高速平均流场对红外成像影响的计算分析

Computation and analysis of IR imaging impacted by the high-speed flow-field

红外导引头光学窗口外流场对红外信号传输成像产生的气动光学效应是高速拦截弹设计必须要解决的关键技术之一。目标的红外信号经过高速流场在探测器上成像时,会产生像偏移、模糊、甚至抖动,导致探测定位不准,降低拦截精度。采用热化学非平衡NS方程,考虑高温真实气体效应,模拟了红外导引头的高速流场,应用光线追迹和物理光学的方法,基于流场密度参数,计算获得了光线经过流场时产生的光程差,进而得到成像的点扩展函数,从而获得了红外成像的像偏移和图像强度衰减参数,并分析了马赫数、迎角、高度、入射角和入射波长对光学传输效应的影响。结果表明:30km以下,气动光学效应对光学成像影响较大,增大入射波长可减小图像强度衰减。

Aero-optic effect induced by the flow-field outside the IR seeker optical window is one of the problems needed to be solved in designing a high-speed interceptor. When IR signatures form the target throughout the high-speed flow-field, the IR image on the seeker will be shifting, blurring and even jittering. These effects bring errors of position-setting, and degrade the intercepting precision. Based on the thermochemical non-equilibrium Navier-Stoke equations, the high-speed flow-field is simulated numerically. The Ray-tracing and physical-optic methods are used to get the OPD and PSF, which can describe the shift ing and blurring of IR image. The affect factors of IR image shift and attenuation are considered, including Mach number, attack angle, altitude, incidence angle and IR wavelength. As a result, the aero-optical effects under 30km altitude have obvious influence on IR imaging, and increasing the incidence wavelength can reduce the attenuation of IR image intensity.