JPH0427845A - Method and apparatus for measuring spectral absorption of opaque sample - Google Patents

Abstract

PURPOSE:To measure the spectral absorption characteristics of a sample having scattering properties with high accuracy without picking up scattering beam and noise by irradiating the sample having scattering properties with beam of a variable wavelength having high directionality to detect the intensity only of beam scattered in a specific direction by a highly directional detection system. CONSTITUTION:The beam having specific frequency omega1 emitted from a laser 1 is split into two beams by a beam splitter BS and a sample S is inserted in the straight advance beam among two beams while the other reflected beam is synthesized with the straight advance beam by a half mirror HM through mirrors M1, M2 and the synthesized beam is photoelectrically converted by a detector 2. When a frequency shifter AO is inserted in the reflected beam, a beat signal having the frequency corresponding to the difference between frequencies omega1, omega2 appears from the detector 2 and the intensity of the AC component thereof is proportional to the transmissivity of the sample S. Therefore, the weak signal transmitted through the sample S can be detected.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method and apparatus for measuring the spectral absorption of scattering materials such as suspensions and powders, and particularly relates to a method for measuring the spectral absorption of scattering materials such as suspensions and powders, and particularly relates to a method for measuring the spectral absorption of scattering materials such as suspensions and powders, and in particular, a method for measuring the spectral absorption of scattering materials such as suspensions and powders. The present invention relates to a method and apparatus for measuring the spectral absorption characteristics of light scattered in a specific direction when applied.

[Conventional technology]

Since the discovery of X-rays, technology for observing the inside of living organisms (human bodies) from the outside without causing damage (non-invasive or non-invasive measurement methods) has been strongly sought after and developed in the field of biology, especially medicine. Ta. This technology uses gamma rays and X-rays, which have the shortest wavelengths of electromagnetic waves, and radio waves, which have the longest wavelengths. The former is an X-ray CT, the latter is an NMR-CT
(Magnetic Re5onance Ima
ing, MRI).

On the other hand, spectroscopy in the ultraviolet-visible, near-infrared, and infrared regions, which are widely used in the fields of physics and chemistry, can be applied to the entire living body (i.e.
There have been relatively few attempts to apply it to n vivo. This is because many problems regarding the most basic "quantitativeness" remain unsolved in biological measurements using light, especially those that utilize absorption and luminescence processes. At present, attempts are being made to measure reflection spectra using solid-state devices, high-sensitivity TV cameras, etc., but this is the reason why the reproducibility and reliability of the obtained absolute values is low.

When light is irradiated onto a scattering object such as biological tissue, it is possible to extract a certain amount of straight light if the light is received 180 degrees facing the object, but at present the spatial resolution is not very good.

The difference in spatial resolution between X-rays and light cannot currently be bridged. However, using light, particularly near-infrared light, it should be possible to image tissue oxygen levels from hemoglobin in the blood. These are other NMR-CT and
It will give you different information than 11CT.

If the tissue is 3 to 5 microns thick, we can detect the light that passes through it. This means that "optical radiographs" can be used for diagnosis. The tissue of the female breast is relatively uniform, making it easy for light to pass through it, and its shape makes it easy to detect transmitted light (about 2 to 3 inches thick).
It has been used under the name phy (Lightscanning).

Under these circumstances, the present inventor filed Japanese Patent Application No. 1-628.
No. 98, Japanese Patent Application No. 1-250034, Japanese Patent Application No. 2-776
No. 90 etc., in order to separate and extract the plane wave mixed in the scattered light and observe it, the 0th order spectrum (inside the first dark ring of the Airy disk) of the Franhofer diffraction image (Airy disk) of the plane wave is used. It is sufficient to observe only the corresponding parts), and it was shown that by doing this, it is possible to almost eliminate the scattered components.

