JP4058865B2 - Total reflection absorption spectrum measuring device - Google Patents

Description

[0001]
BACKGROUND 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]
[Prior art]
In the total reflection absorption spectrum measurement method (ATR), a transparent body having a higher refractive index than that of the sample is brought into contact with the sample surface. From the transparent body side, the measurement light is incident at an incident angle where total reflection occurs at the interface with the sample, and the absorption characteristics of the sample are measured by detecting the absorption attenuation due to the sample of the totally reflected light. Conventionally, when measuring infrared light, an apparatus using an infrared reflection microscope system configured by a reflection optical system is used.
[0003]
According to this method, light in a wavelength region that is not absorbed by the sample is totally reflected as it is, but totally reflected light is absorbed in a wavelength region having infrared absorption, so that almost the same spectrum as the transmitted light spectrum is obtained. .
[0004]
In addition, this method can measure insoluble, infusible, elastic and viscous substances that are difficult to grind, and can easily measure rubber, plastic, etc., which are difficult to process with other measurement methods. Have.
[0005]
The structure of the objective mirror of a conventional Cassegrain type infrared microspectrophotometer is shown in FIG. The objective mirror is composed of a concave primary mirror 8 having a hole in the center and a convex secondary mirror 9 coaxial with the concave primary mirror 8. Monochromatic light emitted from a spectroscope (not shown) is shown in FIG. The right half is made to enter the objective mirror optical system downward, and the light is reflected by the convex secondary mirror 9 and the concave primary mirror 8 and focused on the focal point P of the objective optical system. The condensing point P is provided with a hemispherical ATR prism 10 centered on the point P, and the sample S is brought into contact with the lower surface of the ATR prism 10. In this way, the light condensed at the point P is not refracted by the ATR prism 10, but is condensed at the point P as it is, is totally reflected by the sample surface, and goes up the left half of the optical axis of the objective optical system. Is done.
[0006]
Since the total reflection absorption spectrum measurement method (ATR) uses total reflection, when the prism is at the focal position, all the light is reflected at the bottom of the ATR prism, and the sample at the focal position cannot be visually observed. For this reason, it is necessary to move the ATR prism from the focal position to another position during observation. As this method, the prism is moved in a plane perpendicular to the optical axis, or, as shown in FIGS. 4 and 5, in the objective lens system using a hemispheric lens at the tip, the top of the tip hemisphere lens is arranged. The peripheral portion of the objective lens 11 is used for the convex secondary mirror 12 of the Cassegrain reflection objective optical system, and at the time of ATR measurement, as shown in FIG. 4, an ATR measurement aperture 13 having a ring-shaped aperture is arranged on the optical axis, As shown in FIG. 5, a visual aperture 14 having a circular opening is arranged on the optical axis so that the measurement light is irradiated on the convex secondary mirror 12 and the objective lens 11 is irradiated with the measurement light. In this way, the sample can be viewed with an objective optical system. Alternatively, as shown in FIG. 6, the ATR prism 15 is made movable, and at the time of visual measurement, the ATR prism 15 is lifted in the optical axis direction by the lever 16 with the lens barrel as a fulcrum, and the ATR prism 15 is removed from the measurement optical path. There is an example in which the measurement light is prevented from passing through the ATR prism 15.
[0007]
[Problems to be solved by the invention]
However, as shown in FIG. 5, when the objective optical system and the reflective optical system are performed using one lens, there is a problem that the creation of the special lens and the aperture switching mechanism are not easy and expensive. Further, 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 ATR measurement is performed, if the sample is pressed against the ATR prism, the reproducibility of the position of the ATR prism is poor. There was a problem. Furthermore, since ATR measurement uses total reflection of light, 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. Depending on the type of ATR prism, Since the total reflection condition is not satisfied unless the incident angle is increased, it is necessary to make light incident at a large incident angle. For this reason, a large concave primary mirror and convex secondary mirror are required. However, when such an optical system is used, if the incident angle to the sample is large during visible observation, the image may be blurred due to aberrations or other reasons. Will occur.
