Simulation analysis on absolute measurement of flat with multiple translation method

The precision of flat measured by relative interference is limited by the precision of standard transmission flat. The absolute measurement method can improve the measure precision by removing the error of standard transmission flat. The absolute measurement of plat with multiple translation method is an effective way to test plat surfaces with high accuracy. The surface under test can be expressed by polynomial function. Different surface profile is obtained by orthogonally shifting the tested flat in two directions orthogonal，then the absolute surface is gained by fitting of polynomial coefficients using the least squares. The theory formula of multiple translation method is deduced，and the error caused by number of sampling points, times and interval of translation are analyzed using the simulation. The results of simulation show that the root-mean-square(RMS)of residual figure error is 5.11810-13.Thus the method can realize high accuracy measurement of flat surfaces.