# Patent

## Title
Zoom lens and imaging apparatus

## Abstract

A zoom lens consists of, in order from the object side, a positive first group, a negative second group, one or two middle groups including a positive mp group, and a positive rearmost group disposed at the most image-side position of the entire system. Zooming is effected by changing all distances between the adjacent groups. An A cemented lens formed by a positive lens and a negative lens which are cemented together in this order from the object side is disposed at the most object-side position of the second group, a B cemented lens formed by one positive lens and one negative lens is disposed on the image side of the A cemented lens and on the object side of the mp group, and a C cemented lens formed by one positive lens and one negative lens is disposed in the mp group. The zoom lens satisfies given condition expressions.

## Background
CROSS-REFERENCE TO RELATED APPLICATIONS
The present application claims priority under 35 U.S.C. §119 to Japanese Patent Application No. 2014-174109, filed on Aug. 28, 2014. The above application is hereby expressly incorporated by reference, in its entirety, into the present application.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a zoom lens which is suitable for use with, in particular, digital cameras, lens-replaceable digital cameras, etc., and an imaging apparatus provided with the zoom lens.
2. Description of the Related Art
So-called constant aperture zoom lenses having a zoom ratio of around 2.5 to 3.0, and a constant maximum aperture of around F2.8 or F4 across the entire zoom range are known.
Such a zoom lens has a four-group or five-group configuration including, for example, in order from the object side, a first lens group which has a positive refractive power and is fixed during magnification change, a second lens group which has a negative refractive power and has a strong magnification change effect, about one or two magnification changing groups which are provided in addition to the second lens group and include a lens group having a positive refractive power, and a rearmost lens group which is fixed during magnification change.
As a zoom lens having the above-described configuration, those disclosed in Japanese Unexamined Patent Publication Nos. 2013-007878, 2012-058619, 2012-093548, 2011-099964, and 2013-160997 (hereinafter, Patent Documents 1 to 5) are known.
SUMMARY OF THE INVENTION
With the above-described type of zoom lens, correction of chromatic aberration is one of important problems. To achieve the correction of chromatic aberration, a conventionally known method uses a material having low dispersion and high abnormal dispersion to form a positive lens forming the first lens group, through which the thickest bundle of rays passes at the telephoto end. However, chromatic aberration also tends to occur at the lens groups to be moved, such as the second lens group and the third lens group, which are disposed behind the first lens group, and chromatic aberration occurring at the second lens group, which has a strong magnification changing effect, or at the magnification changing group, which has a negative refractive power, results in significant variation of chromatic aberration between the wide-angle end and the telephoto end.
In the above-described zoom lens, the second lens group is formed by around four to five lenses. As a relatively simple configuration example, the second lens group of Patent Document 1 is formed by four lenses including, in order from the object side, a negative lens, a cemented lens formed by a negative lens and a positive lens, and a negative lens. A conventional way for correcting chromatic aberration is appropriately disposing a cemented lens, and one cemented lens is used in the above example. In order to correct chromatic aberration, a material having an Abbe number of 70.3 is used to form the negative lens and a material having an Abbe number of 23.8 is used to form the positive lens to provide a large difference between the Abbe numbers of the two lenses to achieve achromatization. However, although the material forming the negative lens has low dispersion, it does not have high abnormal dispersion, and it is difficult to suppress secondary chromatic aberration in this case.
Patent Document 2 discloses an example where a material having high abnormal dispersion, which is equivalent to that of S-FPL51 available from Ohara Inc., is used to form the negative lens forming the cemented lens disposed in the second lens group. Patent Document 2 also uses an additional cemented lens in the second lens group to correct chromatic aberration. However, the third lens group, which is another lens group to be moved, is formed by two single lenses, and it is difficult to achieve sufficient achromatization.
Patent Document 3 discloses an example where a material having high abnormal dispersion, which is equivalent to that of J-FKH1 available from Hikari Glass Co., Ltd., is used. However, in Patent Document 3, the second lens group includes one cemented lens, and the first lens includes two cemented lenses, resulting in size increase of the zoom lens.
In Patent Document 4, the second lens group includes two cemented lenses, and the third lens group, which is another magnification changing group, also includes a cemented lens. While this configuration facilitates suppressing variation of chromatic aberration during magnification change, the second lens group does not use glass material having low dispersion and high abnormal dispersion, and it is difficult to achieve sufficient correction of chromatic aberration.
In Patent Document 5, each of the second lens group, the third lens group, and the fourth lens group includes a cemented lens, and this configuration facilitates suppressing variation of chromatic aberration during magnification change. However, the second lens group and the third lens group, which are negative lens groups, do not use a material having low dispersion and high abnormal dispersion like the materials used in Patent Documents 2 and 3.
In view of the above-described circumstances, the present invention is directed to providing a zoom lens having high optical performance with successfully suppressed primary chromatic aberration and secondary chromatic aberration, and an imaging apparatus provided with the zoom lens.
A zoom lens of the invention consists of four or five lens groups as a whole, which consist of, in order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, one or two middle lens groups including a mp lens group having a positive refractive power, and a rearmost lens group disposed at the most image side position of the entire system and having a positive refractive power, wherein magnification change is effected by changing all distances between the adjacent lens groups,
an A cemented lens consisting of a positive lens and a negative lens which are cemented together in this order from the object side is disposed at the most object-side position of the second lens group,
a B cemented lens consisting of one positive lens and one negative lens is disposed on the image side of the A cemented lens and on the object side of the mp lens group,
a C cemented lens consisting of one positive lens and one negative lens is disposed in the mp lens group, and
the condition expressions (1) and (2) below are satisfied:

60<νdBn  (1), and

0.0055<θgFBn+0.00162νdBn−0.6415<0.050  (2),

where νdBn is an Abbe number of the negative lens forming the B cemented lens, and θgFBn is a partial dispersion ratio of the negative lens forming the B cemented lens.

It should be noted that the mp lens group is not a part of a lens group (a sub-lens group) and is one independent lens group. The “independent lens group” herein means such a lens group that the distance between the lens group and the adjacent lens group is changed during magnification change. In the case where the middle lens group consists of two lens groups, and both the two lens groups have a positive refractive power, the mp lens group may be either of the lens groups.
In the zoom lens of the invention, it is preferred that the first lens group be fixed relative to the image plane during magnification change.
It is preferred that the rearmost lens group be fixed relative to the image plane during magnification change.
It is preferred that the first lens group comprise at least two positive lenses, and the condition expression (3) below be satisfied:

80.5<νd1p  (3),

where νd1p is an average Abbe number of the positive lenses in the first lens group.

It is preferred that the condition expression (4) below be satisfied:

57<νdCp  (4),

where νdCp is an Abbe number of the positive lens forming the C cemented lens.

It is preferred that focusing from an object at infinity to a closest object be effected by moving only the entire mp lens group or only a part of lenses forming the mp lens group along the optical axis, and it is more preferred that the focusing be effected by moving only the entire mp lens group.
It is preferred that the mp lens group comprise the C cemented lens and one positive lens.
It is preferred that the first lens group comprise at least one negative lens that satisfies the condition expression (5) below:

28<νd1n<45  (5),

where νd1n is an Abbe number of the negative lens in the first lens group.

It is preferred that the rearmost lens group consist of, in order from the object side, a front group having a positive refractive power, a middle group having a negative refractive power, and a rear group having a positive refractive power, the front group consist of three positive lenses and one negative lens, and image stabilization be effected by moving only the middle group in directions perpendicular to the optical axis direction.
In this case, it is preferred that the middle group consist of two negative lenses and one positive lens.
The zoom lens of the invention may consist of four lens groups which consist of in order from the object side, the first lens group, the second lens group, the mp lens group, and the rearmost lens group, or may consist of five lens groups which consist of, in order from the object side, the first lens group, the second lens group, a lens group having a negative refractive power, the mp lens group, and the rearmost lens group.
It is preferred that the second lens group comprise two or more positive lenses and two or more negative lenses.
It is preferred that the first lens group consist of, in order from the object side, a negative lens, a positive lens, a positive lens, and a positive lens.
It is preferred that the first lens group comprise at least one positive lens, and the condition expression (6) below be satisfied:

83<νd1m  (6),

where νd1m is the largest Abbe number of the least one positive lens in the first lens group.

It is preferred that the first lens group comprise at least one positive lens, and the positive lens having the largest Abbe number in the first lens group be a single lens.
It is preferred that a stop be disposed at the most object-side position of the rearmost lens group.
It is preferred that the positive lens forming the A cemented lens have a center thickness greater than the center thickness of the negative lens forming the A cemented lens.
An imaging apparatus of the invention comprises the above-described zoom lens of the invention.
It should be noted that the expression “consisting/consist of” as used herein means that the zoom lens may include, besides the elements recited above: lenses substantially without any power; optical elements other than lenses, such as a stop, a mask, a cover glass, and filters; and mechanical components, such as a lens flange, a lens barrel, an image sensor, an image stabilization mechanism, etc.
The Abbe numbers are with respect to the d-line (the wavelength of 587.6 nm), and the partial dispersion ratio θgF is expressed by the formula below:

θgF=(ng−nF)/(nF−nC),

where ng is a refractive index with respect to the g-line (the wavelength of 435.8 nm), nF is a refractive index with respect to the F-line (the wavelength of 486.1 nm), and nC is a refractive index with respect to the C-line (the wavelength of 656.3 nm).

The sign (positive or negative) with respect to the surface shape and the refractive power of any lens including an aspheric surface are about the paraxial region.
The zoom lens of the invention consists of four or five lens groups as a whole, which consist of, in order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, one or two middle lens groups including a mp lens group having a positive refractive power, and a rearmost lens group disposed at the most image side position of the entire system and having a positive refractive power, wherein magnification change is effected by changing all distances between the adjacent lens groups, an A cemented lens consisting of a positive lens and a negative lens which are cemented together in this order from the object side is disposed at the most object-side position of the second lens group, a B cemented lens consisting of one positive lens and one negative lens is disposed on the image side of the A cemented lens and on the object side of the mp lens group, a C cemented lens consisting of one positive lens and one negative lens is disposed in the mp lens group, and the condition expressions (1) and (2) below are satisfied:

60<νdBn  (1), and

0.0055<θgFBn+0.00162νdBn−0.6415<0.050  (2).

