JP2014228811A5 - - Google Patents

Description

Zoom lens and imaging device

  The present invention relates to a zoom lens and an imaging apparatus, and more particularly to a zoom lens and an imaging apparatus that are small and light and have a camera shake correction function.

  In a conventional zoom lens for a single-lens reflex camera or the like, an optical element related to the optical viewfinder is disposed, and thus it is necessary to secure a long flange back with respect to the focal length. Therefore, in the rear lens group arranged on the image plane side among the lens groups constituting the zoom lens, a lens group having a positive refractive power is arranged so as to ensure a back focus, and a lens design is performed. A long flange back was secured. However, in recent years, with the spread of digital still cameras and the like that capture images with a live view image displayed on a liquid crystal screen provided on the back surface of the imaging device body or the like for the downsizing of the imaging device body, an optical viewfinder has been developed. An imaging apparatus that is not provided is widely used. For this reason, the number of zoom lenses that do not require a long flange back has increased, and there is a demand for downsizing of the zoom lenses. In addition, in such a small zoom lens, zoom lenses suitable for moving image shooting have been proposed, such as those in which the focus group is reduced in size and those having an anti-vibration lens necessary for camera shake correction.

  In particular, in order to perform autofocus continuously at high speed, such as when shooting a movie, a part of the lens group (focus group) is vibrated at high speed in the direction of the optical axis (wobbling), while it is out of focus → focused. State → Create out-of-focus state, detect the signal component of a certain frequency band in the image area from the output signal of the image sensor, find the optimal position of the focus group in the in-focus state, and focus group at the optimal position It is conceivable to repeat a series of operations such as moving the. When introducing such wobbling, it is necessary to pay attention to the fact that in zoom lens design, the size of the image corresponding to the subject changes during wobbling. Such a zooming action at the time of focusing is due to the fact that the focal length of the entire lens system changes due to the focus group moving in the optical axis direction during wobbling. For example, when live view shooting is performed, if this zooming effect due to wobbling is large, the user feels uncomfortable. In order to reduce this feeling of incongruity, it is known that focusing is performed by a lens group behind the stop so as to be effective. In addition, in order to introduce wobbling and realize high-speed autofocus, it is indispensable to reduce the size and weight of the focus group.

  As described above, the zoom lens itself needs to be downsized in accordance with the recent downsizing of the imaging device body and the shortening of the flange back, and the outer diameter of the focus group so that the focus group can be driven at high speed. It is desired to reduce the weight as much as possible and to reduce its weight.

  Similarly, in the anti-vibration lens group, it is desirable to reduce the outer diameter of the anti-vibration lens group in order to reduce the effects of image degradation due to camera shake and to reduce the load on the anti-vibration drive system. It is rare.

  Under such a background, for example, Patent Document 1 proposes a wide-angle high-magnification zoom lens composed of positive, negative, positive and negative five-group lenses in order from the object side. Patent Document 2 describes a compact high-magnification zoom lens. In Example 7, a positive / negative / positive / negative optical system is proposed.

Japanese Patent No. 3958489 Japanese Patent No. 2773131

  By the way, in a conventional solid-state imaging device that receives an optical image and converts it into an electrical image signal, there is a limitation for efficiently capturing incident light with an on-chip microlens or the like. It has been desired to make the exit pupil larger than a certain level to ensure the telecentricity of the incident light beam to the solid-state imaging device. However, recent solid-state imaging devices have improved aperture ratios and advances in design flexibility of on-chip microlenses, and there are fewer restrictions on the exit pupil required on the lens side. For this reason, conventionally, various proposals have been made to secure telecentricity by arranging a lens group having a positive refractive power behind the zoom lens, but in recent years this has not been limited. For this reason, even when a lens group having negative refractive power is arranged behind the zoom lens and the light beam is obliquely incident on the solid-state image sensor, peripheral dimming (shading) due to a pupil mismatch with the on-chip microlens, etc. ) Has become less noticeable. Further, even if the distortion is large to some extent and is conspicuous in the prior art, it has become possible to correct it by image processing as the software and camera system advance and improve.

  The zoom lens described in Patent Document 1 focuses on correcting various aberrations including distortion aberration well while providing telecentricity. For this reason, as described above, the lens group having a positive refractive power is disposed behind the zoom lens. For example, the lens group is composed of positive, negative, positive and negative five group lenses in order from the object side. Compared with the case where it is left, it cannot be said that the zoom lens optical system described in Patent Document 1 has been sufficiently miniaturized. Also, the flange back is designed on the premise that it is used for a conventional single-lens reflex camera, and the entire length is long even on the surface where the back focus with respect to the entire length of the zoom lens is set long.

  The zoom lens described in Patent Document 2 is an invention relating to an optical system suitable for a film camera, although the optical system itself is compact. Is not what was made.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a zoom lens that is small as a whole and that can keep the change in photographing magnification due to wobbling small, and in particular, can reduce the load on the focus drive system by reducing the weight of the focus group lens system. There is.

  As a result of intensive studies, the present inventors have achieved the above-mentioned problem by employing the following zoom lens.

The zoom lens according to the present invention includes, in order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a negative refractive power. And a fifth lens group having negative refractive power, and when zooming from the wide-angle end to the telephoto end, the distance between the first lens group and the second lens group increases. In addition, the lens group moves so that the distance between the second lens group and the third lens group becomes small, and among all the lens groups, the negative lens group arranged on the image plane side from the stop is set as the focus group , The focus group consists of a single lens block with a meniscus shape whose concave surface is concave with respect to the image plane. When focusing from infinity to a close object, the focus group is moved to the image plane side. Focus by Characterized by satisfying the expression below.

