CN116360084A

CN116360084A - Zoom lens and imaging device

Info

Publication number: CN116360084A
Application number: CN202211638747.0A
Authority: CN
Inventors: 佐藤允基
Original assignee: Tamron Co Ltd
Current assignee: Tamron Co Ltd
Priority date: 2021-12-27
Filing date: 2022-12-20
Publication date: 2023-06-30
Also published as: JP2023096986A

Abstract

An image pickup apparatus having a zoom lens with high optical performance, a wide angle, and a small size and a high magnification is provided. The solution is that a zoom lens comprises, in order from an object side to an image side: a1 st lens group (G1) having negative optical power, a 2 nd lens group (G2) having positive optical power, a 3 rd lens group (G3) having negative optical power, and a 4 th lens group (G4) having positive optical power, wherein the 1 st lens group (G1) is fixed when zooming from a wide-angle end to a telephoto end, at least the 2 nd lens group (G2), the 3 rd lens group (G3), and the 4 th lens group (G4) are moved along an optical axis, an interval between the lens groups on the optical axis is changed, and the zoom lens satisfies a prescribed mathematical formula.

Description

Zoom lens and imaging device

Technical Field

The present invention relates to a zoom lens and an imaging apparatus.

Background

In recent years, imaging devices using solid-state imaging elements such as digital cameras have been increasingly popular. With this, the zoom lens has been advanced in high performance and miniaturization, and a small-sized image pickup apparatus system has been rapidly popularized. Among conventional lenses, particularly in monitoring lenses, video camera lenses, digital camera lenses, single-lens reflex camera lenses, mirror-less single-lens camera lenses, and the like, which are required to be compact and long, there are problems that the conventional lenses have high optical performance, are capable of photographing a wide range with 1 camera (wide angle of view), have high magnification, and are small and lightweight.

The zoom lens described in patent document 1 discloses a zoom lens including a 1 st lens group having negative optical power, a 2 nd lens group having positive optical power, a 3 rd lens group having negative optical power, and a 4 th lens group having positive optical power. However, the zoom magnification is about 3 times, and it is difficult to achieve a high magnification in a small size.

The zoom lens described in patent document 2 discloses a wide-angle zoom lens as follows: the lens system is composed of a 1 st lens group with negative focal power, a 2 nd lens group with positive focal power, a 3 rd lens group with negative focal power, and a rear group comprising more than 1 lens group at the image surface side than the 3 rd lens group, is small in size and high in magnification, and achieves a wide field angle at the wide-angle end. However, since the positive power of the 2 nd lens group is weak with respect to the negative power of the 1 st lens group, distortion aberration is largely generated at the wide angle end to secure a wide angle of view, and it is difficult to realize high resolution.

The zoom lens described in patent document 3 discloses a zoom lens including a 1 st lens group having negative optical power, a 2 nd lens group having positive optical power, a 3 rd lens group having negative optical power, and a 4 th lens group having positive optical power. The zoom lens is intended to achieve a wide angle by disposing 2 negative meniscus lenses having concave surfaces facing the image side in order from the object side in the 1 st lens group, and to achieve a high zoom ratio by moving at least the 1 st to 3 rd lens groups along the optical axis at the time of zooming. However, the zoom magnification is about 6 times, and it is difficult to achieve a high magnification in a small size.

Prior art literature

Patent literature

Patent document 1: japanese patent laid-open publication No. 2019-135552

Patent document 2: japanese patent No. 6711436

Patent document 3: japanese patent No. 6543815

Disclosure of Invention

Problems to be solved by the invention

Accordingly, an object of the present invention is to provide a zoom lens having high optical performance, a wide angle, a small size, and a high magnification.

Means for solving the problems

A zoom lens includes, in order from an object side to an image side: a 1 st lens group having negative optical power, a 2 nd lens group having positive optical power, a 3 rd lens group having negative optical power, and a 4 th lens group having positive optical power, the 1 st lens group being fixed at a time of zooming from a wide angle end to a telephoto end, at least the 2 nd lens group, the 3 rd lens group, and the 4 th lens group being moved along an optical axis, an interval between adjacent lens groups being varied on the optical axis, the zoom lens satisfying the following formula:

0.1≤β23w/tan(ωw)≤0.5···········(1)

1.0≤f2/√(fw×ft)≤3.25···········(2)

0.15≤(β23t/β23w)/(ft/fw)≤0.98··(3)

wherein,,

fw: focal length of the zoom lens at the time of infinity focusing at the wide-angle end

And (2) ft: focal length of the zoom lens at infinity focusing at telephoto end

f2: focal length of the 2 nd lens group

ωw: half field angle of outermost ray at wide angle end

Beta 23w: a combined lateral magnification of the 2 nd lens group and the 3 rd lens group at the time of infinity focusing at the wide-angle end

Beta 23t: a combined lateral magnification of the 2 nd lens group and the 3 rd lens group at the time of infinity focusing at the telephoto end

In order to solve the above-described problems, an image pickup apparatus according to the present invention includes the zoom lens and an image pickup device that converts an optical image formed by the zoom lens into an electrical signal.

Effects of the invention

According to the present invention, a zoom lens having a high magnification, a wide angle, and a small size can be provided.

Drawings

Fig. 1 is a sectional view of a zoom lens of embodiment 1.

Fig. 2 is a longitudinal aberration diagram at the wide-angle end of the zoom lens of embodiment 1.

Fig. 3 is a longitudinal aberration diagram at the telephoto end of the zoom lens of embodiment 1.

Fig. 4 is a sectional view of the zoom lens of embodiment 2.

Fig. 5 is an aberration diagram at the wide-angle end of the zoom lens of embodiment 2.

Fig. 6 is an aberration diagram at the telephoto end of the zoom lens of embodiment 2.

Fig. 7 is a sectional view of the zoom lens of embodiment 3.

Fig. 8 is an aberration diagram at the wide-angle end of the zoom lens of embodiment 3.

Fig. 9 is an aberration diagram at the telephoto end of the zoom lens of embodiment 3.

Fig. 10 is a sectional view of the zoom lens of embodiment 4.

Fig. 11 is an aberration diagram at the wide-angle end of the zoom lens of embodiment 4.

Fig. 12 is an aberration diagram at the telephoto end of the zoom lens of embodiment 4.

Fig. 13 is a sectional view of a zoom lens of embodiment 5.

Fig. 14 is an aberration diagram at the wide-angle end of the zoom lens of embodiment 5.

Fig. 15 is an aberration diagram at the telephoto end of the zoom lens of embodiment 5.

Fig. 16 is a sectional view of a zoom lens of embodiment 6.

Fig. 17 is an aberration diagram at the wide-angle end of the zoom lens of embodiment 6.

