KR102117070B1 - Optical system - Google Patents

Abstract

An imaging optical system according to an embodiment of the present invention includes: a first lens having a positive refractive power in order from an object side and an object side surface convex toward the object side; A second lens having negative refractive power; A third lens having negative refractive power; A fourth lens having positive refractive power and having an image side convex toward the image side; A fifth lens having negative refractive power and having an image side convex toward the image side; And a sixth lens having negative refractive power and having an image side concave toward the image side, so that a high resolution can be realized while being bright.

Description

Imaging optical system {Optical system}

The present invention relates to an imaging optical system.

2. Description of the Related Art Recently, a mobile terminal is equipped with a camera to enable video calling and photo taking. In addition, as the functions occupied by the camera in the portable terminal gradually increase, the demand for high resolution and high performance of the camera for the portable terminal is gradually increasing.

However, since portable terminals are gradually becoming smaller or lighter, there are limitations in realizing high-resolution and high-performance cameras.

To solve this problem, recently, the lens of the camera is made of a plastic material that is lighter than glass, and the lens module is composed of five or more lenses for realization of high resolution.

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

An imaging optical system according to an embodiment of the present invention includes: a first lens having a positive refractive power in order from an object side and an object side surface convex toward the object side; A second lens having negative refractive power; A third lens having negative refractive power; A fourth lens having positive refractive power and having an image side convex toward the image side; A fifth lens having negative refractive power and having an image side convex toward the image side; And a sixth lens having negative refractive power and having an image side concave toward the image side, so that a high resolution can be realized while being bright.

The imaging optical system according to an embodiment of the present invention may improve the sensitivity of the lens to decenter tolerance by disposing an aperture stop between the first lens and the second lens.

The imaging optical system according to an embodiment of the present invention can realize high-resolution performance even in close-up object shooting by largely setting the sag value at the end of the effective mirror of the first surface of the fifth lens.

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, and improve the sensitivity of the lens to decenter tolerance.

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 configuration diagram of an imaging optical system according to a second embodiment of the present invention.
4 is a curve showing aberration characteristics of the imaging optical system shown in FIG. 3.
5 is a configuration diagram of an imaging optical system according to a third embodiment of the present invention.
6 is a curve showing aberration characteristics of the imaging optical system shown in FIG. 5.
7 is a configuration diagram of an imaging optical system according to a fourth embodiment of the present invention.
8 is a curve showing aberration characteristics of the imaging optical system shown in FIG. 7.

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 embodiments presented, and those skilled in the art who understand the spirit of the present invention may add another component, change or delete other components within the scope of the same spirit, or degrade another invention or the present invention. Other embodiments that are included within the scope of the invention idea can be easily proposed, but this will also be included within the scope of the invention idea.

In addition, elements having the same functions within the scope of the same idea appearing in the drawings of the respective embodiments will be described using the same reference numerals.

In the following lens configuration diagram, the thickness, size, and shape of the lens are shown to be somewhat exaggerated for explanation. In particular, the shape of the spherical or aspherical surface presented in the lens configuration diagram is provided as an example, and is not limited to this shape.

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 the side closer to the object side in the imaging optical system, and the back side means the side closer to the image sensor or image side in the imaging optical system. In addition, 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). In addition, in this specification, the values for the radius of curvature, thickness, OAL, BFL, and D1 of the lens are all in mm.

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

That is, the imaging optical system according to an embodiment of the present invention includes a first lens 10, a second lens 20, a third lens 30, a fourth lens 40, a fifth lens 50 and a sixth Includes lens 60.

However, the imaging optical 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 imaging optical system may include an aperture stop ST for adjusting the amount of light. In addition, the imaging optical system may further include an infrared ray blocking filter 70 for blocking infrared rays. In addition, the imaging optical system may further include an image sensor 80 for converting an image of an incident object into an electrical signal. In addition, the imaging optical system may further include a gap maintaining member for adjusting the distance between the lens and the lens.

The first lens 10 to the sixth lens 60 constituting the imaging optical system according to an embodiment of the present invention are made of a plastic material.

