Optical imaging system

Abstract

The 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, arranged sequentially along the optical axis toward the imaging plane. The first lens has positive refractive power, the second lens has negative refractive power, and the third lens has positive refractive power. The system satisfies 0.95 < (TTL / (2×IMG HT))×Fno < 1.00 and 6.9 < TTL / BFL < 8.5, where TTL is the distance along the optical axis from the object surface of the first lens to the imaging plane, IMG HT is half the diagonal length of the imaging plane, Fno is the F-number of the optical imaging system, and BFL is the distance along the optical axis from the image surface of the eighth lens to the imaging plane.

Claims

1. An optical imaging system, comprising: The first lens, second lens, third lens, fourth lens, fifth lens, sixth lens, seventh lens, and eighth lens are arranged in ascending order along the optical axis of the optical imaging system, from the object side of the optical imaging system towards the imaging plane of the optical imaging system. The first lens has positive refractive power, the second lens has negative refractive power, and the third lens has positive refractive power, and they satisfy the following expressions: 0.95 < (TTL / (2×IMG HT))×Fno < 1.00; 6.9 < TTL / BFL < 8.

5. Where TTL is the distance along the optical axis from the object side surface of the first lens to the imaging plane, IMG HT is half the diagonal length of the imaging plane, Fno is the F-value of the optical imaging system, and BFL is the distance along the optical axis from the image side surface of the eighth lens to the imaging plane.

2. The optical imaging system of claim 1, wherein the refractive index of the second lens is greater than the refractive index of the first lens and the refractive index of the third lens, and the refractive index of the fourth lens is greater than the refractive index of the third lens and the refractive index of the fifth lens.

3. The optical imaging system of claim 1, wherein the refractive index of the fourth lens is greater than the refractive index of the third lens and the refractive index of the fifth lens.

4. The optical imaging system of claim 1, wherein the fourth lens has negative refractive power and the Abbe number of the second lens and the fourth lens is less than 20.

5. The optical imaging system of claim 1, wherein one or both of the following conditional expressions are satisfied: 30 < v2 + v4 < 40 15 < v1 - (v2 + v4) < 20 where v1 is the Abbe number of the first lens, v2 is the Abbe number of the second lens, and v4 is the Abbe number of the fourth lens.

6. The optical imaging system as claimed in claim 1, wherein 1.5 < Fno < 1.

58.

7. The optical imaging system as claimed in claim 1, wherein 0.6 < TTL / (2×IMG HT) < 0.

64.

8. The optical imaging system of claim 1, wherein 0 < d45 / TTL < 0.03, where d45 is the distance along the optical axis between the image-side surface of the fourth lens and the object-side surface of the fifth lens.

9. The optical imaging system as claimed in claim 1, wherein 1.1 < TTL / f < 1.25, where f is the total focal length of the optical imaging system.

10. The optical imaging system of claim 1, wherein 0.15 < R1 / R2 < 0.35, where R1 is the radius of curvature of the object surface of the first lens at the optical axis, and R2 is the radius of curvature of the image surface of the first lens at the optical axis.

11. The optical imaging system of claim 1, wherein 0.12 < (R1 / R2) / T1 < 0.3, where R1 is the radius of curvature of the object surface of the first lens at the optical axis, R2 is the radius of curvature of the image surface of the first lens at the optical axis, and T1 is the thickness of the first lens along the optical axis.

12. The optical imaging system of claim 1, wherein 0.85 < f1 / f < 1.05, where f1 is the focal length of the first lens and f is the total focal length of the optical imaging system.

13. The optical imaging system of claim 1, wherein -3 < f2 / f < -1.8, where f2 is the focal length of the second lens and f is the total focal length of the optical imaging system.

14. The optical imaging system of claim 1, wherein 0.3 < |f1 / f2| < 0.5, where f1 is the focal length of the first lens and f2 is the focal length of the second lens.

15. The optical imaging system of claim 1, wherein the seventh lens has positive refractive power and the eighth lens has negative refractive power.

16. The optical imaging system of claim 1, wherein the object-side surface of the first lens is convex in its paraxial region and the image-side surface of the first lens is concave in its paraxial region, the object-side surface of the second lens is convex in its paraxial region and the image-side surface of the second lens is concave in its paraxial region, and the object-side surface of the third lens is convex in its paraxial region and the image-side surface of the third lens is concave in its paraxial region.

17. The optical imaging system of claim 1, wherein 5 < f3 / f < 10, where f3 is the focal length of the third lens and f is the total focal length of the optical imaging system.

18. The optical imaging system of claim 1, wherein -10 < f4 / f < -4, where f4 is the focal length of the fourth lens and f is the total focal length of the optical imaging system.

19. The optical imaging system of claim 1, wherein 0.07 < |f1 / f3| < 0.2, where f1 is the focal length of the first lens and f3 is the focal length of the third lens.

20. The optical imaging system of claim 1, wherein 0.2 < |f2 / f3| < 0.5, where f2 is the focal length of the second lens and f3 is the focal length of the third lens.

Images