METHOD AND SYSTEM FOR REFERENCE-FREE THERMOGRAPHIC DETECTION OF SUBSURFACE DEFECTS USING COMPRESSED IMAGE DATA

摘要

A method and system for non-destructive, reference free thermographic detection of sub-surface defects uses an infrared camera to capture images of a sample (204) that has been heated and allow to cool to equilibrium temperature. The temperature-time data obtained for each pixel in each image is converted into the logarithmic domain and at least squares fit is conducted on the data to generate a polynomial expression corresponding to the temperature-time data for a given pixel (212). This polynomial expression can be transformed into the original time domain to obtain temperature time data with improved signal-to-noise characteristics. Defects can be detected by observing the zero-crossing characteristic of the second derivative of the polynomial (214).