  In the zoom lens according to the present invention, it is preferable that the following conditional expression is satisfied.

  In the zoom lens according to the present invention, it is preferable that the following conditional expression is satisfied.

  In the zoom lens according to the present invention, the third lens group includes at least an anti-vibration group composed of a single lens block, and performs image stabilization by moving the anti-vibration group in a direction perpendicular to the optical axis. It is preferable that the following conditional expression is satisfied.

  In the zoom lens according to the present invention, the fifth lens group includes at least a meniscus single lens block whose outermost surface is concave with respect to the object side, and the meniscus single lens block is negative. It is preferable that the following conditional expression is satisfied.

  An imaging apparatus according to the present invention includes the zoom lens described above, and an imaging element that converts an optical image formed by the zoom lens into an electrical signal on an image plane side.

  According to the present invention, it is possible to provide a zoom lens that is small as a whole and that can keep the change in photographing magnification due to wobbling small, and in particular, can reduce the load on the focus drive system by reducing the weight of the focus group lens system. it can.

It is a figure which shows the lens structural example of the zoom lens of Example 1 of this invention. The upper row is a lens configuration diagram at the wide-angle end, and the lower row is a lens configuration diagram at the telephoto end. FIG. 3 is a longitudinal aberration diagram of spherical aberration, astigmatism, and distortion aberration at the time of focusing on infinity in the wide-angle end state of the zoom lens according to Example 1 of the present invention. It is a longitudinal aberration diagram of spherical aberration, astigmatism, and distortion at the time of focusing on infinity in the intermediate focal length state of the zoom lens of Example 1 of the present invention. FIG. 4 is a longitudinal aberration diagram of spherical aberration, astigmatism, and distortion aberration at the time of focusing on infinity in the telephoto end state of the zoom lens according to Example 1 of the present invention. FIG. 3 is a lateral aberration diagram in the telephoto end state of the zoom lens according to the first embodiment of the present invention. It is a figure which shows the lens structural example of the zoom lens of Example 2 of this invention. The upper row is a lens configuration diagram at the wide-angle end, and the lower row is a lens configuration diagram at the telephoto end. FIG. 6 is a longitudinal aberration diagram of spherical aberration, astigmatism, and distortion in focusing on infinity in the wide-angle end state of the zoom lens according to Example 2 of the present invention. It is a longitudinal aberration diagram of spherical aberration, astigmatism, and distortion at the time of focusing on infinity in the intermediate focal length state of the zoom lens of Example 2 of the present invention. FIG. 6 is a longitudinal aberration diagram of spherical aberration, astigmatism, and distortion in focusing on infinity in the telephoto end state of the zoom lens according to Example 2 of the present invention. It is a lateral aberration figure in the telephoto end state of the zoom lens of Example 2 of the present invention. It is a figure which shows the lens structural example of the zoom lens of Example 3 of this invention. The upper row is a lens configuration diagram at the wide-angle end, and the lower row is a lens configuration diagram at the telephoto end. It is a longitudinal aberration diagram of spherical aberration, astigmatism, and distortion at the time of focusing on infinity in the wide-angle end state of the zoom lens according to Example 3 of the present invention. It is a longitudinal aberration diagram of spherical aberration, astigmatism, and distortion at the time of focusing on infinity in the intermediate focal length state of the zoom lens of Example 3 of the present invention. It is a longitudinal aberration diagram of spherical aberration, astigmatism, and distortion at the time of focusing on infinity in the telephoto end state of the zoom lens according to Example 3 of the present invention. It is a lateral aberration figure in the telephoto end state of the zoom lens of Example 3 of the present invention. It is a figure which shows the lens structural example of the zoom lens of Example 4 of this invention. The upper row is a lens configuration diagram at the wide-angle end, and the lower row is a lens configuration diagram at the telephoto end. It is a longitudinal aberration diagram of spherical aberration, astigmatism, and distortion at the time of focusing on infinity in the wide-angle end state of the zoom lens according to Example 4 of the present invention. It is a longitudinal aberration diagram of spherical aberration, astigmatism, and distortion at the time of focusing on infinity in the intermediate focal length state of the zoom lens of Example 4 of the present invention. It is a longitudinal aberration diagram of spherical aberration, astigmatism, and distortion at the time of focusing on infinity in the telephoto end state of the zoom lens according to Example 4 of the present invention. It is a lateral aberration figure in the telephoto end state of the zoom lens of Example 4 of the present invention. It is a figure which shows the lens structural example of the zoom lens of Example 5 of this invention. The upper row is a lens configuration diagram at the wide-angle end, and the lower row is a lens configuration diagram at the telephoto end. FIG. 10 is a longitudinal aberration diagram of spherical aberration, astigmatism, and distortion in focusing on infinity in the wide-angle end state of the zoom lens according to Example 5 of the present invention. It is a longitudinal aberration diagram of spherical aberration, astigmatism, and distortion at the time of focusing on infinity in the intermediate focal length state of the zoom lens of Example 5 of the present invention. It is a longitudinal aberration diagram of spherical aberration, astigmatism, and distortion at the time of focusing on infinity in the telephoto end state of the zoom lens according to Example 5 of the present invention. It is a lateral aberration figure in the telephoto end state of the zoom lens of Example 5 of the present invention.

  Embodiments of a zoom lens and an imaging apparatus according to the present invention will be described below.

