Simulation of the BSDF measurements for scattering materials with GP-200 goniophotometer for light guiding plates

Abstract

In optics, elements with complex light scattering properties are typically simulated either with the computer models based on the reconstruction of their surface and internal structure or with measured Bi-Directional Scattering Distribution Function (BSDF) which totally describes the dependence of scattering properties on illumination and observation conditions. However, in many cases simulation of precise computer models to specify light scattering properties is impossible because parameters either not available or measured with insufficient accuracy. The approach based on measured BSDF is not applicable in all cases also, for instance, when it is necessary to make a simulation of some light guiding plate (LGP) with rough scattering surfaces. In this case, the properties of light scattering on the rough surfaces should be specified and thus measured separately from the whole LGP. The BSDF for such kinds of surfaces is either impossible to measure at all, or measurements are very expensive due to the need to use additional and very complex equipment. The article considers the third alternative approach to simulate scattering properties based on the reconstruction of the whole BSDF with an optimization process. The objective function is an angular intensity distribution measured with GP-200 goniophotometer. Another problem is the calculation speed of the simulated model. BSDF is a multidimensional function and its calculation with proper resolution can be a difficult task. This work proposes a fast and simple way to simulate the angular intensity distribution of scattering material based on BSDF obtained with a measuring device. The simulation results based on several examples of scattering samples are compared with real measurements.