JP2012083432A - Zoom lens and imaging apparatus having the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a zoom lens which has a large diameter and a wide angle of view, adequately corrects various aberrations depending on chromatic aberration and an aperture diameter, and can obtain high optical performance.SOLUTION: In the zoom lens which includes a first lens group having negative refractive power, a second lens group having positive refractive power, a third lens group having negative refractive power, a fourth lens group having positive refractive power, a fifth lens group having negative refractive power and a sixth lens group having positive refractive power in order from an object side to an image side, and zooms by changing space between the respective lens groups, each of the Abbe's number νd and the partial dispersion ratio θgF of the material of a positive lens constituting the first lens group are appropriately set.

Description

  The present invention relates to a zoom lens and an image pickup apparatus having the same, and is suitable for a photographing system such as a digital camera, a video camera, a silver salt film camera, a surveillance camera, and a TV camera.

  Conventionally, a so-called negative lead type zoom lens in which a lens unit having a negative refractive power precedes (most positioned on the object side) is known. The negative lead type zoom lens can make the close-up shooting distance relatively short, the angle of view is relatively easy, and the back focus is easy to lengthen. For this reason, it is often used as a wide-angle shooting lens for a single-lens reflex camera.

  As a negative lead type zoom lens, there is known a four-unit zoom lens composed of lens groups of negative, positive, negative, and positive refractive power in order from the object side to the image side (Patent Document 1). In this four-group zoom lens, the first lens group and the second lens group as a whole constitute a positive group, and the third lens group and the fourth lens group as a whole constitute a negative group at the telephoto end. Thus, the entire optical system has a so-called telephoto type lens configuration, and a bright F number can be obtained even at the telephoto end.

  Further, as a negative lead type zoom lens, there is known a 6-group zoom lens having a wide angle of view and a high zoom ratio having 6 lens groups of negative, positive, negative, positive, negative and positive in order from the object side to the image side. (Patent Documents 2 and 3). This 6-group zoom lens facilitates a wider angle of view while reducing the effective diameter of the front lens.

JP 2004-212541 A JP 2004-198529 A JP 2006-337647 A

  In general, a negative lead type zoom lens preceded by a lens unit having a negative refractive power is characterized in that a wide angle of view is relatively easy and a long back focus can be easily obtained. However, since the lens configuration of the negative lead type zoom lens is asymmetric with respect to the aperture stop, it is difficult to correct various aberrations, and it is difficult to obtain high optical performance over the entire zoom range. For example, when an attempt is made to increase the aperture ratio, it becomes difficult to correct aberrations and chromatic aberrations depending on the aperture, such as spherical aberration and coma.

  Aberration-dependent aberrations (spherical aberration, coma aberration, etc.) can be easily corrected by using a high refractive index material for the lens group in which the incident height of the axial light beam increases. On the other hand, chromatic aberration (especially axial chromatic aberration) is corrected by using a glass material having a strong anomalous dispersion and a low refractive index in a lens group in which the incident height of the axially high bundle increases. In this way, the use of glass materials in the lens group in which the incident height of the on-axis luminous flux is high is different, so that a large-aperture-ratio zoom lens corrects both aberration and chromatic aberration depending on the aperture such as spherical aberration and coma. It is difficult. In addition, when the angle of view becomes wide with a large aperture ratio, sagittal field curvature (especially field curvature at the periphery of the screen) increases at the wide angle end.

  The sagittal field curvature is largely attributed to the lens shape of the first lens group in which the incident height of the off-axis light beam is high. This aberration can be reduced by using as high a refractive index material as possible for the negative lens in the first lens unit having a negative refractive power. On the other hand, in order to reduce aberration fluctuations due to zooming, it is necessary to reduce the aberration generated in each lens group. For primary achromatization in the first lens group, it is common to use a low dispersion material for the negative lens and a high dispersion material for the positive lens. However, a low dispersion material generally has a low refractive index, and it is difficult to correct both sagittal field curvature and chromatic aberration.

  For the above reasons, in a negative lead type zoom lens, it is particularly necessary to appropriately set the lens configuration of the first lens unit in order to correct chromatic aberration favorably and obtain high optical performance while widening the angle of view. It becomes important.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a zoom lens that can satisfactorily correct various aberrations depending on chromatic aberration and aperture with a large aperture and a wide angle of view, and an imaging apparatus having the same.

