KR102609152B1 - Optical Imaging System - Google Patents

Abstract

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

Description

Optical Imaging System

The present invention relates to an imaging optical system capable of long-distance photography.

The telephoto optical system capable of long-distance shooting has a considerable size. For example, in a telephoto optical system, the ratio (TL/f) of the total focal length (f) to the total length (TL) of the optical system is 1 or more. Therefore, it is difficult to install a telephoto optical system in small electronic products such as mobile terminals.

US 2013-0021678 A1

The purpose of the present invention is to provide an imaging optical system that enables long-distance imaging and can be mounted on a small terminal.

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

The present invention can be mounted on a small terminal.

1 is a configuration diagram of an imaging optical system according to a first embodiment of the present invention.
Figure 2 is a graph showing the aberration curve of the imaging optical system shown in Figure 1
Figure 3 is a table showing the lens characteristics of the imaging optical system shown in Figure 1
Figure 4 is a table showing the aspherical characteristics of the imaging optical system shown in Figure 1
5 is a configuration diagram of an imaging optical system according to a second embodiment of the present invention.
Figure 6 is a graph showing the aberration curve of the imaging optical system shown in Figure 5
Figure 7 is a table showing the lens characteristics of the imaging optical system shown in Figure 5
Figure 8 is a table showing the aspherical characteristics of the imaging optical system shown in Figure 5
9 is a configuration diagram of an imaging optical system according to a third embodiment of the present invention.
Figure 10 is a graph showing the aberration curve of the imaging optical system shown in Figure 9
Figure 11 is a table showing the lens characteristics of the imaging optical system shown in Figure 9
Figure 12 is a table showing the aspherical characteristics of the imaging optical system shown in Figure 9
13 is a rear view of a portable terminal equipped with an imaging optical system according to an embodiment of the present invention.
Figure 14 is a cross-sectional view of the portable terminal shown in Figure 13

Hereinafter, preferred embodiments of the present invention will be described in detail based on the attached illustration 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 should not be understood as limiting the technical components of the present invention.

In addition, throughout the specification, the fact that a certain configuration is 'connected' to another configuration includes not only cases where these configurations are 'directly connected', but also cases where they are 'indirectly connected' with another configuration in between. means that In addition, 'including' a certain component means that other components may be further included rather than excluding other components, unless specifically stated to the contrary.

In addition, in this specification, the first lens refers to the lens closest to the object (or subject), and the fifth lens refers to the lens closest to the image surface (or image sensor). In this specification, the units of lens radius of curvature, thickness, TL, Y (1/2 of the diagonal length of the image surface), and focal length are all in mm units. In addition, the thickness of the lens, the distance between lenses, and TL are distances measured based on the optical axis of the lens. In addition, in the description of the shape of the lens, the shape of one side being convex means that the optical axis part of the surface is convex, and the shape of one side being concave means that the optical axis part of the 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 side of the lens is described as having a concave shape, the edge of the lens may be convex.

The imaging optical system includes an optical system consisting of a plurality of lenses. For example, the imaging optical system consists of five lenses with refractive power. However, the imaging optical system does not consist only of lenses with refractive power. For example, the imaging optical system may include an aperture (stop) to adjust the amount of light. Additionally, 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. Additionally, the imaging optical system may further include a filter configured to block infrared rays.

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

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

Next, the first to fifth lenses constituting the optical system will be described in detail.

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

The first lens has a convex shape on one side. For example, the first lens has a convex shape on the side of the object.

The first lens includes an aspherical surface. For example, both surfaces of the first lens may be aspherical. The first lens can be made of a material with high light transmittance and excellent processability. For example, the first lens may be made of plastic material. However, the material of the first lens is not limited to plastic. For example, the first lens may be made of glass. The first lens has a predetermined refractive index. For example, the refractive index of the first lens may be less than 1.6.

The first lens has a predetermined focal length. For example, the first lens may be determined in the range of 2.6 to 3.0 mm.

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

The second lens has a convex shape on one side. For example, the second lens has a convex shape on the side of the object.

The second lens includes an aspherical surface. For example, both surfaces of the second lens may be aspherical. The second lens can be made of a material with high light transmittance and excellent processability. For example, the second lens may be made of plastic material. However, the material of the second lens is not limited to plastic. For example, the second lens may be made of glass. The second lens has a higher refractive index than the first lens. For example, the refractive index of the second lens may be 1.6 or more.