Fig. 18 is an aberration diagram at the telephoto end of the zoom lens of embodiment 6.

Fig. 19 is a sectional view of a zoom lens of embodiment 7.

Fig. 20 is an aberration diagram at the wide-angle end of the zoom lens of embodiment 7.

Fig. 21 is an aberration diagram at the telephoto end of the zoom lens of embodiment 7.

Fig. 22 is a diagram schematically showing an example of the configuration of an imaging device according to an embodiment of the present invention.

Description of the reference numerals

S.aperture stop

CG. 22. Protective glass

IMG image plane

G1.1 st lens group

G2.2 nd lens group

G3.3 rd lens group

G4.4 th lens group

G5.5 th lens group

G6.6 th lens group

G7.7 th lens group

1- & camera

2. Main body

3.lens barrel

21-CCD sensor for detecting a position of a body

Detailed Description

Embodiments of a zoom lens and an imaging apparatus according to the present invention are described below. The zoom lens and the image pickup apparatus described below are one embodiment of the zoom lens and the image pickup apparatus according to the present invention, and the zoom lens and the image pickup apparatus according to the present invention are not limited to the following embodiments.

1. Zoom lens

1-1 optical constitution

The zoom lens according to the present invention is configured to have, in order from an object side to an image side, at least: consists of a 1 st lens group with negative focal power, a 2 nd lens group with positive focal power, a 3 rd lens group with negative focal power, and a 4 th lens group with positive focal power. With this configuration, a wide angle and miniaturization can be easily achieved. In addition, in terms of further improving performance, it is preferable to have the 5 th lens group on the image side of the 4 th lens group.

(1) 1 st lens group

The 1 st lens group is not particularly limited as long as it has negative optical power and is fixed with respect to the image plane at the time of magnification change. The 1 st lens group is composed of 1 meniscus lens, which facilitates wide angle and miniaturization.

Here, the "lens group" is composed of 1 lens or a plurality of lenses adjacent to each other, and the interval between the adjacent lens groups along the optical axis varies at the time of magnification change or focusing. In the case where one lens group is constituted by a plurality of lenses, the distance on the optical axis between the lenses included in the one lens group does not change at the time of magnification change or focusing.

(2) Lens group 2

The specific configuration of the 2 nd lens group is not particularly limited as long as it is a lens group having positive optical power and moving along the optical axis at the time of magnification change. In order to move on the optical axis at high speed at the time of magnification change, the 2 nd lens group is preferably composed of 2 or less positive lenses. In addition, the 2 nd lens group preferably has a biconvex lens. With this configuration, aberration can be easily corrected and miniaturization can be achieved.

(3) 3 rd lens group

The 3 rd lens group is not particularly limited as long as it is a lens group having negative optical power and moving along the optical axis at the time of magnification change. The 3 rd lens group is preferably configured to have negative lenses of 2 or less. The positive lens included in the 3 rd lens group is preferably 1 sheet only. The 3 rd lens group is preferably composed of a negative lens, and a positive lens from the object side toward the image side. With this configuration, aberration can be easily corrected and miniaturization can be achieved.

(4) 4 th lens group

The 4 th lens group is not particularly limited as long as it has positive optical power and moves along the optical axis at the time of magnification change. The 4 th lens group preferably has a positive lens on the most object side. The 4 th lens group is preferably composed of a positive lens, a negative lens, a positive lens, and a negative lens from the object side toward the image side. With this configuration, aberration can be easily corrected and miniaturization can be achieved.

(5) 5 th lens group

The 5 th lens group is not particularly limited as long as it has positive or negative optical power and is fixed with respect to the image plane at the time of magnification change. The 5 th lens group is preferably composed of only a negative lens and a positive lens from the object side toward the image side. With this configuration, aberration can be easily corrected and miniaturization can be achieved.

(6) Aperture diaphragm

In this zoom lens, the arrangement of the aperture stop is not particularly limited. By disposing the aperture stop between the 3 rd lens group and the 4 th lens group, aberrations can be effectively offset in the front-rear direction of the aperture stop, which is preferable in obtaining a zoom lens having high optical performance.

1-2. Action

(1) Zoom ratio

In this zoom lens, the specific operation is not particularly limited as long as the 1 st lens group is fixed on the optical axis and the 2 nd, 3 rd, and 4 th lens groups are moved on the optical axis when changing magnification from the wide-angle end to the telephoto end.

(2) Focusing

In the zoom lens, the specific operation is not particularly limited as long as the 4 th lens group moves on the optical axis at the time of focusing from infinity to a close distance. In addition, in focusing from infinity to a close distance, the 4 th lens group is preferably moved on the optical axis toward the object side.

1-3. Math

The zoom lens preferably has the above-described configuration, and satisfies at least 1 or more of the following equations.

1-3-1. Formula (1)

0.1≤β23w/tan(ωw)≤0.5···········(1)

Wherein,,

beta 23w: the combined lateral magnification ωw of the 2 nd lens group and the 3 rd lens group at the time of infinity focusing at the wide angle end: half field angle of outermost ray at wide angle end

Equation (1) is an equation for defining a ratio of a combined lateral magnification of the 2 nd lens group and the 3 rd lens group at the wide angle end to a half field angle of the most off-axis ray at the wide angle end. By satisfying the expression (1), it is easy to realize a high magnification and to expand the angle of view at the wide-angle end.

If the value is lower than the lower limit value of the expression (1), it is easy to expand the angle of view at the wide-angle end, but it is difficult to correct curvature of field and distortion aberration at the wide-angle end. On the other hand, if the upper limit value of the expression (1) is exceeded, it is difficult to enlarge the angle of view in a state where the variable magnification ratio is maintained at the wide angle end.

In order to obtain the above-described effect, the lower limit value of the formula (1) is preferably 0.13, more preferably 0.15. The upper limit of the formula (1) is preferably 0.45, more preferably 0.40. In the case where these preferable lower limit or upper limit are used, the inequality sign (. Ltoreq.) with the equal sign may be replaced with the inequality sign (. <) in the formula (1). The same applies to other formulas as the principle.

1-3-2. Formula (2)

1.0≤f2/√(fw×ft)≤3.25···········(2)

Wherein,,

fw: focal length of zoom lens at infinity focusing at wide-angle end

And (2) ft: focal length of zoom lens at infinity focusing at telephoto end

f2: focal length of the 2 nd lens group

Equation (2) is an equation for defining the ratio of the focal length of the 2 nd lens group to "the square root of the product of the focal length of the zoom lens at the time of infinity focusing at the wide-angle end and the focal length of the zoom lens at the time of infinity focusing at the telephoto end". By satisfying the expression (2), curvature of field, distortion aberration, and chromatic aberration occurring in the 1 st lens group can be appropriately corrected, and miniaturization can be easily achieved.

