KR102494344B1 - Optical system - Google Patents

Abstract

An imaging optical system according to an embodiment of the present invention includes, in order from the object side, a first lens having a positive refractive power; a second lens having negative refractive power, an object-side surface being convex, and an image-side surface being concave; a third lens having refractive power; a fourth lens having refractive power; a fifth lens having negative refractive power, an object-side surface being convex, and an image-side surface being concave; and a sixth lens having positive refractive power, wherein, when the Abbe number of the fifth lens is v5 and the Abbe number of the sixth lens is v6, |v5−v6| > 20 can be satisfied.

Description

Imaging optical system {Optical system}

The present invention relates to an imaging optical system.

Recent portable terminals are equipped with cameras to enable video calls and photo taking. In addition, as the function occupied by the camera in the portable terminal gradually increases, the demand for high resolution and high performance of the camera for the portable terminal is gradually increasing.

However, since portable terminals tend to become smaller or lighter, there is a limit to implementing high-resolution and high-performance cameras.

In order to solve this problem, recently, a lens of a camera is made of a plastic material that is lighter than glass, and a lens module is composed of 5 or more lenses to realize high resolution.

An object according to an embodiment of the present invention is to provide an imaging optical system capable of improving an aberration improvement effect and realizing a high resolution while being bright.

An imaging optical system according to an embodiment of the present invention includes, in order from the object side, a first lens having a positive refractive power; a second lens having negative refractive power, an object-side surface being convex, and an image-side surface being concave; a third lens having refractive power; a fourth lens having refractive power; a fifth lens having negative refractive power, an object-side surface being convex, and an image-side surface being concave; and a sixth lens having positive refractive power, wherein, when the Abbe number of the fifth lens is v5 and the Abbe number of the sixth lens is v6, |v5−v6| > 20 can be satisfied.

According to the imaging optical system according to an embodiment of the present invention, it is possible to improve the aberration improvement effect and realize high resolution while being bright.

1 is a configuration diagram of an imaging optical system according to a first embodiment of the present invention;
2 is a curve showing aberration characteristics of the imaging optical system shown in FIG. 1;
3 is a table showing the characteristics of each lens of the imaging optical system shown in FIG. 1;
4 is a table showing the aspheric coefficient of each lens of the imaging optical system shown in FIG. 1;
5 is a configuration diagram of an imaging optical system according to a second embodiment of the present invention;
6 is a curve showing aberration characteristics of the imaging optical system shown in FIG. 5;
7 is a table showing the characteristics of each lens of the imaging optical system shown in FIG. 5;
8 is a table showing aspheric coefficients of each lens of the imaging optical system shown in FIG. 5;
9 is a configuration diagram of an imaging optical system according to a third embodiment of the present invention;
10 is a curve showing aberration characteristics of the imaging optical system shown in FIG. 9;
11 is a table showing the characteristics of each lens of the imaging optical system shown in FIG. 9;
12 is a table showing aspheric coefficients of each lens of the imaging optical system shown in FIG. 9;
13 is a configuration diagram of an imaging optical system according to a fourth embodiment of the present invention;
14 is a curve showing aberration characteristics of the imaging optical system shown in FIG. 13;
15 is a table showing the characteristics of each lens of the imaging optical system shown in FIG. 13;
16 is a table showing aspheric coefficients of each lens of the imaging optical system shown in FIG. 13;
FIG. 17 is a diagram illustrating an angle between a tangent at an end of an effective mirror of an image side surface of a second lens and an image surface of an image sensor in the imaging optical system shown in FIG. 1 .

Hereinafter, specific embodiments of the present invention will be described in detail with reference to the drawings. However, the spirit of the present invention is not limited to the presented embodiments, and those skilled in the art who understand the spirit of the present invention may add, change, or delete other components within the scope of the same spirit, through other degenerative inventions or the present invention. Other embodiments included within the scope of the inventive idea can be easily suggested, but it will also be said to be included within the scope of the inventive idea.

In addition, components having the same function within the scope of the same idea appearing in the drawings of each embodiment are described using the same reference numerals.

In the following lens configuration diagram, the thickness, size, and shape of the lens are somewhat exaggerated for description, and in particular, the spherical or aspherical shape presented in the lens configuration diagram is only presented as an example and is not limited thereto.

In addition, the first lens means a lens closest to the object side, and the sixth lens means a lens closest to the image side.

