Zoom lens and imaging apparatus

Abstract

To prevent the occurrence of aberration fluctuations and offset aperture along with zooming in a small-size, light-weight zoom lens.SOLUTION: A zoom lens consists of: a front group comprising a positive first lens group, a negative second lens group, a negative third lens group, and a fourth lens group having positive or negative refractive power; and a rear group comprising an aperture stop and a plurality of lens groups. The first lens group and a fifth lens group on the most object side in the rear group do not move, and the second, third, and fourth lens groups move in zooming. The rear group includes a focus lens group that moves in focusing. The focal length fFw of the front group at the wide-angle end, and the focal length fw of the zoom lens at the wide-angle end satisfy the condition of -3≤fFw / fw<0.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a zoom lens suitable for photographing devices such as digital cameras and video cameras.

Background Art

[0002] In a zoom lens, when zooming, it is required that the moving lens group be lightweight in order to suppress changes in the center of gravity associated with the movement of the lens group and to reduce the torque required for driving the lens group. Also, when focusing, it is required that the change in the angle of view be small, that is, the focus breathing be small, and that the moving lens group (focus group) be lightweight.

[0003] In a large-aperture telephoto zoom lens, generally the refractive power of the first lens group on the object side is positive. At this time, by fixing the first lens group with the largest weight and adopting rear focusing, it is possible to achieve weight reduction of the lens group that moves during zooming and focusing. Also, since the change in the angle of view due to focus breathing is more prominent when the aperture is stopped down, it is required that the focus breathing be small in the state where the aperture is stopped down.

[0004] However, in order to achieve overall miniaturization and weight reduction of the zoom lens while suppressing the diameter of the first lens group to be small and ensuring sufficient peripheral light quantity, the chief ray of the peripheral light beam is likely to deviate from the center of the aperture, that is, it is likely to be in a state of so-called vignetting. When the aperture is stopped down in the state of vignetting, the focus breathing due to the movement of the lens group on the image side of the aperture is likely to increase. Also, even when the aperture is opened, it is difficult for the light quantity to increase, and the blurred image becomes asymmetric.

[0005] Patent Document 1 discloses a zoom lens that fixes the positive first lens group during zooming, moves the negative second, third, and fourth lens groups toward the image side respectively, and moves two lens groups on the image side of the aperture during focusing. Patent Document 2 discloses a zoom lens that fixes the positive first lens group during zooming, moves the negative second and third lens groups and the positive fourth lens group toward the image side, and moves the negative first focus group toward the image side and the positive second focus group toward the object side during focusing from infinity to the closest distance.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0007] However, in the zoom lens of Patent Document 1, since the number of lenses constituting the moving lens groups is large, they are not sufficiently lightened. Also, since the overall length of the lens is long and the outer diameter of the aperture is large, it is difficult to miniaturize. In the zoom lens of Patent Document 2, since the lens diameter on the object side of the aperture tends to be large by arranging the aperture closer to the image side, the number of lenses is reduced to lighten, but this makes it difficult to correct the fluctuations in axial chromatic aberration and magnification chromatic aberration associated with zooming. Also, single vignetting is likely to occur by arranging the aperture closer to the image side.

[0008] The present invention provides a zoom lens that is small and lightweight, suppresses the occurrence of aberration fluctuations and single vignetting associated with zooming, and has high optical performance throughout the zoom range and the focus range.

Means for Solving the Problems

[0009] The zoom lens as one aspect of the present invention is composed of a front group constituted by a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a negative refractive power, and a fourth lens group having a positive or negative refractive power, which are arranged in order from the object side to the image side, and a rear group constituted by an aperture stop and a plurality of lens groups, and is a zoom lens in which the interval between adjacent lens groups changes. When zooming, the first lens group and the fifth lens group, which is the most object-side lens group in the rear group, are stationary, and the second, third, and fourth lens groups move. The rear group includes a focus lens group that moves during focusing. When the focal length of the front group at the wide-angle end is fFw and the focal length of the zoom lens at the wide-angle end is fw, -3 ≦ fFw / fw < 0 It is characterized by satisfying the condition. Note that the imaging device equipped with the above zoom lens also constitutes another aspect of the present invention.

Effects of the Invention

[0010] According to the present invention, in a small and lightweight zoom lens, it is possible to obtain high optical performance throughout the zoom range and the focus range by suppressing aberration fluctuations and the occurrence of vignetting associated with zooming.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Mode for Carrying Out the Invention

[0012] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0013] FIG. 1, FIG. 2, FIG. 3, FIG. 4 and FIG. 5 each show the configuration of the zoom lenses of Examples 1 to 5 in a state of being focused on an infinite object. The zoom lenses of each example are used in various imaging devices such as digital video cameras, digital still cameras, broadcast cameras, silver halide film cameras, and surveillance cameras.

[0014] In each figure, the left side is the object side and the right side is the image side. img indicates the image plane. On the image plane img, the imaging surface (light receiving surface) of the imaging element and the film surface (photosensitive surface) of the silver halide film are arranged.

[0015] In the zoom lens, the lens group is a group of one or more lenses that move integrally during zooming (zooming) between the wide-angle end and the telephoto end. That is, the distance between adjacent lens groups changes during zooming. In each figure, the i-th lens group from the object side is shown as lens group Bi. The lens group may include an aperture stop. Also, the wide-angle end and the telephoto end respectively indicate the zoom states of the maximum angle of view (shortest focal length) and the minimum angle of view (longest focal length) when the lens group that moves during zooming is located at both ends of the range where it can move on the optical axis mechanically or controllably.

[0016] In each figure, the STO has an aperture stop. The aperture stop STO determines the light beam of the open F value (Fno), and the aperture diameter is variable for changing the depth of field. Also, a plurality of lens groups on the object side of the aperture stop STO are grouped together as the front group LF, and the lens groups on the image side of the front group LF including the aperture stop STO are grouped together as the rear group LR.

[0017] Under the lens group that moves during zooming, the movement locus from the wide-angle end to the telephoto end during zooming is indicated by an arrow. Also, under the lens group (focus lens group) that moves during focusing, the movement loci for compensating the image plane movement associated with zooming in the state of focusing on an infinite object and the state of focusing on a closest object are indicated by a solid line arrow and a dashed line arrow, respectively. Note that the zoom lens of each embodiment includes two focus groups arranged on the image side of the aperture stop STO. Among them, the first focus lens group (the sixth lens group B6: hereinafter referred to as the first focus group) on the object side is denoted as F1, and the second focus lens group (the eighth lens group B8: hereinafter referred to as the second focus group) on the image side is denoted as F2.

[0018] Next, the specific configuration of the zoom lens of each embodiment will be described. The zoom lens of each embodiment includes a front group LF composed of a first lens group B1 with a positive refractive power, a second lens group B2 with a negative refractive power, a third lens group B3 with a negative refractive power, and a fourth lens group B4 with a positive or negative refractive power, which are arranged in order from the object side to the image side, and a rear group LR including an aperture stop STO and a plurality of lens groups. During zooming, the first lens group and the final lens group (the ninth lens group B9) closest to the image side are fixed (immovable) with respect to the image plane, thereby reducing the change in the center of gravity associated with zooming and improving the dustproof performance.

[0019] During zooming from the wide-angle end to the telephoto end, the second lens group B2, the third lens group B3, and the fourth lens group B4 each move toward the image side and appropriately change their intervals. Thereby, the fluctuations in the image plane curvature, axial chromatic aberration, and magnification chromatic aberration due to zooming in the intermediate zoom range are suppressed, and high optical performance can be obtained throughout the zoom range.

[0020] The second lens group B2 and the fourth lens group B4 have a positive lens and a negative lens from the object side, so that chromatic aberration can be corrected. Further, by increasing the refractive power of the third lens group B3 and weakening the refractive powers of the second lens group B2 and the fourth lens group B4, the moving freedom degrees of the second lens group B2 and the fourth lens group B4 are improved, and variations due to zooming of chromatic aberration are suppressed.

[0021] Also, by reducing the weight of the moving lens group, it is possible to achieve a configuration with high performance in maintaining the zoom state and the focus state even when an impact is applied.

[0022] The rear group LR has a fifth lens group B5 that is fixed during zooming on the most object side, and by disposing the aperture stop STO within the fifth lens group B5, an increase in the outer diameter of the lens is prevented. By appropriately setting the refractive power of the lens group on the object side of the aperture stop STO, the on-axis ray is made a diverging ray, and while reducing the outer diameter of the aperture stop STO (hereinafter referred to as the stop outer diameter), the lens diameter on the object side of the aperture stop STO can be made smaller.

[0023] Also, the rear group LR arranges a first focus group F1 and a second focus group F2 on the image side of the first focus group F1 to perform so-called floating focusing, thereby suppressing aberration variations over the entire zoom range and at all object distances and obtaining high optical performance. The first focus group F1 and the second focus group F2 move toward the image side respectively when focusing from an infinite object to a closest object. Also, by making the first focus group F1 and the second focus group F2 negative lens groups respectively and disposing a positive lens group as the final lens group on the most image side, it is possible to obtain a necessary back focus while suppressing the lens diameters of the respective focus groups.

