JP4789349B2 - Zoom lens and optical apparatus having the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a zoom lens and an optical apparatus having the same, and more particularly to a zoom lens having a wide-angle range and a compact, high zoom ratio suitable for a single lens reflex camera, a still video camera, a digital camera, and the like, and an optical apparatus having the same. Is.
[0002]
[Prior art]
Conventionally, optical lenses such as a photographic camera, a video camera, and a digital camera have been required to have a zoom lens having a high zoom ratio and a wide angle of view, high contrast, and high optical performance over the entire zoom range. .
[0003]
Among these, a zoom type suitable for a zoom lens for a single-lens reflex camera is known as a so-called five-group zoom lens composed of five lens groups of positive, negative, positive, negative, and positive refractive power in order from the object side. It has been.
[0004]
This zoom type has a relatively small amount of movement of each lens group at the time of zooming, so it is suitable for a zoom lens with high zooming ratio, and it is easy to secure a back focus, which is also advantageous for widening the short focus side. is there.
[0005]
The zoom type zoom lens is disclosed in, for example, Japanese Patent Publication No. 58-33531, Japanese Patent Publication No. 61-51291, Japanese Patent Publication No. 61-51294, and the like. The present applicant also discloses a similar zoom lens in Japanese Patent Application Laid-Open No. 5-119260, Japanese Patent Application Laid-Open No. 6-230285, Japanese Patent Application Laid-Open No. 8-179213, Japanese Patent Application Laid-Open No. 9-304697, and the like.
[0006]
[Problems to be solved by the invention]
When the zooming ratio of the zoom lens is increased, the variation in chromatic aberration, in particular, among the variation in aberration due to zooming becomes large. In order to suppress this chromatic aberration, it is necessary to increase the number of lenses in each lens group. As a result, the lens configuration tends to be complicated and the size of the optical system increased. On the other hand, if the optical system is forcibly reduced in size, the variation in chromatic aberration increases, and the optical performance cannot be maintained satisfactorily.
[0007]
Therefore, when designing a small zoom lens having a high zoom ratio and high optical performance, the selection of the glass material for each lens is an important task. In a zoom lens including a plurality of lens groups, in the case of a lens group having a positive refractive power, a high refractive index and low dispersion glass is used as the material of the positive lens included therein, and the lens group having a negative refractive power is used. In such a case, it is preferable to use a high refractive index and low dispersion glass as the material of the negative lens contained therein. However, there are few types of glass materials having a high refractive index and low dispersion, and it is difficult to process and is difficult to manufacture if it is frequently used unplanned. Conversely, if only glass materials with a low refractive index are selected, the refractive power of each lens group will be weakened in order to maintain high optical performance, the entire optical system will be enlarged, and a sufficient zoom ratio will be achieved. Can not be secured.
[0008]
For example, in the above-mentioned 5-group zoom lens, if the movement conditions of each lens group accompanying zooming, the lens configuration of each lens group, and the material of these lenses are not set appropriately, the occurrence of various aberrations, particularly chromatic aberration, increases. It becomes difficult to obtain images with good image quality over the zoom range.
[0009]
The present invention mainly has a wide zoom range and a high zoom ratio with a wide zoom ratio by appropriately setting the movement conditions of each lens group accompanying zooming, the lens configuration of each lens group, and the materials of those lenses. Furthermore, an object of the present invention is to provide a zoom lens having high optical performance over the entire screen and an optical apparatus having the same.
[0010]
In addition to this, the present invention has a good optical performance while the entire lens system is compact by appropriately selecting the glass material of each lens constituting the optical system and making the configuration of each lens group appropriate. An object of the present invention is to provide a zoom lens including a wide-angle region and a zoom ratio of about 3.5 times and an optical apparatus having the same.
