JPS58131522A - Spectroscopic device - Google Patents

Abstract

PURPOSE:To minimize the swing angle of a mirror by making a moving direction of a mirror for monitoring zero light orthogonal with a direction of zero light in a wavelength position in the center of a diffraction grating and by having very little moving distance and making a reflecting direction by the monitoring mirror parallel with the moving direction of the mirror. CONSTITUTION:A feed screw 1 is orthogonal with the center of luminous flux of zero light D in the center wavelength position of a diffraction grating G, and a mirror M for monitoring is fitted to nut 2 screwed into this feed screw 1 freely rotatably. The feed screw follows the zero light from the diffraction grating of the mirror M for monitoring which is driven by interlocking with wavelength scanning. The mirror makes an angle of 45 deg. with the feed screw 1, therefore an incident angle of the zero light to the mirror is made 45 deg. at the position of the monitoring mirror M against the center wavelength position of the grating G. The zero light made incident to the mirror is reflected to a direction parallel with the feed screw 1 and is made incident to an optical trap T and absorbed. As the reflecting direction of the zero light by the monitoring mirror is made parallel to a moving direction of the mirror, the swing angle of the mirror is extremely small, and an off-plane Eagle type sepectral device having a simple constitution is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a spectroscopic device that receives zero-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 (0ff-plane Eagle type)
e) Suitable for spectroscopic equipment.

Monitoring changes in the light source using the zero-order light of the 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. There is. In the case of a Vodar spectrometer as shown in FIG. 6, the configuration for receiving and monitoring zero-order light is relatively simple. To explain FIG. 6, 81 is an entrance slit, S2 is an exit slit,
G is a concave diffraction grating, Sl, 82. G indicates the arrangement of the input/output slit and the diffraction grating when light of one wavelength is extracted, and 0 is the center of the Rowland circle in this case. S
1', S 2. G' indicates the arrangement of input/output slits and diffraction gratings for other wavelengths, and 01 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 in a straight line, and the grating G and the entrance slit are arranged so that the input and output image slits and the grating are located on a Rowland circle with a constant radius. They are connected at a point where the incident angle α of the light with respect to the grating G is constant. Since the 0th order light of a diffraction grating is the direction of specularly reflected light with respect to the incident light with respect to the grating plane, the 0th order light with respect to the grating G is
The emission angle α° of the secondary light is constant during the wavelength scanning process and is equal to α. Therefore, a mirror M is provided at a position where the 0th order light is received with a fixed positional relationship with the grating G, and the 0th order light reflected by M is absorbed by the optical trap T. The optical trap T is also fixed in position with respect to the grating G. That is, the grating G, the O-order optical monitor state boundary M, and the optical trap T move integrally. M' and T' indicate the zero-order optical monitor state boundary and the position of the optical trap at the position of the grid ()I. 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, and this potential change causes it to change to 0.
Monitor the next light. Since this monitor element has a mirror surface and the reflected light enters the optical trap T and is absorbed, the generation of stray light due to the structure of the zero-order light monitor can be prevented.

In the border-type spectrometer, since the angle of incidence of light on the grating is constant as described above, the zero-order light monitor state border and the optical trap can be integrated with the grating G, which is mechanically simple.

However, in the case of the Eagle type, since the angle of incidence of light on the grating changes as the wavelength scans, it is not possible to keep the 0th-order light monitor state border and optical monitor integrated with the grating, and the movement mechanism for them cannot be used. Is required. The present invention aims to provide a simple mechanism for moving the state border of the zero-order light monitor 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. Sl, S2
are the entrance slit and the exit slit.

Although these are drawn as one in FIG. 7, their positions are shifted in the direction perpendicular to the plane of the drawing, resulting in a positional relationship as shown in FIG. 2. That is, the entrance slit S1 and the exit slit S2 are located below -F across the plane of the Rowland circle (0ff-plane).

