JP5546618B2 - 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, such as 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, the entire apparatus of an imaging apparatus such as a video camera using a solid-state imaging device, a digital still camera, a broadcasting camera, a surveillance camera, and a camera using a silver salt film has been downsized. A photographing optical system used therefor is required to be a zoom lens having a short overall lens length, a compact size, a high zoom ratio (high zoom ratio), and a high resolution.

  A zoom lens that meets these requirements includes a first, second, and third lens group having positive, negative, and positive refractive power in order from the object side to the image side, followed by one or more lens groups. A positive lead type zoom lens having a group is known. As a positive lead type zoom lens, there is known a zoom lens including four lens groups of positive, negative, positive, and positive refractive power in order from the object side to the image side (Patent Document 1).

  In Patent Document 1, chromatic aberration is favorably corrected on the telephoto side by using a low-dispersion material for the positive lens of the first lens group. In addition, there is known a zoom lens including five lens groups having positive, negative, positive, positive, and positive refractive powers in order from the object side to the image side (Patent Document 2). In addition, there is known a zoom lens including five lens groups having positive, negative, positive, negative, and positive refractive power in order from the object side to the image side (Patent Document 3). Patent Document 3 discloses a zoom lens having a zoom ratio of about 10.

JP 2008-209741 A JP 2007-292994 A JP 2003-255228 A

  In general, in order to reduce the size of a zoom lens with a predetermined zoom ratio, the number of lenses can be reduced while increasing the refractive power (optical power = reciprocal of focal length) of each lens group constituting the zoom lens. good. However, in such a zoom lens, aberration fluctuations accompanying zooming increase, and it becomes difficult to obtain high optical performance over the entire zoom range. In particular, the effective diameter of the front lens increases and the entire lens system is not sufficiently miniaturized. At the same time, it becomes difficult to correct various aberrations such as chromatic aberration at the telephoto end.

  In the above-described four-group zoom lens and five-group zoom lens, in order to obtain good optical performance while achieving a high zoom ratio and downsizing of the entire lens system, the refractive power of each lens group, the lens configuration, and each lens group It is important to appropriately set the movement conditions associated with zooming. In particular, it is important to appropriately set the lens configuration of the first and second lens groups and the movement conditions of the first and third lens groups during zooming. If these configurations are not set appropriately, it becomes difficult to obtain a zoom lens having a high zoom ratio and high optical performance while reducing the size of the entire system.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a zoom lens and an image pickup apparatus having the zoom lens in which the entire optical system is small, has a high zoom ratio, and provides high optical performance over the entire zoom range.

The zoom lens of the present invention includes, in order from the object side to the image side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and one or more lens groups. Having a rear group including
The distance between the first lens group and the second lens group is increased at the telephoto end with respect to the wide angle end, the distance between the second lens group and the third lens group is decreased, and the third lens group and the rear lens group are reduced. A zoom lens in which an interval between the groups is changed, and an interval between a lens group included in the rear group and a lens group adjacent to the lens group included in the rear group is changed during zooming ;
The first lens group includes a positive lens and a negative lens, the positive lens included in the first lens group is two, the second lens group includes a negative lens and a positive lens,
Among the positive lenses constituting the first lens group, the Abbe number of the positive lens material having the largest Abbe number is ν1p, and the refractive index and Abbe number of one positive lens material of the second lens group are N2p, respectively. , Ν2p, f1 is the focal length of the first lens group, f1p is the focal length of the positive lens having the largest Abbe number of the material among the positive lenses constituting the first lens group, and zooming from the wide-angle end to the telephoto end When the movement amount of the third lens group is M3 and the focal length of the entire system at the wide angle end is fw,
80.0 <ν1p
1.190 ≦ f1p / f1 <1.6
ν2p <18.4
1.90 <N2p
−3.8 <M3 / fw <−3.0
It is characterized by satisfying the following conditions.

  According to the present invention, it is possible to obtain a zoom lens in which the entire optical system is small, has a high zoom ratio, and high optical performance over the entire zoom range.

(A), (B), (C) Lens cross-sectional views at the wide-angle end, the intermediate zoom position, and the telephoto end of Numerical Example 1 of the present invention (A), (B), (C) Aberration diagrams at the wide-angle end, the intermediate zoom position, and the telephoto end of Numerical Example 1 of the present invention. (A), (B), (C) Lens cross-sectional views at the wide-angle end, the intermediate zoom position, and the telephoto end according to Numerical Example 2 of the present invention. (A), (B), (C) Aberration diagrams at the wide-angle end, the intermediate zoom position, and the telephoto end according to Numerical Example 2 of the present invention. (A), (B), (C) Lens cross-sectional views at the wide-angle end, the intermediate zoom position, and the telephoto end according to Numerical Example 3 of the present invention. (A), (B), (C) Aberration diagrams at the wide-angle end, the intermediate zoom position, and the telephoto end according to Numerical Example 3 of the present invention. (A), (B), (C) Lens cross-sectional views at the wide-angle end, the intermediate zoom position, and the telephoto end of Numerical Example 4 of the present invention (A), (B), (C) Aberration diagrams at the wide-angle end, the intermediate zoom position, and the telephoto end according to Numerical Example 4 of the present invention. (A), (B), (C) Lens cross-sectional views at the wide-angle end, the intermediate zoom position, and the telephoto end according to Numerical Example 5 of the present invention. (A), (B), (C) Aberration diagrams at the wide-angle end, at the intermediate zoom position, and at the telephoto end according to Numerical Example 5 of the present invention. 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 of the present invention includes, in order from the object side to the image side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and one or more lens groups. Having a rear group. During zooming, the distance between the first lens group and the second lens group increases at the telephoto end with respect to the wide-angle end, the distance between the second lens group and the third lens group decreases, and the distance between the third lens group and the rear group. Changes. Further, the distance between the lens group included in the rear group and the lens group adjacent to the lens group included in the rear group changes during zooming.

  FIGS. 1A, 1B, and 1C show lens cross sections 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 according to Embodiment 1 of the present invention. FIG. 2A, 2B, and 2C are aberration diagrams at the wide-angle end, the intermediate zoom position, and the telephoto end of the zoom lens according to the first exemplary embodiment. The first embodiment is a zoom lens having a zoom ratio of 13.32 and an aperture ratio of 3.21 to 6.08.

