KR20090112128A - Zoom lens - Google Patents

Abstract

PURPOSE: A zoom lens for reducing the color difference of magnification in a high magnification process by using a cemented lens is provided to compensate the difference by forming a concave lens and a non-concave lens from a body. CONSTITUTION: A first lens includes a first lens(1) in a meniscus type, a second lens(2) in the meniscus type and a third lens in the meniscus. The first lens has a refractive index. The second lens includes a definition refractive index. The third lens includes a definition refractive index. The second lens includes a fourth lens, a fifth lens of both concave and a sixth lens(6) in the meniscus type. The third lens group includes a swollen seventh lens(7), an eighth lens(8) in definition index of refraction and a ninth lens.

Description

Zoom lens

 The present invention relates to a high magnification 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.

Furthermore, as the number of users of digital cameras increases recently, the demand for zoom lenses having a wider angle and higher magnification than conventional optical systems is increasing. In the case of the wide angle, miniaturization is difficult due to the increase in lens size and distortion aberration. A wide angle and compact high magnification zoom lens system is disclosed in JP 2003-121,742. Here, from the object side, one lens group of positive refractive power, two lens groups of negative refractive power, three lens groups of positive refractive power, and four lens groups of positive refractive power are provided, and the first lens group and the first lens group are shifted from the wide-angle end to the telephoto end. The spacing between the two lens groups is increased, the spacing between the second lens group and the third lens group is decreased, and the spacing between the third lens group and the fourth lens group is decreased. Such an optical system can obtain a wide angle of view, but when the transition from the wide end to the telephoto end becomes narrower, the distance between groups 3 and 4 becomes narrower, thereby obtaining a compact zoom lens system due to an increase in the back focal length (BFL) in the telephoto end. Is difficult.

An object of the present invention is to provide a compact, high magnification wide-angle zoom lens.

A zoom lens according to an embodiment of the present invention includes a first lens group having positive refractive power, a second lens group having negative refractive power, a third lens group having positive refractive power, and a positive refractive power, in order from the object side. Including a four-lens group, wherein the distance between the first lens group and the second lens group increases when the lens is shifted from the wide-angle end to the telephoto end, and the distance between the second lens group and the third lens group decreases, and the third lens group And the interval between the fourth rene group increases and the following conditional expression is satisfied.

<Conditional expression>

8 ≤ ft / fw ≤ 15

1.2 ≤ Lt / ft ≤ 2.0

Where fw is the focal length of the whole optical system at the wide end, ft is the focal length of the whole optical system at the telephoto end, and Lt is the distance from the first side of the object-side lens of the first lens group to the image plane at the telephoto end, respectively. Indicates.

The zoom lens satisfies the following conditional expression.

<Conditional expression>

1.90 ≤ Nd2 ≤ 2.05

Here, Nd2 represents the refractive index of the last lens from the object side of the second lens group.

The first lens group includes a bonded lens.

The first lens on the object side of the second lens group is a spherical lens.

The third lens group includes a bonded lens.

The first lens group includes a first meniscus type negative lens in which the object side is convex in order from the object side, a second positive lens of the meniscus type in which the object side is convex, and a third meniscus type in which the object side is convex. It includes a positive lens.

The first negative lens and the second positive lens may be configured as a bonding lens.

The second lens group includes one meniscus lens in which the object side is convex in order from the object side, one aspherical lens of both concave and one meniscus lens in which the object side is convex.

The third lens group includes an aspherical convex lens, a positive lens, and a negative lens.

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 includes a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, and an order from the object side O in order. A third lens group G3 having refractive power and a fourth lens group G4 having positive refractive power, wherein the first lens group G1 and the second lens group G2 are shifted from the wide-angle end to the telephoto end. The interval between the two increases, the interval between the second lens group G2 and the third lens group G3 decreases, and the interval between the third lens group G3 and the fourth lens group G4 increases and varies. Do On the other hand, image shift and focus position correction according to the shift are performed by the fourth lens group G4.

