中文摘要：

分析了偏视场用三反系统的杂散光特性，根据遮光罩设计的基本原则，介绍了利用计算机仿真技术进行消杂散光设计和评价的原理。系统为特殊的矩形视场，且在y方向视场偏轴，为此，设计了盒形外壁与锥形内壁相结合的外遮光罩结构，并在CAD中进行建模，采用内部挡光片为方形并且梯度排列的结构。在λ=0．25μm，方位角为0°和90°时分别对0．5—80之间共16个离轴角度进行光线追迹，最后通过计算得到了系统PST曲线。由曲线可以看出，系统PST整体上是下降的，且在离轴角25°时达到10^-8量级。计算杂光系数为3．59％，完全满足要求。实验结果证明了设计的可行性，为应用提供了依据。

英文摘要：

The stray light properties of the three-mirror optical system used in field bias was analyzed and the basic design principles of the light shade and baffle vanes were presented, then the design of them was discussed. The principles of stray light eliminating and evaluation using computer simulation technology were put forward. Considering that the system had a special rectangular field of view, and the field was off-axis in y direction, a certain demand on the external lens hood was proposed. So box- shaped outer wall combined with the cone-shaped wall was designed. The window shades were designed to be square and laid gradient by CAD modeling. Then, the system model was built in the Tracepro stray light analysis software with wavelength λ=0.25 μm in which the light was traced according to the sixteen off-axis angles between 0.5 and 80, at the azimuth angles of 0°and 90°. Finally the PST curves were given through the calculation. It shows that the PST curves are going down in general and reach 10-8 at off-axis angles of 25~. The coefficient of the stray light is 3.59%. It proves the feasibility of design of the stray light eliminating and the further application can be carried out.