Distortion-free camera calibration

Abstract

A universal pixel-by-pixel distortion-free camera calibration technique is described. All camera lenses will cause image distortions. An LCD flat panel can be used as an active calibration panel for camera calibration. Each sensor pixel has its ray vector in space and can be calibrated with the LCD. A set of phase shifting fringes (PSF) can be used to establish the mapping relationship between the LCD pixels and the sensor pixels. For primary camera calibration, a virtual sensor can be created on the LCD and a set of inverse mapping parameters (IMP) for each virtual pixel can be determined. The captured images can be rectified by resampling with the IMP. The output images will be distortion-free with zero geometric distortions and zero chromatic aberrations. For advanced camera calibration, all pixel ray vectors in space can be calibrated. A virtual sensor can be created on any expected planar or curvature surface in space and the IMP can be determined accordingly. After image rectification or 3D reconstruction, for every 2D pixel or 3D point cloud, the mean error will be 0, the std error will be 1/1,000 pixel pitch or smaller. The cameras can be used as non-contact 2D/3D rulers. The distortion-free calibration technique can be applied to any cameras and projectors, no matter how complex their lens structures can be. Interactive and comprehensive intensity calibrations can be made between LCD, cameras and projectors.