JP7027170B2 - Zoom lens and image pickup device with it, image pickup system - Google Patents

Description

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

The zoom lens used in the image pickup device is required to have high optical performance capable of corresponding to high definition of the image pickup element, to have a wide angle of view, and to have a small size in the whole system. For example, there is a strong demand for an image pickup device such as a surveillance camera to have a small size so that it is difficult to recognize from the installation and appearance. Further, it is required that a zoom lens used in an image pickup device such as a surveillance camera has various aberrations, particularly chromatic aberrations, satisfactorily corrected over the entire zoom range and has high optical performance.

Conventionally, as a zoom lens, a first lens group having a negative refractive power is arranged on the object side most, and a wide angle of view negative lead type having three or more lens groups that move during zooming on the image side of the first lens group. Zoom lenses are known (Patent Documents 1 and 2). Patent Documents 1 and 2 have a lens group having a negative refractive power in order from the object side to the image side, and three or more lens groups that move during zooming, and five lenses as a whole in which the distance between adjacent lens groups changes during zooming. A five-group zoom lens composed of groups is disclosed.

Japanese Unexamined Patent Publication No. 2008-309897 Japanese Unexamined Patent Publication No. 2009-6298

In the negative lead type zoom lens, the whole system is small and has a wide angle of view, but various aberrations such as chromatic aberration are well corrected, and in order to obtain high optical performance over the entire zoom range, the number of lens groups and each lens It is important to properly set the lens configuration of the group.

For example, in a zoom lens used for a surveillance camera, it is important that the number of lens groups, the refractive power of each lens group, and various aberrations in each lens group are well corrected. In particular, it is important that chromatic aberration is satisfactorily corrected, aberration fluctuation is small during zooming, and high optical performance is achieved over the entire zoom range.

An object of the present invention is, for example, to provide a zoom lens which is advantageous in terms of wide angle of view, high zoom ratio , and high optical performance over the entire zoom range.

The zoom lens of the present invention has a first lens group, a second lens group, a third lens group, a fourth lens group , and a fifth lens group having a negative refractive force arranged in order from the object side to the image side . A zoom lens having a lens group , the first lens group does not move for zooming, and the second lens group, the third lens group, and the fourth lens group move in different trajectories in zooming . There,
When the Abbe number is νd and the partial dispersion ratio is θgF, the second lens group, the third lens group, and the fourth lens group are all 65 <νd <100.
0.52 <θgf <0.56
It is characterized by having one or more lenses α made of a material satisfying the conditional expression.

According to the present invention, for example, a zoom lens advantageous in terms of wide angle of view, high zoom ratio , and high optical performance over the entire zoom range can be obtained.

Cross-sectional view of the lens at the wide-angle end of the zoom lens of Example 1 (A), (B), (C) Aberration diagram at the wide-angle end, intermediate zoom position, and telephoto end of the zoom lens of Example 1. Cross-sectional view of the lens at the wide-angle end of the zoom lens of Example 2 (A), (B), (C) Aberration diagram at the wide-angle end, intermediate zoom position, and telephoto end of the zoom lens of Example 2. Cross-sectional view of the lens at the wide-angle end of the zoom lens of Example 3 (A), (B), (C) Aberration diagram at the wide-angle end, intermediate zoom position, and telephoto end of the zoom lens of Example 3. Cross-sectional view of the lens at the wide-angle end of the zoom lens of Example 4 (A), (B), (C) Aberration diagram at the wide-angle end, intermediate zoom position, and telephoto end of the zoom lens of Example 4. Cross-sectional view of the lens at the wide-angle end of the zoom lens of Example 5 (A), (B), (C) Aberration diagram at the wide-angle end, intermediate zoom position, and telephoto end of the zoom lens of Example 5. Cross-sectional view of the lens at the wide-angle end of the zoom lens of Example 6 (A), (B), (C) Aberration diagram at the wide-angle end, intermediate zoom position, and telephoto end of the zoom lens of Example 6. Cross-sectional view of the dome cover and the zoom lens of Example 1 Cross-sectional view of the protective cover and the zoom lens of Example 1 (A), (B) Examples of the surveillance camera of the present invention and examples of use of the surveillance camera Zoom locus and explanatory diagram in Example 1.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. The zoom lens of the present invention has a first lens group, a second lens group, a third lens group, and a fourth lens group arranged in order from the object side to the image side. The first lens group is immobile during zooming, and the second lens group, the third lens group, and the fourth lens group move independently of each other. The first lens group has a negative refractive power.

FIG. 1 is a cross-sectional view of the zoom lens according to the first embodiment of the present invention at the wide-angle end (shortest focal length). 2A, 2B, and 2C are aberration diagrams at the wide-angle end, the intermediate zoom position, and the telephoto end (longest focal length) of the zoom lens of Example 1, respectively. The first embodiment is a zoom lens having a zoom ratio of 4.00 and an F number of 1.75 to 4.20.

FIG. 3 is a cross-sectional view of the lens at the wide-angle end of the zoom lens according to the second embodiment of the present invention. 4 (A), (B), and (C) are aberration diagrams at the wide-angle end, the intermediate zoom position, and the telephoto end of the zoom lens of the second embodiment, respectively. The second embodiment is a zoom lens having a zoom ratio of 3.30 and an F number of 1.75 to 4.10.

FIG. 5 is a cross-sectional view of the lens at the wide-angle end of the zoom lens according to the third embodiment of the present invention. 6A, 6B, and 6C are aberration diagrams at the wide-angle end, the intermediate zoom position, and the telephoto end of the zoom lens of Example 3, respectively. Example 3 is a zoom lens having a zoom ratio of 6.00 and an F number of 1.75 to 5.00.

FIG. 7 is a cross-sectional view of the zoom lens according to the fourth embodiment of the present invention at the wide-angle end. 8 (A), (B), and (C) are aberration diagrams at the wide-angle end, the intermediate zoom position, and the telephoto end of the zoom lens of Example 4, respectively. The fourth embodiment is a zoom lens having a zoom ratio of 4.00 and an F number of 1.75 to 4.30.

FIG. 9 is a cross-sectional view of the zoom lens according to the fifth embodiment of the present invention at the wide-angle end. 10 (A), (B), and (C) are aberration diagrams at the wide-angle end, the intermediate zoom position, and the telephoto end of the zoom lens of Example 5, respectively. Example 5 is a zoom lens having a zoom ratio of 4.00 and an F number of 1.75 to 4.30.

