KR20220091964A - Mobile small optical system for ultra small size and high density pixel image sensor - Google Patents

Abstract

The present invention provides a mobile small optical system for an ultra-small-sized high-pixel image sensor. The optical system according to the present invention comprises: a first lens having positive refractive power; a second lens having negative refractive power; a third lens having negative refractive power; a fourth lens having positive refractive power; a fifth lens having negative refractive power; a sixth lens having positive refractive power; and a seventh lens having negative refractive power, wherein the first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens and the seventh lens are sequentially arranged from the object side to the image side, and the condition that 2.0 < TTL / Y < 2.5 (TTL: the total length (mm) of the optical system, Y: half of the diagonal length (mm) of the image sensor) may be satisfied. According to the present invention, provided is a mobile small optical system, wherein high resolution performance that can be applied to an ultra-small-sized high-pixel image sensor with the level of 64 M or more can be exhibited, and the total length (TTL) is very short to be equal to or smaller than 5.6 mm and the performance is bright with the F number equal to or smaller than 1.9 while using seven lenses.

Description

Mobile small optical system for high-pixel and ultra-small image sensor

The present invention relates to a high-pixel optical system mounted on a smart device, and more particularly, to a slim mobile optical system having a very short overall length while having high resolution corresponding to a high-pixel ultra-small image sensor.

Recently, camera modules are being installed as basic specifications in smart devices, portable electronic devices, home appliances, and automobiles, and small camera modules are widely used in various products such as action cams, drones, 360-degree cameras, and virtual reality (VR) devices. is being used

As the camera module is widely used in various fields as described above, the level of demand for the performance of the camera module is also increasing.

Recently, as high-pixel image sensors with ultra-fine pixels of 0.7 to 0.8 μm in size have been commercialized, the size of image sensors is also getting smaller.

However, it is necessary to increase the number of lenses to properly correct aberration while exhibiting high-resolution performance corresponding to high-pixel image sensors of tens of mega-class or higher. Since it becomes difficult to implement a bright optical system, the smaller the size of the image sensor and the more pixels, the more difficult it becomes to design an optical system that perfectly meets all technical requirements.

Therefore, it is necessary to develop an optimal optical system that can minimize the overall length of the optical system and exhibit high-resolution performance in response to a high-pixel and ultra-small image sensor and realize a bright F-number.

Republic of Korea Patent Registration No. 10-1627133 (2016.06.03 Announcement)

The present invention was devised in this background, and an object of the present invention is to provide an optical system capable of minimizing the electric field while realizing a high resolution corresponding to a high-pixel ultra-small image sensor.

In order to achieve this object, an aspect of the present invention, a first lens having a positive refractive power; a second lens having a negative refractive power; a third lens having a negative refractive power; a fourth lens having positive refractive power; a fifth lens having a negative refractive power; a sixth lens having positive refractive power; a seventh lens having a negative refractive power, wherein the first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens and the seventh lens are sequentially arranged from the object side to the image side, An optical system satisfying the conditional expression 2.0 < TTL / Y < 2.5 (TTL: total length (mm) of the optical system, Y: half of the diagonal length (mm) of the image sensor) is provided.

In the optical system according to an aspect of the present invention, the conditional expression 0.2 < (V3-V2) / V5 < 0.3 (V2: Abbe number of the second lens, V3: Abbe number of the third lens, V5: Abbe number of the fifth lens) can be satisfied with

In addition, the optical system according to an aspect of the present invention may satisfy the conditional expression 1.0 < A / AOI < 1.5 (A: full-field half angle of view (°), AOI: full-field principal ray incident angle (°) on the image plane).

In addition, the optical system according to an aspect of the present invention may satisfy the conditional expression 0.8 < f / f1 < 1.5 (f: the overall focal length of the optical system (mm), f1: the focal length of the first lens (L1) (mm)) .

In addition, in the optical system according to an aspect of the present invention, the conditional expression 0.5 < f / f123 < 1.0 (f: the overall focal length of the optical system (mm), f123: the combined focal length of the first lens, the second lens and the third lens (mm) )) can be satisfied.

In addition, the optical system according to an aspect of the present invention, the conditional expression 4.0 < |f4 / f7| <15.0 (f4: focal length (mm) of the fourth lens (L4), f7: focal length (mm) of the seventh lens (L7)) may be satisfied.

