BACKGROUND OF THE INVENTION
1. Field of the Invention

The invention relates to zoom lens systems for compact video cameras, electronic still cameras, digital cameras, etc. and more particularly to such a high zoom ratio wide-angle zoom lens system having a first lens group of positive diopter, a second lens group of negative diopter, a third lens group of positive diopter, and a fourth lens group of positive diopter so as to have a wide angle of view greater than 70 degrees and more than 10× zoom ratio.

2. Description of Related Art

Recently, compact zoom lens systems as the most important component for a compact video camera, an electronic still camera, digital camera, etc. are developed and commercially available. A compact zoom lens has the benefits of decreasing weight and greatly reducing cost. As a result, for example, the size, weight, and unit price of a compact video camera are decreased greatly.

To achieve the above objective, the focus mechanism is moved from the front element (or first element) to the least lens set. It has the benefits of greatly reducing the size of the first lens group so as to achieve the goal of minimizing the zoom lens system. This in turn can decrease power required for focusing. Therefore, a quick focusing can be achieved.

However, aberration of the rear focusing arrangement is not easy to control. This in turn can increase the difficulty of focusing and lower the image quality due to the increase of zooming range.

Moreover, there are a number of drawbacks associated with rear focusing arrangement systems such as lower resolution, limited angle of view (or angle in short), great distortion, somewhat bulky for carry, and inconvenience in use.

For a digital video camera (DVC) having the features of being lightweight and compact, its lens system cannot achieve the goal of having a wide angle (e.g., about 60-degree of angle) due to optical limitations. Further, there is no suggestion in prior art literatures about a high zoom ratio wide-angle zoom lens system having at least 64-degree angle. Thus, the need for improvement still exists.

SUMMARY OF THE INVENTION
It is therefore one object of the invention to provide a high zoom ratio wide-angle zoom lens system comprising a first lens group comprising a first lens of biconcave, a second lens of positive meniscus, a third lens of biconvex, and a fourth lens of biconvex wherein the first lens and the second lens are lenses not cemented together by adhesive; a second lens group comprising a fifth lens of positive meniscus, a sixth lens of biconcave, a seventh lens of biconvex, and an eighth lens of plano-concave; a third lens group comprising a ninth lens of biconvex; and a fourth lens group comprising a tenth lens of biconvex, an eleventh lens of plano-concave, a twelfth lens of biconvex, and a thirteenth lens of aspheric; wherein the zoom lens system satisfies the following conditions (a)-(e): (a): −2 0.03<R**1**/R**2**<−1.89; (b): 0.13<f_{w}/f_{1}<0.14; (c): −0.6<f_{w}/f_{2}<−0.53; (d):0.11<f_{w}/f_{3}<0.14; and (e): 0.18<f_{w}/f_{4}<0.21 where R**1** is a curvature of a first surface of the first lens, R**2** is a curvature of a second surface of the first lens, f_{w }is a focal length of the overall system at a wide angle, f_{1 }is a focal length of the first lens group, f_{2 }is a focal length of the second lens group, f_{3 }is a focal length of the third lens group, and f_{4 }is a focal length of the fourth lens group.

It is another object of the invention to provide a high zoom ratio wide-angle zoom lens system having a wide angle of view greater than 70 degrees and more than 10× zoom ratio. Moreover, the invention is a miniature system so as to greatly decrease size of the image fetching device. Further, the invention can be made of plastic aspheric lenses and conventional glass lenses so as to greatly reduce the manufacturing cost, have a simple construction, and be easy to assemble.

