| 摘要 |
PROBLEM TO BE SOLVED: To ensure a predetermined density by controlling a maximum value of ON/OFF duty ratio of a laser beam for density change due to variation of process characteristics. SOLUTION: Test patterns are developed at respective colors on a photosensitive member, further transferred onto an intermediate transfer unit, and detected as a reflecting light amount value by a density sensor 25. An image data value, ON/OFF duty ratio of a laser beam and density on a sheet have a correlation. The image data value corresponding to a target maximum density value and ON/OFF duty ratio of the beam are unitarily decided. Maximum value of a gradation correcting test pattern used in a gradation characteristic obtaining operation sets CCH, forms 10 patches being sequentially lower in density and obtains gradation characteristic data of an image forming apparatus. |