[0024] The zoom lens of each embodiment satisfies the conditions of the following formula (1) in order to achieve high optical performance while suppressing the occurrence of a single stop and reducing the size and weight of the whole.

[0025] -3 ≦ fFw / fw < 0 (1) In Equation (1), fw is the focal length of the entire zoom lens system at the wide-angle end, and fFw is the focal length of the front group LF at the wide-angle end.

[0026] The condition of Equation (1) indicates an appropriate relationship between the focal lengths fFw and fw of the front group LF and the entire zoom lens system at the wide-angle end. By setting the focal length fFw of the front group LF within the range that satisfies the condition of Equation (1), the incident angle of the on-axis ray to the aperture stop STO can be made to diverge, and vignetting across the zoom range can be improved. If fFw / fw exceeds the upper limit of Equation (1), the incident ray to the aperture stop STO becomes a converging ray, and the number of lower rays passing through the lower edge of the aperture stop STO becomes too small, which is not preferable. If fFw / fw is below the lower limit of Equation (1), the divergence of the incident ray to the aperture stop STO becomes too weak, resulting in insufficient upper rays passing through the upper edge of the aperture stop STO or the outer diameter of the aperture stop STO becoming too large, which is not preferable.

[0027] The numerical range of Equation (1) is more preferably as follows.

[0028] -2.5 ≦ fFw / fw ≦ -0.5 (1a) The numerical range of Equation (1) is even more preferably as follows.

[0029] -2.0 ≦ fFw / fw ≦ -1.0 (1b) The zoom lens of each embodiment preferably satisfies at least one of the conditions of the following Equations (2) to (20).

[0030] -6.5 ≦ fFT / ft < 0 (2) 0.3 ≦ f1 / ft ≦ 0.9 (3) -5.0 ≦ f1 / f3 ≦ -1.0 (4) 0.0 < f3 / f2 ≦ 3.0 (5) -1.0 ≦ f3 / f4 ≦ 1.0 (6) -0.5 ≦ f5 / f4 ≦ 0.5 (7) 0.9 ≦ m2 / m3 ≦ 1.3 (8) 1.0 ≦ m2 / m4 ≦ 3.5 (9) 1.0 ≦ m3 / m4 ≦ 3.0 (10) -2.0 ≤ βzw < 0.0 (11) -12.0 ≤ βzt < 0.0 (12) 0.4 ≤ ST / TTL ≤ 0.7 (13) -30 ≤ fFt / fRt < 0 (14) 0.2 ≤ fF2 / fF1 ≤ 2.0 (15) -2.0 ≤ fF1 / fRa ≤ -0.5 (16) -2.0 ≤ fF1 / fi < 0.0 (17) -2.0 ≤ fF2 / fRb ≤ -0.2 (18) 0.5 ≤ TTL / fT ≤ 1.5 (19) 0.2 ≤ BF / fi ≤ 0.6 (20) In formulas (2) to (20), ft is the focal length of the entire zoom lens system at the telephoto end, fFt is the focal length of the front group LF at the telephoto end, f1 is the focal length of the first lens group B1, f2 is the focal length of the second lens group B2, and f3 is the focal length of the third lens group B3. f4 is the focal length of the fourth lens group B4, and f5 is the focal length of the fifth lens group B5. m2 is the movement amount during zooming from the wide-angle end to the telephoto end of the second lens group B2, m3 is the movement amount during zooming of the third lens group B3 from the wide-angle end to the telephoto end, and m4 is the movement amount during zooming of the fourth lens group B4 from the wide-angle end to the telephoto end. The sign of the movement amount of the lens group is positive when the lens group is located on the image side at the telephoto end compared to the wide-angle end. βzw is the combined imaging magnification at the wide-angle end of the second to fourth lens groups B2 to B4, which are lens groups that move during zooming and are arranged on the object side of the aperture stop STO, and βzt is the combined imaging magnification at the telephoto end of the second to fourth lens groups B2 to B4. fF1 is the focal length of the first focus group F1, and fF2 is the focal length of the second focus group F2. fRa is the focal length of the lens group BRa that is adjacent to the first focus group F1 on the object side among the rear group LR, and fRb is the focal length of the lens group BRb (seventh lens group B7) that is fixed during focusing and is arranged between the first focus group F1 and the second focus group F2. fi is the focal length of the final lens group Bi that is the most image-side among the zoom lens (rear group LR), ST is the length on the optical axis from the aperture stop STO to the image plane img, and TTL is the length on the optical axis from the most object-side surface of the zoom lens (front group LF) to the image plane (total lens length). BF is the back focus of the zoom lens, which is the air-equivalent length on the optical axis from the most image-side surface of the zoom lens (rear group LR) to the image plane img.

[0031] The condition of formula (2) shows an appropriate relationship between the focal length fFT of the front group LF and the focal length ft of the entire zoom lens system at the telephoto end. By satisfying the condition of formula (2), it is possible to reduce the vignetting while miniaturizing the total lens length. If fFT / ft exceeds the upper limit of formula (2), the lower light rays become too few, which is not preferable. If fFT / ft is below the lower limit of formula (2), the upper light rays are insufficient or the aperture outer diameter becomes large, which is not preferable.

[0032] The condition of Equation (3) shows an appropriate relationship between the focal length f1 of the first lens group B1 and the focal length ft of the entire zoom lens at the telephoto end. If f1 / ft exceeds the upper limit of Equation (3), the refractive power of the first lens group B1 becomes too weak with respect to the focal length of the entire system, making it difficult to miniaturize the zoom lens, which is not preferable. If f1 / ft is below the lower limit of Equation (3), the refractive power of the first lens group B1 is too strong, increasing various aberrations such as axial aberration and degrading the imaging performance, which is not preferable.

[0033] The condition of Equation (4) shows an appropriate relationship between the focal lengths f1 and f3 of the first lens group B1 and the third lens group B3, indicating a preferable range of the refractive power arrangement of the main zooming group on the object side from the aperture stop STO. If f1 / f3 exceeds the upper limit of Equation (4), the refractive power of the third lens group B3 becomes too weak, making it difficult to obtain the required zoom ratio or increasing the movement amount of the third lens group B3 during zooming, and making it difficult to miniaturize the overall lens length, which is not preferable. If f1 / f3 is below the lower limit of Equation (4), the refractive power of the third lens group B3 becomes too strong, causing excessive fluctuations in field curvature and spherical aberration associated with zooming, which is not preferable.

[0034] The condition of Equation (5) shows an appropriate relationship between the focal lengths f2 and f3 of the second lens group B2 and the third lens group B3, indicating a preferable range of the refractive power of the second lens group B2. If f3 / f2 exceeds the upper limit of Equation (5), the refractive power of the second lens group B2 becomes too weak, increasing the zooming share of the third lens group B3 too much, which is not preferable. If f3 / f2 is below the lower limit of Equation (5), the refractive power of the second lens group B2, which is away from the aperture stop STO, becomes too strong, making it easy for the aperture outer diameter to increase, which is not preferable.

[0035] The condition of Equation (6) shows an appropriate relationship between the focal lengths f3 and f4 of the third lens group B3 and the fourth lens group B4, and shows a preferable range of the refractive power of the fourth lens group B4. When f3 / f4 exceeds the upper limit of Equation (6), the refractive power of the fourth lens group B4 becomes too strong, making it difficult to correct the variation of axial chromatic aberration associated with zooming, which is not preferable. When f3 / f4 is below the lower limit of Equation (6), the positive refractive power of the fourth lens group B4 becomes too strong, making it easy for the outer diameter of the aperture to increase, which is not preferable.

[0036] The condition of Equation (7) shows an appropriate relationship between the focal lengths f4 and f5 of the fourth lens group B4 and the fifth lens group B5, and shows a preferable refractive power arrangement of the fourth lens group B4 and the fifth lens group B5. When f5 / f4 exceeds the upper limit of Equation (7), the refractive power of the fifth lens group B5 becomes too weak, making it difficult to miniaturize the entire system, which is not preferable. When f5 / f4 is below the lower limit of Equation (7), the refractive power of the fifth lens group B5 becomes too weak, making it easy for the lens diameter on the object side to be larger than the aperture stop STO, which is not preferable.

[0037] The condition of Equation (8) shows a preferable relationship between the movement amounts m2 and m3 of the second lens group B2 and the third lens group B3 during zooming, and shows a preferable range of the movement trajectory of the second lens group B2. When m2 / m3 exceeds the upper limit of Equation (8), the movement amount of the second lens group B2 becomes too large, making it difficult to miniaturize the overall lens length, which is not preferable. When m2 / m3 is below the lower limit of Equation (8), the movement amount of the second lens group B2 becomes too small, making it difficult to reduce the variation of magnification chromatic aberration associated with zooming, which is not preferable.

[0038] The condition of Equation (9) shows the preferable relationship between the movement amounts m2 and m4 of the second lens group B2 and the fourth lens group B4 during zooming, and shows the range of the preferable movement locus of the fourth lens group B4. When m2 / m4 exceeds the upper limit of Equation (9), the movement amount of the fourth lens group B4 becomes too small, making it difficult to reduce the variation in axial chromatic aberration associated with zooming, so this is not preferable. When m2 / m4 is below the lower limit of Equation (9), the movement amount of the fourth lens group B4 becomes too large, making it difficult to reduce the variation in field curvature associated with zooming, so this is not preferable.

