KR101452712B1 - Zoom lens - Google Patents

Abstract

A zoom lens is disclosed.

The disclosed zoom lens includes, in order from the object side, a 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, The interval between the first lens group and the second lens group decreases at bass and the second lens group moves toward the object side and the interval between the second lens group and the third lens group increases, As shown in FIG.

Description

Zoom lens {Zoom lens}

A zoom lens having a small size, a large magnification and an ultra-wide angle used for an imaging optical apparatus is disclosed.

2. Description of the Related Art Recently, digital cameras and video cameras having solid-state image pickup devices such as a CCD (Charge Coupled Device) and a CMOS (Complementary Metal-Oxide Semiconductor) have been widely used. Particularly, the demand for mega pixel camera modules is increasing, and in the entry level digital cameras, more than 5 million pixels and high quality performance are emerging. An imaging optical apparatus such as a digital camera or a mobile phone camera using an imaging device such as a CCD or CMOS is required to be downsized, lightweight, and low in cost. Furthermore, there is an increasing demand for a wide angle range to capture a wider range of subjects.

According to an embodiment of the present invention, there is provided a zoom lens having a small size, a high magnification, and an ultra wide angle.

According to an embodiment of the present invention, there is provided a zoom lens comprising, in order from an object side, a first lens group having negative refractive power, a second lens group having positive refractive power, and a third lens group having positive refractive power, To the telephoto end, the distance between the first lens group and the second lens group decreases, the second lens group moves toward the object side, the interval 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 satisfying the following condition.

<Conditional expression>

2.65 < ft / fw < 4.5

80 ° ≤ wfov

Here, ft represents the focal length at the telephoto end, fw represents the focal length at the wide-angle end, and fov represents the angle of view at the wide-angle end.

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

<Conditional expression>

(ndG1) / m > 1.9

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

Wherein the first lens group includes a first lens having a negative refractive power, a second lens having a negative refractive power, and a third lens having a positive refractive power, wherein the first lens, the second lens, It can have a convex meniscus shape.

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

The third lens group includes a single lens.

And the second lens group moves vertically with respect to the optical axis to perform camera shake correction.

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

1, a zoom lens according to an embodiment of the present invention includes a first lens group G1 having a negative refractive power and a second lens group G2 having a positive refractive power, which are arranged in order from the object side O to the image side I, A second lens group G2, and a third lens group G3 having a positive refractive power. The distance between the first lens group 1 and the second lens group G2 decreases at the time of changing from the wide angle end to the telephoto end and the second lens group G2 moves to the object side O, The interval between the third lens group G2 and the third lens group G3 increases. In the zoom lens according to the embodiment of the present invention, the first to third lens groups G1, G2 and G3 are all moved during variable magnification, and the third lens group G3 performs focusing according to the object distance.

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

According to the embodiment of the present invention, in order to realize high-magnification wide angle imaging, the lens is made of a three-group type and the number of lenses is reduced, thereby reducing the lens barrel size and minimizing the use of aspherical surfaces.

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

2.65 < ft / fw < 4.5

 Here, ft is the focal length of the telephoto end, and fw is the focal length of the wide-angle end.

80 ° ≤ wfov

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

The first lens group G1 includes a high-refractive-index spherical lens to increase the power of the first lens group, thereby realizing an ultra-wide angle. The first lens group G1 may be configured to satisfy the following condition for super-wide angle imaging.

(ndG1) / m > 1.9

Here, ndG1 represents the sum of the refractive indexes of the lenses constituting the first lens group, and m represents the number of lenses constituting the first lens group G1. In other words, (ndG1) / m represents the average refractive index of the first lens unit. According to an embodiment of the present invention, the first lens group includes three lenses, and the value obtained by dividing the sum of the refractive indexes of the three lenses by 3 is 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 with an aspherical surface. Further, the second lens group G2 is provided with one cemented lens, and the aspherical surface and the cemented lens are provided in this manner, thereby miniaturizing the lens and reducing the cost. According to an embodiment of the present invention, the second lens group G2 is moved in a direction perpendicular to the optical axis to implement the camera shake correction.

The definitions of aspherical surfaces in the embodiment of the present invention are as follows.

