JPH0721452B2 - Spectral absorption measuring device for opaque samples - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for measuring spectroscopic absorption of a scatterer such as a suspension or a powder and an apparatus therefor, and particularly, to a beam from a specific direction with respect to a sample. The present invention relates to a device for measuring a spectral absorption characteristic of light scattered in a specific direction when applied.

[Conventional technology]

Since the discovery of X-rays, a technique for observing the inside of a living body (human body) without external damage (pessimistic blood or non-invasive measurement method) has been strongly demanded and developed in the field of biology, particularly in medicine. . This technology uses gamma rays and X-rays having the shortest wavelengths when viewed as electromagnetic waves, and radio waves having the longest wavelength. The former is X-ray CT and the latter is NMR-CT (Magneti
c Resonance Imaging, MRI) has been put to practical use.

On the other hand, spectroscopy in the ultraviolet-visible-near-infrared-infrared region, which is widely used in the fields of physics and chemistry, is called "whole body".
There are relatively few attempts to apply it to (vivo). This is because many problems regarding the most basic "quantitativeness" remain unsolved in biometrics using light, particularly those that utilize absorption and luminescence processes. At present, the measurement of the reflection spectrum using a solid-state element and the measurement with a high-sensitivity TV camera are attempted, but this is the reason why the reproducibility and the absolute value obtained are less reliable.

When a scatterer such as a biological tissue is irradiated with light, it can extract straight-ahead light to some extent if it is received at 180 ° facing each other, but at present, its spatial resolution is not so good.

The difference in spatial separation between X-rays and light cannot be filled up so far. However, the use of light, especially near infrared light, should allow imaging of tissue oxygen concentration from hemoglobin in blood. These are other NMR-CT and X-ray C
It will give different information than T.

With 3-5 cm thick tissue, we can detect the transmitted light. This means that "light-radiography" can be used for diagnosis. Women's breasts have relatively uniform tissue and light is easily transmitted, and the transmitted light can be easily detected (thickness: about 3 cm) due to its shape, and Diaphanography (Lights) has long been used to diagnose breast cancer.
canning) has been used.

Under these circumstances, the present inventor has filed a patent application No. 1-62898.
In Japanese Patent Application No. 1-250034 and Japanese Patent Application No. 2-77690, plane waves mixed in scattered light are separated and taken out.
For observation, it is sufficient to observe only the 0th-order spectrum of the plane wave Franforfer diffraction image (Airy disc) (the portion in the first dark ring of the Airy disc corresponds). It was shown that almost all the scattered components can be removed by doing so. Then, as one of the high-directivity optical systems for realizing such observation, an optical system including two pinholes P ₁ and P _{2 which} are separated from each other as shown in FIG. 15 was proposed. This optical system detects the 0th order light by the detector 23 through the pinhole P ₂ . Further, as shown in FIG. 16, a highly directional optical system which is composed of a linear elongated hollow glass fiber 35, and the inner wall surface of which is coated with a light absorbing material 35 such as carbon. Proposed. Further, as shown in FIG. 17 to FIG. 24, high directivity composed of an objective lens Ob and a pinhole P for passing only the 0th-order diffraction image of the Franforfer diffraction by the objective lens Ob arranged on the focal plane thereof. Directional optical system (Fig. 17), a highly directional optical system (Fig. 18) consisting of a gradient index lens GL and a similar pinhole P arranged at the focal plane at one end of the same, instead of the pinhole P. Optical fiber SM
High directional optical system (Figs. 19 and 20) in which the objective lens Ob similar to the objective lens Ob1 on the incident side is provided on the exit side of the pinhole P or the optical fiber SM of these high directional optical systems.
Highly directional optical system (Figs. 21 and 23) in which b2 is arranged, and a refractive index distribution lens G similar to the incident side refractive index distribution lens GL1.
We have proposed a highly directional optical system (Figs. 22 and 24) with L2.

