KR101532146B1 - Lens module - Google Patents

Abstract

[조건식 2]

(조건식 1에서 Nd1는 제1렌즈의 굴절률이고, Nd2는 제2렌즈의 굴절률이고, 조건식 2에서 R5는 제3렌즈에서 물체측면의 곡률 반지름이고, R6S는 제3렌즈에서 상측면의 유효구경(clear aperture)에서의 스윕 각도(sweep angle)이다)The lens module of the present invention comprises: a first lens having a positive refractive power; A second lens having positive refractive power; And a third lens having a negative refracting power and having an object side concave shape; Wherein the first lens satisfies the conditional expression 1, the third lens satisfies the conditional expression 2, and the thickness of the center of the optical axis of the second lens may be greater than the thickness of the center of the optical axis of the first lens.
[Conditional expression 1]

[Conditional expression 2]

(In the conditional expression 1, Nd1 is the refractive index of the first lens, Nd2 is the refractive index of the second lens, R5 is the radius of curvature of the object side surface in the third lens, R6S is the effective aperture diameter clear aperture (sweep angle)

Description

A lens module {Lens module}

The present invention relates to a lens module, and more particularly, to a lens module capable of forming a high-resolution optical system and a compact optical system.

In recent years, all electronic devices are becoming smaller and lighter, and parts mounted on electronic devices are becoming smaller. Portable telephones are an example of a representative electronic device according to this trend.

Most portable telephones used in recent years are equipped with cameras. However, in recent years, the camera has a lens module including a plurality of lenses for improving the resolution, so there is a limitation in weight and size of the camera.

Recently, some lenses constituting the lens module are made of a plastic material that is lighter than glass.

However, since it is difficult to improve the chromatic aberration of a plastic lens compared to a glass lens, it is difficult to manufacture a high-resolution lens module using a plastic lens.

In addition, since plastic lenses must have a predetermined thickness for mass production, there are many restrictions in designing a high-resolution optical system.

JP 2010-060833 A JP 2005-017358 A KR 2008-039094 A

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to provide a lens module in which a high-resolution optical system can be composed of plastic lenses.

According to an aspect of the present invention, there is provided a lens module including: a first lens having positive refractive power; A second lens having positive refractive power; And a third lens having a negative refracting power and having a concave shape on an object side, wherein the first lens satisfies the conditional expression 1, the third lens satisfies the conditional expression 2, and the center of the optical axis of the second lens May be greater than the thickness of the center of the optical axis of the first lens.

[Conditional expression 1]

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[Conditional expression 2]

(In the conditional expression 1, Nd1 is the refractive index of the first lens, Nd2 is the refractive index of the second lens, R5 in the conditional expression 2 is the object side surface of the third lens, and R6S is the sweep angle of the third lens)

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In the lens module according to an embodiment of the present invention, the object side of the first lens is convex to the object side, and the upper side of the first lens may be concave with respect to the image side.

In the lens module according to an embodiment of the present invention, the first lens may satisfy the conditional expression (3).

[Conditional expression 3]

(In the conditional expression 3, t1 is the thickness of the edge portion of the first lens, and T1 is the thickness of the central portion of the first lens through which the optical axis passes)

In the lens module according to an embodiment of the present invention, the first lens, the second lens, and the third lens may all be plastic materials.

In the lens module according to an embodiment of the present invention, the first lens, the second lens, and the third lens may all have the same Abbe value.

The present invention can constitute a high-resolution optical system with a plastic lens, so that mass production of the lens module is easy.

1 is a configuration diagram of a lens module according to an embodiment of the present invention,
FIG. 2 is a graph showing MTF characteristics of the lens module shown in FIG. 1,
FIG. 3 is a graph illustrating aberration characteristics of the lens module shown in FIG. 1,
4 to 12 are graphs showing characteristics according to other embodiments of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

In describing the present invention, it is to be understood that the terminology used herein is for the purpose of describing the present invention only and is not intended to limit the technical scope of the present invention.

In addition, throughout the specification, a configuration is referred to as being 'connected' to another configuration, including not only when the configurations are directly connected to each other, but also when they are indirectly connected with each other . Also, to "include" an element means that it may include other elements, rather than excluding other elements, unless specifically stated otherwise.

FIG. 1 is a configuration diagram of a lens module according to an embodiment of the present invention, FIG. 2 is a graph showing MTF characteristics of the lens module shown in FIG. 1, and FIG. 3 is a graph showing aberration characteristics of the lens module shown in FIG. And FIGS. 4 to 12 are graphs showing characteristics according to other embodiments of the present invention.

The lens module 100 according to the first embodiment includes a first lens 10, a second lens 20 and a third lens 30 and selectively includes a filter member 40 and a diaphragm 50 . Here, the first lens 10 to the third lens 30 may be arranged in order from the object side to the image side.

