KR101281368B1 - Imaging lens - Google Patents

Abstract

The present invention relates to an imaging lens.
That is, the imaging lens of the present invention comprises: a first lens having positive refractive power in order from the object side; A second lens having a negative refractive power; A third lens having positive refractive power; And a fourth lens having a negative refractive power or a positive refractive power. When the Abbe number of the first lens is Vd1, a conditional expression of 30 <Vd1 <50 is satisfied.

Description

Imaging lens

The present invention relates to an imaging lens.

Recently, a camera module for a communication terminal, a digital still camera (DSC), a camcorder, and a PC camera (image pickup device included with a personal computer) have been studied in relation to an image pick-up system. . The most important component for the camera module associated with such an image pickup system to obtain an image is the lens that forms the image.
Recently, a study has been made to configure the number of lenses into four lenses for compactness and low price.
Here, four lenses are advantageous in terms of price, but they must have satisfactory optical characteristics or aberration characteristics, and an implementation of an optical system having high performance and high resolution is required.

The present invention is to solve the problem of implementing a high resolution optical system.

According to the present invention,

In order from the object side,

A first lens having positive refractive power;

A second lens having a negative refractive power;

A third lens having positive refractive power; And

A fourth lens having a negative refractive power or a positive refractive power,

When the Abbe number of the first lens is Vd1,

30 <Vd1 <50

Is satisfied. &Lt; / RTI &gt;

The first lens is a meniscus in which an object side surface is convex.

The first lens is made of an aspheric glass material.

In addition, the first lens has the strongest refractive power.

In addition, the second lens is made of aspherical plastic material in the form of a diorama.

In addition, the third lens has a meniscus shape in which an image side surface is convex.

The fourth lens has a biconcave surface near the optical axis, and both surfaces are aspherical.

When the total focal length of the imaging lens is f and the focal length of the first lens is f1, a conditional expression of f1 / f <1.0 is satisfied.

Also, when the focal length of the first lens is f1, the total focal length of the second lens is f2, the focal length of the third lens is f3, and the focal length of the fourth lens is f4, f2 / f1 Satisfies the conditional expression of |> 1.5 and | f3 / f4 |> 1.0.

When the refractive index of the first lens is Nd1, the conditional expression of Nd1> 1.7 is satisfied.

When the refractive index of the second lens is Nd2, the conditional expression of Nd2> 1.6 is satisfied.

In addition, when the Abbe number of the second lens is Vd2, a conditional expression of Vd2 <30 is satisfied.

When the Abbe number of the first lens is Vd1 and the refractive index of the first lens is Nd1, the conditional expression of Vd1 / Nd1 <27 is satisfied.

When the Abbe number of the second lens is Vd2 and the refractive index of the second lens is Nd2, the conditional expression of Vd2 / Nd2 <15 is satisfied.

The imaging lens of the present invention includes the first lens, which is an aspherical surface having a strong refractive power, and has an effect of constituting a high resolution optical system.

1 is a block diagram of a camera lens module according to an embodiment of the present invention
2A and 2B are graphs measuring coma aberration of an embodiment of the present invention.
3 is a graph illustrating aberration diagrams of embodiments of the present invention;

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

In the camera lens module according to the present invention, an imaging lens including a plurality of lenses is disposed around the optical axis Z0. In the configuration diagram of FIG. 1, the thickness, size, and shape of the lens may be exaggerated for explanation. Although shown, the spherical or aspherical shape is presented by way of example only and is not limited to this shape.

 Referring to FIG. 1, the camera lens module according to the exemplary embodiment of the present invention may include the first lens 10, the second lens 20, the third lens 30, and the fourth lens 40 in order from the object side. , The filter 50 and the light receiving element are arranged.

Light corresponding to the image information of the subject passes through the first lens 10, the second lens 20, the third lens 30, the fourth lens 40, and the filter 50 to the light receiving element. Incident.

The first lens 10, the second lens 20, the third lens 30, and the fourth lens 40 are image lenses of the present invention, and the present invention is the first lens 10. A separate diaphragm may be positioned between the second lens 20 and the second lens 20 to correct aberrations and to implement a clear image.

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, .

The first lens 10 has a positive refractive power, the object side surface S1 is convex, has a meniscus shape, and has a strong refractive power.

In addition, the second lens 20 has a negative refractive power and is made of an aspherical plastic material in the form of a concave concave.

