U.S. patent application number 09/808220 was filed with the patent office on 2001-09-27 for image capture lens and image capture apparatus.
Invention is credited to Mori, Masao.
Application Number | 20010024332 09/808220 |
Document ID | / |
Family ID | 26587913 |
Filed Date | 2001-09-27 |
United States Patent
Application |
20010024332 |
Kind Code |
A1 |
Mori, Masao |
September 27, 2001 |
Image capture lens and image capture apparatus
Abstract
An image capture lens and an image capture apparatus in which
various kinds of aberrations are corrected and optical performance
suitable for capturing images is obtained. Successively from an
object side provided are a first lens group including a negative
meniscus lens, a second lens group including a positive lens
directing its convex to the object side, a third lend group
including a first cemented lens composed of a bi-convex positive
lens and a bi-concave negative lens, the first cemented lens having
positive refractive power and directing its concave to the object
side, a fourth lens group including a second cemented lens composed
of a bi-concave negative lens and a bi-convex positive lens, the
second cemented lens having negative refractive power and directing
its convex surface to an image side, a fifth lens group including a
positive lens directing its convex to the image side and a sixth
lens group including a negative lens directing its concave to the
object side.
Inventors: |
Mori, Masao; (Omiya City,
JP) |
Correspondence
Address: |
MATTHEW K. RYAN
c/o FROMMER LAWRENCE & HAUG LLP
745 Fifth Avenue
New York
NY
10151
US
|
Family ID: |
26587913 |
Appl. No.: |
09/808220 |
Filed: |
March 14, 2001 |
Current U.S.
Class: |
359/755 ;
359/761 |
Current CPC
Class: |
G02B 13/04 20130101 |
Class at
Publication: |
359/755 ;
359/761 |
International
Class: |
G02B 009/64; G02B
009/62 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 21, 2000 |
JP |
2000-77702 |
Apr 25, 2000 |
JP |
2000-124779 |
Claims
What is claimed is:
1. An image capture lens, comprising successively from an object
side: a first lens group including a negative meniscus lens; a
second lens group including a positive lens directing its convex to
the object side; a third lens group including a first cemented lens
composed of a bi-convex positive lens and a bi-concave negative
lens, the first cemented lens having positive refractive power and
directing its convex to the object side; a fourth lens group
including a second cemented lens composed of a bi-concave negative
lens and a bi-convex positive lens, the second cemented lens having
negative refractive power and directing its convex to an image
side; a fifth lens group including a positive lens directing its
convex to the image side; and a sixth lens group including a
negative lens directing its concave to the object side.
2. An image capture lens according to claim 1, wherein expressions
65<.nu..sub.3, 0.015<.delta..theta..sub.3, 65<.nu..sub.6
and 0.015<.delta..theta..sub.6 are satisfied when the .nu..sub.3
and the .delta..theta..sub.3 represent Abbe number for a wavelength
of d-line and anomalous dispersion of the positive lens in the
third lens group, respectively and the .nu..sub.6 and the
.delta..theta..sub.6 represent Abbe number for the wavelength of
d-line and anomalous dispersion of the positive lens in the fourth
lens group, respectively and the expressions are satisfied on the
condition that anomalous dispersion .delta..theta..sub.g,d is
expressed by .delta..theta..sub.g,d=.theta..sub-
.g,d-(1.365-0.00208*.nu..sub.d) where the .nu..sub.d represents
Abbe number for the wavelength of d-line; the relative partial
dispersion .theta..sub.g,d for wavelengths of g-line and d-line is
expressed by .theta..sub.g,d=(n.sub.g-n.sub.d)/(n.sub.F-n.sub.C)
where the n.sub.g, the n.sub.d, the n.sub.F and the n.sub.C
represent refractive index for wavelengths for g-line, d-line,
F-line and C-line, respectively; and .delta..theta..sub.i and
.nu..sub.i represent the anomalous dispersion
.delta..theta..sub.g,d and the Abbe number .nu.d of the `i`th lens
from the object side, respectively.
3. An image capture lens according to claim 2, wherein
0.09<(.phi..sub.3*.delta..theta..sub.3+.phi..sub.6*.delta..theta..sub.-
6)/.phi..sub.T<0.15,
0.75<(n.sub.3*.nu..sub.4)/(n.sub.4*.nu..sub.3)&- lt;1.10 and
-13.0<.phi..sub.T.sup.2/(.phi..sub.3,4*.phi..sub.5,6)<-0- .3
are satisfied when the .phi..sub.3 and the .delta..theta..sub.3
represent refractive power and anomalous dispersion of the positive
lens in the third lens group, respectively, the .phi..sub.6 and the
.delta..theta..sub.6 represent refractive power and anomalous
dispersion of the positive lens in the fourth lens group,
respectively, the .nu..sub.3 and the n.sub.3 represent Abbe number
and refractive index for the wavelength of d-line of the positive
lens in the third lens group, respectively, the .nu..sub.4 and the
n.sub.4 represent Abbe number and refractive index for the
wavelength of d-line of the negative lens in the third lens group,
respectively, and the .phi..sub.3,4 represents refractive power of
the entire cemented lens in the third lens group, .phi..sub.5,6
represents the refractive power of the entire cemented lens in the
fourth lens group and the .phi..sub.T represents refractive power
of an entire lens system including all the lens groups.
4. An image capture lens, comprising successively from an object
side: a first lens group including a negative meniscus lens; a
second lens group including a positive lens directing its convex to
the object side; a third lens group including a first cemented lens
composed of a bi-convex positive lens and a bi-concave negative
lens, the first cemented lens having positive refractive power and
directing its convex to the object side; a fourth lens group
including a second cemented lens composed of a bi-concave negative
lens and a bi-convex positive lens, the second cemented lens
directing its convex to the image side; a fifth lens group
including a positive lens directing its convex to the image side; a
sixth lens group including a negative lens directing a surface
thereof to the object side, a radius of the surface being smaller
than that of an opposite surface; and a seventh lens group
including a negative meniscus lens and a positive lens.
5. An image capture lens according to claim 4, wherein a third
cemented lens is composed of the negative meniscus lens and the
positive lens in the seventh lens group, the third cemented lens
directing its convex to the object side.
6. An image capture lens according to claim 4, wherein expressions
65<.nu..sub.3, 0.015<.delta..theta..sub.3, 65<.nu..sub.6
and 0.015<.delta..theta..sub.6 are satisfied when the .nu..sub.3
and the .delta..theta..sub.3 represent Abbe number for the
wavelength of d-line and anomalous dispersion of the positive lens
in the third lens group, respectively and the .nu..sub.6 and the
.delta..theta..theta. represent Abbe number for the wavelength of
d-line and anomalous dispersion of the positive lens in the fourth
lens group, respectively, and the expressions are satisfied on the
condition that anomalous dispersion .delta..theta..sub.g,d is
expressed by .delta..theta..sub.g,d=.theta..sub-
.g,d-(1.365-0.00208*.nu..sub.d) where the .nu.d represents Abbe
number for the wavelength of d-line; the relative partial
dispersion .theta..sub.g,d for wavelengths of g-line and d-line is
expressed by .theta..sub.g,d=(n.sub.g-n.sub.d)/(n.sub.F-n.sub.C)
where the n.sub.g, the n.sub.d, the n.sub.F and the n.sub.C
represent refractive index for wavelengths for g-line, d-line,
F-line and C-line, respectively; and .delta..theta..sub.i and
.nu..sub.i represent the anomalous dispersion
.delta..theta..sub.g,d and the Abbe number .nu.d of the `i`th lens
from the object side, respectively.
7. An image capture lens according to claim 6, wherein a third
cemented lens is composed of the negative meniscus lens and the
positive lens in the seventh lens group, the third cemented lens
directing its convex to the object side.