In addition, at least one lens of the first lens 10 to the sixth lens 60 has an aspherical surface. In addition, each of the first lens 10 to the sixth lens 60 may have at least one aspherical surface.

That is, at least one of the first surface and the second surface of the first lens 10 to the sixth lens 60 may be aspherical. Here, the aspherical surfaces of the first lens 10 to the sixth lens 60 are expressed by Equation (1).

In Equation 1, C is a curvature (reciprocal of the radius of curvature), K is a conic constant, and r represents a distance from the optical axis vertex of each lens to a specific position on each lens surface. In addition, the constants A to J mean aspheric coefficients from the 4th to the 20th order. And Z represents a sag at a specific position.

The imaging optical system composed of the first lens 10 to the sixth lens 60 has positive / negative / negative / negative / negative / refractive power in order from the object side.

The optical system configured as described above may improve optical performance through aberration improvement. In addition, the optical system configured as described above can improve the sensitivity of the lens by reducing the refractive angle. Therefore, in the imaging optical system according to an embodiment of the present invention, all six lenses may be used as a plastic material.

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

[Conditional Expression 1]

0.12 <Th6 / f <0.5

In conditional expression 1, Th6 is the thickness [mm] in the paraxial region of the sixth lens, and f is the total focal length [mm] of the imaging optical system.

Here, when the lower limit value of the conditional expression 1 is exceeded, the thickness in the paraxial region of the sixth lens becomes thinner, resulting in image curvature and difficulty in securing the resolution performance of the peripheral portion. Because the focal length is small, the distortion aberration becomes large.

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

[Conditional Expression 2]

20 <v1-v3 <70

In conditional expression 2, v1 is the Abbe number of the first lens, and v3 is the Abbe number of the third lens.

Here, the conditional expression 2 is a condition related to chromatic aberration, and if the deviation from the lower limit of the conditional expression 2 is difficult, chromatic aberration correction becomes difficult, and realization of high resolution is difficult. have.

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

[Conditional Expression 3]

| Sag9 / Th5 | > 1.0

In conditional expression 3, Sag9 is the sag value at the effective diameter end of the object side of the fifth lens, and Th5 is the thickness [mm] in the paraxial region of the fifth lens.

Here, the conditional expression 3 is a condition related to the resolution when photographing a close-up object, and if it exceeds the lower limit value of the conditional expression 3, aberration correction becomes difficult when photographing a close-up object, and thus it is difficult to secure high resolution.

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

[Conditional Expression 4]

f3 / f2> 1.5

In conditional expression 4, f3 is the focal length [mm] of the third lens, and f2 is the focal length [mm] of the second lens.

Here, when the lower limit of the conditional expression (4) is exceeded, the power of the third lens becomes strong and the curvature becomes small, which makes it difficult to manufacture the third lens.

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

[Conditional Expression 5]

0.5 <OAL / f <2.0

In conditional expression 5, OAL is the distance [mm] from the object side of the first lens to the image surface, and f is the total focal length [mm] of the imaging optical system.

Here, when the lower limit of the conditional expression 5 is exceeded, the angle of view of the imaging optical system becomes smaller, and when the upper limit of the conditional expression 5 is exceeded, the length of the imaging optical system becomes longer, making it difficult to downsize.

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

[Conditional Expression 6]

f5 / f1 <-3.0

In conditional expression 6, f5 is the focal length [mm] of the fifth lens, and f1 is the focal length [mm] of the first lens.

Here, when the upper limit of the conditional expression 6 is exceeded, the negative power of the fifth lens becomes strong, and thus it is difficult to secure the resolution performance of the peripheral portion.

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

[Conditional Expression 7]

1.60 <n5 <2.10

In conditional expression 7, n5 is the refractive index of the fifth lens.

Here, if the deviation from the lower limit of the conditional expression 7 is difficult to correct chromatic aberration, it is difficult to implement a high resolution, and if the deviation from the upper limit of the conditional expression 7 is difficult to reduce manufacturing cost.

