Imaging lens system
This invention provides an imaging lens system including, in order from an object side to an image side: a first lens with positive refractive power having a convex object-side surface; a second lens with negative refractive power; a third lens having a concave image-side surface; a fourth lens with positive refractive power; a fifth lens with negative refractive power having a concave image-side surface, at least one surface thereof having at least one inflection point; and an aperture stop disposed between an imaged object and the third lens. The on-axis spacing between the first lens and second lens is T 12 , the focal length of the imaging lens system is f, and they satisfy the relation: 0.5<(T 12 /f)×100<15.
1. An imaging lens system including, in order from an object side to an image side:
a first lens element with positive refractive power having a convex object-side surface;
a second lens element with negative refractive power;
a third lens element;
a fourth lens element with positive refractive power having a convex image-side surface; and
a fifth lens element with negative refractive power having a convex object-side surface and a concave image-side surface, the object-side and image-side surfaces thereof being aspheric, at least one surface thereof being provided with at least one inflection point;
wherein the lens elements with refractive power in the imaging lens system are only the first, second, third, fourth and fifth lens elements; a focal length of the fourth lens element is f 4 , a focal length of the fifth lens element is f 5 , and they satisfy the relation: −1.5<f 4 /f 5 <−0.5.
2. The imaging lens system according to claim 1 , wherein the fourth lens element has a concave object-side surface.
3. The imaging lens system according to claim 1 , wherein the third lens element has a concave image-side surface.
4. The imaging lens system according to claim 1 , wherein an Abbe number of the first lens element is V 1 , an Abbe number of the second lens element is V 2 , and they satisfy the relation: V 1 −V 2 >20.
5. The imaging lens system according to claim 1 , wherein a focal length of the imaging lens system is f, a focal length of the first lens element is f 1 , and they satisfy the relation: 1.0<f/f 1 <1.8.
6. The imaging lens system according to claim 1 , wherein at least one of the third, fourth and fifth lens elements is meniscus in shape, and wherein, of the third, fourth and fifth lens elements, all lens elements which are meniscus in shape satisfy the relation: 0.5<R o /R i <2.0, wherein R o , represents a radius of curvature of an object-side surface of the meniscus lens element and R i represents a radius of curvature of an image-side surface of the meniscus lens element.
7. The imaging lens system according to claim 1 , wherein an on-axis spacing between the first lens element and the second lens element is T 12 , a focal length of the imaging lens system is f, and they satisfy the relation: 0.5<(T 12 /f) ×100<15.
8. The imaging lens system according to claim 1 , wherein the imaging lens system further comprises an aperture stop disposed between an imaged object and the first lens element.
9. The imaging lens system according to claim 1 , wherein an Abbe number of the second lens element is V 2 , an Abbe number of the third lens element is V 3 , and they satisfy the relation: |V 2 −V 3 |<15.
10. The imaging lens system according to claim 1 , wherein a radius of curvature of the object-side surface of the first lens element is R 1 , a focal length of the imaging lens system is f, and they satisfy the relation: 0.2<R 1 /f<0.4.
11. The imaging lens system according to claim 1 , wherein an Abbe number of the first lens element is V 1 , an Abbe number of the second lens element is V 2 , and they satisfy the relation: V 1 −V 2 >30.
12. The imaging lens system according to claim 1 , wherein a radius of curvature of the image-side surface of the second lens element is R 4 , a focal length of the imaging lens system is f, and they satisfy the relation: 0.7<R 4 /f<1.2.
13. An imaging lens system including, in order from an object side to an image side:
a first lens element with positive refractive power having a convex object-side surface;
a second lens element with negative refractive power;
a third lens element with negative refractive power;
a fourth lens element with positive refractive power having a convex image-side surface; and
a fifth lens element with negative refractive power having a convex object-side surface and a concave image-side surface, the object-side and image-side surfaces thereof being aspheric, at least one surface thereof being provided with at least one inflection point;
wherein the lens elements with refractive power in the imaging lens system are only the first, second, third, fourth and fifth lens elements, a focal length of the fourth lens element is f 4 , a focal length of the fifth lens element is f 5 , and they satisfy the relation: −1.5<f 4 /f 5 <−0.5.
