U.S. patent number RE47,517 [Application Number 15/604,961] was granted by the patent office on 2019-07-16 for image pickup lens for solid-state image pickup element.
This patent grant is currently assigned to KANTATSU CO., LTD.. The grantee listed for this patent is KANTATSU CO., LTD.. Invention is credited to Masaya Hashimoto, Yoshio Ise.
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United States Patent |
RE47,517 |
Ise , et al. |
July 16, 2019 |
**Please see images for:
( Certificate of Correction ) ** |
Image pickup lens for solid-state image pickup element
Abstract
Disclosed is a low-cost, compact image pickup lens for a
solid-state image pickup element. The image pickup lens includes,
in the order from an object side, a first lens L1, which has a
convex surface facing the object side on an optical axis and has a
positive refractive power; a second lens L2, which has a concave
surface facing an image side on the optical axis and has a negative
refractive power; a third lens L3, which has a convex surface
facing the object side on the optical axis and has a meniscus
shape; a fourth lens L4, which has a convex surface facing the
image side on the optical axis, has a positive refractive power,
and has a meniscus shape; and a fifth lens L5, which has a concave
surface facing the image side on the optical axis, has a negative
refractive power, and has a meniscus shape.
Inventors: |
Ise; Yoshio (Sukagawa,
JP), Hashimoto; Masaya (Sukagawa, JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
KANTATSU CO., LTD. |
Yaita-shi, Tochigi |
N/A |
JP |
|
|
Assignee: |
KANTATSU CO., LTD. (Yaita,
JP)
|
Family
ID: |
42828012 |
Appl.
No.: |
15/604,961 |
Filed: |
May 25, 2017 |
PCT
Filed: |
March 24, 2010 |
PCT No.: |
PCT/JP2010/055048 |
371(c)(1),(2),(4) Date: |
August 24, 2011 |
PCT
Pub. No.: |
WO2010/113717 |
PCT
Pub. Date: |
October 07, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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14993854 |
Jan 12, 2016 |
RE46455 |
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14684878 |
Apr 13, 2015 |
RE45941 |
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Reissue of: |
13203159 |
Mar 24, 2010 |
8422145 |
Apr 16, 2013 |
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Reissue of: |
13203159 |
Mar 24, 2010 |
8422145 |
Apr 16, 2013 |
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Foreign Application Priority Data
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Mar 31, 2009 [JP] |
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2009-084695 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G02B
13/18 (20130101); G02B 13/0045 (20130101); G02B
13/18 (20130101); G02B 13/0045 (20130101) |
Current International
Class: |
G02B
13/18 (20060101); G02B 13/00 (20060101); G02B
9/60 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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3-138612 |
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Jun 1991 |
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JP |
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3138612 |
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Jun 1991 |
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JP |
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2007-264180 |
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Oct 2007 |
|
JP |
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2007-298572 |
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Nov 2007 |
|
JP |
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2007298572 |
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Nov 2007 |
|
JP |
|
Other References
Hecht, Eugene. Optics, Fourth Edition, Addison Wesley, San
Francisco, CA, U.S.A., 2002, pp. 243-246 (Year: 2002). cited by
examiner .
"F-Number." 2003. In The Macmillan Encyclopedia. Basingstoke,
United Kingdom: Macmillan Publishers Ltd. cited by applicant .
Hobbs, P. C. D. Chapter 4: Lenses, Prisms, and Mirrors, in Building
Electro-Optical Systems: Making it all Work, Second Edition, John
Wiley & Sons, Inc., Hoboken, NJ, USA, 2009, pp. 145-179. cited
by applicant .
International Search Report of PCT/JP2010/055048, mailing date Jun.
15, 2010. cited by applicant.
|
Primary Examiner: Leung; Christina Y.
Attorney, Agent or Firm: Oliff PLC
Parent Case Text
.Iadd.This application is a reissue continuation of application
Ser. No. 14/993,854, which is a reissue continuation of application
Ser. No. 14/684,878 and an application for reissue of U.S. Pat. No.
8,422,145, and application Ser. No. 14/684,878 is an application
for reissue of U.S. Pat. No. 8,422,145; more than one reissue of
U.S. Pat. No. 8,422,145 has been filed, including application Ser.
No. 14/993,878, filed Jan. 12, 2016, which is a reissue
continuation of application Ser. Nos. 14/684,878, 15/604,863, filed
May 25, 2017, which is a reissue continuation of application Ser.
Nos. 14/993,854, 15/604,998, filed May 25, 2017, which is a reissue
continuation of application Ser. Nos. 14/993,854, 15/605,034, filed
May 25, 2017, which is a reissue continuation of application. Ser.
No. 14/993,854..Iaddend.
Claims
The invention claimed is:
.[.1. An image pickup lens for a solid-state image pickup element,
comprising, in the order from an object side: a first lens, which
has a convex surface facing the object side on an optical axis and
has a positive refractive power; a second lens, which has a concave
surface facing an image side on the optical axis and has a negative
refractive power; a third lens, which has a convex surface facing
the object side on the optical axis and has a meniscus shape; a
fourth lens, which has a convex surface facing the image side on
the optical axis, has a positive refractive power, and has a
meniscus shape; and a fifth lens, which has a concave surface
facing the image side on the optical axis, has a negative
refractive power, and has a meniscus shape..].
.[.2. The image pickup lens according to claim 1, wherein the Abbe
number of a material used for the first lens and the second lens
satisfies conditional expressions (1) and (2) below:
45<.nu.1<90 (1) 22<.nu.2<35 (2) where .nu.1 is the Abbe
number for d-line of the first lens, and .nu.2 is the Abbe number
for d-line of the second lens..].
.[.3. The image pickup lens according to claim 1, wherein the
second lens, the third lens, the fourth lens, and the fifth lens
are so-called plastic lenses that have at least one aspherical
surface and are made of a resin material..].
.[.4. The image pickup lens according to claim 1, wherein an
aperture stop is positioned on the object side of the first
lens..].
.[.5. The image pickup lens according to claim 1, wherein the
object-side surface and the image-side surface of the fifth lens
have an aspherical shape that contains at least one inflection
point between the center and the periphery of the lens..].
.[.6. The image pickup lens according to claim 1, wherein the first
lens and the second lens satisfy conditional expressions (3) and
(4) below: 0.5<f1/f<1.00 (3) -1.50<f2/f<-0.65 (4) where
f is the composite focal length of lenses included in the entire
image pickup lens, f1 is the focal length of the first lens, and f2
is the focal length of the second lens..].
.[.7. The image pickup lens according to claim 1, wherein the
fourth lens and the fifth lens satisfy conditional expressions (5)
and (6) below: 0.9<f4/f<1.50 (5) -1.70<f5/f<-0.85 (6)
where f is the composite focal length of lenses included in the
entire image pickup lens, f4 is the focal length of the fourth
lens, and f5 is the focal length of the fifth lens..].
.[.8. The image pickup lens according to claim 1, wherein the first
lens and the third lens satisfy conditional expression (7) below:
-0.15<f1/f3<0.37 (7) where f1 is the focal length of the
first lens, and f3 is the focal length of the third lens..].
.[.9. The image pickup lens according to claim 1, wherein the
second lens, the third lens, and the fourth lens satisfy
conditional expression (8) below: 0.0<f234 (8) where f234 is the
composite focal length of the second, third, and fourth
lenses..].
.[.10. The image pickup lens according to claim 1, wherein the
first lens, the second lens, the third lens, the fourth lens, and
the fifth lens satisfy conditional expressions (9), (10), and (11)
below: f1<|f2|<|f3| (9) f1<f4<|f3| (10)
f1<|f5|<|f3| (11) where f1 is the focal length of the first
lens, f2 is the focal length of the second lens, f3 is the focal
length of the third lens, f4 is the focal length of the fourth
lens, and f5 is the focal length of the fifth lens..].
