JP6486052B2 - Zoom lens and imaging apparatus having the same - Google Patents

Description

  The present invention relates to a zoom lens and an image pickup apparatus having the same. For example, an image pickup apparatus using a solid-state image pickup device such as a video camera, an electronic still camera, a broadcast camera, a surveillance camera, or a camera using a silver salt film. It is suitable for an imaging device.

  In recent years, an imaging optical system used in an imaging apparatus is required to be a high-performance zoom lens with a high zoom ratio while the entire system is small. Further, these zoom lenses are required to be able to focus at high speed and with high accuracy. 2. Description of the Related Art Conventionally, there is known an inner focus type zoom lens in which focusing is performed by using a small and light lens group on the image side of the first lens group closest to the object side with a small zoom lens and a high zoom ratio (Patent Document). 1, 2).

  In general, an inner focus type zoom lens that performs focusing using a lens group other than the first lens group has a smaller effective diameter of the first lens group than a zoom lens that moves the first lens group to perform focusing. Overall size reduction is facilitated. Further, close-up photography, particularly close-up photography is facilitated. Further, since the small and light lens group is moved, the driving force of the lens group is small, and quick focusing is possible.

  Patent Document 1 includes first to sixth lens units having positive, negative, positive, positive, negative, and positive refractive powers in order from the object side to the image side, and zooming is performed by changing the interval between adjacent lens units. A zoom lens is disclosed in which focusing is performed by the fifth lens group. Patent Document 1 includes first to fifth lens units having positive, negative, positive, negative, and positive refractive power in order from the object side to the image side, and performs zooming by changing the interval between adjacent lens groups. A zoom lens in which focusing is performed by the fourth lens group is disclosed.

  Patent Document 2 includes first to fifth lens groups having positive, negative, positive, negative, and positive refractive powers in order from the object side to the image side, and performs zooming by changing the interval between adjacent lens groups. A zoom lens in which focusing is performed by the second lens group is disclosed.

JP 2012-47814 A JP 2008-15251 A

In a zoom lens, in order to obtain high optical performance over the entire zoom range and the entire object distance while securing a predetermined zoom ratio, it is important to appropriately set each element constituting the zoom lens. For example, the zoom type (number of lens groups and the refractive power of each lens group), the movement trajectory associated with zooming of each lens group, the magnification burden of each lens group, the selection of the lens group for focusing and the lens configuration, etc. Setting is important.
If these configurations are not appropriate, the entire system becomes larger when a high zoom ratio is achieved, and fluctuations in various aberrations associated with zooming and focusing increase, resulting in high optical performance over the entire zoom range and overall object distance. It becomes very difficult to get.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a small zoom lens and an image pickup apparatus having the same that can easily focus quickly, have a high zoom ratio, and can obtain high optical performance over the entire zoom range and the entire object distance.

The zoom lens according to the present invention includes 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, arranged in order from the object side to the image side. In a zoom lens comprising a fourth lens group having a refractive power, a fifth lens group having a negative refractive power, and a sixth lens group having a positive refractive power, the distance between adjacent lens groups being changed during zooming.
During zooming, the first lens group moves,
During focusing, the fifth lens group moves,
The fifth lens group includes a positive lens;
The image side surface of the lens disposed closest to the image side of the fifth lens group is a concave surface,
The lateral magnification of the fifth lens group when focused at infinity at the wide angle end is βnfw, the lateral magnification of the sixth lens group when focused at infinity at the wide angle end is βplw, and the total magnification at the wide angle end is When the focal length of the system is fw and the focal length of the second lens group is f2,
−10.0 <(1- (βnfw) ² ) × (βplw) ² ≦ −2.515
0.7 <| f2 / fw | <1.2
It is characterized by satisfying the following conditional expression.

  According to the present invention, it is possible to obtain a small zoom lens that is easy to quickly focus and has a high zoom ratio and high optical performance over the entire zoom range and the entire object distance.

(A), (B), (C) Cross-sectional views of the zoom lens of Reference Example 1 at the wide-angle end, the intermediate zoom position, and the telephoto end (A), (B), (C) aberration diagrams of the zoom lens of Reference Example 1 at the wide-angle end, the intermediate zoom position, and the telephoto end (A), (B), (C) Cross-sectional views of the zoom lens of Example 1 at the wide-angle end, the intermediate zoom position, and the telephoto end (A), (B), (C) Aberration diagrams at the wide-angle end, intermediate zoom position, and telephoto end of the zoom lens of Example 1 . (A), (B), (C) Cross-sectional views of the zoom lens of Reference Example 2 at the wide-angle end, the intermediate zoom position, and the telephoto end (A), (B), (C) aberration diagrams of the zoom lens of Reference Example 2 at the wide-angle end, the intermediate zoom position, and the telephoto end (A), (B), (C) Cross-sectional views of the zoom lens of Example 2 at the wide-angle end, the intermediate zoom position, and the telephoto end (A), (B), (C) Aberration diagrams at the wide-angle end, intermediate zoom position, and telephoto end of the zoom lens of Example 2 . Schematic diagram of main parts of an imaging apparatus of the present invention

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The zoom lens according to the present invention includes a first lens group having a positive refractive power (optical power = reciprocal of focal length), a second lens group having a negative refractive power, and a positive lens arranged in order from the object side to the image side. A third lens group having a refractive power, a fourth lens group having a positive refractive power, a fifth lens group having a negative refractive power, and a sixth lens group having a positive refractive power . The distance between adjacent lens units changes during zooming. The first lens group moves during zooming, and the fifth lens group moves during focusing. The fifth lens group has a positive lens.