The aspheric surface shape of the zoom lens according to the present invention can be expressed by the following equation with the advancing direction of the light ray as a positive direction when the optical axis direction is the x axis and the direction perpendicular to the optical axis direction is the y axis. Where x is the distance from the vertex of the lens to the optical axis direction, y is the distance in the direction perpendicular to the optical axis, k is a conic constant, A, B, C and D are aspheric coefficients, and c represents the inverse number (1 / R) of the radius of curvature at the apex of the lens.

In the present invention, ultraviolet light of the zoom lens is realized by various embodiments according to various designs as follows.

Hereinafter, f denotes the combined focal length of the entire lens system, Fno denotes the F number, 2 denotes the angle of view, R denotes the radius of curvature, Dn denotes the center thickness of the lens or the distance between the lens and the lens, vd represents Abbe number, respectively. In addition, ST represents an aperture, D1, D2 and D3 represent variable distances, and * represents an aspherical surface.

&Lt; Embodiment 1 >

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

   Lens surface 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 1.45650 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 is an 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 distance at the wide angle end, the middle end, and the telephoto end in the first embodiment.

 Variable Distance Wide Angle Short Middle Telephoto

D1 26.016 9.902 3.904

D2 7.625 9.496 12.264

D3 0.552 1.116 0.877

&Lt; Embodiment 2 >

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

 Lens surface 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 is 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 distance at the wide angle end, the middle end, and the telephoto end in the second embodiment.

Variable Distance Wide Angle Short Middle Telephoto

D1 20.768 7.766 0.900

D2 5.402 7.711 17.981

D3 2.717 3.571 1.800

&Lt; Third Embodiment >

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

Lens surface 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 1.49980 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 1.45650 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 is 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 distance at the wide angle end, the middle end, and the telephoto end in the third embodiment.

 Variable Distance Wide Angle Short Middle Telephoto

   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 achieves miniaturization while securing an angle of view of 80 DEG or more at the wide angle end. By implementing the super wide angle in this manner, the subject can be photographed in a wider range. The zoom lens according to the embodiment of the present invention can be suitably used in a digital still camera, a video camera, a portable terminal, etc. using a solid-state image pickup device such as CCD or CMOS.

The above-described embodiments are merely illustrative, and various modifications and equivalent other embodiments are possible without departing from the scope of the present invention. Therefore, the scope of the true technical protection according to the embodiment of the present invention should be determined by the technical idea of the invention described in the following claims.

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

2A shows an aberration diagram at a wide angle end of a zoom lens according to a first embodiment of the present invention.

FIG. 2B illustrates an aberration diagram at the telephoto end of the zoom lens according to the first embodiment of the present invention.

3A shows an aberration diagram at a wide angle end of a zoom lens according to a second embodiment of the present invention.

3B is an aberration diagram at the telephoto end of the zoom lens according to the second embodiment of the present invention.

4A is an aberration diagram of the zoom lens according to the third embodiment of the present invention at a wide angle end.

FIG. 4B illustrates an aberration diagram at the telephoto end of the zoom lens according to the third embodiment of the present invention.

Claims (6)

A second lens group having positive refractive power, and a third lens group having positive refractive power, the first lens group having negative refractive power, the second lens group having positive refractive power, and the third lens group having positive refractive power, The distance between the lens unit and the second lens unit decreases, the second lens unit moves toward the object side, the interval between the second lens unit and the third lens unit increases, and the third lens unit performs focusing according to the object distance And, Wherein the second lens group comprises at least one cemented lens and at least one aspherical lens, wherein the second lens group comprises, in order from the object side, a fourth lens having positive refractive power, a fifth lens and a sixth lens, A zoom lens satisfying the following conditions. <Conditional expression> 2.65 < ft / fw < 4.5 80 ° ≤ wfov Here, ft represents the focal length at the telephoto end, fw represents the focal length at the wide-angle end, and fov represents the angle of view at the wide-angle end. The method according to claim 1, Wherein the first lens group satisfies the following condition. <Conditional expression> (ndG1) / m > 1.9 Here, ndG1 represents the sum of the refractive indexes of the lenses constituting the first lens group, and m represents the number of lenses constituting the first lens group. The method according to claim 1, Wherein the first lens group includes a first lens having a negative refractive power, a second lens having a negative refractive power, and a third lens having a positive refractive power, wherein the first lens, the second lens, A zoom lens having a convex meniscus shape. delete The method according to claim 1, And the third lens group includes one lens. The method according to any one of claims 1, 2, 3, or 5, And the second lens group moves vertically with respect to the optical axis to perform camera-shake correction.

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