Patent ID: 8009999

Claim:
A tandem-type image forming apparatus comprising: a toner mark pattern forming unit configured to form a toner mark pattern on a transfer belt; a sensor configured to detect the toner mark pattern; a first determining unit configured to determine a presence or absence of color misregistration based on a result of the detection obtained by the sensor; and a color misregistration correcting unit configured to correct the color misregistration based on a result of the determination obtained by the first determining unit; wherein the toner mark pattern formed by the toner mark pattern forming unit includes a pair of toner marks which are disposed at different coordinates in a sub-scanning direction, one of the paired toner marks having ends thereof at different coordinates in a main scanning direction with respect to ends of the other one of the paired toner marks, and the first determining unit determines the presence or absence of the color misregistration in the main scanning direction based on the result of the detection of the paired toner marks obtained by the sensor.