ZOOM LENS AND IMAGING APPARATUS USING ZOOM LENS

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the present invention will be described in detail based on the following figures, wherein:

FIG. 1 shows a cross section along an optical axis of a zoom lens according to a preferred embodiment of the present invention;

FIG. 2 shows a cross section along an optical axis of a zoom lens according to a first example of the present invention at a wide angle end;

FIG. 3 shows various aberrations of the zoom lens according to the first example at a short-focal length end;

FIG. 4 shows various aberrations of the zoom lens according to the first example at an intermediate-focal length;

FIG. 5 shows various aberrations of a zoom lens according to the first example at a long-focal length end;

FIG. 6 shows a cross section along an optical axis of a zoom lens according to a second example of the present invention at a wide angle end;

FIG. 7 shows various aberrations of the zoom lens according to the second example at a short-focal length end;

FIG. 8 shows various aberrations of the zoom lens according to the second example at an intermediate-focal length end;

FIG. 9 shows various aberrations of the zoom lens according to the second example at a long-focal length end;

FIG. 10 shows a cross section along an optical axis of a zoom lens according to a third example of the present invention at a wide angle end;

FIG. 11 shows various aberrations of the zoom lens according to the third example at a short-focal length end;

FIG. 12 shows various aberrations of the zoom lens according to the third example at an intermediate-focal length end;

FIG. 13 shows various aberrations of the zoom lens according to the third example at a long-focal length end;

FIG. 14 shows a cross section along an optical axis of a zoom lens according to a fourth example of the present invention at a wide angle end;

FIG. 15 shows various aberrations of the zoom lens according to the fourth example at a short-focal length end;

FIG. 16 shows various aberrations of the zoom lens according to the fourth example at an intermediate-focal length end;

FIG. 17 shows various aberrations of the zoom lens according to the fourth example at a long-focal length end; and

FIG. 18 shows one example of a digital camera equipped with a zoom lens according to the present invention.

DESCRIPTION OF PREFERRED EMBODIMENTS

The best mode for carrying out the invention is described below with reference to the drawings.

FIG. 1 shows a cross section along the optical axis of a zoom lens according to a preferred embodiment of the present invention. As shown in FIG. 1, the zoom lens 10 includes a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, a third lens group G3 having a positive refractive power, a fourth lens group G4 having a positive refractive power and a fifth lens group G5 having a positive refractive power, which are sequentially arranged in this order from the object side. In the preferred embodiment, zooming is performed by independent movement of the first lens group G1, the second lens group G2, the third lens group G3 and the fourth lens group G4 along an optical axis. Image stabilization (vibration control) for correcting camera shake is performed by movement of the fourth lens group G4 perpendicular to the optical axis.

In the preferred embodiment, the first lens group G1 focuses light rays with a positive refractive power. The second lens group G2, with a negative refractive power, then enlarges the object image formed by the first lens group G1. The third lens group G3 and the fourth lens group G4 share a function for converging light rays enlarged by the second lens group G2, and both therefore have a positive refractive power. When zooming from a wide angle view to a telephoto view, that is, when varying the focal length from the wide angle end to the telephoto end, as shown in FIG. 1, each lens group is moved along the optical axis as shown by the arrows, in the direction to which space between the first lens group G1 and the second lens group G2 is increased and in the direction to which space between the second lens group G2 and the third lens group G3 is reduced. Thus, each lens group is independently moved such that each lens group contributes to the adjustment of zoom ratio, enabling the zoom lens to attain miniaturization and high zoom ratio.

The third lens group G3 and the fourth lens group G4 converge light beams by their positive refractive power and share an imaging function. A light amount controlling mechanism IR including a diaphragm function for adjusting the amount of light and a shutter function for opening or closing an optical path is provided on the object side of the third lens group G3. An image stabilizing (vibration dampening) mechanism (not shown) in which the fourth lens group G4 is moved substantially perpendicularly to the optical axis to move the image in a direction opposite to a direction to which the image is moved by external factors such as camera shake is provided in the vicinity of the fourth lens group G4.

In the preferred embodiment, the light amount controlling mechanism IR is provided near the third lens group G3 and the vibration-proof mechanism is provided near the fourth lens group G4. That is to say, the light amount controlling mechanism IR and the vibration-proof mechanism are provided in the vicinity of the lens groups different from each other. As a result, restrictions on space for arranging the light amount controlling mechanism IR and the vibration-proof mechanism are loosened, and a more compact zoom lens can be realized.

In the preferred embodiment, the space between the third lens group G3 and the fourth lens group G4 is varied when zooming from the wide angle end to the telephoto end, to simultaneously correct aberration caused by the vibration control of the fourth lens group G4, curvature of image plane, coma aberration caused by a high zoom ratio, and image plane movement caused at the time of zoom operation, at each zoom ratio range.

Furthermore, each lens group is moved to reduce the space between the third lens group G3 and the fourth lens group G4 at the time of zooming from the wide angle end to the telephoto end to refract off-axis light beams at the periphery of the fourth lens group G4 performing a vibration control. At the telephoto end, off-axis light beams are refracted near the optical axis to satisfactorily correct a curvature of image plane in the focal length range at the wide angle side. Each lens group is further moved so as to reduce the space between the third lens group G3 and the fourth lens group G4, allowing suppressing the occurrence of coma aberration caused by the fourth lens group G4's decentering at the time of the vibration control in the focal length range at the telephoto side.

