U.S. patent application number 17/833892 was filed with the patent office on 2022-09-29 for variable magnification optical system, optical apparatus and method for manufacturing variable magnification optical system.
The applicant listed for this patent is Nikon Corporation. Invention is credited to Satoru Shibata.
Application Number | 20220308324 17/833892 |
Document ID | / |
Family ID | 1000006381002 |
Filed Date | 2022-09-29 |
United States Patent
Application |
20220308324 |
Kind Code |
A1 |
Shibata; Satoru |
September 29, 2022 |
VARIABLE MAGNIFICATION OPTICAL SYSTEM, OPTICAL APPARATUS AND METHOD
FOR MANUFACTURING VARIABLE MAGNIFICATION OPTICAL SYSTEM
Abstract
A variable power optical system used for an optical apparatus,
such as a camera, includes, in order from an object: a first lens
group having positive refractive power; a second lens group having
negative refractive power; a third lens group having positive
refractive power; and a fourth lens group having positive or
negative refractive power. The distances between lens groups change
upon zooming from a wide-angle end state to a telephoto end state.
The third lens group comprises, in order from the object, a first
positive lens, a second positive lens, a first negative lens, a
second negative lens and a third positive lens. The third lens
group includes a vibration-isolating lens group which can move so
as to have a movement component in a direction orthogonal to the
optical axis upon correcting camera shake.
Inventors: |
Shibata; Satoru;
(Yokohama-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Nikon Corporation |
Tokyo |
|
JP |
|
|
Family ID: |
1000006381002 |
Appl. No.: |
17/833892 |
Filed: |
June 6, 2022 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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16528603 |
Jul 31, 2019 |
11366297 |
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17833892 |
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14979409 |
Dec 27, 2015 |
10409043 |
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16528603 |
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PCT/JP2014/003418 |
Jun 26, 2014 |
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14979409 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G02B 15/20 20130101;
G02B 27/646 20130101; G02B 13/18 20130101; G02B 15/145121 20190801;
G02B 15/144113 20190801 |
International
Class: |
G02B 15/14 20060101
G02B015/14; G02B 15/20 20060101 G02B015/20; G02B 13/18 20060101
G02B013/18; G02B 27/64 20060101 G02B027/64 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 28, 2013 |
JP |
2013-136678 |
Jun 28, 2013 |
JP |
2013-136679 |
Nov 18, 2013 |
JP |
2013-237570 |
Nov 18, 2013 |
JP |
2013-237571 |
Claims
1-52. (canceled)
53. A variable power optical system comprising, in order from an
object: a first lens group having positive refractive power; a
second lens group having negative refractive power; a third lens
group having positive refractive power; and a fourth lens group
having positive or negative refractive power, a distance between
the first lens group and the second lens group, a distance between
the second lens group and the third lens group, and a distance
between the third lens group and the fourth lens group changing
respectively upon zooming from a wide-angle end state to a
telephoto end state, the third lens group comprising, in order from
the object, a first positive lens, a second positive lens, a first
negative lens, a second negative lens and a third positive lens,
the third lens group comprising a vibration-isolating lens group
which can move so as to have a movement component in a direction
orthogonal to the optical axis upon correcting camera shake.
54. The variable power optical system according to claim 53,
wherein the vibration-isolating lens group consists of one cemented
lens.
55. The variable power optical system according to claim 53,
wherein the vibration-isolating lens group consists of one negative
lens and one positive lens.
56. The variable power optical system according to claim 53,
wherein the variable power optical system consists of the first
lens group, the second lens group, the third lens group and the
fourth lens group.
57. The variable power optical system according to claim 53,
including, in order from the object and next to the third positive
lens, a fourth positive lens, a third negative lens and a fifth
positive lens.
58. The variable power optical system according to claim 53,
wherein the following conditional expression is satisfied:
0.4<(-f2)/(fw.times.ft).sup.1/2<1.1 where f2 denotes a focal
length of the second lens group, fw denotes a focal length of the
variable power optical system in the wide-angle end state, and ft
denotes a focal length of the variable power optical system in the
telephoto end state.
59. The variable power optical system according to claim 53,
wherein the following conditional expression is satisfied:
.nu.dO>60 where .nu.dO denotes an Abbe number of a medium of the
first positive lens.
60. The variable power optical system according to claim 53,
wherein the first lens group moves toward an image at first and
then moves toward the object upon zooming from the wide-angle end
state to the telephoto end state.
61. The variable power optical system according to claim 53,
wherein the third lens group includes, in order from the object: a
first sub-group of which position with respect to an image plane is
fixed upon correcting camera shake; and a second sub-group serving
as a vibration-isolating lens group which has positive refractive
power, and the following conditional expression is satisfied:
1.5<fv.times.FNOw/fX<5.0 where fX denotes a combined focal
length of the first sub-group and the second sub-group, fv denotes
a focal length of the second sub-group, and FNOw denotes an F
number of the variable power optical system in the wide-angle end
state.
62. The variable power optical system according to claim 53,
wherein the following conditional expression is satisfied:
1.0<f3/.DELTA.T3<2.2 where .DELTA.T3 denotes a moving
distance of the third lens group upon zooming from the wide-angle
end state to the telephoto end state, and f3 denotes a focal length
of the third lens group.
63. The variable power optical system according to claim 53,
wherein the following conditional expression is satisfied:
4.0<fr/fw<11.0 where fr denotes a focal length of a final
lens group closest to an image, and fw denotes a focal length of
the variable power optical system in the wide-angle end state.
64. The variable power optical system according to claim 53,
wherein the following conditional expression is satisfied:
0.9<f3/(fw.times.ft).sup.1/2<2.0 where f3 denotes a focal
length of the third lens group, fw denotes a focal length of the
variable power optical system in the wide-angle end state, and ft
denotes a focal length of the variable power optical system in the
telephoto end state.
65. The variable power optical system according to claim 53,
wherein the third lens group includes, in order from the object: a
first sub-group of which position with respect to an image plane is
fixed upon correcting camera shake; and a second sub-group serving
as the vibration-isolating lens group which has positive refractive
power, the second sub-group comprises at least one positive lens,
and the following conditional expression is satisfied:
(ndVR+0.0052.times..nu.dVR-1.965)<0 .nu.dVR>60 where ndVR
denotes a refractive index of a medium of the positive lens
included in the second sub-group at d-line, and .nu.dVR denotes an
Abbe number of the medium of the positive lens included in the
second sub-group.
66. The variable power optical system according to claim 53,
wherein an aperture stop is provided between the second lens group
and the third lens group.
67. An optical apparatus comprising the variable power optical
system according to claim 53.
68. A method of manufacturing a variable power optical system,
comprising: arranging, in a lens barrel and in order from an
object, a first lens group having positive refractive power, a
second lens group having negative refractive power, a third lens
group having positive refractive power, and a fourth lens group
having positive or negative refractive power, the first to fourth
lens groups being arranged such that a distance between the first
lens group and the second lens group, a distance between the second
lens group and the third lens group, and a distance between the
third lens group and the fourth lens group change respectively upon
zooming from a wide-angle end state to a telephoto end state, with
the third lens group comprising, in order from the object, a first
positive lens, a second positive lens, a first negative lens, a
second negative lens and a third positive lens, and the third lens
group comprising a vibration-isolating lens group which can move so
as to have a movement component in a direction orthogonal to the
optical axis upon correcting camera shake.
Description
TECHNICAL FIELD
[0001] The present invention relates to a variable power optical
system, an optical apparatus and a manufacturing method for a
variable power optical system.
TECHNICAL BACKGROUND
[0002] Variable power optical systems suitable for a photographic
camera, electronic still camera, video camera and the like have
been proposed (e.g. see Patent Document 1).
PRIOR ARTS LIST
Patent Document
[0003] Patent Document 1: Japanese Laid-Open Patent Publication No.
2006-308957(A)
SUMMARY OF THE INVENTION
Problems to be Solved by the Invention
[0004] A conventional variable power optical system, however,
cannot sufficiently satisfy the demand for larger aperture to
further implement brighter lenses, since the F number thereof is
about f/3.5.
[0005] With the foregoing in view, it is an object of the present
invention to provide a variable power optical system having a high
brightness and excellent optical performance, an optical apparatus
that includes this variable power optical system, and a
manufacturing method for this variable power optical system.
Means to Solve the Problems
[0006] To solve the above problem, a variable power optical system
according to Embodiment 1 includes, in order from an object: a
first lens group having positive refractive power; a second lens
group having negative refractive power; a third lens group having
positive refractive power; and a fourth lens group having positive
refractive power. The distance between the first lens group and the
second lens group, the distance between the second lens group and
the third lens group, and the distance between the third lens group
and the fourth lens group change respectively upon zooming from a
wide-angle end state to a telephoto end state, and the third lens
group includes: an intermediate group constituted by, in order from
the object, a positive lens, a negative lens, a negative lens and a
positive lens; and an image side group having negative refractive
power and disposed to an image side of the intermediate group. The
position of the intermediate group with respect to the image plane
is fixed and the image side group moves along the optical axis upon
focusing.
[0007] It is preferable that the variable power optical system
according to Embodiment 1 satisfies the following conditional
expressions:
0.4<(-f2)/(fw.times.ft).sup.1/2<1.1
where f2 denotes a focal length of the second lens group, fw
denotes a focal length of the variable power optical system in the
wide-angle end state, and ft denotes a focal length of the variable
power optical system in the telephoto end state.
[0008] In the variable power optical system according to Embodiment
1, it is preferable that the third lens group includes an object
side group having positive refractive power and disposed to the
object side of the intermediate group.
[0009] In the variable power optical system according to Embodiment
1, it is preferable that the image side group is constituted by one
negative lens.
[0010] In the variable power optical system according to Embodiment
1, it is preferable that the image side group is constituted by one
negative meniscus lens having a concave surface facing the image
plane.
[0011] In the variable power optical system according to Embodiment
1, it is preferable that the image side group includes at least one
negative lens, and satisfies the following conditional
expressions:
ndF+0.0052.times..nu.dF-1.965<0
vdF>60
where ndF denotes a refractive index of a medium of the negative
lens included in the image side group at d-line, and .nu.dF denotes
an Abbe number of the medium of the negative lens included in the
image side group.
[0012] In the variable power optical system according to Embodiment
1, it is preferable that the third lens group includes an object
side group having positive refractive power and disposed to the
object side of the intermediate group, the object side group
includes one positive lens, and the following conditional
expression is satisfied:
.nu.dO>60
where .nu.dO denotes an Abbe number of a medium of the positive
lens included in the object side group.
[0013] It is preferable that the variable power optical system
according to Embodiment 1 satisfies the following conditional
expression:
4.0<f4/fw<11.0
where f4 denotes a focal length of the fourth lens group, and fw
denotes a focal length of the variable power optical system in the
wide-angle end state.
[0014] In the variable power optical system according to Embodiment
1, it is preferable that the first lens group moves toward the
image plane first and then moves toward the object upon zooming
from the wide-angle end state to the telephoto end state.
[0015] In the variable power optical system according to Embodiment
1, it is preferable that the third lens group includes a
vibration-isolating lens group which is disposed to the image side
of the intermediate group, has positive refractive power, and moves
so as to have a component in a direction orthogonal to the optical
axis.
[0016] In the variable power optical system according to Embodiment
1, it is preferable that the third lens group includes, in order
from the object: a first sub-group of which position with respect
to the image plane is fixed upon correcting camera shake; and a
second sub-group used as a vibration-isolating lens group which has
positive refractive power and can move so as to have a component in
a direction orthogonal to the optical axis upon correcting camera
shake, and the following conditional expression is satisfied:
1.5<fv.times.FNOw/f3<5.0
where f3 denotes a focal length of the third lens group, fv denotes
a focal length of the second sub-group, and FNOw denotes an F
number in the wide-angle end state.
[0017] A variable power optical system according to Embodiment 2
includes, in order from an object: a first lens group having
positive refractive power; a second lens group having negative
refractive power; a third lens group having positive refractive
power; and a fourth lens group having positive refractive power.
The distance between the first lens group and the second lens
group, the distance between the second lens group and the third
lens group, and the distance between the third lens group and the
fourth lens group change respectively upon zooming from a
wide-angle end state to a telephoto end state, and the third lens
group includes: an intermediate group constituted by, in order from
the object, a first positive lens, a first negative lens, a second
negative lens and a second positive lens; and an image side group
having negative refractive power and disposed to an image side of
the intermediate group. The position of the intermediate group with
respect to the image plane is fixed and the image side group moves
along the optical axis upon focusing, and the following conditional
expression is satisfied:
-0.8<(R2a+R1b)/(R2a-R1b)<0.5
where R2a denotes a radius of curvature of the image plane side
lens surface of the first negative lens, and Rib denotes a radius
of curvature of the object side lens surface of the second negative
lens.
[0018] It is preferable that the variable power optical system
according to Embodiment 2 satisfies the following conditional
expression:
0.4<(-f2)/(fw.times.ft).sup.1/2<1.1
where f2 denotes a focal length of the second lens group, fw
denotes a focal length of the variable power optical system in the
wide-angle end state, and ft denotes a focal length of the variable
power optical system in the telephoto end state.
[0019] In the variable power optical system according to Embodiment
2, it is preferable that the third lens group includes an object
side group having positive refractive power and disposed to the
object side of the intermediate group.
[0020] In the variable power optical system according to Embodiment
2, it is preferable that the image side group is constituted by one
negative lens.
[0021] In the variable power optical system according to Embodiment
2, it is preferable that the image side group is constituted by one
negative meniscus lens having a concave surface facing the image
plane.
[0022] In the variable power optical system according to Embodiment
2, it is preferable that the image side group includes at least one
negative lens, and satisfies the following conditional
expressions:
ndF+0.0052.times..nu.dF-1.965<0
.nu.dF>60
where ndF denotes a refractive index of a medium of the negative
lens included in the image side group at d-line, and .nu.dF denotes
an Abbe number of the medium of the negative lens included in the
image side group.
[0023] In the variable power optical system according to Embodiment
2, it is preferable that the third lens group includes an object
side group having positive refractive power and disposed to the
object side of the intermediate group, the object side group
includes one positive lens, and the following conditional
expression is satisfied:
.nu.dO>60
where .nu.dO denotes an Abbe number of a medium of the positive
lens included in the object side group.
[0024] It is preferable that the variable power optical system
according to Embodiment 2 satisfies the following conditional
expression:
4.0<f4/fw<11.0
where f4 denotes a focal length of the fourth lens group, and fw
denotes a focal length of the variable power optical system in the
wide-angle end state.
[0025] In the variable power optical system according to Embodiment
2, it is preferable that the first lens group moves toward the
image plane first and then moves toward the object upon zooming
from the wide-angle end state to the telephoto end state.
[0026] In the variable power optical system according to Embodiment
2, it is preferable that the third lens group includes a
vibration-isolating lens group which is disposed to the image side
of the intermediate group, has positive refractive power, and moves
so as to have a component in a direction orthogonal to the optical
axis.
[0027] In the variable power optical system according to Embodiment
2, it is preferable that the third lens group includes, in order
from the object: a first sub-group of which position with respect
to the image plane is fixed upon correcting camera shake; and a
second sub-group used as a vibration-isolating lens group which has
positive refractive power and can move so as to have a component in
a direction orthogonal to the optical axis upon correcting camera
shake, and the following conditional expression is satisfied:
1.5<fv.times.FNOw/f3<5.0
where f3 denotes a focal length of the third lens group, fv denotes
a focal length of the second sub-group, and FNOw denotes an F
number in the wide-angle end state.
[0028] A variable power optical system according to Embodiment 3
includes, in order from an object: a first lens group having
positive refractive power; a second lens group having negative
refractive power; and a rear group having positive refractive power
and disposed to an image side of the second lens group. The
distance between the first lens group and the second lens group,
and the distance between the second lens group and the rear group
change respectively upon zooming from a wide-angle end state to a
telephoto end state, and the rear group includes: an intermediate
group constituted by, in order from the object, a positive lens, a
negative lens, a negative lens, and a positive lens; and a
vibration-isolating lens group having positive refractive power,
disposed to an image side of the intermediate group and moving so
as to have a component in a direction orthogonal to the optical
axis.
[0029] In the variable power optical system according to Embodiment
3, it is preferable that the rear group includes at least a third
lens group having positive refractive power and disposed closest to
the object, each distance between lenses constituting the third
lens group is constant upon zooming from a wide-angle end state to
a telephoto end state, the third lens group includes the
intermediate group, and the following conditional expression is
satisfied:
1.0<f3/.DELTA.T3<2.2
where .DELTA.T3 denotes a moving distance of the third lens group
upon zooming from the wide-angle end state to the telephoto end
state, and f3 denotes a focal length of the third lens group.
[0030] In the variable power optical system according to Embodiment
3, it is preferable that the rear group includes an object side
group having positive refractive power and disposed to the object
side of the intermediate group.
[0031] In the variable power optical system according to Embodiment
3, it is preferable that the vibration-isolating lens group is
constituted by one positive lens.
[0032] In the variable power optical system according to Embodiment
3, it is preferable that the vibration-isolating lens group is
constituted by one biconvex lens.
[0033] In the variable power optical system according to Embodiment
3 it is preferable that the vibration-isolating lens group includes
at least one positive lens, and satisfies the following conditional
expressions:
ndVR+0.0052.times..nu.dVR-1.965<0
.nu.dVR>60
where ndVR denotes a refractive index of a medium of the positive
lens included in the vibration-isolating lens group at d-line, and
.nu.dVR denotes an Abbe number of the medium of the positive lens
included in the vibration-isolating lens group.
[0034] In the variable power optical system according to Embodiment
3, it is preferable that the rear group includes an object side
group having positive refractive power and disposed to the object
side of the intermediate group, the object side group includes one
positive lens, and the following conditional expressions is
satisfied:
.nu.dO>60
where .nu.dO denotes an Abbe number of a medium of the positive
lens included in the object side group.
[0035] In the variable power optical system according to Embodiment
3, it is preferable that the rear group includes a plurality of
lens groups, each distance between the plurality of lens groups
included in the rear group changes upon zooming from a wide-angle
end state to a telephoto end state, and when a lens group closest
to the image, out of the plurality of lens groups, is a final lens
group, the following conditional expression is satisfied:
4.0<fr/fw<11.0
where fr denotes a focal length of the final lens group, and fw
denotes a focal length of the variable power optical system in the
wide-angle end state.
[0036] In the variable power optical system according to Embodiment
3, it is preferable that the rear group includes, in order from the
object, a third lens group having positive refractive power and a
fourth lens group, the distance between the third lens group and
the fourth lens group changes upon zooming from the wide-angle end
state to the telephoto end state, the third lens group includes at
least the intermediate lens group, and the following conditional
expression is satisfied:
0.9<f3/(fw.times.ft).sup.1/2<2.0
where f3 denotes a focal length of the third lens group, fw denotes
a focal length of the variable power optical system in the
wide-angle end state, and ft denotes a focal length of the variable
power optical system in the telephoto end state.
[0037] In the variable power optical system according to Embodiment
3, it is preferable that the first lens group moves toward the
image plane first and then moves toward the object upon zooming
from the wide-angle end state to the telephoto end state.
[0038] A variable power optical system according to Embodiment 4
includes, in order from an object: a first lens group having
positive refractive power; a second lens group having negative
refractive power; and a rear group having positive refractive
power, and the rear group includes at least a third lens group
having positive refractive power and disposed closest to the object
in the rear group. The distance between the first lens group and
the second lens group, and the distance between the second lens
group and the rear group changes respectively and each distance
between lenses constituting the third lens group is constant upon
zooming from a wide-angle end state to a telephoto end state. The
third lens group includes, in order from the object: a first
sub-group of which position with respect to the image plane is
fixed upon correcting camera shake; and a second sub-group used as
a vibration-isolating lens group which has positive refractive
power and can move so as to have a component in a direction
orthogonal to the optical axis upon correcting camera shake, and
the following conditional expression is satisfied:
1.5<fv.times.FNOw/f3<5.0
where f3 denotes a focal length of the third lens group, fv denotes
a focal length of the second sub-group, and FNOw denotes an F
number in the wide-angle end state.
[0039] In the variable power optical system according to Embodiment
4, it is preferable that the first sub-group includes an
intermediate group constituted by, in order from the object, a
positive lens, a negative lens, a negative lens and a positive
lens.
[0040] In the variable power optical system according to Embodiment
4, it is preferable that the first sub-group includes an object
side group having positive refractive power and disposed to the
object side of the intermediate group.
[0041] In the variable power optical system according to Embodiment
4, it is preferable that the second sub-group is constituted by one
positive lens.
[0042] In the variable power optical system according to Embodiment
4, it is preferable that the second sub-group is constituted by one
biconvex lens.
[0043] In the variable power optical system according to Embodiment
4, it is preferable that the second sub-group includes at least one
positive lens, and satisfies the following conditional
expressions:
ndVR+0.0052.times..nu.dVR-1.965<0
.nu.dVR>60
where ndVR denotes a refractive index of a medium of the positive
lens included in the second sub-group at d-line, and .nu.dVR
denotes an Abbe number of the medium of the positive lens included
in the second sub-group.
[0044] In the variable power optical system according to Embodiment
4, it is preferable that the first sub-group includes: an
intermediate group constituted by, in order from the object, a
positive lens, a negative lens, a negative lens, and a positive
lens; and an object side group having positive refractive power and
disposed to the object side of the intermediate group, the object
side group includes one positive lens, and the following
conditional expression is satisfied:
.nu.dO>60
where .nu.dO denotes an Abbe number of a medium of the positive
lens included in the object side group.
[0045] In the variable power optical system according to Embodiment
4, it is preferable that the rear group includes a plurality of
lens groups, each distance between the plurality of lens groups
included in the rear group changes upon zooming from a wide-angle
end state to a telephoto end state, and when a lens group closest
to the image, out of the plurality of lens groups, is a final lens
group, the following conditional expression is satisfied:
4.0<fr/fw<11.0
where fr denotes a focal length of the final lens group, and fw
denotes a focal length of the variable power optical system in the
wide-angle end state.
[0046] In the variable power optical system according to Embodiment
4, it is preferable that the rear group includes, in order from the
object, the third lens group and the fourth lens group, the
distance between the third lens group and the fourth lens group
Changes upon zooming from the wide-angle end state to the telephoto
end state, the third lens group includes at least the intermediate
lens group, and the following conditional expression is
satisfied:
0.9<f3/(fw.times.ft).sup.1/2<2.0
where f3 denotes a focal length of the third lens group, fw denotes
a focal length of the variable power optical system in the
wide-angle end state, and ft denotes a focal length of the variable
power optical system in the telephoto end state.
[0047] In the variable power optical system according to Embodiment
4, it is preferable that the first lens group moves toward the
image plane first and then moves toward the object upon zooming
from the wide-angle end state to the telephoto end state.
[0048] An optical apparatus according to the present invention
includes any one of the above mentioned variable power optical
systems according to Embodiment 1.
[0049] An optical apparatus according to the present invention
includes any one of the above mentioned variable power optical
systems according to Embodiment 2.
[0050] An optical apparatus according to the present invention
includes any one of the above mentioned variable power optical
systems according to Embodiment 3.
[0051] An optical apparatus according to the present invention
includes any one of the above mentioned variable power optical
systems according to Embodiment 4.
