U.S. patent application number 13/801467 was filed with the patent office on 2013-10-03 for optical system and imaging apparatus including the same.
This patent application is currently assigned to CANON KABUSHIKI KAISHA. The applicant listed for this patent is CANON KABUSHIKI KAISHA. Invention is credited to Akira Mizuma.
Application Number | 20130258476 13/801467 |
Document ID | / |
Family ID | 49234683 |
Filed Date | 2013-10-03 |
United States Patent
Application |
20130258476 |
Kind Code |
A1 |
Mizuma; Akira |
October 3, 2013 |
OPTICAL SYSTEM AND IMAGING APPARATUS INCLUDING THE SAME
Abstract
In an optical system in which a focal length of an entire system
is shorter than a back focus, an image stabilizing lens unit, is at
a position adjacent to an aperture on an image side and a cemented
lens obtained by cementing a positive lens and a negative lens is
on an object side of the aperture diaphragm, and the focal length
of the entire system, a focal length of the image stabilizing lens
unit, a focal length of the cemented lens, a distance on the
optical axis from the aperture to a lens surface on the object side
of the image stabilizing lens unit, and a distance on the optical
axis from a first lens surface on a side closest to an object to a
final lens surface on a side closest to an image when an
infinite-distance object is brought into focus are set.
Inventors: |
Mizuma; Akira;
(Utsunomiya-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
CANON KABUSHIKI KAISHA |
Tokyo |
|
JP |
|
|
Assignee: |
CANON KABUSHIKI KAISHA
Tokyo
JP
|
Family ID: |
49234683 |
Appl. No.: |
13/801467 |
Filed: |
March 13, 2013 |
Current U.S.
Class: |
359/557 |
Current CPC
Class: |
G02B 9/64 20130101; G02B
15/1421 20190801; G02B 15/15 20130101; G02B 15/16 20130101; G02B
27/646 20130101; H04N 5/23287 20130101; G02B 13/04 20130101; G02B
15/1425 20190801 |
Class at
Publication: |
359/557 |
International
Class: |
G02B 27/64 20060101
G02B027/64 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 28, 2012 |
JP |
2012-072806 |
Claims
1. An optical system of which a focal length of an entire system is
shorter than a back focus, wherein, when an image stabilizing lens
unit, which moves in a direction including a component
perpendicular to an optical axis to move an imaging position, is
arranged at a position adjacent to an aperture diaphragm on an
image side, a cemented lens obtained by cementing a positive lens
and a negative lens is arranged on an object side of the aperture
diaphragm, the focal length of the entire system is set to f, a
focal length of the image stabilizing lens unit is set to fis, a
focal length of the cemented lens is set to fc, a distance on the
optical axis from the aperture diaphragm to a lens surface on the
object side of the image stabilizing lens unit is set to Dis, and a
distance on the optical axis from a first lens surface on a side
closest to an object to a final lens surface on a side closest to
an image when an infinite-distance object is brought into focus is
set to DL, condition equations 0.00<Dis/DL<0.25,
0.3<fis/f<3.5, and 0.3<-fc/fis<3.5 are satisfied.
2. The optical system according to claim 1, wherein, when lateral
magnification of the image stabilizing lens unit is set to .beta.is
and lateral magnification of a lens unit arranged on the image side
of the image stabilizing lens unit is set to .beta.r, a condition
equation 0.1<|(1-.beta.is).beta.r|<1.3 is satisfied.
3. The optical system according to claim 1, wherein, when the image
stabilizing lens unit includes a single lens and an Abbe number of
a material of the single lens with respect to a d-line is set to
.nu.dis, a condition equation 35<.nu.dis is satisfied.
4. The optical system according to claim 1, comprising: a first
lens unit with positive or negative refractive power and a second
lens unit with positive refractive power in order from the object
side to the image side, wherein the second lens unit moves during
focusing, and the cemented lens, the aperture diaphragm, and the
image stabilizing lens unit are included in the second lens
unit.
5. The optical system according to claim 4, wherein the first lens
unit includes a negative lens in a meniscus shape having a convex
surface on the object side and a positive lens in order from the
object side to the image side, and the second lens unit includes a
negative lens in the meniscus shape having a concave surface on the
image side, a positive lens, the cemented lens obtained by
cementing the positive lens and the negative lens, the aperture
diaphragm, the image stabilizing lens unit, which moves in the
direction including the component in the direction perpendicular to
the optical axis to move the imaging position, a cemented lens
obtained by cementing a negative lens and a positive lens, and a
positive lens in order from the object side to the image side.
