U.S. patent application number 11/552542 was filed with the patent office on 2007-06-21 for optical system and optical apparatus including optical system.
This patent application is currently assigned to CANON KABUSHIKI KAISHA. Invention is credited to Makoto Misaka.
Application Number | 20070139794 11/552542 |
Document ID | / |
Family ID | 38173123 |
Filed Date | 2007-06-21 |
United States Patent
Application |
20070139794 |
Kind Code |
A1 |
Misaka; Makoto |
June 21, 2007 |
OPTICAL SYSTEM AND OPTICAL APPARATUS INCLUDING OPTICAL SYSTEM
Abstract
At least one exemplary embodiment is directed to an optical
system which includes at least one first refractive optical
element, which includes a solid material satisfying the following
conditional expression (1), and at least one second refractive
optical element, which includes a solid material satisfying the
following conditional expression (2):
-1.33.times.10.sup.-3.times..nu.d+6.7.times.10.sup.-1<.theta.gF
(1)
-1.63.times.10.sup.-3.times..nu.d+6.2.times.10.sup.-1>.theta.gF
(2) where .nu.d and .theta.gF indicate the Abbe number and the
partial dispersion ratio, respectively.
Inventors: |
Misaka; Makoto;
(Saitama-shi, JP) |
Correspondence
Address: |
CANON U.S.A. INC. INTELLECTUAL PROPERTY DIVISION
15975 ALTON PARKWAY
IRVINE
CA
92618-3731
US
|
Assignee: |
CANON KABUSHIKI KAISHA
Tokyo
JP
|
Family ID: |
38173123 |
Appl. No.: |
11/552542 |
Filed: |
October 25, 2006 |
Current U.S.
Class: |
359/781 |
Current CPC
Class: |
G02B 15/173 20130101;
G02B 15/144511 20190801; G02B 13/02 20130101; G02B 15/145121
20190801; G02B 27/0062 20130101; G02B 15/146 20190801 |
Class at
Publication: |
359/781 |
International
Class: |
G02B 9/34 20060101
G02B009/34 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 15, 2005 |
JP |
2005-361953 |
Claims
1. An optical system comprising: at least one first refractive
optical element which includes a solid material satisfying the
following conditional expression (1); and at least one second
refractive optical element which includes a solid material
satisfying the following conditional expression (2):
-1.33.times.10.sup.-3.times..nu.d+6.7.times.10.sup.-1<.theta.gF
(1)
-1.63.times.10.sup.-3.times..nu.d+6.2.times.10.sup.-1>.theta.gF
(2) where .nu.d and .theta.gF indicate the Abbe number and the
partial dispersion ratio, respectively.
2. The optical system according to claim 1, further comprising: a
first lens unit having a positive refractive power; a second lens
unit having a negative refractive power; a third lens unit having a
positive refractive power; a fourth lens unit having a negative
refractive power; and a fifth lens unit having a positive
refractive power, the lens units being aligned in this order from a
position adjacent to an object to a position adjacent to an
image-taking side, wherein gaps between each two adjacent lens
units are changed during zooming such that the gap between the
first and second lens units is increased, the gap between the
second and third lens units is reduced, the gap between the third
and fourth lens units is increased, and the gap between the fourth
and fifth lens units is reduced at the telephoto end compared with
those at the wide-angle end.
3. The optical system according to claim 2, wherein the first,
second, and fifth lens units each include at least one of the first
and second refractive optical elements.
4. The optical system according to claim 1, further comprising: a
first lens unit having a negative refractive power; a second lens
unit having a positive refractive power; a third lens unit having a
negative refractive power; and a fourth lens unit having a positive
refractive power, the lens units being aligned in this order from a
position adjacent to an object to a position adjacent to an
image-taking side, wherein gaps between each two adjacent lens
units are changed during zooming such that the gap between the
first and second lens units is reduced, the gap between the second
and third lens units is increased, and the gap between the third
and fourth lens units is reduced at the telephoto end compared with
those at the wide-angle end.
5. The optical system according to claim 4, wherein the first,
second, and fourth lens units each include at least one of the
first and second refractive optical elements.
6. The optical system according to claim 1, wherein an image is
formed on a photoelectric transducer.
7. An optical apparatus comprising: the optical system according to
claim 1; and an imaging device, wherein the optical system forms an
image in the imaging device.
8. The optical apparatus according to claim 7, wherein the imaging
device is a camera.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to optical systems and optical
apparatuses including the optical systems.
[0003] 2. Description of the Related Art
[0004] To date, optical systems having a short lens length (optical
length; length from a first lens adjacent to an object to an image
plane) have been demanded for optical apparatuses such as digital
still cameras, video cameras, and projectors.
[0005] In general, compact optical systems having a short lens
length tend to suffer from a greater amount of aberration, in
particular, a greater amount of longitudinal and lateral chromatic
aberration, resulting in lower optical performance.
[0006] In particular, the amount of chromatic aberration is
increased in optical systems having a shortened lens length.
[0007] Well-known optical systems include lens systems of a
so-called negative-lead type having a lens unit with a negative
refractive power disposed in the anterior position and a lens unit
with a positive refractive power disposed in the posterior
position. Herein, the anterior position of the optical systems
refers to a position adjacent to an object in the case of optical
imaging systems such as cameras, or a position adjacent to a screen
in the case of optical projection systems such as liquid-crystal
projectors (magnification side). Also, the posterior position of
the optical systems refers to a position adjacent to an
image-taking side in the case of the optical imaging systems, or a
position adjacent to an original picture in the case of the optical
projection systems (demagnification side).
[0008] Since optical systems of the negative-lead type have a lens
unit with a negative refractive power in the anterior position,
negative distortion can easily occur. In order to correct the
aberration, materials having high refractive indices may be used
for negative lenses in lens units having a negative refractive
power.
