Spectro-radiometer with means for eliminating background noise

Claim 1

A RADIOMETER COMPRISING MEANS FOR COLLECTING RADIATION FROM A TARGET; A FIRST REFERENCE RADIATOR; A SECOND REFERENCE RADIATOR; MEANS FOR MAINTAINING A KNOWN DIFFERENTIAL BETWEEN THE TEMPERATURE OF SAID FIRST AND SAID SECOND REFERENCE RADIATORS; A RADIATION SENSITIVE DETECTOR CAPABLE OF GENERATING A SIGNAL WHICH IS A FUNCTION OF THE INTENSITY OF THE RADIATION FALLING THEREON; AND HIGH SPEED ALTERNATING MEANS FOR AUTOMATICALLY SEQUENTIALLY DIRECTING ONTO SAID DETECTOR DURING THREE DISTINCT TIME INTERVALS, IN SOME SEQUENTIAL ORDER, COLLECTED RADIATION FROM SAID TARGET, RADIATION FROM SAID FIRST REFERENCE RADIATOR, AND RADIATION FROM SAID SECOND REFERENCE RADIATOR, SAID RADIATION SENSITIVE DETECTOR THEREBY PRODUCING AT LEAST A FIRST DETECTOR SIGNAL WHICH IS A FUNCTION OF THE DIFFERENCE BETWEEN THE RADIATION INTENSITY OF SAID TARGET AND THE RADIATION INTENSITY OF ONE OF SAID REFERENCE RADIATORS AND A SECOND DETECTOR SIGNAL WHICH IS THE SAME FUNCTION OF THE DIFFERENCE IN THE RADIATION INTENSITIES OF SAID FIRST AND SECOND REFERENCE RADIATORS, CAUSED BY SAID KNOWN TEMPERATURE DIFFERENTIAL.