6. The optical system according to claim 1, wherein the lens on the
side closest to the image is a positive lens having an aspherical
surface.
7. An imaging apparatus, comprising: the optical system according
to claim 1.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to an optical system and is
suitable as an imaging optical system used in an imaging apparatus
such as a silver-halide film camera, a digital still camera, a
video camera, a digital video camera, a monitoring camera, and a
broadcasting camera, for example.
[0003] 2. Description of the Related Art
[0004] It is required that the imaging optical system used in the
imaging apparatus have high optical performance across an entire
image area and that various aberrations thereof be corrected in an
excellent manner. The imaging optical system is also required to
have an image stabilizing mechanism for inhibiting deterioration in
image due to an effect of vibration such as a camera shake at the
time of shooting. As the image stabilizing mechanism, a method of
correcting variation in image position caused by the camera shake
and the like by moving a part of lens units of the optical system
in a direction including a component perpendicular to the optical
axis is known.
[0005] It is known that the image stabilizing mechanism is used in
a retrofocus-type wide-angle lens in which a focal length of an
entire system is shorter than a back focus.
[0006] In order to obtain excellent optical performance by
correcting an image shake at the time of vibration of the optical
system, it is important to arrange the image stabilizing mechanism
in an appropriate position of the imaging optical system.
[0007] U.S. Pat. No. 5,917,663 discloses that the wide-angle lens
including a lens unit with negative refractive power and a lens
unit with positive refractive power in order from an object side
performs image stabilization by rotational movement of two positive
lenses on a side closest to an image around a point on the optical
axis.
[0008] Therefore, an incident position of a principal ray of an
off-axis ray incident on an image stabilizing lens unit becomes
high and there is a tendency that image-plane variation occurs at
the time of the image stabilization in the off-axis ray and
aberration correction at the time of the image stabilization
becomes difficult. Also, the incident height of the off-axis ray
incident on the image stabilizing lens unit becomes high and there
is a tendency that coma aberration variation becomes large at the
time of the image stabilization and the optical performance is
deteriorated. Therefore, it is difficult to realize a large
aperture ratio of the wide-angle lens disclosed in U.S. Pat. No.
5,917,663.
[0009] In order to correct the image shake at the time of the
vibration of the optical system while maintaining the excellent
optical performance, a lens configuration and refractive power of
the image stabilizing lens unit are important and it is also
important to arrange the image stabilizing lens unit at an
appropriate position in an optical path.
[0010] An object of an embodiment of the present invention is to
provide an optical system capable of easily obtaining a
high-quality image across the entire image plane and of easily
maintaining the excellent optical performance also at the time of
the image stabilization with a wide angle of view and the large
aperture ratio.
SUMMARY OF THE INVENTION
[0011] An optical system of an embodiment of the present invention
is an optical system of which a focal length of an entire system is
shorter than a back focus, wherein, when an image stabilizing lens
unit, which moves in a direction including a component
perpendicular to an optical axis to move an imaging position, is
arranged at a position adjacent to an aperture diaphragm on an
image side, a cemented lens obtained by cementing a positive lens
and a negative lens is arranged on an object side of the aperture
diaphragm, the focal length of the entire system is set to f, a
focal length of the image stabilizing lens unit is set to fis, a
focal length of the cemented lens is set to fc, a distance on the
optical axis from the aperture diaphragm to a lens surface on the
object side of the image stabilizing lens unit is set to Dis, and a
distance on the optical axis from a first lens surface on a side
closest to an object to a final lens surface on a side closest to
an image when an infinite-distance object is brought into focus is
set to DL, condition equations
0.00<Dis/DL<0.25,
0.3<fis/f<3.5, and
0.3<-fc/fis<3.5
are satisfied.
[0012] Further features of the present invention will become
apparent from the following description of exemplary embodiments
(with reference to the attached drawings).