1A, 1B, and 1C are lens cross-sectional views at the wide-angle end (short focal length end), the intermediate zoom position, and the telephoto end (long focal length end) of the zoom lens of Reference Example 1 of the present invention. is there. 2A, 2B, and 2C are aberration diagrams of the zoom lens of Reference Example 1 at the wide-angle end, the intermediate zoom position, and the telephoto end, respectively . Reference Example 1 is a zoom lens having a zoom ratio of 4.23 and an aperture ratio of about 3.6 to 5.6.

3A, 3B, and 3C are lens cross-sectional views at the wide-angle end, the intermediate zoom position, and the telephoto end of the zoom lens according to Embodiment 1 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 first exemplary embodiment . Example 1 is a zoom lens having a zoom ratio of 4.68 and an aperture ratio of about 4.1 to 5.9.

5A, 5B, and 5C are lens cross-sectional views at the wide-angle end, the intermediate zoom position, and the telephoto end of the zoom lens according to Reference Example 2 of the present invention. 6A, 6B, and 6C are aberration diagrams of the zoom lens of Reference Example 2 at the wide-angle end, the intermediate zoom position, and the telephoto end, respectively. Reference Example 2 is a zoom lens having a zoom ratio of 4.13 and an aperture ratio of about 4.1 to 4.1.

7A, 7B, and 7C are lens cross-sectional views at the wide-angle end, the intermediate zoom position, and the telephoto end of the zoom lens according to Embodiment 2 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 second embodiment . The second embodiment is a zoom lens having a zoom ratio of 3.84 and an aperture ratio of about 3.6 to 5.7. FIG. 9 is a schematic diagram of a main part of the imaging apparatus of the present invention.

  The zoom lens of each embodiment is a photographing lens system used for an imaging apparatus such as a video camera, a digital still camera, a silver salt film camera, and a TV camera. In addition, the zoom lens of each embodiment can also be used as a projection optical system for a projection apparatus (projector). In the lens cross-sectional view, the left side is the object side (front), and the right side is the image side (rear). In the lens cross-sectional view, when i is the order of the lens group from the object side, Li indicates the i-th lens group.

  GP is an intermediate group having a positive refractive power as a whole including one or more lens groups. NF is a lens unit having a negative refractive power, and moves during focusing. PL is a lens unit having a positive refractive power. SP is an aperture stop that determines (limits) a light beam having an open F number (Fno). The FP is a flare cut stop and cuts unnecessary light. IP is an image plane, and when used as a photographing optical system of a video camera or a digital still camera, an imaging plane of a solid-state imaging device (photoelectric conversion device) such as a CCD sensor or a CMOS sensor is placed. Further, when used as a photographing optical system for a silver salt film camera, a photosensitive surface corresponding to the film surface is provided.

  The arrows indicate the movement trajectory of each lens unit during zooming from the wide-angle end to the telephoto end. The arrow related to the focus indicates the moving direction of the lens unit during focusing from infinity to a short distance.

In Reference Example 1 of FIG. 1, L1 is a first lens group having a positive refractive power, L2 is a second lens group having a negative refractive power, L3 is a third lens group having a positive refractive power, and L4 is a negative refractive power. The fourth lens unit L5 is a fifth lens unit having a positive refractive power. The third lens group L3 corresponds to the intermediate group GP, the fourth lens group L4 corresponds to the fifth lens group, and the fifth lens group L5 corresponds to the sixth lens group.

In the zoom lens of Reference Example 1 , the first lens unit L1 monotonously moves toward the object side during zooming from the wide-angle end to the telephoto end. In addition, the distance between the first lens unit L1 and the second lens unit L2 at the telephoto end is wider than that at the wide-angle end, and the interval between the second lens unit L2 and the third lens unit L3 is narrowed. Each lens group is moved so that the distance between the third lens group L3 and the fourth lens group L4 is wide and the distance between the fourth lens group L4 and the fifth lens group L5 is narrow.

In Reference Example 1 , focusing is performed by moving the fourth lens unit L4 on the optical axis. The solid curve 4a and the dotted curve 4b of the fourth lens unit L4 correct image plane fluctuations during zooming from the wide-angle end to the telephoto end zoom position when focusing on an object at infinity and an object at close distance, respectively. It is a movement locus for Further, when focusing from an infinitely distant object to a close object at the zoom position at the telephoto end, the fourth lens unit L4 is moved backward (image side) as indicated by an arrow 4c.

In Example 1, Reference Example 2, and Example 2 of FIGS. 3, 5, and 7, L1 is a first lens unit having a positive refractive power, L2 is a second lens unit having a negative refractive power, and L3 is a positive refractive power. L4 is a fourth lens group having a positive refractive power, L5 is a fifth lens group having a negative refractive power, and L6 is a sixth lens group having a positive refractive power. The third lens group L3 and the fourth lens group L4 correspond to the intermediate group GP, the fifth lens group L5 corresponds to the fifth lens group, and the sixth lens group L6 corresponds to the sixth lens group.