Furthermore, the fifth lens group G5 has functions to move the position of an exit pupil to the object side so that a solid-state imaging device such as a CCD having directivity in an optical sensitivity properly outputs video signals and to supplementally correct image plane movement caused by zooming. The fifth lens group G5 may be structured to be fixed at the time of zooming.

Still furthermore, it is preferable that the zoom lens 10 satisfies the following conditions in order to maintain high zoom ratio and high optical performance over the entire zoom range.

First, if surface distances on the optical axis between the third lens group G3 and the fourth lens group G4 at the wide angle end and the telephoto end are taken as T34w and T34t respectively, the zoom lens 10 preferably satisfies the following Conditional Expression (1):

2.0<T34w/T34t<7.0 (1)

This Conditional Expression (1) defines the ratio of the surface distance on the optical axis between the third lens group G3 and the fourth lens group G4 at the wide angle end and the telephoto end. If T34w/T34t is not less than 7.0, which is the upper limit of the Conditional Expression (1), the lens diameter of the fourth lens group G4 performing a vibration control must be increased because light passing through the fourth lens group G4 is excessively dispersed beyond the optical axis toward the outer periphery at the wide angle end. On the other hand, when T34w/T34t is not less than 7.0, which is the upper limit of the Conditional Expression (1), the variation of the surface distance between the third lens group G3 and the fourth lens group G4 is comparatively larger. For this reason, if T34w/T34t is not less than 7.0 Conditional Expression (1), it is necessary to provide movement space between the third lens group G3 and the fourth lens group G4, resulting in increasing the size of the entire system of the zoom lens. In addition, if T34w/T34t is not greater than 2.0, which is the lower limit of the Conditional Expression (1), the variation of the surface distance between the third lens group G3 and the fourth lens group G4 is significantly smaller. In this case, it is often not possible to correct both off-axis aberrations such as astigmatism and field curvature caused by the fourth lens group G4 at the wide angle end, and coma aberration caused by the fourth lens group G4's decentering on the axis at the time of vibration control at the telephoto end. As described above, according to the preferred embodiment, if the ratio of the surface distance on the optical axis between the third lens group G3 and the fourth lens group G4 satisfies the Conditional Expression (1), a field curvature occurred at the wide angle end and a coma aberration caused at the time of vibration control of the fourth lens group G4 at the telephoto side can be satisfactorily corrected, thereby realizing a compact five-group zoom lens capable of high zoom ratio.

In addition, if the composite focal length of the third lens group G3 and the fourth lens group G4 at the wide angle end and the telephoto end is taken as f34w and f34t respectively, the focal length of the third lens group G3 and the fourth lens group G4 is taken as f3 and f4 respectively, and the focal length of the entire system of the zoom lens 10 at the wide angle end and the telephoto end is taken as fw and ft respectively, the zoom lens 10 preferably satisfies the following Conditional Expressions (2), (3), (4) and (5):

2.7<f34w/fw<4.0 (2)

0.15<f34t/ft<0.36 (3)

3.3<f3/fw<fw<5.5 (4)

0.2<f4/ft<0.6 (5)

Conditional Expression (2) defines the composite focal length of the third lens group G3 and the fourth lens group G4 at the wide angle end. If f34w/fw is not less than 4.0, which is the upper limit of the Conditional Expression (2), the refractive power of the third lens group G3 and the fourth lens group G4 with respect to the overall system becomes excessively weak at the wide angle end, hampering or limiting attempts to increase the zoom ratio. If, on the other hand, f34w/fw is not greater than 2.7, which is the lower limit of the Conditional Expression (2), the refractive power of the third lens group G3 and the fourth lens group G4 at the wide angle end becomes excessively strong, hampering attempts to secure space for arranging the fifth lens group G5 nearer to the image plane than the fourth lens group G4 and arranging optical equivalent members such as an optical low pass filter and the like.

The Conditional Expression (3) defines the composite focal length of the third lens group G3 and the fourth lens group G4 at the telephoto end. If f34t/ft is not less than 0.36, which is the upper limit of the Conditional Expression (3), the refractive power of the third lens group G3 and the fourth lens group G4 with respect to the entire system at the telephoto end becomes excessively weak, making it necessary to lengthen the overall system of the zoom lens in the direction of the optical axis. If f34t/ft is not greater than 0.15, which is the lower limit of the Conditional Expression (3), the refractive power of the third lens group G3 and the fourth lens group G4 with respect to the entire system at the telephoto end becomes excessively strong, which increases coma aberration caused by the fourth lens group G4's decentering at the time of vibration control, which in turn makes correction difficult.

The Conditional Expression (4) defines an appropriate range for the focal length of the third lens group G3 at the wide angle end. If f3/fw is not less than 5.5, which is the upper limit of the Conditional Expression (4), the refractive power of the third lens group G3 with respect to the overall system becomes excessively weak, which makes it difficult to increase the zoom ratio, as well as making it necessary to enlarge the lens diameter of the fourth lens group G4 arranged nearer to the image plane than the third lens group G3, which may in turn increasing both the size and power consumption of the image stabilizing mechanism provided on the fourth lens group G4. Furthermore, if f3/fw is not greater than 3.3, which is the lower limit of the Conditional Expression (4), the refractive power of the third lens group G3 with respect to the entire system becomes excessively strong, which makes it difficult to satisfactorily correct a spherical aberration or an axial chromatic aberration.

