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US-12619054-B2 - Small lens system

US12619054B2US 12619054 B2US12619054 B2US 12619054B2US-12619054-B2

Abstract

Disclosed is a small lens system including a first lens, a second lens, a third lens, a fourth lens, and a fifth lens sequentially arranged from an object, wherein the clear aperture of an object-side surface L 1 S 1 _CA (clear aperture) and the clear aperture of an image-side surface L 1 S 2 _CA (clear aperture) of the first lens satisfy 1<L 1 S 2 _CA/L 1 S 1 _CA<1.2.

Inventors

  • Ki Youn Noh
  • Min Su Jeong
  • Chae Yeong KIM
  • Ji Young Choi
  • Seong Jun BAE
  • In Jeong HWANG

Assignees

  • SEKONIX CO., LTD.

Dates

Publication Date
20260505
Application Date
20230804
Priority Date
20220809

Claims (18)

  1. 1 . A small lens system comprising a first lens, a second lens, a third lens, a fourth lens, and a fifth lens sequentially disposed from an object, wherein a stop is located between the second lens and the third lens, the first lens has a negative refractive power, a convex object-side surface, and a clear aperture of an image-side surface greater than a clear aperture of an object-side surface, the second lens has a positive refractive power and a convex object-side surface, the third lens has a negative refractive power, a concave object-side surface, and a concave image-side surface, the fourth lens has a negative refractive power and a convex object-side surface, the fifth lens has a positive refractive power, a convex object-side surface, and a convex image-side surface, and the clear aperture of the object-side surface L 1 S 1 _CA (clear aperture) and the clear aperture of the image-side surface L 1 S 2 _CA (clear aperture) of the first lens satisfy 1<L 1 S 2 _CA/L 1 S 1 _CA<1.2, wherein at least one of: an axial distance Sag 21 from a center of the object-side surface to an outermost side of the clear aperture of the object-side surface of the first lens and an axial distance Sag 22 from a center of the image-side surface to an outermost side of the clear aperture of the image-side surface of the first lens satisfy 0.3<Sag 22 /Sag 21 <0.6, a center thickness L 1 _CT of the first lens and a center thickness L 2 _CT of the second lens satisfy 0.16<L 1 _CT/L 2 _CT<0.22, a distance TTL from a center of the first lens to an image surface and an image surface height ImageH satisfy TTL/ImageH<4.8, and an effective focal distance f of the lens system and an entrance pupil diameter EPD of the lens system satisfy f/EPD<2.8.
  2. 2 . The small lens system according to claim 1 , wherein the axial distance Sag 21 from the center of the object-side surface to the outermost side of the clear aperture of the object-side surface of the first lens and the axial distance Sag 22 from the center of the image-side surface to the outermost side of the clear aperture of the image-side surface of the first lens satisfy 0.3<Sag 22 /Sag 21 <0.6.
  3. 3 . The small lens system according to claim 1 , wherein an effective focal distance f of the lens system and a focal distance f2 of the second lens satisfy 2<f/f2<3.
  4. 4 . The small lens system according to claim 1 , wherein the center thickness L 1 _CT of the first lens and the center thickness L 2 _CT of the second lens satisfy 0.16<L 1 _CT/L 2 _CT<0.22.
  5. 5 . The small lens system according to claim 1 , wherein the distance TTL from the center of the first lens to the image surface and the image surface height ImageH satisfy TTL/ImageH<4.8.
  6. 6 . The small lens system according to claim 1 , wherein a center thickness L 2 _CT of the second lens and an edge thickness L 2 _ET of the second lens satisfy 1.33<L 2 _CT/L 2 _ET<3.
  7. 7 . The small lens system according to claim 1 , wherein the effective focal distance f of the lens system and the entrance pupil diameter EPD of the lens system satisfy f/EPD<2.8.
  8. 8 . The small lens system according to claim 1 , wherein a field of view FOV of the lens system satisfies FOV<22°.
  9. 9 . The small lens system according to claim 1 , wherein all surfaces of the first to fifth lenses are formed as aspherical surfaces, and each of the first to fifth lenses is made of a plastic material.
  10. 10 . A small lens system comprising a first lens, a second lens, a third lens, a fourth lens, and a fifth lens sequentially disposed from an object, wherein a stop is located between the second lens and the third lens, the first lens has a positive refractive power, a convex object-side surface, and a clear aperture of an image-side surface greater than a clear aperture of the object-side surface, the second lens has a positive refractive power and a convex object-side surface, the third lens has a negative refractive power, a flat object-side surface, and a concave image-side surface, the fourth lens has a negative refractive power and a convex object-side surface, the fifth lens has a positive refractive power and a convex object-side surface, and the clear aperture of the object-side surface L 1 S 1 _CA (clear aperture) and the clear aperture of the image-side surface L 1 S 2 _CA (clear aperture) of the first lens satisfy 1<L 1 S 2 _CA/L 1 S 1 _CA<1.2, wherein at least one of: an axial distance Sag 21 from a center of the object-side surface to an outermost side of the clear aperture of the object-side surface of the first lens and an axial distance Sag 22 from a center of the image-side surface to an outermost side of the clear aperture of the image-side surface of the first lens satisfy 0.3<Sag 22 /Sag 21 <0.6, a center thickness L 1 _CT of the first lens and a center thickness L 2 _CT of the second lens satisfy 0.16<L 1 _CT/L 2 _CT<0.22, a distance TTL from a center of the first lens to an image surface and an image surface height ImageH satisfy TTL/ImageH<4.8, and an effective focal distance f of the lens system and an entrance pupil diameter EPD of the lens system satisfy f/EPD<2.8.
  11. 11 . The small lens system according to claim 10 , wherein the axial distance Sag 21 from the center of the object-side surface to the outermost side of the clear aperture of the object-side surface of the first lens and the axial distance Sag 22 from the center of the image-side surface to the outermost side of the clear aperture of the image-side surface of the first lens satisfy 0.3<Sag 22 /Sag 21 <0.6.
  12. 12 . The small lens system according to claim 10 , wherein an effective focal distance f of the lens system and a focal distance f2 of the second lens satisfy 2<f/f2<3.
  13. 13 . The small lens system according to claim 10 , wherein the center thickness L 1 _CT of the first lens and the center thickness L 2 _CT of the second lens satisfy 0.16<L 1 _CT/L 2 _CT<0.22.
  14. 14 . The small lens system according to claim 10 , wherein the distance TTL from the center of the first lens to the image surface and the image surface height ImageH satisfy TTL/ImageH<4.8.
  15. 15 . The small lens system according to claim 10 , wherein a center thickness L 2 _CT of the second lens and an edge thickness L 2 _ET of the second lens satisfy 1.33<L 2 _CT/L 2 _ET<3.
  16. 16 . The small lens system according to claim 10 , wherein the effective focal distance f of the lens system and the entrance pupil diameter EPD of the lens system satisfy f/EPD<2.8.
  17. 17 . The small lens system according to claim 10 , wherein a field of view FOV of the lens system satisfies FOV<22°.
  18. 18 . The small lens system according to claim 10 , wherein all surfaces of the first to fifth lenses are formed as aspherical surfaces, and each of the first to fifth lenses is made of a plastic material.

