KR102439910B1 - Optical Lens System - Google Patents

Abstract

An imaging optical system according to the present invention includes: a first lens having a positive refractive power and having at least one convex shape; a second lens having a negative refractive power and having a meniscus shape; and a third lens having a negative refractive power and having at least one surface concave. In addition, since the optical system according to the present invention has an Fno of 1.7 or less and the distance from the object side of the first lens to the image plane is 6.0 mm or less, it is easy to mount on a portable terminal.

Description

Imaging optical system {Optical Lens System}

The present invention relates to an optical imaging system that can be easily installed in a small terminal.

The demand for a camera module capable of realizing clear imaging is increasing. For example, a small camera module mounted on a portable terminal is also required to have the same or similar performance (F number less than 2.0) as a general camera module.

However, since the small camera module is limited in size, it is difficult to construct an optical system capable of resolving both brightness and aberration. For example, if the optical system of the camera module is configured with three or less lenses, it is advantageous for miniaturization, but it is difficult to implement a low F number and improve aberration. On the other hand, if the optical system of the camera module is configured with four or more lenses, a low F number can be realized, but it is disadvantageous for miniaturization.

Therefore, there is an urgent need to develop an imaging optical system for a small camera module capable of simultaneously solving the above-mentioned problems.

For reference, as prior art related to the present invention, there are Patent Documents 1 and 2.

JP 2011-253006 A US 2016-0223790 A

An object of the present invention is to solve the above problems, and it is an object of the present invention to provide an imaging optical system that can be mounted on a small camera module and has a low F number.

In order to achieve the above object, an optical imaging system according to an embodiment of the present invention includes a first lens having a positive refractive power; a second lens having a negative refractive power; and a third lens having a negative refractive power; and Fno is 1.7 or less.

The present invention is advantageous for miniaturization of a camera module.

1 is a configuration diagram of an imaging optical system according to an embodiment of the present invention;
FIG. 2 is a lateral aberration curve of the imaging optical system shown in FIG. 1; FIG.
FIG. 3 is a distortion aberration curve of the imaging optical system shown in FIG. 1; FIG.
FIG. 4 is a graph showing the ambient light quantity ratio of the imaging optical system shown in FIG. 1 ;

Hereinafter, a preferred embodiment of the present invention will be described in detail based on the accompanying illustrative drawings.

In describing the present invention below, terms referring to the components of the present invention are named in consideration of the functions of each component, and thus should not be construed as limiting the technical components of the present invention.

Throughout the specification, that a component is 'connected' to another component includes not only cases in which these components are 'directly connected' but also cases in which they are 'indirectly connected' with other components interposed therebetween. do. In addition, 'including' a certain component means that other components may be further included, rather than excluding other components, unless otherwise stated.

In this specification, the first lens means a lens closest to the object (or subject), and the third lens means a lens closest to the image surface (or image sensor). In the present specification, the units of the radius of curvature (Radius), thickness (Thickness), TL (distance from the object side of the first lens to the image plane), and focal length of the lens are all mm. In addition, the thickness of the lenses, the distance between the lenses, and TL are distances measured with respect to the optical axis of the imaging optical system.

In this specification, the expression that the object side or the image side of the lens is convex means that the paraxial region of the corresponding surface is convex, and that the object side or the image side of the lens has a concave shape means that the paraxial region of the corresponding surface is concave. It means concave. Therefore, although it is described herein that the object side or the image side of the lens has a convex shape, the edge portion of the lens may be concave. Likewise, although it is described herein that the object side or the image side of the lens has a concave shape, the edge portion of the lens may be convex.

The imaging optical system according to the present invention is configured to implement a low F number. In addition, the imaging optical system according to the present invention is configured to enable downsizing. To achieve this, the optical imaging system of the present invention may be composed of a three-element lens. However, the configuration of the imaging optical system according to the present invention is not limited to a three-element lens. For example, the imaging optical system according to the present invention may be composed of two or less lenses or four or more lenses.

The imaging optical system includes a first lens, a second lens, and a third lens.

The first lens has positive refractive power. At least one surface of the first lens is convex. The first lens has a relatively low refractive index. For example, the refractive index of the first lens may be less than 1.6. The first lens includes an aspherical surface. For example, at least one of the object side and the image side of the first lens may be an aspherical surface. The first lens is made of a plastic material.

The second lens has a negative refractive power. The second lens has a manisque shape in which one surface is concave. The second lens has a relatively high refractive index. For example, the refractive index of the second lens may be 1.65 or more. The second lens includes an aspherical surface. For example, at least one of an object side surface and an image side surface of the second lens may be an aspherical surface. The second lens is made of a plastic material. The second lens is configured to bond with the first lens. For example, the object side of the second lens may be bonded to the image side of the first lens.

The third lens has negative refractive power. At least one surface of the third lens is concave. The third lens has a relatively low refractive index. For example, the refractive index of the third lens may be less than 1.6. The third lens includes an aspherical surface. For example, at least one of an object side surface and an image side surface of the third lens may be an aspherical surface. The third lens is made of a plastic material.

The imaging optical system further includes a filter, an image sensor, and an iris.

The filter is disposed between the third lens and the image sensor. The filter may block light of some wavelengths from being incident on the image sensor. For example, a filter may block infrared radiation.

The image sensor forms an upper surface. For example, the surface of the image sensor may form an upper surface.

The diaphragm is arranged to adjust the amount of light incident on the lens. For example, the diaphragm may be disposed between the second lens and the third lens.

The imaging optical system may satisfy the following conditional expression.

