Electro-optical error measuring system for determining target displacement

Claim 1

AN ELECTRO-OPTICAL ERROR MEASURING SYSTEM FOR MEASURING THE ANGULAR DISPLACEMENT BETWEEN A TARGET CONTAINING AN INTENSITY MODULATED RADIATING SOURCE OF ENERGY AND A BORE-SIGHTED LINE OF DIRECTION COMPRISING: (A) A HOUSING INCLUDING A MAGNET AND FORMED TO ESTABLISH A MAGNETIC FIELD OF FLUX ACROSS A SPACE BETWEEN TWO SECTIONS THEREOF; (B) A SUPPORT ROD CONNECTED TO SAID HOUSING AND EXTENDING THROUGH SAID SPACE; (C) A COIL FORM JOURNALED TO SAID SUPPORT ROD WITHIN SAID SPACE; (D) A CONDUCTING COIL WRAPPED ON SAID COIL FORM; (E) AT LEAST ONE SPRING CONNECTED TO SAID COIL FORM TO RESTRAIN SAID COIL FORM IN A NEUTRAL POSITION ROTATIONALLY WITH RESPECT TO SAID HOUSING WHEN SUBSTANTIALLY NO CURRENT FLOWS THROUGH SAID COIL; (F) A CENTER-SPLIT PHOTODETECTOR MOUNTED ON SAID COIL FORM, THE CENTER SPLIT THEREOF DISPOSED PARALLEL WITH RESPECT TO THE AXIS OF ROTATION OF SAID COIL FORM AND ALIGNED WITH SAID BORE-SIGHTED LINE OF DIRECTION WHEN SAID COIL FORM IS IN ITS SAID NEUTRAL POSITION WITH RESPECT TO SAID HOUSING, SO AS TO RECEIVE A LIGHT SPOT FROM SAID TARGET THEREON TO GENERATE A PHOTODETECTOR AC OUTPUT SIGNAL IN RESPONSE THERETO SUCH THAT SAID OUTPUT SIGNAL IS AT SUBSTANTIALLY A ZERO POTENTIAL WHEN SAID LIGHT SPOT PRODUCES AN EQUAL ILLUMINATION OF THE TWO SECTIONS OF SAID CENTER-SPLIT PHOTODETECTOR AND SUCH THAT SAID ELECTRICAL SIGNAL HAS A POTENTIAL PROPORTIONAL TO AND IN PHASE WITH THE DISTANCE AND DIRECTION, RESPECTIVELY, OF THE NORMAL DISPLACEMENT OF SAID LIGHT SPOT FROM SAID CENTER SPLIT OF SAID PHOTODETECTOR WHEN SAID LIGHT SPOT PRODUCES AN UNEQUAL ILLUMINATION OF SAID TWO SECTIONS OF SAID CENTER-SPLIT PHOTODETECTOR, THERE BEING AN ANGULAR DISPLACEMENT BETWEEN SAID TARGET AND SAID BORE-SIGHTED LINE OF DIRECTION AT SUCH TIMES PROPORTIONAL TO AND IN PHASE WITH SAID NORMAL DISPLACEMENT OF SAID LIGHT SPOT FROM SAID CENTER SPLIT OF SAID PHOTODETECTOR; AND (G) DEMODULATING MEANS FOR ASCERTAINING THE PHASE OF SAID PHOTODETECTOR AC OUTPUT SIGNAL AND FOR CONVERTING SAID PHOTODETECTOR OUTPUT SIGNAL INTO A PLUS OR A MINUS DC INPUT SIGNAL TO SAID CONDUCTING COIL DEPENDENT UPON THE PHASE DETECTED.