KR20230054819A - Optical Imaging System - Google Patents

Abstract

An imaging optical system of the present invention comprises: a first lens having positive refractive power and having a convex image side; a second lens having positive refractive power; a third lens having negative refractive power; a fourth lens having positive refractive power; and a fifth lens having positive refractive power, wherein the first to fifth lenses are sequentially arranged from an object side to an image surface. Thus, the present invention can provide the imaging optical system that allows clear shooting in low-light environments.

Description

Imaging optical system {Optical Imaging System}

The present invention relates to an imaging optical system capable of imaging an object in both the visible ray region and the near-infrared region.

A miniature surveillance camera is mounted on the vehicle to capture the front and rear view of the vehicle. For example, a small monitoring camera is mounted on a rearview mirror of a vehicle to capture moving vehicles, pedestrians, and the like deployed in front of the vehicle.

These small surveillance cameras need to take pictures not only in a daytime environment but also in a nighttime environment. However, since the night environment has low illumination, it is difficult to take a clear photograph of an object. In particular, since a small surveillance camera mounted on a vehicle is limited in size, it is necessary to mount an optical system capable of taking pictures in both the visible and near-infrared regions while having a small size.

US 2006-0103947 A1 US 2010-0103539 A1 US 2014-0146405 A1

An object of the present invention is to provide an imaging optical system capable of taking clear pictures in a low-illuminance environment.

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

According to the present invention, clear shooting is possible in a low-illuminance environment.

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 table showing lens characteristics of the imaging optical system shown in FIG. 1;
4 is a configuration diagram of an imaging optical system according to a second embodiment of the present invention;
5 is a graph showing an aberration curve of the imaging optical system shown in FIG. 4;
6 is a table showing lens characteristics of the imaging optical system shown in FIG. 4;
7 is a configuration diagram of an imaging optical system according to a third embodiment of the present invention;
8 is a graph showing an aberration curve of the imaging optical system shown in FIG. 7;
9 is a table showing lens characteristics of the imaging optical system shown in FIG. 7;

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 without 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 fifth lens refers to a lens closest to the image surface (or image sensor). In this specification, the units of the radius of curvature of the lens, thickness, TL, Y (half of the diagonal length of the image surface), and focal length are all units of mm. In addition, the thickness of the lens, the distance between the lenses, and TL are distances measured with respect to the optical axis of the lenses. In addition, in the description of the shape of the lens, a convex shape on one surface means that the optical axis portion of the corresponding surface is convex, and a concave shape 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 an optical system composed of a plurality of lenses. For example, an optical system of an imaging optical system is composed of 5 lenses having refractive power. However, the imaging optical system is not composed only of lenses 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 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 gap maintaining member for adjusting a distance between the lenses.

The first to fifth lenses are made of a material having a refractive index different from that of air. For example, the first to fifth lenses are made of plastic or glass.

The imaging optical system includes 5 lenses, an image sensor, and a diaphragm. In the following, the above configurations are described.

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

The first lens has a shape in which one surface is convex. For example, the first lens has a convex 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 first lens has a predetermined refractive index. For example, the refractive index of the first lens may be 1.70 or more.

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

The second lens has a concave shape on one surface. For example, the second lens may have a concave image side surface.

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

The second lens may have a higher refractive index than the first lens. For example, the refractive index of the second lens may be 1.90 or more.

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 concave shape. For example, the third lens may have a concave shape on both sides.

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

The third lens may have a higher refractive index than the first lens. For example, the refractive index of the third lens may be 1.90 or more. The third lens may have a lower Abbe number than the first lens. For example, the Abbe number of the third lens may be 25 or less.

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

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

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

The fourth lens may have a lower refractive index than the third lens. For example, the refractive index of the fourth lens may be less than 1.90. The fourth lens may have a higher Abbe number than the third lens. For example, the Abbe number of the fourth lens may be 40 or more.

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

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

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

The fifth lens may have a lower refractive index than the third lens. For example, the refractive index of the fifth lens may be less than 1.90. The fifth lens may have a higher Abbe number than the third lens. For example, the Abbe number of the fifth lens may be 40 or more.

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. A surface of the image sensor may form an upper surface on which an image is formed.

A diaphragm may be disposed between the lens and the lens. For example, the diaphragm may be disposed between the second lens and the third lens. The diaphragm arranged in this way can adjust the amount of light incident to the image sensor.

The imaging optical system may satisfy the following Conditional Expressions.

[conditional expression] -6.5 < {(1/f)*(Y/tanθ)-1}*100 < -1.0

[conditional expression] TL/2Y < 2.0

[conditional expression] -7.0 < R1/f < 5.0

[conditional expression] -5.5 < (R1+R2)/(R1-R2) < 5.5

[conditional expression] 0.2 < f/f1 < 0.6

[conditional expression] -2.5 < f/f3 < -1.5

[conditional expression] 1.5 < f/EPD < 2.1

[conditional expression] 5.0 < (t1+t2)/t3 < 12.0

[conditional expression] 0 ≤ |n1 - n2| ≤ 0.2

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 R1 is the radius of curvature of the object side of the first lens , R2 is the radius of curvature of the image side of the first lens, f1 is the focal length of the first lens, f3 is the focal length of the third lens, EPD is the diameter of the entrance pupil, and t1 is the center of the optical axis of the first lens , t2 is the thickness of the center of the optical axis of the second lens, t3 is the thickness of the center of the optical axis of the third lens, n1 is the refractive index of the first lens, and n2 is the refractive index of the second 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, and a fifth lens 150.