By the way, conventionally, there is known an absorption measurement method for an opaque sample such as an opal glass method in which a straight traveling component and a transmission scattering component of a sample accompanied by scattering are evenly scattered by an opal glass to measure the transmission integrated extinction of the sample ( For example, see Kazuo Shibata, "Introduction to Photobiology Seeds Spectroscopy," pages 62-82 (sho 51.6.20., Published by Kyoritsu Shuppan Co., Ltd.). Heterogeneous systems, such as suspensions of particles such as cells, granules, solid powders, generally absorb and scatter light. Therefore, it is difficult to obtain only the absorption wavelength characteristic. Therefore, an amount that can be approximated to the absorption wavelength characteristic is obtained and approximated. That is, the transmission integrated extinction is obtained and replaced with absorption. What is this transmission integral extinction?
It is the logarithm of the reciprocal of the ratio of the light flux attenuated by both absorption and scattering to the incident light flux, and generally does not match the absorption characteristics. Therefore, if the parallel transmitted light beam and the scattered transmitted light beam are detected by the detector with the same catch rate in order to make the absorption characteristics as close to each other as possible, the influence of scattering is reduced in the ratio thereof. The opal glass method has been put into practical use as this method. In addition, as another method, a transmissive integrating sphere method, a photoelectric surface contact method, or the like is put into practical use as a method of reducing the influence of scattering by supplementing the total transmitted light flux including the parallel transmitted light flux and the scattered transmitted light flux. . As a method intermediate between the detection of the same capture rate and the detection of all captures, the method using close contact scattering is also used.

[Problems to be Solved by the Invention]

However, the above-mentioned conventional opal glass method has a drawback that the light scattering ability changes depending on the wavelength. The transmission integrating sphere is the best white reflective material in the integrating sphere. Even in the case of MgO powder, the reflectance greatly decreases at short wavelengths, especially in the ultraviolet region, and reliable data cannot be obtained. There is. It is difficult for the photocathode contact method to use two detectors to obtain the same wavelength sensitivity characteristic. With one detector, it is difficult to place the sample and control in a confined space. Although the combined method of close contact scattering is superior to a third party, it has a problem that the size of the sample and the distance and size of the detector must be properly selected.

Moreover, a drawback common to the four conventional methods is that even if the transmission integrated extinction is measured, it cannot be approximated to the absorption wavelength of the suspended particles. That is, if the reflected light flux becomes large, it cannot be approximated. Further, when the scattering space pattern by the sample differs depending on the wavelength, the wavelength change of the scattered transmitted light flux and the wavelength change of the scattered reflected light flux are not the same and cannot be approximated.

The present invention has been made in view of such a situation,
An object thereof is to provide an apparatus for measuring the spectral absorption characteristics of a transmitted or reflected component in a specific direction of a scattering object such as a suspension or a biological tissue.

[Means for Solving the Problems]

A first embodiment of the spectral absorption measuring device for an opaque sample of the present invention which achieves the above object is a frequency for dividing the light from a wavelength-changeable monochromatic light source into two and shifting the frequency of incident light in one optical path. A beam combining method in which a shifter is provided and a scattering sample is arranged in the other optical path, and light with high directivity emitted from the frequency shifter and light emitted in a specific direction from the scattering sample are combined and emitted in the same direction Means for converting the light combined by the beam combining means into an electric signal and detecting the intensity of only the AC component equal to the shift frequency.

A second spectroscopic absorption measuring device for an opaque sample divides light from a wavelength-changeable monochromatic light source into two parts, and provides an optical path length changing means for changing the optical path length at a predetermined speed in one optical path and the other optical path. A scattering sample is arranged inside, and a beam synthesizing means for synthesizing the light with high directivity emitted from the optical path length changing means and the light emitted from the scattering sample in a specific direction to emit in the same direction,
It is characterized in that a detecting means is provided for converting the light combined by the beam combining means into an electric signal and detecting the intensity of only the AC component of the frequency according to the optical path length changing speed.

