Optical system
An optical system includes: a first lens having refractive power and comprising an object-side surface which is convex in a paraxial region; a second lens having refractive power and comprising an object-side surface which is convex in the paraxial region; a third lens having refractive power; a fourth lens having refractive power; and a fifth lens having refractive power. The first to fifth lenses are sequentially disposed from an object side. An Abbe number of the first lens is between 30 and 50. Deteriorations in resolution at high temperatures and/or low temperatures may be decreased, MTF performance may be maintained even during temperature changes, and changes in focusing positions may be decreased. In addition, an aberration improvement effect, a wide field of view and a high degree of resolution may be implemented.
1. An optical system comprising:
a first lens having refractive power and a convex object-side surface;
a second lens having refractive power and a convex object-side surface;
a third lens having refractive power;
a fourth lens having refractive power; and
a fifth lens having refractive power,
wherein the first to fifth lenses are sequentially disposed from an object side,
wherein the optical system has a total of five lenses wherein an Abbe number of the first lens v1satisfies:
30<v1<50, and
wherein the Abbe number of the first lens v1 and an Abbe number of the third lens v3satisfy:
−20< v 1 −v 3<−5.
2. The optical system of claim 1 , wherein a focal length of the first lens f1 and a focal length of the fifth lens f5 satisfy:
f 5 /f 1>0.3.
3. The optical system of claim 1 , wherein a thickness of the second lens Th2 and a thickness of the fifth lens Th5 satisfy:
Th 2 /Th 5<0.4.
4. The optical system of claim 1 , further comprising an image sensor converting an image of a subject incident through the first to fifth lenses into an electrical signal,
wherein a distance from the object-side surface of the first lens to an imaging surface of the image sensor OAL and an overall focal length of the optical system EFL satisfy:
1.0 <OAL/EFL< 2.0.
5. The optical system of claim 1 , wherein a thickness of the fifth lens Th5and an overall focal length of the optical system EFL satisfy:
0.2 <Th 5 /EFL< 0.4.
6. The optical system of claim 1 , wherein a refractive index of the first lens n 1 satisfies:
1.70<n1<2.10.
7. The optical system of claim 1 , wherein a radius of curvature of the object-side surface of the first lens r1 and an overall focal length of the optical system EFL satisfy:
0.5 <r 1 /EFL< 0.7.
8. The optical system of claim 1 , wherein a focal length of the first lens f1 and an overall focal length of the optical system EFL satisfy:
0.5 <EFL/f 1<1.2.
9. The optical system of claim 1 , wherein a focal length of the first lens f1and a focal length of the third lens f3 satisfy:
1 <f 1 /f 3<2.5.
10. The optical system of claim 1 , wherein a focal length of the first lens f1, a focal length of the second lens f2, and an overall focal length of the optical system EFL satisfy:
0.8< EFL/f 1+| EFL/f 2|<1.9.
11. The optical system of claim 1 , wherein a field of view of the optical system FOV satisfies:
75<FOV<90.
12. The optical system of claim 1 , wherein the refractive power of the first lens is positive.
13. The optical system of claim 1 , wherein an image-side surface of the first lens is concave.
14. The optical system of claim 1 , wherein an image-side surface of the first lens is convex.
15. The optical system of claim 1 , wherein the refractive power of the second lens is negative.
16. The optical system of claim 1 , wherein an image-side surface of the second lens is concave.
17. The optical system of claim 1 , wherein the refractive power of the third lens is positive.
18. The optical system of claim 1 , wherein an object-side surface of the third lens is convex.
19. The optical system of claim 1 , wherein an object-side surface of the third lens is concave.
20. The optical system of claim 1 , wherein an image-side surface of the third lens is convex.
21. The optical system of claim 1 , wherein the refractive power of the fourth lens is negative.
22. The optical system of claim 1 , wherein an object-side surface of the fourth lens is concave.
23. The optical system of claim 1 , wherein an image-side surface of the fourth lens is convex.
24. The optical system of claim 1 , wherein the refractive power of the fifth lens is positive.
25. The optical system of claim 1 , wherein an object-side surface of the fifth lens is convex.
26. The optical system of claim 1 , wherein an object-side surface of the fifth lens is concave.
27. The optical system of claim 1 , wherein at least one inflection point is formed on at least one of an object-side surface and an image-side surface of the fifth lens.
28. The optical system of claim 1 , wherein at least one of the object-side surface and an image-side surface of the first lens is aspherical.
29. The optical system of claim 1 , further comprising a stop disposed between the first and second lenses.
30. The optical system of claim 1 , wherein the first lens is formed of glass.
31. An optical system comprising:
a first lens having refractive power;
a second lens having refractive power and a convex object-side surface;
a third lens having refractive power;
a fourth lens having negative refractive power; and
a fifth lens having positive refractive power,
wherein the first to fifth lenses are sequentially disposed from an object side,
wherein the optical system has a total of five lenses,
wherein a refractive index of the first lens n 1 satisfies:
1.70<n1<2.10, and
wherein an Abbe number of the first lens v1 and an Abbe number of the third lens v3 satisfy:
−20< v 1 −v 3<−5.
32. The optical system of claim 31 , wherein an Abbe number of the first lens v1 satisfies:
30<v1<50.
33. The optical system of claim 31 , wherein the first lens is formed of glass.
34. An optical system comprising:
a first lens having refractive power;
a second lens having refractive power and a convex object-side surface;
a third lens having refractive power and a convex object-side surface;
a fourth lens having refractive power; and
a fifth lens having positive refractive power and a concave image-side surface,
wherein the first to fifth lenses are sequentially disposed from an object side,
wherein the optical system has a total of five lenses,
wherein an Abbe number of the first lens v1 satisfies:
30<v1<50, and
wherein the Abbe number of the first lens v1 and an Abbe number of the third lens v3 satisfy:
−20< v 1 −v 3<−5.
35. An optical system comprising: first, second, third, fourth, and fifth lenses disposed sequentially from an object side, wherein the optical system has a total of five lenses, wherein an Abbe number of the first lens v1 is between 30 and 50 and wherein the Abbe number of the first lens v1and an Abbe number of the third lens v3 satisfy:
−20< v 1 −v 3<−5.
36. The optical system of claim 35 , wherein the fifth lens has positive refractive power.
37. The optical system of claim 35 , wherein an object-side surface of the third lens is convex.
38. The optical system of claim 35 , wherein the first lens is formed of glass with a refractive index between 1.7 and 2.1.