The above and other objects, features and advantages of the invention will become apparent from the following detailed description taken with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 schematically depicts in section of locations of all lenses of a zoom lens system according to the invention;

FIG. 2A schematically depicts in section of locations of the lenses of FIG. 1 at a wide angle according to a first preferred embodiment of the invention;

FIG. 2B plots curves of longitudinal spherical aberration versus focal length, astigmatic field curves versus focal length, and a curve of distortion versus focal length according to the first preferred embodiment at the wide angle respectively;

FIG. 2C plots curves of longitudinal spherical aberration versus focal length, astigmatic field curves versus focal length, and a curve of distortion versus focal length according to the first preferred embodiment at an intermediate focal length respectively;

FIG. 2D plots curves of longitudinal spherical aberration versus focal length, astigmatic field curves versus focal length, and a curve of distortion versus focal length according to the first preferred embodiment at a narrow angle respectively;

FIG. 3A schematically depicts in section of locations of the lenses of FIG. 1 at the wide angle according to a second preferred embodiment of the invention;

FIG. 3B plots curves of longitudinal spherical aberration versus focal length, astigmatic field curves versus focal length, and a curve of distortion versus focal length according to the second preferred embodiment at the wide angle respectively;

FIG. 3C plots curves of longitudinal spherical aberration versus focal length, astigmatic field curves versus focal length, and a curve of distortion versus focal length according to the second preferred embodiment at the intermediate focal length respectively;

FIG. 3D plots curves of longitudinal spherical aberration versus focal length, astigmatic field curves versus focal length, and a curve of distortion versus focal length according to the second preferred embodiment at the narrow angle respectively;

FIG. 4A schematically depicts in section of locations of the lenses of FIG. 1 at the wide angle according to a third preferred embodiment of the invention;

FIG. 4B plots curves of longitudinal spherical aberration versus focal length, astigmatic field curves versus focal length, and a curve of distortion versus focal length according to the third preferred embodiment at the wide angle respectively;

FIG. 4C plots curves of longitudinal spherical aberration versus focal length, astigmatic field curves versus focal length, and a curve of distortion versus focal length according to the third preferred embodiment at the intermediate focal length respectively;

FIG. 4D plots curves of longitudinal spherical aberration versus focal length, astigmatic field curves versus focal length, and a curve of distortion versus focal length according to the third preferred embodiment at the narrow angle respectively;

FIG. 5A schematically depicts in section of locations of the lenses of FIG. 1 at the wide angle according to a fourth preferred embodiment of the invention;

FIG. 5B plots curves of longitudinal spherical aberration versus focal length, astigmatic field curves versus focal length, and a curve of distortion versus focal length according to the fourth preferred embodiment at the wide angle respectively;

FIG. 5C plots curves of longitudinal spherical aberration versus focal length, astigmatic field curves versus focal length, and a curve of distortion versus focal length according to the fourth preferred embodiment at the intermediate focal length respectively; and

FIG. 5D plots curves of longitudinal spherical aberration versus focal length, astigmatic field curves versus focal length, and a curve of distortion versus focal length according to the fourth preferred embodiment at the narrow angle respectively.

DETAILED DESCRIPTION OF THE INVENTION
Referring to FIG. 1, a high zoom ratio wide-angle zoom lens system in accordance with the invention is shown. The zoom lens system comprises 13 lenses divided into a front first lens group G**1**, a front second lens group G**2** adjacent to the first lens group G**1**, an intermediate third lens group G**3**, and a rear fourth lens group G**4**. The first lens group G**1** is of positive diopter, the second lens group G**2** is of negative diopter, the third lens group G**3** is of positive diopter, and the fourth lens group G**4** is of positive diopter. Position of the first lens group G**1** is fixed during zooming and focusing. The second lens group G**2** that is moved for zooming along the optical axis. Position of the third lens group G**3** is fixed during zooming and focusing. The fourth lens group G**4** that is moved along the optical axis to correct any shift in the focal position due to zooming.

