Lens assembly

1. A lens assembly, comprising:

a combined lens, wherein the combined lens is formed of two lenses and comprises corresponding adjacent surfaces whose radii of curvature are substantially identical;

a spherical lens and an aspheric lens, wherein the aspheric lens is closer to the image plane of the lens assembly than the combined lens; at most one lens is disposed between the aspheric lens and the image plane of the lens assembly;

more than 3 but less than 8 lenses with a refractive power, wherein D1 is the distance between two edge turning points on a lens surface farthest away from the image plane of the lens assembly; DL is the distance between two edge turning points on a lens surface closest to the image plane of the lens assembly; LT is the length on an optical axis of the lens assembly from the lens surface farthest from the image plane of the lens assembly to the lens surface closest to the image plane of the lens assembly; and

wherein the lens assembly satisfies the following conditions:

(1) 6 mm<DL<20 mm, 1.5<LT/DL<2.4 and D1/DL>0.6 or (2) 6 mm<DL<20 mm, 1.25<LT/DL<1.7 and D1/DL>0.4.

2. The lens assembly according to claim 1 , wherein the aperture value (F/#) of the lens assembly is greater than or equivalent to 2.6.

3. The lens assembly according to claim 1 , wherein the lens assembly comprises at least two lenses whose Abbe numbers are greater than 58.

4. The lens assembly according to claim 1 , wherein the total length of the lens assembly (LT) is less than 25 mm.

5. The lens assembly according to claim 1 , wherein the lens assembly satisfies one of the following conditions: (1) the lenses arranged from the image magnification side to the image reduction side sequentially are a meniscus lens, a meniscus lens, a meniscus lens, a bi-concave lens, a bi-convex lens and an aspheric lens; (2) the lenses arranged from the image magnification side to the image reduction side sequentially are a meniscus lens, a meniscus lens, a bi-concave lens, a bi-convex lens and an aspheric lens; (3) the lenses arranged from the image magnification side to the image reduction side sequentially area plano-convex lens, a bi-convex lens, a bi-concave lens, a bi-convex lens and an aspheric lens; (4) the lenses arranged from the image magnification side to the image reduction side sequentially are a meniscus lens, a bi-concave lens, a meniscus lens, a bi-convex lens and an aspheric lens; (5) the lenses arranged from the image magnification side to the image reduction side sequentially are a bi-concave lens, a bi-convex lens, a plano-convex lens, a bi-concave lens, a bi-convex lens, a bi-convex lens and a meniscus lens.

6. The lens assembly according to claim 1 , wherein the lens assembly satisfies one of the following conditions: (1) the refractive powers of the lenses arranged from the image magnification side to the image reduction side sequentially are positive, negative, positive, negative, positive, positive; (2) the refractive powers of the lenses arranged from the image magnification side to the image reduction side sequentially are positive, negative, negative, positive, positive; (3) the refractive powers of the lenses arranged from the image magnification side to the image reduction side sequentially are positive, positive, negative, positive, negative; (4) the refractive powers of the lenses arranged from the image magnification side to the image reduction side sequentially are positive, negative, positive, positive, negative; (5) the refractive powers of the lenses arranged from the image magnification side to the image reduction side sequentially are negative, positive, positive, negative, positive, positive, negative.

7. The lens assembly according to claim 1 , wherein DFOV is the diagonal field of view of the lens assembly; the lens assembly satisfies the condition of 40°<DFOV<60°.

8. The lens assembly according to claim 7 , wherein the lens assembly satisfies one of the following conditions: (1) the lens assembly further comprises an aperture, and the aspheric lens is disposed between the image reduction side and the aperture; (2) the lens further comprises an aperture, the combined lens is disposed between the image reduction side and the aperture, and the difference in the radius of curvature between two adjacent surfaces of the combined lens is less than 0.005 mm; (3) all lenses are formed of glass.

9. The lens assembly according to claim 7 , wherein the aperture value (F/#) of the lens assembly is greater than or equivalent to 2.6.

10. The lens assembly according to claim 7 , wherein the lens assembly comprises at least two lenses whose Abbe numbers are greater than 58.