This configuration allows achieving a zoom lens having high optical performance with successfully suppressed primary chromatic aberration and secondary chromatic aberration.

The imaging apparatus of the invention, which is provided with the zoom lens of the invention, allows obtaining high quality images with reduced primary chromatic aberration and secondary chromatic aberration.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a sectional view illustrating the lens configuration of a zoom lens according to one embodiment of the present invention (a zoom lens of Example 1),
FIG. 2 is a sectional view illustrating the lens configuration of a zoom lens of Example 2 of the invention,
FIG. 3 is a sectional view illustrating the lens configuration of a zoom lens of Example 3 of the invention,
FIG. 4 is a sectional view illustrating the lens configuration of a zoom lens of Example 4 of the invention,
FIG. 5 is a sectional view illustrating the lens configuration of a zoom lens of Example 5 of the invention,
FIG. 6 is a sectional view illustrating the lens configuration of a zoom lens of Example 6 of the invention,
FIG. 7 is a sectional view illustrating the lens configuration of a zoom lens of Example 7 of the invention,
FIG. 8 is a sectional view illustrating the lens configuration of a zoom lens of Example 8 of the invention,
FIG. 9 is a sectional view illustrating the lens configuration of a zoom lens of Example 9 of the invention,
FIG. 10 is a sectional view illustrating the lens configuration of a zoom lens of Example 10 of the invention,
FIG. 11 is a sectional view illustrating the lens configuration of a zoom lens of Example 11 of the invention,
FIG. 12 shows aberration diagrams of the zoom lens of Example 1 of the invention,
FIG. 13 shows aberration diagrams of the zoom lens of Example 2 of the invention,
FIG. 14 shows aberration diagrams of the zoom lens of Example 3 of the invention,
FIG. 15 shows aberration diagrams of the zoom lens of Example 4 of the invention,
FIG. 16 shows aberration diagrams of the zoom lens of Example 5 of the invention,
FIG. 17 shows aberration diagrams of the zoom lens of Example 6 of the invention,
FIG. 18 shows aberration diagrams of the zoom lens of Example 7 of the invention,
FIG. 19 shows aberration diagrams of the zoom lens of Example 8 of the invention,
FIG. 20 shows aberration diagrams of the zoom lens of Example 9 of the invention,
FIG. 21 shows aberration diagrams of the zoom lens of Example 10 of the invention,
FIG. 22 shows aberration diagrams of the zoom lens of Example 11 of the invention,
FIG. 23 shows lateral aberration diagrams of the zoom lens of Example 1 of the invention,
FIG. 24 shows lateral aberration diagrams of the zoom lens of Example 1 of the invention (with image stabilization),
FIG. 25 shows lateral aberration diagrams of the zoom lens of Example 2 of the invention,
FIG. 26 shows lateral aberration diagrams of the zoom lens of Example 2 of the invention (with image stabilization),
FIG. 27 shows lateral aberration diagrams of the zoom lens of Example 3 of the invention,
FIG. 28 shows lateral aberration diagrams of the zoom lens of Example 3 of the invention (with image stabilization),
FIG. 29 shows lateral aberration diagrams of the zoom lens of Example 4 of the invention,
FIG. 30 shows lateral aberration diagrams of the zoom lens of Example 4 of the invention (with image stabilization),
FIG. 31 shows lateral aberration diagrams of the zoom lens of Example 5 of the invention,
FIG. 32 shows lateral aberration diagrams of the zoom lens of Example 5 of the invention (with image stabilization),
FIG. 33 shows lateral aberration diagrams of the zoom lens of Example 6 of the invention,
FIG. 34 shows lateral aberration diagrams of the zoom lens of Example 6 of the invention (with image stabilization),
FIG. 35 shows lateral aberration diagrams of the zoom lens of Example 7 of the invention,
FIG. 36 shows lateral aberration diagrams of the zoom lens of Example 7 of the invention (with image stabilization),
FIG. 37 shows lateral aberration diagrams of the zoom lens of Example 8 of the invention,
FIG. 38 shows lateral aberration diagrams of the zoom lens of Example 8 of the invention (with image stabilization),
FIG. 39 shows lateral aberration diagrams of the zoom lens of Example 9 of the invention,
FIG. 40 shows lateral aberration diagrams of the zoom lens of Example 9 of the invention (with image stabilization),
FIG. 41 shows lateral aberration diagrams of the zoom lens of Example 10 of the invention,
FIG. 42 shows lateral aberration diagrams of the zoom lens of Example 10 of the invention (with image stabilization),
FIG. 43 shows lateral aberration diagrams of the zoom lens of Example 11 of the invention,
FIG. 44 shows lateral aberration diagrams of the zoom lens of Example 11 of the invention (with image stabilization),
FIG. 45 is a perspective view showing the front side of an imaging apparatus according to one embodiment of the invention, and
FIG. 46 is a perspective view showing the rear side of the imaging apparatus shown in FIG. 45.



DESCRIPTION OF THE PREFERRED EMBODIMENTS
Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a sectional view illustrating the lens configuration of a zoom lens according to one embodiment of the invention. The configuration example shown in FIG. 1 is the same as the configuration of a zoom lens of Example 1, which will be described later. In FIG. 1, the left side is the object side and the right side is the image side. An aperture stop St shown in the drawing does not necessarily represent the size and the shape thereof, but represents the position thereof along the optical axis Z.
As shown in FIG. 1, this zoom lens consists of, in order from the object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, a third lens group G3 having a positive refractive power (which corresponds to an mp lens group of the invention), and a fourth lens group G4 having a positive refractive power (which corresponds to a rearmost lens group of the invention), wherein magnification change is effected by changing all the distances between the adjacent lens groups.
When this zoom lens is used with an imaging apparatus, it is preferred to provide a cover glass, a prism, and various filters, such as an infrared cutoff filter and a low-pass filter, etc., between the optical system and an image plane Sim depending on the configuration of the camera on which the lens is mounted. In the example shown in FIG. 1, an optical member PP in the form of a plane-parallel plate, which is assumed to represent such elements, is disposed between the lens system and the image plane Sim.
At the most object-side position of the second lens group G2, an A cemented lens CA formed by a positive lens L21 and a negative lens L22 which are cemented together in this order from the object side is disposed, and a B cemented lens CB formed by a negative lens L23 and a positive lens L24 which are cemented together in this order from the object side is disposed on the image side of the A cemented lens CA. Disposing the A cemented lens CA, which is formed by a positive lens and a negative lens which are cemented together in this order from the object side, at the most object-side position of the second lens group G2 in this manner is advantageous for correcting longitudinal chromatic aberration. Further, disposing the B cemented lens CB, which is formed by one positive lens and one negative lens, on the image side of the A cemented lens CA and on the object side of the third lens group G3 (the mp lens group) is advantageous for correcting secondary lateral chromatic aberration.
In the third lens group G3 (the mp lens group), a C cemented lens CC formed by a positive lens L32 and a negative lens L33 which are cemented together in this order from the object side is disposed. Disposing the C cemented lens CC, which is formed by one positive lens and one negative lens, in the third lens group G3 (the mp lens group) in this manner allows suppressing variation of chromatic aberration during zoom.
The zoom lens of the invention is configured to satisfy the condition expressions (1) and (2) below. The condition expression (1) relates to the Abbe number of the negative lens L23 forming the B cemented lens CB, and the condition expression (2) relates to the partial dispersion ratio of the negative lens L23 forming the B cemented lens CB. Satisfying the low dispersion defined by the condition expression (1) and the abnormal dispersion defined by the condition expression (2) at the same time allows well-balanced correction of primary chromatic aberration (longitudinal chromatic aberration, lateral chromatic aberration), and secondary chromatic aberration across the entire zoom range.
Satisfying the lower limit of the condition expression (1) allows ensuring a difference between Abbe numbers of the negative lens L23 and the positive lens L24 forming the B cemented lens CB to provide a sufficient primary chromatic aberration correcting effect. Also, when the lower limit of the condition expression (1) is satisfied, it is not necessary to select a material having high dispersion to form the positive lens L24 forming the B cemented lens CB, and this is advantageous for correcting secondary chromatic aberration. Satisfying the upper limit of the condition expression (1) allows providing a desired refractive power without reducing the absolute values of the radius of curvatures of the lens surfaces of the negative lens L23, and this allows successfully suppressing aberrations occurring at the lens surfaces.
Satisfying the lower limit of the condition expression (2) is advantageous for correcting secondary chromatic aberration. A material that satisfies the upper limit of the condition expression (2) has a certain level of refractive index. Therefore satisfying the upper limit of the condition expression (2) allows providing a desired refractive power without reducing the absolute values of the radius of curvatures of the lens surfaces of the negative lens L23, and this allows successfully suppressing aberrations occurring at the lens surfaces and is also advantageous for correcting coma aberration at the wide-angle end.
It should be noted that higher performance can be obtained when the condition expressions (1-1), (1-2), (1-3), and/or (2-1) below is satisfied.

60<νdBn  (1),

60<νdBn<100  (1-1),

65<νdBn  (1-2),

65<νdBn<90  (1-3),

0.0055<θgFBn+0.00162νdBn−0.6415<0.050  (2),

0.010<θgFBn+0.00162νdBn−0.6415<0.045  (2-1),

where νdBn is an Abbe number of the negative lens forming the B cemented lens, and θgFBn is a partial dispersion ratio of the negative lens forming the B cemented lens.

