KR101553837B1 - Small zoom optical system - Google Patents

Abstract

A zoom optical system is disclosed. A zoom lens system comprising: a first lens group which is sequentially arranged from an object side to an image side, the first lens group having a negative refracting power and composed of one negative lens and a positive lens having at least one aspheric surface; A second lens group having a positive refractive power; And a third lens group having a positive refractive power, wherein when zooming from the wide angle end to the telephoto end, the distance between the first lens group and the second lens group is narrowed in the direction of narrowing the distance between the first lens group and the second lens group The lens group moves, the third lens group moves upward, and the following conditional expression is satisfied.

Where f _I, f _w , f _t, the focal length of each of the first lens group, denotes the entire focal length of the overall focal length and the telephoto end of the wide-angle end, _1p N represents the refractive index of the positive lens of the first lens unit.

Description

Compact zoom optics < RTI ID = 0.0 >

The disclosed zooming optical system relates to a zooming optical system which is a small-sized compact structure and realizes a high magnification and a wide angle.

2. Description of the Related Art In recent years, imaging optical devices such as digital cameras or digital camcorders using imaging devices such as CCD (Charge Coupled Device) and CMOS (Complementary Metal-Oxide Semiconductor) have been rapidly expanding and spreading. Such an imaging optical apparatus is required to have a high magnification and a wide angle of view, and at the same time, it is required to have a high performance, a small size, a light weight and a low cost.

In order to satisfy the demand for miniaturization, the lens is led to a certain position at the time of photographing the camera, and the barrel-type lens barrel is stored at the inside of the camera when not shooting. Such an infant-type camera is required to narrow the interval of each lens group as much as possible in order to reduce the thickness of the camera and improve the portability. In order to realize miniaturization and thinning of the telescopic tube, the number of lens groups must be reduced, and at the same time, the optical system should be designed so as to secure high optical performance due to high-definition.

According to the above-mentioned necessity, embodiments of the present invention are intended to provide a zoom optical system that is downsized and realizes a wide angle and a high magnification.

A zooming optical system according to an embodiment of the present invention is a zooming optical system 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 having at least one aspheric surface, A second lens group having a positive refractive power; And a third lens group having a positive refractive power, wherein when zooming from the wide angle end to the telephoto end, the distance between the first lens group and the second lens group is narrowed in the direction of narrowing the distance between the first lens group and the second lens group The lens group moves, the third lens group moves upward, and the following conditional expression is satisfied.

Where f _I, f _w , f _t, the focal length of each of the first lens group, denotes the entire focal length of the overall focal length and the telephoto end of the wide-angle end, _1p N represents the refractive index of the positive lens of the first lens unit.

The second lens group may use an aspherical surface on at least one surface.

The second lens group may include a positive lens of a convex shape on the object side, a cemented lens of a positive lens and a negative lens, and a negative lens of a convex shape on the object side, which are arranged in order from the object side.

At least one surface of the positive lens and the negative lens of the convex shape on the object side may be formed as an aspheric surface.

The third lens group may be composed of a single 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 and 3 are diagrams showing optical arrangements at the wide angle end, the middle end, and the telephoto end of the zoom optical system according to the first and second embodiments of the present invention, respectively. Referring to the drawings, the zoom optical system includes a first lens group G1 having a negative refractive power, a second lens group G2 having a positive refractive power, and a second lens group G2 having a positive refractive power, which are arranged in order from the object O side to the image I side. And a third lens group G3 having refractive power.

In the zoom optical system according to the embodiments of the present invention, the first lens group G1 and the second lens group G2 move when zooming from the wide-angle end to the telephoto end, specifically, the second lens group G1, 2 lens group G2 is narrowed. Also, the third lens group G3 moves upward.

In the zoom optical system according to the embodiments of the present invention, the first lens group G1 may have negative refractive power, and may consist of one negative lens and a positive lens having at least one aspheric surface, .

Where f _I, f _w , f _t represents the focal length of the first lens group, the total focal length at the wide-angle end, and the total focal length at the telephoto end, respectively.

The above formula limits the ratio of the focal length of the first lens group G1 to the combined focal length at the wide-angle end and the telephoto end. The refractive power of the first lens group G1 is weakened and the refracting power of the second lens group G2 is strengthened in the range exceeding the upper limit and the moving amount of the second lens group G2 becomes large at the time of varying the magnification. On the other hand, the refractive power of the first lens group G1 becomes stronger when the lower limit of the above formula is exceeded, so that the refractive power of the positive lens having at least one aspheric surface in the first lens group G1 becomes strong, Can be.

Further, the zoom optical system of the embodiment of the present invention satisfies the following expression.

And N _1p represents the refractive index of the positive lens of the first lens group G1.