1. Zoom lens 1-1. Configuration of Optical System First, the configuration and operation of the optical system of the zoom lens according to the present invention will be described. The zoom lens according to the present invention includes, in order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a negative refractive power. And a fifth lens group having negative refractive power, and when zooming from the wide-angle end to the telephoto end, the distance between the first lens group and the second lens group increases. In addition, the lens group moves so that the distance between the second lens group and the third lens group becomes small, and among all the lens groups, the negative lens group arranged on the image plane side from the stop is set as the focus group , The focus group consists of a single lens block with a meniscus shape whose concave surface is concave with respect to the image plane. When focusing from infinity to a close object, the focus group is moved to the image plane side. Focus by

  The zoom lens according to the present invention is a so-called telephoto type zoom lens, and the first to third lens groups are an object side group having a positive refractive power as a whole, and the fourth to fifth lens groups. The lens group is an image plane side group having a negative refractive power as a whole. In the present invention, by using the telephoto type zoom lens, it is possible to shorten the optical total length at the telephoto end of the zoom lens compared to the focal length at the telephoto end of the zoom lens. For this reason, for example, when the zoom ratio is increased to a focal length of more than 300 mm in terms of 35 mm film, an increase in the total optical length at the telephoto end can be suppressed.

  In the present invention, the telephoto zoom lens is used as described above, and the image side group includes at least a fourth lens group and a fifth lens group having negative refractive power. For this reason, as compared with a conventional zoom lens having a positive, negative, positive and negative five-group configuration, it is easy to increase the overall negative refractive power in the image side group. That is, since it becomes easy to make a zoom lens with a stronger telephoto tendency, it is possible to further shorten the optical total length at the telephoto end with respect to the focal length at the telephoto end even when the zoom ratio is increased.

  Here, in the zoom lens, one or more inner cylinders are generally accommodated in a telescopic manner in a lens barrel (outermost cylinder). The inner cylinder is drawn out to the object side according to the magnification. When the difference between the optical total lengths at the telephoto end and the wide-angle end is increased, a plurality of inner cylinders are accommodated in the outermost cylinder in order to shorten the entire length of the lens barrel when the inner cylinder is accommodated. However, when a plurality of inner cylinders are accommodated in the outermost cylinder, the diameter of the outermost cylinder increases by the thickness of the inner cylinder. Therefore, in the present invention, as described above, the zoom lens having a stronger telephoto tendency can suppress the increase in the total optical length at the telephoto end even when the zoom ratio is increased. An increase in the number of inner cylinders accommodated in the outer cylinder can be suppressed. Therefore, according to the present invention, not only the optical total length at the telephoto end but also the outer diameter of the lens barrel can be reduced.

1-2. Operation Next, focusing and zooming in the zoom lens having the above configuration will be described in order.

(1) Focusing (focusing operation)
First, focusing will be described. In the zoom lens according to the present invention, as described above, the negative lens group disposed on the image plane side of the stop among all the lens groups is a focus group, and when focusing from infinity to a close object, Focusing is performed by moving the focus group to the image plane side. By making the negative lens group arranged on the image plane side from the stop as a focus group and moving it to the image plane side, it is possible to suppress the occurrence of a zooming action due to wobbling during focusing. .

In addition, the negative lens group disposed on the image plane side of the stop, that is, the lens group behind the zoom lens having a relatively small diameter is used as the focus group, thereby reducing the weight of the lens system of the focus group and the focus drive system. Can reduce the load of high-speed autofocusing. At this time, from the viewpoint of reducing the weight of the focus group and realizing higher-speed autofocus, in the present invention, the focus group is constituted by the single lens block . Here, the single lens block may be a single lens or a cemented lens in which a plurality of lenses are cemented (hereinafter the same).

  The position of the stop (aperture stop) is generally disposed on the image plane side with respect to the second lens group, and in the present invention, it is also disposed on the image plane side with respect to the second lens group. The specific aperture position is not particularly limited, and can be appropriately arranged at an appropriate position according to required optical characteristics and the like. Further, regarding the focus group, any lens group may be used as long as it is a lens group having a negative refractive power disposed on the image plane side with respect to the stop. For example, it is preferable to dispose the stop closer to the image plane side than the second lens group and closer to the object side than the fourth lens group, and to set either the fourth lens group or the fifth lens group as the focus group. Which negative lens group is used as a focus group can be appropriately selected according to the specific lens configuration of the zoom lens.

  Here, in order to obtain a zoom lens having a strong telephoto tendency, as described above, it is required to increase the negative refractive power of the image side group. Conventionally, in a telephoto type zoom lens, it is generally performed that the refractive power of the fourth lens group is negative and the refractive power of the fifth lens group is positive. This is because of the necessity of ensuring telecentricity as described above. However, when the fourth lens group is a focus group, if the fourth lens group has a strong refractive power, when the fourth lens group is vibrated in the optical axis direction during focusing, aberrations occur due to this wobbling. Fluctuations and scaling effects occur. Therefore, in the present invention, a negative telephoto power is allocated to each of the fourth lens group and the fifth lens group constituting the image plane side group, thereby forming a zoom lens having a strong telephoto tendency, and configuring the image plane side group. Even when the negative lens group is a focus group, it is possible to suppress aberration fluctuations and zooming effects during focusing. For example, in an imaging apparatus that does not include an optical viewfinder such as a mirrorless single-lens camera, the user captures an image while confirming the image with a live view image displayed on a liquid crystal screen or the like provided on the back of the apparatus main body. . At this time, if the zoom lens according to the present invention is used, an image with high imaging performance can be displayed as a live view image while suppressing zooming or the like during focusing. Therefore, the zoom lens according to the present invention can be suitably used for an imaging apparatus such as a mirrorless single-lens camera.

