Optical: systems and elements – Lens – Multiple component lenses
Reexamination Certificate
1999-03-02
2001-09-25
Schwartz, Jordan M. (Department: 2873)
Optical: systems and elements
Lens
Multiple component lenses
C359S788000
Reexamination Certificate
active
06295169
ABSTRACT:
RELATED APPLICATIONS
This application claims the priority of Japanese Patent Application No. 10-74990 filed on Mar. 9, 1998, which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image readout lens used in an optical system of an image readout apparatus such as facsimile machine or image scanner, for example; and an image readout apparatus using the same. In particular, the present invention relates to a color-image readout lens used for reducing or enlarging an image and an image readout apparatus using the same.
2. Description of the Prior Art
Image readout lenses used in facsimile machines, image scanners, and the like of a type forming a reduced or enlarged image of an original are basically required to have a high resolution, large marginal light quantity, and minimized distortion at the imaging magnification used.
Known as an imaging lens which satisfies these requirements and reduces the weight and cost of the lens system and accordingly the weight and cost of the optical apparatus as a whole is, for example, that disclosed in commonly assigned Japanese Unexamined Patent Publication No. 7-104185, in which the number of lens elements is reduced to 4.
Though the above-mentioned four-element imaging lens disclosed in Japanese Unexamined Patent Publication No. 7-104185 favorably corrects both image surface curvature and distortion, its correction of chromatic aberration may be insufficient as a color-image readout lens.
SUMMARY OF THE INVENTION
In view of such circumstances, it is an object of the present invention to provide an image readout lens which can favorably correct chromatic aberration in particular, form high-quality images, and favorably be used for reading out color images, by defining the lens glass material together with the lens form and configuration.
It is another object of the present invention to provide an image readout apparatus using this image readout lens.
The image readout lens in accordance with the present invention comprises, successively from an object side, a first lens made of a positive meniscus lens which is convex toward the object, second and third lenses each having a surface on an image side concave toward the image and a negative refracting power, and a fourth lens made of a biconvex lens, wherein a lens glass material of at least one of the second and third lenses satisfies the following conditional expression (1):
&thgr;
g·F
+0.0019&ugr;
d
<0.650 (1)
where
&thgr;
g·F
is the relative partial dispersion of the lens glass material defined by &thgr;
g·F
=(N
g
−N
F
)/(N
F
−N
C
); and
&ugr;
d
is the Abbe number of the lens glass material defined by &ugr;
d
=(N
d
−1)/(N
F
−N
C
)
where
N
g
is the refractive index of the glass material at a wavelength of 435.8 nm;
N
F
is the refractive index of the glass material at a wavelength of 486.1 nm;
N
C
is the refractive index of the glass material at a wavelength of 656.3 nm; and
N
d
is the refractive index of the glass material at a wavelength of 587.6 nm.
Preferably, the image readout lens in accordance with the present invention further satisfies the following conditional expression (2):
0.35<f
1
/f<0.58 (2)
where
f is the composite focal length of the whole lens system; and
f
1
is the focal length of the first lens.
Preferably, the image readout lens in accordance with the present invention further satisfies the following conditional expression (3):
−0.66<f
3
/f<−0.40 (3)
where
f is the composite focal length of the whole lens system; and
f
3
is the focal length of the third lens.
Preferably, the image readout lens in accordance with the present invention further satisfies the following conditional expression (4):
−0.79<f
23
/f
4
<−0.51 (4)
where
f
23
is the composite focal length of the second and third lenses; and
f
4
is the focal length of the fourth lens.
Preferably, the image readout lens in accordance with the present invention further satisfies all of the above-mentioned conditional expressions (1) to (4).
The image readout apparatus in accordance with the present invention uses the above-mentioned image readout lens.
While the image readout lens in accordance with the present invention can be used as an image reducing lens when the first to fourth lenses are successively disposed in this order from the object side as mentioned above, it can be used as an image enlarging lens when the whole lens system is reversed as it is such that the first to fourth lenses are disposed in this order from the imaging surface side.
REFERENCES:
patent: 5216548 (1993-06-01), Kung
patent: 5311364 (1994-05-01), Kanoshima et al.
patent: 5493449 (1996-02-01), Yamakawa
patent: 5768021 (1998-06-01), Ori
patent: 07104185 (1995-04-01), None
Fuji Photo Optical Co., Ltd.
Schwartz Jordan M.
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-2463242