消热差红外镜头热光学特性分析

摘要

机械被动式消热差红外镜头的诞生解决了传统红外镜头在高低温下,由于温差原因产生不同的离焦量导致镜头成像质量下降的问题.本文以某款机械被动式消热差红外镜头为研究对象,对其进行了热光学特性分析.首先,在ANSYS中建立有限元模型,通过齐次坐标变化运用最小二乘法得出刚体位移.然后,通过Fringe Zemike多项式拟合得到面形变化.最后,在MATLAB平台下编写了基于施密特正交化法的接口程序,将37项Fringe Zemike系数导入到Zemax中进行分析.分析结果表明:在高低温时,由于补偿组的作用,镜头的轴向离焦量得到良好的补偿.高低温时镜片面形会发生变化,在低温时,镜头的成像质量略差于高温.镜头总体成像质量符合使用要求.%The traditional infrared lens would produce different defocus amounts because of temperature difference,which lead to the decline of the imaging quality.To solve this problem,the thermal optical properties of a mechanical passive athermal infrared lens were analyzed.Firsdy,the finite element model was established by ANSYS,and then the least square method was used to obtain rigid body displacement through the change of homogeneous coordinates.After that,the shape change was gotten by Fringe Zernike polynomial fitting.Finally,the interface program was written based on the Schmidt’s orthogonalization on the MATLAB platform,and 37 Fringe Zemike coefficients were imported into Zemax for analysis.The results show that:at high or low temperature,the axial defocus of the lens was compensated well,due to the role of compensation group.The imaging quality of the lens at a low temperature was slightly worse than that at a high temperature.In a word,the overall imaging quality of the lens is improved and meets the requirements.