KR100927606B1 - Miniature High Resolution Imaging Lens Assembly - Google Patents

Abstract

The present invention relates to an ultra-small high resolution imaging lens assembly, comprising: a first lens, a second lens, a third lens, a fourth lens, and a fifth lens disposed between a subject and an image surface; The first lens has positive refractive power, the second lens has negative refractive power, the front surface of the first lens and the rear surface of the second lens are spherical surfaces, and the first lens and the second lens are optical The lens assembly is bonded to each other as a glass material, the bonding surface is substantially planar, the third lens, the fourth lens and the fifth lens are all made of plastic and each lens is at least one surface aspheric. to provide.

According to the present invention, the periphery performance can be maintained well even at high resolution.

Imaging lens, chromatic aberration, refractive power, high resolution, ultra small

Description

Ultra High Resolution Lens Assembly

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a photographing lens applied to a compact camera using a Charged Coupled Device (CCD) and a Complementary Metal Oxide Semiconductor (CMOS). The present invention relates to an ultra-high resolution imaging lens assembly.

In recent years, an expanded new concept of mobile phones, namely camera phones or camera mobile phones, which combine digital camera technology and mobile phone technology, has been in the spotlight. In addition, the development of so-called camcorder mobile phones (camcorder mobile phones or camcorder phones) that can store and transmit tens of minutes or more of moving image multimedia by integrating digital camcorder technology with mobile phone technology has been attempted.

In addition to mobile phones, the demand for digital cameras and PC cameras is increasing rapidly. Most of these cameras are small cameras using solid-state imaging devices and complementary metal semiconductors, which are very small imaging lenses and lens assemblies suitable for such small imaging devices. Research and development of the has continued.

As an example, Korean Patent No. 10-0428242 discloses a first lens G1, a second lens G2, sequentially from the rear of the aperture on the object side to the front of the image 10, as shown in FIG. The third lens G3 and the fourth lens G4 are disposed, wherein the first lens G1 has positive (plus) refractive power, and the second lens G2 has negative (minus) refractive power. At least one surface of the third lens G3 is aspherical and has positive refractive power, and the fourth lens G4 has at least one surface of an aspherical surface and positive refractive power. At least one of the third lens G3 and the fourth lens G4 discloses a lens assembly composed of a plastic lens.

The lens assembly configured as described above has the effect of obtaining a small size, light weight and high resolution, thereby increasing the manufacturing efficiency of the photographing lens and lowering the unit cost of the photographing lens, so that a camera applied with digital technology can be manufactured with high quality and small size and light weight. In addition, it contributes to lowering the price of the camera, and also has a positive refractive power of the fourth lens (G4) (G4) disposed closest to the image surface to reduce the angle of the chief ray projected onto the image surface to reduce the angle of the image surface. It is said to have an effect of reducing the difference in color sensitivity between the center and the periphery.

As another example, Korean Patent No. 10-00000 is composed of four lenses, as shown in Figure 2, by combining the first lens (G1 ') and the second lens (G2') by processing the lens A shorter light path of the assembly discloses a more compact lens assembly.

By the way, the lens assembly based on these four lenses has a well-corrected chromatic aberration (vertical chromatic aberration), but the performance is somewhat insufficient, for example, when the pixel size of the sensor becomes smaller than 1.75 mu m.

Here, the longitudinal chromatic aberration means the difference in focus position for each wavelength. For example, in the case of a lens assembly composed of two glass lenses and two plastic lenses (abbreviated as 2P2G), the longitudinal chromatic aberration for wavelength 650 nm and wavelength 470 nm is used. Reaches 30 µm.

3 is an astigmatism diagram of the lens assembly according to the related art, as shown in FIG. 3, it can be seen that the aberration of the lens increases, resulting in a sharp decrease in the optical performance of the periphery.

SUMMARY OF THE INVENTION In order to solve the above problem, an object of the present invention is to provide a lens assembly capable of exhibiting good overall performance of a lens including a lens periphery even when the lens resolution is increased and the pixel size is reduced.

The lens assembly according to the present invention arranges the first lens L1, the second lens L2, the third lens L3, the fourth lens L4, and the fifth lens L5 in order from the object side to the image surface. The first lens L1 has a positive refractive power, the second lens L2 has a negative refractive power, and at least one surface of the third lens L3 is aspheric. It has positive (plus) refractive power, the fourth lens has an overall negative refractive power as an aspherical surface, and the fifth lens (L5) has at least one aspherical surface and positive (plus) refractive power. At least one of the third lens L3 to the fifth lens G5 discloses a lens assembly composed of a plastic lens.

In order to increase the resolution, the first lens L1 is positive and the second lens L2 is negative. In addition, both the third lens L3 and the fifth lens L5 have positive refractive power, and the fourth lens has a weak refractive power at the center portion and a negative refractive power at the peripheral portion thereof, and has a refractive index higher than that of the third and fifth lenses. The higher and the lower the Abbe number, the better the resolution.

