U.S. patent application number 17/307529 was filed with the patent office on 2021-08-19 for rear converter lens and imaging apparatus.
This patent application is currently assigned to FUJIFILM Corporation. The applicant listed for this patent is FUJIFILM Corporation. Invention is credited to Tetsuya ORI.
Application Number | 20210255422 17/307529 |
Document ID | / |
Family ID | 1000005556844 |
Filed Date | 2021-08-19 |
United States Patent
Application |
20210255422 |
Kind Code |
A1 |
ORI; Tetsuya |
August 19, 2021 |
REAR CONVERTER LENS AND IMAGING APPARATUS
Abstract
The rear converter lens consists of, in order from an object
side: a first lens group that has a positive refractive power; a
second lens group that has a negative refractive power; and a third
lens group that has a positive refractive power. The first lens
group consists of a cemented lens in which a negative lens concave
toward the image side and a positive lens convex toward the object
side are cemented. The second lens group consists of a cemented
lens in which a negative lens concave toward the image side, a
positive lens convex toward both sides, and a negative lens concave
toward the object side are cemented. The third lens group consists
of a cemented lens in which a positive lens convex toward the
object side and a negative lens are cemented. The rear converter
lens satisfies predetermined Conditional Expressions (1) and
(2).
Inventors: |
ORI; Tetsuya; (Saitama,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
FUJIFILM Corporation |
Tokyo |
|
JP |
|
|
Assignee: |
FUJIFILM Corporation
Tokyo
JP
|
Family ID: |
1000005556844 |
Appl. No.: |
17/307529 |
Filed: |
May 4, 2021 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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17020521 |
Sep 14, 2020 |
11029488 |
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17307529 |
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16112420 |
Aug 24, 2018 |
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17020521 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G02B 13/02 20130101;
G02B 9/30 20130101 |
International
Class: |
G02B 9/30 20060101
G02B009/30; G02B 13/02 20060101 G02B013/02 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 15, 2017 |
JP |
2017-177302 |
Claims
1. A rear converter lens that has a negative refractive power and
is mounted on an image side of a master lens so as to make a focal
length of a whole system including the master lens larger than a
focal length of the master lens alone, the rear converter lens
consisting of, in order from an object side: a first lens group
that has a positive refractive power; a second lens group that has
a negative refractive power; and a third lens group that has a
positive refractive power, wherein the first lens group consists of
a negative lens and a positive lens in order from the object side,
wherein the second lens group consists of a cemented lens in which
a negative lens concave toward both sides, a positive lens convex
toward both sides, and a negative lens concave toward the object
side are cemented in order from the object side, wherein the third
lens group includes, closest to the object side, a cemented lens in
which a positive lens and a negative lens are cemented in order
from the object side, a lens surface closest to an image side of
the third lens group has a convex shape toward the image side.
2. The rear converter lens according to claim 1, wherein assuming
that a focal length of the first lens group is f1, and a focal
length of the rear converter lens is fC, Conditional Expressions
(1) is satisfied, -1.4<f1/fC<-0.5 (1).
3. The rear converter lens according to claim 1, wherein assuming
that a focal length of the second lens group is f2, and a focal
length of the rear converter lens is fC, Conditional Expressions
(2) is satisfied, 0.2<f2/fC<0.36 (2).
4. The rear converter lens according to claim 1, wherein assuming
that a focal length of the third lens group is f3, and a focal
length of the rear converter lens is fC, Conditional Expression (3)
is satisfied, -1.5<f3/fC<-0.8 (3).
5. The rear converter lens according to claim 1, wherein assuming
that an Abbe number of the negative lens of the first lens group is
.nu.1, and an Abbe number of the positive lens of the first lens
group is .nu.2, Conditional Expression (4) is satisfied,
12<.nu.1-.nu.2<45 (4).
6. The rear converter lens according to claim 1, wherein the
negative lens of the first lens group has a shape concave toward
the image side.
7. The rear converter lens according to claim 6, wherein the
negative lens of the first lens group has a meniscus shape concave
toward the image side.
8. The rear converter lens according to claim 1, wherein the
positive lens of the first lens group has a shape convex toward the
object side.
9. The rear converter lens according to claim 8, wherein the
positive lens of the first lens group has a shape convex toward
both sides.
10. The rear converter lens according to claim 1, wherein the
positive lens of the third lens group has a shape convex toward the
object side.
11. The rear converter lens according to claim 10, wherein the
positive lens of the third lens group has a shape convex toward
both sides.
12. The rear converter lens according to claim 2, wherein
Conditional Expression (1-1) is satisfied, -1.35<f1/fC<-0.7
(1-1).
13. The rear converter lens according to claim 3, wherein
Conditional Expression (2-1) is satisfied, 0.25<f2/fC<0.35
(2-1).
14. The rear converter lens according to claim 4, wherein
Conditional Expression (3-1) is satisfied, -1.3<f3/fC<-0.9
(3-1).
15. The rear converter lens according to claim 5, wherein
Conditional Expression (4-1) is satisfied, 14<.nu.1-.nu.2<40
(4-1).
16. An imaging apparatus comprising the rear converter lens
according to claim 1.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application is a Continuation of U.S. patent
application Ser. No. 17/020,521 filed Sep. 14, 2020, which is a
Divisional of U.S. patent application Ser. No. 16/112,420 filed
Aug. 24, 2018, which claims priority under 35 U.S.C. .sctn. 119 to
Japanese Patent Application No. 2017-177302 filed on Sep. 15, 2017.
