Rear conversion lenses

Patent metadata

Field	Value
Publication number	US-9784954-B2
Application number	US-201614994471-A
Country	US
Kind code	B2
Filing date	Jan 13, 2016
Priority date	Jan 30, 2015
Publication date	Oct 10, 2017
Grant date	Oct 10, 2017

Abstract

A rear conversion lens, which may include a plurality of lenses may be disposed at a side of master lenses facing an image side for varying a focal length, and may include: a first lens having a positive refractive power; a second lens having a biconcave shape; a third lens having a positive refractive power; a fourth lens having a positive refractive power; and a fifth lens having a negative refractive power. The first to fifth lenses may be sequentially arranged in a direction from an object side to the image side.

First claim

What is claimed is:

1. A rear conversion lens disposed at a side of a master lens facing an image side for varying a focal length, the rear conversion lens comprising:
a first lens having a meniscus shape convex toward an image side and a positive refractive power;
a second lens having a biconcave shape;
a third lens having a positive refractive power, wherein an absolute value of curvature of a side surface of the third lens facing toward an object side is greater than an absolute value of curvature of an image-side surface of the third lens;
a fourth lens having a positive refractive power and a biconvex shape; and
a fifth lens having a negative refractive power,
wherein the first, second, third, fourth, and fifth lenses are sequentially arranged in a direction from an object side to the image side, and
wherein the rear conversion lens comprises a first lens group disposed at the object side and a second lens group disposed at the image side with a maximum air gap therebetween, wherein a ratio of a focal length of the first lens group with respect to an absolute value of a focal length of the rear conversion lens is between 0.35 and 0.90.

2. The rear conversion lens of claim 1 , wherein the first lens has a refractive index at a d-line that is greater than 1.85.

3. The rear conversion lens of claim 1 , wherein the second lens has a refractive index of greater than 1.85 at a d-line.

4. The rear conversion lens of claim 1 , wherein the fifth lens has a refractive index of greater than 1.85 at a d-line.

5. The rear conversion lens of claim 1 , wherein the fourth lens has a refractive index of greater than 1.65 at a d-line.

6. The rear conversion lens of claim 1 , wherein a ratio of a back focal length of the rear conversion lens with respect to a maximum image height is between 0.8 and 1.2.

7. The rear conversion lens of claim 1 , wherein the focal length of the first lens group with respect to a focal length of the second lens group is between −2.1 and −1.1.

8. The rear conversion lenses of claim 1 , wherein the second lens and the third lens are cemented together as a doublet lens.

9. The rear conversion lenses of claim 1 , wherein at least one of the first lens, the fourth lens, and the fifth lens comprises at least one aspheric surface.

10. A rear conversion lens including a plurality of lenses, the rear conversion lens being disposed at a side of one or more master lenses facing an image side for varying a focal length, the rear conversion lens comprising: a first lens having a positive refractive power, a second lens having a negative refractive power, a third lens having a positive refractive power, a fourth lens having a positive refractive power, and a fifth lens having a negative refractive power,
wherein the first to fifth lenses are sequentially arranged in a direction from an object side to the image side, and wherein N1>1.85, N2>1.85, and N5>1.85, wherein N1 denotes a refractive index of the first lens at a d-line, N2 denotes a refractive index of the second lens at the d-line, and N5 denotes a refractive index of the fifth lens at the d-line.

11. The rear conversion lenses of claim 10 , wherein N4<1.65,
wherein N4 denotes a refractive index of the fourth lens at the d-line.

12. The rear conversion lenses of claim 10 , wherein 0.8<fbRC/Y<1.2, wherein fbRC denotes a back focal length of the rear conversion lenses at a predetermined magnification and Y denotes a maximum image height.

13. The rear conversion lens of claim 10 , wherein the rear conversion lenses are divided into a first lens group disposed at the object side and a second lens group disposed at the image side with a maximum air gap therebetween, and wherein 0.35<f1/|fRC|<0.90, wherein f1 denotes a focal length of the first lens group and fRC denotes a focal length of the rear conversion lenses.

14. The rear conversion lens of claim 13 , wherein
−2.1<f1/f2<−1.1, wherein f2 denotes a focal length of the second lens group.

15. The rear conversion lens of claim 10 , wherein the second lens and the third lens are cemented together as a doublet lens.

16. The rear conversion lens of claim 10 , wherein at least one of the first lens, the fourth lens, and the fifth lens comprises at least one aspheric surface.

Assignees

• Samsung Electronics Co Ltd

Inventors

• Yoneyama Shuji

Classifications

• G02B9/60 Primary

  having five components only · CPC title

• G02B7/105

  with movable lens means specially adapted for focusing at close distances · CPC title

• G02B15/22

  with movable lens means specially adapted for focusing at close distances · CPC title

• G02B15/10 Primary

  by adding a part, e.g. close-up attachment · CPC title

• G02B13/0045

  having five or more lenses · CPC title