KR102109011B1 - Imaging lens - Google Patents

Abstract

The imaging lens according to the first embodiment of the present invention includes, in order from the object side, a first lens that is both convex having a positive refractive power; A second lens having a positive refractive power; And a third lens having negative (−) refractive power. When the third lens has a refractive index of n3, it is characterized by satisfying a conditional expression of 1.6 <n3 <1.7.

Description

Imaging lens {Imaging lens}

The present invention relates to an imaging lens.

2. Description of the Related Art In recent years, demands for a small camera module are increasing for various multimedia fields such as tablet computers, camera phones, PDAs, smart phones, and toys, and also for image input devices such as surveillance cameras or video tape recorder information terminals. In particular, smart phones are in a trend of developing small-sized camera modules according to an increase in demand from consumers who prefer a compact design.

Such a camera module is manufactured using an image sensor chip of CCD or CMOS, condensing an object through a lens on the image sensor chip, converting an optical signal into an electrical signal, and displaying the object on a display medium such as an LCD display device. So that the video is delivered.

The most important component for the camera module to obtain an image is a lens that forms an image. In recent years, the thinning of the thickness of the portable terminal is required, and parts for performing various functions are mounted on the portable terminal. Accordingly, various researches and technology developments have been made to pursue the thinning of the imaging lens optical system of the camera module for a mobile terminal. In particular, if the actuator performing the autofocusing function is changed to a single lens moving method instead of using a conventional voice coil motor, many studies have been conducted on this since it is advantageous for miniaturization of the camera module.

Republic of Korea Patent Publication No. 10-2012-0094729 (2012.08.27.) Republic of Korea Registered Patent No. 10-1171517 (2012.07.27.)

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

The imaging lens according to the first embodiment of the present invention includes, in order from the object side, a first lens that is both convex having a positive refractive power; A second lens having a positive refractive power; And a third lens having negative (−) refractive power. When the third lens has a refractive index of n3, it is characterized by satisfying a conditional expression of 1.6 <n3 <1.7.

The first lens may have the smallest refractive index.

The second lens may be provided in a meniscus shape having a convex surface toward the image side.

The third lens may be provided in the form of a meniscus having convex surfaces on both sides of the object.

The second and third lenses may be formed of high refractive lenses having a refractive index of 1.6 or more.

All of the first to third lenses may have an aspherical surface.

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

When the thickness of the entire optical system is Σd, 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.

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, a conditional expression of 0.70 <d1 / d2 <0.95 can be satisfied.

The imaging lens according to the second embodiment of the present invention includes, in order from the object side, a first lens having a positive refractive power; A second lens having a negative refractive power; And a third lens having negative (−) refractive power. When the refractive index of the third lens is n3, a conditional expression of 1.6 <n3 <1.7 may be satisfied.

The first lens may be provided in the form of a meniscus having a convex surface toward the object.

The second lens may be provided in a meniscus shape having a convex surface toward the image side.

The third lens may be provided in the form of a meniscus having a convex surface toward the object.

The second and third lenses may be formed of high refractive lenses having a refractive index of 1.6 or more.

All of the first to third lenses may have an aspherical surface.

The first lens may have a stop surface formed on any one of an object side surface and an image side surface.

The Abbe numbers of the second and third lenses may be formed in the same way.

When the Abbe numbers of the first to third lenses are v1, v2, and v3, a conditional expression of (v1-v2) / v3> 1 may be satisfied.

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

When the thickness of the entire optical system is Σd and the focal length of the entire optical system is f, the conditional expression of 0.5 <Σd / 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, a conditional expression of 0.5 <f1 / f <1.5 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, a conditional expression of 0.70 <d1 / d2 <0.95 can be satisfied.

When the curvature of the first surface of the second lens is R3 and the focal length of the entire optical system is f, the conditional expression of R3 / f <-0.5 can be satisfied.

When the refractive index of the second lens is N2 and the refractive index of the third lens is N3, a conditional expression of 1.6 <N2, N3 <1.7 can be satisfied.

When the focal length of the entire optical system is f and the effective diameter is D, the conditional expression of FNO = f / D, 2.2 <FNO <3.0 can be satisfied.

When the total length of the optical system is TL and the focal length of the entire optical system is f, the conditional expression of TL / f> 1 can be satisfied.

