KR102375928B1 - Optical system - Google Patents

Abstract

An imaging optical system according to an embodiment of the present invention includes, in order from an object side, a first lens having positive refractive power and having a convex object side surface; a second lens having negative refractive power and having an object-side surface convex and an image-side surface concave; a third lens having positive refractive power and having a convex image side; a fourth lens having refractive power; a fifth lens having refractive power; and a sixth lens having refractive power, wherein when the distance from the object-side surface of the first lens to the imaging surface is TTL, 1.1 < TTL/f < 1.35 is satisfied, and the Abbe's number of the first lens When v1 is v1 and the Abbe's number of the second lens is v2, v1-v2>20 may be satisfied.

Description

imaging optical system

The present invention relates to an imaging optical system.

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

However, since portable terminals are gradually becoming smaller or lighter, there is a limit to realizing a high-resolution and high-performance camera.

In order to solve this problem, recently, the lens of the 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.

SUMMARY OF THE INVENTION An object of the present invention is to provide an imaging optical system capable of improving an aberration improvement effect and realizing a bright and high resolution.

An imaging optical system according to an embodiment of the present invention includes, in order from an object side, a first lens having positive refractive power and having a convex object side surface; a second lens having negative refractive power and having an object-side surface convex and an image-side surface concave; a third lens having positive refractive power and having a convex image side; a fourth lens having refractive power; a fifth lens having refractive power; and a sixth lens having refractive power, wherein when the distance from the object-side surface of the first lens to the imaging surface is TTL, 1.1 < TTL/f < 1.35 is satisfied, and the Abbe's number of the first lens When v1 is v1 and the Abbe's number of the second lens is v2, v1-v2>20 may be satisfied.

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

1 is a block diagram of an imaging optical system according to a first embodiment of the present invention;
2 is a curve showing the 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 block diagram of an imaging optical system according to a second embodiment of the present invention;
6 is a curve showing the 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 the aspheric coefficient of each lens of the imaging optical system shown in FIG. 5;
9 is a block diagram of an imaging optical system according to a third embodiment of the present invention;
10 is a curve showing the 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 the aspheric coefficient of each lens of the imaging optical system shown in FIG. 9;
13 is a block diagram of an imaging optical system according to a fourth embodiment of the present invention;
14 is a curve showing the 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 the aspheric coefficient of each lens of the imaging optical system shown in FIG. 13;
FIG. 17 is a diagram illustrating an angle between a tangent line at an end of an effective mirror of an image side surface of a second lens and an image surface of the 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 elements within the scope of the same spirit, through addition, change, or deletion, etc. Other embodiments included within the scope of the invention may be easily suggested, but this will also be included within the scope of the spirit of the present invention.

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

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

In addition, the first lens means the lens closest to the object side, and the sixth lens means the 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 close to the image sensor or the image side in the imaging optical system. In addition, in each lens, the first surface means a surface close to the object side (or an object-side surface), and the second surface means a surface close to the image side (or an image side surface). In addition, in the present specification, all numerical values for the radius of curvature, thickness, etc. of the lens are in mm units.

In addition, the paraxial region (近軸領域) means a very narrow region near the optical axis, for example, may mean a region in which a distance from which a light beam falls from the optical axis is 0.

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

That is, the optical imaging 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 optical imaging system according to an embodiment of the present invention is not composed of only six lenses and may further include other components as necessary. For example, the optical imaging 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 optical imaging system may further include an image sensor for converting the incident image of the subject into an electrical signal. In addition, the imaging optical system may further include a distance maintaining member for adjusting the distance between the lens and the lens.

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

That is, at least one of the first and second surfaces of the first to sixth lenses may be aspherical. Here, the aspherical surfaces of the first to sixth lenses 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 is the distance in the direction perpendicular to the optical axis. In addition, constants A to F mean aspheric coefficients. And Z represents the distance from the vertex of the lens in the direction of the optical axis.

The imaging optical system including the first lens to the sixth lens has positive/negative/positive/positive or negative/negative/positive refractive power sequentially from the object side.

The optical system configured as described above can improve optical performance by improving aberration. In addition, in the optical system configured as described above, all six lenses may be made of a plastic material.

The 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.

The imaging optical system according to an embodiment of the present invention satisfies Conditional Equation 2.

[Conditional Expression 2]

1.1 < TTL/f < 1.35

In Conditional Expression 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.

The imaging optical system according to an embodiment of the present invention satisfies Conditional Equation 3.

[Conditional Expression 3]

1.0 < |r9|/f < 40

In Condition 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.

The imaging optical system according to an embodiment of the present invention satisfies Conditional Equation 4.

