JP4497851B2 - 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 is particularly suitable for a photographing optical system such as a video camera or a digital still camera.
[0002]
[Prior art]
2. Description of the Related Art In recent years, with the enhancement of functions of imaging devices such as video cameras and digital still cameras using solid-state imaging devices, compact and high-resolution zoom lenses are required as imaging optical systems used for them.
[0003]
As a zoom lens that meets these requirements, 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 positive lens having a positive refractive power. The fourth lens group has four lens groups, performs zooming by moving the second lens group, corrects image plane fluctuations accompanying zooming in the fourth lens group, and performs focusing. A rear focus type zoom lens is known (for example, Patent Documents 1 to 3).
[0004]
In general, a rear focus type zoom lens has a smaller effective diameter of the first lens group than a zoom lens that focuses by moving the first lens group, and the entire lens system can be easily downsized. Further, close-up photography is possible, and the relatively small and light lens group is moved, so that the driving force of the lens group is small and quick focusing is possible. In such an optical system, if it is attempted to keep the size down while increasing the zoom ratio, it becomes difficult to correct the variation in lateral chromatic aberration during zooming.
[0005]
On the other hand, a zoom lens in which a negative lens is arranged closest to the image side of the second lens group and has a total of three negative lenses and one positive lens, thereby correcting the chromatic aberration of magnification at the time of zooming. A lens is known (for example, Patent Document 4).
[0006]
There is known a zoom lens that uses a high-dispersion glass material having an Abbe number νd of about 21 as the material of the positive lens of the second lens group (for example, Patent Documents 5 and 6).
[0007]
On the other hand, first, second, third, and fourth lens groups having positive, negative, positive, and positive refractive powers as anti-vibration optical systems having a function (anti-vibration function) for preventing blurring of captured images. In the zoom lens having a four-group configuration, the third lens group is composed of two lens groups having positive and negative refractive powers, and the image group is corrected by vibrating the lens group having positive refractive power. Is known (for example, Patent Document 7). Further, in the zoom lens having a four-group configuration including the first, second, third, and fourth lens groups having positive, negative, positive, and positive refractive powers, the entire third lens group is vibrated to correct image blur. (For example, Patent Document 8).
[0008]
Further, in a zoom lens having a four-group configuration including first, second, third, and fourth lens groups having positive, negative, positive, and positive refractive powers, the aperture is moved to the first, second, and fourth lens groups. There is known a zoom lens that performs zooming and corrects image blur by vibrating the entire third lens group (for example, Patent Document 9).
[Patent Document 1]
Japanese Patent Laid-Open No. 6-34882 [Patent Document 2]
JP-A-8-292369 [Patent Document 3]
JP-A-11-305124 [Patent Document 4]
JP-A-8-82743 [Patent Document 5]
JP-A-8-160299 [Patent Document 6]
JP 2000-121941 A [Patent Document 7]
JP 7-128619 A [Patent Document 8]
JP-A-7-199124 [Patent Document 9]
Japanese Patent Laid-Open No. 2001-66500
[Problems to be solved by the invention]
In recent years, zoom lenses for use in digital cameras, video cameras, and the like have been demanded to have high optical performance and a small lens system as the image pickup apparatus becomes smaller and the number of pixels of the image pickup element increases. Further, it has been desired to record a still image with a high image quality with a video camera, and a small lens system is required while having high optical performance.
[0010]
In Japanese Patent Laid-Open No. 8-82743, the second lens group is composed of four lenses, which is advantageous in terms of aberration correction. However, since the number of lenses is four, the total length of the lens is increased accordingly. Tend.
[0011]
In Japanese Patent Laid-Open No. 8-160299, although the number of lenses in the second lens group is small, the entire optical system has a large number of lenses, and the entire lens system tends to be large. In Japanese Patent Laid-Open No. 2000-121941, the second lens group is composed of a cemented lens composed of a positive lens and a negative lens, so that the degree of freedom in design tends to decrease.
