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US 5,291,296 AGranted
Specific set of rotated screens for digital halftoning
AssigneeXerox Corporation
InventorCharles M. Hains
Life of this patent
Estimating the term…
Abstract
A set of halftone screens and a write white xerographic system for generating halftone images with a minumum of artifacts. The screens used in a four color printer have at least 64 pixels per pattern and are distributed to creat fourcentered dots that are at either -14, 0,+14 or +45 degrees. The xerographic process involves charging the photoreceptor, partially discharging the photoreceptor with a scanning beam to create an image, and then using toner which adheres to the charged portions of the photoreceptor to create the hard copy.
Claims2
In a printing system, apparatus for producing a toner image on a photoreceptor comprising:
- means for scanning an image and producing therefrom a gray scale output,
- means for generating a multi-centered halftone screen,
- means for comparing said gray scale output and said multi-centered halftone screen and producing therefrom a halftone image signal,
- a photoreceptor comprising a surface which is charged to a voltage,
- a light beam generator for generating a scanning light beam which is turned ON and OFF in response to said halftone image signal, and for scanning said charged surface of said photoreceptor with said beam to create discharged areas on said photoreceptor suface which are the areas scanned when said beam is ON,
- toner which is charged to a voltage that will allow said toner to adhere to charged portions of said photoreceptor and not to adhere to discharged portions of said and
- means for applying said toner to said photoreceptor.
4 more elements
Dependencies are inferred from the claim text.