JP4377994B2 - Rear focus type zoom lens and optical apparatus using the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a rear focus type zoom lens and an optical apparatus using the same, and more particularly to a rear focus which is suitably used for a digital camera, a video camera, a film camera, a broadcast camera, and the like and which has a relatively small number of lenses. The present invention relates to a zoom lens of the type and an optical apparatus using the same.
[0002]
[Prior art]
Various proposals have been made of so-called rear focus systems that focus on zoom lenses used in optical equipment such as photographic cameras and video cameras by moving the lens group behind the first group on the object side. Has been. This is because the rear focus system moves a relatively small and lightweight lens group, so the driving force of the lens group is small, and quick focusing can be performed, making it compatible with the autofocus system. Because there is.
[0003]
Such a rear focus type zoom lens is disclosed in, for example, Japanese Patent Application Laid-Open No. 62-206516, Japanese Patent Application Laid-Open No. 62-24213, Japanese Patent Application Laid-Open No. 63-247316, and Japanese Patent Application Laid-Open No. 4-43311. In order from the side, there are four lens groups, a first group having a positive refractive power, a second group having a negative refractive power, a third group having a positive refractive power, and a fourth group having a positive refractive power. Is moved to change the magnification, and the image plane variation accompanying the change in magnification is corrected by moving the fourth lens group.
[0004]
Japanese Laid-Open Patent Publication No. 63-29718 is composed of a first lens unit having a positive refractive power in order from the object side, a negative lens, a negative lens, and a positive lens, and has a negative refractive power as a whole. A second group that is movable at the time of zooming and mainly controls zooming, and a third group that has positive refractive power and includes an aspherical surface, and has a positive refractive power with a slightly large air gap to zoom. A zoom lens composed of a fourth lens group that corrects the accompanying image plane variation and moves for focusing is disclosed.
[0005]
Japanese Patent Application Laid-Open No. 5-72472 discloses a first group that has a positive refractive power in order from the object side and is fixed when zooming and focusing, a second group that has a negative refractive power and moves for zooming, Disclosed is a zoom lens using an aspherical surface having a fixed third light-collecting group having positive refractive power and a fourth group having positive refractive power that moves on the optical axis in order to maintain the image plane position. is doing.
[0006]
In the zoom lens disclosed in this publication, the second group includes a meniscus negative lens, a negative lens whose both lens surfaces are concave, and a positive lens, and the third group includes a single lens having one or more aspheric surfaces. The fourth group is composed of lenses having one or more aspheric surfaces.
[0007]
In U.S. Pat. No. 4,299,454, at least two lenses including a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a rear positive lens group in order from the object side are included. A zoom lens is disclosed in which zooming is performed by moving the lens group, and the second lens group is composed of first and second negative lenses and a positive tablet from the object side. This publication does not disclose an embodiment in which an aspheric surface is provided in the second group.
[0008]
In JP-A-8-292369, a first group having positive refractive power, a second group having negative refractive power having an aspheric surface, a third group having positive refractive power having an aspheric surface, in order from the object side, It has four lens units of the fourth group with positive refractive power having aspherical surfaces, and the second group is moved to perform zooming, and the image plane variation accompanying zooming is corrected by moving the fourth group. A rear focus type zoom lens that performs focusing is disclosed.
[0009]
Also proposed is a four-group rear focus zoom lens in which the amount of movement in the optical axis direction of the second group is reduced in order to increase the refractive power of the second group for zooming and secure a predetermined zooming ratio. Has been.
[0010]
In the above configuration, the distance between the first group and the second group of the lens unit that is a variable power system is shortened, and the distance from the stop to the first group is shortened, so the front lens diameter is small. This makes it possible to reduce the thickness of the first lens group and facilitate the miniaturization of the entire lens system.
[0011]
Further, in order to reduce the size of the third group and the fourth group which are image forming systems in the four-group zoom lens, the third group is composed of a positive lens and a negative lens in order from the object side, and the third group is a so-called telephoto lens. Various types of zoom lenses have been proposed in which the principal point position of the third lens group is moved to the object side to reduce the actual distance between the third lens group and the fourth lens group, thereby reducing the size.
[0012]
A zoom lens having such a configuration is disclosed in, for example, Japanese Patent Laid-Open Nos. 5-19165, 5-297275, 5-60973, 5-60974, and 5-107473. It has been proposed in JP-A-6-130297, JP-A-8-304700, USP5189558, USP5396367, and the like.