In these spectroscopic absorption measurement devices, the light from the scattering sample is blocked, and the luminous intensity of the highly directional light emitted from the frequency shift means or the optical path length changing means is detected as the reference light intensity, and the beam combining is performed. The light synthesized by the means is converted into an electric signal, and an AC component equal to the shift frequency or an AC component having a frequency corresponding to the optical path length changing speed is used as the signal intensity from the sample, and the transmission integral attenuation is calculated using these intensities. It is desirable to ask.

[Action]

According to the spectral absorption measuring device for an opaque sample of the present invention, the scattering sample is irradiated with light of a variable wavelength with high directivity from a specific direction, and an intensity heterodyne light receiving system of only light scattered in a specific direction, Since the detection is performed using the Michelson light receiving system, it is possible to measure the spectral absorption characteristics of the scattering sample with high accuracy without picking up scattered light in an extra direction and other noise light. Moreover, the measurement of the control is much easier than the conventional method, and the measurement is extremely easy, and the spectral absorption of the transmitted or reflected component in a specific direction of a scattering object such as a suspension or a biological tissue is measured. The device is suitable for.

〔Example〕

Conventionally, a heterodyne light receiving system is known as a means for detecting coherent light with high sensitivity. As shown in FIG. 1 for example, the light receiving system 3 divides the light having a specific frequency ω ₁ emitted from the laser 1 into two by a beam splitter BS, and inserts a sample S into one straight light. The other reflected light passes through the mirrors M1 and M2, and is combined with the above-described straight traveling light by the half mirror HM, and the combined light is photoelectrically converted by the detector 2. When a frequency shifter AO such as an ultrasonic optical modulator that shifts the frequency to ω ₁ is inserted in the reflected light, a beat signal with an observable frequency, which is the difference between the frequencies ω ₁ and ω ₂ , appears from the detector 2. , The strength of the AC component is proportional to the transmittance of the sample S. Therefore, a weak signal transmitted through the sample S can be detected. By the way, such a heterodyne light receiving system 3 can detect not only the weak signal as described above, but also a direction different from the direction of the reflected light (light of frequency ω ₂ ; hereinafter also referred to as reference light) due to the sample S. Since the component scattered to the detector 2 does not overlap with the reference light on the detection surface of the detector 2, it does not generate a beat signal and is simply detected as a DC component. Therefore, such a scattered component is easily removed, It has a property as a highly directional detection system capable of detecting only a light component traveling in the same direction as the reference light. Therefore, in the present invention, the property of the heterodyne light receiving system 3 as shown in FIG. 1 as the high directivity detection system is utilized.

The Michelson light receiving system is well known as a means for detecting a slight change in refractive index. This light receiving system 4
As shown in FIG. 2, the light emitted from the laser 1 is divided into two by a beam splitter BS, the sample S is inserted into the reflected light that has passed through one of the mirrors M1 and M2, and the transmitted light is used as a straight-forward light described later. Combined by half mirror HM. Beam splitter
The straight-ahead light (hereinafter also referred to as reference light) that has passed through the BS passes through the half mirror HM and strikes the moving mirror M that is moved as shown by the double-headed arrow in the figure, and is reflected in the opposite direction, and the half mirror HM Is combined with the light transmitted through the sample, and the combined light is photoelectrically converted by the detector 2. From the detector 2, a signal on which an interference signal having a frequency corresponding to the speed of the movable mirror M is superimposed is obtained. The intensity of the AC component is proportional to the transmittance of the sample S, and depends on the phase and the thickness or the refractive index of the sample S. This Michelson light receiving system 4 is also the heterodyne light receiving system 3 described above.
Similar to the above, it can not only detect minute changes in the refractive index,
The component scattered by the sample S in a direction different from that of the reference light does not overlap the reference light on the detection surface of the detector 2 and thus does not generate an interference signal and is simply detected as a DC component. Such a scattered component can be easily removed, and since it has a property as a highly directional detection system capable of detecting only a light component traveling in the same direction as the reference light, it is shown in FIG. 2 in the present invention. The property of the Michelson light receiving system 4 as the highly directional detection system is utilized.