[0009] However, glass having a high refractive index generally has
a high dispersion, and easily causes a greater amount of negative
lateral chromatic aberration.
[0010] In order to reduce the generation of chromatic aberration,
materials having anomalous partial dispersion may be used, or
diffractive optical elements may be disposed in optical paths.
[0011] In general, a lens having a positive refractive power, which
includes a low-dispersion optical material with an anomalous
partial dispersion such as fluorite, and a lens having a negative
refractive power, which includes a high-dispersion optical
material, are used for reducing the occurrence of chromatic
aberration. Optical systems including such lenses have been
discussed in, for example, Japanese Patent Laid-Open No. 2002-62478
and U.S. Pat. No. 6,404,561.
[0012] Moreover, liquid materials having a relatively high
dispersion and a relatively high anomalous partial dispersion, and
achromatic optical systems including such liquid materials are also
known (U.S. Pat. No. 4,913,535).
[0013] When a material having an anomalous partial dispersion is
used for correcting the chromatic aberration of an optical system,
the number of lenses in the optical system tends to be increased,
thereby increasing the optical length. Moreover, it is very
difficult to machine anomalous partial dispersion glass such as
fluorite.
[0014] Furthermore, the specific gravity of the material is
relatively large compared with that of other low-dispersion glasses
without anomalous partial dispersion, and thus the entire lens
system tends to be increased in weight. For example, the specific
gravity of fluorite is 3.18, and that of a glass known under the
trade name of FK01 is 3.63.
[0015] In contrast, the specific gravities of trade name materials
FK5 and BK7 having low anomalous partial dispersion are 2.46 and
2.52, respectively.
[0016] Surfaces of anomalous partial dispersion glasses are easily
damaged, and anomalous partial dispersion glasses having large
diameters can be easily cracked with sudden temperature changes.
Thus, application of materials having anomalous partial dispersion
to optical systems is limited.
[0017] Liquid materials as discussed in U.S. Pat. No. 4,913,535
require structures for hermetically containing the liquid
materials, resulting in difficulties in manufacturing optical
systems including such materials. Also, it is difficult to apply
the liquid materials to optical systems due to changes in
refractive indices and dispersion characteristics according to
temperature.
SUMMARY OF THE INVENTION
[0018] At least one exemplary embodiment is directed to an optical
system that can be used in an optical apparatus (e.g., silver-salt
film cameras, digital still cameras, video cameras, telescopes,
binoculars, projectors, copying machines, and other optical
apparatus as known by one of ordinary skill in the relevant
arts).
[0019] At least one exemplary embodiment is directed to an optical
system capable of appropriately correct chromatic aberration,
capable of being easily manufactured, and having high optical
performance.
[0020] An optical system according to an aspect of the present
invention includes at least one first refractive optical element
which includes a solid material satisfying the following
conditional expression (1), and at least one second refractive
optical element which includes a solid material satisfying the
following conditional expression (2):
-1.33.times.10.sup.-3.times..nu.d+6.7.times.10.sup.-1<.theta.gF
(1)
-1.63.times.10.sup.-3.times..nu.d+6.2.times.10.sup.-1>.theta.gF
(2)
[0021] where .nu.d and .theta.gF indicate the Abbe number and the
partial dispersion ratio, respectively. The Abbe number .nu.d and
the partial dispersion ratio .theta.gF are defined by the following
expressions:
.nu.d=(Nd-1)/(NF-NC)
.theta.gF=(Ng-NF)/(NF-NC)
[0022] where Ng, Nd, NF, and NC indicate refractive indices of the
corresponding materials with respect to g line (wavelength of 435.8
nm), F line (wavelength of 486.1 nm), d line (wavelength of 587.6
nm), and C line (wavelength of 656.3 nm).
[0023] 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
[0024] FIG. 1 is a cross-sectional view of an optical system
according to a first exemplary embodiment of the present
invention.
[0025] FIGS. 2A, 2B, and 2C illustrate aberration in the first
exemplary embodiment.
[0026] FIG. 3 is a cross-sectional view of an optical system
according to a second exemplary embodiment of the present
invention.
[0027] FIGS. 4A, 4B, and 4C illustrate aberration in the second
exemplary embodiment.
[0028] FIG. 5 is a cross-sectional view of an optical system
according to a third exemplary embodiment of the present
invention.
[0029] FIGS. 6A, 6B, and 6C illustrate aberration in the third
exemplary embodiment.
[0030] FIG. 7 is a cross-sectional view of an optical system
according to a fourth exemplary embodiment of the present
invention.
[0031] FIGS. 8A, 8B, and 8C illustrate aberration in the fourth
exemplary embodiment.
[0032] FIG. 9 is a cross-sectional view of an optical system
according to a fifth exemplary embodiment of the present
invention.
[0033] FIG. 10 illustrates aberration in the fifth exemplary
embodiment.
[0034] FIG. 11 is a cross-sectional view of an optical system
according to a sixth exemplary embodiment of the present
invention.
[0035] FIG. 12 illustrates aberration in the sixth exemplary
embodiment.
[0036] FIG. 13 is a schematic view of an imaging apparatus
according to an exemplary embodiment of the present invention.
DESCRIPTION OF THE EMBODIMENTS
[0037] The following description of at least one exemplary
embodiment is merely illustrative in nature and is in no way
intended to limit the invention, its application, or uses.
[0038] Processes, techniques, apparatus, and materials as known by
one of ordinary skill in the relevant art may not be discussed in
detail but are intended to be part of the enabling description
where appropriate, for example the fabrication of the lens elements
and their materials.
[0039] In all of the examples illustrated and discussed herein any
specific values, for example the zoom ratio and F number, should be
interpreted to be illustrative only and non limiting. Thus, other
examples of the exemplary embodiments could have different
values.
