KR20220103670A - Optical Imaging System - Google Patents

Abstract

An imaging optical system of the present invention includes: a first lens having 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 an image surface. An objective of the present invention is to provide the imaging optical system capable of taking clear pictures in a low-illuminance environment.

Description

Optical Imaging System

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

A small surveillance camera is mounted on the vehicle to capture the front and rear view of the vehicle. For example, a small surveillance camera is mounted on a rearview mirror of a vehicle to photograph a moving vehicle, a pedestrian, etc. deployed in front of the vehicle.

These small surveillance cameras have to take pictures not only in the daytime environment but also in the night environment. However, since the night environment has low illuminance, it is difficult to take a clear picture 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 photographing both in a visible ray region and a near-infrared region while having a small size.

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

SUMMARY OF THE INVENTION An object of the present invention is to provide an imaging optical system capable of capturing clear images 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; a second lens having positive refractive power; a third lens having a 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 to the image plane direction.

The present invention enables clear imaging in a low-illuminance environment.

1 is a configuration 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 block 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 the lens characteristics of the imaging optical system shown in FIG.
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 the lens characteristics of the imaging optical system shown in FIG.

Hereinafter, a preferred embodiment of the present invention will be described in detail based on the accompanying illustrative 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, 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 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 this 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 radius of curvature of the lens, thickness, TL, Y (1/2 of the diagonal length of the image plane), and focal length are all units in mm. In addition, the thickness of the lenses, 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 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 it is described that one surface of the lens has a convex shape, the edge portion of the lens may be concave. Similarly, 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, the optical system of an imaging optical system consists of 5 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 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 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 a plastic or glass material.

The imaging optical system includes five lenses, 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 positive refractive power.

The first lens has a convex surface. 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 a positive refractive power.

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

The second lens includes a spherical surface. For example, both surfaces 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 a negative refractive power.

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

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 an Abbe's number lower than that of the first lens. For example, the Abbe's 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 surface. For example, the fourth lens may have a concave shape on the side of the object.

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's number than the third lens. For example, the Abbe's 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 be convex. For example, the fifth lens may have a shape in which both sides are convex.

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's number than the third lens. For example, the Abbe's number of the fifth lens may be 40 or more.

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

The aperture 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 where 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 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 is composed of a plurality of lenses having refractive power. For example, the optical imaging 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 and a convex image side. The second lens 120 has a positive refractive power, and has a convex object side and a concave image side. The third lens 130 has a 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 and a convex image side. The fifth lens 150 has a positive refractive power and has a convex shape on both sides. The stop ST is disposed between the second lens and the third lens.

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

The imaging optical system configured as above exhibits the aberration characteristic shown in FIG. 2 . 3 is a table showing the 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 optical imaging 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 and a convex image side. The second lens 220 has a positive refractive power, and has a convex object side and a concave image side. The third lens 230 has a 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 and a convex image side. The fifth lens 250 has a positive refractive power and has a convex shape on both sides. The stop ST is disposed between the second lens and the third lens.

The imaging optical system 200 includes a configuration that forms an image surface. For example, the imaging optical system includes an image sensor 260 .

The imaging optical system configured as above exhibits the aberration characteristic shown in FIG. 5 . 6 is a table showing the lens 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. 7 .

* The imaging optical system 300 is composed of a plurality of lenses having refractive power. For example, the optical imaging 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 and a concave image side. The third lens 330 has a 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 and a convex image side. The fifth lens 350 has a positive refractive power and has a convex shape on both sides. The stop ST is disposed between the second lens and the third lens.

The imaging optical system 300 includes a configuration that forms an image surface. For example, the imaging optical system includes an image sensor 360 .

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

Table 1 shows the optical characteristics of the imaging optical systems according to the first to third embodiments. The overall focal length f of the imaging optical system may be generally 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 generally 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 generally 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 generally determined in the range of -3.3 to -2.0. In the imaging optical system, the focal length f4 of the fourth lens may be generally 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 generally determined in the range of 6.0 to 10.0. In the imaging optical system, TL may be generally determined 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 may be determined in the range of 3.2 to 3.4. The total angle of view (2θ) of the imaging optical system may be determined in the range of 52 to 57.

Table 2 shows the conditional expression values of the imaging optical systems according to the first to third embodiments. As can be seen in Table 2, the optical imaging 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, an object can be clearly photographed in both a visible ray region and a near-infrared region as well as in a low-illuminance environment. In addition, since the present imaging optical system uses a spherical lens, it is possible to reduce the manufacturing cost. In addition, the present imaging optical system can guarantee a constant resolution even in a temperature range of -40 to 80 °C. Accordingly, the present optical imaging system can realize high resolution even in an environment with a large temperature change range, such as a vehicle interior.

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 may do so without departing from the spirit of the present invention described in the claims below. It may be implemented with various modifications.

100, 200, 300 imaging optics
110, 210, 310 first lens
120, 220, 320 second lens
130, 230, 330 third lens
140, 240, 340 4th lens
150, 250, 350 5th lens
160, 260, 360 top view or image sensor
ST aperture

Claims (12)

a first lens having refractive power;
a second lens in which the object side is convex;
a third lens having a concave image side;
a fourth lens having positive refractive power and having a convex image side; and
a fifth lens in which the object side is convex;
including,
The first to fifth lenses are sequentially disposed from the object side to the image plane direction, and satisfy the following conditional expressions.
-5.5 < (R1+R2)/(R1-R2) < 5.5
0 ≤ |n1 - n2| ≤ 0.20
(In the above 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, n1 is the refractive index of the first lens, and n2 is the refractive index of the second lens to be) According to claim 1,
The first lens is an imaging optical system having a positive 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 first lens is an imaging optical system having a convex shape on the side of the object. According to claim 1,
The first lens is an imaging optical system having a concave shape on the side of the object. According to claim 1,
The second lens is an imaging optical system having a concave image side surface. According to claim 1,
The fourth lens is an imaging optical system having a concave shape on the side of the object. According to claim 1,
An imaging optical system satisfying the following conditional expression.
TL/2Y < 2.0
(In the above conditional expression, TL is the distance from the object side of the first lens to the image plane, and 2Y is the diagonal length of the image plane) According to claim 1,
An imaging optical system satisfying the following conditional expression.
-7.0 < R1/f < 5.0
(In the above conditional expression, f is the total focal length of the imaging optical system) According to claim 1,
An imaging optical system satisfying the following conditional expression.
-6.5 < {(1/f)*(Y/tanθ)-1}*100 < -1.0
(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.
5.0 < (t1+t2)/t3 < 12.0
(In the above 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)

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