Zoom Lens and Image Pickup Apparatus Using the Same

• US 20140354858A1
• Filed: 05/29/2014
• Published: 12/04/2014
• Est. Priority Date: 05/30/2013
• Status: Active Grant

• Current Assignee: OM Digital Solutions Corporation
• Original Assignee: Olympus Corporation, Olympus Imaging Corporation (Olympus Corporation)
• Inventors: Kawamura, Kazuteru, Naito, Akiko, Yokoyama, Keitaro, Takahashi, Toshio
• Granted Patent: US 9,465,204 B2
• Time in Patent Office: Days
• US Class Current: 348/240.3
• CPC Class Codes: G02B 13/002 having at least one aspherical surface
• CPC Class Codes: G02B 13/0045 having five or more lenses
• CPC Class Codes: G02B 13/006 at least one element being a compound optical element, e.g. cemented elements
• CPC Class Codes: G02B 13/009 having zoom function
• CPC Class Codes: G02B 13/04 Reversed telephoto objectives
• 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 15/144511 arranged -+-+
• CPC Class Codes: G02B 15/16 with interdependent non-linearly related movements between one lens or lens group, and another lens or lens group G02B15/22 takes precedence
• CPC Class Codes: G02B 15/177 having a negative 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 27/0025 for optical correction, e.g. distorsion, aberration
• CPC Class Codes: G02B 3/14 of variable focal length
• CPC Class Codes: G02B 5/005 Diaphragms for cameras G03B9/02
• CPC Class Codes: G02B 7/09 adapted for automatic focusing or varying magnification
• CPC Class Codes: G02B 9/00 Optical objectives characterised both by the number of the components and their arrangements according to their sign, i.e. + or - G02B15/00 takes precedence
• CPC Class Codes: G02B 9/34 having four components only
• CPC Class Codes: G02B 9/60 having five components only
• CPC Class Codes: G03B 13/18 Focusing aids

Abstract

A zoom lens includes a first lens unit having a negative refractive power, a second lens unit having a positive refractive power, and a third lens unit having a negative refractive power. At the time of zooming, distances between the lens units change, and a distance between the first lens unit and the second lens unit at a telephoto end is shorter than at a wide angle end. An aperture stop is disposed on the image side of an image-side surface of the first lens unit, and on the object side of an image-side surface of the second lens unit. The second lens unit includes two sub lens units. The object-side sub lens unit in the second lens unit includes one lens component. The following conditional expressions are satisfied.

3.0<ΔD₁₂/ER_S<4.5

1.05<|f₃/f_UN21|<2.1

Claims

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

a first lens unit having a negative refractive power;

a second lens unit having a positive refractive power; and

a third lens unit having a negative refractive power, wherein

at the time of zooming, distances between the lens units change, and

a distance between the first lens unit and the second lens unit at a telephoto end is shorter than a distance between the first lens unit and the second lens unit at a wide angle end, and

an aperture stop is disposed on the image side of an image-side surface of the first lens unit, and on the object side of an image-side surface of the second lens unit, and

the second lens unit includes in order from the object side to the image side, an object-side sub lens unit having a positive refractive power and an image-side sub lens unit, and

the object-side sub lens unit in the second lens unit includes one lens component, and

in the lens component, only two surfaces, namely, an object-side surface and an image-side surface, are in contact with air in an optical path, and

the following conditional expressions (1) and (2) are satisfied

3.0<

Δ

D₁₂/ER_S<

4.5 

 

(1)

1.05<

|f₃/f_UN21|<

2.1 

 

(2)

where,

Δ

D₁₂−

D_12W−

D_12T,

D_12W denotes the distance between the first lens unit and the second lens unit at the wide angle end,

D_12T denotes the distance between the first lens unit and the second lens unit at the telephoto end,

both D_12W and D_12T are distances on an optical axis at the time of infinite object point focusing,

ER_S denotes the maximum radius of an opening of the aperture stop,

f₃ denotes a focal length of the third lens unit, and

f_UN21 denotes a focal length of the object-side sub lens unit in the second lens unit.

