JP7533020B2 - Optical interference device and biological information analysis device - Google Patents

Description

The present invention relates to an optical interference device and a bioinformation analysis device equipped with the optical interference device.

Conventionally, measurement techniques have been proposed for non-invasively analyzing biological information such as blood flow and blood pressure. For example, Patent Document 1 discloses a blood velocity measurement device that uses the laser Doppler method. In this measurement device, a beam emitted from a light source is split into a sample beam and a reference beam, the sample beam is guided to an area in a biological sample, and the blood velocity is measured by detecting the interference between the sample beam reflected from that area and the reflected reference beam.

In addition, from the description that the sample beam and the reference beam are coupled to an optical fiber over at least a portion of their travel path, and from the depiction in Figure 5 of Patent Document 1, it is presumed that the light guide distance of both beams is quite long. The sample beam is also called the measurement light, the light that is the measurement light reflected inside the living body is also called the detection light, and the reference beam is also called the reference light.

Japanese Patent Application Publication No. 08-206086

However, the measurement device of Patent Document 1 has the problem that it is difficult to achieve a high S/N ratio. More specifically, the detection light from the living body and the reference light have a long light guide distance, so the intensity of the light received by the light receiving unit is low. Furthermore, the detection light reflected inside the living body is scattered light, and while the detection light spreads isotropically, the reference light is a coherent laser light with high linearity. For this reason, most of the vector components of the light rays in the detection light and the reference light do not overlap, so the optical beat signal in the interference light formed by combining the detection light and the reference light is very small.

The optical interference device according to the present application comprises a light emitting unit, a light receiving unit, a light separating unit that separates the light emitted from the light emitting unit into a reference light and a measurement light that is incident on the living body, and a diffuser plate that converts the reference light into scattered light. The measurement light is reflected inside the living body to become a detection light, and the detection light is combined with the reference light and incident on the light receiving unit.

The bioinformation analysis device according to the present application includes the above-mentioned optical interference device and a control unit, and the control unit analyzes bioinformation based on an interference signal of interference light obtained by combining the detection light and the reference light.

FIG. 2 is a side view of the analysis device according to the first embodiment. FIG. 2 is a functional block diagram of the analysis device. FIG. 4 is an explanatory diagram of an optical beat signal. 5 is a graph showing an output voltage per unit time of an optical beat signal. FIG. 13 is a graph showing a power spectrum. FIG. 1 is a graph showing changes in blood flow. FIG. FIG. 11 is a configuration diagram of an optical interference device according to a second embodiment. FIG. 11 is a configuration diagram of an optical interference device according to a third embodiment. FIG. 1 is a diagram showing the configuration of a conventional optical interference device.

EMBODIMENT 1
*** Overview of Biological Information Analysis Device ***
FIG. 1 is a side view of an analysis device according to a first embodiment.
Analysis device 100 is a biological information analysis device that non-invasively measures biological information of a subject.
The analysis device 100 measures the blood flow rate and blood pressure of a specific part of the subject's body as biological information. In the following description, the subject's wrist is used as a suitable example of the body H. The body H to be measured may be any body part that has an arteriole inside, and may be, for example, the upper arm or the neck.

Analysis device 100 is a wristwatch-type portable device having a housing 12 and a belt 14, and in a preferred embodiment is worn on the wrist.
The housing 12 houses the optical interference device 10 and a display device 21, and the optical interference device 10 faces the inside of the wrist. The display device 21 is a display unit such as a liquid crystal panel that displays the measurement results, and is provided on the opposite side of the optical interference device 10 so that the subject can view it.
By adjusting the length of the belt 14 and the design of the housing 12, the optical interference device 10 is positioned opposite the artery of the wrist when worn on the wrist.

FIG. 2 is a functional block diagram of the analysis device.
The housing 12 of the analysis device 100 incorporates a control device 20 as a control unit, a storage device 22, etc., in addition to the optical interference device 10 and a display device 21. The optical interference device 10 will be described in detail later.
The control device 20 is an arithmetic processing device such as a CPU (Central Processing Unit) or an FPGA (Field-Programmable Gate Array), and controls the entire analysis device 100. The control device 20 also includes a calculation unit 25. The calculation unit 25 is a virtual part that performs various calculations when a control program described below is executed. Although details will be described later, the control device 20 works together with the calculation unit 25 and the storage device 22 to analyze biological information such as blood flow and blood pressure based on an interference signal of the interference light detected by the optical interference device 10.

