KR20100010310A - Zoom lens - Google Patents

Abstract

PURPOSE: A zoom lens is provided to offer a wide angle image to contain the subject of a picture with a wide range and high magnification. CONSTITUTION: A first lens group(G1) has negative reflective power. A second lens group(G2) has positive reflective power. A third lens group(G3) has a positive reflective power. When there is a magnification change from a wide angle mode to a telescopic mode, the gap between the first lens group and the second lens group diminishes, the second lens group moves toward an object, and the gap between the second lens group and the third lens group increases. The third lens group plays a role of focusing according to the distance of an object.

Description

Zoom lens

A compact, high magnification, ultra wide-angle zoom lens for use in an imaging optical device is disclosed.

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, the demand for megapixel camera modules has increased, 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 miniaturization, light weight, and low cost. Furthermore, the demand for wide angles is increasing to capture a wider range of subjects.

According to one embodiment of the present invention, a compact, high magnification, ultra wide-angle zoom lens is provided.

According to an embodiment of the present invention, the first lens group having the negative refractive power, the second lens group having the positive refractive power, and the third lens group having the positive refractive power are arranged in order from the object side, and have a wide-angle end. The distance between the first lens group and the second lens group decreases, the second lens group moves toward the object side, and the distance between the second lens group and the third lens group increases, The lens group performs focusing according to the object distance and provides a zoom lens that satisfies the following conditions.

<Conditional expression>

2.65 <ft / fw <4.5

80 ° ≤ wfov

Where ft is the focal length at the telephoto end, fw is the focal length at the wide end, and fov is the angle of view at the wide end.

The first lens group may be configured to satisfy the following conditions.

<Conditional expression>

(ndG1) / m> 1.9

Here, ndG1 is the sum of the refractive indices of the lenses constituting the first lens group, and m is the number of lenses constituting the first lens group.

The first lens group includes a first lens having negative refractive power, a second lens having negative refractive power, and a third lens having positive refractive power, wherein the first lens, the second lens, and the third lens face toward the object side. It may have a convex meniscus shape.

The second lens group includes a fourth lens, a fifth lens, and a sixth lens having positive refractive power in order from an object side, and includes at least one joint lens and at least one aspherical lens.

The third lens group includes one lens.

The second lens group is moved perpendicular to the optical axis to perform image stabilization.

Hereinafter, a 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 zoom lens according to an exemplary embodiment of the present invention is arranged in order from an object side O to an image side I, and includes a first lens group G1 having negative refractive power and a first refractive power having a positive refractive power. The second lens group G2 and the third lens group G3 having positive refractive power are included. When changing from the wide end to the telephoto end, the distance between the first lens group 1 and the second lens group G2 decreases, the second lens group G2 moves to the object side O, and the second lens The interval between the group G2 and the third lens group G3 increases. In the zoom lens according to the exemplary embodiment of the present invention, all of the first to third lens groups G1, G2, and G3 move when shifting, and the third lens group G3 is responsible for focusing according to the object distance.

The first lens group G1 includes a first lens 1 having negative refractive power arranged in order from an object side, a second lens 2 having negative refractive power, and a third lens 3 having positive refractive power. It compensates for the distortion caused by ultra wide angle. The first to third lenses 1, 2 and 3 may have a meniscus shape in which the object side O is convex. The second lens group G2 includes a fourth lens 4 having positive refractive power arranged in order from the object side, a fifth lens 5 having positive refractive power, and a sixth lens 6 having negative refractive power. Correct the aberration. The second lens group G2 includes at least one joint lens and at least one aspherical lens. For example, the fifth lens 6 and the sixth lens 6 are composed of a cemented lens, and chromatic aberration correction can be performed using this lens. The third lens group G3 includes the seventh lens 7 and may be configured as a single lens.

According to an embodiment of the present invention, in order to implement a high magnification wide angle, the group of three types and the number of lenses is configured to reduce the lens barrel size and minimize the use of aspherical surface to reduce the cost.

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

2.65 <ft / fw <4.5

 Where ft is the focal length of the telephoto end and fw is the focal length of the wide end.

80 ° ≤ wfov

Here, wfov represents the angle of view of the wide-angle end, the zoom lens according to the embodiment of the present invention implements an ultra-wide angle.

