U.S. patent application number 16/878599 was filed with the patent office on 2020-09-03 for variable power optical system, optical device and method for manufacturing variable power optical system.
The applicant listed for this patent is Nikon Corporation. Invention is credited to Kosuke MACHIDA.
Application Number | 20200278521 16/878599 |
Document ID | / |
Family ID | 1000004843164 |
Filed Date | 2020-09-03 |
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United States Patent
Application |
20200278521 |
Kind Code |
A1 |
MACHIDA; Kosuke |
September 3, 2020 |
VARIABLE POWER OPTICAL SYSTEM, OPTICAL DEVICE AND METHOD FOR
MANUFACTURING VARIABLE POWER OPTICAL SYSTEM
Abstract
A variable magnification optical system is provided which
includes, in order from an object side, 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, a fourth lens group G4, and a subsequent lens
group GR. Upon zooming, each of distances between the first lens
group G1 and the second lens group G2, between the second lens
group G2 and the third lens group G3, between the third lens group
G3 and the fourth lens group G4, between the fourth lens group G4
and the subsequent lens group GR is varied, and upon focusing, the
third lens group G3 is moved along an optical axis. A predetermined
condition is satisfied. Consequently, the optical system enables a
focusing lens group to be downsized and made light and also enables
high speed auto focusing and quietness upon auto focusing to be
realized without increasing the size of a barrel. Variation in
aberration upon zooming from a wide-angle end state to a telephoto
end state and variation in aberration upon focusing from an
infinite distance object to a close distance object are well
suppressed. Also, an optical apparatus and a method for
manufacturing the variable magnification optical system are
provided.
Inventors: |
MACHIDA; Kosuke; (Tokyo,
JP) |
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Applicant: |
Name |
City |
State |
Country |
Type |
Nikon Corporation |
Tokyo |
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JP |
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Family ID: |
1000004843164 |
Appl. No.: |
16/878599 |
Filed: |
May 19, 2020 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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15004879 |
Jan 22, 2016 |
10670848 |
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16878599 |
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PCT/JP2014/069448 |
Jul 23, 2014 |
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15004879 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G02B 15/173 20130101;
G02B 13/18 20130101; G03B 13/36 20130101; G02B 27/646 20130101;
G02B 15/20 20130101 |
International
Class: |
G02B 15/20 20060101
G02B015/20; G02B 15/173 20060101 G02B015/173; G02B 27/64 20060101
G02B027/64; G03B 13/36 20060101 G03B013/36 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 29, 2013 |
JP |
2013-157111 |
Feb 17, 2014 |
JP |
2014-027494 |
Claims
1-33. (canceled)
34. A variable magnification optical system comprising, in
consecutive order from an object side: a first lens group having
positive refractive power; a second lens group having negative
refractive power; a third lens group having positive refractive
power; a fourth lens group having positive refractive power; a
fifth lens group having negative refractive power; and a sixth lens
group having positive refractive power; upon zooming from a
wide-angle end state to a telephoto end state, a distance between
the first lens group and the second lens group being varied, a
distance between the second lens group and the third lens group
being varied, a distance between the third lens group and the
fourth lens group being varied, a distance between the fourth lens
group and the fifth lens group being varied, and a distance between
the fifth lens group and the sixth lens group being varied; the
following conditional expression being satisfied:
0.60<f3/f4<1.30 where f3 denotes a focal length of the third
lens group; and f4 denotes a focal length of the fourth lens
group.
35. The variable magnification optical system according to claim
34, wherein upon zooming from the wide-angle end state to the
telephoto end state, the first lens group is moved toward the
object side.
36. The variable magnification optical system according to claim
34, wherein upon zooming from the wide-angle end state to the
telephoto end state, the third lens group is moved toward the
object side.
37. The variable magnification optical system according to claim
34, wherein upon zooming from the wide-angle end state to the
telephoto end state, the fourth lens group is moved toward the
object side.
38. The variable magnification optical system according to claim
34, wherein upon zooming from the wide-angle end state to the
telephoto end state, the fifth lens group is moved toward the
object side.
39. The variable magnification optical system according to claim
34, wherein the first lens group consists of three lenses.
40. The variable magnification optical system according to claim
34, wherein a focusing lens group is provided on a nearer side to
an image plane than the first lens group.
41. The variable magnification optical system according to claim
40, wherein the focusing lens group is moved toward the image plane
side for focusing from an infinite distance object to a close
distance object.
42. The variable magnification optical system according to claim
34, wherein a vibration reduction lens group is provided on a
nearer side to an image plane than the first lens group.
43. The variable magnification optical system according to claim
34, wherein the following conditional expression is satisfied:
0.11<(-f2)/f1<0.19 where f2 denotes a focal length of the
second lens group; and f1 denotes a focal length of the first lens
group.
44. A variable magnification optical system comprising, in
consecutive order from an object side: a first lens group having
positive refractive power; a second lens group having negative
refractive power; a third lens group having positive refractive
power; a fourth lens group; and a subsequent lens group comprising
at least one lens group; upon zooming from a wide-angle end state
to a telephoto end state, a distance between the first lens group
and the second lens group being varied, a distance between the
second lens group and the third lens group being varied, a distance
between the third lens group and the fourth lens group being
varied, a distance between the fourth lens group and the subsequent
lens group being varied, and when the subsequent lens group
comprises a plurality of lens groups, each distance between
adjacent lens groups of the plurality of lens groups is varied; a
focusing lens group provided on a nearer side to the image side
than the first lens group, the focusing lens group being moved
toward the image side for focusing from an infinite distance object
to a close distance object; and a vibration reduction lens group
provided on a nearer side to an image plane than the first lens
group.
45. The variable magnification optical system according to claim
44, wherein the following conditional expression is satisfied.
0.60<f3/f4<1.30 where f3 denotes a focal length of the third
lens group; and f4 denotes a focal length of the fourth lens
group.
46. The variable magnification optical system according to claim
44, wherein upon zooming from the wide-angle end state to the
telephoto end state, the first lens group is moved toward the
object side.
47. The variable magnification optical system according to claim
44, wherein upon zooming from the wide-angle end state to the
telephoto end state, the third lens group is moved toward the
object side.
48. The variable magnification optical system according to claim
44, wherein the subsequent lens group includes a fifth lens group;
and upon zooming from the wide-angle end state to the telephoto end
state, the fifth lens group is moved toward the object side.
49. The variable magnification optical system according to claim
44, wherein the first lens group consists of three lenses.
50. The variable magnification optical system according to claim
44, wherein the following conditional expression is satisfied:
0.11<(-f2)/f1<0.19 where f2 denotes a focal length of the
second lens group, and f1 denotes a focal length of the first lens
group.
51. The variable magnification optical system according to claim
44, wherein the following conditional expression is satisfied:
2.00<(-f4)/f5<4.00 where f4 denotes a focal length of the
fourth lens group, and f5 denotes a focal length of the fifth lens
group.
52. A method for manufacturing a variable magnification optical
system A comprising, in consecutive order from an object side along
an optical axis: a first lens group having positive refractive
power; a second lens group having negative refractive power; a
third lens group having positive refractive power; a fourth lens
group having positive refractive power; a fifth lens group having
negative refractive power; and a sixth lens group having positive
refractive power; or a variable magnification optical system B
comprising, in consecutive order from an object side: a first lens
group having positive refractive power; a second lens group having
negative refractive power; a third lens group having positive
refractive power; a fourth lens group; and a subsequent lens group
comprising at least one lens group; the method of the variable
magnification optical system A comprising the steps of: disposing
the lens groups such that, upon zooming from a wide-angle end state
to a telephoto end state, a distance between the first lens group
and the second lens group is varied, a distance between the second
lens group and the third lens group is varied, a distance between
the third lens group and the fourth lens group is varied, a
distance between the fourth lens group and the fifth lens group is
varied, and a distance between the fifth lens group and the sixth
lens group is varied; and configuring the third and fourth lens
groups such that the following conditional expression is satisfied:
0.60<f3/f4<1.30 where f3 denotes a focal length of the third
lens group, f4 denotes a focal length of the fourth lens group; the
method of the variable magnification optical system B comprising
the steps of: disposing the lens groups such that, upon zooming
from a wide-angle end state to a telephoto end state, a distance
between the first lens group and the second lens group is varied, a
distance between the second lens group and the third lens group is
varied, a distance between the third lens group and the fourth lens
group is varied, a distance between the fourth lens group and the
subsequent lens group is varied, and when the subsequent lens group
comprises a plurality of lens groups, each distance between
adjacent lens groups of the plurality of lens groups is varied;
disposing a focusing lens group on the image side of the first lens
group such that the focusing lens group is moved toward the image
side for focusing from an infinite distance object to a close
distance object; disposing a vibration reduction lens group on the
image side of the first lens group; and configuring the third and
fourth lens groups such that the following conditional expression
is satisfied: 0.60<f3/f4<1.30 where f3 denotes a focal length
of the third lens group, f4 denotes a focal length of the fourth
lens group.
Description
TECHNICAL FIELD
[0001] The present invention relates to a variable magnification
optical system, an optical device, and a method for producing the
variable magnification optical system.
BACKGROUND ART
[0002] Conventionally, there have been proposed variable
magnification optical systems whose focusing lens group is made
lighter because of the introduction of IF, that is, an inner focus
system and which are suitable for a photographing camera, an
electronic still camera, a video camera or the like (See, for
example, Patent Documents 1 and 2 given below).
PRIOR ART REFERENCE
Patent Document
[0003] Patent Document 1: Japanese Patent No. 4876509
[0004] Patent Document 2: Japanese patent application Laid-Open
Gazette No. 2010-237453
SUMMARY OF THE INVENTION
Problems to be Solved by the Invention
[0005] However, in the conventional variable magnification optical
systems as described above, there was a problem that the focusing
lens group was only made light to an insufficient degree for
realizing good quietness upon AF, that is, auto focusing.
Additionally, since the focusing lens group was heavy in weight,
high speed auto focusing requires a larger motor or actuator, and
accordingly resulting in a larger barrel.
[0006] The present invention is made in view of the above-described
problem. It is an object of the present invention to provide a
variable magnification optical system that enables the realization
of high speed auto focusing (AF) and good quietness upon auto
focusing without increasing the size of a barrel, by downsizing the
focusing lens group and making the focusing lens group lighter and
that can successfully suppress the variation in aberration upon
zooming from a wide-angle end state to a telephoto end state and
can also successfully suppress the variation in aberration upon
focusing from an infinite distance object to a close distance
object and also to provide an optical apparatus, and a method for
manufacturing the variable magnification optical system.
Means for Solving the Problems
[0007] In order to solve the above-mentioned object, according to a
first aspect of the present invention, there is provided a variable
magnification optical system comprising, in order from an object
side:
[0008] a first lens group having positive refractive power;
[0009] a second lens group having negative refractive power;
[0010] a third lens group having positive refractive power;
[0011] a fourth lens group; and
[0012] a subsequent lens group comprising at least one lens
group;
[0013] upon zooming from a wide-angle end state to a telephoto end
state, a distance between the first lens group and the second lens
group being varied, a distance between the second lens group and
the third lens group being varied, a distance between the third
lens group and the fourth lens group being varied, a distance
between the fourth lens group and the subsequent lens group being
varied, and when the subsequent lens group comprises a plurality of
lens groups, each distance between the plurality of lens groups
being varied;
[0014] upon focusing from an infinite distance object to a close
distance object, the third lens group being moved along an optical
axis, and
[0015] the following conditional expression being satisfied:
0.60<f3/f4<1.30
[0016] where f3 denotes a focal length of the third lens group; and
f4 denotes a focal length of the fourth lens group.
[0017] Further, in order to solve the above-mentioned object,
according to a second aspect of the present invention, there is
provided a variable magnification optical system comprising, in
order from an object side along an optical axis: a first lens group
having positive refractive power; a second lens group having
negative refractive power; a third lens group having positive
refractive power; a fourth lens group having negative refractive
power; and a fifth lens group having positive refractive power;
and
[0018] upon zooming from a wide-angle end state to a telephoto end
state, a distance between the first lens group and the second lens
group being varied, a distance between the second lens group and
the third lens group being varied, a distance between the third
lens group and the fourth lens group being varied, a distance
between the fourth lens group and the fifth lens group being
varied, and the first lens group being moved to an object side;
[0019] upon focusing from infinity to a close distance object, the
third lens group being moved, and
[0020] the following conditional expressions being satisfied:
0.23<f3/ft<0.35
2.60<(-f3)/f2<3.60
where f2 denotes a focal length of the second lens group; f3
denotes a focal length of the third lens group; and ft denotes a
focal length of the whole system.
