Imaging lens

Abstract

An imaging lens includes a first lens having positive refractive power; a second lens; a third lens; a fourth lens; and a fifth lens having negative refractive power, arranged in this order from an object side to an image plane side. The first lens is formed in a shape so that an object side surface thereof has a positive curvature radius. The second lens is formed in a shape so that an object side surface thereof and an image plane side surface thereof have positive curvature radii. The first lens, the third lens, and the second lens have specific Abbe's numbers. The third lens has a specific focal length so that a specific conditional expression is satisfied. The second lens, the third lens, and the fourth lens are arranged so that a specific conditional expression is satisfied.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This is a continuation application of a reissue application Ser. No. 14 / 824,208, filed on Aug. 12, 2015, pending, of U.S. Pat. No. 8,879,167, issued on Nov. 4, 2014.BACKGROUND OF THE INVENTION AND RELATED ART STATEMENT[0002]The present invention relates to an imaging lens for forming an optical image on an imaging element such as a CCD sensor and a CMOS sensor. Particularly, the present invention relates to an imaging lens suitable for mounting in a relatively small camera such as a cellular phone, a digital still camera, a portable information terminal, a security camera, an onboard camera, and a network camera.[0003]Performances of a camera mounted in a cellular phone have been improved every year, and there is even a camera having optical performances comparable to those of a digital still camera. The resolution of an imaging element that used to be several hundred thousand pixels has been improved to several megapixels, and the resolu...

AI Technical Summary

Benefits of technology

The technical effect of this patent text is to describe an imaging lens with a unique configuration that allows for smaller size and improved aberration correction. The lens has a specific shape and refractive power distribution that reduces complicated aberrations and increases the stability of the lens. Additionally, the lens has a small maximum emitting angle, which results in a smaller size of the imaging device while maintaining satisfactory image-forming performance. Overall, this patent provides a technical solution for miniaturizing imaging lenses while improving their aberration correction.

Problems solved by technology

However, optical performances required for such a high-resolution imaging element have been increased each year, so that it is difficult to sufficiently correct aberrations anymore.

Further, it is difficult to meet those optical performance requirements with such a two- or three-lens configuration.

In addition, there are limitations in a lower limit of Abbe's number of the first lens and an upper limit of Abbe's number of the second and the fourth lenses.

However, since the total length of the lens system is long, it is difficult to attain both miniaturization of the imaging lens and satisfactory aberration correction.

Here, such challenge of attaining both miniaturization and satisfactory aberration correction is not specific to the imaging lens for mounting in a cellular phone, but common among imaging lenses for mounting in relatively small cameras such as digital still cameras, portable information terminals, security cameras, onboard cameras, and network cameras.

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