Abstract:
In order to obtain an accurate vertex radius of large-diameter, off-axis aspheric mirrors, a method to determine the geometric parameters of aspheric optical surface based on surface fitting was presented. The accurate aspheric equation under the measuring coordinate system was constructed and an iterative nonlinear least-squares fitting algorithm was given here. Besides, the end surface of the compensator was used to derive the direction of optical axis and then to give appropriate initial values of the surface fitting. The experiments on measured data show that R-square is close to 1 while the root mean square error(RMSE) is about 0.002 6 mm. At the same time, the deviation of the calculated result from the designed value is just 0.018 8% for vertex radius. The method can be utilized to measure and analyze the geometric parameters of aspheric surface-vertex radius for example. It can provide valid data support for the following optical-mechanical assembly.