Phase measuring deflectometry (PMD) has been widely studied to obtain three-dimensional (3D) shape of specular surfaces.Due to the procedure of slope integration, complicated specular components having discontinuous surfaces cannotbe measured by the existing PMD methods. This paper presents a novel Direct PMD (DPMD) method to solve this problemof measuring discontinuous specular objects. A mathematical model is established to directly relate the absolutephase and depth data. Then a hardware measuring system has been set up. The system parameters are calibrated by usinga plane mirror and a translating stage. 3D shape of an artificial specular step, a monolithic multi-mirror array havingmultiple specular surfaces and a reflected diamond distribution surface has been measured. The experimental results verifiedthat the proposed method based on DPMD successfully measured full-field 3D shape of specular objects havingdiscontinuous surfaces accurately and effectively.
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