红外探测系统的激光辐照热效应仿真分析

Simulation analysis of thermal effect of laser irradiation in infrared detection system

为研究红外探测系统受激光辐照后的热效应与二次热辐射对探测器成像的影响,使用Ansys软件对红外探测器进行热辐射仿真和有限元结构仿真;采用黑体辐射定律和DO辐射计算模型模拟计算探测器内光学系统在不同激光辐照度下的温度随时间变化情况以及探测器内部温升对靶面成像的二次热辐射干扰情况;采用热弹性力学模型仿真计算探测器内部的热应力和热变形情况。结果表明:探测器受到1.06μm激光照射,矫正镜激光辐照度在50 W/cm^(2)时,靶面受到二次热辐照度在0.6 s时达到100μW/cm^(2)的量级,使红外探测器达到饱和;探测器受激光辐照后系统最高温度出现在矫正镜中心处,拟合得到系统最高温度与受照时间函数关系,可预测探测器升温结构破坏;最大热变形出现在矫正镜背面中心处,由外向内形成不等附加光程差,干扰探测器的成像效果;最大热应力出现在矫正镜前面中心处,得到最大热应力与激光辐照度间的线性关系曲线,为矫正镜热应力破坏提供预测参数。

To study the thermal effect and secondary thermal radiation of infrared detection system after laser irradiation on the detector imaging, this paper uses Ansys software for thermal radiation simulation and finite element structure simulation of infrared detector. The blackbody radiation law and DO radiation calculation model are used to simulate the temperature variation with time of the optical system in the detector under different laser irradiance and the interference of the secondary thermal radiation caused by the temperature rise in the detector to the imaging of the target surface. The thermal stress and deformation in the detector are simulated by thermoelastic model. The results show that, under the condition that the detector is irradiated by 1.06 μm laser while the laser irradiance of the corrective lenses is 50 W/cm^(2), then, the secondary thermal irradiance of the target reaches the order of 100 μW/cm^(2) in 0.6 seconds, the infrared detector reaches saturation. After the detector is irradiated by laser, the maximum temperature of the system appears at the center of the corrective lenses, and the function relationship between the maximum temperature of the system and the exposure time is obtained by fitting, which can predict the damage of the heating structure of the detector. The maximum thermal deformation appeared at the center of the back of the mirror, which formed unequal additional optical path difference from the outside to the inside and interfered with the imaging effect of the detector. The maximum thermal stress appeared in the front center of the corrective lenses, and the linear relationship between the maximum thermal stress and the laser irradiance was obtained, which provide the prediction parameters for the thermal stress damage of the corrective lenses.