A cost-effective alternative for chessboard pattern to calibrate industrial infrared cameras used in defect measurement with active lock-in thermography
Image-based industrial non-destructive testing techniques are commonly used for assessing material integrity. The cameras used for these tasks have lenses that can present form deviations, promoting anomaly creation on the acquired images. This problem also affects infrared cameras, but very often nothing is done to correct it, usually due to the cost of calibration tools for infrared wavelength. This paper describes then a manufacturing process based on the ablation of copper material with a pulsed laser of a cost-effective, infrared-reflective chessboard pattern for calibrating infrared cameras. Measurements of artificial defects in carbon fiber reinforced plastic plates with active lock-in thermography were performed and a comparison between the results with and without the corrections given by the calibration was done. The metrological benefits of applying the proposed calibration procedure have been evidenced by the reduction of the measurement bias and repeatability, which is important especially considering industrial non-destructive testing evaluations.