KR100833944B1 - Compact zoom optics - Google Patents

Abstract

A small zoom optical system is disclosed. The disclosed zoom optical system includes: a first lens group having positive refractive power in order from an object side; A second lens group having negative refractive power; A third lens group having positive refractive power; And a fourth lens group having a positive refractive power, wherein at least two lens groups are shifted from the wide angle end to the telephoto end, and satisfy the following conditional expressions.

<Expression>

Here, f _t is the total focal length of the telephoto end, f _w is the total focal length of the wide-angle end, L _2w is the distance from the first lens surface of the object side of the second lens group to the image plane at the wide-angle end, L _2t Is the distance from the telephoto end to the first surface of the object-side first lens of the second lens group.

Description

Compact zoom optics

1 is a view showing the optical arrangement in the wide-angle end, the intermediate end and the telephoto end of the zoom optical system according to the first embodiment of the present invention.

2 is aberration diagrams showing spherical aberration, image curvature and distortion at the wide-angle end of the zoom optical system according to the first embodiment of the present invention.

3 is an aberration diagram showing spherical aberration, image curvature and distortion in the telephoto end of the zoom optical system according to the first embodiment of the present invention.

4 is a view showing the optical arrangement in the wide-angle end, the intermediate end and the telephoto end of the zoom optical system according to the second embodiment of the present invention.

5 is aberration diagrams showing spherical aberration, image curvature and distortion at the wide-angle end of the zoom optical system according to the second embodiment of the present invention.

6 is aberration diagrams showing spherical aberration, image curvature and distortion in the telephoto end of the zoom optical system according to the second embodiment of the present invention.

7 is a view showing the optical arrangement in the wide-angle end, the intermediate end and the telephoto end of the zoom optical system according to the third embodiment of the present invention.

8 is aberration diagrams showing spherical aberration, image curvature, and distortion at the wide-angle end of the zoom optical system according to the third embodiment of the present invention.

9 is aberration diagrams showing spherical aberration, image curvature and distortion in the telephoto end of the zoom optical system according to the third embodiment of the present invention.

FIG. 10 is a view showing optical arrangements at the wide-angle end, the intermediate end, and the telephoto end of the zoom optical system according to the fourth embodiment of the present invention.

11 is aberration diagrams showing spherical aberration, image curvature and distortion at the wide-angle end of the zoom optical system according to the fourth embodiment of the present invention.

12 is aberration diagrams showing spherical aberration, image curvature and distortion in the telephoto end of the zoom optical system according to the fourth embodiment of the present invention.

<Description of the symbols for the main parts of the drawings>

10-1,10-2,10-3,10-4 ... 1st lens group 20-1,20-2,20-3,20-4 ... 2nd lens group

30-1,30-2,30-3.30-4 ... Third lens group 40-1,40-2,40-3,40-4 ... Fourth lens group

The present invention relates to a small zoom optical system suitable for a camera using a solid-state imaging device, and more particularly, to a small zoom optical system having a compact compact structure and high performance and low cost.

Recently, an imaging optical device such as a digital camera or a digital camcorder using an imaging device such as a CCD or a CMOS is rapidly expanding. Such image forming optical devices are being promoted to be low in cost and small in weight, and thus, the compact and light in price are required in the zoom lens optical system.

In this regard, the zoom optical system disclosed in Japanese Patent Laid-Open No. 2003-107347 is composed of first to fourth lens groups each having positive, negative, positive, and positive refractive powers in order from the object side. The first lens group is composed of one positive lens and one negative lens, and the fourth lens group is composed of one positive lens. The zoom optical system has a structure in which the 1,3 groups are fixed and the 2,4 groups operate when the variable is shifted, and the magnification change from the wide angle end to the telephoto end is only about 2 times, which is not suitable for high magnification optical systems. In addition, the thickness of the entire lens system is not suitable for compact compactness.