The above application is hereby expressly incorporated by
reference, in its entirety, into the present application.
BACKGROUND OF THE INVENTION
1. Field of the Invention
[0002] The present invention relates to a rear converter lens,
which is detachably mounted on the rear side (image side) of a
master lens and in which a focal length of the whole system is
increased, and an imaging apparatus comprising the rear converter
lens.
2. Description of the Related Art
[0003] In the past, there are known rear converter lenses (rear
conversion lenses) each of which is detachably mounted on a master
lens (main lens) between a camera main body and the master lens and
serves as an optical system in which a focal length of the whole
lens system is increased. For example, JP1992-020165B
(JP-H04-020165B), JP1992-020163B (JP-H04-020163B), JP4639581,
JP4337352, and JP2017-062317A each disclose an optical system in
which a master lens is equipped with a rear converter lens composed
of three groups consisting of: a first lens group that has a
positive refractive power; a second lens group that has a negative
refractive power; and a third lens group that has a positive
refractive power.
SUMMARY OF THE INVENTION
[0004] In recent years, attention has been focused on non-reflex
digital cameras having no optical finders as an imaging apparatus.
Recent improvements in the performance of imaging elements mounted
on digital cameras are progressing. Thus, even for rear converter
lenses mounted on non-reflex digital cameras, there is a demand to
achieve high optical performance for the synthetic optical systems
in which the rear converter lenses are mounted on the master
lenses.
[0005] However, in order to combine recent high-performance imaging
elements with the rear converter lenses described in JP1992-020165B
(JP-H04-020165B), JP1992-020163B (JP-H04-020163B), JP4639581,
JP4337352, and JP2017-062317A, there is a demand to obtain more
favorable characteristics particularly in spherical aberration and
field curvature.
[0006] The present invention has been made in consideration of the
above-mentioned situation, and its object is to provide a rear
converter lens, which has favorable optical performance, and an
imaging apparatus comprising the rear converter lens.
[0007] A rear converter lens of the present invention has a
negative refractive power and is mounted on an image side of a
master lens so as to increase a focal length of the master lens.
The rear converter lens consists of, in order from an object side:
a first lens group that has a positive refractive power; a second
lens group that has a negative refractive power; and a third lens
group that has a positive refractive power. The first lens group
consists of a cemented lens in which a negative lens concave toward
the image side and a positive lens convex toward the object side
are cemented in order from the object side. The second lens group
consists of a cemented lens in which a negative lens concave toward
the image side, a positive lens convex toward both sides, and a
negative lens concave toward the object side are cemented in order
from the object side. The third lens group consists of a cemented
lens in which a positive lens convex toward the object side and a
negative lens are cemented in order from the object side. Assuming
that a focal length of the first lens group is f1, a focal length
of the second lens group is f2, and a focal length of the rear
converter lens is fC, Conditional Expressions (1) and (2) are
satisfied.
-1.4<f1/fC<-0.5 (1)
0.2<f2/fC<0.36 (2)
[0008] It is preferable to satisfy Conditional Expression (1-1)
and/or (2-1).
-1.35<f1/fC<-0.7 (1-1)
0.25<f2/fC<0.35 (2-1)
[0009] In the rear converter lens of the present invention,
assuming that a focal length of the third lens group is f3 and the
focal length of the rear converter lens is fC, it is preferable to
satisfy the Conditional Expression (3), and it is more preferable
to satisfy the Conditional Expression (3-1).
-1.5<f3/fC<-0.8 (3)
-1.3<f3/fC<-0.9 (3-1)
[0010] Assuming that an Abbe number of the negative lens of the
first lens group is .nu.1 and an Abbe number of the positive lens
of the first lens group is .nu.2, it is preferable to satisfy the
Conditional Expression (4), and it is more preferable to satisfy
the Conditional Expression (4-1).
12<.nu.1-.nu.2<45 (4)
14<.nu.1-.nu.2<40 (4-1)
[0011] An imaging apparatus of the present invention comprises the
above-mentioned rear converter lens of the present invention.
[0012] It should be noted that the term "consists of .about." means
that the rear converter lens may include not only the
above-mentioned elements but also lenses substantially having no
powers, optical elements, which are not lenses, such as a stop, a
mask, a cover glass, and a filter, and mechanism parts such as a
lens flange, a lens barrel, an imaging element, and a camera
shaking correction mechanism.
[0013] Further, the Abbe number in each conditional expression is
based on the d line as a reference wavelength.
[0014] Furthermore, surface shapes, signs of refractive powers,
radii of curvature of the lenses are assumed as those in paraxial
regions in a case where some lenses have aspheric surfaces.
[0015] The rear converter lens of the present invention has a
negative refractive power and is mounted on an image side of a
master lens so as to increase a focal length of the master lens.
The rear converter lens consists of, in order from the object side:
the first lens group that has a positive refractive power; the
second lens group that has a negative refractive power; and the
third lens group that has a positive refractive power. The first
lens group consists of a cemented lens in which a negative lens
concave toward the image side and a positive lens convex toward the
object side are cemented in order from the object side. The second
lens group consists of a cemented lens in which a negative lens
concave toward the image side, a positive lens convex toward both
sides, and a negative lens concave toward the object side are
cemented in order from the object side. The third lens group
consists of a cemented lens in which a positive lens convex toward
the object side and a negative lens are cemented in order from the
object side. Assuming that the focal length of the first lens group
is f1, the focal length of the second lens group is f2, and a focal
length of the rear converter lens is fC, Conditional Expressions
(1) and (2) are satisfied. Therefore, it is possible to provide a
rear converter lens, which has favorable optical performance, and
an imaging apparatus comprising the rear converter lens.
