KR20110056105A - Zoom lens and image pickup apparatus having the same - Google Patents

Abstract

PURPOSE: A zoom lens and image photographing apparatus with the same are provided to inexpensively satisfy various demands of a user. CONSTITUTION: A first lens group(G1), a second lens group(G2), a third lens group(G3), and a fourth lens group(G4) are successively arranged from an object side(O) toward an image side(I). The first lens group, the third lens group, and the fourth lens group have plus refraction power. The second lens group has minus refraction power. The gap between the first lens group and the second lens group gets wider, the gap between the second lens group and the third lens group gets narrower, and the fourth lens group moves upward when a zoom lens makes zooming from a wide angle end to a telescopic end.

Description

Zoom lens and image pickup apparatus having the same {Zoom lens and image pickup apparatus having the same}

The present invention relates to a zoom lens and an imaging device having the same.

The spread of imaging devices such as digital cameras and video cameras with solid-state imaging devices such as CCDs and CMOS is expanding. There is an increasing demand for a camera that requires high-pixel and high-definition performance, and a lens system having a high zoom magnification has been developed. In recent years, portability has been emphasized along with the growth of digital cameras, and miniaturization has become an important factor in lens system development. Due to the limitation of miniaturization of imaging sensors and electronic components, miniaturization of the lens system has become a key task in realizing compact and compact cameras.

In order to realize the compactness of the camera, a penetrating barrel system is frequently used in which the lens is fixed to a predetermined position when the camera is photographed and stored inside the camera when the camera is not photographed. In the case of the penetrating barrel, the distance between the lens groups should be as narrow as possible during storage to reduce the thickness of the camera and improve portability. In order to realize miniaturization and thinning in the penetrating barrel, the number of lens groups must be reduced, and the composition of the lens group must be small while satisfying the high optical performance according to the high pixel size.

The present invention provides a compact zoom lens and an imaging device having the same.

According to an embodiment of the present invention, the first lens group having positive refractive power, the second lens group having negative refractive power, the third lens group having positive refractive power, and the positive refractive power are arranged in order from the object side. Including a four lens group, when zooming, the distance between the first lens group and the second lens group is increased, the distance between the second lens group and the third lens group is narrowed, the fourth lens group is moved to the image side The second lens group includes a negative lens and a positive lens, and provides a zoom lens that satisfies the following.

<Expression>

5 <ft / fw <50

1.88 <n _2n <2.3

15 <v _2n <36

Where fw is the total focal length at the wide end, ft is the total focal length at the telephoto end, n _2n is the refractive index of the negative lens of the second lens group, and v _2n is the Abbe of the negative lens of the second lens group. Indicates a number.

The positive lens of the second lens group may satisfy the following equation.

<Expression>

1.9 <n _2p <2.4

0 <v _2p <30

Here, n _2p represents the refractive index of the positive lens of the second lens group, and v _2p represents the Abbe number of the positive lens of the second lens group.

The first lens group may include a negative lens and a positive lens.

The third lens group may include a junction lens including a positive lens, a positive lens, and a negative lens in order from an object side.

The fourth lens group may include one positive lens.

An imaging apparatus according to an embodiment of the present invention includes a zoom lens and an imaging sensor for converting light focused by the zoom lens into an electrical image signal, wherein the zoom lens includes:

Arranged in order from the object side, the first lens group having positive refractive power, the second lens group having negative refractive power, the third lens group having positive refractive power, and the fourth lens group having positive refractive power, The interval between the first lens group and the second lens group is increased, the distance between the second lens group and the third lens group is narrowed, the fourth lens group moves to the image side, and the second lens group is the negative lens. An imaging device including a positive lens and satisfying the following is provided.

<Expression>

5 <ft / fw <50

1.88 <n _2n <2.3

15 <v _2n <36

Where fw is the total focal length at the wide end, ft is the total focal length at the telephoto end, n _2n is the refractive index of the negative lens of the second lens group, and v _2n is the Abbe of the negative lens of the second lens group. Indicates a number.

