U.S. patent application number 17/165058 was filed with the patent office on 2021-05-27 for optical system and image pickup apparatus.
The applicant listed for this patent is CANON KABUSHIKI KAISHA. Invention is credited to Junya Ichimura.
Application Number | 20210157156 17/165058 |
Document ID | / |
Family ID | 1000005374426 |
Filed Date | 2021-05-27 |
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United States Patent
Application |
20210157156 |
Kind Code |
A1 |
Ichimura; Junya |
May 27, 2021 |
OPTICAL SYSTEM AND IMAGE PICKUP APPARATUS
Abstract
Provided is an optical system including: a first lens unit
having a positive refractive power; a second lens unit having a
positive refractive power and disposed at the image side of the
first lens unit; and a third lens unit having a positive refractive
power and disposed closest to the image side, in which intervals
between adjacent lens units are changed during focusing. The first
lens unit does not move during focusing. The second lens unit moves
to the object side along an optical axis during focusing from
infinity to a close distance. The second lens unit includes, in
order from the object side to the image side, a positive lens, a
negative lens, and an aperture stop. The third lens unit includes a
positive lens and a negative lens. A length of the third lens unit
on the optical axis and an air-equivalent back focus are
appropriately set.
Inventors: |
Ichimura; Junya;
(Utsunomiya-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
CANON KABUSHIKI KAISHA |
Tokyo |
|
JP |
|
|
Family ID: |
1000005374426 |
Appl. No.: |
17/165058 |
Filed: |
February 2, 2021 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
16124874 |
Sep 7, 2018 |
10942361 |
|
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17165058 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G02B 27/16 20130101;
G02B 27/40 20130101; G02B 27/0025 20130101; G02B 13/02
20130101 |
International
Class: |
G02B 27/16 20060101
G02B027/16; G02B 27/00 20060101 G02B027/00; G02B 27/40 20060101
G02B027/40; G02B 13/02 20060101 G02B013/02 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 11, 2017 |
JP |
2017-173821 |
Claims
1. An optical system comprising: a first lens unit having a
positive refractive power; a second lens unit having a positive
refractive power and disposed at the image side of the first lens
unit; and a third lens unit having a positive refractive power and
disposed closest to the image side, an interval between each
adjacent ones of the lens units being changed during focusing,
wherein the first lens unit is arranged not to move during
focusing, the second lens unit is arranged to move to the object
side along an optical axis during focusing from infinity to a close
distance, the second lens unit comprises, in order from the object
side to the image side, a positive lens, a negative lens, and an
aperture stop, and the third lens unit comprises a positive lens
and a negative lens.
2. The optical system according to claim 1, wherein the following
conditional expression is satisfied: 2.0<f1/f<10.0 where f
represents a focal length of the optical system and f1 represents a
focal length of the first lens unit.
3. The optical system according to claim 1, wherein the following
conditional expression is satisfied: 0.8<f2/f<1.1 wherein f
represents a focal length of the optical system and f2 represents a
focal length of the second lens unit.
4. The optical system according to claim 1, wherein the following
conditional expression is satisfied: 3.0<f3/f<10.0 where f
represents a focal length of the optical system and f3 represents a
focal length of the third lens unit.
5. The optical system according to claim 1, wherein the second lens
unit comprises an aspherical lens including a lens surface having
an aspherical surface shape, and the following conditional
expression is satisfied: Nasp>1.70 where Nasp represents a
refractive index of a material of the aspherical lens at a
d-line.
6. The optical system according to claim 1, wherein the second lens
unit comprises, in order from the object side to the image side, a
first positive lens, a second positive lens, a negative lens, and
an aperture stop, the negative lens comprises a meniscus shape with
a convex surface directed to the object side, and the negative lens
comprises a lens surface having an aspherical surface shape.
7. The optical system according to claim 1, wherein the third lens
unit comprises a first lens and a second lens disposed adjacent to
the image side of the first lens, a lens surface of the first lens
on the image side is convex toward the object side, a lens surface
of the second lens on the object side is convex shape toward the
image side, and the following conditional expression is satisfied:
-1<(Ra1+Ra2)/(Ra1-Ra2)<5 where Ra1 represents the radius of
curvature of the lens surface of the first lens on the image side
and Ra2 represents the radius of curvature of the lens surface of
the second lens on the object side.
8. The optical system according to claim 1, wherein the third lens
unit consists of, in order from the object side to the image side,
a cemented lens formed by cementing a positive lens and a negative
lens, a negative lens, and a positive lens.
9. The optical system according to claim 1, wherein the first lens
unit consists of, in order from the object side to the image side,
a positive lens, a positive lens, and a negative lens.
