| 摘要 |
The invention provides a light beam scanning device in which an f- theta lens system is constituted by two single lenses, a cylindrical lens having a refractive power in only a deflection plane is located at the side of a deflective reflecting surface, and a toric lens including a surface having a negative refractive index at the side of the deflective reflecting surface and including a surface having a positive refractive power at the side of a surface to be scanned in a sectional plane perpendicular to the deflection plane is located at the output side of the cylindrical lens, thereby realizing scanning at a constant speed of an image-forming beam while preventing pitch variations in the beam and image surface curvature thereof on the surface to be scanned. More particularly, the invention provides a light beam scanning device in which a plastic lens can be used as the cylindrical lens.
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