JP2017107067A - Zoom lens, optical apparatus and method for manufacturing zoom lens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a compact zoom lens having a large diameter.SOLUTION: The zoom lens comprises, arranged successively from an object side along the optical axis, a first lens group G1 having a negative refractive power, a second lens group G2 having a positive refractive power, a third lens group G3 having a negative refractive power, and a fourth lens group G4 having a positive refractive power. Upon varying powers, all of intervals between adjoining lens groups change; the second lens group includes, arranged successively from the object side, a positive lens L21 and a negative lens L22 and has five lenses; and the zoom lens satisfies a conditional formula of 1.15<T2/fw<1.65, where T2 represents a thickness of the second lens group on the optical axis, and fw represents a focal length of the zoom lens as a whole in a wide angle end state.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a zoom lens, an optical apparatus using the same, and a method for manufacturing the zoom lens.

  A zoom lens having a large aperture has been proposed as a zoom lens used in a photographing optical system such as a digital camera, a film camera, and a video camera (see, for example, Patent Document 1). In such a conventional large-diameter zoom lens, even if the lens barrel is stored in the camera when the camera is not used, the thickness of each group is large and the lens barrel is not compact, and the lens barrel is retracted in the camera when the camera is not used. Difficult and compact is required.

JP 2014-41222 A

The zoom lens according to the present invention has a first lens group having a negative refractive power, a second lens group having a positive refractive power, and a negative refractive power, which are arranged in order from the object side along the optical axis. The zoom lens has a third lens group and a fourth lens group having a positive refractive power. During zooming, the distance between all adjacent lens groups changes, and the second lens group is arranged in order from the object side. It comprises a positive lens and a negative lens and has five lenses, and satisfies the following conditional expression.
1.15 <T2 / fw <1.65
Where T2: thickness of the second lens group on the optical axis fw: focal length of the entire zoom lens in the wide-angle end state

  An optical apparatus according to the present invention is configured by mounting the zoom lens.

The manufacturing method according to the present invention has a first lens group having a negative refractive power, a second lens group having a positive refractive power, and a negative refractive power, which are arranged in order from the object side along the optical axis. A method of manufacturing a zoom lens having a third lens group and a fourth lens group having a positive refractive power, wherein the distance between all adjacent lens groups changes during zooming, and the second lens group Includes a positive lens and a negative lens arranged in order from the object side, and includes five lenses, and the first to fourth lens groups are placed in a lens barrel so as to satisfy the following conditional expression: It is the structure to arrange in.
1.15 <T2 / fw <1.65
Where T2: thickness of the second lens group on the optical axis fw: focal length of the entire zoom lens in the wide-angle end state

It is sectional drawing which shows the lens structure of the zoom lens which concerns on 1st Example of this embodiment. FIG. 6 is a diagram illustrating various aberrations of the zoom lens according to Example 1 in a wide-angle end state, an intermediate position separation state, and a telephoto end state. It is sectional drawing which shows the lens structure of the zoom lens which concerns on 2nd Example of this embodiment. FIG. 12 is a diagram illustrating various aberrations of the zoom lens according to Example 2 in a wide-angle end state, an intermediate position separation state, and a telephoto end state. It is sectional drawing which shows the lens structure of the zoom lens which concerns on 3rd Example of this embodiment. FIG. 12 is a diagram illustrating various aberrations of the zoom lens according to Example 3 in the wide-angle end state, the intermediate position separation state, and the telephoto end state. It is sectional drawing which shows the lens structure of the zoom lens which concerns on 4th Example of this embodiment. FIG. 12 is a diagram illustrating various aberrations of the zoom lens according to Example 4 in a wide-angle end state, an intermediate position separation state, and a telephoto end state. It is the schematic which shows the structure of the camera provided with the zoom lens which concerns on this embodiment. 5 is a flowchart illustrating an outline of a method for manufacturing a zoom lens according to the present embodiment.

