In near-field photometric stereo vision, the accurate calibration of the light source position directly affects the precision of the reconstruction results. Traditional calibration techniques rely on a highly reflective sphere and exploit the specular reflection properties at highlight points for determining light source positions. However, in real-world scenarios, nonuniform lighting conditions often leads to errors in extracting the sphere's image edges, affecting the accuracy of light source position calibration. Therefore, we propose a method for calibrating light source position based on a novel target. This method involves detecting planar reference points that are less sensitive to the lighting conditions and leveraging the pose relationship provided by the planar reference points to effectively overcome the adverse effects of lighting conditions on light source position calibration. Experimental results demonstrate that this method significantly enhances the precision of light source position calibration under non-uniform lighting conditions, eliminating the constraint of light source position calibration on specific lighting environments.
In optical three-dimensional imaging and measurement based on fringe projection, wrapped phases may cause a problem of ambiguity, which can be overcome by phase unwrapping generally. In this paper, a method for absolute phase unwrapping using light-field imaging is reported. In a recorded light field under structured illumination, i.e., a structured light field, a wrapped phase-encoded field was retrieved and resampled in diverse image planes associated with several possible fringe orders in a measurement volume. By leveraging phase consistency constraint, the resampled wrapped phase-encoded field correct fringe orders could be determined to unwrap phase without any additional encoding information.
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