In the embodiment of the present invention, an aspherical surface is used for the positive lens of the first lens group G1, and a high refractive index material is used for the negative lens of the first lens group G1. Recently, various aspheric lens materials have been developed, and aspheric lenses having a refractive index of 1.9 or more can be used. It is advantageous to minimize the thickness of the first lens group G1 when the positive lens is composed of an aspherical lens using a high-refraction material. In addition, performance degradation due to stockpiling can be corrected, and a compact, high-performance zoom optical system can be constructed.

A more specific lens configuration will be described with reference to FIGS. 1 and 3. FIG.

The first lens group G1 includes two lenses, for example, a first lens 110 having a negative refractive power and a second lens 120 having a positive refractive power. At least one surface of the lens constituting the first lens group G1 may be an aspherical surface, and for example, an aspherical surface may be employed on at least one surface of the second lens 120, which is a positive lens. Also, the second lens 120 may be formed of a material having a refractive index of 1.9 or more.

This configuration of the first lens group 100-1 is for correcting the aberration of the stock while satisfactorily achieving miniaturization. When the number of lenses of the first lens group G2 is set to three or more, the number of lenses is minimized since the cost and storage size are adversely affected. In addition, the second lens 120, which is a positive lens, The thickness of the lens group G1 is minimized.

The second lens group G2 is a lens group that takes charge of magnification and may be composed of four lenses so as to realize a high magnification. The second lens group G2 includes, for example, a third lens 210 having a positive refractive power, a fourth lens 220 having a positive refractive power, a fifth lens 230 having a negative refractive power, 6 lens 240, and adopts a configuration that facilitates aberration control. The third lens 210, which is a positive lens, and the sixth lens 240, which is a negative lens, may have a convex shape toward the object side. The second lens group G2 includes at least one cemented lens. For example, a fourth lens 220, which is a positive lens, and a fifth lens 230, which is a negative lens, are joined to form a cemented lens. have. This is for chromatic aberration control. At least one of the lenses constituting the second lens group G2 is configured to include an aspherical surface. For example, each of the third lens 210 and the sixth lens 240 may have an aspherical surface So that the aberration can be well corrected even at the time of changing the position.

The third lens group G3 includes, for example, a seventh lens 310 having a positive refractive power, and focuses at the time of focusing to satisfy telecentricity characteristics. In addition, the number of lenses is minimized by adopting a single lens configuration.

The infrared filter 400 may be provided on the upper side of the third lens group G3.

In the zoom optical system according to the embodiment of the present invention, the lens system is structured such that each lens group is sequentially piled on a straight line. In this case, the thickness of the optical system when retracted is determined according to the number of lenses or the movement amount of the lens group. And the distance and the thickness sum of one lens group are minimized.

Hereinafter, specific lens data of various embodiments of the zoom optical system according to the present invention will be described. The definitions of aspheric surface (ASP) in the embodiments of the present invention are as follows.

Where k is a conic constant, A, B, C, and D are aspheric coefficients, c is an aspheric surface coefficient, (1 / R) of the radius of curvature at the apex of the lens.

In the following, f denotes the combined focal length of the entire zooming optical system, Fno denotes the F number, and 2ω denotes the angle of view. In addition, ST denotes an aperture, and * denotes an aspherical surface. D1, D2, and D3 denote the variable distances between the lens groups at the wide angle end, the middle end, and the telephoto end in each embodiment.

≪ Embodiment 1 >

1 shows the optical arrangement of the zoom optical system according to the first embodiment of the present invention. The following is lens data of the first embodiment.

f; 6.41 to 15.43 to 24.83 Fno; 2.81 ~ 4.54 ~ 6.34 2?; 62.68 to 28.60 to 18.14

if Radius of curvature thickness Refractive Index (nd) Abbe number (vd) One 402.958 0.7 1.88300 40.81 2 7.094 1.409 3 * 10.433 1.569 1.97997 20.93 4* 21.444 D1 5 infinity 0.3 6 * 6.549 1.488 1.80610 40.74 7 104.87 0.14 8 6.218 1.601 1.74279 49.81 9 -21.703 0.44 1.82154 24.62 10 3.436 0.392 11 * 5.077 1.304 1.84700 0.02 12 * 6.066 D2 13 -74.9 1.358 1.85649 26.84 14 -14.224 D3 15 infinity 0.8 1.51680 64.20 16 infinity

if K A B C D 3 -6.26290E-01 -1.18791E-04 -7.04337E-07 -1.21748E-07 0.00000E + 00 4 -1.18511E + 01 -1.56750E-04 -2.24638E-06 -2.02821E-07 1.22904E-09 6 -3.37561E-01 -6.50140E-05 4.28540E-06 -3.59779E-07 4.02435E-08 11 0.00000E + 00 8.65608E-04 -5.79223E-05 1.30612E-05 -5.15303E-06 12 0.00000E + 00 1.59666E-03 -3.52659E-05 3.48637E-06 -7.97884E-06

Wide Middle Tele D1 14.18 3.48 0.56 D2 3.40 10.92 18.30 D3 2.77 2.31 2.00

Figs. 2A and 2B show longitudinal spherical aberration, astigmatic field curvature, and distortion aberration at the wide-angle end and the telephoto end of the zoom optical system according to the first embodiment. The longitudinal spherical aberration is shown for the wavelengths of 656.30 (nm), 587.60 (nm), and 486.10 (nm), respectively. The surface curvature is represented by tangential field curvature (T) for the light with a wavelength of 587.60 ) And a sagittal field curvature (S), and the distortion is shown for light having a wavelength of 587.60 (nm).

