Abstract: The surface error of aspheric mirror during grinding ranges from tens of microns to a few microns, proper measurement method will decide the convergent speed and precision of the error in this range. The form error digitization technique is thoroughly analyzed in view of the grinding process, and the linearity error matrix that affects error contraction accuracy is also established. Moreover the matrix is testified utilizing a co-axis parabolic mirror after magnetorheological finishing with figure accuracy of 60 nm (Root Mean Square, RMS), the testing result shows the matrix has good effect to remove line-arity error and provide exact data information, guarantees the testing results closely link with the manufacturing process and decreases the cycles entering into optical polishing process.

Key words: Asphere, Fine lapping, Magnetorheological, Polishing, Profile measurement