JP2020086073A - Zoom lens and imaging apparatus having the same - Google Patents

Abstract

To provide a zoom lens which has a compact total system, nonetheless has a large zoom ratio, and excellent optical performance over an entire zoom range.SOLUTION: The zoom lens is composed of a first lens group having positive refractive power, a second lens group having negative refractive power, a third lens group having positive refractive power, and a rear group comprising one or more lens groups, arranged in order from the object side to the image side, and is configured in such a manner that distances between adjacent lens groups change while zooming, the first lens group and the third lens group being stationary while zooming. Each of the first lens group and the third lens group contains one or more lenses α with positive refractive power made of a material that satisfies predetermined conditional expressions, where νdα and θgfα in the expressions respectively represent an Abbe number and partial dispersion ratio of the material. The zoom lens satisfies a conditional expression: 1.2<fw/φ<3.0, where fw represents a focal length of the zoom lens at the wide-angle end and φ represents an effective image circle diameter of the zoom lens.SELECTED DRAWING: Figure 1

Description

The present invention relates to a zoom lens, and is particularly suitable as an image pickup optical system used in an image pickup apparatus such as a surveillance camera, a digital camera, a video camera.

As an image pickup optical system used in an image pickup apparatus, a zoom lens having high optical performance corresponding to high definition of an image pickup element is desired.

As a zoom lens that meets these requirements, a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a third lens group having a positive refractive power, which are sequentially arranged from the object side to the image side, A zoom lens having a rear group composed of one or more lens groups is known.

In Patent Document 1, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a negative refractive power are arranged in order from the object side to the image side. A zoom lens including a fourth lens unit having a power and a fifth lens unit having a positive refractive power is disclosed.

In Patent Document 2, a first lens unit having a positive refracting power, a second lens unit having a negative refracting power, a third lens unit having a positive refracting power, and a positive refracting power arranged in order from the object side to the image side. A zoom lens comprising a fourth lens group of power is disclosed.

JP, 2016-118736, A JP-A-8-248317

Here, in order to achieve further downsizing of the entire system, high zoom ratio, and high optical performance over the entire zoom range while satisfying the above-mentioned requirements, the refractive power of each lens group and the lens power included in each lens group are included. It is important to properly set the material of the lens to be used. In particular, it is important to suppress variation in chromatic aberration during zooming.

It is an object of the present invention to provide a zoom lens having a high zoom ratio and a high optical performance over the entire zoom range while the entire system is small, and an imaging device having the zoom lens.

The zoom lens of the present invention includes a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a third lens group having a positive refractive power, which are arranged in order from the object side to the image side. A zoom lens comprising a rear group including the lens groups described above, wherein the distance between adjacent lens groups changes during zooming, wherein the first lens group and the third lens group are immovable during zooming, and When the Abbe number is νdα and the partial dispersion ratio is θgfα, the first lens group and the third lens group are respectively
0<θgfα−(−1.665×10 ⁻⁷ ·νdα ³
+5.213×10 ⁻⁵ ·νdα ² −5.656×10 ⁻³ ·νdα +0.737)
0.532<θgfα<0.550
60<νdα<100
When the focal length of the zoom lens at the wide-angle end is fw and the effective image circle diameter of the zoom lens is φ, the lens has at least one lens α having a positive refractive power and is made of a material that satisfies the conditional expression
1.2<fw/φ<3.0
It is characterized by satisfying the following conditional expression.

According to the present invention, it is possible to obtain a zoom lens having a high zoom ratio and a high optical performance over the entire zoom range even though the entire system is small.

Sectional drawing at the wide-angle end of the zoom lens of Embodiment 1. FIG. Aberration diagrams of the zoom lens of Embodiment 1 at the wide-angle end, the intermediate zoom position, and the telephoto end. Sectional drawing at the wide-angle end of the zoom lens of Embodiment 2. FIG. Aberration diagrams of the zoom lens of Embodiment 2 at the wide-angle end, intermediate zoom position, and telephoto end. Sectional drawing at the wide-angle end of the zoom lens of Embodiment 3. FIG. Aberration diagrams of the zoom lens of Embodiment 3 at the wide-angle end, the intermediate zoom position, and the telephoto end. Sectional drawing at the wide-angle end of the zoom lens of Embodiment 4. FIG. Aberration diagrams of the zoom lens of Embodiment 4 at the wide-angle end, the intermediate zoom position, and the telephoto end. Sectional drawing of the zoom lens of Example 1, a dome cover, and a protective cover. Imaging device (monitoring camera) of the embodiment and usage example Explanatory drawing of the zoom locus of the zoom lens of Example 1. FIG. Diagram showing the relationship between Abbe number of materials and partial dispersion ratio

Hereinafter, the zoom lens according to the present embodiment and the image pickup apparatus including the zoom lens will be described.

The zoom lens according to the present embodiment includes a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, which are sequentially arranged from the object side to the image side. It is composed of a rear group including one or more lens groups. The distance between adjacent lens groups changes during zooming.

1, 3, 5 and 7 are cross-sectional views at the wide-angle end (short focal length end) of the zoom lenses of Embodiments 1 to 4 of the present invention. 2, 4, 6 and 8 are aberration diagrams of the zoom lenses of Examples 1 to 4. Each aberration diagram shows aberrations at the wide-angle end (A), the intermediate zoom position (B), and the telephoto end (longest focal length) (C) in order from the top.

