Image density correction for an image forming apparatus

Patent metadata

Field	Value
Publication number	US-10948864-B2
Application number	US-201916578049-A
Country	US
Kind code	B2
Filing date	Sep 20, 2019
Priority date	Sep 27, 2018
Publication date	Mar 16, 2021
Grant date	Mar 16, 2021

Abstract

An image forming apparatus includes an image bearer, an image forming section, an image density difference detector, and control circuitry. The image forming section is configured to form a gradation image pattern on a surface of the image bearer. The gradation image pattern includes gradation images having different image densities stepwise in a sub-scanning direction. The image density difference detector is configured to detect image density differences in a main scanning direction of the gradation images. The control circuitry is configured to execute an image density difference correction mode that corrects the image density differences in the main scanning direction based on detection results detected by the image density difference detector.

First claim

What is claimed is:

1. An image forming apparatus comprising:
at least one image bearer;
an image forming section configured to form a plurality of gradation image patterns on the at least one image bearer, each gradation image pattern formed using a different color toner,
wherein each gradation image pattern comprises a plurality of continuous stripes extending in a main scanning direction,
wherein the continuous stripes have a same target image density in the main scanning direction and different target image densities stepwise in a sub-scanning direction;
an image density difference detector configured to detect image density differences in the main scanning direction; and
in response to executing an image density difference correction mode, control circuitry is configured, for each of the gradation image patterns, to identify a continuous stripe having a largest density variation in the main scanning direction, to generate an image density correction factor for the color toner used for the gradation image pattern based on the identified continuous stripe, and to reduce image density variations in the main scanning direction for the color toner using the image density correction factor.

2. The image forming apparatus according to claim 1 ,
wherein, at a predetermined timing, the image forming section forms the gradation image patterns, and
the control circuitry, for each of the gradation image patterns, identifies the continuous stripe having the largest density variation in the main scanning direction, generates the image density correction factor for the color toner used for the gradation image pattern based on the identified continuous stripe, and reduces image density variations in the main scanning direction for the color toner using the image density correction factor until the image density correction factor is updated when the predetermined timing reoccurs.

3. The image forming apparatus according to claim 1 , further comprising an image density sensor to detect an image density of the continuous stripe at a predetermined position in the main scanning direction,
wherein the control circuitry corrects an image forming condition of the image forming section based on the image density of the continuous stripe detected by the image density sensor, generates the image density correction factor for the color toner used for the gradation image pattern based on the image density of the continuous stripe at the predetermined position in the main scanning direction, and reduces the image density variations in the main scanning direction for the color toner using the image density correction factor.

4. The image forming apparatus according to claim 1 ,
wherein the image forming section includes a rotatable photoconductor and an exposure device that emits exposure light across the photoconductor in the main scanning direction to form a latent image, and
the control circuitry corrects an output of exposure light for each of a plurality of areas divided in the main scanning direction.

5. The image forming apparatus according to claim 4 ,
wherein the control circuitry corrects the output of the exposure light for each of the plurality of areas divided in the main scanning direction, using a sensitivity obtained by dividing an amount of change of the output of the exposure light by an amount of change of an image density determined to correct the image density differences in the main scanning direction.

6. The image forming apparatus according to claim 1 ,
wherein the control circuitry repeats the image density difference correction mode until an image density difference in a gradation image formed at a predetermined image density is equal to or less than a predetermined value.

7. The image forming apparatus according to claim 1 , further comprising an operation unit,
wherein the control circuitry executes the image density difference correction mode based on a manual operation performed on the operation unit.

8. The image forming apparatus according to claim 1 ,
wherein the at least one image bearer is at least one recording medium sheet, and
the image density difference detector is a line sensor that extends in the main scanning direction and is disposed opposite the at least one recording medium sheet on a conveyance path along which the at least one recording medium sheet having passed the image forming section is conveyed.

Assignees

• Akatsu Shinichi
• Ricoh Co Ltd

Inventors

• Akatsu Shinichi

Classifications

• G03G15/5041 Primary

  Detecting a toner image, e.g. density, toner coverage, using a test patch (G03G15/553 takes precedence) · CPC title

• G03G15/556

  for toner consumption, e.g. pixel counting, toner coverage detection or toner density measurement · CPC title

• G03G15/5062

  by measuring the characteristics of an image on the copy material · CPC title

• G03G15/5058 Primary

  using a test patch · CPC title

• H04N1/407

  Control or modification of tonal gradation or of extreme levels, e.g. background level · CPC title