[0052] A manufacturing method for a variable power optical system
according to the present invention is a manufacturing method for a
variable power optical system which includes, in order from an
object: a first lens group having positive refractive power; a
second lens group having negative refractive power; a third lens
group having positive refractive power; and a fourth lens group
having positive refractive power. The method includes: disposing
each lens group so that the distance between the first lens group
and the second lens group, the distance between the second lens
group and the third lens group, and the distance between the third
lens group and the fourth lens group change respectively upon
zooming from a wide-angle end state to a telephoto end state; and
configuring the third lens group so as to include: an intermediate
group constituted by, in order from the object, a positive lens, a
negative lens, a negative lens, and a positive lens; and an image
side group having negative refractive power and disposed to an
image side of the intermediate group, and disposing the third lens
group so that the position of the intermediate group with respect
to the image plane is fixed and the image side group moves along
the optical axis upon focusing.
[0053] A manufacturing method for a variable power optical system
according to the present invention is a manufacturing method for a
variable power optical system which includes, in order from an
object: a first lens group having positive refractive power; a
second lens group having negative refractive power; a third lens
group having positive refractive power; and a fourth lens group
having positive refractive power. The method includes: disposing
each lens group so that the distance between the first lens group
and the second lens group, the distance between the second lens
group and the third lens group, and the distance between the third
lens group and the fourth lens group change respectively upon
zooming from a wide-angle end state to a telephoto end state;
configuring the third lens group so as to include: an intermediate
group constituted by, in order from the object, a positive lens, a
negative lens, a negative lens, and a positive lens; and an image
side group having negative refractive power and disposed to an
image side of the intermediate group, and disposing the third lens
group so that the position of the intermediate group with respect
to the image plane is fixed and the image side group moves along
the optical axis upon focusing; and disposing each lens group so
that the following conditional expression is satisfied:
0.4<(-f2)/(fw.times.ft).sup.1/2<1.1
where f2 denotes a focal length of the second lens group, fw
denotes a focal length of the variable power optical system in the
wide-angle end state, and ft denotes a focal length of the variable
power optical system in the telephoto end state.
[0054] A manufacturing method for a variable power optical system
according to the present invention is a manufacturing method for a
variable power optical system which includes, in order from an
object: a first lens group having positive refractive power; a
second lens group having negative refractive power; a third lens
group having positive refractive power; and a fourth lens group
having positive refractive power. The method includes: disposing
each lens group so that the distance between the first lens group
and the second lens group, the distance between the second lens
group and the third lens group, and the distance between the third
lens group and the fourth lens group change respectively upon
zooming from a wide-angle end state to a telephoto end state;
configuring the third lens group so as to include: an intermediate
group constituted by, in order from the object, a first positive
lens, a first negative lens, a second negative lens, and a second
positive lens; and an image side group having negative refractive
power and disposed to an image side of the intermediate group, and
disposing the third lens group so that the position of the
intermediate group with respect to the image plane is fixed and the
image side group moves along the optical axis upon focusing; and
disposing the third lens group so that the following conditional
expression is satisfied:
-0.8<(R2a-R1b)/(R2a-R1b)<0.5
where R2a denotes a radius of curvature of an image side lens
surface of the first negative lens, and Rib denotes a radius of
curvature of an object side lens surface of the second negative
lens.
[0055] A manufacturing method for a variable power optical system
according to the present invention is a manufacturing method for a
variable power optical system which includes, in order from an
object: a first lens group having positive refractive power; a
second lens group having negative refractive power; and a rear
group having positive refractive power and disposed to an image
side of the second lens group. The method includes: disposing each
lens group so that the distance between the first lens group and
the second lens group, and the distance between the second lens
group and the rear lens group change respectively upon zooming from
a wide-angle end state to a telephoto end state; and disposing, in
the rear group: an intermediate group constituted by, in order from
the object, a positive lens, a negative lens, a negative lens, and
a positive lens; and a vibration-isolating lens group having
positive refractive power, disposed to an image side of the
intermediate group and moving so as to have a component in a
direction orthogonal to the optical axis.
[0056] A manufacturing method for a variable power optical system
according to the present invention is a manufacturing method for a
variable power optical system which includes, in order from an
object: a first lens group having positive refractive power; a
second lens group having negative refractive power; and a rear
group having positive refractive power and disposed to an image
side of the second lens group. The method includes: disposing each
lens group so that the distance between the first lens group and
the second lens group, and the distance between the second lens
group and the rear group change respectively upon zooming from a
wide-angle end state to a telephoto end state; disposing, in the
rear group: an intermediate group constituted by, in order from the
object, a positive lens, a negative lens, a negative lens and a
positive lens; and a vibration-isolating lens group having positive
refractive power, disposed to an image side of the intermediate
group and moving so as to have a component in a direction
orthogonal to the optical axis; disposing, in the rear group, at
least a third lens group having positive refractive power and
disposed closest to the object; disposing the third lens group so
that each distance between lenses constituting the third lens group
is constant upon zooming from the wide-angle end state to the
telephoto end state; disposing the third lens group so as to
include the intermediate group; and disposing the third lens group
so that the following conditional expression is satisfied:
1.0<f3/.DELTA.T3<2.2
where .DELTA.T3 denotes a moving distance of the third lens group
upon zooming from the wide-angle end state to the telephoto end
state, and f3 denotes a focal length of the third lens group.
[0057] A manufacturing method for a variable power optical system
according to the present invention is a manufacturing method for a
variable power optical system which includes, in order from an
object: a first lens group having positive refractive power; a
second lens group having negative refractive power; and a rear
group having positive refractive power. The method includes:
disposing, in the rear group, at least a third lens group having
positive refractive power and disposed closest to the object in the
rear group; disposing each lens group so that the distance between
the first lens group and the second lens group, and the distance
between the second lens group and the rear group change
respectively, and each distance between lenses constituting the
third lens group is constant upon zooming from a wide-angle end
state to a telephoto end state; disposing, in the third lens group
and in order from the object: a first sub-group of which position
with respect to the image plane is fixed upon correcting camera
shake; and a second sub-group used as a vibration-isolating lens
group which has positive refractive power and can move so as to
have a component in a direction orthogonal to the optical axis upon
correcting camera shake; and disposing each lens group so that the
following conditional expression is satisfied:
1.5<fv.times.FNOw/f3<5.0
where f3 denotes a focal length of the third lens group, fv denotes
a focal length of the second sub-group, and FNOw denotes an F
number in the wide-angle end state.
Advantageous Effects of the Invention
[0058] According to the present invention, a variable power optical
system having a high brightness and excellent optical performance,
an optical apparatus that includes this variable power optical
system, and a manufacturing method for this variable power optical
system can be provided.
BRIEF DESCRIPTION OF THE DRAWINGS
[0059] FIG. 1 is a cross-sectional view depicting a lens
configuration of a variable power optical system according to
Example 1;
[0060] FIGS. 2A and 2B are graphs showing various aberrations of
the variable power optical system according to Example 1 upon
focusing on infinity, where FIG. 2A are graphs showing various
aberrations in the wide-angle end state, and FIG. 2B are graphs
showing coma aberrations when image blur is corrected in the
wide-angle end state;
[0061] FIGS. 3A and 3B are graphs showing various aberrations of
the variable power optical system according to Example 1 upon
focusing on infinity, where FIG. 3A are graphs showing various
aberrations in the intermediate focal length state, and FIG. 3B are
graphs showing coma aberrations when image blur is corrected in the
intermediate focal length state;
[0062] FIGS. 4A and 4B are graphs showing various aberrations of
the variable power optical system according to Example 1 upon
focusing on infinity, where FIG. 4A are graphs showing various
aberrations in the telephoto end state, and FIG. 4B are graphs
showing coma aberrations when image blur is corrected in the
telephoto end state;
[0063] FIGS. 5A, 5B and 5C are graphs showing various aberrations
of the variable power optical system according to Example 1 upon
focusing on a close point, where FIG. 5A shows the wide-angle end
state, FIG. 5B shows the intermediate focal length state, and FIG.
5C shows the telephoto end state;
[0064] FIG. 6 is a cross-sectional view depicting a lens
configuration of a variable power optical system according to
Example 2;
[0065] FIGS. 7A and 7B are graphs showing various aberrations of
the variable power optical system according to Example 2 upon
focusing on infinity, where FIG. 7A are graphs showing various
aberrations in the wide-angle end state, and FIG. 7B are graphs
showing coma aberrations when image blur is corrected in the
wide-angle end state;
[0066] FIGS. 8A and 8B are graphs showing various aberrations of
the variable power optical system according to Example 2 upon
focusing on infinity, where FIG. 8A are graphs showing various
aberrations in the intermediate focal length state, and FIG. 8B are
graphs showing coma aberrations when image blur is corrected in the
intermediate focal length state;
[0067] FIGS. 9A and 9B are graphs showing various aberrations of
the variable power optical system according to Example 2 upon
focusing on infinity, where FIG. 9A are graphs showing various
aberrations in the telephoto end state, and FIG. 9B are graphs
showing coma aberrations when image blur is corrected in the
telephoto end state;
[0068] FIGS. 10A, 10B and 10C are graphs showing various
aberrations of the variable power optical system according to
Example 2 upon focusing on a close point, where FIG. 10A shows the
wide-angle end state, FIG. 10B shows the intermediate focal length
state, and FIG. 10C shows the telephoto end state;
[0069] FIG. 11 is a cross-sectional view depicting a lens
configuration of a variable power optical system according to
Example 3;
[0070] FIGS. 12A and 12B are graphs showing various aberrations of
the variable power optical system according to Example 3 upon
focusing on infinity, where FIG. 12A are graphs showing various
aberrations in the wide-angle end state, and FIG. 12B are graphs
showing coma aberrations when image blur is corrected in the
wide-angle end state;
[0071] FIGS. 13A and 13B are graphs showing various aberrations of
the variable power optical system according to Example 3 upon
focusing on infinity, where FIG. 13A are graphs showing various
aberrations in the intermediate focal length state, and FIG. 13B
are graphs showing coma aberrations when image blur is corrected in
the intermediate focal length state;
[0072] FIGS. 14A and 14B are graphs showing various aberrations of
the variable power optical system according to Example 3 upon
focusing on infinity, where FIG. 14A are graphs showing various
aberrations in the telephoto end state, and FIG. 14B are graphs
showing coma aberrations when image blur is corrected in the
telephoto end state;
[0073] FIGS. 15A, 15B and 15C are graphs showing various
aberrations of the variable power optical system according to
Example 3 upon focusing on a close point, where FIG. 15A shows the
wide-angle end state, FIG. 15B shows the intermediate focal length
state, and FIG. 15C shows the telephoto end state;
[0074] FIG. 16 is a cross-sectional view depicting a lens
configuration of a variable power optical system according to
Example 4;
[0075] FIGS. 17A and 17B are graphs showing various aberrations of
the variable power optical system according to Example 4 upon
focusing on infinity, where FIG. 17A are graphs showing various
aberrations in the wide-angle end state, and FIG. 17B are graphs
showing coma aberrations when image blur is corrected in the
wide-angle end state;
[0076] FIGS. 18A and 18B are graphs showing various aberrations of
the variable power optical system according to Example 4 upon
focusing on infinity, where FIG. 18A are graphs showing various
aberrations in the intermediate focal length state, and FIG. 18B
are graphs showing coma aberrations when image blur is corrected in
the intermediate focal length state;
[0077] FIGS. 19A and 19B are graphs showing various aberrations of
the variable power optical system according to Example 4 upon
focusing on infinity, where FIG. 19A are graphs showing various
aberrations in the telephoto end state, and FIG. 19B are graphs
showing coma aberrations when image blur is corrected in the
telephoto end state;
[0078] FIGS. 20A, 20B and 20C are graphs showing various
aberrations of the variable power optical system according to
Example 4 upon focusing on a close point, where FIG. 20A shows the
wide-angle end state, FIG. 20B shows the intermediate focal length
state, and FIG. 20C shows the telephoto end state;
[0079] FIG. 21 is a cross-sectional view depicting a lens
configuration of a variable power optical system according to
Example 5;
[0080] FIGS. 22A and 22B are graphs showing various aberrations of
the variable power optical system according to Example 5 upon
focusing on infinity, where FIG. 22A are graphs showing various
aberrations in the wide-angle end state, and FIG. 22B are graphs
showing coma aberrations when image blur is corrected in the
wide-angle end state;
[0081] FIGS. 23A and 23B are graphs showing various aberrations of
the variable power optical system according to Example 5 upon
focusing on infinity, where FIG. 23A are graphs showing various
aberrations in the intermediate focal length state, and FIG. 23B
are graphs showing coma aberrations when image blur is corrected in
the intermediate focal length state;
[0082] FIGS. 24A and 24B are graphs showing various aberrations of
the variable power optical system according to Example 5 upon
focusing on infinity, where FIG. 24A are graphs showing various
aberrations in the telephoto end state, and FIG. 24B are graphs
showing coma aberrations when image blur is corrected in the
telephoto end state;
[0083] FIGS. 25A, 25B and 25C are graphs showing various
aberrations of the variable power optical system according to
Example 5 upon focusing on a close point, where FIG. 25A shows the
wide-angle end state, FIG. 25B shows the intermediate focal length
state, and FIG. 25C shows the telephoto end state;
[0084] FIG. 26 is a cross-sectional view depicting a lens
configuration of a variable power optical system according to
Example 6;
[0085] FIGS. 27A and 27B are graphs showing various aberrations of
the variable power optical system according to Example 6 upon
focusing on infinity, where FIG. 27A are graphs showing various
aberrations in the wide-angle end state, and FIG. 27B are graphs
showing coma aberrations when image blur is corrected in the
wide-angle end state;
[0086] FIGS. 28A and 28B are graphs showing various aberrations of
the variable power optical system according to Example 6 upon
focusing on infinity, where FIG. 28A are graphs showing various
aberrations in the intermediate focal length state, and FIG. 28B
are graphs showing coma aberrations when image blur is corrected in
the intermediate focal length state;
[0087] FIGS. 29A and 29B are graphs showing various aberrations of
the variable power optical system according to Example 6 upon
focusing on infinity, where FIG. 29A are graphs showing various
aberrations in the telephoto end state, and FIG. 29B are graphs
showing coma aberrations when image blur is corrected in the
telephoto end state;
[0088] FIG. 30 is a cross-sectional view of a camera that includes
the variable power optical system;
[0089] FIG. 31 is a flow chart depicting a manufacturing method for
the variable power optical system according to Embodiment 1
represented by Example 1 to Example 5;
[0090] FIG. 32 is a flow chart depicting a manufacturing method for
the variable power optical system according to Embodiment 2
represented by Example 1 to Example 5;
[0091] FIG. 33 is a flow chart depicting a manufacturing method for
the variable power optical system according to Embodiment 3
represented by Example 1 to Example 6; and
[0092] FIG. 34 is a flow chart depicting a manufacturing method for
the variable power optical system according to Embodiment 4
represented by Example 1 to Example 6.
DESCRIPTION OF THE EMBODIMENTS
[0093] Embodiments of the present invention will now be described
with reference to the drawings. Many of the composing elements in
Embodiments 1 to 4 are the same or similar, therefore same or
similar components are described using a same drawing (same
reference symbol) for convenience of explanation.
Embodiment 1
[0094] Embodiment 1 will now be described with reference to the
drawings. As shown in FIG. 1, a variable power optical system ZL
according to Embodiment 1 includes, in order from an object: a
first lens group G1 having positive refractive power; a second lens
group G2 having negative refractive power; a third lens group G3
having positive refractive power; and a fourth lens group G4 having
positive refractive power. In this variable power optical system
ZL, the distance between the first lens group G1 and the second
lens group G2, the distance between the second lens group G2 and
the third lens group G3, and the distance between the third lens
group G3 and the fourth lens group G4 change respectively upon
zooming from the wide-angle end state to the telephoto end state.
In this variable power optical system ZL, the third lens group G3
includes: an intermediate group G3b constituted by, in order from
the object, a positive lens, a negative lens, a negative lens and a
positive lens; and an image side group G3c having negative
refractive power and disposed to the image side of the intermediate
group G3b, and focusing is performed from infinity to an object at
close distance by moving the image side group G3c along the optical
axis in a state of fixing the position of the intermediate group
G3b with respect to the image plane. By configuring the variable
power optical system ZL of this embodiment in this way, excellent
optical performance can be implemented with bright lenses having
small (or bright) F numbers. In other words, the intermediate group
G3b of the third lens group G3 is constituted by four lenses having
a symmetric structure (positive, negative, negative, positive),
whereby spherical aberration, curvature of field, and coma
aberration can be corrected well while keeping the F numbers small
for high brightness. If an aperture stop S is disposed between the
second lens group G2 and the third lens group G3 (or to the object
side of the third lens group G3), and focusing is performed by the
image side group G3c disposed to the image side of the intermediate
group G3b, the distance between the aperture stop S and the
focusing lens group can be increased, and fluctuation of the image
plane upon focusing can be controlled. "Lens component" refers to a
single lens or to a cemented lens where a plurality of lenses are
cemented.
[0095] It is preferable that the variable power optical system ZL
according to this embodiment satisfies the following conditional
expression (1).
0.4<(-f2)/(fw.times.ft).sup.1/2<1.1 (1)
where f2 denotes a focal length of the second lens group G2, fw
denotes a focal length of the variable power optical system ZL in
the wide-angle end state, and ft denotes a focal length of the
variable power optical system ZL in the telephoto end state.
[0096] The conditional expression (1) specifies a focal length of
the second lens group G2. If the upper limit value of the
conditional expression (1) is exceeded, the refractive power of the
second lens group G2 decreases, hence the moving distance upon
zooming increases and the total length of the optical system
increases, which is not desirable. To demonstrate the effect of the
invention with certainty, it is preferable that the upper limit
value of the conditional expression (1) is 1.0. To demonstrate the
effect of the invention to the maximum, it is preferable that the
upper limit value of the conditional expression (1) is 0.9. On the
other hand, if the lower limit value of the conditional expression
(1) is not reached, the refractive power of the second lens group
G2 increases, and curvature of field and astigmatism cannot be
corrected well, which is not desirable. To demonstrate the effect
of the invention with certainty, it is preferable that the lower
limit value of the conditional expression (1) is 0.5. To
demonstrate the effect of the invention to the maximum, it is
preferable that the lower limit value of the conditional expression
(1) is 0.6.
[0097] In the variable power optical system ZL according to this
embodiment, it is preferable that the third lens group G3 includes
an object side group G3a having positive refractive power and
disposed to the object side of the intermediate group G3b. By this
configuration, even better optical performance can be implemented
with bright lenses having small (bright) F numbers. Further
high-order spherical aberration, which tends to be generated in
bright lenses, can be corrected well.
[0098] In the variable power optical system ZL according to this
embodiment, it is preferable that the image side group G3c, which
is included in the third lens group G3 and is used for focusing, is
constituted by one negative lens. By this configuration, the
focusing lens can be lighter and focusing speed can be easily
increased. Further, it is preferable that the image side group G3c
is constituted by one negative meniscus lens having a concave
surface facing the image plane. By this configuration, fluctuation
of spherical aberration generated upon focusing can be controlled,
and high speed focusing can be implemented.
[0099] In the variable power optical system ZL according to this
embodiment, it is preferable that the image side group G3c included
in the third lens group G3 has at least one negative lens, and this
negative lens satisfies the following conditional expression
(2).
ndF+0.0052.times..nu.dF-1.965<0 (2)
where ndF denotes a refractive index of a medium of the negative
lens included in the image side group G3c at d-line.
[0100] The conditional expression (2) specifies the refractive
index of the medium of the negative lens included in the image side
group G3c at d-line. If the upper limit value of the conditional
expression (2) is exceeded, glass material having relatively high
refractive power and high color dispersibility must be used for
this negative lens, and longitudinal chromatic aberration cannot be
corrected well in a range from infinity to an object at a close
distance upon focusing, which is not desirable.
[0101] It is preferable that the negative lens included in the
image side group G3c of the third lens group G3 satisfies the
following conditional expression (3).
.nu.dF>60 (3)
where .nu.dF denotes an Abbe number of the medium of the negative
lens included in the image side group G3c.
[0102] The conditional expression (3) specifies an Abbe number of
the medium of the negative lens included in the image side group
G3c. If the lower limit value of the conditional expression (3) is
not reached, dispersibility of the focusing lens increases, and
longitudinal chromatic aberration, which tends to stand out in a
bright lens, cannot be corrected sufficiently in the range from
infinity to an object at close distance upon focusing, which is not
desirable. To demonstrate the effect of the invention with
certainty, it is preferable that the lower limit value of the
conditional expression (3) is 62.
[0103] In the variable power optical system ZL according to this
embodiment, if the third lens group G3 includes an object side
group G3a having positive refractive power and disposed to the
object side of the intermediate group G3b, it is preferable that
this object side group G3a includes one positive lens and satisfies
the following conditional expression (4).
.nu.dO>60 (4)
where .nu.dO denotes an Abbe number of a medium of the positive
lens included in the object side group G3a.
[0104] The conditional expression (4) specifies the Abbe number of
the medium of the positive lens included in the object side group
G3a of the third lens group G3. If the lower limit value of the
conditional expression (4) is not reached, longitudinal chromatic
aberration, which tends to be generated in bright lenses,
increases, and correction thereof becomes difficult, which is not
desirable. To demonstrate the effect of the invention with
certainty, it is preferable that the lower limit value of the
conditional expression (4) is 62. To demonstrate the effect of the
invention to the maximum, it is preferable that the lower limit
value of the conditional expression (4) is 65.
[0105] It is preferable that that the variable power optical system
ZL according to this embodiment satisfies the following conditional
expression (5).
4.0<f4/fw<11.0 (5)
where f4 denotes a focal length of the fourth lens group G4, and fw
denotes a focal length of the variable power optical system ZL in
the wide-angle end state.
[0106] The conditional expression (5) specifies the focal length of
the fourth lens group G4. If the upper limit value of the
conditional expression (5) is exceeded, the refractive power of the
fourth lens group G4 decreases, and correction of curvature of
field upon zooming becomes difficult, which is not desirable. To
demonstrate the effect of the invention with certainty, it is
preferable that the upper limit value of the conditional expression
(5) is 10.0. To demonstrate the effect of the invention to the
maximum, it is preferable that the upper limit value of the
conditional expression (5) is 9.0. On the other hand, if the lower
limit value of the conditional expression (5) is not reached, the
refractive power of the fourth lens group G4 increases, and
correction of distortion becomes difficult, and back focus cannot
be secured, which is not desirable. To demonstrate the effect of
the invention with certainty, it is preferable that the lower limit
value of the conditional expression (5) is 5.0. To demonstrate the
effect of the invention to the maximum, it is preferable that the
lower limit value of the conditional expression (5) is 6.0.
[0107] In the variable power optical system ZL according to this
embodiment, it is preferable that the first lens group G1 moves
toward the image plane first, then moves toward the object upon
zooming from the wide-angle end state to the telephoto end state.
By this configuration, the diameter of the first lens group G1 is
kept small while preventing abaxial light interrupt when the
distance between the first lens group G1 and the second lens group
G2 is increased, and a sudden change of distortion can be
controlled.
[0108] In the variable power optical system ZL according to this
embodiment, it is preferable that the third lens group G3 is
disposed to the image side of the intermediate group G3b, and
includes an image side group having positive refractive power, and
camera shake (image blur) is corrected by using this image side
group as a vibration-isolating lens group (hereafter called
"vibration-isolating lens group G32") that moves so as to have a
component in a direction orthogonal to the optical axis in a state
of fixing the position of the intermediate group G3b with respect
to the image plane. By disposing the vibration-isolating lens group
G32 having positive refractive power to the image side of the
intermediate group G3b in this way, a vibration-isolating function
can be provided without increasing the number of lenses of the
vibration-isolating lens group G32, even if bright lenses having
small (bright) F numbers are used.