The storage device 22 is configured with a RAM (Random Access Memory) and a ROM (Read Only Memory). The RAM is used for temporary storage of various data, and the ROM stores control programs for controlling the operation of the analysis device 100 and associated data. The control programs include a startup program that indicates the order and content of processing when starting up the analysis device 100, a blood flow measurement program that specifies the order and content of processing in measuring blood flow, and a blood pressure calculation program that includes an algorithm for deriving blood pressure from blood flow. The associated data includes a blood vessel diameter index table used in blood pressure calculation.

The functions of the control device 20 may be distributed across multiple integrated circuits, or some or all of the functions of the control device 20 may be implemented by a dedicated electronic circuit.
In addition, in FIG. 2, the control device 20 and the storage device 22 are separate elements, but the control device 20 including the storage device 22 may be realized by, for example, an ASIC (Application Specific Integrated Circuit) or the like.

***Blood flow measurement principle***
Fig. 3 is an explanatory diagram of an optical beat signal. Fig. 4 is a graph showing an output voltage per unit time of an optical beat signal. Fig. 5 is a graph showing a power spectrum. Fig. 6 is a graph showing a change in blood flow rate. Fig. 10 is a configuration diagram of a conventional optical interference device.

First, the principle of blood flow measurement using the conventional optical interference device 90 will be described.
A conventional optical interference device 90 shown in Fig. 10 is a Michelson interferometer including a light emitting unit 1, a beam splitter 2, a mirror 4, and a light receiving unit 7. In Fig. 10, only light that contributes to the measurement is shown. The same is true in other drawings.
The light emitting unit 1 is a laser light source that emits coherent laser light, and the emitted laser light 70 is split by the half mirror film 3 of the cube-shaped beam splitter 2 into a measurement light 71 directed toward the living body H and a reference light 72 directed toward the mirror 4. A part of the detection light 75, which is the measurement light 71 reflected inside the living body H, enters the light receiving unit 7 through the half mirror film 3. A part of the reference light 76 reflected by the mirror 4 is reflected by the half mirror film 3 and enters the light receiving unit 7. The light receiving unit 7 is equipped with a light receiving element such as a photodiode. Here, the detection light 75 that contributes to the measurement of blood flow rate has been mainly described, but there is also detection light 75 that is reflected by the half mirror film 3 and directed toward the light emitting unit 1, but this is omitted from the illustration. Similarly, the reference light 76 also passes through the half mirror film 3 and goes toward the light emitting unit 1.

When the frequency of the measurement light 71 incident on the living body H is set to frequency f0, the incident measurement light 71 propagates while being repeatedly scattered and reflected within the tissue of the living body H, becoming scattered light, a part of which is incident on the light receiving unit 7 as detection light 75.
Here, the frequency of the detection light by the measurement light 71 reflected by stationary tissue such as the skin on the surface of the living body H or subcutaneous tissue remains at frequency f0. In contrast, the frequency of the detection light 75 by the measurement light 71 reflected by blood cells such as red blood cells 56 in the blood moving at a certain flow velocity in the blood vessel 55 changes according to the flow velocity due to the Doppler effect, and becomes a frequency fd different from frequency f0.

Generally, the frequency of laser light is several hundreds of THz, and it has been difficult to directly measure the Doppler shift frequency with the response characteristics of existing light receiving elements such as photodiodes.
Therefore, as shown in Fig. 3, an optical beat signal generated by interference between detection light of frequency f0 in stationary tissue and detection light of frequency fd from blood cells is detected, and the Doppler shift frequency fb is measured to obtain information on the velocity of blood flow. This makes it possible to obtain information on the velocity of blood flow in a living body H non-invasively through optical measurement. The optical beat signal is also called a beat signal.

