JP4323796B2 - Zoom lens and imaging apparatus having the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a zoom lens and an image pickup apparatus having the same, and is suitable for, for example, a digital camera, a video camera, and a silver salt photographic camera.
[0002]
[Prior art]
Four lens groups of 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 fourth lens group having a positive refractive power in order from the object side. There is known a zoom lens that performs zooming by moving the first, second, third, and fourth lens groups (for example, Patent Documents 1 to 3).
[0003]
A zoom lens is also known in which the lens configuration of the third lens group is composed of a plurality of lenses with a large air gap in the above-described four-group zoom lens (for example, Patent Documents 4 and 5).
[0004]
In addition, as a means for achieving a reduction in the total lens length and a reduction in the front lens diameter, 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. (For example, Patent Documents 6 and 7).
[0005]
In general, a rear focus type zoom lens has a smaller effective diameter of the first lens unit than a zoom lens that focuses by moving the first lens unit, making it easy to reduce the size of the entire lens system. In particular, close-up photography is facilitated, and the small and lightweight lens group is moved, so that the driving force of the lens group is small and rapid focusing is possible.
[Patent Document 1]
JP-A-8-50244 [Patent Document 2]
US Pat. No. 4,632,519 [Patent Document 3]
JP 2001-194586 A [Patent Document 4]
JP 2001-242379 A [Patent Document 5]
JP 2001-356269 A [Patent Document 6]
JP-A-11-305124 [Patent Document 7]
Japanese Patent Laid-Open No. 10-62687
[Problems to be solved by the invention]
In the zoom lens disclosed in Japanese Patent Application Laid-Open No. 8-50244, the third lens group is configured as a single positive lens, and a part of the zooming action is partially performed by the movement of the third lens group. In this case, the aberration variation of the third lens group becomes a problem.
[0007]
In U.S. Pat. No. 4,632,519, the zoom ratio is about 5.7, and the distance between the third lens group and the fourth lens group decreases from the wide-angle end to the telephoto end, so the zooming action of the third lens group is weak. When the zoom ratio is increased by 6 times or more, the total lens length at the telephoto end increases, and there is a problem in miniaturization.
[0008]
In Japanese Patent Laid-Open Nos. 2001-242379 and 2001-356269, the zoom ratio is about 3, and the first lens group is a single positive lens. There is a problem that it is difficult to cancel aberration fluctuations occurring in one group with another lens group.
[0009]
The present invention achieves downsizing of the entire lens length by appropriately setting the moving amount of each lens unit and the refractive power of each lens unit during zooming, and is excellent over the entire zooming range from the wide-angle end to the telephoto end. An object of the present invention is to provide a zoom lens having optical performance and an image pickup apparatus having the same.
[0010]
[Means for Solving the Problems]
The zoom lens of the present 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 fourth lens having a positive refractive power. And the distance between the first lens group and the second lens group at the telephoto end is larger than that at the wide-angle end, the distance between the second lens group and the third lens group is small, and the third lens group and the second lens group In a zoom lens that performs zooming by moving each lens group so that the interval between the four lens groups is large,
The first lens group has one or more positive lenses and one negative lens, and the third lens group has a positive refractive power third a lens group and a positive refractive power third b with the widest air gap. The third lens group includes two positive lenses, and the distance on the optical axis from the most object-side lens surface to the most image-side lens surface of the third-a lens group is D3a, 3b lens group is composed of one positive lens, D3b a distance on the optical axis to the lens surface or al image side lens surface of the object side of the positive lens, said 3a lens group and said 3b lens Where d is the air spacing, f3a and f3b are the focal lengths of the 3a lens group and the 3b lens group, and ν3b is the Abbe number of the material of the positive lens of the 3b lens group,
(0.6 × D3b) <d <D3a
0.7 <f3b / f3a <1.3
75 <ν3b
It is characterized by satisfying.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of a zoom lens and an imaging apparatus having the same according to the present invention will be described.