The second lens has a predetermined focal length. For example, the second lens may be determined in the range of -9.0 to -3.0 mm.

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

The third lens has a concave shape on one side. For example, the third lens has a concave image side.

The third lens includes an aspherical surface. For example, both sides of the third lens may be aspherical. The third lens can be made of a material with high light transmittance and excellent processability. For example, the third lens may be made of plastic material. However, the material of the third lens is not limited to plastic. For example, the third lens may be made of glass. The third lens has a predetermined refractive index. For example, the refractive index of the third lens may be selected in the range of 1.5 to 1.7.

The third lens has a predetermined focal length. For example, the third lens may be determined in the range of -30 to -6.0 mm.

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

The fourth lens has a concave shape on both sides.

The fourth lens includes an aspherical surface. For example, both surfaces of the fourth lens may be aspherical. The fourth lens can be made of a material with high light transmittance and excellent processability. For example, the fourth lens may be made of plastic material. However, the material of the fourth lens is not limited to plastic. For example, the fourth lens may be made of glass. The fourth lens has substantially the same refractive index as the first lens. For example, the refractive index of the fourth lens may be less than 1.6.

The fourth lens has a shape including an inflection point. For example, one or more inflection points are formed on the image side of the fourth lens. However, the formation location of the inflection point is not limited to the image side of the fourth lens. For example, one or more inflection points may be formed on the object side of the fourth lens.

The fourth lens has a predetermined focal length. For example, the fourth lens may be determined in the range of -9.0 to -4.0 mm.

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

The fifth lens has a convex shape on one side. For example, the fifth lens has a convex image side.

The fifth lens includes an aspherical surface. For example, both sides of the fifth lens may be aspherical. The fifth lens can be made of a material with high light transmittance and excellent processability. For example, the fifth lens may be made of plastic material. However, the material of the fifth lens is not limited to plastic. For example, the fifth lens may be made of glass. The fifth lens has a higher refractive index than the first lens. For example, the refractive index of the fifth lens may be 1.6 or more.

The fifth lens has a predetermined focal length. For example, the fifth lens may be determined in the range of 16.0 to 24.0 mm.

Next, the lens and other components are explained.

The imaging optical system includes an image sensor. The surface of the image sensor forms an imaging plane. The upper surface may have a generally rectangular shape. However, the shape of the upper surface is not limited to a rectangle. For example, the upper surface may be formed in a square shape. The image sensor may be configured to implement high resolution. For example, the unit size of the pixels constituting the image sensor may be 1.12 ㎛ or less.

The imaging optical system includes a filter. For example, the imaging optical system includes a filter configured to block infrared rays. The filter may be made of glass. For example, the filter may be transparent glass with an infrared blocking film formed thereon. The refractive index of the filter may generally be 1.5 or more. The filter configured in this way is placed between the fifth lens and the image sensor.

The imaging optical system includes an aperture configured to adjust the amount of light. For example, an aperture can be placed between lenses to control the amount of light incident on the image sensor.

The imaging optical system can satisfy the following conditional expressions.

[Conditional expression 1] 0.7 < TL/f < 1.0

[Conditional Expression 2] 0.15 < R1/f < 1.5

[Conditional Expression 3] -3.5 < f/f2 < -0.5

[Conditional Expression 4] 0.1 < d34/TL < 0.7

[Conditional Expression 5] 1.60 < Nd5 < 1.75

[Conditional Expression 6] 0.3 < tanθ < 0.5

In the above conditional expression, f is the total focal length of the imaging optical system, θ is the half angle of view of the imaging optical system, 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, and f1 is is the focal length of the first lens, f2 is the focal length of the second lens, d34 is the distance from the image side of the third lens to the object side of the fourth lens, Nd5 is the refractive index of the fifth lens, and θ is the imaging It is the half angle of view of the optical system.

Conditional Expression 1 is a numerical range that limits the telephoto ratio of the imaging optical system. For example, an imaging optical system that exceeds the lower limit of Conditional Expression 1 has strong telephoto characteristics and the angle of view becomes small, and an imaging optical system that exceeds the upper limit of Conditional Expression 1 has a large angle of view and the telephoto characteristics become weak.