By the way, it can be said that both the heterodyne light receiving system 3 and the Michelson light receiving system 4 detect the intensity of the light transmitted through the sample S or the light scattered by the sample S based on the same principle. This point will be briefly described. The reference light to be combined is V ₂ , and the light transmitted through the sample S or the light scattered by the sample S (hereinafter, also referred to as sample light) is V _1, and they are respectively expressed as follows.

V ₁ = A ₁ exp [−i (ω ₁ t + φ ₁ )], V ₂ = A ₂ exp [−i (ω ₂ t + φ ₂ )] These two light waves V ₁ and V ₂ are superposed and observed (detected). )
Then, the detection signal S becomes as follows.

S = | V ₁ + V ₂ | ² = V ₁ · V ₁ ^* + V ₂ · V ₂ ^* + V ₁ · V ₂ ^* + V ₁ ^* · V ₂ By the way, V ₁ · V ₁ ^* = A ₁ ² , V ₂ · V ₂ ^* = A ₂ ² and V ₁ · V ₂ ^* = A ₁ A ₂ exp [i (ω ₁ −ω ₂ ) t−i (φ ₁ −
φ ₂ )], V ₁ ^* · V ₂ = A ₁ A ₂ exp [+ i (ω ₁ −ω ₂ ) t + i (φ ₁ −
φ ₂ )] V ₁ · V ₂ ^* + V ₁ ^* · V ₂ = 2A ₁ A ₂ cos [ω ₁ −ω ₂ ) t + (φ ₁ −
φ ₂ )], S = A ₁ ² + A ₂ ² + 2A ₁ A ₂ cos [(ω ₁ −ω ₂ ) t + (φ ₁ −
φ ₂ )].

By the way, in the heterodyne light receiving system 3, since ω ₂ = ω ₁ −Δω and φ ₁ = φ ₂ can be written, S = A ₁ ² + A ₂ ² + 2A ₁ A ₂ cos Δωt, and the AC component of the detected signal The amplitude A ₁ of the sample light V ₁ can be known from the magnitude of.

Similarly, according to the Michelson light receiving system 4, ω ₁ = ω ₂ ,
Since it can be written that φ ₂ = φ ₁ + kt, the detection signal S is S = A ₁ ² + A ₂ ² + 2A ₁ A ₂ coskt, and the same signal as in the case of the hetrodyne light receiving system 3 is obtained. That is, similarly to the heterodyne light receiving system 3 and the Michelson light receiving system 4, the amplitude A ₁ of the sample light V ₁ can be known from the magnitude of the AC component of the detection signal.

In the present invention, the above-mentioned heterodyne light receiving system 3 and Michelson light receiving system 4 are used as the high directional detection system, but in addition to these, the high directional optical system illustrated in FIGS. 15 to 24 is used. Further, in the present invention, as the high directivity detection system, a multi-beam high directivity optical system configured by bundling a plurality of the same high directivity optical systems can also be used. For details of these, see Japanese Patent Application No. 2-77690 mentioned above. As a representative of these high directivity optical systems, an objective lens Ob1 on the incident side, a pinhole P that is arranged on the focal plane of the objective lens Ob1 and passes only the 0th-order diffraction image of the Fraunforfer diffraction by the objective lens Ob1, FIG. 3 shows a highly directional optical system 5 including a similar objective lens Ob2 arranged so that the front focal point coincides with the pinhole P. (The highly directional optical system 5 in the figure is the same as the optical system shown in FIG. 21.). However, in the following description, the high directivity optical system 5 is not limited to that shown in FIG.

Now, first, the opaque sample that is the target of the spectral absorption measurement in the present invention is not a sample that completely blocks incident light and does not allow it to pass forward, but it does not depend on the sample such as a biological sample. There is almost no light that is directly transmitted without being scattered, but a sample in which light scattered forward due to multiple scattering due to scattering fine particles in the sample emerges from the sample. Of course, a sample in which light that directly transmits exists can also be a measurement target as described later. The second measurement target of the present invention is a sample, such as a powder, which almost completely blocks incident light and reflects and scatters only backward. The former sample is called a transmission sample, and the latter sample is called a reflection sample.