In the zoom lens of this embodiment, it is preferred that the first lens group G1 be fixed relative to the image plane Sim during magnification change. Fixing the first lens group G1 in this manner allows simplifying the frame structure. Comparing to a configuration where the first lens group G1 is moved forward toward its telephoto end position, this configuration has advantages such as reducing influence of decentering of the lenses due to flexure of the lens frame, etc., and facilitating use of a dustproof, weather sealed structure.
It is preferred that the fourth lens group G4 (the rearmost lens group) be fixed relative to the image plane Sim during magnification change. Reducing the number of lens groups to be moved in this manner allows reducing influence of decentering. Also, this configuration allows suppressing variation of F-number during magnification change, and this is advantageous for forming a zoom lens having a constant aperture.
It is preferred that the first lens group G1 include at least two positive lenses, and satisfy the condition expression (3) below. Using a material having low dispersion in the first lens group G1, through which the thickest bundle of rays passes at the telephoto end, in this manner allows successfully correcting longitudinal chromatic aberration, in particular, at the telephoto side. It should be noted that higher performance can be obtained when the condition expression (3-1) below is satisfied.

80.5<νd1p  (3),

80.5<νd1p<100  (3-1),

where νd1p is an average Abbe number of the positive lenses in the first lens group.

It is preferred that the condition expression (4) below be satisfied. Satisfying the lower limit of the condition expression (4) allows successfully correcting longitudinal chromatic aberration. Also, satisfying the lower limit of the condition expression (4) allows suppressing variation of chromatic aberration between the wide-angle end and the telephoto end. Satisfying the upper limit of the condition expression (4) allows well-balanced correction of chromatic aberrations. It should be noted that higher performance can be obtained when the condition expression (4-1), (4-2), or (4-3) below is satisfied.

57<νdCp  (4),

57<νdCp<85  (4-1),

59<νdCp  (4-2),

59<νdCp<85  (4-3),

where νdCp is an Abbe number of the positive lens forming the C cemented lens.

It is preferred that focusing from an object at infinity to a closest object is effected by moving only the entire third lens group G3 (the mp lens group) or only a part of lenses forming the third lens group G3 (the mp lens group) along the optical axis. Employing the above-described inner focusing system allows weight reduction of the focusing lens to thereby allow speeding up the autofocus operation. Further, effecting focusing by moving the entire third lens group G3 (the mp lens group) allows suppressing variation of aberrations during focusing.
It is preferred that the third lens group G3 (the mp lens group) includes a C cemented lens CC and one positive lens. This configuration allows successfully correcting aberrations at the third lens group G3 (the mp lens group), and suppressing variation of aberrations during magnification change. Further, using the third lens group G3 (the mp lens group) as a focusing group, as described above, allows suppressing variation of chromatic aberration during focusing.
It is preferred that the first lens group G1 includes at least one negative lens that satisfies the condition expression (5) below. Satisfying the lower limit of the condition expression (5) is advantageous for correcting secondary chromatic aberration. Satisfying the upper limit of the condition expression (5) allows preventing the refractive powers of the negative lens and the positive lens from becoming excessively strong, and this is advantageous for correcting spherical aberration, in particular, at the telephoto side. It should be noted that higher performance can be obtained when the condition expression (5-1) below is satisfied.

28<νd1n<45  (5),

30<νd1n<43  (5-1),

where νd1n is an Abbe number of the negative lens in the first lens group.

It is preferred that the fourth lens group G4 (the rearmost lens group) consist of, in order from the object side, a front group having a positive refractive power, a middle group having a negative refractive power, and a rear group having a positive refractive power, wherein the front group consist of three positive lenses and one negative lens, and image stabilization be effected by moving only the middle group in directions perpendicular to the optical axis direction. Providing the image stabilizing group with a power of the opposite sign from that of the lens groups in front of and behind the image stabilizing group in this manner allows providing the image stabilizing group with a strong power, and this allows smoothly increasing sensitivity of the image shift to shift of the image stabilizing group. This, in turn, allows reducing a range of shift of the image stabilizing lens which is necessary to obtain the same level of image stabilization effect. This configuration also allows the lens groups to cancel aberrations with one another.
In this case, it is preferred that the middle group consist of two negative lenses and one positive lens. Using three lenses to form the image stabilizing group in this manner allows suppressing decentering coma and variation of chromatic aberration along with shift of the image stabilizing group.
The zoom lens of the invention may consist of four lens groups which consist of, in order from the object side, the first lens group, the second lens group, the mp lens group, and the rearmost lens group, or may consist of five lens groups which consist of, in order from the object side, the first lens group, the second lens group, a lens group having a negative refractive power, the mp lens group, and the rearmost lens group. Minimizing the number of lens groups and forming the zoom lens having the above-described four-group configuration allows simplifying the frame structure, and reducing influence of decentering. Forming a zoom lens having the five-group configuration is advantageous for suppressing variation of aberrations and suppressing field curvature. The zoom lens of this embodiment has the four-group configuration.
It is preferred that the second lens group G2 include two or more positive lenses and two or more negative lenses. The second lens group G2 having the above configuration allows smoothly correcting aberrations even when the second lens group G2 is provided with a strong power to achieve size reduction of the front lens element or to reduce the amount of movement of the second lens group G2, and allows successfully correcting coma aberration and chromatic aberration, in particular, at the wide-angle end.
It is preferred that the first lens group G1 consist of, in order from the object side, a negative lens, a positive lens, a positive lens, and a positive lens. The first lens group G1 including three positive lenses in this manner allows successfully correcting chromatic aberration and spherical aberration, in particular, at the telephoto side. Further, in a case where the first lens group G1 as a whole has a strong power for the purpose of size reduction, etc., the above-described configuration allows distributing the power among the lenses, resulting in smaller aberrations at each lens surface.
It is preferred that the condition expression (6) below be satisfied. Satisfying the condition expression (6) allows successfully correcting longitudinal chromatic aberration and secondary chromatic aberration at the telephoto end.

83<νd1m  (6),

where νd1m is the largest Abbe number of the positive lenses in the first lens group.

It is preferred that the positive lens having the largest Abbe number in the first lens group G1 be a single lens. A material that satisfies the condition expression (6) above has high abnormal dispersion and is very advantageous for correcting chromatic aberration; however, such a material is a soft material and is difficult to be worked when it is used to form a cemented lens. It is therefore preferred to use such a material to form a single lens.
It is preferred that the aperture stop St be disposed at the most object-side position of the fourth lens group G4 (the rearmost lens group). Disposing the aperture stop St at the most object-side position of the fourth lens group G4 (the rearmost lens group) in place of between lenses of the fourth lens group G4 allows simplifying the frame structure. Further, in the case where the fourth lens group G4 (the rearmost lens group) is fixed relative to the image plane Sim during magnification change, a constant aperture zoom lens can be formed without changing the so-called aperture stop diameter.
It is preferred that the positive lens forming the A cemented lens CA have a center thickness greater than the center thickness of the negative lens forming the A cemented lens CA. This configuration allows providing the positive lens with a sufficient refractive power, and this is advantageous for correcting chromatic aberration.
In a case where the zoom lens is used in a harsh environment, it is preferred that the zoom lens be provided with a protective multi-layer coating. Besides the protective coating, the zoom lens may be provided with an antireflection coating for reducing ghost light, etc., during use.
In the example shown in FIG. 1, the optical member PP is disposed between the lens system and the image plane Sim. However, in place of disposing the various filters, such as a lowpass filter and a filter that cuts off a specific wavelength range, between the lens system and the image plane Sim, the various filters may be disposed between the lenses, or coatings having the same functions as the various filters may be applied to the lens surfaces of some of the lenses.
Next, numerical examples of the zoom lens of the invention are described.
First, a zoom lens of Example 1 is described. FIG. 1 is a sectional view illustrating the lens configuration of the zoom lens of Example 1. It should be noted that, in FIG. 1, and FIGS. 2 to 11 corresponding to Examples 2 to 11, which will be described later, the left side is the object side and the right side is the image side. The aperture stop St shown in the drawings does not necessarily represent the size and the shape thereof, but represents the position thereof along the optical axis Z. The symbol “Focus” in the drawings denotes a lens group used to effect focusing, and the symbol “Ois” denotes a lens group used to effect image stabilization.
The zoom lens of Example 1 has a four-group configuration which consists of, in order from the object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, a third lens group G3 (the mp lens group) having a positive refractive power, and a fourth lens group G4 (the rearmost lens group) having a positive refractive power.
Table 1 shows basic lens data of the zoom lens of Example 1, Table 2 shows data about specifications of the zoom lens, and Table 3 shows data about distances between surfaces to be moved of the zoom lens. In the following description, meanings of symbols used in the tables are explained with respect to Example 1 as an example. The same explanations basically apply to those with respect to Examples 2 to 11.
In the lens data shown in Table 1, each value in the column of “Surface No.” represents a surface number, where the object-side surface of the most object-side element is the 1st surface and the number is sequentially increased toward the image side, each value in the column of “Radius of Curvature” represents the radius of curvature of the corresponding surface, and each value in the column of “Surface Distance” represents the distance along the optical axis Z between the corresponding surface and the next surface. Each value in the column of “nd” represents the refractive index with respect to the d-line (the wavelength of 587.6 nm) of the corresponding optical element, each value in the column of “νd” represents the Abbe number with respect to the d-line (the wavelength of 587.6 nm) of the corresponding optical element, and each value in the column of “θgF” represents the partial dispersion ratio of the corresponding optical element.
It should be noted that the partial dispersion ratio θgF is expressed by the formula below:

θgF=(ng−nF)/(nF−nC),

where ng is a refractive index with respect to the g-line (the wavelength of 435.8 nm), nF is a refractive index with respect to the F-line (the wavelength of 486.1 nm), and nC is a refractive index with respect to the C-line (the wavelength of 656.3 nm).

