Evaluating an image-based bidirectional reflectance distribution function measurement setup

Abstract

We evaluate an image-based multiangle bidirectional reflectance distribution function measurement setup by comparing it to measurements from two commercially available goniospectrophotometers. The image-based setup uses an RGB camera to perform bidirectional measurements of the sample material. We use a conversion matrix to calculate luminance from the captured data. The matrix is calculated using camera spectral sensitivities that are measured with a monochromator. Radiance factor of the sample material is measured using a commercially available tabletop goniospectrophotometer and compared to measurements made using the image-based setup in the colorimetric domain. Our measurement setup is validated by comparing the measurements performed using a goniospectrophotometer. Uncertainty and error propagation is calculated and taken into account for validation. The sample material measured is wax-based ink printed on packaging paper substrate commonly used in the print and packaging industry. Results obtained show that the image-based setup can perform bidirectional reflectance measurements with a known uncertainty. The goniospectrophotometer measurements lie within the uncertainty of the measurements performed by the image-based measurement setup. The setup can be used to perform bidirectional reflectance measurements on samples with properties similar to the samples used in this paper.