14. The imaging lens system according to claim 13 , wherein the fourth lens element has a concave object-side surface.
15. The imaging lens system according to claim 13 , wherein the third lens element has a concave image-side surface.
16. The imaging lens system according to claim 13 , wherein an Abbe number of the first lens element is V 1 , an Abbe number of the second lens element is V 2 , and they satisfy the relation: V 1 −V 2 >30.
17. The imaging lens system according to claim 13 , wherein a radius of curvature of the image-side surface of the second lens element is R 4 , a focal length of the imaging lens system is f, and they satisfy the relation: 0.7<R 4 /f<1.2.
18. The imaging lens system according to claim 13 , wherein the imaging lens system further comprises an aperture stop disposed between an imaged object and the first lens element.
19. The imaging lens system according to claim 13 , wherein at least one of the third, fourth and fifth lens elements is meniscus in shape, and wherein, of the third, fourth and fifth lens elements, all lens elements which are meniscus in shape satisfy the relation:
0.5<R o /R i <2.0, wherein R o represents a radius of curvature of an object-side surface of the meniscus lens element and R i represents a radius of curvature of an image-side surface of the meniscus lens element.
20. The imaging lens system according to claim 13 , wherein the Abbe number of the second lens element is V 2 , an Abbe number of the third lens element is V 3 , and they satisfy the relation: |V 2 −V 3 |<15.
21. An imaging lens system including, in order from an object side to an image side:
a first lens element with positive refractive power having a convex object-side surface;
a second lens element;
a third lens element;
a fourth lens element with positive refractive power having a convex image-side surface; and
a fifth lens element with negative refractive power having a convex object-side surface and a concave image-side surface, the object-side and image-side surfaces thereof being aspheric, at least one surface thereof being provided with at least one inflection point;
wherein the lens elements with refractive power in the imaging lens system are only the first, second, third, fourth and fifth lens elements; a focal length of the fourth lens element is f 4 , a focal length of the fifth lens element is f 5 , and they satisfy the relation: −1.5<f 4 /f 5 ≦0.79.
22. The imaging lens system according to claim 21 , wherein the second lens element has negative refractive power.
23. The imaging lens system according to claim 21 , wherein the fourth lens element has a concave object-side surface.
24. The imaging lens system according to claim 21 , wherein the third lens element has a concave image-side surface.
25. The imaging lens system according to claim 21 , wherein an Abbe number of the first lens element is V 1 , an Abbe number of the second lens element is V 2 , and they satisfy the relation: V 1 −V 2 >20.
26. The imaging lens system according to claim 21 , wherein a focal length of the imaging lens system is f, a focal length of the first lens element is f 1 , and they satisfy the relation: 1.0<f/f 1 <1.8.
27. The imaging lens system according to claim 21 , wherein at least one of the third, fourth and fifth lens elements is meniscus in shape, and wherein, of the third, fourth and fifth lens elements, all lens elements which are meniscus in shape satisfy the relation: 0.5<R o /R i <2.0, wherein R o represents a radius of curvature of an object-side surface of the meniscus lens element and R i represents a radius of curvature of an image-side surface of the meniscus lens element.
28. The imaging lens system according to claim 21 , wherein an on-axis spacing between the first lens element and the second lens element is T 12 , a focal length of the imaging lens system is f, and they satisfy the relation: 0.5<(T 12 /f)×100<15.
29. The imaging lens system according to claim 21 , wherein the imaging lens system further comprises an aperture stop disposed between an imaged object and the first lens element.
30. The imaging lens system according to claim 21 , wherein an Abbe number of the second lens element is V 2 , an Abbe number of the third lens element is V 3 , and they satisfy the relation: |V 2 −V 3 |<15.
31. The imaging lens system according to claim 21 , wherein the third lens element has negative refractive power.
32. The imaging lens system according to claim 21 , wherein a radius of curvature of the object-side surface of the first lens element is R 1 , a focal length of the imaging lens system is f, and they satisfy the relation: 0.2<R 1 /f<0.4.
33. The imaging lens system according to claim 21 , wherein an Abbe number of the first lens element is V 1 , an Abbe number of the second lens element is V 2 , and they satisfy the relation: V 1 −V 2 >30.
34. The imaging lens system according to claim 21 , wherein a radius of curvature of the image-side surface of the second lens element is R 4 , a focal length of the imaging lens system is f, and they satisfy the relation: 0.7<R 4 /f<1.2.