MULTI-BEAM EXPOSER UNIT

摘要

A multi-beam exposer unit 1 includes 1 $\sum _{i=1}^M$ (Ni-1) half mirror 11 for synthesizing 2 $\sum _{i=1}^M$ Ni light to M groups of light beams, M sets of optical members 12, having positive power with a large absolute value as compared with a case of a main scanning direction, for further converging the beam in a sub-scanning direction, a synthesizing reflection mirror 13 for reflecting M groups of beams to be substantially overlaid on each other in a first direction, a polygon mirror unit 5 for deflecting M groups of beams, and a dust prevention glass 14 inclined to a direction opposite to a direction where the half mirror is inclined, thereby reducing influence of coma aberration exerted on M groups of beams by the half mirror.