[0039] The condition of Equation (10) shows the preferable relationship between the movement amounts m3 and m4 of the third lens group B3 and the fourth lens group B4 during zooming, and shows the range of the preferable movement locus of the fourth lens group B4. When m3 / m4 exceeds the upper limit of Equation (10), the movement amount of the fourth lens group B4 becomes too small, making it difficult to reduce the variation in axial chromatic aberration associated with zooming, so this is not preferable. When m3 / m4 is below the lower limit of Equation (10), the movement amount of the fourth lens group B4 becomes too large, making it difficult to reduce the variation in field curvature associated with zooming, so this is not preferable.

[0040] The condition of Equation (11) shows the appropriate range of the combined imaging magnification βzw at the wide-angle end of the second to fourth lens groups B2 to B4. When βzw exceeds the upper limit of Equation (11), the incident angle of the axial ray to the aperture stop STO becomes too small, making it difficult to miniaturize the aperture stop STO, so this is not preferable. When βzw is below the lower limit of Equation (11), the incident angle of the axial ray to the aperture stop STO becomes too large, making it difficult to correct the aberrations generated in the fifth lens group B5 including the aperture stop STO, so this is not preferable.

[0041] The condition of Equation (12) indicates an appropriate range of the combined imaging magnification βzt at the telephoto end of the second to fourth lens groups B2 to B4. If βzt exceeds the upper limit of Equation (12), the incident angle of the on-axis ray to the aperture stop STO becomes too small, making it difficult to reduce the size of the aperture stop STO, which is not preferable. If βzt is below the lower limit of Equation (12), the incident angle of the on-axis ray to the aperture stop STO becomes too large, making it difficult to correct the aberrations generated in the fifth lens group B5 including the aperture stop STO, which is not preferable.

[0042] The condition of Equation (13) indicates an appropriate position of the aperture stop STO (distance ST from the image plane img) with respect to the overall lens length TTL, and it is a condition for suppressing the angular change of the chief ray when the aperture stop STO is stopped down. If ST / TTL exceeds the upper limit of Equation (13), the aperture stop STO will be located closer to the image side than the appropriate position, and it is likely that the light quantity of the lower ray will be insufficient at the telephoto end, which is not preferable. If ST / TTL is below the lower limit of Equation (13), the aperture stop STO will be located closer to the object side than the appropriate position, and the movement amount of the second to fourth lens groups B2 to B4 during zooming will be too small, so it is necessary to increase the power of these second to fourth lens groups B2 to B4. As a result, the fluctuations in field curvature and spherical aberration associated with zooming are likely to increase, which is not preferable.

[0043] The condition of Equation (14) indicates an appropriate relationship between the focal lengths fFt and fRt of the front group LF and the rear group LR at the telephoto end, and it shows the condition for suppressing the outer diameter of the stop while improving the vignetting. If fFt / fRt exceeds the upper limit of Equation (14), the outer diameter of the stop can be suppressed, but the vignetting at the telephoto end is likely to increase, which is not preferable. If fFt / fRt is below the lower limit of Equation (14), the vignetting is improved, but the outer diameter of the stop is likely to increase, which is not preferable.

[0044] By setting the focal length of the front group LF to negative and the focal length of the rear group LR to positive, the on-axis ray is made divergent at the position of the aperture stop STO. Even if the aperture stop STO is arranged on the object side within the rear group LR, its outer diameter can be made less likely to increase.

[0045] Further, it is preferable that the second lens group B2 has a configuration including a positive lens and a negative lens from the object side. Further, it is preferable that the fourth lens group B4 has a configuration including a positive lens and a negative lens from the object side. By adopting this lens arrangement, it is possible to favorably correct chromatic aberration generated in the lens group that moves during zooming. Further, by using a lens group having positive and negative refractive power arrangements from the object side, the principal point position can be moved to the image side and the overall lens length can be shortened.

[0046] Also, as the focus lens group included in the rear group LR, it is preferable to arrange the first focus group F1 and the second focus group F2 on the image side of the first focus group F1. When shortening the closest focusing distance of the telephoto zoom lens, the focus sensitivity of the focus lens group becomes too high, making it easy for focus shift to occur during zooming. However, by sharing the focus sensitivity among a plurality of focus lens groups, it is possible to reduce focus shift during zooming. Further, since spherical aberration can be favorably corrected when focusing on a closest object, it is easy to obtain high imaging performance throughout the focus range.

[0047] Preferably, by making both the first focus group F1 and the second focus group F2 lens groups with negative refractive power, it becomes easier to reduce their lens diameters and achieve weight reduction.

[0048] The condition of Equation (15) shows an appropriate relationship between the focal lengths fF1 and fF2 of the first focus group F1 and the second focus group F2. By satisfying the condition of Equation (15), it is possible to reduce focus fluctuation during zooming. If fF2 / fF1 exceeds the upper limit of Equation (15), the focus sensitivity of the first focus group F1 becomes too high and the focus accuracy decreases, which is not preferable. If fF2 / fF1 is below the lower limit of Equation (15), the focus sensitivity of the first focus group F1 becomes too low, the movement amount of the first focus group F1 increases, and it becomes difficult to shorten the overall lens length, which is not preferable.

[0049] In order to reduce focus breathing, it is preferable to move the first focus group F1 and the second focus group F2 toward the image side respectively when focusing from an infinite object to a closest object.

[0050] The condition of Equation (16) shows an appropriate relationship between the focal lengths fF1 and fRa of the first focus group F1 and the lens group BRa adjacent to it on the object side, and shows the preferable range of the focal length of the first focus group F1. If fF1 / fRa exceeds the upper limit of Equation (16), the focal length of the first focus group F1 becomes too long, making it difficult to shorten the closest distance, which is not preferable. If fF1 / fRa is below the lower limit of Equation (16), the focal length of the first focus group F1 becomes too short, resulting in a decrease in focus accuracy, which is not preferable.

[0051] The condition of Equation (17) shows an appropriate relationship between the focal lengths fF1 and fi of the first focus group F1 and the innermost final lens group Bi, and is a condition for obtaining an appropriate back focus. In a telephoto zoom lens, since an extender is often attached to change the focal length range, it is necessary to ensure a sufficient back focus. If fF1 / fi exceeds the upper limit of Equation (17), the focal length of the final lens group Bi becomes too long, making it difficult to miniaturize the first focus group F1, which is not preferable. If fF1 / fi is below the lower limit of Equation (17), the focal length of the first focus group F1 becomes too short, resulting in a decrease in focus accuracy, which is not preferable.

[0052] Also, in order to suppress the lens diameter of the first focus group F1 and reduce the weight, it is preferable that the refractive power of the first focus group F1 is negative and the refractive power of the lens group adjacent to the first focus group F1 on the image side is positive.

[0053] Furthermore, in order to suppress the lens diameter of the second focus group F2 and reduce the weight, it is preferable that the refractive power of the second focus group F2 is negative and the refractive power of the lens group adjacent to the second focus group F2 on the image side is positive.

[0054] The condition of Equation (18) shows an appropriate relationship between the focal length fF2 of the second focus group F2 and the focal length fRb of the fixed lens group BRb disposed between the first focus group F1 and the second focus group F2, and is a condition for reducing the lens diameter of the second focus group F2. If fF2 / fRb exceeds the upper limit of Equation (18), the focal length of the fixed lens group BRb is too long, and the effect of miniaturizing the zoom lens is reduced, which is not preferable. If fF2 / fRb is below the lower limit of Equation (18), the focal length of the fixed lens group BRb becomes too short, and it becomes difficult to secure the necessary back focus, which is not preferable.

[0055] The condition of Equation (19) shows an appropriate relationship between the overall lens length TTL and the focal length ft of the entire zoom lens system at the telephoto end. If TTL / ft exceeds the upper limit of Equation (19), it becomes difficult to shorten the overall lens length while suppressing the lens diameter of the first lens group B1, which is not preferable. If TTL / ft is below the lower limit of Equation (19), it becomes difficult to arrange the aperture stop STO at a preferable position while securing the necessary zoom ratio, which is not preferable.

[0056] The condition of Equation (20) shows an appropriate relationship between the focal length fi of the final lens group Bi and the back focus BF, and is a condition for miniaturizing each focus group while enabling the insertion of the extender. If BF / fi is below the lower limit of Equation (20), the refractive power of the final lens group Bi is too weak to obtain a converging effect, and the lens diameter of each focus group becomes large, which is not preferable. If BF / fi exceeds the upper limit of Equation (20), the refractive power of the final lens group Bi is too strong, and it becomes difficult to secure a sufficient back focus, which is not preferable.

[0057] In addition, when an anti-vibration group that moves in a direction perpendicular to the optical axis is provided in the zoom lens to correct image shake, it is preferable to use a part of the rear group LR as the anti-vibration group. In particular, by moving a part of the lens group BRa adjacent to the object side of the first focus group F1 with respect to the optical axis, it is possible to reduce the weight of the anti-vibration group while ensuring good anti-vibration performance.

