| 摘要 |
PROBLEM TO BE SOLVED: To obtain an optical information recording medium wherein the existence of information recording parts is concealed to raise the security by that a diffraction grating cell itself does not constitute record information, but the information is recorded, depending on the spacing of the disposed grating cells. SOLUTION: An optical information recording medium has a recording area where diffraction grating cells of one type diffraction grating are arranged with changing the size and spacing. The diffracting grating cell itself does not constitute record information and hence a pattern of decorative picture, etc., composed of aggregates of diffraction grating cells is intensively seen at a glance to result in that the existence of the record information is hardly recognizable. When a light is incident on the recording medium, e.g. to observe a first- and higher-order diffracted lights from the diffraction grating, a light pattern of rainbow colors similar to a rainbow hologram can be seen. Thus, such a decorative picture represented by the diffraction grating cells themselves is recognizable by naked eyes while information quite independent thereof can be read by a machine from the same area as the decorative picture, etc. |