(2) Zooming (zooming operation)
Next, zooming will be described. In the zoom lens according to the present invention, as described above, when zooming from the wide-angle end to the telephoto end, the distance between the first lens group and the second lens group becomes large, and the second lens group and the third lens group. As long as the lens group moves so that the interval between the lens group and the lens group moves, the specific operation of each lens group is not particularly limited. However, from the viewpoint of improving the degree of freedom of aberration correction and obtaining high imaging performance over the entire zoom range, the distance between the lens groups of the first lens group to the fifth lens group is changed at the time of zooming. It is preferable to move each lens group relatively. This is because by changing the distance between the lens groups at the time of zooming, it becomes easy to adjust the position of each lens group to a preferred position for aberration correction at each zooming ratio. At this time, by moving all the lens groups separately at the time of zooming, the interval between the lens groups may be changed, or a part of all the lens groups may be moved together and the remaining lens groups may be moved together. The lens group may be moved separately. Also, not all the lens groups may be moving groups, but some lens groups may be fixed groups.

(3) Anti-Vibration Operation In the zoom lens configured as described above, in the present invention, the third lens group is provided with an anti-vibration group consisting of a single lens block, and the anti-vibration group is moved in the direction perpendicular to the optical axis. Therefore, it is preferable that the camera shake correction can be performed. By placing the anti-vibration group in the third lens group and configuring the anti-vibration group with a single lens block, the anti-vibration group can be reduced in size and weight, reducing the load on the anti-vibration drive system. Can be made.

  The zoom lens according to the present invention described above is an aspect of the zoom lens according to the present invention, and the specific lens configuration and the like may be changed as appropriate without departing from the spirit of the present invention. Of course.

1-3. Conditional Expressions Next, conditional expressions that the zoom lens according to the present invention should satisfy or preferably satisfy are described. The zoom lens according to the present invention satisfies the following conditional expression (1) and conditional expression (5) to be described later, and satisfies conditional expressions (2) to (4) and conditional expression (6) to be described later. It is preferable to satisfy.

1-3-1. Conditional expression (1)
First, conditional expression (1) will be described. Conditional expression (1) defines the moving distance of the third lens unit with respect to the effective focal length of the entire lens system. In a zoom lens optical system having positive and negative groups in order from the object side, it is well known to move the positive third lens group to the object side at the telephoto end rather than the wide angle end in order to increase the zoom ratio. However, when the optical diaphragm is moved together with the third lens group at the time of zooming, there is a problem that the F number at the telephoto end becomes dark. Although it is conceivable to increase the aperture diameter of the optical stop so as not to darken, it is not desirable because the effective diameter near the optical stop is increased. In the present invention, as described above, in order to reduce the performance deterioration with respect to the design performance after assembly due to the influence of relative eccentricity or the like, and in order to simplify the mechanical configuration, Also proposed is a configuration in which the lens group and the fifth lens group move along the same locus. In this case, the third lens group to the fifth lens group are moved as a group by a cam or the like at the time of zooming, but the movement amount is reduced in order to reduce the increase in weight and the load to be moved. It is hoped to take. Therefore, conditional expression (1) stipulates that the amount of movement of the third lens group does not become too large in order to solve the above problem.

  From the above viewpoint, regarding the conditional expression (1), the numerical value is preferably within the range of the following (1a), and more preferably within the range of (1b).

−0.05 ≦ m3 / √ (fw × ft) ≦ 0.05 (1a)
−0.03 ≦ m3 / √ (fw × ft) ≦ 0.03 (1b)

1-3-2. Conditional expression (2)
Next, conditional expression (2) will be described. The zoom lens according to the present invention preferably satisfies the following conditional expression (2).

  Conditional expression (2) defines the focal length of the first lens group with respect to the effective focal length of the entire optical system of the zoom lens. Regarding conditional expression (2), when the numerical value falls below the lower limit, the refractive power of the first lens group is strong, so that there is a risk that performance degradation with respect to design performance will increase after assembly due to the influence of relative eccentricity or the like. If the numerical value exceeds the upper limit, the refractive power of the first lens group is weak, and it becomes difficult to shorten the total optical length particularly in the telephoto end state.

  From these viewpoints, regarding the conditional expression (2), the numerical value is preferably within the range of the following (2a), and more preferably within the range of (2b).

1.10 ≦ f1 / √ (fw × ft) ≦ 1.90 (2a)
1.20 ≦ f1 / √ (fw × ft) ≦ 1.70 (2b)

1-3-3. Conditional expression (3)
Next, conditional expression (3) will be described. The zoom lens according to the present invention preferably satisfies the following conditional expression (3).

  Conditional expression (3) defines the product of the lateral magnification at the wide-angle end of the fourth lens group and the lateral magnification at the wide-angle end of the fifth lens group. Regarding conditional expression (3), if the numerical value falls below the lower limit, it becomes difficult to shorten the focal length from the first lens group to the third lens group, and as a result, the optical total length in the wide-angle end state can be shortened. It becomes difficult. Further, when the numerical value exceeds the upper limit, the lateral magnification of the fourth lens group and the fifth lens group is large and the refractive power is strong, so that the performance degradation with respect to the design performance after assembly is large due to the influence of relative eccentricity or the like. Become.

  From these viewpoints, regarding the conditional expression (3), the numerical value is preferably within the range of the following (3a), and more preferably within the range of (3b).

1.40 ≦ β4W × β5W ≦ 3.30 (3a)
1.50 ≦ β4W × β5W ≦ 3.00 (3b)

1-3-4. Conditional expression (4)
Next, conditional expression (4) will be described. In the zoom lens according to the present invention, it is preferable that the following conditional expression (4) is satisfied when the third lens group includes the anti-vibration group. In this case, as described above, the image stabilizing group is configured by a single lens block, and performs camera shake correction by moving perpendicularly to the optical axis direction. It is preferable that it constitutes a part.

