Optical imaging system including seven lenses of +−+−++− or +−+−−+− refractive powers
An optical imaging system includes a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, and a seventh lens, sequentially arranged from an object side, wherein TTL/(2*Img HT)<0.7, where a distance on an optical axis from an object-side surface of the first lens to an imaging plane of an image sensor is TTL, and half of a diagonal length of the imaging plane of the image sensor is Img HT, and Fno <1.9, where an F-number of the optical imaging system is Fno.
1 . An optical imaging system, comprising:
a first lens having positive refractive power, a convex object-side surface in a paraxial region thereof and a concave image-side surface in a paraxial region thereof;
a second lens having negative refractive power, a convex object-side surface in a paraxial region thereof and a concave image-side surface in a paraxial region thereof;
a third lens having positive refractive power and a convex image-side surface in a paraxial region thereof;
a fourth lens having negative refractive power, a concave object-side surface in a paraxial region thereof, and a concave image-side surface in a paraxial region thereof;
a fifth lens having positive refractive power;
a sixth lens having a concave image-side surface in a paraxial region thereof; and
a seventh lens having negative refractive power,
wherein the first to seventh lenses are sequentially arranged from an object side,
wherein the optical imaging system has a total of seven lenses,
wherein f3/f>1.5 and |f4/f|>3.0 are satisfied, where f is an overall focal length of the optical imaging system, f3 is a focal length of the third lens, and f4 is a focal length of the fourth lens,
wherein v1-v3<25 is satisfied, where v1 is an Abbe number of the first lens, and v3 is an Abbe number of the third lens, and
wherein TTL/(2*Img HT)<0.7, where a distance on an optical axis from an object-side surface of the first lens to an imaging plane of an image sensor is TTL, and half of a diagonal length of the imaging plane of the image sensor is Img HT.
2 . The optical imaging system of claim 1 , wherein the third lens comprises a convex object-side surface in a paraxial region thereof.
3 . The optical imaging system of claim 1 , wherein the sixth lens comprises a convex object-side surface in a paraxial region thereof.
4 . The optical imaging system of claim 3 , wherein the seventh lens comprises a concave image-side surface in a paraxial region thereof.
5 . The optical imaging system of claim 1 , wherein 0<f1/f<2.0 is satisfied, where f1 is a focal length of the first lens.
6 . The optical imaging system of claim 1 , wherein −10.0<f2/f<0 is satisfied, where f2 is a focal length of the second lens.
7 . The optical imaging system of claim 1 , wherein −2.0<f2/f3<0.0 is satisfied, where f2 is a focal length of the second lens.
8 . The optical imaging system of claim 1 , wherein 25<v1−v2<45 is satisfied, where v1 is an Abbe number of the first lens, and v2 is an Abbe number of the second lens.
9 . The optical imaging system of claim 1 , wherein TTL/f<1.4 is satisfied, where TTL is a distance on an optical axis from the object-side surface of the first lens to an imaging plane of an image sensor, and
BFL/f<0.4 is satisfied, where BFL is a distance on the optical axis from an image-side surface of the seventh lens to the imaging plane of the image sensor.
10 . The optical imaging system of claim 1 , wherein D1/f<0.1 is satisfied, where D1 is a distance on the optical axis from the image-side surface of the first lens to the object-side surface of the second lens.
11 . The optical imaging system of claim 1 , wherein Fno<1.9 is satisfied, where Fno is an F-number of an optical imaging system.
12 . The optical imaging system of claim 1 , wherein all of object-side surfaces and image-side surfaces of the first to seventh lenses are aspherical.
13 . The optical imaging system of claim 1 , wherein at least one inflection point is formed on an object-side surface of the seventh lens.
14 . The optical imaging system of claim 1 , wherein at least one inflection point is formed on an image-side surface of the seventh lens.
15 . The optical imaging system of claim 1 , wherein a refractive index of one or more of the first to seventh lenses is 1.66 or more.
16 . The optical imaging system of claim 15 , wherein refractive indices of the second lens and the fourth lens are 1.66 or more.