KR102279304B1 - Optical Imaging System - Google Patents

Abstract

An imaging optical system of the present invention includes a first lens having a negative refractive power; a second lens having positive refractive power; a third lens having refractive power; a fourth lens having refractive power; a fifth lens having positive refractive power; a sixth lens having a negative refractive power and having a convex side surface of the object; and a seventh lens having refractive power and an inflection point formed on the image side.

Description

Optical Imaging System

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

Since the surveillance camera for an unmanned aerial vehicle has a large monitoring area and a fairly large distance to the target, an imaging optical system capable of realizing high resolution while having a wide angle of view is required. As a similar example, since a vehicle surveillance camera needs to photograph a vehicle moving rapidly from the front and rear of the vehicle, an imaging optical system capable of realizing high resolution is required.

An imaging optical system made of a glass material may implement a camera having a high resolution. However, an imaging optical system made of a glass material has a considerable weight compared to an imaging optical system made of a plastic material. Therefore, it is difficult to mount it on a small unmanned aerial vehicle, a small terminal, or the like.

In contrast, the optical imaging system made of a plastic material can be lightweight. However, the resolution is lower than that of an imaging optical system made of glass. Therefore, it is necessary to develop an imaging optical system capable of reducing weight while having high resolution.

US 2011-0071807 A JP 5671190 B2 US 2012-0212836 A1

An object of the present invention is to provide an imaging optical system having a short overall length.

An imaging optical system for achieving the above object includes a first lens having a negative refractive power; a second lens having positive refractive power; a third lens having refractive power; a fourth lens having refractive power; a fifth lens having positive refractive power; a sixth lens having a negative refractive power and having a convex side surface of the object; and a seventh lens having refractive power and an inflection point formed on the image side.

The present invention can implement a high-resolution imaging optical system that can be mounted on a small terminal.

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

Hereinafter, a preferred embodiment 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 function of each component, and thus should not be construed as limiting the technical components of the present invention.

In addition, throughout the specification, that a component is 'connected' with another component includes not only the case where these components are 'directly connected', but also the case where the component is 'indirectly connected' with another component interposed therebetween. 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 the present specification, the first lens means a lens closest to the object (or subject), and the fifth lens means a lens closest to the image surface (or image sensor). In the present specification, the units of the radius of curvature of the lens, thickness, TTL, ImgH (1/2 of the diagonal length of the image plane), and focal length are all in mm. In addition, the thickness of the lenses, the distance between the lenses, and the TTL are the 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 means that the optical axis portion of the corresponding surface is concave. Therefore, even if it is described that one surface of the lens has a convex shape, the edge portion of the lens may be concave. Similarly, although one surface of the lens is described as being concave, the edge portion of the lens may be convex.

The imaging optical system includes an optical system composed of a plurality of lenses. For example, the optical system of an imaging optical system consists of 7 lenses which have refractive power. However, the imaging optical system is not composed of only a lens having refractive power. For example, the imaging optical system may include a stop for adjusting the amount of light. In addition, the imaging optical system may include an infrared cut filter for blocking infrared rays. Also, the optical imaging system may further include an image sensor (ie, an imaging device) for converting an image of a subject incident through the optical system into an electrical signal. In addition, the imaging optical system may further include a distance maintaining member for adjusting the distance between the lens and the lens.

The first to seventh lenses are made of a material having a refractive index different from that of air. For example, the first to seventh lenses are made of a plastic or glass material. At least one of the first to seventh lenses has an aspherical shape. For example, only the seventh lens among the first to seventh lenses may have an aspherical shape. Also, at least one surface of the first to seventh lenses may have an aspherical 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 any point on the aspherical surface to the optical axis, A to J are the aspheric constants, and Z (or SAG) is the aspherical surface It is the height in the optical axis direction from any point on the image to the vertex of the aspherical surface.

The imaging optical system includes seven lenses, a filter, an image sensor, and an iris. In the following, the above-described configurations will be described.

The first lens has refractive power. For example, the first lens has a negative refractive power.

At least one surface of the first lens is concave. For example, the first lens has a concave image side surface.

The first lens includes a spherical surface. For example, both surfaces of the first lens may be spherical. 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 glass material. However, the material of the first lens is not limited to glass. For example, the first lens may be made of a plastic material.

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

At least one surface of the second lens is convex. For example, the second lens may have a shape in which both surfaces are convex.

The second lens includes an aspherical surface. For example, the second lens may have an aspherical side surface of the object. The second lens may be made of a material having high light transmittance and excellent processability. 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 positive or negative refractive power.

The third lens has a convex surface. For example, the third lens may have a convex image side.

The third lens includes an aspherical surface. For example, the image side 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 positive or negative refractive power.

The fourth lens has a meniscus shape. For example, the fourth lens may have a concave shape on the side of the object.