[0013]
An object of the present invention is to provide a zoom lens that has a high zoom ratio with a simple configuration and has a high zoom ratio that can sufficiently cope with, for example, a solid-state imaging device having a high pixel.
[0014]
[Means for Solving the Problems]
The zoom lens according to 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 positive lens having a positive refractive power. The zoom lens includes a fourth lens group. The zoom lens moves to the object side and the second lens group moves to the image side during zooming from the wide-angle end to the telephoto end. The lens group includes, in order from the object side to the image side, a negative lens 21 having a larger absolute value of refractive power on the image side lens surface than on the object side lens surface, and a negative lens 22 having a concave lens surface on the object side. The negative lens 22 is spaced from the negative lens 22 and the object-side lens surface is formed of a convex positive lens 23. The positive lens 23 has an Abbe number of ν23, and the negative lens 21 and the negative lens 22 Refractive index of the material is N21 and N22, respectively, from the wide-angle end to the telephoto end. The amount of movement of the first lens group and the second lens group at the timing each M1, M2, respectively the focal length of the entire system at the wide Kakutan the telephoto end fw, ft, the focal length of the second lens group and f2 and when,
ν23 <20.0
1.65 <(N21 + N22) / 2
0.03 <| M1 / M2 | <0.4
A zoom lens characterized by satisfying the following conditions:
[Expression 2]
It is characterized by satisfying the following conditions.
[0015]
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.
[0016]
FIG. 1 is a lens cross-sectional view at the wide-angle end of a zoom lens according to Reference Example 1 of the present invention. FIGS. 2, 3, and 4 are aberration diagrams at the wide-angle end, intermediate zoom position, and telephoto end of the zoom lens according to Reference Example 1, respectively. It is.
[0017]
FIG. 5 is a lens cross-sectional view at the wide-angle end of the zoom lens of Reference Example 2 according to the present invention, and FIGS. 6, 7, and 8 are aberration diagrams at the wide-angle end, intermediate zoom position, and telephoto end of the zoom lens of Reference Example 2, respectively. It is.
[0018]
Figure 9 is a lens cross sectional view at the wide-angle end of the zoom lens according to the first embodiment of the present invention, FIGS. 10, 11 and 12 respectively, at the wide angle end of the zoom lens according to the first embodiment, the intermediate zoom position, the telephoto end It is.
[0019]
FIG. 13 is a lens cross-sectional view at the wide-angle end of the zoom lens according to Embodiment 2 of the present invention, and FIGS. 14, 15, and 16 are aberration diagrams at the wide-angle end, the intermediate zoom position, and the telephoto end of Embodiment 2 , respectively. It is.
[0020]
FIG. 17 is a schematic diagram of a main part of a video camera (imaging device) including the zoom lens of the present invention.
[0021]
The zoom lens of each embodiment and each reference example is a photographing lens system used in an imaging apparatus. In the lens cross-sectional views, the left side is the subject side (front) and the right side is the image side (rear). In the lens cross-sectional view, L1 is a first lens group having a positive refractive power (optical power = reciprocal of focal length), L2 is a second lens group having a negative refractive power, and L3 is a third lens group having a positive refractive power. , L4 is a fourth lens unit having a positive refractive power. SP is an aperture stop, which is located on the object side of the third lens unit L3. FP is a flare stop, which is disposed on the image side of the third lens unit L3.
[0022]
G is an optical block corresponding to an optical filter, a face plate, or the like. IP is an image plane, and when used as a photographing optical system for a video camera or a digital still camera, when the imaging surface of a solid-state imaging device (photoelectric conversion device) such as a CCD sensor or a CMOS sensor is a silver salt film camera Corresponds to the film surface.
[0023]
In the aberration diagrams, d and g are d-line and g-line, respectively, ΔM and ΔS are meridional image plane, sagittal image plane, and lateral chromatic aberration are represented by g-line.
[0024]
In the following embodiments and reference examples , the wide-angle end and the telephoto end are zoom positions when the zoom lens unit is positioned at both ends of a range in which the zoom lens group can move on the optical axis.