Description

CROSS REFERENCE TO RELATED APPLICATION The present application claims priority to Korean Patent Application No. 10-2022-0098925, filed Aug. 9, 2022, the entire contents of which is incorporated herein for all purposes by this reference. BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to a small lens system including a total of five lenses, and more particularly to a small lens system configured such that aberration of the lens system is corrected while the lens system is small and lightweight by appropriately designing the refractive power, shape, etc. of each lens. Description of the Related Art With recent increasing demand for high quality, high performance, miniaturization, and weight lightening of electronic equipment having a camera function, particularly smartphones, research to realize the same through improvement in performance of a subminiature lens optical system has been conducted. In addition, as zoom functions of smartphones are extended and foldable smartphones are launched, the overall length of a lens system has become shorter and shorter and high-resolution, miniaturization, and weight lightening technologies are in greater demand. Furthermore, it is advantageous to miniaturize a camera by reducing the size of a camera opening. To this end, it is important to reduce an effective diameter of a first lens. Particularly, for a small lens mounted in a smartphone, it is advantageous to reduce the length of the lens system (total track length) as much as possible due to limitation in the thickness of the smartphone. An optical lens system disclosed in Korean Patent Application Publication No. 10-2022-0019487, as the prior art, includes a total of five lenses sequentially arranged from an object, wherein TTL/ImageH=5.363, which is long. In addition, Fno=2.84. That is, the diameter of a stop is small, whereby picture quality is low, and therefore there is a limitation in designing a small high-resolution lens system. SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and it is an object of the present invention to provide a small lens system including a total of five lenses and configured such that aberration of the lens system is corrected while the lens system is small and lightweight by appropriately designing the refractive power, shape, etc. of each lens. In accordance with an aspect of the present invention, the above and other objects can be accomplished by the provision of a small lens system including a first lens, a second lens, a third lens, a fourth lens, and a fifth lens sequentially disposed from an object, wherein a stop is located between the second lens and the third lens, the first lens has a negative refractive power, a convex object-side surface, and a clear aperture of an image-side surface greater than the clear aperture of an object-side surface, the second lens has a positive refractive power and a convex object-side surface, the third lens has a negative refractive power, a concave object-side surface, and a concave image-side surface, the fourth lens has a negative refractive power and a convex object-side surface, the fifth lens has a positive refractive power, a convex object-side surface, and a convex image-side surface, and the clear aperture of the object-side surface L1S1_CA (clear aperture) and the clear aperture of the image-side surface L1S2_CA (clear aperture) of the first lens satisfy 1<L1S2_CA/L1S1_CA<1.2. In accordance with another aspect of the present invention, there is provided a small lens system including a first lens, a second lens, a third lens, a fourth lens, and a fifth lens sequentially disposed from an object, wherein a stop is located between the second lens and the third lens, the first lens has a positive refractive power, a convex object-side surface, and a clear aperture of an image-side surface greater than the clear aperture of the object-side surface, the second lens has a positive refractive power and a convex object-side surface, the third lens has a negative refractive power, a flat object-side surface, and a concave image-side surface, the fourth lens has a negative refractive power and a convex object-side surface, the fifth lens has a positive refractive power and a convex object-side surface, and the clear aperture of the object-side surface L1S1_CA (clear aperture) and the clear aperture of the image-side surface L1S2_CA (clear aperture) of the first lens satisfy 1<L1S2_CA/L1S1_CA<1.2. In accordance with a further aspect of the present invention, there is provided a small lens system including a first lens, a second lens, a third lens, a fourth lens, and a fifth lens sequentially disposed from an object, wherein a stop is located between the second lens and the third lens, the first lens has a negative infinite refractive power, a convex object-side surface, and a clear aperture of an image-side surface greater than the clear aperture of the object-side surfa