JP2006078964A - Zoom lens and image pickup device having the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a zoom lens which may miniaturize whole lens system and has high optical performance over the whole range of zoom. <P>SOLUTION: The zoom lens has a first lens group L1 of positive refractive power, a second lens group L2 of negative refractive power, a third lens group L3 of positive refractive power, a fourth lens group L4 of negative refractive power and a fifth lens group L5 of positive refractive power in order from the object side to the image side. Upon the zooming in the zoom lens in which each lens group moves, the fifth lens group L5 has a positive lens that satisfies the condition; νd>75, 0.53<θgf<0.545, where νd is Abbe number and θgf is partial dispersion ratio and the fifth lens group satisfies the condition; 1.1<¾f2/fw¾<1.8, ft/fw>4.0, where fw and ft are focal distances at the wide angle end and the telephoto end of the whole system respectively and f2 is focal distance of the second lens group L2. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a zoom lens and an image pickup apparatus having the same, and is suitable for an image pickup apparatus using a solid-state image pickup device such as a video camera or a digital still camera.

  Recently, along with the reduction in size and weight of home video cameras and the like, remarkable progress has been made in reducing the size of zoom lenses for imaging, particularly in reducing the overall lens length, reducing the front lens diameter, and simplifying the lens configuration. Has been poured.

  As one means for achieving these objects, a so-called rear focus type zoom lens that performs focusing by moving a lens group other than the first lens group on the object side is known.

  In general, a rear focus type zoom lens has a smaller effective diameter of the first lens group than a zoom lens that moves the first lens group to perform focusing, and the entire lens system can be easily downsized. Further, close-up photography, particularly close-up photography is facilitated, and focusing is performed by moving a small and lightweight lens group, so that there is a feature that the driving force of the lens group is small and quick focusing is possible.

  As a rear focus type zoom lens, in order from the object side to the image side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a positive lens having a positive refractive power. A zoom lens having four lens groups of the fourth lens group, performing zooming by moving the second lens group, and compensating for and focusing on image plane variation accompanying zooming by moving the fourth lens group Known (Patent Documents 1 and 2).

  On the other hand, in a video camera using a solid-state image pickup device such as a CCD or a digital still camera as an image pickup device, a low-pass filter and a color correction filter are arranged between the last lens portion and the image pickup device.

  In addition to this, various optical members such as a color separation prism for 3CCD and a prism for splitting a light beam into a TTL finder system are also arranged according to the specifications of the camera. In particular, in an optical system using a color separation prism or an optical path splitting prism, a photographing lens system having a relatively long back focus is required.

  In general, an image pickup apparatus using a CCD such as a video camera is composed of a positive, negative, positive, and positive refractive power lens group in which the first lens group closest to the object is fixed during zooming. A four-group zoom lens with a long back focus is known (Patent Document 3).

  Further, there is a demand for a zoom lens in which chromatic aberration is favorably corrected as the number of pixels of the image sensor increases. It is effective to use a glass material having anomalous dispersion for correcting chromatic aberration, especially the secondary spectrum, and a zoom lens related to these is known (Patent Document 4).

In Patent Document 4, in the 6-group zoom lens including a lens group having positive, negative, negative, positive, negative, and positive refractive power in order from the object side to the image side, the lens group closest to the object side is made of an anomalous dispersion glass material. Axial chromatic aberration near the zoom position at the telephoto end is corrected by using a lens, and chromatic aberration of magnification at the zoom position at the wide-angle end is corrected by using a lens made of an anomalous dispersion glass material in the lens group closest to the image plane. is doing.
JP 7-270684 A JP-A-11-305124 JP-A-6-511199, etc. Japanese Patent Laid-Open No. 2002-62478

  During zooming in the above-described four-group zoom lens, the zoom lens in which the first lens group is fixed performs zooming mainly by moving the second lens group. For this reason, the distance between the first lens group and the third lens group needs to be at least a movement stroke necessary for performing desired zooming in the second lens group.

  In such a lens configuration, it is difficult to shorten the distance between the aperture stop arranged in the vicinity of the third lens group and the first lens group, and therefore, when using a large solid-state imaging device, the total lens length is long. In addition, the diameter of the front lens becomes larger. In particular, when the lens system is widened, there has been a problem that the front lens diameter is remarkably increased.

  Further, since Patent Document 4 has six lens groups as a whole, the mechanical structure for zooming tends to be complicated.