[0012]
FIG. 1 is an explanatory diagram of the paraxial refractive power arrangement of the zoom lens according to the present invention. 2 is a cross-sectional view of a main part of the zoom lens according to the first embodiment of the present invention, and FIGS. 3 to 5 are aberration diagrams at the wide angle end, the intermediate focal length, and the telephoto end of the zoom lens according to the first embodiment of the present invention.
[0013]
6 is a cross-sectional view of a main part of a zoom lens according to Embodiment 2 of the present invention, and FIGS. 7 to 9 are aberration diagrams at the wide-angle end, intermediate focal length, and telephoto end of the zoom lens according to Embodiment 2 of the present invention.
[0014]
FIG. 10 is a cross-sectional view of a main part of a zoom lens according to Embodiment 3 of the present invention, and FIGS. 11 to 13 are aberration diagrams at the wide-angle end, intermediate focal length, and telephoto end of the zoom lens according to Embodiment 3 of the present invention.
[0015]
FIG. 14 is a cross-sectional view of a main part of the zoom lens of Reference Example 1 of the present invention, and FIGS. 15 to 17 are aberration diagrams at the wide angle end, intermediate focal length, and telephoto end of the zoom lens of Reference Example 1 of the present invention.
[0016]
18 is a cross-sectional view of a main part of a zoom lens according to Embodiment 4 of the present invention, and FIGS. 19 to 21 are aberration diagrams at the wide-angle end, intermediate focal length, and telephoto end of the zoom lens according to Embodiment 4 of the present invention.
[0017]
FIG. 22 is a schematic view of the imaging apparatus of the present invention.
[0018]
In the lens cross-sectional views of the zoom lens according to each embodiment, L1 is a first lens group having a positive refractive power, and L2 is a second lens group having a negative refractive power. L3 is a third lens unit having a positive refractive power, and includes a third a lens unit L3a having a positive refractive power and a third b lens unit L3b having a positive refractive power with the widest air interval. L4 is a fourth lens unit having a positive refractive power. 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 such as a CCD sensor or a CMOS sensor is located.
[0019]
In the aberration diagrams, d and g are d-line and g-line, ΔM and ΔS are meridional image surface, sagittal image surface, and lateral chromatic aberration are represented by g-line.
[0020]
In each embodiment, each lens group is moved as indicated by an arrow during zooming from the wide-angle end to the telephoto end. Note that the wide-angle end and the telephoto end are zoom positions when the zooming lens groups are positioned at both ends of a range in which the lens group can be moved in the optical axis direction.
[0021]
In the first to fourth embodiments, the distance between the first lens unit L1 and the second lens unit L2 at the telephoto end is larger than that at the wide-angle end, the interval between the second lens unit L2 and the third lens unit L3 is small, and the third lens unit. Each lens unit is moved and zoomed so that the distance between L3 and the fourth lens unit L4 is increased.
[0022]
Specifically, during zooming from the wide-angle end to the telephoto end, the first lens unit L1 moves to the object side along a part of a locus convex to the image side. By moving the first lens unit L1 during zooming, the total lens length at the wide-angle end is shortened to reduce the size in the optical axis direction. Further, by shortening the distance between the first lens unit L1 and the stop SP on the wide angle side, the effective diameter of the first lens unit L1 is reduced, and the front lens diameter is reduced.
[0023]
The second lens unit L2 is moved along a locus convex toward the image surface side or linearly toward the image side.
[0024]
In addition, the third lens unit L3 is moved from the wide-angle end toward the telephoto end toward the object side, and the distance between the third lens unit L3 and the fourth lens unit L4 is larger at the telephoto end than at the wide-angle end. As a locus, the third lens unit L3 is made to share the zooming action. As a result, the zooming effect due to the change in the distance between the first lens group L1 and the second lens group L2 can be weakened, and therefore the distance between the first lens group L1 and the second lens group L2 at the telephoto end can be shortened. As a result, the total lens length is shortened on the telephoto side, and the front lens diameter is reduced.
