Off-Axis catadioptric partial compensator design for interferometric measurement of optical freeform surface

Optical freeform surfaces have been widely used in optical systems owing to their design degrees of freedom, which can simplify the structure and improve the performance of optical systems. High accuracy testing for freeform surface is needed due to the improvement of machining accuracy. However, it is still a challenge to achieve high measuring accuracy because freeform surfaces lack rotational symmetry. In this paper, an off-Axis catadioptric partial compensator (OACPC) design for non-null interferometric method is proposed to measure freeform surface. The design of OACPC consists of two parts: constructing initial structure and optimizing. The initial structure is obtained by the vector aberration theory and PW method. Based on the initial structure, the OACPC is generated by modelling and optimizing in the optical design software. In order to verify the feasibility, universality and effectiveness, a design example is given. Theoretical analysis and simulation results demonstrate that the design can realize the measurement of freeform surfaces.