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 is a cross-sectional view of a lens of a first
embodiment;
[0014] FIG. 2 is a longitudinal aberration diagram of the first
embodiment;
[0015] FIGS. 3A and 3B are lateral aberration diagrams in a
reference state and at the time of 0.3.degree. image stabilization
correction of the first embodiment of the present invention,
respectively;
[0016] FIG. 4 is a cross-sectional view of a lens of a second
embodiment;
[0017] FIG. 5 is a longitudinal aberration diagram of the second
embodiment;
[0018] FIGS. 6A and 6B are lateral aberration diagrams in a
reference state and at the time of 0.3.degree. image stabilization
correction of the second embodiment of the present invention,
respectively;
[0019] FIG. 7 is a cross-sectional view of a lens of a third
embodiment;
[0020] FIG. 8 is a longitudinal aberration diagram of the third
embodiment;
[0021] FIGS. 9A and 9B are lateral aberration diagrams in a
reference state and at the time of 0.3.degree. image stabilization
correction of the third embodiment of the present invention,
respectively;
[0022] FIG. 10 is a cross-sectional view of a lens of a fourth
embodiment;
[0023] FIG. 11 is a longitudinal aberration diagram of the fourth
embodiment;
[0024] FIGS. 12A and 12B are lateral aberration diagrams in a
reference state and at the time of 0.3.degree. image stabilization
correction of the fourth embodiment of the present invention,
respectively; and
[0025] FIG. 13 is a schematic diagram of a substantial part of an
imaging apparatus according to an embodiment of the present
invention.
DESCRIPTION OF THE EMBODIMENTS
[0026] A preferred embodiment of the present invention is
hereinafter described in detail with reference to the attached
drawings. In an optical system of an embodiment of the present
invention, a focal length of an entire system is shorter than a
back focus. An image stabilizing lens unit, which moves in a
direction including a component perpendicular to an optical axis to
move an imaging position, is arranged at a position adjacent to an
aperture diaphragm on an image side. A cemented lens obtained by
cementing a positive lens and a negative lens is arranged on an
object side of the aperture diaphragm.
[0027] FIG. 1 is a cross-sectional view of a lens of a first
embodiment of the present invention and FIG. 2 is a longitudinal
aberration diagram when an infinite-distance object is brought into
focus of the first embodiment. FIGS. 3A and 3B are lateral
aberration diagrams in a reference state and at the time of
0.3.degree. image stabilization correction of the first embodiment
of the present invention, respectively. FIG. 4 is a cross-sectional
view of a lens of a second embodiment of the present invention and
FIG. 5 is a longitudinal aberration diagram when an
infinite-distance object is brought into focus of the second
embodiment. FIGS. 6A and 6B are lateral aberration diagrams in a
reference state and at the time of 0.3.degree. image stabilization
correction of the second embodiment of the present invention,
respectively.
[0028] FIG. 7 is a cross-sectional view of a lens of a third
embodiment of the present invention and FIG. 8 is a longitudinal
aberration diagram when an infinite-distance object is brought into
focus of the third embodiment. FIGS. 9A and 9B are lateral
aberration diagrams in a reference state and at the time of
0.3.degree. image stabilization correction of the third embodiment
of the present invention, respectively. FIG. 10 is a
cross-sectional view of a lens of a fourth embodiment of the
present invention and FIG. 11 is a longitudinal aberration diagram
when an infinite-distance object is brought into focus of the
fourth embodiment. FIGS. 12A and 12B are lateral aberration
diagrams in a reference state and at the time of 0.3.degree. image
stabilization correction of the fourth embodiment of the present
invention, respectively. FIG. 13 is a schematic diagram of a
substantial part of a single-lens reflex camera (imaging apparatus)
provided with the optical system in an embodiment of the present
invention.
[0029] The optical system of each embodiment is an imaging optical
system used in the imaging apparatus (optical apparatus) such as a
digital still camera, a video camera, and a silver-halide film
camera. In the cross-sectional view of the lens, a left side is the
object side (front side) and a right side is the image side (rear
side). Meanwhile, the optical system of each embodiment may also be
used as a projection lens of a projector and the like. At that
time, the left side is a screen and the right side is an image to
be projected.
[0030] In the cross-sectional view of the lens, a reference sign LA
represents the optical system. The optical system LA includes a
front lens unit LF on the object side and a rear lens unit LR with
positive refractive power on the image side across an aperture
diaphragm SP. Reference signs L1 and L2 represent a first lens unit
with positive or negative refractive power, which does not move
during focusing, and a second lens unit with positive refractive
power, which moves during focusing, respectively.
[0031] The second lens unit L2 includes a lens unit on each of the
object side and the image side of the aperture diaphragm
(diaphragm) SP. The second lens unit L2 includes an image
stabilizing lens unit Gis including a single lens or a cemented
lens at the position adjacent to the aperture diaphragm SP on the
image side. A reference sign Lc represents the cemented lens with
negative refractive power arranged on the object side of the image
stabilizing lens unit Gis. A reference sign IP represents an image
plane, which corresponds to an image sensing plane of a solid-state
image sensing device (photoelectric transducer) such as a CCD
sensor and a CMOS sensor when the imaging optical system is used as
that of the video camera and the digital still camera and
corresponds to a film plane when this is used in the silver-halide
film camera.