The sign with respect to the radius of curvature is provided such that a positive radius of curvature indicates a surface shape that is convex toward the object side, and a negative radius of curvature indicates a surface shape that is convex toward the image side. The basic lens data also includes data of the aperture stop St and the optical member PP, and the surface number and the text “(stop)” are shown at the position in the column of the surface number corresponding to the aperture stop St. In the lens data shown in Table 1, the value of each surface distance that is changed during magnification change is represented by the symbol “DD[surface number]”. The numerical values corresponding to each DD[surface number] at the wide-angle end, at the middle position, and at the telephoto end are shown in Table 3.
The data about specifications shown in Table 2 show values of zoom magnification, focal length f′, back focus Bf′, F-number FNo., and total angle of view 2ω at the wide-angle end, at the middle position, and at the telephoto end.
With respect to the basic lens data, the data about specifications, and the data about distances between surfaces to be moved, the unit of angle is degrees, and the unit of length is millimeters; however, any other suitable units may be used since optical systems are usable when they are proportionally enlarged or reduced.







TABLE 1







Example 1 - Lens Data














Surface





Surface No.
Radius of Curvature
Distance
nd
νd
θgF















 1
274.96102
2.390
1.80100
34.97
0.58642


 2
77.90148
7.850
1.49700
81.54
0.53748


 3
−1203.47290
0.200





 4
97.12166
5.000
1.43875
94.94
0.53433


 5
3892.40898
0.200





 6
62.76476
6.000
1.49700
81.54
0.53748


 7
583.05158
DD[7]





 8
110.71627
5.710
1.72047
34.71
0.58350


 9
−42.66766
1.550
1.62230
53.17
0.55424


10
24.37958
4.958





11
−78.43069
1.260
1.49700
81.54
0.53748


12
25.54612
5.501
1.84661
23.88
0.62072


13
105.31259
4.001





14
−28.87373
1.250
1.91082
35.25
0.58224


15
391.32559
DD[15]





16
−349.16836
2.950
1.80100
34.97
0.58642


17
−38.22034
0.100





18
63.65733
4.310
1.61800
63.33
0.54414


19
−39.25049
1.150
1.80518
25.42
0.61616


20
∞
DD[20]





21 (stop)
∞
1.300





22
27.59915
6.985
1.49700
81.54
0.53748


23
−58.46986
0.150





24
34.60348
2.550
1.65412
39.68
0.57378


25
95.96990
1.610





26
−53.62431
1.210
1.90366
31.31
0.59481


27
22.84961
6.512
1.49700
81.54
0.53748


28
−84.57206
2.500





29
293.69564
3.771
1.80518
25.42
0.61616


30
−23.04083
0.950
1.58913
61.13
0.54067


31
33.63593
2.693





32
−43.53615
1.050
1.80100
34.97
0.58642


33
62.25169
3.752





34
51.53927
6.921
1.80000
29.84
0.60178


35
−39.86271
3.848





36
50.27571
7.368
1.48749
70.24
0.53007


37
−26.02866
1.310
1.80518
25.42
0.61616


38
−69.72800
3.069





39
−30.18711
1.310
1.91082
35.25
0.58224


40
−51.30966
26.063 





41
∞
2.850
1.51633
64.14
0.53531


42
∞
















TABLE 2







Example 1 - Specifications (d-line)











Wide-Angle End
Middle
Telephoto End













Zoom Magnification
1.0
1.8
2.6


f′
51.517
92.224
135.968


Bf′
29.940
29.940
29.940


FNo.
2.88
2.89
2.88


2ω[°]
30.4
17.0
11.6
















TABLE 3







Example 1 - Distances Relating to Zoom











Wide-Angle End
Middle
Telephoto End















DD[7]
1.647
24.961
34.686



DD[15]
11.849
7.355
2.477



DD[20]
32.001
13.182
8.334









FIG. 12 shows aberration diagrams of the zoom lens of Example 1. The aberration diagrams shown at the top of FIG. 12 are those of spherical aberration, offense against the sine condition, astigmatism, distortion, and lateral chromatic aberration at the wide-angle end in this order from the left side, the aberration diagrams shown at the middle of FIG. 12 are those of spherical aberration, offense against the sine condition, astigmatism, distortion, and lateral chromatic aberration at the middle position in this order from the left side, and the aberration diagrams shown at the bottom of FIG. 12 are those of spherical aberration, offense against the sine condition, astigmatism, distortion, and lateral chromatic aberration at the telephoto end in this order from the left side. The aberration diagrams of spherical aberration, offense against the sine condition, astigmatism, and distortion show those with respect to the d-line (the wavelength of 587.6 nm), which is used as a reference wavelength. The aberration diagrams of spherical aberration show those with respect to the d-line (the wavelength of 587.6 nm), the C-line (the wavelength of 656.3 nm), the F-line (the wavelength of 486.1 nm), and the g-line (the wavelength of 435.8 nm) in the solid line, the long dashed line, the short dashed line, and the gray line, respectively. The aberration diagrams of astigmatism show those in the sagittal direction and the tangential direction in the solid line and the short dashed line, respectively. The aberration diagrams of lateral chromatic aberration show those with respect to the C-line (the wavelength of 656.3 nm), the F-line (the wavelength of 486.1 nm), and the g-line (the wavelength of 435.8 nm) in the long dashed line, the short dashed line, and the gray line, respectively. It should be noted that these longitudinal aberration diagrams show aberrations when the zoom lens is focused on an object at infinity. The symbol “FNo.” in the aberration diagrams of spherical aberration and offense against the sine condition means “F-number”, and the symbol “ω” in the other aberration diagrams means “half angle of view”.
FIG. 23 shows lateral aberration diagrams of the zoom lens of Example 1 without image stabilization. FIG. 23 shows, in order from the top, lateral aberration diagrams at the wide-angle end, at the middle position, and at the telephoto end. Among the lateral aberration diagrams shown in two columns, the lateral aberration diagrams on the left show those with respect to the tangential direction, and the lateral aberration diagrams on the right show those with respect to the sagittal direction. Among the lateral aberration diagrams, one at the top shows aberrations at the center of the image plane, two at the middle show aberrations at the position where the image height is 80% of the maximum image height on the positive (+) side, and two at the bottom show aberrations at the position where the image height is 80% of the maximum image height on the negative (−) side. FIG. 24 shows lateral aberration diagrams of the zoom lens of Example 1 with image stabilization. The contents of the aberration diagrams are similar to those without image stabilization. It should be noted that, in FIGS. 23 and 24, aberrations with respect to the d-line (the wavelength of 587.6 nm), the C-line (the wavelength of 656.3 nm), the F-line (the wavelength of 486.1 nm), and the g-line (the wavelength of 435.8 nm) are shown in the solid line, the long dashed line, the short dashed line, and the gray line, respectively. These lateral aberration diagrams show lateral aberrations when the zoom lens is focused on an object at infinity. The symbol “ω” in the aberration diagrams means “half angle of view”.
The above-described symbols, meanings and manners of description of the various data of Example 1 apply also to the examples described below, unless otherwise noted, and the same explanations are not repeated in the following description.
Next, a zoom lens of Example 2 is described. The zoom lens of Example 2 has a lens group configuration similar to that of the zoom lens of Example 1. FIG. 2 is a sectional view illustrating the lens configuration of the zoom lens of Example 2. Table 4 shows basic lens data of the zoom lens of Example 2, Table 5 shows data about specifications of the zoom lens, Table 6 shows data about distances between surfaces to be moved of the zoom lens, FIG. 13 shows aberration diagrams of the zoom lens, FIG. 25 shows lateral aberration diagrams of the zoom lens without image stabilization, and FIG. 26 shows lateral aberration diagrams of the zoom lens with image stabilization.







TABLE 4







Example 2 - Lens Data












Surface

Surface





No.
Radius of Curvature
Distance
nd
νd
θgF















 1
147.14684
2.312
1.90366
31.31
0.59481


 2
71.34579
6.799
1.49700
81.54
0.53748


 3
4466.14983
0.262





 4
82.92060
4.599
1.45562
91.31
0.53429


 5
222.61947
0.209





 6
72.46651
7.001
1.48749
70.24
0.53007


 7
2229.87611
DD[7]





 8
83.14047
6.305
1.64769
33.79
0.59393


 9
−54.99973
1.501
1.61772
49.81
0.56035


10
22.65737
6.228





11
−129.46710
1.009
1.53775
74.70
0.53936


12
23.41440
5.501
1.84661
23.88
0.62072


13
90.28797
3.246





14
−32.56444
0.999
1.91082
35.25
0.58224


15
−754.10763
DD[15]





16
−139.28102
3.100
1.91082
35.25
0.58224


17
−37.20322
0.100





18
45.57357
5.511
1.48749
70.24
0.53007


19
−45.00113
1.100
1.80518
25.42
0.61616


20
302.73331
DD[20]





21 (stop)
∞
1.300





22
29.00638
5.564
1.53775
74.70
0.53936


23
−83.12098
0.182





24
28.22418
2.499
1.65412
39.68
0.57378


25
48.84185
1.900





26
−76.98887
1.210
1.90366
31.31
0.59481


27
20.91613
7.501
1.53775
74.70
0.53936


28
−71.39743
3.663





29
101.15891
4.706
1.80518
25.42
0.61616


30
−24.63022
0.882
1.60300
65.44
0.54022


31
26.11599
3.199





32
−41.59530
0.899
1.80100
34.97
0.58642


33
49.70954
2.255





34
43.72156
5.600
1.80000
29.84
0.60178


35
−36.00246
2.992





36
36.16338
5.708
1.48749
70.24
0.53007


37
−25.22381
1.199
1.80518
25.42
0.61616


38
−148.78795
4.102





39
−27.60609
1.199
1.91082
35.25
0.58224


40
−43.25152
23.562 





41
∞
2.850
1.51633
64.14
0.53531


42
∞
















TABLE 5







Example 2 - Specifications (d-line)











Wide-Angle End
Middle
Telephoto End













Zoom Magnification
1.0
1.8
2.6


f′
51.492
92.178
135.901


Bf′
27.440
27.440
27.440


FNo.
2.89
2.89
2.89


2ω[°]
30.2
17.0
11.6
















TABLE 6







Example 2 - Distances Relating to Zoom











Wide-Angle End
Middle
Telephoto End















DD[7]
1.199
24.644
34.908



DD[15]
12.356
7.391
1.751



DD[20]
31.802
13.322
8.698









Next, a zoom lens of Example 3 is described. The zoom lens of Example 3 has a lens group configuration similar to that of the zoom lens of Example 1. FIG. 3 is a sectional view illustrating the lens configuration of the zoom lens of Example 3. Table 7 shows basic lens data of the zoom lens of Example 3, Table 8 shows data about specifications of the zoom lens, Table 9 shows data about distances between surfaces to be moved of the zoom lens, FIG. 14 shows aberration diagrams of the zoom lens, FIG. 27 shows lateral aberration diagrams of the zoom lens without image stabilization, and FIG. 28 shows lateral aberration diagrams of the zoom lens with image stabilization.







