Robustness against defocusing of images in optical watermarking technique

We describes in this paper the robustness of optical watermarking against the defocusing of images, which usually occurs in images taken with digital cameras under nonoptimal conditions. We evaluated measurements of the defocusing of images against the accuracy of detection of optical watermarking. The value of full width at half maximum (FWHM) of the Gaussian function was used to measure the defocusing of images. We found from the results of evaluation that optical watermarking technology was extremely robust against defocusing of images. As a result, we demonstrated the practicality of optical watermarking in a real-use environment along with the robustness against geometric distortion we previously proposed.