SINGLE-COLOR SCREEN PATTERNS FOR COPY PROTECTION

摘要

A verifiable/copy-protected document features a combination of nearly identical line-screen patterns for embedding latent images within visually integrated settings. The latent images can be detected for purposes of verification with a matching viewer but are indistinguishable from their visually integrated settings under ordinary viewing conditions. The line-screen patterns, which can be incorporated into document artwork, are printed at certain combinations of line frequencies and print densities so that the line-screen patterns digitally reproduce as a largely undifferentiated solid tint.