ELECTRONIC WATERMARK PRINTED MATTER, READING SYSTEM OF ELECTRONIC WATERMARK PRINTED MATTER, READING METHOD OF ELECTRONIC WATERMARK PRINTED MATTER, AND MANUFACTURING SYSTEM OF ELECTRONIC WATERMARK PRINTED MATTER

摘要

PPROBLEM TO BE SOLVED: To provide an electronic watermark printed matter, along with a reading system and a reading method thereof, in which a relative rotational angle around an optical axis can be detected even in the case of a small electronic watermark. PSOLUTION: An electronic watermark (20) of an electronic watermark printed matter includes: a first pattern (22) which is acquired by inverse Fourier transform of the sum of a unique information pattern and a temporary rotational angle detection pattern for detecting a relative rotational angle as a temporary rotational angle of 0 to less than 180; and a second pattern (24), which is provided by partially replacing the first pattern (22), to determine whether the relative rotational angle is the temporary rotational angle or a corrected rotational angle acquired by adding an offset angle of 180 to the temporary rotational angle. The shape itself in the real space of the second pattern (24) contains the information for determining whether the relative rotational angle is the temporary rotational angle or the corrected rotational angle. PCOPYRIGHT: (C)2011,JPO&INPIT