WO2016121540A1 - Spectrometry device and spectrometry method - Google Patents

Abstract

A spectrometry device according to the present invention is provided with: a light source 101 that causes p-polarized light, which is linearly polarized light having an electric field vibration direction parallel to the incidence surface, to be incident on the surface of an object of measurement at Brewster's angle; an introduction optical system 103 for introducing measurement light emitted from the object of measurement struck by the p-polarized light into a phase shifter 105 and dividing the same into two measurement light beams; an interference light optical system 106 for forming interference light from the two measurement light beams; an interference light detection unit 107 for detecting the intensity of the interference light; a processing unit 201 for creating an interferogram of the measurement light on the basis of the intensity variation of the interference light obtained through the driving of the phase shifter 105; and a calculation unit 202 for obtaining a measurement light spectrum by applying the Fourier transform to the measurement light interferogram.

Description

Spectrometer and spectroscopic method

The present invention relates to a spectroscopic measurement apparatus and a spectroscopic measurement method that can non-invasively measure biological components in the body, such as blood sugar and blood cholesterol, and can be used for semiconductor defect evaluation.

In various diseases such as diabetes and hyperlipidemia, the concentration of biological components in blood such as blood glucose (blood glucose) and blood cholesterol is used as an indicator of the disease. Therefore, management of the concentrations of these biological components in blood is important for the prevention and treatment of diseases. For the measurement of the concentration of biological components in blood, blood collected from a subject is usually used. In recent years, it has become possible to measure the concentration of various biological components from a very small amount of blood, and the burden on the subject has been reduced, but blood collection is painful. Moreover, since troublesome operations such as disinfection of blood collection sites and processing of consumables are necessary, there is a need for a device that non-invasively measures biological components without collecting blood. A non-invasive measuring device can be easily used at home, and is useful, for example, for patients who need to measure biological component concentrations on a daily basis for the prevention or treatment of diseases.

There is a device invented by the inventor of the present application as one of the devices for non-invasively measuring the concentration of biological components in blood (see Patent Document 1). In this device, an interferogram of a biological component is obtained by using an interference phenomenon of an object light beam generated from each bright spot that optically constitutes the biological component, and the object light is separated by Fourier transforming the interferogram. Get characteristics (spectrum).

Specifically, as shown in FIG. 1A, light from a light source, for example, near-infrared light having high permeability to a biological membrane is irradiated to a fingertip that is a measurement target, and is generated from the transmitted light and biological components in the fingertip. Object light such as diffused light and scattered light is introduced into the phase shifter via the objective lens. Then, the object light beam reflected by the fixed mirror part and the movable mirror part constituting the phase shifter is caused to interfere with the imaging lens, and the interference light is detected by a detection part such as a CCD camera. Therefore, by setting the focal plane of the objective lens at the position of a predetermined vein in the fingertip, it is possible to detect the interference light of the object light generated from the target component in the vein.

The movable mirror unit is moved by a piezoelectric element or the like, and a phase difference corresponding to the amount of movement of the movable mirror unit is given to the object light beam reflected from the fixed mirror unit and the movable mirror unit. For this reason, when the movable mirror unit is moved continuously and the phase difference is changed, the intensity of the interference light of each wavelength component continuously distributed in a predetermined wavelength region changes accordingly, and the synthesis of these interference lights An interferogram that is a waveform is obtained. A spectral characteristic (spectrum) of the object light can be acquired by performing a Fourier transform on the interferogram.

JP 2008-309707 A WO2013 / 129519 A1

There are many veins in the fingertip. In addition to veins, there are various biological components. For this reason, near-infrared light irradiated to the fingertip passes through many veins and biological components existing in the fingertip, and then exits from the fingertip as transmitted light, scattered light, or diffused light. Therefore, even if the focal plane of near-infrared light is set at the position of a specific vein in the fingertip, object light generated from another vein or other biological component located in the vicinity of the specific vein Since interference light is formed together with object light generated from the target component, it is difficult to remove the influence of biological components other than the target component contained in a specific vein from the interferogram. An accurate spectrum of the target component cannot be obtained from such an interferogram. For example, FIG. 1B shows an interferogram obtained by introducing near-infrared light transmitted through the tip of a human index finger into a phase shifter. From FIG. 1B, it is estimated that the interferogram is superimposed with a change in the luminance value of the interference light due to a biological component other than the target component and a change in the luminance value of the interference light accompanying the pulsation of the artery.

On the other hand, a spectroscopic measurement method using internal diffused light when light from a light source is irradiated on a fingertip is considered. Since the internal diffused light is light that has entered a relatively shallow portion near the surface layer of the fingertip and is diffused by the biological component, it is possible to avoid the influence of the biological component existing in the deep part of the fingertip. Therefore, if the spectroscopic measurement can be performed using only the internal diffused light, the spectral characteristics of the biological component existing in the vicinity of the surface of the fingertip can be accurately measured. However, when the fingertip is irradiated with light from the light source, not only internally diffused light but also reflected light from the surface of the fingertip is generated. Since the intensity of the surface reflection light is very large compared to the internal diffusion light, the internal diffusion light is buried in the surface reflection light.

In order to reduce the influence of surface reflected light, it is considered to irradiate the fingertip with oblique illumination as shown in FIG. 2 (see Patent Document 2). In this method, the influence of the specularly reflected light component is removed by letting the specularly reflected light component out of the objective lens out of the reflected light on the fingertip surface. However, since there are many minute irregularities such as fingerprints on the surface of the fingertip, the reflected light of the light irradiated on the surface of the fingertip includes not only a regular reflection light component but also a diffuse reflection component. Like the regular reflection component, the intensity of the diffuse reflection component is much higher than that of the internal diffused light, so that it is difficult to detect the internal diffused light even if the regular reflective component is removed.