Explain in detail.
The frequency fd of the detection light 75 reflected by a blood cell moving at a constant speed is determined by the speed Vel, the wavelength λ of the incident light, and the angle θ between the speed vector and the incident light vector, as shown in formula (1).

しかし、生体計測では組織での入射光の散乱による入射角θの分布や、血管内の血流速度Ｖｅｌの分布があるため、様々なドップラシフト周波数のうなりが重畳した信号が受光部７に入射する。

However, in biological measurements, there is a distribution of the incident angle θ due to scattering of the incident light in tissue and a distribution of the blood flow velocity Vel within the blood vessels, so a signal on which beats of various Doppler shift frequencies are superimposed is incident on the light receiving unit 7.

FIG. 4 is a graph showing the output voltage per unit time of the optical beat signal, with the horizontal axis representing time t (ms) and the vertical axis representing the output voltage (V).
When the optical beat signal I(t) is frequency-expanded in units of time ta in Fig. 4, the power spectrum shown in Fig. 5 is obtained. The power spectrum in Fig. 5 shows the blood flow velocity distribution, with the frequency f (kHz) on the horizontal axis corresponding to the velocity of blood cells and the power P(f) on the vertical axis corresponding to the number of moving blood cells. In other words, the power P(f) is the frequency expansion of the AC component of the optical beat signal I(t).
The value obtained by integrating the frequency-weighted power spectrum over a predetermined frequency band can be defined as FLOW, which is a relative value of blood flow. Therefore, as shown in Figure 6, the transient response of FLOW can be obtained by plotting FLOW on the vertical axis for each time t unit. The horizontal axis represents time t (ms).

Return to Figure 10.
As described above, the Doppler-shifted detection light 75 from the living body H travels to the light receiving unit 7 through the half mirror film 3, and the reference light 76 reflected by the mirror 4 is reflected by the half mirror film 3 and travels to the light receiving unit 7, where the two are combined, interfere, and enter the light receiving unit 7. However, as described above, the detection light 75 reflected inside the living body is scattered light, and while the detection light 75 spreads isotropically, the reference light 76 is a coherent laser light with high straightness, so most of the vector components of the light rays in the detection light 75 and the reference light 76 do not overlap, and the optical beat signal in the interference light obtained by combining the two is small. In FIG. 10, the straight light is shown by a solid line, and the scattered light is shown by a broken line. This is the same in other figures.
When the optical path difference between the detection light 75 and the reference light 76 does not vary with time, the intensity I(t) of the optical beat signal resulting from interference between the two is expressed by equation (2).

なお、数式（２）において、検出光の電場強度をＡｓ、参照光の電場強度をＡｒとしている。また、右辺の第１項と第２項は直流成分として、第３項は交流成分として観測される。

In formula (2), the electric field strength of the detection light is As, and the electric field strength of the reference light is Ar. The first and second terms on the right side are observed as DC components, and the third term is observed as an AC component.

The Fourier spectrum F(f) is a function of frequency obtained by Fourier transforming the intensity I(t) of the optical beat signal, and is expressed by the following equation (3).
The power spectrum P(f) in FIG. 5 is proportional to the product of the detected light intensity Is and the reference light intensity Ir, as shown in equation (4).

Similar to the power spectrum P(f), the relative value FLOW of the blood flow in Figure 6 is proportional to the product of the detection light intensity Is and the reference light intensity Ir, as shown in equation (5).

So far, the principle of blood flow measurement has been explained.
The blood pressure can be derived by calculation if the blood flow rate and the vascular diameter of the arteriole of the living body H are known. In particular, since the blood pressure is correlated with the blood flow rate and the vascular diameter, it can be derived if both are known. The relative value of the blood flow rate and the vascular diameter (vascular resistance) can be obtained by laser Doppler measurement.

According to the inventors' experimental results, it is difficult to increase the detection light intensity Is in biomeasurements, but formula (4) shows that if the reference light intensity Ir can be increased, the power spectrum and FLOW can be increased.

***Configuration of optical interference device***
FIG. 7 is a configuration diagram of the optical interference device of this embodiment, and corresponds to FIG.
The optical interference device 10 of this embodiment is composed of a light emitting unit 1, a beam splitter 2 as a light separating unit, a diffusion plate 5, a lens 6 as a light collecting unit, and a light receiving unit 7. Note that Fig. 7 shows the basic optical configuration of the optical interference device 10.