FIG. 11 is a cross-sectional view of the zoom lens according to the sixth embodiment of the present invention at the wide-angle end. 12 (A), (B), and (C) are aberration diagrams at the wide-angle end, the intermediate zoom position, and the telephoto end of the zoom lens of Example 6, respectively. Example 6 is a zoom lens having a zoom ratio of 3.90 and an F number of 1.75 to 4.09.

FIG. 13 is a schematic view of a main part when the zoom lens of the present invention is attached to the dome cover. FIG. 14 is a schematic view of a main part when the zoom lens of the present invention is attached to the protective cover. 15 (A) and 15 (B) are schematic views of a main part of a surveillance camera (imaging device) having a zoom lens of the present invention. 16 (A), (B), and (C) are explanatory views of the zoom locus of each lens group by zooming of the zoom lens of the first embodiment of the present invention.

The zoom lens of each embodiment is an imaging optical system used in a surveillance camera. The zoom lens of each embodiment may be used in an image pickup device such as a video camera, a digital camera, a silver salt film camera, and a TV camera.

In the cross-sectional view of the lens, the left side is the object side (front) and the right side is the image side (rear). Further, in the cross-sectional view of the lens, L0 is a zoom lens. When i is the order of the lens group from the object side, Li indicates the i-th lens group. SP is an aperture stop. G is an optical block such as a filter. IP is an image plane. The image plane IP corresponds to the image pickup surface of an image pickup element (photoelectric conversion element) such as a CCD sensor or a CMOS sensor when a zoom lens is used as an image pickup optical system of a digital camera, a video camera, or a surveillance camera.

In the zoom lens of each embodiment, the distance between adjacent lens groups changes during zooming. The arrows show the movement trajectory of each lens group when zooming from the wide-angle end to the telephoto end. The arrow on focus indicates the direction of movement of the lens group when focusing from infinity to a short distance.

In the spherical aberration diagram, the solid line d is the d line (wavelength 587.6 nm), the two-dot chain line g is the g line (wavelength 435.8 nm), the one-dot chain line C is the C line (wavelength 656.3 nm), and the dotted line F. Indicates the F line (wavelength 486.1 nm). 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. Distortion indicates the value on the d-line. Chromatic aberration of magnification is represented by g-line, F-line, and C-line. ω is the imaged half angle of view (degrees), and Fno is the F number. In each embodiment, the wide-angle end and the telephoto end refer to the zoom positions when the lens group for scaling is mechanically located at both ends of a movable range on the optical axis.

The zoom lens of each embodiment has a first lens group L1 to a fourth lens group L4 having negative, positive, negative, and positive refractive powers in order from the object side to the image side. The fifth lens group L5 having a negative refractive power may be provided on the image side of the fourth lens group L4.

Examples 1 to 3 and 6 are zoom lenses having a four-group configuration. The four-group zoom lenses are arranged in order from the object side to the image side, the first lens group L1 having a negative refractive power, the second lens group L2 having a positive refractive power, and the third lens group L3 having a negative refractive power. It is composed of a fourth lens group L4 having a positive refractive power. During zooming, the first lens group L1 is immobile, and the second lens group L2, the third lens group L3, and the fourth lens group L4 move independently of each other in different trajectories as shown by arrows.

Examples 4 and 5 are zoom lenses having a 5-group configuration. The five-group zoom lenses are arranged in order from the object side to the image side, the first lens group L1 with negative power, the second lens group L2 with positive power, and the third lens group L3 with negative power. It is composed of a fourth lens group L4 having a positive refractive power and a fifth lens group L5 having a negative refractive power.

During zooming, the first lens group L1 is immobile, and the second lens group L2, the third lens group L3, and the fourth lens group L4 move independently of each other in different trajectories as shown by the arrows. The fifth lens group L5 is immovable or moves.

In each embodiment, the aperture stop SP is arranged on the object side of the second lens group L2 and moves in the same locus as the second lens group L2 during zooming. The aperture diameter of the aperture stop SP may be constant or may be changed during zooming.

By changing the aperture diameter of the aperture stop SP, it is possible to cut the underlined coma flare due to the off-axis luminous flux that is greatly generated at the telephoto end, and better optical performance can be obtained. Focusing is performed by moving the third lens group L3 on the optical axis. When focusing from infinity to a short distance at the telephoto end, as shown by the arrow 3c in the cross-sectional view of the lens, the third lens group L3 is advanced to the image side.

The curve 3a in the figure shows a movement locus for correcting the image plane fluctuation due to zooming from the wide-angle end to the telephoto end when focusing at infinity. The curve 3b shows a movement locus for correcting the fluctuation of the image plane due to zooming from the wide-angle end to the telephoto end when focusing on a short distance. Focusing is not the third lens group L3, but all the lenses or some lenses of the second lens group L2, or all the lenses or some lenses of the fourth lens group L4 are moved on the optical axis. You may go.

The zoom type of the zoom lens according to the present invention has a 4-group configuration or a 5-group configuration consisting of the above-mentioned lens groups. This zoom type has a bright F-number (Fno) while downsizing the entire system, and when zooming by changing the distance between adjacent lens groups in order to obtain high optical performance over the entire zoom range from the wide-angle end to the telephoto end. It is a lens configuration suitable for.

Regarding the method of moving each lens group in zooming, each lens group is used with reference to FIGS. 16A, 16B, and 16C, taking a 4-group zoom lens consisting of the 4 lens groups of the zoom lens of Example 1 as an example. I will explain the movement of.

When zooming from the wide-angle end to the telephoto end, the second lens group L2, the third lens group L3, and the fourth lens group L4 lens group are independent as shown in FIGS. 16A, 16B, and 16C. Move (with different trajectories).

Specifically, the second lens group L2 monotonically moves from the image side to the object side and inflections, and at the same time, the third lens group L3 moves convexly toward the object side, and the fourth lens group L4 changes at least one. It is moving in a trajectory that has a curved point. In order to form such a movement trajectory of each lens group, it is easy to properly secure the distance between each lens group of the second lens group L2, the third lens group L3, and the fourth lens group L4 at the wide-angle end and increase the magnification. It has a structure. During focusing, the third lens group L3 moves.

Since the outer diameter of the first lens group of a wide-angle zoom lens is large, the weight is large and it is difficult to follow quickly during zooming. In order to solve this problem, in each embodiment, the lens of the second lens group or later, which is light in weight, is driven during zooming, so that rapid zooming can be facilitated.

