KR102526440B1 - Optical Imaging System - Google Patents

Abstract

An imaging optical system of the present invention includes a first lens having positive refractive power; a second lens having positive refractive power; a third lens having positive refractive power; a fourth lens having negative refractive power; A fifth lens having a positive refractive power and having a concave object side surface; and a sixth lens having negative refractive power and having an inflection point formed on an image side surface, wherein the first to sixth lenses are sequentially disposed from the object side toward the image plane.

Description

Imaging optical system {Optical Imaging System}

The present invention relates to an imaging optical system composed of six lenses.

A small camera is mounted on a portable terminal. For example, cameras may be mounted on the front and rear surfaces of the mobile phone, respectively. Among them, the first camera mounted on the front of the portable phone is mainly used to photograph a short distance, and the second camera mounted on the rear is mainly used to photograph a long distance. For this reason, the first camera is composed of an optical system having a relatively lower resolution than the second camera.

However, as the usage rate of the first camera mounted on the front of the mobile phone increases, the first camera having a view angle suitable for short distance shooting while having high resolution and brightness like the second camera and an imaging optical system that can be mounted on the camera development is required.

KR 2014-0035829 A US 2013-0003193 A1 US 2013-0335833 A1

An object of the present invention is to provide an imaging optical system having high resolution.

An imaging optical system for achieving the above object includes a first lens having positive refractive power; a second lens having positive refractive power; a third lens having positive refractive power; a fourth lens having negative refractive power; A fifth lens having a positive refractive power and having a concave object side surface; and a sixth lens having negative refractive power and having an inflection point formed on an image side surface, wherein the first to sixth lenses are sequentially disposed from the object side toward the image plane.

The present invention can implement an imaging optical system having high resolution and high brightness.

1 is a configuration diagram of an imaging optical system according to a first embodiment of the present invention;
2 is a graph showing an aberration curve of the imaging optical system shown in FIG. 1;
3 is a graph showing an MTF curve of the imaging optical system shown in FIG. 1;
4 is a table showing lens characteristics of the imaging optical system shown in FIG. 1;
5 is a table showing aspheric characteristics of the imaging optical system shown in FIG. 1;
6 is a configuration diagram of an imaging optical system according to a second embodiment of the present invention;
7 is a graph showing an aberration curve of the imaging optical system shown in FIG. 6;
8 is a graph showing an MTF curve of the imaging optical system shown in FIG. 6;
9 is a table showing lens characteristics of the imaging optical system shown in FIG. 6;
10 is a table showing aspherical characteristics of the imaging optical system shown in FIG. 6;
11 is a configuration diagram of an imaging optical system according to a third embodiment of the present invention;
12 is a graph showing an aberration curve of the imaging optical system shown in FIG. 11;
13 is a graph showing an MTF curve of the imaging optical system shown in FIG. 11;
14 is a table showing lens characteristics of the imaging optical system shown in FIG. 11;
15 is a table showing aspheric characteristics of the imaging optical system shown in FIG. 11;
16 is a configuration diagram of an imaging optical system according to a fourth embodiment of the present invention;
17 is a graph showing an aberration curve of the imaging optical system shown in FIG. 16;
18 is a graph showing an MTF curve of the imaging optical system shown in FIG. 16;
19 is a table showing lens characteristics of the imaging optical system shown in FIG. 16;
20 is a table showing aspheric characteristics of the imaging optical system shown in FIG. 16;

Hereinafter, preferred embodiments of the present invention will be described in detail based on the accompanying drawings.

In describing the present invention below, terms referring to the components of the present invention are named in consideration of the functions of each component, so they should not be understood as limiting the technical components of the present invention.

In addition, throughout the specification, that a component is 'connected' to another component includes not only the case where these components are 'directly connected', but also the case where they are 'indirectly connected' through other components. means that In addition, 'including' a certain component means that other components may be further included, rather than excluding other components unless otherwise stated.

In addition, in this specification, the first lens refers to a lens closest to the object (or subject), and the sixth lens refers to a lens closest to the image surface (or image sensor). In this specification, the units of the radius of curvature, thickness, TTL, Img HT (half of the diagonal length of the image surface), and focal length of the lens are all units of mm. In addition, the thickness of the lens, the distance between the lenses, and the TTL are distances from the optical axis of the lenses. In addition, in the description of the shape of the lens, the convex shape of one surface means that the optical axis portion of the corresponding surface is convex, and the concave shape of one surface means that the optical axis portion of the corresponding surface is concave. Therefore, even if one surface of the lens is described as having a convex shape, the edge portion of the lens may be concave. Likewise, even if one surface of the lens is described as having a concave shape, the edge portion of the lens may be convex.