[0011]
[Means for Solving the Problems]
The zoom lens according to the first aspect of the invention includes, in order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a negative lens group. The second lens group having a refractive power and the fifth lens group having a positive refractive power have a larger distance between the first lens group and the second lens group at the telephoto end than at the wide-angle end. The lens so that the distance between the lens group and the third lens group is decreased, the distance between the third lens group and the fourth lens group is increased, and the distance between the fourth lens group and the fifth lens group is decreased. In a zoom lens that changes magnification by moving the group,
The first lens group includes, in order from the object side, a cemented lens 1ab including a negative meniscus lens 1a having a convex surface facing the object side and a positive meniscus lens 1b having a convex surface facing the object side, and a convex surface facing the object side. Consists of a positive meniscus lens 1c,
The third lens group includes, in order from the object side, a negative meniscus lens 3a having a convex surface facing the object side, a cemented lens 3ab composed of a positive lens 3b having convex both lens surfaces, and a positive lens 3c having convex both surfaces. Consisting of
The Abbe number of the material of the positive lens 1b of the first lens group is ν1b, the refractive index of the material of the positive lens 1b of the first lens group is N1b,
The average Abbe number of the positive lens material of the third lens group is ν3p, the average refractive index of the positive lens material of the third lens group is N3p, the focal length of the nth lens group is fn, and the wide angle end of the zoom lens is When the focal length is fw,
50 <ν3p <65
−0.001 × ν3p + 1.61 <N3p <−0.006 × ν3p + 2.04
0.6 <f3 / fw <0.9
49 <ν1b <62
−0.001 × ν1b + 1.62 <N1b <−0.008 × ν1b + 2.13
2.4 <f1 / fw <2.9
It is characterized by satisfying the following conditions.
[0012]
According to a second aspect of the invention, in the first aspect of the invention, the fourth lens group is composed of a cemented lens including a positive lens 4a and a negative lens 4b in order from the object side.
The Abbe number of the material of the negative lens 4b in the fourth lens group is ν4b,
The refractive index of the material of the negative lens 4b in the fourth lens group is N4b,
The Abbe number of the material of the positive lens 4a in the fourth lens group is ν4a,
When 36 <ν4b <61
−0.005 × ν4b + 1.90 <N4b <−0.005 × ν4b + 2.03
12 <ν4b−ν4a <34
1.0 <| f4 | / fw <1.6
It is characterized by satisfying the following conditions.
[0013]
According to a third aspect of the present invention, in the first or second aspect of the invention, the second lens group includes, in order from the object side, a negative meniscus lens 2a, a negative lens 2b, a positive lens 2c, and a negative lens 2d with a convex surface facing the object side. And
The Abbe number of the material of the negative lens 2d in the second lens group is ν2d
The refractive index of the material of the negative lens 2d in the second lens group is N2d.
When 36 <ν2d <59
−0.008 × ν2d + 2.11 <N2d <−0.005 × ν2d + 2.03
0.4 <| f2 | / fw <0.6
It is characterized by satisfying the following conditions.
[0014]
According to the invention of claim 4, the fifth lens group has, in order from the object side, a positive lens 5a, a positive lens 5b having a convex surface having a strong refractive power toward the image surface side as compared with the object side, and a convex surface toward the image surface side. A negative meniscus lens 5c;
The Abbe number of the material of the positive lens 5b in the fifth lens group is ν5b
The refractive index of the material of the positive lens 5b in the fifth lens group is N5b.
When 36 <ν5b <64
−0.001 × ν5b + 1.62 <N5b < −0.006 × ν5b + 1.97
1.4 <f5 / fw < 2.1
It is characterized by satisfying the following conditions.
[0015]
An optical apparatus according to a fifth aspect of the invention includes the zoom lens according to any one of the first to fourth aspects.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
1A, 1B, and 1C are lens cross-sectional views at the wide-angle end, the intermediate zoom position, and the telephoto end of Numerical Embodiment 1. FIG. 2 to 4 are aberration diagrams at the wide-angle end, the intermediate zoom position, and the telephoto end according to Numerical Example 1 of the present invention.
[0018]
FIG. 5 is a lens cross-sectional view at the wide-angle end of Numerical Example 2, and FIGS. 6 to 8 are aberration diagrams at the wide-angle end, intermediate zoom position, and telephoto end of Numerical Example 2 of the present invention.
[0019]
9 is a lens cross-sectional view at the wide-angle end of Numerical Example 3, and FIGS. 10 to 12 are aberration diagrams at the wide-angle end, the intermediate zoom position, and the telephoto end of Numerical Example 3 of the present invention.
