KR20090065149A - Compact zoom lens - Google Patents

Abstract

A compact zoom lens is provided to have a high magnification ratio and to minimize a size by reducing the number of lenses. A compact zoom lens includes a first lens group, a second lens group, and a third lens group. The first lens group(G1) is successively arranged from an object side, and has a negative refractive power. The second lens group(G2) has a positive refractive power. The third lens group(G3) has a positive refractive power. The first lens group, the second lens group, and the third lens group are moved in being magnified from a wide-angle part to a telephoto part. The second lens group is moved into a right-angled direction about an optical axis. A shaking image due to vibration is corrected.

Description

Compact zoom lens

The present invention relates to a compact and inexpensive zoom lens.

Recently, digital cameras and video cameras having solid-state imaging devices such as charge coupled devices (CCDs) and complementary metal-oxide semiconductors (CMOS) are widely used. In particular, demand for megapixel camera modules has been demanded, and cameras having high-definition performance and more than 5 million pixels have emerged in entry-level digital cameras. An imaging optical device such as a digital camera or a mobile phone camera using an imaging device such as a CCD or a CMOS requires a small size, light weight, and low cost. In order to satisfy this demand, a zoom lens composed of three lens groups is frequently used. However, it is difficult to satisfy miniaturization and low cost at the same time.

On the other hand, a zoom lens having a high aspect ratio has an advantage of taking a large distance from a subject. However, zoom lenses having a high magnification are more likely to fail to shoot due to the sway in the telephoto. Vibration caused by a slight hand shake during shooting or scratching during light emission of the flash may deteriorate the quality of the picture. In the case of the high-side zoom lens, the angle of view becomes smaller in the telephoto end, resulting in a larger amount of image stabilization than in the wide-angle end, and when the vibration of the camera is constant, the image is increased by causing a large amount of image shake.

SUMMARY OF THE INVENTION An object of the present invention is to provide a zoom lens having a small number of lenses in a configuration suitable for a photographing optical system using a solid state image pickup device, having a high aspect ratio, and a correction function for image shake due to vibration.

The present invention includes a first lens group having a negative refractive power arranged in sequence from the object side, a second lens group having a positive refractive power, a third lens group having a positive refractive power, when shifting from the wide-angle end to the telephoto end, The first lens group, the second lens group and the third lens group all move, the second lens group moves in a direction orthogonal to the optical axis to correct image shake due to vibration, and satisfies the following conditional expression. A compact zoom lens is provided.

<Conditional expression>

-One. 5≤ m _2t ≤ -1.2

Here, m2t represents the magnification of the second lens group in the telephoto end.

The present invention includes a first lens group having a negative refractive power arranged in sequence from the object side, a second lens group having a positive refractive power, a third lens group having a positive refractive power, when shifting from the wide-angle end to the telephoto end, The first lens group, the second lens group and the third lens group all move, and the second lens group moves in a direction orthogonal to the optical axis to compensate for image shake due to vibration, and a small zoom that satisfies the following conditional expression. Provide a lens.

<Conditional expression>

Here, f _I represents the focal length of the first lens group G1 and f _II represents the focal length of the second lens group G2.

The second lens group includes a bonding lens formed so that at least one surface is aspheric.

The second lens group corrects spherical aberration.

The third lens group performs focusing according to a change in object distance.

Hereinafter, a small zoom lens according to an exemplary embodiment of the present invention will be described in detail with reference to the accompanying drawings.

Referring to FIG. 1, a small zoom lens according to an exemplary embodiment of the present invention may include a first lens group G1 having a negative refractive power, a second lens group G2 having a positive refractive power, and a positive refractive power from an object side O. Including a third lens group (G3) having a, and when changing from the wide-angle end to the telephoto end, the first lens group (G1), the second lens group (G2) and the third lens group (G3) all move. .

The first lens group G1 has a meniscus first lens 11-1 having a convex shape and a negative refractive power in the order from the object side O to the object side O, and a positive refractive power. It may include two lenses (12-1). At least one surface of the first lens is composed of an aspherical surface, and when the aspherical surface is used on the surface of the first lens group where the height of the chief ray is increased, it is easy to correct the distortion aberration.

The second lens group G2 includes the third lens 21-1 having positive refractive power from the object side O, the fourth lens 22-1 having negative refractive power, and the third lens 23-having positive refractive power. It may include 1). The second lens group includes a bonded lens having positive refractive power and at least one surface consisting of aspherical surfaces. In the second lens group, aspherical aberration can be easily corrected by using an aspherical surface on the lens surface of which the beam width of the axial light beam is widened or the lens surface of which the incident height is the highest. For example, the third lens 21-1 and the fourth lens 22-1 may be formed of a cemented lens, and the third lens may be formed as an aspherical surface. The second lens group G2 is moved in a direction orthogonal to the optical axis to correct image shake due to hand shake.

