JP2001133400A - Total reflection/absorption spectrum measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a total reflection/absorption spectrum measuring device capable of providing a clear image of an analysis point of a sample in visual observation. SOLUTION: A total reflection/absorption Cassegrainian reflecting objective mirror 1 is made up of a primary concave mirror 2 having a hole in the middle, a secondary convex mirror 3 coaxial with the concave mirror 2, and an ATR (attenuated total reflection) prism 4. The concave mirror 2 is in a fixed position, and two kinds of secondary convex mirrors 3, 6 and the prism 4 are installed on a turntable 5 for selection. In ATR measurement, the larger mirror 3 and the prism 4 are selected by turning the turntable 5. The incident angle of light coming into the prism 4 can be increased according to the refraction factor of the prism 4, thus easily satisfying the total reflection condition of the incoming light. In visual observation, the smaller mirror 6 is selected to decrease the incident angle of light coming into a focal position, thereby providing a clear image having very small aberration and little distortion.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a total reflection absorption spectrum measuring apparatus widely used for qualitative analysis and identification analysis of various substances including organic substances such as polymer materials.

[0002]

2. Description of the Related Art Total reflection absorption spectrum measuring method (ATR)
Is to bring a transparent body with a higher refractive index than the sample into contact with the sample surface (if infrared light is used, it is only necessary to be transparent to the infrared light). A method for measuring the absorption characteristics of a sample by irradiating the measurement light at an incident angle at which total reflection occurs and detecting absorption extinction by the sample of the totally reflected light, conventionally measuring infrared light In this case, an apparatus using an infrared reflection microscope system constituted by a reflection optical system is used.

According to this method, light in a wavelength region where the sample does not absorb light is totally reflected as it is, but in a wavelength region where infrared light is absorbed, the totally reflected light is absorbed, so that the spectrum is almost the same as the transmitted light spectrum. Is obtained.

Moreover, this method can measure insoluble, infusible, elastic and viscous substances which are difficult to pulverize, and can easily measure rubber, plastic, etc., which are difficult to process with other measuring methods. It has the feature of.

FIG. 3 shows the structure of an objective mirror of a conventional Cassegrain infrared microspectrophotometer. The objective mirror comprises a concave main mirror 8 having a hole at the center and a convex sub-mirror 9 coaxial with the concave main mirror 8. Monochromatic light emitted from a spectroscope (not shown) passes through the optical axis in FIG. The right half is made to enter the objective mirror optical system downward, and the light is reflected by the convex sub-mirror 9 and the concave primary mirror 8, and is condensed at the focal point P of the objective mirror optical system. Focus point P is P
A hemispherical ATR prism 10 centered on a point is provided, and the sample S is brought into contact with the lower surface of the ATR prism 10. In this case, the light condensed at the point P is not refracted by the ATR prism 10, but is condensed as it is at the point P, is totally reflected on the sample surface, and moves up the left half of the optical axis of the objective optical system.
Is detected.

[0006] Total reflection absorption spectrum measurement method (ATR)
Uses total reflection, so that when the prism is at the focal position, all light is reflected at the bottom of the ATR prism, and the sample at the focal position cannot be observed visually. Therefore, at the time of observation, it is necessary to move the ATR prism from the focal position to another position. As this method, a prism is translated in a plane perpendicular to the optical axis, or FIG.
As shown in the figure, in an objective lens system using a hemispherical lens at the tip, the objective lens 1 at the top of the hemispherical lens at the tip
The periphery of 1 is a convex sub-mirror 1 of a Cassegrain type reflection objective optical system.
4, the ATR measurement aperture 13 having a ring-shaped aperture is arranged on the optical axis at the time of ATR measurement, so that the measurement light is irradiated to the convex sub-mirror 12, as shown in FIG. As shown in FIG. 5, a viewing aperture 14 having a circular opening is arranged on the optical axis so that the measurement light is irradiated on the objective lens 11 so that the sample can be viewed with the objective optical system. I have. Alternatively, as shown in FIG. 6, the ATR prism 15 is made movable, and at the time of visual measurement, the ATR prism 1 is
There is an example in which the ATR prism 15 is lifted in the optical axis direction to remove the ATR prism 15 from the measurement optical path so that the measurement light does not pass through the ATR prism 15.

[0007]

However, as shown in FIG. 5, when the objective optical system and the reflection optical system are performed by using one lens, it is not easy to manufacture a special lens and an aperture switching mechanism, and it is expensive. There was a problem of becoming. Also, as shown in FIG. 6, when the ATR prism is made movable, the ATR prism is moved in the optical axis direction. Therefore, when the sample is pressed against the ATR prism during ATR measurement, the reproducibility of the position of the ATR prism is poor. There was a problem. Furthermore, in the ATR measurement, since the total reflection of light is used, it is necessary to use an ATR prism made of a material that transmits infrared rays and has a large refractive index with respect to infrared rays. If the incident angle is not increased, the condition of total reflection is not satisfied, so that light must be incident at a large incident angle. For this reason, a large concave primary mirror and a convex secondary mirror are required.However, when such an optical system is used, if the incident angle to the sample is large at the time of visible observation, an adverse effect such as blurring of an image due to aberration or the like is caused. Occurs.

