Clocking-optimization method for figure-error balancing in complex optical systems

Figure errors of optical surfaces degrade the performance of optical systems. When predicting the performance and performing system assembly, compensation by clocking of optical components around the optical axis is a conventional but user-dependent method. Commercial optical software cannot optimize this clocking, and existing automatic figure-error balancing methods have limitations. To overcome these limitations, a global and general optimization method based on analyzing the precise relationships between the figure errors and the wavefront error (WFE) is proposed. Using the footprint data of each optical surface, the resulting WFE is calculated. Direct map operation is used for intercepting and rotating the figure-error maps. The simulated annealing algorithm is used to seek the optimal combination of clocking angles for the optical components. This method can be applied to most coaxial optics systems, including dioptric, catoptrics, and catadioptric complex lenses. It is successfully implemented for a catadioptric immersion lithographic optics system with artificial figure errors, and for an experimental lithographic optics system with actual manufacturing figure errors.