[0040] Notice that similar reference numerals and letters refer to
similar items in the following figures, and thus once an item is
defined in one figure, it may not be discussed for following
figures.
[0041] Note that herein when referring to correcting or corrections
of an error (e.g., an aberration), a reduction of the error and/or
a correction of the error is intended.
First Exemplary Embodiment
[0042] FIGS. 1, 3, 5, and 7 are cross-sectional views of lenses at
a wide-angle end. FIGS. 2A to 2C, 4A to 4C, 6A to 6C, and 8A to 8C
illustrate aberration at the wide-angle end (A), at an intermediate
position of a zoom range (B), and at a telephoto end (C). FIGS. 10
and 12 illustrate aberration when a focus of an optical system is
adjusted to an object at infinity.
[0043] Optical systems (e.g., OL1-OL6) according to exemplary
embodiments of the present invention can be used for imaging and/or
optical apparatus (e.g., silver-salt film cameras, digital still
cameras, video cameras, telescopes, binoculars, projectors, copying
machines, and other optical apparatus as known by one of ordinary
skill in the relevant arts). In the cross-sectional views of the
lenses, the left side is adjacent to an object (the anterior
position), and the right side is adjacent to an image-taking side
(the posterior position).
[0044] When the optical systems according to the exemplary
embodiments of the present invention are used as projector lenses
for projectors, the left side is adjacent to a screen and the right
side is adjacent to an original picture.
[0045] In the cross-sectional views of the lenses, reference
characters OL, SP, FS, and FC indicate an optical system, an
aperture stop, an F-number stop, and a flare-cutting stop,
respectively.
[0046] Reference characters Lij indicate ith lens units where i
indicates the ordinal position of the lens unit from the object
side, and j identifies a particular exemplary embodiment's lens
unit (e.g., L1a-f, L2a-f, L3a-f, L4a-f, L5a-c, and L6a).
[0047] An image plane IP corresponds to an imaging surface (e.g.,
the imaging surface) of a solid-state image-pickup device
(photoelectric transducer) such as a charge-coupled device (CCD)
sensor and a complementary metal-oxide semiconductor (CMOS) sensor
when the optical systems are used for video cameras or digital
still cameras; and corresponds to a film surface when the optical
systems are used for silver-salt film cameras.
[0048] Arrows denote tracks of the lens units during zooming from
the wide-angle end to the telephoto end (e.g., A1-A4; B1-B4; C1-C4;
D1-D4; and E1-E3).
[0049] In the aberration drawings, reference characters d and g
denote d line and g line, respectively; and reference characters
.DELTA.M and .DELTA.S denote a meridional image surface and a
sagittal image surface, respectively. The lateral chromatic
aberration is illustrated with the g line. A reference character SC
denotes the offence against the sine condition. Fno and .omega.
indicate the F-number, and the half-angle of view, respectively,
and the Y-axis in the spherical aberration's graph is entrance
pupil radius, the Y-axis in the astigmatism's, distortion's and
chromatic aberration of magnification's graphs is image height.
[0050] The optical systems according to the exemplary embodiments
of the present invention include one or more first refractive
optical elements which include a solid material satisfying the
following conditional expression (1), and one or more second
refractive optical elements which include a solid material
satisfying the following conditional expression (2):
-1.33.times.10.sup.-3.times..nu.d+6.7.times.10.sup.-1<.theta.gF
(1)
-1.63.times.10.sup.-3.times..nu.d+6.2.times.10.sup.-1>.theta.gF
(2)
[0051] Herein, the term "solid materials" refers to materials in a
solid state while the optical systems are used, and can be in any
state before the optical systems are used, for example, during
manufacturing. For example, materials that are in a liquid state
during manufacturing and are hardened into solids correspond to the
solid materials here.
[0052] Moreover, the term "refractive optical elements" herein
refers to refractive lenses that affect incident light by the
action of refraction, and do not include diffractive optical
elements that affect incident light by the action of
diffraction.
[0053] Features of dispersion characteristics of the optical
materials used for the optical systems will now be described.
[0054] In general, during correction of lateral chromatic
aberration in lens systems having a wide angle of view, the g line
becomes overcorrected when the C line and the F line are
appropriately corrected with respect to the d line serving as a
reference wavelength, whereas the F line becomes undercorrected
when the C line and the g line are appropriately corrected with
respect to the d line serving as the reference wavelength.
[0055] In contrast, during correction of lateral chromatic
aberration in telephoto lens systems, the g line becomes
undercorrected when the C line and the F line are appropriately
corrected with respect to the d line serving as the reference
wavelength, whereas the F line becomes overcorrected when the C
line and the g line are appropriately corrected with respect to the
d line serving as the reference wavelength.
[0056] In order to appropriately correct the above types of
aberration, a positive lens, which includes a material having a
small partial dispersion ratio .theta.gF, or a negative lens, which
includes a material having a large partial dispersion ratio
.theta.gF, can be disposed adjacent to the object remote from the
aperture stop in the lens systems having a wide angle of view, for
example.
[0057] Alternatively, a positive lens, which includes a material
having a large partial dispersion ratio .theta.gF, or a negative
lens, which includes a material having a small partial dispersion
ratio .theta.gF, can be disposed adjacent to the image-taking side
remote from the aperture stop.
[0058] In the telephoto lens systems, a positive lens, which
includes a material having a large partial dispersion ratio
.theta.gF, or a negative lens, which includes a material having a
small partial dispersion ratio .theta.gF, can be disposed adjacent
to the object remote from the aperture stop.
[0059] Alternatively, a positive lens, which includes a material
having a small partial dispersion ratio .theta.gF, or a negative
lens, which includes a material having a large partial dispersion
ratio .theta.gF, can be disposed adjacent to the image-taking side
remote from the aperture stop.
