This paper presents a new Phase Measuring Deflectometry (PMD) method to measure specular object havinguddiscontinuous surfaces. A mathematical model is established to directly relate absolute phase and depth, instead of phaseudand gradient. Based on the model, a hardware measuring system has been set up, which consists of a beam splitter toudchange the optical path, and two LCD screens to display the same sinusoidal fringe patterns. By using model-based andudmachine vision method, system calibration is accomplished to provide the required parameters and conditions. Theudverification tests are given to evaluate the effectiveness of the developed system. The 3D shape of an artificial stepudhaving multiple specular surfaces and a concave mirror has been measured. Initial experimental results show that theudproposed measurement method can obtain 3D shape of specular objects with discontinuous surface effectively.
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