JP7794628B2 - Optical system and imaging device - Google Patents

Description

This invention relates to an optical system and an imaging device, and in particular to an optical system and an imaging device suitable for imaging devices using solid-state imaging elements (CCD, CMOS, etc.), such as digital still cameras and digital video cameras.

Image capture devices using various solid-state image sensors, such as video cameras, digital still cameras, single-lens reflex cameras, and single-lens non-reflex cameras, have become widespread. As imaging optical systems for these devices, there is a demand for high-resolution, compact zoom lenses that can cover a wide imaging angle of view. There is also a demand for such zoom lenses to achieve high-speed, high-precision autofocus.

In recent years, imaging devices with video capture capabilities in addition to still images have become widespread. While phase-difference autofocusing is used when capturing still images, contrast autofocusing is often used when capturing video. For example, by rapidly wobbling some of the lens groups (focus lens groups) along the optical axis to create out-of-focus and in-focus states, detecting signal components in a certain frequency band from the output signal of the image sensor in a certain image region, determining the optimal position for the focus lens group to achieve the in-focus state, and then moving the focus group to that optimal position, this series of operations can be repeated to enable continuous autofocusing on the subject even when capturing video.

However, wobbling can sometimes cause the size of the image corresponding to the subject to change. This is mainly due to the fact that movement of the focus lens group along the optical axis changes the focal length of the entire lens system. If the fluctuation in the angle of view due to wobbling is significant, an unnatural feeling can appear in the captured image. One way to alleviate this unnatural feeling is to use the lens group behind the aperture as the focus lens group. As non-reflex cameras become more compact, there is a demand for smaller zoom lenses themselves, so of course there is a demand for smaller and lighter focus lens groups. In order to drive the focus lens group quickly and continuously during video capture, an even smaller and lighter focus lens group is desirable.

Conventionally, image sensors that receive optical images and convert them into electrical image signals have limitations due to the efficient capture of incident light using on-chip microlenses, etc., which has led to the need to enlarge the exit pupil on the lens side to ensure telecentricity of the light beam entering the image sensor. However, with the recent improvement in the numerical aperture of image sensors and advances in the design freedom of on-chip microlenses, the limitations on the exit pupil required on the lens side have become less. For this reason, various inventions have been made to ensure telecentricity by placing a positive lens group behind the zoom lens, but this has become less common in recent years. By placing a negative lens group behind the lens, even when light beams are obliquely incident on the image sensor, peripheral shading caused by mismatches between the pupil and the on-chip microlens is less noticeable. Furthermore, advances and improvements in software and camera systems have made it possible to correct distortion, even if it is relatively large and previously noticeable, through image processing.

Against this background, for example, Patent Document 1 proposes a wide-angle zoom lens consisting of six groups (negative-positive-negative-positive-negative-positive), with the fifth lens group serving as a focus lens group. Because the wide-angle zoom lens disclosed in Patent Document 1 was designed as an imaging optical system for a single-lens reflex camera, it has a long back focus relative to its overall optical length. Therefore, for use as an imaging optical system for a single-lens non-reflex camera, the overall optical length of this wide-angle zoom lens is too long, and it cannot be said that it has been sufficiently compact and lightweight. Consequently, the focus lens group is also insufficiently compact and lightweight.

Patent Document 2 also proposes a wide-angle zoom lens consisting of six groups (negative-positive-negative-positive-negative-positive), with the fifth lens group being a focus lens group. The wide-angle zoom lens disclosed in Patent Document 2 was designed as an imaging optical system for a single-lens non-reflex camera, and is therefore small and lightweight, with a short back focus relative to the overall optical length. However, its zoom ratio is small, at around 2x, and it cannot be said that the size and weight have been sufficiently reduced relative to the zoom ratio. Therefore, attempting to realize a zoom lens with a high zoom ratio would result in an increase in size and weight not only for the entire lens, but also for the focus lens group.

Patent No. 4845993 Patent No. 5699950

The objective of the present invention is to provide a zoom lens and imaging device that are compact and lightweight while providing high imaging performance throughout the entire zoom range.

In order to solve the above problem, the zoom lens of the present invention is composed of, in order from the object side, a first lens group having negative refractive power, a second lens group having positive refractive power, a third lens group having negative refractive power, a fourth lens group having positive refractive power, a fifth lens group having negative refractive power, and a rear group having one or more lens groups, and is a zoom lens in which the distance on the optical axis between adjacent lens groups changes during zooming, and is characterized by satisfying the following conditional expression:
(1) 6.05 ≦ β2t/β2w ≦ 15.00
however,
β2w: lateral magnification of the second lens group at the wide-angle end when focusing on infinity; β2t: lateral magnification of the second lens group at the telephoto end when focusing on infinity.

Furthermore, in order to solve the above problem, the imaging device according to the present invention is characterized by including the above zoom lens and an imaging element that converts the optical image formed by the zoom lens into an electrical signal.

This invention makes it possible to provide a zoom lens and imaging device that are compact and lightweight while providing high imaging performance throughout the entire zoom range.

1 is a lens cross-sectional view of a zoom lens according to a first embodiment of the present invention. 4A and 4B are aberration diagrams of the zoom lens of Example 1 in the wide-angle end state. 1A and 1B are aberration diagrams of the zoom lens of Example 1 in an intermediate focal length state. 4A and 4B are aberration diagrams of the zoom lens of Example 1 in the telephoto end state. FIG. 10 is a lens cross-sectional view of a zoom lens according to a second embodiment of the present invention. 10A and 10B are aberration diagrams of the zoom lens of Example 2 in the wide-angle end state. 10A and 10B are aberration diagrams of the zoom lens of Example 2 in an intermediate focal length state. 10A and 10B are aberration diagrams of the zoom lens of Example 2 in the telephoto end state. FIG. 10 is a cross-sectional view of a zoom lens according to a third embodiment of the present invention. 10A and 10B are aberration diagrams of the zoom lens of Example 3 in the wide-angle end state. 10A and 10B are aberration diagrams of the zoom lens of Example 3 in the intermediate focal length state. 10A and 10B are aberration diagrams of the zoom lens of Example 3 in the telephoto end state. FIG. 10 is a cross-sectional view of a zoom lens according to a fourth embodiment of the present invention. 10A and 10B are aberration diagrams of the zoom lens of Example 4 in the wide-angle end state. 10A and 10B are aberration diagrams of the zoom lens of Example 4 in the intermediate focal length state. 10A and 10B are aberration diagrams of the zoom lens of Example 4 in the telephoto end state. FIG. 10 is a lens cross-sectional view of a zoom lens according to a fifth embodiment of the present invention. 10A and 10B are aberration diagrams of the zoom lens of Example 5 in the wide-angle end state. 10A and 10B are aberration diagrams of the zoom lens of Example 5 in the intermediate focal length state. 10A and 10B are aberration diagrams of the zoom lens of Example 5 in the telephoto end state.

The following describes embodiments of the zoom lens and imaging device according to the present invention. However, the zoom lens and imaging device described below are one aspect of the optical system and imaging device according to the present invention, and the zoom lens and imaging device according to the present invention are not limited to the following aspects.

