Three stepped calibration of structured light system with adaptive thresholding for 3D measurements

Structured light (SL) methods are widely used in 3D measurement systems because of their speed and contactless operation. These methods provide high resolution 3D modeling. Phase shifting is one of the SL algorithms that give high resolution with less number of pattern requirements. Since reflected patterns and obtained results are commonly distorted due to the lenses in cameras and projector systems, system calibration must be fulfilled before starting 3D modeling with SL system. Uncalibrated SL system may model the object much greater/smaller than the real dimension of it. In this study, a three step calibration system is proposed for an SL system that uses a three phase shifting algorithm with automatic thresholding. These calibration steps include camera calibration, projector calibration and depth calibration. Experimental studies showed that proposed calibrated system reduces the camera and projector lens errors. Depth calibration is applied as a last calibration step provided a 3D modeling of the object with accurate dimension. Dimensions of the objects and their 3D models are compared to have accuracy of the proposed 3D modeling system. After system calibration, obtained results showed that proposed 3D modeling system gives high accuracy with acceptable depth measurements.