A problem to be solved by the present invention is a spectroscopic measurement apparatus and spectroscopic measurement capable of accurately measuring the spectral characteristics of a substance contained in the measurement target by reducing the influence of diffuse reflected light on the surface of the measurement target Is to provide a method.

The spectroscopic measurement device according to the first aspect of the present invention, which has been made to solve the above problems,
a) a movable reflector that is arranged alongside the fixed reflector and is movable along a direction perpendicular to the reflecting surface;
b) a light irradiating means for causing P-polarized light, which is linearly polarized light whose vibration direction of the electric field is parallel to the incident surface, to be incident on the surface to be measured at a Brewster angle;
c) an introduction optical system that introduces measurement light emitted from the measurement object on which the P-polarized light is incident into the fixed reflection portion and the movable reflection portion;
d) an interference optical system that forms interference light of measurement light introduced into the fixed reflection part and reflected by the fixed reflection part and measurement light introduced into the movable reflection part and reflected by the movable reflection part;
e) an interference light detector for detecting the intensity of the interference light;
f) a processing unit for obtaining an interferogram of the measurement light based on a change in intensity of the interference light detected by the interference light detection unit by moving the movable reflection unit;
and g) a calculation unit that obtains a spectrum of the measurement light by subjecting the interferogram to Fourier transform.

The spectroscopic measurement device according to the second aspect of the present invention is:
a) a light irradiating means for causing P-polarized light, which is linearly polarized light whose vibration direction of the electric field is parallel to the incident surface, to be incident on the surface to be measured at a Brewster angle;
b) a splitting optical system that splits the measurement light emitted from the measurement object on which the P-polarized light is incident into a first measurement light and a second measurement light;
c) an interference optical system that forms interference light between the first measurement light and the second measurement light;
d) optical path length difference providing means for providing a continuous optical path length difference between the first measurement light and the second measurement light;
e) an interference light detector having a plurality of pixels for detecting an intensity distribution of the interference light corresponding to the continuous optical path length difference;
f) a processing unit for obtaining an interferogram of the measurement light from an intensity distribution of the interference light detected by the interference light detection unit;
and g) a calculation unit that obtains a spectrum of the measurement light by subjecting the interferogram to Fourier transform.

Brewster's angle refers to the direction of vibration of an electric field when light is incident on the interface between two substances having different refractive indices from the one substance (incident side medium) side to the other substance (transmission side medium) side. The linearly polarized light component (P-polarized light) parallel to the incident surface (the surface including the incident light and the reflected light beam) is incident on the inside of the material, and only the linearly polarized light component (S-polarized light) whose electric field vibration direction is perpendicular to the incident surface is reflected. The angle to do. When the Brewster angle is θ _B , the refractive index of the incident side medium is n ₁ , and the refractive index of the transmission side medium is n ₂ , the angle θ _B is expressed by the following equation.
tan θ _B = n ₂ / n ₁

For example, FIG. 3 is a graph showing the reflectance for each incident angle of P-polarized light and S-polarized light at the interface of water (refractive index 1.33) and air (refractive index 1.00), which are the main components of the skin. The reflectance of each polarized light was obtained from an equation according to the Fresnel reflection law. FIG. 3 shows that the Brewster angle at the interface between water and air is 53 [deg.].

Therefore, when only P-polarized light is incident at the Brewster angle on the surface that is the interface between the measurement object and the surrounding medium (usually air), the reflectance of the P-polarized light becomes 0, and much of the measurement light emitted from the measurement object. Is diffused light in which P-polarized light that has entered a relatively shallow portion near the surface layer to be measured is diffused by a substance contained in the shallow portion. Here, the incident angle when P-polarized light is incident on the measurement object from the air can be obtained from the refractive index of air (= 1) and the refractive index of the measurement object.

In the spectroscopic measurement apparatus according to the first aspect, the measurement light emitted from the measurement target is introduced into the fixed reflection portion and the movable reflection portion by the introduction optical system, and is reflected by the fixed reflection portion and the movable reflection portion. A phase difference is given between the measurement beams reflected by the. Then, interference light of both measurement lights is formed by the interference optical system, and an interferogram is obtained from a change in the intensity of the interference light. In the spectroscopic measurement apparatus according to the second aspect, the measurement light emitted from the measurement target is divided into the first measurement light and the second measurement light by the splitting optical system, and is continuously provided between the two by the optical path length difference providing unit. Difference in optical path length. Then, interference light of the measurement light divided into two by the interference optical system is formed, and an interferogram is obtained from the intensity distribution of the interference light. In any embodiment, since the interferogram is subjected to Fourier transform, the spectrum of the measurement light (spectral characteristics), that is, the spectral characteristics of the substance contained in the vicinity of the surface layer to be measured is obtained. Qualitative analysis or quantitative analysis can be performed.

When the surface to be measured is a flat surface, the reflectance of P-polarized light incident on the surface at a Brewster angle is zero. However, in the case of a measurement target having a large number of minute irregularities on the surface like a fingertip, not all incident angles of P-polarized light incident on the surface are Brewster angles. Diffusely reflects on the surface. Such surface diffuse reflection light is all P-polarized light. On the other hand, the internally diffused light becomes random polarized light including P-polarized light and S-polarized light.

Therefore, in the above-described spectroscopic measurement apparatus, between the measurement target surface and the introduction optical system, or between the measurement target surface and the split optical system, or between the introduction optical system and the fixed reflection unit and the movable reflection unit, or division. Between the optical system and the optical path length difference providing means, there is disposed a polarizing plate that allows the S-polarized light whose electric field is perpendicular to the electric field of the P-polarized light to pass therethrough and does not pass the P-polarized light. preferable.
According to such a configuration, the surface diffuse reflection light included in the measurement light can be removed.