The first embodiment is a zoom lens having a zoom ratio of 4.80 and an F number of 1.85 to 2.47. The second embodiment is a zoom lens having a zoom ratio of 3.00 and an F number of 1.70. The third embodiment is a zoom lens having a zoom ratio of 5.50 and an F number of 1.85 to 2.47. The fourth embodiment is a zoom lens having a zoom ratio of 11.94 and an F number of 1.85 to 2.47.

The zoom lens of each embodiment is an image pickup optical system used in an image pickup apparatus such as a video camera, a digital camera, a TV camera, and a surveillance camera. In the cross-sectional view, the left side is the subject side (object side) (front side), and the right side is the image side (rear side). In the sectional view, L0 is a zoom lens. i indicates the order of the lens groups from the object side, and Li is the i-th lens group. LR is a rear group having one or more lens groups.

In the sectional view, SP is an aperture stop, which is arranged on the object side of the third lens unit L3. In the sectional view, G is an optical element corresponding to an optical filter, a face plate, a crystal low-pass filter, an infrared cut filter, or the like. IP is an image plane, and when used as an image pickup optical system of a video camera or a digital still camera, an image pickup element (photoelectric conversion element) such as a CCD sensor or a CMOS sensor is placed.

The arrows indicate the movement loci of the respective lens groups during zooming (variation of magnification) from the wide-angle end to the telephoto end, and the movement directions of the lens groups during focusing. In the spherical aberration of the aberration diagram, the solid line d is the d line (wavelength 587.6 nm), and the dashed-dotted line g is the g line (wavelength 435.8 nm). The one-dot chain line C is the C line (wavelength 656.3 mm), and the dotted line F is the F line (wavelength 435.8 mm). In the astigmatism diagram, the dotted line M is the d-line meridional image plane, and the solid line S is the d-line sagittal image plane. The chromatic aberration of magnification is represented by the g line with respect to the d line. ω is a half angle of view (half of the image pickup angle of view) (degrees), and Fno is an F number.

In the sectional views of Examples 1, 2, and 4, L1 is a first lens group having a positive refractive power, L2 is a second lens group having a negative refractive power, and L3 is a third lens group having a positive refractive power. LR is the rear group. The rear lens group LR includes a fourth lens unit L4 having a negative refractive power and a fifth lens unit L5 having a positive refractive power. Examples 1, 2, and 4 are five-group zoom lenses.

In Examples 1, 2, and 4, the first lens unit L1, the third lens unit L3, and the fifth lens unit L5 do not move during zooming. During zooming from the wide-angle end to the telephoto end, the second lens unit L2 moves toward the image side as indicated by the arrow. The fourth lens unit L4 moves toward the image side while drawing a convex locus. The aperture stop SP does not move during zooming.

The fourth lens unit L4 is moved to correct the image plane variation due to zooming, and focusing is performed. A solid-line curve 4a and a dotted-line curve 4b relating to the fourth lens unit L4 are movement loci for correcting image plane fluctuations due to zooming when focusing on infinity and short distance, respectively. Focusing from infinity to a short distance is performed by moving the fourth lens unit L4 rearward (toward the image side) as indicated by an arrow 4C. The focusing is not limited to the fourth lens unit L4, and other lens units may be used alone or a plurality of lens units may be used. For example, part or all of the second lens group L2 or the fifth lens group L5 may be used.

In the sectional view of the third embodiment, L1 is a first lens group having a positive refractive power, L2 is a second lens group having a negative refractive power, and L3 is a third lens group having a positive refractive power. LR is the rear group. The rear group LR is the fourth lens group having a positive refractive power. The fifth lens unit L5 has a negative refractive power and the sixth lens unit L6 has a positive refractive power. Example 3 is a 6-group zoom lens.

In Example 3, the first lens unit L1 and the third lens unit L3 do not move during zooming. During zooming from the wide-angle end to the telephoto end, the second lens unit L2 moves toward the image side as indicated by the arrow. The fourth lens unit L4 and the sixth lens unit L6 move in a convex locus on the object side. The fifth lens unit L5 moves in a convex locus toward the image side. The aperture stop SP does not move during zooming.

The fifth lens unit L5 is moved to correct the image plane variation due to zooming, and at the same time focusing is performed. A solid curve 5a and a dotted curve 5b relating to the fifth lens unit L5 are movement loci for correcting image plane fluctuations due to zooming when focusing on infinity and short distance, respectively. Focusing from infinity to a short distance is performed by retracting the fifth lens unit L5 rearward (toward the image side) as shown by an arrow 5C. Note that focusing is not limited to the fifth lens unit L5, and other lens units may be used alone or a plurality of lens units may be used. For example, part or all of the second lens group L2 or the fifth lens group L5 may be used.

In each embodiment, the aperture stop SP is installed in front of the third lens unit L3 and is stationary during zooming. The aperture stop SP may be independently moved, which facilitates appropriately cutting flare rays at each zoom position during zooming.

Next, taking the zoom lens of Example 1 as an example, a method of moving each lens group during zooming will be described with reference to FIGS. 11(A), (B), and (C).

Zooming from the wide-angle end to the telephoto end is performed by moving the second lens unit L2 and the fourth lens unit L4 independently. Specifically, during zooming from the wide-angle end (FIG. 11A) to the telephoto end (FIG. 11C), the second lens unit L2 monotonously moves from the object side to the image side, and at the same time, the fourth lens unit. L4 is a trajectory that moves to the object side.