[0032] Each longitudinal aberration diagram illustrates a spherical
aberration, astigmatism, a distortion, and a magnification
chromatic aberration in order from left to right. In the diagrams,
which illustrate the spherical aberration and the magnification
chromatic aberration, a solid line indicates a d-line (587.6 nm)
and a broken line indicates a g-line (435.8 nm). In the diagram,
which illustrates the astigmatism, a solid line S indicates a
sagittal direction of the d-line and a broken line M indicates a
meridional direction of the d-line. The diagram, which illustrates
the distortion, illustrates the distortion in the d-line. In the
lateral aberration diagram, a solid line, a broken line, and a
two-dot chain line indicate the meridional direction of the d-line,
the sagittal direction of the d-line, and the meridional direction
of the g-line, respectively. Reference signs Fno, .omega., and hgt
represent an F-number, a half angle of view (degree) of an angle of
view for shooting, and an image height, respectively.
[0033] A specific configuration of the optical system of an
embodiment of the present invention is an imaging optical system
including the first lens unit L1 with positive or negative
refractive power and the second lens unit L2 with positive
refractive power in order from the object side to the image side.
The imaging optical system performs focusing by moving the second
lens unit L2 on the optical axis. The first lens unit L1 includes a
negative lens in a meniscus shape having a convex surface on the
object side and a positive lens having a surface in a convex shape
on the object side in order from the object side to the image side.
The second lens unit L2 includes a lens with negative refractive
power (negative lens) in the meniscus shape having a concave
surface on the image side, a lens with positive refractive power
(positive lens), the cemented lens with negative refractive power
obtained by cementing the positive lens and the negative lens, and
the aperture diaphragm in order from the object side to the image
side.
[0034] The second lens unit L2 further includes the image
stabilizing lens unit Gis with positive refractive power, which
reduces an image shake by moving in the direction including the
component in the direction perpendicular to the optical axis, a
cemented lens obtained by cementing a negative lens and a positive
lens, and a positive lens on the image side of the aperture
diaphragm SP.
[0035] In general, in the imaging optical system, a height of an
off-axis ray at a maximum angle of view from the optical axis is
higher as a distance from the aperture diaphragm SP in an optical
axis direction is larger. Therefore, an effective ray diameter of
the lens arranged at a position apart from the aperture diaphragm
SP becomes larger. Therefore, when the image stabilizing lens unit
Gis is arranged in the vicinity of the aperture diaphragm SP, the
effective ray diameter thereof becomes smaller and a small lens
diameter may be easily realized even when movement for image
stabilization is taken into account. Since an incident height of a
ray, which passes through the image stabilizing lens unit Gis, is
low, aberration variation at the time of the image stabilization
may easily be made small.
[0036] Therefore, in the optical system of each embodiment, the
image stabilizing lens unit is arranged in a position near the
aperture diaphragm SP as described above for inhibiting an
effective diameter of the image stabilizing lens unit from becoming
large. As a result, a load on a driving mechanism of the image
stabilizing lens is decreased and an entire lens may be made
compact easily. At the same time, the lens unit at the position
near the aperture diaphragm SP in an entire system is made the
image stabilizing lens unit, which moves in the direction including
the component in the direction perpendicular to the optical axis.
According to this, the optical system in which the height of the
off-axis ray, which passes through the image stabilizing lens unit,
is low and the aberration variation of the off-axis ray at the time
of the image stabilization is small is realized.
[0037] Especially, when a large aperture is realized, a lens
diameter of the optical system becomes larger and the lens diameter
of the image stabilizing lens unit also becomes larger. The image
stabilizing lens unit becomes heavier along with the increase in
lens diameter and an image stabilizing driving mechanism becomes
further larger. When the large aperture is realized, a light-weight
image stabilizing lens unit is preferable and the number of lenses
is desirably made small. However, when the large aperture is
realized, a diameter of luminous flux of the on-axis ray becomes
larger and optical performance is deteriorated due to coma
aberration variation at the time of the image stabilization.
[0038] For the above-described reason, in the imaging optical
system, it is important to efficiently cancel out the aberration
occurring in the image stabilizing lens unit Gis including a small
number of lenses by another lens unit such that the aberration may
be sufficiently corrected also at the time of the image
stabilization using a small number of lenses. Therefore, in the
optical system of each embodiment, the cemented lens Lc with
negative refractive power as a whole obtained by cementing the lens
with positive refractive power and the lens with negative
refractive power as a supplementary lens unit is arranged on the
object side of the image stabilizing lens unit Gis.
