High zoom-ratio zoom lens system
View Patent ↗A high zoom-ratio zoom lens system includes a positive first lens group, a negative second lens group, a positive third lens group, a negative fourth lens group, a positive fifth lens group, and a negative sixth lens group, in this order from an object. Upon zooming from the short focal length extremity to the long focal length extremity, a distance between the positive first lens group and the negative second lens group increases, and a distance between the negative second lens group and the positive third lens group decreases. The high zoom-ratio zoom lens system satisfies the following conditions: 5.0< f 1/| f 2|<9.0( f 2<0) (1) 4.1< f 1/ f 5<6.0 (2) wherein f 1 designate the focal length of the positive first lens group; f 2 designate the focal length of the negative second lens group; and f 5 designate the focal length of the positive fifth lens group.
1. A high zoom-ratio zoom lens system comprising a positive first lens group, a negative second lens group, a positive third lens group, a negative fourth lens group, a positive fifth lens group, and a negative sixth lens group, in this order from an object,
wherein upon zooming from the short focal length extremity to the long focal length extremity, a distance between said positive first lens group and said negative second lens group increases, and a distance between said negative second lens group and said positive third lens group decreases;
wherein said high zoom-ratio zoom lens system satisfies the following conditions:
5.0 <f 1 /|f 2<9.0( f 2<0)
4.1 <f 1 /f 5<6.0
wherein
f 1 designate the focal length of said positive first lens group;
f 2 designate the focal length of said negative second lens group; and
f 5 designate the focal length of said positive fifth lens group.
2. The high zoom-ratio zoom lens system according to claim 1 , wherein said positive fifth lens group comprises more than three positive lens elements, and at least three positive lens elements satisfy the following condition:
ν5p>60
wherein
ν5p designates the Abbe number of each of said at least three positive lens elements of said positive fifth lens group.
3. The high zoom-ratio zoom lens system according to claim 1 , wherein when zooming is being performed, said negative second lens group remains stationary with respect to the imaging plane of said high zoom-ratio zoom lens system.
4. The high zoom-ratio zoom lens system according to claim 1 , wherein said negative sixth lens group comprises a negative lens element, a negative lens element and a positive lens element, in this order from the object.
5. The high zoom-ratio zoom lens system according to claim 1 , wherein each of said positive first lens group and said positive fifth lens group comprises at least one positive lens element that is made from a glass lens-material of anomalous dispersion characteristics; and, said at least one positive lens element satisfies the following conditions:
νd>80
P g,F >0.535
wherein
νd designates the Abbe number of said at least one positive lens element; and
P g,F designates the partial dispersion ratio of said at least one positive lens element.
6. The high zoom-ratio zoom lens system according to claim 5 , further satisfying the following condition:
P g,F >0.540
wherein
P g,F designates the partial dispersion ratio of said at least one positive lens element.