# US 2013/0278951 A1 · Image forming apparatus which performs tone correction

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- Number: US 2013/0278951 A1
- Document ID: US20130278951A1
- Status: Published application
- Kind: A1
- Application number: 13/858,129
- Filed: 2013-04-08
- Published: 2013-10-24
- Earliest claimed: 2012-04-19
- Assignees: Canon Kabushiki Kaisha
- Applicants: Canon Kabushiki Kaisha
- Inventors: Daisuke Makino
- Web page: https://patentgrep.com/patent/US20130278951A1

## CPC

- G06K 15/02: using printers
- G03G 15/5041: {Detecting a toner image, e.g. density, toner coverage, using a test patch (G03G15/553 takes precedence)}
- G03G 15/5062: {by measuring the characteristics of an image on the copy material}
- G06K: GRAPHICAL DATA READING (image or video recognition or understanding G06V); PRESENTATION OF DATA; RECORD CARRIERS; HANDLING RECORD CARRIERS
- G03G: ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY

## Abstract

An image forming apparatus includes: a holding unit configured to hold image processing coefficients, each of which representing a relationship between an input density and an output density of an image signal output to an image forming unit; and an updating unit configured to update an image processing coefficient based on the relationship between densities of measurement images and densities of image signals for forming the measurement images. The updating unit is further configured to, when a maximum value of an output density of the image processing coefficients is smaller than a maximum value of the density of the image signal, form at least one first measurement image in accordance with an image signal indicating a density higher than the maximum value of the output density of the image processing coefficients.

## Claims

### Claim 1

An image forming apparatus comprising:
an image forming unit configured to form an image on an image carrier based on an image signal;
a holding unit configured to hold an image processing coefficients, each image processing coefficient of the image processing coefficients representing a relationship between an input density and an output density corresponding to a density of the image signal to determine the density of the image signal to be output to said image forming unit when performing tone correction;
a reading unit configured to read a density of the image formed on the image carrier; and
an updating unit configured to, when a plurality of measurement images are formed on the image carrier by said image forming unit and read by said reading unit, update an image processing coefficient based on the relationship between densities of the measurement images read by said reading unit and densities of image signals for forming the measurement images,
wherein said updating unit is further configured to, when a maximum value of an output density of the image processing coefficients is smaller than a maximum value of the density of the image signal, form at least one first measurement image out of the plurality of measurement images in accordance with an image signal indicating a density higher than the maximum value of the output density of the image processing coefficients.

### Claim 2 (depends on 1)

The apparatus according to claim 1, wherein
said holding unit is further configured to hold first image data representing a density of the first measurement image out of the plurality of measurement images, and second image data representing a density of a second measurement image different from the first measurement image out of the plurality of measurement images, and
said updating unit is further configured to output an image signal indicating a density represented by the first image data to said image forming unit to form the first measurement image, and output an image signal indicating a density obtained by performing tone correction for the second image data based on the image processing coefficient to said image forming unit to form the second measurement image.

### Claim 3 (depends on 1)

The apparatus according to claim 1, wherein
said holding unit is further configured to hold first image data representing a density of the first measurement image out of the plurality of measurement images, and second image data representing a density of a second measurement image different from the first measurement image out of the plurality of measurement images, and
said updating unit is further configured to modify the output density of an image processing coefficient with respect to the density represented by the first image data into a value larger than a maximum value of the output density of the image processing coefficients, output image signals obtained by performing tone correction for the first image data and the second image data based on the image processing coefficients to said image forming unit, to form the first measurement image and the second measurement image.

### Claim 4 (depends on 1)

The apparatus according to claim 1, wherein the density of the image signal to be output to said image forming unit to form the first measurement image has the maximum value of the density of the image signal.

### Claim 5 (depends on 1)

The apparatus according to claim 1, wherein before updating the image processing coefficient, said updating unit controls an image forming condition of said image forming unit to set a density of a solid image which is formed by said image forming unit on the image carrier and read by said reading unit, to be not lower than a target maximum density.

### Claim 6 (depends on 5)

The apparatus according to claim 5, wherein the image forming condition includes an exposure intensity when forming an electrostatic latent image on a photosensitive member.