Infrared analyzer with means responsive to a detector output to control radiant energy emission from a reference source

Claim 1

AN INFRARED ANALYZER FOR DETECTION OF A SUBSTANCE ALONG AN OPEN OPTICAL PATH BETWEEN SAID ANALYZER AND AN UNCONTROLLED RADIATING BACKGROUND, SAID SUBSTANCE EXHIBITING AN ABSORPTION CHARACTERISTIC AT A FIRST WAVELENGTH COMPRISING A FIRST DETECTOR FOR GENERATING A SIGNAL IN RESPONSE TO RADIATION OF SAID FIRST WAVELENGTH, A SECOND DETECTOR FOR GENERATING A SIGNAL IN RESPONSE TO RADIATION OF A SECOND WAVELENGTH IN PART OF THE SPECTRUM OTHER THAN THAT AT WHICH SAID SUBSTANCE EXHIBITS ABSORPTION CHARACTERISTICS, A SOURCE, MEANS FOR ALTERNATELY DIRECTING RADIATION EMITTED ALONG SAID OPTICAL PATH AND RADIATION EMITTED BY SAID SOURCE TO SAID FIRST AND SECOND DETECTORS, AND TEMPERATURE CONTROL MEANS RESPONSIVE TO THE ALTERNATING SIGNAL PRODUCED IN SAID SECOND DETECTOR AND EFFECTIVE TO CONTROL THE TEMPERATURE OF SAID SOURCE SO AS TO REDUCE THE ALTERNATING SIGNAL PRODUCED IN SAID SECOND DETECTOR THE ALTERNATING SIGNAL PRODUCED IN SAID SECOND DETECTOR TO A MIMIMUM, WHEREBY THE AMPLITUDE OF THE ALTERNATING SIGNAL PRODUCED IN SAID FIRST DETECTOR IS A FUNCTION OF THE PRESENCE OF SAID SUBSTANCE ALONG SAID OPTICAL PATH.