1. Zoom Lens 1-1. Optical Configuration This zoom lens is composed of, arranged in order from the object side, a first lens group having negative refractive power, a second lens group having positive refractive power, a third lens group having negative refractive power, a fourth lens group having positive refractive power, a fifth lens group having negative refractive power, and a rear group having one or more lens groups, and the distance on the optical axis between adjacent lens groups changes during zooming.

By using a multi-group configuration of six or more groups in this zoom lens, it becomes easier to suppress aberration fluctuations during zooming, making it easier to achieve high imaging performance regardless of the imaging distance. Furthermore, by positioning the first lens group with negative refractive power closest to the object and using a negative-lead type refractive power configuration, it becomes easier to achieve a zoom lens with a short back focus while achieving a wide angle of view. These factors make it easier to achieve high imaging performance throughout the entire zoom range while also achieving compactness and weight reduction. Furthermore, by reducing the overall size and weight, it becomes possible to reduce the size and weight of the focus lens group as well, enabling fast autofocus.

The specific lens configuration of each lens group is not particularly limited, but it is preferable to adopt the following configuration, for example.

(1) First Lens Group The first lens group has negative refractive power and therefore includes one or more negative lenses. It is preferable that at least one of the negative lenses included in the first lens group is a meniscus lens with a concave shape facing the image side. By including a negative lens with such a lens shape, it is possible to provide the first lens group with strong negative refractive power while preventing off-axial light rays from being strongly bent when passing through each surface constituting the first lens group. This reduces the occurrence of aberrations such as field curvature and distortion, resulting in a zoom lens with excellent image surface characteristics. Furthermore, to improve image surface characteristics, it is preferable that at least one of the lenses in the first lens group has one or more aspherical surfaces. Furthermore, it is preferable that the first lens group includes at least one lens with positive refractive power in order to effectively correct various aberrations such as spherical aberration and coma.

(2) Second Lens Group The specific lens configuration of the second lens group is not particularly limited as long as it has positive refractive power. Since the second lens group has positive refractive power, it includes one or more positive lenses. If the second lens group includes two positive lenses, it is possible to provide the strong positive refractive power required to achieve a high zoom ratio in the second lens group, while suppressing field curvature and distortion, making it easy to achieve good imaging performance. Furthermore, by making the object-side surface convex, spherical aberration can be suppressed. Furthermore, by including a negative lens, spherical aberration can be suppressed even more effectively.

(3) Third Lens Group The specific lens configuration of the third lens group is not particularly limited as long as it has negative refractive power. Since the third lens group has negative refractive power, it has at least one negative lens. Furthermore, a configuration including at least one positive lens is preferable in terms of correcting various aberrations.

While there is no particular limitation on the presence or absence of an image stabilization group in this zoom lens, for example, the third lens group may be composed of, from the object side, a 3a group having positive refractive power and a 3b group having negative refractive power, with the 3b group being movable in a direction perpendicular to the optical axis and used as an image stabilization group in the event of vibrations such as camera shake. Note that even when the 3b group is used as an image stabilization group, the air gap between the 3a group and the 3b group does not change during zooming.

(4) Fourth Lens Group The fourth lens group is not particularly limited in its specific lens configuration, as long as it has positive refractive power. Since the fourth lens group has positive refractive power, it includes at least one positive lens. Furthermore, in order to ensure the refractive power required of the fourth lens group while suppressing the occurrence of various aberrations, such as spherical aberration, it is preferable for the fourth lens group to include two or more positive lenses, and it is also preferable for the fourth lens group to include one or more negative lenses. For example, by configuring the fourth lens group from the object side with a positive lens, a negative lens, a positive lens, and a negative lens, various aberrations, such as spherical aberration, can be effectively corrected, making it easier to realize a zoom lens with high imaging performance. Furthermore, by configuring the fourth lens group with multiple lenses in this way, it is possible to prevent the refractive power that each lens must contribute from becoming too large, thereby reducing the effects of decentering errors during assembly.

It is also preferable that at least one of the lenses in the fourth lens group has one or more aspherical surfaces. In particular, it is preferable that the lens in the fourth lens group closest to the object has one or more aspherical surfaces. In this case, it is even more preferable that the lens in the fourth lens group closest to the object is a positive lens, as described above. By providing an aspherical surface in the fourth lens group, it becomes possible to effectively correct various aberrations, and in particular spherical aberration.

(5) Fifth Lens Group The fifth lens group is not particularly limited in its specific lens configuration, as long as it has negative refractive power. Light beams converged by the fourth lens group, which has a positive refractive power, are incident on the fifth lens group. The fifth lens group is also positioned on the image plane side of the zoom lens. These features allow the height of light rays incident on the fifth lens group to be kept low, thereby suppressing fluctuations in light ray height during zooming. Therefore, using the fifth lens group as a focus lens group facilitates the miniaturization and weight reduction of the focus lens group, making it easier to achieve rapid autofocus. Furthermore, because fluctuations in light ray height are small, using the fifth lens group as a focus lens group can suppress fluctuations in the angle of view even during wobbling, enabling excellent live view imaging and video capture.

Furthermore, if the fifth lens group is composed of only a single lens element with negative refractive power, when the fifth lens group is used as a focus lens group, the focus lens group can be made lighter and smaller, which is preferable for achieving rapid autofocus. Note that a "single lens element" refers to an element composed of only one lens or a cemented lens formed by cementing multiple lenses together.

(6) Rear Group In the zoom lens, the rear group has one or more lens groups. That is, the rear group may be composed of only one lens group, or may be composed of two or more lens groups. The rear group may have positive or negative refractive power as a whole. Therefore, each lens group constituting the rear group may have positive or negative refractive power. From the viewpoint of achieving a compact and lightweight zoom lens, it is preferable that the rear group be composed of one or two lens groups.

(7) Aperture Stop An aperture stop is disposed within the zoom lens. The position of the aperture stop within the zoom lens is not particularly limited, but it is preferably disposed, for example, between the image plane side of the first lens group and the object plane side of the rear lens group. In particular, it is preferably disposed closer to the image plane than the second lens group, more preferably closer to the object plane than the fifth lens group, and even more preferably closer to the object plane than the fourth lens group.

1-2. Operation (1) Zooming This zoom lens changes magnification by changing the distance between adjacent lens groups on the optical axis during zooming. It is sufficient that the distance between each lens group on the optical axis changes during zooming. All of the lens groups may be moved along the optical axis during zooming, or some of the lens groups may be fixed in the optical axis direction while the other lens groups are moved along the optical axis.