If the focal length of the 2 nd lens group is too short to correct curvature of field, distortion aberration, and chromatic aberration of magnification at the wide-angle end if it is below the lower limit value of expression (2), the number of lens pieces required to correct the aberration increases, and thus miniaturization is difficult. On the other hand, if the upper limit value of the formula (2) is exceeded, the focal length of the 2 nd lens group becomes long, and correction of curvature of field, distortion aberration, and chromatic aberration generated in the 1 st lens group becomes insufficient. In addition, the amount of movement of the 2 nd lens group increases when changing magnification from the wide-angle end to the telephoto end, and it is difficult to achieve miniaturization.

In order to obtain the above-described effect, the lower limit value of the formula (2) is preferably 1.10, more preferably 1.20. The upper limit of the formula (2) is preferably 2.80, more preferably 2.60.

1-3-3. 1 (3)

0.15≤(β23t/β23w)/(ft/fw)≤0.98··(3)

Wherein,,

beta 23t: combined lateral magnification of 2 nd lens group and 3 rd lens group at infinity focusing at telephoto end

Equation (3) is an equation for defining a ratio contributing to the zoom magnifications of the 2 nd lens group and the 3 rd lens group. By satisfying the expression (3), the ratio contributing to the zoom magnifications of the 2 nd lens group and the 3 rd lens group can be made appropriate, and the high magnification and the miniaturization can be easily achieved.

If it is lower than the lower limit value of the formula (3), the ratio contributing to the zoom magnifications of the 2 nd lens group and the 3 rd lens group becomes small, and thus it is difficult to realize a high magnification. On the other hand, if the upper limit value of the formula (3) is exceeded, the ratio contributing to the zoom magnifications of the 2 nd lens group and the 3 rd lens group becomes large, so that the number of lens sheets required for reducing the amount of aberration occurrence at the time of zooming from the wide-angle end to the telephoto end increases, and miniaturization is difficult.

In order to obtain the above-described effect, the lower limit value of the formula (3) is preferably 0.30, more preferably 0.40. The upper limit of the formula (3) is preferably 0.97, more preferably 0.95.

1-3-4. 1 (4)

5.0≤|f1/fw|≤20.0···(4)

Wherein,,

f1: focal length of 1 st lens group

Equation (4) is an equation for defining an absolute value of a ratio of a focal length of the 1 st lens group to a focal length of the zoom lens at the time of infinity focusing at the wide-angle end. By satisfying the expression (4), field curvature and distortion aberration can be corrected at the wide-angle end, and the angle of view can be enlarged, which facilitates miniaturization.

If the focal length of the 1 st lens group is smaller than the lower limit value of the expression (4), the field curvature and distortion aberration generated in the 1 st lens group increase, and the number of lens sheets required for correcting these aberrations in the group on the image side of the 1 st lens increases, which makes it difficult to achieve downsizing. On the other hand, if the upper limit value of the formula (4) is exceeded, the focal length of the 1 st lens group is excessively long, and correction of curvature of field at the wide-angle end is insufficient, making it difficult to obtain good optical performance. In addition, it is difficult to enlarge the angle of view at the wide-angle end.

In order to obtain the above-described effect, the lower limit value of the formula (4) is preferably 5.5, more preferably 6.0. The upper limit of the formula (4) is preferably 18.0, more preferably 17.0.

1-3-5. 1. 5)

0.5≤|f1/f2|≤4.0···(5)

Equation (5) is an equation for defining the absolute value of the ratio of the focal length of the 2 nd lens group to the focal length of the 1 st lens group. By satisfying the expression (5), curvature of field and distortion aberration can be corrected appropriately, and the angle of view can be enlarged at the wide-angle end, so that high optical performance can be easily obtained.

If the focal length of the 1 st lens group is smaller than the lower limit value of the expression (5), the focal length of the 2 nd lens group becomes shorter, and curvature of field and distortion aberration increase at the wide-angle end, which makes it difficult to achieve high optical performance. On the other hand, if the upper limit value of the expression (5) is exceeded, the focal length of the 1 st lens group becomes longer than that of the 2 nd lens group, and negative optical power becomes weaker, so that it is difficult to expand the angle of view at the wide-angle end.

In order to obtain the above-described effect, the lower limit value of the formula (5) is preferably 0.70, more preferably 1.00. The upper limit of the formula (5) is preferably 3.70, more preferably 35.0.

1-3-6. 1 (6)

0.5≤|f12t/ft|≤3.0···(6)

Wherein,,

f12t: composite focal length of 1 st lens group and 2 nd lens group at infinity focusing at telephoto end

Equation (6) is an equation for specifying a ratio of a focal length of the zoom lens at the telephoto end at the time of infinity focusing to a combined focal length of the 1 st lens group and the 2 nd lens group at the telephoto end. By satisfying the formula (6), it is easy to correct spherical aberration, astigmatism, axial chromatic aberration occurring in the 1 st lens group and the 2 nd lens group appropriately at the telephoto end, and high optical performance is obtained or miniaturization is achieved.

If the total focal length of the 1 st lens group and the 2 nd lens group at the telephoto end is less than the lower limit value of the formula (6), the combined focal length becomes short, the spherical aberration, the astigmatism, and the axial chromatic aberration increase, and it is difficult to obtain high optical performance. On the other hand, if the upper limit value of the formula (6) is exceeded, the combined focal length of the 1 st lens group and the 2 nd lens group at the telephoto end becomes long, the correction of spherical aberration, astigmatism, axial chromatic aberration is insufficient, and it is difficult to achieve miniaturization of the optical system.

In order to obtain the above-described effect, the lower limit value of the formula (6) is preferably 0.55, more preferably 0.60. The upper limit of the formula (6) is preferably 2.70, more preferably 2.50.

1-3-7. Formula (7)

0.3≤|X3|/√(fw×ft)≤2.0···(7)

Wherein,,

x3: the formula (7) of the amount of movement of the 3 rd lens group in the optical axis direction at the time of zooming from the wide-angle end to the telephoto end is a formula for defining the ratio of the amount of movement of the 3 rd lens group at the time of zooming from the wide-angle end to the telephoto end to "square root of the product of the focal length of the zoom lens at the time of infinity focusing at the wide-angle end and the focal length of the zoom lens at the time of infinity focusing at the telephoto end". By satisfying the expression (7), the amount of movement of the 3 rd lens group is appropriately set when changing magnification from the wide-angle end to the telephoto end, so that it is easy to correct spherical aberration and high magnification and miniaturization are achieved.