11. The lens assembly according to claim 7 , wherein the total length of the lens assembly (LT) is less than 25 mm.

12. The lens assembly according to claim 7 , wherein the lens assembly satisfies one of the following conditions: (1) the lenses arranged from the image magnification side to the image reduction side sequentially are a meniscus lens, a meniscus lens, a meniscus lens, a bi-concave lens, a bi-convex lens and an aspheric lens; (2) the lenses arranged from the image magnification side to the image reduction side sequentially are a meniscus lens, a meniscus lens, a bi-concave lens, a bi-convex lens and an aspheric lens; (3) the lenses arranged from the image magnification side to the image reduction side sequentially area plano-convex lens, a bi-convex lens, a bi-concave lens, a bi-convex lens and an aspheric lens; (4) the lenses arranged from the image magnification side to the image reduction side sequentially are a meniscus lens, a bi-concave lens, a meniscus lens, a bi-convex lens and an aspheric lens; (5) the lenses arranged from the image magnification side to the image reduction side sequentially are a bi-concave lens, a bi-convex lens, a plano-convex lens, a bi-concave lens, a bi-convex lens, a bi-convex lens and a meniscus lens.

13. The lens assembly according to claim 7 , wherein the lens assembly satisfies one of the following conditions: (1) the refractive powers of the lenses arranged from the image magnification side to the image reduction side sequentially are positive, negative, positive, negative, positive, positive; (2) the refractive powers of the lenses arranged from the image magnification side to the image reduction side sequentially are positive, negative, negative, positive, positive; (3) the refractive powers of the lenses arranged from the image magnification side to the image reduction side sequentially are positive, positive, negative, positive, negative; (4) the refractive powers of the lenses arranged from the image magnification side to the image reduction side sequentially are positive, negative, positive, positive, negative; (5) the refractive powers of the lenses arranged from the image magnification side to the image reduction side sequentially are negative, positive, positive, negative, positive, positive, negative.

14. The lens assembly according to claim 1 , wherein an Abbe number of at least one lens of the combined lens and an Abbe number of the aspheric lens both are greater than 60; the surface of the aspheric lens facing the image plane of the lens assembly on the lens optical path is protruded towards the image plane of the lens assembly.

15. The lens assembly according to claim 14 , wherein the lens assembly satisfies one of the following conditions: (1) the lens assembly further comprises an aperture, and the aspheric lens is disposed between the image reduction side and the aperture; (2) the lens assembly further comprises an aperture, the combined lens is disposed between the image reduction side and the aperture, and the difference in the radius of curvature between two adjacent surfaces of the combined lens is less than 0.005 mm; (3) all lenses are formed of glass.

16. The lens assembly according to claim 14 , wherein the aperture value (F/#) of the lens assembly is greater than or equivalent to 2.6.

17. The lens assembly according to claim 14 , wherein the lens assembly comprises at least two lenses whose Abbe numbers are greater than 58.

18. The lens assembly according to claim 14 , wherein the total length of the lens assembly (LT) is less than 25 mm.

19. The lens assembly according to claim 14 , wherein the lens assembly satisfies one of the following conditions: (1) the lenses arranged from the image magnification side to the image reduction side sequentially are a meniscus lens, a meniscus lens, a meniscus lens, a bi-concave lens, a bi-convex lens and an aspheric lens; (2) the lenses arranged from the image magnification side to the image reduction side sequentially are a meniscus lens, a meniscus lens, a bi-concave lens, a bi-convex lens and an aspheric lens; (3) the lenses arranged from the image magnification side to the image reduction side sequentially area plano-convex lens, a bi-convex lens, a bi-concave lens, a bi-convex lens and an aspheric lens; (4) the lenses arranged from the image magnification side to the image reduction side sequentially are a meniscus lens, a bi-concave lens, a meniscus lens, a bi-convex lens and an aspheric lens; (5) the lenses arranged from the image magnification side to the image reduction side sequentially are a bi-concave lens, a bi-convex lens, a plano-convex lens, a bi-concave lens, a bi-convex lens, a bi-convex lens and a meniscus lens.

20. The lens assembly according to claim 14 , wherein the lens assembly satisfies one of the following conditions: (1) the refractive powers of the lenses arranged from the image magnification side to the image reduction side sequentially are positive, negative, positive, negative, positive, positive; (2) the refractive powers of the lenses arranged from the image magnification side to the image reduction side sequentially are positive, negative, negative, positive, positive; (3) the refractive powers of the lenses arranged from the image magnification side to the image reduction side sequentially are positive, positive, negative, positive, negative; (4) the refractive powers of the lenses arranged from the image magnification side to the image reduction side sequentially are positive, negative, positive, positive, negative; (5) the refractive powers of the lenses arranged from the image magnification side to the image reduction side sequentially are negative, positive, positive, negative, positive, positive, negative.