Image forming apparatus with control of maximum output of colorant

• US 7,274,490 B2
• Filed: 02/11/2003
• Issued: 09/25/2007
• Est. Priority Date: 02/19/2002
• Status: Active Grant

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Sasanuma, Nobuatsu
• Primary Examiner(s): NGUYEN, MADELEINE ANH VINH
• Application Number:
  US10/361,776
• Publication Number:
  US 20030156120A1
• Time in Patent Office: 1,687 Days
• Field of Search: 358/1.9, 358/518, 358/520, 358/523, 358/530, 358/525, 358/504, 358/521, 358/519, 358/515, 358/534, 382/167, 382/162
• US Class Current: 358/1.9
• CPC Class Codes: H04N 1/6027 Correction or control of colour gradation or colour contrast H04N1/6058 takes precedence

Abstract

In an image forming apparatus which forms a color image by superposing cyan, magenta, yellow and black toners on a recording medium, a circuit to limit image signals is provided immediately before a gamma correction circuit which corrects an output characteristic inherent in the apparatus so that the sum total of the signal levels of the image signals of the respective colors does not exceeds a predetermined value. Thus, even if a user arbitrarily sets color profile data for color management, a toner spread amount can be controlled not to exceed the predetermined value.

Claims

1. An image forming method in an image forming apparatus which forms a color image by adhering plural coloring materials to a recording medium, said method comprising:

an input step of inputting an image signal;

a color conversion step of performing a color conversion process on the image signal input in said input step, on the basis of profile data, and outputting plural color component signals;

a gradation conversion step of performing a gradation conversion process on the plural color component signals output in said color conversion step;

a correction step of correcting an output characteristic inherent in the image forming apparatus; and

a limitation step, executed after said color conversion step and before said correction step, of reducing respective signal levels of the plural color component signals so that a sum total of the respective signal levels does not exceed a limitation value, so as to limit a sum total amount of the coloring materials when adhering the plural coloring materials respectively corresponding to the plural color component signals.

2. An image forming method according to claim 1, wherein said limitation step includes reducing, in a case where the respective signal levels of the two or more color component signals from among the plural color component signals are equal to or higher than a predetermined value, the respective signal levels of the two or more color component signals.

3. An image forming method according to claim 1, wherein said limitation step includes reducing the respective signal levels of the plural color component signals in correspondence with a combination of the respective signal levels of the plural color component signals.

4. An image forming method according to claim 1, wherein said limitation step changes the limitation value, in accordance with a kind of recording medium on which the image is to be formed.

5. An image forming method according to claim 1, wherein said limitation step includes changing the limitation value to a further smaller value, if a mode to reduce a use amount of the coloring materials less than ordinary is set.

6. An image forming apparatus which forms a color image by adhering plural coloring materials to a recording medium, comprising:

an input unit arranged to input an image signal;

a color conversion unit arranged to perform a color conversion process on the image signal input by said input unit, on the basis of profile data, to output plural color component signals;

a gradation conversion unit arranged to perform a gradation conversion process on the plural color component signals output by said color conversion unit;

a gamma correction unit arranged to correct an output characteristic inherent in said image forming apparatus; and

a limitation unit arranged to perform a process, executed after the conversion process by said color conversion unit and before correction processing by said gamma correction unit, of reducing respective signal levels of the color component signals so that a sum total of the respective signal levels does not exceed a limitation value, so as to limit a sum total amount of the coloring materials when adhering the plural coloring materials respectively corresponding to the plural color component signals.

7. An image forming apparatus according to claim 6, wherein said limitation unit, in a case where the respective signal levels of the two or more color component signals from among the plural color component signals are equal to or higher than a predetermined value, reduces the respective signal levels of the two or more color component signals.

8. An image forming apparatus according to claim 6, wherein said limitation unit reduces the respective signal levels of the plural color component signals in correspondence with a combination of the respective signal levels of the plural color component signals.