U.S. patent application number 14/684457 was filed with the patent office on 2015-07-30 for imaging lens.
The applicant listed for this patent is FUJIFILM Corporation. Invention is credited to Toru ITO, Toshiaki KATSUMA, Hiromitsu YAMAKAWA.
Application Number | 20150212299 14/684457 |
Document ID | / |
Family ID | 47422291 |
Filed Date | 2015-07-30 |
United States Patent
Application |
20150212299 |
Kind Code |
A1 |
YAMAKAWA; Hiromitsu ; et
al. |
July 30, 2015 |
IMAGING LENS
Abstract
An imaging lens substantially consists of five lenses of a first
lens having a meniscus shape with its convex surface facing an
object side and negative refractive power, a second lens having
negative refractive power, and the image-side surface of which has
a convex shape facing an image side in the vicinity of an optical
axis, a third lens having positive refractive power, a stop, a
fourth lens having positive refractive power, and a fifth lens
having negative refractive power. At least one of the surfaces of
the first lens through the fifth lens is aspherical. A
predetermined conditional formula about a distance on the optical
axis from an object-side surface of the first lens to an image
plane and a distance on the optical axis from the object-side
surface of the first lens to the image-side surface of the second
lens is satisfied.
Inventors: |
YAMAKAWA; Hiromitsu;
(Saitama-ken, JP) ; ITO; Toru; (Saitama-ken,
JP) ; KATSUMA; Toshiaki; (Saitama-ken, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
FUJIFILM Corporation |
Tokyo |
|
JP |
|
|
Family ID: |
47422291 |
Appl. No.: |
14/684457 |
Filed: |
April 13, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14109110 |
Dec 17, 2013 |
9036269 |
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14684457 |
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PCT/JP2012/003983 |
Jun 19, 2012 |
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14109110 |
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Current U.S.
Class: |
359/714 |
Current CPC
Class: |
G02B 9/60 20130101; G02B
13/18 20130101; G02B 13/0045 20130101; G02B 13/06 20130101 |
International
Class: |
G02B 13/00 20060101
G02B013/00; G02B 9/60 20060101 G02B009/60; G02B 13/06 20060101
G02B013/06 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 22, 2011 |
JP |
2011-137937 |
Claims
1. An imaging lens consisting of five lenses of: a first lens
having a meniscus shape with its convex surface facing an object
side and negative refractive power; a second lens having negative
refractive power; a third lens having positive refractive power; a
fourth lens having positive refractive power; and a fifth lens
having negative refractive power, which are in this order from the
object side, wherein at least one of the surfaces of the first lens
through the fifth lens is aspherical, and wherein the following
conditional formulas are satisfied: 0.11<d1-4/L (2-1);
0.08<d4-5/f (7); 0.08<d10/f<0.54 (8-2); 0.48<f3/f (9);
1.5<Bf/f<3.0 (10-1); -5.0<r10/f<-0.50 (11-1);
5.0<L/f<20.0 (12-1); and (r8+r9)/(r8-r9)<2.0 (13-1), where
L: a distance on the optical axis from an object-side surface of
the first lens to an image plane (a distance between the fifth lens
and the image plane is a distance in air), d1-4: a distance on the
optical axis from the object-side surface of the first lens to the
image-side surface of the second lens, d4-5: a distance on the
optical axis from the image-side surface of the second lens to the
object-side surface of the third lens, f: a focal length of an
entire system, d10: the thickness of a fifth lens on an optical
axis, f3: a focal length of a third lens, Bf: a back focus of an
entire system, r10: a curvature radius of an object-side surface of
a fifth lens in the vicinity of an optical axis, r8: a curvature
radius of an object-side surface of a fourth lens in the vicinity
of an optical axis, and r9: a curvature radius of an image-side
surface of a fourth lens in the vicinity of an optical axis.
2. The imaging lens, as defined in claim 1, wherein the following
conditional formula is satisfied: 2.0<f3/f<20.0 (9-1), where
f3: a focal length of the third lens, and f: a focal length of an
entire system.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to an imaging lens and an
imaging apparatus. In particular, the present invention relates to
a wide-angle imaging lens appropriate for use in an in-vehicle
camera, a surveillance camera, or the like using an imaging device,
such as a CCD (Charge Coupled Device) and a CMOS (Complementary
Metal Oxide Semiconductor). Further, the present invention relates
to an imaging apparatus including the imaging lens.
[0003] 2. Description of the Related Art
[0004] In recent years, the size of an imaging device, such as a
CCD and a CMOS, became very small, and the resolution of the
imaging device became very high. Therefore, the size and the weight
of the body of imaging equipment and an imaging lens mounted on the
imaging equipment also need to be reduced. Meanwhile, an imaging
lens used in an in-vehicle camera, a surveillance camera or the
like needs to have high weather-resistance characteristics and high
optical performance with a wide angle of view so that an excellent
view is secured for a wide range.
[0005] Imaging lenses in the aforementioned fields are disclosed,
for example, in U.S. Pat. No. 7,684,127 (Patent Document 1),
Japanese Unexamined Patent Publication No. 2009-216956 (Patent
Document 2), and U.S. Patent Application Publication No.
20110102541 (Patent Document 3). Patent Documents 1 through 3
disclose imaging lenses, each consisting of five lenses including
an aspherical lens.
SUMMARY OF THE INVENTION
[0006] In recent years, a need for a wider angle of view is
increasing in the fields of an in-vehicle camera, a surveillance
camera and the like. For example, a full angle of view exceeding
180 degrees is needed. Further, as the size of an imaging device
became smaller and the resolution of the imaging device became
higher in recent years, an imaging lens having high resolution and
high optical performance in which an excellent image is obtainable
in a wide range of an image formation area is needed. Further, a
faster lens is needed. However, in conventional lens systems, it
has been difficult to achieve a wide angle of view and high optical
performance to satisfy the need of recent years while structuring
the lens systems at low cost and in small size.
[0007] The lens disclosed in Patent Document 1 has an F-number of
2.0, and the lens is a relatively fast lens. However, a full angle
of view is less than 163 degrees. Therefore, the performance of the
lens is insufficient when the lens is applied to an imaging lens
with a full angle of view exceeding 180 degrees.
[0008] The lenses disclosed in Patent Documents 2 and 3 are
wide-angle lenses with full angles of view of 190 degrees or
greater. However, F-number is 2.8. Therefore, performance
deteriorates if F-number is reduced to 2.0 to obtain a faster lens,
or if a full angle of view is increased to exceed about 210
degrees.
[0009] In view of the foregoing circumstances, it is an object of
the present invention to provide an imaging lens that can achieve a
wider angle of view and high performance while making the imaging
lens in small size and at low cost. Further, it is another object
of the present invention to provide an imaging apparatus including
the imaging lens.
[0010] A first imaging lens of the present invention is an imaging
lens substantially consisting of five lenses of:
[0011] a first lens having a meniscus shape with its convex surface
facing an object side and negative refractive power;
[0012] a second lens having negative refractive power, and the
image-side surface of which has a convex shape facing an image side
in the vicinity of an optical axis;
[0013] a third lens having positive refractive power;
[0014] a stop;
[0015] a fourth lens having positive refractive power; and
[0016] a fifth lens having negative refractive power, which are in
this order from the object side,
[0017] wherein at least one of the surfaces of the first lens
through the fifth lens is aspherical, and
[0018] wherein the following conditional formula (2-1) is
satisfied:
0.11<d1-4/L (2-1),
where
[0019] L: a distance on the optical axis from an object-side
surface of the first lens to an image plane (a distance between the
fifth lens and the image plane is a distance in air), and
[0020] d1-4: a distance on the optical axis from the object-side
surface of the first lens to the image-side surface of the second
lens.
[0021] A second imaging according of the present invention is an
imaging lens substantially consisting of five lenses of:
[0022] a first lens having a meniscus shape with its convex surface
facing an object side and negative refractive power;
[0023] a second lens having negative refractive power;
[0024] a third lens having positive refractive power;
[0025] a stop;
[0026] a fourth lens having positive refractive power; and
[0027] a fifth lens having negative refractive power, which are in
this order from the object side,
[0028] wherein at least one of the surfaces of the first lens
through the fifth lens is aspherical, and
[0029] wherein the following conditional formula (2-2) is
satisfied:
0.40<d1-4/L (2-2),
where
[0030] L: a distance on the optical axis from an object-side
surface of the first lens to an image plane (a distance between the
fifth lens and the image plane is a distance in air), and
[0031] d1-4: a distance on the optical axis from the object-side
surface of the first lens to the image-side surface of the second
lens.
[0032] The expression about the first lens "having a meniscus shape
with its convex surface facing an object side and negative
refractive power" is considered in a paraxial region when the first
lens includes an aspherical surface.
[0033] The expression "substantially consisting of five lenses"
means that a lens substantially without power, an optical element,
such as a stop and a cover glass, which is not a lens, a mechanism
part, such as a lens flange, a lens barrel, an imaging device and a
hand shake blur correction mechanism, and the like may be included
besides the five lenses.
[0034] In the second lens, the third lens, the fourth lens and the
fifth lens, when a lens includes an aspherical surface, whether
refractive power is positive or negative is considered in a
paraxial region unless particularly mentioned.
[0035] In the first and second imaging lenses of the present
invention, it is desirable that the following conditional formulas
(1) through (13) are satisfied. In a desirable mode, the imaging
lens of the present invention may include structure of one of the
following conditional formulas (1) through (13). Alternatively, the
imaging lens of the present invention may include structure of
arbitrary two or more of them in combination:
0.10<f34/L<0.17 (1);
0.40<d1-4/L<0.50 (2);
0.45<d3-11/L<0.54 (3);
0.02<d4-5/L<0.05 (4);
0.012<d6-8/L<0.04 (5);
L/r3<-6.0 (6);
0.08<d4-5/f (7);
0.04<d10/f (8);
0.48<f3/f (9);
0.71<Bf/f (10);
r10/f<-0.25 (11);
1.2<L/f (12);
and
(r8+r9)/(r8-r9)<2.9 (13),
where
[0036] f34: a combined paraxial focal length of a third lens and a
fourth lens,
[0037] L: a distance on an optical axis from an object-side surface
of a first lens to an image plane (a distance between a fifth lens
and the image plane is a distance in air),
[0038] d1-4: a distance on an optical axis from an object-side
surface of a first lens to an image-side surface of a second
lens,
[0039] d3-11: a distance on an optical axis from an object-side
surface of a second lens to an image-side surface of a fifth
lens,
[0040] d4-5: a distance on an optical axis from an image-side
surface of a second lens to an object-side surface of a third
lens,
[0041] d6-8: a distance on an optical axis from an image-side
surface of a third lens to an object-side surface of a fourth
lens,
[0042] r3: a curvature radius of an object-side surface of a second
lens in the vicinity of an optical axis,
[0043] f: a focal length of an entire system,
[0044] d10: the thickness of a fifth lens on an optical axis,
[0045] f3: a focal length of a third lens,
[0046] Bf: a back focus of an entire system,
[0047] r10: a curvature radius of an object-side surface of a fifth
lens in the vicinity of an optical axis,
[0048] r8: a curvature radius of an object-side surface of a fourth
lens in the vicinity of an optical axis, and
[0049] r9: a curvature radius of an image-side surface of a fourth
lens in the vicinity of an optical axis.
[0050] In the first and second imaging lenses of the present
invention, it is desirable that the following conditional formulas
(7-1) through (13-1) are satisfied. In a desirable mode, the
imaging lens of the present invention may include structure of one
of the following conditional formulas (7-1) through (13-1).
Alternatively, the imaging lens of the present invention may
include structure of arbitrary two or more of them in
combination:
0.20<d4-5/f<0.60 (7-1);
0.20<d10/f<0.80 (8-1);
2.0<f3/f<20.0 (9-1);
1.5<Bf/f<3.0 (10-1);
-5.0<r10/f<-0.50 (11-1);
5.0<L/f<20.0 (12-1);
and
(r8+r9)/(r8-r9)<2.0 (13-1).
[0051] An imaging apparatus of the present invention includes the
aforementioned imaging lens of the present invention.
[0052] According to the first and second imaging lenses of the
present invention, the shape and the refractive power of each lens
is appropriately set in a lens system of at least five lenses.
