SU1094432A1 - Spectrograph - Google Patents

Abstract

EPECTROGRAPH, containing sequentially located on the optical axis of the entrance slit, a concave diffraction grating with curvilinear strokes and a variable distance between them and a recording device, so that in order to increase the aperture ratio of the spectral range and improve image quality, lattice strokes are made with a radius of curvature f: p 1.56 g + 1.1 y, the variable distance between strokes 1 is chosen according to the ratio 1 (y) 1 °

Description

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The present invention relates to the field of optical instrumentation and can be used to create spectral instruments.

Spectrographs with flat diffraction gratings mounted in parallel beams are known.

Such spectrographs contain successively located slits, a collimator lens, a flat diffraction grating, a chamber lens, and a three-dimensional device. However, the use of collimating and focusing optics leads to a decrease in the transmission light, an increase in the level of scattered light, an increase in size and cost of the instrument.

The closest in technical essence and the achieved result to the proposed spectrograph is a spectrograph containing an entrance slit sequentially arranged along the optical axis, a concave diffraction grating with curvilinear strokes and a variable distance between them and a recording device.

The disadvantage is a small luminosity, an increase in the values of aberrations with an increase in the relative aperture, since in this spectra graph there are no aberrations minimized.

In addition, the correction capabilities of this spectrograph significantly reduce the need for a flat surface of focusing the spectrum, which, in turn, leads to a narrowing of the working spectral range.

The aim of the invention is to increase the aperture ratio, broaden the spectral range and improve image quality.

This goal is achieved by the fact that in a special tropograph containing a series of entrance slits along the optical axis, a concave diffraction grating with curvilinear strokes and a variable distance between them and a recording device, strokes and grids are performed; with radius of curvature fi p 1.56g + 1.1y,

  l

the variable distance between strokes 1 is selected according to the ratio 1 (y) 1 (1-2,2-to- y +

+ 0.8 -Y- y - 10-®UZ),

, and the lattice is located at a distance of 0.8 g from the slit and at a distance of 0, 95 g from the recording device, where

g is the radius of curvature of the lattice;

y is the coordinate in the meridional section of the lattice;

Ij, is the distance between the strokes in the center of the lattice.

Figure 1 shows the optical axis of the spectrograph; figure 2 is a view along arrow a in figure 1

The spectrograph contains an entrance slit 1, a concave diffraction grating 2, a recording device 3

The slit is set at 0.8g from the top of the lattice, and the image surface is at 0.95g and has the shape of a cylindrical segment with a radius equal to O, 52g. The strokes of the lattice have a radius p of 1j56r - 1.1y, and the lattice spacing changes according to the law

1 (y) 1, (1-2.2-10 y + + 0.8 -10 yg - 10H).

The operation of the device is as follows.

The radiation transmitted through the entrance slit 1 falls on the diffraction grating 2. The diffracted beam is focused on the surface of the image, which has the shape of a cylindrical segment with a radius of 0.52 g.

The specified choice of the design parameters of the spectrograph at a given mutual position of the circuit elements provides for the correction of the astigmatism of the meridional coma for two wavelengths A. d

i. average wavelength range; BUT, ,

j are the extreme values of the wavelengths, and the correction of the sagittal coma and the spherical aberration of the third order in the center of the working range. The lattice can be made both by mechanical cutting and holographic. To obtain such a lattice by the holographic method, when recording the lattice, cylindrical lenses must be placed between the workpiece and point sources, which increases the number of parameters to be corrected.

Such an implementation of the spectrograph will allow to obtain a high quality spectrum with a large relative aperture in a wide spectral range.

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Claims (1)

A SPECTROGRAPH containing an entrance slit sequentially arranged along the optical axis, a concave diffraction grating with curved strokes and a variable distance between them, and a recording device, which is based on the fact that, in order to increase the light intensity, expand the spectral range and improve quality images, strokes of the lattice made with a radius of curvature? : p = 1.56 g + 1, 1y, variable distance between strokes * 1 is selected according to the ratio 1 (y) = 1 ₀ (1-2.2-10 * y + + 0.8 y ² - 10 ® y ³ ), and the grating is located at a distance of 0.8 g from the gap and at a distance of 0.95 g from the recording device where r is the radius of curvature of the lattice; y is the coordinate in the meridional section of the lattice; 1 ₀ - the distance between the strokes in the center of the lattice.