Imaging lens

Details Imaging lens Imaging lens

2002-11-08

2003-10-28

Nguyen, Thong (Department: 2872)

Optical: systems and elements

Lens

Multiple component lenses

C359S656000, C359S661000, C359S645000

Reexamination Certificate

active

06639738

ABSTRACT:

RELATED APPLICATIONS
This application claims the priority of Japanese Patent Application No. 9-147156 filed on May 21, 1997, which is incorporated herein by reference. This application is a Continuation of application Ser. No. 09/048,287, filed on Mar. 26, 1998, now abandoned.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an imaging lens and, in particular, to an imaging lens suitable as a taking lens for a video camera, still video camera, or the like used for TV phone, door phone, monitoring purposes, and so forth.
2. Description of the Prior Art
Recently, solid-state imaging devices have often been disposed on imaging surfaces of various kinds of video cameras and still video cameras. With the advance of technology, such solid-state imaging devices have been reducing their size year by year, while requiring imaging lenses with smaller size and wider angle of view.
Also, there is a strong demand for high brightness and low cost.
Known as such an imaging lens is the one made of two sheets of lenses disclosed in a commonly-assigned application (Japanese Patent Application No. 9-25900).
In the case where there is a demand for further improving resolution, it is desirable that three sheets of lenses be used instead of two.
When such an imaging lens is made of three sheets of lenses, however, due to the increase in the number of lens sheets, it becomes difficult to achieve the aimed object of lowering cost.
SUMMARY OF THE INVENTION
In view of these circumstances, it is an object of the present invention to provide a small-size, bright imaging lens having a wide angle of view, which can restrain the manufacturing cost from increasing while being constituted by three sheets of lenses.
The imaging lens in accordance with the present invention comprises, successively from an object side, a negative power lens, a first biconvex lens, and a second biconvex lens, in which the first and second biconvex lenses have forms substantially similar to each other while each having at least one aspheric surface.
Preferably, the first and second biconvex lenses are made of a plastic material.


REFERENCES:
patent: 3893752 (1975-07-01), Tojyo
patent: 4623224 (1986-11-01), Clarke
patent: 5202795 (1993-04-01), Kashima
patent: 4-56814 (1992-02-01), None
patent: 4-270309 (1992-09-01), None
patent: 10-206730 (1998-08-01), None
patent: 63-318514 (1998-12-01), None
Heavens, O.S. et al, Insight into Optics, 1stedition, 1991, pp. 211-213.*
Born, Max et al, Principles of Optics, 6th(corrected) edition, 1980, pp. 235, 239, 242-243.

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