JP2013160935A - Zoom lens and imaging apparatus having the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a zoom lens capable of easily obtaining an excellent image having a high zoom ratio and reducing a thickness of a camera and others when applied to the camera.SOLUTION: The zoom lens includes: a first lens group having positive refractive power; a second lens group having negative refractive power; reflection means for folding an optical path; and a rear group including a plurality of lens groups, in order from an object side to an image side. The rear group includes a Ln-th lens group having at least one negative refractive power, the lens group being moved during zooming. When zooming is performed from a wide angle end to a telephoto end, the first lens group is moved so as to be positioned on the object side at the telephoto end compared to the wide engle end, and the second lens group is moved to the image side. Lateral magnifications βLnw and βLnt of the Ln-th lens group at the wide angle end and the telephoto end are appropriately set, respectively.

Description

  The present invention relates to a zoom lens and an image pickup apparatus having the same, and is suitable for, for example, a video camera, a digital still camera, a surveillance camera, a TV camera, a silver salt photograph camera, and the like.

  In recent years, imaging devices (cameras) such as a video camera using a solid-state imaging device, a digital still camera, and a film camera using a silver salt film have become highly functional, and the entire device has been downsized. Along with this, the photographic optical system used in these cameras is required to be a zoom lens that has a high zoom ratio, is small overall, and can reduce the thickness of the camera (thickness in the front-rear direction). .

  In order to reduce the size of the camera and increase the zoom ratio of the zoom lens, a so-called collapsible zoom lens is known in which the distance between the lens groups is reduced to a different distance from the shooting state during non-shooting. Yes. In order to reduce the thickness of the camera, a so-called bending zoom lens is known in which reflecting means (mirror member or prism member) for bending the optical axis of the photographing optical system by 90 ° is arranged in the optical path. Among these, zoom lenses are known that are provided with bending means (reflecting means) for bending the optical path between lens groups in order to reduce the thickness of the camera when retracted and to increase the zoom ratio. (Patent Documents 1 and 2).

  In Patent Documents 1 and 2, a lens unit having positive, negative, positive, and positive refractive powers is arranged in order from the object side to the image side, and the first lens unit and the third lens unit move during zooming, A bending means for bending the optical path is provided between the lens group and the third lens group. Patent Documents 1 and 2 disclose zoom lenses having a zoom ratio of about 6 to 10. In addition, in order from the object side to the image side, the lens unit includes five lens groups having positive, negative, positive, negative, and positive refractive power, and a reflecting unit that folds the optical path in the first lens group or the second lens group is provided. A zoom lens is known (Patent Document 3).

JP 2007-025123 A JP 2007-279541 A JP 2008-191291 A

  Generally, it has a reflecting means for bending the optical path between the lens groups constituting the zoom lens, and if the optical path is bent, the camera is thinned in the thickness direction of the camera while achieving a high zoom ratio and after bending. It is easy to reduce the lens length of the camera and to reduce the size of the entire camera. However, to achieve high optical performance over the entire zoom range while reducing the size and zoom ratio of the zoom lens, the position of the reflecting means in the optical path, the lens configuration of the zoom lens, and the refraction of the lens group for zooming It is important to set force and amount of movement appropriately.

  For example, the refractive power of each lens unit on the object side relative to the reflecting means and the amount of movement during zooming, and the refractive power and imaging magnification of the lens group moving during zooming arranged on the image side relative to the reflecting means are set appropriately. It becomes important. If these structures are inappropriate, the variation of various aberrations increases during zooming, and it becomes difficult to reduce the size of the entire lens system.

  An object of the present invention is to provide a zoom lens capable of easily obtaining a good image with a high zoom ratio and reducing the thickness of the camera or the like when applied to a camera, and an imaging apparatus using the zoom lens. .

The zoom lens of the present invention includes, in order from the object side to the image side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, reflecting means for bending an optical path, and a plurality of lens groups. The rear group includes at least one Ln lens group having a negative refractive power that moves during zooming, and the first lens group moves to the object side at the telephoto end compared to the wide-angle end. In the zoom lens in which the second lens group moves to the image side during zooming from the wide-angle end to the telephoto end, when the lateral magnification of the Ln lens group at the wide-angle end and the telephoto end is βLnw and βLnt,
1.0 <βLnt / βLnw <5.0
It satisfies the following conditional expression.

  According to the present invention, it is possible to obtain a zoom lens capable of easily obtaining a good image with a high zoom ratio and reducing the thickness of the camera or the like when applied to the camera.

Sectional view of the lens at the wide-angle end of Embodiment 1 of the present invention (A), (B), (C) Aberration diagrams at the wide-angle end, the intermediate zoom position, and the telephoto end of Numerical Example 1 corresponding to Example 1 of the present invention. Sectional view of the lens at the wide-angle end of Embodiment 2 of the present invention (A), (B), (C) Aberration diagrams at the wide-angle end, the intermediate zoom position, and the telephoto end of Numerical Example 2 corresponding to Example 2 of the present invention. Sectional view of the lens at the wide-angle end of Embodiment 3 of the present invention (A), (B), (C) Aberration diagrams at the wide-angle end, the intermediate zoom position, and the telephoto end of Numerical Example 3 corresponding to Example 3 of the present invention. Cross-sectional view of a lens at a wide angle end according to Embodiment 4 of the present invention (A), (B), (C) Aberration diagrams at the wide-angle end, the intermediate zoom position, and the telephoto end of Numerical Example 4 corresponding to Example 4 of the present invention. 1 is a lens cross-sectional view of a zoom lens according to a first embodiment of the present invention. Schematic diagram of main parts of an imaging apparatus of the present invention

  Hereinafter, the zoom lens of the present invention and an image pickup apparatus having the same will be described. The zoom lens of the present invention includes a first lens group having a positive refractive power, a second lens group having a negative refractive power, a reflecting member for bending an optical path, and a plurality of lens groups in order from the object side to the image side. It consists of groups. The rear group includes at least one Ln lens group having a negative refractive power that moves during zooming. The first lens unit moves so as to be positioned on the object side with respect to the imaging surface at the telephoto end compared to the wide-angle end. During zooming from the wide-angle end to the telephoto end, the second lens group moves to the image side.