[0025]
In Reference Example 1 shown in FIG. 1, when zooming from the wide-angle end to the telephoto end, as shown by the arrow, the second lens unit L2 is moved to the image side to perform zooming, and the image plane variation caused by zooming is fourth. The lens unit L4 is moved and corrected so as to have a convex locus on the object side.
[0026]
In addition, a rear focus type that performs focusing by moving the fourth lens unit L4 on the optical axis is employed. A solid curve 4a and a dotted curve 4b relating to the fourth lens unit L4 are movement trajectories for correcting image plane fluctuations accompanying zooming when focusing on an object at infinity and an object at close distance, respectively. Thus, by making the fourth lens unit L4 a locus convex toward the object side, the space between the third lens unit L3 and the fourth lens unit L4 can be effectively used, and the entire lens length can be shortened effectively. Has been achieved.
[0027]
In Reference Example 1, for example, 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. The first lens unit L1 and the third lens unit L3 are fixed in the optical axis direction for zooming and focusing, but may be moved as necessary for aberration correction.
[0028]
In Reference Example 2 of FIG. 5, there is a part of a locus that is convex on the second lens unit L2 toward the image side and the third lens unit L3 toward the object side as indicated by the arrows during zooming from the wide-angle end to the telephoto end. The fourth lens unit L4 is also moved while having a part of a convex locus on the object side.
[0029]
In addition, a rear focus type that performs focusing by moving the fourth lens unit L4 on the optical axis is employed. A solid curve 4a and a dotted curve 4b relating to the fourth lens unit L4 indicate the movement trajectories when focusing on an object at infinity and an object at close distance, respectively.
[0030]
In Reference Example 2, for example, when focusing from an infinitely distant object to a close object at the telephoto end, the fourth lens unit L4 is extended forward as indicated by an arrow 4c. The first lens unit L1 is fixed in the optical axis direction for zooming and focusing, but may be moved as necessary for aberration correction.
[0031]
The aperture stop SP is disposed between the second lens unit L2 and the third lens unit L3, and achieves simplification of the mechanical structure by moving together with the third lens unit L3 during zooming.
[0032]
In Reference Example 2, in particular, the third lens unit L3 is moved to the object side during zooming from the wide-angle end to the intermediate zoom position, thereby speeding up the change in focal length on the wide-angle side and reducing the front lens diameter. ing. In addition, since the aperture stop SP moves to the object side, an increase in the front lens diameter for securing the lower light beam in the intermediate zoom range can be reduced, thereby further reducing the front lens diameter.
[0033]
In addition, since the fourth lens unit L4 is moved so that the third lens unit L3 is also located on the object side at the zoom position where the fourth lens unit L4 moves closest to the object side, the third lens unit L3 and the fourth lens unit L4 are moved. The distance can be secured, the distance between the third lens unit L3 and the fourth lens unit L4 at the wide-angle end can be shortened, and the total lens length is shortened.
[0034]
In Embodiments 1 and 2 of FIGS. 9 and 13, as zoomed from the wide-angle end to the telephoto end, the first lens unit L1 is directed to the object side, the second lens unit L2 is moved to the image side, and the third lens, as indicated by arrows. The group L3 is moved while having a part of the convex locus on the object side, and the fourth lens group L4 is moved while having a part of the convex locus on the object side. In addition, a rear focus type that performs focusing by moving the fourth lens unit L4 on the optical axis is employed.
[0035]
A solid curve 4a and a dotted curve 4b relating to the fourth lens unit L4 indicate the movement trajectories when focusing on an object at infinity and an object at close distance, respectively.
[0036]
In Embodiments 1 and 2 , for example, 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.
[0037]
The aperture stop SP is disposed between the second lens unit L2 and the third lens unit L3, and moves mechanically with the third lens unit L3, thereby simplifying the mechanical structure.
[0038]
In Embodiments 1 and 2, as compared with Reference Example 2, the first lens unit L1 is moved during zooming, so that the total lens length at the wide-angle end is reduced and the front lens diameter is reduced.