.[.11. The image pickup lens according to claim 10, wherein the
curvature radius of the first lens satisfies conditional expression
(12) below: -0.40<r1/r2<0.10 (12) where r1 is the curvature
radius of the object-side surface of the first lens, and r2 is the
curvature radius of the image-side surface of the first
lens..].
.[.12. The image pickup lens according claim 10, wherein the
curvature radius of the fourth lens satisfies conditional
expression (13) below: 1.4<r7/r8<3.0 (13) where r7 is the
curvature radius of the object-side surface of the fourth lens, and
r8 is the curvature radius of the image-side surface of the fourth
lens..].
.[.13. The image pickup lens according to claim 10, wherein the
optical length and focal length of an optical system thereof
satisfy conditional expression (14) below: 1.05<L/f<1.30 (14)
where L is the distance between the front surface of the first lens
and an image surface, and f is the composite focal length of lenses
included in the entire image pickup lens..].
.[.14. The image pickup lens according to claim 4, wherein the
diameter of the aperture stop satisfies conditional expression (15)
below: 0.30<CA1/f<0.50 (15) where CA1 is the diameter of the
aperture stop, and f is the composite focal length of lenses
included in the entire image pickup lens..].
.[.15. The image pickup lens according to claim 10, wherein the
Abbe number of a material used for the first lens and the second
lens satisfies conditional expressions (1) and (2) below:
45<.nu.1<90 (1) 22<.nu.2<35 (2) where .nu.1 is the Abbe
number for d-line of the first lens, and .nu.2 is the Abbe number
for d-line of the second lens..].
.[.16. The image pickup lens according to claim 10, wherein the
second lens, the third lens, the fourth lens, and the fifth lens
are so-called plastic lenses that have at least one aspherical
surface and are made of a resin material..].
.[.17. The image pickup lens according to claim 10, wherein an
aperture stop is positioned on the object side of the first
lens..].
.[.18. The image pickup lens according to claim 10, wherein the
object-side surface and the image-side surface of the fifth lens
have an aspherical shape that contains at least one inflection
point between the center and the periphery of the lens..].
.Iadd.19. An image pickup lens for a solid-state image pickup
element, comprising, in order from an object side: a first lens,
which has a convex surface facing the object side on an optical
axis and has a positive refractive power; a second lens; a third
lens; a fourth lens, which has a convex surface facing an image
side on the optical axis; and a fifth lens, which has a concave
surface facing the image side on the optical axis and has a
negative refractive power, wherein the second lens, the third lens,
the fourth lens, and the fifth lens are plastic lenses that have at
least one aspherical surface and are made of a resin material, each
of the first lens, the second lens, the third lens, the fourth
lens, and the fifth lens is positioned without being joined on
surfaces facing each other; and the first lens and the third lens
satisfy a conditional expressions (7) and (9) below:
-0.15<f1/f3<0.37 (7) f1<|f2|<|f3| (9) where f1 is a
focal length of the first lens, f2 is the focal length of the
second lens, and f3 is a focal length of the third
lens..Iaddend.
.Iadd.20. The image pickup lens according to claim 19, wherein Abbe
numbers of materials used for the first lens and the second lens
satisfy conditional expressions (1) and (2) below:
45<.nu.1<90 (1) 22<.nu.2<35 (2) where .nu.1 is an Abbe
number for d-line of the first lens, and .nu.2 is an Abbe number
for d-line of the second lens..Iaddend.
.Iadd.21. The image pickup lens according to claim 19, wherein the
second lens has a concave surface facing the image side on the
optical axis and has a negative refractive power..Iaddend.
.Iadd.22. The image pickup lens according to claim 19, wherein the
third lens has a convex surface facing the object side on the
optical axis and has a meniscus shape..Iaddend.
.Iadd.23. The image pickup lens according to claim 19, wherein an
image-side surface of the fifth lens has an aspherical shape that
contains at least one inflection point between a center and a
periphery of the fifth lens..Iaddend.
.Iadd.24. The image pickup lens according to claim 19, wherein the
first lens and the second lens satisfy conditional expressions (3)
and (4) below: 0.5<f1/f<1.00 (3) -1.50<f2/f<-0.65 (4)
where f is a composite focal length of lenses included in an
entirety of the image pickup lens..Iaddend.
.Iadd.25. An image pickup lens for a solid-state image pickup
element, comprising, in order from an object side: a first lens,
which has a convex surface facing the object side on an optical
axis and has a positive refractive power; a second lens; a third
lens; a fourth lens, which has a convex surface facing an image
side on the optical axis; and a fifth lens, which has a concave
surface facing the image side on the optical axis and has a
negative refractive power, wherein: the second lens, the third
lens, the fourth lens, and the fifth lens are plastic lenses that
have at least one aspherical surface and are made of a resin
material, each of the first lens, the second lens, the third lens,
the fourth lens, and the fifth lens is positioned without being
joined on surfaces facing each other; and the second lens, the
third lens, and the fourth lens satisfy a conditional expression
(8) below: 0.0<f234 (8) where f234 is the composite focal length
of the second, third, and fourth lenses..Iaddend.
.Iadd.26. The image pickup lens according to claim 25, wherein Abbe
numbers of materials used for the first lens and the second lens
satisfy conditional expressions (1) and (2) below:
45<.nu.1<90 (1) 22<.nu.2<35 (2) where .nu.1 is an Abbe
number for d-line of the first lens, and .nu.2 is an Abbe number
for d-line of the second lens..Iaddend.
.Iadd.27. The image pickup lens according to claim 25, wherein the
second lens has a concave surface facing the image side on the
optical axis and has a negative refractive power..Iaddend.
.Iadd.28. The image pickup lens according to claim 25, wherein the
third lens has a convex surface facing the object side on the
optical axis and has a meniscus shape..Iaddend.
.Iadd.29. The image pickup lens according to claim 25, wherein an
image-side surface of the fifth lens has an aspherical shape that
contains at least one inflection point between a center and a
periphery of the fifth lens..Iaddend.
.Iadd.30. The image pickup lens according to claim 25, wherein the
first lens and the second lens satisfy conditional expressions (3)
and (4) below: 0.5<f1/f<1.00 (3) -1.50<f2/f<-0.65 (4)
where f is a composite focal length of lenses included in an
entirety of the image pickup lens, f1 is a focal length of the
first lens, and f2 is a focal length of the second
lens..Iaddend.
.Iadd.31. The image pickup lens according to claim 25, wherein the
first lens and the third lens satisfy a conditional expression (7)
below: -0.15<f1/f3<0.37 (7) where f1 is a focal length of the
first lens, and f3 is a focal length of the third
lens..Iaddend.
.Iadd.32. An image pickup lens for a solid-state image pickup
element, comprising, in order from an object side: a first lens,
which has a convex surface facing the object side on an optical
axis and has a positive refractive power; a second lens; a third
lens; a fourth lens, which has a convex surface facing an image
side on the optical axis; and a fifth lens, which has a concave
surface facing the image side on the optical axis and has a
negative refractive power, wherein: the second lens, the third
lens, the fourth lens, and the fifth lens are plastic lenses that
have at least one aspherical surface and are made of a resin
material, each of the first lens, the second lens, the third lens,
the fourth lens, and the fifth lens is positioned without being
joined on surfaces facing each other; and the first lens, the
second lens, and the third lens satisfy a conditional expressions
(9) below: f1<|f2|<|f3| (9) where f1 is the focal length of
the first lens, f2 is the focal length of the second lens, and f3
is the focal length of the third lens..Iaddend.
.Iadd.33. The image pickup lens according to claim 32, wherein Abbe
numbers of materials used for the first lens and the second lens
satisfy conditional expressions (1) and (2) below:
45<.nu.1<90 (1) 22<.nu.2<35 (2) where .nu.1 is an Abbe
number for d-line of the first lens, and .nu.2 is an Abbe number
for d-line of the second lens..Iaddend.