8. An image capture lens according to claim 6, wherein
0.09<(.phi..sub.3*.delta..theta..sub.3+.phi..sub.6*.delta..theta..sub.-
6)/.phi..sub.T<0.15 is satisfied when the .phi..sub.3 and the
.delta..theta..sub.3 represent refractive power and anomalous
dispersion of the positive lens in the third lens group,
respectively, the .phi..sub.6 and the .delta..theta..sub.6
represent refractive power and anomalous dispersion of the positive
lens in the fourth lens group, respectively and the .phi..sub.T
represents refractive power of an entire lens system including all
the lens groups, and -0.2<r.sub.16/r.sub.18&- lt;1.2,
0.35<.phi..sub.T*r.sub.17<1.2 and 13<.nu..sub.9-.nu..sub.-
10 are satisfied when the .nu..sub.9 and the .nu..sub.10 represent
Abbe number for the wavelength of d-line of the negative meniscus
lens and the positive lens in the seventh lens group, respectively
and the r.sub.16, the r.sub.17 and the r.sub.18 represent radius of
curvature of lens surfaces of the seventh lens group in this order
from the object side.
9. An image capture lens according to claim 8, wherein a third
cemented lens is composed of the negative meniscus lens and the
positive lens in the seventh lens group, the third cemented lens
directing its convex surface to the object side.
10. An image capture apparatus for reading an image through an
image capture lens, the image capture lens comprising successively
from an object side: a first lens group including a negative
meniscus lens; a second lens group including a positive lens
directing its convex to the object side; a third lens group
including a first cemented lens composed of a bi-convex positive
lens and a bi-concave negative lens, the first cemented lens having
positive refractive power and directing its convex to the object
side; a fourth lens group including a second cemented lens composed
of a bi-concave negative lens and a bi-convex positive lens, the
second cemented lens having negative refractive power and directing
its convex to an image side; a fifth lens group including a
positive lens directing its convex to the image side; and a sixth
lens group including a negative lens directing its concave to the
object side.
11. An image capture apparatus for reading an image through an
image capture lens, the image capture lens comprising successively
from an object side: a first lens group including a negative
meniscus lens; a second lens group including a positive lens
directing its convex to the object side; a third lens group
including a first cemented lens composed of a bi-convex positive
lens and a bi-concave negative lens, the first cemented lens having
positive refractive power and directing its convex to the object
side; a fourth lens group including a second cemented lens composed
of a bi-concave negative lens and a bi-convex positive lens, the
second cemented lens directing its convex to an image side; a fifth
lens group including a positive lens directing its convex to the
image side; a sixth lens group including a negative lens directing
a surface thereof to the object side, a radius of the surface being
smaller than that of an opposite surface; and a seventh lens group
including a negative meniscus lens and a positive lens.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to an image capture lens and
an image capture apparatus which are used for reading various kinds
of images.
[0003] 2. Description of the Related Art
[0004] An image capture apparatus, in which an image of an original
such as a negative film or positive film is formed on a solid state
image sensor such as a charge-coupled device (CCD) serving as a
light-receiving device through a image capture optical system, and
then image information is read, has been developed. With the
increase of high density in the light-receiving device, high
resolution of an image capture lens employed in the optical system
of the image capture apparatus is in demand in recent years.
Particularly, with regard to the image capture lens which is
utilized in the image capture apparatus in which color images are
read with one CCD, for example, achromatization needs to be
performed preferably in order that imaging points of images
composed of each color: red (R), green (G) and blue (B) correspond
to each other on the light-receiving surface of the CCD, and
desirably resolution levels of each color on the device are
maintained. Specifically, the image capture lens is required to
exhibit imaging performance such that axial chromatic aberration
and chromatic aberration of magnification of each RGB color are
small, and images from the center to peripheries are formed on a
plane substantially vertical to the optical axis. When the image
capture lens has such imaging performance, high-contrast images
with each RGB color can be obtained.
[0005] However, there exists a problem such that, if axial
chromatic aberration is not corrected enough in the image capture
lens, imaging points of each RGB color do not correspond to each
other. Therefore, even though individual resolution of each RGB
color is in high contrast, variations in contrast of each RGB color
occur depending on the imaging point. To correct such variations in
contrast, a mechanism which focuses each color individually or a
method such that an image plane is shifted in accordance with the
magnitude of chromatic aberration is necessary.
[0006] When `f` and .beta.(.beta.<0) represent focus length and
imaging magnification of a lens, the magnitude of axial chromatic
aberration AS is expressed by .DELTA.S.varies.(1-.beta.).sup.2*f,
which denotes that as the focal length f becomes longer or the
absolute value .vertline..beta..vertline. of the imaging
magnification becomes larger, the amount of axial chromatic
aberration occurred increases. This is noticeable in a lens made of
a material with no anomalous dispersion. In such a lens, axial
chromatic aberration is not sufficiently corrected. Particularly,
it is difficult to obtain high contrast simultaneously between each
RGB color in a magnification range. Thus, when such high-level
axial chromatic aberration is subjected to correct in the image
capture lens, use of a lens material with high anomalous dispersion
is effective. In that case, as the anomalous dispersion is larger,
the effect of correction is larger. Further, as the refractive
power is larger, the effect of correction is larger. However, if
the refractive power is made too large, the magnitude of various
kinds of aberrations becomes larger resulting in deterioration of
image quality. Accordingly, when the material with large anomalous
dispersion is used for the `i`th lens element in the image capture
lens, for example, desirably by giving a moderate value for
.SIGMA..phi..sub.i*.delta..theta..sub.i which is the sum of the
products of the refractive power .phi..sub.i(.phi..sub.i=1/f.s-
ub.i) and the anomalous dispersion .delta..theta..sub.i of the lens
elements made of the material, axial chromatic aberration is made
smaller and other aberrations are preferably corrected.
[0007] Although many image capture lenses in which achromatization
is utilized have been proposed heretofore, magnification used in
most of the conventional capture lenses is reducing imaging
magnification such as -0.1.times. to -0.2.times., thus large axial
chromatic aberration which occurs in magnifying images is difficult
to correct. Therefore, the conventional image capture lenses are
not adequate for capturing images with scaling them up or down
crossing over the magnification of the actual size, for example.
For example, if the conventional image capture lenses are used in
the magnification range of -0.6.times. to -1.6.times., it is
difficult to form preferable images by scaling them up in
particular.
SUMMARY OF THE INVENTION
[0008] The present invention has been achieved in view of the above
problems. It is an object of the invention to provide an image
capture lens and an image capture apparatus in which various kinds
of aberrations are corrected and optical performance suitable for
capturing images is obtained.
[0009] In the image capture lens of the first aspect of the
invention, successively from an object side provided are a first
lens group including a negative meniscus lens; a second lens group
including a positive lens directing its convex to the object side;
a third lens group including a first cemented lens composed of a
bi-convex positive lens and a bi-concave negative lens, the first
cemented lens having positive refractive power and directing its
convex to the object side; a fourth lens group including a second
cemented lens composed of a bi-concave negative lens and a
bi-convex positive lens, the second cemented lens having negative
refractive power and directing its convex to an image side; a fifth
lens group including a positive lens directing its convex to the
image side; and a sixth lens group including a negative lens
directing its con cave to the object side.
[0010] The image capture apparatus of the first aspect of the
invention reads images through the image capture lens of the first
aspect of the invention.
[0011] In the image capture lens of the first aspect of the
invention, desirably expressions 65<.nu..sub.3,
0.015<.delta..theta..sub.3, 65<.nu..sub.6 and
0.015<.delta..theta..sub.6 are satisfied when the .nu..sub.3 and
the .delta..theta..sub.3 represent Abbe number for a wavelength of
d-line and anomalous dispersion of the positive lens in the third
lens group, and the .nu..sub.6 and the .delta..theta..sub.6
represent Abbe number for the wavelength of d-line and anomalous
dispersion of the positive lens in the fourth lens group.
