Description and tolerance analysis of freeform surface figure error using specific-probability-distributed Gaussian radial basis functions

Freeform surfaces have important applications in optical design. However, the complex surface figure error of freeform imaging systems affects the performance of as-built systems. In this paper, a method for the representation and tolerance analysis of the freeform surface figure error using a sum of specific-probability-distributed Gaussian radial basis functions is presented. This method is easy-used and practical. In addition, the actual manufacturing difficulty of different areas of the freeform surface is considered. Tolerance analysis of a nonsymmetric freeform off-axis three-mirror system was performed, including considering only the surface figure error, as well as an overall tolerance analysis considering both figure error and assembly error. The results demonstrated the effectiveness and feasibility of the proposed method.