The zoom optical system disclosed in Japanese Patent Laid-Open No. 2004-094233 is composed of first to fourth lens groups each having positive, negative, positive, and positive refractive powers in order from the object side. This zoom optical system is configured to move each lens group when shifting, and in particular, when shifting from the wide-angle end to the telephoto end, the distance between the first lens group and the second lens group increases, and between the second lens group and the third lens group. The spacing of? Is reduced, the spacing between the third lens group and the fourth lens group is increased, and the spacing between the first lens group and the third lens group is not changed. In this case, in order to maintain the distance between the first lens group and the third lens group, the amount of movement of the second lens group increases when moving from the wide-angle end to the telephoto end, thus making it difficult to compact the storage.

The zoom optical system disclosed in Japanese Patent Laid-Open No. 2004-252204 has four groups of positive, negative, positive, and positive in order from the object side. In this configuration, the first lens group is fixed and the zoom magnification is less than three times, which is not suitable for a high magnification optical system.

In addition, the zoom optical system disclosed in Japanese Patent Laid-Open No. 2006-106111 has four groups of positive, negative, positive, and positive in order from the object side. The entire group is operated at the time of shift for miniaturization, and the third lens group includes at least one aspherical surface. This zoom optical system does not achieve a high magnification compared to the number of lenses used and the cost with a magnification of 4 times or less.

Accordingly, an object of the present invention is to provide a zoom lens optical system that is suitable for a camera using a solid-state image sensor and has a compact, compact structure and high performance and low cost.

A zoom optical system according to an embodiment of the present invention for achieving the above object comprises a first lens group having a positive refractive power in order from the object side; A second lens group having negative refractive power; A third lens group having positive refractive power; And a fourth lens group having a positive refractive power, wherein at least two lens groups are shifted from the wide angle end to the telephoto end, and satisfy the following conditional expressions.

<Expression>

Here, f _t is the total focal length of the telephoto end, f _w is the total focal length of the wide-angle end, L _2w is the distance from the first lens surface of the object side of the second lens group to the image plane at the wide-angle end, L _2t Is the distance from the first lens side of the object side of the second lens group to the image surface.

Hereinafter, a zoom optical system according to a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings. However, the examples exemplified below are not intended to limit the scope of the present invention, but are provided to fully explain the present invention to those skilled in the art. In the 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 description.

1 is a view showing the optical arrangement in the wide-angle end, the intermediate end and the telephoto end of the zoom optical system according to the first embodiment of the present invention.

Referring to the drawings, the zoom optical system according to the present invention has a first lens group 10-1 having positive refractive power, a second lens group 20-1 having negative refractive power, and positive refractive power from the object OBJ side. And a third lens group 30-1 and a fourth lens group 40-1 having positive refractive power. In addition, between the second lens group 20-1 and the third lens group 30-1, an aperture ST which is moved in association with the third lens group 30-1 is further provided. At least two lens groups of the first to fourth lens groups 10-1, 20-1, 30-1, and 40-1 are shifted from the wide-angle end to the telephoto end. Satisfies the expression.

Where f _t is the focal length of the telephoto end and f _w is the focal length of the wide end.

In addition, when the position difference of the second lens group 20-1 when moving from the wide-angle end to the telephoto end is expressed as a ratio with respect to the focal length of the wide-angle end, the following equation is satisfied.

Here, L _2w is the distance between the object-side first lens surface and the image surface of the second lens group 20-1 at the wide-angle end and L _2t is the object-side first of the second lens group 20-1 at the telephoto end. The distance between the lens surface and the image surface, f _w is the focal length of the wide-angle end. It is difficult for L _2w -L _{2t to} have a negative value in the imaging optical system, and its lower limit is zero. In this case, the positions of the second lens group 20-1 are the same at the wide-angle end and the telephoto end, and the position difference of the cam of the lens mechanism to which the optical system is applied is small, which is very advantageous in reducing the overall storage length of the lens system. When the upper limit value is exceeded, the position difference at the time of shifting of the second lens group 20-1 becomes large, so that the trajectory of the cam for moving the second lens group 20-1 becomes large and it is difficult to miniaturize the storage overall length.

