KR20100056269A - Zoom lens - Google Patents

Abstract

PURPOSE: A zoom lens is provided to reduce eccentricity sensitivity between lenses by including a cemented lens. CONSTITUTION: A zoom lens comprises a first lens group(G1), a second lens group(G2), and a third lens group(G3). The first lens group has a negative refractive power. The second lens group has a positive refractive power. The third lens group has a positive refractive power. The magnification of the zoom lens is changed by movement from a wide angle end to a telescopic end. The interval(D1) of the second lens group and the first lens group decrease. The interval(D2) of the third lens group and the second lens group increase. The first lens group comprises two cemented lenses.

Description

Zoom lens

The present invention relates to a zoom lens.

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, demand for megapixel camera modules has been demanded, 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 a small size, light weight, and low cost.

In order to satisfy the demand for miniaturization, a penetrating barrel is often used to store the lens in a fixed position when the camera is photographed and to be stored inside the camera when the camera is not photographed. Such penetrating cameras should be as narrow as possible when storing the lens group, so that the thickness of the camera can be reduced and portability can be improved. In order to realize miniaturization and thinning in the penetrating barrel, the number of lens groups must be reduced. On the other hand, high optical performance due to high pixel size must be secured.

In order to satisfy this demand, a zoom lens composed of three lens groups is frequently used. A zoom lens system having a magnification ratio of two or more times and having a small photographing lens system includes a first lens group having negative refractive power in the order of the object side, a second lens group having positive refractive power as a whole, and a third lens group having positive refractive power A zoom lens system is known, which is configured to change the interval of each group at the time of shifting to perform shifting. However, it is difficult to satisfy both miniaturization and low cost while achieving high variable ratio.

It is an object of the present invention to provide a compact and low cost high magnification lens.

 According to an embodiment of the present invention, 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, in order from the object side,

When changing from the wide-angle end to the telephoto end, the distance between the first lens group and the second lens group is decreased, the distance between the second lens group and the third lens group is increased, and the zoom lens satisfies the following conditional expression. do.

<Conditional expression>

Where fw is the total focal length at the wide-angle end, L2w is the distance from the first lens surface of the second lens group to the image surface at the wide-angle end, and L2t is the object-side first of the second lens group at the telephoto end. The distance from the first lens surface to the image surface is respectively shown.

The first lens group includes two bonded lenses.

The first lens group may include only a spherical lens.

The object-side first surface of the first lens group may be concave with respect to the object-side.

The second lens group may be configured to include three bonded lenses.

The second lens group may include two or more aspherical lenses.

The third lens group may be composed of one aspherical lens.

The zoom lens according to the embodiment of the present invention can realize high zoom and miniaturization, and is easy to manufacture and assemble by reducing manufacturing sensitivity. In a small zoom lens, assembling is not easy due to high eccentricity between lenses, but in the present invention, a bonding lens is provided to reduce the eccentricity between lenses, thereby facilitating manufacture.

As shown in FIG. 1, the zoom lens according to the exemplary embodiment of the present invention includes a first lens group G1 having negative refractive power and a second lens group G2 having positive refractive power in order from the object side O. And a third lens group G3 having positive refractive power. The distance D1 between the first lens group G1 and the second lens group G2 decreases when the lens is shifted from the wide angle end to the telephoto end, and the second lens group G2 and the third lens group ( The interval D2 between G3) increases. On the other hand, image shift and focus position correction are performed by the third lens group G3.

The first lens group G1 may include the first lens 1 and the second lens 2 in order from the object side O. FIG. The first lens 1 may be a concave lens 1, and the second lens 2 may be configured as a meniscus positive lens that is convex toward the object side (O). It is possible to correct the distortion aberration that is very large without using an aspherical lens by concave the most object side surface of the first lens group G1, that is, the first lens 1 toward the object side. The first lens 1 and the second lens 2 may be composed of a bonding lens C1. In this way, it is possible to facilitate manufacture by preventing the occurrence of eccentricity between the lenses generated when the lens is assembled by the bonding lens. By using one or more aspherical lenses in the first lens group G1, it is possible to design to facilitate distortion aberration correction at the wide-angle end. However, recently, due to the development of software technology, distortion aberration can be corrected through software processing, and thus, the first lens group G1 can be configured by two spherical lenses which are easy to manufacture. The lens material cost can be reduced by configuring the first lens group G1 using only spherical lenses.