One of the highly directional optical systems that realizes this type of observation is
As one example, we proposed an optical system consisting of two mutually separated pinholes P, , P, as shown in Fig. 15. In this optical system, the zero-order light is detected by the detector 23 through the pinhole P2. In addition, as shown in FIG. 16, the highly directional optical system is made of a straight, elongated hollow glass fiber 35, and the inner wall surface of the glass fiber 35 is coated with a light absorbing material such as carbon. proposed. Furthermore, as shown in FIGS. 17 to 24, a pinhole P through which only the 0th-order diffraction image of Franhofer diffraction due to the objective lens Ob and the objective lens Ob placed at its focal plane passes through.
(Fig. 17), a highly directional optical system (Fig. 18) consisting of a gradient index lens GL and a similar pinhole P placed in the focal plane at one end of the lens, and a pinhole P (Fig. 18). Optical fiber S with the same effect as that instead of
Highly directional optical system with M (Fig. 19, Fig. 20),
A highly directional optical system in which an objective lens Ob2 similar to the objective lens Obl on the incident side is arranged on the output side of the pinhole P or optical fiber SM of these highly directional optical systems (Figs. 21 and 23); We have proposed a highly directional optical system (FIGS. 22 and 24) in which a gradient index lens GL2 similar to the gradient index lens GLI on the incident side is arranged.

By the way, absorption measurement methods for opaque samples are known, such as the opal glass method, which measures the transmitted integrated attenuation of the sample by uniformly scattering the linear component and the transmitted scattering component of the sample accompanied by scattering with an opal glass ( For example, "Photobiology Seeds: Introduction to Spectrometry" by Kazuo Shibata, pp. 62-82 (1972).
6. 20. .

(Refer to Kyoritsu Shuppan ■Published)). Heterogeneous systems such as particle suspensions such as cells, granules, solid powders, etc. generally absorb and scatter light. Therefore, it is difficult to obtain only the absorption wavelength characteristics. Therefore, an amount that can be approximated to the absorption wavelength characteristic is determined and approximated.

That is, the transmission integral attenuation is calculated and replaced with absorption. The transmission integral attenuation 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 characteristic. Therefore, in order to approximate the absorption characteristics as much as possible, if the parallel transmitted light flux and the scattered transmitted light flux are detected with the same capture rate by the detector, then
Their ratio becomes less affected by scattering. As this method, the opal glass method has been put into practical use. In addition, as another method, the transmission type integrating sphere method and the photocathode contact method are used to reduce the influence of scattering by capturing the total transmitted light beam consisting of the parallel transmitted light beam and the scattered transmitted light beam. . A combined close scattering method is also used as an intermediate method between the same-completion rate detection and the total complement detection.

[Problem to be solved by the invention]

However, the above-mentioned conventional opal glass method has the drawback that the light scattering ability changes depending on the wavelength. ■The transmission integrating sphere has the disadvantage that even if the white reflective material inside the sphere is MgO powder, which is known to be the best, the reflectance decreases significantly at short wavelengths, especially near the ultraviolet region, making it impossible to obtain reliable data. There is. ■In the photocathode contact method, which uses two detectors, it is difficult to obtain the same wavelength sensitivity characteristics. A single detector makes it difficult to install the sample and control in a confined space. ■Although the combined contact scattering method is superior to the former champion, there is a problem in that the size of the sample and the distance and size of the detector must be appropriately selected.

Moreover, a common drawback of the four conventional methods is that even if the transmission integral attenuation is measured, it may not be able to approximate the absorption wavelength of suspended particles. In other words, if the reflected light flux becomes large, approximation cannot be achieved. Further, if the scattering spatial 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 will not be the same, and it will no longer be possible to approximate them.

The present invention was made in view of this situation, and
The purpose is to provide a method and apparatus for measuring the spectral absorption characteristics of transmitted or reflected components in a specific direction of a scattering object such as a suspension or biological tissue.

[Means to solve the problem]

The spectral absorption measurement method of an opaque sample according to the present invention achieves the above object by irradiating a scattering sample with highly directional variable wavelength light from a specific direction to increase the intensity of only the light scattered in a specific direction. This method is characterized by measuring the spectral absorption characteristics of a scattering sample by detecting it using a directional detection system.

In this case, the specific direction in which the intensity is detected by the highly directional detection system may be a direction in which transmitted and scattered light by the sample is detected, or a direction in which reflected and scattered light by the sample is detected.

