| 摘要 |
PURPOSE:To form a fine spot without the generation of unevenness over the whole range of a scanning direction and to attain scanning also in the vertical sub-scanning direction by scanning a condensed beam reflected by a polyhedral reflector at a constant speed and reflecting the condensed beam reflected by the constant speed reflector upon a surface to be scanned. CONSTITUTION:The minimum spot of the condensed beam draws an arc-like locus around the reflecting surface of the polyhedral reflector 5 with the radius defined by the opical length up to a recoding part 8. Since an auto-focusing condenser 10 can be moved in the optical axis direction, the arc-like locus of the condensed spot is converted into a linear locus by the condenser 10, so that the defocusing of the condensed spot beam is not generated. Since a reflector 14 arranged on the front of the recording part 8 is set up so as to be up and down, the defocusing is compensated by combining the up/down operation with the moving operation of the condenser 10 in the optical axis direction and sub-scanning in the direction vertical to the main scanning direction can be attained. |
