Research on Partial Null Compensator with Double-sided Switching Off-axial Reflector

Wavefront-based aspheric metrology techniques generally require a compensation lens to compensate for the primary aberrations. To expand the adaptability of the surface to be tested, this paper proposes and demonstrates a partial null compensator structure that can switch between the front and back mirror sides. The presented compensator comprises two sets of off-axis reflecting parts and a pre-compensation spheric lens in an integrated structure. An appropriate off-axis reflection combination mode can be selected for the range of the conic coefficient of the measured surface. With the simulation result, the presented compensator can adapt to a large-scale variation of the surface conic coefficient K from -10 to +10. The average residual wavefront aberration is no more than 1 lambda(PV)and 1/4 lambda(RMS). The results show that the proposed structure can be efficiently applied to wavefront detection or interferometer for data post-processing.