Development of a table-top surface inspection system based on phase-measuring deflectometry

In this research, we developed a surface inspection system based on Phase-Measuring Deflectometry for specular surfaces. PMD is a non-contact, full-field optical measuring technique that measures the phase shifts caused by surface deformations. While PMD has seen significant advancements and increasing use in various industries due to its simple configuration and moderate precision, uncertainties in alignment and calibration can limit the practical performance of the system for industrial applications. To address this, we propose a system that measures freeform optical surfaces smaller than 50x50 mm2 using stereoscopic redundancy to eliminate height ambiguity. We apply self-calibration methods to maintain measurement precision below sub-micrometer level. Our measurement results of specular surfaces demonstrate a measurement precision of less than 0.1 um, with excellent convenience and less throughput time.