[Conditional Expression 4]

|v5-v6| > 20

In Condition 4, the Abbe's number of the fifth lens, v6, is the Abbe's number of the sixth lens.

The imaging optical system according to an embodiment of the present invention satisfies condition 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.

The 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 overall focal length of the imaging optical system, and f1 is the focal length of the first lens.

The imaging optical system according to an embodiment of the present invention satisfies Conditional Equation 7.

[Conditional Expression 7]

0.1 < f/f3 < 0.3

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

The imaging optical system according to an embodiment of the present invention satisfies condition 8.

[Conditional Expression 8]

0.2 < |f/f5| < 0.4

In Condition 8, f is the overall focal length of the imaging optical system, and f5 is the focal length of the fifth lens.

The 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.

The 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 overall 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.

The imaging optical system according to an embodiment of the present invention satisfies Conditional Equation 11.

[Conditional Expression 11]

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

In Conditional Expression 11, f is the overall 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.

The imaging optical system according to an embodiment of the present invention satisfies Conditional Equation 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.

The imaging optical system according to an embodiment of the present invention satisfies Conditional Equation 13.

[Conditional Expression 13]

1.5 < TTL/ImgH < 1.7

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

The imaging optical system according to an embodiment of the present invention satisfies condition 14.

[Conditional Expression 14]

65 < FOV < 80

In condition 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 a degree.

The imaging optical system according to an embodiment of the present invention satisfies condition 15.

[Conditional Expression 15]

SA2 ≤ 30

In Condition 15, SA2 is an angle (refer to FIG. 17 ) between a tangent line at the end of the effective mirror of the image side of the second lens and the upper surface of the image sensor. Here, the unit of the angle is a degree.

Hereinafter, 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 shape in which both sides are convex. In more detail, 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. In more detail, the first surface and the second surface of the first lens may be convex toward the object in the paraxial region.

At least one 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 aspherical.

The second lens has a negative refractive power. In addition, the second lens has a meniscus shape convex toward the object. In more detail, the first surface and the second surface of the second lens may be convex toward the object in the paraxial region.

At least one of the first surface and the second surface of the second lens may be an aspherical 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 toward the image. In more detail, the first surface and the second surface of the third lens may be convex upward in the paraxial region.

In addition, the third lens may have a shape in which both surfaces are convex. In more detail, 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 of the first surface and the second surface of the third lens may be an aspherical surface. For example, both surfaces of the third lens may be aspherical.

The fourth lens has positive or negative refractive power. In addition, the fourth lens has a meniscus shape convex toward the image. In more detail, the first surface and the second surface of the fourth lens may be convex upward in the paraxial region.

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

The fifth lens has negative refractive power. In addition, the fifth lens may have a concave shape on both sides. In more detail, 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 toward the image in the paraxial region.

Also, the fifth lens may have a meniscus shape convex toward the object. In more detail, the first surface and the second surface of the fifth lens may be convex toward the object in the paraxial region.

At least one 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. In more detail, the first surface and the second surface of the sixth lens may be convex toward the object in the paraxial region.

At least one 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, the aberration improvement performance may 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 .

The imaging optical system according to the 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 having a 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 that of the third lens 130 is 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, and the sixth lens 160 ), the focal length f6 is 32.76 mm, and the overall focal length f of the imaging optical system is 4.16 mm.

Here, the lens characteristics (radius of curvature, thickness or distance between lenses, thickness, refractive index, and Abbe's number) of each lens 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 a negative refractive power and has a meniscus shape convex toward the object. 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 toward the image. 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 toward the image. For example, the first and second surfaces of the fourth lens 140 are convex upward in the paraxial region.

The fifth lens 150 has a 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 surface and the second surface of the fifth lens 150 .

The sixth lens 160 has a positive refractive power and has a meniscus shape convex toward the object. 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 surface and the second surface of the sixth lens 160 .

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

In addition, the stop may be disposed in front of the object-side surface of the first lens 110 .

In addition, the optical system configured as described above may have the aberration characteristic 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 .

The imaging optical system according to the 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 having a 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 focal length f1 of the third lens 230 is -7.24 mm. 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, and the sixth lens 260 is ), the focal length f6 is 1380 mm, and the overall focal length f of the imaging optical system is 4.71 mm.

Here, the lens characteristics (radius of curvature, thickness or distance between lenses, thickness, refractive index, 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. For example, the first surface and the second surface of the first lens 210 may be convex toward the object in the paraxial region.

The second lens 220 has a negative refractive power and has a meniscus shape convex toward the object. 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 toward the image. 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 a negative refractive power and has a meniscus shape convex toward the object. For example, the first surface and the second surface 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 surface and the second surface of the fifth lens 250 .