  Hereinafter, the zoom lens of the present embodiment will be described with reference to the drawings. As shown in FIG. 1, the zoom lens ZL (1) as an example of the zoom lens ZL according to the present embodiment includes a first lens group G1 having negative refractive power arranged in order from the object side, and positive refraction. A second lens group G2 having a power, a third lens group G3 having a negative refractive power, and a fourth lens group G4 having a positive refractive power. The interval of changes. Further, the second lens group G2 includes a positive lens L21 and a negative lens L22 arranged in order from the object side, and includes five lenses.

Under the above configuration, the zoom lens ZL according to the present embodiment satisfies the following conditional expression (1).
1.15 <T2 / fw <1.65 (1)
Where T2: thickness of the second lens group G2 on the optical axis fw: focal length of the entire zoom lens in the wide-angle end state

  Conditional expression (1) defines the thickness of the second lens group G2 as a ratio to the focal length of the entire zoom lens in the wide-angle end state. By satisfying this conditional expression (1), spherical aberration is achieved. The coma aberration can be corrected well.

  If the upper limit of conditional expression (1) is exceeded, the thickness of the second lens group G2 increases, and in order to make the zoom lens compact, it is necessary to reduce the thickness of the other lens groups. This makes it difficult to correct astigmatism, field curvature, and lateral chromatic aberration. On the other hand, if the lower limit of conditional expression (1) is not reached, correction of spherical aberration and coma becomes difficult.

  In order to secure the effect of the present embodiment, it is preferable to set the upper limit of conditional expression (1) to 1.60. In order to secure the effect of the present embodiment, it is preferable to set the upper limit of conditional expression (1) to 1.55. In order to secure the effect of the present embodiment, it is preferable to set the lower limit of conditional expression (1) to 1.20. In order to make the effect of the present embodiment more reliable, it is preferable to set the lower limit value of the conditional expression (1) to 1.25. In order to secure the effect of the present embodiment, it is preferable to set the lower limit of conditional expression (1) to 1.30.

  The zoom lens according to the present embodiment is preferably configured such that the fourth lens group moves to the image plane side upon zooming from the wide-angle end state to the telephoto end state. With this configuration, it is possible to correct image plane variations caused by zooming (magnification operation).

It is desirable that the zoom lens according to the present embodiment satisfies the following conditional expression (2).
1.00 <T2 / T1 <2.50 (2)
T1: Thickness of the first lens group G1 on the optical axis

  Conditional expression (2) defines the ratio of the thicknesses of the first lens group G1 and the second lens group G2. By satisfying this conditional expression (2), spherical aberration, coma aberration, field curvature Astigmatism can be corrected well.

  If the upper limit of conditional expression (2) is exceeded, the thickness of the second lens group G2 is increased with respect to the first lens group G1, which is advantageous in terms of a large aperture, but it is advantageous in terms of field curvature and astigmatism. Correction becomes difficult. If the lower limit of conditional expression (2) is not reached, the thickness of the second lens group G2 is smaller than the first lens group G1, which is advantageous in terms of widening the angle, but it is difficult to correct spherical aberration and coma aberration. It becomes.

  In order to ensure the effect of the present embodiment, it is preferable to set the upper limit of conditional expression (2) to 2.35. In order to make the effect of the present embodiment more reliable, it is preferable to set the upper limit of conditional expression (2) to 2.20. In order to ensure the effect of the present embodiment, it is preferable to set the lower limit of conditional expression (2) to 1.20. In order to make the effect of the present embodiment more reliable, it is preferable to set the lower limit value of the conditional expression (2) to 1.40. In order to secure the effect of the present embodiment, it is preferable to set the lower limit of conditional expression (2) to 1.50.

It is desirable that the zoom lens according to the present embodiment satisfies the following conditional expression (3).
2.40 <f3 / fw <5.50 (3)
Where f3: focal length of the third lens group G3

  Conditional expression (3) defines the focal length of the third lens group G3 as a ratio to the focal length of the entire zoom lens in the wide-angle end state. By satisfying this conditional expression (3), spherical aberration is satisfied. In addition, it is possible to reduce the angle of incidence of the outermost ray on the image plane while reducing the curvature of field. If the upper limit of conditional expression (3) is exceeded, the refractive power (power) of the third lens group G3 becomes too weak, making it difficult to correct spherical aberration and image plane position fluctuations. In order to perform these corrections satisfactorily while exceeding the upper limit, there arises a problem that the size of the optical system is increased. If the lower limit of conditional expression (3) is not reached, the refractive power (power) of the third lens group G3 becomes too strong, which is advantageous for downsizing, but the incident angle of peripheral rays on the image plane becomes too large. Not desirable.

