JP7183032B2 - Zoom lens and imaging device - Google Patents

Description

The present invention relates to a zoom lens and an imaging device, and more particularly to a zoom lens and an imaging device suitable for a compact imaging device using a solid-state imaging device or the like.

2. Description of the Related Art Conventionally, imaging apparatuses using solid-state imaging devices, such as digital still cameras and digital video cameras, have been widely used. 2. Description of the Related Art As an optical system of an image pickup apparatus, for example, a zoom lens is widely known that includes a plurality of lens groups and changes the focal length by changing the distance between adjacent lens groups on the optical axis during zooming. Since the zoom lens can adjust the focal length according to the distance to the subject, it is highly convenient when taking an image. In recent years, there has been an increasing demand for so-called wide-angle zoom lenses that include a wide-angle range in the variable power range.

As a wide-angle zoom lens, a lens group having a negative refractive power, a lens group having a positive refractive power, a lens group having a negative refractive power, and a lens group having a positive refractive power are provided in order from the object side. Prior-type zoom lenses are known (see, for example, Patent Documents 1 to 3). Such a negative lead type zoom lens can easily widen the angle of view and can be made compact while maintaining optical performance. Widely used.

In these zoom lenses, by moving the two lens groups having positive refractive power along the same trajectory during zooming, both lens groups can be configured as one unit. By adopting such a configuration, it is possible to suppress the occurrence of an eccentricity error or the like during assembly, reduce manufacturing errors, and improve the yield.

JP 2013-130675 A JP 2014-26211 A JP 2009-169051 A

By the way, compared to a single focal length lens, a zoom lens is likely to be a dark lens because it consists of a large number of lenses. Further, when the above two lens groups having positive refractive power are constructed as one unit during zooming, it is advantageous in terms of reducing eccentric errors and manufacturing errors as described above, but it is possible to maintain high optical performance while maintaining high optical performance. , there are restrictions on increasing the diameter and reducing the size. The zoom lenses disclosed in Patent Documents 1 and 2 have an Fno of about 5.8 at the telephoto end, and are not designed to have a large aperture. The zoom lens disclosed in Patent Document 3 has an Fno of 2.8 and a large aperture, but two lens groups are moved during focusing, and the moving mechanism of the lens groups during focusing and zooming is complicated. is. Therefore, the zoom lens has not been sufficiently miniaturized.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a wide-angle zoom lens and an image pickup apparatus that are small in size and have high optical performance.

In order to solve the above-mentioned problems, a zoom lens according to the present invention includes a first lens group having negative refractive power closest to the object side, and having positive refractive power closer to the image side than the first lens group. A zoom lens that includes a lens group Pa, a lens group N having negative refractive power, and a lens group Pb having positive refractive power, and performs zooming by changing the distance on the optical axis between adjacent lens groups. The lens group Pa, the lens group N, and the lens group Pb are arranged adjacent to each other in this order from the object side, and the lens group Pa and the lens group Pb are arranged in the same order during zooming. It is characterized by moving along a trajectory and satisfying the following conditions.
0.2<(Rnf+Rnr)/(Rnf-Rnr)<1.3 (1)
-4.0 < fn/fw < -1.5 (2)
however,
Rnf: the radius of curvature of the lens surface closest to the object side in the lens group N Rnr: the radius of curvature of the lens surface closest to the image side in the lens group N fn: the focal length of the lens group N fw: the size of the zoom lens at the wide-angle end Focal length

In order to solve the above-mentioned problems, an image pickup apparatus according to the present invention includes a zoom lens according to the present invention, and an image pickup device that converts an optical image formed by the zoom lens into an electrical signal on the image side of the zoom lens. and an element.

According to the present invention, it is possible to provide a wide-angle zoom lens and an image pickup apparatus that are small in size and have high optical performance.

FIG. 2 is a cross-sectional view showing an example of lens configuration at the wide-angle end, the intermediate focal length state, and the telephoto end of the zoom lens of Example 1 of the present invention; 4 is a longitudinal aberration diagram of the zoom lens of Example 1 at the telephoto end when focusing on infinity. FIG. However, spherical aberration, astigmatism, and distortion are shown in order from the left in the drawing (the same applies to longitudinal aberration diagrams below). FIG. 10 is a longitudinal aberration diagram at an intermediate focal position when focusing on infinity of the zoom lens of Example 1; 4 is a longitudinal aberration diagram at the wide-angle end of the zoom lens of Example 1 when focusing on infinity; FIG. FIG. 10 is a cross-sectional view showing a lens configuration example at the wide-angle end, the intermediate focal length state, and the telephoto end of the zoom lens of Example 2 of the present invention; FIG. 11 is a longitudinal aberration diagram of the zoom lens of Example 2 at the telephoto end when focusing on infinity. FIG. 10 is a longitudinal aberration diagram of the zoom lens of Example 2 at an intermediate focal position when focusing on infinity. FIG. 11 is a longitudinal aberration diagram of the zoom lens of Example 2 at the wide-angle end when focusing on infinity; FIG. 10 is a cross-sectional view showing an example of lens configuration at the wide-angle end, the intermediate focal length state, and the telephoto end of the zoom lens of Example 3 of the present invention; FIG. 11 is a longitudinal aberration diagram of the zoom lens of Example 3 at the telephoto end when focusing on infinity. FIG. 10 is a longitudinal aberration diagram of the zoom lens of Example 3 at an intermediate focal position when focusing on infinity. FIG. 11 is a longitudinal aberration diagram of the zoom lens of Example 3 at the wide-angle end when focusing on infinity; FIG. 12 is a cross-sectional view showing a lens configuration example at the wide-angle end, the intermediate focal length state, and the telephoto end of the zoom lens of Example 4 of the present invention; FIG. 10 is a longitudinal aberration diagram of the zoom lens of Example 4 at the telephoto end when focusing on infinity. FIG. 12 is a longitudinal aberration diagram of the zoom lens of Example 4 at an intermediate focal position when focusing on infinity; FIG. 10 is a longitudinal aberration diagram of the zoom lens of Example 4 at the wide-angle end when focusing on infinity. FIG. 11 is a cross-sectional view showing a lens configuration example at the wide-angle end, the intermediate focal length state, and the telephoto end of the zoom lens of Example 5 of the present invention; FIG. 11 is a longitudinal aberration diagram of the zoom lens of Example 5 at the telephoto end when focusing on infinity. FIG. 12 is a longitudinal aberration diagram of the zoom lens of Example 5 at an intermediate focal position when focusing on infinity. FIG. 12 is a longitudinal aberration diagram of the zoom lens of Example 5 at the wide-angle end when focusing on infinity.

Embodiments of a zoom lens and an imaging device according to the present invention will be described below. However, the zoom lens and imaging device described below are aspects of the zoom lens 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 of Zoom Lens The zoom lens of the present embodiment includes a first lens group having negative refractive power closest to the object side, and a lens group Pa having positive refractive power closer to the image side than the first lens group. , a lens group N having a negative refractive power, and a lens group Pb having a positive refractive power. At this time, the lens group Pa, the lens group N, and the lens group Pb are arranged adjacent to each other in this order from the object side.

By adopting the refractive power arrangement described above, the zoom lens can widen the angle of view at the wide-angle end and facilitate aberration correction during zooming. Therefore, it is possible to realize a wide-angle zoom lens that is compact and has high optical performance.

Here, the zoom lens may include the first lens group, and the lens group Pa, lens group N, and lens group Pb arranged adjacent to each other in this order from the object side. The zoom lens may be substantially composed of these four lens groups, or may be provided with other lens groups. One or more other lens groups may be arranged between the first lens group and the lens group Pa, or one or more may be arranged on the image side of the lens group Pb. For example, a four-group configuration having negative/positive/negative/positive refractive power arrangement in order from the object side, negative/positive/positive/negative/positive refractive power arrangement in order from the object side, or negative/negative/positive・Five-group configuration having negative/positive refractive power arrangement, negative/negative/positive/positive/negative/positive refractive power arrangement or negative/positive/positive/negative/positive/negative refractive power arrangement in order from the object side Various configurations may be employed, such as a six-group configuration having . In any configuration, by changing the distance between adjacent lens groups on the optical axis during zooming, aberration correction becomes easier, and a zoom lens with high optical performance over the entire zooming range can be realized. .

