KR102495882B1 - Mobile small optical system for ultra small size and high density pixel image sensor - Google Patents

Abstract

The present invention provides a mobile compact optical system for a high-pixel subminiature image sensor. An optical system according to the present invention includes 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; 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, 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) may be satisfied.
According to the present invention, it not only exhibits high resolution performance that can be applied to a high-pixel subminiature image sensor of 64M or more, but also has a very short total length (TTL) of 5.6mm or less and bright performance of F number 1.9 or less while using 7 lenses. A compact optical system for mobile use can be provided.

Description

Mobile compact optical system for high-pixel micro image sensor {MOBILE SMALL OPTICAL SYSTEM FOR ULTRA SMALL SIZE AND HIGH DENSITY PIXEL IMAGE SENSOR}

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

Recently, camera modules have been 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. It is being used.

As such, as the camera module is widely used in various fields, the level of performance of the camera module is gradually increasing.

Recently, as high-pixel image sensors using ultra-fine pixels of 0.7 to 0.8 μm have been commercialized, the size of image sensors has been getting smaller and smaller. Therefore, it is becoming very important to design an optical system suitable for high-pixel, ultra-small image sensors.

However, in order to properly correct aberrations while exhibiting high-resolution performance corresponding to high-pixel image sensors of tens of megapixels or more, the number of lenses must be increased. Since it becomes difficult to implement a bright optical system, it becomes more difficult to design an optical system that perfectly meets all technical requirements as the size of the image sensor becomes smaller and the number of pixels increases.

Therefore, it is necessary to develop an optimal optical system that can exhibit high-resolution performance in response to a high-pixel subminiature image sensor and realize a bright F-number while minimizing the electric field of the optical system.

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

The present invention has been conceived against this background, and an object of the present invention is to provide an optical system capable of minimizing an electric field while realizing a high resolution corresponding to a high-pixel subminiature image sensor.

In order to achieve this object, one aspect of the present invention, a first lens having a 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; 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; 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's number of the second lens, V3: Abbe's number of the third lens, V5: Abbe's number of the fifth lens) can be satisfied.

In addition, the optical system according to one 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 chief ray incident angle (°) on the top surface).

In addition, the optical system according to one aspect of the present invention may satisfy the 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)) .

In addition, the optical system according to an aspect of the present invention, conditional expression 0.5 < f / f123 < 1.0 (f: focal length of the entire optical system (mm), f123: 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: center thickness (mm) of the first lens).

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

According to the present invention, it not only exhibits high resolution performance that can be applied to a high-pixel subminiature image sensor of 64M class or higher, but also has a very short total length (TTL) of 5.6mm or less and bright performance of F number 1.9 or less while using 7 lenses. A compact optical system for mobile use can be provided.

1 is a configuration 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 configuration 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 configuration 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, preferred embodiments of the present invention will be described with reference to the drawings.

An optical system according to an embodiment of the present invention includes first lenses L1 to seventh lenses L7 arranged in order from the object side to the image side, as shown in FIGS. 1, 3, and 5, respectively. A lens filter LF for blocking infrared light 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 preferably designed to satisfy the following Conditional Expressions 1 to 7 in order to realize a bright F-number and minimize the electric field of the optical system while exhibiting high resolution applicable to a high-pixel subminiature image sensor. do.

<conditional expression 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 becomes difficult to secure a short overall length, and if it is smaller than the lower limit, it is necessary to configure the optical system with a large number of lenses (eg, 7 lenses) as in the embodiment of the present invention. It gets difficult.

<conditional expression 2>

4.0 < |f4 / f7| < 15.0

In conditional expression 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 seventh lens (L7) (mm)

<conditional expression 3>

0.5 < f / f123 < 1.0

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

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

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

<conditional expression 4>

2.0 < TTL / Y < 2.5

TTL: overall length of optics (mm)

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

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

<conditional expression 5>

0.2 < (V3-V2) / V5 < 0.3

V2: Abbe number of the second lens L2

V3: Abbe number of the third lens (L3)

V5: Abbe number of the fifth lens L5

In Condition 5 above, if the value of (V3-V2)/V5 exceeds the upper limit, the refractive power around the aperture decreases, making it difficult to implement high-resolution performance.

<conditional expression 6>

1.0 < A/AOI < 1.5

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

AOI: angle of incidence of the chief ray of the full field on the image plane (°)

In Condition 6 above, if the A/AOI value exceeds the upper limit, it becomes difficult to secure performance usable for a 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 of the first lens L1 (mm)

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

In the above Conditional Equation 7, if the ET1/CT1 value exceeds the upper limit, it becomes difficult to secure the incident angle (CRA) of the chief ray incident on the image surface, and if it is smaller than the lower limit, the ejectability of the lens deteriorates, making it difficult to manufacture the lens.

Hereinafter, various embodiments of an optical system that satisfies Conditional Expressions 1 to 7 above will be described.

Example 1

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

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

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

The third lens L3 has 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 may have a convex object side surface and a concave image side surface.