[0039] According to this, sufficient aberration correction may be
performed even with a small number of lenses. Since the image
stabilizing lens unit Gis includes one lens (image stabilizing
lens), the image stabilizing lens unit Gis is not excessively heavy
also when a large aperture ratio is realized and it becomes easy to
compose the image stabilizing lens unit without a large burden on
the image stabilizing driving mechanism. Since the refractive power
with different signs is applied to the image stabilizing lens unit
Gis and the supplementary lens unit Lc adjacent to the same in this
manner, it becomes easy to apply appropriate image shaking
sensitivity to the image stabilizing lens unit Gis.
[0040] In each embodiment, the image stabilizing lens unit Gis is
displaced in a direction including a component perpendicular to the
optical axis for the image stabilization to correct the image shake
caused by vibration such as a camera shake. Herein, the "direction
including the component in the direction orthogonal to the optical
axis" includes not only a direction orthogonal to the optical axis
but also a direction shifted from the direction orthogonal to the
optical axis (for example, a direction inclined with respect to the
direction orthogonal to the optical axis and a rotation direction
around a point on the optical axis).
[0041] In each embodiment, the focal length of the entire system is
set to f, the focal length of the image stabilizing lens unit Gis
is set to fis, and the focal length of the cemented lens Lc is set
to fc. A distance on the optical axis from the aperture diaphragm
SP to a lens surface on an aperture diaphragm SP side of the image
stabilizing lens unit Gis is set to Dis and the distance on the
optical axis from a first lens surface on the object side to a
final lens surface when the infinite-distance object is brought
into focus is set to DL. At that time, condition equations
0.00<Dis/DL<0.25 (1),
0.3<fis/f<3.5 (2), and
0.3<-fc/fis<3.5 (3)
are satisfied.
[0042] Herein, the "distance on the optical axis" in a direction
from the object side to the image side is with a positive sign and
that in an opposite direction (direction from the image side to the
object side) is with a negative sign.
[0043] Next, a technical meaning of each condition equation
described above is described. The condition equation (1) represents
a condition for realizing an appropriate distance on the optical
axis from the aperture diaphragm SP to the lens surface closest to
the aperture diaphragm SP of the image stabilizing lens unit
Gis.
[0044] When the image stabilizing lens unit Gis is too much away
from the aperture diaphragm SP toward the image side beyond an
upper limit of the condition equation (1), the effective diameter
of the image stabilizing lens unit Gis adversely increases. The
incident height of the off-axis ray, which passes through the image
stabilizing lens unit Gis, from the optical axis also becomes
higher, so that the aberration correction of the off-axis ray at
the time of the image stabilization becomes difficult. When the
image stabilizing lens unit Gis gets so closer to the aperture
diaphragm SP as to approach a lower limit of the condition equation
(1), interference between the aperture diaphragm SP and the image
stabilizing lens unit Gis adversely easily occurs. Meanwhile, a
numerical range of the condition equation (1) is more preferably
set as follows:
0.00<Dis/DL<0.07 (1a).
[0045] The condition equation (2) is the condition equation for
maintaining sensitivity in aberration variation and sensitivity in
displacement of an image position in a balanced manner when the
image stabilizing lens unit Gis is displaced in the direction
perpendicular to the optical axis by realizing an appropriate ratio
of the focal length of the image stabilizing lens unit Gis to the
focal length of the entire system. When the refractive power of the
image stabilizing lens unit Gis becomes weaker beyond the upper
limit of the condition equation (2), an amount of movement in the
direction including the component in the direction perpendicular to
the optical axis becomes larger at the time of the image
stabilization, so that the driving mechanism becomes larger.
[0046] When the refractive power of the image stabilizing lens unit
Gis becomes stronger beyond the lower limit of the condition
equation (2), a large eccentric aberration occurs at the time of
the image stabilization and the optical performance at the time of
the image stabilization is adversely deteriorated. An amount of
change of the image position with respect to an amount of
displacement of the image stabilizing lens unit Gis (hereinafter,
referred to as the image shaking sensitivity) becomes large, so
that the amount of displacement of the image stabilizing lens unit
Gis for obtaining a required image stabilization effect becomes too
small and it becomes difficult to electrically or mechanically
control the amount of displacement at high accuracy. The numerical
range of the condition equation (2) is further preferably set as
follows:
0.5<fis/f<3.0 (2a).