.Iadd.34. The image pickup lens according to claim 32, wherein the
second lens has a concave surface facing the image side on the
optical axis and has a negative refractive power..Iaddend.
.Iadd.35. The image pickup lens according to claim 32, wherein the
third lens has a convex surface facing the object side on the
optical axis and has a meniscus shape..Iaddend.
.Iadd.36. The image pickup lens according to claim 32, wherein an
image-side surface of the fifth lens has an aspherical shape that
contains at least one inflection point between a center and a
periphery of the fifth lens..Iaddend.
.Iadd.37. The image pickup lens according to claim 32, wherein the
first lens and the second lens satisfy conditional expressions (3)
and (4) below: 0.5<f1/f<1.00 (3) -1.50<f2/f<-0.65 (4)
where f is a composite focal length of lenses included in an
entirety of the image pickup lens, f1 is a focal length of the
first lens, and f2 is a focal length of the second
lens..Iaddend.
.Iadd.38. The image pickup lens according to claim 14, wherein the
first lens and the third lens satisfy a conditional expression (7)
below: -0.15<f1/f3<0.37 (7) where f1 is a focal length of the
first lens, and f3 is a focal length of the third lens..Iaddend.
Description
TECHNICAL FIELD
The present invention relates to an image pickup lens for a
solid-state image pickup element that is used in a small-size image
pickup device for mobile terminals, PDA (Personal Digital
Assistance) devices, and other small-size, thin electronic
devices.
BACKGROUND ART
In recent years, the market for mobile terminals having an image
pickup device has grown. Consequently, the image pickup device has
begun to incorporate a small-size, high-pixel-number, solid-state
image pickup element.
As an increasing number of small-size, high-pixel-number, image
pickup elements are used, it is demanded that image pickup lenses
be improved in terms of resolution and image quality. It is also
demanded that such high-resolution, high-quality image pickup
lenses become widespread and available at low cost.
An image pickup lens having plural lenses is made commonly
available to meet the demand for high performance. An image pickup
lens having five lenses, which exhibit higher performance than a
lens having two to four lenses, is also proposed.
An image pickup lens disclosed, for instance, in Patent Document 1
exhibits high performance by including, in the order from an object
side, a first lens, a second lens, a third lens, a fourth lens, and
a fifth lens. The first lens has a convex surface on the object
side and has a positive refractive power. The second lens has a
concave surface facing an image side, has a negative refractive
power, and has a meniscus shape. The third lens has a convex
surface facing the image side, has a positive refractive power, and
has a meniscus shape. The fourth lens has an aspherical surface on
both sides, has a concave surface on the image side on an optical
axis, and has a negative refractive power. The fifth lens has an
aspherical surface on both sides and has a positive or negative
refractive power.
An image pickup lens disclosed, for instance, in Patent Document 2
exhibits high performance by including, in the order from an object
side, a first lens, a second lens, a third lens, a fourth lens, and
a fifth lens. The first lens has an aperture stop and has a
positive refractive power. The second lens is joined to the first
lens and has a negative refractive power. The third lens has a
concave surface facing the object side and has a meniscus shape.
The fourth lens has a concave surface facing the object side and
has a meniscus shape. The fifth lens has at least one aspherical
surface, has a convex surface facing the object side, and has a
meniscus shape.
CITATION LIST
Patent Documents
Patent Document 1: JP-A No. 2007-264180 Patent Document 2: JP-A No.
2007-298572
SUMMARY OF INVENTION
Problems to be Solved by the Invention
The image pickup lenses described in Patent Documents 1 and 2 each
include five lenses to exhibit high performance. From the viewpoint
of their optical length, however, they are not adequately designed
to reduce their size and thickness.
The present invention has been made in view of the above
circumstances and has an object to provide a small-size, low-cost,
high-performance image pickup lens for a solid-state image pickup
element.
Means for Solving the Problems
The above-mentioned problem can be addressed when the image pickup
lens for a solid-state image pickup element is configured as
described below.
The image pickup lens described in aspect 1 of the invention
includes, in the order from an object side, a first lens, a second
lens, a third lens, a fourth lens, and a fifth lens. The first lens
has a convex surface facing the object side on an optical axis and
has a positive refractive power. The second lens has a concave
surface facing an image side on the optical axis and has a negative
refractive power. The third lens has a convex surface facing the
object side on the optical axis and has a meniscus shape. The
fourth lens has a convex surface facing the image side on the
optical axis, has a positive refractive power, and has a meniscus
shape. The fifth lens has a concave surface facing the image side
on the optical axis, has a negative refractive power, and has a
meniscus shape.
The image pickup lens described in aspect 2 of the invention
satisfies conditional expressions (1) and (2) below, which concern
the Abbe number of a material used for the first lens and the
second lens: 45<.nu.1<90 (1) 22<.nu.2<35 (2) where
.nu.1 is the Abbe number for d-line of the first lens, and .nu.2 is
the Abbe number for d-line of the second lens.
Conditional expression (1) above defines the Abbe number of the
first lens. If the lower limit indicated by conditional expression
(1) is exceeded, the variance value difference from the second lens
is decreased so that chromatic aberration correction is
insufficient. If, on the contrary, the upper limit is exceeded, the
balance between axial chromatic aberration and chromatic aberration
of magnification is impaired so that performance deterioration
occurs at the periphery of an image area.
Conditional expression (2) above defines the Abbe number of the
second lens. If the lower limit indicated by conditional expression
(2) is exceeded, the balance between axial chromatic aberration and
off-axis chromatic aberration is impaired so that performance
deterioration occurs at the periphery of the image area. If, on the
contrary, the upper limit is exceeded, the variance value
difference from the first lens is decreased so that chromatic
aberration correction is insufficient.
The image pickup lens described in aspect 3 of the invention is
configured so that the second lens, the third lens, the fourth
lens, and the fifth lens are so-called plastic lenses that have at
least one aspherical surface and are made of a resin material.
Cost reduction can be achieved when at least the second lens, the
third lens, the fourth lens, and the fifth lens are made of an
inexpensive resin material exhibiting high production
efficiency.
The image pickup lens described in aspect 4 of the invention is
configured so that an aperture stop is positioned on the object
side of the first lens.
As the aperture stop is positioned on the object side of the first
lens, it is easy to reduce a CRA (Chief Ray Angle) and obtain
sufficient light intensity at the periphery of an image surface at
which light intensity decreases.
The image pickup lens described in aspect 5 of the invention is
configured so that the object-side surface and image-side surface
of the fifth lens have an aspherical shape, which contains at least
one inflection point between the center and the periphery of the
lens.
As the object-side surface and image-side surface of the fifth lens
have an aspherical shape that contains at least one inflection
point between the center and the periphery of the lens, it is
possible to obtain adequate off-axis performance and CRA.
The image pickup lens described in aspect 6 of the invention is
configured so that the first lens and the second lens satisfy
conditional expressions (3) and (4) below: 0.50<f1/f<1.00 (3)
-1.50<f2/f<-0.65 (4)
where f is the composite focal length of lenses included in the
entire image pickup lens, f1 is the focal length of the first lens,
and f2 is the focal length of the second lens.
Conditional expression (3) above defines the range of the focal
length of the first lens with respect to the focal length of the
entire image pickup lens. If the lower limit indicated by
conditional expression (3) is exceeded, the focal length of the
first lens is too small. This makes it difficult to correct
spherical aberration and coma aberration. If, on the contrary, the
upper limit is exceeded, the optical length is too great so that
the thickness of the image pickup lens cannot be sufficiently
reduced.
Conditional expression (4) above defines the range of the focal
length of the second lens with respect to the focal length of the
entire image pickup lens. If the lower limit indicated by
conditional expression (4) is exceeded, the power of the second
lens is insufficient so that chromatic aberration cannot be
adequately corrected. If, on the contrary, the upper limit is
exceeded, the focal length of the second lens is too small. This
not only makes it difficult to correct spherical aberration and
coma aberration, but also decreases manufacturing error
sensitivity.