The spectroscopic measurement apparatus may further include a plate-like light transmissive member having a placement surface on which the measurement target is placed and a light irradiation surface that is a surface opposite to the placement surface. It is a good configuration.
In the said structure, the surface of a measuring object can be closely approached to a flat surface by lightly pressing a measuring object, such as a fingertip, on the mounting surface of the said light transmissive member. For this reason, the surface diffuse reflection light emitted from the measurement object when the P-polarized light is incident on the surface of the measurement object through the light transmissive member can be reduced. In this configuration, the Brewster angle is obtained from the refractive index of the light transmissive member and the refractive index of the measurement target.

Moreover, the spectroscopic measurement method according to the first aspect of the present invention includes:
a) P-polarized light, which is linearly polarized light whose vibration direction of the electric field is parallel to the incident surface, is incident on the surface to be measured at a Brewster angle.
b) Movable reflection movable in the direction perpendicular to the reflection surface, which is arranged alongside the fixed reflection portion and the fixed reflection portion by the introducing optical system with the measurement light emitted from the measurement object on which the P-polarized light is incident Introduced to the department,
c) forming interference light of measurement light introduced into the fixed reflection part and reflected by the fixed reflection part and measurement light introduced into the movable reflection part and reflected by the movable reflection part using an interference optical system;
d) detecting the intensity of the interference light by an interference light detector;
e) obtaining an interferogram of the measurement light based on a change in the intensity of the interference light detected by the interference light detection unit by moving the movable reflection unit,
f) The spectrum of the measurement light is obtained by Fourier transforming the interferogram.

Furthermore, the spectroscopic measurement method according to the second aspect of the present invention includes:
a) P-polarized light, which is linearly polarized light whose vibration direction of the electric field is perpendicular to the incident surface, is incident on the surface to be measured at a Brewster angle.
b) Dividing the measurement light emitted from the measurement object on which the P-polarized light is incident into a first measurement light and a second measurement light by a splitting optical system;
c) after giving a continuous optical path length difference between the first measurement light and the second measurement light, forming interference light between the first measurement light and the second measurement light by an interference optical system;
d) detecting the intensity distribution of the interference light corresponding to the continuous optical path length difference by an interference light detection unit having a plurality of pixels;
e) obtaining an interferogram of the measurement light from the intensity distribution of the interference light detected by the interference light detection unit,
f) A spectrum of the measurement light is obtained by performing a Fourier transform on the interferogram of the measurement light.

In the spectroscopic measurement method, between the measurement target surface and the introduction optical system, or between the measurement target surface and the split optical system, or between the introduction optical system and the fixed reflection portion and the movable reflection portion. Alternatively, by the polarizing plate disposed between the splitting optical system and the optical path length difference providing means, the S-polarized light whose electric field is linearly polarized light perpendicular to the electric field of the P-polarized light is passed through the measurement light, and the P-polarized light It is good not to let pass.

In addition, a plate-like light transmissive member having a placement surface on which the measurement object is placed and a light irradiation surface that is a surface opposite to the placement surface,
You may make it irradiate this P polarized light to the light irradiation surface of the said transparent member so that the said P polarized light may inject into the surface of the said measuring object with a Brewster angle.

In the present invention having the above-described configuration, the measurement light emitted from the measurement target when the light from the light source is incident on the surface of the measurement target is divided into two and a phase difference is given between the two. Then, interference light of the measurement light divided into two is formed by the interference optical system, and an interferogram is obtained. The interferogram is Fourier transformed to obtain the spectrum of the measurement light (spectral characteristics), that is, the spectral characteristics of the substance contained in the vicinity of the surface layer to be measured. From this spectral characteristic, qualitative analysis or quantitative analysis of the substance is performed. It can be performed. At this time, since only the P-polarized light is incident on the surface of the measurement object at the Brewster angle, the reflectance becomes 0, and most of the measurement light emitted from the measurement object is placed in a relatively shallow portion near the surface layer of the measurement object. The diffused light in which the invading P-polarized light is diffused by the substance contained in the shallow portion can be obtained. For this reason, the spectral characteristics of the substance in the vicinity of the surface layer to be measured can be obtained with high accuracy.

Schematic showing the main components of the spectroscopic optical system of a conventional biological component measuring device using transmitted light An example of an interferogram obtained when a human index finger is irradiated with light from a light source. Schematic which shows the main components of the spectroscopy optical system of the conventional biological component measuring apparatus using reflected light. The graph which shows the relationship between an incident angle and a reflectance when P polarized light and S polarized light are made incident on the skin from the air. Explanatory drawing which shows the measurement light which goes to a phase shifter when a polarizing plate is not provided in the latter part of an objective lens Explanatory drawing which shows the measurement light which goes to a phase shifter, when a polarizing plate is provided in the back | latter stage of an objective lens. 1 is a schematic configuration diagram of a spectrometer according to a first embodiment of the present invention. The schematic block diagram of the spectrometer which concerns on 2nd Embodiment of this invention. The schematic block diagram of the spectrometer which concerns on 3rd Embodiment of this invention. The schematic block diagram of the spectrometer which concerns on 4th Embodiment of this invention. The schematic block diagram of the spectrometer which concerns on 5th Embodiment of this invention. The schematic block diagram of the optical system used for the experiment verified about the polarization characteristic of the light irradiated to a measuring object. Observation image obtained when the fingertip is irradiated with P-polarized light Observation image obtained when s-polarized light is irradiated on fingertip An observation image obtained when P-polarized light is applied to the fingertip and a second polarizing plate is further installed. Observation image of vein near skin surface of fingertip when first polarizing plate and second polarizing plate are installed FIG. 12B is an interferogram obtained when P-polarized light is irradiated to a region surrounded by a square frame in FIG. 12A with the first polarizing plate and the second polarizing plate installed. Spectrum obtained by Fourier transform of the interferogram in the area surrounded by the square frame in FIG. 12A The spectrum acquired when light was irradiated to the blood of a rat on the same conditions as FIG. 13A. Observation image of fingertip surface by reflected illumination Spectra of hemoglobin in veins near the surface of the fingertip surface General water absorption spectrum. Spectrum of veins in the vicinity of the skin surface of the fingertip when there is no window Observation image of the fingertip when there is a window. Spectrum of veins in the vicinity of the skin surface of the fingertip with and without a window Rat blood spectrum. The schematic block diagram of the spectrometer which concerns on other embodiment.

