Wide-angle lens system

1. A wide-angle lens system comprises a negative first lens group, a negative second lens group and a positive third lens group, in this order from an object,

wherein said negative first lens group comprises a negative meniscus lens element having the convex surface facing toward the object, and a positive lens element having a convex surface facing toward the object, in this order from the object;

wherein said negative first lens group comprises at least one aspherical surface;

wherein said negative second lens group comprises a negative meniscus lens element having the convex surface facing toward the object, and cemented lens elements having a positive lens element and a negative lens element, in this order from the object;

wherein said positive third lens group comprises cemented lens elements having a negative lens element and a positive lens element, and a positive lens element having a convex surface facing toward the image, in this order from the object; and

wherein said wide-angle lens system satisfies following conditions:

1.30< f 3/ f< 1.70

−13.50< f 2/ f<− 3.80

wherein

f designates the focal length of the entire lens system;

f 2 designates the combined focal length of said negative second lens group; and

f 3 designates the combined focal length of said positive third lens group.

2. The wide-angle lens system according to claim 1 , wherein said negative meniscus lens element of said negative first lens group satisfies the following condition of the shaping factor:

−2.20<SF<−1.60

wherein

SF=( R 2+ R 1)/( R 2− R 1);

R 1 designates the radius of curvature of the object-side surface of said negative meniscus lens element of said negative first lens group; and

R 2 designates the radius of curvature of the image-side surface of said negative meniscus lens element of said negative first lens group.

3. The wide-angle lens system according to claim 2 , wherein the image-side surface of said negative meniscus lens element of said negative first lens group is made aspherical; and

wherein the paraxial radius of curvature of said aspherical surface is used in calculations to obtain the shaping factor.

4. The wide-angle lens system according to claim 2 , wherein the image-side surface of said negative meniscus lens element having the convex surface facing toward the object, in said negative first lens group, comprises a hybrid aspherical surface formed by a layer of a synthetic resin provided over the image-side surface of said negative meniscus lens element; and

wherein the paraxial radius of curvature of said aspherical surface is used in calculations to obtain the shaping factor.

5. The wide-angle lens system according to claim 1 , satisfying the following conditions:

−1.75< fL 1/ f<− 1.40

2.90< fL 2/ f< 5.90

wherein

fL 1 designates the focal length of said negative meniscus lens element, in said negative first lens group, having the convex surface facing toward the object;

fL 2 designates the focal length of said positive lens element, in said negative first lens group, having the convex surface facing toward the object; and

f designates the focal length of the entire lens system.

6. The wide-angle lens system according to claim 1 , wherein upon focusing from infinity to an object at a closer distance, a front lens group comprising said negative first lens group and said negative second lens group, and a rear lens group comprising said positive third lens group are moved independently toward the object.

7. The wide-angle lens system according to claim 1 , wherein said negative meniscus lens element, of said negative first lens group, having the convex surface facing toward the object is position at the most object-side in the negative first lens group.