The light emitting unit 1 is a laser light source that emits narrow-band coherent laser light 70. In a preferred example, a semiconductor laser or a gas laser that emits laser light by resonance within a resonator can be used.

The beam splitter 2 is a cube-shaped beam splitter formed by bonding two triangular prisms together, and is equipped with a half mirror film 3. The shape of the beam splitter 2 is not limited to a cube, and may be a rectangular parallelepiped. The laser light 70 from the light emitting unit 1 is split into a measurement light 71 that is reflected by the half mirror film 3 and directed toward the living body H, and a reference light 72 that passes through the half mirror film 3 and directs toward the diffusion plate 5. In the preferred embodiment, the split ratio is 50:50, but the split ratio can be appropriately set by adjusting the transmittance/reflectance of the half mirror film 3 according to the intensity of the laser light 70 and the optical configuration. The transmittance/reflectance can be adjusted by changing the stacking configuration and thickness of the multiple optical thin films that make up the half mirror film 3. The beam splitter 2 is not limited to a half mirror film, and may be any optical film having a similar optical function, for example, a non-polarizing beam splitter or a polarizing beam splitter.

The diffuser plate 5 is a diffuser plate that changes the incident reference light 72 into scattered light. In a preferred example, a reflector plate made of a fluororesin foam sheet such as foamed resin processed PTFE (Poly Tetra Fluoro Ethylene) or a scattering plate such as frosted glass can be used. Note that in FIG. 7, the beam splitter 2 and the diffuser plate 5 are depicted with a gap between them, but the diffuser plate 5 may be attached to the surface of the beam splitter 2. A reflecting mirror may also be placed on the back of the diffuser plate 5. By stacking the reflecting mirrors, the light utilization efficiency can be increased.

The lens 6 is a condenser lens that condenses the detection light 75 and the reference light 76 and guides them to the light receiving unit 7. In a preferred example, a convex lens or a collimator lens can be used. Alternatively, a condenser lens may be built into the beam splitter 2.
The light receiving unit 7 is an optical sensor that receives the detection light 75 and the reference light 76 and converts them into an electrical quantity. In a preferred example, a photodiode that generates an electric charge according to the intensity of the received light can be used. It is preferred that the optical sensor is a light receiving element selected according to the emission wavelength of the light emitting unit 1. When the light source wavelength is in the near infrared region, an optical sensor having a photoelectric conversion layer formed of InGaAs (indium gallium arsenide) or GaAs (gallium arsenide), which have high sensitivity, is preferred. When the light source wavelength is in the visible light to near infrared region (up to 900 nm), an optical sensor formed of silicon is preferred.

A cover member (not shown) may also be provided on the surface of the beam splitter 2 facing the living body H. The cover member is a transparent optical member that comes into contact with the skin surface of the living body H to irradiate the living body H with the measurement light 71 and to capture light including the detection light 75 from the living body H. In a preferred example, optical glass with a low reflection coating, optical plastic, a Fresnel lens, or the like can be used.

In the beam splitter 2, when the surface on the lens 6 side is defined as a first surface, the surface opposite to the first surface and facing the living body H is defined as a second surface. In the beam splitter 2, when the surface on the light emitting unit 1 side is defined as a third surface, a diffuser plate 5 is disposed on the fourth surface side opposite to the third surface.
The half-mirror film 3 of the beam splitter 2 is positioned at an angle of approximately 45° to the direction of travel of the laser light 70 from the light-emitting unit 1, and the measurement light 71 reflected by the half-mirror film 3 enters the second surface at approximately a right angle and is emitted toward the living body H.

*** Detection mode by optical interference device ***
The detection mode by the optical interference device 10 of this embodiment will be described with reference to FIG.
Coherent laser light 70 emitted from the light emitting unit 1 is split by the half mirror film 3 of the beam splitter 2 into measurement light 71 directed toward the living body H and reference light 72 directed toward the diffusion plate 5 .