Conditional equation 2 is a numerical range for improving the telephoto characteristics and formability of the first lens. For example, a first lens that exceeds the lower limit of Conditional Expression 2 can improve the telephoto characteristics of the imaging optical system, but injection molding is difficult, and a first lens that exceeds the upper limit of Conditional Expression 2 increases the longitudinal spherical aberration and shortens the focal length, resulting in telephoto characteristics. It is difficult to construct an optical system.

Conditional equation 3 is the numerical range for implementing a high-resolution imaging optical system. For example, a second lens that deviates from the lower or upper limit of Conditional Expression 3 not only increases the astigmatism of the imaging optical system but also causes image deterioration.

Conditional equation 4 is the numerical range for implementing telephoto characteristics and small optical systems. For example, an imaging optical system that exceeds the lower limit of Conditional Expression 4 has a short overall focal length, making it difficult to construct a telephoto optical system, and an imaging optical system that exceeds the upper limit of Conditional Expression 4 has a long total length (TL) of the optical system, making it difficult to implement a compact optical system. .

Conditional expression 5 is a condition for selecting the material of the fifth lens. For example, the fifth lens that satisfies the numerical range of Conditional Expression 5 is not only advantageous for correcting astigmatism, but is also advantageous for correcting longitudinal chromatic aberration and magnification chromatic aberration.

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 imaging optical system 100 consists of 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 shape where the object side is convex and the image side is concave. The second lens 120 has negative refractive power and has a shape where the side of the object is convex and the side of the image is concave. The third lens 130 has negative refractive power and has a shape where the side of the object is convex and the side of the image is concave. The fourth lens 140 has negative refractive power and has a concave shape on both sides. In addition, inflection points are formed on both sides of the fourth lens 140. The fifth lens 150 has positive refractive power and has a shape in which the object side is concave and the image side is convex.

The imaging optical system 100 includes an aperture (ST), a filter 160, and an image sensor 170.

The aperture ST is disposed between the second lens 120 and the third lens 130. The filter 160 is disposed between the fifth lens 150 and the image sensor 170.

The imaging optical system configured as above exhibits the aberration characteristics shown in FIG. 2. FIG. 3 is a table showing lens characteristics of the imaging optical system according to this embodiment, and FIG. 4 is a table showing aspherical characteristics of the imaging optical system according to this embodiment.

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

The imaging optical system 200 is composed of a plurality of lenses having refractive power. For example, the imaging optical system 200 consists of 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 positive refractive power and has a convex shape on both sides. The second lens 220 has negative refractive power and has a shape where the side of the object is convex and the side of the image is concave. The third lens 230 has negative refractive power and has a concave shape on both sides. The fourth lens 240 has negative refractive power and has a concave shape on both sides. In addition, inflection points are formed on both sides of the fourth lens 240. The fifth lens 250 has positive refractive power and has a shape in which the object side is concave and the image side is convex.

The imaging optical system 200 includes an aperture (ST), a filter 260, and an image sensor 270.

The aperture ST is disposed between the second lens 220 and the third lens 230. The filter 260 is disposed between the fifth lens 250 and the image sensor 270.

The imaging optical system configured as above exhibits the aberration characteristics shown in FIG. 6. FIG. 7 is a table showing lens characteristics of the imaging optical system according to this embodiment, and FIG. 8 is a table showing aspherical characteristics of the imaging optical system according to this embodiment.

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

The imaging optical system 300 is composed of a plurality of lenses having refractive power. For example, the imaging optical system 300 consists of 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 positive refractive power and has a convex shape on both sides. The second lens 320 has negative refractive power and has a shape where the side of the object is convex and the side of the image is concave. The third lens 330 has negative refractive power and has a shape where the object side is convex and the image side is concave. The fourth lens 340 has negative refractive power and has a concave shape on both sides. In addition, inflection points are formed on both sides of the fourth lens 340. The fifth lens 350 has positive refractive power and has a convex shape on both sides.

The imaging optical system 300 includes an aperture (ST), a filter 360, and an image sensor 370.

The aperture ST is disposed between the second lens 320 and the third lens 330. The filter 360 is disposed between the fifth lens 350 and the image sensor 370.