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

  The zoom lens of the present invention includes, in order from the object side to the image side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a rear group. The rear group has one or more lens groups, and the lens group closest to the image side is a lens group having a positive refractive power, and the zoom lens is such that the first to third lens groups move during zooming.

In such a zoom lens, when the most image side lens group included in the rear group has an Abbe number of νd and a partial dispersion ratio of θdf,
νd> 75
0.53 <θgf <0.545
A positive lens that satisfies the following conditions:
When the focal lengths at the wide-angle end and the telephoto end of the entire system are fw and ft, respectively, and the focal length of the second lens group is f2.
1.1 <| f2 / fw | <1.8
ft / fw> 4.0
It is characterized by satisfying the following conditions.

  Note that the Abbe number νd and the partial dispersion ratio θgf are Ng, Nd, NF, and NC when the refractive indexes of the materials for the g-line, d-line, F-line, and C-line are Ng, Nd, NF, and NC, respectively.

It is a value defined by.

  According to the present invention, a zoom lens having a high optical performance over the entire zoom range can be obtained by downsizing the entire lens system.

  Embodiments of the zoom lens of the present invention and an image pickup apparatus having the same will be described below.

  FIG. 1 is a lens cross-sectional view of a zoom lens according to Embodiment 1 of the present invention, and FIGS. 2 to 4 are aberration diagrams at the wide angle end, intermediate focal length, and telephoto end of the zoom lens according to Embodiment 1 of the present invention.

  5 to 7 are aberration diagrams at the wide-angle end, the intermediate focal length, and the telephoto end of the zoom lens according to the second embodiment of the present invention.

  Note that the lens cross-sectional view of the zoom lens of Example 2 is omitted because it is substantially the same as FIG.

  FIG. 8 is a lens cross-sectional view of Embodiment 3 of the present invention, and FIGS. 9 to 11 are aberration diagrams of the zoom lens of Embodiment 3 of the present invention at the wide-angle end, intermediate focal length, and telephoto end.

  In the aberration diagrams, d and g are represented by d-line and g-line, ΔM and ΔS are represented by meridional image surface and sagittal image surface, and lateral chromatic aberration is represented by g-line.

  FIG. 12 is a schematic diagram of the imaging apparatus of the present invention.

  First, Example 1 of FIG. 1 will be described. The second embodiment is substantially the same as the first embodiment.

  In the lens cross-sectional view of FIG. 1, L1 is a first lens group having a positive refractive power, L2 is a second lens group having a negative refractive power, L3 is a third lens group having a positive refractive power, and L4 is a negative refractive power. The fourth lens unit L5 is a fifth lens unit having a positive refractive power. The fourth lens group L4 and the fifth lens group L5 constitute a rear group BG. SP is an aperture stop, which is located in front of the third lens unit L3 (on the object side) and moves together with the third lens unit L3 during zooming.

  Note that the aperture stop SP may be arranged in the third lens unit L3 or behind the third lens unit L3 (image side).

  G corresponds to an optical filter, a face plate, etc., and is an optical block provided by design. IP is an image plane on which an imaging plane of a solid-state imaging device (photoelectric conversion device) such as a CCD sensor or a CMOS sensor is located.

  In Example 1, the aperture stop SP and the lens units L1 to L5 are moved as indicated by arrows during zooming from the wide-angle end to the telephoto end.

  Note that the wide-angle end and the telephoto end refer to zoom positions when the zooming lens unit (second lens unit L2) is positioned at both ends of a range that can move in the optical axis direction due to the mechanism.

  In Example 1, during zooming from the wide-angle end to the telephoto end, the first lens unit L1 is moved to the object side, and the second lens unit L2 is moved to the image side. Further, the third lens unit L3 is moved integrally with the aperture stop SP. The fourth lens unit L4 is moved to the image side, and the fifth lens unit is moved to the object side.

  The first embodiment employs a rear focus type in which the fifth lens unit L5 is moved on the optical axis to perform focusing. When focusing from an infinitely distant object to a close object at the telephoto end, the fifth lens unit L5 is extended forward as indicated by an arrow 5c in the figure. A solid line curve 5a and a dotted line curve 5b of the fifth lens unit L5 correct image plane variations caused by zooming from the wide-angle end to the telephoto end when focusing on an object at infinity and a short-distance object, respectively. The movement locus for this is shown.

  In the first embodiment, the use of the lightweight fifth lens unit L5 for focusing facilitates quick automatic focus detection.

  The basic configuration of the zoom lens of the second embodiment is the same as that of the first embodiment of FIG.