[0109] In the variable power optical system ZL according to this
embodiment, it is preferable that the third lens group G3 includes,
in order from the object: a first sub-group G31; and a second
sub-group G32 having positive refractive power. And the camera
shake (image blur) is corrected using a second sub-group G32 as a
vibration-isolating lens group, which moves so as to have a
component in a direction orthogonal to the optical axis in a state
of fixing the position of the first sub-group G31 with respect to
the image plane. If the second sub-group (vibration-isolating lens
group) G32 having positive refractive power is disposed to the
image side of the first sub-group G31 in this way, a
vibration-isolating function can be provided without increasing the
number of lenses of the second sub-group (vibration-isolating lens
group) G32, even if the bright lenses with small (bright) F numbers
are used.
[0110] It is preferable that the variable power optical system ZL
according to this embodiment satisfies the following conditional
expression (6).
1.5<fv.times.FNOw/f3<5.0 (6)
where f3 denotes a focal length of the third lens group G3, fv
denotes a focal length of the second sub-group G32, and FNOw
denotes an F number in the wide-angle end state.
[0111] The conditional expression (6) specifies the focal length of
the second sub-group G32, used as the vibration-isolating lens
group, and the focal length of the third lens group G3. If the
upper limit value of the conditional expression (6) is exceeded,
the refractive power of the second sub-group G32 decreases.
Further, the moving distance of the second sub-group G32 upon
vibration isolation (upon image blur correction) increases, and the
diameter of the second sub-group G32 increases, which makes the
second sub-group G32 heavier, and makes it difficult to correct
eccentric coma aberration well upon vibration isolation, which is
not desirable. To demonstrate the effect of the invention with
certainty, it is preferable that the upper limit value of the
conditional expression (6) is 4.5. To demonstrate the effect of the
invention to the maximum, it is preferable that the upper limit
value of the conditional expression (6) is 4.0. On the other hand,
if the lower limit value of the conditional expression (6) is not
reached, the refractive power of the second sub-group G32
increases, and eccentric astigmatism and eccentric coma aberration
cannot be corrected well upon vibration isolation, which is not
desirable. To demonstrate the effect of the invention with
certainty, it is preferable that the lower limit value of the
conditional expression (6) is 1.6. To demonstrate the effect of the
invention with even higher certainty, it is preferable that the
lower limit value of the conditional expression (6) is 1.8. To
demonstrate the effect of the invention to the maximum, it is
preferable that the lower limit value of the conditional expression
(6) is 2.2.
[0112] In the variable power optical system ZL according to this
embodiment, at least one positive lens component may or may not be
disposed between the intermediate group G3b and the image side
group G3c of the third lens group G3. In the same manner, the
object side group G3a disposed to the object side of the
intermediate group G3b of the third lens group G3 may be omitted.
In the four lenses (positive, negative, negative, positive)
included in the intermediate group G3b, the positive lens and the
negative lens may be cemented or each lens may be disposed as a
single lens respectively.
[0113] By the above configuration, a variable power optical system
ZL having high brightness and excellent optical performance can be
provided.
[0114] A camera, which is an optical apparatus including the
variable power optical system ZL according to this embodiment, will
be described with reference to FIG. 30. This camera 1 is an
interchangeable lens type mirrorless camera that includes the
variable power optical system ZL according to this embodiment as an
image capturing lens 2. In this camera 1, the light from an object
(not illustrated) is collected by the image capturing lens 2, and
forms an object image on an image plane of the imaging unit 3 via
an OLPF (Optical Low-Pass Filter), which is not illustrated. Then
the object image is photo-electric converted by a photo-electric
conversion element disposed in the imaging unit 3, whereby the
image of the object is generated. This image is displayed on an EVF
(Electronic View Finder) 4 disposed in the camera 1. Thereby the
user can view the object via the EVF 4.
[0115] If a release button (not illustrated) is pressed by the
user, the photo-electric-converted image is stored in a memory (not
illustrated) by the imaging unit 3. Thus the user can capture the
image of the object using this camera 1. In this embodiment, an
example of the mirrorless camera was described, but an effect
similar to the case of this camera 1 can be demonstrated even when
the variable power optical system ZL according to this embodiment
may be included in a single lens reflex type camera, which has a
quick return mirror in the camera main unit and views the object
using a finder optical system.
[0116] The following content can be adopted within a range where
the optical performance is not diminished.
[0117] In this example, the variable power optical system ZL
constituted by four lens groups was shown, but the present
invention can also be applied to a configuration using a different
number of lens groups, such as five lens groups or six lens groups.
A lens or a lens group may be added to the configuration on the
side closest to the object, or a lens or a lens group may be added
to the configuration on the side closest to the image. "Lens group"
refers to a portion having at least one lens isolated by an air
space which Changes upon zooming. In the variable power optical
system ZL of this embodiment, the first lens group G1 to the fourth
lens group G4 move along the optical axis respectively, such that
each air space between the lens groups changes upon zooming.
[0118] A single or plurality of lens group(s) or a partial lens
group may be designed to be a focusing lens group, which performs
focusing from an object at infinity to an object at a close
distance by moving in the optical axis direction. This focusing
lens group can be applied to auto focus, and is also suitable for
driving a motor for auto focusing (driving using an ultrasonic
motor or the like). It is particularly preferable that a part of
the third lens group G3 (image side group G3c, as mentioned above)
is designed to be the focusing lens group, and the positions of
other lenses with respect to the image plane are preferably fixed
upon focusing.
[0119] A lens group or a partial lens group may be designed to be a
vibration-isolating lens group, which corrects image blurs
generated by camera shake, by moving the lens group or the partial
lens group so as to have a component in a direction orthogonal to
the optical axis or rotating (oscillating) the lens group or the
partial lens group in an in-plane direction that includes the
optical axis. It is particularly preferable that at least a part of
the third lens group G3 (e.g. lens disposed to the image side of
the four lenses (positive, negative, negative, positive) of the
intermediate group G3b) is designed to be the vibration-isolating
lens group.
[0120] The lens surface may be formed to be a spherical surface or
a plane, or an aspherical surface. If the lens surface is a
spherical surface or a plane, lens processing, assembly and
adjustment are easy, and deterioration of optical performance, due
to an error generated in processing, assembly and adjustment, can
be prevented. Even if the image plane is shifted, the drawing
performance is not affected very much, which is desirable. If the
lens surface is aspherical, the aspherical surface can be any
aspherical surface out of an aspherical surface generated by
grinding, a glass-molded aspherical surface generated by forming
glass in an aspherical shape using a die, and a composite
aspherical surface generated by forming resin on the surface of the
glass to be an aspherical shape. The lens surface may be a
diffraction surface, and the lens may be a refractive
index-distributed lens (GRIN lens) or a plastic lens.
[0121] It is preferable that the aperture stop S is disposed near
the third lens group G3, but the role of the aperture stop may be
substituted by the frame of the lens, without disposing a separate
member as the aperture stop.
[0122] Each lens surface may be coated with an anti-reflection
film, which has high transmittance in a wide wavelength region, in
order to decrease flares and ghosts, and implement high optical
performance with high contrast.
[0123] The zoom ratio of the variable power optical system ZL of
this embodiment is about 2.5 to 4.
[0124] An outline of a manufacturing method for the variable power
optical system ZL according to this embodiment will now be
described with reference to FIG. 31. First each lens is disposed to
prepare the first to fourth lens groups G1 to G4 (step S110). Each
lens group is disposed so that the distance between the first lens
group G1 and the second lens group G2, the distance between the
second lens group G2 and the third lens group G3, and the distance
between the third lens group G3 and the fourth lens group G4 change
respectively upon zooming from the wide-angle end state to the
telephoto end state (step S120). The third lens group G3 includes:
the intermediate group G3b constituted by, in order from the
object, the positive lens, the negative lens, the negative lens and
the positive lens; and the image side group G3c having negative
refractive power and disposed to the image side of the intermediate
group G3b, and the third lens group G3 is disposed so that the
position of the intermediate group G3b with respect to the image
plane is fixed, and the image side group G3c moves along the
optical axis upon focusing (step S130).
[0125] In the manufacturing method for the variable power optical
system ZL according to this embodiment, it is preferable that each
lens group is disposed so that the above mentioned conditional
expression (1) is satisfied.
[0126] As shown in FIG. 1, according to a concrete example of this
embodiment, the first lens group G1 is prepared by disposing a
cemented lens, where a negative meniscus lens L11 having a convex
surface facing the object and a positive meniscus lens L12 having a
convex surface facing the object are cemented in order from the
object. The second lens group G2 is prepared by disposing: a
negative lens L21, of which aspherical shape is formed by creating
a resin layer on an object side lens surface of a negative meniscus
lens having a convex surface facing the object; a cemented lens
where a biconcave lens L22 and a biconvex lens L23 are cemented;
and a cemented lens where a positive meniscus lens L24 having a
concave surface facing the object, and a negative lens L25 which
has a concave surface facing the object and of which image side
lens surface is aspherical, are cemented. The third lens group G3
is prepared by disposing: a positive lens L31 of which object side
and image side lens surfaces are aspherical; a cemented lens where
a biconvex lens L32 and a biconcave lens L33 are cemented; a
cemented lens where a biconcave lens L34 and a biconvex lens L35
are cemented; a positive lens L36 of which object side and image
side lens surfaces are aspherical; and a negative meniscus lens L37
having a convex surface facing the object. The fourth lens group G4
is prepared by disposing a positive lens L41 of which object side
lens surface is aspherical. These lens groups are disposed
according to the above mentioned procedure, whereby the variable
power optical system ZL is manufactured.
Embodiment 2
[0127] Embodiment 2 will now be described with reference to the
drawings. As shown in FIG. 1, a variable power optical system ZL
according to Embodiment 2 includes, in order from an object: a
first lens group G1 having positive refractive power; a second lens
group G2 having negative refractive power; a third lens group G3
having positive refractive power; and a fourth lens group G4 having
positive refractive power. In this variable power optical system
ZL, the distance between the first lens group G1 and the second
lens group G2, the distance between the second lens group G2 and
the third lens group G3, and the distance between the third lens
group G3 and the fourth lens group G4 change respectively upon
zooming from the wide-angle end state to the telephoto end state.
In this variable power optical system ZL, the third lens group G3
includes: an intermediate group G3b constituted by, in order from
the object, a first positive lens, a first negative lens, a second
negative lens and a second positive lens; and an image side group
G3c having negative refractive power and disposed to an image side
of the intermediate group G3b, and focusing is performed from
infinity to an object at close distance by moving the image side
group G3c along the optical axis in a state of fixing the position
of the intermediate group G3b with respect to the image plane. By
designing the variable power optical system ZL of this embodiment
to have this configuration, excellent optical performance can be
implemented with bright lenses having small (bright) F numbers. In
other words, the intermediate group G3b of the third lens group G3
is constituted by four lenses having a symmetric structure
(positive, negative, negative, positive), whereby spherical
aberration, curvature of field, and coma aberration can be
corrected well while keeping the F numbers small for high
brightness. If an aperture stop S is disposed between the second
lens group G2 and the third lens group G3 (or to the object side of
the third lens group G3), and focusing is performed by the image
side group G3c disposed to the image side of the intermediate group
G3b, the distance between the aperture stop S and the focusing lens
group can be increased, and fluctuation of the image plane upon
focusing can be controlled. "Lens component" refers to a single
lens or to a cemented lens where a plurality of lenses are
cemented.
[0128] In the variable power optical system ZL according to this
embodiment, it is preferable that an air lens created by the first
negative lens and the second negative lens included in the
intermediate group G3b of the third lens group G3 satisfies the
following conditional expression (7).
-0.8<(R2a+R1b)/(R2a-R1b)<0.5 (7)
where R2a denotes a radius of curvature of an image side lens
surface of the first negative lens, and Rib denotes a radius of
curvature of an object side lens surface of the second negative
lens.
[0129] The conditional expression (7) specifies the shape of the
air lens created by the first negative lens and the second negative
lens included in the intermediate group G3b of the third lens group
G3. If the upper limit value of the conditional expression (7) is
exceeded, the positive refractive power of the image side of the
third lens group G3 (image side of the air lens) is required to be
increased, which makes it difficult to correct abaxial aberrations,
such as coma aberration, and is not desirable. To demonstrate the
effect of the invention with certainty, it is preferable that the
upper limit value of the conditional expression (7) is 0.4. To
demonstrate the effect of the invention with even higher certainty,
it is preferable that the upper limit value of the conditional
expression (7) is 0.3. To demonstrate the effect of the invention
to the maximum, it is preferable that the upper limit value of the
conditional expression (7) is 0.2. On the other hand, if the lower
limit value of the conditional expression (7) is not reached, the
object side of the third lens group G3 (object side of the air
lens) requires strong positive refractive power, which makes it
difficult to correct spherical aberration, and is not desirable. To
demonstrate the effect of the invention with certainty, it is
preferable that the lower limit value of the conditional expression
(7) is -0.7. To demonstrate the effect of the invention with even
higher certainty, it is preferable that the lower limit value of
the conditional expression (7) is -0.6. To demonstrate the effect
of the invention to the maximum, it is preferable that the lower
limit value of the conditional expression (7) is -0.5.
[0130] It is preferable that the variable power optical system ZL
according to this embodiment satisfies the following conditional
expression (1).
0.4<(-f2)/(fw.times.ft).sup.1/2<1.1 (1)
where f2 denotes a focal length of the second lens group G2, fw
denotes a focal length of the variable power optical system ZL in
the wide-angle end state, and ft denotes a focal length of the
variable power optical system ZL in the telephoto end state.
[0131] The conditional expression (1) specifies a focal length of
the second lens group G2. If the upper limit value of the
conditional expression (1) is exceeded, the refractive power of the
second lens group G2 decreases, hence the moving distance upon
zooming increases and the total length of the optical system
increases, which is not desirable. To demonstrate the effect of the
invention with certainty, it is preferable that the upper limit
value of the conditional expression (1) is 1.0. To demonstrate the
effect of the invention to the maximum, it is preferable that the
upper limit value of the conditional expression (1) is 0.9. On the
other hand, if the lower limit value of the conditional expression
(1) is not reached, the refractive power of the second lens group
G2 increases, and curvature of field and astigmatism cannot be
corrected well, which is not desirable. To demonstrate the effect
of the invention with certainty, it is preferable that the lower
limit value of the conditional expression (1) is 0.5. To
demonstrate the effect of the invention to the maximum, it is
preferable that the lower limit value of the conditional expression
(1) is 0.6.
[0132] In the variable power optical system ZL according to this
embodiment, it is preferable that the third lens group G3 includes
an object side group G3a having positive refractive power and
disposed to the object side of the intermediate group G3b. By this
configuration, even better optical performance can be implemented
with bright lenses having small F numbers. Further high-order
spherical aberration, which tends to be generated in bright lenses,
can be corrected well.
[0133] In the variable power optical system ZL according to this
embodiment, it is preferable that the image side group G3c, which
is included in the third lens group G3 and is used for focusing, is
constituted by one negative lens. By this configuration, the
focusing lens can be lighter and focusing speed can be easily
increased. Further, it is preferable that the image side group G3c
is constituted by one negative meniscus lens having a concave
surface facing the image plane. By this configuration, fluctuation
of spherical aberration generated upon focusing can be controlled,
and high speed focusing can be implemented.
[0134] In the variable power optical system ZL according to this
embodiment, it is preferable that the image side group G3c included
in the third lens group G3 has at least one negative lens, and this
negative lens satisfies the following conditional expression
(2).
ndF+0.0052.times..nu.dF-1.965<0 (2)
where ndF denotes a refractive index of a medium of the negative
lens included in the image side group G3c at d-line.
[0135] The conditional expression (2) specifies the refractive
index of the medium of the negative lens included in the image side
group G3c at d-line. If the upper limit value of the conditional
expression (2) is exceeded, glass material having relatively high
refractive power and high color dispersibility must be used for
this negative lens, and longitudinal chromatic aberration cannot be
corrected well in a range from infinity to an object at close
distance upon focusing, which is not desirable.
[0136] It is preferable that the negative lens included in the
image side group G3c of the third lens group G3 satisfies the
following conditional expression (3).
.nu.dF>60 (3)
where .nu.dF denotes an Abbe number of the medium of the negative
lens included in the image side group G3c.
[0137] The conditional expression (3) specifies an Abbe number of
the medium of the negative lens included in the image side group
G3c. If the lower limit value of the conditional expression (3) is
not reached, dispersibility of the focusing lens increases, and
longitudinal chromatic aberration, which tends to stand out in a
bright lens, cannot be corrected sufficiently in the range from
infinity to an object at close distance upon focusing, which is not
desirable. To demonstrate the effect of the invention with
certainty, it is preferable that the lower limit value of the
conditional expression (3) is 62.
[0138] In the variable power optical system ZL according to this
embodiment, if the third lens group G3 includes an object side
group G3a having positive refractive power and disposed to the
object side of the intermediate group G3b, it is preferable that
this object side group G3a includes one positive lens and satisfies
the following conditional expression (4).
.nu.dO>60 (4)
where .nu.dO denotes an Abbe number of a medium of the positive
lens included in the object side group G3a.
[0139] The conditional expression (4) specifies the Abbe number of
the medium of the positive lens included in the object side group
G3a of the third lens group G3. If the lower limit value of the
conditional expression (4) is not reached, longitudinal chromatic
aberration, which tends to be generated in bright lenses,
increases, and correction thereof becomes difficult, which is not
desirable. To demonstrate the effect of the invention with
certainty, it is preferable that the lower limit value of the
conditional expression (4) is 62. To demonstrate the effect of the
invention to the maximum, it is preferable that the lower limit
value of the conditional expression (4) is 65.
[0140] It is preferable that that the variable power optical system
ZL according to this embodiment satisfies the following conditional
expression (5).
4.0<f4/fw<11.0 (5)
where f4 denotes a focal length of the fourth lens group G4, and fw
denotes a focal length of the variable power optical system ZL in
the wide-angle end state.
[0141] The conditional expression (5) specifies the focal length of
the fourth lens group G4. If the upper limit value of the
conditional expression (5) is exceeded, the refractive power of the
fourth lens group G4 decreases, and correction of curvature of
field upon zooming becomes difficult, which is not desirable. To
demonstrate the effect of the invention with certainty, it is
preferable that the upper limit value of the conditional expression
(5) is 10.0. To demonstrate the effect of the invention to the
maximum, it is preferable that the upper limit value of the
conditional expression (5) is 9.0. On the other hand, if the lower
limit value of the conditional expression (5) is not reached, the
refractive power of the fourth lens group G4 increases, and
correction of distortion becomes difficult, and back focus cannot
be secured, which is not desirable. To demonstrate the effect of
the invention with certainty, it is preferable that the lower limit
value of the conditional expression (5) is 5.0. To demonstrate the
effect of the invention to the maximum, it is preferable that the
lower limit value of the conditional expression (5) is 6.0.
[0142] In the variable power optical system ZL according to this
embodiment, it is preferable that the first lens group G1 moves
toward the image plane first, then moves toward the object upon
zooming from the wide-angle end state to the telephoto end state.
By this configuration, the diameter of the first lens group G1 is
kept small while preventing abaxial light interrupt when the
distance between the first lens group G1 and the second lens group
G2 is increased, and a sudden change of distortion can be
controlled.
[0143] In the variable power optical system ZL according to this
embodiment, it is preferable that the third lens group G3 is
disposed to the image side of the intermediate group G3b, and
includes an image side group having positive refractive power, and
camera shake (image blur) is corrected by using this image side
group as a vibration-isolating lens group (hereafter called
"vibration-isolating lens group G32") which moves so as to have a
component in a direction orthogonal to the optical axis in a state
of fixing the position of the intermediate group G3b with respect
to the image plane. By disposing the vibration-isolating lens group
G32 having positive refractive power to the image side of the
intermediate group G3b in this way, a vibration-isolating function
can be provided without increasing the number of lenses of the
vibration-isolating lens group G32, even if the bright lenses
having small F numbers are used.
[0144] In the variable power optical system ZL according to this
embodiment, it is preferable that the third lens group G3 includes,
in order from the object: a first sub-group G31; and a second
sub-group G32 having positive refractive power. And the camera
shake (image blur) is corrected using the second sub-group G32 as a
vibration-isolating lens group which moves so as to have a
component in a direction orthogonal to the optical axis, in a state
of fixing the position of the first sub-group G31 with respect to
the image plane. By disposing the second sub-group
(vibration-isolating lens group) G32 having positive refractive
power to the image side of the first sub-group G31 in this way, a
vibration-isolating function can be provided without increasing the
number of lenses of the second sub-group (vibration-isolating lens
group) G32, even if the bright lenses having small F numbers are
used.
[0145] It is preferable that the variable power optical system ZL
according to this embodiment satisfies the following conditional
expression (6).
1.5<fv.times.FNOw/f3<5.0 (6)
where f3 denotes a focal length of the third lens group G3, fv
denotes a focal length of the second sub-group G32, and FNOw
denotes an F number in the wide-angle end state.
[0146] The conditional expression (6) specifies the focal length of
the second sub-group G32 used as the vibration-isolating lens
group, and the focal length of the third lens group G3. If the
upper limit value of the conditional expression (6) is exceeded,
the refractive power of the second sub-group G32 decreases.
Further, the moving distance of the second sub-group G32, upon
vibration isolation (image blur correction) increases, and the
diameter of the second sub-group G32 increases, which increases the
weight of the second sub-group G32, and makes it difficult to
correct the eccentric coma aberration well upon vibration
isolation, which is not desirable. To demonstrate the effect of the
invention with certainty, it is preferable that the upper limit
value of the conditional expression (6) is 4.5. To demonstrate the
effect of the invention to the maximum, it is preferable that the
upper limit value of the conditional expression (6) is 4.0. On the
other hand, if the lower limit value of the conditional expression
(6) is not reached, the refractive power of the second sub-group
G32 increases, and eccentric astigmatism and eccentric coma
aberration cannot be corrected well upon vibration isolation, which
is not desirable. To demonstrate the effect of the invention with
certainty, it is preferable that the lower limit value of the
conditional expression (6) is 1.6. To demonstrate the effect of the
invention with even higher certainty, it is preferable that the
lower limit value of the conditional expression (6) is 1.8. To
demonstrate the effect of the invention to the maximum, it is
preferable that the lower limit value of the conditional expression
(6) is 2.2.
[0147] In the variable power optical system ZL according to this
embodiment, at least one positive lens component may or may not be
disposed between the intermediate group G3b and the image side
group G3c of the third lens group G3. In the same manner, the
object side group G3a disposed to the object side of the
intermediate group G3b of the third lens group G3 may be omitted.
In the intermediate group G3b, the positive lens and the negative
lens may be cemented or each lens may be disposed as a single lens
respectively.
[0148] By the above configuration, a variable power optical system
ZL having high brightness and excellent optical performance can be
provided.
[0149] A camera, which is an optical apparatus including the
variable power optical system ZL according to this embodiment, will
be described with reference to FIG. 30. This camera 1 is an
interchangeable lens type mirrorless camera that includes the
variable power optical system ZL according to this embodiment as an
image capturing lens 2. In this camera 1, the light from an object
(not illustrated) is collected by the image capturing lens 2, and
forms an object image on an image plane of the imaging unit 3 via
an OLPF (Optical Low-Pass Filter), which is not illustrated. Then
the object image is photo-electric converted by a photo-electric
conversion element disposed in the imaging unit 3, whereby the
image of the object is generated. This image is displayed on an EVF
(Electronic View Finder) 4 disposed in the camera 1. Thereby the
user can view the object via the EVF 4.
