Method for measuring plane mirror absolute surface shape based on conjugate difference method

Abstract

The invention discloses a method for measuring plane mirror absolute surface shape based on a conjugate difference method. The method comprises the following steps: a plane mirror to be measured and a standard plane mirror forming interference images on a CCD of an interferometer respectively, judging the sizes of light spots of the plane mirror to be measured and the standard plane mirror formed on the CCD of the interferometer and enabling the light spot of the standard plane mirror to be larger than the light spot of the plane mirror to be measured; determining translation amount delta of the plane mirror to be measured corresponding to one pixel in the CCD of the interferometer, delta>0; defining the direction of optical axis of the interferometer as the z axis and carrying four-step test in the positive and negative directions of the x axis and y axis respectively and recording wavefront data phi (x+delta, y), phi (x-delta, y), phi (x, y+delta) and phi (x, y-delta) respectively; obtaining surface shape gradient of the plane mirror to be measured according to the measured wavefront data; and recovering the surface shape w of the plane mirror to be measured according to the surface shape gradient of the plane mirror to be measured by utilizing a wave surface recovering method. The method improves precision of differential approximation and prevents coupling between step-by-step tests, thereby improving stability of the test; and the method can also be used for measuring the absolute surface shape of a cylindrical mirror, a conical mirror and a spherical mirror.

Description

technical field [0001] The invention belongs to the technical field of absolute detection of plane mirrors, in particular to a method for measuring the absolute surface shape of a plane mirror based on a conjugate difference method. Background technique [0002] At present, the research on the absolute detection of plane mirrors mainly includes the three-plane mutual detection method, the liquid level reference method and the difference method, that is, the pseudo-shear method. The traditional three-plane mutual inspection method cannot obtain the two-dimensional surface shape of the entire plane of the surface to be tested, but can only obtain the situation of a line. The improved method can obtain the surface shape of the entire surface, but the testing process is very complicated; The surface reference method uses a liquid flat crystal as the standard surface, but the liquid surface reference is difficult to manufacture, requires high environmental conditions and is not e...

AI Technical Summary

Problems solved by technology

The traditional three-plane mutual inspection method cannot obtain the two-dimensional surface shape of the entire plane of the surface to be tested, but can only obtain the situation of a line. The improved method can obtain the surface shape of the entire surface, but the testing process is very complicated; The surface reference method uses a liquid flat crystal as the standard surface, but the liquid surface reference is difficult to manufacture, requires high environmental conditions and is not easy to move, and the systematic error in the test results cannot be eliminated; The three positions have a coupling relationship with each other. It is necessary to maintain the stability of the environment and other factors in the three tests to ensure the constant static error, but the external environment and other factors are difficult to control, and it is difficult to maintain its stability, so it is difficult to ensure the constant static error, which affects the difference method. detection accuracy

Images