KR100389529B1 - Compact zoom lens - Google Patents

Abstract

The present invention discloses a compact zoom lens.

A first lens group having negative refractive power in order from the object side; A second lens group having positive refractive power; A third lens group having negative refractive power; And a fourth lens group having positive refractive power. Then, when zooming from the wide-angle end to the telephoto end, the first lens group moves closer to the image plane and moves away from each other, and the second lens group and the third lens group move away from the image plane on the fourth lens group. Is fixed, in particular, the zoom lens according to the present invention has telecentricity, , (f _I : focal length of the first lens group, f _II : focal length of the second lens group, f _III : focal length of the third lens group and f _IV : focal length of the fourth lens group).

According to the present invention, a wide-angle zoom lens having a high ratio of two to three times in a relatively simple configuration, small in a relatively simple configuration, and particularly having telecentricity suitable for a solid-state imaging device such as a CCD or a CMOS Can be provided.

Description

Compact zoom lens {COMPACT ZOOM LENS}

TECHNICAL FIELD The present invention relates to a zoom lens, and more particularly, to a compact zoom lens used for a camera using an imaging element such as a digital still camera.

In recent years, the spread of electronic still cameras and video cameras using a charge coupled device (CCD) or a solid-state image pickup device has been rapidly expanded, and has become smaller and lighter and lower cost. Accordingly, there is a strong demand for a compact, lightweight, and low-cost lens for a zoom lens built into a camera.

In the optical system using the solid-state image sensor, since the crystal filter is used to prevent moiré phenomenon caused by the periodic structure of the image sensor, the thickness and position of the crystal filter should be taken into consideration when designing the optical system. In particular, the telecentricity of the light rays incident on the top surface is an important variable in the design.

Conventional optical systems using such a solid-state imaging device include the following.

1) Japanese Patent Publication No. 56-123512

2) Japanese Patent Laid-Open No. 63-292106

3) Japanese Patent Application Laid-Open No. 6-94996

4) Japanese Patent Laid-Open No. 5-173071

The zoom lens disclosed in 1) of the prior art includes a first lens group having negative refractive power and a second lens group having positive refractive power in order from the object side, and the first lens group and the second lens group move on the optical axis. As a lens system for zooming, the overall length is greatly changed during zooming. As described above, in the case of a lens system in which the overall length is greatly changed, it is difficult to implement a barrel ratio, that is, it is difficult to implement a zoom ratio more than twice as large, and in particular, it is difficult to miniaturize.

And the zoom lens disclosed in 2) has a structure in which the electric field does not change during zooming, and has a first lens group having a negative refractive power fixed, a second lens group having a positive refractive power, and a positive refractive power fixed during zooming. A lens system comprising a third lens group, wherein the second lens group and the third lens group move on the optical axis during zooming. Since the zoom lens has a structure in which the second lens group and the third lens group move toward the object side during zooming, the overall length of the entire optical system is increased for the performance correction at the wide-angle end. Therefore, miniaturization is difficult.

The zoom lens disclosed in 3) comprises a first lens group having negative refractive power from the object side, a second lens group having positive refractive power, and a third lens group having positive refractive power, wherein the first lens group and the second lens group The zooming is performed by moving on the optical axis. The third lens group is fixed at the time of zooming but has a structure in which the overall length is changed, and the aspect ratio is only about 2 times.

The zoom lens disclosed in 4) includes a first lens group having negative refractive power, a second lens group having positive refractive power, a third lens group having negative refractive power, and a fourth lens group having positive refractive power sequentially from the object side. In this case, the barrel structure is complicated because the lens group is moved when zooming.

Therefore, the present invention has been made in an effort to provide a compact wide-angle zoom lens having a relatively simple structure having a telecentricity with a variable ratio of about 2 to 3 times.

1 is a diagram illustrating a zoom position structure of a compact zoom lens according to a first exemplary embodiment of the present invention.

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

3 is a diagram illustrating a zoom position structure of a compact zoom lens according to a second exemplary embodiment of the present invention.

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

5 is a diagram illustrating a zoom position structure of a compact zoom lens according to a third exemplary embodiment of the present invention.

6A and 6B are aberration diagrams at the wide-angle end and the telephoto end of the compact zoom lens according to the third embodiment of the present invention, respectively.