In addition, the optical system according to an aspect of the present invention may satisfy the conditional expression 0.25 < ET1 / CT1 < 0.6 (ET1: edge thickness (mm) of the first lens, CT1: thickness of the center of the first lens (mm)).

In addition, in the optical system according to an aspect of the present invention, each of the fifth lens, the sixth lens, and the seventh lens may have an inflection point formed on at least one of an object side surface and an image side surface.

According to the present invention, it not only exhibits high resolution that can be applied to high-pixel ultra-small image sensors of 64M or higher, but also has a very short overall length (TTL) of 5.6mm or less and bright performance of 1.9 or less while using 7 lenses. It is possible to provide a compact optical system for mobile.

1 is a block diagram of an optical system according to a first embodiment of the present invention;
2 is an aberration diagram of an optical system according to a first embodiment of the present invention;
3 is a block diagram of an optical system according to a second embodiment of the present invention;
4 is an aberration diagram of an optical system according to a second embodiment of the present invention;
5 is a block diagram of an optical system according to a third embodiment of the present invention;
6 is an aberration diagram of an optical system according to a third embodiment of the present invention;

Hereinafter, a preferred embodiment of the present invention will be described with reference to the drawings.

The optical system according to an embodiment of the present invention includes first to seventh lenses L1 to L7 sequentially arranged from the object side to the image side, as shown in FIGS. 1, 3 and 5 , respectively. A lens filter LF that blocks infrared rays and the like may be installed between the seventh lens L7 and the image sensor.

On the other hand, the optical system according to an embodiment of the present invention is designed to satisfy the following conditional expressions 1 to 7 in order to realize a bright F-number and minimize the overall length of the optical system while exhibiting high resolution applicable to a high-pixel ultra-small image sensor. do.

<Condition 1>

0.8 < f / f1 < 1.5

f: Focal length of the entire optical system (mm)

f1: focal length of the first lens (L1) (mm)

In the above conditional expression 1, if the f/f1 value exceeds the upper limit, it is difficult to secure a short overall length, and if it is smaller than the lower limit, it is better to configure the optical system with a large number (eg, 7) lenses as in the embodiment of the present invention. it gets difficult

<Condition 2>

4.0 < |f4 / f7| < 15.0

In condition 2 above, |f4/f7| If the value exceeds the upper limit, it becomes difficult to secure a back focal length suitable for a mobile optical system, and if it is smaller than the lower limit, it becomes difficult to secure the required performance due to insufficient refractive power of the lens.

f4: focal length of the fourth lens (L4) (mm)

f7: Focal length of the 7th lens (L7) (mm)

<Condition 3>

0.5 < f / f123 < 1.0

f: Focal length of the entire optical system (mm)

f123: Composite focal length of the first lens (L1), second lens (L2) and third lens (L3) (mm)

In the above condition 3, when the f/f123 value exceeds the upper limit, it becomes difficult to secure a short electric length, and when it is smaller than the lower limit, it becomes difficult to implement a bright optical system.

<Condition 4>

2.0 < TTL / Y < 2.5

TTL: overall length of the optical system (mm)

Y: Half of the diagonal length (mm) of the image sensor

In the above condition 4, when the TTL/Y value exceeds the upper limit, it becomes difficult to secure a short electric length, and when the TTL/Y value exceeds the upper limit, it becomes difficult to secure the performance usable for the high-pixel image sensor when it is smaller than the lower limit.

<Conditional Expression 5>

0.2 < (V3-V2) / V5 < 0.3

V2: Abbe number of second lens L2

V3: Abbe number of the third lens L3

V5: Abbe number of the fifth lens L5

In condition 5 above, when the (V3-V2)/V5 value exceeds the upper limit, the refractive power of the diaphragm periphery is lowered, making it difficult to realize high-resolution performance.

<Conditional Expression 6>

1.0 < A / AOI < 1.5

A: Half field of view (°) of full field

AOI: Angle of incidence of the chief ray of the full field in the image plane (°)

In condition 6 above, if the A/AOI value exceeds the upper limit, it becomes difficult to secure the performance usable for the high-pixel image sensor, and if it is smaller than the lower limit, it becomes difficult to secure an appropriate angle of view.

<Conditional Expression 7>

0.25 < ET1/CT1 < 0.6

ET1: Edge thickness (mm) of the first lens (L1)

CT1: central thickness of the first lens (L1) (mm)

In the above condition 7, if the ET1/CT1 value exceeds the upper limit, it becomes difficult to secure the angle of incidence (CRA) of the chief ray incident on the image plane.