  In order to secure the effect of the present embodiment, it is preferable to set the upper limit of conditional expression (3) to 5.30. In order to secure the effect of the present embodiment, it is preferable to set the upper limit of conditional expression (3) to 5.10. In order to secure the effect of the present embodiment, it is preferable to set the lower limit of conditional expression (3) to 2.50. In order to secure the effect of the present embodiment, it is preferable to set the lower limit of conditional expression (3) to 2.60.

Under the above configuration, the zoom lens ZL according to the present embodiment satisfies the following conditional expression (4).
1.60 <(− f1) / fw <2.50 (4)
F1: Focal length of the first lens group G1

  Conditional expression (4) defines the thickness of the first lens group G1 as a ratio to the focal length of the entire zoom lens in the wide-angle end state. By satisfying this conditional expression (4), the angle of view Astigmatism, curvature of field, lateral chromatic aberration, and coma, which increase with an increase in chromaticity, can be corrected well.

  If the lower limit of conditional expression (4) is not reached, it is advantageous for shortening the overall length, but it becomes difficult to correct astigmatism, field curvature, and lateral chromatic aberration. Exceeding the upper limit of conditional expression (4) is advantageous for correction of astigmatism, curvature of field, etc., but has the problem of increasing the size of the optical system for correcting spherical aberration and coma.

  In order to secure the effect of the present embodiment, it is preferable to set the lower limit of conditional expression (4) to 1.65. In order to secure the effect of the present embodiment, it is preferable to set the lower limit of conditional expression (4) to 1.68. In order to secure the effect of the present embodiment, it is preferable to set the upper limit of conditional expression (4) to 2.30. In order to secure the effect of the present embodiment, it is preferable to set the upper limit of conditional expression (4) to 2.10.

Under the above configuration, the zoom lens ZL according to the present embodiment satisfies the following conditional expression (5).
1.20 <f3 / (− f1) <3.00 (5)
Where f1: focal length of the first lens group G1 f3: focal length of the third lens group G3

  Conditional expression (5) defines the focal length of the third lens group G3 by the ratio of the focal length of the first lens group G1. By satisfying this conditional expression (5), spherical aberration, image surface It is possible to reduce the angle of incidence of the outermost ray on the image plane while reducing the curvature. When the upper limit of conditional expression (5) is exceeded, the refractive power (power) of the third lens group G3 becomes too weak, and it becomes difficult to correct spherical aberration and image plane position fluctuation. In order to perform these corrections satisfactorily while exceeding the upper limit, there arises a problem that the size of the optical system is increased. If the lower limit of conditional expression (5) is not reached, the refractive power (power) of the third lens group G3 becomes too strong, which is advantageous for downsizing, but the incident angle of peripheral rays on the image plane becomes too large. Not desirable. Further, there is a problem that the size of the optical system is increased to correct spherical aberration and coma aberration.

  In order to secure the effect of the present embodiment, it is preferable to set the upper limit of conditional expression (5) to 2.80. In order to secure the effect of the present embodiment, it is preferable to set the upper limit of conditional expression (5) to 2.60. In order to secure the effect of the present embodiment, it is preferable to set the lower limit of conditional expression (5) to 1.30. In order to make the effect of the present embodiment more reliable, it is preferable to set the lower limit of conditional expression (5) to 1.40.

It is desirable that the zoom lens according to the present embodiment satisfies the following conditional expression (6).
35.0 <ωw <65.0 (6)
Where ωw is the half angle of view of the entire zoom lens in the wide-angle end state (unit: degree)

Conditional expression (6) is a conditional expression that defines an optimum value of the half angle of view at the wide-angle end.
By satisfying this conditional expression, various aberrations such as coma, curvature of field, and distortion can be favorably corrected while having a wide half angle of view.