The fifth lens L5 has negative refractive power, and may have a convex object-side surface and a concave image-side surface in the paraxial region near the optical axis. 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 of the lens surfaces of the fifth lens L5 may include an inflection point.

The sixth lens L6 may have a positive refractive power, and may have both an object-side surface and an image-side surface 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 of the sixth lens L6 may include an inflection point.

The seventh lens L7 has negative refractive power, and may have a convex object-side surface and a concave image-side surface in the paraxial region near the optical axis. 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 of 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 diaphragm STOP may be disposed on the image side of the second lens L2. However, since it is not limited thereto, the diaphragm STOP may be disposed between the second lens L2 and the third lens L3 or may be disposed at other positions.

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, the full field angle (A) 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 - is as shown in Table 1 below.

[Table 1] Design specifications of the first embodiment

[Table 2] Aspherical surface coefficient of the first embodiment

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

Meanwhile, the aspherical shape of each lens surface can be calculated through the following equation.

[mathematical expression]

In the above equation, Z is the distance from the apex 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 apex of the lens, K is the Conic constant, A4, A6, A8, A10, A12, A14, A16, .... are aspheric coefficients respectively.

Table 2 above shows aspheric coefficients applied to each lens surface of the first to seventh lenses (L1, L2, L3, L4, L5, L6, L7) of the optical system according to the first embodiment.

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

Second embodiment

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

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

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

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

The fourth lens L4 may have positive refractive power, and may have both an object-side surface and an image-side surface convex.

The fifth lens L5 has negative refractive power, and may have a convex object-side surface and a concave image-side surface in the paraxial region near the optical axis. 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 of the lens surfaces of the fifth lens L5 may include an inflection point.

The sixth lens L6 has positive refractive power, and may have a convex object side surface and a concave image side surface 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 concave in the paraxial region and convex in the periphery of the paraxial region. Accordingly, at least one lens surface of the sixth lens L6 may include an inflection point.

The seventh lens L7 has negative refractive power and may be concave on both the object side surface and the image side surface 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 of 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 diaphragm STOP may be disposed on the image side of the second lens L2. However, since it is not limited thereto, the diaphragm STOP may be disposed between the second lens L2 and the third lens L3 or may be disposed at other positions.

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 full field angle of view (A) is 44.22 °, The F-No is 1.86.

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

[Table 3] Design specifications of the second embodiment

[Table 4] Aspherical surface coefficient of the second embodiment

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

Table 4 above shows aspheric coefficients applied to each lens surface 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 seen that the optical system according to the second embodiment of the present invention has good astigmatism and distortion.

Third embodiment

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

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

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

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

The fourth lens L4 may have positive refractive power, and may have both an object-side surface and an image-side surface convex.

The fifth lens L5 has negative refractive power, and may have a convex object-side surface and a concave image-side surface in the paraxial region near the optical axis. 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 of the fifth lens L5 may include an inflection point.

The sixth lens L6 has positive refractive power, and may have a convex object side surface and a concave image side surface 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 concave in the paraxial region and convex in the periphery of the paraxial region. Accordingly, at least one lens surface of the sixth lens L6 may include an inflection point.

The seventh lens L7 has negative refractive power, and may have a convex object-side surface and a concave image-side surface in the paraxial region near the optical axis. 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 of 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 diaphragm STOP may be disposed on the image side of the second lens L2. However, since it is not limited thereto, the diaphragm STOP may be disposed between the second lens L2 and the third lens L3 or may be disposed at other positions.

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, the full field angle of view (A) is 44.40 °, The F-No is 1.88.

In addition, 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] Aspherical surface coefficient of the third embodiment

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

Table 6 above shows aspheric coefficients applied to each lens surface of the first to seventh lenses (L1, L2, L3, L4, L5, L6, 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.

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 Conditional Expressions 1 to 7 above.

[Table 7]

As described above, according to an embodiment of the present invention, a 7-element lens is used to demonstrate high-resolution performance suitable for a high-pixel subminiature image sensor of 64 megapixels or more, while having a total length (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 can be modified or modified in various forms. If it includes the technical idea, it will be taken for granted that it belongs to 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 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;
The seventh lens having 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 arranged in order from the object side to the image side, and the following conditional expression is satisfied. .
2.0 < TTL / Y < 2.5
0.8 < f / f1 < 1.5
(TTL: total length of the optical system (mm), Y: half of the diagonal length (mm) of the image sensor, 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.
0.2 < (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 chief ray incident angle (°) delete According to claim 1,
An optical system characterized in that it satisfies the following conditional expression
0.5 < f / f123 < 1.0
(f: focal length of the entire optical system (mm), f123: combined focal length of the first lens, second lens, and 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 (mm) of the fourth lens (L4), f7: focal length (mm) of the seventh lens (L7)) According to claim 1,
An optical system characterized in that it 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)) The method of any one of claims 1 to 3 and 5 to 7,
The fifth lens, the sixth lens, and the seventh lens have an inflection point formed on at least one of the object side surface and the image side surface, respectively.

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