Image forming apparatus, density-shift correction method, and computer program product
AssigneeRicoh Company, Ltd.
InventorTomohide Kondoh
Life of this patent
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Abstract
A density detector detects a first density of a first pattern and a second density of a second pattern from a density-correction determination patch. A density-correction-value calculator calculates a density correction value from the first and the second densities. A noise-occurrence determination unit determines whether a target pixel is a noise generating pixel that causes a change of a local density due to a change in a relation with a nearby pixel. A density correction processor performs a density correction process on the target pixel by adding or subtracting the density correction value to or from the target pixel or the nearby pixel.
Claims12
An image forming apparatus that divides pixels expressing one line of image in a main-scanning direction, outputs divided pixels by shifting the pixels in a sub-scanning direction opposite to a skew to thereby correct the skew, and performs a density correction process on a target pixel adjacent to a shift position or a nearby pixel of the target pixel to correct a density variation due to a shift of the pixel upon correction of the skew, the image forming apparatus comprising:
- a density detector that detects a first density of a first pattern formed by repeating a specific pixel array and a second density of a second pattern in which a repetition of the specific pixel array is shifted by one pixel with a boundary from a density-correction determination patch that is composed of the first pattern and the second pattern and transferred to a transfer belt;
- a density-correction-value calculator that calculates a density correction value from the first density and the second density;
- a noise-occurrence determination unit that determines whether the target pixel is a noise generating pixel that causes a change of a local density due to a change in an adjacency relationship between the target pixel and the nearby pixel;
- and
- a density correction processor that performs the density correction process on the target pixel, when the target pixel is determined as the noise generating pixel, by adding or subtracting the density correction value to or from the target pixel or the nearby pixel.
A method of correcting a density shift in an image forming apparatus that divides pixels expressing one line of image in a main-scanning direction, outputs divided pixels by shifting the pixels in a sub-scanning direction opposite to a skew to thereby correct the skew, and performs a density correction process on a target pixel adjacent to a shift position or a nearby pixel of the target pixel to correct a density variation due to a shift of the pixel upon correction of the skew, the method comprising:
- detecting a first density of a first pattern formed by repeating a specific pixel array and a second density of a second pattern in which a repetition of the specific pixel array is shifted by one pixel with a boundary from a density-correction determination patch that is composed of the first pattern and the second pattern and transferred to a transfer belt;
- calculating a density correction value from the first density and the second density;
- determining whether the target pixel is a noise generating pixel that causes a change of a local density due to a change in an adjacency relationship between the target pixel and the nearby pixel;
- and
- performing the density correction process on the target pixel, when the target pixel is determined as the noise generating pixel, by adding or subtracting the density correction value to or from the target pixel or the nearby pixel.
A computer program product comprising a computer-usable medium having computer-readable program codes embodied in the medium for correcting a density shift in an image forming apparatus that divides pixels expressing one line of image in a main-scanning direction, outputs divided pixels by shifting the pixels in a sub-scanning direction opposite to a skew to thereby correct the skew, and performs a density correction process on a target pixel adjacent to a shift position or a nearby pixel of the target pixel to correct a density variation due to a shift of the pixel upon correction of the skew, the program codes when executed causing a computer to execute:
- detecting a first density of a first pattern formed by repeating a specific pixel array and a second density of a second pattern in which a repetition of the specific pixel array is shifted by one pixel with a boundary from a density-correction determination patch that is composed of the first pattern and the second pattern and transferred to a transfer belt;
- calculating a density correction value from the first density and the second density;
- determining whether the target pixel is a noise generating pixel that causes a change of a local density due to a change in an adjacency relationship between the target pixel and the nearby pixel;
- and
- performing the density correction process on the target pixel, when the target pixel is determined as the noise generating pixel, by adding or subtracting the density correction value to or from the target pixel or the nearby pixel.
Dependencies are inferred from the claim text.