[0060] These lenses are not used unconditionally. The Petzval sum
of all the optical systems, effects on aberration such as spherical
aberration and distortion, and fixing of the lens systems to lens
barrels should be considered in order to find the best
solution.
[0061] Accordingly, the optical systems according to the exemplary
embodiments of the present invention include at least one first
refractive optical element such as a lens and a film having a
refractive power, which includes a solid material satisfying the
above-described conditional expression (1), and at least a second
refractive optical element satisfying the above-described
conditional expression (2).
[0062] A non-limiting example of a solid material that satisfies
the conditional expressions (1) and (2) include a resin containing
inorganic particulates dispersed therein.
[0063] For example, solid materials that satisfy the conditional
expression (1) include an ultraviolet (UV) curable resin (Nd=1.635,
.nu.d=22.7, .theta.gF=0.69), and an N-polyvinylcarbazole (Nd=1.696,
.nu.d=17.7, .theta.gF=0.69).
[0064] Other solid materials can be employed as long as the
conditional expression (1) is satisfied.
[0065] Solid materials that satisfy the conditional expression (2)
include a UV curable acrylic polymer containing indium-tin oxide
(ITO) particulates in a mixture ratio of about 1 to 20%, the
acrylic polymer being used as materials for replica aspheric
lenses. When the mixture ratio is 20%, Nd, .nu.d, and .theta.gF of
the material are 1.56987, 13.27, and 0.289, respectively.
[0066] Other sold materials can be employed as long as the
conditional expression (2) is satisfied.
[0067] Signs of refractive power of the lenses or the films having
a refractive power which includes the solid materials can be
arbitrarily selected regardless of directions of correction of the
lateral chromatic aberration as long as the conditional expressions
(1) and (2) are satisfied. As a result, the lateral chromatic
aberration can be appropriately corrected, and at the same time,
corrections of, for example, the longitudinal aberration and the
oblique aberration are facilitated.
[0068] Moreover, correction of the lateral chromatic aberration
using a plurality of refractive optical elements facilitates
balancing the lateral chromatic aberration against the longitudinal
chromatic aberration.
[0069] A more useful range of the conditional expressions (1) and
(2) can be set as below:
-1.33.times.10.sup.-3.times..nu.d+7.0.times.10.sup.-1<.theta.gF
(1a)
-1.63.times.10.sup.-3.times..nu.d+5.0.times.10.sup.-1>.theta.gF
(2a)
Resins used as the solid materials can improve efficiency in mass
production when the resins are shaped by the action of photo
polymerization or thermal polymerization using forming molds.
[0070] Next, features of the individual exemplary embodiments of
the present invention will be described.
[0071] A first exemplary embodiment shown in FIG. 1 discloses a
zoom lens including a first lens unit L1a having a positive
refractive power (optical power; a reciprocal of focal length), a
second lens unit L2a having a negative refractive power, a third
lens unit L3a having a positive refractive power, a fourth lens
unit L4a having a negative refractive power, and a fifth lens unit
L5a having a positive refractive power, the lens units being
aligned in this order from a position adjacent to the object to a
position adjacent to the image-taking side.
[0072] Gaps between the lens units can be changed during zooming
from the wide-angle side to the telephoto side. That is, the gaps
between two adjacent lens units can be changed such that the gap
between the first lens unit L1a and the second lens unit L2a is
increased, the gap between the second lens unit L2a and the third
lens unit L3a is reduced, the gap between the third lens unit L3a
and the fourth lens unit L4a is increased, and the gap between the
fourth lens unit L4a and the fifth lens unit L5a is reduced at the
telephoto end compared with those at the wide-angle end.
[0073] Lenses P1a and P2a can include curable materials, for
example a UV curable acrylic polymer containing ITO particulates in
a mixture ratio of 15% (Nd=1.579, .nu.d=16.5, .theta.gF=0.362).
That is, the lenses P1a and P2a correspond to the second refractive
optical elements according to the first exemplary embodiment of the
present invention.
[0074] A lens P3a can also include curable material, for example a
UV curable resin (Nd=1.635, .nu.d=22.7, .theta.gF=0.69). That is,
the lens P3a corresponds to the first refractive optical element
according to the first exemplary embodiment of the present
invention.
[0075] A second exemplary embodiment shown in FIG. 3 discloses a
zoom lens including a first lens unit L1b having a positive
refractive power, a second lens unit L2b having a negative
refractive power, a third lens unit L3b having a positive
refractive power, a fourth lens unit L4b having a negative
refractive power, and a fifth lens unit L5b having a positive
refractive power, the lens units being aligned in this order from a
position adjacent to the object to a position adjacent to the
image-taking side.
[0076] Gaps between the lens units can be changed during zooming
from the wide-angle side to the telephoto side. That is, the gaps
between two adjacent lens units can be changed such that the gap
between the first lens unit L1b and the second lens unit L2b is
increased, the gap between the second lens unit L2b and the third
lens unit L3b is reduced, the gap between the third lens unit L3
and the fourth lens unit L4b is increased, and the gap between the
fourth lens unit L4b and the fifth lens unit L5b is reduced at the
telephoto end compared with those at the wide-angle end.
[0077] Lenses P1b, P3b, and P4a can include curable material, for
example a UV curable resin (Nd=1.635, .nu.d=22.7, .theta.gF=0.69).
That is, the lenses P1b, P3b, and P4b correspond to the first
refractive optical elements according to the second exemplary
embodiment of the present invention.
[0078] A lens P2b can also include curable material, for example a
UV curable acrylic polymer containing ITO particulates in a mixture
ratio of 15% (Nd=1.579, .nu.d=16.5, .theta.gF=0.362). That is, the
lens P2b corresponds to the second refractive optical element
according to the second exemplary embodiment of the present
invention.
