Method for printing high information density machine-readable composite images

摘要

A method for printing a large invisible luminescent bar code on a mail piece addresses the problem of obscuration of modules by printed text such as the address. The bar code is printed large enough so that the line width of the characters is substantially less than the module size of the bar code components. Overprinting does not then completely obscure any module and so the bar code is still readable. The readability is especially enhanced by the high contrast of the luminescent image. When a fluorescent bar code is viewed under UV illumination, the bar code emits fluorescence in the areas of printed modules without text overprinted. Because the modules are wider than the text line width, the text does not completely obscure any module. The contrast of the bar code is reversed in fluorescence-that is, printed areas emit light.