KR101571337B1 - Compact zoom lens - Google Patents

Abstract

A zoom lens is disclosed. A zoom lens comprising: a first lens group which is sequentially arranged from an object side to an image side and has a negative refractive power and includes a negative lens and a positive lens; A second lens group having positive refractive power and including at least one positive lens; A third lens group having negative refractive power; And a fourth lens group consisting of a single lens having positive refractive power; Wherein the first lens group moves upward and then moves toward the object side when the zoom lens is moved from the wide angle end to the telephoto end, the interval between the first lens group and the second lens group decreases, The distance between the second lens group and the third lens group increases, the third lens group moves from the image side to the object side, and the fourth lens group moves toward the object side And the distance from the top surface is the closest to the telephoto end.

Description

Compact zoom lens {Compact zoom lens}

The present disclosure relates to a zoom lens having a compact size and a high aspect ratio.

2. Description of the Related Art In recent years, imaging optical devices such as digital still cameras and digital camcorders using solid-state image pickup devices such as CCD (Charge Coupled Device) and CMOS (Complementary Metal-Oxide Semiconductor) that convert optical images into electric signals are rapidly expanding and spreading.

In accordance with such spread, there is a demand for a high-resolution image pickup device, and a photographing lens, particularly a zoom lens, having excellent imaging performance is required in correspondence with a solid-state image pickup device having a large number of pixels. In addition, high performance, such as a high aspect ratio and a demand for a wide angle of view, is required, and portability is emphasized, and various designs for high performance and small size and light weight have been proposed.

As such a zoom lens, a zoom lens having a four-group structure including first through fourth lens groups having positive, negative, positive, and positive refractive powers in order from the object side is often used. The zoom lens has a high aspect ratio, And there is a growing interest in a design that realizes an advantageous structure for miniaturization.

Embodiments provide a zoom lens that is miniaturized and has a high aspect ratio.

A first lens group which is sequentially arranged from the object side to the image side and has a negative refractive power and includes one negative lens and one positive lens; A second lens group having positive refractive power and including at least one positive lens; A third lens group having negative refractive power; And a fourth lens group consisting of a single lens having positive refractive power; Wherein the first lens group moves upward and then moves toward the object side when the zoom lens is moved from the wide angle end to the telephoto end, the interval between the first lens group and the second lens group decreases, The distance between the second lens group and the third lens group increases, the third lens group moves from the image side to the object side, and the fourth lens group moves toward the object side The zoom lens moves back to the upper side and the distance from the upper side is closest to the telephoto end.

Each of the first lens group, the second lens group, and the fourth lens group may have at least one aspheric surface.

The zoom lens may satisfy the following expression.

Nd1? 1.8

Where Nd1 is the refractive index of the positive lens included in the first lens group.

The zoom lens may satisfy the following expression.

0 < D2 &lt; 3

Here, D2 represents the distance (mm) between the second lens group and the third lens group.

The third lens group may be composed of a cemented lens in which a positive lens and a negative lens are bonded.

The third lens group may be composed of a triple-cemented lens joined in the order of a positive lens, a negative lens, and a positive lens.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following drawings, like reference numerals refer to like elements, and the size of each element in the drawings may be exaggerated for clarity and convenience of explanation.

FIGS. 1, 5, and 9 are views showing the optical arrangement of the zoom lens according to the first, second, and third embodiments of the present invention, respectively. Referring to the drawings, the zoom optical system includes, in order from the object OBJ side to the image IMG side, a first lens group G1 having a negative refractive power, a second lens group G2 having a positive refractive power, 3 lens group G3, and a fourth lens group G4 having a positive refractive power. An infrared filter and a cover glass may be provided on the upper side of the fourth lens group G4. The upper surface IMG is an image sensing surface of an image pickup element (not shown) such as a CCD (Charge Coupled Device) or CMOS.

Each lens group of the zoom lens according to the embodiments of the present invention moves along the optical axis direction. When the zoom lens is changed from the wide angle end to the telephoto end and the zoom lens is changed from the wide angle end to the telephoto end, the first lens group G1 is moved upward The distance between the first lens group G1 and the second lens group G2 decreases, the second lens group moves toward the object side from the image side, and the distance between the second lens group and the third lens group G2 decreases, The third lens group G3 moves from the image side toward the object side, the fourth lens group G4 moves toward the object side, moves back to the image side, and the distance from the image side to the image side increases from the telephoto end It becomes close. The diaphragm ST is disposed on the object side or the image side of the second lens group G2 and moves together with the second lens group G2 when zooming.