[0079] A third exemplary embodiment shown in FIG. 5 discloses a
zoom lens including a first lens unit L1c having a negative
refractive power, a second lens unit L2c having a positive
refractive power, a third lens unit L3c having a negative
refractive power, a fourth lens unit L4c having a positive
refractive power, a fifth lens unit L5c having a negative
refractive power, and a sixth lens unit L6a having a negative
refractive power, the lens units being aligned in this order from a
position adjacent to the object to a position adjacent to the
image-taking side.
[0080] Gaps between the lens units can be changed during zooming
from the wide-angle side to the telephoto side. That is, the gaps
between two adjacent lens units can be changed such that the gap
between the first lens unit L1c and the second lens unit L2c is
reduced, the gap between the second lens unit L2c and the third
lens unit L3c is increased, the gap between the third lens unit L3c
and the fourth lens unit L4c is reduced, the gap between the fourth
lens unit L4c and the fifth lens unit L5c is increased, and the gap
between the fifth lens unit L5c and the sixth lens unit L6a is
increased at the telephoto end compared with those at the
wide-angle end. The sixth lens unit L6a may not move for
zooming.
[0081] During zooming, the F-number stop FS and the aperture stop
SP move together with the third lens unit L3c.
[0082] Lenses P1c and P2c in the drawing can include curable
materials, for example a UV curable resin (Nd=1.635, .nu.d=22.7,
.theta.gF=0.69). That is, the lenses P1c and P2c correspond to the
first refractive optical elements according to the third exemplary
embodiment of the present invention.
[0083] A lens P3c can also include curable material, for example a
UV curable acrylic polymer containing ITO particulates in a mixture
ratio of 15% (Nd=1.579, .nu.d=16.5, .theta.gF=0.362). That is, the
lens P3c corresponds to the second refractive optical element
according to the third exemplary embodiment of the present
invention.
[0084] A fourth exemplary embodiment shown in FIG. 7 discloses a
zoom lens including a first lens unit L1d having a negative
refractive power, a second lens unit L2d having a positive
refractive power, a third lens unit L3d having a negative
refractive power, and a fourth lens unit L4d having a positive
refractive power, the lens units being aligned in this order from a
position adjacent to the object to a position adjacent to the
image-taking side.
[0085] Gaps between the lens units can be changed during zooming
from the wide-angle side to the telephoto side. That is, the gaps
between two adjacent lens units can be changed such that the gap
between the first lens unit L1d and the second lens unit L2d is
reduced, the gap between the second lens unit L2d and the third
lens unit L3d is increased, and the gap between the third lens unit
L3d and the fourth lens unit L4d is reduced at the telephoto end
compared with those at the wide-angle end.
[0086] During zooming, the F-number aperture stop FS and the
aperture stop SP move together with the third lens unit L3d. The
flare-cutting stop FC may not move during zooming.
[0087] Lenses P1d and P3d in the drawing can include curable
materials, for example a UV curable acrylic polymer containing ITO
particulates in a mixture ratio of 15% (Nd=1.579, .nu.d=16.5,
.theta.gF=0.362). That is, the lenses P1d and P3d correspond to the
second refractive optical elements according to the fourth
exemplary embodiment of the present invention.
[0088] Lenses P2d and P4b can also include curable material, for
example a UV curable resin (Nd=1.635, .nu.d=22.7, .theta.gF=0.69).
That is, the lenses P2d and P4b correspond to the first refractive
optical elements according to the fourth exemplary embodiment of
the present invention.
[0089] A fifth exemplary embodiment shown in FIG. 9 discloses an
image-taking lens of an inverted telephoto (retrofocus) type.
Herein, the image-taking lens of the inverted telephoto type is a
lens system (e.g., including lens units L1e, L2e, L3e, and L4e)
having a lens length longer than the focal length.
[0090] A lens P1e in the drawing can include a curable material,
for example a UV curable resin (Nd=1.635, .nu.d=22.7,
.theta.gF=0.69). That is, the lens P1e corresponds to the first
refractive optical element according to fifth exemplary embodiment
of the present invention.
[0091] A lens P2e can include a curable material, for example a UV
curable acrylic polymer containing ITO particulates in a mixture
ratio of 15% (Nd=1.579, .nu.d=16.5, .theta.gF=0.362), the acrylic
polymer being used as materials for replica aspheric lenses. That
is, the lens P2e corresponds to the second refractive optical
element according to the fifth exemplary embodiment of the present
invention.
[0092] A sixth exemplary embodiment shown in FIG. 11 discloses an
image-taking lens (e.g., including lens units L1f, L2f, L3f, and
L4f) having a wide angle of view.
[0093] A lens P2f in the drawing can include curable material, for
example a UV curable acrylic polymer containing ITO particulates in
a mixture ratio of 15% (Nd=1.579, .nu.d=16.5, .theta.gF=0.362), the
acrylic polymer being used as materials for replica aspheric
lenses. That is, the lens P2f corresponds to the second refractive
optical element according to the sixth exemplary embodiment of the
present invention.
[0094] A lens P1f can also include curable material, for example a
UV curable resin (Nd=1.635, .nu.d=22.7, .theta.gF=0.69). That is,
the lens P1f corresponds to the first refractive optical element
according to the sixth exemplary embodiment of the present
invention.
[0095] Numerical Examples 1 to 6 correspond to the first to sixth
exemplary embodiments, respectively, and will be described below.
In the numerical examples, i, Ri, Di, Ni, and .nu.i, indicate the
ordinal position of the surfaces from the object side, the ith
curvature radius (of the ith surface), the gap between the ith
surface and the (i+1)th surface, the refractive index with respect
to the d line, and the Abbe number with respect to the d line,
respectively.
[0096] The displacement X in the optical-axis direction at a height
h from the optical axis with respect to the vertex of the plane of
the aspherical surface can be expressed by Expression 1.
