Imaging lens

Details Imaging lens Imaging lens

1999-09-28

2001-04-24

Sugarman, Scott J. (Department: 2873)

Optical: systems and elements

Lens

Multiple component lenses

C359S714000, C359S753000, C359S763000

Reexamination Certificate

active

06222685

ABSTRACT:

RELATED APPLICATIONS
This application claims the priority of Japanese Patent Application No. 10-276318 filed on Sep. 30, 1998, which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates, in particular, to an imaging lens employed in an image pickup instrument such as a compact electronic still camera or the like. More specifically, the present invention relates to an imaging lens which can also match an imaging device having a large number of pixels such as CCD.
2. Description of the Prior Art
In recent years, electronic still cameras with which pictures are easier to take and view than with conventional cameras using silver halide films have rapidly been coming into widespread use.
There have been strong demands for imaging lenses used in this kind of electronic still cameras to be of a high resolution, high performances, a small size, and a low cost. In addition, in the electronic still camera using a CCD imaging device, the imaging lens is required to be telecentric.
As an imaging lens satisfying such a requirement, a two-group, five-element configuration disclosed in Japanese Unexamined Patent Publication No. 10-20188 has been known.
Meanwhile, the recent development of CCD imaging devices is so remarkable that those having 1.5 million pixels have lately come into practice use. Hence, it has been demanded that such a CCD imaging device having a large number of pixels should be mounted to an electronic still camera, so as to yield images with a higher resolution.
When the prior art disclosed in the above-mentioned publication is employed in an instrument with a CCD having such a large number of pixels, its chromatic aberration in magnification would increase in particular, so that inconsistencies in color may occur on a reproduced picture.
SUMMARY OF THE INVENTION
In order to solve such a problem, it is an object of the present invention to provide an imaging lens having a high resolution and a relatively far exit pupil, satisfying demands for a smaller size and a lower cost, and being capable of allowing various kinds of aberration, such as chromatic aberration in magnification in particular, to become favorable even when employed in an instrument with a CCD imaging device having a large number of pixels.
The imaging lens in accordance with the present invention comprises, successively from an object side,
a front group comprising, successively from the object side, a first lens of a meniscus form having a negative refracting power and at least one aspheric surface, a convex surface thereof being directed onto the object side, and a second lens having a positive refracting power and a surface with a greater curvature directed onto the a object side; and
a rear group comprising one lens having a negative refracting power and two lenses each having a positive refracting power;
the imaging lens satisfying the following conditional expression (1):
1.0<
d/f<
2.0  (1)
where
d is the distance from the object-side surface of the first lens to the image-side surface of the second lens; and
f is the focal length of the whole lens system.
Also, the imaging lens preferably satisfies at least one of the following conditional expressions (2) and (3):
n
A
>1.76  (2)
&ngr;
A
>45.0  (3)
where n
A
and &ngr;
A
are average values of refractive index and Abbe number, respectively, in the two lenses each having a positive refracting power.
The object-side surface of the first lens may be made aspheric. Also, both surfaces of the first lens may be made aspheric.


REFERENCES:
patent: 5706141 (1998-01-01), Abe
patent: 6057971 (2000-06-01), Mihara
patent: 09166748 (1997-06-01), None
patent: 10020188 (1998-01-01), None

Affiliated with

Also associated with

Rating

Imaging lens does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Imaging lens, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Imaging lens will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2537552