[0047] The condition equation (3) is for appropriately setting
refractive power balance between the image stabilizing lens unit
Gis and the cemented lens (supplementary lens) Lc obtained by
cementing the lens with positive refractive power and the lens with
negative refractive power on the object side thereof. This is
especially the condition equation for maintaining appropriate
balance between aberration correction share and sensitivity in
image position correction when the image stabilizing lens unit Gis
is displaced in the direction perpendicular to the optical axis. In
each embodiment, the cemented lens Lc is arranged on the object
side of the image stabilizing lens unit Gis for inhibiting an axial
chromatic aberration, which occurs when the appropriate refractive
power balance is realized.
[0048] When the refractive power of the image stabilizing lens unit
Gis becomes stronger beyond the upper limit of the condition
equation (3), the larger eccentric aberration occurs at the time of
the image stabilization and the optical performance is
deteriorated. When the refractive power of the image stabilizing
lens unit Gis becomes weaker beyond the lower limit of the
condition equation (3), the image shaking sensitivity becomes too
low and the amount of drive in the direction including the
component perpendicular to the optical axis becomes larger at the
time of the image stabilization, so that the driving mechanism
becomes adversely larger. The numerical range of the condition
equation (3) is further preferably set as follows:
0.5<-fc/fis<3.0 (3a).
[0049] In each embodiment, the above-described conditions are
satisfied for obtaining a wide-view-angle lens, which makes it easy
to obtain a compact image stabilizing lens unit Gis and makes it
possible to obtain an excellent image also at the time of the image
stabilization with the high optical performance. Also, in each
embodiment, the lens with positive refractive power having an
aspherical surface is preferably arranged on a side closest to the
image plane. By arranging the lens with positive refractive power
having an aspherical surface shape on a side closest to the image,
tilt of a sagittal image plane may be reduced and it becomes easy
to obtain the excellent optical performance also on the periphery
of an image plane.
[0050] In each embodiment, one or more of following condition
equations is desirably satisfied in order to obtain the high
optical performance while maintaining the excellent optical
performance at the time of the image stabilization. Lateral
magnification of the image stabilizing lens unit Gis is set to
.beta.is and the lateral magnification of the lens unit arranged on
the image side of the image stabilizing lens unit Gis is set to
.beta.r. The image stabilizing lens unit Gis includes the single
lens and an Abbe number of a material of the single lens with
respect to the d-line is set to .nu.dis. At that time, one or more
of the following condition equations is preferably satisfied:
0.1<|(1-.beta.is).beta.r|<1.3 (4) and
35<.nu.dis (5).
[0051] The condition equation (4) relates to a ratio between the
amount of movement of the image stabilizing lens unit Gis in the
direction perpendicular to the optical axis and an image point
moving amount on an imaging plane generated according to this, and
the larger this value is, the smaller the amount of movement for
large and easy movement of the image point is. Hereinafter, a value
of the condition equation (4) is referred to as the image shaking
sensitivity.
[0052] When the image shaking sensitivity is too high beyond the
upper limit of the condition equation (4), the amount of
displacement (amount of movement) of the image stabilizing lens
unit Gis for obtaining a certain image stabilization effect becomes
too small and electrical or mechanical drive for the amount of
movement at high accuracy becomes difficult. When the image shaking
sensitivity is too low beyond the lower limit of the condition
equation (4), the amount of movement so as to include the component
in the direction perpendicular to the optical axis at the time of
the image stabilization becomes larger and the driving mechanism
adversely becomes larger. The numerical range of the condition
equation (4) is further preferably set as follows:
0.2<|(1-.beta.is).beta.r|<1.0 (4a).
[0053] The condition equation (5) relates to the Abbe number of the
material of the image stabilizing lens, which composes the image
stabilizing lens unit Gis, with respect to the d-line and is the
condition equation for correcting especially a chromatic aberration
such as the axial chromatic aberration and the magnification
chromatic aberration out of the aberrations occurring at the time
of the image stabilization in an excellent manner.
[0054] The image stabilizing lens unit Gis desirably includes as
few lenses as possible for downsizing and weight saving. The image
stabilizing lens unit Gis most preferably includes one positive
lens or one negative lens. That is, the image stabilizing lens unit
Gis most preferably includes the single lens. When the Abbe number
of the material, which composes the image stabilizing lens unit
Gis, is small beyond the lower limit of the condition equation (5),
the chromatic aberration such as the axial chromatic aberration and
the magnification chromatic aberration occurring at the time of the
image stabilization becomes large and it becomes difficult to
correct them. The numerical range of the condition equation (5) is
further preferably set as follows:
40<.nu.dis (5a).