The zoom optical system of the present invention may further satisfy the following equation.

Here, f ₂ is the focal length of the second lens group 20-1. This equation represents the ratio of the ratio to the focal length of the second lens group 20-1. If it is out of the lower limit, the refractive power of the second lens group 20-1 becomes weak, so that the amount of movement of the second lens group 20-1 during zooming increases, and thus, the total length of the optical system is long, making it difficult to achieve miniaturization. Departing from the upper limit means that the refractive power of the second lens group 20-1 has an excessively large value when the variable ratio satisfies the expression (1), making it difficult to maintain overall optical system performance.

Further, the zoom optical system of the present invention may further satisfy the following equation.

This equation shows the ratio of the telephoto focal length f _t and the focal length f ₄ of the fourth lens group 40-1. If the value falls outside the lower limit, the amount of movement of the fourth lens group 40-1 becomes large during image position correction, and it is difficult to realize miniaturization. If the value falls outside the upper limit, the cost increases due to astigmatism correction and an increase in refractive index.

Further, the zoom optical system of the present invention may further satisfy the following equation.

This equation represents the difference between the optical field length (L _t ) at the telephoto end and the optical field length (L _w ) at the wide-angle end, as a ratio to the ratio. If the upper limit is exceeded, the difference between the telephoto end and the wide-angle end is increased, which makes it difficult to apply the compact lens system of a compact camera. Outside the lower limit, it becomes difficult to correct the performance of the telephoto when the variable ratio satisfies Equation (1).

Shifting is performed by moving at least two lens groups of the first to fourth lens groups 10-1, 20-1, 30-1, and 40-1 on the optical axis, and at this time, the telephoto end at the wide-angle end. In this case, the distance between the first lens group 10-1 and the second lens group 20-1 increases and the distance between the second lens group 20-1 and the third lens group 30-1 increases. The interval is reduced, and the interval between the third lens group 30-1 and the fourth lens group 40-1 is increased. When shifting, the first to third lens groups 30-1 follow a monotonous movement or a nonlinear movement, and the fourth lens group 40-1 corrects the focus position according to the image shift and the subject position generated accordingly. . In this way, the electric field of the whole optical system is minimized and the amount of movement of each group is reduced during zooming, which is advantageous in miniaturizing the optical system. In addition, the refractive power of the fourth lens group 40-1 is set to be positive so that the telecentric required for a solid-state imaging device such as a CCD, that is, the incident angle of the light source incident on the peripheral part of the image is close to the image plane.

More specifically, the lens configuration of each of the first to fourth lens groups 10-1, 20-1, 30-1, and 40-1 is as follows.

The first lens group 10-1 is configured to have a positive refractive power as a whole. The first lens group 10-1 may include a plurality of lenses, and includes, for example, a first lens 11-1 and a second lens 12-1. A negative lens may be used as the first lens 11-1 and a positive lens may be used as the second lens 12-1, and the first lens 11-1 and the second lens 12-1 are bonded to each other. It may be composed of a lens. When a material having a large dispersion is used for the first lens 11-1, which is a negative lens, chromatic aberration may be sufficiently corrected even at a high magnification of about 5 times.

The second lens group 20-1 is configured to have negative refractive power as a whole and is composed of a plurality of lenses. For example, the third lens 21-1, the fourth lens 22-1, and the fifth lens 23-1 are sequentially disposed from the object side, and the third lens 21-1 is disposed toward the object side. The convex negative lens, the fourth lens 22-1 may be a biconvex negative lens, and the fifth lens 23-1 may be a meniscus positive lens that is convex toward the object. A chromatic aberration correction can be facilitated by including a lens made of a material with high dispersion in the second lens group 20-1. For example, the fourth lens 22-1, which is a negative lens, uses a material having low dispersion, and the fifth lens 23-1, which is a meniscus positive lens, uses a material having high dispersion.