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

1 illustrates a zoom lens according to an embodiment of the present invention. The zoom lenses according to the embodiment of the present invention are sequentially arranged from the object side (O) to the image side (I), and have a first lens group G1 having positive refractive power and a second lens group G2 having negative refractive power. And a third lens group G3 having positive refractive power and a fourth lens group G4 having positive refractive power. The zoom lens according to the embodiment of the present invention increases the distance between the first lens group G1 and the second lens group G2 when zooming from the wide-angle end to the telephoto end, and the second lens group G2 and the third lens. The interval of the group G3 can be narrowed. The fourth lens group G4 moves to the image side I during zooming.

The first lens group G1 may include a first lens 1 having negative refractive power and a second lens 2 having positive refractive power. The second lens group G2 may include a third lens 3 having negative refractive power and a fourth lens 4 having positive refractive power. The third lens 3 may have a concave lens shape, and the fourth lens 4 may have a convex shape toward the object side (O). However, the shape of the lens included in the second lens group is not limited thereto. In the present invention, the second lens group G2 includes two lenses to reduce the thickness on the optical axis, and contribute to reducing the sum of the thicknesses of the entire lens groups when stored. Each of the negative lens and the positive lens of the second lens group G2 may have at least one aspherical surface.

The third lens group G3 may include a fifth lens 5 having positive refractive power, a sixth lens 6 having positive refractive power, and a seventh lens 7 having negative refractive power. The third lens group G3 may include an aperture stop ST. The third lens group G3 may be responsible for shifting during zooming. When zooming, the aperture stop ST may move together with the third lens group G3. The fifth lens 5 may have a convex shape toward the object side (O). The sixth lens 6 and the seventh lens 7 may be composed of a bonded lens, and may have positive refractive power as a whole. The third lens group G3 may include at least one aspherical lens to correct aberrations at zooming. In addition, the third lens group may move in a direction perpendicular to the optical axis to perform image stabilization.

The fourth lens group G4 may include an eighth lens 8 having positive refractive power. The fourth lens group G4 performs focusing at zooming and improves telecentric characteristics.

In the zoom lens according to the exemplary embodiment of the present invention, an aspherical surface may be used for at least one lens of the second lens group G2 in order to reduce the sum of the distance and thickness of each lens group as much as possible. At least one of the third lens 4 and the fourth lens 4 may include an aspherical surface. The third lens 4 and the fourth lens 4 are made of a high refractive material to reduce the thickness of each lens. Generally, the minimum required lens thickness for an aspherical lens is about 1/10 of the outer diameter, and the thickness for securing optical performance is getting thinner, but considering the optical performance and processing, there is a limit to reducing the thickness. In the present invention, the second lens group G2 includes a high refractive aspherical lens to achieve miniaturization and to correct the performance degradation due to the stockpile. In addition, in the present invention, it is possible to correct the distorted image by the computer. Distortion aberration is an aberration caused by the angle of view, which allows distortion aberration at the wide-angle end corresponding to the correction amount by the computer, thereby reducing the diameter of the lens and the optical length. The distortion tolerance may range from -10 to -50%.

In the zoom lens according to the present invention, the ratio of the total focal length ft at the telephoto end and the total focal length fw at the wide angle end may have a range of the following equation.

5 <ft / fw <50

The second lens group G2 may satisfy the following.

1.88 <n _2n <2.3

15 <v _2n <36

Here, n _2n represents the refractive index of the negative lens of the second lens group, and v _2n represents the Abbe number of the negative lens of the second lens group.

The second lens group G2 includes two lenses, a negative lens and a positive lens, to reduce the thickness on the optical axis and to suppress the occurrence of aberration so as to maintain high optical performance for the entire zooming region even during zooming. There is. When the negative lens of the second lens group G2 is formed of an optical material satisfying Equations 2 and 3, even if the lens curvature of the negative lens of the second lens group G2 is not increased, It is easy to correct the upper surface curvature. Here, it may be difficult to secure a material that exceeds the upper limit of the equation (2). When the negative lens of the second lens group G2 exceeds the lower limit of Equation 2, the lens curvature of the negative lens of the second lens group becomes large, which is disadvantageous in miniaturization of the lens. Equation 3 is for correcting the axial and magnification chromatic aberration, but when v _2n exceeds the upper limit, it is advantageous to correct the chromatic aberration, but the refractive index is small, which increases the curvature of the lens, which is disadvantageous for thinning the axial and edge thickness of the lens. easy. When the lower limit of Equation 3 is exceeded, the refractive index of the lens may increase, and securing of the material may be difficult.