The first lens group G**1** comprises a first lens L**1** of biconcave, a second lens L**2** of positive meniscus, a third lens L**3** of biconvex, and a fourth lens L**4** of biconvex. The second lens group G**2** comprises a fifth lens L**5** of positive meniscus, a sixth lens L**6** of biconcave, a seventh lens L**7** of biconvex, and an eighth lens L**8** of plano-concave. The third lens group G**3** comprises a ninth lens L**9** of biconvex. Aperture is designated by reference numeral “S” in front of the ninth lens L**9**. The fourth lens group G**4** comprises a tenth lens L**10** of biconvex, an eleventh lens L**11** of plano-concave, a twelfth lens L**12** of biconvex, and a thirteenth lens L**13** of biconcave. Preferably, the first lens L**1** and the second lens L**2** are lenses not cemented together by adhesive.

For achieving the goals of having a wide angle of at least 70-degree and “10×” zoom (“10×” zoom means a zoom lens with focal lengths ranging from 100 mm to 1,000 mm), the zoom lens system of the invention is required to satisfy the following conditions:

−20.03<*R*1/*R*2<−1.89; (a)

0.13<*f*_{w}*/f*_{1}<0.14; (b)

−0.60<*f*_{w}*/f*_{2}<−0.53; (c)

0.11<*f*_{w}*/f*_{3}<0.14; and (d)

0.18<*f*_{w}*/f*_{4}<0.21; (e)

where R**1** is a curvature of a first surface of the first lens L**1**, R**2** is a curvature of a second surface of the first lens L**2**, f_{w }is a focal length of the overall system at a wide angle, f_{1 }is a focal length of the first lens group G**1**, f_{2 }is a focal length of the second lens group G**2**, f_{3 }is a focal length of the third lens group G**3**, and f_{4 }is a focal length of the fourth lens group G**4**.

Preferably, the seventh and the thirteenth lenses L**7**, L**13** are aspheric lenses. The remaining lenses are conventional glass lenses so as to reduce the production cost. The invention can have a wide angle and an increased ratio of its longest to shortest focal lengths, and can be made compact and has improved image quality because the aspheric lenses can greatly decrease aberration beyond the optical axis. Preferably, the second and third lenses L**2**, L**3** are formed as single lenses and are cemented together by applying adhesive therebetween. Hence, there is no distance between the second and third lenses L**2** and L**3** so as to facilitate assembly.

First Embodiment
Referring to FIGS. 2A to 2D, a high zoom ratio wide-angle zoom lens system in accordance with a first preferred embodiment of the invention is shown. FIG. 2A is similar to FIG. 1 except minor changes in the shapes. Further, distances of some lenses with respect to a reference point along an optical axis are designated by reference numerals d**8**, d**16**, d**19**, and **26**. Above is also applied to second to fourth preferred embodiments of the invention as detailed later.

Initial optical data of the first embodiment is Fno=1:4.15-5.33, f=3.85-40.40, and w=36.98°−4.00°

where Fno is the diameter of aperture at a wide angle or at a narrow angle, f is the focal length of the overall system at the wide angle or at the narrow angle, and w is half view angle at the wide angle or at the narrow angle. Specific numerical examples are shown in the following Table 1 in which r is the radius of curvature, d is an axial distance between any two lenses, n is the refractive index, and v is Abbe number which represents a value of chromatic aberration of a material, and v is inversely proportional to the value of chromatic aberration.

TABLE 1

r
d
n
v

Surface
INFINITY
8000.000000
AIR

1:
−65.09
1.00
1.836108
26.3

2:
28.37
2.58

3:
−225.87
2.48
1.640601
58.3

4:
−50.86
0.10

5:
76.59
2.82
1.731556
54.1

6:
−87.75
0.10

7:
27.21
4.22
1.750631
49.7

8:
−80.30
d8

9:
29.60
1.00
1.806098
40.9

10:
4.56
2.55
AIR

11:
−15.67
1.00
1.799227
41.8

12:
21.96
0.10

13:
10.67
2.98
1.744132
26.6

14:
−9.51
0.10

15:
−14.49
1.00
1.795994
42.2

16:
47.34
d16

Aperture
INFINITY
0.10

18:
24.43
1.39
1.588071
49.0

19:
−57.36
d19
AIR

20:
10.63
3.80
1.530666
65.7

21:
−7.74
1.00
1.819815
32.7

22:
36.78
0.10

23:
11.65
3.02
1.500616
61.3

24:
−13.17
6.09

25:
A(1)
2.75
1.528992
53.6

26:
A(2)
d26

27:
INFINITY
1.00
n = 1.51680
v = 64.2

28:
INFINITY
1.00

IMG
INFINITY
0.00
AIR

(Imaging surface)