-1.4<f1/fC<-0.5 (1)
0.2<f2/fC<0.36 (2)
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 is a cross-sectional view illustrating an example of
a lens configuration of a master lens to be combined with a rear
converter lens of the present invention.
[0017] FIG. 2 is a cross-sectional view illustrating a lens
configuration in a state where a rear converter lens according to
an embodiment of the present invention (common to Example 1) is
mounted on the master lens.
[0018] FIG. 3 is a cross-sectional view illustrating a lens
configuration in a state where a rear converter lens according to
Example 2 of the present invention is mounted on the master
lens.
[0019] FIG. 4 is a cross-sectional view illustrating a lens
configuration in a state where a rear converter lens according to
Example 3 of the present invention is mounted on the master
lens.
[0020] FIG. 5 is a cross-sectional view illustrating a lens
configuration in a state where a rear converter lens according to
Example 4 of the present invention is mounted on the master
lens.
[0021] FIG. 6 is a diagram of aberrations of the master lens
combined with the rear converter lens according to each embodiment
of the present invention.
[0022] FIG. 7 is a diagram of aberrations in the state where the
rear converter lens of Example 1 of the present invention is
mounted on the master lens.
[0023] FIG. 8 is a diagram of aberrations in the state where the
rear converter lens of Example 2 of the present invention is
mounted on the master lens.
[0024] FIG. 9 is a diagram of aberrations in the state where the
rear converter lens of Example 3 of the present invention is
mounted on the master lens.
[0025] FIG. 10 is a diagram of aberrations in the state where the
rear converter lens of Example 4 of the present invention is
mounted on the master lens.
[0026] FIG. 11 is a schematic configuration diagram of an imaging
apparatus comprising the rear converter lens according to the
above-mentioned embodiment of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0027] Hereinafter, an embodiment of the present invention will be
described with reference to drawings. FIG. 1 is a cross-sectional
view illustrating an example of a lens configuration of a master
lens to be combined with a rear converter lens of the present
invention. FIG. 2 is a cross-sectional view illustrating a lens
configuration in a state where a rear converter lens according to
an embodiment of the present invention (common to Example 1) is
mounted on the master lens. The exemplary configuration shown in
FIG. 2 is the same as the configuration of the rear converter lens
of Example 1. In each of FIGS. 1 and 2, the left side is an object
side, and the right side is an image side. In addition, an aperture
stop St shown in the drawing does not necessarily show its real
size and shape, but show a position on an optical axis Z.
[0028] A rear converter lens RCL has a negative refractive power
and is mounted on an image side of a master lens ML so as to
increase a focal length of the master lens ML. Hereinafter, a
synthetic optical system (whole system), in which the rear
converter lens RCL is mounted on the master lens ML, is simply
referred to as a synthetic optical system.
[0029] The rear converter lens RCL of the present embodiment is
composed of, in order from an object side: a first lens group RG1
that has a positive refractive power; a second lens group RG2 that
has a negative refractive power; and a third lens group RG3 that
has a positive refractive power. As described above, in the rear
converter lens RCL, lens groups are arranged to have positive,
negative, and positive refractive powers. Thereby, it is possible
to suppress fluctuation in spherical aberration and curvature of
field curvature caused by mounting the rear converter lens RCL.
Further, by making the first lens group RG1 to have a positive
refractive power, it is possible to make the position of the front
principal point of the synthetic optical system closer to the image
side. Thus, the back focal length of the synthetic optical system
can be shortened, and in particular, it is possible to obtain a
length suitable for a non-reflex digital camera.
[0030] The first lens group RG1 is composed of a cemented lens in
which a negative lens RL1a concave toward the image side and a
positive lens RL1b convex toward the object side are cemented in
order from the object side. With such a configuration, it is
possible to suppress fluctuation in longitudinal chromatic
aberration caused by mounting of the rear converter lens RCL.
Further, by cementing two lenses in the first lens group RG1, it is
possible to suppress occurrence of a ghost between lens surfaces,
and it is possible to reduce an effect of relative position error
between lens groups, such as eccentricity.
[0031] The second lens group RG2 is composed of a cemented lens in
which a negative lens RL2a concave toward the image side, a
positive lens RL2b convex toward both sides, and a negative lens
RL2c concave toward the object side are cemented in order from the
object side. In a case where the negative refractive power is
increased in the second lens group RG2, longitudinal chromatic
aberration of the synthetic optical system tends to change greatly.
However, by forming a three-piece cemented lens composed of the
negative lens RL2a, the positive lens RL2b, and the negative lens
RL2c, it is possible to minimize occurrence of longitudinal
chromatic aberration caused by mounting the rear converter lens
RCL. Further, by cementing three lenses in the second lens group
RG2, it is possible to suppress occurrence of a ghost between lens
surfaces, and it is possible to reduce an effect of relative
position error between lens groups, such as eccentricity.
[0032] The third lens group RG3 is composed of a cemented lens in
which a positive lens RL3a convex toward the object side and a
negative lens RL3b are cemented in order from the object side. As
described above, the object side surface of the third lens group
RG3 is formed as a convex surface. Thereby, it is possible to
suppress fluctuation in spherical aberration caused by mounting the
rear converter lens RCL. Further, by cementing two lenses in the
third lens group RG3, it is possible to suppress occurrence of a
ghost between lens surfaces, and it is possible to reduce an effect
of relative position error between lens groups, such as
eccentricity.
