Patent ID: 6795222
Filing Date: 2004-09-21
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; and synchronism-detecting optical means for converging part of the plurality of beams deflected by the deflecting means, on a slit surface, thereafter guiding the beams to a synchronism detector, and controlling timing of a scan start position on the surface to be scanned by use of a signal from the synchronism detector, wherein, where &dgr;M1 is a defocus amount in a main scanning section of the beams guided to the sychronism detector and in a view from the slit surface and &dgr;X is a defocus amount at each image height on the surface to be scanned, the following condition is satisfied: |&dgr;Xâˆ’&dgr;M1|&lE;&dgr;Ymax/&thgr;max â€ƒwhere â€ƒ&dgr;Ymax: permissible dot shift amount per scan line, which is not more than half of resolution in a sub-scanning direction; â€ƒ&thgr;max: maximum angle difference between angles of incidence to the slit surface of the beams used for detection of synchronism.