  In Example 1, the fifth lens unit L5 is used for focusing, so that it is possible to focus continuously from an object at infinity to an object at a short distance of several centimeters.

  By moving the first lens unit L1 and the third lens unit L3 to the object side and the fourth lens unit L4 to the image side during zooming, the amount of movement of the second lens unit L2 necessary for zooming can be reduced. Thus, the distance from the first lens unit L1 to the stop SP can be shortened. This achieves a reduction in the diameter of the front lens.

  In the first embodiment, the mechanical structure is simplified by moving the aperture stop SP integrally with the third lens unit L3 during zooming.

  The first lens unit L1 according to the first exemplary embodiment includes, in order from the object side to the image side, a cemented lens having a concave meniscus lens and a positive lens on the image side, and a meniscus positive lens having a convex surface on the object side. .

  By disposing a negative lens in the first lens unit L1, in particular, spherical aberration, coma, axial chromatic aberration, and the like that occur at the zoom position on the telephoto side are corrected well.

  The second lens unit L2 includes, in order from the object side to the image side, a negative meniscus lens having a concave surface on the image side, a negative lens having a concave surface on both lens surfaces, a positive lens having a convex surface on the object side, and both lens surfaces Is composed of a negative negative lens.

  In particular, by adopting a configuration in which a negative lens is disposed on the image side, the asymmetry of the second lens unit L2 is relaxed to enhance the achromatic effect of the chromatic aberration at the principal point, thereby reducing variations in chromatic aberration due to zooming. If an aspherical shape is introduced into the surface of the second lens unit L2, distortion at the zoom position at the wide angle end and coma at the zoom position in the intermediate region can be corrected more satisfactorily.

  The third lens unit L3 includes, in order from the object side to the image side, a cemented lens of a meniscus negative lens having a concave surface on the image side and a positive lens, and a positive lens.

  By making the third lens unit L3 a negative leading type retrofocus type lens arrangement preceded by a lens having a negative refractive power, a sufficiently long back focus is secured, and an optical component such as a prism can be inserted.

  In addition, by dividing the positive lens component of the third lens unit L3 into two or more, generation of spherical aberration is suppressed while maintaining a large aperture. If an aspherical shape is introduced into the surface of the third lens unit L3, the spherical aberration can be further corrected, and further enlargement of the aperture becomes easy.

  The fourth lens unit L4 includes, in order from the object side to the image side, a positive lens having a convex surface on the image side and a negative lens having concave surfaces on both lens surfaces.

  By using a configuration having a positive lens, fluctuations in axial chromatic aberration and spherical aberration due to zooming are corrected well. If an aspherical shape is introduced into the surface of the fourth lens unit L4, the variation in spherical aberration can be further improved, and an increase in the diameter becomes easy.

  The fifth lens unit L5 is composed of a positive lens having a convex surface on the image side, a negative lens having a concave shape on both lens surfaces, and a positive lens having a convex shape on both lens surfaces in order from the object side to the image side. It consists of a lens and a positive lens.

  In particular, the astigmatism is satisfactorily corrected by making the surface of the positive lens closest to the object side into an aspherical shape. Further, by using a low-dispersion glass material for the positive lens material constituting the cemented lens, the lateral chromatic aberration at the zoom position at the wide-angle end is corrected well.

  Next, Example 3 in FIG. 8 will be described.

  In the lens cross-sectional view of FIG. 8, L1 is a first lens group having a positive refractive power, L2 is a second lens group having a negative refractive power, L3 is a third lens group having a positive refractive power, and L4 is a positive refractive power. 4th lens group. The fourth lens unit L4 alone constitutes the rear group BG. SP is an aperture stop, which is located in front of the third lens unit L3.

  G is an optical block corresponding to an optical filter, a face plate, or the like. IP is an image plane on which an imaging plane of a solid-state imaging device (photoelectric conversion device) such as a CCD sensor or a CMOS sensor is located.

  In Example 3, the aperture stop SP and the lens groups L1 to L4 are moved as indicated by arrows during zooming from the wide-angle end to the telephoto end.

  In Example 3, during zooming from the wide-angle end to the telephoto end, the first lens unit L1 is moved to the object side, and the second lens unit L2 is moved to the image side. Further, the third lens unit L3 is moved to the object side. Further, the fourth lens unit L4 is moved along a convex locus toward the object side.

