Correlation techniques in adaptive template matching with uncalibrated cameras
Paolo Remagnino, Pascal Brand, Roger Mohr · Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE · 1995
The use of correlation as a measure of similarity between two signals is a well known technique. Correlation is commonly used in stereo vision to solve the correspondence problem. In this context the aim is to find the position of a point in one of the two images of a weakly calibrated stereo pair which corresponds to a point in the other image. Template windows are chosen from the first image as 2D information samples to be matched in a region of interest of the second image. We propose a technique which exploits an adaptive template matching. It works as an iterative optimization of the involved parameters with a consequent iterative refinement of the correspondence. Matching is performed by transforming a template window using the current image-to-image affine transformation and exploiting the epipolar geometry to reduce the degrees of freedom of the template position in the region of interest. As a validation test of the presented technique we report a study on the accuracy of the obtained results with various template sizes. We show that subpixel accuracy can be reached with relatively small templates. A major concern of our work is the accuracy of the correspondence. Higher accuracy of the correspondences results in fact in a more realistic reconstruction of the viewed scene. In the case of a stereo pair having undergone an estimated distortion of 0.5 pixel (10 micrometers of pixel size) it shows an accuracy in the correspondence of 3 micrometers for template windows of 17 X 17 size selected in textured image patches. Experiments are under process to improve the mentioned results.