| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a projection lens in which an F value is reduced while aberrations and an enlargement of the size of an apparatus are suppressed. <P>SOLUTION: The projection lens includes, in order from an enlargement side, a first lens L1 having a negative refractive power and a concave surface facing a reduction side, a second lens L2 having a positive refractive power and a convex surface facing the enlargement side, a third lens L3 having a negative refractive power and a concave surface facing the enlargement side, a fourth lens L4 having a positive refractive power and a convex surface facing the reduction side, and a fifth lens L5 having a positive refractive power, and satisfies the following conditional expressions: (A): 1.2≤Bf/f≤2.5, (B): -3.0≤f3F/f≤-0.8, (C): 1.4≤f5F/f5≤8.5, and (D): 1.0≤d12/f≤2.7, where Bf is a back focus, f is the focal length of the entire lens system, f3F is the focal length of the enlargement side surface of the third lens, f5F is the focal length of the enlargement side surface of the fifth lens, f5 is the focal length of the fifth lens, and d12 is an air distance between the first lens and the second lens. <P>COPYRIGHT: (C)2012,JPO&INPIT |