Among the lens group, one surface (R**25**) of the thirteenth lens L**13** and the other surface (R**26**) thereof are aspheric lenses and data of the aspheric coefficient is detailed below.

ASPHERIC
CURV
K
A
B
C
D

A(1)
−0.01195716
133.280681
−2.28426E−03
−5.47008E−05
6.49244E−06
−6.97404E−07

A(2)
0.06611263
−30.924561
−7.11475E−04
−7.87725E−05
9.10356E−06
−7.45500E−07

Variables d**8**, d**16**, d**19** and d**26** have the following data when the focal length changes:

Z1
Z2
Z3

Fno
4.15
5.32
5.33

f
3.85
23.11
40.40

w
36.98°
7.1°
4.0°

d8
1.00
16.77
20.42

d16
20.27
4.58
1.19

d19
13.40
4.94
4.10

d26
1.98
9.48
10.14

For achieving the goals of having a wide angle of at least 70-degree and “10×” zoom, the zoom lens system of the invention is required to satisfy the following conditions:

*R*1/*R*2=−2.3; (a)

*f*_{w}*/f*_{1}=0.14; (b)

*f*_{w}*/f*_{2}=−0.6; (c)

*f*_{w}*/f*_{3}=0.13; and (d)

*f*_{w}*/f*_{4}=0.2; (e)

where R**1** is a curvature of a first surface of the first lens L**1**, R**2** is a curvature of a second surface of the first lens L**2**, f_{w }is a focal length of the overall system at a wide angle, f_{1 }is a focal length of the first lens group G**1**, f_{2 }is a focal length of the second lens group G**2**, f_{3 }is a focal length of the third lens group G**3**, and f_{4 }is a focal length of the fourth lens group G**4**.

Radial changes of the aspheric lens can be expressed in the following equation:

$Z=\frac{\left(\mathrm{curv}\right)\ue89e{Y}^{2}}{1+\left(1-\left(1+K\right)\ue89e{\left(\mathrm{curv}\right)}^{2}\ue89e{Y}^{2}\right)}+\left(A\right)\ue89e{Y}^{4}+\left(B\right)\ue89e{Y}^{6}+\left(C\right)\ue89e{Y}^{8}+\left(D\right)\ue89e{Y}^{10}$

where Z is the amount of sag, curv is the radius of curvature, K is the second curvature constant, Y is the height of the lens with respect to the optical axis, A is fourth aspheric coefficient, B is sixth aspheric coefficient, C is eighth aspheric coefficient, and D is tenth aspheric coefficient.

Second Embodiment
Referring to FIGS. 3A to 3D, a high zoom ratio wide-angle zoom lens system in accordance with a second preferred embodiment of the invention is shown. Initial optical data of the second embodiment is Fno=1:4.2-6.52, f=3.76-39.74, and w=37.1°-4.0°

where Fno is the diameter of aperture at the wide angle or at the narrow angle, f is the focal length of the overall system at the wide angle or at the narrow angle, and w is half view angle at the wide angle or at the narrow angle. Specific numerical examples are shown in the following Table 2 in which r is the radius of curvature, d is an axial distance between any two lenses, n is the refractive index, and v is Abbe number.