Expression 1 : ##EQU00001## X = ( 1 / R ) h 2 1 + { 1 - ( 1 + k ) (
h / R ) 2 } + A h 2 + Bh 4 + Ch 6 + Dh 8 + Eh 10 + Fh 12
##EQU00001.2##
[0097] where R and k indicate a paraxial curvature radius and a
conic constant, respectively; and A, B, C, D, E, and F are
aspherical coefficients.
[0098] Notation "e-X" refers to ".times.10.sup.-X". f, Fno, and
.omega. indicate the focal length, the F-number, and the half-angle
of view, respectively. Relationships between the above-described
conditional expressions and the numerical values in the numerical
examples are shown in Table 1.
NUMERICAL EXAMPLE 1
[0099] f=28.90.about.193.15Fno=3.63.about.5.88
2.omega.=73.6.about.12.8
R1=102.694D1=1.50N1=1.846660.nu.1=23.9
R2=67.525D2=0.05N2=1.578566.nu.2=16.5
R3=57.448D3=9.29N3=1.603112.nu.3=60.6
R4=-938.598D4=0.12
R5=48.476D5=4.44N4=1.622992.nu.4=58.2
R6=82.382D6=variable
*R7=73.541D7=1.20N5=1.834807.nu.5=42.7
R8=13.885D8=5.65
R9=-33.988D9=0.60N6=1.578566.nu.6=16.5
R10=-24.239D10=1.00N7=1.834807.nu.7=42.7
R11=52.693D11=0.12
R12=30.334D12=4.52N8=1.755199.nu.8=27.5
R13=-21.950D13=0.60
R14=-17.654D14=0.90N9=1.772499.nu.9=49.6
R15=-69.021D15=variable
R16=SP D16=0.94
R17=43.224D17=4.08N10=1.487490.nu.10=70.2
R18=-30.236D18=0.15
R19=26.744D19=8.13N11=1.487490.nu.11=70.2
R20=-21.083D20=0.90N12=1.805181.nu.12=25.4
R21=-63.759D21=variable
R22=-51.876D22=4.69N13=1.740769.nu.13=27.8
R23=-14.998D23=0.90N14=1.882997.nu.14=40.8
R24=123.097D24=variable
R25=85.239D25=5.21N15=1.583126.nu.15=59.4
*R26=-20.371D26=8.80
R27=-15.933D27=1.50N16=1.698947.nu.16=30.1
R28=-16.645D28=1.01N17=1.635550.nu.17=22.7
R29=-14.231D29=1.50N18=1.805181.nu.18=25.4
R30=-24.910 [0100] \Focal length 28.90 80.81 193.15 [0101] Variable
gap\ [0102] D 6 2.38 29.66 48.63 [0103] D15 19.64 8.93 1.39 [0104]
D21 1.13 6.32 8.17 [0105] D24 7.85 2.66 0.81 [0106] Aspherical
coefficient [0107] 7th surface:A=0.00000e+00 B=3.02479e-06
C=1.16978e-08 D=-1.03310e-10 E=5.98212e-13 F=0.00000e+00 [0108]
26th surface:A=0.00000e+00 B=5.57442e-06 C=2.59073e-08
D=-2.75874e-10 E=1.02062e-12 F=0.00000e+00
NUMERICAL EXAMPLE 2
[0109] f=28.90.about.193.17Fno=3.63.about.5.88
2.omega.=73.6.about.12.8
R1=132.527D1=1.50N1=1.846660.nu.1=23.9
R2=49.733D2=2.52N2=1.635550.nu.2=22.7
R3=67.379D3=7.08N3=1.622992.nu.3=58.2
R4=984.359D4=0.12
R5=51.358D5=7.04N4=1.622992.nu.4=58.2
R6=234.151D6=variable
*R7=73.837D7=1.20N5=1.834807.nu.5=42.7
R8=14.793D8=5.59
R9=-44.796D9=0.21N6=1.578566.nu.6=16.5
R10=-37.512D10=1.00N7=1.834807.nu.7=42.7
R11=45.257D11=0.12
R12=27.772D12=4.32N8=1.755199.nu.8=27.5
R13=-30.460D13=1.02
R14=-19.218D14=0.90N9=1.772499.nu.9=49.6
R15=101.774D15=2.03N10=1.784723.nu.10=25.7
R16=-93.904D16=variable
R17=SP D17=0.70
R18=34.666D18=4.41N11=1.518229.nu.11=58.9
R19=-28.082D19=0.15
R20=37.367D20=4.95N12=1.517417.nu.12=52.4
R21=-20.919D21=0.30N13=1.635550.nu.13=22.7
R22=-18.412D22=0.90N14=1.846660.nu.14=23.9
R23=-118.206D23=variable
R24=-39.813D24=2.43N15=1.728250.nu.15=28.5
R25=-18.948D25=0.90N16=1.882997.nu.16=40.8
R26=-97.865D26=variable
R27=52.675D27=6.09N17=1.583126.nu.17=59.4
*R28=-20.674D28=1.27
R29=315.706D29=2.16N18=1.487490.nu.18=70.2
R30=-126.226D30=3.07
R31=-21.208D31=1.00N19=1.834000.nu.19=37.2
R32=284.744D32=0.66N20=1.635550.nu.20=22.7
R33=-127.140D33=1.00 N21=1.487490.nu.21=70.2
R34=-1536.395 [0110] \Focal length 28.90 80.32 193.17 [0111]
Variable gap\ [0112] D 6 2.42 29.11 48.39 [0113] D16 19.53 9.12
1.56 [0114] D23 1.76 10.01 13.38 [0115] D26 12.22 3.97 0.60 [0116]
Aspherical coefficient [0117] 7th surface:A=0.00000e+00
B=2.67286e-06 C=1.84979e-08 D=-1.56477e-10 E=6.99280e-13
F=0.00000e+00 [0118] 28th surface:A=0.00000e+00 B=1.77385e-05
C=2.96988e-08 D=-1.06404e-10 E=3.66833e-13 F=0.00000e+00
NUMERICAL EXAMPLE 3
[0119] f=24.70.about.67.92Fno=2.90.about.2.90
2.omega.=82.4.about.35.3
*R1=164.900D1=2.50N1=1.772499.nu.1=49.6
R2=32.229D2=12.62
