| 主权项 |
1. An image forming apparatus comprising:
an image carrier rotatable at a predetermined speed to carry an image on a surface thereof; an image forming unit to form a multi-gradation image on the image carrier; a density detector to detect density of the multi-gradation image formed on the image carrier; a gradation characteristic data generator to form a gradation correction pattern on the image carrier via the image forming unit, to detect image density of the gradation correction pattern via the density detector, and to generate gradation characteristic data that shows a relation between the image density and a plurality of gradation levels in a gradation range used for forming the multi-gradation image according to a detected image density of the gradation correction pattern; and a gradation corrector to correct image data of the multi-gradation image to be outputted, according to the gradation characteristic data, the gradation correction pattern being a continuous gradation pattern including:
a first pattern having gradation levels changing continuously from a maximum gradation level to a minimum gradation level in the gradation range; anda second pattern having gradation levels changing continuously from the minimum gradation level to the maximum gradation level in the gradation range,the second pattern continuous with the first pattern in a direction in which the image carrier rotates, the gradation characteristic data generator continuously detecting image density of the continuous gradation pattern formed on the image carrier and image density of background areas next to an upstream end and a downstream end of the gradation correction pattern, respectively, in the direction in which the image carrier rotates, in a predetermined sampling period, via the density detector, to generate the gradation characteristic data according to detected image density of the continuous gradation pattern and image density of the background areas. |