[0058] In the zoom lens of each embodiment, the fifth lens group B5, which is the fifth from the object side, is divided into a sub-lens group 5a with positive refractive power, a sub-lens group 5b with positive refractive power, and a sub-lens group 5c with positive refractive power, and the sub-lens group 5b is used as the anti-vibration group.

[0059] Also, in order to suppress the occurrence of color shift when the anti-vibration group moves with respect to the optical axis, it preferably includes at least a positive lens and a negative lens. Furthermore, by having an aspherical surface, the anti-vibration group can suppress the change in coma aberration during anti-vibration without increasing the number of lens elements.

[0060] The numerical ranges of formulas (2) to (20) are more preferably as follows.

[0061] -6.0 ≦ fFT / ft ≦ -0.4 (2a) 0.35 ≦ f1 / ft ≦ 0.85 (3a) -3.5 ≦ f1 / f3 ≦ -1.2 (4a) 0.01 ≦ f3 / f2 ≦ 2.00 (5a) -0.5 ≦ f3 / f4 ≦ 0.5 (6a) -0.3 ≦ f5 / f4 ≦ 0.3 (7a) 0.8 ≦ m2 / m3 ≦ 1.2 (8a) 1.1 ≦ m2 / m4 ≦ 2.5 (9a) 1.1 ≦ m3 / m4 ≦ 2.5 (10a) -1.8 ≦ βzw ≦ -0.2 (11a) -11.0 ≦ βzt ≦ -1.0 (12a) 0.45 ≦ ST / TTL ≦ 0.65 (13a) -20.0 ≦ fFt / fRt ≦ -1.5 (14a) 0.4 ≦ fF2 / fF1 ≦ 1.5 (15a) -1.8 ≦ fF1 / fRa ≦ -0.8 (16a) -1.5 ≦ fF1 / fi ≦ -0.2 (17a) -1.0 ≦ fF2 / fRb ≦ -0.4 (18a) 0.6 ≦ TTL / fT ≦ 1.4 (19a) 0.25 ≦ BF / fi ≦ 0.50 (20a) When the numerical ranges of formulas (2) to (20) are as follows, it is even more preferable.

[0062] -5.5 ≦ fFT / ft ≦ -0.8 (2b) 0.4 ≦ f1 / ft ≦ 0.8 (3b) -2.5 ≦ f1 / f3 ≦ -1.5 (4b) 0.05 ≦ f3 / f2 ≦ 1.00 (5b) -0.3 ≦ f3 / f4 ≦ 0.3 (6b) -0.15 ≦ f5 / f4 ≦ 0.15 (7b) 0.75 ≦ m2 / m3 ≦ 1.05 (8b) 1.2 ≦ m2 / m4 ≦ 2.0 (9b) 1.2 ≦ m3 / m4 ≦ 2.0 (10b) -1.5 ≦ βzw ≦ -0.5 (11b) -10.5 ≦ βzt ≦ -1.5 (12b) 0.48 ≦ ST / TTL ≦ 0.60 (13b) -15.0 ≦ fFt / fRt ≦ -2.5 (14b) 0.6 ≦ fF2 / fF1 ≦ 1.2 (15b) -1.5 ≦ fF1 / fRa ≦ -1.0 (16b) -1.0 ≦ fF1 / fi ≦ -0.4 (17b) -0.8 ≦ fF2 / fRb ≦ -0.4 (18b) 0.70 ≦ TTL / fT ≦ 1.35 (19b) 0.3 ≦ BF / fi ≦ 0.4 (20b) Note that a lens group with substantially no refractive power may be disposed on the object side or the image side of the zoom lens in each embodiment.

[0063] The numerical examples 1 to 6 corresponding to Examples 1 to 5 are shown below. In the surface data of each numerical example, the surface number i indicates the order of the surface when counted from the object side. r is the radius of curvature (mm) of the i-th surface from the object side, d is the lens thickness or air interval (mm) between the i-th and (i + 1)-th surfaces, nd is the refractive index at the d-line of the optical material between the i-th surface and the (i + 1)-th surface. νd is the Abbe number based on the d-line of the optical material between the i-th surface and the (i + 1)-th surface. The Abbe number νd based on the d-line is defined as follows when the refractive indices at the d-line (587.6 nm), F-line (486.1 nm), and C-line (656.3 nm) of the Fraunhofer lines are Nd, NF, and NC, respectively: νd = (Nd - 1) / (NF - NC).

[0064] The effective diameter is the radius (mm) of the region through which the light rays contributing to imaging pass on the i-th lens surface.

[0065] In various data, the focal length and F-number are the values in the state of focusing on an infinitely distant object. The image height indicates the real image height. BF represents the back focus (mm). The back focus is the distance on the optical axis from the final surface (the surface closest to the image side) of the zoom lens to the paraxial image plane, expressed in terms of the air-equivalent length as described above. The overall length of the lens is the length obtained by adding the back focus to the distance on the optical axis from the frontmost surface (the surface closest to the object side) of the zoom lens to the final surface.

[0066] The "*" attached to the surface number means that the surface has an aspherical shape. The aspherical shape is represented by the following formula when x is the displacement amount from the vertex of the surface in the optical axis direction, y is the height from the optical axis in the direction perpendicular to the optical axis, the direction of light propagation is positive, R is the paraxial radius of curvature, K is the conic constant, and A4, A6, A8, A10, A12 are the aspherical coefficients:

[0067] x = (y 2 / R) / [1 + {1 - (1 + K)(y 2 / R 2 )} 1 / 2 ) + A4y 4 + A6y 6 + A8y8 +A10y 10 +A12y 12 Also, FIGS. 6, 7, 8, 9, and 10 respectively show the longitudinal aberrations (spherical aberration, astigmatism, distortion, and chromatic aberration) of the zoom lenses of Numerical Examples 1 to 5 at (A) the wide-angle end and (B) the telephoto end. In the spherical aberration figure, Fno indicates the F-number, the solid line indicates the spherical aberration at the d-line (wavelength 587.6 nm), the dashed line indicates the spherical aberration at the F-line (486.13 nm), the one-dot chain line indicates the spherical aberration at the C-line (656.27 nm), and the two-dot chain line indicates the spherical aberration at the g-line (435.83 nm). The scale on the horizontal axis is the defocus amount, which is -0.4 to +0.4 [mm]. In the astigmatism figure, the solid line S indicates the astigmatism at the sagittal image plane, and the dashed line M indicates the astigmatism at the meridional image plane. The horizontal axis is the same as that of the spherical aberration. The distortion figure shows the distortion at the d-line. The scale on the horizontal axis is -15 to +15 [%]. The chromatic aberration figure shows the lateral chromatic aberration at the F-line, C-line, and g-line. The scale on the horizontal axis is the defocus amount, which is -0.05 to +0.05 [mm]. ω is the semi-field angle (°). [Numerical Example 1] Unit: mm Surface data Surface number r d nd νd Effective diameter 1 118.641 1.45 1.74951 35.3 67.72 2 75.807 10.58 1.43875 94.7 66.17 3 -665.627 0.20 65.63 4 74.187 7.71 1.43875 94.7 64.07 5 280.505 (Variable) 63.15 6 71.420 5.82 1.56732 42.8 46.31 7 -798.337 0.20 44.70 8 233.290 1.40 1.65160 58.5 41.82 9 38.096 (Variable) 36.43 10 -74.807 1.40 1.53775 74.7 34.56 11 61.389 (Variable) 33.04 12 52.538 3.55 1.85478 24.8 33.57 13 149.814 3.46 33.25 14 -62.946 1.40 1.59349 67.0 33.21 15 283.696 (Variable) 33.65 16 (Aperture) ∞ 0.40 34.39 17* 31.136 10.95 1.49700 81.5 35.88 18* -70.106 0.20 35.11 19 321.201 1.40 1.77047 29.7 33.74 20 35.344 4.34 32.10 21 69.827 1.05 1.85478 24.8 32.51 22 36.387 6.37 1.80400 46.5 32.14 23 -336.651 0.07 1.58946 30.6 31.90 24* -302.040 3.01 31.89 25 44.773 5.10 1.59522 67.7 30.31 26 -541.557 (Variable) 29.34 27 795.915 2.78 1.92286 20.9 27.23 28 -86.227 1.10 1.62299 58.2 26.99 29 26.939 (Variable) 25.80 30* -154.619 4.65 1.58313 59.4 30.94 31* -41.311 (Variable) 31.40 32 -48.413 1.30 1.77047 29.7 31.25 33 ∞ (Variable) 32.25 34 126.157 3.10 2.00100 29.1 38.91 35 - 1961.022 (Variable) 39.01 Image plane ∞ Aspherical data 17th surface K = 0.00000e+00 A 4=-4.11423e-06 A 6=-4.02996e-10 A 8=-4.42991e-12 A10 = 5.14141e-16 18th surface K = 0.00000e+00 A 4 = 3.38559e-06 A 6=-7.98271e-10 A 8=-3.40353e-12 A10 = 4.45865e-15 24th surface K = 0.00000e+00 A 4 = 5.60156e-07 A 6 = 5.19683e-10 A 8=-2.15534e-13 A10=-1.04557e-15 30th surface K = 0.00000e+00 A 4 = 7.95991e-06 A 6=-1.42359e-08 A 8 = 1.09768e-10 A10=-4.12759e-13 A12 = 5.90882e-16 31st surface K = 0.00000e+00 A 4 = 6.06354e-06 A 6=-1.52294e-08 A 8 = 1.08850e-10 A10=-4.00403e-13 A12 = 5.48878e-16 Various data Zoom ratio 2.69 Wide angle Middle Telephoto Focal length 72.00 120.07 194.00 F-number 2.90 2.90 2.90 Half field angle (°) 16.72 10.21 6.36 Image height 21.64 21.64 21.64 Overall lens length 217.10 217.10 217.10 BF 37.13 37.13 37.13 d 5 1.48 24.67 42.97 d 9 8.46 10.54 13.14 d11 20.31 8.04 1.81 d15 31.22 18.22 3.55 d26 1.88 2.65 1.54 d29 18.60 17.83 18.94 d31 5.56 6.75 2.28 d33 9.48 8.29 12.76 d35 37.13 37.13 37.13 Entrance pupil position 87.99 147.59 199.11 Exit pupil position -80.55 -77.00 -88.84 Front principal point position 115.94 141.34 94.34 Rear principal point position -34.87 -82.94 -156.87 Lens group data Group Starting surface Focal length Lens configuration length Front principal point position Rear principal point position 1 1 138.69 19.94 4.25 -9.53 2 6 -197.36 7.42 13.35 8.06 3 10 -62.48 1.40 0.50 -0.41 4 12 86681.55 8.41 -6517.96 -6068.02 5 16 37.05 32.89 13.85 -13.35 6 27 -54.40 3.88 2.39 0.26 7 30 95.23 4.65 3.95 1.05 8 32 -62.84 1.30 -0.00 -0.73 9 34 118.50 3.10 0.09 -1.46 Single lens data Lens Starting surface Focal length 1 1 -284.27 2 2 155.79 3 4 227.30 4 6 115.83 5 8 -70.07 6 10 -62.48 7 12 93.09 8 14 -86.67 9 17 45.00 10 19 -51.66 11 21 -90.20 12 22 41.16 13 23 4980.24 14 25 69.70 15 27 84.43 16 28 -32.83 17 30 95.23 18 32 -62.84 19 34 118.50 [Numerical Example 2] Unit: mm Surface data Surface number r d nd νd Effective diameter 1 114.373 1.40 1.90366 31.3 65.03 2 83.254 9.20 1.43875 94.7 63.81 3 -687.171 0.20 63.24 4 72.870 7.55 1.43875 94.7 60.01 5 372.512 (Variable) 58.77 6 188.724 3.60 1.72047 34.7 41.43 7 -294.244 0.20 40.01 8 774.429 1.40 1.72916 54.7 37.87 9 36.916 (Variable) 33.22 10 -56.442 1.40 1.53775 74.7 31.54 11 154.766 (Variable) 31.97 12 67.137 3.90 1.85478 24.8 32.88 13 -294.768 2.25 32.80 14 -54.934 1.40 1.61340 44.3 32.76 15 213.549 (Variable) 33.28 16 (Aperture) ∞ 2.10 33.98 17* 29.294 10.00 1.49700 81.5 36.33 18* -74.795 1.58 35.80 19 132.142 1.40 1.77047 29.7 33.37 20 31.454 4.85 31.48 21 71.942 1.05 1.85478 24.8 31.81 22 36.789 6.00 1.80400 46.5 31.43 23 -473.050 0.07 1.58946 30.6 31.18 24* -424.100 1.95 31.17 25 42.310 4.75 1.59522 67.7 29.91 26 -1172.836 (Variable) 29.07 27 233.568 2.80 1.92286 20.9 26.49 28 -97.675 1.10 1.70300 52.4 25.97 29 28.249 (Variable) 24.95 30* -88.284 4.50 1.58313 59.4 29.99 31* -33.732 (Variable) 30.39 32 -45.317 1.30 1.77047 29.7 30.30 33 ∞ (Variable) 31.42 34 75.461 3.10 2.00100 29.1 38.00 35 212.837 (Variable) 37.97 Image plane ∞ Aspherical data The 17th surface K = 0.00000e+00 A 4=-4.73081e-06 A 6=-9.47473e-10 A 8=-3.88020e-12 A10=-3.54263e-15 The 18th surface K = 0.00000e+00 A 4= 3.21449e-06 A 6=-4.15483e-11 A 8=-4.31937e-12 A10= 4.21989e-15 The 24th surface K = 0.00000e+00 A 4= 4.20899e-07 A 6= 3.18000e-10 A 8= 5.69604e-13 A10=-2.62648e-15 The 30th surface K = 0.00000e+00 A 4= 1.07860e-05 A 6=-1.03082e-08 A 8= 1.31462e-10 A10=-3.35533e-13 A12= 6.90525e-16 The 31st surface K = 0.00000e+00 A 4= 1.01449e-05 A 6=-6.86964e-09 A 8= 1.02439e-10 A10=-2.54359e-13 A12= 6.58551e-16 Various data Zoom ratio 3.00 Wide angle, middle, telephoto Focal length 60.00 119.96 180.00 F-number 2.90 2.90 2.90 Half field angle (°) 19.83 10.22 6.85 Image height 21.64 21.64 21.64 Overall lens length 210.00 210.00 210.00 BF 37.12 37.12 37.12 d 5 1.52 31.86 47.37 d 9 8.20 9.28 8.47 d11 13.80 3.81 1.48 d15 36.95 15.51 3.15 d26 1.50 3.49 2.61 d29 19.16 17.17 18.05 d31 3.32 5.78 2.49 d33 9.38 6.93 10.22 d35 37.12 37.12 37.12 Entrance pupil position 67.95 141.27 182.71 Exit pupil position -79.66 -71.84 -80.38 Front principal point position 97.13 129.15 86.98 Rear principal point position -22.88 -82.84 -142.88 Lens group data Group Starting surface Focal length Lens configuration length Front principal point position Rear principal point position 1 1 128.72 18.35 3.89 -8.75 2 6 -81.46 5.20 4.39 1.23 3 10 -76.73 1.40 0.24 -0.67 4 12 417.63 7.55 -23.95 -27.61 5 16 36.64 33.75 14.95 -14.10 6 27 -54.19 3.90 2.65 0.53 7 30 90.86 4.50 4.46 1.71 8 32 -58.82 1.30 -0.00 -0.73 9 34 115.49 3.10 -0.84 -2.37 Single lens data Lens Starting surface Focal length 1 1 -345.99 2 2 169.87 3 4 204.90 4 6 160.09 5 8 -53.20 6 10 -76.73 7 12 64.29 8 14 -71.09 9 17 43.75 10 19 -53.90 11 21 -89.31 12 22 42.68 13 23 6949.10 14 25 68.71 15 27 74.93 16 28 -31.06 17 30 90.86 18 32 -58.82 19 34 115.49 [Numerical Example 3] Unit: mm Surface Data Surface Number r d nd νd Effective Diameter 1 172.753 2.10 1.89190 37.1 100.34 2 110.864 16.40 1.43875 94.7 98.59 3 -669.069 0.30 98.38 4 110.587 11.20 1.43875 94.7 96.23 5 431.001 (Variable) 95.11 6 192.334 6.30 1.74951 35.3 63.66 7 -467.535 0.30 62.57 8 -1438.668 2.10 1.51742 52.4 61.66 9 68.833 (Variable) 56.97 10 -108.485 2.10 1.53775 74.7 45.95 11 115.605 (Variable) 45.41 12 70.118 5.40 1.85478 24.8 45.69 13 243.257 2.53 45.00 14 -191.736 2.10 1.61340 44.3 44.95 15 104.468 (Variable) 44.30 16 (Aperture) ∞ 0.40 44.52 17* 48.817 10.20 1.49700 81.5 45.00 18* -135.473 9.25 44.21 19 4215.717 2.10 1.77047 29.7 38.90 20 48.855 11.75 37.44 21 85.709 1.57 1.85478 24.8 39.40 22 44.786 8.70 1.80400 46.5 38.96 23 -304.217 0.10 1.58946 30.6 38.62 24* -265.675 1.00 38.61 25 55.204 5.00 1.59522 67.7 37.29 26 400.814 (Variable) 36.35 27 1772.602 4.20 