Nonlinear filtering method for emissivity correction of PCB infrared thermal images

In the diagnosis of Printed Circuit Board (PCB) based on infrared radiation, emissivity correction must be performed on the thermal image to retrieve the true temperature distribution on the PCB surface. Taking the measured PCB surface temperature as a combination of its true temperature distribution and its emissivity distribution, a non-linear filtering method was proposed to separate the true temperature from this combination based on the differences in the continuity of these two contributions. As the key step of the proposed method, the discontinuity detection is implemented through wavelet transform. Experimental results indicated that the true temperature distribution can be estimated precisely by the proposed method.