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 negative refractive power, a second lens group having a positive refractive power, a third lens group having a negative refractive power, and a positive lens having a positive refractive power. In a zoom lens that includes a fourth lens group, a fifth lens group having a negative refractive power, and a sixth lens group having a positive refractive power, and performs zooming by changing the interval between the lens groups, the first lens group includes: When the Abbe number of the material is νd and the partial dispersion ratio is θgF,
0.02 <θgF−0.6438 + 0.001682 × νd <0.1
And a positive lens that satisfies the following conditional expression.

  According to the present invention, it is possible to obtain a zoom lens that can correct chromatic aberration and various aberrations depending on the aperture with a large aperture and a wide angle of view and obtain high optical performance.

(A), (B), (C) Lens configuration diagrams at the wide-angle end, the intermediate zoom position, and the telephoto end of Numerical Example 1. (A), (B), (C) Aberration diagrams in Example 1 when the object distance is 50 times the focal length at each zoom position Lens configuration diagram at the wide-angle end of Example 2 (A), (B), (C) Aberration diagrams in Example 2 when the object distance is 50 times the focal length at each zoom position Schematic diagram of main parts of an imaging apparatus of the present invention

  Embodiments of a zoom lens and an image pickup apparatus having the same according to the present invention will be described below in detail with reference to the accompanying drawings. 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 negative refractive power, a second lens group having a positive refractive power, a third lens group having a negative refractive power, and a positive lens having a positive refractive power. The lens unit includes a fourth lens group, a fifth lens group having a negative refractive power, and a sixth lens group having a positive refractive power. Then, zooming is performed by moving the first to fifth lens groups and changing the interval between the lens groups.

  1A, 1B, and 1C are cross-sectional views of the zoom lens of Embodiment 1 of the present invention at the wide-angle end (short focal length end), the intermediate zoom position, and the telephoto end (long focal length end), respectively. FIG. 2A, 2 </ b> B, and 2 </ b> C are obtained when the object at a distance of 50 times the focal length is focused at the wide-angle end, the intermediate zoom position, and the telephoto end of the zoom lens of Embodiment 1, respectively. FIG. FIG. 3 is a lens cross-sectional view at the wide-angle end of the zoom lens according to Embodiment 2 of the present invention.

  4A, 4 </ b> B, and 4 </ b> C are obtained when the object at a distance of 50 times the focal length is focused at the wide-angle end, the intermediate zoom position, and the telephoto end of the zoom lens according to the second embodiment. FIG. FIG. 5 is a schematic diagram of a main part of a single-lens reflex camera (imaging device) including the zoom lens of the present invention.

  The zoom lens of each embodiment is a photographing lens system (optical system) used in an imaging apparatus such as a video camera, a digital camera, or a silver salt film camera. In the lens cross-sectional view, the left side is the object side (front), and the right side is the image side (rear). In the lens cross-sectional view, i indicates the order of the lens groups from the object side, and Li is the i-th lens group. SP is an aperture stop. SSP is an F-number aperture (Fno aperture).

  IP is an image plane, and when used as a photographing optical system for a video camera or a digital still camera, on the imaging surface of a solid-state imaging device (photoelectric conversion device) such as a CCD sensor or a CMOS sensor, Corresponds to the film surface. The arrows indicate the movement trajectory of each lens unit during zooming from the wide-angle end to the telephoto end.

  The spherical aberration diagram shows d-line, g-line, and sine condition (SC). In the astigmatism diagram, ΔM and ΔS are a meridional image surface and a sagittal image surface at d-line. The lateral chromatic aberration diagram shows the g-line. Fno is the F number, and ω is the half angle of view. In the following embodiments, the wide-angle end and the telephoto end refer to zoom positions when the zoom lens unit is positioned at both ends of a range in which the mechanism can move on the optical axis. The zoom lens of each embodiment includes, in order from the object side to the image side, a first lens unit L1 having a negative refractive power, a second lens unit L2 having a positive refractive power, a third lens unit L3 having a negative refractive power, and a positive lens unit. A fourth lens unit L4 having a negative refractive power, a fifth lens unit L5 having a negative refractive power, and a sixth lens unit L6 having a positive refractive power.

