Research on detection method of large-aperture aspheric surface by laser tracker

In the grinding stage of large-aperture aspheric mirror, the geometric parameters should be measured accurately, and the surface shape should also meet certain accuracy requirements. By means of numerical simulation of the test process, the accuracy of measuring geometric parameters and surface shape using three-coordinate measuring machine (3-CMM) and laser tracker was evaluated. An effective contour detection method was proposed to meet the requirements of the detection index of a 2 m-aperture parabolic mirror. Four laser trackers were used to build a multilateral measurement system, the Levenberg_Marquardt algorithm was used to calibrate the system, the new target ball was used to realize the synchronous and rapid acquisition of mirror points by multiple trackers, and the test data were adjusted and coordinate system transformation was processed. Finally, the geometric parameters and surface shape were obtained. After grinding, the 2 m-aperture parabolic mirror was tested. The errors of vertex curvature radius, aspheric coefficient and surface shape RMS are 0.16 mm, 0.000 6 and 1.06 μm, respectively.