The second lens group G2 may include a third lens 3, a fourth lens 4, and a fifth lens 5 in order from the object side O. FIG. The aperture ST may be provided at the object side O of the third lens 3. The third lens 3 is composed of a biconvex aspherical positive lens, the fourth lens 4 is composed of a biconvex negative lens, and the fifth lens 5 is convex toward the object side O. It may be composed of a varnish aspherical positive lens. The third lens 4, the fourth lens 4 and the fifth lens 5 are composed of a bonded lens to reduce magnification chromatic aberration generated at the telephoto end. In order to secure a high magnification in the second lens group, the focal length of the second lens group may be shortened, and an aspherical lens and a bonded lens may be configured for spherical aberration and magnification chromatic aberration control. However, in such a small optical system, such a configuration is difficult to manufacture due to the high eccentric sensitivity between the lenses when the lens is assembled. In the present invention, three lenses are composed of the bonding lens C2, and the aberration correction is easily performed by using the object side surface of the third lens 3 and the image side surface of the fifth lens 5 as aspherical surfaces. With this configuration, it is possible to shorten the assembly time, increase productivity, and realize low cost. Meanwhile, spherical aberration can be minimized by using the third lens 3 as an aspherical lens. In the second lens group G2, two or more aspherical lenses are provided to facilitate spherical aberration correction and coma aberration correction.

The third lens group G3 includes a sixth lens 6. The sixth lens 6 uses a material having a refractive index of 1.8 or more to prevent the incident angle of the light beam from increasing and minimizes the chromatic aberration that occurs when correcting the image position due to the change in the position of the subject. In addition, the third lens group G3 uses an aspherical lens to facilitate astigmatism correction and distortion correction. Through such a configuration, it is possible to obtain an optical system having a small size, high performance, and high productivity in an indeterminate 3 group type. In general, when the optical system is designed to be very small, the eccentricity between the lenses increases when assembling the lens. In the present invention, assembling is facilitated by arranging the lenses of each lens group as a bonded lens or a single lens so that the eccentricity between the lenses is relatively small during assembly.

Meanwhile, the zoom lens according to the embodiment of the present invention satisfies the following Equation 1, where Equation 1 changes the position of the second lens group G2 and the focal length at the wide-angle end when shifting from the wide-angle end to the telephoto end. Rain is defined.

Where fw is the total focal length at the wide-angle end, L2w is the distance from the first lens surface of the second lens group to the image plane at the wide-angle end, and L2t is the object-side first of the second lens group at the telephoto end. The distance from the lens surface to the image surface is respectively shown.

When the upper limit of Equation 1 is exceeded, the shift amount of the second lens group is increased compared to the wide-angle end focal length, so that high magnification is easily secured, but it is difficult to make a small optical system. If it is less than the lower limit of Equation 1, it is difficult to secure a zoom magnification of 2.5 times or more, or the focal length of the second lens group G2 is very small, which increases manufacturing sensitivity, making manufacturing difficult. By satisfying the range of Equation 1 it is possible to secure a high zoom, to implement a small optical system, it is easy to manufacture low manufacturing sensitivity.

On the other hand, the definition of the aspherical surface in the embodiment of the present invention is as follows.

Aspherical shape of the zoom lens according to the embodiment of the present invention can be expressed by the following equation with the light beam traveling direction as positive when the optical axis direction is the x axis and the direction perpendicular to the optical axis direction is the y axis. have. 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, miniaturization 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 ASP represents an aspherical surface. In the drawings of the embodiments, the same reference numerals are given to the lenses configuring each lens group.