[0039]
Hereinafter, matters common to the zoom lenses of the embodiments (Embodiments 1 and 2 ) will be described.
[0040]
In each embodiment, the second lens unit L2 is moved in order from the object side to the image side, and the meniscus negative lens 21 having a concave image side (the image side surface of the lens 21 has a refractive power compared to the object side surface). The absolute lens has a large negative value), and both lenses are constituted by a negative lens 22 having a concave surface and a positive lens 23 having a convex surface on the object side, and a high dispersion glass material is used for the positive lens 23.
[0041]
In a zoom lens having a four-group configuration that requires a small size, a high zoom ratio, and high performance, the second lens unit L2 is configured by a four-lens configuration of three negative lenses and one positive lens, or a larger number of lenses. It is common. On the other hand, in the zoom lens according to each embodiment, a glass material having a large dispersion is used for the positive lens 23 of the second lens unit L2, and thus the chromatic aberration that occurs while the second lens unit L2 has a total of three lenses. And corrects astigmatism and distortion fluctuations during zooming to achieve good optical performance.
[0042]
In each embodiment, a part or all of the third lens unit L3 is moved (shifted) so as to have a component perpendicular to the optical axis so as to correct image blur when the entire optical system vibrates. Yes. As a result, image stabilization is performed without newly adding an optical member such as a variable apex angle prism or a lens group for image stabilization, and the entire optical system is prevented from being enlarged. In addition, in order to achieve a reduction in the change in the amount of light when correcting the blur of the photographed image, the peripheral light amount is relatively increased by limiting the center light flux by reducing the aperture diameter at the telephoto side during zooming. I am doing so.
[0043]
Further, by introducing an aspherical surface into the third lens unit L3, the spherical aberration at the wide-angle end is corrected well and high optical performance is obtained while shortening the total lens length.
[0044]
Also, by reducing the number of lenses in the entire optical system excluding low-pass filters and infrared cut filters (that is, excluding optical members having no refractive power) to 11 or less, miniaturization and high performance are achieved. Yes.
[0045]
Next, features of the lens configuration of each embodiment will be described.
[0046]
In the zoom lenses of Embodiments 1 and 2 , when the Abbe number of the material of the positive lens 23 is ν23 and the refractive indexes of the materials constituting the negative lens 21 and the negative lens 22 are N21 and N22, respectively.
ν23 <20.0 (1)
1.65 <(N21 + N22) / 2 (2)
Is satisfied.
[0047]
Conditional expression (1) is for effectively correcting chromatic aberration with a single positive lens. If the Abbe number increases beyond the upper limit of conditional expression (1), the achromatic effect of the second lens unit L2 becomes weak, making it difficult to achieve both high zoom ratio and high performance with a small number of lenses. Become. Further, when the material of the positive lens 23 is made highly dispersed, the refractive index generally increases. At this time, the Petzval sum increases in the positive direction and the sagittal image plane becomes over. In order to reduce the deterioration of the optical performance due to this influence, it is effective to increase the refractive index of the material of the negative lenses 21 and 22 so as to satisfy the conditional expression (2). If the lower limit of conditional expression (2) is exceeded and the refractive index of the materials 21 and 22 of the negative lens decreases, the Petzval sum increases in the negative direction, which makes it difficult to correct sagittal curvature of field.
[0048]
More desirably, the conditional expression (1) is expressed as ν23 <19 (1a).
It is good to do. Conditional expression (2) is changed to 1.72 <(N21 + N22) / 2 (2a).
It is good to do.
[0049]
If the refractive indexes of the materials 21 and 22 of the negative lens are set in the range of the conditional expression (2a), it becomes easier to correct the curvature of field.
[0050]
In the zoom lenses of Embodiments 1 and 2, when the focal lengths of the second lens unit L2 and the positive lens 23 in the second lens unit L2 are f2 and f23, respectively.
1.8 <| f23 / f2 | <3.7 (3)
Is satisfied.
[0051]
Conditional expression (3) is mainly for correcting fluctuations in various aberrations such as field curvature and astigmatism while correcting fluctuations in chromatic aberration during zooming.