The Conditional Expression (5) defines an appropriate range for the focal length of the fourth lens group G4 at the telephoto end. If f4/fw is not less than 0.6, which is the upper limit of the Conditional Expression (5), the refractive power of the fourth lens group G4 with respect to the overall system is weak, such that the effect of the fourth lens group G4 is insufficient, such that elongation of the overall system of the zoom lens in the direction of the optical axis is required. If, on the other hand, f4/ft is not greater than 0.2, which is the lower limit of the Conditional Expression (5), the refractive power of the fourth lens group G4 with respect to the entire system becomes excessively strong, which makes it difficult to satisfactorily correct astigmatism and lateral chromatic aberration caused at the time of vibration control of the fourth lens group G4 in a the focal length region at the telephoto side.

As stated above, ensuring that the Conditional Expressions (2) to (5) are satisfied makes it possible to realize a compact five-group zoom lens of high zoom ratio capable of satisfactorily correcting various aberrations at each zoom range and reducing variation in aberration at the time of vibration control.

In addition, when the focal length of the first lens group G1 and the second lens group G2 are f1 and f2, respectively, and the focal length of the entire system of the zoom lens at the wide angle end and at the telephoto end is taken as fw and ft respectively, the zoom lens 10 preferably satisfies the following Conditional Expressions (6) and (7):

6.7<f1/fw<14.0 (6)

0.08<|f2/ft|<0.16 (7)

Conditional Expression (6) defines an appropriate range for the focal length of the first lens group G1 at the wide angle end. If f1/fw is not less than 14.0, which is the upper limit of the Conditional Expression (6), the refractive power of the first lens group G1 with respect to the entire system becomes excessively weak, which hampers efforts to increase the zoom ratio. If, on the other hand, f1/fw is not greater than 6.7, which is the lower limit of the Conditional Expression (6), the refractive power of the first lens group G1 with respect to the entire system becomes excessively strong, which makes it difficult to satisfactorily correct a spherical aberration or an axial chromatic aberration at the wide angle end.

The Conditional Expression (7) defines an appropriate range for the focal length of the second lens group G2 at the telephoto end. If f2/ft is less than 0.16, which is the upper limit of the Conditional Expression (7), the refractive power of the second lens group G2 with respect to the overall system becomes excessively weak, which hampers attempts to increase the zoom ratio of the zoom lens. If, on the other hand, f2/fw is not greater than 0.08, which is the lower limit of the Conditional Expression (7), the refractive power of the second lens group G2 with respect to the entire system becomes excessively strong, which making it difficult to satisfactorily correct a spherical aberration or an axial chromatic aberration at the telephoto end.

Furthermore, in the preferred embodiment, the lens face of the fourth lens group G4 positioned nearest to the image plane has a convex shape facing the image plane. If the radius of curvature is taken as Ra, it is desirable to satisfy the following Conditional Expression (8):

|Ra/fw|<5.5 (8)

Conditional Expression (8) defines an appropriate shape of lens face of the fourth lens group G4, which performs vibration control, positioned nearest to the image plane. If |Ra/fw| is not greater than 5.5, which is the lower limit of the Conditional Expression (8), the angle of incidence of light upon the surface of the lens in the fourth lens group G4 positioned nearest to the image plane becomes large, which makes it difficult to satisfactorily correct aberration at the time of vibration control.

In addition, in the preferred embodiment, it is preferable that the fourth lens group G4 is constituted by a cemented lens in which a negative meniscus lens with its convex surface facing the object side and a positive lens with its convex surface facing back to back are sequentially arranged in this order from the object side and joined together. Constituting the fourth lens group G4 in this manner makes it possible to minimize the occurrence of a chromatic aberration at the time of vibration control and downsizing the vibration-proof mechanism provided near the fourth lens group G4.

In the preferred embodiment, the fifth lens group G5 is moved to focus an image. If the focal length of the fifth lens group G5 is taken as f5, it is preferable that the following Conditional Expression (9) be satisfied:

0.24<f5/ft<0.80 (9)

Conditional Expression (9) defines an appropriate range for the focal length of the fifth lens group G5 in the overall system of the zoom lens at the telephoto end. If f5/ft is not less than 0.80, which is the upper limit of the Conditional Expression (9), the overall refractive power of the fifth lens group G5 is reduced, reducing the efficiency of that lens group and making it necessary to lengthen the overall system of the zoom lens along the direction of the optical axis. If, on the other hand, f5/ft is not more than 0.24, which is the lower limit of the Conditional Expression (9), the refractive power of the fifth lens group G5 with respect to the entire system becomes excessively strong, which makes it difficult to satisfactorily correct an astigmatism and a lateralchromatic aberration.

In addition, in the preferred embodiment, the use of an aspherical lens instead of at least some of the lenses constituting the second lens group G2 and the third lens group G3 makes it possible to effectively correct aberration and to realize the zoom lens 10 with a higher zoom ratio and a wider angle. Further, constituting some component of the second lens group G2 with an aspherical lens makes it possible to satisfactorily correct distortion aberration and astigmatism at the wide angle range. Still furthermore, constituting a part of the third lens group G3 with an aspherical lens makes it possible to satisfactorily correct spherical aberration, especially at the telephoto end.

