Forward reflection characteristics of typical smooth building walls and the simulation analysis

Non-line-of-sight optical imaging technology is a novel application of imaging technology developed recently, achieving the effective imaging of the corner, basements and other scenes which are difficult to be directly observed by traditional vision with intermediate reflective surface. Smooth building walls, such as tiles and marbles, are typical intermediate reflective surfaces. Because reflecting surface is neither ideal specular reflective nor Lambertian reflective, the reflection characteristics of the intermediate reflective surface have a significant impact on the non-line-of-sight imaging. Based on the test data of the spectral bidirectional reflectance distribution function (BRDF) of common smooth tiles, the surface transfer function and angle spread function of smooth tiles are established according to the Harvey-Shack surface scatter theory in the paper. And the descriptions of the characteristics of specular reflection and forward scattering are implemented. Furthermore, according to the measured BRDF data at a certain wavelength for a certain angle of incidence, we can predict the reflection and scattering distribution at any other wavelengths or for other incident angles. The simulation results indicate that the curves fitted by the model basically are in agreement with the measured data, so that the simulation of the specular reflection and the forward scattering in the model is valid.