If the amount is less than the lower limit value of expression (7), the amount of movement of the 3 rd lens group becomes shorter when changing magnification from the wide-angle end to the telephoto end, and it is difficult to achieve a high magnification of the optical system. On the other hand, if the upper limit value of expression (7) is exceeded, the movement amount of the 3 rd lens group becomes long when changing magnification from the wide-angle end to the telephoto end, and it is difficult to achieve miniaturization.

In order to obtain the above-described effect, the lower limit value of the formula (7) is preferably 0.35, more preferably 0.40. The upper limit of the formula (7) is preferably 1.90, more preferably 1.80.

1-3-8. 1 (8)

1.5≤|f2/f3|≤6.0···(8)

Equation (8) is an equation for defining a ratio of the focal length of the 2 nd lens group to the focal length of the 3 rd lens group. By satisfying the expression (8), it is easy to correct spherical aberration and curvature of field occurring in the 2 nd lens group and the 3 rd lens group well at the time of magnification change from the wide-angle end to the telephoto end, and high optical performance is obtained or miniaturization is achieved.

If the value is lower than the lower limit value of expression (8), the focal length of the 2 nd lens group becomes shorter than that of the 3 rd lens group, and the correction of spherical aberration from the wide-angle end to the telephoto end becomes excessive and the curvature of field cannot be corrected, making it difficult to obtain high optical performance. On the other hand, if the upper limit value of expression (8) is exceeded, the spherical aberration cannot be corrected from the wide-angle end to the telephoto end, and miniaturization is difficult.

In order to obtain the above-described effect, the lower limit value of the formula (8) is preferably 1.70, more preferably 2.00. The upper limit of the formula (8) is preferably 5.50, more preferably 5.00.

1-3-9. 1 (9)

ν2p＿max≤70···(9)

Wherein,,

v 2 p_max: maximum value of Abbe number of positive lens in 2 nd lens group

The expression (9) is an expression for defining the abbe number of the positive lens in the 2 nd lens group. By satisfying the expression (9), the axial chromatic aberration from the wide-angle end to the telephoto end can be corrected, and high optical performance can be easily obtained.

If the upper limit value of the formula (9) is exceeded, axial chromatic aberration and chromatic aberration of magnification from the wide-angle end to the telephoto end cannot be corrected, and it is difficult to obtain high optical performance.

In order to obtain the above-described effect, the lower limit value of the formula (9) is preferably 40.0, more preferably 45.0. The upper limit of the formula (9) is preferably 68.0, more preferably 67.0.

2. Image pickup apparatus

Next, an imaging device according to the present invention will be described. An imaging device according to the present invention is characterized by comprising the zoom lens according to the present invention and an imaging element for converting an optical image formed by the zoom lens into an electrical signal. Further, the image pickup element is preferably provided on the image side of the zoom lens.

Here, the image pickup device and the like are not particularly limited, and a solid-state image pickup device and the like such as a CCD (Charge Coupled Device: charge coupled device) sensor, a CMOS (Complementary Metal Oxide Semiconductor: complementary metal oxide semiconductor) sensor and the like can also be used. The imaging device according to the present invention is suitable for imaging devices such as digital cameras and video cameras using these solid-state imaging elements. The imaging device can be applied to various imaging devices such as a single-lens reflex camera, a mirror-less single-lens camera, a digital camera, a monitoring camera, a vehicle-mounted camera, and a unmanned aerial vehicle-mounted camera. The imaging device may be a lens-interchangeable imaging device or a fixed lens type imaging device in which a lens is fixed to a housing. The zoom lens according to the present invention is particularly suitable as a zoom lens for an imaging device mounted with an imaging element having a large size such as a full size. The zoom lens is compact and lightweight as a whole, and has high optical performance, so that a high-quality captured image can be obtained even when the zoom lens is used as a zoom lens for such an imaging device.

Fig. 22 is a diagram schematically showing an example of the configuration of the imaging device according to the present embodiment. As shown in fig. 21, the camera 1 includes a main body 2 and a lens barrel 3 that is detachable from the main body 2. The camera 1 is one embodiment of an imaging device.

The main body 2 has a CCD sensor 21 as an image pickup element and a cover glass 22. The CCD sensor 21 is disposed in the body 2 at a position where the optical axis of the zoom lens 30 mounted in the barrel 3 of the body 2 becomes the center thereof. The main body 2 may also have an IR cut filter or the like instead of the cover glass 22.

Next, examples are shown and the present invention is specifically explained. However, the present invention is not limited to the following examples.

Example 1

(1) Optical structure

Fig. 1 is a sectional view of a wide-angle end and a telephoto end of a zoom lens according to embodiment 1 of the present invention at the time of infinity focusing. The zoom lens is composed of, in order from the object side, a 1 st lens group G1 having negative optical power, a 2 nd lens group G2 having positive optical power, a 3 rd lens group G3 having negative optical power, a 4 th lens group G4 having positive optical power, and a 5 th lens group G5 having negative optical power.

When changing magnification from the wide-angle end to the telephoto end, the 2 nd lens group G2 moves toward the object side along the optical axis in a locus convex toward the image plane side, the 3 rd lens group G3 moves from the image side toward the object side, and the 4 th lens group G4 moves toward the object side in a locus convex toward the object side.

The 4 th lens group G4 moves from the image side to the object side along the optical axis upon focusing from an infinitely distant object to a close object.

The 1 st lens group G1 is composed of a negative meniscus lens having a convex object side.

The 2 nd lens group G2 is composed of a lenticular lens and a lenticular lens in order from the object side.

The 3 rd lens group G3 is composed of a biconcave lens, and a biconvex lens in order from the object side.

The 4 th lens group G4 is composed of a biconvex lens, a negative meniscus lens, and a cemented lens formed by a biconvex lens and a negative meniscus lens cemented together in order from the object side.

The 5 th lens group G5 is composed of a negative meniscus lens and a biconvex lens in order from the object side.

The aperture stop S is located between the 3 rd lens group G3 and the 4 th lens group G4, and is fixed to the image plane IMG when zooming from the wide-angle end to the telephoto end and focusing from an infinitely distant object to a close object.

In fig. 1, "IMG" is an image plane, and specifically, indicates an image pickup plane of a solid-state image pickup device such as a CCD sensor or a CMOS sensor, a film plane of a silver halide film, or the like. In addition, a cover glass CG is provided on the object side of the image plane IMG. This point is also the same in the cross-sectional views of the lenses shown in the other embodiments, and therefore, the description thereof will be omitted.

(2) Numerical examples

Next, a numerical example to which specific numerical values are applied to the zoom lens will be described. The following indicates "lens data", "various specifications", "variable interval", "aspherical coefficient", "focal length of each lens group". The values of the respective formulas (table 1) are summarized in example 7. In the following numerical examples, the units of the numerical values of the length units are not described as "mm" and the units of the angles are all "°. "INF" means infinity.