TABLE 2

r
d
n
v

Surface
INFINITY
8000.000000
AIR

1:
−426.16
1.00
1.774841
25.6

2:
21.27
2.63

3:
408.78
3.99
1.562885
63.0

4:
−22.27
2.25
1.807752
36.9

5:
−31.38
0.10

6:
23.00
4.27
1.759989
47.8

7:
−93.93
1.00

8:
−240.75
d8
1.727911
54.7

9:
4.78
1.95
AIR

10:
−48.13
1.00
1.640778
58.3

11:
14.09
0.11

12:
A(1)
1.62
1.755201
27.6

13:
A(2)
0.10

14:
15.99
1.55
1.846660
23.8

15:
57.07
21.73

Aperture:
INFINITY
0.10

17:
47.78
1.31
1.792813
42.6

18:
−44.59
14.00
AIR

19:
8.92
d19
1.528851
65.8

20:
−7.60
1.40
1.812367
32.1

21:
28.86
0.10

22:
13.09
2.56
1.508057
57.3

23:
−11.91
5.63

24:
A(3)
1.86
1.525976
55.8

25:
A(4)
1.77

26:
INFINITY
d26
n = 1.51680
v = 64.2

27:
INFINITY
1.00

IMG:
INFINITY
0.00
AIR

(imaging surface)

Among the lens group, one surface (R**12**) of the seventh lens L**7** and the other surface (R**13**) thereof, and one surface (R**24**) of the thirteenth lens L**13** and the other surface (R**25**) thereof are aspheric lenses and data of the aspheric coefficient is detailed below.

ASPHERIC
CURV
K
A
B
C
D

A(1)
0.03225408
−83.262065
1.22060E−03
−6.27430E−05
8.04419E−06
−2.19785E−07

A(2)
0.00031715
1000.000000
2.54885E−04
−4.53630E−05
6.06969E−06
−1.74155E−07

A(3)
−0.03855038
−98.309044
−4.38115E−03
2.37560E−05
−2.59511E−06
−2.20317E−07

A(4)
0.06040181
20.411890
−3.61585E−03
2.37991E−05
−1.95211E−06
−4.87501E−07

Variables d**7**, d**15**, d**18** and d**25** have the following data when the focal length changes:

Z1
Z2
Z3

Fno
4.20
5.82
6.52

f
3.7585
22.5360
39.7414

w
37.1°
7.1°
4.0°

d7
1.00
18.71
21.69

d15
21.73
4.84
1.00

d18
14.00
7.24
4.02

d25
1.766
8.52
10.82

For achieving the goals of having a wide angle of at least 70-degree and “10×” zoom, the zoom lens system of the invention is required to satisfy the following conditions:

*R*1/*R*2=−20.0; (a)

*f*_{w}*/f*_{1}=0.13; (b)

*f*_{w}*/f*_{2}=−0.53; (c)

*f*_{w}*/f*_{3}=0.13; and (d)

*f*_{w}*/f*_{4}=0.20; (e)

where R**1** is a curvature of a first surface of the first lens L**1**, R**2** is a curvature of a second surface of the first lens L**2**, f_{w }is a focal length of the overall system at a wide angle, f_{1 }is a focal length of the first lens group G**1**, f_{2 }is a focal length of the second lens group G**2**, f_{3 }is a focal length of the third lens group G**3**, and f_{4 }is a focal length of the fourth lens group G**4**.

Third Embodiment
Referring to FIGS. 4A to 4D, a high zoom ratio wide-angle zoom lens system in accordance with a third preferred embodiment of the invention is shown. Initial optical data of the second embodiment is Fno=1:4.23-6.22, f=3.88-40.8, and w=36.2°-3.95° where Fno is the diameter of aperture at the wide angle or at the narrow angle, f is the focal length of the overall system at the wide angle or at the narrow angle, and w is half view angle at the wide angle or at the narrow angle. Specific numerical examples are shown in the following Table 3 in which r is the radius of curvature, d is an axial distance between any two lenses, n is the refractive index, and v is Abbe number.

