Measurement of surface temperature and emissivity with stereo dual-wavelength IR thermography

This work describes a temperature and emissivity measurement methodology that applies the multi-wavelength pyrometry principle to IR thermography using two IR cameras in a stereo arrangement with detectors working in different wavelength bands. The two radiation distributions measured by the IR cameras are rebuilt on the object surface mesh by means of the pinhole camera model and are used to write a system of equations in which emissivities and temperatures are unknown quantities. By solving the system, the temperature and directional emissivity of the material under test can be measured for each wavelength band. The influence on the proposed methodology of the IR camera noise and of the temperature bias between the two cameras is numerically analysed in the case of gray and non-gray bodies. To validate the proposed methodology, an experimental test was performed on an object with known emissivity (measured in a conventional way).