Optical system
There is provided an optical system including: a first lens having positive refractive power and having a convex object-side surface; a second lens having positive refractive power; a third lens having refractive power; a fourth lens having refractive power; a fifth lens having refractive power; a sixth lens having refractive power; and a seventh lens having negative refractive power and having a concave image-side surface, wherein the first to seventh lenses are sequentially disposed from an object side, whereby an aberration improvement effect may be increased and a high degree of resolution may be realized.
1. An optical system comprising:
a first lens having positive refractive power and having a convex object-side surface;
a second lens having positive refractive power;
a third lens having refractive power;
a fourth lens having refractive power;
a fifth lens having refractive power and having a concave object-side surface in a paraxial region;
a sixth lens having refractive power and a convex image-side surface in a paraxial region; and
a seventh lens having negative refractive power and having a concave image-side surface,
wherein the first to seventh lenses are sequentially disposed from an object side.
2. The optical system of claim 1 , wherein the first lens has a meniscus shape of which the object-side surface is convex.
3. The optical system of claim 1 , wherein both surfaces of the second lens are convex.
4. The optical system of claim 1 , wherein the third lens has negative refractive power.
5. The optical system of claim 1 , wherein both surfaces of the third lens are concave.
6. The optical system of claim 1 , wherein the fourth lens has positive or negative refractive power.
7. The optical system of claim 1 , wherein the fourth lens has a meniscus shape of which an object-side surface is convex.
8. The optical system of claim 1 , wherein both surfaces of the fourth lens are convex.
9. The optical system of claim 1 , wherein the fifth lens has positive or negative refractive power.
10. The optical system of claim 1 , wherein the fifth lens has a meniscus shape of which an image-side surface is convex.
11. The optical system of claim 1 , wherein the sixth lens has positive refractive power.
12. The optical system of claim 1 , wherein the sixth lens has a meniscus shape.
13. The optical system of claim 1 , wherein both surfaces of the seventh lens are concave.
14. The optical system of claim 1 , wherein the seventh lens has a meniscus shape of which an object-side surface is convex.
15. The optical system of claim 1 , wherein at least one surface of the seventh lens is aspherical.
16. The optical system of claim 1 , further comprising an image sensor converting an image of a subject incident thereon through the first to seventh lenses into an electrical signal,
wherein Conditional Expression 1 is satisfied:
IMH/EPD< 2.0 [Conditional Expression 1]
where IMH is a diagonal length of the image sensor, and EPD is an entrance pupil diameter of the optical system.
17. The optical system of claim 1 , wherein Conditional Expression 2 is satisfied:
BFL/TTL< 0.25 [Conditional Expression 2]
where BFL is a distance from the image-side surface of the seventh lens to an imaging surface, and TTL is a distance from the object-side surface of the first lens to the imaging surface.
18. The optical system of claim 1 , wherein Conditional Expression 3 is satisfied:
TTL/F< 1.2 [Conditional Expression 3]
where TTL is a distance from the object-side surface of the first lens to an imaging surface, and F is an overall focal length of the optical system.
19. The optical system of claim 1 , wherein Conditional Expression 4 is satisfied:
| Nd 4− Nd 6|<0.1 [Conditional Expression 4]
where Nd4 is a refractive index of the fourth lens, and Nd6 is a refractive index of the sixth lens.
20. The optical system of claim 1 , wherein Conditional Expression 5 is satisfied:
( r 3− r 4)/( r 3+ r 4)<−1.0 [Conditional Expression 5]
where r3 is a radius of curvature of an object-side surface of the second lens, and r4 is a radius of curvature of an image-side surface of the second lens.
21. The optical system of claim 1 , wherein Conditional Expression 7 is satisfied:
r 14/ F> 0.3 [Conditional Expression 7]
where r14 is a radius of curvature of the image-side surface of the seventh lens, and F is an overall focal length of the optical system.
22. The optical system of claim 1 , wherein Conditional Expression 8 is satisfied:
F 12/ F> 0.5 [Conditional Expression 8]
where F12 is a composite focal length of the first and second lenses, and F is an overall focal length of the optical system.
23. The optical system of claim 1 , wherein both surfaces of the fourth lens are aspherical.
24. An optical system comprising:
a first lens having positive refractive power and having a convex object-side surface;
a second lens having positive refractive power;
a third lens having refractive power;
a fourth lens having refractive power;
a fifth lens having refractive power and having a concave object-side surface in a paraxial region;
a sixth lens having refractive power; and
a seventh lens having negative refractive power and having a concave image-side surface,
wherein the first to seventh lenses are sequentially disposed from an object side, and Conditional Expression 6 is satisfied:
|( r 7− r 8)/( r 7+ r 8)|<1.4 [Conditional Expression 6]
where r7 is a radius of curvature of an object-side surface of the fourth lens, and r8 is a radius of curvature of an image-side surface of the fourth lens.
25. An optical system comprising:
a first lens having positive refractive power;
a second lens having positive refractive power;
a third lens having negative refractive power;
a fourth lens having positive or negative refractive power;
a fifth lens having positive or negative refractive power and having a concave object-side surface in a paraxial region;
a sixth lens having positive refractive power and a convex image-side surface in a paraxial region; and
a seventh lens having negative refractive power,
wherein the first to seventh lenses are sequentially disposed from an object side.
26. The optical system of claim 25 , wherein the first lens has a meniscus shape of which an object-side surface is convex.
27. The optical system of claim 25 , wherein both surfaces of the second lens are convex.
28. The optical system of claim 25 , wherein both surfaces of the third lens are concave.
29. The optical system of claim 25 , wherein the fifth lens has a meniscus shape of which an image-side surface is convex.
30. The optical system of claim 25 , wherein the sixth lens has a meniscus shape.
31. The optical system of claim 25 , wherein both surfaces of the seventh lens are concave.
32. The optical system of claim 25 , wherein the seventh lens has a meniscus shape of which an object-side surface is convex.