| 摘要 |
An f theta lens for use in a light beam scanning device is constituted by a meniscus lens having a small power and located on the side of a deflection point, and a planoconvex lens having a large power and disposed with its convex surface on the side of a surface to be scanned. The lenses are constructed to satisfy the following conditions: -0.3</=f/f1</=0.2(a) -0.6/f1+0.85/f</=1/f2 1/f2</=-0.6/f1+0.95/f(b) where f represents a focal length of a lens system constituted by the two lenses, and f1 and f2 respectively represent focal lengths of the meniscus lens and the plano-convex lens.
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