[0021] According to the present invention, there is provided an
optical apparatus comprising any of the above-mentioned variable
magnification optical systems.
[0022] Further, there is provided a method for manufacturing a
variable magnification optical system according to the first aspect
of the present invention, the optical system comprising, in order
from an object side: a first lens group having positive refractive
power; a second lens group having negative refractive power; a
third lens group having positive refractive power; a fourth lens
group; and a subsequent lens group comprising at least one lens
group; the method comprising the steps of:
[0023] disposing the lens groups such that, upon zooming from a
wide-angle end state to a telephoto end state, a distance between
the first lens group and the second lens group is varied, a
distance between the second lens group and the third lens group is
varied, a distance between the third lens group and the fourth lens
group is varied, a distance between the fourth lens group and the
subsequent lens group is varied, and when the subsequent lens group
comprises a plurality of lens groups, each distance between the
plurality of lens groups is varied;
[0024] disposing the third lens group so as to move along an
optical axis upon focusing from infinity to a close distance
object; and
[0025] disposing the lens groups such that the following
conditional expression is satisfied:
0.60<f3/f4<1.30
where f3 denotes a focal length of the third lens group; and f4
denotes a focal length of the fourth lens group.
[0026] Further, there is provided a method for manufacturing a
variable magnification optical system according to the second
aspect of the present invention, the optical system comprising, in
order from an object side along an optical axis: a first lens group
having positive refractive power; a second lens group having
negative refractive power; a third lens group having positive
refractive power; a fourth lens group having negative refractive
power; and a fifth lens group having positive refractive power; the
method comprising the steps of:
[0027] configuring the lens groups such that upon zooming from a
wide-angle end state to a telephoto end state, a distance between
the first lens group and the second lens group is varied, a
distance between the second lens group and the third lens group is
varied, a distance between the third lens group and the fourth lens
group is varied, a distance between the fourth lens group and the
fifth lens group is varied, and the first lens group is moved
toward an object side;
[0028] configuring the third lens group so as to move upon focusing
from an infinite distance object point to a close distance object
point; and
[0029] constructing the variable magnification optical system so as
to satisfy the following conditional expressions:
0.23<f3/ft<0.35
2.60<(-f3)/f2<3.60
[0030] where f2 denotes a focal length of the second lens group; f3
denotes a focal length of the third lens group; and ft denotes a
focal length of the whole system in the telephoto end state.
Effect of the Invention
[0031] According to the present invention, it is possible to
provide a variable magnification optical system which enables the
realization of high speed auto focusing and good quietness upon
auto focusing without increasing the size of a barrel, by
downsizing a focusing lens group and making it lighter and which
also enables good suppression of aberration upon zooming from a
wide-angle end state to a telephoto end state and good suppression
of aberration upon focusing from an infinite distance object to a
close distance object. It is also possible to provide an optical
apparatus and a method for manufacturing the variable magnification
optical system.
BRIEF DESCRIPTION OF THE DRAWINGS
[0032] FIG. 1 is a sectional view showing a lens arrangement of a
variable magnification optical system according to a First
Example.
[0033] FIGS. 2A, 2B and 2C are graphs showing various aberrations
of the variable magnification optical system according to the First
Example upon focusing on infinity, in which FIG. 2A shows a
wide-angle end state, FIG. 2B shows an intermediate focal length
state, and FIG. 2C shows a telephoto end state, respectively.
[0034] FIGS. 3A, 3B and 3C are graphs showing various aberrations
of the variable magnification optical system according to the First
Example upon focusing on a close distance object, in which FIG. 3A
shows a wide-angle end state, FIG. 3B shows an intermediate focal
length state, and FIG. 3C shows a telephoto end state,
respectively.
[0035] FIG. 4 is a sectional view showing a lens arrangement of a
variable magnification optical system according to a Second
Example.
[0036] FIGS. 5A, 5B and 5C are graphs showing various aberrations
of the variable magnification optical system according to the
Second Example upon focusing on infinity, in which FIG. 5A shows a
wide-angle end state, FIG. 5B shows an intermediate focal length
state, and FIG. 5C shows a telephoto end state, respectively.
[0037] FIGS. 6A, 6B and 6C are graphs showing various aberrations
of the variable magnification optical system according to the
Second Example upon focusing on a close distance object, in which
FIG. 6A shows a wide-angle end state, FIG. 6B shows an intermediate
focal length state, and FIG. 6C shows a telephoto end state,
respectively.
[0038] FIG. 7 is a view showing a lens arrangement of a variable
magnification optical system according to a Third Example of the
present application.
[0039] FIGS. 8A, 8B and 8C are graphs showing various aberrations
of the variable magnification optical system according to the Third
Example upon focusing on infinity, in a wide-angle end state, in an
intermediate focal length state, and in a telephoto end state,
respectively.
[0040] FIGS. 9A, 9B and 9C are graphs showing various aberrations
of the variable magnification optical system according to the Third
Example upon focusing on a close distance object, in a wide-angle
end state, in an intermediate focal length state, and in a
telephoto end state, respectively.
[0041] FIG. 10 is a view showing a lens arrangement of a variable
magnification optical system according to a Fourth Example of the
present application.
[0042] FIGS. 11A, 11B and 11C are graphs showing various
aberrations of the variable magnification optical system according
to the Fourth Example upon focusing on infinity, in a wide-angle
end state, in an intermediate focal length state, and in a
telephoto end state, respectively.
[0043] FIGS. 12A, 12B and 12C are graphs showing various
aberrations of the variable magnification optical system according
to the Fourth Example upon focusing on a close distance object, in
a wide-angle end state, in an intermediate focal length state, and
in a telephoto end state, respectively.
[0044] FIG. 13 is a view showing a lens arrangement of a variable
magnification optical system according to a Fifth Example of the
present application.
[0045] FIGS. 14A, 14B and 14C are graphs showing various
aberrations of the variable magnification optical system according
to the Fifth Example upon focusing on infinity, in a wide-angle end
state, in an intermediate focal length state, and in a telephoto
end state, respectively.
[0046] FIGS. 15A, 15B and 15C are graphs showing various
aberrations of the variable magnification optical system according
to the Fifth Example upon focusing on a close distance object, in a
wide-angle end state, in an intermediate focal length state, and in
a telephoto end state, respectively.
[0047] FIG. 16 is a sectional view showing a configuration of a
camera equipped with the above-mentioned variable magnification
optical system.
[0048] FIG. 17 is a flowchart schematically showing a method for
manufacturing the above-mentioned variable magnification optical
system.
[0049] FIG. 18 is a flowchart schematically showing a method for
manufacturing the above-mentioned variable magnification optical
system.
EMBODIMENTS FOR CARRYING OUT THE INVENTION
First Embodiment
[0050] Preferred embodiments of the present invention are described
below with reference to the drawings attached hereto. As shown in
FIG. 1, the variable magnification optical system ZL according to
the first Embodiment of the present application comprises, in order
from an object side: 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; a
fourth lens group G4 having positive refractive power; and a
subsequent lens group GR comprising at least one lens group. In the
variable magnification optical system ZL, upon zooming from a
wide-angle end state to a telephoto end state, a distance between
the first lens group G1 and the second lens group G2 is varied, a
distance between the second lens group G2 and the third lens group
G3 is varied, a distance between the third lens group G3 and the
fourth lens group G4 is varied, and a distance between the fourth
lens group G4 and the subsequent lens group GR is varied, and also
when the subsequent lens group GR comprises a plurality of lens
groups, each distance between the plurality of lens groups is
varied. As a result, a good aberration correction can be made upon
zooming.
[0051] The variable magnification optical system ZL is constructed
such that, upon zooming from the wide-angle end state to the
telephoto end state, the distance between the first lens group G1
and the second lens group G2 is increased, the distance between the
second lens group G2 and the third lens group G3 is decreased, the
distance between the third lens group G3 and the fourth lens group
G4 is increased, and the distance between the fourth lens group G4
and the fifth lens group G5 is increased, so that a predetermined
variable modification ratio can be secured. Further, the variable
magnification optical system ZL is constructed in such a manner
that the first lens group G1 is moved to the direction of an object
upon zooming from the wide-angle end state to the telephoto end
state with the result that the total lens length in the wide-angle
end state can be shortened and the effective aperture of the first
lens group can be reduced, thereby realizing a downsized variable
magnification optical system ZL.
[0052] The variable magnification optical system ZL is constructed
so that the third lens group G3 is moved along the optical axis
upon focusing from an infinite distance object to a close distance
object. With such construction, it is possible to suppress a change
in the size of an image during focusing, and it is also possible to
suppress satisfactorily the variation of aberrations such as
spherical aberration. Hereinafter, the third lens group G3 is also
referred to as "focusing lens group".
[0053] It is desirable that the variable magnification optical
system ZL satisfies the following conditional expression (1):
0.60<f3/f4<1.30 (1)
[0054] where f3 denotes a focal length of the third lens group G3,
and f4 denotes a focal length of the fourth lens group G4.
[0055] The conditional expression (1) defines a range of the focal
length of the third lens group G3 relative to the focal length of
the fourth lens group G4, which range is proper to the suppression
of variation in aberration upon focusing from an infinite distance
object to a close distance object and is also proper to a good
correction of various aberrations. When the value of f3/f4 is equal
to or exceeds the upper limit value of the conditional expression
(1), the fourth lens group G4 becomes larger in the refractive
power, and as a result, it is difficult to make a correction of
various aberrations including spherical aberration. Also, the third
lens group G3 becomes smaller in the refractive power, and upon
focusing from an infinite distance object to a close distance
object, the third lens group G3 moves in a larger amount, which
results in an increased size of the total length of the lenses.
Note that the advantageous effect of the present application can be
further ensured by setting the upper limit value of the conditional
expression (1) to 1.10. On the other hand, when the value of f3/f4
is equal to or falls below the lower limit value of the conditional
expression (1), the third lens group G3 becomes larger in the
refractive power, and the variation in aberration upon focusing
from the infinite distance object to the close distance object
becomes larger. Note that the advantageous effect of the present
application can be further ensured by setting the lower limit value
of the conditional expression (1) to 0.80.
[0056] In the variable magnification optical system ZL, it is
desirable that the third lens group G3 as the focusing lens group
is composed only of a single positive lens or a single cemented
lens having positive refractive power. With such configuration, it
is possible to make the focusing lens group lighter and realize
high speed auto focusing (AF) and good quietness upon auto focusing
(AF) without increasing the size of the barrel.
[0057] In the variable magnification optical system ZL, it is
desirable that the third lens group G3 as the focusing lens group
has an aspherical surface as the most object side surface. In this
case, more desirably, the aspherical surface is formed into such a
shape that the positive refractive power is weakened with
increasing distance from the optical axis. With such configuration,
it is possible to achieve both making the weight of the focusing
lens group lighter and suppressing the variation in aberration upon
focusing from the infinite distance object to the close distance
object, thereby realizing high speed auto focusing and good
quietness upon auto focusing without increasing the size the
barrel.
[0058] It is desirable that the variable magnification optical
system ZL satisfies the following conditional expression (2):
0.11<(-f2)/f1<0.19 (2)
where f2 denotes a focal length of the second lens group G2, and f1
denotes a focal length of the first lens group G1.
