Optical system

1. An optical system, comprising:

a first lens comprising positive refractive power, an object-side surface that is convex with a meniscus shape, and an image-side surface that is concave;

a second lens comprising an object-side surface that is convex and an image-side surface that is convex;

a third lens comprising negative refractive power, an object-side surface that is convex, and an image-side surface that is concave;

a fourth lens comprising positive refractive power, an object-side surface that is convex, and an image-side surface that is convex;

a fifth lens comprising negative refractive power, an object-side surface that is convex, and an image-side surface that is concave;

a sixth lens,

wherein the first to sixth lenses are sequentially disposed from an object side to an image side; and

an image sensor configured to convert an image of a subject incident through the first through sixth lenses into an electrical signal,

wherein 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 satisfying 0.95<TTL/f<1.45,

wherein, f34, a synthetic focal length of the third and fourth lenses satisfies −2.5<f/f34<−0.2,

wherein among the first to sixth lenses, the fifth lens has a largest absolute focal length value,

wherein among the first to sixth lenses, the fourth lens has a second largest absolute focal length value,

wherein each of the fifth lens and the sixth lens has a thickness greater than a thickness of each of the first lens, the second lens, the third lens, and the fourth lenses along an optical axis, and

wherein, r9, a radius of curvature of the object-side surface of the fifth lens and, r10, a radius of curvature of the image-side surface of the fifth lens satisfy 0<(r9−r10)/(r9+r10)<2.5.

2. The optical system of claim 1 , wherein, ImgH, half a diagonal length of the imaging surface of the image sensor is at least 3.43 mm.

3. The optical system of claim 1 , wherein, f1, a focal length of the first lens satisfies 0<f/f1<1.5.

4. The optical system of claim 1 , wherein, f3, a focal length of the third lens satisfies 0.2<|f/f3|<2.5.

5. The optical system of claim 1 , wherein, f5, a focal length of the fifth lens, and, f6, a focal length of the sixth lens satisfy 0.2<|f/f5|+|f/f6|<6.0.

6. The optical system of claim 1 , wherein ImgH is half a diagonal length of the imaging surface of the image sensor satisfying 0.35<TTL/(2*ImgH)<0.95.

7. The optical system of claim 1 , wherein FOV is a field of view of the optical system satisfying 65<FOV<100.

8. The optical system of claim 1 , wherein, f3, a focal length of the third lens, and, f4, a focal length of the fourth lens satisfy 0<|f/f3|+|f/f4|<3.

9. The optical system of claim 1 , wherein, r12, a radius of curvature of an image-side surface of the sixth lens satisfies 0.15<r12/f<0.9.

10. The optical system of claim 1 , wherein, f1, a focal length of the first lens and, f3, a focal length of the third lens satisfy 0<|f1/f3|<25.

11. The optical system of claim 1 , wherein, f1, a focal length of the first lens, and, f2, a focal length of the second lens satisfy 0.2<|f/f1|+|f/f2|<4.

12. The optical system of claim 1 , wherein, DL, a distance from the object-side surface of the first lens to an image-side surface of the sixth lens satisfies 0.7<DL/f<1.2.

13. The optical system of claim 1 , wherein, v4, an Abbe number of the fourth lens and, v5, an Abbe number of the fifth lens satisfy 42<v4+v5<115.

14. The optical system of claim 1 , wherein, f5, a focal length of the fifth lens satisfies |f5/f|>2.

15. The optical system of claim 1 , wherein, f12, a synthetic focal length of the first and second lenses satisfies 0.5<f/f12<2.5.

16. The optical system of claim 1 , wherein, v12, an average value of an Abbe number of the first lens and an Abbe number of the second lens and, v34, an average value of an Abbe number of the third lens and an Abbe number of the fourth lens satisfy 10<v12−v34<45.

17. The optical system of claim 1 , wherein at least one inflection point is formed on at least one of an object-side surface and the image-side surface of the fifth lens, and an absolute value of a radius of curvature of the object-side surface of the fifth lens in a paraxial region is larger than an absolute value of a radius of curvature of the image-side surface of the fifth lens in the paraxial region.

18. The optical system of claim 1 , wherein ImgH, half a diagonal length of the imaging surface of the image sensor, is 3.43 mm, or 3.68 mm, or 3.97 mm.

19. An optical system, comprising:

a first lens comprising positive refractive power, an object-side surface that is convex, and an image-side surface that is concave;

a second lens comprising an object-side surface that is convex and an image-side surface that is convex;

a third lens comprising negative refractive power, an object-side surface that is convex, and an image-side surface that is concave;

a fourth lens comprising positive refractive power, an object-side surface that is convex, and an image-side surface that is convex;

a fifth lens comprising negative refractive power, an object-side surface that is convex, and an image-side surface that is concave;

a sixth lens comprising refractive power,

wherein the first through sixth lenses are sequentially arranged from an object side to an image side; and

an image sensor configured to convert an image of a subject incident through the first through sixth lenses into an electrical signal,

wherein, ImgH, half a diagonal length of the imaging surface of the image sensor is at least 3.43 mm,

wherein, f, an overall focal length of the optical system, and, f34, a synthetic focal length of the third and fourth lenses satisfy −2.5<f/f34<−0.2,

wherein among the first to sixth lenses, the fifth lens has a largest absolute focal length value,

wherein among the first to sixth lenses, the fourth lens has a second largest absolute focal length value,

wherein each of the fifth lens and the sixth lens has a thickness greater than a thickness of each of the first lens, the second lens, the third lens, and the fourth lenses along an optical axis, and

wherein, r9, a radius of curvature of the object-side surface of the fifth lens and, r10, a radius of curvature of the image-side surface of the fifth lens satisfy 0<(r9−r10)/(r9+r10)<2.5.

20. The optical system of claim 19 , wherein 0.35<TTL/(2*ImgH)<0.95 is satisfied, where TTL is a distance from the object-side surface of the first lens to an imaging surface of the image sensor and the ImgH is 3.43 mm, or 3.68 mm, or 3.97 mm.