Display Technique for Embedding Information in Real Object Images Using Temporally and Spatially Luminance-Modulated Light

We propose a display technique that can invisibly embed information into an image of a real object captured with a video camera. It uses illumination light that illuminates a real object. This light invisibly contains information. As the light contains information, the image of an object illuminated by such light also contains information. Information in the light is produced by modulating luminance with a small amplitude according to the embedded pattern at half-frame frequency. The differences between every other frame image over a certain period are summed up. Changes in brightness by modulation in each frame are accumulated over the frames, while the object image is removed by this processing. This makes it possible to read out the embedded patterns. However, the object image cannot be removed completely and still remains as noise. This lowers the readability of an invisible pattern. In this paper, we present a technique that improves the readability of an invisible pattern by reducing the noise drastically. We propose a method that uses the correlation between channels in which the pattern is embedded and not embedded to reduce the noise. Moreover, it also uses the size features of an embedded pattern to reduce the noise. We demonstrate the effectiveness of the proposed technique from experimental results.