KR102597148B1 - 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 and a convex surface on the object side; a second lens having a negative refractive power and a meniscus shape convex toward the object; a third lens having a negative refractive power and a meniscus shape convex toward the object; a fourth lens having positive refractive power and having a concave object-side surface; a fifth lens having negative refractive power; and a sixth lens having negative refractive power. When the focal length of the fifth lens is f5 and the focal length of the first lens is f1, f5/f1 < -3.0 may be satisfied.

Description

Imaging optical system {Optical system}

The present invention relates to an imaging optical system.

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

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

To solve this problem, camera lenses are recently made of plastic, which is lighter than glass, and lens modules are made up of five or more lenses to achieve high resolution.

The purpose of an embodiment of the present invention is to provide an imaging optical system that can improve the aberration improvement effect, achieve high resolution, and improve lens sensitivity.

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 and a convex surface on the object side; a second lens having a negative refractive power and a meniscus shape convex toward the object; a third lens having a negative refractive power and a meniscus shape convex toward the object; a fourth lens having positive refractive power and having a concave object-side surface; a fifth lens having negative refractive power; and a sixth lens having negative refractive power. When the focal length of the fifth lens is f5 and the focal length of the first lens is f1, f5/f1 < -3.0 may be satisfied.

According to the imaging optical system according to an embodiment of the present invention, the aberration improvement effect can be improved, high resolution can be realized, and sensitivity to the decenter tolerance of the lens can be improved.

1 is a configuration diagram of an imaging optical system according to a first embodiment of the present invention.
FIG. 2 is a curve showing the 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.
FIG. 4 is a curve showing the aberration characteristics of the imaging optical system shown in FIG. 3.
Figure 5 is a configuration diagram of an imaging optical system according to a third embodiment of the present invention.
FIG. 6 is a curve showing the aberration characteristics of the imaging optical system shown in FIG. 5.
Figure 7 is a configuration diagram of an imaging optical system according to a fourth embodiment of the present invention.
FIG. 8 is a curve showing the 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 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, or create other degenerative inventions or this invention. Other embodiments that are included within the scope of the inventive idea can be easily proposed, but it will also be said that this is included within the scope of the inventive idea of the present application.

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.

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

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

Additionally, the front refers to the side closer to the object side in the imaging optical system, and the back refers to the side closer to the image sensor or image side in the imaging optical system. Additionally, in each lens, the first side refers to the side close to the object side (or, object side), and the second side refers to the side close to the image side (or image side). Additionally, in this specification, the values for the radius of curvature, thickness, OAL, BFL, and D1 of the lens are all in mm units.

An 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 lens. Includes a lens 60.

However, the imaging optical system according to an embodiment of the present invention does not consist only of six lenses and may further include other components as needed. For example, the imaging optical system may include an aperture stop (ST) for controlling the amount of light. Additionally, the imaging optical system may further include an infrared ray blocking filter 70 to block infrared rays. Additionally, the imaging optical system may further include an image sensor 80 for converting an image of an incident subject into an electrical signal. Additionally, the imaging optical system may further include a gap maintenance member for adjusting the distance between the lenses.

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

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

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

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

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

An imaging optical system configured in this way can improve optical performance by improving aberration. In addition, the imaging optical system configured in this way can improve the sensitivity of the lens by reducing the angle of refraction. Therefore, the imaging optical system according to an embodiment of the present invention can use all six lenses made of plastic.

The imaging optical system according to an embodiment of the present invention satisfies Condition Equation 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, if it deviates from the lower limit of Conditional Expression 1, the thickness in the paraxial region of the sixth lens becomes thin, causing field curvature and making it difficult to secure resolution performance in the peripheral area, and if it deviates from the upper limit of Conditional Expression 1, the entire imaging optical system Because the focal distance is small, distortion aberration increases.

The imaging optical system according to an embodiment of the present invention satisfies Condition Equation 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, Conditional Expression 2 is a condition regarding chromatic aberration. If it exceeds the lower limit of Conditional Expression 2, chromatic aberration correction becomes difficult, making it difficult to implement high resolution, and if it exceeds the upper limit of Conditional Expression 2, it is difficult to reduce the manufacturing cost of the third lens. there is.

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

[Conditional expression 3]

|Sag9/Th5| > 1.0

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

Here, Conditional Expression 3 is a condition regarding resolution when photographing a close object. If the lower limit of Conditional Expression 3 is exceeded, aberration correction becomes difficult when photographing a close object, making it difficult to secure high resolution.

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

[Conditional expression 4]

f3/f2 > 1.5

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

Here, if the lower limit of Conditional Equation 4 is exceeded, the power of the third lens becomes stronger and the curvature becomes smaller, making it difficult to manufacture the third lens.

The imaging optical system according to an embodiment of the present invention satisfies Condition Equation 5.

[Conditional expression 5]

0.5 < OAL/f < 2.0

In Conditional Equation 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 of the imaging optical system [mm].

Here, if it exceeds the lower limit of Conditional Expression 5, the angle of view of the imaging optical system becomes smaller, and if it exceeds the upper limit of Conditional Expression 5, the length of the imaging optical system becomes longer, making it difficult to miniaturize it.

The imaging optical system according to an embodiment of the present invention satisfies Condition Equation 6.

[Conditional expression 6]

f5/f1 < -3.0

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

Here, if it exceeds the upper limit of Conditional Expression 6, the negative power of the fifth lens becomes strong, making it difficult to secure resolution performance in the peripheral area.

The imaging optical system according to an embodiment of the present invention satisfies Conditional Equation 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 lower limit of conditional expression 7 is exceeded, chromatic aberration correction becomes difficult, making it difficult to implement high resolution, and if it exceeds the upper limit of conditional expression 7, it is difficult to reduce manufacturing costs.

Next, the first lens 10 to the sixth lens 60, which constitute an 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. To elaborate, the first and second surfaces of the first lens 10 may be convex toward the object.

Additionally, the first lens 10 may have a convex shape on both sides.

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 that is convex toward the object. To explain further, the first and second surfaces of the second lens 20 are convex toward the object.

At least one of the first and second surfaces 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 that is convex toward the object. To elaborate, 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. To elaborate, 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 side.

Additionally, the fourth lens 40 may have a convex shape on both sides.

At least one of the first and second surfaces of the fourth lens 40 may be aspherical. 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 that is convex toward the image side. To elaborate, the first surface of the fifth lens 50 may be concave toward the object, and the second surface of the fifth lens 50 may be convex toward the image side.

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 that is convex toward the object. To elaborate, the first and second surfaces of the sixth lens 60 are convex toward the object.

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

Additionally, at least one 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.

The imaging optical system configured as above can improve aberration improvement performance because multiple lenses perform the aberration correction function. In addition, the imaging optical system can improve the sensitivity of the lens by reducing the refraction angle of the lens. Therefore, in the imaging optical system, all lenses can be made of plastic material, which has lower optical performance than glass material, and this can lower the manufacturing cost of the lens module and increase 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 may include an optical system including (60), and may further include an infrared cut-off filter (70), an image sensor (80), and an aperture stop (ST).

Here, as shown in Table 1, the distance (OAL) from the object side 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 top side to the top surface is 1.351 mm. Also, 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 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, and the focal length of the sixth lens 60 is -29.043 mm. (f6) is -11.265 mm, and the total focal length (f) of the imaging optical system is 4.655 mm.

Other lens characteristics (radius of curvature (Ri), thickness of the lens or distance between lenses (Thi), refractive index (Nd), Abbe number (Vi)) are shown in Table 2.

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

By disposing the aperture stop (ST) between the first lens 10 and the second lens 20, sensitivity to the decenter tolerance of each lens can be reduced.

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

Meanwhile, 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 equations 1 to 7 described above, and through this, the optical performance of the lens can be improved.

Additionally, the imaging optical system configured in this way may have the 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. 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 may include an optical system including (60), and may further include an infrared cut-off filter (70), an image sensor (80), and an aperture stop (ST).

Here, as shown in Table 5, the distance (OAL) from the object side of the first lens 10 to the image surface of the image sensor 80 is 5.610 mm, and the distance from the image side of the sixth lens 60 to the image surface is 5.610 mm. The distance to (BFL) is 1.438 mm. Also, 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 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, and the focal length of the sixth lens 60 is -16.144 mm. (f6) is -56.424 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 the lens or distance between lenses (Thi), refractive index (Nd), Abbe number (Vi)) are shown in Table 6.