In order to form such a movement locus of each lens group, each of the second lens group L2, the third lens group L3, the fourth lens group L4, and the fifth lens group L5 at the wide-angle end of FIG. The lens group spacing is properly secured, and the zoom lens has a large diameter and is easily miniaturized. The fourth lens unit L4 is responsible for focusing.

In order to realize a large aperture, the effective diameter and weight of the first lens unit L1 and the third lens unit L3 are large. Therefore, if the above lens group is moved during zooming, quick follow-up becomes difficult. In order to solve this, in the present invention, the first lens unit L1 and the third lens unit L3 are immovable during zooming.

Further, in each embodiment, the conditions of the abnormal partial dispersion glass used for the first lens unit L1 and the third lens unit L3 are defined in order to correct the axial chromatic aberration in the entire zoom range and downsize the zoom lens. ..

Specifically, the Abbe number of the material is νdα and the partial dispersion ratio is θgfα. At this time, the first lens unit L1 and the third lens unit L3 respectively
0<θgfα−(−1.665×10 ⁻⁷ ·νdα ³
+5.213×10 ⁻⁵ ·νdα ² −5.656×10 ⁻³ ·νdα +0.737) (1)
0.532<θgfα<0.550 (2)
60<νdα<100 (3)
It has at least one lens α (positive lens α) having a positive refractive power and made of a material that satisfies the following conditional expression.

Further, the focal length of the zoom lens at the wide-angle end is fw, and the effective image circle diameter of the zoom lens is φ. At this time,
1.2<fw/φ<3.0 (4)
The following conditional expression is satisfied.

Next, the technical meaning of the above conditional expressions will be described.

Conditional expression (1) defines the partial dispersion ratio of the material of the positive lens α included in the first lens unit L1 and the third lens unit L3. Mainly, it defines the numerical range of the anomalous partially dispersed glass for suppressing the variation of chromatic aberration of a plurality of wavelengths during zooming. When chromatic aberration is corrected in a wide wavelength band, chromatic aberration remains for other than the specific two wavelengths. In order to reduce this residual chromatic aberration (secondary spectrum), it is preferable to use anomalous partially dispersed glass.

Generally, in most optical glasses, there is a substantially linear relationship between the partial dispersion ratio and the Abbe number. On the other hand, the type of glass that is located away from this linear relationship is called anomalous partial dispersion glass and is used when reducing the secondary spectrum. Conditional expression (1) means the above-mentioned amount of separation.

Here, the Abbe number νd and the partial dispersion ratio θgf of the material are given by the following equations.

νd=(nd-1)/(nF-nC)
θgF=(ng-nF)/(nF-nC)
Here, the refractive indices of F-line (486.1 nm), d-line (587.6 nm), C-line (656.3 nm), and g-line (435.8 nm) of the Fraunforfer line are nF, nd, and nC, respectively. , Ng.

By providing the first lens unit L1 and the third lens unit L3 with the lens α having a positive refractive power that satisfies the conditional expression (1), the secondary spectrum is reduced over the zooming from the wide-angle end to the telephoto end. ing. If the range of conditional expression (1) is exceeded, the secondary spectrum will increase during zooming.

The conditional expression (2) directly defines the numerical range of the partial dispersion ratio θgf of the abnormal partial dispersion glass, and mainly reduces the secondary spectrum during zooming. If the lower limit of conditional expression (2) is exceeded, the secondary spectrum will increase during zooming.

Conditional expression (3) defines the Abbe number of the material of the positive lens α included in the first lens unit L1 and the third lens unit L3, and is mainly for suppressing the variation of chromatic aberration for two specific wavelengths. It is a thing. If the lower limit of conditional expression (3) is exceeded, fluctuations in chromatic aberration will increase during zooming, which is not preferable. In addition, the secondary spectrum also increases. If the upper limit of conditional expression (3) is exceeded, chromatic aberration will be overcorrected, which is not preferable.

FIG. 12 shows a glass material region assumed by the positive lens α in the conditional expressions (1) to (3). The horizontal axis of FIG. 12 represents the Abbe number and the vertical axis represents the partial dispersion ratio. The solid line indicates the cubic function on the right side of Expression (1). The shaded area is the above numerical range.

Conditional expression (4) defines the ratio of the focal length of the zoom lens at the wide-angle end to the effective image circle diameter of the zoom lens, thereby defining a favorable correction region of the secondary spectrum. If the lower limit of conditional expression (4) is exceeded, the focal length of the zoom lens at the wide-angle end becomes short with respect to the effective image circle diameter. As a result, the power of the third lens unit L3 becomes strong, and various aberrations of the peripheral performance at the wide angle end increase. If the upper limit of conditional expression (4) is exceeded, the focal length of the zoom lens at the wide-angle end becomes longer than the effective image circle diameter. As a result, it becomes excessively telescopic, and it becomes difficult to correct the secondary spectrum.

Conditional expressions (2) to (4) are more preferably limited as follows.

0.532<θgfα<0.549 (2a)
72<νdα<98 (3a)
1.3<fw/φ<2.8 (4a)
More preferably, the numerical ranges of conditional expressions (3) and (4) should be set as follows.

75<νdα<96 (3b)
1.5<fw/φ<2.5 (4b)
In each embodiment, it is desirable to satisfy at least one of the following conditional expressions.

The focal length of the first lens unit L1 is f1, and the focal length of the zoom lens at the telephoto end is ft. The focal length of the third lens unit L3 is f3. The focal length of the second lens unit L2 is f2. At this time, it is preferable to satisfy at least one of the following conditional expressions.

