CALIBRATION METHOD OF COLOR LASER PRINTER AND TEST CHART

摘要

PROBLEM TO BE SOLVED: To enable a calibration, having gradation characteristics using the visual observation of users, without having to specially prepare a reference image subjected to density control, and to contrive the stabilization of a reproducing image in the image output device of a color laser printer or the like. SOLUTION: A calibration method is constituted of a test chart 18, arranged with a test chart 6 of each color and a calculating means, which calculates a gradation correction table and downloads the table on a gradation correction circuit 3, on the basis of a value which is read from this test chart 18. Moreover, the chart 6 is constituted of a continuous region 10, where gradation is augmented stepwise, and a checkered check pattern of a reference region 11, which makes a comparison with this region 10. The parts of the region 11 respectively consist of the white ground of a paper in a highlight calibration part 7, the highest density of a solid pattern in a shadow calibration part 8 and a network point of a resolution rougher than that of the region 10 or tens of thousand-line pattern in an intermediate calibration part 9. As a result of such a constitution of the calibration method, a gradation correction value is calculated by the characteristic values of highlight, shadow and intermediate gradations, which are obtained only from visual data on the chart 18 printed from a printer.