Thermal defocus and compensation analysis of glass-plastic hybrid fixed-focus lens

In the glass-plastic hybrid fixed-focus security lens, the material properties of the plastic lens, glass lens and frame are quite different. Under the complex temperature environment, the thermal deformation of the lens mechanical structure and the optical heat dissipation design will jointly affect the image quality. In order to ensure the stability of the lens imaging, according to the test temperature of −40 ℃~80 ℃ of the security lens, the optical, mechanical and thermal integration analysis of the lens was carried out. A finite element model of the thermal structure of the lens was established in Ansys workbench to calculate the thermoelastic deformation of the lens. Zernike polynomial was used to fit the surface shape change of the mirror, and the fitting results were imported into Zemax to judge the influence of temperature load on image quality. The simulation results show that under the ultimate test temperature load, when the base material is polycarbonate mixed with 20% glass fiber, the thermal defocus amount of the simulated optical system itself in Zemax is effectively compensated. When the frame material is polycarbonate mixed with 30% glass fiber, the maximum extrusion strain of the plastic lens is 2.36×10⁻³ mm. When the frame material is polycarbonate mixed with 20% glass fiber, the maximum extrusion strain of the plastic lens is 0.53×10⁻³ mm, which can keep the image quality of the lens stable. Finally, through the high and low temperature flange focal length measurement test of lens, the temperature adaptability of the lens and the correctness of the optical-mechanical-thermal integration analysis were verified.