The measurement light 71 incident on the living body H propagates while being repeatedly scattered and reflected within the tissue of the living body H, becoming scattered light, a part of which enters the beam splitter 2 as detection light 75. A part of the detection light 75 incident on the beam splitter 2 enters the lens 6 via the half mirror film 3, is collected, and enters the light receiving unit 7.

On the other hand, the reference light 72 incident on the diffuser 5 is scattered and reflected by the diffuser 5 and converted into scattered light to become reference light 76, a part of which enters the beam splitter 2. A part of the reference light 76 incident on the beam splitter 2 is reflected by the half mirror film 3 and enters the lens 6, where it is collected and enters the light receiving unit 7.
7, the reference light 76 reflected by the diffusion plate 5 becomes scattered light indicated by the dashed line. The reference light 76 is combined with the detection light 75, which is also scattered light, to become interference light, which is then incident on the light receiving unit 7.

As described above, the optical interference device 10 and the analysis device 100 of this embodiment can provide the following advantages.
The optical interference device 10 comprises a beam splitter 2 that separates laser light 70 emitted from an emitter 1 into reference light 72 and measurement light 71 that is incident on the living body H, and a diffuser plate 5 that converts the reference light 72 into scattered light. The measurement light 71 is reflected inside the living body H and becomes detection light 75, and the detection light 75 is combined with reference light 76 that has been converted into scattered light and incident on the light receiver 7.
The detection light 75 reflected inside the living body H is scattered light. The reference light 76 reflected by the diffusion plate 5 is also scattered light.
As a result, there is more overlap between the vector components of the detection light 75 and the reference light 76, both of which are scattered light, and the number of light rays involved in the interference increases, making it possible to perform measurement using an optical beat signal with a higher S/N ratio than in the past.
Therefore, it is possible to provide an optical interference device 10 capable of performing measurements with a high S/N ratio.

Moreover, by changing the division ratio of the transmittance/reflectance of the half mirror film 3 provided in the beam splitter as the light separating section and increasing the reflectance, the reference light intensity Ir can be increased.
Therefore, the power spectrum and FLOW can be increased, and measurement can be performed using an optical beat signal with a higher S/N ratio than in the past.
Furthermore, the light splitting portion may be any optical film having a similar optical function, and may be, for example, a polarization splitting film such as a non-polarizing beam splitter or a polarizing beam splitter.

Furthermore, a lens 6 serving as a light collecting section is provided in front of the light receiving section 7 , and the lens 6 collects interference light obtained by combining the detection light 75 and the reference light 76 onto the light receiving section 7 .
This allows the detection light 75 and the reference light 76 to be efficiently incident on the light receiving section 7 .

In addition, the biological information analysis device 100 includes an optical interference device 10 and a control device 20, and the control device 20 analyzes biological information based on an interference signal of interference light obtained by combining the detection light 75 and the reference light 76.
According to this, the analyzing apparatus 100 includes the optical interference device 10 capable of performing measurements with a high S/N ratio, and therefore it is possible to provide a non-invasive and highly sensitive analyzing apparatus 100 for biological information.

EMBODIMENT 2
***Different Aspects of Optical Interference Device (1)***
FIG. 8 is a configuration diagram of the optical interference device of this embodiment, and corresponds to FIG.
The optical interference device 10b of this embodiment has a small configuration that takes into consideration the ease of incorporation into an actual product. More specifically, the optical interference device 10b has a configuration in which the various components of the optical interference device 10 of the first embodiment are concentrated around the beam splitter 2. The basic optical action is the same as that of the optical interference device 10 of the first embodiment, and the same components are assigned the same numbers and overlapping explanations are omitted.

The optical interference device 10b has a compact configuration so that it can be stored inside a housing 12 (FIG. 1) that is approximately the size of a wristwatch, and each component is arranged around a beam splitter 2 that is approximately 5 mm square.
The optical interference device 10b is composed of a light emitting section 11, a beam splitter 2, a diffusion plate 15, a cover member 18, a mirror 19, a lens 16 as a light collecting section, a light receiving section 17, and the like.

