Non-Contact Measurement of the Spectral Emissivity through Active/Passive Synergy of CO2 Laser at 10.6 µm and 102F FTIR (Fourier Transform Infrared) Spectrometer
Non-Contact Measurement of the Spectral Emissivity through Active/Passive Synergy of CO2 Laser at 10.6 µm and 102F FTIR (Fourier Transform Infrared) Spectrometer.
In the inversion of land surface temperature (LST) from satellite data, obtaining the
information on land surface emissivity is most challenging. How to solve both the emissivity
and the LST from the underdetermined equations for thermal infrared radiation is a hot research
topic related to quantitative thermal infrared remote sensing. The academic research and practical
applications based on the temperature-emissivity retrieval algorithms show that directly measuring
the emissivity of objects at a fixed thermal infrared waveband is an important way to close the
underdetermined equations for thermal infrared radiation. Based on the prior research results of both
the authors and others, this paper proposes a new approach of obtaining the spectral emissivity of
the object at 8–14 µm with a single-band CO2 laser at 10.6 µm and a 102F FTIR spectrometer. Through
experiments, the spectral emissivity of several key samples, including aluminum plate, iron plate,
copper plate, marble plate, rubber sheet, and paper board, at 8–14 µm is obtained, and the measured
data are basically consistent with the hemispherical emissivity measurement by a Nicolet iS10 FTIR
spectrometer for the same objects. For the rough surface of materials, such as marble and rusty
iron, the RMSE of emissivity is below 0.05. The differences in the field of view angle and in the
measuring direction between the Nicolet FTIR method and the method proposed in the paper, and the
heterogeneity in the degree of oxidation, polishing and composition of the samples, are the main
reasons for the differences of the emissivities between the two methods.