挠性压圈在被动式热分析中的应用研究

Investigation of Flexible Element in Passive Athermalisation

为了实现红外光学系统的被动式无热化,设计了挠性压圈,建立了有限元分析模型,对透镜表面的接触应力和挠性压圈结构参数的灵敏度进行了研究。首先,根据光机结构的无热化要求介绍了挠性压圈,对两种常用的挠性压圈进行了热变形分析;然后,在分析挠性压圈的灵敏度系数的基础之上,对单透镜组件设计了相应的挠性结构,说明了挠性构件在被动式无热化中能够减小透镜表面的接触应力以及增加对镜座材料的选择;最后,将挠性压圈应用在三片式透镜的光学系统当中。通过分析计算,当调制传递函数(MTF)的空间频率为10 lp/mm时,挠性压圈作用下的三片式光学系统的MTF能够达到0.5以上;普通压圈在60℃和-20℃的像面离焦量分别为4.765 mm和-6.312 mm,而相同温度下挠性压圈的像面离焦量分别为1.261 mm和-1.563 mm。基本满足了红外光学系统的被动式无热化要求。

In order to realize the athermalisation of infrared optical system, an finite element analysis （FEA） model is established to analysize the contact stress of the lens and sensitivity of the structure. First, based on the athermal requirements of the optical system, the concept of the flexible pressure ring is introduced. Then, thermal deformation analysis is made on the flexible elements. After that, we design the flexible elements based on the sensitivity analysis, which gets that the flexible elements can reduce the contact stress of the lens and makes the choice of the lens sear materials more easily. Finally, the flexible elements is introduced to the triplet system. The simulation results indicate that the modulation transfer function （MTF） of the triplet system is above 0.5 under the use of flexible elements when the spacial frequency of MTF is 10 lp/mm. The defocus of the ordinary pressure ring under 60 ℃ and -20 ℃ are 4.765 mm and -6.312 mm respectively while the flexible are 1.261 mm and -1.563 mm respectively. The use of the flexible elements can meet the athermal requirements of the infrared system.