Lens module
A lens module includes a first lens having a convex object-side surface and a convex image-side surface, a second lens having a concave object-side surface; a third lens having a meniscus shape; and a fourth lens having an inflection point formed on an image-side surface and a convex object-side surface. A distance from an image-side surface of the third lens to the object-side surface of the fourth lens may be less than 0.05. In an embodiment, r2, a radius of curvature of an image-side surface of the first lens, and, f, an overall focal length of an optical system including the first through fourth lenses may satisfy −0.94<r2/f<−0.79. In an alternative embodiment, FOV, a field of view of an optical system including the first through fourth lenses is greater than 80.
1. A lens module, comprising:
a first lens comprising a convex object-side surface and a convex image-side surface;
a second lens comprising a concave object-side surface;
a third lens comprising a meniscus shape; and
a fourth lens comprising an inflection point formed on an image-side surface and a convex object-side surface,
wherein a distance from an image-side surface of the third lens to the object-side surface of the fourth lens is less than 0.05 millimeters (mm), and
wherein BFL, a distance from the image-side surface of the fourth lens to an image plane, and f, an overall focal length of an optical system including the first to fourth lenses, satisfy BFL/f<0.41, and BFL and f have a same unit of measure.
2. The lens module of claim 1 , wherein the first lens comprises a positive refractive power, the second lens comprises a negative refractive power, the third lens comprises a positive refractive power, and the fourth lens comprises a negative refractive power.
3. The lens module of claim 1 , wherein the third lens has a refractive power stronger than a refractive power of the first lens, and the second lens has a refractive power stronger than a refractive power of the fourth lens.
4. The lens module of claim 1 , wherein the first through fourth lenses are sequentially disposed from an object side to an image side.
5. The lens module of claim 1 , wherein the image-side surface of the fourth lens is concave in a paraxial region and gradually curves to be convex at an edge portion thereof.
6. The lens module of claim 1 , wherein an image-side surface of the second lens is concave.
7. The lens module of claim 1 , wherein the image-side surface of the fourth lens is concave.
8. The lens module of claim 1 , wherein, D6, a distance from the image-side surface of the third lens to the object-side surface of the fourth lens, and, f, an overall focal length of an optical system including the first to fourth lenses satisfy D6/f<0.19, and D6 and f have a same unit of measure.
9. The lens module of claim 1 , wherein,
r2, a radius of curvature of an image-side surface of the first lens satisfies −2.10 mm<r2<−1.70 mm.
10. The lens module of claim 1 , wherein, r2, a radius of curvature of an image-side surface of the first lens, and, f, an overall focal length of an optical system including the first to fourth lenses satisfy −0.94<r2/f<−0.79, and r2 and f have a same unit of measure.
11. The lens module of claim 1 , wherein,
r1, a radius of curvature of an object-side surface of the first lens, and, r2, a radius of curvature of an image-side surface of the first lens satisfy −0.50<(r1+r2)/(r1−r2)<0.10, and r1 and r2 have a same unit of measure.
12. A lens module, comprising:
a first lens comprising a convex object-side surface and a convex image-side surface;
a second lens comprises a concave object-side surface;
a third lens comprises a concave object-side surface; and
a fourth lens comprising inflection point formed on an image-side surface and a convex object-side surface,
wherein, r2, a radius of curvature of an image-side surface of the first lens, and f, an overall focal length of an optical system including the first through fourth lenses satisfy −0.94<r2/f<−0.79, and
wherein BFL, a distance from the image-side surface of the fourth lens to an image plane, and f satisfy BFL/f<0.41, and BFL, r2 and f have a same unit of measure.
13. The lens module of claim 12 , wherein the first lens comprises a positive refractive power, the second lens comprises a negative refractive power, the third lens comprises a positive refractive power, and the fourth lens comprises a negative refractive power.
14. The lens module of claim 12 , wherein the first through fourth lenses are sequentially disposed from an object side to an image side.
15. The lens module of claim 12 , wherein an image-side surface of the third lens is convex.
16. A lens module comprising:
a first lens comprising a convex object-side surface and a convex image-side surface;
a second lens comprising a concave object-side surface;
a third lens comprising a concave object-side surface; and
a fourth lens comprising an inflection point formed on an image-side surface and a convex object-side surface,
wherein, FOV, a field of view of an optical system including the first through fourth lenses is greater than 80 degrees, and
wherein BFL, a distance from the image-side surface of the fourth lens to an image plane, and f, an overall focal length of an optical system including the first to fourth lenses, satisfy BFL/f<0.41, and BFL and f have a same unit of measure.
17. The lens module of claim 16 , wherein the first lens comprises a positive refractive power, the second lens comprises a negative refractive power, the third lens comprises a positive refractive power, and the fourth lens comprises a negative refractive power.
18. The lens module of claim 16 , wherein the first through fourth lenses are sequentially disposed from an object side to an image side.
19. The lens module of claim 16 , wherein an image-side surface of the second lens is concave.
20. The lens module of claim 16 , wherein an image-side surface of the third lens is convex.