	US 7,542,168 B2
	Gradation conversion calibration by comparing grayscale and color chart measurements to target values and repeated correction amount calculations to tolerance values
Tatsuji Goma, Wakayama (Japan); Yoshiyuki Nakatani, Wakayama (Japan); and Takeshi Nishihara, Wakayama (Japan)
Assigned to Noritsu Koki Co., Ltd., Wakayama (Japan)
Filed on Apr. 10, 2006, as Appl. No. 11/401,063.
Claims priority of application No. 2005-114635 (JP), filed on Apr. 12, 2005.
Prior Publication US 2006/0227397 A1, Oct. 12, 2006
Int. Cl. H04N 1/60 (2006.01)

U.S. Cl. 358—1.9 [358/504; 358/521]

4 Claims

1. A gradation conversion calibration method of determining a correction amount to be used when converting an image data gradation to a print data gradation in an image forming device that outputs color images by forming them on recording media, said method comprising the steps of:

outputting a color chart made of a test image for each basic color of three basic colors for creating a color image, and a grayscale chart made of a test image that combines each basic color of said three basic colors; and

repeating a calibration task of calculating a correction amount based on the grayscale chart by comparing a measured density value that has been obtained by measuring a density of said grayscale chart with a target density value that has been found in advance, until said correction amount based on the grayscale chart is equal to or less than a first tolerance value;

wherein as long as said correction amount based on the grayscale chart is equal to or greater than a second tolerance value that is larger than said first tolerance value, a correction amount based on said color chart is additionally calculated by comparing a measured density value that has been obtained by measuring a density of said color chart and a target density value that has been found in advance, and this correction amount is used in place of said correction amount based on the grayscale chart.