| 发明名称 | Zoom lens unit and imaging apparatus | ||
| 摘要 | A zoom lens unit comprises a first and fourth lens groups with positive refractive power, a second and third lens groups with negative refractive power. The first and the fourth lens groups are fixed, the second lens group moves toward an image side and the fourth lens group moves when changing a magnification ratio from a wide-angle end to a telephoto end. The fourth lens group includes a negative resin lens and at least one positive lens. At least one of said positive lenses fulfills following conditions: 1.40<nd<1.6565.0<νd<100.00.015<Pg, F−(−0.001802×νd+0.6483)<0.060where nd, νd, and Pg, F, each represents a refractive index, an Abbe number, a partial dispersion ratio of the positive lens. Pg, F is (ng−nF)/(nF−nC), where ng, nF, and nC represent refractive indexes at g-line, F-line, and C-line of the positive lens. | ||
| 申请公布号 | US9500876(B2) | 申请公布日期 | 2016.11.22 |
| 申请号 | US201414584167 | 申请日期 | 2014.12.29 |
| 申请人 | RICOH COMPANY, LTD. | 发明人 | Sudoh Yoshifumi |
| 分类号 | G02B15/14;G02B27/42;G02B15/173;G02B13/00;G02B13/18;G02B27/00;G02B9/36;G02B5/00;G02B9/34;G02B15/20;G02B27/09;G02B5/18;G02B15/24;G02B7/00 | 主分类号 | G02B15/14 |
| 代理机构 | Oblon, McClelland, Maier & Neustadt, L.L.P | 代理人 | Oblon, McClelland, Maier & Neustadt, L.L.P |
| 主权项 | 1. A zoom lens unit comprising: in order from an object side to an image plane side, a first lens group with positive refractive power; a second lens group with negative refractive power; a third lens group with negative refractive power; and a fourth lens group with positive refractive power; wherein the first lens group and the fourth lens group are fixed relative to the image plane, while the second lens group moves toward the image plane side and the third lens group moves when changing a magnification ratio from a wide-angle end to a telephoto end, the fourth lens group includes a resin lens with negative refractive power, and at least one positive lens, and said at least one positive lens of the fourth lens group fulfils conditions (1), (2), and (3): 1.40<nd<1.65 (1)65.0<νd<100.0 (2)0.015<Pg, F−(−0.001802×νd+0.6483)<0.060 (3) where nd represents a refractive index of the positive lens, νd represents an Abbe number of the positive lens, and Pg, F represents a partial dispersion ratio of the positive lens and is expressed by: Pg, F=(ng−nF)/(nF−nC), where ng, nF, and nC represent refractive indexes at g-line, F-line, and C-line of the positive lens respectively, wherein a condition (4) is fulfilled: −12.0<f—pla/f4<−3.0 (4) where f—pla represents a focal length of the resin lens in the fourth lens group, and f4 represents a focal length of the fourth lens group. | ||
| 地址 | Tokyo JP | ||