| 摘要 |
PROBLEM TO BE SOLVED: To increase the degree of freedom of design for aberration correction and compensate aberrations with good balance by forming three lenses as anamorphic lenses. SOLUTION: The scanning lens 5 is constituted by arranging a 1st lens 5a as a negative anamorphic lens which has its negative power larger in a vertical scanning direction than in a horizontal scanning direction, a 2nd lens 5b as an anamorphic lens which has its positive power set larger in the horizontal scanning direction than in the vertical scanning directions, and a 3rd lens 5c as an anamorphic lens which has its positive power set larger in the vertical scanning direction than in the horizontal scanning direction in order from the side of a polygon mirror 4 to the side of a scanned surface 6. |