TABLE 7







Example 3 - Lens Data












Surface

Surface





No.
Radius of Curvature
Distance
nd
νd
θgF















 1
263.09263
2.312
1.88100
40.14
0.57010


 2
65.86876
7.199
1.49700
81.54
0.53748


 3
−571.64100
0.262





 4
65.97392
6.200
1.45562
91.31
0.53429


 5
1175.27258
0.209





 6
81.36467
5.500
1.53775
74.70
0.53936


 7
614.16494
DD[7]





 8
120.18724
5.912
1.72047
34.71
0.58350


 9
−42.77946
1.200
1.62230
53.17
0.55424


10
26.30170
5.468





11
−3031.67199
1.009
1.43875
94.94
0.53433


12
24.69032
4.403
1.84661
23.88
0.62072


13
52.10852
4.001





14
−29.01944
0.999
1.88300
40.76
0.56679


15
677.75184
DD[15]





16
−624.58221
3.099
1.91082
35.25
0.58224


17
−48.99609
0.100





18
84.61141
4.859
1.62041
60.29
0.54266


19
−45.52887
1.100
1.84666
23.78
0.62054


20
−11814.82817
DD[20]





21 (stop)
∞
1.300





22
28.94841
7.001
1.49700
81.54
0.53748


23
−70.94964
2.298





24
35.48837
2.499
1.65412
39.68
0.57378


25
125.19811
1.799





26
−55.44889
1.210
1.90366
31.31
0.59481


27
24.47948
7.501
1.49700
81.54
0.53748


28
−71.45146
2.001





29
93.11345
4.160
1.80518
25.42
0.61616


30
−26.87211
0.849
1.58313
59.37
0.54345


31
26.83474
3.501





32
−31.98401
0.901
1.80100
34.97
0.58642


33
64.79704
2.718





34
52.34160
5.499
1.80000
29.84
0.60178


35
−36.46191
4.001





36
56.45949
7.310
1.48749
70.24
0.53007


37
−23.44294
1.199
1.80518
25.42
0.61616


38
−60.82914
2.999





39
−26.37941
1.199
1.91082
35.25
0.58224


40
−35.96318
22.238 





41
∞
2.850
1.51633
64.14
0.53531


42
∞
















TABLE 8







Example 3 - Specifications (d-line)











Wide-Angle End
Middle
Telephoto End













Zoom Magnification
1.0
1.8
3.1


f′
50.359
90.150
157.119


Bf′
26.122
26.122
26.122


FNo.
2.89
2.90
2.92


2ω[°]
31.0
17.2
10.0
















TABLE 9







Example 3 - Distances Relating to Zoom











Wide-Angle End
Middle
Telephoto End















DD[7]
1.199
24.327
37.203



DD[15]
16.502
10.829
1.100



DD[20]
32.001
14.546
11.399









Next, a zoom lens of Example 4 is described. The zoom lens of Example 4 has a lens group configuration similar to that of the zoom lens of Example 1. FIG. 4 is a sectional view illustrating the lens configuration of the zoom lens of Example 4. Table 10 shows basic lens data of the zoom lens of Example 4, Table 11 shows data about specifications of the zoom lens, Table 12 shows data about distances between surfaces to be moved of the zoom lens, FIG. 15 shows aberration diagrams of the zoom lens, FIG. 29 shows lateral aberration diagrams of the zoom lens without image stabilization, and FIG. 30 shows lateral aberration diagrams of the zoom lens with image stabilization.







TABLE 10







Example 4 - Lens Data












Surface

Surface





No.
Radius of Curvature
Distance
nd
νd
θgF















 1
188.13090
2.312
1.80610
33.27
0.58845


 2
76.50883
7.200
1.49700
81.54
0.53748


 3
−3204.67292
0.262





 4
71.91851
6.200
1.43875
94.94
0.53433


 5
718.81472
0.209





 6
63.83157
5.500
1.43875
94.94
0.53433


 7
286.11890
DD[7]





 8
127.11673
5.510
1.72047
34.71
0.58350


 9
−52.90722
1.200
1.62230
53.17
0.55424


10
24.99227
6.501





11
−273.45110
1.511
1.59522
67.74
0.54426


12
26.07897
5.501
1.84661
23.88
0.62072


13
90.43692
4.000





14
−28.20939
1.001
1.88300
40.76
0.56679


15
−219.42843
DD[15]





16
4368.42118
3.099
1.91082
35.25
0.58224


17
−45.70178
0.100





18
75.53670
5.511
1.49700
81.54
0.53748


19
−37.32451
1.100
1.80518
25.42
0.61616


20
−582.89400
DD[20]





21 (stop)
∞
1.300





22
31.57617
7.001
1.49700
81.54
0.53748


23
−84.25408
1.501





24
32.66369
2.500
1.65412
39.68
0.57378


25
452.11337
1.799





26
−77.71874
1.210
1.90366
31.31
0.59481


27
23.15115
5.500
1.49700
81.54
0.53748


28
−93.31207
2.001





29
664.84163
4.161
1.80518
25.42
0.61616


30
−28.96139
1.201
1.58313
59.37
0.54345


31
23.87736
3.200





32
−37.84433
0.899
1.80100
34.97
0.58642


33
66.37072
2.215





34
45.41616
8.001
1.80518
25.42
0.61616


35
−36.36637
1.453





36
44.07982
7.310
1.48749
70.24
0.53007


37
−23.31946
1.200
1.80518
25.42
0.61616


38
−147.09849
2.999





39
−27.43891
1.200
1.91082
35.25
0.58224


40
−35.75126
22.213 





41
∞
2.850
1.51633
64.14
0.53531


42
∞
















TABLE 11







Example 4 - Specifications (d-line)











Wide-Angle End
Middle
Telephoto End













Zoom Magnification
1.0
1.8
3.0


f′
51.153
91.572
154.995


Bf′
26.096
26.096
26.096


FNo.
2.89
2.89
2.89


2ω[°]
30.6
17.2
10.2
















TABLE 12







Example 4 - Distances Relating to Zoom











Wide-Angle End
Middle
Telephoto End















DD[7]
1.199
22.851
34.047



DD[15]
17.079
11.080
1.673



DD[20]
28.994
13.341
11.552









Next, a zoom lens of Example 5 is described. The zoom lens of Example 5 has a lens group configuration similar to that of the zoom lens of Example 1. FIG. 5 is a sectional view illustrating the lens configuration of the zoom lens of Example 5. Table 13 shows basic lens data of the zoom lens of Example 5, Table 14 shows data about specifications of the zoom lens, Table 15 shows data about distances between surfaces to be moved of the zoom lens, FIG. 16 shows aberration diagrams of the zoom lens, FIG. 31 shows lateral aberration diagrams of the zoom lens without image stabilization, and FIG. 32 shows lateral aberration diagrams of the zoom lens with image stabilization.







TABLE 13







Example 5 - Lens Data












Surface

Surface





No.
Radius of Curvature
Distance
nd
νd
θgF















 1
308.24145
2.390
1.80100
34.97
0.58642


 2
78.18266
7.850
1.49700
81.54
0.53748


 3
−340.82791
0.200





 4
66.71039
6.600
1.43875
94.94
0.53433


 5
720.82813
0.200





 6
71.57189
4.950
1.49700
81.54
0.53748


 7
271.98720
DD[7]





 8
100.51474
5.710
1.72047
34.71
0.58350


 9
−47.31525
1.550
1.62230
53.17
0.55424


10
25.05895
5.799





11
−81.14905
1.260
1.49700
81.54
0.53748


12
26.42066
5.385
1.84661
23.88
0.62072


13
110.30764
3.945





14
−30.83422
1.250
1.91082
35.25
0.58224


15
339.66055
DD[15]





16
−578.30556
2.950
1.80100
34.97
0.58642


17
−44.53935
0.100





18
76.28815
4.310
1.61800
63.33
0.54414


19
−43.38154
1.150
1.80518
25.42
0.61616


20
∞
DD[20]





21 (stop)
∞
1.300





22
27.81766
6.849
1.49700
81.54
0.53748


23
−58.16078
0.150





24
34.51417
2.550
1.65412
39.68
0.57378


25
107.98255
1.610





26
−54.74993
1.210
1.90366
31.31
0.59481


27
23.44507
5.499
1.49700
81.54
0.53748


28
−83.55949
2.500





29
343.99918
3.771
1.80518
25.42
0.61616


30
−24.56535
0.950
1.58913
61.13
0.54067


31
39.79185
2.559





32
−45.16452
1.050
1.80100
34.97
0.58642


33
60.11939
4.533





34
51.91667
6.541
1.80000
29.84
0.60178


35
−39.70261
4.000





36
54.95096
6.950
1.48749
70.24
0.53007


37
−27.73386
1.310
1.80518
25.42
0.61616


38
−89.67633
3.413





39
−27.15780
1.310
1.91082
35.25
0.58224


40
−45.53256
24.577 





41
∞
2.850
1.51633
64.14
0.53531


42
∞
















TABLE 14







Example 5 - Specifications (d-line)











Wide-Angle End
Middle
Telephoto End













Zoom Magnification
1.0
1.8
2.4


f′
51.515
92.219
125.696


Bf′
28.455
28.455
28.455


FNo.
2.88
2.89
2.89


2ω[°]
30.4
17.0
12.4
















TABLE 15







Example 5 - Distances Relating to Zoom











Wide-Angle End
Middle
Telephoto End















DD[7]
1.199
22.040
29.321



DD[15]
14.144
8.593
3.929



DD[20]
27.855
12.565
9.948









Next, a zoom lens of Example 6 is described. The zoom lens of Example 6 has a lens group configuration similar to that of the zoom lens of Example 1. FIG. 6 is a sectional view illustrating the lens configuration of the zoom lens of Example 6. Table 16 shows basic lens data of the zoom lens of Example 6, Table 17 shows data about specifications of the zoom lens, Table 18 shows data about distances between surfaces to be moved of the zoom lens, FIG. 17 shows aberration diagrams of the zoom lens, FIG. 33 shows lateral aberration diagrams of the zoom lens without image stabilization, and FIG. 34 shows lateral aberration diagrams of the zoom lens with image stabilization.