[0150] If a release button (not illustrated) is pressed by the
user, the photo-electric-converted image is stored in a memory (not
illustrated) by the imaging unit 3. Thus the user can capture the
image of the object using this camera 1. In this embodiment, an
example of the mirrorless camera was described, but an effect
similar to the case of this camera 1 can be demonstrated even when
the variable power optical system ZL according to this embodiment
may be included in a single lens reflex type camera, which has a
quick return mirror in the camera main unit and views the object
using a finder optical system.
[0151] The following content can be adopted within a range where
the optical performance is not diminished.
[0152] In this example, the variable power optical system ZL
constituted by four lens groups was shown, but the present
invention can also be applied to a configuration using a different
number of lens groups, such as five lens groups or six lens groups.
A lens or a lens group may be added to the configuration on the
side closest to the object, or a lens or a lens group may be added
to the configuration on the side closest to the image. "Lens group"
refers to a portion having at least one lens isolated by an air
space which changes upon zooming. In the variable power optical
system ZL of this embodiment, the first lens group G1 to the fourth
lens group G4 move along the optical axis respectively, such that
each air space between the lens groups changes upon zooming.
[0153] A single or plurality of lens group(s) or a partial lens
group may be designed to be a focusing lens group, which performs
focusing from an object at infinity to an object at a close
distance by moving in the optical axis direction. This focusing
lens group can be applied to auto focus, and is also suitable for
driving a motor for auto focusing (driving using an ultrasonic
motor or the like). It is particularly preferable that a part of
the third lens group G3 (image side group G3c, as mentioned above)
is designed to be the focusing lens group, and the positions of
other lenses with respect to the image plane are preferably fixed
upon focusing.
[0154] A lens group or a partial lens group may be designed to be a
vibration-isolating lens group, which corrects image blurs
generated by camera shake, by moving the lens group or the partial
lens so as to have a component in a direction orthogonal to the
optical axis or rotating (oscillating) the lens group or the
partial lens group in an in-plane direction that includes the
optical axis. It is particularly preferable that at least a part of
the third lens group G3 (e.g. lens disposed to the image side of
the four lenses (positive, negative, negative, positive) of the
intermediate group G3b) is designed to be the vibration-isolating
lens group.
[0155] The lens surface may be formed to be a spherical surface or
a plane, or an aspherical surface. If the lens surface is a
spherical surface or a plane, lens processing, assembly and
adjustment are easy, and deterioration of optical performance, due
to an error generated in processing, assembly and adjustment, can
be prevented. Even if the image plane is shifted, the drawing
performance is not affected very much, which is desirable. If the
lens surface is aspherical, the aspherical surface can be any
aspherical surface out of an aspherical surface generated by
grinding, a glass-molded aspherical surface generated by forming
glass in an aspherical shape using a die, and a composite
aspherical surface generated by forming resin on the surface of the
glass to be an aspherical shape. The lens surface may be a
diffraction surface, and the lens may be a refractive
index-distributed lens (GRIN lens) or a plastic lens.
[0156] It is preferable that the aperture stop S is disposed near
the third lens group G3, but the role of the aperture stop may be
substituted by the frame of the lens, without disposing a separate
member as the aperture stop.
[0157] Each lens surface may be coated with an anti-reflection
film, which has high transmittance in a wide wavelength region, in
order to decrease flares and ghosts, and implement high optical
performance with high contrast.
[0158] The zoom ratio of the variable power optical system ZL of
this embodiment is about 2.5 to 4.
[0159] An outline of a manufacturing method for the variable power
optical system ZL according to this embodiment will now be
described with reference to FIG. 32. First each lens is disposed to
prepare the first to fourth lens groups G1 to G4 (step S210). Each
lens group is disposed so that the distance between the first lens
group G1 and the second lens group G2, the distance between the
second lens group G2 and the third lens group G3, and the distance
between the third lens group G3 and the fourth lens group G4 change
respectively upon zooming from the wide-angle end state to the
telephoto end state (step S220). The third lens group G3 includes:
the intermediate group G3b constituted by, in order from the
object, the first positive lens, the first negative lens, the
second negative lens and the second positive lens; and an image
side group G3c having negative refractive power and disposed to the
image side of the intermediate group G3b, and the third lens group
G3 is disposed so that the position of the intermediate group G3b
with respect to the image plane is fixed, and the image side group
G3c moves along the optical axis upon focusing (step S230).
[0160] Further, each lens group is disposed so that at least the
above mentioned conditional expression (7) is satisfied (step
S240). As shown in FIG. 1, according to a concrete example of this
embodiment: the first lens group G1 is prepared by disposing a
cemented lens, where a negative meniscus lens L11 having a convex
surface facing the object and a positive meniscus lens L12 having a
convex surface facing the object are cemented in order from the
object. The second lens group G2 is prepared by disposing: a
negative lens L21, of which aspherical shape is formed by creating
a resin layer on the object side lens surface of a negative
meniscus lens having a convex surface facing the object; a cemented
lens where a biconcave lens L22 and a biconvex lens L23 are
cemented; and a cemented lens where a positive meniscus lens L24
having a concave surface facing the object, and a negative lens L25
which has a concave surface facing the object and of which image
side lens surface is aspherical, are cemented. The third lens group
G3 is prepared by disposing: a positive lens L31 of which object
side and image side lens surfaces are aspherical; a cemented lens
where a biconvex lens L32 and a biconcave lens L33 are cemented; a
cemented lens where a biconcave lens L34 and a biconvex lens L35
are cemented; a positive lens L36 of which object side and image
side lens surfaces are aspherical, and a negative meniscus lens L37
having a convex surface facing the object. The fourth lens group G4
prepared by disposing a positive lens L41 of which object side lens
surface is aspherical. These lens groups are disposed according to
the above mentioned procedure, whereby the variable power optical
system ZL is manufactured.
Embodiment 3
[0161] Embodiment 3 will now be described with reference to the
drawings. As shown in FIG. 1, a variable power optical system ZL
according to this embodiment includes, in order from an object: a
first lens group G1 having positive refractive power; a second lens
group G2 having negative refractive power; and a rear group GR
having positive refractive power and disposed to the image side of
the second lens group G2. The variable power optical system ZL is
configured such that the distance between the first lens group G1
and the second lens group G2, and the distance between the second
lens group G2 and the rear group GR change respectively upon
zooming from the wide-angle end state to the telephoto end state.
In the variable power optical system ZL, the rear group GR
includes: an intermediate group G3b constituted by, in order from
the object, a positive lens, a negative lens, a negative lens and a
positive lens; and an image side group having positive refractive
power and disposed to the image side of the intermediate group G3b.
Camera shake (image blur) is corrected by using the image side
group as a vibration-isolating lens group (hereafter called
"vibration-isolating lens group G32") which moves so as to have a
component in a direction orthogonal to the optical axis in a state
of fixing the position of the intermediate group G3b with respect
to the image plane. By configuring the variable power optical
system ZL of this embodiment in this way, excellent optical
performance can be implemented with bright lenses having small F
numbers. In other words, the intermediate group G3b of the rear
group GR is constituted by four lenses having a symmetric structure
(positive, negative, negative, positive), whereby spherical
aberration, curvature of field and coma aberration can be corrected
well while keeping the F numbers small for high brightness.
Further, by disposing the vibration-isolating lens group G32 having
positive refractive power, to the image side of the intermediate
group G3b, a vibration-isolating function can be provided without
increasing the number of lenses of the vibration-isolating lens
group G32, even if brightness lenses having small F numbers are
used. "Lens component" refers to a single lens or to a cemented
lens where a plurality of lenses are cemented.
[0162] The variable power optical system ZL according to this
embodiment may be configured such that the rear group GR includes
at least a third lens group G3 having positive refractive power and
disposed closest to the object, and each distance between lenses
constituting the third lens group G3 is constant upon zooming from
the wide-angle end state to the telephoto end state. The third lens
group G3 includes the above mentioned intermediate group G3b. It is
preferable that the variable power optical system ZL having this
configuration satisfies the following conditional expression
(8).
1.0<f3/.DELTA.T3<2.2 (8)
where .DELTA.T3 denotes a moving distance of the third lens group
G3 upon zooming from the wide-angle end state to the telephoto end
state, and f3 denotes a focal length of the third lens group
G3.
[0163] The conditional expression (8) specifies the focal length of
the third lens group G3 and the moving distance of the third lens
group G3 upon zooming. If the upper limit value of the conditional
expression (8) is exceeded, the power of the third lens group G3
becomes too weak with respect to the moving distance, and the
moving of the third lens group G3 cannot contribute to zooming. As
a result, the power of the first lens group G1 and the second lens
group G2 increase, and the sizes of the first lens group G1 and the
second lens group G2 are increased, or curvature of field cannot be
corrected well, which is not desirable. To demonstrate the effect
of the invention with certainty, it is preferable that the upper
limit value of the conditional expression (8) is 2.0. To
demonstrate the effect of the invention with even higher certainty,
it is preferable that the upper limit value of the conditional
expression (8) is 1.8. To demonstrate the effect of the invention
to the maximum, it is preferable that the upper limit value of the
conditional expression (8) is 1.75. On the other hand, if the lower
limit value of the conditional expression (8) is not reached, the
power of the third lens group G3 becomes too strong with respect to
the moving distance, and the spherical aberration cannot be
corrected well, which is not desirable. To demonstrate the effect
of the invention with certainty, it is preferable that the lower
limit value of the conditional expression (8) is 1.2. To
demonstrate the effect of the invention with even higher certainty,
it is preferable that the lower limit value of the conditional
expression (8) is 1.3. To demonstrate the effect of the invention
to the maximum, it is preferable that the lower limit value of the
conditional expression (8) is 1.4.
[0164] In the variable power optical system ZL of this embodiment,
it is preferable that the rear group GR includes an object side
group G3a having positive refractive power and disposed to the
object side of the intermediate group G3b. By this configuration,
good optical performance can be maintained using bright lenses
having small F numbers. Further, high-order spherical aberration,
which tends to be generated in bright lenses, can be corrected
well.
[0165] In the variable power optical system ZL, it is preferable
that the vibration-isolating lens group G32 is constituted by one
positive lens. By this configuration, the lens used for vibration
isolation can be lighter, and the vibration-isolating mechanism can
be lighter, and the vibration-isolating performance can easily be
improved. Further, it is preferable that the vibration-isolating
lens group G32 is constituted by one biconvex lens. By this
configuration, fluctuation of coma aberration, which is generated
upon vibration isolation, can be controlled.
[0166] In the variable power optical system ZL according to this
embodiment, it is preferable that the vibration-isolating lens
group G32 includes at least one positive lens, and this positive
lens satisfies the following conditional expression (9).
ndVR+0.0052.times..nu.dVR-1.965<0 (9)
where ndVR denotes a refractive index of a medium of the positive
lens included in the vibration-isolating lens group G32, and
.nu.dVR denotes an Abbe number of the medium of the positive lens
included in the vibration-isolating lens group G32.
[0167] The conditional expression (9) specifies the refractive
index of the medium of the positive lens included in the
vibration-isolating lens group G32 at d-line. If the upper limit
value of the conditional expression (9) is exceeded, glass material
having relatively high refractive power and high color
dispersibility must be used for this positive lens, and the lateral
chromatic aberration cannot be corrected well in a range of camera
shake correction, which is not desirable.
[0168] It is also preferable that the positive lens included in the
vibration-isolating lens group G32 satisfies the following
conditional expression (10).
.nu.dVR>60 (10)
where .nu.dVR denotes an Abbe number of the medium of the positive
lens included in the vibration-isolating lens group G32.
[0169] The conditional expression (10) specifies an Abbe number of
the medium of the positive lens included in the vibration-isolating
lens group G32. If the lower limit value of the conditional
expression (10) is not reached, dispersibility of the
vibration-isolating lens group G32 increases, and lateral chromatic
aberration, which tends to stand out upon camera shake correction,
cannot be sufficiently corrected in the range of camera shake
correction, which is not desirable. To demonstrate the effect of
the invention with certainty, it is preferable that the lower limit
value of the conditional expression (10) is 62.
[0170] In the variable power optical system ZL according to this
embodiment, if the rear group GR includes an object side group G3a
having positive refractive power and disposed to the object side of
the intermediate group G3b, it is preferable that this object side
group G3a includes one positive lens and satisfies the following
conditional expression (4).
.nu.dO>60 (4)
where .nu.dO denotes an Abbe number of a medium of the positive
lens included in the object side group G3a.
[0171] The conditional expression (4) specifies the Abbe number of
the medium of the positive lens included in the object side group
G3a of the rear group GR. If the lower limit value of the
conditional expression (4) is not reached, longitudinal chromatic
aberration, which tends to be generated in bright lenses,
increases, and correction thereof becomes difficult, which is not
desirable. To demonstrate the effect of the invention with
certainty, it is preferable that the lower limit value of the
conditional expression (4) is 62. To demonstrate the effect of the
invention to the maximum, it is preferable that the lower limit
value of the conditional expression (4) is 65.
[0172] The variable power optical system ZL according to this
embodiment is configured such that the rear group GR includes a
plurality of lens groups (e.g. third lens group G3 and fourth lens
group G4 in FIG. 1), and each distance of the plurality of lense
groups included in the rear group GR changes upon zooming from the
wide-angle end state to the telephoto end state. When a lens group
closest to the image (e.g. fourth lens group G4 in FIG. 1), out of
the plurality of lens groups, is the final lens group, it is
preferable that the variable power optical system ZL according to
this embodiment satisfies the following conditional expression
(11).
4.0<fr/fw<11.0 (11)
where fr denotes a focal length of the final lens group, and fw
denotes a focal length of the variable power optical system ZL in
the wide-angle end state.
[0173] The conditional expression (11) specifies the focal length
of the final lens group. If the upper limit value of the
conditional expression (11) is exceeded, the refractive power of
the final lens group decreases, and correction of curvature of
field upon zooming becomes difficult, which is not desirable. To
demonstrate the effect of the invention with certainty, it is
preferable that the upper limit value of the conditional expression
(11) is 10.0. To demonstrate the effect of the invention to the
maximum, it is preferable that the upper limit value of the
conditional expression (11) is 9.0. On the other hand, if the lower
limit value of the conditional expression (11) is not reached, the
refractive power of the final lens group increases, and correction
of distortion becomes difficult and back focus cannot be secured,
which is not desirable. To demonstrate the effect of the invention
with certainty, it is preferable that the lower limit value of the
conditional expression (11) is 5.0. To demonstrate the effect of
the invention to the maximum, it is preferable that the lower limit
value of the conditional expression (11) is 6.0.
[0174] The variable power optical system ZL according to this
embodiment may be configured such that the rear group GR includes,
in order from the object, a third lens group G3 having positive
refractive power and a fourth lens group G4, and the distance
between the third lens group G3 and the fourth lens group G4
changes upon zooming from the wide-angle end state to the telephoto
end state. The third lens group G3 includes at least the above
mentioned intermediate lens group G3b. It is preferable that the
variable power optical system ZL having this configuration
satisfies the following conditional expression (12).
0.9<f3/(fw.times.ft).sup.1/2<2.0 (12)
where f3 denotes a focal length of the third lens group G3, fw
denotes a focal length of the variable power optical system ZL in
the wide-angle end state, and ft denotes a focal length of the
variable power optical system ZL in the telephoto end state.
[0175] The conditional expression (12) specifies the focal length
of the third lens group G3. If the upper limit value of the
conditional expression (12) is exceeded, the refractive power of
the third lens group G3 decreases and the total length of the
optical system increases, which is not desirable. To demonstrate
the effect of the invention with certainty, it is preferable that
the upper limit value of the conditional expression (12) is 1.8. To
demonstrate the effect of the invention to the maximum, it is
preferable that the upper limit value of the conditional expression
(12) is 1.6. On the other hand, if the lower limit value of the
conditional expression (12) is not reached, the refractive power of
the third lens group G3 increases and correction of spherical
aberration becomes difficult, which is not desirable. To
demonstrate the effect of the invention with certainty, it is
preferable that the lower limit value of the conditional expression
(12) is 1.0. To demonstrate the effect of the conditional
expression (12) to the maximum, it is preferable that the lower
limit value of the conditional expression (12) is 1.1.
[0176] It is preferable that the variable power optical system ZL
according to this embodiment satisfies the following conditional
expression (7).
1.5<fv.times.FNOw/f3<5.0 (7)
where f3 denotes a focal length of the third lens group G3, fv
denotes a focal length of the vibration-isolating lens group G32,
and FNOw denotes an F number in the wide-angle end state.
[0177] The conditional expression (7) specifies the focal length of
the vibration-isolating lens group G32 and the focal length of the
third lens group G3. If the upper limit value of the conditional
expression (7) is exceeded, the refractive power of the
vibration-isolating lens group G32 decreases. Further, the moving
distance of the vibration-isolating lens group G32 upon vibration
isolation (upon image blur correction) increases, and the diameter
of the vibration-isolating lens group G32 increases, which makes
the vibration-isolating lens group G32 heavier, and makes it
difficult to correct eccentric coma aberration well upon vibration
isolation, which is not desirable. To demonstrate the effect of the
invention with certainty, it is preferable that the upper limit
value of the conditional expression (7) is 4.5. To demonstrate the
effect of the invention to the maximum, it is preferable that the
upper limit value of the conditional expression (7) is 4.0. On the
other hand, if the lower limit value of the conditional expression
(7) is not reached, the refractive power of the vibration-isolating
lens group G32 increases, and eccentric astigmatism and eccentric
coma aberration cannot be corrected well upon vibration isolation,
which is not desirable. To demonstrate the effect of the invention
with certainty, it is preferable that the lower limit value of the
conditional expression (7) is 1.6. To demonstrate the effect of the
invention with even higher certainty, it is preferable that the
lower limit value of the conditional expression (7) is 1.8. To
demonstrate the effect of the invention to the maximum, it is
preferable that the lower limit value of the conditional expression
(7) is 2.2.
[0178] In the variable power optical system ZL according to this
embodiment, it is preferable that the first lens group G1 moves
toward the image plane first, then moves toward the object upon
zooming from the wide-angle end state to the telephoto end state.
By this configuration, the diameter of the first lens group G1 is
kept small while preventing abaxial light interrupt when the
distance between the first lens group G1 and the second lens group
G2 is increased, and a sudden change of distortion can be
controlled.
[0179] The variable power optical system ZL according to this
embodiment may be configured such that the rear group GR is
constituted by, in order from the object: a third lens group G3
having positive refractive power; and a fourth lens group G4 having
positive refractive power, and the distance between the third lens
group G3 and the fourth lens group G4 changes upon zooming, or may
be configured such that the rear group GR is constituted by, in
order from the object: a third lens group G3 having positive
refractive power; a fourth lens group G4 having negative refractive
power; and a fifth lens group G5 having positive refractive power,
and the distance between the third lens group G3 and the fourth
lens group G4 and the distance between the fourth lens group G4 and
the fifth lens group G5 change respectively upon zooming. In the
variable power optical system ZL according to this embodiment, it
is preferable that the third lens group G3 includes, in order from
the object: a front side group G3a; an intermediate group G3b; and
a vibration-isolating lens group G32, which move together upon
zooming, and the intermediate group G3b is constituted by four
lenses (positive, negative, negative, positive). The
vibration-isolating lens group G32 may be designed as the fourth
lens group G4, instead of being included in the third lens group
G3. The object side group G3a disposed to the object side of the
intermediate group G3b of the rear group GR may be omitted. In the
four lenses (positive, negative, negative, positive) included in
the intermediate group G3b, the positive lens and the negative lens
may be cemented, or each lens thereof may be disposed as a single
lens.
[0180] In the variable power optical system ZL according to this
embodiment, it is preferable that the third lens group G3 includes
at least two lens components disposed to the image side of the
intermediate group G3b. By disposing at least two lens components
to the image side of the intermediate group G3b, the focusing lens
group and the vibration-isolating lens group G32 can be disposed in
the third lens group G3. It is preferable that the third lens group
G3 is constituted by, in order from the object: the front side
group G3a; the intermediate lens group G3b; the vibration-isolating
lens group G32; and the focusing lens group. The
vibration-isolating lens group G32 is preferably constituted by one
positive lens, but may be constituted by one cemented lens, or
constituted by a plurality of lens components.
[0181] In the variable power optical system ZL according to this
embodiment, the front side group G3a is constituted by one
aspherical lens, but may be constituted by two spherical
lenses.
[0182] By the above configuration, a variable power optical system
ZL having high brightness and excellent optical performance can be
provided.
[0183] A camera, which is an optical apparatus including the
variable power optical system ZL according to this embodiment, will
be described with reference to FIG. 30. This camera 1 is an
interchangeable lens type mirrorless camera that includes the
variable power optical system ZL according to this embodiment as an
image capturing lens 2. In this camera 1, the light from an object
(not illustrated) is collected by the image capturing lens 2, and
forms an object image on an image plane of the imaging unit 3 via
an OLPF (Optical Low-Pass Filter), which is not illustrated. Then
the object image is photo-electric converted by a photo-electric
conversion element disposed in the imaging unit 3, whereby the
image of the object is generated. This image is displayed on an EVF
(Electronic View Finder) 4 disposed in the camera 1. Thereby the
user can view the object via the EVF 4.
[0184] If a release button (not illustrated) is pressed by the
user, the photo-electric-converted image is stored in a memory (not
illustrated) by the imaging unit 3. Thus the user can capture the
image of the object using this camera 1. In this embodiment, an
example of the mirrorless camera was described, but an effect
similar to the case of this camera 1 can be demonstrated even when
the variable power optical system ZL according to this embodiment
may be included in a single lens reflex type camera, which has a
quick return mirror in the camera main unit and views the object
using a finder optical system.
[0185] The following content can be adopted within a range where
the optical performance is not diminished.
[0186] In this example, the variable power optical system ZL
constituted by four lens groups or five lens groups was shown, but
the present invention can also be applied to a configuration using
a different number of lens groups, such as six lens groups or seven
lens groups. A lens or a lens group may be added to the
configuration on the side closest to the object, or a lens or a
lens group may be added to the configuration on the side closest to
the image. In concrete terms, a lens group, of which position with
respect to the image plane is fixed upon zooming, may be added to
the configuration one the side closest to the image. "Lens group"
refers to a portion having at least one lens isolated by an air
space which changes upon zooming. In the variable power optical
system ZL of this embodiment, the first lens group G1 to the fourth
lens group G4 (or the fifth lens group G5) move along the optical
axis respectively, such that each air space between the lens groups
changes upon zooming.
[0187] A single or plurality of lens group(s) or a partial lens
group may be designed to be a focusing lens group, which performs
focusing from an object at infinity to an object at a close
distance by moving in the optical axis direction. This focusing
lens group can be applied to auto focus, and is also suitable for
driving a motor for auto focusing (driving using an ultrasonic
motor or the like). It is particularly preferable that a part of
the rear group (third lens group G3) (e.g. a negative lens
component disposed to the image side of the vibration-isolating
lens group G32, or the fourth lens group G4 disposed to the image
side of the third lens group G3) is designed to be the focusing
lens group, and the positions of other lenses with respect to the
image plane are fixed upon focusing. Considering the load applied
to the motor, it is preferable that the focusing lens group is
constituted by single lenses.
[0188] A lens group or a partial lens group may be designed to be a
vibration-isolating lens group, which corrects image blurs
generated by camera shake, by moving the lens group or the partial
lens group so as to have a component in a direction orthogonal to
the optical axis or rotating (oscillating) the lens group or the
partial lens group in an in-plane direction that includes the
optical axis. It is particularly preferable that at least a part of
the rear group GR (e.g. vibration-isolating lens group G32 of the
third lens group G3) is designed to be the vibration-isolating lens
group, as mentioned above.