0.2<f1/ft<1.5 (5)
0.1<f3/f1<0.4 (6)
-0.4<f2/f1<-0.1 (7)
Next, the technical meanings of the above conditional expressions will be described.

Conditional expression (5) defines an appropriate power arrangement by defining the ratio of the focal length of the first lens unit L1 and the focal length of the zoom lens at the telephoto end. If the lower limit of conditional expression (5) is exceeded, the focal length of the first lens unit L1 becomes shorter than the focal length of the zoom lens at the telephoto end. As a result, the positive power (refractive power) of the first lens unit L1 becomes strong, it becomes difficult to correct various aberrations at the telephoto end, and it becomes difficult to downsize the zoom lens and correct the secondary spectrum.

If the upper limit of conditional expression (5) is exceeded, the focal length of the zoom lens at the telephoto end becomes shorter than the focal length of the first lens unit L1. Therefore, the correction amount of the secondary spectrum by the positive lens α becomes excessive.

Conditional expression (6) defines the ratio of the focal length of the third lens unit L3 and the focal length of the first lens unit L1 to determine the optimum power arrangement (refractive power arrangement) when correcting the secondary spectrum. Stipulates. If the lower limit of conditional expression (6) is exceeded, the focal length of the third lens unit L3 becomes shorter than the focal length of the first lens unit L1. As a result, the positive power of the third lens unit L3 becomes strong, and the correction of the secondary spectrum becomes excessive at the wide-angle end.

If the upper limit of conditional expression (6) is exceeded, the focal length of the first lens unit L1 becomes shorter than the focal length of the third lens unit L3. As a result, the positive power of the first lens unit L1 becomes strong, and the secondary spectrum is excessively corrected at the telephoto end.

Conditional expression (7) defines the ratio of the focal length of the first lens unit L1 and the focal length of the second lens unit L2, and thus defines the optimum power arrangement when correcting the secondary spectrum. If the upper limit of conditional expression (7) is exceeded, the negative focal length of the second lens unit L2 becomes shorter than the negative focal length of the first lens unit L1. As a result, the negative power of the second lens unit L2 becomes strong, and the aberration variation becomes large during zooming.

If the lower limit of conditional expression (7) is exceeded, the focal length of the first lens unit L1 becomes shorter than the focal length of the second lens unit L2. As a result, the positive power of the first lens unit L1 becomes strong, it becomes difficult to correct various aberrations at the telephoto end, and it becomes difficult to downsize the zoom lens and correct the secondary spectrum.

Preferably, the numerical ranges of conditional expressions (5) to (7) are set as follows.

0.30<f1/ft<1.48 (5a)
0.12<f3/f1<0.38 (6a)
-0.35<f2/f1<-0.10 (7a)
More preferably, the numerical ranges of conditional expressions (5) to (7) should be set as follows.

0.35<f1/ft<1.45 (5b)
0.15<f3/f1<0.35 (6b)
-0.3<f2/f1<-0.1 (7b)
Next, a preferable mode in each embodiment will be described.

The first lens unit L1 has a weight larger than that of the other lens units, and thus is stationary during zooming. In addition, the first lens group L1 has a widest space, and in order from the object side to the image side, the first lens group (first sub-group) 1a having a positive refractive power and the first lens group b having a negative refractive power are arranged. It is composed of the lens group (second sub-group) 1b, which is the most suitable for telephoto.

Further, in order from the object side to the image side, the first lens unit L1 has a positive refractive power that does not move during zooming, and the second lens unit L2 has a negative refractive power that moves during zooming. The third lens group L3 has a positive refractive power that does not move during zooming, the fourth lens group L4 has a negative refractive power that moves during zooming, and the fifth lens group L5 has a positive refractive power.

Since the first lens unit L1 has a larger weight than the other lens units, the first lens unit L1 is immovable during zooming to improve the followability of zooming.

The second lens unit L2 as a main variable power lens unit obtains a variable power effect by moving from the object side to the image side during zooming from the wide-angle end to the telephoto end.

Since the third lens unit L3 has a larger weight than the other lens units, the third lens unit L3 is immovable during zooming to improve the followability of zooming.

The fourth lens group L4 moves during zooming, but also functions as a focus lens group. It is desirable that the fourth lens unit L4 be downsized in order to obtain high tracking performance when focusing. The fourth lens unit L4 is preferably one element from the viewpoint of weight reduction. Here, the element means a single lens or a cemented lens.

The fifth lens unit L5 has an effect of suppressing the image plane variation and the magnification chromatic aberration variation during zooming. The fifth lens unit L5 may move during zooming. This facilitates suppression of off-axis aberration variation during zooming. However, even if the lens does not move, it is easy to correct the aberration by properly setting the lens configuration.

It is preferably applied to an image pickup apparatus having an element that receives an image captured by a zoom lens. In recent years, a CCD (Charge Coupled Device), a CMOS (Complementary Metal Oxide Semiconductor) sensor, and the like have been mainly used for digitally processing an image. The present invention is also preferably applied to an image pickup apparatus having an image pickup element corresponding to this.

Further, the image pickup apparatus of the present invention may have a configuration in which a dome is attached when used as a surveillance camera, for example.

Next, the lens configuration of the embodiment will be described.

