Measuring magnetic properties to discriminate between different laser printers

Magnetism used to be a qualitative property to discriminate between different laser printers: magnetic single-component toners versus non-magnetic bi-component toners. Within the examination of security documents, quantitative measurements of magnetic properties are used to discriminate between genuine and counterfeited documents. The question has risen whether quantitative measurements of magnetism can also be used to discriminate between printers which use magnetic single-component toner. This paper presents a preliminary evaluation of this technology on normal laser printed documents.
This study used 72 print samples from 19 different laser printers which all use magnetic toner. For each sample the flux and magnetic induction of the toner was measured on several locations with the Regula Magmouse Model 4197. Different comparison algorithms to discriminate between printers were studied within the Bayesian Likelihood-Ratio framework. Furthermore, repeatability and reproducibility of the Magmouse were studied. This study shows that this technology has the potential to discriminate between different printers. The Magmouse is easy to operate and measurements can be done quickly without contaminating, damaging or destroying other traces on the document. However, the range of application is limited to documents printed with magnetic single component toner.