  The rear group, as an aspect, sequentially from the object side to the image side, has a third lens group having a negative refractive power, a fourth lens group having a positive refractive power, a fifth lens group having a negative refractive power, and a positive refractive power. It is composed of a sixth lens group. The third lens group does not move for zooming, and the fourth, fifth, and sixth lens groups move during zooming. The other aspects of the rear group are composed of a third lens group having a positive refractive power, a fourth lens group having a negative refractive power, and a fifth lens group having a positive refractive power in order from the object side to the image side. . During zooming, the third, fourth, and fifth lens groups move.

  FIG. 1 is a lens cross-sectional view at the wide-angle end (short focal length end) of the zoom lens according to Embodiment 1 of the present invention. FIGS. 2A, 2B, and 2C are aberration diagrams at the wide-angle end, the intermediate zoom position, and the telephoto end (long focal length end), respectively, of the zoom lens according to the first exemplary embodiment. FIG. 3 is a lens cross-sectional view at the wide-angle end of the zoom lens according to Embodiment 2 of the present invention. 4A, 4B, and 4C are aberration diagrams at the wide-angle end, the intermediate zoom position, and the telephoto end, respectively, of the zoom lens according to the second embodiment.

  FIG. 5 is a lens cross-sectional view at the wide-angle end of the zoom lens according to Embodiment 3 of the present invention. FIGS. 6A, 6B, and 6C are aberration diagrams at the wide-angle end, the intermediate zoom position, and the telephoto end, respectively, of the zoom lens according to the third exemplary embodiment. FIG. 7 is a lens cross-sectional view at the wide-angle end of the zoom lens according to a fourth exemplary embodiment of the present invention. 8A, 8B, and 8C are aberration diagrams at the wide-angle end, the intermediate zoom position, and the telephoto end, respectively, of the zoom lens according to the fourth exemplary embodiment. In each embodiment, an internal reflection prism is used as the reflecting means, and the optical path is bent by 90 degrees on the internal reflection surface provided in the prism. However, in each lens sectional view, the optical path is shown in a developed state for convenience.

  FIG. 9 is a lens cross-sectional view when the optical path is bent by 90 degrees on the inner reflecting surface of the reflecting means (prism) in the first embodiment of the present invention. FIG. 10 is a schematic diagram of a main part of a camera (imaging device) including the zoom lens of the present invention. The zoom lens of each embodiment is used for an imaging device (camera) such as a video camera, a digital camera, and a silver salt film camera. This is a photographic lens system. In the lens cross-sectional view, the left side is the subject side (object side) (front), and the right side is the image side (rear). In the lens cross-sectional view, i indicates the order of the lens groups from the object side, and Li is the i-th lens group.

  LR is a rear group including a plurality of lens groups. SP is an aperture stop for limiting the F-number light beam, and FR is a flare stop for cutting unnecessary light. PR is a reflection means having an inner surface reflection surface and comprising a prism that bends the optical path on the optical path by 90 degrees or around 90 degrees (± 10 degrees). A reflecting mirror may be used as the reflecting means PR instead of the prism. G is an optical block corresponding to an optical filter, a face plate, a quartz low-pass filter, an infrared cut filter, or the like.

  IP is an image plane, and when used as a photographing optical system for a video camera or a digital still camera, on the imaging surface of a solid-state imaging device (photoelectric conversion device) such as a CCD sensor or a CMOS sensor, Is provided with a photosensitive surface corresponding to the film surface. Among the aberration diagrams, in the spherical aberration diagram, the solid line d and the two-dot chain line g are the d line and the g line, respectively, and in the astigmatism diagram, the dotted line ΔM and the solid line ΔS are the meridional image surface and the sagittal image surface. Lateral chromatic aberration is represented by the g-line. ω is a half angle of view (a value half the shooting angle of view), and Fno is an F number. In the following embodiments, the wide-angle end and the telephoto end refer to zoom positions when the zoom lens unit is positioned at both ends of a range in which the mechanism can move on the optical axis.

  The zoom lens of each embodiment includes, in order from the object side to the image side, a first lens unit L1 having a positive refractive power, a second lens unit L2 having a negative refractive power, reflecting means PR for bending an optical path, and a plurality of lenses. It has a rear group LR including a group. During zooming from the wide-angle end to the telephoto end, the first lens unit L1 moves so as to be positioned closer to the object side with respect to the imaging surface (image plane) at the telephoto end than at the wide-angle end. The second lens unit L2 moves to the image side during zooming from the wide-angle end to the telephoto end.

  In each embodiment, during zooming, the first lens unit L1 is moved to the object side at the telephoto end compared to the wide-angle end. This shortens the overall lens length (distance from the first lens surface to the image plane) at the wide-angle end, and achieves a high zoom ratio while reducing the effective diameter of the front lens.

  In particular, in each embodiment, during zooming from the wide-angle end to the telephoto end, the second lens unit L2 has a large zooming effect by moving the first lens unit L1 having a positive refractive power toward the object side. . Further, by moving the Ln lens unit Ln having negative refractive power in the rear unit LR during zooming, a zooming effect is provided, and the refractive powers of the first lens unit L1 and the second lens unit L2 are made too large. A high zoom ratio of 15 times or more is obtained. In each embodiment, the lateral magnifications of the Ln lens unit Ln in the rear group LR at the wide-angle end and the telephoto end are βLnw and βLnt, respectively.

At this time,
1.0 <βLnt / βLnw <5.0 (1)
The following conditional expression is satisfied.