In addition, the first apparatus for spectroscopic absorption measurement of opaque samples of the present invention, which implements such a method, divides light from a wavelength-changeable monochromatic light source into two, and enters the frequency of the incident light into one optical path. A scattering sample is placed in the other optical path, and the highly directional light emitted from the frequency shift means and the light emitted from the scattering sample in a specific direction are combined and directed in the same direction. A beam combining means for emitting is provided,
The present invention is characterized in that a detection means is provided for converting the light combined by the beam combining means into an electrical signal and detecting the intensity of only the alternating current component equal to the shift frequency.

The second spectroscopic absorption measuring device for an opaque sample divides the light from the wavelength-changeable monochromatic light source into two parts, is provided with an optical path length changing means for changing the optical path length at a predetermined speed in one optical path, and is provided with an optical path length changing means for changing the optical path length at a predetermined speed, and the other optical path is divided into two parts. A scattering sample is placed inside, and a beam combining means is provided for combining highly directional light emitted from the optical path length changing means and light emitted from the scattering sample in a specific direction and emitting the same in the same direction.
The present invention is characterized in that a detection means is provided for converting the light combined by the beam combining means into an electrical signal and detecting the intensity of only the alternating current component of a frequency corresponding to the speed of changing the optical path length.

The third opaque sample spectroscopic absorption measuring device places a scattering sample in the optical path of light emitted from a wavelength-changeable monochromatic light source,
The present invention is characterized in that a highly directional optical system is arranged to extract light emitted from a scattering sample in a specific direction, and a detection means is provided to detect the intensity of the light extracted by the highly directional optical system.

In the case of the third device, two optical path switching means are provided in the optical path of the light emitted from the wavelength-changeable monochromatic light source, and the one optical path and the other optical path are configured to be coaxial and the traveling direction of the light is opposite. , a highly directional optical system is placed in the coaxial optical path, a scattering sample is placed on one side of the highly directional optical system, and the sample is transmitted in a specific direction from the other side of the highly directional optical system. By configuring the device to take out the light reflected or scattered in a specific direction by the sample, it is possible to measure the spectral absorption characteristics of both transmitted scattered light and reflected scattered light by the sample with one device.

In both of these devices, the intensity of light transmitted through the sample or the intensity of light reflected in a specific direction is used as the signal light intensity, and all or part of the irradiated light beam is taken out and used as the reference light intensity to calculate the integrated attenuation of the transmitted light. be able to. When using a highly directional detection system, a part of the irradiated light beam is taken out and used as a reference light intensity, and the transmitted integral attenuation degree is determined using the light intensity detected using the highly directional detection system as a signal intensity. When using a heterodyne light receiving system or a Michelson light receiving system, the light from the scattering sample is blocked, and the luminous flux intensity of the directional light emitted from the frequency shift means or optical path length changing means is detected to obtain a reference light intensity. Then, the combined light is converted into an electric signal by the beam combining means, and an AC component equal to the shift frequency or an AC component with a frequency corresponding to the optical path length change speed is used as the signal intensity from the sample, and these intensities are used to transmit the signal. Calculate the integral attenuation.

[Effect]

According to the method and apparatus for measuring spectral absorption of an opaque sample of the present invention, a scattering sample is irradiated with highly directional variable wavelength light from a specific direction, and the intensity of only the light scattered in the specific direction is received by heterodyne. Since detection is performed using a highly directional detection system such as a Michelson light receiving system, a highly directional optical system, etc., it is possible to detect the spectral absorption of a scattering sample with high precision without picking up scattered light in extra directions or other noise light. Characteristics can be measured.

Moreover, the measurement of the control is much simpler than with conventional methods, and the measurement is extremely easy. The method and apparatus are suitable for

〔Example〕

Conventionally, a heterodyne light receiving system is known as a means for detecting coherent light with high sensitivity. This light receiving system 3, as briefly shown in FIG.
The sample S is inserted into one of the straight beams, and the reflected light of the other passes through mirrors M1 and M2 to form the straight beam and the half mirror H.
The combined light is photoelectrically converted by the detector 2. When a frequency shifter A○ such as an ultrasonic optical modulator that shifts the frequency to ω2 in the reflected light is inserted, a beat signal with an observable frequency difference between frequencies ω1 and ω2 appears from the detector 2, and the beat signal is 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 not only detect the above-mentioned weak signals, but also detect the above-mentioned reflected light (light with frequency ω2; hereinafter also referred to as reference light) by the sample S.

