为提高漫反射参照体双向反射比因子(BRF)测量准确度,设计了漫反射参照体BRF绝对测量系统。该系统以积分球辐 射源为照明光源,高精度陷阱(Trap)辐亮度计为探测器,通过对积分球辐射源辐亮度、漫反射参照体反射辐亮度和 几何因子的测量,实现了漫反射参照体BRF绝对测量。结果分析表明,测量不确定度优于1%(k=2),通过对630 nm波 长下漫反射参照体BRF数值积分得到的方向－半球反射比因子(DHRF)比溯源到中国计量科学研究院的采用积分球方 法得到的DHRF高0.57%,差别在二者测量不确定度范围之内,进而验证了BRF绝对测量的准确性。

A gonioreflectometer which concentrated on absolute measurement of diffuse reflection standards’ bidirectional reflectance factor (BRF) is described. The instrument employs a specially built integrating sphere as a light source and a mechanically simple, radiometrically stable filter trap radiometer as a detector. Analysis of its initial performance in 630 nm shows that the combined standard uncertainty of the measurement is 0.87 % (k=2). The hemispherical reflectance factor is obtained through integration of BRF measurement results, and it is 0.57% higher than the results scaled in National Institute of Metrology (NIM) using integrating sphere method. The difference is within the uncertainty of the two measurements, and it can validate the accuracy of absolute measurement.