Patent ID: 8768094
Filing Date: 2014-07-01
Classification: G06T,H04N

Abstract:
1. A calibration method to correct for image distortion of a camera that is positioned freely with respect to a viewing surface characterized by an aspect ratio and bounded by a rectangular frame, said method comprising: displaying at least one test image comprising a set of reference markers with known shapes and coordinates on the viewing surface; acquiring an image of the viewing surface such that the frame is captured in its entirety; identifying the four corners of the frame and the markers, as distorted, in camera image space; obtaining a transformation that corrects for perspective distortion of the acquired image by mapping the images of the four corners of the frame to a second set of four-corners forming a straight rectangle that maintains the aspect ratio and is characterized with an origin and a scale in the camera image space; constructing a calibration grid that maps the identified markers to their respective undistorted positions with respect to the frame, onto the straight rectangle in the camera image space; generating a camera distortion correction map from the calibration grid, that can be applied to all image pixels.