) does not overlap with the reference light on the detection surface of the detector 2, so it does not generate a beat signal and is simply detected as a DC component.
It has the property of being a highly directional detection system that can easily remove such scattered components and detect only light components traveling in the same direction as the reference light. Therefore, in the present invention, the properties of the heterodyne light receiving system 3 as shown in FIG. 1 as the above-mentioned highly directivity detection system are utilized.

Furthermore, a Michelson light receiving system is well known as a means for detecting minute changes in refractive index. This light receiving system 4 is
As shown in Figure 2, the light emitted from the laser 1 is split into two by a beam splitter BS, a sample S is inserted into the reflected light that has passed through one of the mirrors M1 and M2, and the transmitted light is a straight beam that will be described later. and half mirror HM. The straight light that has passed through the beam splitter BS (hereinafter also referred to as reference light).

) passes through the half mirror HM and hits the movable mirror M, which is moved as shown by the double arrow mark, is reflected in the opposite direction and is combined with the light that has passed through the sample by the half mirror HM, resulting in the combined light, The detector 2 performs photoelectric conversion. The detector 2 obtains a signal on which an interference signal having a frequency corresponding to the speed of the movable mirror M is superimposed. The strength of the AC component is proportional to the transmittance of the sample S, and the phase depends on the thickness or refractive index of the sample S. Like the heterodyne light receiving system 3 described above, this Michelson light receiving system 4 is also capable of detecting minute changes in refractive index, etc., and the components scattered by the sample S in a direction different from the reference light are detected by the detector 2. Since it does not overlap with the reference light on the surface, it does not generate an interference signal and is simply detected as a DC component, so such scattered components can be easily removed and the light component traveling in the same direction as the reference light can be detected. In the present invention, the characteristics of the Michelson light receiving system 4 as shown in FIG. 2 as a highly directional detection system are utilized. do.

By the way, it can be said that the heterodyne light receiving system 3 and the Michelson light receiving system 4 detect the intensity of light transmitted through the sample S or light scattered by the sample S based on the same principle. This point will be briefly explained. ■Reference light to be synthesized.

, the light transmitted through the sample S or the light scattered by the sample S (hereinafter also referred to as sample light) is represented by Vl, and each is expressed as follows.

Vl =A+expc-i(a+,t-φ1)1,V
2 = A2 eXI][-1(a+3t-φ2)] When these two light waves V, , V are observed (detected) in a superimposed manner, the detection signal S is as follows.

S = : V 1+ V 2 =V ・Vl" 10V2HV- +V+ HV2 "+V+" ・V2By the way, Vl'Vl" =A+, V2 ・V2"=A
2, and Vl ・V2 ” = A+ A2expnee i(a+
, -ω2) t=1 (φ knee φ2)] , V+ ” ・Va = A+ A2 exp[+
+(ωt-ω2)t+1(φ1-φ2)] ■1 ・V2 ” +v,” ・V2= 2 A
IAzcos[(ω1-ω2)t+(φ1-φ2)1, so S=A+ 20A2 + 2 A+A 2CO5[(ω1-ω2)t”(
φ1−φ2)1.

By the way, in the heterodyne light receiving system 3, ω2=ω
Since it can be written as 1-Δω, φ1=φ2, S =/'+ 2
+A22+ 2 A+ A2cosΔωt, and the amplitude A) of the sample light V1 can be determined from the magnitude of the AC component of the detected signal.

Similarly, according to the Michelson light receiving system 4, ω=ω2, φ
Since it can be written as 2=φ, +kt, the detection signal S is: S = A+ ” + Al ” + 2 A+ A2c
osk t, and the same signal as in the case of the heterodyne light receiving system 3 is obtained. That is, in both the heterodyne light receiving system 3 and the Michelson light receiving system 4, the amplitude A1 of the sample light Vl can be determined from the magnitude of the AC component of the detection signal.