1.92286 20.9 32.88 28 -101.531 1.65 1.70300 52.4 32.47 29 37.887 (Variable) 31.18 30* -1039.603 5.90 1.58313 59.4 38.59 31* -52.894 (Variable) 38.77 32 -56.554 1.95 1.77047 29.7 37.42 33 ∞ (Variable) 38.45 34 87.148 4.20 2.00100 29.1 45.44 35 322.866 (Variable) 45.25 Image plane ∞ Aspherical data The 17th surface K = 0.00000e+00 A 4=-8.52024e-07 A 6=-4.15328e-10 A 8= 9.29658e-14 A10=-5.44870e-16 The 18th surface K = 0.00000e+00 A 4= 4.68123e-07 A 6=-3.73033e-10 A 8= 8.15517e-14 A10=-2.75722e-16 The 24th surface K = 0.00000e+00 A 4= 3.55470e-07 A 6= 1.31857e-10 A 8=-1.95555e-14 A10=-2.25525e-16 The 30th surface K = 0.00000e+00 A 4= 2.11329e-06 A 6= 2.02480e-10 A 8= 1.84288e-11 A10=-5.61258e-14 A12= 9.40795e-17 The 31st surface K = 0.00000e+00 A 4= 1.34443e-06 A 6=-2.32714e-09 A 8= 2.98680e-11 A10=-8.65384e-14 A12= 1.25435e-16 Various data Zoom ratio 2.91 Wide angle, medium, telephoto Focal length 100.00 185.26 291.00 F-number 2.90 2.88 2.90 Half field angle (°) 12.21 6.66 4.25 Image height 21.64 21.64 21.64 Overall lens length 320.20 320.20 320.20 BF 37.14 37.14 37.14 d 5 1.48 42.15 65.62 d 9 21.10 30.28 38.63 d11 41.33 11.62 1.49 d15 46.71 26.58 4.88 d26 8.96 7.41 1.76 d29 21.03 22.59 28.23 d31 14.97 14.31 7.17 d33 8.67 9.33 16.46 d35 37.14 37.14 37.14 Entrance pupil position 152.02 281.50 363.03 Exit pupil position -134.29 -140.79 -195.97 Front principal point position 193.69 273.88 290.77 Rear principal point position -62.86 -148.11 -253.86 Lens group data Group Starting surface Focal length Lens configuration length Front principal point position Rear principal point position 1 1 213.61 30.00 7.29 -13.38 2 6 -449.97 8.70 15.88 10.24 3 10 -103.73 2.10 0.66 -0.70 4 12 3347.99 10.03 -226.57 -218.59 5 16 58.80 50.08 29.60 -20.05 6 27 -63.28 5.85 3.40 0.24 7 30 95.36 5.90 3.92 0.20 8 32 -73.40 1.95 -0.00 -1.10 9 34 118.19 4.20 -0.77 -2.85 Single lens data Lens Starting surface Focal length 1 1 -352.60 2 2 218.16 3 4 335.47 4 6 182.57 5 8 -126.90 6 10 -103.73 7 12 113.62 8 14 -109.95 9 17 73.56 10 19 -64.17 11 21 -111.72 12 22 49.10 13 23 3553.87 14 25 106.98 15 27 104.17 16 28 -39.06 17 30 95.36 18 32 -73.40 19 34 118.19 [Numerical Example 4] Unit: mm Surface data Surface number r d nd νd Effective diameter 1 184.967 2.30 1.89190 37.1 96.34 2 114.981 14.00 1.43875 94.7 94.79 3 -1238.511 0.20 94.64 4 107.157 11.50 1.43875 94.7 93.34 5 538.899 (Variable) 92.34 6 545.415 3.20 1.72047 34.7 68.49 7 -1145.045 16.60 67.99 8 250.430 3.00 1.77250 49.6 56.80 9 116.759 (Variable) 54.79 10 -107.629 2.00 1.53775 74.7 43.62 11 110.642 (Variable) 42.97 12 74.737 5.50 1.85478 24.8 43.11 13 1551.268 1.28 42.51 14 -215.491 2.00 1.80400 46.6 42.47 15 104.892 (Variable) 41.71 16 (Aperture) ∞ 0.40 41.86 17* 98.698 7.50 1.43875 94.7 42.00 18* -83.153 12.41 41.81 19 -1305.936 2.00 1.77047 29.7 37.91 20 63.691 10.60 37.31 21 94.885 1.80 1.85478 24.8 39.94 22 47.782 8.68 1.80400 46.5 39.71 23 -274.151 0.07 1.58946 30.6 39.58 24* -257.021 3.00 39.58 25 76.973 5.20 1.49700 81.5 38.50 26 -228.030 (Variable) 37.94 27 -415.039 3.60 1.92286 20.9 32.70 28 -102.980 1.50 1.59522 67.7 32.00 29 48.936 (Variable) 30.02 30* -119.435 4.00 1.58313 59.4 33.40 31* -46.042 (Variable) 33.67 32 -53.950 2.00 1.77047 29.7 32.03 33 ∞ (Variable) 32.79 34 95.445 3.50 2.00069 25.5 45.27 35 305.293 (Variable) 45.11 Image plane ∞ Aspherical data The 17th surface K = 0.00000e+00 A 4=-8.11761e-07 A 6=-3.11349e-10 A 8=-5.54235e-13 A10= 9.06329e-16 The 18th surface K = 0.00000e+00 A 4= 2.46153e-08 A 6=-5.32016e-10 A 8=-1.22159e-13 A10= 6.27543e-16 The 24th surface K = 0.00000e+00 A 4= 2.66397e-07 A 6= 2.59983e-10 A 8=-5.24974e-13 A10= 3.52651e-16 The 30th surface K = 0.00000e+00 A 4= 1.42270e-06 A 6= 4.66364e-09 A 8= 1.24821e-12 A10=-3.80692e-14 A12= 9.18092e-17 The 31st surface K = 0.00000e+00 A 4= 1.21595e-06 A 6= 4.54091e-09 A 8= 8.58489e-13 A10=-3.23705e-14 A12= 8.09394e-17 Various data Zoom ratio 1.93 Focal length 205.00 300.19 395.00 F-number 4.10 4.07 4.10 Half angle of view (°) 6.02 4.12 3.14 Image height 21.64 21.64 21.64 Overall lens length 350.00 350.00 350.00 BF 43.54 43.54 43.54 d 5 5.03 32.32 54.04 d 9 34.32 35.97 33.79 d11 24.73 7.01 1.50 d15 29.84 18.62 4.59 d26 13.37 8.40 1.49 d29 24.44 29.40 36.32 d31 18.52 15.48 8.80 d33 28.38 31.42 38.10 d35 43.54 43.54 43.54 Entrance pupil position 232.87 311.22 350.47 Exit pupil position -199.79 -228.05 -298.41 Front principal point position 265.16 279.60 289.19 Rear principal point position -161.46 -256.65 -351.46 Lens group data Group Starting surface Focal length Lens configuration length Front principal point position Rear principal point position 1 1 221.30 28.00 6.55 -12.65 2 6 -711.84 22.80 53.03 30.71 3 10 -101.13 2.00 0.64 -0.66 4 12 8523.32 8.78 -500.49 -477.81 5 16 66.50 51.65 33.51 -16.32 6 27 -89.03 5.10 2.51 -0.29 7 30 125.96 4.00 4.03 1.55 8 32 -70.02 2.00 -0.00 -1.13 9 34 137.61 3.50 -0.79 -2.52 Single lens data Lens Starting surface Focal length 1 1 -346.08 2 2 240.56 3 4 302.39 4 6 513.19 5 8 -285.96 6 10 -101.13 7 12 91.70 8 14 -87.51 9 17 104.17 10 19 -78.77 11 21 -114.63 12 22 51.23 13 23 6967.51 14 25 116.45 15 27 147.59 16 28 -55.53 17 30 125.96 18 32 -70.02 19 34 137.61 [Numerical Example 5] Unit: mm Surface data Surface number r d nd νd Effective diameter 1 220.924 2.30 1.89190 37.1 86.09 2 122.179 11.90 1.43875 94.7 85.02 3 -604.088 0.20 84.98 4 104.403 10.70 1.43875 94.7 84.11 5 846.907 (Variable) 83.19 6 463.042 3.20 1.86966 20.0 54.82 7 -1680.439 10.93 54.22 8 311.700 2.50 1.96300 24.1 47.43 9 148.755 (Variable) 46.21 10 -180.458 2.00 1.53775 74.7 39.96 11 84.993 (Variable) 39.01 12 67.245 4.70 1.85478 24.8 38.95 13 204.581 1.93 38.18 14 -203.975 2.00 1.77250 49.6 38.13 15 112.360 (Variable) 37.58 16 (Aperture) ∞ 0.93 37.69 17* 63.256 7.50 1.43875 94.7 37.86 18* -102.807 18.84 37.41 19 435.031 2.00 1.77047 29.7 31.56 20 52.815 5.40 30.84 21 100.912 1.80 1.85478 24.8 31.50 22 58.660 4.00 1.80400 46.5 31.32 23 2875.153 0.07 1.58946 30.6 31.23 24* 3462.436 3.00 31.22 25 73.524 4.00 1.53172 48.8 30.85 26 -263.703 (Variable) 30.46 27 -30268.917 2.00 1.92286 20.9 25.56 28 -180.650 1.50 1.59522 67.7 25.19 29 46.455 (Variable) 24.05 30* -202.629 4.00 1.51742 52.4 29.91 31* -48.359 (Variable) 29.98 32 -46.434 2.00 1.77047 29.7 29.44 33 ∞ (Variable) 30.35 34 116.221 4.50 2.00069 25.5 47.77 35 -942.807 (Variable) 47.71 Image plane ∞ Aspherical data The 17th surface K = 0.00000e+00 A 4=-5.28875e-07 A 6= 2.50706e-10 A 8=-1.82712e-12 A10= 1.86109e-15 The 18th surface K = 0.00000e+00 A 4= 3.89908e-07 A 6= 1.92869e-10 A 8=-1.90820e-12 A10= 2.20542e-15 The 24th surface K = 0.00000e+00 A 4= 8.95598e-08 A 6= 2.11795e-10 A 8=-2.48501e-13 A10=-2.29274e-16 The 30th surface K = 0.00000e+00 A 4= 3.31118e-06 A 6= 1.34769e-08 A 8= 1.55479e-11 A10=-6.82790e-14 A12= 5.04607e-16 The 31st surface K = 0.00000e+00 A 4= 2.02798e-06 A 6= 1.40695e-08 A 8= 1.16908e-11 A10=-7.37995e-14 A12= 5.64000e-16 Various data Zoom ratio 2.41 Wide angle, medium, telephoto Focal length 205.00 300.08 495.00 F-number 5.75 5.70 5.75 Half field angle (°) 6.02 4.12 2.50 Image height 21.64 21.64 21.64 Overall lens length 350.00 350.00 350.00 BF 37.96 37.96 37.96 d 5 1.87 28.08 67.87 d 9 19.00 23.07 18.58 d11 17.47 3.54 2.82 d15 55.02 38.67 4.08 d26 22.25 17.63 1.49 d29 33.80 38.42 54.56 d31 20.68 17.51 3.95 d33 28.05 31.23 44.78 d35 37.96 37.96 37.96 Entrance pupil position 174.37 246.93 316.03 Exit pupil position -322.30 -404.51 -2267.76 Front principal point position 262.71 343.49 704.76 Rear principal point position -167.04 -262.12 -457.04 Lens group data Group Starting surface Focal length Lens configuration length Front principal point position Rear principal point position 1 1 210.87 25.10 7.29 -9.90 2 6 -1181.55 16.63 58.81 42.82 3 10 -107.16 2.00 0.88 -0.42 4 12 -697.76 8.63 46.33 38.15 5 16 75.29 47.54 23.03 -25.80 6 27 -90.84 3.50 2.13 0.15 7 30 121.69 4.00 3.43 0.82 8 32 -60.27 2.00 -0.00 -1.13 9 34 103.62 4.50 0.25 -2.01 Single lens data Lens Starting surface Focal length 1 1 -309.89 2 2 232.79 3 4 270.23 4 6 417.71 5 8 -297.73 6 10 -107.16 7 12 115.37 8 14 -93.53 9 17 90.50 10 19 -78.20 11 21 -167.19 12 22 74.43 13 23 28755.34 14 25 108.58 15 27 196.92 16 28 -61.93 17 30 121.69 18 32 -60.27 19 34 103.62 The values of formulas (1) to (20) in each numerical example are summarized in Table 1 below.