10. The optical system according to claim 1, wherein the second
lens unit comprises a first positive lens disposed closest to the
object side in the second lens unit, and the following conditional
expression is satisfied: .theta.gF21>0.61 where .theta.gF21
represents a partial dispersion ratio between a g-line and a F-line
of a material of the first positive lens.
11. The optical system according to claim 1, wherein the second
lens unit comprises, in order from the object side to the image
side, a first positive lens, and a second positive lens, and the
following conditional expression is satisfied: .theta.gF22<0.55
where .theta.gF22 represents a partial dispersion ratio between a
g-line and a F-line of a material of the second positive lens.
12. The optical system according to claim 1, wherein during
focusing, the third lens unit moves along a locus different from
that of the second lens unit.
13. The optical system according to claim 1, wherein the optical
system consists of, in order from the object side to the image
side, the first lens unit, the second lens unit, and the third lens
unit.
14. The optical system according to claim 1, wherein the following
conditional expression is satisfied: 1.0<D3/BF<3.0 where D3
represents a length of the third lens unit on the optical axis and
BF represents an air-equivalent back focus.
15. An image pickup apparatus comprising: an optical system; and an
image pickup element that receives light of an image formed by the
optical system, wherein the optical system comprises: a first lens
unit having a positive refractive power; a second lens unit having
a positive refractive power and disposed at the image side of the
first lens unit; and a third lens unit having a positive refractive
power and disposed closest to the image side, an interval between
each adjacent ones of the lens units being changed during focusing,
the first lens unit is arranged not to move during focusing, the
second lens unit is arranged to move to the object side along an
optical axis during focusing from infinity to a close distance, the
second lens unit comprises, in order from the object side to the
image side, a positive lens, a negative lens, and an aperture stop,
and the third lens unit comprises a positive lens and a negative
lens.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 16/124,874, filed on Sep. 7, 2018, which
claims the benefit of and priority to Japanese Patent Application
No. 2017-173821, filed on Sep. 11, 2017, each of which are hereby
incorporated by reference herein in their entirety.
BACKGROUND OF THE INVENTION
Field of the Invention
[0002] The present invention relates to an optical system and an
image pickup apparatus. The optical system is usable, for example,
as an image pickup optical system for a digital still camera, a
digital video camera, a television camera, a monitoring camera, and
the like.
Description of the Related Art
[0003] As an image pickup optical system used for an image pickup
apparatus, an image pickup optical system of medium telephoto-type
is known which has a large aperture ratio, that is, an f-number
(Fno) of approximately 1.2 to 2.0 and also has a relatively long
focal length. The image pickup optical system of medium
telephoto-type has been widely used for portrait photography and
indoor sports photography. In addition, there is a demand that such
an image pickup optical system be capable of rapidly focusing and
have a small variation in aberration during focusing.
[0004] As a focusing system having a high focus speed, an inner
focus system is known which focuses by moving a small-size
light-weight lens unit, which is located in a middle of a lens
system. An image pickup apparatus of medium telephoto-type that
uses the inner focus system and has a high optical performance is
known (Japanese Patent Application Laid-Open No. 2013-25157).
Japanese Patent Application Laid-Open No. 2013-25157 discloses an
optical system consisting of, in order from the object side to the
image side, a first lens unit having a positive refractive power, a
second lens unit having a positive refractive power, an aperture
stop, and a third lens unit having a positive refractive power, the
optical system performing focusing by moving the second lens unit
on an optical axis.
[0005] Among focusing systems, the inner focus system is capable of
focusing with a small-size light-weight lens unit and allow for
rapid focusing.
[0006] In optical systems of medium telephoto-type having a large
aperture ratio and a relatively long focal length, it is important
to appropriately select focus lens units and appropriately
establish a lens configuration in order to achieve a high optical
performance over the entire object distance with a small variation
in aberration during focusing.
[0007] Particularly, in an optical system of medium telephoto-type
having a large aperture, since the depth of field is narrow, it is
difficult to obtain a high optical performance in the entire screen
without favorably correcting various aberrations such as the axial
chromatic aberration and the field curvature, besides the spherical
aberration.
SUMMARY OF THE INVENTION
[0008] Provided is an optical system including a first lens unit
having a positive refractive power, a second lens unit having a
positive refractive power and disposed at the image side of the
first lens unit and a third lens unit having a positive refractive
power and disposed closest to the image side in which an interval
between each adjacent ones of the lens units is changed during
focusing. The first lens unit does not move during focusing. The
second lens unit moves to the object side along an optical axis
during focusing from infinity to a close distance. The second lens
unit includes, in order from the object side to the image side, a
positive lens, a negative lens and an aperture stop. The third lens
unit includes a positive lens and a negative lens. The optical
system satisfies a conditional expression of
1.0<D3/BF<3.0
where D3 represents a length of the third lens unit on the optical
axis and BF represents an air-equivalent back focus.
