Optical: systems and elements – Lens – Multiple component lenses
Reexamination Certificate
2000-02-22
2001-11-20
Lester, Evelyn A (Department: 2873)
Optical: systems and elements
Lens
Multiple component lenses
Reexamination Certificate
active
06320704
ABSTRACT:
RELATED APPLICATIONS
This application claims the priority of Japanese Patent Application No. 11-056567 filed on Mar. 4, 1999, which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image readout apparatus such as facsimile machine, image scanner, or the like; and an imaging lens for image readout mounted with an optical system thereof. In particular, the present invention relates to a five-group, six-element imaging lens in which first and second lenses are cemented to each other.
2. Description of the Prior Art
Conventionally, a solid-state image sensor made of CCD has been used in general as a photosensitive member disposed in an imaging section of an image readout apparatus such as facsimile machine, scanner, or the like. Recently, as the pixel density in CCD has rapidly been increasing, imaging lenses with a higher resolution have been demanded as those employed in the image readout apparatus.
As an imaging lens which can respond to such a demand, a six-element image readout apparatus disclosed in Japanese Unexamined Patent Publication No. 10-253881 has been known.
In the prior art disclosed in the above-mentioned publication, however, a greater depth is hard to obtain as the resolution of the imaging lens becomes higher, whereby a higher degree of focus adjustment is required in the image readout apparatus.
Also, there has been a fear of the resolution deteriorating due to fluctuations in flatness of an original or due to the flotation thereof.
SUMMARY OF THE INVENTION
In view of such circumstances, it is an object of the present invention to provide a six-element imaging lens which can reduce curvature of field and enhance the depth, thereby alleviating the burden of focus adjustment in an image readout apparatus, and can lower the deterioration in resolution due to fluctuations in flatness of the original or due to the flotation thereof.
It is another object of the present invention to provide an image readout apparatus using such an imaging lens.
In one aspect, the imaging lens in accordance with the present invention comprises, successively from an object side, a positive first lens having a convex surface directed onto the object side, a negative second lens having a concave surface directed onto an image side, a third lens made of a positive meniscus lens having a convex surface directed onto the object side, a fourth lens made of a positive meniscus lens having a convex surface directed onto the image side, a negative fifth lens having a concave surface directed onto the object side, and a positive sixth lens having a convex surface directed onto the image side, the first and second lenses being cemented to each other, the imaging lens satisfying the following conditional expressions (1) to (3):
0.51
<f
34
/f<
0.72 (1)
0.83
<f
1
/f
6
<1.17 (2)
1.17<(
v
1
×v
3
)
½
/v
2
<1.62 (3)
where
f is the focal length of the whole system;
f
34
is the composite focal length of the third and fourth lenses;
f
1
is the focal length of the first lens;
f
6
is the focal length of the sixth lens;
v
1
is the Abbe number of a material of the first lens;
v
2
is the Abbe number of a material of the second lens; and
v
3
is the Abbe number of a material of the third lens.
In another aspect, the imaging lens in accordance with the present invention comprises, successively from an object side, a positive first lens having a convex surface directed onto the object side, a negative second lens having a concave surface directed onto an image side, a third lens made of a positive meniscus lens having a convex surface directed onto the object side, a fourth lens made of a positive meniscus lens having a convex surface directed onto the image side, a negative fifth lens having a concave surface directed onto the object side, and a positive sixth lens having a convex surface directed onto the image side, the first and second lenses being cemented to each other, the second and fifth lenses satisfying the following conditional expression (4):
&thgr;
g,F
+0.0019
v
d
<0.650 (4)
where
&thgr;
g,F
is a partial dispersion ratio of a lens material expressed by:
&thgr;
g,F
=(
N
g
−N
F
)/(
N
F
−N
C
)
v
d
is an Abbe number of the lens material expressed by:
v
d
=(
N
d
−1)/(
N
F
−N
C
)
where
N
g
is the refractive index of the lens material at a wavelength of 435.8 nm;
N
F
is the refractive index of the lens material at a wavelength of 486.1 nm;
N
C
is the refractive index of the lens material at a wavelength of 656.3 nm; and
N
d
is the refractive index of the lens material at a wavelength of 587.6 nm.
In still another aspect, the imaging lens in accordance with the present invention comprises, successively from an object side, a positive first lens having a convex surface directed onto the object side, a negative second lens having a concave surface directed onto an image side, a third lens made of a positive meniscus lens having a convex surface directed onto the object side, a fourth lens made of a positive meniscus lens having a convex surface directed onto the image side, a negative fifth lens having a concave surface directed onto the object side, and a positive sixth lens having a convex surface directed onto the image side, the first and second lenses being cemented to each other, the first and sixth lenses satisfying the following conditional expression (5):
N
d
+0.015
v
d
>2.58 (5)
where
N
d
is the refractive index of a lens material at d-line; and
v
d
is the Abbe number of the lens material.
The imaging lens in accordance with the present invention satisfying the above-mentioned conditional expressions (1) to (3) may be configured so as to satisfy at least one of the above-mentioned conditional expression (4) concerning the second and fifth lenses and the above-mentioned conditional expression (5) concerning the first and sixth lenses.
Also, the above-mentioned imaging lens may be configured so as to satisfy the following conditional expression (6):
&phgr;
6
≦&phgr;
5
≦&phgr;
4
≦&phgr;
3
≦&phgr;
12
or &phgr;
12
≦&phgr;
3
≦&phgr;
4
≦&phgr;
5
≦&phgr;
6
(6)
where
&phgr;
12
is the larger outside diameter in any of the first and second lenses;
&phgr;
3
is the outside diameter of the third lens;
&phgr;
4
is the outside diameter of the fourth lens;
&phgr;
5
is the outside diameter of the fifth lens; and
&phgr;
6
is the outside diameter of the sixth lens.
Further, the above-mentioned imaging lens may be configured so as to satisfy the following conditional expression (7):
0.05≦|&bgr;|≦0.7 (7)
where
&bgr; is the magnification of the whole system.
The image readout apparatus of the present invention is characterized in that it uses any of the above-mentioned imaging lenses.
REFERENCES:
patent: 3088371 (1963-05-01), Lowenthal
patent: 3302991 (1967-02-01), Bechtold
patent: 3439976 (1969-04-01), Lynch
patent: 3592531 (1971-07-01), McCroble
patent: 3871749 (1975-03-01), Harada
patent: 4319819 (1982-03-01), Mori
patent: 6028720 (2000-02-01), Wartmann et al.
Japanes Patent Office,Patent Abstracts of Japan, Publication No. 10253881 A, Date of Publication: Sep. 25, 1998.
Noda Takayuki
Otomo Ryoko
Yamakawa Hiromitsu
Fuji Photo Optical Co., Ltd.
Lester Evelyn A
Snider Ronald R.
Snider & Associates
LandOfFree
Image readout lens and image readout apparatus using the same does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Image readout lens and image readout apparatus using the same, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Image readout lens and image readout apparatus using the same will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2617908