WO2016105074A1

WO2016105074A1 - Lens optical system

Info

Publication number: WO2016105074A1
Application number: PCT/KR2015/014082
Authority: WO
Inventors: 조재훈; 김세진; 강선명; 이영민
Original assignee: (주)파트론
Priority date: 2014-12-22
Filing date: 2015-12-22
Publication date: 2016-06-30
Also published as: KR20160076341A; KR101661922B1

Abstract

A lens optical system is disclosed. The lens optical system of the present invention comprises a first lens, a second lens, a third lens, and a fourth lens sequentially arranged from an object side to a sensor side between an object and a sensor at which an image of the object is focused, wherein the first lens has a positive refracting power, an object side surface of the first lens is convex toward the object side, the second lens has a negative refracting power, an object side surface of the second lens is flat at least near an optical axis, the third lens has a positive refracting power and has a meniscus shape convex toward the sensor side, the fourth lens has a negative refracting power, and a sensor side surface of the fourth lens is concave toward the sensor side, has at least one point of inflection, and satisfies the following conditional expression. <Conditional Expression> 1.0<|f2/f|<3.0, wherein f2 represents a focal length of the second lens, and f represents a focal length of the lens optical system.

Description

Lens optics

The present invention relates to a lens optical system, and more particularly to a lens optical system that can be mounted in the camera module for imaging.

The imaging camera module includes a lens optical system including at least one lens and an image sensor that receives light passing through the lens optical system and converts the light into an electrical signal. As the image sensor, a solid-state imaging device such as a charge coupled device (CCD) or a complementary metal oxide semiconductor image sensor (CMOS image sensor) is widely used.

Recently, camera modules are widely used in electronic devices such as smartphones, tablet computers, and laptop-top computers. Such electronic devices tend to be gradually miniaturized and thinned to improve user convenience and aesthetics. In addition, the conventional camera device also tends to develop in the form of miniaturization and thinning. Accordingly, camera modules mounted in such electronic devices have also been miniaturized and require a small thickness.

In addition, a recent camera module requires a lens having a wide angle of view so that more information can be captured with one shot. However, it is difficult to design a lens having a wide field of view and combined with a high resolution image sensor and having excellent optical performance such as aberration and distortion.

Accordingly, there is a demand for the development of a high performance lens optical system that can be used in combination with a high resolution image sensor while being compact and having a wide angle of view.

The problem to be solved by the present invention is to provide a high-performance lens optical system that can be used in combination with a high resolution image sensor while being compact and wide field of view to solve the above problems.

The lens optical system of the present invention for solving the above problems is a first lens, a second lens, a third lens, and a fourth lens sequentially arranged from the object side to the sensor side between an object and a sensor in which the image of the object is formed. Wherein the first lens has positive refractive power, the object side surface of the first lens is convex toward the object side, the second lens has negative refractive power, and the object side surface of the second lens is at least near the optical axis Wherein the third lens has positive refractive power, has a meniscus shape convex toward the sensor side, the fourth lens has negative refractive power, and the sensor side of the fourth lens is concave toward the sensor side and has at least one inflection point. And the following conditional expression is satisfied.

1.0 <| f2 / f | <3.0

Here, f2 denotes a focal length of the second lens, and f denotes a focal length of the lens optical system.

In one embodiment of the present invention, the sensor side surface of the first lens may be convex toward the sensor side, and the sensor side surface of the second lens may be concave toward the sensor side.

In one embodiment of the present invention, the object side surface of the fourth lens may be convex toward the object side and have at least one inflection point near the optical axis.

In one embodiment of the present invention, the object-side surface of the second lens may be a plane within the effective diameter.

In one embodiment of the present invention, the object side surface of the second lens may be a plane.

In one embodiment of the present invention, all surfaces except the object side surface of the second lens may be aspherical.

In one embodiment of the present invention, the aperture may further include an aperture located between the object side surface of the first lens.

In one embodiment of the present invention, the following conditional expression may be further satisfied.

0.75 <SL / TTL <1.25

Here, SL represents the distance on the optical axis between the aperture and the sensor, TTL represents the distance on the optical axis between the object-side surface of the first lens and the sensor.

1.0 <tan (θ) / f <4.0

Is the angle of view of the lens optical system, and f is the focal length of the lens optical system.

50 <(V3 + V4) / 2 <60

Here, V3 represents the Abbe number of the third lens, and V4 represents the Abbe number of the fourth lens.

30deg <CRA <35deg

Where CRA

2.0 <TTL / BFL <4.0

Here, TTL represents a distance on the optical axis between the object side surface of the first lens and the sensor, and BFL represents a distance on the optical axis between the sensor side surface of the fourth lens and the sensor.

