用于快速BRDF测量的子孔径扫描傅里叶变换系统

A Sub-Aperture Scanning Fourier Transform System for Fast BRDF Measurements

提出了一种快速测量双向反射分布函数(BRDF)的子孔径扫描傅里叶变换系统.子孔径扫描傅里叶变换方法,使用单个傅里叶变换透镜进行测量,具有扩展单次测量视场、工作距离长、成本低以及系统简单等优点,可以在大空间频率范围内实现BRDF的快速有效测量.与角度细分光谱辐射计测量方法相比,子孔径扫描傅里叶变换方法具有更高的灵敏度和精度,提高了检测速度.该方法通过与子孔径扫描方法结合,测量样品平面上散射的光场,并在傅里叶空间中进行数值拼接,扩大了测量BRDF的角度范围.最后,利用对比实验数据对该方法进行了验证.实验结果表明,该方法与角度细分光谱辐射计的相对误差小于1%,测量时间是角度细分光谱辐射计的1/10,角度分辨率可以达到0.005°.这些结果为子孔径扫描傅里叶变换系统在快速BRDF测量中的应用提供了理论依据和技术支持.

In this study,a sub-aperture scanning Fourier transform system is proposed for performing the fast measurement of the bidirectional reflectance distribution function(BRDF).The sub-aperture scanning Fourier transform method that uses a single Fourier transform lens exhibits an expanded single-measurement field of view,a long working distance,and a low cost.Furthermore,the system is simple;thus,rapid and effective measurement of the BRDF can be realized over a large space frequency range.When compared with the angular subdivision spectroradiometer method,the proposed method exhibits higher sensitivity,accuracy,and detection speed.The scattered light field on the sample plane was evaluated through sub-aperture scanning,and numerical splicing was conducted in the Fourier space;the BRDF angle measurement range was expanded.Finally,the proposed method was verified based on the experimental data.The experimental results denote that the relative error between the proposed method and the angular subdivision spectroradiometer method is less than 1%.Further,the measurement time of the proposed method is 1/10 of that of the angular subdivision spectroradiometer method,and the system accuracy can become 0.005°.These results provide theoretical basis and technical support for the application of sub-aperture scanning Fourier transform systems in BRDF measurement.