Optical sensing system

Claim 1

IN AN OPTICAL RADIATION SENSING SYSTEM FOR DERIVING SIGNALS INDICATIVE OF THE POSITION OF A TARGET SOURCE OF RADIATIONS INCLUDING A TARGET IMAGE FORMING OPTICAL SYSTEM, A GRATICULE ROTATABLY MOUNTED IN THE FOCAL PLANE OF THE TARGET IMAGE FORMING OPTICAL SYSTEM AND COMPRISING ALTERNATE RADIATIONS TRANSMITTING AND RADIATION NON-TRANSMITTING AREAS EMANATING FROM THE CENTRE OF THE GRATICULE AND DIRECTED OUTWARDLY FROM THE CENTRE TOWARDS ITS CIRCUMFERENCE, THE ANGULAR WIDTH OF THE AREAS PROGRESSIVELY VARYING THROUGH OUT IN THE DIRECTION OF ROTATION TO PRODUCE A FREQUENCY MODULATED SIGNAL, THE PHASE OF MODULATION OF THE SIGNAL OBTAINED BEING DETERMINED BY THE ANGULAR POSITIONING OF THE TARGET IMAGE ON THE SURFACE OF THE GRATICULE, AND THE ANGULAR WIDTH OF EACH AREA PROGRESSIVELY VARYING ALSO RADIALLY TO A CIRCULAR LIMIT, BEYOND WHICH THE ANGULAR WIDTH OF EACH AREA REMAINS CONSTANT, WHEREBY THE FREQUENCY DEVIATION IS DETERMINED BY THE RADIAL DEVIATION OF THE TARGET IMAGE UP TO A PREDETERMINED IMAGE DEVIATION, BEYOND WHICH A CONSTANT MAXIMUM FREQUENCY DEVIATION IS OBTAINED.