[0052]
Not good when exceeding the lower limit of the condition (3) refraction power of positive lens 23 is stronger astigmatism at the wide-angle end increases in the negative direction (insufficient correction). On the other hand, if the refractive power of the positive lens 23 becomes weaker than the upper limit, it is not good because fluctuations in chromatic aberration, particularly fluctuations in lateral chromatic aberration, are difficult to correct.
[0053]
More preferably, the numerical range of conditional expression (3) is set as follows.
[0054]
2.0 <| f23 / f2 | <3.0 (3a)
In the zoom lenses of Embodiments 1 and 2 , when the curvature radii of the object side surface and the image side surface of the positive lens 23 in the second lens unit L2 are R23a and R23b, respectively,
0.8 <(R23b + R23a) / (R23b−R23a) <2.0 (4)
Is satisfied.
[0055]
Conditional expression (4) is for satisfactorily correcting various aberrations over the entire zoom range by appropriately setting the shape of the positive lens 23.
[0056]
If the lower limit of conditional expression (4) is exceeded, astigmatism at the wide-angle end increases in the negative direction, which is not good. On the other hand, if the upper limit is exceeded, astigmatism at the wide-angle end increases in the positive direction (overcorrection), which is not good.
[0057]
More preferably, conditional expression (4)
1.0 <(R23b + R23a) / (R23b−R23a) <1.7 (4a)
If it is set in the range, better optical performance can be achieved.
[0058]
The focal length f2 of the second lens unit L2 of the zoom lens of Embodiments 1 and 2 is set so that the focal lengths of the entire system at the wide-angle end and the telephoto end are fw and ft, respectively.
[0059]
[Expression 2]
[0060]
Is satisfied.
[0061]
Conditional expression (5) relates to the refractive power (the reciprocal of the focal length) of the second lens unit L2 and is intended to achieve a reduction in the overall optical length while mainly maintaining optical performance.
[0062]
When the refractive power of the second lens unit L2 increases beyond the lower limit of conditional expression (5), the amount of movement of the second lens unit L2 during zooming decreases, but the Petzval sum increases in the negative direction as a whole. This is not good because it is difficult to correct curvature of field. On the contrary, if the upper limit of conditional expression (5) is exceeded, the amount of movement of the second lens unit L2 during zooming becomes large, and the entire lens system is not downsized.
[0063]
More preferably, conditional expression (5)
[0064]
[Equation 3]
[0065]
It is good to do.
[0066]
In the zoom lenses of Embodiments 1 and 2 , when the curvature radii of the object side surface and the image side surface of the negative lens 22 in the second lens unit L2 are R22a and R22b, respectively,
[Expression 2]
Is satisfied.
[0067]
Conditional expression (6) relates to the lens shape of the negative lens 22 and is mainly for satisfactorily correcting astigmatism. If the lower limit of conditional expression (6) is exceeded, astigmatism at the wide-angle end increases in the positive direction, which is not good. Conversely, if the upper limit is exceeded, astigmatism at the wide-angle end increases in the negative direction, which is not good.
[0068]
More preferably, conditional expression (6) is
−0.15 <(R22b + R22a) / (R22b−R22a) <0.3
... (6a)
It is good to do.
[0069]
In the zoom lenses of Embodiments 1 and 2, the amount of movement of the second lens unit L2 required for zooming from the wide-angle end to the telephoto end is M2, and the third lens unit L3 is closest to the object side during zooming from the wide-angle end to the telephoto end. When the moving amount to the moving position is M3 (however, the sign of the moving amount is positive when moving to the image side and negative when moving to the object side)
0.1 <| M3 / M2 | <0.3 (7)
Is satisfied.
[0070]
Conditional expression (7) is a preferable condition when the third lens unit L3 moves during zooming (Embodiments 1 and 2 ). If the lower limit of conditional expression (7) is exceeded and the amount of movement of the third lens unit L3 becomes small, the front lens diameter cannot be sufficiently reduced. Conversely, if the amount of movement of the third lens unit L3 is too large with respect to the second lens unit L2, the total amount of lens movement necessary for zooming becomes large, which is disadvantageous for shortening the overall lens length. .