The first lens group G1 has a high refractive spherical lens to increase the power of the first lens group to realize ultra wide angle. The first lens group G1 may be configured to satisfy the following conditions for ultra wide angle.

(ndG1) / m> 1.9

Here, ndG1 is the sum of the refractive indices of the lenses constituting the first lens group, and m is the number of lenses constituting the first lens group G1. In other words, (ndG1) / m represents an average refractive index of the first lens group. According to an embodiment of the present invention, the first lens group includes three lenses, and the sum of the refractive indices of the three lenses divided by three may be configured to be greater than 1.9.

On the other hand, the second lens group G2 includes at least one aspherical surface, and for example, only one surface of the most image side I may be provided as an aspherical surface. In addition, the second lens group G2 includes one bonded lens, and thus, the aspherical surface and the bonded lens are provided in order to reduce the size and cost of the lens. According to an embodiment of the present invention, the camera shake correction is implemented by moving the second lens group G2 in a direction perpendicular to the optical axis.

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, y 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.

In the present invention, an ultra wide angle of the zoom lens is realized through embodiments according to various designs as follows.

F is the composite focal length of the entire lens system, Fno is the F number, 2ω 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 nd is the refractive index, vd represents Abbe's number, respectively. In addition, ST represents an aperture, D1, D2, and D3 represent a variable distance, and * represents an aspherical surface.

<First Embodiment>

Wide angle Middle Telephoto f 4.1 7.38 10.83 Fno 2.7 3.19 3.77 2ω 86.38 52.14 36.08

   Lens plane R Dn nd vd

   obj

    S1 15.119 0.829 2.00069 25.46

    S2 10.811 3.252-

    S3 29.746 0.600 1.83603 44.02

    S4 * 7.703 2.637-

    S5 12.136 1.682 1.94594 17.98

    S6 21.043 D1-

    ST infinity-

    S8 * 7.211 1.087 1.49980 59.88

    S9 -16.564 1.022-

    S10 11.334 1.190 1.87476 41.31

    S11 -4.953 0.600 1.60867 30.68

    S12 3.787 D2-

    S13 6.143 1.128 1.45 650 90.27

    S14 12.257 D3-

    S15 infinity 0.300 1.51680 64.20

    S16 infinity 0.300-

    S17 infinity 0.500 1.51680 64.20

    S18 infinity

    img infinity

The following shows the aspherical surface coefficient of the first embodiment.

Lens surface K A B C D

 S4 -1.000000 1.526912e-004 5.079392e-007 0.000000e + 000 0.000000e + 000

 S8 -7.292688 6.297396e-004 -1.300328e-004 0.000000e + 000 0.000000e + 000

The following shows the variable distances from the wide-angle end, the middle end, and the telephoto end of the first embodiment.

 Variable distance wide-angle end telephoto end

D1 26.016 9.902 3.904

D2 7.625 9.496 12.264

D3 0.552 1.116 0.877

Second Embodiment

Wide angle Middle Telephoto f 4.1 7.38 15.7 Fno 2.58 3.1 4.86 2ω 85.54 53.04 25.7

 Lens plane R Dn nd vd

   obj

   S1 15.089 1.000 2.00000 25.50

   S2 11.082 2.305

   S3 20.055 0.800 1.84000 44.02

   S4 * 6.091 2.941

   S5 10.003 1.954 1.95000 17.90

   S6 14.907 D1

   ST infinity 0.400

   S8 * 7.010 1.511 1.50000 59.88

   S9 -16.947 1.052

   S10 10.638 1.037 1.87000 41.31

   S11 -5.299 0.300 1.61000 30.68

   S12 3.823 D2

   S13 12.193 1.128 1.46000 90.27

   S14 -43.001 D3

   S15 infinity 0.300 1.51680 64.20

   S16 infinity 0.300

   S17 infinity 0.500 1.51680 64.20

   S18 infinity-

   img infinity-

The following shows the aspherical surface coefficient of the second embodiment.

Lens surface K A B C D

  S4 -1.000000 2.738732e-004 2.521421e-006 0.000000e + 000 0.000000e + 000

  S8 -6.665617 7.242783e-004 -1.167586e-004 0.000000e + 000 0.000000e + 000

The following shows the variable distances from the wide-angle end, the middle end, and the telephoto end of the second embodiment.

