Selective radiation detector and free-air thermometer

Claim 1

A DEVICE FOR MEASURING TEMPERATURE OF THE ATMOSPHERE WHICH IS SUBSTANTIALLY UNAFFECTED BY LOCAL HEAT CONDITIONS WHICH COMPRISES, IN COMBINATION AND IN OPTICAL ALIGNMENT MEANS, FOR PERMITTING INFRARED RADIATION IN THE FORM OF A BEAM TO ENTER THE DEVICE, A SELECTIVE DETECTOR SYSTEM RESPONSIVE SUBSTANTIALLY ONLY TO INFRARED RADIATION WITHIN THE BAND OF EMISSION OF THE MOLECULES OF A SELECTED GASEOUS COMPONENT OF THE ATMOSPHERE, A REFERENCE BLACK BODY MAINTAINED AT A PREDETERMINED TEMPERATURE, PERIODIC OCCULTING MEANS FOR THE INFRARED BEAM, SAID OCCULTING MEANS BEING PROVIDED WITH REFLECTING MEANS FOR REFLECTING AN IMAGE OF THE REFERENCE BLACK BODY ON THE DETECTOR DURING OCCULTATION, SAID OCCULTING MEANS OPERATING AT A FREQUENCY SUFFICIENTLY LOW SO THAT THE INFRARED DETECTOR IS RESPONSIVE THERETO, WHEREBY THE INFRARED DETECTOR PRODUCES A PERIODIC RESPONSE COMPARING THE TEMPERATURE PRODUCED FROM THE INFRARED BEAM WITH THAT OF THE BLACK BODY.