热致梯度折射率对非球面光学系统成像质量的影响

机载相机在上升过程中,由于温度降低和镜头各部分材料的导热率大小不同,镜头部分会产生温度梯度,从而导致非球面光学系统产生梯度折射率.利用有限元分析软件对镜头部分进行瞬态热分析以模拟机载相机上升过程中温度的变化情况,将有限元分析不同时间节点温度分布结果导入编写的折射率梯度系数拟合程序,将所求解的梯度折射率系数通过镜面类型接口在光学软件中建立光学系统模型,利用点列图的弥散斑半径评价不同时间节点梯度折射率对成像质量的影响.结果表明,机载相机刚升入工作高度时温度梯度最大,对成像质量影响也最严重,梯度折射率系数随着温度梯度系数的降低而降低,同时成像质量提高,该结果对光学系统的设计具有指导意义.

Effect of Thermally Induced Gradient Index on Imaging Quality of Aspherical Optical System

During the ascent of the airborne camera,due to the temperature drop and the thermal conductivity of the material of each part of the lens,the lens portion can have a temperature gradient,which causes the aspherical optical system to produce a gradient index.Using the finite element analysis software to perform transient thermal analysis on the lens part to simulate the temperature change during the ascent of the airborne camera,the finite element analysis of the temperature distribution results of different time nodes was introduced into the prepared refractive index gradient coefficient fitting program,and the solution was solved.The gradient index coefficient established the optical system model in the optical software through the mirror type interface,and use the speckle radius of the dot-column diagram to evaluate the influence of the image quality on the gradient index of the different time nodes.The results show that the temperature gradient of the airborne camera is the highest when it is lifted into the working height,and the influence on the imaging quality is also the most serious.The gradient refractive index coefficient decreases with the decrease of the temperature gradient coefficient,and the imaging quality is improved,which has guiding significance for the optical system design.