  During zooming from the wide-angle end to the telephoto end, the first lens unit L1 moves to the image side, and the second lens unit L2 moves to the object side. The third lens unit L3 moves together with the aperture stop SP and the Fno stop SSP while drawing a convex locus on the object side. The fourth lens unit L4 moves to the object side integrally with the second lens unit L2. The fifth lens unit L5 moves along a locus convex toward the object side. The sixth lens unit L6 does not move during zooming and focusing. Focusing from an infinitely distant object to a close object is performed by moving the fifth lens unit L5 to the image side. A rear focus type is employed in which the fifth lens unit L5 is moved on the optical axis to perform focusing.

  When focusing from an object at infinity to an object at a short distance at the telephoto end, the fifth lens unit L5 is moved backward as indicated by an arrow 5c in FIG. A solid line curve 5a and a dotted line curve 5b of the fifth lens unit L5 are for correcting image plane fluctuations during zooming from the wide-angle end to the telephoto end when focusing on an object at infinity and an object at close distance, respectively. The movement trajectory is shown. By moving the lightweight fifth lens unit L5 for focusing, quick autofocusing is facilitated. In each embodiment, focusing may be performed using a lens group other than the fifth lens group.

  In the zoom lens of the present invention, a lens group having a refractive power such as a converter lens or an afocal lens group may be positioned on at least one of the object side of the first lens group L1 or the image side of the final lens group.

In the zoom lens of each embodiment, the first lens unit L1 and the second lens unit L2 move so that the distance between the first lens unit L1 and the second lens unit L2 is narrowed during zooming from the wide-angle end to the telephoto end. In the first lens unit L1, the Abbe number of the material is νd and the partial dispersion ratio is θgF. At this time,
0.02 <θgF−0.6438 + 0.001682 × νd <0.1 (1)
A positive lens satisfying the following conditional expression.

The Abbe number νd and the partial dispersion ratio θgF of the material are Nd as the refractive index of the d-line of the Fraunhofer line, Ng as the refractive index of the g-line, NF as the refractive index of the F-line, and NC as the refractive index of the C-line. To do. At this time,
νd = (Nd−1) / (NF−NC)
θgF = (Ng−NF) / (NF−NC)
Defined by

  In many conventional 6-group zoom lenses, in order to correct chromatic aberration on the telephoto side, a glass material with strong abnormal partial dispersion is used as the material of the positive lens of the second lens group in which the incident height of the axial light beam increases. . On the other hand, in the second lens group in which the incident height of the axial light beam is high, the use of a glass material having a high refractive index for correcting the spherical aberration is very effective. Therefore, in the zoom lens of each embodiment, a partially dispersible glass material necessary for the second lens group is used as a positive lens in the first lens group. Accordingly, spherical aberration and chromatic aberration (especially axial chromatic aberration) are corrected by using a high refractive index material for the second lens group. In each embodiment, conditional expression (1) is satisfied in view of the above.

  If the upper limit of conditional expression (1) is exceeded, chromatic aberration will be overcorrected. On the other hand, if the lower limit is exceeded, the correction effect of chromatic aberration correction decreases, which is not good. In each embodiment, it is more preferable to set the numerical range of conditional expression (1) as follows.

0.02 <θgF−0.6438 + 0.001682 × νd <0.04 (1a)
The material satisfying conditional expression (1) is preferably a material mainly composed of SiO ₂ in terms of productivity and processing freedom.

  In each embodiment, the lens configuration is specified as described above. This makes it suitable for single-lens reflex cameras, has a wide angle of view, achieves a large aperture ratio, corrects various aberrations depending on chromatic aberration and aperture, and obtains a zoom lens with high optical performance. ing.

  In each embodiment, it is more preferable to satisfy one or more of the following conditions. The Abbe number of the material of the positive lens that is included in the first lens unit L1 and satisfies the conditional expression (1) is νd. The second lens unit L2 includes a plurality of positive lenses, and the average value of the refractive indexes of the materials of the plurality of positive lenses is nd_ave. The first lens unit L1 has a meniscus negative lens having a convex surface on the object side on the most object side, and the refractive index of the material of the negative lens and the radius of curvature of the lens surface on the object side are nd_G1, r1 respectively. And Let the focal length of the first lens unit L1 be f1.