Further, if the chromatic aberration fluctuates due to zooming, it becomes difficult to correct the chromatic aberration over the entire zoom range. Therefore, in each embodiment, the material used for the movable lens group is appropriately set to reduce the correction of chromatic aberration during zooming.

The zoom lenses of each embodiment are the first lens group L1 having a negative refractive power that is immovable during zooming in order from the object side, and the second lens group L2, the third lens group L3, and the fourth lens group L4 that move during subsequent zooming. It has at least three lens groups.

The second lens group L2, the third lens group L3, and the fourth lens group L4 are all set when the Abbe number of the material is νd and the partial dispersion ratio is θgF.
65 <νd <100 ... (1)
0.52 <θgf <0.56 ... (2)
It has one or more lenses α made of a material satisfying the conditional expression.

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

The conditional expression (1) defines the Abbe number of the material possessed by each moving lens group, and is for reducing the fluctuation of chromatic aberration during zooming. If the lower limit of the conditional expression (1) is exceeded, the fluctuation of chromatic aberration becomes large during zooming, which is not preferable. If the upper limit of the conditional expression (1) is exceeded, chromatic aberration will be overcorrected, which is not preferable.

The conditional expression (2) defines the partial dispersion ratio of the material possessed by each moving lens group, and is for reducing the fluctuation of chromatic aberration at a plurality of wavelengths during zooming. Conditional expression (2) defines the numerical range of the abnormal partial dispersion material possessed by the moving lens group. When correcting chromatic aberration in a wide wavelength band, chromatic aberration often remains for wavelengths other than the specific two wavelengths. In each embodiment, an anomalous partial dispersion material is used in order to reduce this residual chromatic aberration (secondary spectrum).

In general, most optical materials have a nearly linear relationship between the partial dispersion ratio and the Abbe number. On the other hand, the material located away from this linear relationship is called an anomalous partial dispersion material and is often used to reduce the secondary spectrum. 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 indexes of the Fraunforfa line for the F line (486.1 nm), d line (587.6 nm), C line (656.3 nm), and g line (435.8 nm) are set to nF, nd, and nC, respectively. , Ng.

If the upper limit of the conditional expression (2) is exceeded, the fluctuation in zooming of the second-order spectrum of chromatic aberration becomes overcorrected. If the lower limit of the conditional expression (2) is exceeded, the fluctuation of the second-order spectrum of chromatic aberration during zooming becomes insufficient.

It is more preferable to limit the numerical range of the conditional expressions (1) and (2) as follows.
70 <νd <96 ... (1a)
0.53 <θgf <0.55 ... (2a)

The code of the refractive power of the lens α made of the material satisfying the conditional equations (1) and (2) included in the second lens group L2, the third lens group L3, and the fourth lens group L4, respectively, is the lens including the lens α. It is the same as the sign of the refractive power of the group. Here, the refractive power (power) is the reciprocal of the focal length, and the shorter the focal length, the stronger the refractive power. The sign of the refractive power of the lens α made of a material satisfying the conditional equations (1) and (2) included in the lens group having a positive refractive power (second lens group L2 and fourth lens group L4) is positive.

It is the positive lens that is responsible for the positive refractive power of the lens group with positive refractive power, and by using an abnormal partial dispersion material for this positive lens, it is effective to change the chromatic aberration of multiple wavelengths during zooming. It is reduced to.

The refractive power of the lens α made of a material satisfying the conditional equations (1) and (1) and (2) included in the lens group (third lens group L3) having a negative refractive power. The sign is negative. It is the negative lens that is responsible for the negative refractive power of the lens group with negative refractive power, and by using an anomalous partial dispersion material for this negative lens, fluctuations in chromatic aberration of multiple wavelengths can be effectively used during zooming. It is mitigating.

In each embodiment, since the first lens group L1 is relatively heavy, it is immovable during zooming to relax the followability during zooming. When zooming from the wide-angle end to the telephoto end, the second lens group L2 obtains a high magnification effect by moving from the image side to the object side as the main variable magnification lens group.

The third lens group L3 moves in a convex locus toward the object side. The third lens group L3 also has a function as a focus lens group. In order to obtain high tracking performance when the third lens group L3 is in focus, it is desirable to reduce the size of the entire system. The third lens group L3 is preferably a single optical element from the viewpoint of weight reduction. Here, the optical element means a single lens or a junction lens.

Further, the fourth lens group L4 secures the magnification ratio by moving from the object side to the image side. That is, the scaling ratio is efficiently obtained by simultaneously driving the lens group responsible for the scaling effect of the second lens group L2 and the fourth lens group L4.

Next, in each embodiment, it is preferable to satisfy one or more of the following conditional expressions. The focal length of the second lens group L2 is f2, and the focal length of the entire system at the wide-angle end is fw. The focal length of the third lens group L3 is f3. The focal length of the fourth lens group L4 is f4. The second lens group L2 has one or more positive lenses, and the focal length of one positive lens (lens α) included in the second lens group L2 is f2p.

The third lens group L3 has one or more negative lenses, and the focal length of one negative lens (lens α) included in the third lens group L3 is f3n. The fourth lens group L4 has one or more positive lenses, and the focal length of one positive lens (lens α) included in the fourth lens group L4 is f4p. The lateral magnification of the second lens group L2 at the wide-angle end is β2w, and the lateral magnification of the second lens group L2 at the telephoto end is β2t.

At this time, it is preferable to satisfy one or more of the following conditional expressions.
1.0 <f2 / fw <3.5 ... (3)
-5.5 <f3 / fw <-1.0 ... (4)
2.0 <f4 / fw <5.0 ... (5)
0.4 <f2p / f2 <2.0 ... (6)
0.5 <f3n / f3 <2.0 ... (7)
0.4 <f4p / f4 <2.0 ... (8)
2.0 <β2t / β2w <6.0 ... (9)

Next, the technical meaning of each of the above conditional expressions will be described. The conditional expression (3) defines the focal length of the second lens group L2. The conditional expression (3) is for reducing the fluctuation of chromatic aberration during zooming. When the focal length of the second lens group becomes longer than the focal length of the entire system at the wide-angle end beyond the upper limit of the conditional equation (3), the fluctuation of the axial chromatic aberration during zooming is reduced, but the total lens length is increased. Therefore, it is not preferable. If the focal length of the second lens group is shorter than the focal length of the entire system at the wide-angle end beyond the lower limit of the conditional equation (3), the total lens length is shortened, but the fluctuation of chromatic aberration becomes large during zooming, which is preferable. do not have.