In particular, the fourth lens is configured such that its center has very weak refractive power and negative refractive power toward the periphery. By having such a shape, astigmatism can be corrected to improve performance of the lens periphery.

The infrared filter 20 may further include an infrared filter between the fifth lens L5 and the image surface 10.

According to the present invention, it is possible to provide a micro lens assembly that reduces the length of the lens and increases peripheral performance even at high resolution (eg, pixel size of 1.75 μm or less).

Hereinafter, with reference to the accompanying drawings will be described in detail the configuration of the present invention.

In order to easily understand the configuration of the lens assembly according to the present invention, a configuration of a lens assembly assembled with four lenses will be described with reference to FIG. 2.

As shown in FIG. 2, in order to reduce the optical path of the lens assembly, the first lens G1 ′ and the second lens G2 ′ may be bonded to each other.

In the embodiment of FIG. 2, the configuration of the first and second lenses is shown in FIG. 3, and specific values are as follows.

First lens

Front curvature radius: 1.9mm, rear radius: infinity, center thickness: 0.5mm, outer diameter: Φ2.5mm

Second lens

Front curvature radius: infinity, rear radius: 3.9mm, center thickness: 0.1mm, outer diameter: Φ2.5mm

Table 1 shows lens data of the embodiment shown in FIG. 2.

Surface RDY (Curvature Radius) THI (thickness) Nd (refractive index) Vd (Abe number) OBJ INFINITY INFINITY One 1.90000 0.500000 1.883 40.8 2 INFINITY 0.100000 1.923 20.9 3 3.90000 0.100000 STO INFINITY 0.944813 5 (*) -1.73110 0.419073 1.531 55.8 6 (*) -1.96679 0.255822 7 (*) 1.25920 0.568848 1.531 55.8 8(*) 1.12184 0.650000 9 INFINITY 0.300000 1.517 64.2 10 INFINITY 0.261445 IMG INFINITY

(OBJ: object plane; STO: aperture; IMG: image; Infinity: plane)

Aspheric coefficients are shown in Table 2 below.

S5 K -2.104119 A B C D E F -.270644E-02 -.154638E + 00 -.518016E + 00 0.796820E + 00 0.152296E + 00 -.270954E + 00 S6 K -6.217451 A B C D E F -.375272E + 00 0.497518E + 00 -.592576E + 00 0.164247E + 00 0.339056E + 00 -.163195E + 00 S7 K -7.000000 A B C D E F -.224558E + 00 0.547025E-01 0.474057E-02 -.411883E-02 0.165911E-02 -.309039E-03 S8 K -4.232665 A B C D E F -.169631E + 00 0.567504E-01 -.165578E-01 0.219399E-02 -.107957E-03 -.185273E-05

The aspherical equation of the lens assembly according to the present embodiment is represented by Equation 1 below.

X is the sag from the lens vertex to the optical axis direction, Y is the height from the optical axis, R is the radius of curvature at the vertex of the lens, K is the Conic constant, A, B, C, D, E And F represent the fourth, sixth, eighth, tenth, twelfth, and fourteenth aspherical coefficients, respectively.

In the lens assembly illustrated in FIG. 2, the power distribution is very weak because the first and second glass-bonded lenses play most of the refractive power, and the third and fourth lenses play aberration correction. In the embodiment, the total refractive power is 0.28, the refractive power of the glass bonded lens is 0.26, the third lens refractive power is -0.01, and the fourth lens refractive power is 0.02.

That is, the refractive power of the first and second glass bonded lenses is 91% of the total refractive power.

On the other hand, the position of the stop (STOP) in the conventional lens with respect to the aperture is generally advantageously located in the center of the lens. However, when the aperture is located in the center, it is disadvantageous to the chief ray angle (CRA), and the length of the lens is long to overcome this problem, but it is advantageous to block unnecessary light and is insensitive to manufacturing tolerances. have. Therefore, the position of the stop can be positioned between the second lens and the third lens to reduce the sensitivity to the manufacturing tolerance, while reducing the length of the CRA to about 25 degrees or less.

4 is a view showing a lens assembly according to a preferred embodiment of the present invention.

As shown, the lens assembly of the present invention is provided between the third lens (L3) and the fifth lens (L5) corresponding to the conventional third lens (G3 or G3 ') and the fourth lens (G4 or G4'). In addition, aspherical plastic lenses (L4) having a high refractive index and a large dispersion value were added to improve performance and shorten the lens length.

