KR101933960B1 - Imaging lens - Google Patents

Abstract

The present invention relates to an imaging lens.
That is, the imaging lens of the present invention comprises, in order from the object side, a first lens having a positive refractive power, the object side being convex; A second lens having a negative refractive power and in the form of a concave lens having a concave shape in the object direction; A third lens having a positive refractive power and having an inflection point on all sides in the form of a meniscus; And a fourth lens having a negative refractive power.

Description

[0001] IMAGING LENS [0002]

The present invention relates to an imaging lens.

Recently, a camera module for a communication terminal, a digital still camera (DSC), a camcorder, a PC camera (an image pickup device attached to a personal computer), and the like have been studied in connection with an image pick-up system . The most important component for obtaining an image of a camera module related to such an image pickup system is a lens for imaging an image.

In recent years, the number of lenses has been reduced to three or four for the purpose of compactness and cost reduction.

In Korean Patent Laid-Open No. 2005-0014108, which is a background technique, an attempt has been made to construct a compact optical system using four lenses.

Although these four lenses are advantageous in terms of cost, they must have satisfactory optical characteristics or aberration characteristics, and it is required to realize an optical system having high performance and high resolution.

An object of the present invention is to provide a compact imaging lens having a wide angle of view and high resolution and high resolution.

According to the present invention,

In order from the object side,

A first lens having positive refracting power and having an object side convex;

A second lens having a negative refractive power and in the form of a concave lens having a concave shape in the object direction;

A third lens having a positive refractive power and having an inflection point on all sides in the form of a meniscus;

There is provided an imaging lens including a fourth lens having negative refractive power.

The second lens has an inflection point on the upper side.

Further, a diaphragm is positioned in front of the object side surface of the first lens.

The fourth lens has an inflection point of at least one plane.

In addition, the first lens to the fourth lens have an aspherical shape on one or both surfaces.

When the total focal length of the imaging lens is f and the focal lengths of the first, second, third, and fourth lenses are f1, f2, f3, and f4,

0.8, 0.8 <f1 / f2 <1.3, 0.8 <f1 / f2 <1, 1.2 <f / f3 <1.8, 0.6 < F1 / f | <1.2, 1 <| f2 / f | <1.5, 0.85 <| f / f1 | <1.15.

When the focal length of the first lens is f1 and the distance on the optical axis from the side surface of the first lens object to the image plane is L,

1.2 < L / f1 < 1.4.

When the distance from the side of the first lens object to the image plane on the optical axis is L,

4.3 < L < 4.5.

Further, when the diagonal field of view (angle of view) is FOV, the conditional expression 70 <FOV <90 is satisfied.

1.5, n1 <1.6, 1.5 <n3 <1.6, 1.5 <n4 <1.6, where n1, The conditional expression is satisfied.

50 <V1 <60, 50 <V3 <60, 50 <V4 <60 where V2, V3 and V4 are the Abbe numbers of the first, second, Lt; / RTI &gt;

When the F-number is F / #, the conditional expression 2.0 <F / # <3.0 is satisfied.

When the radius of curvature of the object side surface and the image side surface of the second lens is r3 and r4,

0 <(r3 + r4) / (r3-r4) <1.

When the curvature radius of the second surface of the third lens is L3R2 and the curvature radius of the second surface of the fourth lens is L4R2,

L3R2 &gt; -1 and L4R2 &lt; 1.

The present invention has the effect of realizing a compact imaging lens having a wide angle of view, high performance and high resolution.

1 is a block diagram of a camera lens module according to the present invention;
FIGS. 2A and 2B are graphs showing the coma aberration of the embodiment of the present invention
Fig. 3 is a graph showing the aberration diagram of the embodiment of the present invention
FIGS. 4A and 4B are graphs showing MTF (Modulation Transfer Function) characteristics with respect to a spatial frequency at a zoom position and MTF characteristics with respect to a defocusing position at a zoom position according to an embodiment of the present invention;

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

1 is a block diagram of a camera lens module according to the present invention.

