A Hilbert Warping Algorithm for Recognizing Characters from Moving Camera

We present a method for recognizing characters from image sequences captured by moving camera. In the proposed method, the sequence of the captured images is compared with those of reference character patterns using the concept of analytic signal. Since the captured image sequence can be nonlinearly warped along the time axis due to the movement of a hand-held camera, phase synchronization of two analytic signals is used for the alignment of two image sequences. Hilbert transform is used to convert all the image sequences into analytic signals whose phases are supposed to be increasing. Experimental results showed the usefulness of the proposed phase-based alignment algorithm.