[0059] The conditional expression (2) defines a range of the focal
length of the second lens group G2 relative to the focal length of
the first lens group G1, which range is proper to ensure a
sufficient variable magnification ratio and realize good optical
properties. When the value of (-f2)/f1 is equal to or exceeds the
upper limit value of the conditional expression (2), that is not
preferable because the first lens group G1 becomes stronger in the
refractive power and the spherical aberration at a telephoto end is
remarkably deteriorated. Also, the lateral chromatic aberration at
a wide-angle end is significantly deteriorated. Note that the
advantageous effect of the present application can be further
ensured by setting the upper limit value of the conditional
expression (2) to 0.16. On the other hand, when the value (-f2)/f1
is equal to or falls below the lower limit value of the conditional
expression (2), the second lens group G2 becomes stronger in the
refractive power, so that it is difficult to make a correction of
off-axis aberration at the wide-angle end, in particular a
correction of curvature of field and astigmatism. Note that the
advantageous effect of the present application can be further
ensured by setting the lower limit value of the conditional
expression (2) to 0.14.
[0060] It is also desirable that the variable magnification optical
system ZL satisfies the following conditional expression (3):
3.00<f1/fw<6.00 (3)
where f1 denotes a focal length of the first lens group G1, and fw
denotes a focal length of the whole system in the wide-angle end
state.
[0061] The conditional expression (3) defines a proper range of the
focal length of the first lens group G1 relative to the focal
length of the variable magnification optical system ZL in the
wide-angle end state. By satisfying conditional expression (3), the
optical system can achieve both downsizing of the total lens length
and good correcting of the curvature of field, distortion and
spherical aberration. When the value of f1/fw is equal to or falls
below the lower limit of the conditional expression (3), the first
lens group G1 becomes larger in the refractive power, and as a
result, it is difficult to make a correction of various aberrations
including spherical aberration. Note that the advantageous effect
of the present application can be further ensured by setting the
lower limit value of the conditional expression (3) to 4.00. On the
other hand, when the value of f1/fw is equal to or exceeds the
upper limit value of the conditional expression (3), the first lens
group G1 becomes smaller in the refractive power, and as a result,
it is difficult to downsize the total lens length. Note that the
advantageous effect of the present application can be further
ensured by setting the upper limit value of the conditional
expression (3) to 5.00.
[0062] It is also desirable that the variable magnification optical
system ZL has a lens group for correcting the displacement of the
imaging position caused by a camera shake or the like in such a way
that at least a part of the subsequent lens group GR is moved so as
to have a component in the direction perpendicular to the optical
axis. With this configuration, it is possible to effectively
correct the displacement of the imaging position due to a camera
shake or the like.
Second Embodiment
[0063] The variable magnification optical system according to the
second Embodiment of the present application comprises, in order
from an object side along the optical axis, a first lens group
having positive refractive power; a second lens group having
negative refractive power; a third lens group having positive
refractive power; a fourth lens group having negative refractive
power; and a fifth lens group having positive refractive power, and
the optical system has such a construction that upon zooming from a
wide-angle end state to a telephoto end state, the first lens group
is moved to the object side, a distance between the first lens
group and the second lens group is increased, a distance between
the second lens group and the third lens group is decreased, and a
distance between the third lens group and the fourth lens group is
varied, a distance between fourth lens group and the fifth lens
group is varied, and upon focusing from an infinite distance object
point to a close distance object point, the third lens group is
moved.
[0064] The variable magnification optical system of the present
application has five lens groups and, upon zooming from the
wide-angle end state to the telephoto end state, can make good
correction of aberration upon zooming in such a way that each
distance between the lens groups is varied. Also, it is possible to
secure an approximately 4 times or more variable magnification
ratio in such a way that, upon zooming from the wide-angle end
state to the telephoto end state, the distance between the first
lens group and the second lens group is increased and the distance
between the second lens group and the third lens group is
decreased. Furthermore, it is also possible to shorten the total
lens length at the wide angle end state and reduce the effective
aperture of the first lens group in such a way that, upon zooming
from the wide-angle end state to the telephoto end state, the first
lens group is moved to the object side, with the result that the
variable magnification optical system can be downsized.
[0065] When the focal length of the third lens group is represented
by f3 and the focal length of the whole system in the telephoto end
state is represented by ft, the variable magnification optical
system of the present application is constructed so as to satisfy
the following conditional expression (4):
0.23<f3/ft<0.35 (4)
[0066] The conditional expression (4) defines an appropriate range
of the focal length of the third lens group relative to the focal
length of the variable magnification optical system in the
telephoto end state to control the size of the variable
magnification optical system and suppress the variation in
aberration upon focusing from an infinite distance object point to
a close distance object point.
[0067] When the value of f3/ft is equal to or exceeds the upper
limit value of the conditional expression (4), the third lens group
becomes smaller in the refractive power and the movement amount of
the third lens group moved for zooming from the wide-angle end
state to the telephoto end state and focusing from an infinite
distance object point to a close distance object point is
increased, and as a result, the optical system become larger
undesirably. Also, when the value of f3/ft is equal to or exceeds
the upper limit value of the conditional expression (4), since the
movement amount of the third lens group moved for focusing from the
infinite distance object to the close distance object point is
increased, the variation in various aberrations including the
spherical aberration is increased upon focusing from the infinite
distance object point to the close distance object point in the
telephoto end state. Note that the advantageous effect of the
present application can be further ensured by setting the upper
limit value of the conditional expression (4) to 0.32. Also, note
that the advantageous effect of the present application can be even
further ensured by setting the upper limit value of the conditional
expression (4) to 0.31.
[0068] On the other hand, when the value of f3/ft is equal to or
falls below the lower limit value of the conditional expression
(4), the third lens group G3 becomes larger in the refractive
power, and the variation in spherical aberration upon focusing from
an infinite distance object to a close distance object in the
telephoto end state is increased. Note that the advantageous effect
of the present application can be further ensured by setting the
lower limit value of the conditional expression (4) to 0.26. Also,
note that the advantageous effect of the present application can be
even further ensured by setting the lower limit value of the
conditional expression (4) to 0.27.
[0069] When the focal length of the second lens group is
represented by f2 and the focal length of the third lens group is
represented by f3, the variable magnification optical system of the
present application is constructed to satisfy the following
conditional expression (5):
2.60<(-f3)/f2<3.60 (5)
[0070] The conditional expression (5) defines a proper range of the
focal length of the third lens group relative to the focal length
of the second lens group, which range is suitable for the
suppression of variation in aberration upon focusing from the
infinite distance object point to the close distance object point
and for a good correction of various aberrations.
[0071] When the value of (-f3)/f2 is equal to or exceeds the upper
limit value of the conditional expression (5), the second lens
group becomes larger in the refractive power, and as a result, it
is difficult to make a correction of various aberrations including
spherical aberration. Also, the third lens group is moved in a
larger amount, which leads to upsizing of the total lens length.
Note that the advantageous effect of the present application can be
further ensured by setting the upper limit value of the conditional
expression (5) to 3.40. Also, note that the advantageous effect of
the present application can be even further ensured by setting the
upper limit value of the conditional expression (5) to 3.20.
[0072] On the other hand, when the value of (-f3)/f2 is equal to or
falls below the lower limit value of the conditional expression
(5), the third lens group becomes larger in the refractive power,
and the variation in aberration upon focusing from the infinite
distance object point to the close distance object point becomes
larger. Note that the advantageous effect of the present
application can be further ensured by setting the lower limit value
of the conditional expression (5) to 2.80. Also, note that the
advantageous effect of the present application can be even further
ensured by setting the lower limit value of the conditional
expression (5) to 2.90.
[0073] With the above described configuration, a downsized and
light weight focusing lens group is provided, and it is possible
for the present application to realize high speed and good
quietness autofocusing without increasing the size of the barrel.
Additionally, with the above described configuration, it is
possible to realize a variable magnification optical system which
successfully suppresses the variation in aberration upon zooming
from the wide-angle end state to the telephoto end state and the
variation in aberration upon focusing from the infinite distance
object point to the close distance object point.
[0074] In the variable magnification optical system according to
the present application, it is desirable that, upon zooming from
the wide-angle end state to the telephoto end state, the fourth
lens group and the fifth lens group are moved toward the object
side, the distance between the third lens group and the fourth lens
group is increased, and the distance between the fourth lens group
and the fifth lens group is decreased.
[0075] With the above described configuration, a correction of
aberration upon zooming from the wide-angle end state to the
telephoto end state, suppression of the variation in aberration
upon focusing from the infinite distance object point to the close
distance object point and an approximately 4 times or more variable
magnification ratio can be further ensured.
[0076] In the variable magnification optical system according to
the present application, it is desirable that the third lens group
comprises a cemented lens composed of, in order from the object
side along the optical axis, a double convex positive lens and a
negative meniscus lens having a concave surface facing the object
side.
[0077] With the above described configuration, the focusing lens
group is made much lighter. Higher-speed and better quietness
autofocusing can be realized without increasing the size of the
barrel. Additionally, since the third lens group is a cemented
lens, the variation in chromatic aberration upon focusing from the
infinite distance object point to the close distance object point
can be corrected successfully.
[0078] When the refractive index of the negative meniscus lens is
represented by nN and the refractive index of the double convex
positive lens is represented by nP, the variable magnification
optical system of the present application desirably satisfies the
following conditional expression (6):
0.15<nN-nP<0.45 (6)
[0079] The conditional expression (6) defines a difference in the
refractive index between the double convex positive lens and the
negative meniscus lens, of the cemented lens forming the third lens
group, which difference is proper to suppress the variation in
aberration upon focusing from the infinite distance object point to
the close distance object point.
[0080] When the value of nN-nP is equal to or exceeds the upper
limit value of the conditional expression (6), the correction of
spherical aberration by the cemented surface becomes excessively
large. As a result, the variation in spherical aberration upon
focusing from the infinite distance object point to the close
distance object point becomes large, so that it becomes difficult
to correct the aberration. Note that the advantageous effect of the
present application can be further ensured by setting the upper
limit value of the conditional expression (6) to 0.38. Also, note
that the advantageous effect of the present application can be even
further ensured by setting the upper limit value of the conditional
expression (6) to 0.35.
[0081] On the other hand, when the value of nN-nP is equal to or
falls below the lower limit value of the conditional expression
(6), the correction of spherical aberration by the cemented surface
of the cemented lens becomes insufficient. As a result, the
variation in spherical aberration upon focusing from the infinite
distance object point to the close distance object point becomes
large, so that it becomes difficult to correct the aberration. Note
that the advantageous effect of the present application can be
further ensured by setting the lower limit value of the conditional
expression (6) to 0.22. Also, note that the advantageous effect of
the present application can be even further ensured by setting the
lower limit value of the conditional expression (6) to 0.23.
[0082] When the Abbe number of the double convex positive lens is
represented by .nu.P and the Abbe number of the negative meniscus
lens is represented by .nu.N, the variable magnification optical
system of the present application desirably satisfies the following
conditional expression (7):
25.00<.nu.P-.nu.N<45.00 (7)
[0083] The conditional expression (7) defines a difference in the
Abbe number between the double convex positive lens and the
negative meniscus lens, of the cemented lens forming the third lens
group, to realize a good correction of chromatic aberration by the
third lens group.
[0084] When the value of .nu.P-.nu.N is equal to or exceeds the
upper limit value of the conditional expression (7), the correction
of chromatic aberration by the third lens group becomes excessively
large. As a result, the variation in chromatic aberration upon
focusing from the infinite distance object point to the close
distance object point becomes excessively large. Note that the
advantageous effect of the present application can be further
ensured by setting the upper limit value of the conditional
expression (7) to 40.00. Also, note that the advantageous effect of
the present application can be even further ensured by setting the
upper limit value of the conditional expression (7) to 36.00.
[0085] On the other hand, when the value of .nu.P-.nu.N is equal to
or falls below the lower limit value of the conditional expression
(7), the correction of chromatic aberration by the third lens group
becomes insufficient. As a result, the variation in chromatic
aberration upon focusing from the infinite distance object point to
the close distance object point becomes excessively large. Note
that the advantageous effect of the present application can be
further ensured by setting the lower limit value of the conditional
expression (7) to 30.00. Also, note that the advantageous effect of
the present application can be even further ensured by setting the
lower limit value of the conditional expression (7) to 32.00.
[0086] When the focal length of the first lens group is represented
by f1 and the focal length of the whole system in the wide-angle
end state is represented by fw, the variable magnification optical
system of the present application desirably satisfies the following
conditional expression (8):
3.50<f1/fw<5.30 (8)
[0087] The conditional expression (8) defines a proper focal length
of the first lens group relative to the focal length of the whole
system in the wide-angle end state. By satisfying conditional
expression (8), the optical system can achieve both downsizing of
the total lens length and good correcting of the curvature of
field, distortion and spherical aberration.