The third lens group 30-1 is configured to have a positive refractive power as a whole. For example, the sixth lens 31-1 of the positive lens, the seventh lens 32-1 of the positive lens, and the negative lens of the third lens group 30-1. An eighth lens 33-1. When the sixth lens 31-1 employs an aspherical surface, spherical aberration can be minimized. In addition, the seventh lens 32-1 and the eighth lens 33-1 may be formed of a bonded lens, and the seventh lens 32-1 is made of a material having low dispersion and the eighth lens 33-1. ) Is a material with high dispersion, which can minimize chromatic aberration occurring at high magnification.

The fourth lens group 40-1 is configured to have positive refractive power. For example, it consists of one ninth lens 41-1 made of positive lens to correct distortion and image curvature. In addition, the ninth lens (41-1) is composed of a spherical lens to reduce the cost.

Definition of aspherical surface (ASP) appearing in embodiments of the present invention are as follows.

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 ' Is the inverse of the radius of curvature at the vertex of the lens (1 / R).

Next, specific lens data of various embodiments of the zoom optical system according to the present invention will be described. F denotes the focal length of the entire zoom optical system, Fno denotes the F number, ω denotes the angle of view, R denotes the radius of curvature, Nd denotes the refractive index, and Vd denotes the Abbe number. In addition, ST represents an aperture and in each embodiment, the variable distance between lenses is represented by D1, D2, D3, and D4. In addition, the embodiment number is displayed in association with the reference number of each component for each embodiment.

First Embodiment

1 illustrates a zoom lens optical system according to a first embodiment, in which the first lens group 10-1 includes a first lens 11-1 and a second lens 12-1, and a second lens. The group 20-1 is composed of third, fourth, and fifth lenses 21-1, 22-1, and 23-1, and the third lens group 30-1 is sixth and seventh. , The eighth lens 31-1, and the fourth lens group is composed of the ninth lens. Reference numeral 50-1 denotes an infrared filter, and 51-1 denotes a cover glass. The following is the lens data of the first embodiment.

  f; 6.45 ~ 18.68 ~ 30.64 Fno; 2.86 ~ 3.72 ~ 4.70 2ω; 63.54 ~ 22.67 ~ 13.92

 Surface (S) Curvature radius (R) Thickness or distance between lenses Refractive index (Nd) Abbe number (Vd)

  OBJ: INFINITY INFINITY

    1: 18.89000 0.700000 1.84666 23.78

    2: 13.30000 2.940000 1.73400 52.60

    3: 107.00000 D1

    4: 25.50000 0.600000 1.83481 42.72

    5: 5.53000 3.060000

    6: -15.68000 0.600000 1.48479 70.44

    7: 20.22000 0.100000

    8: 10.81000 1.560000 1.92286 20.88

    9: 26.71000 D2

   ST: INFINITY 0.300000

   11: 8.81300 1.860000 1.58313 59.46

      ASP:

      K: 0.000000

      A:-. 389417E-03 B:-. 252150E-05 C: 0.000 D: 0.000

   12: -16.17000 0.100000

   13: 4.30000 1.630000 1.48479 70.44

   14: 8.02000 0.500000 1.84666 23.78

   15: 3.64500 D3

   16: 11.79000 1.700000 1.58913 61.25

   17: 145.00000 D4

   18: INFINITY 0.500000 1.51680 64.20

   19: INFINITY 0.500000

   20: INFINITY 0.500000 1.51680 64.20

   21: INFINITY 0.590000

  IMG: INFINITY

Table 1 shows examples of the variable distances D1, D2, D3, and D4 in the zoom lens optical system according to the first embodiment, respectively, at the wide end, the middle end, and the telephoto end.

	Wide angle	Middle	Telephoto
D1	0.600	9.257	11.18
D2	13.948	4.713	1.700
D3	6.335	11.119	17.557
D4	3.380	4.369	3.791

FIG. 2 is an aberration diagram showing longitudinal spherical aberration, image curvature, and distortion at the wide-angle end of the zoom optical system according to the first embodiment. Longitudinal spherical aberration is shown for light with wavelengths of 486.1300 (nm), 587.5600 (nm), and 656.2700 (nm), respectively, and the astigmatic field curvature is the tangential field curvature (T) and the spherical surface curvature. It is divided into (S: sagittal field curvature). 3 is aberration diagrams showing longitudinal spherical aberration, image curvature, and distortion aberration in the telephoto end of the zoom optical system according to the first embodiment.