TABLE 16







Example 6 - Lens Data












Surface

Surface





No.
Radius of Curvature
Distance
nd
νd
θgF















 1
379.59503
2.390
1.80100
34.97
0.58642


 2
87.06343
7.850
1.49700
81.54
0.53748


 3
−423.40525
0.200





 4
77.08956
6.600
1.43875
94.94
0.53433


 5
505.15031
0.200





 6
74.14509
4.950
1.49700
81.54
0.53748


 7
428.65265
DD[7]





 8
95.00168
5.710
1.72047
34.71
0.58350


 9
−42.18184
1.550
1.62230
53.17
0.55424


10
25.82252
4.852





11
−127.50772
1.260
1.49700
81.54
0.53748


12
27.56506
4.000
1.84661
23.88
0.62072


13
102.12490
3.395





14
−31.04306
1.250
1.91082
35.25
0.58224


15
593.08219
DD[15]





16
−587.37289
2.950
1.80100
34.97
0.58642


17
−43.88242
0.100





18
78.12881
4.310
1.61800
63.33
0.54414


19
−42.34007
1.150
1.80518
25.42
0.61616


20
∞
DD[20]





21 (stop)
∞
1.300





22
27.72433
6.373
1.49700
81.54
0.53748


23
−59.65321
0.150





24
34.01198
2.550
1.65412
39.68
0.57378


25
93.88248
1.610





26
−54.41210
1.210
1.90366
31.31
0.59481


27
23.35543
5.569
1.49700
81.54
0.53748


28
−77.98799
2.500





29
394.61491
3.771
1.80518
25.42
0.61616


30
−24.49939
0.950
1.58913
61.13
0.54067


31
37.65964
2.511





32
−48.39346
1.050
1.80100
34.97
0.58642


33
60.29812
4.948





34
52.39389
5.299
1.80000
29.84
0.60178


35
−39.28541
3.134





36
53.75550
7.501
1.48749
70.24
0.53007


37
−26.62926
1.310
1.80518
25.42
0.61616


38
−98.73317
6.921





39
−26.89205
1.310
1.91082
35.25
0.58224


40
−46.99846
18.856 





41
∞
2.850
1.51633
64.14
0.53531


42
∞
















TABLE 17







Example 6 - Specifications (d-line)











Wide-Angle End
Middle
Telephoto End













Zoom Magnification
1.0
1.8
2.4


f′
51.515
92.219
125.696


Bf′
22.736
22.736
22.736


FNo.
2.88
2.89
2.88


2ω[°]
30.4
17.0
12.4
















TABLE 18







Example 6 - Distances Relating to Zoom











Wide-Angle End
Middle
Telephoto End















DD[7]
1.199
26.087
34.640



DD[15]
13.697
7.573
2.495



DD[20]
32.001
13.236
9.762









Next, a zoom lens of Example 7 is described. The zoom lens of Example 7 has a lens group configuration similar to that of the zoom lens of Example 1. FIG. 7 is a sectional view illustrating the lens configuration of the zoom lens of Example 7. Table 19 shows basic lens data of the zoom lens of Example 7, Table 20 shows data about specifications of the zoom lens, Table 21 shows data about distances between surfaces to be moved of the zoom lens, FIG. 18 shows aberration diagrams of the zoom lens, FIG. 35 shows lateral aberration diagrams of the zoom lens without image stabilization, and FIG. 36 shows lateral aberration diagrams of the zoom lens with image stabilization.







TABLE 19







Example 7 - Lens Data













Radius of






Surface No.
Curvature
Surface Distance
nd
νd
θgF















 1
358.57195
2.320
1.80100
34.97
0.58642


 2
85.09780
7.200
1.49700
81.54
0.53748


 3
−386.19076
0.200





 4
72.25745
6.972
1.43875
94.94
0.53433


 5
∞
0.200





 6
69.93587
5.200
1.49700
81.54
0.53748


 7
235.70554
DD[7]





 8
96.21157
6.291
1.72047
34.71
0.58350


 9
−43.59489
1.530
1.62230
53.17
0.55424


10
24.59706
5.600





11
−73.29120
1.410
1.49700
81.54
0.53748


12
27.09637
4.000
1.84661
23.88
0.62072


13
123.98633
2.799





14
−30.96977
1.200
1.91082
35.25
0.58224


15
353.74684
DD[15]





16
−406.80952
2.850
1.80100
34.97
0.58642


17
−43.60631
0.100





18
74.86402
4.260
1.61800
63.33
0.54414


19
−43.68363
1.170
1.80518
25.42
0.61616


20
∞
DD[20]





21 (stop)
∞
1.300





22
28.04424
7.050
1.49700
81.54
0.53748


23
−59.60296
0.150





24
34.77250
2.570
1.65412
39.68
0.57378


25
89.21437
1.800





26
−51.39895
1.110
1.90366
31.31
0.59481


27
24.25217
5.266
1.49700
81.54
0.53748


28
−60.88125
2.800





29
733.80887
3.771
1.80518
25.42
0.61616


30
−23.29690
0.950
1.58913
61.13
0.54067


31
39.10301
2.801





32
−39.71546
1.000
1.80100
34.97
0.58642


33
62.34880
4.199





34
54.23606
5.285
1.80000
29.84
0.60178


35
−37.12789
4.367





36
51.75623
6.461
1.48749
70.24
0.53007


37
−25.77385
1.310
1.80518
25.42
0.61616


38
−86.83396
4.400





39
−27.43970
1.260
1.91082
35.25
0.58224


40
−40.98080
25.514





41
∞
2.850
1.51633
64.14
0.53531


42
∞
















TABLE 20







Example 7 - Specifications (d-line)











Wide-Angle End
Middle
Telephoto End













Zoom Magnification
1.0
1.8
2.6


f′
51.516
92.222
135.965


Bf′
29.393
29.393
29.393


FNo.
2.88
2.89
2.88


2ω[°]
30.6
17.0
11.6
















TABLE 21







Example 7 - Distances Relating to Zoom











Wide-Angle End
Middle
Telephoto End















DD[7]
1.191
22.931
32.107



DD[15]
14.409
8.821
2.687



DD[20]
29.090
12.939
9.896









Next, a zoom lens of Example 8 is described. The zoom lens of Example 8 has a five-group configuration which consists of, in order from the object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, a third lens group G3 having a negative refractive power, a fourth lens group G4 (the mp lens group) having a positive refractive power, and a fifth lens group G5 (the rearmost lens group) having a positive refractive power. FIG. 8 is a sectional view illustrating the lens configuration of the zoom lens of Example 8. Table 22 shows basic lens data of the zoom lens of Example 8, Table 23 shows data about specifications of the zoom lens, Table 24 shows data about distances between surfaces to be moved of the zoom lens, FIG. 19 shows aberration diagrams of the zoom lens, FIG. 37 shows lateral aberration diagrams of the zoom lens without image stabilization, and FIG. 38 shows lateral aberration diagrams of the zoom lens with image stabilization.







TABLE 22







Example 8 - Lens Data













Radius of






Surface No.
Curvature
Surface Distance
nd
νd
θgF















 1
303.47850
2.390
1.80100
34.97
0.58642


 2
75.71759
7.850
1.49700
81.54
0.53748


 3
−338.62836
0.200





 4
67.27723
6.600
1.43875
94.94
0.53433


 5
706.55071
0.200





 6
67.16666
4.950
1.49700
81.54
0.53748


 7
287.46150
DD[7]





 8
98.18370
5.710
1.72047
34.71
0.58350


 9
−49.05401
1.550
1.62230
53.17
0.55424


10
24.62771
DD[10]





11
−75.51985
1.260
1.49700
81.54
0.53748


12
25.58057
5.388
1.84661
23.88
0.62072


13
106.72525
3.704





14
−31.24101
1.250
1.91082
35.25
0.58224


15
268.03486
DD[15]





16
−521.95122
2.950
1.80100
34.97
0.58642


17
−44.70833
0.100





18
73.37158
4.310
1.61800
63.33
0.54414


19
−43.22381
1.150
1.80518
25.42
0.61616


20
∞
DD[20]