[0088] When the value of f1/fw is equal to or falls below the lower
limit of the conditional expression (8), the first lens group
becomes larger in the refractive power, and as a result, it is
difficult to make a correction of various aberrations including
spherical aberration. Note that the advantageous effect of the
present application can be further ensured by setting the lower
limit value of the conditional expression (8) to 3.90. Also, note
that the advantageous effect of the present application can be even
further ensured by setting the lower limit value of the conditional
expression (8) to 4.20.
[0089] On the other hand, when the value of f1/fw is equal to or
exceeds the upper limit value of the conditional expression (8),
the first lens group becomes smaller in the refractive power, and
as a result, it is difficult to downsize the total lens length.
Note that the advantageous effect of the present application can be
further ensured by setting the upper limit value of the conditional
expression (8) to 4.90. Also, note that the advantageous effect of
the present application can be even further ensured by setting the
upper limit value of the conditional expression (8) to 4.70.
[0090] The variable magnification optical system according to the
present application can be constructed so that the fourth lens
group and the fifth lens group are substantially afocal in the
wide-angle end state and can be also constructed to have such a
structure that the distance between the lens groups is varied so as
to decrease upon zooming from the wide-angle end to the telephoto
end, making a much better correction of the various aberrations in
the range from the wide-angle end to the telephoto end. When the
focal length of the fourth lens group is represented by f4 and the
focal length of the fifth lens group is represented by f5, the
variable magnification optical system of the present application
desirably satisfies the following conditional expression (9):
2.00<(-f4)/f5<4.00 (9)
[0091] The conditional expression (9) defines an appropriate ratio
between the focal length of the fourth lens group and the focal
length of the fifth lens group. The variable magnification optical
system according to the present application can realize a good
correction of the curvature of field, distortion and spherical
aberration by satisfying the conditional expression (9).
[0092] When the value of (-f4)/f5 is equal to or falls below the
lower limit of conditional expression (9), the refractive power of
the fourth lens group becomes large relative to the refractive
power of the fifth lens group, it becomes difficult to correct
various aberrations such as spherical aberration. Note that the
advantageous effect of the present application can be further
ensured by setting the lower limit value of the conditional
expression (9) to 2.50. Also, note that the advantageous effect of
the present application can be even further ensured by setting the
lower limit value of the conditional expression (9) to 2.70.
[0093] On the other hand, when the value of (-f4)/f5 is equal to or
exceeds the upper limit value of the conditional expression (9),
the refractive power of the fourth lens group becomes small
relative to the refractive power of the fifth lens group, and it is
difficult to correct various aberrations including the curvature of
field. Note that the advantageous effect of the present application
can be further ensured by setting the upper limit value of the
conditional expression (9) to 3.50. Also, note that the
advantageous effect of the present application can be even further
ensured by setting the upper limit value of the conditional
expression (9) to 3.30.
[0094] When the distance between the fourth lens group and the
fifth lens group in the wide-angle end state is represented by
D45w, the distance between the fourth lens group and the fifth lens
group in the telephoto end state is represented by D45t, and the
focal length of the whole system in the wide-angle end state is
represented by fw, the variable magnification optical system of the
present application desirably satisfies the following conditional
expression (10):
0.15<(D45w-D45t)/fw<0.40 (10)
[0095] The conditional expression (10) defines an appropriate range
of difference between an air distance between the fourth lens group
and the fifth lens group in the wide-angle end state and an air
distance between the fourth lens group and the fifth lens group in
the telephoto end state. The optical system can suppress the
variation in the curvature of field upon zooming from the
wide-angle end to the telephoto end to further downsize the whole
lens length by satisfying the conditional expression (10).
[0096] When the value of (D45w-D45t)/fw is equal to or falls below
the lower limit of conditional expression (10), the difference
between the air distance between the fourth lens group and the
fifth lens group in the wide-angle end state and the air distance
between the fourth lens group and the fifth lens group in the
telephoto end state becomes smaller, and it becomes difficult to
make a good correction of the variation in the curvature of field
upon zooming from the wide-angle end to the telephoto end. Note
that the advantageous effect of the present application can be
further ensured by setting the lower limit value of the conditional
expression (10) to 0.22. Also, note that the advantageous effect of
the present application can be even further ensured by setting the
lower limit value of the conditional expression (10) to 0.25.
[0097] On the other hand, when the value of (D45w-D45t)/fw is equal
to or exceeds the upper limit value of the conditional expression
(10), the difference between the air distance between the fourth
lens group and the fifth lens group in the wide-angle end state and
the air distance between the fourth lens group and the fifth lens
group in the telephoto end state becomes larger, and the total lens
length becomes longer. Note that the advantageous effect of the
present application can be further ensured by setting the upper
limit value of the conditional expression (10) to 0.33. Also, note
that the advantageous effect of the present application can be even
further ensured by setting the upper limit value of the conditional
expression (10) to 0.32.
[0098] In the variable magnification optical system according to
the present application, it is desirable that the most object side
surface of the third lens group is an aspherical surface. With the
configuration, it is possible to achieve both the light weight of
the focusing lens group and the suppression of the variation in
aberration upon focusing from the infinite distance object point to
the close distance object point to realize much higher speed, much
better quietness autofocusing, without increasing the size of the
barrel.
[0099] Also in the variable magnification optical system according
to the present application, it is desirable to make a correction of
image blur by moving a part of the fourth lens group in the
direction including a directional component perpendicular to the
optical axis. With this configuration, it is possible to make an
effective correction of the image blur, in other words, imaging
position displacement caused by a camera shake or the like.
[0100] Next, a camera as an optical apparatus equipped with the
variable magnification optical system ZL according to the above
embodiment of the present application will be explained with
referring to FIG. 16. The present camera 1 is a so-called
mirrorless camera with an interchangeable lens equipped with the
variable magnification optical system ZL according to the present
embodiment as an imaging lens 2. In the present camera 1, light
emitted from an unillustrated object (an object to be photographed)
is converged by the imaging lens 2, so that an object image is
formed on an imaging surface of an imaging part 3 through an
unillustrated OLPF, that is, optical low pass filter. The object
image then undergoes photoelectric conversion with a photoelectric
conversion device in the imaging part 3 to generate an image of the
object. The image is displayed on an EVF 4, that is, electronic
view finder mounted on the camera 1. Accordingly, a photographer
can observe the object through the EVF 4.
[0101] Moreover, when the photographer presses an unillustrated
release button down, the image subjected to the photoelectric
conversion with the imaging part 3 is stored in an unillustrated
memory. In this manner, the photographer can take a picture of an
object by the camera 1. In the present embodiment, an example of
mirrorless camera is described. Even if the variable magnification
optical system according to the present embodiment is installed in
a single-lens reflex camera, which includes a quick return mirror
in the camera body and is capable of observing an object through a
finder optical system, the same effect as that of the camera 1 can
be achieved.
[0102] Thus, the optical apparatus according to the present
embodiment can realize a high speed auto focus and good quietness
upon auto focusing by using the variable magnification optical
system ZL of the above-mentioned features without the need to
increase the size of the barrel. Additionally, it is possible to
provide an optical apparatus which satisfactorily suppresses the
variation in aberration upon zooming from a wide-angle end state to
a telephoto end state and upon focusing from an infinite distance
object to a close distance object.
[0103] The contents described below can be adopted so far as the
optical performance is not deteriorated.
[0104] Although the variable magnification optical system having a
five lens-group configuration is described in the present
embodiment, the above-mentioned configuration conditions and the
like can be applied to variable magnification optical systems
having other lens-group configurations such as six or seven
lens-group configuration. Also, a lens or a lens group may be added
to the most object side of the variable magnification optical
system, and alternatively, a lens or a lens group may be added to
the most image side thereof. Incidentally, the lens group refers to
a portion including at least one lens separated by an air space
changing upon zooming.
[0105] Further, a single lens group or a plurality of lens groups
or a segment lens group may be configured to move along the optical
axis and be used as a focusing lens group for focusing from an
infinite distance object to a close distance object. In this case,
the focusing lens group can be applied to an auto focus and is
suitable for being driven by a motor for auto focusing (such as an
ultrasonic motor). In particular, it is preferable that, as
described above, the third lens group G3 is used as the focusing
lens group.
[0106] Further, a lens group or a segment lens group may be moved
so as to have a component in a direction perpendicular to the
optical axis or may be rotationally moved in an intra-plane
direction including the optical axis (swayed) as a vibration
reduction lens group for correcting an image blur caused by a
camera shake. In particular, it is preferable that, as described
above, at least a part of the subsequent lens group GR is used as a
vibration reduction lens group.
[0107] Further, the lens surface may be formed into a spherical
surface, a plane surface, or an aspherical surface. When the lens
surface is a spherical surface or a plane surface, it is preferable
because lens processing, assembling and adjustment become easy, and
the optical performance can be prevented from being deteriorated by
errors in the lens processing, assembling and adjustment. Also, it
is preferable because even if the image plane is shifted, the
deterioration in the optical performance is little. When the lens
surface is an aspherical surface, the aspherical surface may be
formed by a grinding process, a glass molding process in which a
glass material is formed into an aspherical shape using a mold, or
a compound type process in which a resin material on a glass
surface is formed into an aspherical shape. The lens surface may be
a diffractive optical surface, and the lens may be a gradient index
lens (GRIN lens) or a plastic lens.
[0108] It is preferable that the aperture stop S is disposed in the
vicinity of the third lens group G3, and its role may be
substituted by the frame of the lens without providing a member as
the aperture stop.
[0109] Moreover, each of the surfaces of the lenses may be coated
with an anti-reflection coating having a high transmittance in a
broad range of wavelength to reduce flare as well as ghost and
attain high contrast and high optical performance.
[0110] Additionally, the variable magnification optical system ZL
according to the above first Embodiment has a variable
magnification ratio of approximately 5 to 15 times.
[0111] An outline of a method for manufacturing the variable
magnification optical system ZL according to the first Embodiment
of the present application is described with reference to FIG. 17.
First, as step S100, a first to a fourth lens groups G1 to G4, and
a subsequent lens group GR are prepared by disposing the lenses. As
step S200, the lens groups are disposed in such a manner that, upon
zooming from a wide-angle end state to a telephoto end state, the
distance between the first lens group G1 and the second lens group
G2 is varied, the distance between the second lens group G2 and the
third lens group G3 is varied, the distance between the third lens
group G3 and the fourth lens group G4 is varied, and the distance
between the fourth lens group G4 and the subsequent lens group GR
is varied. As step S300, the third lens group G3 is disposed so as
to move along the optical axis upon focusing from an infinite
distance object to a close distance object. As step S400, the lens
groups G1 to G4 and GR are disposed so as to satisfy the
above-mentioned conditional expression (1).
[0112] Specifically, in the first Embodiment of the present
application, for example as shown in FIG. 1, in order from the
object side, a cemented positive lens composed of a negative
meniscus lens L11 having a convex surface facing the object side
and a double convex positive lens L12, and a positive meniscus lens
L13 having a convex surface facing the object side are disposed to
form the first lens group G1; a negative lens L21 having a convex
surface facing the object side, constructed by a negative meniscus
lens whose surface on the object side is provided with an
aspherical surface formed of a plastic resin, a double concave
negative lens L22, a double convex positive lens L23, and a double
concave negative lens L24 are disposed to form the second lens
group G2; a cemented lens composed of a positive lens 31 having an
object side lens surface formed into an aspherical surface and a
negative meniscus lens L32 having a concave surface facing the
object side is disposed to construct the third lens group G3; and a
cemented positive lens composed of a negative meniscus lens L41
having a convex surface facing the object side and a double convex
positive lens L42 is disposed to form the fourth lens group G4.
Additionally, the fifth lens group G5 consisting of a cemented
negative lens of a negative lens 51 having an object side lens
surface formed into an aspherical shape cemented with a positive
meniscus lens L52 having a convex surface facing the object side,
and the sixth lens group consisting of a double convex positive
lens L61 and a cemented positive lens of a double convex positive
lens L62 cemented with a negative meniscus lens L63 having a
concave surface facing the object side are disposed to form the
subsequent lens group GR. The lens groups thus prepared are
disposed by the above-mentioned procedure to manufacture the
variable magnification optical system ZL.
[0113] An outline of a method for manufacturing the variable
magnification optical system according to the second Embodiment of
the present application is described with reference to FIG. 18.
[0114] The method for manufacturing a variable magnification
optical system according to the present application shown in FIG.
18 is a method for manufacturing a variable magnification optical
system comprising, in order from an object side along the optical
axis: a first lens group having positive refractive power, a second
lens group having negative refractive power, a third lens group
having positive refractive power, a fourth lens group having
negative refractive power, and a fifth lens group having positive
refractive power, and the method comprises the following steps S100
to S300.
[0115] Step S100: Configuring the lens groups such that, upon
zooming from a wide-angle end state to a telephoto end state, the
first lens group is moved toward an object side, a distance between
the first lens group and the second lens group is increased, a
distance between the second lens group and the third lens group is
decreased, a distance between the third lens group and the fourth
lens group is varied, and a distance between fourth lens group and
the fifth lens group is varied.
[0116] Step S200: Configuring the third lens group so as to move
upon focusing from an infinite distance object point to a close
distance object point.
[0117] Step S300: Constructing the variable magnification optical
system so as to satisfy the following conditional expressions (4)
and (5) in which the focal length of the second lens group is
represented by f2, the focal length of the third lens group is
represented by f3, and the focal length of the whole system in the
telephoto end state is represented by ft:
0.23<f3/ft<0.35 (4)
2.60<(-f3)/f2<3.60 (5)
[0118] According to the above manufacturing method, the focusing
lens group is downsized and made light, and thus, it is possible to
provide a variable magnification optical system which enables the
realization of high speed and good quietness autofocusing without
increasing the size of the barrel, and good suppression of the
variation in aberration upon zooming from the wide-angle end state
to the telephoto end state and good suppression of the variation in
aberration upon focusing from the infinite distance object point to
the close distance object point, and further the realization of
good optical performance.
EXAMPLE
[0119] Hereinafter, examples of the present application will be
described with reference to the accompanying drawings. A first
Example and a second Example correspond to the above first
Embodiment, and a third Example, a fourth Example and a fifth
Example correspond to the above second Embodiment. FIGS. 1 and 4
are sectional views, respectively, showing the configuration and
refractive power distribution of the variable magnification optical
systems ZL according to the first and the second Examples, that is,
variable magnification optical systems ZL1 and ZL2. Below the
sectional views of the variable magnification optical systems ZL1
and ZL2 are shown directions of movement of the lens groups G1 to
G4 and the lens group GR consisting of the lens groups G5 and G6
which are moved along the optical axis upon zooming from a
wide-angle end state W to a telephoto end state T by arrows.
[0120] In the Examples, an aspherical surface is represented by the
following expression (a) where a height in the direction
perpendicular to the optical axis is represented by y; a sag
amount, which is a distance along the optical axis from a tangent
surface at the vertex of the aspherical surface to the aspherical
surface at the height y, is represented by S(y); a radius of
curvature of a reference sphere, that is, a paraxial radius of
curvature is represented by r; a conical coefficient is represented
by K; and an aspherical surface coefficient of n-th order is
represented by An:
S(y)=(y.sup.2/r)/[1+(1-K.times.y.sup.2/r.sup.2).sup.1/2]+A4.times.y.sup.-
4+A6.times.y.sup.6+A8.times.y.sup.8+A10.times.y.sup.10 (a)
In the following Examples, "E-n" denotes ".times.10.sup.-n".
[0121] In the Examples, the 2nd order aspherical surface
coefficient A2 is 0. In the tables of the Examples, a surface
number for an aspherical surface is marked with an asterisk "*" on
the right side.
First Example
[0122] FIG. 1 shows a configuration of variable magnification
optical system ZL1 according to the first Example. The variable
magnification optical system ZL1 shown in FIG. 1 is composed of, in
order from an object side, a first lens group G1 having positive
refractive power, a second lens group G2 having negative refractive
power, an aperture stop S, a third lens group G3 having positive
refractive power, a fourth lens group G4 having positive refractive
power, and a subsequent lens group GR. In this case, the subsequent
lens group GR is composed of, in order from an object side, a fifth
lens group G5 having negative refractive power and a sixth lens
group G6 having positive refractive power.
[0123] In the variable magnification optical system ZL1, the first
lens group G1 consists of, in order from the object side, a
cemented positive lens constructed by a negative meniscus lens L11
having a convex surface facing the object side cemented with a
double convex positive lens L12, and a positive meniscus lens L13
having a convex surface facing the object side. The second lens
group G2 consists of, in order from the object side, a negative
lens L21 having a convex surface facing the object side,
constructed by a negative meniscus lens whose surface on the object
side is provided with an aspherical surface formed of a plastic
resin, a double concave negative lens L22, a double convex positive
lens L23, and a double concave negative lens L24. The third lens
group G3 consists of a cemented lens constructed by, in order from
the object side, a positive lens L31 having an object side lens
surface formed into an aspherical shape cemented with a negative
meniscus lens L32 having a concave surface facing the object side.
The fourth lens group G4 consists of a cemented positive lens
constructed by, in order from the object side, a negative meniscus
lens L41 having a convex surface facing the object side cemented
with a double convex positive lens L42. The fifth lens group G5
consists of a cemented negative lens constructed by, in order from
the object side, a negative lens L51 having an object side lens
surface formed into an aspherical shape cemented with a positive
meniscus lens L52 having a convex surface facing the object side.
The sixth lens group G6 consists of, in order from the object side,
a double convex positive lens L61, and a cemented positive lens
constructed by a double convex positive lens L62 cemented with a
negative meniscus lens L63 having a concave surface facing the
object side.
[0124] In the variable magnification optical system ZL1 according
to the present first Example, each lens group of the first lens
group G1 to the sixth lens group G6 is moved in the direction of an
object, such that, upon zooming from a wide angle end state to a
telephoto end state, an air distance between the first lens group
G1 and the second lens group G2 is increased, an air distance
between the second lens group G2 and the third lens group G3 is
decreased, an air distance between the third lens group G3 and the
fourth lens group G4 is increased, an air distance between the
fourth lens group G4 and the fifth lens group G5 is increased, and
an air distance between the fifth lens group G5 and the sixth lens
group G6 is decreased. At that time, the aperture stop S and the
fourth lens group G4 are integrally moved, that is, in the same
amount of movement.
[0125] In the variable magnification optical system ZL1 according
to the present first Example, the third lens group G3 as a focusing
lens group is moved along the optical axis toward the image surface
side to thereby conduct focusing from the infinite distance object
to the close distance object.
[0126] Also in the variable magnification optical system ZL1
according to the present first Example, the fifth lens group G5 is
moved so as to have a component in a direction perpendicular to the
optical axis. Consequently, the displacement of imaging position
which may be caused by a camera shake or the like is corrected.
[0127] Values for various specifications for the variable
magnification optical system ZL1 according to the first Example are
shown in Table 1 given below. For Table 1, in [Whole
Specifications], f denotes a focal length of the optical system in
its entirety, FNO denotes an F-number, 2.omega. denotes an angle of
view, Ymax denotes a maximum image height, TL denotes a total
length of the optical system, OP denotes an object plane, I denotes
an image plane. The total length TL denotes a distance along the
optical axis from the first surface of the lens surfaces to the
image plane I upon focusing on infinity. W, M and T denote the
wide-angle end state, intermediate focal length state and telephoto
end state, respectively. In the [Lens Data], the first column m
denotes an order of lens surfaces counted from the object side
along the direction of travel of light, that is, a surface number.
The second column r denotes a radius of curvature of lens surface,
the third column d denotes a distance along the optical axis from
an optical surface to a subsequent optical surface, that is, a
surface-to-surface distance, the fourth column nd and the fifth
column .nu.d denote a refractive index and an Abbe number, for
d-line (wavelength .lamda.=587.6 nm). Meanwhile, the radius of
curvature .infin. denotes a plane surface, and a refractive index
of air 1.00000 is omitted. Surface numbers 1 to 29 in Table 1
correspond to reference numerals 1 to 29 shown in FIG. 1. In [Lens
Group Focal Length], there are shown a starting surface number ST
of each of the first to the sixth lens groups G1 to G6, that is, a
surface number of the most object side lens surface, and a focal
length f of each of the lens groups.
[0128] It is noted, here, the "mm" is generally used as the unit of
length such as the focal length f, the radius of curvature r, the
surface-to-surface distance d, and the unit for other lengths in
connection with all the values for specifications described below.
However, since similar optical performance can be obtained even by
an optical system proportionally enlarged or reduced for its
dimension, the unit is not necessarily limited to "mm". The
description of the reference symbols and specifications in the
tables below is also used in the same way for the second
Example.
TABLE-US-00001 TABLE 1 First Example [Whole Specifications]
Variable magnification ratio = 7.44 W M T f = 18.5 - 69.5 - 137.5
FNO = 3.37 - 5.07 - 5.87 2.omega. = 78.10 - 22.38 - 11.42 Ymax =
14.25 - 14.25 - 14.25 TL = 149.23 - 191.09 - 211.23 [Lens Data] m r
d nd .nu.d op .infin. 1 198.0585 2.000 1.84666 23.78 2 71.0593
8.436 1.59319 67.90 3 -281.2745 0.100 4 64.3516 4.808 1.81600 46.62
5 209.7899 d5 6* 91.7725 0.150 1.55389 38.23 7 87.5466 1.200
1.77250 49.61 8 13.5061 5.769 9 -35.0552 1.000 1.81600 46.62 10
42.8672 0.839 11 31.6462 5.245 1.84666 23.78 12 -26.4739 0.392 13
-23.1802 1.000 1.88300 40.76 14 937.7494 d14 15 .infin. d15
Aperture Stop S 16* 28.1133 5.000 1.48749 70.40 17 -30.8336 1.000
1.84666 23.78 18 -46.1545 d18 19 34.2511 1.000 2.00069 25.45 20
23.7294 5.400 1.49782 82.51 21 -34.5514 d21 22* -77.1085 1.400
1.77250 49.61 23 17.7029 2.768 1.84666 23.78 24 31.2636 d24 25
182.8242 3.970 1.57221 46.67 26 -34.4813 0.100 27 37.3517 6.951
1.48749 70.40 28 -21.1812 1.300 1.90265 35.70 29 -119.3320 BF I
.infin. [Lens Group Focal Length] ST f G1 1 85.560 G2 6 -13.001 G3
16 42.405 G4 19 45.251 G5 22 -30.006 G6 25 44.754
[0129] In the variable magnification optical system ZL1 according
to the first Example, the 6th surface, 16th surface and 22nd
surface are formed into an aspherical surface shape. Data for the
aspherical surfaces, that is, values of a conical coefficient K and
aspherical surface coefficients A4 to A10 are shown in Table 2
below. The letter "m" denotes an order of lens surfaces (surface
number) counted from the object side along the direction of travel
of light.
TABLE-US-00002 TABLE 2 [Aspherical Surface Data] m K A4 A6 A8 A10 6
11.2598 6.09566E- -4.17845E- 1.53230E- -3.43299E- 06 08 10 13 16
-0.5485 -1.67764E- 1.74753E- -1.42820E- 0.00000E+ 05 08 10 00 22
0.6725 8.48847E- -1.22182E- 1.81567E- 0.00000E+ 06 08 10 00
[0130] In the variable magnification optical system ZL1 according
to the first Example, an on-axis distance d5 between the first lens
group G1 and the second lens group G2, an on-axis distance d14
between the second lens group G2 and the aperture stop S, an
on-axis distance d15 between the aperture stop S and the third lens
group G3, an on-axis distance d18 between the third lens group G3
and the fourth lens group G4, an on-axis distance d21 between the
fourth lens group G4 and the fifth lens group G5, an on-axis
distance d24 between the fifth lens group G5 and the sixth lens
group G6, and a back focal length BF are each varied upon zooming
as described above. The following Table 3 shows values of variable
distance and back focal length BF in each focal length in the
wide-angle end state W, in the intermediate focal length state M
and in the telephoto end state T upon focusing on infinity and upon
focusing on a close distance. Note that the back focal length BF
means a distance on the optical axis from the most image side lens
surface (29th surface shown in FIG. 1) to the image plane I. This
explanation is the same in a second Example described later.
