Patent ID: 6798549
Filing Date: 2004-09-28
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, where &dgr;M2 is a defocus amount in a main scanning section of the beams guided to said synchronism detector and in a view from a photoreceptive surface of said synchronism detector and &dgr;X is a defocus amount at each image height on said surface to be scanned, a dot shift per scan line on the surface to be scanned, which occurs because of a difference between the two defocus amounts &dgr;M2, &dgr;X, is not more than half of resolution in a sub-scanning direction.