Patent ID: 6538677
Filing Date: 2003-03-25
Classification: H04N

Abstract:
A method for generating variable density halftone images with electrography comprising the steps of:grouping sets of adjacent pixels into a set of adjacent cells where each cell corresponds to a halftone dot of an image; selectively setting exposure levels for a gray scale writer to grow halftone dots from zero size to a desired size equal to or less than a maximum size by increasing exposure of one pixel in the cell one exposure level at a time until the pixel reaches a first total level of exposure and selectively repeating this step for the rest of the pixels until the cell is at its desired size and at an initial density; selectively adjusting exposure of the initial density of cells at the maximum size by sequentially increasing the level of exposure of each pixel in the maximum size cell by one exposure level at a time for each pixel until all pixels are at the same next level of exposure and then repeating this step to further increase the density of the cell to desired density; discharging areas of a charged image member in accordance with the selected levels of exposure of the prior steps to form a latent image of variable density halftone dots on the image member; enclosing a cylindrical magnetic roller in a concentric sleeve; rotating the magnetic roller in a first direction; disposing the magnetic roller and the sleeve in a container holding a two-component toner comprising hard magnetic carrier particles and toner particles; rotating the concentric sleeve in a direction opposite to the direction of the magnetic roller and in a direction co-current with an imaging member; contacting the sleeve and the latent image on the image member; transferring toner particles from the sleeve to the latent image to develop the latent image; transferring the developed image to a copy sheet; fixing the developed image on the copy sheet.