Optical Path Design for Catadioptric Star Sensor with Large Aperture

In order to improve the ability of the star sensor to detect limited magnitude,a combination of the improved Cassegrain system,aperture-corrected spherical lens group and field-of-view corrected spherical lens group is adopted to design an optical system of a large aperture catadioptric star sensor capable of correcting astigmatism,field curvature and distortion,with the spectral range of 450～950 nm,the semifield of 1.4°,an entrance pupil diameter of 250 mm and the focal length of 425 mm.According to the calculation of the initial structure parameters of the system based on the aberration theory and the optimization design of Ray tracing in Zemax software,the blocking ratio of the secondary mirror of the optical system reaches 0.43,the energy concentration of the imaging point is 80% within30μm,and the maximum distortion is 0.081%.The modulation transfer function is greater than 0.75 at a Nyquist frequency of 34 lp/mm,and the maximum magnification chromatic aberration is 1.138μm,which meets the imaging requirements of star sensor pairs.Through the tolerance analysis of optical system,in the 20 Monte Carlo analysis results,the best structure is the 13 th structure with the performance function of 4.975 16μm,the worst structure is the 20 th structure with the performance function of 7.799 57μm.Through the performance function analysis of 20 times Monte Carlo structure,the selected tolerance value can well meet the basic requirements of optical system performance,and provide the basis for the errors in the process of processing and installation.

This article is based on a combination of R-C system, aperture corrected spherical lens group, and field of view corrected spherical lens group. A large aperture refractive star sensor optical system is designed with an inlet pupil diameter of 250mm, a half field of view of 1.4 °, a spectral range of 450-950nm, a focal length of 425mm, and the ability to correct astigmatism, chromatic aberration, and distortion. The secondary lens obstruction of this optical system is 0.43, and 80% of the energy is concentrated in 30 μ Within m, the maximum distortion is 0.081%, the optical transfer function MTF is greater than 0.75 at the Nyquist frequency of 33.3lp/mm, and the maximum magnification color difference is 1.138 μ m. The final design results indicate that the image quality of the entire optical system is good, with uniform scattered spots in all fields of view and good roundness. The size of the scattered spots is controlled within the required range, meeting the imaging requirements of star sensors for star detection. Through tolerance analysis, it can be seen that the selected tolerance value can well meet the basic performance requirements of the optical system. Among the performance functions of the 20 Monte Carlo structures, the performance function is less than or equal to 7.509 63 μ The structure of m is 90%, and the performance function is less than or equal to 7.303 33 μ The structure of m has 80%, and the performance function is less than or equal to 6.310 13 μ The structure of m has 50%, and the performance function is less than or equal to 5.389 58 μ The structure of m has 20%, and the performance function is less than or equal to 5.136 95 μ The structure of m has 10%, and the tolerance is compensated by changing the back focus, with a change range of -0.32~0.17mm