  In order to secure the effect of the present embodiment, it is preferable to set the lower limit of conditional expression (6) to 36.0. In order to secure the effect of the present embodiment, it is preferable to set the lower limit of conditional expression (6) to 37.0. In order to secure the effect of the present embodiment, it is preferable to set the upper limit of conditional expression (6) to 60.0. In order to secure the effect of the present embodiment, it is preferable to set the upper limit of conditional expression (6) to 55.0. In order to make the effect of the present embodiment more certain, it is preferable to set the upper limit of conditional expression (6) to 50.0.

  In the zoom lens of the present embodiment, the second lens group G2 includes the positive lens, the negative lens, the cemented lens of the negative lens and the positive lens, and the positive lens arranged in order from the object side, that is, five lenses. It is preferable that it is comprised from these. As a result, it is possible to satisfactorily correct spherical aberration and coma aberration due to a large aperture while reducing the thickness of the second lens group G2.

  In the zoom lens according to the present embodiment, it is preferable that the first lens group G1 includes a negative lens, a negative lens, and a positive lens arranged in order on the object side. This makes it possible to suppress spherical aberration that occurs in the first lens group G1 while correcting astigmatism and curvature of field, and to suppress variations in spherical aberration that occur due to zooming (magnification operation).

  In the zoom lens ZL according to the present embodiment, it is preferable that at least a part of the third lens group G3 constitutes a focusing lens group that moves in the optical axis direction when focused. As a result, variations in various aberrations such as spherical aberration and coma during focusing can be reduced.

  In the zoom lens ZL according to the present embodiment, it is preferable that at least a part of the second lens group G2 constitutes an anti-vibration lens group having a displacement component in a direction perpendicular to the optical axis. As a result, fluctuations in various aberrations such as coma during correction of camera shake can be reduced.

  The optical apparatus according to this embodiment includes the zoom lens (variable magnification optical system) configured as described above. As a specific example, a camera (optical apparatus) including the zoom lens ZL will be described with reference to FIG. This camera 1 is a digital camera provided with the zoom lens according to the above-described embodiment as a photographing lens 2 as shown in FIG. In the camera 1, light from an object (subject) (not shown) is collected by the photographing lens 2 and reaches the image sensor 3. Thereby, the light from the subject is picked up by the image pickup device 3 and recorded as a subject image in a memory (not shown). In this way, the photographer can shoot the subject with the camera 1. This camera may be a mirrorless camera or a single-lens reflex camera having a quick return mirror.

  With the above configuration, the camera 1 equipped with the zoom lens ZL as the photographing lens 2 has a large-aperture zoom lens configuration, and can be retracted when the camera is not used by making the lens barrel compact while performing various aberration corrections satisfactorily. It can be set as a simple structure.

  Next, the method for manufacturing the zoom lens ZL described above will be outlined with reference to FIG. First, the first lens group G1 having a negative refractive power, the second lens group G2 having a positive refractive power, and a negative refractive power, which are arranged in order from the object side along the optical axis in the lens barrel. A third lens group G3 and a fourth lens group G4 having a positive refractive power are arranged (step ST1). At the time of zooming, the interval between all adjacent lens groups is changed (step ST2). At this time, the second lens group G2 includes a positive lens and a negative lens arranged in order from the object side, and includes five lenses (step ST3). Further, each lens is arranged in the lens barrel so as to satisfy at least the conditional expression (1) (step ST4).

  Hereinafter, zoom lenses ZL according to examples of the present embodiment will be described with reference to the drawings. FIGS. 1, 3, 5, and 7 are cross-sectional views illustrating the configuration and refractive power distribution of the zoom lenses ZL {ZL (1) to ZL (4)} according to the first to fourth embodiments. In the lower part of the sectional view of the zoom lenses ZL (1) to ZL (4), each zooming (magnification operation) from the wide-angle end state (w) through the intermediate position (m) to the telephoto end state (t) is shown. The movement direction along the optical axis of the lens group is indicated by an arrow. In the zoom lens ZL, the fourth lens group G4 moves to the image plane side when zooming (zooming operation) from the wide-angle end state (w) to the telephoto end state (t) through the intermediate position (m). It is a configuration.