[0020]
In the lens sectional view, L1 is a positive first lens group, L2 is a negative second lens group, L3 is a positive third lens group, L4 is a negative fourth lens group, L5 is a positive fifth lens group, SP Is an aperture, and IP is an image plane. During zooming from the wide-angle end to the telephoto end, the first lens unit L1 moves toward the object side as indicated by an arrow, and the second lens unit L2 moves toward the object side while increasing the distance from the first lens unit L1. The third lens unit L3 moves to the object side while reducing the distance from the second lens unit L2, and the fourth lens unit L4 moves to the object side while increasing the interval from the third lens unit L3. The fifth lens unit L5 moves toward the object side integrally with the third lens unit L3 while reducing the distance from the fourth lens unit L4, and the stop SP moves toward the object side integrally with the third lens unit L3.
[0021]
In this embodiment, focusing from an infinite object to a close object may be performed by moving the whole lens or a single lens group and a plurality of lens groups. However, if the second lens group is used, good optical performance can be easily obtained. In addition, since the lens group is relatively small, the mechanical mechanism may be simplified.
[0022]
The fifth lens group is moved integrally with the third lens group, but may be moved independently. The stop SP is moved integrally with the third lens group, but may be moved independently.
[0023]
In the zoom lens according to the present embodiment, the third lens group in order from the object side is a negative meniscus lens 3a having a convex surface facing the object side, a cemented lens 3ab composed of a positive lens 3b having convex both lens surfaces, and both lens surfaces are Consists of a convex positive lens 3c,
The average Abbe number of the material of the positive lens in the third lens group is ν3p,
The average refractive index of the positive lens material in the third lens group is N3p,
The focal length of the nth lens group is fn,
The focal length at the wide-angle end of the zoom lens is fw,
When 50 <ν3p <65 (1)
−0.001 × ν3p + 1.61 <N3p <−0.006 × ν3p + 2.04
... (2)
0.6 <f3 / fw <0.9 (3)
It is characterized by satisfying the following conditions.
[0024]
The above content will be described below.
[0025]
In general, when a zoom lens has a high zoom ratio, aberration fluctuations accompanying zooming tend to increase. Among these, suppression of chromatic aberration fluctuation is particularly important in satisfying good optical performance. In the zoom lens according to the present embodiment, a negative meniscus lens 3a having a convex surface facing the object side and a cemented lens composed of a positive lens 3b having convex surfaces are arranged in order from the object side in the third lens group. In particular, it is easy to correct the variation of the on-axis aberration caused by zooming. Further, by arranging the positive lens 3c having convex surfaces on both sides of the image surface, it is easy to ensure the positive refractive power necessary for zooming. Furthermore, conditional expression {circle around (1)} that achieves good optical performance by making the materials of the two positive lenses appropriate glass materials is the average Abbe of the materials of the positive lenses (3b and 3c) of the third lens group. It is a condition for setting the number appropriately, and if the upper limit is exceeded, it will be difficult to manufacture lenses such as phosphoric crown and fluoric crown, and if it exceeds the lower limit, axial chromatic aberration due to zooming will be It becomes difficult to correct the fluctuation.
[0026]
Conditional expression (2) is a condition for appropriately setting the average refractive index and Abbe number of the material of the positive lens (3b and 3c) in the third lens group. If the upper limit is exceeded, it is difficult to manufacture the lens and the expensive high refractive index lantern. If the lower limit is exceeded, it becomes difficult to correct spherical aberration particularly on the telephoto side.
[0027]
Conditional expression (3) appropriately sets the focal length of the third lens group when the glass material set in the above conditions (1) and (2) is used for the positive lens of the third lens group. If it exceeds, it will be difficult to secure a zoom ratio, and if it exceeds the lower limit, it will be difficult to correct spherical aberration on the telephoto side, or it will be difficult to arrange a retro-type refractive power arrangement on the wide angle side. Correction of curvature of field becomes difficult.
[0028]
More preferably, conditional expressions (1), (2), and (3) should be in the following numerical range.
[0029]
55 <ν3p <62 (1a)
−0.007 × ν3p + 2.01 <N3p <−0.006 × ν3p + 1.98 (2a)
0.68 <f3 / fw <0.83 (3a)
By adopting the configuration described above, this embodiment achieves a zoom lens having a compact and good optical performance, including a wide angle region with a half angle of view of about 37 degrees and a zoom ratio of about 3.5 times.