  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 2 of the present invention. 4A, 4B, and 4C are aberration diagrams at the wide-angle end, the intermediate zoom position, and the telephoto end of the zoom lens according to the second embodiment. The second embodiment is a zoom lens having a zoom ratio of 11.41 and an aperture ratio of 3.43 to 5.72.

  FIGS. 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 Embodiment 3 of the present invention. 6A, 6B, and 6C are aberration diagrams at the wide-angle end, the intermediate zoom position, and the telephoto end of the zoom lens according to the third exemplary embodiment. The third exemplary embodiment is a zoom lens having a zoom ratio of 13.82 and an aperture ratio of 3.36 to 6.09.

  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 4 of the present invention. FIGS. 8A, 8B, and 8C are aberration diagrams at the wide-angle end, the intermediate zoom position, and the telephoto end of the zoom lens according to the fourth exemplary embodiment. Example 4 is a zoom lens having a zoom ratio of 13.54 and an aperture ratio of 3.37 to 6.09.

  9A, 9B, and 9C 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 5 of the present invention. FIGS. 10A, 10B, and 10C are aberration diagrams at the wide-angle end, the intermediate zoom position, and the telephoto end of the zoom lens according to Embodiment 5. FIGS. The fifth exemplary embodiment is a zoom lens having a zoom ratio of 12.27 and an aperture ratio of 3.50 to 5.97.

  FIG. 11 is a schematic diagram of a main part of a camera (image pickup apparatus) including the zoom lens according to the present invention. The zoom lens according to each embodiment is a photographing lens system used in an imaging apparatus such as a video camera, a digital camera, and a silver salt film camera. In the lens cross-sectional view, the left side is the object side, and the right side is the image side. Further, i indicates the order of the lens groups from the object side to the image side, and Li is the i-th lens group. Lr is a rear group including one or more lens groups.

  In the lens cross-sectional views of Examples 1, 3, and 4 in FIGS. 1, 5, and 7, L1 is a first lens unit having a positive refractive power (optical power = reciprocal of focal length), and L2 is a negative refractive power. The second lens group L3 is a third lens group having a positive refractive power. The rear group Lr includes a fourth lens unit L4 having a negative refractive power and a fifth lens unit L5 having a positive refractive power. Examples 1, 3, and 4 are positive lead type five-group zoom lenses.

  In the lens cross-sectional view of Example 2 in FIG. 3, L1 is a first lens group having a positive refractive power, L2 is a second lens group having a negative refractive power, and L3 is a third lens group having a positive refractive power. The rear group Lr includes a fourth lens unit L4 having a positive refractive power. Example 2 is a positive lead type four-group zoom lens.

  9, 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 third lens unit having a positive refractive power. The rear group Lr includes a fourth lens unit L4 having a positive refractive power and a fifth lens unit L5 having a positive refractive power. Example 5 is a positive lead type 5-group zoom lens. In each lens cross-sectional view, SP is an F-number determining member (hereinafter also referred to as “aperture stop”) that functions as an aperture stop that determines (limits) an open F-number (Fno) light beam.

  G is an optical block corresponding to an optical filter, a face plate, a quartz low-pass filter, an infrared cut filter, or the like. IP is an image plane, and when used as a photographing optical system 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. In the spherical aberration diagram, the solid line d indicates the d line, and the two-dot chain line g indicates the g line.

  In the astigmatism diagram, the dotted line ΔM is represented by the meridional image plane, the solid line ΔS is represented by the sagittal image plane, and the lateral chromatic aberration is represented by the g line. ω is a half angle of view (a value half the shooting angle of view), and Fno is an F number. In the following embodiments, the wide-angle end and the telephoto end refer to zoom positions when the zoom lens unit is positioned at both ends of a range in which the mechanism can move on the optical axis. In each embodiment, an arrow indicates a movement locus during zooming or focusing from the wide-angle end to the telephoto end.

  In the zoom lens of each embodiment, the distance between the first lens unit L1 and the aperture stop SP is reduced at the wide angle end by increasing the refractive power of the first lens unit L1 and the second lens unit L2 to some extent. As a result, the lens diameter of the first lens unit L1 is reduced. Further, the distance from the aperture stop SP to the image plane IP is reduced (shortened) by increasing the refractive power of the third lens unit L3 to some extent. This shortens the total lens length (the length from the first lens surface to the image plane) at the wide-angle end.

  In the zoom lens of each embodiment, the first lens unit L1 is moved to the object side during zooming from the wide-angle end to the telephoto end, and the distance between the first lens unit L1 and the second lens unit L2 is set at the telephoto end rather than the wide-angle end. By zooming in (increasing), the zooming effect is obtained. Further, during zooming from the wide-angle end to the telephoto end, the third lens unit L3 is moved to the object side, and the distance between the second lens unit L2 and the third lens unit L3 is reduced (decreased) at the telephoto end rather than the wide-angle end. Has an effect.

  By sharing the zooming action at a plurality of locations (lens groups) in this way, the moving stroke of each lens group for zooming is shortened and the total lens length is shortened at the telephoto end while maintaining a high zoom ratio. . The focus variation caused by zooming is corrected by moving the most image side lens unit in a convex locus toward the object side. For focusing, the first lens unit L1 or the lens unit closest to the image side is moved to the object side to focus from an object at infinity to a near object.

  In the 5-group zoom lens of FIGS. 1, 5, 7, and 9, when focusing from an infinite object to a close object at the telephoto end, as shown by an arrow 5c in each lens sectional view, the fifth lens group L5. This is done by feeding it forward. A solid curve 5a and a dotted curve 5b relating to the fifth lens unit L5 are for correcting image plane fluctuations during zooming from the wide-angle end to the telephoto end when focusing on an object at infinity and a short-distance object, respectively. The movement trajectory is shown.