The presence or absence of movement for each lens group is not particularly limited, and the direction and amount of movement for each lens group can be set as appropriate. While the presence or absence, direction, and amount of movement may be different for all lens groups, it is preferable, for example, to designate the fourth lens group as the moving group and to make the amount of movement of the fourth lens group during zooming equal to the amount of movement of at least one of the lens groups arranged after the fifth lens group. The lens groups arranged after the fifth lens group refer to the sixth lens group if the rear group consists of one lens group, or at least one of the lens groups included in the rear group if the rear group consists of two or more lens groups. This zoom lens employs a multi-group configuration of six or more groups. Therefore, if all lens groups were to move by different amounts depending on the imaging distance, the drive mechanism for each lens group would become complex, leading to an increase in the number of parts and an overall increase in size. Furthermore, a complex drive mechanism and an increase in the number of parts would increase the likelihood of manufacturing errors, making it difficult to achieve the intended imaging performance. Therefore, if the fourth lens group and at least one of the lens groups arranged after the fifth lens group are moved by the same amount, these lens groups can be mounted in the same lens frame and moved, simplifying the drive mechanism and preventing an increase in the number of parts. This makes it easier to maintain a compact and lightweight overall structure while suppressing aberration fluctuations during zooming using a multi-group configuration.

(2) Focusing In the zoom lens, it is preferable to focus from infinity to an object at a finite distance by moving the lens group located closer to the image plane than the aperture diaphragm along the optical axis. By locating the focus lens group closer to the image plane than the aperture diaphragm in this way, it is possible to suppress fluctuations in the angle of view during wobbling. In particular, it is preferable to locate the aperture diaphragm closer to the object than the fifth lens group and to use the fifth lens group as the focus lens group, in order to suppress fluctuations in the angle of view during wobbling and to achieve a reduction in the size and weight of the focus lens group.

As described above, by constructing the fifth lens group from a single lens element, when the fifth lens group is used as the focus lens group, the focus lens group can be made smaller and lighter. This allows for the drive mechanism, such as an actuator, that moves the focus lens group along the optical axis during focusing to be made smaller and lighter, thereby enabling the entire zoom lens to be made smaller and lighter. In particular, it is preferable for the focus lens group to be constructed from only one negative lens, as this allows for even faster autofocusing while also making the zoom lens even smaller and lighter.

1-3. Conditional Expressions It is preferable that the zoom lens satisfy one or more of the following conditional expressions.

1-3-1. Conditional Expression (1)
(1) 6.05 ≦ β2t/β2w ≦ 15.00
however,
β2w: Lateral magnification of the second lens group at the wide-angle end when focusing on infinity β2t: Lateral magnification of the second lens group at the telephoto end when focusing on infinity

Conditional formula (1) defines the ratio between the lateral magnification of the second lens group when focused at infinity at the wide-angle end and the lateral magnification of the second lens group when focused at infinity at the telephoto end, and defines the magnification ratio provided by the second lens group during zooming. By satisfying conditional formula (1), it is possible to obtain a zoom lens with good imaging performance while ensuring the required specified zoom ratio. Furthermore, by satisfying conditional formula (1), the negative refractive power of the second lens group falls within an appropriate range, making it possible to prevent degradation of imaging performance due to decentering errors during assembly, etc.

In contrast, if the numerical value of conditional formula (1) falls below the lower limit, the negative refractive power disposed in the second lens group becomes small, and in order to ensure the required specified zoom ratio, it is necessary to increase the amount of movement of the second lens group during zooming. This makes it difficult to ensure the required zoom ratio. Alternatively, the total optical length of the zoom lens becomes long, making it difficult to maintain the zoom lens compact. On the other hand, if the numerical value of conditional formula (1) exceeds the upper limit, the negative refractive power disposed in the second lens group becomes too large, which increases the impact on imaging performance due to decentering errors during assembly, and undesirably increases the difficulty in manufacturing to achieve the designed imaging performance.

To achieve the above effect, the lower limit of conditional formula (1) is more preferably 6.17, and even more preferably 6.50. Furthermore, the upper limit of conditional formula (1) is more preferably 13.00, and even more preferably 10.00. When adopting these preferred values, the inequality sign with an equal sign (≦) in conditional formula (1) may be replaced with an inequality sign (<). The same applies to other conditional formulas; when other conditional formulas are expressed with inequality signs, the inequality sign may be replaced with an inequality sign with an equal sign.

1-3-2. Conditional Expression (2)
In the zoom lens, when the third lens group is composed of, in order from the object side as described above, a 3a group having positive refractive power and a 3b group having negative refractive power, and when the 3b group is used as an image stabilization group, it is preferable that the following conditional expression (2) be satisfied:
(2) 0.28 < f3B/f3 < 1.35
however,
f3B: focal length of the 3b lens group f3: focal length of the 3rd lens group

The above conditional expression (2) defines the ratio between the focal length of the 3b group and the focal length of the third lens group. By satisfying conditional expression (2), the refractive power of the 3b group, which serves as the image stabilization group, falls within an appropriate range. Therefore, when the 3b group is moved perpendicular to the optical axis during image stabilization, i.e., when the 3b group is decentered, the occurrence of decentering coma and decentering astigmatism can be suppressed, and deterioration of imaging performance during image stabilization can be suppressed. Furthermore, because the amount of movement of the 3b group during image stabilization can be suppressed within an appropriate range, the load on the image stabilization drive mechanism can be reduced, allowing for a smaller and lighter image stabilization drive mechanism. Therefore, even when the zoom lens is equipped with image stabilization functionality, it is possible to maintain the zoom lens small and lightweight while maintaining good imaging performance during image stabilization.

On the other hand, if the value of conditional expression (2) is below the lower limit, the refractive power of the 3b group becomes too strong, and the decentering coma and astigmatism that occur when the 3b group is decentered become large, which undesirably leads to a deterioration in imaging performance during image stabilization. On the other hand, if the value of conditional expression (2) is above the upper limit, the negative refractive power of the 3rd lens group becomes too weak, and the amount of movement of the 3b lens group during image stabilization increases. As a result, the load on the image stabilization drive mechanism increases, which leads to an increase in the size of the image stabilization drive mechanism and makes it difficult to reduce the size of the entire zoom lens, including the lens barrel, which is undesirable.

To achieve the above effect, the lower limit of conditional expression (2) is preferably 0.29, and more preferably 0.30. Furthermore, the upper limit of conditional expression (2) is preferably 1.17, and even more preferably 0.90.

1-3-3. Conditional Expression (3)
In the zoom lens, when the lens group arranged on the image plane side of the aperture stop is the focus lens group, it is preferable that the following conditional expression (3) be satisfied.
(3) 0.25 < Dwif/Dw < 0.44
however,
Dwif: the distance on the optical axis between the aperture stop and the focus lens group when focusing at infinity at the wide-angle end. Dw: the total optical length of the zoom lens at the wide-angle end.

The above conditional expression (3) defines the positional relationship between the aperture stop and the focus lens group when focusing on infinity at the wide-angle end. By satisfying conditional expression (3), fluctuations in the angle of view during wobbling can be suppressed, enabling good live view imaging and video capture. Note that the total optical length refers to the distance on the optical axis from the vertex of the surface closest to the object in the optical system to the image plane.

On the other hand, if the value of conditional expression (3) is below the lower limit, fluctuations in the angle of view during wobbling will be large, which may cause unnatural images during live view imaging or video capture, which is undesirable. On the other hand, if the value of conditional expression (3) is above the upper limit, it will undesirably result in an increase in the size of the lens group located closer to the image plane than the aperture stop.

