One-shot colored reflectance direction field imaging system for optical inspection

Detecting microscale defects on the surface of an object is often difficult with conventional cameras. Microscale defects are known to greatly affect the bidirectional reflectance distribution function (BRDF) of light rays reflected from the surface. Therefore, an imaging system for capturing the reflectance direction field by color mapping using a multicolor filter placed in front of an imaging lens is proposed, which can have a simple structure. From the color variations of light rays passing through several different color regions of the multicolor filter, this imag-ing system can detect the extent of broadening of the BRDF. The effectiveness of the imaging system for optical inspection is experimentally validated by testing it on a plastic surface that has a shallow scratch with a depth of a few micrometers. & COPY; 2023 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement