Automated Optimization of Void Pantograph Settings

Aronoff, Jason S. ; Simske, Steven J. ; Sturgill, Margaret

HP Development Company

关键词: Copy Evidence;    Covert Printing;    Print-Scan Cycle;    VDP;   

RP-ID  :  HPL-2011-179

学科分类：计算机科学（综合）

美国|英语

来源: HP Labs

【 摘 要 】

Void pantographs (VPs) have been an important part of the security printing toolkit for several decades. When crafted for a specific printing technology, VPs provide an almost "magical" effect - they are nearly invisible in the original print and then stand out strikingly when they are copied. However, this effect comes at an expense - VPs have historically been designed only for a specific printing technology, and so cannot be extended to a mobile-printing world, where the VP needs to be supported by a wide range of printers. In this paper, we describe an automated process for optimizing the VP settings. These are the background and foreground pattern used in the VP - the background "disappears" when copied and the foreground "bolds". VP test sheets are created using the ranges of background and foreground settings necessary to guarantee identification of at least one "readable" pair of settings. This can be automated by writing the VP as a readable mark.for example, a barcode that can be read (or not read) by a barcode reader; text that can be read (or not read) by an optical character recognition (OCR) engine; or even a face that can be recognized by a face recognition engine. The successful VPs will not be readable (using camera images to prevent a "copying" effect) when originally printed but accurately readable (using a camera) after a single copy, or print-scan, cycle.