Patent ID: 6825961
Filing Date: 2004-11-30
Classification: G02B,H04N

Abstract:
A multi-beam scanning optical system comprising:incidence optical means for guiding a plurality of beams emitted from light source means having a plurality of light-emitting regions spaced apart from each other in a main scanning direction, to deflecting means; scanning optical means for focusing the plurality of beams deflected by the deflecting means on a surface to be scanned, to form a plurality of scan lines; and synchronism-detecting optical means for guiding part of the plurality of beams deflected by the deflecting means, to a synchronism detector and controlling timing of a scan start position on the surface to be scanned for the plurality of beams by use of a signal from the synchronism detector, wherein the following condition is satisfied: |&dgr;M2|&lE;&dgr;Ymax/tan(&thgr;max) where &dgr;M2: defocus amount in a main scanning section of the beams guided to the synchronism detector and in a view from a photoreceptive surface of the synchronism detector; &dgr;Ymax: permissible dot shift amount per scan line, which is not more than half of resolution in a sub-scanning direction; &thgr;max: maximum angle difference between angles of incidence to the photoreceptive surface of the beams used for detection of synchronism.