JPH049248B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a spectroscopic device that uses a diffraction grating and has a Rowland circle, and particularly relates to a slit drive mechanism in the spectroscopic device.

When a spectrometer using a concave diffraction grating also drives the exit slit during wavelength scanning, the spectral image plane is curved along a Rowland circle, and the exit slit must be driven along this spectral image plane. , and the exit slit surface is preferably perpendicular to the line connecting the center of the diffraction grating and the center of the exit slit, that is, the main diffraction ray. The driving mechanism for the exit slit that satisfies such requirements is complicated. Therefore, the present invention was made with the object of simplifying the driving mechanism for such an exit slit.

First, the object of the present invention will be explained in more detail with reference to FIG. FIG. 1 shows an off-plane Eagle type spectrometer, where S1 is an entrance slit, G is a concave reflection grating, and R is a Rowland circle. The entrance slit S1 is located on the Rowland circle R, and the diffraction grating G
is tangent to the Roland circle. O is the center of the Rowland circle. The spectral image is Rowland circle R
A spectral image of light with a wavelength near the lasing wavelength of the diffraction grating G is formed along the incident slit S1.
It is designed to be formed in a range of I close to .
The exit slit is driven in the range I along the Rowland circle as the wavelength is scanned, but the positions of both are shifted in the direction perpendicular to the plane of the drawing so as not to collide with the entrance slit. The present invention is directed to a mechanism for providing such movement of the exit slit.
Although an off-plane Eagle type spectrometer was used in the above description, the present invention can be applied to any spectroscopic device in general that requires a slit to be moved along a Roland circle that moves a slit along a Roland circle that moves. .

An example of a conventional mechanism for providing slit movement as described above is shown in FIG. B is the substrate,
It is pivoted at a rotation center 11 and can rotate within the plane of the figure. 1 is the first gear attached to the motor shaft;
Reference numeral 2 denotes a second gear meshing with the first gear, which is centered around the rotation center 11 of the substrate B and loosely fitted onto the rotation axis of the substrate B. A third gear 3 meshes with the second gear 2 and is pivotally attached to the board B. The second gear 2 is the board 1
1, the meshing relationship between the third gear and the second gear does not change even if the substrate B rotates. In the board B, 10 is an arc-shaped protruding guide with the same curvature as the Roland circle, and the center of rotation 11 is
passing above. A slit unit 9 straddles the guide 10 and is slidable along the guide. Reference numeral 6 is a feed screw attached to the board B approximately parallel to the guide 10, and the third gear 3 connects the bevel gears 4 and 5.
It is rotated through. Numeral 7 is a nut screwed onto a feed screw and pushes a bar 8 protruding from the slit unit 9. With this configuration, the first
By rotating the gear 1, the slit unit 9 can be moved along the guide 10. In this mechanism, the guide 10 is an arc with the same curvature as a Rowland circle, making it difficult to work with.Also, since the slit unit slides along this curved guide, it is more likely to wobble than in the case of a straight guide, resulting in poor precision. It is difficult to obtain good equipment. Further, the slit unit has a certain relationship with the tangential direction of the guide 10, and the normal line of the slit surface does not point toward the center of the diffraction grating except at a specific position, which causes an optical problem. The present invention attempts to eliminate such drawbacks of the conventional example.

FIG. 3 is a diagram explaining the principle of the present invention. S
1 is an entrance slit, and G is a diffraction grating. T is a linear guide that passes through the center of the entrance slit S1 and is rotatable about an axis perpendicular to the plane of the drawing. can be slid. The angle θ is constant. By driving the exit slit S2 along the guide T by a mechanism not shown and rotating the guide around its fulcrum, the center of the exit slit S2 can be moved along the Rowland circle R. . Under such a relationship, the angle ψ between the guide T and the straight line connecting the center of the grating G and the center of the exit slit S2 at any position of the exit slit S2 as shown in the figure is on the chord S1-G in the circle R. Since it is the circumferential angle that spans S2
is constant regardless of the position of Output slit S2
The surface is inclined by θ with respect to the guide T, and since θ is also constant, ψ+θ is also constant, and θ can be set so that ψ+θ=right angle. By doing this, the exit slit S2 will always move on the Rowland circle R while keeping its surface on the diffraction grating G.
can be directed towards the center of Considering the case where the exit slit passes over the input slit and reaches position S2' in the figure, in this case the linear guide is
Since it is located at T' and the exterior angle of the circumferential angle of chord S1-G is ψ, the relationship that the surface of S2' faces the center of the lattice G is maintained. The above is the principle of the present invention.

FIG. 4 shows an embodiment of the present invention. B is a board that can rotate within the paper plane of the figure around a fulcrum 11. The fulcrum 11 passes through the center of an elongated entrance slit (not shown) in a direction perpendicular to the plane of the drawing. An arm 12 protrudes from the board B, and the tip of the arm 12 is connected to the feed screw 13.
The substrate B can be rotated about the fulcrum 11 by rotating the feed screw 13 with a motor (not shown). The substrate B is provided with a linear guide 14 and a feed screw 6 parallel to the linear guide 14. Reference numeral 9 denotes an output slit unit which is screwed into the feed screw 6 and abuts against the guide 14, and is moved along the guide 14 by rotation of the feed screw 6. An output slit S2 is mounted on the slit unit 9.
The surface of the exit slit S2 is at an angle θ with respect to the feed screw 6.
It is installed only at an angle. Output slit S2
The movement locus of the center is parallel to the feed screw 6 and corresponds to the guide T in FIG. Feed screw 6 is gear 1
5. Rotated by a motor (not shown) via bevel gears 4 and 5. The center of the rotation axis of the bevel gear 4 coincides with the fulcrum of the board B, and even if the board B is rotated, the rotation can be transmitted to the feed screw 6 without any problem. The motors driving the feed screws 6 and 13 are different and are each driven by pulses.
By predetermining the relationship between the number of pulses applied to each motor and controlling it by a computer, the exit slit S2 can be moved along an assumed Rowland circle.

The spectroscopic device of the present invention has the above-described configuration, and since a curved guide is not required, it is easy to work and can easily obtain high accuracy, and a spectroscopic device with little mechanical rattling and high accuracy as a whole can be obtained. Furthermore, the normal to the slit surface can be automatically and always directed toward the center of the diffraction grating without using any special mechanism.

[Brief explanation of drawings]

Fig. 1 is a schematic plan view of an off-plane Eagle type spectrometer, Fig. 2 is a plan view of a conventional device, Fig. 3 is a plan view showing the principle of the present invention, and Fig. 4 is a schematic diagram of an embodiment of the device of the present invention. FIG. S1...Incidence slit, S2...Output slit, G...Diffraction grating, B...Substrate, 6...Feed screw, 9...Slit unit.

Claims (1)

[Claims] 1 During wavelength scanning, in a type of spectrometer in which the exit slit is restrained to move along the Rowland circle, the exit slit has a fulcrum at a point on the Rowland circle within the movement range of the exit slit on the Rowland circle. The diffraction grating is slidable along a linear guide that can be rotated by the diffraction grating, and is tilted at a certain angle with respect to the guide so that the normal to the slit surface erected at the center of the exit slit is directed toward the center of the diffraction grating. A spectroscopic device.