  The third embodiment employs a rear focus type in which the fourth lens unit L4 is moved on the optical axis to perform focusing. When focusing from an infinitely distant object to a close object at the telephoto end, the fourth lens unit L4 is moved forward as indicated by an arrow 4c in the figure. A solid line curve 4a and a dotted line curve 4b of the fourth lens unit L4 correct the image plane variation caused by zooming from the wide-angle end to the telephoto end when focusing on an object at infinity and a short-distance object, respectively. The movement locus for this is shown. In the third embodiment, the automatic focusing detection can be quickly performed by using the lightweight fourth lens unit L4 for focusing.

  By using the fourth lens unit L4 for focusing, it is possible to continuously focus from an object at infinity to an object at a close distance of several centimeters.

  In the third embodiment, the third lens unit L3 is composed of, in order from the object side, a cemented lens having a negative refractive power as a whole by bonding a negative meniscus lens and a positive lens having a concave surface on the object side, and both lens surfaces are convex. The positive lens and the meniscus negative lens are bonded together to form a cemented lens having a positive refractive power as a whole, and a positive lens having a convex surface on the image side. The lens surface closest to the object side of the third lens unit L3 has a concave shape, and the third lens unit L3 has a negative leading type retrofocus type lens arrangement preceded by a lens having a negative refractive power. And optical parts such as prisms can be inserted.

  In addition, by dividing the positive lens component of the third lens unit L3 into two or more, generation of spherical aberration is suppressed while maintaining a large aperture. Further, the most image side lens surface of the third lens unit L3 has a convex shape on the image side to suppress the occurrence of spherical aberration.

  Further, by making the most image side surface of the third lens unit L3 an aspherical shape, the spherical aberration generated in the third lens unit L3 can be corrected more satisfactorily, and the off-axis coma can be corrected well. ing.

  Further, the third lens unit L3 is composed of a cemented lens having a negative refractive power as a whole and a cemented lens having a positive refractive power as a whole, so that chromatic aberration is corrected well. By constructing the third lens unit L3 in this way, the lens unit arrangement with negative and positive refractive power is strengthened as a retrofocus arrangement that can secure a sufficiently long back focus while satisfactorily correcting axial chromatic aberration. ing.

  In addition, the fourth lens unit L4 is composed of a positive lens, a negative lens, and a positive lens in order from the object side, so that correction of chromatic aberration and correction of the image plane are performed satisfactorily with a relatively small lens configuration.

  In particular, the curvature of field is favorably corrected by making the surface of the positive lens closest to the object side into an aspherical shape. Further, the lateral chromatic aberration is corrected well by using a low-dispersion glass material for the positive lens on the most image side.

  Thus, in each embodiment, in order from the object side to the image side, the first lens unit L1 having a positive refractive power, the second lens unit L2 having a negative refractive power, and the third lens unit L3, 1 having a positive refractive power. The above-described lens group includes a rear group in which the most image side lens group is a lens group having a positive refractive power, and the first to third lens groups L1 to L3 move respectively during zooming. Therefore, one or more of the following conditional expressions are satisfied, thereby obtaining an effect corresponding to each conditional expression.

  That is, the most image side lens group in the rear group (the fifth lens group L5 in Examples 1 and 2 and the fourth lens group L4 in Example 3) is a material for the g-line, d-line, F-line, and C-line. And Ng, Nd, NF, NC, respectively,

When the Abbe number νd and the partial dispersion ratio θgf are
νd> 75 (1)
0.53 <θgf <0.545 (2)
A positive lens that satisfies the following condition.

When the focal lengths at the wide-angle end and the telephoto end of the entire system are fw and ft, respectively, and the focal length of the second lens unit L2 is f2.
1.1 <| f2 / fw | <1.8 (3)
ft / fw> 4.0 (4)
Is satisfied.

Further, when zooming from the wide-angle end to the telephoto end to the zoom position, the maximum movement amounts in the optical axis direction of the first lens unit L1 and the third lens unit L3 are M1 and M3, respectively (the sign is toward the image side). Positive travel)
0.1 <| M3 | / fw <1.0 (5)
1.1 <| M1 | / fw <2.5 (6)
Is satisfied.

When the focal length of the most image side lens group included in the rear group (the fifth lens group L5 in Examples 1 and 2 and the fourth lens group L4 in Example 3) is fR,
2.0 <fR / fw <4.8 (7)
Is satisfied.

  Next, the technical meaning of each conditional expression described above will be described.