8. The zoom lens according to claim 1, further comprising:

a fourth lens unit having a positive refractive power, disposed on the image side of the third lens unit, wherein

at the time of zooming, a distance between the third lens unit and the fourth lens unit changes.

9. The zoom lens according to claim 8, wherein a distance between the third lens unit and the fourth lens unit at the telephoto end is longer than a distance between the third lens unit and the fourth lens unit at the wide angle end.

10. The zoom lens according to claim 8, wherein the total number of lens units in the zoom lens is four, namely, the first lens unit, the second lens unit, the third lens unit, and the fourth lens unit.

11. The zoom lens according to claim 1, wherein the object-side sub lens unit and the image-side sub lens unit in the second lens unit are disposed such that, an axial air space between the object-side sub lens unit and the image-side sub lens unit is the maximum in the second lens unit.

12. The zoom lens according to claim 11, wherein

the image-side sub lens unit in the second lens unit includes one lens component, and

in the lens component, only two surfaces, namely, the object-side surface and the image-side surface, are in contact with air in the optical path.

13. The zoom lens according to claim 1, wherein the following conditional expression (5) is satisfied

0.8<

|f₃/f_W|<

2.5 

 

(5)

where,

f₃ denotes a focal length of the third lens unit, and

f_W denotes a focal length of the overall zoom lens system at the time of infinite object point focusing at the wide angle end.

14. The zoom lens according to claim 1, wherein the following conditional expression (12) is satisfied

−

20.0%<

DT_W<

−

6.0% 

 

(12)

where,

DT_W={IH_W−

f_W×

tan(ω

_W)}/{f_W×

tan(ω

_W)}×

100(%),

f_W denotes a focal length of the overall zoom lens system at the time of infinite object point focusing at the wide angle end,

IH_W denotes the maximum image height at the time of infinite object point focusing at the wide angle end, and

ω

_W denotes a half angle of view at the time of infinite object point focusing at the wide angle end.

15. The zoom lens according to claim 1, wherein

the second lens unit includes in order from the object side to the image side, the object-side sub lens unit having a positive refractive power and the image-side sub lens unit, and

the object-side sub lens unit in the second lens unit includes one lens component, and

in the lens component, only to surfaces, namely, the object-side surface and the image-side surface, are in contact with air in the optical path, and

the following conditional expression (13) is satisfied

−

1.5<

Sf_UN21<

0.5 

 

(13)

where,

SF_UN21=(R_UN21O+R_UN21I)/R_UN21O−

R_UN21I)

R_UN21O denotes a paraxial radius of curvature of an object-side surface of the object-side sub lens unit in the second lens unit, and

R_UN21I denotes a paraxial radius of curvature of an image-side surface of the object-side sub lens unit in the second lens unit.

16. The zoom lens according to claim 1, wherein the following conditional expression (14) is satisfied

0.38<

Σ

_2G/f_W<

0.75 

 

(14)

where,

Σ

_2G denotes a thickness of the second lens unit on an optical axis, and

f_W denotes a focal length of the overall zoom lens system at the time of infinite object point focusing at the wide angle end.

17. The zoom lens according to claim 1, wherein

the second lens unit includes in order from the object side to the image side, the object-side sub lens unit having a positive refractive power and the image-side sub lens unit, and

the object-side sub lens unit in the second lens unit includes one lens component, and

in the lens component, only two surfaces, namely, the object-side surface and the image-side surface, are in contact with air in the optical path, and

the image-side sub lens unit in the second lens unit includes a lens surface having a negative refractive power, and a positive lens which is disposed on the image side of the lens surface.

18. The zoom lens according to claim 1, wherein the following conditional expression (8) is satisfied

1.17<

|f₃/f₂|<

1.95 

 

(8)

where,

f₂ denotes a focal length of the second lens unit, and

f₃ denotes a focal length of the third lens unit.

19. The zoom lens according to claim 1, wherein the following conditional expression (15) is satisfied

1.3<

|f₃/IH_MAX|<

2.5 

 

(15)

where,

f₃ denotes the focal length of the third lens unit, and

IH_MAX denotes the maximum image height, and denotes the maximum value in a case in which, the maximum image height changes with zooming.