Lens optical system according to an embodiment of the present invention is a high-performance lens optical system that can be used in combination with a high resolution image sensor while being compact and wide angle of view.

Lens optical system according to an embodiment of the present invention has the advantage that the distance between the sensor side of the last lens and the sensor is relatively short, the overall length of the lens optical system is short, and as a result the camera module can be miniaturized.

One embodiment of the present invention has the advantage that the spherical aberration and the coma aberration are maintained at a predetermined level or less while the angle of view is wider than the focal length of the lens optical system.

1 is a lens configuration of a lens optical system of a first embodiment according to an embodiment of the present invention.

2 is a lens configuration of the lens optical system of the second embodiment according to an embodiment of the present invention.

3 is a lens configuration diagram of the lens optical system of the third embodiment according to the embodiment of the present invention.

4 is a lens configuration of the lens optical system of the fourth embodiment according to an embodiment of the present invention.

FIG. 5 sequentially shows spherical aberration, astigmatism, and distortion aberration of the lens optical system of the first embodiment shown in FIG.

FIG. 6 sequentially shows spherical aberration, astigmatism, and distortion aberration of the lens optical system of the second embodiment shown in FIG.

FIG. 7 sequentially shows spherical aberration, astigmatism, and distortion aberration of the lens optical system of the third embodiment shown in FIG.

FIG. 8 sequentially shows spherical aberration, astigmatism, and distortion aberration of the lens optical system of the fourth embodiment shown in FIG.

Hereinafter, with reference to the accompanying drawings will be described embodiments of the present invention; In describing the present invention, if it is determined that adding specific descriptions of techniques or configurations already known in the art may make the gist of the present invention unclear, some of them will be omitted from the detailed description. In addition, terms used in the present specification are terms used to properly express the embodiments of the present invention, which may vary according to related persons or customs in the art. Therefore, the definitions of the terms should be made based on the contents throughout the specification.

Hereinafter, a lens optical system according to an exemplary embodiment of the present invention will be described with reference to FIGS. 1 to 5.

1 to 4 are lens configuration diagrams of the lens optical system according to the first to fourth embodiments, respectively.

1 to 4, the lens optical system according to the embodiments of the present invention may include a first lens L1 and a second lens between an object corresponding to a subject of the lens optical system and a sensor IS in which an image of the object is formed. L2, the third lens L3, and the fourth lens L4 are positioned. The first to fourth lenses L1, L2, L3, and L4 are sequentially arranged from the object side to the sensor side.

Each lens has two sides facing each other. In one lens, the plane facing the object side corresponds to the plane of incidence, which is the plane where light enters the lens. In addition, in one lens, the surface facing the sensor side corresponds to an emission surface which is a surface from which light is emitted from the lens. In the present specification, the surface that is the object side and the incident surface of the n-th lens is represented by Sn1, and the surface that is the sensor side and the emission surface is represented by Sn2. Therefore, the object-side surface and the incident surface of the first lens L1 are represented by S11, and the sensor-side surface and the exit surface are represented by S12. In addition, the object side surface and the incident surface of the second lens (L2) is represented by S21, the sensor side surface and the exit surface is represented by S22. In addition, the object-side surface and the incident surface of the third lens L3 are represented by S31, and the sensor-side surface and the exit surface are represented by S32. In addition, the object-side surface and the incident surface of the fourth lens L4 are represented by S41, and the sensor-side surface and the exit surface are represented by S42.

The first lens L1 has a positive refractive power. In the first lens L1, S11 is convex on the object side, and S12 is convex on the sensor side. S11 and S12 may both be formed as an aspherical surface. The first lens L1 may be formed of a plastic material.

The second lens L2 has negative refractive power. In the second lens L2, S21 is a plane at least near the optical axis, and S22 is concave toward the sensor side. S21 may be planar not only near the optical axis but also within the effective diameter of the optical lens system. In addition, S21 may be formed in a plane as a whole. S22 may be formed as an aspherical surface. The second lens L2 may be formed of a plastic material.

The third lens L3 has a positive refractive power. The third lens L3 has a meniscus shape in which it is convex toward the sensor. Specifically, in the third lens L3, S31 is concave to the object side, and S32 is convex to the sensor side. S31 and S32 may both be formed as an aspherical surface. The third lens L3 may be formed of a plastic material.