The fourth lens includes an aspherical 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.

At least one surface of the fifth lens may be convex. For example, the fifth lens may have a shape in which both sides are convex.

The fifth lens includes an aspherical 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 meniscus shape. For example, the sixth lens may have a concave image side.

The sixth lens may have a shape having an inflection point. For example, inflection points may be formed on both surfaces of the sixth lens.

The sixth lens includes an aspherical 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 seventh lens has refractive power. For example, the seventh lens has positive or negative refractive power.

The seventh lens may have a meniscus shape. For example, the seventh lens may have a concave image side.

The seventh lens may have a shape having an inflection point. For example, inflection points may be formed on both surfaces of the seventh lens.

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

The optical imaging system configured as above may be divided into two lens groups. For example, the first lens and the second lens may form a first lens group, and the third to seventh lenses may form a second lens group. The first lens group is fixed to the object side. Alternatively, the second lens group is movable. For example, the second lens group may be moved between the first lens group and the image plane for focusing.

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.

The filter may be made thin. To this end, the filter may be made of a plastic material.

The image sensor may be configured to implement high resolution. For example, the unit size of pixels constituting the image sensor may be 1.12 μm or less.

The diaphragm is arranged to adjust the amount of light incident on the lens. For example, the diaphragm may be disposed between the second lens and the third lens.

The imaging optical system may satisfy the following conditional expressions.

[Conditional Expression] -80 < {(1/f)*(Y/tanθ)-1}*100 < -20

[Conditional Expression] TL/2Y < 1.3

[Conditional Expression] 1.0 < tanθ < 4.0

[Conditional Expression] 0.4 < R2/f < 1.5

[Conditional Expression] -1.5 < f/f1 < -0.05

[Conditional Expression] 0.3 < f/f2 < 0.8

[Conditional Expression] 1.5 < f/EPD < 3.2

[Conditional Expression] 0.4 < f/fG2 < 1.1

In the above conditional expression, f is the total focal length of the imaging optical system, 2Y is the diagonal length of the image plane, Y is 1/2 of 2Y, θ is the half angle of view of the imaging optical system, and R2 is the radius of curvature of the image side of the first lens , f1 is the focal length of the first lens, f2 is the focal length of the second lens, EPD is the diameter of the entrance pupil, and fG2 is the combined focal length of the second lens group.

An imaging optical system that satisfies the above conditional expressions may realize miniaturization and high resolution.

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

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

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 , a sixth lens 160 , and a seventh lens. It includes an optical system composed of a lens 170 .

In the above lens configuration, the first lens 110 and the second lens 120 form a first lens group G1, and the third lens 130 to the seventh lens 170 are the second lens group. (G2) is formed.

The imaging optical system 100 includes a filter 180 , an image sensor 190 , and an aperture ST. The filter 180 is disposed on the image side of the seventh lens 170 , and the stop ST is disposed between the second lens 120 and the third lens 130 .

In this embodiment, the first lens 110 has a negative refractive power, and has a concave object side and a concave image side. The second lens 120 has a positive refractive power and has a convex shape on both sides. The third lens 130 has a negative refractive power, and has a concave object side and a convex image side. The fourth lens 140 has a positive refractive power, and has a concave object side and a convex image side. The fifth lens 150 has a positive refractive power and has a convex shape on both sides. The sixth lens 160 has a negative refractive power, and has a convex object side and a concave image side. In addition, the sixth lens 160 has a shape in which inflection points are formed on both surfaces. The seventh lens 170 has a positive refractive power, and has a convex object side and a concave image side. In addition, the seventh lens 170 has a shape in which inflection points are formed on both surfaces.

The imaging optical system configured as above exhibits aberration characteristics as shown in FIG. 2 . 3 and 4 are tables showing lens characteristics and aspherical characteristics of the imaging optical system according to the first embodiment.

An imaging optical system according to a second embodiment will be described with reference to FIG. 5 .

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 , a sixth lens 260 , and a seventh lens. It includes an optical system composed of a lens 270 .

In the above lens configuration, the first lens 210 and the second lens 220 form a first lens group G1, and the third lens 230 to the seventh lens 270 are the second lens group. (G2) is formed.

The imaging optical system 200 includes a filter 280 , an image sensor 290 , and an aperture ST. The filter 280 is disposed on the image side of the seventh lens 270 , and the stop ST is disposed between the second lens 220 and the third lens 230 .

