To achieve rapid and precise non-contact measurements of coating emissivity at room temperature, a measurement method based on infrared thermal imager was proposed. By applying two irradiations with different energies to the target and reference surfaces, the influences of atmospheric transmittance, radiation of the target itself, environmental radiation, and atmospheric path radiation were eliminated, thereby enabling accurate emissivity measurement. Experiments were designed for validation with a mid-wave infrared thermal imager and a surface blackbody as the radiation source. Several combinations of irradiation energy were set to investigate the effects of average energy and energy difference between the two irradiations on the measured results. The normal emissivity of the coated sample plate in the mid-wave band was measured to generate the image of coating surface emissivity. Then, the emissivity measurement results of the proposed method were compared with those of the energy method and the point emissivity measuring instrument under the same conditions, and the comparison indicated that the proposed method can effectively measure the emissivity of coating. Some factors causing measurement errors were analyzed. Finally, an experiment was designed to compare the measurement speed between the proposed method and the currently used methods, and the experimental results were analyzed.

In this paper, a measurement correction method is proposed to correct the error of the irradiation reflection method when measuring the emissivity of curved surface targets. First, by introducing an angle parameter related to the target surface shape, the formulas of emissivity measurements for curved surface targets under various types of radiation sources were obtained. Then, the variation law of these emissivity measurement formulas was analyzed, the concept of the measurement correction factor was proposed, and then a unified correction measurement formula was obtained. Finally, a scene of measuring the emissivity of a curved surface target based on the irradiation reflection method was simulated. Different target emissivities and different distances between the radiation source and target were set, and the errors between the measured and corrected emissivities were compared. The results revealed that the proposed method could effectively correct the error caused by the curvature of the target surface when measuring its emissivity by the irradiation reflection method. This is of great significance to expanding the application scope of the irradiation reflection method and improving the measurement accuracy.

Spectroradiometers exhibit the smallest aberration and the optimum response at the field-of-view (FOV) center. The aberration increases and the response deteriorates at positions further away from the FOV center, which leads to nonuniformity in the spectroradiometer FOV. In this study, a concentric-circles method for correcting the spectroradiometer FOV nonuniformity was developed. The calibration experiment for FOV nonuniformity was conducted by establishing the experimental platform. The nonuniformity correction coefficients were obtained and then used to fit the correction function curve within the whole FOV, allowing for correction of measurement targets with an arbitrary shape. The radiation intensity of the blackbody at different temperatures was obtained by measurement, and the nonuniformity coefficient was used to correct it. After correction, the error was within 1.84% for the spectrally integrated radiant intensity in the non-absorption band. Using this correction method, efficient calibration of spectroradiometer nonuniformity can be achieved, thereby enhancing the measurement accuracy of the spectroradiometer.