4 to 9 show an outline of an apparatus for measuring the spectral absorption characteristic of the transmission sample 20, and FIGS. 10 and 11 show an apparatus for measuring the spectral absorption characteristic of the reflective sample 21. This is an overview.

The opaque sample spectral absorption measurement apparatus shown in FIG. 4 uses the heterodyne light receiving system 3 shown in FIG. 1 as a highly directional detection system to extract only the light scattered by the transmitted sample 20 in a specific forward direction. It is intended to measure the spectral absorption characteristics of the sample 20. For such measurement, a variable wavelength laser 10 capable of continuously sweeping and emitting monochromatic light in a wide spectrum range is used as a monochromatic light source.
In order to convert the light flux emitted from the laser 10 into a parallel light flux having an appropriate diameter, a beam converter 11 is arranged in front of the laser 10. The light beam emitted from the beam converter 11 is divided into two by the beam splitter BS, and the straight-ahead light strikes the transparent sample 20, undergoes multiple scattering therein, and is normally isotropically scattered forward. The scattered light is selectively absorbed by the fine particles in the transmitted sample 20 according to the incident wavelength.
20 It has a unique wavelength dependence. Of the forward scattered light, the light in a specific direction, in the case of FIG. 4, the same direction as the incident light is combined with the reference light by the half mirror HM. The reference light reflected by the beam splitter BS has its frequency slightly changed by a frequency shifter AO such as an ultrasonic optical modulator before the above combining, and when the light is combined with the sample light and photoelectrically converted, the reference light and the sample A signal including an AC signal having a frequency corresponding to the frequency difference of light is output from the detector 2. Since the magnitude of the AC component of the signal obtained from the detector 2 is proportional to the amplitude of the sample light, the AC component of the output of the detector 2 is separated, and the relative transmissivity or the corresponding transmittance depending on the incident wavelength is determined from the magnitude. Absorption characteristics are obtained. The direction of the scattered light combined with the reference light does not necessarily have to be the same as the direction of the incident light on the sample 20. In the absorption spectrum measured by sweeping the wavelength of the laser 10 as described above, the light intensity generally changes when the wavelength of the laser 10 is swept. Therefore, in the case of using the high directivity detection system, a part of the irradiation light flux is extracted, and for example, in FIG. 3, a half mirror is inserted between the laser 1 and the sample S to detect the output laser light intensity. When the heterodyne detection system is used, a light blocking element is inserted behind the sample 20 in FIG. 4, and the detector 2 monitors the output intensity of the laser. Alternatively, the half mirror HM shown in FIG.
A detector for monitoring the light intensity may be installed in the rear of the position for detection. (Not shown).

By the way, FIG. 5 shows a modification of the one using the heterodyne light receiving system 3 of FIG. 4 to show a reflection type spectroscopic device in a specific direction in which a specific sample is present in a scattering medium. In this case, do not place the sample immediately after the beam splitter BS,
The direction of the half mirror HM is changed, and the light transmitted through the beam splitter BS is scattered to a position where it is transmitted through the half mirror HM.
20 schematically shows a specific sample S that reflects the forward scattered light in the opposite direction behind the scattering medium 20,
The reflected light is again transmitted through the scattering medium 20 from the opposite direction, and the transmitted scattered light is combined with the reference light by the half mirror HM. This is an effective configuration when the thickness of the scattering medium 20 is small and the ratio of the direct transmission component is high.

