With the fast development of integrated circuits, photovoltaics, automobile industry, advanced manufacturing, andastronomy, it is particularly important to obtain the three-dimensional (3D) shape data of specular objects quickly andaccurately. Owing to the advantages of large dynamic range, non-contact operation, full-field and fast acquisition, highaccuracy, and automatic data processing, phase-measuring deflectometry (PMD, also called fringe reflectionprofilometry) has been widely studied and applied in many fields. Direct PMD (DPMD) can directly establish therelationship between phase and depth data without gradient integration process, so it can be used for 3D shapemeasurement of specular objects having discontinuous surfaces. However, compared with gradient data, depth data ismore sensitive to measurement noise, so the measurement accuracy obtained by gradient field integration is higher. Inorder to make use of the anti-noise property of gradient measurement structure, some PMD techniques usually abandonthe height data obtained from the intermediate process and use the gradient data to complete the surface reconstruction.Stereo deflectometry is a typical representative to retrieve 3D shape of the measured object according to the gradientintegration. It calculates the gradient field based on the uniqueness of the normal vector of the object points by using twocameras. Although obtaining high-precision measurement results, this method cannot be used for the measurement ofdiscontinuous objects. In this paper, a new stereo DPMD method is proposed to obtain 3D shape of specular objectshaving discontinuous surfaces. Some experimental results on measuring discontinuous specular objects verify the highprecision of the proposed stereo DPMD method.
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