The first lens group G1 is a meniscus type in which the object side O is convex in order from the object side O, and one negative first lens 1 and the menis in which the object side O are convex. It is curvilinear, and includes a positive meniscus type and one positive third lens 3 having one positive second lens 2 and the object side O convex. The first lens 1 and the second lens 2 are bonded to each other to form a bonded lens. The outermost lens of the first lens group G1, that is, the first lens 1, is manufactured by using a material having a refractive index of 1.9 or more, so that the outer diameter of the lens can be reduced even at a wide angle, thereby miniaturizing the lens. For example, when the first lens 1 is made of a high refractive material having a refractive index of 1.9 or more, the outer diameter of the lens can be reduced even when the angle of view is 80 degrees or more. In addition, by constructing the bonded lens using a relatively high dispersion material and a relatively low dispersion material, it is advantageous to correct chromatic aberration generated at high magnification.

The second lens group G2 includes one meniscus fourth lens 4 in which the object side is convex in order from the object side O, one aspherical fifth lens 5 in both concave, and an object. The sixth lens 6 of the meniscus type in which the side O is convex is included. The cost is reduced by using the first lens on the object side O of the second lens group G2, that is, the fourth lens 4 as a spherical lens instead of an aspheric surface. If the first lens on the object side of the second lens group uses an aspherical lens with a large outer diameter, the manufacturing cost may increase. As a fifth lens 5, a concave aspherical lens was used to reduce distortion and astigmatism. In addition, a high refractive lens of 1.9 or more may be used as the sixth lens 6 to minimize the lens thickness. In order to secure an angle of view of the wide-angle end, the first lens on the object side of the second lens group should be used as a lens having a large outer diameter. However, when the first lens on the object side is an aspherical lens, the manufacturing cost may increase due to the large outer diameter. Therefore, in order to reduce cost, the first lens on the object side is used as a spherical lens, and the aspherical lens is disposed on the second lens on the object side to enable aberration correction at low cost.

The third lens group G3 includes a convex seventh lens 7, a positive eighth lens 8, and a negative ninth lens 9. Aspheric aberration is reduced as the seventh lens 7 by using an aspherical convex lens. In addition, magnification chromatic aberration generated at the time of high magnification variation was reduced by using a junction lens in which the eighth lens 8 and the ninth lens 9 were joined.

The fourth lens group G4 includes one aspherical convex lens 10. The convex lens 10 is made of a low dispersion material to reduce the chromatic aberration of magnification generated during image correction due to a change in object distance.

Meanwhile, the zoom lens according to the embodiment of the present invention may be configured to satisfy the following conditional expression.

8 ≤ ft / fw ≤ 15

1.2 ≤ Lt / ft ≤ 2.0

Where fw is the focal length of the whole optical system at the wide-angle end, ft is the focal length of the whole optical system at the telephoto end, and Lt is the distance from the first surface of the object-side lens of the first lens group to the image plane at the telephoto end, respectively. Indicates. Equation 1 defines the magnification ratio of the zoom lens, and is intended to obtain a high magnification optical system of 10 times or more with a wide angle of 24 mm at a focal length of 35 mm film conversion.

Equation 2 defines the ratio of the distance from the first surface of the object side of the first lens group G1 to the image plane and the entire optical system focal length ratio in the telephoto end, and when the upper limit is exceeded, the telephoto distance is compared to the telephoto focal length. The total optical focal length ratio is defined, and when the upper limit is exceeded, the telephoto electric field increases compared to the telephoto focal length, making it difficult to miniaturize the optical system. It is difficult to obtain an optical system.