Next, the device shown in FIG. 6 measures the spectral absorption characteristics of the transmission sample 20 by applying the Michelson light receiving system 4 shown in FIG. The beam converter 11 converts the light into a parallel light beam having an appropriate diameter, and the beam splitter BS bisects the light beam. The transparent sample 20 is inserted into the reflected light that has passed through one of the mirrors M1 and M2. And the half mirror HM. The reference light that has passed through the beam splitter BS hits the movable mirror M that is transmitted through the half mirror HM and is moved as shown by the double-headed arrow in the figure, is reflected in the opposite direction, and is combined with the sample light by the half mirror HM. The combined light is photoelectrically converted by the detector 2. From the detector 2, a signal on which an interference signal having a frequency corresponding to the speed of the movable mirror M is superimposed is obtained. Since the intensity of the AC component is proportional to the intensity of the scattered light of the transmission sample 20, the wavelength of the variable wavelength laser 10 can be swept to obtain the spectral absorption characteristic from the intensity of the AC component.

FIG. 7 shows the Michelson light receiving system 4 of the reflection type. The reflection spectrum of a specific sample is schematically shown in the scattering medium. In this case, the sample is arranged at a position where the beam splitter BS is reflected, and the reflection spectroscopic sample S that reflects the forward scattered light in the opposite direction is schematically shown behind the scattering medium 20. The scattered light is again transmitted through the scattering medium 20 in the opposite direction, and the transmitted scattered light is combined with the reference light reflected from the movable mirror M by the beam splitter BS. Also in this case, as in the case of FIG. 5, the arrangement is effective when the thickness of the scattering medium 20 is thin and the ratio of the direct transmission component is high.

Now, FIGS. 8 and 9 show the use of the highly directional optical system 5 typified by FIG. 3 to measure the spectral absorption characteristics of the scattering component in a specific direction of the transmission type scattering object sample 20. Only the scattered component in a specific direction is extracted, and FIG. 8 is a transmission type and FIG. 9 is a reflection type. The light from the variable wavelength laser 10 which is emitted from the beam converter 11 after being converted into a parallel light beam having an appropriate diameter is directly transmitted in the case of FIG. 8 and is transmitted through the half mirror HM in the case of FIG. When it hits the scattering medium 20 schematically shown, it is subjected to multiple scattering and absorption, is transmitted forward, and is reflected by the reflection spectral characteristic from the sample S. In the case of FIG. 8, only the component scattered in a specific direction is extracted by the highly directional optical system 5 and its intensity is detected by the detector 2. Therefore, in the case of FIG. 8, the oscillation wavelength of the tunable laser 10 is swept, a half mirror is arranged between the beam converter 11 and the sample 20 (not shown), and the reflected light from the half mirror is detected. Thus, the output of the laser is monitored to obtain the transmission integrated extinction degree. In the case of FIG. 9, the laser light reflected by the half mirror HM is detected (the detector is not shown), the output of the laser is monitored, and the transmission integrated extinction degree is obtained. Note that, in the case of FIG. 9, as in FIGS. 5 and 7, a reflection spectral sample S that reflects forward scattered light in the opposite direction is schematically shown behind the schematically written scattering medium 20. It was The scattered light is again transmitted through the scattering medium 20 from the opposite direction, the transmitted scattered light is reflected by the half mirror HM in a direction different from the direction of the incident light, and only the component scattered in a specific direction is highly directional optical system 5 To extract. Others are the same as in the case of FIGS. 4 to 7.

The above is the device configuration when the sample for measuring the spectral absorption characteristics is transmissive and when it is reflective.If the sample is reflective, or if the surface reflected light is strong, these configurations can be easily used for that purpose. Can be changed. However, in a reflection sample, when the intensity of the specular reflection component of incident light is extremely high, the specular reflection component usually contains almost no information about the absorption characteristics near the surface of the reflection sample. It must be removed. FIG. 10 and FIG. 11 show an example of the device configured as described above. The apparatus shown in FIG. 10 measures the spectral absorption characteristics by extracting the components scattered in a specific direction from the vicinity of the surface of the reflective sample 21 using the highly directional optical system 5, and a mirror is provided on the surface of the reflective sample 21. The monochromatic light from the tunable wavelength laser 10 incident via M4 is set so as to form an angle to the normal to the sample surface, and its specular reflection component is beam trapped via the mirror M5.
I try to remove it by BT. Further, the apparatus of FIG. 11 uses the heterodyne light receiving system 3 as a highly directional detection system to extract a component scattered in a specific direction from the vicinity of the surface of the reflective sample 21, and measures the spectral absorption characteristics. With the configuration similar to that of FIG. 11, the specular reflection component reflected on the surface of the sample 21 by the beam trap BT is removed.