In the present invention, the above-described heterodyne light receiving system 3 and Michelson light receiving system 4 are used as the high directivity detection system, but in addition to these, the high directivity optical systems illustrated in FIGS. 15 to 24 are used. As representative of these highly directional optical systems, there is an objective lens Obl on the incident side, a pinhole P arranged at its focal plane and which allows only the zero-order diffraction image of Franff-Offer diffraction by the objective lens Obl to pass;
A third highly directional optical system 5 consisting of a similar objective lens Ob2 arranged so that its front focus 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 explanation,
The highly directional optical system 5 is not limited to the third rgJ.

First of all, the opaque sample that is the subject of spectral absorption measurement in the present invention is not a sample that completely blocks incident light and does not transmit it forward; for example, it is not a sample that completely blocks incident light and does not transmit it forward. Although there is almost no light that directly passes through the sample without being scattered, the sample is one in which light is subjected to multiple scattering by scattering particles in the sample, and light that is scattered forward comes out of the sample. Of course, samples in which directly transmitted light exists can also be measured as described later. Furthermore, the second measurement object of the present invention is a sample, such as a powder, which substantially completely blocks incident light and reflects and scatters it only backwards. The former sample will be called a transmission sample, and the latter sample will be called a reflection sample.

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

The opaque sample spectroscopic absorption measuring device shown in FIG. 4 uses the heterodyne light receiving system 3 shown in FIG. , the spectral absorption characteristics of the sample 20 are to be measured. For such measurements, a tunable wavelength laser 10 that can continuously sweep and emit monochromatic light in a wide spectral range is used as a monochromatic light source. A beam converter 11 is placed in front of the laser 10 in order to convert the light beam emitted from the laser 10 into a parallel light beam of an appropriate diameter. The light flux emitted from the beam converter 11 is split into two by the beam splitter BS, and the straight light hits the transmission sample 20, undergoes multiple scattering therein, and is generally isotropically scattered forward.

The scattered light is selectively absorbed by fine particles in the transmitted sample 20 depending on the incident wavelength, so the intensity of the scattered light is
It has wavelength dependence peculiar to 0. Among this forward scattered light, light in a specific direction, in the case of FIG. 4, light in the same direction as the incident light is combined with the reference light by the half mirror HM. The frequency of the reference light reflected by the beam splitter BS is slightly changed by a frequency filter AO such as an ultrasonic optical modulator before the above synthesis, and when it is combined with the sample light and photoelectrically converted, it becomes the reference light and The detector 2 outputs a signal including an alternating current signal with a frequency corresponding to the frequency difference between the sample lights.

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 based on its magnitude, the relative transmission characteristics or Absorption properties are obtained. The direction of the scattered light combined with the reference light does not necessarily have to be in the same direction as the light incident on the sample 20. Note that 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, when using a highly directional detection system, a part of the irradiated light beam is taken out 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 using a heterodyne detection system, in Figure 4, sample 20
A light blocking element is inserted behind the laser, and the output intensity of the laser is monitored by a detector 2. Alternatively, a light intensity monitoring detector may be installed behind the half mirror HM in FIG. 4 for detection (not shown).

Now, FIG. 5 shows a reflection type spectrometer which uses the heterodyne light-receiving system 3 of FIG. 4 and which is modified to look at a specific sample in a specific direction in a scattering medium. In this case, do not place the sample immediately after the beam splitter BS, change the direction of the half mirror HM, and place the sample directly behind the beam splitter BS.
A scattering medium 20 is schematically shown at the position where the light transmitted through the BS passes through the half mirror HM, and a specific sample S that reflects the forward scattered light in the opposite direction is schematically shown behind the scattering medium 20. , the reflected light is transmitted through the scattering medium 20 again from the opposite direction, and the transmitted and scattered light is combined with the reference light by a half mirror HM. This configuration is effective when the thickness of the scattering medium 20 is thin and the proportion of directly transmitted components is high.

Next, the apparatus 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 beam into a parallel beam of an appropriate diameter, the beam splitter BS splits the beam into two, and the transmitted sample 20 is inserted into the reflected light that has passed through one of the mirrors M1 and M2, and the scattered transmitted light is referred to. Synthesize using light and half mirror HM. The reference light that has passed through the beam splitter BS passes through the half mirror HM, hits the movable mirror M that is moved as shown by the side 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.