[0009] 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
[0010] FIG. 1A is a lens sectional view of an optical system of
Example 1 when focused on an object at infinity.
[0011] FIG. 1B is a longitudinal aberration diagram of the optical
system of Example 1 when focused on the object at infinity.
[0012] FIG. 2A is a lens sectional view of an optical system of
Example 2 when focused on an object at infinity.
[0013] FIG. 2B is a longitudinal aberration diagram of the optical
system of Example 2 when focused on the object at infinity.
[0014] FIG. 3A is a lens sectional view of an optical system of
Example 3 when focused on an object at infinity.
[0015] FIG. 3B is a longitudinal aberration diagram of the optical
system of Example 3 when focused on the object at infinity.
[0016] FIG. 4A is a lens sectional view of an optical system of
Example 4 when focused on an object at infinity.
[0017] FIG. 4B is a longitudinal aberration diagram of the optical
system of Example 4 when focused on the object at infinity.
[0018] FIG. 5 is a schematic view illustrating main portions of an
image pickup apparatus of an Example.
DESCRIPTION OF THE EMBODIMENTS
[0019] Hereinafter, optical systems and an image pickup apparatus
of the present invention will be described. Optical systems of
Examples include: a first lens unit having a positive refractive
power; a second lens unit having a positive refractive power and
disposed at the image side of the first lens unit; and a third lens
unit having a positive refractive power and disposed closest to the
image side. During focusing, the first lens unit does not move, and
during focusing from infinity to a close distance, at least the
second lens unit moves to the object side along the optical
axis.
[0020] FIGS. 1A and 1B are a lens sectional view and a longitudinal
aberration diagram of an optical system of Example 1 when the
optical system is focused at infinity, respectively. Example 1 is
an optical system having a focal length of 86.5 and an f-number of
approximately 1.24. FIGS. 2A and 2B are a lens sectional view and a
longitudinal aberration diagram of an optical system of Example 2
when the optical system is focused at infinity, respectively.
Example 2 is an optical system having a focal length of 86.5 and an
f-number of approximately 1.24.
[0021] FIGS. 3A and 3B are a lens sectional view and a longitudinal
aberration diagram of an optical system of Example 3 when the
optical system is focused at infinity, respectively. Example 3 is
an optical system having a focal length of 100.0 and an f-number of
approximately 1.46. FIGS. 4A and 4B are a lens sectional view and a
longitudinal aberration diagram of an optical system of Example 4
when the optical system is focused at infinity, respectively.
Example 4 is an optical system having a focal length of 100.0 and
an f-number of approximately 1.45. FIG. 5 is a schematic view
illustrating main portions of an image pickup apparatus.
[0022] In the lens sectional view, the left side is the object side
(or the front side, the magnifying side) and the right side is the
image side (or the rear side, the reducing side). L0 denotes the
optical system. L1 denotes the first lens unit having a positive
refractive power; L2, the second lens unit having a positive
refractive power; and L3, the third lens unit having a positive
refractive power. SP denotes an aperture stop. The arrow regarding
the focus indicates the direction of movement of a lens unit during
focusing from infinity to the closest distance.
[0023] IP denotes an image plane, which corresponds to an image
pickup plane of a solid-state image pickup element (a photoelectric
conversion element) such as a CCD sensor or a CMOS sensor when the
optical system is used as an image pickup optical system for a
video camera or a digital still camera.
[0024] In the spherical aberration diagram, d represents the d-line
(a wavelength of 587.6 nm); g, the g-line (a wavelength of 435.8
nm); C, the C-line (a wavelength of 656.3 nm); and F, the F-line (a
wavelength of 486.1 nm). In the astigmatism diagram, M represents
the meridional image plane of the d-line; and S, the sagittal image
plane of the d-line. The distortion is expressed regarding the
d-line. In the lateral chromatic aberration diagram, g represents
the g-line; C, the C-line; and F, the F-line. Fno is the f-number,
and H is the image height.
[0025] The optical system L0 of the Example consists of: in order
from the object side to the image side, a first lens unit L1 having
a positive refractive power; a second lens unit L2 having a
positive refractive power and disposed at the image side of the
first lens unit L1; and a third lens unit L3 having a positive
refractive power and disposed closest to the image side. During
focusing, the interval between each adjacent lens units changes.
