Detection of Image Coincidence in Stereo Pairs Using Phase Correlation

Abstract

ABSTRACTA simple method for generating real time equal height fringes from two stereo transparencies is explained and demonstrated. The two transparencies are bleached converting them to phase transparencies. An image plane hologram is made of one of the transparencies, using a plane wave as the object wave. The second transparency is used to reconstruct the hologram. On those regions where the two transparencies are phase correlated the reconstructed wave is plane. A suitable filter is placed behind the hologram that allows only those regions of the reconstructed wave that are plane to pass. The light that is allowed to pass is used to illuminate an image plane giving a fringe of equal height. INTRODUCTION Several methods for obtaining equal height contours from the information contained in two vertical or rectified stereo transparencies have been proposed, and some have been demonstrated, for application to close-range photo- grammetry. Two of these methods, which use coherent optics provide a direct visual contour fringe. In 1967 workers at Bendix1 generated a visual contour as the region where Mach-Zehnder fringes show good contrast. In 1969 Real2 proposed a method where a contour fringe would appear as a bright line against a dark background and thus the contrast of interferometric fringes need not be considered. Unfortunately this method requires a separate hologram to be made for each contour. The method demonstrated here is in concept similar to that of Real in that it gives a bright contour, but it does not require a separate hologram for each contour.