≪ Embodiment 2 >

3 shows the optical arrangement of the zoom optical system according to the second embodiment of the present invention. The following is lens data of the second embodiment.

f; 6.22 to 14.98 to 24.08 Fno; 2.76 ~ 4.39 ~ 6.14 2?; 64.42 ~ 29.48 ~ 18.76

if Radius of curvature thickness Refractive Index (nd) Abbe number (vd) One 40.114 0.62 1.88300 40.8054 2 5.955 1.303 3 * 8.259 1.548 1.99537 20.7 4* 13.182 D1 5 infinity 0.3 6 * 5.938 1.527 1.77377 47.167 7 117.488 0.16 8 9.926 1.531 1.83991 43.6023 9 -8.828 0.44 1.76915 26.3974 10 4.133 0.111 11 * 4.014 0.927 1.85324 25.7237 12 * 4.192 D2 13 -29.875 1.833 1.90366 31.315 14 -12.36 D3 15 infinity 0.8 1.51680 64.1983 16 infinity

if K A B C D 3 -1.119911E + 00 -2.025622E-04 2.063970E-06 -2.276097E-07 0.000000E + 00 4 -8.868031E + 00 -1.806407E-04 -8.405172E-06 -6.536872E-08 -6.699034E-09 6 -2.831410E-01 -3.701152E-05 8.879997E-06 -1.364971E-06 1.151016E-07 11 0.000000E + 00 3.881585E-04 -2.255706E-04 3.608661E-05 -1.130083E-05 12 0.000000E + 00 2.816065E-03 -1.383257E-04 6.418838E-05 -2.206903E-05

Wide Middle Tele D1 13.50 3.29 0.66 D2 4.51 11.15 18.23 D3 2.44 2.46 2.05

Figs. 4A and 4B show longitudinal spherical aberration, astigmatic field curvature, and distortion aberration at the wide-angle end and the telephoto end of the zoom optical system according to the second embodiment. The longitudinal spherical aberration is shown for the wavelengths of 656.30 (nm), 587.60 (nm), and 486.10 (nm), respectively. The surface curvature is represented by tangential field curvature (T) for the light with a wavelength of 587.60 ) And sagittal field curvature (S), and the distortion is for light with a wavelength of 587.60 (nm).

Next, the above embodiments show that the conditional expressions (1) and (2) are satisfied, and the corresponding values are as follows.

First Embodiment Second Embodiment Conditional expression 1 1.2 1.13 Conditional expression 2 1.96987 1.99537

The zoom optical system of the present invention has a high optical power by realizing a high magnification and a wide angle while being miniaturized through the above-described lens configuration.

Although the zoom optical system 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 not limited to the above embodiments and various modifications and equivalent embodiments may be made by those skilled in the art I will understand the point. Accordingly, the true scope of the present invention should be determined by the appended claims.

1 is a diagram showing optical arrangements at a wide angle end, a middle end, and a telephoto end of a zoom optical system according to a first embodiment of the present invention.

2A and 2B are aberration diagrams showing spherical aberration, field curvature and distortion at the wide-angle end and the telephoto end of the zoom optical system according to the first embodiment of the present invention.

3 is a diagram showing the optical arrangement of the zoom optical system according to the second embodiment of the present invention at a wide angle end, a middle end, and a telephoto end.

4A and 4B are aberration diagrams showing spherical aberration, field curvature and distortion at the wide-angle end and the telephoto end of the zoom optical system according to the second embodiment of the present invention.

Claims (5)

Which are sequentially arranged from the object side to the image side, A first lens group having negative refractive power and made up of one negative lens and a positive lens having at least one aspheric surface; A second lens group having a positive refractive power; And And a third lens group having positive refractive power, The second lens group includes a positive lens of a convex shape on the object side, a cemented lens of a positive lens and a negative lens, and a negative lens convex on the object side, which are arranged in order from the object side, The first lens group and the second lens group move in a direction in which the distance between the first lens group and the second lens group is narrowed, and the third lens group moves upward And a zoom optical system satisfying the following conditional expression.

Where f _I, f _w , f _t, the focal length of each of the first lens group, denotes the entire focal length of the overall focal length and the telephoto end of the wide-angle end, _1p N represents the refractive index of the positive lens of the first lens unit. The method according to claim 1, And at least one lens of the second lens group includes an aspherical surface. delete The method according to claim 1, Wherein at least one surface of the positive lens and the negative lens of convex shape toward the object side is an aspherical surface. The method according to any one of claims 1, 2, and 4, And the third lens group is a single lens configuration.

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