Optically written watermarking technology using temporally and spatially luminance-modulated light

Abstract

This paper describes a technique that can invisibly embed information into images captured with a video camera. It uses illumination that contains invisible patterns. As the illumination contains patterns, a captured image of a real object illuminated by such light also contains the same patterns. It uses a luminance modulated pattern whose amplitude is too small to be perceived. Four frames are used for a cycle of the modulating. The difference frame images of every other frame of the captured image over a certain period are added up. Changes in brightness by modulating are accumulated over the frames while the object image is removed because difference frame images are used. This makes it possible to read out the embedded patterns. The experimental results demonstrate that the embedded pattern is invisible and can be read out by choosing some conditions properly, although a small amount of noise results from the remaining object image.