7 is a diagram illustrating a zoom position structure of a compact zoom lens according to a fourth exemplary embodiment of the present invention.

8A and 8B are aberration diagrams at the wide-angle end and the telephoto end of the compact zoom lens according to the fourth embodiment of the present invention, respectively.

9 is a diagram illustrating a zoom position structure of a compact zoom lens according to a fifth exemplary embodiment of the present invention.

10A and 10B are aberration diagrams at the wide-angle end and the telephoto end of the compact zoom lens according to the fifth embodiment of the present invention, respectively.

11 is a diagram illustrating a structure of each zoom position of a compact zoom lens according to a sixth exemplary embodiment of the present invention.

12A and 12B are aberration diagrams at the wide-angle end and the telephoto end of the compact zoom lens according to the sixth embodiment of the present invention, respectively.

In order to achieve the technical problem of the present invention, the compact zoom lens according to the characteristics of the present invention, in order from the object side, the first lens group having negative refractive power; A second lens group having a positive refractive power; A third lens group having negative refractive power; And a fourth lens group having positive refractive power, and has telecentricity.

In addition, the compact zoom lens according to another feature of the present invention,

A first lens group having negative refractive power in order from the object side; A second lens group having positive refractive power; A third lens group having negative refractive power; And a fourth lens group having positive refractive power, , (f _I : focal length of the first lens group, f _II : focal length of the second lens group, f _III : focal length of the third lens group, f _IV : focal length of the fourth lens group).

Small zoom lens according to this feature, (f _IIn : focal length of the lens having negative deflection force in the second lens group) is further satisfied.

In accordance with still another aspect of the present invention, a small zoom lens includes: a first lens group having negative refractive power in order from an object side; A second lens group having positive refractive power; A third lens group having negative refractive power; And a fourth lens group having positive refractive power, wherein when zooming from the wide-angle end to the telephoto end, the first lens group approaches the image plane and moves away from the image plane, and the second lens group and the third lens group Far from the image, the fourth lens group is fixed and telecentric. In particular, the third lens group moves to the image side during focusing.

In the small zoom lens according to the present invention having the above characteristics, the second lens group and the fourth lens group may include at least one aspherical surface.

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1, 3, 5, 7, 7, and 11 illustrate the structure of the compact zoom lens according to each embodiment of the present invention for each zoom position.

As shown in FIGS. 1, 3, 5, 7, 7, and 11, the small zoom lens according to the embodiment of the present invention has a first lens having negative refractive power, which is sequentially located from the object side. A group (I), a second lens group (II) having positive refractive power, a third lens group (III) having negative refractive power, and a fourth lens group (IV) having positive refractive power. An aperture A is located between I) and the second lens group II.

The first lens group I consists of a lens having at least one negative refractive power and a lens having positive refractive power. In the first to third embodiments of the present invention, the first lens 1, which is a meniscus lens having negative refractive power and the object side surface is convex, the second lens 2 having negative refractive power and concave both sides, and the positive refractive power object It consists of three lenses, the third lens (3) which is a convex meniscus lens on the side, and in the fourth to sixth embodiments, except for the first lens (1), the second lens (2) and the third lens ( It consists of two lenses which are 3).

The second lens group II includes at least one bonded lens and at least one aspherical lens. In the present embodiment, the fourth lens 4 having positive flexural force and convexity on both sides, the fifth lens 5 having positive refractive power and convexity on both sides, and negative refractive power, both sides are concave and bonded to the fifth lens 5, And a sixth lens 6, wherein the object side of the fourth lens 4 is aspheric.

The third lens group III includes a seventh lens 7 which is a meniscus lens having negative refractive power and a convex object side surface. Here, the third lens group III is composed of one lens, but the present invention is not limited thereto.

The fourth lens group IV includes an eighth lens 8 having positive refractive power and both convex surfaces. In the present embodiment, the fourth lens group IV is an optical device for preventing moiré phenomenon or the like caused by the solid-state imaging device in the fourth lens group IV. A filter 9 is included. Meanwhile, the fourth lens group IV may include at least one aspherical surface.