The light-emitting unit 11 is a laser light source having the same function as the light-emitting unit 1 of the first embodiment, but uses a small-sized laser light source that can be accommodated on one surface of the beam splitter 2. In a preferred example, the size of the light-emitting unit 11 is about 2 mm square.
The beam splitter 2 is a cube-shaped light separating section with a side length of about 5 mm, and includes a half mirror film 3 .
The diffusion plate 15 is a diffusion plate similar to the diffusion plate 5 of the first embodiment, but is sized to fit the surface of the beam splitter 2 opposite the surface on which the light emitting portion 11 is disposed, and is attached to said surface.

The cover member 18 is an optical member provided on the living body H side of the beam splitter 2. The cover member 18 is a transparent optical member that comes into contact with the skin surface of the living body H, irradiates the measuring light 71 to the living body H, and takes in light including the detection light 75 from the living body H. In a preferred example, optical glass with a low reflection coating is used.
The mirror 19 is a reflective mirror that is laminated on the back side of the diffusion plate 15. For the diffusion plate 15 and the mirror 19, it is efficient to attach parts cut to about 5 mm square from a large sheet member in which the diffusion plate 15 and the mirror 19 are previously bonded together to the beam splitter 2.

The light receiving unit 17 is an optical sensor similar to the light receiving unit 7 of the first embodiment, but uses a small photodiode of about 2 mm square. A lens 16 made of a convex lens is provided on the light receiving surface of the light receiving unit 17. Alternatively, a configuration in which a condenser lens is built inside the beam splitter 2 may be used.
In addition, although the above describes preferred examples of each part, these are merely examples and may be replaced with members having similar functions. For example, they may be replaced with the members described as options for each part in the first embodiment.

*** Detection mode by optical interference device ***
The detection mode by the optical interference device 10b of this embodiment will be described with reference to FIG.
Coherent laser light 70 emitted from the light emitting unit 11 is split by the half mirror film 3 of the beam splitter 2 into measurement light 71 directed toward the living body H and reference light 72 directed toward the diffusion plate 15 .

The measurement light 71 incident on the living body H propagates while being repeatedly scattered and reflected within the tissue of the living body H, becoming scattered light, a part of which enters the beam splitter 2 as detection light 75. A part of the detection light 75 incident on the beam splitter 2 enters the lens 16 via the half mirror film 3, is collected, and enters the light receiving unit 17.

On the other hand, the reference light 72 incident on the diffuser 15 is scattered and reflected by the diffuser 15 to become reference light 76 converted into scattered light, and then incident on the beam splitter 2. A part of the light transmitted through the diffuser 15 is reflected by the mirror 19 and incident on the diffuser 15. A part of the reference light 76 incident on the beam splitter 2 is reflected by the half mirror film 3 to enter the lens 16, where it is collected and incident on the light receiving unit 17.
8, the reference light 76 reflected by the diffusion plate 15 becomes scattered light indicated by the dashed line. The reference light 76 is combined with the detection light 75, which is also scattered light, to become interference light, which is then incident on the light receiving unit 17.

As described above, according to the optical interference device 10b of this embodiment, in addition to the effects of the first embodiment, the following effects can be obtained.
Since the diffusion plate 15 is provided on one surface of the rectangular beam splitter 2, the optical interference device 10b can be made compact. Furthermore, the light emitter 11 and the light receiver 17 are also provided facing the beam splitter 2.
Therefore, it is possible to provide a compact optical interference device 10b that can be stored inside the housing 12 (FIG. 1) that is approximately the size of a wristwatch.

EMBODIMENT 3
***Different Aspects of Optical Interference Device (2)***
FIG. 9 is a configuration diagram of the optical interference device of this embodiment, and corresponds to FIGS.
The optical interference device 10c of this embodiment is also small in size, taking into consideration the ease of incorporation into an actual product. The basic optical action is the same as that of the optical interference device 10 and the optical interference device 10b of the above embodiment, and the same parts are assigned the same numbers, and duplicated explanations will be omitted.

The optical interference device 10c has a compact configuration so that it can be stored inside a housing 12 (FIG. 1) that is approximately the size of a wristwatch, and its entire size fits within a cube of about 5 mm square.
The optical interference device 10b is composed of a frame 30, a light emitting section 11, a light receiving section 17, half mirrors 33 and 34, a diffusion plate 35, a cover member 18, a lens 36 as a light collecting section, and the like.

