TWO-DIMENSIONAL ADDITIVE NALF- TONE SCREEN IMPLEMENTATION
Original Publication Date: 1979-Oct-31
Included in the Prior Art Database: 2004-Apr-02
Xerox Disclosure Journal
One-dimensional additive halftone screens cannot achieve linear TRC (tone reproduction curve) over a density range larger than unity. To increase the linear density range, two basic methods have been proposed; one is to image on the xerographic drum a two-dimensional halftone screen by flashing on and off a halftone pattern as the drum rotates, and the second method is to use an addressable screen whose amplitude is made dependent on the image content. It can be produced by a scanning laser beam whose irradiance is modulated by the image content The beam either produces the halftone pattern directly, or it is used to scan a halftone mask. The second method can also be used to perform low-resolution image corrections like color masking or unsharp masking.