Simulation of Phase Measuring Deflectometry of Freeform Surfaces

Abstract

Optical three-dimensional shape metrology has become a key technology in scientific and industrial applications. Phase Measuring Deflectometry (PMD)is one optical three-dimensional shape metrology technique which is based on two-dimensional fringe patterns measurements for specular reflecting surfaces. There are several configurations of PMD to measure the arbitrary specular surfaces. Here, a single camera is used to capture the reflected image of a single LCD monitor to construct the deflectometry system. Distance laser sensors, multiple cameras, and multiple monitors will not be considered here. This investigation focuses on creating simulated PMD images for an arbitrary specular surface. Such images are useful for testing slope calculations and surface reconstruction algorithms. System geometry calibration and an inverse ray-tracing algorithm are explored. This thesis demonstrates the preliminary results of PMD for a flat mirror, a concave mirror and a freeform surface with the phase shifting method. The specific feature of the image simulation shows the inverse ray-tracing can deduce the captured image correctly. Included is a discussion about the ambiguity of fringe numbers and the uncertainty of the phase value calculation with insufficient fringe sampling.