To achieve the above effect, the lower limit of conditional expression (3) is preferably 0.26, and more preferably 0.27. Furthermore, the upper limit of conditional expression (3) is preferably 0.38, and even more preferably 0.29.

1-3-4. Conditional Expressions (4) and (5)
In the zoom lens, when the focus lens unit is composed of only one negative lens, it is preferable that the following conditional expressions (4) and (5) be satisfied.
(4) nd > 1.83
(5) νd>30
however,
nd: refractive index of the negative lens at the d line νd: Abbe number of the negative lens at the d line

The above conditional formula (4) defines the refractive index at the d-line of the negative lens that constitutes the focus lens group, and the above conditional formula (5) defines the Abbe number at the d-line of the negative lens that constitutes the focus lens group. By configuring the focus lens group with negative lenses that satisfy conditional formulas (4) and (5), it is possible to suppress chromatic aberration while ensuring sufficient refractive power for the focus lens group. As a result, the amount of movement of the focus lens group during focusing can be kept small, preventing an increase in the number of lenses required for chromatic aberration correction, and making it easier to achieve good imaging performance while reducing the size and weight of the zoom lens.

On the other hand, if the numerical value of conditional expression (4) falls below the lower limit, the refractive power of the focus lens group weakens, and if the focus lens group were to be constructed from this single negative lens, the amount of movement during focusing would need to be increased. This is undesirable because it would increase the overall optical length or make it difficult to construct the focus lens group from only one negative lens. Furthermore, if the numerical value of conditional expression (5) falls below the lower limit, chromatic dispersion would increase, making it difficult to suppress chromatic aberration. This is undesirable because it would require the inclusion of a positive lens to correct chromatic aberration, making it difficult to construct the focus lens group from only one negative lens.

To achieve the above effect, the lower limit of conditional expression (4) is preferably 1.85, and more preferably 1.87. Furthermore, the lower limit of conditional expression (5) is preferably 32, and even more preferably 37.

2. Imaging Device Next, we will explain the imaging device of the present invention. The imaging device of the present invention is characterized by including the imaging lens of the present invention described above and an imaging element that converts an optical image formed by the imaging lens into an electrical signal. It is preferable that the imaging element is provided on the image side of the optical system.

Here, there are no particular limitations on the imaging element, and solid-state imaging elements such as CCD (Charge Coupled Device) sensors and CMOS (Complementary Metal Oxide Semiconductor) sensors can also be used. The imaging device of the present invention is suitable for imaging devices using these solid-state imaging elements, such as digital cameras and video cameras. Furthermore, the imaging device can be applied to various imaging devices, such as single-lens reflex cameras, mirrorless single-lens cameras, digital still cameras, surveillance cameras, in-vehicle cameras, and drone-mounted cameras. Furthermore, these imaging devices may be interchangeable lens imaging devices, or fixed lens imaging devices in which the lens is fixed to the housing.

Next, the present invention will be explained in detail using examples. However, the present invention is not limited to the following examples.

(1) Optical Configuration Figure 1 is a lens cross-sectional view of a zoom lens according to Example 1 of the present invention, with the upper diagram showing the wide-angle end state (W), the middle diagram showing the intermediate focal length state (M), and the lower diagram showing the telephoto end state (T). Since the lens cross-sectional views shown in each Example are the same, a description thereof will be omitted below.

As shown in Figure 1, the zoom lens comprises, from the object side, a first lens group G1 having negative refractive power, a second lens group G2 having positive refractive power, a third lens group G3 having negative refractive power, a fourth lens group G4 having positive refractive power, a fifth lens group G5 having negative refractive power, and a sixth lens group G6 having negative refractive power. An aperture stop SP is located on the object side of the third lens group G3.

Specifically, the first lens group G1 is composed of, in order from the object side, a negative meniscus lens with a convex surface facing the object side, a negative meniscus lens with a convex surface facing the object side, a biconcave lens, and a biconvex lens.

The second lens group G2 is composed of, from the object side, a biconvex lens and a cemented lens formed by cementing a biconvex lens and a biconcave lens.

The third lens group G3 is composed of, from the object side, a positive meniscus lens with its convex surface facing the object side, and a concave-plano lens with its concave surface facing the object side.

The fourth lens group G4 is composed of, in order from the object side, a biconvex lens, a negative meniscus lens with its convex surface facing the object side, and a cemented lens consisting of three lenses cemented together: a biconvex lens and a negative meniscus lens with its concave surface facing the object side.

The fifth lens group G5 is composed of a biconcave lens.

The sixth lens group G6 consists of a biconvex lens and a biconcave lens.

In this zoom lens, when zooming from the wide-angle end to the telephoto end, the first lens group G1 moves in a convex path toward the image plane, while the second lens group G2 to the sixth lens group G6 each move toward the object. At that time, the fourth lens group G4 and the sixth lens group G6 move toward the object by the same amount. Also, in this zoom lens, the fifth lens group G5 is the focus lens group, and focusing from infinity to an object at a finite distance is achieved by moving the fifth lens group G5 toward the image plane along the optical axis.

(2) Numerical Examples Numerical examples of the optical system will now be described. The surface data, aspherical surface data, various data, and variable intervals of the optical system are shown below.
In the (Surface Data) table, "Surface No." indicates the order of the lens surface counted from the object side (surface number), "r" indicates the radius of curvature of the lens surface, "d" indicates the spacing on the optical axis of the lens surface, "Nd" indicates the refractive index for the d-line (wavelength λ=587.6 nm), and "νd" indicates the Abbe number for the d-line. In the "Surface No." column, "*" next to the surface number indicates that the surface is aspherical, and "SP" indicates that the surface is an aperture stop SP. In the "d" column, "D○○" (e.g., D9 in this embodiment) indicates a variable spacing during zooming. In the following numerical examples, all length units are "mm," and all angle of view units are "°." In the numerical examples, "∞" indicates infinity.

(Aspherical surface data) indicates the aspherical coefficient of each aspherical surface. Note that the aspherical surface is defined by the following equation, where x is the amount of displacement from the vertex of the surface in the optical axis direction.
x=(h ² /r)/[1+{1-(1+K)×(h/r) ² } ^1/2 )]
+A4 x ^h4 +A6 x ^h6 +A8 x ^h8 +A10 x ^h10 +A12 x ^h12
In the above formula, h is the height from the optical axis, r is the paraxial radius of curvature, K is the conic coefficient, and An is the n-th order aspheric coefficient. Also, "E±XX" represents exponential notation and means "×10 ^±XX ".

In (various data), the zoom ratio represents the ratio of the focal length at the telephoto end of the zoom lens to the focal length at the wide-angle end, while the focal length, F-number, angle of view, image height, total optical length, and BF (back focus) represent the values at the wide-angle end, mid-focal length, and telephoto end, respectively.

(Variable Distance) shows the variable distances at the wide-angle end, mid-focal length, and telephoto end.

Furthermore, the values of conditional expressions (1) to (5) are shown in Table 1 (discussed below). The matters relating to these numerical examples are similar to the numerical examples shown in the other examples, so further explanation will be omitted below.