[0013]
[Problems to be solved by the invention]
An object of the present invention is to provide a rear focus type zoom lens that employs a rear focus system, downsizes the entire lens system, enables quick focusing, and has a relatively small number of lenses, and an optical apparatus using the same. To do.
[0014]
[Means for Solving the Problems]
According to the first aspect of the present invention, in order from the object side, the first group having a positive refractive power, the second group having a negative refractive power, the third group having a positive refractive power, and the fourth group having a positive refractive power. An image surface associated with zooming, which is composed of two lens groups, widens the distance between the first group and the second group, narrows the distance between the second group and the third group, and zooms from the wide angle end to the telephoto end. The movement is corrected by moving the fourth group and focusing is performed by moving the fourth group. The third group has a stop closest to the object side, and both lens surfaces are convex on the image plane side. The fourth lens unit is composed of a cemented lens of a positive lens and a negative lens, and a meniscus negative lens having a concave surface facing the image surface. The fourth group is a positive single lens having a convex surface facing the object side or a positive lens and a negative lens. It consists of a bonded lens ,
The radius of curvature of the lens surface on the image surface side of the negative lens disposed closest to the image plane in the third group is Rr, and the refractive index of the medium of the negative lens disposed closest to the image surface in the third group is Nr. , D3L is the distance on the optical axis from the lens surface closest to the object side to the lens surface closest to the image plane in the third group, the F number at the wide angle end is FNW, and the focal length of the entire system at the wide angle end and the telephoto end Are fw and ft, respectively.
[Equation 3]
When
0.4 <Rr / {(Nr-1) fA} <1.2 (5)
[Expression 4]
It is characterized by satisfying the following conditions .
[0015]
The invention of claim 2 is the invention of claim 1, wherein when the magnification of the fourth group when focusing on an object at infinity at the telephoto end is β4T,
0.20 <β4T <0.63 (1)
It satisfies the following conditional expression.
[0016]
The invention of claim 3 is the invention of claim 1 or 2, wherein the focal length of the second group is f2.
0.31 <| f2 / fA | × FNW <0.52 (2)
It satisfies the following conditional expression.
[0017]
According to a fourth aspect of the present invention, in the first, second or third aspect of the invention, when the focal length of the i-th group is set to fi, 0.63 <f3 / f4 <1.16 (3)
It satisfies the following conditional expression.
[0018]
The invention of claim 5 is the invention of any one of claims 1 to 4, wherein the second group has a negative lens closest to the object side, and the refractive index of the medium of the negative lens is N2f. 80 <N2f <1.95 (4)
It satisfies the following conditional expression.
[0019]
The invention of claim 6 is the invention of any one of claims 1 to 5, characterized in that the second group is composed of two or more negative lenses and one positive lens.
[0020]
According to a seventh aspect of the present invention, in the sixth aspect of the invention, the second group includes a negative twenty-first lens having a concave surface directed toward the image surface in order from the object side, a negative twenty-second lens having both concave surfaces, and an object. It is characterized by being composed of a positive 23rd lens having a convex surface on the side.
[0021]
The invention of claim 8 is the invention of claim 7, wherein the twenty-second lens and the twenty-third lens are cemented.
[0022]
The invention of claim 9 is the invention of any one of claims 1 to 8, wherein the second group has an aspherical surface.
[0023]
The invention of claim 10 is the invention of claim 9, wherein the aspherical surface in the second group has a radius of curvature near the optical axis as R0 and the focal length of the second group as f2.
1.1 <| R0 / f2 | <3.0 (7)
It is characterized by being arranged on a lens surface that satisfies the conditional expression (1).
[0024]
The invention of claim 11 is the invention of any one of claims 1 to 10, wherein the third group or the fourth group has an aspherical surface.
[0025]
The invention of claim 12 is the invention of any one of claims 1 to 11, wherein the distance from the first lens surface on the object side of the zoom lens to the paraxial image surface is L,
2.9 <L / fA <4.3 (8)
It satisfies the following conditional expression.
[0026]
An optical apparatus according to a thirteenth aspect of the present invention includes the rear focus type zoom lens according to any one of the first to twelfth aspects of the present invention.