Next, some examples of the apparatus for specifically measuring the spectral absorption characteristics of the sample in the macro size region will be briefly described. FIG. 12 shows a schematic configuration of an apparatus capable of measuring the transmission spectral absorption characteristics and the reflection spectral absorption characteristics of the sample 20 arranged on the sample table 13. Monochromatic light from the variable wavelength laser 10 is switched by the switching mirror MS. The transmission path of the solid line and the reflection path of the dotted line are switched. When the solid optical path is selected, the light that has passed through the mirror M7 and the Cassegrain reflection optical system K3 that is placed confocal
The scattered light in a specific direction, which is converted into a parallel light flux having a predetermined diameter by the beam converter 11 made of K4, is incident on the sample 20, and is transmitted through the sample 20, is a Cassegrain reflection optical system K1 and K2 arranged confocal. And the mirrors M10 and M11 extracted by the highly directional optical system 5 consisting of the pinhole P arranged at the focal point
After that, the wavelength is measured by the detector 2 and the wavelength of the variable wavelength laser 10 is swept to obtain the spectral absorption characteristic of the transmitted component of the sample 20. When the switching mirror MS is switched to the reflection optical path indicated by the dotted line, the monochromatic light from the tunable laser 10 is reflected downward by the half mirror HM via the mirror M9 and the beam converter.
The beam diameter is reduced by the highly directional optical system 5 having the function of 11, and is incident on the sample 20. Only the light completely scattered back from the sample 20 is extracted by the highly directional optical system 5, measured by the detector 2 via the half mirror HM, the mirrors M10 and M11, and the wavelength of the variable wavelength laser 10 is swept. Due to
The spectral absorption characteristics of the reflection component of the sample 20 can be obtained. The sample
When extracting backscattering components other than the 20 specular reflection components,
The sample 20 may be tilted so that light is incident.

The apparatus shown in FIGS. 13 and 14 is obtained by only vertically modifying the apparatus using the heterodyne light receiving system 3 shown in FIG. 4 and the apparatus using the Michelson light receiving system 4 shown in FIG. No special explanation may be needed. In FIG. 14, the drive diameter 14 is for moving the movable mirror M in the optical axis direction.

In the above description, the variable wavelength laser 10 is based on the assumption that it continuously oscillates, but a variable wavelength laser that performs pulse operation may be used. In particular, in the case of a sample whose characteristics change rapidly when continuously irradiated with laser light, it is preferable to use a variable wavelength laser that performs pulse operation. Further, the detector 2 is not particularly described, but any known means can be used. Also, as a processing method of the detection signal, for example, intensity modulation of incident light by a chopper or the like and phase-locked detection of the detection signal can be considered. In this case, since the time constant of infrared light detection is long, it is necessary to reduce the synchronous modulation frequency. Also, photon counting method (visible light), charge accumulation method (infrared light)
A sync signal integration detection method, a heterodyne beat signal detection method, or the like may be used. Further, as the frequency shifter, not only the one using an ultrasonic light diffraction such as an ultrasonic modulator but also the combination of the wave plate and the rotating grating, and the electro-optic effect of the crystal can be used. Further, the reflecting mirror may be moved at a constant speed or may be vibrated by a sawtooth wave.

〔The invention's effect〕

In the spectroscopic absorption measuring apparatus for an opaque sample of the present invention, the scattering sample is irradiated with light having a variable wavelength with high directivity from a specific direction, and the intensity of only the light scattered in the specific direction is measured by the heterodyne light receiving system, Michael. Since the detection is performed using the Son light receiving system, the spectral absorption characteristics of the scattering sample can be measured with high accuracy without picking up scattered light in an extra direction and other noise light. Moreover, the measurement of the control is much easier than the conventional method, and the measurement is extremely easy.Spectral absorption of the transmitted or reflected component in a specific direction is possible even for scattering objects such as suspensions and biological tissues with large scattering. It is a device suitable for measuring.

