Optical System Design of Dual-Band and Small Remote Sensing Camera

Traditional visible light aerospace remote sensing cameras are easily affected by clouds, rain and fog, resulting in a decline in their Earth observation capabilities. To solve this problem, this paper designed a visible light and shortwave infrared dual-band remote sensing camera optical system, which can achieve the observation of the Earth in the visible light (0.4 μm–0.8 μm) and short-wave infrared (0.8 μm–2.5 μm) range. The actual working platform of aerospace remote sensing cameras requires miniaturization and lightweight of the camera, so the structure of the optical system adopts an off-axis three-mirror type. It can be lightweight and miniaturized due to optical path folding, and has the advantages of long focal length and no chromatic aberration. The coaxial three-mirror optical system design method is improved by off-axis diaphragm, and the improved method is used to design the off-axis three-mirror optical system. The focal length of the optical system is 600 mm and the total length is only 214 mm. The design results show that the MTF (modulation transfer function) value of each band at the cut-off frequency of 50 lp/mm is greater than 0.4, and the MTF value of each band at the cut-off frequency of 75 lp/mm is greater than 0.25; The diameter of the spot diagram of each band in the entire field of view is smaller than the Airy disk diameter. The RMS (root mean square) value of the system wave aberration in the visible light band is less than λ/16 (λ = 0.633 μm), and the RMS value of the system wave aberration in the short-wave infrared band is less than λ/50 (λ = 2.000 μm). The performance of the off-axis three-mirror optical system designed in this paper is close to the diffraction limit, which can meet the application needs of miniaturization and lightweight of remote sensing cameras and improve the observation capabilities of remote sensing cameras.