The image pickup lens described in aspect 7 of the invention is
configured so that the fourth lens and the fifth lens satisfy
conditional expressions (5) and (6) below: 0.9<f4/f<1.50 (5)
-1.70<f5/f<-0.85 (6) where f is the composite focal length of
lenses included in the entire image pickup lens, f4 is the focal
length of the fourth lens, and f5 is the focal length of the fifth
lens.
Conditional expression (5) above defines the range of the focal
length of the fourth lens with respect to the focal length of the
entire image pickup lens. If the lower limit indicated by
conditional expression (5) is exceeded, the focal length of the
fourth lens is too small. This makes it difficult to correct
astigmatism and coma aberration, and decreases the manufacturing
error sensitivity. If on the contrary, the upper limit is exceeded,
chromatic aberration of magnification and astigmatism are not
adequately corrected so that expected performance is not
obtained.
Conditional expression (6) above defines the range of the focal
length of the fifth lens With respect to the focal length of the
entire image pickup lens. If the lower limit indicated by
conditional expression (6) is exceeded, the power of the fifth lens
is insufficient. This makes it difficult to decrease the optical
length. If, on the contrary, the upper limit is exceeded, it is
difficult to decrease the CRA, thereby decreasing the manufacturing
error sensitivity at low image height.
The image pickup lens described in aspect 8 of the invention is
configured so that the first lens and the third lens satisfy
conditional expression (7) below: -0.15<f1/f3<0.37 (7) where
f1 is the focal length of the first lens, and f3 is the focal
length of the third lens.
Conditional expression (7) above defines the ratio between the
focal length of the first lens and the focal length of the third
lens. If the lower limit indicated by conditional expression (7) is
exceeded, the focal length of the third lens is negative and too
small. This makes it difficult to provide aberration correction.
If, on the contrary, the upper limit is exceeded, the focal length
of the third lens is positive and too small. This impairs the
balance between astigmatism and coma aberration and decreases the
manufacturing error sensitivity.
The image pickup lens described in aspect 9 of the invention is
configured so that the second lens, the third lens, and the fourth
lens satisfy conditional expression (8) below: 0.0<f234 (8)
where f234 is the composite focal length of the second, third, and
fourth lenses.
Conditional expression (8) above defines the composite focal length
of the second, third, and fourth lens. If the lower limit indicated
by conditional expression (8) is exceeded, the negative power of
the second lens is too strong so that the manufacturing error
sensitivity is excessively low, or the positive power of the fourth
lens is too weak so that it is difficult to correct astigmatism and
distortion.
The image pickup lens described in aspect 10 of the invention is
configured so that the first lens, the second lens, the third lens,
the fourth lens, and the fifth lens satisfy conditional expressions
(9), (10), and (11) below: f1<|f2|<|f3| (9) f1<f4<|f3|
(10) f1<|f5|<|f3| (11) where f1 is the focal length of the
first lens, f2 is the focal length of the second lens, f3 is the
focal length of the third lens, f4 is the focal length of the
fourth lens, and f5 is the focal length of the fifth lens.
Conditional expression (9) above defines the power relationship,
that is, the focal length relationship, between the first lens, the
second lens, and the third lens. If the lower limit indicated by
conditional expression (9) is exceeded, the negative power of the
second lens is too strong. This increases the optical length and
decreases the manufacturing error sensitivity. If, on the contrary,
the upper limit is exceeded, the power of the third lens is too
strong so that it is difficult to obtain adequate off-axis
performance.
Conditional expression (10) above defines the power relationship,
that is, the focal length relationship, between the first lens, the
third lens, and the fourth lens. If the lower limit indicated by
conditional expression (10) is exceeded, the power of the fourth
lens is too strong. This increases the optical length and makes it
difficult to correct astigmatism and distortion. If, on the
contrary, the upper limit is exceeded, the power of the third lens
is too strong so that it is difficult to obtain adequate off-axis
performance.
Conditional expression (11) above defines the power relationship,
that is, the focal length relationship, between the first lens, the
third lens, and the fifth lens. If the lower limit indicated by
conditional expression (11) is exceeded, the negative power of the
fifth lens is too strong. This makes it difficult to correct coma
aberration and astigmatism. If, on the contrary, the upper limit is
exceeded, the power of the third lens is too strong so that it is
difficult to obtain adequate off-axis performance.
The third lens has a weaker power than the other lenses. However,
its front and rear aspherical surfaces effectively work to reduce
an aberration caused within the second lens. Particularly, its
fourth-order aspherical coefficient effectively works and plays an
important role to exhibit performance characteristics specific to a
combination of five lenses.
The image pickup lens described in aspect 11 of the invention is
configured so that the curvature radius of the first lens satisfies
conditional expression (12) below: -0.40<r1/r2<0.10 (12)
where r1 is the curvature radius of the object-side surface of the
first lens, and r2 is the curvature radius of the image-side
surface of the first lens.
Conditional expression (12) above defines the lens shape of the
first lens. If the lower limit indicated by conditional expression
(12) is exceeded, the optical length cannot be readily reduced. In
addition, the error sensitivity prevailing during the manufacture
of the first lens becomes low. If, on the contrary, the upper limit
is exceeded, it is difficult to maintain a proper aberration
balance so that expected performance is not obtained.
The image pickup lens described in aspect 12 of the invention is
configured so that the curvature radius of the fourth lens
satisfies conditional expression (13) below: 1.4<r7/r8<3.0
(13) where r7 is the curvature radius of the object-side surface of
the fourth lens, and r8 is the curvature radius of the image-side
surface of the fourth lens.
Conditional expression (13) above defines the lens shape of the
fourth lens. If the lower limit indicated by conditional expression
(13) is exceeded, the power of the fourth lens is too weak.
Consequently, performance deterioration occurs because it is
difficult to correct various aberrations. If, on the contrary, the
upper limit is exceeded, the fourth lens has an excessively strong
power or has a small degree of meniscus curvature. In this
instance, too, it is difficult to maintain a proper aberration
balance so that expected performance is not obtained.
The image pickup lens described in aspect 13 of the invention is
configured so that its image pickup optical system's optical length
and focal length satisfy conditional expression (14) below:
1.05<L/f<1.30 (14) where L is the distance between the front
surface of the first lens and the image surface, and f is the
composite focal length of lenses included in the entire image
pickup lens.
Conditional expression (14) above defines the optical length with
respect to the focal length. If the lower limit indicated by
conditional expression (14) is exceeded, it is difficult to correct
various aberrations due to an excessively decreased optical length.
In addition, the manufacturing error sensitivity becomes
excessively low. If, on the contrary, the upper limit is exceeded,
it is difficult to reduce the thickness of the image pickup lens
due to an excessively increased optical length.
The image pickup lens described in claim 14 of the invention is
configured so that the diameter of the aperture stop satisfies
conditional expression (15) below: 0.30<CA1/f<0.50 (15) where
CA1 is the diameter of the aperture stop, and f is the composite
focal length of lenses included in the entire image pickup
lens.
Conditional expression (15) above defines the F-number (Fno), which
is an indication of lens brightness. If the lower limit indicated
by conditional expression (15) is exceeded, the F-number is
excessively great so that requested brightness is not achieved in
most cases. If, on the contrary, the upper limit is exceeded, the
F-number is excessively small or the distance between an aperture
stop (F-number light flux restriction plate) and the front surface
of the first lens is excessively great. In either of these cases,
expected optical performance is not obtained.
Effects of the Invention
The image pickup lens according to the present invention includes
five lenses (the first to fifth lenses). Further, the third lens
plays a role that is not found in a conventional four-lens
configuration. Therefore, the present invention makes it possible
to provide a high-performance, low-cost, compact lens in which
various aberrations are properly corrected to support large-size,
high-resolution image pickup elements having highly minute
pixels.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a cross-sectional view of an image pickup lens according
to a first embodiment of the present invention.