(1) First lens group The first lens group is the lens group arranged closest to the object side in the zoom lens. A so-called negative leading type zoom lens in which a lens group having a negative refractive power is arranged closest to the object side can shorten the close-up distance and relatively easily widen the angle of view. Also, it is relatively easy to secure the back focus. For these reasons, it is suitable for wide-angle zoom lenses such as single-lens reflex cameras.

The specific lens configuration of the first lens group is not particularly limited as long as it has negative refractive power. In a wide-angle zoom lens equipped with a first lens group having a negative refractive power closest to the object side, the height of the maximum off-axis ray incident on the first lens group, that is, the maximum off-axis ray with respect to the first lens group Since the incident position of is high, off-axis rays are incident on the periphery of the lens. Therefore, in order to achieve a wider angle of view at the wide-angle end while maintaining the size of the zoom lens, it is preferable to use a plurality of lenses having negative refractive power. In particular, it is preferable that at least one, preferably two or more lenses among the lenses having negative refractive power constituting the first lens group are meniscus lenses concave toward the image side. By adopting such a configuration, it is possible to prevent off-axis rays from being strongly bent when passing through each surface constituting the first lens group, while providing a strong negative refractive power in the first lens group. can be done. Therefore, it is possible to reduce the occurrence of field curvature, distortion, and the like, and obtain a zoom lens with excellent field characteristics. In order to improve the image plane characteristics, it is preferable that at least one of the concave meniscus lenses on the image side has at least one aspherical surface.

Moreover, the first lens group preferably includes at least one lens having positive refractive power in order to satisfactorily correct various aberrations such as spherical aberration and coma.

An optical element having no refractive power or having very small refractive power may be arranged on the object side of the first lens group. Examples of such optical elements include protective filters for protecting lenses from dirt and scratches, ND filters for reducing the amount of incident light, and various filters such as PL filters for color adjustment. is mentioned.

(2) Lens group Pa and lens group Pb
Lens group Pa and lens group Pb each have a positive refractive power. Here, the lens group Pa and the lens group Pb move along the same trajectory during zooming. By moving the lens group Pa and the lens group Pb, which have positive refractive power, along the same locus, the lens group Pa and the lens group Pb can be configured as one unit. Therefore, compared to the case where the lens group Pa and the lens group Pb are moved along separate trajectories, it is possible to simply configure the zooming mechanism for moving each lens group during zooming. Furthermore, it is possible to suppress the occurrence of eccentricity errors or the like during assembly, thereby reducing manufacturing errors and improving the yield.

As long as each of the lens group Pa and the lens group Pb has positive refractive power, the specific lens configuration is not particularly limited. It is arranged on the image side in the zoom lens. Along with the zooming operation of the zoom lens, the height of the maximum off-axis light flux incident on the lens group Pb varies. That is, the ray height of the maximum off-axis luminous flux incident on the lens group Pb differs between the wide-angle end and the telephoto end. Therefore, it is preferable that the lens group Pb includes at least one aspherical surface in order to satisfactorily correct coma, curvature of field, and the like.

(3) Lens group N
The lens group N has a negative refractive power and is arranged between the lens group Pa and the lens group Pb adjacent to these lens groups. As long as the distance on the optical axis between the lens group N and the lens group Pb changes, the specific lens configuration is not particularly limited. For example, the lens group N preferably consists of one single lens unit. Here, the single lens unit means one single lens, or a cemented lens in which a plurality of single lenses are integrated without an air gap. That is, even if the single lens unit has a plurality of optical surfaces, only the side closest to the object and the side closest to the image are in contact with the air, and the other surfaces are not in contact with the air. In this specification, a single lens may be either a spherical lens or an aspherical lens. The aspherical lens also includes a so-called compound aspherical lens having an aspherical film attached to the surface.

By constructing the lens group N from one single lens unit, it is possible to reduce various manufacturing errors such as eccentricity error and air gap error between a plurality of single lens units. Therefore, deterioration in optical performance due to manufacturing errors can be reduced, and variations in performance between products can be reduced. Therefore, a zoom lens with high optical performance can be manufactured with high yield.

Various aberrations are satisfactorily corrected over the entire zoom range by changing the distance on the optical axis between lens group N and lens group Pa and the distance on the optical axis between lens group N and lens group Pb when zooming. It is possible to realize a zoom lens with a large zoom ratio. Further, by changing the distance on the optical axis between the lens group N and the lens group Pa and the distance on the optical axis between the lens group N and the lens group Pb, good image plane property is maintained during zooming. becomes possible.

Further, it is preferable to use the lens group N as a focusing group and move the lens group N along the optical axis to focus from infinity to near objects. As described above, when the lens group Pa and the lens group Pb are configured as one unit, the lens group N is movably supported with respect to the unit so that the lens group N can be moved during zooming and focusing. Even when the lens group N is directly driven by a stepping motor or the like, the decentration error associated with the movement of the lens group N can be suppressed. Therefore, even if the imaging distance changes according to the position of the subject, it is possible to suppress aberration fluctuations due to the eccentricity error and obtain an excellent subject image regardless of the imaging distance.

Further, when the lens group N is used as a focusing group, by configuring the lens group N with one single lens as described above, the focusing group can be made lighter, and the focusing group can be controlled. It is possible to improve the quality and achieve quick autofocus.

(4) Aperture diaphragm In the zoom lens, the arrangement of the aperture diaphragm is not particularly limited. An aperture stop is preferably arranged between the surface and the most object-side lens surface of the lens group Pa. However, the aperture stop here means the stop that defines the axial beam diameter of the zoom lens, that is, the stop that defines the Fno of the zoom lens.

The zoom lens includes a first lens group having a negative refractive power closest to the object side. Therefore, if the aperture stop is arranged on the image side of the lens group Pa, the entrance pupil position will be positioned on the image side in the entire zoom lens system. If the entrance pupil position is positioned on the image side, the diameter of the front lens increases, making it difficult to reduce the size of the zoom lens. Further, in this case, it becomes difficult to allow off-axis light beams to pass through sufficiently, and it becomes difficult to increase the diameter of the zoom lens while ensuring the amount of peripheral light.

When one or more lens groups are arranged between the first lens group and the lens group Pa, the distance between the lens surface of the first lens group closest to the image side and the lens surface of the lens group Pa closest to the object side The aperture stop may be placed in between, and the position of the aperture stop in this space is not particularly limited. If an aperture stop is arranged between the lens group Pa and the lens group arranged on the object side of the lens group Pa, it is more preferable to obtain the above effect.

(5) Operation during zooming In the zoom lens, zooming is performed by changing the distance between adjacent lens groups on the optical axis. At this time, as described above, the lens group Pa and the lens group Pb are assumed to move along the same trajectory during zooming. Except for this point, the direction and amount of movement of each lens group during zooming are not particularly limited. If the distance between adjacent lens groups on the optical axis changes, each lens group may be a movable group that moves along the optical axis during zooming, or it may be fixed with respect to the image plane. It may be a fixed group.

1-2. Conditional Expressions It is preferable that the zoom lens adopts the configuration described above and satisfies one or more of the following conditional expressions.