Hereinafter, unless otherwise specified, the lens configurations will be described in the order of arrangement from the object side to the image side.
(Example 1)
The first lens group L1 includes a positive lens G11, a positive lens G12, a positive lens G13, and a negative lens G14. The first lens group is stationary during zooming. The positive lens G13 satisfactorily corrects the fluctuation of the axial chromatic aberration during zooming by using an abnormal partial dispersion glass having a low dispersion property. Examples of the abnormal partially dispersed glass having low dispersibility include S-FPL51 (trade name, manufactured by OHARA Co., Ltd.) and the like.

The second lens group L2 includes a negative lens G21, a negative lens G22, a negative lens G23, and a positive lens G24.

The third lens group L3 includes a positive lens G31, a positive lens G32, a positive lens G33, a negative lens G34, and a positive lens G35. The positive lens G31, the positive lens G32, and the positive lens G33 use abnormal partial dispersion glass having low dispersion in consideration of correction of chromatic aberration. Examples of the abnormal partially dispersed glass having low dispersibility include trade name S-FPL51 (manufactured by OHARA Co., Ltd.) and trade name S-FPL55 (manufactured by OHARA Co., Ltd.).

The fourth lens unit L4 includes a negative lens G41. The fourth lens group L4 may have a plurality of lenses.

The fifth lens unit L5 is composed of a positive lens G51 and a negative lens G52, and satisfactorily corrects off-axis image plane variation and lateral chromatic aberration.
(Example 2)
The second lens group L2 includes a negative lens G21, a negative lens G22, and a positive lens G23. The other configurations of the respective lens groups are the same as those in the first embodiment.
(Example 3)
The third lens unit L3 includes a positive lens G31 and a positive lens G32. The positive lens G31 and the positive lens G32 lenses use extraordinary partial dispersion glass having low dispersion in consideration of chromatic aberration correction. Examples of the abnormal partially dispersed glass having low dispersibility include S-FPL51 (trade name, manufactured by OHARA Co., Ltd.) and the like. The third lens unit L3 is fixed during zooming.

The fourth lens group L4 includes a positive lens G41, a negative lens G42, and a positive lens G43. The fourth lens unit L4 moves during zooming. By moving the fourth lens unit L4, fluctuations of various aberrations during zooming are suppressed.

The fifth lens unit L5 is composed of a negative lens G51. The fifth lens group L5 may have a plurality of lenses. The fifth lens unit L5 moves as shown by an arrow F when focusing from infinity to a short distance.

The sixth lens unit L6 is composed of a positive lens G61 and a negative lens G62, and satisfactorily corrects off-axis image plane variation and lateral chromatic aberration. The sixth lens unit L6 moves during zooming. Others are the same as those in the first embodiment.
(Example 4)
The first lens group L1 includes a positive lens G11, a positive lens G12, a positive lens G13, a positive lens G14, and a negative lens G15. The first lens unit does not move during zooming. The positive lens G12 and the positive lens G13 use an extraordinary partial dispersion glass having a low dispersibility so that the fluctuation of the axial chromatic aberration during the zooming is well corrected. Examples of the abnormal partially dispersed glass having low dispersibility include trade name S-FPL51 (manufactured by OHARA) and trade name S-FPL55 (manufactured by OHARA).

The third lens group L3 includes a positive lens G31, a positive lens G32, a negative lens G33, and a positive lens G34. Abnormal partial dispersion glass having low dispersion is used for the positive lens G31 and the positive lens G32 in consideration of correction of chromatic aberration. Examples of the abnormal partially dispersed glass having low dispersibility include trade name S-FPL51 (manufactured by OHARA Co., Ltd.) and trade name S-FPL55 (manufactured by OHARA Co., Ltd.). The configurations of the other groups are the same as those in the first embodiment.

FIG. 9 is a schematic view of a main part when the dome cover 15 or the protective cover 17 is attached to the zoom lens of the first embodiment. The dome cover 15 and the protective cover 17 are formed of a plastic material such as polymethylmethacrylate (PMMA) or polycarbonate (PC) with a thickness of about several millimeters. The zoom lens may be designed in consideration of the influences (focal length and material) of the dome cover 15 and the protective cover 17 to correct various aberrations.

FIG. 10 is a schematic view of a main part of an imaging device (monitoring camera) using the zoom lens of the embodiment as an imaging optical system. In FIG. 10A, 11 is a camera body of the surveillance camera 10, 12 is a built-in camera body 11, and an image pickup element (photoelectric conversion element) such as a CCD sensor or a CMOS sensor that receives a subject image formed by the lens unit 16 is received. ). A memory unit 13 records information corresponding to the subject image photoelectrically converted by the image sensor 12. Reference numeral 14 is a network cable for transferring a subject image photoelectrically converted by the image sensor 12. FIG. 10B is an example when the dome-shaped cover 15 is attached to the imaging device 10 of FIG. 10A and is used by being attached to the ceiling.

The image pickup device is not limited to the surveillance camera, and can be used in a video camera, a digital camera, or the like.

As described above, according to each of the embodiments, it is possible to obtain a zoom lens in which miniaturization and variation in axial chromatic aberration during zooming are suppressed, and an image pickup apparatus including the zoom lens.

The following means may be adopted in each embodiment.
-It is not limited to the shape and number of glass shown in the examples, and may be changed as appropriate.
-Move some lenses and lens groups so that they have a component in the direction perpendicular to the optical axis, thereby correcting image blur caused by vibration such as camera shake.
-Correct distortion, chromatic aberration, etc. by electrical correction means.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments and optical specifications (angle of view and Fno), and various modifications can be made within the scope of the invention.

