Lighting Technique for Attaching Invisible Information Onto Real Objects Using Temporally and Spatially Color-Intensity Modulated Light

This article describes a lighting technique which enables us to invisibly attach information onto a real object by using illumination light and to extract the information from a video image of the object captured with a video camera. A temporally and spatially color-intensity modulation embeds information into a color component of the light beam. First, we assessed the invisibility to the human eye of the information attached onto a real object visible to the human eye. The experiments showed an upper limit value of modulation amplitude that satisfied invisibility for each color component. The experimental results revealed that the blue color component had a much higher degree of invisibility than the red and green components. We also examined the readability of the information attached to the object with a video camera when the information was embedded in the blue color component of the light beam. The experimental results showed a lower limit value of modulation amplitude that satisfied readability. The experimental results showed the range of modulation amplitude of intensity in the blue color that satisfied the invisibility and readability of the information attached to the object. The results of our experiments demonstrated the effectiveness of the proposed technique.