The frame 30 is a housing in which each part including the half mirrors 33 and 34 is arranged at a predetermined position, and has a rectangular shape in a side view. One long side of the rectangle faces the living body H, and the light emitting unit 11 and the light receiving unit 17 are arranged side by side on the surface of the other long side. In the frame 30, the surface on which the light emitting unit 11 and the light receiving unit 17 are arranged is the first surface, and the surface facing the first surface and on the living body H side is the second surface. In a preferred example, the frame 30 is made of a black hard resin, and the length of the long side is about 5 mm. In addition, other materials may be used as long as the light is not reflected on the inner surface of the frame 30, for example, a pressed metal plate may be used. When a metal plate is used, the inner surface is coated with a black non-reflective paint. In addition, the frame 30 is not limited to a space inside, and may have a similar function, for example, a configuration in which three triangular prisms are combined.

The light emitting unit 11 and the light receiving unit 17 are arranged side by side on the first surface of the frame body 30. The light emitting unit 11 and the light receiving unit 17 use small components similar to those described in the embodiment 2. The light emitting unit 11 and the light receiving unit 17 are mounted on the substrate 39 and attached with their light exit ports and light receiving surfaces facing the frame body 30.
Inside the frame 30, two half mirrors 33, 34 and a lens 36 are arranged in a V-shape. The half mirror 33 is arranged directly below the light-emitting unit 11 with an inclination of about 45°. The half mirror 34 is arranged directly below the light-receiving unit 17 with an inclination of about 45° in the opposite direction to the half mirror 33. The half mirror 33 corresponds to the first optical film, and the half mirror 34 corresponds to the second optical film. The lens 36 will be described later. The inside of the frame 30 other than these parts is a space, which is an air layer.

A diffusion plate 35 is provided on the surface of the half mirror 34 facing the light receiving unit 17. The diffusion plate 35 is a diffusion plate similar to the diffusion plate 5 of the first embodiment, but has a size equal to that of the half mirror 34 and is attached to the surface.
The cover member 18 is a transparent plate-like member similar to that described in the second embodiment, and is provided on the surface of the frame body 30 on the living body H side.
In a preferred embodiment, the lens 36 is a convex lens, and is disposed in front of the light receiving unit 17. Note that a lens may be provided on the light receiving surface of the light receiving unit 17, like the lens 16 in the second embodiment.
Although the above describes preferred examples of each part, these are merely examples and may be replaced with parts having similar functions. For example, they may be replaced with the parts described as options for each part in the first embodiment.

***Detection mode by optical interference device***
The detection mode by the optical interference device 10c of this embodiment will be described with reference to FIG.
Coherent laser light 70 emitted from the light emitting unit 11 is separated by the half mirror 33 into measurement light 71 directed toward the living body H and reference light 72 directed toward the diffusion plate 35 .

The measurement light 71 incident on the living body H propagates while being repeatedly scattered and reflected within the tissue of the living body H, becoming scattered light, a part of which is incident on the half mirror 34 as detection light 75. A part of the detection light 75 incident on the half mirror 34 is incident on the lens 36 as scattered light via the half mirror 34 and the diffuser plate 35, where it is collected and incident on the light receiving unit 17.

On the other hand, the reference light 72 incident on the diffusion plate 35 is scattered and reflected by the diffusion plate 35 to become scattered light, which becomes reference light 76 , a part of which enters the lens 36 .
9, the reference light 76 reflected by the diffusion plate 35 becomes scattered light indicated by the dashed line. The reference light 76 is combined with the detection light 75, which is also scattered light, to become interference light, which is then incident on the light receiving unit 17.

