KR100363964B1 - 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 2-1 lens having positive flexural force and having both sides convex and an object side aspheric, a 2-2 lens having positive refractive power and both sides convex, and negative refractive power, both sides being concave and bonded to the 2-2 lens A second lens group including a second-3 lens having a positive refractive power; And a third lens group having a positive refractive power, wherein the second lens group shifts back and forth on the optical axis when zooming from the wide-angle end to the telephoto end, and the first lens group is associated with the second lens group. To shift the focus position caused by the shift, and the third lens group is fixed. Especially , Satisfies the conditions.

According to the present invention, it is possible to provide a zoom lens having a high magnification ratio of 2.5 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.

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 imaging device has been rapidly expanding, and it 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

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.

Therefore, an object of the present invention is to provide a zoom lens having a small size and a high aspect ratio as an optical system using a solid-state imaging device.

In particular, it is an object of the present invention to provide a compact wide-angle zoom lens having a relatively simple configuration having a lens group having a variable ratio of about 2.5 to 3 times and fixed at the time of zooming.

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.

In order to achieve the technical problem of the present invention, the compact zoom lens according to the characteristics of the present invention

A first lens group having negative refractive power in order from the object side; A second lens group including a lens having at least one negative refractive power and a lens having at least one surface aspherical and having positive refractive power; And a third lens group having a positive refractive power, wherein the second lens group shifts back and forth on the optical axis when zooming from the wide-angle end to the telephoto end, and the first lens group is associated with the second lens group. To shift the focus position caused by the shift, and the third lens group is fixed. And, (f _I : focal length of the first lens group, f _W : total focal length at the wide-angle end, f _T : total focal length at the telephoto end), (f _II : focal length of the second lens group, f _IIn : focal length of the lens having negative excavation force in the second lens group).

In the small zoom lens according to the present invention, the third lens group may include a lens having an aspherical surface, and the second lens group may include a lens having an aspherical surface and a bonding lens.

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

1, 3, 5, 7 and 9 show the structure of the compact zoom lens according to each embodiment of the present invention for each zoom position.

1, 3, 5, 7, and 9, the small zoom lens according to the embodiment of the present invention includes a first lens group (I) having negative refractive power, which is sequentially located from the object side. ), A second lens group II having positive refractive power, and a third lens group III having positive refractive power. An aperture A is positioned between the first lens group I and the second lens group II.

The first lens group I has a negative refractive power and a first lens 1 which is a meniscus lens having a convex object side, a second lens 2 having a negative refractive power and concave both sides, and a positive refractive power and a convex object side. And a third lens 3 which is a meniscus lens.

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

The third lens group III includes a seventh lens 7 having positive refractive power and both surfaces thereof are convex. In the present embodiment, the third lens group III is an optical device for preventing moiré phenomenon or the like caused by a solid-state image pickup device in the third lens group III. A filter 8 is included.

1, 3, 5, and 7 according to the embodiment of the present invention, when zooming from the wide-angle end to the telephoto end, the second lens group II moves forward and backward on the optical axis. The shifting is performed, and the first lens group I moves in association with the second lens group II to correct the focus position shift occurring at the shifting. At this time, the third lens group III is fixed, and the distance between the third lens 3 and the fourth lens 4 as the first lens group I and the second lens group II move. The distance between the sixth lens 6 and the seventh lens 7 is variable.

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

The zoom lens according to the present invention performs a zooming by moving the second lens group II while the third lens group III is fixed so as to have a high ratio of magnification while having a relatively simple configuration. I) was moved to compensate for image shift caused by the movement of the second lens group II.

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 having a strong positive refractive power with respect to the third lens group (III) (the seventh lens) 7)) to enable telecentricity.

More specifically, in order for the chief ray of the light beam incident on the periphery to be incident at right angles to the imaging device, the exit pupil position should be located as far from the imaging device as possible. For this purpose, the third lens group III having a strong positive refractive power is positioned on the image side of the second lens group II, so that a long post focal length is ensured and it is easy to match the telecentric of the light beam. It became.

The small zoom lens according to the present invention satisfies the following conditions to enable miniaturization and high magnification ratio.

Here, f _I represents the focal length of the first lens group I, f _W represents the total focal length at the wide-angle end, and f _T represents the total focal length at the telephoto end. F _II denotes a focal length of the second lens group II, and f _IIn denotes a focal length of a lens having a negative refractive power in the second lens group II (for example, the sixth lens 6). Indicates.

Equation 1 above defines the ratio of the focal length of the first lens group I to the focal length of the wide-angle end and the telephoto end, and is a condition for securing a long postfocal distance for telecentricity. .

If the upper limit of Equation 1 is exceeded, the negative refractive power of the first lens group I becomes weak, making it difficult to secure a necessary postfocal distance at the wide-angle end, and correction of spherical aberration, coma aberration, and astigmatism at the telephoto end is difficult. Not enough.

On the contrary, when the lower limit value of Equation 1 is exceeded, the negative refractive power of the first lens group I becomes stronger, thereby increasing the lens length and worsening telecentricity.