The present invention adopts the four-group type of negative, positive, negative, and positive to realize a high aspect ratio and a wide angle of view, and at the same time to achieve miniaturization. And all the lens groups are moved along the optical axis when varying the magnification, thereby increasing the degree of design freedom.

The first lens group G1 is composed of at least two negative lenses, one negative lens and one positive lens. The first lens group G1 focuses and collects incident light in an angle of view, and controls the astigmatism such as astigmatism and coma aberration do. At this time, each lens may include an aspherical surface, effectively reducing such aberration. Further, the following conditional expression is satisfied.

Nd1? 1.8

Here, Nd1 is the refractive index of the positive lens included in the first lens group G1.

In this way, when the positive lens of the first lens group G1 is composed of an aspheric lens using a high-refractive index material, it is advantageous to minimize the thickness of the first lens group G1. In addition, performance degradation due to stockpiling can be corrected, and a compact, high-performance zoom optical system can be constructed.

The optical diaphragm is positioned in front of or behind the second lens group G2 so that the rays of light incident on the second lens group G2 are collected by the second lens group G2, Spherical aberration is more effectively controlled by using an aspherical surface.

The third lens group G3 is composed of two or more lenses including at least one positive lens and one negative lens. For example, it may be composed of a cemented lens in which one positive lens and one negative lens are bonded, or may be composed of a triple cemented lens joined in the order of a positive lens, a negative lens and a positive lens, It is possible to reduce chromatic aberration and spherical aberration.

The fourth lens group G4 includes a single positive lens, and forms an image on the image-forming surface through the first through third lens groups G1-G3.

Each lens group is configured to move independently along the optical axis to maximize optical performance. Specifically, the first lens group G1 moves slightly toward the upper side when moving from the wide-angle end to the middle end, and then moves toward the object side toward the telephoto end. The second lens group G2 moves from the wide angle end to the telephoto end and moves from the image side toward the object side. The third lens group G3 is almost identical to the movement mode of the second lens group G2, The distance from the second lens group G2 is gradually increased. The fourth lens group G4 moves from the wide-angle end to the telephoto end, moves to the object side from the middle end to the middle end, and then moves to the image side toward the telephoto end. When transformed, the following conditional expression can be satisfied.

0 < D2 &lt; 3

Here, D2 represents the distance (mm) between the second lens group G2 and the third lens group G3.

This condition defines the variable distance range between the second lens group G2 and the third lens group G3 to be not more than 3 mm when varying from the wide-angle end to the telephoto end. The upper limit value of the conditional formula is proposed to be the maximum value for making the optical system as slim as possible. In the range exceeding the upper limit, the configuration of the mechanical unit becomes complicated when the optical system is constructed, and the configuration of the slim optical system becomes difficult.

Hereinafter, specific configurations and lens data of various embodiments of the zoom lens according to the present invention will be described. The definition of the aspherical surface in the embodiments of the present invention is as follows.

Where y is the height in a direction perpendicular to the optical axis, x is the distance from the vertex of the lens to the optical axis direction at height y, K is a conic constant, A, B, C, D are aspheric coefficients , and c 'is an inverse number (1 / R) of the radius of curvature at the apex of the lens. Here,

Hereinafter, f denotes the combined focal length of the entire zooming optical system, Fno denotes the F number, f denotes the focal length, and 2ω denotes the angle of view. ASP represents an aspherical surface, and STO represents an aperture. In each embodiment, the variable distances at the wide angle end, the middle end, and the telephoto end are denoted by D1, D2, D3, D4, and D5. RDY denotes the radius of curvature, THI denotes the lens thickness or inter-lens distance, and GLA denotes the refractive index and Abbe number.

&Lt; Embodiment 1 >

1 shows a zoom lens according to the first embodiment. The first lens group G1 includes one negative lens and one positive lens. For example, a first lens 110, which is an inverted negative lens, and a second lens 120, which is a positive lens. The second lens group G2 includes a third lens 210 which is a positive lens having a biconvex shape. The third lens group G3 includes a fourth lens 310 as a positive lens and a fifth lens 320 as a negative lens and the fourth lens 310 and the fifth lens 320 form a cemented lens. The fourth lens group G4 is composed of a fourth lens group G4 and a sixth lens 410 which is a positive lens.