  Conditional expressions (1) and (2) are for satisfactorily correcting the lateral chromatic aberration at the wide angle end in each embodiment.

  If the lower limit of conditional expression (1) is exceeded, the refractive power of each lens becomes too strong to correct lateral chromatic aberration at the wide-angle end, and higher-order spherical aberration may not occur.

  When the lower limit of conditional expression (2) is exceeded, the secondary spectrum of lateral chromatic aberration becomes too large near the wide-angle end, and it becomes difficult to correct lateral chromatic aberration on the short wavelength side and long wavelength side in a balanced manner. If the upper limit is exceeded, selection of the glass material is lost unless the dispersion is increased.

  Conditional expressions (3) and (4) are for achieving good optical performance over the entire zoom range.

  If the refractive power of the second lens unit L2 exceeds the lower limit of the conditional expression (3) while maintaining the zoom ratio of the conditional expression (4), the distortion and astigmatism associated with zooming are corrected. It becomes difficult. If the upper limit of conditional expression (3) is exceeded and the refractive power of the second lens unit L2 becomes too weak, the amount of movement of the second lens unit L2 necessary for zooming becomes too large, and the entire lens system is reduced in size. Becomes difficult.

  Conditional expressions (5) and (6) are for appropriately setting the movement amounts of the first and third lens units L1 and L3 during zooming.

  If the amount of movement of the third lens unit L3 becomes smaller than the lower limit of conditional expression (5), it will be difficult to reduce the front lens diameter. If the upper limit is exceeded, it becomes difficult to correct spherical aberration associated with zooming.

  If the movement amount M1 of the first lens unit L1 exceeds the upper limit of the conditional expression (6), the dimension of the cam ring that determines the movement locus of the first lens unit L1 increases, and the size of the mechanical member increases. It is not good to invite. In particular, it is difficult to reduce the size of the entire lens group by retracting each lens group during non-photographing.

  If the movement amount of the first lens unit L1 is too small beyond the lower limit, it is necessary to increase the movement amount of the second lens unit L2 in order to ensure a desired zoom ratio. As a result, the dimension in the optical axis direction of the cam ring that determines the movement locus of the first lens unit L1 at the zoom position at the wide-angle end becomes large, and the size of the mechanical member should not be increased. In particular, it is difficult to reduce the size of the entire lens group by retracting each lens group during non-photographing.

  In addition, when the amount of movement of the first lens unit L1 is too small beyond the lower limit, it is necessary to increase the amount of movement of the second lens unit L2 in order to secure a desired zoom ratio. As a result, the distance between the first lens unit L1 and the third lens unit L3 at the zoom position at the wide-angle end is increased. When the aperture stop SP is in the vicinity of the third lens unit L3, the distance between the first lens unit L1 and the aperture stop SP at the zoom position at the wide-angle end increases, leading to an increase in the diameter of the front lens.

  Conditional expression (7) defines the focal length fR of the most image-side lens unit when focusing is performed with the most image-side lens unit included in the rear group in each embodiment.

  If the refractive power of the focusing lens group exceeds the lower limit of conditional expression (7), the distortion and astigmatism fluctuations during focusing cannot be corrected. On the other hand, if the upper limit is exceeded and the refractive power of the focusing lens group becomes too weak, the amount of movement of the lens group necessary for focusing becomes too large, which is not desirable.

  In each embodiment, it is more preferable to set the numerical ranges of the conditional expressions (1) to (7) as follows.

νd> 80 (1a)
0.532 <θgf <0.54 (2a)
1.2 <| f2 / fw | <1.6 (3a)
ft / fw> 4.3 (4a)
0.15 <| M3 | / fw <0.7 (5a)
1.4 <| M1 | / fw <2.0 (6a)
2.5 <fR / fW <4.1 (7a)
As described above, each embodiment has a long back focus into which an optical member such as a color separation prism for 3CCD or a prism for splitting a light beam for a TTL finder can be inserted, and at the wide-angle end. In addition to reducing the overall lens length and diameter of the front lens at the zoom position, a high-performance zoom lens compatible with high-pixel digital cameras and video cameras has been achieved.

  Next, numerical examples 1 to 3 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 indicate the refractive index and Abbe number of the material of the i-th optical member with respect to the d-line, respectively.