R3=-187.833D3=2.30N2=1.772499.nu.2=49.6
R4=77.226D4=0.15
R5=58.470D5=5.16N3=1.805181.nu.3=25.4
R6=259.048D6=0.05N4=1.635550.nu.4=22.7
R7=116.957D7=variable
R8=117.293D8=1.90N5=1.846660.nu.5=23.8
R9=42.078D9=0.34N6=1.635550.nu.6=22.7
R10=46.333D10=6.98N7=1.696797.nu.7=55.5
R11=-197.890D11=0.15
R12=88.758D12=4.09N8=1.834807.nu.8=42.7
R13=-247.127D13=0.15
R14=45.684D14=4.82N9=1.696797.nu.9=55.5
R15=387.307D15=variable
R16=FS D16=2.10
R17=-154.972D17=1.30N10=1.882997.nu.10=40.8
R18=44.398D18=2.50
R19=-103.592D19=1.61N10=1.772499.nu.10=49.6
R20=28.669D20=4.45N11=1.805181.nu.11=25.4
R21=-214.785D21=1.03
R22=SP D22=variable
R23=130.641D23=1.30N12=1.846660.nu.12=23.9
R24=27.680D24=0.05N13=1.578566.nu.13=16.5
R25=25.754D25=7.33N14=1.516330.nu.14=64.1
R26=-40.387D26=0.15
R27=32.774D27=4.68N15=1.620411.nu.15=60.3
R28=-124.828D28=variable
R29=-97.100D29=2.82N16=1.882997.nu.16=40.8
R30=-41.123D30=0.15
R31=-45.224D31=1.20N17=1.772499.nu.17=49.6
R32=29.258D32=variable
R33=78.519D33=7.61N18=1.583126.nu.18=59.4
*R34=-76.846 [0120] \Focal length 24.70 35.30 67.92 [0121] Variable
gap\ [0122] D 7 54.09 28.54 1.50 [0123] D15 2.98 5.70 17.79 [0124]
D22 16.60 13.88 1.79 [0125] D28 1.19 3.67 9.10 [0126] D32 4.24
11.69 15.90 [0127] Aspherical coefficient [0128] 1st
surface:A=0.00000e+00 B=1.18117e-06 C=1.06699e-09 D=-3.06461e-12
E=3.17212e-15 F=-1.19658e-18 [0129] 34th surface:A=-0.00000e+00
B=8.11421e-07 C=-2.03354e-08 D=1.22131e-10 E=-3.54783e-13
F=3.93194e-16
NUMERICAL EXAMPLE 4
[0130] f=16.49.about.33.98Fno=2.90.about.2.90
2.omega.=105.4.about.65.0
*R1=802.400D1=2.00N1=1.772499.nu.1=49.6
R2=21.308D2=0.32N2=1.578566.nu.2=16.5
R3=21.638D3=16.86
R4=-63.782D4=1.20N3=1.834807.nu.3=42.7
R5=44.159D5=0.34N4=1.524200.nu.4=51.4
*R6=63.976D6=0.15
R7=39.553D7=4.34N5=1.805181.nu.5=25.4
R8=1131.513D8=variable
R9=41.991D9=1.30N6=1.805181.nu.6=25.4
R10=20.820D10=0.54N7=1.635550.nu.7=22.7
R11=23.803D11=8.30N8=1.517417.nu.8=52.4
R12=-107.329D12=0.15
R13=40.735D13=4.22N9=1.696797.nu.9=55.5
R14=-102.029D14=variable
R15=SP D15=1.56
R16=-1875.433D16=1.52N10=1.882997.nu.10=40.8
R17=56.883D17=3.14
R18=-31.008D18=1.00N11=1.617722.nu.11=49.8
R19=29.627D19=5.44N12=1.805181.nu.12=25.4
R20=-108.394D20=1.02
R21=FS D21=variable
R22=32.026D22=7.49N13=1.496999.nu.13=81.5
R23=-26.456D23=0.05N14=1.578566.nu.14=16.5
R24=-28.882D24=1.30N15=1.846660.nu.15=23.9
R25=-44.405D25=0.20
R26=-251.883D26=1.20N16=1.846660.nu.16=23.9
R27=26.924D27=2.31N17=1.635550.nu.17=22.7
R28=71.847D28=4.55N18=1.496999.nu.18=81.5
R29=-68.447D29=0.15
R30=264.450D30=3.00N19=1.730770 .nu.19=40.5
*R31=-132.564D31=variable
R32=FC [0131] \Focal length 16.49 24.00 33.98 [0132] Variable gap\
[0133] D 8 21.43 8.55 1.13 [0134] D14 0.85 5.68 11.12 [0135] D21
10.28 5.45 0.01 [0136] D31 0.00 8.55 20.30 [0137] Aspherical
coefficient [0138] 1st surface:A=0.00000e+00 B=1.62651e-05
C=-2.41951e-08 D=3.40722e-11 E=-2.82586e-14 F=1.10415e-17 [0139]
6th surface:A=0.00000e+00 B=1.41432e-05 C=6.38426e-09
D=-2.43697e-10 E=1.14082e-12 F=-1.78942e-15 [0140] 31st
surface:A=0.00000e+00 B=9.83727e-06 C=8.54996e-09 D= 6.55809e-11
E=-3.22925e-13 F=6.78586e-16
NUMERICAL EXAMPLE 5
[0141] f=24.60Fno=1.46 2.omega.=82.7
R1=65.313D1=2.80N1=1.696797.nu.1=55.5
R2=31.601D2=6.86
R3=76.307D3=2.30N2=1.696797.nu.2=55.5
R4=35.016D4=6.48
R5=322.917D5=4.38N3=1.834000.nu.3=37.2
R6=-101.191D6=3.64
R7=78.925D7=3.46N4=1.846660.nu.4=23.8
R8=-527.679D8=0.05N5=1.635550.nu.5=22.7
R9=173.236D9=1.65N6=1.487490.nu.6=70.2
R10=23.776D10=7.10
R11=FC D11=4.98
R12=30.832D12=7.82N7=1.804000.nu.7=46.6
R13=-59.395D13=0.15
R14=-353.576D14=1.48N8=1.755199.nu.8=27.5
R15=40.441D15=5.13
R16=SP D16=8.68
R17=-16.042D17=1.50N9=1.805181.nu.9=25.4
R18=-76.756D18=0.05N10=1.578566.nu.10=16.5
R19=-146.535D19=2.98N11=1.834807.nu.11=42.7
*R20=-32.582D20=0.15
R21=-193.002D21=7.37N12=1.603112.nu.12=60.7
R22=-22.620D22=0.15
R23=-69.417D23=4.85N13=1.772499.nu.13=49.6