Equation 2 above defines the ratio of the focal length of the lens having the negative refractive power of the second lens group (II) to the focal length of the second lens group (II) as a condition for aberration correction.

When the upper limit of Equation 2 is exceeded, the lens length is increased, and astigmatism at the wide-angle end and aberration correction at the telephoto end are particularly difficult.

Embodiment values of the small zoom lens according to the embodiment of the present invention satisfying these conditions (Equations 1 and 2) are as follows.

F represents the focal length, ri (i = 1 to 16) represents the radius of curvature of the refractive surface, di (i = 1 to 16) represents the thickness of the lens or the distance between the lenses, nd represents the refractive index, v is 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 2.81 to 5.03 between the wide-angle end and the telephoto end, the focal length f has a value of 8.35 mm to 23.0 mm, and an angle of view (2ω). ) Has a value of 60.97 ° to 22.63 °. In particular, the F number Fno at the middle stage is 3.51, the focal length f is 13.0 mm, and the angle of view 2ω is 39.23 °.

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 31.97000 1.100 1.806104 40.7344 2 8.76700 2.910 3 -33.44400 1.100 1.516798 64.1983 4 71.85000 0.100 5 14.23000 2.230 1.846663 23.7848 6 33.44400 D1 7 iris 1.750 * 8 12.91100 2.720 1.589128 61.2526 9 -20.39600 0.100 10 16.18000 3.060 1.806104 40.7344 11 -8.52000 3.800 1.717359 29.5003 12 5.82000 D2 13 42.62700 2.830 1.589128 61.2526 * 14 -12.11900 0.800 15 ∞ 2.630 1.516798 64.1983 16 ∞ D3

* 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 14th surface K -1.790500 K -19.741000 A -0.129123E-03 A -0.803298E-03 B 0.264592E-05 B 0.325950E-04 C -0.333784E-06 C -0.794578E-06 D 0.109533E-07 D 0.803288E-08

And 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 filter 8. The change amount of the distance D3 between the upper surfaces is shown in Table 3 below.

Face number Wide angle Middle Telephoto D1 16.76396 8.44377 1.94787 D2 6.10686 10.81505 20.94017 D3 2.00002 2.00003 2.00004

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 3.10 to 5.50 between the wide-angle end and the telephoto end, and the focal length f has a value of 7.55 mm to 20.55 mm. (2ω) has a value of 58.94 ° to 22.05 °. In particular, the F number Fno at the middle stage is 3.92, the focal length f is 12.0 mm, and the angle of view 2ω is 37.20 °.

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 32.74000 1.000 1.806104 40.7344 2 7.64800 2.020 3 322.82700 1.000 1.622994 58.1223 4 22.45700 0.260 5 10.33200 2.100 1.846663 23.7848 6 20.67000 D1 7 iris 1.550 * 8 8.31300 2.140 1.589128 61.2526 9 -19.55200 0.100 10 12.04000 1.990 1.772500 49.6243 11 -21.24200 2.250 1.698944 30.0506 12 4.66600 D2 13 -59.65900 2.240 1.589128 61.2526 * 14 -9.42300 1.710 15 ∞ 2.630 1.516798 64.1983 16 ∞ D3

* 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 14th surface K -1.276000 K -1.419000 A -0.136407E-03 A 0.266928E-03 B 0.423893E-05 B -0.830456E-05 C -0.672100E-06 C 0.834921E-07 D 0.311155E-07 D 0.131025E-08

And 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 filter 8. The change amount of the distance D3 between the upper surfaces is shown in Table 6 below.

Face number Wide angle Middle Telephoto D1 14.51648 7.33424 2.26433 D2 5.21070 9.79199 18.59424 D3 2.00482 2.00481 2.00479

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 3.09 to 5.53 between the wide-angle end and the telephoto end, and the focal length f has a value of 8.0 mm to 21.8 mm. (2ω) has a value of 60.42 ° to 22.61 °. In particular, the F number Fno at the intermediate stage is 3.97, the focal length f is 13.0 mm, and the angle of view 2ω is 37.32 °.

Table 7 shows an example value 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 32.74000 1.000 1.806104 40.7344 2 8.00000 2.310 3 -161.81700 1.000 1.622994 58.1223 4 30.56100 0.100 5 11.28000 2.140 1.846663 23.7848 6 23.57300 D1 7 iris 1.550 * 8 10.24900 2.150 1.589128 61.2526 9 -22.77700 0.100 10 11.28000 2.600 1.772500 49.6243 11 -17.69600 2.350 1.698944 30.0506 12 5.00000 D2 13 -1999.80000 2.370 1.589128 61.2526 * 14 -10.78400 1.750 15 ∞ 2.630 1.516798 64.1983 16 ∞ D3

* 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 14th surface K -1.252000 K -2.980000 A -0.100288E-03 A 0.849723E-04 B 0.176154E-05 B -0.388991E-05 C -0.241452E-06 C 0.178224E-07 D 0.899781E-08 D 0.809718E-09

And 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 filter 8. The change amount of the distance D3 between the upper surfaces is shown in Table 9 below.

