Mobile device and optical imaging lens thereof

1. An optical imaging lens, sequentially from an object side to an image side along an optical axis, comprising an aperture stop, first, second, third, fourth and fifth lens elements, each of said first, second, third, fourth and fifth lens elements having an object-side surface facing toward the object side and an image-side surface facing toward the image side, wherein:

said first lens element has positive refracting power, and said image-side surface thereof comprises a convex portion in a vicinity of a periphery of the first lens element;

said second lens element has negative refracting power;

said image-side surface of said third lens element comprises a concave portion in a vicinity of the optical axis;

said fourth lens element has positive refracting power;

said fifth lens element is constructed by plastic material, and said object-side surface thereof comprises a concave portion in a vicinity of the optical axis;

the optical imaging lens as a whole has only the five lens elements having refracting power; and

wherein a central thickness of the third lens element along the optical axis is CT3, a central thickness of the fifth lens element along the optical axis is CT5, and CT3 and CT5 satisfy the equation:

1.9 ≦CT 5 /CT 3≦3.0;

wherein a central thickness of the first lens element along the optical axis is CT1, an air gap between the second lens element and the third lens element along the optical axis is AG23, and CT1 and AG23 satisfy the equation:

CT 1 /AG 23 ≦1.6; and

wherein said third lens element has negative refracting power.

2. The optical imaging lens according to claim 1 , wherein the sum of all four air gaps from the first lens element to the fifth lens element along the optical axis is AAG, an air gap between the third lens element and the fourth lens element along the optical axis is AG34, and AAG and AG34 satisfy the equation:

2.7 ≦AAG/AG 34≦20.0.

3. The optical imaging lens according to claim 2 , wherein the sum of the thickness of all five lens elements along the optical axis is ALT, a central thickness of the fourth lens element along the optical axis is CT4, and ALT, CT4 and CT5 satisfy the equation:

ALT/ ( CT 4 +CT 5)≦2.

4. The optical imaging lens according to claim 1 , wherein a central thickness of the fourth lens element along the optical axis is CT4, and CT1 and CT4satisfy the equation:

1.4 ≦CT 4 /CT 1≦3.0.

5. The optical imaging lens according to claim 4 , wherein a central thickness of the second lens element along the optical axis is CT2, and CT2 and CT5 satisfy the equation:

1.2≦ CT 5 /CT 2≦3.0.

6. The optical imaging lens according to claim 5 , wherein an air gap between the third lens element and the fourth lens element along the optical axis is AG34, and wherein AG23 and AG34 further satisfy the equation:

1.5 ≦AG 23 /AG 34≦10.0.

7. The optical imaging lens according to claim 5 , wherein the sum of the thickness of all five lens elements along the optical axis is ALT, wherein the sum of all four air gaps from the first lens element to the fifth lens element along the optical axis is AAG, and wherein ALT and AAG satisfy the equation:

2.5 ≦ALT/AAG ≦4.0.

8. The optical imaging lens according to claim 1 , wherein a central thickness of the second lens element along the optical axis is CT2, and CT2 and CT5satisfy the equation:

1.9 ≦CT 5 /CT 2≦3.0.

9. The optical imaging lens according to claim 1 , wherein the sum of the thickness of all five lens elements along the optical axis is ALT, a central thickness of the fourth lens element along the optical axis is CT4, and ALT, CT4 and CT5 satisfy the equation:

ALT /( CT 4 +CT 5)≦2.

10. The optical imaging lens according to claim 1 , wherein said object-side surface of said third lens element further comprises a concave portion in a vicinity of the optical axis.

11. The optical imaging lens according to claim 1 , wherein said object-side surface of said fifth lens element further comprises a convex portion in a vicinity of a periphery of the fifth lens element.

12. A mobile device, comprising:

a housing; and

a photography module positioned in the housing and comprising:

the optical imaging lens as claimed in claims 1 ;

a lens barrel for positioning the optical imaging lens;

a module housing unit for positioning the lens barrel;

a substrate for positioning the module housing unit; and

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

13. The mobile device according to claim 12 , wherein the module housing unit comprises a first seat element for positioning the lens barrel and moving along with the optical axis of the optical imaging lens.