Hereinafter, various embodiments of the optical system satisfying the above-described Conditional Expressions 1 to 7 will be described.

first embodiment

First, FIGS. 1 and 2 are diagrams and aberration diagrams of an optical system according to a first embodiment of the present invention, respectively.

The first lens L1 may have positive refractive power, and the object side surface may be convex and the image side surface may be concave.

The second lens L2 may have negative refractive power, and the object side surface may be convex and the image side surface may be concave.

The third lens L3 has a negative refractive power, and both the object side surface and the image side surface may be concave.

The fourth lens L4 has positive refractive power, and the object side surface may be convex and the image side surface may be concave.

The fifth lens L5 has negative refractive power, and in the paraxial region near the optical axis, the object side surface may be convex and the image side surface may be concave. Also, the object-side surface of the fifth lens L5 may be convex in the paraxial region and concave in the periphery of the paraxial region. Also, the image side surface of the fifth lens L5 may be concave in the paraxial region and convex in the periphery of the paraxial region. Accordingly, at least one lens surface among the lens surfaces of the fifth lens L5 may include an inflection point.

The sixth lens L6 has positive refractive power, and both the object side surface and the image side surface may be convex in the paraxial region near the optical axis. Also, the object-side surface of the sixth lens L6 may be convex in the paraxial region and concave in the periphery of the paraxial region. Also, the image side surface of the sixth lens L6 may be convex in the paraxial region and concave in the periphery of the paraxial region. Accordingly, at least one lens surface among the lens surfaces of the sixth lens L6 may include an inflection point.

The seventh lens L7 has a negative refractive power, and in the paraxial region near the optical axis, the object side surface may be convex and the image side surface may be concave. Also, the object-side surface of the seventh lens L7 may be convex in the paraxial region and concave in the periphery of the paraxial region. Also, the image side surface of the seventh lens L7 may be concave in the paraxial region and convex in the periphery of the paraxial region. Accordingly, at least one lens surface among the lens surfaces of the seventh lens L7 may include an inflection point.

Also, in the optical system according to the first embodiment of the present invention, the stop STOP may be disposed on the image side surface of the second lens L2. However, since the present invention is not limited thereto, the stopper STOP may be disposed between the second lens L2 and the third lens L3 or may be disposed at a different position.

The total length (TTL) of the optical system according to the first embodiment of the present invention is 5.58 mm, the diagonal length (2Y) of the image sensor is 4.84 mm, and the half angle (A) of the full field is 43.33°, The F-No is 1.90.

In addition, design specifications of each lens constituting the optical system according to the first embodiment of the present invention - radius of curvature (mm), thickness (mm), lens spacing (mm), refractive index (Nd), Abbe number (Vd) of each lens etc. - are as shown in Table 1 below.

[Table 1] Design specifications of the first embodiment

[Table 2] Aspheric coefficient of the first embodiment

Also, each lens surface of the optical system according to the first embodiment of the present invention may be formed of an aspherical surface. However, since the present invention is not limited thereto, at least one of the entire lens surfaces of the first to seventh lenses may be formed as a spherical surface.

On the other hand, the aspherical shape of each lens surface can be calculated through the following equation.

[Equation]

In the above equation, Z is the distance from the vertex of the lens in the direction of the optical axis, h is the distance in the direction perpendicular to the optical axis, c is the reciprocal of the radius of curvature at the vertex of the lens, K is the Conic constant, A4, A6, A8, A10, A12, A14, A16, .... are aspheric coefficients, respectively.

Table 2 above shows the aspheric coefficients applied to the respective lens surfaces of the first to seventh lenses L1, L2, L3, L4, L5, L6, and L7 of the optical system according to the first embodiment.

Meanwhile, referring to FIG. 2 , it can be confirmed that both astigmatism and distortion aberration are good in the optical system according to the first embodiment of the present invention.

second embodiment

3 and 4 are configuration diagrams and aberration diagrams of an optical system according to a second embodiment of the present invention, respectively.

The first lens L1 may have positive refractive power, and the object side surface may be convex and the image side surface may be concave.

The second lens L2 may have negative refractive power, and the object side surface may be convex and the image side surface may be concave.

The third lens L3 has negative refractive power, and the object side surface may be convex and the image side surface may be concave.

