Patent ID: 9575430
Date: 2017-02-21
CPC Classifications: B41J,G02B,G03G,H04N

Claim:
1. An image forming apparatus operable to switch a speed of image forming from one image forming speed to another, comprising: a photosensitive member; a scanning unit including a light source having a plurality of light emitting elements including a first light emitting element and a second light emitting element, each of which emits laser beams, a polygon mirror configured to deflect the laser beam emitted from each such light emitting element so that the laser beam emitted from each of the light emitting elements scans the photosensitive member, and a sensor configured to output, by receiving the laser beams emitted from the first and second light emitting elements and deflected by the polygon mirror, detection signals respectively corresponding to the first and second light emitting elements, wherein the plurality of light emitting elements are arranged such that the light emitting elements expose respective different positions on the photosensitive member in a scanning direction, and wherein the scanning unit is configured to control the scanning speed of the laser beams to be a speed corresponding to the image forming speed by controlling a rotation speed of the polygon mirror based on scanning speed information; a storage unit configured to store a reference time interval corresponding to a reference scanning speed of the laser beams; a measuring unit configured to: a control unit configured to compare the corrected time interval with the reference time interval and to control a relative light emitting start timing of the plurality of light emitting elements in one scanning period of the light beams based on a comparison result of the corrected time interval and the reference time interval, wherein the relative light emitting start timing corresponds to the scanning speed represented by the scanning speed information.