Zoom lens system

Patent metadata

Field	Value
Publication number	US-9753263-B2
Application number	US-201514855851-A
Country	US
Kind code	B2
Filing date	Sep 16, 2015
Priority date	Jun 9, 2015
Publication date	Sep 5, 2017
Grant date	Sep 5, 2017

Abstract

A zoom lens system includes: a first lens group having a negative refractive power; a second lens group having a positive refractive power; and an aperture between the first and second lens groups, wherein the first lens group and the second lens group are sequentially arranged from an object side to an image side, wherein the zoom lens system performs zooming and focusing by moving the second and first lens groups, respectively, along an optical axis, and satisfies

2.5<( f w /f t )×( T w /Y )<4.5,
where f w denotes an entire focal length at a wide-angle end, f t denotes an entire focal length at a telephoto end, and Tw denotes a distance between an image plane and an object side lens surface of a lens closest to the object side of the first lens group at the wide-angle end, and Y denotes a radical axis image height.

First claim

What is claimed is:

1. A zoom lens system comprising:
a first lens group having a negative refractive power;
a second lens group having a positive refractive power; and
an aperture disposed between the first lens group and the second lens group,
wherein the first lens group and the second lens group are sequentially arranged from an object side to an image side,
wherein the zoom lens system is configured to perform zooming by moving the second lens group along an optical axis, and perform focusing by moving the first lens group along the optical axis, and
wherein the zoom lens system satisfies a conditional expression below:
2.5<( f w /f 1 )×( T w /Y )<4.5,

where f w denotes an entire focal length at a wide-angle end, f t denotes an entire focal length at a telephoto end, and Tw denotes a distance between an image plane and an object side lens surface of a lens that is closest to the object side of the first lens group at the wide-angle end, and Y denotes a radical axis image height.

2. The zoom lens system of claim 1 , wherein the zoom lens system satisfies conditional expressions below:
2.5 <|f 1 /f w |<3.0,
0.8 <|f 1 /f 2 |<1.0, and
3.1 <|f 2 /f w |<3.5,
where f 1 denotes a focal length of the first lens group, and f 2 denotes a focal length of the second lens group.

3. The zoom lens system of claim 1 , wherein the first lens group comprises:
a first lens having a negative refractive power;
a second lens having a negative refractive power; and
a third lens having a positive refractive power,
wherein the first lens, the second lens, and the third lens are sequentially arranged from the object side to the image side.

4. The zoom lens system of claim 3 , wherein the second lens and the third lens are cemented lenses.

5. The zoom lens system of claim 4 , wherein the zoom lens system satisfies a conditional expressions below:
vd 12 >65, and
Nd 13 >1.90,
where vd 12 denotes an Abbe number of the second lens, and Nd 13 denotes a refractive index of the third lens at a d-line.

6. The zoom lens system of claim 1 , wherein the second lens group comprises:
a fourth lens, a fifth lens, and a sixth lens each having a positive refractive power;
a seventh lens having a negative refractive power; and
an eighth lens and a ninth lens each having a positive refractive power,
wherein the fourth lens, the fifth lens, the sixth lens, the seventh lens and the eighth lens are sequentially arranged from the object side to the image side.

7. The zoom lens system of claim 6 , wherein the fourth lens comprises at least one aspherical lens,
wherein the zoom lens system satisfies a conditional expression below:
vd 24 >60,

where vd 24 denotes an Abbe number of the fourth lens.

8. The zoom lens system of claim 6 , wherein the sixth lens, the seventh lens, and the eighth lens are triple cemented lenses.

9. The zoom lens system of claim 8 , wherein the zoom lens system satisfies a conditional expression below:
3.5<|( vd 28 −vd 27 )|/ vd 26 <5.0,
where vd 26 , vd 27 , and vd 28 respectively denote Abbe numbers of the sixth lens, the seventh lens, and the eighth lens.

10. The zoom lens system of claim 8 , wherein the zoom lens system satisfies a conditional expression below:
vd 26 <vd 27 <vd 28 ,
where vd 26 , vd 27 , and vd 28 respectively denote Abbe numbers of the sixth lens, the seventh lens, and the eighth lens.

