Imaging lens system and electronic apparatus employing the same

1. An imaging lens system comprising:

a first lens that comprises a convex object-side surface and has a positive refractive power;

a second lens that comprises a concave image plane-side surface and has a negative refractive power;

a third lens;

a fourth lens that comprises two spherical surfaces and has a negative refractive power;

a fifth lens that comprises a convex image plane-side surface and has a positive refractive power; and

a sixth lens that has a negative refractive power,

wherein the first through sixth lenses are arranged in order from an object side to an image plane side.

2. The imaging lens system of claim 1 , wherein the fifth lens has at least one spherical surface.

3. The imaging lens system of claim 1 , wherein the imaging lens system satisfies the following conditions,

20< V 1- V 2<45, and

20< V 1- V 4<45,

wherein V1, V2, and V4 are Abbe numbers of the first lens, the second lens, and the fourth lens, respectively.

4. The imaging lens system of claim 1 , wherein the imaging lens system satisfies the following condition,

1.5< f/EPD≦ 2.4,

wherein f is a focal length of the imaging lens system and EPD is an entrance pupil diameter of the imaging lens system.

5. The imaging lens system of claim 1 , wherein the imaging lens system satisfies the following condition,

0.7< f/f 1<1.9,

wherein f is a focal length of the imaging lens system and f1 is a focal length of the first lens.

6. The imaging lens system of claim 1 , wherein the imaging lens system satisfies the following condition,

0.9< TL/f< 2.0,

wherein f is a focal length of the imaging lens system and TL is a distance from a vertex of the object-side surface of the first lens to the image plane.

7. The imaging lens system of claim 1 , wherein the imaging lens system satisfies the following condition,

1.0< f/f 5<3.0,

wherein f is a focal length of the imaging lens system and f5 is a focal length of the fifth lens.

8. The imaging lens system of claim 1 , wherein an image plane-side surface of the sixth lens is an aspherical surface that is concave near an optical axis and has at least one inflection point.

9. The imaging lens system of claim 1 , wherein the imaging lens system satisfies the following conditions,

1.58< N 2<1.68,

1.58< N 4<1.68,

1.51< N 5<1.56, and

1.51< N 6<1.56,

wherein N2, N4, N5, and N6 are refractive indexes of the second lens, the fourth lens, the fifth lens, and the sixth lens, respectively, measured at a d-line wavelength.

10. The imaging lens system of claim 1 , wherein the imaging lens system satisfies the following condition,

Y img/Tan ω>5.5 mm,

wherein Yimg is a maximum image height on the image plane and ω is a half angle of view.

11. The imaging lens system of claim 1 , wherein a stop is disposed on the object side of the first lens or between the first lens and the second lens.

12. The imaging lens system of claim 1 , wherein at least one of the first lens, the second lens, the third lens, the fourth lens, the fifth lens, and the sixth lens moves along an optical axis to perform focusing.

13. The imaging lens system of claim 12 , wherein the at least one of the first lens, the second lens, the third lens, the fourth lens, the fifth lens, and the sixth lens, which is relatively located on the object side, forms a focusing lens group, and when performing focusing, the focusing lens group moves along the optical axis and the remaining lenses are fixed.

14. The imaging lens system of claim 13 , wherein the focusing lens group is formed of the first lens, the second lens, and the third lens.

15. The imaging lens system of claim 13 , wherein the focusing lens group is formed of the first lens, the second lens, the third lens, and the fourth lens.

16. The imaging lens system of claim 1 , wherein the first through sixth lenses are divided into a front group formed of at least one lens that is relatively located on the object side and a rear group formed of the remaining lenses that are relatively located on the image plane side,

in a photographing mode, the front group and the rear group are arranged along a common optical axis, and

in a non-photographing mode, the rear group is arranged by moving in a direction perpendicular to the optical axis, and the front group is arranged by moving toward the image plane side along the optical axis.

17. The imaging lens system of claim 16 , wherein the front group is formed of the first lens, the second lens, and the third lens, and the rear group is formed of the fourth lens, the fifth lens, and the sixth lens.

18. The imaging lens system of claim 16 , wherein the front group is formed of the first lens, the second lens, the third lens, and the fourth lens, and the rear group is formed of the fifth lens and the sixth lens.

19. An electronic apparatus comprising:

the imaging lens system of claim 1 ; and

an image sensor that converts an optical image formed by the imaging lens system into an electrical signal.

20. The electronic apparatus of claim 19 , wherein at least one lens selected from the group consisting of the first lens, the second lens, the third lens, the fourth lens, the fifth lens, and the sixth lens moves along an optical axis to perform focusing.

21. The electronic apparatus of claim 19 , wherein the first through sixth lenses of the imaging lens system are divided into a front group formed of at least one lens that is relatively located on the object side and a rear group formed of the remaining lenses that are relatively located on the image plane side,

in a photographing mode, the front group and the rear group are arranged along a common optical axis, and

in a non-photographing mode, the rear group is arranged by moving in a direction perpendicular to the optical axis, and the front group is arranged by moving toward the image plane side along the optical axis.