Image forming apparatus and image density controlling method

Abstract

An image forming apparatus, forming an image by two-dimensionally fast and slow-scanning and exposing with light that has been modulated in accordance with image data representing an image and visualizing an electrostatic latent image with toner, includes a calculating unit that divides an image region in a fast-scanning direction into plural regions and calculates image data amounts to be used for image formation in the image data per each of the plural regions, and a correcting unit that corrects, on the basis of the calculation result of the calculating unit, unevenness of density in the fast-scanning direction in the toner image resulting from a distance between a position where the toner is supplied to a developing roll and a position where the toner is supplied to each of the plural regions.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

An exemplary embodiment of the present invention will be described in detail based on the following figures, wherein:

FIG. 1 is a diagram showing the general configuration of a tandem color printer that is applicable to an image forming apparatus pertaining to the exemplary embodiment of the invention;

FIG. 2A is a diagram showing the general configuration of a developing unit and the positional relationship between an ADC sensor and an ATC sensor in a fast-scanning direction;

FIG. 2B is a diagram showing the general configuration of a developing unit and the positional relationship between an ADC sensor and an ATC sensor in a fast-scanning direction;

FIG. 3 is a block diagram showing the configuration of a control system of the tandem color printer pertaining to the exemplary embodiment of the invention;

FIG. 4 is a diagram showing an example where the fast-scanning direction is divided into plural regions;

FIG. 5A is a chart showing an example of counts of image data amounts of an image counting unit;

FIG. 5B is a chart showing an example of correction coefficients for correcting density unevenness in the fast-scanning direction;

FIG. 5C is a chart showing an example of correction coefficients when correcting density unevenness in accordance with numbers of continuous pages in one job;

FIG. 6A is a diagram showing an example of a density decrease distribution in the fast-scanning direction;

FIG. 6B is a diagram showing an example of a fast-scanning direction exposure amount correction distribution;

FIG. 7 is a flowchart showing an example of the flow of image density correction that is conducted by an image density control unit at the time of image formation;

FIG. 8 is a chart showing an example of image data amount counts, accumulated image data amount counts, correction coefficients, corrected image data amount counts, density decrease amounts, and exposure amount increases in each region;

FIG. 9 is a chart showing another example of image data amount counts, accumulated image data amount counts, correction coefficients, corrected image data amount counts, density decrease amounts, and exposure amount increases in each region;

FIG. 10 is a flowchart showing an example of the flow of image density control that is conducted by an exposure correction amount control unit; and

FIG. 11 is a flowchart showing an example of the flow of toner density control that is conducted by a toner supply amount control unit.

Claims

1. An image forming apparatus that forms an image by two-dimensionally fast and slow-scanning and exposing with light that has been modulated in accordance with image data representing an image and visualizing an electrostatic latent image with toner, the apparatus comprising: a calculating unit that divides an image region in a fast-scanning direction into a plurality of regions and calculates image data amounts to be used for image formation in the image data per each of the plurality of regions; anda correcting unit that corrects, on the basis of the calculation result of the calculating unit, unevenness of density in the fast-scanning direction in the toner image resulting from a distance between a position where the toner is supplied to a developing roll and a position where the toner is supplied to each of the plurality of regions.

2. The image forming apparatus of claim 1, wherein the correcting unit includes a density decrease calculating unit that calculates, from the calculation result of the calculating unit, a density decrease distribution in the fast-scanning direction of the toner image resulting from the distance from the position where the toner is supplied to the developing roll to each of the plurality of regions,an exposure amount calculating unit that calculates an exposure amount increase distribution corresponding to the calculation result of the density decrease calculating unit, andan exposure control unit that controls exposure amounts on the basis of the calculation result of the exposure amount calculating unit.

3. The image forming apparatus of claim 2, wherein the density decrease calculating unit calculates the density decrease distribution in consideration of the amounts of toner consumed between the position where the toner is supplied to the developing roll and a position where the toner is supplied to each of the plurality of regions.

4. The image forming apparatus of claim 2, wherein the exposure amount calculating unit calculates an exposure amount increase distribution in consideration of a number of images to be formed continuously within one job.

5. The image forming apparatus of claim 3, wherein the exposure amount calculating unit calculates an exposure amount increase distribution in consideration of a number of images to be formed continuously within one job.

6. The image forming apparatus of claim 1, wherein the calculating unit calculates the image data amounts with the smallest unit of the image data or an accumulation of image data to be used for image formation within one job.

7. The image forming apparatus of claim 1, further comprising: a toner image density detecting unit that detects the density of the toner image; anda toner density control unit that controls exposure amounts on the basis of the detection result of the toner image density detecting unit.

8. The image forming apparatus of claim 1, further comprising: a density detecting unit that detects toner density inside a developing unit that visualizes the electrostatic latent image as a toner image;a supply unit that supplies the toner to the developing unit;a stirring unit that stirs the toner inside the developing unit; anda control unit which, when the toner density detected by the density detecting unit is lower than a predetermined target value, controls at least one of the supply unit and the stirring unit.

9. The image forming apparatus of claim 8, further comprising a detecting unit which, when the toner density detected by the density detecting unit is lower than the predetermined target value after control by the control unit, gives notification to replace a toner cartridge in which the toner is stored.

10. An image density controlling method for an image forming apparatus that forms an image by two-dimensionally fast and slow-scanning and exposing with light that has been modulated in accordance with image data representing an image and visualizing an electrostatic latent image with toner, the method comprising: dividing an image region in a fast-scanning direction into a plurality of regions; calculating image data amounts to be used for image formation in the image data per each of the plurality of regions; andcorrecting, on the basis of the calculation result, unevenness of density in the fast-scanning direction in the toner image resulting from a distance between a position where the toner is supplied to a developer roll and a position where the toner is supplied to each of the plurality of regions.