In the zoom lens of Example 1 , the first lens unit L1 monotonously moves toward the object side during zooming from the wide-angle end to the telephoto end. The distance between the first lens unit L1 and the second lens unit L2 at the telephoto end is made wider than at the wide angle end. The distance between the second lens group L2 and the third lens group L3 is narrow, the distance between the third lens group L3 and the fourth lens group L4 is narrow, and the distance between the fourth lens group L4 and the fifth lens group L5 is wide. The distance between the fifth lens unit L5 and the sixth lens unit L6 is increased.

In the zoom lens of Reference Example 2 , the first lens unit L1 monotonously moves toward the object side during zooming from the wide-angle end to the telephoto end. The distance between the first lens unit L1 and the second lens unit L2 at the telephoto end is made wider than at the wide angle end. Further, the distance between the second lens group L2 and the third lens group L3 is narrow, the distance between the third lens group L3 and the fourth lens group L4 is wide, and the distance between the fourth lens group L4 and the fifth lens group L5 is wide. The distance between the fifth lens unit L5 and the sixth lens unit L6 is increased.

In the zoom lens of Example 2 , the first lens unit L1 monotonously moves toward the object side during zooming from the wide-angle end to the telephoto end. The distance between the first lens unit L1 and the second lens unit L2 at the telephoto end is made wider than at the wide angle end. Further, the distance between the second lens group L2 and the third lens group L3 is narrow, the distance between the third lens group L3 and the fourth lens group L4 is wide, and the distance between the fourth lens group L4 and the fifth lens group L5 is wide. The distance between the fifth lens unit L5 and the sixth lens unit L6 is increased.

In Example 1, Reference Example 2, and Example 2 , focusing is performed by moving the fifth lens unit L5 on the optical axis. The solid curve 5a and the dotted curve 5b of the fifth lens unit L5 correct image plane fluctuations during zooming from the wide-angle end to the telephoto end zoom position when focusing on an object at infinity and an object at close distance, respectively. It is a movement locus for Further, when focusing from an infinitely distant object to a close object at the zoom position at the telephoto end, the fifth lens unit L5 is retracted backward (image side) as indicated by an arrow 5c.

  In the aberration diagrams, Fno is the F number, ω is the half field angle (degrees), and the field angle based on the ray tracing value. In the spherical aberration diagram, d is the d-line (wavelength 587.56 nm), and g is the g-line (wavelength 435.835 nm). In the astigmatism diagram, ΔS is a sagittal image plane at d-line, and ΔM is a meridional image plane at d-line. Distortion is shown for the d-line. In the lateral chromatic aberration diagram, g is a g-line. In each of the following embodiments, the wide-angle end and the telephoto end refer to zoom positions when the zoom lens group is positioned at both ends of a range in which the zoom lens unit can move on the optical axis.

  The zoom lens of the present invention is configured as follows in order from the object side to the image side in order to ensure a predetermined zoom ratio and correct aberrations satisfactorily. The first lens unit L1 having a positive refractive power, the second lens unit L2 having a negative refractive power, and one or more lens units, the intermediate group GP having a positive refractive power as a whole, and the fifth lens having a negative refractive power And a sixth lens group having a positive refractive power.

During the focusing, the fifth lens group moves. The lateral magnification of the fifth lens group when focusing at infinity at the wide-angle end is βnfw, and the lateral magnification of the sixth lens group when focusing at infinity at the wide-angle end is βplw. At this time,
−10.0 <(1- (βnfw) ² ) × (βplw) ² ≦ −2.515 (1)
This satisfies the conditional expression

  By disposing the sixth lens group having a positive refractive power on the image side of the fifth lens group having a negative refractive power, the sixth lens group having a positive refractive power can function as a field lens, and the exit pupil position can be determined. Keep away. As a result, for example, the telecentricity is improved on the image side necessary for a photographing apparatus using a solid-state imaging device or the like. Then, during zooming from the wide-angle end to the telephoto end, the first lens unit L1 moves to the object side. During zooming from the wide-angle end to the telephoto end, the distance between the first lens unit L1 and the second lens unit L2 is increased, and the subsequent lens unit is also moved to arbitrarily move the entrance pupil at the telephoto end. In this way, the entire system is reduced in size.

  In addition, the zooming operation of the first lens unit L1 and the second lens unit L2 is shared by moving the intermediate group GP having a positive refractive power as a whole during zooming. Thus, the amount of movement of the first lens unit L1 and the second lens unit L2 is reduced during zooming, and the total lens length at the telephoto end is shortened. Further, the fifth lens unit having a negative refractive power moves during focusing. In the inner focus type zoom lens, the focusing lens group is small and light, easy to operate, and easy to operate at high speed. In addition, there is an advantage that the center of gravity of the entire lens system changes little when focusing on an object at infinity and a close object, and holding is easy.

  On the other hand, if the inner focus type is adopted in a bright zoom lens having a small F value (F number), the aberration fluctuation at the time of focusing becomes large, and it is difficult to correct the aberration fluctuation at this time, and the optical performance is good. Difficult to maintain. Therefore, in the present invention, in order to reduce the variation in curvature of field on the wide-angle side due to focusing and the variation in spherical aberration on the telephoto side, and to reduce the size of the entire system, the fifth lens unit having a negative refractive power is positive. The sixth lens unit has a refractive power.

  In particular, the lens surface closest to the image side of the fifth lens unit having a negative refractive power has a concave shape on the image side to reduce the variation of spherical aberration on the telephoto side.