FIG. 2 shows various aberrations of the image pickup lens according
to the first embodiment of the present invention.
FIG. 3 is a cross-sectional view of the image pickup lens according
to a second embodiment of the present invention.
FIG. 4 shows various aberrations of the image pickup lens according
to the second embodiment of the present invention.
FIG. 5 is a cross-sectional view of the image pickup lens according
to a third embodiment of the present invention.
FIG. 6 shows various aberrations of the image pickup lens according
to the third embodiment of the present invention.
FIG. 7 is a cross-sectional view of the image pickup lens according
to a fourth embodiment of the present invention.
FIG. 8 shows various aberrations of the image pickup lens according
to the fourth embodiment of the present invention.
FIG. 9 is a cross-sectional view of the image pickup lens according
to a fifth embodiment of the present invention.
FIG. 10 shows various aberrations of the image pickup lens
according to the fifth embodiment of the present invention.
FIG. 11 is a cross-sectional view of the image pickup lens
according to a sixth embodiment of the present invention.
FIG. 12 shows various aberrations of the image pickup lens
according to the sixth embodiment of the present invention.
BEST MODE FOR CARRYING OUT THE INVENTION
Embodiments of the present invention will now be described by using
concrete numerical values. In the first to sixth embodiments, the
image pickup lens for a solid-state image pickup element includes,
in the order from the object side, an aperture stop S, a first lens
L1, a second lens L2, a third lens L3, a fourth lens L4, a fifth
lens L5, a plane-parallel glass plate IR, and an image surface.
In the first to sixth embodiments, the second lens L2, the third
lens L3, the fourth lens L4, and the fifth lens L5 are so-called
plastic lenses that have at least one aspherical surface and are
made of a resin material. It should also be noted that the aperture
stop S is positioned on the object side of the first lens L1.
The object-side surface and image-side surface of the fifth lens L5
have an aspherical shape that contains at least one inflection
point between the center and the periphery of the lens. The
aspherical shape in each embodiment is expressed by the following
aspherical surface formula in which the vertex of a plane is
regarded as the origin, the Z-axis is oriented in the direction of
an optical axis, and the height measured perpendicularly to the
optical axis is h:
Z=(h2/r)/[1+{1-(1+K)(h2/r2)}1/2]+A.sub.4h.sup.4+A.sub.6h.sup.6+A.sub.8h.s-
up.8+ . . .
It should be noted that the following symbols are used in the above
aspherical surface formula and in the description of each
embodiment:
Ai: ith-order aspherical coefficient
r: Curvature radius
K: Conical constant
f: Focal length of the entire image pickup lens
F: F-number
d: On-axis surface spacing
nd: Refractive index of a lens material relative to d-line
.nu.: Abbe number of a lens material
In the subsequent description, the exponent of 10 (e.g.,
4.5.times.10.sup.-04) is expressed by using the letter E (e.g.,
4.5E-04), and surface numbers for lens data are sequentially
assigned so that, for example, the object-side surface of the first
lens L1 is surface 1.
First Embodiment
Table 1 shows numerical data about the image pickup lens according
to the first embodiment. FIG. 1 is a cross-sectional view of the
image pickup lens. FIG. 2 shows various aberrations.
TABLE-US-00001 TABLE 1 Surface Number r d n d .nu. K 1 (S) 2.297
0.550 1.5247 56.26 0.175 2 8384.615 0.411 0 3 -6.170 0.299 1.6142
25.58 2.471 4 8.586 0.242 0 5 2.383 0.481 1.5247 56.26 -7.218 6
3.460 0.658 -1.443 7 -2.320 0.815 1.5094 56.00 -0.455 8 -1.502
0.217 -0.645 9 2.288 0.897 1.5094 56.00 -3.909 10 1.274 0.714
-3.515 11 .infin. 0.300 1.5168 64.20 12 .infin. 0.635 Surface
Number A4 A6 A8 A10 A12 A14 A16 1 (S) -5.423E-3 -2.923E-3 -1.511E-2
2.424E-3 -1.233E-2 3.275E-3 4.002E-3 2 8.525E-3 -2.136E-2 -1.410E-2
-1.071E-2 3.924E-3 0 0 3 1.427E-1 -1.124E-1 5.307E-2 -1.649E-2
-1.541E-2 1.183E-2 0 4 9.163E-2 -4.267E-2 9.557E-3 1.336E-2
-1.497E-2 5.154E-3 0 5 -4.203E-2 -4.711E-3 -2.518E-3 2.523E-3 0 0 0
6 -4.458E-2 -3.915E-3 -4.687E-4 4.421E-4 0 0 0 7 5.934E-2 -4.778E-2
2.552E-2 -7.375E-3 9.592E-4 0 0 8 2.946E-2 -6.592E-3 -1.052E-3
1.407E-3 -1.257E-4 0 0 9 -6.925E-2 1.547E-2 -1.984E-3 4.124E-5
2.050E-5 -1.537E-6 -5.993E-9 10 -4.400E-2 1.076E-2 -2.049E-3
2.486E-4 -1.983E-5 1.014E-6 -2.577E-8 f = 4.815 F = 2.8
Second Embodiment
Table 2 shows numerical data about the image pickup lens according
to the second embodiment. FIG. 3 is a cross-sectional view of the
image pickup lens. FIG. 4 shows various aberrations.
TABLE-US-00002 TABLE 2 Surface Number r d n d .nu. K 1 (S) 2.035
0.605 1.497 81.60 0.145 2 -19.788 0.233 0 3 -4.221 0.295 1.6142
25.58 -1.602 4 13.376 0.341 0 5 3.098 0.486 1.5247 56.26 -11.308 6
4.140 0.731 0.271 7 -2.446 0.818 1.5247 56.26 -0.334 8 -1.493 0.239
-0.653 9 3.310 0.855 1.5247 56.26 -12.446 10 1.488 0.849 -4.788 11
.infin. 0.300 1.5168 64.20 12 .infin. 0.803 Surface Number A4 A6 A8
A10 A12 A14 A16 1 (S) -7.452E-3 -1.617E-4 -1.335E-2 4.383E-3
-9.221E-3 4.483E-3 -3.834E-3- 2 1.998E-2 -2.240E-2 -1.467E-2
-1.152E-2 3.209E-3 0 0 3 1.470E-1 -1.118E-1 5.112E-2 -1.648E-2
-1.373E-2 1.325E-2 0 4 9.526E-2 -4.060E-2 1.128E-2 1.414E-2
-1.462E-2 5.794E-3 0 5 -4.356E-2 -4.909E-3 -2.662E-3 2.513E-3 0 0 0
6 -4.106E-2 -3.596E-3 3.640E-7 6.811E-4 0 0 0 7 5.620E-2 -4.763E-2
2.579E-2 -7.309E-3 9.426E-4 0 0 8 3.109E-2 -6.202E-3 -9.889E-4
1.388E-3 -1.345E-4 0 0 9 -7.078E-2 1.540E-2 -1.993E-3 4.351E-5
2.090E-5 1.538E-6 -1.030E-8 10 -4.561E-2 1.071E-2 -2.036E-3
2.488E-4 -1.998E-5 9.963E-7 -2.502E-8 f = 5.372 F = 2.8
Third Embodiment
Table 3 shows numerical data about the image pickup lens according
to the third embodiment. FIG. 5 is a cross-sectional view of the
image pickup lens. FIG. 6 shows various aberrations.