During focusing from infinity to a close distance, at least the
second lens unit L2 moves to the object side along the optical
axis. During focusing, the first lens unit L1 does not move.
[0026] A medium telephoto-type lens having a so-called large
aperture ratio, that is, an Fno of 2.0 or less has a large entrance
pupil diameter, and accordingly the front lens effective diameter
of the lens tends to be large. In order to move this lens having a
large front lens effective diameter during focusing, the focus lens
units become quite heavy. For this reason, it is preferable that
the first lens unit having a positive refractive power do not move
during focusing.
[0027] In the optical system of the Example, the second lens unit
L2 has a lens configuration similar to a so-called double gauss
configuration, where a plurality of lenses are arranged on each of
the object side and the image side with the aperture stop SP in
between. In this way, the optical performance during focusing is
favorably maintained while the high optical performance is ensured.
The third lens unit L3 includes a plurality of lenses utilizing its
short back focus. This makes it possible to reduce the whole
Petzval sum, achieving a favorable image plane characteristics,
while enhancing the optical performance during focusing.
[0028] The second lens unit L2 includes: a positive lens; a
negative lens disposed at the image side of the positive lens; and
an aperture stop disposed at the image side of the negative lens.
The third lens unit L3 includes: a positive lens; and a negative
lens, and the optical system satisfies a conditional expression
of
1.0<D3/BF<3.0 (1)
[0029] where D3 denotes the length of the third lens unit L3 on the
optical axis and BF denotes the air-equivalent back focus length.
The length of the third lens unit L3 indicates a distance on the
optical axis from the object-side lens surface of the lens closest
to the object side to the image-side lens surface of the lens
closest to the image side in the third lens unit L3.
[0030] Conditional Expression (1) allows the chromatic aberration
and the Petzval sum to be effectively corrected, by making it
possible to effectively arrange the plurality of lenses utilizing
the short back focus. If the ratio falls below the lower limit
value in Conditional Expression (1), the lens unit length of the
third lens unit L3 becomes too short, which makes it difficult to
obtain a sufficient refractive power of each lens, resulting in
insufficient corrections of the various aberrations. If the ratio
exceeds the upper limit value in Conditional Expression (1), this
is not preferable because the third lens unit L3 becomes too long,
making impossible to obtain a necessary amount of movement of the
second lens unit L2.
[0031] It is preferable that each Example satisfy one or more of
the following Conditional Expressions. Here, f denotes the focal
length of the optical system; f1, the focal length of the first
lens unit L1; f2, the focal length of the second lens unit L2; and
f3, the focal length of the third lens unit L3. The second lens
unit L2 includes an aspherical lens including a lens surface of an
aspherical surface shape, and Nasp denotes the refractive index of
the material of the aspherical lens at the d-line. The third lens
unit L3 includes an air lens having a surface consisting of a
convex shape on the object side and a surface consisting of a
convex shape on the image side, and Ra1 denotes the curvature
radius of a lens surface R1 on the object side of the air lens and
Ra2 the curvature radius of a lens surface R2 on the image side of
the air lens. It should be noted that the statement "includes an
air lens having a surface consisting of a convex shape on the
object side and a surface consisting of a convex shape on the image
side" means to encompass a configuration in which the lens surface
R1 on the image side of a certain lens (first lens) is convex
toward the object side and the lens surface R2 on the object side
of a lens (second lens) disposed adjacent to the image side of the
first lens is convex toward the image side.
[0032] The second lens unit L2 includes a positive lens 21 disposed
closest to the object side in this second lens unit, and
.theta.gF21 denotes the partial dispersion ratio between the g-line
and the F-line of the material of the positive lens 21. The second
lens unit L2 includes, in order from the object side to the image
side, the positive lens 21 and a positive lens 22, and .theta.gF22
denotes the partial dispersion ratio between the g-line and the
F-line of the material of the positive lens 22.
[0033] Then, ng, nF, nd, and nC denote the refractive indices of
the material at the g-line, the F-line, the d-line, and the C-line,
respectively. In this case, the Abbe number .nu.d and the partial
dispersion ratio .theta.gF of the material are expressed by the
following expressions:
.nu.d=(nd-1)/(nF-nC)
.theta.gF=(ng-nF)/(nF-nC)
[0034] Here, it is preferable that one or more of the following
Conditional Expressions be satisfied:
2.0<f1/f<10.0 (2)
0.8<f2/f<1.1 (3)
3.0<f3/f<10.0 (4)
Nasp>1.70 (5)
-1<(Ra1+Ra2)/(Ra1-Ra2)<5 (6)
.theta.gF21>0.61 (7)
.theta.gF22<0.55 (8)
[0035] Next, the technical significance of each of the
above-described Conditional Expressions will be described.