The detector 2 obtains a signal on which an interference signal having a frequency corresponding to the speed of the movable mirror M is superimposed. Since the intensity of the alternating current component is proportional to the intensity of the scattered light of the transmitted sample 20, the spectral absorption characteristics can be determined from the intensity of this alternating current component by sweeping the wavelength of the variable wavelength laser 10.

FIG. 7 shows the Michelson light receiving system 4 of a reflective type. The reflection spectrum of a specific sample in a scattering medium is schematically shown. In this case, a reflection spectroscopy sample S is schematically shown in which the sample is placed at a position reflected by the beam splitter BS and the forward scattered light is reflected in the opposite direction behind the scattering medium 20. The scattered light is transmitted through the scattering medium 20 from the opposite direction again, and the transmitted scattered light is sent to the movable mirror M by the beam splitter BS.
The light is combined with the reference light reflected from the light source. In this case as well, the scattering medium 2
This is an effective arrangement when the thickness of the 0 is small and the proportion of directly transmitted components is high.

Now, FIGS. 8 and 9 show that the third
The highly directional optical system 5 shown in the figure is used to extract only the scattered components in a specific direction. Figure 8 shows a transmission type configuration, and Figure 9 a reflection type configuration. be. The light from the variable wavelength laser 10 that is converted into a parallel beam of appropriate diameter from the beam converter 11 is transmitted directly in the case of FIG. 8, or via a half mirror HM in the case of FIG. The light hits the schematically illustrated scattering medium 20, undergoes multiple scattering and absorption, is transmitted forward, and is reflected by the reflection spectral characteristics 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 variable wavelength laser 10 is swept, a half mirror is placed between the beam converter 11 and the sample 20 (not shown), and the reflected light from the half mirror is detected. The laser output is monitored and the transmission integral attenuation is determined. In addition, in the case of Fig. 9, half mirror H
The laser light reflected by M is detected (the detector is not shown), and the laser output is monitored to determine the transmission integrated attenuation degree.

In addition, in the case of FIG. 9, similarly to FIGS. 5 and 7, a reflection spectroscopy sample S that reflects forward scattered light in the opposite direction is schematically shown behind the schematically drawn scattering medium 20. Ta. The scattered light is transmitted through the scattering medium 20 from the opposite direction again, and 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 passed through the highly directional optical system 5. Extract by Others are the 4th
This is the same as in the case shown in FIGS.

The above is the configuration of the apparatus when the sample whose spectral absorption characteristics are to be measured is transmissive and reflective. However, if the sample is reflective or the surface reflected light is strong, these configurations can be easily changed for that purpose. can be changed to . However, in a reflective sample, if the intensity of the specular reflection component of the incident light is extremely high,
Normally, the specular reflection component contains almost no information regarding the absorption characteristics near the surface of the reflective sample, so the structure must be designed to remove this specular reflection component. An example of a device configured in this manner is shown in FIGS. 10 and 11.

The apparatus shown in FIG. 10 uses a highly directional optical system 5 to extract components scattered in a specific direction from near the surface of the reflective sample 21 and measure spectral absorption characteristics. The monochromatic light from the variable wavelength laser 10 that enters through the mirror M4 is set to form a certain angle with respect to the normal to the sample surface, and its regular reflection component is reflected by the mirror M4.
5 and is removed by a beam trap BT. Further, the apparatus shown in FIG. 11 uses the heterodyne light receiving system 3 as a highly directional detection system to extract components scattered in a specific direction from near the surface of the reflective sample 21 and measure the spectral absorption characteristics. With a configuration similar to that shown in FIG. 11, the specular reflection component reflected on the surface of the sample 21 is removed by the beam trap BT.

