Large telescopic optical system with null alignment optics

摘要

An optical system for monitoring an alignment state of a large telescope comprises a primary mirror and an annular null mirror which is placed at the outside of a secondary mirror. The optical system functions as a null system, where the wave front of the reflected rays from the null mirror is consistent with the surface shape of the primary mirror in regional band. Since the null system uses a small annular lens on the outside of the secondary mirror, it has the advantages of light weight and small overall size.