SU1295211A1 - Interferometer for checking shape of aspherical surfaces - Google Patents

Abstract

This invention relates to a measurement technique. The purpose of the invention is to control surfaces with a large gradient of asphericity. The interferometer includes a rotating scanning head consisting of lighting and measuring systems and of a beam splitter 7, test spherical glass y, 23 in the form of a concentric meniscus, the center of curvature of the reference surface of which is aligned with the image of the center of the aperture 3 of the lighting system. The input system 9 and the output lens 11 are installed in the measuring system so that the focus of the input lens 9 is aligned with the reference surface of the test glass 23. The relative aperture of the input lens 9 of the measuring system is made at least twice the relative aperture of the output lens 6 of the lighting system. The splitter 7 is installed between the output lens 6 of the lighting system and the test glass 23. 1 sludge. 10 s (C (L s

Description

11.2

The invention relates to a measurement technique and can be used, in particular, to control the shape of aspherical surfaces.

The purpose of the invention is to control surfaces with a large gradient of asphericity due to the implementation of the measuring system of the interferometer as a separate optical system with

at the same time increasing the Nose input lens of the input lens compared with the relative aperture of the output lens of the Illumination System and combining the focus of the input lens of the interferometer measurement system with the reference surface of the test glass, which reduces the vignetting of the interfering beams and improves the image quality of the measuring system regardless of the position of the interference pattern relative to the input - Go pupil interferometer.

The drawing shows an optical interferometer design for controlling the shape of aspherical surfaces.

The interferometer contains a re-scanning head consisting of

lighting and measuring systems

The illumination system consists of a monochromatic light source 1 located along the beam of the condenser 2, diaphragm 3, input lens 4, flat mirror 5, output lens 6, beam splitter 7. Diaphragm 3 is set in the focus of the input lens 4, its image (input the interferometer pupil) is in the focus of the output lens 6 and is aligned with the axis 00 of rotation of the scanning head.

The measuring system consists of a flat mirror 8, an input lens 9, a flat mirror 10, an output lens 11, flat mirrors 12 - 4 grids 15 and an eyepiece 16, a switching-state flat mirror 17, a diaphragm 18, a diverging lens 19 and a photodetector 20. Relative the opening of the input lens 9 of the measuring system exceeds at least two times the relative aperture of the output lens 6 of the lighting system.

Lifting table 21 is used to install the test piece 22 and a spherical test glass 23. De, tal 22 and test glass 23 on

five

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The power of table 21 is set so that the center of curvature of the reference surface of the test glass 23 is aligned with the exit pupil of the interferometer.

Parts 22 and 24 and test glasses 23 and 25 are shown when inspecting a part with concave and convex surfaces, respectively.

The interferometer works as follows.

The light from the monochromatic source 1 by the condenser 2 is directed to the diaphragm 3 installed in the focus 7 of the input lens 4 of the lighting system. Using a flat mirror 5, an output lens 6 and a splitter 7, the image of the diaphragm 3 is formed at the focus Fg of the lens 6, aligned with the axis 00 of rotation of the scanning head. The rays did not penetrate the test spherical glass 23, since the center of curvature of the reference surface of the test glass 23 is combined with the image of the aperture 3 of the lighting system and, reflecting from the etched surface of the test glass 23 and the controlled surface of the part 22, interfere to form an interference pattern localized in the air gap between the reference surface of the test glass 23 and the part 22. The interfering rays, having passed the beam splitter 7 and having reflected from the flat mirror 8, fall into the input lens 9 measuring system, the focus of which is combined with the surface of the localization of the interference pattern. Using an iO flat mirror, an output lens 11, flat mirrors 12-14, the image of the interference rings is projected into the focal plane of the lens 11 where the f5 grid is placed, and viewed with an eyepiece 16. A flat mirror 17 is inserted into the beam path. , the interference rings are projected into the plane of the diaphragm 18 located in the focal plane of the lens 11. The scattering lens 19 serves to evenly distribute the light flux over the working surface of the photodetector 20, using a co orogo manufactured measurement of the radii of the interference rings.

To ensure the required image quality

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The system, regardless of the sign and magnitude of the radius of curvature of the reference surface of the test glass, of the input lens 9 is adapted to move along the optical axis in order to displace the focus of the objective 9 with the localization surface of interference rings. The implementation of the interchangeable lens 9 (with different focal lengths) makes it possible to further expand the range of the vertex radii of the surfaces to be tested. To increase the sensitivity of the measurement of the radii of the interference rings, the increase in the system of lenses 9 and P of the measuring system is at least 1.

The interferometer makes it possible to control aspherical surfaces with a gradient of up to 27 µm / mm for surfaces with radii of the nearest sphere within ± 300 mm and up to 20 µm / mm for surfaces with radii of the nearest sphere from -600 to -300 mm. The magnification of the lenses of the measuring system is 2 for surfaces with radii of the nearest sphere within ± 300 mm and 1.5 for surfaces with radii of the nearest sphere from -600 to -300 mm.

Claims (1)

Invention Formula An interferometer for controlling the shape of aspherical surfaces, containing a scanning head consisting of a lighting system including a sequentially installed monochromatic light source, Editor M.Blanar. Order 608/46 Compiled by L. Lobzova Tehred A. Kravchuk Corrector o Circulation 678 Subscription VNIIPI USSR State Committee for inventions and discoveries 113035, Moscow, Zh-35, Raushsk nab., 4/5 Production and printing company, Uzhgorod, Projecto st., 4 0 five 0 five 0 five condenser, diaphragm, input and output lenses that form the image of the center of the diaphragm on the optical axis of the lighting system, from the measuring system with a recording unit and from the beam splitter, combining the optical axes of the lighting and measuring systems into the optical axis of the scanning head, and installed with the possibility of rotation around the axis, perpendicular to the optical axis of the scanning head and intersecting it at the point of the image of the center of the aperture of the lighting system, and test spherical glass at the end tricar meniscus located so that the top of its reference surface is aligned with a plane perpendicular to the axis of rotation of the scanning head and passing through its optical axis, and the center of curvature of the reference surface is aligned with the image of the center of the aperture of the lighting system, characterized in that control surfaces with a large gradient of asphericity, it is equipped with a second input and output lenses located in the measuring system so that the focus of the second input lens is aligned with the reference the test glass surface, the second input lens is made with a relative aperture greater than at least two times the relative aperture of the output lens of the lighting system, and a beam splitter is installed between the output lens of the lighting system and the test glass. Proofreader O.Lugov