KR20090047350A - Compact zoom lens - Google Patents

Abstract

A zoom lens is disclosed. The disclosed zoom lens comprises: a first lens group arranged in sequence from an object side to an image side and having positive refractive power; A second lens group having negative refractive power; A third lens group having positive refractive power; A fourth lens group having negative refractive power; And a fifth lens group having positive refractive power. The second lens group, the fourth lens group, and the fifth lens group move along the optical axis when shifted.

Description

Compact zoom lens

Disclosed is a zoom lens having various focal lengths and which can be employed in photo cameras, television cameras, and the like.

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. Such imaging optical apparatuses are becoming smaller, lighter and cheaper, and at the same time, there is an increasing demand for high performance, for example, high aspect ratio and excellent image quality.

Accordingly, various designs for an auto zoom lens having a large range of change in focal length have been proposed. To this end, a zoom lens is composed of a plurality of lens groups, some lens groups are fixed, and some lens groups are moved to implement various focal lengths. However, it is difficult to realize the required image quality over the entire focal length variation range, and in fact, since image quality is guaranteed only at three zoom positions, for example, a zoom lens design is required to improve this. Do.

In accordance with the aforementioned needs, embodiments of the present invention seek to provide a zoom lens having various focal lengths and excellent image quality.

A zoom lens according to an embodiment of the present invention includes: a first lens group having a positive refractive power, arranged sequentially from an object side to an image side; A second lens group having negative refractive power; A third lens group having positive refractive power; A fourth lens group having negative refractive power; And a fifth lens group having positive refractive power. The second lens group, the fourth lens group, and the fifth lens group move along the optical axis when shifted.

When shifting from the wide-angle end to the telephoto end, the second lens group and the fourth lens group are moved from the object side to the image side, and the fifth lens group is moved monotonically.

The first lens group is provided between two meniscus lenses that are convex toward the object side and the two meniscus lenses, and may include a bonding lens formed by joining two lenses.

The object-side first meniscus lens of the first lens group is a negative lens, and may be made of a flint glass material.

The second lens group may include one meniscus lens which is convex toward the object side, and a bonding lens formed by joining two lenses.

The third lens group may include a biconvex lens and a bonding lens formed by bonding two lenses.

The fourth lens group may include a bilateral lens and a joint lens formed by joining two lenses.

The fifth lens group may include a biconvex lens and a joint lens formed by joining two lenses.

Hereinafter, exemplary 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, and the size of each element in the drawings may be exaggerated for clarity and convenience of description.

1A and 1B are views showing optical arrangement of a zoom lens according to an embodiment of the present invention at two zoom positions corresponding to both ends, respectively.

Referring to the drawings, the zoom lens according to the embodiment of the present invention is composed of five lens groups, for example, the first lens group G1 having a positive refractive power, arranged in order from the object side to the image side, The second lens group G2 having refractive power, the third lens group G3 having positive refractive power, the fourth lens group G4 having negative refractive power, and the fifth lens group G5 having positive refractive power are included. The diaphragm STO is provided in front of the third lens group G3. Although not shown, an image pickup device such as a charge coupled device (CCD) or a complementary metal-oxide semiconductor (CMOS) is provided on the image surface IMG, and the image pickup device is disposed between the fifth lens group G5 and the image surface IMG. A cover glass 17 for protection is provided. In addition, an infrared filter may be further provided.

In the zoom lens according to the exemplary embodiment of the present invention, the first lens group G1 and the third lens group G3 are fixed, and the second lens group G2 and the fourth lens group G4 are moved when shifting. . The second lens group G2 moves in the image direction from the object side when shifting from the wide angle end to the telephoto end, and moves in a quasi linearly, for example. The fourth lens group G4 also moves in the image direction from the object side when shifting from the wide angle end to the telephoto end. The fifth lens group G5 moves along the optical axis direction and focuses according to the movement of the second lens group G2 and the fourth lens group G4. That is, precise focusing is performed by moving the second lens group G2 and the fourth lens group G4 to compensate for inaccuracies.

More specifically, the configuration of each lens group is as follows.

The first lens group G1 includes a first lens 1, a second lens 2, a third lens 3, and a fourth lens 4. The first lens 1 and the fourth lens 4 may be meniscus lenses that are convex toward the object side. Between the first lens 1 and the fourth lens 4, a bonding lens in which the second lens 2 and the third lens 3 are bonded is provided. The first lens 1 is a negative lens and may be made of a flint glass material. The first lens group G1 is fixed without moving when shifting.