[0012] In the image capture lens of the first aspect of the
invention, desirably expressions
0.09<(.phi..sub.3*.delta..theta..sub.3+.phi..sub-
.6*.delta..theta..sub.6)/.phi..sub.T<0.15, 0.75<(n.sub.3*
.nu..sub.4)/(n.sub.4*.nu..sub.3)<1.10 and
-13.0<.phi..sub.T.sup.2/(- .phi..sub.3,4*.phi..sub.5,6)<-0.3
are satisfied when the .phi..sub.3 and the .delta..theta..sub.3
represent refractive power and anomalous dispersion of the positive
lens in the third lens group, respectively, the .phi..sub.6 and the
.delta..theta..sub.6 represent refractive power and anomalous
dispersion of the positive lens in the fourth lens group,
respectively, the .nu..sub.3 and the n.sub.3 represent Abbe number
and refractive index for the wavelength of d-line of the positive
lens in the third lens group, respectively, the .nu..sub.4 and the
n.sub.4 represent Abbe number and refractive index for the
wavelength of d-line of the negative lens in the third lens group,
respectively, and the .phi..sub.3,4 represents refractive power of
the entire cemented lens in the third lens group, .phi..sub.5,6
represents the refractive power of the entire cemented lens in the
fourth lens group and the .phi..sub.T represents refractive power
of an entire lens system including all the lens groups.
[0013] In the image capture lens of the second aspect of the
invention, successively from an object side provided are a first
lens group including a negative meniscus lens; a second lens group
including a positive lens directing its convex to the object side;
a third lens group including a first cemented lens composed of a
bi-convex positive lens and a biconcave negative lens, the first
cemented lens having positive refractive power and directing its
convex to an object side; a fourth lens group including a second
cemented lens composed of a biconcave negative lens and a bi-convex
positive lens, the second cemented lens directing its convex to the
image side; a fifth lens group including a positive lens directing
its convex to the image side; a sixth lens group including a
negative lens directing a surface thereof to the object side, a
radius of the surface being smaller than that of an opposite
surface; and a seventh lens group including a negative meniscus
lens and a positive lens. In the image capture lens of the second
aspect of the invention, a third cemented lens may be composed of
the negative meniscus lens and the positive lens in the seventh
lens group, the third cemented lens directing its convex to the
object side.
[0014] The image capture apparatus of the second aspect of the
invention reads images through the image capture lens of the second
aspect of the invention.
[0015] In the image capture lens of the second aspect of the
invention, expressions 65<.nu..sub.3,
0.015<.delta..theta..sub.3, 65<.nu..sub.6 and
0.015<.delta..theta..sub.6 are satisfied when the .nu..sub.3 and
the .delta..theta..sub.3 represent Abbe number for the wavelength
of d-line and anomalous dispersion of the positive lens in the
third lens group, respectively and the .nu..sub.6 and the
.delta..theta..sub.6 represent Abbe number for the wavelength of
d-line and anomalous dispersion of the positive lens in the fourth
lens group, respectively.
[0016] In the image capture lens of the second aspect of the
invention,
0.09<(.phi..sub.3*.delta..theta..sub.3+.phi..sub.6*.delta..theta..sub.-
6)/.phi..sub.T<0.15 is satisfied when the .phi..sub.3 and the
.delta..theta..sub.3 represent refractive power and anomalous
dispersion of the positive lens in the third lens group,
respectively, the .phi..sub.6 and the .delta..theta..sub.6
represent refractive power and anomalous dispersion of the positive
lens in the fourth lens group, respectively and the .phi..sub.T
represents refractive power in an entire lens system including all
the lens groups, and -0.2<r.sub.16/r.sub.18&- lt;1.2,
0.35<.phi..sub.T*r.sub.17<1.2 and 13<.nu..sub.9-.nu..sub.-
10 are satisfied when the .nu..sub.9 and the .nu..sub.10 represent
Abbe number for the wavelength of d-line of the negative meniscus
lens and the positive lens in the seventh lens group, respectively
and the r.sub.16, the r.sub.17 and the r.sub.18 represent radius of
curvature of lens surfaces of the seventh lens group from the
object side.
[0017] The image capture lens of the first and second aspects of
the invention is constituted as described above. Thus, various
kinds of aberrations are preferably corrected so that imaging
performance suitable for capturing images is obtained. Further, in
the image capture apparatus of the first and second aspects of the
invention, high-quality images obtained through the image capture
lens of the first and the second aspects of the invention are
read.
[0018] Other and further objects, features and advantages of the
invention will appear more fully from the following
description.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] FIG. 1 is a diagram showing the configuration of an image
capture apparatus according to a first embodiment of the
invention;
[0020] FIG. 2 is a cross sectional view showing the structure of
the image capture lens according to the first embodiment of the
invention;
[0021] FIGS. 3A and 3B are tables of a first example (Example 1-1)
with specific numeric values of the image capture lens according to
the first embodiment of the invention;
[0022] FIG. 4 is a table containing various conditions for the
image capture lens of Example 1-1 as in FIGS. 3A and 3B;
[0023] FIGS. 5A to 5C are aberration charts of spherical
aberration, astigmatism, distortion and chromatic aberration of
magnification at each magnification with regard to the image
capture lens of Example 1-1 as in FIGS. 3A and 3B;
[0024] FIGS. 6A to 6C are aberration charts of coma at each
magnification with regard to the image capture lens of Example 1-1
as in FIGS. 3A and 3B;
[0025] FIG. 7 is a cross sectional view showing the structure of
the image capture apparatus according to a second example (Example
1-2) of the first embodiment of the invention;
[0026] FIGS. 8A and 8B are tables of Example 1-2 with specific
numeric values of the image capture lens according to the first
embodiment of the invention;
[0027] FIG. 9 is a table containing various conditions for the
image capture lens of Example 1-2 as in FIGS. 8A and 8B;
[0028] FIGS. 10A to 10C are aberration charts of spherical
aberration, astigmatism, distortion and chromatic aberration of
magnification at each magnification with regard to the image
capture lens of Example 1-2 as in FIGS. 8A and 8B;
[0029] FIGS. 11A to 11C are aberration charts of coma at each
magnification with regard to the image capture lens of Example 1-2
as in FIGS. 8A and 8B;
[0030] FIG. 12 is a cross sectional view showing the structure of
the image capture lens according to a third example (Example 1-3)
of the first embodiment of the invention;
[0031] FIGS. 13A and 13B are tables of Example 1-3 with specific
numeric values of the image capture lens according to the first
embodiment of the invention;
[0032] FIG. 14 is a table containing various conditions for the
image capture lens of Example 1-3 as in FIGS. 13A and 13B;
[0033] FIGS. 15A to 15C are aberration charts of spherical
aberration, astigmatism, distortion and chromatic aberration of
magnification at each magnification with regard to the image
capture lens of Example 1-3 as in FIGS. 13A and 13B;
[0034] FIGS. 16A to 16C are aberration charts of coma at each
magnification with regard to the image capture lens of Example 1-3
as in FIGS. 13A and 13B;
[0035] FIG. 17 is a cross sectional view showing the structure of
the image capture lens according to a second embodiment of the
invention;
[0036] FIGS. 18A and 18B are tables of Example 2-1 with specific
numeric values of the image capture lens according to the second
embodiment of the invention;
[0037] FIG. 19 is a table containing various conditions for the
image capture lens of Example 2-1 as in FIGS. 18A and 18B;
[0038] FIGS. 20A to 20C are aberration charts of spherical
aberration, astigmatism, distortion and chromatic aberration of
magnification at each magnification with regard to the image
capture lens of Example 2-1 as in FIGS. 18A and 18B;
[0039] FIGS. 21A to 21C are aberration charts of coma at each
magnification with regard to the image capture lens of Example 2-1
as in FIGS. 18A and 18B;
[0040] FIG. 22 is a cross sectional view showing the structure of
the image capture lens according to a second example (Example 2-2)
of the second embodiment of the invention;
[0041] FIGS. 23A and 23B are tables of Example 2-2 with specific
numeric values of the image capture lens according to the second
embodiment of the invention;
[0042] FIG. 24 is a table containing various conditions for the
image capture lens of Example 2-2 as in FIGS. 23A and 23B;
[0043] FIGS. 25A to 25C are aberration charts of spherical
aberration, astigmatism, distortion and chromatic aberration of
magnification at each magnification with regard to the image
capture lens of Example 2-2 as in FIGS. 23A and 23B; and
[0044] FIGS. 26A to 26C are aberration charts of coma at each
magnification with regard to the image capture lens of Example 2-2
as in FIGS. 23A and 23B.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0045] Embodiments of the present invention will be described below
in detail with reference to the accompanying drawings.
