Wide-angle zoom lens system
View Patent ↗A wide-angle zoom lens system includes a negative first lens group, a positive second lens group, a negative 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 negative first lens group and the positive second lens group decreases, a distance between the positive second lens group and the negative third lens group increases, and a distance between the negative third lens group and the positive fourth lens group decreases. The wide-angle zoom lens system satisfies the following conditions: 1.1<| f 1|/ fw< 2.0 ( f 1< 0 ) (1) 2.0< f 4/ fw< 3.5 (2) 2.5< fBw/fw< 3.5 (3)
1. A wide-angle zoom lens system comprises a negative first lens group, a positive second lens group, a negative 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 negative first lens group and said positive second lens group decreases, a distance between said positive second lens group and said negative third lens group increases, and a distance between said negative third lens group and said positive fourth lens group decreases; and
wherein said wide-angle zoom lens system satisfies the following conditions:
1.1 <|f 1 |/fw <2.0( f 1 <0)
2.0 <f 4 / fw <3.5
2.5 <fBw/fw <3.5
0.5 <f 2 / ft< 1.2
0.5 <|f 3 |/ft< 1.4( f 3 <0)
wherein
f 1 designates the focal length of said negative first lens group;
f 2 designates the focal length of said positive second lens group;
f 3 designates the focal length of said negative third lens group;
f 4 designates the focal length of said positive fourth lens group;
ft designates the focal length of the entire wide-angle zoom lens system at the long focal length extremity;
fw designates the focal length of the entire wide-angle zoom lens system at the short focal length extremity; and
fBw designates the equivalent air thickness from the most image-side lens surface to the image plane at the short focal length extremity.
2. The wide-angle zoom lens system according to claim 1 , wherein said negative first lens group comprises, at least, a negative meniscus lens element having the convex surface facing toward the object, another negative meniscus lens element having the convex surface facing toward the object, a negative lens element having a concave surface facing toward the image, and a positive lens element, in this order from the object.
3. The wide-angle zoom lens system according to claim 1 , wherein said positive second lens group comprises positive cemented lens elements and a positive lens element, or two sets of positive cemented lens elements.
4. The wide-angle zoom lens system according to claim 1 , wherein said negative third lens group comprises negative cemented lens elements and a positive lens element, or, two sets of negative cemented lens elements.
5. The wide-angle zoom lens system according to claim 1 , wherein said positive fourth lens group comprises cemented lens elements and two positive lens elements, or two sets of cemented lens elements and a positive lens element.
6. A wide-angle zoom lens system comprises a negative first lens group, a positive second lens group, a negative 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 negative first lens group and said positive second lens group decreases, a distance between said positive second lens group and said negative third lens group increases, and a distance between said negative third lens group and said positive fourth lens group decreases; and
wherein said wide-angle zoom lens system satisfies the following conditions:
0.5 <f 2 / ft< 1.2
0.5 <|f 3 |/ft< 1.4( f 3 <0)
wherein
ft designates the focal length of the entire wide-angle zoom lens system at the long focal length extremity;
f 2 designates the focal length of said positive second lens group; and
f 3 designates the focal length of said negative third lens group.
7. The wide-angle zoom lens system according to claim 6 , further satisfying the following conditions:
1.1 <|f 1 |/fw< 2.0( f 1 <0)
2.0 <f 4 /fw <3.5
wherein
f 1 designates the focal length of said negative first lens group;
f 4 designates the focal length of said positive fourth lens group; and
fw designates the focal length of the entire wide-angle zoom lens system at the short focal length extremity.
8. The wide-angle zoom lens system according to claim 6 , wherein said negative first lens group comprises, at least, a negative meniscus lens element having the convex surface facing toward the object, another negative meniscus lens element having the convex surface facing toward the object, a negative lens element having a concave surface facing toward the image, and a positive lens element, in this order from the object.
9. The wide-angle zoom lens system according to claim 6 , wherein said positive second lens group comprises positive cemented lens elements and a positive lens element, or two sets of positive cemented lens elements.
10. The wide-angle zoom lens system according to claim 6 , wherein said negative third lens group comprises negative cemented lens elements and a positive lens element, or, two sets of negative cemented lens elements.
11. The wide-angle zoom lens system according to claim 6 , wherein said positive fourth lens group comprises cemented lens elements and two positive lens elements, or two sets of cemented lens elements and a positive lens element.
12. A wide-angle zoom lens system comprises a negative first lens group, a positive second lens group, a negative third lens group and a positive fourth lens group, in this order from an object,
said negative first lens group comprises, at least, a negative meniscus lens element having the convex surface facing toward the object, another negative meniscus lens element having the convex surface facing toward the object, a negative lens element having a concave surface facing toward the image, and a positive lens element, in this order from the object;
wherein upon zooming from the short focal length extremity to the long focal length extremity, a distance between said negative first lens group and said positive second lens group decreases, a distance between said positive second lens group and said negative third lens group increases, and a distance between said negative third lens group and said positive fourth lens group decreases; and
wherein said wide-angle zoom lens system satisfies the following conditions:
1.1 <|f 1 |/fw< 2.0( f 1 <0)
2.0 <f 4 / fw< 3.5
2.5 <fBw/fw< 3.5
wherein
f 1 designates the focal length of said negative first lens group;
f 4 designates the focal length of said positive fourth lens group;
fw designates the focal length of the entire wide-angle zoom lens system at the short focal length extremity; and
fBw designates the equivalent air thickness from the most image-side lens surface to the image plane at the short focal length extremity.
13. The wide-angle zoom lens system according to claim 12 , wherein said positive second lens group comprises positive cemented lens elements and a positive lens element, or two sets of positive cemented lens elements.
14. The wide-angle zoom lens system according to claim 12 , wherein said negative third lens group comprises negative cemented lens elements and a positive lens element, or, two sets of negative cemented lens elements.
15. The wide-angle zoom lens system according to claim 12 , wherein said positive fourth lens group comprises cemented lens elements and two positive lens elements, or two sets of cemented lens elements and a positive lens element.