[0025]
It should be noted that the aperture stop SP may be moved integrally with the third lens unit L3 during zooming or may be moved separately. When integrated, the number of movable lens groups can be reduced, and the mechanical structure can be simplified. In addition, when the lens is moved separately from the third lens unit L3, it is easy to reduce the front lens diameter particularly when the lens is moved along a convex locus on the object side.
[0026]
The fourth lens unit L4 is moved along a convex locus toward the object side or toward the image side to correct the image plane variation due to zooming.
[0027]
In each embodiment, the third-a lens unit L3a is composed of two positive lenses and two negative lenses. Specifically, in order from the object side to the third lens unit L3, a first cemented lens in which a positive lens having a convex surface facing the object side and a negative lens having a concave surface facing the image side are cemented, and a negative lens and a positive lens. It consists of a cemented second cemented lens and a positive lens. Here, the partial system consisting of the first and second cemented lenses constitutes the third-a lens unit L3a, and the partial system consisting of the remaining one positive lens constitutes the third-b lens unit L3b, and the third-a lens unit L3a and the third-b lens. The third b lens unit L3b is moved away from the stop SP by a certain distance between the units L3b.
[0028]
When the stop SP moves during zooming, the exit pupil changes easily. In particular, when the stop SP moves toward the object side for zooming from the wide-angle end to the telephoto end, the exit pupil changes from minus to plus. It is easy to happen. The third lens unit L3b is arranged close to the fourth lens unit L4 at the wide-angle end, and has an action of moving the exit pupil away from the image plane by the synthesis system of the third lens unit L3b and the fourth lens unit L4. At the telephoto end, the third lens unit L3 moves toward the object side, so that the third lens unit L3b is separated from the image plane, and the fourth lens unit L4 is mainly responsible for moving the exit pupil away from the image plane. . In this way, the movement of the exit SP due to the movement of the stop SP is canceled by providing an action of moving the exit pupil of the third lens group L3b away from the zoom position on the wide angle side. As a result, even when the aperture stop SP is moved during zooming, the variation of the exit pupil is small, and the entire zooming area is obtained when the zoom lens of each embodiment is applied to an imaging device using a solid-state imaging device in which microlenses are arranged in pixel units. Can reduce shading.
[0029]
The third-a lens unit L3a is composed of two sets of cemented lenses to correct various aberrations satisfactorily. When the third lens unit L3 is moved to share the magnification, it is necessary to satisfactorily correct various aberrations generated in the third lens unit L3 including the fluctuation component due to the magnification. When the lateral magnification of the third lens unit L3 is close to the same magnification, it is easy to correct various aberrations in a balanced manner by providing symmetry to the third-a lens unit L3a. A triplet is a representative example of a symmetrical lens arrangement, but in each embodiment, the negative and positive refractive powers of the triplet are divided into two components to increase the degree of freedom of aberration correction, thereby providing spherical aberration and coma aberration. Various aberrations such as field curvature are corrected more satisfactorily.
[0030]
In addition, the first lens unit L1 includes at least one positive lens and one negative lens to reduce fluctuations in chromatic aberration during zooming. In addition, when the refractive power is shared by using two or more positive lenses, spherical aberration on the telephoto side and on-axis secondary spectrum can be reduced.
[0031]
In an optical system that requires high resolution, such as a digital camera using a high-pixel solid-state image pickup device or a photographing lens for a video camera, it is necessary to sufficiently correct the variation in lateral chromatic aberration accompanying zooming. For this purpose, the second lens unit L2 is configured to have three or more negative lenses and one or more positive lenses.