Conditional expression (1) defines the position sensitivity of the fifth lens group at the wide-angle end. Here, the position sensitivity ES is the ratio of the moving amount Δsk in the optical axis direction of the imaging position (focus position) when the moving lens group is moved in the optical axis direction by the distance Δx ES = Δsk / Δx
It is. The shift amount of the back focus of the movement amount of the fifth lens group is Δsk, the lateral magnification of the fifth lens group at the wide-angle end is βnfw, the lateral magnification of the sixth lens group on the image side from the fifth lens group is βplw, and the fifth lens When the movement amount of the group is Δx, the deviation amount Δsk is approximately expressed by the following equation.

Δsk = {(1− (βnfw) ² ) × (βplw) ² } × Δx
According to the above equation, it can be seen that the position sensitivity is 0 when the absolute value of the lateral magnification of the moving lens group is 1, and increases as the absolute value of the lateral magnification is away from 1. When the fifth lens group is a focus lens group, a sufficient distance is set in advance in the optical axis direction so that the fifth lens group and the sixth lens group on the image side from the fifth lens group do not interfere with each other. The lens group must be released.

  When the upper limit of conditional expression (1) is exceeded, the amount of movement required to move the image by a predetermined amount increases, making it difficult to downsize the entire system. In addition, on the wide-angle side when the fifth lens group is moved in order to move the image by a predetermined amount, suppression of variations in spherical aberration and field curvature increases. When the lower limit of conditional expression (1) is exceeded, the imaging position moves greatly with respect to the minute movement of the fifth lens group, and high-accuracy position control is required.

In each embodiment, the numerical range of conditional expression (1) is more preferably set as follows.
−6.0 <(1− (βnfw) ² ) × (βplw) ² ≦ −2.515 (1a)
By satisfying conditional expression (1a), the position sensitivity of the fifth lens group at the wide-angle end is set more appropriately, and it becomes easy to perform high-speed and high-precision focus adjustment. More preferably, the numerical range of the conditional expression (1a) is set as follows.
−5.6 <(1− (βnfw) ² ) × (βplw) ² ≦ −2.515 (1b)

  As described above, by appropriately configuring the lens groups and satisfying conditional expression (1), a zoom lens having a high zoom ratio and high overall zoom performance with high imaging performance over the entire zoom range can be obtained. Furthermore, quick focusing becomes easy.

  In each embodiment, it is more preferable to satisfy one or more of the following conditional expressions. The focal length of the entire system at the wide angle end is fw, and the focal length of the fifth lens group is fnf. Let Da be the lens interval on the optical axis between the fifth lens group and the sixth lens group when focusing to infinity at the telephoto end. Let the focal length of the second lens unit L2 be f2. Let ft be the focal length of the entire system at the telephoto end. Let the focal length of the sixth lens group be fpl. When the fifth lens group includes one positive lens NFp and one negative lens NFn, the Abbe number of the material of the positive lens NFp is νnfp and the Abbe number of the material of the negative lens NFn is νnfn.

  When the fifth lens group includes one negative lens NFnA, the Abbe number of the material of the negative lens NFnA is νnfnA. The lateral magnification of the fifth lens group when focused at infinity at the telephoto end is βnft, and the lateral magnification of the sixth lens group when focused at infinity at the telephoto end is βplt. At this time, one or more of the following conditional expressions should be satisfied.

0.8 <| fnf / fw | <4.0 (2)
0.10 <| Da / fnf | <0.95 (3)
0.7 <| f2 / fw | <1.2 (4)
0.2 <| fnf / ft | <0.8 (5)
0.22 <| fnf / fpl | <0.90 (6)
1.3 <νnfn / νnfp <2.8 (7)
55 <νnfnA <90 (8)
−8.0 <(1- (βnft) ² ) × (βplt) ² <−1.5 (9)

Note that the Abbe number νd of the material is Nd, NF, and NC, respectively, for the refractive indices of the Fraunhofer line d-line, F-line, and C-line. At this time,
νd = (Nd−1) / (NF−NC)
Defined by

  Next, the technical meaning of each conditional expression described above will be described. Conditional expression (2) is an expression in which the focal length of the fifth lens unit having negative refractive power is defined by the focal length of the entire system at the wide angle end. If the negative refracting power of the fifth lens unit becomes too weak beyond the upper limit of the conditional expression (2) (the absolute value of the negative refracting power becomes too small), when performing focusing, a desired size is obtained. It is necessary to secure a space in advance, and the total lens length increases.

  When the lower limit of conditional expression (2) is exceeded, the divergence of the light beam emitted from the fifth lens group becomes too strong, and the curvature of field and the variation of spherical aberration increase with focusing on the wide angle side. It also becomes difficult to ensure a desired back focus length.

  Conditional expression (3) is a condition for favorably performing focusing with the fifth lens unit having a negative refractive power. If the negative refracting power of the fifth lens unit increases beyond the upper limit of conditional expression (3) (the absolute value of the negative refracting power increases), the entire system can be easily downsized, but the intermediate focal length It becomes difficult to correct astigmatism from the area to the telephoto end. When the lower limit of conditional expression (3) is exceeded and the negative refractive power of the fifth lens group decreases, the amount of movement of the fifth lens group increases when focusing on a short-distance object, and the entire system becomes larger. . Also, when trying to obtain a desired zoom ratio at the telephoto end, the effective diameter of the front lens increases.

