KR20140076419A - Imaging lens - Google Patents

Abstract

According to an embodiment of the present invention, an imaging lens comprises in order from an object side: a first lens which is a biconvex lens having positive (+) refractive power; a second lens which has positive (+) refractive power; and a third lens which has negative (-) refractive power. If the refractive index of the second lens is n2, a conditional expression of 1.5 < n2 <1.6 is satisfied.

Description

[0001] IMAGING LENS [0002]

The present invention relates to an imaging lens.

2. Description of the Related Art In recent years, there has been an increasing demand for a small camera module for various multimedia fields such as a tablet computer, a camera phone, a PDA, a smart phone, a toy, and an image input device such as a surveillance camera or an information terminal of a video tape recorder. In particular, smart phones are in the trend of developing small-sized camera modules in response to the increasing demand of consumers who prefer miniaturized designs.

Such a camera module is manufactured using an image sensor chip of a CCD or a CMOS. The image sensor chip is used to condense an object through a lens, convert an optical signal into an electric signal, and display objects on a display medium such as an LCD display device So as to transmit the image.

The most important component for obtaining an image of a camera module is a lens for imaging an image. 2. Description of the Related Art [0002] In recent years, a thinner portable terminal has been required to be thin, and components for performing various functions are mounted on the portable terminal. Accordingly, various researches and technologies for pursuing thinning of the imaging lens optical system of a camera module for a portable terminal have been developed. Particularly, when an actuator that performs an auto focusing function is changed to a single lens moving method instead of using a conventional voice coil motor, it is advantageous to miniaturize a camera module, and thus much research has been conducted on the actuator.

Korean Patent Publication No. 10-2012-0094729 (Aug. 27, 2012) Korean Patent No. 10-1171517 (Jul. 27, 2012)

An object of the present invention is to provide an imaging lens for providing an ultra-thin camera module.

An imaging lens according to an embodiment of the present invention includes, in order from an object side, a first lens having positive refracting power and a positive refracting power; A second lens having positive refractive power; And a third lens having negative refractive power, wherein the refractive index of the second lens is n2, the conditional expression 1.5 < n2 < 1.6 can be satisfied.

The refractive indices of the first through third lenses may be all the same.

The Abbe numbers of the first and second lenses may be formed identically.

The second lens may be provided in a meniscus shape having a convex surface upward.

The second lens has a greater refractive power than the first and third lenses, and a stop surface may be formed between the first lens and the second lens.

The third lens may be provided in a meniscus shape having a convex surface on the object side.

Both surfaces of the third lens may have inflection points.

V1, v2, and v3 <60, where the Abbe number of the first lens is v1, the Abbe number of the second lens is v2, and the Abbe number of the third lens is v3.

When the Abbe number of the first lens is v1, the Abbe number of the second lens is v2, and the Abbe number of the third lens is v3, the conditional expression (v1-v2) / v3 <1 can be satisfied.

When the thickness of the entire optical system is? D and the focal length of the entire optical system is f, the conditional expression of 0.5 <? D / f <1.5 can be satisfied.

When the focal length of the entire optical system is f and the focal length of the first lens is f1, the conditional expression of 0.5 < f1 / f < 1.5 can be satisfied.

A conditional equation of 0.70 < d1 / d2 < 0.95 can be satisfied when the center thickness of the first lens is d1, and the distance between the image side surface of the first lens and the object side surface of the second lens is d2.

When the distance from the side of the first lens object to the imaging plane is? T and the focal length of the entire optical system is f, the conditional expression of 0.5 <? T / f <1.5 can be satisfied.

When the curvature radius of the object side surface of the first lens is r1 and the focal length of the entire optical system is f, the conditional formula 1 > r1 / f > 0.5 can be satisfied.

When the curvature radius of the object side surface of the first lens is r1 and the focal length of the first lens is f1, the conditional expression of r1 / f1> 0.5 can be satisfied.

(R1 / r2) 10 < 2 &gt;, where r1 is an object side curvature radius of the first lens, and r2 is an object side curvature radius of the second lens, <0.5 can be satisfied.

When the focal length of the entire optical system is f and the focal length of the second lens is f2, the conditional expression of -0.2 <f / f2 <2 can be satisfied.

The conditional expression 1.5 <N1, N2, N3 <1.6 can be satisfied when the refractive index of the first lens is N1, the refractive index of the second lens is N2, and the refractive index of the third lens is N3.

When the focal length of the entire optical system is f and the thickness of the entire optical system is D, FNO, which is a numerical value representing the lens brightness of the infinite original, can satisfy the conditional expression of FNO = f / D and 2.2 <FNO <3.0.

It is possible to provide an imaging lens usable in an ultra-thin camera module using three lenses.

1 is a configuration diagram of an imaging lens according to an embodiment of the present invention,
2 is a graph showing spherical aberration, astigmatism, and distortion aberration of an imaging lens according to an embodiment of the present invention.

Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

FIG. 1 is a configuration diagram of an imaging lens according to an embodiment of the present invention, and FIG. 2 is a graph showing spherical aberration, astigmatism, and distortion aberration of an imaging lens according to an embodiment of the present invention.

In the imaging lens of the camera module according to the embodiment of the present invention, the imaging lens composed of a plurality of lenses may be arranged around the optical axis. Here, the thickness, size, and shape of the lens shown in FIGS. 1 and 3 are exaggerated for explanatory purposes, and the spherical or aspherical shape is not limited thereto.

1 is a view showing a configuration of an imaging lens applied to a camera module according to an embodiment of the present invention.

1, the camera lens module of the present invention may include a diaphragm, a first lens 10, a second lens 20, a third lens 30, and a filter 40 in this order from the object side. have.

Light corresponding to the image information of the subject may be incident on the image sensor side not shown through the first lens 10, the second lens 20, the third lens 30 and the filter 40.

Hereinafter, the term "object side" refers to a surface of the lens that faces the object side with respect to the optical axis, and "upper side" refers to a lens that faces the imaging surface with respect to the optical axis, .

A feature of the present invention resides in that the three lenses are formed to form the optical system of the ultra-thin camera module.

The first lens 10 has a positive refractive power and the second lens 20 has a positive refractive power and the third lens 30 has a negative refractive power. . Here, the first lens 10 may be formed in a biconvex shape, the second lens 20 may be formed in a meniscus shape having an upward convex surface, and the third lens 30 may be formed And a meniscus shape having a convex surface on the object side.

At this time, the first lens 10, the second lens 20, and the third lens 30 may all have the same refractive index.

The second lens 20 may have a greater refractive power than the first and third lenses 10 and 30 and a stop surface may be formed between the first and second lenses 10 and 20 A diaphragm or the like may be disposed to adjust the amount of light incident on the optical system.

The filter 40 is at least one of an infrared cut filter and an optical filter such as a cover glass. When the infrared cut filter is used as the filter 40, infrared rays emitted from the external light can be blocked from being transmitted to the image sensor (not shown). The infrared cut filter transmits visible light and does not transmit infrared light.

It will be apparent to those skilled in the art that the conditional expressions and embodiments described below are preferred embodiments for increasing the operating effect, and that the present invention is not necessarily constituted by the following conditions. For example, the lens configuration of the present invention may have an elevated action effect even if only the conditional formulas of some of the conditional expressions described below are satisfied.

[Conditional expression 1] 0.5 <? D / f <1.5

[Conditional expression 2] 0.5 <f1 / f <1.5

[Conditional expression 3] 0.70 <d1 / d2 <0.95

here,

Σd is the total optical system thickness

f is the total optical system focal length

f1 is the focal length of the first lens

d1 is the center thickness of the first lens

and d2 is the distance between the image side surface of the second lens and the image side surface of the first lens.

[Conditional expression 4] 50 <v1, v2, v3 <60

[Conditional expression 5] (v1-v2) / v3 < 1

here,

v1 is the Abbe number of the first lens,

v2 is the Abbe number of the second lens,

and v3 is the Abbe number of the third lens.

[Conditional expression 6] 0.5 < T / f < 1.5

[Conditional expression 7] 1 > r1 / f > 0.5

[Conditional expression 8] r1 / f1 > 0.5

[Conditional expression 9] | (r1 / r2) * 10 | <0.5

[Conditional expression 10] -0.2 < f / f2 < 2

[Conditional expression 11] 1.5 <N1, N2, N3 <1.6

[Conditional expression 12] 2.2 <FNO <3.0

here,

r1 is the radius of curvature of the object side surface of the first lens,

r2 is the radius of curvature of the object side surface of the second lens,

N1 is the refractive index of the first lens,

N2 is the refractive index of the second lens,

And N3 is the refractive index of the third lens.

Table 1 below shows an embodiment that conforms to the above-described conditional expression.

value f 2 f1 2.37 f2 1.69 f3 -1.74 | f2 / f1 | 0.96 T 2.92 T / f 1.46

here,

f is an optical system focal length,

f1, f2, and f3 are the first to third lens focal lengths,

And T is the distance from the side of the first lens object to the imaging plane.

Table 2 shows lens surface data of each lens surface.

R D N Material (Reference) One* 1.26 0.45 1.53 Plastic (P) 2* -300 0.19 (Stop) 0.00 0.45 4* -0.89 0.52 1.53 Plastic (P) 5 * -0.54 0.1 6 * 5.38 0.56 1.53 Plastic (P) 7 * 0.79 0.26 8* 0 0.3 1.52 Plastic (P) 9 * 0 0.100 image 0.00 0.00

In Table 2 and Table 3 below, an asterisk (*) next to the surface number indicates an aspherical surface.

