The use of moiré deflectometry for quality control applications is investigated. Moiré deflectometers were designed and used in the experiments, most importantly the retroreflected moiré deflectometer. Two parts were addressed: phase object analysis and specular object analysis. First, a density variation in a piece of glass (phase object) was examined. Moiré deflectograms were obtained using a conventional moiré deflectometer coupled with a retroreflector and a retroreflective deflectometer with a white light source. Ray deflection versus position graphs as well as 3-D ray deflection maps were generated. Second, both a large and a small outdent on a specular surface were investigated. The attempt to replace the laser with the white light source in a traditional moiré deflectometer did not yield any useful results. Moiré deflectograms were, however, obtained with the use of the traditional moiré deflectometer and with the arrangement employing a retroreflector. Slope versus position graphs were generated and compared to a calibrated artifact. The comparisons were very poor. Despite these results, moiré deflectometry can be used to locate such flaws.
Walter P. T. North,
"Retroreflective moiré deflectometry: phase and specular object inspection," Optical Engineering 33(4), (1 April 1994). https://doi.org/10.1117/12.163206