  Conditional expression (4) is an expression in which the focal length f2 of the second lens unit L2 is defined by the focal length fw of the entire system at the wide angle end. If the negative refracting power of the second lens unit L2 is reduced beyond the upper limit of conditional expression (4), the total lens length increases when a high zoom ratio is achieved. If the negative refractive power of the second lens unit L2 exceeds the lower limit of the conditional expression (4), it is advantageous for increasing the zoom ratio and shortening the overall lens length, but the Petzval sum increases in the negative direction. The curvature of field increases.

  Conditional expression (5) is an expression in which the focal length of the fifth lens unit having a negative refractive power is defined by the focal length of the entire system at the telephoto end. The lateral magnification when focusing to the near side is smaller than the lateral magnification when focusing at infinity at the telephoto end, because the fifth lens unit having negative refractive power moves to the image side. . When the absolute value of the focal length of the fifth lens unit having a negative refractive power increases beyond the upper limit of conditional expression (5), the variation in spherical aberration accompanying focusing at the telephoto end increases. If the absolute value of the focal length of the fifth lens unit having a negative refractive power is smaller than the lower limit of conditional expression (5), the angle of view varies greatly with focusing to the closest side, which is not good.

  Conditional expression (6) is an expression in which the focal length of the fifth lens unit having negative refractive power is defined by the focal length of the sixth lens unit having positive refractive power, and the entire system is compact while achieving a high zoom ratio. This is to make it easier. If the upper limit of conditional expression (6) is exceeded and the focal length of the sixth lens group is shortened, various aberrations occur during zooming from the wide-angle end to the telephoto end, and in order to correct this, You will have to increase the number of lenses. When the lower limit of conditional expression (6) is exceeded, the exit pupil position becomes too close at the wide-angle end, making it difficult to maintain good telecentricity. Also, the variation of spherical aberration and axial chromatic aberration increases during focusing.

  Conditional expression (7) indicates that the Abbe number of the material of the positive lens NFp and the material of the negative lens NFn when the fifth lens unit having negative refractive power is composed of one positive lens NFp and one negative lens NFn. It is the formula which prescribed | regulated ratio of Abbe number of. When the Abbe number ratio increases beyond the upper limit of conditional expression (7), it becomes difficult to reduce fluctuations in coma during focusing while reducing fluctuations in axial chromatic aberration during zooming. If the ratio of the Abbe number becomes smaller than the lower limit of conditional expression (7), the power of each lens surface of the fifth lens group must be increased in order to eliminate the color in the fifth lens group. The aberration coefficient becomes large and correction of various aberrations becomes difficult.

  Conditional expression (8) defines the Abbe number of the material of the negative lens NFnA when the fifth lens unit having negative refractive power is composed of one negative lens NFnA, and changes in axial chromatic aberration during focusing. Defines the conditions to keep the value small. If the lower limit of conditional expression (8) is exceeded, the variation in axial chromatic aberration during focusing increases, and the variation increases particularly on the telephoto side. If the upper limit value of conditional expression (8) is exceeded, it is necessary to increase the curvature of the lens surface in order to provide the desired refractive power. As a result, it is difficult to sufficiently correct the variation in curvature of field due to focusing, which is not preferable.

  Conditional expression (9) relates to the ratio of βnft for the lateral magnification of the fifth lens group at the telephoto end and βplt for the lateral magnification of the sixth lens group on the image side of the lens group NF at the telephoto end. If the upper limit of conditional expression (9) is exceeded, the amount of movement of the fifth lens unit during focusing on the telephoto side increases, making it difficult to reduce the size of the entire system. If the lower limit of conditional expression (9) is exceeded, the variation in field curvature accompanying the focusing of the fifth lens group will increase on the telephoto side.

  As described above, according to the present invention, a high zoom ratio, a small lens system as a whole, quick focusing, and high optical performance with excellent correction of various aberrations such as spherical aberration, coma and curvature of field. The resulting zoom lens is obtained.

More preferably, the numerical ranges of the conditional expressions (2) to (9) are set as follows.
0.9 <| fnf / fw | <2.8 (2a)
0.15 <| Da / fnf | <0.88 (3a)
0.7 <| f2 / fw | <1.0 (4a)
0.23 <| fnf / ft | <0.70 (5a)
0.25 <| fnf / fpl | <0.80 (6a)
1.4 <νnfn / νnfp <2.5 (7a)
60 <νnfnA <82 (8a)
-7.7 <(1- (βnft) ² ) × (βplt) ² <-1.7 (9a)

  By satisfying conditional expression (2a), the ratio of the fifth lens unit having a negative refractive power to the focal length of the entire system at the wide-angle end becomes more appropriate, and fluctuations in spherical aberration due to widening the angle and focusing are further reduced. it can. By satisfying conditional expression (3a), it is possible to optimize the moving space during focusing of the fifth lens unit having negative refractive power, and it is further easier to shorten the total lens length at the wide angle end and to reduce the effective diameter of the front lens. become. By satisfying conditional expression (4a), it becomes easy to reduce fluctuations in field curvature during zooming while achieving a wide angle of view and a high zoom ratio.

