KR101804842B1 - Image pickup lens system having spherical lens - Google Patents

Abstract

< 1.9 [조건식 1]

= 0 [조건식 2]
여기서,

는 렌즈의 곡률반경 중심의 정점에서부터 광축방향의 거리를 나타내고, Y는 광축으로부터 렌즈 면까지의 거리(높이)이고, K는 코닉(Conic) 상수(이심률)이고, C는 근축 곡률(=1/R)이고, R은 근축 곡률 반경이고, Ai는 비구면 계수(Aspheric constant)이고, i는 비구면 계수의 차수이다.
이러한 구성에 따르면, 제조 민감도를 낮춤과 동시에 구면수차, 비점수차, 왜곡의 보정 상태를 양호하게 유지함으로써 우수한 품질이 화상과 함께 생산성을 향상시킬 수 있는 구면 렌즈를 갖는 촬상 렌즈 시스템을 제공할 수 있다. The present invention relates to an imaging lens system having a spherical lens that can be applied to a camera for a mobile phone or the like. The imaging lens system having the spherical lens includes a first plastic lens in meniscus form having a positive refractive power and concave toward the image side in order from the object side; A second plastic lens having a meniscus shape concave upward with negative refractive power; A third plastic lens having positive refractive power and a meniscus shape convex upward; A fourth plastic lens having negative refractive power, the center of the upper side being concave upward and being convexly formed toward the periphery; Wherein the first plastic lens, the third plastic lens and the fourth plastic lens each have at least one aspheric surface, the object side surface of the second plastic lens is an aspherical surface, 2. An imaging lens system having a spherical lens satisfying condition (2).
1.85 <

<1.9 [Conditional expression 1]

= 0 [Conditional expression 2]
here,

Y is the distance (height) from the optical axis to the lens surface, K is the Conic constant (eccentricity), C is the paraxial curvature (= 1 / R), R is a paraxial radius of curvature, Ai is an aspheric constant and i is a degree of an aspheric coefficient.
According to such a configuration, it is possible to provide an imaging lens system having a spherical lens that can improve productivity with excellent image quality by maintaining good correction of spherical aberration, astigmatism, and distortion while reducing manufacturing sensitivity .

Description

[0001] The present invention relates to an imaging lens system having a spherical lens,

The present invention relates to an imaging lens system having a spherical lens that can be applied to a camera for a mobile phone or the like.

Due to the development of the communication environment and the multifunctionalization of communication devices, the camera functions of portable devices have been treated as basic specifications, and mobile phones and tablet PCs equipped with small-sized imaging devices are rapidly spreading.

Particularly, in a mobile phone imaging optical system, miniaturization of a pixel becomes possible due to the development of a semiconductor technology, so that miniaturization of an imaging module such as a CCD (Charge Coupled Device) or a CMOS (Complementary Metal Oxide Semiconductor) And the miniaturization of the imaging lens has been promoted.

As the technology upgrades for miniaturization and high-definition are progressing rapidly, there is a growing demand for a small-sized imaging lens system having high performance, and the sensitivity of an optical lens for satisfying high performance is increasing.

In the case of a lens mounted on a conventional camera module, it is difficult to realize a design with a low manufacturing sensitivity while increasing the angle of view while limiting the number of constituent elements and the total length.

In recent years, as the CCD and CMOS image sensor have been miniaturized, the imaging lens system has required high pixel performance with a small size and high pixel count. In addition, while the overall length is limited, a wide angle of view is required, thus increasing manufacturing sensitivity.

Korean Patent Application No. 10-2012-0158535

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide an imaging lens system having a spherical lens that can reduce manufacturing sensitivity while achieving miniaturization and high performance of a lens.

According to an aspect of the present invention, there is provided an imaging lens system having a spherical lens, comprising: a first plastic lens having meniscus shape concave upward with positive refractive power, in order from an object side; A second plastic lens having a meniscus shape concave upward with negative refractive power; A third plastic lens having positive refractive power and a meniscus shape convex upward; A fourth plastic lens having negative refractive power, the center of the upper side being concave upward and being convexly formed toward the periphery; Wherein the first plastic lens, the third plastic lens and the fourth plastic lens each have at least one aspheric surface, the object side surface of the second plastic lens is an aspherical surface, 2. An imaging lens system having a spherical lens satisfying condition (2).