  In Example 2 of FIG. 3, when focusing from an infinitely distant object to a close object at the telephoto end, the fourth lens unit L4 is extended forward as indicated by an arrow 4c in the lens cross-sectional view. A solid curve 4a and a dotted curve 4b relating to the fourth lens unit L4 are for correcting image plane fluctuations during zooming from the wide-angle end to the telephoto end when focusing on an object at infinity and a short-distance object, respectively. The movement trajectory is shown.

In each embodiment, the first lens unit L1 includes a positive lens and a negative lens, and the first lens unit L1 includes two positive lenses. The second lens unit L2 has a negative lens and a positive lens. Of the positive lenses included in the first lens unit L1, the Abbe number of the material of the positive lens G1p having the largest material Abbe number is denoted by ν1p. The refractive index and Abbe number of one positive lens material of the second lens unit L2 are N2p and ν2p, respectively. The focal length of the first lens unit L1 is f1, and the focal length of the positive lens G1p having the largest Abbe number of the material among the positive lenses of the first lens unit L1 is f1p.
At this time,
80.0 <ν1p (1)
1.190 ≦ f1p / f1 <1.6 (2)
ν2p <18.4 (3)
1.90 <N2p (4)
Is satisfied.

  Conditional expression (1) defines the Abbe number of the material of the positive lens G1P having the largest material Abbe number among the positive lenses included in the first lens unit L1. If the lower limit of conditional expression (1) is exceeded and the Abbe number is too small, that is, if the dispersion is large, it is difficult to correct axial chromatic aberration and lateral chromatic aberration well on the telephoto side. A low dispersion material with an Abbe number exceeding 80 that satisfies the conditional expression (1) tends to have a large partial dispersion ratio, and therefore has an effect of favorably correcting the secondary spectrum on the telephoto side. In order to obtain such an effect, it is preferable not to exceed the lower limit of conditional expression (1).

  Conditional expression (2) is an expression that defines the focal length of the positive lens G1P having the largest Abbe number of the material among the positive lenses of the first lens unit L1. If the upper limit of conditional expression (2) is exceeded and the focal length of the positive lens G1P is too large, that is, if the refractive power is too weak, axial chromatic aberration and lateral chromatic aberration will occur on the telephoto side even if a low dispersion material is used for the positive lens G1P. It becomes difficult to correct well. If the focal length of the positive lens G1P is too small beyond the lower limit of the conditional expression (2), that is, if the refractive power is too strong, more spherical aberration occurs on the telephoto side than the positive lens G1P, which is not good.

  Conditional expression (3) defines the Abbe number of one positive lens G2P included in the second lens unit L2. If the upper limit is exceeded, that is, if the dispersion is small, a sufficient difference in Abbe number from the material of the negative lens in the second lens unit L2 cannot be obtained, and the refractive power of each lens necessary for achromaticity will increase. As a result, the second lens unit L2 becomes larger. Further, a large amount of distortion aberration, field curvature, and spherical aberration occur on the telephoto side on the wide angle side, which is not good.

  Conditional expression (4) defines the refractive index of the material of one positive lens G2P included in the second lens unit L2. If the refractive index is too small beyond the lower limit, the curvature of the lens surface for obtaining a desired refractive power becomes tight and the lens thickness increases, which is not good. In addition, the Petzval sum becomes too large in the positive direction, and a lot of field curvature occurs, which is not good. In order to satisfactorily reduce the size of the second lens unit L2 and correct various aberrations, it is preferable that both conditional expressions (3) and (4) are satisfied. In each embodiment, it is more preferable to set the numerical values of the conditional expressions (1) to (4) as follows.

81.0 <ν1p (1a)
1.190 ≦ f1p / f1 <1.595 (2a)
ν2p <18.2 (3a)
1.92 <N2p (4a)
As described above, according to each embodiment, it is possible to easily reduce the effective diameter of the front lens while maintaining a high zoom ratio of about 12 or more, and to obtain a zoom lens that corrects chromatic aberration well on the telephoto side. In each embodiment, it is more preferable to satisfy one or more of the following conditions.

  The amount of movement of the third lens unit L3 during zooming from the wide-angle end to the telephoto end is M3. Let fw be the focal length of the entire system at the wide-angle end. The focal lengths of the second lens unit L2 and the third lens unit L3 are defined as f2 and f3, respectively. A difference in refractive index between the materials of the two positive lenses of the first lens unit L1 is ΔN1p. In the second lens unit L2, in order from the object side to the image side, the absolute value of the refractive power is larger on the image side than on the object side, and a negative lens having a concave surface on the image side and a positive lens having a convex surface on the object side. Has a lens.

The distance on the optical axis from the image side lens surface of the negative lens to the object side lens surface of the positive lens is d2. The Abbe number of the material of the negative lens having the largest absolute value of refractive power among the negative lenses included in the second lens unit L2 is denoted by ν2n.
At this time,
−3.8 <M3 / fw <−3.0 (5)
7.0 <f1 / fw <10.0 (6)
1.2 <| f2 | / fw <1.6 (7)
1.7 <f3 / fw <4.6 (8)
0.1 <ΔN1p <0.4 (9)
0.52 <d2 / fw <1.00 (10)
0.029 <(1 / ν2p−1 / ν2n) <0.050 (11)
It is preferable to satisfy one or more of the following conditions.
Here, the moving amount M3 is the difference in position of each lens group with respect to the image plane in the optical axis direction at the telephoto end compared to the wide-angle end, and the sign is negative when it is located on the object side and positive when it is located on the image side. And

  Next, the technical meaning of each conditional expression described above will be described. Conditional expression (5) is an expression that defines the amount of movement of the third lens unit L3 during zooming. If the amount of movement to the object side during zooming is too small exceeding the upper limit of conditional expression (5), the zooming action is weakened. If the refractive power of the first lens unit L1 is increased to compensate for the zooming action at this time, a large amount of spherical aberration occurs on the telephoto side. Further, when the refractive power of the second lens group is increased to compensate for the zooming effect, a large amount of field aberration occurs on the wide angle side and spherical aberration occurs on the telephoto side.