In addition, when k is an eccentricity, B, C, D, and E are aspherical coefficients, and the displacement in the optical axis direction at a height h from the optical axis is x with respect to the surface vertex, the aspherical shape is ,
x = (h ² / R) / [1+ [1− (1 + k) (h / R) ² ] ^1/2 ]
+ Bh ⁴ + Ch ⁴ + Dh ⁸ + Eh ¹⁰
It is represented by

Where R is the radius of curvature. Further, for example, the display of “e-Z” means “10 ^−Z ”. Table 1 shows the correspondence with the above-described conditional expressions in each numerical example. f indicates a focal length, Fno indicates an F number, and ω indicates a half angle of view.

  In Numerical Examples 1 to 3, R30 and R31 are surfaces constituting the optical block G.

Numerical example 1
f = 7.36 to 33.32 Fno = 2.47 to 3.05 2ω = 73.6 ° to 18.7 °

R 1 = 69.304 D 1 = 1.51 N 1 = 1.846660 ν 1 = 23.9
R 2 = 45.156 D 2 = 4.26 N 2 = 1.487490 ν 2 = 70.2
R 3 = 487.781 D 3 = 0.14
R 4 = 41.864 D 4 = 2.61 N 3 = 1.696797 ν 3 = 55.5
R 5 = 116.231 D 5 = variable
R 6 = 41.387 D 6 = 1.03 N 4 = 1.743997 ν 4 = 44.8
R 7 = 8.717 D 7 = 5.27
R 8 = -46.431 D 8 = 0.82 N 5 = 1.696797 ν 5 = 55.5
R 9 = 26.937 D 9 = 0.14
R10 = 14.566 D10 = 3.85 N 6 = 1.805181 ν 6 = 25.4
R11 = -361.891 D11 = 0.48
R12 = -49.961 D12 = 0.72 N 7 = 1.603420 ν 7 = 38.0
R13 = 26.174 D13 = variable
R14 = Aperture D14 = 0.96
R15 = -141.268 D15 = 0.48 N 8 = 1.806100 ν 8 = 33.3
R16 = 10.185 D16 = 2.61 N 9 = 1.693501 ν 9 = 53.2
R17 = -24.560 D17 = 0.08
R18 = 19.394 D18 = 2.20 N10 = 1.719995 ν10 = 50.2
R19 = -33.434 D19 = variable
R20 = -20.682 D20 = 1.41 N11 = 1.846660 ν11 = 23.9
R21 = -10.347 D21 = 0.52 N12 = 1.638539 ν12 = 55.4
R22 = 33.636 D22 = variable
R23 = 102.024 (Aspherical) D23 = 2.75 N13 = 1.583126 ν13 = 59.4
R24 = -21.152 D24 = 0.10
R25 = -17.585 D25 = 0.62 N14 = 1.761821 ν14 = 26.5
R26 = 29.256 D26 = 3.30 N15 = 1.496999 ν15 = 81.5
R27 = -15.034 D27 = 0.14
R28 = -90.592 D28 = 1.51 N16 = 1.696797 ν16 = 55.5
R29 = -19.083 D29 = variable
R30 = ∞ D30 = 18.56 N17 = 1.516330 ν17 = 64.1
R31 = ∞

\ Focal length 7.36 20.95 33.32
Variable interval \
D 5 0.87 22.46 31.24
D13 22.17 6.63 2.75
D19 1.66 5.95 7.88
D22 9.72 4.57 1.85
D29 0.50 2.75 3.42

Aspheric coefficient
R23 k = -2.70471e + 02 B = -7.22077e-05 C = -8.98595e-08 D = -2.50692e-09
E = 7.64238e-11