The second lens group G2 includes a fifth lens 5, a sixth lens 6, and a seventh lens 7. For example, the second lens group G2 may be configured as a bonded lens in which a fifth lens 5, a sixth lens 6, and a seventh lens 7, which are meniscus lenses convex toward the object side, are joined. . The second lens group G2 is configured to move along the optical axis when shifted, and moves according to a predetermined rule to implement a required focal length.

The third lens group G3 includes an eighth lens 8, a ninth lens 9, and a tenth lens 10. For example, the third lens group G3 may include an eighth lens 8 that is an enveloping lens, and a junction lens in which the ninth lens 9 and the tenth lens 10 are bonded to each other. The third lens group G3 is fixed without moving when shifting.

The fourth lens group G4 includes an eleventh lens 11, a twelfth lens 12, and a thirteenth lens 13. For example, the fourth lens group G4 may include an eleventh lens 11 which is a biconcave lens, and a junction lens in which the twelfth lens 12 and the thirteenth lens 13 are joined. The fourth lens group G4 is arranged to move along the optical axis together with the second lens group G2 to perform a shift, and move according to a predetermined rule to implement a required focal length.

The fifth lens group G5 includes the fourteenth lens 14, the fifteenth lens 15, and the sixteenth lens 16. For example, the fifth lens group G5 may be configured as a junction lens in which the fourteenth lens 14, which is an enveloping lens, and the fifteenth lens 15 and the sixteenth lens 16 are bonded to each other. The fifth lens group G5 is provided to ensure image quality when implementing various focal lengths due to variation. That is, the fifth lens group G5 compensates for inaccuracies in the movement of the second lens group G2 or the fourth lens group G4, so that the focusing is performed more accurately. The fifth lens group G5 moves in a smaller range than the range in which the second lens group G2 or the fourth lens group G4 moves when shifted, and for example, moves non-linearly and monotonically.

Lens data of the zoom lens in the embodiment of the present invention are as follows. Lens data includes curvature radius, thickness, lens material and diameter, and the like. The variable distance between the lenses at the time of shifting is represented by D1 to D5, and the * mark following the surface number indicates the aspherical surface.

Surface Curvature Radius Thickness Material Diameter Conic Constant

OBJ Infinity Infinity

1 57.52859 1.653052 SF57 58.61237 0

2 43.51602 1.580064 54.08977 0

3 49.73049 19.37032 FCD10 53.9433 0

4 -44.59086 3.024693 BK7 47.87725 0

5 -193.5404 0.1423909 37.60098 0

6 32.39125 6.63269 FK5 26.51158 0

7 123.038 D1 18.42883 0

8 490.7384 0.6772056 S-LAH58 17.82152 0

9 * 7.109 735 4.404882 12.93184 -0.5833861

10 -19.97442 3.492044 N-LAF34 12.90678 0

11 9.252809 4.484457 SF57 12.92831 0

12 107.2223 D2 12.77297 0

STO Infinity 0.2 11.32573 0

14 * 24.87885 3.344874 N-SK5 11.71668 -2.455584

15 -26.41103 0.1514151 11.96365 0

16 18.42726 0.7331302 SF57 11.82418 0

17 9.919783 4.663668 N-SK5 11.29697 0

18 -36.27423 D3 10.81353 0

19 -28.51005 0.6716656 N-LASF44 10.77818 0

20 11.31392 0.2705404 10.54105 0

21 10.69 522 0.9175533 SF2 10.913 0

22 7.096664 2.805791 SF57 10.79377 0

23 12.02057 D4 10.36933 0

24 15.82589 4.680485 FK5 15.6301 -1.086487

25 -21.60283 0.7964118 15.44503 0

26 14.24238 4.897596 N-SK5 13.00893 0

27 -8.344696 1.52174 SF57 12.70265 0

28 * -42.00647 D5 12.02195 25.1624

29 Infinity 2 BK7 7.706 20 1 0

30 Infinity 2 6.319 276 0

IMG Infinity 4.550047 0

Zoom lens according to an embodiment of the present invention implements a zoom magnification of 39x, the angle of view (2ω) range is 80 ° ~ 2 °, f number range is 1.6 ~ 3.9. The following shows the focal length f at six standard zoom positions, the variable distance between the lenses D1 to D5, and the aperture size.