1-2-1. Conditional expression (1)
0.2<(Rnf+Rnr)/(Rnf−Rnr)<1.3 (1)
however,
Rnf: radius of curvature of the lens surface closest to the object side in the lens group N Rnr: radius of curvature of the lens surface closest to the image side in the lens group N

Conditional expression (1) defines the shapes of the entrance surface and the exit surface of the lens group N. As shown in FIG. By satisfying conditional expression (1), it is possible to satisfactorily correct spherical aberration during zooming. In addition, when the lens group N is used as a focusing group, fluctuations in spherical aberration when focusing on a near object can be suppressed, and a zoom lens with high optical performance over the entire focusing range can be realized. can.

On the other hand, when the numerical value of conditional expression (1) is equal to or less than the lower limit, the effect of bouncing up the rays converged by the lens group Pa on the incident surface of the lens group N increases. In this case, spherical aberration fluctuates greatly during zooming and focusing. Therefore, in order to obtain a zoom lens with high optical performance, lens group Pa and lens group Pb must be moved along the same trajectory during zooming. becomes difficult. As a result, the lens group Pa and the lens group Pb cannot be configured as a single unit, and the mechanism for moving each lens group during zooming becomes complicated, and the structure of the lens barrel also becomes complicated. It becomes difficult to miniaturize the entire lens unit. On the other hand, when the numerical value of conditional expression (1) exceeds the upper limit, the effect of bouncing off-axis rays on the exit surface of the lens group N increases. In this case, fluctuations in curvature of field and distortion increase during zooming and focusing. Therefore, the lens group Pa and the lens group Pb cannot be moved along the same trajectory during zooming, and for the same reason as above, it becomes difficult to reduce the size of the zoom lens unit as a whole.

To obtain the above effects, the lower limit of conditional expression (1) is preferably 0.3, more preferably 0.35, and even more preferably 0.4. The upper limit of conditional expression (1) is preferably 1.2, more preferably 1.1, and even more preferably 1.0. In the conditional expression (1), preferable numerical values for the above lower limit and upper limit can be selected as appropriate, and in that case, the inequality sign (<) in the conditional expression (1) is converted to an inequality sign with an equal sign (≤). You may The same applies to other conditional expressions.

1-2-2. Conditional expression (2)
-4.0 < fn/fw < -1.5 (2)
however,
fn: focal length of lens group N fw: focal length of the zoom lens at the wide-angle end

Conditional expression (2) defines the ratio between the focal length of the lens group N and the focal length of the zoom lens at the wide-angle end. By satisfying the conditional expression (2), the refractive power of the lens group N is within an appropriate range, and the amount of movement of the lens group N during zooming can be within an appropriate range. A zoom lens with high optical performance over the entire range can be realized.

On the other hand, if the numerical value of conditional expression (2) is equal to or less than the lower limit, the refractive power of the lens group N becomes weak. It is necessary to increase the amount of movement of . Therefore, it becomes difficult to reduce the size of the zoom lens while maintaining high optical performance, which is not preferable. On the other hand, when the numerical value of conditional expression (2) is equal to or greater than the upper limit, the refractive power of the lens group N increases, and the amount of movement of the lens group N during zooming can be reduced. However, when the refractive power of the lens group N increases, aberration fluctuations accompanying movement of the lens group N increase. In order to obtain a zoom lens with high optical performance, it becomes difficult to move the lens group Pa and the lens group Pb along the same trajectory during zooming. become difficult.

To obtain the above effect, the lower limit of conditional expression (2) is preferably -3.8, more preferably -3.6, and even more preferably -3.4. The upper limit of conditional expression (2) is preferably -1.7, more preferably -1.9, and even more preferably -2.1.

1-2-3. Conditional expression (3)
−2.0 < (1−βnw ² )×βrw ² < −1.2 (3)
however,
βnw: Lateral magnification of the lens group N at the wide-angle end βrw: Combined lateral magnification of all lens groups located closer to the image side than the lens group N at the wide-angle end

Conditional expression (3) is an expression for defining the sensitivity of the lens group N. Here, the sensitivity represents the amount of movement of the imaging plane when the lens group moves by a unit amount. When the lens group N is used as a focusing group, by satisfying the conditional expression (3), the amount of movement of the lens group N when focusing from infinity to a close object can be kept within an appropriate range, It becomes easy to implement quick autofocus and to miniaturize the zoom lens.

On the other hand, when the numerical value of conditional expression (3) is equal to or less than the lower limit, the sensitivity of the lens group N increases. Therefore, when the lens group N is used as a focusing group, the amount of movement of the lens group N when focusing on a near object becomes small. must be done. On the other hand, if the numerical value of conditional expression (3) is equal to or greater than the upper limit, the sensitivity of the lens group N becomes low. The amount of movement of the lens group N increases. Therefore, it becomes difficult to reduce the size of the zoom lens.

To obtain the above effects, the lower limit of conditional expression (3) is preferably -1.9, more preferably -1.85, and even more preferably -1.8. The upper limit of conditional expression (3) is preferably -1.3, more preferably -1.35, and even more preferably -1.4.

1-2-4. Conditional expression (4)
vdn > 50 (4)
however,
vdn: when the single lens unit consists of a single lens, the Abbe number of the single lens with respect to the d-line; It refers to the Abbe number at the d-line of the lens having the largest negative refractive power.

Conditional expression (4) defines the Abbe number for the d-line of the single lens unit when the lens group N is composed of a single lens unit. As described above, when the single lens unit consists of a single lens, vdn means the Abbe number for the d-line of the single lens. When the single lens unit is composed of a cemented lens, vdn means the Abbe number for the d-line of the lens having the largest negative refractive power among the plurality of lenses constituting the cemented lens.

The occurrence of chromatic aberration in the lens group N can be suppressed by satisfying conditional expression (4). In a zoom lens, for example, longitudinal chromatic aberration can be well corrected at the wide-angle end, but lateral chromatic aberration increases. At the telephoto end, lateral chromatic aberration can be satisfactorily corrected, but longitudinal chromatic aberration increases. , it may be difficult to correct axial chromatic aberration and lateral chromatic aberration in a well-balanced manner. Satisfying conditional expression (4) facilitates well-balanced correction of both axial chromatic aberration and lateral chromatic aberration at both the wide-angle end and telephoto end. Furthermore, when the lens group N is used as the focusing group, it is possible to suppress the occurrence of axial chromatic aberration due to changes in the imaging distance, and to satisfactorily correct chromatic aberration over the entire focusing range.

On the other hand, if the numerical value of conditional expression (4) is equal to or less than the lower limit, the chromatic dispersion of the single lens unit constituting the lens group N becomes large, making it difficult to correct longitudinal chromatic aberration and lateral chromatic aberration in a well-balanced manner. become. Furthermore, if the lens group N is used as a focusing group to focus on a close object, correction of longitudinal chromatic aberration becomes difficult, which is not preferable.

In order to obtain the above effect, the lower limit of conditional expression (4) is preferably 60, more preferably 65, and even more preferably 70. On the other hand, the above effect can be obtained by satisfying conditional expression (4), and the upper limit of conditional expression (4) need not be specified. However, a glass material with a large Abbe number is more expensive than a glass material with a small Abbe number. In order to correct chromatic aberration well, it is preferable to use a glass material with a large Abbe number, but the larger the Abbe number, the lower the cost-effectiveness. Therefore, from this point of view, the numerical value of conditional expression (4) is preferably 100 or less, more preferably 95, and even more preferably 85.

1-2-5. Conditional expression (5)
0.7<Ymax/BFw<1.6 (5)
however,
Ymax: Maximum image height of the zoom lens BFw: Air conversion length from the side closest to the image of the zoom lens to the imaging plane at the wide-angle end

Conditional expression (5) defines the ratio between the maximum image height of the zoom lens and the air conversion length from the side closest to the image of the zoom lens to the imaging plane at the wide-angle end. By satisfying the conditional expression (5), it is possible to secure an appropriate back focus for an interchangeable lens of an imaging device that employs an interchangeable lens system such as a mirrorless camera while miniaturizing and widening the angle of the zoom lens. can.