  Conditional expression (4) defines the ratio between the radius of curvature of the outermost object side surface of the image stabilizing group and the radius of curvature of the most image side surface of the image stabilizing group. Regarding conditional expression (4), if the numerical value falls below the lower limit value, the refractive power of the vibration-proofing group is strong, and therefore, decentration coma and decentering astigmatism when the vibration-proofing group is decentered increase. . If this value exceeds the upper limit, the refractive power of the anti-vibration group is weak, so the stroke of the anti-vibration group becomes large, the outer diameter of the lens barrel increases, and it is difficult to increase the drive speed of the anti-vibration group. Become.

  From these viewpoints, regarding the conditional expression (4), the numerical value is preferably within the range of the following (4a), and more preferably within the range of (4b).

−1.10 ≦ ra3 / rb3 ≦ −0.50 (4a)
−0.95 ≦ ra3 / rb3 ≦ −0.70 (4b)

1-3-5. Conditional expression (5)
Next, conditional expression (5) will be described. In the zoom lens according to the present invention, as described above, the focus group is configured by a single lens block from the viewpoints of realizing high-speed autofocus and reducing the size and weight of the zoom lens . At this time, the single lens block is assumed to be a single lens or a cemented lens having a meniscus shape with the concave facing the image plane side . In this case, the focus group satisfies the following conditional expression .

  Conditional expression (5) defines the ratio of the radius of curvature of the most object side surface to the radius of curvature of the most image side surface of the focus group when the focus group is composed of a single lens block having a meniscus shape. . Regarding conditional expression (5), if the numerical value falls below the lower limit value, the refractive power of the focus group becomes weak, and the focus stroke from the object at infinity to the closest object becomes large. This is not preferable in reducing the size of the device. If this value exceeds the upper limit, the refractive power of the focus group becomes strong, and the sensitivity to movement of the focus group on the optical axis, that is, the focus sensitivity becomes high, which makes it difficult to control the focus drive system. .

  From these viewpoints, regarding the conditional expression (5), the numerical value is preferably within the range of the following (5a), and more preferably within the range of (5b).

3.30 ≦ ra4 / rb4 ≦ 190.00 (5a)
3.50 ≦ ra4 / rb4 ≦ 170.00 (5b)

1-3-6. Conditional expression (6)
Next, conditional expression (6) will be described. Conditional expression (6) relates to the fifth lens group. In the zoom lens according to the present invention, it is preferable that the fifth lens group includes a single lens block having a meniscus shape having a concave object side surface. In this case, it is preferable that the meniscus single lens block has a negative focal length and satisfies the following conditional expression (6).

  When the fifth lens group includes a negative lens composed of a single lens block having a meniscus shape in which the most object side surface is concave with respect to the object side, the curvature of the most object side surface is satisfied. It defines the ratio between the radius and the radius of curvature of the side of the most image surface. Regarding conditional expression (6), if the numerical value falls below the lower limit, both surfaces become negative lenses having concave surfaces. Therefore, the side surface of the most image surface is not preferable because the illuminance of the ghost due to the multiple reflection with the image surface becomes high with the concave surface facing the image surface side. If this numerical value exceeds the upper limit value, the refractive power of the negative lens becomes strong, and various aberrations such as astigmatism and field curvature increase, and the fifth lens group is configured to correct this. Since the number of lenses increases, it becomes difficult to shorten the total optical length.

  From these viewpoints, regarding the conditional expression (6), the numerical value is preferably within the range of (6a) below, and more preferably within the range of (6b).

0.01 ≦ ra5 / rb5 ≦ 2.60 (6a)
0.02 ≦ ra5 / rb5 ≦ 2.20 (6b)

2. Next, an imaging apparatus according to the present invention will be described. An image pickup apparatus according to the present invention includes the zoom lens, and an image pickup device that converts an optical image formed by the zoom lens into an electric signal on the image plane side. Here, there is no limitation in particular in an image pick-up element. However, as described above, since the flange back of the zoom lens according to the present invention can be shortened, the zoom lens is suitable for an imaging apparatus that does not include an optical finder, a reflex mirror, or the like. In particular, since the zoom lens according to the present invention is small and can realize a high zoom ratio, it is preferable that the zoom lens is a small-sized imaging device equipped with a small solid-state imaging device such as a so-called mirrorless single-lens camera. In the present invention, since high-speed autofocus can be realized even in moving image shooting, it is also preferable to apply to an imaging apparatus capable of moving image shooting.

  Next, the present invention will be specifically described with reference to examples and comparative examples. However, the present invention is not limited to the following examples, and the lens configurations described in the following examples are merely examples of the present invention, and the lens configuration of the zoom lens according to the present invention departs from the spirit of the present invention. Of course, it can be appropriately changed within the range not to be.

  Next, the present invention will be specifically described with reference to examples and comparative examples. However, the present invention is not limited to the following examples.

  Embodiments of a zoom lens according to the present invention will be described with reference to the drawings. FIG. 1 is a diagram illustrating a lens configuration example of the zoom lens according to the first embodiment. The upper stage is a lens configuration diagram in the wide-angle end state, and the lower stage is a lens configuration diagram in the telephoto end state.

  First, the optical system of the zoom lens of Example 1 will be described with reference to the drawings. FIG. 1 is a diagram illustrating a lens configuration example of the zoom lens according to the first embodiment. The zoom lens of Example 1 has a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, a third lens group G3 having a positive refractive power, and a negative refractive power. The fourth lens group G4 includes a fifth lens group G5 having negative refractive power, and a stop S is disposed between the second lens group and the third lens group. The third lens group includes an anti-vibration group VC composed of a single positive lens, and the fourth lens group G4 is a cemented lens in which a positive lens having a meniscus shape having a concave surface on the image surface side and a negative lens are cemented. The fourth lens group G4 functions as the focus group F. Furthermore, a meniscus lens having a concave object side surface is disposed on the most object side of the fifth lens group. The specific lens configuration of each lens group is as shown in FIG.