In the present embodiment, the first lens 210 has a negative refractive power, and has a convex object side and a concave image side. The second lens 220 has a positive refractive power and has a convex shape on both sides. The third lens 230 has a negative refractive power, and has a concave object side and a convex image side. The fourth lens 240 has a positive refractive power, and has a concave object side and a convex image side. The fifth lens 250 has a positive refractive power and has a convex shape on both sides. The sixth lens 260 has a negative refractive power, and has a convex object side and a concave image side. In addition, the sixth lens 260 has a shape in which inflection points are formed on both surfaces. The seventh lens 270 has a positive refractive power, and has a convex object side and a concave image side. In addition, the seventh lens 270 has a shape in which inflection points are formed on both surfaces.

The imaging optical system configured as above exhibits aberration characteristics as shown in FIG. 6 . 7 and 8 are tables showing lens characteristics and aspherical characteristics of the imaging optical system according to the second embodiment.

An imaging optical system according to a third embodiment will be described with reference to FIG. 9 .

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 , a sixth lens 360 , and a seventh lens. It includes an optical system composed of a lens (370).

In the above lens configuration, the first lens 310 and the second lens 320 form a first lens group G1, and the third lens 330 to the seventh lens 370 are the second lens group (G2) is formed.

The imaging optical system 300 includes a filter 380 , an image sensor 390 , and an aperture ST. The filter 380 is disposed on the image side of the seventh lens 370 , and the stop ST is disposed between the second lens 320 and the third lens 330 .

In this embodiment, the first lens 310 has a negative refractive power, and has a convex object side and a concave image side. The second lens 320 has a positive refractive power and has a convex shape on both sides. The third lens 330 has a positive refractive power and has a convex shape on both sides. The fourth lens 340 has a negative refractive power and has a concave shape on both sides. The fifth lens 350 has a positive refractive power and has a convex shape on both sides. The sixth lens 360 has a negative refractive power, and has a convex object side and a concave image side. In addition, the sixth lens 360 has a shape in which inflection points are formed on both surfaces. The seventh lens 370 has positive refractive power, and has a convex object side and a concave image side. In addition, the seventh lens 370 has a shape in which inflection points are formed on both surfaces.

The imaging optical system configured as above exhibits aberration characteristics as shown in FIG. 10 . 11 and 12 are tables showing lens characteristics and aspherical characteristics of the imaging optical system according to the third embodiment.

The imaging optical system is capable of focusing. For example, the second lens group G2 may move between the first lens group G1 and the image plane 390 . Accordingly, the distance D1 between the second lens 320 and the third lens 330 may be changed in the range of -0.025 to 0, and the distance D2 between the seventh lens 370 and the image plane 390 . may be changed in the range of 0.74 to 0.765.

The optical system configured as described above may perform high-resolution imaging by changing the position of the second lens group G2.

An imaging optical system according to a fourth embodiment will be described with reference to FIG. 13 .

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 , a sixth lens 460 , and a seventh lens. It includes an optical system composed of a lens 470 .

In the above lens configuration, the first lens 410 and the second lens 420 form the first lens group G1, and the third lens 430 to the seventh lens 470 are the second lens group. (G2) is formed.

The imaging optical system 400 includes a filter 480 , an image sensor 490 , and an aperture ST. The filter 480 is disposed on the image side of the seventh lens 470 , and the stop ST is disposed between the second lens 420 and the third lens 430 .

In this embodiment, the first lens 410 has a negative refractive power, and has a convex object side and a concave image side. The second lens 420 has a positive refractive power and has a convex shape on both sides. The third lens 430 has a negative refractive power, and has a concave object side and a convex image side. The fourth lens 440 has a positive refractive power, and has a concave object side and a convex image side. The fifth lens 450 has a positive refractive power and has a convex shape on both sides. The sixth lens 460 has a negative refractive power, and has a convex object side and a concave image side. In addition, the sixth lens 460 has a shape in which inflection points are formed on both surfaces. The seventh lens 470 has a positive refractive power, and has a convex object side and a concave image side. In addition, the seventh lens 470 has a shape in which inflection points are formed on both surfaces.

The imaging optical system configured as above exhibits aberration characteristics as shown in FIG. 14 . 15 and 16 are tables showing lens characteristics and aspheric characteristics of the imaging optical system according to the fourth embodiment.

An imaging optical system according to a fifth embodiment will be described with reference to FIG. 17 .

The imaging optical system 500 includes a first lens 510 , a second lens 520 , a third lens 530 , a fourth lens 540 , a fifth lens 550 , a sixth lens 560 , and a seventh lens. It includes an optical system composed of a lens 570 .

In the above lens configuration, the first lens 510 and the second lens 520 form a first lens group G1, and the third lens 530 to the seventh lens 570 are the second lens group. (G2) is formed.

The imaging optical system 500 includes a filter 580 , an image sensor 590 , and an aperture ST. The filter 580 is disposed on the image side of the seventh lens 570 , and the stop ST is disposed between the second lens 520 and the third lens 530 .

