Zoom lens and photographing system

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a zoom lens suitable for a TV camera, video camera, and the like.

2. Related Background Art

As an autofocus (AF) system in a video camera or the like, a system called “hill-climbing AF” which obtains the distance to a principal object and drives a focus unit to an appropriate position is widely used.

In this system, the direction of the best imaging position is detected from a change in a video signal by using some of the lens units of an image pickup system for imaging, and the extension direction of a focusing lens is calculated. A merit of this system is that no optical system need be newly used for distance measurement.

In addition, in this system, in order to check whether the best imaging position is located before or after the image pickup surface (CCD surface or film surface), a partial optical system of the image pickup system is slightly amplitude-driven (to be referred to as wobbled hereinafter) in the optical axis direction. A focus unit is driven to set the best focus on the image pickup surface on the basis of the detected signal.

At this time, since part of the optical system is wobbled, the imaging magnification greatly changes to result in poor screen display unless lens units and the like are properly arranged.

As a method of reducing a change in imaging magnification, the method disclosed in Japanese Patent No. 2744336 is available. This method is associated with a rear focus zoom lens which has the first unit having a positive refractive power, the second unit having a negative refractive power for magnification changing operation, the third unit having a positive refractive power, and the fourth unit having a positive refractive power and serving to correct an image plane fluctuation with a change in magnification, and is designed to perform focusing by using the fourth unit.

A change in imaging magnification accompanying wobbling can be expressed by a paraxial trace. Several conditions for suppressing a change in imaging magnification accompanying wobbling small are described in U.S. Pat. No. 5,138,492.

These conditions are, however, insufficient to be applied to an image pickup system which has a wobbling lens unit placed in a relay lens unit located closer to the image side than the stop and allows insertion/removal of an extender for shifting the focal length to the telephoto side.

More specifically, the conditions described in the above reference are effective for a method of reducing a change in imaging magnification in a state where an optical arrangement behind the stop is fixed, but are not sufficient to be applied to a case wherein the arrangement of an optical system is changed upon insertion/removal of an extender or the like and the incident angle of an off-axis principal ray on a wobbling lens unit, in particular, changes.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a 4-unit zoom lens which exhibits a small change in imaging magnification accompanying wobbling even with insertion of an optical system such as an extender in the fourth unit serving as a relay lens unit and also exhibits excellent optical performance throughout the entire magnification change range.

In order to achieve the above object, according to the present invention, in a zoom lens in/from which a magnification changing optical unit for changing an overall focal length of the zoom lens can be inserted/removed, a wobbling unit which can be slightly amplitude-driven in an optical axis direction to detect a best imaging position is placed closer to an image side than an insertion position of the magnification changing optical unit.

With this arrangement, a change in imaging magnification caused when the wobbling unit is slightly driven in the optical axis direction can be reduced regardless of insertion/removal of the magnification changing optical unit.

The zoom lens sequentially includes, from an object side, a first unit which is fixed in magnification changing operation and has a positive refractive power, a second unit which moves in the optical axis direction in magnification changing operation and has a negative refractive power, a third unit for correcting an image plane fluctuation accompanying magnification changing operation, and a fourth unit having a positive refractive power for imaging, and a magnification changing optical unit which changes the overall focal length of the zoom lens can be inserted/removed in/from the fourth unit. In this zoom lens, a wobbling unit which can be slightly amplitude-driven in the optical axis direction to detect a best imaging position is placed closer to the image side than the insertion position of the magnification changing optical unit, and a stop for adjustment of light amount is preferably disposed at the object side with respect to the fourth unit.

More specifically, for example, when the wobbling unit is placed in the fourth unit and amplitude-driven to make an amplitude halfwidth of a backfocus change amount become ½ a depth of focus,

|α1(S1−E1)/fw1|<0.6 (1)

is satisfied, where α1 is an angle of an off-axis sub-principal ray incident on an object-side principal plane of the wobbling unit (without insertion of the magnification changing optical unit), S1 is a distance to a stop viewed from the object-side principal plane of the wobbling unit (without insertion of the magnification changing optical unit), E1 is a distance to an image pickup plane viewed from an image-side principal plane of the wobbling unit (without insertion of the magnification changing optical unit), and fw1 is a focal length at a wide-angle end without insertion of the magnification changing optical unit.

With this arrangement, a change in imaging magnification accompanying wobbling without insertion of the magnification changing optical unit can be suppressed sufficiently small.

In addition, when the wobbling unit is placed in the fourth unit amplitude-driven to make an amplitude halfwidth of a backfocus change amount become ½ a depth of focus,

|α2(S2−E2)/fw2|<2.2 (2)

is satisfied, where α2 is an angle of an off-axis sub-principal ray incident on the object-side principal plane of the wobbling unit (with insertion of the magnification changing optical unit), S2 is a distance to the stop viewed from the object-side principal plane of the wobbling unit (with insertion of the magnification changing optical unit), E2 is a distance to the image pickup plane viewed from the image-side principal plane of the wobbling unit (with insertion of the magnification changing optical unit), and fw2 is a focal length at the wide-angle end with insertion of the magnification changing optical unit.

In addition, in the fourth unit,

−0.001<φ/Im<0.0015 (3)

is satisfied, where φ is a refractive power of a lens unit located immediately before the wobbling unit in the fourth unit, and Im is an image size of an image pickup element.

With this arrangement, a change in incident angle on the wobbling unit upon insertion/removal of the magnification changing optical unit can be made small. This makes it possible to reduce a change in imaging magnification more reliably.

Further, the amplitude halfwidth of the wobbling unit before/after insertion of the magnification changing optical system is preferably so set as to satisfy the following condition (4).

Δx₂=F·Δx₁ (4)

Note that a reduction in the size and weight of the wobbling unit to be slightly amplitude-driven may be attained by placing the wobbling unit closest to the image side in the fourth unit.