  The third lens group G3 is used as a focusing lens, and in the figure, the moving direction when the focusing lens focuses on an object at a short distance from infinity is indicated by an arrow together with the symbol “∞”. Further, at least a part of the second lens group G2 is used as an anti-vibration lens having a displacement component perpendicular to the optical axis.

  In FIG. 1, FIG. 3, FIG. 5, and FIG. 7, each lens group is represented by a combination of symbol G and a number, and each lens is represented by a combination of symbol L and a number. In this case, in order to prevent complications due to an increase in the types and numbers of codes and numbers, the lens groups and the like are represented using combinations of codes and numbers independently for each embodiment. For this reason, even if the combination of the same code | symbol and number between different Examples is used, it does not mean that it is the same structure.

  Tables 1 to 4 are shown below, and these are tables showing various data in the first to fourth examples.

  In the table of [lens specifications], the surface number indicates the order of the optical surfaces from the object side along the light traveling direction, and R is the radius of curvature of each optical surface (the surface whose curvature center is located on the image side). D is a positive value), D is a surface interval that is the distance on the optical axis from each optical surface to the next optical surface (or image surface), nd is the refractive index of the material of the optical member with respect to d-line, and νd is optical The Abbe numbers based on the d-line of the material of the member are shown respectively. “∞” of the radius of curvature indicates a plane or aperture, (FC) indicates a flare cut FC, (aperture S) indicates an aperture stop S, and an image plane indicates an image plane I. Description of the refractive index of air nd = 1.000 is omitted. When the lens surface is an aspherical surface, the surface number is marked with * and the radius of curvature R column indicates the paraxial radius of curvature.

  In the [Overall Specifications] table, f is the focal length of the entire lens system, Fno is the F number, ω is the half angle of view (unit is ° (degrees)), and Y is the image height. BF indicates the distance (back focus) from the final lens surface to the image plane I on the optical axis, and BF (air conversion) indicates the air conversion length of BF. TL indicates the distance obtained by adding BF to the distance from the foremost lens surface to the last lens surface on the optical axis at the time of focusing on infinity, and TL (air conversion) indicates the air conversion length of TL. These values are shown for each zoom state at the wide-angle end (w), the intermediate position (m), and the telephoto end (t).

In the [Aspherical Data] table, the shape of the aspherical surface shown in [Lens Specifications] is shown by the following equation (a). X (y) is the distance along the optical axis direction from the tangential plane at the apex of the aspheric surface to the position on the aspheric surface at height y (zag amount), and R is the radius of curvature of the reference sphere (paraxial curvature radius) , Κ is the conic constant, and Ai is the i-th aspherical coefficient. “E-n” indicates “× 10 ⁻ⁿ ”. For example, 1.234E-05 = 1.234 × 10 ⁻⁵ . The secondary aspheric coefficient A2 is 0, and the description thereof is omitted.

X (y) = (y ² / R) / {1+ (1−κ × y ² / R ² ) ^1/2 } + A4 × y ⁴ + A6 × y ⁶ + A8 × y ⁸ + A10 × y ¹⁰ (a )

  The table of [variable distance data] is a surface number in which the surface distance is “variable” in the table indicating [lens specifications] (for example, surface numbers 6, 17, 19, and 22 in Example 1 described later). (For example, surface intervals D6, D17, D19, and D22 in Example 1 to be described later) are shown for each zoom state at the wide angle end (w), the intermediate position (m), and the telephoto end (t).

  In the table of [Lens Group Data], the start surfaces (most object side surfaces) and focal lengths of the first to fourth lens groups G1 to G4 are shown.

  The table corresponding to the conditional expressions (1) to (6) shows values corresponding to the conditional expressions (1) to (6).

  Hereinafter, in all the specification values, “mm” is generally used for the focal length f, curvature radius R, surface distance D, and other lengths, etc. unless otherwise specified, but the optical system is proportionally enlarged. Alternatively, the same optical performance can be obtained even by proportional reduction, and the present invention is not limited to this.

