Patent ID: 8274538

Claim:
An optical scanner comprising: a laser beam source for emitting a laser beam; an optical scanning device for scanning a laser beam emitted from the laser beam source; an exposure controller for forming an electrostatic latent image corresponding to image data on a photoreceptor by controlling light emission of the laser beam source on the basis of the image data; a laser beam detector which is provided in a predetermined position on a scanning path of a laser beam scanned by the optical scanning device and which detects when the laser beam has an emission intensity equal to or higher than a predetermined reference emission intensity; an exposure-start timing controller for controlling a start timing of formation of an electrostatic latent image by the exposure controller on the basis of a time at which the laser beam is detected by the laser beam detector; an exposure intensity changing unit for changing an emission intensity of the laser beam source at the time of electrostatic latent image formation; an emission intensity setting unit for setting the emission intensity at detection of the laser beam source at a time when a laser beam is detected by the laser beam detector to a predetermined constant emission intensity irrespective of a change in beam emission intensity effected by the exposure intensity changing unit at the time of electrostatic latent image formation; and an automatic emission intensity adjusting unit for automatically adjusting an emission intensity of the laser beam source to a preset automatically-adjusted emission intensity, wherein the exposure intensity changing unit changes the emission intensity of the laser beam source at the time of electrostatic latent image formation by the exposure controller, by changing a setting value of the automatically-adjusted emission intensity of the automatic emission intensity adjusting unit, the emission intensity setting unit at detection changes an emission intensity of the laser beam source to the emission intensity at detection after the end of adjustment by the automatic emission intensity adjusting unit, and the exposure intensity changing unit changes the emission intensity of the laser beam source to the automatically-adjusted emission intensity adjusted by the automatic emission intensity adjusting unit when the exposure controller starts the electrostatic latent image formation according to the laser beam detection by the laser beam detector, thereby a position of an electrostatic latent image formed on the photoreceptor in a main scanning direction is held constant.