TABLE-US-00003 TABLE 3 Surface Number r d n d .nu. K 1 (S) 2.093
0.608 1.5441 56.00 0.123 2 -25.611 0.211 0 3 -4.074 0.307 1.5850
30.00 -1.357 4 11.977 0.336 0 5 3.166 0.478 1.5441 56.00 -11.659 6
4.064 0.731 0.351 7 -2.478 0.790 1.5247 56.26 -0.290 8 -1.540 0.274
-0.648 9 3.353 0.859 1.5247 56.26 -12.746 10 1.488 0.794 -4.901 11
.infin. 0.300 1.5168 64.20 12 .infin. 0.713 Surface Number A4 A6 A8
A10 A12 A14 A16 1 (S) -8.004E-3 4.932E-5 -1.335E-2 4.345E-3
-9.202E-3 4.586E-3 -3.708E-3 2 1.747E-2 -2.375E-2 -1.468E-2
-1.094E-2 3.436E-3 0 0 3 1.466E-1 -1.114E-1 5.110E-2 -1.663E-2
-1.384E-2 1.328E-2 0 4 9.639E-2 -4.030E-2 1.113E-2 1.390E-2
-1.439E-2 5.879E-3 0 5 -4.371E-2 -5.274E-3 -3.020E-3 2.317E-3 0 0 0
6 -4.084E-2 -3.546E-3 -2.715E-5 7.200E-4 0 0 0 7 5.558E-2 -4.774E-2
2.575E-2 -7.317E-3 9.431E-4 0 0 8 3.087E-2 -6.449E-3 -1.021E-3
1.386E-3 -1.344E-4 0 0 9 -7.043E-2 1.531E-2 -2.006E-3 4.195E-5
2.091E-5 -1.493E-6 8.400E-10 10 -4.574E-2 1.069E-2 -2.047E-3
2.484E-4 -1.994E-5 1.002E-6 -2.527E-8 f = 5.269 F = 2.8
Fourth Embodiment
Table 4 shows numerical data about the image pickup lens according
to the fourth embodiment. FIG. 7 is a cross-sectional view of the
image pickup lens. FIG. 8 shows various aberrations.
TABLE-US-00004 TABLE 4 Surface Number r d n d .nu. K 1 (S) 2.119
0.626 1.5441 56.00 0.177 2 -11.544 0.208 0 3 -3.147 0.298 1.5850
30.00 -5.094 4 9.796 0.373 0 5 2.701 0.428 1.5441 56.00 -11.168 6
3.842 0.837 0.129 7 -2.253 0.750 1.5247 56.26 -0.654 8 -1.467 0.401
-0.694 9 1.656 0.587 1.5247 56.26 -10.501 10 0.981 0.874 -4.578 11
.infin. 0.300 1.5168 64.20 12 .infin. 0.742 Surface Number A4 A6 A8
A10 A12 A14 A16 1 (S) -7.510E-3 1.743E-3 -1.246E-2 5.493E-3
-8.377E-3 4.978E-3 -3.500E-3 2 2.507E-2 -1.481E-2 -1.129E-2
-1.181E-2 3.172E-3 0 0 3 1.526E-1 -1.113E-1 5.074E-2 -1.533E-2
-1.395E-2 1.133E-2 0 4 9.710E-2 -4.050E-2 1.124E-2 1.365E-2
-1.474E-2 5.407E-3 0 5 -3.599E-2 -8.738E-3 -4.179E-3 2.048E-3 0 0 0
6 -4.051E-2 -4.801E-3 -6.520E-4 5.650E-4 0 0 0 7 6.564E-2 -4.702E-2
2.607E-2 -7.359E-3 8.648E-4 0 0 8 3.490E-2 -3.356E-3 -1.098E-3
1.296E-3 -1.421E-4 0 0 9 -7.077E-2 1.589E-2 -1.963E-3 4.145E-5
2.045E-5 -1.557E-6 -2.866E-9 10 -5.003E-2 1.088E-2 -1.968E-3
2.477E-4 -2.068E-5 9.622E-7 -1.548E-8 f = 5.187 F = 2.7
Fifth Embodiment
Table 5 shows numerical data about the image pickup lens according
to the fifth embodiment. FIG. 9 is a cross-sectional view of the
image pickup lens. FIG. 10 shows various aberrations.
TABLE-US-00005 TABLE 5 Surface Number r d n d .nu. K 1 (S) 1.974
0.720 1.5311 56.00 0.260 2 -14.375 0.150 0 3 -4.100 0.350 1.6142
25.58 1.248 4 55.800 0.360 0 5 5.600 0.340 1.5311 56.00 -20.645 6
3.868 0.750 1.356 7 -3.010 0.820 1.5311 56.00 -0.508 8 -1.634 0.270
-0.656 9 4.156 0.880 1.5311 56.00 -29.637 10 1.582 0.830 -5.617 11
.infin. 0.300 1.5168 64.20 12 .infin. 0.770 Surface Number A4 A6 A8
A10 A12 A14 A16 1 (S) -6.011E-3 4.555E-3 -1.140E-2 5.896E-3
-7.660E-3 5.633E-3 -3.706E-3 2 3.346E-2 -2.148E-2 -1.342E-2
-1.061E-2 3.525E-3 0 0 3 1.407E-1 -1.057E-1 4.976E-2 -1.790E-2
-1.431E-2 1.182E-2 0 4 1.000E-1 -4.704E-2 1.326E-2 1.542E-2
-1.468E-2 5.766E-3 0 5 -5.387E-2 -6.340E-3 -1.971E-3 2.628E-3 0 0 0
6 -4.023E-2 2.476E-4 1.005E-3 6.170E-4 0 0 0 7 5.679E-2 -4.556E-2
2.594E-2 -7.443E-3 8.944E-4 0 0 8 3.073E-2 -5.791E-3 -8.590E-4
1.367E-3 -1.517E-4 0 0 9 -6.996E-2 1.530E-2 -1.966E-3 5.619E-5
2.207E-5 -1.613E-6 -4.417E-8 10 -4.594E-2 1.064E-2 -2.039E-3
2.506E-4 -2.003E-5 9.526E-7 -2.202E-8 f = 5.700 F = 2.8
Sixth Embodiment
Table 6 shows numerical data about the image pickup according to
the sixth embodiment. FIG. 11 is a cross-sectional view of the
image pickup lens. FIG. 12 shows various aberrations.
TABLE-US-00006 TABLE 6 Surface Number r d n d .nu. K 1 (S) 2.084
0.604 1.5311 56.00 0.168 2 -21.296 0.222 0 3 -3.958 0.300 1.6142
25.58 -1.423 4 13.768 0.323 0 5 3.075 0.497 1.5311 56.00 -11.809 6
4.139 0.624 0.275 7 -2.412 0.870 1.5247 56.26 -0.378 8 -1.484 0.208
-0.649 9 3.407 0.955 1.5247 56.26 -5.620 10 1.561 0.802 -4.276 11
.infin. 0.300 1.5168 64.20 12 .infin. 0.674 Surface Number A4 A6 A8
A10 A12 A14 A16 1 (S) -6.789E-3 2.618E-4 -1.386E-2 3.682E-3
-9.711E-3 4.535E-3 -2.955E-3 2 1.842E-2 -2.358E-2 -1.510E-2
-1.166E-2 3.030E-3 0 0 3 1.465E-1 -1.117E-1 5.082E-2 -1.681E-2
-1.391E-2 1.334E-2 0 4 9.611E-2 -4.021E-2 1.153E-2 1.421E-2
-1.461E-2 5.550E-3 0 5 -4.518E-2 -5.504E-3 -2.914E-3 2.385E-3 0 0 0
6 -4.104E-2 -3.503E-3 -5.896E-5 6.932E-4 0 0 0 7 5.684E-2 -4.751E-2
2.584E-2 -7.290E-3 9.508E-4 0 0 8 3.092E-2 -6.249E-3 -1.018E-3
1.379E-3 -1.373E-4 0 0 9 -6.971E-2 1.550E-2 -1.986E-3 4.363E-5
2.079E-5 -1.571E-6 -1.765E-8 10 -4.447E-2 1.070E-2 -2.036E-3
2.489E-4 -1.996E-5 1.000E-6 -2.448E-8 f = 4.986 F = 2.8
Table 7 below relates to the first to sixth embodiments and shows
values for conditional expressions (1) to (17) below.
