Imaging lens

Abstract

It is to provide an imaging lens that can maintain telecentricity, sufficiently correct various aberrations, and acquire an excellent resolution, while being small and light. The imaging lens comprises, in order from an object side towards an image surface side, a first lens which is a biconvex lens, a diaphragm, a second lens which is a meniscus lens having a negative power whose convex surface faces the image surface side, and a third lens which is a meniscus lens having a positive power whose convex surface faces the object side, wherein conditions expressed by each of following expressions are to be satisfied: 0.7≦f1/fl≦1, −6≦f2/fl≦−2.8, and 3

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram for showing an embodiment of the imaging lens according to the present invention;

FIG. 2 is a schematic diagram for showing FIRST EXAMPLE of the imaging lens according to the present invention;

FIG. 3 shows graphs for describing the spherical aberration, astigmatism, and distortion of the imaging lens shown in FIG. 2;

FIG. 4 is a schematic diagram for showing SECOND EXAMPLE of the imaging lens according to the present invention;

FIG. 5 shows graphs for describing the spherical aberration, astigmatism, and distortion of the imaging lens shown in FIG. 4;

FIG. 6 is a schematic diagram for showing THIRD EXAMPLE of the imaging lens according to the present invention;

FIG. 7 shows graphs for describing the spherical aberration, astigmatism, and distortion of the imaging lens shown in FIG. 6;

FIG. 8 is a schematic diagram for showing FOURTH EXAMPLE of the imaging lens according to the present invention;

FIG. 9 shows graphs for describing the spherical aberration, astigmatism, and distortion of the imaging lens shown in FIG. 8;

FIG. 10 is a schematic diagram for showing FIFTH EXAMPLE of the imaging lens according to the present invention;

FIG. 11 shows graphs for describing the spherical aberration, astigmatism, and distortion of the imaging lens shown in FIG. 10;

FIG. 12 is a schematic diagram for showing SIXTH EXAMPLE of the imaging lens according to the present invention;

FIG. 13 shows graphs for describing the spherical aberration, astigmatism, and distortion of the imaging lens shown in FIG. 12;

FIG. 14 is a schematic diagram for showing SEVENTH EXAMPLE of the imaging lens according to the present invention;

FIG. 15 shows graphs for describing the spherical aberration, astigmatism, and distortion of the imaging lens shown in FIG. 14;

FIG. 16 is a schematic diagram for showing EIGHTH EXAMPLE of the imaging lens according to the present invention;

FIG. 17 shows graphs for describing the spherical aberration, astigmatism, and distortion of the imaging lens shown in FIG. 16;

FIG. 18 is a schematic diagram for showing NINTH EXAMPLE of the imaging lens according to the present invention;

FIG. 19 shows graphs for describing the spherical aberration, astigmatism, and distortion of the imaging lens shown in FIG. 18;

FIG. 20 is a schematic diagram for showing TENTH EXAMPLE of the imaging lens according to the present invention;

FIG. 21 shows graphs for describing the spherical aberration, astigmatism, and distortion of the imaging lens shown in FIG. 20;

FIG. 22 is a schematic diagram for showing ELEVENTH EXAMPLE of the imaging lens according to the present invention;

FIG. 23 shows graphs for describing the spherical aberration, astigmatism, and distortion of the imaging lens shown in FIG. 22;

FIG. 24 is a schematic diagram for showing TWELFTH EXAMPLE of the imaging lens according to the present invention;

FIG. 25 shows graphs for describing the spherical aberration, astigmatism, and distortion of the imaging lens shown in FIG. 24.

Claims

1. An imaging lens, comprising: in order from an object side towards an image surface side, a first lens which is a biconvex lens, a diaphragm, a second lens which is a meniscus lens having a negative power whose convex surface faces the image surface side, and a third lens which is a meniscus lens having a positive power whose convex surface faces the object side, wherein conditions expressed by each of following expressions (1) to (3) are to be satisfied: 0.7≦f1/fl≦1   (1)−6≦f2/fl≦−2.8 (2)3≦f3/fl≦10   (3)

2. The imaging lens according to claim 1, wherein: a condition expressed by a following expression (4) is to be further satisfied: −0.3≦r1/r2≦0   (4)

3. The imaging lens according to claim 1, wherein: a condition expressed by a following expression (5) is to be further satisfied: 0.7≦r5/fl≦1.2   (5)

4. The imaging lens according to any one of claim 1, wherein: conditions expressed by each of following expressions (6) to (8) are to be further satisfied: v1≧50   (6)v2≦40   (7)v3≧50   (8)

5. The imaging lens according to any one of claims 1 to 4, wherein: an image surface side face of the third lens has an aspherical shape in which the negative power is weakened towards the periphery.

6. The imaging lens according to any one of claims 1 to 4, wherein: an image surface side face of the third lens has an aspherical shape which is convex towards the periphery.