Abstract:In order to improve the environmental adaptability of the large aperture off-axis optical system,a large aperture off-axis optical system with passive athermalization was designed.Firstly,the route of mechanical passive compensation was determined by technical comparison.Then,through the selection of the optical and mechanical materials,the optimization of the opto-mechanical structure and the calculation of the compensation structure,a simple mechanical structure was adopted to realize the athermalization of the system.Finally,the design of the system was simulated and the MTF of the system at -40 ℃,20 ℃ and +55 ℃ was analyzed.The results show that the designed large aperture off-axis optical system can meet the requirement of temperature compensation,and has the advantages of small volume,light weight,easy realization and high compensation precision,and so on.