The fourth lens L4 has negative refractive power. In the fourth lens L4, S41 is convex toward the object side near the optical axis, and S42 is convex toward the sensor side near the optical axis. S41 and S42 may both be formed as an aspherical surface. Specifically, S41 may include a portion that is convex toward the object side near the optical axis and becomes concave toward the peripheral portion of the lens near the optical axis. S41 may include at least one inflection point. In addition, S42 may include a portion that is concave toward the sensor near the optical axis and becomes convex toward the peripheral portion of the lens near the optical axis. S42 may include at least one inflection point.

1 to 4, the lens optical system may include an aperture S.

The aperture S may be located on the object side of the first lens L1 or may be positioned over the first lens L1. In more detail, the aperture S may be positioned over the object side surface of the first lens L1. The aperture S may block a part of the light to adjust the amount of light irradiated into the lens optical system.

The lens optical system may include an optical filter OF. The optical filter OF may be positioned between the fourth lens L4 and the sensor IS. The optical filter OF may block light in a band other than visible light. Specifically, the optical filter OF may block light in the infrared band.

The sensor IS may be an image sensor that receives light passing through the lens and converts the light into an electrical signal. The sensor IS is preferably positioned on the rear surface of the fourth lens L4 such that light passing through the first to fourth lenses L4 forms on the object side surface of the sensor.

The lens optical system of the embodiments of the present invention having the above configuration may satisfy the following conditional expression.

1.0 <| f2 / f | <3.0

Here, f2 denotes a focal length of the second lens L2 and f denotes a focal length of the lens optical system.

Conditional Expression 1 is a conditional expression for limiting the focal length of the second lens L2 with respect to the focal length of the entire lens optical system. When the focal length of the second lens L2 satisfies the above condition with respect to the focal length of the lens optical system, the angle of view of the lens optical system may be increased.

0.75 <SL / TTL <1.25

Here, SL represents a distance on the optical axis between the aperture S and the sensor IS, and TTL represents a distance on the optical axis between the object side surface of the first lens L1 and the sensor IS.

Conditional Expression 2 is a conditional expression for limiting the position of the aperture in the lens optical system. In the conditional expression 2, when the SL / TTL is smaller than the lower limit value 0.75, the aperture is positioned on the sensor side with respect to the first lens L1. When the SL / TTL is larger than the upper limit value 1.25 in Conditional Expression 2, the aperture is positioned on the object side with respect to the first lens L1. As shown in FIGS. 1 to 4, in order to position the diaphragm S over the object side surface of the first lens L1, the SL / TTL must satisfy the above range.

1.0 <tan (θ) / f <4.0

Conditional Expression 3 is a conditional expression that defines the angle of view in the lens optical system. When tan (θ) / f is less than the lower limit value (1.0) in Conditional Expression 3, the angle of view is too small to implement an optical lens optical system. On the other hand, when tan (θ) / f is greater than the upper limit (4.0) in Conditional Equation 3, the angle of view may be increased, so that a wide-angle lens optical system may be realized, but spherical aberration and coma aberration may be increased, thereby performing the performance of the lens optical system. Will fall.

50 <(V3 + V4) / 2 <60

Here, V3 represents the Abbe number of the third lens L3, and V4 represents the Abbe number of the fourth lens L4.

Conditional Expression 4 is a conditional expression for limiting the optical characteristics of the material forming the third lens (L3) and the fourth lens (L4). (V3 + V4) / 2 in Conditional Expression 4 means an average of Abbe's numbers of the third lens L3 and the fourth lens L4. As the third lens L3 and the fourth lens L4, a plastic resin material having an Abbe number of 50 or more may be used. For example, the third lens L3 and the fourth lens L4 may be made of Z-E48R having an Abbe number of 55.8559 or APEL-5514ML having an Abbe number of 56.0928.

When the third lens L3 and the fourth lens L4 are formed of a plastic material that satisfies the above conditions, the manufacturing cost can be lowered and the lens can be formed compared to the glass lens having similar characteristics. You can increase the range.

30deg <CRA <35deg

Here, CRA represents the maximum value among the angles at which the chief ray is incident on the sensor.

Conditional Expression 5 is a conditional expression for defining the sensor incident angle of the chief ray. By limiting the CRA, it is possible to design a lens with a large enough field of view and a small back focal length (BFL).

2.0 <TTL / BFL <4.0

Here, TTL is the distance on the optical axis between the object side surface of the first lens (L1) and the sensor IS, the BFL is on the optical axis between the sensor side surface of the fourth lens (L4) and the sensor (IS). Indicates distance.

