Opt Express. 2023 Feb 27;31(5):8049-8067. doi: 10.1364/OE.481105.
For purpose of improving the accuracy of in-orbit radiometric calibration of Chinese Space-based Radiometric Benchmark (CSRB) reference payload on the reflected solar band and reduce resource consumption, this paper proposed a freeform reflector radiometric calibration light source system based on the beam shaping characteristics of the freeform surface. The design method of initial structure discretization based on Chebyshev points was used to design and solve the freeform surface, and the feasibility of the design method was verified by optical simulation. The designed freeform surface is machined and tested, and the test results show that the surface roughness root mean square (RMS) of the freeform reflector is 0.61 μm, which indicates that the continuity of the machined surface is good. The optical characteristics of the calibration light source system are measured, the results show that the irradiance uniformity and radiance uniformity are better than 98% in the effective illumination area of 100 mm × 100 mm on the target plane. The constructed freeform reflector calibration light source system can meet the requirements of large area, high uniformity and light weight for onboard calibration of the payload of the radiometric benchmark, improving the measurement accuracy of spectral radiance on the reflected solar band.
为了提高星载基准辐射定标载荷反射光谱波段在轨辐射定标精度，降低资源消耗，提出了一种基于自由曲面光束整形特性的自由曲面反射辐射定标光源系统。采用基于切比雪夫点的初始结构离散化设计方法进行自由曲面设计与求解，并通过光学仿真验证了设计方法的可行性。加工并测试了设计的自由曲面，测试结果表明，自由曲面反射镜的表面粗糙度均方根（RMS）为 0.61μm，表明加工表面的连续性良好。对定标光源系统的光学特性进行了测量，结果表明，在目标平面上 100mm×100mm 的有效照明区域内，辐照度均匀性和亮度均匀性均优于 98%。构建的自由曲面反射镜定标光源系统能够满足星载基准辐射定标载荷大面积、高均匀性和轻量化的要求，提高了反射光谱波段光谱辐亮度的测量精度。