As shown in FIGS. 1, 3, 5, 7, and 9, the compact zoom lens according to the exemplary embodiment of the present invention has a first lens group I and a second lens when zooming from a wide-angle end to a telephoto end. The interval between the group II is decreased, the interval between the second lens group II and the third lens group III is increased, and the interval between the third lens group III and the fourth lens group IV is increased. The lens groups move in an increasing direction to perform a shift.

Specifically, the first lens group I moves toward and away from the image surface, and the second lens group II and the third lens group III move away from the image surface, and the fourth lens group I moves. (IV) is fixed.

Next, the operation of the small zoom lens according to the embodiment of the present invention having such a structure will be described.

In the zoom lens according to the present invention, the second lens group II shifts back and forth on the optical axis so as to have a high ratio of magnification while having a relatively simple configuration, and the first lens group I is the second lens group. It moves in association with (II) to compensate for image movement generated during zooming, and the third lens group III moves to perform focus position correction, that is, focusing according to a subject position.

In particular, the first lens group (I) is composed of a lens having a relatively high dispersion value to reduce magnification chromatic aberration so that high resolution is realized and a convex lens (eighth lens) having a strong positive refractive power with respect to the fourth lens group (IV). 8)) to secure a sufficiently long post-focal length while making it possible to position the exit pupil position as far away from the imaging device as possible so that the chief ray of the telecentric, i.e., the light beam incident on the periphery, is incident at right angles to the imaging device. .

The compact zoom lens according to the present invention satisfies the following conditions in order to implement high resolution with high aspect ratio while securing telecentricity.

(Condition 1)

(Condition 2)

(Condition 3)

Here, f _I represents the focal length of the first lens group I, f _II represents the focal length of the second lens group II, f _III represents the focal length of the third lens group III, _fIV represents the focal length of the fourth lens group IV. In addition, f _IIn represents the focal length of the lens (for example, the sixth lens 6) having a negative refractive power in the second lens group II.

Condition 1 above defines the ratio of the focal length of the first lens group I to the focal length of the second lens group II. When the upper limit of Condition 1 is exceeded, the first lens group I Since the refractive power of is weak, it is difficult to secure the necessary postfocal distance at the wide-angle end, and spherical aberration, coma aberration, and astigmatism are not easily corrected in the telephoto end.

On the contrary, when the lower limit value of Conditional Expression 1 is exceeded, the negative refractive power of the first lens group I becomes strong, the overall length of the lens system becomes long, the telecentricity becomes worse, and the miniaturization becomes difficult.

Condition (2) defines the ratio of the focal length of the third lens group (III) to the focal length of the fourth lens group (IV), and the refractive power of the third lens group (III) when the upper limit value of the conditional formula (2) is exceeded. This weakens and the movement amount of the lens group due to focusing becomes large. Accordingly, the overall length of the lens system is not only deteriorated telecentricity but also difficult to miniaturize.

On the contrary, when the lower limit value of Conditional Expression 2 is exceeded, the refractive power of the third lens group III becomes stronger, which makes it difficult to control aberration, in particular, astigmatism, resulting in severe performance change due to focusing.

Condition Equation 3 defines the ratio of the focal length of the second lens group II to the focal length of the second lens group II. When the upper limit value of Condition 3 is exceeded, The amount of movement of the second lens group II increases during zooming, which increases the overall length of the lens system, making it difficult to correct astigmatism at the wide-angle end and spherical aberration at the telephoto end.

Example values of the small zoom lens according to the embodiment of the present invention satisfying these conditions (Conditions 1 to 3) are as follows.

F represents the focal length, ri (i = 1-18 or i = 1-16) is the radius of curvature of the lens surface, di (i = 1-18 or i = 1-16) is the lens thickness or lens Represents the distance between, nd represents the refractive index and v represents the dispersion value. The unit of the value representing length is mm.

The F number Fno of the zoom lens according to the first embodiment of the present invention has a value of 2.79 to 4.88 between the wide-angle end and the telephoto end, the focal length f has a value of 7.18 mm to 20.49 mm, and an angle of view (2ω). ) Has a value of 66.15 ° to 23.60 °. In particular, the F number Fno at the middle stage is 3.56, the focal length f is 12.21 mm, and the angle of view 2ω is 39.21 °.