< 1.9 [조건식 1] 1.85 <

<1.9 [Conditional expression 1]

= 0 [조건식 2]

= 0 [Conditional expression 2]

는 렌즈의 곡률반경 중심의 정점에서부터 광축방향의 거리를 나타내고, Y는 광축으로부터 렌즈 면까지의 거리(높이)이고, K는 코닉(Conic) 상수(이심률)이고, C는 근축 곡률(=1/R)이고, R은 근축 곡률 반경이고, Ai는 비구면 계수(Aspheric constant)이고, i는 비구면 계수의 차수이다. here,

Y is the distance (height) from the optical axis to the lens surface, K is the Conic constant (eccentricity), C is the paraxial curvature (= 1 / R), R is a paraxial radius of curvature, Ai is an aspheric constant and i is a degree of an aspheric coefficient.

Further, an imaging lens system having a spherical lens satisfying Conditional Expressions 3 to 5 below.

V ₂ <25 [Conditional expression 3]

< 1.78 [조건식 4] 1.75 <

&Lt; 1.78 [Conditional expression 4]

0.85 < R ₄ / F < 0.9 [Conditional expression 5]

Here, V ₂ is the Abbe number of the second plastic lens, F ₂ is the focal length of the second plastic lens, R ₄ is the central curvature radius of the upper surface of the second plastic lens, F is the effective focal length to be.

The Abbe number of the first plastic lens, the third plastic lens and the fourth plastic lens is 50 or more, and the spherical lens having the highest refractive index of the second plastic lens among the first to fourth plastic lenses Imaging lens system.

Further, an imaging lens system having a spherical lens satisfying Conditional Expression 6 and Conditional Expression 7 below.

1.1 < TTL / F < 1.15 [Conditional expression 6]

0.77 < TTL / 2ImgH < 0.8 [Conditional expression 7]

Here, TTL is the distance from the object-side incident surface to the image surface of the first plastic lens, F is the effective focal length of the entire lens system, and ImgH is the image height.

According to the present invention, it is possible to provide an imaging lens system having a spherical lens capable of improving productivity with excellent image quality by maintaining good correction of spherical aberration, astigmatism, and distortion while reducing manufacturing sensitivity .

1 is a diagram showing the configuration of an imaging lens system according to an embodiment of the present invention.
Fig. 2 is a view for tracking the flow of light when an object is photographed in the imaging lens system of Fig. 1. Fig.
3 is an aberration diagram according to an embodiment of the imaging lens system of Fig.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the drawings, like reference numerals refer to like elements throughout. The same reference numerals in the drawings denote like elements throughout the drawings.

1 is a diagram showing the configuration of an imaging lens system according to an embodiment of the present invention. Fig. 2 is a view for tracking the flow of light when an object is photographed in the imaging lens system of Fig. 1. Fig.

The imaging lens system 100 of the present invention can be utilized by being mounted on a camera for a mobile phone or a digital camera using a CCD or a CMOS image sensor.

The imaging lens system 100 includes, in order from the object side, a first plastic lens L1, a second plastic lens L2, a third plastic lens L3, a fourth plastic lens L4, (150).

The first plastic lens L1 is formed of plastic and can be formed into a meniscus type having a concave surface with the object side surface 111 and the image side surface 112 both having a positive refractive power. At least one of the object side surface 111 and the upper side surface 112 of the first plastic lens L1 is formed as an aspherical surface, and preferably both surfaces are formed as an aspherical surface.

The second plastic lens L2 is formed of plastic and can be formed into a meniscus type in which the object side surface 121 and the upper side surface 122 are both concave upward with a negative refracting power. In the second plastic lens L2, it is preferable that the object side surface 121 is formed as an aspherical surface and the upper surface 122 is configured as a spherical surface.