In addition, the front side means a side closer to the object side in the imaging optical system, and the rear side means a side closer to the image sensor or image side in the imaging optical system. Also, in each lens, the first surface means a surface close to the object side (or object-side surface), and the second surface means a surface close to the image side (or image side surface). Further, in the present specification, values for the radius of curvature and thickness of the lens are all in mm units.

Also, a paraxial region refers to a very narrow region near an optical axis, and may mean, for example, a region in which a distance from which a light ray falls from the optical axis is zero.

An imaging optical system according to an embodiment of the present invention includes 6 lenses.

That is, the imaging optical system according to an embodiment of the present invention includes a first lens, a second lens, a third lens, a fourth lens, a fifth lens, and a sixth lens.

However, the imaging optical system according to an embodiment of the present invention is not composed of only 6 lenses and may further include other components as needed. For example, the imaging optical system may further include a diaphragm for adjusting the amount of light. In addition, the imaging optical system may further include an infrared cut filter for blocking infrared rays. In addition, the imaging optical system may further include an image sensor for converting an incident image of a subject into an electrical signal. In addition, the imaging optical system may further include a gap maintaining member for adjusting a distance between the lenses.

The first to sixth lenses constituting the imaging optical system according to an embodiment of the present invention may be made of a plastic material.

In addition, at least one of the first to sixth lenses has an aspheric surface. In addition, each of the first lens to the sixth lens may have at least one aspherical surface.

That is, at least one of the first surface and the second surface of the first lens to the sixth lens may be an aspherical surface. Here, the aspheric surfaces of the first lens to the sixth lens are expressed by Equation 1.

In Equation 1, c is the curvature (reciprocal of the radius of curvature) at the apex of the lens, K is the conic constant, and Y represents the distance in a direction perpendicular to the optical axis. In addition, the constants A to F mean aspheric coefficients. And Z represents the distance from the apex of the lens in the optical axis direction.

An imaging optical system composed of the first lens to the sixth lens has positive/negative/positive/positive or negative/negative/positive refractive power in order from the object side.

The imaging optical system configured as described above can improve optical performance through aberration improvement. In addition, in the imaging optical system configured as described above, all six lenses may be made of plastic.

An imaging optical system according to an embodiment of the present invention satisfies Conditional Expression 1.

[conditional expression 1]

0.2 < SD/f < 0.6

In Conditional Expression 1, SD is the radius of the diaphragm, and f is the total focal length of the imaging optical system.

An imaging optical system according to an embodiment of the present invention satisfies Conditional Expression 2.

[conditional expression 2]

1.1 < TTL/f < 1.35

In Condition 2, TTL is the distance from the object-side surface of the first lens to the image surface of the image sensor, and f is the total focal length of the imaging optical system.

An imaging optical system according to an embodiment of the present invention satisfies Conditional Expression 3.

[conditional expression 3]

1.0 < |r9|/f < 40

In Conditional Expression 3, f is the total focal length of the imaging optical system, and r9 is the radius of curvature of the object-side surface of the fifth lens.

An imaging optical system according to an embodiment of the present invention satisfies Conditional Expression 4.

[conditional expression 4]

|v5-v6| > 20

In Conditional Expression 4, the Abbe number v6 of the fifth lens is the Abbe number of the sixth lens.

An imaging optical system according to an embodiment of the present invention satisfies Conditional Expression 5.

[conditional expression 5]

v1-v2 > 20

In Conditional Expression 5, v1 is the Abbe's number of the first lens, and v2 is the Abbe's number of the second lens.

An imaging optical system according to an embodiment of the present invention satisfies Conditional Expression 6.

[conditional expression 6]

1.3 < f/f1 < 1.6

In Conditional Expression 6, f is the total focal length of the imaging optical system, and f1 is the focal length of the first lens.

An imaging optical system according to an embodiment of the present invention satisfies Conditional Expression 7.

[conditional expression 7]

0.1 < f/f3 < 0.3

In Conditional Expression 7, f is the total focal length of the imaging optical system, and f3 is the focal length of the third lens.

An imaging optical system according to an embodiment of the present invention satisfies Conditional Expression 8.

[conditional expression 8]

0.2 < |f/f5| < 0.4

In Conditional Expression 8, f is the total focal length of the imaging optical system, and f5 is the focal length of the fifth lens.