Constituting the lens groups so as to simultaneously satisfy all of the above conditions makes it possible to provide zoom lens 10 which is compact, has a zoom ratio as high as 11× to 17×, and is suited for use in conjunction with a high-resolution solid-state imaging device having a relatively larger number of pixels. Because a zoom lens 10 which satisfies each of the conditions defined above can provide high performance imaging and suppresses change in aberration during vibration dampening, aberration can be satisfactorily corrected image stabilization. Thus, an imaging apparatus equipped with the zoom lens 10 can simultaneously attain reduction in size, high zoom ratio, and include an image stabilization function.

In the following, first, second, third, and fourth preferred embodiments of the present invention are described with reference to the drawings. FIGS. 2 to 5 relate to the first example of the present invention; FIGS. 6 to 9 relate to the second example; FIGS. 10 to 13 relate to the third example; and FIGS. 14 to 17 relate to the fourth example.

First, items common among the embodiments will be described.

In the following description, “Si” denotes the i-th surface numbered from an object side, “Ri” a radius of curvature on a surface Si, “Ti” a surface space on the optical axis between the i-th and the i+1-th surface from the object side, “ndLi” a refractive index of the lens Li for d-line (wavelength of 587.6 nm), “vdLi” the Abbe number of the lens Li for d-line, “f” the focal length of the entire lens system, “Fno” an open aperture f-number, and “ω” a value equal to one half the viewing angle.

Lenses used in the embodiments include lenses constituted by an aspheric surface lens.

If the distance from the apex of a lens toward the optical axis is “x”, the distance from the apex of a lens to the direction perpendicular to the optical axis is “y”, the paraxial radius of curvature is R, and an aspheric surface coefficient is k, A, B, C and D, the aspheric surface shape can be expressed by the following equation:

$\begin{matrix} x = \frac{(1 / R) y^{2}}{1 + \sqrt{1 - (1 + k) {(y / R)}^{2}}} + {Ay}^{4} + {By}^{6} + {Cy}^{8} + {Dy}^{10} & [Numerical Expression 1] \end{matrix}$

As shown in FIGS. 2, 6, 10 and 14, the zoom lenses in the first to fourth examples include a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, a third lens group G3 having a positive refractive power, a fourth lens group G4 having a positive refractive power, and a fifth lens group G5 having a positive refractive power, sequentially arranged in that order from the object side to image plane IMG. FIGS. 2, 6, 10 and 14 show a positional relationship between the lens groups at the wide angle end.

The light amount controlling mechanism IR functioning as a diaphragm and a shutter is arranged between the second lens group G2 and the third lens group G3. In addition, an optical equivalent member L15 is arranged between the fifth lens group G5 and the image plane IMG. The optical equivalent member L15 may be constituted by a low pass filter, an infrared cut filter, and a cover glass for a solid-state imaging device, for example, with the components being sequentially arranged in that order from the object side.

FIRST EXAMPLE

FIG. 2 shows a cross section along the optical axis of the zoom lens 10 according to a first example of the present invention, at the wide angle end. As shown in FIG. 2, in the first example, the first lens group G1 is composed of a cemented lens in which a negative meniscus lens L1 and a biconvex lens L2 are joined together and then a positive meniscus lens L3 with its convex surface facing the object side is provided, with the lenses provided in that order from the object side. As a unit, the first lens group G1 has a positive refractive power.

The second lens group G2 is composed of a negative meniscus lens L4, a biconcave lens L5, and a cemented lens in which a biconvex lens L6 and a biconcave lens L7 are joined together, sequentially arranged in that order from the object side. As a unit, the second lens group G2 has a negative refractive power.

The third lens group G3 is composed of a biconvex lens L8 and a cemented lens in which a biconvex lens L9 and a biconcave lens L10 are joined together, sequentially arranged in that order from the object side. As a unit, the second lens group G3 has a positive refractive power. The light amount controlling mechanism IR is provided adjacent to the third lens group G3 on the object side.

The fourth lens group G4 is constituted by a cemented lens in which a negative meniscus lens L11 and a biconvex lens L12 are sequentially arranged, in that order from the object side, and joined together. As a unit, the fourth lens group G4 has a positive refractive power. The vibration-proof mechanism is provided in the vicinity of the fourth lens group G4 to move the fourth lens group G4 substantially perpendicularly to the optical axis thereof to compensate for vibration of images caused by camera shake.

The fifth lens group G5 is constituted by a cemented lens in which a biconvex lens L13 and a negative meniscus lens L14 are sequentially arranged, in that order from the object side, and joined together. As a whole, the fifth lens group G5 has a positive refractive power.

Table 1 shows the focal length, F number and half viewing angle of the zoom lens according to the first example for short, intermediate, and long focal lengths. Length “f” is measured in mm, and angle “ω” in degrees.

TABLE 1

FOCAL LENGTH
f
Fno
ω

SHORT
6.03
2.88
32.03

INTERMEDIATE
20.26
3.42
10.08

LONG
68.11
4.67
2.99

Table 2 shows numerical data of a zoom lens according to the first example. Lengths R and T are measured in mm, and INF in the table indicates infinity.