The imaging optical system includes 6 lenses sequentially disposed in the image plane direction from the object side. Next, each lens is described in detail.

The first lens has refractive power. For example, the first lens has positive refractive power.

The first lens has a shape including a flat surface. For example, the paraxial region of the object side of the first lens may be flat. The first lens thus formed is easy to process.

The first lens includes an aspherical surface. For example, both surfaces of the first lens may be aspherical. The first lens may be made of a material having high light transmittance and excellent workability. For example, the first lens may be made of a plastic material. However, the material of the first lens is not limited to a plastic material. For example, the first lens may be made of a glass material.

The second lens has refractive power. For example, the second lens has positive refractive power.

At least one surface of the second lens has a convex shape. For example, the second lens may have a shape in which the side of the object is convex.

The second lens includes an aspheric surface. For example, the object side of the second lens may have an aspheric surface. The second lens may be made of a material having high light transmittance and excellent workability. For example, the second lens may be made of a plastic material. However, the material of the second lens is not limited to plastic. For example, the second lens may be made of a glass material.

The third lens has refractive power. For example, the third lens may have negative refractive power.

At least one surface of the third lens has a convex shape. For example, the third lens may have a convex shape on both sides.

The third lens includes an aspheric surface. For example, an image side surface of the third lens may be an aspherical surface. The third lens may be made of a material having high light transmittance and excellent workability. For example, the third lens may be made of a plastic material. However, the material of the third lens is not limited to plastic. For example, the third lens may be made of a glass material.

The fourth lens has refractive power. For example, the fourth lens has negative refractive power.

The fourth lens has a shape in which one surface is convex. For example, the fourth lens may have a shape in which an object side surface is convex. The fourth lens has a shape having an inflection point. For example, one or more inflection points may be formed on the object side and the image side of the fourth lens.

The fourth lens includes an aspheric surface. For example, both surfaces of the fourth lens may be aspherical. The fourth lens may be made of a material having high light transmittance and excellent workability. For example, the fourth lens may be made of a plastic material. However, the material of the fourth lens is not limited to plastic. For example, the fourth lens may be made of a glass material.

The fifth lens has refractive power. For example, the fifth lens has positive refractive power.

The fifth lens has one surface concave. For example, the fifth lens may have a concave object side surface.

The fifth lens includes an aspheric surface. For example, both surfaces of the fifth lens may be aspherical. The fifth lens may be made of a material having high light transmittance and excellent workability. For example, the fifth lens may be made of a plastic material. However, the material of the fifth lens is not limited to plastic. For example, the fifth lens may be made of a glass material.

The sixth lens has refractive power. For example, the sixth lens has negative refractive power.

The sixth lens may have a shape in which one surface is convex. For example, the sixth lens may have a shape in which an object side surface is convex. The sixth lens may have a shape having an inflection point. For example, one or more inflection points may be formed on both sides of the sixth lens.

The sixth lens includes an aspheric surface. For example, both surfaces of the sixth lens may be aspherical. The sixth lens may be made of a material having high light transmittance and excellent workability. For example, the sixth lens may be made of a plastic material. However, the material of the sixth lens is not limited to plastic. For example, the sixth lens may be made of a glass material.

The first to sixth lenses are made of a material having a refractive index different from that of air. For example, the first to sixth lenses are made of plastic or glass. At least one of the first to sixth lenses has an aspherical shape. For example, all of the first to sixth lenses may have an aspheric shape. Here, the aspherical surface of each lens is expressed by Equation 1.

In Equation 1, c is the reciprocal of the radius of curvature of the corresponding lens, K is the conic constant, r is the distance from an arbitrary point on the aspherical surface to the optical axis, A to J are aspheric constants, and Z (or SAG) is the aspheric surface It is the height in the optical axis direction from an arbitrary point on the image to the apex of the aspherical surface.

The imaging optical system includes a diaphragm. The diaphragm may be disposed between the second lens and the third lens.

The imaging optical system includes a filter. The filter blocks some wavelengths from incident light incident through the first to fifth lenses. For example, the filter may block infrared wavelengths of incident light. Filters can be made thin. To this end, the filter may be made of a plastic material.