An imaging optical system according to an embodiment of the present invention satisfies Conditional Expression 9.

[conditional expression 9]

0 < f1/f3 < 0.2

In Conditional Expression 9, f1 is the focal length of the first lens, and f3 is the focal length of the third lens.

An imaging optical system according to an embodiment of the present invention satisfies Conditional Expression 10.

[conditional expression 10]

2 < |f/f1| + |f/f2| < 2.5

In Conditional Expression 10, f is the total focal length of the imaging optical system, f1 is the focal length of the first lens, and f2 is the focal length of the second lens.

An imaging optical system according to an embodiment of the present invention satisfies Conditional Expression 11.

[conditional expression 11]

0.1 < |f/f3| + |f/f4| < 0.4

In Conditional Expression 11, f is the total focal length of the imaging optical system, f3 is the focal length of the third lens, and f4 is the focal length of the fourth lens.

An imaging optical system according to an embodiment of the present invention satisfies Conditional Expression 12.

[conditional expression 12]

0.3 < |f/f5| + |f/f6| < 0.6

In Conditional Expression 12, f is the total focal length of the imaging optical system, f5 is the focal length of the fifth lens, and f6 is the focal length of the sixth lens.

An imaging optical system according to an embodiment of the present invention satisfies Conditional Expression 13.

[conditional expression 13]

1.5 < TTL/ImgH < 1.7

In Conditional Expression 13, TTL is the distance from the object-side surface of the first lens to the top surface of the image sensor, and ImgH is half of the diagonal length of the top surface of the image sensor.

An imaging optical system according to an embodiment of the present invention satisfies Conditional Expression 14.

[conditional expression 14]

65 < FOV < 80

In Conditional Expression 14, FOV is the angle of view of the imaging optical system. Here, the unit of the angle of view of the imaging optical system is degree.

An imaging optical system according to an embodiment of the present invention satisfies Conditional Expression 15.

[conditional expression 15]

SA2 ≤ 30

In Conditional Expression 15, SA2 is the angle between the tangent at the tip of the effective mirror of the image side surface of the second lens and the image surface of the image sensor (see FIG. 17). Here, the unit of the angle is degree.

Next, the first to sixth lenses constituting the imaging optical system according to an embodiment of the present invention will be described.

The first lens has positive refractive power. In addition, the first lens may have a convex shape on both sides. In other words, the first surface of the first lens is convex toward the object in the paraxial region, and the second surface of the first lens is convex toward the image in the paraxial region.

Also, the first lens may have a meniscus shape convex toward the object side. In other words, the first and second surfaces of the first lens may be convex toward the object in the paraxial region.

At least one surface of the first surface and the second surface of the first lens may be an aspherical surface. For example, both surfaces of the first lens may be aspheric.

The second lens has negative refractive power. In addition, the second lens has a meniscus shape convex toward the object side. In other words, the first and second surfaces of the second lens may be convex toward the object in the paraxial region.

At least one surface of the first surface and the second surface of the second lens may be an aspheric surface. For example, both surfaces of the second lens may be aspherical.

The third lens has positive refractive power. In addition, the third lens may have a meniscus shape convex upward. In other words, the first and second surfaces of the third lens may be convex upward in the paraxial region.

Also, the third lens may have a convex shape on both sides. In other words, the first surface of the third lens is convex toward the object in the paraxial region, and the second surface of the third lens is convex toward the image in the paraxial region.

At least one surface of the first surface and the second surface of the third lens may be an aspheric surface. For example, both surfaces of the third lens may be aspheric surfaces.

The fourth lens has positive or negative refractive power. In addition, the fourth lens has a meniscus shape convex upward. In other words, the first and second surfaces of the fourth lens may be convex upward in the paraxial region.

At least one surface of the first surface and the second surface of the fourth lens may be an aspheric surface. For example, both surfaces of the fourth lens may be aspheric surfaces.

The fifth lens has negative refractive power. In addition, the fifth lens may have a concave shape on both sides. In other words, the first surface of the fifth lens may be concave toward the object in the paraxial region, and the second surface of the fifth lens may be concave upward in the paraxial region.

Also, the fifth lens may have a meniscus shape convex toward the object side. In other words, the first and second surfaces of the fifth lens may be convex toward the object in the paraxial region.

At least one surface of the first surface and the second surface of the fifth lens may be an aspherical surface. For example, both surfaces of the fifth lens may be aspherical.