In (lens data), "surface No." denotes a number of a lens surface counted from the object side, "r" denotes a radius of curvature of the lens surface, "D" denotes a lens wall thickness or an air interval on the optical axis, "Nd" denotes a refractive index at D-line (wavelength λ=587.56 nm), and "vd" denotes an abbe number at D-line. In addition, the column "face No." is followed by a numeral "" indicates that the lens face is aspherical, and "S" indicates that the face is an aperture stop. In the column of "D", the meaning of "D (7)", "D (10)", etc. is that the interval on the optical axis of the lens surface is a variable interval that varies at the time of magnification or at the time of focusing. In addition, "BF" means back focus.

In (various specification tables), "F" is the focal length of the zoom lens, "fno" is the F value, "ω" is the half field angle, "Y" is the image height, and "L" is the total lens length. The values at the time of infinity focusing at the wide-angle end, intermediate end, and telephoto end are shown, respectively.

In (variable interval), values at the wide-angle end, intermediate end, and telephoto end at the time of infinity focusing and at the time of finite distance focusing are shown, respectively.

The (aspherical surface coefficient) means an aspherical surface coefficient when an aspherical surface shape is defined as follows. Where x is the displacement amount with respect to the reference plane in the optical axis direction, r is the paraxial radius of curvature, H is the height with respect to the optical axis in the direction perpendicular to the optical axis, K is the conic coefficient, and An is the aspherical coefficient n times. In the table of "aspherical coefficients", the "E.+ -. XX" represents an index mark, which means ". Times.10 ^±XX ”。

[ number 1]

The matters in each numerical embodiment are the same as those in other embodiments, and therefore, the explanation thereof will be omitted.

Fig. 2 and 3 show longitudinal aberration diagrams of the zoom lens at the wide-angle end and the telephoto end when an object at infinity is in focus. The longitudinal aberration diagrams shown in the respective figures are spherical aberration (mm), astigmatism (mm), and distortion aberration (%) in order from the left side of the figure. In the spherical aberration diagram, the solid line represents the spherical aberration at the d-line (wavelength 587.56 nm), the short-dashed line represents the spherical aberration at the g-line (wavelength 435.84 nm), and the long-dashed line represents the spherical aberration at the C-line (wavelength 656.28 nm). In the astigmatic diagram, the vertical axis represents the half field angle (ω), the horizontal axis represents defocus, the solid line represents the sagittal image plane of the d-line, and the broken line represents the meridional image plane of the d-line. In the distortion aberration diagram, the vertical axis is a half field angle (ω), and the horizontal axis is distortion aberration. These matters are the same in the aberration diagrams shown in other embodiments, and therefore, description thereof will be omitted later.

(lens data)

Surface NO.	r	D	Nd	vd
						1	152.469	1.100	1.79999	29.84
2	25.610	D(2)
					3	42.712	4.100	1.60300	65.44
4	-79.438	0.150
					5	22.379	4.300	1.61799	63.4
6	-268.591	D(6)
					7	-148.152	0.500	1.95375	32.32
8	10.486	2.170
					9	-11.948	0.500	1.91082	35.25
10	14.890	0.380
					11	17.550	2.401	1.98613	16.48
12	-32.183	D(12)
					13S	INF	D(13)
14*	7.136	3.785	1.55332	71.68
					15*	-37.444	1.250
16	8.506	0.600	1.79360	37.09
					17	5.461	0.762
18	6.519	3.880	1.59282	68.62
					19	-5.691	0.500	2.00100	29.13
20	-14.215	D(20)
					21	359.787	0.500	2.00100	29.13
22	5.905	1.607
					23*	21.301	2.226	1.63973	23.53
24*	-10.833	3.200
					25	INF	0.800	1.51633	64.14
26	INF	BF

(various specification sheets)

	Wide angle end	Intermediate part	Telephoto end
				f	4.465	13.703	44.388
Fno.	1.838	2.507	3.596
				ω	41.188	12.783	3.975
Y	3.300	3.300	3.300
				L	66.000	66.000	66.000

(variable spacing)

	Wide angle end	Intermediate part	Telephoto end
				Photographic distance	INF	INF	INF
D(2)	6.445	5.956	3.296
				D(6)	1.100	12.397	22.578
D(12)	19.328	8.520	1.000
				D(13)	2.315	0.759	1.346
D(20)	1.100	2.656	2.069
				BF	1.000	1.000	1.000
	Wide angle end	Intermediate part	Telephoto end
				Photographic distance	0.3m	1.0m	1.2m
D(13)	2.290	0.672	0.598
				D(20)	1.125	2.743	2.816

(aspherical coefficient)

Surface NO.	K	A4	A6	A8	A10
						14	0.0000E+00	-1.6033E-04	-2.5593E-06	8.1019E-09	-2.1009E-09
15	0.0000E+00	2.2852E-04	-5.3631E-07	-9.8586E-08	1.5727E-09
						23	0.0000E+00	-6.7519E-05	5.5632E-06	1.3150E-06	-9.7898E-08
24	0.0000E+00	-6.3664E-06	6.4237E-06	-9.8230E-07	1.4817E-08

(focal Length of each lens group)

Group of	Surface NO.	Focal length
			G1	1-2	-38.625
G2	3-6	20.048
			G3	7-12	-7.055
G4	14-20	8.827
			G5	21-24	-23.029

Example 2

(1) Optical structure

Fig. 4 is a sectional view of the zoom lens according to embodiment 2 of the present invention at the time of infinity focusing. The zoom lens is composed of, in order from the object side, a 1 st lens group G1 having negative optical power, a 2 nd lens group G2 having positive optical power, a 3 rd lens group G3 having negative optical power, a 4 th lens group G4 having positive optical power, and a 5 th lens group G5 having negative optical power.

(2) Numerical examples

Next, a numerical example of the zoom lens to which specific numerical values are applied is shown. Fig. 5 and 6 show longitudinal aberration diagrams of the zoom lens at the time of infinity focusing at the wide-angle end and the telephoto end.