The first lens 10, the second lens 20, and the third lens 30 may all be made of a plastic material. If all the lenses 10, 20 and 30 constituting the lens module 100 are made of a plastic material, the manufacturing cost of the lens module 100 can be reduced, Can be advantageous.

The first lens 10 may be disposed closest to the object side in the lens module 100. [ The first lens 10 may have a positive refractive power as a whole. In other words, the first surface 12 (the object side surface) of the first lens 10 may have a convex shape toward the object side, and the second surface 14 (the upper surface side) may have a concave shape with respect to the image side.

The first lens 10 thus formed may have a meniscus shape that is convex on the object side as a whole. At least one of the first surface 12 and the second surface 14 of the first lens 10 may be an aspherical surface. However, both the first surface 12 and the second surface 14 may be aspherical, if necessary.

On the other hand, the first lens 10 has a thickness t1 and a thickness t1 of the edge portion (exactly, the outermost portion through which the effective light passes on the first surface 12 of the first lens 10) May be different from each other. Specifically, the thickness of the first lens 10 can satisfy Equation (1).

Equation (1) can be used in a numerical range that defines the effective thickness of the first lens 10. That is, when the first lens 10 is made of a plastic material, if the first lens 10 is too thin, accurate molding may not be possible. On the other hand, if the first lens 10 is relatively too thick, the length of the optical system constituting the lens module 100 (the distance from the first lens to the third lens) becomes large, It can be interrupted.

The Applicant recognizes this point and limits the thickness of the first lens 10 through the equation (1).

The second lens 20 may be disposed on the back (upper side) of the first lens 10. The second lens 20 may have a positive refractive power as a whole and may be made of a plastic material as in the case of the first lens 10.

The first surface 22 (object side surface) of the second lens 20 may be concave and the second surface 24 (upper surface side) may be convex upward. At least one of the first surface 22 and the second surface 24 of the second lens 20 may be aspherical and if necessary both the first surface 22 and the second surface 24 may be aspherical Lt; / RTI >

The second lens 20 may have substantially the same refractive index as the first lens 10. In other words, the second lens 20 may have a refractive index satisfying the expression (2), and may have the same Abbe value as the first lens 10.

(Where Nd1 is the refractive index of the first lens and Nd2 is the refractive index of the second lens)

As described above, when the refractive index Nd2 of the second lens 20 and the refractive index Nd1 of the first lens 10 satisfy the expression (2), it is easy to manufacture the first lens 10 and the second lens 20 .

That is, when the first lens 10 and the second lens 20 satisfy the condition of the expression (2), the first lens 10 and the second lens 20 can be made of the same material, And the second lens 20 can be collectively produced, and thus the production cost of the first lens 10 and the second lens 20 can be reduced.

In addition, if the refractive index and the Abbe value of the first lens 10 and the second lens 20 are the same or similar, the optical design of the lens module 100 is easy, so that the production cost of the lens module 100 can be effectively reduced .

The third lens 30 may be disposed between the second lens 20 and the image sensor 60. [ The third lens 30 may have a negative refracting power as a whole, and may be made of a plastic material so as to be easily manufactured.

The first surface 32 (object side surface) of the third lens 30 may be generally planar or concave. The second surface 34 (upper surface) of the third lens 30 may be concave in the optical axis portion and convex in the vicinity of the edge. That is, the second surface 34 of the third lens 30 may have one or more inflection points.

In addition, the third lens 30 can satisfy Equation (3). That is, the first surface 32 and the second surface 34 of the third lens 30 may have a shape satisfying Equation (3). When the shape of the third lens 30 does not satisfy the expression (3), the light incident on the third lens 30 is reflected by the third lens 30 from the second surface 34 of the third lens 30, To the first side 32 of the substrate.

(Where R5 is the radius of curvature of the first surface in the third lens and R6S is the sweep angle in the third lens at the clear aperture of the second surface)

That is, Equation (3) is a conditional expression for minimizing the reflection of the inner surface of the third lens 30.

It is ideal that the light incident on the lens module is refracted while passing through the lens to form an image on the image sensor. However, depending on the material of the lens, inner reflection may occur. For example, incident light that has passed through the first lens and the second lens in the lens module composed of three lenses tends to cause internal reflection to be reflected toward the object side in the vicinity of the edge of the third lens having the inflection point.

The present invention is for minimizing the inner reflection, and the problem of reflection on the inner surface can be solved by limiting the shape of the third lens 30 to Equation (3).

The filter member 40 may be disposed between the third lens 30 and the image sensor 60.

The filter member 40 may be an IR filter for blocking infrared rays, and may be made of a glass material. Further, the filter member 40 may be integrally formed with the image sensor 60, in which case the lens module 100 may be omitted.

The diaphragm 50 may be disposed in front of the first lens 10 (in the object side direction). The diaphragm 50 can improve the resolution of the image sensor 60 by adjusting the amount of light incident on the lens module 100.