Conditional Expressions (2) to (4) enable the optical system L0
including a lens configuration in which the second lens unit L2 for
focus is sandwiched by the first lens unit L1 having a weak
refractive power and the third lens unit L3 having a weak positive
refractive power.
[0036] The first lens unit L1 contributes to increasing the
aperture, and causes the incident light beam to converge to reduce
the diameter of the incident light beam after the second lens unit
L2. If the ratio falls below the lower limit value in Conditional
Expression (2), the positive refractive power of the first lens
unit L1, which does not move during focusing, increases relative to
the entire refractive power. As a result, the amount of focusing
movement of the second lens unit L2 becomes unfavorably too large.
If the ratio exceeds the upper limit value in Conditional
Expression (2), the on-axis beam less converges. For this reason,
the refractive power after the second lens unit L2 increases,
making it difficult to correct the spherical aberration and the
chromatic aberration.
[0037] It is preferable that the focal length of the second lens
unit L2 be substantially equal to the focal length of the optical
system. If the ratio falls below the lower limit value in
Conditional Expression (3), the positive refractive power of the
second lens unit L2 becomes unfavorably too strong, making the
aberration correction difficult and reducing the space for
arranging the third lens unit L3. If the ratio exceeds the upper
limit value in Conditional Expression (3), the amount of focusing
movement of the second lens unit L2 becomes too large, so that the
optical system increases in size.
[0038] The third lens unit L3 performs the entire aberration
correction and reduces a variation in aberration during focusing to
the closest distance, and preferably has a weak positive refractive
power. If the ratio falls below the lower limit value in
Conditional Expression (4), the illumination at the edge tends to
be insufficient. On the other hand, if the ratio exceeds the upper
limit value in Conditional Expression (4), the on-axis light beam
increases at the second lens unit L2, so that the curvature of the
lens surface tends to be large, making it difficult to correct the
spherical aberration and the axial chromatic aberration.
[0039] In order to reduce the spherical aberration, it is
preferable to dispose the aspherical surface in the second lens
unit L2, which includes the aperture stop SP. In addition, in order
to increase the aspherical surface effect of the aspherical surface
shape, it is preferable that the aspherical lens be formed of a
material having a high refractive index that satisfies Conditional
Expression (5).
[0040] The Petzval sum is effectively reduced by making the
thickness of the third lens unit L3 large and including the air
lens that satisfies Conditional Expression (6). If the ratio falls
below the lower limit value in Conditional Expression (6), the
Petzval sum increases. On the other hand, if the ratio exceeds the
upper limit value in Conditional Expression (6), the curvatures of
the lens surfaces of the respective lenses come too close to each
other, so that the correction effect by the Petzval sum is
reduced.
[0041] In the case of an optical system having a large aperture
ratio, the depth of field is very shallow. For this reason, being
slightly out of focus causes the optical performance of the entire
screen to decrease. Particularly when there is a difference in
focus between colors due to the axial chromatic aberration, this
difference in focus lowers the sense of resolution as color
bleeding. For this reason, it is necessary to favorably correct the
axial chromatic aberration.
[0042] In general, it is known to suppress generation of axial
chromatic aberration using a material having a low dispersion for a
positive lens and perform achromatization using a material having a
high dispersion for a negative lens. However, with this measure
only, the chromatic aberration is likely to remain, especially on
the short wavelength side.
[0043] In view of this, it is preferable for the optical system of
each Example to satisfy Conditional Expressions (7) and (8) in the
above-described lens configuration. Conditional Expression (7) is
to increase the refractive power on the short wavelength side with
the positive lens 21 and to reduce the axial chromatic aberration
in a wide wavelength band together with the achromatization.
Conditional Expression (8) is to reduce the amount of axial
chromatic aberration to be generated. It becomes easy to
effectively achieve the achromatization by arranging a negative
lens having a low refractive index and a high dispersion and a
positive lens having a high refractive index and a low dispersion
so as to satisfy Conditional Expressions (7) and (8).
[0044] The second lens unit L2 preferably includes, in order from
the object side to the image side, a positive lens 21, a positive
lens 22, a negative lens 23, and an aperture stop. Moreover, the
negative lens 23 preferably has a meniscus shape with a convex
surface directed to the object side and includes a lens surface
having an aspherical surface shape.
