Optical system
There is provided an optical system including: a first lens having negative refractive power and having a meniscus shape of which an object-side surface is convex; a second lens having positive refractive power; a third lens having refractive power; and a fourth lens having positive refractive power and having a meniscus shape of which an object-side surface is convex, wherein the first to fourth lenses are sequentially disposed from an object side, whereby an aberration improvement effect, a wide field of view and a high degree of resolution may be realized.
1. An optical system comprising:
a first lens having negative refractive power and having a meniscus shape of which an object-side surface is convex;
a second lens having positive refractive power;
a third lens having refractive power; and
a fourth lens having positive refractive power and having a meniscus shape of which an object-side surface is convex,
wherein the first to fourth lenses are sequentially disposed from an object side, and a focal length of the first lens F 1 and an overall focal length of the optical system F satisfy Conditional Expression 1:
−2.3< F 1/ F<− 2.0. [Conditional Expression 1]
2. The optical system of claim 1 , wherein both surfaces of the second lens are convex.
3. The optical system of claim 1 , wherein the third lens has negative refractive power.
4. The optical system of claim 1 , wherein the third lens has a meniscus shape of which an image-side surface is convex.
5. The optical system of claim 1 , wherein Conditional Expression 2 is satisfied:
FOV≧80 [Conditional Expression 2]
where FOV is a field of view of the optical system.
6. The optical system of claim 1 , further comprising an image sensor converting an image of a subject incident through the first to fourth lenses into an electrical signal,
wherein Conditional Expression 3 is satisfied:
FOV/ TTL> 25 [Conditional Expression 3]
where FOV is a field of view of the optical system, and TTL is a distance from the object-side surface of the first lens to an imaging surface of the image sensor.
7. The optical system of claim 1 , further comprising an image sensor converting an image of a subject incident through the first to fourth lenses into an electrical signal,
wherein Conditional Expression 4 is satisfied:
TTL/F≦ 2.30 [Conditional Expression 4]
where TTL is a distance from the object-side surface of the first lens to an imaging surface of the image sensor, and F is an overall focal length of the optical system.
8. The optical system of claim 1 , wherein Conditional Expression 5 is satisfied:
F 2/ F≧ 0.73 [Conditional Expression 5]
where F 2 is a focal length of the second lens, and F is an overall focal length of the optical system.
9. The optical system of claim 1 , wherein Conditional Expression 6 is satisfied:
−5.0< F 3/ F< 20.0 [Conditional Expression 6]
where F 3 is a focal length of the third lens, and F is an overall focal length of the optical system.
10. The optical system of claim 1 , wherein Conditional Expression 7 is satisfied:
4.0< F 4/ F< 8.0 [Conditional Expression 7]
where F 4 is a focal length of the fourth lens, and F is an overall focal length of the optical system.
11. The optical system of claim 1 , further comprising an image sensor converting an image of a subject incident through the first to fourth lenses into an electrical signal,
wherein Conditional Expression 8 is satisfied:
2.1 <TTL /Img H <2.7 [Conditional Expression 8]
where TTL is a distance from the object-side surface of the first lens to an imaging surface of the image sensor, and ImgH is a diagonal length of the imaging surface of the image sensor.
12. The optical system of claim 1 , wherein the first to fourth lenses are plastic lenses.
13. The optical system of claim 1 , wherein the fourth lens has at least one inflection point on the object-side surface thereof.
14. The optical system of claim 1 , wherein the fourth lens has at least one inflection point on an image-side surface thereof.
15. An optical system comprising:
a first lens having negative refractive power and having a meniscus shape of which an object-side surface is convex;
a second lens having positive refractive power of which both surfaces are convex;
a third lens having refractive power; and
a fourth lens having positive refractive power,
wherein the first to fourth lenses are sequentially disposed from an object side, and
Conditional Expression 1 is satisfied:
FOV≧80 [Conditional Expression 1]
where FOV is a field of view of the optical system, and a wherein a focal length of the first lens F 1 and an overall focal length of the optical system F satisfy Conditional Expression 2:
−2.3< F 1/ F<− 2.0. [Conditional Expression 2]
16. The optical system of claim 15 , further comprising an image sensor converting an image of a subject incident through the first to fourth lenses into an electrical signal,
wherein Conditional Expression 3 is satisfied:
FOV/ TTL> 25 [Conditional Expression 3]
where TTL is a distance from the object-side surface of the first lens to an imaging surface of the image sensor.
17. The optical system of claim 15 , further comprising an image sensor converting an image of a subject incident through the first to fourth lenses into an electrical signal,
wherein Conditional Expression 4 satisfied:
TTL/F ≦2.30 [Conditional Expression 4]
where TTL is a distance from the object-side surface of the first lens to an imaging surface of the image sensor, and F is an overall focal length of the optical system.
18. The optical system of claim 15 , wherein Conditional Expression 5 is satisfied:
F 2 /F ≧0.73 [Conditional Expression 5]
where F 2 is a focal length of the second lens, and F is an overall focal length of the optical system.
19. The optical system of claim 15 , wherein Conditional Expression 6 is satisfied:
−5.0< F 3/ F< 20.0 [Conditional Expression 6]
where F 3 is a focal length of the third lens, and F is an overall focal length of the optical system.
20. The optical system of claim 15 , wherein Conditional Expression 7 is satisfied:
4.0< F 4/ F< 8.0 [Conditional Expression 7]
where F 4 is a focal length of the fourth lens, and F is an overall focal length of the optical system.
21. The optical system of claim 15 , further comprising an image sensor converting an image of a subject incident through the first to fourth lenses into an electrical signal,
wherein Conditional Expression 8 is satisfied:
2.1 <TTL /Img H <2.7 [Conditional Expression 8]
where TTL is a distance from the object-side surface of the first lens to an imaging surface of the image sensor, and ImgH is a diagonal length of the imaging surface of the image sensor.
22. The optical system of claim 15 , wherein the third lens has negative refractive power.
23. The optical system of claim 15 , wherein the third lens has a meniscus shape of which an image-side surface is convex.
24. The optical system of claim 15 , wherein the fourth lens has a meniscus shape of which an object-side surface is convex.
25. The optical system of claim 15 , wherein the fourth lens has at least one inflection point on each of an object-side surface and an image-side surface thereof.