Conditional Expression 6 is a conditional expression for limiting the overall length of the lens optical system to a predetermined level or less. In the case of lens optics having a relatively short overall length, the distance between the sensor side and the sensor side of the last lens tends to decrease. In the lens optical system shown in Figs. 1 to 4, it is preferable that the TTL / BFL is close to the upper limit (4.0) in the conditional expression 6. As the TTL / BFL increases in the lens optical system, the electric field may be shortened.

Hereinafter, a first embodiment of the present invention will be described with reference to FIGS. 1 and 5.

The following is a table of optical data of the lens optical system of the first embodiment shown in FIG. The following table shows the curvature radius (r), lens thickness and distance between lenses (d), refractive index (N _d ), focal length (f), Abbe's number (V _d ), and lens optics of each lens constituting the lens optical system. Data about focal length, Fno, TTL, and field of view.

In the table, * indicates that the lens surface is aspheric. And the distance unit of r, d and f is mm.

In addition, the aspherical surface of the lens surface of the lens optical system of the first embodiment shown in Fig. 1 satisfies the aspherical equation of the following equation.

Equation

Here, z represents the distance from the vertex of the lens in the optical axis direction, and y represents the distance in the direction perpendicular to the optical axis. R denotes the radius of curvature at the apex of the lens, and K denotes the conic constant. In addition, A <_2> -A <_12> represents an aspherical surface coefficient, respectively.

The following is a table of aspherical coefficients of the aspherical surface of the lens surface of the lens optical system of the first embodiment shown in FIG.

The following is a table summarizing the values of Conditional Expressions 1 to 6 in the lens optical system of the first embodiment shown in FIG.

As shown in the above table, it can be seen that the target values of the conditional expressions 1 to 6 of the lens optical system of the first embodiment correspond to the conditional expressions 1 to 6.

FIG. 5 sequentially shows spherical aberration, astigmatism, and distortion aberration of the lens optical system of the first embodiment shown in FIG. The wavelengths used to measure spherical aberration are 435.8 nm, 486.1 nm, 546.1 nm 587.6 nm and 656.3 nm. The wavelength measured to measure astigmatism and distortion is 546.1 nm.

Hereinafter, a second embodiment of the present invention will be described with reference to FIGS. 2 and 6.

The following is a table relating to optical data of the lens optical system of the second embodiment shown in FIG. The following table shows the curvature radius (r), lens thickness and distance between lenses (d), refractive index (N _d ), focal length (f), Abbe's number (V _d ), and lens optics of each lens constituting the lens optical system. Data about focal length, Fno, TTL, and field of view.

In addition, the aspherical surface of the lens surface of the lens optical system of the second embodiment shown in Fig. 2 satisfies the aspherical equation of the following equation.

Equation

The following is a table of aspherical surface coefficients of the aspherical surface among the lens surface of the lens optical system of the second embodiment shown in FIG.

The following is a table summarizing the values of Conditional Expressions 1 to 6 in the lens optical system of the second embodiment shown in FIG. 2.

As shown in the above table, it can be seen that the target values of the conditional expressions 1 to 6 of the lens optical system of the second embodiment correspond to the conditional expressions 1 to 6.

FIG. 6 sequentially shows spherical aberration, astigmatism, and distortion aberration of the lens optical system of the second embodiment shown in FIG. The wavelengths used to measure spherical aberration are 435.8 nm, 486.1 nm, 546.1 nm 587.6 nm and 656.3 nm. The wavelength measured to measure astigmatism and distortion is 546.1 nm.

Hereinafter, a third embodiment of the present invention will be described with reference to FIGS. 3 and 7.

The following is a table regarding optical data of the lens optical system of the third embodiment shown in FIG. The following table shows the curvature radius (r), lens thickness and distance between lenses (d), refractive index (N _d ), focal length (f), Abbe's number (V _d ), and lens optics of each lens constituting the lens optical system. Data about focal length, Fno, TTL, and field of view.

In addition, the aspherical surface of the lens surface of the lens optical system of the third embodiment shown in Fig. 3 satisfies the aspherical equation of the following equation.

Equation

The following is a table of aspherical coefficients of the aspherical surface of the lens surface of the lens optical system of the third embodiment shown in FIG.

The following is a table summarizing the values of Conditional Expressions 1 to 6 in the lens optical system of the third embodiment shown in FIG.

As shown in the above table, it can be seen that the target values of the conditional expressions 1 to 6 of the lens optical system of the third embodiment correspond to the conditional expressions 1 to 6.