[0046] [First Embodiment]
[0047] An image capture apparatus 1 according to a first embodiment
of the present invention illustrated in FIG. 1 comprises a subject
stage 2 for mounting an original 4 such as a negative film or a
positive film, for example, an imaging device 3 for picking up an
image of the original 4 and an image capture lens 10 for forming
the image of the original 4 on an imaging surface of the imaging
device 3. The imaging device 3 is constituted of a charge-coupled
device (CCD) or the like. In the image capture apparatus 1, between
the original 4 and the image capture lens 10, an optical element 5
such as a glass or a filter for holding down the original 4 on the
subject table 2 as necessary. Further, between the image capture
lens 10 and the imaging device 3, an optical element 6 such as a
cover glass for protecting the imaging device 3 or a filter is
provided as necessary. In the image capture apparatus 1, the image
of the original 4 obtained through the image capture lens 10 is
formed and read by the imaging device 3.
[0048] FIG. 2 is a schematic diagram of the configuration of the
image capture lens 10 according to the embodiment showing each lens
element in cross section within a single plane including an optical
axis O. In FIG. 2, the side represented by `Z.sub.OBJ` denotes an
object side, i.e., the side where the original 4 is disposed and
the image thereof to be read is provided, whereas the side
represented by `Z.sub.IMG` denotes an image side, i.e., the side
where the image on the object side is formed. On an imaging surface
S.sub.IM of the image capture lens 10, the imaging surface of the
imaging device 3 is disposed. In FIG. 2, `P` represents the
position of the center of image formation of the image capture lens
10; `r.sub.i` represents the radius of curvature of the lens
surface of the ith lens from the object side; and `d.sub.i`
represents the surface separation between the ith lens surface and
the [i+1]th lens surface from the object side on the optical axis,
where `i` is integer. The line represented by `r8` is a stop of the
lens system in FIG. 2.
[0049] In the image capture lens 10, successively from the object
side provided are a first lens group G1 including a negative
meniscus lens L1, a second lens group G2 including a positive lens
L2 directing its convex to the object side, a third lens group G3
including a cemented lens which is composed of a bi-convex positive
lens L3 and a bi-concave negative lens L4, the cemented lens having
positive refractive power with its convex facing the object side, a
fourth lens group G4 including a cemented lens which is composed of
a bi-concave negative lens L5 and a bi-convex positive lens L6, the
cemented lens having negative refractive power with its convex
facing the image side, a fifth lens group G5 including a positive
lens L7 directing its convex to the image side and a sixth lens
group G6 including a negative lens L8 directing its concave to the
objective side.
[0050] As shown in FIG. 2, the convex of the negative meniscus lens
L1 in the first lens group G1 faces the object side, for example.
Both of the surfaces of the positive lens L2 in the second lens
group G2 are convex, for example. Both of the surfaces of the
positive lens L7 in the fifth lens group G5 are convex, for
example. The negative lens L8 in the sixth lens group G6 has a
meniscus shape directing its concave to the object side. However,
shapes of the lens elements are not limited to those illustrated in
FIG. 2. For example, the positive lens L2 in the second lens group
G2 may have a meniscus shape directing its convex to the object
side as shown in Example 1-2 to be described later instead of
having a bi-convex shape as in the embodiment.
[0051] In the image capture lens 10, when `.nu.3` and
`.delta..theta.3` are Abbe number for a wavelength of d-line
(wavelength .lambda..sub.d=587.6 nm) and anomalous dispersion of
the positive lens L3 in the third lens group G3, respectively and
`.nu.6` and `.delta..theta.6` are Abbe number for the wavelength of
d-line and anomalous dispersion of the positive lens L6 in the
fourth lens group G4, respectively, preferably the following
conditional expressions (1) and (2) are satisfied. More preferably,
the following conditional expressions (1-1) and (2-1) are satisfied
in the image capture lens 10.
65<.nu.3, 0.015<.delta..theta.3 (1)
65<.nu.6, 0.015<.delta..theta.6 (2)
65<.nu.3, 0.02<.delta..theta.3 (1-1)
65<.nu.6, 0.02<.delta..theta.6 (2-1)
[0052] In the image capture lens 10, when `.phi.3` and `.phi.6` are
the refractive power of the positive lens L3 in the third lens
group G3 and the positive lens L6 in the fourth lens group G4,
respectively and `.phi.T` is the refractive power of the entire
lens system including all lens groups, preferably the following
conditional expression (3) is satisfied.
0.09<(.phi.3*.delta..theta.3+.phi.6*.delta..theta.6)/.phi.T<0.15
(3)
[0053] Prior to the description of the action brought by the
conditional expressions (1) to (3), the anomalous dispersion is set
forth herein below. Generally when a .nu. versus .theta. graph is
drawn taking the Abbe number .nu. as the horizontal-axis and the
relative partial dispersion .theta. as the vertical axis, for
example, it is well known that most of glass materials are
distributed along a predetermined reference line on the graph. As a
glass material is distributed in a position farther from the
predetermined reference line, the glass material has larger
anomalous dispersion.
[0054] For example, glass materials K7 and F2 from Schott are
selected as a reference supposing K7 and F2 are normal optical
glasses, and points of K7 and F2 are plotted on a .nu..sub.d (Abbe
number at the d-line) versus .theta..sub.g,d (relative partial
dispersion at the g-d line) graph, thus a reference line L is
formed. The reference line L is defined by the following expression
(B).
.theta..sub.L=1.365-0.00208*.nu..sub.d (B)
[0055] Relative partial dispersion .theta..sub.g,d of a given glass
material minus .theta..sub.L obtained by the above expression (B)
is equal to a deviation of the relative partial dispersion, i.e., a
value .delta..theta..sub.g,d of anomalous dispersion. In the
embodiment, the anomalous dispersion is defined by the following
expression (A) and this expression is used as a standard for
anomalous dispersion.
.delta..theta..sub.g,d=.theta..sub.g,d-(1.365-0.00208*.nu..sub.d)
(A)
[0056] When n.sub.g, n.sub.d, n.sub.F and n.sub.C represent the
refractive index at g-line, d-line, F-line and C-line,
respectively, the relative partial dispersion
.delta..theta..sub.g,d at g-d-line is defined as
.theta..sub.g,d=(n.sub.g-n.sub.d)/(n.sub.F-n.sub.C).
[0057] The wavelengths of g-line, F-line and C-line are
approximately 435.8 nm, 486.1 nm and 656.3 nm, respectively.
[0058] Next, the conditional expressions (1) to (3) will now be
described. These expressions (1) to (3) provide conditions such
that a glass material with large anomalous dispersion is put to use
for the positive lenses L3 and L6 of the cemented lenses in the
third lens group G3 and the fourth lens group G4 so as to have
moderate refractive power, thus chromatic aberration is preferably
corrected in particular. The conditional expressions (1) and (2)
define conditions such that a glass material having anomalous
dispersion with a deviation in a positive direction relative to the
reference line L expressed by the expression (B) is put to use for
the positive lenses L3 and L6. The refractive power of the positive
lenses L3 and L6 is distributed in balance so as to satisfy the
conditional expressions (1), (2) and (3). Thus, particularly
high-order axial chromatic aberration which occurs on the
magnification side is corrected and further various kinds of
aberrations such as spherical aberration or coma are prevented from
increasing.
