Optical lens

1. An optical lens, comprising:

two lens groups, a total number of lenses with refractive power of the two lens groups being larger than three, a total number of aspheric lenses of the two lens groups is no more than two, and at least one aspheric lens of the optical lens having negative refractive power; and

an aperture stop disposed between the two lens groups, the aspheric lens with negative refractive power being located on one side of the aperture stop and further away from the aperture stop than any other lens on the same side of the aperture stop, and the optical lens satisfying the following condition:

0.05>[ y (θ)−(EFL*sin θ)]/(EFL*sin θ)>−0.3

where θ denotes a half field of view, y(θ) denotes an image height of an image plane for visible light with respect to the half field of view θ, and EFL denotes an effective focal length for visible light of the optical lens.

2. The optical lens as claimed in claim 1 , wherein the two lens groups comprises two lenses with positive refractive power located closer to the aspheric lens with negative refractive power than any other lens of the optical lens.

3. The optical lens as claimed in claim 2 , wherein one of the two lenses with positive refractive power that is disposed further away from the aspheric lens with negative refractive power has a refractive index variation as a function of temperature (dn/dt) of smaller than −6×10 −6 ° C. −1 .

4. The optical lens as claimed in claim 2 , wherein one of the two lenses with positive refractive power that is disposed further away from the aspheric lens with negative refractive power satisfies the condition:

EFL/ f 3>0.5

where f3 denotes an effective focal length for visible light of the one of the two lenses, and EFL denotes an effective focal length for visible light of the optical lens.

5. The optical lens as claimed in claim 2 , wherein one of the two lenses with positive refractive power that is located closer to the aspheric lens with negative refractive power is a spherical lens.

6. The optical lens as claimed in claim 1 , wherein a total track length of the optical lens is equal to or greater than 19.66 mm.

7. The optical lens as claimed in claim 1 , wherein a distance between any two lenses in the optical lens remains fixed on picking-up images at various object distances.

8. The optical lens as claimed in claim 1 , wherein the lenses of the two lens groups are separate from each other.

9. The optical lens as claimed in claim 1 , wherein a ratio of a maximum image circle diameter to a total track length of the optical lens is no more than 0.1607.

10. The optical lens as claimed in claim 1 , wherein the aspheric lens with negative refractive power has a surface facing away from the aperture stop and a clear aperture, a first point of the surface is located in a position corresponding to 50% of the clear aperture, a second point of the surface is located in a position corresponding to 95% of the clear aperture, a slope of the surface at the first point having an absolute value of larger than 0.25, and a slope of the surface at the second point having an absolute value of smaller than 0.1.

11. The optical lens as claimed in claim 10 , wherein one of the two lenses with positive refractive power that is disposed further away from the aspheric lens with negative refractive power has a refractive index variation as a function of temperature (dn/dt) of smaller than −6×10 −6 ° C. −1 .

12. The optical lens as claimed in claim 10 , wherein one of the two lenses with positive refractive power that is disposed further away from the aspheric lens with negative refractive power satisfies the condition:

EFL/ f 3>0.5

where f3 denotes an effective focal length for visible light of the one of the two lenses, and EFL denotes an effective focal length for visible light of the optical lens.

13. The optical lens as claimed in claim 10 , wherein one of the two lenses with positive refractive power that is located closer to the aspheric lens with negative refractive power is a spherical lens.

14. The optical lens as claimed in claim 10 , wherein a total track length of the optical lens is equal to or greater than 19.66 mm.

15. The optical lens as claimed in claim 10 , wherein a distance between any two lenses in the optical lens remains fixed on picking-up images at various object distances.

16. The optical lens as claimed in claim 10 , wherein the lenses of the two lens groups are separate from each other.

17. The optical lens as claimed in claim 10 , wherein the aspheric lens with negative refractive power is fabricated by glass molding.

18. The optical lens as claimed in claim 1 , wherein the two lens groups comprising a first lens, a second lens, a third lens, a fourth lens and a fifth lens arranged in order from a magnified side to a minified side, the first lens being aspherical, and the third lens having a refractive index variation as a function of temperature (dn/dt) of smaller than −6×10 −6 ° C. −1 .

19. The optical lens as claimed in claim 18 , wherein the first lens to the fifth lens have respective refractive powers of (i) negative, positive, positive, negative and positive, or (ii) negative, positive, positive, positive and negative.

20. The optical lens as claimed in claim 18 , wherein the second lens is an aspheric lens, a meniscus lens or a biconvex lens, the third lens is a biconvex lens, and the fifth lens is an aspheric lens or a meniscus lens.