Patent ID: 8150302

Claim:
An image forming apparatus comprising: a pattern forming unit that forms a color-misalignment detection pattern on an image carrier; a light-intensity detecting unit that detects the color-misalignment detection pattern formed on the image carrier by irradiating the image carrier with a light and detecting light intensity of a reflected light from the image carrier; and a color-misalignment-amount detecting unit that detects an amount of a color misalignment of an image based on the light intensity of the reflected light detected by the light-intensity detecting unit, wherein: a spot of the light on the image carrier is elongated in a main-scanning direction, the color-misalignment detection pattern includes a main-scanning-direction misalignment detection pattern for detecting a color misalignment in the main-scanning direction, the pattern forming unit forms the main-scanning-direction misalignment detection pattern including a first pattern for a predetermined reference color and a second pattern for a non-reference color other than the reference color arranged being overlapped with each other on the image carrier, a plurality of the first patterns and a plurality of the second patterns are arranged in the sub-scanning direction with different amounts of the color misalignment in the main-scanning direction, and the light-intensity detecting unit detects the amount of the color misalignment in the main-scanning direction based on a variation in the light intensity caused by shifts of the reflected lights from the first pattern and the second pattern in the main-scanning direction, and a length of the second pattern in the sub-scanning direction is shorter than a length of the spot in the sub-scanning direction.