Structured light system calibration with unidirectional fringe patterns

For the calibration of a structured light system, one type of highly accurate calibration method was developed by treating the projector as an inverse camera. This type of method typically creates pixel-to-pixel mapping between a camera point and a projector point using fringe patterns and resultant phase maps in orthogonal directions. However, requiring orthogonal patterns limits its feasibility of implementation on systems where the illumination device (e.g. grating projectors, interferometers, etc.) only supports fringe projection in one direction. This paper introduces a novel calibration method that only uses patterns in a single direction. We have theoretically proved that there exists one degree-of-freedom of redundancy in conventional calibration methods, making it possible to reduce the requirement of using orthogonal fringe patterns. Experiments show that under a measurement range of 200 mm(X) x 150 mm (Y) x 120 nun (Z), our measurement results are comparable to the results obtained using conventional calibration method. Evaluated by repeatedly measuring a sphere with 147.726 mm diameter, our measurement accuracy on average can be as high as 0.20 mm with a standard deviation of 0.12 mm. (C) 2018 Elsevier Ltd. All rights reserved.