[0032]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a cross-sectional view of an essential part of Embodiment 1 of an image pickup apparatus having a rear focus type zoom lens according to the present invention, and FIGS. 2, 3, and 4 are zoom positions at the wide-angle end, intermediate, and telephoto end of Embodiment 1. FIG. FIG. 5 is a cross-sectional view of an essential part of Embodiment 2 of an imaging apparatus having a rear focus type zoom lens according to the present invention, and FIGS. 6, 7 and 8 are zoom positions at the wide-angle end, intermediate and telephoto ends of Embodiment 2. FIG. FIG. 9 is a cross-sectional view of an essential part of Embodiment 3 of an imaging apparatus having a rear focus zoom lens according to the present invention, and FIGS. 10, 11, and 12 are zoom positions at the wide-angle end, middle, and telephoto end of Embodiment 3. FIG. FIG. 13 is a cross-sectional view of a main part of Embodiment 4 of an image pickup apparatus having a rear focus type zoom lens according to the present invention, and FIGS. 14, 15, and 16 are zoom positions at the wide-angle end, middle, and telephoto end of Embodiment 4. FIG. FIG. 17 is a schematic view of the main part of the optical apparatus of the present invention.
[0033]
In the figure, L1 is a first group having a positive refractive power, L2 is a second group having a negative refractive power, L3 is a third group having a positive refractive power, and L4 is a fourth group having a positive refractive power. SP is an aperture stop, which is disposed in front of the third lens unit L3. P is a glass block such as a color separation prism, a CCD face plate, or a low-pass filter. IP is an image plane, and an image pickup device such as a CCD is disposed.
[0034]
In this embodiment, when zooming from the wide-angle end to the telephoto end, the second lens unit is moved to the image plane side as indicated by an arrow, and the image plane variation caused by zooming is convex toward the object side. It is corrected by moving while having a trajectory. Further, a rear focus type is employed in which focusing is performed by moving the fourth lens group on the optical axis. The solid curve 4a and the dotted curve 4b of the fourth group shown in the figure show the image plane fluctuations accompanying the zooming from the wide-angle end to the telephoto end when focusing on an object at infinity and an object at close distance, respectively. A movement trajectory for correction is shown. The first group and the third group are fixed during zooming and focusing.
[0035]
The zoom ratio is a high zoom ratio of 12 times, and the F number is about 1.6, which is a large aperture.
[0036]
In the present embodiment, for example, when focusing from an infinitely distant object to a close object at the telephoto end, the fourth group is moved forward as shown by a straight line 4c in FIG.
[0037]
The lens configuration of the present invention is characterized in that the third lens unit has a diaphragm closest to the object side, a cemented lens of a positive lens and a negative lens whose convex surfaces are convex on the image surface side, and a concave surface on the image surface side. The fourth lens unit consists of a positive single lens with a convex surface facing the object side or a cemented lens of a positive lens and a negative lens.
[0038]
In the present embodiment, the third lens group is configured as described above, so that the relay lens group can be reduced in size without difficulty. In addition, the third group greatly affects the on-axis aberration, and affects the spherical aberration, coma aberration, and chromatic aberration. A pasted lens is disposed there to maintain good aberrations, and a negative lens is disposed on the object side to achieve a shortened back focus as a retro type.
[0039]
In this embodiment, by setting the lens configuration as described above, the zoom ratio is 12 times and a high zoom ratio, and the entire zoom range is satisfied, and the F number 1.6 and a large aperture ratio are provided. In addition, high optical performance is obtained over the entire object distance.
[0040]
The rear focus type zoom lens of the present invention is realized by satisfying the above-described configuration, and in order to maintain good optical performance while maintaining a high zoom ratio, the following conditions are satisfied. It is desirable to satisfy at least one of them.
[0041]
(A-1) When the magnification of the fourth group when focusing on an object at infinity at the telephoto end is β4T,
0.20 <β4T <0.63 (1)
The following conditional expression is satisfied.
[0042]
By setting the range in the conditional expression (1), the third to fourth groups and the image plane, which are the imaging system, are effectively shortened. When the upper limit of conditional expression (1) is exceeded, the back focus becomes too short and interferes with the CCD optical member disposed on the image plane. On the other hand, if the lower limit is exceeded, the back focus becomes too long, which leads to an increase in the overall length of the lens.
[0043]
(A-2) The focal lengths of the entire system at the wide-angle end and the telephoto end are fw and ft, respectively, and the F-number at the wide-angle end is FNW.
[0044]
[Equation 5]
[0045]
0.31 <| f2 / fA | × FNW <0.52 (2)
The following conditional expression is satisfied.
