Calibration of a structure light based windshield inspection system

Abstract

Three dimensional optic measurement system's accuracy is highly related with the field of inspection. Increasing of field inspection costs increasing camera / projector pixel area on the test surface. Small surface changes within one pixel area cannot be directly detected, which will lower the system accuracy. A pixel-to-pixel strategy is developed to solve this problem. Increasing field of inspection also costs a longer standoff distance. The random image noise from the environment, uncertainties functions by lens distortion and resolution variation are all amplified. Therefore, a more complicated calibration model for each pixel is proposed to calibrate the system. In traditional structured light vision systems, a single sensor usually detects around 10,000 – 50,000 mm2, and the 3D vision sensor in this paper needs to detect around 2,400,000 mm2. Larger detection range gives more challenge to finish the calibration tasks. This paper proposes a clear calibration procedure to a large field of inspection structured light system. Last the comparison with the CMM measured results is used to prove that the calibration tasks have been successfully achieved.