SU746232A1 - Zero-aperture compensator for monitoring large-telescope astronomic-mirrow surface shape - Google Patents

Description

The invention relates to the field of optical instrument making and can be used to control the shape of concave parabolic, hyperbolic and elliptical mirrors of large telescopes, in particular, the main mirror with a diameter of six meters of the world's largest optical telescope BTA.

Known compensators for counterfl astronomical mirrors flJ.

The most important characteristic of the quality of an astronomical mirror is that its theoretical form reflects the reflective surface of the mirror. The overwhelming majority of compensators have a final aperture, i.e. convert the spherical wave front to aspherical. Apply such. Compressors in interferometers require the use of either a lens that creates a spherical wavefront or a dividing cube installed in a convergent beam of rays. These additional elements (a lens or a cube) introduce errors into the results of the control, reducing its reliability and accuracy.

The closest to the invention according to the technical essence is a compensator for controlling the quality of astronomical mirrors 2, consisting of two lenses: meniscus, facing towards the center of curvature of the monitored mirror and having equal radii of curvature, and two convex, constructive parameters of which are associated with parameters of the meniscus lens a certain ratio. The optical powers of both lenses are non-zero and have positive values.

15

In a known compensator, the light source is installed in the front focus of the first meniscus surface, i.e. the aperture of the compensator is not zero, which is its disadvantage,

20 since it requires the use of additional optical elements that reduce the reliability and accuracy of control.

The aim of the invention is to increase the reliability and accuracy of control.

25 forms of astronomical mirrors of large telescopes.

. This goal is achieved by the fact that the meniscus is made afocal, and the second positive lens in the form

thirty

meniscus, both meniscus facing concavity to the light source, located 9 infinity.

The drawing shows the compensator and the scheme of its application, as well as the course of the extreme and paraxial rays.

Here, 1 is the meniscus lens, the optical power of which is zero (afocal lens), 2 is the meniscus -positive lens, 3 is the controlled astronomical mirror. Co is the center of curvature at the apex of the mirror. 3 Fg is the rear paraxial focus of the compensator, combined with point C.

The compensator follows the same way.

A parallel beam of rays going into the working branch of the interferometer enters the afocal lens 1, after which the paraxial rays go exactly parallel to the optical axis, and the de-rays form a converging beam of rays. A positive meniscus lens 2 converts a beam of rays incoming to it into a converging beam, all the rays of which are directed strictly along the normal to the theoretical surface.

monitored mirror 3. Reflecting from the latter, the rays of light repeat their path in the opposite direction and create a WAVE front carrying information about the quality of the monitored mirror.

Claims (2)

1.Pur ev D.T. Control methods . Optical aspherical surfaces, M., Mashinostroenie, 1976, p. 10-27. 2. USSR author's certificate 5 № 508671, cl. G 01 B 11/30, 1973 (prototype).