An off-axis Golay3 sparse aperture telescope with a freeform secondary mirror

摘要

The application of freeform surface in an optical system can effectively increase the freedom of optical design and reduce the number of optical elements. In this work, a two-mirror off-axis sparse aperture telescope is proposed. The primary mirror is made of three sub-mirrors arranged in the Golay3 configuration while the secondary is a freeform surface defined by a polynomial of two variables X and Y. The off-axis configuration is used to remove the obstruction of the secondary mirror. The results indicate that the fill factor of the Golay3 primary mirror increases to 58.4%, which is significantly higher than that of the on-axis configuration. The image quality is improved within 2.5 degrees full field of view from its spot diagram, distortion, modulation transfer function, and encircled energy.