(lens data)

(various specification sheets)

	Wide angle end	Intermediate part	Telephoto end
				f	4.521	13.698	42.745
Fno.	1.900	2.510	3.630
				ω	40.986	12.599	4.080
Y	3.300	3.300	3.300
				L	68.000	68.000	68.000

(variable spacing)

	Wide angle end	Intermediate part	Telephoto end
				Photographic distance	INF	INF	INF
D(2)	5.830	4.531	3.087
				D(6)	1.321	13.915	24.029
D(12)	20.965	9.670	1.000
				D(13)	2.291	1.013	0.987
D(20)	1.099	2.378	2.404
				BF	1.000	1.000	1.000
	Wide angle end	Intermediate part	Telephoto end
				Photographic distance	0.3m	1.0m	1.2m
D(13)	2.269	0.940	0.359
				D(20)	1.122	2.450	3.032

(aspherical coefficient)

Surface NO.	K	A4	A6	A8	A10
						14	0.0000E+00	-1.5721E-04	-2.6048E-06	1.5255E-08	-2.2799E-09
15	0.0000E+00	2.2305E-04	-3.3196E-07	-1.0576E-07	1.6823E-09
						23	0.0000E+00	-6.9128E-05	3.0041E-05	2.3662E-06	-2.4054E-07
24	0.0000E+00	2.0961E-04	1.9349E-05	1.6146E-06	-1.7801E-07

(focal Length of each lens group)

Group of	Surface NO.	Focal length
			G1	1-2	-28.342
G2	3-6	18.284
			G3	7-12	-7.731
G4	14-20	8.920
			G5	21-24	-34.185

Example 3

(1) Optical structure

Fig. 7 is a cross-sectional view showing the zoom lens according to embodiment 3 of the present invention in infinity focusing. The zoom lens is composed of, in order from the object side, a 1 st lens group G1 having negative optical power, a 2 nd lens group G2 having positive optical power, a 3 rd lens group G3 having negative optical power, a 4 th lens group G4 having positive optical power, and a 5 th lens group G5 having positive optical power.

The 3 rd lens group G3 is composed of a biconcave lens and a cemented lens formed by joining the biconcave lens and a biconvex lens in order from the object side.

(2) Numerical examples

Next, a numerical example of the zoom lens to which specific numerical values are applied is shown. Fig. 8 and 9 show longitudinal aberration diagrams of the zoom lens at the time of infinity focusing at the wide-angle end and the telephoto end.

(lens data)

Surface NO.	r	D	Nd	vd
						1	49.662	1.100	1.75211	25.05
2	24.365	D(2)
					3	52.199	2.817	1.60300	65.44
4	-455.288	0.150
					5	22.145	4.502	1.60300	65.44
6	-250.778	D(6)
					7	-131.554	0.500	2.00100	29.13
8	10.294	2.316
					9	-9.965	0.500	1.91082	35.25
10	13.339	2.626	1.98613	16.48
					11	-27.147	D(11)
12S	INF	D(12)
					13*	7.282	3.782	1.55332	71.68
14*	-29.011	1.299
					15	8.720	0.600	1.79360	37.09
16	5.810	1.435
					17	6.829	3.614	1.59282	68.62
18	-6.176	0.500	2.00100	29.13
					19	-17.876	D(19)
20	84.650	0.500	2.00100	29.13
					21	5.140	2.890
22*	13.941	2.911	1.61608	25.80
					23*	-7.974	2.207
24	INF	0.800	1.51633	64.14
					25	INF	BF

(various specification sheets)

(variable spacing)

	Wide angle end	Intermediate part	Telephoto end
				Photographic distance	INF	INF	INF
D(2)	5.867	8.221	3.613
				D(6)	1.100	10.778	20.678
D(11)	18.323	6.292	1.000
				D(12)	4.849	2.332	1.589
D(19)	1.150	3.667	4.410
				BF	1.000	1.000	1.000
	Wide angle end	Intermediate part	Telephoto end
				Photographic distance	0.3m	1.0m	1.2m
D(12)	4.823	2.229	0.311
				D(19)	1.176	3.769	5.687

(aspherical coefficient)

Surface NO.	K	A4	A6	A8	A10
						13	0.0000E+00	-1.7913E-04	-2.9441E-06	-1.4515E-09	-1.5791E-09
14	0.0000E+00	2.1837E-04	-1.2362E-06	-7.6305E-08	1.5419E-09
						22	0.0000E+00	-1.7083E-04	-3.7080E-05	2.6028E-06	-2.0109E-09
23	0.0000E+00	1.5029E-04	-5.5221E-06	-1.6829E-06	1.1828E-07

(focal Length of each lens group)

Group of	Surface NO.	Focal length
			G1	1-2	-64.212
G2	3-6	23.976
			G3	7-11	-6.492
G4	13-19	9.064
			G5	20-23	50.855

Example 4

(1) Optical structure

Fig. 10 is a sectional view of a zoom lens according to embodiment 4 of the present invention at the time of infinity focusing. The zoom lens is composed of, in order from the object side, a 1 st lens group G1 having negative optical power, a 2 nd lens group G2 having positive optical power, a 3 rd lens group G3 having negative optical power, a 4 th lens group G4 having positive optical power, and a 5 th lens group G5 having negative optical power.

(2) Numerical examples

Next, a numerical example of the zoom lens to which specific numerical values are applied is shown. Fig. 11 and 12 show longitudinal aberration diagrams of the zoom lens at the time of infinity focusing at the wide-angle end and the telephoto end.

(lens data)

(various specification sheets)

	Wide angle end	Intermediate part	Telephoto end
				f	4.543	13.698	43.216
Fno.	2.000	2.510	3.629
				ω	40.827	12.767	4.070
Y	3.300	3.300	3.300
				L	66.501	66.501	66.501

(variable spacing)

	Wide angle end	Intermediate part	Telephoto end
				Photographic distance	INF	INF	INF
D(2)	7.471	6.087	3.439
				D(6)	1.100	12.759	23.009
D(12)	18.877	8.601	1.000
				D(13)	2.051	0.763	1.870
D(20)	1.100	2.388	1.282
				BF	1.000	1.000	1.000
	Wide angle end	Intermediate part	Telephoto end
				Photographic distance	0.3m	1.0m	1.2m
D(13)	2.024	0.676	1.080
				D(20)	1.127	2.475	2.072

(aspherical coefficient)

Surface NO.	K	A4	A6	A8	A10
						14	0.0000E+00	-1.5967E-04	-2.5363E-06	6.3789E-09	-2.2278E-09
15	0.0000E+00	2.3047E-04	-6.1012E-07	-1.0092E-07	1.4691E-09
						23	0.0000E+00	-9.2171E-05	4.3552E-06	9.6814E-07	-1.1530E-07
24	0.0000E+00	4.9774E-06	4.9500E-06	-1.2885E-06	-6.5196E-09

(focal Length of each lens group)

Group of	Surface NO.	Focal length
			G1	1-2	-38.662
G2	3-6	20.084
			G3	7-12	-7.414
G4	14-20	8.890
			G5	21-24	-24.780

Example 5

(1) Optical structure

Fig. 13 is a sectional view of a zoom lens according to embodiment 5 of the present invention at the time of infinity focusing. The zoom lens is composed of, in order from the object side, a 1 st lens group G1 having negative optical power, a 2 nd lens group G2 having positive optical power, a 3 rd lens group G3 having negative optical power, a 4 th lens group G4 having positive optical power, and a 5 th lens group G5 having negative optical power.

