Wide-angle zoom lens system
View Patent ↗A wide-angle zoom lens system includes a positive first lens group, a negative second lens group, a positive third lens group and a positive fourth lens group, in this order from the 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, a distance between the negative second lens group and the positive third lens group decreases, and a distance between the positive third lens group and the positive fourth lens group decreases. The wide-angle zoom lens system satisfies a number of conditions.
1. A wide-angle zoom lens system comprises a positive first lens group, a negative second lens group, a positive third lens group and a positive fourth 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, a distance between said negative second lens group and said positive third lens group decreases, and a distance between said positive third lens group and said positive fourth lens group decreases;
wherein said wide-angle zoom lens system satisfies the following conditions:
6.0< f 1 /fw< 8.0
7.0 <f 1/ |f 2|<9.0( f 2<0)
2.5 <f 3 /fw< 4.5
wherein
f 1 designates the focal length of said positive first lens group;
f 2 designates the focal length of said negative second lens group;
f 3 designates the focal length of said positive third lens group; and
fw designates the focal length of the entire wide-angle zoom lens system at the short focal length extremity.
2. The wide-angle zoom lens system according to claim 1 , further satisfying the following condition:
1.0 <f 3/ f 4<2.5
wherein
f 3 designates the focal length of said positive third lens group; and
f 4 designates the focal length of said positive fourth lens group.
3. The wide-angle zoom lens system according to claim 1 , wherein said positive third lens group comprises a positive 3 a -sub-lens group and a negative 3 b -sub-lens group, in this order from the object; and
wherein said wide-angle zoom lens satisfies the following conditions:
1.0 <f 4/ f 3 a< 2.0
0.2 <f 2/ f 3 b< 0.5
wherein
f 4 designates the focal length of said positive fourth lens group;
f 2 designates the focal length of said negative second lens group;
f 3 a designates the focal length of said positive 3 a -sub-lens group (>0); and
f 3 b designates the focal length of said negative 3 b -sub-lens group(<0).
4. A wide-angle zoom lens system comprises a positive first lens group, a negative second lens group, a positive third lens group and a positive fourth 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, a distance between said negative second lens group and said positive third lens group decreases, and a distance between said positive third lens group and said positive fourth lens group decreases;
wherein said positive third lens group comprises a positive 3 a -sub-lens group and a negative 3 b -sub-lens group, in this order from the object;
wherein said wide-angle zoom lens satisfies the following conditions:
1.0 <f 3/ f 4<2.5
1.0 <f 4/ f 3 a< 2.0
0.2 <f 2/ f 3 b < 0.5
wherein
f 3 designates the focal length of said positive third lens group;
f 4 designates the focal length of said positive fourth lens group;
f 2 designates the focal length of said negative second lens group;
f 3 a designates the focal length of said positive 3 a -sub-Lens group (>0); and
f 3 b designates the focal length of said negative 3 b -sub-lens group(<0).
5. The wide-angle zoom lens system according to claim 4 , wherein said negative 3 b -sub-lens group, which is positioned on the image-side of said positive 3 a -sub-lens group, comprises cemented lens elements having a positive lens element and a negative lens element.
6. The wide-angle zoom lens system according to claim 3 , wherein said negative 3 b -sub-lens group, which is positioned on the image-side of said positive 3 a -sub-lens group, comprises cemented lens elements having a positive lens element and a negative lens element.