20. The zoom lens according to claim 1, wherein the third lens unit includes a lens having a specific gravity more than 0.9 g/cm³ and smaller than 1.3 g/cm³.

21. The zoom lens according to claim 1, wherein the second lens unit includes a negative lens and a positive lens that satisfies the following conditional expression (16).

63<

ν

_p1<

96 

 

(16)

where,

ν

_p1 denotes Abbe'"'"'s number for a d-line of any of the positive lenses in the second lens unit.

22. The zoom lens according to claim 1, wherein

the first lens unit includes in order from the object side to the image side, an object-side sub lens unit and an image-side sub lens unit, and

the object-side sub lens unit in the first lens unit includes a first negative lens, and

the image-side sub lens unit in the first lens unit includes a second negative lens and a first positive lens.

23. The zoom lens according to claim 22, wherein the following conditional expression (3) is satisfied

−

0.9<

SF_2N<

1.5 

 

(3)

where,

SF_2N=(R_2NO+R_2NI)/(R_2NO−

R_2NI),

R_2NO denotes a paraxial radius of curvature of an object-side surface of the second negative lens in the first lens unit, and

R_2NI denotes a paraxial radius of curvature of an image-side surface of the second negative lens in the first lens unit.

24. The zoom lens according to claim 1, wherein the following conditional expression (17) is satisfied

0.6<

fb_W/IH_MAX<

1.8 

 

(17)

where,

fb_W denotes an air-converted back-focus at the time of infinite object point focusing at the wide angle end, and

IH_MAX denotes the maximum image height, and denotes the maximum value in a case in which, the maximum image height changes with zooming.

25. The zoom lens according to claim 1, wherein the following conditional expression (18) is satisfied

0.4<

f₁/f₃<

1.2 

 

(18)

where,

f₁ denotes a focal length of the first lens unit, and

f₃ denotes a focal length of the third lens unit.

26. The zoom lens according to claim 1, wherein the following conditional expression (6′

) is satisfied

0.45<

Σ

_2G/f₂<

0.75 

 

(6′

)

where,

Σ

_2G denotes a thickness on an optical axis of the second lens unit, and

f₂ denotes a focal length of the second lens unit.

27. The zoom lens according to claim 1, wherein the following conditional expression (7) is satisfied

0.6<

f_UN21/f₂<

1.8 

 

(7)

where,

f_UN21 denotes a focal length of the object-side sub lens unit in the second lens unit,

f₂ denotes a focal length of the second lens unit.

28. The zoom lens according to claim 1, wherein the following conditional expression (19) is satisfied

3<

LTL_W/fb_W<

13 

 

(19)

where,

LTL denotes a sum of an overall length of the zoom lens at the time of infinite object point focusing at the wide angle end and an air-converted back focus,

the overall length is a distance on an optical axis from a refracting surface of the zoom lens nearest to the object side and a refracting surface of the zoom lens nearest to the image side, and

fb_W denotes the air-converted back focus at LTL_W.

29. The zoom lens according to claim 1, wherein the following conditional expression (20) is satisfied

0.6<

f_UN21/f_W<

1.9 

 

(20)

where,

f_UN21 denotes a focal length of the object-side sub lens unit in the second lens unit, and

f_W denotes a focal length of the overall zoom lens system at the time of infinite object point focusing at the wide angle end.

30. The zoom lens according to claim 29, wherein the following conditional expression (20′

) is satisfied

0.6<

f_UN21/f_W<

1.6 

 

(20′

)

where,

f_UN21 denotes the focal length of the object-side sub lens unit in the second lens unit,

f_W denotes the focal length of the overall zoom lens system at the time of infinite object point focusing at the wide angle end.

31. The zoom lens according to claim 1, wherein the following conditional expression (21) is satisfied

0.35<

Δ

D₁₂/f_T<

0.6 

 

(21)

where,

Δ

D₁₂=D_12W−

D_12T,

D_12W denotes the distance between the first lens unit and the second lens unit at the wide angle end,

D_12T denotes the distance between the first lens unit and the second lens unit at the telephoto end,

both D_12W and D_12T are distances on an optical axis at the time of infinite object point focusing, and

f_T denotes a focal length of the overall zoom lens system at the time of infinite object point focusing at the telephoto end.