The imaging optical system configured as above exhibits the aberration characteristics shown in FIG. 6. FIG. 7 is a table showing lens characteristics of the imaging optical system according to this embodiment, and FIG. 8 is a table showing aspherical characteristics of the imaging optical system according to this embodiment.

Table 1 below is a table showing the conditional equation values of the optical system according to the first to third embodiments. As can be seen in Table 1, the optical systems according to the first to third embodiments satisfy all numerical ranges according to Conditional Expressions 1 to 6.

Next, a mobile terminal equipped with an imaging optical system according to an embodiment of the present invention will be described with reference to FIGS. 13 and 14.

The portable terminal 10 includes a plurality of camera modules 20 and 30. The first camera module 20 includes a first imaging optical system 101 configured to photograph a nearby subject, and the second camera module 30 includes a second imaging optical system 100, 200, configured to photograph a distant object. 300).

The first imaging optical system 101 is composed of a plurality of lenses. For example, the first imaging optical system 101 may include four or more lenses. The first imaging optical system 101 may have a wide angle of view. For example, the first imaging optical system 101 may have an angle of view of 50 degrees or more.

The second imaging optical system (100, 200, 300) is composed of a plurality of lenses. For example, the second imaging optical system 100, 200, and 300 may be composed of 5 lenses. In addition, the second imaging optical system 100, 200, and 300 may be any one of the imaging optical systems according to the first to third embodiments described above. The second imaging optical systems 100, 200, and 300 may have a narrow angle of view. For example, the second imaging optical systems 100, 200, and 300 may have an angle of view of 40 degrees or less.

The first imaging optical system 101 and the second imaging optical system 100, 200, and 300 may have substantially the same size. For example, the overall length L1 of the first imaging optical system 101 may be substantially equal to the overall length L2 of the second imaging optical systems 100, 200, and 300. Alternatively, the ratio (L1/L2) of the total length (L2) of the second imaging optical system (100, 200, 300) to the total length (L1) of the first imaging optical system (101) may be 0.8 to 1.0. Alternatively, the ratio (L2/h) of the thickness (h) of the portable terminal 10 to the total length (L2) of the second imaging optical system 100, 200, and 300 may be 0.8 or less.

The present invention is not limited to the embodiments described above, and those of ordinary skill in the technical field to which the present invention pertains can make any changes without departing from the gist of the technical idea of the present invention as set forth in the claims below. It can be implemented with various changes.

100, 200, 300 imaging optical system
110, 210, 310 1st lens
120, 220, 420 2nd lens
130, 230, 430 Third lens
140, 240, 440 4th lens
150, 250, 450 5th lens
160, 260, 460 filters
170, 270, 470 image sensor
ST aperture
10 mobile terminal
20 1st camera module
30 Second camera module

Claims (8)

A first lens having a concave image side;
a second lens having refractive power;
A third lens having a convex shape on the side of the object;
a fourth lens having refractive power; and
A fifth lens having a concave shape on the side of the object;
Including,
The first to fifth lenses are sequentially arranged from the object side,
The focal length of the first lens is determined in the range of 2.6 mm to 3.0 mm,
An imaging optical system that satisfies the following conditional expression.
TL/f < 1.0
(In the above conditional expression, TL is the distance from the object side of the first lens to the image surface, and f is the total focal length of the imaging optical system.) According to paragraph 1,
The second lens is an imaging optical system in which the side of the object has a convex shape. According to paragraph 1,
The fourth lens is an imaging optical system in which the side of the object has a concave shape. According to paragraph 1,
An imaging optical system that satisfies the following conditional expression.
0.15 < R1/f < 1.5
(In the above conditional expression, R1 is the radius of curvature of the object side of the first lens) According to paragraph 1,
An imaging optical system that satisfies the following conditional expression.
-3.5 < f/f2 < -0.5
(In the above conditional expression, f2 is the focal length of the second lens) According to paragraph 1,
An imaging optical system that satisfies the following conditional expression.
0.1 < d34/TL < 0.7
(In the above conditional expression, d34 is the distance from the image side of the third lens to the object side of the fourth lens) delete According to paragraph 1,
An imaging optical system in which the focal length of the fifth lens is determined in the range of 16 mm to 24 mm.