KR20230110462A - Optical Imaging System - Google Patents

Abstract

An imaging optical system of the present invention includes a first lens having a positive refractive power that is sequentially disposed from an object side toward an image plane; a second lens having negative refractive power; a third lens having negative refractive power; a fourth lens having refractive power; a fifth lens having refractive power; and a sixth lens having positive refractive power and having a convex image side surface.

Description

Imaging optical system {Optical Imaging System}

The present invention relates to an optical system for telephoto imaging composed of five or more 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 2016-0016931 A JP 2009-294527 A US 2013-0021678 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 positive refractive power, sequentially disposed from the object side; a second lens having negative refractive power; a third lens having negative refractive power; a fourth lens having negative refractive power; and a fifth lens having positive refractive power, and satisfies the conditional expression 0.7<TL/f<1.0.

In the above conditional expression, TL is the distance from the side of the object to the image surface of the first lens, and f is the total focal length of the imaging optical system.

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 table showing aspheric characteristics of the imaging optical system shown in FIG. 1;
4 is a configuration diagram of an imaging optical system according to a second embodiment of the present invention;
5 is a graph showing an aberration curve of the imaging optical system shown in FIG. 4;
6 is a table showing aspherical characteristics of the imaging optical system shown in FIG. 5;
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 aspheric characteristics of the imaging optical system shown in FIG. 7;
10 is a rear view of a portable terminal equipped with an imaging optical system according to an embodiment of the present invention;
11 is a cross-sectional view of the portable terminal shown in FIG. 10;

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 means not only the case where these components are 'directly connected', but also the case where they are 'indirectly connected' through another component. 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 refers to a lens closest to the object (or subject), and the sixth lens refers to a lens closest to the image surface (or image sensor). In this specification, the units of the radius of curvature of the lens, thickness, TL, 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 the distances from 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 of one surface 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 two lens groups. For example, the imaging optical system is composed of a first lens group and a second lens group.

The first lens group is composed of a plurality of lenses. For example, the first lens group may include 3 lenses or 4 lenses.

In the former case, the first lens group includes a first lens having positive refractive power, a second lens having negative refractive power, and a third lens having negative refractive power. The first lens has a convex object side surface, the second lens has a convex object side surface and a concave image side surface, and the third lens has a concave image side surface.

In the case of the latter, the first lens group includes a first lens having positive refractive power, a second lens having negative refractive power, a third lens having negative refractive power, and a fourth lens having positive refractive power. The first lens has a convex object side surface, the second lens has a convex object side surface and a concave image side surface, the third lens has a concave shape on both sides, and the fourth lens has a convex shape on both sides.

The first lens group includes an aspherical lens. For example, at least one surface of all the lenses constituting the first lens group may be an aspheric surface. The first lens group includes plastic lenses. For example, all lenses constituting the first lens group may be made of plastic.

The second lens group is composed of a plurality of lenses. For example, the second lens group may include a lens having negative refractive power and a lens having positive refractive power. Here, the lens having negative refractive power may have a concave shape on both sides, and the lens having positive refractive power may have a shape on both sides convex.

The second lens group includes an aspherical lens. For example, at least one surface of all the lenses constituting the second lens group may be an aspherical surface. The second lens group includes plastic lenses. For example, all lenses constituting the second lens group may be made of plastic.

An aspherical surface of a lens in an imaging optical system 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 any point on the aspheric surface to the optical axis, A to J are aspheric constants, and Z (or SAG) is the height in the optical axis direction from any point on the aspheric surface to the apex of the aspherical surface.

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

The filter is disposed between the rearmost lens of the second lens group and the image sensor. The filter may block some wavelengths of light so that clear images can be realized. 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 between the second lens and the third lens.

The imaging optical system may satisfy the following Conditional Expressions.

