KR102482314B1 - Optical Imaging System - Google Patents

Abstract

An imaging optical system of the present invention includes a first lens having a concave image side surface; a second lens having a convex shape on the side of the object; a third lens having a convex shape on the side of the object; a fourth lens having a convex image side surface; a fifth lens having a convex image side surface; and a sixth lens having a shape in which an image side surface is concave and an inflection point is formed on the image side surface.

Description

Imaging optical system {Optical Imaging System}

The present invention relates to an optical system for telephoto imaging composed of six lenses.

A 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 mount the telephoto optical system on small electronic products such as portable terminals.

KR 10-1690481 B1 US 2016-187621 A1 US 2016-187622 A1

An object of the present invention is to provide an imaging optical system capable of long-distance shooting and mounted in a small terminal.

An imaging optical system for achieving the above object includes a first lens having a concave image side surface; a second lens having a convex shape on the side of the object; a third lens having a convex shape on the side of the object; a fourth lens having a convex image side surface; a fifth lens having a convex image side surface; and a sixth lens having a shape in which an image side surface is concave and an inflection point is formed on the image side surface.

The present invention can implement an imaging optical system capable of long-distance shooting and mounted in a small terminal.

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 configuration diagram of an imaging optical system according to a second embodiment of the present invention;
4 is a graph showing an aberration curve of the imaging optical system shown in FIG. 3;
5 is a configuration diagram of an imaging optical system according to a third 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 rear view of a portable terminal equipped with an imaging optical system according to an embodiment of the present invention;
8 is a cross-sectional view of the portable terminal 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, 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 seventh lens means 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, IMG HT (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 calculated based on 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 6 lenses. For example, the imaging optical system may include a first lens, a second lens, a third lens, a fourth lens, a fifth lens, and a sixth lens sequentially disposed from the object side. The first to sixth lenses are disposed with an air gap. For example, the object side of any lens does not contact the image side of an adjacent lens, and the image side of any lens does not contact the object side of an adjacent lens.

The first lens has refractive power. For example, the first lens has positive refractive power. The first lens has a concave shape on one surface. For example, the first lens has a concave image side surface.

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 a plastic material. For example, the first lens may be made of a glass material. The first lens has a low refractive index. For example, the refractive index of the first lens may be less than 1.6.

The second lens has refractive power. For example, the second lens has negative refractive power. The second lens has a convex shape on one surface. For example, the second lens may have a shape in which the side of the object is convex.

The second lens includes an aspheric 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 1.63 or more.

The third lens has refractive power. For example, the third lens may have positive or negative refractive power. The third lens has a shape in which one surface is convex. For example, the third lens may have a shape in which an object side surface is convex.

The third lens may include an aspherical surface. For example, both surfaces of the third lens may be aspheric. 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 substantially the same refractive index as the first lens. For example, the refractive index of the third lens may be less than 1.6.

The fourth lens has refractive power. For example, the fourth lens has positive refractive power. The fourth lens has a shape in which one surface is convex. For example, the fourth lens may have a convex image side surface.

The fourth lens may include an aspheric 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 a higher refractive index than the first lens. For example, the refractive index of the fourth lens may be 1.63 or more.

The fifth lens has refractive power. For example, the fifth lens may have negative refractive power. The fifth lens has a shape in which one surface is convex. For example, the fifth lens may have a convex image side surface.

The fifth lens includes an aspheric 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 predetermined refractive index. For example, the refractive index of the fifth lens may be 1.5 or more.

The sixth lens has refractive power. For example, the sixth lens has negative refractive power. The sixth lens may have a concave shape. For example, the sixth lens may have a concave image side surface.

The sixth lens includes an aspheric surface. For example, both surfaces of the sixth lens may be aspherical. The sixth lens may be made of a material having high light transmittance and excellent workability. For example, the sixth lens may be made of a plastic material. However, the material of the sixth lens is not limited to plastic. For example, the sixth lens may be made of a glass material. The sixth lens has a lower refractive index than the first lens. For example, the refractive index of the sixth lens may be less than 1.54.

Aspheric surfaces of the first to sixth lenses may be 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 an arbitrary point on the aspherical surface to the optical axis, A to J are aspheric constants, and Z (or SAG) is the aspheric surface It is the height in the optical axis direction from an arbitrary point on the image to the apex of the aspheric surface.

The imaging optical system further includes a filter, an image sensor, and a diaphragm.

A filter is disposed between the sixth lens and the image sensor. Filters can block some wavelengths of light. For example, a filter may block infrared wavelengths of light.

An image sensor forms an upper surface. For example, the surface of the image sensor may form a top surface.

The diaphragm is arranged to adjust the amount of light incident on the lens. For example, the diaphragm may be disposed in front of the first lens or between the first and second lenses.

The imaging optical system may satisfy one or more of the following conditional expressions.