[0033] Assuming that a focal length of the first lens group RG1 is
f1, a focal length of the second lens group RG2 is f2, and a focal
length of the rear converter lens RCL is fC, the lens is configured
to satisfy Conditional Expressions (1) and (2).
-1.4<f1/fC<-0.5 (1)
0.2<f2/fC<0.36 (2)
[0034] Conditional Expression (1) is a condition suitable for a
high-performance rear converter lens RCL, particularly for a
non-reflex digital camera. By not allowing the result of
Conditional Expression (1) to be equal to or less than the lower
limit, it is possible to prevent the front principal point of the
rear converter lens RCL from becoming excessively close to the
object side, and the object point position of the rear converter
lens RCL becomes excessively close to the object side. Thus, it is
possible to ensure the back focal length of the synthetic optical
system and to facilitate attachment to the digital camera. Further,
there is also an advantage in correcting field curvature. By not
allowing the result of Conditional Expression (1) to be equal to or
greater than the upper limit, it is possible to prevent the front
principal point of the rear converter lens RCL from becoming
excessively close to the image side, and the object point position
of the rear converter lens RCL becomes excessively close to the
image side. Thus, it is possible to prevent the back focal length
of the synthetic optical system from becoming longer and to shorten
the total lens length. Further, there is also an advantage in
correcting spherical aberration. In this case, in a case where the
distance between the master lens ML and the rear converter lens RCL
is increased, the composite back focal length is shortened, but the
enlarging magnification of the focal length is decreased by
mounting the rear converter lens RCL. In addition, in a case where
Conditional Expression (1-1) is satisfied, it is possible to obtain
more favorable characteristics.
-1.35<f1/fC<-0.7 (1-1)
[0035] Conditional Expression (2) is also a condition suitable for
a high-performance rear converter lens RCL, particularly for a
non-reflex digital camera. By not allowing the result of
Conditional Expression (2) to be equal to or less than the lower
limit, it is possible to prevent the front principal point of the
rear converter lens RCL from becoming excessively close to the
image side, and the object point position of the rear converter
lens RCL becomes excessively close to the image side. Thus, it is
possible to prevent the back focal length of the synthetic optical
system from becoming longer and to shorten the total lens length.
Further, there is also an advantage in correcting field curvature.
In this case, in a case where the distance between the master lens
ML and the rear converter lens RCL is increased, the composite back
focal length is shortened, but the enlarging magnification of the
focal length is decreased by mounting the rear converter lens RCL.
By not allowing the result of Conditional Expression (2) to be
equal to or greater than the upper limit, it is possible to prevent
the front principal point of the rear converter lens RCL from
becoming excessively close to the object side, and the object point
position of the rear converter lens RCL becomes excessively close
to the object side. Thus, it is possible to ensure the back focal
length of the synthetic optical system and to facilitate attachment
to the digital camera. Further, there is also an advantage in
correcting spherical aberration. In addition, in a case where
Conditional Expression (2-1) is satisfied, it is possible to obtain
more favorable characteristics.
0.25<f2/fC<0.35 (2-1)
[0036] In the rear converter lens of the present embodiment,
assuming that a focal length of the third lens group RG3 is f3 and
the focal length of the rear converter lens RCL is fC, it is
preferable to satisfy the Conditional Expression (3). Conditional
Expression (3) is also a condition suitable for a high-performance
rear converter lens RCL, particularly for a non-reflex digital
camera. By not allowing the result of Conditional Expression (3) to
be equal to or less than the lower limit, it is possible to prevent
the front principal point of the rear converter lens RCL from
becoming excessively close to the image side, and the object point
position of the rear converter lens RCL becomes excessively close
to the image side. Thus, it is possible to prevent the back focal
length of the synthetic optical system from becoming longer and to
shorten the total lens length. Further, there is also an advantage
in correcting field curvature. In this case, in a case where the
distance between the master lens ML and the rear converter lens RCL
is increased, the composite back focal length is shortened, but the
enlarging magnification of the focal length is decreased by
mounting the rear converter lens RCL. By not allowing the result of
Conditional Expression (3) to be equal to or greater than the upper
limit, it is possible to prevent the front principal point of the
rear converter lens RCL from becoming excessively close to the
object side, and the object point position of the rear converter
lens RCL becomes excessively close to the object side. Thus, it is
possible to ensure the back focal length of the synthetic optical
system and to facilitate attachment to the digital camera. Further,
there is also an advantage in correcting distortion. In addition,
in a case where Conditional Expression (3-1) is satisfied, it is
possible to obtain more favorable characteristics.
-1.5<f3/fC<-0.8 (3)
-1.3<f3/fC<-0.9 (3-1)
[0037] Assuming that an Abbe number of the negative lens RL1a of
the first lens group RG1 is .nu.1 and an Abbe number of the
positive lens RL1b of the first lens group RG1 is .nu.2, it is
preferable to satisfy the Conditional Expression (4). Conditional
Expression (4) is a condition for suppressing fluctuation in
chromatic aberration caused by mounting the rear converter lens
RCL. By not allowing the result of Conditional Expression (4) to be
equal to or less than the lower limit, there is an advantage in
correcting longitudinal chromatic aberration. By not allowing the
result of Conditional Expression (4) to be equal to or greater than
the upper limit, there is an advantage in correcting lateral
chromatic aberration. In addition, in a case where Conditional
Expression (4-1) is satisfied, it is possible to obtain more
favorable characteristics.
