Void Pantograph Software4/3/2023 ![]() In: Optical Security and Counterfeit Deterrence Techniques V, San Jose, California Jp. New Digital Anti-Copy/Scan and Verification Technologies. Printing method and copy-evident secure document. Lee and J Choi, 'Development of Visible Anticopy Patterns,' in TrustBus 2004, LNCS 3184, pp. Automated Optimization of Void Pantograph Settings. Numerous variations exist, including printing the marks using a raster of lines in one direction on a background of lines in another direction, or using fine line patterns that alias into a visible moire pattern when copied. This makes it possible to see a pattern that had been invisible. This means that if a grey region consists of a grid of very small dark dots the filtering will produce a lighter grey, while a region of larger dots will be affected differently ('big-dot-little-dot'). In addition, human vision is sensitive to luminancecontrast ratio. Features smaller than the resolution will also not be reproduced. It will also not be perfectly aligned with the directions of the document, causing aliasing. A scanner or photocopier will act as a low-pass filter on the original image, blurring edges slightly. ![]() Void pantographs work by exploiting the limitations and features of copying equipment. ![]()
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