Design of a focusing system for micro-nano satellite remote sensing camera based on thermal control technology

Remote sensing cameras mounted on micro-nano satellite mare susceptible to optical system defocusing during launch and operation due to environmental influences. Traditional focusing system encounter issues such as large volume and mass, making them unsuitable for the design requirements of micro-nano satellite. Proposes a thermal control-based focusing system for compact systems with maintained imaging quality. The design is developed according to the characteristics of a compact coaxial four-mirror remote sensing camera optical system and the overall structure of the system. The focusing system utilizes structural thermal expansion to alter the distance between the primary and secondary mirrors, achieving the purpose of adjusting the system's focal length. Finite element simulations were conducted to analyze the modal and thermal deformations of the overall structure, validating the rationality of the system design. Experimental verification of the thermal control focusing system demonstrated its adjustment accuracy and range, with clear imaging obtained after system focusing. The results indicate that when the temperature control accuracy reaches +/- 0.5 degrees C, the focal length adjustment accuracy can reach 0.0052 mm. This article proposed thermal control focusing system can adjust the camera's focal length in orbit, exhibiting advantages such as a small volume, high stiffness, and high precision.