Optical imaging system including seven lenses of +−++−+−, +−++++− or +−+++−− refractive powers
The present disclosure discloses an optical imaging system. The optical imaging system satisfies: f/EPD≤1.5; 0.3<T23*10/R4<1.8; −0.6<f2/f4<−0.1; and TTL/ImgH<1.4, where f is an effective focal length of the optical imaging system, EPD is an entrance pupil diameter of the optical imaging system, T23 is a spaced interval between the second lens and the third lens along the optical axis, R4 a radius of curvature of an image-side surface of the second lens, f2 is an effective focal length of the second lens, f4 is an effective focal length of the fourth lens, TTL is a distance along the optical axis from an object-side surface of the first lens to an imaging plane of the optical imaging system, and ImgH is half of a diagonal length of an effective pixel area on the imaging plane.
1. An optical imaging system, comprising: a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens and a seventh lens, which are sequentially arranged from an object side to an image side of the optical imaging system along an optical axis,
wherein,
f/ EPD≤1.5;
0.3< T 23*10/ R 4<1.8;
0.5<SAG61/SAG62<1;
−0.6< f 2/ f 4<−0.1; and
TTL/ImgH<1.4,
where f is an effective focal length of the optical imaging system, EPD is an entrance pupil diameter of the optical imaging system, T23 is a spaced interval between the second lens and the third lens along the optical axis, R4 a radius of curvature of an image-side surface of the second lens, SAG61 is an on-axis distance from an intersection of an object-side surface of the sixth lens and the optical axis to a vertex of an effective radius of the object-side surface of the sixth lens, SAG62 is an on-axis distance from an intersection of an image-side surface of the sixth lens and the optical axis to a vertex of an effective radius of the image-side surface of the sixth lens, f2 is an effective focal length of the second lens, f4 is an effective focal length of the fourth lens, TTL is a distance along the optical axis from an object-side surface of the first lens to an imaging plane of the optical imaging system, and ImgH is half of a diagonal length of an effective pixel area on the imaging plane.
2. The optical imaging system according to claim 1 , wherein,
the first lens has positive refractive power, the object-side surface of the first lens is convex and an image-side surface of the first lens is concave;
the second lens has negative refractive power, an object-side surface of the second lens is convex, and the image-side surface of the second lens is concave;
the third lens has positive refractive power;
the fourth lens has positive refractive power, and an object-side surface of the fourth lens is convex;
an object-side surface of the sixth lens is convex, and an image-side surface of the sixth lens is concave; and
the seventh lens has negative refractive power, an object-side surface of the seventh lens is convex, and an image-side surface of the seventh lens is concave.
3. The optical imaging system according to claim 1 , wherein f*tan(Semi-FOV)>4.5 mm,
where f is the effective focal length of the optical imaging system, and Semi-FOV is half of a maximal field-of-view of the optical imaging system.
4. The optical imaging system according to claim 1 , wherein 0.3<DT51/DT71<0.8,
where DT51 is a maximum effective radius of an object-side surface of the fifth lens, and DT71 is a maximum effective radius of an object-side surface of the seventh lens.
5. The optical imaging system according to claim 1 , wherein 0.7<DT41/DT42<1.2,
where DT41 is a maximum effective radius of an object-side surface of the fourth lens and DT42 is a maximum effective radius of an image-side surface of the fourth lens.
6. The optical imaging system according to claim 1 , wherein 0.1<(R14−R13)/f7<0.6,
where f7 is an effective focal length of the seventh lens, R13 is a radius of curvature of an object-side surface of the seventh lens and R14 is a radius of curvature of an image-side surface of the seventh lens.
7. The optical imaging system according to claim 1 , wherein 0.1<R1/R2<0.6,
where R1 is a radius of curvature of the object-side surface of the first lens and R2 is a radius of curvature of an image-side surface of the first lens.
8. The optical imaging system according to claim 1 , wherein 0.1<(R3−R4)/(R3+R4)<0.6,
where R3 is a radius of curvature of an object-side surface of the second lens and R4 is the radius of curvature of the image-side surface of the second lens.
9. The optical imaging system according to claim 1 , wherein 0.5<f/f1<1.5,
where f is the effective focal length of the optical imaging system and f1 is an effective focal length of the first lens.
10. The optical imaging system according to claim 1 , wherein 0.3<(CT2+CT3)/(CT4+CT5)<0.8,
where CT2 is a center thickness of the second lens along the optical axis, CT3 is a center thickness of the third lens along the optical axis, CT4 is a center thickness of the fourth lens along the optical axis, and CT5 is a center thickness of the fifth lens along the optical axis.
11. The optical imaging system according to claim 1 , wherein 0.3<CT6/CT1<0.8,
where CT1 is a center thickness of the first lens along the optical axis, and CT6 is a center thickness of the sixth lens along the optical axis.
12. The optical imaging system according to claim 1 , wherein 0.5<T45/T67<1,
where T45 is a spaced interval between the fourth lens and the fifth lens along the optical axis, and T67 is a spaced interval between the sixth lens and the seventh lens along the optical axis.
13. The optical imaging system according to claim 1 , wherein,
0.3<R11/ f< 0.8;
where f is an effective focal length of the optical imaging system, R11 is a radius of curvature of an object-side surface of the sixth lens.
14. The optical imaging system according to claim 13 , wherein,
the first lens has positive refractive power, the object-side surface of the first lens is convex and an image-side surface of the first lens is concave;
the second lens has negative refractive power, an object-side surface of the second lens is convex, and an image-side surface of the second lens is concave;
the third lens has positive refractive power;
the fourth lens has positive refractive power, and an object-side surface of the fourth lens is convex;
the object-side surface of the sixth lens is convex, and an image-side surface of the sixth lens is concave; and
the seventh lens has negative refractive power, an object-side surface of the seventh lens is convex, and an image-side surface of the seventh lens is concave.
15. The optical imaging system according to claim 13 , wherein f*tan(Semi-FOV)>4.5,
where f is the effective focal length of the optical imaging system, and Semi-FOV is half of a maximal field-of-view of the optical imaging system.
16. The optical imaging system according to claim 13 , wherein 0.5<SAG61/SAG62<1,
where SAG61 is an on-axis distance from an intersection of the object-side surface of the sixth lens and the optical axis to a vertex of an effective radius of the object-side surface of the sixth lens, and SAG62 is an on-axis distance from an intersection of an image-side surface of the sixth lens and the optical axis to a vertex of an effective radius of the image-side surface of the sixth lens.
17. The optical imaging system according to claim 13 , wherein 0.1<(R14−R13)/f7<0.6,
where f7 is an effective focal length of the seventh lens, R13 is a radius of curvature of an object-side surface of the seventh lens, and R14 is a radius of curvature of an image-side surface of the seventh lens.
18. The optical imaging system according to claim 13 , wherein 0.5<f/f1<1.5,
where f is the effective focal length of the optical imaging system, and f1 is an effective focal length of the first lens.
19. The optical imaging system according to claim 13 , wherein 0.3<(CT2+CT3)/(CT4+CT5)<0.8,
where CT2 is a center thickness of the second lens along the optical axis, CT3 is a center thickness of the third lens along the optical axis, CT4 is a center thickness of the fourth lens along the optical axis, and CT5 is a center thickness of the fifth lens along the optical axis.