At this time,
νd <23 (2)
nd_ave> 1.75 (3)
nd_G1> 1.80 (4)
-4 <r1 / f1 <-1 (5)
It is preferable to satisfy one or more of the following conditional expressions. Conditional expression (2) is for correcting chromatic aberration by using a high dispersion material having a small Abbe number for the positive lens in the first lens unit L1.

  In each embodiment, since the first lens unit L1 has a negative refractive power, a high-dispersion material is used for the positive lens in order to satisfactorily erase the lens unit. This makes it possible to use a high-dispersion material and a high-refractive index material for the achromatic pair in the lens group, and to improve the sagittal field curvature that is likely to occur with a wide-angle zoom lens. It is corrected. If the upper limit of conditional expression (2) is exceeded, a low dispersion material must be used for the negative lens in the first lens unit L1 in order to eliminate the color in the first lens unit L1. In general, a low dispersion material has a low refractive index, which makes it difficult to correct sagittal field curvature.

More preferably, conditional expression (2) is expressed as 18 <νd <23 (2a)
It is preferable to set as follows.

  Conditional expression (3) relates to the average refractive index of the material of the positive lens in the second lens unit L2. Conventionally, in order to correct chromatic aberration on the telephoto side, the positive lens of the second lens unit L2 in which the incident height of the axial light beam is high has used a material having high partial dispersion and a low refractive index. As a result, the partial dispersion required in the second lens unit L2 in each embodiment is transferred to the positive lens in the first lens unit L1. Accordingly, spherical aberration and chromatic aberration (particularly axial chromatic aberration) are favorably corrected so that a material having a high refractive index can be used for the second lens unit L2. If the lower limit of conditional expression (3) is exceeded, spherical aberration and coma depending on the aperture will increase, which is not good.

  Conditional expressions (4) and (5) relate to the refractive index and lens shape of the material of the negative meniscus lens located closest to the object side. The sagittal curvature of field is largely attributed to the lens shape of the first lens group in which the incident height of the off-axis light beam is high. For this reason, a high refractive index material that satisfies the conditional expression (4) is used for the negative lens in the first lens unit L1, and the field curvature is corrected well so that the lens shape satisfies the conditional expression (5). is doing.

If the conditional expressions (4) and (5) are not satisfied, it is difficult to satisfactorily correct field curvature over the entire zoom range. More preferably, conditional expressions (4) and (5) are replaced with nd_G1> 1.85 (4a).
−3.5 <r1 / f1 <−1.5 (5a)
It is preferable to set as follows.

  Next, the lens configuration of each lens group will be described. Hereinafter, it is assumed that the lens configuration of each lens group is arranged in order from the object side to the image side. The first lens unit L1 includes a negative lens G11 having a convex meniscus shape on the object side, a negative lens G12 having a concave shape on both lens surfaces, and a positive lens G13 having a convex surface on the object side. The second lens unit L2 includes a cemented lens in which a negative lens G21 having a concave surface on the image side and a positive lens G22 having convex surfaces on both lens surfaces, a positive lens G23 having convex surfaces on both surfaces, and an object side surface. Is composed of a convex positive lens G24.

  The third lens unit L3 includes a negative lens G31 having concave concave surfaces, a cemented lens in which a negative lens G32 having concave concave surfaces and a positive lens G33 having convex convex surfaces are cemented. The fourth lens unit L4 includes a cemented lens in which a negative lens G41 having a concave surface on the image side and a positive lens G42 having convex both surfaces are cemented, and a positive lens G43 having both convex surfaces. The fifth lens unit L5 includes a positive lens G51 whose convex surfaces are convex and a negative lens G52 whose concave surfaces are concave. The sixth lens unit L6 is composed of a positive lens having convex lens surfaces.

  Next, an embodiment in which the zoom lens shown in Embodiments 1 and 2 is applied to an imaging apparatus will be described with reference to FIG. FIG. 5 is a schematic diagram of a main part of a single-lens reflex camera. In FIG. 5, reference numeral 10 denotes a photographing lens having the zoom lens 1 of the first and second embodiments. The zoom lens 1 is held by a lens barrel 2 that is a holding member. Reference numeral 20 denotes a camera body, which includes a quick return mirror 3 that reflects the light beam from the photographing lens 10 upward, and a focusing screen 4 that is disposed at an image forming position of the photographing lens 10. Further, it is constituted by a penta roof prism 5 for converting an inverted image formed on the focusing screen 4 into an erect image, an eyepiece 6 for observing the erect image, and the like.