The positive lens of the second lens group G2 may satisfy the following.

1.9 <n _2p <2.4

0 <v _2p <30

Here, n _2p represents the refractive index of the positive lens of the second lens group, and v _2p represents the Abbe number of the positive lens of the second lens group.

When the positive lens of the second lens group satisfies Equation 4, the lens curvature of the positive lens of the second lens group may be moderated. When the Abbe number of the positive lens of the second lens group exceeds the upper limit of Equation 5, the dispersion becomes small, making chromatic aberration correction difficult when combined with the negative lens of the second lens group, and the refractive index tends to be low. When the Abbe number of the positive lens of the second lens group exceeds the lower limit of the equation (5), dispersion is large and chromatic aberration easily occurs.

On the other hand, the definition of the aspherical surface used for the zoom lens of the present invention is as follows.

The aspherical shape can be expressed by the following equation with the x-axis as the optical axis and the y-axis as the direction perpendicular to the optical axis. 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.

The following shows an embodiment according to various designs of the zoom lens of the present invention. f is the total focal length, 2ω is the angle of view, Fno is the F number, nd is the refractive index, vd is the Abbe number, and D1, D2, D3, and D4 are variable distances. In the drawings of each embodiment, the same reference numerals are given to the respective lenses, and P1 and P2 denote filters and cover glasses.

<First Embodiment>

1 shows a zoom lens of the first embodiment.

f; 5.47 ~ 13.12 ~ 36.37 Fno; 3.03 kPa-3.53 kPa-5.99 kPa 2ωk; 71.2 ~ 33.16 ~ 12.34

Lens surface Radius of curvature thickness nd vd S1 18.927 0.60 1.92558 29.65 S2 11.503 0.00 S3 11.503 2.54 1.70877 52.7 S4 382.755 A S5 -16.671 0.93 1.91082 35.25 S6 6.269 1.04 S7 11.751 1.45 2.1435 17.8 S8 51.504 B S9 0.000 0.00 S10 4.877 1.35 1.63747 58.47 S11 -26.119 0.12 S12 10.490 1.22 1.81996 44.11 S13 -8.508 0.50 1.70439 32.02 S14 3.420 C S15 27.771 2.04 1.46507 87.06 S16 -10.488 D S17 0 0.30 1.5168 64.2 S18 0 0.30 S19 0 0.50 1.5168 64.2 S20 0 E

The following shows the aspherical coefficients.

Lens surface K A B C D S5 0.9632 2.9767E-04 -8.8024E-07 -1.8932E-08 0.0000E + 00 S6 -3.9098 1.5947E-03 -3.3929E-05 1.3537E-06 -2.5359E-08 S7 0.0000 -3.7748E-05 3.6698E-06 1.2750E-08 2.7746E-09 S8 -27.4455 -5.2380E-05 -8.7677E-07 2.5835E-08 0.0000E + 00 S10 -1.0595 1.0268E-04 -5.4514E-06 3.0642E-06 -3.3110E-07 S11 9.0634 4.9967E-04 -1.5528E-05 4.1203E-06 -4.2635E-07 S15 7.9755 3.1523E-04 -9.1026E-06 7.2032E-08 0.0000E + 00 S16 -4.3818 3.1636E-04 -2.0186E-05 2.3505E-07 9.1630E-10

Variable distance Wide angle Middle stage 1 Middle stage 2 Middle stage 3 Telephoto D1 1.112 2.781 6.524 12.214 14.021 D2 15.202 10.200 6.696 2.883 0.789 D3 3.635 5.977 9.476 13.709 17.271 D4 4.132 4.207 3.806 2.955 2.000

2A and 2B illustrate longitudinal spherical aberration, astigmatic field curvature, and distortion at the wide-angle end and the telephoto end of the zoom lens according to the first embodiment. In the boiling point curve, the solid line represents the aberration for the sagittal top surface, and the dotted line represents the aberration for the tangential top surface.