  Conditional expression (1) indicates that the lateral magnification βLnw at the wide-angle end and the telephoto end of the Ln lens unit Ln having a negative refractive power that moves during zooming in the rear lens group LR in order to reduce the size of the entire system and increase the zoom ratio. The ratio with βLnt is appropriately determined. If the lower limit of conditional expression (1) is exceeded and the lateral magnification βLnt at the telephoto end of the Ln lens unit Ln is too small compared to the lateral magnification βLnw at the wide angle end, the Ln lens unit Ln has a reduction action, High zoom ratio becomes difficult. In order to increase the zoom ratio, it is necessary to increase the variable magnification sharing ratio of the other lens units, and the variation in field curvature and spherical aberration increases during zooming.

  If the upper limit of conditional expression (1) is exceeded and the lateral magnification βLnt at the telephoto end of the Ln lens unit Ln is too large compared to the lateral magnification βLnw at the wide-angle end, the amount of movement of the Ln lens unit Ln increases. For this reason, the total lens length becomes long, and it becomes difficult to reduce the size of the entire system.

  In each embodiment, by configuring as described above, a small zoom lens having a small front lens effective diameter with a high zoom ratio of 15 times or more while maintaining high optical performance over the entire zoom range is achieved. More preferably, the numerical range of conditional expression (1) should be set as follows.

1.0 <βLnt / βLnw <3.0 (1a)
More preferably, the numerical range of the conditional expression (1a) is set as follows.

1.0 <βLnt / βLnw <2.0 (1b)
By configuring as described above, a small zoom lens having a high zoom ratio and high optical performance over the entire zoom range can be obtained.

  In each embodiment, it is more preferable to satisfy one or more of the following conditions. The focal lengths of the entire system at the wide-angle end and the telephoto end are denoted by fw and ft, respectively. Let the focal length of the second lens unit L2 be f2. The focal length is fLn of the Ln lens unit Ln having negative refractive power that moves during zooming in the rear unit LR. The sum of the thickness of the first lens unit L1 and the thickness of the second lens unit L2 is TD12. The relative movement amounts of the first lens unit L1 and the second lens unit L2 with respect to the image plane during zooming from the wide-angle end to the telephoto end are M1 and M2, respectively. However, the relative movement amount is the absolute value of the displacement amount (positional difference) with respect to the image plane in the optical axis direction at the telephoto end compared to the wide-angle end of each lens group.

The distance on the optical axis from the first lens surface at the wide angle end to the intersection of the optical axis and the reflecting surface of the reflecting means PR is defined as DRw. At this time,
0.01 <| f2 / ft | <0.15 (2)
0.01 <| fLn / ft | <0.60 (3)
0.05 <TD12 / ft <0.25 (4)
0.05 <(M1 + M2) / ft <0.35 (5)
3.0 <DRw / fw <7.0 (6)
It is preferable to satisfy one or more of the following conditional expressions.

  Next, the technical meaning of each conditional expression described above will be described. Conditional expression (2) is for obtaining a good optical performance in the entire zoom range while making the ratio of the focal length f2 of the second lens unit L2 and the focal length ft of the entire system at the telephoto end appropriate to achieve a high zoom ratio. Is. If the lower limit of conditional expression (2) is exceeded and the focal length of the second lens unit L2 becomes smaller than the focal length ft of the entire system at the telephoto end, the curvature of field, the correction of lateral chromatic aberration, and the entire zoom range will be mainly at the wide angle end. In this case, it is difficult to suppress fluctuations in the image plane around the screen.

  In addition, since the refractive power of the second lens unit L2, which mainly contributes to zooming, increases, the sensitivity of the tilt and parallel decentering of each lens unit increases. It becomes difficult to obtain good optical performance due to eccentricity caused by looseness of parts. When the focal length of the second lens unit L2 exceeds the upper limit of the conditional expression (2) and becomes larger than the focal length ft of the entire system at the telephoto end, the movement amount of the second lens unit L2 is set to increase the zoom ratio. It must be increased. As a result, the total lens length becomes longer and the camera becomes larger. In addition, the effective diameter of the first and second lens groups increases, which is not good.

  Conditional expression (3) sets the ratio of the focal length fLn of the Ln lens unit Ln in the rear lens group LR to the focal length ft of the entire system at the telephoto end to achieve a high zoom ratio, while providing good optical performance over the entire zoom range. To get.

  If the absolute value of the focal length fLn of the Ln lens group Ln exceeds the lower limit of the conditional expression (3) and becomes too small compared to the focal length ft of the entire system at the telephoto end, the total lens length of the rear group LR is shortened. Needs to increase the power (reciprocal of the focal length) of the lens group in the rear group LR. As a result, image plane fluctuations increase during zooming from the wide-angle end to the telephoto end. If the absolute value of the focal length fLn of the Ln lens unit Ln exceeds the upper limit of the conditional expression (3) and becomes too large compared to the focal length ft of the entire system at the telephoto end, the Lnth The amount of movement associated with zooming of the lens unit Ln increases, making it difficult to downsize the entire system.

  Conditional expression (4) is the sum TD12 of the thickness of the first lens unit L1 and the thickness of the second lens unit L2 and the focal point of the entire system at the telephoto end in order to reduce the thickness of the camera while maintaining good optical performance. The ratio with the distance ft is appropriately determined. If the sum TD12 of the thicknesses of the first lens unit L1 and the second lens unit L2 exceeds the lower limit of the conditional expression (4) and becomes too small compared to the focal length ft of the entire system at the telephoto end, the effective diameter of the front lens When the size is reduced, the powers of the first lens unit L1 and the second lens unit L2 must be increased. As a result, chromatic aberration and spherical aberration increase at the telephoto end, making it difficult to correct them.