[0030]
The zoom lens according to the present invention achieves the initial purpose by satisfying the above-mentioned various conditions, but further corrects aberration fluctuations at the time of further zooming, and has high optical performance over the entire screen. In order to obtain the above, it is preferable to satisfy at least one of the following conditions.
[0031]
(A-1) The fourth lens group includes a cemented lens including a positive lens 4a and a negative lens 4b in order from the object side.
The Abbe number of the material of the negative lens 4b in the fourth lens group is ν4b
The refractive index of the material of the negative lens 4b in the fourth lens group is N4b.
The Abbe number of the material of the positive lens 4a in the fourth lens group is ν4a
36 <ν4b <61 (4)
−0.005 × ν4b + 1.90 <N4b <−0.005 × ν4b + 2.03
... (5)
12 <ν4b−ν4a <34 (6)
1.0 <| f4 | / fw <1.6 (7)
The above condition is satisfied.
[0032]
Conditional expressions (4) to (7) are composed of a cemented lens composed of a positive lens 4a and a negative lens 4b in order from the object side to correct the variation in axial chromatic aberration due to compactification and zooming. This is to make it easy to remove and to achieve good optical performance and low cost.
[0033]
Conditional expression (4) is a condition for appropriately setting the Abbe number of the material of the negative lens 4b of the fourth lens group. If a glass material is set within this range, the axial chromatic aberration due to the reduction in cost and the magnification change is achieved. It becomes easier to correct the fluctuation.
[0034]
Conditional expression (5) is a condition for appropriately setting the refractive index and Abbe number of the material of the negative lens 4b of the fourth lens group. If a glass material is set within this range, the cost is reduced and the image in the over direction on the telephoto side is set. Correction of surface curvature is further facilitated.
[0035]
Conditional expression (6) is a condition for appropriately setting the Abbe numbers of the materials of the positive lens 4a and the negative lens 4b of the fourth lens group. If a glass material is set within this range, the longitudinal chromatic aberration associated with zooming It is even easier to correct the fluctuations.
[0036]
Conditional expression (7) appropriately sets the focal length of the fourth lens group when the glass material set under the above conditions is used for the positive lens 4a and the negative lens 4b of the fourth lens group, and satisfies the condition. This makes it easier to secure the zoom ratio and to correct the flare of the upper ray of the off-axis light beam in the intermediate zoom region.
[0037]
More preferably, conditional expressions (4), (5), (6), and (7) should be in the following numerical ranges.
[0038]
49 <ν4b <59 (4a)
−0.008 × ν4b + 2.11 <N4b <−0.008 × ν4b + 2.15 (5a)
19 <ν4b−ν4a <24 (6a)
1.15 <| f4 | / fw <1.5 (7a)
(A-2) The second lens group includes, in order from the object side, a negative meniscus lens 2a, a negative lens 2b, a positive lens 2c, and a negative lens 2d having a convex surface directed toward the object side.
The Abbe number of the material of the negative lens 2d in the second lens group is ν2d,
The refractive index of the material of the negative lens 2d in the second lens group is N2d,
When 36 <ν2d <59 (8)
−0.008 × ν2d + 2.11 <N2d <−0.005 × ν2d + 2.03
... (9)
0.4 <| f2 | / fw <0.6 (10)
The above condition is satisfied.
[0039]
In general, in order to reduce the front lens diameter (effective diameter of the first lens group), it is preferable to dispose a lens group having a strong negative refractive power at a position away from the stop toward the object side. This condition is based on the above reasons, and by making the refractive index of the glass material of the negative lens 2d, which is a lens close to the stop in the second lens group, relatively low, and satisfying a predetermined condition, The cost is reduced while maintaining good optical performance, and the enlargement of the front lens diameter is easily suppressed.
[0040]
Conditional expression (8) is a condition for appropriately setting the Abbe number of the material of the negative lens 2d of the second lens group. If a glass material is set within this range, fluctuations in axial chromatic aberration due to zooming are corrected. It is even easier to do.
[0041]
Conditional expression (9) is a condition for appropriately setting the refractive index and the Abbe number of the material of the negative lens 2d of the second lens group. If a glass material is set within this range, low cost and coma aberration on the wide angle side are corrected. It is even easier to do.