Second Embodiment

3 shows a zoom lens according to a second embodiment.

f; 5 ~ 14.5 ~ 46.7 Fno; 3.11 ~ 4.86 ~ 6.32 2ω; 74.6 ~ 29.6 ~ 9.5

Lens surface Radius of curvature thickness nd Vd S1 16.029 0.50 1.90098 37.02 S2 10.350 0.65 S3 10.728 2.75 1.56978 70.99 S4 -69.688 A S5 -15.835 0.90 1.96 33.3 S6 5.108 0.95 S7 10.193 1.43 2.1417 17.8 S8 77.452 B S9 4.880 2.22 1.59202 67.01 S10 -15.684 0.10 S11 5.244 1.20 1.7317 54.3 S12 -15.511 0.40 1.87649 35.76 S13 3.200 C S14 21.500 1.90 1.4586 90.19 S15 -12.836 D S16 infinity 0.30 1.5168 64.2 S17 infinity 0.30 S18 infinity 0.50 1.5168 64.2 S19 infinity E

Lens surface K A B C D S5 3.7776 2.1065E-04 7.5061E-06 -1.3040E-07 8.2293E-25 S6 -3.1694 1.3458E-03 -3.0824E-06 2.0826E-06 -9.3481E-08 S7 -3.5234 -1.7827E-04 2.8692E-05 5.9427E-08 -1.4280E-24 S8 0.0000 -3.6295E-04 3.0126E-06 1.7805E-07 0.0000E + 00 S9 -1.0000 2.4082E-04 5.2713E-06 -1.2469E-21 0.0000E + 00 S10 15.0676 8.8645E-04 2.6459E-05 -1.0023E-07 0.0000E + 00 S14 -4.2606 7.5424E-04 -6.1913E-05 4.2092E-06 -9.8185E-08 S15 -26.5435 -1.5276E-04 -4.4479E-05 3.8716E-06 -9.5743E-08

Variable distance Wide angle Middle stage 1 Middle stage 2 Middle stage 3 Telephoto D1 0.695 2.776 6.742 13.597 16.100 D2 14.865 9.349 6.257 2.554 0.360 D3 3.675 7.936 10.963 14.753 16.990 D4 3.615 3.337 3.628 3.182 2.000

4A and 4B illustrate longitudinal spherical aberration, astigmatic field curvature, and distortion at the wide-angle end and the telephoto end of the zoom lens according to the second embodiment.

Third Embodiment

5 shows a zoom lens according to the third embodiment.

f; 5.5 ~ 17.3 ~ 49.1 Fno; 3.05 to 4.53 to 6.40 2 ω; 69.7 ~ 25 ~ 9.1

Lens surface Radius of curvature thickness nd Vd S1 20.989 0.50 2.00126 23.37 S2 15.273 0.35 S3 16.050 2.63 1.72916 54.67 S4 991.094 A S5 -15.969 0.83 1.961 33.5 S6 6.272 1.08 S7 14.440 1.51 2.14179 17.8 S8 -518.966 B S9 4.914 1.38 1.67507 55.66 S10 -25.306 0.12 S11 9.081 1.32 1.74631 46.85 S12 -6.771 0.40 1.74814 33.3 S13 3.413 C S14 36.082 1.73 1.4971 81.56 S15 -12.170 D S16 infinity 0.30 1.5168 64.2 S17 infinity 0.30 S18 infinity 0.50 1.5168 64.2 S19 infinity E