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

[Conditional Expression 2] |Nd2 - Nd3| < 0.2

[Conditional Expression 3] 0.5 < f1/f < 1.0

[Conditional Expression 4] -2.0 < f2/f < -1.0

[Conditional Expression 5] |f3/f| < 20

[Conditional Expression 6] 2.0 < f4/f < 3.6

[Conditional Expression 7] -4.0 < f5/f < -1.0

[Conditional Expression 8] -4.0 < f6/f < -1.0

[Conditional Expression 9] -2.0 < f4/f5 < -1.0

[Conditional Expression 10] 2.0 < D56/D6F < 5.0

* In the above conditional expression, TL is the distance from the object side of the first lens to the image plane, f is the total focal length of the imaging optical system, Nd2 is the refractive index of the second lens, Nd3 is the refractive index of the third lens, and f1 is the first f2 is the focal length of lens 1, f2 is the focal length of lens 2, f3 is the focal length of lens 3, f4 is the focal length of lens 4, f5 is the focal length of lens 5, and f6 is the focal length of lens 5 6 is the focal length of the lens, D56 is the distance from the object side of the 5th lens to the object side of the 6th lens, and D6F is the distance from the image side of the 6th lens to the filter.

The imaging optical system may further satisfy the following conditional expression.

[Conditional Expression 11] 3.0 < |f3/f| < 10

Conditional Expression 1 is a condition for miniaturization of the imaging optical system. For example, an imaging optical system exceeding the upper limit of Conditional Expression 1 is difficult to mount in a portable terminal because it is difficult to miniaturize, and an imaging optical system exceeding the lower limit of Conditional Expression 1 is difficult to manufacture.

Conditional Expression 2 is a relational expression for the material of the second lens and the material of the third lens. An imaging optical system that satisfies Conditional Expression 2 is advantageous in correcting chromatic aberration through the second lens and the third lens.

Conditional Expression 3 is a conditional expression for increasing the aberration correction effect through the third lens. For example, the refractive power of the third lens outside the upper limit of Conditional Expression 3 is weak and the aberration correction effect is negligible.

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

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

The imaging optical system 100 includes a first lens 110, a second lens 120, a third lens 130, a fourth lens 140, a fifth lens 150, and a sixth lens 160. .

The first lens 110 has a positive refractive power, and has a convex object side surface and a concave image side surface. The second lens 120 has negative refractive power and has a convex object side surface and a concave image side surface. The third lens 130 has a positive refractive power and has a convex object side surface and a concave image side surface. 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 negative refractive power and has a concave object side surface and a convex image side surface. The sixth lens 160 has negative refractive power and has a convex object side surface and a concave image side surface. In addition, the sixth lens 160 has a shape in which inflection points are formed on the object side and the image side.

The imaging optical system 100 further includes a filter 170, an image sensor 180, and a diaphragm ST. The filter 170 is disposed between the sixth lens 160 and the image sensor 180, and the diaphragm ST is disposed on the object side of the first lens 110.

The imaging optical system configured as above exhibits aberration characteristics as shown in FIG. 2 . The lens characteristics and aspheric surface values of the imaging optical system according to the present embodiment are shown in Tables 1 and 2.

An imaging optical system according to a second embodiment will be described with reference to FIG. 3 .

The imaging optical system 200 includes a first lens 210, a second lens 220, a third lens 230, a fourth lens 240, a fifth lens 250, and a sixth lens 260. .

The first lens 210 has a positive refractive power and has a convex object side surface and a concave image side surface. The second lens 220 has negative 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 convex object side surface and a concave image side surface. The fourth lens 240 has a positive refractive power, and has a shape in which an object side surface is convex and an image side surface is convex. The fifth lens 250 has negative refractive power and has a concave object side surface and a convex image side surface. The sixth lens 260 has negative refractive power and has a convex object side surface and a concave image side surface. In addition, the sixth lens 260 has a shape in which inflection points are formed on the object side and the image side.

The imaging optical system 200 further includes a filter 270, an image sensor 280, and an aperture ST. The filter 270 is disposed between the sixth lens 260 and the image sensor 280, and the diaphragm ST is disposed on the object side of the first lens 210.

The imaging optical system configured as above exhibits aberration characteristics as shown in FIG. 4 . The lens characteristics and aspheric surface values of the imaging optical system according to the present embodiment are shown in Tables 3 and 4.

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

The imaging optical system 300 includes a first lens 310, a second lens 320, a third lens 330, a fourth lens 340, a fifth lens 350, and a sixth lens 360. .

The first lens 310 has a positive refractive power, and has a convex object side surface and a concave image side surface. The second lens 320 has negative 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 convex object side surface and a concave image side surface. The fourth lens 340 has a positive refractive power, and has a shape in which an object side surface is convex and an image side surface is convex. The fifth lens 350 has negative refractive power and has a concave object side surface and a convex image side surface. The sixth lens 360 has negative refractive power and has a convex object side surface and a concave image side surface. In addition, the sixth lens 360 has a shape in which inflection points are formed on the object side and the image side.

