Design of an optical system for sub-reflector measurement of large-aperture antennas

In response to the state measurement requirements of the sub-reflector of large-aperture antennas of radio telescopes, this paper adopts the visual imaging measurement method to solve this problem and designs a long focal length measurement system through optimized design; clear imaging of a lens with a focal length of 75 mm within the range of 1.5-10 m was achieved, and the influence of different focusing methods on the performance of the measurement system was analyzed. This system adopts a non-thermal design. The lens is made of molten silica and can operate in a vacuum environment ranging from -20 to +40^∘C. It has stable imaging performance over a wide temperature range and can resist space radiation. The focal length of the system is 75 mm, the working band is 486-656 nm, the total length is 100 mm, the maximum distortion is less than or equal to 0.5%, it is small in size, light in weight, and has high stability, which is more in line with the measurement requirements of a large-aperture antenna's sub-reflector.