：基于离轴抛物面镜的准直光学系统因其无色差、材料易得、工作谱段宽、无中心遮挡等优点被广泛应用于传感系统校准、辐射测量、红外目标模拟器等系统中。为了分析设计的准直系统是否满足实际需求，对准直系统输出的辐照度特性进行了理论分析及仿真研究。基于辐照度传输模型给出了准直系统输出面辐照度分布表达式，并给出了准直光束发散角与抛物面焦距、光源口径及离轴角之间等的定量关系。采用光线追迹方法仿真分析了准直系统在不同光源口径情况下的输出面辐照度分布情况，并对输出辐照度均匀性进行了定量分析。文中所提出的分析方法对提高离轴抛物面镜的准直性和输出辐照度均匀性有重要的意义。

Off-axis parabolic mirror has been widely used in sensor calibration, radiation measurement, infrared target simulation system and so on, because it takes many advantages such as no chromatic-aberration, common used material, broadband, no center block. The irradiance characteristic of the off-axis parabolic collimating mirror was evaluated by both theoretical analysis and simulation study. Both the expression for the irradiance distribution on the exit pupil plane of the off-axis parabolic collimator and the relations between the angle of divergence and the parameters of the collimator such as the focal length of the mirror, the aperture size of the source and the angle of off axis, were theoretically derived based on the radiation transfer model. The irradiance distribution on the exit pupil plane of the collimator was simulated by ray tracing method. The uniformity of the distribution was also analyzed. The method proposed here is useful to increase the collimation and uniformity of the off-axis parabolic mirror.