[0046]
That is, in the zoom lens of the type as in the present invention, it is possible to increase the refractive power of the second group by setting the refractive power of the second group that greatly contributes to zooming as described above. As a result, the amount of movement of the second group can be reduced, and the overall length of the lens can be shortened.
[0047]
However, this is also related to the F-number of the zoom lens, and this factor needs to be considered. If the F-number is dark, the focal length f2 can be reduced as much as possible, but in fact, it is difficult to make a lens with such specifications.
[0048]
When the focal length f2 is longer than the upper limit value of the conditional expression (2), it is preferable in terms of aberration, but in order to obtain a desired zoom ratio, the amount of movement of the second group must be increased, and the lens This leads to an increase in the size of the entire system, which is not preferable. On the contrary, if the lower limit is exceeded, the Petzval sum becomes negatively large and the image plane collapses, making it difficult to maintain good optical performance.
[0049]
(A-3) When the focal length of each group is set to fi, 0.63 <f3 / f4 <1.16 (3)
The following conditional expression is satisfied.
[0050]
Conditional expression (3) represents the optimum refractive power distribution for reducing the size of the third group and the fourth group as the imaging system. In particular, when the distance between the third group and the fourth group is optimized, the light beam emitted from the third group is made to enter the fourth group almost afocally to ensure an optimal back focus.
[0051]
When the upper limit is exceeded, the light beam emitted from the third group deviates from the afocal, and the fourth group becomes larger. In addition, the aberration variation accompanying the movement of the fourth group becomes large, which is not preferable. Conversely, when the lower limit is exceeded, the refractive power of the fourth group becomes weak, the amount of movement for focusing becomes large, and the total length becomes long.
[0052]
(A-4) The second group has a negative lens closest to the object side, and when the refractive index of the medium of the negative lens is N2f, 1.80 <N2f <1.95 (4)
The following conditional expression is satisfied. This is related to the Petzpearl sum and is a condition for correcting the field curvature in a balanced manner.
[0053]
Exceeding the upper limit value of conditional expression (4) is advantageous for correcting curvature of field, but considering glass materials that can actually be used, the Abbe number becomes small, making it difficult to correct chromatic aberration. On the contrary, when the lower limit is exceeded, the image surface is curved so as to be concave toward the object side, which is not preferable.
[0054]
(A-5) The radius of curvature of the lens surface on the image surface side of the negative lens disposed closest to the image plane in the third group is Rr, and the medium of the negative lens disposed closest to the image surface in the third group Is Nr, the distance on the optical axis from the most object side lens surface of the third lens unit to the most image side lens surface is D3L, and the F number at the wide angle end is FNW.
0.4 <Rr / {(Nr-1) fA} <1.2 (5)
[0055]
[Formula 6]
[0056]
The above condition is satisfied.
[0057]
Conditional expressions (5) and (6) are mainly for shortening the imaging system. Exceeding the upper limit の of conditional expression (5) is not preferable because the effect of the telephoto type in the third group becomes small and the back focus becomes short. On the other hand, if the lower limit is exceeded, the radius of curvature becomes too small and the aberration generated on the surface becomes large, making it difficult to correct in the third group, and at the same time the distance from the fourth group becomes narrow. Interact with the group. If the upper limit of conditional expression (6) is exceeded, an increase in the overall length is caused. Conversely, if the lower limit is exceeded, the overall length is advantageous, but it is difficult to increase the F-number.
[0058]
(A-6) The second group is composed of two or more negative lenses and one positive lens.
[0059]
When the zoom ratio is increased in the zoom type as in the present invention, the movement amount of the second group that greatly contributes to the zooming function is increased or the focal length of the second group is shortened (refractive power of the second group). Need to be strong).
[0060]
The former method is not preferable because it leads to an increase in the size of the zoom lens, and the latter method does not increase the size of the lens, but places a heavy burden on the second group and makes it difficult to maintain good optical performance. Therefore, if the second group is configured as described above, the optical performance can be favorably corrected while increasing the zoom ratio.
[0061]
(A-7) In the second group, in order from the object side, a negative 21st lens having a concave surface facing the image surface side, a negative 22nd lens having both lens surfaces concave, and a positive lens having a convex surface facing the object side It is constituted by the 23rd lens.
[0062]
As a result, various aberrations when the zoom ratio is raised are corrected satisfactorily.
[0063]
(A-8) The twenty-second lens and the twenty-third lens are cemented.
