KR102368759B1 - Optical Imaging System - Google Patents

Abstract

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

Description

Optical Imaging System

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

A telephoto optical system capable of long-distance photography has a considerable size. For example, in the telephoto optical system, the ratio (TL/f) of the total focal length f to the total optical system length TL is 1 or more. Therefore, it is difficult to mount the telephoto optical system in a small electronic product such as a portable terminal.

US 2013-0021678 A1

An object of the present invention is to provide an optical imaging system that can be mounted on a small terminal while allowing long-distance imaging.

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 a negative refractive power; a third lens having a negative refractive power; a fourth lens having a negative refractive power and having an inflection point formed on an image side; and a fifth lens having positive refractive power and having a convex image side, wherein the first to fifth lenses are sequentially disposed from the object side to the image plane direction.

The present invention 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.
FIG. 4 is a table showing the aspherical characteristics of the imaging optical system shown in FIG. 1; FIG.
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 rear view of a portable terminal equipped with an optical imaging system according to an embodiment of the present invention;
14 is a cross-sectional view of the mobile terminal shown in FIG. 13

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 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 cases where these components are 'directly connected' but also 'indirectly connected' through other components. means that In addition, 'including' a certain component means that other components may be further included, rather than excluding other components, unless otherwise stated.

In addition, in this specification, the first lens 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 the 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, 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. Accordingly, even if one surface of the lens is described as having a convex shape, the edge portion of the lens may be concave. Similarly, although 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 imaging optical system consists of five 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. 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 filter configured to block infrared rays.

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. 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 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 aspherical 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.

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 surface. 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 may be made of a material having high light transmittance and excellent workability. For example, the first lens may be made of a plastic material. However, the material of the first lens is not limited to plastic. For example, the first lens may be made of a glass material. 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 a range of 2.6 to 3.0 mm.

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

The second lens has a convex surface. 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 may be made of a material having high light transmittance and excellent workability. For example, the second lens may be made of a plastic material. However, the material of the second lens is not limited to plastic. For example, the second lens may be made of a glass material. The 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 a 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 surface. For example, the third lens has a concave image side surface.

The third lens includes an aspherical surface. For example, both surfaces of the third lens may be aspherical. 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 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 a 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 shape in which both surfaces are concave.

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 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 position 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 a 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 surface. For example, the fifth lens has a convex image side surface.

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 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 a range of 16.0 to 24.0 mm.

Next, the configuration other than the lens will be described.

The imaging optical system includes an image sensor. The surface of the image sensor forms an imaging plane. The upper surface may have a substantially 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 pixels constituting the image sensor may be 1.12 μm or less.

The imaging optical system includes a filter. For example, the imaging optical system includes a filter configured to block infrared radiation. The filter may be made of a glass material. For example, the filter may be a transparent glass having an infrared blocking film formed thereon. The refractive index of the filter may be generally greater than or equal to 1.5. The filter configured as described above is disposed between the fifth lens and the image sensor.

The imaging optical system includes a diaphragm configured to adjust the amount of light. For example, the aperture may be disposed between the lens and the lens to adjust the amount of light incident to the image sensor.

The imaging optical system may satisfy the following conditional expressions.

[Condition 1] 0.7 < TL/f < 1.0

[Condition 2] 0.15 < R1/f < 1.5

[Condition 3] -3.5 < f/f2 < -0.5

[Condition 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-field of the optical system.

Conditional Expression 1 is a numerical range limiting the telephoto ratio of the imaging optical system. For example, an optical imaging system that exceeds the lower limit of Conditional Expression 1 has a strong telephoto characteristic, and thus the angle of view becomes small.

Conditional Expression 2 is a numerical range for improving telephoto characteristics and moldability of the first lens. For example, the first lens deviating from the lower limit of Conditional Equation 2 may improve the telephoto characteristics of the imaging optical system, but injection molding is difficult, and the first lens deviating from the upper limit of Condition 2 increases longitudinal spherical aberration and shortens the focal length to telephoto. It is difficult to construct an optical system.

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

Condition 4 is a numerical range for realizing telephoto characteristics and a small optical system. For example, an imaging optical system that deviates from the lower limit of Conditional Equation 4 has a shorter overall focal length, making it difficult to construct a telephoto optical system. For an imaging optical system that deviates from the upper limit of Condition 4, the overall length (TL) of the optical system becomes longer, 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 satisfying the numerical range of Conditional Expression 5 is advantageous not only in correcting astigmatism, but also in correcting axial chromatic aberration and chromatic aberration of magnification.

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 convex object side and a concave image side. The second lens 120 has a negative 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 convex object side and a concave image side. The fourth lens 140 has a negative refractive power and has a concave shape on both sides. In addition, inflection points are formed on both surfaces of the fourth lens 140 . The fifth lens 150 has a positive refractive power, and has a concave object side and a convex image side.

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

The diaphragm 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 characteristic shown in FIG. 2 . 3 is a table showing the lens characteristics of the imaging optical system according to the present embodiment, and FIG. 4 is a table showing the aspherical characteristics of the imaging optical system according to the present embodiment.