In this embodiment, the first lens 110 has a positive refractive power and has a concave object side surface and a convex image side surface. 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 negative refractive power and has a concave shape on both sides. The fourth lens 140 has a positive refractive power and has a concave object side surface and a convex image side surface. The fifth lens 150 has a positive refractive power and has a convex shape on both sides. The diaphragm ST is disposed between the second lens and the third lens.

The imaging optical system 100 includes a configuration for forming an image surface. For example, the imaging optical system includes the image sensor 160 .

The imaging optical system configured as above exhibits the aberration characteristics shown in FIG. 2 . 3 is a table showing lens 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. 4 .

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, and a fifth lens 250.

In this embodiment, the first lens 210 has a positive refractive power and has a concave object side surface and 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 negative refractive power and has a concave shape on both sides. The fourth lens 240 has a positive refractive power and has a concave object side surface and a convex image side surface. The fifth lens 250 has a positive refractive power and has a convex shape on both sides. The diaphragm ST is disposed between the second lens and the third lens.

The imaging optical system 200 includes a component forming an image surface. For example, the imaging optical system includes the image sensor 260 .

The imaging optical system configured as above exhibits the aberration characteristics shown in FIG. 5 . 6 is a table showing lens characteristics of an imaging optical system according to a second embodiment.

An imaging optical system according to a third embodiment will be described with reference to FIG. 7 .

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, and a fifth lens 350.

In this embodiment, the first lens 310 has a positive refractive power and has a convex shape on both sides. 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 negative refractive power and has a concave shape on both sides. The fourth lens 340 has a positive refractive power and has a concave object side surface and a convex image side surface. The fifth lens 350 has a positive refractive power and has a convex shape on both sides. The diaphragm ST is disposed between the second lens and the third lens.

The imaging optical system 300 includes a component forming an image surface. For example, the imaging optical system includes the image sensor 360 .

The imaging optical system configured as above exhibits the aberration characteristics shown in FIG. 8 . 9 is a table showing lens characteristics of an imaging optical system according to a third embodiment.

Table 1 shows the optical characteristics of the imaging optical system according to the first to third embodiments. The total focal length (f) of the imaging optical system may be determined in the range of 5.9 to 6.4. In the imaging optical system, the focal length f1 of the first lens may be determined in the range of 12.0 to 26.0. In the imaging optical system, the focal length f2 of the second lens may be determined in the range of 11.0 to 31.0. In the imaging optical system, the focal length f3 of the third lens may be set in the range of -3.3 to -2.0. In the imaging optical system, the focal length f4 of the fourth lens may be determined in the range of 5.0 to 6.0. In the imaging optical system, the focal length f5 of the fifth lens may be determined in the range of 6.0 to 10.0. In the imaging optical system, TL can be generally set in the range of 9.0 to 12.0. The F number of the imaging optical system may be 1.9 or less. In the imaging optical system, EPD can be set in the range of 3.2 to 3.4. The entire angle of view (2θ) of the imaging optical system may be determined in the range of 52 to 57.

Table 2 shows conditional expression values of the imaging optical system according to the first to third embodiments. As can be seen in Table 2, the imaging optical systems according to the first to third embodiments satisfy all of the numerical ranges of the above-described conditional expressions.

Since the imaging optical system configured as above has an F number of 1.9 or less, it is possible to clearly photograph an object in both the visible ray region and the near-infrared region as well as in an environment with low illumination. In addition, since the present imaging optical system uses a spherical lens, manufacturing costs can be reduced. In addition, the present imaging optical system can guarantee constant resolution even in a temperature range of -40 to 80 °C. Accordingly, the present imaging optical system can implement high resolution even in an environment where the temperature change range is large, such as in a vehicle interior.

The present invention is not limited only to the embodiments described above, and those skilled in the art can do so without 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 imaging optics
110, 210, 310 1st lens
120, 220, 320 2nd lens
130, 230, 330 3rd lens
140, 240, 340 4th lens
150, 250, 350 5th lens
160, 260, 360 top view or image sensor
ST Aperture

Claims (10)

a first lens having refractive power;
a second lens having a concave image side surface;
a third lens having refractive power;
a fourth lens having positive refractive power; and
a fifth lens having refractive power;
including,
The first to fifth lenses are sequentially disposed from the object side toward the image plane, and satisfy the following Conditional Expressions.
-5.5 < (R1+R2)/(R1-R2) < 5.5
-6.5 < {(1/f)*(Y/tanθ)-1}*100 < -1.0
(In the conditional expression, R1 is the radius of curvature of the object side of the first lens, R2 is the radius of curvature of the image side of the first lens, f is the focal length of the imaging optical system, Y is the diagonal length of the image plane 1/2, and θ is the half angle of view of the imaging optical system) According to claim 1,
The second lens is an imaging optical system having a shape in which an object side surface is convex. According to claim 1,
The third lens has a concave image side surface. According to claim 1,
The fourth lens is an imaging optical system in which an object side surface is concave. According to claim 1,
The fourth lens is an imaging optical system having a convex image side surface. According to claim 1,
The fifth lens has a shape in which an object side surface is convex. According to claim 1,
An imaging optical system that satisfies the following conditional expression.
TL/2Y < 2.0
(In the above conditional expression, TL is the distance from the object side surface of the first lens to the image surface, and 2Y is the diagonal length of the image surface) According to claim 1,
An imaging optical system that satisfies the following conditional expression.
-7.0 < R1/f < 5.0 According to claim 1,
An imaging optical system that satisfies the following conditional expression.
5.0 < (t1+t2)/t3 < 12.0
(In the conditional expression, t1 is the thickness of the center of the optical axis of the first lens, t2 is the thickness of the center of the optical axis of the second lens, and t3 is the thickness of the center of the optical axis of the third lens) According to claim 1,
The fifth lens has an Abbe number of 40 or more.

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