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

By disposing the aperture stop (ST) between the first lens 10 and the second lens 20, sensitivity to the decenter tolerance of each lens can be reduced.

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

Meanwhile, 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 equations 1 to 7 described above, and through this, the optical performance of the lens can be improved.

Additionally, the imaging optical system configured in this way may have the aberration characteristics shown 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 may include an optical system including (60), and may further include an infrared cut-off filter (70), an image sensor (80), and an aperture stop (ST).

Here, as shown in Table 9, the distance (OAL) from the object side of the first lens 10 to the image surface of the image sensor 80 is 4.857 mm, and the distance from the image side of the sixth lens 60 to the image surface is 4.857 mm. The distance to (BFL) is 1.124 mm. Also, 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 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, and the focal length (f6) of the sixth lens is is -6.893 mm, and the total focal length (f) of the imaging optical system is 3.962 mm.

Other lens characteristics (radius of curvature (Ri), thickness of the lens or distance between lenses (Thi), refractive index (Nd), Abbe number (Vi)) are shown in Table 10.

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

By disposing the aperture stop (ST) between the first lens 10 and the second lens 20, sensitivity to the decenter tolerance of each lens can be reduced.

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

Meanwhile, 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 equations 1 to 7 described above, and through this, the optical performance of the lens can be improved.

Additionally, the imaging optical system configured in this way may have the aberration characteristics shown 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 may include an optical system including (60), and may further include an infrared cut-off filter (70), an image sensor (80), and an aperture stop (ST).

Here, as shown in Table 13, the distance (OAL) from the object side 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 of the sixth lens 60 is 5.620 mm. The distance to (BFL) is 1.368 mm. Also, 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 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, and the focal length of the sixth lens 60 is -19.275 mm. (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 the lens or distance between lenses (Thi), refractive index (Nd), Abbe number (Vi)) are shown in Table 14.

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

By disposing the aperture stop (ST) between the first lens 10 and the second lens 20, sensitivity to the decenter tolerance of each lens can be reduced.

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

Meanwhile, 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 equations 1 to 7 described above, and through this, the optical performance of the lens can be improved.

Additionally, the imaging optical system configured in this way may have the aberration characteristics shown 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 thereto, and various changes or modifications may be made within the spirit and scope of the present invention. It is obvious to those skilled in the art, and therefore, it is stated that such changes or modifications fall within the scope of the appended patent claims.

10: first lens 20: second lens
30: third lens 40: fourth lens
50: 5th lens 60: 6th lens
70: Infrared cut-off filter 80: Image sensor
ST: Aperture stop

Claims (9)

In order from the object side,
a first lens having positive refractive power and having a convex object-side surface;
a second lens having a negative refractive power and a meniscus shape convex toward the object;
a third lens having a negative refractive power and a meniscus shape convex toward the object;
a fourth lens having positive refractive power and having a concave object-side surface;
a fifth lens having negative refractive power; and
It includes a sixth lens having negative refractive power,
When the focal length of the fifth lens is f5 and the focal length of the first lens is f1, f5/f1 < -3.0 is satisfied,
When the sag value at the effective diameter end of the object side of the fifth lens is Sag9, and the thickness in the paraxial region of the fifth lens is Th5,
|Sag9/Th5| > 1.0 is satisfied,
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 paragraph 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 paragraph 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 is f, an imaging optical system that satisfies 0.5 < OAL/f < 2.0.
According to paragraph 1,
The fourth lens is an imaging optical system in which the image side surface is convex.
According to paragraph 1,
The fifth lens is an imaging optical system in which the object-side surface is concave.
According to paragraph 1,
The first to sixth lenses are made of plastic.
According to paragraph 1,
An imaging optical system wherein the object-side surface and the image-side surface of the first to sixth lenses are aspherical surfaces.
According to paragraph 1,
An imaging optical system in which an inflection point is formed on at least one of the object-side surface and the image-side surface of the sixth lens.
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