[0059] If the lenses exceed the restriction of the conditional
expressions (1) and (2), the refractive power becomes too large and
negative spherical aberration and coma flare increase caused by
correcting high-order axial chromatic aberration which occurs on
the magnification side. Thus, it is difficult to attain high
resolution. If the lenses exceed the lower limit of the conditional
expression (3), the axial chromatic aberration is not sufficiently
corrected. Accordingly, it is difficult to achieve high resolution
with all RGB color. If the lenses exceed the upper limit of the
conditional expression (3), the axial chromatic aberration is
corrected preferably but the radius of curvature of each lens
becomes smaller. Thus, when an attempt to obtain a bright lens is
made, spherical aberration in a negative direction becomes larger
Thus, coma flare and curvature of field occur even off the optical
axis, resulting in failing to obtain preferable performance.
[0060] In the image capture lens 10, when `.nu..sub.3` and
`n.sub.3` denote the Abbe number and refractive index at d-line of
the positive lens L3 in the third lens group G3, respectively;
`.nu..sub.4` and `n.sub.4` denote the Abbe number and refractive
index at d-line of the positive lens L4 in the third lens group G3,
respectively; `.phi..sub.3,4` denotes the refractive power of the
entire cemented lens in the third lens group G3; and
`.phi..sub.5,6` denotes the refractive power of the entire cemented
lens in the fourth lens group G4, preferably the following
conditional expressions (4) and (5) are satisfied.
0.75<(n3*.nu.4)/(n4*.nu.3)<1.10 (4)
-13.0<.phi.T.sup.2/(.phi..sub.3,4*.phi..sub.5,6)<-0.3)
(5)
[0061] The conditional expression (4) provides a condition on
correction of chromatic aberration and curvature of field. By
selecting the glass material of the lenses L3 and L4 so as to
satisfy the condition, obtained is a combination of the lenses L3
and L4 with which chromatic aberration is preferably corrected and
even when the lenses have large refractive power, the curvature of
field is corrected preferably.
[0062] The conditional expression (5) provides a condition for each
of the third lens group G3 and the fourth lens group G4 including
the cemented lens to have positive or negative refractive power
with moderate intensity, respectively. When the glass material of
the lenses L3 and L4 is selected so as to satisfy the conditional
expression (4), the power of the convex lens in the entire third
lens group G3 increases, resulting in increasing negative spherical
aberration. To correct this increased negative spherical
aberration, providing the action of the concave lens as appropriate
to the fourth lens group G4 enables the spherical aberration to be
preferably corrected. If each refractive power of the cemented
lenses in the third lens group G3 and the fourth lens group G4
becomes too large or small exceeding the range of the conditional
expression (5), the balance in correction between a various kinds
of aberrations is lost, thereby increasing spherical aberration
flare or coma flare in a part where field angle is large in
particular.
[0063] The image capture lens 10 of the embodiment constituted as
described above exhibits optical performance such that color images
of an original such as a negative film or positive film are
captured by scaling them up or down crossing over the magnification
of the actual size, for example. Scaling is performed in a manner
that the entire lens system is shifted in accordance with the
magnification, thereby changing object distance or image distance,
for example.
[0064] Generally in the image capture lens, in order to correct
axial chromatic aberration at magnifications close to that of the
actual size, particularly, at larger magnifications, a lens element
is made of a material having high anomalous dispersion and the
refractive power thereof is made large so that the axial chromatic
aberration is greatly corrected. However, when the refractive power
is made large, the radius of curvature of the lens surface becomes
small. When seeking to obtain bright optical performance, various
kinds of aberrations such as spherical aberration, coma flare or
curvature of field occur in the lens surface. Accordingly,
preferable performance over a wide magnification range cannot be
obtained. Therefore, in the image capture lens 10 of the
embodiment, auxiliary lens elements such as the lens L8 with
negative power are added to the Gauss lens system. Thus, with the
use of the lens material having high anomalous dispersion, each
lens has moderate refractive power, so that bright optical
performance in which various aberrations are preferably corrected
over a wide magnification range, e.g., -0.6.times. to -1.6.times.
is obtained.
[0065] As has been described, in the image capture lens 10
according to the embodiment, various kinds of aberrations are
corrected and optical performance suitable for capturing images is
obtained. Further, in the image capture apparatus 1 according to
the embodiment, images suitable for capturing images are obtained
through the image capture lens 10, thus high-quality image
capturing is performed.
EXAMPLE 1-1
[0066] Next, a first example (Example 1-1) of the image capture
lens 10 according to the embodiment will now be described with
reference to FIGS. 3A to 6C.
[0067] FIGS. 3A and 3B are tables of an image capture lens 10-1
using specific values according to Example 1-1. In FIG. 3A, a
surface number Si denotes the sequence of lens surfaces from the
object side. With regard to the refractive index and the Abbe
number, values at d-line (wavelength .lambda.=587.6 nm) are shown.
The `r.sub.i` represents radius of curvature of the `i`th lens
surface from the object side similar to the `r.sub.i` shown in FIG.
2. Similar to the `d.sub.i` as in FIG. 2, the `d.sub.i` represents
surface separation between the `i`th lens surface S.sub.i and the
[i+1]th lens surface S.sub.i+1 from the object side on the optical
axis. The radius of curvature `r.sub.i` and the surface separation
`d.sub.i` are expressed in millimeter (mm).
[0068] FIG. 3B shows values for the object distance and the image
distance at three typical imaging magnification (-0.6.times.,
-1.0.times. and -1.6.times.) of the image capture lens 10-1. The
object distance d0 denotes a distance from an object point to a
first lens surface S1 on the optical axis, while the image distance
d15 denotes a distance from a last lens surface S15 to an image
point on the optical axis.
[0069] FIG. 4 shows values corresponding to the conditional
expressions (1) to (5). With reference to FIG. 3A, in the image
capture lens 10-1 according to Example 1-1, with respect to the
positive lens L3 in the third lens Group G3, the Abbe number
.nu..sub.3 at d-line is 71.3; the relative partial dispersion
.theta..sub.3 is 1.243; and the anomalous dispersion .delta..sub.3
is 0.0263, which satisfies the conditional expression (1). With
respect to the positive lens L6 in the fourth lens group G4, the
Abbe number .nu..sub.6 at d-line is 71.3; the relative partial
dispersion .theta..sub.6 is 1.243; and the anomalous dispersion
.delta..sub.6 is 0.0263, which satisfies the conditional expression
(2).
[0070] In the image capture lens 10-1, the value for
.phi..sub.3*.delta..theta..sub.3+.phi..sub.6*.delta..theta..sub.6
is 0.122, which satisfies the conditional expression (3). The value
for (n.sub.3*.nu..sub.4)/(n.sub.4* .nu..sub.3) is 0.96, which
satisfies the conditional expression (4). The value for
.phi.T.sup.2/(.phi..sub.3,4*.ph- i..sub.5,6) is -0.49, which
satisfies the conditional expression (5).
[0071] FIGS. 5A to 5C are aberration charts of spherical
aberration, astigmatism, distortion and chromatic aberration of
magnification at each magnification in the image capture lens 10-1.
FIGS. 5A, 5B and 5C show aberrations at imaging magnification of
-0.6.times., -1.0.times. and -1.6.times., respectively. FIGS. 5A to
5C also show effective F number (Fno) at each magnification. FIGS.
6A to 6C show coma at each imaging magnification in the image
capture lens 10-1. FIGS. 6A, 6B and 6C show coma at magnification
of -0.6.times., -1.0.times. and -1.6.times., respectively. In these
aberration charts, `H` represents image height and `R`, `G` and `B`
represent red, green and blue, respectively. In these aberration
charts, C-line, d-line and F-line represent R (red), G (green) and
B (blue), respectively. In the aberration charts showing
astigmatism, `S` represents the sagittal image surface and `T`
represents the meridional (tangential) image surface. Coma of green
is shown in the aberration charts of coma.
