Image forming apparatus

An image forming apparatus, comprising an image processing means for determining a arrangement of pixel gradations that indicate gray levels in each pixel for every unit pixel group forming a plurality of pixels by an area coverage modulation method based upon a prescribed image data, and an exposing means for writing an electrostatic latent image onto a photoreceptor by exposing a surface of said photoreceptor previously electrified by an electrification means with an exposure amount obtained by transforming said pixel gradation determined by said image processing means, said image forming apparatus further comprising;

• an memory means for individual slope information for individually memorizing said slope information that defines a slope of when said pixel gradation is approximately linear-transformed into said exposure amount within a partial or whole range of said pixel gradation for each segment multi-divided a surface of said photoreceptor, and
• a means of individual exposure amount transformation for individually transforming said pixel gradation into said exposure amount for each of said segments based upon said slope information,
• wherein said slope information is an information which, with a reference electric potential that is common between all of said segments, approximately matches an electric potential after exposure of when an exposure amount, obtained by transforming a reference pixel gradation that is an approximate average value of said pixel gradations in a partial or whole pixels of said unit pixel group determined based upon one or multiple prescribed image data by said image processing means as utilizing said means of individual exposure amount transformation, is applied, to an approximately-linear exposure property excepting a converging region to a residual potential, or to a exposure property extending said approximately-linear exposure property by extrapolation operation, among exposure properties showing correspondences between exposure amounts and electric potentials after exposure in each of said segments.

An image forming apparatus, comprising an image processing means for determining a pixel gradations indicating gray levels in each pixel based upon a prescribed image data, and an exposing means for writing an electrostatic latent image onto a photoreceptor by exposing a surface of said photoreceptor previously electrified by an electrification means with an exposure amount obtained by transforming said pixel gradation determined by said image processing means, said image forming apparatus further comprising;

• a memory means for individual transformation information for memorizing a plurality of candidates for individual transformation information employed in order to transform said pixel gradation into said exposure amount for each segment multi-divided a surface of said photoreceptor;
• a selecting means for individual transformation information for selecting a said individual transformation information to be employed from a plurality of said candidates for individual transformation information based upon a condition related to development except for an exposure amount by said exposing means and/or an environmental condition;
• and
• a means of individual exposure amount transformation for individually transforming said pixel gradation into said exposure amount in each of the segments based upon said individual transformation information selected by said selecting means for individual transformation information.