If this system is designed to retract part of the fourth unit from the optical axis by inserting the magnification changing optical unit, a large space for the insertion of the magnification changing optical unit can be ensured while a reduction in the overall size of the zoom lens is attained. This makes it possible to suppress a deterioration in optical performance at the time of insertion of the magnification changing optical unit.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of a zoom lens according to the first embodiment of the present invention at the wide-angle end in the first numerical embodiment;

FIG. 2 is a sectional view of a zoom lens according to the first embodiment of the present invention at the wide-angle end in the second numerical embodiment;

FIG. 3 is a sectional view of a zoom lens according to the first embodiment of the present invention at the wide-angle end in the third numerical embodiment;

FIG. 4 is a sectional view of a zoom lens according to the first embodiment of the present invention at the wide-angle end in the fourth numerical embodiment;

FIG. 5 is a sectional view of a zoom lens according to the first embodiment of the present invention at the wide-angle end in the fifth numerical embodiment;

FIG. 6 is a sectional view of a zoom lens according to the first embodiment of the present invention at the wide-angle end in the sixth numerical embodiment;

FIG. 7 is a schematic view showing an optical configuration after the stop of the zoom lens according to the first embodiment (without insertion of an extender);

FIG. 8 is a schematic view showing an optical configuration after the stop of the zoom lens according to the first embodiment (with insertion of the extender);

FIG. 9 is an aberration diagram at the wide-angle end in the first numerical embodiment;

FIG. 10 is an aberration diagram at the telephoto end in the first numerical embodiment;

FIG. 11 is an aberration diagram at the wide-angle end in the second numerical embodiment;

FIG. 12 is an aberration diagram at the telephoto end in the second numerical embodiment;

FIG. 13 is an aberration diagram at the wide-angle end in the fourth numerical embodiment;

FIG. 14 is an aberration diagram at the telephoto end in the fourth numerical embodiment;

FIG. 15 is an aberration diagram at the wide-angle end in the fifth numerical embodiment;

FIG. 16 is an aberration diagram at the telephoto end in the fifth numerical embodiment;

FIG. 17 is an aberration diagram at the wide-angle end in the sixth numerical embodiment;

FIG. 18 is an aberration diagram at the telephoto end in the sixth numerical embodiment;

FIG. 19 is an aberration diagram at the wide-angle end in the first numerical embodiment at the time of insertion of the extender;

FIG. 20 is an aberration diagram at the wide-angle end in the second numerical embodiment at the time of insertion of the extender;

FIG. 21 is an aberration diagram at the wide-angle end in the third numerical embodiment at the time of insertion of the extender;

FIG. 22 is an aberration diagram at the wide-angle end in the fourth numerical embodiment at the time of insertion of the extender;

FIG. 23 is an aberration diagram at the wide-angle end in the fifth numerical embodiment at the time of insertion of the extender;

FIG. 24 is an aberration diagram at the wide-angle end in the sixth numerical embodiment at the time of insertion of the extender;

FIG. 25 is a view showing the arrangement of a photographing system using the zoom lens according to the first embodiment as a photographing optical system; and

FIG. 26 is view showing a photographing system according to another embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(First Embodiment)

FIGS. 1 to 6 show the cross-sectional configurations of lenses, of zoom lenses according to the first embodiment of the present invention, which are located at the wide-angle end and infinity focus position in the first to sixth numerical embodiments.

Referring to FIGS. 1 to 6, a first unit (front element) I has a positive refractive power, and a variator II serves as the second unit having a negative refractive power and capable of moving in the optical axis direction in magnification changing operation. The second unit II is monotonously moved to the image side on the optical axis to change the magnification from the wide-angle end to the telephoto end. In magnification changing operation, the second unit II is moved within a range including an imaging magnification of 1× (−1×) (i.e. equal magnification).

A compensator III serves as the third unit which can move in the optical axis direction to correct an image plane fluctuation accompanying magnification changing operation.

A stop SP is used for light amount adjustment. A fourth unit IV having a positive refractive power is used for imaging.

A glass block G is a color separation prism, optical filter, or the like. A wobbling unit wo can be slightly amplitude-driven in the optical axis direction to detect the best imaging position. A lens unit L4b is placed immediately before the wobbling unit in the fourth unit.

An extender (magnification changing optical unit) EX for increasing or decreasing the overall focal length of the zoom lens system can be inserted/removed (or mounted/dismounted) in/from the space in the fourth unit.

In this embodiment, the configuration of a lens unit (to be referred to as a relay unit hereinafter) located closer to the image side than the stop SP is properly set such that a change in imaging magnification accompanying wobbling of the wobbling unit wo is reduced regardless of whether the extender EX is inserted/removed.

The wobbling unit wo needs to be amplitude-driven at high speed in the optical axis direction. It is therefore preferable that the wobbling unit wo have a proper backfocus sensitivity degree and be light in weight. A zoom lens for a TV set needs to have a long backfocus and a small F-number, and hence requires many lenses constituting each unit. In addition, each lens has a large effective diameter, and an extender, macro photographing mechanism, flange-back adjustment mechanism, and the like must be arranged in the relay unit, resulting in a low degree of freedom in placing the wobbling unit.

FIGS. 7 and 8 schematically show lens units behind the stop SP. FIG. 7 shows a state where the extender EX is not inserted. FIG. 8 shows a state where the extender EX is inserted. Referring to FIG. 8, the magnification of the extender EX is set to 2×, and an image is enlarged by 2× on an image plane.

Referring to FIG. 7, an image height change ratio can be expressed as follows. Letting α1 be the incident angle of sub-principal ray on the wobbling unit wo, φwo be the power of the wobbling unit wo, S1 be the distance between the wobbling unit wo and an image plane, φ4c be the power of lens unit L4c located closer to the image side than the wobbling unit wo, Δx be the wobbling amount, (S1−E1) be the difference between the distance to a virtual image of the stop SP viewed from the wobbling unit wo and the distance to a virtual image of the image plane viewed from the wobbling unit wo, and Δy be the image height change amount at the time of wobbling, an image height change ratio Δy/fw (where fw is the focal length of the overall system at the wide-angle end) can be expressed by
$\frac{Δ y}{f_{w}} = α_{1} \cdot ϕ_{w o} \cdot (S_{1} ϕ_{4 c} - 1) \cdot Δ x \cdot {Δ x - (S_{1} - E_{1})} \cdot \frac{1}{f_{w}}$

The wobbling amount Δx is a sufficiently small value relative to (S1−E1), and hence can be expressed by
$\frac{Δ y}{f_{w}} = α_{1} \cdot (S_{1} ϕ_{4 c} - 1) \cdot (S_{1} - E_{1}) \cdot \frac{1}{f_{w}}$

In the configuration of the zoom lens according to this embodiment, parameters that change upon insertion/removal of the extender EX and have great influences on the image height change ratio Δy/fw are the incident angle α1 of a principal ray on the wobbling unit wo and (S1−E1).