TABLE 2

ABBE

RADIUS OF
SURFACE
REFRACTIVE
NUMBER

SURFACE
CURVATURE R
SPACE T
INDEX ndL
νdL

L1
S1
R1
40.000
T1
1.500
ndL1
1.8467
νdL1
23.8

L2
S2
R2
27.860
T2
5.500
ndL2
1.4875
νdL2
70.4

S3
R3
−218.300
T3
0.200

—

—

L3
S4
R4
25.890
T4
3.200
ndL3
1.4970
νdL3
81.6

S5
R5
70.900
T5
VARIABLE

—

—

L4
S6
R6
95.800
T6
1.300
ndL4
1.7550
νdL4
52.3

S7
R7
6.554
T7
3.816

—

—

L5
S8
R8
−21.920
T8
0.800
ndL5
1.5891
νdL5
61.3

S9
R9
21.920
T9
0.200

—

—

L6
S10
R10
11.570
T10
3.000
ndL6
1.8467
νdL6
23.8

L7
S11
R11
−46.290
T11
0.800
ndL7
1.8061
νdL7
33.3

S12
R12
21.800
T12
VARIABLE

—

—

IR
—
R13
—
T13
0.500

—

—

L8
S13
R14
21.900
T14
2.000
ndL8
1.4970
νdL8
81.6

S14
R15
−21.900
T15
0.100

—

—

L9
S15
R16
8.960
T16
3.300
ndL9
1.6230
νdL9
58.1

L10
S16
R17
−9.900
T17
1.800
ndL10
1.7015
νdL10
41.1

S17
R18
7.506
T18
VARIABLE

—

—

L11
S18
R19
13.950
T19
0.800
ndL11
1.8042
νdL11
46.5

L12
S19
R20
9.100
T20
3.000
ndL12
1.4875
νdL12
70.4

S20
R21
−90.000
T21
VARIABLE

—

—

L13
S21
R22
18.460
T22
3.500
ndL13
1.8042
νdL13
46.5

L14
S22
R23
−18.460
T23
1.000
ndL14
1.8052
νdL14
25.5

S23
R24
−509.000
T24
VARIABLE

—

—

L15
S24
R25
INF
T25
1.500
ndL15
1.5168
νdL15
64.2

S25
R26
INF
T26
—

—

—

Table 3 shows the values of surface intervals T5, T12, T18, T21 and T24 which can be varied by zooming at the short, intermediate, and long focal lengths.

TABLE 3

FOCAL LENGTH

6.03
20.26
68.11

S5
1.013
14.308
23.893

S12
21.984
7.653
3.000

S17
7.799
2.800
2.000

S20
3.500
11.617
24.832

S23
3.401
7.684
3.300

Table 4 shows parameters of Conditional Expressions (1) to (9) according to the first example.

TABLE 4

(1)
T34w/T34t
3.90

(2)
f34w/fw
3.02

(3)
f34t/ft
0.23

(4)
f3/fw
3.49

(5)
f4/ft
0.51

(6)
f1/fw
7.33

(7)
|f2/ft|
0.11

(8)
|Ra/fw|
14.93

(9)
f5/ft
0.33

FIGS. 3 to 5 show various aberrations of the zoom lens 10 according to the first example at the short, intermediate and long focal length ends. In FIGS. 3 to 5, A denotes a spherical aberration, B an astigmatism, C a distortion, D a ray intercept curve without vibration control, and E a ray intercept curve with vibration control. In FIGS. 3 to 5, image height is Y. This applies to the second through forth examples.

As shown in FIGS. 3 to 5, a zoom lens 10 according to the first example is capable of realizing a high zoom ratio and of satisfactorily correcting various aberrations, even while performing image stabilization, at zoom ranges from wide angle end to telephoto.

SECOND EXAMPLE

Next, a second example of the present invention will be described. As shown in FIG. 6, the first lens group G1 in the second example has the same structure as that of the first example. The second lens group G2 is composed of a negative meniscus lens L4 with its convex surface facing the object side, a biconcave lens L5, and a cemented lens in which a biconvex lens L6 and a biconcave lens L7 are joined together, which are sequentially arranged, in that order, from the object side. As a unit, the second lens group G2 has a negative refractive power. It should be noted that the surface S8 of the biconcave lens L5 is aspherical on the object side.

The third lens group G3 is composed a biconvex lens L8, a biconvex lens L9, and a biconcave lens L10, which are sequentially arranged, in that order, from the object side. As a unit, the third lens group G3 has a positive refractive power. The light amount controlling mechanism IR is provided adjacent to the third lens group G3 on the object side as is the case with the first example.

The fourth lens group G4 has the same structure as that of the first example. The fifth lens group G5 is composed of a biconvex lens L13 and a biconcave lens L14, which are sequentially arranged in that order from the object side. As a whole, the fifth lens group G5 has a positive refractive power.

Table 5 shows the focal length, F number, and half viewing angle of the zoom lens according to the second example for short, intermediate. and long focal lengths.

TABLE 5

FOCAL LENGTH
f
Fno
ω

SHORT
4.73
2.49
38.69

INTERMEDIATE
18.30
3.11
11.04

LONG
71.00
5.05
2.87

Table 6 shows numerical data of a zoom lens according to the second example.