The conditional expression (4) defines the focal length of the third lens group L3. Conditional expression (4) is for reducing fluctuations in axial chromatic aberration during zooming. When the negative refractive power of the third lens group L3 becomes stronger (when the absolute value of the negative refractive power becomes larger) with respect to the focal length of the entire system at the wide-angle end beyond the upper limit of the conditional equation (4), zooming and It is not preferable because the fluctuation of chromatic aberration becomes large at the time of focusing.

Zooming and focusing when the negative refractive power of the third lens group L3 becomes weaker (when the absolute value of the negative refractive power becomes smaller) with respect to the focal length of the entire system at the wide-angle end beyond the lower limit of the conditional equation (4). At this time, the total length of the lens increases because the amount of movement of the third lens group L3 increases. Therefore, it is not preferable.

The conditional expression (5) defines the focal length of the fourth lens group L4. The conditional expression (5) is for reducing the fluctuation of the chromatic aberration of magnification during zooming. If the focal length of the fourth lens group L4 becomes longer than the focal length of the entire system at the wide-angle end beyond the upper limit of the conditional equation (5), the amount of movement during zooming increases and the total lens length increases, which is not preferable. .. If the focal length of the fourth lens group L4 becomes shorter than the focal length of the entire system at the wide-angle end beyond the lower limit of the conditional equation (5), the variation in chromatic aberration of magnification becomes large during zooming, which is not preferable.

Conditional expression (6) defines the ratio of the focal length of the second lens group L2 to the focal length of one positive lens f2p (lens α) included in the second lens group L2. Conditional expression (6) is for reducing fluctuations in axial chromatic aberration during zooming. If the focal length of the positive lens f2p becomes longer than the focal length of the second lens group L2 beyond the upper limit of the conditional equation (6), the positive refractive power of the second lens group L2 becomes insufficient, and during zooming. The amount of movement of the lens increases, making it difficult to reduce the size of the entire system.

When the focal length of the positive lens f2p becomes shorter than the focal length of the second lens group L2 beyond the lower limit of the conditional equation (6), the refractive power of the positive lens f2p becomes too strong, resulting in spherical aberration and coma aberration. It is not preferable because a lot of such things occur.

Conditional expression (7) defines the ratio of the focal length of the third lens group L3 to the focal length of one negative lens f3n (lens α) included in the third lens group L3. Conditional expression (7) is for reducing fluctuations in axial chromatic aberration during focusing and zooming. If the negative focal length of the negative lens f3n becomes longer than the focal length of the third lens group L3 beyond the upper limit of the conditional equation (7), the negative refractive power of the third lens group L3 becomes insufficient. The amount of movement during zooming increases, making it difficult to miniaturize the entire system.

When the focal length of the negative lens f3n becomes shorter and the negative refractive power becomes stronger with respect to the focal length of the third lens group L3 beyond the lower limit of the conditional equation (7), spherical aberration, coma aberration, etc. occur. It is not preferable because it increases.

Conditional expression (8) defines the ratio of the focal length of the fourth lens group L4 to the focal length of one positive lens f4p (lens α) included in the fourth lens group L4. The conditional expression (8) is for reducing the fluctuation of the chromatic aberration of magnification during zooming. If the focal length of the positive lens f4p becomes longer than the focal length of the fourth lens group L4 beyond the upper limit of the conditional equation (8), the positive refractive power of the fourth lens group L4 becomes insufficient, and during zooming. The amount of movement of the lens increases, making it difficult to miniaturize the entire system.

When the focal length of the positive lens f4p becomes shorter than the focal length of the fourth lens group L4 beyond the lower limit of the conditional expression (8), the positive refractive power becomes stronger. As a result, the occurrence of spherical aberration, coma aberration, etc. increases, which is not preferable.

Conditional expression (9) defines the ratio of the lateral magnification of the second lens group L2 at the wide-angle end and the telephoto end. Conditional expression (9) defines appropriate conditions under which the second lens group L2 is responsible for scaling. If the scaling factor of the second lens group L2 becomes too large beyond the upper limit of the conditional expression (9), the amount of movement for scaling becomes large, and it becomes difficult to reduce the size of the entire system. If the lower limit of the conditional expression (9) is exceeded and the scaling factor of the second lens group L2 becomes too small, it becomes difficult to obtain a desired zoom ratio.

More preferably, it is preferable to set the numerical range of the conditional expressions (3) to (9) as follows.
1.5 <f2 / fw <2.7 ... (3a)
-5.0 <f3 / fw <-2.0 ... (4a)
2.3 <f4 / fw <4.0 ... (5a)
0.7 <f2p / f2 <1.5 ... (6a)
0.6 <f3n / f3 <1.5 ... (7a)
0.6 <f4p / f4 <1.5 ... (8a)
2.3 <β2t / β2w <4.5 ... (9a)

As described above, according to each embodiment, the image pickup half angle of view is 40 degrees or more, the zoom ratio is 3 or more, and the F number at the wide-angle end is less than 2.0, which is sufficient for an image sensor with a 4K pixel count. You can get a zoom lens that can be used. Next, the lens configuration of each embodiment will be described.

(Example 1)
The first lens group L1 is composed of a meniscus-shaped negative lens G11 having a convex surface on the object side, a negative lens G12 having a biconcave shape, and a positive lens G13 having a meniscus shape on the object side. The first lens group L1 is immovable during zooming.

The second lens group L2 is composed of a biconvex positive lens G21, a biconvex positive lens G22 (lens α), a meniscus-shaped negative lens G23 having a convex object side, and a biconvex positive lens G24 (lens α). It is made up. Both sides of the positive lens G21 are aspherical, thereby satisfactorily correcting spherical aberration.

The positive lens G24 satisfactorily corrects fluctuations in axial chromatic aberration during zooming by using an abnormal partial dispersion material having low dispersibility. Examples of the abnormal partial dispersion material having low dispersibility include trade name S-FPL51 (manufactured by OHARA) and trade name S-FPL55 (manufactured by OHARA).

The third lens group L3 is composed of a negative lens G31 (lens α) having a biconcave shape. The third lens group L3 is a focus lens group. An abnormal partial dispersion material having low dispersibility is used in consideration of correction of chromatic aberration.

The fourth lens group L4 is composed of a biconvex positive lens G41, a biconcave negative lens G42, and a biconvex positive lens G43 (lens α). The positive lens G41 and the negative lens G42 are composed of a bonded lens. There is an air gap between the negative lens G42 and the positive lens G43, and the meniscus shape is such that the air lens has a convex surface on the object side, whereby coma aberration is satisfactorily corrected.