Lens surface K A B C D S5 3.5685 2.1380E-04 3.3651E-06 -2.0270E-08 0.0000E + 00 S6 -3.6128 1.2487E-03 -2.9075E-05 1.2630E-06 -2.5674E-08 S7 0.0000 -9.1653E-05 9.1106E-06 4.8871E-08 0.0000E + 00 S8 0.0000 -1.8813E-04 5.3589E-06 -3.8586E-08 0.0000E + 00 S9 -1.0000 2.0912E-04 4.5319E-06 0.0000E + 00 0.0000E + 00 S10 33.7311 6.5061E-04 7.2674E-07 3.5774E-07 0.0000E + 00 S14 18.4608 5.5721E-04 -2.2077E-05 1.0201E-06 -2.7150E-08 S15 -14.1557 1.4558E-04 -1.0813E-05 5.5679E-07 -1.9143E-08

Variable distance Wide angle Middle stage 1 Middle stage 2 Middle stage 3 Telephoto D1 1.027 5.221 10.549 14.970 17.511 D2 16.435 10.931 6.896 2.368 0.350 D3 4.748 7.921 12.276 18.414 20.439 D4 4.191 4.028 3.345 2.927 2.000

6A and 6B illustrate longitudinal spherical aberration, astigmatic field curvature, and distortion at the wide-angle end and the telephoto end of the zoom lens according to the third embodiment.

<Fourth Embodiment>

7 shows a zoom lens according to the fourth embodiment.

f; 5 ~ 14.5 ~ 46.6 Fno; 3.14 ~ 4.85 ~ 6.29 2ω; 74.9 ~ 29.6 ~ 9.6

Lens surface Radius of curvature thickness nd vd S1 15.717 0.50 1.89857 37.48 S2 10.269 0.66 S3 10.638 2.74 1.5566 72.52 S4 -67.627 A S5 -15.730 0.90 1.95265 33.59 S6 5.138 0.95 S7 10.108 1.41 2.14352 17.77 S8 64.271 B S9 4.887 2.21 1.59201 67.02 S10 -15.180 0.10 S11 5.256 1.18 1.73723 53.4 S12 -16.886 0.41 1.88011 35.29 S13 3.193 C S14 24.589 1.88 1.4586 90.19 S15 -12.004 D S16 infinity 0.80 1.5168 64.2 S17 infinity 0.00 S18 infinity 0.00 S19 infinity E

Lens surface K A B C D S5 3.5553 2.2673E-04 6.8639E-06 -1.2483E-07 -5.6665E-26 S6 -3.1141 1.3147E-03 -2.4214E-06 2.1671E-06 -9.5876E-08 S7 -3.4175 -1.7199E-04 2.7938E-05 -1.2280E-09 -1.9313E-26 S8 0.0000 -3.5182E-04 2.4682E-06 1.1767E-07 0.0000E + 00 S9 -1.0000 2.0913E-04 -4.0986E-06 -6.7536E-23 0.0000E + 00 S10 11.9115 8.0891E-04 9.9169E-06 0.0000E + 00 0.0000E + 00 S14 -6.2519 7.3118E-04 -6.0274E-05 4.2424E-06 -1.0592E-07 S15 -21.0508 -1.5569E-04 -4.1367E-05 3.6833E-06 -9.7465E-08

Variable distance Wide angle Middle stage 1 Middle stage 2 Middle stage 3 Telephoto D1 0.698 2.634 6.739 13.478 16.196 D2 14.868 9.308 6.256 2.568 0.360 D3 3.745 7.797 10.992 15.015 16.878 D4 3.843 3.657 3.800 3.388 2.290

Next, the present invention shows that each embodiment satisfies the equations 1,2,3,4,5.

First embodiment Second embodiment Third embodiment Fourth embodiment Equation 1 (ft / fw) 6.65 9.315 8.91 9.315 Equation 2 1.91082 1.960 1.961 1.95265 Equation 3 35.25 33.3 33.5 33.59 Equation 4 2.1435 2.1417 2.14179 2.14352 Math Poetry 5 17.8 17.8 17.8 17.77

The zoom lens according to the embodiment of the present invention has a high zoom ratio and realizes miniaturization. The zoom lens according to the embodiment of the present invention can be suitably used for an imaging device such as a digital still camera, a video camera, a portable terminal, or the like using a solid state imaging device such as a CCD or a CMOS.