Table 3 below shows values of the aspherical surface coefficients of the respective lenses in the embodiment of Table 2 above.

k A B C D One* -0.420518 -.294747E-01 -.924352E-01 -.175545E + 00 -.195160E + 00 2* -0.169948e27 -.942088E-01 -.438920E + 00 0.101529E + 01 -.268995E + 01 4* 0.441273 -.607080E + 00 0.537315E + 00 -.990601E + 01 0.485091E + 02 5 * -0.909230 0.112051E + 00 0.275398E + 00 -.310644E + 01 0.538891E + 01 6 * -1176.976256 0.182918E-01 0.101451E + 00 -.644291E-01 0.155947E-01 7 * -6.580117 -.108027E + 00 0.791496E-01 -.325968E-01 0.383014E-02

FIG. 2 is a graph showing aberration diagrams according to an embodiment of the present invention, and is a graph measuring longitudinal spherical aberration, astigmatic field curves, and distortion in order from the left. In Fig. 2, as the curves approach the Y-axis, it is interpreted that the aberration correction function is better. In the illustrated aberration diagrams, since the values of the images are adjacent to the Y axis in almost all fields, spherical aberration, astigmatism, and distortion aberration are all excellent values.

The embodiments of the present invention described above and shown in the drawings should not be construed as limiting the technical idea of the present invention. The scope of protection of the present invention is limited only by the matters described in the claims, and those skilled in the art will be able to modify the technical idea of the present invention in various forms. Accordingly, such improvements and modifications will fall within the scope of the present invention as long as they are obvious to those skilled in the art.

10; A first lens 20; The second lens
30; A third lens 40; Infrared cut filter

Claims (19)

In order from the object side,
A first lens having positive refracting power and being a biconvex;
A second lens having positive refractive power; And
And a third lens having negative refractive power,
And the refractive index of the second lens is n2,
1.5 < n2 < 1.6
Satisfies the following conditional expression.
The method according to claim 1,
Wherein the refractive indices of the first to third lenses are all the same.
The method according to claim 1,
Wherein the Abbe numbers of the first and second lenses are the same.
2. The zoom lens according to claim 1,
And a meniscus shape having an upward convex surface.
2. The zoom lens according to claim 1,
A second lens having a larger refractive power than the first and third lenses,
And a stop surface is formed between the first lens and the second lens.
2. The zoom lens according to claim 1,
And a meniscus shape having a convex surface on the object side.
2. The zoom lens according to claim 1,
And both surfaces have an inflection point.
The method according to claim 1,
Assuming that the Abbe number of the first lens is v1, the Abbe number of the second lens is v2, and the Abbe number of the third lens is v3,
50 < v1, v2, v3 < 60
Is satisfied.
The method according to claim 1,
Assuming that the Abbe number of the first lens is v1, the Abbe number of the second lens is v2, and the Abbe number of the third lens is v3,
(v1-v2) / v3 < 1
Satisfies the following conditional expression.
The method according to claim 1,
When the thickness of the entire optical system is? D and the focal length of the entire optical system is f,
0.5 <? D / f <1.5
Satisfies the following conditional expression.
The method according to claim 1,
When the focal length of the entire optical system is f and the focal length of the first lens is f1,
0.5 < f1 / f < 1.5
Satisfies the following conditional expression.
The method according to claim 1,
When the center thickness of the first lens is d1 and the distance between the image side surface of the first lens and the object side surface of the second lens is d2,
0.70 < d1 / d2 < 0.95
Satisfies the following conditional expression.
The method according to claim 1,
When the distance from the first lens object side surface to the imaging plane is? T and the focal length of the entire optical system is f,
0.5 < T / f < 1.5
Satisfies the following conditional expression.
The method according to claim 1,
When the radius of curvature of the object side surface of the first lens is r1 and the focal length of the entire optical system is f,
1 > r1 / f > 0.5
Satisfies the following conditional expression.
The method according to claim 1,
When the radius of curvature of the object side surface of the first lens is r1 and the focal length of the first lens is f1,
r1 / f1 > 0.5
Satisfies the following conditional expression.
The method according to claim 1,
When the radius of curvature of the object side surface of the first lens is r1 and the radius of curvature of the object side surface of the second lens is r2,
| (r1 / r2) 10 | <0.5
Satisfies the following conditional expression.
The method according to claim 1,
When the focal length of the entire optical system is f and the focal length of the second lens is f2,
-0.2 < f / f2 < 2
Satisfies the following conditional expression.
The method according to claim 1,
When the refractive index of the first lens is N1, the refractive index of the second lens is N2, and the refractive index of the third lens is N3,
1.5 < N1, N2, N3 < 1.6
Satisfies the following conditional expression.
The method according to claim 1,
Assuming that the focal length of the entire optical system is f and the thickness of the entire optical system is D, FNO, which is a numerical value representing the lens brightness of the infinite original,
FNO = f / D,
2.2 < FNO < 3.0
Satisfies the following conditional expression.

Images