On the other hand, if the numerical value of conditional expression (5) is equal to or less than the lower limit, the back focus of the zoom lens becomes too long, making it difficult to reduce the size of the zoom lens. Further, in this case, the refractive power arrangement is of a retrofocus type at the wide-angle end, and the asymmetry becomes strong. Therefore, the barrel-shaped distortion generated on the object side becomes large. On the other hand, if the numerical value of conditional expression (5) is equal to or greater than the upper limit, the back focus of the zoom lens becomes too short, making it difficult to secure an appropriate back focus for the interchangeable lens.

To obtain the above effects, the lower limit of conditional expression (5) is preferably 0.75, more preferably 0.8, and even more preferably 0.85. Also, the upper limit of conditional expression (5) is preferably 1.55, more preferably 1.5, and even more preferably 1.45.

1-2-6. Conditional expression (6)
0.5<βpbt/βpbw<1.5 (6)
however,
βpbw: Lateral magnification of the lens group Pb at the wide-angle end βpbt: Lateral magnification of the lens group Pb at the telephoto end

Conditional expression (6) defines the ratio between the lateral magnification of the lens group Pb at the wide-angle end and the lateral magnification of the lens group Pb at the telephoto end. As described above, the ray height of the maximum off-axis luminous flux incident on the lens group Pb fluctuates with the zooming operation of the zoom lens. Therefore, by configuring the lens group Pb to include at least one aspherical surface and satisfying conditional expression (6), coma and curvature of field can be effectively corrected. A zoom lens with high optical performance can be realized.

On the other hand, when the numerical value of conditional expression (6) is equal to or less than the lower limit, or the numerical value of conditional expression (6) is equal to or greater than the upper limit, the maximum axis incident on lens group Pb at the wide-angle end and telephoto end The difference in ray height of the external luminous flux increases. Therefore, it becomes difficult to satisfactorily correct coma and curvature of field at both the wide-angle end and the telephoto end.

In order to obtain the above effect, the lower limit of conditional expression (6) is preferably 0.5, more preferably 0.6, and even more preferably 0.7. Also, the upper limit of conditional expression (6) is preferably 1.4, more preferably 1.3, and even more preferably 1.2.

2. Imaging Apparatus Next, an imaging apparatus according to the present invention will be described. An imaging device according to the present invention includes the zoom lens according to the present invention, and an imaging device provided on the image plane side of the zoom lens for converting an optical image formed by the zoom lens into an electrical signal. characterized by

Here, the imaging element or the like is not particularly limited, and a solid-state imaging element such as a CCD (Charge Coupled Device) sensor or a CMOS (Complementary Metal Oxide Semiconductor) sensor can also be used. The imaging device according to the present invention is suitable for imaging devices using these solid-state imaging devices, such as digital cameras and video cameras. Further, the imaging device may be a lens-fixed imaging device in which a lens is fixed to a housing, or may be a lens-exchangeable imaging device such as a single-lens reflex camera or a mirrorless single-lens camera. is of course.

The imaging apparatus includes an image processing unit that electrically processes captured image data acquired by a solid-state imaging device to change the shape of the captured image, and an image correction that is used to process the captured image data in the image processing unit. It is more preferable to have an image correction data holding unit for holding data, an image correction program, and the like. When the size of the zoom lens is reduced, the shape of the captured image formed on the imaging plane is likely to be distorted. At that time, the distortion correction data for correcting the distortion of the captured image shape is held in advance in the image correction data holding unit, and the image processing unit uses the distortion correction data held in the image correction data holding unit. , it is preferable to correct the distortion of the captured image shape. According to such an image pickup apparatus, it is possible to further reduce the size of the zoom lens, obtain an excellent captured image, and reduce the size of the entire image pickup apparatus.

Further, in the image pickup apparatus according to the present invention, the image correction data holding unit holds the magnification chromatic aberration correction data in advance, and the image processing unit uses the magnification chromatic aberration correction data held in the image correction data holding unit. , it is preferable to correct the chromatic aberration of magnification of the captured image. By correcting lateral chromatic aberration, that is, color distortion aberration, the image processing unit can reduce the number of lenses constituting the optical system. Therefore, according to such an image pickup apparatus, it is possible to further reduce the size of the zoom lens, obtain an excellent captured image, and reduce the size of the entire image pickup apparatus.

EXAMPLES Next, the present invention will be described in detail with reference to Examples. However, the present invention is not limited to the following examples.

(1) Optical Configuration of Zoom Lens FIG. 1 is a lens sectional view showing the lens configuration of a zoom lens of Example 1 according to the present invention. In FIG. 1, the upper stage shows the state at the wide-angle end, the middle stage the state at the intermediate focal length, and the lower stage the state at the telephoto end.

The zoom lens includes, 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 positive refractive power, and a negative lens group G3. and a fifth lens group G5 having a positive refractive power. Magnification is changed by changing the distance between adjacent lens groups on the optical axis. An aperture stop S is arranged on the object side of the third lens group G3. In this embodiment, the third lens group G3 corresponds to the lens group Pa referred to in the present invention, the fourth lens group G4 corresponds to the lens group N referred to in the present invention, and the fifth lens group G5 corresponds to the lens group Pb referred to in the present invention. is.

The configuration of each lens group will be described below. The first lens group G1 is composed of, in order from the object side, a negative meniscus lens concave on the image side, a negative meniscus lens concave on the image side, a biconcave lens, and a biconvex lens.

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

The third lens group G3 includes, in order from the object side, an aperture diaphragm S, a cemented lens in which a biconvex lens and a negative meniscus lens having a concave shape on the object side are cemented together, and a negative meniscus lens and a biconvex lens in a concave shape on the image side. It consists of a cemented lens and a cemented lens.

The fourth lens group G4 is composed of a negative meniscus lens concave on the image side.

The fifth lens group G5 is composed of, in order from the object side, a biconvex lens, a biconcave lens, and a negative meniscus lens concave on the object side.

In the zoom lens of Example 1, when zooming from the wide-angle end to the telephoto end, the first lens group G1 moves toward the image side, the second lens group G2 moves toward the object side, and the third lens group G2 moves toward the image plane. The group G3 and the fifth lens group G5 move on the same locus toward the object side, and the fourth lens group G4 moves toward the object side. Also, when focusing on a close object from infinity, the fourth lens group G4 moves toward the image side.

"IP" shown in FIG. 1 is an imaging plane, and specifically represents an imaging plane of a solid-state imaging device such as a CCD sensor or a CMOS sensor, or a film plane of a silver halide film. A parallel flat plate having no substantial refractive power, such as a cover glass CG, is provided on the object side of the imaging plane IP. Since these points are the same in each lens cross-sectional view shown in other embodiments, description thereof will be omitted below.

(2) Numerical Examples Next, numerical examples to which specific numerical values of the zoom lens are applied will be described. Table 1 shows surface data of the zoom lens. In Table 1, "surface number" is the order of the lens surfaces counted from the object side, "r" is the radius of curvature of the lens surface, "d" is the distance between the lens surfaces on the optical axis, and "nd" is the d-line (wavelength λ=587.6 nm), and “vd” indicates the Abbe number for the d-line. "*" displayed next to the surface number indicates that the lens surface is aspheric, and "S" indicates the aperture stop. Furthermore, "D1", "D2", etc. in the column of the distance between the lens surfaces on the optical axis are variable distances in which the distance between the lens surfaces on the optical axis changes during zooming or focusing. means that The unit of length in each table is all "mm", and the unit of angle of view is "°". Also, "∞" in the column of radius of curvature means a plane. The 30th and 31st surfaces in Table 1 are the surface data of the cover glass CG.

Table 2 shows the aspheric coefficients of each aspheric surface. The aspherical surface coefficient is a value when each aspherical surface shape is defined by the following equation.

