非平表面的红外热像测温修正方法研究

Compensation Method for Temperature Distribution Measured by Infrared Thermography for Non-flat Surfaces

利用红外热像仪测温需先设定被测表面的法向发射率,该发射率通常为定值。而当热像仪处于被测点的天顶角大于50°的位置范围时,由于被测点定向发射率的变化,必造成这些点的测温误差。对于非平表面,这样的点大量存在。因此,必须对其测温结果进行修正。本文针对使用单目红外热像仪测量非平表面温度时由于各点定向发射率的变化引起的测量误差进行研究,并依据物体表面定量发射率的变化规律,给出了测量点的温度修正系数。同时,通过点云三维建模,利用热像仪的几何成像原理推导出红外热像图与实际被测表面中点与点的对应关系,给出了通过红外热像仪测量非平表面的温度分布的误差修正方法。实验证明了该方法的有效性。

When employing an infrared thermal imager to measure surface temperature,the emissivity of the surface to be measured should be set first and kept constant during the measurement process.However,when the infrared imager is placed in the range of more than 50° of the zenith angle of the points to be measured,the emissivities of the points in this angle will vary significantly;hence,temperature measurement errors will occur,especially for points on non-flat surfaces.In view of the measurement error caused by the variation of emissivity of different points in the measured non-flat surface when using a monocular infrared thermal imager,this paper provides a compensation factor based on the variation rules of the emissivity with the measuring angle.In addition,based on 3D modeling technology,the relationship between the positions of the points in the thermographic image and those in the actual surface is determined.The compensation method of the temperature measurements for a non-flat surface is presented.The feasibility of the method was verified through experiments.