A new calibration method for structured light systems of defocused projectors

Structured light systems using binary defocusing techniques have the potential to gain wider applications due to their fast speed, no need for gamma calibration, and lack of strict synchronization requirements between the camera and projector. However, existing calibration methods cannot achieve high accuracy for structured light systems with out-of-focus projectors. In this paper, we propose a method to accurately calibrate structured light systems even when the projector is out of focus, enabling high-precision and high-speed measurements using the binary defocusing method. Experiments show that our calibration method performs consistently across different defocus levels and can achieve a root mean square error of approximately 73 μm with a calibration volume of 150 (H) mm x 250 (W) mm x 200 (D) mm.

[method]

This article proposes a new calibration method to accurately calibrate structured light systems with binary defocus technology, achieving high-precision and high-speed measurements even when the projector is not in focus. The method implements standard stereo system calibration methods by virtually creating a one-to-one mapping between camera pixels and projector pixel centers in the phase domain and aligning the world coordinate system with the camera lens coordinate system. Experimental results show that the method shows consistent performance under different degrees of defocus and can achieve an accuracy of about 73 microns for a calibration volume of 150mmx250mmx200mm.

[Summarize]

In this paper, we propose a calibration method for structured light systems using out-of-focus projectors. Our theoretical analysis provides a basis for accurately calibrating out-of-focus projectors by creating a one-to-one mapping between camera pixels and projector pixel centers in the phase domain.

For a calibration volume of 150 (H) mmx250 (W) mmx200 (D) mm, our calibration method has consistent performance at different defocus amounts, with an accuracy of about 73μm. Our experimental results confirm that high calibration accuracy can indeed be achieved through this calibration method. One may realize that this study ignores the nonlinear distortion of the projector lens, which can be further considered for higher accuracy measurements. The reason for ignoring the nonlinearity of the projector is that our research goal is high-speed 3D shape measurement,