Numerical example 2
f = 7.36 to 33.32 Fno = 2.47 to 3.18 2ω = 73.6 ° to 18.7 °

R 1 = 63.035 D 1 = 1.51 N 1 = 1.846660 ν 1 = 23.9
R 2 = 41.982 D 2 = 4.26 N 2 = 1.487490 ν 2 = 70.2
R 3 = 316.274 D 3 = 0.14
R 4 = 36.774 D 4 = 2.75 N 3 = 1.696797 ν 3 = 55.5
R 5 = 84.125 D 5 = variable
R 6 = 36.711 D 6 = 1.03 N 4 = 1.743997 ν 4 = 44.8
R 7 = 8.336 D 7 = 5.13
R 8 = -46.858 D 8 = 0.82 N 5 = 1.696797 ν 5 = 55.5
R 9 = 23.149 D 9 = 0.14
R10 = 13.733 D10 = 3.71 N 6 = 1.805181 ν 6 = 25.4
R11 = 150.998 D11 = 0.48
R12 = -69.647 D12 = 0.72 N 7 = 1.603420 ν 7 = 38.0
R13 = 27.846 D13 = variable
R14 = Aperture D14 = 0.96
R15 = -212.096 D15 = 0.48 N 8 = 1.806100 ν 8 = 33.3
R16 = 10.899 D16 = 2.61 N 9 = 1.693501 ν 9 = 53.2
R17 = -23.514 D17 = 0.08
R18 = 20.460 D18 = 2.20 N10 = 1.719995 ν10 = 50.2
R19 = -35.018 D19 = variable
R20 = -20.526 D20 = 1.41 N11 = 1.846660 ν11 = 23.8
R21 = -10.552 D21 = 0.52 N12 = 1.638539 ν12 = 55.4
R22 = 34.046 D22 = variable
R23 = 294.400 (Aspheric) D23 = 2.54 N13 = 1.583126 ν13 = 59.4
R24 = -20.473 D24 = 0.10
R25 = -21.284 D25 = 0.62 N14 = 1.761821 ν14 = 26.5
R26 = 21.726 D26 = 3.30 N15 = 1.438750 ν15 = 95.0
R27 = -20.656 D27 = 0.14
R28 = 95.350 D28 = 3.09 N16 = 1.696797 ν16 = 55.5
R29 = -18.840 D29 = variable
R30 = ∞ D30 = 18.56 N17 = 1.516330 ν17 = 64.1
R31 = ∞

\ Focal length 7.36 20.69 33.31
Variable interval \
D 5 0.89 21.52 30.25
D13 20.23 6.36 2.75
D19 1.66 7.04 9.65
D22 10.72 5.09 2.07
D29 1.00 2.56 3.03

Aspheric coefficient
R23 k = -4.54515e + 01 B = -8.57589e-05 C = 1.38659e-08 D = 1.37270e-09
E = -1.34690e-12

Numerical Example 3
f = 9.17 to 52.31 Fno = 2.06 to 2.55 2ω = 61.9 ° to 12.0 °

R 1 = 91.824 D 1 = 1.86 N 1 = 1.846660 ν 1 = 23.9
R 2 = 52.464 D 2 = 0.14
R 3 = 52.464 D 3 = 7.01 N 2 = 1.438750 ν 2 = 95.0
R 4 = -153.137 D 4 = 0.14
R 5 = 40.506 D 5 = 4.12 N 3 = 1.712995 ν 3 = 53.9
R 6 = 104.531 D 6 = variable
R 7 = 61.479 D 7 = 1.24 N 4 = 1.712995 ν 4 = 53.9
R 8 = 11.379 D 8 = 6.05
R 9 = -34.960 D 9 = 0.96 N 5 = 1.603112 ν 5 = 60.6
R10 = 19.777 D10 = 0.21
R11 = 16.630 D11 = 5.16 N 6 = 1.800999 ν 6 = 35.0
R12 = -28.759 D12 = 0.96
R13 = -19.772 D13 = 0.89 N 7 = 1.696797 ν 7 = 55.5
R14 = 85.090 D14 = variable
R15 = Aperture D15 = 2.18
R16 = -12.997 D16 = 0.76 N 8 = 1.516330 ν 8 = 64.1
R17 = -96.803 D17 = 2.20 N 9 = 1.805181 ν 9 = 25.4
R18 = -31.520 D18 = 0.14
R19 = 57.143 D19 = 3.44 N10 = 1.487490 ν10 = 70.2
R20 = -22.054 D20 = 0.89 N11 = 1.805181 ν11 = 25.4
R21 = -45.181 D21 = 0.14
R22 = 126.882 D22 = 2.61 N12 = 1.583126 ν12 = 59.4
R23 = -28.042 (Aspherical) D23 = Variable
R24 = 30.351 (Aspherical) D24 = 3.44 N13 = 1.583126 ν13 = 59.4
R25 = -130.364 D25 = 0.14
R26 = 47.961 D26 = 0.96 N14 = 1.846660 ν14 = 23.9
R27 = 19.626 D27 = 0.14
R28 = 19.626 D28 = 4.12 N15 = 1.438750 ν15 = 95.0
R29 = -53.414 D29 = variable
R30 = ∞ D30 = 20.63 N16 = 1.516330 ν16 = 64.1
R31 = ∞

\ Focal length 9.17 29.10 52.31
Variable interval \
D 6 1.09 24.82 34.64
D14 26.39 7.28 2.06
D23 7.50 7.96 10.82
D29 2.75 6.30 4.40

Aspheric coefficient
R23 K = -2.01645 B = -3.82429e-06 C = 6.08325e-08 D = -1.82298e-10
E = -1.21333e-12

R24 K = -5.07410 B = 2.44222e-06 C = 9.56324e-09 D = -2.18449e-10
E = 3.76684e-13

  Next, an embodiment of a digital still camera using the zoom lens of the present invention as a photographing optical system will be described with reference to FIG.