Figs. 2 to 4 show longitudinal spherical aberration, astigmatic field curvature, and distortion aberration at the wide-angle end, the middle end, and the telephoto end of the zoom lens according to the first embodiment. The longitudinal spherical aberration is shown for light at wavelengths of 656.28 (nm), 587.56 (nm), and 486.13 (nm). The curvature of the surface represents the tangential field curvature (T) and the sagittal field curvature (S).

The following is lens data of the first embodiment.

f; 4.429 to 10.85 to 20.86, Fno; 3.37 to 5.29 to 6.10, 2?; 84.18 ~ 40.48 ~ 21.72

RDY THI GLA

OBJ: INFINITY INFINITY

    1: 55.99628 0.500000 729030.540413

ASP:

      K: 0.000000

      A: 0.420080E-03 B: - 288317E-04 C: 0.952927E-06 D: - 979082E-08

    2: 5.79397 1.157437

ASP:

      K: -0.074692

      A: -. 116402E-03 B: 0.130706E-03 C: - 791583E-05 D: 0.190713E-06

    3: 6.41585 1.600000 2.0017: 19.324

ASP:

      K: -6.494520

      A: 0.139496E-02 B: 0.269491E-04 C: - 103610E-05 D: - 498169E-07

    4: 6.98138 D1

ASP:

      K: -3.844870

      A: -. 648147E-03 B: 0.150293E-03 C: - 895520E-05 D: 0.114663E-06

  STO: INFINITY 0.000000

    6: 5.20000 1.450000 693500.532008

ASP:

      P: -2.000223

      A: - 296008E-03 B: - 123774E-03 C: - 109712E-04 D: - 258021E-05

    7: -13.81338 D2

ASP:

      K: 0.000000

      A: -. 492909E-03 B: - 985102E-04 C: - 267790E-04 D: 0.000000E + 00

    8: 9.95622 1.000000 724635.549359

    9: -6.72827 0.300000 625730.333656

   10: 3.18126 D3

   11: -23.26716 1.550000 834410.372851

ASP:

      K: 0.000000

      A: - 355743E-03 B: - 219942E-04 C: 0.315184E-05 D: - 446979E-07

   12: -7.87974 D4

ASP:

      K: 0.146731

      A: 0.364229E-03 B: - 289928E-04 C: 0.235713E-05 D: - 117915E-07

   13: INFINITY 0.300000 516798.641983

   14: INFINITY 0.300000

   15: INFINITY 0.500000 516798.641983

   16: INFINITY 0.520000

  IMG: INFINITY D5

Wide angle stage Middle stage Telescope D1 13.3000 4.2346 1.2000 D2 0.1000 0.4004 0.6543 D3 3.8713 10.0599 18.5824 D4 2.9858 2.4759 1.8000 D5 -0.0159 0.0074 0.0045

&Lt; Embodiment 2 >

1 shows a zoom lens according to the first embodiment. The first lens group G1 includes one negative lens and one positive lens. For example, a first lens 110, which is an inverted negative lens, and a second lens 120, which is a positive lens. The second lens group G2 includes a third lens 210 which is a positive lens having a biconvex shape. The third lens group G3 includes a fourth lens 310 as a positive lens and a fifth lens 320 as a negative lens and the fourth lens 310 and the fifth lens 320 form a cemented lens. The fourth lens group G4 is composed of a sixth lens 410 which is a positive lens.

Figs. 2 to 4 show longitudinal spherical aberration, astigmatic field curvature, and distortion aberration at the wide-angle end, the middle end, and the telephoto end of the zoom lens according to the first embodiment. The longitudinal spherical aberration is shown for light at wavelengths of 656.28 (nm), 587.56 (nm), and 486.13 (nm). The curvature of the surface represents the tangential field curvature (T) and the sagittal field curvature (S).