(Example 2)
The fourth lens group L4 is composed of a meniscus-shaped positive lens G41 having a convex surface on the object side, a meniscus-shaped negative lens G42 having a convex surface on the object side, and a biconvex positive lens G43 (lens α). The positive lens G41 and the negative lens G42 are composed of a bonded lens. There is an air gap between the negative lens G42 and the positive lens G43, and the lens has a meniscus shape that is convex toward the object as an air lens, thereby satisfactorily correcting coma. The configuration of each other lens group is the same as that of the first embodiment.

(Example 3)
The first lens group L1 is composed of a meniscus-shaped negative lens G11 having a convex object side, a biconcave negative lens G12, and a biconvex positive lens G13. The negative lens G12 and the positive lens G13 are bonded lenses. The first lens group is immovable during zooming.

The fourth lens group L4 is composed of a biconvex positive lens G41, a meniscus-shaped negative lens G42 having a convex object side, and a biconvex positive lens G43 (lens α). The configuration of each other lens group is the same as that of the first embodiment.

(Example 4)
The third lens group L3 is composed of a negative lens G31 (lens α) having a concave shape and a positive lens G32 having a convex shape on the object side. The negative lens G31 and the positive lens G32 are bonded lenses. The third lens group L3 is a focus lens group.

The fifth lens group L5 is formed by a negative lens G51 having a meniscus shape whose image side is convex. By using an anomalous partial dispersion material, fluctuations in chromatic aberration of magnification during zooming are satisfactorily corrected. The fifth lens group L5 moves during zooming. The configuration of each other lens group is the same as that of the first embodiment.

(Example 5)
The third lens group L3 is composed of a negative lens G31 (lens α) having a concave shape and a positive lens G32 having a convex shape on the object side. The negative lens G31 and the positive lens G32 are bonded lenses. The third lens group L3 is a focus lens group.

The fifth lens group L5 is formed by a negative lens G51 having a meniscus shape whose image side is convex. By using an anomalous partial dispersion material, fluctuations in chromatic aberration of magnification during zooming are satisfactorily corrected. The fifth lens group L5 is immovable during zooming. The configuration of each other lens group is the same as that of the first embodiment.

(Example 6)
The second lens group L2 includes a biconvex positive lens G21, a convex positive lens G22 (lens α) on the object side, a concave negative lens G23 on the image side, a concave meniscus-shaped negative lens G24 on the image side, and biconvex. It is made up of a positive lens G25 (lens α) having a shape. The positive lens G21 has an aspherical shape on both sides, thereby satisfactorily correcting spherical aberration.

The positive lens G22 and the negative lens G23 are formed of a bonded bonded lens, and the negative lens G24 and the positive lens G25 are composed of a bonded bonded lens, whereby various aberrations are satisfactorily corrected. The positive lens G22 and the positive lens G25 satisfactorily correct fluctuations in axial chromatic aberration during zooming by using an abnormal partial dispersion material.

The fourth lens group L4 is composed of a meniscus-shaped positive lens G41 having a convex surface on the object side, a meniscus-shaped negative lens G42 having a convex surface on the object side, and a biconvex positive lens G43 (lens α). The positive lens G41 and the negative lens G42 are made of a bonded lens. There is an air gap between the negative lens G42 and the positive lens G43, and the meniscus shape is such that the air lens has a convex surface on the object side, whereby coma aberration is satisfactorily corrected. The configuration of each other lens group is the same as that of the first embodiment.

FIG. 13 shows a cross-sectional view when the zoom lens 16 of the first embodiment is used in a surveillance camera together with the dome cover 15. The dome cover 15 is formed of a plastic material such as polymethylmethacrylate (PMMA) or polycarbonate (PC) to a thickness of about several millimeters. As a result, when the image pickup device is premised on having a dome cover, the design may be made in consideration of the influence of the dome cover (focal length and material) and various aberrations may be corrected.

Next, FIG. 14 shows a cross-sectional view when the zoom lens 16 of the first embodiment is used for a surveillance camera together with a flat plate-shaped protective cover 17.

Next, an example of an image pickup device (surveillance camera) using the zoom lens of the present invention as an image pickup optical system will be described with reference to FIGS. 15 (A) and 15 (B). In FIG. 15A, 11 is a surveillance camera main body, and 16 is an imaging optical system composed of any of the zoom lenses described in Examples 1 to 6. Reference numeral 12 is an image pickup element (photoelectric conversion element) such as a CCD sensor or a CMOS sensor, which is built in the camera body and receives a subject image formed by the image pickup optical system 16.

Reference numeral 13 is a memory for recording information corresponding to the subject image photoelectrically converted by the image pickup device 12. Reference numeral 14 is a network cable for transferring the subject image photoelectrically converted by the image pickup device 12.

FIG. 15B is an example in which a dome-shaped cover 15 is attached to the image pickup apparatus 10 and attached to the ceiling for use. The image pickup device is not limited to the surveillance camera, but can also be used in a video camera, a digital camera, or the like.

As described above, according to each embodiment, it is possible to obtain a zoom lens having a high zoom ratio while the entire system is small, and having high optical performance with a small FNo at the wide-angle end, and an image pickup apparatus having the same.

In each embodiment, the following configuration may be adopted.
-The shape and number of lenses shown in the examples are not limited, 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 and chromatic aberration 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 gist thereof.

For example, an image pickup system (surveillance camera system) including the zoom lens of each embodiment and a control unit for controlling the zoom lens may be configured. In this case, the control unit may control the zoom lens so that each lens group moves as described above during zooming. At this time, the control unit does not have to be integrally configured with the zoom lens, and the control unit may be configured as a separate body from the zoom lens.

For example, a control unit (control device) arranged far away from the drive unit that drives each lens of the zoom lens is provided with a transmission unit that sends a control signal (command) for controlling the zoom lens. You may. According to such a control unit, the zoom lens can be remotely controlled.

Further, by providing an operation unit such as a controller or a button for remotely controlling the zoom lens in the control unit, a configuration may be adopted in which the zoom lens is controlled in response to an input to the user's operation unit. For example, an enlargement button and a reduction button are provided as an operation unit, and when the user presses the enlargement button, the magnification of the zoom lens is increased. A signal may be sent from the control unit to the drive unit of the zoom lens so that the magnification of the zoom lens is reduced when the user presses the reduction button.

Further, the image pickup system may have a display unit such as a liquid crystal panel that displays information (moving state) regarding the 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 control 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.

