KR102584988B1 - Optical Imaging System - Google Patents

Abstract

The imaging optical system of the present invention includes a first lens having positive refractive power arranged in order from the object side to the image surface; 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.

Description

Optical Imaging System

The present invention relates to a telephoto imaging optical system composed of six elements.

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 2012-0314301 A US 2015-0260960 A

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 positive refractive power; a second lens having negative refractive power; a third lens having negative refractive power; a fourth lens having refractive power; a fifth lens having negative refractive power; and a sixth lens having positive refractive power and having a convex image side.

The present invention can implement an imaging optical system that allows long-distance shooting and can be incorporated into 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 aspherical characteristics of the imaging optical system shown in Figure 1
4 is a configuration diagram of an imaging optical system according to a second embodiment of the present invention.
Figure 5 is a graph showing the aberration curve of the imaging optical system shown in Figure 4
Figure 6 is a table showing the aspherical characteristics of the imaging optical system shown in Figure 5
7 is a configuration diagram of an imaging optical system according to a third embodiment of the present invention.
Figure 8 is a graph showing the aberration curve of the imaging optical system shown in Figure 7
Figure 9 is a table showing the aspherical characteristics of the imaging optical system shown in Figure 7
Figure 10 is a rear view of a portable terminal equipped with an imaging optical system according to an embodiment of the present invention.
Figure 11 is a cross-sectional view of the portable terminal shown in Figure 10

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 sixth 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, IMG HT (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 the distance from 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 six 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 that are sequentially arranged from the object side.

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

The second lens includes an aspherical surface. For example, the second lens may have an aspherical side surface of the object. 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 third lens has refractive power. For example, the third lens may have negative refractive power. The third lens has a concave shape on at least one side. For example, the third lens may have a concave shape on the side of the object.

The third lens includes an aspherical surface. For example, the third lens may have an aspherical image side. 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 higher refractive index than the first lens. For example, the refractive index of the third lens may be 1.6 or more.

The fourth lens has refractive power. For example, the fourth lens has positive or negative refractive power. The fourth lens has a shape in which at least one side is convex. For example, the fourth lens may have a convex shape on the side of the object.

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 a higher refractive index than the first lens. For example, the refractive index of the fourth lens may be 1.6 or more.

The fifth lens has refractive power. For example, the fifth lens has negative refractive power. The fifth lens has a concave shape on at least one side. For example, the fifth lens may have a concave shape on both sides.

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 substantially the same refractive index as the first lens. For example, the refractive index of the fifth lens may be less than 1.6.

The sixth lens has refractive power. For example, the sixth lens has positive refractive power. The sixth lens may have a convex shape on at least one side. For example, the sixth lens may have a convex image side. The sixth lens may have a shape with an inflection point. For example, one or more inflection points may be formed on both sides of the sixth lens.

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

The aspherical surface of the first to sixth lenses can be 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.

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

The filter is disposed between the sixth lens and the image sensor. Filters can block some wavelengths of light so that clear images can be created. For example, a filter can block light in infrared wavelengths. The filter may have a predetermined refractive index. For example, the filter may have a refractive index of 1.53 or less. Additionally, the filter may have a predetermined Abbe number. For example, the filter may have an Abbe number of 40 or less.

The image sensor forms the upper surface. For example, the surface of the image sensor may form an upper surface.

The aperture is arranged to adjust the amount of light entering the lens. For example, the aperture may be disposed between the third and fourth lenses.

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 < 0.32

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

[Conditional Expression 4] 0.1 < d45/TL < 0.7

[Conditional Expression 5] 1.6 < Nd6 < 1.75

[Conditional Expression 6] 0.3 < tanθ < 0.5

[Conditional Expression 7] 2.0 < f/EPD < 2.7

In the above conditional expression, TL is the distance from the object side of the first lens to the image surface, f is the total focal length of the imaging optical system, f2 is the focal length of the second lens, and R1 is the radius of curvature of the object side of the first lens. , d45 is the distance from the image side of the fourth lens to the object side of the fifth lens, Nd6 is the refractive index of the sixth lens, θ is the half angle of view of the imaging optical system, and EPD is the diameter of the entrance pupil.

Conditional expression 1 is a condition for miniaturization of the imaging optical system. For example, an imaging optical system that exceeds the upper limit of Conditional Expression 1 is difficult to miniaturize and is difficult to mount on a portable terminal, and an imaging optical system that exceeds the lower limit of Conditional Expression 1 is difficult to manufacture.