12<.nu.1-.nu.2<45 (4)
14<.nu.1-.nu.2<40 (4-1)
[0038] In a case where the rear converter lens RCL is used in a
severe environment, it is preferable to apply protective multilayer
film coating. Not only the protective coating but also
antireflective coating for reducing ghost light in use may be
performed.
[0039] In each of the examples shown in FIGS. 1 and 2, a
plane-parallel-plate-like optical member PP, which is assumed as a
low-pass filter and various filters for cutting specific wavelength
regions, is disposed between the lens system and the image plane
Sim. The present invention is not limited to this, and these
various filters do not have to be disposed between the lens system
and the image plane Sim. Instead, these various filters may be
disposed between the respective lenses. Further, for example,
coating having the same function as the various filters may be
applied to a lens surface of any one of the lenses.
[0040] Next, a configuration example of the master lens ML and
numerical examples of the rear converter lens RCL of the present
invention will be described.
[0041] First, the master lens ML will be described. FIG. 1 shows a
cross-sectional view of the master lens ML. Further, Table 1 shows
specific lens data corresponding to a configuration using the
master lens ML alone, and Table 2 shows data about specification
and variable surface distances.
[0042] In the lens data of Table 1, the column of the surface
number shows surface numbers. The surface of the elements closest
to the magnification side is the first surface, and the surface
numbers sequentially increase toward the reduction side. The column
of the radius of curvature shows radii of curvature of the
respective surfaces. The column of the on-axis surface distance
shows spacings on the optical axis Z between the respective
surfaces and the subsequent surfaces. Further, the column of n
shows a refractive index of each optical element at the d line (a
wavelength of 587.6 nm (nanometers)), and the column of .nu.d shows
an Abbe number of each optical element at the d line (a wavelength
of 587.6 nm (nanometers)). It should be noted that the sign of the
radius of curvature is positive in a case where a surface has a
shape convex toward the object side, and is negative in a case
where a surface has a shape convex toward the image side. Table 1
additionally shows the stop St and the optical member PP, and in a
place of a surface number of a surface corresponding to the stop
St, the surface number and a term of (stop) are noted.
[0043] Table 2 shows values of the focal length f of the whole
system, the back focal length Bf of the whole system, the F number
FNo., and the maximum angle of view 2.omega.. It should be noted
that the back focal length Bf is an air-converted value. In the
lens data and the expression data, a degree (.degree.) is used as a
unit of an angle, and mm is used as a unit of a length, but
appropriate different units may be used since the optical system
can be used even in a case where the system is enlarged or reduced
in proportion.
TABLE-US-00001 TABLE 1 Example 1 (Master Lens Only).cndot.Lens Data
(n and .nu. are based on d line) Surface Radius of Surface Number
Curvature Distance n .nu. 1 437.9481 4.3400 1.48749 70.24 2
-437.9481 0.2300 3 88.2356 9.2300 1.49700 81.54 4 -318.6800 1.9500
1.65160 58.62 5 184.2906 1.0500 6 52.2197 2.0600 1.51742 52.43 7
35.0700 10.6000 1.49700 81.54 8 99.3624 10.1100 9 58.2609 4.3800
1.90366 31.31 10 128.2200 1.9500 1.80610 40.93 11 34.8158 16.6200
12 41.4281 2.3200 1.56732 42.82 13 29.5030 7.1100 1.43875 94.66 14
439.0296 8.5200 15(Stop) .infin. 3.7100 16 356.6297 1.0300 1.85150
40.78 17 50.9986 2.8900 18 -79.3300 0.9000 1.72916 54.09 19 34.9710
3.2800 1.84666 23.78 20 109.9049 6.4100 21 130.5900 2.6300 1.89286
20.36 22 45.9840 7.6100 1.67003 47.20 23 -108.5346 20.1500 24
129.0771 5.6900 1.60342 38.03 25 -82.4767 16.4200 26 -104.7176
1.7500 1.72916 54.68 27 -1000.2365 68.8437 28 .infin. 3.2000
1.51680 64.20 29 .infin. 0.0000
TABLE-US-00002 TABLE 2 Example 1 (Master Lens Only) Specification
(d Line) f 242.54 Bf 70.95 FNo. 4.12 2.omega.[.degree.] 13.4
[0044] Regarding meanings of signs in the above Tables, Tables 1
and 2 are used as examples. However, Tables 3 to 10 are basically
the same. Tables 3 to 10 shows respective data pieces of all
configurations in which the master lenses ML shown in Tables 1 and
2 and the rear converter lenses RCL corresponding to Examples 1 to
4 each are combined. The master lens ML is exemplified to be the
same in Examples 1 to 4, and the lens data pieces about the rear
converter lenses RCL of Examples 1 to 4 correspond to surface
numbers 28 to 37 in Tables 3, 5, 7 and 9. Further, the focal length
f of the whole system indicates the focal length of the master lens
ML alone in Table 2, and indicates the composite focal length of
the synthetic optical system, in which the rear converter lens RCL
and the master lens ML are combined, in Tables 4, 6, 8, and 10. The
back focal length Bf of the whole system indicates the back focal
length of the master lens alone in Table 2, and indicates the back
focal length of the synthetic optical system, in which the rear
converter lens RCL and the master lens ML are combined, in Tables
4, 6, 8 and 10.