[0072] As apparent from these aberration charts and values for the
conditions as in FIG. 4, in the image capture lens 10-1 of Example
1-1, various kinds of aberrations are preferably corrected all the
area from the center to peripheries of the image at each
magnification, thereby exhibiting preferable optical performance
suitable for capturing images.
EXAMPLE 1-2
[0073] With reference to FIGS. 7 to 11C, a second example (Example
1-2) of the image capture lens 10 of the embodiment will be
described herein below.
[0074] FIGS. 8A and 8B are tables of an image capture lens 10-2
using specific values according to Example 1-2. FIG. 7 is
illustrated corresponding to the values for elements of the image
capture lens 10-2 as in FIGS. 8A and 8B. Symbols in FIG. 7 and
FIGS. 8A and 8B represent the same as those in FIG. 2 and FIGS. 3A
and 3B.
[0075] FIG. 8B shows values for the object distance and the image
distance at three typical imaging magnification (-0.6.times.,
-1.0.times. and -1.8.times.) of the image capture lens 10-2. The
object distance d0 denotes a distance from an object point to a
first lens surface S1 on the optical axis, while the image distance
d15 denotes a distance from a last lens surface S15 to an image
point on the optical axis.
[0076] FIG. 9 shows values corresponding to the conditional
expressions (1) to (5). With reference to FIG. 8A, in the image
capture lens 10-2 according to Example 1-2, with respect to the
positive lens L3 in the third lens Group G3, the Abbe number
.nu..sub.3 at d-line is 71.3; the relative partial dispersion
.theta..sub.3 is 1.243; and the anomalous dispersion .delta..sub.3
is 0.0263, which satisfies the conditional expression (1). With
respect to the positive lens L6 in the fourth lens group G4, the
Abbe number .nu..sub.6 at d-line is 71.3; the relative partial
dispersion .theta..sub.6 is 1.243; and the anomalous dispersion
.delta..sub.6 is 0.0263, which satisfies the conditional expression
(2).
[0077] In the image capture lens 10-2, the value for
.phi..sub.3*.delta..theta..sub.3+.phi..sub.6*.delta..theta..sub.6
is 0.119, which satisfies the conditional expression (3). The value
for (n.sub.3*.nu..sub.4)/(n.sub.4* .nu..sub.3) is 0.86, which
satisfies the conditional expression (4). The value for
.phi..sub.T.sup.2/(.phi..sub.3,- 4*.phi..sub.5,6) is -5.29, which
satisfies the conditional expression (5).
[0078] FIGS. 10A to 10C are aberration charts of spherical
aberration, astigmatism, distortion and chromatic aberration of
magnification at each imaging magnification in the image capture
lens 10-2. FIGS. 10A, 10B and 10C show aberrations at imaging
magnification of -0.6.times., -1.0.times. and -1.8.times.,
respectively. FIGS. 10A to 10C also show effective F number (Fno)
at each imaging magnification. FIGS. 11A to 11C show coma at each
magnification in the image capture lens 10-2. FIGS. 11A, 11B and
11C show coma at magnification of -0.6.times., -1.0.times. and
-1.8.times., respectively. Symbols in these aberration charts
represent the same as those in FIGS. 5A to 5C and 6A to 6C.
[0079] As apparent from these aberration charts and values for the
conditions as in FIG. 9, in the image capture lens 10-2 of Example
1-2, various kinds of aberrations are preferably corrected all the
area from the center to peripheries of the image at each
magnification, thereby exhibiting preferable optical performance
suitable for capturing images.
EXAMPLE 1-3
[0080] With reference to FIGS. 12 to 16C, a third example (Example
1-3) of the image capture lens 10 of the embodiment will be
described herein below.
[0081] FIGS. 13A and 13B are tables of an image capture lens 10-3
using specific values according to Example 1-3. FIG. 12 is
illustrated corresponding to the values for elements of the image
capture lens 10-3 of the Example 1-3 as in FIGS. 13A and 13B.
Symbols in FIG. 12 and FIGS. 13A and 13B represent the same as
those in FIG. 2 and FIGS. 3A and 3B.
[0082] FIG. 13B shows values for the object distance and the image
distance at three typical imaging magnification (-0.6.times.,
-1.0.times. and -1.6.times.) of the image capture lens 10-3. The
object distance d0 denotes a distance from an object point to a
first lens surface S1 on the optical axis, while the image distance
d15 denotes a distance from a last lens surface S15 to an image
point on the optical axis.
[0083] FIG. 14 shows values corresponding to the conditional
expressions (1) to (5). With reference to FIG. 13A, in the image
capture lens 10-3 according to Example 1-3, with respect to the
positive lens L3 in the third lens group G3, the Abbe number
.nu..sub.3 at d-line is 81.6; the relative partial dispersion
.theta..sub.3 is 1.232; and the anomalous dispersion .delta..sub.3
is 0.0367, which satisfies the conditional expression (1). With
respect to the positive lens L6 in the fourth lens group G4, the
Abbe number .nu..sub.6 at d-line is 71.3; the relative partial
dispersion .theta..sub.6 is 1.234; and the anomalous dispersion
.delta..sub.6 is 0.263, which satisfies the conditional expression
(2).
[0084] In the image capture lens 10-3, the value for
.phi..sub.3*.delta..theta..sub.3+.phi..sub.6*.delta..theta..sub.6
is 0.146, which satisfies the conditional expression (3). The value
for (n.sub.3*.nu..sub.4)/(n.sub.4* .nu..sub.3) is 0.80, which
satisfies the conditional expression (4). The value for
.phi..sub.T.sup.2/(.phi..sub.3,- 4*.phi..sub.5,6,) is -0.51, which
satisfies the conditional expression (5).
[0085] FIGS. 15A to 15C are aberration charts of spherical
aberration, astigmatism, distortion and chromatic aberration of
magnification at each imaging magnification in the image capture
lens 10-3. FIGS. 15A, 15B and 15C show aberrations at imaging
magnification of -0.6.times., -1.0.times. and -1.6.times.,
respectively. FIGS. 15A to 15C also show effective F number (Fno)
at each magnification. FIGS. 16A to 16C show coma at each imaging
magnification in the image capture lens 10-3. FIGS. 16A, 16B and
16C show coma at magnification of -0.6.times., -1.0.times. and
-1.6.times., respectively. Symbols in these aberration charts
represent the same as those in FIGS. 5A to 5C and 6A to 6C.
[0086] As apparent from these aberration charts and values for the
conditions as in FIG. 14, in the image capture lens 10-3 of Example
1-3, various kinds of aberrations are preferably corrected all the
area from the center to peripheries of the image at each
magnification, thereby exhibiting optical performance suitable for
capturing images.
[0087] [Second Embodiment]
[0088] A second embodiment of the present invention will now be
described herein below. The same elements as those of the first
embodiment are indicated by the same reference numerals and the
description is appropriately omitted.
[0089] FIG. 17 is a schematic diagram of the configuration of the
image capture lens 20 according to the second embodiment showing
each lens element in cross section within a single plane including
an optical axis O.
[0090] Similar to the image capture lens 10 of the first
embodiment, the image capture lens 20 of the second embodiment is
applicable to the readout optical system of the image capture
apparatus 1 as in FIG. 1. In the image capture lens 20 successively
from the object side provided are a first lens group G1 including a
negative meniscus lens L1, a second lens group G2 including a
positive lens L2 directing its convex to the object side, a third
lens group G3 including a cemented lens which is composed of a
bi-convex positive lens L3 and a bi-concave negative lens L4, the
cemented lens having positive refractive power with its convex
facing the object side, a fourth lens group G4 including a cemented
lens which is composed of a bi-concave negative lens L5 and a
bi-convex positive lens L6, the cemented lens having positive
refractive power with its convex facing the image side, a fifth
lens group G5 including a positive lens L7 directing its convex to
the image side and a sixth lens group G6 including a negative lens
L8 directing a surface thereof whose radius of curvature is small
to the objective side.