Further, the first and second imaging lenses satisfy conditional
formula (2-1) and conditional formula (2-2), respectively.
Therefore, it is possible to achieve a sufficiently wide angle of
view, a sufficiently large maximum aperture and high optical
performance while structuring the lens system at low cost and in
small size.
[0053] The imaging apparatus of the present invention includes the
first or second imaging lens of the present invention. Therefore,
the imaging apparatus is structurable at low cost and in small
size. Further, imaging at a wide angle of view is possible, and
high quality images are obtainable.
BRIEF DESCRIPTION OF THE DRAWINGS
[0054] FIG. 1 is a cross section illustrating a lens structure and
optical paths of an imaging lens in Example 1 of the present
invention;
[0055] FIG. 2 is a cross section illustrating a lens structure and
optical paths of an imaging lens in Example 2 of the present
invention;
[0056] FIG. 3 is a cross section illustrating a lens structure and
optical paths of an imaging lens in Example 3 of the present
invention;
[0057] FIG. 4 is a cross section illustrating a lens structure and
optical paths of an imaging lens in Example 4 of the present
invention;
[0058] FIG. 5 is a cross section illustrating a lens structure and
optical paths of an imaging lens in Example 5 of the present
invention;
[0059] FIG. 6 is a cross section illustrating a lens structure and
optical paths of an imaging lens in Example 6 of the present
invention;
[0060] FIG. 7 is a cross section illustrating a lens structure and
optical paths of an imaging lens in Example 7 of the present
invention;
[0061] FIG. 8 is a cross section illustrating a lens structure and
optical paths of an imaging lens in Example 8 of the present
invention;
[0062] FIG. 9, Sections A through G illustrate aberration diagrams
of the imaging lens in Example 1 of the present invention;
[0063] FIG. 10, Sections A through G illustrate aberration diagrams
of the imaging lens in Example 2 of the present invention;
[0064] FIG. 11, Sections A through G illustrate aberration diagrams
of the imaging lens in Example 3 of the present invention;
[0065] FIG. 12, Sections A through G illustrate aberration diagrams
of the imaging lens in Example 4 of the present invention;
[0066] FIG. 13, Sections A through G illustrate aberration diagrams
of the imaging lens in Example 5 of the present invention;
[0067] FIG. 14, Sections A through G illustrate aberration diagrams
of the imaging lens in Example 6 of the present invention;
[0068] FIG. 15, Sections A through G illustrate aberration diagrams
of the imaging lens in Example 7 of the present invention;
[0069] FIG. 16, Sections A through G illustrate aberration diagrams
of the imaging lens in Example 8 of the present invention; and
[0070] FIG. 17 is a diagram for explaining arrangement of an
imaging apparatus for in-vehicle use according to an embodiment of
the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0071] Embodiments of an imaging lens of the present invention will
be described in detail with reference to drawings. FIG. 1 through
FIG. 8 are cross sections illustrating structural examples of
imaging lenses according to embodiments of the present invention.
FIG. 1 through FIG. 8 correspond to imaging lenses in Examples 1
through 8, which will be described later, respectively. The basic
structure is similar to each other in the examples illustrated in
FIG. 1 through FIG. 8, and similar illustration methods are used.
Therefore, the imaging lenses according to the first and second
embodiments of the present invention will be described mainly with
reference to FIG. 1.
[0072] First, the structure of the first embodiment of the present
invention will be described. The imaging lens according to the
first embodiment of the present invention is a lens system composed
of five lenses, in which first lens L1, second lens L2, third lens
L3, fourth lens L4 and fifth lens L5 are arranged along optical
axis Z in this order from an object side. Aperture stop St is
arranged between third lens L3 and fourth lens L4. Since aperture
stop St is arranged between third lens L3 and fourth lens L4, it is
possible reduce the size of the imaging lens in the diameter
direction.
[0073] In FIG. 1, the left side is the object side and the right
side is the image side. Illustrated aperture stop St does not
necessarily represent the size nor the shape of aperture stop St,
but represents the position of aperture stop St on the optical
axis. In FIG. 1, sign ri (i=1, 2, 3, . . . ) represents the
curvature radius of each lens surface, and sign di (i=1, 2, 3 . . .
) represents a distance between surfaces. Further, FIG. 1
illustrates axial rays 2 from an object point at infinity, and
off-axial rays 3 at maximum angle of view.
[0074] In FIG. 1, a case of applying the imaging lens to an imaging
apparatus is taken into consideration, and an imaging device 5
arranged at image plane Sim of the imaging lens is also
illustrated. When the imaging lens is applied to an imaging
apparatus, it is desirable to set a cover glass, and a low-pass
filter or an infrared ray cut filter, or the like based on the
structure of a camera on which the lens is mounted. FIG. 1
illustrates an example in which parallel-flat-plate-shaped optical
member PP, which is assumed to be such elements, is arranged
between fifth lens L5 and the imaging device 5 (image plane
Sim).
[0075] First lens L1 is a meniscus lens having negative refractive
power, and the object-side surface of which is convex. Such
structure in which first lens L1 is a meniscus lens having negative
refractive power, and the object-side surface of which is convex,
is advantageous to widening an angle of view and correcting
distortion. First lens L1, which is arranged on the most object
side, is likely be exposed to wind and rain or solvent for
cleaning. Therefore, there is a risk that dirt, dust, droplets of
water or the like remains on first lens L1. The convex shape of the
object-side surface of first lens L1 is advantageous to reducing
such a risk.
[0076] In the example illustrated in FIG. 1, first lens L1 is a
spherical lens. Alternatively, first lens L1 may be an aspherical
lens. However, as the material of first lens L1, which is arranged
on the most object side, glass is more desirable than resin, as
will be described later. Therefore, when first lens L1 is a
spherical lens, first lens L1 is producible at lower cost, compared
with a case in which first lens L1 is an aspherical lens.
[0077] At least one of the surfaces of each of second lens L2,
third lens L3, fourth lens L4 and fifth lens L5 is aspherical. When
at least one of the surfaces of each of second lens L2, third lens
L3, fourth lens L4 and fifth lens L5 is aspherical, it is possible
to achieve high resolution while reducing the total length of the
optical system in the optical axis direction. Further, it is
possible to excellently correct various aberrations, such as a
spherical aberration, a coma aberration, curvature of field and
distortion, while structuring the system using a small number of
lenses. It is desirable that both surfaces of each of second lens
L2, third lens L3, fourth lens L4 and fifth lens L5 are aspherical
to more excellently correct aberrations.
[0078] The image-side surface of second lens L2 has a convex shape
facing the image side in the vicinity of the optical axis, and
second lens L2 has negative refractive power.
[0079] With reference to FIG. 1, the shape of the image-side
surface of second lens L2 will be described. In FIG. 1, point Q1
and point Q2 are two effective diameter outermost edge points on
the image-side surface of second lens L2, and point Q3 is a point
on the optical axis on the image-side surface of second lens L2. In
FIG. 1, arc C2 is an arc that passes through the three points of
point Q1, point Q2 and point Q3. Arc C2 will be described
later.
[0080] Further, a point on the image-side surface of second lens L2
in the vicinity of point Q3 is point X4, and an intersection of a
normal at point X4 and the optical axis is point P4. At this time,
the shape of second lens L2 at point X4 is defined based on whether
point P4 is located on the object side of point Q3 or on the image
side of point Q3. The shape of the image-side surface is defined as
a convex shape facing the image side when point P4 is located on
the object side of point Q3. The shape of the image-side surface is
defined as a concave shape facing the image side when point P4 is
located on the image side of point Q3.
[0081] The expression "the image-side surface has a convex shape
facing the image side in the vicinity of the optical axis" means a
shape in which point P4 is located on the object side of point Q3
in the vicinity of the optical axis.
[0082] When the image-side surface of second lens L2 has a convex
shape facing the image side in the vicinity of the optical axis,
and second lens L2 has negative refractive power, it is possible to
suppress an angle of incidence of axial rays passing through the
image-side surface of second lens L2 so that the angle is small.
Therefore, it is possible to excellently correct a spherical
aberration.
[0083] Third lens L3, fourth lens L4 and fifth lens L5 have
positive refractive power, positive refractive power and negative
refractive power, respectively.
[0084] Further, the imaging lens according to the first embodiment
satisfies the following conditional formula (2-1):
0.11<d1-4/L (2-1),
where
[0085] L: a distance on the optical axis from an object-side
surface of first lens L1 to an image plane (a distance between
fifth lens L5 and the image plane is a distance in air), and
[0086] d1-4: a distance on the optical axis from the object-side
surface of first lens L1 to the image-side surface of second lens
L2.
[0087] If the value is lower than the lower limit of conditional
formula (2-1), first lens L1 and second lens L2 are located close
to each other at their peripheral portions, and it becomes
impossible to arrange them in an appropriate manner.
[0088] In the imaging lens according to the first embodiment of the
present invention, the refractive power and the shape of each of
first lens L1 through fifth lens L5 are appropriate set, as
described above, in a five-group five-element lens structure.
Further, aperture stop St is arranged between third lens L3 and
fourth lens L4. Therefore, a sufficiently wide angle of view and a
sufficiently large maximum aperture are achieved while the imaging
lens consists of a small number of lenses, and the total length of
the imaging lens is short, and the size of the imaging lens is
small, and the cost of the imaging lens is low. Further, it is
possible to correct various aberrations including a spherical
aberration, a coma aberration, curvature of field and distortion in
an excellent manner. Further, according to the imaging lens in the
first embodiment of the present invention, it is possible to
achieve high resolution in a wide range of image formation area.
Therefore, it is possible to cope with an imaging device the
resolution of which became higher in recent years.
[0089] Next, the structure of the second embodiment of the present
invention will be described. The imaging lens according to the
second embodiment of the present invention is a lens system
composed of five lenses, in which first lens L1, second lens L2,
third lens L3, fourth lens L4 and fifth lens L5 are arranged along
optical axis Z in this order from an object side. Aperture stop St
is arranged between third lens L3 and fourth lens L4. Since
aperture stop St is arranged between third lens L3 and fourth lens
L4, it is possible reduce the size of the imaging lens in the
diameter direction.
[0090] First lens L1 is a meniscus lens having negative refractive
power, and the object-side surface of which is convex. Such
structure in which first lens L1 is a meniscus lens having negative
refractive power, and the object-side surface of which is convex,
is advantageous to widening an angle of view and correcting
distortion. First lens L1, which is arranged on the most object
side, is likely be exposed to wind and rain or solvent for
cleaning. Therefore, there is a risk that dirt, dust, droplets of
water or the like remains on first lens L1. The convex shape of the
object-side surface of first lens L1 is advantageous to reducing
such a risk.
[0091] At least one of the surfaces of each of second lens L2,
third lens L3, fourth lens L4 and fifth lens L5 is aspherical. When
at least one of the surfaces of each of second lens L2, third lens
L3, fourth lens L4 and fifth lens L5 is aspherical, it is possible
to achieve high resolution while reducing the total length of the
optical system in the optical axis direction. Further, it is
possible to excellently correct various aberrations, such as a
spherical aberration, a coma aberration, curvature of field and
distortion, while structuring the system using a small number of
lenses. It is desirable that both surfaces of each of second lens
L2, third lens L3, fourth lens L4 and fifth lens L5 are aspherical
to more excellently correct aberrations.
[0092] Second lens L2, third lens L3, fourth lens L4 and fifth lens
L5 have negative refractive power, positive refractive power,
positive refractive power and negative refractive power,
respectively.
[0093] Further, the imaging lens according to the second embodiment
satisfies the following conditional formula (2-2):
0.40<d1-4/L (2-2),
where
[0094] L: a distance on the optical axis from an object-side
surface of first lens L1 to an image plane (a distance between
fifth lens L5 and the image plane is a distance in air), and
[0095] d1-4: a distance on the optical axis from the object-side
surface of first lens L1 to the image-side surface of second lens
L2.
[0096] If the value is lower than the lower limit of conditional
formula (2-2), first lens L1 and second lens L2 are located close
to each other at their peripheral portions, and it becomes
impossible to arrange them in an appropriate manner.