Accordingly, an object of the present invention is to provide a clear image of an analysis point of a sample during visible observation with a simple mechanism.

[0009]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention provides a concave primary mirror having a hole in the center, a total reflection absorbing Cassegrain comprising a convex secondary mirror coaxial with the concave primary mirror and an ATR prism. In the reflection objective mirror, the concave primary mirror is fixed, and a mechanism for simultaneously switching and moving only the convex secondary mirror and the ATR prism portion is incorporated, so that the optimal convex secondary mirror can be used according to each use condition of ATR measurement and visible observation. A combination of a mirror and an ATR prism can be selected.

According to the present invention, the concave primary mirror is fixed, but the convex secondary mirror and the ATR prism are movable at the same time. Can be limited to a small angle, and a clear image can be obtained during visible observation. Further, in the case of ATR measurement, it is possible to switch to a large convex sub-mirror and to increase the incident angle of light incident on the ATR prism according to the refractive index of the prism, thereby easily satisfying the condition of total reflection of incident light. It becomes possible. In addition, A having different refractive indices
Switching to TR prism and convex secondary mirror suitable for this, AT
By changing the incident angle of the light incident on the R prism, the penetration depth of the measurement light into the measurement sample can be changed, thereby measuring the ATR spectrum at different depth positions in the sample. It becomes possible to do.

[0011] As an example of a mechanism for simultaneously switching the convex sub-mirror and the ATR prism, a switching turntable that can rotate around an axis parallel to the optical axis of the reflection objective optical system is installed, and this switching turntable is rotated. When this is done, two or more types of convex secondary mirrors are provided with their centers on the path of the optical axis of the reflective objective optical system drawn on the turntable,
Further, an ATR prism is fixed at a position on the optical axis of each convex sub-mirror and below the convex sub-mirror to be the focal point of the concave primary mirror, and one of the convex sub-mirrors is aligned with the optical axis of the reflection objective optical system. This can be realized by positioning the other one outside the reflection objective optical system when it is used for positioning and measurement.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a total reflection absorption spectrum measuring apparatus according to the present invention will be described with reference to the drawings. FIG. 1 shows an embodiment of the present invention, and schematically shows an embodiment of a total reflection absorption spectrum measuring apparatus. FIG. 1A is a side sectional view. The Cassegrain reflection objective 1 is composed of a concave primary mirror 2 having a hole in the center, a convex secondary mirror 3, and a hemispherical ATR prism 4. Concave primary mirror 2, convex secondary mirror 3 and A
The TR prism 4 is on the same optical axis and the ATR prism 4
Are arranged such that the center of curvature is located at the focal point of the concave primary mirror 2. The convex secondary mirror 3 and the ATR prism 4 are installed on a switching turntable 5. The switching turntable 5 is rotatable about an axis parallel to the optical axis of the concave primary mirror 2, and the convex secondary mirror 3 and the ATR prism 4 switch with respect to the fixed concave primary mirror 2. By turning the turntable 5 for use, it can be moved at the same time. FIG.
FIG. 6A is a view of the turntable 5 when viewed from below, in addition to the convex sub-mirror 3 and the ATR prism 4, the visual convex sub-mirror 6 turns the switching turntable 5. It is installed centered on the locus of the optical axis of the convex sub-mirror 2 drawn on the turntable. Furthermore, a positioning pivot 7 is arranged on the Cassegrain reflecting objective 1.

When the measurement is performed by this total reflection absorption spectrum measuring apparatus, first, the switching turntable 5 is rotated, and the optical axis of the convex secondary mirror 6 for visual observation coincides with the optical axis of the concave primary mirror 2. The position of the convex secondary mirror 6 is fixed using the positioning pivot 7 so as to come to the position. The measurement interference light is emitted from a spectrophotometer (not shown), passes through the hole of the concave primary mirror, enters the objective optical system below the right half of the optical axis, and enters the convex secondary mirror 6.
The light is reflected by the concave primary mirror 2 and collected. At this time, by using the small convex sub-mirror 6 for visual observation, the angle of incidence of light on the focal position can be limited to a small value, and a clear image can be obtained during visible observation. Next, the switching turntable 5 is rotated again, and the positioning auxiliary pivot 7 is used to move the convex sub-mirrors 3 and A to positions where the optical axes of the convex sub-mirror 3 and the ATR prism 4 coincide with the optical axes of the concave main mirror 2.
ATR measurement is performed with the TR prism 4 fixed. At this time, by using a large convex sub-mirror for the convex sub-mirror 3, the incident angle of light incident on the ATR prism 4 can be adjusted to AT
This can be increased according to the refractive index of the R prism 4, and the condition for total reflection of incident light can be easily satisfied.

