DOCUMENT SCREENS FOR ELECTROPHOTORAPHIC RANGE EXTENSION
Original Publication Date: 1977-Jun-30
Included in the Prior Art Database: 2004-Mar-29
Xerox Disclosure Journal
It is well known that the tonal range of electrophotographic copies can be extended by inserting spatially modulated ab-sorbing screens in the optical path during image exposure. The problem with these screens is that they absorb light, and thus they require substantially more exposure light. In order to reduce the required light exposure and to further extend the tonal range, the following types of optical patterns can be used on document screens (i.e., optical screens that are placed in front of the document to be copied) : (1) diffusely reflecting patterns, (2) specularly reflecting patterns, (3) partially absorbing partially transmitting patterns (gray patterns) , (4) partially reflecting partially transmitting patterns (either diffusely or specularly reflecting) , (5) any combination of all of the above, The optimum arrangement will depend upon many factors including the reproduction character-istics of the entire electrophotographic system under consid-erat ion.