[0045] FIG. 6 shows diagrams of aberrations of the master lens ML
alone. In addition, in order from the left side of FIG. 6,
spherical aberration, astigmatism, distortion, and lateral
chromatic aberration are shown. The aberration diagrams
illustrating spherical aberration, astigmatism, and distortion
indicate aberrations that occur in a case where the d line (a
wavelength of 587.6 nm (nanometers)) is set as a reference
wavelength. In the spherical aberration diagram, aberrations at the
d line (a wavelength of 587.6 nm (nanometers)), the C line (a
wavelength of 656.3 nm (nanometers)), and the F line (a wavelength
of 486.1 nm (nanometers)) are respectively indicated by the solid
line, the long dashed line, and the short dashed line. In the
astigmatism diagram, aberrations in sagittal and tangential
directions are respectively indicated by the solid line and the
short dashed line. In the lateral chromatic aberration, aberrations
at the C line (a wavelength of 656.3 nm (nanometers)) and F line (a
wavelength of 486.1 nm (nanometers)) are respectively indicated by
the long dashed line and the short dashed line. In addition, in the
spherical aberration diagram, FNo. means an F number. In the other
aberration diagrams, to means a half angle of view. The meanings of
the reference signs are, for example, as described in FIG. 6, and
are basically the same as those in FIGS. 7 to 10. Further, all the
aberration diagrams shown in FIGS. 6 to 10 are based on a case
where the object distance is at the infinity.
[0046] Next, the rear converter lens RCL of Example 1 will be
described. FIG. 2 shows a cross-sectional view illustrating the
entire configuration in a state where the rear converter lens RCL
of Example 1 is mounted on the master lens ML. Table 3 shows lens
data of the synthetic optical system in which the rear converter
lens RCL of Example 1 is mounted on the master lens ML. Table 4
shows data about specification. Further, FIG. 7 shows aberration
diagrams in a state where the rear converter lens RCL of Example 1
is mounted on the master lens ML.
TABLE-US-00003 TABLE 3 Example 1.cndot.Lens Data (n and .nu. are
based on d line) Surface Radius of Surface Number Curvature
Distance n .nu. 1 437.9481 4.3400 1.48749 70.24 2 -437.9481 0.2300
3 88.2356 9.2300 1.49700 81.54 4 -318.6800 1.9500 1.65160 58.62 5
184.2906 1.0500 6 52.2197 2.0600 1.51742 52.43 7 35.0700 10.6000
1.49700 81.54 8 99.3624 10.1100 9 58.2609 4.3800 1.90366 31.31 10
128.2200 1.9500 1.80610 40.93 11 34.8158 16.6200 12 41.4281 2.3200
1.56732 42.82 13 29.5030 7.1100 1.43875 94.66 14 439.0296 8.5200
15(Stop) .infin. 3.7100 16 356.6297 1.0300 1.85150 40.78 17 50.9986
2.8900 18 -79.3300 0.9000 1.72916 54.09 19 34.9710 3.2800 1.84666
23.78 20 109.9049 6.4100 21 130.5900 2.6300 1.89286 20.36 22
45.9840 7.6100 1.67003 47.20 23 -108.5346 20.1500 24 129.0771
5.6900 1.60342 38.03 25 -82.4767 16.4200 26 -104.7176 1.7500
1.72916 54.68 27 -1000.2365 16.4997 28 425.3981 1.7000 1.71299
53.87 29 53.7890 6.9700 1.59551 39.24 30 -88.1371 6.8500 31
-91.6290 1.7000 1.88300 39.22 32 43.0030 11.2000 1.62588 35.74 33
-43.0030 1.7000 1.75500 52.32 34 173.8058 0.2000 35 57.9507 8.1500
1.65412 39.68 36 -151.5200 1.7300 2.00272 19.32 37 898.0469 38.9201
38 .infin. 3.2000 1.51680 64.20 39 .infin. 0.0000
TABLE-US-00004 TABLE 4 Example 1.cndot.Specification (d Line) f
339.58 Bf 41.03 FNo. 5.77 2.omega.[.degree.] 9.8
[0047] Next, the rear converter lens RCL of Example 2 will be
described. FIG. 3 shows a cross-sectional view illustrating the
entire configuration in a state where the rear converter lens RCL
of Example 2 is mounted on the master lens ML. Table 5 shows lens
data of the synthetic optical system in which the rear converter
lens RCL of Example 2 is mounted on the master lens ML. Table 6
shows data about specification. Further, FIG. 8 shows aberration
diagrams in a state where the rear converter lens RCL of Example 2
is mounted on the master lens ML.