2, 3, and 4 show longitudinal aberration diagrams of the zoom lens when focused at infinity in the wide-angle end state, mid-focal length state, and telephoto end state. Each longitudinal aberration diagram, from left to right, shows spherical aberration, astigmatism, and distortion. In the diagrams showing spherical aberration, the vertical axis shows the ratio to the maximum aperture (FNO.) and the horizontal axis shows defocus (mm), indicating spherical aberration at the d-line (wavelength λ=587.56 nm). In the diagrams showing astigmatism, the vertical axis shows the half angle of view (ω) and the horizontal axis shows defocus (mm), with the solid line indicating the sagittal image plane (S) relative to the d-line and the dotted line indicating the meridional image plane (M) relative to the d-line. In the diagrams showing distortion, the vertical axis shows the half angle of view (ω) and the horizontal axis shows distortion in %, representing distortion in %. The details of these diagrams are the same as those of the longitudinal aberration diagrams shown in other embodiments, so further explanation will be omitted below.

(surface data)
Surface No. r d Nd νd
1 116.662 1.500 1.900 37.372
2 22.255 7.287
3 125.511 1.500 1.589 61.252
4 42.479 0.150 1.515 49.963
5* 34.738 7.483
6 -58.107 1.500 1.497 81.607
7 36.299 0.300
8 36.657 6.331 1.750 35.332
9 -98.710 (D9)
10 250.808 3.271 1.517 64.197
11 -39.893 0.150
12 30.971 5.064 1.497 81.607
13 -46.946 1.000 1.911 35.249
14 238.287 (D14)
15SP∞1.000
16 70.422 2.427 1.923 20.880
17 96925.576 2.693
18* -32.894 1.000 1.851 40.104
19*∞ (D19)
20* 36.888 5.947 1.851 40.104
21* -33.900 0.162
22 119.269 0.900 1.905 35.036
23 17.848 9.876 1.497 81.607
24 -15.385 1.000 2.001 25.458
25 -21.416 (D25)
26 -8321.643 0.800 1.881 40.138
27 31.452 (D27)
28 230.024 3.136 1.808 22.760
29 -60.347 0.300
30 -457.051 1.200 1.835 42.721
31 42.221 (D31)
Image plane ∞

(aspheric data)
Surface No. Κ A4 A6 A8 A10 A12
5 0.00000 -8.35908E-06 -1.48501E-08 2.14604E-11 2.70591E-14 -1.68907E-16
18 0.00000 -2.23588E-05 7.43485E-08 -9.71180E-11 7.50728E-13 -8.81094E-15
19 0.00000 -3.20168E-05 1.29894E-07 -7.34265E-10 4.83003E-12 -2.17461E-14
20 0.00000 -5.01801E-06 1.04674E-07 2.59949E-10 -1.61574E-12 1.96338E-14
21 0.00000 3.01366E-05 2.27937E-08 1.05286E-09 -8.29506E-12 5.14222E-14

(Various data)
Zoom ratio 2.767
Focal length 17.520 29.114 48.483
F-number 4.120 4.120 4.120
Angle of view 110.747 71.937 47.366
Image height 21.633 21.633 21.633
Optical total length 134.456 133.533 134.456
BF 18.462 27.816 50.815

(variable interval)
Focal length 17.520 29.114 48.483
D9 30.694 13.079 1.000
D14 1.588 16.382 8.584
D19 10.720 3.263 1.065
D25 2.087 2.159 2.005
D27 4.926 4.855 5.009
D31 18.462 27.816 50.815

(1) Optical Configuration Figure 5 is a cross-sectional view of a zoom lens according to Example 2 of the present invention. As shown in Figure 5, the zoom lens comprises, in order from the object side, a first lens group G1 having negative refractive power, a second lens group G2 having positive refractive power, a third lens group G3 having negative refractive power, a fourth lens group G4 having positive refractive power, a fifth lens group G5 having negative refractive power, and a sixth lens group G6 having negative refractive power. An aperture stop SP is located on the object side of the third lens group.

Specifically, the first lens group G1 is composed of, in order from the object side, a negative meniscus lens with a convex surface facing the object side, a negative meniscus lens with a convex surface facing the object side, a biconcave lens, and a biconvex lens.

The second lens group G2 is composed of, from the object side, a biconvex lens and a cemented lens formed by cementing a biconvex lens and a biconcave lens.

The third lens group G3 consists of, from the object side, a biconvex lens and a concave-plano lens with its concave surface facing the object side.

The fourth lens group G4 is composed of, in order from the object side, a biconvex lens, a negative meniscus lens with its convex surface facing the object side, and a cemented lens consisting of three lenses cemented together: a biconvex lens and a negative meniscus lens with its concave surface facing the object side.

The fifth lens group G5 is composed of a biconcave lens.

The sixth lens group G6 consists of a biconvex lens and a biconcave lens.

In this zoom lens, when zooming from the wide-angle end to the telephoto end, the first lens group G1 moves in a convex path toward the image plane, while the second lens group G2 to the sixth lens group G6 each move toward the object. At that time, the fourth lens group G4 and the sixth lens group G6 move toward the object by the same amount. Also, in this zoom lens, the fifth lens group G5 is the focus lens group, and focusing from infinity to an object at a finite distance is achieved by moving the fifth lens group G5 toward the image plane along the optical axis.

(2) Numerical Examples Numerical examples of the zoom lens will now be described. The surface data, aspherical surface data, various data, and variable interval data of the zoom lens are shown below.

Figures 6, 7, and 8 show longitudinal aberration diagrams of the zoom lens when focused at infinity in the wide-angle end state, the intermediate focal length state, and the telephoto end state.

(surface data)
Surface No. r d Nd νd
1 122.190 1.500 1.900 37.372
2 22.553 7.539
3 164.876 1.500 1.589 61.252
4 43.515 0.150 1.515 49.963
5* 35.422 7.553
6 -61.782 1.500 1.497 81.607
7 36.974 0.300
8 37.345 6.388 1.750 35.332
9 -97.540 (D9)
10 158.314 3.433 1.517 64.197
11 -40.854 0.150
12 30.050 5.178 1.497 81.607
13 -47.703 1.000 1.911 35.249
14 187.128 (D14)
15SP∞1.000
16 82.239 2.469 1.923 20.880
17 -347.090 2.541
18* -30.431 1.000 1.851 40.104
19*∞ (D19)
20* 35.817 5.965 1.851 40.104
21* -33.819 0.100
22 115.184 0.900 1.905 35.036
23 17.641 9.860 1.497 81.607
24 -15.385 1.000 2.001 25.458
25 -21.393 (D25)
26 -655.514 0.800 1.881 40.138
27 31.675 (D27)
28 389.512 3.095 1.808 22.760
29 -56.426 0.300
30 -894.549 1.200 1.835 42.721
31 43.209 (D31)
Image plane ∞

(aspheric data)
Surface No. Κ A4 A6 A8 A10 A12
5 0.00000 -8.49948E-06 -1.39065E-08 2.71461E-11 -2.84477E-15 -1.13437E-16
18 0.00000 -1.08768E-05 1.42275E-08 2.34536E-10 4.42543E-14 -8.81094E-15
19 0.00000 -2.18182E-05 5.84966E-08 -2.67964E-10 3.37438E-12 -2.17461E-14
20 0.00000 -3.21034E-06 1.03186E-07 3.79315E-10 -1.57233E-12 1.96337E-14
21 0.00000 3.29171E-05 2.87556E-08 1.03088E-09 -7.14554E-12 5.14222E-14