[0045] The effect of achromatization by the negative lens and the
positive lens arranged closer to the image side than the aperture
stop SP is increased by causing the light beam incident on the
second lens unit L2 to further converge at the positive lens 21,
the positive lens 22, and the negative lens 23. In addition, using
an aspherical lens as the negative lens 23 makes it efficiently
correct spherical aberration, which occurs due to the positive lens
21 and the positive lens 22 which tend to have a large curvature of
their lens surfaces, and allows the lens effective diameter after
the negative lens 23 to be reduced.
[0046] The third lens unit L3 preferably consists of, in order from
the object side to the image side, a cemented lens formed by
cementing a positive lens and a negative lens, a negative lens, and
a positive lens. This configuration makes it easier to efficiently
correct the Petzval sum with a smaller number of lenses. The third
lens unit L3 preferably includes at least one aspherical surface.
Since in an optical system having a short back focus, particularly,
the off-axis aberration is likely to increase, the field curvature
and the distortion are corrected and further the sagittal flare is
effectively corrected by using an aspherical surface.
[0047] The first lens unit L1 preferably consists of, in order from
the object side to the image side, a positive lens, a positive
lens, and a negative lens. This configuration allows the incident
light beam to be condensed at the positive lens and to be dispersed
at the negative lens to efficiently cause the light beam to
converge.
[0048] In Examples 2 and 3, the second lens unit L2 moves during
focusing. In Example 3, the third lens unit L3 moves along a locus
different from that of the second lens unit L2 during focusing.
This configuration makes it easier to effectively correct a
variation in aberration during focusing.
[0049] Next, an Example of a digital still camera (image pickup
apparatus) using the optical system of one of Examples as an image
pickup optical system will be described using FIG. 5.
[0050] In FIG. 5, 10 denotes a camera body; 11, an image pickup
optical system formed by the optical system of the Example; 12, a
solid-state image pickup element (photoelectric conversion element)
such as a CCD sensor or a CMOS sensor that is incorporated in the
camera body and receives light of a subject image formed by the
image pickup optical system 11.
[0051] As described above, it is possible to obtain an image pickup
optical system whose entire system is small in size and which has a
good optical performance, by applying the optical system of the
Example to an image pickup apparatus such as a digital still
camera.
[0052] The following present specific numerical data of Examples 1
to 4. In each numerical data, i indicates the order counted from
the object side; ri, the curvature radius of the i-th optical
surface (the i-th surface); di, the distance on the axis between
the i-th surface and the (i+1)-th surface. EA indicates the
effective diameter (the diameter of a range through which a light
beam passes). Moreover, ndi and .nu.di respectively indicate the
refractive index and the Abbe number of the material of an optical
member between the i-th surface and the (i+1)-th surface for the
d-line. When the X axis is the optical-axis direction, the H axis
is a direction perpendicular to the optical axis, the direction of
travel of light is positive; R is the paraxial curvature radius; K
is the conic constant; A, B, C, and D are aspherical coefficients
respectively, the aspherical shape is expressed by the following
expression:
X = H 2 / R 1 + 1 - ( 1 + K ) ( H / R ) 2 + AH 4 + BH 6 + CH 8 + DH
10 . ##EQU00001##
[0053] In the following table, * means a surface having an
aspherical surface shape. The "e-x" means 10.sup.-x. OBJ indicates
the object distance. The object distance 1E+30 means infinity. BF
indicates the air-equivalent back focus length (the distance from
the lens surface closest to the image side in the optical system to
the image plane on the optical axis). The total lens length is a
value obtained by adding a value of the back focus BF to the
distance from the first lens surface to the last lens surface (the
lens surface closest to the image side). In addition, the relations
between the above-described Conditional Expressions and numerical
data are shown in Table 1.
TABLE-US-00001 (Numerical data 1) Unit i EA R d glass nd .nu.d 1 1
70.87 68.4564 8.2000 SFPM2 1.59522 67.73 2 69.33 144.7664 0.5000 3
66.77 68.5861 12.0000 SFPL51 1.49700 81.54 4 65.05 -800.0000 2.8000
SNBM51 1.61340 44.27 5 58.59 57.7047 15.3149 2 6 55.60 55.8845
5.0000 SNPH4 1.89286 20.36 7 54.03 78.7959 0.5000 8 50.60 36.0000
11.5000 SFPM2 1.59522 67.73 9 47.96 191.1367 3.8524 10* 39.81
65.7976 2.0000 SNBH56 1.85478 24.80 11 33.90 25.3489 8.5000 12
33.00 .infin. 4.0000 (aperture stop) 13 32.17 -67.4064 1.6000
STIM22 1.64769 33.79 14 32.01 46.6554 9.0000 SLAH55V 1.83481 42.72
15 31.88 -56.3647 1.7000 16 31.64 -36.4167 1.5000 STIM35 1.69895
30.13 17 32.19 69.5252 7.5000 TAFD25 1.90366 31.31 18 32.32
-50.0834 2.0000 3 19 36.39 111.1397 7.0000 TAFD30 1.88300 40.80 20
36.41 -56.7163 1.7000 STIM1 1.62588 35.70 21 35.61 49.5256 7.0000
22* 35.71 -50.0584 2.3000 LBAL42 1.58313 59.38 23* 38.37 .infin.