Table 1 shows the example values of each lens constituting the zoom lens according to the first embodiment of the present invention.

Face number Radius of curvature (r) Thickness, distance (d) Refractive index (nd) Variance (v) One 19.47200 0.800000 1.785896 43.9344 2 8.48100 3.140000 3 -476.34800 0.800000 1.712999 53.9389 4 19.13900 0.960000 5 12.53600 2.260000 1.846663 23.7848 6 25.01300 D1 7 iris 1.200000 * 8 11.04300 2.440000 1.583129 59.4609 9 -20.63400 0.100000 10 12.28000 2.430000 1.806104 40.7344 11 -6.57200 2.100000 1.698949 30.0505 12 5.12800 D2 13 -166.91100 0.800000 1.517419 52.1508 14 29.82000 D3 15 30.85100 2.710000 1.583129 59.4609 * 16 -12.11500 1.850000 17 ∞ 2.500000 1.516798 64.1983 18 ∞ 1.999579

* Denotes aspherical surface, and the formula for aspherical surface coefficient is as follows.

x: distance from lens vertex to optical axis direction

y: distance in the direction perpendicular to the optical axis

c: Inverse of the radius of curvature at the vertex of the lens (1 / R)

K: Conic constant

A, B, C, D: Aspheric coefficient

The coefficients of each aspherical surface according to the first embodiment of the present invention calculated according to Equation 3 are shown in Table 2 below.

Aspheric coefficient of the eighth page Aspheric coefficient of the 16th surface K -1.736897 K 1.714376 A -0.206887E-03 A 0.372312E-03 B -0.322542E-05 B 0.470649E-05 C 0.265270E-07 C -0.178995E-06 D -0.668279E-08 D 0.346417E-08

The distance D1 between the third lens 3 and the fourth lens 4 changed during zooming, the distance D2 between the sixth lens 6 and the seventh lens 7, and the seventh lens ( A change in distance D3 between 7) and the eighth lens 8 is shown in Table 3 below.

Face number Wide angle Middle Telephoto D1 18.90807 8.21379 2.27751 D2 1.48983 5.18701 9.77877 D3 3.66155 4.66155 7.89965

Fig. 2A shows the aberration characteristics at the wide-angle end of the zoom lens according to the first embodiment of the present invention which consists of these embodiment values, and Fig. 2B shows the aberration characteristics at the telephoto end.

In addition, the F number Fno of the zoom lens according to the second embodiment of the present invention has a value of 2.80 to 5.30 between the wide-angle end and the telephoto end, and the focal length f has a value of 7.19 mm to 20.50 mm. (2ω) has a value of 66.07 ° to 23.58 °. In particular, the F number Fno at the intermediate stage is 3.70, the focal length f is 12.00 mm, and the angle of view 2ω is 39.83 °.

Table 4 shows the example values of each lens constituting the zoom lens according to the second embodiment of the present invention.

Face number Radius of curvature (r) Thickness, distance (d) Refractive index (nd) Variance (v) One 20.16600 0.880000 1.744001 44.8991 2 8.28000 3.180000 3 -180.00000 0.800000 1.712999 53.9389 4 21.76000 0.940000 5 12.50000 2.180000 1.846663 23.7848 6 23.67000 D1 7 iris 1.200000 * 8 11.77700 2.500000 1.583129 59.4609 9 -17.79000 0.170000 10 16.27000 2.480000 1.834999 42.9842 11 -6.10000 2.100000 1.672699 32.1705 12 5.40000 D2 13 90.00000 1.100000 1.517419 52.1508 14 21.76000 D3 15 62.53000 2.550000 1.583129 59.4609 * 16 -11.10700 1.700000 17 ∞ 2.500000 1.516798 64.1983 18 ∞ 2.135379

* Indicates an aspherical surface, and the coefficients of each aspherical surface are shown in Table 5 below.

Aspheric coefficient of the eighth page Aspheric coefficient of the 16th surface K -2.815053 K 0.072884 A -0.289443E-03 A 0.300711E-03 B -0.522318E-05 B 0.196268E-05 C -0.129096E-06 C -0.138580E-06 D -0.369022E-08 D 0.209439E-08

The distance D1 between the third lens 4 and the fourth lens 4 changed during zooming, the distance D2 between the sixth lens 6 and the seventh lens 7, and the seventh lens ( A change in distance D3 between 7) and the eighth lens 8 is shown in Table 6 below.