9 illustrates an image capturing apparatus 100 including a zoom lens 111 according to an exemplary embodiment of the present invention. The imaging device includes a zoom lens 111 described in accordance with an embodiment, and an imaging sensor 112 for converting the light focused by the zoom lens 111 into an electrical image signal. The imaging apparatus 100 may include recording means 113 on which information corresponding to a photoelectrically converted object is recorded from the imaging sensor 112, and a viewfinder 114 for observing the subject image. Can be. In addition, the display unit 115 displaying the subject image may be provided. Here, an example in which the view finder 114 and the display unit 115 are provided separately, but only the display unit may be provided without the view finder. The imaging device shown in FIG. 10 is only an example and is not limited thereto. The imaging device shown in FIG. 10 may be applied to various optical devices other than a camera. By applying the zoom lens of the present invention to an imaging device such as a digital camera as described above, an optical device that is compact, inexpensive, bright and capable of wide-angle imaging is provided.

The imaging apparatus according to the embodiment of the present invention can satisfy various needs of the user at low cost by simply replacing some lens groups to implement various focal lengths without replacing the entire lens system. In addition, since it is not necessary to carry a lens system having two types of focal lengths separately, a user can use the imaging device of the present invention very conveniently.

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 a first 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.

3 is a block diagram of a zoom lens according to a second embodiment of the present invention.

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

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

5 is a configuration diagram of a zoom lens according to a third embodiment of the present invention.

6A illustrates aberration diagrams at wide-angle ends of a zoom lens according to a third exemplary embodiment of the present invention.

6B illustrates aberration diagrams at a telephoto end of a zoom lens according to a third exemplary embodiment of the present invention.

7 is a configuration diagram of a zoom lens according to a fourth embodiment of the present invention.

8A illustrates aberration diagrams at wide-angle ends of a zoom lens according to a fourth exemplary embodiment of the present invention.

8B illustrates aberration diagrams at a telephoto end of a zoom lens according to a fourth exemplary embodiment of the present invention.

9 shows an imaging device according to an embodiment of the present invention.

<Description of main part of drawing>

G1 ... 1st lens group, G2 ... 2nd lens group

G3 ... 3rd lens group, G4 ... 4th lens group

Claims (10)

Arranged in order from the object side, the first lens group having positive refractive power, the second lens group having negative refractive power, the third lens group having positive refractive power, and the fourth lens group having positive refractive power, The interval between the first lens group and the second lens group is increased, the distance between the second lens group and the third lens group is narrowed, the fourth lens group moves to the image side, and the second lens group is the negative lens. And a zoom lens including a positive lens and satisfying the following. <Expression> 5 <ft / fw <50 1.88 <n _2n <2.3 15 <v _2n <36 Where fw is the total focal length at the wide end, ft is the total focal length at the telephoto end, n _2n is the refractive index of the negative lens of the second lens group, and v _2n is the Abbe of the negative lens of the second lens group. Indicates a number. The method of claim 1, The positive lens of the second lens group satisfies the following equation. <Expression> 1.9 <n _2p <2.4 0 <v _2p <30 Here, n _2p represents the refractive index of the positive lens of the second lens group, and v _2p represents the Abbe number of the positive lens of the second lens group. The method according to claim 1 or 2, The first lens group includes a negative lens and a positive lens. The method according to claim 1 or 2, The third lens group includes a zoom lens including a positive lens, a positive lens, and a negative lens in order from an object side. The method according to claim 1 or 2, The fourth lens group includes a positive lens. The method of claim 5, The fourth lens group is a zoom lens for performing focusing at zooming. The method according to claim 1 or 2, The zoom lens and the positive lens of the second lens group each have at least one aspherical surface. The method according to claim 1 or 2, The third lens group is a zoom lens for performing image stabilization. The method according to claim 1 or 2, The zoom lens has a distortion tolerance range of -10 to -50%. The zoom lens according to claim 1 or 2; And And an imaging sensor for converting the light focused by the zoom lens into an electrical image signal.

Images