[0042]
Conditional expression (10) is for appropriately setting the focal length of the second lens group when the glass material set under the above conditions is used for the negative lens 2d of the second lens group. It becomes easier to secure the ratio and correct negative distortion especially on the wide angle side.
[0043]
More preferably, conditional expressions (8), (9), and (10) should be in the following numerical ranges.
[0044]
44 <ν2d <56 (8a)
−0.008 × ν2d + 2.13 <N2d <−0.005 × ν2d + 2.03
... (9a)
0.45 <| f2 | / fw <0.55 (10a)
(A-3) The first lens group includes, in order from the object side, a cemented lens 1ab including a negative meniscus lens 1a having a convex surface facing the object side and a positive meniscus lens 1b having a convex surface facing the object side. When a positive meniscus lens 1c having a convex surface is formed, the Abbe number of the material of the positive lens 1b in the first lens group is ν1b, and the refractive index of the material of the positive lens 1b in the first lens group is N1b. 49 <ν1b <62 (11)
−0.001 × ν1b + 1.62 <N1b <−0.008 × ν1b + 2.13
(12)
2.4 <f1 / fw < 2.9 (13)
The above condition is satisfied.
[0045]
As described above, in order to reduce the front lens diameter, it is preferable to dispose a lens unit having a strong negative refractive power at a position away from the stop toward the object side. However, the first lens unit is a lens unit having a positive refractive power. Therefore, the same effect can be obtained if the lens located away from the aperture toward the object side has a weak positive refractive power and the lens close to the aperture has a strong positive refractive power.
[0046]
This condition is based on the above reasons. In the first lens group, the refractive index of the glass material of the negative lens 1b, which is a lens relatively far from the stop to the object side, is set to a relatively low refractive index, and a predetermined value is set. By satisfying the conditions, it is possible to reduce the cost while maintaining good optical performance, and to easily suppress the increase in the diameter of the front lens.
[0047]
Conditional expression (11) is a condition for appropriately setting the Abbe number of the material of the positive lens 1b of the first lens group. If a glass material is set within this range, the fluctuation of axial chromatic aberration due to zooming is corrected. It is even easier to do.
Conditional expression (12) is a condition for appropriately setting the refractive index and Abbe number of the material of the positive lens 1b of the first lens group. If a glass material is set within this range, low cost and spherical aberration on the telephoto side are corrected. It is even easier to do.
[0048]
Conditional expression (13) appropriately sets the focal length of the first lens group when the glass material set under the above conditions is used for the positive lens 1b of the first lens group. Securing the F number and correcting spherical aberration becomes easier.
[0049]
More preferably, conditional expressions (11) and (12 ) should be in the following ranges.
[0050]
55 <ν1b <62 (11a)
−0.007 × ν1b + 2.01 <N1b <−0.006 × ν1b + 1.98
... (12a )
( A-4) The fifth lens group includes, in order from the object side, a positive lens 5a and a positive lens 5b having a convex surface having a strong refractive power on the image surface side compared to the object side, and a negative meniscus having a convex surface on the image surface side. A lens 5c,
The Abbe number of the material of the positive lens 5b in the fifth lens group is ν5b
The refractive index of the material of the positive lens 5b in the fifth lens group is N5b.
36 <ν5b <64 (14)
−0.001 × ν5b + 1.62 <N5b <−0.006 × ν5b + 1.97
... (15)
1.4 <f5 / fw <2.1 (16)
The above condition is satisfied.
[0051]
In general, in order to reduce the rear lens diameter, a lens group having a strong negative refractive power is preferably disposed at a position away from the stop toward the image side. This condition is based on the above reasons. The lens 5c closest to the image side of the fifth lens group is a negative lens, and the refractive index of the glass material of the positive lens 5b close to the image plane in the fifth lens group is relatively low. By setting the refractive index and satisfying predetermined conditions, it is possible to reduce the cost while maintaining good optical performance, and to easily suppress the increase in the rear lens diameter. Further, under this condition, the positive lens 5a closest to the object side is formed into a lens shape with a convex surface having a strong refractive power directed to the image surface side as compared with the object side, thereby facilitating correction of coma aberration on the wide angle side.