Conditional equation 2 is the manufacturing condition for the first lens to construct the telephoto optical system. For example, a first lens that exceeds the upper limit of Conditional Expression 2 increases the longitudinal spherical aberration and shortens the focal length of the imaging optical system, and a first lens that exceeds the lower limit of Conditional Expression 2 increases the focal length of the imaging optical system, but is difficult to manufacture. difficult. In addition, the first lens that exceeds the lower limit of conditional equation 2 is difficult to manufacture because the thickness of the edge of the lens becomes thin.

Conditional equation 3 is the design condition for the second lens to implement a high-resolution imaging optical system. For example, a second lens that is outside the numerical range of Conditional Equation 3 may increase astigmatism of the imaging optical system and cause image deterioration.

Conditional equation 4 is a design condition for configuring a telephoto optical system. For example, an imaging optical system that exceeds the lower limit of Conditional Expression 4 has a short focal length and is difficult to use for telephoto purposes, and an imaging optical system that exceeds the upper limit of Conditional Expression 4 has a large overall length (TL) of the optical system, making it difficult to miniaturize.

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

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

In the imaging optical system, the refractive power of the lens (the absolute value of the reciprocal of the focal length) may be arranged in a predetermined order. For example, the refractive power of an odd-numbered lens may be greater than the refractive power of an even-numbered lens disposed on the image side. That is, the refractive power of the first lens may be greater than that of the second lens, the refractive power of the third lens may be greater than that of the fourth lens, and the refractive power of the fifth lens may be greater than the refractive power of the sixth lens.

In the imaging optical system, the lens with the greatest refractive power may be placed close to the object side, and the lens with the smallest refractive power may be placed close to the image side. For example, in an imaging optical system, the first lens may have the greatest refractive power, and the fourth or sixth lens may have the smallest refractive power.

In an imaging optical system, the first lens may have the most convex surface. For example, the object side of the first lens may have the most convex shape. In the imaging optical system, the second lens may have the most concave surface. For example, the image side of the second lens may have the most concave shape. In the imaging optical system, the fourth lens may have a generally flat surface. For example, the image side of the fourth lens may have a shape close to a plane.

In an imaging optical system, three or more adjacent lenses may have generally similar refractive indices. For example, the second to fourth lenses may have substantially the same or similar refractive index. The refractive index of the second to fourth lenses may be selected in the range of 1.63 to 1.68.

The focal length of the lenses constituting the imaging optical system can be selected within a predetermined range. For example, the focal length of the first lens may be selected in the range of 2.4 to 3.1 mm, the focal length of the second lens may be selected in the range of -8.5 to -5.8 mm, and the focal length of the third lens may be selected in the range of -11.5 to - It can be selected from the range of 3.8 mm, the focal length of the fifth lens can be selected from the range of -4.7 to -3.7 mm, and the focal length of the sixth lens can be selected from the range of 9.0 to 13.5 mm.

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 consists of 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. Includes optical system.

The first lens 110 has positive refractive power and has a convex shape on both sides. 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 concave shape on both sides. The fourth lens 140 has positive refractive power and has a convex shape on both sides. The fifth lens 150 has negative refractive power and has a concave shape on both sides. In addition, the fifth lens 150 has a shape in which inflection points are formed on both sides. The sixth lens 160 has positive refractive power and has a convex shape on both sides. In addition, the sixth lens 160 has a shape in which an inflection point is formed on the side or image side of the object.

Among the lenses, the first lens 110 has the greatest refractive power, and the sixth lens 160 has the smallest refractive power.

The imaging optical system 100 further includes a filter 170, an image sensor 180, and an aperture (ST). The filter 170 is disposed between the sixth lens 160 and the image sensor 180, and the aperture ST is disposed between the third lens 130 and the fourth lens 140.

The imaging optical system configured as above exhibits aberration characteristics as shown in FIG. 2. Figure 3 shows aspherical characteristics of the imaging optical system according to this embodiment. The lens characteristics of the imaging optical system 100 according to this embodiment are shown in Table 1.

An imaging optical system according to a second embodiment will be described with reference to FIG. 4 .

The imaging optical system 200 consists of 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. Includes optical system.