Next, some examples of devices that specifically measure the spectral absorption characteristics of a macroscopic region of a sample will be briefly described. FIG. 12 shows a schematic configuration of an apparatus capable of measuring the transmission spectral absorption characteristics and reflection spectral absorption characteristics of the sample 20 placed on the sample stage 13. Monochromatic light from the tunable wavelength laser 10 is transmitted by the switching mirror MS. The transmission optical path is switched to the solid line and the reflected optical path is shown as the dotted line. When the solid optical path is selected, the light passing through the mirror M7 is converted into a parallel light beam of a predetermined diameter by the beam converter 11 consisting of 3 and 4 in the Cassegrain reflective optical system arranged confocal, and is incident on the sample 20. The scattered light in a specific direction that has passed through the sample 20 is extracted by a highly directional optical system 5 consisting of a Cassegrain reflective optical system 1 and 2 placed confocal and a pinhole P placed at its focal point. The light is measured by the detector 2 via the mirror MIO1Mll, and by sweeping the wavelength of the variable wavelength laser 10, the spectral absorption characteristics of the transmitted component of the sample 20 are determined. When the switching mirror MS is switched to the reflection optical path indicated by the dotted line, the monochromatic light from the variable wavelength laser 10 is reflected downward by the half mirror HM via the mirror M9, and is converted into a beam by the highly directional optical system 5 acting as the beam converter 11. diameter is reduced,
incident on the sample 20. Only the light that is completely backward scattered from the sample 20 is extracted by the highly directional optical system 5, passes through the half mirror HM, the mirror MIO1Mll, and is measured by the detector 2. By sweeping the wavelength of the variable wavelength laser 10, The spectral absorption characteristics of the reflected component of the sample 20 are determined. Note that when extracting backscattered components other than the specular reflection component of the sample 20, the sample 20 may be tilted to allow light to be incident thereon.

The devices shown in FIGS. 13 and 14 are simply vertical versions of the device using the heterogain light receiving system 3 shown in FIG. 4 and the device using the Feikelson light receiving system 4 shown in FIG. , no special explanation is necessary. In the one shown in FIG. 14, the driving diameter 14 is for moving the movable mirror M in the optical axis direction.

In the above description, it is assumed that the tunable wavelength laser 10 oscillates continuously, but a tunable wavelength laser that operates in pulses may also 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 operates in pulses. Moreover, although the detector 2 was not specifically explained, any known means can be used. Further, as a method of processing the detection signal, for example, intensity modulation of incident light may be performed using a chopper or the like, and phase synchronization detection of the detection signal may be considered. In this case, since the time constant of infrared light detection is long, it is necessary to reduce the synchronous modulation frequency. Furthermore, a synchronous signal integral detection method such as a photon counting method (visible light) or a charge accumulation method (infrared light), a heterodyne beat signal detection method, or the like may be used. Further, as the frequency shifter, not only those using ultrasonic light diffraction such as an ultrasonic modulator, but also a combination of wave plates, a rotating grating, and the electro-optic effect of a crystal can be used.

Alternatively, the reflector may be moved at a constant speed or oscillated with a sawtooth wave.

[Effects of the Invention] In the method and apparatus for measuring spectral absorption of an opaque sample according to the present invention, a scattering sample is irradiated with highly directional variable wavelength light from a specific direction, and only the light scattered in a specific direction is measured. Since the intensity is detected using a highly directional detection system such as a heterodyne light receiving system, a Michelson light receiving system, or a highly directional optical system, it is possible to detect scattering with high precision without picking up scattered light in extra directions or other noise light. Spectral absorption characteristics of a sample can be measured.

Moreover, it is extremely easy to measure the control compared to conventional methods, and the spectral absorption of transmitted or reflected components in a specific direction even for highly scattering objects such as suspensions and biological tissues. This is a method and apparatus suitable for measuring.

[Brief explanation of drawings]

Fig. 1 is a diagram for explaining the configuration and operation of a heterodyne light receiving system, one of the high directivity detection systems used in the method and apparatus for spectroscopic absorption measurement of opaque samples of the present invention, and 2nd r Figure 3 is a diagram to explain the configuration and operation of the Michelson light receiving system, which is a system. Figures 5 and 5 are diagrams showing the configuration of an embodiment of a spectroscopic absorption measuring device using a heterogain light receiving system of the present invention applied to a transmission sample, and Figures 6 and 7 are diagrams showing the configuration of an embodiment of a spectroscopic absorption measuring device using a heterogain light receiving system of the present invention applied to a transmission sample. Figures 8 and 9 are diagrams showing the configuration of an embodiment of a spectroscopic absorption measuring device using a light-receiving system. Figures 10 and 11 are diagrams showing the configuration of an embodiment of the spectroscopic absorption measuring device of the present invention applied to a reflective sample, and Figures 12 to 14 are diagrams showing the macro size region of the sample. Figures 15 to 24 are diagrams showing the configuration of the highly directional optical system proposed earlier. DESCRIPTION OF SYMBOLS 1... Laser, 2... Detector, 3... Heterodyne light receiving system, 4... Michelson light receiving system, 5... Highly directional optical system, lO... Variable wavelength laser, 11. ... Beam converter, 13... Sample stage, 20... Scattering medium,
21... Reflection sample, S... Sample, BS... Beam splitter-1HM... No. 1-F mirror, M1 to Ml
l...Mirror, AO...Frequency shifter, M...
Moving mirror, Obl, Ob2...objective lens, P...pinhole, M3...mirror, BT...beam trap,
MS...Switching iron, K1-4...Cassegrain reflective optical system output