  If the sum TD12 of the thickness of the first lens unit L1 and the thickness of the second lens unit L2 exceeds the upper limit of the conditional expression (4) and becomes too large compared to the focal length ft of the entire system at the telephoto end, the camera thickness is increased. As the thickness increases, the effective diameter of the front lens increases.

  Conditional expression (5) makes the ratio of the focal length ft of the entire system at the telephoto end to the moving amounts M1, M2 of the first lens unit L1 and the second lens unit L2 during zooming from the wide-angle end to the telephoto end, This is to reduce the size of the entire system while increasing the zoom ratio. If the total of the movement amounts M1 and M2 exceeds the lower limit of the conditional expression (5) and becomes too small compared with the focal length ft of the entire system at the telephoto end, the field curvature at the wide-angle end and spherical aberration and chromatic aberration at the telephoto end. Correction becomes difficult. Further, when the zoom ratio is increased, the power of the first lens unit L1 and the second lens unit L2 is increased, and thus the relative decentering sensitivity between the first lens unit L1 and the second lens unit L2 is increased, which is favorable. It becomes difficult to obtain a good optical performance.

  If the total of the movement amounts M1 and M2 exceeds the upper limit of the conditional expression (5) and becomes too large compared to the focal length ft of the entire system at the telephoto end, the first lens group is retracted to reduce the thickness of the camera. This is not good because the camera thickness increases due to the amount of movement of L1 and the second lens unit L2.

  Conditional expression (6) is that the distance DRw on the optical axis from the first lens surface at the wide-angle end to the intersection of the optical axis and the reflecting surface of the reflecting means PR and the focal length fw of the entire system at the wide-angle end for thinning the camera. The ratio is determined appropriately. If the distance DRw from the first lens surface at the wide-angle end to the intersection of the optical axis and the reflecting surface exceeds the lower limit of the conditional expression (6) compared to the focal length fw of the entire system at the wide-angle end, it is mainly near the wide-angle end. In this case, it becomes difficult to correct curvature of field.

  When the distance DRw from the first lens surface at the wide-angle end to the intersection of the optical axis and the reflecting surface exceeds the upper limit of conditional expression (6) as compared with the focal length fw of the entire system at the wide-angle end, the effective diameter of the front lens becomes growing. Accordingly, the thickness of the lens in front of the reflecting surface is increased, so that it is difficult to downsize the entire system. In order to further reduce the size of the entire lens system while further reducing aberration fluctuations during aberration correction and zooming, it is preferable to set the numerical ranges of conditional expressions (2) to (6) as follows.

0.03 <| f2 / ft | <0.10 (2a)
0.03 <| fLn / ft | <0.50 (3a)
0.10 <TD12 / ft <0.20 (4a)
0.10 <(M1 + M2) / ft <0.25 (5a)
4.0 <DRw / fw <6.0 (6a)
By specifying the lens configuration as described above, in each embodiment, it is possible to easily obtain a zoom lens having a zoom ratio exceeding 15 times while maintaining downsizing of the entire system.

  In each embodiment, in order to reduce the effective lens diameter of the first lens unit L1, the number of lenses constituting the first lens unit L1 is reduced as much as possible. In each embodiment, the first lens unit L1 is composed of three lenses in order from the object side to the image side: a negative lens (a lens having a negative refractive power), a positive lens (a lens having a positive refractive power), and a positive lens. ing.

  Specifically, it is composed of a cemented lens in which a positive lens and a negative lens are cemented, and a positive lens. Further, it is preferable to use a glass material having an Abbe number of 80 or more as the material of the positive lens of the cemented lens. As a result, spherical aberration and chromatic aberration that occur when a high zoom ratio is achieved are corrected satisfactorily. As a material of the prism constituting the reflecting means PR of each embodiment, a glass material having a refractive index of 1.9 or more is used. As a result, the overall length of the lens is shortened.

  Next, the lens configurations of Examples 1 to 3 in FIGS. 1, 3, and 5 will be described. In the lens cross-sectional views of Examples 1 to 3, L1 is a first lens unit having a positive refractive power, and L2 is a second lens unit having a negative refractive power. The rear group LR includes a third lens unit L3 having a negative refractive power, a fourth lens unit L4 having a positive refractive power, a fifth lens unit L5 having a negative refractive power, and a sixth lens unit L6 having a positive refractive power. ing. Examples 1 to 3 are 6-group zoom lenses. The fifth lens unit L5 corresponds to the Ln lens unit Ln.

  During zooming from the wide-angle end to the telephoto end, the first, second, fourth, fifth, and sixth lens groups L1, L2, L4, L5, and L6 are moved as indicated by arrows. Specifically, when zooming from the wide-angle end to the telephoto end, the first lens unit L1 is moved to the object side, the second lens unit L2 is moved to the image side, and the fourth lens is relative to the image plane as indicated by an arrow. The group L4 and the fifth lens group L5 are moved to the object side.

  As a result, the burden of zooming on the second lens unit L2 when achieving a high zoom ratio is reduced, and the entire second lens unit L2 is reduced in size while being thinned when applied to the camera. In addition, high optical performance is obtained over the entire zoom range while reducing curvature of field in the entire zoom range. The sixth lens unit L6 is moved nonlinearly during zooming. In addition, a rear focus type is employed in which the sixth lens unit L6 is moved on the optical axis to perform focusing, and the entire system is downsized compared to focusing in the front group (first and second lens units L1, L2). I am trying.

  When focusing from an infinitely distant object to a close object at the telephoto end, the sixth lens unit L6 is moved forward as indicated by an arrow 6c. A solid line curve 6a and a dotted line curve 6b relating to the sixth lens unit L6 are used to correct image plane fluctuations during zooming from the wide-angle end to the telephoto end when focusing on an object at infinity and a short-distance object, respectively. The movement trajectory is shown. In Examples 1 to 3, focusing may be performed by the fifth lens unit L5 having a negative refractive power. At this time, focusing from an infinitely distant object to a close object is performed by moving the fifth lens unit L5 backward.