Next, the first lens 10 to the sixth lens 60 constituting the imaging optical system according to an embodiment of the present invention will be described.

The first lens 10 has positive refractive power. In addition, the first lens 10 may have a meniscus shape convex toward the object. In other words, the first surface and the second surface of the first lens 10 may be convex toward the object.

In addition, both surfaces of the first lens 10 may be convex.

At least one of the first and second surfaces of the first lens 10 may be aspherical. For example, both surfaces of the first lens may be aspherical.

The second lens 20 has negative refractive power. In addition, the second lens 20 has a meniscus shape convex toward the object. To explain further, the second lens 20 has a first surface and a second surface convex toward the object.

At least one surface of the first lens and the second surface of the second lens 20 may be aspherical. For example, both surfaces of the second lens 20 may be aspherical.

The third lens 30 has negative refractive power. In addition, the third lens 30 has a meniscus shape convex toward the object. In other words, the first and second surfaces of the third lens 30 are convex toward the object.

At least one of the first and second surfaces of the third lens 30 may be aspherical. For example, both surfaces of the third lens 30 may be aspherical.

The fourth lens 40 has positive refractive power. In addition, the fourth lens 40 may have a meniscus shape convex toward the image side. In other words, the first surface of the fourth lens 40 may be concave toward the object, and the second surface of the fourth lens 40 may be convex toward the image.

In addition, both surfaces of the fourth lens 40 may be convex.

At least one of the first and second surfaces of the fourth lens 40 may be an aspherical surface. For example, both surfaces of the fourth lens 40 may be aspherical.

The fifth lens 50 has negative refractive power. In addition, the fifth lens 50 has a meniscus shape convex toward the image side. In other words, the first surface of the fifth lens 50 may be concave toward the object, and the second surface of the fifth lens 50 is convex toward the image.

At least one of the first and second surfaces of the fifth lens 50 may be aspherical. For example, both surfaces of the fifth lens 50 may be aspherical.

The sixth lens 60 has negative refractive power. In addition, the sixth lens 60 has a meniscus shape convex toward the object. In other words, the first and second surfaces of the sixth lens 60 are convex toward the object.

In addition, an inflection point is formed on at least one of the first and second surfaces of the sixth lens 60. For example, the second surface of the sixth lens 60 may be concave in the paraxial region and convex toward the edge.

In addition, at least one surface of the first and second surfaces of the sixth lens 60 may be aspherical. For example, both surfaces of the sixth lens 60 may be aspherical.

In the imaging optical system configured as described above, since a plurality of lenses perform aberration correction functions, aberration improvement performance may be improved. In addition, the imaging optical system may improve the sensitivity of the lens by reducing the refractive angle of the lens. Therefore, the imaging optical system can be constructed of all lenses made of a plastic material having a lower optical performance than a glass material, thereby lowering the manufacturing cost of the lens module and increasing the manufacturing efficiency.

An imaging optical system according to a first embodiment of the present invention will be described with reference to FIGS. 1 and 2.

The imaging optical system according to the first embodiment of the present invention includes a first lens 10, a second lens 20, a third lens 30, a fourth lens 40, a fifth lens 50, and a sixth lens It includes an optical system having a 60, the infrared cut filter 70, the image sensor 80 and may further include an aperture stop (ST).

Here, as shown in Table 1, the distance (OAL) from the object side surface of the first lens 10 to the first surface (image surface) of the image sensor 80 is 5.606 mm, and the sixth lens 60 The distance (BFL) from the upper side to the upper side is 1.351 mm. In addition, FNO is 2.2.

In addition, the focal length f1 of the first lens 10 is 3.477 mm, the focal length f2 of the second lens 20 is -6.265 mm, and the focal length f3 of the third lens 30 Is -100 mm, the focal length (f4) of the fourth lens (40) is 6.277 mm, the focal length (f5) of the fifth lens (50) is -29.043 mm, the focal length of the sixth lens (60) (f6) is -11.265 mm, and the total focal length (f) of the imaging optical system is 4.655 mm.

