Conventional stereocompilation, whether carried out manually or automatically, involves a sequential point-by-point measurement of x parallax. This paper describes an "instant-profile" correlator, a coherent optical parallel processor which measures and displays x parallax point by point simultaneously rather than sequentially. With this optical processor, one can select any y strip of the overlapping stereo imagery, measure simultaneously the x parallax over the entire strip, and display at the output x parallax as a function of y photocoordinate. All of the overlapping imagery may be processed in this matter by simply scanning of the stereo photographs with a slit. The theory of operation of the optical parallel processor is discussed and experimental results with aerial photography are presented.