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Invisible barcode method base on NDT photoacoustic imaging

The use of barcode technology has spread in many fields since it is cheaper and easier to use. To date, the barcode technology is applied by placing a code on a label surface. This makes access easier but also increases security risks. Security breaches can occur either due to physical damage to the code or code hijacking for inappropriate purposes. This paper reports the development of the subsurface barcode coding method by utilizing Non-Destructive Testing (NDT) photoacoustic imaging. Referring to the Rosencwig-Gersho theory, photoacoustics can image the subsurface conditions by adjusting the thermal conductivity length. In this experiment, a number of cavities representing barcodes were embedded in a metal object. The experimental results show that this method can decode the 3-digit Flattermarken code embedded in a 1 mm thick metal object again. The success of this new method is expected to open up more opportunities for barcodes that are more secure and resistant to tampering.