Face number Wide angle Middle Telephoto D1 18.37484 8.23082 2.28741 D2 2.28286 4.93530 7.30929 D3 2.69205 4.70929 10.83057

Fig. 4A shows the aberration characteristics at the wide-angle end of the zoom lens according to the second embodiment of the present invention, which consists of these embodiment values, and Fig. 4B shows the aberration characteristics at the telephoto end.

In addition, the F number Fno of the zoom lens according to the third embodiment of the present invention has a value of 2.82 to 5.01 between the wide-angle end and the telephoto end, and the focal length f has a value of 7.19 mm to 20.51 mm. (2ω) has a value of 65.95 ° to 23.65 °. In particular, the F number Fno at the intermediate stage is 3.90, the focal length f is 13.80 mm, and the angle of view 2ω is 34.67 °.

Table 7 shows an example value of each lens constituting the zoom lens according to the third embodiment of the present invention.

Face number Radius of curvature (r) Thickness, distance (d) Refractive index (nd) Variance (v) One 23.080000 0.800000 1.744001 44.8991 2 7.95300 3.130000 3 -75.54000 0.800000 1.712999 53.9389 4 29.67300 0.510000 5 12.15000 2.170000 1.846663 23.7848 6 23.30000 D1 7 iris 1.200000 * 8 11.18800 2.250000 1.583129 59.4609 9 -17.06400 0.350000 10 13.44000 2.550000 1.834999 42.9842 11 -6.14600 0.800000 1.672699 32.1705 12 5.40000 D2 13 19.67500 1.200000 1.517419 52.1508 14 9.66500 D3 15 1000.00000 2.600000 1.583129 59.4609 * 16 -9.66500 1.690000 17 ∞ 2.500000 1.516798 64.1983 18 ∞ 2.153390

* Represents an aspherical surface, and the coefficients of each aspherical surface are shown in Table 8 below.

Aspheric coefficient of the eighth page Aspheric coefficient of the 16th surface K -2.747860 K 1.099667 A -0.289427E-03 A 0.532457E-03 B -0.624610E-05 B 0.241358E-05 C -0.522833E-06 C -0.681199E-07 D -0.935972E-08 D 0.384880E-08

The distance D1 between the third lens 3 and the fourth lens 4 changed during zooming, the distance D2 between the sixth lens 6 and the seventh lens 7, and the seventh lens ( A change in distance D3 between 7) and the eighth lens 8 is shown in Table 9 below.

Face number Wide angle Middle Telephoto D1 18.28747 7.05283 3.10217 D2 2.35102 4.02953 5.28024 D3 4.01813 9.37232 15.06813

Fig. 6A shows the aberration characteristics at the wide-angle end of the zoom lens according to the third embodiment of the present invention, which consists of these embodiment values, and Fig. 6B shows the aberration characteristics at the telephoto end.

In addition, the F number Fno of the zoom lens according to the fourth embodiment of the present invention has a value of 2.82 to 4.81 between the wide-angle end and the telephoto end, and the focal length f has a value of 7.19 mm to 20.51 mm. (2ω) has a value of 65.78 ° to 23.74 °. In particular, the F number Fno at the middle stage is 3.78, the focal length f is 13.40 mm, and the angle of view 2ω is 35.74 °.

Table 10 shows an example value of each lens constituting the zoom lens according to the fourth embodiment of the present invention.

Face number Radius of curvature (r) Thickness, distance (d) Refractive index (nd) Variance (v) One -400.00000 0.800000 1.696802 55.4597 2 9.32000 2.280000 3 15.50000 2.510000 1.820267 29.6963 * 4 29.94000 D1 5 Aperture L 1.150000 * 6 10.59500 2.120000 1.516329 64.1420 7 -14.69900 0.100000 8 11.93700 2.480000 1.772500 49.6243 9 -5.68200 0.700000 1.620039 36.3006 10 5.68200 D2 11 13.26000 0.700000 1.804199 46.5025 12 6.86100 D3 13 -175.00000 2.510000 1.516329 64.1420 * 14 -8.52800 2.710013 15 ∞ 2.500000 1.516798 64.1983 16 ∞ 2.139852

* Represents an aspherical surface, and the coefficients of each aspherical surface are shown in Table 11 below.

