| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an optical system capable of suppressing generation of a ghost. <P>SOLUTION: A telephoto lens TL includes a plurality of lenses L1, L2, ..., arranged in order from an object side along an optical axis and a diffraction optical element DOE having a diffraction grating which is rotationally symmetric with respect to the optical axis. The diffraction optical element DOE is arranged on any lens surface of the plurality of lenses L1, L2,..., and the telephoto lens TL satisfies a conditional expression: 0.50<fa/Rd<0.90 or a conditional expression: 1.10<fa/Rd<2.00, where fa is a composite focal length of each lens from the lens L1 closest to the object side in the plurality of lenses L1, L2,... to the lens L2 on which the diffraction optical element DOE is provided, and Rd is a curvature radius of the lens surface on which the diffraction optical element DOE is arranged. <P>COPYRIGHT: (C)2012,JPO&INPIT |