The first lens 210 has positive refractive power and has both sides convex. 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 positive refractive power and has a convex shape on both sides. The fifth lens 250 has negative refractive power and has a concave shape on both sides. Additionally, the fifth lens 250 has a shape in which inflection points are formed on both sides. The sixth lens 260 has positive refractive power and has a convex shape on both sides. In addition, the sixth lens 260 has a shape in which an inflection point is formed on at least one surface.

Among the lenses, the first lens 210 has the greatest refractive power, and the sixth lens 260 has the smallest refractive power.

The imaging optical system 200 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 aperture ST is disposed between the third lens 230 and the fourth lens 240.

The imaging optical system configured as above exhibits aberration characteristics as shown in FIG. 5. Figure 6 shows aspherical characteristics of the imaging optical system according to this embodiment. The lens characteristics of the imaging optical system 200 according to this embodiment are shown in Table 2.

An imaging optical system according to a third embodiment will be described with reference to FIG. 7 .

The imaging optical system 300 consists of 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. Includes optical system.

In this embodiment, the first lens 310 has a positive refractive power and has a shape where the object side is convex and the image side is concave. The second lens 320 has negative refractive power and has a shape where the object side is convex and the image side is concave. The third lens 330 has negative refractive power and has a shape in which the object side is concave and the image side is convex. The fourth lens 340 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 fifth lens 350 has negative refractive power and has a concave shape on both sides. Additionally, the fifth lens 350 has a shape in which inflection points are formed on both sides. The sixth lens 360 has 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 at least one surface.

The imaging optical system 300 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 aperture ST is disposed between the third lens 330 and the fourth lens 340.

Among the lenses, the first lens 310 has the greatest refractive power, and the fourth lens 340 has the smallest refractive power.

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

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

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. 10 and 11.

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 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 photograph objects located at a short distance as one unit. For example, the first imaging optical system 101 may have a wide viewing angle of 50 degrees or more, and the TL/f ratio may be 1.0 or more.

The second imaging optical system 100, 200, and 300 includes a plurality of lenses. For example, the second imaging optical system 100, 200, and 300 may be composed of six lenses. 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 system (100, 200, 300) is configured to photograph objects located at a distance. For example, the second imaging optical systems 100, 200, and 300 may have an angle of view of 40 degrees or less and an L/f ratio may be 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 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, 320 2nd lens
130, 230, 330 Third lens
140, 240, 340 4th lens
150, 250, 350 5th lens
160, 260, 360 6th lens
170, 270, 370 (infrared blocking) filter
180, 280, 380 image sensor or upper surface

Claims (14)

A first lens having refractive power;
a second lens having refractive power;
A third lens with a focal length selected from the range of -11.5 mm to -3.8 mm;
A fourth lens having a concave image side;
A fifth lens that has refractive power and has a concave image side; and
It includes a sixth lens having refractive power,
The first to sixth lenses are arranged sequentially from the side of the object, and satisfy the following conditional equation.
0.7 < 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 first lens is an imaging optical system with positive refractive power. According to paragraph 1,
The first lens is an imaging optical system in which the side of the object has a convex shape. According to paragraph 1,
The second lens is an imaging optical system having negative refractive power. According to paragraph 1,
The third lens is an imaging optical system in which the side of the object has a concave shape. According to paragraph 1,
The fourth lens is an imaging optical system in which the side of the object has a convex shape. According to paragraph 1,
The fifth lens is an imaging optical system having negative refractive power. According to paragraph 1,
The sixth lens is an imaging optical system having positive refractive power. According to paragraph 1,
An imaging optical system that satisfies the following conditional expression.
0.15 < R1/f < 0.32
(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.
1.6 < Nd6 < 1.75
(In the above conditional equation, Nd6 is the refractive index of the sixth lens) According to paragraph 1,
An imaging optical system that satisfies the following conditional expression.
0.3 < tanθ < 0.5
(In the above conditional expression, θ is the half angle of view of the imaging optical system) According to paragraph 1,
An imaging optical system that satisfies the following conditional expression.
2.0 < f/EPD < 2.7
(In the above conditional equation, EPD is the entrance pupil diameter of the imaging optical system) A first lens having refractive power;
a second lens having refractive power;
A third lens with a focal length selected from the range of -11.5 mm to -3.8 mm;
A fourth lens having a concave image side;
A fifth lens having refractive power; and
It includes a sixth lens having refractive power,
The first to sixth lenses are sequentially arranged from the side of the object,
The focal length of the second lens is selected in the range of -8.50 mm to -5.80 mm,
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 of the first lens to the image surface, and f is the total focal length of the imaging optical system.)