Aspheric coefficient of the fourth side Aspheric coefficient of page 6 Aspheric coefficient of the 14th surface K -13.4588888 K -3.625703 K -0.705699 A -0.290027E-04 A -0.342617E-03 A 0.351048E-03 B -0.270758E-06 B -0.980875E-05 B -0.155277E-04 C -0.435836E-08 C -0.130822E-06 C 0.577762E-06 D -0.804233E-10 D -0.142240E-07 D -0.884541E-08

The distance D1 between the third lens 4 and the fourth lens 4 changed during zooming, the distance D2 between the sixth lens 6 and the seventh lens 7, and the seventh lens ( A change in distance D3 between 7) and the eighth lens 8 is shown in Table 12 below.

Face number Wide angle Middle Telephoto D1 21.98985 8.73678 2.95000 D2 2.16293 2.59889 3.36377 D3 2.10434 7.77774 13.12224

Fig. 8A shows the aberration characteristics at the wide-angle end of the zoom lens according to the fourth embodiment of the present invention made up of these embodiment values, and Fig. 8B shows the aberration characteristics at the telephoto end.

In addition, the F number Fno of the zoom lens according to the fifth embodiment of the present invention has a value of 2.80 to 4.77 between the wide-angle end and the telephoto end, and the focal length f has a value of 7.19 mm to 20.49 mm. (2ω) has a value of 65.89 ° to 23.73 °. In particular, the F number Fno at the intermediate stage is 3.74, the focal length f is 13.20 mm, and the angle of view 2ω is 36.35 °.

Table 13 shows an example value of each lens constituting the zoom lens according to the fifth embodiment of the present invention.

Face number Radius of curvature (r) Thickness, distance (d) Refractive index (nd) Variance (v) One 300.00000 0.800000 1.772500 49.6243 2 9.32000 2.180000 3 15.04700 2.450000 1.845060 23.6600 * 4 26.77700 D1 5 iris 1.150000 * 6 11.27700 2.190000 1.513160 64.0600 7 -11.72600 0.100000 8 18.15000 2.630000 1.772500 49.6243 9 -5.00000 0.700000 1.603419 38.0106 10 6.77000 D2 11 13.00000 0.700000 1.806104 40.7344 12 6.86100 D3 13 -77.56200 2.480000 1.513160 64.0600 * 14 -8.36100 3.160000 15 ∞ 2.500000 1.516798 64.1983 16 ∞ 2.152605

* Indicates an aspherical surface, and the coefficients of each aspherical surface are shown in Table 14 below.

Aspheric coefficient of the fourth side Aspheric coefficient of page 6 Aspheric coefficient of the 14th surface K 0.099026 K -5.322017 K -0.415773 A -0.925188E-04 A -0.473133E-03 A 0.355515E-03 B 0.117093E-06 B -0.213332E-04 B -0.877710E-05 C -0.991256E-08 C 0.484108E-06 C 0.340916E-06 D -0.308087E-10 D -0.618753E-07 D -0.552005E-08

The distance D1 between the third lens 4 and the fourth lens 4 changed during zooming, the distance D2 between the sixth lens 6 and the seventh lens 7, and the seventh lens ( A change in distance D3 between 7) and the eighth lens 8 is shown in Table 15 below.

Face number Wide angle Middle Telephoto D1 20.57350 8.64446 2.96325 D2 1.81407 2.33761 3.39437 D3 2.87755 8.75595 14.10114

Fig. 10A shows the aberration characteristics at the wide-angle end of the zoom lens according to the fifth embodiment of the present invention made up of these embodiment values, and Fig. 10B shows the aberration characteristics at the telephoto end.

In addition, the F number Fno of the zoom lens according to the sixth embodiment of the present invention has a value of 2.79 to 4.78 between the wide-angle end and the telephoto end, and the focal length f has a value of 7.17 mm to 20.48 m. (2ω) has a value of 66.10 ° to 23.80 °. In particular, the F number Fno at the middle stage is 3.74, the focal length f is 13.15 mm, and the angle of view 2ω is 36.58 °.

