Possessing with the plane to be scanned information is written

摘要

PPROBLEM TO BE SOLVED: To provide an optical scanner constituted so that dot-misregistration in a main scanning direction due to an environmental fluctuation may be reduced and color slippage may be suppressed in a color image forming apparatus, and to provide an image forming apparatus using the optical scanner. PSOLUTION: The optical scanner is provided with photodetecting parts 21 and 22 arranged at least in two positions on the writing start side and the terminal side outside an effective writing area, a measuring means 15 for measuring a scanning time when light beams deflected and scanned by the optical deflector 11 cross between the photodetecting parts 21 and 22, and a correcting means for correcting each dot position of image data to an optional position in the effective writing area based on the fluctuation of the measured scanning time. It is allowed to install a temperature sensor, a lookup table wherein a relation between the temperature fluctuation detected by the temperature sensor and a phase shift is previously recorded, and a correcting means for correcting each dot position of the image data to an optional position in the effective writing area based on the temperature fluctuation. PCOPYRIGHT: (C)2003,JPO