In this embodiment, the first lens 510 has a negative refractive power and has a concave shape on both sides. The second lens 520 has a positive refractive power and has a convex shape on both sides. The third lens 530 has a negative refractive power, and has a concave object side and a convex image side. The fourth lens 540 has a positive refractive power, and has a concave object side and a convex image side. The fifth lens 550 has a positive refractive power and has a convex shape on both sides. The sixth lens 560 has a negative refractive power, and has a convex object side and a concave image side. In addition, the sixth lens 560 has a shape in which inflection points are formed on both surfaces. The seventh lens 570 has a negative refractive power, and has a convex object side and a concave image side. In addition, the seventh lens 570 has a shape in which inflection points are formed on both surfaces.

The imaging optical system configured as above exhibits aberration characteristics as shown in FIG. 18 . 19 and 20 are tables showing lens characteristics and aspherical characteristics of an imaging optical system according to the fifth embodiment.

The half-angle of view of the imaging optical system according to the first to fifth embodiments may be approximately 59 degrees or more. Therefore, the present optical imaging system is useful for devices requiring a wide angle of view, such as a surveillance camera for an unmanned aerial vehicle or a surveillance camera for a vehicle.

Table 1 shows the conditional expression values of the imaging optical systems according to the first to fifth embodiments.

The present invention is not limited only to the embodiments described above, and those of ordinary skill in the art to which the present invention pertains can freely do without departing from the spirit of the present invention described in the claims below. It may be implemented with various modifications.

100, 200, 300, 400, 500 imaging optical system
G11, G21, G31, G41, G51 1st lens group
G12, G22, G32, G42, G52 2nd lens group
110, 210, 310, 410, 510 first lens
120, 220, 320, 420, 520 second lens
130, 230, 330, 430, 530 third lens
140, 240, 340, 440, 540 4th lens
150, 250, 350, 450, 550 5th lens
160, 260, 360, 460, 560 6th lens
170, 270, 370, 470, 570 7th lens
180, 280, 380. 480, 580 (infrared cut off) filter
190, 290, 390, 490, 590 image sensor or top view

Claims (15)

arranged in order from the object side to the upper surface direction,
a first lens group consisting of a first lens and a second lens; and
a second lens group including a third lens, a fourth lens, a fifth lens, a sixth lens, and a seventh lens;
including,
The third lens has a convex image side,
An imaging optical system satisfying the following conditional expressions.
[Conditional Expression 1] TL/2Y < 1.3
[Condition 2] 0.4 < R2/f < 1.5
(In the above conditional expression, TL is the distance from the object side surface of the first lens to the image plane, 2Y is the diagonal length of the image plane, f is the total focal length of the imaging optical system, and R2 is the image side surface of the first lens is the radius of curvature of According to claim 1,
and the second lens group is configured to be movable in an optical axis direction. According to claim 1,
The first lens is an imaging optical system having a negative refractive power. According to claim 1,
The second lens is an imaging optical system having a positive refractive power. According to claim 1,
The third lens is an imaging optical system having a negative refractive power. According to claim 1,
The fourth lens is an imaging optical system having a positive refractive power. According to claim 1,
The fifth lens is an imaging optical system having a positive refractive power. According to claim 1,
The sixth lens is an imaging optical system having a negative refractive power. According to claim 1,
The seventh lens is an imaging optical system having a positive refractive power. According to claim 1,
An imaging optical system satisfying the following conditional expression.
[Conditional Expression] -80 < {(1/f)*(Y/tanθ)-1}*100 < -20
(In the above conditional expression, f is the total focal length of the imaging optical system, Y is 1/2 of the diagonal length of the image plane, and θ is the half angle of view of the imaging optical system) According to claim 1,
An imaging optical system satisfying the following conditional expression.
[Conditional Expression] 1.0 < tanθ < 4.0
(In the above conditional expression, θ is the half angle of view of the optical system) According to claim 1,
An imaging optical system satisfying the following conditional expression.
[Conditional Expression] -1.5 < f/f1 < -0.05
(In the above conditional expression, f is the overall focal length of the imaging optical system, and f1 is the focal length of the first lens) According to claim 1,
An imaging optical system satisfying the following conditional expression.
[Conditional Expression] 0.3 < f/f2 < 0.8
(In the above conditional expression, f is the overall focal length of the imaging optical system, and f2 is the focal length of the second lens) According to claim 1,
An imaging optical system satisfying the following conditional expression.
[Conditional Expression] 1.5 < f/EPD < 3.2
(In the above conditional expression, f is the total focal length of the imaging optical system, and EPD is the diameter of the entrance pupil) According to claim 1,
An imaging optical system satisfying the following conditional expression.
[Conditional Expression] 0.4 < f/fG2 < 1.1
(In the above conditional expression, f is the total focal length of the imaging optical system, and fG2 is the combined focal length of the second lens group)

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