Method for improving printer uniformity

In a printing apparatus that uses an image forming assembly comprising a plurality of exposure elements, wherein an amount of exposure energy is capable of being varied at each one of said plurality of exposure elements in order to provide a corresponding output colorant density, a method for non-uniformity correction, the method comprising:

• (a) generating an output test print formed by the image forming assembly, said test print having a predetermined set of output colorant density levels;
• (b) scanning said output test print and providing a plurality of scanned density data values corresponding to each one of said plurality of exposure elements;
• (c) providing an image data manager that accepts a plurality of image data values from an image data source and, within each one of said predetermined set of output colorant density levels, performs the steps of:
• (1) computing, from said plurality of scanned density data values, an exposure element average density value for each of said plurality of exposure elements, to generate a set of exposure element average density values for said plurality of exposure elements;
• (2) computing, from said set of exposure element average density values for said plurality of exposure elements, a density level average density value;
• (3) computing, for each one of said plurality of exposure elements, a non-uniformity correction value based on the difference between said exposure element average density value and said density level average density value;
• (d) conditioning, corresponding to each one of said plurality of exposure elements, each of said plurality of image data values from said image data source using said non-uniformity correction value to generate a conditioned image density data value;
• and
• (e) providing said conditioned image density data value to the image forming assembly.

A method for improving uniformity in a printed image comprising:

• (a) printing a test image;
• (b) scanning said test image;
• (c) computing a first average density of a first column at a first density level for a first exposure element;
• (d) repeating step (c) for each column for each exposure element for said first density level;
• (e) averaging all of said average densities to obtain first average level density;
• (f) subtracting said first average density from said first average level density to obtain a uniformity correction factor for said first exposure element for said first density level;
• (g) repeating step (f) for each average density for each column at said first density level to obtain a non-uniformity correction value for each of said exposure elements;
• and
• (h) repeating steps (c)-(g) for a plurality of density levels to obtain a non-uniformity correction value for each of said exposure elements for each of said plurality of density levels.

In a printing apparatus that uses an image forming assembly comprising a plurality of exposure elements, wherein an amount of exposure energy is capable of being varied at each one of said plurality of exposure elements in order to provide a corresponding output colorant density, the therein improvement comprising:

• an image data manager that accepts a plurality of image data values from an image data source and is capable of:
• (a) computing, from a plurality of scanned density data values corresponding to each one of said plurality of exposure elements, a non-uniformity correction value for each one of said plurality of exposure elements and for each one of a plurality of output colorant density;
• (b) conditioning, corresponding to each one of said plurality of exposure elements and to each one of said plurality of output colorant densities, each of said plurality of image data values from said image data source using said non-uniformity correction value to generate a conditioned image density data value;
• and
• (c) providing said conditioned image density data value to the image forming assembly.

In a printing apparatus that uses an image forming assembly comprising a plurality of exposure elements, wherein an amount of exposure energy is capable of being varied at each one of said plurality of exposure elements in order to provide a corresponding output colorant density, a method for non-uniformity correction, the method comprising:

• providing an image data manager that accepts a plurality of image data values from an image data source and performs the steps of:
• (a) computing, from a plurality of scanned density data values corresponding to each one of said plurality of exposure elements, a non-uniformity correction value for each one of said plurality of exposure elements and for each one of a plurality of output colorant densities;
• (b) conditioning, corresponding to each one of said plurality of exposure elements and to each one of said plurality of output colorant densities, each of said plurality of image data values from said image data source using said non-uniformity correction value to generate a conditioned image density data value;
• and
• (c) providing said conditioned image density data value to the image forming assembly.

In a printing apparatus that uses an image forming assembly comprising a plurality of exposure elements, wherein an amount of exposure energy is capable of being varied at each one of said plurality of exposure elements in order to provide a corresponding output colorant density, the improvement comprising:

• (a) an output test print formed by the image forming assembly, said test print having a predetermined set of output colorant density levels;
• (b) a scanner capable of scanning said output test print and providing a plurality of scanned density data values corresponding to each one of said plurality of exposure elements;
• (c) an image data manager that accepts a plurality of image data values from an image data source and, within each one of said predetermined set of output colorant density levels, is capable of:
• (1) computing, from said plurality of scanned density data values, an exposure element average density value for each of said plurality of exposure elements, to generate a set of exposure element average density values for said plurality of exposure elements;
• (2) computing, from said set of exposure element average density values for said plurality of exposure elements, a density level average density value;
• (3) computing, for each one of said plurality of exposure elements, a non-uniformity correction value based on a difference between said exposure element average density value and said density level average density value;
• said image data manager further capable of conditioning, corresponding to each one of said plurality of exposure elements, each of said plurality of image data values from said image data source using said non-uniformity correction value to generate a conditioned image density data value and capable of providing said conditioned image density data value to the image forming assembly;
• and
• wherein an interpolated non-uniformity correction value is obtained from non-uniformity correction values corresponding to two closest output colorant density levels when an output colorant density level is not in said predetermined set.

In a printing apparatus that uses an image forming assembly comprising a plurality of exposure elements, wherein an amount of exposure energy is capable of being varied at each one of said plurality of exposure elements in order to provide a corresponding output colorant density, a method for non-uniformity correction, the method comprising:

• (a) generating an output test print formed by the image forming assembly, said test print having a predetermined set of output colorant density levels;
• (b) scanning said output test print and providing a plurality of scanned density data values corresponding to each one of said plurality of exposure elements;
• (c) providing an image data manager that accepts a plurality of image data values from an image data source and, within each one of said predetermined set of output colorant density levels, performs the steps of:
• (1) computing, from said plurality of scanned density data values, an exposure element average density value for each of said plurality of exposure elements, to generate a set of exposure element average density values for said plurality of exposure elements;
• (2) computing, from said set of exposure element average density values for said plurality of exposure elements, a density level average density value;
• (3) computing, for each one of said plurality of exposure elements, a non-uniformity correction value based on the difference between said exposure element average density value and said density level average density value;
• (d) conditioning, corresponding to each one of said plurality of exposure elements, each of said plurality of image data values from said image data source using said non-uniformity correction value to generate a conditioned image density data value;
• (e) providing said conditioned image density data value to the image forming assembly;
• and
• wherein an interpolated non-uniformity correction value is obtained from non-uniformity correction values corresponding to two closest output colorant density levels when an output colorant density level is not in said predetermined set.