[Conditional Expression] 0.4 < D4/D1 < 0.7

In the above conditional expression, D1 is the thickness at the center of the optical axis of the first lens, and D4 is the optical axis distance from the image side of the second lens to the object side of the third lens.

Next, an optical imaging system according to an embodiment will be described in detail with reference to FIG. 1 .

The optical imaging system 100 includes a first lens 110 , a second lens 120 , and a third lens 130 .

The first lens 110 has a positive refractive power and has a convex shape on both sides. The first lens 110 has a refractive index of less than 1.60 and an Abbe's number of 50 or more. The first lens 110 may be made of a plastic material to facilitate manufacture.

The first lens 110 has a focal length in the range of 2.0 to 4.0. For example, in this embodiment, the focal length of the first lens 110 is 2.706 mm. The first lens 110 may be the thickest lens in the optical imaging system 100 . For example, the distance D1 from the object side of the first lens 110 to the image side of the first lens 110 is from the object side of the second lens 120 to the image side of the second lens 120 . is greater than the distance D3 and the distance D5 from the object side of the third lens 130 to the image side of the third lens 130 .

The second lens 120 has a negative refractive power, and the object side is concave and the image side is convex. The second lens 120 has a refractive index of 1.65 or more, and an Abbe's number of less than 30. The second lens 120 may be made of a plastic material for easy manufacture.

The second lens 120 has a focal length in the range of -20 to -10. For example, in this embodiment, the focal length of the second lens 120 is -14.17 mm. The second lens 120 may be the thinnest lens in the optical imaging system 100 . For example, the distance D3 from the object side of the second lens 120 to the image side of the second lens 120 is from the object side of the first lens 110 to the image side of the first lens 110 . is smaller than the distance D1 and the distance D5 from the object side of the third lens 130 to the image side of the third lens 130 .

The third lens 130 has a negative refractive power and has a concave shape on both sides. The third lens 130 has a refractive index of less than 1.60 and an Abbe's number of 50 or more. The third lens 130 may be made of a plastic material to facilitate manufacture. The third lens 130 may be made of the same material as the first lens 110 .

The third lens 120 has a focal length in the range of -3.0 to -1.0. For example, in this embodiment, the focal length of the third lens 130 is -1.649 mm.

The optical imaging system 100 further includes a filter 140 , an image sensor 150 , and an aperture 160 . The filter 140 is disposed between the third lens 130 and the image sensor 150 , and the diaphragm 160 is disposed between the second lens 120 and the third lens 130 .

Table 1 shows the lens characteristics of the imaging optical system 100 according to the present embodiment.

The overall focal length f of the imaging optical system may be determined in the range of 4.0 to 6.0. For example, the total focal length f of the imaging optical system according to the present embodiment is 4.5 mm. The overall length TL of the imaging optical system may be less than 6.0 mm. For example, the total length TL of the imaging optical system according to the present embodiment is 5.905 mm.

The imaging optical system according to the present invention exhibits lateral aberration that satisfies the quality standard. For example, the lateral aberration of the imaging optical system according to the present embodiment does not deviate from the 1.6 μm range as shown in FIG. 2 .

The imaging optical system according to the present invention exhibits distortion aberration that satisfies the quality standard. For example, the distortion aberration of the imaging optical system according to the present embodiment does not deviate from the range of 3.6% as shown in FIG. 3 .

The imaging optical system according to the present invention exhibits an ambient light quantity ratio that satisfies the quality standard. For example, the ambient light intensity ratio of the imaging optical system according to the present embodiment is about 40%, which exceeds the general standard of 30%, as shown in FIG. 4 .

The present invention is not limited only to the embodiments described above, and those of ordinary skill in the art to which the present invention pertains can do as much as possible without departing from the spirit of the present invention described in the claims below. It may be implemented with various modifications. For example, various features described in the above-described embodiments may be applied in combination to other embodiments unless a description to the contrary is expressly stated.

100 imaging optics
110 first lens
120 second lens
130 third lens
140 filters
150 image sensor
160 aperture

Claims (15)

a first lens having positive refractive power;
a second lens having a negative refractive power; and
a third lens having a negative refractive power;
is composed of
The first lens to the third lens are sequentially arranged from the object side,
The distance from the object side of the first lens to the image plane is 6.0 mm or less,
An imaging optical system with an Fno of 1.7 or less. According to claim 1,
The first lens is an imaging optical system having a convex shape on the side of the object. According to claim 1,
The first lens is an imaging optical system having a convex image side. According to claim 1,
The second lens is an imaging optical system having a concave shape on the side of the object. According to claim 1,
The second lens is an imaging optical system having a convex image side. According to claim 1,
The third lens is an imaging optical system having a concave shape on the side of the object. According to claim 1,
The third lens is an imaging optical system having a concave image side surface. According to claim 1,
The second lens is an imaging optical system disposed to contact the image side of the first lens. delete According to claim 1,
and an iris disposed between the second lens and the third lens. According to claim 1,
The refractive index of the second lens is greater than the refractive index of the first lens and the refractive index of the third lens. According to claim 1,
An Abbe's number of the first lens and an Abbe's number of the third lens are 50 or more. According to claim 1,
The first to third lenses are an imaging optical system made of a plastic material. According to claim 1,
One pair of the first to third lenses is an imaging optical system made of the same material. According to claim 1,
An imaging optical system satisfying the following conditional expression.
[Conditional Expression] 0.4 < D4/D1 < 0.7
(In the above conditional expression, D1 is the thickness at the center of the optical axis of the first lens, and D4 is the optical axis distance from the image side of the second lens to the object side of the third lens)

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