TABLE 6

ABBE

RADIUS OF
SURFACE
REFRACTIVE
NUMBER

SURFACE
CURVATURE
SPACE T
INDEX Nd
νd

L1
S1
R1
74.870
T1
1.700
ndL1
1.8467
νdL1
23.8

L2
S2
R2
48.640
T2
8.130
ndL2
1.4875
νdL2
70.4

S3
R3
−271.800
T3
0.200

—

—

L3
S4
R4
33.950
T4
4.580
ndL3
1.4970
νdL3
81.6

S5
R5
101.000
T5
VARIABLE

—

—

L4
S6
R6
66.390
T6
1.400
ndL4
1.7550
νdL4
52.3

S7
R7
7.495
T7
4.870

—

—

L5
S8
R8
−21.823
T8
1.500
ndL5
1.7433
νdL5
49.3

S9
R9
22.542
T9
0.150

—

—

L6
S10
R10
16.040
T10
3.700
ndL6
1.8467
νdL6
23.8

L7
S11
R11
−24.935
T11
0.800
ndL7
1.8350
νdL7
43.0

S12
R12
77.440
T12
VARIABLE

—

—

IR
—
R13
—
T13
0.500

—

—

L8
S13
R14
16.848
T14
1.800
ndL8
1.8155
νdL8
44.5

S14
R15
−61.470
T15
0.100

—

—

L9
S15
R16
12.163
T16
2.800
ndL9
1.4970
νdL9
61.6

S16
R17
−31.700
T17
0.120

L10
S17
R18
−22.524
T18
2.000
ndL10
1.7174
νdL10
29.5

S18
R19
9.948
T19
VARIABLE

—

—

L11
S19
R20
14.198
T20
0.700
ndL11
1.8042
νdL11
46.5

L12
S20
R21
8.782
T21
4.000
ndL12
1.4875
νdL12
70.4

S21
R22
−29.390
T22
VARIABLE

—

—

L13
S22
R23
13.655
T23
3.000
ndL13
1.7170
νdL13
48.0

S23
R24
−48.420
T24
0.500

—

—

L14
S24
R25
−35.420
T25
1.200
ndL14
1.8061
νdL14
33.3

S25
R26
53.390
T26
VARIABLE

—

—

L15
S26
R27
INF
T27
1.500
ndL15
1.5168
νdL15
64.2

S27
R28
INF

—

—

—

Table 7 shows the values of surface intervals T5, T12, T19, T22, and T26, which according to the second example can be varied by zooming at the short, intermediate, and long focal lengths.

TABLE 7

FOCAL LENGTH

4.73
18.30
71.00

S5
1.000
24.599
36.000

S12
27.000
10.061
2.000

S18
6.000
2.500
2.000

S21
3.600
11.230
36.000

S25
2.241
4.764
4.000

Table 8 shows parameters of the Conditional Expressions (1) to (9) according to the second example.

TABLE 8

(1)
T34w/T34t
3.00

(2)
f34w/fw
3.79

(3)
f34t/ft
0.23

(4)
f3/fw
5.10

(5)
f4/ft
0.38

(6)
f1/fw
13.70

(7)
|f2/ft|
0.11

(8)
|Ra/fw|
6.20

(9)
f5/ft
0.42

The surface S8 of the biconcave lens L5 constituting the second lens group G2 is aspherical on the object side. Table 9 shows aspheric surface coefficients on the surface S8.

TABLE 9

SURCFACE

NUMBER
k
A
B
C
D

S8
0.00000E+00
1.4680E−06
8.0185E−07
−1.7286E−08
0.0000E+00

The “E” in Table 9 and below denotes an exponential representation with 10 as a base.

FIGS. 7 to 9 show various aberrations of the zoom lens 10 according to the second example at short, intermediate, and long focal lengths.

THIRD EXAMPLE

Next, a third example of the present invention will be described. As shown in FIG. 10, in the zoom lens 10 according to the third example, the first lens group G1 has the same structure as that of the first and the second example and the second lens group G2 is also the same in structure as that in the second example.

The third lens group G3 is composed of a biconvex lens L8, a positive meniscus lens L9 with its convex surface facing the object side, and a biconcave lens L10, which are sequentially arranged, in that order, from the object side. As a unit, the third lens group G3 has a positive refractive power. The light amount controlling mechanism IR is provided adjacent to the third lens group G3 on the object side.

The fourth lens group G4 has the same structure as that of the first and the second example. The fifth lens group G5 is constituted by a cemented lens in which a positive meniscus lens L13 with its convex surface facing the object side and a negative meniscus lens L14 are sequentially arranged in that order from the object side and joined together. As a unit, the fifth lens group G5 has a positive refractive power.

Table 10 shows the focal length, F number and half viewing angle of the zoom lens according to the third example at the short, intermediate and long focal length ends.

TABLE 10

FOCAL LENGTH
f
Fno
ω

SHORT
4.73
2.78
38.50

INTERMEDIATE
16.33
3.53
12.29

LONG
49.93
4.91
4.08

Table 11 shows numerical data or a zoom lens according to the third example.