[0052]
Conditional expression (14) is a condition for appropriately setting the Abbe number of the material of the positive lens 5b of the fifth lens group. If a glass material is set within this range, the change in the chromatic aberration of magnification due to zooming is corrected. It is even easier to do.
[0053]
Conditional expression (15) is a condition for appropriately setting the refractive index and the Abbe number of the material of the positive lens 5b of the fifth lens group. If a glass material is set within this range, the cost is reduced and distortion on the wide angle side is corrected. It is even easier to do.
[0054]
Conditional expression (16) is for appropriately setting the focal length of the fifth lens group when the glass material set under the above conditions is used for the positive lens 5b of the fifth lens group. This makes it easier to secure back focus and correct distortion.
[0055]
More preferably, conditional expressions (14), (15), and (16) should be in the following ranges.
55 <ν5b <62 (14a)
−0.007 × ν5b + 2.01 <N5b <−0.006 × ν5b + 1.98 (15a)
1.6 <f5 / fw <1.9 (16a)
Next, an embodiment of a single lens reflex camera (optical apparatus) having the zoom lens of the present invention will be described with reference to FIG.
[0056]
In FIG. 17, reference numeral 10 denotes a camera body, 11 denotes a zoom lens according to the present invention, and 12 denotes an image pickup means, which includes a film, a CCD, and the like. Reference numeral 13 denotes a viewfinder system, which includes a focusing screen 15 on which a subject image is formed, a pentaprism 16 as an image inverting means, and an eyepiece 17 for observing the subject image on the focusing screen 15. Reference numeral 14 denotes a quick return mirror.
[0057]
Thus, by applying the zoom lens of the present invention to an electronic camera or a film camera such as a video camera or a digital still camera, a small optical device having high optical performance is realized.
[0058]
Next, numerical examples of the zoom lens of the present invention will be shown. In each numerical example, i indicates the order of the optical surfaces from the object side, Ri is the radius of curvature of the i-th optical surface (i-th surface), Di is the distance between the i-th surface and the i + 1-th surface, ni and νi represent the refractive index and Abbe number of the material of the i-th optical member with respect to the d-line, respectively. Further, when k is an eccentricity, B, C, D, E... Are aspherical coefficients, and the displacement in the optical axis direction at the position of the height h from the optical axis is x with respect to the surface vertex, The spherical shape is
x = (h ² / R) / [1+ [1- (1 + k) (h / R) ² ] ^1/2 ] + Bh ⁴ + Ch ⁶ + Dh ⁸ + Eh ^10.
Is displayed. Where R is the radius of curvature. Table 1 shows the correspondence with the above-described conditional expressions in each numerical example.
[0059]
[Outside 1]
[0060]
[Outside 2]
[0061]
[Outside 3]
[0062]
[Outside 4]
[0063]
[Table 1]
[0064]
【The invention's effect】
According to the present invention, it is possible to change the entire zoom ratio with a wide angle of view and a high zoom ratio by appropriately setting the movement conditions of each lens group accompanying the zooming, the lens configuration of each lens group, and the material of those lenses. A zoom lens having high optical performance over a double range and over the entire screen and an optical apparatus having the zoom lens can be achieved.
[0065]
In addition, according to the present invention, by appropriately selecting the glass material of each lens constituting the optical system and appropriately configuring each lens group, the entire lens system is compact but has good optical performance. Thus, it is possible to achieve a zoom lens including a wide angle region and a zoom ratio of about 3.5 times and an optical apparatus having the same.
