| 摘要 |
PROBLEM TO BE SOLVED: To provide an optical scanner excellent in the characteristic of the field curvature, especially, and capable of excellently reproducing an image at high speed. SOLUTION: This scanner is equipped with a light beam source 1, a deflector 4 having plural reflection surfaces reflecting and deflecting a light beam from the beam source 1, a transmission optical system 22 being an afocal optical system in a main scanning direction, which transmits light beams reflected and deflected by the 1st reflection surface 5 of the deflector 4 and being parallel at least in the main scanning direction and makes them incident on the 2nd reflection surface 6 of the deflector 4, and a scanning optical system 23 performing scanning with the light beam reflected and deflected by the 2nd reflection surface 6 of the deflector 4 and formed as a beam spot on a surface to be scanned 17. In such a case, the front group of the optical system 22 is composed of a single lens 7 at least one surface of which is aspherical (non circular-arc surface) in the main scanning direction and has the field curvature concave in the main scanning direction with respect to the advancing direction of the light. |