Variable distance wide-angle end telephoto end

D1 20.768 7.766 0.900

D2 5.402 7.711 17.981

D3 2.717 3.571 1.800

Third Embodiment

Wide angle Middle Telephoto f 4.1 7.38 18.45 Fno 2.65 3.12 5.28 2ω 86.79 53.17 21.52

Lens plane R Dn nd vd

   obj-

   S1 17.136 1.698 2.00069 25.46

   S2 11.665 2.387-

   S3 21.880 0.600 1.83603 44.02

   S4 * 6.801 2.731-

   S5 10.650 1.584 1.94594 17.98

   S6 16.337 D1-

   ST infinity 0.100-

   S8 * 6.958 0.926 1.49 980 59.88

   S9 -16.901 1.172-

   S10 12.011 1.202 1.87476 41.31

   S11 -5.021 0.600 1.60867 30.68

   S12 3.829 D2-

   S13 8.663 1.128 1.45 650 90.27

   S14 57.913 D3-

   S15 infinity 0.300 1.51680 64.20

   S16 infinity 0.300-

   S17 infinity 0.500 1.51680 64.20

   S18 infinity-

   img infinity-

  The following shows the aspherical surface coefficient of the third embodiment.

Lens surface K A B C D

 S4 -1.000000 2.187173e-004 1.665461e-006 0.000000e + 000 0.000000e + 000

 S8 -6.715733 7.429873e-004 -1.224249e-004 0.000000e + 000 0.000000e + 000

 The following shows the variable distances from the wide-angle end, the middle end, and the telephoto end of the third embodiment.

 Variable distance wide-angle end telephoto end

   D1 24.806 9.496 0.197

   D2 6.378 7.854 18.887

   D3 1.619 2.964 0.880

The zoom lens according to the embodiment of the present invention has a high aspect ratio and realizes miniaturization while securing an angle of view of 80 ° or more at the wide-angle end. In this way, the ultra wide angle is realized so that the subject can be photographed in a wider range. The zoom lens according to the embodiment of the present invention can be suitably used for digital still cameras, video cameras, portable terminals and the like using solid state imaging devices such as CCDs and CMOS.

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 according to the embodiment of the present invention will be defined by the technical spirit of the invention described in the claims below.

1 is a block diagram of a zoom lens according to an embodiment of the present invention.

2A illustrates aberration diagrams at wide-angle ends of a zoom lens according to the first exemplary embodiment of the present invention.

2B shows aberration diagrams at the telephoto end of the zoom lens according to the first embodiment of the present invention.

3A illustrates aberration diagrams at wide-angle ends of a zoom lens according to a second exemplary embodiment of the present invention.

3B illustrates aberration diagrams at a telephoto end of a zoom lens according to a second exemplary embodiment of the present invention.

4A illustrates aberration diagrams at wide-angle ends of a zoom lens according to a third exemplary embodiment of the present invention.

4B illustrates aberration diagrams at a telephoto end of a zoom lens according to a third exemplary embodiment of the present invention.

Claims (6)

Arranged in order from the object side, the first lens group having a negative refractive power, a second lens group having a positive refractive power, and a third lens group having a positive refractive power, wherein the first lens group changes from a wide-angle end to a telephoto end. The distance between the lens group and the second lens group decreases, the second lens group moves toward the object side, the distance between the second lens group and the third lens group increases, and the third lens group performs focusing according to the object distance. A zoom lens that performs the following conditions. <Conditional expression> 2.65 <ft / fw <4.5 80 ° ≤ wfov Where ft is the focal length at the telephoto end, fw is the focal length at the wide end, and fov is the angle of view at the wide end. The method of claim 1, And the first lens group satisfies the following conditions. <Conditional expression> (ndG1) / m> 1.9 Here, ndG1 is the sum of the refractive indices of the lenses constituting the first lens group, and m is the number of lenses constituting the first lens group. The method of claim 1, The first lens group includes a first lens having negative refractive power, a second lens having negative refractive power, and a third lens having positive refractive power, wherein the first lens, the second lens, and the third lens face toward the object side. Zoom lens with a convex meniscus shape. The method of claim 1, The second lens group includes a fourth lens, a fifth lens, and a sixth lens having positive refractive power in order from an object side, and includes at least one joint lens and at least one aspherical lens. The method of claim 1, The third lens group includes a lens. The method according to any one of claims 1 to 5, And the second lens group moves perpendicularly to the optical axis to perform image stabilization.

Images