[0071]
More preferably, conditional expression (7)
0.12 <| M3 / M2 | <0.2 (7a)
It is good to do.
[0072]
In the zoom lenses of Embodiments 1 and 2, the amount of movement of the first lens unit L1 and the second lens unit L2 required for zooming from the wide-angle end to the telephoto end is M1, M2 (however, the sign of the amount of movement moves to the image side) When moving to the object side and negative when moving to the object side)
0.03 <| M1 / M2 | <0.4 (8)
Is satisfied.
[0073]
Conditional expression (8) is a preferable condition when the first lens unit L1 moves during zooming (Embodiments 3 and 4). If the lower limit of conditional expression (8) is exceeded and the amount of movement of the first lens unit L1 becomes small, the total lens length at the wide angle end is not shortened, and the lens diameter on the object side is insufficiently reduced from the second lens unit L2. become. Conversely, when the amount of movement of the first lens unit L1 exceeds the upper limit, the cam angle in the cam ring for providing the cam for moving each lens unit becomes strict, and the actuator for moving the lens unit This increases the load on the lens and increases the front lens diameter to ensure a sufficient amount of peripheral light at the telephoto end.
[0074]
More preferably, conditional expression (8)
0.04 <| M1 / M2 | <0.2 (8a)
It is good to do.
[0075]
Hereinafter, Numerical Examples 1 to 4 corresponding to Reference Examples 1 and 2 and Embodiments 1 and 2 , respectively, are shown. In each numerical example, i indicates the order of the surfaces from the object side, Ri is the radius of curvature of each surface, Di is the member thickness or air space between the i-th surface and the (i + 1) -th surface, Ni and νi are Refractive index and Abbe number for d line are shown. In Numerical Example 1, the five surfaces closest to the image side, and in Numerical Examples 2, 3, and 4, the two surfaces closest to the image are planes corresponding to a crystal low-pass filter, an infrared cut filter, and the like. When the aspherical shape is X with the displacement in the optical axis direction at the position of the height H from the optical axis as a reference with respect to the surface vertex,
[0076]
[Expression 4]
[0077]
It is represented by Where R is a paraxial radius of curvature, k is a conic constant, and A, A ′, B, B ′, C, C ′, D, D ′, and E are aspherical coefficients.
[0078]
[E-X] means “× 10 ^−X ”. f represents a focal length, Fno represents an F number, and ω represents a half angle of view. Table 1 shows the relationship between the above-described conditional expressions and numerical values in the numerical examples.
[0079]
[Outside 1]
[0080]
[Outside 2]
[0081]
[Outside 3]
[0082]
[Outside 4]
[0083]
[Table 1]
[0084]
Next, an embodiment of a video camera using the zoom lens of the present invention as a photographing optical system will be described with reference to FIG.
[0085]
In FIG. 17, 10 is a video camera body, 11 is a photographing optical system constituted by the zoom lens of the present invention, and 12 is a solid-state imaging device (photoelectric conversion) such as a CCD sensor or a CMOS sensor that receives a subject image by the photographing optical system 11. (Element), 13 is a memory for storing information corresponding to the subject image photoelectrically converted by the image sensor 12, and 14 is a finder for observing the subject image displayed on a display element (not shown). The display element is constituted by a liquid crystal panel or the like, and a subject image formed on the image sensor 12 is displayed.
[0086]
Thus, by applying the zoom lens of the present invention to an imaging apparatus such as a video camera, an imaging apparatus having a small size and high optical performance can be realized.
[0087]
【The invention's effect】
As described above, according to the present invention, it is possible to achieve a zoom lens having a desired zoom ratio and high optical performance with a simple configuration.