In addition, at least one inflection point is formed on at least one of the first surface and the second surface of the fifth lens. For example, the second surface of the fifth lens may be concave in the paraxial region and convex toward the edge.

The sixth lens has positive refractive power. In addition, the sixth lens may have a meniscus shape convex toward the object side. In other words, the first and second surfaces of the sixth lens may be convex toward the object in the paraxial region.

At least one surface of the first surface and the second surface of the sixth lens may be an aspherical surface. For example, both surfaces of the sixth lens may be aspherical.

In addition, at least one inflection point is formed on at least one of the first surface and the second surface of the sixth lens. For example, the second surface of the sixth lens may be concave in the paraxial region and convex toward the edge.

In the imaging optical system configured as described above, since a plurality of lenses perform an aberration correction function, aberration improvement performance can be improved.

An imaging optical system according to a first embodiment of the present invention will be described with reference to FIGS. 1 to 4 .

An imaging optical system according to a first embodiment of the present invention 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. It includes an optical system including 160, and may further include a stop, an infrared cut filter 170, and an image sensor 180.

As shown in Table 1, the focal length f1 of the first lens 110 is 2.85 mm, the focal length f2 of the second lens 120 is -5.3 mm, and the third lens 130 The focal length f3 is 28.86 mm, the focal length f4 of the fourth lens 140 is 741.25 mm, the focal length f5 of the fifth lens 150 is -12.35 mm, the sixth lens 160 The focal length f6 of ) is 32.76 mm, and the total focal length f of the imaging optical system is 4.16 mm.

Here, the lens characteristics of each lens (radius of curvature, thickness of the lens or distance between the lenses (thickness), index of refraction, and Abbe number) are as shown in FIG. 3 .

In the first embodiment of the present invention, the first lens 110 has a positive refractive power and has a convex shape on both sides. For example, the first surface of the first lens 110 is convex toward the object in the paraxial region, and the second surface of the first lens 110 is convex toward the image in the paraxial region.

The second lens 120 has negative refractive power and has a meniscus shape convex toward the object side. For example, the first and second surfaces of the second lens 120 are convex toward the object in the paraxial region.

The third lens 130 has a positive refractive power and has a meniscus shape convex upward. For example, the first and second surfaces of the third lens 130 are convex upward in the paraxial region.

The fourth lens 140 has a positive refractive power and has a meniscus shape convex upward. For example, the first and second surfaces of the fourth lens 140 are convex upward in the paraxial region.

The fifth lens 150 has negative refractive power and has a concave shape on both sides. For example, the first surface of the fifth lens 150 is concave toward the object in the paraxial region, and the second surface of the fifth lens 150 is concave toward the image in the paraxial region. In addition, at least one inflection point is formed on at least one of the first and second surfaces of the fifth lens 150 .

The sixth lens 160 has a positive refractive power and has a meniscus shape convex toward the object side. For example, the first and second surfaces of the sixth lens 160 are convex toward the object in the paraxial region. In addition, at least one inflection point is formed on at least one of the first and second surfaces of the sixth lens 160 .

Meanwhile, each surface of the first lens 110 to the sixth lens 160 has an aspherical surface coefficient as shown in FIG. 4 .

And, the diaphragm (Stop) may be disposed in front of the object-side surface of the first lens 110 .

Also, the imaging optical system configured as described above may have aberration characteristics shown in FIG. 2 .

An imaging optical system according to a second embodiment of the present invention will be described with reference to FIGS. 5 to 8 .

An imaging optical system according to a second embodiment of the present invention 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. It includes an optical system including 260, and may further include an aperture, an infrared cut filter 270, and an image sensor 280.

As shown in Table 2, the focal length f1 of the first lens 210 is 3.42 mm, the focal length f2 of the second lens 220 is -7.24 mm, and the third lens 230 The focal length f3 is 33.42 mm, the focal length f4 of the fourth lens 240 is 64.65 mm, the focal length f5 of the fifth lens 250 is -12.94 mm, the sixth lens 260 The focal length f6 of ) is 1380 mm, and the total focal length f of the imaging optical system is 4.71 mm.

Here, the lens characteristics (radius of curvature, thickness of the lens or distance between the lenses, index of refraction, and Abbe number) of each lens are as shown in FIG. 7 .

