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Abstract

A method for incorporating fraud detection features in a printed image. The method includes the steps of providing an impact printer having a plurality of impact pins for producing pixels on a substrate, developing an encoding scheme within the printed image, and controlling the impact printer to produce the pixels in accordance with the encoding scheme. More specifically, the encoding scheme is characterized by predefining a group of pixels within the printed image and determining the pixel density characteristics thereof, e.g., light or dark pixels. Furthermore, the impact printer is controlled to vary the magnetic flux density across each solenoid, thereby varying the impact pressure applied by the impact pins on the print ribbon. By selectively controlling the magnetic flux density at least some of the respective print densities of each of the respective printed pixels are different from each other to define an encoding scheme within the printed image. Variation in pixel density may be produced by changing the magnitude, pulse width or frequency of the voltage/pulse applied to the solenoids of the impact printer.

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First Claim