The imaging optical system includes an image sensor. The image sensor provides an image surface on which light refracted by lenses can form an image. For example, the surface of the image sensor may form a top surface. The image sensor may be configured to implement high resolution. For example, a unit size of a pixel constituting an image sensor may be 1.12 μm or less.

The imaging optical system may satisfy the following Conditional Expressions.

[Conditional Expression] 0.015 < (TTL/f)/FOV < 0.025

[Conditional expression] BL/f < 0.5

[Conditional expression] R3/f < 0.5

[conditional expression] V1 - V2 < -25

[Conditional Expression] 0.2 < (R7 - R8)/(R7 + R8) < 0.8

[Conditional Expression] 0.4 < (R9 - R10)/(R9 + R10) < 0.6

[Conditional expression] SL/TTL < 0.85

[Conditional expression] D12/TTL < 0.03

[Conditional expression] D56/TTL < 0.85

In the conditional expression, TTL is the distance from the object side of the first lens to the image plane, BL is the distance from the image side of the sixth lens to the image plane, f is the total focal length of the imaging optical system, and R3 is is the radius of curvature of the object side of the second lens, V1 is the Abbe's number of the first lens, V2 is the Abbe's number of the second lens, R7 is the radius of curvature of the object side of the fourth lens, R8 is is the radius of curvature of the image side of the fourth lens, R9 is the radius of curvature of the object side of the fifth lens, R10 is the radius of curvature of the image side of the fifth lens, and SL is the distance from the diaphragm to the image surface; , D12 is the distance from the image side surface of the first lens to the object side surface of the second lens, and D56 is the distance from the image side surface of the fifth lens to the object side surface of the sixth lens. An imaging optical system that satisfies the above Conditional Expressions can be miniaturized and implemented with high resolution.

Next, an imaging optical system according to various embodiments will be described.

First, an imaging optical system according to the first embodiment will be described with reference to FIG. 1 .

The imaging optical system 100 is composed of a plurality of lenses having refractive power. For example, the imaging optical system 100 includes a first lens 110, a second lens 120, a third lens 130, a fourth lens 140, a fifth lens 150, and a sixth lens 160. ) is composed of

The first lens 110 has a positive refractive power, has a paraxial region of an object side surface is flat, and an image side surface is convex. The second lens 120 has a positive refractive power and has a convex object side surface and a concave image side surface. The third lens 130 has a positive refractive power and has a shape in which an object side surface is convex and an image side surface is convex. The fourth lens 140 has negative refractive power and has a convex object side surface and a concave image side surface. In addition, the fourth lens 140 has a shape in which an inflection point is formed. For example, the image side surface of the fourth lens 140 may be concave in the paraxial region and convex in the periphery of the paraxial region. The fifth lens 150 has a positive refractive power and has a concave object side surface and a convex image side surface. The sixth lens 160 has negative refractive power and has a convex object side surface and a concave image side surface. In addition, the sixth lens 160 has a shape in which inflection points are formed on both sides. For example, the object side surface of the sixth lens may be convex in the paraxial region and concave in the periphery of the paraxial region. Similarly, the image side surface of the sixth lens may be concave in the paraxial region and convex in the periphery of the paraxial region.

The imaging optical system 100 includes a diaphragm ST. For example, the diaphragm ST may be disposed between the second lens 120 and the third lens 130 . The diaphragm ST disposed in this way controls the amount of light incident on the upper surface 180 .

The imaging optical system 100 includes a filter 170 . For example, the filter 170 may be disposed between the sixth lens 160 and the image surface 180 . The filter 170 disposed in this way blocks infrared rays from being incident on the upper surface 180 .

The imaging optical system 100 includes an image sensor. The image sensor provides an upper surface 180 on which light refracted through lenses is formed. In addition, the image sensor converts the optical signal reflected on the upper surface 180 into an electrical signal.

The imaging optical system configured as above exhibits aberration characteristics and MTF characteristics as shown in FIGS. 2 and 3 . 4 and 5 are tables showing lens characteristics and aspherical surface characteristics of the imaging optical system according to the present embodiment.

An imaging optical system according to a second embodiment will be described with reference to FIG. 6 .

