The forensic examination of laser printers and photocopiers using digital image analysis to assess print characteristics

299-309
JIS&T is a peer reviewed international journal.
The evolution of digital printing techniques has lead to the accessibility of cheap high quality printers and has created opportunities for criminal activity. It is therefore important that new methods are developed to counteract document fraud and counterfeiting threats. Digital image analysis techniques have been considered here to assist this area of research and development.

This research is a proof of concept, which demonstrates how banding phenomena defined here as dark or light bands both horizontally and vertically on a printed page, can be used to link printed documents to the machine that produced it. The bands are a common defect in digital printing systems and are shown to affect the print density and size of text characters. This is a statistical approach that uses a highly accurate and precise digital imaging system and associated techniques to quantify the banding defects in sequences of text characters across and down printed pages. Since many of the banding patterns from a printing machine are irregular and are likely to be different from other machines it can be use to identify whether a document had been printed from a particular machine with high probability. Results were achieved by developing both the hardware and algorithms of an image analysis system used in previous work by the author.

This research is a major step towards producing a system that can fingerprint printing systems. The technique is an advance on that adopted by Jan Allebach at Purdue University, USA. The American research group have devised a scanning method that measures the texture of the print that has a direct relationship to banding. The approach adopted here measures physical features that are concerned with image intensity and size using higher resolutions and therefore have a greater accuracy.