In the camera lens module according to the present invention, an image pickup lens composed of a plurality of lenses is arranged around the optical axis Z0. In the configuration diagram of Fig. 1, the thickness, size and shape of the lens are slightly exaggerated And the spherical or aspherical shape is shown as an embodiment, and the present invention is not limited to this shape.

 1, a camera lens module according to the present invention includes a first lens 10, a second lens 20, a third lens 30, a fourth lens 40, a filter 50, And a light receiving element 60 are arranged.

The light corresponding to the image information of the object passes through the first lens 10, the second lens 20, the third lens 30, the fourth lens 40 and the filter 50, .

Here, the present invention has an advantage that a compact imaging lens having a wide angle of view, high performance, high resolution can be realized.

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, and the object side surface S1 is convex.

The second lens 20 has a negative refractive power, is a concave lens having a concave surface in the object direction, and has an inflection point on the upper side S4.

In addition, a separate diaphragm may be disposed at the front end of the object side surface S1 of the first lens 10.

In addition, the third lens 30 has a positive refractive power, and has an inflection point on all surfaces in the form of a meniscus.

The fourth lens 40 has a negative refractive power and has an inflection point of at least one plane.

The first lens 10 to the fourth lens 40 have an aspherical shape on one or both surfaces.

In FIG. 1, 'S2' is the upper side of the first lens 10, 'S3' is the object side of the second lens 20, 'S5' is the object side of the third lens 30 S7 and S8 are the object side and upper side of the fourth lens 40 and S9 and S10 are the upper and lower sides of the filter 50, Is the object side and the upper side of FIG.

The filter 50 is at least one of an infrared filter, an optical filter such as a cover glass, and the like. When the infrared filter is applied as the filter 50, the radiation heat emitted from the external light is blocked from being transmitted to the light receiving element 60. In addition, the infrared ray filter transmits visible light, and the infrared ray reflects the infrared ray to the outside.

The light receiving element 60 is an image sensor such as a CCD (Charge Coupled Device) or a CMOS (Complementary Metal Oxide Semiconductor).

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] 0.6 <f / f2 | <1, 1.2 <f / f3 <1.8, 0.6 <f / f4 <1

[Conditional expression 2] 0.3 <| f3 / f4 | <0.8, 0.8 <| f1 / f2 | <1.3

[Conditional expression 3] 0.8 <| f1 / f | <1.2, 1 <| f2 / f | <1.5

[Conditional expression 4] 0.85 < f / f1 < 1.15

[Conditional expression 5] 1.2 < L / f1 < 1.4

[Conditional expression 6] 4.3 < L < 4.5

[Conditional expression 7] 70 <FOV <90

[Conditional expression 8] 1.6 <n2 <1.7, 1.5 <n1 <1.6, 1.5 <n3 <1.6, 1.5 <n4 <1.6

[Conditional expression 9] 22 <V2 <32, 50 <V1 <60, 50 <V3 <60, 50 <V4 <60

[Conditional expression 10] 2.0 <F / # <3.0

[Conditional expression 11] 0 <(r3 + r4) / (r3-r4) <1

[Conditional expression 12] L3R2> -1, L4R2 <1

The above-described conditional expressions and characters and numbers of the embodiments described below are defined as follows.

f: total focal length of the imaging lens

f1, f2, f3, f4: the focal length of the first, second, third, and fourth lenses

D12, D23, D34: The distance between the first and second lens, the second and third lens, and the third and fourth lenses on the optical axis

D1, D2, D3, D4: the center thickness of the first, second, third and fourth lenses

L: distance on the optical axis from the side surface of the first lens object to the image surface

n1, n2, n3, n4: the refractive index of the first, second,

V1, V2, V3, V4: Abbe number of 1st, 2nd, 3rd, 4th lens

bf2, bf3, bf4: the distance on the optical axis from the image side to the image plane of the second, third,

FOV: Diagonal Field of View

L3R2: radius of curvature of the second surface of the third lens

L4R2: radius of curvature of the second surface of the fourth lens

F / #: F-number

r3, r4: radius of curvature of the object side surface and the image side surface of the second lens

Conditional expression 8 defines the refractive powers of the first to fourth lenses 10, 20, 30, The first through fourth lenses 10, 20, 30, and 40 have a refractive power having a proper chromatic aberration and correcting the spherical aberration according to the conditional expression (8).