In the spectroscopic measurement apparatus and spectroscopic measurement method according to the present invention, light from the light source is incident on the surface of the measurement object at a Brewster angle with P-polarized light, which is linearly polarized light whose vibration direction is parallel to the incident surface. As a result, the measurement light emitted from the measurement target is introduced into the fixed reflection portion and the movable reflection portion or the phase shifter by the introduction optical system such as an objective lens. For example, as shown in FIG. 4A, the P-polarized light can be extracted from the light emitted from the light source by disposing the polarizing plate 1 between the light source and the measurement target.
Thus, the measurement light is divided into two, and interference light of the measurement light divided into these two is formed. From the change in the intensity of the interference light detected by the interference light detection unit, a continuous phase difference is provided between the two measurement lights by moving the movable reflection unit or by the optical path length difference providing unit. An interferogram of measurement light is obtained. And the spectral characteristic of the substance contained in a measuring object is measured by calculating | requiring the spectrum of measurement light by Fourier-transforming this interferogram.

In particular, according to the present invention, P-polarized light only the vibration direction of the electric field is incident side and parallel to the linearly polarized light is incident on the surface to be measured at the Brewster angle theta _B, the vibration direction of electric field at the incident surface perpendicular linear polarization Some S-polarized light is not incident on the object to be measured. Therefore, the reflectance of P-polarized light on the surface of the measurement object is theoretically 0, and the P-polarized light that has entered the relatively shallow part near the surface layer of the measurement object is included in the shallow part from the measurement object. Only the diffused internal diffused light is emitted.

However, as shown in FIG. 4A, when the measurement target is a living body such as a fingertip, since the surface of the skin has a large number of irregularities, the incident angle at the incident point of each light beam constituting the light from the light source toward the measurement target is The light does not necessarily have a Brewster angle, and some light rays are incident on the surface of the measurement object at an angle other than the Brewster angle. Since the P-polarized light incident on the surface of the measurement object at an angle other than the Brewster angle is reflected on the surface, the light emitted from the measurement object includes both internal diffused light and surface diffuse reflected light. Usually, the intensity of the surface diffuse reflection light is very large compared to the intensity of the internal diffusion light. Therefore, when the internal diffused light and the surface diffuse reflected light are incident on the objective lens, the internal diffused light is buried in the surface diffuse reflected light.

It is known that the surface diffuse reflection light maintains the polarization characteristics of incident light, but the internal diffuse light is depolarized. That is, the surface diffuse reflected light is the same P-polarized light as the incident light, but the internal diffused light is randomly polarized. Therefore, paying attention to such an optical phenomenon, when the surface of the object to be measured has irregularities, as shown in FIG. 4B, a so-called crossed Nicols condition is applied to the polarizing plate 1 after the objective lens. The polarizing plate 2 was installed. The condition of crossed Nicols means a condition in which an electric field transmitted through one polarizing plate and an electric field transmitted through the other polarizing plate are orthogonal to each other. With such a configuration, it is possible to prevent the surface diffuse reflection light from being introduced into the fixed reflection portion and the movable reflection portion or the phase shifter. In this case, the P-polarized light contained in the internal diffused light is shielded by the polarizing plate 2 installed at the subsequent stage of the objective lens, but a part of the internal diffused light (S-polarized light) is transmitted, so that the measurement consists of only the internal diffused light. Interference light of light can be detected.

Hereinafter, specific embodiments of the present invention will be described with reference to FIGS.
[First Embodiment]
FIG. 5 is a schematic configuration diagram of the spectrometer according to the first embodiment of the present invention. The spectroscopic measurement apparatus includes a spectroscopic measurement unit 10 and a control device 20 that processes the measurement results obtained by the spectroscopic measurement unit 10.

The spectroscopic measurement unit 10 includes a light source 101, a first polarizing plate 102, an objective lens 103, a second polarizing plate 104, a phase shifter 105, an imaging lens 106, and a detection unit 107. Although not shown, the spectroscopic measurement unit 10 is housed in a casing made of a material that does not transmit light, such as plastic or metal. An opening is formed in the casing, and light from the light source 101 is irradiated to the measurement object through the opening. In this embodiment, the objective lens 103 and the imaging lens 106 correspond to an introduction optical system and an interference optical system, respectively. The objective lens 103 is disposed to face the opening of the casing. On the other hand, the imaging lens 106 is disposed in a direction in which the optical axis is orthogonal to the objective lens 103.

The light source 101 is a light source that emits light having a wavelength that penetrates the surface of the measurement target and enters the measurement target, and the emitted light is incident on the surface of the measurement target at a predetermined angle. It is arranged in such a direction. For example, when the measurement target is a fingertip, a light source that emits near infrared light having a good skin permeability and a wavelength of about 1 μm is used. The predetermined angle is an angle corresponding to the Brewster angle θ _B on the surface of the measurement target, where the refractive index of the atmosphere that is the surrounding environment of the measurement target is n ₁ , and the refractive index of the measurement target is n _2. θ _B is obtained by the following equation.
tan θ _B = n ₂ / n ₁

In the present embodiment, as can be changeable angle theta _B in accordance with the refractive index of the measuring object, and is adjustably configured in the direction of light emitted from the light source 101.
The detection unit 107 is composed of, for example, a 16 × 16 pixel two-dimensional CCD (Charge Coupled Device) camera, and is arranged such that the light receiving surface of the detection unit 107 is positioned on the imaging surface of the imaging lens 106.

