Security image printing

摘要

Printing with a single colorant a security feature imperceptible to the naked eye. For a digital security image having a first region formed by a first pattern of binary pixels and a second region formed by a different second pattern of binary pixels, the first and second patterns are printed with the single colorant. A darker one of the first and second printed patterns is determined. The security image is printed with the single colorant, the region corresponding to the darker printed pattern printed at a reduced gray level such that the printed first and second regions appear substantially indistinguishable to the naked eye.

主权项

1. A method of digitally printing a security feature with a single colorant, comprising:
printing, with the single colorant, first and second patterns of binary pixels of a digital security image, the image having a first region formed by the first pattern and an abutting second region formed by the different second pattern, the first and second printed regions each having a gray level; determining a darker one of the first and second printed patterns; and printing the security image with the single colorant, the region corresponding to the darker printed pattern printed at a reduced gray level such that the printed first and second regions appear substantially indistinguishable to the naked eye, wherein printing the security image comprises: printing each of the binary pixels of the security image having an ON value in the region corresponding to a lighter one of the first and second printed patterns at a nominal darkness; and printing each of the binary pixels of the security image having an ON value in the region corresponding to the darker one of the first and second printed patterns at a reduced darkness lower than the nominal darkness.