| 摘要 |
A gradation patch image Ip used for determination of tone characteristics of an apparatus is progressively varied in the tone level thereof from the maximum tone level (level 255) to the minimum tone level (level 0). The gradation patch image is either a toner image continuously and consistently varied in the tone level thereof (Lotted TID-line) or a toner image having the tone levels varied stepwise at a smaller pitch than a width of a detection region of a patch sensor (solid TID-line). In density detection of such a gradation patch image Ip, toner image densities TID at portions on either sides in the detection region of the patch sensor cancel each other out by averaging and hence, only substantially the toner image density at the center of the detection region can be obtained. <IMAGE> |