The following is lens data of the second embodiment.

f; 4.429 to 10.85 to 22.15, Fno; 3.44 to 5.30 to 6.20, 2? 84.18 to 40.48 to 20.48

RDY THI GLA

  OBJ: INFINITY INFINITY

    1: 100.00000 0.500000 729030.540413

      ASP:

      K: 0.000000

      A: - 144190E-03 B: 0.176136E-04 C: - 370997E-06 D: 0.268535E-08

    2: 6.02361 0.963753

      ASP:

      K: -0.091882

      A: -. 632873E-03 B: 0.163218E-03 C: - 751872E-05 D: 0.144900E-06

    3: 7.12664 1.588272 983762.189765

      ASP:

      K: -6.978837

      A: 0.117080E-02 B: 0.586870E-04 C: - 351627E-05 D: 0.324146E-07

    4: 8.05696 D1

      ASP:

      K: -3.439123

      A: -. 617584E-03 B: 0.124284E-03 C: - 677759E-05 D: 0.852391E-07

  STO: INFINITY 0.000000

    6: 5.20000 1.450000 708882.535718

      ASP:

      K: -1.783376

      A: -. 122430E-03 B: - 837726E-04 C: - 886305E-05 D: - 128480E-05

    7: -14.96277 D2

      ASP:

      K: 0.000000

      A: -. 239213E-03 B: - 773628E-04 C: - 168971E-04 D: 0.000000E + 00

    8: 8.98189 1.000000 686846.573773

    9: -5.21391 0.300000 643895.352128

   10: 3.19616 D3

   11: -26.15349 1.650000 834410.372851

      ASP:

      K: 0.000000

      A: -. 150041E-03 B: - 189542E-04 C: 0.329615E-05 D: - 698173E-07

   12: -8.23879 D4

      ASP:

      K: 1.377971

      A: 0.704334E-03 B: - 167217E-04 C: 0.255001E-05 D: - 185604E-07

  13: INFINITY 0.300000 516798.641983

   14: INFINITY 0.300000

   15: INFINITY 0.500000 516798.641983

   16: INFINITY 0.520002

  IMG: INFINITY D5

Wide angle stage Middle stage Telescope D1 13.8000 4.3605 1.2000 D2 0.1000 0.5191 0.9815 D3 3.7535 9.5978 18.7933 D4 3.2417 3.0171 1.8000 D5 -0.0240 0.0074 -0.0036

&Lt; Third Embodiment >

9 shows a zoom lens according to the third embodiment. The first lens group G1 includes one negative lens and one positive lens. For example, a first lens 110, which is an inverted negative lens, and a second lens 120, which is a positive lens. The second lens group G2 includes a third lens 210 which is a positive lens having a biconvex shape. The third lens group G3 includes a fourth lens 310 as a positive lens, a fifth lens 320 as a negative lens, and a sixth lens 330 as a positive lens, and includes a fourth lens 310, The lens 320 and the sixth lens 330 form a triple junction lens. The fourth lens group G4 is composed of a seventh lens 410 which is a positive lens.

Figs. 10 to 12 show longitudinal spherical aberration, astigmatic field curvature, and distortion aberration at the wide-angle end, the middle end, and the telephoto end of the zoom lens according to the third embodiment. The longitudinal spherical aberration is shown for light at wavelengths of 656.28 (nm), 587.56 (nm), and 486.13 (nm). The curvature of the surface represents the tangential field curvature (T) and the sagittal field curvature (S).

The following is lens data of the third embodiment.

f; 4.43 to 10.47 to 26.27, Fno; 3.66 to 5.27 to 6.20, 2? 84.14 to 41.82 to 17.314

RDY THI GLA

  OBJ: INFINITY INFINITY

    1: 52.38134 0.400000 729030.540413

      ASP:

      K: 0.000000

      A: 0.681073E-05 B: - 481243E-05 C: 0.311370E-06 D: - 428810E-08

    2: 5.50016 0.940000

      ASP:

      K: -0.223424

      A: -. 125457E-02 B: 0.160618E-03 C: - 312535E-05 D: - 190504E-07

    3: 6.06871 1.280000 2.0126: 21.420

      ASP:

      K: -3.819488

      A: -. 716184E-03 B: 0.137329E-03 C: - 173943E-05 D: - 553448E-07

    4: 6.80000 D1

      ASP:

      K: -6.262651

      A: - 379533E-03 B: 0.782764E-04 C: - 667811E-06 D: - 611659E-07

  STO: INFINITY 0.000000

    6: 5.20000 1.309757 729030.540413

      ASP:

      K: -1.408986

      A: 0.191623E-03 B: - 163362E-04 C: 0.533527E-08 D: 0.173466E-07

    7: -15.50856 D2

      ASP:

      K: 0.000000

      A: 0.388013E-03 B: - 369397E-04 C: 0.134340E-05 D: 0.000000E + 00

    8: 7.42251 1.153658 883000.408054

    9: -4.04295 0.300000 896228.336696

   10: 2.80000 0.880654 489672.727608

   11: 3.65163 D3

   12: -38.89062 1.500000 834410.372851

      ASP:

      K: 0.000000

      A: 0.420315E-04 B: - 601725E-04 C: 0.529640E-05 D: - 161072E-06

   13: -8.51758 D4

      ASP:

      K: -0.891307

      A: 0.437704E-03 B: - 804238E-04 C: 0.550925E-05 D: - 145360E-06

   14: INFINITY 0.300000 516798.641983

   15: INFINITY 0.300000

  16: INFINITY 0.500000 516798.641983

   17: INFINITY 0.521322

IMG: INFINITY D5

Wide angle stage Middle stage Telescope D1 16.0000 5.2232 1.1000 D2 0.2272 0.6906 1.3000 D3 4.0210 7.5857 18.9121 D4 1.7756 2.4778 1.8000 D5 -0.0069 0.0067 0.0069

The embodiments described above provide a zoom lens having a structure that is advantageous for miniaturization and thinness and has aberration well corrected through a lens configuration having a high aspect ratio of 4 times or more and a wide angle of view.

The zoom lens of the embodiments can be employed in various kinds of image pickup apparatuses together with an image pickup element that generates an image of a subject from light incident through such a zoom lens.

Although the zoom lens of the present invention has been described with reference to the embodiments shown in the drawings for the sake of understanding, it should be understood that the present invention is by way of example only and that various modifications and equivalent embodiments are possible without departing from the scope of the present invention. I will understand the point. Accordingly, the true scope of the present invention should be determined by the appended claims.

FIG. 1 is a view showing the optical arrangement of a zoom lens according to the first embodiment of the present invention and the movement in magnification.

FIGS. 2, 3, and 4 are aberration diagrams showing spherical aberration, surface curvature, and distortion in the wide angle end, the middle end, and the telephoto end, respectively, of the zoom lens according to the first embodiment of the present invention.

FIG. 5 is a diagram showing the optical arrangement of the zoom lens according to the second embodiment of the present invention and the movement of the zoom lens in magnification variation.

6, 7, and 8 are aberration diagrams showing spherical aberration, surface curvature, and distortion in the wide angle end, the middle end, and the telephoto end, respectively, of the zoom lens according to the second embodiment of the present invention.

9 is a diagram showing the optical arrangement of the zoom lens according to the third embodiment of the present invention and the movement of the zoom lens according to the magnification variation.

FIGS. 10, 11, and 12 are diagrams showing spherical aberration, field curvature, and distortion at the wide angle end, the middle end, and the telephoto end, respectively, of the zoom lens according to the third embodiment of the present invention.

Claims (7)

Which are sequentially arranged from the object side to the image side, A first lens group having negative refractive power and including one negative lens and one positive lens; A second lens group having positive refractive power and including at least one positive lens; A third lens group having negative refractive power; And A fourth lens group consisting of a single lens having positive refractive power; / RTI &gt; When transformed from the wide-angle end to the telephoto end, Wherein the first lens group moves upward and then moves toward the object side, the interval between the first lens group and the second lens group decreases, the second lens group moves toward the object side from the image side, The distance between the lens group and the third lens group increases, the third lens group moves from the image side to the object side, the fourth lens group moves toward the object side, Zoom lens closest to the stage. The method according to claim 1, Wherein each of the first lens group, the second lens group, and the fourth lens group has at least one aspheric surface. The method according to claim 1, A zoom lens satisfying the following expression. Nd1? 1.8 Where Nd1 is the refractive index of the positive lens included in the first lens group. The method according to claim 1, A zoom lens satisfying the following expression. 0 < D2? 3 (mm) Here, D2 represents the distance (mm) between the second lens group and the third lens group. 5. The method according to any one of claims 1 to 4, And the third lens group is composed of a cemented lens in which a positive lens and a negative lens are bonded. 5. The method according to any one of claims 1 to 4, Wherein the third lens group is composed of a triple cemented lens joined in order of a positive lens, a negative lens, and a positive lens. A zoom lens according to any one of claims 1 to 4, And an image pickup device for generating an image of a subject from light incident through the zoom lens.

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