Second Embodiment

4 illustrates a zoom optical system according to a second embodiment, in which the first lens group 10-2 includes a first lens 11-2 and a second lens 12-2, and a second lens. The group 20-2 includes the third lens 21-2, the fourth lens 22-2, and the fifth lens 23-2, and the third lens group 30-1 includes the sixth lens. 31-2, the seventh lens 32-2, the eighth lens 33-2, and the fourth lens group 40-2 is composed of the ninth lens 41-2. Reference numeral 50-2 denotes an infrared filter and 51-2 denotes a cover glass. The following is the lens data of the first embodiment.

f; 6.19 ~ 16.28 ~ 29.45 Fno; 2.88 ~ 3.64 ~ 4.75 2ω; 62.82 ~ 24.79 ~ 13.74

 Surface (S) Curvature radius (R) Thickness or distance between lenses Refractive index (Nd) Abbe number (Vd)

  OBJ: INFINITY INFINITY

    1: 17.79619 0.700000 1.84666 23.78

    2: 12.44738 2.858761 1.73400 52.60

    3: 101.57884 D1

    4: 26.17130 0.600000 1.83481 42.72

    5: 5.18499 2.710350

    6: -15.38987 0.600000 1.48479 70.44

    7: 12.85727 0.150000

    8: 9.52224 1.669804 1.84666 23.78

    9: 37.47255 D2

   ST: INFINITY 0.300000

   11: 8.47726 1.892093 1.58313 59.46

      ASP:

      K: 0.432866

      A:-. 523974E-03 B:-. 541935E-05 C: 0.000 D: 0.000

   12: -15.82160 0.100000

   13: 4.07266 1.592417 1.48479 70.44

   14: 7.48 124 0.508 720 1.84666 23.78

   15: 3.42464 D3

   16: 10.75363 1.641363 1.58913 61.25

   17: 78.47848 D4

   18: INFINITY 0.500000 1.51680 64.20

   19: INFINITY 0.500000

   20: INFINITY 0.500000 1.51680 64.20

   21: INFINITY 0.590000

  IMG: INFINITY

Table 2 below shows examples of the variable distances D1, D2, D3, and D4 in the zoom lens optical system according to the second embodiment, at the wide-angle end, the intermediate end, and the telephoto end, respectively.

	Wide angle	Middle	Telephoto
D1	0.700	8.109	10.866
D2	12.760	4.538	1.700
D3	5.436	8.977	16.511
D4	3.553	4.944	3.497

5 illustrates longitudinal spherical aberration, image curvature and distortion at the wide-angle end of the zoom optical system according to the second embodiment, and FIG. 6 illustrates longitudinal spherical aberration and image surface at the telephoto end of the zoom optical system according to the second embodiment. Indicates curvature and distortion.

Third Embodiment

FIG. 7 illustrates a zoom optical system according to a third embodiment, in which the first lens group 10-3 includes a first lens 11-3 and a second lens 12-3. The group 20-3 includes the third lens 21-3, the fourth lens 22-3, and the fifth lens 23-3, and the third lens group 30-3 includes the sixth lens. (31-3), the seventh lens (32-3), the eighth lens (33-3), and the fourth lens group (40-3) is composed of a ninth lens (41-3). Reference numeral 50-3 denotes an infrared filter and 51-3 denotes a cover glass. The following is lens data of the third embodiment.

 f; 6.23 ~ 17.06 ~ 29.63 Fno; 2.88 ~ 3.69 ~ 4.80 2ω; 62.35 ~ 23.56 ~ 13.62

  Surface (S) Curvature radius (R) Thickness or distance between lenses Refractive index (Nd) Abbe number (Vd)