0.5000 24 41.47 67.7770 5.5000 TAFD35 1.91082 35.25 25 41.59
8469.3686 13.5279 IMG Aspherical coefficient R10 R22 R23 R 65.7976
-50.0584 1E+13 k 0 0 0 A -2.9208E-06 -2.7151E-06 -3.0334E-06 B
-4.6570E-10 5.6754E-09 4.1049E-09 C 3.5596E-13 -4.9970E-12
-4.2155E-12 D 5.5963E-16 1.5780E-14 1.1825E-14 Lens interval OBJ d5
d18 1E+30 15.315 2.000 4100 13.140 4.175 700 2.500 14.815
TABLE-US-00002 (Numerical data 2) Unit i EA R d glass nd .nu.d 1 1
70.08 63.4639 9.0000 SYGH51 1.75500 52.32 2 68.66 151.8003 0.5000 3
65.04 61.8854 11.0000 SFPL55 1.43875 94.66 4 63.14 800.0000 2.0000
SNBM51 1.61340 44.27 5 55.11 42.4980 16.2666 2 6 52.97 52.6458
5.5000 SNPH1W 1.80809 22.76 7 51.65 88.0595 0.5000 8 47.85 33.5000
11.8000 SFPL51 1.49700 81.54 9 45.40 347.7223 1.2000 10* 40.76
73.9307 2.0000 SNBH56 1.85478 24.80 11 34.75 25.9345 8.7000 12
34.00 .infin. 4.5000 (aperture stop) 13 33.24 -57.3706 1.6000 SNBH8
1.72047 34.71 14 33.49 127.0378 8.0000 TAFD37 1.90043 37.37 15
33.64 -54.2677 1.7176 16 33.35 -37.6961 1.5000 STIM5 1.60342 38.03
17 33.79 54.8160 9.0000 TAFD30 1.88300 40.80 18 33.69 -55.6956
2.0000 3 19 38.10 94.3506 10.0000 TAFD30 1.88300 40.80 20 37.84
-49.1069 1.7000 STIM22 1.64769 33.79 21 36.07 45.7002 7.7933 22*
36.27 -68.8229 2.3000 STIM28 1.68893 31.07 23* 38.61 .infin. 0.5000
24 41.95 64.7739 5.3000 SNBH56 1.85478 24.80 25 42.01 502.6807
13.9170 IMG Aspherical coefficient R10 R22 R23 R 73.9307 -68.8229
1E+13 k 0 0 0 A -2.34369E-06 -1.35723E-05 -0.000011349 B
-4.57974E-10 2.80731E-08 2.66457E-08 C 3.89088E-13 -4.82515E-11
-4.04256E-11 D -2.38394E-16 4.46053E-14 3.66763E-14 Lens interval
OBJ d5 d18 1E+30 16.27 2 4000 13.88 4.39 700 2.5 15.77
TABLE-US-00003 (Numerical data 3) Unit i EA R d glass nd .nu.d 1 1
77.18 70.7213 10.8178 PCD51 1.59349 67.00 2 75.54 249.8665 0.5000 3
69.06 72.9663 12.0622 SFPL55 1.43875 94.66 4 66.92 -425.5839 2.0000
SNBH5 1.65412 39.68 5 58.70 70.5590 19.3840 2 6 53.22 61.3718
5.5000 SNPH4 1.89286 20.36 7 51.55 124.5569 0.5000 8 45.53 32.7351
11.0000 SFPL55 1.43875 94.66 9 42.30 196.9214 2.8412 10* 36.39
74.4943 2.0000 SNBH56 1.85478 24.80 11 31.12 24.6139 8.7546 12
29.57 .infin. 7.2975 (aperture stop) 13 28.12 -75.8069 1.5000 SNBH5
1.65412 39.68 14 28.40 33.7056 8.0000 SLAL14 1.69680 55.53 15 28.65
-56.3206 2.2485 16 28.62 -31.3990 1.5000 STIL1 1.54814 45.78 17
32.03 132.0308 8.0000 TAFD30 1.88300 40.80 18 33.97 -45.1046 3.0000
3 19 37.27 122.2481 4.7000 TAFD45 1.95375 32.32 20 37.24 -160.7110
1.7000 STIM8 1.59551 39.24 21 36.85 58.4894 5.7902 22* 37.05
-79.5321 2.3000 STIL1 1.54814 45.78 23 39.58 74.1827 0.5000 24
41.26 56.8279 6.0000 TAFD30 1.88300 40.80 25 41.40 2949.8738