In general, in order to obtain a wide-angle optical system having a focal length of 24mm equivalent to 35mm film in the positive, negative, positive, and positive type optical systems, a lens for correcting aberration and an aspherical lens should be properly applied to the first lens group and the second lens group due to distortion aberration. However, since the manufacturing cost increases according to the outer diameter of the aspherical lens, it is necessary to properly arrange the lens to satisfy both the manufacturing cost and the aberration correction. In order to have a wide angle and high magnification ratio, the electric field is increased in the telephoto end. However, when the equation 2 is satisfied, a small optical system can be obtained while having a high magnification ratio.

Next, the zoom lens of the present invention may be configured to satisfy the following conditional expression.

1.90 ≤ Nd2 ≤ 2.05

Here, Nd2 represents the refractive index of the last lens, that is, the sixth lens 6, from the object side of the second lens group. Equation 3 defines the refractive index of the object-side last lens of the second lens group G2, that is, the sixth lens 6, and easily implements a small high magnification zoom lens using a high refractive lens of 1.9 or more and 2.05 or less. Can be. In order to realize small size and high magnification in the positive, negative, positive, and positive type optical systems, high refractive index lenses should be properly arranged to minimize aberration correction while minimizing lens group shifting. When the last lens on the object side of the second lens group uses a lens having a refractive index of 1.9 or more, astigmatism correction and high magnification can be easily realized.

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.

The present invention specifically includes lenses according to optimization conditions for realizing miniaturization of a zoom lens through embodiments according to various designs as follows.

F is the composite focal length of the entire lens system, Fno is the F number, 2w 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, D3, and D4 represent a variable distance, and ASP represents an aspherical surface. Incidentally, in the drawings showing the embodiments, the same numbers are indicated for the lenses constituting 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. The zoom lens according to the present invention includes first to fourth lens groups G1 (G2 (G3) and G4), and reference numerals 11 and 12 denote filters.

 f; 4.28-12.97-40.68 Fno; 3.13 to 3.80 to 5.58 2ω; 83.91 to 33.05 to 10.81

                  R Dn nd vd

  OBJ: INFINITY INFINITY

   S1: 32.04722 0.900000 1.922860 20.88

   S2: 21.99996 3.745691 1.487489 70.44

   S3: 89.90278 0.150000

   S4: 29.42392 2.297229 1.834810 42.72

   S5: 120.56540 D1

   S6: 76.02367 0.700000 1.883000 40.80

   S7: 6.39 386 3.503 128

   S8: -28.04374 1.000000 1.804700 40.93

      ASP:

      K: 15.475451

     A: 0.150059E-03 B: -0.294426E-06 C: 0.379931E-07 D: 0.851112E-09

   S9: 19.08167 0.285136

   S10: 13.96944 1.941837 1.945945 17.98

   S11: 201.51002 D2

  SST: INFINITY 0.300000

   S13: 5.03261 1.802281 1.583310 58.92

      ASP:

      K: -0.825355

     A: -0.383418E-04 B: -0.266999E-04 C: 0.287633E-05 D: -0.546903E-06

   S14: -20.54500 0.100000

      ASP:

      K: -1.000000

      A: 0.201734E-03 B:-. 185078E-04 C:-. 192365E-05 D:-. 172375E- 06

   S15: 5.97321 1.168561 1.755000 52.32

   S16: 8.87 260 0.450000 1.846663 23.78

   S17: 3.26610 D3

   S18: 24.00866 1.921371 1.514700 63.78

   S19: -16.87345 D4

      ASP:

      K: -1.000000

      A: 0.125415E-03 B: -0.319841E-04 C: 0.171401E-05 D: -0.349768E-07

   S20: INFINITY 0.300000 1.516798 64.20

   S21: INFINITY 0.300000

   S22: INFINITY 0.500000 1.516798 64.20

   S23: INFINITY 0.590000

  IMG: INFINITY

Next, the variable distances D1, D2, D3, and D4 of the zoom lens according to the first embodiment are shown for the wide-angle end, the intermediate end, and the telephoto end.