  OBJ: INFINITY INFINITY

    1: 17.96148 0.700000 1.84666 23.78

    2: 12.58808 2.920000 1.73400 52.60

    3: 127.06030 D1

    4: 30.23113 0.600000 1.83481 42.72

    5: 5.27928 2.720000

    6: -14.89111 0.600000 1.48479 70.44

    7: 14.89111 0.150000

    8: 10.03420 1.654000 1.84666 23.78

    9: 40.63258 D2

  STO: INFINITY 0.300000

   11: 8.82991 2.230000 1.58313 59.46

      ASP:

      K: 1.000000

      A: -.596957E-03 B:-. 639126E-05 C: 0.000 D: 0.000

   12: -15.40364 0.100000

   13: 4.33330 1.750000 1.48479 70.44

   14: 8.31602 0.600000 1.84666 23.78

   15: 3.57110 D3

   16: 11.12454 1.800000 1.58913 61.25

   17: 113.47133 D4

   18: INFINITY 0.500000 1.51680 64.20

   19: INFINITY 0.500000

   20: INFINITY 0.500000 1.51680 64.20

   21: INFINITY 0.590000

  IMG: INFINITY

Table 3 below shows examples of the variable distances D1, D2, D3, and D4 in the zoom lens optical system according to the third embodiment at the wide-angle end, the intermediate end, and the telephoto end, respectively.

	Wide angle	Middle	Telephoto
D1	0.700	7.964	10.328
D2	13.014	4.295	1.700
D3	4.971	8.835	16.396
D4	3.608	5.100	3.645

8 illustrates longitudinal spherical aberration, image curvature and distortion at the wide-angle end of the zoom optical system according to the third embodiment, and FIG. 9 illustrates longitudinal spherical aberration and image surface at the telephoto end of the zoom optical system according to the third embodiment. Indicates curvature and distortion.

Fifth Embodiment

FIG. 10 illustrates a zoom optical system according to a fourth embodiment, in which the first lens group 10-4 is composed of a first lens 11-4 and a second lens 12-4. The group 20-4 is composed of a third lens 21-4, a fourth lens 22-4, and a fifth lens 23-4, and the third lens group 30-4 is a sixth lens. 31-4, the seventh lens 32-4, and the eighth lens 33-4, and the fourth lens group 40-4 is composed of the ninth lens 41-4. Reference numeral 50-4 denotes an infrared filter and 51-4 denotes a cover glass. The following is lens data of the fourth embodiment.

 f; 6.23 ~ 18.47 ~ 29.63 Fno; 2.86 ~ 3.70 ~ 4.67 2ω; 62.45 ~ 22.01 ~ 13.72

  Surface (S) Curvature radius (R) Thickness or distance between lenses Refractive index (Nd) Abbe number (Vd)

  OBJ: INFINITY INFINITY

    1: 17.21075 0.700000 1.84666 23.78

    2: 12.41162 2.853000 1.73400 52.60

    3: 60.88556 D1

    4: 16.30 133 0.600000 1.83481 42.72

    5: 4.83016 2.859000

    6: -13.81273 0.600000 1.48479 70.44

    7: 13.41658 0.120000

    8: 9.13527 1.590000 1.84666 23.78

    9: 27.15269 D2

   ST: INFINITY 0.500000

   11: 9.12810 2.220000 1.58313 59.46

      ASP:

      K: 1.000000

      A:-. 639971E-03 B:-. 565810E-05 C:-. 112915E-06 D: 0.000

   12: -12.96186 0.100000

   13: 4.2016 4 1.680000 1.48479 70.44

   14: 8.29337 0.500000 1.84666 23.78

   15: 3.58292 D3

   16: 10.96109 1.690000 1.58913 61.25

   17: 131.62501 3.299530

   18: INFINITY 0.500000 1.51680 64.20

   19: INFINITY 0.500000

   20: INFINITY 0.500000 1.51680 64.20

   21: INFINITY 0.730000

  IMG: INFINITY

Table 4 below shows examples of the variable distances D1, D2, D3, and D4 in the zoom lens optical system according to the fourth embodiment, at the wide-angle end, the intermediate end, and the telephoto end, respectively.

