A Study on the Optical Properties of Diffuse Reflector Surface Structure

Abstract

In this paper, the relationship between the optical properties and the surface structure of the diffuse reflector used in the LED lighting fixtures was studied. Ten samples with different levels of the surface roughness and surface gloss characteristics were prepared using the sand blast method. Measured surface roughness represented by average Ra was widely distributed from 3.34 to 22.59㎛. The surface gloss characteristics of sample were influenced by the frequency of period of the measured roughness. Reflectance for each wavelength (360∼740nm) was same within 1% of deviation and total reflectance was 88% within 0.12% of deviation regardless of surface roughness and surface gloss characteristics. Scattering characteristics were analyzed by BSDF(Bidirectional scattering distribution function) measurement system at the incident angles from 0 to 60° and wavelengths of 645nm and 530nm to analyze the dependency of scattering characteristics on the surface roughness and gloss characteristics of samples. The higher the roughness, the higher FWHM value was regardless of the surface gloss characteristics. At the same condition of roughness, the FWHM value of the matt type sample is higher than that of the glossy type sample with matte type. The deviation of the FWHM value between the sample with matt type and the one with glossy type was smaller as the roughness increased. There was not so much difference in scattering effect on wavelength of incident beam depending on the surface of roughness and gloss characteristics.