<title>Image Coincidence Detection Using Optical Correlation Techniques</title>

Abstract

Data reduction from stereo-photography forms a powerful tool not only for measuring the size, shape and location of an object or a scene but also to ascertain other desired parameters such as surface areas, volumes, etc. from space coordinates. In a truly vertical overlapping pair of photographs the relief information pertaining to the object or the scene is stored in terms of differential x-parallax. The x-parallax difference is the principal cause of stereoperception and it is through the measurement of x-parallax dif-ference that terrain elevation measurements are made from a pair of aerial photographs using a stereoscopic instrument. All automated stereo-compilation instruments whether electronic or optical are based on the ability to match conjugate images and automatically measure the x-parallax difference. In the electronic correlation system this is achieved by correlating the electrical signals representing the image detail generated using a scanning process. In the optical systems a direct two-dimensional correlation is performed using the intensity or amplitude distribution of light representing the image detail.