The conditional expression (9) defines the Abbe number of the first to fourth lenses (10, 20, 30, 40). The specification of the Abbe number of each lens is a condition for satisfactorily correcting the 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 f 2.8600 f1 3.1736 f2 -3.5966 f3 1.8987 f4 -2.9509 V1 56.5 V2 23.9 V3 56.5 V4 56.5 n1 1.5350 n2 1.6340 n3 1.5350 n4 1.5310 D12 0.377 D23 0.132 D34 0.100 D1 0.596 D2 0.348 D3 0.890 D4 0.530 L 4.360 f / f1 0.901 L / f1 1.374 bf2 3.387 bf3 2.907 bf4 1.917

Referring to Table 1, it can be seen that | f / f1 | is 0.90, which is in accordance with the conditional expression 4, and L / f1 is 1.37, which satisfies the conditional expression 5.

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

Face number The radius of curvature (R) Thickness or distance (d) Refractive index (N) Stop * 2.53 0.596 1.537 2* -4.78 0.377 3 * -4.97 0.348 1.634 4* 4.43 0.132 5 * -4.63 0.890 1.537 6 * -0.89 0.100 7 * 1.50 0.530 1.531 8* 0.67 0.953 9 Infinity 0.300 1.52 10 Infinity 0.118 image Infinity 0.017

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

The following Tables 3 and 4 show values of aspherical surface coefficients of the respective lenses in the embodiment of Table 2 above.

Face number k A B C D E One* -3.9254 -0.0451 -0.0497 -0.1754 0.0800 -0.0711 2* 28.3069 -0.1739 0.0500 -0.3034 0.4228 -0.1819 3 * -22.1905 -0.4794 0.2440 -0.4502 1.0276 -0.5663 4* -169.7252 -0.1200 0.0182 0.0848 -0.0510 0.0091 5 * -9.6926 0.0274 0.0265 -0.0356 0.0318 -0.0084 6 * -0.6198 0.1626 -0.0283 0.0129 0.0205 -0.0003

Face number k 3rd 4th 5th 6th 7th 8th 9th 10th 11th 12th One* -7.3113 -0.0854 -0.0280 -0.0265 0.0465 -0.0093 -0.0069 0.0020 -0.0003 0.0005 -0.0001 2* -2.6912 -0.1566 -0.0249 0.1017 -0.0683 0.0234 -0.0039 -0.0003 -0.0003 0.0003 -0.0001

FIGS. 2A and 2B are graphs illustrating coma aberration of an embodiment of the present invention. The tangential aberration and the sagittal aberration of each wavelength are measured according to the field height of the upper surface. It is a graph. In FIGS. 2A and 2B, when the graph showing the experimental results is closer to the X axis on the positive axis and negative axis, it is interpreted that the coma aberration correction function is good. The measurement examples of FIGS. 2A and 2B are interpreted to show excellent coma aberration correction functions because the values of the phases appear near the X axis in almost all fields.

FIG. 3 is a graph showing aberration diagrams of 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. 3, the Y axis represents the size of the image, and the X side represents the focal length (in mm) and distortion (in%). In FIG. 3, 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.

That is, since the range of the pupil plane difference is -0.029 mm to +0.0125 mm, the range of the astigmatism is -0.015 mm to +0.01 mm, and the range of the distortion aberration is -0.90 mm to +0.15 mm, Can correct the characteristics of the spherical aberration, the astigmatism, and the distortion aberration, and it can be seen that it has excellent lens characteristics.

FIG. 4A is a graph showing MTF (Modulation Transfer Function) characteristics for a spatial frequency at a zoom position according to an embodiment of the present invention, and MTF characteristics depending on a change in a spatial frequency (cycle / mm) of a cycle per millimeter . Here, the MTF characteristic is a ratio value obtained by calculating the difference from the image formed after the light originating from the original object surface passes through the lens. The MTF value is most ideal when the MTF value is '1' .