Table 2 shows other lens characteristics (radius of curvature (Ri), thickness of lens or distance between lenses (Thi), refractive index (Nd), and Abbe's number (Vi)).

In the first embodiment of the present invention, the first lens 10 has a positive refractive power and has a meniscus shape convex toward the object. The second lens 20 has a negative refractive power and has a meniscus shape convex toward the object. The third lens 30 has a negative refractive power and has a meniscus shape convex toward the object. The fourth lens 40 has a positive refractive power and has a meniscus shape convex toward the image side. The fifth lens 50 has negative refractive power and has a meniscus shape convex toward the image side. The sixth lens 60 has a negative refractive power and has a meniscus shape convex toward the object. In addition, an inflection point is formed on at least one of the first and second surfaces of the sixth lens 60. In addition, the aperture stop ST is disposed between the first lens 10 and the second lens 20.

By arranging the aperture stop ST between the first lens 10 and the second lens 20, it is possible to reduce the sensitivity of each lens to decenter tolerance.

On the other hand, each surface of the first lens 10 to the sixth lens 60 has an aspherical surface coefficient as shown in Table 3. That is, all of the first surface of the first lens 10 to the second surface of the sixth lens 60 are aspherical surfaces.

On the other hand, referring to Table 4, it can be seen that the imaging optical system according to the first embodiment of the present invention satisfies the conditional expressions 1 to 7 described above, thereby improving the optical performance of the lens.

In addition, the optical system configured as described above may have aberration characteristics illustrated in FIG. 2.

An imaging optical system according to a second embodiment of the present invention will be described with reference to FIGS. 3 and 4.

The imaging optical system according to the second embodiment of the present invention includes a first lens 10, a second lens 20, a third lens 30, a fourth lens 40, a fifth lens 50, and a sixth lens It includes an optical system having a 60, the infrared cut filter 70, the image sensor 80 and may further include an aperture stop (ST).

Here, as shown in Table 5, the distance (OAL) from the object side of the first lens 10 to the top surface of the image sensor 80 is 5.610 mm, and the top surface from the top surface of the sixth lens 60 The distance to BFL is 1.438 mm. In addition, FNO is 2.2.

In addition, the focal length f1 of the first lens 10 is 3.523 mm, the focal length f2 of the second lens 20 is -5.593 mm, and the focal length f3 of the third lens 30 Is -100 mm, the focal length f4 of the fourth lens 40 is 6.728 mm, the focal length f5 of the fifth lens 50 is -16.144 mm, the focal length of the sixth lens 60 (f6) is -56.424 mm, and the total focal length (f) of the imaging optical system is 4.65 mm.

Table 6 shows other lens characteristics (radius of curvature (Ri), thickness of lens or distance between lenses (Thi), refractive index (Nd), and Abbe's number (Vi)).

In the second embodiment of the present invention, the first lens 10 has a positive refractive power, and both surfaces are convex. The second lens 20 has a negative refractive power and has a meniscus shape convex toward the object. The third lens 30 has a negative refractive power and has a meniscus shape convex toward the object. The fourth lens 40 has positive refractive power and has convex surfaces on both sides. The fifth lens 50 has negative refractive power and has a meniscus shape convex toward the image side. The sixth lens 60 has a negative refractive power and has a meniscus shape convex toward the object. In addition, an inflection point is formed on at least one of the first and second surfaces of the sixth lens 60. In addition, the aperture stop ST is disposed between the first lens 10 and the second lens 20.

By arranging the aperture stop ST between the first lens 10 and the second lens 20, it is possible to reduce the sensitivity of each lens to decenter tolerance.

Meanwhile, each surface of the first lens 10 to the sixth lens 60 has an aspherical surface coefficient as shown in Table 7. That is, all of the first surface of the first lens 10 to the second surface of the sixth lens 60 are aspherical surfaces.

On the other hand, referring to Table 8, it can be seen that the imaging optical system according to the second embodiment of the present invention satisfies the conditional expressions 1 to 7 described above, thereby improving the optical performance of the lens.

