Optical imaging lens

1. An optical imaging lens, comprising:

a plurality of lens elements arranged in order from an object side to an image side along an optical axis, the lens elements comprising a first lens element, a second lens element, a third lens element, and a fourth lens element, arranged in order from the object side to the image side along the optical axis, the first lens element is arranged to be a lens element having refracting power in a first order from the object side to the image side, the fourth lens element is arranged to be a lens element having refracting power in a first order from the image side to the object side, the third lens element is arranged to be a lens element having refracting power in a second order from the image side to the object side, the second lens element is arranged to be a lens element having refracting power in a third order from the image side to the object side, each of the first to the fourth lens elements respectively having an object-side surface facing the object side and allowing image rays to pass through, and an image-side surface facing the image side and allowing the image rays to pass through;

the first lens element having a positive refracting power and the object-side surface of the first lens element having a convex portion in a vicinity of the optical axis;

at least one of the object-side surface and the image-side surface of the third lens element being an aspheric surface;

the object-side surface and the image-side surface of the fourth lens element being both aspheric surfaces; and

the optical imaging lens having only one variable gap, and the variable gap being a gap between adjacent two lens elements,

wherein the optical imaging lens satisfies:

0.7≤EFL/( fG×F /#),

where EFL is an effective focal length of the optical imaging lens, fG is a focal length of a lens group formed from all of lens elements at an object side of the variable gap, and F/# is a f-number of the optical imaging lens.

2. The optical imaging lens of claim 1 , wherein the optical imaging lens further satisfies 1.5≤EFL/fG.

3. The optical imaging lens of claim 1 , wherein the optical imaging lens further satisfies HFOV≤25°, where HFOV is a half field of view of the optical imaging lens.

4. The optical imaging lens of claim 1 , wherein the optical imaging lens further satisfies AAG>ALT, wherein AAG is a summation of a distance on the optical axis from the first lens element to the second lens element, a distance on the optical axis from the second lens element to the third lens element, and a distance on the optical axis from the third lens element to the fourth lens element, and ALT is a summation of thicknesses on the optical axis of the first lens element, the second lens element, the third lens element, and the fourth lens element.

5. The optical imaging lens of claim 1 , wherein the optical imaging lens further satisfies 1≤EFL/TTL, where TTL is a distance on the optical axis from the objet-side surface of the first lens element to an image plane of the optical imaging lens.

6. The optical imaging lens of claim 1 , wherein the optical imaging lens further satisfies 2.4≤EFL/ALT, where ALT is a summation of thicknesses on the optical axis of the first lens element, the second lens element, the third lens element, and the fourth lens element.

7. An optical imaging lens, comprising:

a plurality of lens elements, arranged in order from an object side to an image side along an optical axis, the lens elements comprising a first lens element, a second lens element, a third lens element, and a fourth lens element, arranged in order from the object side to the image side along the optical axis, the first lens element is arranged to be a lens element having refracting power in a first order from the object side to the image side, the fourth lens element is arranged to be a lens element having refracting power in a first order from the image side to the object side, the third lens element is arranged to be a lens element having refracting power in a second order from the image side to the object side, the second lens element is arranged to be a lens element having refracting power in a third order from the image side to the object side, each of the first to the fourth lens elements having an object-side surface facing the object side and allowing image rays to pass through, and an image-side surface facing the image side and allowing the image rays to pass through;

the first lens element having a positive refracting power and the object-side surface of the first lens element having a convex portion in a vicinity of the optical axis;

at least one of the object-side surface and the image-side surface of the third lens element being an aspheric surface;

the object-side surface and the image-side surface of the fourth lens element being both aspheric surfaces; and

the optical imaging lens having only one variable gap,

wherein the optical imaging lens satisfies:

0.5≤EFL/( fG×F /#); and

( TTL×F /#)/EFL≤2.4,

where EFL is an effective focal length of the optical imaging lens, fG is a focal length of a lens group formed from all of lens elements at an object side of the variable gap, F/# is a f-number of the optical imaging lens, and TTL is distance on the optical axis between the object-side surface of the first lens element and an image plane of the optical image lens.

8. The optical imaging lens of claim 7 , wherein the optical imaging lens further satisfies (BFL×F/#)/T 1 ≤4, where BFL is a distance on the optical axis from the image-side surface of the fourth lens element to the image plane of the optical imaging lens, and T 1 is a thickness of the first lens element on the optical axis.

9. The optical imaging lens of claim 7 , wherein the optical imaging lens further satisfies (BFL×F/#)/AAG ≤1.3, where BFL is a distance on the optical axis from the image-side surface of the fourth lens element to the image plane of the optical imaging lens, and AAG is a summation of a distance on the optical axis from the first lens element to the second lens element, a distance on the optical axis from the second lens element to the third lens element, and a distance on the optical axis from the third lens element to the fourth lens element.