[0008]
Therefore, an object of the present invention is to obtain a clear image of an analysis point of a sample during visible observation by a simple mechanism.
[0009]
[Means for Solving the Problems]
In order to solve the above problems, the present invention provides a total reflection absorption cassegrain reflection objective mirror composed of a concave primary mirror having a hole in the center, a convex secondary mirror coaxial with the concave primary mirror, and an ATR prism. By fixing and incorporating a mechanism for switching and moving only the convex secondary mirror and the ATR prism part at the same time, the optimum combination of convex secondary mirror and ATR prism can be selected according to each use condition of ATR measurement and visible observation I did it.
[0010]
According to the present invention, although the concave primary mirror is fixed, the convex secondary mirror and the ATR prism can be moved at the same time. Therefore, during visible observation, switch to a small convex secondary mirror, and the incident angle of light at the focal position. Can be limited, and a clear image can be obtained during visible observation. In addition, the ATR measurement can be switched to a large convex secondary mirror, and the incident angle of light incident on the ATR prism can be increased according to the refractive index of the prism, so that the total reflection condition of incident light can be easily satisfied. It becomes possible. In addition, by switching between an ATR prism having a different refractive index and a convex secondary mirror suitable for this, and changing the incident angle of the light incident on the ATR prism, the penetration depth of the measurement light with respect to the measurement sample can be changed. This makes it possible to measure ATR spectra at different depth positions in the sample.
[0011]
As an example of a mechanism that switches between the convex secondary mirror and the ATR prism at the same time, a switching turntable that can be rotated about an axis parallel to the optical axis of the reflective objective optical system is installed, and this switching turntable is rotated. Two or more types of convex secondary mirrors are provided centered on the path of the optical axis of the reflective objective optical system drawn on the turntable, and further on the optical axis of each convex secondary mirror. An ATR prism is fixed at a position that becomes the focal point of the concave primary mirror below, and when one of the convex secondary mirrors is positioned on the optical axis of the reflective objective optical system and used for measurement, the other is used as the reflective objective optical system. This can be realized by positioning it outside.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of a total reflection absorption spectrum measuring apparatus of the present invention will be described with reference to the drawings. FIG. 1 shows an embodiment of the present invention and shows an outline of an embodiment of a total reflection absorption spectrum measuring apparatus. FIG. 1A is a side sectional view, and the Cassegrain reflection objective mirror 1 includes a concave primary mirror 2, a convex secondary mirror 3 and a hemispherical ATR prism 4 having a hole in the center. The concave primary mirror 2, the convex secondary mirror 3 and the ATR prism 4 are on the same optical axis, and the ATR prism 4 is arranged such that the center of curvature is located at the condensing 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 are switched with respect to the fixed concave primary mirror 2. The turn table 5 can be moved simultaneously by rotating. FIG. 1 (b) is a view of FIG. 1 (a) as viewed from the bottom. In addition to the convex secondary mirror 3 and the ATR prism 4, a visual convex secondary mirror 6 is provided on the turntable 5 as a switching turntable. When 5 is rotated, it is placed centered on the trajectory of the optical axis of the convex secondary mirror 2 drawn on the turntable. Further, a positioning pivot 7 is disposed in the Cassegrain reflection objective mirror 1.
[0013]
When measurement is performed with this total reflection absorption spectrum measuring apparatus, first, the switching turntable 5 is rotated so that 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. The measurement interference light exits from a spectrophotometer (not shown), passes through the hole of the concave primary mirror, enters the objective optical system downward on the right half of the optical axis, and is reflected by the convex secondary mirror 6 and the concave primary mirror 2. And condensed. At this time, by using the small convex sub-mirror 6 for visual observation, the incident angle of light to the focal position can be limited to be small, and a clear image can be obtained during visible observation. Next, the switching turntable 5 is rotated again, and the convex secondary mirror 3 and the ATR are moved to a position where the optical axis of the convex secondary mirror 3 and the ATR prism 4 coincides with the optical axis of the concave primary mirror 2 by using the positioning pivot 7. The prism 4 is fixed and ATR measurement is performed. At this time, by using a large convex secondary mirror for the convex secondary mirror 3, the incident angle of the light incident on the ATR prism 4 can be increased according to the refractive index of the ATR prism 4, and the incident light The total reflection condition can be easily satisfied.