[0055] As described above, according to each embodiment, a
so-called retrofocus-type optical system in which the focal length
of the entire system is shorter than the back focus having the
excellent optical performance without large various aberrations
occurring at the time of the image stabilization is obtained. At
the same time, a compact optical system having a simple lens
configuration in which an excessive load does not occur in the
mechanism for driving the image stabilizing lens unit is easily
obtained.
[0056] Next, an embodiment of a single-lens reflex camera system
(imaging apparatus) in which the optical system of an embodiment of
the present invention is used is described with reference to FIG.
13. In FIG. 13, reference numerals 10 and 11 represent a
single-lens reflex camera main body and an interchangeable lens
equipped with the optical system according to an embodiment of the
present invention, respectively. A reference numeral 12 represents
a recording unit such as a film and an image sensing device for
recording a subject image obtained through the interchangeable lens
11. Reference numerals 13 and 14 represent a viewfinder optical
system for observing the subject image from the interchangeable
lens 11 and a quick-return mirror, which rotates, for transmitting
the subject image formed by the interchangeable lens 11 to the
recording unit 12 and the viewfinder optical system 13 in a
switching manner.
[0057] When the subject image is observed in the viewfinder, the
subject image formed on a focusing plate 15 through the
quick-return mirror 14 is made an erect image by a pentagonal prism
16 and enlarged to be observed by an eyepiece optical system 17. At
the time of shooting, the quick-return mirror 14 rotates in a
direction indicated by an arrow and the subject image is formed on
the recording unit 12 to be recorded. Reference numerals 18 and 19
represent a sub mirror and a focus detecting unit, respectively. It
is possible to realize the imaging apparatus having the high
optical performance by applying the optical system of an embodiment
of the present invention to the imaging apparatus such as the
interchangeable lens of the single-lens reflex camera and the like
in this manner. Meanwhile, the optical system of an embodiment of
the present invention may also be applied to a mirrorless camera
without the quick-return mirror.
[0058] First to fourth numerical embodiments corresponding to the
first to fourth embodiments, respectively, are hereinafter
described. In each numerical embodiment, reference signs i and ri
represent an order of surfaces from the object side and a curvature
radius of i-th one (i-th surface), respectively. A reference sign
di represents an interval between the i-th surface and an (i+1)-th
surface. Reference signs ndi and .nu.di represent a refractive
index and the Abbe number based on the d-line, respectively. A
reference sign BF represents the back focus. The surface with a
mark * is the aspherical surface. (Aspherical surface data)
indicates an aspherical surface coefficient when the aspherical
surface is represented by an equation
x=(h.sup.2/R)/[1+{1-(1+k)(h/R).sup.2}.sup.1/2+A4h.sup.4+A6h.sup.6+A8h.su-
p.8+A10h.sup.10+A12h.sup.12,
wherein x represents an amount of displacement from a reference
plane in the optical axis direction, h represents a height in the
direction perpendicular to the optical axis, and R represents a
radius of a secondary curved surface, which is a base.
[0059] Reference signs A4, A6, A8, A10, and A12 are fourth-order,
sixth-order, eighth-order, tenth-order, and twelfth-order
aspherical surface coefficients, respectively. Meanwhile,
representation "e-Z" is intended to mean "10.sup.-z". A
relationship between each of the above-described condition
equations and various values in the numerical embodiments is
indicated in table 1.
