| 摘要 |
A projection lens includes, in order from a magnification side, a first lens group, a second lens group and a third lens group. The first lens group includes, in order from the magnification side, a negative lens whose lens made of a non-resin, a plastic lens at least one surface of which is aspheric and a positive lens. The second lens group includes a plastic lens at least one surface of which is aspheric, a positive lens and a negative lens. The third lens group includes a positive lens. The following conditional expressions are satisfied. <?in-line-formulae description="In-line Formulae" end="lead"?>1.0<Bf/f<=1.8<?in-line-formulae description="In-line Formulae" end="tail"?> <?in-line-formulae description="In-line Formulae" end="lead"?>2.0<f1/f <?in-line-formulae description="In-line Formulae" end="tail"?> <?in-line-formulae description="In-line Formulae" end="lead"?>2.0<f2/f <?in-line-formulae description="In-line Formulae" end="tail"?> where Bf denotes a air-conversion back focus of the entire system, f denotes a focal length of the entire system, f1 denotes a focal length of the first lens group and f2 denotes a focal length of the second lens group.
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