	Wide angle	Middle	Telephoto
D1	0.823	10.208	12.222
D2	11.315	3.235	1.150
D3	5.017	9.150	15.703
D4	3.300	4.696	3.689

10 illustrates longitudinal spherical aberration, image curvature and distortion at the wide-angle end of the zoom optical system according to the fourth embodiment, and FIG. 11 illustrates longitudinal spherical aberration and image surface at the telephoto end of the zoom optical system according to the fourth embodiment. Indicates curvature and distortion.

The following shows that the embodiments satisfy the equations 1 to 5 and the corresponding values are as follows.

	Equation 1	Equation 2	Equation 3	Equation 4	Equation 5
First embodiment	4.752	0.088	0.579	1.588	2.104
Second embodiment	4.750	0.001	0.615	1.578	2.139
Third embodiment	4.750	0.031	0.614	1.600	2.067
Fourth embodiment	4.754	0.156	0.624	1.648	2.602

The present invention has excellent optical performance while being miniaturized through a lens configuration satisfying the above-described equations.

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 should be defined within the following claims.

The zoom optical system according to the present invention has a zoom factor of 4 times or more and adjusts the positional difference between the wide-angle end and the telephoto end of the second lens group, thereby realizing miniaturization and excellent optical performance. In addition, by controlling the difference between the focal length of the second lens group, the telephoto focal length and the fourth lens group, and the difference between the telephoto end and the wide-angle end length, more efficient miniaturization, low cost, and high performance zoom optical system can be realized. Can be.

Claims (14)

1. In order from the object side,

   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 fourth lens group having a positive refractive power, wherein the at least two lens groups move when shifting from the wide angle end to the telephoto end, and satisfy the following conditional expression.

   <Expression>

   

   

   Here, f _t is the total focal length of the telephoto end, f _w is the total focal length of the wide-angle end, L _2w is the distance from the first lens surface of the object side of the second lens group to the image plane at the wide-angle end, L _2t Is the distance from the telephoto end to the first surface of the object-side first lens of the second lens group.
2. The method of claim 1,

   A zoom optical system characterized by satisfying the following conditional expression.

   <Expression>

   

   Here, f ₂ is the focal length of the second lens group.
3. The method of claim 1,

   A zoom optical system characterized by satisfying the following conditional expression.

   <Expression>

   

   Here, f ₄ is the focal length of the fourth lens group.
4. The method of claim 1,

   A zoom optical system characterized by satisfying the following conditional expression.

   <Expression>

   

   Where L _t is the optical field length at the telephoto end and L _w is the optical field length at the wide angle end.
5. The method according to any one of claims 1 to 4,

   When changing from wide-angle to telephoto,

   The interval between the first lens group and the second lens group is increased, the interval between the second lens group and the third lens group is decreased, and the interval between the third lens group and the fourth lens group is Zoom optical system, characterized in that larger.
6. The method according to any one of claims 1 to 4,

   And the first lens group comprises two negative and positive lenses arranged in order from the object side.
7. The method of claim 6,

   The negative lens is a zoom optical system, characterized in that made of a material having a relatively greater dispersion than the positive lens.
8. The method according to any one of claims 1 to 4,

   The first optical lens group includes a zoom lens.
9. The method according to any one of claims 1 to 4,

   The second lens group,

   A zoom optical system comprising three lenses: negative, negative, and positive, arranged sequentially from the object side.
10. The method of claim 9,

    The positive lens is a zoom optical system, characterized in that made of a material having a relatively high dispersion compared to the negative lenses.
11. The method according to any one of claims 1 to 4,

    And the third lens group comprises three positive, positive and negative lenses arranged in order from the object side.
12. The method according to any one of claims 1 to 4,

    The third lens group includes a bonding lens formed by joining two lenses having different dispersions.
13. The method according to any one of claims 1 to 4,

    And the fourth lens group comprises one positive lens.
14. The method according to any one of claims 1 to 4,

    And a iris interlocked with the third lens group.

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