[0097] In the imaging lens according to the second embodiment of
the present invention, the refractive power and the shape of each
of first lens L1 through fifth lens L5 are appropriate set, as
described above, in a five-group five-element lens structure.
Further, aperture stop St is arranged between third lens L3 and
fourth lens L4. Therefore, a sufficiently wide angle of view and a
sufficiently large maximum aperture are achieved while the imaging
lens consists of a small number of lenses, and the total length of
the imaging lens is short, and the size of the imaging lens is
small, and the cost of the imaging lens is low. Further, it is
possible to correct various aberrations including a spherical
aberration, a coma aberration, curvature of field and distortion in
an excellent manner. Further, according to the imaging lens in the
second embodiment of the present invention, it is possible to
achieve high resolution in a wide range of image formation area.
Therefore, it is possible to cope with an imaging device the
resolution of which became higher in recent years.
[0098] In the imaging lens according to the first and second
embodiments of the present invention (hereinafter, referred to as
embodiments of the present invention), it is desirable that the
Abbe number of the material of first lens L1 for d-line is greater
than or equal to 40. It is desirable that the Abbe number of the
material of second lens L2 for d-line is greater than or equal to
50. It is desirable that the Abbe number of the material of third
lens L3 for d-line is less than or equal to 30. It is desirable
that the Abbe number of the material of fourth lens L4 for d-line
is greater than or equal to 50. It is desirable that the Abbe
number of the material of fifth lens L5 for d-line is less than or
equal to 30.
[0099] When first lens L1, second lens L2, third lens L3, fourth
lens and fifth lens L5 have negative refractive power, negative
refractive power, positive refractive power, positive refractive
power and negative refractive power, respectively, in the vicinity
of the optical axis, and materials with appropriate Abbe numbers
are selected for the lenses, it is possible to excellently correct
a lateral chromatic aberration while achieving a wide angle lens
exceeding 200 degrees.
[0100] It is desirable that a distance between fourth lens L4 and
fifth lens L5 is short, and does not substantially change from a
central portion through a peripheral portion of the lenses.
Further, it is desirable that the thickness of fifth lens L5 at its
central portion and the thickness of fifth lens L5 at its
peripheral portion do not substantially differ from each other.
Then, rays pass through the image-side surface of fourth lens L4,
the object-side surface of fifth lens L5 and the image-side surface
of fifth lens L5 at substantially the same angle for any angle of
view. Therefore, it is possible to prevent sudden generation of
aberrations by production error or the like.
[0101] It is desirable that the imaging lens according to the
embodiment of the present invention further includes the following
structure or structures. A desirable mode may include one of the
following structures, or arbitrary two or more of them in
combination.
[0102] It is desirable that the following conditional formula (7)
is satisfied:
0.08<d4-5/f (7),
where
[0103] d4-5: a distance on the optical axis from the image-side
surface of second lens L2 to the object-side surface of third lens
L3, and
[0104] f: a focal length of an entire system.
[0105] If the value is lower than the lower limit of conditional
formula (7), second lens L2 and third lens L3 are too close to each
other, and a risk of touching each other increases. Further, it
becomes difficult to remove ghost light caused by the two surfaces
of the image-side surface of second lens L2 and the object-side
surface of third lens L3.
[0106] It is desirable that the following conditional formula (8)
is satisfied:
0.04<d10/f (8),
where
[0107] d10: the thickness of fifth lens L5 on the optical axis.
[0108] If the value is lower than the lower limit of conditional
formula (8), the thickness of fifth lens L5 becomes too small, and
production becomes difficult.
[0109] It is desirable that the following conditional formula (9)
is satisfied:
0.48<f3/f (9),
where
[0110] f3: a focal length of third lens L3.
[0111] If the value is lower than the lower limit of conditional
formula (9), the refractive power of third lens L3 becomes too
strong, and the sensitivity to a change in aberrations caused by an
error in shape and eccentricity becomes high. Therefore, high
accuracy in shape and assembly becomes required.
[0112] It is desirable that the following conditional formula (10)
is satisfied:
0.71<Bf/f (10),
where
[0113] Bf: a back focus of an entire system.
[0114] If the value is lower than the lower limit of conditional
formula (10), the image-side surface of fifth lens L5 and the image
plane become too close to each other, and a defect, such as a
scratch on a lens, greatly affects an image. Further, it becomes
difficult to arrange the lens in an appropriate manner.
[0115] It is desirable that the following conditional formula (11)
is satisfied:
r10/f<-0.25 (11),
where
[0116] r10: a curvature radius of an object-side surface of fifth
lens L5 in the vicinity of the optical axis.
[0117] If the value exceeds the upper limit of conditional formula
(11), the absolute value of the curvature radius of the object-side
surface of fifth lens L5 in the vicinity of the optical axis
becomes too small. Therefore, it becomes difficult to excellently
correct a spherical aberration. When the curvature radius of the
object-side surface of fifth lens L5 is set at an appropriate value
so that desirable optical performance is achievable, if the value
exceeds the upper limit of conditional formula (11), a focal length
becomes long. Hence, it becomes impossible to secure a necessary
angle of view.
[0118] It is desirable that the following conditional formula (12)
is satisfied:
1.2<L/f (12).
[0119] If the value is lower than the lower limit of conditional
formula (12), when a distance on the optical axis from the
object-side surface of first lens L1 to the image plane is set at
an appropriate length, the focal length becomes long. Therefore, it
becomes impossible to obtain a large angle of view.
[0120] It is desirable that the following conditional formula (13)
is satisfied:
(r8+r9)/(r8-r9)<2.9 (13),
where
[0121] r8: a curvature radius of an object-side surface of fourth
lens L4 in the vicinity of the optical axis, and
[0122] r9: a curvature radius of an image-side surface of fourth
lens L4 in the vicinity of the optical axis.
[0123] If the value exceeds the upper limit of conditional formula
(13), the absolute value of the curvature radius of the object-side
surface of fourth lens L4 in the vicinity of the optical axis
becomes too small, or the absolute value of the curvature radius of
the image-side surface of fourth lens L4 in the vicinity of the
optical axis becomes too small. Therefore, it becomes difficult to
excellently correct a spherical aberration.
[0124] It is more desirable that the following conditional formulas
(7-1) through (13-1) are satisfied. When conditional formulas (7-1)
and (13-1) are satisfied, it is possible to achieve effects similar
to those achievable by satisfying conditional formulas (7) through
(13), or to further enhance the effects:
0.20<d4-5/f<0.60 (7-1);
0.20<d10/f<0.80 (8-1);
2.0<f3/f<20.0 (9-1);
1.5<Bf/f<3.0 (10-1);
-5.0<r10/f<-0.50 (11-1);
5.0<L/f<20.0 (12-1);
and
(r8+r9)/(r8-r9)<2.0 (13-1).
[0125] If the value exceeds the upper limit of conditional formula
(7-1), the structure is disadvantageous to minimizing the total
lens length.
[0126] If the value exceeds the upper limit of conditional formula
(8-1), the structure is disadvantage to reducing the total lens
length. Further, it becomes difficult to provide a sufficient back
focus.
[0127] If the value exceeds the upper limit of conditional formula
(9-1), the refractive power of third lens L3 becomes too weak, and
correction of a lateral chromatic aberration becomes
insufficient.
[0128] If the value exceeds the upper limit of conditional formula
(10-1), it is possible to provide a sufficient distance between
fifth lens L5 and an image plane. However, a distance from the
object-side surface of first lens L1 to the image plane becomes
long. Therefore, the size of the imaging lens according to the
embodiment of the present invention and the size of an imaging
apparatus, such as a camera, to which the imaging lens according to
the embodiment of the present invention has been applied become
large.
[0129] If the value is lower than the lower limit of conditional
formula (11-1), a space between fourth lens L4 and fifth lens L5
tends to become larger from the optical axis toward the outside.
Therefore, rays passing through fifth lens L5 are away from the
optical axis, and the outer diameter of fifth lens L5 becomes
large. Hence, the flexibility in selection of the shape of a lens
barrel of the imaging lens according to the embodiment of the
present invention becomes low.
[0130] If the value exceeds the upper limit of conditional formula
(12-1), a distance from the object-side surface of first lens L1 to
the image plane becomes long. Therefore, the size of the imaging
lens according to the embodiment of the present invention and the
size of an imaging apparatus, such as a camera, to which the
imaging lens according to the embodiment of the present invention
has been applied become large.
[0131] With respect to second lens L2, third lens L3, fourth lens
L4 and fifth lens L5, arcs, each of which passes through three
points of two effective diameter outermost edge points and a point
on an optical axis, are defined for an object-side surface and an
image-side surface in a cross section including the optical axis.
When it is assumed that each of the lenses has a whole shape in
which the object-side surface and the image-side surface have
curvature radii of the arcs, respectively, if the image-side
surface of second lens L2 has a concave shape facing the image
side, and second lens L2 has negative refractive power, and the
object-side surface of third lens L3 has a convex shape facing the
object side, and third lens has positive refractive power, and the
image-side surface of fourth lens L4 has a convex shape facing the
image side, and fourth lens L4 has positive refractive power, and
fifth lens L5 has a meniscus shape with its convex surface facing
the image side and negative refractive power, it is desirable that
the following conditional formulas (1) through (6) are
satisfied:
0.10<f34/L<0.17 (1);
0.40<d1-4/L<0.50 (2);
0.45<d3-11/L<0.54 (3);
0.02<d4-5/L<0.05 (4);
0.012<d6-8/L<0.04 (5);
and
L/r3<-6.0 (6),
where
[0132] f34: a combined paraxial focal length of third lens L3 and
fourth lens L4,
[0133] L: a distance on an optical axis from an object-side surface
of first lens L1 to an image plane (a distance between fifth lens
L5 and the image plane is a distance in air),
[0134] d1-4: a distance on an optical axis from an object-side
surface of first lens L1 to an image-side surface of second lens
L2,
[0135] d3-11: a distance on an optical axis from an object-side
surface of second lens L2 to an image-side surface of fifth lens
L5,
[0136] d4-5: a distance on an optical axis from an image-side
surface of second lens L2 to an object-side surface of third lens
L3,
[0137] d6-8: a distance on an optical axis from an image-side
surface of third lens L3 to an object-side surface of fourth lens
L4, and
[0138] r3: a curvature radius of an object-side surface of second
lens L2 in the vicinity of an optical axis.
[0139] Here, with reference to FIG. 1, the shape of the image-side
surface of second lens L2 when second lens L2 is assumed to have
the aforementioned whole shape will be described. As described
above, arc C2 is an arc that passes through three points Q1, Q2 and
Q3.
[0140] Regarding second lens L2, the expression "the image-side
surface has a concave shape facing the image side" means that arc
C2, which passes through the three points of point Q1, point Q2 and
point Q3, has a concave shape facing the image side when it is
assumed that the image-side surface of second lens L2 has a lens
surface defined by arc C2. In other words, the image-side surface
of second lens L2 has a shape in which point Q3 is located at a
more object-side position, compared with point Q1 and point Q2.
Further, the expression "has negative refractive power" means that
the refractive power of a lens having a whole shape assumed with
respect to the object side and the image side is negative.
[0141] When it is assumed that third lens L3 has a whole shape as
described above, the shape of the object-side surface of third lens
L3 may be considered in a similar manner to second lens L2, which
has been described already. Specifically, the expression "the
object-side surface has a convex shape facing the object side"
means that arc C3, which passes through three points of two
effective diameter outermost edge points Q11 and Q12 on the
object-side surface of third lens L3 and point Q13 on an optical
axis on the object-side surface of third lens L3, has a convex
shape facing the object side when it is assumed that the
object-side surface of third lens L3 has a lens surface defined by
arc C3. In other words, the object-side surface of third lens L3
has a shape in which point Q13 is located at a more object-side
position, compared with point Q11 and point Q12. Further, the
expression "has positive refractive power" means that the
refractive power of a lens having a whole shape assumed with
respect to the object side and the image side is positive.