  If the amount of movement toward the object side exceeds the lower limit of conditional expression (5), the movement of the aperture stop SP that moves together with the third lens unit L3 also increases. As a result, the change in the open F number accompanying zooming becomes large and the F number at the telephoto end becomes dark, which is not good. When a solid-state imaging device with a small pixel pitch is used, the photographing lens is required to have a high frequency MTF. If the open F number is dark, it is difficult to increase the MTF due to the influence of diffraction, which is not good.

  Conditional expression (6) defines the focal length, that is, the refractive power of the first lens unit L1. If the upper limit of conditional expression (6) is exceeded and the refractive power is too weak, the zooming action is weakened. If the amount of movement of the first lens unit L1 during zooming is increased to compensate for the zooming action at this time, the total lens length increases at the telephoto end. In addition, when the refractive power of the third lens unit L3 is increased to compensate for the zooming action, various aberrations such as spherical aberration, coma aberration, and longitudinal chromatic aberration increase. If the number of lenses is increased in order to correct various aberrations at this time, the thickness of the lens group increases and it becomes difficult to reduce the size.

  If the lower limit of conditional expression (6) is exceeded and the refractive power is too strong, more spherical aberration occurs on the telephoto side than the first lens unit L1. Increasing the number of lenses for aberration correction at this time is not preferable because the first lens group becomes larger and the front lens diameter increases.

  Conditional expression (7) defines the focal length, that is, the refractive power of the second lens unit L2. If the upper limit of conditional expression (7) is exceeded and the refractive power is too weak, the zooming action of the second lens unit L2 will be diminished, making it difficult to obtain the desired zoom ratio. If the lower limit of conditional expression (7) is exceeded and the refractive power is too strong, more field aberrations occur on the wide-angle side than on the second lens unit L2, and spherical aberration occurs more on the telephoto side.

  Conditional expression (8) defines the focal length, that is, the refractive power of the third lens unit L3. If the upper limit of conditional expression (8) is exceeded and the refractive power is too weak, the zooming action of the third lens unit L3 will be diminished, making it difficult to obtain the desired zoom ratio. If the lower limit of conditional expression (8) is exceeded and the refractive power is too strong, more spherical aberration, coma and axial chromatic aberration are generated than in the third lens unit L3.

  Conditional expression (9) is an expression that defines the difference in refractive index between the materials of the two positive lenses included in the first lens unit L1. If the refractive index difference is too large beyond the upper limit of conditional expression (9), this corresponds to the case where the refractive index of one positive lens is too large. In general, a material having a high refractive index is a highly dispersed material having a small Abbe number. For this reason, when the upper limit is exceeded, the dispersion is too high and axial chromatic aberration and lateral chromatic aberration are often generated on the telephoto side.

  On the other hand, if the difference in refractive index is too small beyond the lower limit of conditional expression (9), this corresponds to a case where both of the two positive lenses have a low refractive index. If the refractive power of the first lens unit L1 is to be increased to some extent, a large amount of spherical aberration occurs on the telephoto side even if it is shared by the two positive lenses.

  Conditional expression (10) represents the distance on the optical axis from the image-side lens surface of the negative lens having the concave surface facing the image side of the second lens unit L2 to the object-side lens surface of the positive lens having the convex surface facing the object side. It is a formula that prescribes. The second lens unit L2 is designed to have a wide angle and a small size as a retrofocus type refractive power arrangement preceded by a lens unit having a negative refractive power. This refractive power arrangement strongly depends on the arrangement of the concave surface facing the image side of the negative lens and the convex surface facing the object side of the positive lens. If the refracting power of each lens surface is set to be strong after reducing the distance to some extent, widening and miniaturization are facilitated.

  If the interval exceeds the upper limit of conditional expression (10), the thickness of the second lens unit L2 in the optical axis direction increases, and the second lens unit L2 becomes larger, which is not good. When the second lens unit L2 increases in size, the distance between the first lens unit L1 and the aperture stop SP increases, and the effective diameter of the front lens increases. If the distance is too small beyond the lower limit of the conditional expression (10), it is easy to reduce the size. However, the refractive power of each lens surface becomes too strong, and distortion on the wide angle side, curvature of field, and spherical aberration on the telephoto side. Many occur.

  Conditional expression (11) is an expression that defines the difference between the reciprocals of the Abbe numbers of the negative lens G2n and the positive lens G2p having the largest absolute value of refractive power among the negative lenses of the second lens unit L2. The larger the difference between the reciprocals of the Abbe number, the smaller the refractive power of each lens required for achromaticity. The difference in the reciprocal of the Abbe number exceeding the upper limit of conditional expression (11) is too large when the material of the positive lens G2p is too highly dispersed. Generally, a high dispersion material has a large partial dispersion ratio. When the upper limit is exceeded, the partial dispersion ratio of the material of the positive lens G2p is too large, and the secondary spectrum increases on the telephoto side.

  If the difference between the reciprocals of the Abbe number is too small beyond the lower limit of conditional expression (11), the refractive power of each lens necessary for achromaticity becomes too large, and distortion, field curvature, and telephoto are wide at the wide angle side. A lot of spherical aberration occurs on the side.

  In each embodiment, it is more preferable to set the numerical ranges of conditional expressions (6) to (11) as follows.

7.4 <f1 / fw <9.0 (6a)
1.3 <| f2 | / fw <1.5 (7a)
1.8 <f3 / fw <4.5 (8a)
0.103 <ΔN1p <0.360 (9a)
0.56 <d2 / fw <0.95 (10a)
0.030 <(1 / ν2p−1 / ν2n) <0.045 (11a)

  The features of the zoom lenses of Examples 1 to 5 will be described. In the zoom lenses according to the first, third, and fourth embodiments shown in FIGS. 1, 5, and 7, the distance between the lens groups is changed as follows during zooming from the wide-angle end to the telephoto end zoom position. That is, the third lens group L3 and the fourth lens group L4 are arranged so that the distance between the second lens group L2 and the third lens group L3 is narrowed so that the distance between the first lens group L1 and the second lens group L2 is widened. The interval is changed. Further, each lens group is moved so that the distance between the fourth lens group L4 and the fifth lens group L5 is increased.