Conditional expression (1) concerns the Abbe number of a material
used for the first lens L1. Conditional expression (2) concerns the
Abbe number of a material used for the second lens L2.
45<.nu.1<90 Conditional expression (1) 22<.nu.2<35
Conditional expression (2) where .nu.1 is the Abbe number for
d-line of the first lens, and .nu.2 is the Abbe number for d-line
of the second lens.
Conditional expression (3) defines the range of the focal length of
the first lens L1 with respect to the focal length of the entire
image pickup lens. Conditional expression (4) defines the range of
the focal length of the second lens L2 with respect to the focal
length of the entire image pickup lens. 0.5<f1/f<1.00
Conditional expression (3) -1.50<f2/f<-0.65 Conditional
expression (4) where f is the composite focal length of lenses
included in the entire image pickup lens, f1 is the focal length of
the first lens, and f2 is the focal length of the second lens.
Conditional expression (5) defines the range of the focal length of
the fourth lens L4 with respect to the focal length of the entire
image pickup lens. Conditional expression (6) defines the range of
the focal length of the fifth lens L5 with respect to the focal
length of the entire image pickup lens. 0.9<f4/f<1.50
Conditional expression (5) -1.70<f5/f<-0.85 Conditional
expression (6) where f is the composite focal length of lenses
included in the entire image pickup lens, f4 is the focal length of
the fourth lens, and f5 is the focal length of the fifth lens.
Conditional expression (7) defines the ratio between the focal
length of the first lens L1 and the focal length of the third lens
L3. -0.15<f1/f3<0.37 Conditional expression (7) where f1 is
the focal length of the first lens, and f3 is the focal length of
the third lens.
Conditional expression (8) defines the composite focal length of
the second lens L2, the third lens L3, and the fourth lens L4.
0.0<f234 Conditional expression (8)
Conditional expression (9) defines the power relationship, that is,
the focal length relationship, between the first lens L1, the
second lens L2, and the third lens L3. Conditional expression (10)
defines the power relationship, that is, the focal length
relationship, between the first lens L1, the third lens L3, and the
fourth lens L4. Conditional expression (11) defines the power
relationship, that is, the focal length relationship, between the
first lens L1, the third lens L3, and the fifth lens L5.
f1<|f2|<|f3| Conditional expression (9) f1<f4<|f3|
Conditional expression (10) f1<|f5|<|f3| Conditional
expression (11)
Conditional expression (12) defines the lens shape of the first
lens L1. -0.40<r1/r2<0.10 Conditional expression (12) where
r1 is the curvature radius of the object-side surface of the first
lens, and r2 is the curvature radius of the image-side surface of
the first lens.
Conditional expression (13) defines the lens shape of the fourth
lens L4. 1.4<r7/r8<3.0 Conditional expression (13) where r7
is the curvature radius of the object-side surface of the fourth
lens, and r8 is the curvature radius of the image-side surface of
the fourth lens.
Conditional expression (14) defines the optical length with respect
to the focal length. 1.05<L/f<1.30 Conditional expression
(14) where L is the distance between the front surface of the first
lens and the image surface, and f is the composite focal length of
lenses included in the entire image pickup lens.
Conditional expression (15) defines the F-number (Fno), which is an
indication of lens brightness. 0.30<CA1/f<0.50 Conditional
expression (15) where CA1 is the diameter of the aperture stop, and
f is the composite focal length of lenses included in the entire
image pickup lens.
Conditional expression (16) defines the range of the focal length
of the second lens L2 with respect to the focal length of the
entire image pickup lens, and relates to a case where conditions
more stringent than those defined by conditional expression (4) are
satisfied. -1.30<f2/f<-0.75 Conditional expression (16) where
f is the composite focal length of lenses included in the entire
image pickup lens, and f2 is the focal length of the second
lens.
Conditional expression (17) defines the lens shape of the fourth
lens L4 and relates to a case where conditions more stringent than
those defined by conditional expression (13) are satisfied.
1.45<r7/r8<2.0 Conditional expression (17) where r7 is the
curvature radius of the object-side surface of the fourth lens, and
r8 is the curvature radius of the image-side surface of the fourth
lens.
TABLE-US-00007 TABLE 7 First Second Third Fourth Fifth Sixth
Embodiment Embodiment Embodiment Embodiment Embodiment Embodiment
Conditional 56.26 81.60 56.00 56.00 56.00 56.00 Expression (1)
Conditional 25.58 25.58 30.00 30.00 25.58 25.58 Expression (2)
Conditional 0.909 0.698 0.680 0.645 0.582 0.723 Expression (3)
Conditional -1.205 -0.966 -0.979 -0.778 -1.089 -0.997 Expression
(4) Conditional 1.300 1.050 1.141 1.163 0.978 1.115 Expression (5)
Conditional -1.671 -1.144 -1.150 -1.262 -0.957 -1.340 Expression
(6) Conditional 0.346 0.185 0.162 0.226 -0.131 0.186 Expression (7)
Conditional 10.266 10.597 13.323 15.698 18.816 10.806 Expression
(8) Conditional Expression (9) f 1 4.379 3.747 3.584 3.344 3.319
3.606 |f 2| 5.800 5.191 5.160 4.037 6.205 4.973 |f 3| 12.647 20.214
22.174 14.764 25.268 19.382 Conditional Expression (10) f 1 4.379
3.747 3.584 3.344 3.319 3.606 f 4 6.258 5.638 6.011 6.033 5.577
5.558 |f 3| 12.647 20.214 22.174 14.764 25.268 19.382 Conditional
Expression (11) f 1 4.379 3.747 3.584 3.344 3.319 3.606 |f 5| 8.045
6.144 6.059 6.546 5.457 6.680 |f 3| 12.647 20.214 22.174 14.764
25.268 19.382 Conditional 0.000 -0.103 -0.082 -0.184 -0.137 -0.098
Expression (12) Conditional 1.545 1.638 1.609 1.536 1.842 1.625
Expression (13) Conditional 1.292 1.220 1.215 1.238 1.147 1.279
Expression (14) Conditional 0.357 0.355 0.357 0.385 0.355 0.355
Expression (15)
As shown in Table 7, the first to sixth embodiments of the present
invention satisfy all of conditional expressions (1) to (17).
Conditional expressions (1) and (2) define the Abbe number of the
first lens Li or the second lens L2. If the lower limit indicated
by conditional expression (1) or (2) is exceeded, the variance
value difference from the second lens L2 is decreased so that
chromatic aberration correction is insufficient. If, on the
contrary, the upper limit is exceeded, the balance between axial
chromatic aberration and chromatic aberration of magnification is
impaired so that performance deterioration occurs at the periphery
of the image area. However, when conditional expressions (1) and
(2) are satisfied, a proper balance is maintained between axial
chromatic aberration and chromatic aberration of magnification.
This makes it possible to prevent performance deterioration at the
periphery of the image area and provide excellent chromatic
aberration correction.
Conditional expressions (3) and (4) define the range of the focal
length of the first lens L1 or the second lens L2 with respect to
the focal length of the entire image pickup lens. If the lower
limit indicated by conditional expression (3) is exceeded, the
focal length of the first lens L1 is too small. This makes it
difficult to correct spherical aberration and coma aberration. If,
on the contrary, the upper limit is exceeded, the optical length is
too great so that the thickness of the image pickup lens cannot be
sufficiently reduced. If the lower limit indicated by conditional
expression (4) is exceeded, the power of the second lens L2 is
insufficient so that chromatic aberration cannot be adequately
corrected. If, on the contrary, the upper limit is exceeded, the
focal length of the second lens L2 is too small. This makes it
difficult to correct spherical aberration and coma aberration, and
decreases manufacturing error sensitivity. However, when
conditional expressions (3) and (4) are satisfied, it is possible
to properly correct spherical aberration and coma aberration.
