| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a compact and high-performance focusing lens which does not vary an entire optical length when focusing. <P>SOLUTION: The imaging lens includes in order from an object side to an image side: a first lens group Gr1 having a negative refractive power; a second lens group Gr2 having a positive refractive power; a third lens group Gr3 having a negative refractive power, and an optical aperture disposed in the second group. The focusing is performed by fixing the first lens group and displacing at least the second group Gr2 out of the second lens group and the third lens group in the optical axis direction without varying the entire optical length. When the focal length of the entire optical system when focused on infinity is F, the focal length of the first lens group is F1, the focal length of the second lens group is F2, the focal length of the third lens group is F3, a distance from a lens surface of the first lens group closest to the object side, to the image surface is OAL, and a maximal image height is Y', the following conditional expressions are satisfied: (1)0.4<F1/F3<1.9, (2)0.4<F2/F<0.7, and (3)2.1<OAL/Y'<2.6. <P>COPYRIGHT: (C)2013,JPO&INPIT |
