Abstract
Shadow and background are two common factors in digital fringe projection, which lead to ambiguity in three-dimensional measurement and thereby need to be seriously considered. Preprocessing is often needed to segment the object from invalid points. The existing segmentation approaches based on modulation normally perform well in pure dark background circumstances, which, however, lose accuracy in situations of white or complex background. In this paper, an accurate shadow and background removal technique is proposed, which segments the shadow by one threshold from modulation histogram and segments the background by the threshold in intensity histogram. Experiments are well designed and conducted to verify the effectiveness and reliability of the proposed method.
Highlights
Digital fringe projection (DFP) techniques are widely employed in flexible, non-contact and high-speed 3D shape measurement [1]
In a DFP system, a sequence of phase-shifted sinusoidal fringes is often projected on the object by the projector, and the fringes are distorted by the object surface and captured by a camera
Phase map can be retrieved from the deformed fringes, and the object height information is calculated from the phase map in a calibrated DFP system [2]
Summary
Digital fringe projection (DFP) techniques are widely employed in flexible, non-contact and high-speed 3D shape measurement [1]. Lu et al [7] proposed a technique to remove shadow points by mapping the 3D results into projector coordinates, and the modulation is not needed. This method can only detect shadow caused by the DFP system [8]. The literature [8] utilized the automatic thresholding method in modulation histogram for object detection Their method can only deal with dark background with low modulation, since the background and shadow are with similar low modulation, while the object is with obviously higher modulation level, and only one threshold is needed to segment the object.
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