<First Embodiment>

1 illustrates a wide-angle end, an intermediate end, and a telephoto end of the zoom lens according to the first embodiment, respectively. Reference numerals 7 and 8 denote filters.

 f; 6.48-11.02-18.44 Fno; 3.29 to 4.38 to 6.06 2ω; 61.43-38.53-23.59

                  R Dn Nd Vd

  OBJ: INFINITY INFINITY

   S1: -20.00000 0.500000 1.698950 30.0

   S2: 6.60532 1.661167 1.945945 17.9

   S3: 15.40521 D1

   ST: INFINITY 0.000000

   S5: 4.46867 1.435487 1.851348 40.1

      ASP:

      K: -0.439184

A: 0.532684E-03 B: -0.839061E-04 C: 0.192983E-04 D: -0.246243E-05

   S6: -4.87287 0.645288 1.728250 28.3

   S7: 3.00000 0.753248 1.688930 31.1

   S8: 5.05068 D2

      ASP:

      K: -0.284436

A: 0.515241E-02 B: -0.364566E-03 C: 0.459410E-03 D: -0.109370E-03

   S9: -21.68107 1.604809 1.804700 40.9

   S10: -7.30063 D3

      ASP:

      K: -0.911982

      A: 0.512393E-03 B: -0.188808E-04 C: 0.309298E-06 D: -0.135725E-08

   S11: INFINITY 0.300000 1.516798 64.1

   S12: INFINITY 0.300000

   S13: INFINITY 0.500000 1.516798 64.1

   S14: INFINITY 0.600000

   IMG: INFINITY

The following is the data on the variable distance when shifting.

Wide angle Middle Telephoto D1 10.4727 4.5282 0.77 D2 4.1201 8.5118 14.2232 D3 3.1162 2.381 1.7

2A and 2B illustrate spherical aberration, image curvature, and distortion aberration at the wide-angle end and the telephoto end of the zoom lens according to the first embodiment of the present invention, respectively. Top curves show tangential field curvature (T) and sagittal field curvature (S).

Second Embodiment

3 shows a lens system according to a second embodiment, and the following shows design data of the second embodiment.

 f; 6.48-11.02-18.43 Fno; 3.25 to 4.34 to 6.04 2ω; 61.43-38.53-23.60

                 R Dn Nd Vd

  OBJ: INFINITY INFINITY

   S1: -17.89005 0.500000 1.657462 34.28

   S2: 6.27667 1.624075 1.945945 17.98

   S3: 12.50475 9.448887

   ST: INFINITY 0.000000

   S5: 4.59859 1.548997 1.851348 40.10

      ASP:

      K: -0.441644

A: 0.519950E-03 B: -0.332118E-04 C: 0.134007E-04 D: -0.216218E-05

   S6: -6.90158 0.430000 1.693608 28.23

   S7: 3.18280 1.040428 1.682798 56.45

   S8: 5.35448 3.414280

      ASP:

      K: -0.446639

      A: 0.496482E-02 B: -0.205756E-04 C: 0.227432E-03 D: -0.508568E-04

   S9: -11.49414 1.456500 1.908448 25.20

   S10: -6.48759 3.550647

      ASP:

      K: -0.775301

      A: 0.485354E-03 B: -0.238571E-04 C: 0.106075E-05 D: -0.264927E-07

   S11: INFINITY 0.300000 1.516798 64.1

   S12: INFINITY 0.300000

   S13: INFINITY 0.500000 1.516798 64.1

   S14: INFINITY 0.600000

   IMG: INFINITY

The following is data on the variable distance when the zoom lens is shifted according to the second embodiment.