The allowable value of the wobbling amount Δx will be described. It is said that the resolution of the visual sense of a person having 20/20 vision is about one minute. If, for example, the person watches a 30-inch TV screen (having a screen size of about 50 cm in the horizontal direction) at a distance of 2.5 m, the viewing angle in the horizontal direction becomes about 680 minutes. A resolution of one minute therefore corresponds to 0.15% of the screen.

If the lens is stopped down, the depth of focus increases as compared with that at full aperture. In addition, a larger wobbling amount is required to detect the best focus position, and hence the image height change ratio increases.

In consideration of the fact that the highest frequency in use of an F-number range is about full aperture: F/5.6, an image height change ratio is allowed at most 0.15% at F/5.6. An allowable value at full aperture (F/1.752) becomes about 0.06% which is about ⅓ the image height change ratio at F/5.6. The upper limit of conditional expression (1) is determined such that the image height change ratio at full aperture (F/1.752) falls within an image height change ratio of 0.06% (0.15% at F/5.6), and falls within the allowable range even if the image height change ratio changes upon insertion of the extender EX.

The relationship between the wobbling amount Δx and the change amount in backfocus Δsk is expressed by
$Δ x = \frac{Δ s k}{(1 - β_{1}^{2}) \cdot β_{2}^{2}}$

where β₁is a lateral magnification of the wobbling unit, and β₂is a lateral magnification of an optical system placed at the image side with respect to the wobbling unit. When the change amount in backfocus Δsk is ½ the depth of focus, the relationship between the change amount in backfocus Δsk and the F-number fno is expressed by

Δsk=δ·fno/2

where δ is a permissible circle of confusion determined by the camera system.

In the present invention, the wobbling lens unit is disposed closer to the image side than the magnification changing optical unit capable of being inserted and removed, so that the wobbling amount Δx has a relation proportional to the F-number since both β₁and β₂are constant before/after insertion of the magnification changing optical system.

Considering the wobbling amount after insertion of a 2× extender, since the F-number becomes doubled, the depth of focus also becomes doubled. The amplitude driving amount of the wobbling unit must also be doubled.

The F-number in practical use at the time of insertion of the 2× extender falls within a narrow range of about F/4 to F/5.6 because the F-number at the full aperture end increases. For this reason, if a maximum of 0.15% of the value at F/5.6 is allowed at the time of insertion of the extender, the allowable amount at full aperture (F/4) becomes about 0.1%. That is, an allowable amount as large as double the value before the insertion of the extender can be allowed.

The allowable upper limit value of an image height change ratio indicated by conditional expressions (1) and (2) is the value set when the wobbling unit is amplitude-driven in the optical axis direction such that the amplitude halfwidth of a change in backfocus becomes ½ the depth of focus. In practice, this value changes depending on the manner of determining a wobbling amount with respect to the depth of focus (e.g., setting the amplitude halfwidth to ⅓ the depth of focus or to be equal to it), an assumed screen size, and the like.

Considering a system frequency using F-numbers equal to or larger than F/5.6 or setting of smaller full aperture F-numbers, a system is required in which the image height change ratio at full aperture is further suppressed and a change before/after insertion of an extender is smaller.

Consider only a state where no extender is inserted. In this case, to reduce a change in imaging magnification accompanying wobbling, the incident angle α1 of a sub-principal ray on the wobbling unit and the difference (S1−E1) between the distance E1 to the stop viewed from the wobbling unit and the distance S1 to the image plane viewed from the wobbling unit must be reduced.

When the extender EX in the state shown in FIG. 7 is inserted (FIG. 8), the incident angle of sub-principal ray on the wobbling unit wo changes to α2, and a distance E2 to the stop SP viewed from the wobbling unit wo changes. However, a distance S2 to the image plane viewed from the wobbling unit wo is almost constant (S2≃S1) regardless of insertion/removal of the extender, and hence a change in imaging magnification at the time of insertion of the extender remains.

In order to reduce a change in imaging magnification accompanying wobbling in a state where the extender is not inserted, the following condition must be satisfied:

0.05<|α1(S1−E1)/fw1|<0.6 (1)

With approach to the lower limit value of conditional expression (1), a change in imaging magnification while the extender is not inserted is reduced, and an ideal condition is obtained.

While the extender is inserted, it is difficult to cancel out the distance E2 with respect to the distance S2 in FIG. 8, and a change in imaging magnification remains. This condition is not necessarily a desired condition for an optical system in/from which the extender is inserted/removed.

If the upper limit value is exceeded, a change in imaging magnification without insertion of the extender is large. It indicates that this condition is not suitable for wobbling.

Therefore, while the extender is inserted, the following is preferably satisfied:

0.05<|α2(S2−E2)/fw2|<2.2 (2)

If the upper limit value of this conditional expression (2) is exceeded, it indicates that a change in imaging magnification at the time of insertion/removal of the extender is large.

In addition, the refractive power φ4b of the lens unit L4b located immediately before the wobbling unit wo in the fourth unit IV preferably satisfies

−0.001<φ4b/Im<0.0015 (3)

where Im is the image size of the image pickup element.

If the positive or negative refractive power of the lens unit L4b is increased beyond the range of conditional expression (3), the incident angle of a principal ray on the wobbling unit wo greatly changes from α1 to α2 or from α2 to α1, and a change in imaging magnification becomes large under one of the conditions.

It is preferable to set the amplitude amount of the wobbling unit to the following condition (4) before/after insertion of the magnification changing optical system.

Δx₂=F·Δx₁ (4)

where Δx₁is an amplitude halfwidth of the wobbling unit before insertion of the magnification changing optical system, Δx₂is an amplitude halfwidth of the wobbling unit after insertion of the magnification changing optical system, and F is a rate of change of F-number due to insertion/removal of the magnification changing optical system. This enables the best focus position to be detected and a system in which blur is not conspicuous on a screen upon detection to be provided irrespective of whether the magnification changing optical system is inserted or not.

<<Numerical Embodiments>>

The numerical embodiments of this embodiment will be described below. In the numerical embodiments 5 to 6, let ri be the radius of curvature of the ith lens from the object side, di be the thickness or air gap of the ith optical member from the object side, and ni and γi (“vi” in the tables) be the refractive index and Abbe number, respectively, of the glass of the ith lens from the object side with respect to a d line.

