| 摘要 |
PURPOSE:To correct the surface inclination at the time of scanning by arranging at least a pair of upper and lower piezoelectric elements at both side parts of a folding mirror, and providing a folding mirror rotating means for rotating the folding mirror by a prescribed angle against the surface perpendicular to the optical axis of an image forming lens, based on a control signal. CONSTITUTION:A photodetector 40 on which a light beam is made incident outputs, for instance, two position signals having a value corresponding to a light receiving position to a control part 50. The control part 50 calculates the error of a light receiving reference position and the actual light receiving position of the photodetector 40, based on each inputted, position signal, and outputs a control signal to a folding mirror rotating means 20 so as to rotate a folding mirror 10 by an angle corresponding to this error. The folding mirror rotating means 20 to which the control signal is inputted drives each piezoelectric element, based on the control signal, and rotates the folding mirror 10 by a prescribed angle. This control is executed at every one scan. In such a manner, a light beam which transmits through an image forming lens and made incident on the folding mirror is corrected as to its surface inclination with high accuracy. |