Further, the detection signal of the detection unit 107 is input to the control device 20. The control device 20 obtains an interferogram from the detection signal of the detection unit 107, mathematically Fourier transforms the interferogram, and obtains a spectral characteristic (spectrum) that is a relative intensity for each wavelength of the measurement light. A calculation unit 202, a display for outputting calculation results, and an output device 203 such as a printer are provided.

The phase shifter 105 is disposed between the objective lens 103 and the imaging lens 106. The phase shifter 105 includes a fixed mirror unit 51, a movable mirror unit 52 arranged side by side with the fixed mirror unit 51, and a drive mechanism 53 that moves the movable mirror unit 52. The fixed mirror unit 51 and the movable mirror unit 52 correspond to the fixed reflection unit and the movable reflection unit of the present invention, respectively. Both the fixed mirror unit 51 and the movable mirror unit 52 have a rectangular reflecting surface that is inclined at an angle of 45 ° with respect to the optical axis of the objective lens 103 and the optical axis of the imaging lens 106. The reflecting surfaces of both mirror parts are arranged side by side with a very slight gap.

The drive mechanism 53 is composed of, for example, a piezoelectric element having a capacitance sensor, receives a signal from the control device 20, and maintains a tilt angle of the reflecting surface with respect to the optical axis at 45 ° with the movable mirror portion. 52 is moved in the direction (arrow A direction) perpendicular to the reflecting surface. With such a configuration, the relative position of the movable mirror unit 52 with respect to the fixed mirror unit 51 changes, and a phase difference is given between the light beam reflected by the fixed mirror unit 51 and the light beam reflected by the movable mirror unit 52. .

Specifically, the movement amount of the objective lens 103 or the imaging lens 106 of the movable mirror unit 52 in the optical axis direction is 1 / √2 of the movement amount of the movable mirror unit 52 in the arrow A direction. The optical path length difference that gives a relative phase change between the fixed light beam and the movable light beam is twice the amount of movement of the movable mirror 52 in the optical axis direction. *

The first polarizing plate 102 transmits only the P-polarized light, which is linearly polarized light in which the vibration direction of the electric field is parallel to the incident surface, out of the light emitted from the light source 101. Here, the incident surface refers to a surface including incident light and reflected light. On the other hand, the second polarizing plate 104 is a polarizing plate that allows only the S-polarized light in which the polarization direction of the electric field and the vibration direction of the electric field are orthogonal to pass through the light transmitted through the objective lens 103 and does not pass the P-polarized light.

[Second Embodiment]
FIG. 6 is a schematic configuration diagram of a spectrometer according to the second embodiment of the present invention. This embodiment is different from the first embodiment in that light from a light source is irradiated to a measurement object through a window portion. Although not shown, the detection signal of the detection unit 107 is also input to the control device 20 in the spectroscopic measurement apparatus according to the second embodiment.

In this embodiment, the window part 11 which is a rectangular plate-shaped light transmissive member is inserted in the opening provided in the casing, and the measurement object is on the surface of the window part 11 located outside the casing. The light from the light source 101 is irradiated on the surface that is placed and located inside the casing. Of the two surfaces of the window portion 11, the surface on which the measurement target is placed corresponds to the placement surface of the present invention, and the surface irradiated with light from the light source corresponds to the light irradiation surface of the present invention. By placing the measurement object on the window 11, the surface of the measurement object can be brought close to a flat surface in the case of a measurement object whose surface is not flat, such as a fingertip.

Light emitted from the light source 101 enters the window 11 and then enters the surface of the measurement target. Therefore, when the emitted light enters the window portion 11 and is refracted when emitted from the window portion 11, it enters the surface of the measurement object. Therefore, in this embodiment, the Brewster angle on the surface of the measurement target is the Brewster angle θ _{B at} the interface between the measurement target and the window portion 11. Since the light emitted from the light source 101 is refracted at a predetermined angle when entering the window portion 11, the incident angle from the light source 101 to the window portion 11 is set in consideration of this refraction angle. Since configurations other than those described above are the same as those in the first embodiment, the same reference numerals are given and description thereof is omitted.

[Third Embodiment]
FIG. 7 is a schematic configuration diagram of a spectrometer according to the third embodiment of the present invention. This embodiment is different from the first embodiment in that the second polarizing plate is not provided. Since other configurations are the same as those of the first embodiment, the same reference numerals are given and description thereof is omitted. Although not shown, the detection signal of the detection unit 107 is also input to the control device 20 in the spectroscopic measurement device according to the third embodiment.

The third embodiment is an example of an apparatus suitable for measuring spectral characteristics of a measurement target having a flat surface. In the case of a measurement target having a substantially flat surface, almost no surface diffuse reflection light is generated. Therefore, even if there is no second polarizing plate, the measurement light does not include surface diffuse reflection light. Also in this embodiment, a window portion as shown in the second embodiment may be provided. By providing the window portion, it is possible to prevent dust and the like from entering the casing.

[Fourth Embodiment]
FIG. 8 is a schematic configuration diagram of a spectrometer according to the fourth embodiment of the present invention. The configuration of the phase shifter and the interference optical system are different between the fourth embodiment and the second embodiment. Since the other configuration is the same as that of the second embodiment, the same reference numerals as those of the second embodiment are given and description thereof is omitted. Although not shown, the detection signal of the detection unit 107 is also input to the control device 20 in the spectroscopic measurement device according to the fourth embodiment.