Letting the X-axis be the optical axis direction, the H-axis be a direction perpendicular to the optical axis, a traveling direction of light be positive, R be the paraxial radius of curvature, and B, C, D, and E be aspherical coefficients, an aspherical shape is expressed by
$X = \frac{(1 / R) H^{2}}{1 + \sqrt{1 - {(H / R)}^{2}}} + B H^{4} + C H^{6} + D H^{8} + E H^{10}$

(Numerical Embodiment 1)

TABLE 1

Numerical Embodiment 1

f = 9.50˜185.25 Fno: 1.85˜2.85 2ω: 60.1°˜3.4°

r1 =
600.261
d1 =
2.20
n1 =
1.76168
v1 =
27.5

r2 =
81.461
d2 =
11.42
n2 =
1.49845
v2 =
81.6

r3 =
−290.956
d3 =
7.63

r4 =
86.701
d4 =
7.86
n3 =
1.62267
v3 =
60.3

r5 =
3044.710
d5 =
0.15

r6 =
66.016
d6 =
6.01
n4 =
1.73234
v4 =
54.7

r7 =
145.708
d7 =
Variable

r8 =
111.445
d8 =
0.80
n5 =
1.88814
v5 =
40.8

r9 =
16.812
d9 =
4.65

r10 =
−47.842
d10 =
0.70
n6 =
1.82017
v6 =
46.6

r11 =
33.779
d11 =
2.24

r12 =
28.944
d12 =
5.20
n7 =
1.81264
v7 =
25.4

r13 =
−29.192
d13 =
0.54

r14 =
−24.664
d14 =
0.70
n8 =
1.79196
v8 =
47.4

r15 =
132.572
d15 =
Variable

r16 =
−28.806
d16 =
0.75
n9 =
1.74679
v9 =
49.3

r17 =
37.218
d17 =
3.81
n10 =
1.85501
v10 =
23.9

r18 =
449.023
d18 =
Variable

r19 =
∞ (stop)
d19 =
1.80

r20 =
−231.233
d20 =
3.33
n11 =
1.67340
v11 =
47.2

r21 =
−49.133
d21 =
0.20

r22 =
−170.365
d22 =
4.05
n12 =
1.51976
v12 =
52.4

r23 =
−38.625
d23 =
0.20

r24 =
36.315
d24 =
10.16
n13 =
1.48915
v13 =
70.2

r25 =
−35.564
d25 =
1.66
n14 =
1.83932
v14 =
37.2

r26 =
0.000
d26 =
36.00

r27 =
97.385
d27 =
6.35
n15 =
1.50349
v15 =
56.4

r28 =
−44.438
d28 =
0.20

r29 =
−535.654
d29 =
1.40
n16 =
1.83932
v16 =
37.2

r30 =
21.016
d30 =
7.22
n17 =
1.50349
v17 =
56.4

r31 =
−424.093
d31 =
1.50

r32 =
36.505
d32 =
8.29
n18 =
1.52033
v18 =
58.9

r33 =
−27.482
d33 =
1.40
n19 =
1.77621
v19 =
49.6

r34 =
91.360
d34 =
0.30

r35 =
38.429
d35 =
6.84
n20 =
1.53430
v20 =
48.8

r36 =
−52.407
d36 =
5.00

r37 =
∞
d37 =
30.00
n21 =
1.60718
v21 =
38.0

r38 =
∞
d38 =
16.20
n22 =
1.51825
v22 =
64.2

r39 =
∞

TABLE 2

Extender portion

d26 =
1.60

r27 =
64.675
d27 =
6.74
n15 = 1.49845
v15 = 81.5

r28 =
−54.795
d28 =
0.20

r29 =
25.068
d29 =
6.49
n16 = 1.49845
v16 = 81.5

r30 =
−128.700
d30 =
0.80
n17 = 1.85501
v17 = 23.9

r31 =
56.237
d31 =
11.25

r32 =
−106.936
d32 =
0.90
n18 = 1.64254
v18 = 60.1

r33 =
10.653
d33 =
2.65
n19 = 1.85501
v19 = 23.9

r34 =
14.647
d34 =
5.37

Focal

Variable
Length

Interval
9.50
38.00
185.25

d 7
0.65
35.60
52.03

d 15
53.75
13.79
6.32

d 18
5.10
10.11
1.15

In the numerical embodiment 1 shown in FIG. 1, to reduce variations in optical performance upon insertion of the extender EX, the extender EX is preferably placed in a substantially afocal parallel light beam. In addition, a wide gap is required to satisfy the extender magnification requirement and optical performance requirement.

As a wobbling unit which satisfies conditional expression (1), has a proper backfocus sensitivity degree accompanying slight amplitude driving of the wobbling unit wo, and exhibits a small change in imaging magnification, all or some of lens units located closer to the image side than the extender EX are preferably used.

In the numerical embodiment 1, three lenses of which form two units in the fourth unit and are located closest to the image side, are used as wobbling unit lenses. By making some lenses of the fourth unit movable, a reduction in the weight of the wobbling unit wo is achieved. In addition, by setting the refractive power of the lens unit L4b located immediately before the wobbling unit within the range of conditional expression (3), a change in imaging magnification is small regardless of the presence/absence of the extender EX.

In the numerical embodiment 1, the extender EX can be inserted/removed in/from a space with gap d26=36 mm.

Table 12 shows the numerical values of conditional expressions and imaging magnification change ratios in the respective numerical embodiments. Each imaging magnification change ratio is the value obtained when wobbling is performed upon setting the amplitude halfwidth to ½ the depth of focus at the full aperture end.

If, for example, the permissible circle of confusion of a ⅔-inch CCD (image size: φ11 mm) which is the mainstream in TV cameras is set to about 0.021 mm, the depth of focus at F/2 becomes about 0.04 mm.

FIGS. 9 and 10 are aberration diagrams at the wide-angle end and telephoto end without insertion of the extender in the first numerical embodiment. FIG. 19 is an aberration diagram at the wide-angle end with insertion of the extender.