The 2 nd lens group G2 is composed of a biconvex lens and a positive meniscus lens in order from the object side.

The 3 rd lens group G3 is composed of a biconcave lens, a cemented lens formed by a negative meniscus lens cemented with a positive meniscus lens, and a negative meniscus lens in order from the object side.

The 5 th lens group G5 is composed of a negative meniscus lens and a positive meniscus lens in order from the object side.

(2) Numerical examples

Next, a numerical example of the zoom lens to which specific numerical values are applied is shown. Fig. 14 and 15 show longitudinal aberration diagrams of the zoom lens at the time of infinity focusing at the wide-angle end and the telephoto end.

(lens data)

Surface NO.	r	D	Nd	vd
						1	157.165	1.100	1.84666	23.78
2	44.488	D(2)
					3	66.576	2.977	1.59349	67.00
4	-106.692	0.150
					5	30.559	3.184	1.65844	50.85
6	306.103	D(6)
					7	-2515.812	0.500	2.00100	29.13
8	12.800	2.232
					9	-8.950	0.500	1.91082	35.25
10	-215.924	3.481	1.94595	17.98
					11	-11.344	0.150
12	-14.692	0.600	1.95375	32.32
					13	-31.030	D(13)
14S	INF	D(14)
					15*	6.946	3.712	1.55332	71.68
16*	-39.702	0.273
					17	8.251	0.600	1.64850	53.02
18	5.450	0.927
					19	6.856	3.800	1.59282	68.62
20	-5.734	0.500	2.00100	29.13
					21	-14.292	D(21)
22	41.044	0.500	2.00100	29.13
					23	4.908	2.933
24*	-90.351	2.222	1.63973	23.53
					25*	-6.610	2.200
26	INF	0.800	1.51633	64.14
					27	INF	BF

(various specification sheets)

(variable spacing)

	Wide angle end	Intermediate part	Telephoto end
				Photographic distance	INF	INF	INF
D(2)	11.859	9.629	2.526
				D(6)	1.171	16.301	30.092
D(13)	20.589	7.688	0.999
				D(14)	2.444	1.173	0.991
D(21)	1.096	2.368	2.550
				BF	1.000	1.000	1.000
	Wide angle end	Intermediate part	Telephoto end
				Photographic distance	0.3m	1.0m	1.2m
D(14)	2.425	1.111	0.376
				D(21)	1.116	2.429	3.164

(aspherical coefficient)

Surface NO.	K	A4	A6	A8	A10
						15	0.0000E+00	-1.5421E-04	-2.6083E-06	4.3172E-09	-2.3523E-09
16	0.0000E+00	2.6011E-04	-1.4695E-06	-9.9759E-08	1.6512E-09
						24	0.0000E+00	-4.4671E-04	2.0712E-06	7.2361E-06	-4.3248E-07
25	0.0000E+00	6.8398E-04	-5.5083E-06	4.4141E-06	-2.4151E-07

(focal Length of each lens group)

Group of	Surface NO.	Focal length
			G1	1-2	-72.901
G2	3-6	29.672
			G3	7-13	-8.369
G4	15-21	8.220
			G5	22-25	-59.503

Example 6

(1) Optical structure

Fig. 16 is a sectional view of a zoom lens according to embodiment 6 of the present invention at the time of infinity focusing. The zoom lens is composed of, in order from the object side, a 1 st lens group G1 having negative optical power, a 2 nd lens group G2 having positive optical power, a 3 rd lens group G3 having negative optical power, a 4 th lens group G4 having positive optical power, and a 5 th lens group G5 having positive optical power.

The 2 nd lens group G2 is constituted by a biconvex lens.

The 3 rd lens group G3 is composed of a biconcave lens and a cemented lens formed by a biconcave lens and a positive meniscus lens, in order from the object side.

The 4 th lens group G4 is composed of, in order from the object side, a biconvex lens, a cemented lens formed by joining a negative meniscus lens and the biconvex lens, and a cemented lens formed by joining a biconcave lens and the biconvex lens.

The 5 th lens group G5 is constituted by a biconvex lens.

(2) Numerical examples

Next, a numerical example of the zoom lens to which specific numerical values are applied is shown. Fig. 17 and 18 show longitudinal aberration diagrams of the zoom lens at the time of infinity focusing at the wide-angle end and the telephoto end.

(lens data)

(various specification sheets)

	Wide angle end	Intermediate part	Telephoto end
				f	4.431	13.695	41.809
Fno.	1.854	3.065	3.357
				ω	41.211	12.924	4.225
Y	3.300	3.300	3.300
				L	63.000	63.000	63.000

(variable spacing)

	Wide angle end	Intermediate part	Telephoto end
				Photographic distance	INF	INF	INF
D(2)	8.327	7.353	1.559
				D(4)	1.372	7.719	16.337
D(9)	10.394	5.020	2.197
				D(10)	11.714	5.247	0.868
D(18)	2.382	8.850	13.229
				BF	0.200	0.200	0.200
	Wide angle end	Intermediate part	Telephoto end
				Photographic distance	0.3m	1.0m	1.2m
D(10)	11.526	6.645	3.385
				D(18)	2.570	7.452	10.710

(aspherical coefficient)

Surface NO.	K	A4	A6	A8	A10
						11	0.0000E+00	1.8960E-04	5.7996E-06	-7.7026E-09	1.2534E-09
12	0.0000E+00	6.3995E-04	9.5312E-06	1.1571E-07	9.3991E-10
						19	0.0000E+00	-3.2148E-04	-1.8335E-06	1.3205E-06	1.3701E-08
20	0.0000E+00	7.1958E-05	6.6237E-06	1.5684E-07	6.2622E-08

(focal Length of each lens group)

Example 7

(1) Optical structure

Fig. 19 is a sectional view of a zoom lens according to embodiment 7 of the present invention at the time of infinity focusing. The zoom lens is composed of, in order from the object side, a 1 st lens group G1 having negative optical power, a 2 nd lens group G2 having positive optical power, a 3 rd lens group G3 having negative optical power, and a 4 th lens group G4 having positive optical power.

The 2 nd lens group G2 is composed of a lenticular lens and a lenticular lens.

The 3 rd lens group G3 is composed of, in order from the object side, a negative meniscus lens, and a cemented lens formed by a biconcave lens and a biconvex lens.