TABLE 11

ABBE

RADIUS OF
SURFACE
REFRACTTVE
NUMBER

SURFACE
CURVATURE
SPACE T
INDEX Nd
νd

L1
S1
R1
77.650
T1
1.500
ndL1
1.8467
νdL1
23.8

L2
S2
R2
49.780
T2
8.000
ndL2
1.4875
νdL2
70.4

S3
R3
−251.600
T3
0.200

—

—

L3
S4
R4
30.940
T4
4.800
ndL3
1.4970
νdL3
81.6

S5
R5
106.100
T5
VARIABLE

—

—

L4
S6
R6
105.746
T6
1.300
ndL4
1.7550
νdL4
52.3

S7
R7
7.940
T7
5.925

—

—

L5
S8
R8
−26.410
T8
1.500
ndL5
1.7433
νdL5
49.3

S9
R9
19.112
T9
0.200

—

—

L6
S10
R10
16.268
T10
3.600
ndL6
1.8467
νdL6
23.8

L7
S11
R11
−18.080
T11
0.800
ndL7
1.8350
νdL7
43.0

S12
R12
61.312
T12
VARIABLE

—

—

IR
—
R13
—
T13
0.500

—

—

L8
S13
R14
15.710
T14
2.200
ndL8
1.7550
νdL8
52.3

S14
R15
−31.780
T15
0.100

—

—

L9
S15
R16
11.208
T16
2.800
ndL9
1.4970
νdL9
81.6

S16
R17
253.900
T17
0.398

L10
S17
R18
−24.727
T18
1.800
ndL10
1.7408
νdL10
27.8

S18
R19
9.898
T19
VARIABLE

—

—

L11
S19
R20
14.732
T20
0.700
ndL11
1.8042
νdL11
46.5

L12
S20
R21
8.831
T21
3.800
ndL12
1.4875
νdL12
70.4

S21
R22
−27.570
T22
VARIABLE

—

—

L13
S22
R23
11.557
T23
3.200
ndL13
1.8042
νdL13
46.5

L14
S23
R24
44.390
T24
1.000
ndL14
1.8052
νdL14
25.5

S24
R25
27.595
T25
VARIABLE

—

—

L15
S25
R26
INF
T26
1.500
ndL15
1.5168
νdL15
64.2

S26
R27
INF

—

—

—

Table 12 shows values of surface intervals T5, T12, T19, T22, and T25 which according to the third example can be varied by zooming at short, intermediate, and long focal lengths.

TABLE 12

FOCAL LENGTH

4.73
16.33
49.93

S5
1.000
20.935
28.935

S12
25.170
10.648
3.667

S18
7.150
3.000
2.000

S21
4.000
13.434
35.000

S25
1.460
2.710
2.548

Table 13 shows the parameters of the Conditional Expressions (1) to (9) in the third example.

TABLE 13

(1)
T34w/T34t
3.58

(2)
f34w/fw
3.89

(3)
f34t/ft
0.33

(4)
f3/fw
4.78

(5)
f4/ft
0.54

(6)
f1/fw
12.25

(7)
|f2/ft|
0.15

(8)
|Ra/fw|
5.83

(9)
f5/ft
0.47

The surface S8 of the biconcave lens L5 constituting the second lens group G2 is aspherical on the object side. Table 14 shows aspheric surface coefficients on the surface S8.

TABLE 14

SURCFACE

NUMBER
k
A
B
C
D

S8
−4.34320E+00
−4.1708E−06
4.1300E−07
8.6421E−09
−2.6955E−10

FIGS. 11 to 13 show various aberrations of the zoom lens 10 according to the third example at the short, intermediate and long focal length ends.

FOURTH EXAMPLE

Next, a fourth example of the present invention will be described. As shown in FIG. 14, in the zoom lens 10 according to the fourth example, the first lens group G1 has the same structure as that of the first to the third example, and the second lens group G2 also has the same structure as that of the second and third examples.

The third lens group G3 is composed of a biconvex lens L8 and a cemented lens in which a positive meniscus lens L9 with its convex surface facing the object side and a negative meniscus lens L10 are joined together, and in which these lenses are sequentially arranged in that order from the object side. As a unit, the third lens group G3 has a positive refractive power. The surface S13 of the biconvex lens L8 is aspherical on the side of an object. In addition, the light amount controlling mechanism IR is provided adjacent to the third lens group G3 on the object side.

The fourth lens group G4 has the same structure as that of the first to the third example. The fifth lens group G5 is constituted by a cemented lens in which a biconvex lens L13 and a biconcave lens L14 are sequentially arranged, in that order, from the object side and joined together. As a unit, the fifth lens group G5 has a positive refractive power.

Table 15 shows the focal length, F number and half viewing angle of the zoom lens according to the fourth example at short, intermediate, and long focal lengths.

TABLE 15

FOCAL LENGTH
f
Fno
ω

SHORT
4.74
2.72
38.58

INTERMEDIATE
19.42
3.84
10.32

LONG
80.00
5.80
2.53

Table 16 shows numerical data of a zoom lens according to the fourth example.