TABLE-US-00003 TABLE 3 [Variable Distance Data] Infinite focusing
state Close distance focusing state W M T W M T f 18.5 69.5 137.5
18.5 69.5 137.5 d5 1.500 28.095 44.228 1.500 28.095 44.228 d14
21.923 5.441 3.000 21.923 5.441 3.000 d15 6.423 4.512 2.000 6.862
4.833 2.504 d18 3.063 4.974 7.486 2.624 4.653 6.982 d21 2.500 6.346
7.564 2.500 6.346 7.564 d24 10.064 6.218 5.000 10.064 6.218 5.000
BF 38.02 69.76 76.21 38.02 69.76 76.21
[0131] Table 4 below shows values corresponding to respective
conditional expressions for the variable magnification optical
system ZL1 according to the present first Example. In Table 4, f1
denotes a focal length of the first lens group G1, f2 denotes a
focal length of the second lens group G2, f3 denotes a focal length
of the third lens group G3, f4 denotes a focal length of the fourth
lens group G4, and fw denotes a focal length of the whole system of
the variable magnification optical system ZL1 in the wide-angle end
state. The description of the reference symbols is also applied to
the second Example in the same way.
TABLE-US-00004 TABLE 4 [Values for Conditional Expressions] (1)
f3/f4 = 0.937 (2) (-f2)/f1 = 0.152 (3) f1/fw = 4.627
[0132] Thus, the variable magnification optical system ZL1
according to the first Example satisfies all the conditional
expressions (1)-(3).
[0133] Graphs of various aberrations of the variable magnification
optical system ZL1 according to the First Example upon focusing on
infinity in the wide-angle end state, in the intermediate focal
length state, and in the telephoto end state are shown in FIG. 2.
Graphs of various aberrations of the variable magnification optical
system upon focusing on the close distance, in the wide-angle end
state, in the intermediate focal length state, and in the telephoto
end state are shown in FIG. 3. In the aberration graphs, FNO
denotes an F-number, NA denotes a numerical aperture, and Y denotes
an image height. Incidentally, the spherical aberration graphs
shows an F-number, corresponding to the maximum aperture, or a
value of the numerical aperture, the astigmatism graphs and
distortion graphs show a maximum value of image height, and the
coma aberration graphs shows values of image heights. In the
graphs, d and g denote a d-line (.lamda.=587.6 nm) and a g-line
(.lamda.=435.8 nm), respectively. In the astigmatism graph, a solid
line indicates a sagittal image plane, and a broken line indicates
a meridional image plane. Incidentally, the same symbols as in the
present Example are used also in aberration graphs in the second
Example given later. As is seen from these aberration graphs, the
variable magnification optical system ZL1 according to the present
first Example shows superb imaging performance as a result of a
good correction of various aberrations in the range from the
wide-angle end state to the telephoto end state and provides
superior imaging performance also upon focusing on the close
distance.
Second Example
[0134] FIG. 4 shows a configuration of variable magnification
optical system ZL2 according to the second Example. The variable
magnification optical system ZL2 shown in FIG. 4 is composed of, in
order from an object side, a first lens group G1 having positive
refractive power, a second lens group G2 having negative refractive
power, an aperture stop S, a third lens group G3 having positive
refractive power, a fourth lens group G4 having positive refractive
power, and a subsequent lens group GR. In this case, the subsequent
lens group GR is composed of, in order from an object side, a fifth
lens group G5 having negative refractive power and a sixth lens
group G6 having positive refractive power.
[0135] In the variable magnification optical system ZL2, the first
lens group G1 consists of, in order from the object side, a
cemented positive lens constructed by a negative meniscus lens L11
having a convex surface facing the object side cemented with a
double convex positive lens L12, and a positive meniscus lens L13
having a convex surface facing the object side. The second lens
group G2 consists of, in order from the object side, a negative
lens L21 having a convex surface facing the object side,
constructed by a negative meniscus lens whose surface on the object
side is provided with an aspherical surface formed of a plastic
resin, a double concave negative lens L22, a double convex positive
lens L23, and a double concave negative lens L24. The third lens
group G3 consists of a positive lens L31 having an object side lens
surface formed into an aspherical shape. The fourth lens group G4
consists of a cemented positive lens constructed by, in order from
the object side, a negative meniscus lens L41 having a convex
surface facing the object side cemented with a double convex
positive lens L42. The fifth lens group G5 consists of a cemented
negative lens constructed by, in order from the object side, a
negative lens L51 having an object side lens surface formed into an
aspherical shape cemented with a positive meniscus lens L52 having
a convex surface facing the object side. The sixth lens group G6
consists of, in order from the object side, a double convex
positive lens L61, and a cemented positive lens constructed by a
double convex positive lens L62 cemented with a negative meniscus
lens L63 having a concave surface facing the object side.
[0136] In the variable magnification optical system ZL2 according
to the present second Example, each lens group of the first lens
group G1 to the sixth lens group G6 is moved in the direction of an
object such that, upon zooming from a wide angle end state to a
telephoto end state, an air distance between the first lens group
G1 and the second lens group G2 is increased, an air distance
between the second lens group G2 and the third lens group G3 is
decreased, an air distance between the third lens group G3 and the
fourth lens group G4 is increased, an air distance between the
fourth lens group G4 and the fifth lens group G5 is increased, and
an air distance between the fifth lens group G5 and the sixth lens
group G6 is decreased. At that time, the aperture stop S is moved
integrally with the fourth lens group G4 (in the same amount of
movement).
[0137] In the variable magnification optical system ZL2 according
to the present second Example, the third lens group G3 as a
focusing lens group is moved along the optical axis toward the
image surface side to thereby conduct focusing from an infinite
distance object to a close distance object.
[0138] Also in the variable magnification optical system ZL2
according to the present second Example, the fifth lens group G5 is
moved so as to have a component in a direction perpendicular to the
optical axis. Consequently, the displacement of imaging position
which may be caused by a camera shake or the like is corrected.
[0139] Values of various specification for the variable
magnification optical system ZL2 according to the second Example
are shown in Table 5 given below. The surface numbers 1 to 28 in
Table 5 correspond to the reference numerals 1 to 28 in FIG. 4.
TABLE-US-00005 TABLE 5 Second Example [Whole Specifications]
Variable magnification ratio = 7.41 W M T f = 18.5 - 70.1 - 137.2
FNO = 3.45 - 5.13 - 5.89 2.omega. = 78.06 - 22.18 - 11.50 Ymax =
14.25 - 14.25 - 14.25 TL = 150.24 - 192.79 - 211.18 [Lens Data] m r
d nd .nu.d op .infin. 1 164.7224 2.000 1.84666 23.78 2 69.2610
9.569 1.49782 82.51 3 -215.6328 0.100 4 59.9128 5.133 1.77250 49.61
5 210.3577 d5 6* 151.4197 0.150 1.55389 38.23 7 141.4818 1.200
1.77250 49.61 8 13.4456 5.852 9 -46.9540 1.000 1.81600 46.62 10
50.1225 0.500 11 27.2349 5.330 1.84666 23.78 12 -29.7129 0.313 13
-26.7614 1.000 1.88300 40.76 14 69.1420 d14 15 .infin. d15 Aperture
Stop S 16* 28.2763 4.500 1.49782 82.51 17 -63.7625 d17 18 41.6479
1.000 1.84666 23.78 19 25.3852 6.300 1.48749 70.40 20 -26.7000 d20
21* -67.5835 1.400 1.77250 49.61 22 18.4411 2.600 1.85026 32.35 23
30.5414 d23 24 126.3398 3.816 1.54282 48.67 25 -47.7988 0.100 26
42.8945 7.746 1.48749 70.40 27 -20.5949 1.300 1.90265 35.70 28
-57.7623 BF I .infin. [Lens Group Focal Length] ST f G1 1 85.126 G2
6 -12.427 G3 16 40.000 G4 18 41.836 G5 21 -28.132 G6 24 43.839
[0140] In the variable magnification optical system ZL2 according
to the second Example, the 6th surface, 16th surface and 21st
surface are formed into an aspherical shape. Data for the
aspherical surfaces, that is, values of a conical coefficient K and
aspherical surface coefficients A4 to A10 are shown in Table 6
below. The letter "m" denotes an order of lens surfaces counted
from the object side along the direction of progress of light, that
is, a surface number.
TABLE-US-00006 TABLE 6 [Aspherical Surface Data] m K A4 A6 A8 A10 6
3.5648 8.42661E- -5.67193E- 2.35593E- -4.71958E- 06 08 10 13 16
-0.6804 -2.20261E- 1.26254E- -2.16161E- 0.00000E+ 05 08 10 00 21
1.4368 7.94766E- 4.75605E- 1.24853E- 0.00000E+ 06 09 10 00
[0141] In the variable magnification optical system ZL2 according
to the second Example, an on-axis distance d5 between the first
lens group G1 and the second lens group G2, an on-axis distance d14
between the second lens group G2 and the aperture stop S, an
on-axis distance d15 between the aperture stop S and the third lens
group G3, an on-axis distance d17 between the third lens group G3
and the fourth lens group G4, an on-axis distance d20 between the
fourth lens group G4 and the fifth lens group G5, an on-axis
distance d23 between the fifth lens group G5 and the sixth lens
group G6, and a back focal length BF are varied upon zooming as
described above. Table 7 below shows values of variable distances
and back focal length BF in each of the focal lengths in the
wide-angle end state W, the intermediate focal length state M and
the telephoto end state T upon focusing on infinity and focusing on
a close distance object.
TABLE-US-00007 TABLE 7 [Variable Distance Data] Infinite focusing
state Close distance object state W M T W M T f 18.5 70.1 137.2
18.5 70.1 137.2 d5 1.500 29.460 43.956 1.500 29.460 43.956 d14
21.129 6.175 3.000 21.129 6.175 3.000 d15 5.970 3.536 2.000 6.367
3.851 2.459 d17 3.062 5.497 7.033 2.665 5.182 6.573 d20 2.500 6.941
8.730 2.500 6.941 8.730 d23 11.230 6.789 5.000 11.230 6.789 5.000
BF 38.02 67.56 74.63 38.02 67.56 74.63
[0142] Table 8 below shows values for conditional expressions for
the variable magnification optical system ZL2 according to the
present second Example.
TABLE-US-00008 TABLE 8 [Values for Conditional Expressions] (1)
f3/f4 = 0.956 (2) (-f2)/f1 = 0.146 (3) f1/fw = 4.602
[0143] Thus, the variable magnification optical system ZL2
according to the second Example satisfies all the conditional
expressions (1)-(3).
[0144] Graphs for various aberrations of the variable magnification
optical system ZL2 according to the second Example upon focusing on
infinity in the wide-angle end state, in the intermediate focal
length state and in the telephoto end state are shown in FIG. 5.
Graphs for various aberrations of the variable magnification
optical system upon focusing on a close distance object in the
wide-angle end state, in the intermediate focal length state and in
the telephoto end state are shown in FIG. 6. As is seen from these
aberration diagrams, the variable magnification optical system ZL2
according to the present second Example shows superb imaging
performance as a result of a good correction of various aberrations
in the range from the wide-angle end state to the telephoto end
state and provides superior imaging performance also upon focusing
on the close distance object.
[0145] Hereinafter, variable magnification optical systems
according to a third Example to a fifth Example of the present
application, corresponding to the above second Embodiment, will be
described with reference to the accompanying drawings.
Third Example
[0146] FIG. 7 shows a lens arrangement of a variable magnification
optical system according to a third Example of the present
application.
[0147] The variable magnification optical system according to the
present third Example is composed of, in order from an object side
along the optical axis, a first lens group G1 having positive
refractive power, a second lens group G2 having negative refractive
power, an aperture stop S, 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.
