| 摘要 |
PROBLEM TO BE SOLVED: To provide a laser beam scanning optical device capable of preventing a focusing error due to the erroneous detection of a beam converging state as much as possible. SOLUTION: A laser beam radiated from a laser diode 1 is converged on a photosensitive drum 40 through a focusing lens 3, a polygon mirror 6 and an fθlens and scanned in the direction of an arrow (b). The scanned laser beam is made incident on a converging state detector 10 and the deviated amount of the converged position is detected. A position changing amount for correcting the converging position is calculated based on the detected deviating amount, the lens 3 is moved on the optical axis by a motor 21 and a beam converging position is corrected. When the correction of a converging position is performed in the intermediate band of an image forming area and calculated position changing amount exceeds a limiting value, it is considered to be erroneous detection and the lens 3 is moved within the limiting value.
|
