Radiation sensitive ground speed indicator

Claim 1

ELECTRO-OPTICAL APPARATUS FOR MEASURING GROUND VELOCITY OF AN AERIAL VERICLE COMPRISING A PAIR OF RADIATIONSENSITIVE ELEMENTS, POSITIONED IN SPACED APART, CO-PLANAR RELATION AND ADAPTED TO PRODUCE INDIVIDUAL TIME SPACED ELECTRICAL SIGNALS REPRESENTATIVE OF THE RADIATIONS RECEIVED FROM A TARGET AREA, OPTICAL MEANS ASSOCIATED WITH EACH RADIATION-SENSITIVE ELEMENT FOR DIRECTING THE RADIATIONS UPON THE ELEMENTS, VARIABLE TIME DELAY MEANS CONNECTED TO THE ELEMENT FIRST RECEIVING THE ELECTRICAL SIGNALS FOR PROVIDING A TIME DELAY FOR SAID ELECTRICAL SIGNALS, A SIGNAL COMPARISON CIRCUIT CONNECTED TO THE OTHER ONE OF SAID ELEMENTS AND TO SAID VARIABLE TIME DELAY MEANS FOR PRODUCING A CONTROL SIGNAL WHENEVER THE SIGNAL OUTPUTS FROM SAID VARIABLE TIME DELAY MEANS AND FROM THE SECOND ELEMENT ARE IN COINCIDENCE, CORRECTION MEANS CONNECTED TO THE VARIABLE TIME DELAY MEANS FOR CYCLICALLY INCREASING AND DECREASING THE TIME DELAY IN ACCORDANCE WITH SAID CONTROL SIGNAL TO CYCLICALLY EFFECT COINCIDENCE OF THE SIGNALS APPLIED TO SAID COMPARISON CIRCUIT, AND SIGNAL GENERATING MEANS ASSOCIATED WITH SAID CORRECTION MEANS FOR GENERATING AN OUTPUT SIGNAL INDICATIVE OF THE GROUND SPEED AS REPRESENTED BY A CONDITION OF SAID CORRECTION MEANS WHEN THE SIGNALS APPLIED TO SAID COMPARISON CIRCUIT ARE IN COINCIDENCE.