Design of large off-axis aberration correction system for liquid mirror telescope based on MFDM and concave mirror

As an important branch of astronomical observation equipment, liquid mirror telescope (LMT) has the advantages of low manufacturing cost and simple implementation compared with solid-state telescope. However, due to the structural characteristics of liquid mirror telescope, it can only observe the fixed zenith area, and be hard to complete the real-time tracking of the established target. In order to expand the application range of LMT, off-axis aberration correction has become an inevitable core topic in practical astronomical observation. Based on the adaptive optical system with off-axis angle of 20° and LMT radius of 1m, a Paul-Baker aberration correction system based on magnetic-fluid deformable mirror (MFDM) is designed according to the characteristics of large off-axis aberration. The off-axis aberration is first simulated according to ZEMAX and MATLAB simulation software, and the low-order aberration is corrected by concave mirror. According to the characteristics of residual aberration, a waveform corrector MFDM is designed to linearize the response under the action of large magnetic field generated by Maxwell coil, so as to correct the high-order aberration. The performance of the designed coil is simulated and verified by COMSOL simulation software. The results show that the dual mirror system which designed in this paper can obtain better correction effect under large off-axis angle.