R24=-30.218D24=36.47 [0142] Aspherical coefficient [0143] 20th
surface:A=0.00000e+00 B=2.13762e-05 C=2.72007e-08 D=-1.80717e-11
E=-1.75506e-13
NUMERICAL EXAMPLE 6
[0144] f=24.83Fno=1.46 2.omega.=82.1
R1=67.697D1=2.80N1=1.696797.nu.1=55.5
R2=35.617D2=5.28
R3=68.261D3=2.30N2=1.696797.nu.2=55.5
R4=30.886D4=7.72
R5=286.375D5=4.38N3=1.712995.nu.3=53.8
R6=-90.506D6=3.68
R7=60.777D7=2.81N4=1.755199.nu.4=27.5
R8=177.484D8=0.70N5=1.635550.nu.5=22.7
R9=2235.655D9=1.70N6=1.487490.nu.6=70.2
R10=22.928D10=7.10
R11=.infin.D11=4.87
R12=30.895D12=6.78N7=1.804000.nu.7=46.6
R13=-59.022D13=0.15
R14=-2922.376D14=1.48N8=1.728250.nu.8=28.5
R15=39.587D15=5.13
R16=SP D16=6.89
R17=-17.193D17=1.50N9=1.805181.nu.9=25.4
R18=48.968D18=1.22N5=1.578566.nu.5=16.5
R19=124.262D19=4.00N11=1.834807.nu.11=42.7
*R20=-40.549D20=0.15
R21=-422.369D21=6.62N12=1.603112.nu.12=60.7
R22=-25.797D22=0.15
R23=-87.810D23=5.41N13=1.772499.nu.13=49.6
R24=-29.834D24=36.47 [0145] Aspherical coefficient [0146] 20th
surface:A=0.00000e+00 B=1.76037e-05 C=1.33192e-08 D=-2.62982e-12
E=-1.42186e-13
TABLE-US-00001 [0146] TABLE 1 Left-hand side Left-hand side of
conditional of conditional Example expression (1) .theta.gF
expression (2) 1 First refractive 0.64 0.69 -- optical element
Second refractive -- 0.36 0.59 optical element 2 First refractive
0.64 0.69 -- optical element Second refractive -- 0.36 0.59 optical
element 3 First refractive 0.64 0.69 -- optical element Second
refractive -- 0.36 0.59 optical element 4 First refractive 0.64
0.69 -- optical element Second refractive -- 0.36 0.59 optical
element 5 First refractive 0.64 0.69 -- optical element Second
refractive -- 0.36 0.59 optical element 6 First refractive 0.64
0.69 -- optical element Second refractive -- 0.36 0.59 optical
element
[0147] Next, an exemplary embodiment of a single-lens reflex (SLR)
camera system including the optical system according to at least
one exemplary embodiment of the present invention serving as an
image-taking lens will be described with reference to FIG. 13.
[0148] The SLR camera system shown in FIG. 13 includes a body 10,
an interchangeable lens 11 including the optical system according
to the present invention, and a photosurface 12 of a film, an
image-pickup device, or the like that records object images
obtained through the interchangeable lens 11.
[0149] The SLR camera system further includes a finder optical
system 13 through which a photographer can view the object images
obtained through the interchangeable lens 11, and a rotatable
quick-return mirror 14 that transmits the object images obtained
through the interchangeable lens 11 to the photosurface 12 or the
finder optical system 13.
[0150] When the photographer views the object images through the
finder, the object images formed on a focusing plate 15 via the
quick-return mirror 14 are converted into erect images using a
pentaprism 16, and then enlarged by an ocular optical system
17.
[0151] During capturing of images, the quick-return mirror 14 is
rotated in the direction of an arrow such that the object images
are formed on the photosurface 12. Herein, reference numerals 18
and 19 denote a sub-mirror and a focus detector, respectively.
[0152] The imaging optical system according to at least one
exemplary embodiment of the present invention applied to imaging
devices such as interchangeable lenses for SLR cameras in this
manner can achieve high optical performance.
[0153] Exemplary embodiments of the present invention are also
applicable to SLR cameras without quick-return mirrors.
[0154] 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 modifications, equivalent
structures and functions.
[0155] This application claims the priority of Japanese Patent
Application No. 2005-361953 filed Dec. 15, 2005, which is hereby
incorporated by reference herein in its entirety.
* * * * *