[Brief description of the drawings]
[1] in the lens cross-sectional view Figure 2 various aberrations in the wide-angle end of the zoom lens in Example 1 [3] the intermediate zoom position of the zoom lens of Example 1 at the wide-angle end of the zoom lens Example 1 aberration diagrams [4] the wide-angle end of the aberration diagrams [5] lens cross section at a wide angle end in the reference example 2 zoom lens 6 of reference example 2 zoom lens at the telephoto end of the zoom lens example 1 aberration diagrams 7 aberration diagrams [9] embodiment 1 zoom lens at the telephoto end of the aberration diagrams 8 of reference example 2 zoom lens in the intermediate zoom position of the zoom lens of example 2 in various aberrations in the lens sectional view [10] the intermediate zoom position of the aberration diagrams [11] embodiment 1 zoom lens at the wide-angle end of the zoom lens according to the first embodiment at the wide-angle end in FIG. 12 embodiment 1 Aberration diagrams at the telephoto end of the zoom lens 13 aberration diagrams at the wide-angle end of the lens cross section [14] of the second embodiment the zoom lens at the wide-angle end of the zoom lens embodiment 2 [15] Embodiment 2 FIG. 16 is a diagram of various aberrations at the telephoto end of the zoom lens of Embodiment 2. FIG. 17 is a schematic diagram of the main part of the optical apparatus of the present invention.
L1 First lens unit L2 Second lens unit L3 Third lens unit L4 Fourth lens unit SP Aperture stop FP Flare stop G Glass block IP Image surface d d line g g line ΔM Meridional image surface ΔS Sagittal image surface

Claims (9)

In order from the object side to the image side, the lens unit includes 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 group having a positive refractive power. In zooming from the wide-angle end to the telephoto end, the first lens group is moved to the object side, and the second lens group is moved to the image side. The second lens group is moved from the object side. In order toward the image side, the negative lens 21 having a larger refractive power on the image side lens surface than the lens surface on the object side, the negative lens 22 having a concave lens surface on the object side, and the distance from the negative lens 22 And the lens surface of the object side is made up of a convex positive lens 23, the Abbe number of the material of the positive lens 23 is ν23, and the refractive indices of the materials of the negative lens 21 and the negative lens 22 are N21, respectively. , N22, the first in zooming from the wide-angle end to the telephoto end Each M1 the amount of movement of the lens group and the second lens group, M2, when each fw the focal length of the entire system at the wide Kakutan and the telephoto end, ft, the focal length of the second lens group and f2,
ν23 <20.0
1.65 <(N21 + N22) / 2
0.03 <| M1 / M2 | <0.4
A zoom lens characterized by satisfying the following conditions:
A zoom lens characterized by satisfying the following conditions: When the focal lengths of the positive lens 23 and the second lens group are f23 and f2, respectively.
1.8 <| f23 / f2 | <3.7
The zoom lens according to claim 1, wherein the following condition is satisfied. When the curvature radii of the object-side lens surface and the image-side lens surface of the positive lens 23 are R23a and R23b, respectively.
0.8 <(R23b + R23a) / (R23b-R23a) <2.0
The zoom lens according to claim 1, wherein the following condition is satisfied. When the curvature radii of the object-side lens surface and the image-side lens surface of the negative lens 22 are R22a and R22b, respectively.
−0.2 <(R22b + R22a) / (R22b−R22a) <0.4
The zoom lens according to any one of claims 1 to 3 , wherein the following condition is satisfied. The zoom lens according to any one of claims 1 to 4 , wherein the third lens group moves during zooming. In zooming from the wide-angle end to the telephoto end, when the amount of movement from the wide-angle end until the third lens group is closest to the object side is M3,
0.1 <| M3 / M2 | <0.3
The zoom lens according to claim 5 , wherein the following condition is satisfied. The zoom lens according to any one of claims 1 6, wherein the number of lenses having a refractive power is less than 11 sheets in total. Any one of the zoom lens of claim 1, wherein the forming an image on the photoelectric conversion element 7. A zoom lens of any one of claims 1 to 8, the image pickup apparatus characterized by having a photoelectric conversion element for receiving an image formed by the zoom lens.