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: 1.3<| f 1 |/fw <1.7 ( f 1<0) (1) 2.5< f 4/ fw <3.3 (2) wherein f 1 designates the focal length of the negative first lens group; f 4 designates the focal length of the positive fourth lens group; and fw designates the focal length of the entire wide-angle zoom lens system at the short focal length extremity.
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;
wherein said wide-angle zoom lens system satisfies the following conditions:
1.3<| f 1|/ fw< 1.7 ( f 1<0)
2.5 <f 4/ fw< 3.3
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.
2. The wide-angle zoom lens system according to claim 1 , further satisfying the following condition:
0.6< f 2/ ft< 0.8
wherein
f 2 designates the focal length of said positive second lens group; and
ft designates the focal length of the entire wide-angle zoom lens system at the long focal length extremity.
3. The wide-angle zoom lens system according to claim 1 , further satisfying the following condition:
0.4 <|f 3|/ ft< 0.9 ( f 3<0)
wherein
f 3 designates the focal length of said negative third lens group; and
ft designates the focal length of the entire wide-angle zoom lens system at the long focal length extremity.
4. 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.
5. 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.
6. The wide-angle zoom lens system according to claim 1 , wherein said negative third lens group comprises two sets of negative cemented lens elements.
7. 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.
8. 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;
wherein said wide-angle zoom lens system satisfies the following conditions:
0.6 <f 2/ ft< 0.8
0.4 <|f 3|/ ft< 0.9 ( f 3<0)
wherein
f 2 designates the focal length of said positive second lens group;
f 3 designates the focal length of said negative third lens group; and
ft designates the focal length of the entire wide-angle zoom lens system at the long focal length extremity.
9. The wide-angle zoom lens system according to claim 8 , further satisfying the following condition:
2.5 <f 4/ fw< 3.3
wherein
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.
10. The wide-angle zoom lens system according to claim 8 , further satisfying the following conditions:
1.2 <f 2/ |f 1|<1.6 ( f 1<0)
1.2 <f 4/ |f 3|<1.6 ( 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; and
f 4 designates the focal length of said positive fourth lens group.
11. The wide-angle zoom lens system according to claim 8 , 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.
12. The wide-angle zoom lens system according to claim 8 , wherein said positive second lens group comprises positive cemented lens elements and a positive lens element, or two sets of positive cemented lens elements.
13. The wide-angle zoom lens system according to claim 8 , wherein said negative third lens group comprises two sets of negative cemented lens elements.
14. The wide-angle zoom lens system according to claim 8 , 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.
15. 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;
wherein said wide-angle zoom lens system satisfies the following conditions:
1.2 <f 2/ |f 1|<1.6 ( f 1<0)
1.2 <f 4/| f 3|<1.6 ( 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; and
f 4 designates the focal length of said positive fourth lens group.
16. The wide-angle zoom lens system according to claim 15 , 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.
17. The wide-angle zoom lens system according to claim 15 , wherein said positive second lens group comprises positive cemented lens elements and a positive lens element, or two sets of positive cemented lens elements.
18. The wide-angle zoom lens system according to claim 15 , wherein said negative third lens group comprises two sets of negative cemented lens elements.
19. The wide-angle zoom lens system according to claim 15 , 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.