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

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

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

1 is a configuration diagram of an imaging lens according to a first embodiment of the present invention, Figure 2 is a graph showing spherical aberration, astigmatism and distortion of the imaging lens according to the first embodiment of the present invention, Figure 3 is a view The configuration diagram of the imaging lens according to the second embodiment of the present invention, and FIG. 4 is a graph showing spherical aberration, astigmatism and distortion of the imaging lens according to the second embodiment of the present invention.

In the imaging lens of the camera module according to an embodiment of the present invention, an imaging lens including a plurality of lenses may be disposed around an optical axis. At this time, the thickness, size, and shape of the lenses shown in FIGS. 1 and 3 are exaggerated for explanation, and the spherical or aspherical shape is presented as an example and is not limited to this shape.

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

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

The light corresponding to the image information of the subject may pass through the first lens 10, the second lens 20, the third lens 30, and the filter 40, and enter the side of the image sensor, not shown.

In the following description of the configuration of each lens, the term “object side” refers to the surface of the lens facing the object side with respect to the optical axis, and the term “image side” refers to the lens facing the imaging surface based on the optical axis. It means the side of.

The feature of the present invention is to form the optical system of the ultra-thin camera module by configuring the three lenses described above.

The first lens 10 has a positive (+) refractive power, the second lens 20 has a positive (+) refractive power, and the third lens 30 has a negative (-) refractive power. Can be.

Here, the first lens 10 is a convex lens on both sides having a convex surface toward the object, and the second lens 20 may be formed in a meniscus shape having a convex surface toward the image side, and the third lens 30 may be formed in the form of a meniscus having a convex surface toward the object.

In this case, the first lens 10, the second lens 20, and the third lens 30 may have aspherical surfaces on all surfaces.

In addition, the second lens 20 and the third lens 30 may be formed of a high refractive material having a refractive index of 1.6 or more.

The filter 40 is at least one of an optical filter such as an infrared cut filter and a cover glass. As the filter 40, when an infrared blocking filter is applied, infrared rays emitted from external light may be blocked from being transmitted to an image sensor (not shown). The infrared cut filter transmits visible light, but does not transmit light in the infrared wavelength band.

The conditional expressions and examples described below are preferred examples of increasing the effect of action, and it will be apparent to those skilled in the art that the present invention is not necessarily composed of the following conditions. For example, even if only some of the conditional expressions described below are satisfied, the lens configuration of the present invention may have an increased effect.

[Conditional Expression 1] 0.5 <Σd / 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

N2 is the refractive index of the second lens

d1 is the center thickness of the first lens

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

Table 1 shows an example that satisfies the above conditional expression.

value f 2.65 f1 2.14 f2 26.78 f3 -3.71 | f2 / f1 | 12.5 ∑T 3.41 ∑T / f 1.33

here,

f is the focal length of the optical system,

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

ΣT is the distance from the first lens object side surface to the imaging surface.

Table 2 below shows the lens surface data of each lens surface.

R D N Material (reference) One* 1.14 0.69 1.53 Plastic (P) 2* -300 0.10 (Stop) 0.00 0.43 4* -1.51 0.75 1.64 Plastic (P) 5 * -1.65 0.1 6 * 5.56 0.78 1.64 Plastic (P) 7 * 1.57 0.25 8* 0 0.21 1.52 Plastic (P) 9 * 0 0.100 image 0.00 0.00

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

Table 3 below shows the values of the aspheric coefficients of each lens in the embodiment of Table 2 above.

k A B C D One* -0.255798 -.126330E-01 -.317299E-03 -.199677E + 00 0.247382E + 00 2* -0.512754e23 -.596831E-01 -.403916E + 00 0.126808E + 01 -.326366E + 01 4* -3.314001 -.324518E + 00 0.399115E + 00 -.883348E + 01 0.437213E + 02 5 * 0.160917 -.233820E + 00 0.984839E + 00 -.200409E + 01 0.279993E + 01 6 * -410.636463 -.270169E + 00 0.232766E + 00 -.256957E-01 -.459275E-02 7 * -0.699115 -.280265E + 00 0.153215E + 00 -.637520E-0 0.139237E-01

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 aberration in order from the left. In FIG. 2, it is interpreted that as the curves approach the Y-axis, the aberration correction function is good. In the illustrated aberration diagram, since the values of the images appear in the vicinity of the Y axis in almost all fields, spherical aberration, astigmatism, and distortion aberration all show excellent values.