(Numerical Embodiment 2)

TABLE 3

Numerical Embodiment 2

f = 9.50˜185.25 Fno: 2.0˜2.85 2ω:60.1°˜3.4°

r1 =
622.723
d1 =
2.20
n1 =
1.76168
v1 =
27.5

r2 =
77.855
d2 =
12.34
n2 =
1.48915
v2 =
70.2

r3 =
−323.998
d3 =
7.78

r4 =
86.923
d4 =
8.56
n3 =
1.62032
v3 =
63.4

r5 =
−1529.464
d5 =
0.15

r6 =
64.688
d6 =
6.06
n4 =
1.73234
v4 =
54.7

r7 =
134.784
d7 =
Variable

r8 =
111.445
d8 =
0.80
n5 =
1.88814
v5 =
40.8

r9 =
16.812
d9 =
4.65

r10 =
−47.842
d10 =
0.70
n6 =
1.82017
v6 =
46.6

r11 =
33.779
d11 =
2.24

r12 =
28.944
d12 =
5.20
n7 =
1.81264
v7 =
25.4

r13 =
−29.192
d13 =
0.54

r14 =
24.664
d14 =
0.70
n8 =
1.79196
v6 =
47.4

r15 =
132.572
d15 =
Variable

r16 =
−28.806
d16 =
0.75
n9 =
1.74679
v9 =
49.3

r17 =
37.218
d17 =
3.81
n10 =
1.85501
v10 =
23.9

r18 =
449.023
d18 =
Variable

r19 =
∞ (Stop)
d19 =
1.40

r20 =
−1109.872
d20 =
4.46
n11 =
1.67340
v11 =
47.2

r21 =
−30.372
d21 =
0.20

r22 =
104.731
d22 =
6.31
n12 =
1.48915
v12 =
70.2

r23 =
−26.574
d23 =
1.20
n13 =
1.83932
v13 =
37.2

r24 =
−74.569
d24 =
30.00

r25 =
170.165
d25 =
3.69
n14 =
1.48915
v14 =
70.2

r26 =
−86.018
d26 =
2.50

r27 =
46.559
d27 =
4.04
n15 =
1.69979
v15 =
55.5

r28 =
178.870
d28 =
5.00

r29 =
−66.299
d29 =
1.20
n16 =
1.88815
v16 =
40.8

r30 =
151.817
d30 =
7.03
n17 =
1.48915
v17 =
70.2

r31 =
−37.731
d31 =
0.15

r32 =
74.679
d32 =
1.20
n18 =
1.80642
v18 =
35.0

r33 =
28.773
d33 =
4.28

r34 =
78.908
d34 =
8.64
n19 =
1.52033
v19 =
58.9

r35 =
−20.059
d35 =
1.20
n20 =
1.88615
v20 =
40.8

r36 =
−66.519
d36 =
4.03

r37 =
1248.781
d37 =
4.71
n21 =
1.66152
v21 =
50.9

r38 =
−35.175
d38 =
4.00

r39 =
∞
d39 =
30.00
n22 =
1.60718
v22 =
38.0

r40 =
∞
d40 =
16.20
n23 =
1.51825
v23 =
64.2

r41 =
∞

TABLE 4

Extender Portion

d24 = 1.60

r25 =
−377.553
d25 = 2.81
n14 = 1.52033
v14 = 58.9

r26 =
−49.636
d26 = 0.20

r27 =
19.162
d27 = 5.72
n15 = 1.51976
v15 = 52.4

r28 =
96.555
d28 = 0.20

r29 =
15.020
d29 = 5.62
n16 = 1.51625
v16 = 64.1

r30 =
137.066
d30 = 0.60
n17 = 1.85501
v17 = 23.9

r31 =
10.484
d31 = 6.63

r32 =
49.330
d32 = 0.90
n18 = 1.64254
v18 = 60.1

r33 =
11.941
d33 = 2.99
n19 = 1.85501
v19 = 23.9

r34 =
30.619
d34 = 2.67

Focal

Variable
Length

Interval
9.50
38.00
185.25

d 7
1.08
36.03
52.46

d 15
53.75
13.79
6.32

d 18
5.10
10.11
1.15

In the numerical embodiment 2 shown in FIG. 2, the second lens located closer to the image side than the insertion gap of the extender EX is used as a wobbling unit lens. The extender EX can be inserted/removed in/from a space with d24=30 mm.

Since the positive refractive power φ4b of the lens unit L4b located immediately before the wobbling unit wo is brought near to the upper limit in the numerical embodiment 1, a change (conditional expression (2)) in imaging magnification upon insertion/removal of the extender takes a large value.

The lens unit L4c constituted by six lenses which form four units in the fourth unit and are located closer to the image side than the wobbling unit wo are constituted by two lens units L4c1 and L4c2. In addition, the use of the lens unit L4c2 allows macro photographing for proximity photographing and flange-back adjustment for adjusting the dimensional error between the reference surface of a lens (flange surface) and an image plane in a lens-interchangeable camera, independently of the main focusing lens.

FIGS. 11 and 12 are aberration diagrams at the wide-angle end and telephoto end without insertion of the extender in the numerical embodiment 1. FIG. 20 is an aberration diagram at the wide-angle end with insertion of the extender.

(Numerical Embodiment 3)

TABLE 5

Numerical Embodiment 3

Extender Portion

d24 = 1.60

r25 =
722.998
d25 = 3.37
n14 = 1.52033
v14 = 58.9

r26 =
−69.098
d26 = 0.20

r27 =
21.904
d27 = 5.85
n15 = 1.51976
v15 = 52.4

r28 =
156.587
d28 = 0.20

r29 =
17.349
d29 = 5.19
n16 = 1.51825
v16 = 64.1

r30 =
117.012
d30 = 0.80
n17 = 1.85501
v17 = 23.9

r31 =
12.697
d31 = 8.57

r32 =
378.277
d32 = 0.90
n18 = 1.64254
v18 = 60.1

r33 =
12.453
d33 = 3.52
n19 = 1.85501
v19 = 23.9

r34 =
25.927
d34 = 6.00

In contrast to the lens system in the numerical embodiment 2, in the numerical embodiment 3 shown in FIG. 3, the extender can be inserted in the space with d24 to d26 by retracting (ejecting) part (L4b) of the fourth unit from the optical axis at the time of insertion of the extender EX. By retracting part of the fourth unit, a reduction in the space for insertion/removal of the extender can be attained. This makes it possible to achieve a reduction in the size of the lens system and suppress a deterioration in optical performance at the time of insertion of the extender by effectively using the wide space.

Even in a case where part of the fourth unit is retracted at the time of insertion of the extender, an appropriate imaging magnification change ratio can be kept by properly setting the refractive power of the lens unit L4b.

FIG. 21 is an aberration diagram at the wide-angle end at the time of insertion of the extender in the numerical embodiment 3.