  In the zoom lenses of Examples 1, 3, and 4 in FIGS. 1, 5, and 7, the first lens unit L1, the third lens unit L3, and the fourth lens unit L4 are objects at the telephoto end compared to the wide-angle end. Located on the side. The second lens unit L2 moves with a convex locus on the image side, and the fifth lens unit L5 moves with a convex locus on the object side. In the zoom lenses of Examples 1, 3, and 4 in FIGS. 1, 5, and 7, the F-number determining member SP is disposed in the third lens unit L3 with respect to the optical axis direction.

  By disposing the aperture stop SP in this way, the distance between the second lens group L2 and the third lens group L3 at the telephoto end is reduced, and therefore the distance between the second lens group L2 and the third lens group L3 for zooming. A sufficient amount of change can be secured. This achieves a zoom lens with a high zoom ratio. Further, in the zoom lenses of Embodiments 1, 3, and 4 of FIGS. 1, 5, and 7, further zooming can be performed by increasing the distance between the third lens unit L3 and the fourth lens unit L4 at the telephoto end rather than at the wide angle end. Has an effect.

  In the zoom lens of Example 2 shown in FIG. 3, when zooming from the wide-angle end to the telephoto end zoom position, the distance between the lens groups is changed as follows. That is, the distance between the third lens group L4 and the fourth lens group L4 is set so that the distance between the second lens group L2 and the third lens group L3 is narrowed so that the distance between the first lens group L1 and the second lens group L2 is widened. Each lens group moves so as to expand. In the zoom lens of Example 2 in FIG. 3, the first lens unit L1 and the third lens unit L3 are located on the object side at the telephoto end compared to the wide-angle end.

  The second lens unit L2 moves with a convex locus on the image side, and the fourth lens unit L5 moves with a convex locus on the object side. In the zoom lens of Example 2 shown in FIG. 3, the F-number determining member SP is disposed on the object side of the third lens unit L3 with respect to the optical axis direction.

  In the zoom lens of Example 5 shown in FIG. 9, the distance between the lens groups is changed as follows during zooming from the wide-angle end to the telephoto end zoom position. That is, the third lens group L3 and the fourth lens group L4 are arranged so that the distance between the second lens group L2 and the third lens group L3 is narrowed so that the distance between the first lens group L1 and the second lens group L2 is widened. The interval is narrowed. Further, each lens group is moved so that the distance between the fourth lens group L4 and the fifth lens group L5 is increased.

  In the zoom lens of Example 5 in FIG. 9, the first lens unit L1, the third lens unit L3, and the fourth lens unit L4 are located on the object side at the telephoto end compared to the wide-angle end. The second lens unit L2 moves with a convex locus on the image side, and the fifth lens unit L5 moves with a convex locus on the object side. In the zoom lens of Example 5 shown in FIG. 9, the F-number determining member SP is disposed on the object side of the third lens unit L3 with respect to the optical axis direction. In the zoom lens of Example 5 in FIG. 9, a further zooming effect is obtained by narrowing the distance between the third lens unit L3 and the fourth lens unit L4 at the telephoto end rather than at the wide angle end.

  In each embodiment, the above-described configuration achieves a high zoom ratio while shortening the total lens length at the wide-angle end and the telephoto end. In each embodiment, an arbitrary lens group may be moved so as to have a component in a direction perpendicular to the optical axis to move the image position, and camera shake correction may be performed.

  Next, the lens configuration of each lens group will be described. The first lens unit L1 has, in order from the object side to the image side, a cemented lens 14 including a negative (negative refractive power) lens 11 and a positive (positive refractive power) lens 12, and a convex surface directed toward the object side. There are 13 meniscus positive lenses. In each embodiment, the refractive power of the first lens unit L1 is increased to some extent in order to obtain a compact zoom lens with a high zoom ratio.

  At this time, many aberrations occur in the first lens unit L1. In particular, a large amount of spherical aberration occurs on the telephoto side. In each embodiment, the positive refractive power of the first lens unit L1 is shared by the cemented lens 14 and the positive lens 13 to reduce the occurrence of these various aberrations.

  Further, a low dispersion material having an Abbe number exceeding 80 is used for the positive lens 12. As a result, axial chromatic aberration and lateral chromatic aberration are corrected well on the telephoto side. The positive lens 12 enhances the refractive power by increasing the refractive power to some extent. In terms of correcting spherical aberration on the telephoto side, it is preferable that the positive lens of the first lens unit L1 is made of a material having a high refractive index. In general, a low-dispersion material has a low refractive index. Therefore, if the positive lens 12 is a low-dispersion material, the refractive index cannot be increased.

  Therefore, in the zoom lens of each embodiment, the positive lens 13 is made of a material having a higher refractive power than the material of the positive lens 12 to reduce the occurrence of spherical aberration on the telephoto side. By configuring the first lens unit L1 as described above, chromatic aberration is favorably corrected on the telephoto side while ensuring a high zoom ratio.

  In the second lens unit L2, in order from the object side to the image side, the absolute value of the refractive power is larger on the image side than on the object side, and the negative lens 21 with the concave surface facing the image side, the negative lens 22, and the object side It is composed of a positive lens 23 having a convex surface. In each embodiment, the refractive power of the second lens unit L2 is increased to some extent in order to reduce the size of the first lens unit L1 while obtaining a wide angle of view at the wide angle end.

  At this time, various aberrations generated in the second lens unit L2, particularly, field curvature on the wide angle side and spherical aberration on the telephoto side are generated. Therefore, in each embodiment, the negative refractive power of the second lens unit L2 is shared by the two negative lenses to reduce the occurrence of these various aberrations. With such a lens configuration, the front lens is reduced in size and performance while achieving a wider angle.

  Further, by using a highly dispersed material with an Abbe number smaller than 18.4 for the positive lens 23, the refractive power of each lens of the second lens unit L2 necessary for achromaticity is kept as small as possible. As a result, the number of lenses in the second lens unit L2 is reduced to reduce the size of the entire system. In addition, the use of a highly dispersed material for the positive lens 23 reduces the variation in lateral chromatic aberration from the wide-angle end to the telephoto end. By making the second lens unit L2 have the above-described lens configuration, the entire system is reduced in size and chromatic aberration is favorably corrected while increasing the refractive power of the second lens unit L2.

