US Patent 7145705 Optical scanner and image forming apparatus

A scanner which optically scans n positions, where n≧2, has m light sources which emits p beams, where 1≦m<n and p≦1; a unit which splits each beam into q beams in a sub-scanning direction and forms each beam into a predetermined form, where 2≦q≦n; a deflector having a plurality of planes around a rotation axis and configured to deflect a number of beams equal to (q·m·p) from the m sources which are incident on the deflector; n optical systems which guide n sets of beams deflected to corresponding positions to form light spots; and a selecting unit which selects a path for each of the n sets of beams, wherein the deflector is at least a part of the selecting unit.