[0032]
When only two negative lenses are used, if the refractive power of the second lens unit L2 is increased to reduce the amount of movement of the first lens unit L1 and the second lens unit L2 in order to shorten the total lens length, the lateral chromatic aberration will be reduced. Correction becomes difficult. The second lens group L2 is composed of, in order from the object side, a meniscus negative lens having a concave surface facing the image surface side, a negative lens, a positive lens having a convex surface facing the object side, and a negative lens. By reducing the symmetry before and after L2, the achromatic effect of the principal point is enhanced and the lateral chromatic aberration is effectively corrected.
[0033]
In each embodiment, focusing is performed by the fourth lens unit L4 or the third b lens unit L3b. When focusing with the fourth lens unit L4, a relatively small and light lens unit is moved as compared with the front lens focus, so that the driving force of the lens unit is small, and quick focusing can be performed. There is a point that compatibility with is good.
[0034]
When focusing with the third lens group L3b, a new driving mechanism is required. However, the distance between the third lens group L3b and the fourth lens group L4 at the wide-angle end is larger than when focusing with the fourth lens group L4. To shorten the overall lens length. In addition, it is possible to reduce the size of the photographing apparatus by the retracting mechanism by reducing the interval between the lens groups when not photographing. When the third b lens unit L3b has a moving mechanism, the third b lens unit L3b is retracted toward the object side to be retracted, and the retractable length can be further shortened.
[0035]
In addition, when the zoom lens of each embodiment is applied to an imaging apparatus, a parallel plate-shaped optical filter may be disposed between the 3a lens unit L3a and the 3b lens unit L3b. In this way, there is an advantage that the space of the 3a lens unit L3a and the 3b lens unit L3b is used more and it is not necessary to provide another space for arranging the filter. As the optical filter, an ND filter for attenuating the amount of light, an infrared cut filter for absorbing or reflecting near-infrared light, and the like can be applied. In either case, the lens may be fixed between the third-a lens unit L3a and the third-b lens unit L3b, but may be configured so that it can be inserted into and removed from the optical path. The ND filter is normally disposed in the vicinity of the aperture stop SP. However, if the ND filter is disposed between the third lens unit L3a and the third b lens unit L3b, the second lens unit L2 and the third lens unit L3 at the zoom position at the telephoto end correspondingly. This is advantageous in terms of shortening the overall lens length. The infrared cut filter is usually disposed between the photographing lens and the solid-state image sensor. However, if the infrared cut filter is disposed between the 3a lens group L3a and the 3b lens group L3b, the effective range of the light beam is reduced, so that the outer dimension of the filter is small. Can be In particular, when the configuration is detachable, the entire imaging apparatus can be reduced in size. In addition, since the distance between the 3a lens unit L3a and the 3b lens unit L3b is relatively afocal, variation in focus during insertion and removal is reduced.
[0036]
In each embodiment, the distance on the optical axis from the most object-side lens surface of the 3a lens unit L3a to the most image-side lens surface is D3a, and the distance from the most object-side lens surface of the 3b lens unit L3b is the most. The distance on the optical axis to the lens surface on the image side is D3b, the air interval between the 3a lens group L3a and the 3b lens group L3b is d, and the focal length of the 3a lens group L3a and the 3b lens group L3b is f3a, respectively. f3b, the focal length of the first lens unit L1 is f1, the focal length of the entire system at the telephoto end is ft, the most image side lens surface of the second lens unit L2 at the telephoto end, and the most object side of the third lens unit L3 The distance between the lens surfaces is d23, the lateral magnifications at the wide-angle ends of the second lens unit L2 and the third lens unit L3 are β2w and β3w, respectively, and the lateral magnifications at the telephoto end of the second lens unit L2 and the third lens unit L3. Respectively, β2t, β3t, When the ν3b the Abbe number of the single positive lens material 3b lens group L3b,
(0.6 × D3b) <d <D3a (1)
0.7 <f3b / f3a <1.3 (2)
1.0 <f1 / ft <2.5 (3)
0.01 <d23 / ft <0.20 (4)
0.5 <(β3t / β3w) / (β2t / β2w) <1.0 (5)
75 <ν3b (6)
Is satisfied.