  In particular, when the second lens unit L2 is downsized, the distance between the first lens unit L1 and the stop SP is shortened, so that the front lens diameter can be easily downsized. In Examples 1 to 4 of FIGS. 1, 3, 5, and 7, the third lens unit L3 has a positive lens 31 with a convex surface facing the object side and a concave surface facing the image side in order from the object side to the image side. A negative lens 32 and a positive lens 33 are used.

  In each embodiment, the refractive power of the third lens unit L3 is increased to some extent in order to increase the zooming action of the third lens unit L3 and to shorten the total lens length at the wide angle end. At this time, various aberrations occurring in the third lens unit L3, particularly spherical aberration, coma aberration, and axial chromatic aberration, are often generated over the entire zoom range. Therefore, in each embodiment, the positive refractive power of the third lens unit L3 is shared by the two positive lenses, thereby reducing the occurrence of these various aberrations. In each embodiment, the third lens unit L3 includes two positive lenses and one negative lens.

  In Example 5 of FIG. 9, the third lens unit L3 includes, in order from the object side to the image side, a positive lens 31 having a convex surface facing the object side and a negative lens 32 having a concave surface facing the image side. In Example 5 of FIG. 9, the fourth lens unit L4 is used as a positive refractive power, and the positive refractive power of the third lens unit L3 is weakened. Accordingly, in Example 5 of FIG. 9, the number of positive lenses included in the third lens unit L3 is one. The fourth lens unit L4 includes only the negative lens 41 in the first, third, and fourth embodiments of FIGS.

  In each embodiment, the fourth lens unit L4 is configured with a small number of constituent lenses to reduce the thickness and weight. In the second embodiment shown in FIG. 3, the fourth lens unit L4 includes a cemented lens 413 in which a positive lens 411 and a negative lens 412 are cemented. As a result, even when the refractive power is strengthened, fluctuations in chromatic aberration during zooming are reduced. The fourth lens unit L4 includes only the positive lens 421 in the fifth embodiment shown in FIG. In each embodiment, the fourth lens group is configured with a small number of constituent lenses to achieve a reduction in thickness and weight.

  In the first, third, fourth, and fifth embodiments shown in FIGS. 1, 5, 7, and 9, the fifth lens unit L5 is a cemented lens 53 including a positive lens 51 and a negative lens 52 in order from the object side to the image side. It consists of. Even if the refractive power of each lens group is increased to some extent by using a cemented lens, the occurrence of lateral chromatic aberration is satisfactorily suppressed over the entire zooming range.

  Next, numerical examples corresponding to the respective embodiments of the present invention will be shown. In each numerical example, i indicates the order of the optical surfaces from the object side. In the numerical examples, ri is the radius of curvature of the i-th lens surface in order from the object side. di is the i-th lens thickness and air spacing in order from the object side. ndi and νdi are respectively the refractive index and Abbe number for the d-line of the glass of the i-th material in order from the object side. In the numerical example, the last two surfaces are surfaces of an optical block such as a filter and a face plate.

  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. When using coefficients

It is expressed by the following formula. [E + X] means [× 10 + x], and [e-X] means [× 10-x]. The angle of view indicates a half angle of view (degree). BF is the air-converted distance (back focus) from the final lens surface to the paraxial image plane. The total lens length is obtained by adding the back focus BF to the distance from the lens front surface to the lens final surface. An aspherical surface is indicated by adding * after the surface number. Table 1 shows the relationship between the above conditional expressions and various numerical values in the numerical examples.

[Numerical Example 1]
Unit mm

Surface data surface number rd nd νd
1 47.198 0.90 1.84666 23.9
2 28.488 2.50 1.49700 81.5
3 539.546 0.20
4 27.858 1.95 1.69680 55.5
5 130.634 (variable)
6 -142.993 1.03 1.85135 40.1
7 * 5.724 2.27
8 -32.718 0.60 1.80 400 46.6
9 20.754 0.20
10 10.630 1.40 1.94595 18.0
11 41.156 (variable)
12 * 7.790 1.40 1.58313 59.4
13 * -42.498 0.92
14 (Aperture) ∞ 1.48
15 14.621 0.60 1.94595 18.0
16 7.752 0.51
17 38.232 1.45 1.60311 60.6
18 -10.112 (variable)
19 -22.588 0.50 1.48749 70.2
20 23.874 (variable)
21 15.072 2.00 1.69680 55.5
22 -42.895 0.60 1.72825 28.5
23 240.459 (variable)
24 ∞ 0.80 1.51633 64.1
25 ∞ 0.90
Image plane ∞

Aspheric data 7th surface
K = -1.12918e + 000 A 4 = 7.09263e-004 A 6 = 1.64697e-005 A 8 = -3.81294e-007
A10 = 1.79401e-008

12th page
K = -1.22101e + 000 A 4 = 4.95648e-005 A 6 = 7.55352e-006 A 8 = 3.03893e-006
A10 = -1.83896e-007

Side 13
K = -1.36363e + 002 A 4 = 9.00236e-007 A 6 = 2.00697e-005 A 8 = 2.20070e-006
A10 = -1.36759e-007

Various data Zoom ratio 13.32
Wide angle Medium telephoto focal length 5.12 17.53 68.25
F number 3.21 4.62 6.08
Angle of view 33.04 12.46 3.25
Image height 3.33 3.88 3.88
Total lens length 48.61 56.13 75.70
BF 6.95 13.90 7.26

d 5 0.95 11.54 25.33
d11 15.79 4.21 0.71
d18 1.90 2.57 3.04
d20 2.51 3.39 18.85
d23 5.52 12.48 5.84

Zoom lens group data group Start surface Focal length
1 1 41.07
2 6 -6.74
3 12 10.27
4 19 -23.73
5 21 23.41
6 24 ∞

