| 摘要 |
PROBLEM TO BE SOLVED: To provide a large aperture ratio lens which is light and has a large aperture ratio and a long back focus, can easily arrange a prism and a filter, and has low aberration fluctuation in accompaniment to a change of an object distance. SOLUTION: The large aperture ratio lens includes the first lens group having a positive refractive power, and the second lens group having a positive or negative refractive power, sequentially from an object side. The first lens group has a positive lens, a negative meniscus lens with a convex face directed to the object side, a negative lens, and an aperture diaphragm, sequentially from the object side. The lens in the side nearest to an image and the lens in the object side nearest to the aperture diaphragm are positive lens, in the first lens group. COPYRIGHT: (C)2010,JPO&INPIT |