The third plastic lens L3 is formed of plastic and can be formed into a meniscus type convex upward with the object side surface 131 and the upper side surface 132 both having a positive refractive power. At least one of the object side surface 131 and the upper side surface 132 of the third plastic lens L3 is formed as an aspherical surface, and preferably both surfaces are formed as an aspherical surface.

The fourth plastic lens L4 is formed of plastic, and can be formed into a meniscus type having a negative refractive power and concave toward the image side. The fourth plastic lens L4 may be formed such that the center of the upper surface 142 is concave upward and convex toward the periphery. In addition, the fourth plastic lens L4 may be formed such that the center of the object side surface 141 is convex toward the object side and concave toward the periphery. This shape of the object side surface 141 and the upper side surface 142 of the fourth plastic lens L4 is for uniformly spreading light on the upper surface.

At least one of the object side surface 141 and the upper side surface 142 of the fourth plastic lens L4 is formed as an aspherical surface, and preferably both surfaces are formed as an aspherical surface. An optical filter 150 may be positioned between the fourth plastic lens L4 and the upper surface 160. [

In the present invention, the first plastic lens L1, the second plastic lens L2, the third plastic lens L3, and the fourth plastic lens L4 are all made of plastic, so that aberration is reduced, Weight reduction can be realized. Further, each lens includes at least one aspherical surface, and cost reduction and aberration generation can be suppressed.

In the imaging lens system 100 of the present invention, the upper surface 122 of the second plastic lens L2 may satisfy the following conditional expression (2).

[조건식 2]

[Conditional expression 2]

delete

Here, A _i is the aspheric constant, Y is the distance (height) from the optical axis to the lens surface, and i is the order of the aspherical coefficient. In conditional expression 2, A _i , that is, aspherical surface coefficients are all 0, and consequently, the upper surface 122 of the second plastic lens L2 becomes a spherical surface rather than an aspherical surface.
By making the upper surface 122 of the second plastic lens L2 be a spherical surface, it is possible to reduce the number of mistakes in the processing step as much as possible and to improve the productivity. In addition, it is possible to obtain an effect of reducing the change due to decentration and tilt generated at the time of assembling the lens. Thereby, the imaging lens system 100 with low manufacturing sensitivity can be obtained.

delete

delete

The imaging lens system 100 of the present invention can satisfy the following conditional expressions 3 and 4.

V ₂ <25 [Conditional expression 3]

< 1.78 [조건식 4] 1.75 <

&Lt; 1.78 [Conditional expression 4]

Here, V ₂ is the second and the Abbe number of the plastic lens (L2), F ₂ is a focal length of the second plastic lens (L2), F is the effective focal length of the entire lens system.

The Abbe number of the second plastic lens L2 is less than 25 and the Abbe number of the remaining first plastic lens L1, third plastic lens L3 and fourth plastic lens L4 is 50 or more.

Among the first to fourth plastic lenses, the refractive index of the second plastic lens L2 is preferably the highest.

If the second plastic lens L2 satisfies the conditional expression 3 and the conditional expression 4, the influence on the entire refractive power is reduced, and the imaging lens system 100 having high sensitivity can be formed. In addition, by reducing the influence on the entire refractive power, it is possible to obtain a fine correction effect on the curvature of field and the astigmatism. If the imaging lens system is designed to be smaller or larger than the upper limit value of the conditional expression (4), it is difficult to finely correct the curvature of field and the astigmatism by the second plastic lens (L2).

F2 F Conditional expression 4 Example -5.6659 3.2043 1.7682

The imaging lens system 100 of the present invention can satisfy the following conditional expression (5).

0.85 < R ₄ / F < 0.9 [Conditional expression 5]

Here, R ₄ is the radius of curvature of the center of the upper surface 122 of the second plastic lens L2, and F is the effective focal length of the entire lens system.

The conditional expression (5) can reduce the refractive power of the second plastic lens L2 while correcting aberrations such as spherical aberration and chromatic aberration. If the imaging lens is designed to be smaller or larger than the upper limit value of the conditional expression (5), it is difficult to finely correct the spherical aberration and the chromatic aberration caused by the second plastic lens (L2).

