A novel optical measurement technique for the in situ determination of surface temperature is presented. The technique employs modulation of the object temperature by an energy source of high intensity, such as a laser. By modulation of the temperature at the point from which the emitted spectrum of electro-magnetic radiation is being monitored, routine calculations involving the observed modulated component of the radiation spectrum will determine the temperature and, for some conditions, emissivity. The region to be measured is thus defined by the intersection of the laser and the beam which enters the collection optics of the Fourier transform Infrared spectrometer. Analysis of the modulated radiation results in a temperature determination which is independent of material emissivity, surrounding radiation sources, and instrument calibration for optical path.
James R. Markham, Philip E. Best, and Peter R. Solomon, "Spectroscopic Method for Measuring Surface Temperature That Is Independent of Material Emissivity, Surrounding Radiation Sources, and Instrument Calibration," Appl. Spectrosc. 48, 265-270 (1994)