TABLE 16

ABBE

RADIUS OF
SURFACE
REFRACTIVE
NUMBER

SURFACE
CURVATURE
SPACE T
INDEX Nd
νd

L1
S1
R1
67.090
T1
1.560
ndL1
1.8467
νdL1
23.8

L2
S2
R2
42.920
T2
6.800
ndL2
1.4970
νdL2
81.6

S3
R3
−253.800
T3
0.155

—

—

L3
S4
R4
31.469
T4
3.300
ndL3
1.4970
νdL3
81.6

S5
R5
90.020
T5
VARIABLE

—

—

L4
S6
R6
57.000
T6
1.200
ndL4
1.7550
νdL4
52.3

S7
R7
8.090
T7
4.670

—

—

L5
S8
R8
−22.260
T8
1.000
ndL5
1.7433
νdL5
49.3

S9
R9
21.780
T9
0.840

—

—

L6
S10
R10
19.857
T10
3.200
ndL6
1.8467
νdL6
23.8

L7
S11
R11
−13.938
T11
0.700
ndL7
1.8350
νdL7
43.0

S12
R12
−526.000
T12
VARIABLE

—

—

IR
—
R13
—
T13
0.400

—

—

L8
S13
R14
17.397
T14
1.800
ndL8
1.7550
νdL8
52.3

S14
R15
−41.070
T15
0.160

—

—

L9
S15
R16
8.140
T16
2.300
ndL9
1.4970
νdL9
81.6

L10
S16
R17
41.990
T17
2.000
ndL10
1.7408
νdL10
27.8

S17
R18
7.716
T18
VARIABLE

—

—

L11
S18
R19
18.583
T19
0.630
ndL11
1.8042
νdL11
46.5

L12
S19
R20
10.881
T20
3.200
ndL12
1.4875
νdL12
70.4

S20
R21
−37.388
T21
VARIABLE

—

—

L13
S21
R22
16.297
T22
2.400
ndL13
1.8042
νdL13
46.5

L14
S22
R23
−14.920
T23
0.630
ndL14
1.8052
νdL14
25.5

S23
R24
133.300
T24
VARIABLE

—

—

L15
S24
R25
INF
T25
1.500
ndL15
1.5168
νdL15
64.2

S25
R26
INF

—

—

—

Table 17 shows values of surface intervals T5, T12, T18, T21 and T24 which, according to the fourth example, can be varied by zooming at short, intermediate, and long focal lengths.

TABLE 17

FOCAL LENGTH

4.73
16.33
49.93

S5
1.000
20.935
28.935

S12
25.170
10.648
3.667

S18
7.150
3.000
2.000

S21
4.000
13.434
35.000

S25
1.460
2.710
2.548

Table 18 shows the parameters of the Conditional Expressions (1) to (9) in the fourth example.

TABLE 18

(1)
T34w/T34t
3.87

(2)
f34w/fw
3.94

(3)
f34t/ft
0.20

(4)
f3/fw
4.44

(5)
f4/ft
0.43

(6)
f1/fw
13.33

(7)
|f2/ft|
0.11

(8)
|Ra/fw|
7.89

(9)
f5/ft
0.44

The surface S8 of the biconcave lens L5 constituting the second lens group G2 and the surface S13 of the biconvex lens L8 constituting the third lens group G3 are aspherical on the object side. Table 19 shows aspheric surface coefficients on the surfaces S8 and S13.

TABLE 19

SURFACE

NUMBER
k
A
B
C
D

S8
−1.20200E+00
−3.4361E−07
7.4765E−07
−2.0054E−08
0.0000E+00

S13
−2.30800E+00
0.0000E+00
0.0000E+00
0.0000E+00
0.0000E+00

FIGS. 15 to 17 show various aberrations of the zoom lens 10 related to the fourth example at short, intermediate, and long focal lengths.

Next, an example imaging apparatus equipped with the zoom lens 10 will be described. FIG. 18 shows an example digital camera equipped with the zoom lens 10. The digital camera comprises a lens block 100 for capturing an object image and a main unit 200 for performing various processes on image signals and various control functions related to capturing an image. The lens block 100 includes the zoom lens 10 composed of five lens groups and a solid-state imaging device 12 for converting an object image introduced by the zoom lens 10 to an electric signal. The solid-state imaging device 12 outputs the object image converted to the electric signal to the main unit 200 as video data.

A controlling section 24 in the main unit 200 executes various processes based on user instructions input through an operating section 26. A signal processing section 28 subjects the image data output from the solid-state imaging device 12 to various signal processings such as A/D conversion and noise reduction. The signal-processed image data are output to a display section 30 or a recording medium 32. The recording medium 32 may be a data recording medium such as a memory card and the like. Captured image data is recorded in this recording medium. A display section 30 is a display device such as an LCD or the like on which users may view captured images. A lens drive controlling section 22 outputs a driving signal to a lens moving mechanism equipped with the zoom lens when focusing or zooming is required and to instruct the move of the lens groups. A motor for the lens moving mechanism equipped with the zoom lens is driven in response to an instruction to move the lens groups.

PARTS LIST

10 zoom lens

12 imaging device

22 controlling section

24 controlling section

26 operating section

28 signal processing section

30 display section

32 recording medium

100 lens block

200 main unit

G1 first lens group

G2 second lens group

G3 third lens group

G4 fourth lens group

G5 fifth lens group

L1 negative meniscus lens

L2 biconvex lens

L3 positive meniscus lens

L4 negative meniscus lens

L5 biconcave lens

L6 biconvex lens

L7 biconcave lens

L8 biconvex lens

L9 biconvex lens

L10 biconcave lens

L11 negative meniscus lens

L12 biconvex lens

L13 biconcave lens

L14 negative meniscus lens

L15 optical equivalent member

ZOOM LENS AND IMAGING APPARATUS USING ZOOM LENS

Information

Publication Number

Date Filed

Date Published

Inventors

CPC

US Classifications

International Classifications

Abstract

Description

Claims

Priority Claims (1)