[0148] The first lens group G1 consists of, in order from the
object side along the optical axis, a cemented positive lens
constructed by a negative meniscus lens L11 having a convex surface
facing the object side cemented with a double convex positive lens
L12, and a positive meniscus lens L13 having a convex surface
facing the object side.
[0149] The second lens group G2 consists of, in order from the
object side along the optical axis, a negative meniscus lens L21
having a convex surface facing the object side, a double concave
negative lens L22, a double convex positive lens L23, and a
negative meniscus lens L24 having a concave surface facing the
object side. The negative meniscus lens L21 of the second lens
group G2 has an object side lens surface provided with a thin layer
of plastic resin formed into an aspherical shape.
[0150] The third lens group G3 consists of a cemented positive lens
constructed by a double convex positive lens 31 cemented with a
negative meniscus lens L32 having a concave surface facing the
object side. The positive lens L31 of the third lens group G3 has
an object side lens surface formed into an aspherical shape.
[0151] The fourth lens group G4 consists of, in order from the
object side along the optical axis, a cemented positive lens
constructed by a negative meniscus lens L41 having a convex surface
facing the object side cemented with a double convex positive lens
L42, and a cemented negative lens constructed by a double concave
negative lens L43 cemented with a positive meniscus lens L44 having
a convex surface facing the object side. The negative lens L43 of
the fourth lens group G4 has an object side lens surface formed
into an aspherical shape.
[0152] The fifth lens group G5 consists of, in order from the
object side along the optical axis, a double convex positive lens
L51, and a cemented positive lens constructed by a double convex
positive lens L52 cemented with a negative meniscus lens L53 having
a concave surface facing the object side.
[0153] In the variable magnification optical system according to
the present Example, each lens group of the first lens group G1 to
the fifth lens group G5 is moved to the side of an object such
that, upon zooming from a wide angle end state to a telephoto end
state, an air distance between the first lens group G1 and the
second lens group G2 is increased, an air distance between the
second lens group G2 and the third lens group G3 is decreased, an
air distance between the third lens group G3 and the fourth lens
group G4 is increased, and an air distance between the fourth lens
group G4 and the fifth lens group G5 is decreased. At that time,
the aperture stop S is moved together with the fourth lens group
G4.
[0154] In the variable magnification optical system according to
the present Example, the third lens group G3 is moved toward the
image plane side to thereby conduct focusing from an infinite
distance object point to a close distance object point.
[0155] In the variable magnification optical system according to
the present Example, the cemented negative lens of the negative
lens L43 and positive meniscus lens L44 in the fourth lens group G4
is moved in a direction including a directional component
perpendicular to the optical axis. Consequently, the displacement
of imaging position which may be caused by a camera shake or the
like is corrected.
[0156] Values of specifications for the variable magnification
optical system according to the present Example are shown in Table
9 given below.
[0157] In [Surface Data], "m" denotes an order of a lens surface
counted from the object side along the optical axis, "r" denotes a
radius of curvature, "d" denotes a surface distance, which is a
distance between an n-th surface and an (n+1)-th surface, where n
is an integer, "nd" denotes refractive index for d-line (wavelength
.lamda.=587.6 nm) and ".nu.d" denotes an Abbe number for d-line
(wavelength .lamda.=587.6 nm). Further, "OP" denotes an object
plane, and "variable" denotes a variable surface distance. Also,
"stop" denotes an aperture stop S, "BF" denotes a back focal
length, and "I" denotes an image plane. Meanwhile, in the column of
radius of curvature "r", ".infin." denotes a plane surface, and a
refractive index of air nd=1.00000 is omitted. For the aspherical
surface, the surface number is marked with the asterisk "*", and in
the column of the radius of curvature r, a paraxial radius of
curvature is shown.
[0158] In [Aspherical Surface Data], with respect to an aspherical
surface shown in [Surface Data], an aspherical surface coefficient
and a conical coefficient are shown in the case where the
aspherical surface is represented by the following expression:
x=(h.sup.2/r)/[1+[1-.kappa.(h/r).sup.2].sup.1/2]+A4h.sup.4+A6h.sup.6+A8h-
.sup.8+A10h.sup.-10
[0159] In the expression, "x" denotes a sag amount, which is a
distance along the optical axis from a tangent surface at the
vertex of an aspherical surface to the aspherical surface at a
vertical height h from the optical axis, ".kappa." denotes a
conical coefficient, "A4", "A6", "A8", and "A10" denote respective
aspherical coefficients, and "r" denotes a paraxial radius of
curvature, which is a radius of curvature of a reference sphere.
Additionally, "E-n", where n is an integer, denotes
".times.10.sup.-n", and for example, "1.234E-05" denotes
"1.234.times.10.sup.-5".
[0160] In [Various Data], "f" denotes a focal length, "FNO" denotes
an F-number, "2.omega." denotes an angle of view using the degree
".degree." as the unit, "Ymax" denotes a maximum image height, "TL"
denotes a total length of the variable magnification optical
system, that is, a distance along the optical axis from the first
surface of lens surface to the image plane I, and "BF" denotes a
back focal length.
[0161] In [Variable Distance Data], "dn" denotes a variable surface
distance between an n-th surface and an (n+1)-th surface.
[0162] In [Various Data] and [Variable Distance Data], "W" denotes
the wide-angle end state, "M" denotes the intermediate focal length
state, and "I" denotes the telephoto end state. Also, "infinity"
denotes upon focusing on an infinite distance object point, and
"close distance" denotes upon focusing on a close distance object
point.
[0163] In [Lens Group Data], there are shown a starting surface
number ST and a focal length f of each lens group.
[0164] In [Values for Conditional Expressions] are shown values
corresponding to the conditional expressions for the variable
magnification optical system according to the present Example.
[0165] It is noted, here, that "mm" is generally used as the unit
of a length, such as the focal length f, the radius of curvature r,
the surface distance, and the like shown in Table 9. However, since
similar optical performance can be obtained by an optical system
proportionally enlarged or reduced for its dimension, the unit is
not necessarily limited to "mm".
[0166] The reference symbols in Table 9 described above are also
used in Tables for a fourth Example and a fifth Example provided
later in the same way.
TABLE-US-00009 TABLE 9 [Surface Data] m r d nd .nu.d op .infin. 1
168.3247 2.000 1.84666 23.78 2 63.5937 8.546 1.59319 67.90 3
-343.9262 0.100 4 61.2261 5.226 1.81600 46.62 5 223.1789 d5 6*
222.2854 0.150 1.55389 38.23 7 153.3735 1.200 1.77250 49.61 8
12.7983 5.804 9 -34.0102 1.000 1.81600 46.62 10 60.7684 0.500 11
30.1743 5.169 1.84666 23.78 12 -28.1317 0.447 13 -23.6928 1.000
1.88300 40.76 14 -1288.8278 d14 15(Stop) .infin. d15 16* 25.5131
5.026 1.52144 67.00 17 -31.6553 1.000 1.85026 32.35 18 -55.3019 d18
19 40.3899 1.000 2.00069 25.45 20 25.8165 5.400 1.49782 82.51 21
-29.3499 2.500 22* -73.6144 1.400 1.77250 49.61 23 19.1936 2.600
1.84666 23.78 24 33.2373 d24 25 178.7403 3.089 1.65311 47.08 26
-69.5056 0.100 27 48.3544 7.163 1.48749 70.40 28 -18.2461 1.300
1.90265 35.70 29 -44.2532 BF I .infin. [Aspherical Surface Data]
6th Surface .kappa. = 11.2598 A4 = 1.24040E-05 A6 = -3.23075E-08 A8
= 7.25627E-11 A10 = -1.73701E-13 16th Surface .kappa. = -0.2264 A4
= -1.61628E-05 A6 = -4.70348E-09 A8 = -4.64530E-11 A10 =
0.00000E+00 22th Surface .kappa. = 0.6725 A4 = 5.63011E-06 A6 =
2.27657E-08 A8 = -2.38116E-11 A10 = 0.00000E+00 [Various Data]
Variable magnification ratio 7.46 W M T f 18.5 69.9 138.0 FNO 3.43
5.19 5.89 2.omega. 77.98 22.24 11.42 Ymax 14.25 14.25 14.25 TL
143.38 186.38 204.92 BF 38.08 73.94 83.31 [Variable Distance Data]
Infinity focusing state Close distance focusing state W M T W M T
d5 1.500 28.127 41.786 1.500 28.127 41.786 d14 21.548 6.770 3.000
21.548 6.770 3.000 d15 7.138 3.763 2.000 7.619 4.135 2.572 d18
2.962 6.338 8.101 2.481 5.966 7.529 d24 10.431 5.722 5.000 10.431
5.722 5.000 [Lens Group Data] ST f G1 1 80.001 G2 6 -12.957 G3 16
40.001 G4 19 -152.169 G5 25 47.918 [Values for Conditional
Expressions] (4) f3/ft = 0.290 (5) (-f3)/f2 = 3.087 (6) nN - nP =
0.329 (7) .nu.P - .nu.N = 34.65 (8) f1/fw = 4.319 (9) (-f4)/f5 =
3.176 (10) (D45w - D45t)/fw = 0.293
[0167] FIGS. 8A, 8B and 8C are graphs showing various aberrations
of the variable magnification optical system according to the third
Example of the present application upon focusing on infinity, in
the wide angle end state, in the intermediate focal length state,
and in the telephoto end state, respectively.
[0168] FIGS. 9A, 9B and 9C are graphs showing various aberrations
of the variable magnification optical system according to the third
Example of the present application upon focusing on a close
distance object, in the wide angle end state, in the intermediate
focal length state, and in the telephoto end state,
respectively.
[0169] In the aberration graphs in FIGS. 8A, 8B, 8C, 9A, 9B, and
9C, "FNO" denotes an F-number, "NA" denotes a numerical aperture,
and "Y" denotes an image height. In the graphs of spherical
aberration are shown values for the F-number, corresponding to the
maximum aperture, or values of the numerical aperture. In the
graphs of astigmatism and distortion are shown maximum values of
the image height. In the graphs of coma aberration are shown values
for the image heights. In the graphs, d denotes an aberration curve
at d-line (wavelength .lamda.=587.6 nm), and g denotes an
aberration curve at g-line (wavelength .lamda.=435.8 nm). In the
astigmatism graphs, a solid line indicates a sagittal image plane,
and a broken line indicates a meridional image plane. Incidentally,
the same symbols as in the present Example are used also in various
aberration graphs in the Examples given later.
[0170] As is seen from the aberration graphs, the variable
magnification optical system according to the present Example shows
superb imaging performance as a result of a good correction of
various aberrations in the range from the wide-angle end state to
the telephoto end state and exhibits superior imaging performance
also upon focusing on the close distance object.
Fourth Example
[0171] FIG. 10 shows a sectional view of a lens arrangement of a
variable magnification optical system according to a fourth Example
of the present application.
[0172] The variable magnification optical system according to the
present fourth Example is composed of, in order from an object side
along the optical axis, a first lens group G1 having positive
refractive power, a second lens group G2 having negative refractive
power, an aperture stop S, 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.
[0173] The first lens group G1 consists of, in order from the
object side along the optical axis, a cemented positive lens
constructed by a negative meniscus lens L11 having a convex surface
facing the object side cemented with a double convex positive lens
L12, and a positive meniscus lens L13 having a convex surface
facing the object side.
[0174] The second lens group G2 consists of, in order from the
object side along the optical axis, a negative meniscus lens L21
having a convex surface facing the object side, a double concave
negative lens L22, a double convex positive lens L23, and a
negative meniscus lens L24 having a concave surface facing the
object side.
[0175] The third lens group G3 consists of a cemented positive lens
constructed by a double convex positive lens 31 cemented with a
negative meniscus lens L32 having a concave surface facing the
object side. The positive lens L31 of the third lens group G3 has
an object side lens surface formed into an aspherical shape.
[0176] The fourth lens group G4 consists of, in order from the
object side along the optical axis, a double convex positive lens
L41, and a cemented negative lens constructed by a double concave
negative lens L42 cemented with a positive meniscus lens L43 having
a convex surface facing the object side. The negative lens L42 of
the fourth lens group G4 has an object side lens surface formed
into an aspherical shape.