  The explanation of the table so far is common to all the embodiments, and the duplicate explanation below will be omitted.

(First embodiment)
The first embodiment will be described with reference to FIGS. 1 and 2 and Table 1. FIG. FIG. 1 is a diagram illustrating a lens configuration of a zoom lens according to Example 1 of the present embodiment. The zoom lens ZL (1) according to the first example includes a first lens group G1 having a negative refractive power, a second lens group G2 having a positive refractive power, and negative refraction, which are arranged in order from the object side. The third lens group G3 having power and the fourth lens group G4 having positive refractive power are configured. The sign (+) or (-) attached to each lens group symbol indicates the refractive power of each lens group, and this is the same in all the following embodiments. A flare cut FC is provided on the most object side of the second lens group G2, an aperture stop S is provided therein, and an image plane I is provided on the image plane side of the fourth lens group G4. A filter FL and a cover glass CG (protective glass for the image plane I) are provided in the vicinity of the image plane I on the image side of the fourth lens group G4. The filter FL includes a low-pass filter, an infrared cut filter, and the like.

  The first lens group G1 is composed of a negative meniscus L11 having a convex surface facing the object side, a biconcave negative lens L12, and a positive meniscus lens L13 having a convex surface facing the object side, which are arranged in order from the object side. As a whole, it has a negative refractive power.

  The second lens group G2 includes, in order from the object side, a biconvex positive lens L21, a negative meniscus lens L22 having a convex surface facing the object side, a biconcave negative lens L23, and a biconvex positive lens L24. And a positive biconvex lens L25, and has a positive refractive power as a whole. The negative lens L23 and the positive lens L24 are cemented to form a cemented lens. Both surfaces of the positive lens L21 are aspherical.

  The third lens group G3 includes a negative meniscus lens L31 having a convex surface directed toward the object side.

  The fourth lens group G4 includes a biconvex positive lens L41 and a negative meniscus lens L42 having a convex surface directed to the image side. The both lenses L41 and L42 are cemented to form a cemented lens, and are positive as a whole. Has refractive power. To do. The object side surface of the positive lens L41 has an aspheric shape.

  In the zoom lens ZL (1), the negative meniscus lens L31 constituting the third lens group G3 is moved in the image plane direction, thereby focusing from an infinite distance (far distance object) to a near distance object.

  Furthermore, at least a part of the second lens group G2 (the entire second lens group G2 or any of the lenses L21 to L25 constituting the second lens group G2 or a combination thereof) is perpendicular to the optical axis. An anti-vibration lens group having a directional displacement component is formed, and image blur correction (anti-vibration, camera shake correction) on the image plane I is performed.

  Table 1 below lists values of specifications of the optical system according to the first example.

(Table 1) First Example
[Lens specifications]
Surface number RD nd νd
1 2.9444 0.0649 1.72916 54.61
2 1.0385 0.3846
3 -6.7173 0.0541 1.48749 70.32
4 1.9323 0.0432
5 1.3883 0.147 1.80518 25.45
6 2.4362 (variable)
7 (FC) ∞ 0.027
* 8 1.1541 0.3243 1.6935 53.2
* 9 -6.3139 0.2053
10 (Aperture S) ∞ 0.01081
11 6.7266 0.0324 1.62588 35.72
12 0.852 0.1761
13 -1.2272 0.1709 1.68893 31.16
14 1.3038 0.2457 1.804 46.6
15 -1.3264 0.0108
16 1.2386 0.2216 1.603 65.44
17 -21.4089 (variable)
18 1.1607 0.0432 1.48749 70.32
19 0.7771 (variable)
* 20 2.7103 0.2811 1.696799 55.46
21 -5.3319 0.0432 1.84666 23.8
22 -23.3847 (variable)
23 ∞ 0.0378 1.516798 64.2
24 ∞ 0.0811
25 ∞ 0.0378 1.516798 64.2
26 ∞

[Overall specifications]
Zoom ratio 1.76
Wide angle end Intermediate position Telephoto end f 1 1.35 1.76
Fno 2.07 2.54 2.90
ω 38.1 30.1 25.2
Y 0.676 0.719 0.784
BF 0.6372 0.5875 0.4835
BF (air equivalent) 0.6115 0.5617 0.4577
TL 5.3513 5.0355 5.0005
TL (air equivalent) 5.3256 5.0098 4.9747