FIG. 2 is a side sectional view of the ATR Cassegrain reflecting objective in FIG. FIG. 2A shows an ATR Cassegrain reflection objective used for visual observation. It can be seen that the use of the small convex sub-mirror 6 reduces the angle of incidence of light on the focal position. On the other hand, FIG. 2B shows an ATR Cassegrain reflecting objective mirror used for ATR measurement. By using the large convex sub-mirror 3, the incident angle of light incident on the ATR prism 4 can be made large. You can see that it is.

By the simple operation of rotating the switching turntable 5, it is possible to easily select the optimum combination of the convex sub-mirror and the ATR prism in accordance with the use conditions of the ATR measurement and the visual observation. At the time of ATR measurement, it is possible to easily satisfy the condition for total reflection of incident light, and at the time of visible observation, it is possible to obtain a clear image with very small aberration and little distortion. Further, two or more types of ATR prisms having different refractive indices and a convex secondary mirror suitable for the ATR prism are installed on the switching turntable 5,
By making it possible to change the incident angle of light incident on the ATR prism, it becomes possible to change the penetration depth of the measurement light with respect to the measurement sample.
This makes it possible to measure ATR spectra at different depth positions in the sample.

The embodiments of the present invention have been described above.
The present invention is not limited to the above embodiments, and various changes can be made within the scope of the present invention described in the appended claims. For example, in the above embodiment, two types of convex sub-mirrors are used, but three or more types of convex sub-mirrors can be used as needed depending on measurement conditions. Further, a disk-shaped table was used as the switching turntable 5, and the convex sub-mirror and the ATR prism were moved by rotating the disk-shaped table. However, a rectangular table was used, and the convex sub-mirror and the ATR prism were arranged on a straight line. Alternatively, it may be moved by a linear motor. Further, as a positioning method of the turntable 5, various well-known methods such as a positioning method by transmitting and receiving laser light can be used.

[0017]

According to the present invention, two or more types of convex sub-mirrors and an ATR prism are installed on a switching turntable with respect to a fixed concave primary mirror, and the switching turntable is rotated. By incorporating a mechanism to switch and move the convex sub-mirror and the ATR prism at the same time,
The optimal combination of convex sub-mirror and ATR prism can be easily selected according to the usage conditions of ATR measurement and visible observation, and the ATR measurement can easily satisfy the condition of total reflection of incident light. This makes it possible to obtain a clear image with very small aberration and little distortion during visible observation. At this time, the concave primary mirror and the convex secondary mirror can be made by a combination of only spherical surfaces which are easy to manufacture. Further, the structure is simple, and the manufacturing cost can be reduced. Furthermore, two or more types of ATR prisms having different refractive indices and a convex sub-mirror suitable for the ATR prism are installed on the switching turntable, and the incident angle of light incident on the ATR prism is changed to perform ATR measurement at different incident angles. By doing so, it became possible to measure ATR spectra at different depth positions in the sample.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an embodiment of a total reflection absorption spectrum measuring apparatus according to the present invention. (A) It is a side sectional view of the total reflection absorption spectrum measuring device of the present invention. (B) It is the figure seen from the lower part of the total reflection absorption spectrum measuring device of the present invention.

FIG. 2 is a side sectional view of the ATR Cassegrain reflective objective according to the embodiment. (A) It is side sectional drawing of the ATR Cassegrain reflection objective used at the time of visual observation. (B) It is a side sectional view of the ATR Cassegrain reflection objective used at the time of ATR measurement.

FIG. 3 is a side sectional view of a conventional total reflection absorption spectrum measuring apparatus.

FIG. 4 is a side sectional view of another conventional total reflection absorption spectrum measuring apparatus.

FIG. 5 is a side sectional view at the time of visual observation of the conventional example.

FIG. 6 is a side sectional view of another conventional example.

[Explanation of symbols]

 1 --- Cassegrain reflection objective mirror 2,8 --- Concave primary mirror 3,6,9,12 --- Convex secondary mirror 4,10,15 --- ATR prism 5 --- Switching turntable 7- -Positioning pivot 11 --- Objective lens 13,14 --- Aperture 16 --- Lever P --- Condensing point S --- Sample

Claims (1)

[Claims] 1. A total reflection absorption spectrum measuring apparatus comprising: a reflecting objective optical system comprising a concave primary mirror and a convex secondary mirror; and a hemispherical ATR prism centered on a focal point of the optical system. A total reflection absorption spectrum measuring apparatus having a convex sub-mirror, wherein one of these convex sub-mirrors is selectively used for measurement.