| 摘要 |
PROBLEM TO BE SOLVED: To protect low-volume and low-value documents, such as coupons and gift cards. SOLUTION: The method for providing security for documents comprises printing a public portion of a document at an optical density for public; and printing a private portion, in the position of a part of the disclosed portion of the document at optical density for non-disclosure. The optical density for non-disclosure is made sufficiently different from the optical density for disclosure to be perceptible in contrast with respect to the optical density for public, when the document is viewed in transmission at a glancing angle or when the document is scanned and processed for contrast enhancement, but is insufficient to be perceptible, when viewed normally in reflection by a human ocular system, and is sufficient to generate optical density for non-disclosure. COPYRIGHT: (C)2007,JPO&INPIT
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