Method for Expanding Field-of-View of Cassegrain System with Computational Imaging

The structure of Cassegrain optical system severely limits its field of view (FOV). Generally, additional optical elements arc needed to expand the FOV, but this approach leads to a complicated structure and does not facilitate a miniaturized and lightweight optical system. In this paper, a new method to expand the FOV of Cassegrain system using computational imaging was proposed. First, the structural parameters of the system were optimized to control the aberrations; then, a point spread function model was established; finally, a deconvolution algorithm was used to process the image. Eventually, the FOV of the Cassegrain system could be expanded using the structure that only comprised primary and secondary mirrors. A simulation experiment was conducted wherein a Cassegrain system with an F of 5.5 and 470-mm focal length was developed. The experimental result shows that in the FOV of 1.5 degrees, the off-axis FOV modulation transfer function of the processed image is approximately improved by 0.2 at 20 lp/mm. Moreover, the quality of the image is significantly improved.