Design of Automatic Temperature Compensation Mechanism for Beam Expanding Optical System

The beam expanding optical system is highly sensitive to temperature. In order to reduce the influence of temperature on the optical system, an automatic temperature compensation mechanism is designed. The mechanism compensates each other through the difference of thermal expansion coefficient between materials, thus ensuring the stability of mirror spacing. ANSYS software is used to analyze the change of primary and secondary mirror spacing when the beam expansion system temperature rises from 20℃ to 30℃, 40℃, 50℃. Finally, the optical simulation analysis of the changed system is carried out by ZMAX software. The analysis results show that without the design of automatic temperature compensation mechanism, the distance between primary and secondary mirrors of the beam expansion system optical system changes by 0.027 22 mm, 0.054 43 mm, 0.081 64 mm respectively, and the system wavefront error RMS changes from 0.001 3λ to 1.389 8λ, 2.778 2λ, 4.165 6λ (λ=632.8 nm), unable to meet the requirements of optical imaging quality; After the automatic temperature compensation structure is adopted, the primary and secondary mirror spacing of the beam expanding optical system changes by 0.000 05 mm, 0.000 09 mm and 0.000 14 mm respectively, and the system wavefront error RMS changes from 0.001 3λ to 0.002 6λ, 0.004 6λ, 0.007 2λ. It can still meet the requirements of optical imaging quality. Therefore, the automatic temperature compensation mechanism can effectively restrain the influence of large temperature difference on the imaging quality of the beam expanding optical system.