[0064]
As a result, the chromatic aberration in the second group is corrected well.
[0065]
(A-9) The second group has an aspherical surface.
[0066]
By disposing an aspheric surface in the second group, the off-axis optical performance in the entire zoom range is corrected well.
[0067]
(A-10) When the aspherical surface in the second group has a radius of curvature R0 near the optical axis and the focal length of the second group is f2,
1.1 <| R0 / f2 | <3.0 (7)
It is arranged on a lens surface that satisfies the conditional expression (1).
[0068]
In the present invention, an aspherical surface is arranged on a lens surface having a small radius of curvature, so that aberration can be corrected more effectively. In particular, off-axis flare is corrected well.
[0069]
Exceeding the upper limit of conditional expression (7) is not preferable because the effect of correcting off-axis performance decreases. Conversely, when the lower limit is exceeded, the curvature becomes too small, making it difficult to manufacture an aspherical surface.
[0070]
It is desirable that the aspherical surface has a shape in which the refractive power becomes weaker toward the periphery of the lens.
[0071]
(A-11) The third group or the fourth group has an aspherical surface.
[0072]
In the zoom lens of the present invention, it is preferable to arrange an aspherical surface in the third group or the fourth group in order to improve the aberration of the imaging system. In particular, the arrangement in the third group makes it easy to reduce the F number.
[0073]
(A-12) Value obtained by converting the distance from the first lens surface on the object side of the zoom lens to the paraxial image surface as L, and converting the glass (glass flat plate) such as a low-pass filter disposed closest to the image surface into air. When
2.9 <L / fA <4.3 (8)
The following conditional expression is satisfied.
[0074]
If the upper limit of conditional expression (8) is exceeded, the total lens length becomes long, which is not good. On the contrary, if the lower limit is exceeded, the Petzval sum becomes negatively large and the image plane collapses, making it difficult to maintain good optical performance.
[0075]
Next, an embodiment of a video camera using the zoom lens of the present invention as a photographing optical system will be described with reference to FIG.
[0076]
In FIG. 17, 10 is a video camera body, 11 is a photographing optical system constituted by the zoom lens of the present invention, 12 is an image pickup device such as a CCD that receives a subject image by the photographing optical system 11, and 13 is light receiving by the image pickup device 12. A recording means 14 for recording the subject image, and a finder for observing the subject image displayed on a display element (not shown). The display element is constituted by a liquid crystal panel or the like, and a subject image formed on the image sensor 12 is displayed. Reference numeral 15 denotes a liquid crystal display panel having a function equivalent to that of the finder.
[0077]
Thus, by applying the zoom lens of the present invention to an optical apparatus such as a video camera, a small-sized optical apparatus having high optical performance is realized.
[0078]
The numerical examples of the present invention will be described below.
[0079]
In 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, and Ni and νi are i-th in order from the object side. The refractive index and Abbe number of the lens material. The aspherical shape has an X axis in the optical axis direction, an H axis in the direction perpendicular to the optical axis, a positive light traveling direction, R is a paraxial radius of curvature, and each aspheric coefficient is K, B, C, D, E. , F,
[0080]
[Expression 7]
[0081]
It is expressed by the following formula. For example, “e-Z” means “10 ^−Z ”.
[0082]
Table 1 shows the relationship between the above-described conditional expressions and various numerical values in the numerical examples.
[0083]
[Outside 1]
[0084]
[Outside 2]
[0085]
[Outside 3]
[0086]
[Outside 4]
[0087]
[Table 1]
[0088]
【The invention's effect】
According to the present invention, the rear lens zoom lens and the optical apparatus using the same are configured as described above to reduce the size of the entire lens system, enable quick focusing, and reduce the number of lenses. Can be realized.