FIG. 7 sequentially shows spherical aberration, astigmatism, and distortion aberration of the lens optical system of the third embodiment shown in FIG. The wavelengths used to measure spherical aberration are 435.8 nm, 486.1 nm, 546.1 nm 587.6 nm and 656.3 nm. The wavelength measured to measure astigmatism and distortion is 546.1 nm.

Hereinafter, a fourth embodiment of the present invention will be described with reference to FIGS. 4 and 8.

The following is a table regarding optical data of the lens optical system of the fourth embodiment shown in FIG. The following table shows the curvature radius (r), lens thickness and distance between lenses (d), refractive index (N _d ), focal length (f), Abbe's number (V _d ), and lens optics of each lens constituting the lens optical system. Data about focal length, Fno, TTL, and field of view.

In addition, the aspherical surface of the lens surface of the lens optical system of the fourth embodiment shown in Fig. 4 satisfies the aspherical equation of the following equation.

Equation

The following is a table of aspherical surface coefficients of the aspherical surface among the lens surface of the lens optical system of the fourth embodiment shown in FIG.

The following is a table summarizing the values of Conditional Expressions 1 to 6 in the lens optical system of the fourth embodiment shown in FIG. 4.

As shown in the table, it can be seen that the target values of the conditional expressions 1 to 6 of the lens optical system of the fourth embodiment correspond to the conditional expressions 1 to 6.

FIG. 8 sequentially illustrates spherical aberration, astigmatism, and distortion aberration of the lens optical system of the fourth embodiment shown in FIG. The wavelengths used to measure spherical aberration are 435.8 nm, 486.1 nm, 546.1 nm 587.6 nm and 656.3 nm. The wavelength measured to measure astigmatism and distortion is 546.1 nm.

In the above, embodiments of the lens optical system of the present invention have been described. The present invention is not limited to the above-described embodiment and the accompanying drawings, and various modifications and variations will be possible in view of those skilled in the art to which the present invention pertains. Therefore, the scope of the present invention should be defined not only by the claims of the present specification but also by the equivalents of the claims.

Claims

A first lens, a second lens, a third lens, and a fourth lens sequentially arranged from the object side to the sensor side between an object and a sensor on which the image of the object is formed,

The first lens has a positive refractive power, the object side surface of the first lens is convex toward the object side,

The second lens has negative refractive power, the object-side surface of the second lens is planar at least near the optical axis,

The third lens has a positive refractive power, has a meniscus shape convex toward the sensor side,

The fourth lens has a negative refractive power, the sensor side of the fourth lens is concave toward the sensor and has at least one inflection point,

Lens optical system that satisfies the following conditional formula.

<Conditional expression>

1.0 <| f2 / f | <3.0

Here, f2 denotes a focal length of the second lens, and f denotes a focal length of the lens optical system.
According to claim 1,

The sensor side of the first lens is convex toward the sensor side,

The lens side of the second lens is concave toward the sensor optical system.
According to claim 1,

And an object side surface of the fourth lens is convex toward the object side near the optical axis and has at least one inflection point.
According to claim 1,

The object side surface of the second lens is a lens optical system that is flat in the effective mirror.
According to claim 1,

The object side surface of the second lens is a lens optical system.
According to claim 1,

The lens optical system, wherein all surfaces except the object side surface of the second lens are aspherical.
According to claim 1,

The lens optical system of claim 1, further comprising an aperture positioned between the object side surfaces of the first lens.
The method of claim 7, wherein

Lens optical system that satisfies the following conditional expression further.

<Conditional expression>

0.75 <SL / TTL <1.25

Here, SL represents the distance on the optical axis between the aperture and the sensor, TTL represents the distance on the optical axis between the object-side surface of the first lens and the sensor.
According to claim 1,

Lens optical system that satisfies the following conditional expression further.

<Conditional expression>

1.0 <tan (θ) / f <4.0

Is the angle of view of the lens optical system, and f is the focal length of the lens optical system.
According to claim 1,

Lens optical system that satisfies the following conditional expression further.

<Conditional expression>

50 <(V3 + V4) / 2 <60

Here, V3 represents the Abbe number of the third lens, and V4 represents the Abbe number of the fourth lens.
According to claim 1,

Lens optical system that satisfies the following conditional expression further.

<Conditional expression>

30deg <CRA <35deg

Here, CRA represents the maximum value among the angles at which the chief ray is incident on the sensor.
According to claim 1,

Lens optical system that satisfies the following conditional expression further.

<Conditional expression>

2.0 <TTL / BFL <4.0

Here, TTL represents a distance on the optical axis between the object side surface of the first lens and the sensor, and BFL represents a distance on the optical axis between the sensor side surface of the fourth lens and the sensor.