61 and the second light receiving element 62. The concentration of the substance to be measured can be calculated from the correlation between the amounts of received light.

[0064] Hereinafter, as an example, a case where the specific substance is bilirubin will be described. However, the specific substance in this embodiment is not limited to bilirubin. Note that a transcutaneous bilirubin concentration measuring device is also called a "jaundice meter."

[0065] Bilirubin is a yellow pigment. When bilirubin levels in the body become excessive, it deposits in the skin, causing the skin to appear yellow. This condition is called "jaundice." Severe jaundice, especially in newborns, is highly likely to be fatal. Even if death is avoided, it may progress to kernicterus, which can leave aftereffects such as cerebral palsy. Therefore, early detection is important. The severity of jaundice can be accurately determined by measuring the bilirubin concentration in serum collected from newborns. However, collecting blood samples from all newborns is difficult and often unnecessary. By using the above-described biological information measurement device 20, the bilirubin concentration in serum can be measured transcutaneously without the need for blood sampling. The specific concentration measured by a jaundice meter is called the "transcutaneous bilirubin concentration." The transcutaneous bilirubin concentration correlates with the bilirubin concentration in blood.

[0066] 11 is a graph showing the light absorption characteristics of bilirubin. Bilirubin has a peak in the absorption coefficient, i.e., light absorption characteristics, around a wavelength of 450 nm. The absorption coefficient of bilirubin decreases as the wavelength moves from 450 nm to the shorter or longer wavelength side. Bilirubin does not have light absorption characteristics around a wavelength of 550 nm.

[0067] Based on the light absorption characteristics of bilirubin, the first wavelength range of the wavelength filter is set to the bilirubin light absorption band (near 450 nm), and the second wavelength range is set to the bilirubin light non-absorption band (near 550 nm). That is, a filter that transmits blue light is used as the first wavelength filter 51, and a filter that transmits green light is used as the second wavelength filter 52.

[0068] The degree of yellowness in the living body can be measured from the amount of blue light relative to the green light in the detection light L, i.e., the ratio of the amount of light received by the first light-receiving element 61 to the amount of light received by the second light-receiving element 62. The degree of yellowness of bilirubin present in the subcutaneous tissue 9c of the living body 9 is detected as the difference in optical density between the two wavelength ranges of blue and green. As shown in Figure 2, when the light-receiving system is a two-light-path type, even if the thickness of the epidermis 9a varies, the intensity of jaundice can be measured more accurately by taking the difference in measurements obtained through the two light paths. Furthermore, even if the color of the epidermis 9a varies due to the influence of melanin, the intensity of jaundice can be measured more accurately by taking the difference in measurements obtained through the two light paths.

[0069] 12 is a graph showing exemplary light transmission characteristics of the first wavelength filter 51 and the second wavelength filter 52. The amount of light transmitted through the first wavelength filter 51 and received by the first light receiving element 61 depends on the bilirubin concentration. On the other hand, the amount of light transmitted through the second wavelength filter 52 and received by the second light receiving element 62 is a constant amount independent of the bilirubin concentration. The bilirubin concentration can be calculated from the relationship between the amount of light received by the first light receiving element 61 and the amount of light received by the second light receiving element 62.

[0070] As shown in FIG. 12, the half width of the transmission band of the first wavelength filter 51 is preferably narrower than the half width of the transmission band of the second wavelength filter 52 .

[0071] According to the Beer-Lambert law, the intensity I of light transmitted through the skin is expressed by the following formula (1): I=I ０ 10 －εｃｄ... (1) In the formula, ε is the molar absorption coefficient of bilirubin, c is the molar concentration of bilirubin, d is the light propagation distance in the skin, and I0 is the intensity of light incident on the skin. The intensity E of light received by the light-receiving element is expressed by the following formula (2): E = T · I ... (2) In the formula, T is the total transmittance T of light guided through the measuring device, including wavelength filters and the like (excluding the skin).

[0072] From the above equations (1) and (2), it can be seen that the intensity E of received light and the molar concentration c of bilirubin change exponentially and are not proportional to each other. When measuring the bilirubin concentration, it is preferable to extract a value proportional to the bilirubin concentration as the measured value. For this reason, the intensity E of received light is logarithmically converted according to the following equation (3): log(E) = log(T·I ０ 10 －εｃｄ ) =-εcd+log(T・I ０ ) ... (3)

[0073] In the above formula (3), ε, d, T and I ０ When is a constant value, log(E) is proportional to c. In calculating the concentration, the measured value is subjected to log conversion processing.