Table 16 shows an example value of each lens constituting the zoom lens according to the sixth embodiment of the present invention.

Face number Radius of curvature (r) Thickness, distance (d) Refractive index (nd) Variance (v) One 300.00000 0.800000 1.772500 49.6243 2 9.32000 2.410000 3 16.27000 2.290000 1.845060 23.6116 * 4 30.63500 D1 5 iris 1.150000 * 6 11.56000 2.300000 1.515400 63.1618 7 -13.83700 0.100000 8 12.19000 2.660000 1.772500 49.6243 9 -5.57000 0.700000 1.620039 36.3006 10 5.57000 D2 11 14.31000 1.100000 1.744001 44.8991 12 7.50300 D3 13 -300.00000 2.700000 1.515400 63.1618 * 14 -8.75000 2.690000 15 ∞ 2.500000 1.516798 64.1983 16 ∞ 2.115656

* Represents an aspherical surface, and the coefficients of each aspherical surface are shown in Table 17 below.

Aspheric coefficient of the fourth side Aspheric coefficient of page 6 Aspheric coefficient of the 14th surface K 0.402991 K -4.660218 K -0.509068 A -0.910044E-04 A -0.356272E-03 A 0.322033E-03 B 0.165044E-06 B 0.917357E-06 B -0.859522E-05 C -0.137158E-07 C -0.152725E-05 C 0.319966E-06 D 0.256295E-10 D 0.410936E-07 D -0.525628E-08

The distance D1 between the third lens 4 and the fourth lens 4 changed during zooming, the distance D2 between the sixth lens 6 and the seventh lens 7, and the seventh lens ( A change in distance D3 between 7) and the eighth lens 8 is shown in Table 18 below.

Face number Wide angle Middle Telephoto D1 20.67976 8.72873 2.95107 D2 1.82000 2.51548 4.02189 D3 2.73671 8.25145 12.95527

Fig. 12A shows the aberration characteristics at the wide-angle end of the zoom lens according to the sixth embodiment of the present invention which consists of these embodiment values, and Fig. 12B shows the aberration characteristics at the telephoto end.

The zoom lenses according to each embodiment of the present invention constituted by such embodiment values satisfy the above-described conditions (conditions 1 to 3), and the embodiment values of the conditional expressions are shown in Table 19 below.

Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Equation 1 1.43 1.42 1.36 1.89 1.75 1.65 Equation 2 3.20 3.40 2.33 1.07 1.05 1.30 Equation 3 0.29 0.30 0.33 0.40 0.42 0.37 The invention is not limited to the embodiments described above, and various modifications and changes are possible within the scope of the following claims.

As described above, according to the embodiment of the present invention, it is possible to provide a zoom lens having a high magnification ratio of 2 to 3 times or more with a relatively simple configuration.

In particular, it is possible to provide a small wide-angle zoom lens that can be used at a wide angle and has telecentricity suitable for solid-state imaging devices such as CCD and CMOS.

Claims (6)

delete In order from the object side, A first lens group having negative refractive power; A second lens group having positive refractive power; A third lens group having negative refractive power; And Fourth lens group having positive refractive power Including a zoom lens that satisfies the following conditions. f _I : Focal length of the first lens group f _Ⅱ : Focal length of the second lens group f _III : Focal length of the third lens group f _Ⅳ : Focal length of the fourth lens group (Correction) in order from the object side, A first lens group having negative refractive power; A second lens group having positive refractive power; A third lens group having negative refractive power; And Fourth lens group having positive refractive power In the zooming from the wide-angle end to the telephoto end, the first lens group is moved closer to the image plane and moving away from the second lens group and the third lens group away from the image plane, the fourth lens group A zoom lens that is fixed, has telecentricity, and meets the following conditions. f _III : Focal length of the third lens group f _Ⅳ : Focal length of the fourth lens group The method of claim 3, And the third lens group moves to an image side during focusing. The zoom lens according to claim 2, further comprising the following condition. f _IIn : Focal length of the lens having the negative bending force in the second lens group The method according to claim 2 or 3, The second lens group and the fourth lens group includes at least one aspherical surface.