Patent ID: 8670013

Claim:
A light scanning device comprising: a light source which emits a laser beam modulated and driven in response to an image forming signal; a deflection scanning unit which scans the laser beam emitted from the light source in a main scanning direction; a scanning position correction unit configured to change a scanting position of the laser beam emitted from the light source in a sub-scanning direction; and a laser beam detector including a light acceptance element and detecting a sub-scanning position in the sub-scanning direction of the laser beam configured to pass over the light acceptance element, wherein the laser beam is emitted by the light source at a timing such that the laser beam is scanned upon the laser beam detector, such that the laser beam detector always detects the sub-scanning position even at the time when the image is not formed irrespective of the presence or absence of the image forming signal, wherein a changing operation of the scanning position in the sub-scanning direction by the scanning position correction unit is performed asynchronously with output timing of the image forming signal in accordance with a detection result of the laser beam detector and performed at the time when forming the image, at which the light source is modulated and driven in accordance with the image forming signal, wherein the scanning position correction unit is a liquid crystal deflecting element disposed between the light source and the deflection scanning unit, the liquid crystal deflecting element being configured to change an optical axis of the incident laser beam and correct the scanning position by receiving an applied voltage and wherein the changing operation of the scanning position is performed at a time when forming the image in response to the image forming signal where the liquid crystal deflecting element is in a state that provides an amount of correction of 50% for the scanning position.