In addition, the optical system configured as described above may have aberration characteristics illustrated in FIG. 4.

An imaging optical system according to a third embodiment of the present invention will be described with reference to FIGS. 5 and 6.

The imaging optical system according to the third embodiment of the present invention includes a first lens 10, a second lens 20, a third lens 30, a fourth lens 40, a fifth lens 50, and a sixth lens It includes an optical system having a 60, the infrared cut filter 70, the image sensor 80 and may further include an aperture stop (ST).

Here, as shown in Table 9, the distance (OAL) from the object side of the first lens 10 to the top surface of the image sensor 80 is 4.857 mm, and the top surface from the top surface of the sixth lens 60 The distance to BFL is 1.124 mm. In addition, FNO is 2.0.

In addition, the focal length f1 of the first lens 10 is 3.094 mm, the focal length f2 of the second lens 20 is -6.975 mm, and the focal length f3 of the third lens 30 Is -11.248 mm, the focal length (f4) of the fourth lens 40 is 4.286 mm, the focal length (f5) of the fifth lens 50 is -119.767 mm, the focal length (f6) of the sixth lens Is -6.893 mm, and the total focal length (f) of the imaging optical system is 3.962 mm.

Table 10 shows other lens characteristics (radius of curvature (Ri), thickness of lens or distance between lenses (Thi), refractive index (Nd), and Abbe's number (Vi)).

In the third embodiment of the present invention, the first lens 10 has a positive refractive power and has a meniscus shape convex toward the object. The second lens 20 has a negative refractive power and has a meniscus shape convex toward the object. The third lens 30 has a negative refractive power and has a meniscus shape convex toward the object. The fourth lens 40 has positive refractive power and has convex surfaces on both sides. The fifth lens 50 has negative refractive power and has a meniscus shape convex toward the image side. The sixth lens 60 has a negative refractive power and has a meniscus shape convex toward the object. In addition, an inflection point is formed on at least one of the first and second surfaces of the sixth lens 50. In addition, the aperture stop ST is disposed between the first lens 10 and the second lens 20.

By arranging the aperture stop ST between the first lens 10 and the second lens 20, it is possible to reduce the sensitivity of each lens to decenter tolerance.

On the other hand, each surface of the first lens 10 to the sixth lens 60 has an aspherical surface coefficient as shown in Table 11. That is, all of the first surface of the first lens 10 to the second surface of the sixth lens 60 are aspherical surfaces.

On the other hand, referring to Table 12, it can be seen that the imaging optical system according to the third embodiment of the present invention satisfies the conditional expressions 1 to 7 described above, thereby improving the optical performance of the lens.

In addition, the optical system configured as described above may have aberration characteristics illustrated in FIG. 6.

An imaging optical system according to a fourth embodiment of the present invention will be described with reference to FIGS. 7 and 8.

The imaging optical system according to the fourth embodiment of the present invention includes a first lens 10, a second lens 20, a third lens 30, a fourth lens 40, a fifth lens 50, and a sixth lens It includes an optical system having a 60, the infrared cut filter 70, the image sensor 80 and may further include an aperture stop (ST).

Here, as shown in Table 13, the distance (OAL) from the object side surface of the first lens 10 to the image surface of the image sensor 70 is 5.620 mm, and the image surface from the image side surface of the sixth lens 60 The distance to BFL is 1.368 mm. In addition, FNO is 2.2.

In addition, the focal length f1 of the first lens 10 is 3.241 mm, the focal length f2 of the second lens 20 is -5.686 mm, and the focal length f3 of the third lens 30 Is -44.607 mm, the focal length (f4) of the fourth lens 40 is 6.763 mm, the focal length (f5) of the fifth lens 50 is -19.275 mm, the focal length of the sixth lens 60 (f6) is -17.418 mm, and the total focal length (f) of the imaging optical system is 4.65 mm.

Other lens characteristics (radius of curvature (Ri), thickness of lens or distance between lenses (Thi), refractive index (Nd), Abbe's number (Vi)) are shown in Table 14.