(Numerical Embodiment 4)

TABLE 6

Numerical Embodiment 4

f = 9.50˜185.25 Fno: 2.0˜2.85 2ω: 60.1°˜3.4°

r1 =
622.723
d1 =
2.20
n1 =
1.76168
v1 =
27.5

r2 =
77.855
d2 =
12.34
n2 =
1.48915
v2 =
70.2

r3 =
−323.998
d3 =
7.78

r4 =
86.923
d4 =
8.56
n3 =
1.62032
v3 =
63.4

r5 =
−1529.464
d5 =
0.15

r6 =
64.688
d6 =
6.06
n4 =
1.73234
v4 =
54.7

r7 =
134.784
d7 =
Variable

r8 =
111.445
d8 =
0.80
n5 =
1.88814
v5 =
40.8

r9 =
16.812
d9 =
4.65

r10 =
−47.842
d10 =
0.70
n6 =
1.82017
v6 =
46.6

r11 =
33.779
d11 =
2.24

r12 =
28.944
d12 =
5.20
n7 =
1.81264
v7 =
25.4

r13 =
−29.192
d13 =
0.54

r14 =
−24.664
d14 =
0.70
n8 =
1.79196
v8 =
47.4

r15 =
132.572
d15 =
Variable

r16 =
−28.806
d16 =
0.75
n9 =
1.74679
v9 =
49.3

r17 =
37.218
d17 =
3.81
n10 =
1.85501
v10 =
23.9

r18 =
449.023
d18 =
Variable

r19 =
∞ (Stop)
d19 =
1.40

r20 =
−167.968
d20 =
4.19
n11 =
1.66152
v11 =
50.9

r21 =
−28.839
d21 =
0.20

r22 =
216.499
d22 =
2.57
n12 =
1.48915
v12 =
70.2

r23 =
−159.531
d23 =
0.00

r24 =
88.816
d24 =
6.34
n13 =
1.48915
v13 =
70.2

r25 =
−29.606
d25 =
1.20
n14 =
1.83932
v14 =
37.2

r26 =
−76.274
d26 =
30.00

r27 =
−59.688
d27 =
1.20
n15 =
1.48915
v15 =
70.2

r28 =
35.023
d28 =
2.50

r29 =
43.898
d29 =
4.98
n16 =
1.69979
v16 =
55.5

r30 =
−79.430
d30 =
2.50

r31 =
−45.969
d31 =
1.20
n17 =
1.88815
v17 =
40.8

r32 =
72.323
d32 =
7.79
n18 =
1.48915
v18 =
70.2

r33 =
−28.720
d33 =
0.15

r34 =
129.989
d34 =
1.20
n19 =
1.80642
v19 =
35.0

r35 =
29.797
d35 =
3.71

r36 =
66.757
d36 =
9.33
n20 =
1.51976
v20 =
52.4

r37 =
−17.449
d37 =
1.20
n21 =
1.888185
v21 =
40.8

r38 =
−49.582
d38 =
3.79

r39 =
819.738
d39 =
4.62
n22 =
1.66152
v22 =
50.9

r40 =
−31.246
d40 =
4.00

r41 =
∞
d41 =
30.00
n23 =
1.60718
v23 =
38.0

r42 =
∞
d42 =
16.20
n24 =
1.51825
v24 =
64.2

r43 =
∞

TABLE 7

Extender Portion

d26 = 1.60

r27 =
746.348
d27 = 3.32
n15 = 1.48915
v15 = 70.2

r28 =
−55.071
d28 = 0.20

r29 =
16.521
d29 = 5.27
n16 = 1.49845
v16 = 81.5

r30 =
36.028
d30 = 0.20

r31 =
13.452
d31 = 4.96
n17 = 1.51825
v17 = 64.1

r32 =
31.044
d32 = 0.80
n18 = 1.85501
v18 = 23.9

r33 =
9.442
d33 = 7.64

r34 =
37.409
d34 = 0.90
n19 = 1.75844
v19 = 52.3

r35 =
11.531
d35 = 3.17
n20 = 1.85501
v20 = 23.9

r36 =
45.968
d36 = 1.97

Focal

Variable
Length

Interval
9.50
38.00
185.25

d 7
1.08
36.03
52.46

d 15
53.75
13.79
6.32

d 18
5.10
10.11
1.15

In the numerical embodiment 4 shown in FIG. 4, the second lens located closer to the image side than the insertion gap for the extender EX is used as a wobbling unit lens. In addition, the extender EX can be inserted in a space with d26=30 mm.

In the numerical embodiment 4, the lens unit L4b located closer to the object side than the wobbling unit wo has a negative refractive power. In contrast to the numerical embodiment 1, since φ4b is brought closer to the lower limit, a change in imaging magnification (conditional expression (2)) accompanying insertion of the extender EX takes a large value.

FIGS. 13 and 14 are aberration diagrams at the wide-angle end and telephoto end without insertion of the extender in the numerical embodiment 4. FIG. 22 is an aberration diagram at the wide-angle end with insertion of the extender.

(Numerical Embodiment 5)