[0142] When it is assumed that fourth lens L4 has a whole shape as
described above, the shape of the image-side surface of fourth lens
L4 may be considered in a similar manner to second lens L2, which
has been described already. Specifically, the expression "the
image-side surface has a convex shape facing the image side" means
that arc C4, which passes through three points of two effective
diameter outermost edge points Q21 and Q22 on the image-side
surface of fourth lens L4 and point Q23 on an optical axis on the
image-side surface of fourth lens L4, has a convex shape facing the
image side when it is assumed that the image-side surface of fourth
lens L4 has a lens surface defined by arc C4. In other words, the
image-side surface of fourth lens L4 has a shape in which point Q23
is located at a more image-side position, compared with point Q21
and point Q22. Further, the expression "has positive refractive
power" means that the refractive power of a lens having a whole
shape assumed with respect to the object side and the image side is
positive.
[0143] When it is assumed that fifth lens L5 has a whole shape as
described above, the shape of the image-side surface of fifth lens
L5 may be considered in a similar manner to second lens L2, which
has been described already. Specifically, the expression "a
meniscus shape with its convex surface facing the image side" means
a meniscus shape in which arc C5, which passes through three points
of two effective diameter outermost edge points Q31 and Q32 on the
image-side surface of fifth lens L5 and point Q33 on an optical
axis on the image-side surface of fifth lens L5, is convex toward
the image side when it is assumed that the image-side surface of
fifth lens L5 has a lens surface defined by arc C5. In other words,
fifth lens L5 has a meniscus shape in which point Q33 is located at
a more image-side position, compared with point Q31 and point Q32.
Further, the expression "has negative refractive power" means that
the refractive power of a lens having a whole shape assumed with
respect to the object side and the image side is negative.
[0144] If the value is lower than the lower limit of conditional
formula (1), the absolute value of the refractive power of third
lens L3 and fourth lens L4 becomes too large, and requirement
regarding production error of each lens and accurate registration
becomes high. Therefore, the production characteristics become
lower, and that causes an increase in cost. If the value exceeds
the upper limit of conditional formula (1), the refractive power of
the entire lens system becomes insufficient, and a necessary angle
of view is not obtainable.
[0145] If the value is lower than the lower limit of conditional
formula (2), first lens L1 and second lens L2 are located close to
each other at their peripheral portions, and it becomes impossible
to arrange them in an appropriate manner. If the value exceeds the
upper limit of conditional formula (2), the effective diameter of
first lens L1 becomes large, and the total length and the outer
diameter of the entire lens system become large.
[0146] If the value is lower than the lower limit of conditional
formula (3), the thicknesses of second lens L2 through fifth lens
L5 and distances between lenses of second lens L2 through fifth
lens L5 need to be reduced. Therefore, the production
characteristics of each lens deteriorate, and it becomes impossible
to appropriately set the refractive power of each lens. Further, it
becomes difficult to correct chromatic aberrations in an excellent
manner. If the value exceeds the upper limit of conditional formula
(3), it becomes impossible to achieve reduction in the size of the
lens, and the size of the lens becomes large.
[0147] If the value is lower than the lower limit of conditional
formula (4), second lens L2 and third lens L3 are too close to each
other, and a risk of touching each other increases. Further, it
becomes difficult to remove ghost light caused by the two surfaces
of the image-side surface of second lens L2 and the object-side
surface of third lens L3. If the value exceeds the upper limit of
conditional formula (4), it becomes difficult to reduce the total
length of the lens.
[0148] If the value is lower than the lower limit of conditional
formula (5), third lens L3 and fourth lens L4 are too close to each
other, and it becomes difficult to form aperture stop St between
them. If the value exceeds the upper limit of conditional formula
(5), it becomes difficult to reduce the total length of the
lens.
[0149] If the value exceeds the upper limit of conditional formula
(6), it becomes difficult to correct a spherical aberration in an
excellent manner.
[0150] When second lens L2 has negative refractive power, it is
desirable that the aforementioned conditional formula (2-2) and the
following conditional formula (2-3) are satisfied:
0.40<d1-4/L<0.60 (2-3).
[0151] If the value is lower than the lower limit of conditional
formula (2-3), a peripheral portion of first lens L1 and a
peripheral portion of second lens L2 become close to each other.
Therefore, it becomes impossible to arrange the lenses in an
appropriate manner. If the value exceeds the upper limit of
conditional formula (2-3), the effective diameter of first lens L1
becomes large, and the total length and the outer diameter of the
entire lens system become large.
[0152] When second lens L2 has negative refractive power, it is
desirable that the following conditional formulas (7-2) and (8-2)
are satisfied:
d4-5/f<1.76 (7-2);
and
0.08<d10/f<0.54 (8-2).
[0153] If the value exceeds the upper limit of conditional formula
(7-2), the distance between second lens L2 and third lens L3
becomes too long, and the size of the entire lens becomes large.
Further, it becomes difficult to correct a coma aberration.
[0154] If the value is lower than the lower limit of conditional
formula (8-2), the thickness of fifth lens L5 becomes too small,
and production becomes difficult. If the value exceeds the upper
limit of conditional formula (8-2), the thickness of fifth lens L5
becomes too large, and the size of a lens becomes large. If a
distance from the object-side surface of first lens L1 to the image
plane is tried to be suppressed, it becomes difficult to secure a
sufficient back focus.
[0155] When second lens L2 has negative refractive power, it is
more desirable that the following conditional formulas (7-3) and
(8-3) are satisfied. When conditional formulas (7-3) and (8-3) are
satisfied, it is possible to enhance the effect achievable by
satisfying conditional formulas (7-2) and (8-2).
0.15<d4-5/f<0.66 (7-3)
0.46<d10/f<0.54 (8-3)
[0156] If the value is lower than the lower limit of conditional
formula (7-3), second lens L2 and third lens L3 are too close to
each other, and a risk of touching each other increases. Further,
it becomes difficult to remove ghost light caused by the two
surfaces of the image-side surface of second lens L2 and the
object-side surface of third lens L3.
[0157] When second lens L2 has negative refractive power, it is
desirable that the following conditional formulas (9-2) and (10-2)
are satisfied:
4.7<f3/f (9-2);
and
1.84<Bf/f (10-2).
[0158] If the value is lower than the lower limit of conditional
formula (9-2), the refractive power of third lens L3 becomes too
strong, and the sensitivity to a change in aberrations caused by an
error in shape and eccentricity becomes high. Hence, high accuracy
in shape and assembly becomes required.
[0159] If the value is lower than the lower limit of conditional
formula (10-2), the image-side surface of fifth lens L5 and the
image plane become too close to each other, and a defect, such as a
scratch on a lens, greatly affects an image. Further, it becomes
difficult to arrange the lens in an appropriate manner.
[0160] When second lens L2 has negative refractive power, it is
more desirable that the following conditional formulas (9-3) and
(10-3) are satisfied. When conditional formulas (9-3) and (10-3)
are satisfied, it is possible to enhance the effect achievable by
satisfying conditional formulas (9-2) and (10-2).
4.7<f3/f<20.0 (9-3)
1.77<Bf/f<2.3 (10-3)
[0161] If the value exceeds the upper limit of conditional formula
(9-3), the refractive power of third lens L3 becomes too weak, and
correction of a lateral chromatic aberration becomes insufficient.
If the value exceeds the upper limit of conditional formula (10-3),
it is possible to make a distance from fifth lens L5 to the image
plane sufficient, but a distance from the object-side surface of
first lens L1 to the image plane becomes long. Therefore, the size
of the imaging lens according to the embodiment of the present
invention and the size of an imaging apparatus, such as a camera,
to which the imaging lens according to the embodiment of the
present invention has been applied become large.
[0162] It is desirable that the following conditional formulas
(11-2) and (12-2) are satisfied:
-1.33<r10/f<-0.64 (11-2);
and
11.9<L/f (12-2).
[0163] If the value is lower than the lower limit of conditional
formula (11-2), when a focal length required for the angle of view
is appropriately set, the curvature radius of the object-side
surface of fifth lens L5 in the vicinity of the optical axis
becomes large. Therefore, the effect of correcting a spherical
aberration becomes low. If the value exceeds the upper limit of
conditional formula (11-2), the absolute value of the curvature
radius of the object-side surface of fifth lens L5 in the vicinity
of the optical axis becomes too small. Therefore, it becomes
difficult to excellently correct a spherical aberration. When the
curvature radius of the object-side surface of fifth lens L5 is set
at an appropriate value so that desirable optical performance is
achievable, if the value exceeds the upper limit of conditional
formula (11-2), a focal length becomes long. Hence, it becomes
impossible to secure a necessary angle of view.
[0164] If the value is lower than the lower limit of conditional
formula (12-2), when a distance on the optical axis from the
object-side surface of first lens L1 to the image plane is set at
an appropriate length, the focal length becomes long. Hence, it
becomes impossible to obtain a large angle of view.
[0165] It is more desirable that the following conditional formula
(12-3) is satisfied:
11.9<L/f<20.0 (12-3).
[0166] If the value exceeds the upper limit of conditional formula
(12-3), a distance from the object-side surface of first lens L1 to
the image plane becomes long. Therefore, the size of the imaging
lens according to the embodiment of the present invention becomes
large. Further, the size of an imaging apparatus, such as a camera,
to which the imaging lens according to the embodiment of the
present invention has been applied becomes large.
[0167] When the object-side surface of second lens L2 has a concave
shape facing the object side in the vicinity of the optical axis,
and second lens L2 has negative refractive power, it is desirable
that the following conditional formulas (13-2) and (12-4) are
satisfied:
0.75<(r8+r9)/(r8-r9)<2.96 (13-2);
and
1.6<L/f<15.7 (12-4).
[0168] Here, the shape of the object-side surface of second lens L2
may be considered in a similar manner to the shape of the
image-side surface of second lens L2. In FIG. 1, an intersection of
the object-side surface of second lens L2 and the optical axis is
point Q13, and a point on the object-side surface of second lens L2
in the vicinity of point Q13 is point X3. Further, an intersection
of a normal at point X3 and the optical axis is point P3. At this
time, the shape of second lens L2 at point X3 is defined based on
whether point P3 is located on the object side of point Q13 or on
the image side of point Q13. The shape of an object-side surface is
defined as a concave shape facing the object side when point P3 is
located on the object side of point Q13. The shape of the
object-side surface is defined as a convex shape facing the object
side when point P3 is located on the image side of point Q13.
[0169] The expression "the object-side surface has a concave shape
facing the object side in the vicinity of the optical axis" means a
shape in which point P3 is located on the object side of point Q13
in the vicinity of the optical axis.
[0170] When the object-side surface of second lens L2 has a concave
shape facing the object side in the vicinity of the optical axis,
and second lens L2 has negative refractive power, it is possible to
suppress an angle of incidence of axial rays passing through the
image-side surface of second lens L2 so that the angle is small.
Therefore, it is possible to excellently correct a spherical
aberration.
[0171] If the value is lower than the lower limit of conditional
formula (13-2) or exceeds the upper limit of conditional formula
(13-2), the absolute value of the curvature radius of the
object-side surface of fourth lens L4 in the vicinity of the
optical axis becomes too small, or the absolute value of the
curvature radius of the image-side surface of fourth lens L4 in the
vicinity of the optical axis becomes too small. Therefore, it
becomes difficult to excellently correct a spherical
aberration.
[0172] If the value is lower than the lower limit of conditional
formula (12-4), when a distance on the optical axis from the
object-side surface of first lens L1 to the image plane is set at
an appropriate length, the focal length becomes long. Therefore, it
becomes impossible to obtain a large angle of view. If the value
exceeds the upper limit of conditional formula (12-4), when a
necessary angle of view is secured, a distance from the object-side
surface of first lens L1 to the image plane becomes too long.
Therefore, the size of the imaging lens according to the embodiment
of the present invention and the size of an imaging apparatus, such
as a camera, to which the imaging lens according to the embodiment
of the present invention has been applied become large.
[0173] When the object-side surface of second lens L2 has a concave
shape facing the object side in the vicinity of the optical axis,
and second lens L2 has negative refractive power, it is more
desirable that the following conditional formulas (13-3) and (12-5)
are satisfied. When conditional formulas (13-3) and (12-5) are
satisfied, it is possible to further enhance the effect achievable
by satisfying conditional formulas (13-2) and (12-4).