  Reference numeral 7 denotes a photosensitive surface, on which a solid-state imaging device (photoelectric conversion device) for receiving an image such as a CCD sensor or a CMOS sensor or a silver salt film is disposed. At the time of photographing, the quick return mirror 3 is retracted from the optical path, and an image is formed on the photosensitive surface 7 by the photographing lens 10. The benefits described in the first and second embodiments are effectively enjoyed in the imaging apparatus as disclosed in the present embodiment. In this embodiment, the present invention can be similarly applied to a single-lens reflex camera without a quick return mirror.

  Numerical examples 1 and 2 corresponding to the examples 1 and 2 are shown below. In each numerical example, i indicates the order of the surfaces from the object side. In numerical examples, ri is the radius of curvature of the i-th lens surface in order from the object side, di is the i-th lens thickness and air spacing in order from the object side, and ndi and νdi are the i-th lens in order from the object side. The refractive index and Abbe number of the material. BF is a back focus. The aspherical shape is the X axis in the optical axis direction, the H axis in the direction perpendicular to the optical axis, the light traveling direction is positive, r is the paraxial radius of curvature, and each aspheric coefficient is A4, A6, A8, A10, A12. When

Shall be given in “E−x” means 10 ^−x . Table 1 shows the relationship between the above-described conditional expressions and numerical examples.

[Numerical Example 1]
Unit mm

Surface data surface number rd nd νd
1 * 118.198 2.50 1.85400 40.4
2 32.634 13.07
3 -163.403 2.30 1.77250 49.6
4 81.290 0.55
5 70.200 4.08 1.92286 18.9
6 152.179 (variable)
7 711.348 1.90 1.80518 25.4
8 53.949 5.71 1.77250 49.6
9 -165.565 0.15
10 100.780 3.80 1.83481 42.7
11 -271.032 2.39
12 44.062 4.89 1.69680 55.5
13 704.565 (variable)
14 ∞ 1.92
15 -124.320 1.30 1.88300 40.8
16 46.486 2.44
17 -87.213 1.30 1.72000 50.2
18 41.011 4.26 1.80518 25.4
19 -88.417 0.48
20 (Aperture) ∞ (Variable)
21 103.464 1.30 1.84666 23.9
22 23.591 6.12 1.49700 81.5
23 -82.833 1.20
24 34.667 4.40 1.61800 63.3
25 -116.798 (variable)
26 347.196 3.07 1.80809 22.8
27 -43.713 0.10
28 -51.755 1.20 1.83400 37.2
29 27.958 (variable)
30 51.982 6.34 1.58313 59.4
31 * -149.954 (variable)
Image plane ∞

Aspheric data 1st surface
K = 0.00000e + 000 A 4 = 1.12374e-006 A 6 = 7.74070e-010 A 8 = -1.85284e-012
A10 = 1.79073e-015 A12 = -6.28159e-019

No. 31
K = 0.00000e + 000 A 4 = 6.83372e-007 A 6 = -1.01210e-008 A 8 = 6.39805e-011
A10 = -1.95942e-013 A12 = 2.35213e-016

Various data Zoom ratio 2.75
Wide angle Medium Telephoto focal length 24.70 35.70 68.00
Angle of view 41.21 31.21 17.65
Image height 21.64 21.64 21.64
Total lens length 201.98 185.29 168.85
BF 41.71 41.71 41.71

d 6 56.98 31.56 3.45
d13 2.60 6.90 20.13
d20 19.08 14.78 1.56
d25 0.96 3.40 12.55
d29 3.89 10.16 12.69
d31 41.71 41.71 41.71

Zoom lens group data group Start surface Focal length
1 1 -36.10
2 7 33.02
3 14 -45.33
4 21 43.61
5 26 -40.27
6 30 66.97