X(Y)= ^CY2 /[1+{1-( ¹ +Κ)・^C2Y2 } ^1/2 ]+A4・^Y4 +A6・^Y6 +A8・^Y8 +A10・^Y10 + A12・^Y12

However, in Table 2, "Ea" indicates "×10 ^-a ". In the above formula, "X" is the amount of displacement from the reference plane in the direction of the optical axis, "C" is the curvature at the surface vertex, "Y" is the height from the optical axis in the direction perpendicular to the optical axis, " K” is the conic coefficient, and “An” is the n-th order aspheric coefficient.

Table 3 shows the wide-angle end, intermediate focal length state, focal length at the telephoto end, Fno, angle of view, and variable spacing on the optical axis of the zoom lens when focused on infinity. As shown in Table 3, this zoom lens is a bright large-aperture lens with an angle of view of about 112° at the wide-angle end and an Fno of 2.90.

Table 4 shows the variable distances on the optical axis at the wide-angle end, the intermediate focal length state, and the telephoto end when focusing on a close object (focusing at a finite distance) when the shooting distance (imaging distance) is 280.0 mm. show.

Table 5 shows the focal length of each lens group that constitutes the zoom lens. Table 26 shows the values of conditional expressions (1) to (6) and the values used in the calculations of conditional expressions (1) to (6). Matters related to these tables are the same for each table shown in other embodiments, so the description is omitted below.

[Table 1]
Face number rd nd vd
1 84.508 1.800 1.72916 54.09
2 21.420 5.014
3* 47.143 2.500 1.69350 53.19
4* 18.764 11.069
5 -39.543 1.200 1.49700 81.61
6 50.299 0.200
7 39.196 7.061 1.59551 39.24
8-62.864 (D1)
9 46.823 5.753 1.48749 70.24
10 -28.360 1.000 1.90525 35.04
11 2144.120 0.200
12 41.043 3.518 1.74077 27.79
13-1112.850 (D2)
14S ∞ 1.000
15* 66.725 0.300 1.51460 49.96
16 173.315 7.374 1.63854 55.38
17 -18.559 1.000 1.83481 42.74
18 -39.208 0.200
19 52.060 1.000 1.83481 42.74
20 18.291 8.881 1.49700 81.61
21 -27.927 (D3)
22 27261.500 0.800 1.48749 70.24
23 25.712 (D4)
24 28.722 7.956 1.43700 95.10
25 -21.103 0.200
26 -47.037 1.000 1.72916 54.09
27 46.722 3.852
28* -131.078 1.800 1.85108 40.12
29* ∞ (D5)
30 ∞ 2.500 1.51680 64.17
31 ∞ 1.000

[Table 2]
Surface number k A4 A6 A8 A10 A12
3 -1.7301 2.91775E-05 -6.99735E-08 2.00903E-10 -3.35129E-13 2.35090E-16
4 -0.0660 1.51401E-05 -7.60478E-08 2.16156E-12 2.15621E-13 -1.48774E-15
15 0.0000 -2.44834E-05 -2.41951E-09 8.41905E-11 -4.63377E-13 1.58082E-15
28 0.0000 -9.57917E-05 -1.44295E-07 2.66649E-09 -1.59355E-11 5.63130E-15
29 0.0000 -6.18944E-05 -2.80254E-08 2.84367E-09 -1.67632E-11 3.29353E-14

[Table 3]
(When focusing on infinity)
Wide-angle end Intermediate Telephoto end focal length 15.454 21.199 29.106
Fno 2.90 2.90 2.90
Angle of view 111.748 91.720 72.321
D1 24.598 11.875 2.000
D2 7.940 3.909 1.000
D3 1.993 2.234 3.704
D4 6.955 6.714 5.244
D5 14.266 21.491 29.188

[Table 4]
(at finite distance focusing)
Wide-angle end Middle Telephoto end shooting distance 280.0 280.0 280.0
D3 2.838 3.417 5.483
D4 6.109 5.531 3.465

[Table 5]
Group surface number range Focal length
G1 1-8 -23.366
G2 9-13 72.135
G3 14-21 31.548
G4 22-23 -52.795
G5 24-29 2430.99
CG 30-31 ∞

2 to 4 show longitudinal aberration diagrams of the zoom lens of Example 1 at the wide-angle end, the intermediate focal length state, and the telephoto end when focusing on infinity. The longitudinal aberration diagrams shown in each figure are spherical aberration (mm), astigmatism (mm), and distortion (%) in order from the left side of the drawing. In the graph showing spherical aberration, the vertical axis is the ratio to the maximum F-number, and the horizontal axis is defocus. shows spherical aberration at . In the figure representing astigmatism, the vertical axis represents the half angle of view (ω) and the horizontal axis represents the defocus. show. In the diagrams representing distortion, the vertical axis represents the half angle of view (ω) and the horizontal axis represents %. Matters relating to these longitudinal aberration diagrams are the same for the longitudinal aberration diagrams shown in other examples, and therefore description thereof will be omitted below.

(1) Optical Configuration of Zoom Lens FIG. 5 is a lens sectional view showing the lens configuration of the zoom lens of Example 2 according to the present invention. The zoom lens includes, 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 positive refractive power, and a negative lens group G3. and a fifth lens group G5 having a positive refractive power. Magnification is changed by changing the distance between adjacent lens groups on the optical axis. An aperture stop S is arranged on the object side of the third lens group G3. In this embodiment, the third lens group G3 corresponds to the lens group Pa referred to in the present invention, the fourth lens group G4 corresponds to the lens group N referred to in the present invention, and the fifth lens group G5 corresponds to the lens group Pb referred to in the present invention. is.

The configuration of each lens group will be described below. The first lens group G1 is composed of, in order from the object side, a negative meniscus lens concave on the image side, a negative meniscus lens concave on the image side, a biconcave lens, and a biconvex lens.

The second lens group G2 consists of, in order from the object side, a positive meniscus lens convex on the object side, a cemented lens in which a negative meniscus lens concave on the image side and a positive meniscus lens convex on the object side are cemented together. be done.

The third lens group G3 is composed of, in order from the object side, an aperture stop S, a biconvex lens, and a cemented lens in which a concave negative meniscus lens and a biconvex lens are cemented together on the image side.

The fourth lens group G4 is composed of a biconcave lens.

The fifth lens group G5 is composed of, in order from the object side, a biconvex lens, a biconcave lens, and a negative meniscus lens concave on the object side.

In the zoom lens of Example 2, when zooming from the wide-angle end to the telephoto end, the first lens group G1 moves toward the image side, the second lens group G2 moves toward the object side, and the third lens group G2 moves toward the image plane. The group G3 and the fifth lens group G5 move on the same locus toward the object side, and the fourth lens group G4 moves toward the object side. Also, when focusing on a close object from infinity, the fourth lens group G4 moves toward the image side.

(2) Numerical Examples Next, numerical examples to which specific numerical values of the zoom lens are applied will be described. Table 6 shows surface data of the zoom lens. Table 7 shows the aspheric coefficients of each aspheric surface. Table 8 shows the wide-angle end, intermediate focal length state, focal length at the telephoto end, Fno, angle of view, and variable spacing on the optical axis of the zoom lens when focused on infinity. As shown in Table 8, this zoom lens is a bright large-aperture lens with an angle of view of approximately 105° at the wide-angle end and an Fno of 2.90.

Table 9 shows the variable distances on the optical axis at the wide-angle end, intermediate focal length state, and telephoto end when focusing on a close object (focusing at a finite distance) when the shooting distance (image pickup distance) is 280.0 mm. show. Table 10 shows the focal length of each lens group constituting the zoom lens. Table 26 shows the values of conditional expressions (1) to (6) and the values used in the calculations of conditional expressions (1) to (6).

Further, FIGS. 6 to 8 show longitudinal aberration diagrams of the zoom lens of Example 2 at the wide-angle end, the intermediate focal length state, and the telephoto end when focusing on infinity.

