ZOOM LENS AND IMAGING APPARATUS

• US 20180299642A1
• Filed: 06/21/2018
• Published: 10/18/2018
• Est. Priority Date: 01/27/2016
• Status: Active Grant

• Current Assignee: Fujifilm Corporation (Fujifilm Holdings Corporation)
• Original Assignee: Fujifilm Corporation (Fujifilm Holdings Corporation)
• Inventors: YONEZAWA, Masaru, IKEDA, Shinkichi
• Granted Patent: US 10,641,986 B2
• Time in Patent Office: Days
• CPC Class Codes: G02B 13/0015 characterised by the lens design
• CPC Class Codes: G02B 13/0045 having five or more lenses
• CPC Class Codes: G02B 13/009 having zoom function
• CPC Class Codes: G02B 13/18 with lenses having one or more non-spherical faces, e.g. for reducing geometrical aberration G02B13/002 takes precedence
• CPC Class Codes: G02B 15/14 by axial movement of one or more lenses or groups of lenses relative to the image plane for continuously varying the equivalent focal length of the objective
• CPC Class Codes: G02B 15/144109 arranged +--+
• CPC Class Codes: G02B 15/167 having an additional fixed front lens or group of lenses
• CPC Class Codes: G02B 15/20 having an additional movable lens or lens group for varying the objective focal length
• CPC Class Codes: G02B 3/04 with continuous faces that are rotationally symmetrical but deviate from a true sphere , e.g. so called "aspheric" lenses
• CPC Class Codes: G02B 5/005 Diaphragms for cameras G03B9/02
• CPC Class Codes: G02B 7/10 by relative axial movement of several lenses, e.g. of varifocal objective lens
• CPC Class Codes: G02B 9/34 having four components only
• CPC Class Codes: G02B 9/60 having five components only
• CPC Class Codes: G02B 9/62 having six components only
• CPC Class Codes: G02B 9/64 having more than six components

Abstract

The zoom lens includes, in order from the object side: a first lens group G1 that has a positive refractive power and remains stationary during zooming; a plurality of movable lens groups that move by changing distances between groups adjacent to each other in a direction of an optical axis during zooming; and a final lens group Ge that has a positive refractive power and remains stationary during zooming. At least one movable lens group has a negative refractive power. The first lens group G1 has an image side positive lens, which is a positive lens disposed to be closest to the image side, and one or more positive lenses which are disposed to be closer to the object side than the image side positive lens. The zoom lens satisfies predetermined conditional expressions relating to the image side positive lens.

Claims

1. A zoom lens comprising, in order from an object side:

a first lens group that has a positive refractive power and remains stationary with respect to an image plane during zooming;

a plurality of movable lens groups that move by changing distances between groups adjacent to each other in a direction of an optical axis during zooming; and

a final lens group that has a positive refractive power and remains stationary with respect to the image plane during zooming,

wherein in the plurality of movable lens groups, at least one movable lens group has a negative refractive power,

wherein the first lens group has an image side positive lens, which is a positive lens disposed to be closest to the image side, and one or more positive lenses which are disposed to be closer to the object side than the image side positive lens, and

wherein all Conditional Expressions (1) to (5) are satisfied,

0.25<

fl/fz<

0.7 

 

(1),

55<

ν

z<

68 

 

(2),

15<

ν

mx−

ν

z<

50 

 

(3),

2.395<

Nz+0.012×

ν

z 

 

(4), and

0.634<

θ

gFz+0.001625×

ν

z<

0.647 

 

(5),

where fl is a focal length of the first lens group,

fz is a focal length of the image side positive lens,

ν

z is an Abbe number of the image side positive lens at the d line,

ν

mx is an Abbe number of a positive lens, of which the Abbe number at the d line is at a maximum value, among positive lenses disposed to be closer to the object side than the image side positive lens,

Nz is a refractive index of the image side positive lens at the d line, and

θ

gFz is a partial dispersion ratio of the image side positive lens between the g line and the F line.

2. The zoom lens according to claim 1, wherein Conditional Expression (6) is satisfied,

1.2<

ft/fl<

2.8 

 

(6),

where ft is a focal length of the whole system at a telephoto end.

3. The zoom lens according to claim 1, wherein Conditional Expression (7) is satisfied,

0.1<

fw/fl<

0.4 

 

(7),

where fw is a focal length of the whole system at a wide-angle end.

4. The zoom lens according to claim 1, wherein focusing is performed by moving one or more lenses in the first lens group in the direction of the optical axis.

5. The zoom lens according to claim 1, wherein in the plurality of movable lens groups, a movable lens group closest to the image side has a negative refractive power.

6. The zoom lens according to claim 1, wherein the first lens group includes, in order from the object side, a first lens group front group that has a negative refractive power and remains stationary with respect to the image plane during focusing, a first lens group intermediate group that has a positive refractive power and moves in the direction of the optical axis during focusing, and a first lens group rear group that is set such that a distance in the direction of the optical axis between the first lens group rear group and the first lens group intermediate group changes during focusing and has a positive refractive power.

7. The zoom lens according to claim 6, wherein Conditional Expression (8) is satisfied,

0.5<

flc/fz<

0.7 

 

(8),

where flc is a focal length of the first lens group rear group.

8. The zoom lens according to claim 6, wherein the first lens group front group has at least one negative lens that satisfies Conditional Expressions (9) and (10),

55<

ν

n 

 

(9), and

0.635<

θ

gFn+0.001625×

ν

n<

0.675 

 

(10),

where ν

n is an Abbe number of the negative lens of the first lens group front group at the d line, and

θ

gFn is a partial dispersion ratio of the negative lens of the first lens group front group between the g line and the F line.

9. The zoom lens according to claim 6, wherein the first lens group rear group has, successively in order from the object side, a cemented lens which is formed by cementing a negative lens and a positive lens in order from the object side, and a positive lens.

10. The zoom lens according to claim 6, wherein the first lens group rear group remains stationary with respect to the image plane during focusing.

11. The zoom lens according to claim 1, wherein Conditional Expression (1-1) is satisfied.

0.35<

fl/fz<

0.65 

 

(1-1)

12. The zoom lens according to claim 1, wherein Conditional Expression (2-1) is satisfied.

56<

ν

z<

65 

 

(2-1)

13. The zoom lens according to claim 1, wherein Conditional Expression (3-1) is satisfied.

30<

ν

mx−

ν

z<

45 

 

(3-1)

14. The zoom lens according to claim 1, wherein Conditional Expression (6-1) is satisfied,

1.5<

ft/fl<

2.5 

 

(6-1),

where ft is a focal length of the whole system at a telephoto end.

15. The zoom lens according to claim 1, wherein Conditional Expression (7-1) is satisfied,

0.11<

fw/fl<

0.35 

 

(7-1),

where fw is a focal length of the whole system at a wide-angle end.

16. The zoom lens according to claim 6, wherein Conditional Expression (8-1) is satisfied,

0.55<

flc/fz<

0.68 

 

(8-1),

where flc is a focal length of the first lens group rear group

17. The zoom lens according to claim 1, wherein the plurality of movable lens groups includes a lens group having a negative refractive power and a lens group having a negative refractive power.

18. The zoom lens according to claim 1, wherein the plurality of movable lens groups includes, in order from the object side, a lens group having a positive refractive power, a lens group having a negative refractive power, and a lens group having a negative refractive power.

19. The zoom lens according to claim 1, wherein the plurality of movable lens groups includes, in order from the object side, a lens group having a negative refractive power, a lens group having a positive refractive power, and a lens group having a negative refractive power.

20. An imaging apparatus comprising the zoom lens according to claim 1.