For example, the zoom lens according to each embodiment has a configuration in which the rear group includes two or three lens groups and the entire system includes five or six lens groups, but the invention is not limited to this. .. That is, the effect of the present invention can be obtained as long as the rear group has at least one lens group.

An imaging system (surveillance camera system) including the zoom lens of each embodiment and a control unit that controls the zoom lens may be configured. In this case, the control unit can control the zoom lens so that each lens group moves as described above during zooming, focusing and image blur correction. At this time, the control unit does not have to be configured integrally with the zoom lens, and the control unit may be configured separately from the zoom lens. For example, a configuration is adopted in which a control unit (control device) arranged far from a drive unit that drives each lens of the zoom lens includes a transmission unit that sends a control signal (command) for controlling the zoom lens. May be. With such a control unit, the zoom lens can be operated remotely.

Further, a configuration may be adopted in which an operating unit such as a controller or a button for remotely operating the zoom lens is provided in the control unit, and the zoom lens is controlled according to an input to the operating unit by the user. For example, an enlargement button and a reduction button are provided as the operation unit, and when the user presses the enlargement button, the magnification of the zoom lens increases, and when the user presses the reduction button, the magnification of the zoom lens decreases. Thus, the control unit may be configured to send a signal to the drive unit of the zoom lens.

Further, the imaging system may include a display unit such as a liquid crystal panel that displays information (moving state) regarding zoom of the zoom lens. The information regarding the zoom of the zoom lens is, for example, the zoom magnification (zoom state) and the movement amount (movement state) of each lens group. In this case, the user can remotely operate the zoom lens via the operation unit while viewing the information regarding the zoom of the zoom lens displayed on the display unit. At this time, the display unit and the operation unit may be integrated by adopting, for example, a touch panel.

Numerical data 1 to 4 corresponding to Examples 1 to 4 are shown below. In each numerical data, the surface number indicates the order of the optical surface from the object side. r is the radius of curvature (mm) of the optical surface, and d in the surface number i is the distance (mm) between the i-th optical surface and the (i+1)th optical surface. Further, nd is the refractive index of the material of the optical member at the d-line, νd and θgF are the Abbe number and the partial dispersion ratio of the material of the optical member, and the definition is as described above. Further, in the numerical data 1 to 4, the two surfaces closest to the image are planes corresponding to glass blocks.

BF is a back focus and represents the distance from the final lens surface to the paraxial image plane by the air conversion length. The total lens length is the length from the first lens surface to the final lens surface, plus the value of the back focus BF. The display of "e±x" means "10 ^±x ".

When the optical surface is an aspherical surface, the symbol * is added to the right of the surface number. As for the aspherical shape, X is the displacement amount from the surface vertex in the optical axis direction, h is the height from the optical axis in the direction perpendicular to the optical axis, R is the paraxial radius of curvature, k is the conic constant, A4, A6, When A8 and A10 are aspherical coefficients of each order, they are expressed by the following equation.

(Numerical data 1)
Unit: mm

Surface data Surface number rd nd vd θgf
1 177.486 6.54 1.48749 70.2 0.5300
2 -570.048 0.47
3 63.403 10.21 1.59522 67.7 0.5442
4 424.856 3.78
5 48.814 11.53 1.49700 81.5 0.5375
6 7611.880 2.54 1.76200 40.1 0.5765
7 39.143 (variable)
8 33.686 1.32 1.91650 31.6 0.5911
9 27.368 4.93
10 -76.736 1.32 1.65160 58.5 0.5425
11 30.838 4.54
12 -38.137 1.32 1.64000 60.1 0.5484
13 -718.761 1.21
14 81.191 2.34 1.92286 18.9 0.6495
15 -543.272 (variable)
16 (aperture) ∞ 1.88
17 30.879 5.71 1.49700 81.5 0.5484
18 180.174 1.00
19 25.230 5.16 1.49700 81.5 0.5484
20 61.579 3.53
21 23.836 4.94 1.43875 94.7 0.5340
22 108.627 1.41 1.73800 32.3 0.5899
23 15.479 0.50
24* 15.034 6.54 1.58313 59.4 0.5434
25* 127.687 (variable)
26 85.194 1.33 1.49700 81.5 0.5484
27 19.082 (variable)
28 33.920 5.28 1.58144 40.8 0.5774
29 -21.421 1.13 1.48749 70.2 0.5300
30 160.609 8.83
31 ∞ 1.13 1.51633 64.1 0.5353
32 ∞ 1.18
Image plane ∞

Aspheric data 24th surface
K =-1.40010e+000 A 4= 3.98647e-005 A 6= 6.00554e-008 A 8= 2.25658e-011 A10= 1.50540e-012

Surface 25
K = 0.00000e+000 A 4= 3.00349e-005 A 6= 5.91386e-008 A 8=-5.13754e-011 A10= 1.77241e-012

Various data Zoom ratio 4.80
Wide-angle mid-telephoto focal length 36.00 89.82 172.80
F number 1.85 2.25 2.47
Half angle of view (degrees) 12.53 5.09 2.65
Image height 8.00 8.00 8.00
Total lens length 174.64 174.64 174.64
BF 10.76 10.76 10.76

d 7 2.67 32.23 48.86
d15 48.18 18.62 1.99
d25 1.97 8.22 1.99
d27 20.62 14.38 20.60


Lens group Data group Start surface Focal length
1 1 138.07
2 8 -26.62
3 16 30.27
4 26 -49.81
5 28 54.16
6 31 ∞