[0091] In addition to these lens groups, the image capture lens 20
further comprises a seventh lens group G7 including a negative
meniscus lens L9 and a positive lens L10. The seventh lens group G7
is provided on the image side relative to the sixth lens group G6.
In the seventh lens group G7, the meniscus lens L9 and the positive
lens L10 constitute a cemented lens directing its convex to the
object side. Alternatively, the meniscus lens L9 and the positive
lens L10 may be constituted having a clearance therebetween.
Further, in the embodiment, the positive lens L10 has a meniscus
shape directing its convex to the object side as in FIG. 17 but may
have a bi-convex shape as shown in Example 2-2 to be described
later.
[0092] In the embodiment, as shown in FIG. 17 the concave of the
negative meniscus lens L1 in the first lens group G1 faces the
object side, for example. The positive lens L2 in the second lens
group L2 has a bi-convex shape, for example. The positive lens L7
in the fifth lens group G5 has a plano-concave shape, for example.
The negative lens L8 in the sixth lens group G6 has a meniscus
shape, directing its concave to the object side. However, shapes of
the lens element are not limited to those illustrated in FIG. 17.
For example, the negative meniscus lens L1 in the first lens group
G1 have not only a shape such that its concave faces the object
side but also the lens L1 have a shape such that its convex faces
the object side as shown in Example 2-2 to be described later. For
example, the negative lens L8 in the sixth lens group G6 takes not
only a meniscus shape but also a bi-concave shape as shown in
Example 2-2 to be described later.
[0093] Similar to the image capture lens 10 of the first
embodiment, preferably the image capture lens 20 of the second
embodiment satisfies the conditional expressions (1) to (3). The
action and effect brought by satisfying the conditional expressions
(1) to (3) are similar to those of the first embodiment.
[0094] When `.nu.9` and `.nu.10` are the Abbe number at d-line of
the negative meniscus lens L9 and the positive lens L10 in the
seventh lens group G7 and `r.sub.16`, `r.sub.17` and `r.sub.18` are
the radius of curvature of lens surfaces of the seventh lens group
G7 from the object side, preferably the image capture lens 20 of
the second embodiment satisfies the following conditional
expressions (6) to (8). `.phi..sub.T` in the conditional expression
(7) represents the refractive power of the entire lens system
including all lens groups.
-0.2<r.sub.16/r.sub.18<1.2 (6)
0.35<.phi..sub.T*r.sub.17<1.2 (7)
13<.nu..sub.9-.nu..sub.10 (8)
[0095] The conditional expression (6) provides a condition for
preferably correcting curvature of field or coma in a part where
field angle is large. In the image capture lens 20, if a radius of
curvature r.sub.16 of a 16th surface becomes large, exceeding the
upper limit of the conditional expression (6), a change of an
incident angle of a light entering the 16th surface relative to a
change of a field angle becomes small, resulting in reducing the
effect of correcting curvature of field. If a radius of curvature
r.sub.18 of an 18th surface becomes small, exceeding the
conditional expression (6), astigmatism or coma flare at
peripheries of a flux becomes large. Therefore, it is difficult to
perform preferable correction of aberrations which is necessary for
obtaining high resolution. If the refractive power of the concave
becomes large in the seventh lens group G7, exceeding the lower
limit of the conditional expression (6), correction to the
curvature of field is difficult.
[0096] The conditional expression (7) defines the condition for
effectively correcting aberration off the optical axis. In the case
where the seventh lens group G7 constitutes the cemented lens, by
defining the radius of curvature r.sub.17 of the cemented surface
within the range of the conditional expression (7), an influence on
correction of the axial aberrations, particularly, spherical
aberration is suppressed as well as aberration off the optical axis
can be corrected.
[0097] The conditional expression (8) defines a condition on the
correction of chromatic aberration of magnification. With respect
to lenses L9 and L10 in the seventh lens group G7, by selecting a
glass material so as to satisfy the conditional expression (8),
obtained is a combination of the Abbe number of the convex lens and
the Abbe number of the concave lens with which excess correction of
chromatic aberration of magnification is achromatized, the excess
correction of chromatic aberration of magnification occurring due
to intensive correction of the axial chromatic aberration in the
third lens group G3 and the fourth lens group G4.
[0098] Similar to the image capture lens 10 according to the first
embodiment, the image capture lens 20 of the second embodiment
constituted as described above exhibits optical performance such
that color images provided by an original such as a negative film
or positive film are captured by scaling them up or down crossing
over the magnification of the actual size, for example. More
specifically, in the image capture lens 20 of the second
embodiment, auxiliary lens elements such as the lens L8 with
negative power are added to the Gauss lens system. Thus, with the
use of the lens material with high anomalous dispersion, each lens
has moderate refractive power, so that bright optical performance
in which various aberrations are preferably corrected over a wide
magnification range, e.g., -0.6.times. to -1.6.times. is obtained.
Scaling is performed in a manner that the entire lens system is
shifted in accordance with the magnification, thereby changing
object distance or image distance, for example.
[0099] As has been described in the image capture lens 20 according
to the embodiment, optical performance suitable for capturing
images is obtained, similar to the image capture lens 10 of the
first embodiment.
EXAMPLE 2-1
[0100] Next, a first example (Example 2-1) of the image capture
lens 20 according to the embodiment will now be described with
reference to FIGS. 18A to 21C.
[0101] FIGS. 18A and 18B are tables of an image capture lens 20-1
using specific values according to Example 2-1. Symbols used in
FIGS. 18A and 18B represent the same as those used in FIGS. 3A and
3B.
[0102] FIG. 18B shows values for the object distance and the image
distance at three typical imaging magnification (-0.6.times.,
-1.0.times. and -1.6.times.) of the image capture lens 20-1. The
object distance d0 denotes a distance from an object point to a
first lens surface S1 on the optical axis, while the image distance
d18 denotes a distance from a last lens surface S18 to an image
point on the optical axis.
[0103] FIG. 19 shows values corresponding to the conditional
expressions (1) to (3) and (6) to (8). With reference to FIG. 18A,
in the image capture lens 20-1 of Example 2-1, with respect to the
positive lens L3 in the third lens group G3, the Abbe number
.nu..sub.3 at d-line is 71.3; the relative partial dispersion
.theta..sub.3 is 1.243; and the anomalous dispersion .delta..sub.3
is 0.0263, which satisfies the conditional expression (1). With
respect to the positive lens L6 in the fourth lens group G4, the
Abbe number .nu..sub.6 at d-line is 71.3; the relative partial
dispersion .theta..sub.6 is 1.243; and the anomalous dispersion
.delta..sub.6 is 0.0263, which satisfies the conditional expression
(2).
[0104] In the image capture lens 20-1, the value for
.phi..sub.3*.delta..theta..sub.3+.phi..sub.6*.delta..theta..sub.6
is 0.124, which satisfies the conditional expression (3). The value
for r.sub.16/r.sub.18 is 1.12, which satisfies the conditional
expression (6). The value for .phi..sub.T*r.sub.17 is 0.45, which
satisfies the conditional expression (7). The value for
.nu..sub.9-.nu..sub.10 is 21.0, which satisfies the conditional
expression (8).
[0105] FIGS. 20A to 20C are aberration charts of spherical
aberration, astigmatism, distortion and chromatic aberration of
magnification at each imaging magnification in the image capture
lens 20-1. FIGS. 21A, 21B and 21C show aberrations at imaging
magnification of -0.6.times., -1.0.times. and -1.6.times.,
respectively. FIGS. 20A to 20C also show effective F number (Fno)
at each magnification. FIGS. 21A to 21C show coma at each imaging
magnification in the image capture lens 20-1. FIGS. 21A, 21B and
21C show coma at magnification of -0.6.times., -1.0.times. and
-1.6.times., respectively. Symbols in these aberration charts
represent the same in FIGS. 5A to 5C and 6A to 6C.