  In FIG. 12, 20 is a camera body, 21 is a photographing optical system constituted by the zoom lens of the present invention, 22 is a CCD sensor or CMOS sensor incorporated in the camera body and receiving a subject image formed by the photographing optical system 21. A solid-state imaging device (photoelectric conversion device) such as 23, a memory 23 for recording information corresponding to a subject image photoelectrically converted by the solid-state imaging device 22, and a liquid crystal display panel 24 are formed on the solid-state imaging device 22. It is a finder for observing the subject image.

  In this way, by applying the zoom lens of the present invention to an imaging apparatus such as a digital still camera, a compact imaging apparatus having high optical performance can be realized.

Lens cross-sectional view at the wide-angle end of the zoom lens of Example 1 Various aberration diagrams at the wide-angle end of the zoom lens of Example 1 Various aberration diagrams at the intermediate zoom position of the zoom lens of Example 1 Various aberration diagrams at the telephoto end of the zoom lens of Example 1 Various aberration diagrams at the wide-angle end of the zoom lens of Example 2 Various aberration diagrams at the intermediate zoom position of the zoom lens of Example 2 Various aberration diagrams at the telephoto end of the zoom lens of Example 2 Lens sectional view at the wide-angle end of the zoom lens according to Embodiment 3 Various aberration diagrams at the wide-angle end of the zoom lens of Example 3 Various aberration diagrams at the intermediate zoom position of the zoom lens of Example 3 Various aberration diagrams at the telephoto end of the zoom lens of Example 3 Schematic diagram of the main part of a digital still camera

Explanation of symbols

L1 1st lens group L2 2nd lens group L3 3rd lens group L4 4th lens group SP stop FP flare stop IP image surface d d line g g line ΔM meridional image surface ΔS sagittal image surface G glass block

Claims (11)

In order from the object side to the image side, there are a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a rear group. In the zoom lens in which the lens group on the most image side is a lens group having a positive refractive power, and the first to third lens groups move during zooming,
The most image-side lens group in the rear group has an Abbe number of νd and a partial dispersion ratio of θgf.
νd> 75
0.53 <θgf <0.545
A positive lens that satisfies the following conditions:
When the focal lengths at the wide-angle end and the telephoto end of the entire system are fw and ft, respectively, and the focal length of the second lens group is f2.
1.1 <| f2 / fw | <1.8
ft / fw> 4.0
A zoom lens characterized by satisfying the following conditions:   The zoom lens according to claim 1, wherein the rear group includes a fourth lens group having a negative refractive power and a fifth lens group having a positive refractive power in order from the object side to the image side.   The zoom lens according to claim 1, wherein the rear group includes a fourth lens group having a positive refractive power.   During zooming, the second lens group moves to the image side at the telephoto end compared to the wide-angle end, and the third lens group moves to be positioned on the object side at the telephoto end compared to the wide-angle end. The zoom lens according to claim 1, 2 or 3. When zooming from the wide-angle end to the telephoto end, the maximum movement amount in the optical axis direction of the third lens group is M3.
0.1 <| M3 | / fw <1.0
The zoom lens according to claim 1, wherein the following condition is satisfied. When zooming from the wide-angle end to the telephoto end, the maximum movement amount in the optical axis direction of the first lens group is M1,
1.1 <| M1 | / fw <2.5
The zoom lens according to claim 1, wherein the following condition is satisfied.   7. The zoom lens according to claim 1, wherein the most image side lens group in the rear group is a lens group that moves during focusing.   8. The zoom lens according to claim 1, further comprising an aperture stop that moves integrally with the third lens group during zooming. 9. When the focal length of the most image side lens unit in the rear group is fR,
2.0 <fR / fw <4.8
The zoom lens according to claim 1, wherein the following condition is satisfied.   The zoom lens according to claim 1, wherein the zoom lens is an optical system for forming an image on a solid-state imaging device.   An image pickup apparatus comprising: the zoom lens according to claim 1; and a solid-state image pickup device that receives an image formed by the zoom lens.