The imaging optical system 200 is composed of a plurality of lenses having refractive power. For example, the imaging optical system 200 includes a first lens 210, a second lens 220, a third lens 230, a fourth lens 240, a fifth lens 250, and a sixth lens 260. ) is composed of

The first lens 210 has a positive refractive power, has a paraxial region on an object side surface, and has a convex image side surface. The second lens 220 has a positive refractive power and has a convex object side surface and a concave image side surface. The third lens 230 has a positive refractive power and has a shape in which an object side surface is convex and an image side surface is convex. The fourth lens 240 has negative refractive power and has a convex object side surface and a concave image side surface. In addition, the fourth lens 240 has a shape in which an inflection point is formed. For example, the image side surface of the fourth lens 240 may be concave in the paraxial region and convex in the periphery of the paraxial region. The fifth lens 250 has a positive refractive power and has a concave object side surface and a convex image side surface. The sixth lens 260 has negative refractive power and has a convex object side surface and a concave image side surface. In addition, the sixth lens 260 has a shape in which inflection points are formed on both sides. For example, the object side surface of the sixth lens may be convex in the paraxial region and concave in the periphery of the paraxial region. Similarly, the image side surface of the sixth lens may be concave in the paraxial region and convex in the periphery of the paraxial region.

The imaging optical system 200 includes a diaphragm ST. For example, the diaphragm ST may be disposed between the second lens 220 and the third lens 230 . The diaphragm ST disposed as described above controls the amount of light incident on the upper surface 280 .

The imaging optical system 200 includes a filter 270 . For example, the filter 270 may be disposed between the sixth lens 260 and the image surface 280 . The filter 270 disposed in this way blocks infrared rays from being incident on the upper surface 280 .

The imaging optical system 200 includes an image sensor. The image sensor provides an upper surface 280 on which light refracted through lenses is formed. In addition, the image sensor converts the optical signal reflected on the upper surface 280 into an electrical signal.

The imaging optical system configured as above exhibits aberration characteristics and MTF characteristics as shown in FIGS. 7 and 8 . 9 and 10 are tables showing lens characteristics and aspherical surface characteristics of the imaging optical system according to the present embodiment.

An imaging optical system according to a third embodiment will be described with reference to FIG. 11 .

The imaging optical system 300 is composed of a plurality of lenses having refractive power. For example, the imaging optical system 300 includes a first lens 310, a second lens 320, a third lens 330, a fourth lens 340, a fifth lens 350, and a sixth lens 360. ) is composed of

The first lens 310 has a positive refractive power, has a paraxial region on an object side surface, and has a convex image side surface. The second lens 320 has a positive refractive power and has a convex object side surface and a concave image side surface. The third lens 330 has a positive refractive power, and has a shape in which an object side surface is convex and an image side surface is convex. The fourth lens 340 has negative refractive power and has a convex object side surface and a concave image side surface. In addition, the fourth lens 340 has a shape in which an inflection point is formed. For example, an image side surface of the fourth lens 340 may be concave in the paraxial region and convex in the periphery of the paraxial region. The fifth lens 350 has a positive refractive power and has a concave object side surface and a convex image side surface. The sixth lens 360 has negative refractive power and has a convex object side surface and a concave image side surface. In addition, the sixth lens 360 has a shape in which inflection points are formed on both sides. For example, the object side surface of the sixth lens may be convex in the paraxial region and concave in the periphery of the paraxial region. Similarly, the image side surface of the sixth lens may be concave in the paraxial region and convex in the periphery of the paraxial region.

The imaging optical system 300 includes a diaphragm ST. For example, the diaphragm ST may be disposed between the second lens 320 and the third lens 330 . The diaphragm ST disposed as described above controls the amount of light incident on the upper surface 380 .

The imaging optical system 300 includes a filter 370 . For example, the filter 370 may be disposed between the sixth lens 360 and the image surface 380 . The filter 370 disposed in this way blocks infrared rays from being incident on the upper surface 380 .

The imaging optical system 300 includes an image sensor. The image sensor provides an upper surface 380 on which light refracted through lenses is formed. In addition, the image sensor converts the optical signal reflected on the upper surface 380 into an electrical signal.

The imaging optical system configured as above exhibits aberration characteristics and MTF characteristics as shown in FIGS. 12 and 13 . 14 and 15 are tables showing lens characteristics and aspherical surface characteristics of the imaging optical system according to the present embodiment.

An imaging optical system according to a fourth embodiment will be described with reference to FIG. 16 .