[0177] In the variable magnification optical system according to
the present fourth Example, each lens group of the first lens group
G1 to the fifth lens group G5 is moved to the side of an object
such that, upon zooming from a wide angle end state to a telephoto
end state, an air distance between the first lens group G1 and the
second lens group G2 is increased, an air distance between the
second lens group G2 and the third lens group G3 is decreased, an
air distance between the third lens group G3 and the fourth lens
group G4 is increased, and an air distance between the fourth lens
group G4 and the fifth lens group G5 is decreased. At that time,
the aperture stop S is moved together with the fourth lens group
G4.
[0178] In the variable magnification optical system according to
the present Example, the third lens group G3 is moved toward the
image plane side to thereby conduct focusing from an infinite
distance object point to a close distance object point.
[0179] In the variable magnification optical system according to
the present Example, the cemented negative lens of the negative
lens L42 and positive meniscus lens L43 in the fourth lens group G4
is moved in a direction including a directional component
perpendicular to the optical axis. Consequently, the displacement
of imaging position which may be caused by a camera shake or the
like is corrected.
[0180] Values of specifications for the variable magnification
optical system according to the present fourth Example are shown in
Table 10 given below.
TABLE-US-00010 TABLE 10 [Surface Data] m r d nd .nu.d op .infin. 1
162.9959 2.000 1.84666 23.78 2 64.5555 8.419 1.59319 67.90 3
-306.7473 0.100 4 62.8075 5.118 1.81600 46.62 5 218.0207 d5 6*
189.4081 0.150 1.55389 38.23 7 165.1712 1.200 1.81600 46.59 8
13.5444 5.538 9 -34.1114 1.000 1.81600 46.62 10 58.5413 0.562 11
31.5714 5.179 1.84666 23.78 12 -27.5725 0.342 13 -24.7465 1.000
1.88300 40.76 14 -1085.5444 d14 15(Stop) .infin. d15 16* 27.7563
5.587 1.56973 66.58 17 -20.8159 1.000 1.85026 32.35 18 -46.2372 d18
19 91.8595 4.279 1.49782 82.51 20 -30.3088 2.646 21* -84.0769 1.400
1.82199 43.16 22 22.4074 2.600 1.84666 23.78 23 36.4556 d23 24
211.1920 3.515 1.57737 66.30 25 -45.7168 0.100 26 49.0134 7.154
1.54032 53.56 27 -18.5326 1.300 1.90265 35.70 28 -67.8485 BF I
.infin. [Aspherical Surface Data] 6th Surface .kappa. = 11.2598 A4
= 8.34883E-06 A6 = -3.33818E-08 A8 = 1.28598E-10 A10 = -3.80577E-13
16th Surface .kappa. = 0.0714 A4 = -1.41128E-05 A6 = -1.42043E-08
A8 = -4.71168E-13 A10 = 0.00000E+00 21th Surface .kappa. = 0.6725
A4 = 6.04257E-06 A6 = 1.76635E-08 A8 = -3.55283E-11 A10 =
0.00000E+00 [Various Data] Variable magnification ratio 7.41 W M T
f 18.5 69.6 137.1 FNO 3.44 5.33 5.88 2.omega. 78.12 22.34 11.44
Ymax 14.25 14.25 14.25 TL 143.30 184.42 200.72 BF 38.00 74.24 80.27
[Variable Distance Data] Infinity focusing state Close distance
focusing state W M T W M T d5 1.500 26.954 41.730 1.500 26.954
41.730 d14 22.266 6.835 3.000 22.266 6.835 3.000 d15 7.448 3.683
2.000 7.992 4.061 2.628 d18 3.085 6.849 8.533 2.541 6.471 7.905 d23
10.812 5.669 5.000 10.812 5.669 5.000 [Lens Group Data] ST f G1 1
79.999 G2 6 -13.407 G3 16 40.000 G4 19 -136.276 G5 24 48.301
[Values for Conditional Expressions] (4) f3/ft = 0.292 (5) (-f3)/f2
= 2.984 (6) nN - nP = 0.281 (7) .nu.P - .nu.N = 34.23 (8) f1/fw =
4.328 (9) (-f4)/f5 = 2.821 (10) (D45w - D45t)/fw = 0.314
[0181] FIGS. 11A, 11B and 11C are graphs showing various
aberrations of the variable magnification optical system according
to the fourth Example of the present application upon focusing on
infinity, in the wide angle end state, in the intermediate focal
length state, and in the telephoto end state, respectively.
[0182] FIGS. 12A, 12B and 12C are graphs showing various
aberrations of the variable magnification optical system according
to the fourth Example of the present application upon focusing on a
close distance object, in the wide angle end state, in the
intermediate focal length state, and in the telephoto end state,
respectively.
[0183] As is seen from the aberration graphs, the variable
magnification optical system according to the present Example shows
superb imaging performance as a result of a good correction of
various aberrations in the range from the wide-angle end state to
the telephoto end state and provides superior imaging performance
also upon focusing on a close distance object.
Fifth Example
[0184] FIG. 13 shows a lens arrangement of a variable magnification
optical system according to a fifth Example of the present
application.
[0185] The variable magnification optical system according to the
present fifth Example is composed of, in order from an object side
along the optical axis, a first lens group G1 having positive
refractive power, a second lens group G2 having negative refractive
power, an aperture stop S, 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.
[0186] The first lens group G1 consists of, in order from the
object side along the optical axis, a cemented positive lens
constructed by a negative meniscus lens L11 having a convex surface
facing the object side cemented with a double convex positive lens
L12, and a positive meniscus lens L13 having a convex surface
facing the object side.
[0187] The second lens group G2 consists of, in order from the
object side along the optical axis, a negative meniscus lens L21
having a convex surface facing the object side, a double concave
negative lens L22, a double convex positive lens L23, and a double
concave negative lens L24. The negative meniscus lens L21 of the
second lens group G2 has an object side lens surface provided with
a thin layer of plastic resin formed into an aspherical shape.
[0188] The third lens group G3 consists of a cemented positive lens
constructed by a double convex positive lens 31 cemented with a
negative meniscus lens L32 having a concave surface facing the
object side. The positive lens L31 of the third lens group G3 has
an object side lens surface formed into an aspherical shape.
[0189] The fourth lens group G4 consists of, in order from the
object side along the optical axis, a double convex positive lens
L41, and a cemented negative lens constructed by a double concave
negative lens L42 cemented with a positive meniscus lens L43 having
a convex surface facing the object side. The negative lens L42 of
the fourth lens group G4 has an object side lens surface formed
into an aspherical shape.
[0190] The fifth lens group G5 consists of, in order from the
object side along the optical axis, a cemented positive lens
constructed by a negative meniscus lens L51 having a convex surface
facing the object side cemented with a double convex positive lens
L52, and a cemented positive lens constructed by a double convex
positive lens L53 cemented with a negative meniscus lens L54 having
a concave surface facing the object side.
[0191] In the variable magnification optical system according to
the present fifth Example, each lens group of the first lens group
G1 to the fifth lens group G5 is moved to the side of an object
such that, upon zooming from a wide angle end state to a telephoto
end state, an air distance between the first lens group G1 and the
second lens group G2 is increased, an air distance between the
second lens group G2 and the third lens group G3 is decreased, an
air distance between the third lens group G3 and the fourth lens
group G4 is increased, and an air distance between the fourth lens
group G4 and the fifth lens group G5 is decreased. At that time,
the aperture stop S is moved together with the fourth lens group
G4.
[0192] In the variable magnification optical system according to
the present Example, the third lens group G3 is moved toward the
image plane side to thereby conduct focusing from an infinite
distance object point to a close distance object point.
[0193] In the variable magnification optical system according to
the present Example, the cemented negative lens of the negative
lens L42 and positive meniscus lens L43 in the fourth lens group G4
is moved in a direction including a directional component
perpendicular to the optical axis. Consequently, the displacement
of imaging position which may be caused by a camera shake or the
like is corrected.
[0194] Values of specifications for the variable magnification
optical system according to the present fifth Example are shown in
Table 11 given below.
TABLE-US-00011 TABLE 11 [Surface Data] m r d nd .nu.d op .infin. 1
182.4197 2.000 1.84666 23.80 2 65.9296 8.477 1.59319 67.90 3
-251.6345 0.100 4 62.6306 5.205 1.81600 46.62 5 216.8104 d5 6*
500.0000 0.150 1.55389 38.23 7 317.0099 1.200 1.81600 46.59 8
14.2613 4.974 9 -58.5533 1.000 1.81600 46.62 10 42.1167 0.500 11
25.4178 5.399 1.84666 23.78 12 -29.8839 0.371 13 -25.9080 1.000
1.88300 40.76 14 102.0955 d14 15(Stop) .infin. d15 16* 25.9625
5.241 1.60300 65.44 17 -25.0195 1.000 1.85026 32.35 18 -71.4459 d18
19 131.4303 4.270 1.49782 82.51 20 -26.9040 2.500 21* -76.8762
1.400 1.82124 43.55 22 22.2058 2.400 1.84666 23.78 23 36.3161 d23
24 187.1289 1.300 1.82674 25.92 25 98.6389 3.596 1.69966 53.90 26
-58.9299 0.100 27 40.1643 7.682 1.54032 53.56 28 -18.8168 1.300
1.90265 35.70 29 -70.7430 BF I .infin. [Aspherical Surface Data]
6th Surface .kappa. = 11.2598 A4 = 7.62346E-06 A6 = -1.78269E-08 A8
= 8.46129E-11 A10 = -2.47130E-13 16th Surface .kappa. = -0.0666 A4
= -1.51323E-05 A6 = -3.60576E-08 A8 = -3.25380E-11 A10 =
0.00000E+00 21th Surface .kappa. = 0.6725 A4 = 6.45447E-06 A6 =
2.78317E-08 A8 = 2.78317E-08 A10 = 0.00000E+00 [Various Data]
Variable magnification ratio 7.56 W M T f 18.5 70.2 139.8 FNO 3.47
5.29 5.88 2.omega. 78.06 22.16 11.24 Ymax 14.25 14.25 14.25 TL
143.30 185.46 201.71 BF 38.00 73.20 79.61 [Variable Distance Data]
Infinity focusing state Close distance focusing state W M T W M T
d5 1.500 27.734 42.208 1.500 27.734 42.208 d14 21.546 6.826 3.000
21.546 6.826 3.000 d15 7.716 3.829 2.000 8.222 4.219 2.648 d18
3.009 6.895 8.724 2.502 6.506 8.076 d23 10.365 5.813 5.000 10.365
5.813 5.000 [Lens Group Data] ST f G1 1 80.001 G2 6 -13.280 G3 16
40.000 G4 19 -125.226 G5 24 44.290 [Values for Conditional
Expressions] (4) f3/ft = 0.286 (5) (-f3)/f2 = 3.012 (6) nN - nP =
0.247 (7) .nu.P - .nu.N = 33.09 (8) f1/fw = 4.325 (9) (-f4)/f5 =
2.827 (10) (D45w - D45t)/fw = 0.290
[0195] FIGS. 14A, 14B and 14C are graphs showing various
aberrations of the variable magnification optical system according
to the fifth Example of the present application upon focusing on
infinity, in the wide angle end state, in the intermediate focal
length state, and in the telephoto end state, respectively.
[0196] FIGS. 15A, 15B and 15C are graphs showing various
aberrations of the variable magnification optical system according
to the fifth Example of the present application upon focusing on a
close distance object, in the wide angle end state, in the
intermediate focal length state, and in the telephoto end state,
respectively.
[0197] As is seen from the aberration graphs, the variable
magnification optical system according to the present Example shows
superb imaging performance as a result of a good correction of
various aberrations in the range from the wide-angle end state to
the telephoto end state and provides superior imaging performance
also upon focusing on a close distance object.
[0198] According to the above Examples, the focusing lens group is
downsized and made lighter, and thus, it is possible to provide a
variable magnification optical system which enables the realization
of high speed and good quietness auto focusing without increasing
the size of the barrel and which also enables good suppression of
the variation in aberrations upon zooming from the wide-angle end
state to the telephoto end state and good suppression of the
variation in aberrations upon focusing from the infinite distance
object point to the close distance object point.
* * * * *