Using Infrared Thermography for Detecting Defects on Surfaces With Low and Variable Emissivity

Currently infrared scanning technology has been successfully applied for the detection of a wide variety of defects in many applications provided that the surfaces have a high emissivity that doesn’t reflect radiation from outside sources. However, surfaces with low and variable emissivity present a challenge for the application of this technology because infrared cameras and sensors cannot differentiate between the emitted radiation from the surface of interest and those reflected from outside sources. The system presented is an attempt to reduce and/or remove the effects of reflected radiation to increase the system’s applicability beyond the limit of high emissivity surfaces. Physical hardware and computer software are used in concert with radiative heat transfer equations to first determine the emissivity of each point on the surface, then use that information obtained to accurately depict the surface temperature. While this newest iteration of the system development has addressed many important issues regarding accuracy, efficiency as well as performance enhancement in the removal of the artifacts of reflected radiation, the technique still has difficulties to be applied to most surfaces with variable emissivity.