[0068] [Table 1]

[0069] [Imaging device] FIG. 11 shows a digital still camera as an imaging device using the zoom lens of each of the above embodiments as an imaging optical system. 20 is a camera body, and 21 is an imaging optical system composed of any one of the zoom lenses of Embodiments 1 to 6. 22 is an imaging element such as a CCD sensor or a CMOS sensor built in the camera body 20 and imaging an optical image (subject image) formed by the imaging optical system 21. 23 is a recording unit that records image data generated by processing an imaging signal from the imaging element 22, and 24 is a rear display that displays the image data.

[0070] By using the zoom lenses of the respective embodiments, a camera having a small size, a light weight, and high optical performance can be obtained. Note that the camera may be a single-lens reflex camera having a quick-return mirror or a mirrorless camera not having a quick-return mirror.

[0071] The above embodiments include the following configurations.

[0072] [Configuration 1] A front group composed of a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a negative refractive power, and a fourth lens group having a positive or negative refractive power, which are arranged in order from the object side to the image side, and a rear group composed of an aperture stop and a plurality of lens groups, the zoom lens having a variable interval between adjacent lens groups, when zooming, the first lens group and the fifth lens group, which is the most object-side lens group in the rear group, are stationary, and the second, third, and fourth lens groups move, the rear group includes a focus lens group that moves during focusing, when the focal length of the front group at the wide-angle end is fFw and the focal length of the zoom lens at the wide-angle end is fw, -3 ≦ fFw / fw < 0 A zoom lens characterized by satisfying the above conditions. [Configuration 2] when the focal length of the front group at the telephoto end is fFt and the focal length of the zoom lens at the telephoto end is ft, -6.5 ≦ fFt / ft < 0 The zoom lens according to Configuration 1, characterized by satisfying the above conditions. [Configuration 3] The zoom lens according to Configuration 1 or 2, characterized in that the second lens group has a positive lens and a negative lens from the object side. [Configuration 4] The zoom lens according to any one of Configurations 1 to 3, characterized in that the fourth lens group has a positive lens and a negative lens from the object side. [Configuration 5] The zoom lens according to any one of Configurations 1 to 4, wherein the aperture stop is disposed closest to the object side in the rear lens group. [Configuration 6] When the focal length of the first lens group is f1 and the focal length of the zoom lens at the telephoto end is ft, 0.3 ≦ f1 / ft ≦ 0.9 The zoom lens according to any one of Configurations 1 to 5, characterized by satisfying the condition. [Configuration 7] When the focal length of the first lens group is f1 and the focal length of the third lens group is f3, -5.0 ≦ f1 / f3 ≦ -1.0 The zoom lens according to any one of Configurations 1 to 6, characterized by satisfying the condition. [Configuration 8] When the focal length of the second lens group is f2 and the focal length of the third lens group is f3, 0.0 < f3 / f2 ≦ 3.0 The zoom lens according to any one of Configurations 1 to 7, characterized by satisfying the condition. [Configuration 9] When the focal length of the third lens group is f3 and the focal length of the fourth lens group is f4, -1.0 ≦ f3 / f4 ≦ 1.0 The zoom lens according to any one of Configurations 1 to 8, characterized by satisfying the condition. [Configuration 10] When the focal length of the fourth lens group is f4 and the focal length of the fifth lens group is f5, -0.5 ≦ f5 / f4 ≦ 0.5 The zoom lens according to any one of Configurations 1 to 9, characterized by satisfying the condition. [Configuration 11] When the movement amount of the second lens group during zooming from the wide-angle end to the telephoto end is m2, the movement amount of the third lens group during zooming from the wide-angle end to the telephoto end is m3, and the movement amount when each lens group is located on the image side at the telephoto end compared to the wide-angle end is positive, 0.9 ≦ m2 / m3 ≦ 1.3 The zoom lens according to any one of Configurations 1 to 10, characterized by satisfying the following conditions. [Configuration 12] When the moving amount of the second lens group during zooming from the wide-angle end to the telephoto end is m2, the moving amount of the fourth lens group during zooming from the wide-angle end to the telephoto end is m4, and the moving amount is positive when each lens group is located on the image side at the telephoto end compared to the wide-angle end, 1.0 ≦ m2 / m4 ≦ 3.5 The zoom lens according to any one of Configurations 1 to 11, characterized by satisfying the following conditions. [Configuration 13] When the moving amount of the third lens group during zooming from the wide-angle end to the telephoto end is m3, the moving amount of the fourth lens group during zooming from the wide-angle end to the telephoto end is m4, and the moving amount is positive when each lens group is located on the image side at the telephoto end compared to the wide-angle end, 1.0 ≦ m3 / m4 ≦ 3.0 The zoom lens according to any one of Configurations 1 to 12, characterized by satisfying the following conditions. [Configuration 14] When the combined imaging magnification at the wide-angle end of the second to fourth lens groups is βzw, -2.0 ≦ βzw < 0.0 The zoom lens according to any one of Configurations 1 to 13, characterized by satisfying the following conditions. [Configuration 15] When the combined imaging magnification at the telephoto end of the second to fourth lens groups is βzt, -12.0 ≦ βzt < 0.0 The zoom lens according to any one of Configurations 1 to 14, characterized by satisfying the following conditions. [Configuration 16] When the length on the optical axis from the aperture stop to the image plane is ST, and the length on the optical axis from the most object-side surface of the zoom lens to the image plane is TTL, 0.4 ≦ ST / TTL ≦ 0.7 The zoom lens according to any one of Configurations 1 to 15, characterized by satisfying the following conditions. [Configuration 17] When the focal length of the front group at the telephoto end is fFt and the focal length of the rear group at the telephoto end is fRt, -30 ≦ fFt / fRt < 0 The zoom lens according to any one of Configurations 1 to 16, characterized by satisfying the condition. [Configuration 18] The rear group includes, as the focus lens group, a first focus lens group and a second focus lens group disposed on the image side of the first focus lens group. The zoom lens according to any one of Configurations 1 to 17, characterized by this. [Configuration 19] When the focal length of the first focus lens group is fF1 and the focal length of the second focus lens group is fF2, 0.2 ≦ fF2 / fF1 ≦ 2.0 The zoom lens according to Configuration 18, characterized by satisfying the condition. [Configuration 20] When focusing from an infinite object to a close object, the first focus lens group and the second focus lens group each move toward the image side. The zoom lens according to Configuration 18 or 19, characterized by this. [Configuration 21] When the focal length of the first focus lens group is fF1 and the focal length of the lens group adjacent to the first focus lens group on the object side among the rear group is fRa, -2.0 ≦ fF1 / fRa ≦ -0.5 The zoom lens according to any one of Configurations 18 to 20, characterized by satisfying the condition. [Configuration 22] The final lens group is stationary during zooming and focusing. When the focal length of the first focus lens group is fF1 and the focal length of the final lens group is fi, -2.0 ≦ fF1 / fi < 0.0 The zoom lens according to any one of Configurations 18 to 21, characterized by satisfying the condition. [Configuration 23] A fixed lens group that remains stationary during zooming and focusing is disposed between the first focus lens group and the second focus lens group. When the focal length of the second focus lens group is f2 and the focal length of the fixed lens group is fRb, -2.0 ≦ fF2 / fRb ≦ -0.2 The zoom lens according to any one of Configurations 18 to 22, characterized by satisfying the condition. [Configuration 24] When the focal length of the zoom lens at the telephoto end is ft and the length on the optical axis from the surface closest to the object side to the image plane in the zoom lens is TTL, 0.5 ≦ TTL / ft ≦ 1.5 The zoom lens according to any one of Configurations 1 to 23, characterized by satisfying the condition. [Configuration 25] When the back focus of the zoom lens is BF and the focal length of the final lens group is fi, 0.2 ≦ BF / fi ≦ 0.6 The zoom lens according to any one of Configurations 1 to 24, characterized by satisfying the condition. [Configuration 26] A part of the rear group moves with respect to the optical axis as an anti-vibration group. The zoom lens according to any one of Configurations 1 to 25, characterized by this. [Configuration 27] As the plurality of lens groups constituting the rear group, a fifth lens group with a positive refractive power, a sixth lens group with a negative refractive power as the first focus lens group, a seventh lens group with a positive refractive power, an eighth lens group with a negative refractive power as the second focus lens group, and a ninth lens group with a positive refractive power, which are arranged in order from the object side to the image side. The zoom lens according to any one of Configurations 1 to 26, characterized by having these. [Configuration 28] The zoom lens according to any one of Configurations 1 to 27, An imaging device having an imaging element that images a subject through the zoom lens.