10. The optical imaging lens of claim 7 , wherein the optical imaging lens further satisfies (BFL×F/#)/|G 23 −G 34 |≤6, where BFL is a distance on the optical axis from the image-side surface of the fourth lens element to the image plane of the optical imaging lens, G 23 is a distance on the optical axis from the second lens element to the third lens element, and G 34 is a distance on the optical axis from the third lens element to the fourth lens element.

11. The optical imaging lens of claim 7 , wherein the optical imaging lens further satisfies (T 2 +T 3 +T 4 )/T 1 ≤1.8, where T 2 is a thickness of the second lens element on the optical axis, T 3 is a thickness of the third lens element on the optical axis, T 4 is a thickness of the fourth lens element on the optical axis, and T 1 is a thickness of the first lens element on the optical axis.

12. The optical imaging lens of claim 7 , wherein the optical imaging lens further satisfies ((T 2 +T 3 +T 4 )×F/#)/AAG≤1.8, where T 2 is a thickness of the second lens element on the optical axis, T 3 is a thickness of the third lens element on the optical axis, T 4 is a thickness of the fourth lens element on the optical axis, and AAG is a summation of a distance on the optical axis from the first lens element to the second lens element, a distance on the optical axis from the second lens element to the third lens element, and a distance on the optical axis from the third lens element to the fourth lens element.

13. The optical imaging lens of claim 7 , wherein the optical imaging lens further satisfies ((T 2 +T 3 +T 4 )×F/#)/|G 23 −G 34 |≤8, where T 2 is a thickness of the second lens element on the optical axis, T 3 is a thickness of the third lens element on the optical axis, T 4 is a thickness of the fourth lens element on the optical axis, G 23 is a distance on the optical axis from the second lens element to the third lens element, and G 34 is a distance on the optical axis from the third lens element to the fourth lens element.

14. The optical imaging lens of claim 7 , wherein the optical imaging lens further satisfies ((T 2 +T 3 +T 4 )×F/#)/(T 2 +G 23 +T 3 +G 34 +T 4 ) ≤1.3, where T 2 is a thickness of the second lens element on the optical axis, T 3 is a thickness of the third lens element on the optical axis, T 4 is a thickness of the fourth lens element on the optical axis, G 23 is a distance on the optical axis from the second lens element to the third lens element, and G 34 is a distance on the optical axis from the third lens element to the fourth lens element.

15. The optical imaging lens of claim 7 , wherein the optical imaging lens further satisfies ((T 2 +T 3 )×F/#)/T 1 ≤2.8, where T 2 is a thickness of the second lens element on the optical axis, T 3 is a thickness of the third lens element on the optical axis, and T 1 is a thickness of the first lens element on the optical axis.

16. The optical imaging lens of claim 7 , wherein the optical imaging lens further satisfies ((T 2 +T 3 )×F/#)/AAG≤1, where T 2 is a thickness of the second lens element on the optical axis, T 3 is a thickness of the third lens element on the optical axis, and AAG is a summation of a distance on the optical axis from the first lens element to the second lens element, a distance on the optical axis from the second lens element to the third lens element, and a distance on the optical axis from the third lens element to the fourth lens element.

17. The optical imaging lens of claim 7 , wherein the optical imaging lens further satisfies ((T 2 +T 3 )×F/#)/|G 23 −G 34 |≤4.7, where T 2 is a thickness of the second lens element on the optical axis, T 3 is a thickness of the third lens element on the optical axis, G 23 is a distance on the optical axis from the second lens element to the third lens element, and G 34 is a distance on the optical axis from the third lens element to the fourth lens element.

18. The optical imaging lens of claim 7 , wherein the optical imaging lens further satisfies ((T 2 +T 4 )×F/#)/T 1 ≤3.8, where T 2 is a thickness of the second lens element on the optical axis, T 4 is a thickness of the fourth lens element on the optical axis, and T 1 is a thickness of the first lens element on the optical axis.

19. The optical imaging lens of claim 7 , wherein the optical imaging lens further satisfies ((T 2 +T 4 )×F/#)/AAG≤1.3, where T 2 is a thickness of the second lens element on the optical axis, T 4 is a thickness of the fourth lens element on the optical axis, and AAG is a summation of a distance on the optical axis from the first lens element to the second lens element, a distance on the optical axis from the second lens element to the third lens element, and a distance on the optical axis from the third lens element to the fourth lens element.

20. The optical imaging lens of claim 7 , wherein the optical imaging lens further satisfies ((T 2 +T 4 )×F/#)/|G 23 −G 34 |≤4.7, where T 2 is a thickness of the second lens element on the optical axis, T 4 is a thickness of the fourth lens element on the optical axis, G 23 is a distance on the optical axis from the second lens element to the third lens element, and G 34 is a distance on the optical axis from the third lens element to the fourth lens element.