  In the zoom lens of Example 1, when zooming from the wide angle end to the telephoto end, the first lens group G1, the third lens group G3, and the fifth lens group G5 are fixed with respect to the image plane. The other lens groups (G2, G4) move so that the distance between the lens group G1 and the second lens group G2 increases and the distance between the second lens group G2 and the third lens group G3 decreases. In focusing from an infinite distance to a short distance object, the fourth lens group moves to the image plane side.

  The amount of movement in the direction perpendicular to the optical axis of the image stabilizing group VC in the camera shake correction state at the telephoto end is 0.328 mm. The image decentering amount when the shooting distance is ∞ and the zoom lens system is tilted by 0.3 ° at the telephoto end is equal to the image decentering amount when the image stabilizing group is translated in a direction perpendicular to the optical axis. In the zoom lenses of Examples 2 to 9 as well, the amount of movement of each anti-vibration group in the direction perpendicular to the optical axis and the image decentration when the zoom lens system is tilted by 0.3 °. The amount is equal.

  2 to 4 show longitudinal aberration diagrams of spherical aberration, astigmatism, and distortion aberration at the time of focusing on infinity in the wide-angle end state, the intermediate focal length state, and the telephoto end state of the zoom lens according to the first embodiment. . Each longitudinal aberration diagram shows spherical aberration (SA (mm)), astigmatism (AST (mm)), and distortion (DIS (%)) in order from the left side. In the spherical aberration diagram, the vertical axis represents the F number (indicated by FNO in the figure), the solid line is d line (d-line), the short broken line is F line (Fline), and the long broken line is C line (C-line). It is a characteristic. In the graph showing astigmatism, the vertical axis represents the angle of view (indicated by ω in the figure), the solid line represents the sagittal plane (indicated by S in the figure), and the broken line represents the meridional plane (indicated by M in the figure). is there. In the distortion diagram, the vertical axis represents the angle of view (indicated by ω in the figure). These are the same in FIGS. 7 to 9, 12 to 14, 17 to 19, and 22 to 24.

  FIG. 5 is a lateral aberration diagram at the telephoto end of the zoom lens of Example 1. FIG. In each lateral aberration diagram shown in FIG. 5, the three aberration diagrams located on the left side in the drawing correspond to a basic state in which no camera shake correction is performed at the telephoto end. The three aberration diagrams located on the right side in the drawing correspond to the camera shake correction state at the telephoto end in which the image stabilizing group (camera shake correcting optical system) is moved by a predetermined amount in the direction perpendicular to the optical axis. These are the same in FIGS. 5, 10, 15, 20, and 25.

  Of the lateral aberration diagrams in the basic state, the upper row shows the lateral aberration at the image point of 70% of the maximum image height, the middle row shows the lateral aberration at the axial image point, and the lower row shows the lateral aberration at the image point of -70% of the maximum image height. Respectively. Among the lateral aberration diagrams in the state of camera shake correction, the upper row shows the lateral aberration at the image point of 70% of the maximum image height, the middle row shows the lateral aberration at the axial image point, and the lower row shows the lateral aberration at the image point of -70% of the maximum image height. Each corresponds to an aberration. In each lateral aberration diagram, the horizontal axis represents the distance from the principal ray on the pupil plane, the solid line is the d line (d-line), the short broken line is the F line (F-line), and the long broken line is the C line ( C-line) characteristics.

  As is apparent from FIG. 5, the symmetry of the lateral aberration at the axial image point is good. Further, when the lateral aberration at the + 70% image point and the lateral aberration at the -70% image point are compared in the basic state, the curvature is small and the inclinations of the aberration curves are almost equal. It can be seen that the aberration is small. This means that sufficient imaging performance is obtained even in the camera shake correction state. When the camera shake correction angle of the zoom lens system is the same, the amount of parallel movement required for camera shake correction decreases as the focal length of the entire zoom lens system decreases. Therefore, at any zoom position, it is possible to perform sufficient camera shake correction without deteriorating the imaging characteristics for camera shake correction angles up to 0.3 °. Further, by applying the parallel movement amount of the camera shake correction optical system at the telephoto end to the wide angle end and the intermediate focus position state, the camera shake correction angle can be made larger than 0.3 °. These points are the same for Examples 2 to 9 described later.

  Next, Table 1 shows lens data of Numerical Example 1 to which specific numerical values are applied in Example 1. The lens data shown in Table 1 is as follows. “Surface No.” is the surface number of the lens and indicates the order of the lens surfaces counted from the object side. “R” indicates a radius of curvature of the lens surface, “d” indicates a lens thickness or an interval between adjacent lens surfaces on the optical axis, and “Nd” indicates a refractive index with respect to the d-line (wavelength λ = 587.6 nm). “Νd” indicates the Abbe number with respect to the d-line (wavelength λ = 587.6 nm). When the lens surface is aspherical, “* (asterisk)” is added after the surface number, and the paraxial radius of curvature is shown in the column of the radius of curvature “r”.

  In the zoom lens system of Example 1, the F number (FNO.), The focal length (f) of the entire system, and the half angle of view (ω (°)) in the wide-angle end state, the intermediate focal length state, and the telephoto end state. Is as follows. In the following formula, numerical values in the wide-angle end state, the intermediate focal length state, and the telephoto end state are shown in order from the right side through hyphens (-).