0.75<(r8+r9)/(r8-r9)<2.0 (13-3)
5.0<L/f<20.0 (12-5)
[0174] It is desirable that the full angle of view of the imaging
lens according to the embodiment of the present invention is
greater than 200 degrees. The full angle of view is twice an angle
formed by a principal ray of off-axial rays 3 at the maximum angle
of view and optical axis Z. When the lens system has a wide angle
of view with a full angle of view greater than 200 degrees, the
lens system can cope with a need for a wider angle in recent
years.
[0175] In the imaging lens according to the embodiment of the
present invention, it is desirable that each of all of first lens
L1 through fifth lens L5 is a single lens, which is not a cemented
lens, for example, as illustrated in the example of FIG. 1. When
use of an imaging lens according to the embodiment of the present
invention in tough environment conditions, such as use in an
in-vehicle camera or a surveillance camera, is expected, it is
desirable that the imaging lens does not include any cemented lens.
When the imaging lens does not include any cemented lens, it is
possible to produce the imaging lens at low cost.
[0176] When an imaging lens according to an embodiment of the
present invention is used in tough environment conditions, for
example, such as use in an in-vehicle camera or a surveillance
camera, first lens L1, which is arranged on the most object side,
needs to use a material resistant to a deterioration of a surface
by wind and rain and a change in temperature by direct sun light.
Further, the material needs to be resistant to chemicals, such as
oils and fats and detergents. In other words, the material needs to
be highly water-resistant, weather-resistant, acid-resistant,
chemical-resistant, and the like. For example, it is desirable to
use a material with water durability of 1 by the powder method
regulated by Japan Optical Glass Manufacturers' Association.
Further, in some cases, first lens L1 needs to use a material that
is hard and not easily breakable. If the material of first lens L1
is glass, it is possible to satisfy such needs. Alternatively,
transparent ceramic may be used as the material of first lens
L1.
[0177] Here, a protection means may be applied to the object-side
surface of first lens L1 to increase the strength,
scratch-resistance, and chemical-resistance of the surface. In that
case, the material of first lens L1 may be plastic. The protection
means may be a hard coating or a water-repellent coating.
[0178] It is desirable that plastic is used as the material of
second lens L2, third lens L3, fourth lens L4 and fifth lens L5. In
such a case, it is possible to accurately produce an aspherical
shape and to reduce the weight and the cost.
[0179] When plastic is used as the material, it is desirable to
select a material having low water absorption characteristics to
minimize a change in performance by absorption of water. Further,
it is desirable that the double refraction characteristics of the
material, which cause a drop in resolution, are low. As material
satisfying these conditions, it is desirable to select
cycloolefin-based plastic for second lens L2 and fourth lens L4,
and to select polycarbonate-based plastic or polyester-based
plastic for third lens L3 and fifth lens L5.
[0180] When plastic is used as the material of at least one of
second lens L2, third lens L3, fourth lens L4 and fifth lens L5,
so-called nano composite material, in which particles smaller than
the wavelength of light are mixed into plastic, may be used, as the
material.
[0181] In the imaging lens according to an embodiment of the
present invention, an anti-reflection coating may be applied to
each lens to reduce ghost light, or the like. In that case, for
example, in the imaging lens illustrated in FIG. 1, angles formed
by tangent lines on a peripheral portion of the image-side surface
of first lens L1 and an optical axis, angles formed by tangent
lines on a peripheral portion of the image-side surface of second
lens L2 and the optical axis, and angles formed by tangent lines on
a peripheral portion of the object-side surface of third lens L3
and the optical axis are small. Therefore, the thickness of the
anti-reflection coating in the peripheral portion is less than the
thickness of the anti-reflection coating in a central portion.
Therefore, it is possible to evenly reduce reflectance for the
whole effective diameter by applying anti-reflection coating to at
least one surface including the image-side surface of first lens L1
of the three surfaces so that a wavelength at which reflectance in
the vicinity of the center is the lowest is longer than or equal to
600 nm and shorter than or equal to 900 nm. Consequently, it is
possible to reduce ghost light.
[0182] If the wavelength at which reflectance in the vicinity of
the center is the lowest is shorter than 600 nm, a wavelength at
which reflectance in the peripheral portion is the lowest becomes
too short. Therefore, reflectance on a long wavelength side becomes
high. Hence, reddish ghost tends to be generated. If the wavelength
at which reflectance in the vicinity of the center is the lowest is
longer than 900 nm, a wavelength at which reflectance in the
central portion is the lowest becomes too long. Therefore,
reflectance on a short wavelength side becomes high. Hence, the
tone of an image becomes quite reddish, and bluish ghost tends to
be generated.
[0183] Further, in the imaging lens according to an embodiment of
the present invention, rays of light passing through the outside of
the effective diameter between lenses may become stray light, and
reach the image plane. Further, the stray light may become ghost.
Therefore, it is desirable that a light shield means for blocking
the stray light is provided, if necessary. The light shield means
may be provided, for example, by applying an opaque paint to a
portion outside the effective diameter on the image side of a lens,
or by providing there an opaque plate member. Alternatively, an
opaque plate member, as a light shield means, may be provided in
the optical path of rays that will become stray light.
[0184] Here, a filter that cuts ultraviolet light through blue
light, or an IR (InfraRed) cut filter, which cuts infrared light,
may be inserted between the lens system and the imaging device 5
based on the purpose of use of the imaging lens. Alternatively, a
coating having properties similar to those of the filter may be
applied to a lens surface.
[0185] FIG. 1 illustrates a case in which optical member PP, which
is assumed to be various filters, is arranged between a lens system
and the imaging device 5. Instead, the various filters may be
arranged between lenses. Alternatively, a coating having an action
similar to that of the various filters may be applied to a lens
surface of one of the lenses included in the imaging lens.
[0186] Next, numerical value examples of imaging lenses of the
present invention will be described. Lens cross sections of imaging
lenses of Example 1 through Example 8 are illustrated in FIG. 1
through FIG. 8, respectively.
[0187] Table 1 shows lens data and aspherical surface data of the
imaging lens of Example 1. Similarly, Tables 2 through 8 show lens
data and aspherical surface data of the imaging lenses of Examples
2 through 8, respectively. Next, the meanings of signs in the
tables will be described by using Example 1, as an example. The
meanings of the signs are basically the same for Examples 2 through
8.
[0188] In the lens data of Table 1, the column of "surface" shows
the surface number of the i-th surface (i=1, 2, 3, . . . ). The
most object-side surface of composition elements is the first
surface, and surface numbers sequentially increase toward the image
side. The column of ri shows the curvature radius of the i-th
surface, and the column of di shows a distance on optical axis Z
between the i-th surface and the (i+1)th surface. Here, the sign of
a curvature radius is positive when a surface is convex toward the
object side, and the sign of a curvature radius is negative when a
surface is convex toward the image side. In each example, signs ri,
di (i=1, 2, 3, . . . ) in the table of lens data correspond to
signs ri, di in the lens cross section.
[0189] In the lens data of Table 1, the column of Ndj shows the
refractive index of the j-th lens (j=1, 2, 3, . . . ) for e-line
(wavelength is 546.07 nm). The most-object side lens is the first
lens, and the number j sequentially increases toward the image
side. The column of vdj shows the Abbe number of the j-th optical
element for d-line (wavelength is 587.6 nm). Here, the lens data
include aperture stop St. In the column of curvature radius, the
sign ".infin." is written for a surface corresponding to aperture
stop St.
[0190] In FIG. 1 through FIG. 8, optical member PP arranged between
fifth lens L5 and image plane Sim is assumed to be a cover glass, a
filter or the like. In all of Examples 1 through 8, optical member
PP uses a glass material with a refractive index of 1.52, and the
thickness of optical member PP is 0.3 mm.
[0191] The lens data of Table 1 show, as the curvature radius of an
aspherical surface, the numerical value of a curvature radius in
the vicinity of an optical axis (a paraxial curvature radius). The
aspherical surface data show the surface numbers of aspherical
surfaces and aspherical surface coefficients related to the
respective aspherical surfaces. In the aspherical surface data,
"E-n" (n: integer) means ".times.10.sup.-n", and "E+n" means
".times.10.sup.n". Here, the aspherical surface coefficients are
values of coefficients K, am (m=3, 4, 5, . . . 20) in the following
aspherical surface equation:
Zd=Ch.sup.2/{1+(1-KC.sup.2h.sup.2).sup.1/2}+.SIGMA.amh.sup.m,
where
[0192] Zd: the depth of an aspherical surface (the length of a
perpendicular from a point on the aspherical surface at height h to
a plane that contacts with the vertex of the aspherical surface and
is perpendicular to the optical axis),
[0193] h: height (a length from the optical axis to the lens
surface),
[0194] C: paraxial curvature, and
[0195] K, am: aspherical surface coefficients (m=3, 4, 5, . . .
20).
TABLE-US-00001 TABLE 1 EXAMPLE 1 LENS DATA SURFACE ri di Nej .nu.
dj 1 13.985 1.373 1.77250 49.6 2 3.926 2.741 *3 -1.141 1.079
1.53391 55.9 *4 -4.611 0.435 *5 3.518 1.907 1.61399 25.5 *6 -26.288
0.342 7 .infin. 0.049 *8 7.402 1.532 1.53391 55.9 *9 -0.659 0.078
*10 -0.641 0.441 1.61399 25.5 *11 -1.078 ASPHERICAL SURFACE DATA
SURFACE NUMBER S3 S4 S5 S6 K 0 0 0 0 a3 3.576464E-01 7.706201E-01
3.515082E-01 -7.947400E-02 a4 -1.016111E-01 -6.044794E-01
-4.246929E-01 3.505654E-01 a5 8.479838E-03 2.856369E-01
3.918567E-01 -3.154111E-01 a6 -4.623276E-04 4.358390E-01
7.984634E-02 -1.394462E-01 a7 -3.409172E-03 -9.495146E-02
-4.286800E-01 6.793783E-01 a8 1.625375E-03 -3.510710E-01
3.279487E-01 -4.308856E-01 a9 1.534663E-04 -7.505533E-02
-1.131106E-01 -9.795827E-02 a10 -5.995773E-05 9.423859E-02
3.871380E-02 -2.133580E-01 a11 -1.411097E-05 7.736418E-02
-3.450454E-02 3.899051E-01 a12 -3.829580E-06 -1.422350E-02
1.047480E-02 1.022302E+00 a13 -1.805495E-06 1.923155E-02
-6.770055E-03 -1.881608E+00 a14 1.156699E-06 -1.060713E-02
6.295750E-03 8.744934E-01 a15 -5.925829E-08 -4.498603E-03
4.715367E-03 -3.435509E-01 a16 4.734991E-08 -8.998241E-03
1.533831E-03 6.730979E-01 a17 4.849819E-09 1.707355E-03
-3.396328E-03 -1.036047E+00 a18 -6.436196E-09 1.433295E-03
-2.127777E-04 3.160080E-01 a19 -9.040534E-10 2.016128E-03
-7.678793E-04 7.705161E-01 a20 3.473144E-10 -9.504585E-04
6.405319E-04 -4.699698E-01 SURFACE NUMBER S8 S9 S10 S11 K 0 0 0 0
a3 -1.396500E-01 7.025409E-02 1.078557E-01 4.663454E-02 a4
1.352860E+00 -1.527332E-01 -7.438782E-01 -7.122033E-01 a5
-7.713490E+00 1.910193E+00 2.833043E+00 2.475412E+00 a6
2.783909E+01 -4.052031E+00 -4.603685E+00 -4.172161E+00 a7
-6.159921E+01 2.020579E+00 2.150063E+00 2.085344E+00 a8
1.205453E+02 1.294629E+00 9.379704E-01 1.113230E+00 a9
-3.909677E+02 1.255004E+00 1.346708E+00 1.276477E+00 a10
7.844087E+02 -2.094913E+00 -1.532997E+00 -1.782637E+00 a11
1.161999E+03 -5.908116E+00 -6.106926E+00 -5.795929E+00 a12
-8.651383E+03 8.044380E+00 8.112672E+00 7.829564E+00 a13
1.412214E+04 -1.729469E+00 -1.750387E+00 -1.789756E+00 a14
-5.230743E+03 -7.030856E-02 1.419159E-01 -1.259836E-02 a15
5.891316E+03 -6.305335E-01 -8.208504E-01 -7.646552E-01 a16
-3.904402E+04 1.108659E-01 -6.985194E-02 6.854295E-02 a17
1.845009E+04 -8.579107E-01 -5.781271E-01 -4.924041E-01 a18
1.008726E+05 1.224937E+00 1.032975E+00 9.225144E-01 a19
-1.476223E+05 -3.756974E-01 -4.717136E-01 -3.442198E-01 a20
5.987350E+04 -2.590228E-02 9.186641E-02 1.025721E-02
TABLE-US-00002 TABLE 2 EXAMPLE 2 LENS DATA SURFACE ri di Nej .nu.