[0106] As apparent from these aberration charts and values for the
conditions as in FIG. 19, in the image capture lens 20-1 of Example
2-1, various kinds of aberrations are preferably corrected all the
area from the center to peripheries of the image at each
magnification, thereby exhibiting preferable optical performance
suitable for capturing images.
EXAMPLE 2-2
[0107] With reference to FIGS. 22 to 26C, a second example (Example
2-2) of the image capture lens 20 of the embodiment will be
described herein below.
[0108] FIGS. 23A and 23B are tables of an image capture lens 20-2
using specific values according to Example 2-2. FIG. 22 is
illustrated corresponding to the values for elements of the image
capture lens 20-2 as in FIGS. 23A and 23B. Symbols in FIG. 22 and
FIGS. 23A and 23B represent the same as those in FIG. 2 and FIGS.
3A and 3B.
[0109] FIG. 23B shows values for the object distance and the image
distance at three typical imaging magnification (-0.6.times.,
-1.0.times. and -1.6.times.) of the image capture lens 20-2. The
object distance d.sub.0 denotes a distance from an object point to
a first lens surface S1 on the optical axis, while the image
distance d.sub.18 denotes a distance from a last lens surface S18
to an image point on the optical axis.
[0110] FIG. 24 shows values corresponding to the conditional
expressions (1) to (3) and (6) to (8). With reference to FIG. 23A,
in the image capture lens 20-2 of Example 2-2, with respect to the
positive lens L3 in the third lens group G3, the Abbe number
.nu..sub.3 at d-line is 71.3; the relative partial dispersion
.theta..sub.3 is 1.243; and the anomalous dispersion .delta..sub.3
is 0.0263, which satisfies the conditional expression (1). With
respect to the positive lens L6 in the fourth lens group G4, the
Abbe number .nu..sub.6 at d-line is 71.3; the relative partial
dispersion .theta..sub.6 is 1.243; and the anomalous dispersion
.delta..sub.6 is 0.0263, which satisfies the conditional expression
(2).
[0111] In the image capture lens 20-2, the value for
.phi..sub.3*.delta..theta..sub.3+.phi..sub.6*.delta..theta..sub.6
is 0.135, which satisfies the conditional expression (3). The value
for r.sub.16/r.sub.18 is -0.10, which satisfies the conditional
expression (6). The value for .phi..sub.T*r.sub.17 is 1.09, which
satisfies the conditional expression (7). The value for
.nu..sub.9-.nu..sub.10 is 13.8, which satisfies the conditional
expression (8).
[0112] FIGS. 25A to 25C are aberration charts of spherical
aberration, astigmatism, distortion and chromatic aberration of
magnification at each imaging magnification in the image capture
lens 20-2. FIGS. 25A, 25B and 25C show aberrations at magnification
of -0.6.times., -1.0.times. and -1.6.times., respectively. FIGS.
25A to 25C also show effective F number (Fno) at each
magnification. FIGS. 26A to 26C show coma at each imaging
magnification in the image capture lens 20-2. FIGS. 26A, 26B and
26C show coma at magnification of -0.6.times., -1.0.times. and
-1.6.times., respectively. Symbols in these aberration charts
represent the same as those in FIGS. 5A to 5C and 6A to 6C.
[0113] As apparent from these aberration charts and values for the
conditions as in FIG. 24, in the image capture lens 20-2 of Example
2-2, various kinds of aberrations are preferably corrected all the
area from the center to peripheries of the image at each
magnification, thereby exhibiting preferable optical performance
suitable for capturing images.
[0114] The present invention is not limited to the above
embodiments and various modifications are possible. For example,
values of each lens element such as the radius of curvature r, the
surface separation d, the refractive index n and the Abbe number
.nu. are not limited to the values shown in the above examples and
may take other values.
[0115] According to the image capture lens of the invention,
successively from an object side provided are a first lens group
including a negative meniscus lens; a second lens group including a
positive lens directing its convex to the object side; a third lens
group including a first cemented lens composed of a bi-convex
positive lens and a bi-concave negative lens, the first cemented
lens having positive refractive power and directing its convex to
the object side; a fourth lens group including a second cemented
lens composed of a bi-concave negative lens and a bi-convex
positive lens, the second cemented lens having negative refractive
power and directing its convex to an image side; a fifth lens group
including a positive lens directing its convex to the image side;
and a sixth lens group including a negative lens directing its
concave to the object side. Thus, various kinds of aberrations are
corrected and optical performance suitable for capturing images is
obtained.
[0116] According to the image capture lens of another aspect of the
invention, successively from an object side provided are a first
lens group including a negative meniscus lens; a second lens group
including a positive lens directing its convex to the object side;
a third lens group including a first cemented lens composed of a
bi-convex positive lens and a bi-concave negative lens, the first
cemented lens having positive refractive power and directing its
convex to an image side; a fourth lens group including a second
cemented lens composed of a bi-concave negative lens and a
bi-convex positive lens, the second cemented lens directing its
convex to the image side; a fifth lens group including a positive
lens directing its convex to the image side; a sixth lens group
including a negative lens directing a surface thereof to the object
side, a radius of the surface being smaller than that of an
opposite surface; and a seventh lens group including a negative
meniscus lens and a positive lens. Thus, various kinds of
aberrations are corrected and high-quality images are read.
[0117] According to the image capture lens of still another aspect
of the invention,
0.09<(.phi..sub.3*.delta..theta..sub.3+.phi..sub.6*.delta..-
theta..sub.6)/.phi..sub.T<0.15 is satisfied when the .phi..sub.3
and the .delta..theta..sub.3 represent refractive power and
anomalous dispersion of the positive lens in the third lens group,
respectively, the .phi..sub.6 and the .delta..theta..sub.6
represent refractive power and anomalous dispersion of the positive
lens in the fourth lens group, respectively, and the .phi..sub.T
represents refractive power of an entire lens system including all
the lens groups, for example. Thus, the third lens group and the
fourth lens group have moderate refractive power with the use of a
lens material having large anomalous dispersion. Accordingly,
chromatic aberration is preferably corrected in particular.
[0118] According to the image capture apparatus of the invention,
in the image capture lens successively from an object side provided
are a first lens group including a negative meniscus lens; a second
lens group including a positive lens directing its convex to the
object side; a third lens group including a first cemented lens
composed of a bi-convex positive lens and a bi-concave negative
lens, the first cemented lens having positive refractive power and
directing its convex to an image side; a fourth lens group
including a second cemented lens composed of a bi-concave negative
lens and a bi-convex positive lens, the second cemented lens having
negative refractive power and directing its convex to the image
side; a fifth lens group including a positive lens directing its
convex to the image side; and a sixth lens group including a
negative lens directing its concave to the object side. Thus, in
the image capture lens, various kinds of aberrations are corrected.
Accordingly, optical performance suitable for capturing images is
obtained and high-quality image capturing is possible.
[0119] According to the image capture lens of yet another aspect of
the invention, successively from an object side provided are a
first lens group including a negative meniscus lens; a second lens
group including a positive lens directing its convex to the object
side; a third lens group including a first cemented lens composed
of a bi-convex positive lens and a bi-concave negative lens, the
first cemented lens having positive refractive power and directing
its convex to the object side; a fourth lens group including a
second cemented lens composed of a bi-concave negative lens and a
bi-convex positive lens, the second cemented lens directing its
convex to an image side; a fifth lens group including a positive
lens directing its convex to the image side; a sixth lens group
including a negative lens directing a surface thereof to the object
side, a radius of the surface being smaller than that of an
opposite surface; and a seventh lens group including a negative
meniscus lens and a positive lens. In the image capture lens,
various kinds of aberrations are corrected. Thus, optical
performance suitable for capturing images is obtained and
high-quality image capturing is possible.
[0120] Obviously many modifications and variations of the present
invention are possible in the light of the above teachings. It is
therefore to be understood that within the scope of the appended
claims the invention may be practiced otherwise than as
specifically described.
* * * * *