Next, numerical data 1 to 6 corresponding to Examples 1 to 6 of the present invention are shown. In each numerical data, i indicates the order of the optical planes from the object side.

ri is the radius of curvature of the i-th optical plane (i-plane), di is the distance between the i-th plane and the i + 1 plane, and ndi and νdi are the refractions of the material of the i-th optical member with respect to the d line, respectively. Shows the rate and Abbe number. The two optical surfaces on the image side are glass materials such as face plates. BF (back focus) represents the distance from the final surface of the lens to the paraxial image plane by the air conversion length. The total length of the lens is a value obtained by adding the back focus (BF) to the distance from the frontmost surface of the lens to the final surface of the lens.

* Attached to the surface number means an aspherical surface. Further, when k is the eccentricity factor, A4, A6, A8, A10, and A12 are the aspherical surface coefficients, and the displacement in the optical axis direction at the position of the height h from the optical axis with respect to the surface vertex is x, the aspherical shape. teeth,
x = (h ² / R) / [1 + {1- (1 + k) (h / R) ² } ^1/2 ] + A4h ⁴ + A6h ⁶ + A8h ⁸ + A10h ¹⁰ + A12h ¹²
It is represented by. The display of "ez" means "10 ^-z ". However, R is the radius of curvature of the paraxial axis. Table 1 shows the correspondence between the above-mentioned conditional expressions in each numerical data.

[Numerical data 1]
Unit mm

Surface data Surface number rd nd νd θgf
1 191.892 2.00 1.83481 42.7 0.5648
2 21.122 11.88
3-48.942 1.50 1.48749 70.2 0.5300
4 176.773 2.00
5 63.664 2.68 1.89286 20.4 0.6393
6 243.745 (variable)
7 (Aperture) ∞ 2.11
8 * 45.281 5.16 1.58313 59.4 0.5423
9 * -72.200 3.00
10 22.298 6.06 1.49700 81.5 0.5375
11 -65.669 2.28
12 68.647 0.90 1.90366 31.3 0.5947
13 17.579 2.45
14 39.276 3.30 1.49700 81.5 0.5375
15 -36.706 (variable)
16 -50.271 0.80 1.49700 81.5 0.5375
17 27.179 (variable)
18 27.447 6.09 1.83481 42.7 0.5648
19 -75.046 1.20 1.68893 31.1 0.6004
20 21.558 2.04
21 34.199 4.14 1.49700 81.5 0.5375
22 -85.407 (variable)
23 ∞ 1.20 1.51633 64.1 0.5353
24 ∞ 4.35
Image plane ∞

Aspherical data surface 8
K = 0.00000e + 000 A 4 = -1.30185e-005 A 6 = 3.96680e-008 A 8 = -2.25320e-010 A10 = 6.55663e-013 A12 = 5.58643e-015

Side 9
K = 0.00000e + 000 A 4 = 2.67549e-006 A 6 = 2.76907e-008 A 8 = 1.16606e-010 A10 = -1.77003e-012 A12 = 1.27104e-014

Various data Zoom ratio 4.00
Wide-angle medium telephoto focal length 12.06 23.80 48.26
F number 1.75 2.80 4.20
Half angle of view (degrees) 41.70 24.31 12.56
Image height 10.75 10.75 10.75
Lens total length 127.99 127.99 127.99
BF 16.58 6.75 6.14

d 6 49.34 27.44 5.54
d15 0.92 5.94 14.83
d17 1.58 28.29 41.91
d22 11.44 1.61 1.00

Lens group data group Start surface focal length
1 1 -27.03
2 7 27.16
3 16 -35.37
4 18 46.40

[Numerical data 2]
Unit mm

Surface data Surface number rd nd νd θgf
1 215.778 2.00 1.83481 42.7 0.5648
2 21.390 11.45
3 -48.017 1.50 1.48749 70.2 0.5300
4 85.153 2.00
5 52.905 2.86 1.89286 20.4 0.6393
6 176.248 (variable)
7 (Aperture) ∞ 1.57
8 * 71.848 5.41 1.58313 59.4 0.5423
9 * -47.799 2.21
10 20.696 7.52 1.49700 81.5 0.5375
11 -73.506 1.40
12 49.609 0.90 1.90366 31.3 0.5947
13 15.856 2.30
14 35.756 3.12 1.49700 81.5 0.5375
15 -49.242 (variable)
16 -50.319 0.80 1.49700 81.5 0.5375
17 27.093 (variable)
18 27.112 4.26 1.83481 42.7 0.5648
19 188.985 1.20 1.68893 31.1 0.6004
20 21.977 2.16
21 32.586 4.93 1.49700 81.5 0.5375
22 -53.147 (variable)
23 ∞ 1.20 1.51633 64.1 0.5353
24 ∞ 4.35
Image plane ∞

Aspherical data surface 8
K = 0.00000e + 000 A 4 = -3.51294e-005 A 6 = -7.19525e-008 A 8 = -2.78685e-011 A10 = -2.80560e-012 A12 = 1.62205e-014

Side 9
K = 0.00000e + 000 A 4 = -1.96741e-005 A 6 = -5.25613e-008 A 8 = 1.31302e-011 A10 = -1.85017e-012 A12 = 1.00084e-014

Various data Zoom ratio 3.30
Wide-angle medium telephoto focal length 12.00 24.12 39.60
F number 1.75 2.80 4.10
Half angle of view (degrees) 41.86 24.02 15.19
Image height 10.75 10.75 10.75
Lens total length 127.99 127.99 127.99
BF 17.27 8.86 23.25

d 6 48.96 27.06 5.16
d15 2.60 8.48 16.49
d17 1.58 26.01 25.52
d22 12.13 3.72 18.11

Lens group data group Start surface focal length
1 1 -25.48
2 7 27.43
3 16 -35.31
4 18 42.75

[Numerical data 3]
Unit mm

Surface data Surface number rd nd νd θgf
1 78.372 2.00 1.83481 42.7 0.5648
2 20.741 12.27
3 -30.190 1.50 1.59522 67.7 0.5442
4 74.369 2.42 1.92286 18.9 0.6495
5 1067.731 (variable)
6 (Aperture) ∞ 0.69
7 * 25.875 6.21 1.58313 59.4 0.5423
8 * -157.352 0.70
9 52.195 4.41 1.53775 74.7 0.5392
10 -78.215 1.40
11 50.077 1.10 1.90366 31.3 0.5947
12 19.789 0.78
13 20.940 7.57 1.43875 94.7 0.5340
14 -31.077 (variable)
15 -108.848 0.80 1.49700 81.5 0.5375
16 16.182 (variable)
17 208.488 4.23 1.83481 42.7 0.5648
18 -70.250 2.23
19 -40.013 1.20 1.78472 25.7 0.6161
20 -659.355 0.49
21 51.723 5.32 1.49700 81.5 0.5375
22 -31.930 (variable)
23 ∞ 1.20 1.51633 64.1 0.5353
24 ∞ 4.35
Image plane ∞