[Numerical Example 2]
Unit mm

Surface data surface number rd nd νd
1 40.508 1.10 1.84666 23.9
2 26.505 2.85 1.49700 81.5
3 117.405 0.20
4 28.036 2.30 1.69680 55.5
5 115.344 (variable)
6 496.060 0.80 1.83481 42.7
7 6.978 3.11
8 -19.492 0.65 1.69680 55.5
9 27.002 0.95
10 17.132 1.30 1.94595 18.0
11 86.758 (variable)
12 (Aperture) ∞ 1.10
13 * 6.129 2.60 1.55332 71.7
14 * -19.640 1.44
15 30.262 0.70 1.80610 33.3
16 5.458 0.36
17 7.690 2.20 1.48749 70.2
18 43.575 (variable)
19 16.720 2.50 1.65844 50.9
20 -30.217 0.80 1.84666 23.9
21 -745.365 (variable)
22 ∞ 0.80 1.51633 64.1
23 ∞ 0.23
Image plane ∞

Aspheric data 13th surface
K = 8.82654e-002 A 4 = -3.72261e-004 A 6 = -6.26683e-006 A 8 = 7.60386e-007
A10 = -1.17611e-008

14th page
K = -1.54914e + 001 A 4 = 1.11231e-004 A 6 = 9.16897e-006 A 8 = 4.07239e-007
A10 = 2.20754e-008

Various data Zoom ratio 11.41
Wide angle Medium Telephoto focal length 5.13 27.84 58.49
F number 3.43 4.75 5.72
Angle of view 33.64 7.92 3.79
Image height 3.41 3.88 3.88
Total lens length 58.03 68.24 80.67
BF 5.83 14.87 8.72

d 5 0.85 19.50 26.21
d11 20.70 3.30 1.55
d18 5.69 5.62 19.24
d21 4.90 13.94 7.79

Zoom lens group data group Start surface Focal length
1 1 44.91
2 6 -7.55
3 12 13.79
4 19 28.92
5 22 ∞

[Numerical Example 3]
Unit mm

Surface data surface number rd nd νd
1 46.369 0.90 1.84666 23.9
2 27.571 2.50 1.43875 94.9
3 559.981 0.20
4 30.024 1.95 1.77250 49.6
5 181.678 (variable)
6 1208.784 1.03 1.85 135 40.1
7 * 5.930 2.52
8 -37.450 0.60 1.80 400 46.6
9 24.691 0.20
10 10.171 1.00 2.15000 15.0
11 18.413 (variable)
12 * 7.811 1.40 1.58313 59.4
13 * -47.243 0.92
14 (Aperture) ∞ 1.48
15 14.957 0.60 1.94595 18.0
16 7.736 0.51
17 30.949 1.45 1.60311 60.6
18 -9.935 (variable)
19 -22.814 0.50 1.48749 70.2
20 27.914 (variable)
21 14.636 2.00 1.69680 55.5
22 -213.155 0.60 1.72825 28.5
23 80.738 (variable)
24 ∞ 0.80 1.51633 64.1
25 ∞ 0.90
Image plane ∞

Aspheric data 7th surface
K = -1.06717e + 000 A 4 = 6.59232e-004 A 6 = 1.99244e-005 A 8 = -6.18757e-007
A10 = 2.60294e-008

12th page
K = -1.58528e + 000 A 4 = 6.04929e-005 A 6 = 3.14605e-006 A 8 = 4.09286e-006
A10 = -3.60415e-007

Side 13
K = -1.45184e + 002 A 4 = -4.52161e-005 A 6 = 1.30432e-005 A 8 = 3.34384e-006
A10 = -3.15471e-007

Various data Zoom ratio 13.82
Wide angle Medium Telephoto focal length 4.96 16.36 68.60
F number 3.36 4.65 6.09
Angle of view 33.88 13.33 3.23
Image height 3.33 3.88 3.88
Total lens length 48.67 55.53 74.48
BF 6.49 13.36 7.17

d 5 0.80 10.94 25.72
d11 16.55 4.87 0.47
d18 1.90 1.84 2.50
d20 2.57 4.15 18.26
d23 5.06 11.93 5.75

Zoom lens group data group Start surface Focal length
1 1 41.50
2 6 -6.86
3 12 10.21
4 19 -25.67
5 21 25.57
6 24 ∞

[Numerical Example 4]
Unit mm

Surface data surface number rd nd νd
1 40.829 0.90 1.84666 23.9
2 28.443 2.80 1.45600 90.3
3 -111.369 0.20
4 28.907 1.60 1.60311 60.6
5 74.324 (variable)
6 -62.226 1.03 1.85135 40.1
7 * 6.063 2.28
8 -23.222 0.60 1.80 400 46.6
9 28.259 0.20
10 12.482 1.40 2.14352 17.8
11 41.723 (variable)
12 * 7.730 1.40 1.58313 59.4
13 * -44.307 0.92
14 (Aperture) ∞ 1.48
15 14.928 0.60 1.94595 18.0
16 7.828 0.51
17 44.931 1.45 1.60311 60.6
18 -10.044 (variable)
19 -20.840 0.50 1.48749 70.2
20 39.734 (variable)
21 15.540 2.00 1.69680 55.5
22 -31.360 0.60 1.72825 28.5
23 -2306.962 (variable)
24 ∞ 0.80 1.51633 64.1
25 ∞ 0.90
Image plane ∞

Aspheric data 7th surface
K = -8.76488e-001 A 4 = 4.28897e-004 A 6 = 1.21461e-005 A 8 = -2.23456e-007
A10 = 7.87605e-009

12th page
K = -1.39680e + 000 A 4 = 2.06320e-004 A 6 = 1.68052e-005 A 8 = 1.98340e-006
A10 = -1.05023e-007

Side 13
K = -1.22659e + 002 A 4 = 1.72540e-004 A 6 = 2.
21046e-005 A 8 = 2.00595e-006
A10 = -9.89895e-008

Various data Zoom ratio 13.54
Wide angle Medium Telephoto focal length 5.07 14.88 68.60
F number 3.37 4.32 6.09
Angle of view 33.33 14.60 3.23
Image height 3.33 3.88 3.88
Total lens length 49.91 56.87 77.21
BF 5.73 12.88 7.79

d 5 1.20 10.84 25.80
d11 16.27 5.10 0.28
d18 1.90 1.12 3.26
d20 4.34 6.46 19.60
d23 4.30 11.46 6.36