In addition, the third lens 30 has a positive refractive power and has a meniscus shape in which the image side surface S6 is convex.

In addition, the fourth lens 40 has a negative refractive power or a positive refractive power, has a positive concave surface near the optical axis, and both surfaces are aspherical.

For reference, 'S2' of FIG. 1 is an image side surface of the first lens 10, 'S3' and 'S4' are object side and image side surfaces of the second lens 20, and 'S5' and 'S6' Are the object side and image side of the third lens 30, 'S7' and 'S8' are the object side and image side of the fourth lens 40, 'S9' and 'S10' of the filter 60 Object side and top side.

The filter 50 is at least one of an optical filter such as an infrared filter and a cover glass. As the filter 50, when an infrared filter is applied, radiant heat emitted from external light is blocked from being transmitted to the light receiving element. In addition, the infrared ray filter transmits visible light, and the infrared ray reflects the infrared ray to the outside.

The light receiving device is an image sensor such as a charge coupled device (CCD) or a complementary metal oxide semiconductor (CMOS).

Therefore, the imaging lens of the present invention includes the first lens, which is an aspherical surface having a strong refractive power, and thus can form a high resolution optical system.

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.

[Condition 1] f1 / f <1.0

[Condition 2] │f2 / f1│> 1.5

[Condition 3] │f3 / f4│> 1.0

Conditional Expression 4 Nd1> 1.7

[Condition 5] Nd2> 1.6

[Condition 6] 30 <Vd1 <50

[Condition 7] Vd2 <30

[Condition 8] Vd1 / Nd1 <27

Conditional Expression 9 Vd2 / Nd2 <15

Where f is the total focal length of the imaging lens

f1: Focal length of the first lens

f2: Focal length of the second lens

f3: Focal length of the third lens

f4: Focal length of the fourth lens

Nd1: refractive index of the first lens

Nd2: refractive index of the second lens

Vd1: Abbe number of the first lens

Vd2: Abbe number of the second lens

Conditional Expressions 1 to 3 define the refractive power of the first to fourth lenses 10, 20, 30, and 40. The first to fourth lenses 10, 20, 30, and 40 have refractive power with appropriate spherical aberration correction and appropriate chromatic aberration according to conditional equation (1).

Conditional Expressions 4 and 5 define the refractive indices of the first and second lenses 10 and 20, and Conditional Expressions 6 and 7 define the Abbe numbers of the first and second lenses 10 and 20. The definition of the Abbe number of each lens is a condition for satisfactorily correcting chromatic aberration.

Hereinafter, the operation and effect of the present invention will be described with reference to specific examples. The aspherical surface referred to in the following embodiments is obtained from the known equation (1), and the 'E and the following number' used for the conic constant k and the aspherical coefficients A, B, C, D, Lt; / RTI &gt; For example, E + 01 represents 10 ¹ and E-02 represents 10 ^-2 .

Where z is the distance from the apex of the lens in the direction of the optical axis

c: The basic curvature of the lens

Y: Distance in the direction perpendicular to the optical axis

K: Conic constant

A, B, C, D, E, F: aspheric coefficient

[Example]

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

Example Nd1 1.77 Nd2 1.63 Vd1 47 Vd2 23 f1 3.08 f2 -5.06 f3 2.83 f4 -3.06 f 4.25

Referring to Table 1, it can be seen that f1 / f satisfies Condition 1 as 0.724.

The following Table 2 shows a more specific embodiment in comparison with the embodiment of Table 1. [

Cotton number The radius of curvature (R) Thickness or distance (d) Refractive index (N) One* 2.05 0.62 1.77 2* 13.00 0.12 3 Infinity 0.11 4* -10.70 0.55 1.63 5 * 4.65 0.51 6 * -3.10 1.04 1.53 7 * -1.13 0.50 8* -3.79 0.53 1.53 9 * 2.97 0.19 10 Infinity 0.30 1.52 11 Infinity 0.81 image Infinity 0

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

Table 3 below shows the values of the aspherical coefficients of each lens in the example of Table 2 above.