[Numerical Example 2]
Unit mm

Surface data surface number rd nd νd
1 * 106.468 2.50 1.85400 40.4
2 32.905 13.10
3 -149.850 2.30 1.77250 49.6
4 83.237 0.86
5 80.026 3.89 1.92286 18.9
6 184.393 (variable)
7 -472.687 1.90 1.80518 25.4
8 60.248 5.52 1.77250 49.6
9 -154.955 0.20
10 106.156 4.00 1.88300 40.8
11 -183.624 0.15
12 42.726 4.78 1.72916 54.7
13 330.022 (variable)
14 ∞ 1.89
15 -156.023 1.30 1.88300 40.8
16 45.965 2.48
17 -87.778 1.30 1.72000 50.2
18 59.283 3.62 1.80809 22.8
19 -94.325 0.49
20 (Aperture) ∞ (Variable)
21 112.332 1.30 1.84666 23.9
22 22.167 6.49 1.49700 81.5
23 -77.614 1.40
24 34.311 4.31 1.67790 55.3
25 -147.476 (variable)
26 493.290 3.09 1.80809 22.8
27 -41.809 0.05
28 -50.890 1.20 1.83400 37.2
29 27.760 (variable)
30 54.178 6.56 1.58313 59.4
31 * -119.504 (variable)
Image plane ∞

Aspheric data 1st surface
K = 0.00000e + 000 A 4 = 1.00056e-006 A 6 = 1.05287e-009 A 8 = -2.23584e-012
A10 = 2.08279e-015 A12 = -7.18763e-019

No. 31
K = 0.00000e + 000 A 4 = 1.03251e-007 A 6 = -9.37908e-009 A 8 = 6.31048e-011
A10 = -1.95942e-013 A12 = 2.35213e-016

Various data Zoom ratio 2.75
Wide angle Medium Telephoto focal length 24.70 35.60 68.00
Angle of view 41.22 31.28 17.65
Image height 21.64 21.64 21.64
Total lens length 200.09 183.25 166.09
BF 39.82 39.82 39.82

d 6 56.43 31.37 3.21
d13 4.16 8.56 22.48
d20 19.90 15.51 1.58
d25 0.96 3.12 11.38
d29 4.13 10.19 12.93
d31 39.82 39.82 39.82

Zoom lens group data group Start surface Focal length
1 1 -36.50
2 7 32.58
3 14 -45.11
4 21 42.81
5 26 -39.61
6 30 64.83

SP aperture stop, SSP F number stop, ΔS sagittal image plane,
ΔM meridional image plane, L1 first lens group, L2 second lens group,
L3 third lens group, L4 fourth lens group, L5 fifth lens group, L6 sixth lens group

Claims (7)

In order from the object side to the image side, a first lens group having a negative refractive power, a second lens group having a positive refractive power, a third lens group having a negative refractive power, a fourth lens group having a positive refractive power, and a negative lens group In a zoom lens that includes a fifth lens group having a refractive power and a sixth lens group having a positive refractive power, and performs zooming by changing the interval between the lens groups, the first lens group has an Abbe number of a material νd When the partial dispersion ratio is θgF,
0.02 <θgF−0.6438 + 0.001682 × νd <0.1
A zoom lens having a positive lens that satisfies the following conditional expression: The Abbe number νd of the positive lens material is νd <23
The zoom lens according to claim 1, wherein the following conditional expression is satisfied. When the second lens group has a plurality of positive lenses and the average value of the refractive indexes of the materials of the plurality of positive lenses is nd_ave,
nd_ave> 1.75
The zoom lens according to claim 1 or 2, wherein the following conditional expression is satisfied. The first lens group has a meniscus negative lens having a convex surface on the object side closest to the object side, and the refractive index of the material of the negative lens is nd_G1,
nd_G1> 1.80
The zoom lens according to claim 1, wherein the following conditional expression is satisfied. The first lens group has a meniscus negative lens with the object side surface most convex on the object side, the radius of curvature of the object side surface of the negative lens is r1, and the focal length of the first lens group is f1. And when
-4 <r1 / f1 <-1
The zoom lens according to claim 1, wherein the following conditional expression is satisfied.   During zooming from the wide-angle end to the telephoto end, the first lens group moves toward the image side, the second lens group moves toward the object side, and the third lens group moves toward the object side with a convex locus, 6. The fourth lens group moves toward the object side integrally with the second lens group, and the fifth lens group moves along a locus that is convex toward the object side. 1 zoom lens.   An image pickup apparatus comprising: the zoom lens according to claim 1; and a photoelectric conversion element that receives an image formed by the zoom lens.