[Table 6]
Face number rd nd vd
1 93.140 1.800 1.72916 54.09
2 21.226 4.511
3* 51.960 2.500 1.69350 53.19
4* 21.333 10.232
5 -74.933 1.200 1.49700 81.61
6 60.640 0.200
7 36.298 5.351 1.63980 34.47
8-568.284 (D1)
9 44.099 2.450 1.62004 36.26
10 94.831 0.200
11 31.988 1.000 1.90525 35.04
12 19.107 5.964 1.51742 52.43
13 135.264 (D2)
14S ∞ 1.000
15* 21.713 6.118 1.61875 63.73
16* -112.880 0.200
17 63.220 1.000 1.83481 42.74
18 15.006 9.382 1.43700 95.10
19 -31.682 (D3)
20 -148.201 0.800 1.48749 70.24
21 23.890 (D4)
22 27.433 7.896 1.49700 81.61
23 -23.231 0.200
24 -44.279 1.000 1.51633 64.14
25 32.589 4.898
26* -209.427 1.800 1.80604 40.74
27* ∞ (D5)
28 ∞ 2.500 1.51680 64.17
29 ∞ 1.000

[Table 7]
Surface number k A4 A6 A8 A10 A12
3 -1.1370 4.48965E-05 -1.44818E-07 4.30024E-10 -6.07926E-13 2.27321E-16
4 0.3201 3.62198E-05 -1.40519E-07 4.07174E-11 1.32161E-12 -4.88514E-15
15 0.0000 -7.22219E-06 6.91089E-10 -5.40334E-11 9.44001E-13 -4.80746E-15
16 0.0000 1.37264E-05 -5.60616E-09 -2.57615E-11 5.07729E-13 -3.54696E-15
26 0.0000 -1.25954E-04 1.90283E-08 -1.39817E-10 6.95165E-12 -2.46050E-14
27 0.0000 -1.00330E-04 1.47696E-07 6.19499E-11 4.61917E-12 -1.43308E-14

[Table 8]
(When focusing on infinity)
Wide-angle end Intermediate Telephoto end focal length 17.515 24.408 33.955
Fno 2.90 2.90 2.90
Angle of view 105.020 83.104 63.722
D1 19.637 10.062 2.836
D2 17.168 7.930 1.567
D3 2.809 1.990 2.975
D4 4.684 5.503 4.518
D5 12.500 21.405 30.434

[Table 9]
(at finite distance focusing)
Wide-angle end Middle Telephoto end shooting distance 280.0 280.0 280.0
D3 3.958 3.598 5.486
D4 3.536 3.895 2.007

[Table 10]
Group surface number range Focal length
G1 1-8 -24.518
G2 9-13 80.465
G3 14-19 31.126
G4 20-21-42.139
G5 22-27 100.585
CG 28-29 ∞

(1) Optical Configuration of Zoom Lens FIG. 9 is a lens sectional view showing the lens configuration of the zoom lens of Example 3 according to the present invention. The zoom lens includes, 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 positive refractive power, and a negative lens group G3. and a fifth lens group G5 having a positive refractive power. Magnification is changed by changing the distance between adjacent lens groups on the optical axis. The aperture stop S is located closest to the image side in the second lens group G2. In this embodiment, the third lens group G3 corresponds to the lens group Pa referred to in the present invention, the fourth lens group G4 corresponds to the lens group N referred to in the present invention, and the fifth lens group G5 corresponds to the lens group Pb referred to in the present invention. is.

The configuration of each lens group will be described below. The first lens group G1 is composed of, in order from the object side, a negative meniscus lens concave on the image side, a negative meniscus lens concave on the image side, a biconcave lens, and a biconvex lens.

The second lens group G2 is composed of a cemented lens in which a negative meniscus lens having a concave shape on the image side and a positive meniscus lens having a convex shape on the object side are cemented together, and an aperture stop S in order from the object side.

The third lens group G3 is composed of, in order from the object side, a biconvex lens and a cemented lens in which a concave negative meniscus lens and a biconvex lens are cemented together on the image side.

The fourth lens group G4 is composed of a biconcave lens.

The fifth lens group G5 is composed of, in order from the object side, a biconvex lens and a biconcave lens.

In the zoom lens of Example 3, when zooming from the wide-angle end to the telephoto end, the first lens group G1 moves toward the image side, the second lens group G2 moves toward the object side, and the third lens group G2 moves toward the image plane. The group G3 and the fifth lens group G5 move on the same locus toward the object side, and the fourth lens group G4 moves toward the object side. Also, when focusing on a close object from infinity, the fourth lens group G4 moves toward the image side.

(2) Numerical Examples Next, numerical examples to which specific numerical values of the zoom lens are applied will be described. Table 11 shows surface data of the zoom lens. Table 12 shows the aspheric coefficients of each aspheric surface. Table 13 shows the wide-angle end, intermediate focal length state, focal length at the telephoto end, Fno, angle of view, and variable spacing on the optical axis of the zoom lens when focused on infinity. As shown in Table 13, this zoom lens is a bright large-aperture lens with an angle of view of approximately 105° at the wide-angle end and an Fno of 2.90.

Table 14 shows the variable distances on the optical axis at the wide-angle end, the intermediate focal length state, and the telephoto end when focusing on a close object (when focusing at a finite distance) when the shooting distance (image pickup distance) is 280.0 mm. show. Table 15 shows the focal length of each lens group constituting the zoom lens. Table 26 shows the values of conditional expressions (1) to (6) and the values used in the calculations of conditional expressions (1) to (6).

10 to 12 show longitudinal aberration diagrams of the zoom lens of Example 3 at the wide-angle end, the intermediate focal length state, and the telephoto end when focusing on infinity.

[Table 11]
Surface data surface number rd nd vd
1 68.881 1.800 1.72916 54.09
2 18.656 4.280
3* 47.831 2.500 1.69350 53.19
4* 20.068 12.165
5 -45.944 1.200 1.49700 81.61
6 44.215 0.200
7 33.452 5.233 1.60342 38.03
8-86.321 (D1)
9 25.013 1.000 1.90525 35.04
10 16.314 5.897 1.51742 52.43
11 2220.950 3.390
12S∞ (D2)
13* 23.283 0.299 1.51460 49.96
14 26.502 4.725 1.61800 63.39
15 -139.154 0.200
16 46.633 1.000 1.83481 42.74
17 15.289 7.185 1.43700 95.10
18 -43.777 (D3)
19 -61.398 0.800 1.48749 70.24
20 26.165 (D4)
21 25.333 7.948 1.49700 81.61
22 -22.994 3.029
23* -115.326 1.800 1.80604 40.74
24* 36.583 (D5)
25 ∞ 2.500 1.51680 64.17
26 ∞ 1.000

[Table 12]
Surface number k A4 A6 A8 A10 A12
3 -0.2625 6.61122E-05 -3.10824E-07 1.40182E-09 -3.23112E-12 2.64667E-15
4 0.6163 5.60801E-05 -3.38331E-07 7.52862E-10 2.41690E-12 -2.11262E-14
13 0.0000 -1.41507E-05 -1.13717E-08 -7.49395E-12 -5.25011E-14 6.74832E-16
23 0.0000 -1.10423E-04 6.49873E-07 -3.58914E-09 8.50912E-12 -2.25147E-14
24 0.0000 -7.37204E-05 7.72062E-07 -4.17146E-09 1.24066E-11 -2.09504E-14

[Table 13]
(When focusing on infinity)
Wide-angle end Intermediate Telephoto end focal length 17.511 21.801 27.163
Fno 2.90 2.90 2.90
Angle of view 104.963 90.082 76.129
D1 14.268 7.625 2.021
D2 6.709 3.302 1.000
D3 2.220 2.000 2.640
D4 4.792 5.012 4.372
D5 18.861 24.230 29.502

[Table 14]
(at finite distance focusing)
Wide-angle end Middle Telephoto end shooting distance 280.0 280.0 280.0
D3 3.258 3.396 4.588
D4 3.754 3.616 2.423

[Table 15]
Group surface number range Focal length
G1 1-8 -23.142
G2 9-12 79.028
G3 13-18 32.240
G4 19-20 -37.523
G5 21-24 58.322
CG 25-26 ∞

(1) Optical Configuration of Zoom Lens FIG. 13 is a lens sectional view showing the lens configuration of the zoom lens of Example 4 according to the present invention. The zoom lens includes, 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, and a positive lens group G3. and a fourth lens group G4 having a refractive power of . An aperture stop S is arranged in the second lens group G2. In this embodiment, the second lens group G2 corresponds to the lens group Pa referred to in the present invention, the third lens group G3 corresponds to the lens group N referred to in the present invention, and the fourth lens group G4 corresponds to the lens group Pb referred to in the present invention. is.