Zoom lens group data group Start surface Focal length
1 1 42.00
2 6 -6.67
3 12 10.41
4 19 -27.97
5 21 22.63
6 24 ∞

[Numerical Example 5]
Unit mm

Surface data surface number rd nd νd
1 41.069 1.10 1.84666 23.9
2 26.300 2.85 1.49700 81.5
3 121.593 0.20
4 26.171 2.30 1.69680 55.5
5 94.129 (variable)
6 110.635 0.80 1.83481 42.7
7 6.355 3.11
8 -15.251 0.65 1.69680 55.5
9 65.380 0.95
10 17.018 1.30 2.00000 16.0
11 53.947 (variable)
12 (Aperture) ∞ 1.10
13 * 6.428 2.60 1.55332 71.7
14 * -16.276 1.44
15 43.996 0.70 1.80610 33.3
16 6.230 (variable)
17 11.376 2.20 1.48749 70.2
18 -380.889 (variable)
19 19.187 2.50 1.65844 50.9
20 -19.742 0.80 1.84666 23.9
21 -109.516 (variable)
22 ∞ 0.80 1.51633 64.1
23 ∞ 0.40
Image plane ∞

Aspheric data 13th surface
K = -7.75765e-002 A 4 = -3.85283e-004 A 6 = 5.74360e-006 A 8 = -6.92005e-007 A10 =
8.51546e-008

14th page
K = -9.64194e + 000 A 4 = -2.31393e-005 A 6 = 1.79539e-005 A 8 = -9.53438e-007 A10 =
1.11464e-007

Various data Zoom ratio 12.27
Wide angle Medium Telephoto focal length 5.13 27.56 63.00
F number 3.50 4.63 5.97
Angle of view 33.59 8.00 3.52
Image height 3.41 3.88 3.88
Total lens length 60.48 70.69 83.12
BF 6.14 15.43 8.28

d 5 0.85 19.50 26.21
d11 20.70 3.30 1.55
d16 2.50 1.50 0.50
d18 5.69 6.37 21.98
d21 5.21 14.50 7.36

Zoom lens group data group Start surface Focal length
1 1 44.45
2 6 -7.29
3 12 22.27
4 17 22.70
5 19 30.75
6 22 ∞

  Next, an embodiment of a digital still camera using a zoom lens as shown in each embodiment as a photographing optical system will be described with reference to FIG. In FIG. 11, reference numeral 20 denotes a camera body, and reference numeral 21 denotes a photographing optical system constituted by any of the zoom lenses described in the first to fifth embodiments. Reference numeral 22 denotes a solid-state imaging device (photoelectric conversion device) such as a CCD sensor or a CMOS sensor that receives a subject image formed by the photographing optical system 21 and is built in the camera body. A memory 23 records information corresponding to a subject image photoelectrically converted by the solid-state imaging device 22.

  Reference numeral 24 denotes a finder for observing a subject image formed on the solid-state image sensor 22, which includes a liquid crystal display panel or the like. In this way, by applying the zoom lens of the present invention to an imaging apparatus such as a digital still camera, a compact imaging apparatus having high optical performance can be realized.

  L1 is the first lens group, L2 is the second lens group, L3 is the third lens group, L4 is the fourth lens group, L5 is the fifth lens group, Lr is the rear group, d is the d-line, g is the g-line, ΔM is a meridional image plane, ΔS is a sagittal image plane, SP is an aperture, G is a glass block such as a CCD force plate or low-pass filter, ω is a half field angle, and fno is an F number.

Claims (8)

In order from the object side to the image side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a rear group including one or more lens groups. ,
The distance between the first lens group and the second lens group is increased at the telephoto end with respect to the wide angle end, the distance between the second lens group and the third lens group is decreased, and the third lens group and the rear lens group are reduced. A zoom lens in which an interval between the groups is changed, and an interval between a lens group included in the rear group and a lens group adjacent to the lens group included in the rear group is changed during zooming ;
The first lens group includes a positive lens and a negative lens, the positive lens included in the first lens group is two, the second lens group includes a negative lens and a positive lens,
Among the positive lenses constituting the first lens group, the Abbe number of the positive lens material having the largest Abbe number is ν1p, and the refractive index and Abbe number of one positive lens material of the second lens group are N2p, respectively. , Ν2p, f1 is the focal length of the first lens group, f1p is the focal length of the positive lens having the largest Abbe number of the material among the positive lenses constituting the first lens group, and zooming from the wide-angle end to the telephoto end When the movement amount of the third lens group is M3 and the focal length of the entire system at the wide angle end is fw,
80.0 <ν1p
1.190 ≦ f1p / f1 <1.6
ν2p <18.4
1.90 <N2p
−3.8 <M3 / fw <−3.0
A zoom lens characterized by satisfying the following conditions: 7.0 <f1 / fw <10.0
The zoom lens according to claim 1, wherein the following condition is satisfied. When the focal length of the second lens group is f2,
1.2 <| f2 | / fw <1.6
The zoom lens according to claim 1, wherein the following condition is satisfied. When the focal length of the third lens group is f3,
1.7 <f3 / fw <4.6
The zoom lens according to claim 1, wherein the following condition is satisfied. When the difference in refractive index between the materials of the two positive lenses constituting the first lens group is ΔN1p,
0.1 <ΔN1p <0.4
The zoom lens according to claim 1, wherein the following condition is satisfied. In the second lens group, in order from the object side to the image side, the absolute value of refractive power is larger on the image side than on the object side, and a negative lens with a concave surface on the image side and a convex surface on the object side. When the distance on the optical axis from the image-side lens surface of the negative lens to the object-side lens surface of the negative lens is d2, and the focal length of the entire system at the wide-angle end is fw,
0.52 <d2 / fw <1.00
The zoom lens according to claim 1, wherein the following condition is satisfied. When the Abbe number of the negative lens material having the largest absolute value of refractive power among the negative lenses constituting the second lens group is ν2n,
0.029 <(1 / ν2p−1 / ν2n) <0.05
The zoom lens according to claim 1, wherein the following condition 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.