Search

US-20260126618-A1 - OPTICAL IMAGING SYSTEM

US20260126618A1US 20260126618 A1US20260126618 A1US 20260126618A1US-20260126618-A1

Abstract

An optical imaging system includes a first lens having positive refractive power, a second lens having positive refractive power, a third lens having positive refractive power, and a fourth lens having positive refractive power, and an F No. of the optical imaging system is equal to or less than 1.0. The optical imaging system is capable of achieving miniaturization while capturing an image at low illumination.

Inventors

  • Hag Chul KIM
  • Yong Joo Jo

Assignees

  • SAMSUNG ELECTRO-MECHANICS CO., LTD.

Dates

Publication Date
20260507
Application Date
20260107
Priority Date
20181119

Claims (12)

  1. 1 . An optical imaging system, comprising: a first lens having a refractive power; a second lens having positive refractive power; a third lens having a convex object-side surface in a paraxial region thereof; and a fourth lens having positive refractive power, wherein the first to fourth lenses are sequentially disposed from an object side to an image surface of the optical imaging system, wherein the optical imaging system has a total number of four lenses with refractive power, wherein a thickness of the third lens is greater than a distance from an image-side surface of the second lens to an object-side surface of the third lens, and wherein an absolute value of a radius of curvature of an image-side surface of the second lens is greater than an absolute value of a radius of curvature of an image-side surface of the third lens.
  2. 2 . The optical imaging system of claim 1 , wherein the first lens has a convex object-side surface in a paraxial region thereof.
  3. 3 . The optical imaging system of claim 1 , wherein the second lens has a convex object-side surface in a paraxial region thereof.
  4. 4 . The optical imaging system of claim 1 , wherein the second lens has a concave image-side surface in a paraxial region thereof.
  5. 5 . The optical imaging system of claim 1 , wherein the fourth lens has a convex object-side surface in a paraxial region thereof.
  6. 6 . The optical imaging system of claim 1 , wherein 0.3<R1/f<2.0, where R1 is a radius of curvature of an object-side surface of the first lens and f is a focal length of the optical imaging system.
  7. 7 . An optical imaging system, comprising: a first lens having a refractive power; a second lens having positive refractive power; a third lens having a refractive power; and a fourth lens having positive refractive power, wherein the first to fourth lenses are sequentially disposed from an object side to an image surface of the optical imaging system, wherein the optical imaging system has a total number of four lenses with refractive power, wherein 1.580<Nd1<1.640, where Nd1 is a refractive index of the first lens, wherein a thickness of the third lens is greater than a distance from an image-side surface of the second lens to an object-side surface of the third lens, and wherein an absolute value of a radius of curvature of an image-side surface of the second lens is greater than an absolute value of a radius of curvature of an image-side surface of the third lens.
  8. 8 . The optical imaging system of claim 7 , wherein the first lens has a convex object-side surface in a paraxial region thereof.
  9. 9 . The optical imaging system of claim 7 , wherein the second lens has a convex object-side surface in a paraxial region thereof.
  10. 10 . The optical imaging system of claim 7 , wherein the second lens has a concave image-side surface in a paraxial region thereof.
  11. 11 . The optical imaging system of claim 7 , wherein the fourth lens has a convex object-side surface in a paraxial region thereof.
  12. 12 . The optical imaging system of claim 7 , wherein 0.3<R1/f<2.0, where R1 is a radius of curvature of an object-side surface of the first lens and f is a focal length of the optical imaging system.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application is a continuation of U.S. application Ser. No. 18/584,202 filed on Feb. 22, 2024, which is a continuation of U.S. application Ser. No. 17/408,749 filed on Aug. 23, 2021, now U.S. Pat. No. 11,940,666 issued on Mar. 26, 2024 which is a continuation of U.S. application Ser. No. 16/506,063 filed on Jul. 9, 2019, now U.S. Pat. No. 11,125,973 issued on Sep. 21, 2021, which claims the benefit under 35 USC 119(a) of Korean Patent Application No. 10-2018-0142402 filed on Nov. 19, 2018 in the Korean Intellectual Property Office, the entire disclosures of which are incorporated herein by reference for all purposes. BACKGROUND 1. Field The following description relates to an optical imaging system capable of implementing a bright image. 2. Description of Background An optical system for a camera, mounted in a small terminal, has a short total length, and thus, it may be difficult to implement a low F number. In this regard, a camera for a small terminal may not be able to obtain a high-resolution image pickup of an object and image an object in a low-illuminance environment. SUMMARY This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter. An optical imaging system capable of imaging a subject in a low-illuminance environment while being mounted on a small terminal. In one general aspect, an optical imaging system includes a first lens having positive refractive power, a second lens having positive refractive power, a third lens having positive refractive power, and a fourth lens having positive refractive power, and an F No. of the optical imaging system is equal to or less than 1.0. Visible light transmission of the first lens may be equal to or less than 5%. The second lens may include an inflection point on an image-side surface. The third lens may include a convex image-side surface. The fourth lens may include a concave image-side surface. The optical imaging system may satisfy 5.0<(f1+f2)/f<80, where f is a focal length of the optical imaging system, f1 is a focal length of the first lens, and f2 is a focal length of the second lens. The optical imaging system may satisfy 1.0<f3/f<2.5, where f is a focal length of the optical imaging system, and f3 is a focal length of the third lens. The optical imaging system may satisfy 1.0<f4/f<6.0, where f is a focal length of the optical imaging system, and f4 is a focal length of the fourth lens. The optical imaging system may satisfy 0.3<R1/f<2.0, where f is a focal length of the optical imaging system, and R1 is a radius of curvature of an object-side surface of the first lens. The optical imaging system may satisfy 0.3<R3/f<2.0, where f is a focal length of the optical imaging system, and R3 is a radius of curvature of an object-side surface of the second lens. The optical imaging system may satisfy 5.0<R5/f<80, where f is a focal length of the optical imaging system, and R5 is a radius of curvature of an object-side surface of the third lens. The optical imaging system may satisfy 1.580<Nd1<1.640, where Nd1 is a refractive index of the first lens. In another general aspect, an optical imaging system includes lenses sequentially disposed from an object side to an image surface of the optical imaging system, and each of the lenses has refractive power. A lens closest to the object side, among the lenses, has positive refractive power, and an F No. of the optical imaging system is equal to or less than 1.0. The optical imaging system may satisfy 1.0<TTL/f<2.0, where TTL is a distance from an object-side surface of the lens closest to the object side to the image surface, and f is a focal length of the optical imaging system. The optical imaging system may satisfy 0.3<R1/TTL<5.0, where TTL is a distance from an object-side surface of the lens closest to the object side to the image surface, and R1 is a focal length of the lens closest to the object side. The optical imaging system may satisfy 0.5<EPD/TTL<0.7, where TTL is a distance from an object-side surface of the lens closest to the object side to the image surface, and EPD is a diameter of an entrance pupil. Other features and aspects will be apparent from the following detailed description, the drawings, and the claims. BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a view illustrating an optical imaging system according to a first example. FIG. 2 is an aberration curve of the optical imaging system illustrated in FIG. 1. FIG. 3 is a view illustrating an optical imaging system according to a second example. FIG. 4 is an aberration curve of the optical imaging system illustrated in FIG. 3. FIG. 5 is a view illustrating an optical imaging system according to a third example. FIG. 6 is