Coding line structured light based on a line-scan camera and its calibration

In a conventional three-dimensional (3D) measurement technique of a line-scan camera, the projection system based on surface structured light is a compromise of traditional projection technology, which suffers from complex calibration, complex structure and low accuracy. To this end, the coding line structured light based on the coded line laser projection system is proposed to address the 3D measurement of a line-scan camera. The single-line projection and codeable characteristics of coded line laser projection system (constructed by a point laser and a micro-electro-mechanical system (MEMS) scanning galvanometer and modeled as the line projection model) are fully matched with the imaging mode of the line-scan camera. The 3D measurement model based on the height information, lateral information and absolute phase of the coding line structured light is derived. The multi-position flat display calibration method is proposed to calibrate the system parameters. In addition, in order to obtain the accurate absolute phase from the phase shift combined binary code, the periodic error correction method based on expansion-corrosion is proposed to correct the phase error. Contrary to conventional structured light methods based on a line-scan camera, the proposed method has the advantages of high measurement accuracy, high efficiency, more compactness and low cost. The experiments affirm that the coding line structured light is valid and the proposed calibration method is feasible. Experimental results also indicate that the proposed method performs well for both diffuse reflective surfaces and reflective surfaces that are difficult to measure with conventional structured light methods based on a line-scan camera.