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.