dj 1 13.797 1.373 1.77250 49.6 2 3.926 2.881 *3 -1.170 1.079
1.53391 55.9 *4 -5.492 0.435 *5 3.631 1.932 1.61399 25.5 *6 -20.410
0.300 7 .infin. 0.049 *8 8.977 1.463 1.53391 55.9 *9 -0.661 0.078
*10 -0.748 0.441 1.61399 25.5 *11 -1.349 ASPHERICAL SURFACE DATA
SURFACE NUMBER S3 S4 S5 S6 K 0 0 0 0 a3 3.539595E-01 7.808703E-01
3.654480E-01 -7.591526E-02 a4 -1.021603E-01 -5.988237E-01
-4.428854E-01 4.182345E-01 a5 8.449642E-03 2.696675E-01
4.008681E-01 -4.420593E-01 a6 -4.445336E-04 4.303864E-01
8.175390E-02 -2.159074E-02 a7 -3.400541E-03 -8.697305E-02
-4.260987E-01 7.077475E-01 a8 1.630302E-03 -3.514382E-01
3.273276E-01 -4.434090E-01 a9 1.548438E-04 -7.537073E-02
-1.137188E-01 -8.739877E-02 a10 -5.970371E-05 9.491822E-02
3.862484E-02 -2.348962E-01 a11 -1.408423E-05 7.665647E-02
-3.490593E-02 3.673860E-01 a12 -3.899113E-06 -1.411874E-02
1.050747E-02 9.820261E-01 a13 -1.840153E-06 1.911943E-02
-6.664320E-03 -1.939137E+00 a14 1.135292E-06 -1.050423E-02
6.329345E-03 1.034345E+00 a15 -7.052008E-08 -4.898382E-03
4.760936E-03 -4.396754E-01 a16 5.808032E-08 -8.712266E-03
1.546386E-03 5.903603E-01 a17 4.311106E-09 1.688484E-03
-3.390084E-03 -1.058621E+00 a18 -6.579684E-09 1.439408E-03
-2.093136E-04 4.583074E-01 a19 -9.301822E-10 2.011399E-03
-7.712580E-04 8.622714E-01 a20 3.443170E-10 -9.533207E-04
6.331388E-04 -5.745744E-01 SURFACE NUMBER S8 S9 S10 S11 K 0 0 0 0
a3 -1.455975E-01 5.034487E-02 9.931259E-02 4.663454E-02 a4
1.401127E+00 -7.834891E-02 -6.751775E-01 -6.880257E-01 a5
-7.739998E+00 1.886268E+00 2.886397E+00 2.455138E+00 a6
2.767881E+01 -3.992784E+00 -4.562947E+00 -4.160256E+00 a7
-6.141640E+01 1.887307E+00 2.101811E+00 2.136864E+00 a8
1.204464E+02 1.077434E+00 7.686593E-01 1.074442E+00 a9
-3.917929E+02 1.673703E+00 1.012838E+00 1.267042E+00 a10
7.857260E+02 -2.156610E+00 -9.260374E-01 -1.786298E+00 a11
1.163933E+03 -5.726527E+00 -5.980687E+00 -5.796457E+00 a12
-8.649674E+03 7.945970E+00 8.013340E+00 7.825704E+00 a13
1.410989E+04 -2.139901E+00 -1.880021E+00 -1.792560E+00 a14
-5.242394E+03 -9.506382E-02 -1.218706E-02 -7.919194E-03 a15
5.944578E+03 -1.259505E-01 -7.611840E-01 -7.641308E-01 a16
-3.908654E+04 1.329437E-01 -8.087464E-02 8.185696E-02 a17
1.837677E+04 -1.169882E+00 -6.050233E-01 -4.754929E-01 a18
1.012467E+05 1.271018E+00 1.071267E+00 8.913210E-01 a19
-1.481055E+05 -3.571733E-01 -3.787190E-01 -3.411988E-01 a20
6.005159E+04 -9.483955E-03 3.026210E-02 1.415507E-02
TABLE-US-00003 TABLE 3 EXAMPLE 3 LENS DATA SURFACE ri di Nej .nu.
dj 1 13.751 1.373 1.77250 49.6 2 3.926 2.881 *3 -1.193 1.079
1.53391 55.9 *4 -6.700 0.435 *5 3.373 1.952 1.61399 25.5 *6 -26.519
0.300 7 .infin. 0.049 *8 9.686 1.434 1.53391 55.9 *9 -0.665 0.078
*10 -0.736 0.441 1.61399 25.5 *11 -1.271 ASPHERICAL SURFACE DATA
SURFACE NUMBER S3 S4 S5 S6 K 0 0 0 0 a3 3.528750E-01 7.858190E-01
3.624675E-01 -7.577756E-02 a4 -1.027724E-01 -5.977613E-01
-4.462824E-01 4.075845E-01 a5 8.525890E-03 2.644539E-01
4.044869E-01 -4.194860E-01 a6 -4.291818E-04 4.285901E-01
8.187106E-02 -3.787963E-02 a7 -3.400936E-03 -8.755624E-02
-4.255482E-01 6.991522E-01 a8 1.629023E-03 -3.518754E-01
3.264400E-01 -4.382556E-01 a9 1.543706E-04 -7.407803E-02
-1.138905E-01 -6.431617E-02 a10 -5.975998E-05 9.448077E-02
3.792990E-02 -2.200397E-01 a11 -1.407886E-05 7.671916E-02
-3.467486E-02 3.757396E-01 a12 -3.866936E-06 -1.406532E-02
1.060082E-02 9.848795E-01 a13 -1.835094E-06 1.902902E-02
-6.623064E-03 -1.963793E+00 a14 1.131884E-06 -1.043651E-02
6.322980E-03 1.010611E+00 a15 -6.939696E-08 -4.890632E-03
4.793065E-03 -4.590771E-01 a16 5.808784E-08 -8.696599E-03
1.562045E-03 5.269904E-01 a17 4.279327E-09 1.672175E-03
-3.363745E-03 -1.114633E+00 a18 -6.605801E-09 1.439893E-03
-2.253217E-04 3.013455E-01 a19 -9.244114E-10 2.015326E-03
-7.604448E-04 1.500243E+00 a20 3.436345E-10 -9.555031E-04
6.223962E-04 -9.165478E-01 SURFACE NUMBER S8 S9 S10 S11 K 0 0 0 0
a3 -1.519224E-01 3.387135E-02 8.350297E-02 4.663454E-02 a4
1.415819E+00 -5.282771E-02 -6.337962E-01 -6.769970E-01 a5
-7.739690E+00 1.909825E+00 2.902839E+00 2.445728E+00 a6
2.767716E+01 -4.023987E+00 -4.563562E+00 -4.164501E+00 a7
-6.157586E+01 1.880916E+00 2.089935E+00 2.189921E+00 a8
1.203542E+02 1.080773E+00 7.648836E-01 1.028038E+00 a9
-3.919358E+02 1.690765E+00 9.986478E-01 1.270538E+00 a10
7.865038E+02 -2.159752E+00 -9.238030E-01 -1.789935E+00 a11
1.164389E+03 -5.737750E+00 -5.998119E+00 -5.796278E+00 a12
-8.645452E+03 7.939014E+00 8.026614E+00 7.825187E+00 a13
1.410403E+04 -2.149209E+00 -1.893462E+00 -1.792557E+00 a14
-5.240310E+03 -9.249844E-02 -1.817119E-02 -5.863436E-03 a15
5.941697E+03 -1.144137E-01 -7.704640E-01 -7.573736E-01 a16
-3.909321E+04 9.036724E-02 -5.816305E-02 8.208472E-02 a17
1.836772E+04 -1.148644E+00 -6.025709E-01 -4.762212E-01 a18
1.012382E+05 1.281340E+00 1.075507E+00 8.865069E-01 a19
-1.481062E+05 -3.542013E-01 -3.701229E-01 -3.421460E-01 a20
6.010184E+04 -1.377516E-02 1.927957E-02 1.626847E-02
TABLE-US-00004 TABLE 4 EXAMPLE 4 LENS DATA SURFACE ri di Nej .nu.
dj 1 13.820 1.373 1.77250 49.6 2 3.926 2.532 *3 -1.203 1.079
1.53391 55.9 *4 -5.840 0.435 *5 3.610 2.004 1.61399 25.5 *6
-549.752 0.246 7 .infin. 0.049 *8 8.749 1.559 1.53391 55.9 *9
-0.685 0.080 *10 -0.767 0.441 1.61399 25.5 *11 -1.240 ASPHERICAL
SURFACE DATA SURFACE NUMBER S3 S4 S5 S6 K 0 0 0 0 a3 3.528239E-01
7.871707E-01 3.709377E-01 -6.747215E-02 a4 -1.027089E-01
-5.866915E-01 -4.476078E-01 4.248430E-01 a5 8.443777E-03
2.548925E-01 4.058227E-01 -4.089012E-01 a6 -4.443869E-04
4.285302E-01 7.981317E-02 -3.170450E-02 a7 -3.405141E-03
-8.673852E-02 -4.209582E-01 7.159112E-01 a8 1.629517E-03
-3.505121E-01 3.246846E-01 -4.241142E-01 a9 1.572621E-04
-7.434330E-02 -1.139138E-01 -1.038036E-02 a10 -5.995026E-05
9.432114E-02 3.763748E-02 -1.645824E-01 a11 -1.407746E-05
7.668187E-02 -3.477317E-02 2.609583E-01 a12 -3.858858E-06
-1.385195E-02 1.099434E-02 9.574234E-01 a13 -1.839226E-06
1.898585E-02 -6.515933E-03 -2.013487E+00 a14 1.128370E-06
-1.044912E-02 6.260058E-03 9.565004E-01 a15 -7.074088E-08
-4.906149E-03 4.735694E-03 -4.454686E-01 a16 5.737447E-08
-8.712883E-03 1.551375E-03 5.201021E-01 a17 4.316429E-09
1.711487E-03 -3.379790E-03 -1.077566E+00 a18 -6.365026E-09
1.412073E-03 -2.027941E-04 3.101408E-01 a19 -9.592938E-10
2.011982E-03 -7.575931E-04 1.485990E+00 a20 3.399841E-10
-9.504919E-04 6.210215E-04 -9.317541E-01 SURFACE NUMBER S8 S9 S10
S11 K 0 0 0 0 a3 -1.451242E-01 4.567079E-02 1.030004E-01
4.663454E-02 a4 1.380315E+00 -3.232278E-02 -6.241143E-01
-6.798062E-01 a5 -7.587330E+00 1.966645E+00 2.878062E+00
2.434198E+00 a6 2.788068E+01 -4.142655E+00 -4.582913E+00
-4.169406E+00 a7 -6.145819E+01 1.901703E+00 2.089935E+00
2.188735E+00 a8 1.185564E+02 1.080371E+00 7.301002E-01 1.036921E+00
a9 -3.917860E+02 1.740564E+00 9.836524E-01 1.259764E+00 a10
7.887811E+02 -2.164846E+00 -9.961103E-01 -1.806298E+00 a11
1.160670E+03 -5.695600E+00 -5.930647E+00 -5.804193E+00 a12
-8.637423E+03 7.967917E+00 8.021326E+00 7.832240E+00 a13
1.411073E+04 -2.214012E+00 -1.879911E+00 -1.791759E+00 a14
-5.261047E+03 -1.647241E-01 -1.543738E-02 -1.107038E-03 a15
6.000001E+03 -2.072213E-01 -8.197889E-01 -7.514075E-01 a16
-3.918723E+04 2.979513E-01 -4.723724E-02 8.973097E-02 a17
1.837965E+04 -1.251498E+00 -5.454829E-01 -4.832081E-01 a18
1.012366E+05 1.311809E+00 1.068657E+00 8.830409E-01 a19
-1.481151E+05 -3.247293E-01 -3.638416E-01 -3.436322E-01 a20
6.016779E+04 -3.928186E-02 1.291888E-03 1.853297E-02
TABLE-US-00005 TABLE 5 EXAMPLE 5 LENS DATA SURFACE ri di Nej .nu.
