KR102348000B1 - Optical Imaging System - Google Patents

Abstract

The optical imaging system of the present invention includes a first lens, a second lens, a third lens, a fourth lens, a fifth lens, and a sixth lens sequentially arranged from the object side, wherein the second lens has a negative refractive power , the fifth lens has positive refractive power and satisfies the conditional expression TTL/f < 1.0. Here, in the conditional expression, TTL is the distance from the object side to the image plane of the first lens, and f is the total focal length of the imaging optical system.

Description

Optical Imaging System

The present invention relates to a telephoto imaging optical system comprising six lenses.

The small camera may be mounted on a portable terminal. For example, a miniature camera can also be mounted on a thinned device, such as a portable telephone. Such a small camera includes an imaging optical system configured with a small number of lenses to enable thinning. For example, the imaging optical system of a small camera is comprised of 4 or less lenses. However, such an imaging optical system is difficult to implement telephoto characteristics and high resolution characteristics.

US 2016-0033744 A1 US 2017-0299846 A1 US 2014-0293453 A1

An object of the present invention is to provide an imaging optical system that can be applied to a high-performance compact camera.

An imaging optical system for achieving the above object includes a first lens, a second lens, a third lens, a fourth lens, a fifth lens, and a sixth lens sequentially arranged from the object side, wherein the second lens is negative It has refractive power, and the fifth lens has positive refractive power, and the conditional expression TTL/f < 1.0 is satisfied. Here, in the conditional expression, TTL is the distance from the object side to the image plane of the first lens, and f is the total focal length of the imaging optical system.

The present invention can implement an imaging optical system suitable for a small camera with high performance.

1 is a block diagram of an imaging optical system according to a first embodiment of the present invention;
FIG. 2 is a graph showing an aberration curve of the imaging optical system shown in FIG. 1; FIG.
3 is a configuration diagram of an imaging optical system according to a second embodiment of the present invention;
4 is a graph showing an aberration curve of the imaging optical system shown in FIG. 3
5 is a configuration diagram of an imaging optical system according to a third embodiment of the present invention;
6 is a graph showing an aberration curve of the imaging optical system shown in FIG. 5;
7 is an enlarged view of edges of the fourth lens and the fifth lens 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 function of each component, and thus should not be construed as limiting the technical components of the present invention.

In addition, throughout the specification, that a component is 'connected' with another component includes not only the case where these components are 'directly connected', but also the case where the component is 'indirectly connected' through another component. means that In addition, 'including' a certain component means that other components may be further included, rather than excluding other components, unless otherwise stated.

In addition, in the present specification, the first lens means a lens closest to the object (or subject), and the sixth lens means a lens closest to the image surface (or image sensor). In the present specification, the units of the radius of curvature of the lens, thickness, TTL, IMG HT (1/2 of the diagonal length of the image plane), and focal length are all in mm. In addition, the thickness of the lenses, the distance between the lenses, and the TTL are distances calculated based on the optical axis of the lenses. In addition, in the description of the shape of the lens, the convex shape of one surface means that the optical axis portion of the corresponding surface is convex, and the concave shape means that the optical axis portion of the corresponding surface is concave. Therefore, even if it is described that one surface of the lens has a convex shape, the edge portion of the lens may be concave. Similarly, although one surface of the lens is described as having a concave shape, the edge portion of the lens may be convex.

The imaging optical system includes six lenses. For example, the imaging optical system may include a first lens, a second lens, a third lens, a fourth lens, a fifth lens, and a sixth lens sequentially arranged from the object side. The first to sixth lenses are disposed with an air gap. For example, the image side and object side of neighboring lenses do not contact.

The first lens has refractive power. For example, the first lens has positive refractive power. The first lens has a convex surface. For example, the first lens has a convex shape on the side of the object.

The first lens includes an aspherical surface. For example, both surfaces of the first lens may be aspherical. The first lens may be made of a material having high light transmittance and excellent workability. For example, the first lens may be made of a plastic material. However, the material of the first lens is not limited to a plastic material. For example, the first lens may be made of a glass material. The first lens has a low refractive index. For example, the refractive index of the first lens may be less than 1.6.

The second lens has refractive power. For example, the second lens has a negative refractive power. The second lens has a concave surface. For example, the second lens may have a concave image side surface.

The second lens includes an aspherical surface. For example, the second lens may have an aspherical side surface of the object. The second lens may be made of a material having high light transmittance and excellent workability. For example, the second lens may be made of a plastic material. However, the material of the second lens is not limited to plastic. For example, the second lens may be made of a glass material. The second lens has a higher refractive index than the first lens. For example, the refractive index of the second lens may be 1.65 or more.

