Optical imaging system
An optical imaging system includes a first lens, a second lens, a third lens, a fourth lens having a negative refractive power, a fifth lens having a negative refractive power, a sixth lens, and a seventh lens having a positive refractive power. The first lens to seventh lens are sequentially disposed in a direction from an object side toward an imaging plane.
1. An optical imaging system, comprising:
a first lens comprising a convex object-side surface;
a second lens comprising a refractive power;
a third lens comprising a convex object-side surface;
a fourth lens comprising negative refractive power and a convex object-side surface;
a fifth lens comprising negative refractive power;
a sixth lens comprising a concave image-side surface; and
a seventh lens comprising a refractive power,
wherein the first to seventh lenses are sequentially disposed from an object side to an image plane, and
wherein a distance from an image-side surface of the fourth lens to an object-side surface of the fifth lens is greater than a thickness along an optical axis of the fifth lens.
2. The optical imaging system of claim 1 , wherein BFL/f<0.15, where BFL represents a distance from an image-side surface of the seventh lens to the imaging plane and f is a focal length of the optical imaging system.
3. The optical imaging system of claim 1 , wherein 0.1<f/(IMG HT)<2.5, where IMG HT is a half diagonal length of the imaging plane and f is a focal length of the optical imaging system.
4. The optical imaging system of claim 1 , wherein 1.5<Nd7<1.7, where Nd7 represents a refractive index of the seventh lens.
5. The optical imaging system of claim 1 , wherein −45<f5/f<45, where f5 represents a focal length of the fifth lens and f is a focal length of the optical imaging system.
6. The optical imaging system of claim 1 , wherein 2.0<f/EPD<2.8, where EPD represents a diameter of an entrance pupil and f is a focal length of the optical imaging system.
7. The optical imaging system of claim 1 , wherein the first lens has positive refractive power.
8. The optical imaging system of claim 1 , wherein the second lens has negative refractive power.
9. The optical imaging system of claim 1 , wherein the third lens has negative refractive power.
10. An optical imaging system, comprising:
a first lens comprising a refractive power;
a second lens comprising a concave image-side surface;
a third lens comprising a refractive power;
a fourth lens comprising negative refractive power and a convex object-side surface;
a fifth lens comprising a refractive power;
a sixth lens comprising a concave image-side surface; and
a seventh lens comprising a refractive power,
wherein the first to seventh lenses are sequentially disposed from an object side to an image plane,
wherein a radius of curvature of an object-side surface of the second lens is greater than a radius of curvature of an image-side surface of the seventh lens, and
wherein BFL/f<0.15, where BFL represents a distance from an image-side surface of the seventh lens to the imaging plane and f is a focal length of the optical imaging system.
11. The optical imaging system of claim 10 , wherein 0.1<f/(IMG HT)<2.5, where IMG HT is a half diagonal length of the imaging plane.
12. The optical imaging system of claim 10 , wherein 1.5<Nd7<1.7, where Nd7 represents a refractive index of the seventh lens.
13. The optical imaging system of claim 10 , wherein −45<f5/f<45, where f5 represents a focal length of the fifth lens.
14. The optical imaging system of claim 10 , wherein 2.0<f/EPD<2.8, where EPD represents a diameter of an entrance pupil.
15. The optical imaging system of claim 10 , wherein the fifth lens has a concave object-side surface.
16. The optical imaging system of claim 10 , wherein the seventh lens has a convex object-side surface.