[0014]
FIG. 2 is a side sectional view of the ATR Cassegrain reflection objective mirror in FIG. FIG. 2A shows an ATR Cassegrain reflection objective mirror used at the time of visual observation, and it can be seen that the incident angle of light to the focal position is reduced by using the small convex sub-mirror 6. On the other hand, FIG. 2 (b) shows an ATR Cassegrain reflection objective mirror used at the time of ATR measurement. By using the large convex secondary mirror 3, the incident angle of light incident on the ATR prism 4 can be increased. You can see that
[0015]
With the simple operation of turning the switching turntable 5, the optimum combination of convex secondary mirror and ATR prism can be easily selected according to the use conditions of ATR measurement and visible observation. It is possible to easily satisfy the total reflection conditions of incident light, and it is possible to obtain a clear image with very little aberration and little distortion during visible observation. Furthermore, by providing two or more types of ATR prisms having different refractive indexes and a suitable convex secondary mirror on the switching turntable 5, it is possible to change the incident angle of light incident on the ATR prism. The penetration depth of the measurement light with respect to the measurement sample can be changed. This makes it possible to measure ATR spectra at different depth positions in the sample.
[0016]
Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the gist of the present invention described in the claims. it can. For example, although two types of convex secondary mirrors are used in the above-described embodiment, three or more types of convex secondary mirrors can be used as needed depending on the measurement conditions. Also, a disk-shaped table was used as the switching turntable 5, and the convex secondary mirror and the ATR prism were moved by rotating the table. However, the rectangular secondary table was used and the convex secondary mirror and the ATR prism were arranged on a straight line. However, it may be moved by a linear motor. Furthermore, as a positioning method of the turntable 5, various known methods such as a positioning method by transmitting and receiving laser light can be used.
[0017]
【The invention's effect】
According to the present invention, with respect to a fixed concave primary mirror, two or more types of convex secondary mirrors and an ATR prism are installed on a switching turntable, and the switching turntable is rotated to By incorporating a mechanism to switch and move the ATR prism part at the same time, it is possible to easily select the optimal combination of convex secondary mirror and ATR prism according to the usage conditions of ATR measurement and visible observation. Therefore, it is possible to easily satisfy the total reflection condition of the light to be obtained, and it is 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 of a combination of only spherical surfaces that are easy to manufacture. In addition, the structure is simple, and the manufacturing cost can be reduced. Furthermore, two or more types of ATR prisms with different refractive indexes and a suitable convex secondary mirror 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 was 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 side surface sectional drawing of the total reflection absorption spectrum measuring apparatus of this invention.
(B) It is the figure seen from the lower part of the total reflection absorption spectrum measuring apparatus of this invention.
FIG. 2 is a side sectional view of the ATR Cassegrain reflection objective of the above embodiment.
(A) It is side surface sectional drawing of the ATR Cassegrain reflection objective mirror used at the time of visual observation.
(B) It is side surface sectional drawing of the ATR Cassegrain reflective objective mirror 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 cross-sectional view of another conventional example of a total reflection absorption spectrum measuring apparatus.
FIG. 5 is a side cross-sectional view during 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-Focusing point S-Sample

Claims (1)

A total reflection absorption spectrum measuring apparatus having a reflective objective optical system composed of a concave primary mirror and a convex secondary mirror and a hemispherical ATR prism centered on the condensing point of the optical system, and having two or more types of convex secondary mirrors And a total reflection absorption spectrum measuring apparatus configured to selectively use one of these convex secondary mirrors for measurement.

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