[0073] Each of the embodiments described above is merely a representative example, and various modifications and changes can be made to each embodiment when implementing the present invention.

Explanation of Reference Numerals

[0074] LF front group LR rear group Bi i-th lens group F1 first focus lens group F2 second focus lens group STO aperture stop img image plane

Claims

1. A front group composed of a first lens group with positive refractive power, a second lens group with negative refractive power, a third lens group with negative refractive power, and a fourth lens group with positive or negative refractive power, arranged in order from the object side to the image side, and a rear group composed of a diaphragm and a plurality of lens groups, a zoom lens in which the interval between adjacent lens groups changes, when zooming, the first lens group and the fifth lens group, which is the most object-side lens group in the rear group, are stationary, and the second, third, and fourth lens groups move, the rear group includes a focus lens group that moves during focusing, when the focal length of the front group at the wide-angle end is fFw and the focal length of the zoom lens at the wide-angle end is fw, -3 ≤ fFw / fw < 0 A zoom lens characterized by satisfying the condition.

2. when the focal length of the front group at the telephoto end is fFt and the focal length of the zoom lens at the telephoto end is ft, -6.5 ≤ fFt / ft < 0 The zoom lens according to claim 1, characterized by satisfying the condition.

3. The zoom lens according to claim 1, wherein the second lens group has a positive lens and a negative lens from the object side.

4. The zoom lens according to claim 1, wherein the fourth lens group has a positive lens and a negative lens from the object side.

5. The zoom lens according to claim 1, wherein the diaphragm is arranged on the most object side in the rear group.

6. when the focal length of the first group is f1 and the focal length of the zoom lens at the telephoto end is ft, 0.3 ≤ f1 / ft ≤ 0.9 The zoom lens according to claim 1, characterized by satisfying the condition.

7. when the focal length of the first group is f1 and the focal length of the third group is f3, -5.0 ≤ f1 / f3 ≤ -1.0 The zoom lens according to claim 1, characterized by satisfying the condition.

8. when the focal length of the second lens group is f2 and the focal length of the third lens group is f3, 0.0 < f3 / f2 ≤ 3.0 The zoom lens according to claim 1, characterized by satisfying the condition.

9. when the focal length of the third lens group is f3 and the focal length of the fourth lens group is f4, -1.0 ≤ f3 / f4 ≤ 1.0 The zoom lens according to claim 1, characterized by satisfying the condition.

10. When the focal length of the fourth lens group is f4 and the focal length of the fifth lens group is f5, -0.5 ≤ f5 / f4 ≤ 0.5 The zoom lens according to claim 1, characterized in that the condition is satisfied.

11. When the movement amount of the second lens group during zooming from the wide-angle end to the telephoto end is m2, the movement amount of the third lens group during zooming from the wide-angle end to the telephoto end is m3, and the movement amount is positive when each lens group is located on the image side at the telephoto end compared to the wide-angle end, 0.9 ≤ m2 / m3 ≤ 1.3 The zoom lens according to claim 1, characterized in that the condition is satisfied.

12. When the movement amount of the second lens group during zooming from the wide-angle end to the telephoto end is m2, the movement amount of the fourth lens group during zooming from the wide-angle end to the telephoto end is m4, and the movement amount is positive when each lens group is located on the image side at the telephoto end compared to the wide-angle end, 1.0 ≤ m2 / m4 ≤ 3.5 The zoom lens according to claim 1, characterized in that the condition is satisfied.

13. When the movement amount of the third lens group during zooming from the wide-angle end to the telephoto end is m3, the movement amount of the fourth lens group during zooming from the wide-angle end to the telephoto end is m4, and the movement amount is positive when each lens group is located on the image side at the telephoto end compared to the wide-angle end, 1.0 ≤ m3 / m4 ≤ 3.0 The zoom lens according to claim 1, characterized in that the condition is satisfied.

14. When the combined imaging magnification at the wide-angle end of the second to fourth lens groups is βzw, -2.0 ≤ βzw < 0.0 The zoom lens according to claim 1, characterized in that the condition is satisfied.

15. When the combined imaging magnification at the telephoto end of the second to fourth lens groups is βzt, -12.0 ≤ βzt < 0.0 The zoom lens according to claim 1, characterized in that the condition is satisfied.

16. When the length on the optical axis from the aperture stop to the image plane is ST and the length on the optical axis from the most object-side surface of the zoom lens to the image plane is TTL, 0.4 ≤ ST / TTL ≤ 0.7 The zoom lens according to claim 1, characterized in that the condition is satisfied.

17. When the focal length of the front group at the telephoto end is fFt and the focal length of the rear group at the telephoto end is fRt, -30 ≤ fFt / fRt < 0 The zoom lens according to claim 1, characterized in that the condition is satisfied.

18. The zoom lens according to claim 1, wherein the rear group includes, as the focus lens group, a first focus lens group and a second focus lens group disposed on the image side of the first focus lens group.

19. When the focal length of the first focus lens group is fF1 and the focal length of the second focus lens group is fF2, 0.2 ≦ fF2 / fF1 ≦ 2.0 The zoom lens according to claim 18, characterized in that the condition is satisfied.

20. The zoom lens according to claim 18, wherein the first focus lens group and the second focus lens group each move toward the image side when focusing from an infinite object to a closest object.

21. When the focal length of the first focus lens group is fF1 and the focal length of the lens group adjacent to the first focus lens group on the object side among the rear group is fRa, -2.0 ≦ fF1 / fRa ≦ -0.5 The zoom lens according to claim 18, characterized in that the condition is satisfied.

22. The final lens group is stationary during zooming and focusing, When the focal length of the first focus lens group is fF1 and the focal length of the final lens group is fi, -2.0 ≦ fF1 / fi < 0.0 The zoom lens according to claim 18, characterized in that the condition is satisfied.

23. A fixed lens group that is stationary during zooming and focusing is disposed between the first focus lens group and the second focus lens group, When the focal length of the second focus lens group is f2 and the focal length of the fixed lens group is fRb, -2.0 ≦ fF2 / fRb ≦ -0.2 The zoom lens according to claim 18, characterized in that the condition is satisfied.

24. When the focal length of the zoom lens at the telephoto end is ft and the length on the optical axis from the most object-side surface to the image plane in the zoom lens is TTL, 0.5 ≦ TTL / ft ≦ 1.5 The zoom lens according to claim 1, characterized in that the condition is satisfied.

25. When the back focus of the zoom lens is BF and the focal length of the final lens group is fi, 0.2 ≦ BF / fi ≦ 0.6 The zoom lens according to claim 1, characterized in that the condition is satisfied.

26. A part of the rear group moves with respect to the optical axis as an anti-vibration group. The zoom lens according to claim 1.

27. As the plurality of lens groups constituting the rear group, a fifth lens group having a positive refractive power, a sixth lens group having a negative refractive power as a first focus lens group, a seventh lens group having a positive refractive power, and a negative refractive power as a second focus lens group are arranged in order from the object side to the image side. The zoom lens according to claim 1, further comprising an eighth lens group and a ninth lens group having a positive refractive power.

28. A zoom lens according to any one of claims 1 to 27, An imaging device comprising: an imaging element that images a subject through the zoom lens.

Images