TABLE 8

Numerical Embodiment 5

f = 9.50˜185.25 Fno: 2.0˜2.85 2ω: 60.1°˜3.4°

r1 =
622.723
d1 =
2.20
n1 =
1.76168
v1 =
27.5

r2 =
77.855
d2 =
12.34
n2 =
1.48915
v2 =
70.2

r3 =
−323.998
d3 =
7.78

r4 =
86.923
d4 =
8.56
n3 =
1.62032
v3 =
63.4

r5 =
−1529.464
d5 =
0.15

r6 =
64.658
d6 =
6.06
n4 =
1.73234
v4 =
54.7

r7 =
134.784
d7 =
Variable

r8 =
111.445
d8 =
0.80
n5 =
1.88814
v5 =
40.8

r9 =
16.812
d9 =
4.65

r10 =
−47.842
d10 =
0.70
n6 =
1.82017
v6 =
46.6

r11 =
33.779
d11 =
2.24

r12 =
28.944
d12 =
5.20
n7 =
1.81264
v7 =
25.4

r13 =
−29.192
d13 =
0.54

r14 =
−24.664
d14 =
0.70
n8 =
1.79196
v8 =
47.4

r15 =
132.572
d15 =
Variable

r16 =
−28.806
d16 =
0.75
n9 =
1.74679
v9 =
49.3

r17 =
37.218
d17 =
3.81
n10 =
1.85501
v10 =
23.9

r18 =
449.023
d18 =
Variable

r19 =
∞ (Stop)
d19 =
1.40

r20 =
−285.753
d20 =
4.45
n11 =
1.66152
v11 =
50.9

r21 =
−27.952
d21 =
0.20

r22 =
64.233
d22 =
7.14
n12 =
1.48915
v12 =
70.2

r23 =
−25.959
d23 =
1.20
n13 =
1.83932
v13 =
37.2

r24 =
−72.322
d24 =
30.00

r25 =
47.982
d25 =
5.34
n14 =
1.48915
v14 =
70.2

r26 =
−125.570
d26 =
2.50

r27 =
−96.426
d27 =
1.20
n15 =
1.69979
v15 =
55.5

r28 =
191.570
d28 =
5.00

r29 =
−122.237
d29 =
1.20
n16 =
1.66815
v16 =
40.8

r30 =
1090.682
d30 =
5.32
n17 =
1.48915
v17 =
70.2

r31 =
−30.494
d31 =
0.15

r32 =
106.004
d32 =
1.20
n18 =
1.80642
v18 =
35.0

r33 =
34.262
d33 =
2.67

r34 =
47.028
d34 =
8.44
n19 =
1.50349
v19 =
56.4

r35 =
−20.185
d35 =
1.20
n20 =
1.88815
v20 =
40.8

r36 =
−76.910
d36 =
2.56

r37 =
90.553
d37 =
4.83
n21 =
1.66152
v21 =
50.9

r38 =
−49.369
d38 =
4.00

r39 =
∞
d39 =
30.00
n22 =
1.60718
v22 =
38.0

r40 =
∞
d40 =
16.20
n23 =
1.51825
v23 =
64.2

r41 =
∞

TABLE 9

Extender Portion

d24 = 1.60

r25 =
1327.342
d25 = 2.96
n14 = 1.52033
v14 = 56.9

r26 =
−65.631
d26 = 0.20

r27 =
19.393
d27 = 5.95
n15 = 1.52033
v15 = 58.9

r28 =
92.908
d28 = 0.20

r29 =
16.254
d29 = 5.90
n16 = 1.51825
v16 = 64.1

r30 =
88.347
d30 = 0.80
n17 = 1.85501
v17 = 23.9

r31 =
10.562
d31 = 6.15

r32 =
−61.482
d32 = 0.90
n18 = 1.64254
v18 = 60.1

r33 =
11.288
d33 = 2.81
n19 = 1.85501
v19 = 23.9

r34 =
24.985
d34 = 2.54

Focal

Variable
Length

Interval
9.50
38.00
185.25

d 7
1.08
36.03
52.46

d 15
53.75
13.79
6.32

d 18
5.10
10.11
1.15

In the numerical embodiment 5 shown in FIG. 5, the second lens located closer to the image side than the insertion gap for the extender EX is used as a wobbling unit lens, and the extender EX can be inserted/removed in/from a space with d24=30 mm. In the numerical embodiment 5, the wobbling unit wo has a negative refractive power.

In the numerical embodiment 5, φ4b is brought closer to the upper limit, a change in imaging magnification (conditional expression (2)) accompanying insertion/removal of the extender takes a large value.

In this numerical embodiment, the unit L4c is integrally moved to allow macro photographing and flange-back adjustment.

FIGS. 15 and 16 are aberration diagrams at the wide-angle end and telephoto end without insertion of the extender in the numerical embodiment 5. FIG. 23 is an aberration diagram at the wide-angle end with insertion of the extender.

(Numerical Embodiment 6)

