Photosensitive detectors and methods utilizing photosensitive detectors for positioning articles

Claim 1

IN AN APPARATUS FOR POSITIONING AN ARTICLE WHEREIN A SERVO POSITIONING SYSTEM HAVING A KNOWN DYNAMIC RESPONSE CHARACTERISTIC TENDING TO CAUSE A CONDITION OF SERVO HUNTING OF THE SERVO POSITIONING SYSTEM IS CONTROLLED IN RESPONSE TO THE POSITION OF A PAIR OF STRIPS OF ILLUMINATION INDICATIVE OF THE POSITION OF THE ARTICLE, THE COMBINATION COMPRISING: TWO PHOTOCONDUCTIVE FILMS UPON WHICH FILMS THE PAIR OF STRIPS OF ILLUMINATION ARE DIRECTED, THE POSITION OF THE PAIR OF STRIPS OF LIGHT ON THE FILMS BEING DIRECTLY RELATED TO THE POSITION OF THE ARTICLE, THE FILMS BEING SYMMETRICALLY FORMED ABOUT COORDINATE AXES (X,Y) WITH OPPOSED SIDE EDGES CONVERGING TOWARD SAID X-AXIS AND HAVING OPPOSED END EDGES, THE DISTANCE (Y) FROM THE X-AXIS OF ANY POINT ON A SIDE EDGE BEING A FUNCTION OF THE DISTANCE ALONG THE X-AXIS FROM THE ORIGIN OF THE COORDINATE AXES (X,Y); AND MEANS CONNECTING THE RESPECTIVE END EDGES OF EACH PHOTOCONDUCTIVE FILM FOR GENERATING AN OUTPUT SIGNAL TO OPERATE SAID SERVO POSITIONING SYSTEM, SAID OUTPUT SIGNAL BEING PROPORTIONAL TO THE POSITION OF THE STRIPS OF ILLUMINATION ON THE FILMS, THE FILMS BEING POSITIONED RELATIVE TO THE ARTICLE SO THAT THE OUTPUT SIGNAL FROM EACH FILM WILL BE THE SAME WHEN THE ARTICLE IS IN A PREDETERMINED POSITION, AND THE RELATIONSHIP BETWEEN THE DISTANCE (Y) OF A POINT ON A SIDE EDGE WITH RESPECT TO ITS DISTANCE (X) FROM THE ORIGIN OF THE COORDINATE AXES (X,Y) BEING CHOSEN SO THAT THE OUTPUT SIGNAL FROM THE FILMS COMPENSATES FOR THE KNOWN DYNAMIC RESPONSE CHARACTERISTICS OF THE SERVO POSITIONING SYSTEM TO ELIMINATE SERVO HUNTING OF THE SYSTEM.