[0074] However, because the value of the molar extinction coefficient ε varies depending on the wavelength, if the transmission band of the first wavelength filter 51 is too wide, the molar extinction coefficient ε cannot be treated as a constant value. As a result, even if the measured value is subjected to log conversion, it cannot be treated as a value proportional to the bilirubin concentration. The measured value becomes a nonlinear value relative to the bilirubin concentration, and measurement errors are likely to occur when the bilirubin concentration is relatively low or high.

[0075] Therefore, the transmission band of the first wavelength filter 51 is made relatively narrow. This reduces the change in the molar absorption coefficient ε with wavelength and allows it to be treated as a substantially constant value, thereby reducing errors in measuring the bilirubin concentration. Furthermore, when the first wavelength filter 51 is a dielectric multilayer film filter, it is possible to achieve a sharp change between the transmission band and the non-transmission band (forbidden band), making it easy to narrow the transmission band.

[0076] On the other hand, the amount of light transmitted through the second wavelength filter 52 is a constant amount independent of the bilirubin concentration. Therefore, from the viewpoint of increasing the S / N ratio and improving the accuracy of the measurement, it is preferable that the amount of light transmitted through the second wavelength filter 52 is large, and it is preferable that the transmission band of the second wavelength filter 52 is relatively wide.

[0077] From these viewpoints, the full width at half maximum of the transmission band of the first wavelength filter 51, i.e., the first wavelength range, is preferably 50 nm or less, at which point the change in the molar extinction coefficient ε of bilirubin is less than 2. Furthermore, the full width at half maximum of the transmission band of the second wavelength filter 52, i.e., the second wavelength range, is preferably 50 nm or more.

[0078] The higher the concentration of bilirubin in the living body, the more light with a wavelength around 450 nm is absorbed by bilirubin, and the less light is transmitted through the first wavelength filter 51. On the other hand, light with a wavelength around 550 nm is not absorbed by bilirubin, and a relatively large amount of light is transmitted through the second wavelength filter 52. For this reason, it is preferable that the area of ​​the opening surface of the first opening 711 in the first diaphragm 71 be larger than the area of ​​the opening surface of the second opening 721 in the second diaphragm 72.

[0079] In this embodiment, a biological information measuring device 20 for measuring the concentration (biological information) of a specific substance in a living organism includes a light-projecting unit 1 that emits light, a light-projecting light-guiding unit 2 that projects the light emitted by the light-projecting unit 1 onto a living organism 9, a light-receiving light-guiding unit 3 that receives light scattered within the living organism 9, a filter unit 5 having a wavelength filter into which the light emitted from the light-receiving light-guiding unit 3 is incident, and a light-detecting unit 6 that detects light transmitted through the wavelength filter. The filter unit 5 includes a first wavelength filter 51 that transmits light in a first wavelength range and reflects light in a second wavelength range, and a second wavelength filter 52 that transmits light in the second wavelength range and reflects light in the first wavelength range. The light-detecting unit 6 includes a first light-receiving element 61 that receives light transmitted through the first wavelength filter 51 and a second light-receiving element 62 that receives light transmitted through the second wavelength filter 52. This improves the accuracy of the measurement.

[0080] In this embodiment, the incident surface of the first wavelength filter 51 through which light is incident and the incident surface of the second wavelength filter 52 through which light is incident are arranged parallel to each other, thereby allowing more light to be incident on the filter unit 5 and improving the accuracy of measurement.

[0081] In this embodiment, the wavelength filter is a dielectric multilayer filter, which makes it easier to freely set the optimum transmission band of the wavelength filter, thereby improving the accuracy of measurement.

[0082] In this embodiment, the diaphragm unit 7 has a diaphragm section 7 that limits the amount of light that has passed through the wavelength filter, and the diaphragm section 7 has a first opening 711 that limits the amount of light received by the first light receiving element 61 and a second opening 721 that limits the amount of light received by the second light receiving element 62, and the diaphragm section 7 absorbs light in at least the first wavelength range and the second wavelength range. This allows the biological information measuring device 20 to be miniaturized and stray light to be reduced, improving the accuracy of measurement.

[0083] In this embodiment, the shapes of the opening surfaces of the first opening 711 and the second opening 721 include arcs and straight lines, which allows the diaphragm section 7 to absorb light reflected by the wavelength filter and suppress the maximum angle of incidence of light incident on the wavelength filter to a certain value or less.

[0084] In this embodiment, the area of ​​the opening surface of the first opening 711 is larger than the area of ​​the opening surface of the second opening 721. This allows the light detection unit 6 to receive a sufficient amount of light for measurement, thereby improving the accuracy of the measurement.

