Leather-Check uses a variant of IR thermography known as ‘lock-in’ thermography to analyze samples under test. In this method, the sample to be tested is heated at its surface by an intensity modulated source. This heat penetrates into the interior of the sample as a thermal wave and any change in the properties of the sample material such as cracks, cause a change in the propagation characteristics of the wave.
After the thermal wave is reflected to the surface of the sample, it becomes superimposed (or ‘locked-in’) onto the initial wave such that any defect is revealed by a local change in the phase angle. By recording the surface temperature of the sample with an IR camera, the temperature-time function of the image can be analyzed on a host computer. By calculating a phase image, the internal structure of the component and its interior defects are revealed. Depending on the modulation parameters of the heat source during the measurement, different depth ranges within the image can be displayed.
