Abstract: The calibration process of traditional line scan cameras is complex and requires high accuracy of calibration objects, it is difficult to ensure the positioning accuracy of defects. This paper proposes a ring rotation calibration method for line scan cameras to improve the positioning accuracy of defects. This method designs a new type of circular calibration board. On the basic of static calibration, the coordinates of the intersection of the camera’s line of sight and the circle are collected by a rotating line camera to obtain the rotation angle and multiple sets of calibration points to establish the imaging model and radial distortion model of the line camera. The internal parameters and distortion parameters of the camera are solved by nonlinear optimization of the global overall function, and the impact of different camera rotation angles on the calibration accuracy are analyzed. The experimental results show that when θ≤20°, the calibration accuracy of this method is within 0.35 pixel, which meets the positioning requirements of actual detection. The PCB defect detection is well verified.

Key words: linear camera calibration, circular calibration board, nonlinear optimization, imaging model, calibration error