In the fourth embodiment, a cylindrical lens 30 is used as the interference optical system. Further, the phase shifter 40 includes a first transmission unit 401 in which the light irradiation surface and the light emission surface are parallel, and one of the light irradiation surface and the light emission surface is the light irradiation surface or the emission surface of the first transmission unit 401. The optical member is formed of a wedge-shaped second transmitting portion 402 that is on the same plane and in which the other of the light irradiation surface and the light emission surface is inclined. In the present embodiment, the second transmission part 402 is configured such that the thickness of the second transmission part 402 at the boundary surface between the first transmission part 401 and the second transmission part 402 gradually decreases from one side to the other side. The light irradiation surface is inclined. Although the inclination angle of the light irradiation surface of the second transmission unit 402 is determined by the phase shift amount determined by the wave number resolution and the sampling interval for each pixel of the detection unit 107, there is no problem even if they are slightly shifted. In addition, the 1st transmission part 401 and the 2nd transmission part 402 may each be comprised from a separate optical member, and it is good also as the 1st transmission part 401 and the 2nd transmission part 402 by processing one surface of one optical member. .

In this embodiment, the measurement light introduced into the phase shifter 40 enters the first transmission unit 401 and the second transmission unit 402 separately, and passes through the first transmission unit 401 and the second transmission unit 402, and then is cylindrical. Head to the lens 30. At this time, since the second transmission part 402 has a wedge shape, the measurement light transmitted through the second transmission part 402 (second measurement light) and the measurement light transmitted through the first transmission part 401 (first measurement light). Is given a continuous optical path length difference. That is, in this embodiment, the phase shifter 40 functions as a splitting optical system and an optical path length difference providing unit.

The cylindrical lens 30 is arranged such that the convex surface portion faces the phase shifter 40 side and the flat surface portion faces the light receiving surface side of the detection unit 107. The light receiving surface of the detection unit 107 is located on the imaging surface of the cylindrical lens 30. For this reason, the first and second measurement lights incident on the cylindrical lens 30 are converged by the cylindrical lens 30 and condensed on the same straight line on the light receiving surface of the detection unit 107 to form an interference image. As described above, since a continuous optical path length difference is provided between the first measurement light and the second measurement light, the intensity of the interference image formed on the light receiving surface of the detection unit 107 is the continuous measurement. It changes according to the optical path length difference. Accordingly, an interferogram (interference light intensity distribution) of the measurement light is obtained from the detection result of the detection unit 107. By performing Fourier transform on this interferogram, the spectral characteristics (spectrum) of the internal biological components in the vicinity of the surface layer to be measured can be obtained as in the first and second embodiments.

[Fifth Embodiment]
FIG. 9 is a schematic configuration diagram of a spectrometer according to the fifth embodiment of the present invention. In the fifth embodiment, the second polarizing plate is not provided, and this point is different from the fourth embodiment. Since other configurations are the same as those of the fourth embodiment, the same reference numerals are given and description thereof is omitted.

[Explanation of operation of spectrometer]
Next, the operation of the spectrometer according to the present invention will be described by taking the spectrometer (see FIG. 5) according to the first embodiment as an example. Here, the operation of measuring the spectral characteristics inside the fingertip of the subject's hand will be described. However, the same applies to the case of a measurement target having a flat surface.
First, the fingertip is aligned with the position of the opening of the casing, and in this state, light (near infrared light) from the light source 101 is irradiated to the surface of the fingertip through the first polarizing plate 102. Then, only the P-polarized light component of the near-infrared light passes through the first polarizing plate 102 and enters the fingertip. At this time, near-infrared light from the light source 101 is incident on the surface of the fingertip at a Brewster angle, so most of the P-polarized light penetrates the skin of the fingertip and enters the inside of the fingertip. The diffused light (internal diffused light) diffuses again through the skin of the fingertip, reaches the inside of the casing through the opening, and enters the objective lens 103. . Since the light that has entered and diffused into the fingertip has its polarization characteristics canceled, the internally diffused light includes both a P-polarized component and an S-polarized component.

On the other hand, since the surface of the fingertip is uneven, a part of the P-polarized component of the near infrared light incident on the fingertip surface is incident on the fingertip surface at an angle different from the Brewster angle and diffusely reflected. This diffuse reflected light (surface diffuse reflected light) reaches the inside of the casing from the opening and enters the objective lens 103. In order to maintain the polarization characteristics of the surface diffuse reflection light, the surface diffuse reflection light incident on the objective lens 103 is composed of a P-polarized component.

The internal diffused light and the surface diffuse reflected light incident on the objective lens 103 are incident on the second polarizing plate 104 as substantially parallel light beams. Since the second polarizing plate 104 blocks the P-polarized light component and allows only the S-polarized light component to pass therethrough, the P-polarized light component of the internal diffused light incident on the second polarizing plate 104 and the surface diffused reflected light pass through the second polarizing plate 104. The S-polarized component of the internally diffused light does not pass through the second polarizing plate 104 and reaches the entire surfaces of the fixed mirror unit 51 and the movable mirror unit 52 of the phase shifter 105. As a result, a part of the S-polarized component of the internally diffused light is reflected by the reflecting surface of the fixed mirror unit 51, and the rest is reflected by the reflecting surface of the movable mirror unit 52, and enters the imaging lens 106, respectively. In the following description, the light reflected by the fixed mirror unit 51 is also called fixed reflected light, and the light reflected by the movable mirror unit 52 is also called movable reflected light.

The fixed reflected light and the movable reflected light incident on the imaging lens 106 are imaged on the light receiving surface of the detection unit 107 to form an interference image. At this time, since the internal diffused light emitted from the fingertip of the hand includes light of various wavelengths, the movable mirror unit 52 is moved to continuously change the optical path length difference between the movable reflected light and the fixed reflected light. By changing, a waveform of an imaging intensity change (interference light intensity change) called an interferogram is obtained. The spectral characteristic of the S-polarized component of the internally diffused light can be obtained by mathematically Fourier transforming this interferogram. In the spectroscopic measurement apparatus described above, only the internal diffused light emitted from the focusing surface located at a specific depth of the objective lens 103 within the fingertip forms an image on the light receiving surface of the detection unit 107. Accordingly, it is possible to obtain the spectral characteristics inside the fingertip with the depth limited to the in-focus surface.