21 (stop)
∞
1.300





22
27.81729
6.868
1.49700
81.54
0.53748


23
−57.84476
0.150





24
34.09999
2.550
1.65412
39.68
0.57378


25
102.68991
1.610





26
−54.83237
1.210
1.90366
31.31
0.59481


27
23.14151
5.662
1.49700
81.54
0.53748


28
−87.93105
2.500





29
372.91281
3.771
1.80518
25.42
0.61616


30
−24.31863
0.950
1.58913
61.13
0.54067


31
36.29877
3.256





32
−44.08151
1.050
1.80100
34.97
0.58642


33
60.80519
3.831





34
50.53032
5.748
1.80000
29.84
0.60178


35
−39.43779
4.000





36
48.86127
8.012
1.48749
70.24
0.53007


37
−26.40743
1.310
1.80518
25.42
0.61616


38
−86.68447
3.157





39
−27.70770
1.310
1.91082
35.25
0.58224


40
−44.10429
24.901





41
∞
2.850
1.51633
64.14
0.53531


42
∞
















TABLE 23







Example 8 - Specifications (d-line)











Wide-Angle End
Middle
Telephoto End













Zoom Magnification
1.0
1.8
2.6


f′
51.514
92.218
135.960


Bf′
28.781
28.781
28.781


FNo.
2.88
2.89
2.88


2ω[°]
30.4
17.0
11.6
















TABLE 24







Example 8 - Distances Relating to Zoom











Wide-Angle End
Middle
Telephoto End















DD[7]
1.199
20.933
29.242



DD[10]
6.235
6.638
6.783



DD[15]
14.153
8.593
2.488



DD[20]
26.710
12.132
9.785









Next, a zoom lens of Example 9 is described. The zoom lens of Example 9 has a lens group configuration similar to that of the zoom lens of Example 8. FIG. 9 is a sectional view illustrating the lens configuration of the zoom lens of Example 9. Table 25 shows basic lens data of the zoom lens of Example 9, Table 26 shows data about specifications of the zoom lens, Table 27 shows data about distances between surfaces to be moved of the zoom lens, FIG. 20 shows aberration diagrams of the zoom lens, FIG. 39 shows lateral aberration diagrams of the zoom lens without image stabilization, and FIG. 40 shows lateral aberration diagrams of the zoom lens with image stabilization.







TABLE 25







Example 9 - Lens Data













Radius of






Surface No.
Curvature
Surface Distance
nd
νd
θgF















 1
257.91881
2.390
1.83400
37.16
0.57759


 2
73.18612
7.850
1.49700
81.54
0.53748


 3
−329.42308
0.200





 4
62.30117
6.600
1.43700
95.10
0.53364


 5
849.43043
0.200





 6
72.87230
4.950
1.49700
81.54
0.53748


 7
263.78540
DD[7]





 8
107.78333
5.710
1.72047
34.71
0.58350


 9
−47.76821
1.550
1.62230
53.17
0.55424


10
25.18309
5.631





11
−93.23488
1.260
1.49700
81.54
0.53748


12
26.34063
3.999
1.84661
23.88
0.62072


13
99.67576
DD[13]





14
−31.09640
1.250
1.91082
35.25
0.58224


15
318.83279
DD[15]





16
−974.57258
2.950
1.80100
34.97
0.58642


17
−43.76266
0.100





18
65.14269
4.310
1.53775
74.70
0.53936


19
−49.97731
1.150
1.80518
25.42
0.61616


20
∞
DD[20]





21 (stop)
∞
1.300





22
28.69392
7.001
1.49700
81.54
0.53748


23
−59.87797
0.150





24
34.09590
2.550
1.65412
39.68
0.57378


25
85.63948
1.610





26
−54.93056
1.210
1.90366
31.31
0.59481


27
24.95033
6.359
1.49700
81.54
0.53748


28
−76.31225
2.500





29
141.63653
3.771
1.80518
25.42
0.61616


30
−23.83965
0.950
1.58913
61.13
0.54067


31
30.73799
2.499





32
−37.50492
1.050
1.80100
34.97
0.58642


33
53.05759
2.617





34
55.65453
6.802
1.83400
37.16
0.57759


35
−41.09507
4.001





36
52.54294
6.611
1.48749
70.24
0.53007


37
−38.16059
1.310
1.80518
25.42
0.61616


38
−57.00236
3.270





39
−28.19030
1.310
1.91082
35.25
0.58224


40
−47.93144
28.451





41
∞
2.850
1.51633
64.14
0.53531


42
∞
















TABLE 26







Example 9 - Specifications (d-line)











Wide-Angle End
Middle
Telephoto End













Zoom Magnification
1.0
1.8
2.6


f′
51.526
92.240
135.992


Bf′
32.332
32.332
32.332


FNo.
2.88
2.89
2.88


2ω[°]
30.4
17.0
11.6
















TABLE 27







Example 9 - Distances Relating to Zoom











Wide-Angle End
Middle
Telephoto End















DD[7]
1.199
21.287
29.769



DD[13]
4.000
4.585
4.348



DD[15]
14.542
8.794
2.472



DD[20]
26.846
11.921
9.998









Next, a zoom lens of Example 10 is described. The zoom lens of Example 10 has a lens group configuration similar to that of the zoom lens of Example 1. FIG. 10 is a sectional view illustrating the lens configuration of the zoom lens of Example 10. Table 28 shows basic lens data of the zoom lens of Example 10, Table 29 shows data about specifications of the zoom lens, Table 30 shows data about distances between surfaces to be moved of the zoom lens, FIG. 21 shows aberration diagrams of the zoom lens, FIG. 41 shows lateral aberration diagrams of the zoom lens without image stabilization, and FIG. 42 shows lateral aberration diagrams of the zoom lens with image stabilization.







TABLE 28







Example 10 - Lens Data












Surface
Radius of






No.
Curvature
Surface Distance
nd
νd
θgF















 1
206.18300
2.390
1.80100
34.97
0.58642


 2
77.37033
7.850
1.43875
94.94
0.53433


 3
−468.12933
0.200





 4
68.18946
6.600
1.43875
94.94
0.53433


 5
665.76128
0.200





 6
75.70042
4.950
1.49700
81.54
0.53748


 7
318.83987
DD[7]





 8
97.24407
5.710
1.72047
34.71
0.58350


 9
−43.72645
1.550
1.62230
53.17
0.55424


10
24.36854
5.706





11
−73.08228
1.260
1.49700
81.54
0.53748


12
25.31089
4.204
1.84661
23.88
0.62072


13
107.97061
2.799





14
−30.56048
1.250
1.91082
35.25
0.58224


15
253.08206
DD[15]





16
−16125.23228
2.950
1.80100
34.97
0.58642


17
−40.12049
0.100





18
80.78359
4.310
1.59282
68.62
0.54414


19
−40.99835
1.150
1.84666
23.78
0.62054


20
−145.20798
7.757





21
−92.18977
1.500
1.80000
29.84
0.60178


22
−254.53436
DD[22]





23 (stop)
∞
1.300





24
27.68095
7.001
1.49700
81.54
0.53748


25
−56.35341
0.150





26
32.42093
2.550
1.65412
39.68
0.57378


27
119.28847
1.610





28
−55.80214
1.210
1.90366
31.31
0.59481


29
23.16845
6.126
1.49700
81.54
0.53748


30
−90.54469
2.500





31
590.71987
3.771
1.80518
25.42
0.61616


32
−24.23391
0.950
1.58913
61.13
0.54067


33
37.50164
3.358





34
−43.90672
1.050
1.80100
34.97
0.58642


35
57.93149
4.715





36
51.33459
5.893
1.80000
29.84
0.60178


37
−38.45068
1.953





38
50.11025
7.136
1.48749
70.24
0.53007


39
−28.43175
1.310
1.80518
25.42
0.61616


40
−83.91857
4.329





41
−26.99010
1.310
1.91082
35.25
0.58224


42
−47.11637
24.016





43
∞
2.850
1.51633
64.14
0.53531


44
∞
















TABLE 29







Example 10 - Specifications (d-line)











Wide-Angle End
Middle
Telephoto End













Zoom Magnification
1.0
1.8
2.6


f′
51.519
92.228
135.974


Bf′
27.894
27.894
27.894


FNo.
2.87
2.87
2.88


2ω[°]
30.4
17.0
11.6
















TABLE 30







Example 10 - Distances Relating to Zoom











Wide-Angle End
Middle
Telephoto End















DD[7]
1.279
23.274
32.917



DD[15]
11.721
7.221
2.117



DD[22]
23.835
6.340
1.801









Next, a zoom lens of Example 11 is described. The zoom lens of Example 11 has a lens group configuration similar to that of the zoom lens of Example 1. FIG. 11 is a sectional view illustrating the lens configuration of the zoom lens of Example 11. Table 31 shows basic lens data of the zoom lens of Example 11, Table 32 shows data about specifications of the zoom lens, Table 33 shows data about distances between surfaces to be moved of the zoom lens, FIG. 22 shows aberration diagrams of the zoom lens, FIG. 43 shows lateral aberration diagrams of the zoom lens without image stabilization, and FIG. 44 shows lateral aberration diagrams of the zoom lens with image stabilization.







