Optical imaging system
An optical imaging system is provided. The optical imaging system includes a first lens, a second lens, a third lens, a fourth lens, and a fifth lens disposed in order from an object side to an imaging side. The first lens has positive refractive power, while the second lens has negative refractive power. TTL>10.2 mm, and TTL/(2×IMG HT)≤1.7, where TTL is a distance from an object-side surface of the first lens to an imaging plane on an optical axis, and IMG HT is equal to half a diagonal length of the imaging plane.
1 . An optical imaging system, comprising:
a first lens, a second lens, a third lens, a fourth lens, and a fifth lens disposed in order from an object side to an imaging side, wherein:
the optical imaging system has a total of five lenses,
the first lens has positive refractive power and a convex object-side surface in a paraxial region thereof, the second lens has negative refractive power, and the third lens has positive refractive power; and
TTL> 10.2 mm, R 1/ f≤ 0.35, 1.5< f/IMG HT< 3.5, and TTL /(2× IMG HT )≤1.7,
where TTL is a distance from an object-side surface of the first lens to an imaging plane on an optical axis, R1 is a radius of curvature of the object-side surface of the first lens, f is a total focal length of the optical imaging system, and IMG HT is equal to half a diagonal length of the imaging plane.
2 . The optical imaging system of claim 1 , wherein:
IMG HT≥ 4.5 mm.
3 . The optical imaging system of claim 1 , wherein:
n 2+ n 3>3.20,
where n2 is a refractive index of the second lens, and n3 is a refractive index of the third lens.
4 . The optical imaging system of claim 1 , wherein:
| f/f 1+ f/f 2|<1.2,
where f1 is a focal length of the first lens, and f2 is a focal length of the second lens.
5 . The optical imaging system of claim 1 , wherein:
BFL/f< 0.4,
where BFL is a distance from an image-side surface of the fifth lens to the imaging plane on an optical axis.
6 . The optical imaging system of claim 1 , wherein:
0.80≤ TTL/f≤ 1.05.
7 . The optical imaging system of claim 1 , wherein:
0≤ D 1/ f≤ 0.05,
where D1 is a distance between an image-side surface of the first lens and an object-side surface of the second lens on an optical axis.
8 . The optical imaging system of claim 1 , wherein:
the fourth lens has negative refractive power, and the fifth lens has negative refractive power.
9 . The optical imaging system of claim 1 , wherein:
the fourth lens has positive refractive power, and the fifth lens has negative refractive power.
10 . The optical imaging system of claim 1 , wherein:
a refractive index of at least one of the second and third lenses is greater than 1.64.
11 . The optical imaging system of claim 1 , wherein:
an absolute value of a focal length of each of the first and second lenses is less than an absolute value of focal lengths of each of the third lens, the fourth lens, and the fifth lens.