  By satisfying conditional expression (5a), it is easy to shorten the total lens length at the telephoto end while further reducing the size and weight of the fifth lens unit having negative refractive power. By satisfying the conditional expression (6a), it becomes easier to further reduce the fluctuation of the field curvature accompanying the focusing over the entire zoom range. By satisfying conditional expression (7a), it becomes easier to further reduce the variation in longitudinal chromatic aberration and the variation in lateral chromatic aberration during zooming. By satisfying conditional expression (8a), it becomes easier to reduce the eccentric coma aberration generated from the fifth lens unit having a negative refractive power.

  By satisfying conditional expression (9a), it becomes easier to further reduce aberration fluctuations during focusing. Preferably, the numerical ranges of conditional expressions (2a) to (9a) are set as follows.

1.01 <| fnf / fw | <2.60 (2b)
0.18 <| Da / fnf | <0.80 (3b)
0.7 <| f2 / fw | <0.9 (4b)
0.25 <| fnf / ft | <0.65 (5b)
0.27 <| fnf / fpl | <0.72 (6b)
1.5 <νnfn / νnfp <2.3 (7b)
65 <νnfnA <75 (8b)
−7.5 <(1- (βnft) ² ) × (βplt) ² <−1.9 (9b)

In Example 1 and Reference Example 2 , when the positive lens on the image side of the fourth lens unit L4 is moved so as to have a component perpendicular to the optical axis, the entire optical system vibrates (tilts). The camera shake is corrected. In each embodiment, image blur correction may be performed by moving an arbitrary lens group so as to have a component in a direction perpendicular to the optical axis.

Next, an embodiment of a digital still camera (imaging device) using the zoom lens of the present invention as an imaging optical system will be described with reference to FIG. In FIG. 9, reference numeral 10 denotes a camera body, and 11 denotes a photographing optical system constituted by any one of the zoom lenses described in Reference Example 1, Example 1, Reference Example 2, and Example 2 . Reference numeral 12 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 11 and is built in the camera body.

Hereinafter, Reference Example 1, Example 1, Reference Example 2, numerical reference example 1 corresponding to Example 2, Numerical Example 1, numerical reference example 2, Numerical data of Numerical Example 2. In each numerical example and each numerical reference example , i indicates a surface number counted from the object side. ri is the radius of curvature of the i-th optical surface (i-th surface). di is the axial distance between the i-th surface and the (i + 1) -th surface. ndi and νdi are the refractive index and Abbe number of the material of the i-th optical member with respect to the d-line, respectively. The aspherical shape is the X axis in the optical axis direction, the H axis in the direction perpendicular to the optical axis, the light traveling direction is positive, R is the paraxial radius of curvature, K is the conic constant, and A4, A6, A8, and A10 are aspherical surfaces. As a coefficient

It is expressed by the following formula. * Means a surface having an aspherical shape. “E-x” means 10-x. BF is a back focus and indicates a distance from the final lens surface to the image plane. The wide angle indicates the wide angle end, the middle indicates the intermediate zoom position, and the telephoto indicates the telephoto end. Table 1 shows the relationship between the parameters relating to the above-described conditional expressions and the numerical examples for the conditional expressions.

[Numerical reference example 1]
Unit mm

Surface data surface number rd nd vd
1 152.084 1.50 1.84666 23.8
2 87.856 5.60 1.60311 60.6
3 666.732 0.20
4 53.075 4.38 1.69680 55.5
5 87.855 (variable)
6 68.608 1.48 1.83481 42.7
7 16.086 9.11
8 -98.918 1.35 1.80 400 46.6
9 38.593 0.20
10 27.267 4.89 1.80809 22.8
11 -748.017 1.23 1.77250 49.6
12 69.141 (variable)
13 ∞ (variable) (Flare cut aperture)
14 31.223 1.00 2.00069 25.5
15 18.182 6.74 1.61800 63.3
16 -69.750 2.00
17 (Aperture) ∞ 2.00
18 * 32.539 4.79 1.55332 71.7
19 * -48.623 (variable)
20 -49.741 2.62 1.84666 23.8
21 -19.832 1.00 1.69350 53.2
22 32.513 (variable)
23 * 62.039 4.97 1.55332 71.7
24 -27.814 0.50
25 -102.764 4.68 1.59522 67.7
26 -18.865 0.00
27 -18.865 1.30 1.91082 35.3
28 58.577 1.01
29 269.777 2.59 1.85026 32.3
30 -64.164 (variable)
Image plane ∞

Aspheric data 18th surface
K = 0.00000e + 000 A 4 = -4.92991e-006 A 6 = -1.14326e-008 A 8 = 1.68392e-011

19th page
K = 0.00000e + 000 A 4 = 1.05318e-006 A 6 = -9.33790e-009

23rd page
K = 0.00000e + 000 A 4 = -5.40775e-006 A 6 = -6.88030e-010 A 8 = 7.08343e-012

Various data Zoom ratio 4.23
Wide angle Medium Telephoto focal length 24.70 44.23 104.57
F number 3.60 4.50 5.60
Half angle of view (degrees) 41.22 26.07 11.69
Image height 21.64 21.64 21.64
Total lens length 164.73 170.65 201.71
BF 38.60 49.38 64.11

d 5 1.50 17.62 48.21
d12 17.21 9.67 5.80
d13 22.10 12.00 2.78
d19 1.86 5.00 9.29
d22 18.34 11.86 6.41
d30 38.60 49.38 64.11

Zoom lens group data group Start surface Focal length
1 1 136.23
2 6 -18.34
3 13 ∞
4 14 23.37
5 20 -32.18
6 23 114.78