7th surface of aspherical data
K = 0.00000e + 000 A 4 = -5.72822e-006 A 6 = -5.53282e-008 A 8 = 6.85585e-010 A10 = -2.83359e-012 A12 = 4.59793e-015

8th page
K = 0.00000e + 000 A 4 = 1.87082e-005 A 6 = -4.44276e-008 A 8 = 5.91147e-010 A10 = -2.21901e-012 A12 = 3.46366e-015

Various data Zoom ratio 6.00
Wide-angle medium telephoto focal length 12.00 22.77 72.00
F number 1.75 3.20 5.00
Half angle of view (degrees) 41.86 25.27 8.49
Image height 10.75 10.75 10.75
Lens total length 127.17 127.17 127.17
BF 19.39 21.50 6.63

d 5 45.38 23.48 1.58
d14 1.52 4.99 30.79
d16 5.56 21.88 32.86
d22 14.25 16.36 1.49

Lens group data group Start surface focal length
1 1 -19.70
2 6 23.19
3 15 -28.29
4 17 45.67

[Numerical data 4]
Unit mm

Surface data Surface number rd nd νd θgf
1 107.430 2.00 1.83481 42.7 0.5648
2 20.329 12.15
3 -56.059 1.50 1.48749 70.2 0.5300
4 99.972 1.25
5 52.095 3.18 1.89286 20.4 0.6393
6 158.838 (variable)
7 (Aperture) ∞ 0.70
8 * 47.544 6.25 1.58313 59.4 0.5423
9 * -70.350 4.00
10 26.719 4.89 1.49700 81.5 0.5375
11 -71.207 1.60
12 130.892 0.90 1.90366 31.3 0.2910
13 21.914 1.79
14 55.244 2.91 1.49700 81.5 0.5375
15 -39.195 (variable)
16 -33.133 0.80 1.49700 81.5 0.5375
17 47.935 2.44 1.68893 31.1 0.6004
18 116.359 (variable)
19 32.660 6.38 1.83481 42.7 0.5648
20 -60.130 1.20 1.68893 31.1 0.6004
21 21.586 1.09
22 26.117 5.17 1.49700 81.5 0.5375
23 -40.854 (variable)
24 -26.074 1.00 1.49700 81.5 0.5375
25 -110.316 (variable)
26 ∞ 1.20 1.51633 64.1 0.5353
27 ∞ 4.00
Image plane ∞

Aspherical data surface 8
K = 0.00000e + 000 A 4 = -1.66569e-005 A 6 = -1.28563e-008 A 8 = -5.41482e-010 A10 = 3.44305e-012 A12 = -1.06396e-014

Side 9
K = 0.00000e + 000 A 4 = -6.10487e-006 A 6 = -1.14451e-008 A 8 = -4.37860e-010 A10 = 2.76154e-012 A12 = -8.14534e-015

Various data Zoom ratio 4.00
Wide-angle medium telephoto focal length 12.35 24.78 49.40
F number 1.75 2.80 4.30
Half angle of view (degrees) 41.04 23.46 12.28
Image height 10.75 10.75 10.75
Lens total length 127.93 127.93 127.93
BF 6.29 7.29 7.03

d 6 46.75 24.85 2.95
d15 1.34 12.33 35.03
d18 1.66 19.52 18.99
d23 10.69 2.73 2.73
d25 1.50 2.50 2.24

Lens group data group Start surface focal length
1 1 -28.57
2 7 31.24
3 16 -58.73
4 19 37.78
5 24 -68.97

[Numerical data 5]
Unit mm

Surface data Surface number rd nd νd θgf
1 174.795 2.00 1.83481 42.7 0.5648
2 21.425 12.04
3 -48.088 1.50 1.48749 70.2 0.5300
4 149.952 0.70
5 58.187 4.98 1.89286 20.4 0.6393
6 259.762 (variable)
7 (Aperture) ∞ 0.70
8 * 40.966 6.23 1.58313 59.4 0.5423
9 * -97.306 4.00
10 30.041 4.73 1.49700 81.5 0.5375
11 -64.147 1.40
12 117.409 0.90 1.90366 31.3 0.2910
13 22.675 1.65
14 49.824 3.00 1.49700 81.5 0.5375
15 -40.815 (variable)
16 -38.456 0.80 1.49700 81.5 0.5375
17 44.379 1.88 1.68893 31.1 0.6004
18 80.193 (variable)
19 29.709 6.08 1.83481 42.7 0.5648
20 -101.500 1.20 1.68893 31.1 0.6004
21 20.465 1.34
22 27.558 4.62 1.49700 81.5 0.5375
23 -44.485 (variable)
24 -25.132 1.00 1.49700 81.5 0.5375
25 -67.081 1.50
26 ∞ 1.20 1.51633 64.1 0.5353
27 ∞ 4.00
Image plane ∞

Aspherical data surface 8
K = 0.00000e + 000 A 4 = -1.47811e-005 A 6 = -5.54400e-008 A 8 = 7.77209e-011 A10 = -7.02865e-013 A12 = -1.67398e-015

Side 9
K = 0.00000e + 000 A 4 = -3.42729e-006 A 6 = -5.24578e-008 A 8 = 1.20213e-010 A10 = -9.58136e-013 A12 = -6.66911e-018

Various data Zoom ratio 4.00
Wide-angle medium telephoto focal length 12.35 24.76 49.40
F number 1.75 2.80 4.30
Half angle of view (degrees) 41.04 23.47 12.28
Image height 10.75 10.75 10.75
Lens total length 127.99 127.99 127.99
BF 6.29 6.29 6.29

d 6 46.26 24.36 2.46
d15 1.35 13.28 35.50
d18 1.65 20.45 20.12
d23 11.69 2.87 2.87

Lens group data group Start surface focal length
1 1 -28.19
2 7 31.11
3 16 -57.80
4 19 40.11
5 24 -81.51