The lens assembly according to the present invention includes the first lens L1, the second lens L2, the third lens L3, the fourth lens L4, and the fifth lens in order from the rear of the aperture on the object side to the front of the image surface. L5), wherein the first lens L1 has a positive (plus) refractive power, the second lens L2 has a negative (minus) refractive power, and the third lens L3 has at least one The surface has a positive (plus) refractive power as an aspherical surface, the fourth lens has a negative refractive power as a whole as an aspherical surface, the at least one surface of the fifth lens (L5) is aspherical, the positive (plus) refractive power Have At least one of the third lens L3 to the fifth lens G5 may be formed of a plastic lens.

In order to correct chromatic aberration, the first lens L1 is positive and the second lens L2 is negative. In addition, both the third lens L3 and the fifth lens L5 have positive refractive power, thereby minimizing the angle of the chief ray, thereby correcting distortion aberration and improving color sensitivity of the center and the periphery of the image.

In the present invention, chromatic aberration can be well corrected by varying the material of the glass lens. In the present invention, a material having a high refractive index is selected for the first lens and the second lens to reduce the optical path length of the lens assembly, and a material having a different abbe number is selected for the chromatic aberration correction.

In particular, the fourth lens L4, which is a main technical point of the present invention, is an aspherical plastic lens having a high refractive index and a large dispersion value, and is effective in reducing performance and optical path length.

The central portion of the fourth lens is substantially planar and configured to have negative refractive power toward the periphery. By having such a shape, astigmatism can be corrected to improve performance of the lens periphery.

Equations 2 and 3 below are ASP equations for the fourth lens L4 and SPS odd-asphere surface (ODS) equations for the fifth lens L5 according to the present invention, respectively.

Where z is the rate of decrease in the plane parallel to the z axis (parallel plane),

       c is the curvature of the planar pole (CUP)

       k is the cone coefficient (K). therefore,

               k = 0: sphere

               -1 <k <0:-Ellipsoid of the long axis on the optical axis

               k = -1: parabola

               k <-1: hyperbolic surface

, (e 는 이심률임) K =

, (e is the eccentricity)

       When k> 0, it is a spherical surface, the surface of which is created by an elliptic rotation about its mirror axis.

: 이때 e 는 산출된 타원의 이심률.k =

Where e is the calculated eccentricity of the ellipse.

에 대하여, A=B=C=D=E=F=G=H=J=0 이다.A, B, C, D, E, F, G, H, J are 4th, 6th, 8th, 10th, 12th, 14th, 16th, 18th, 20th, 20th order deformation coefficients

For A = B = C = D = E = F = G = H = J = 0.

Where z is the rate of decrease to the parallel plane (parallel plane) in the z-axis

      c is the curvature of the planar vertex (CUY)

, 이때 e= 이심률)k is the cone constant (k =

, Where e = eccentricity)

           k> 1 spherical surface (not conic)

           k = 0 sphere

          -1 <k <0 Ellipsoid of the major axis on the optical axis

           k = -1 parabola

           k <-1 hyperbolic

:

의 상수 (최대값 30)

:

Constant (max 30)

Lens data of the lens assembly according to the preferred embodiment of the present invention is as follows.

<Lens data>

RDY THI Nd Vd

  OBJ: INFINITY INFINITY

    1: 2.28630 0.700000 1.729160 54.6735

    2: INFINITY 0.100000 1.922860 20.8804: joint surface

    3: 7.88226 0.070000

  STO: INFINITY 1.057871

    5: -2.48384 0.506904 1.53113 55.8

      SPS ODD:

             K: 1.3675E + 00 AR3: -5.4046E-02 AR4: -2.7173E-02

           AR5: 1.6143E-03 AR6: 1.0148E-02 AR7: 5.0961E-02

           AR8: -4.7091E-02 AR9: -2.7070E-02 AR10: 8.9637E-02

          AR11: -1.1025E-02 AR12: 3.5085E-03 AR13: 1.0577E-02

          AR14: -2.6297E-02

    7: -6.82869 0.1

      SPS ODD:

K: -7.3615E + 01 AR3: -9.0434E-02 AR4: -2.8235E-01

          AR5: 3.2103E-02 AR6: 2.4563E-01 AR7: 2.8705E-03

          AR8: -1.6574E-01 AR9: 4.1175E-03 AR10: 3.5423E-02

          AR11: -2.1225E-03 AR12: 4.1774E-02 AR13: -1.5858E-03

          AR14: -1.6183E-02

    8: 8.15950 0.469953 1.632 23.6

      ASP:

       K: -61.315227

       IC: YES CUF: 0.000000

       A:-. 167525E-01 B:-. 298327E-01 C: 0.168429E-01 D:-. 112899E-01

       E: 0.316019E-02 F:-. 336593E-03 G: 0.000000E + 00 H: 0.000000E + 00

       J: 0.000000E + 00

    9: 6.07112 0.100000

      ASP:

      K: -13.429105

      IC: YES CUF: 0.000000

      A:-. 220384E-01 B:-. 313728E-02 C:-. 878776E-03 D: 0.415119E-03

      E:-. 249643E-04 F:-. 216580E-05 G: 0.000000E + 00 H: 0.000000E + 00

      J: 0.000000E + 00

   10: 1.25719 0.813027 1.53113 55.8

      SPS ODD:

 K: -3.5370E + 00 AR3: -4.2024E-02 AR4: -1.9005E-01

           AR5: 3.5600E-02 AR6: 3.6904E-02 AR7: 2.9296E-03

           AR8: -1.3694E-03 AR9: -1.5758E-03 AR10: -1.1169E-03

           AR11: 3.1601E-06 AR12: 2.4672E-04 AR13: 6.1133E-05

           AR14: -3.4130E-05

   11: 1.54145 0.329135

      SPS ODD:

K: -3.9893E + 00 AR3: 1.2215E-02 AR4: -1.5638E-01

          AR5: 3.8383E-02 AR6: 2.4374E-02 AR7: -5.9060E-03

          AR8: -5.3823E-03 AR9: 9.8806E-04 AR10: 4.9698E-04

          AR11: 3.4969E-05 AR12: -3.7514E-05 AR13: -9.5277E-06

          AR14: 1.7466E-06

   12: INFINITY 0.300000 1.5168 64.1673

   13: INFINITY 0.903934

> IMG: INFINITY 0.000000

In an embodiment of the invention,

Combined refractive power of the first lens and the second lens (P ₁₂ ) absolute │P ₁₂ │ = 0.219

Absolute power (P ₃ ) of the third lens │P ₃ │ = 0.131

Absolute power (P ₄ ) of the fourth lens │P ₄ │ = 0.025

Absolute power (P ₅ ) of the fifth lens │P ₅ │ = 0.156

The fourth lens has weak refractive power, and as the lens gets thicker, the fourth lens has negative refractive power. In particular, the refractive index P ₁₂ of the first lens and the second lens combined has a refractive index of 1/3 of the absolute value, thereby reducing the influence on the refractive ability of the center portion and improves the performance of the peripheral portion.

In addition, the refractive index and the Abbe's number of the fourth lens are different from those of the third lens and the fourth lens, thereby improving the chromatic aberration. The fourth lens has a refractive index (Nd) of 1.632, an Abbe's number (Vd) of 23.6, the third lens and a fifth lens have a refractive index (Nd) of 1.53113, and an Abbe's number (Vd) of 55.8.

5 is an astigmatism diagram showing optical performance of a lens assembly according to a preferred embodiment of the present invention.

In FIG. 5, the solid line represents a sagittal plane and the dotted line represents a tangential plane. When comparing FIG. 5 with FIG. 3, it can be seen that the performance improvement of the peripheral portion of the lens assembly of the present invention is clearly shown as compared with the conventional lens assembly.

As mentioned above, although the structure of this invention was demonstrated with reference to the preferred embodiment of the present invention and attached drawing, this is only an illustration and the scope of the present invention is not limited to this.

1 illustrates a conventional lens assembly.

2 illustrates another conventional lens assembly.

3 is an astigmatism diagram of a conventional lens assembly.

4 illustrates a lens assembly according to a preferred embodiment of the present invention.

FIG. 5 is an astigmatism diagram of the lens assembly shown in FIG. 4. FIG.

Claims (6)

An ultra-high resolution imaging lens assembly comprising a first lens, a second lens, a third lens, a fourth lens, and a fifth lens disposed between a subject and an image surface. The first lens has positive refractive power, the second lens has negative refractive power, the front surface of the first lens and the rear surface of the second lens are spherical surfaces, and the first lens and the second lens are Optical glass material, which is bonded together and the bonding surface is substantially planar, And the third lens, the fourth lens, and the fifth lens are all made of plastic, and each lens has at least one surface aspheric surface. The method of claim 1, The sum of the absolute values of the refractive power of the first lens and the second lens is greater than twice the absolute value of the refractive power of the fourth lens. The method of claim 1, And the fourth lens has a higher refractive index and a smaller Abbe's number than the third and fifth lenses. The method of claim 1, An infrared filter is further disposed between the fifth lens and the upper surface. In the method of manufacturing an ultra-high resolution imaging lens assembly, Disposing at least one lens having a high refractive power and responsible for refraction of reflected light from an object, disposing a lens for axial aberration correction; A method of manufacturing a lens assembly comprising the steps of: arranging a lens for correcting image curvature aberration while reducing the angle of the chief ray; and arranging a lens for correcting chromatic aberration and degrading optical performance of a peripheral part. The method of claim 5, wherein the disposing a lens having high refractive power includes: Disposing a first lens having positive refractive power; Disposing a second lens having negative refractive power; Bonding the first and second lenses to each other; Lens assembly manufacturing method comprising a.

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