Passive infrared tracking and ranging system

Claim 1

IN AN OPTICAL TRACKING SYSTEM, THE COMBINTION COMPRISING: A LENS FOR FOCUSING RAYS OF LIGHT TO A FOCAL POINT; FIRST AND SECOND OPAQUE CHOPPER GRIDS FIXEDLY SPACED ON A ROTATABLE SHAFT, EACH OF SAID CHOPPER GRIDS COMPRISING AT LEAST ONE SEGMENT, THE SEGMENTS OF SAID FIRST AND SECOND GRINDS BEING ALTERNATELY DISPOSED AROUND THE PERIPHERY OF SAID SHAFT, EACH OF SAID SEGMENTS HAVING A PLURALITY OF AXIALLY SPACED ROWS OF SLOTS, EACH OF SAID ROWS HAVING A PREDETERMINED DIFFERENT NUMBER OF SLOTS; MEANS ROTATABLY MOUNTING SAID SHAFT SO THAT THE SEGMENTS OF SAID FIRST GRID TRANSVERSE THE OPTICAL AXIS OF SAID LENS BEFORE SAID FOCAL POINT, AND SO THAT SAID SEGMENTS OF SAID SECOND GRID TRAVERSE SAID OPTICAL AXIS AFTER SAID FOCAL POINT, WHEREBY SAID RAYS OF LIGHT WILL BE INTERRUPTED BY THE OPAQUE PORTIONS OF SAID GRIDS AND WILL BE PERMITTED TO PASS THROUGH SAID SLOTS, THEREBY PRODUCING ALTERNATE SERIES OF PULSES OF LIGHT; MEANS FOR COMPARING THE AVERAGE INTENSITIES OF SAID ALTERNATE SERIES OF PULSES OF LIGHT TO LOCATE SAID FOCAL POINT ALONG SAID OPTICAL AXIS; MEANS FOR DETERMING THE PHASE WITH RESPECT TO A REFERENCE OF SAID ALTERNATE SERIES OF PULSES OF LIGHT TO LOCATE THE POSITION OF SAID FOCAL POINT IN ONE DIRECTION PERPENDICULAR TO SAID AXIS; AND MEANS RESPONSIVE TO THE NUMBER OF PULSES OF LIGHT IN EACH SERIES FOR DETERMINING THE LOCATION OF SAID FOCAL POINT IN A SECONE DIRECTION MUTUALLY PERPENDICULAR TO SAID AXIS AND SAID FIRST DETECTION.