Abstract:The infrared thermal imager has advantages of real-time on-line, non-contact acquisition of the two-dimensional temperature distribution of the measured object, which is widely used in steel, agriculture, power electronics and other fields. However, infrared temperature measurement results are easily affected by interference factors. To address the infrared temperature measurement error caused by the change of directional emissivity, a temperature compensation method based on directional emissivity correction is proposed in this article. Firstly, based on the principle of infrared temperature measurement, an infrared temperature measurement compensation model for the change of directional emissivity is formulated. Secondly, to determine the directional emissivity in the compensation model, a 3D thermal imaging system constructed with an infrared thermal imager and a laser scanner is used, and a reference body-based directional emissivity correction method is proposed. Then, the law of the directional emissivity changing with the viewing angle is determined by polynomial fitting. Experimental results show that the proposed infrared temperature measurement compensation method is effective in reducing the infrared temperature measurement error caused by the change of directional emissivity. After temperature compensation, the maximum error of infrared temperature measurement is reduced from 9. 64℃ to 2. 97℃ , and the standard deviation is reduced from 3. 57℃ to 0. 71℃ .