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. Businesses are protecting their lesser-value documents such as transcripts, coupons and prescription pads by incorporating some of the features listed below to ensure that they cannot be forged or that alteration of the data cannot occur undetected. More recently many of the techniques used to protect these high-value documents have become more available to commercial printers whether they are using the more traditional offset and flexographic presses or the newer digital platforms. The main goal of security printing is to prevent forgery, tampering, or counterfeiting. Security printing is the field of the printing industry that deals with the printing of items such as banknotes, cheques, passports, tamper-evident labels, security tapes, product authentication, stock certificates, postage stamps and identity cards.
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