New dispersed-dot halftoning technique by elimination of unstable pixels for electrophotography

Printing processes of electrophotography basically involve some unstableness of analog nature. These instabilities make small dot reproduction stochastic and degrade image quality. To overcome the analog instabilities in this paper, we have developed a dispersed-dot halftoning technique for high resolution electrophotography. Based on the characteristic of electrophotography, a combination of a Gaussian filter with a sigmoid nonlinear function was used to calculate the probability of toner transfer in print. We can obtain a predicted image in print using this nonlinear printer model. Halftone images having good image quality are formed under this model in a way so that the perceptive error with respect to an original gray scale image is small. To achieve this, unstable pixels that have their transfer probabilities within a band in our nonlinear printer model are eliminated as much as possible by an iterative improvement method. As a result, perceptive error was much improved compared to conventional cluster-dot halftoning