The configuration of each lens group will be described below. The first lens group G1 is composed of, in order from the object side, a negative meniscus lens concave on the image side, a negative meniscus lens concave on the image side, and a cemented lens in which a biconcave lens and a biconvex lens are cemented together.

The second lens group G2 includes, in order from the object side, a cemented lens obtained by cementing a negative meniscus lens concave to the image side and a biconvex lens, an aperture diaphragm S, a biconvex lens, a negative meniscus lens concave to the object side, and a biconvex lens. It is composed of a cemented lens in which biconvex lenses are cemented together.

The third lens group G3 is composed of a biconcave lens.

The fourth lens group G4 is composed of, in order from the object side, a cemented lens obtained by cementing a biconvex lens and a concave negative meniscus lens on the object side, and a biconcave lens.

In the zoom lens of Example 4, when zooming from the wide-angle end to the telephoto end, the first lens group G1 moves toward the image side with respect to the image plane, and the second lens group G2 and the fourth lens group G4 are the same. It moves to the object side along a trajectory, and the third lens group G3 moves to the object side. Also, when focusing on a close object from infinity, the third lens group G3 moves toward the image side.

(2) Numerical Examples Next, numerical examples to which specific numerical values of the zoom lens are applied will be described. Table 16 shows surface data of the zoom lens. Table 17 shows the aspheric coefficients of each aspheric surface. Table 18 shows the wide-angle end, intermediate focal length state, focal length at the telephoto end, Fno, angle of view, and variable spacing on the optical axis of the zoom lens when focused on infinity. As shown in Table 18, this zoom lens is a bright large-aperture lens with an angle of view of about 105° at the wide-angle end and an Fno of 2.90.

Table 19 shows the variable distances on the optical axis at the wide-angle end, the intermediate focal length state, and the telephoto end when focusing on a close object (when focusing at a finite distance) when the shooting distance (imaging distance) is 280.0 mm. show. Table 20 shows the focal length of each lens group constituting the zoom lens. Table 26 shows the values of conditional expressions (1) to (6) and the values used in the calculations of conditional expressions (1) to (6).

Further, FIGS. 14 to 16 show longitudinal aberration diagrams of the zoom lens of Example 4 at the wide-angle end, the intermediate focal length state, and the telephoto end when focusing on infinity.

[Table 16]
Surface data surface number rd nd vd
1 46.388 1.350 1.95375 32.32
2 20.000 3.869
3* 42.449 1.700 1.69350 53.19
4* 18.079 15.488
5 -30.445 0.800 1.59319 67.90
6 38.760 5.410 1.87070 40.73
7-50.478 (D1)
8* 36.319 0.150 1.51460 49.96
9 42.306 0.900 1.80610 33.27
10 25.854 4.533 1.57501 41.50
11 -98.531 1.000
12S ∞ 5.475
13 34.064 3.930 1.61800 63.39
14 -118.864 0.100
15 104.240 0.700 1.87070 40.73
16 17.006 7.120 1.49700 81.61
17 -28.456 (D2)
18 -108.828 0.700 1.72916 54.09
19 47.059 (D3)
20 27.423 8.223 1.59319 67.90
21 -13.423 0.900 1.80400 46.53
22 -19.273 0.100
23* ∞ 1.878 1.85108 40.12
24* 19.138 (D4)
25 ∞ 2.500 1.51633 64.14
26 ∞ 1.000

[Table 17]
Surface number k A4 A6 A8 A10 A12
3 0.1532 4.95803E-05 -2.62829E-07 1.08144E-09 -2.38164E-12 1.94055E-15
4 0.1699 3.95986E-05 -2.68048E-07 4.25372E-10 1.79383E-12 -1.20306E-14
8 1.0000 -1.74604E-05 -2.01950E-08 1.59165E-11 -4.63944E-14 0.00000E+00
23 0.0000 -2.29594E-04 2.46435E-06 -2.29265E-08 1.27311E-10 -3.16258E-13
24 0.0000 -2.11389E-04 2.70152E-06 -2.51585E-08 1.38235E-10 -3.38539E-13

[Table 18]
(When focusing on infinity)
Wide-angle end Intermediate Telephoto end focal length 17.501 22.416 27.506
Fno 2.90 2.90 2.90
Angle of view 104.715 87.717 74.984
D1 19.714 8.547 1.200
D2 2.197 2.841 3.454
D3 4.586 3.942 3.329
D4 21.676 26.366 31.175

[Table 19]
(at finite distance focusing)
Wide-angle end Middle Telephoto end shooting distance 280.0 280.0 280.0
D2 3.087 4.064 5.052
D3 3.696 2.719 1.732

[Table 20]
Group surface number range Focal length
G1 1-7 -27.226
G2 8-17 26.563
G3 18-19 -44.971
G4 20-24 134.150
CG 25-26 ∞

(1) Optical Configuration of Zoom Lens FIG. 17 is a lens sectional view showing the lens configuration of the zoom lens of Example 5 according to the present invention. The zoom lens includes, 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 positive refractive power, and a negative lens group G3. A fourth lens group G4 having a refractive power of , a fifth lens group G5 having a positive refractive power, and a sixth lens group G6 having a negative refractive power. Magnification is performed by changing the interval. An aperture stop S is arranged on the object side of the third lens group G3. In this embodiment, the third lens group G3 corresponds to the lens group Pa referred to in the present invention, the fourth lens group G4 corresponds to the lens group N referred to in the present invention, and the fifth lens group G5 corresponds to the lens group Pb referred to in the present invention. is.

The configuration of each lens group will be described below. The first lens group G1 is composed of, in order from the object side, a negative meniscus lens concave on the image side, a negative meniscus lens concave on the image side, a biconcave lens, and a biconvex lens.

The second lens group G2 is composed of a cemented lens in which a concave negative meniscus lens and a biconvex lens are cemented to the image side in order from the object side.

The third lens group G3 is composed of, in order from the object side, an aperture stop S, a biconvex lens, and a cemented lens in which a concave negative meniscus lens and a biconvex lens are cemented together on the image side.

The fourth lens group G4 is composed of a negative meniscus lens concave on the image side.

The fifth lens group G5 is composed of, in order from the object side, a biconvex lens and a biconcave lens.

The sixth lens group G6 is composed of a negative meniscus lens concave on the image side.

In the zoom lens of Example 5, when zooming from the wide-angle end to the telephoto end, the first lens group G1 moves toward the image side, the second lens group G2 moves toward the object side, and the third lens group G2 moves toward the image plane. The group G3 and the fifth lens group G5 move on the same locus toward the object side, the fourth lens group G4 moves toward the object side, and the sixth lens group G6 is fixed. Also, when focusing on a close object from infinity, the fourth lens group G4 moves toward the image side.