[0085] This embodiment further includes a diffusion section 4 that diffuses the light emitted from the light receiving and guiding section 3, and the diaphragm section 7 is disposed between the diffusion section 4 and the wavelength filter, with the diffusion surface of the diffusion section 4, the incident surface of the wavelength filter, and the opening surface of the diaphragm section 7 being disposed parallel to each other. This allows a large amount of light to be incident on the filter section 5, and the amount of light that passes through the wavelength filter can be sufficiently limited by the diaphragm section 7, improving the accuracy of measurement.

[0086] In this embodiment, the first wavelength range is a band in which the substance to be measured absorbs light, and the second wavelength range is a band in which the substance to be measured does not absorb light, and the first wavelength range is narrower than the second wavelength range, thereby improving the accuracy of the measurement.

[0087] In this embodiment, the biological information is the concentration of bilirubin in the living body 9. This allows the biological information measurement device 20 to be used as a jaundice meter, and improves the accuracy of measuring the intensity of jaundice.

[0088] 2 is a two-path type, but the number of paths is not limited, and it may be a one-path type. Furthermore, the detailed configurations and operations of the devices that make up the optical property measuring device may be modified as appropriate without departing from the spirit of the present disclosure.

[0089] By using the present disclosure, it is possible to provide a biological information measuring device that can perform measurements more accurately.

[0090] REFERENCE SIGNS LIST 1 Light projecting section 2 Light projecting and guiding section 2p Incident opening 2q Exit opening 3 Light receiving and guiding section 3p Incident opening 3q Exit opening 4 Diffusion section 5 Filter section 51 First wavelength filter 52 Second wavelength filter 53 Boundary section 6 Light detecting section 61 First light receiving element 611 Center of first light receiving element 62 Second light receiving element 621 Center of second light receiving element 7 Aperture section 71 First aperture 711 First opening 712 Center of first opening 72 Second aperture 721 Second opening 722 Center of second opening 8 Dielectric multilayer film filter 81 High refractive index layer 82 Low refractive index layer 83 Transparent substrate 9 Living body 9a Epidermis 9b Dermis 9c Subcutaneous tissue 11 Light projecting and receiving system 20 Biological information measuring device 21 Control section 22 Display section LW Illumination light L Detection light AS Tip

Claims

1. A biological information measuring device for measuring biological information, comprising: a light-projecting unit that emits light; a light-projecting light-guiding unit that projects the light emitted by the light-projecting unit onto a living organism; a light-receiving light-guiding unit that receives light scattered within the living organism; a filter unit having a wavelength filter into which the light emitted from the light-receiving light-guiding unit is incident; and a light-detecting unit that detects light that has passed through the wavelength filter, wherein the filter unit has: a first wavelength filter that transmits light in a first wavelength range and reflects light in a second wavelength range; and a second wavelength filter that transmits light in the second wavelength range and reflects light in the first wavelength range, and the light-detecting unit has: a first light-receiving element that receives light that has passed through the first wavelength filter; and a second light-receiving element that receives light that has passed through the second wavelength filter.

2. The biological information measuring device according to claim 1, wherein the incident surface onto which the light of the first wavelength filter is incident and the incident surface onto which the light of the second wavelength filter is incident are arranged parallel to each other.

3. The biological information measuring device according to claim 1 or 2, wherein the wavelength filter is a dielectric multilayer filter.

4. A biological information measuring device as described in claim 1 or 2, which has an aperture section that limits the amount of light that passes through the wavelength filter, the aperture section having a first opening that limits the amount of light received by the first light receiving element and a second opening that limits the amount of light received by the second light receiving element, and the aperture section absorbing light in at least the first wavelength range and the second wavelength range.

5. A biological information measuring device as described in claim 4, wherein the distance between the centers of the areas of the opening surfaces of the first opening and the second opening is longer than the distance between the centers of the areas of the light receiving surfaces of the first light receiving element and the second light receiving element.

6. The biological information measuring device according to claim 4, wherein the shapes of the opening surfaces of the first opening and the second opening include arcs and straight lines.

7. The biological information measuring device according to claim 4, wherein the area of ​​the opening surface of the first opening is larger than the area of ​​the opening surface of the second opening.

8. A biological information measuring device as described in claim 4, further comprising a diffusion section that diffuses light emitted from the light receiving and guiding section, the diaphragm section being disposed between the diffusion section and the wavelength filter, and the diffusion surface of the diffusion section, the incident surface of the wavelength filter, and the opening surface of the diaphragm section being disposed in parallel.

9. A biological information measuring device as described in claim 1 or 2, wherein the first wavelength range is a light absorption band of the substance to be measured, the second wavelength range is a light non-absorption band of the substance to be measured, and the first wavelength range is narrower than the second wavelength range.

10. A biological information measuring device according to claim 1 or 2, wherein the biological information is a bilirubin concentration in the living body.

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