if
number k A B C D E F One* -1.059122 2.10E-02 -7.17E-03 2.05E-02 -2.10E-02 0 0 2* 13 9.62E-03 -8.41E-03 -4.15E-02 6.63E-03 0 0 4* 0 5.66E-02 -5.25E-02 -5.51E-02 0 0 0 5 * 18.080108 8.67E-02 -1.79E-02 -2.96E-02 0 0 0 6 * -3.557288 -6.84E-02 3.72E-02 -3.68E-02 8.54E-02 -4.10E-02 0 7 * -4.741082 -2.93E-01 2.87E-01 -2.40E-01 1.23E-01 -2.36E-02 0 8* 1.688274 -8.44E-02 5.29E-02 -7.09E-03 -5.01E-04 2.09E-04 -1.36E-05 9 * -22.0383712 -8.19E-02 2.95E-02 -8.19E-03 1.36E-03 -8.66E-05 -3.99E-07

FIG. 2A and FIG. 2B are graphs of coma aberration of an embodiment of the present invention, in which tangential and sagittal aberrations of respective wavelengths are measured according to a field height. One graph. In FIG. 2A and FIG. 2B, the graph showing the experimental results is interpreted as having a better coma aberration correction function as the X axis is closer to each of the positive and negative axes. The measurement examples of Figs. 2A and 2B are interpreted to show excellent coma aberration correction functions, since the values of the phases appear in the nearly all fields adjacent to the X axis.

3 is a graph illustrating an aberration diagram of an embodiment of the present invention, in which longitudinal spherical aberration, astigmatic field curves, and distortion are measured in order from the left.

In FIG. 3, the Y axis denotes the size of an image, and the X side denotes a focal length (mm unit) and a distortion degree (% unit). In FIG. 3, as the curves approach the Y axis, 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.

That is, the range of the longitudinal spherical aberration is -0.044 mm to +0.021 mm, the range of astigmatism is -0.042 mm to +0.023 mm, and the range of the distortion aberration is -1.23 mm to +0.31 mm, so that the imaging lens of the present invention It can be seen that the characteristics of spherical aberration, astigmatism, and distortion can be corrected and have excellent lens characteristics.

Although the invention has been described in detail only with respect to specific examples, it will be apparent to those skilled in the art that various modifications and variations are possible within the spirit of the invention, and such modifications and variations belong to the appended claims.

Claims (14)

In order from the object side,
A first lens having positive refractive power;
A second lens having a negative refractive power;
A third lens having positive refractive power; And
A fourth lens having a negative refractive power or a positive refractive power,
An imaging lens satisfying a conditional expression of 30 <Vd1 <50 when the Abbe number of the first lens is Vd1 and satisfying a conditional expression of Nd1> 1.7 when the refractive index of the first lens is Nd1.
The method of claim 1,
Wherein the first lens comprises:
An imaging lens that is a meniscus with an object side surface convex.
3. The method of claim 2,
Wherein the first lens comprises:
Imaging lens made of glass.
The method of claim 1,
The first lens,
Imaging lens with the strongest refractive power.
The method of claim 1,
And the second lens comprises:
Imaging lens in the form of a diorama.
The method of claim 1,
The third lens includes:
And the image side surface is convex.
The method of claim 1,
The fourth lens includes:
Imaging lens in the form of a diorama near the optical axis.
The method of claim 1,
When the total focal length of the imaging lens is f and the focal length of the first lens is f1,
f1 / f <1.0
Satisfies the following conditional expression.
The method of claim 1,
When the focal length of the first lens is f1, the total focal length of the second lens is f2, the focal length of the third lens is f3, and the focal length of the fourth lens is f4,
│f2 / f1│ ＞ 1.5, │f3 / f4│> 1.0
Satisfies the following conditional expression.
delete The method of claim 1,
When the refractive index of the second lens is Nd2,
Nd2 ＞ 1.6
Satisfies the following conditional expression.
The method of claim 1,
When the Abbe number of the second lens is Vd2,
Vd2 <30
Satisfies the following conditional expression.
The method of claim 1,
When the Abbe number of the first lens is Vd1 and the refractive index of the first lens is Nd1,
Vd1 / Nd1 <27
Satisfies the following conditional expression.
It consists of four lenses in order from the object side,
A first lens having positive refractive power;
A second lens having a negative refractive power;
A third lens having positive refractive power; And
A fourth lens having a negative refractive power or a positive refractive power,
An imaging lens that satisfies the conditional expression of Vd2 / Nd2 &lt; 15 when the Abbe number of the second lens is Vd2 and the refractive index of the second lens is Nd2.

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