Patent ID: 8755082

Claim:
An image forming apparatus comprising: a plurality of photoreceptors; a plurality of developing devices for forming toner patterns on the plurality of photoreceptors; an intermediate transfer medium for receiving the toner patterns transferred from the plurality of photoreceptors; a controller for controlling the plurality of developing devices to form first toner patterns that are lines extending in a main-scanning direction and second toner patterns that are lines slanting from the main-scanning direction on the plurality of photoreceptors such that the first toner pattern and the second toner pattern transferred from the same photoreceptor will be arranged on the intermediate transfer medium at an interval in a sub-scanning direction, the interval equal to a circumferential length of the photoreceptor from which the first toner pattern and the second toner pattern are transferred; and a sensor for detecting the first toner patterns and the second toner patterns transferred onto the intermediate transfer medium.