TABLE 3

r
d
n
v

Surface
INFINITY
8000.000000
AIR

1:
−60.26
1.00
1.836326
26.5

2:
31.31
2.13

3:
−743.32
2.35
1.710459
55.3

4:
−51.14
0.10

5:
59.32
2.57
1.690783
56.1

6:
−165.56
0.10

7:
27.32
3.95
1.756432
48.5

8:
−96.56
d8

9:
48.84
1.00
1.802704
41.3

10:
4.60
1.83
AIR

11:
26.401
1.00
1.748836
44.4

12:
9.61
0.22

13:
A(1)
2.712
1.759941
26.0

14:
A(2)
0.10

15:
−11.52
1.00
1.740384
51.9

16:
79.28
d16

Aperture:
INFINITY
0.10

18:
29.08
1.34
1.627436
54.3

19:
−42.25
d19
AIR

20:
11.83
3.77
1.533543
64.7

21:
−7.07
1.00
1.823039
31.2

22:
−578.37
0.11

23:
19.68
3.93
1.495832
64.2

24:
−11.14
6.49

25:
A(3)
1.17
1.693112
49.5

26:
A(4)
d26

27:
INFINITY
1.00
n = 1.51680
v = 64.2

28:
INFINITY
1.00

IMG:
INFINITY
0.00
AIR

(imaging surface)

Among the lens group, one surface (R**13**) of the seventh lens L**7** and the other surface (R**14**) thereof, and one surface (R**25**) of the thirteenth lens L**13** and the other surface (R**26**) thereof are aspheric lenses and data of the aspheric coefficient is detailed below.

ASPHERIC
CURV
K
A
B
C
D

A(1)
0.08295635
−5.448513
6.00781E−04
−1.36227E−05
1.26162E−06
−3.32472E−08

A(2)
−0.08662060
3.294174
−1.78116E−04
−9.47821E−06
1.05270E−06
−5.11438E−08

A(3)
0.02330392
68.871182
−4.12361E−03
7.85338E−05
−6.66906E−06
−3.42850E−07

A(4)
0.08615762
2.252122
−4.20989E−03
1.46807E−04
−1.12529E−05
−3.51121E−08

Variables d**8**, d**16**, d**19** and d**26** have the following data when the focal length changes:

Z1
Z2
Z3

Fno
4.23
5.62
6.22

f
3.8800
23.2902
40.8018

w
36.2°
6.95°
3.95°

d8
1.02
16.39
21.00

d16
20.92
4.36
1.05

d19
10.69
4.59
4.49

d26
1.75
9.03
7.86

For achieving the goals of having a wide angle of at least 70-degree and “10×” zoom, the zoom lens system of the invention is required to satisfy the following conditions:

*R*1/*R*2 =−1.9; (a)

*f*_{w}*/f*_{1}=0.13; (b)

*f*_{w}/f_{2}=−0.58; (c)

*f*_{w}*/f*_{3}=0.14; and (d)

*f*_{w}/f_{4}=0.21; (e)

where R**1** is a curvature of a first surface of the first lens L**1**, R**2** is a curvature of a second surface of the first lens L**2**, f_{w }is a focal length of the overall system at a wide angle, f_{1 }is a focal length of the first lens group G**1**, f_{2 }is a focal length of the second lens group G**2**, f_{3 }is a focal length of the third lens group G**3**, and f_{4 }is a focal length of the fourth lens group G**4**.

Fourth Embodiment
Referring to FIGS. 5A to 5D, a high zoom ratio wide-angle zoom lens system in accordance with a fourth preferred embodiment of the invention is shown. Initial optical data of the second embodiment is Fno=1:4.23-6.72, f=3.85-40.396, and w=36.98°-4.07°

where Fno is the diameter of aperture at the wide angle or at the narrow angle, f is the focal length of the overall system at the wide angle or at the narrow angle, and w is half view angle at the wide angle or at the narrow angle. Specific numerical examples are shown in the following Table 4 in which r is the radius of curvature, d is an axial distance between any two lenses, n is the refractive index, and v is Abbe number.