[0037]
It is only necessary to satisfy one or more of these conditional expressions, and an effect according to the satisfied conditional expression is obtained.
[0038]
Next, a technical explanation of each conditional expression will be given.
[0039]
Conditional expression (1) is an expression that defines the distance between the third-a lens unit L3a and the third-b lens unit L3b. If the distance between the 3a lens group L3a and the 3b lens group L3b is too large beyond the upper limit, the third lens group L3 moves greatly in the optical axis direction, which is not good. On the other hand, if it is too small beyond the lower limit, the effect of reducing the variation of the exit pupil at the time of zooming by separating the third lens unit L3b is weakened.
[0040]
Conditional expression (2) defines the refractive power ratio of the 3a lens unit L3a and the 3b lens unit L3b. When the focal length of the 3b lens unit L3b is too large with respect to the 3a lens unit L3a exceeding the upper limit, that is, when the refractive power of the 3b lens unit L3b is too weak with respect to the 3a lens unit L3a, the off-axis light beam Is too weak, even if the distance between the 3a lens unit L3a and the 3b lens unit L3b is somewhat deviated, the operation of moving the exit pupil away from the image plane at the wide angle end is weakened. When the refractive power of the 3b lens unit L3b is too strong for the 3a lens unit L3a beyond the lower limit, the share of the 3b lens unit L3b with respect to the zooming action of the third lens unit L3 increases, and the number of constituent lenses Aberration correction is difficult with the 3b lens unit L3b having a small amount. In particular, the Petzval sum becomes too large, making it difficult to correct field curvature.
[0041]
Conditional expression (3) defines the focal length of the first lens unit L1. If the upper limit is exceeded and the focal length of the first lens unit L1 is too long, that is, if the refractive power of the first lens unit L1 is too weak, the total lens length at the telephoto end becomes too long. If the lower limit is exceeded and the focal length of the first lens unit L1 becomes too short, that is, if the refractive power of the first lens unit L1 is too strong, spherical aberration at the telephoto end increases, which is not good.
[0042]
Conditional expression (4) defines the distance between the second lens unit L2 and the third lens unit L3 at the telephoto end. If the distance exceeds the upper limit and the distance is too long, not only the total length of the lens at the telephoto end is increased, but also the distance between the stop SP at the telephoto end and the first lens unit L1 is increased, leading to an increase in the front lens diameter. . If the distance exceeds the lower limit and is too short, it is difficult to dispose the aperture unit between the second lens unit L2 and the third lens unit L3.
[0043]
Conditional expression (5) is an expression that defines the variable magnification sharing of the second lens unit L2 and the third lens unit L3. When the variable magnification share of the third lens unit L3 is excessively large with respect to the second lens unit L2 exceeding the upper limit, spherical aberration, coma aberration, astigmatism, etc. generated in the third lens unit L3 during zooming Aberration variation increases, making it difficult to obtain good optical performance over the entire zoom range. When the zoom ratio of the third lens unit L3 is too small with respect to the second lens unit L2 beyond the lower limit, the distance between the first lens unit L1 and the second lens unit L2 at the telephoto end is widened to change the entire system. It is not good because it is necessary to ensure the magnification ratio and the total lens length becomes large.
[0044]
Conditional expression (6) defines the Abbe number of the material of the positive lens of the 3b lens unit L3b. If the lower limit is exceeded and the Abbe number is too small, the secondary component of chromatic aberration of magnification on the wide angle side becomes too large. This secondary component must be corrected as much as possible in order to suppress the color blur at the periphery when a subject with high contrast is photographed.
[0045]
In each embodiment, it is more preferable to set the conditional expressions (1) to ( 5 ) as follows.