The third lens group G3 includes one sixth lens 31-1 having positive refractive power. By configuring the third lens group G3 with one lens, the motor capacity for moving the third lens group is reduced, and the power consumption of the motor battery is reduced. In the present invention, the third lens group G3 performs image movement and focusing according to a change in object distance.

The second lens group G2 is configured to satisfy the following conditional expression to perform image stabilization.

-One. 5≤ m _2t ≤ -1.2

Here, m2t represents the magnification of the second lens group in the telephoto end. By satisfying Equation 1, an optical system that can correct an image shake due to hand shake can be configured to have a more compact optical system, and move the second lens group in a direction perpendicular to the optical axis, thereby causing an image caused by vibration during shooting. Shake can be corrected.

The zoom lens according to the exemplary embodiment of the present invention may be configured to satisfy the following conditional expression.

f _I represents the focal length of the first lens group G1, and f _II represents the focal length of the second lens group G2. Equation (2) is appropriately arranged so that the first lens group has a negative refractive power and the second lens group has a positive refractive power as a condition for the power of the first lens group and the second lens group, thereby making it possible to change the aberration change at the time of shifting. At the same time, it allows for compactness. When the upper limit of Equation 2 is exceeded, the positive refractive power of the second lens group becomes stronger, making it difficult to balance spherical aberration and chromatic aberration in a balanced manner, making it difficult to secure a sufficient postfocal distance. When the lower limit of Equation 2 is exceeded, the positive refractive power of the second lens group is weakened, so that the shift amount of the second lens group increases when shifting, and the length of the entire optical system becomes long, which hinders miniaturization.

The following shows the equation regarding the power of the third lens group.

Here, f _III represents the focal length of the third lens group and fw represents the focal length at the wide-angle end of the entire lens system. Equation 3 is a condition for obtaining good telecentricity without weakening the chromatic aberration well corrected by the first lens group G1 and the second lens group g2. When the upper limit of Equation 3 is exceeded, the positive refractive power of the third lens group G3 becomes stronger, which is advantageous to secure telecentricity, but it is difficult to correct spherical aberration and image curvature in a balanced manner. When the lower limit of Equation 3 is exceeded, the positive refractive power of the third lens group G3 is weakened and the telecentricity is worsened, so that the amount of movement when moving for focusing is increased, making it difficult to be tongued.

The following defines the total length ratio of the optical system at the wide-angle end by the first lens group and the focal length.

Here, L _II represents a moving distance of the second lens group G2, ft represents a focal length at the telephoto end of the entire lens system, and fw represents a focal length at the wide-angle end of the entire lens system.

When the upper limit of the equation 4 is exceeded, the total length of the optical system becomes long at the wide-angle end, making it difficult to miniaturize the optical system. When the upper limit is exceeded, the focal length of the first lens group becomes long, and it becomes difficult to correct distortion and astigmatism.

On the other hand, the definition of the aspherical surface in the embodiment of the present invention is as follows.

The aspherical shape of the zoom lens according to the present invention can be expressed by the following equation with the X-axis as the optical axis direction and the Y-axis as the direction perpendicular to the optical axis direction. Where x is the distance from the vertex of the lens in the optical axis direction, h is the distance in the direction perpendicular to the optical axis, K is the conic constant, A, B, C, D are aspherical coefficients, c represents the inverse of the radius of curvature (1 / R) at the vertex of the lens, respectively.

The present invention specifically includes lenses according to optimization conditions for realizing miniaturization of a zoom lens through embodiments according to various designs as follows.

F is the composite focal length of the entire lens system, Fno is the F number, 2w is the angle of view, R is the radius of curvature, Dn is the center thickness of the lens or the distance between the lens and the lens, and nd is the refractive index of the material. And vd represent Abbe numbers, respectively. In addition, ST represents an aperture, D1, D2, and D3 represent a variable distance, and ASP represents an aspherical surface. In addition, in the drawing showing each embodiment, the reference numerals of the embodiments are indicated by the reference numerals of the respective lens groups, and the same numbers are indicated for the lenses constituting the respective lens groups.