  In Examples 1 to 3, the reflecting means PR and the third lens unit L3 are not moved for zooming. In zooming, the third lens unit L3 may be moved independently of other lens units (with different movement trajectories) as necessary. Each of the third lens unit L3 and the fifth lens unit L5 is composed of a single negative lens (a lens having a negative refractive power) to shorten the entire lens length and to reduce the size of the entire system. The fourth lens unit L4 has at least one negative lens and at least two positive lenses for good aberration correction.

  Specifically, a positive lens, a negative lens, and a cemented lens in which a positive lens and a negative lens are cemented in order from the object side to the image side. As a result, spherical aberration and coma aberration in the entire zoom range, as well as coma aberration and lateral chromatic aberration due to decentering during image stabilization are satisfactorily corrected. The fourth lens unit L4 has one or more aspheric surfaces. As a result, fluctuations in spherical aberration caused by zooming are corrected well.

  In Examples 1 to 3, the aperture stop SP is disposed in the fourth lens unit L4, and the flare stop FP is disposed on the image side of the fourth lens unit L4. In any case, the fourth lens unit L4 is moved integrally during zooming. doing. In Examples 1 to 3, a part or the whole of the fourth lens unit L4 having a positive refractive power is moved in a direction having a component perpendicular to the optical axis, and an image (image) is perpendicular to the optical axis. It is moved. As a result, the shake of the captured image when the entire optical system (zoom lens) vibrates (tilts) is corrected, and good optical performance is obtained.

  Note that the blur of the captured image may be corrected by moving the fifth lens unit L5 in a direction having a component perpendicular to the optical axis instead of a part or all of the fourth lens unit L4.

  In this embodiment and in each of the embodiments described below, image stabilization is performed without newly adding an optical member such as a variable apex angle prism or a lens group for image stabilization, thereby increasing the size of the entire optical system. Is prevented.

  In this embodiment and each of the following embodiments, the whole or a part of the lens group is moved in the direction perpendicular to the optical axis to perform image stabilization. If it is moved so as to have a component perpendicular to the axis, it is possible to correct image blurring. For example, if the lens barrel structure is allowed to be complicated, the entire lens group or a part of the lens group may be rotated so as to have a rotation center on the optical axis.

  Next, the lens configuration of Example 4 in FIG. 7 will be described. In the lens cross-sectional view of Example 4, L1 is a first lens unit having a positive refractive power, and L2 is a second lens unit having a negative refractive power. The rear group LR includes a third lens unit L3 having a positive refractive power, a fourth lens unit having a negative refractive power, and a fifth lens unit L5 having a positive refractive power. Example 4 is a five-group zoom lens. During zooming from the wide-angle end to the telephoto end, the first, second, third, fourth, and fifth lens groups L1, L2, L3, L4, and L5 are moved as indicated by arrows.

  Specifically, during zooming from the wide-angle end to the telephoto end, the first lens unit L1 is moved to the object side, the second lens unit L2 is moved to the image side, the third lens unit L3 is moved to the object side, and the fourth lens unit L4 is moved to the object side. Moved to the side. As a result, the burden of zooming on the second lens unit L2 when achieving a high zoom ratio is reduced, and the entire second lens unit L2 is reduced in size while being thinned when applied to the camera. In addition, high optical performance is obtained over the entire zoom range while reducing curvature of field in the entire zoom range.

  Then, the fifth lens unit L5 is moved to a convex locus toward the object side to correct the image plane variation due to zooming. Further, focusing is performed by the fifth lens unit L5. By making the movement locus of the fifth lens unit L5 convex toward the object side, the space between the fourth lens unit L4 and the fifth lens unit L5 can be effectively used, and the entire lens length can be effectively shortened. Have achieved. When focusing from an infinitely distant object to a close object at the telephoto end, the fifth lens unit L5 is extended forward as indicated by an arrow 5c.

  A solid line curve 5a and a dotted line curve 5b relating to the fifth lens unit L5 are movement trajectories for correcting image plane fluctuations caused by zooming when focusing on an object at infinity and an object at close distance, respectively. In the fifth embodiment, the reflecting means PR does not move during zooming. The aperture stop SP is disposed in the third lens unit L3, and the flare stop FP is disposed on the image side of the third lens unit L3, both of which move integrally with the third lens unit L3 during zooming.

  In Example 4, a part or all of the third lens unit L3 is moved in a direction having a component perpendicular to the optical axis, and an image (image) is moved in a direction perpendicular to the optical axis. As a result, the shake of the captured image when the entire optical system (zoom lens) vibrates (tilts) is corrected, and good optical performance is obtained. The third lens unit L3 has at least one negative lens and at least two positive lenses to perform good aberration correction. Specifically, the lens includes a positive lens, a negative lens, and a cemented lens in which a positive lens and a negative lens are cemented.

  Thereby, spherical aberration and coma aberration in the entire zoom range, and coma aberration and lateral chromatic aberration due to decentering during image stabilization are satisfactorily corrected. The third lens unit L3 has one or more aspheric surfaces. As a result, fluctuations in spherical aberration caused by zooming are corrected well.

  According to each embodiment, by configuring as described above, it is possible to obtain a zoom lens having a compact optical system as a whole, a high zoom ratio of 15 times or more, and high optical performance over the entire zoom range. In addition, the zoom lens of each embodiment includes a reflecting member PR that bends light from the object side between the second lens unit L2 and the third lens unit L3 as shown in FIG. It is easy to make it thinner.

  In FIG. 9, the reference numerals given to the respective members are the same as the reference numerals shown in the first embodiment of FIG.