TABLE 31







Example 11 - Lens Data













Radius of






Surface No.
Curvature
Surface Distance
nd
νd
θgF















 1
180.37474
2.390
1.80100
34.97
0.58642


 2
69.14868
7.850
1.49700
81.54
0.53748


 3
−481.66507
0.200





 4
60.15068
7.500
1.43875
94.94
0.53433


 5
1142.76498
0.200





 6
76.86117
4.500
1.49700
81.54
0.53748


 7
187.53228
DD[7]





 8
111.60159
5.710
1.72047
34.71
0.58350


 9
−39.89381
1.550
1.62230
53.17
0.55424


10
24.07077
4.980





11
−64.75230
1.260
1.49700
81.54
0.53748


12
24.25512
5.408
1.84661
23.88
0.62072


13
94.37171
2.799





14
−28.39083
1.250
1.91082
35.25
0.58224


15
193.35819
DD[15]





16
−2763.02905
2.950
1.80100
34.97
0.58642


17
−42.42344
0.100





18
118.96564
4.310
1.59282
68.62
0.54414


19
−37.94715
1.150
1.84666
23.78
0.62054


20
−229.69252
7.412





21
389.16162
2.200
1.68893
31.07
0.60041


22
−215.34129
DD[22]





23 (stop)
∞
1.300





24
27.53581
7.001
1.49700
81.54
0.53748


25
−57.95147
0.150





26
36.50795
2.550
1.65412
39.68
0.57378


27
105.69164
1.610





28
−54.28866
1.210
1.90366
31.31
0.59481


29
22.84035
6.968
1.49700
81.54
0.53748


30
−80.66013
2.500





31
381.31349
3.771
1.80518
25.42
0.61616


32
−25.25989
0.950
1.58913
61.13
0.54067


33
39.74943
3.501





34
−39.07424
1.050
1.80100
34.97
0.58642


35
67.59646
4.073





36
53.40416
5.837
1.80000
29.84
0.60178


37
−38.04851
4.001





38
47.49724
6.893
1.48749
70.24
0.53007


39
−27.13146
1.310
1.80518
25.42
0.61616


40
−85.37597
3.001





41
−29.19153
1.310
1.91082
35.25
0.58224


42
−47.66122
25.665





43
∞
2.850
1.51633
64.14
0.53531


44
∞
















TABLE 32







Example 11 - Specifications (d-line)











Wide-Angle End
Middle
Telephoto End













Zoom Magnification
1.0
1.8
2.6


f′
51.511
92.212
135.951


Bf′
29.545
29.545
29.545


FNo.
2.88
2.89
2.88


2ω[°]
30.6
17.0
11.6
















TABLE 33







Example 11 - Distances Relating to Zoom











Wide-Angle End
Middle
Telephoto End















DD[7]
1.697
21.960
30.401



DD[15]
10.593
6.211
1.452



DD[22]
21.360
5.480
1.796









Table 34 shows values corresponding to the condition expressions (1) to (6) of the zoom lenses of Examples 1 to 11. In all the examples, the d-line is used as a reference wavelength, and the values shown in Table 34 below are with respect to the reference wavelength.














TABLE 34







No.
Condition Expression
Example 1
Example 2
Example 3
Example 4
Example 5
Example 6





(1)
νdBn
81.54
74.70
94.94
67.74
81.54
81.54


(2)
θgFBn + 0.00162νdBn − 0.6415
0.0281
0.0189
0.0466
0.0125
0.0281
0.0281


(3)
νd1p
86.01
81.03
82.52
90.47
86.01
86.01


(4)
νdCp
63.33
70.24
60.29
81.54
63.33
63.33


(5)
νd1n
34.97
31.31
40.14
33.27
34.97
34.97


(6)
νd1m
94.94
91.31
91.31
94.94
94.94
94.94
















No.
Condition Expression
Example 7
Example 8
Example 9
Example 10
Example 11





(1)
νdBn
81.54
81.54
81.54
81.54
81.54


(2)
θgFBn + 0.00162νdBn − 0.6415
0.0281
0.0281
0.0281
0.0281
0.0281


(3)
νd1p
86.01
86.01
86.06
90.47
86.01


(4)
νdCp
63.33
63.33
74.70
68.62
68.62


(5)
νd1n
34.97
34.97
37.16
34.97
34.97


(6)
νd1m
94.94
94.94
95.10
94.94
94.94









As can be seen from the above-described data, each of the zoom lenses of Examples 1 to 11 satisfies the condition expressions (1) to (6), and is a telephoto zoom lens having an angle of view of about 10 to 13 degrees at the telephoto end, a zoom ratio of about 2.4 to 3.1, a large aperture with a maximum aperture of about F2.8 across the entire zoom range, and successfully suppressed primary chromatic aberration and secondary chromatic aberration.
Next, one embodiment of an imaging apparatus according to the invention is described with reference to FIGS. 45 and 46. FIGS. 45 and 46 are perspective views showing the front side and the rear side, respectively, of a camera 30. The camera 30 is a non-reflex digital camera, to which a replaceable lens 20 formed by a zoom lens 1 according to the embodiment of the invention housed in a lens barrel is removably mounted.
The camera 30 includes a camera body 31, and a shutter button 32 and a power button 33 are disposed on the top side of the camera body 31. On the rear side of the camera body 31, operation sections 34 and 35, and a display section 36 are disposed. The display section 36 displays a taken image, and an image within the angle of view before an imaging operation is performed.
At the center of the front side of the camera body 31, an imaging aperture, through which light from the subject enters, is formed, and a mount 37 is disposed at the position corresponding to the imaging aperture. The replaceable lens 20 is mounted on the camera body 31 via the mount 37.
In the camera body 31, an image sensor (not shown), such as a CCD, for receiving an image of the subject formed by the replaceable lens 20 and outputting an image signal according to the image of the subject, a signal processing circuit for processing the image signal outputted from the image sensor to generate an image, a recording medium for recording the generated image, etc., are disposed. With this camera 30, a still image or a moving image can be taken when the shutter button 32 is pressed, and the image data obtained by the imaging operation is recorded in the recording medium.
The camera 30 of this embodiment, which is provided with the zoom lens 1 of the invention, allows obtaining high quality images with reduced primary chromatic aberration and secondary chromatic aberration.
The present invention has been described with reference to the embodiments and the examples. However, the invention is not limited to the above-described embodiments and examples, and various modifications may be made to the invention. For example, the values of the radius of curvature, the surface distance, the refractive index, the Abbe number, the aspheric coefficients, etc., of each lens are not limited to the values shown in the above-described examples and may take different values.
While the embodiment of the imaging apparatus is described and shown in the drawings as a non-reflex (so-called mirrorless) digital camera as an example, this is not intended to limit the imaging apparatus of the invention. For example, the invention is also applicable to imaging apparatuses, such as video cameras, digital cameras, motion picture cameras, and broadcasting cameras.

## Claims

1. A zoom lens consisting of four or five lens groups as a whole, which consist of, in order from an object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, one or two middle lens groups including a mp lens group having a positive refractive power, and a rearmost lens group disposed at the most image side position of the entire system and having a positive refractive power,
wherein magnification change is effected by changing all distances between the adjacent lens groups,
an A cemented lens consisting of a positive lens and a negative lens which are cemented together in this order from the object side is disposed at the most object-side position of the second lens group,
a B cemented lens consisting of one positive lens and one negative lens is disposed on the image side of the A cemented lens and on the object side of the mp lens group,
a C cemented lens consisting of one positive lens and one negative lens is disposed in the mp lens group, and
the condition expressions (1) and (2) below are satisfied:


60<νdBn  (1), and



0.0055<θgFBn+0.00162νdBn−0.6415<0.050  (2),



where νdBn is an Abbe number of the negative lens forming the B cemented lens, and θgFBn is a partial dispersion ratio of the negative lens forming the B cemented lens.

2. The zoom lens as claimed in claim 1, wherein the first lens group is fixed relative to an image plane during magnification change.

3. The zoom lens as claimed in claim 1, wherein the rearmost lens group is fixed relative to an image plane during magnification change.

4. The zoom lens as claimed in claim 1, wherein
the first lens group comprises at least two positive lenses, and
the condition expression (3) below is satisfied:


80.5<νd1p  (3),



where νd1p is an average Abbe number of the positive lenses in the first lens group.

5. The zoom lens as claimed in claim 1, wherein the condition expression (4) below is satisfied:


57<νdCp  (4),


where νdCp is an Abbe number of the positive lens forming the C cemented lens.

6. The zoom lens as claimed in claim 1, wherein focusing from an object at infinity to a closest object is effected by moving only the entire mp lens group or only a part of lenses forming the mp lens group along the optical axis.

7. The zoom lens as claimed in claim 1, wherein focusing from an object at infinity to a closest object is effected by moving only the entire mp lens group along the optical axis.

8. The zoom lens as claimed in claim 1, wherein the mp lens group comprises the C cemented lens and one positive lens.

9. The zoom lens as claimed in claim 1, wherein the first lens group comprises at least one negative lens that satisfies the condition expression (5) below:


28<νd1n<45  (5),


where νd1n is an Abbe number of the negative lens in the first lens group.

10. The zoom lens as claimed in claim 1, wherein
the rearmost lens group consists of, in order from the object side, a front group having a positive refractive power, a middle group having a negative refractive power, and a rear group having a positive refractive power,
the front group consists of three positive lenses and one negative lens, and
image stabilization is effected by moving only the middle group in directions perpendicular to the optical axis direction.

11. The zoom lens as claimed in claim 10, wherein the middle group consists of two negative lenses and one positive lens.

12. The zoom lens as claimed in claim 1, consisting of four lens groups which consist of, in order from the object side, the first lens group, the second lens group, the mp lens group, and the rearmost lens group.

13. The zoom lens as claimed in claim 1, consisting of five lens groups which consist of, in order from the object side, the first lens group, the second lens group, a lens group having a negative refractive power, the mp lens group, and the rearmost lens group.

14. The zoom lens as claimed in claim 1, wherein the second lens group comprises two or more positive lenses and two or more negative lenses.

15. The zoom lens as claimed in claim 1, wherein the first lens group consists of, in order from the object side, a negative lens, a positive lens, a positive lens, and a positive lens.

16. The zoom lens as claimed in claim 1, wherein the first lens group comprises at least one positive lens, and
the condition expression (6) below is satisfied:


83<νd1m  (6),



where νd1m is the largest Abbe number of the least one positive lens in the first lens group.

17. The zoom lens as claimed in claim 1, wherein the first lens group comprises at least one positive lens, and
the positive lens having the largest Abbe number in the first lens group is a single lens.

18. The zoom lens as claimed in claim 1, wherein a stop is disposed at the most object-side position of the rearmost lens group.

19. The zoom lens as claimed in claim 1, wherein the positive lens forming the A cemented lens has a center thickness greater than the center thickness of the negative lens forming the A cemented lens.

20. An imaging apparatus comprising the zoom lens as claimed in claim 1.