Jia Hui, Li Fu-tian
State Key Laboratory of Applied Optics, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130022, China.
Guang Pu Xue Yu Guang Pu Fen Xi. 2004 Jan;24(1):4-8.
Sprayed BaSO4 diffuser plate is the most Lambertian surface actually used in spectral radiance calibration known by now. Its hemispheric reflectance and Bi-directional Reflectance Distribution Functions (BRDF) were measured in the experiment. Its diffuse characteristics were compared with Lambertian surface. In order to calibrate spectral radiance more accurately, the small variation of diffuser's BRDF with scattered angles and the nonuniformity of spectral irradiance on diffuser surface illuminated by the standard lamp should be considered. By integrating the radiation flux reflected by the element area and that entering the entrance slit within the viewing area of spectrometer, the measured spectral radiance can be calculated. Furthermore, the spectral radiance of Lambertian surface whose BRDF was derived from hemispheric reflectance was compared with that from the average of the measured BRDF.
喷涂硫酸钡漫射板是目前已知的光谱辐射度校准中实际使用的最接近朗伯面的表面。在实验中测量了其半球反射率和双向反射分布函数（BRDF）。将其漫射特性与朗伯面进行了比较。为了更准确地校准光谱辐射度，应考虑漫射器BRDF随散射角的微小变化以及标准灯照射下漫射器表面光谱辐照度的不均匀性。通过对元件面积反射的辐射通量和进入光谱仪视场范围内入口狭缝的辐射通量进行积分，可以计算出测量的光谱辐射度。此外，还将由半球反射率导出BRDF的朗伯面的光谱辐射度与测量BRDF平均值的光谱辐射度进行了比较。