[Experimental result]
Next, experimental results for verifying the polarization characteristics of the light irradiated to the measurement object will be described with reference to FIGS. FIG. 10 shows an optical system used in the experiment. FIGS. 11A and 11B show images obtained when P-polarized light and S-polarized light are irradiated to the fingertip to be measured at the Brewster angle, respectively. From these images, it can be seen that a brighter image is observed when s-polarized light is irradiated. This is considered to be because the diffusely reflected light on the surface of the fingertip was suppressed in the P-polarized light than in the S-polarized light. Further, FIG. 11C shows an image obtained when a second polarizing plate that is in a crossed Nicols state with the first polarizing plate is disposed between the measuring target and the introduction optical system, and the P-polarized light is irradiated onto the measuring target. The image in FIG. 11C is much darker than that in FIG. 11A, indicating that the surface diffused light is further suppressed. From the above, it is effective to reduce the surface diffuse reflection light of the measurement target by irradiating the measurement target with P-polarized light at the Brewster angle and disposing a polarizing plate that is crossed Nicol between the measurement target and the introduction optical system. It was proved.

FIG. 12A shows an observation image of veins near the skin surface of the fingertip when the first polarizing plate and the second polarizing plate are installed. FIG. 12B shows the result of detecting the intensity of interference light by irradiating P-polarized light in the area surrounded by the square in FIG. 12A under the same optical conditions as the image shown in FIG. 11C (hereinafter referred to as optical condition Pc). The obtained interferogram is shown. Unlike the interferogram shown in FIG. 1B, the interferogram shown in FIG. 12B does not have a change in the luminance value of the interference light accompanying pulsation. From this result, it can be seen that only the spectral characteristics of the biological components contained in the vein near the surface of the fingertip can be measured.

FIG. 13A shows a spectrum obtained by Fourier-transforming the interferogram obtained by irradiating the region surrounded by the square in FIG. 12A with P-polarized light in the wavelength band of 600 nm to 900 nm under the optical condition Pc. FIG. 13B shows a spectrum obtained when the blood of a rat is irradiated with light having a wavelength band of 600 nm to 900 nm under the same conditions as in FIG. 13A. From the comparison with FIG. 13B, it was inferred that the spectrum of FIG. 13A represents the spectral characteristics of the biological component contained in the vein inside the fingertip.

FIG. 14B shows a spectrum obtained by Fourier-transforming the interferogram obtained by irradiating the region shown in FIG. 14A with P-polarized light in the wavelength band of 900 nm to 1700 nm under the optical condition Pc. FIG. 14C shows a generally known absorption spectrum of water (see Non-Patent Document 1). From the comparison between FIG. 14B and FIG. 14C, it can be seen that the absorption spectrum of water existing near the surface of the fingertip can be obtained satisfactorily.

FIGS. 15A to 15D show experimental results for verifying the difference in the observed image and the spectrum depending on the presence or absence of the window portion 11. FIG. 15A shows the wavelength of 600 nm to 900 nm at the fingertip using the spectroscopic measurement apparatus (without window part) according to the first embodiment, and FIG. 15B shows the spectroscopic measurement apparatus (with window part) according to the second embodiment. The observation image obtained by irradiating P-polarized light of a zone | band with the optical conditions Pc is shown. FIG. 15C shows a spectrum obtained by Fourier transform of the interferogram obtained at that time. FIG. 15D shows a spectrum obtained by Fourier transforming the interferogram obtained when the blood of the rat is irradiated with light in the wavelength band of 600 nm to 900 nm under the same conditions as in FIG. 15C.

15A and 15B show that the observation image of the fingertip is brighter when the window is provided. This was presumed to be because the surface of the fingertip was flattened by the window and the surface diffuse reflection light was reduced. Further, FIG. 15C shows that an absorption spectrum of veins existing in the vicinity of the surface of the fingertip can be satisfactorily obtained in any state with a window portion and without a window portion.

Note that the present invention is not limited to the above-described embodiment. For example, in the first to third embodiments, the phase shifter is configured by the fixed mirror unit and the movable mirror unit. However, as shown in FIG. 16, the phase shifter 60 may be configured by the reference mirror unit 601 and the inclined mirror unit 602. good. The reflecting surface of the reference mirror unit 601 is inclined by 45 ° with respect to the optical axis of the objective lens 104, and the reflecting surface of the inclined mirror unit 602 is slightly inclined with respect to the reflecting surface of the reference mirror unit 61. As a result, a continuous optical path length difference is given between the measurement light reflected by the reference mirror unit 601 and the measurement light reflected by the inclined mirror unit 602, and then enters the cylindrical lens 30. Therefore, the same effect as the fourth and fifth embodiments can be obtained.

DESCRIPTION OF SYMBOLS 10 ... Spectroscopic measurement part 101 ... Light source 102 ... 1st polarizing plate 103 ... Objective lens 104 ... 2nd polarizing plate 105 ... Phase shifter 106 ... Imaging lens 107 ... Detection part 11 ... Window part 20 ... Control apparatus 201 ... Processing part 202 ... Calculation unit 203 ... Output device 30 ... Cylindrical lens 40 ... Phase shifter 401 ... First transmission unit 402 ... Second transmission unit 51 ... Fixed mirror unit 52 ... Movable mirror unit 53 ... Drive mechanism 60 ... Phase shifter 601 ... Reference mirror unit 602 ... Tilt mirror section

Claims (10)