[Brief description of the drawings]
1 is a lens cross-sectional view of Numerical Example 1. FIG. 2 is an aberration diagram at the wide-angle end of Numerical Example 1. FIG. 3 is an aberration diagram at an intermediate zoom position of Numerical Example 1. FIG. FIG. 5 is a lens cross-sectional view of Numerical Example 2. FIG. 6 is an aberration diagram at the wide-angle end of Numerical Example 2. FIG. 7 is an aberration diagram at an intermediate zoom position of Numerical Example 2. 8] Aberration diagram at the telephoto end of Numerical Example 2 [FIG. 9] Lens cross-sectional view of Numerical Example 3 [FIG. 10] Aberration diagram at the wide-angle end of Numerical Example 3 [FIG. 11] Intermediate zoom of Numerical Example 3 Aberration diagram of position [FIG. 12] Aberration diagram at telephoto end of Numerical Example 3 [FIG. 13] Cross-sectional view of lens of Numerical Example 4 [FIG. 14] Aberration diagram at wide angle end of Numerical Example 4 [FIG. Aberration diagram at the intermediate zoom position in Example 4 [FIG. 16] Aberration diagram at the telephoto end in Numerical Example 4 [FIG. 17] Main parts of the optical apparatus of the present invention Schematic DESCRIPTION OF SYMBOLS
L1 1st group L2 2nd group L3 3rd group L4 4th group L5 5th group SP Aperture IP image plane d d line g g line ΔS sagittal image plane ΔM meridional image plane

Claims (5)

In order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, a fourth lens group having a negative refractive power, and a positive lens The distance between the first lens group and the second lens group is larger at the telephoto end than at the wide-angle end, and the distance between the second lens group and the third lens group. Zoom in which zooming is performed by moving the lens group so that the distance between the third lens group and the fourth lens group increases and the distance between the fourth lens group and the fifth lens group decreases. In the lens,
The first lens group includes, in order from the object side, a cemented lens 1ab including a negative meniscus lens 1a having a convex surface facing the object side and a positive meniscus lens 1b having a convex surface facing the object side, and a convex surface facing the object side. Consists of a positive meniscus lens 1c,
The third lens group includes, in order from the object side, a negative meniscus lens 3a having a convex surface facing the object side, a cemented lens 3ab composed of a positive lens 3b having convex both lens surfaces, and a positive lens 3c having convex both surfaces. Consists of
The Abbe number of the material of the positive lens 1b of the first lens group is ν1b, the refractive index of the material of the positive lens 1b of the first lens group is N1b,
The average Abbe number of the positive lens material of the third lens group is ν3p, the average refractive index of the positive lens material of the third lens group is N3p, the focal length of the nth lens group is fn, and the wide angle end of the zoom lens is When the focal length is fw,
50 <ν3p <65
−0.001 × ν3p + 1.61 <N3p <−0.006 × ν3p + 2.04
0.6 <f3 / fw <0.9
49 <ν1b <62
−0.001 × ν1b + 1.62 <N1b <−0.008 × ν1b + 2.13
2.4 <f1 / fw <2.9
A zoom lens that satisfies the following conditions. The fourth lens group is composed of a cemented lens including a positive lens 4a and a negative lens 4b in order from the object side.
The Abbe number of the material of the negative lens 4b of the fourth lens group is ν4b, the refractive index of the material of the negative lens 4b of the fourth lens group is N4b, and the Abbe number of the material of the positive lens 4a of the fourth lens group is ν4a. And when
36 <ν4b <61
−0.005 × ν4b + 1.90 <N4b <−0.005 × ν4b + 2.03
12 <ν4b−ν4a <34
1.0 <| f4 | / fw <1.6
The zoom lens according to claim 1, wherein the following condition is satisfied. The second lens group includes, in order from the object side, a negative meniscus lens 2a, a negative lens 2b, a positive lens 2c, and a negative lens 2d having a convex surface facing the object side.
When the Abbe number of the material of the negative lens 2d of the second lens group is ν2d and the refractive index of the material of the negative lens 2d of the second lens group is N2d,
36 <ν2d <59
−0.008 × ν2d + 2.11 <N2d <−0.005 × ν2d + 2.03
0.4 <| f2 | / fw <0.6
The zoom lens according to claim 1, wherein the zoom lens satisfies the following condition. The fifth lens group includes, in order from the object side, a positive lens 5a, a positive lens 5b, and a negative meniscus lens 5c with a convex surface facing the image surface side. Configured,
When the Abbe number of the material of the positive lens 5b of the fifth lens group is ν5b and the refractive index of the material of the positive lens 5b of the fifth lens group is N5b,
36 <ν5b <64
−0.001 × ν5b + 1.62 <N5b < −0.006 × ν5b + 1.97
1.4 <f5 / fw < 2.1
The zoom lens according to claim 1, wherein the zoom lens satisfies the following condition. An optical apparatus comprising the zoom lens according to claim 1 .