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

[conditional expression 2] 0.9 < d1G2G < 1.7

[conditional expression 3] -2.5 < f/f2 < -0.5

[conditional expression 4] -3.5 < f/f3 < -0.4

[conditional expression 4] 1.6 < Ndi < 1.75

[conditional expression 6] 0.3 < tanθ < 0.5

[conditional expression 7] -1.0 < f1G/f2G < -0.2

[conditional expression 8] TL/f1 < 2.0

In the 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, d1G2G is the distance from the image side of the lens closest to the image plane in the first lens group to the object side of the lens closest to the object side in the second lens group, f1 is the focal length of the first lens, f2 is the focal length of the second lens, f3 is the focal length of the third lens, and Ndi is the refractive index of the lens disposed closest to the image plane , θ is the half angle of view of the imaging optical system, f1G is the combined focal length of the first lens group, and f2G is the combined focal length of the second lens group.

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 design condition for constructing an optical system for telephoto. For example, an imaging optical system that exceeds the lower limit of Condition 2 has a shorter focal length and is difficult to mount on a telephoto camera, and an imaging optical system that exceeds the upper limit of Condition 2 has a larger total length TL, making it difficult to miniaturize.

Conditional Expression 3 is a design condition of the second lens for realizing a high-resolution imaging optical system. For example, the second lens out of the numerical range of Conditional Expression 3 may cause image deterioration by increasing astigmatism of the imaging optical system.

Conditional Expression 4 is a design condition of the third lens for realizing a high-resolution imaging optical system. For example, the third lens out of the numerical range of Conditional Expression 4 may cause image deterioration by increasing astigmatism of the imaging optical system.

Conditional Expression 5 is a design condition for a lens closest to the image plane for a high-resolution imaging optical system. For example, since a lens that satisfies the numerical range of Conditional Expression 5 has a low Abbe number of 26 or less, it is advantageous in correcting astigmatism, longitudinal chromatic aberration, and magnification aberration.

Conditional Expression 6 is a range of angles of view for constituting a telephoto imaging optical system, and Conditional Expression 7 is a numerical range of F No. for a high-resolution imaging optical system.

Conditional Equation 8 proposes an appropriate focal ratio between the first lens group for aberration correction of the imaging optical system and the first lens group for field curvature correction.

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

First, an imaging optical system according to the first embodiment will be described with reference to FIG. 1 .

The imaging optical system 100 is composed of a first lens group 1G and a second lens group 2G.

The first lens group 1G includes a first lens 110 , a second lens 120 , and a third lens 130 .

The first lens 110 has a positive refractive power and has a convex shape on both sides. 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 negative refractive power and has a convex object side surface and a concave image side surface.

The second lens group 2G includes a fourth lens 140 and a fifth lens 150 .

The fourth lens 140 has negative refractive power and has a concave shape on both sides. In addition, the fourth lens 140 has a shape in which an inflection point is formed on an image side surface. For example, an image side surface of the fourth lens 140 may be concave near an optical axis and convex at an edge. The fifth lens 150 has a positive refractive power and has a convex shape on both sides. In addition, the fifth lens 150 has a shape in which an inflection point is formed on the side of the object.

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 fifth lens 150 and the image sensor 180, and the diaphragm ST is disposed between the second lens 120 and the third lens 130.

The imaging optical system configured as above exhibits aberration characteristics as shown in FIG. 2 . 3 shows aspheric characteristics of the imaging optical system according to the present embodiment. Table 1 shows the lens characteristics of the imaging optical system 100 according to the present 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 first lens group 1G and a second lens group 2G.

The first lens group 1G includes a first lens 210 , a second lens 220 , and a third lens 230 .

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 concave shape on both sides.

* The second lens group 2G includes a fourth lens 240 and a fifth lens 250 .

The fourth lens 240 has negative refractive power and has a concave shape on both sides. In addition, the fourth lens 240 has a shape in which an inflection point is formed on an image side surface. For example, an image side surface of the fourth lens 240 may be concave near an optical axis and convex at an edge. The fifth lens 250 has a positive refractive power and has a convex shape on both sides. In addition, the fifth lens 250 has a shape in which an inflection point is formed on the side of the object.