1. a) a movable reflector that is arranged alongside the fixed reflector and is movable along a direction perpendicular to the reflecting surface;
   b) a light irradiating means for causing P-polarized light, which is linearly polarized light whose vibration direction of the electric field is parallel to the incident surface, to be incident on the surface to be measured at a Brewster angle;
   c) an introduction optical system that introduces measurement light emitted from the measurement object on which the P-polarized light is incident into the fixed reflection portion and the movable reflection portion;
   d) an interference optical system that forms interference light of measurement light introduced into the fixed reflection part and reflected by the fixed reflection part and measurement light introduced into the movable reflection part and reflected by the movable reflection part;
   e) an interference light detector for detecting the intensity of the interference light;
   f) a processing unit for obtaining an interferogram of the measurement light based on a change in intensity of the interference light detected by the interference light detection unit by moving the movable reflection unit;
   g) A spectroscopic measurement apparatus comprising: an arithmetic unit that obtains a spectrum of the measurement light by performing Fourier transform on the interferogram.
2. a) a light irradiating means for causing P-polarized light, which is linearly polarized light whose vibration direction of the electric field is parallel to the incident surface, to be incident on the surface to be measured at a Brewster angle;
   b) a splitting optical system that splits the measurement light emitted from the measurement object on which the P-polarized light is incident into a first measurement light and a second measurement light;
   c) an interference optical system that forms interference light between the first measurement light and the second measurement light;
   d) optical path length difference providing means for providing a continuous optical path length difference between the first measurement light and the second measurement light;
   e) an interference light detection unit having a plurality of ancestors for detecting the intensity distribution of the interference light corresponding to the continuous optical path length difference;
   f) a processing unit for obtaining an interferogram of the measurement light from an intensity distribution of the interference light detected by the interference light detection unit;
   g) A spectroscopic measurement apparatus comprising: an arithmetic unit that obtains a spectrum of the measurement light by performing Fourier transform on the interferogram.
3. The spectrometer according to claim 1, further comprising:
   Of the measurement light disposed between the surface of the measurement object and the introduction optical system or between the introduction optical system and the fixed reflection unit and the movable reflection unit, the vibration direction of the electric field is the P-polarized light. A spectroscopic measurement apparatus comprising: a polarizing plate that allows S-polarized light, which is linearly polarized light perpendicular to the vibration direction of an electric field, to pass but does not allow the P-polarized light to pass.
4. The spectrometer according to claim 2, further comprising:
   Of the measurement light, disposed between the surface of the measurement object and the splitting optical system, or between the splitting optical system and the optical path length difference providing unit, the vibration direction of the electric field is vibration of the P-polarized electric field. A spectroscopic measurement apparatus comprising: a polarizing plate that passes S-polarized light that is linearly polarized light perpendicular to a direction but does not pass the P-polarized light.
5. The spectrometer according to any one of claims 1 to 4, further comprising:
   A spectroscopic measurement apparatus comprising: a plate-like light transmissive member having a placement surface on which the measurement target is placed and a light irradiation surface that is a surface opposite to the placement surface.
6. a) P-polarized light, which is linearly polarized light whose vibration direction of the electric field is parallel to the incident surface, is incident on the surface to be measured at a Brewster angle.
   b) Movable reflection movable in the direction perpendicular to the reflection surface, which is arranged alongside the fixed reflection portion and the fixed reflection portion by the introducing optical system with the measurement light emitted from the measurement object on which the P-polarized light is incident Introduced to the department,
   c) forming interference light of measurement light introduced into the fixed reflection part and reflected by the fixed reflection part and measurement light introduced into the movable reflection part and reflected by the movable reflection part using an interference optical system;
   d) detecting the intensity of the interference light by an interference light detector;
   e) obtaining an interferogram of the measurement light based on a change in the intensity of the interference light detected by the interference light detection unit by moving the movable reflection unit,
   f) A spectroscopic measurement method characterized by obtaining a spectrum of the measurement light by Fourier transforming the interferogram.
7. a) P-polarized light, which is linearly polarized light whose vibration direction of the electric field is parallel to the incident surface, is incident on the surface to be measured at a Brewster angle.
   b) Dividing the measurement light emitted from the measurement object on which the P-polarized light is incident into a first measurement light and a second measurement light by a splitting optical system;
   c) after giving a continuous optical path length difference between the first measurement light and the second measurement light, forming interference light between the first measurement light and the second measurement light by an interference optical system;
   d) detecting the intensity distribution of the interference light corresponding to the continuous optical path length difference by an interference light detection unit having a plurality of pixels;
   e) obtaining an interferogram of the measurement light from the intensity distribution of the interference light detected by the interference light detection unit,
   f) A spectroscopic measurement method characterized by obtaining a spectrum of the measurement light by Fourier transforming the interferogram.
8. The spectroscopic measurement method according to claim 6,
   The polarization direction of the electric field of the measurement light is changed between the surface of the measurement object and the introduction optical system, or between the introduction optical system and the fixed reflection unit and the movable reflection unit. A spectroscopic measurement method characterized by passing S-polarized light that is linearly polarized light perpendicular to the vibration direction of the electric field of P-polarized light and not allowing the P-polarized light to pass therethrough.
9. The spectroscopic measurement method according to claim 7,
   The electric field of the measurement light is orthogonal to the electric field of the P-polarized light by the polarizing plate disposed between the surface of the measurement object and the divided optical system, or between the divided optical system and the optical path length difference providing unit. A spectroscopic measurement method characterized by allowing S-polarized light that is linearly polarized light to pass through and not allowing the P-polarized light to pass.
10. The spectroscopic measurement method according to any one of claims 6 to 9,
    A plate-shaped light-transmitting member having a mounting surface on which the measurement object is mounted and a light irradiation surface that is a surface opposite to the mounting surface;
    A spectroscopic measurement method comprising irradiating a light irradiation surface of the light transmissive member with the P-polarized light so that the P-polarized light is incident on the surface of the measurement object at a Brewster angle.

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