1st standard zoom position (f = 2.63mm)

D1: 0.334677

D2: 38.86532

D3: 0.1787433

D4: 18.24062

D5: 3.130411

Aperture: 1.64

2nd standard zoom position (f = 5.12mm)

D1: 11.578

D2: 27.622

D3: 2.119287

D4: 16.89185

D5: 2.538272

Aperture: 2.95

3rd standard zoom position (f = 10.26mm)

D1: 21.58687

D2: 17.61313

D3: 4.433143

D4: 14.1920 2

D5: 2.924905

Aperture: 6.6

4th standard zoom position (f = 22.0mm)

D1: 28.78316

D2: 10.41684

D3: 8.375212

D4: 10.37058

D5: 2.803959

Aperture: 10

5th standard zoom position (f = 44.5mm)

D1: 34.1428

D2: 5.057203

D3: 12.31351

D4: 4.827702

D5: 4.408089

Aperture: 13

6th standard zoom position (f = 102.5mm)

D1: 38.28184

D2: 0.9181604

D3: 18.60366

D4: 0.4797248

D5: 2.466178

Aperture: 25.63

2A, 2B-6A, and 6B show aberration diagrams for MTF (modulation transfer function) graphs, field curvature, and distortion at first to sixth standard zoom positions, respectively. In the graphs, T and S represent meridional and saggital, respectively, and the wavelength range of light used is 0.436um to 0.656um.

In particular, the zoom lens according to the embodiment of the present invention introduces the fifth lens group G5 for precise focusing, thereby greatly reducing the movement of the second lens group G2 and the fourth lens group G4 during shifting. The burden of controlling with a high degree of accuracy is being reduced.

The zoom lens according to the embodiment of the present invention implements excellent optical performance at six standard zoom positions through the lens configuration described above.

The present invention has been described with reference to the embodiments shown in the drawings for ease of understanding, but this is merely exemplary, those skilled in the art that various modifications and equivalent other embodiments are possible from this. I will understand. Therefore, the true technical protection scope of the present invention will be defined by the appended claims.

1A and 1B are views showing optical arrangement of a zoom lens according to an embodiment of the present invention at two zoom positions corresponding to both ends, respectively.

2A and 2B are aberration diagrams showing an MTF graph and image curvature and distortion at a first standard zoom position of a zoom lens according to an exemplary embodiment of the present invention, respectively.

2A and 2B are aberration diagrams showing an MTF graph and image curvature and distortion at a first standard zoom position of a zoom lens according to an exemplary embodiment of the present invention, respectively.

3 is an aberration diagram illustrating image curvature and distortion at a second standard zoom position of a zoom lens according to an exemplary embodiment of the present invention.

4A and 4B are aberration diagrams showing an MTF graph and image curvature and distortion at a third standard zoom position of a zoom lens according to an exemplary embodiment of the present invention, respectively.

5A and 5B are aberration diagrams showing an MTF graph and image curvature and distortion at a fourth standard zoom position of a zoom lens according to an exemplary embodiment of the present invention, respectively.

6A and 6B are aberration diagrams showing an MTF graph and image curvature and distortion at a fifth standard zoom position of a zoom lens according to an exemplary embodiment of the present invention, respectively.

7A and 7B are aberration diagrams showing an MTF graph and image curvature and distortion at a sixth standard zoom position of a zoom lens according to an embodiment of the present invention, respectively.

Claims (9)

From the object side to the upper side, arranged in sequence, A first lens group having positive refractive power; A second lens group having negative refractive power; A third lens group having positive refractive power; A fourth lens group having negative refractive power; Includes; the fifth lens group having a positive refractive power, And a zoom lens configured to move the second lens group, the fourth lens group, and the fifth lens group along the optical axis when shifting. The method of claim 1, A zoom lens, wherein the second lens group and the fourth lens group are moved from an object side to an image side when changing from a wide angle end to a telephoto end. The method of claim 1, A zoom lens, wherein the fifth lens group moves in a monotonous manner when shifting from a wide angle end to a telephoto end. The method according to any one of claims 1 to 3, The first lens group includes two meniscus lenses convex toward the object side; A zoom lens provided between the two meniscus lenses, wherein the zoom lens comprises a bonding lens formed by bonding two lenses. The method of claim 4, wherein The object-side first meniscus lens of the first lens group is a negative lens, the zoom lens made of a flint glass material. The method according to any one of claims 1 to 3, The second lens group includes one meniscus lens that is convex toward the object side; A zoom lens comprising a bonding lens formed by joining two lenses. The method according to any one of claims 1 to 3, The third lens group is a biconvex lens, A zoom lens comprising a bonding lens formed by joining two lenses. The method according to any one of claims 1 to 3, The fourth lens group includes a bi-focal lens, A zoom lens comprising a bonding lens formed by joining two lenses. The method according to any one of claims 1 to 3, The fifth lens group includes a biconvex lens, A zoom lens comprising a bonding lens formed by joining two lenses.

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