11. The zoom lens system of claim 1 , further comprising a near infrared light blocking filter between the first lens group and the second lens group.

12. A zoom lens system comprising:
a first lens group having a negative refractive power;
a second lens group having a positive refractive power; and
an aperture disposed between the first lens group and the second lens group,
wherein the first lens group and the second lens group are sequentially arranged from an object side to an image side,
wherein the zoom lens system is configured to perform zooming by moving the second lens group along an optical axis and perform focusing by moving the first lens group along the optical axis,
wherein the second lens group comprises:
a fourth lens, a fifth lens, and a sixth lens each having a positive refractive power;
a seventh lens having a negative refractive power; and
an eighth lens and a ninth lens each having a positive refractive power,
wherein the fourth lens, the fifth lens, the sixth lens, the seventh lens and the eighth lens are sequentially arranged from the object side to the image side,
wherein the zoom lens system satisfies a conditional expression below:
3.5<|( vd 28 −vd 27 )|/ vd 26 <5.0,

where vd 26 , vd 27 , and vd 28 respectively denote Abbe numbers of the sixth lens, the seventh lens, and the eighth lens.

13. The zoom lens system of claim 12 , wherein the sixth lens, the seventh lens, and the eighth lens are cemented lenses.

14. The zoom lens system of claim 13 , wherein the zoom lens system satisfies a conditional expression below:
vd 26 <vd 27 <vd 28 ,
where vd 26 , vd 27 , and vd 28 respectively denote Abbe numbers of the sixth lens, the seventh lens, and the eighth lens.

15. The zoom lens system of claim 12 , wherein the fourth lens comprises at least one aspherical lens, and
wherein the zoom lens system satisfies a conditional expression below:
vd 24 >60,

where vd 24 denotes an Abbe number of the fourth lens.

16. The zoom lens system of claim 12 , wherein the zoom lens system satisfies a conditional expression below:
2.5<( f w /f 1 )×( T w /Y )<4.5,

where f w denotes an entire focal length at a wide-angle end, f t denotes an entire focal length at a telephoto end, and Tw denotes a distance between an image plane and an object side lens surface of a lens that is closest to the object side of the first lens group at a wide-angle end, and Y denotes a radical axis image height.

17. The zoom lens system of claim 12 , wherein the zoom lens system satisfies conditional expressions below:
2.5 <|f 1 /f w |<3.0,
0.8 <|f 1 /f 2 |<1.0, and
3.1 <|f 2 /f w |<3.5,
where f 1 denotes a focal length of the first lens group, and f 2 denotes a focal length of the second lens group.

18. The zoom lens system of claim 12 , wherein the first lens group comprises:
a first lens having a negative refractive power;
a second lens having a negative refractive power; and
a third lens having a positive refractive power,
wherein the first lens, the second lens, and the third lens are sequentially arranged from the object side to the image side, and the second lens and the third lens are cemented lenses.

19. The zoom lens system of claim 18 , wherein the zoom lens system satisfies conditional expressions below:
vd 12 >65, and
Nd 13 >1.90,
where vd 12 denotes an Abbe number of the second lens, and Nd 13 denotes a refractive index of the third lens at a d-line.

20. The zoom lens system of claim 11 , further comprising a near infrared light blocking filter between the first lens group and the second lens group.

Assignees

• Hanwha Techwin Co Ltd

Inventors

• Yoo Jiyeong

Classifications

• G02B15/163

  having a first movable lens or lens group and a second movable lens or lens group, both in front of a fixed lens or lens group (G02B15/177 takes precedence) · CPC title

• G02B15/177 Primary

  having a negative front lens or group of lenses · CPC title

• G02B5/208

  for use with infrared or ultraviolet radiation, e.g. for separating visible light from infrared and/or ultraviolet radiation · CPC title

• G02B15/20

  having an additional movable lens or lens group for varying the objective focal length · CPC title

• G02B13/146

  with corrections for use in multiple wavelength bands, such as infrared and visible light, e.g. FLIR systems · CPC title