  Next, an embodiment of a digital still camera using a zoom lens as shown in each embodiment as a photographing optical system will be described with reference to FIG. In FIG. 10, reference numeral 20 denotes a camera body, and reference numeral 21 denotes a photographing optical system constituted by any of the zoom lenses described in the first to fourth embodiments. PR is a reflecting means comprising a prism. Reference numeral 22 denotes a solid-state imaging device (photoelectric conversion device) such as a CCD sensor or a CMOS sensor that receives a subject image formed by the photographing optical system 21 and is built in the camera body. A memory 23 records information corresponding to a subject image photoelectrically converted by the solid-state imaging device 22. Reference numeral 24 denotes a finder for observing a subject image formed on the solid-state image sensor 22, which includes a liquid crystal display panel or the like.

  In this way, by applying the zoom lens of the present invention to an imaging apparatus such as a digital still camera, a compact imaging apparatus having high optical performance can be realized.

Next, numerical examples 1 to 4 corresponding to the first to fourth embodiments of the present invention will be described. In each numerical example, i indicates the order of the optical surfaces from the object side. ri is the radius of curvature of the i-th optical surface (i-th surface), di is the distance between the i-th surface and the i + 1-th surface, and ndi and νdi are the refractions of the material of the i-th optical member with respect to the d-line, respectively. Indicates the rate and Abbe number. Further, when k is the eccentricity A4, A6, A8, A10 is an aspheric coefficient, and the displacement in the optical axis direction at the position of the height h from the optical axis is x with respect to the surface vertex, the aspheric shape is
x = (h ² / R) / [1+ [1- (1 + k) (h / R) ² ] ^1/2 ] + A4h ⁴ + A6h ⁶
+ A8h ⁸ + A10h ¹⁰
Is displayed.

Where R is the paraxial radius of curvature. Also for example, a display of the "E-Z" means ^{"10 -Z".} In the numerical example, the last two surfaces are surfaces of an optical block such as a filter and a face plate. In each embodiment, the back focus (BF) represents the distance from the lens final surface to the paraxial image surface by an air-converted length. The total lens length is obtained by adding back focus to the distance from the lens surface closest to the object side to the final lens surface. Table 1 shows the correspondence with the above-described conditional expressions in each numerical example.

[Numerical Example 1]
Unit mm

Surface data surface number rd nd νd
1 38.089 0.65 1.85478 24.8
2 16.270 3.75 1.49700 81.5
3 -345.616 0.05
4 17.314 2.10 1.83481 42.7
5 101.546 (variable)
6 * -72.035 0.30 1.85135 40.1
7 * 5.553 3.00
8 -9.874 0.40 1.88300 40.8
9 131.106 0.15
10 23.588 1.45 1.95906 17.5
11 -21.490 (variable)
12 ∞ 6.80 2.00 100 29.1
13 ∞ 1.00
14 -13.423 0.40 1.48749 70.2
15 -57.158 (variable)
16 * 7.290 1.70 1.55332 71.7
17 * -33.455 0.80
18 (Aperture) ∞ 1.00
19 7.879 0.50 1.90366 31.3
20 5.653 1.40
21 * 35.782 2.60 1.58313 59.4
22 -5.325 0.40 1.83400 37.2
23 -11.332 0.60
24 ∞ (variable) (Flare aperture)
25 -49.512 0.40 1.88300 40.8
26 37.472 (variable)
27 * 12.702 1.95 1.48749 70.2
28 -33.425 (variable)
29 ∞ 1.00 1.51633 64.1
30 ∞ 1.00
Image plane ∞

Aspheric data 6th surface
K = -5.14066e + 002 A 4 = 2.83228e-005 A 6 = 2.13210e-007

7th page
K = 3.70015e-001 A 4 = -2.21201e-004 A 6 = -2.34074e-005 A 8 = 1.14761e-006
A10 = -7.98571e-008

16th page
K = -1.26531e-001 A 4 = -3.41758e-004 A 6 = 1.25899e-005 A 8 = -1.77405e-006
A10 = 7.89790e-008

17th page
K = 7.77560e + 000 A 4 = 3.55419e-006 A 6 = 2.03751e-005 A 8 = -2.70124e-006
A10 = 1.33983e-007

21st page
K = -6.35924e + 001 A 4 = 2.65517e-004 A 6 = 1.12919e-005 A 8 = -1.54736e-006
A10 = 1.24433e-007

27th page
K = -6.31234e-001 A 4 = 9.11226e-005 A 6 = -4.51116e-006 A 8 = 1.86389e-007

Various data Zoom ratio 16.93
Wide angle Medium telephoto focal length 4.13 10.27 69.94
F number 3.61 4.70 6.70
Angle of View 32.76 16.56 2.50
Image height 2.66 3.06 3.06
Total lens length 64.17 64.44 73.38
BF 6.09 8.72 4.39

d 5 0.50 4.75 14.24
d11 5.10 1.12 0.57
d15 12.87 6.34 0.32
d24 2.54 6.71 9.71
d26 5.67 5.39 12.74
d28 4.43 7.06 2.73

Zoom lens group data group Start surface Focal length
1 1 23.74
2 6 -6.07
3 12 -36.10
4 16 11.52
5 25 -24.10
6 27 19.15
7 29 ∞