Face number Wide angle Middle Telephoto D1 14.98877 7.25683 2.26299 D2 5.57073 10.81609 20.04792 D3 2.00924 2.00923 2.00919

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 3.10 to 5.54 between the wide-angle end and the telephoto end, and the focal length f has a value of 7.36 mm to 20.51 mm. (2ω) has a value of 59.65 ° to 21.39 °. In particular, the F number Fno at the middle stage is 3.96, the focal length f is 12.01 mm, and the angle of view 2ω is 36.06 °.

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 26.92700 0.900 1.806104 40.7344 2 7.64800 2.330 3 -134.51000 0.900 1.622994 58.1223 4 26.12800 0.170 5 11.00000 2.070 1.846663 23.7848 6 23.00100 D1 7 iris 1.570 * 8 9.49900 2.080 1.589128 61.2526 9 -22.44000 0.100 10 10.33000 2.070 1.772500 49.6243 11 -19.10000 2.380 1.698944 30.0506 12 4.66600 D2 13 -72.55500 2.190 1.589128 61.2526 * 14 -9.58900 1.670 15 ∞ 2.630 1.516798 64.1983 16 ∞ D3

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

Aspheric coefficient of the eighth page Aspheric coefficient of the 14th surface K -1.069987 K 0.506631 A -0.112950E-03 A 0.542087E-03 B -0.317600E-05 B -0.788554E-05 C 0.431575E-06 C 0.274685E-06 D -0.245485E-07 D -0.301132E-08

And 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 filter 8. The distance D3 variation between the upper surfaces is shown in Table 12 below.

Face number Wide angle Middle Telephoto D1 14.98877 7.25683 2.26299 D2 5.57073 10.81609 20.04792 D3 2.00924 2.00923 2.00919

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 2.9 to 5.0 between the wide-angle end and the telephoto end, and the focal length f has a value of 6.09 mm to 16.9 mm. (2ω) has a value of 60.04 ° to 22.01 °. In particular, the F number Fno at the intermediate stage is 3.7, the focal length f is 10.0 mm, and the angle of view 2ω is 36.78 °.

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 18.64000 1.000 1.806104 40.7344 2 6.67100 2.140 3 -159.09000 0.800 1.622994 58.1223 4 17.72200 0.310 5 9.53000 2.000 1.846663 23.7848 6 18.64000 D1 7 iris 1.450 * 8 8.60500 2.050 1.583129 59.4596 9 -18.68800 0.100 10 9.13000 2.060 1.772500 49.6243 11 -14.90000 1.720 1.698944 30.0506 12 4.28000 D2 13 -45.70600 2.000 1.583129 59.4596 * 14 -7.98600 0.620 15 ∞ 2.500 1.516798 64.1983 16 ∞ D3

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

Aspheric coefficient of the eighth page Aspheric coefficient of the 14th surface K -1.511642 K -0.672301 A -0.162169E-03 A 0.565291E-03 B 0.259769E-04 B -0.270089E-04 C -0.499421E-05 C 0.176487E-05 D 0.312800E-06 D -0.494456E-07

And 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 filter 8. The distance D3 change amount between the upper surfaces is shown in Table 15 below.

Face number Wide angle Middle Telephoto D1 14.05635 6.85221 2.26673 D2 3.84163 8.07622 15.55044 D3 2.90180 2.90180 2.90180

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.

The zoom lenses according to the exemplary embodiments of the present invention configured as such exemplary embodiments satisfy the above-described conditions (Equation 1 and Equation 2).

First embodiment Second embodiment Third embodiment Fourth embodiment Fifth Embodiment Equation 1 1.46 1.32 1.34 1.37 1.44 Equation 2 0.31 0.43 0.41 0.42 0.41

The invention is not limited to the embodiments described above, and various modifications and changes are possible within the scope of the following claims.

According to the embodiment of the present invention as described above, it is possible to provide a zoom lens having a high magnification ratio of 2.5 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 (5)

(Correction) in order from the object side, A first lens group having negative refractive power; A 2-1 lens having positive flexural force and having both sides convex and an object side aspheric, a 2-2 lens having positive refractive power and both sides convex, and negative refractive power, both sides being concave and bonded to the 2-2 lens A second lens group including a second-3 lens having a positive refractive power; And Third lens group having positive refractive power And zooming from the wide-angle end to the telephoto end, wherein the second lens group moves back and forth on the optical axis to perform shifting, and the first lens group moves in association with the second lens group to generate focus. A zoom lens, characterized in that the positional shift is corrected and the third lens group is fixed and the following conditions are satisfied. f _I : Focal length of the first lens group f _W : Total focal length at wide end f _T : total focal length from telephoto f _II : Focal length of the second lens group f _IIn : Focal length of the lens having the negative bending force in the second lens group (delete) The zoom lens of claim 1, wherein the third lens group includes a lens having an aspherical surface. (delete) (Correction) The method according to claim 1, The first lens group has a negative refractive power and is a meniscus lens having a convex object side, a 1-2 lens having negative refractive power and a concave both sides, and a positive lens having a positive refractive power and a convex object side. It includes a lens 1-3 lens, And the third lens group includes a 3-1 lens having positive refractive power and both convex surfaces.