The diaphragm 50 may be formed integrally with the first lens 10. In this case, the diaphragm 50 may be a light-shielding film integrally formed when the first lens 10 is molded.

Although the diaphragm 50 is shown as being disposed in front of the first lens 10 in the present embodiment, the diaphragm 50 may be disposed between the first lens 10 and the second lens 20 or between the second lens 20 And the third lens 30, as shown in Fig.

Tables 1 to 8 below show numerical values for various embodiments of the lens module 100 having the above configuration.

(Example 1)

In Example 1, the first lens 10 and the second lens 20 had the same refractive index of 1.544, and the Abbe values of the first lens 10 and the second lens 20 were 56, which is the same. In addition, the refractive index and the Abbe's value of the third lens 30 were 1.544 and 56, which were the same as those of the first lens 10 and the second lens 20.

In this embodiment configured as described above, the shape of the first lens 10 satisfies the expression (1), the refractive indexes of the first lens 10 and the second lens 20 satisfy the expression (2) 30) satisfies the expression (3).

Therefore, the present embodiment shows a relatively excellent MTF characteristic and a chromatic aberration curve as shown in FIGS.

(Example 2)

In Example 2, the refractive index and Abbe value of the first lens 10, the second lens 20, and the third lens 30 were all 1.544 and 56, as in Example 1, and the conditions of Equations 1 to 3 Respectively.

However, in this embodiment, the shape of the third lens 30 is changed and the characteristics thereof are compared with the embodiments. That is, in the present embodiment, the first surface 32 of the first lens 30 has a relatively large curvature radius (-15.1353) than that of Embodiment 1, and the second surface 34 of the third lens 30 has a curvature radius Had a sweep angle (35.8077) greater than that of Example 1.

However, the MTF characteristic and the chromatic aberration curve of the present embodiment having such a configuration are not significantly different from those of the first embodiment as shown in Figs. 5 and 6.

(Examples 3 and 4)

Embodiments 3 and 4 have experimented with an optical system that increases the sweep angle on the second surface 34 instead of gradually reducing the radius of curvature of the first surface 32 of the third lens 30.

Accordingly, the R5 / R6S values of Examples 3 and 4 were -0.2853 and -0.2583, respectively, which were close to the limiting values shown in Equation (3).

However, as can be seen from FIGS. 9 to 12, the MTF characteristic and the chromatic aberration curve of these embodiments can have a similar form to those of the other embodiments.

Table 9 is a table showing the main numerical values of the embodiments related to Equations (1) to (3).

The embodiments according to the present invention satisfy all of the numerical conditions (Equations 1 to 3) presented in the present invention as shown in Table 9, and accordingly, as shown in FIGS. 1 to 12, The chromatic aberration curves are shown.

Therefore, according to the present invention, it is possible to realize a lens module having a high resolution by using a plastic lens which is easy to manufacture, thereby lowering the manufacturing cost of the lens module.

In addition, the lens module of the present invention having such characteristics can have a TTL (distance from the first surface of the first lens to the image surface, distance from the surface No. 2 to the surface No. 10) of less than 2.9 [mm]. For example, the lens module according to the first to third embodiments may have a TTL of 2.887, 2.832, 2.884. Therefore, the lens module of the present invention can be advantageous for miniaturization.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the inventions And various modifications may be made. For example, various features described in the foregoing embodiments can be applied in combination with other embodiments unless the description to the contrary is explicitly stated.

100 lens module
10 First lens
20 Second lens
30 Third lens
40 Filter element (or cover glass)
50 aperture
60 Image Sensor

Claims (7)

A first lens having positive refractive power;
A second lens having positive refractive power; And
A third lens having a negative refracting power and having an object side concave shape;
Lt; / RTI >
The first lens satisfies conditional expression 1, the third lens satisfies conditional expression 2,
Wherein the thickness of the center of the optical axis of the second lens is larger than the thickness of the center of the optical axis of the first lens.
[Conditional expression 1]

[Conditional expression 2]

(In the conditional expression 1, Nd1 is the refractive index of the first lens, Nd2 is the refractive index of the second lens, R5 is the radius of curvature of the object side surface in the third lens, R6S is the effective aperture diameter clear aperture (sweep angle)
delete delete The method according to claim 1,
Wherein an object side surface of the first lens is convex to the object side and an upper surface side of the first lens is concave shape with respect to the image side.
5. The method of claim 4,
Wherein the first lens satisfies the condition (3).
[Conditional expression 3]

(In the conditional expression 3, t1 is the thickness of the edge portion of the first lens, and T1 is the thickness of the central portion of the first lens through which the optical axis passes)
The method according to claim 1,
Wherein the first lens, the second lens, and the third lens are all plastic materials.
The method according to claim 1,
Wherein the first lens, the second lens, and the third lens all have an Abbe value of the same size.

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