Wide-angle lens system

1. A wide-angle lens system comprises a negative first meniscus lens element having the convex surface facing toward an object, a positive second lens element, a positive third biconvex lens element, and a negative fourth meniscus lens element having the convex surface facing toward an image, in this order from the object;

wherein said wide-angle lens system satisfies the following condition:

0.25< H /( p 3+ p 4)<0.60

wherein

H designates the distance between the second principal point of said positive third biconvex lens element and the first principal point of said negative fourth meniscus lens element, when the focal length of the entire wide-angle lens system is normalized to 1.0;

p 3 designates the refractive power of said positive third biconvex lens element when the focal length of the entire wide-angle lens system is normalized to 1.0;

f 3 designates the focal length of said positive third biconvex lens element when the focal length of the entire wide-angle lens system is normalized to 1.0, i.e., p 3 =1/f 3 ;

p 4 designates the refractive power of said negative fourth meniscus lens element when the focal length of the entire wide-angle lens system is normalized to 1.0; and

f 4 designates the focal length of said negative fourth meniscus lens element wherein the focal length of the entire wide-angle lens system is normalized to 1.0, i.e., p 4 =1/f 4 .

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

1.00< R 7/ R 8<1.30

−1.2<( R 7+ R 8)/2 f<− 0.8

wherein

R 7 designates the radius of curvature of the image-side surface of said positive third biconvex lens element;

R 8 designates the radius of curvature of the object-side surface of said negative fourth meniscus lens element; and

f designates the focal length of the entire wide-angle lens system.

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

v4<23

25<( v 3− v 4)

wherein

v 3 designates the Abbe number of said positive third biconvex lens element; and

v 4 designates the Abbe number of said negative fourth meniscus lens element.

4. The wide-angle lens system according to claim 1 , further satisfying the following condition:

1.95<( d 2+ d 3+ d 4)/ f< 3.00

Wherein

d 2 designates the distance between said negative first meniscus lens element and said positive second lens element;

d 3 designates the thickness of said positive second lens element;

d 4 designates the distance between the image-side surface of said positive second lens element and a diaphragm; and

f designates the focal length of the entire wide-angle lens system.

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

0.03< A−B< 0.06

wherein

A =(nt3−1)×(1-nt4)/( R 7 ×R 8/ f 2 );

B =(nd3−1)×(1-nd4)/( R 7 33 R 8/ f 2 );

nt 3 designates the refractive index of the t-line of said positive third biconvex lens element;

nt 4 designates the refractive index of the t-line of said negative fourth meniscus lens element;

nd 3 designates the refractive index of the d-line of said positive third biconvex lens element;

nd 4 designates the refractive index of the d-line of said negative fourth meniscus lens element;

R 7 designates the radius of curvature of the image-side surface of said positive third biconvex lens element;

R 8 designates the radius of curvature of the object-side surface of said negative fourth meniscus lens element; and

f designates the focal length of the entire wide-angle lens system.

6. A wide-angle lens system comprises a negative first meniscus lens element having the convex surface facing toward an object, a positive second lens element, a positive third biconvex lens element, and a negative fourth meniscus lens element having the convex surface facing toward an image, in this order from the object;

wherein said wide-angle lens system satisfies the following condition:

0.032< A−B< 0.06

wherein

A =(nt3−1)×(1-nt4)/( R 7 ×R 8 /f 2 );

B =(nd3−1)×(1-nd4)/( R 7 ×R 8 /f 2 );

nt 3 designates the refractive index of the t-line of said positive third biconvex lens element;

nt 4 designates the refractive index of the t-line of said negative fourth meniscus lens element;

nd 3 designates the refractive index of the d-line of said positive third biconvex lens element;

nd 4 designates the refractive index of the d-line of said negative fourth meniscus lens element;

R 7 designates the radius of curvature of the image-side surface of said positive third biconvex lens element;

R 8 designates the radius of curvature of the object-side surface of said negative fourth meniscus lens element; and

f designates the focal length of the entire wide-angle lens system.