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 fifth lens 250 and the image sensor 280, and the diaphragm ST is disposed between the second lens 220 and the third lens 230.

The imaging optical system configured as above exhibits aberration characteristics as shown in FIG. 5 . 6 shows aspheric characteristics of the imaging optical system according to the present embodiment. Table 2 shows the lens characteristics of the imaging optical system 200 according to the present 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 first lens group 1G and a second lens group 2G.

The first lens group 1G includes a first lens 310 , a second lens 320 , a third lens 330 , and a fourth lens 340 .

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 concave shape on both sides. The fourth lens 340 has a positive refractive power and has a convex shape on both sides.

The second lens group 2G includes a fifth lens 350 and a sixth lens 360 .

The fifth lens 350 has negative refractive power and has a concave shape on both sides. In addition, the fifth lens 350 has a shape in which an inflection point is formed on an image side surface. For example, an image side surface of the fifth lens 350 may be concave near an optical axis and convex at an edge. The sixth lens 360 has a positive refractive power and has a convex shape on both sides. In addition, the sixth lens 360 has a shape in which an inflection point is formed on the side of the object.

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 between the second lens 320 and the third lens 330.

The imaging optical system configured as above exhibits aberration characteristics as shown in FIG. 8 . 9 shows aspherical characteristics of the imaging optical system according to the present embodiment. Table 3 shows the lens characteristics of the imaging optical system 300 according to this embodiment.

Table 4 shows conditional expression values of the imaging optical system according to the first to third embodiments.

Next, referring to FIGS. 10 and 11 , 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 20 and 30 . The first camera module 20 includes a first imaging optical system 101 configured to photograph a subject at a short distance, and the second camera module 30 includes a second imaging optical system 100, 200, 300 configured to photograph a subject at a distance.

The first imaging optical system 101 includes a plurality of lenses. For example, the first imaging optical system 101 may include four or more lenses. The first imaging optical system 101 is configured to integrally photograph objects located at a short distance. For example, the first imaging optical system 101 may have a wide angle of view of 50 degrees or more, and a TL/f ratio of 1.0 or more.

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 five or more 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 a TL/f ratio of less than 1.0.

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 the same as 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, 300 may be 0.8 or less.

The present invention is not limited to the embodiments described above, and those skilled in the art to which the present invention pertains can make various changes without departing from the gist of the technical idea of the present invention described in the claims below.

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
360 6th lens
170, 270, 370 (infrared cut) filter
180, 280, 380 image sensor or top surface
1G 1st lens group
2G 2nd lens group

Claims (8)

a first lens having refractive power;
a second lens having negative refractive power;
a third lens having a concave shape on the side of the object;
a fourth lens having a convex object side surface;
a fifth lens having refractive power; and
a sixth lens having positive refractive power;
including,
The first lens to the sixth lens are sequentially disposed from the object side,
The image side of the first lens or the object side of the second lens has a concave shape,
An imaging optical system that satisfies the following conditional expression.
0.7 < TL/f < 1.0
(In the above conditional expression, TL is the distance from the object side surface of the first lens to the image surface, and f is the total focal length of the imaging optical system) According to claim 1,
The first lens is an imaging optical system having a shape in which an object side surface is convex. According to claim 1,
The second lens has a concave image side surface. According to claim 1,
The third lens has a convex image side surface. According to claim 1,
The fifth lens has a concave image side surface. According to claim 1,
The sixth lens is an imaging optical system having a convex image side surface. According to claim 1,
An imaging optical system that satisfies the following conditional expression.
-2.5 < f/f2 < -0.5
(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.
-3.5 < f/f3 < -0.4
(In the conditional expression, f3 is the focal length of the third lens)