As described above, according to the optical interference device 10c of this embodiment, in addition to the effects of the above embodiment, the following effects can be obtained.
On the first surface of the frame body 30, the light emitting unit 11 and the light receiving unit 17 are arranged side by side, and the second surface opposite to the first surface is the surface facing the living body H. Between the first surface and the second surface, a half mirror 33 and a half mirror 34 are arranged in a V shape from the first surface toward the second surface. A diffuser 35 is provided on the surface of the half mirror 34. The half mirror 33 is a light separating unit. The light emitted from the light emitting unit 11 is separated by the half mirror 33 into reference light 72 and measurement light 71. The measurement light 71 enters the living body H from the second surface. The detection light 75 reflected inside the living body H passes through the half mirror 34 and the diffuser 35 and then proceeds to the light receiving unit 17. The reference light 72 proceeds to the diffuser 35, where it is scattered and reflected at the diffuser 35 to become reference light 76 which is converted into scattered light, and is combined with the detection light 75 and enters the light receiving unit 17.

As a result, there is more overlap between the vector components of the detection light 75 and the reference light 76, both of which are scattered light, and the number of light rays involved in the interference increases, making it possible to perform measurement using an optical beat signal with a higher S/N ratio than in the past.
Therefore, it is possible to provide an optical interference device 10c capable of performing measurements with a high S/N ratio.

The optical interference device 10c contains half mirrors 33 and 34, a diffuser 35, and a lens 36. The light emitter 11 and the light receiver 17 are mounted on a substrate 39 and provided on the second surface of the frame 30. Furthermore, the cover member 18 is provided on the second surface of the frame 30.
In this way, since each part is arranged inside or around the small frame 30, the optical interference device 10c can be made compact.
Therefore, it is possible to provide a compact optical interference device 10c that can be stored inside the housing 12 (FIG. 1) that is approximately the size of a wristwatch.

1...light emitting unit, 2...beam splitter, 3...half mirror film, 4...mirror, 5...diffuser, 6...lens, 7...light receiving unit, 10, 10b, 10c...optical interference device, 11...light emitting unit, 12...housing unit, 14...belt, 15...diffuser, 16...lens, 17...light receiving unit, 18...cover member, 19...mirror, 20...control device, 21...display device, 22...storage device, 30...frame, 33, 34...half mirror, 35...diffuser, 36...lens, 39...substrate, 70...laser light, 71...measurement light, 72...reference light, 75...detection light, 76...reference light, 100...analysis device.

Claims (5)

A light emitting portion;
A light receiving unit;
a light separation unit that separates the light emitted from the light emitting unit into a reference light and a measurement light that is incident on a living body;
a diffusion plate that converts the reference light into scattered light,
the light separation unit is a rectangular beam splitter having an optical film therein,
The diffusion plate is provided on one surface of the beam splitter,
The measurement light is reflected inside the living body to become detection light,
The detection light is combined with the reference light and is incident on the light receiving unit.
Optical interference device. A light collecting unit is provided in front of the light receiving unit,
The light collecting unit collects interference light obtained by combining the detection light and the reference light on the light receiving unit.
The optical interference device according to claim 1 . The optical film of the light separation unit is a half mirror film or a polarization separation film.
The optical interference device according to claim 1 . A light emitting portion;
A light receiving unit;
A light source for separating the light emitted from the light emitting unit into a reference light and a measurement light to be incident on a living body.
A separation unit;
a diffusion plate that converts the reference light into scattered light,
The measurement light is reflected inside the living body to become detection light,
the detection light is combined with the reference light and is incident on the light receiving unit;
The light emitting portion and the light receiving portion are provided adjacent to each other on a first surface,
The second surface opposite to the first surface is a surface facing the living body,
a first optical film and a second optical film are provided between the first surface and the second surface and are arranged in a V-shape from the first surface toward the second surface,
the diffusion plate is provided on a surface of the second optical film,
the first optical film is the light separating unit, and the light emitted from the light emitting unit is separated into the reference light and the measurement light by the first optical film;
The measurement light is incident on the living body from the second surface, and the detection light reflected inside the living body passes through the second optical film and the diffusion plate and then travels to the light receiving unit,
The reference light travels to the diffusion plate, is scattered and reflected by the diffusion plate, and becomes the reference light converted into scattered light, and is combined with the detection light to be incident on the light receiving unit.
Optical interference device. An optical interference device according to any one of claims 1 to 4;
A control unit,
The control unit, based on an interference signal of interference light obtained by combining the detection light and the reference light,
Analyzing biological information,
Biometric analysis device.

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