(Numerical data 2)
Unit: mm

Surface data Surface number rd nd vd θgf
1 205.028 4.45 1.48749 70.2 0.5300
2 69 20.672 0.47
3 80.811 8.65 1.59522 67.7 0.5442
4 -1743.642 9.80
5 84.390 7.82 1.49700 81.5 0.5375
6 -206.220 2.54 1.76200 40.1 0.5765
7 76.223 (variable)
8 -141.996 1.32 1.65160 58.5 0.5425
9 34.236 5.17
10 -86.986 1.32 1.64000 60.1 0.5484
11 245.617 1.25
12 56.256 3.00 1.92286 18.9 0.6495
13 117.191 (variable)
14 (aperture) ∞ 1.88
15 27.776 4.79 1.49700 81.5 0.5484
16 61.048 1.01
17 22.037 6.62 1.49 700 81.5 0.5484
18 87.996 0.49
19 18.827 5.81 1.43875 94.7 0.5340
20 74.755 1.41 1.73800 32.3 0.5899
21 12.621 0.90
22* 12.209 5.54 1.58313 59.4 0.5434
23* 35.833 (variable)
24 82.961 1.33 1.49700 81.5 0.5375
25 15.371 (variable)
26 25.252 5.55 1.58144 40.8 0.5774
27 -18.332 1.13 1.48749 70.2 0.5300
28 45.911 8.87
29 ∞ 1.13 1.51633 64.1 0.5353
30 ∞ 1.18
Image plane ∞

Aspheric data 22nd surface
K =-9.83655e-001 A 4= 5.97388e-005 A 6= 2.73721e-007 A 8= 1.06072e-010 A10= 1.76266e-011

Surface 23
K = 0.00000e+000 A 4= 7.81134e-005 A 6= 2.24806e-007 A 8= 3.14407e-009 A10= 9.92728e-012

Various data Zoom ratio 3.00
Wide-angle mid-telephoto focal length 36.36 71.06 109.09
F number 1.70 1.70 1.70
Half angle of view 12.41 6.42 4.19
Image height 8.00 8.00 8.00
Total lens length 161.24 161.24 161.24
BF 10.80 10.80 10.80

d 7 5.21 34.77 51.39
d13 50.18 20.62 3.99
d23 2.67 4.68 2.57
d25 10.15 8.14 10.25

Lens group Data group Start surface Focal length
1 1 154.58
2 8 -40.05
3 14 29.30
4 24 -38.21
5 26 54.95
6 29 ∞




(Numerical data 3)
Unit: mm

Surface data Surface number rd nd vd θgf
1 160.424 6.41 1.48749 70.2 0.5300
2 -730.190 0.47
3 63.139 9.14 1.59522 67.7 0.5442
4 633.822 3.98
5 51.358 9.27 1.49700 81.5 0.5375
6 -744.121 2.54 1.76200 40.1 0.5765
7 44.130 (variable)
8 28.542 1.32 1.91650 31.6 0.5911
9 23.521 4.89
10 -70.054 1.32 1.65 160 58.5 0.5425
11 26.228 4.23
12 -37.396 1.32 1.64000 60.1 0.5370
13 -403.382 0.72
14 71.194 2.88 1.92286 18.9 0.6495
15 -770.077 (variable)
16 (aperture) ∞ 1.88
17 29.112 4.67 1.49700 81.5 0.5375
18 74.236 2.00
19 28.270 6.17 1.49700 81.5 0.5375
20 288.103 (variable)
21 21.842 5.95 1.43875 94.7 0.5340
22 -1231.375 1.41 1.73800 32.3 0.5899
23 17.375 0.89
24* 15.929 5.34 1.58313 59.4 0.5423
25* 71.275 (variable)
26 372.205 1.33 1.49 700 81.5 0.5375
27 20.921 (variable)
28 30.886 5.44 1.58144 40.8 0.5774
29 -34.881 1.13 1.48749 70.2 0.5300
30 -503.278 (variable)
31 ∞ 1.13 1.51633 64.1 0.5353
32 ∞ 1.18
Image plane ∞

Aspheric data 24th surface
K =-1.36837e+000 A 4= 3.89880e-005 A 6= 1.10569e-007 A 8= 3.89689e-011 A10= 3.52452e-012

Surface 25
K = 0.00000e+000 A 4= 4.70870e-005 A 6= 1.55506e-007 A 8= 1.98178e-010 A10= 4.60760e-012

Various data Zoom ratio 5.50
Wide-angle mid-telephoto focal length 28.56 75.44 157.02
F number 1.85 2.25 2.47
Half angle of view (degrees) 15.65 6.05 2.92
Image height 8.00 8.00 8.00
Total lens length 168.52 168.52 168.52
BF 15.45 16.98 13.69

d 7 2.01 31.56 48.19
d15 49.07 19.51 2.89
d20 2.13 2.35 3.38
d25 1.98 7.18 1.99
d27 13.18 6.23 13.68
d30 13.52 15.05 11.76

Lens group Data group Start surface Focal length
1 1 124.78
2 8 -24.47
3 16 39.07
4 21 123.52
5 26 -44.66
6 28 44.98
7 31 ∞