[Brief description of drawings]

FIG. 1 is a diagram for explaining the configuration and operation of one heterodyne light receiving system of a high directional detection system used in the spectral absorption measuring apparatus for opaque samples of the present invention, and FIG. 2 is another high directional detection system. FIG. 4 is a diagram for explaining the configuration and operation of the Michelson light receiving system, and FIG. 3 is a diagram for showing the configuration of a typical high directional optical system which is another high directional detection system, and FIG. ,
FIG. 5 is a diagram showing a configuration of an embodiment of a spectral absorption measuring apparatus using a heterodyne light receiving system of the present invention applied to a transmission sample,
6 and 7 are diagrams showing the configuration of an embodiment of a spectral absorption measuring apparatus using the Michelson light receiving system of the present invention applied to a transmission sample, and FIGS. 8 and 9 are books applied to a transmission sample. Diagram showing the configuration of an embodiment of a spectral absorption measuring apparatus using a highly directional optical system of the invention, FIG. 10, FIG. 11 shows the configuration of an embodiment of the spectral absorption measuring apparatus of the present invention applied to a reflective sample FIGS. 12 to 14 are views for showing some specific examples of the apparatus for measuring the spectral absorption characteristics of the sample in the macro size region, and FIG.
24 to 24 are diagrams showing the configuration of the previously proposed highly directional optical system. 1 ... Laser, 2 ... Detector, 3 ... Heterodyne light receiving system, 4 ... Michelson light receiving system, 5 ... High directivity optical system, 10 ... Variable wavelength laser, 11 ... Beam converter, 13 …
… Sample stand, 20 …… Scattering medium, 21 …… Reflective sample, S …… Sample, BS …… Beam splitter, HM …… Half mirror,
M1 to M11 …… Mirror, AO …… Frequency shifter, M …… Movable mirror, Ob1, Ob2 …… Objective lens, P …… Pinhole, M3
…… Mirror, BT …… Beam trap, MS …… Switching mirror, K1
~ K4 …… Cassegrain reflective optical system

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-63-274848 (JP, A) JP-A-63-243839 (JP, A)

Claims (3)

[Claims] 1. A frequency shift means for dividing the light from a wavelength-changeable monochromatic light source into two and shifting the frequency of incident light in one optical path, and disposing a scattering sample in the other optical path, A beam synthesizing means for synthesizing the light with high directivity emitted from the frequency shift means and the light emitted in a specific direction from the scattering sample and emitting in the same direction is provided, and the light synthesized by the beam synthesizing means is converted into an electric signal. Then, a spectral absorption measuring device for an opaque sample is provided with a detecting means for detecting the intensity of only the AC component equal to the shift frequency. 2. An optical path length changing means for dividing the light from a wavelength-changeable monochromatic light source into two and changing the optical path length at a predetermined speed in one optical path, and disposing a scattering sample in the other optical path. Then
A beam synthesizing means for synthesizing the light having a high directivity emitted from the optical path length changing means and the light emitted from the scattering sample in a specific direction and emitting in the same direction is provided, and the light synthesized by the beam synthesizing means is converted into an electric signal. A spectroscopic absorption measuring apparatus for an opaque sample, which is provided with a detecting means for converting and detecting the intensity of only an alternating-current component having a frequency corresponding to the optical path length changing speed. 3. The light from the scattering sample is blocked, the luminous flux intensity of the highly directional light emitted from the frequency shift means or the optical path length changing means is detected as the reference light intensity, and is synthesized by the beam synthesizing means. The converted light is converted into an electric signal, and the AC component equal to the shift frequency or the AC component of the frequency according to the optical path length changing speed is used as the signal intensity from the sample, and the transmitted integrated extinction is obtained using these intensities. The spectral absorption measuring device for an opaque sample according to claim 1 or 2.