TABLE 4

r
d
n
v

Surface
INFINITY
8000.000000
AIR

1:
−56.37
1.00
1.839256
25.7

2:
29.89
2.82

3:
−118.33
2.95
1.636770
48.4

4:
−42.12
0.10

5:
41.51
3.77
1.707429
55.4

6:
−87.75
0.10

7:
36.95
3.67
1.763127
47.3

8:
−98.52
d8

9:
36.74
1.00
1.810630
37.7

10:
4.41
3.85
AIR

11:
−23.40
4.16
1.781827
26.6

12:
−6.85
0.10

13:
−12.16
1.00
1.744428
51.0

14:
−177.04
0.28

15:
−15.72
1.00
1.693641
56.0

16:
−37.18
d16

Aperture:
INFINITY
0.10

18:
14.86
1.34
1.600761
58.6

19:
54.05
d19
AIR

20:
9.44
2.97
1.518162
52.8

21:
−8.48
1.00
1.818500
33.2

22:
20.98
0.10

23:
7.27
2.66
1.492027
69.7

24:
−24.35
5.59

25:
A(1)
1.71
1.648858
33.9

26:
A(2)
d26

27:
INFINITY
1.00
n = 1.51680
v = 64.2

28:
INFINITY
1.00

IMG:
INFINITY
0.00
AIR

(imaging surface)

Among the lens group, one surface (R**25**) of the thirteenth lens L**13** and the other surface (R**26**) thereof are aspheric lenses and data of the aspheric coefficient is detailed below.

ASPHERIC
CURV
K
A
B
C
D

A(1)
−0.01702400
424.063941
−4.59088E−03
−2.55640E−05
1.04552E−06
−1.34991E−06

A(2)
0.05361846
−115.549432
−1.81870E−03
−1.67702E−04
1.71618E−05
−1.28758E−06

Variables d**8**, d**16**, d**19** and d**26** have the following data when the focal length changes:

Z1
Z2
Z3

Fno
4.23
5.92
6.72

f
3.8500
23.2902
40.396

w
36.98°
7.12°
4.07°

d8
1.00
18.00
21.77

d16
21.81
4.81
1.00

d19
12.44
5.30
4.62

d26
4.46
11.88
12.37

For achieving the goals of having a wide angle of at least 70-degree and “10×” zoom, the zoom lens system of the invention is required to satisfy the following conditions:

*R*1/*R*2=−1.9; (a)

*f*_{w}*/f*_{1}=0.13; (b)

*f*_{w}*/f*_{2}=−0.56; (c)

*f*_{w}*/f*_{3}=0.11; and (d)

*f*_{w}*/f*_{4}=0.18; (e)

where R**1** is a curvature of a first surface of the first lens L**1**, R**2** is a curvature of a second surface of the first lens L**2**, f_{w }is a focal length of the overall system at a wide angle, f_{1 }is a focal length of the first lens group G**1**, f_{2 }is a focal length of the second lens group G**2**, f_{3 }is a focal length of the third lens group G**3**, and f_{4 }is a focal length of the fourth lens group G**4**.

The zoom lens system of the invention has the following advantages and characteristics: Wide angle of view of at least 70-degree, high zoom ratio (e.g., as high as “10×”), compactness, and lightweight. Moreover, the thirteenth lens L**13** is an aspheric lens formed of a plastic material. The remaining lenses are conventional glass lenses. The aspheric lens can compensate aberration of the zoom lens system. Hence, the production cost is greatly reduced. In addition, the second and third lenses L**2**, L**3** are formed as a doublet lens by applying adhesive therebetween so as to facilitate assembly.

While the invention has been described in terms of preferred embodiments, those skilled in the art will recognize that the invention can be practiced with modifications within the spirit and scope of the appended claims.