32. The zoom lens according to claim 1, wherein the following conditional expression (22) is satisfied

0.35<

|f₃/ER_S|<

1.05 

 

(22)

where,

f₃ denotes the focal length of the third lens unit, and

ER_S denotes the maximum radius of an opening of the aperture stop.

33. The zoom lens according to claim 1, wherein the first lens unit includes a plastic aspherical lens which satisfied the following conditional expression (23)

0.0001<

|ASP_O−

ASP_I|/IH_33W<

0.02 

 

(23)

where,

IH_33W denotes a distance from an optical axis of a position at which, a principal ray intersects with a paraxial image plane such that, an incidence-side half angle of view of the zoom lens at the time of infinite object point focusing at the wide angle end becomes 33°

.

ASP_O denotes an amount of aspherical deviation at a position at which, a distance of an object-side surface of the plastic aspherical lens from the optical axis becomes IH_33W,

ASP_I denotes an amount of aspherical deviation at a position at which, a distance of an image-side surface of the plastic aspherical lens from the optical axis becomes IH_33W, and

the amount of aspherical deviation is a distance in an optical axial direction, from a reference spherical surface for which, a vertex of a surface intended is let to be the vertex, and a radius of curvature is let to be same as a paraxial radius of curvature of the surface intended, up to the surface intended, and a case in which, the intended surface is on the image side with respect to the reference spherical surface is let to have a positive sign.

34. The zoom lens according to claim 33, wherein both the object-side surface and the image-side surface of the plastic aspherical lens are aspheric surfaces.

36. The zoom lens according to claim 1, wherein

the second lens unit includes a single lens having a positive refractive power which is disposed nearest to the object side in the second lens unit, and a cemented lens of a negative lens and a positive lens in order from the object side, and

the aperture stop is positioned between the single lens and the cemented lens in the second lens unit.

37. An image pickup apparatus comprising:

a zoom lens; and

an image pickup element which has an image pickup surface, and which converts an image formed on the image pickup surface by the zoom lens, to an electric signal, wherein

the zoom lens is the zoom lens according to claim 1.

2. A zoom lens comprising in order from an object side to an image side:

a first lens unit having a negative refractive power;

a second lens unit having a positive refractive power; and

a third lens unit having a negative refractive power, wherein

at the time of zooming, distances between the lens units change, and

a distance between the first lens unit and the second lens unit at a telephoto end is shorter than a distance between the first lens unit and the second lens unit at a wide angle end, and

an aperture stop is disposed on the image side of an image-side surface of the first lens unit, and on the object side of an image-side surface of the second lens unit, and

the first lens unit includes in order from the object side to the image side, an object-side sub lens unit and an image-side sub lens unit, and

the object-side sub lens unit in the first lens unit includes a first negative lens, and

the image-side sub lens unit in the first lens unit includes a second negative lens and a first positive lens, and

the second lens unit includes in order from the object side to the image side, an object-side sub lens unit having a positive refractive power, and an image-side sub lens unit, and

the object-side sub lens unit in the second lens unit includes one lens component, and

in the lens component, only two surfaces, namely, an object-side surface and an image-side surface, are in contact with air in an optical path, and

the following conditional expressions (1) and (3) are satisfied

3.0<

Δ

D₁₂/ER_S<

4.5 

 

(1)

−

0.9<

SF₂N<

1.5 

 

(3)

where,

Δ

D₁₂=D_12W−

D_12T,

D_12W denotes the distance between the first lens unit and the second lens unit at the wide angle end,

D_12T denotes the distance between the first lens unit and the second lens unit at the telephoto end,

both D_12W and D_12T are distances on an optical axis at the time of infinite object point focusing,

ER_S denotes the maximum radius of an opening of the aperture stop,

SF_2N=(R_2NO+R_2NI)/(R_2NO−

R_2NI),

R_2NO denotes a paraxial radius of curvature of an object-side surface of the second negative lens in the first lens unit, and

R_2NI denotes a paraxial radius of curvature of an image-side surface of the second negative lens in the first lens unit.