FNO. = 4.12-4.12-4.12
f = 18.36-43.50-102.77
ω = 38.81-16.39-6.92

  Next, the optical system of the zoom lens of Example 2 will be described with reference to the drawings. FIG. 6 is a diagram illustrating a lens configuration example of the zoom lens according to the second embodiment. The zoom lens of Example 2 has substantially the same configuration as the zoom lens of Example 1, and includes a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, and positive refraction. A third lens group G3 having power, a fourth lens group G4 having negative refracting power, and a fifth lens group G5 having negative refracting power, and a stop between the second lens group and the third lens group S is arranged. The third lens group has an anti-vibration group VC composed of a single positive lens, the fourth lens group G4 is composed of a single negative lens whose image surface side is concave, and the fourth lens group G4 is a focus lens. Function as group F. Furthermore, a meniscus lens having a concave object side surface is disposed on the most object side of the fifth lens group. The specific lens configuration of each lens group is as shown in FIG. Further, when zooming from the wide-angle end to the telephoto end, the distance between the first lens group G1 and the second lens group G2 is increased, and the distance between the second lens group G2 and the third lens group G3 is decreased. The lens group moves so that At the time of zooming, the third lens group G3 and the fifth lens group move along the same locus. During focusing from infinity to a short distance object, the fourth lens group G4 moves to the image plane side. The amount of movement in the direction perpendicular to the optical axis of the image stabilization group VC in the camera shake correction state at the telephoto end is 0.430 mm.

  FIGS. 7 to 9 show longitudinal aberration diagrams of spherical aberration, astigmatism, and distortion aberration at the time of focusing at infinity in the wide-angle end state, the intermediate focal length state, and the telephoto end state of the zoom lens according to the second embodiment. . FIG. 10 is a lateral aberration diagram at the telephoto end. Tables 4 to 6 are lens data of Numerical Example 6 to which specific numerical values are applied, and are the same as the numerical data shown in Tables 1 to 3, and thus the description regarding each table is omitted.

  In the zoom lens system of Example 2, the F number (FNO.), The focal length (f) of the entire system, and the half angle of view (ω (°)) in the wide-angle end state, the intermediate focal length state, and the telephoto end state. Is as follows. In the following formula, numerical values in the wide-angle end state, the intermediate focal length state, and the telephoto end state are shown in order from the right side through hyphens (-).

FNO. = 4.12-4.12-4.12
f = 72.09-119.95-203.44
ω = 10.97-6.48-3.82

  Next, the optical system of the zoom lens of Example 3 will be described with reference to the drawings. FIG. 11 is a diagram illustrating a lens configuration example of the zoom lens according to the third embodiment. The zoom lens of Example 3 has substantially the same configuration as the zoom lens of Example 1, and includes a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, and positive refraction. A third lens group G3 having power, a fourth lens group G4 having negative refracting power, and a fifth lens group G5 having negative refracting power, and a stop between the second lens group and the third lens group S is arranged. The third lens group has an anti-vibration group VC composed of a single positive lens, the fourth lens group G4 is composed of a single negative lens whose image surface side is concave, and the fourth lens group G4 is a focus lens. Function as group F. Furthermore, a meniscus lens having a concave object side surface is disposed on the most object side of the fifth lens group. The specific lens configuration of each lens group is as shown in FIG. Further, when zooming from the wide-angle end to the telephoto end, the distance between the first lens group G1 and the second lens group G2 is increased, and the distance between the second lens group G2 and the third lens group G3 is decreased. The lens group moves so that At the time of zooming, the third lens group G3 and the fifth lens group move along the same locus. During focusing from infinity to a short distance object, the fourth lens group G4 moves to the image plane side. The movement amount in the direction perpendicular to the optical axis of the image stabilizing group VC in the camera shake correction state at the telephoto end is 0.451 mm.

  FIGS. 12 to 14 show longitudinal aberration diagrams of spherical aberration, astigmatism, and distortion aberration at the time of focusing on infinity in the wide-angle end state, the intermediate focal length state, and the telephoto end state of the zoom lens according to the third embodiment. . FIG. 15 is a lateral aberration diagram at the telephoto end. Tables 7 to 9 are lens data of Numerical Example 7 to which specific numerical values are applied, and are the same as the numerical data shown in Tables 1 to 3, and thus the description regarding each table is omitted.

  In the zoom lens system of Example 3, the F number (FNO.), The focal length (f) of the entire system, and the half angle of view (ω (°)) in the wide-angle end state, the intermediate focal length state, and the telephoto end state. Is as follows. In the following formula, numerical values in the wide-angle end state, the intermediate focal length state, and the telephoto end state are shown in order from the right side through hyphens (-).

FNO. = 4.12-4.12-4.12
f = 72.14 -120.11 -203.68
ω = 11.00-6.48-3.83

  Next, an optical system of a zoom lens according to Example 4 will be described with reference to the drawings. FIG. 16 is a diagram illustrating a lens configuration example of the zoom lens according to the fourth embodiment. The zoom lens of Example 4 has substantially the same configuration as the zoom lens of Example 1, and includes a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, and positive refraction. A third lens group G3 having power, a fourth lens group G4 having negative refracting power, and a fifth lens group G5 having negative refracting power, and a stop between the second lens group and the third lens group S is arranged. In addition, the third lens group includes a vibration-proof group VC composed of a single positive lens, and the fourth lens group G4 is composed of a cemented lens having a concave meniscus shape on the image surface side. G4 functions as the focus group F. Furthermore, a meniscus lens having a concave object side surface is disposed on the most object side of the fifth lens group. The specific lens configuration of each lens group is as shown in FIG. Further, when zooming from the wide-angle end to the telephoto end, the distance between the first lens group G1 and the second lens group G2 is increased, and the distance between the second lens group G2 and the third lens group G3 is decreased. The lens group moves so that At the time of zooming, the third lens group G3 and the fifth lens group are fixed with respect to the image plane. During focusing from infinity to a short distance object, the fourth lens group G4 moves to the image plane side. The amount of movement in the direction perpendicular to the optical axis of the image stabilizing group VC in the camera shake correction state at the telephoto end is 0.398 mm.