The 4 th lens group G4 is composed of, in order from the object side, a biconvex lens, a negative meniscus lens, a cemented lens formed by joining the biconvex lens and the negative meniscus lens, a biconcave lens, and a biconvex lens.

(2) Numerical examples

Next, a numerical example of the zoom lens to which specific numerical values are applied is shown. Fig. 20 and 21 show longitudinal aberration diagrams of the zoom lens at the time of infinity focusing at the wide-angle end and the telephoto end.

(lens data)

Surface NO.	r	D	Nd	vd
						1	160.265	1.100	1.95375	32.32
2	33.798	D(2)
					3	91.299	4.469	1.59349	67.00
4	-50.765	0.150
					5	23.387	4.500	1.59349	67.00
6	-648.643	D(6)
					7	55.085	0.500	2.00100	29.13
8	10.545	2.896
					9	-9.384	0.500	1.91082	35.25
10	23.986	2.414	1.98613	16.48
					11	-21.800	D(11)
12S	INF	D(12)
					13*	7.101	3.586	1.55332	71.68
14*	-58.637	1.148
					15	6.868	0.600	1.61799	63.40
16	4.789	0.848
					17	6.100	3.634	1.59282	68.62
18	-7.218	0.500	2.00100	29.13
					19	-12.615	0.416
20	-33.584	0.500	1.96300	24.11
					21	5.235	1.804
22*	7.819	2.306	1.63973	23.53
					23*	-121.819	D(23)
24	INF	0.800	1.51633	64.14
					25	INF	BF

(various specification sheets)

	Wide angle end	Intermediate part	Telephoto end
				f	4.564	13.487	36.162
Fno.	2.001	2.508	3.628
				ω	40.942	13.111	4.954
Y	3.300	3.300	3.300
				L	71.500	71.500	71.500

(variable spacing)

(aspherical coefficient)

Surface NO.	K	A4	A6	A8	A10
						13	0.0000E+00	-2.1448E-04	-2.4845E-06	-2.1469E-08	-1.9870E-09
14	0.0000E+00	1.2206E-04	8.3942E-07	-8.3526E-08	9.7903E-10
						22	0.0000E+00	-6.3481E-04	-1.4507E-05	-5.4029E-06	2.8740E-07
23	0.0000E+00	-5.7961E-04	-2.9081E-05	-4.5313E-06	2.2271E-07

(focal Length of each lens group)

Group of	Surface NO.	Focal length
			G1	1-2	-48.070
G2	3-6	23.760
			G3	7-11	-8.238
G4	13-23	11.255

(Table 1)

	Example 1	Example 2	Example 3	Example 4	Example 5	Example 6	Example 7
								(1)β23w/tan(ωw)	0.26	0.37	0.16	0.27	0.15	0.31	0.23
(2)f2/√(fw×ft)	1.42	1.32	1.74	1.43	2.16	1.36	1.85
								(3)(β23t/β23w)/(ft/fw)	0.74	0.66	0.47	0.94	0.59	0.38	0.75
(4)\|f1/fw\|	8.59	6.27	14.27	8.51	16.20	9.15	10.53
								(5)\|f1/f2\|	1.92	1.55	2.68	1.93	2.46	2.19	2.02
(6)\|f12t/ft\|	0.73	0.77	0.81	0.75	1.10	0.77	1.05
								(7)\|X3\|/√(fw×ft)	1.30	1.44	1.26	1.28	1.43	0.60	1.07
(8)\|f2/f3\|	2.83	2.36	3.69	2.71	3.55	2.34	2.88
								(9)ν2p_max	65.44	63.40	65.44	65.44	67.00	40.42	67.00

Industrial applicability

The zoom lens according to the present invention can be suitably used as a zoom lens of an imaging device such as a monitoring camera, a film camera, a digital camera, or a digital video camera.

Claims

1. A zoom lens includes, in order from an object side to an image side: a 1 st lens group having negative optical power, a 2 nd lens group having positive optical power, a 3 rd lens group having negative optical power, and a 4 th lens group having positive optical power, the 1 st lens group being fixed at a time of zooming from a wide angle end to a telephoto end, at least the 2 nd lens group, the 3 rd lens group, and the 4 th lens group being moved along an optical axis, an interval between adjacent lens groups being varied on the optical axis, the zoom lens satisfying the following formula:

0.1≤β23w/tan(ωw)≤0.5···········(1)

1.0≤f2/√(fw×ft)≤3.25···········(2)

0.15≤(β23t/β23w)/(ft/fw)≤0.98··(3)

wherein,,

And (2) ft: focal length of the zoom lens at infinity focusing at telephoto end

f2: focal length of the 2 nd lens group

ωw: half field angle of outermost ray at wide angle end

Beta 23t: and a combined lateral magnification of the 2 nd lens group and the 3 rd lens group at the time of infinity focusing at a telephoto end.

2. The zoom lens of claim 1, satisfying the following formula:

5.0≤|f1/fw|≤20.0···(4)

wherein,,

f1: focal length of the 1 st lens group.

3. The zoom lens according to claim 1 or claim 2,

the 2 nd lens group is composed of 2 or less positive lenses.

4. The zoom lens according to any one of claim 1 to 3,

the 1 st lens group is composed of 1 piece of negative lenses.

5. The zoom lens according to any one of claims 1 to 4, satisfying the following formula:

0.5≤|f1/f2|≤4.0···(5)。

6. the zoom lens according to any one of claims 1 to 5, satisfying the following formula:

0.5≤|f12t/ft|≤3.0···(6)

wherein,,

f12t: a combined focal length of the 1 st lens group and the 2 nd lens group at the time of infinity focusing at the telephoto end.

7. The zoom lens according to any one of claims 1 to 6, satisfying the following formula:

0.3≤|X3|/√(fw×ft)≤2.0···(7)

wherein,,

x3: and a movement amount of the 3 rd lens group in the optical axis direction when changing magnification from the wide-angle end to the telephoto end.

8. The zoom lens according to any one of claims 1 to 7, satisfying the following formula:

1.5≤|f2/f3|≤6.0···(8)

f3: focal length of the 3 rd lens group.

9. The zoom lens according to any one of claims 1 to 8, satisfying the following formula:

ν2p＿max≤70···(9)

wherein,,

v 2 p_max: and the maximum value of Abbe numbers of the positive lenses in the 2 nd lens group.

10. The zoom lens according to any one of claim 1 to 9,

an aperture stop is disposed between the 3 rd lens group and the 4 th lens group, and is fixed when zooming from a wide-angle end to a telephoto end and focusing from infinity to a close-range.

11. An image pickup apparatus provided with the zoom lens according to any one of claims 1 to 10, and an image pickup element that converts an optical image formed by the zoom lens into an electric signal on an image side of the optical system.