IMAGE FORMING APPARATUS

• US 20170277056A1
• Filed: 03/15/2017
• Published: 09/28/2017
• Est. Priority Date: 03/22/2016
• Status: Active Grant

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Nakahara, Hisashi, Uchiyama, Akihiko
• Granted Patent: US 10,168,633 B2
• Time in Patent Office: Days
• CPC Class Codes: G03G 15/0121 for developing
• CPC Class Codes: G03G 15/5008 Driving control for rotary photosensitive medium, e.g. speed control, stop position control
• CPC Class Codes: G03G 15/5087 for receiving image data

Abstract

An image forming apparatus includes a controller capable of executing a normal mode in which an electrostatic image formed on an image bearing member is developed by setting a peripheral velocity ratio of a developer bearing member relative to the image bearing member to a prescribed peripheral velocity ratio, and a color gamut enlargement mode in which a color gamut of an image to be formed on a recording medium is enlarged as compared to the normal mode by setting the peripheral velocity ratio of the developer bearing member relative to the image bearing member to a larger peripheral velocity ratio than the peripheral velocity ratio in the normal mode, wherein the controller identifies image color gamut information included in image data and forms an image by selecting the normal mode or the color gamut enlargement mode in accordance with the image color gamut information.

Claims

1. An image forming apparatus, for forming an image on a recording medium based on image data, comprising:

an image bearing member on which an electrostatic image is formed;

a developer bearing member configured to bear a developer for developing the electrostatic image formed on the image bearing member; and

a controller configured to be capable of executing a normal mode in which the electrostatic image formed on the image bearing member is developed by setting a peripheral velocity ratio of the developer bearing member to the image bearing member to a prescribed peripheral velocity ratio, and a color gamut enlargement mode in which a color gamut of an image to be formed on the recording medium is enlarged as compared to the normal mode by setting the peripheral velocity ratio of the developer bearing member to the image bearing member to a larger peripheral velocity ratio than the peripheral velocity ratio in the normal mode, wherein

the controller is configured to identify image color gamut information included in the image data, and form an image by selecting the normal mode or the color gamut enlargement mode in accordance with the image color gamut information.

2. The image forming apparatus according to claim 1, wherein

the controller is configured to:

form an image in the normal mode when a color gamut in the image color gamut information included in the image data is within a range of a first color gamut; and

form an image in the color gamut enlargement mode when the color gamut in the image color gamut information included in the image data is beyond the range of the first color gamut and within a range of a second color gamut which is larger than the first color gamut.

3. The image forming apparatus according to claim 2, wherein

the image data is formed by a plurality of dots, and

when a color of at least one of the plurality of dots is not included in the first color gamut, the image forming apparatus is controlled to execute the color gamut enlargement mode.

4. The image forming apparatus according to claim 1, wherein

the image bearing member is a photosensitive drum,

the developer bearing member is a developing roller, and

in the color gamut enlargement mode, a color gamut of an image to be formed on the recording medium is enlarged as compared to the normal mode by setting a peripheral velocity of the developer bearing member to a higher peripheral velocity than a peripheral velocity of the image bearing member.

5. The image forming apparatus according to claim 4, wherein in the color gamut enlargement mode, the peripheral velocity of the developer bearing member is set to a higher peripheral velocity than the peripheral velocity of the image bearing member by reducing the peripheral velocity of the image bearing member.

6. The image forming apparatus according to claim 1, wherein the image data is expressed by values of red, green, and blue.

7. The image forming apparatus according to claim 6, wherein the image data expressed by the values of red, green, and blue is transformed into coordinates in a L*a*b* color system.

8. The image forming apparatus according to claim 7, wherein in the image data expressed by the coordinates in the L*a*b* color system, an L coordinate representing brightness of an image is transformed into a value which enables an image to be formed by the image forming apparatus.

9. The image forming apparatus according to claim 8, wherein

when the image data expressed by the coordinates in the L*a*b* color system is within prescribed coordinates in the L*a*b* color system, a color gamut in the image color gamut information included in the image data is determined to be within a range of a first color gamut and an image is formed in the normal mode, and

when the image data expressed by the coordinates in the L*a*b* color system is not within the prescribed coordinates in the L*a*b* color system, the color gamut in the image color gamut information included in the image data is determined to be within a range of a second color gamut and an image is formed in the color gamut enlargement mode.

10. The image forming apparatus according to claim 9, wherein the image data expressed by the coordinates in the L*a*b* color system is transformed into values of yellow, magenta, and cyan.

11. The image forming apparatus according to claim 10, wherein a color of the image data transformed into values of yellow, magenta, and cyan is corrected so as to most closely approximate a color corresponding to a value of L*a*b* coordinates.

12. The image forming apparatus according to claim 11, wherein for a portion which becomes black by mixing yellow, magenta, and cyan among colors expressed by yellow, magenta, and cyan, an image is formed using a black developer.