dj 1 14.044 1.373 1.77250 49.6 2 4.000 2.531 *3 -1.262 1.079
1.53391 55.9 *4 -5.428 0.435 *5 4.799 2.051 1.61399 25.5 *6 405.687
0.290 7 .infin. 0.049 *8 6.867 1.631 1.53391 55.9 *9 -0.762 0.080
*10 -0.887 0.441 1.61399 25.5 *11 -1.279 ASPHERICAL SURFACE DATA
SURFACE NUMBER S3 S4 S5 S6 K 0 0 0 0 a3 3.517460E-01 7.998652E-01
3.752971E-01 -6.554253E-02 a4 -1.043551E-01 -5.747079E-01
-4.221723E-01 3.762600E-01 a5 8.075871E-03 2.505510E-01
3.933647E-01 -4.031976E-01 a6 -3.246340E-04 4.316264E-01
7.343820E-02 3.447437E-03 a7 -3.391957E-03 -8.629798E-02
-4.226439E-01 7.732548E-01 a8 1.636731E-03 -3.534020E-01
3.288067E-01 -5.754362E-01 a9 1.566353E-04 -7.423862E-02
-1.113689E-01 -6.684742E-02 a10 -6.025618E-05 9.502495E-02
3.835654E-02 -2.103687E-01 a11 -1.393241E-05 7.670111E-02
-3.581056E-02 1.981708E-01 a12 -3.946482E-06 -1.372719E-02
1.060292E-02 8.791662E-01 a13 -1.803564E-06 1.917962E-02
-6.622284E-03 -1.577738E+00 a14 1.119655E-06 -1.044754E-02
6.143874E-03 8.027891E-01 a15 -6.934616E-08 -4.831869E-03
4.714941E-03 -3.173624E-01 a16 5.712386E-08 -8.745329E-03
1.527680E-03 7.169571E-01 a17 4.175144E-09 1.630074E-03
-3.388350E-03 -1.069141E+00 a18 -6.417671E-09 1.379726E-03
-1.806104E-04 2.621830E-01 a19 -9.133102E-10 2.021259E-03
-6.985975E-04 1.184311E+00 a20 3.339660E-10 -9.379156E-04
5.920708E-04 -7.895090E-01 SURFACE NUMBER S8 S9 S10 S11 K 0 0 0 0
a3 -1.569576E-01 -5.785700E-02 2.199658E-02 4.663454E-02 a4
1.445080E+00 7.307219E-02 -5.522280E-01 -6.283695E-01 a5
-7.973389E+00 1.938968E+00 2.890316E+00 2.370031E+00 a6
2.822992E+01 -4.242168E+00 -4.650883E+00 -4.179706E+00 a7
-6.078376E+01 1.885186E+00 1.986147E+00 2.223874E+00 a8
1.189684E+02 1.099570E+00 7.016923E-01 1.051424E+00 a9
-3.967461E+02 1.789500E+00 1.174900E+00 1.271725E+00 a10
7.884569E+02 -2.135554E+00 -1.028083E+00 -1.825452E+00 a11
1.169903E+03 -5.663039E+00 -5.814384E+00 -5.829268E+00 a12
-8.621938E+03 8.123190E+00 8.030797E+00 7.821014E+00 a13
1.405177E+04 -2.312655E+00 -1.868411E+00 -1.794051E+00 a14
-5.228863E+03 -2.235316E-01 -1.698062E-01 4.448708E-03 a15
6.095878E+03 -2.785967E-01 -8.828839E-01 -7.104149E-01 a16
-3.928297E+04 2.686292E-01 -7.518570E-02 8.802676E-02 a17
1.828881E+04 -1.281496E+00 -5.265268E-01 -4.916333E-01 a18
1.014150E+05 1.424467E+00 1.128666E+00 8.717200E-01 a19
-1.483395E+05 -2.884570E-01 -2.628355E-01 -3.514156E-01 a20
6.032913E+04 -8.769461E-02 -7.904207E-02 2.708975E-02
TABLE-US-00006 TABLE 6 EXAMPLE 6 LENS DATA SURFACE ri di Nej .nu.
dj 1 14.408 1.400 1.77250 49.6 2 4.000 2.475 *3 -1.278 1.079
1.53391 55.9 *4 -4.751 0.435 *5 5.334 1.916 1.63350 23.6 *6 45.812
0.356 7 .infin. 0.049 *8 6.161 1.589 1.53391 55.9 *9 -0.740 0.080
*10 -0.900 0.441 1.63350 23.6 *11 -1.361 ASPHERICAL SURFACE DATA
SURFACE NUMBER S3 S4 S5 S6 K 0 0 0 0 a3 3.524498E-01 7.989919E-01
3.651150E-01 -4.655623E-02 a4 -1.044993E-01 -5.663033E-01
-4.130300E-01 3.429548E-01 a5 8.048027E-03 2.382772E-01
3.849733E-01 -4.530138E-01 a6 -3.174982E-04 4.323168E-01
7.163680E-02 3.098542E-02 a7 -3.391149E-03 -8.412983E-02
-4.238448E-01 8.003525E-01 a8 1.635585E-03 -3.533945E-01
3.310835E-01 -5.792977E-01 a9 1.552534E-04 -7.439558E-02
-1.108394E-01 -6.312032E-02 a10 -6.014004E-05 9.539393E-02
3.830496E-02 -2.349675E-01 a11 -1.387944E-05 7.700832E-02
-3.550636E-02 1.912835E-01 a12 -4.003721E-06 -1.350166E-02
1.008123E-02 9.258604E-01 a13 -1.737582E-06 1.908142E-02
-6.452826E-03 -1.532484E+00 a14 1.118464E-06 -1.050076E-02
6.189673E-03 9.534326E-01 a15 -7.032009E-08 -4.835253E-03
4.621763E-03 -5.898509E-01 a16 5.981000E-08 -8.781092E-03
1.551225E-03 6.925632E-01 a17 1.546138E-09 1.622368E-03
-3.391123E-03 -1.022029E+00 a18 -6.107714E-09 1.372453E-03
-1.935510E-04 2.165629E-01 a19 -8.779158E-10 2.029179E-03
-6.763937E-04 1.206105E+00 a20 3.396878E-10 -9.366952E-04
5.831153E-04 -7.387666E-01 SURFACE NUMBER S8 S9 S10 S11 K 0 0 0 0
a3 -1.623173E-01 -9.111810E-02 -4.879146E-03 4.663454E-02 a4
1.512853E+00 7.762031E-02 -5.097085E-01 -6.308846E-01 a5
-8.157718E+00 1.976173E+00 2.813067E+00 2.349505E+00 a6
2.806116E+01 -4.237071E+00 -4.679813E+00 -4.187304E+00 a7
-6.061270E+01 1.846252E+00 1.983409E+00 2.228751E+00 a8
1.196912E+02 1.131017E+00 7.826555E-01 1.040340E+00 a9
-4.003859E+02 1.722891E+00 1.218952E+00 1.295411E+00 a10
7.954933E+02 -2.135716E+00 -1.020532E+00 -1.816854E+00 a11
1.175057E+03 -5.591724E+00 -5.820776E+00 -5.828777E+00 a12
-8.629280E+03 8.177616E+00 8.005213E+00 7.809661E+00 a13
1.404758E+04 -2.360695E+00 -1.893193E+00 -1.798908E+00 a14
-5.284112E+03 -2.254872E-01 -1.963544E-01 1.920924E-03 a15
6.189004E+03 -3.138562E-01 -8.770561E-01 -7.094354E-01 a16
-3.938952E+04 2.629516E-01 -7.417069E-02 9.144957E-02 a17
1.832155E+04 -1.269368E+00 -5.162215E-01 -4.901532E-01 a18
1.017780E+05 1.417278E+00 1.142494E+00 8.734231E-01 a19
-1.487501E+05 -2.698764E-01 -2.575360E-01 -3.563668E-01 a20
6.038908E+04 -9.408334E-02 -8.922199E-02 2.907484E-02
TABLE-US-00007 TABLE 7 EXAMPLE 7 LENS DATA SURFACE ri di Nej .nu.
dj 1 14.193 1.400 1.77250 49.6 2 4.000 2.464 *3 -1.263 1.079
1.53391 55.9 *4 -4.310 0.435 *5 5.482 1.826 1.63350 23.6 *6 -34.903
0.338 7 .infin. 0.049 *8 13.493 1.482 1.53391 55.9 *9 -0.727 0.080
*10 -0.946 0.441 1.63350 23.6 *11 -1.541 ASPHERICAL SURFACE DATA
SURFACE NUMBER S3 S4 S5 S6 K 0 0 0 0 a3 3.536316E-01 7.880292E-01
3.636482E-01 -5.450196E-02 a4 -1.043745E-01 -5.517757E-01
-4.138785E-01 3.517165E-01 a5 8.086207E-03 2.398230E-01
3.818633E-01 -4.796000E-01 a6 -2.994103E-04 4.323625E-01
7.144213E-02 3.960320E-02 a7 -3.388562E-03 -8.420763E-02
-4.238731E-01 8.223170E-01 a8 1.634511E-03 -3.546101E-01
3.312432E-01 -6.193223E-01 a9 1.556796E-04 -7.463500E-02
-1.106446E-01 -1.075655E-01 a10 -6.044533E-05 9.537100E-02
3.828044E-02 -2.890252E-01 a11 -1.396756E-05 7.702696E-02
-3.584384E-02 2.628614E-01 a12 -4.027163E-06 -1.354858E-02
1.000754E-02 1.006265E+00 a13 -1.754572E-06 1.908346E-02
-6.363856E-03 -1.490531E+00 a14 1.128860E-06 -1.051568E-02
6.127168E-03 9.900953E-01 a15 -6.998458E-08 -4.830924E-03
4.606509E-03 -5.221199E-01 a16 6.003370E-08 -8.793153E-03
1.539101E-03 6.256196E-01 a17 1.538872E-09 1.612821E-03
-3.392311E-03 -1.123885E+00 a18 -6.176671E-09 1.373416E-03
-1.903847E-04 7.472199E-02 a19 -8.764735E-10 2.031628E-03
-6.727749E-04 1.187511E+00 a20 3.414674E-10 -9.350254E-04
5.836051E-04 -6.048059E-01 SURFACE NUMBER S8 S9 S10 S11 K 0 0 0 0
a3 -1.986025E-01 -1.132695E-01 -3.514693E-02 4.663454E-02 a4
1.641797E+00 5.135863E-02 -4.792778E-01 -6.440957E-01 a5
-8.266542E+00 2.054769E+00 2.763917E+00 2.319567E+00 a6
2.777359E+01 -4.239523E+00 -4.751269E+00 -4.192740E+00 a7
-6.062212E+01 1.768389E+00 2.019805E+00 2.238442E+00 a8
1.205466E+02 1.066157E+00 7.727097E-01 1.040022E+00 a9
-4.016043E+02 1.730008E+00 1.243217E+00 1.301277E+00 a10
7.982730E+02 -2.107178E+00 -9.996106E-01 -1.811002E+00 a11
1.177784E+03 -5.518539E+00 -5.804124E+00 -5.828996E+00 a12
-8.627874E+03 8.331675E+00 8.051564E+00 7.806956E+00 a13
1.401829E+04 -2.436742E+30 -1.893387E+00 -1.810157E+00 a14
-5.285169E+03 -2.776904E-01 -2.602873E-01 3.764943E-03 a15
6.222585E+03 -4.294121E-01 -8.897787E-01 -7.062445E-01 a16
-3.942633E+04 2.175910E-01 -6.209887E-02 9.343433E-02 a17
1.833709E+04 -1.225244E+00 -5.158942E-01 -4.893234E-01 a18
1.019349E+05 1.504704E+00 1.147729E+00 8.732742E-01 a19
-1.488307E+05 -2.400129E-01 -2.469541E-01 -3.584106E-01 a20
6.029847E+04 -1.425801E-01 -9.647233E-02 2.993228E-02
TABLE-US-00008 TABLE 8 EXAMPLE 8 LENS DATA SURFACE ri di Nej .nu.