[0189] The lens surface may be formed to be a spherical surface or
a plane, or an aspherical surface. If the lens surface is a
spherical surface of plane, lens processing, assembly and
adjustment are easy, and deterioration of optical performance, due
to an error generated in processing, assembly and adjustment can be
prevented. Even if the image plane is shifted, the drawing
performance is not affected very much, which is desirable. If the
lens surface is aspherical, the aspherical surface can be any
aspherical surface out of an aspherical surface generated by
grinding, a glass-molded aspherical surface generated by forming
glass in an aspherical shape using a die, and a composite
aspherical surface generated by forming resin on the surface of the
glass to be an aspherical shape. The lens surface may be a
diffraction surface, and the lens may be a refractive
index-distributed lens (GRIN lens) or a plastic lens.
[0190] It is preferable that the aperture stop S is disposed near
the third lens group G3, but the role of the aperture stop may be
substituted by the frame of the lens, without disposing a separate
member as the aperture stop.
[0191] Each lens surface may be coated with an anti-reflection
film, which has high transmittance in a wide wavelength region, in
order to decrease flares and ghosts, and implement high optical
performance with high contrast.
[0192] The zoom ratio of the variable power optical system ZL of
this embodiment is about 2.5 to 4. The F number of the variable
power optical system ZL of this embodiment is smaller than 3.5 in
the wide-angle end state to the telephoto end state.
[0193] An outline of a manufacturing method for the variable power
optical system ZL according to this embodiment will now be
described with reference to FIG. 33. First each lens is disposed to
prepare the first lens group G1, the second lens group G2 and the
rear group GR respectively (step S310). Each lens group is disposed
so that the distance between the first lens group G1 and the second
lens group G2, and the distance between the second lens group G2
and the rear group GR change respectively upon zooming from the
wide-angle end state to the telephoto end state (step S320). In the
rear group GR, the intermediate group G3b constituted by, in order
from the object, a positive lens, a negative lens, a negative lens,
and a positive lens; and the vibration-isolating lens group G32
having positive refractive power which is disposed to the image
side of the intermediate group G3b and moves to have a component in
a direction orthogonal to the optical axis, are disposed (steps
S330).
[0194] In the manufacturing method for the variable power optical
system ZL according to this embodiment, each lens group is disposed
such that the rear group GR includes at least the third lens group
G3 having positive refractive power and disposed closest to the
object, the distance between lenses constituting the third lens
group G3 is constant upon zooming from the wide-angle end state to
the telephoto end state. It is preferable that the third lens group
G3 includes the intermediate group G3b and satisfies the above
mentioned conditional expression (8).
[0195] As shown in FIG. 1, according to a concrete example of this
embodiment, the first lens group G1 is prepared by disposing a
cemented lens, where a negative meniscus lens L11 having a convex
surface facing the object and a positive meniscus lens L12 having a
convex surface facing the object are cemented in order from the
object. The second lens group G2 is prepared by disposing: a
negative lens L21, of which aspherical shape is formed by creating
a resin layer on the object side lens surface of a negative
meniscus lens having a convex surface facing the object; a cemented
lens where a biconcave lens L22 and a biconvex lens L23 are
cemented; and a cemented lens where a positive meniscus lens L24
having a concave surface facing the object, and a negative lens L25
which has a concave surface facing the object and of which image
side lens surface is aspherical, are cemented. The third lens group
G3 is prepared by disposing: a positive lens L31 of which object
side and image side lens surfaces are aspherical, a cemented lens
where a biconvex lens L32 and a biconcave lens L33 are cemented; a
cemented lens where a biconcave lens L34 and a biconvex lens L35
are cemented; a positive lens L36 of which object side and image
side lens surfaces are aspherical; and a negative meniscus lens L37
having a convex surface facing the object. The fourth lens group G4
is prepared by disposing a positive lens L41 of which object side
lens surface is aspherical. The third lens group G3 and the fourth
lens group G4 constitute the rear group GR. These lens groups are
disposed according to the above mentioned procedure, whereby the
variable power optical system ZL is manufactured.
Embodiment 4
[0196] Embodiment 4 will now be described with reference to the
drawings. As shown in FIG. 1, a variable power optical system ZL
according to this embodiment includes, in order from an object: a
first lens group G1 having positive refractive power; a second lens
group G2 having negative refractive power; and a rear group GR
having positive refractive power. The rear group GR includes a
third lens group G3 having positive refractive power and disposed
on the side closest to the object in the rear group GR. The
variable power optical system ZL is configured such that the
distance between the first lens group G1 and the second lens group
G2 and the distance between the second lens group G2 and the rear
group GR change respectively, and each distance between lenses
constituting the third lens group G3 is constant upon zooming from
the wide-angle end state to the telephoto end state. In the
variable power optical system ZL, the third lens group G3 includes,
in order from the object, a first sub-group G31 and a second
sub-group G32 having positive refractive power. Camera shake (image
blur) is corrected using a second sub-group G32 as a
vibration-isolating lens group, which moves so as to have a
component in a direction orthogonal to the optical axis in a state
of fixing the position of the first sub-group G31 with respect to
the image plane. By configuring the variable power optical system
ZL in this way, excellent optical performance can be implemented
with bright lenses having small F numbers. Further, by disposing
the second sub-group (vibration-isolating lens group) G32 having
positive refractive power to the image side of the first sub-group
G31, a vibration-isolating function can be provided without
increasing the number of lenses of the second sub-group
(vibration-isolating lens group) G32, even if the bright lenses
having small F numbers are used. "Lens component" refers to a
single lens or to a cemented lens where a plurality of lenses are
cemented.
[0197] It is preferable that the variable power optical system ZL
according to this embodiment satisfies the following conditional
expression (6).
1.5<fv.times.FNOw/f3<5.0 (6)
where f3 denotes a focal length of the third lens group G3, fv
denotes a focal length of the second sub-group G32, and FNOw
denotes an F number in the wide-angle end state.
[0198] The conditional expression (6) specifies the focal length of
the second sub-group G32 used as the vibration-isolating lens
group, and the focal length of the third lens group G3. If the
upper limit value of the conditional expression (6) is exceeded,
the refractive power of the second sub-group G32 decreases.
Further, the moving distance of the second sub-group G32 upon
vibration isolation (upon image blur correction) increases, and the
diameter of the second sub-group G32 increases, which makes the
second sub-group G32 heavier, and makes it difficult to correct
eccentric coma aberration well upon vibration isolation, which is
not desirable. To demonstrate the effect of the invention with
certainty, it is preferable that the upper limit value of the
conditional expression (6) is 4.5. To demonstrate the effect of the
invention to the maximum, it is preferable that the upper limit
value of the conditional expression (6) is 4.0. On the other hand,
if the lower limit value of the conditional expression (6) is not
reached, the refractive power of the second sub-group G32
increases, and eccentric astigmatism and eccentric coma aberration
cannot be corrected well upon vibration isolation, which is not
desirable. To demonstrate the effect of the invention with
certainty, it is preferable that the lower limit value of the
conditional expression (6) is 1.6. To demonstrate the effect of the
invention with even higher certainty, it is preferable that the
lower limit value of the conditional expression (6) is 1.8. To
demonstrate the effect of the invention to the maximum, it is
preferable that the lower limit value of the conditional expression
(6) is 2.2.
[0199] In the variable power optical system ZL according to this
embodiment, the first sub-group G31 includes an intermediate group
G3b, constituted by, in order from the object, a positive lens, a
negative lens, a negative lens, and a positive lens. In other
words, the intermediate group G3b of the rear group GR is
constituted by four lenses having a symmetric structure (positive,
negative, negative, positive), whereby spherical aberration,
curvature of field and coma aberration can be corrected well, while
keeping the F numbers small for high brightness.
[0200] In the variable power optical system ZL of this embodiment,
it is preferable that the first sub-group G31 of the third lens
group G3 includes an object side group G3a having positive
refractive power and disposed to the object side of the
intermediate group G3b. By this configuration, good optical
performance can be maintained using bright lenses having small F
numbers. Further, high-order spherical aberration, which tends to
be generated in bright lenses, can be corrected well.
[0201] In the variable power optical system ZL, it is preferable
that the second sub-group G32, which is the vibration-isolating
lens group G32, and which is included in the third lens group G3
and is used for vibration isolation, is constituted by one positive
lens. By this configuration, the lens used for vibration isolation
can be lighter, and the vibration-isolating mechanism can be
lighter, and the vibration-isolating performance can easily be
improved. Further, it is preferable that the second sub-group G32
is constituted by one biconvex lens. By this configuration,
fluctuation of coma aberration, which is generated upon vibration
isolation, can be controlled.
[0202] In the variable power optical system ZL according to this
embodiment, it is preferable that the second sub-group G32 included
in the third lens group G3 includes at least one positive lens, and
this positive lens satisfies the following conditional expression
(9).
ndVR+0.0052.times..nu.dVR-1.965<0 (9)
where ndVR denotes a refractive index of a medium of the positive
lens included in the second sub-group G32, and .nu.dVR denotes an
Abbe number of the medium of the positive lens included in the
second sub-group G32.
[0203] The conditional expression (9) specifies the refractive
index of the medium of the positive lens included in the second
sub-group G32 at d-line. If the upper limit value of the
conditional expression (9) is exceeded, glass material having
relatively high refractive power and high color dispersibility must
be used for this positive lens, and the lateral chromatic
aberration cannot be corrected well in a range of camera shake
correction, which is not desirable.
[0204] It is also preferable that the positive lens included in the
second sub-group G32 of the third lens group G3 satisfies the
following conditional expression (10).
.nu.dVR>60 (10)
where .nu.dVR denotes an Abbe number of the medium of the positive
lens included in the second sub-group G32.
[0205] The conditional expression (10) specifies an Abbe number of
the medium of the positive lens included in the second sub-group
G32. If the lower limit value of the conditional expression (10) is
not reached, dispersibility of the second sub-group G32 used as the
vibration-isolating lens group increases, and lateral chromatic
aberration, which tends to stand out upon camera shake correction,
cannot be sufficiently corrected in the range of camera shake
correction, which is not desirable. To demonstrate the effect of
the invention with certainty, it is preferable that the lower limit
value of the conditional expression (10) is 62.
[0206] In the variable power optical system ZL according to this
embodiment, if the first sub-group G31 of the third lens group G3
includes an object side group G3a having positive refractive power
and disposed to the object side of the intermediate group G3b, it
is preferable that this object side group G3a includes one positive
lens and satisfies the following conditional expression (4).
.nu.dO>60 (4)
where .nu.dO denotes an Abbe number of a medium of the positive
lens included in the object side group G3a.
[0207] The conditional expression (4) specifies the Abbe number of
the medium of the positive lens included in the object side group
G3a of the first sub-group G31 of the third lens group G3. If the
lower limit value of the conditional expression (4) is not reached,
longitudinal chromatic aberration, which tends to be generated in
bright lenses, increases, and correction thereof becomes difficult,
which is not desirable. To demonstrate the effect of the invention
with certainty, it is preferable that the lower limit value of the
conditional expression (4) is 62. To demonstrate the effect of the
invention to the maximum, it is preferable that the lower limit
value of the conditional expression (4) is 65.
[0208] The variable power optical system ZL according to this
embodiment is configured such that the rear group GR includes a
plurality of lens groups (e.g. third lens group G3 and fourth lens
group G4 in FIG. 1), and each distance of the plurality of lense
groups included in the rear group GR changes upon zooming from the
wide-angle end state to the telephoto end state. When a lens group
closest to the image (e.g. fourth lens group G4 in FIG. 1), out of
the plurality of lens groups, is the final lens group, it is
preferable that the variable power optical system ZL according to
this embodiment satisfies the following conditional expression
(11).
4.0<fr/fw<11.0 (11)
where fr denotes a focal length of the final lens group, and fw
denotes a focal length of the variable power optical system ZL in
the wide-angle end state.
[0209] The conditional expression (11) specifies the focal length
of the final lens group. If the upper limit value of the
conditional expression (11) is exceeded, the refractive power of
the final lens group decreases, and correction of curvature of
field upon zooming becomes difficult, which is not desirable. To
demonstrate the effect of the invention with certainty, it is
preferable that the upper limit value of the conditional expression
(11) is 10.0. To demonstrate the effect of the invention to the
maximum, it is preferable that the upper limit value of the
conditional expression (11) is 9.0. On the other hand, if the lower
limit value of the conditional expression (11) is not reached, the
refractive power of the final lens group increases, and correction
of distortion becomes difficult and back focus cannot be secured,
which is not desirable. To demonstrate the effect of the invention
with certainty, it is preferable that the lower limit value of the
conditional expression (11) is 5.0. To demonstrate the effect of
the invention to the maximum, it is preferable that the lower limit
value of the conditional expression (11) is 6.0.
[0210] The variable power optical system ZL according to this
embodiment may be configured such that the rear group GR includes,
in order from the object, a third lens group G3 having positive
refractive power and a fourth lens group G4, and the distance
between the third lens group G3 and the fourth lens group G4
changes upon zooming from the wide-angle end state to the telephoto
end state. The third lens group G3 includes at least the
intermediate lens group G3b. It is preferable that the variable
power optical system ZL having this configuration satisfies the
following conditional expression (12).
0.9<f3/(fw.times.ft).sup.1/2<2.0 (12)
where f3 denotes a focal length of the third lens group G3, fw
denotes a focal length of the variable power optical system ZL in
the wide-angle end state, and ft denotes a focal length of the
variable power optical system ZL in the telephoto end state.
[0211] The conditional expression (12) specifies the focal length
of the third lens group G3. If the upper limit value of the
conditional expression (12) is exceeded, the refractive power of
the third lens group G3 decreases and the total length of the
optical system increases, which is not desirable. To demonstrate
the effect of the invention with certainty, it is preferable that
the upper limit value of the conditional expression (12) is 1.8. To
demonstrate the effect of the invention to the maximum, it is
preferable that the upper limit value of the conditional expression
(12) is 1.6. On the other hand, if the lower limit value of the
conditional expression (12) is not reached, the refractive power of
the third lens group G3 increases and correction of spherical
aberration becomes difficult, which is not desirable. To
demonstrate the effect of the invention with certainty, it is
preferable that the lower limit value of the conditional expression
(12) is 1.0. To demonstrate the effect of the conditional
expression (12) to the maximum, it is preferable that the lower
limit value of the conditional expression (12) is 1.1.
[0212] It is preferable that the variable power optical system ZL
according to this embodiment satisfies the following conditional
expression (8).
1.0<f3/.DELTA.T3<2.2 (8)
where .DELTA.T3 denotes a moving distance of the third lens group
G3 upon zooming from the wide-angle end state to the telephoto end
state, and f3 denotes a focal length of the third lens group
G3.
[0213] The conditional expression (8) specifies the focal length of
the third lens group G3 and the moving distance of the third lens
group G3 upon zooming. If the upper limit value of the conditional
expression (8) is exceeded, the power of the third lens group G3
becomes too weak with respect to the moving distance, and the
moving of the third lens group G3 cannot contribute to zooming. As
a result, the power of the first lens group G1 and the second lens
group G2 increase, and the sizes of the first lens group G1 and the
second lens group G2 are increased, or curvature of field cannot be
corrected well, which is not desirable. To demonstrate the effect
of the invention with certainty, it is preferable that the upper
limit value of the conditional expression (8) is 2.0. To
demonstrate the effect of the invention with even higher certainty,
it is preferable that the upper limit value of the conditional
expression (8) is 1.8. To demonstrate the effect of the invention
to the maximum, it is preferable that the upper limit value of the
conditional expression (8) is 1.75. On the other hand, if the lower
limit value of the conditional expression (8) is not reached, the
power of the third lens group G3 becomes too strong with respect to
the moving distance, and the spherical aberration cannot be
corrected well, which is not desirable. To demonstrate the effect
of the invention with certainty, it is preferable that the lower
limit value of the conditional expression (8) is 1.2. To
demonstrate the effect of the invention with even higher certainty,
it is preferable that the lower limit value of the conditional
expression (8) is 1.3. To demonstrate the effect of the invention
to the maximum, it is preferable that the lower limit value of the
conditional expression (8) is 1.4.
[0214] In the variable power optical system ZL according to this
embodiment, it is preferable that the first lens group G1 moves
toward the image plane first, then moves toward the object upon
zooming from the wide-angle end state to the telephoto end state.
By this configuration, the diameter of the first lens group G1 is
kept small while preventing abaxial light interrupt when the
distance between the first lens group G1 and the second lens group
G2 is increased, and a sudden change of distortion can be
controlled.
[0215] The variable power optical system ZL according to this
embodiment may be configured such that the rear group GR is
constituted by, in order from the object: a third lens group G3
having positive refractive power and a fourth lens group G4 having
positive refractive power; and the distance between the third lens
group G3 and the fourth lens group G4 changes upon zooming, or may
be configured such that the rear group GR is constituted by, in
order from the object: a third lens group G3 having positive
refractive power; a fourth lens group G4 having negative refractive
power; and a fifth lens group G5 having positive refractive power,
and the distance between the third lens group G3 and the fourth
lens group G4 and the distance between the fourth lens group G4 and
the fifth lens group G5 change respectively upon zooming. In the
variable power optical system ZL according to this embodiment, it
is preferable that the third lens group G3 includes, in order from
the object: a first sub-group G31 constituted by an object side
group G3a and an intermediate group G3b; and a second sub-group G32
used as the vibration-isolating lens group, which move together
upon zooming, and the intermediate group G3b is constituted by four
lenses (positive, negative, negative, positive). The second
sub-group G32 used as the vibration-isolating lens group may be
designed as the fourth lens group G4, instead of being included in
the third lens group G3. The object side group G3a disposed to the
object side of the intermediate group G3b of the first sub-group
G31 constituting the rear group GR may be omitted. In the four
lenses (positive, negative, negative, positive) included in the
intermediate group G3b, the positive lens and the negative lens may
be cemented, or each lens thereof may be disposed as a single
lens.
[0216] In the variable power optical system ZL according to this
embodiment, it is preferable that the third lens group G3 includes
at least two lens components disposed to the image side of the
intermediate group G3b. By disposing at least two lens components
to the image side of the intermediate group G3b, the focusing lens
group and the vibration-isolating lens group G32 can be disposed in
the third lens group G3. It is preferable that the third lens group
G3 is constituted by, in order from the object: a first sub-group
G31 constituted by an object side group G3a and an intermediate
group G3b; a second sub-group G32 used as the vibration-isolating
lens group; and a focusing lens group. The second sub-group G32
used as the vibration-isolating lens group is preferably
constituted by one positive lens, but may be constituted by one
cemented lens, or constituted by a plurality of lens
components.
[0217] In the variable power optical system ZL according to this
embodiment, the object side group G3a is constituted by one
aspherical lens, but may be constituted by two spherical
lenses.
[0218] By the above configuration, a variable power optical system
ZL having high brightness and excellent optical performance can be
provided.
[0219] A camera, which is an optical apparatus including the
variable power optical system ZL according to this embodiment, will
be described with reference to FIG. 30. This camera 1 is an
interchangeable lens type mirrorless camera that includes the
variable power optical system ZL according to this embodiment as an
image capturing lens 2. In this camera 1, the light from an object
(not illustrated) is collected by the image capturing lens 2, and
forms an object image on an image plane of the imaging unit 3 via
an OLPF (Optical Low-Pass Filter), which is not illustrated. Then
the object image is photo-electric converted by a photo-electric
conversion element disposed in the imaging unit 3, whereby the
image of the object is generated. This image is displayed on an EVF
(Electronic View Finder) 4 disposed in the camera 1. Thereby the
user can view the object via the EVF 4.
[0220] If a release button (not illustrated) is pressed by the
user, the photo-electric-converted image is stored in a memory (not
illustrated) by the imaging unit 3. Thus the user can capture the
image of the object using this camera 1. In this embodiment, an
example of the mirrorless camera was described, but an effect
similar to the case of this camera 1 can be demonstrated even when
the variable power optical system ZL according to this embodiment
may be included in a single lens reflex type camera, which has a
quick return mirror in the camera main unit and views the object
using a finder optical system.
[0221] The following content can be adopted within a range where
the optical performance is not diminished.
[0222] In this example, the variable power optical system ZL
constituted by four or five lens groups was shown, but the present
invention can also be applied to a configuration using a different
number of lens groups, such as six lens groups or seven lens
groups. A lens or a lens group may be added to the configuration on
the side closest to the object, or a lens or a lens group may be
added to the configuration on the side closest to the image. In
concrete terms, a lens group, of which position with respect to the
image plane is fixed upon zooming, may be added to the
configuration on the side closest to the image. "Lens group" refers
to a portion having at least one lens isolated by an air space
which changes upon zooming. In the variable power optical system ZL
of this embodiment, the first lens group G1 to the fourth lens
group G4 move along the optical axis respectively, such that each
air space between the lens groups changes upon zooming. "Lens
component" refers to a single lens or a cemented lens where a
plurality of lenses are cemented.
[0223] A single or plurality of lens group(s) or a partial lens
group may be designed to be a focusing lens group, which performs
focusing from an object at infinity to an object at a close
distance by moving in the optical axis direction. This focusing
lens group can be applied to auto focus, and is also suitable for
driving a motor for auto focusing (driving using an ultrasonic
motor or the like). It is particularly preferable that a part of
the rear group (third lens group G3) (e.g. negative lens component
disposed to the image side of the second sub-group G32, or the
fourth lens group G4 disposed at the image side of the third lens
group G3) is designed to be the focusing lens group, and the
positions of other lenses with respect to the image plane are
preferably fixed upon focusing. Considering the load applied to the
motor, it is preferable that the focusing lens group is constituted
by single lenses.
[0224] A lens group or a partial lens group may be designed to be a
vibration-isolating lens group, which corrects image blurs
generated by camera shake, by moving the lens group or the partial
lens group so as to have a component in a direction orthogonal to
the optical axis or rotating (oscillating) the lens group or the
partial lens group in an in-plane direction that includes the
optical axis. It is particularly preferable that at least a part of
the rear group GR (e.g. second sub-group G32 of the third lens
group G3) is designed to be the vibration-isolating lens group, as
mentioned above.
[0225] The lens surface may be formed to be a spherical surface or
a plane, or an aspherical surface. If the lens surface is a
spherical surface or plane, lens processing, assembly and
adjustment are easy, and deterioration of optical performance, due
to an error generated in processing, assembly and adjustment can be
prevented. Even if the image plane is shifted, the drawing
performance is not affected very much, which is desirable. If the
lens surface is aspherical, the aspherical surface can be any
aspherical surface out of an aspherical surface generated by
grinding, a glass-molded aspherical surface generated by forming
glass in an aspherical shape using a die, and a composite
aspherical surface generated by forming resin on the surface of the
glass to be an aspherical shape. The lens surface may be a
diffraction surface, and the lens may be a refractive
index-distributed lens (GRIN lens) or a plastic lens.
[0226] It is preferable that the aperture stop S is disposed near
the third lens group G3, but the role of the aperture stop may be
substituted by the frame of the lens, without disposing a separate
member as the aperture stop.
[0227] Each lens surface may be coated with an anti-reflection
film, which has high transmittance in a wide wavelength region, in
order to decrease flares and ghosts, and implement high optical
performance with high contrast.
[0228] The zoom ratio of the variable power optical system ZL of
this embodiment is about 2.5 to 4. The F number of the variable
power optical system ZL of this embodiment is smaller than 3.5 in
the wide-angle end state to the telephoto end state.