  Variable distance Wide angle Middle Telephoto D1 0.60 10.00 20.64 D2 18.47 7.99 1.40 D3 4.94 11.70 16.04 D4 3.09 2.22 1.95

2 and 3 show 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

4 illustrates a zoom lens according to a second embodiment, and includes first, second, third, and fourth lens groups G1, G2, G3, and G4.

 f; 4.17-12.63-45.87 Fno; 3.03 to 4.38 to 6.14 2ω; 85.43-33.89-9.59

                R Dn nd vd

  OBJ: INFINITY INFINITY

   S1: 38.18241 0.900000 1.922860 20.88

   S2: 24.01080 4.369289 1.487489 70.44

   S3: 129.13446 0.150000

   S4: 28.36098 3.243606 1.834810 42.72

   S5: 121.32459 D1

   S6: 111.65502 0.700000 1.883000 40.80

   S7: 6.57405 3.541811

   S8: -27.50660 1.000000 1.804700 40.93

      ASP:

      K: 12.624723

     A: 0.159957E-03 B: 0.621721E-06 C: -0.425085E-07 D: 0.110201E-08

   S9: 15.81579 0.100000

   S10: 12.75657 2.085363 1.945945 17.98

   S11: 477.28937 D2

  ST: INFINITY 0.300000

  S13: 5.72277 1.585179 1.583310 58.92

      ASP:

      K: -0.851494

      A: -0.643075E-04 B: -0.192812E-04 C: 0.219689E-05 D: -0.490467E-06

   S14: -20.85304 0.682521

      ASP:

      K: -1.000000

      A: 0.178866E-03 B: -0.181348E-04 C: 0.134461E-06 D: -0.346159E-06

   S15: 6.28010 1.189816 1.755000 52.32

   S16: 12.68944 0.450000 1.846663 23.78

   S17: 3.68762 D3

   S18: 24.70 150 2.002415 1.514700 63.78

   S19: -13.94791 D4

      ASP:

      K: -1.000000

      A: 0.386568E-03 B: -0.319969E-04 C: 0.159328E-05 D: -0.321147E-07

   S20: INFINITY 0.300000 1.516798 64.20

   S21: INFINITY 0.300000

   S22: INFINITY 0.500000 1.516798 64.20

   S23: INFINITY 0.590000

  IMG: INFINITY

Next, the variable distances D1, D2, D3, and D4 of the zoom lens according to the second embodiment are shown for the wide-angle end, the intermediate end, and the telephoto end.

  Variable distance Wide angle Middle Telephoto D1 0.60 10.00 20.64 D2 18.47 7.99 1.40 D3 3.93 10.65 18.66 D4 3.68 3.47 1.95

5 and 6 show spherical aberration, image curvature, and distortion aberration at the wide-angle end and the telephoto end of the zoom lens according to the second embodiment of the present invention, respectively.

Third Embodiment

7 shows a zoom lens according to the third embodiment.

 f; 3.91 to 11.85 to 33.24 Fno; 2.75 to 3.82 to 5.71 2ω; 89.11-36.00-13.21

                R Dn nd vd

  OBJ: INFINITY INFINITY

   S1: 40.86174 0.900000 1.922860 20.88

   S2: 26.05548 4.724850 1.487489 70.44

   S3: 161.77520 0.150000

   S4: 27.58211 2.711824 1.834810 42.72

   S5: 90.06177 0.600000

   S6: 78.13185 0.700000 1.883000 40.80

   S7: 6.82694 3.771506

   S8: -22.79639 1.000000 1.804700 40.93

      ASP:

      K: 10.885307

     A: 0.205286E-03 B: -0.776241E-07 C: -0.389302E-07 D: 0.218783E-08

   S9: 17.11103 0.100000

   S0: 13.94553 2.080834 1.945945 17.98

   S1: -377.77787 17.640090

  ST: INFINITY 0.300000

  S13: 5.69507 1.833179 1.583310 58.92

      ASP:

