Optical imaging system
An optical imaging system includes a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, and an eighth lens, sequentially disposed from an object side to an imaging plane. The optical imaging system satisfies the expression BFL/f<0.15, where BFL represents a distance from an image-side surface of the eighth lens to an imaging plane of an image sensor and f represents an overall focal length of the optical imaging system.
1. An optical imaging system comprising:
a first lens comprising a positive refractive power, a second lens comprising a negative refractive power, a third lens comprising a refractive power, a fourth lens comprising a positive refractive power, a fifth lens comprising a negative refractive power, a sixth lens comprising a refractive power and a concave object-side surface along an optical axis, a seventh lens comprising a negative refractive power, and an eighth lens comprising a positive refractive power sequentially disposed from an object side to an imaging plane,
wherein 0.7<TTL/f<1.0, where TTL represents a distance from an object-side surface of the first lens to an imaging plane, and f represents an overall focal length of the optical imaging system.
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 eighth lens to the imaging plane.
3. The optical imaging system of claim 1 , wherein f/ImgH <2.9, where ImgH represents a half of a diagonal length of the imaging plane.
4. The optical imaging system of claim 1 , wherein−30<f6/f<30, where f6 represents a focal length of the sixth lens.
5. The optical imaging system of claim 1 , wherein TTL/ImgH >1.0, where ImgH represents a half of a diagonal length of the imaging plane.
6. The optical imaging system of claim 1 , further comprising a stop disposed between the third lens and the fourth lens or between the fourth lens and the fifth lens.
7. The optical imaging system of claim 1 , wherein object-side surfaces and image-side surfaces of the first to eighth lenses are aspherical.
8. The optical imaging system of claim 1 , wherein the first lens has a convex object-side surface along an optical axis.
9. The optical imaging system of claim 1 , wherein the second lens has a convex object-side surface along an optical axis, and a concave image-side surface along the optical axis.
10. The optical imaging system of claim 1 , wherein the third lens has a positive or negative refractive power, a convex object-side surface along an optical axis, and a concave image-side surface along the optical axis.
11. The optical imaging system of claim 1 , wherein the fourth lens has a convex object-side surface along an optical axis and a concave image-side surface along the optical axis.
12. The optical imaging system of claim 1 , wherein the fifth lens has a concave image-side surface along an optical axis.
13. The optical imaging system of claim 1 , wherein the sixth lens has a positive or negative refractive power.
14. The optical imaging system of claim 1 , wherein the seventh lens has a concave object-side surface along an optical axis and a concave image-side surface along the optical axis.
15. The optical imaging system of claim 1 , wherein the eighth lens has a convex object-side surface along an optical axis.
16. The optical imaging system of claim 1 , wherein the fourth lens and the fifth lens are spaced apart from each other along the optical axis.