[0229] An outline of a manufacturing method for the variable power
optical system ZL according to this embodiment will now be
described with reference to FIG. 34. First each lens is disposed to
prepare the first lens group G1, the second lens group G2 and the
rear group GR respectively (step S410). In the rear group GR, at
least the third lens group G3 having positive refractive power is
disposed to the side closest to the object in the rear group GR
(step S420). Each lens group is disposed so that the distance
between the first lens group G1 and the second lens group G2 and
the distance between the second lens group G2 and the rear group GR
change respectively, and each distance of lenses constituting the
third lens group G3 is constant upon zooming from the wide-angle
end state to the telephoto end state (step S430). In the third lens
group G3, the first sub-group G31 of which position with respect to
the image plane is fixed upon correcting camera shake, and the
second sub-group G32 used as the vibration-isolating lens which has
positive refractive power and can move so as to have a component in
a direction orthogonal to the optical axis upon correcting camera
shake, are disposed (step S440). Each lens group is disposed so
that the above mentioned conditional expression (6) is satisfied
(step S450).
[0230] As shown in FIG. 1, according to a concrete example of this
embodiment, the first lens group G1 is prepared by disposing a
cemented lens, where a negative meniscus lens L11 having a convex
surface facing the object and a positive meniscus lens L12 having a
convex surface facing the object are cemented in order from the
object. The second lens group G2 is prepared by disposing: a
negative lens L21, of which aspherical shape is formed by creating
a resin layer on the object side lens surface of a negative
meniscus lens having a convex surface facing the object; a cemented
lens where a biconcave lens L22 and a biconvex lens L23 are
cemented; and a cemented lens, where a positive meniscus lens L24
having a concave surface facing the object, and a negative lens L25
which has a concave surface facing the object and of which image
side lens surface is aspherical, are cemented. The third lens group
G3 is prepared by disposing: a positive lens L31 of which object
side and image side lens surfaces are aspherical; a cemented lens
where a biconvex lens L32 and a biconcave lens L33 are cemented; a
cemented lens where a biconcave lens L34 and a biconvex lens L35
are cemented; a positive lens L36 of which object side and image
side lens surfaces are aspherical; and a negative meniscus lens L37
having a convex surface facing the object. The fourth lens group G4
is prepared by disposing a positive lens L41 of which object side
lens surface is aspherical. The third lens group G3 and the fourth
lens group G4 constitute the rear group GR. These lens groups are
disposed according to the above mentioned procedure, whereby the
variable power optical system ZL is manufactured.
EXAMPLES
[0231] Each example of the invention will now be described with
reference to the drawings. Embodiment 1 corresponds to Example 1 to
5. Embodiment 2 corresponds to Examples 1 to 5. Embodiment 3
corresponds to Examples 1 to 6. Embodiment 4 corresponds to
Examples 1 to 6. FIG. 1, FIG. 6, FIG. 11, FIG. 16, FIG. 21 and FIG.
26 are cross-sectional views depicting the configuration and
refractive power allocation of the variable power optical system ZL
(ZL1 to ZL6) according to each example. In the lower part of the
cross-sectional views of the variable power optical systems ZL1 to
ZL6, the moving direction of each lens group G1 to G4 (or G5) along
the optical axis upon zooming from the wide-angle end state (W) to
the telephoto end state (T) is indicated by an arrow mark.
[0232] In each example, an aspherical surface is expressed by the
following expression (a), where y denotes a height in a direction
orthogonal to the optical axis, S(y) denotes a distance (sag) along
the optical axis from the tangential plane at the vertex of each
aspherical surface to the position on the aspherical surface at
height y, r denotes a radius of curvature (paraxial radius of
curvature) of the reference spherical surface, K denotes a conical
coefficient, and An denotes an aspherical coefficient at degree n.
In the following example "E-n" indicates ".times.10.sup.-n".
S .function. ( y ) = ( y 2 / r ) / { 1 + ( 1 - K .times. y 2 / r 2
) 1 / 2 } + A .times. 4 .times. y 4 + A .times. 6 .times. y 6 + A
.times. 8 .times. y 8 + A .times. 10 .times. y 1 .times. 0 + A
.times. 12 .times. y 1 .times. 2 ( a ) ##EQU00001##
[0233] In each example, the aspherical coefficient at degree 2 (A2)
is 0. In the table of each example, * is attached to the right side
of the surface number if the surface is aspherical.
Example 1
[0234] FIG. 1 shows a configuration of a variable power optical
system ZL1 according to Example 1. The variable power optical
system ZL1 shown in FIG. 1 includes, in order from an object: a
first lens group G1 having positive refractive power; a second lens
group G2 having negative refractive power; and a rear group GR, and
the rear group GR is constituted by, in order from the object: a
third lens group G3 having positive refractive power; and a fourth
lens group G4 having positive refractive power.
[0235] In the variable power optical system ZL1, the first lens
group G1 is constituted by a cemented lens where a negative
meniscus lens L11 having a convex surface facing the object and a
positive meniscus lens L12 having a convex surface facing the
object are cemented in order from the object. The second lens group
G2 is constituted by, in order from the object: a negative lens
L21, of which aspherical shape is formed by creating a resin layer
on the object side lens surface of a negative meniscus lens having
a convex surface facing the object; a cemented lens where a
biconcave lens L22 and a biconvex lens L23 are cemented; and a
cemented lens where a positive meniscus lens L24 having a concave
surface facing the object and a negative lens L25 which has a
concave surface facing the object and of which image side lens
surface is aspherical, are cemented. The third lens group G3 is
constituted by, in order from the object: a positive lens L31 of
which object side and image side lens surfaces are aspherical; a
cemented lens where a biconvex lens L32 and a biconcave lens L33
are cemented; a cemented lens where a biconcave lens L34 and a
biconvex lens L35 are cemented; a positive lens L36 of which object
side and image side lens surfaces are aspherical; and a negative
meniscus lens L37 having a convex surface facing the object. The
fourth lens group G4 is constituted by a positive lens L41 of which
object side lens surface is aspherical. An aperture stop S is
disposed between the second lens group G2 and the third lens group
G3. A filter group FL including a low-pass filter, an infrared
filter or the like is disposed between the fourth lens group G4 and
the image plane I. The negative lens L25, the positive lens L31,
the positive lens L36 and the positive lens L41 are glass-molded
aspherical lenses.
[0236] In this variable power optical system ZL1, upon zooming from
the wide-angle end state to the telephoto end state, the first lens
group G1 and the second lens group G2 move toward the image plane
first and then move toward the object, the third lens group G3
moves toward the object, and the fourth lens group G4 moves toward
the object first and then moves toward the image plane, so that the
distance between the first lens group G1 and the second lens group
G2 increases, the distance between the second lens group G2 and the
third lens group G3 decreases, and the distance between the third
lens group G3 and the fourth lens group G4 increases. The aperture
stop S moves together with the third lens group G3.
[0237] In the variable power optical system ZL1, focusing from
infinity to an object at a close distance is performed by moving an
image side group G3c (negative meniscus lens L37), which is
disposed to the image side of a vibration-isolating lens group G32
of the third lens group G3, toward the image plane.
[0238] In the variable power optical system ZL1, the positive lens
L36 of the third lens group G3 is used as the vibration-isolating
lens group G32, and image blur correction (vibration isolation) is
performed by moving the vibration-isolating lens group G32 so as to
have a component in a direction orthogonal to the optical axis. To
correct a rotation blur at angle A when the focal length of the
variable power optical system is f and the vibration-isolation
coefficient (ratio of the image moving distance on the image
forming plane with respect to the moving distance of the
vibration-isolating lens group G32 in the image blur correction) is
K, the vibration-isolating lens group G32 for blur correction is
moved in a direction orthogonal to the optical axis by (ftan
.theta.)/K. (This is the same for the other examples described
later.) In the wide-angle end state of Example 1, the
vibration-isolation coefficient is -0.62 and the focal length is
9.3 (mm), therefore the moving distance of the vibration-isolating
lens group G32, to correct a 1.03.degree. rotation blur is -0.170
(mm). In the intermediate focal length state of Example 1, the
vibration-isolation coefficient is -0.831 and the focal length is
19.1 (mm), therefore the moving distance of the vibration-isolating
lens group G32, to correct a 0.605.degree. rotation blur, is -0.177
(mm). In the telephoto end state of Example 1, the
vibration-isolation coefficient is -0.963 and the focal length is
29.1 (mm), therefore the moving distance of the vibration-isolating
lens group G32, to correct a 0.500.degree. rotation blur, is -0.264
(mm).
[0239] Table 1 shows the data values of the variable power optical
system ZL1. In [General Data] in Table 1, f indicates a focal
length of the variable power optical system, FNO indicates an F
number, 2.omega. indicates an angle of view, Y indicates the
maximum image height, TL indicates a total length, and BF indicates
a value of back focus in the wide-angle end state, the intermediate
focal length state, and the telephoto end state respectively. The
total length TL here indicates a distance (air conversion length)
on the optical axis from the lens surface closest to the object
(Surface 1 in FIG. 1) to the image plane I upon focusing on
infinity. BF indicates a distance (air conversion length) on the
optical axis from the lens surface closest to the image plane
(Surface 27 in FIG. 1) to the image plane I upon focusing on
infinity. The first column m in [Lens Data] indicates the
sequential number assigned to the lens surface (surface number)
counted from the object side along the light traveling direction,
the second column r indicates a radius of curvature of each lens
surface, the third column d indicates a distance from each optical
surface to the next optical surface on the optical axis (surface
distance), the fourth column .nu.d and the fifth column nd indicate
an Abbe number and a refractive index at d-line (.lamda.=587.6 nm).
The radius of curvature 0.000 indicates a plane, and the refractive
index of air 1.00000 is omitted. The surface numbers 1 to 33 in
Table 1 correspond to the numbers 1 to 33 in FIG. 1. The [Lens
Group Focal Length] indicates the first surface and focal length of
the first to fourth lens groups G1 to G4 respectively.
[0240] For all the data values, "mm" is normally used as the unit
of focal length f, radius of curvature r, surface distance d and
other lengths, but the unit is not limited to "mm", since an
equivalent optical performance is acquired even if the optical
system is proportionally expanded or proportionally reduced. The
description on the symbols and the description on the data table
are the same for the other examples herein below.
TABLE-US-00001 TABLE 1 Example 1 [General Data] Zoom ratio = 3.14
Wide-angle Intermediate Telephoto end state focal length state end
state f =9.3 ~19.1 ~29.1 FNO =1.8 ~2.5 ~2.9 2.omega. =85.1 ~44.7
~29.8 Y = =8.0 ~8.0 ~8.0 TL (air =95.9 ~101.1 ~114.1 conversion
length) BF (air =13.8 ~18.9 ~18.4 conversion length) [Lens Data] m
r d .nu.d nd Object .infin. plane 1 52.520 1.60 17.98 1.94595 2
38.097 6.31 46.60 1.80400 3 299.948 D3 4* 4632.762 0.20 36.64
1.56093 5 105.387 1.51 40.66 1.88300 6 11.700 6.42 7 -78.778 4.04
54.61 1.72916 8 44.775 3.44 23.78 1.84666 9 -31.132 1.04 10 -18.713
2.38 30.13 1.69895 11 -13.113 0.90 40.10 1.85135 12* -35.882 D12 13
0.000 0.80 Aperture stop S 14 21.574 3.26 71.67 1.55332 15* -59.840
0.30 16 35.781 4.78 23.78 1.84666 17 -14.139 0.80 28.38 1.72825 18
24.505 2.16 19 -28.756 1.50 22.74 1.80809 20 24.289 4.30 82.57
1.49782 21 -14.921 0.50 22* 24.289 2.68 81.49 1.49710 23* -70.000
D23 24 34.328 0.80 82.57 1.49782 25 16.185 D25 26* 28.150 2.21
81.49 1.49710 27 254.991 D27 28 0.000 0.50 63.88 1.51680 29 0.000
1.11 30 0.000 1.59 63.88 1.51680 31 0.000 0.30 32 0.000 0.70 63.88
1.51680 33 0.000 0.70 [Lens Group Focal Length] Lens group First
surface Focal length First lens group 1 84.50 Second lens group 4
-13.26 Third lens group 14 22.97 Fourth lens group 26 63.45
[0241] In this variable power optical system ZL1, surface 4,
surface 12, surface 14, surface 15, surface 22, surface 23 and
surface 26 are aspherical. Table 2 shows aspherical data, that is,
the values of the conical coefficient K and each aspherical
coefficient A4 to A10.
TABLE-US-00002 TABLE 2 [Aspherical Data] K A4 A6 A8 A10 Surface 4 0
4.41073E-05 -1.57931E-07 4.69697E-10 -7.44801E-13 Surface 12 0
-1.20350E-05 -8.15569E-08 3.91594E-10 -3.58987E-12 Surface 14 0
-3.13883E-06 -1.57686E-08 -1.08799E-09 0.00000E+00 Surface 15 0
5.63460E-05 4.70520E-09 0.00000E+00 0.00000E+00 Surface 22 0
-1.41390E-05 -4.37524E-07 0.00000E+00 0.00000E+00 Surface 23 0
-5.50201E-07 -4.06545E-07 -1.23018E-09 1.33941E-11 Surface 26 0
4.04787E-06 -4.49391E-08 2.97650E-10 0.00000E+00
[0242] In the variable power optical system ZL1, the axial air
distance D3 between the first lens group G1 and the second lens
group G2, the axial air distance D12 between the second lens group
G2 and the third lens group G3 (aperture stop S), the axial air
distance D25 between the third lens group G3 and the fourth lens
group G4 and the axial air distance D27 between the fourth lens
group G4 and the filter group FL change upon zooming, as mentioned
above. The axial air distance D23 to the object side and the axial
air distance D25 to the image side of the image side group G3c of
the third lens group G3 Change upon focusing. Table 3 shows the
variable distance in each focal length state of the wide-angle end
state, intermediate focal length state and telephoto end state upon
focusing on infinity and upon focusing on a close point. Upon
focusing on a close point, only the values of D23 and D25 are
shown, and the omitted values are the same as the respective values
obtained upon focusing on infinity.
TABLE-US-00003 TABLE 3 [Variable Distance Data] Focusing on
infinity Focusing on close point Wide- Inter- Telephoto Wide-
Inter- Telephoto angle end mediate end angle end mediate end f 9.3
19.1 29.1 9.3 19.1 29.1 D3 1.2 13.4 23.6 D12 21.4 5.4 1.5 D23 1.50
1.50 1.50 2.42 3.64 5.44 D25 5.20 8.94 16.23 4.28 6.80 12.30 D27
9.8 15.0 14.5
[0243] Table 4 shows each conditional expression correspondence
value of the variable power optical system ZL1. In Table 4, f2
denotes a focal length of the second lens group G2, fw denotes the
focal length of the variable power optical system in the wide-angle
end state, ft denotes a focal length of the variable power optical
system in the telephoto end state, ndF denotes a refractive index
of a medium of a negative lens included in the image side group G3c
of the third lens group G3 at d-line, .nu.dF denotes an Abbe number
of the medium of the negative lens included in the image side group
G3c of the third lens group G3, .nu.dO denotes an Abbe number of a
positive lens included in the object side group G3a of the rear
group (third lens group G3), f4 denotes a focal length of the
fourth lens group G4, fv denotes a focal length of the
vibration-isolating lens group G32, FNOw denotes an F number in the
wide-angle end state, f3 denotes the focal length of the third lens
group G3, R2a and R1b denote a radius of curvature of the image
side lens surface and that of the object side lens surface of the
first negative lens and the second negative lens included in the
intermediate group G3b of the third lens group G3 respectively,
.DELTA.T denotes a moving distance of the rear group (third lens
group G3) upon zooming from the wide-angle end state to the
telephoto end state, ndVR denotes a refractive index of a medium of
the positive lens included in the vibration-isolating lens group
G32 at d-line, .nu.dVR denotes an Abbe number of the medium of the
positive lens included in the vibration-isolating lens group G32,
and fr denotes a focal length of the final lens group. This
description on the reference symbols is the same for the other
examples herein below. In Example 1, the negative lens included in
the image side group G3c of the third lens group G3 is the negative
meniscus lens L37, the positive lens included in the object side
group G3a of the third lens group G3 is the positive lens L31, the
positive lens included in the vibration-isolating lens group G32 is
the positive lens L36, and the final lens group is the fourth lens
group G4. R2a indicates a radial distance of Surface 18, and R1b
indicates a radius of curvature of Surface 19.
TABLE-US-00004 TABLE 4 [Conditional Expression Correspondence
Value] (1) (-f2)/(fw .times. ft).sup.1/2 = 0.807 (2) ndF - 0.0052
.times. .nu.dF - 1.965 = -0.038 (3) .nu.dF = 82.6 (4) .nu.dO = 71.7
(5) f4/fw = 6.85 (6) fv .times. FNOw/f3 = 2.92 (7) (R2a + R1b)/(R2a
- R1b) = -0.080 (8) f3/.DELTA.T3 = 1.46 (9) ndVR - 0.0052 .times.
.nu.dVR - 1.965 = -0.044 (10) .nu.dVR = 81.5 (11) fr/fw = 6.85 (12)
f3/(fw .times. ft).sup.1/2 = 1.40
[0244] Thus the variable power optical system ZL1 satisfies all the
conditional expressions (1) to (12).
[0245] FIG. 2A, FIG. 3A and FIG. 4A are graphs showing spherical
aberration, astigmatism, distortion, lateral chromatic aberration
and coma aberration of the variable power optical system ZL1 upon
focusing on infinity in the wide-angle end state, intermediate
focal length state, and telephoto end state, and FIG. 2B, FIG. 3B
and FIG. 4B are graphs showing coma aberration when image blur is
corrected upon focusing on infinity in the wide-angle end state,
intermediate focal length state and telephoto end state. FIG. 5 are
graphs showing spherical aberration, astigmatism, distortion,
lateral chromatic aberration and coma aberration upon focusing on a
close point in the wide-angle end state, intermediate focal length
state and telephoto end state. In each graph showing aberration,
FNO indicates an F number, and Y indicates an image height. In the
graphs showing spherical aberration upon focusing on infinity, a
value of an F number corresponding to the maximum aperture is
shown; in the graphs showing spherical aberration upon focusing on
a close point, a value of numerical aperture corresponding to the
maximum aperture is shown; and in the graphs showing astigmatism
and distortion, a maximum value of image height is shown
respectively. d indicates d-line (.lamda.=587.6 nm), and g
indicates g-line (.lamda.=435.8 nm) respectively. In each graph
showing astigmatism, the sold line indicates the sagittal image
plane, and the broken line indicates the meridional image plane.
The same reference symbols as this example are also used for the
graphs showing aberrations of the other examples herein below. As
each graph showing aberrations clarifies, various aberrations are
corrected well in the variable power optical system ZL1 from the
wide-angle end state to the telephoto end state.
Example 2
[0246] FIG. 6 shows a configuration of a variable power optical
system ZL2 according to Example 2. The variable power optical
system ZL2 shown in FIG. 6 includes, in order from an object: a
first lens group G1 having positive refractive power; a second lens
group G2 having negative refractive power; and a rear group GR, and
the rear group GR is constituted by, in order from the object: a
third lens group G3 having positive refractive power; and a fourth
lens group G4 having positive refractive power.
[0247] In the variable power optical system ZL2, the first lens
group G1 is constituted by a cemented lens where a negative
meniscus lens L11 having a convex surface facing the object and a
positive meniscus lens L12 having a convex surface facing the
object are cemented in order from the object. The second lens group
G2 is constituted by, in order from the object: a negative lens
L21, of which aspherical shape is formed by creating a resin layer
on the object side lens surface of a negative meniscus lens having
a convex surface facing the object; a biconcave lens L22; a
biconvex lens L23; and a cemented lens where a positive meniscus
lens L24 having a concave surface facing the object and a negative
lens L25 which has a concave surface facing the object and of which
image side lens surface is aspherical, are cemented. The third lens
group G3 is constituted by, in order from the object: a positive
lens L31 of which object side and image side lens surfaces are
aspherical; a cemented lens where a biconvex lens L32 and a
biconcave lens L33 are cemented; a cemented lens where a biconcave
lens L34 and a biconvex lens L35 are cemented, a positive lens of
which object side and image side lens surfaces are aspherical, and
a negative meniscus lens L37 having a convex surface facing the
object. The fourth lens group G4 is constituted by a positive lens
L41 of which object side lens surface is aspherical. An aperture
stop S is disposed between the second lens group G2 and the third
lens group G3. A filter group FL including a low-pass filter, an
infrared filter or the like is disposed between the fourth lens
group G4 and the image plane I. The negative lens L25, the positive
lens L31, the positive lens L36 and the positive lens L41 are
glass-molded aspherical lenses.
[0248] In this variable power optical system ZL2, upon zooming from
the wide-angle end state to the telephoto end state, the first lens
group G1 and the second lens group G2 move toward the image plane
first and then move toward the object, the third lens group G3
moves toward the object, and the fourth lens group G4 moves toward
the object first and then moves toward the image plane, so that the
distance between the first lens group G1 and the second lens group
G2 increases, the distance between the second lens group G2 and the
third lens group G3 decreases, and the distance between the third
lens group G3 and the fourth lens group G4 increases. The aperture
stop S moves together with the third lens group G3.
[0249] In the variable power optical system ZL2, focusing from
infinity to an object at a close distance is performed by moving an
image side group G3c (negative meniscus lens L37), which is
disposed to the image side of a vibration-isolating lens group G32
of the third lens group G3, toward the image plane.
[0250] In the variable power optical system ZL2, the positive lens
L36 of the third lens group G3 is used as the vibration-isolating
lens group G32, and image blur correction (vibration isolation) is
performed by moving the vibration-isolating lens group G32 so as to
have a component in a direction orthogonal to the optical axis. In
the wide-angle end state of Example 2, the vibration-isolation
coefficient is -0.625 and the focal length is 9.3 (mm), therefore
the moving distance of the vibration-isolating lens group G32, to
correct a 1.03.degree. rotation blur is -0.170 (mm). In the
intermediate focal length state, the vibration-isolation
coefficient is -0.814 and the focal length is 19.1 (mm), therefore
the moving distance of the vibration-isolating lens group G32, to
correct a 0.615.degree. rotation blur, is -0.205 (mm). In the
telephoto end state, the vibration-isolation coefficient is -0.939
and the focal length is 29.1 (mm), therefore the moving distance of
the vibration-isolating lens group G32, to correct a 0.534.degree.
rotation blur, is -0.271 (mm).
[0251] Table 5 shows the data values of the variable power optical
system ZL2. The surface numbers 1 to 34 in Table 5 corresponds to
the numbers 1 to 34 in FIG. 6.
