基于二维函数PST的离轴四反系统杂散光分析

Stray light analysis of off-axis four mirrors system based on two-dimensional function PST

离轴四反系统是顺应多光合一机载观瞄系统未来发展的光机核心部件。该类型系统容易受到视场外部强杂散光的影响,系统杂散光的点源透射率(PST)一般要求不大于10^(-4)量级,因此,对系统PST进行全方位扫描计算是分析和抑制其杂散光的关键。针对系统的非对称性,将PST作为随杂散光入射空间水平角和垂直角变化的二维函数,用以评价外部杂散光的影响,同时建立了水平角、垂直角与光机建模所需绕坐标轴旋转的过程量的对应转换关系,编制了仿真控制程序,通过调用LightTools软件实现杂散光的自动追迹和PST的二维扫描计算。对多光合一离轴四反系统,计算了整个入射半球空间内、所有方向的杂散光对应的PST分布情况,从而筛选出对机载观瞄应用影响较大的三路杂散光,寻找到其传输的路径和关键表面。基于此,设计了内部遮光罩和挡光环,优化系统内部的杂散光陷阱结构,使得系统的PST峰值由原来10^(-1)量级降低至10^(-4)量级,在规避角范围以外小于10^(-7),可满足机载光电观瞄系统的使用要求。为离轴四反系统杂散光分析及抑制提供了依据。

Off-axis four mirrors systems are opto-mechanical core components of multiband common aperture airborne observation and aiming systems to adapt to their future development. This type of systems is easily affected by strong stray light outside the field of view. The point source transmittance(PST) of stray light in those systems is generally required to be no more than 10^(-4) order of magnitude. Accordingly, omnidirectional scanning calculation of PST is the key to analyze and suppress stray light of them. For the asymmetry of the optical system,PST as a two-dimensional function varying with the horizontal and vertical angle of stray light was set up to evaluate the influence of external stray light. Besides, the conversion relationship between the horizontal and vertical angle and the process quantity of rotation about coordinate axis required for opto-mechanical modeling was established. The simulation control program was compiled, which realized the automatic tracking of stray light and the two-dimensional scanning calculation of PST by calling LightTools software. For a multiband common aperture off-axis four mirrors system, the PST distribution of stray light in all directions within the whole incident hemispherical space was calculated, so as to screen out 3 series of stray light that had a great impact on the application of airborne observation and then find their transmission paths and key surfaces. Based on this, the inner baffles and vanes were designed to optimize the stray light trap structure in the system, so that the peak value of PST of the system was reduced from the original 10^(-1) level to 10^(-4) level, especially less than10-7outside the avoidance angle range, which could meet the application requirements of airborne photoelectric observation and aiming systems. It provides a basis for the analysis and suppression of stray light of off-axis four mirrors systems.