R ₄ F Conditional expression 5 Example 2.816 3.2043 0.8788

The imaging lens system 100 of the present invention can satisfy the following conditional expression (6).

1.1 < TTL / F < 1.15 [Conditional expression 6]

Here, TTL is the distance from the object-side incident surface to the image surface of the first plastic lens L1, and F is the effective focal length of the entire lens system. By satisfying the conditional expression (6), optical performance can be more easily ensured and a high resolution can be satisfied.

When the imaging lens system is designed to have a value smaller or larger than the upper limit of the conditional expression (6), distortion aberration occurs, and the amount of light decreases as it goes to the periphery, making it difficult to obtain a clear image.

TTL F Conditional expression 6 Example 3.6 3.2043 1.12

The imaging lens system 100 of the present invention can satisfy the following condition (7).

0.77 < TTL / 2ImgH < 0.8 [Conditional expression 7]

Here, TTL is the distance from the object-side incident surface to the image surface of the first plastic lens L1, and ImgH is the image height (Image Height). By satisfying the conditional expression (7), the imaging lens system can be formed in a slim form.

TTL ImgH Conditional expression 7 Example 3.6 2.3 0.7826

Example

Next, a specific embodiment of the imaging lens system 100 according to the present invention will be described.

Table 6 below is numerical data of the lenses constituting the imaging lens system 100. The unit of distance or length applied in Table 6 is "mm".

Face number Radius of curvature Thickness or distance (t) Refractive index (Nd) Abbe number (Vd) Lens Shape Remarks One
(First plastic lens) 1.1275 0.4980 1.53 55.86 Asphere Aperture and first plastic
lens 2
(First plastic lens) 7.9349 0.0815 Asphere 3
(Second plastic lens) 12.5768 0.2500 1.64 22.44 Asphere Second plastic
lens 4
(Second plastic lens) 2.816 0.4339 Sphere 5
(Third plastic lens) -1.7084 0.4580 1.53 55.86 Asphere Third plastic
lens 6
(Third plastic lens) -1.1697 0.4005 Asphere 7
(Fourth plastic lens) 1.7102 0.3800 1.53 55.86 Asphere Fourth plastic
lens 8
(Fourth plastic lens) 0.8986 0.1482 Asphere 9 0.0500 Flat 10 0.2100 Flat Optical filter 11 0.6899 Flat 12 0.0000 Flat Top surface

Table 7 below shows the conic constant and aspherical coefficient for the lenses of the imaging lens system 100 according to an embodiment of the present invention.

Face number K A ₄ A ₆ A ₈ A ₁₀ One
(First plastic lens) 1.113133 -0.957824E-01 -0.882643E-01 -0.732361E-01 -0.252072E + 01 2
(First plastic lens) 93.074988 -0.201170E + 00 -0.391822E + 00 0.988310E + 00 -0.838898E + 01 3
(Second plastic lens) 0.000000 -0.237420E + 00 -0.415373E + 00 0.131383E + 01 -0.726628E + 01 4
(Second plastic lens) 0 0 0 0 0 5
(Third plastic lens) 4.677740 -0.957954E-02 0.249735E + 00 -0.235834E + 00 0.119203E + 01 6
(Third plastic lens) -2.305506 -0.354159E + 00 0.861092E + 00 -0.188012E + 01 0.283976E + 01 7
(Fourth plastic lens) -30.337813 -0.434141E + 00 0.341634E + 00 -0.123904E + 00 0.223638E-01 8
(Fourth plastic lens)  -7.175880 -0.233974E + 00 0.150541E + 00 -0.765112E-01 0.243382E-01

As shown in Table 6, the first plastic lens L1, the second plastic lens L2, the third plastic lens L3, and the fourth plastic lens L3 of the imaging lens system 100 according to the embodiment of the present invention, All surfaces except the upper surface 122 of the second plastic lens L2 are aspherical surfaces.

