Quantifying Appearance for Opaque Surfaces Using Spectral Bidirectional Reflectivity

• Main Author: Brooks, Christopher Richard
• Format: Others
• Published: BYU ScholarsArchive 2019
• Subjects: spectral; bidirectional reflectivity; quality control; appearance
• Online Access: https://scholarsarchive.byu.edu/etd/7498; https://scholarsarchive.byu.edu/cgi/viewcontent.cgi?article=8498&context=etd

Quantifying the appearance of a surface is an important aspect in quality control. Becauseobjects at room temperature emit negligible amounts of radiation into the visible spectrum, aspectsof their appearance may be quantified using reflected light. Therefore, the appearance of opaquesurfaces may be quantified using measurements of the spectral, bidirectional reflectivity. However,measuring the spectral, bidirectional reflectivity of even one point at every set of incident andreflected directions is a time intensive process that is infeasible for quality control.The objective of this work was to determine whether a limited number of spectral, bidirectionalreflectance measurements may be used to characterize the appearance of an opaque surfaceat room temperatures. The results presented in this thesis demonstrate that measurements of thespectral bidirectional reflectivity in the visible spectrum at four sets of specular reflections - 20°,45°, 60°, and 85° - with a resolution of 5 nm may be used to quantify the appearance of an opaquesurface at room temperature. These measurements are converted into parameters called the bidirectionalreflectance appearance parameters (BRAPs). These BRAPs include L*, a*, b* (whichdefine the color of the surface), G20, G60, G85 (which define the gloss of the surface), and H(which describes the haze of the surface). It is shown that surfaces which appear similar havesimilar BRAPs and surfaces which appear different have different BRAPs.