(Specifications)
Zoom ratio 2.767
Focal length 17.521 29.120 48.481
F-number 4.120 4.120 4.120
Angle of view 110.742 71.975 47.354
Image height 21.633 21.633 21.633
Optical total length 134.497 132.478 134.497
BF 18.324 27.660 50.655

(variable interval)
Focal length 17.521 29.120 48.481
D9 30.396 12.940 1.000
D14 1.617 14.823 8.249
D19 10.599 3.495 1.031
D25 2.168 2.138 2.005
D27 4.972 5.002 5.135
D31 18.324 27.660 50.655

(1) Optical Configuration Figure 9 is a cross-sectional view of a zoom lens according to Example 3 of the present invention. As shown in Figure 9, the zoom lens comprises, in order from the object side, a first lens group G1 having negative refractive power, a second lens group G2 having positive refractive power, a third lens group G3 having negative refractive power, a fourth lens group G4 having positive refractive power, a fifth lens group G5 having negative refractive power, and a sixth lens group G6 having negative refractive power. An aperture stop SP is located on the object side of the third lens group.

Specifically, the first lens group G1 is composed of, in order from the object side, a negative meniscus lens with a convex surface facing the object side, a negative meniscus lens with a convex surface facing the object side, and a cemented lens formed by cementing together a biconcave lens and a biconvex lens.

The second lens group G2 is composed of, in order from the object side, a positive meniscus lens with its concave surface facing the object side, and a cemented lens formed by cementing together a biconvex lens and a biconcave lens.

The third lens group G3 is composed of, from the object side, group 3a, which has positive refractive power, and group 3b, which has negative refractive power. Group 3a is composed of a positive meniscus lens with its convex surface facing the object side. Group 3b is composed of a cemented lens consisting of a biconcave lens and a biconvex lens.

The fourth lens group G4 is composed of, in order from the object side, a biconvex lens, a negative meniscus lens with its convex surface facing the object side, and a cemented lens consisting of three lenses cemented together: a biconvex lens and a negative meniscus lens with its concave surface facing the object side.

The fifth lens group G5 consists of a negative meniscus lens with its convex surface facing the object side.

The sixth lens group G6 consists of a biconvex lens and a biconcave lens.

In this zoom lens, when zooming from the wide-angle end to the telephoto end, the first lens group G1 moves in a convex trajectory toward the image plane, while the second lens group G2 to the sixth lens group G6 each move toward the object. At that time, the fourth lens group G4 and the sixth lens group G6 move toward the object by the same amount. In addition, in this zoom lens, the fifth lens group G5 is the focus lens group, and focusing from infinity to an object at a finite distance is achieved by moving the fifth lens group G5 toward the image plane along the optical axis. In addition, in this zoom lens, the 3b group is configured to be movable perpendicular to the optical axis, and functions as the vibration control group VC.

(2) Numerical Examples Numerical examples of the zoom lens will now be described. The surface data, aspherical surface data, various data, and variable interval data of the zoom lens are shown below.

Figures 10, 11, and 12 show longitudinal aberration diagrams of the zoom lens when focused at infinity in the wide-angle end state, the intermediate focal length state, and the telephoto end state.

(surface data)
Surface No. r d Nd νd
1 88.560 1.500 1.881 40.138
2 19.158 8.350
3 202.429 1.750 1.497 81.607
4 40.577 0.150 1.536 41.207
5* 31.862 6.437
6 -130.488 1.510 1.497 81.607
7 29.564 5.527 1.750 35.332
8 -197.722 (D8)
9 -428.459 2.750 1.673 32.099
10 -41.705 0.150
11 24.729 6.687 1.497 81.607
12 -36.641 1.000 1.855 24.799
13 182.449 (D13)
14SP∞1.113
15 47.106 1.787 1.850 30.046
16 52.050 2.908
17* -50.678 1.200 1.882 37.221
18 31.198 3.351 1.808 22.764
19 -444.033 (D19)
20* 29.959 5.269 1.851 40.104
21* -46.453 0.100
22 51.709 0.900 1.905 35.047
23 15.431 10.473 1.497 81.607
24 -15.385 1.000 2.001 25.458
25 -22.483 (D25)
26 439.664 0.800 1.881 40.138
27 28.474 (D27)
28 113.580 3.005 1.923 20.880
29 -89.615 0.100
30 -163.142 1.200 1.871 40.744
31 47.217 (D31)
Image plane ∞

(aspheric data)
Surface No. Κ A4 A6 A8 A10 A12
5 0.00000 -1.19398E-05 -1.10752E-09 -1.54010E-10 5.81099E-13 -1.08575E-15
17 0.00000 5.47310E-06 -6.69571E-09 -5.83936E-11 8.47422E-13 -2.65483E-15
20 0.00000 -7.54991E-06 2.77768E-08 -6.99811E-11 -2.17135E-14 0.00000E+00
21 0.00000 1.89851E-05 -1.51570E-08 -5.20330E-12 -1.14685E-13 0.00000E+00

(Specifications)
Zoom ratio 2.767
Focal length 17.524 29.093 48.479
F-number 4.120 4.120 4.120
Angle of view 110.761 74.502 47.796
Image height 21.633 21.633 21.633
Optical total length 131.927 124.228 131.927
BF 18.590 31.102 53.306

(variable interval)
Focal length 17.524 29.093 48.479
D8 27.912 10.970 1.000
D13 2.582 4.268 1.870
D19 8.092 3.138 1.000
D25 0.990 1.046 1.013
D27 4.744 4.687 4.720
D31 18.590 31.102 53.306

(1) Optical Configuration Figure 13 is a cross-sectional view of a zoom lens according to Example 4 of the present invention. As shown in Figure 13, the zoom lens comprises, in order from the object side, a first lens group G1 having negative refractive power, a second lens group G2 having positive refractive power, a third lens group G3 having negative refractive power, a fourth lens group G4 having positive refractive power, a fifth lens group G5 having negative refractive power, and a sixth lens group G6 having negative refractive power. An aperture stop SP is located on the object side of the third lens group.

Specifically, the first lens group G1 is composed of, in order from the object side, a negative meniscus lens with a convex surface facing the object side, a negative meniscus lens with a convex surface facing the object side, and a cemented lens formed by cementing together a biconcave lens and a positive meniscus lens with a convex surface facing the object side.

The second lens group G2 is composed of, in order from the object side, a positive meniscus lens with its concave surface facing the object side, and a cemented lens formed by cementing together a biconvex lens and a negative meniscus lens with its concave surface facing the object side.

The third lens group G3 is composed of, from the object side, a group 3a with positive refractive power and a group 3b with negative refractive power. Group 3a is composed of a positive meniscus lens with its convex surface facing the object side. Group 3b is composed of a cemented lens consisting of a biconcave lens and a positive meniscus lens with its convex surface facing the object side.