The imaging optical system 400 is composed of a plurality of lenses having refractive power. For example, the imaging optical system 400 includes a first lens 410, a second lens 420, a third lens 430, a fourth lens 440, a fifth lens 450, and a sixth lens 460. ) is composed of

The first lens 410 has a positive refractive power, has a paraxial region on an object side surface, and has a convex image side surface. The second lens 420 has a positive refractive power and has a convex object side surface and a concave image side surface. The third lens 430 has a positive refractive power and has a shape in which an object side surface is convex and an image side surface is convex. The fourth lens 440 has negative refractive power and has a convex object side surface and a concave image side surface. In addition, the fourth lens 440 has a shape in which an inflection point is formed. For example, an image side surface of the fourth lens 440 may be concave in the paraxial region and convex in the periphery of the paraxial region. The fifth lens 450 has a positive refractive power and has a concave object side surface and a convex image side surface. The sixth lens 460 has negative refractive power and has a convex object side surface and a concave image side surface. In addition, the sixth lens 460 has a shape in which inflection points are formed on both sides. For example, the object side surface of the sixth lens may be convex in the paraxial region and concave in the periphery of the paraxial region. Similarly, the image side surface of the sixth lens may be concave in the paraxial region and convex in the periphery of the paraxial region.

The imaging optical system 400 includes a diaphragm ST. For example, the diaphragm ST may be disposed between the second lens 420 and the third lens 430 . The diaphragm ST disposed as described above controls the amount of light incident on the upper surface 480 .

The imaging optical system 400 includes a filter 470 . For example, the filter 470 may be disposed between the sixth lens 460 and the image surface 480 . The filter 470 disposed in this way blocks infrared rays from being incident on the upper surface 480 .

The imaging optical system 400 includes an image sensor. The image sensor provides an upper surface 480 on which light refracted through lenses is formed. In addition, the image sensor converts the optical signal reflected on the upper surface 480 into an electrical signal.

The imaging optical system configured as above exhibits aberration characteristics and MTF characteristics as shown in FIGS. 17 and 18 . 19 and 20 are tables showing lens characteristics and aspherical surface characteristics of the imaging optical system according to the present embodiment.

Table 1 shows conditional expression values of imaging optical systems according to the first to fourth embodiments. As can be seen from Table 1 below, the imaging optical systems according to the first to fourth embodiments satisfy all numerical ranges according to conditional expressions described in this specification.

* The present invention is not limited to the embodiments described above, and those of ordinary skill in the art to which the present invention pertains, within the range of not departing from the gist of the technical idea of the present invention described in the claims below. It can be implemented by making various changes.

100, 200, 300, 400 imaging optics
110, 210, 310, 410 1st lens
120, 220, 320, 420 2nd lens
130, 230, 330, 430 3rd lens
140, 240, 340, 440 4th lens
150, 250, 350, 450 5th lens
160, 260, 360, 460 6th lens
170, 270, 370, 470 filters
180, 280, 380, 480 (of image sensor) top surface

Claims (8)

a first lens having positive refractive power;
a second lens having a concave image side surface;
a third lens having refractive power;
a fourth lens having negative refractive power and having a convex object side surface;
a fifth lens having refractive power; and
a sixth lens having negative refractive power, an object side surface being convex, and an inflection point formed on an image side surface;
including,
The first lens to the sixth lens are sequentially disposed from the object side toward the image plane, and satisfy the following conditional expression.
0.2 < (R7 - R8)/(R7 + R8) < 0.8
(In the conditional expression, R7 is the radius of curvature of the object side of the fourth lens, and R8 is the radius of curvature of the image side of the fourth lens) According to claim 1,
The first lens is an imaging optical system having a convex image side surface. According to claim 1,
The fourth lens has a concave image side surface. According to claim 1,
The fifth lens has a convex image side surface. According to claim 1,
The fifth lens has a positive refractive power. According to claim 1,
An imaging optical system that satisfies the following conditional expression.
BL/f < 0.5
(In the conditional expression, BL is the distance from the image side of the sixth lens to the image plane, and f is the total focal length of the imaging optical system) According to claim 1,
An imaging optical system that satisfies the following conditional expression.
R3/f < 0.5
(In the above conditional expression, R3 is the radius of curvature of the object side of the second lens, and f is the total focal length of the imaging optical system) According to claim 1,
An imaging optical system that satisfies the following conditional expression.
D12/TTL < 0.03
(In the conditional expression, D12 is the distance from the image side surface of the first lens to the object side surface of the second lens, and TTL is the distance from the object side surface of the first lens to the image surface)

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