[Brief description of the drawings]
1 is a lens cross-sectional view of Numerical Example 1 of the present invention. FIG. 2 is an aberration diagram at the wide angle end of Numerical Example 1 of the present invention. FIG. 3 is an intermediate aberration diagram of Numerical Example 1 of the present invention. 4 is an aberration diagram at the telephoto end of Numerical Example 1 of the present invention. FIG. 5 is a sectional view of a lens of Numerical Example 2 of the present invention. FIG. 6 is an aberration diagram at the wide-angle end of Numerical Example 2 of the present invention. FIG. 8 is an aberration diagram at the telephoto end of Numerical Example 2 of the present invention. FIG. 9 is a lens cross-sectional view of Numerical Example 3 of the present invention. FIG. 11 is an aberration diagram at the wide-angle end of Numerical Example 3 of the invention. FIG. 11 is an aberration diagram at the middle of Numerical Example 3 of the invention. FIG. 12 is an aberration diagram at the telephoto end of Numerical Example 3 of the invention. FIG. 14 is a lens cross-sectional view of Numerical Example 4 of the invention. FIG. 14 is an aberration diagram at the wide-angle end of Numerical Example 4 of the invention. FIG. 15 is an intermediate aberration diagram of Numerical Example 4 of the invention. Main part schematic diagram of the optics of the aberration diagrams at the telephoto end according to Numerical Embodiment 4 [17] The present invention in FIG. 16 the present invention Description of Reference Numerals]
L1 1st group L2 2nd group L3 3rd group L4 4th group SP Aperture G Glass block IP Image plane d d line g g line ΔM Meridional image plane ΔS Sagittal image plane

Claims (13)

In order from the object side, the lens unit includes four lens groups including a first group having a positive refractive power, a second group having a negative refractive power, a third group having a positive refractive power, and a fourth group having a positive refractive power. The distance between the first group and the second group is widened, the distance between the second group and the third group is narrowed, and zooming is performed from the wide-angle end to the telephoto end. The lens is moved and corrected, and the fourth group is moved for focusing. The third group has a stop closest to the object side, and a positive lens and a negative lens having convex surfaces on both sides of the image surface are bonded. and combined lens consists of a meniscus-shaped negative lens having a concave surface facing the image side, the fourth group is composed of a positive single lens or a positive lens and a negative lens of the cemented lens having a convex surface on the object side And
The radius of curvature of the lens surface on the image surface side of the negative lens disposed closest to the image plane in the third group is Rr, and the refractive index of the medium of the negative lens disposed closest to the image surface in the third group is Nr. , D3L is the distance on the optical axis from the lens surface closest to the object side to the lens surface closest to the image plane in the third group, the F number at the wide angle end is FNW, and the focal length of the entire system at the wide angle end and the telephoto end Are fw and ft, respectively.
When
0.4 <Rr / {(Nr-1) fA} <1.2
A rear-focus zoom lens that satisfies the above conditions . When the magnification of the fourth group when focusing on an object at infinity at the telephoto end is β4T,
0.20 <β4T <0.63
The rear focus zoom lens according to claim 1, wherein the following conditional expression is satisfied. When the focal length of the second group is f2,
0.31 <| f2 / fA | × FNW <0.52
The rear focus zoom lens according to claim 1 or 2, wherein the following conditional expression is satisfied. When the focal length of the i-th group is set to fi, 0.63 <f3 / f4 <1.16
4. The rear focus type zoom lens according to claim 1, wherein the following conditional expression is satisfied. The second group has a negative lens closest to the object side. When the refractive index of the medium of the negative lens is N2f, 1.80 <N2f <1.95.
5. The rear focus type zoom lens according to claim 1, wherein the following conditional expression is satisfied. The second group of two or more negative lenses and one any one of the rear-focusing type zoom lens according to claim 1 to 5, characterized in that and a positive lens. The second group includes a negative 21st lens having a concave surface directed toward the image surface side in order from the object side, a negative 22nd lens having concave surfaces on both lens surfaces, and a positive 23rd lens having a convex surface directed toward the object side. The rear focus zoom lens according to claim 6 , wherein the zoom lens is a rear focus zoom lens. 8. The rear focus zoom lens according to claim 7 , wherein the twenty-second lens and the twenty-third lens are cemented. It said second group any one of the rear-focusing type zoom lens according to claim 1 to 8, characterized in that it has an aspherical surface. The aspherical surface in the second group has a radius of curvature near the optical axis as R0 and the focal length of the second group as f2.
1.1 <| R0 / f2 | <3.0
10. The rear focus zoom lens according to claim 9 , wherein the zoom lens is disposed on a lens surface that satisfies the following conditional expression. The third group or the fourth group is any one of the rear-focusing type zoom lens according to claim 1 to 10, characterized in that it has an aspherical surface. Let L be the distance from the first lens surface on the object side of the zoom lens to the paraxial image plane,
2.9 <L / fA <4.3
Any one of the rear-focusing type zoom lens according to claim 1 to 11, characterized by satisfying the conditional expression. An optical apparatus comprising the rear focus zoom lens according to any one of claims 1 to 12 .