| 摘要 |
<p>The present invention is directed to a compact large-aperture-ratio inner-focusing telephoto zoom lens of the reduced total lens extension where minimizing a photo-shooting distance down to as short as 1 meter does not cause the lens optics to displace accordingly greater during the focusing. The large-aperture-ratio inner-focusing telephoto zoom lens has four lens groups, the 1st lens group (1-5) of positive refractive power, the 2nd lens group (6-10) of negative refractive power, the 3rd lens group (11-13) of positive refractive power and the 4th lens group (14-18) of positive refractive power and that has the 2nd and 3rd lens groups moved along the optical axis for zooming. In such a telephoto zoom lens, the 1st lens group includes a foremost lens subgroup G1F and a rear lens subgroup G1R where G1F has two positive lenses and a negative lens cemented together while G1R has a doublet with one negative lens and two positive lenses. The rear lens subgroup G1R in the 1st lens group is moved along the optical axis for focusing, and the telephoto zoom lens satisfies the following inequalities: 1.45 < f �¢ 41 / fw < 1.8 where f1 is the focal length of the 1st lens group, and fw is the focal length of the telephoto zoom lens at wide-angle end.</p> |
