Two channel radiant energy background signal elimination means

Claim 1

IN AN ELECTRO-OPTICAL RADIATION DETECTION SYSTEM IN WHICH RADIANT ENERGY IS RECEIVED FROM A TARGET HAVING A GIVEN SPECTRAL DISTRIBUTION ALONG WITH ABIENT BACKGROUND RADIATION HAVING A SPECTRAL DISTRIBUTION WHICH DIFFERS SUBSTANTIALLY FROM THE SPECTRAL DISTRIBUTION WHICH DIFDIANT ENERGY RECEIVED FROM THE TARGET, THE COMBINATION OF AN OPTICAL SYSTEM FOR COLLECTING RADIANT ENERGY EMANATING FROM A VOLUME OF SPACE FALLING WITHIN A CONDITIONALLY MOVABLE FIELD OF VIEW, A FIRST SIGNAL CHANNEL INCLUDING A RADIATION SENSITIVE CELL ARRANGED TO RECEIVE RADIANT ENERGY COLLECTED BY SAID OPTICAL SYSTEM FALLING WITHIN A FIRST SPECTRAL BAND, A SECOND SIGNAL CHANNEL INCLUDING A RADIATION SENSITIVE CELL ARRANGED TO RECEIVE ENERGY COLLECTED BY THE OPTICAL SYSTEM FALLING WITHIN A SECOND SPECTRAL BAND, CONTINUOUSLY OPERABLE BACKGROUND SUPPRESSION MEANS COMPRISING AT LEAST ONE VARIABLE GAIN AMPLIFIER INCLUDED IN ONE OF SAID SIGNAL CHANNELS, MEANS COUPLED TO SAID FIRST AND SECOND SIGNAL CHANNELS AND TO SAID VARIABLE GAIN AMPLIFIER FOR EFFECTING AN EQUALIZATION OF SIGNAL COMPONENTS IN EACH OF SAID CHANNELS HAVING FREQUENCIES FALLING BELOW A PREDETERMINED FREQUENCY CORRESPONDING TO BACKGROUND ENERGY, AND TARGET INDICATING MEANS COUPLED TO SAID FIRST AND SECOND SIGNAL CHANNELS FOR GENERATING AN OUTPUT SIGNAL CORRESPONDING TO TARGET ENERGY SUBSTANTIALLY FREE FROM THE EFFECTS OF BACKGROUND RADIATION.