(Numerical data 4)
Unit: mm

Surface data Surface number rd nd vd θgf
1 137.519 19.61 1.48749 70.2 0.5300
2 121 01.141 0.47
3 98.586 15.76 1.43875 94.7 0.5340
4 217.958 0.27
5 162.814 10.10 1.43875 94.7 0.5340
6 429.133 10.10
7 73.984 18.97 1.43875 94.7 0.5340
8 7639.670 2.54 1.85478 24.8 0.6122
9 115.810 (variable)
10 22.930 1.32 1.91650 31.6 0.5911
11 16.089 5.35
12 -37.299 1.32 1.65160 58.5 0.5425
13 22.404 4.72
14 -22.593 1.32 1.64000 60.1 0.5370
15 -282.894 0.10
16 77.745 2.80 1.92286 18.9 0.6495
17 -98.134 (variable)
18 (aperture) ∞ 2.05
19 26.877 6.67 1.49700 81.5 0.5375
20 92.719 9.10
21 19.780 11.19 1.43875 94.7 0.5340
22 358.662 1.41 1.80000 29.8 0.6017
23 26.079 0.64
24* 17.903 5.91 1.58313 59.4 0.5423
25* 180.447 (variable)
26 203.343 1.33 1.49700 81.5 0.5375
27 23.319 (variable)
28 22.595 6.07 1.58144 40.8 0.5774
29 -109.681 8.27
30 ∞ 1.13 1.51633 64.1 0.5353
31 ∞ 1.18
Image plane ∞

Aspheric data 24th surface
K =-1.69544e+000 A 4= 1.30469e-005 A 6=-5.80980e-008 A 8= 1.16252e-010 A10=-4.67955e-012

Surface 25
K = 0.00000e+000 A 4= 2.68113e-005 A 6= 2.90892e-008 A 8=-7.37051e-010 A10=-1.36981e-012

Various data Zoom ratio 11.94
Wide-angle mid-telephoto focal length 28.00 99.17 334.37
F number 1.85 2.25 2.47
Half angle of view (degree) 15.95 4.61 1.37
Image height 8.00 8.00 8.00
Total lens length 240.13 240.13 240.13
BF 10.20 10.20 10.20

d 9 1.81 31.37 47.99
d17 48.04 18.48 1.85
d25 1.75 20.67 2.01
d27 39.22 20.30 38.96


Lens group Data group Start surface Focal length
1 1 129.10
2 10 -14.57
3 18 32.12
4 26 -53.13
5 28 32.78
6 30 ∞

Tables 1 and 2 show the relationships between the above-mentioned conditional expressions and the numerical values in the numerical data.

L0 zoom lens,
L1 first lens group L2 second lens group L3 third lens group,
LR rear group 1a 1a lens group (first partial group)
1b 1b lens group (2nd subgroup)

Claims (14)

Rear including a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and one or more lens groups, which are sequentially arranged from the object side to the image side. Consists of groups,
A zoom lens in which the first lens group and the third lens group do not move during zooming, and the distance between adjacent lens groups changes.
When the Abbe number of the material is νdα and the partial dispersion ratio of the material is θgfα,
The first lens group and the third lens group have 0<θgfα−(−1.665×10 ⁻⁷ ·νdα ³ +5.213×10 ⁻⁵ ·νdα ² −5.656×10 ⁻³ ·νdα+0. 737)
0.532<θgfα<0.550
60<νdα<100
Has a positive lens made of a material that satisfies the conditional expression
When the focal length of the zoom lens at the wide angle end is fw and the effective image circle diameter of the zoom lens is φ,
1.2<fw/φ<3.0
A zoom lens that satisfies the following conditional expression. The first lens group includes a first part group having a positive refracting power and a second part having a negative refracting power, which are arranged in order from the object side to the image side with the widest spacing in the first lens group. The zoom lens according to claim 1, wherein the zoom lens comprises a group. When the focal length of the first lens group is f1 and the focal length of the zoom lens at the telephoto end is ft,
0.2<f1/ft<1.5
The zoom lens according to claim 1 or 2, wherein the following conditional expression is satisfied. When the focal length of the first lens group is f1 and the focal length of the third lens group is f3,
0.1<f3/f1<0.4
The zoom lens according to any one of claims 1 to 3, wherein the following conditional expression is satisfied. When the focal length of the first lens group is f1 and the focal length of the second lens group is f2,
-0.4<f2/f1<-0.1
The zoom lens according to any one of claims 1 to 4, wherein the following conditional expression is satisfied. 6. The rear lens group is composed of a fourth lens group having a negative refractive power and a fifth lens group having a positive refractive power, which are sequentially arranged from the object side to the image side. The zoom lens according to any one of items. 7. The zoom lens according to claim 6, wherein the fourth lens group moves toward the image side when focusing from infinity to a short distance. The rear group includes a fourth lens group having a positive refractive power, a fifth lens group having a negative refractive power, and a sixth lens group having a positive refractive power, which are arranged in order from the object side to the image side. The zoom lens according to claim 1, wherein the zoom lens is a zoom lens. 9. The zoom lens according to claim 8, wherein the fifth lens group moves toward the image side when focusing from infinity to a short distance. An image pickup apparatus comprising: the zoom lens according to any one of claims 1 to 9; and an image pickup element that receives an image formed by the zoom lens. An imaging system comprising: the zoom lens according to any one of claims 1 to 9; and a control unit that controls the zoom lens during zooming. The imaging system according to claim 11, wherein the control unit is configured separately from the zoom lens, and includes a transmission unit that transmits a control signal for controlling the zoom lens. The imaging system according to claim 11, wherein the control unit is configured as a separate body from the zoom lens, and has an operation unit for operating the zoom lens. The imaging system according to claim 11, further comprising a display unit that displays information regarding zoom of the zoom lens.