The fourth lens group G4 is composed of, in order from the object side, a biconvex lens, a negative meniscus lens with its convex surface facing the object side, and a cemented lens consisting of three lenses cemented together: a biconvex lens and a negative meniscus lens with its concave surface facing the object side.

The fifth lens group G5 consists of a negative meniscus lens with its convex surface facing the object side.

The sixth lens group G6 consists of a biconvex lens and a biconcave lens.

In this zoom lens, when zooming from the wide-angle end to the telephoto end, the first lens group G1 moves in a convex trajectory toward the image plane, while the second lens group G2 to the sixth lens group G6 each move toward the object. At that time, the fourth lens group G4 and the sixth lens group G6 move toward the object by the same amount. In addition, in this zoom lens, the fifth lens group G5 is the focus lens group, and focusing from infinity to an object at a finite distance is achieved by moving the fifth lens group G5 toward the image plane along the optical axis. In addition, in this zoom lens, the 3b group is configured to be movable perpendicular to the optical axis, and functions as the vibration control group VC.

(2) Numerical Examples Numerical examples of the zoom lens will now be described. The surface data, aspherical surface data, various data, and variable interval data of the zoom lens are shown below.

Figures 14, 15, and 16 show longitudinal aberration diagrams of the zoom lens when focused at infinity in the wide-angle end state, the intermediate focal length state, and the telephoto end state.

(surface data)
Surface No. r d Nd νd
1 114.979 1.500 1.881 40.138
2 20.742 5.306
3 40.818 1.750 1.497 81.607
4 28.571 0.150 1.536 41.207
5* 23.179 10.536
6 -169.114 1.510 1.497 81.607
7 27.504 5.016 1.750 35.332
8 629.103 (D8)
9 -67.550 2.750 1.673 32.099
10 -33.351 0.150
11 33.570 6.145 1.497 81.607
12 -35.508 1.000 1.855 24.799
13 -174.454 (D13)
14SP∞1.216
15 39.048 3.244 1.850 30.046
16 211.203 2.336
17* -40.091 1.200 1.882 37.221
18 36.434 2.345 1.808 22.764
19 124.943 (D19)
20* 34.601 4.820 1.851 40.104
21* -51.530 0.100
22 47.586 0.900 1.905 35.047
23 14.618 10.273 1.497 81.607
24 -15.385 1.000 2.001 25.458
25 -22.501 (D25)
26 187.347 0.800 1.881 40.138
27 27.588 (D27)
28 111.335 3.050 1.923 20.880
29 -87.318 0.100
30 -162.558 1.200 1.871 40.744
31 49.650 (D31)
Image plane ∞

(aspheric data)
Surface No. Κ A4 A6 A8 A10 A12
5 0.00000 -1.29756E-05 -1.21587E-08 -1.25616E-10 4.19080E-13 -8.30275E-16
17 0.00000 9.69098E-06 2.10582E-08 -2.90183E-10 1.62250E-12 -3.55012E-15
20 0.00000 3.30964E-06 3.34192E-09 8.68898E-11 -5.60914E-13 0.00000E+00
21 0.00000 2.56252E-05 -2.23895E-08 3.72866E-12 -3.42994E-13 0.00000E+00

(Specifications)
Zoom ratio 2.766
Focal length 17.529 29.104 48.479
F-number 4.120 4.120 4.120
Angle of view 110.806 72.896 47.493
Image height 21.633 21.633 21.633
Optical total length 134.520 130.515 134.520
BF 18.643 29.793 52.873

(variable interval)
Focal length 17.529 29.104 48.479
D8 30.892 13.243 2.132
D13 1.200 9.893 4.161
D19 9.431 3.232 1.000
D25 0.981 0.999 1.006
D27 4.976 4.957 4.951
D31 18.643 29.793 52.873

(1) Optical Configuration Figure 17 is a cross-sectional view of a zoom lens according to Example 5 of the present invention. As shown in Figure 17, the zoom lens comprises, in order from the object side, a first lens group G1 having negative refractive power, a second lens group G2 having positive refractive power, a third lens group G3 having negative refractive power, a fourth lens group G4 having positive refractive power, a fifth lens group G5 having negative refractive power, a sixth lens group G6 having positive refractive power, and a seventh lens group G7 having negative refractive power. An aperture stop SP is located on the object side of the third lens group.

Specifically, the first lens group G1 is composed of, in order from the object side, a negative meniscus lens with a convex surface facing the object side, a negative meniscus lens with a convex surface facing the object side, a biconcave lens, and a biconvex lens.

The second lens group G2 is composed of, in order from the object side, a biconvex lens and a cemented lens formed by cementing together a biconvex lens and a negative meniscus lens with its concave surface facing the object side.

The third lens group G3 is composed of, from the object side, a plano-convex lens with a flat surface facing the object side and a concave-plano lens with a concave surface facing the object side.

The fourth lens group G4 is composed of, in order from the object side, a biconvex lens, a negative meniscus lens with its convex surface facing the object side, and a cemented lens consisting of three lenses cemented together: a biconvex lens and a negative meniscus lens with its concave surface facing the object side.

The fifth lens group G5 consists of a negative meniscus lens with its convex surface facing the object side.

The sixth lens group G6 consists of a biconvex lens and a negative meniscus lens with its concave surface facing the object side.

The seventh lens group G7 is composed of a biconcave lens.

In this zoom lens, when zooming from the wide-angle end to the telephoto end, the first lens group G1 moves in a convex path toward the image plane, the second lens group G2 to the sixth lens group G6 each move toward the object, and the seventh lens group G7 is fixed in the optical axis direction. At that time, the fourth lens group G4 and the sixth lens group G6 move toward the object by the same amount. Also, in this zoom lens, the fifth lens group G5 is the focus lens group, and focusing from infinity to a finite distance object is achieved by moving the fifth lens group toward the image plane along the optical axis.

(2) Numerical Examples Numerical examples of the zoom lens will now be described. The surface data, aspherical surface data, various data, and variable interval data of the zoom lens are shown below.

Figures 18, 19, and 20 show longitudinal aberration diagrams of the zoom lens when focused at infinity in the wide-angle end state, the intermediate focal length state, and the telephoto end state.