[0046]
(0.65 × D3b) <d <0.8 × D3a (1a)
0.8 <f3b / f3a <1.2 (2a)
1.0 <f1 / ft <2.3 (3a)
0.02 <d23 / ft <0.15 (4a)
0.6 <(β3t / β3w) / (β2t / β2w) <0.9 (5a)
Next, Numerical Examples 1 to 4 and Reference Example 1 corresponding to Embodiments 1 to 4 of the present invention will be described. 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. Further, when k is an eccentricity, B, C, D, and E are aspheric 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 aspheric shape is ,
x = (h ² / R) / [1+ [1− (1 + k) (h / R) ² ] ^1/2 ] + Bh ⁴ + Ch ⁴ + Dh ⁸ + Eh ¹⁰
Is displayed. 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 represents a focal length, Fno represents an F number, and ω represents a half angle of view.
[0047]
In the numerical examples, R26 and R27 are glass blocks such as filters.
[0048]
Table 1 also shows values of exit pupil distances at the wide-angle end and the telephoto end.
[0049]
[Outside 1]
[0050]
[Outside 2]
[0051]
[Outside 3]
[0052]
[Outside 4]
[0053]
[Outside 5]
[0054]
[Table 1]
[0055]
According to the zoom lens of the embodiment described above, the third lens group acts as a front lens group and a rear lens group with a certain air gap therebetween, and the rear lens group of the third lens group acts as a field lens particularly on the wide angle side. By doing so, the exit pupil on the wide-angle side can be moved away from the image plane, the fluctuation of the exit pupil during zooming can be reduced, and a zoom lens with good matching with the solid-state imaging device can be realized in the entire zoom range.
[0056]
Next, an embodiment of a digital still camera (imaging device) including the zoom lenses of Numerical Examples 1 to 4 will be described with reference to FIG.
[0057]
22A is a front view of the digital still camera, and FIG. 22B is a side sectional view. In the figure, 10 is a camera body (housing), 11 is a photographing optical system using any of the zoom lenses of Numerical Examples 1 to 4 , 12 is a finder optical system, 13 is a solid-state imaging such as a CCD sensor or a CMOS sensor. It is an element (photoelectric conversion element). The solid-state imaging device 13 receives an image of the subject formed on the photographing optical system 11 and converts it into electrical information. Image information of the subject converted into electrical information is recorded in a storage unit (not shown).
[0058]
Thus, by applying the zoom lenses of Numerical Examples 1 to 4 to the photographing optical system of a digital still camera, a compact imaging device can be realized.
[0070]
【The invention's effect】
According to the present invention, it is possible to achieve a zoom lens having an excellent optical performance over the entire zooming range from the wide-angle end to the telephoto end and an image pickup apparatus having the same while achieving a reduction in the total lens length.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of a paraxial refractive power arrangement of a zoom lens according to the present invention. FIG. 2 is a lens cross-sectional view at a wide angle end according to Embodiment 1 of the present invention. FIG. 4 is an aberration diagram at an intermediate zoom position of Numerical Example 1 corresponding to Embodiment 1 of the present invention. FIG. 5 is Numerical Example 1 corresponding to Embodiment 1 of the present invention. FIG. 6 is a lens cross-sectional view at the wide-angle end of Embodiment 2 of the present invention. FIG. 7 is an aberration diagram at the wide-angle end of Numerical Example 2 corresponding to Embodiment 2 of the present invention. FIG. 9 is an aberration diagram at the intermediate zoom position of Numerical Example 2 corresponding to Embodiment 2 of the present invention. FIG. 9 is an aberration diagram at the telephoto end of Numerical Example 2 corresponding to Embodiment 2 of the present invention. FIG. 11 corresponds to a third embodiment of the present invention. Aberration diagram at wide-angle end of value example 3 [FIG. 12] Aberration diagram at an intermediate zoom position of numerical example 3 corresponding to embodiment 3 of the present invention [FIG. 13] Numerical operation corresponding to embodiment 3 of the present invention FIG. 14 is a lens cross-sectional view at the wide-angle end of Reference Example 1 of the present invention. FIG. 15 is an aberration diagram at the wide-angle end of Numerical Example 4 corresponding to Reference Example 1 of the present invention. 