In the second embodiment of the present invention, the first lens 210 has a positive refractive power and has a meniscus shape convex toward the object side. For example, the first and second surfaces of the first lens 210 may be convex toward the object in the paraxial region.

The second lens 220 has negative refractive power and has a meniscus shape convex toward the object side. For example, the first and second surfaces of the second lens 220 may be convex toward the object in the paraxial region.

The third lens 230 has a positive refractive power and has a convex shape on both sides. For example, the first surface of the third lens 230 may be convex toward the object in the paraxial region, and the second surface of the third lens 230 may be convex toward the image in the paraxial region.

The fourth lens 240 has a positive refractive power and has a meniscus shape convex upward. For example, the first and second surfaces of the fourth lens 240 may be convex upward in the paraxial region.

The fifth lens 250 has negative refractive power and has a meniscus shape convex toward the object side. For example, the first and second surfaces of the fifth lens 250 may be convex toward the object in the paraxial region. In addition, at least one inflection point is formed on at least one of the first and second surfaces of the fifth lens 250 .

The sixth lens 260 has negative refractive power and has a meniscus shape convex toward the object side. For example, the first and second surfaces of the sixth lens 260 may be convex toward the object in the paraxial region. In addition, at least one inflection point is formed on at least one of the first and second surfaces of the sixth lens 260 .

Meanwhile, each surface of the first lens 210 to the sixth lens 260 has an aspherical surface coefficient as shown in FIG. 8 .

Also, the diaphragm may be disposed in front of the object-side surface of the first lens 210 .

Also, the imaging optical system configured as described above may have aberration characteristics shown in FIG. 6 .

An imaging optical system according to a third embodiment of the present invention will be described with reference to FIGS. 9 to 12 .

An imaging optical system according to a third embodiment of the present invention 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. An optical system including 360 may be included, and a stop, an infrared cut filter 370 and an image sensor 380 may be further included.

As shown in Table 3, the focal length f1 of the first lens 310 is 3.16 mm, the focal length f2 of the second lens 320 is -5.71 mm, and the third lens 330 The focal length f3 is 19.16 mm, the focal length f4 of the fourth lens 340 is 39 mm, the focal length f5 of the fifth lens 350 is -15 mm, and the sixth lens 360 The focal length f6 of ) is 84 mm, and the total focal length f of the imaging optical system is 4.2 mm.

Here, the lens characteristics (radius of curvature, thickness of the lens or distance between the lenses, index of refraction, and Abbe number) of each lens are as shown in FIG. 11 .

In the third embodiment of the present invention, the first lens 310 has a positive refractive power and has a convex shape on both sides. For example, the first surface of the first lens 310 is convex toward the object in the paraxial region, and the second surface of the first lens 310 is convex toward the image in the paraxial region.

The second lens 320 has negative refractive power and has a meniscus shape convex toward the object side. For example, the first and second surfaces of the second lens 320 are convex toward the object in the paraxial region.

The third lens 130 has a positive refractive power and has a convex shape on both sides. For example, the first surface of the third lens 330 is convex toward the object in the paraxial region, and the second surface of the third lens 330 is convex toward the image in the paraxial region.

The fourth lens 340 has a positive refractive power and has a meniscus shape convex upward. For example, the first and second surfaces of the fourth lens 340 are convex upward in the paraxial region.

The fifth lens 350 has negative refractive power and has a concave shape on both sides. For example, the first surface of the fifth lens 350 is concave toward the object in the paraxial region, and the second surface of the fifth lens 350 is concave toward the image in the paraxial region. In addition, at least one inflection point is formed on at least one of the first and second surfaces of the fifth lens 350 .

The sixth lens 360 has a positive refractive power and has a meniscus shape convex toward the object side. For example, the first and second surfaces of the sixth lens 360 are convex toward the object in the paraxial region. In addition, at least one inflection point is formed on at least one of the first surface and the second surface of the sixth lens 360 .

Meanwhile, each surface of the first lens 310 to the sixth lens 360 has an aspherical surface coefficient as shown in FIG. 12 .

Also, the diaphragm (Stop) may be disposed in front of the object-side surface of the first lens 310 .

In addition, the imaging optical system configured as described above may have aberration characteristics shown in FIG. 10 .

An imaging optical system according to a fourth embodiment of the present invention will be described with reference to FIGS. 13 to 16 .

