| 摘要 |
An image forming apparatus includes an image carrier, an image forming unit, a density sensor, a gradation characteristic data generator, and a gradation corrector. The density sensor includes a low-pass filter to remove a high-frequency component of an output of the image density sensor. The gradation characteristic data generator forms a gradation correction pattern on the image carrier. The gradation correction pattern is a continuous gradation pattern including first and second patterns. The gradation characteristic data generator continuously detects image density of the continuous gradation pattern and background areas adjacent to the continuous gradation pattern to generate the gradation characteristic data. The gradation characteristic data generator forms a compensation pattern on the image carrier next to and continuous with a leading end of the first pattern in an image carrier rotational direction, to compensate for a response delay of the output of the density sensor due to the low-pass filter. |
| 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 sensor to detect density of the multi-gradation image formed on the image carrier, comprising a low-pass filter to remove a high-frequency component of an output of the density sensor; a gradation characteristic data generator to form a gradation correction pattern on the image carrier with the image forming unit, to detect image density of the gradation correction pattern using the density sensor, 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 continuous with the first pattern in a direction in which the image carrier rotates, and having gradation levels changing continuously from the minimum gradation level to the maximum gradation level in the gradation range, the gradation characteristic data generator continuously detecting, with the density sensor, image density of the continuous gradation pattern formed on the image carrier and image density of background areas adjacent to a leading end and a trailing end of the continuous gradation pattern, respectively, in the direction in which the image carrier rotates, in a predetermined sampling period, to generate the gradation characteristic data according to detected image density of the continuous gradation pattern and image density of the background areas, the gradation characteristic data generator forming a compensation pattern on the surface of the image carrier next to a leading end of the first pattern in the direction in which the image carrier rotates, the compensation pattern being continuous with the first pattern and having a length in the direction in which the image carrier rotates sufficient to compensate for a response delay of the output of the density sensor due to the low-pass filter. |
