Lens assembly

1. A lens assembly comprising:

a first lens which is with positive refractive power;

a second lens which is with negative refractive power;

a third lens which is with refractive power; and

a fourth lens which is with negative refractive power;

wherein the first lens, the second lens, the third lens, and the fourth lens are arranged in order from an object side to an image side along an optical axis;

wherein the lens assembly satisfies:

0.2< D 4 /TTL< 0.6,

wherein D 4 is an effective diameter of the fourth lens and TTL is an interval from an object side surface of the first lens to an image plane along the optical axis.

2. The lens assembly as claimed in claim 1 , further comprising a fifth lens disposed between the third lens and the fourth lens, wherein the fifth lens is with positive refractive power.

3. The lens assembly as claimed in claim 1 , wherein the lens assembly satisfies:

f 234 <0,

wherein f 234 is an effective focal length of a combination of the second lens, the third lens, and the fourth lens.

4. The lens assembly as claimed in claim 1 , wherein the lens assembly satisfies:

TC 34 <TTL/ 5,

wherein TC 34 is an air interval from an image side surface of the third lens to an object side surface of the fourth lens along the optical axis and TTL is an interval from an object side surface of the first lens to an image plane along the optical axis.

5. The lens assembly as claimed in claim 1 , wherein the lens assembly satisfies:

R 41 /R 11 <0,

wherein R 11 is a radius of curvature of an object side surface of the first lens and R 41 is a radius of curvature of an object side surface of the fourth lens.

6. The lens assembly as claimed in claim 1 , wherein the lens assembly satisfies:

( f 1 +f 3 )/ f 2 <0,

wherein f 1 is an effective focal length of the first lens, f 2 is an effective focal length of the second lens, and f 3 is an effective focal length of the third lens.

7. The lens assembly as claimed in claim 1 , wherein the lens assembly satisfies:

TC 23 <TTL/ 5,

wherein TC 23 is an air interval from an image side surface of the second lens to an object side surface of the third lens along the optical axis and TTL is an interval from an object side surface of the first lens to an image plane along the optical axis.

8. The lens assembly as claimed in claim 1 , further comprising a stop disposed between the object side and the second lens, wherein the lens assembly satisfies:

0.6< SL/TTL< 1.1,

wherein SL is an interval from the stop to an image plane along the optical axis and TTL is an interval from an object side surface of the first lens to the image plane along the optical axis.

9. The lens assembly as claimed in claim 1 , further comprising a non-circular stop, wherein the non-circular stop comprises an outer circumferential portion and an inner circumferential portion, at least one of the outer circumferential portion and the inner circumferential portion is non-circular, the inner circumferential portion surrounds the optical axis to form a hole, and the non-circular stop satisfies:

1< Dx/Dy< 28,

wherein Dx is a maximum dimension of the hole through which the optical axis passes and Dy is a minimum dimension of the hole through which the optical axis passes.

10. The lens assembly as claimed in claim 2 , wherein the lens assembly satisfies:

f 2354 <0,

wherein f 2354 is an effective focal length of a combination of the second lens, the third lens, the fifth lens, and the fourth lens.

11. The lens assembly as claimed in claim 1 , wherein the lens assembly satisfies:

0.07<( TC 12 +TC 23 )/ TTL< 0.25,

wherein TC 12 is an air interval from an image side surface of the first lens to an object side surface of the second lens along the optical axis, TC 23 is an air interval from an image side surface of the second lens to an object side surface of the third lens along the optical axis, and TTL is an interval from an object side surface of the first lens to an image plane along the optical axis.

12. A lens assembly comprising:

a first lens which is with positive refractive power;

a second lens which is with negative refractive power;

a third lens which is with refractive power; and

a fourth lens which is with negative refractive power;

wherein the first lens, the second lens, the third lens, and the fourth lens are arranged in order from an object side to an image side along an optical axis;

wherein the lens assembly satisfies:

0.07<( TC 12 +TC 23 )/ TTL< 0.25,

wherein TC 12 is an air interval from an image side surface of the first lens to an object side surface of the second lens along the optical axis, TC 23 is an air interval from an image side surface of the second lens to an object side surface of the third lens along the optical axis, and TTL is an interval from an object side surface of the first lens to an image plane along the optical axis.

13. The lens assembly as claimed in claim 12 , further comprising a fifth lens disposed between the third lens and the fourth lens, wherein the fifth lens is with positive refractive power.

14. The lens assembly as claimed in claim 12 , wherein the lens assembly satisfies:

f 234 <0,

wherein f 234 is an effective focal length of a combination of the second lens, the third lens, and the fourth lens.

15. The lens assembly as claimed in claim 12 , wherein the lens assembly satisfies:

TC 34 <TTL/ 5,

wherein TC 34 is an air interval from an image side surface of the third lens to an object side surface of the fourth lens along the optical axis and TTL is an interval from an object side surface of the first lens to an image plane along the optical axis.

16. The lens assembly as claimed in claim 12 , wherein the lens assembly satisfies:

R 41 /R 11 <0,

wherein R 11 is a radius of curvature of an object side surface of the first lens and R 41 is a radius of curvature of an object side surface of the fourth lens.

17. The lens assembly as claimed in claim 12 , wherein the lens assembly satisfies:

( f 1 +f 3 )/ f 2 <0,

wherein f 1 is an effective focal length of the first lens, f 2 is an effective focal length of the second lens, and f 3 is an effective focal length of the third lens.

18. The lens assembly as claimed in claim 12 , further comprising a stop disposed between the object side and the second lens, wherein the lens assembly satisfies:

0.6< SL/TTL< 1.1,

wherein SL is an interval from the stop to an image plane along the optical axis and TTL is an interval from an object side surface of the first lens to the image plane along the optical axis.

19. A lens assembly comprising:

a first lens which is with positive refractive power;

a second lens which is with negative refractive power;

a third lens which is with refractive power; and

a fourth lens which is with negative refractive power;

wherein the first lens, the second lens, the third lens, and the fourth lens are arranged in order from an object side to an image side along an optical axis;

wherein the lens assembly satisfies:

1< f/TTL≤ 1.5,

wherein f is an effective focal length of the lens assembly and TTL is an interval from an object side surface of the first lens to an image plane along the optical axis; wherein the lens assembly further comprises a non-circular stop, wherein the non-circular stop comprises an outer circumferential portion and an inner circumferential portion, at least one of the outer circumferential portion and the inner circumferential portion is non-circular, the inner circumferential portion surrounds the optical axis to form a hole, and the non-circular stop satisfies:

1< Dx/Dy< 28,

wherein Dx is a maximum dimension of the hole through which the optical axis passes and Dy is a minimum dimension of the hole through which the optical axis passes.

20. The lens assembly as claimed in claim 12 , wherein the lens assembly satisfies:

1< f/TTL< 1.5,

wherein f is an effective focal length of the lens assembly and TTL is an interval from an object side surface of the first lens to an image plane along the optical axis.