The fourth lens L4 has positive refractive power, and both the object side surface and the image side surface may be convex.

The fifth lens L5 has negative refractive power, and in the paraxial region near the optical axis, the object side surface may be convex and the image side surface may be concave. Also, the object-side surface of the fifth lens L5 may be convex in the paraxial region and concave in the periphery of the paraxial region. Also, the image side surface of the fifth lens L5 may be concave in the paraxial region and convex in the periphery of the paraxial region. Accordingly, at least one lens surface among the lens surfaces of the fifth lens L5 may include an inflection point.

The sixth lens L6 has positive refractive power, and in the paraxial region near the optical axis, the object side surface may be convex and the image side surface may be concave. Also, the object-side surface of the sixth lens L6 may be convex in the paraxial region and concave in the periphery of the paraxial region. Also, the image side surface of the sixth lens L6 may be concave in the paraxial region and convex in the periphery of the paraxial region. Accordingly, at least one lens surface among the lens surfaces of the sixth lens L6 may include an inflection point.

The seventh lens L7 has negative refractive power, and both the object side surface and the image side surface may be concave in the paraxial region near the optical axis. Also, the object-side surface of the seventh lens L7 may be concave in the paraxial region and convex in the periphery of the paraxial region. Also, the image side surface of the seventh lens L7 may be concave in the paraxial region and convex in the periphery of the paraxial region. Accordingly, at least one lens surface among the lens surfaces of the seventh lens L7 may include an inflection point.

Also, in the optical system according to the second embodiment of the present invention, the stop STOP may be disposed on the image side of the second lens L2. However, since the present invention is not limited thereto, the stopper STOP may be disposed between the second lens L2 and the third lens L3 or may be disposed at a different position.

The total length (TTL) of the optical system according to the second embodiment of the present invention is 5.55 mm, the diagonal length (2Y) of the image sensor is 4.84 mm, the half-field angle (A) of the full field is 44.22°, The F-No is 1.86.

In addition, the design specifications of each lens constituting the optical system according to the second embodiment of the present invention are as shown in Table 3 below.

[Table 3] Design specifications of the second embodiment

[Table 4] Aspheric coefficient of the second embodiment

Each lens surface of the optical system according to the second embodiment of the present invention may be formed of an aspherical surface. However, since the present invention is not limited thereto, at least one of the entire lens surfaces of the first to seventh lenses may be formed as a spherical surface.

Table 4 above shows the aspheric coefficients applied to the respective lens surfaces of the first to seventh lenses L1, L2, L3, L4, L5, L6, and L7 of the optical system according to the second embodiment.

Meanwhile, referring to FIG. 4 , it can be confirmed that both astigmatism and distortion aberration are good in the optical system according to the second embodiment of the present invention.

third embodiment

5 and 6 are diagrams and aberration diagrams of an optical system according to a third embodiment of the present invention, respectively.

The first lens L1 may have positive refractive power, and the object side surface may be convex and the image side surface may be concave.

The second lens L2 may have negative refractive power, and the object side surface may be convex and the image side surface may be concave.

The third lens L3 has negative refractive power, and the object side surface may be convex and the image side surface may be concave.

The fourth lens L4 has positive refractive power, and both the object side surface and the image side surface may be convex.

The fifth lens L5 has a negative refractive power, and in the paraxial region near the optical axis, the object side surface may be convex and the image side surface may be concave. Also, the object-side surface of the fifth lens L5 may be convex in the paraxial region and concave in the periphery of the paraxial region. Also, the image side surface of the fifth lens L5 may be concave in the paraxial region and convex in the periphery of the paraxial region. Accordingly, at least one lens surface among the lens surfaces of the fifth lens L5 may include an inflection point.

The sixth lens L6 has positive refractive power, and in the paraxial region near the optical axis, the object side surface may be convex and the image side surface may be concave. Also, the object-side surface of the sixth lens L6 may be convex in the paraxial region and concave in the periphery of the paraxial region. Also, the image side surface of the sixth lens L6 may be concave in the paraxial region and convex in the periphery of the paraxial region. Accordingly, at least one lens surface among the lens surfaces of the sixth lens L6 may include an inflection point.

The seventh lens L7 has a negative refractive power, and in the paraxial region near the optical axis, the object side surface may be convex and the image side surface may be concave. Also, the object-side surface of the seventh lens L7 may be convex in the paraxial region and concave in the periphery of the paraxial region. Also, the image side surface of the seventh lens L7 may be concave in the paraxial region and convex in the periphery of the paraxial region. Accordingly, at least one lens surface among the lens surfaces of the seventh lens L7 may include an inflection point.