16 aberration diagrams in the telephoto end according to numerical embodiment 4 corresponding to example 1 of reference example aberration view of an intermediate zoom position of a numerical example 4 corresponding to 1 [17] the present invention of the present invention [18] numerical value corresponding to the exemplary embodiment 4 lens cross section at a wide angle end according to a fourth aberration diagram at the wide-angle end according to numerical embodiment 5 corresponding to embodiment 4 of the 19 present invention Figure 20 invention of the present invention to respond to the fourth embodiment of the aberration diagrams Figure 21 the present invention an intermediate zoom position of the example 5 Main part schematic diagram of an image pickup apparatus of the aberration diagrams at the telephoto end [22] The present invention of a numerical example 5 [Description of symbols]
L1 1st lens group L2 2nd lens group L3 3rd lens group L3a 3a lens group L3b 3b lens group L4 4th lens group 3a ... 3a lens group 3b ... 3b lens group d d line g g line ΔM meridional Image surface ΔS Sagittal image surface SP Aperture IP Imaging surface G Glass block such as CCD force plate and low-pass filter ω Half angle of view Fno F number

Claims (9)

In order from the object side, a first lens unit having a positive refractive power, a second lens unit having a negative refractive power, a third lens unit having a positive refractive power and a fourth lens unit having positive refractive power, the wide-angle end The distance between the first lens group and the second lens group at the telephoto end is large, the distance between the second lens group and the third lens group is small, and the distance between the third lens group and the fourth lens group is large. In the zoom lens where each lens group moves and zooms so that
The first lens group has one or more positive lenses and one negative lens, and the third lens group has a positive refractive power third a lens group and a positive refractive power third b with the widest air gap. The third lens group includes two positive lenses, and the distance on the optical axis from the most object-side lens surface to the most image-side lens surface of the third-a lens group is D3a, 3b lens group is composed of one positive lens, D3b a distance on the optical axis to the lens surface or al image side lens surface of the object side of the positive lens, said 3a lens group and said 3b lens Where d is the air spacing, f3a and f3b are the focal lengths of the 3a lens group and the 3b lens group, and ν3b is the Abbe number of the material of the positive lens of the 3b lens group,
(0.6 × D3b) <d <D3a
0.7 <f3b / f3a <1.3
75 <ν3b
A zoom lens characterized by satisfying The focal length of the first lens group is f1, the focal length of the entire system at the telephoto end is ft, the most image side lens surface of the second lens group and the most object side lens surface of the third lens group at the telephoto end. When the interval of d23 is
1.0 <f1 / ft <2.5
0.01 <d23 / ft <0.20
The zoom lens according to claim 1, wherein: When the lateral magnifications at the wide-angle end of the second lens group and the third lens group are β2w and β3w, respectively, and the lateral magnifications at the telephoto end of the second lens group and the third lens group are β2t and β3t, respectively. ,
0.5 <(β3t / β3w) / (β2t / β2w) <1.0
The zoom lens according to claim 1 , wherein the zoom lens according to claim 1 is satisfied. The zoom lens according to any one of claims 1 to 3 , wherein the third-a lens group includes two positive lenses and two negative lenses. The 3a lens group includes a first cemented lens in which a positive lens having a convex surface directed toward the object side and a negative lens having a concave surface directed toward the image side are cemented in order from the object side, and the negative lens and the positive lens are cemented together. any one of the zoom lens of claims 1 4, characterized in that consists of the second cemented lens. Any one of the zoom lens of claims 1 to 5, and performs focusing by the 3b-th lens group. The zoom lens according to any one of claims 1 to 6 , wherein an optical filter is disposed between the third-a lens group and the third-b lens group. Any one of the zoom lens according to claim 1 to 8, characterized in that an optical system for forming an image on a solid-state imaging device. And any one of the zoom lens of claims 1 to 8, the image pickup apparatus characterized by and an image pickup that images are formed by the zoom lens.