<First Embodiment>

1 illustrates a wide-angle end, an intermediate end, and a telephoto end of a zoom lens according to a first embodiment, respectively, and reference numeral 41-1 denotes a filter.

 f: 6.41 ~ 10.80 ~ 18.19 Fno: 2.89 ~ 3.78 ~ 5.35 2ω: 64.08 ~ 39.70 ~ 23.92

                 R Dn nd vd

    S1: 83.71310 1.000000 1.80400 40.70

      ASP:

      K: 0.000000

      A: 0.953860E-04 B: 0.507532E-06 C: 0.000000E + 00

      D: 0.000000E + 00

    S2: 5.18650 1.198351

      ASP:

      K: -0.345343

      A: 0.125159E-05 B: 0.111076E-05 C: 0.000000E + 00

      D: 0.000000E + 00

    S3: 7.40456 1.776398 1.846663 23.7848

    S4: 17.83933 D1

    ST (S5): 4.61700 2.330000 1.804000 40.7000

      ASP:

      K: -1.000000

      A: 0.678410E-03 B: 0.000000E + 00 C: 0.000000E + 00

      D: 0.000000E + 00

    S6: -8.57900 0.600000 1.728250 28.3205

    S7: 3.69 500 0.510000

    S8: 12.33 117 0.988663 1.620409 60.3438

    S9: -22.15553 D2

   S10: 64.42499 1.203573 1.834810 42.7207

   S11: -26.09675 D3

   S12: INFINITY 1.100000 1.516798 64.1983

   S13: INFINITY

 Next, the variable distances D1, D2, and D3 of the zoom lens according to the first embodiment are shown for the wide-angle end, the intermediate end, and the telephoto end.

Wide angle Middle Telephoto D1 12.39 6.07 1.66 D2 4.33 10.44 17.69 D3 4.99 3.39 2.4

2 and 3 show spherical aberration, image curvature, and distortion aberration at the wide-angle end and the telephoto end of the zoom lens according to the first embodiment of the present invention, respectively. Top curves show tangential field curvature (T) and sagittal field curvature (S).

Second Embodiment

4 illustrates a zoom lens according to the second embodiment, and includes first, second, and third lens groups G1, G2, and G3.

 f: 6.07 ~ 10.14 ~ 16.95 Fno: 2.84 ~ 3.81 ~ 5.11 2ω: 66.68 ~ 42.04 ~ 25.44

                R Dn nd vd

    S1: 44.78581 1.250000 1.804000 40.7000

      ASP:

      K: 0.000000

      A: 0.256811E-03 B:-. 466009E-05 C: 0.969807E-07

      D: 0.000000E + 00

    S2: 5.59929 1.427327

      ASP:

      K: -1.725655

      A: 0.132088E-02 B: 0.110317E-05 C: 0.000000E + 00

      D: 0.000000E + 00

    S3: 7.32 137 1.771 420 1.922860 20.8804

    S4: 11.91412 D1

    ST: INFINITY 1.000000

    S6: 4.40486 1.791066 1.804000 40.7000

      ASP:

      K: -0.402266

      A: 0.000000E + 00 B: 0.000000E + 00 C: 0.000000E + 00

      D: 0.000000E + 00

    S7: -11.19704 0.704467 1.728250 28.3205

    S8: 3.62446 0.574048

    S9: 13.81055 1.081973 1.620409 60.3438

   S10: -21.79466 D2

   S11: 24.14970 1.311388 1.883000 40.8054

   S12: -55.49020 D3

   S13: INFINITY 1.100000 1.516798 64.1983

   S14: INFINITY

 Next, the variable distances D1, D2, and D3 of the zoom lens according to the second embodiment are shown for the wide-angle end, the intermediate end, and the telephoto end.

Wide angle Middle Telephoto D1 12.49 6.58 1.80 D2 4.58 11.15 17.95 D3 4.78 2.88 2.10

5 and 6 show spherical aberration, image curvature, and distortion aberration at the wide-angle end and the telephoto end of the zoom lens according to the second embodiment of the present invention, respectively.

Third Embodiment

7 shows a zoom lens according to the third embodiment.

 f: 6.49 ~ 10.86 ~ 18.86 Fno: 3.2 ~ 4.37 ~ 6.06 2ω: 63.2 ~ 39.04 ~ 23.88

                 R Dn nd vd

   S1: 49.23921 0.600000 1.883000 40.8054

   S2: 5.93229 1.412545

   S3: 10.53968 1.560478 1.821145 24.0583

      ASP:

      K: -0.000000

      A:-. 575145E-05 B:-. 750961E-05 C: 0.000000E + 00

      D: 0.000000E + 00

   S4: 35.13689 D1

      ASP:

      K: 0.000000

      A:-. 324457E-03 B:-. 789584E-05 C: 0.000000E + 00

      D: 0.000000E + 00

   ST: INFINITY 0.000000

   S6: 4.99682 1.416 110 1.685806 49.3403

      ASP:

      K: -0.974338

      A:-. 737839E-04 B: 0.000000E + 00 C: 0.000000E + 00

      D: 0.000000E + 00

   S7: -22.16108 0.200000

      ASP:

      K: 0.000000

      A: 0.471495E-03 B: 0.251399E-04 C: 0.000000E + 00

      D: 0.000000E + 00

    S8: 11.81 106 1.378489 1.725766 33.1278

    S9: -4.01483 0.605401 1.668018 26.8107

    S10: 3.17417 D2

    S11: 40.49889 1.526978 1.725689 46.3184

      ASP:

      K: -1.000000

      A:-. 404629E-04 B: 0.000000E + 00 C: 0.000000E + 00

      D: 0.000000E + 00

   S12: -16.52566 D3

   S13: INFINITY 1.100000 1.516798 64.1983

   S14: INFINITY

Next, the variable distances D1, D2, and D3 of the zoom lens according to the third embodiment are shown for the wide-angle end, the intermediate end, and the telephoto end.

Wide angle Middle Telephoto D1 11.02 5.61 1.48 D2 4.52 9.88 16.15 D3 3.63 2.35 2.00

8 and 9 illustrate spherical aberration, image curvature, and distortion aberration at the wide-angle end and the telephoto end of the zoom lens according to the third embodiment of the present invention, respectively.

The following shows that the first to third embodiments satisfy the conditions of Equations 1 to 4, respectively.

Example 1 Example 2 Example 3 Equation 1 -1.45 -1.36 -1.5 Equation 2 1.4 1.38 1.52 Equation 3 3.5 3.17 2.51 Equation 4 1.0 1.06 0.92

The above embodiments are merely exemplary, and various modifications and equivalent other embodiments are possible to those skilled in the art. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the invention described in the claims below.

1 illustrates a zoom lens according to a first embodiment of the present invention for a wide-angle end, an intermediate end, and a telephoto end.

2 and 3 show aberration diagrams at the wide-angle end and the telephoto end of the zoom lens according to the first embodiment of the present invention.

4 illustrates a zoom lens according to a second embodiment of the present invention for each of a wide-angle end, an intermediate end, and a telephoto end.

5 and 6 illustrate aberration diagrams at the wide-angle end and the telephoto end of the zoom lens according to the second exemplary embodiment of the present invention.

7 illustrates a zoom lens according to a third embodiment of the present invention for each of a wide-angle end, an intermediate end, and a telephoto end.

8 and 9 illustrate aberration diagrams at the wide-angle end, the intermediate end, and the telephoto end of the zoom lens according to the third embodiment of the present invention.

<Description of main part of drawing>

G1 ... first lens group, G2 ... second lens group,

G3 ... the third lens group,

D1, D2, D3 ... variable distance

Claims (9)

A first lens group having a negative refractive power arranged in sequence from an object side, a second lens group having a positive refractive power, and a third lens group having a positive refractive power, wherein the first lens group is shifted from a wide angle end to a telephoto end , The second lens group and the third lens group are all moved, the second lens group is moved in a direction orthogonal to the optical axis to correct image shake due to vibration, and satisfies the following conditional expression zoom lens. <Conditional expression> -One. 5≤ m _2t ≤ -1.2 Here, m2t represents the magnification of the second lens group in the telephoto end. And the zoom lens satisfies the following conditional expression. <Conditional expression>

Here, f _I represents the focal length of the first lens group G1 and f _II represents the focal length of the second lens group G2. A first lens group having a negative refractive power arranged in sequence from an object side, a second lens group having a positive refractive power, and a third lens group having a positive refractive power, wherein the first lens group is shifted from a wide angle end to a telephoto end , The second lens group and the third lens group are all moved, the second lens group is moved in a direction orthogonal to the optical axis to correct image shake due to vibration, and satisfies the following conditional expression zoom lens. <Conditional expression>

Here, f _I represents the focal length of the first lens group G1 and f _II represents the focal length of the second lens group G2. The method according to any one of claims 1 to 3, And the zoom lens satisfies the following conditional expression. <Conditional expression>

Here, f _III represents the focal length of the third lens group and fw represents the focal length at the wide-angle end of the entire lens system. The method according to any one of claims 1 to 3, And the zoom lens satisfies the following conditional expression. <Conditional expression>

Here, L _II represents a moving distance of the second lens group G2, ft represents a focal length at the telephoto end of the entire lens system, and fw represents a focal length at the wide-angle end of the entire lens system. The method according to any one of claims 1 to 3, And the first lens group comprises a meniscus lens having at least one surface formed as an aspheric surface. The method according to any one of claims 1 to 3, The second zoom lens group is small, characterized in that the zoom lens comprises at least one surface of the aspherical lens formed aspherical. The method according to any one of claims 1 to 3, And the second lens group corrects spherical aberration. The method according to any one of claims 1 to 3, And the third lens group performs focusing according to an object distance change.

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