The third lens has refractive power. For example, the third lens may have a negative refractive power. The third lens has a convex surface. For example, the third lens may have a convex shape on the side of the object. An inflection point is formed in the third lens. For example, four inflection points are formed on the object side of the third lens.

The third lens may include an aspherical surface. For example, both surfaces of the third lens may be aspherical. The third lens may be made of a material having high light transmittance and excellent workability. For example, the third lens may be made of a plastic material. However, the material of the third lens is not limited to plastic. For example, the third lens may be made of a glass material. The third lens has a high refractive index. For example, the refractive index of the third lens may be 1.6 or more.

The fourth lens has refractive power. For example, the fourth lens has positive refractive power. The fourth lens has a convex surface. For example, the fourth lens may have a convex shape on the side of the object.

The fourth lens may include an aspherical surface. For example, an object side surface of the fourth lens may be a spherical surface and an image side surface may be an aspherical surface. The fourth lens may be made of a material having high light transmittance and excellent workability. For example, the fourth lens may be made of a plastic material. However, the material of the fourth lens is not limited to plastic. For example, the fourth lens may be made of a glass material. The fourth lens has a high refractive index. For example, the refractive index of the fourth lens may be 1.6 or more.

The fifth lens has refractive power. For example, the fifth lens may have positive refractive power. The fifth lens has a convex surface. For example, the fifth lens may have a concave shape on the side of the object. The fifth lens has a shape having an inflection point. For example, an inflection point may be formed on the object side of the fifth lens.

The fifth lens includes an aspherical surface. For example, both surfaces of the fifth lens may be aspherical. The fifth lens may be made of a material having high light transmittance and excellent workability. For example, the fifth lens may be made of a plastic material. However, the material of the fifth lens is not limited to plastic. For example, the fifth lens may be made of a glass material. The fifth lens has a lower refractive index than the fourth lens. For example, the refractive index of the fifth lens may be less than 1.6.

The sixth lens has refractive power. For example, the sixth lens has negative refractive power. The sixth lens may have a convex shape. For example, the sixth lens may have a convex shape on the side of the object. The sixth lens has an inflection point. For example, an inflection point may be formed on at least one of the object side and the image side of the sixth lens.

The sixth lens includes an aspherical surface. For example, both surfaces of the sixth lens may be aspherical. The sixth lens may be made of a material having high light transmittance and excellent workability. For example, the sixth lens may be made of a plastic material. However, the material of the sixth lens is not limited to plastic. For example, the sixth lens may be made of a glass material. The sixth lens has a low refractive index. For example, the refractive index of the sixth lens may be less than 1.6.

The aspherical surfaces of the first to sixth lenses may be expressed by Equation (1).

In Equation 1, c is the reciprocal of the radius of curvature of the corresponding lens, k is the conic constant, r is the distance from any point on the aspherical surface to the optical axis, A to J are the aspheric constants, and Z (or SAG) is the aspherical surface It is the height in the optical axis direction from any point on the image to the vertex of the aspherical surface.

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

The filter is disposed between the sixth lens and the image sensor. Filters can block some wavelengths of light. For example, the filter may block light of infrared wavelengths.

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 first lens and the second lens.

The imaging optical system may satisfy the following conditional expressions.

[Conditional Expression 1] F No. < 2.5

[Conditional Expression 2] 50 < FOV

[Conditional Expression 3] TTL/f < 1.0

[Condition 4] 0.52 < f1/f < 0.57

[Conditional Expression 5] D34/D45 <1.0

[Conditional Expression 6] 1.6 < Nd2

[Conditional Expression 7] 1.6 < Nd3

[Conditional Expression 8] 1.6 < Nd4

[Conditional Expression 9] 0.5 < DT4/D45 < 1.0

[Conditional Expression 10] 0.1 < DP45 < 0.3

[Conditional Expression 11] 1.0 < (Nd2*2)/(Nd3+Nd4)

In the above conditional expression, FOV is the total field of view of the imaging optical system, TTL is the distance from the object side to the image plane of the first lens, f is the overall focal length of the imaging optical system, f1 is the focal length of the first lens, and D34 is the is the distance from the image side of the third lens to the object side of the fourth lens, D45 is the distance from the image side of the fourth lens to the object side of the fifth lens, Nd2 is the refractive index of the second lens, and Nd3 is the third is the refractive index of the lens, Nd4 is the refractive index of the fourth lens, DT4 is the thickness of the fourth lens, and DP45 is the distance from the image side edge of the fourth lens to the object side edge of the fifth lens (see FIG. 7 ).

