玻塑混合定焦镜头热离焦与补偿分析

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

  • 摘要: 在玻塑混合定焦安防镜头中塑胶镜片、玻璃镜片、镜框的材料性质差异较大,复杂温度环境下,镜头机械结构热变形与光学消热设计会共同影响像质。为保证镜头复杂温度环境下成像稳定,根据安防镜头−40 ℃~80 ℃的测试温度,对镜头进行光机热一体化分析。在Ansys workbench中建立镜头热结构有限元模型,计算镜头的热弹性变形;使用Zernike多项式拟合镜面的面型变化,将拟合结果导入Zemax中,判断温度载荷对像质的影响。光机热一体化分析结果表明:在极限测试温度载荷下,镜头底座的材料为聚碳酸酯混合20%玻璃纤维时,有效补偿了Zemax中模拟光学系统本身的热离焦量;镜框材料为聚碳酸酯混合30%玻璃纤维时,塑胶镜片所受挤压应变最大为2.36×10−3 mm;镜框材料为聚碳酸酯混合20%玻璃纤维时,塑胶镜片所受挤压应变最大为0.53×10−3 mm,第二种镜框材料可以使镜头像质保持稳定。最后通过对镜头高低温法兰焦距测量试验,验证了镜头的温度适应能力和光机热一体化分析的准确性。

     

    Abstract: 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.

     

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