(surface data)
Surface No. r d Nd νd
1 93.705 1.500 1.900 37.372
2 23.164 6.452
3 105.606 1.500 1.589 61.252
4 31.484 0.150 1.515 49.963
5* 26.768 7.204
6 -63.204 1.500 1.497 81.607
7 37.051 0.300
8 36.738 5.448 1.750 35.332
9 -133.368 (D9)
10 56.387 3.947 1.517 64.197
11 -41.149 0.150
12 45.255 4.469 1.497 81.607
13 -34.708 1.000 1.911 35.249
14 -733.604 (D14)
15SP∞1.000
16 ∞ 2.642 1.923 20.880
17 -51.384 2.061
18* -22.797 1.000 1.851 40.104
19*∞ (D19)
20* 29.045 5.627 1.851 40.104
21* -32.899 0.100
22 204.332 0.900 1.905 35.036
23 15.616 10.489 1.497 81.607
24 -15.385 1.000 2.001 25.458
25 -21.552 (D25)
26 166.252 0.800 1.881 40.138
27 27.647 (D27)
28 119.930 3.480 1.808 22.760
29 -56.608 0.300
30 -60.219 1.200 1.835 42.721
31 -9609.655 (D31)
32 -10000.003 0.950 1.755 27.512
33 72.488 19.219
Image plane ∞

(aspheric data)
Surface No. Κ A4 A6 A8 A10 A12
5 0.00000 -1.08858E-05 -1.79866E-08 4.17985E-11 -2.22629E-14 -1.14401E-16
18 0.00000 -3.95092E-05 7.10557E-07 -6.04300E-09 2.28934E-11 -8.81094E-15
19 0.00000 -5.57906E-05 7.02750E-07 -6.09063E-09 2.45401E-11 -2.17461E-14
20 0.00000 -8.01562E-06 6.99384E-09 1.20370E-09 -1.38755E-11 5.88224E-14
21 0.00000 3.08260E-05 -4.40833E-08 1.05042E-09 -1.16373E-11 5.14222E-14

(Specifications)
Zoom ratio 2.767
Focal length 17.525 29.144 48.493
F-number 4.120 4.120 4.120
Angle of view 110.717 71.408 46.937
Image height 21.633 21.633 21.633
Optical total length 136.148 130.882 136.148
BF 19.219 19.219 19.219

(variable interval)
Focal length 17.525 29.144 48.493
D9 31.232 12.302 1.000
D14 1.471 12.971 12.863
D19 11.139 5.058 1.000
D25 1.985 2.580 2.003
D27 4.932 4.337 4.915
D31 1.000 9.244 29.979

[Table 1]
Example 1 Example 2 Example 3 Example 4 Example 5
(1) β2t/β2w 10.00 6.50 6.50 7.01 10.00
(2) f3B/f3 - - 0.87 0.33 -
(3) Dwif/Dw 0.281 0.280 0.282 0.281 0.279
(4)nd 1.881 1.881 1.881 1.881 1.881
(5) νd 40.138 40.138 40.138 40.138 40.138

According to the present invention, it is possible to provide a zoom lens and an imaging device that are compact and lightweight, while providing high imaging performance throughout the entire zoom range.

Claims (8)

A zoom lens comprising, in order from the object side, a first lens group having negative refractive power, a second lens group having positive refractive power, a third lens group having negative refractive power, a fourth lens group having positive refractive power, a fifth lens group having negative refractive power, and a rear group having one or more lens groups, wherein the spacing between adjacent lens groups changes during zooming,
the fourth lens group is composed of a positive lens, a negative lens, a positive lens, and a negative lens, which are arranged in this order from the object side,
A zoom lens characterized by satisfying the following conditional expression:
(1) 6.05 ≦ β2t/β2w ≦ 15.00
however,
β2w: lateral magnification of the second lens group at the wide-angle end when focusing on infinity; β2t: lateral magnification of the second lens group at the telephoto end when focusing on infinity. A zoom lens comprising, in order from the object side, a first lens group having negative refractive power, a second lens group having positive refractive power, a third lens group having negative refractive power, a fourth lens group having positive refractive power, a fifth lens group having negative refractive power, and a rear group having one or more lens groups, wherein the spacing between adjacent lens groups changes during zooming,
the third lens group is composed of, in order from the object side, a third-a group having positive refractive power and a third-b group having negative refractive power;
the 3b group is configured to be movable in a direction perpendicular to the optical axis,
A zoom lens characterized by satisfying the following conditional expression:
(1) 6.05 ≦ β2t/β2w ≦ 15.00
(2) 0.28 < f3B/f3 < 1.35
however,
β2w: lateral magnification of the second lens group at the wide-angle end when focusing on infinity; β2t: lateral magnification of the second lens group at the telephoto end when focusing on infinity.
f3B: focal length of the 3b lens group
f3: focal length of the third lens group A zoom lens comprising, in order from the object side, a first lens group having negative refractive power, a second lens group having positive refractive power, a third lens group having negative refractive power, a fourth lens group having positive refractive power, a fifth lens group having negative refractive power, and a rear group having one or more lens groups, wherein the spacing between adjacent lens groups changes during zooming,
The zoom lens has an aperture stop therein;
a focus lens group that moves along the optical axis when focusing from infinity to a finite distance object, located closer to the image plane than the aperture stop;
the focus lens group is composed of only one negative lens,
A zoom lens characterized by satisfying the following conditional expression:
(1) 6.05 ≦ β2t/β2w ≦ 15.00
(4) nd > 1.83
(5) νd>30
however,
β2w: lateral magnification of the second lens group at the wide-angle end when focusing on infinity; β2t: lateral magnification of the second lens group at the telephoto end when focusing on infinity.
nd: refractive index at the d line of the negative lens constituting the focus lens group
νd: Abbe number at the d-line of the negative lens constituting the focus lens group A zoom lens comprising, in order from the object side, a first lens group having negative refractive power, a second lens group having positive refractive power, a third lens group having negative refractive power, a fourth lens group having positive refractive power, a fifth lens group having negative refractive power, and a rear group having one or more lens groups, wherein the spacing between adjacent lens groups changes during zooming,
During zooming, the amount of movement of the fourth lens group is equal to the amount of movement of at least one of the lens groups included in the rear group,
the fifth lens group is a focus lens group that moves when focusing from infinity to a finite distance object,
A zoom lens characterized by satisfying the following conditional expression:
(1) 6.05 ≦ β2t/β2w ≦ 15.00
however,
β2w: lateral magnification of the second lens group at the wide-angle end when focusing on infinity; β2t: lateral magnification of the second lens group at the telephoto end when focusing on infinity. A zoom lens comprising, in order from the object side, a first lens group having negative refractive power, a second lens group having positive refractive power, a third lens group having negative refractive power, a fourth lens group having positive refractive power, a fifth lens group having negative refractive power, and a rear group having one or more lens groups, wherein the spacing between adjacent lens groups changes during zooming,
During zooming, the amount of movement of the fourth lens group is equal to the amount of movement of at least one of the lens groups included in the rear group,
The zoom lens has an aperture stop therein,
a focus lens group that moves along the optical axis when focusing from infinity to a finite distance object, on the image plane side of the aperture stop;
A zoom lens characterized by satisfying the following conditional expression:
(1) 6.05 ≦ β2t/β2w ≦ 15.00
however,
β2w: lateral magnification of the second lens group at the wide-angle end when focusing on infinity; β2t: lateral magnification of the second lens group at the telephoto end when focusing on infinity. 2. The zoom lens according to claim 1 , wherein the positive lens arranged closest to the object in the fourth lens group has an aspherical surface. 6. The zoom lens according to claim 3 , wherein the focus lens group satisfies the following condition: (3) 0.25<Dwif/Dw<0.44
however,
Dwif: the distance on the optical axis between the aperture stop and the focus lens group when focusing on infinity at the wide-angle end. Dw: the total optical length of the zoom lens at the wide-angle end. 8. An imaging device comprising: the zoom lens according to claim 1; and an imaging element that converts an optical image formed by the zoom lens into an electrical signal.