Lens assembly

1. A lens assembly, in sequence from an object side to an image side along an optical axis, comprising:

a first lens with negative refractive power, which includes a convex surface facing the object side;

a second lens with positive refractive power;

a third lens with positive refractive power;

a fourth lens with negative refractive power;

a fifth lens with positive refractive power; and

a sixth lens with positive refractive power, which includes a convex surface facing the object side;

wherein the lens assembly satisfies:

0.2<| f 5 /f|< 1.5;

wherein f 5 is a focal length in mm of the fifth lens and f is an effective focal length in mm of the lens assembly;

wherein the lens assembly satisfies at least one of following conditions:

24 mm<f+f 2 <25 mm;

103.7 mm<f+f 3 <199.8 mm;

4.5 mm<f+f 4 <5.7 mm;

14.5 mm<f+f 5 <15 mm;

wherein f 2 is an effective focal length in mm of the second lens, f 3 is an effective focal length in mm of the third lens, and f 4 is an effective focal length in mm of the fourth lens.

2. The lens assembly as claimed in claim 1 , wherein the fifth lens further comprises a convex surface facing the object side and a convex surface facing the image side.

3. The lens assembly as claimed in claim 1 , wherein the fourth lens further comprises a concave surface facing the object side and a concave surface facing the image side.

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

the second lens further comprises a convex surface facing the object side and a convex surface facing the image side; and

the third lens further comprises a convex surface facing the object side and a concave surface facing the image side.

5. The lens assembly as claimed in claim 1 , wherein the first lens further comprises a concave surface facing the image side.

6. The lens assembly as claimed in claim 1 , wherein the sixth lens further comprises a convex surface facing the image side.

7. The lens assembly as claimed in claim 1 , wherein the sixth lens further comprises a plane surface facing the image side.

8. The lens assembly as claimed in claim 1 , wherein further comprising a stop disposed between the third lens and the fourth lens, the fourth lens and the fifth lens are cemented together.

9. The lens assembly as claimed in claim 1 , wherein the lens assembly satisfies at least one of the following conditions:

0.8<|f 1 /f|<2.9;

0.5<|f 2 /f|<2.6;

0.2<|f 4 /f|<1.5;

0.3<|f 6 /f|<2.4;

0.1<|BFL/TTL|<0.6;

wherein f 1 is an effective focal length in mm of the first lens, f 2 is an effective focal length in mm of the second lens, f 4 is an effective focal length in mm of the fourth lens, f 6 is an effective focal length in mm of the sixth lens, f is an effective focal length in mm of the lens assembly, BFL is an interval in mm from an image side surface of the sixth lens to the image plane along the optical axis, and TTL is an interval in mm from an object side surface of the first lens to the image plane along the optical axis.

10. The lens assembly as claimed in claim 1 , wherein the lens assembly satisfies at least one of the following conditions:

−10 mm<f+f 1 <−7 mm;

21.2 mm<f+f 6 <23.6 mm;

wherein f 1 is an effective focal length in mm of the first lens, f 6 is an effective focal length in mm of the sixth lens, and f is an effective focal length in mm of the lens assembly.

11. A lens assembly, in sequence from an object side to an image side along an optical axis, comprising:

a first lens with negative refractive power, which includes a convex surface facing the object side;

a second lens with positive refractive power;

a third lens with positive refractive power;

a fourth lens with negative refractive power;

a fifth lens with positive refractive power; and

a sixth lens with positive refractive power, which includes a convex surface facing the object side;

wherein the lens assembly satisfies:

21.2 mm<f+f 6 <23.6 mm;

wherein f 6 is a focal length in mm of the sixth lens and f is an effective focal length in mm of the lens assembly;

wherein the lens assembly satisfies at least one of following conditions:

24 mm<f+f 2 <25 mm;

103.7 mm<f+f 3 <199.8 mm;

4.5 mm<f+f 4 <5.7 mm;

14.5 mm<f+f 5 <15 mm;

wherein f 2 is an effective focal length in mm of the second lens, f 3 is an effective focal length in mm of the third lens, f 4 is an effective focal length in mm of the fourth lens, and f 5 is an effective focal length in mm of the fifth lens.

12. The lens assembly as claimed in claim 11 , wherein the fifth lens further comprises a convex surface facing the object side and a convex surface facing the image side.

13. The lens assembly as claimed in claim 11 , wherein the fourth lens further comprises a concave surface facing the object side and a concave surface facing the image side.

14. The lens assembly as claimed in claim 11 , wherein:

the second lens further comprises a convex surface facing the object side and a convex surface facing the image side; and

the third lens further comprises a convex surface facing the object side and a concave surface facing the image side.

15. The lens assembly as claimed in claim 11 , wherein the first lens further comprises a concave surface facing the image side.

16. The lens assembly as claimed in claim 11 , wherein the sixth lens further comprises a convex surface facing the image side.

17. The lens assembly as claimed in claim 11 , wherein the sixth lens further comprises a plane surface facing the image side.

18. The lens assembly as claimed in claim 11 , wherein further comprising a stop disposed between the third lens and the fourth lens, the fourth lens and the fifth lens are cemented together.

19. The lens assembly as claimed in claim 11 , wherein the lens assembly satisfies at least one of the following conditions:

0.8<|f 1 /f|<2.9;

0.5<|f 2 /f|<2.6;

0.2<|f 4 /f|<1.5;

0.2<|f 5 /f|<1.5;

0.3<|f 6 /f|<2.4;

0.1<|BFL/TTL|<0.6;

wherein f 1 is an effective focal length in mm of the first lens, f 2 is an effective focal length in mm of the second lens, f 4 is an effective focal length in mm of the fourth lens, f 5 is an effective focal length in mm of the fifth lens, f 6 is an effective focal length in mm of the sixth lens, f is an effective focal length in mm of the lens assembly, BFL is an interval in mm from an image side surface of the sixth lens to the image plane along the optical axis, and TTL is an interval in mm from an object side surface of the first lens to the image plane along the optical axis.

20. The lens assembly as claimed in claim 11 , wherein the lens assembly satisfies following conditions:

−10 mm<f+f 1 <−7 mm;

wherein f 1 is an effective focal length in mm of the first lens and f is an effective focal length in mm of the lens assembly.