SU996873A1 - Diffraction monochromator - Google Patents

Description

The invention relates to spectral instruments, and more specifically to monochromators with double dispersion, and can be used in optical devices for obtaining monochromatic radiation and, as well as in spectrometers for the ultraviolet region of the spectrum.

Known diffraction monochromators with the addition of the dispersion of two concave diffraction gratings}

In these devices, focusing of radiation beams dispersed from the gratings occurs near the Rowland circles, which limits the relative aperture and luminosity of the device. On conventional spherical diffraction gratings, the largest relative aperture (up to 1: 8) is monochromators, in which the angle between the incident and diffracted beam is about 70. But devices of this type have very large astigmatism (up to 0.7 from the height of the lattice line), which ultimately causes a decrease in the flux of radiation emerging from the monochromator. The smallest aberrations are possessed by normal-fall spectral instruments, but in this case

relative opening of the device is not more than 1:12.

The closest to the proposed technical solution is a diffraction monochromator, which contains two concave diffraction gratings in the entrance and exit slits, kinematically connected with the scanning mechanism and installed on their front sides.

10 to each other and vertices on a common optical axis U 2.

The disadvantage of this monochromator is the limited working spectral region, low relative separation and light transmission.

The purpose of the invention is to expand the working area of the spectrum, increase the relative aperture and increase the light transmission MOHOxpoMiaTopa,

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Claims (2)

This goal is achieved by the fact that, in a monochromator containing an entrance and exit slit, two concave diffraction gratings, kinematically connected with the scanning mechanism and set facing to each other and the vertices on a common optical axis, the gratings are made with holes in their central the zones, the entrance and the exit slits are combined with the focal surfaces of the gratings and are located on the optical axis that is common with the vertices of the gratings, and the scanning mechanism is designed so that it provides the possibility of synchronous reversal of the grids. In addition, to eliminate the illumination of the exit slit by direct radiation not directly spreading into the spectrum on the optical axis MOHo: ipoMaTopa, an opaque screen is installed between the array. The drawing shows an optical monochromator circuit. The monochromator contains an entrance slit 1, concave grids 2 and 3, the vertices of which are located on the axis passing through the entrance 1 and the exit slit. The gaps are fixed. Lattices 2 and installed on the front sides are met and kinematically connected with the skulling mechanism 5, which performs a synchronous reversal of the lattices. There are holes in the center of the gratings for input and output of radiation. An opaque screen 6 is installed between the gratings on the optical axis. The device operates as follows. The radiation through the entrance slit 1, installed in the focal plane of the grating 3, is directed by a diverging beam to the grating. The grating 3 gives a diffraction radiation spectrum in the form of parallel beams, arranged depending on the radiation wavelength at different angles to the front side of the grating. Monochromatic parallel beams of radiation are incident on the grating 2, are again dispersed by it and are focused by the same grating on the exit slit 4. Spectrum scanning is performed by synchronous rotation of gratings 2 and 3 towards each other around the axes O to O, passing through their vertices parallel to the strokes. The angle of the gate of the gratings is simultaneously the angle of incidence and diffraction. Therefore, the main wavelength at the output of the monochromator is 2o S t pd where A is the main wavelength; a is the lattice constant; 1 angle of grating rotation; K is the order of the spectrum. The focus of the spectral image in this case is described by the simple equation. -J, e e iso5d where t is the distance from the entrance slit to the top of the collimating lattice 3; the distance from the top of the focusing lattice 2 to the meridional focus, r is the radius of spherical lattices. The defocusing that occurs when the grids 2 and 3 are rotated is completely eliminated if the vertices of the gratings are simultaneously shifted according to the law Lj created. Such a scanning method is easily performed by a cosine mechanism. When working in a vacuum ultraviolet, in narrow spectral regions x /, r 3, and in cases where individual requirements for the instrument are lowered, defocusing of the spectrum can be neglected and scanning can be performed by simply turning the grids. An opaque screen 6 is inserted into the monochromator design prevents direct illumination of the exit slit. To reduce the light diffraction, this screen is best performed in the form of a polar cone, which is an effective trap of undecomposed radiation. The working area of the monochromator covers the entire ultraviolet, the relative aperture in the proposed monochromator using conventional spherical gratings of not less than 1: 6. The proposed device uses the minimum number of optical surfaces in the presence of double dispersion. Therefore, the light transmission of the monochromator is several times higher than that of the existing structures, and is determined only by the diffraction gratings efficiency. The positive qualities of the device should also include its constructive compactness. The largest linear dimension slightly exceeds half the radius of curvature of the lattices. Thus, the holes in the diffraction gratings allow the monochromator elements to be placed on one optical axis and reduce to a minimum the number of optical surfaces of the proposed monochromator with double monochromatization, as a result of which the spectral range of the instrument is expanded and the light transmission increases. Installing the input and output slits in the focal points of the diffraction grating Doubles the relative aperture of the monochromator. DETAILED DESCRIPTION OF THE INVENTION A diffraction monochromator comprising an entrance and an output slit, two concave diffraction gratings, kinematically associated with a scanning mechanism and set up by the front sides to each other and the vertices on a common optical axis, i.e. so that expanding the spectral range, increasing the relative aperture and transmitting the instrument, the grids are made with holes in their central zones, the entrance and output slits are aligned with the focal surfaces of the grids and placed on the optical axis common with the vertices of the gratings, and the scanning mechanism is designed so that provides a cart There is a synchronous counter reversal of the grids. Sources of information, which are considered in the examination 1. Zaydel A.I., Shreyder E.Ya. Vacuum spectroscopy and its application. M., Science, 1976, p. 174 .. 2. USSR author's certificate 504100, cl. G 01 J 3/18, 1974.