Further, the power of the second lens L2 becomes sufficient, making
it possible to properly correct chromatic aberration, spherical
aberration, and coma aberration.
Conditional expression (5) defines the range of the focal length of
the fourth lens L4 with respect to the focal length of the entire
image pickup lens. If the lower limit indicated by conditional
expression (5) is exceeded, the focal length of the fourth lens L4
is too small. This makes it difficult to correct astigmatism and
coma aberration, and decreases the manufacturing error sensitivity.
If, on the contrary, the upper limit is exceeded, chromatic
aberration of magnification and astigmatism are not adequately
corrected so that expected performance is not obtained. However,
when conditional expression (5) is satisfied, it is easy to correct
astigmatism, coma aberration, and chromatic aberration of
magnification. This makes it possible to obtain expected
performance.
Conditional expression (6) defines the range of the focal length of
the fifth lens L5 with respect to the focal length of the entire
image pickup lens. If the lower limit indicated by conditional
expression (6) is exceeded, the power of the fifth lens L5 is
insufficient. This makes it difficult to decrease the optical
length. If, on the contrary, the upper limit is exceeded, it is
difficult to decrease the CRA, thereby decreasing the manufacturing
error sensitivity at low image height. However, when conditional
expression (6) is satisfied, the fifth lens L5 has a sufficient
power, making it possible to reduce the optical length. This makes
it easy to decrease the CRA so that the manufacturing error
sensitivity at low image height increases.
Conditional expression (7) defines the ratio between the focal
length of the first lens L1 and the focal length of the third lens
L3. If the lower limit indicated by conditional expression (7) is
exceeded, the focal length of the third lens L3 is negative and too
small. This makes it difficult to provide aberration correction.
If, on the contrary, the upper limit is exceeded, the focal length
of the third lens L3 is positive and too small. This impairs the
balance between astigmatism and coma aberration and decreases the
manufacturing error sensitivity. However, when conditional
expression (7) is satisfied, it is easy to provide aberration
correction. Further, it is possible not only to prevent the focal
length of the third lens L3 from being positive and too small, but
also to maintain an excellent balance between astigmatism and coma
aberration.
Conditional expression (8) defines the composite focal length of
the second lens L2, the third lens L3, and the fourth lens L4. If
the lower limit indicated by conditional expression (8) is
exceeded, the negative power of the second lens L2 is too strong so
that the manufacturing error sensitivity is excessively low, or the
positive power of the fourth lens L4 is too weak so that it is
difficult to correct astigmatism and distortion. However, when
conditional expression (8) is satisfied, it is easy to correct
astigmatism and distortion.
Conditional expression (9) defines the power relationship, that is,
the focal length relationship, between the first lens L1, the
second lens L2, and the third lens L3. If the lower limit indicated
by conditional expression (9) is exceeded, the negative power of
the second lens L2 is too strong. This increases the optical length
and decreases the manufacturing error sensitivity. If, on the
contrary, the upper limit is exceeded, the power of the third lens
is too strong so that it is difficult to obtain adequate off-axis
performance. However, when conditional expression (9) is satisfied,
it is possible to decrease the optical length and easily obtain
adequate off-axis performance.
Conditional expression (10) defines the power relationship, that
is, the focal length relationship, between the first lens L1, the
third lens L3, and the fourth lens L4. If the lower limit indicated
by conditional expression (10) is exceeded, the power of the fourth
lens L4 is too strong. This increases the optical length and makes
it difficult to correct astigmatism and distortion. If, on the
contrary, the upper limit is exceeded, the power of the third lens
L3 is too strong so that it is difficult to obtain adequate
off-axis performance. However, when conditional expression (10) is
satisfied, it is easy to correct astigmatism and distortion and
obtain adequate off-axis performance.
Conditional expression (11) defines the power relationship, that
is, the focal length relationship, between the first lens L1, the
third lens L3, and the fifth lens L5. If the lower limit indicated
by conditional expression (11) is exceeded, the negative power of
the fifth lens L5 is too strong. This makes it difficult to correct
coma aberration and astigmatism. If, on the contrary, the upper
limit is exceeded, the power of the third lens L3 is too strong so
that it is difficult to obtain adequate off-axis performance.
However, when conditional expression (11) is satisfied, it is easy
to correct coma aberration and astigmatism and obtain adequate
off-axis performance.
Conditional expression (12) defines the lens shape of the first
lens L1. If the lower limit indicated by conditional expression
(12) is exceeded, the optical length cannot be readily reduced. In
addition, the error sensitivity prevailing during the manufacture
of the first lens L1 becomes low. If, on the contrary, the upper
limit is exceeded, it is difficult to maintain a proper aberration
balance so that expected performance is not obtained. However, when
conditional expression (12) is satisfied, the optical length can be
readily reduced. In addition, it is possible to maintain a proper
aberration balance and obtain expected performance.
Conditional expression (13) defines the lens shape of the fourth
lens L4. If the lower limit indicated by conditional expression
(13) is exceeded, the power of the fourth lens L4 is too weak.
Consequently, performance deterioration occurs because it is
difficult to correct various aberrations. If, on the contrary, the
upper limit is exceeded, the fourth lens L4 has an excessively
strong power or has a small degree of meniscus curvature. In this
instance, too, it is difficult to maintain a proper aberration
balance so that expected performance is not obtained. However, when
conditional expression (13) is satisfied, it is easy to correct
various aberrations and maintain a proper aberration balance. As a
result, expected performance is obtained.
Conditional expression (14) defines the optical length with respect
to the focal length. If the lower limit indicated by conditional
expression (14) is exceeded, it is difficult to correct various
aberrations due to an excessively decreased optical length. In
addition, the manufacturing error sensitivity becomes excessively
low. If, on the contrary, the upper limit is exceeded, it is
difficult to reduce the thickness of the image pickup lens due to
an excessively increased optical length. However, when conditional
expression (14) is satisfied, it is easy to correct various
aberrations. In addition, the thickness of the image pickup lens
can be readily reduced because the optical length is not
excessively small.
Conditional expression (15) defines the F-number (Fno), which is an
indication of lens brightness. If the lower limit indicated by
conditional expression (15) is exceeded, the F-number is
excessively great so that requested brightness is not achieved in
most cases. If, on the contrary, the upper limit is exceeded, the
F-number is excessively small or the distance between the aperture
stop (F-number light flux restriction plate) and the front surface
of the first lens is excessively great. In either of these cases,
expected optical performance is not obtained. However, when
conditional expression (15) is satisfied, the expected optical
performance can be obtained with ease.
Further, the second lens L2, the third lens L3, the fourth lens L4,
and the fifth lens L5 are so-called plastic lenses that have at
least one aspherical surface and are made of a resin material. Cost
reduction can be achieved when at least the second lens L2, the
third lens L3, the fourth lens L4, and the fifth lens L5 are made
of an inexpensive resin material exhibiting high production
efficiency.
Furthermore, as the aperture stop S is positioned on the object
side of the first lens L1 to decrease the CRA (Chief Ray Angle), it
is easy to reduce the CRA (Chief Ray Angle) and obtain sufficient
light intensity at the periphery of the image surface at which
light intensity decreases.
Moreover, as the object side surface and image side surface of the
fifth lens L5 have an aspherical shape that contains at least one
inflection point between the center and the periphery of the lens,
it is possible to obtain adequate off-axis performance and CRA.
While the present invention has been described in terms of
exemplary embodiments, it should be understood that the invention
is not limited to those exemplary embodiments. Those skilled in the
art will understand that various changes and modifications can be
made within the scope and spirit of the invention.
TABLE-US-00008 EXPLANATION OF REFERENCE NUMERALS AND SYMBOLS L1
First lens L2 Second lens L3 Third lens L4 Fourth lens L5 Fifth
lens S Aperture stop
* * * * *