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

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 convex shape on both sides. The second lens 220 has a negative refractive power, and the object side is convex and the image side is concave. The third lens 230 has a negative refractive power and has a concave shape on both sides. The fourth lens 240 has a negative refractive power and has a concave shape on both sides. In addition, inflection points are formed on both surfaces of the fourth lens 240 . The fifth lens 250 has a positive refractive power, and has a concave object side and a convex image side.

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

The stopper 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 characteristic shown in FIG. 6 . 7 is a table showing the lens characteristics of the imaging optical system according to the present embodiment, and FIG. 8 is a table showing the aspherical characteristics of the imaging optical system according to the present embodiment.

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

The optical imaging system 300 includes 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 negative 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 convex object side and a concave image side. The fourth lens 340 has a negative refractive power and has a concave shape on both sides. In addition, inflection points are formed on both surfaces of the fourth lens 340 . The fifth lens 350 has a positive refractive power and has a convex shape on both sides.

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

The stopper 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 characteristic shown in FIG. 6 . 7 is a table showing the lens characteristics of the imaging optical system according to the present embodiment, and FIG. 8 is a table showing the aspherical characteristics of the imaging optical system according to the present embodiment.

Table 1 below is a table showing the conditional expression values of the optical systems according to the first to third embodiments. As can be seen from 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 portable terminal equipped with an optical imaging 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 optical system 101 configured to photograph a short-range subject, and the second camera module 30 includes a second optical system 100, 200, configured to photograph a distant subject. 300) is included.

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 optical system 101 may have an angle of view of 50 degrees or more.

The second imaging optical system 100 , 200 , and 300 includes a plurality of lenses. For example, the second imaging optical systems 100 , 200 , and 300 may be configured with five lenses. In addition, the second imaging optical systems 100 , 200 , and 300 may be any one of the optical imaging 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 optical system 101 and the second optical system 100 , 200 , and 300 may have substantially the same size. For example, the total length L1 of the first optical system 101 may be substantially equal to the length L2 of the second optical system 100 , 200 , and 300 . Alternatively, the ratio (L1/L2) of the total length L2 of the second imaging optical systems 100, 200, and 300 to the overall length L1 of the first 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 overall length L2 of the second imaging optical systems 100 , 200 , and 300 may be 0.8 or less.

* 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 within the scope not departing from the gist of the present invention described in the claims below It can be implemented with various changes.

100, 200, 300 imaging optics
110, 210, 310 first lens
120, 220, 420 second lens
130, 230, 430 third lens
140, 240, 440 4th lens
150, 250, 450 5th lens
160, 260, 460 filters
170, 270, 470 top or image sensor
ST aperture
10 mobile terminal
20 first camera module
30 Second camera module

Claims (17)

a first lens having positive refractive power and having a convex image side;
a second lens having a negative refractive power;
a third lens having a negative refractive power;
a fourth lens having a negative refractive power and having an inflection point formed on an image side; and
a fifth lens having positive refractive power and having a concave object side and a convex image side;
An imaging optical system comprising a. 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 second lens is an imaging optical system having a convex shape on the side of the object. According to claim 1,
The second lens is an imaging optical system having a concave shape in the image side. According to claim 1,
The third lens is an imaging optical system having a concave shape on the side of the object. delete According to claim 1,
The fourth lens is an imaging optical system in which both surfaces are concave. delete delete According to claim 1,
An imaging optical system satisfying the following conditional expression.
[Conditional Expression] TL/f < 1.0
(In the above conditional expression, TL is the distance from the object side to the image plane of the first lens, and f is the total focal length of the imaging optical system) a first lens having refractive power;
a second lens having refractive power;
a third lens having a negative refractive power;
a fourth lens having a concave side surface of the object; and
a fifth lens having refractive power and having a concave shape on the side of the object;
An imaging optical system that includes and satisfies the following conditional expressions.
TL/f < 1.0
0.15 < R1/f < 1.5
-3.5 < f/f2 < -0.5
(In the above conditional expression, TL is the distance from the object side of the first lens to the image plane, R1 is the radius of curvature of the object side of the first lens, f is the total focal length of the imaging optical system, and f2 is the second lens is the focal length of 12. The method of claim 11,
The fifth lens is an imaging optical system having a convex image side. delete delete 12. The method of claim 11,
An imaging optical system satisfying the following conditional expression.
[Conditional Expression] 0.1 < d34/TL < 0.7
(d34 in the above conditional expression is the distance from the image side of the third lens to the object side of the fourth lens) 12. The method of claim 11,
An imaging optical system satisfying the following conditional expression.
[Conditional Expression] 1.60 < Nd5 < 1.75
(In the above conditional expression, Nd5 is the refractive index of the fifth lens) 12. The method of claim 11,
An imaging optical system satisfying the following conditional expression.
[Conditional Expression] 0.3 < tanθ < 0.5
(In the above conditional expression, θ is the half angle of view of the imaging optical system)

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