As shown in Table 6 and Table 7, the surface No. 1 is an aperture stop used for adjusting the amount of light and is the object side surface 111 of the first plastic lens L1.

In the present invention, the aspherical shape of each lens can be obtained from the following equation (1).

Z: Distance from the lens apex to the optical axis direction

Y: Distance from the optical axis to the lens surface (height)

K: Conic constant (eccentricity)

C: paraxial curvature (= 1 / R)

R: Paraxial radius of curvature

Ai: Aspheric constant

(i means the degree of aspherical coefficient)

The following Table 8 shows performance values of the lens according to the preferred embodiment of the present invention.

F ₁ 2.402 F-number 2.7 F ₂ -5.666 FOV 70.8 F ₃ 5.366 OAL 3.6 F ₄ -4.240 TTL 3.7 F 3.204 BFL 1.1

In Table 8, F ₁ is a focal point of the first plastic lens (L1), F ₂ is a focal point of the second plastic lens (L2), F ₃ is the focal of the third plastic lens (L3), F ₄ is a fourth plastic lens FTL is the distance from the object to the image plane, TTL is the total distance of the lens system, BFL is the distance from the object to the final lens, Represents the distance from the surface to the top surface.

The F-number of the embodiment is 2.7, which makes it possible to increase the amount of received light and secure high resolution by chromatic aberration correction. The F-number of the imaging lens system is a value obtained by dividing the equivalent focal length of the imaging lens system by the entrance pupil diameter of the imaging lens system.

FIG. 3 is an aberration diagram according to the embodiment of the imaging lens system 100 of FIG. 1, showing spherical aberration according to each wavelength, aberration of a tangential plane and a sagittal plane, The astigmatism representing the characteristic, and the distortion aberration along the height of the image surface. As shown in the figure, spherical aberration, astigmatism, and distortion aberration are all within the permissible range and exhibit good characteristics.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit and scope of the invention will be.

100: imaging lens system
111, 121, 131, 141: object side surface
112, 122, 132, 142: upper side
150: Optical filter
160: upper surface
L1: first plastic lens
L2: Second plastic lens
L3: Third plastic lens
L4: fourth plastic lens

Claims (4)

delete In order from the object side,
A first plastic lens having a positive refractive power and a meniscus shape concave upward;
A second plastic lens having a meniscus shape concave upward with negative refractive power;
A third plastic lens having positive refractive power and a meniscus shape convex upward;
A fourth plastic lens having negative refractive power, the center of the upper side being concave upward and being convexly formed toward the periphery;
Lt; / RTI &gt;
Wherein the first plastic lens, the third plastic lens and the fourth plastic lens each have at least one aspheric surface,
The object side surface of the second plastic lens is an aspherical surface, the upper surface satisfies the following conditional expression 2,

[Conditional expression 2]
Here, Ai is the aspheric constant, Y is the distance (height) from the optical axis to the lens surface, i is the order of the aspherical surface coefficient,
Satisfies the following conditional expressions (3) to (5).
V ₂ <25 [Conditional expression 3]
1.75 <

&Lt; 1.78 [Conditional expression 4]
0.85 < R ₄ / F &lt; 0.9 [Conditional expression 5]
Here, V ₂ is the Abbe number of the second plastic lens, F ₂ is the focal length of the second plastic lens, R ₄ is the central curvature radius of the upper surface of the second plastic lens, F is the effective focal length to be. 3. The method of claim 2,
The Abbe number of the first plastic lens, the third plastic lens, and the fourth plastic lens is 50 or more,
And the spherical lens having the highest refractive index of the second plastic lens among the first to fourth plastic lenses. 3. The method of claim 2,
And a spherical lens satisfying Conditional Expression 6 and Conditional Expression 7 below.
1.1 < TTL / F < 1.15 [Conditional expression 6]
0.77 < TTL / 2ImgH < 0.8 [Conditional expression 7]
Here, TTL is the distance from the object-side incident surface to the image surface of the first plastic lens, F is the effective focal length of the entire lens system, and ImgH is the image height.

Images