Automatic Metal Parts Inspection: Use of Thermographic Images and Anomaly Detection Algorithms
Résumé
A fully-automatic approach based on the use of induction thermography and detection algorithms is proposed to inspect industrial metallic parts containing different surface and sub-surface anomalies such as open cracks, open and
closed notches with different sizes and depths. A practical experimental setup is developed, where lock-in and pulsed
thermography (LT and PT, respectively) techniques are used to establish a dataset of thermal images for three different
mockups. Data cubes are constructed by stacking up the temporal sequence of thermogram images. After the
reduction of the data space dimension by means of denoising and dimensionality reduction methods; anomaly detection
algorithms are applied on the reduced data cubes. The dimensions of the reduced data spaces are automatically
calculated with arbitrary criterion. The results show that, when reduced data cubes are used, the anomaly detection
algorithms originally developed for hyperspectral data, that of Reed and Xiaoli Yu (RX) and the regularized adaptive
RX (RARX), give good detection performances for both surface and sub-surface defects in a non-supervised way.