[Aspherical data]
Surface number κ A4 A6 A8 A10
8 1 -4.10623E-02 5.80793E-02 0.00000E + 00 0.00000E + 00
9 1 1.25831E-01 5.01887E-02 0.00000E + 00 0.00000E + 00
20 1 -2.73376E-03 1.71606E-02 9.08276E-03 0.00000E + 00

[Variable interval data]
Wide angle end Intermediate position Telephoto end
D6 1.1727 0.5154 0.1081
D17 0.0487 0.1291 0.2054
D19 1.0065 1.3173 1.7173
D22 0.4805 0.4308 0.3268

[Lens group data]
Group number Group first surface Focal length G1 1 -1.887
G2 7 1.425
G3 18 -5.008
G4 20 3.779

[Conditional expression values]
Conditional expression (1) T2 / fw 1.398
Conditional expression (2) T2 / T1 2.015
Conditional expression (3) f3 / fw 5.008
Conditional expression (4) (-f1) / fw 1.887
Conditional expression (5) f3 / (-f1) 2.655
Conditional expression (6) ωw 38.1

  As shown in the table of [Conditional Expression Corresponding Values], the zoom lens ZL (1) according to Example 1 shown in FIG. 1 satisfies all of the conditional expressions (1) to (6).

  FIGS. 2A, 2B, and 2C are graphs showing various aberrations when the zoom lens ZL (1) according to the first example is in focus at infinity in the wide-angle end state, the intermediate position state, and the telephoto end state, respectively. It is.

  From the various aberration diagrams, it can be seen that the zoom lens ZL (1) according to the first example has excellent imaging performance by properly correcting various aberrations from the wide-angle end state to the telephoto end state. Note that distortion can be corrected by image processing after imaging, and optical correction is not required.

  In FIG. 2, FNO represents an F number, and ω represents a half angle of view (unit: “°”) with respect to each image height. d is the d-line (λ = 587.6 nm), g is the g-line (λ = 435.8 nm), C is the C-line (λ = 656.3 nm), and F is the F-line (λ = 486.1 nm). Each is shown. In the spherical aberration diagram, the astigmatism diagram, and the coma aberration diagram, the solid line indicates the sagittal image plane, and the broken line indicates the meridional image plane aberration. This description is the same in all aberration diagrams of the following examples, and a duplicate description is omitted below.

(Second embodiment)
A second embodiment will be described with reference to FIGS. 3 and 4 and Table 2. FIG. FIG. 3 is a diagram illustrating a lens configuration of a zoom lens according to Example 2 of the present embodiment. The zoom lens ZL (2) according to the second example includes a first lens group G1 having negative refractive power, a second lens group G2 having positive refractive power, and negative refraction, which are arranged in order from the object side. The third lens group G3 having power and the fourth lens group G4 having positive refractive power are configured. A flare cut FC is provided on the most object side of the second lens group G2, an aperture stop S is provided therein, and an image plane I is provided on the image plane side of the fourth lens group G4. A filter FL and a cover glass CG (protective glass for the image plane I) are provided in the vicinity of the image plane I on the image side of the fourth lens group G4. The filter FL includes a low-pass filter, an infrared cut filter, and the like.

  The first lens group G1 is composed of a negative meniscus L11 having a convex surface facing the object side, a biconcave negative lens L12, and a positive meniscus lens L13 having a convex surface facing the object side, which are arranged in order from the object side. As a whole, it has a negative refractive power.

  The second lens group G2 includes, in order from the object side, a positive meniscus lens L21 having a convex surface facing the object side, a negative meniscus lens L22 having a convex surface facing the object side, a biconcave negative lens L23, and a biconvex lens. This positive lens L24 and a biconvex positive lens L25 have a positive refractive power as a whole. The negative lens L23 and the positive lens L24 are cemented to form a cemented lens. The image side surface of the positive lens L21 has an aspherical shape.

