Patent ID: 6856336

Claim:
A color image forming apparatus comprising: a plurality of scanning optical apparatuses for forming images of different colors, wherein each scanning optical apparatus comprises: scanning optical means for causing the beam deflected by said deflecting means to be imaged in a spot shape on a surface to be scanned, wherein a scanning line scanning on said surface to be scanned has two or more extremums within an effective range of a scanning area; a plurality of image bearing members disposed on said surfaces to be scanned of said plurality of scanning optical apparatuses, respectively; and two or more registration detecting means for detecting a color misregistration component, wherein said two or more registration detecting means are disposed at an intermediate image height between the center of an effective scanning area and the end of the effective scanning area in the main scanning direction, wherein when the distance from the center of the effective scanning area to the end of the effective scanning area in the main scanning direction is defined as T, and the distance from the center of the effective scanning area to the detecting position of said registration detecting means in the main scanning direction is defined as S, said registration detecting means are disposed at such a position as satisfies 0.3 |T|<|S|<|T|.