An imaging optical system according to a fourth embodiment of the present invention includes a first lens 410, a second lens 420, a third lens 430, a fourth lens 440, a fifth lens 450, and a sixth lens. An optical system including 460 may be included, and a stop, an infrared cut filter 470 and an image sensor 480 may be further included.

As shown in Table 4, the focal length f1 of the first lens 410 is 2.88 mm, the focal length f2 of the second lens 420 is -4.95 mm, and the third lens 430 The focal length f3 is 20.7 mm, the focal length f4 of the fourth lens 440 is -74.3 mm, the focal length f5 of the fifth lens 450 is -12.4 mm, the sixth lens ( 460) has a focal length f6 of 25.66 mm, and a total focal length f of the imaging optical system is 4.4 mm.

Here, the lens characteristics (radius of curvature, thickness of the lens or distance between lenses, index of refraction, and Abbe number) of each lens are as shown in FIG. 15 .

In the fourth embodiment of the present invention, the first lens 410 has a positive refractive power and has a convex shape on both sides. For example, the first surface of the first lens 410 is convex toward the object in the paraxial region, and the second surface of the first lens 410 is convex toward the image in the paraxial region.

The second lens 420 has negative refractive power and has a meniscus shape convex toward the object side. For example, the first and second surfaces of the second lens 420 are convex toward the object in the paraxial region.

The third lens 430 has a positive refractive power and has a meniscus shape convex upward. For example, the first and second surfaces of the third lens 430 are convex upward in the paraxial region.

The fourth lens 440 has negative refractive power and has a meniscus shape convex upward. For example, the first and second surfaces of the fourth lens 440 are convex upward in the paraxial region.

The fifth lens 450 has negative refractive power and has a concave shape on both sides. For example, the first surface of the fifth lens 450 is concave toward the object in the paraxial region, and the second surface of the fifth lens 450 is concave toward the image in the paraxial region. In addition, at least one inflection point is formed on at least one of the first and second surfaces of the fifth lens 450 .

The sixth lens 460 has a positive refractive power and has a meniscus shape convex toward the object side. For example, the first and second surfaces of the sixth lens 460 are convex toward the object in the paraxial region. In addition, at least one inflection point is formed on at least one of the first and second surfaces of the sixth lens 460 .

Meanwhile, each surface of the first lens 410 to the sixth lens 460 has an aspherical surface coefficient as shown in FIG. 16 .

Also, the diaphragm (Stop) may be disposed in front of the object-side surface of the first lens 410 .

Also, the imaging optical system configured as above may have aberration characteristics shown in FIG. 14 .

In the above, the configuration and characteristics of the present invention have been described based on the embodiments according to the present invention, but the present invention is not limited thereto, and various changes or modifications can be made within the spirit and scope of the present invention. It is apparent to those skilled in the art, and therefore such changes or modifications are intended to fall within the scope of the appended claims.

110, 210, 310, 410: first lens
120, 220, 320, 420: second lens
130, 230, 330, 430: third lens
140, 240, 340, 440: fourth lens
150, 250, 350, 450: 5th lens
160, 260, 360, 460: sixth lens
170, 270, 370, 470: infrared cut filter
180, 280, 380, 480: image sensor
Stop: Aperture

Claims (8)

In order from the object side,
a first lens having positive refractive power;
a second lens having negative refractive power, an object-side surface being convex, and an image-side surface being concave;
a third lens having refractive power and having a convex object-side surface;
a fourth lens having refractive power;
a fifth lens having negative refractive power, an object-side surface being convex, and an image-side surface being concave; and
A sixth lens having positive refractive power; includes,
When the Abbe number of the fifth lens is v5 and the Abbe number of the sixth lens is v6,
|v5-v6| > Imaging optics that satisfies 20.
According to claim 1,
When the Abbe number of the first lens is v1 and the Abbe number of the second lens is v2,
An imaging optical system that satisfies v1-v2 > 20.
According to claim 1,
The first lens is an imaging optical system having a convex object-side surface.
delete According to claim 1,
The sixth lens is an imaging optical system having a convex object-side surface.
According to claim 1,
The first lens to the sixth lens are all plastic materials.
According to claim 6,
An object-side surface and an image-side surface of each of the first lens to the sixth lens are aspheric.
According to claim 7,
At least one of the object-side surface and the image-side surface of the sixth lens has at least one inflection point.

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