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

Referring to FIG. 3, the camera lens module of the present invention may include an aperture, a first lens 10, a second lens 20, a third lens 30, and a filter 40 in order from the object side. have.

The light corresponding to the image information of the subject may pass through the first lens 10, the second lens 20, the third lens 30, and the filter 40, and enter the side of the image sensor, not shown.

The difference between the above-described first and second embodiments is in the arrangement of the refractive power of each lens.

The first lens 10 has a positive (+) refractive power, the second lens 20 has a negative (-) refractive power, and the third lens 30 has a negative (-) refractive power. Can be.

Here, the first lens 10 is a meniscus shape having a convex surface toward the object, and the second lens 20 may be formed in a meniscus shape having a convex surface toward the image side, and the third lens ( 30) may be formed in the form of a meniscus having a convex surface toward the object.

In this case, the first lens 10, the second lens 20, and the third lens 30 may be formed of a lens having at least one surface aspherical.

The first lens 10 may have the smallest refractive index, and the second lens 20 and the third lens 30 may be formed of a high refractive material having a refractive index of 1.6 or more. At this time, the second and third lenses 20 and 30 may have the same Abbe number.

The conditional expressions and examples described below are preferred examples of increasing the effect of action, and it will be apparent to those skilled in the art that the present invention is not necessarily composed of the following conditions. For example, even if only some of the conditional expressions described below are satisfied, the lens configuration of the present invention may have an increased effect.

[Conditional Expression 4] (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 5] 0.5 <ΣT / f <1.5,

[Condition 6] 0.5 <Σd / f <1.5,

[Conditional Expression 7] 0.5 <f1 / f <1.5,

[Conditional Expression 8] 0.70 <d1 / d2 <0.95,

[Conditional Expression 9] R3 / f <-0.5,

[Conditional Expression 10] 1.6 <N2, N3 <1.7,

[Conditional Expression 11] FNO = f / D

[Conditional Expression 12] 2.2 <FNO <3.0,

[Conditional Expression 13] TL / f> 1

here,

R3 is the curvature of the first side of the second lens,

TL is the total length of the optical system,

ΣT is the distance from the first lens object side surface to the imaging surface,

f is the total optical system focal length,

f1 is the focal length of the first lens,

N2 is the refractive index of the second lens,

Σd is the total optical system thickness,

d1 is the center thickness of the first lens,

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

Only when the above conditional expression is satisfied, a high resolution lens optical system can be formed.

Table 4 shows an example that satisfies the above conditional expression.

value F 2.56 f1 2.42 f2 -17.28 f3 -13.34 | f2 / f1 | 7.14 ∑T 3.23 ∑T / f 1.26

here,

F is the focal length of the optical system

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

ΣT is the distance from the first lens object side surface to the imaging surface.

Table 5 below shows the lens surface data of each lens.

R D N Material (reference) One* 0.98 0.59 1.53 Plastic (P) 2* 3.37 0.16 (Stop) 0.00 0.25 4* -2.09 0.58 1.64 Plastic (P) 5 * -2.86 0.32 6 * 1.70 0.69 1.64 Plastic (P) 7 * 1.19 0.30 8* 0 0.21 1.52 Plastic (P) 9 * 0 0.10 image 0.00 0.00

In Table 5 and Table 6 below, * in the side of the surface number indicates an aspherical surface.

The following Table 6 shows the values of the aspheric coefficients of each lens in the Example of Table 5 above.

k A B C D One* -0.055095 0.914706E-02 0.663337E-01 -.998979E-01 0.203596E + 00 2*  -55.779083 0.212173E + 00 -.378335E + 00 0.816366E + 00 -.145359E + 01 4* -5.866942 -.316010E + 00 -.821756E + 00 0.313202E + 01 -.924147E + 01 5 *  2.320822 -.405899E + 00 0.105896E + 01 -.212787E + 01 0.246252E + 01 6 * -20.346180 -.217572E + 00 0.113045E + 00 -.231635E-01 0.376088E-02 7 * -8.328981 -.823764E-01 0.270507E-01 -.443559E-02 -.933466E-03

4 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 aberration in order from the left. In FIG. 4, it is interpreted that as the curves approach the Y-axis, the aberration correction function is good. In the illustrated aberration diagram, since the values of the images appear in the vicinity of the Y axis in almost all fields, spherical aberration, astigmatism, and distortion aberration all show excellent values.