The sixth lens 260 has a negative refractive power and has a meniscus shape convex toward the object. For example, the first surface and the second surface 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 surface and the second surface of the sixth lens 260 .

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

In addition, the aperture may be disposed in front of the object-side surface of the first lens 210 .

In addition, the optical system configured as described above may have the aberration characteristic 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 .

The imaging optical system according to the 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. It includes an optical system having a 360 , and may further include a stop, an infrared cut filter 370 and an image sensor 380 .

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 that of the third lens 330 is 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 is 84 mm, and the overall focal length f of the imaging optical system is 4.2 mm.

Here, the lens characteristics (radius of curvature, thickness or distance between lenses, thickness, index of refraction, and Abbe's 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 a negative refractive power and has a meniscus shape convex toward the object. 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 toward the image. For example, the first and second surfaces of the fourth lens 340 are convex upward in the paraxial region.

The fifth lens 350 has a 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 surface and the second surface of the fifth lens 350 .

The sixth lens 360 has a positive refractive power and has a meniscus shape convex toward the object. 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 coefficient as shown in FIG. 12 .

In addition, the stop may be disposed in front of the object-side surface of the first lens 310 .

In addition, the optical system configured as described above may have the aberration characteristic 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 .

The imaging optical system according to the 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. It includes an optical system having a 460 , and may further include a stop, an infrared cut filter 470 , and an image sensor 480 .

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 that of the third lens 430 is 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, and the sixth lens ( 460) has a focal length f6 of 25.66 mm, and an overall focal length f of the imaging optical system is 4.4 mm.

Here, the lens characteristics (radius of curvature, thickness or distance between lenses (Thickness), refractive index (Index), and Abbe's 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 a negative refractive power and has a meniscus shape convex toward the object. 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 toward the image. For example, the first and second surfaces of the third lens 430 are convex upward in the paraxial region.

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

The fifth lens 450 has a negative refractive power and has a concave shape on both sides. For example, the first surface of the fifth lens 450 has a shape concave toward the object in the paraxial region, and the second surface of the fifth lens 450 has a shape concave toward the image side 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 fifth lens 450 .

The sixth lens 460 has a positive refractive power and has a meniscus shape convex toward the object. 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 surface and the second surface of the sixth lens 460 .

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

In addition, the stop may be disposed in front of the object-side surface of the first lens 410 .

In addition, the optical system configured as described above may have the aberration characteristic shown in FIG. 14 .

In the above, the configuration and features 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 it is understood that various changes or modifications can be made within the spirit and scope of the present invention. It is intended that such changes or modifications will be apparent to those skilled in the art, and therefore 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: fifth lens
160, 260, 360, 460: sixth lens
170, 270, 370, 470: infrared cut filter
180, 280, 380, 480: image sensor
Stop: Iris

Claims (13)

In order from the object side,
a first lens having positive refractive power and having an object-side surface convex;
a second lens having negative refractive power and having an object-side surface convex and an image-side surface concave;
a third lens having positive refractive power and having a convex image side;
a fourth lens having refractive power and having a concave object-side surface and a convex image-side surface;
a fifth lens having refractive power and having a convex object-side surface and a concave image-side surface; and
A sixth lens having refractive power, the object-side surface is convex and the image-side surface is concave;
When the distance from the object-side surface of the first lens to the imaging surface is TTL, 1.1 < TTL/f < 1.35,
When the Abbe's number of the first lens is v1 and the Abbe's number of the second lens is v2,
v1-v2 > 20 is satisfied,
When f5 is the focal length of the fifth lens, and f is the total focal length of the optical system including the first to sixth lenses,
0.2 < |f/f5| An imaging optical system satisfying < 0.4.
According to claim 1,
The first lens is an imaging optical system in which an image side surface is concave.
According to claim 1,
The third lens is an imaging optical system in which the object-side surface is convex.
delete delete delete According to claim 1,
When the field of view of the imaging optical system is FOV,
An imaging optical system that satisfies 65° < FOV < 80°.
delete According to claim 1,
When the focal length of the sixth lens is f6,
0.3 < |f/f5| + |f/f6| An imaging optical system satisfying < 0.6.
According to claim 1,
When the distance from the object-side surface of the first lens to the imaging plane is TTL, and a half of the diagonal length of the imaging plane is ImgH,
An imaging optical system satisfying 1.5 < TTL/ImgH < 1.7.
According to claim 1,
The first to sixth lenses are all made of a plastic material.
12. The method of claim 11,
The first to sixth lenses have an object-side surface and an image-side surface of each aspherical surface.
13. The method of claim 12,
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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