      K: -0.857387

      A: -0.685415E-04 B: -0.167940E-04 C: 0.167606E-05 D: -0.461967E-06

  S14: -20.12565 0.210119

      ASP:

      K: -1.000000

     A: 0.198046E-03 B:-. 238817E-04 C: 0.973079E-06 D:-. 410440E-06

  S15: 5.82946 1.216915 1.755000 52.32

  S16: 11.67418 0.483839 1.846663 23.78

  S17: 3.56960 3.999385

  S18: 28.06231 2.116933 1.514700 63.78

  S19: -10.47241 2.998921

      ASP:

      K: -1.000000

      A: 0.847315E-03 B: -0.423088E-04 C: 0.144313E-05 D: -0.237285E-07

  S20: INFINITY 0.300000 1.516798 64.20

  S21: INFINITY 0.300000

  S22: INFINITY 0.500000 1.516798 64.20

  S23: INFINITY 0.590000

  IMG: INFINITY

Next, the variable distances D1, D2, D3, and D4 of the zoom lens according to the third embodiment are shown for the wide-angle end, the intermediate end, and the telephoto end.

   Variable distance Wide angle Middle Telephoto D1 0.60 11.17 18.30 D2 17.64 7.10 1.40 D3 4.00 9.41 17.80 D4 3.00 2.88 1.95

The following shows that the first to third embodiments satisfy the conditions of Equations 1, 2, and 3, respectively.

Example 1 Example 2 Example 3 Equation 1 9.499 11.00 8.500 Equation 2 1.524 1.452 1.909 Equation 3 1.946 1.946 1.946

As described above, the zoom lens according to the exemplary embodiment of the present invention may have a high magnification ratio and ensure a small and wide angle. 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 of the present invention will be defined by the technical spirit of the invention described in the claims below.

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.

2 and 3 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.

4 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.

5 and 6 illustrate aberration diagrams at the wide-angle end and the telephoto end of the zoom lens according to the second exemplary embodiment of the present invention.

7 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.

8 and 9 illustrate aberration diagrams at the wide-angle end and the telephoto end of the zoom lens according to the 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, G4 ... 4th lens group

D1, D2, D3, D4 ... variable distance

Claims (9)

A first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a fourth lens group having a positive refractive power, sequentially from the object side, and having a telephoto end at a wide-angle end. The interval between the first lens group and the second lens group increases, the distance between the second lens group and the third lens group decreases, and the distance between the third lens group and the fourth len group increases, and A zoom lens, characterized by satisfying a conditional expression. <Conditional expression> 8 ≤ ft / fw ≤ 15 1.2 ≤ Lt / ft ≤ 2.0 Where fw is the focal length of the whole optical system at the wide end, ft is the focal length of the whole optical system at the telephoto end, and Lt is the distance from the first side of the object-side lens of the first lens group to the image plane at the telephoto end, respectively. Indicates. The method of claim 1, And the zoom lens satisfies the following conditional expression. <Conditional expression> 1.90 ≤ Nd2 ≤ 2.05 Here, Nd2 represents the refractive index of the last lens from the object side of the second lens group. The method of claim 1, And the first lens group comprises a bonded lens. The method of claim 1, And the first lens on the object side of the second lens group is a spherical lens. The method of claim 1, And the third lens group comprises a bonded lens. The method according to any one of claims 1 to 5, The first lens group includes a first meniscus type negative lens in which the object side is convex in order from the object side, a second positive lens of the meniscus type in which the object side is convex, and a third meniscus type in which the object side is convex. A zoom lens comprising a positive lens. The method of claim 6, And the first negative lens and the second positive lens are combined lenses. The method according to any one of claims 1 to 5, The second lens group includes one meniscus lens in which the object side is convex in order from the object side, one aspherical lens of both concave and one meniscus lens in which the object side is convex. Zoom lens. The method according to any one of claims 1 to 5, And the third lens group includes an aspherical convex lens, a positive lens, and a negative lens.

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