Claims (9)

[Claims] (1) By irradiating a scattering sample with highly directional variable wavelength light from a specific direction and detecting the intensity of only the light scattered in a specific direction using a highly directional detection system, scattering A method for measuring spectral absorption of an opaque sample, characterized by measuring the spectral absorption characteristics of the sample. (2) The method for measuring spectral absorption of an opaque sample according to claim 1, wherein the specific direction in which the intensity is detected by the highly directional detection system is a direction in which transmitted and scattered light by the sample is detected. (3) The method for measuring spectral absorption of an opaque sample according to claim 1, wherein the specific direction in which the intensity is detected by the highly directional detection system is a direction in which reflected and scattered light by the sample is detected. (4) Split the light from a wavelength-changeable monochromatic light source into two, provide a frequency shift means to shift the frequency of the incident light in one optical path, place a scattering sample in the other optical path, and shift the frequency. A beam combining means is provided to combine highly directional light emitted from the means and light emitted in a specific direction from the scattering sample and emit the same in the same direction, and the combined light by the beam combining means is converted into an electrical signal. 1. A spectroscopic absorption measuring device for an opaque sample, characterized in that it is provided with a detection means for detecting the intensity of only an alternating current component equal to a shift frequency. (5) splitting the light from a wavelength-changeable monochromatic light source into two, providing an optical path length changing means for changing the optical path length at a predetermined speed in one optical path, and placing a scattering sample in the other optical path; A beam combining means is provided to combine the highly directional light emitted from the optical path length changing means and the light emitted in a specific direction from the scattering sample and emit the same in the same direction, and convert the combined light by the beam combining means into an electrical signal. 1. A spectroscopic absorption measuring device for an opaque sample, comprising a detection means for converting and detecting the intensity of only an alternating current component of a frequency corresponding to an optical path length change speed. (6) A scattering sample is placed in the optical path of light emitted from a wavelength-changeable monochromatic light source, and a highly directional optical system is placed to extract light emitted from the scattering sample in a specific direction. 1. A spectroscopic absorption measuring device for an opaque sample, characterized in that it is provided with a detection means for detecting the intensity of extracted light. (7) In the optical path of the light emitted from the wavelength-changeable monochromatic light source,
An optical path switching means is provided, one optical path and the other optical path are coaxial, and the traveling direction of the light is opposite, and a highly directional optical system is placed in the coaxial optical path. A scattering sample is placed on one side of the system, and the system is configured to extract light that has passed through the sample in a specific direction or light that has been reflected and scattered in a specific direction by the sample from the other side of the highly directional optical system. The spectroscopic absorption measuring device for an opaque sample according to claim 6. (8) Taking out a part of the irradiated light flux, detecting the intensity of the light flux and using it as a reference intensity, and using the light intensity detected using a highly directional detection system as the signal intensity of the sample light to calculate the integrated attenuation of the transmitted light. The spectroscopic absorption measuring device for an opaque sample according to any one of claims 1 to 3, 6, and 7. (9) 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 and used as the reference light intensity, and the light is synthesized by the beam combining means. is converted into an electrical signal, an alternating current component equal to the shift frequency or an alternating current component with a frequency corresponding to the optical path length change speed is used as the signal intensity from the sample, and these intensities are used to determine the transmission integral attenuation degree. Item 5. Spectroscopic absorption measuring device for an opaque sample according to item 4 or 5.