Optical watermarking robust to object with low-reflectance

We propose a new optically written watermarking technology that can prevent the illegal use of images of objects that cannot contain watermarking such as paintings. The new method involves DCT and iDCT of the whole area to increase robustness that enables the embedded information from watermarking to be accurately read out even when some parts of the information have been lost because of, for example, low reflectance from the object´s surface. We conducted simulations and experiments where one-bit binary data were embedded in some tens of components in a high-frequency area. The experimental results revealed that embedded data could be read out extremely accurately at 100% even when up to 40% of the object´s surface was dark. As a result, we demonstrated the feasibility of the technology we propose is practical.