Next, an imaging optical system according to various embodiments will be described.

An imaging optical system according to a first embodiment will be described with reference to FIG. 1 .

The optical imaging system 100 includes a first lens 110 , a second lens 120 , a third lens 130 , a fourth lens 140 , a fifth lens 150 , and a sixth lens 160 . .

The first lens 110 has a positive refractive power, and has a convex object side and a concave image side. The second lens 120 has a negative refractive power, and has a concave object side and a concave image side. The third lens 130 has a negative refractive power, and has a convex object side and a concave image side. Six inflection points are formed on the object side of the third lens 130 . The fourth lens 140 has a positive refractive power, and has a convex object side and a convex image side. The fifth lens 150 has a positive refractive power, and has a concave object side and a convex image side. An inflection point is formed on the object side of the fifth lens 150 . The sixth lens 160 has a negative refractive power, and has a convex object side and a concave image side. Inflection points are formed on both surfaces of the sixth lens 160 .

The optical imaging system 100 further includes a filter 170 , an image sensor 180 , and an aperture ST. The filter 170 is disposed between the sixth lens 160 and the image sensor 180 , and the diaphragm ST is disposed between the first lens 110 and the second lens 120 .

In the optical imaging system 100 , the second lens 120 to the fourth lens 140 have a higher refractive index than other lenses. In the present embodiment, all of the refractive indices of the second lens 120 to the fourth lens 140 are 1.6 or more. The second lens 120 has the highest refractive index. In this embodiment, the refractive index of the second lens 120 is 1.65 or more. The sixth lens 160 has the lowest refractive index. In this embodiment, the refractive index of the sixth lens 160 is less than 1.54.

The imaging optical system configured as above exhibits aberration characteristics as shown in FIG. 2 . Tables 1 and 2 show the lens characteristics and the aspherical surface values of the imaging optical system according to the present embodiment.

An imaging optical system according to a second embodiment will be described with reference to FIG. 3 .

The optical imaging system 200 includes a first lens 210 , a second lens 220 , a third lens 230 , a fourth lens 240 , a fifth lens 250 , and a sixth lens 260 . .

The first lens 210 has a positive refractive power, and has a convex object side and a concave image side. The second lens 220 has a negative refractive power, and has a concave object side and a concave image side. The third lens 230 has a negative refractive power, and has a convex object side and a concave image side. Four inflection points are formed on the object side of the third lens 230 . The fourth lens 240 has a positive refractive power, and has a convex object side and a convex image side. The fifth lens 250 has a positive refractive power, and has a concave object side and a convex image side. An inflection point is formed on the object side of the fifth lens 250 . The sixth lens 260 has a negative refractive power, and has a convex object side and a concave image side. Inflection points are formed on both surfaces of the sixth lens 260 .

The optical imaging system 200 further includes a filter 270 , an image sensor 280 , and an aperture ST. The filter 270 is disposed between the sixth lens 260 and the image sensor 280 , and the stop ST is disposed between the first lens 210 and the second lens 220 .

In the optical imaging system 200 , the second lens 220 to the fourth lens 240 have a higher refractive index than other lenses. In this embodiment, all of the refractive indices of the second lens 220 to the fourth lens 240 are 1.6 or more. The second lens 220 has the highest refractive index. In this embodiment, the refractive index of the second lens 220 is 1.65 or more. The sixth lens 260 has the lowest refractive index. In this embodiment, the refractive index of the sixth lens 260 is less than 1.54.

The imaging optical system configured as above exhibits aberration characteristics as shown in FIG. 4 . Tables 3 and 4 show the lens characteristics and the aspherical surface values of the imaging optical system according to the present embodiment.

An imaging optical system according to a third embodiment will be described with reference to FIG. 5 .

The optical imaging system 300 includes a first lens 310 , a second lens 320 , a third lens 330 , a fourth lens 340 , a fifth lens 350 , and a sixth lens 360 . .

The first lens 310 has a positive refractive power, and has a convex object side and a concave image side. The second lens 320 has a negative refractive power, and has a concave object side and a concave image side. The third lens 330 has a negative refractive power, and has a convex object side and a concave image side. Six inflection points are formed on the object side of the third lens 330 . The fourth lens 340 has positive refractive power, and has a convex object side and a convex image side. The fifth lens 350 has positive refractive power, and has a concave object side and a convex image side. An inflection point is formed on the object side of the fifth lens 350 . The sixth lens 360 has a negative refractive power, and has a convex object side and a concave image side. Inflection points are formed on both surfaces of the sixth lens 360 .