First Numerical Embodiment
TABLE-US-00001 [0060] unit: mm Surface Data surface number r d nd
.nu.d 1 107.841 2.00 1.48749 70.2 2 36.325 3.37 3 60.900 4.53
1.77250 49.6 4 253.393 9.91 5 478.362 1.50 1.58144 40.8 6 19.063
9.05 7 32.422 4.55 1.88300 40.8 8 -98.623 3.98 9 -54.460 3.64
1.88300 40.8 10 -20.463 1.00 1.61293 37.0 11 63.422 3.24 12
(diaphragm) .infin. 2.68 13 69.180 2.29 1.69680 55.5 14 -128.073
5.46 15 -15.746 0.95 1.73800 32.3 16 -131.434 4.37 1.59522 67.7 17
-18.862 0.20 18* -91.820 3.48 1.58313 59.4 19 -23.365 Aspherical
Surface Data 18th surface K = 0.00000e+000 A 4 = -1.49529e-005 A 6
= 4.91763e-009 A 8 = -4.11063e-011 focal length 34.49 F number 2.05
half angle of view (degree) 32.10 image height 21.64 total lens
length 104.50 BF 38.30
Second Numerical Embodiment
TABLE-US-00002 [0061] unit: mm Surface Data surface number r d nd
.nu.d 1 132.460 2.00 1.62299 58.2 2 34.266 4.76 3 93.710 4.21
1.77250 49.6 4 -524.055 9.95 5 68.381 1.50 1.60562 43.7 6 22.966
7.04 7 27.744 6.32 1.83481 42.7 8 -106.109 2.76 9 -52.472 3.53
1.83400 37.2 10 -23.397 1.10 1.59551 39.2 11 36.125 3.72 12
(diaphragm) .infin. 2.35 13 72.096 2.30 1.72916 54.7 14 -124.797
5.65 15 -14.420 1.00 1.78472 25.7 16 -102.223 3.96 1.83481 42.7 17
-20.023 0.20 18* -58.818 4.29 1.58313 59.4 19 -20.458 Aspherical
Surface Data 18th surface K = 0.00000e+000 A 4 = -1.82729e-005 A 6
= 3.11467e-008 A 8 = -5.17296e-010 A10 = 2.93372e-012 A12 =
-5.92984e-015 focal length 34.49 F number 2.02 half angle of view
(degree) 32.10 image height 21.64 total lens length 104.24 BF
37.58
Third Numerical Embodiment
TABLE-US-00003 [0062] unit: mm Surface Data surface number r d nd
.nu.d 1 71.195 2.00 1.48749 70.2 2 36.050 3.76 3 63.886 4.12
1.77250 49.6 4 221.701 11.17 5 -214.904 1.50 1.58144 40.8 6 19.706
8.54 7 37.566 4.39 1.88300 40.8 8 -77.437 4.20 9 -49.840 3.75
1.88300 40.8 10 -19.588 1.00 1.60342 38.0 11 202.255 2.40 12
(diaphragm) .infin. 2.64 13 98.946 1.79 1.72916 54.7 14 -203.419
5.7 15 -15.432 0.95 1.68893 31.1 16 -78.954 4.52 1.49700 81.5 17
-17.330 0.20 18* -104.072 3.57 1.58313 59.4 19 -23.339 Aspherical
Surface Data 18th surface K = 0.00000e+000 A 4 = -1.57839e-005 A 6
= 8.94837e-009 A 8 = -5.94828e-011 focal length 34.5 F number 2.05
half angle of view (degree) 32.09 image height 21.64 total lens
length 104.5 BF 38.3
Fourth Numerical Embodiment
TABLE-US-00004 [0063] unit: mm Surface Data surface number r d nd
.nu.d 1 156.683 2.00 1.48749 70.2 2 39.154 3.56 3 75.419 4.65
1.77250 49.6 4 -24596.307 10.41 5 -220.720 1.50 1.58144 40.8 6
19.974 7.76 7 32.644 4.39 1.88300 40.8 8 -112.408 4.77 9 -61.668
3.78 1.88300 40.8 10 -20.465 1.00 1.62004 36.3 11 114.664 2.62 12
(diaphragm) .infin. 2.52 13 74.645 2.15 1.72916 54.7 14 -129.232
5.32 15 -16.296 0.95 1.73800 32.3 16 -293.682 5.27 1.59522 67.7 17
-20.362 0.20 18* -67.364 3.35 1.58313 59.4 19 -22.066 Aspherical
Surface Data 18th surface K = 0.00000e+000 A 4 = -1.61559e-005 A 6
= 3.74810e-009 A 8 = -5.07547e-011 focal length 34.47 F number 2.05
half angle of view (degree) 32.11 image height 21.64 total lens
length 104.5 BF 38.3
TABLE-US-00005 TABLE 1 Condition First Second Third Fourth
equations embodiment embodiment embodiment embodiment (1) 0.040
0.035 0.040 0.038 (2) 1.88 1.83 2.65 1.89 (3) 1.23 0.71 1.81 2.30
(4) 0.614 0.603 0.432 0.613 (5) 55.5 54.7 54.7 54.7
[0064] While the present invention has been described with
reference to exemplary embodiments, it is to be understood that the
invention is not limited to the disclosed exemplary embodiments.
The scope of the following claims is to be accorded the broadest
interpretation so as to encompass all such modifications and
equivalent structures and functions.
[0065] This application claims the benefit of Japanese Patent
Application No. 2012-072806, filed Mar. 28, 2012, which is hereby
incorporated by reference herein in its entirety.
* * * * *