TABLE-US-00005 TABLE 5 Example 2 [General Data] Zoom ratio = 3.13
Wide-angle Intermediate Telephoto end state focal length state end
state f =9.3 ~19.1 ~29.1 FNO =1.8 ~2.5 ~2.9 2.omega. =85.2 ~44.9
~30.1 Y =8.0 ~8.0 ~8.0 TL (air =95.4 ~100.7 ~112.1 conversion
length) BF (air =13.8 ~18.7 ~19.8 conversion length) [Lens Data] m
r d .nu.d nd Object .infin. plane 1 49.101 1.60 17.98 1.94595 2
35.955 6.34 46.60 1.80400 3 238.109 D3 4* 32230.587 0.20 36.64
1.56093 5 92.951 1.51 40.66 1.88300 6 11.709 6.33 7 -61.701 1.00
54.61 1.72916 8 40.995 0.94 9 38.612 4.05 23.78 1.84666 10 -35.701
1.00 11 -18.790 2.40 31.16 1.68893 12 -13.145 1.00 40.10 1.85135
13* -31.982 D13 14 0.000 0.80 Aperture stop S 15* 22.706 3.20 71.68
1.55332 16* -58.429 0.30 17 46.573 5.34 23.78 1.84666 18 -12.743
0.90 28.38 1.72825 19 35.112 1.91 20 -28.666 1.21 22.74 1.80809 21
24.685 4.43 82.57 1.49782 22 -15.272 0.50 23* 24.333 2.63 81.56
1.49710 24* -70.000 D24 25 43.446 0.80 63.88 1.51680 26 15.925 D26
27* 24.203 2.37 81.56 1.49710 28 220.780 D28 29 0.000 0.50 63.88
1.51680 30 0.000 1.11 31 0.000 1.59 63.88 1.51680 32 0.000 0.30 33
0.000 0.70 63.88 1.51680 34 0.000 0.70 [Lens Group Focal Length]
Lens group First surface Focal length First lens group 1 81.70
Second lens group 4 -13.37 Third lens group 15 23.47 Fourth lens
group 27 54.46
[0252] In this variable power optical system ZL2, surface 4,
Surface 13, Surface 15, Surface 16, Surface 23, Surface 24 and
Surface 27 are aspherical. Table 6 shows aspherical data, that is,
the values of the conical coefficient K and each aspherical
coefficient A4 to A10.
TABLE-US-00006 TABLE 6 [Aspherical Data] K A4 A6 A8 A10 Surface 4 0
4.81180E-05 -1.64047E-07 4.26213E-10 -5.47014E-13 Surface 13 0
-8.45829E-06 2.53106E-08 -1.62200E-09 1.06953E-11 Surface 15 0
-8.35604E-06 3.00666E-08 -1.56105E-09 0.00000E+00 Surface 16 0
4.98849E-05 4.71546E-08 0.00000E+00 0.00000E+00 Surface 23 0
-1.46890E-05 -3.34594E-07 0.00000E+00 0.00000E+00 Surface 24 0
3.77210E-07 -3.15609E-07 -1.42238E-09 1.85664E-11 Surface 27 0
-9.43792E-07 -4.37993E-08 2.66683E-10 0.00000E+00
[0253] In the variable power optical system ZL2, the axial air
distance D3 between the first lens group G1 and the second lens
group G2, the axial air distance D13 between the second lens group
G2 and the third lens group G3 (aperture stop S), the axial air
distance D26 between the third lens group G3 and the fourth lens
group G4 and the axial air distance D28 between the fourth lens
group G4 and the filter group FL change upon zooming, as mentioned
above. The axial air distance D24 to the object side and the axial
air distance D26 to the image side of the image side group G3c of
the third lens group G3 Change upon focusing. Table 7 shows the
variable distance in each focal length state of the wide-angle end
state, intermediate focal length state and telephoto end state upon
focusing on infinity and upon focusing on a close point. Upon
focusing on a close point, only the values of D24 and D26 are
shown, and the omitted values are the same as the respective values
obtained upon focusing on infinity.
TABLE-US-00007 TABLE 7 [Variable Distance Data] Focusing on
infinity Focusing on close point Wide- Inter- Telephoto Wide-
Inter- Telephoto angle end mediate end angle end mediate end f 9.3
19.1 29.1 9.3 19.1 29.1 D3 1.2 13.9 23.2 D13 22.0 6.1 1.5 D24 1.50
1.50 1.50 2.21 3.19 4.68 D26 5.20 8.78 14.40 4.48 7.10 11.22 D28
9.8 14.8 15.9
[0254] Table 8 shows the conditional expression correspondence
value of the variable power optical system ZL2. In Example 2, the
negative lens included in the image side group G3c of the third
lens group G3 is the negative meniscus lens L37, the positive lens
included in the object side group G3a of the third lens group G3 is
the positive lens L31, the positive lens included in the
vibration-isolating lens group G32 is the positive lens L36, and
the final lens group is the fourth lens group G4. R2a indicates the
radial distance of Surface 19, and Rib indicates a radial of
curvature of Surface 20.
TABLE-US-00008 TABLE 8 [Conditional Expression Correspondence
Value] (1) (-f2)/(fw .times. ft).sup.1/2 = 0.814 (2) ndF - 0.0052
.times. .nu.dF - 1.965 = -0.116 (3) .nu.dF = 63.9 (4) .nu.dO = 71.7
(5) f4/fw = 5.88 (6) fv .times. FNOw/f3 = 2.86 (7) (R2a + R1b)/(R2a
- R1b) = 0.101 (8) f3/.DELTA.T3 = 1.54 (9) ndVR - 0.0052 .times.
.nu.dVR - 1.965 = -0.044 (10) .nu.dVR = 81.5 (11) fr/fw = 5.88 (12)
f3/(fw .times. ft).sup.1/2 = 1.43
[0255] Thus the variable power optical system ZL2 satisfies all the
conditional expressions (1) to (12).
[0256] FIG. 7A, FIG. 8A and FIG. 9A are graphs showing spherical
aberration, astigmatism, distortion, lateral chromatic aberration
and coma aberration of the variable power optical system ZL2 upon
focusing on infinity in the wide-angle end state, intermediate
focal length state, and telephoto end state, and FIG. 7B, FIG. 8B
and FIG. 9B are graphs showing coma aberration when image blur is
corrected upon focusing on infinity in the wide-angle end state,
intermediate focal length state and telephoto end state. FIG. 10
are graphs showing spherical aberration, astigmatism, distortion,
lateral chromatic aberration and coma aberration upon focusing on a
close point in the wide-angle end state, intermediate focal length
state and telephoto end state. As each graph showing aberration
clarifies, various aberrations are corrected well in the variable
power optical system ZL2, from the wide-angle end state to the
telephoto end state.
Example 3
[0257] FIG. 11 shows a configuration of a variable power optical
system ZL3 according to Example 3. The variable power optical
system ZL3 shown in FIG. 11 includes, in order from an object: a
first lens group G1 having positive refractive power; a second lens
group G2 having negative refractive power; and a rear group GR, and
the rear group GR is constituted by, in order from the object: a
third lens group G3 having positive refractive power; and a fourth
lens group G4 having positive refractive power.
[0258] In the variable power optical system ZL3, the first lens
group G1 is constituted by a cemented lens where a negative
meniscus lens L11 having a convex surface facing the object and a
positive meniscus lens L12 having a convex surface facing the
object are cemented in order from the object. The second lens group
G2 is constituted by, in order from the object: a negative lens L21
which has a convex surface facing the object and of which object
image side lens surfaces are aspherical; a negative meniscus lens
L22 having a concave surface facing the object; a cemented lens
where a biconcave lens L23 and a biconvex lens L24 are cemented;
and a negative lens L25 which has a concave surface facing the
object and of which object side and image side lens surface is
aspherical. The third lens group G3 is constituted by, in order
from the object: a positive lens L31 of which object side and image
side lens surfaces are aspherical; a cemented lens where a biconvex
lens L32 and a biconcave lens L33 are cemented; a cemented lens
where a biconcave lens L34 and a biconvex lens L35 are cemented; a
cemented positive lens where a negative meniscus lens L36 having a
convex surface facing the object and a positive lens L37 of which
image side lens surface is aspherical are cemented; and a negative
lens L38 which has a convex surface facing the object and of which
image side lens surface is aspherical. The fourth lens group G4 is
constituted by a positive meniscus lens L41 having a convex surface
facing the object. An aperture stop S is disposed between the
second lens group G2 and the third lens group G3. A filter group FL
including a low-pass filter, an infrared filter or the like is
disposed between the fourth lens group G4 and the image plane I.
The negative lens L21, the negative lens L25, the positive lens
L31, the negative lens L36 and the positive lens L37 are
glass-molded aspherical lenses.
[0259] In this variable power optical system ZL3, upon zooming from
the wide-angle end state to the telephoto end state, the first lens
group G1 and the second lens group G2 move toward the image plane
first and then move toward the object, the third lens group G3
moves toward the object, and the fourth lens group G4 moves toward
the object first and then moves toward the image plane, so that the
distance between the first lens group G1 and the second lens group
G2 increases, the distance between the second lens group G2 and the
third lens group G3 decreases, and the distance between the third
lens group G3 and the fourth lens group G4 increases. The aperture
stop S moves together with the third lens group G3.
[0260] In the variable power optical system ZL3, focusing from
infinity to an object at a close distance is performed by moving an
image side group G3c (negative meniscus lens L38), which is
disposed to the image side of a vibration-isolating lens group G32
of the third lens group G3, toward the image plane.
[0261] In the variable power optical system ZL3, the cemented
positive lens constituted by the negative lens L36 and the positive
lens L37 of the third lens group G3 is used as the
vibration-isolating lens group G32, and image blur correction
(vibration isolation) is performed by moving this
vibration-isolating lens group G32 so as to have a component in a
direction orthogonal to the optical axis. In the wide-angle end
state of Example 3, the vibration-isolation coefficient is -0.723,
and the focal length is 9.3 (mm), therefore the moving distance of
the vibration-isolating lens group G32, to correct a 0.911.degree.
rotation blur, is -0.147 (mm). In the intermediate focal length
state, the vibration-isolation coefficient is -0.934 and the focal
length is 19.1 (mm), therefore the moving distance of the
vibration-isolating lens group G32, to correct a 0.534.degree.
rotation blur, is -0.177 (mm). In the telephoto end state, the
vibration-isolation coefficient is -1.06 and the focal length is
29.1 (mm), therefore the moving distance of the vibration-isolating
lens group G32, to correct a 0.474.degree. rotation blur, is -0.236
(mm).
[0262] Table 9 shows the data values of the variable power optical
system ZL3. The surface numbers 1 to 35 in Table 9 correspond to
the numbers 1 to 35 in FIG. 11.
TABLE-US-00009 TABLE 9 Example 3 [General Data] Zoom ratio = 3.12
Intermediate Wide-angle focal length Telephoto end state state end
state f =9.3 ~19.1 ~29.1 FNO =1.8 ~2.3 ~2.6 2.omega. =84.3 ~45.3
~30.7 Y =8.0 ~8.0 ~8.0 TL (air =93.4 ~99.2 ~110.9 conversion
length) BF (air =13.7 ~21.1 ~21.5 conversion length) [Lens Data] m
r d .nu.d nd Object plane .infin. 1 43.371 1.60 17.98 1.94595 2
32.926 6.90 45.31 1.79500 3 140.257 D3 4* 175.520 1.50 42.65
1.82080 5* 10.809 7.48 6 -15.455 0.92 29.14 2.00100 7 -20.858 0.28
8 -101.287 0.80 46.60 1.80400 9 38.949 0.00 10 36.831 4.78 23.78
1.84666 11 -25.842 0.94 12 -14.557 0.92 45.46 1.80139 13* -25.880
D13 14 0.000 1.20 Aperture stop S 15* 18.690 3.57 81.56 1.497103
16* -63.173 0.78 17 42.863 3.79 22.74 1.80809 18 -17.820 1.00 28.69
1.79504 19 28.455 2.21 20 -54.464 0.90 22.74 1.80809 21 34.705 4.33
82.57 1.49782 22 -16.135 0.50 23 21.394 0.80 29.14 2.00100 24
17.003 3.74 71.67 1.55332 25* -60.926 D25 26 29.947 0.80 81.49
1.49710 27* 14.925 D27 28 29.674 1.90 82.57 1.49782 29 96.000 D29
30 0.000 0.50 63.88 1.51680 31 0.000 1.11 32 0.000 1.59 63.88
1.51680 33 0.000 0.30 34 0.000 0.70 63.88 1.51680 35 0.000 0.70
[Lens Group Focal Length] Lens group First surface Focal length
First lens group 1 82.51 Second lens group 4 -11.97 Third lens
group 15 21.69 Fourth lens group 28 85.46
[0263] In this variable power optical system ZL3, Surface 4,
Surface 5, Surface 13, Surface 15, Surface 16, Surface 25 and
Surface 27 are aspherical. Table 10 shows aspherical data, that is,
the values of the conical coefficient K and each aspherical
coefficient A4 to A12.
TABLE-US-00010 TABLE 10 [Aspherical Data] K A4 A6 A8 A10 A12
Surface 4 0 6.79E-05 -4.38E-07 3.57E-09 -1.72E-11 3.66E-14 Surface
5 0 3.02E-05 -1.77E-07 2.51E-09 2.36E-11 0.00E+00 Surface 13 0
-1.03E-05 -1.42E-07 2.00E-09 -1.18E-11 0.00E+00 Surface 15 0
1.60E-05 1.53E-08 4.77E-09 0.00E+00 0.00E+00 Surface 16 0 9.01E-05
4.44E-09 5.55E-09 0.00E+00 0.00E+00 Surface 25 0 2.01E-05 -2.52E-07
4.90E-09 -3.50E-11 0.00E+00 Surface 27 0 -1.52E-05 2.25E-07
-5.15E-09 4.70E-11 0.00E+00
[0264] In the variable power optical system ZL3, the axial air
distance D3 between the first lens group G1 and the second lens
group G2, the axial air distance D13 between the second lens group
G2 and the third lens group G3 (aperture stop S), the axial air
distance D27 between the third lens group G3 and the fourth lens
group G4, and the axial air distance D29 between the fourth lens
group G4 and the filter group FL change upon zooming, as mentioned
above. The axial air distance D25 to the object side and the axial
air distance D27 to the image side of the image side group G3c of
the third lens group G3 Change upon focusing. Table 11 shows the
variable distance in each focal length state of the wide-angle end
state, intermediate focal length state and telephoto end state upon
focusing on infinity and upon focusing on a close point. Upon
focusing on a close point, only the values of D25 and D27 are
shown, and omitted values are the same as the respective values
obtained upon focusing on infinity.
TABLE-US-00011 TABLE 11 [Variable Distance Data] Focusing on
infinity Focusing on close point Wide- Inter- Telephoto Wide-
Inter- Telephoto angle end mediate end angle end mediate end f 9.3
19.0 29.1 9.3 19.0 29.1 D3 1.0 13.9 23.9 D13 19.2 4.9 1.2 D25 1.60
1.60 1.60 2.52 4.05 5.19 D27 5.20 5.20 10.08 4.38 2.75 6.49 D29 9.8
17.2 17.5
[0265] Table 12 shows each conditional expression correspondence
value of the variable power optical system ZL3. In Example 3, the
negative lens included in the image side group G3c of the third
lens group G3 is the negative lens L38, the positive lens included
in the object side group G3a of the third lens group G3 is the
positive lens L31, the positive lens included in the
vibration-isolating lens group G32 is the positive lens L37, and
the final lens group is the fourth lens group G4. R2a indicates a
radial distance of the Surface 19, and Rib indicates a radius of
curvature of Surface 20.
TABLE-US-00012 TABLE 12 [Conditional Expression Correspondence
Value] (1) (-f2)/(fw .times. ft).sup.1/2 = 0.736 (2) ndF - 0.0052
.times. .nu.dF - 1.965 = -0.044 (3) .nu.dF = 81.5 (4) .nu.dO = 81.6
(5) f4/fw = 9.22 (6) fv .times. FNOw/f3 = 2.87 (7) (R2a + R1b)/(R2a
- R1b) = -0.314 (8) f3/.DELTA.T3 = 1.72 (9) ndVR - 0.0052 .times.
.nu.dVR - 1.965 = -0.044 (10) .nu.dVR = 71.7 (11) fr/fw = 9.22 (12)
f3/(fw .times. ft).sup.1/2 = 1.33
[0266] Thus the variable power optical system ZL3 satisfies all the
conditional expressions (1) to (12).
[0267] FIG. 12A, FIG. 13A and FIG. 14A are graphs showing spherical
aberration, astigmatism, distortion, lateral chromatic aberration
and coma aberration of the variable power optical system ZL3 upon
focusing on infinity in the wide-angle end state, intermediate
focal length state, and telephoto end state, and FIG. 12B, FIG. 13B
and FIG. 14B are graphs showing coma aberration when image blur is
corrected upon focusing on infinity in the wide-angle end state,
intermediate focal length state and telephoto end state. FIG. 15
are graphs showing spherical aberration, astigmatism, distortion,
lateral chromatic aberration and coma aberration upon focusing on a
close point in the wide-angle end state, intermediate focal length
state and telephoto end state. As each graph showing aberration
clarifies, various aberrations are corrected well in the variable
power optical system ZL3, from the wide-angle end state to the
telephoto end state.
Example 4
[0268] FIG. 16 shows a configuration of a variable power optical
system ZL4 according to Example 4. The variable power optical
system ZL4 shown in FIG. 16 includes, in order from an object: a
first lens group G1 having positive refractive power; a second lens
group G2 having negative refractive power; and a rear group GR, and
the rear group GR is constituted by, in order from the object: a
third lens group G3 having positive refractive power; and a fourth
lens group G4 having positive refractive power.
[0269] In the variable power optical system ZL4, the first lens
group G1 is constituted by a cemented lens where a negative
meniscus lens L11 having a convex surface facing the object and a
positive meniscus lens L12 having a convex surface facing the
object are cemented in order from the object. The second lens group
G2 is constituted by, in order from the object: a negative lens
L21, which has a convex surface facing the object and of which
object side lens surface is aspherical; a cemented lens where
biconcave lens L22 and a biconvex lens L23 are cemented; and a
cemented lens where a positive meniscus lens L24 having a concave
surface facing the object and a negative lens L25 of which image
side lens surface is aspherical are cemented. The third lens group
G3 is constituted by, in order from the object: a positive lens L31
of which object side and image side lens surface are aspherical; a
cemented lens where a biconvex lens L32 and a biconcave lens L33
are cemented; a cemented lens where a biconcave lens L34 and a
biconvex lens L35 are cemented; a positive lens L36 of which image
side lens surface is aspherical; and a negative meniscus lens L37
having a convex surface facing the object. The fourth lens group G4
is constituted by a positive lens L41 which has a convex surface
facing the object and of which object side lens surface is
aspherical. An aperture stop S is disposed between the second lens
group G2 and the third lens group G3. A filter group FL including a
low-pass filter, an infrared filter or the like is disposed between
the fourth lens group G4 and the image plane I. The negative lens
L21, the negative lens L25, the positive lens L31, the positive
lens L36 and the positive lens L41 are glass-molded aspherical
lenses.
[0270] In this variable power optical system ZL4, upon zooming from
the wide-angle end state to the telephoto end state, the first lens
group G1 and the second lens group G2 move toward the image plane
first and then move toward the object, the third lens group G3
moves toward the object, and the fourth lens group G4 moves toward
the object first and then moves toward the image plane, so that the
distance between the first lens group G1 and the second lens group
G2 increases, the distance between the second lens group G2 and the
third lens group G3 decreases, and the distance between the third
lens group G3 and the fourth lens group G4 increases. The aperture
stop S moves together with the third lens group G3.
[0271] In the variable power optical system ZL4, focusing from
infinity to an object at a close distance is performed by moving an
image side group G3c (negative meniscus lens L37), which is
disposed to the image side of a vibration-isolating lens group G32
of the third lens group G3, toward the image plane.
[0272] In the variable power optical system ZL4, the positive lens
L36 of the third lens group G3 is used as the vibration-isolating
lens group G32, and image blur correction (vibration isolation) is
performed by moving the vibration-isolating lens group G32 so as to
have a component in a direction orthogonal to the optical axis. In
the wide-angle end state of Example 4, the vibration-isolation
coefficient is -0.701 and the focal length is 9.26 (mm), therefore
the moving distance of the vibration-isolating lens group G32, to
correct a 0.940.degree. rotation blur, is -0.152 (mm). In the
intermediate focal length state, the vibration-isolation
coefficient is -0.929 and the focal length is 19.1 (mm), therefore
the moving distance of the vibration-isolating lens group G32, to
correct a 0.537.degree. rotation blur, is -0.179 (mm). In the
telephoto end state, the vibration-isolation coefficient is -1.05
and the focal length is 29.1 (mm), therefore the moving distance of
the vibration-isolating lens group G32, to correct a 0.475.degree.
rotation blur, is -0.241 (mm).
[0273] Table 13 shows the data values of the variable power optical
system ZL4. The surface numbers 1 to 32 in Table 13 correspond to
the numbers 1 to 32 in FIG. 16.
TABLE-US-00013 TABLE 13 Example 4 [General Data] Zoom ratio = 3.13
Intermediate Wide-angle focal length Telephoto end state state end
state f =9.26 ~19.1 ~29.1 FNO =1.8 ~2.3 ~2.6 2.omega. =85.1 ~45.0
~29.9 Y =8.0 ~8.0 ~8.0 TL (air =93.2 ~98.8 ~110.7 conversion
length) BF (air =13.71 ~19.12 ~20.67 conversion length) [Lens Data]
m r d .nu.d nd Object plane .infin. 1 47.558 1.60 17.98 1.94595 2
35.327 6.23 46.60 1.80400 3 222.036 D3 4* 5814.989 1.61 40.10
1.85135 5 11.700 6.30 6 -90.767 1.94 49.62 1.77250 7 47.951 3.78
23.78 1.84666 8 -36.068 1.81 9 -14.307 2.06 22.74 1.80809 10
-12.194 0.90 45.46 1.80139 11* -25.687 D11 12 0.000 0.80 Aperture
stop S 13* 16.293 3.67 67.05 1.59201 14* -77.139 0.30 15 70.431
3.48 25.45 1.80518 16 -16.780 0.80 33.73 1.64769 17 24.325 2.59 18
-33.946 1.09 25.45 1.80518 19 18.705 4.24 82.57 1.49782 20 -16.422
0.50 21 21.829 2.84 81.49 1.49710 22* -60.000 D22 23 113.472 0.80
82.57 1.49782 24 22.646 D24 25* 26.180 2.35 81.49 1.49710 26
607.278 D26 27 0.000 0.50 63.88 1.51680 28 0.000 1.11 29 0.000 1.59
63.88 1.51680 30 0.000 0.30 31 0.000 0.70 63.88 1.51680 32 0.000
0.70 [Lens Group Focal Length] Lens group First surface Focal
length First lens group 1 79.52 Second lens group 4 -12.62 Third
lens group 13 22.96 Fourth lens group 25 54.96
[0274] In this variable power optical system ZL4, Surface 4,
Surface 11, Surface 13, Surface 14, Surface 22 and Surface 25 are
aspherical. Table 14 shows aspherical data, that is, the values of
the conical coefficient K and each aspherical coefficient A4 to
A10.
TABLE-US-00014 TABLE 14 [Aspherical Data] K A4 A6 A8 A10 Surface 4
0 3.94307E-05 -1.29628E-07 3.43564E-10 -3.78498E-13 Surface 11 0
-1.30254E-05 -1.98133E-08 -6.57557E-10 4.01106E-12 Surface 13 0
-3.22653E-06 1.73408E-07 -7.04126E-11 0.00000E+00 Surface 14 0
7.18116E-05 1.79256E-07 0.00000E+00 0.00000E+00 Surface 22 0
1.05439E-05 2.55453E-08 8.37397E-10 -1.64088E-12 Surface 25 0
-1.35591E-05 1.71835E-07 -3.32810E-09 2.04907E-11
[0275] In the variable power optical system ZL4, the axial air
distance D3 between the first lens group G1 and the second lens
group G2, the axial air distance D11 between the second lens group
G2 and the third lens group G3 (aperture stop S), the axial air
distance D24 between the third lens group G3 and the fourth lens
group G4, and the axial air distance D26 between the fourth lens
group G4 and the filter group FL change upon zooming, as mentioned
above. The axial air distance D22 to the object side and the axial
air distance D24 to the image side of the image side group G3c of
the third lens group G3 Change upon focusing. Table 15 shows the
variable distance in each focal length state of the wide-angle end
state, intermediate focal length state and telephoto end state upon
focusing on infinity and upon focusing on a close point. Upon
focusing on a close point, only the values of D22 and D24 are
shown, and omitted values are the same as the respective values
obtained upon focusing on infinity.
