Optical imaging system
An optical imaging system includes a first lens having an object-side surface that is convex; a second lens having a refractive power and a refractive index of 1.65 or more; a third lens having a refractive power; a fourth lens having a refractive power and an object-side surface that is convex; a fifth lens having a refractive power; a sixth lens having a positive refractive power; and a seventh lens having an object-side surface that is convex, wherein the first lens through the seventh lens are sequentially disposed in numerical order from an object side of the optical imaging system toward an imaging plane of the optical imaging system, and two or more of the first lens and the third lens through the seventh lens have a refractive index of 1.6 or more.
1. An optical imaging system comprising:
a first lens having an object-side surface that is convex in a paraxial region thereof;
a second lens having a negative refractive power and a refractive index of 1.65 or more;
a third lens having a refractive power;
a fourth lens having a refractive power and an object-side surface that is convex in a paraxial region thereof;
a fifth lens having a refractive power and an image-side surface that is convex in a paraxial region thereof;
a sixth lens having a positive refractive power and an image-side surface that is convex in a paraxial region thereof; and
a seventh lens having an object-side surface that is convex in a paraxial region thereof,
wherein the first lens through the seventh lens are sequentially disposed in numerical order from an object side of the optical imaging system toward an imaging plane of the optical imaging system, and
two or more of the first lens and the third lens through the seventh lens have a refractive index of 1.6 or more.
2. The optical imaging system of claim 1 , wherein the first lens has a positive refractive power.
3. The optical imaging system of claim 1 , wherein at least three of the third lens through the sixth lens have a positive refractive power.
4. The optical imaging system of claim 1 , wherein the seventh lens has a negative refractive power.
5. The optical imaging system of claim 1 , wherein an object-side surface of the second lens is convex in a paraxial region thereof.
6. The optical imaging system of claim 1 , wherein an object-side surface of the third lens is convex in a paraxial region thereof.
7. The optical imaging system of claim 1 , wherein an object-side surface of the sixth lens is convex in a paraxial region thereof.
8. The optical imaging system of claim 1 , wherein there is an inflection point on either one or both of an object-side surface of the sixth lens and an image-side surface of the sixth lens.
9. The optical imaging system of claim 1 , wherein there is an inflection point on either one or both of the object-side surface of the seventh lens and an image-side surface of the seventh lens.
10. The optical imaging system of claim 1 , wherein the optical imaging system satisfies the following conditional expression:
50<| f 5/ f|
where f5 is a focal length of the fifth lens, and f is an overall focal length of the optical imaging system.
11. An optical imaging system comprising:
a first lens having a positive refractive power;
a second lens having a refractive power and a refractive index of 1.6 or more;
a third lens having a refractive power;
a fourth lens having a positive refractive power;
a fifth lens having a refractive power, an image-side surface that is convex in a paraxial region thereof, and a refractive index of 1.6 or more;
a sixth lens having a positive refractive power, an image-side surface that is convex in a paraxial region thereof, and a refractive index of 1.6 or more; and
a seventh lens having a refractive power and an object-side surface that is convex in a paraxial region thereof,
wherein the first lens through the seventh lens are sequentially disposed in numerical order from an object side of the optical imaging system toward an imaging plane of the optical imaging system, and
an f-number (F No.) of the optical imaging system is less than 1.7.
12. The optical imaging system of claim 11 , wherein the optical imaging system satisfies the following conditional expression:
−1.0<( R 11+ R 12)/( R 11− R 12)<1.0
where R11 is a radius of curvature of an object-side surface of the sixth lens, and R12 is a radius of curvature of the image-side surface of the sixth lens.
13. The optical imaging system of claim 11 , wherein the optical imaging system satisfies the following conditional expression:
−1.0<( R 9− R 10)/( R 9+ R 10)<1.0
where R9 is a radius of curvature of an object-side surface of the fifth lens, and R10 is a radius of curvature of the image-side surface of the fifth lens.
14. The optical imaging system of claim 11 , wherein the optical imaging system satisfies the following conditional expression:
35< V 1− V 2
where V1 is an Abbe number of the first lens, and V2 is an Abbe number of the second lens.
15. The optical imaging system of claim 11 , wherein the optical imaging system satisfies the following conditional expression:
−31< V 3− V 4
where V3 is an Abbe number of the third lens, and V4 is an Abbe number of the fourth lens.
16. The optical imaging system of claim 11 , wherein the optical imaging system satisfies the following conditional expression:
1.5< Th 1/ Sag 1
where Th1 is a center thickness of the first lens, and Sag1 is a center thickness of an object-side surface of the first lens.
17. The optical imaging system of claim 11 , wherein the optical imaging system satisfies the following conditional expression:
50<| f 5/ f|
where f5 is a focal length of the fifth lens, and f is an overall focal length of the optical imaging system.
18. An optical imaging system comprising:
a first lens having a refractive power;
a second lens having a refractive power and a refractive index of more than 1.6;
a third lens having a refractive power;
a fourth lens having a positive refractive power and an object-side surface that is convex in a paraxial region thereof;
a fifth lens having a refractive power and an image-side surface that is convex in a paraxial region thereof;
a sixth lens having a refractive power, an image-side surface that is convex in a paraxial region thereof, and a refractive index of 1.6 or more but less than the refractive index of the second lens; and
a seventh lens having a refractive power and an object-side surface that is convex in a paraxial region thereof,
wherein the first lens through the seventh lens are sequentially disposed in numerical order from an object side of the optical imaging system toward an imaging plane of the optical imaging system, and
the optical imaging system has a total number of seven lenses having a refractive power.
19. The optical imaging system of claim 18 , wherein a radius of curvature of an object-side surface of the fifth lens in a paraxial region thereof, a radius of curvature of the image-side surface of the fifth lens, a radius of curvature of an object-side surface of the sixth lens in a paraxial region thereof, and a radius of curvature of the image-side surface of the sixth lens have a same magnitude.
20. The optical imaging system of claim 18 , wherein a radius of curvature of an object-side surface of the fifth lens in a paraxial region thereof and a radius of curvature of an object-side surface of the sixth lens in a paraxial region thereof have opposite signs, and
a radius of curvature of the image-side surface of the fifth lens and a radius of curvature of the image-side surface of the sixth lens have a same sign.
21. The optical imaging system of claim 18 , wherein the optical imaging system satisfies the following conditional expression:
50<| f 5/ f|
where f5 is a focal length of the fifth lens, and f is an overall focal length of the optical imaging system.