G indicates the position of the diffraction grating at the center wavelength of the wavelength scanning range, and is the center of the Rowland circle at 0. During wavelength scanning, the diffraction grating G moves linearly in the directions of the entrance and exit slits 81 and 82, and its direction is always changed along the Rowland circle. G1 indicates the position of the diffraction grating for one wavelength different from the center wavelength, and 01 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, and 0 at the center wavelength position of the grating G.
It is perpendicular to the center of the luminous flux of the next light, and is used as a mirror M for monitoring the zero-order light.
is rotatably attached to a nut 2 which is screwed onto this feed screw l. The feed screw 1 is driven in conjunction with wavelength scanning, so that the O-order light monitor state boundary M follows the zero-order light from the diffraction grating G. At the position of the monitor state border M with respect to the central wavelength position of the grating G, the mirror is at an angle of 45° with the feed screw], so the incident angle of the zero-order light to the mirror is 45°.
The zero-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. As the wavelength scans, the monitor state border M moves along the feed screw 1, but the feed screw l and 0
Since the angle formed with the secondary light deviates from 45°, it is necessary to rotate the monitor state border slightly in conjunction with wavelength scanning. This rotation angle is 1/2 of the angle β between the zero-order light at the center wavelength position and the O-order light D' at other wavelength positions, and changes monotonically from one end of the wavelength scan to the other end. Figure 3 shows the mechanism for preventing the rotation of this monitor state line M. A guide rod 3 is placed 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 is also a cam that rotates the monitor state line M. In other words, mirror M has arm 5.
is fixed, arm 5 is biased counterclockwise in FIG. 3A by a spring 6, and roller 7 at the end of arm 5 is in contact with the guide. The guide 3 is slightly inclined from being parallel to the feed screw l, so that when the mirror M is at the center wavelength position of the spectrometer, it is inclined at an angle of 45° with respect to the feed screw l. Because the guide 3 is slightly tilted relative to the feed screw 1, the mirror M rotates monotonically as it moves, and the reflected light of the zero-order light is always approximately parallel to the feed screw L. , Therefore, the track T does not need to be moved with wavelength scanning.

FIG. 4 shows another embodiment of the invention. 81. S2 is the second
The entrance and exit slits are the same as in the example shown, and G is a diffraction grating. Ll and L2 are links of equal length, and the length of each person is equal to the radius of the Rowland circle, and one end of the link L1 is pivoted at a position below the input/output sleeves) Sl and S2 (on the opposite side of the paper in the figure). A grating G is fixed to one end of the link L2 so as to be perpendicular to the link. The connection point between links Ll and L2 becomes the center of the Rowland circle. The diffraction grating G is still 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 〇, 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, and the core and shaft of the lattice G are passed through the shell. The central axis of the lattice G is the slider 9 mentioned above.
c It is pivoted. Therefore, the center gear A is pivotally attached to the diffraction grating G9, and when the grating G is rotated by an angle α with respect to the guide groove X, the center gear A is pivoted to the diffraction grating G. A is designed to rotate 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 into it, is expandable and retractable, and is always 2α with respect to the guide groove XK (α beam/angle between beam L2 and guide groove X, variable).
holding the corner of Y is a guide groove corresponding to the feed screw IK in FIG.
The sliding case is mated. The sliding wheel H is equipped with a planetary gear mechanism exactly the same as that shown in the last figure, and the end of the arm E is fixed to the central gear A.

An O-order optical monitor state border M is fixed to an internal gear B outside A. The central axis of the mirror M is pivotally fixed to the slider H. With this configuration, the O-order light monitor state border M is rotated by an angle that is half the rotation angle of the arm E with respect to the groove Y. Therefore, if the mirror M is set so as to form an angle of 45° with respect to the guide Y at the center wavelength position, the zero-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 zero-order light monitoring mirror is orthogonal to the direction of the zero-order light at the center wavelength position of the diffraction grating, the moving distance is smaller than in any other direction. Since the direction of reflection of the 0th order light by the 0th order light monitoring mirror is parallel to the moving direction of the mirror, the deflection angle of the mirror is extremely small, and as a result, the 0th order light monitoring mirror The moving mechanism is small and simple, and the optical trap need only be fixed, so that the entire off-plane Eagle type spectrometer equipped with a zero-order light monitor can have a simple configuration.

[BRIEF DESCRIPTION OF THE DRAWINGS] Fig. 1 is a plan view of an embodiment of the present invention, Fig. 2 is a schematic side view, and Fig. 3 shows a state border movement mechanism for the ○th optical monitor in the above embodiment. A is a plan view, B is a side view, FIG. 4 is a plan view of another embodiment of the present invention, FIG. 5 is a plan view of the planetary gear mechanism used in the same embodiment, and FIG. 6 is a plan view of the planetary gear mechanism used in the same embodiment. FIG. 2 is a plan view of a border-type spectrometer. 81...Incidence slit, S2...Output slit, G
...Diffraction grating, M...Mirror for 0th order light monitoring, T...
Optical trap, ]...Feed screw, 2...Nut, 3.
...Guide rod, Ll, L2...Link, X, Y...
guide groove. -12?

Claims (1)

[Claims] 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. It is characterized by being equipped with an O-order light monitoring mirror that can move along a guide that is substantially orthogonal to the direction of the 0-order light from the diffraction grating, and that receives the 0-order light of the diffraction grating and reflects it in a direction parallel to the guide. A spectroscopic device.