Referring to FIG. 4A, since the MTF value is high at the zoom position, it can be seen that the imaging lens according to the embodiment has excellent optical performance.

Also, FIG. 4B is a graph showing MTF characteristics for a defocusing position at a zoom position according to an embodiment of the present invention, and is a through focus MTF at a frequency of 143 c / mm.

It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims (18)

In order from the object side,
A first lens having positive refracting power and having an object side convex;
A second lens having a negative refractive power and in the form of a concave lens having a concave shape in the object direction;
A third lens having a positive refractive power and having an inflection point on both sides in a meniscus form;
And a fourth lens having a negative refractive power,
And f denotes a focal length of the first lens, and L denotes a distance on the optical axis from the object side surface to the image plane of the first lens,
1.2 < L / f1 < 1.4.
The method according to claim 1,
And the second lens comprises:
And an inflection point on the image side.
The method according to claim 1,
Wherein a front surface of the object side surface of the first lens,
An imaging lens in which the diaphragm is located.

The method according to claim 1,
The fourth lens includes:
An imaging lens having an inflection point on at least one surface.
The method according to claim 1,
Wherein the first lens to the fourth lens are arranged such that,
An imaging lens having an aspherical shape on one side or on both sides.
The method according to claim 1,
And f1, f2, f3, and f4 are the focal lengths of the first, second, third, and fourth lenses,
0.8, 0.8 <f1 / f2 <1.3, 0.8 <f1 / f2 <1, 1.2 <f / f3 <1.8, 0.6 < F1 / f | <1.2, 1 <f2 / f | <1.5, 0.85 <| f / f1 | <1.15.
delete The method according to claim 1,
And a distance on the optical axis from the side surface of the first lens object to the image surface is L,
4.3 < L < 4.5.
The method according to claim 1,
When the diagonal field of view (angle of view) is FOV,
70 < FOV < 90.
The method according to claim 1,
When the refractive indexes of the first, second, third, and fourth lenses are n1, n2, n3, and n4,
The imaging lens satisfies the following conditional expressions: 1.6 <n2 <1.7, 1.5 <n1 <1.6, 1.5 <n3 <1.6, 1.5 <n4 <1.6.
The method according to claim 1,
When the Abbe numbers of the first, second, third, and fourth lenses are V1, V2, V3, and V4,
The imaging lens satisfies the following conditional expressions: 22 <V2 <32, 50 <V1 <60, 50 <V3 <60, 50 <V4 <60.
The method according to claim 1,
When the F-number is F / #,
2.0 < F / # < 3.0.
The method according to claim 1,
And r3 and r4 are curvature radii of the object side surface and the image side surface of the second lens,
0 < (r3 + r4) / (r3-r4) < 1.
The method according to claim 1,
The curvature radius of the upper side of the third lens is L3R2, and the curvature radius of the upper side of the fourth lens is L4R2,
L3R2 &gt; -1, and L4R2 &lt; 1.

In order from the object side,
A first lens having positive refracting power and having an object side convex;
A second lens having a negative refractive power and in the form of a concave lens having a concave shape in the object direction;
A third lens having a positive refractive power and having an inflection point on both sides in a meniscus form;
And a fourth lens having a negative refractive power,
And a distance on the optical axis from the side surface of the first lens object to the image surface is L,
4.3 < L < 4.5.
16. The method of claim 15,
When the diagonal field of view (angle of view) is FOV,
70 < FOV < 90.
16. The method of claim 15,
When the refractive indexes of the first, second, third, and fourth lenses are n1, n2, n3, and n4,
The imaging lens satisfies the following conditional expressions: 1.6 <n2 <1.7, 1.5 <n1 <1.6, 1.5 <n3 <1.6, 1.5 <n4 <1.6.
16. The method of claim 15,
And r3 and r4 are curvature radii of the object side surface and the image side surface of the second lens,
0 < (r3 + r4) / (r3-r4) < 1.

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