Temperature measurement of plastic film

Claim 1

IN A METHOD OF HEATING A PLASTIC FILM WITH A SOURCE OF INFRA-RED RADIANT HEAT AND MEASURING THE TEMPERATURE OF THE PLASTIC FILM BY RADIATION PYROMETRY WHICH COMPRISES MEASURING THE INFRA-RED EMISSION FROM THE FILM SUBSTANTIALLY OVER A GROUP OF WAVE-LENGTHS OF STRONG EMISSION AT WHICH THE RADIATION IS SUBSTANTIALLY COMPELETELY ABSORBD BY THE MATERIAL OF THE FILM AND USING AN INFRA-RED MEASURING INSTRUMENT INCORPORATING A RADIANT ENERGY SENSITIVE MEANS WHICH IS SENSITIVE ONLY TO THOSE WAVE-LENGTHS THE IMPROVEMENT WHICH COMPRISES PASSING THE INFRA-RED EMISSION FROM THE FILM THROUGH A FILTER SYSTEM COMPRISING A FIRST MEANS WHICH TRANSMITS ONLY SAID GROUP OF WAVELENGTHS AND PERIODICALLY INTERRUPTING ITS PATH OF TRAVEL TO SAID RADIANT ENERGY SENSITIVE MEANS BY A SECOND MEANS WHICH ABSORBS SUBSTANTIALLY AT LEAST SAID GROUP OF WAVELENGTHS, SAID IMPROVEMENT FURTHER COMPRISING FOCUSING AN IMAGE OF SAID INFRA-RED RADIANT SOURCE ONTO STOP MEANS WHICH ABSORBS THE RADIATION OF SAID SOURCE, SAID STOP MEANS BEING LOCATED SO AS TO PREVENT SAID RADIATION FROM REACHING SAID RADIANT ENERGY SENSITIVE MEANS.