The imaging optical system 300 further includes a filter 370, an image sensor 380, and an aperture ST. The filter 370 is disposed between the sixth lens 360 and the image sensor 380, and the diaphragm ST is disposed on the object side of the first lens 310.

The imaging optical system configured as above exhibits aberration characteristics as shown in FIG. 6 . The lens characteristics and aspheric surface values of the imaging optical system according to the present embodiment are shown in Tables 5 and 6.

Table 7 shows conditional expression values of the imaging optical system according to the first to third embodiments.

Next, referring to FIGS. 7 and 8 , a portable terminal equipped with an imaging optical system according to an embodiment of the present invention will be described.

The portable terminal 10 includes a plurality of camera modules 30 and 40 . The first camera module 30 includes a first imaging optical system 32 configured to photograph a subject at a short distance, and the second camera module 40 includes a second imaging optical system 100, 200, configured to photograph a subject at a distance. 300).

The first imaging optical system 32 includes a plurality of lenses. For example, the first imaging optical system 32 may include four or more lenses. The first imaging optical system 32 is configured to integrally photograph objects located at a short distance. For example, the first imaging optical system 32 may have a wide angle of view of 50 degrees or more, and an h1/Cf ratio of 1.0 or more. Here, h1 is the total length of the first imaging optical system, and Cf is the total focal length of the first imaging optical system.

The second imaging optical system 100, 200, 300 includes a plurality of lenses. For example, the second imaging optical systems 100, 200, and 300 may include six lenses. The second imaging optical system 100, 200, 300 may be any one of the imaging optical systems according to the first to third embodiments described above. The second imaging optical system 100, 200, 300 is configured to photograph an object located at a long distance. For example, the second imaging optical systems 100, 200, and 300 may have an angle of view of 50 degrees or less, and an h2/f ratio may be less than 1.0.

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 6th lens
170, 270, 370 (infrared cut) filter
180, 280, 380 image sensor or top surface

Claims (15)

A first lens having refractive power and having a convex object side surface;
a second lens having refractive power and having a convex object side surface and a concave image side surface;
a third lens having negative refractive power;
a fourth lens having refractive power and having a convex image side surface;
A fifth lens having refractive power and having a concave object side surface; and
a sixth lens having negative refractive power;
including,
The first lens to the sixth lens are sequentially disposed from the object side, and satisfy the following conditional expressions.
0.7 < TL/f < 1.0
2.0 < f4 / f < 3.6
(In the above conditional expression, TL is the distance from the object side surface of the first lens to the image plane, f is the total focal length of the imaging optical system, and f4 is the focal length of the fourth lens) According to claim 1,
The first lens has a positive refractive power. According to claim 1,
The second lens has negative refractive power. delete According to claim 1,
The third 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,
An imaging optical system that satisfies the following conditional expression.
0.5 < f1/f < 1.0
(In the conditional expression, f1 is the focal length of the first lens) According to claim 1,
An imaging optical system that satisfies the following conditional expression.
-2.0 < f2/f < -1.0
(In the conditional expression, f2 is the focal length of the second lens) According to claim 1,
An imaging optical system that satisfies the following conditional expression.
|f3/f| < 20
(In the conditional expression, f3 is the focal length of the third lens) According to claim 1,
An imaging optical system that satisfies the following conditional expression.
-4.0 < f5/f < -1.0
(In the above conditional expression, f5 is the focal length of the fifth lens) According to claim 1,
An imaging optical system that satisfies the following conditional expression.
-4.0 < f6/f < -1.0
(In the above conditional expression, f6 is the focal length of the sixth lens) According to claim 1,
An imaging optical system that satisfies the following conditional expression.
-2.0 < f4/f5 < -1.0
(In the conditional expression, f4 is the focal length of the fourth lens, and f5 is the focal length of the fifth lens) A first lens having a positive refractive power and having a convex object side surface;
a second lens having negative refractive power;
a third lens having negative refractive power;
a fourth lens having refractive power and having a convex object side surface;
a fifth lens having negative refractive power; and
a sixth lens having refractive power;
including,
The first lens to the sixth lens are sequentially disposed from the object side, and satisfy the following conditional expressions.
0.7 < TL/f < 1.0
-2.0 < f2/f < -1.0
(In the above conditional expression, TL is the distance from the object side surface of the first lens to the image plane, f is the total focal length of the imaging optical system, and f2 is the focal length of the second lens) According to claim 13,
An imaging optical system that satisfies the following conditional expression.
|f3/f| < 20
(In the conditional expression, f3 is the focal length of the third lens) According to claim 13,
An imaging optical system that satisfies the following conditional expression.
-4.0 < f5/f < -1.0
(In the above conditional expression, f5 is the focal length of the fifth lens)

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