Wide angle Middle Telephoto D1 9.4489 4.0906 0.77 D2 3.4143 7.8146 13.4945 D3 3.5506 2.6687 1.7

Third Embodiment

5 shows a zoom lens according to the third embodiment, and the following shows design data of the third embodiment.

 f; 6.48-11.02-18.44 Fno; 3.14 to 4.29 to 6.08 2ω; 61.43-38.53-23.59

                 R Dn Nd Vd

  OBJ: INFINITY INFINITY

   S1: -18.12855 0.500000 1.662043 37.19

   S2: 5.83947 1.492386 1.922912 20.87

   S3: 12.10308 8.052939

   ST: INFINITY 0.000000

   S5: 5.03938 1.522 194 1.851348 40.10

      ASP:

      K: -0.446989

A: 0.538656E-03 B: -0.327974E-04 C: 0.143769E-04 D: -0.256747E-05

   S6: -6.51663 0.430000 1.693824 28.22

   S7: 3.06582 1.038329 1.883000 40.80

   S8: 4.89 181 3.521346

      ASP:

      K: -0.888133

A: 0.455116E-02 B: 0.114344E-03 C: 0.106696E-03 D: -0.256545E-04

   S9: -31.39283 1.617091 1.804700 40.95

   S10: -7.93781 3.360906

      ASP:

      K: -0.946601

A: 0.539083E-03 B: -0.254961E-04 C: 0.100457E-05 D: -0.187181E-07

   S11: INFINITY 0.300000 1.516798 64.1

   S12: INFINITY 0.300000

   S13: INFINITY 0.500000 1.516798 64.1

   S14: INFINITY 0.600000

   IMG: INFINITY

The following is data on the variable distance when the zoom lens is shifted according to the third embodiment.

First embodiment Second embodiment Third embodiment Equation 1 1.341 1.27 1.48

The following shows that the first to third embodiments satisfy the condition of Equation 1, respectively.

Wide angle Middle Telephoto D1 9.4489 4.0906 0.77 D2 3.4143 7.8146 13.4945 D3 3.5506 2.6687 1.7

The zoom lens according to the embodiment of the present invention may be used in a digital still camera or a video camera using imaging equipment such as a CCD and a CMOS. The zoom lens according to the embodiment of the present invention has a compact, high performance, and easy to manufacture structure.

The above embodiments are merely exemplary, and various modifications and equivalent other embodiments are possible to those skilled in the art. Accordingly, the true scope of protection of the present invention should be determined by the technical idea of the invention described in the following claims.

1 illustrates a zoom lens according to a first embodiment of the present invention for a wide-angle end, an intermediate end, and a telephoto end.

2A and 2B show aberration diagrams at the wide-angle end and the telephoto end of the zoom lens according to the first embodiment of the present invention.

3 illustrates a zoom lens according to a second embodiment of the present invention for each of a wide-angle end, an intermediate end, and a telephoto end.

4A and 4B show aberration diagrams at the wide-angle end and the telephoto end of the zoom lens according to the second embodiment of the present invention.

5 illustrates a zoom lens according to a third embodiment of the present invention for each of a wide-angle end, an intermediate end, and a telephoto end.

6A and 6B illustrate aberration diagrams at a wide-angle end and a telephoto end of a zoom lens according to a third exemplary embodiment of the present invention.

<Description of main part of drawing>

G1 ... first lens group, G2 ... second lens group,

G3 ... 3rd lens group, D1, D2, D3 ... variable distance

Claims (7)

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 in order from an object side, And the distance between the first lens group and the second lens group decreases, and the distance between the second lens group and the third lens group increases, and satisfies the following condition when changing from the wide-angle end to the telephoto end. <Conditional expression>

Where fw is the total focal length at the wide-angle end, L2w is the distance from the first lens surface of the second lens group to the image surface at the wide-angle end, and L2t is the object-side first of the second lens group at the telephoto end. The distance from the first lens surface to the image surface is respectively shown. According to claim 1, A zoom lens, wherein the first lens group comprises two bonded lenses. According to claim 1, The first lens group includes only a spherical lens. According to claim 1, A zoom lens in which the object-side first surface of the first lens group is concave with respect to the object-side. The method according to any one of claims 1 to 4, A zoom lens, wherein the second lens group includes three bonded lenses. The method according to any one of claims 1 to 4, And a second lens group including two or more aspherical lenses. The method according to any one of claims 1 to 4, A zoom lens, wherein the third lens group is composed of one aspherical lens.

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