The optical imaging system 300 further includes a filter 370 , an image sensor 380 , and an aperture ST. The filter 370 is disposed between the sixth lens 360 and the image sensor 380 , and the stop ST is disposed between the first lens 310 and the second lens 320 .

In the optical imaging system 300 , the second lens 320 to the fourth lens 340 have a higher refractive index than other lenses. In the present embodiment, the refractive indices of the second lens 320 to the fourth lens 340 are all greater than or equal to 1.6. The second lens 320 has the highest refractive index. In this embodiment, the refractive index of the second lens 320 is 1.65 or more. The sixth lens 360 has the lowest refractive index. In this embodiment, the refractive index of the sixth lens 360 is less than 1.54.

The imaging optical system configured as above exhibits aberration characteristics as shown in FIG. 6 . Tables 5 and 6 show the lens characteristics and the aspherical surface values of the imaging optical system according to the present embodiment.

Table 7 shows the conditional expression values of the imaging optical systems according to the first to third embodiments.

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 long as they do not depart from the spirit of the present invention described in the claims below. It may be implemented with various modifications.

100, 200, 300 imaging optics
110, 210, 310 first lens
120, 220, 320 second lens
130, 230, 330 third lens
140, 240, 340 4th lens
150, 250, 350 5th lens
160, 260, 360 6th lens
170, 270, 370 (infrared cut off) filters
180, 280, 380 image sensor or top view

Claims (16)

It includes a first lens, a second lens, a third lens, a fourth lens, a fifth lens, and a sixth lens sequentially arranged from the object side and having refractive power,
An imaging optical system that has an overall angle of view of 50 degrees or more and satisfies the following conditional expressions.
[Conditional Expression] TTL/f < 1.0
[Conditional Expression] 0.52 < f1/f < 0.57
[Conditional Expression] D34/D45 < 1.0
(In the above conditional expression, TTL is the distance from the object side of the first lens to the image plane, f is the overall focal length of the imaging optical system, f1 is the focal length of the first lens, and D34 is the image side of the third lens is the distance to the object side of the fourth lens, and D45 is the distance from the image side of the fourth lens to the object side of the fifth lens) According to claim 1,
An imaging optical system in which a plurality of inflection points are formed on the object side of the third lens. delete delete According to claim 1,
An imaging optical system satisfying the following conditional expression.
[Conditional Expression] 1.6 < Nd2
(In the above conditional expression, Nd2 is the refractive index of the second lens) According to claim 1,
An imaging optical system satisfying the following conditional expression.
[Conditional Expression] 1.6 < Nd3
(In the above conditional expression, Nd3 is the refractive index of the third lens) According to claim 1,
An imaging optical system satisfying the following conditional expression.
[Conditional Expression] 1.6 < Nd4
(In the above conditional expression, Nd4 is the refractive index of the fourth lens) It includes a first lens, a second lens, a third lens, a fourth lens, a fifth lens, and a sixth lens sequentially arranged from the object side,
The second lens has a negative refractive power,
The third lens has a negative refractive power and has a convex shape on the side of the object,
The fifth lens has refractive power,
The sixth lens has a convex shape on the side of the object,
An imaging optical system satisfying the following conditional expression.
[Conditional Expression] TTL/f < 1.0
(In the above conditional expression, TTL is the distance from the object side to the image plane of the first lens, and f is the total focal length of the imaging optical system) 9. The method of claim 8,
An imaging optical system satisfying the following conditional expression.
[Conditional Expression] 0.5 < DT4/D45 < 1.0
(In the above conditional expression, DT4 is the thickness of the fourth lens, and D45 is the distance from the image side of the fourth lens to the object side of the fifth lens) 9. The method of claim 8,
The second lens is an imaging optical system having a concave shape in the image side. 9. The method of claim 8,
The fourth lens is an imaging optical system having a convex shape on the side of the object. 9. The method of claim 8,
The fifth lens is an imaging optical system having a convex image side. delete 9. The method of claim 8,
and an iris disposed between the first lens and the second lens. 9. The method of claim 8,
An imaging optical system in which four inflection points are formed on the object side of the third lens. 9. The method of claim 8,
An inflection point is formed on an object side and an image side of the sixth lens.

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