JPH049247B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a spectroscopic device that receives O-order light from a diffraction grating and monitors fluctuations in a light source, etc., and in particular, it emits light of a target wavelength in the same direction as the incident light. off-plane eagle type (off
-plane Eagle) is suitable for spectroscopic equipment.

Monitoring changes in the light source using the O-order light from a diffraction grating has the advantage of eliminating the need for a separate means to separate the light from the light source for monitoring purposes, and is often used when measuring gas absorption. It is being However, in the case of a Vodar spectrometer as shown in FIG. 6, the configuration for receiving and monitoring O-order light is relatively simple. To explain Figure 6,
S1 is an input slit, S2 is an output slit, G is a concave diffraction grating, S1, S2, and G indicate the arrangement of the input and output slits and the diffraction grating when light of a certain wavelength is extracted, and O is the arrangement of the diffraction grating in that case. It is the center of the Roland circle. S1', S2', and G' indicate the arrangement of input/output slits and diffraction gratings for other wavelengths;
O′ is the center of the Rowland circle at that time. The characteristic of the border type spectrometer is that the exit slit S2 is fixed, the grating G moves linearly, and the grating G and the entrance slit are arranged so that both the entrance and exit slits and the grating are located on a Rowland circle with a constant radius. They are connected at a point where the angle of incidence α of the light with respect to the grating G is constant. Since the O-order light of the diffraction grating is in the direction of specularly reflected light relative to the incident light with respect to the grating plane, the exit angle α' of the O-order light with respect to the grating G is constant during the wavelength scanning process and is equal to α. Therefore, a mirror M is provided at a position where the O-order light is received with a fixed positional relationship with the grating G, and the optical trap T absorbs the O-order light reflected by M. The optical trap T is also fixed in position with respect to the grating G. That is, lattice G
The O-order light monitoring mirror M and the optical trap T move integrally. M′, T′ are O at the position of lattice G′
The position of the optical monitor mirror and optical trap is shown. The mirror M is made by depositing gold on molybdenum or the like, and when light enters it, it emits photoelectrons and changes its potential.
The O-order light is monitored based on this potential change. Since this monitor element has a mirror surface and the reflected light is incident on the optical trap T and absorbed, the occurrence of stray light can be prevented by the configuration for O-order light monitoring.

In the border-type spectrometer, since the angle of incidence of light on the grating is constant as described above, the O-order light monitoring mirror and the optical trap can be integrated with the grating G, which is mechanically simple. However, in the case of eagle type,
Since the angle of incidence of light on the grating changes with wavelength scanning, it is not possible to keep the O-order light monitoring mirror and the optical monitor integral with the grating, and a mechanism for moving them is required. The present invention aims to provide a simple moving mechanism for a mirror for monitoring O-order light in an off-plane Eagle type spectrometer. The present invention will be explained below with reference to Examples.

FIG. 1 is a plan view of one embodiment of the present invention. S
1 and S2 are an entrance slit and an exit slit. In Figure 1, these are drawn as one, but their positions are shifted in the direction perpendicular to the page of the figure, and the second
The positional relationship is as shown in the figure. That is, the entrance slit S1 and the exit slit S2 are located above and below the surface of the Rowland circle (off-
plane). G indicates the position of the diffraction grating at the center wavelength of the wavelength scanning range, and O is the center of the Rowland circle at that time. During wavelength scanning, the diffraction grating G moves linearly in the directions of the input and output slits S1 and S2, and its direction is always changed along the Rowland circle. G' indicates the position of the diffraction grating for one wavelength different from the above-mentioned center wavelength, and O' is the center of the Rowland circle at that time. Since the off-plane Eagle type spectrometer has such a configuration, the incident angle α of light to the diffraction grating changes as the wavelength is scanned.

1 is a feed screw which is orthogonal to the center of the luminous flux of the O-order light D at the center wavelength position of the grating G, and the O-order light monitoring mirror M is rotated by a nut 2 screwed onto this feed screw 1. installed as possible. The feed screw 1 is driven in conjunction with wavelength scanning, so that the O-order light monitoring mirror M follows the O-order light from the diffraction grating G. At the position of the monitoring mirror M with respect to the center wavelength position of the grating G, the mirror is at an angle of 45° with the feed screw 1, so that the incident angle of the O-order light to the mirror is
The angle is 45 degrees, and the O-order light incident on the mirror is reflected in a direction parallel to the feed screw 1, enters the optical trap T in the extending direction of the feed screw 1, and is absorbed. The monitor mirror M moves along the feed screw 1 as the wavelength scans, but the angle between the feed screw 1 and the O-order light is
Since it deviates from 45 degrees, it is necessary to rotate the monitor mirror a little while scanning the wavelength. This rotation angle is 1/2 of the angle β between the O-th order light D at the center wavelength position and the O-th order light D' at other wavelength positions, and changes monotonically from one end of the wavelength scan to the other end. Fig. 3 shows a mechanism for rotating the monitor mirror M. A guide rod 3 is arranged approximately parallel to the feed screw 1, and is fitted into a groove 4 on the side of the nut 2 to prevent the nut 2 from rotating. It also serves as a cam for rotating the monitor mirror M. That is, the arm 5 of the mirror M is fixed, and the arm 5 is biased counterclockwise in FIG. 3A by a spring 6, and the roller 7 at the end of the arm 5 is in contact with the guide. However, the guide 3 is slightly inclined from being parallel to the feed screw 1, so that when the mirror M is at the center wavelength position of the spectrometer, it is inclined at an angle of 45 degrees with respect to the feed screw 1. Since the guide 3 is slightly inclined with respect to the feed screw 1, the mirror M rotates monotonically as the guide 3 moves, and the reflected light of the O-order light is always approximately parallel to the feed screw 1. Therefore, the trap T does not need to be moved in conjunction with wavelength scanning.