TABLE 10

Numerical Embodiment 6

f = 10.0˜440.0 Fno:1.75˜3.0 2ω:57.6°˜1.4°

r1 =
370.170
d1 =
5.50
n 1 =
1.72311
v 1 =
29.5

r2 =
179.081
d2 =
0.47

r3 =
177.086
d3 =
21.52
n 2 =
1.43496
v 2 =
95.1

r4 =
−738.246
d4 =
0.30

r5 =
179.834
d5 =
16.94
n 3 =
1.43496
v 3 =
95.1

r6 =
−18484.355
d6 =
0.30

r7 =
136.803
d7 =
11.61
n 4 =
1.49845
v 4 =
81.6

r8 =
299.938
d8 =
Variable

r9 =
2064.706
d9 =
2.00
n 5 =
1.82017
v 5 =
46.6

r10 =
56.194
d10 =
4.93

r11 =
−200.836
d11 =
1.80
n 6 =
1.77621
v 6 =
49.6

r12 =
58.527
d12 =
5.92

r13 =
−70.671
d13 =
1.80
n 7 =
1.82017
v 7 =
46.6

r14 =
47.059
d14 =
7.61
n 8 =
1.93306
v 8 =
21.3

r15 =
−741.457
d15 =
Variable

r16 =
−3286.891
d16 =
6.09
n 9 =
1.50014
v 9 =
65.0

r17 =
−100.506
d17 =
0.30

r18 =
181.499
d18 =
2.50
n10 =
1.65223
v10 =
33.8

r19 =
80.299
d19 =
11.32
n11 =
1.59143
v11 =
61.2

r20 =
−160.387
d20 =
0.20

r21 =
153.942
d21 =
11.39
n12 =
1.60548
v12 =
60.7

r22 =
−78.774
d22 =
2.50
n13 =
1.85501
v13 =
23.9

r23 =
−210.812
d23 =
0.20

r24 =
126.354
d24 =
7.22
n14 =
1.48915
v14 =
70.2

r25 =
−511.899
d25 =
Variable

r26 =
∞ (Stop)
d26 =
3.20

r27 =
−61.995
d27 =
1.80
n15 =
1.79013
v15 =
44.2

r28 =
27.859
d28 =
5.10
n16 =
1.81266
v16 =
25.4

r29 =
95.165
d29 =
5.38

r30 =
−36.960
d30 =
1.60
n17 =
1.73234
v17 =
54.7

r31 =
61.070
d31 =
13.54
n18 =
1.59911
v18 =
39.2

r32 =
−42.108
d32 =
10.38

r33 =
−161.981
d33 =
6.30
n19 =
1.77621
v19 =
49.6

r34 =
−78.477
d34 =
8.00

r35 =
122.002
d35 =
6.76
n20 =
1.48915
v20 =
70.2

r36 =
−60.053
d36 =
3.00

r37 =
−251.658
d37 =
2.20
n21 =
1.83932
v21 =
37.2

r38 =
35.540
d38 =
6.45
n22 =
1.50349
v22 =
56.4

r39 =
−139.587
d39 =
2.65

r40 =
638.436
d40 =
5.93
n23 =
1.55099
v23 =
45.8

r41 =
−36.259
d41 =
2.20
n24 =
1.81265
v24 =
25.4

r42 =
−97.233
d42 =
0.20

r43 =
101.200
d43 =
5.15
n25 =
1.51977
v25 =
52.4

r44 =
−76.148
d44 =
5.00

r45 =
∞
d45 =
50.00
n26 =
1.51825
v26 =
64.2

r46 =
∞

Seventeenth Surface Aspherical Surface

R = −1.01 × 10⁺², B = 5.06 × 10⁻⁸, C = 4.27 × 10⁻¹², D = 2.70 × 10⁻¹⁴,

E = −2.56 × 10⁻¹⁷

TABLE 11

Extender Portion

d29 =
9.29

r30 =
51.233
d30 =
6.13
n17 = 1.48915
v17 = 70.2

r31 =
−81.169
d31 =
6.03

r32 =
2003.963
d32 =
5.29
n18 = 1.69979
v18 = 55.5

r33 =
−41.347
d33 =
1.20
n19 = 1.85501
v19 = 23.9

r34 =
−86.830
d34 =
0.85

r35 =
49.570
d35 =
1.40
n20 = 1.82017
v20 = 46.6

r36 =
33.003
d36 =
4.09

r37 =
−672.531
d37 =
0.90
n21 = 1.82017
v21 = 46.6

r38 =
17.840
d38 =
4.10
n22 = 1.85501
v22 = 23.9

r39 =
35.205
d39 =
5.92

Focal

Variable
Length

Interval
10.00
65.04
440.00

d 8
4.88
93.03
123.88

d 15
178.94
72.57
2.98

d 25
3.30
21.52
60.26

In the numerical embodiment 6 shown in FIG. 6, the sixth lens of the fourth unit from the image side is used as a wobbling unit lens, and the extender EX can be inserted/removed in/from a space with d34=45.2 mm.

In the numerical embodiment 6, unlike in the numerical embodiments 1 to 5, an optical system is placed in the space in the fourth unit, in/from which the extender EX is inserted/removed, instead of setting a large space as an air gap at the time of 1×, and the optical system at the time of 1× is retracted (ejected) from the optical axis upon insertion of the extender.

In this case as well, by setting the refractive power of the lens unit L4b within an appropriate range, an image height change ratio can be suppressed low regardless of the insertion/removal of the extender EX.

In each numerical embodiment described above, the lens units located closer to the object side than the extender EX are fixed regardless of insertion/removal of the extender EX. By placing an optical system at the time of 1× and insertion of the extender, the degree of freedom in design increases, and high optical performance with a low image height change ratio can be realized.

FIGS. 17 and 18 are aberration diagrams at the wide-angle end and telephoto end without insertion of the extender in the numerical embodiment 6. FIG. 24 is an aberration diagram at the wide-angle end with insertion the extender.

TABLE 12

Embodiment 1
Embodiment 2
Embodiment 3
Embodiment 4
Embodiment 5
Embodiment 6

Conditional Expression (1)
0.27
0.14
0.14
0.16
0.52
0.08

Conditional Expression (2)
0.14
0.45
0.49
0.54
2.06
0.64

Conditional Expression (3)
0.0000
0.0008
0.0008
−0.0005
0.0013
0.0002

Rate of change (%)
−0.01
0.00
0.00
0.01
0.01
0.00

in Imaging Magnification

Rate of change (%)
0.01
0.02
0.03
0.05
0.10
0.04

in Imaging Magnification

Upon Insertion of

Extender Portion

As described above, according to this embodiment, there is provided a zoom lens suitable for a TV camera, video camera, or the like, which has a large aperture of an F-number of about 1.8 to 2 and a high magnification ratio of 10× or more, exhibits a small change in imaging magnification accompanying wobbling regardless of insertion/removal of an optical system such as the extender EX in the relay unit, and has excellent optical performance throughout the entire magnification change range.

(Second Embodiment)

A photographing system (TV camera system) using one of the zoom lenses in the numerical embodiments 1 to 6 as a photographing optical system will be described next with reference to FIG. 25.

Referring to FIG. 25, this photographing system includes a photographing system body 106 including lenses, a photographing optical system 101 formed by one of the zoom lenses in the numerical embodiments 1 to 6, a glass block 102 corresponding to a filter or color separation prism, an image pickup element 103 such as a CCD for receiving an object image formed by the photographing optical system 101, and CPUs 104 and 105 for controlling the photographing system and lenses.

By using one of the zoom lenses in the numerical embodiments 1 to 6 for a photographing system such as a TV camera, a photographing system can be realized, in which a change in imaging magnification upon slight amplitude driving of a wobbling unit wo in the optical axis direction for autofocus operation is small regardless of whether an extender EX is inserted/removed, i.e., poor screen display can be prevented.

The present invention is not limited to the zoom lenses shown in FIGS. 1 to 6. A lens unit other than the lens units shown in FIGS. 1 to 6 may be added to the zoom lens.

For example, as shown in FIG. 26, the lens unit may be constituted by I, II, III, IV, and V units. The same reference numerals as in FIG. 26 denote the same parts in FIG. 25.

As has been described above, according to the present invention, a change in imaging magnification caused when the wobbling unit is slightly amplitude-driven in the optical axis direction can be suppressed small regardless of the insertion/removal of the magnification changing optical unit.

Note that if conditional expression (1) is satisfied, a change in imaging magnification accompanying wobbling without insertion of the magnification changing optical unit can be sufficiently suppressed small.

If conditional expression (2) is satisfied, a change in imaging magnification accompanying wobbling with insertion of the magnification changing optical unit can be sufficiently suppressed small.

If conditional expression (3) is satisfied, a change in incident angle on the wobbling unit upon insertion/removal of the magnification changing optical unit can be made small. This makes it possible to reduce a change in imaging magnification more reliably.

Note that if the wobbling unit is placed closest to the image side in the fourth unit, a reduction in the size and weight of the wobbling unit to be slightly amplitude-driven can be attained.

Number	Date	Country	Kind
2000-403516	Dec 2000	JP	national
2001-384439	Dec 2001	JP	national

Number	Name	Date	Kind
5138492	Hamano et al.	Aug 1992	A
5521758	Hamano	May 1996	A
5758206	Imaoka	May 1998	A
5771123	Hamano	Jun 1998	A
5786853	Ohkawara et al.	Jul 1998	A

Zoom lens and photographing system

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CPC

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