TABLE-US-00005 TABLE 5 Example 2.cndot.Lens Data (n and .nu. are
based on d line) Surface Radius of Surface Number Curvature
Distance n .nu. 1 437.9481 4.3400 1.48749 70.24 2 -437.9481 0.2300
3 88.2356 9.2300 1.49700 81.54 4 -318.6800 1.9500 1.65160 58.62 5
184.2906 1.0500 6 52.2197 2.0600 1.51742 52.43 7 35.0700 10.6000
1.49700 81.54 8 99.3624 10.1100 9 58.2609 4.3800 1.90366 31.31 10
128.2200 1.9500 1.80610 40.93 11 34.8158 16.6200 12 41.4281 2.3200
1.56732 42.82 13 29.5030 7.1100 1.43875 94.66 14 439.0296 8.5200
15(Stop) .infin. 3.7100 16 356.6297 1.0300 1.85150 40.78 17 50.9986
2.8900 18 -79.3300 0.9000 1.72916 54.09 19 34.9710 3.2800 1.84666
23.78 20 109.9049 6.4100 21 130.5900 2.6300 1.89286 20.36 22
45.9840 7.6100 1.67003 47.20 23 -108.5346 20.1500 24 129.0771
5.6900 1.60342 38.03 25 -82.4767 16.4200 26 -104.7176 1.7500
1.72916 54.68 27 -1000.2365 17.3554 28 -370.3267 1.7000 1.48749
70.24 29 57.7238 7.8583 1.56732 42.82 30 -57.7238 5.5688 31
-57.3848 1.7000 1.88300 39.22 32 57.3848 10.0990 1.64769 33.84 33
-43.9167 1.7000 1.83481 42.74 34 313.7482 0.2000 35 64.4023 8.5923
1.51742 52.43 36 -92.5109 1.7726 2.00100 29.13 37 -226.3306 38.3473
38 .infin. 3.2000 1.51680 64.20 39 .infin. 0.0000
TABLE-US-00006 TABLE 6 Example 2.cndot.Specification (d Line) f
339.54 Bf 40.46 FNo. 5.77 2.omega.[.degree.] 9.8
[0048] Next, the rear converter lens RCL of Example 3 will be
described. FIG. 4 shows a cross-sectional view illustrating the
entire configuration in a state where the rear converter lens RCL
of Example 3 is mounted on the master lens ML. Table 7 shows lens
data of the synthetic optical system in which the rear converter
lens RCL of Example 3 is mounted on the master lens ML. Table 8
shows data about specification. Further, FIG. 9 shows aberration
diagrams in a state where the rear converter lens RCL of Example 3
is mounted on the master lens ML.
TABLE-US-00007 TABLE 7 Example 3.cndot.Lens Data (n and .nu. are
based on d line) Surface Radius of Surface Number Curvature
Distance n .nu. 1 437.9481 4.3400 1.48749 70.24 2 -437.9481 0.2300
3 88.2356 9.2300 1.49700 81.54 4 -318.6800 1.9500 1.65160 58.62 5
184.2906 1.0500 6 52.2197 2.0600 1.51742 52.43 7 35.0700 10.6000
1.49700 81.54 8 99.3624 10.1100 9 58.2609 4.3800 1.90366 31.31 10
128.2200 1.9500 1.80610 40.93 11 34.8158 16.6200 12 41.4281 2.3200
1.56732 42.82 13 29.5030 7.1100 1.43875 94.66 14 439.0296 8.5200
15(Stop) .infin. 3.7100 16 356.6297 1.0300 1.85150 40.78 17 50.9986
2.8900 18 -79.3300 0.9000 1.72916 54.09 19 34.9710 3.2800 1.84666
23.78 20 109.9049 6.4100 21 130.5900 2.6300 1.89286 20.36 22
45.9840 7.6100 1.67003 47.20 23 -108.5346 20.1500 24 129.0771
5.6900 1.60342 38.03 25 -82.4767 16.4200 26 -104.7176 1.7500
1.72916 54.68 27 -1000.2365 16.4994 28 -244.0325 1.7000 1.49700
81.54 29 59.0027 7.6565 1.54814 45.78 30 -59.0027 7.2101 31
-58.8371 1.7000 1.88300 39.22 32 77.2890 9.5200 1.62005 36.35 33
-43.0000 1.7000 1.83481 42.74 34 500.0063 0.2000 35 69.0352 8.5807
1.51742 52.43 36 -85.4299 1.7000 1.87070 40.73 37 -187.8275 38.5450
38 .infin. 3.2000 1.51680 64.20 39 .infin. 0.0000
TABLE-US-00008 TABLE 8 Example 3.cndot.Specification (d Line) f
339.54 Bf 40.65 FNo. 5.77 2.omega.[.degree.] 9.8
[0049] Next, the rear converter lens RCL of Example 4 will be
described. FIG. 5 shows a cross-sectional view illustrating the
entire configuration in a state where the rear converter lens RCL
of Example 4 is mounted on the master lens ML. Table 9 shows lens
data of the synthetic optical system in which the rear converter
lens RCL of Example 4 is mounted on the master lens ML. Table 10
shows data about specification. Further, FIG. 10 shows aberration
diagrams in a state where the rear converter lens RCL of Example 4
is mounted on the master lens ML.