Also, in the optical system according to the third embodiment of the present invention, the stop STOP may be disposed on the image side surface of the second lens L2. However, since the present invention is not limited thereto, the stopper STOP may be disposed between the second lens L2 and the third lens L3 or may be disposed at a different position.

The total length (TTL) of the optical system according to the third embodiment of the present invention is 5.55 mm, the diagonal length (2Y) of the image sensor is 4.84 mm, and the half-field angle (A) of the full field is 44.40°, The F-No is 1.88.

In addition, the design specifications of each lens constituting the optical system according to the third embodiment of the present invention are shown in Table 5 below.

[Table 5] Design specifications of the third embodiment

[Table 6] Aspheric coefficient of the third embodiment

Each lens surface of the optical system according to the third embodiment of the present invention may be formed of an aspherical surface. However, since the present invention is not limited thereto, at least one of the entire lens surfaces of the first to seventh lenses may be formed as a spherical surface.

Table 6 above shows the aspheric coefficients applied to the respective lens surfaces of the first to seventh lenses L1, L2, L3, L4, L5, L6, and L7 of the optical system according to the third embodiment.

Meanwhile, referring to FIG. 6 , it can be seen that the optical system according to the third embodiment of the present invention has good astigmatism and distortion aberration.

Table 7 below shows that the design specifications of the optical systems according to the first to third embodiments of the present invention satisfy all of the aforementioned Conditional Expressions 1 to 7.

[Table 7]

As described above, according to an embodiment of the present invention, a high-resolution performance suitable for a high-pixel ultra-small image sensor of 64 mega or more using a 7-element lens, while exhibiting a TTL of 5.6 mm or less, F-No. Since it can be reduced to 1.9 or less, it is possible to provide an optical system suitable for high-pixel mobile devices.

In the above, preferred embodiments of the present invention have been described, but the present invention is not limited to the above-described embodiments, and may be modified or modified in various forms and implemented. If the technical idea is included, it will be natural to fall within the scope of the present invention.

L1: first lens L2: second lens L3: third lens
L4: 4th lens L5: 5th lens L6: 6th lens
L7: 7th lens STOP: Aperture LF: Lens filter

Claims (8)

a first lens having positive refractive power;
a second lens having a negative refractive power;
a third lens having a negative refractive power;
a fourth lens having positive refractive power;
a fifth lens having a negative refractive power;
a sixth lens having positive refractive power;
7th lens with negative refractive power
including,
The first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens and the seventh lens are sequentially arranged from the object side to the image side, and the following conditional expression is satisfied. .
2.0 < TTL / Y < 2.5
(TTL: total length of the optical system (mm), Y: half of the diagonal length (mm) of the image sensor) According to claim 1,
An optical system that satisfies the following conditional expression.
0.2 < (V3-V2) / V5 < 0.3
(V2: Abbe number of the second lens, V3: Abbe number of the third lens, V5: Abbe number of the fifth lens) According to claim 1,
An optical system characterized in that it satisfies the following conditional expression
1.0 < A / AOI < 1.5
(A: Full-field half angle of view (°), AOI: Full-field principal ray incident angle from image (°) According to claim 1,
An optical system characterized in that it satisfies the following conditional expression
0.8 < f / f1 < 1.5
(f: focal length of the entire optical system (mm), f1: focal length of the first lens (L1) (mm)) According to claim 1,
An optical system characterized in that it satisfies the following conditional expression
0.5 < f / f123 < 1.0
(f: the overall focal length of the optical system (mm), f123: the combined focal length of the first lens, the second lens, and the third lens (mm)) According to claim 1,
An optical system characterized in that it satisfies the following conditional expression
4.0 < |f4 / f7| < 15.0
(f4: focal length of the fourth lens (L4) (mm), f7: focal length of the seventh lens (L7) (mm)) According to claim 1,
An optical system that satisfies the following conditional expression.
0.25 < ET1/CT1 < 0.6
(ET1: edge thickness of the first lens (mm), CT1: center thickness of the first lens (mm)) 8. The method according to any one of claims 1 to 7,
The fifth lens, the sixth lens, and the seventh lens each have an inflection point formed on at least one of an object-side surface and an image-side surface, respectively.

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