The embodiments of the invention described above and illustrated in the drawings should not be construed as limiting the technical spirit of the invention. The protection scope of the present invention is limited only by the matters described in the claims, and a person having ordinary knowledge in the technical field of the present invention can improve and modify the technical spirit of the present invention in various forms. Therefore, such improvements and modifications will fall within the protection scope of the present invention as long as it is apparent to those skilled in the art.

10; First lens 20; 2nd lens
30; Third lens 40; Infrared cut filter

Claims (26)

In order from the object side,
A first lens having a positive refractive power;
A second lens having a positive refractive power; And
It includes a third lens having a negative (-) refractive power,
The refractive index of the third lens is between 1.6 and 1.7,
The refractive index of the first lens is smaller than the refractive index of the second and third lenses,
The refractive index of the second lens is 1.6 or more imaging lens.
The method of claim 1, wherein the first lens,
Biconvex imaging lens.
The method of claim 1, wherein the second lens,
An imaging lens in the form of a meniscus having a convex surface toward the image side.
The method of claim 1, wherein the third lens,
An imaging lens in the form of a meniscus having a convex surface toward the object.
delete According to claim 1,
The first to third lenses all have an aspherical imaging lens.
According to claim 1,
When the thickness of the entire optical system is Σd and the focal length of the entire optical system is f,
0.5 <Σd / f <1.5
Imaging lens that satisfies the conditional expression of
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
Imaging lens that satisfies the conditional expression of
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
Imaging lens that satisfies the conditional expression of
In order from the object side,
A first lens having a positive refractive power;
A second lens having a negative refractive power; And
It includes a third lens having a negative (-) refractive power,
The refractive index of the third lens is between 1.6 and 1.7,
The refractive index of the first lens is smaller than the refractive index of the second and third lenses,
The refractive index of the second lens is 1.6 or more imaging lens.
The method of claim 10, wherein the first lens,
An imaging lens in the form of a meniscus having a convex surface toward the object.
The method of claim 10, wherein the second lens,
An imaging lens in the form of a meniscus having a convex surface toward the image side.
The method of claim 10, wherein the third lens,
An imaging lens in the form of a meniscus having a convex surface toward the object.
delete The method of claim 10,
The first to third lenses all have an aspherical imaging lens.
The method of claim 10, wherein the first lens,
An imaging lens in which a stop surface is formed on either an object side or an image side.
The method of claim 10,
The Abbe number of the second and third lenses is the same imaging lens.
The method of claim 10,
When the Abbe number of the first to third lenses is v1, v2, v3,
(v1-v2) / v3> 1
Imaging lens that satisfies the conditional expression of
The method of claim 10,
When the distance from the object-side surface of the first lens to the imaging surface is ΣT, and the focal length of the entire optical system is f,
0.5 <ΣT / f <1.5
Imaging lens that satisfies the conditional expression of
The method of claim 10,
When the thickness of the entire optical system is Σd and the focal length of the entire optical system is f,
0.5 <Σd / f <1.5
Imaging lens that satisfies the conditional expression of
The method of claim 10,
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
Imaging lens that satisfies the conditional expression of
The method of claim 10,
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
Imaging lens that satisfies the conditional expression of
The method of claim 10,
When the curvature of the first surface of the second lens is R3 and the focal length of the entire optical system is f,
R3 / f <-0.5
Imaging lens that satisfies the conditional expression of
The method of claim 10,
When the refractive index of the second lens is N2 and the refractive index of the third lens is N3,
1.6 <N2, N3 <1.7
Imaging lens that satisfies the conditional expression of
The method of claim 10,
When the focal length of the entire optical system is f and the effective diameter is D,
FNO = f / D,
2.2 <FNO <3.0
Imaging lens that satisfies the conditional expression of
The method of claim 10,
When the total length of the optical system is TL and the focal length of the entire optical system is f,
TL / f> 1
Imaging lens that satisfies the conditional expression of

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