FIG. 4 shows another embodiment of the invention. S1,S
2 has the same entrance and exit slits as the example in Figure 2, and G
is a diffraction grating. L1 and L2 are links of equal length, and the length of each is equal to the radius of the Roland circle. One end of link L1 is pivoted at a position below the input and output slits S1 and S2 (on the opposite side of the paper in the figure). A lattice G is fixed to one end of L2 so as to be orthogonal to the link. The connection point between links L1 and L2 becomes the center of the Roland circle. Diffraction grating G
is also adapted to move along the linear guide groove X. Wavelength scanning is performed by sliding the grating G along the grooves X. A planetary gear mechanism as shown in FIG. 5 is attached to the grid G. In Fig. 5, the internal gear B is integral with the diffraction grating G, and the planetary gear C interposed between the central gear A and the internal gear B is connected to a slider (not shown) fitted in the guide groove X. It is pivoted. The shaft of the central gear A is a hollow shaft with a lattice G
The central axis passes through it. The central axis of the lattice G is pivotally supported by the slider. Therefore, the central gear A is pivotally attached to the diffraction grating G, so that when the grating G rotates by an angle α with respect to the guide groove X, the central gear A rotates by an angle 2α. An arm E shown in FIG. 5 is fixed to this central gear A. The arm E is made up of a tube and a rod inserted therein, and is expandable and retractable, and always holds an angle of 2α (α is the angle formed by the link L2 and the guide groove X, variable) with respect to the guide groove X. Y is a guide groove corresponding to the feed screw 1 in FIG. 1, which is perpendicular to the direction of the arm E at the position of the diffraction grating G corresponding to the center wavelength;
A slider H is slidably fitted into this groove. The slider H is provided with a planetary gear mechanism exactly the same as that shown in FIG. 5, and the end of the arm E is fixed to the center gear A. An O-order light monitoring mirror M is fixed to an internal gear B outside A. The central axis of the mirror M is the name H
It is pivoted on. With this configuration, the groove Y of the arm E
The O-order light monitoring mirror M rotates by half the rotation angle relative to the rotation angle. Therefore, at the center wavelength position,
If the mirror M is set at 45 degrees to the guide Y, the O-order light will always be correctly reflected in the direction of the guide Y.

The present invention has the above-described configuration, and since the moving direction of the O-order light monitoring mirror is perpendicular to the direction of the O-order light at the center wavelength position of the diffraction grating, the moving distance is smaller than in any other direction. Tesumi, KatsuO
Since the direction in which the O-order light is reflected by the mirror for monitoring the O-order light is parallel to the direction in which the mirror moves, the swing angle of the mirror is extremely small.As a result, the mechanism for moving the O-order light monitor mirror is small and simple. Since the optical trap may remain fixed, the off-plane Eagle type spectrometer equipped with the O-order optical monitor device can have a simple configuration as a whole.

[Brief explanation of drawings]

FIG. 1 is a plan view of an embodiment of the present invention, FIG. 2 is a schematic side view, and FIG. 3 is a schematic diagram of an embodiment of the invention.
The mirror moving mechanism for the next light monitor is shown in which Figure A is a plan view, Figure B is a side view, Figure 4 is a plan view of another embodiment of the present invention, and Figure 5 is a mechanism used in the same embodiment. FIG. 6 is a plan view of a border-type spectrometer. S1...Incidence slit, S2...Output slit, G...Diffraction grating, M...O-order light monitoring mirror,
T...Optical trap, 1...Feed screw, 2...Nut, 3...Guide rod, L1, L2...Link,
X, Y...Guide groove.

Claims (1)

[Claims] 1. In a spectrometer that uses a diffraction grating as a spectroscopic element and is configured to extract light of a target wavelength from approximately the same direction as the incident light, when the wavelength approximately at the center of the scanning wavelength range is made to exit from the exit slit. The O-order light is movable along a guide that is substantially orthogonal to the direction of the O-order light from the diffraction grating and extends in the direction of spectrum development, and receives the O-order light of the diffraction grating and reflects it in a direction parallel to the guide. A spectroscopic device characterized by being equipped with a monitor mirror.