Lens module

1. A lens module comprising:

a first lens having refractive power;

a second lens having refractive power, both surfaces thereof being convex;

a third lens having refractive power, both surfaces thereof being concave;

a fourth lens having refractive power;

a fifth lens having refractive power, an object-side surface thereof being convex; and

a sixth lens having refractive power and having one or more inflection points on an image-side surface thereof, an object-side surface thereof being convex;

wherein the first to sixth lenses are sequentially disposed in numerical order from the first lens to the sixth lens from an object side of the lens module toward an image side of the lens module;

an object-side surface of the fourth lens is convex, or an image-side surface of the fourth lens is concave; and

an image-side surface of the first lens is convex, or an object-side surface of the fourth lens is concave, or an image-side surface of the fifth lens is concave.

2. The lens module of claim 1 , wherein an object-side surface of the first lens is convex.

3. The lens module of claim 1 , wherein the image-side surface of the first lens is convex.

4. The lens module of claim 1 , wherein the object-side surface of the fourth lens is convex.

5. The lens module of claim 1 , wherein the image-side surface of the fourth lens is concave.

6. The lens module of claim 1 , wherein the object-side surface of the fourth lens is concave.

7. The lens module of claim 1 , wherein an image-side surface of the fourth lens is convex.

8. The lens module of claim 1 , wherein the image-side surface of the fifth lens is concave.

9. The lens module of claim 1 , wherein the image-side surface of the sixth lens is concave.

10. The lens module of claim 1 , wherein |r1/T1|<17.0 is satisfied,

where r1 is a radius of curvature of an object-side surface of the first lens, and

T1 is a thickness of the first lens on an optical axis.

11. The lens module of claim 1 , wherein |f6/f|<79.0 is satisfied,

where f is an overall focal length of an optical system comprising the first to sixth lenses, and

f6 is a focal length of the sixth lens.

12. The lens module of claim 1 , wherein f5/f<−3.0 is satisfied,

where f is an overall focal length of an optical system comprising the first to sixth lenses, and

f5 is a focal length of the fifth lens.

13. The lens module of claim 1 , wherein |(r7+r8)/(r7−R8)|<200 is satisfied,

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.

14. The lens module of claim 1 , wherein |n3−n4|<0.1 is satisfied,

where n3 is a refractive index of the third lens, and

n4 is a refractive index of the fourth lens.

15. A lens module comprising:

a first lens having negative refractive power;

a second lens having positive refractive power;

a third lens having negative refractive power;

a fourth lens having negative refractive power;

a fifth lens having negative refractive power; and

a sixth lens having negative refractive power and having one or more inflection points on an image-side surface thereof;

wherein the first to sixth lenses are sequentially disposed in numerical order from the first lens to the sixth lens from an object side of the lens module toward an image side of the lens module.

16. The lens module of claim 15 , wherein 5.0<|(r9+r10)/(r9−r10)|<21.0 is satisfied,

where r9 is a radius of curvature of an object-side surface of the fifth lens, and

r10 is a radius of curvature of an image-side surface of the fifth lens.