7. The wide-angle lens system according to claim 6 , further satisfying the following conditions:

1.00< R 7/ R 8<1.30

−1.2<( R 7+ R 8)/2 f<− 0.8

wherein

R 7 designates the radius of curvature of the image-side surface of said positive third biconvex lens element;

R 8 designates the radius of curvature of the object-side surface of said negative fourth meniscus lens element; and

f designates the focal length of the entire wide-angle lens system.

8. The wide-angle lens system according to claim 6 , further satisfying the following conditions:

v4<23

25<( v 3− v 4)

wherein

v 3 designates the Abbe number of said positive third biconvex lens element; and

v 4 designates the Abbe number of said negative fourth meniscus lens element.

9. The wide-angle lens system according to claim 6 , further satisfying the following condition:

1.95<( d 2+ d 3+ d 4)/ f< 3.00

Wherein

d 2 designates the distance between said negative first meniscus lens element and said positive second lens element;

d 3 designates the thickness of said positive second lens element;

d 4 designates the distance between the image-side surface of said positive second lens element and a diaphragm; and

f designates the focal length of the entire wide-angle lens system.

10. A wide-angle lens system comprises a negative first meniscus lens element having the convex surface facing toward an object, a positive second lens element, a positive third biconvex lens element, and a negative fourth meniscus lens element having the convex surface facing toward an image, in this order from the object;

wherein said wide-angle lens system satisfies the following condition:

v4<23

25<( v 3− v 4)

wherein

v 3 designates the Abbe number of said positive third biconvex lens element; and

v 4 designates the Abbe number of said negative fourth meniscus lens element.

11. The wide-angle lens system according to claim 10 , further satisfying the following conditions:

1.00< R 7/ R 8<1.30

−1.2<( R 7+ R 8)/2 f<− 0.8

wherein

R 7 designates the radius of curvature of the image-side surface of said positive third biconvex lens element;

R 8 designates the radius of curvature of the object-side surface of said negative fourth meniscus lens element; and

f designates the focal length of the entire wide-angle lens system.

12. The wide-angle lens system according to claim 10 , further satisfying the following conditions:

0.25< H /( p 3+ p 4)<0.60

wherein

H designates the distance between the second principal point of said positive third biconvex lens element and the first principal point of said negative fourth meniscus lens element, when the focal length of the entire wide-angle lens system is normalized to 1.0;

p 3 designates the refractive power of said positive third biconvex lens element when the focal length of the entire wide-angle lens system is normalized to 1.0;

f 3 designates the focal length of said positive third biconvex lens element when the focal length of the entire wide-angle lens system is normalized to 1.0, i.e., p 3 =1/f 3 ;

p 4 designates the refractive power of said negative fourth meniscus lens element when the focal length of the entire wide-angle lens system is normalized to 1.0; and

f 4 designates the focal length of said negative fourth meniscus lens element wherein the focal length of the entire wide-angle lens system is normalized to 1.0, i.e., p 4 =1/f 4 .

13. The wide-angle lens system according to claim 10 , further satisfying the following condition;

1.95<( d 2+ d 3+ d 4)/ f< 3.00

Wherein

d 2 designates the distance between said negative first meniscus lens element and said positive second lens element;

d 3 designates the thickness of said positive second lens element;

d 4 designates the distance between the image-side surface of said positive second lens element and a diaphragm; and

f designates the focal length of the entire wide-angle lens system.

14. The wide-angle lens system according to claim 10 , further satisfying the following condition:

0.03< A−B< 0.06

wherein

A =(nt3−1)×(1-nt4)/( R 7× R 8/ f 2 );

B =(nd3−1)×(1-nd4)/( R 7× R 8/ f 2 );

nt 3 designates the refractive index of the t-line of said positive third biconvex lens element;

nt 4 designates the refractive index of the t-line of said negative fourth meniscus lens element;

nd 3 designates the refractive index of the d-line of said positive third biconvex lens element;

nd 4 designates the refractive index of the d-line of said negative fourth meniscus lens element;

R 7 designates the radius of curvature of the image-side surface of said positive third biconvex lens element;

R 8 designates the radius of curvature of the object-side surface of said negative fourth meniscus lens element; and

f designates the focal length of the entire wide-angle lens system.