[Numerical data 6]
Unit mm

Surface data Surface number rd nd νd θgf
1 206.340 2.00 1.83481 42.7 0.5648
2 20.274 12.65
3-36.422 1.50 1.48749 70.2 0.5300
4 ∞ 0.70
5 60.762 2.50 1.89286 20.4 0.6393
6 302.776 (variable)
7 (Aperture) ∞ 0.81
8 * 44.891 6.60 1.58313 59.4 0.5423
9 * -47.024 0.81
10 17.758 6.00 1.49700 81.5 0.5375
11 771.057 1.00 1.51742 52.4 0.5564
12 15.710 3.45
13 74.624 0.90 1.90366 31.3 0.2910
14 22.377 5.30 1.49700 81.5 0.5375
15 -29.313 (variable)
16 -53.205 0.80 1.49700 81.5 0.5375
17 42.356 (variable)
18 23.122 6.80 1.83481 42.7 0.5648
19 122.738 1.20 1.68893 31.1 0.6004
20 16.917 1.79
21 23.562 6.30 1.49700 81.5 0.5375
22 -57.412 (variable)
23 ∞ 1.20 1.51633 64.1 0.5353
24 ∞ 5.35
Image plane ∞

Aspherical data surface 8
K = 0.00000e + 000 A 4 = -6.78351e-006 A 6 = -2.5739e-009 A 8 = 6.82474e-011 A10 = -4.18054e-013 A12 = 1.16584e-015

Side 9
K = 0.00000e + 000 A 4 = 4.46895e-006 A 6 = -5.85355e-009 A 8 = 8.33723e-011 A10 = -3.80119e-013 A12 = 9.88314e-016

Various data Zoom ratio 3.90
Wide-angle medium telephoto focal length 12.16 23.45 47.44
F number 1.75 2.69 4.09
Half angle of view (degrees) 41.48 24.63 12.77
Image height 10.75 10.75 10.75
Lens total length 127.97 127.97 127.97
BF 13.60 8.77 9.59

d 6 46.87 24.97 3.07
d15 2.71 11.27 38.58
d17 3.68 21.85 15.61
d22 7.46 2.63 3.45

Lens group data group Start surface focal length
1 1 -26.08
2 7 30.36
3 16 -47.32
4 18 39.80

L0 Zoom lens L1 1st lens group L2 2nd lens group L3 3rd lens group L4 4th lens group L5 5th lens group

Claims (19)

It has a first lens group, a second lens group, a third lens group, a fourth lens group , and a fifth lens group having a negative refractive force arranged in order from the object side to the image side . The first lens group does not move for zooming, and the second lens group, the third lens group, and the fourth lens group are zoom lenses that move in different trajectories in zooming .
When the Abbe number is νd and the partial dispersion ratio is θgF, the second lens group, the third lens group, and the fourth lens group are all 65 <νd <100.
0.52 <θgf <0.56
A zoom lens characterized by having one or more lenses α made of a material satisfying the conditional expression. When the focal length of the fourth lens group is f4 and the focal length of the zoom lens at the wide-angle end is fw,
2.0 <f4 / fw <5.0
The zoom lens according to claim 1, wherein the zoom lens satisfies the conditional expression. It has a first lens group, a second lens group, a third lens group, and a fourth lens group having negative refractive power arranged in order from the object side to the image side, and the first lens group is used for zooming. The second lens group, the third lens group, and the fourth lens group are zoom lenses that do not move and move in different trajectories in zooming.
When the Abbe number is νd and the partial dispersion ratio is θgF, the second lens group, the third lens group, and the fourth lens group are all.
65 <νd <100
0.52 <θgf <0.56
Having one or more lenses α made of a material that satisfies the conditional expression
When the focal length of the fourth lens group is f4 and the focal length of the zoom lens at the wide-angle end is fw,
2.0 <f4 / fw <5.0
A zoom lens characterized by satisfying the conditional expression. The sign of the refractive power of the lens α included in the second lens group is the same as the sign of the refractive power of the second lens group.
The sign of the refractive power of the lens α included in the third lens group is the same as the sign of the refractive power of the third lens group.
The zoom according to any one of claims 1 to 3, wherein the sign of the refractive power of the lens α included in the fourth lens group is the same as the sign of the refractive power of the fourth lens group. lens. The zoom lens according to any one of claims 1 to 4, wherein the second lens group has a positive refractive power. The zoom lens according to any one of claims 1 to 5 , wherein the third lens group has a negative refractive power. The zoom lens according to any one of claims 1 to 6 , wherein the fourth lens group has a positive refractive power. When the focal length of the second lens group is f2 and the focal length of the zoom lens at the wide-angle end is fw,
1.0 <f2 / fw <3.5
The zoom lens according to any one of claims 1 to 7 , wherein the zoom lens satisfies the conditional expression. When the focal length of the third lens group is f3 and the focal length of the zoom lens at the wide-angle end is fw,
-5.5 <f3 / fw <-1.0
The zoom lens according to any one of claims 1 to 8 , wherein the zoom lens satisfies the conditional expression. When at least one of the lenses α included in the second lens group is a positive lens, the focal length of the positive lens is f2p, and the focal length of the second lens group is f2.
0.4 <f2p / f2 <2.0
The zoom lens according to any one of claims 1 to 9, wherein the zoom lens satisfies the conditional expression. When at least one of the lenses α included in the third lens group is a negative lens, the focal length of the negative lens is f3n, and the focal length of the third lens group is f3.
0.5 <f3n / f3 <2.0
The zoom lens according to any one of claims 1 to 10, wherein the zoom lens satisfies the conditional expression. When at least one of the lenses α included in the fourth lens group is a positive lens, the focal length of the positive lens is f4p, and the focal length of the fourth lens group is f4.
0.4 <f4p / f4 <2.0
The zoom lens according to any one of claims 1 to 11, wherein the zoom lens satisfies the conditional expression. When the lateral magnification of the second lens group at the wide-angle end is β2w and the lateral magnification of the second lens group at the telephoto end is β2t.
2.0 <β2t / β2w <6.0
The zoom lens according to any one of claims 1 to 12, wherein the zoom lens satisfies the conditional expression. The zoom lens according to any one of claims 1 to 13, wherein the third lens group is composed of a single optical element. An image pickup apparatus comprising the zoom lens according to any one of claims 1 to 14 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 14 and a control unit for controlling the zoom lens. The imaging system according to claim 16 , wherein the control unit transmits a control signal for controlling the zoom lens. The imaging system according to claim 16 or 17, further comprising an operation unit for operating the zoom lens. The imaging system according to any one of claims 16 to 18, further comprising a display unit for displaying information regarding the zoom of the zoom lens.

Images