TABLE-US-00009 TABLE 9 Example 4.cndot.Lens Data (n and .nu. are
based on d line) Surface Radius of Surface Number Curvature
Distance n .nu. 1 437.9481 4.3400 1.48749 70.24 2 -437.9481 0.2300
3 88.2356 9.2300 1.49700 81.54 4 -318.6800 1.9500 1.65160 58.62 5
184.2906 1.0500 6 52.2197 2.0600 1.51742 52.43 7 35.0700 10.6000
1.49700 81.54 8 99.3624 10.1100 9 58.2609 4.3800 1.90366 31.31 10
128.2200 1.9500 1.80610 40.93 11 34.8158 16.6200 12 41.4281 2.3200
1.56732 42.82 13 29.5030 7.1100 1.43875 94.66 14 439.0296 8.5200
15(Stop) .infin. 3.7100 16 356.6297 1.0300 1.85150 40.78 17 50.9986
2.8900 18 -79.3300 0.9000 1.72916 54.09 19 34.9710 3.2800 1.84666
23.78 20 109.9049 6.4100 21 130.5900 2.6300 1.89286 20.36 22
45.9840 7.6100 1.67003 47.20 23 -108.5346 20.1500 24 129.0771
5.6900 1.60342 38.03 25 -82.4767 16.4200 26 -104.7176 1.7500
1.72916 54.68 27 -1000.2365 16.4673 28 32790.3739 1.7000 1.59282
68.62 29 66.5820 7.3100 1.58144 40.75 30 -84.7954 7.2101 31
-96.5684 1.7000 1.88300 39.22 32 57.5699 10.6486 1.59270 35.31 33
-40.0355 1.7000 1.87070 40.73 34 336.5662 0.2000 35 68.9256 7.0100
1.51823 58.90 36 -506.8420 1.7000 2.00100 29.13 37 -754.5895
38.2207 38 .infin. 3.2000 1.51680 64.20 39 .infin. 0.0000
TABLE-US-00010 TABLE 10 Example 4.cndot.Specification (d Line) f
339.55 Bf 40.33 FNo. 5.77 2.omega.[.degree.] 9.8
[0050] Table 11 shows values corresponding to Conditional
Expressions (1) to (4) of the rear converter lenses RCL of Examples
1 to 4. It should be noted that, in the above-mentioned examples,
the d line is set as the reference wavelength, and the values shown
in Table 11 are values at the reference wavelength.
TABLE-US-00011 TABLE 11 Expres- sion Conditional Number Expression
Example 1 Example 2 Example 3 Example 4 (1) fl/fC -1.303 -0.818
-0.942 -1.234 (2) f2/fC 0.342 0.296 0.298 0.335 (3) f3/fC -1.019
-1.124 -0.974 -1.057 (4) .nu.1 - .nu.2 14.7 27.4 35.7 28.0
[0051] As can be seen from the above-mentioned data, all the rear
converter lenses RCL of Examples 1 to 4 each have favorable optical
performance
[0052] Next, an imaging apparatus 10 according to an embodiment of
the present invention will be described. FIG. 11 shows a schematic
configuration diagram of the imaging apparatus 10 using the rear
converter lens RCL according to the above-mentioned embodiment of
the present invention. The related imaging apparatus 10 is a
non-reflex digital camera in which the rear converter lens RCL is
detachably mounted on the image side of the master lens ML. It
should be noted that, in FIG. 11, each lens group is schematically
illustrated.
[0053] The imaging apparatus 10 shown in FIG. 11 comprises an
imaging lens that is a synthetic optical system consisting of the
rear converter lens RCL and the master lens ML, a filter 6 that has
a function such as a lowpass filter disposed on the image side of
the imaging lens, an imaging element 7 that is disposed on the
image side of the filter 6, and a signal processing circuit 8.
Further, the imaging apparatus 10 comprises a focus control section
(not shown in the drawing) for performing focusing of the master
lens ML.
[0054] The rear converter lens RCL is detachably formed on the
master lens ML. The imaging element 7 converts an optical image,
which is formed through the imaging lens, into an electrical
signal. For example, as the imaging element 7, it is possible to
use a charge coupled device (CCD), complementary metal oxide
semiconductor (CMOS), and the like. The imaging element 7 is
disposed such that the imaging surface thereof is coplanar with the
image plane of the imaging lens. An image, which is captured
through the imaging lens, is formed on the imaging surface of the
imaging element 7, an output signal of the image from the imaging
element 7 is calculated by the signal processing circuit 8, and the
image is displayed on the display device 9. In addition, the focus
control section, which is not shown in the drawing, performs the
focusing operation.
[0055] In the imaging apparatus 10 according to the embodiment of
the present invention, a captured image signal corresponding to an
optical image, which is formed through the synthetic optical system
in which the high-performance rear converter lens RCL and the
master lens ML according to the embodiment of the present invention
are combined, is output. Therefore, it is possible to obtain a
photographed image with a high resolution.
[0056] The present invention has been hitherto described through
embodiments and examples, but the present invention is not limited
to the above-mentioned embodiments and examples, and may be
modified into various forms. For example, values such as the radius
of curvature, the surface distance, the refractive index, and the
Abbe number of each lens component are not limited to the values
shown in the numerical examples, and different values may be used
therefor.
[0057] In the above-mentioned embodiment of the imaging apparatus
10, the rear converter lens mounted on the non-reflex digital
camera has been described as an example, and the imaging apparatus
of the present invention is not limited to this. For example, the
rear converter lens of the present invention may be applied to
imaging apparatuses such as a video camera, a single-lens reflex
camera, a film camera, a movie camera, and a broadcast camera.
EXPLANATION OF REFERENCES
[0058] 6: filter [0059] 7: imaging element [0060] 8: signal
processing circuit [0061] 9: display device [0062] 10: imaging
apparatus [0063] L1a to L1p: lens [0064] ML: master lens [0065] PP:
optical member [0066] RCL: rear converter lens [0067] RG1: first
lens group (first lens group included in rear converter lens)
[0068] RG2: second lens group (second lens group included in rear
converter lens) [0069] RG3: third lens group (third lens group
included in rear converter lens) [0070] RL1a to RL3b: lens [0071]
Sim: image plane [0072] St: aperture stop [0073] Z: optical
axis
* * * * *