dj 1 13.743 1.400 1.77250 49.6 2 4.000 2.429 *3 -1.287 1.079
1.53391 55.9 *4 -4.814 0.435 *5 5.404 1.838 1.63350 23.6 *6 -26.456
0.284 7 .infin. 0.049 *8 22.755 1.455 1.53391 55.9 *9 -0.715 0.080
*10 -0.940 0.441 1.63350 23.6 *11 -1.566 ASPHERICAL SURFACE DATA
SURFACE NUMBER S3 S4 S5 S6 K 0 0 0 0 a3 3.506778E-01 7.772335E-01
3.582847E-01 -4.414017E-02 a4 -1.042539E-01 -5.575118E-01
-4.154740E-01 3.508350E-01 a5 8.140741E-03 2.409301E-01
3.818183E-01 -4.688635E-01 a6 -2.844764E-04 4.322594E-01
7.063641E-02 4.316327E-02 a7 -3.385726E-03 -8.380970E-02
-4.236176E-01 8.090826E-01 a8 1.634681E-03 -3.554378E-01
3.307002E-01 -6.351442E-01 a9 1.556112E-04 -7.448361E-02
-1.107577E-01 -1.171813E-01 a10 -6.041497E-05 9.545300E-02
3.831190E-02 -3.012934E-01 a11 -1.400335E-05 7.711454E-02
-3.607236E-02 2.433253E-01 a12 -4.049491E-06 -1.361338E-02
1.008879E-02 1.019471E+00 a13 -1.751262E-06 1.908552E-02
-6.373578E-03 -1.474077E+00 a14 1.124692E-06 -1.052616E-02
6.130714E-03 1.003956E+00 a15 -6.941398E-08 -4.828610E-03
4.616366E-03 -5.076498E-01 a16 6.024756E-08 -8.792558E-03
1.541588E-03 6.215624E-01 a17 1.628210E-09 1.610212E-03
-3.389529E-03 -1.111912E+00 a18 -6.154272E-09 1.372216E-03
-1.916274E-04 6.300090E-02 a19 -8.811687E-10 2.031670E-03
-6.737538E-04 1.163022E+00 a20 3.367721E-10 -9.343571E-04
5.821869E-04 -5.894363E-01 SURFACE NUMBER S8 S9 S10 S11 K 0 0 0 0
a3 -1.888038E-01 -1.127371E-01 -2.847947E-02 4.663454E-02 a4
1.630949E+00 7.311934E-02 -4.164898E-01 -6.237245E-01 a5
-8.260487E+00 2.059160E+00 2.769265E+00 2.307714E+00 a6
2.784732E+01 -4.245308E+00 -4.770518E+00 -4.225150E+00 a7
-6.111454E+01 1.713799E+00 1.837298E+00 2.246912E+00 a8
1.208860E+02 1.007759E+00 7.590351E-01 1.044298E+00 a9
-4.015334E+02 1.756595E+00 1.221748E+00 1.309595E+00 a10
7.985542E+02 -2.067003E+00 -9.949671E-01 -1.834193E+00 a11
1.178196E+03 -5.456405E+00 -5.814775E+00 -5.829078E+00 a12
-8.630859E+03 8.346115E+00 8.151069E+00 7.803273E+00 a13
1.401975E+04 -2.460936E+00 -1.883252E+00 -1.811998E+00 a14
-5.282007E+03 -3.114714E-01 -1.926864E-01 3.335478E-03 a15
6.234216E+03 -4.853828E-01 -8.971702E-01 -6.973534E-01 a16
-3.944046E+04 1.936234E-01 -8.255051E-02 9.582838E-02 a17
1.830284E+04 -1.305738E+00 -5.513875E-01 -4.865091E-01 a18
1.019791E+05 1.668648E+00 1.138204E+00 8.683002E-01 a19
-1.488147E+05 -1.922452E-01 -2.421398E-01 -3.587166E-01 a20
6.026590E+04 -2.124734E-01 -9.083226E-02 3.042821E-02
[0196] In Examples 1 through 8, the material of first lens L1 is
optical glass, and both surfaces of first lens L1 are spherical.
Therefore, first lens L1 has excellent weather resistance
characteristics, and first lens L1 is not easily damaged by earth
and sand, or the like. Further, it is possible to produce first
lens L1 relatively at low cost. In Examples 1 through 8,
cycloolefin-based plastic is selected as the material of second
lens L2 and fourth lens L4. Further, polycarbonate-based plastic is
selected as the material of third lens L3 and fifth lens L5.
Accordingly, materials having low water absorption characteristics
are selected to minimize a change in performance by absorption of
water.
[0197] Table 9 shows various data and values corresponding to
conditional formulas (1) through (13) in the imaging lenses of
Examples 1 through 8. In Examples 1 through 8, e-line is a
reference wavelength, and Table 9 shows values for the reference
wavelength.
[0198] In Table 9, f is a focal length of an entire system, and Bf
is a distance (corresponding to back focus) on an optical axis from
the image-side surface of the most-image-side lens to an image
plane, and L is a distance on the optical axis from the object-side
surface of first lens L1 to image plane Sim, and 2.omega. is a full
angle of view. Bf is a distance in air. Specifically, Bf shows a
value calculated by using an equivalent length in air, as the
thickness of optical member PP. Similarly, a distance in air is
used for a back focus portion of L. As Table 9 shows, all of
Examples 1 through 8 satisfy conditional formulas (1) through
(13).
TABLE-US-00009 TABLE 9 EXAM- EXAM- EXAM- EXAM- EXAM- EXAM- EXAM-
EXAM- PLE 1 PLE 2 PLE 3 PLE 4 PLE 5 PLE 6 PLE 7 PLE 8 Fno. 2.0 2.0
2.0 2.0 2.0 2.0 2.0 2.0 f 0.910 0.899 0.887 0.890 0.863 0.886 0.950
0.969 Bf 1.982 1.987 1.995 1.987 1.991 2.005 2.095 2.145 L 11.960
12.020 12.018 11.787 11.953 11.825 11.689 11.636 2.omega.
220.8.degree. 223.8.degree. 224.2.degree. 219.2.degree.
219.0.degree. 217.6.degree. 218.6.degree. 220.4.degree. f.sub.34/L
0.133 0.129 0.132 0.136 0.138 0.133 0.131 0.130 d.sub.1-4/L 0.434
0.444 0.444 0.423 0.417 0.419 0.423 0.422 d.sub.3-11/L 0.490 0.481
0.480 0.500 0.507 0.503 0.490 0.487 d.sub.4-5/L 0.036 0.036 0.036
0.037 0.036 0.037 0.037 0.037 d.sub.6-8/L 0.033 0.029 0.029 0.025
0.028 0.034 0.033 0.029 L/r.sub.3 -10.479 -10.272 -10.078 -9.797
-9.474 -9.254 -9.257 -9.040 d.sub.4-5/f 0.479 0.484 0.491 0.489
0.504 0.491 0.458 0.449 d.sub.10/f 0.485 0.491 0.497 0.496 0.511
0.498 0.464 0.455 f.sub.3/f 5.640 5.711 5.582 6.514 9.060 10.450
7.930 7.402 Bf/f 2.178 2.211 2.249 2.234 2.306 2.262 2.204 2.213
r.sub.10/f -0.704 -0.832 -0.830 -0.862 -1.027 -1.016 -0.996 -0.970
L/f 13.145 13.374 13.546 13.249 13.843 13.339 12.298 12.004
(r.sub.8 + r.sub.9)/(r.sub.8 - r.sub.9) 0.837 0.863 0.871 0.855
0.800 0.786 0.898 0.939
[0199] In each of the tables, numerical values are rounded at
predetermined digits. As the unit of each numerical value,
".degree." is used for angle, and "mm" is used for length. However,
these units are only examples. Since an optical system can be used
by proportionally enlarging or reducing the optical system, other
appropriate units may be used.
[0200] FIG. 9, Sections A through G illustrate aberration diagrams
of the imaging lens of Example 1. FIG. 9, Sections A through D
illustrate a spherical aberration, astigmatism, distortion
(distortion aberration), and a lateral chromatic aberration (a
chromatic aberration of magnification), respectively. FIG. 9,
Sections E through G illustrate lateral aberrations in a tangential
direction for each half angle of view. Each aberration diagram
illustrates aberrations when e-line is a reference wavelength.
However, the diagram of a spherical aberration and the diagram of a
lateral chromatic aberration illustrate aberrations also for g-line
(wavelength is 436 nm) and C-line (wavelength is 656.27 nm). In the
diagram of a spherical aberration, Fno. represents F-number, and in
the other diagrams, co represents a half angle of view.
[0201] Similarly, FIG. 10, Sections A through G, FIG. 11, Sections
A through G, FIG. 12, Sections A through G, FIG. 13, Sections A
through G, FIG. 14, Sections A through G, FIG. 15, Sections A
through G, and FIG. 16, Sections A through G illustrate aberration
diagrams of a spherical aberration, astigmatism, distortion (a
distortion aberration), a lateral chromatic aberration, and lateral
aberrations of the imaging lenses of Examples 2 through 8,
respectively.
[0202] The aberration diagram of distortion illustrates a shift
amount from an ideal image height 2.times.f.times.tan(.phi./2) by
using focal length f of the entire system and half angle .phi. of
view (variable, 0.ltoreq..phi..ltoreq..omega.). Therefore, the
value is minus in a peripheral portion. However, the distortion of
the imaging lenses in Examples 1 through 8 is large positive values
when the distortion is calculated by using, as reference, an image
height based on equidistant projection. That is because the imaging
lenses of Examples 1 through 8 are designed so that images in
peripheral portions are large, compared with a lens designed in
such a manner to suppress distortion at an image height based on
equidistant projection.
[0203] As these data show, each of the imaging lenses of Examples 1
through 8 consists of five lenses, which are a small number of
lenses, and the size is small, and the cost is low. Further, it is
possible to achieve an extremely wide full angle of view of about
220 degrees. Further, F-number is 2.0, which is small. Further, the
imaging lens has excellent optical performance in which each
aberration has been corrected in an excellent manner and resolution
is high. These imaging lenses are appropriate for use in a
surveillance camera, an in-vehicle camera for imaging an image on
the front side, the lateral sides, the rear side or the like of a
car, or the like.
[0204] FIG. 17 illustrates, as an example of usage, a manner of
mounting an imaging apparatus including the imaging lens of the
embodiment of the present invention in a car 100. In FIG. 17, the
car 100 includes an exterior camera 101 for imaging a driver's
blind spot on a side of a seat next to the driver, an exterior
camera 102 for imaging a driver's blind spot on a rear side of the
car 100, and an interior camera 103 for imaging the same range as
the driver's visual field. The interior camera 103 is attached to
the back side of a rearview mirror. The exterior camera 101, the
exterior camera 102, and the interior camera 103 are imaging
apparatuses according to an embodiment of the present invention,
and they include an imaging lens according to an example of the
present invention and an imaging device for converting an optical
image formed by the imaging lens into electrical signals.
[0205] The imaging lenses according to the examples of the present
invention have the aforementioned advantages. Therefore, the
exterior cameras 101 and 102, and the interior camera 103 can be
structured in small size and at low cost, and have wide angles of
view. Further, they can obtain excellent images with high
resolution.
[0206] So far, the present invention has been described by using
embodiments and examples. However, the present invention is not
limited to the aforementioned embodiments nor examples, and various
modifications are possible. For example, values of a curvature
radius, a distance between surfaces, a refractive index, an Abbe
number and aspherical surface coefficients of each lens element are
not limited to the values in the aforementioned examples of
numerical values, but may be other values. Further, the material of
the lens is not limited to the material used in each example of
numerical values, but may be other materials.
[0207] In the embodiment of the imaging apparatus, a case in which
the present invention is applied to an in-vehicle camera was
described with reference to the drawing. However, the use of the
present invention is not limited to this purpose. For example, the
present invention may be applied to a camera for a mobile terminal,
a surveillance camera, and the like.
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