[Numerical Example 2]
Unit mm

Surface data surface number rd nd νd
1 37.713 0.65 1.85478 24.8
2 15.927 3.75 1.49700 81.5
3 -326.925 0.05
4 16.918 2.10 1.83481 42.7
5 98.201 (variable)
6 * -61.435 0.30 1.85135 40.1
7 * 5.764 3.00
8 -10.371 0.40 1.88300 40.8
9 51.416 0.15
10 22.336 1.45 1.95906 17.5
11 -20.515 (variable)
12 ∞ 6.80 2.00 100 29.1
13 ∞ 1.00
14 -10.596 0.40 1.48749 70.2
15 -45.479 (variable)
16 * 7.095 1.70 1.55332 71.7
17 * -24.698 0.80
18 (Aperture) ∞ 1.00
19 7.719 0.50 1.90366 31.3
20 5.501 1.40
21 * 31.915 2.60 1.58313 59.4
22 -5.462 0.40 1.83400 37.2
23 -11.823 0.60
24 ∞ (variable) (Flare aperture)
25 -30.511 0.40 1.88300 40.8
26 25.947 (variable)
27 * 11.131 1.95 1.48749 70.2
28 -22.569 (variable)
29 ∞ 1.00 1.51633 64.1
30 ∞ 1.00
Image plane ∞

Aspheric data 6th surface
K = -7.34343e + 002 A 4 = -9.11867e-005 A 6 = 3.59460e-006

7th page
K = 5.51688e-001 A 4 = -2.17628e-004 A 6 = -4.31994e-005 A 8 = 1.48711e-006
A10 = -7.98571e-008

16th page
K = 8.29487e-002 A 4 = -4.10648e-004 A 6 = 1.03929e-005 A 8 = -1.72474e-006
A10 = 7.89790e-008

17th page
K = -9.04688e + 000 A 4 = 6.02166e-006 A 6 = 2.03751e-005 A 8 = -2.70124e-006
A10 = 1.33983e-007

21st page
K = -4.68129e + 001 A 4 = 2.73770e-004 A 6 = 8.65424e-006 A 8 = -1.42002e-006
A10 = 1.24433e-007

27th page
K = -6.49547e-001 A 4 = 5.32177e-005 A 6 = -5.14998e-006 A 8 = 1.62766e-007

Various data Zoom ratio 20.49
Wide angle Medium Telephoto focal length 4.15 10.60 84.94
F number 3.60 4.48 6.69
Angle of View 32.66 16.08 2.06
Image height 2.66 3.06 3.06
Total lens length 64.17 64.44 73.38
BF 6.09 8.69 3.90

d 5 0.50 4.75 14.24
d11 5.10 1.12 0.57
d15 12.87 6.34 0.32
d24 2.54 6.71 9.71
d26 5.67 5.42 13.24
d28 4.43 7.03 2.24

Zoom lens group data group Start surface Focal length
1 1 23.33
2 6 -6.12
3 12 -28.45
4 16 10.80
5 25 -15.83
6 27 15.59
7 29 ∞

[Numerical Example 3]

Unit mm

Surface data surface number rd nd νd
1 33.686 0.70 1.84666 23.9
2 16.813 3.50 1.48749 70.2
3 1089.750 0.05
4 17.468 2.05 1.77250 49.6
5 94.435 (variable)
6 4383.672 0.30 1.88300 40.8
7 5.425 2.70
8 -17.562 0.30 1.88300 40.8
9 19.388 0.15
10 11.950 1.55 1.95906 17.5
11 -111.277 (variable)
12 ∞ 7.30 2.00069 25.5
13 ∞ 1.00
14 -16.068 0.40 1.48749 70.2
15 -56.335 (variable)
16 * 7.382 1.70 1.55332 71.7
17 * -46.469 0.80
18 (Aperture) ∞ 1.00
19 8.075 0.50 1.90366 31.3
20 5.763 1.40
21 * 22.306 2.50 1.58313 59.4
22 -5.029 0.40 1.80610 40.9
23 -12.141 0.60
24 ∞ (variable) (Flare aperture)
25 -23.099 0.40 1.53172 48.8
26 23.099 (variable)
27 11.089 2.10 1.48749 70.2
28 -35.273 (variable)
29 ∞ 1.00 1.51633 64.1
30 ∞ 1.00
Image plane ∞

Aspheric data 16th surface
K = -4.03172e-001 A 4 = -1.69303e-004 A 6 = -2.57545e-006 A 8 = 1.61077e-008

17th page
K = -1.46793e + 002 A 4 = -1.36521e-004

21st page
K = 4.83049e + 000 A 4 = 1.63029e-004 A 6 = -6.99481e-008 A 8 = 4.75734e-007
A10 = -1.25256e-009

Various data Zoom ratio 15.54
Wide angle Medium telephoto focal length 4.12 14.85 64.01
F number 3.23 4.41 6.08
Angle of View 32.83 11.63 2.73
Image height 2.66 3.06 3.06
Total lens length 63.58 66.88 74.26
BF 6.59 9.31 4.11

d 5 0.45 7.31 14.54
d11 3.97 0.41 0.56
d15 13.99 4.84 0.35
d24 2.31 8.48 11.92
d26 4.86 5.13 11.38
d28 4.93 7.65 2.45

Zoom lens group data group Start surface Focal length
1 1 25.42
2 6 -6.04
3 12 -46.26
4 16 11.64
5 25 -21.66
6 27 17.57
7 29 ∞

[Numerical Example 4]
Unit mm

Surface data surface number rd nd νd
1 45.904 0.65 1.85478 24.8
2 17.745 3.20 1.49700 81.5
3 -107.405 0.05
4 16.890 2.10 1.83481 42.7
5 82.058 (variable)
6 * -143.248 0.30 1.85135 40.1
7 * 5.727 2.50
8 -7.516 0.40 1.88300 40.8
9 23.940 0.15
10 16.498 1.45 1.95906 17.5
11 -23.506 (variable)
12 ∞ 6.80 2.00 100 29.1
13 ∞ (variable)
14 * 7.593 1.70 1.55332 71.7
15 * -79.362 0.80
16 (Aperture) ∞ 1.00
17 7.302 0.50 1.90366 31.3
18 5.447 1.40
19 * 29.408 2.60 1.58313 59.4
20 -5.091 0.40 1.83400 37.2
21 -11.719 0.60
22 ∞ (variable) (Flare aperture)
23 -2826.038 0.40 1.48749 70.2
24 15.130 (variable)
25 * 11.986 1.95 1.48749 70.2
26 -31.007 (variable)
27 ∞ 1.00 1.51633 64.1
28 ∞ 1.00
Image plane ∞