[Numerical Example 1]
Unit mm

Surface data surface number rd nd vd
1 200.000 2.00 1.90366 31.3
2 77.733 7.43 1.59522 67.7
3 -280.363 0.10
4 51.743 3.78 1.77250 49.6
5 83.493 (variable)
6 * 115.999 1.37 1.85135 40.1
7 19.098 7.45
8 -39.190 1.10 1.80 400 46.6
9 45.778 0.14
10 35.008 6.87 1.85478 24.8
11 -39.058 1.18
12 -25.770 1.10 1.85135 40.1
13 * -59.332 (variable)
14 (Aperture) ∞ 1.00
15 * 20.502 7.09 1.61881 63.9
16 * -44.855 2.00
17 97.510 5.16 1.59522 67.7
18 -28.310 1.20 1.83400 37.2
19 17.939 1.45
20 37.907 3.19 1.69680 55.5
21 -45.709 (variable)
22 -47.839 1.59 1.84666 23.8
23 -31.983 1.00 1.74400 44.8
24 70.197 2.00
25 32.043 4.67 1.43875 94.9
26 -26.503 (variable)
27 275.115 2.74 1.92286 18.9
28 -35.437 1.00 1.90270 31.0
29 * 31.031 (variable)
30 -83.298 5.03 1.53775 74.7
31 -32.444 (variable)
Image plane ∞

Aspheric data 6th surface
K = 0.00000e + 000 A 4 = 1.68557e-006 A 6 = 1.48638e-008 A 8 = -6.90836e-011 A10 = 1.50692e-013

Side 13
K = -1.83261e + 000 A 4 = -2.27230e-006 A 6 = 2.61258e-008 A 8 = -1.32016e-010 A10 = 3.98803e-013

15th page
K = -4.60320e-001 A 4 = -4.31200e-006 A 6 = 1.59871e-008 A 8 = 8.25859e-012

16th page
K = -1.23264e + 001 A 4 = -2.18402e-006 A 6 = 3.28436e-008 A 8 = -5.47342e-011

29th page
K = -5.78822e-001 A 4 = 6.08432e-006 A 6 = -6.57045e-009

Various data Zoom ratio 4.68
Wide angle Medium Telephoto focal length 28.80 41.68 134.79
F number 4.12 5.00 5.88
Half angle of view (degrees) 36.92 27.43 9.12
Image height 21.64 21.64 21.64
Total lens length 158.46 162.93 211.19
BF 36.97 36.95 38.38

d 5 1.50 9.87 45.61
d13 36.57 24.90 7.08
d21 2.11 1.98 1.95
d26 1.88 6.94 16.47
d29 7.78 10.64 30.05
d31 36.97 36.95 38.38

Zoom lens group data group Start surface Focal length
1 1 115.54
2 6 -20.50
3 14 30.79
4 22 128.71
5 27 -40.05
6 30 95.52

[Numerical reference example 2]
Unit mm

Surface data surface number rd nd vd
1 200.000 2.00 1.84666 23.8
2 89.175 7.82 1.59522 67.7
3 -1693.392 0.10
4 49.417 5.80 1.83481 42.7
5 84.598 (variable)
6 * 84.364 1.37 1.85135 40.1
7 15.304 9.77
8 -38.939 1.10 1.81600 46.6
9 64.380 0.14
10 41.625 6.12 1.85478 24.8
11 -46.574 1.30
12 -27.668 1.10 1.85135 40.1
13 * -40.123 (variable)
14 (Aperture) ∞ 1.00
15 * 23.424 7.60 1.69680 55.5
16 * -60.498 2.00
17 153.559 6.18 1.59522 67.7
18 -16.363 1.20 1.83400 37.3
19 22.075 1.27
20 46.064 3.49 1.71300 53.9
21 -37.666 (variable)
22 -64.880 1.70 1.80518 25.4
23 -36.876 1.00 1.76200 40.1
24 65.168 2.00
25 40.524 4.22 1.48749 70.2
26 -30.481 (variable)
27 -614.890 1.50 1.55332 71.7
28 * 36.346 (variable)
29 -333.699 4.63 1.59522 67.7
30 -45.052 (variable)
Image plane ∞

Aspheric data 6th surface
K = 0.00000e + 000 A 4 = 6.39715e-006 A 6 = -1.11244e-008 A 8 = 9.00320e-012 A10 = -3.43385e-015

Side 13
K = 1.93305e + 000 A 4 = 1.64349e-006 A 6 = 9.39889e-009 A 8 = -8.21934e-011 A10 = 2.65274e-013

15th page
K = -4.03860e + 000 A 4 = 3.51670e-005 A 6 = -4.98430e-008 A 8 = 1.82645e-010 A10 = -9.19935e-014

16th page
K = 1.31581e + 001 A 4 = 1.56671e-005 A 6 = 6.37646e-009 A 8 = 8.30086e-011

28th page
K = -9.80403e-001 A 4 = 4.75909e-006 A 6 = -1.00540e-008

Various data Zoom ratio 4.13
Wide angle Medium Telephoto focal length 24.70 32.04 102.11
F number 4.10 4.10 4.10
Half angle of view (degrees) 41.22 34.03 11.96
Image height 21.64 21.64 21.64
Total lens length 148.96 152.86 207.64
BF 35.80 36.22 53.51

d 5 1.50 8.52 42.05
d13 29.63 21.94 3.41
d21 1.40 1.85 1.99
d26 0.73 3.77 2.64
d28 5.50 6.16 29.64
d30 35.80 36.22 53.51

