| 摘要 |
PURPOSE:To excellently obtain a light beam scanning device which has the residual aberrations of a whole system corrected, a small F number, and a surface tilt correcting function by constituting a 1st image formation optical system so that an excessively corrected spherical aberration is obtained and making a 2nd image formation optical system meet specific requirements. CONSTITUTION:The 1st image formation optical system 5 has a converging effect only at a direction orthogonal to a scanning direction and is further constituted as to have the excessively corrected spherical aberration, and its polarized wave reflecting surface and a scanned surface are in geometric optical conjugation relation. The 2nd image formation optical system 11, on the other hand, consists of three lenses 8, 9 and 10, i.e., a positive meniscus spherical lens having its concave surface on a deflector side, a positive spherical surface which has its convex surface on the deflector side, and a toric surface, and inequalities (1) and (2) are satisfied. Here, (f) is the focal distance of the whole system, fP and fV the focal distance of the 2nd image formation optical system in the scanning directions and the focal distance at the direction orthogonal to the scanning direction respectively, and L2 is the overall length of the lens of the 2nd image formation optical system. |