3. A zoom lens comprising in order from an object side to an image side:

a first lens unit having a negative refractive power;

a second lens unit having a positive refractive power; and

a third lens unit having a negative refractive power, wherein

at the time of zooming, distances between the lens units change, and

a distance between the first lens unit and the second lens unit at a telephoto end is shorter than a distance between the first lens unit and the second lens unit at a wide angle end, and

an aperture stop is disposed on the image side of an image-side surface of the first lens unit, and on the object side of an image-side surface of the second lens unit, and

the following conditional expressions (4) and (5′

) are satisfied

1.2<

Δ

D₁₂/IH_MAX<

1.85 

 

(4)

1.1<

|f₃/f_W|<

1.9 

 

(5′

)

where,

Δ

D₁₂=D_12W−

D_12T,

D_12W denotes the distance between the first lens unit and the second lens unit at the wide angle end,

D_12T denotes the distance between the first lens unit and the second lens unit at the telephoto end,

both D_12W and D_12T are distances on an optical axis at the time of infinite object point focusing,

IH_MAX denotes the maximum image height, and denotes the maximum value in a case in which, the maximum image height changes with zooming,

f₃ denotes a focal length of the third lens unit, and

f_W denotes a focal length of the overall zoom lens system at the time of infinite object point focusing at the wide angle end.

4. A zoom lens comprising in order from an object side to an image side:

a first lens unit having a negative refractive power;

a second lens unit having a positive refractive power; and

a third lens unit having a negative refractive power, wherein

at the time of zooming, distances between the lens units change, and

a distance between the first lens unit and the second lens unit at a telephoto end is shorter than a distance between the first lens unit and the second lens unit at a wide angle end, and

an aperture stop is disposed on the image side of an image-side surface of the first lens unit, and on the object side of an image-side surface of the second lens unit, and

the following conditional expressions (4) and (6) are satisfied

1.2<

Δ

D₁₂/IH_MAX<

1.85 

 

(4)

0.43<

Σ

_2G/f₂<

0.78 

 

(6)

where,

Δ

D₁₂=D_12W−

D_12T,

D_12W denotes the distance between the first lens unit and the second lens unit at the wide angle end,

D_12T denotes the distance between the first lens unit and the second lens unit at the telephoto end,

both D_12W and D_12T are distances on an optical axis at the time of infinite object point focusing,

IH_MAX denotes the maximum image height, and denotes the maximum value in a case in which, the maximum image height changes with zooming,

Σ

_2G denotes a thickness on an optical axis of the second lens unit, and

f₂ denotes a focal length of the second lens unit.

5. A zoom lens comprising in order from an object side to an image side:

a first lens unit having a negative refractive power;

a second lens unit having a positive refractive power; and

a third lens unit having a negative refractive power, wherein

at the time of zooming, distances between the lens units change, and

a distance between the first lens unit and the second lens unit at a telephoto end is shorter than a distance between the first lens unit and the second lens unit at a wide angle end, and

an aperture stop is disposed on the image side of an image-side surface of the first lens unit, and on the object side of an image-side surface of the second lens unit, and

the second lens unit includes in order from the object side to the image side, an object-side sub lens unit having a positive refractive power, and an image-side sub lens unit, and

the object-side sub lens unit in the second lens unit includes one lens component, and

in the lens component, only two surfaces, namely, an object-side surface and an image-side surface, are in contact with air in an optical path, and

the following conditional expressions (7), (8), and (9) are satisfied

0.6<

f_UN21/f₂<

1.8 

 

(7)

1.17<

|f₃/f₂|<

1.95 

 

(8)

1.15<

f₂/IH_MAX<

1.5 

 

(9)

where,

f_UN21 denotes a focal length of the object-side sub lens unit in the second lens unit,

f₂ denotes a focal length of the second lens unit,

f₃ denotes a focal length of the third lens unit, and

IH_MAX denotes the maximum image height, and denotes the maximum value in a case in which, the maximum image height changes with zooming.