(2) Numerical Examples Next, numerical examples to which specific numerical values of the zoom lens are applied will be described. Table 21 shows surface data of the zoom lens. Table 22 shows the aspheric coefficients of each aspheric surface. Table 23 shows the wide-angle end, intermediate focal length state, focal length at the telephoto end, Fno, angle of view, and variable spacing on the optical axis of the zoom lens when focused on infinity. As shown in Table 23, this zoom lens is a bright large-aperture lens with an angle of view of approximately 105° at the wide-angle end and an Fno of 2.90.

Table 24 shows the variable distances on the optical axis at the wide-angle end, the intermediate focal length state, and the telephoto end when focusing on a close object (when focusing at a finite distance) when the shooting distance (image pickup distance) is 280.0 mm. show. Table 25 shows the focal length of each lens group constituting the zoom lens. Table 26 shows the values of conditional expressions (1) to (6) and the values used in the calculations of conditional expressions (1) to (6).

18 to 20 show longitudinal aberration diagrams of the zoom lens of Example 5 at the wide-angle end, the intermediate focal length state, and the telephoto end when focusing on infinity.

[Table 21]
Surface data surface number rd nd vd
1 53.748 1.600 1.80400 46.53
2 18.140 4.135
3* 47.221 2.500 1.69350 53.19
4* 19.061 11.903
5 -39.991 1.000 1.49700 81.61
6 82.331 0.200
7 39.131 4.432 1.64769 33.79
8-93.122 (D1)
9 28.726 1.000 1.83481 42.74
10 16.822 5.801 1.51633 64.14
11-213.120 (D2)
12S ∞ 1.544
13* 26.594 4.922 1.59201 67.02
14 -116.740 2.890
15 43.588 1.000 1.83481 42.74
16 15.145 6.931 1.43700 95.10
17 -38.123 (D3)
18 252.707 0.800 1.48749 70.24
19 22.763 (D4)
20 29.495 7.648 1.49700 81.61
21 -19.479 0.200
22* -32.403 1.600 1.80139 45.45
23* 116.089 (D5)
24 204.014 1.200 1.48749 70.44
25 63.294 16.588
26 ∞ 2.500 1.51680 64.17
27 ∞ 1.000

[Table 22]
Surface number k A4 A6 A8 A10 A12
3 1.7035 7.76467E-05 -3.46756E-07 1.31752E-09 -2.53243E-12 1.06503E-15
4 0.5112 7.32281E-05 -3.21519E-07 -2.99448E-11 7.03942E-12 -3.60850E-14
13 0.0000 -9.19433E-06 -1.09305E-08 1.85619E-10 -1.13341E-12 3.09984E-15
22 0.0000 -8.26319E-07 -6.95253E-08 -2.57085E-09 2.84216E-11 -1.06783E-13
23 0.0000 3.11647E-05 -6.19614E-08 -1.39613E-09 1.63344E-11 -5.65753E-14

[Table 23]
(When focusing on infinity)
Wide-angle end Intermediate Telephoto end focal length 17.509 21.797 27.163
Fno 2.90 2.90 2.90
Angle of view 104.938 89.246 75.719
D1 18.978 10.161 4.090
D2 5.051 3.603 1.200
D3 1.930 2.589 2.183
D4 5.614 4.956 5.361
D5 2.032 6.221 12.295

[Table 24]
(at finite distance focusing)
Wide-angle end Middle Telephoto end Shooting distance 280.000 280.000 280.000
D3 3.133 4.225 4.341
D4 4.412 3.320 3.204

[Table 25]
Group surface number range Focal length
G1 1-8 -23.679
G2 9-11 78.642
G3 12-17 33.498
G4 18-19 -51.374
G5 20-23 86.050
G6 24-25-188.761
CG 30-31 ∞

[Table 26]
Example 1 Example 2 Example 3 Example 4 Example 5
Conditional expression (1) 1.002 0.722 0.402 0.396 1.198
Conditional expression (2) -3.416 -2.406 -2.143 -2.570 -2.934
Conditional expression (3) -1.697 -1.570 -1.591 -1.781 -1.399
Conditional expression (4) 70.235 70.235 70.235 54.094 70.235
Conditional expression (5) 1.279 1.428 1.006 0.889 1.125
Conditional expression (6) 0.993 0.729 0.514 0.892 0.818
fn -52.795 -42.139 -37.523 -44.971 -51.374
fw 15.454 17.515 17.511 17.501 17.509
βnw 1.806 2.162 3.511 2.275 1.926
βrw 0.866 0.654 0.375 0.653 0.719
BFw 16.914 15.148 21.509 24.325 19.236
Ymax 21.633 21.633 21.633 21.633 21.633
βpbw 0.866 0.654 0.375 0.653 0.653
βpbt 0.860 0.476 0.193 0.583 0.534

According to the present invention, it is possible to provide a wide-angle zoom lens and an image pickup apparatus that are small in size and have high optical performance.

G1...first lens group G2...second lens group G3...third lens group G4...fourth lens group G5...fifth lens group G6...sixth lens group S ... Aperture diaphragm CG ... Cover glass IP ... Imaging plane

Claims (7)

Equipped with a first lens group having a negative refractive power on the most object side,
A lens group Pa having a positive refractive power, a lens group N having a negative refractive power, and a lens group Pb having a positive refractive power are provided on the image side of the first lens group. A zoom lens that performs zooming by changing an interval on the optical axis,
the first lens group includes at least two meniscus lenses having a concave shape on the image side, at least one of which includes at least one aspherical surface;
The lens group Pa, the lens group N, and the lens group Pb are arranged adjacent to each other in this order from the object side, and the lens group Pa and the lens group Pb move along the same trajectory during zooming. ,
A zoom lens that satisfies the following conditions.
0.2<(Rnf+Rnr)/(Rnf-Rnr)<1.3 (1)
-4.0 < fn/fw < -1.5 (2)
−2.0 < (1−βnw ² )×βrw ² < −1.35 (3)
however,
Rnf: the radius of curvature of the lens surface closest to the object side in the lens group N Rnr: the radius of curvature of the lens surface closest to the image side in the lens group N fn: the focal length of the lens group N fw: the size of the zoom lens at the wide-angle end Focal length
βnw: Lateral magnification of the lens group N at the wide-angle end
βrw: Combined lateral magnification of all lens units located closer to the image side than the lens unit N at the wide-angle end 2. The zoom lens according to claim 1, wherein the lens unit N is moved along the optical axis toward the image side to focus from infinity to a close object. 3. The zoom lens according to claim 1, wherein an aperture is arranged between a lens surface of the first lens group closest to the image side and a lens surface of the lens group Pa closest to the object side. The lens group N is composed of one single lens or a single lens unit composed of a cemented lens in which a plurality of single lenses are integrated without an air gap,
4. The zoom lens according to any one of claims 1 to 3, which satisfies the following conditional expression.
vdn > 50 (4)
however,
vdn: when the single lens unit consists of a single lens, the Abbe number of the single lens with respect to the d-line; It refers to the Abbe number at the d-line of the lens having the largest negative refractive power. 5. The zoom lens according to any one of claims 1 to 4, wherein the following conditions are satisfied.
0.7<Ymax/BFw<1.6 (5)
however,
Ymax: Maximum image height of the zoom lens BFw: Air conversion length from the side closest to the image of the zoom lens to the imaging plane at the wide-angle end the lens group Pb includes at least one aspherical surface;
6. The zoom lens according to any one of claims 1 to 5, which satisfies the following conditional expression.
0.5<βpbt/βpbw<1.5 (6)
however,
βpbw: Lateral magnification of the lens group Pb at the wide-angle end βpbt: Lateral magnification of the lens group Pb at the telephoto end 7. A zoom lens according to any one of claims 1 to 6 , and an imaging device provided on the image side of the zoom lens for converting an optical image formed by the zoom lens into an electrical signal. An imaging device characterized by:

Images