TABLE-US-00015 TABLE 15 [Variable Distance Data] Focusing on
infinity Focusing on close point Wide- Inter- Telephoto Wide-
Inter- Telephoto angle end mediate end angle end mediate end f 9.3
19.1 29.1 9.3 19.1 29.1 D3 1.0 13.9 23.9 D11 19.2 4.9 1.2 D22 1.60
1.60 1.60 2.44 3.60 5.50 D24 5.20 9.06 13.43 4.36 7.06 9.53 D26 9.8
17.2 17.5
[0276] Table 16 shows each conditional expression correspondence
value of the variable power optical system ZL4. In Example 4, the
negative lens included in the image side group G3c of the third
lens group G3 is the negative meniscus lens L37, the positive lens
included in the object side group G3a of the third lens group G3 is
the positive lens L31, the positive lens included in the
vibration-isolating lens group G32 is the positive lens L36, and
the final lens group is the fourth lens group G4. R2a indicates a
radial distance of the Surface 17, and R1b indicates a radius of
curvature of Surface 18.
TABLE-US-00016 TABLE 16 [Conditional Expression Correspondence
Value] (1) (-f2)/(fw .times. ft).sup.1/2 = 0.769 (2) ndF - 0.0052
.times. .nu.dF - 1.965 = -0.038 (3) .nu.dF = 82.6 (4) .nu.dO = 67.1
(5) f4/fw = 5.94 (6) fv .times. FNOw/f3 = 2.60 (7) (R2a + R1b)/(R2a
- R1b) = -0.165 (8) f3/.DELTA.T3 = 1.51 (9) ndVR - 0.0052 .times.
.nu.dVR - 1.965 = -0.044 (10) .nu.dVR = 81.49 (11) fr/fw = 5.94
(12) f3/(fw .times. ft).sup.1/2 = 1.40
[0277] Thus the variable power optical system ZL4 satisfies all the
conditional expressions (1) to (12).
[0278] FIG. 17A, FIG. 18A and FIG. 19A are graphs showing spherical
aberration, astigmatism, distortion, lateral chromatic aberration
and coma aberration of the variable power optical system ZL4 upon
focusing on infinity in the wide-angle end state, intermediate
focal length state, and telephoto end state, and FIG. 17B, FIG. 18B
and FIG. 19B are graphs showing coma aberration when image blur is
corrected upon focusing on infinity in the wide-angle end state,
intermediate focal length state and telephoto end state. FIG. 20
are graphs showing spherical aberration, astigmatism, distortion,
lateral chromatic aberration and coma aberration upon focusing on a
close point in the wide-angle end state, intermediate focal length
state and telephoto end state. As each graph showing aberration
clarifies, various aberrations are corrected well in the variable
power optical system ZL4, from the wide-angle end state to the
telephoto end state.
Example 5
[0279] FIG. 21 shows a configuration of a variable power optical
system ZL5 according to Example 5. The variable power optical
system ZL5 shown in FIG. 21 includes, in order from an object: a
first lens group G1 having positive refractive power; a second lens
group G2 having negative refractive power; and a rear group GR, and
the rear group GR is constituted by, in order from the object: a
third lens group G3 having positive refractive power; and a fourth
lens group G4 having positive refractive power.
[0280] In the variable power optical system ZL5, the first lens
group G1 is constituted by a cemented lens where a negative
meniscus lens L11 having a convex surface facing the object and a
positive meniscus lens L12 having a convex surface facing the
object are cemented in order from the object. The second lens group
G2 is constituted by, in order from the object: a negative lens L21
of which aspherical shape is formed by creating a resin layer on
the object side lens surface of a negative meniscus lens having a
convex surface facing the object; a biconcave lens L22; a biconvex
lens L23; and a cemented lens where a positive meniscus lens L24
having a concave surface facing the object and a negative lens L25
which has a concave surface facing the object and of which image
side lens surface is aspherical are cemented. The third lens group
G3 is constituted by, in order from the object: a positive lens L31
of which object side and image side lens surfaces are aspherical; a
cemented lens where a biconvex lens L32 and a biconcave lens L33
are cemented; a cemented lens where a biconcave lens L34 and a
biconvex lens L35 are cemented; a positive lens L36 of which object
side and image side lens surfaces are aspherical; and negative
meniscus lens L37 having a convex surface facing the object. The
fourth lens group G4 is constituted by a positive lens L41 of which
object side lens surface is aspherical. An aperture stop S is
disposed between the second lens group G2 and the third lens group
G3. A filter group FL including a low-pass filter, an infrared
filter or the like is disposed between the fourth lens group G4 and
the image plane I. The negative lens L25, the positive lens L31,
the positive lens L36 and the positive lens L41 are glass-molded
aspherical lenses.
[0281] In this variable power optical system ZL5, upon zooming from
the wide-angle end state to the telephoto end state, the first lens
group G1 and the second lens group G2 move toward the image plane
first and then move toward the object, the third lens group G3
moves toward the object, and the fourth lens group G4 moves toward
the object first and then moves toward the image plane, so that the
distance between the first lens group G1 and the second lens group
G2 increases, the distance between the second lens group G2 and the
third lens group G3 decreases, and the distance between the third
lens group G3 and the fourth lens group G4 increases. The aperture
stop S moves together with the third lens group G3.
[0282] In the variable power optical system ZL5, focusing from
infinity to an object at a close distance is performed by moving an
image side group G3c (negative meniscus lens L37), which is
disposed to the image side of a vibration-isolating lens group G32
of the third lens group G3, toward the image plane.
[0283] In the variable power optical system ZL5, the positive lens
L36 of the third lens group G3 is used as the vibration-isolating
lens group G32, and image blur correction (vibration isolation) is
performed by moving the vibration-isolating lens group G32 so as to
have a component in a direction orthogonal to the optical axis. In
the wide-angle end state of Example 5, the vibration-isolation
coefficient is -0.636 and the focal length is 9.3 (mm), therefore
the moving distance of the vibration-isolating lens group G32, to
correct a 1.03.degree. rotation blur, is -0.167 (mm). In the
intermediate focal length state, the vibration-isolation
coefficient is -0.859 and the focal length is 19.1 (mm), therefore
the moving distance of the vibration-isolating lens group G32, to
correct a 0.574.degree. rotation blur, is -0.194 (mm). In the
telephoto end state, the vibration-isolation coefficient is -0.963
and the focal length is 29.1 (mm), therefore the moving distance of
the vibration-isolating lens group G32, to correct a 0.519.degree.
rotation blur, is -0.271 (mm).
[0284] Table 17 shows the data values of the variable power optical
system ZL5. The surface numbers 1 to 34 in Table 17 correspond to
the numbers 1 to 34 in FIG. 21.
TABLE-US-00017 TABLE 17 Example 5 [General Data] Zoom ratio = 3.14
Intermediate Wide-angle focal length Telephoto end state state end
state f =9.3 ~19.1 ~29.1 FNO =1.8 ~2.6 ~2.9 2.omega. =85.0 ~45.2
~30.1 Y =8.0 ~8.0 ~8.0 TL (air =95.9 ~98.8 ~112.6 conversion
length) BF (air =13.79 ~20.56 ~21.34 conversion length) [Lens Data]
m r d .nu.d nd Object plane .infin. 1 48.703 1.60 17.98 1.94595 2
34.692 6.38 42.73 1.83481 3 197.349 D3 4* 5896.385 0.20 36.64
1.56093 5 93.609 1.51 40.66 1.88300 6 11.700 6.47 7 -54.231 1.00
54.61 1.72916 8 54.855 1.56 9 49.676 3.34 23.78 1.84666 10 -32.621
1.12 11 -18.908 2.35 33.73 1.64769 12 -13.263 0.90 44.98 1.79050
13* -37.964 D13 14 0.000 0.80 Aperture stop S 15* 20.379 3.57 71.67
1.55332 16* -42.773 0.30 17 46.219 4.49 23.78 1.84666 18 -14.503
0.90 27.57 1.75520 19 27.482 2.80 20 -29.885 1.34 25.45 1.80518 21
23.770 4.30 82.57 1.49782 22 -15.009 0.50 23* 23.770 2.70 81.49
1.49710 24* -70.000 D24 25 54.480 0.80 67.90 1.59319 26 19.345 D26
27* 26.011 2.37 81.49 1.49710 28 500.000 D28 29 0.000 0.50 63.88
1.51680 30 0.000 1.11 31 0.000 1.59 63.88 1.51680 32 0.000 0.30 33
0.000 0.70 63.88 1.51680 34 0.000 0.70 [Lens Group Focal Length]
Lens group First surface Focal length First lens group 1 80.99
Second lens group 4 -12.86 Third lens group 15 22.96 Fourth lens
group 27 55.11
[0285] In this variable power optical system ZL5, Surface 4,
Surface 13, Surface 15, Surface 16, Surface 23, Surface 24 and
Surface 27 are aspherical. Table 18 shows aspherical data, that is,
the values of the conical coefficient K and each aspherical
coefficient A4 to A10.
TABLE-US-00018 TABLE 18 [Aspherical Data] K A4 A6 A8 A10 Surface 4
0 4.87287E-05 -1.73017E-07 4.92743E-10 -6.73284E-13 Surface 13 0
-8.09198E-06 -3.28390E-08 -3.69807E-10 1.91943E-12 Surface 15 0
-1.61042E-05 3.65268E-08 -5.12033E-10 0.00000E+00 Surface 16 0
4.30711E-05 5.71263E-08 0.00000E+00 0.00000E+00 Surface 23 0
-1.46815E-05 -3.11565E-07 0.00000E+00 0.00000E+00 Surface 24 0
-7.08073E-07 -3.08275E-07 -7.09313E-10 1.17051E-11 Surface 27 0
-2.64761E-06 -4.55080E-08 2.47961E-10 0.00000E+00
[0286] In the variable power optical system ZL5, the axial air
distance D3 between the first lens group G1 and the second lens
group G2, the axial air distance D13 between the second lens group
G2 and the third lens group G3 (aperture stop S), the axial air
distance D26 between the third lens group G3 and the fourth lens
group G4, and the axial air distance D28 between the fourth lens
group G4 and the filter group FL change upon zooming, as mentioned
above. The axial air distance D24 to the object side and the axial
air distance D26 to the image side of the image side group G3c of
the third lens group G3 Change upon focusing. Table 19 shows the
variable distance in each focal length state of the wide-angle end
state, intermediate focal length state, and telephoto end state
upon focusing on infinity and upon focusing on a close point. Upon
focusing on a close point, only the values of D24 and D26 are
shown, and the omitted values are the same as the respective values
obtained upon focusing on infinity.
TABLE-US-00019 TABLE 19 [Variable Distance Data] Focusing on
infinity Focusing on close point Wide- Inter- Telephoto Wide-
Inter- Telephoto angle end mediate end angle end mediate end f 9.3
19.1 29.1 9.3 19.1 29.1 D3 1.2 11.3 22.9 D13 22.0 5.0 1.5 D24 1.50
1.50 1.50 2.24 3.25 4.86 D26 5.20 8.12 13.07 4.46 6.37 9.70 D28 9.8
16.6 16.9
[0287] Table 20 shows each conditional expression correspondence
value of the variable power optical system ZL5. In Example 5, the
negative lens included in the image side group G3c of the third
lens group G3 is a negative meniscus lens L37, the positive lens
included in the object side group G3a of the third lens group G3 is
the positive lens L31, the positive lens included in the
vibration-isolating lens group G32 is the positive lens L36, and
the final lens group is the fourth lens group G4. R2a indicates a
radial distance of Surface 19, and Rib indicates a radius of
curvature of Surface 20.
TABLE-US-00020 TABLE 20 [Conditional Expression Correspondence
Value] (1) (-f2)/(fw .times. ft).sup.1/2 = 0.782 (2) ndF - 0.0052
.times. .nu.dF - 1.965 = -0.019 (3) .nu.dF = 67.9 (4) .nu.dO = 71.7
(5) f4/fw = 5.93 (6) fv .times. FNOw/f3 = 2.81 (7) (R2a + R1b)/(R2a
- R1b) = -0.042 (8) f3/.DELTA.T3 = 1.53 (9) ndVR - 0.0052 .times.
.nu.dVR - 1.965 = -0.044 (10) .nu.dVR = 81.49 (11) fr/fw = 5.94
(12) f3/(fw .times. ft).sup.1/2 = 1.44
[0288] Thus the variable power optical system ZL5 satisfies all the
conditional expressions (1) to (12).
[0289] FIG. 22A, FIG. 23A and FIG. 24A are graphs showing spherical
aberration, astigmatism, distortion, lateral chromatic aberration
and coma aberration of the variable power optical system ZL5 upon
focusing on infinity in the wide-angle end state, intermediate
focal length state, and telephoto end state, and FIG. 22B, FIG. 23B
and FIG. 24B are graphs showing coma aberration when image blur is
corrected upon focusing on infinity in the wide-angle end state,
intermediate focal length state and telephoto end state. FIG. 25
are graphs showing spherical aberration, astigmatism, distortion,
lateral chromatic aberration and coma aberration upon focusing on a
close point in the wide-angle end state, intermediate focal length
state and telephoto end state. As each graph showing aberration
clarifies, various aberrations are corrected well in the variable
power optical system ZL5, from the wide-angle end state to the
telephoto end state.
Example 6
[0290] FIG. 26 shows a configuration of a variable power optical
system ZL6 according to Example 6. The variable power optical
system ZL6 shown in FIG. 26 includes, in order from an object: a
first lens group G1 having positive refractive power; a second lens
group G2 having negative refractive power; and a rear group GR, and
the rear group GR is constituted by, in order from the object: a
third lens group G3 having positive refractive power; a fourth lens
group G4 having negative refractive power; and a fifth lens group
G5 having positive refractive power.
[0291] In the variable power optical system ZL6, the first lens
group G1 is constituted by a cemented lens where a negative
meniscus lens L11 having a convex surface facing the object and a
positive meniscus lens L12 having a convex surface facing the
object are cemented in order from the object. The second lens group
G2 is constituted by, in order from the object: a negative lens L21
of which aspherical shape is formed by creating a resin layer on
the object side lens surface of a negative meniscus lens having a
convex surface facing the object; a biconcave lens L22; a biconvex
lens L23; and a negative lens L24 of which image side lens surface
is aspherical. The third lens group G3 is constituted by, in order
from the object: a positive lens L31 of which object side and image
side lens surfaces are aspherical; a cemented lens where a biconvex
lens L32 and a biconcave lens L33 are cemented; a cemented lens
where a biconcave lens L34 and a biconvex lens L35 are cemented; a
positive lens L36 of which object side and image side lens surfaces
are aspherical. The fourth lens group G4 is constituted by a
negative meniscus lens L41 having a convex surface facing the
object. The fifth lens group G5 is constituted by a positive lens
L51 of which object side lens surface is aspherical. An aperture
stop S is disposed between the second lens group G2 and the third
lens group G3. A filter group FL including a low-pass filter, an
infrared filter or the like is disposed between the fourth lens
group G4 and the image plane I. The negative lens L25, the positive
lens L31, the positive lens L41 and the positive lens L51 are
glass-molded aspherical lenses.
[0292] In this variable power optical system ZL6, upon zooming from
the wide-angle end state to the telephoto end state, the first lens
group G1 and the second lens group G2 move toward the image plane
first and then move toward the object, the third lens group G3
moves toward the object, the fourth lens group G4 moves toward the
image plane first and then moves toward the object, and the fifth
lens group G5 moves toward the object first, and then moves toward
the image plane, so that the distance between the first lens group
G1 and the second lens group G2 increases, the distance between the
second lens group G2 and the third lens group G3 decreases, and the
distance between the third lens group G3 and the fourth lens group
G4 increases first and then decreases. The aperture stop S moves
together with the third lens group G3.
[0293] In the variable power optical system ZL6, focusing from
infinity to an object at a close distance is performed by moving
the fourth lens group G4 toward the image plane.
[0294] In the variable power optical system ZL6, the positive lens
L36 of the third lens group G3 is used as the vibration-isolating
lens group G32, and image blur correction (vibration isolation) is
performed by moving the vibration-isolating lens group G32 so as to
have a component in a direction orthogonal to the optical axis. In
the wide-angle end state of Example 6, the vibration-isolation
coefficient is -0.647 and the focal length is 9.3 (mm), therefore
the moving distance of the vibration-isolating lens group G32, to
correct a 1.02.degree. rotation blur, is -0.165 (mm). In the
intermediate focal length state, the vibration-isolation
coefficient is -0.897 and the focal length is 19.1 (mm), therefore
the moving distance of the vibration-isolating lens group G32, to
correct a 0.559.degree. rotation blur, is -0.187 (mm). In the
telephoto end state, the vibration-isolation coefficient is -1.02
and the focal length is 29.1 (mm), therefore the moving distance of
the vibration-isolating lens group G32, to correct a 0.493.degree.
rotation blur, is -0.250 (mm).
[0295] Table 21 shows the data values of the variable power optical
system ZL6. The surface numbers 1 to 34 in Table 21 correspond to
the numbers 1 to 34 in FIG. 26.
TABLE-US-00021 TABLE 21 Example 6 [General Data] Zoom ratio = 3.14
Intermediate Wide-angle focal length Telephoto end state state end
state f =9.3 ~19.1 ~29.1 FNO =1.8 ~2.5 ~2.9 2.omega. =81.8 ~45.4
~30.3 Y =7.3 ~8.0 ~8.0 TL (air =97.6 ~97.9 ~111.2 conversion
length) BF (air =13.77 ~20.21 ~22.17 conversion length) [Lens Data]
m r d .nu.d nd Object plane .infin. 1 50.656 1.60 17.98 1.94595 2
37.840 4.41 46.60 1.80400 3 233.428 D3 4* 4632.762 0.20 36.64
1.56093 5 109.440 1.50 42.73 1.83481 6 11.704 6.92 7 -23.983 1.00
55.52 1.69680 8 45.374 0.84 9 52.381 4.25 28.69 1.79504 10 -21.378
1.30 11 -13.669 0.00 12 -13.669 0.90 49.26 1.74330 13* -20.257 D13
14 0.000 0.80 Aperture stop S 15* 20.620 3.77 71.67 1.55332 16*
-59.068 0.15 17 73.847 7.46 22.74 1.80809 18 -17.447 0.90 27.57
1.75520 19 32.860 2.95 20 -133.340 0.90 23.78 1.84666 21 22.909
4.14 82.57 1.49782 22 -18.768 0.50 23* 23.489 2.71 81.49 1.49710
24* -70.000 D24 25 75.360 0.80 67.90 1.59319 26 20.437 D26 27*
29.723 2.36 81.49 1.49710 28 2125.803 D28 29 0.000 0.50 63.88
1.51680 30 0.000 1.11 31 0.000 1.59 63.88 1.51680 32 0.000 0.30 33
0.000 0.70 63.88 1.51680 34 0.000 0.70 [Lens Group Focal Length]
Lens group First surface Focal length First lens group 1 85.36
Second lens group 4 -14.13 Third lens group 15 20.88 Fourth lens
group 25 -47.53 Fifth lens group 27 60.62
[0296] In this variable power optical system ZL6, Surface 4,
Surface 13, Surface 15, Surface 16, Surface 23, Surface 24 and
Surface 27 are aspherical. Table 22 shows aspherical data, that is,
the values of the conical coefficient K and each aspherical
coefficient A4 to A10.
TABLE-US-00022 TABLE 22 [Aspherical Data] K A4 A6 A8 A10 Surface 4
0 4.14925E-05 -1.40193E-07 3.89689E-10 -2.54524E-13 Surface 13 0
-1.53196E-05 -7.94859E-08 -1.88545E-11 -1.26565E-12 Surface 15 0
-9.91269E-06 7.57161E-08 3.07024E-11 0.00000E+00 Surface 16 0
3.48959E-05 8.65483E-08 0.00000E+00 0.00000E+00 Surface 23 0
-1.31286E-05 -1.33696E-07 0.00000E+00 0.00000E+00 Surface 24 0
-2.92174E-06 -1.15116E-07 6.91626E-11 8.78230E-13 Surface 27 0
-1.97816E-06 -1.62889E-08 1.79202E-10 0.00000E+00
[0297] In the variable power optical system ZL6, the axial air
distance D3 between the first lens group G1 and the second lens
group G2, the axial air distance D13 between the second lens group
G2 and the third lens group G3 (aperture stop S), the axial air
distance D24 between the third lens group G3 and the fourth lens
group G4, the axial air distance D26 between the fourth lens group
G4 and the fifth lens group G5 and the axial air distance D28
between the fifth lens group G5 and the filter group FL change upon
zooming, as mentioned above. Table 23 shows the variable distance
in each focal length state of the wide-angle end state,
intermediate focal length state and telephoto end state upon
focusing on infinity.
TABLE-US-00023 TABLE 23 [Variable Distance Data] Wide-angle
Telephoto end Intermediate end f 9.3 19.1 29.1 D3 1.20 10.52 22.40
D13 25.66 6.03 1.50 D24 1.50 1.61 1.50 D26 5.10 9.21 13.32 D28 9.82
16.26 18.22
[0298] Table 24 shows each conditional expression correspondence
value of the variable power optical system ZL6. In Example 6, the
positive lens included in the vibration-isolating lens group G32 is
the positive lens L36, the positive lens included in the object
side group G3a is the positive lens L31, and the final lens group
is the fifth lens group G5.
TABLE-US-00024 TABLE 24 [Conditional Expression Correspondence
Value] (4) .nu.dO = 71.7 (6) fv .times. FNOw/f3 = 3.15 (8)
f3/.DELTA.T3 = 1.49 (9) ndVR - 0.0052 .times. .nu.dVR - 1.965 =
-0.044 (10) .nu.dVR = 81.49 (11) fr/fw = 6.54 (12) f3/(fw .times.
ft).sup.1/2 = 1.27
[0299] Thus the variable power optical system ZL6 satisfies the
above conditional expressions (4), (6), (8) to (12).
[0300] FIG. 27A, FIG. 28A and FIG. 29A are graphs showing spherical
aberration, astigmatism, distortion, lateral chromatic aberration
and coma aberration of the variable power optical system ZL6 upon
focusing on infinity in the wide-angle end state, intermediate
focal length state, and telephoto end state, and FIG. 27B, FIG. 28B
and FIG. 29B are graphs showing coma aberration when image blur is
corrected upon focusing on infinity in the wide-angle end state,
intermediate focal length state and telephoto end state. As each
graph showing aberration clarifies, various aberrations are
corrected well in the variable power optical system ZL6, from the
wide-angle end state to the telephoto end state.
EXPLANATION OF NUMERALS AND CHARACTERS
[0301] 1 camera (optical apparatus) [0302] ZL (ZL1 to ZL6) ariable
power optical system [0303] G1 first lens group [0304] G2 second
lens group [0305] G3 rear group (third lens group) [0306] G3a
object side group [0307] G3b intermediate group [0308] G32
vibration-isolating lens group [0309] G4 fourth lens group (final
lens group) [0310] G5 fifth lens group (final lens group)
RELATED APPLICATIONS
[0311] This is a continuation of PCT International Application No.
PCT/JP2014/003418, filed on Jun. 26, 2014, which is hereby
incorporated by reference. This application also claims the benefit
of Japanese Patent Application Nos. 2013-136678 and 2013-136679
filed in Japan on Jun. 28, 2013, and Nos. 2013-237570 and
2013-237571 filed in Japan on Nov. 18, 2013, which are hereby
incorporated by reference.
* * * * *