6. A zoom lens comprising in order from an object side to an image side:

a first lens unit having a negative refractive power;

a second lens unit having a positive refractive power; and

a third lens unit having a negative refractive power, wherein

at the time of zooming, distances between the lens units change, and

a distance between the first lens unit and the second lens unit at a telephoto end is shorter than a distance between the first lens unit and the second lens unit at a wide angle end, and

an aperture stop is disposed on the image side of an image-side surface of the first lens unit, and on the object side of an image-side surface of the second lens unit, and

the first lens unit includes in order from the object side to the image side, an object-side sub lens unit and an image-side sub lens unit, and

the object-side sub lens unit in the first lens unit includes a first negative lens, and

the image-side sub lens unit in the first lens unit includes a second negative lens and a first positive lens, and

the second lens unit includes in order from the object side to the image side, an object-side sub lens unit having a positive refractive power, and an image-side sub lens unit, and

the object-side sub lens unit in the second lens unit includes one lens component, and

in the lens component, only two surfaces, namely, an object-side surface and an image-side surface, are in contact with air in an optical path, and

the image-side sub lens unit in the second lens unit includes a lens surface having a negative refractive power and a positive lens which is disposed on the image side of the lens surface, and

the following conditional expressions (3), (10), and (11) are satisfied

−

0.9<

SF_2N<

1.5 

 

(3)

1.5<

f_UN21/ER_S<

3.9 

 

(10)

3<

LTL_min/fb_LTLmin<

13 

 

(11)

where,

SF_2N=R_2NO+R_2NI)/R_2NO−

R_2NI),

R_2NO denotes a paraxial radius of curvature of an object-side surface of the second negative lens in the first lens unit, and

R_2NI denotes a paraxial radius of curvature of an image-side surface of the second negative lens in the first lens unit,

f_UN21 denotes a focal length of the object-side sub lens unit in the second lens unit,

ER_S denotes the maximum radius of an opening of the aperture stop,

LTL_min denotes a sum of an overall length of the zoom lens at the time of infinite object point focusing and an air-converted back focus, and is the minimum value thereof in a case in which, the overall length changes with zooming, and

the overall length is a distance on an optical axis from a refracting surface of the zoom lens nearest to the object side and a refracting surface of the zoom lens nearest to the image side, and

fb_LTLmin denotes the air-converted back focus at LTL_min.

7. A zoom lens comprising in order from an object side to an image side:

a first lens unit having a negative refractive power;

a second lens unit having a positive refractive power; and

a third lens unit having a negative refractive power, wherein

at the time of zooming, distances between the lens units change, and

a distance between the first lens unit and the second lens unit at a telephoto end is shorter than a distance between the first lens unit and the second lens unit at a wide angle end, and

an aperture stop is disposed on the image side of an image-side surface of the first lens unit, and on the object side of an image-side surface of the second lens unit, and

the second lens unit includes in order from the object side to the image side, an object-side sub lens unit having a positive refractive power, and an image-side sub lens unit, and

the object-side sub lens unit in the second lens unit includes one lens component, and

in the lens component, only two surfaces, namely, an object-side surface and an image-side surface, are in contact with air in an optical path, and

the following expressions (2) and (4) are satisfied

1.05<

|f₃/f_UN21|<

2.1 

 

(2)

1.2<

Δ

D₁₂/IH_MAX<

1.85 

 

(4)

where,

f₃ denotes a focal length of the third lens unit, and

f_UN21 denotes a focal length of the object-side sub lens unit in the second lens unit,

Δ

D₁₂=D_12W−

D_12T,

D_12W denotes the distance between the first lens unit and the second lens unit at the wide angle end,

D_12T denotes the distance between the first lens unit and the second lens unit at the telephoto end,

both D_12W and D_12T are distances on an optical axis at the time of infinite object point focusing, and

IH_MAX denotes the maximum image height, and denotes the maximum value in a case in which, the maximum image height changes with zooming.

35. The zoom lens according to claim 35, wherein

at the wide angle end, a light ray of half angle of view 33°

or more is capable of passing through the zoom lens, and

the following conditional expression (24) is satisfied

2.6<

f_T/f_W<

5.0 

 

(24)

where,

f_T denotes a focal length of the overall zoom lens system at the time of infinite object point focusing at the telephoto end, and

f_W denotes a focal length of the overall zoom lens system at the time of infinite object point focusing at the wide angle end.