  17 to 19 are longitudinal aberration diagrams of spherical aberration, astigmatism, and distortion aberration at the time of focusing on infinity in the wide-angle end state, the intermediate focal length state, and the telephoto end state of the zoom lens according to the fourth embodiment. . FIG. 20 is a lateral aberration diagram at the telephoto end. Tables 22 to 24 are lens data of Numerical Example 4 to which specific numerical values are applied, and are the same as the numerical data shown in Tables 1 to 3, and thus the description regarding each table is omitted.

  In the zoom lens system according to Example 4, the F number (FNO.), The focal length (f) of the entire system, and the half angle of view (ω (°)) in the wide-angle end state, the intermediate focal length state, and the telephoto end state. Is as follows. In the following formula, numerical values in the wide-angle end state, the intermediate focal length state, and the telephoto end state are shown in order from the right side through hyphens (-).

FNO. = 4.12-4.12-4.12
f = 72.08 -120.11 -203.44
ω = 11.02-6.49-3.82

  Next, an optical system of the zoom lens of Example 5 will be described with reference to the drawings. FIG. 21 is a diagram illustrating a lens configuration example of the zoom lens according to the fifth embodiment. The zoom lens of Example 5 has substantially the same configuration as the zoom lens of Example 1, and includes a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, and positive refraction. A third lens group G3 having power, a fourth lens group G4 having negative refracting power, and a fifth lens group G5 having negative refracting power, and a stop between the second lens group and the third lens group S is arranged. The third lens group includes a vibration-proof group VC configured by a single positive lens, the fourth lens group G4 is configured by a meniscus single negative lens having a concave surface on the image surface side, and the fourth lens group G4 includes It functions as a focus group F. Furthermore, a meniscus lens having a concave object side surface is disposed on the second lens group from the object side in the fifth lens group. The specific lens configuration of each lens group is as shown in FIG. Further, when zooming from the wide-angle end to the telephoto end, the distance between the first lens group G1 and the second lens group G2 is increased, and the distance between the second lens group G2 and the third lens group G3 is decreased. The lens group moves so that At the time of zooming, the third lens group G3 and the fifth lens group are fixed with respect to the image plane. During focusing from infinity to a short distance object, the fourth lens group G4 moves to the image plane side. The amount of movement in the direction perpendicular to the optical axis of the image stabilizing group VC in the camera shake correction state at the telephoto end is 0.586 mm.

  22 to 24 show longitudinal aberration diagrams of spherical aberration, astigmatism, and distortion aberration at the time of focusing on infinity in the wide-angle end state, the intermediate focal length state, and the telephoto end state of the zoom lens according to the fifth embodiment. . FIG. 25 is a lateral aberration diagram at the telephoto end. Tables 13 to 15 are lens data of Numerical Example 5 to which specific numerical values are applied, and are the same as the numerical data shown in Tables 1 to 3, and thus the description regarding each table is omitted.

  In the zoom lens system of Example 5, the F number (FNO.), The focal length (f) of the entire system, and the half angle of view (ω (°)) in the wide-angle end state, the intermediate focal length state, and the telephoto end state Is as follows. In the following formula, numerical values in the wide-angle end state, the intermediate focal length state, and the telephoto end state are shown in order from the right side through hyphens (-).

FNO. = 4.12-4.12-4.12
f = 72.10-120.03-203.58
ω = 10.87-6.40-3.74

  Table 16 shows numerical values corresponding to the mathematical expressions described in the conditional expressions (1) to (6) of the first to fifth embodiments.

  According to the present invention, the overall size is small, and the change in photographing magnification due to wobbling is kept small. In particular, the lens system of the focus group is reduced in weight to reduce the load on the focus drive system, and the vibration-proof lens system is reduced in size and weight. It is possible to provide a zoom lens capable of reducing the load of the image stabilization drive system.

G1 ... 1st lens group G2 ... 2nd lens group G3 ... 3rd lens group G4 ... 4th lens group G5 ... 5th lens group F ... Focus group VC ... Anti-vibration group S ... Aperture stop

Claims (6)

In order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, a fourth lens group having a negative refractive power, and A fifth lens group having negative refractive power,
When zooming from the wide-angle end to the telephoto end, the lens group is arranged so that the distance between the first lens group and the second lens group is large and the distance between the second lens group and the third lens group is small. Move and
A single lens block having a meniscus shape in which the negative lens group disposed on the image plane side of the stop among all the lens groups is a focus group, and the side of the most image surface is concave with respect to the image plane When focusing from infinity to a short distance object, focus by moving the focus group to the image plane side,
A zoom lens satisfying the following conditional expression:

The zoom lens according to claim 1, wherein the following conditional expression is satisfied.

The zoom lens according to claim 1 or 2, wherein the following conditional expression is satisfied.

The third lens group includes at least a vibration proof group composed of a single lens block,
By moving the anti-vibration group in the direction perpendicular to the optical axis,
The zoom lens according to any one of claims 1 to 3, wherein the following conditional expression is satisfied.

The fifth lens group includes at least a meniscus single lens block whose outermost object side surface is concave with respect to the object side,
The zoom lens according to any one of claims 1 to 4 , wherein the meniscus single lens block has a negative focal length and satisfies the following conditional expression.

A zoom lens according to any one of claims 1 to 5 , and an image pickup device that converts an optical image formed by the zoom lens into an electrical signal on an image plane side thereof. An imaging device.