In the fourth embodiment of the present invention, the first lens 10 has a positive refractive power, and both surfaces are convex. The second lens 20 has a negative refractive power and has a meniscus shape convex toward the object. The third lens 30 has a negative refractive power and has a meniscus shape convex toward the object. The fourth lens 40 has a positive refractive power and has a convex meniscus on both sides. The fifth lens 50 has negative refractive power and has a meniscus shape convex toward the image side. The sixth lens 60 has a negative refractive power and has a meniscus shape convex toward the object. In addition, an inflection point is formed on at least one of the first and second surfaces of the sixth lens 60. And the aperture stop ST is disposed between the first lens 10 and the second lens 20.

By arranging the aperture stop ST between the first lens 10 and the second lens 20, it is possible to reduce the sensitivity of each lens to decenter tolerance.

On the other hand, each surface of the first lens 10 to the sixth lens 60 has an aspherical surface coefficient as shown in Table 15. That is, all of the first surface of the first lens 10 to the second surface of the sixth lens 60 are aspherical surfaces.

On the other hand, referring to Table 16, it can be seen that the imaging optical system according to the fourth embodiment of the present invention satisfies the conditional expressions 1 to 7 described above, thereby improving the optical performance of the lens.

In addition, the optical system configured as described above may have aberration characteristics illustrated in FIG. 8.

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 to this, and various modifications or changes can be made within the spirit and scope of the present invention. It is apparent to those skilled in the art, and thus, such changes or modifications are found to be within the scope of the appended claims.

10: first lens 20: second lens
30: third lens 40: fourth lens
50: fifth lens 60: sixth lens
70: infrared cut filter 80: image sensor
ST: aperture aperture

Claims (14)

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;
A third lens having refractive power;
A fourth lens having refractive power;
A fifth lens having negative refractive power, the object-side surface is concave, and the image-side surface is convex; And
Includes; a sixth lens having a refractive power, the image side is concave to the image side,
An aperture stop is disposed between the first lens and the second lens,
When the Abbe number of the first lens is v1 and the Abbe number of the third lens is v3, an imaging optical system that satisfies 20 <v1-v3 <70.
According to claim 1,
When the thickness in the paraxial region of the sixth lens is Th6 and the total focal length of the imaging optical system including the first to sixth lenses is f, an imaging optical system that satisfies 0.12 <Th6 / f <0.5.
delete According to claim 1,
When the sag value at the end of the effective diameter of the object-side surface of the fifth lens is Sag9 and the thickness in the paraxial region of the fifth lens is Th5, | Sag9 / Th5 | > Optical system that satisfies 1.0.
The method of claim 4,
When the refractive index of the fifth lens is n5, an imaging optical system that satisfies 1.60 <n5 <2.10.
The method of claim 5,
When the focal length of the first lens is f1 and the focal length of the fifth lens is f5, an imaging optical system that satisfies f5 / f1 <-3.0.
According to claim 1,
When the focal length of the second lens is f2 and the focal length of the third lens is f3, an imaging optical system that satisfies f3 / f2> 1.5.
According to claim 1,
When the distance from the object-side surface of the first lens to the image surface is OAL and the total focal length of the imaging optical system including the first to sixth lenses is f, 0.5 <OAL / f <2.0 is satisfied. Imaging optical system.
According to claim 1,
The first lens is an imaging optical system having a meniscus shape convex toward the object.
According to claim 1,
The third lens has an optical power of negative refractive power and has a meniscus shape convex toward the object.
According to claim 1,
The fourth lens has a positive refractive power, and an image pickup optical system with a convex image surface.
According to claim 1,
The fifth lens has a negative refractive power, and an imaging optical system having a meniscus shape convex upward.
According to claim 1,
The sixth lens has a negative refractive power, and an imaging optical system having a meniscus shape convex toward the object.
According to claim 1,
The first lens to the sixth lens is provided with a plastic material, and the object-side surface and the image-side surface of the first lens to the sixth lens are aspherical surfaces.

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