Zoom lens group data group Start surface Focal length
1 1 107.61
2 6 -21.00
3 14 32.86
4 22 139.58
5 27 -61.97
6 29 86.98

[Numerical Example 2]
Unit mm

Surface data surface number rd nd vd
1 143.229 1.90 1.85478 24.8
2 61.995 6.60 1.77250 49.6
3 251.772 0.15
4 57.137 4.16 1.77250 49.6
5 101.019 (variable)
6 45.867 1.80 1.88300 40.8
7 15.170 10.23
8 -87.815 1.30 1.80 400 46.6
9 31.799 0.40
10 26.618 5.96 1.85478 24.8
11 -153.523 1.20 1.77250 49.6
12 99.251 3.00
13 ∞ (variable) (Flare cut aperture)
14 (Aperture) ∞ 0.80
15 20.252 2.56 1.49700 81.5
16 56.927 3.11
17 40.058 1.00 1.77250 49.6
18 13.755 7.70 1.51742 52.4
19 -97.041 (variable)
20 * 40.197 5.67 1.58313 59.4
21 -21.225 0.80 1.80809 22.8
22 -42.723 (variable)
23 -25.097 3.55 1.80 100 35.0
24 -14.903 1.00 1.59522 67.7
25 29.926 (variable)
26 42.007 5.33 1.49700 81.5
27 -57.908 0.50
28 108.364 1.30 1.80518 25.4
29 38.873 2.12
30 141.052 3.72 1.59522 67.7
31 -62.382 (variable)
Image plane ∞

Aspheric data 20th surface
K = 0.00000e + 000 A 4 = -2.84828e-006 A 6 = 5.68576e-009 A 8 = 4.07031e-011

Various data Zoom ratio 3.84
Wide angle Medium Telephoto focal length 25.39 46.78 97.55
F number 3.60 5.75 5.74
Half angle of view (degrees) 40.44 24.82 12.51
Image height 21.64 21.64 21.64
Total lens length 161.27 177.91 202.87
BF 42.60 51.08 52.16

d 5 0.90 19.20 46.35
d13 29.96 13.29 0.93
d19 2.57 3.65 5.27
d22 4.30 8.16 15.61
d25 5.10 6.70 6.71
d31 42.60 51.08 52.16

Zoom lens group data group Start surface Focal length
1 1 130.67
2 6 -19.50
3 14 46.57
4 20 44.74
5 23 -25.91
6 26 49.62

L1 1st lens group L2 2nd lens group L3 3rd lens group L4 4th lens group L5 5th lens group L6 6th lens group Gp Lens group Gp NF 5th 6th lens group 6th lens group

Claims (8)

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 fourth lens group having a positive refractive power, which are arranged in order from the object side to the image side. In a zoom lens that includes a fifth lens group having a negative refractive power and a sixth lens group having a positive refractive power, and in which the distance between adjacent lens groups changes during zooming,
During zooming, the first lens group moves,
During focusing, the fifth lens group moves,
The fifth lens group includes a positive lens;
The image side surface of the lens disposed closest to the image side of the fifth lens group is a concave surface,
The lateral magnification of the fifth lens group when focused at infinity at the wide angle end is βnfw, the lateral magnification of the sixth lens group when focused at infinity at the wide angle end is βplw, and the total magnification at the wide angle end is When the focal length of the system is fw and the focal length of the second lens group is f2,
−10.0 <(1- (βnfw) ² ) × (βplw) ² ≦ −2.515
0.7 <| f2 / fw | <1.2
A zoom lens characterized by satisfying the following conditional expression: When the focal length of the fifth lens group is fnf,
0.8 <| fnf / fw | <4.0
The zoom lens according to claim 1, wherein the following conditional expression is satisfied. When the focal distance of the fifth lens group is fnf, and the lens interval on the optical axis of the fifth lens group and the sixth lens group when focusing at infinity at the telephoto end is Da,
0.10 <| Da / fnf | <0.95
The zoom lens according to claim 1, wherein the following conditional expression is satisfied. When the focal length of the fifth lens group is fnf and the focal length of the entire system at the telephoto end is ft,
0.2 <| fnf / ft | <0.8
The zoom lens according to claim 1, wherein the following conditional expression is satisfied. When the focal length of the fifth lens group is fnf and the focal length of the sixth lens group is fpl,
0.22 <| fnf / fpl | <0.90
The zoom lens according to claim 1, wherein the following conditional expression is satisfied. The fifth lens group includes the positive lens and the negative lens, and when the Abbe number of the material of the positive lens is νnfp and the Abbe number of the material of the negative lens is νnfn,
1.3 <νnfn / νnfp <2.8
The zoom lens according to claim 1, wherein the following conditional expression is satisfied. When the lateral magnification of the fifth lens group when focusing at infinity at the telephoto end is βnft, and the lateral magnification of the sixth lens group when focusing at infinity at the telephoto end is βplt,
−8.0 <(1− (βnft) ² ) × (βplt) ² <−1.5
The zoom lens according to claim 1, wherein the following conditional expression is satisfied. An image pickup apparatus comprising: the zoom lens according to claim 1; and an image pickup element that receives an image formed by the zoom lens.