Error analysis of spherical scanning mechanism used for surface defects detection

Subaperture stitching method is used for optics surface defects detection by defects imaging. Stitching based on position is efficient while stitching error induced by the error of the scanning mechanism may cause defects dislocation. According to the stitching error analysis of spherical optics defects, a method based on Monte Carlo simulation is proposed in this paper. Firs t the volumetric error model is established based on mult ibody system theory. On this basis, the stitching error model is established and applied to compute error by Monte Carlo simulation. Analyze error and then define the tolerance of the scanning mechanism to limit stitching error. Simulation results of an optical element whose diameter is 60mm show that the scanning mechanism should satisfy that the positioning accuracy and straightness in Y direction of X axis, the run-out errors in X and Y direction of B axis, and the verticality between X and Y axis are less than 1μm, the run-out errors in X and Y direction of C axis are less than 2.8μ m, the run-out errors of B and C are less than 4.6μm. Under such conditions, the stitching error will be less than 10μm.