14.0824 IMG Aspherical coefficient R10 R22 R 74.4943 -79.5321 k 0 0
A -1.90055E-06 -2.99483E-07 B 1.00991E-10 2.41357E-09 C
-9.37309E-14 -2.75377E-12 D 5.65326E-16 7.35518E-16 Lens interval
OBJ d5 d18 1.00E+30 19.384 3 4106 16.355 6.029 706 2.5 19.884
TABLE-US-00004 (Numerical data 4) Unit i EA R d glass nd .nu.d 1 1
76.73 67.4702 11.0000 PCD51 1.59349 67.00 2 74.70 193.2837 0.5000 3
69.32 74.8550 12.5000 SFPL55 1.43875 94.66 4 66.28 -550.3944 2.0000
SNBH5 1.65412 39.68 5 58.92 74.4220 30.4001 2 6 49.92 56.0347
6.0000 SNPH4 1.89286 20.36 7 47.83 107.8774 0.5000 8 42.65 32.3851
10.0000 SFPL55 1.43875 94.66 9 39.69 277.8320 2.9974 10* 33.46
79.4323 2.0000 SNBH56 1.85478 24.80 11 28.78 24.1970 6.7447 12
27.85 .infin. 3.5143 (aperture stop) 13 27.17 -60.7450 1.5000 SNBH5
1.65412 39.68 14 27.37 29.2377 8.0000 SYGH51 1.75500 52.32 15 27.47
-50.9260 1.8825 16 27.41 -30.5521 1.5000 STIL1 1.54814 45.78 17
30.09 210.4584 7.0000 TAFD30 1.88300 40.80 18 31.80 -43.0700 3.0000
3 19 35.15 -803.3981 6.0000 TAFD45 1.95375 32.32 20 35.51 -47.2877
1.7000 STIM28 1.68893 31.07 21 35.70 77.0121 5.7610 22* 35.90
-54.3484 2.3000 LBSL7 1.51633 64.06 23 39.37 140.3451 0.5000 24
42.36 61.7179 6.5000 TAFD35 1.91082 35.25 25 42.57 -261.0109
14.4943 IMG Aspherical coefficient R10 R22 R 79.4323 -54.3484 k 0 0
A -3.22032E-06 -1.5876E-06 B 3.14236E-10 1.91273E-09 C -5.64278E-13
3.991E-13 D 1.79148E-15 -5.06168E-15 Lens interval OBJ d5 d18 d25
1.00E+30 30.40 3 14.50 4100 27.87 5.50 14.53 350 2.5 27.38
18.02
TABLE-US-00005 TABLE 1 Example 1 2 3 4 Focal length f 86.5 86.5
100.0 100.0 Fno 1.24 1.24 1.46 1.45 Focal length of first 380.9
431.3 269.6 261.0 lens unit f1 Focal length of 87.8 86.3 104.1 90.3
second lens unit f2 Focal length of third 468.3 447.5 820 833.3
lens unit f3 Thickness of first 23.5 22.5 25.38 26.0 lens unit D1
Thickness of second 56.7 56.0 59.1 51.6 lens unit D2 Thickness of
third 24.0 27.6 21.0 22.8 lens unit D3 Back focus BF 13.5 13.9 14.1
14.5 Ra1 49.53 45.70 54.13 77.01 Ra2 -50.06 -68.82 -84.95 -54.35
Conditional Total lens length 135.0 138.3 142.0 148.3 expression
(1) D3/BF 1.77 1.98 1.49 1.57 (2) f1/f 4.40 4.99 2.70 2.61 (3) f2/f
1.02 1.00 1.04 0.90 (4) f3/f 5.41 5.17 8 8.33 (5) Nasp 1.855 1.855
1.855 1.855 (6) (Ra1 + Ra2)/ -0.005 -0.202 -0.222 0.173 (Ra1 - Ra2)
(7) .theta.gF21 0.639 0.631 0.639 0.639 (8) .theta.gF22 0.544 0.537
0.534 0.534
[0054] 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.
[0055] This application claims the benefit of Japanese Patent
Application No. 2017-173821, filed Sep. 11, 2017, which is hereby
incorporated by reference herein in its entirety.
* * * * *