Imaging lens

Abstract

An imaging lens is provided and has, in order from the object side, a first lens of a positive lens having a convex surface on the object side thereof; a second lens in a meniscus shape having a concave surface on an image side thereof; a third lens in a meniscus shape having a convex surface on the image side thereof; and a fourth lens of a positive or negative lens, both surfaces of the fourth lens being aspheric and the fourth lens having a concave surface on the image side and in a vicinity of an optical axis of the fourth lens. The Abbe numbers of the first and second lenses as well as the focal distances of the first to fourth lenses satisfies specific conditions.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

The features of the invention will appear more fully upon consideration of the exemplary embodiment of the invention, which are schematically set forth in the drawings, in which:

FIG. 1 is a section view of an imaging lens according to Example 1 of the invention;

FIG. 2 is a section view of an imaging lens according to Example 2 of the invention;

FIG. 3 is a section view of an imaging lens according to Example 3 of the invention;

FIG. 4 is a section view of an imaging lens according to Example 4 of the invention;

FIG. 5 shows lens data on the imaging lens according to Example 1 of the invention;

and, specifically, (A) shows basic lens data and (B) shows lens data on the aspheric surface;

FIG. 6 shows lens data on the imaging lens according to Example 2 of the invention;

and, specifically, (A) shows basic lens data and (B) shows lens data on the aspheric surface;

FIG. 7 shows lens data on the imaging lens according to Example 3 of the invention; and, specifically, (A) shows basic lens data and (B) shows lens data on the aspheric surface;

FIG. 8 shows lens data on the imaging lens according to Example 4 of the invention; and, specifically, (A) shows basic lens data and (B) shows lens data on the aspheric surface;

FIG. 9 shows values relating to the formulae in the respective Examples;

FIG. 10 shows an aberration view of the respective aberrations of the imaging lens according to Example 1 of the invention; and, specifically, (A) shows spherical aberrations, (B) shows astigmatisms and (C) shows distortions.

FIG. 11 shows an aberration view of the respective aberrations of the imaging lens according to Example 2 of the invention; and, specifically, (A) shows spherical aberrations, (B) shows astigmatisms and (C) shows distortions.

FIG. 12 shows an aberration view of the respective aberrations of the imaging lens according to Example 3 of the invention; and, specifically, (A) shows spherical aberrations, (B) shows astigmatisms and (C) shows distortions.

FIG. 13 shows an aberration view of the respective aberrations of the imaging lens according to Example 4 of the invention; and, specifically, (A) shows spherical aberrations, (B) shows astigmatisms and (C) shows distortions.

Claims

1. An imaging lens comprising: in order from an object side of the imaging lens, a first lens of a positive lens having a convex surface on the object side thereof;a second lens of a negative lens in a meniscus shape having a concave surface on an image side thereof;a third lens of a positive lens in a meniscus shape having a convex surface on the image side thereof; anda fourth lens of a positive or negative lens, wherein both surfaces of the fourth lens are aspheric and the fourth lens has a concave surface on the image side in a vicinity of an optical axis of the fourth lens,wherein the imaging lens satisfies formulae (1) to (4): vd 1>50   (1)vd 2>30   (2)|f2/f1|>1   (3)0.5<|f3/f4|<1.5   (4)

2. The imaging lens according to claim 1, further comprising an aperture stop disposed nearer to an object than an image-side surface of the first lens.

3. The imaging lens according to claim 1, further comprising an aperture stop disposed between the first and second lenses.

4. The imaging lens according to claim 1, wherein the fourth lens has an image-side surface that is concave in the vicinity of the optical axis and convex at the periphery of the fourth lens.

5. The imaging lens according to claim 2, wherein the fourth lens has an image-side surface that is concave in the vicinity of the optical axis and convex at the periphery of the fourth lens.

6. The imaging lens according to claim 3, wherein the fourth lens has an image-side surface that is concave in the vicinity of the optical axis and convex at the periphery of the fourth lens.