Mobile device and optical imaging lens thereof

1. An optical imaging lens, comprising:

a first lens element, a second lens element, a third lens element, a fourth lens element, a fifth lens element and a sixth lens element;

wherein each of the lens elements are arranged sequentially from an object side to an image side along an optical axis;

wherein each of the lens elements comprises an object-side surface facing toward the object side and an image-side surface facing toward the image side;

wherein each of the object-side surfaces and the image-side surfaces has a vicinity of the optical axis and a vicinity of a periphery of each lens element;

wherein the first lens element comprises a positive refractive power;

wherein the object-side surface of the second lens element comprises a convex portion in the vicinity of the optical axis, and the second lens element comprises a positive refractive power;

wherein the object-side surface of the third lens element comprises a concave portion in the vicinity of the optical axis, the image-side surface of the third lens element comprises a concave portion in the vicinity of the optical axis, and the third lens element comprises a negative refractive power;

wherein the image-side surface of the fourth lens element comprises a convex portion in the vicinity of the optical axis, and the fourth lens element comprises a positive refractive power; and

wherein the image-side surface of the sixth lens element comprises a concave portion in the vicinity of the optical axis and a convex portion in the vicinity of the periphery of said sixth lens element;

the optical imaging lens as a whole comprises only the six lens elements each comprising refractive power.

2. The optical imaging lens according to claim 1 , wherein a central thickness of said second lens element along the optical axis is represented by T 2 , a central thickness of said fifth lens element along the optical axis is represented by T 5 , and T 2 and T 5 satisfy the equation:

T2>T5.

3. A mobile device, comprising:

a housing; and

a photography module positioned in the housing and comprising:

a lens barrel;

an optical imaging lens as claimed in claim 1 and positioned in the lens barrel;

a module housing unit for positioning the lens barrel; and

an image sensor positioned at the image side of the optical imaging lens.

4. The optical imaging lens according to claim 1 , wherein the image-side surface of the second lens element comprises a convex portion in the vicinity of the optical axis, and the image-side surface of the third lens element comprises a concave portion in the vicinity of the periphery of said third lens element.

5. The optical imaging lens according to claim 4 , wherein the sum of all five air gaps from the first lens element to the sixth lens element along the optical axis is represented by Gaa, an air gap between the fourth lens element and the fifth lens element along the optical axis is represented by G 45 , and Gaa and G 45 satisfy the equation:

( Gaa/G 45) ≦21.0.

6. The optical imaging lens according to claim 5 , wherein the sum of the thickness of all six lens elements along the optical axis is represented by ALT, an air gap between the second lens element and the third lens element along the optical axis is represented by G 23 , and ALT and G 23 satisfy:

ALT/G 23≦55.0.

7. The optical imaging lens according to claim 6 , wherein, a central thickness of said fifth lens element along the optical axis is represented by T 5 , and Gaa and T 5 satisfy the equation:

Gaa/T 5≦3.85.

8. The optical imaging lens according to claim 7 , wherein a central thickness of said third lens element along the optical axis is represented by T 3 , and Gaa and T 3 satisfy the equation:

Gaa/T 3≦6.5.

9. The optical imaging lens according to claim 4 , wherein the sum of the thickness of all six lens elements along the optical axis is represented by ALT, a central thickness of said sixth lens element along the optical axis is represented by T 6 , and ALT and T 6 satisfy the equation:

ALT/T 6≦8.5.

10. The optical imaging lens according to claim 9 , the sum of all five air gaps from the first lens element to the sixth lens element along the optical axis is represented by Gaa, an air gap between the fourth lens element and the fifth lens element along the optical axis is represented by G 45 , and Gaa and G 45 satisfy the equation:

Gaa/G 45≦21.0.

11. The optical imaging lens according to claim 10 , wherein a central thickness of said third lens element along the optical axis is represented by T 3 , and Gaa and T 3 satisfy the equation:

Gaa/T 3≦6.5.

12. The optical imaging lens according to claim 11 , wherein a distance from said object-side surface of said first lens element to the image side of the optical imaging lens along the optical axis is the system length of the optical imaging lens is represented by TTL, a central thickness of said first lens element along the optical axis is represented by T 1 , and TTL and T 1 satisfy the equation:

TTL/T 1≦11.5.

13. The optical imaging lens according to claim 4 , wherein the sum of the thickness of all six lens elements along the optical axis is represented by ALT, an air gap between the fifth lens element and the sixth lens element along the optical axis is represented by G 56 , and ALT and G 56 satisfy

ALT/G 56≦30.0.

14. The optical imaging lens according to claim 13 , wherein the sum of all five air gaps from the first lens element to the sixth lens element along the optical axis is represented by Gaa, a central thickness of said second lens element along the optical axis is represented by T 2 , and Gaa and T 2 satisfy the equation:

Gaa/T 2≦5.5.

15. The optical imaging lens according to claim 14 , wherein an air gap between the second lens element and the third lens element along the optical axis is represented by G 23 , and ALT and G 23 satisfy the equation:

ALT/G 23≦55.0.

16. The optical imaging lens according to claim 15 , wherein a distance from said object-side surface of said first lens element to the image side of the optical imaging lens along the optical axis is the system length of the optical imaging lens is represented by TTL, a central thickness of said first lens element along the optical axis is represented by T 1 , and TTL and T 1 satisfy the equation:

TTL/T 1≦11.5.

17. The optical imaging lens according to claim 4 , wherein the sum of all five air gaps from the first lens element to the sixth lens element along the optical axis is represented by Gaa, a central thickness of said first lens element along the optical axis is represented by T 1 , and Gaa and T 1 satisfy the equation:

Gaa/T 1≦3.8.

18. The optical imaging lens according to claim 17 , an air gap between the second lens element and the third lens element along the optical axis is represented by G 23 , and ALT and G 23 satisfy the equation:

ALT/G 23≦55.0.

19. The optical imaging lens according to claim 18 , wherein an air gap between the fourth lens element and the fifth lens element along the optical axis is represented by G 45 , and Gaa and G 45 satisfy the equation:

Gaa/G 45≦21.0.

20. The optical imaging lens according to claim 19 , wherein a central thickness of said sixth lens element along the optical axis is represented by T 6 , and ALT and T 6 satisfy the equation:

ALT/T 6≦8.5.