Aspheric data 6th surface
K = -1.33283e + 001 A 4 = 4.18722e-004 A 6 = -4.83416e-006

7th page
K = 9.24526e-001 A 4 = -1.15427e-004 A 6 = -1.36060e-005 A 8 = 1.47434e-006
A10 = -7.98571e-008

14th page
K = -4.44882e-001 A 4 = -2.57237e-004 A 6 = 1.37501e-005 A 8 = -1.78739e-006
A10 = 7.89790e-008

15th page
K = -2.26579e + 002 A 4 = -2.30789e-004 A 6 = 2.03751e-005 A 8 = -2.70124e-006
A10 = 1.33983e-007

19th page
K = 1.02062e + 001 A 4 = 1.32687e-004 A 6 = 7.96522e-006 A 8 = -6.84849e-007
A10 = 1.24433e-007

25th page
K = 3.19075e-001 A 4 = 6.11997e-005 A 6 = -4.50822e-006 A 8 = 9.26333e-008

Various data Zoom ratio 16.82
Wide angle Medium Telephoto focal length 4.15 9.80 69.84
F number 3.61 4.49 6.70
Angle of View 32.63 17.32 2.50
Image height 2.66 3.06 3.06
Total lens length 62.22 62.49 71.43
BF 6.59 10.38 3.82

d 5 0.50 4.75 14.24
d11 5.10 1.12 0.57
d13 12.87 6.34 0.32
d22 2.54 6.71 9.71
d24 5.67 4.22 13.82
d26 4.93 8.73 2.16

Zoom lens group data group Start surface Focal length
1 1 23.30
2 6 -4.69
3 12 ∞
4 14 12.74
5 23 -30.87
6 25 18.00
7 27 ∞

L1 1st lens group L2 2nd lens group L3 3rd lens group L4 4th lens group L5 5th lens group L6 6th lens group LR Rear group PR Prism (reflective member) SP stop FP flare cut stop

Claims (17)

In order from the object side to the image side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a reflecting means for bending the optical path, and a rear group including a plurality of lens groups,
The rear group includes at least one Ln lens unit having a negative refractive power that moves during zooming, and the first lens unit moves so as to be positioned closer to the object side at the telephoto end than at the wide angle end. In zooming the second lens group to the image side during zooming to the telephoto end,
When the lateral magnifications of the Ln lens group at the wide-angle end and the telephoto end are βLnw and βLnt, respectively,
1.0 <βLnt / βLnw <5.0
A zoom lens satisfying the following conditional expression: When the focal length of the second lens group is f2, and the focal length of the entire system at the telephoto end is ft,
0.01 <| f2 / ft | <0.15
The zoom lens according to claim 1, wherein the following conditional expression is satisfied. When the focal length of the entire system at the telephoto end is ft and the focal length of the Ln lens group is fLn,
0.01 <| fLn / ft | <0.60
The zoom lens according to claim 1, wherein the following conditional expression is satisfied. When the focal length of the entire system at the telephoto end is ft and the sum of the thickness of the first lens group and the thickness of the second lens group is TD12,
0.05 <TD12 / ft <0.25
The zoom lens according to claim 1, wherein the following conditional expression is satisfied. When the focal length of the entire system at the telephoto end is ft, and the movement amounts of the first lens group and the second lens group during zooming from the wide-angle end to the telephoto end are M1 and M2, respectively.
0.05 <(M1 + M2) / ft <0.35
The zoom lens according to claim 1, wherein the following conditional expression is satisfied. When the focal length of the entire system at the wide angle end is fw, and the distance on the optical axis from the first lens surface on the object side at the wide angle end to the intersection of the optical axis and the reflecting surface of the reflecting means is DRw,
3.0 <DRw / fw <7.0
The zoom lens according to claim 1, wherein the following conditional expression is satisfied.   The rear group includes, in order from the object side to the image side, a third lens group having a negative refractive power, a fourth lens group having a positive refractive power, a fifth lens group having a negative refractive power, and a sixth lens having a positive refractive power. 2. The zoom lens according to claim 1, wherein the third lens group is stationary for zooming, and the fourth lens group, the fifth lens group, and the sixth lens group move during zooming. The zoom lens of any one of thru | or 6.   The zoom lens according to claim 7, wherein the third lens group includes one negative lens.   The zoom lens according to claim 7 or 8, wherein the fifth lens group includes one negative lens.   10. The apparatus according to claim 7, wherein the fourth lens group is moved in a direction having a component perpendicular to the optical axis direction to move the image in a direction perpendicular to the optical axis. The described zoom lens.   11. The fourth lens group includes a positive lens, a negative lens, and a cemented lens in which a positive lens and a negative lens are cemented in order from the object side to the image side. Zoom lens.   The rear group includes, in order from the object side to the image side, a third lens group having a positive refractive power, a fourth lens group having a negative refractive power, and a fifth lens group having a positive refractive power. The zoom lens according to claim 1, wherein the lens group, the fourth lens group, and the fifth lens group move.   The zoom lens according to claim 12, wherein the fourth lens group includes one negative lens.   14. The zoom lens according to claim 12, wherein the third lens group is moved in a direction having a component perpendicular to the optical axis direction to move the image in a direction perpendicular to the optical axis. .   15. The third lens group includes a positive lens, a negative lens, and a cemented lens in which a positive lens and a negative lens are cemented in order from the object side to the image side. Zoom lens.   The zoom lens according to claim 1, wherein an image is formed on a solid-state image sensor.   An image pickup apparatus comprising: the zoom lens according to claim 1; and a solid-state image pickup device that receives an image formed by the zoom lens.