  The third lens group G3 includes a positive meniscus lens L31 having a convex surface directed toward the object side, and a negative meniscus lens L32 having a convex surface directed toward the object side, and has a negative refracting power as a whole. Both lenses L31 and L32 are cemented to form a cemented lens.

  The fourth lens group G4 includes a biconvex positive lens L41 and a biconcave negative lens L42, and has a positive refractive power as a whole. Both lenses L41 and L42 are cemented to form a cemented lens. The object side surface of the positive lens L41 has an aspheric shape.

  In the zoom lens ZL (2), the third lens group G3 is moved in the image plane direction, thereby focusing from an infinite distance (a long distance object) to a short distance object.

  Furthermore, at least a part of the second lens group G2 (the entire second lens group G2 or any of the lenses L21 to L25 constituting the second lens group G2 or a combination thereof) is perpendicular to the optical axis. An anti-vibration lens group having a directional displacement component is formed, and image blur correction (anti-vibration, camera shake correction) on the image plane I is performed.

  Table 2 below lists values of specifications of the optical system according to the second example.

(Table 2) Second Example
[Lens specifications]
Surface number RD nd νd
1 6.7818 0.0649 1.58913 61.22
2 1.0836 0.3889
3 -3.4914 0.0541 1.48749 70.32
4 2.5348 0.0108
5 1.5417 0.1373 1.80518 25.45
6 2.6905 (variable)
7 (FC) ∞ 0.027
8 1.2976 0.2973 1.618806 63.85
* 9 166.3952 0.474
10 (Aperture S) ∞ 0.0108
11 2.2807 0.0324 1.60342 38.03
12 1.1349 0.1136
13 -8.4358 0.0324 1.69895 30.13
14 0.9554 0.2056 1.603 65.44
15 -3.6769 0.0108
16 1.5346 0.1788 1.816 46.59
17 -3.9897 (variable)
18 1.6299 0.0909 1.834 37.18
19 2.5648 0.0324 1.51742 52.2
20 0.7443 (variable)
* 21 2.7082 0.227 1.72903 54.04
22 -9.3215 0.0432 1.801 34.92
23 14.2371 (variable)
24 ∞ 0.0378 1.516798 64.2
25 ∞ 0.0811
26 ∞ 0.0378 1.516798 64.2
27 ∞

[Overall specifications]
Zoom ratio 1.76
Wide angle end Intermediate position Telephoto end f 1 1.35 1.76
Fno 2.06 2.31 2.64
ω 38.1 30.1 24.8
Y 0.676 0.73 0.784
BF 0.6115 0.5986 0.4728
BF (air equivalent) 0.5858 0.5729 0.4470
TL 5.2270 4.7743 4.6588
TL (air equivalent) 5.2013 4.7486 4.6330

[Aspherical data]
Surface number κ A4 A6 A8 A10
9 1 1.24539E-01 -3.17736E-03 -1.68554E-02 0.00000E + 00
21 1 -9.05856E-03 1.03536E-01 -5.84366E-02 7.21522E-02

[Variable interval data]
Wide angle end Intermediate position Telephoto end
D6 1.2713 0.5603 0.1409
D17 0.2208 0.4354 0.6399
D20 0.6912 0.7478 0.9730
D23 0.4548 0.4419 0.3161

[Lens group data]
Group number Group first surface Focal length G1 1 -1.8865
G2 7 1.4245
G3 18 -5.00798
G4 21 3.7785

[Conditional expression values]
Conditional expression (1) T2 / fw 1.356
Conditional expression (2) T2 / T1 2.067
Conditional expression (3) f3 / fw 3.567
Conditional expression (4) (-f1) / fw 1.709
Conditional expression (5) f3 / (-f1) 2.087
Conditional expression (6) ωw 38.1

  As shown in the table of [Conditional Expression Corresponding Values], the zoom lens ZL (2) according to Example 2 shown in FIG. 3 satisfies all of the conditional expressions (1) to (6).

  FIGS. 4A, 4B, and 4C are graphs showing various aberrations when the zoom lens ZL (2) according to the second example is in focus at infinity in the wide-angle end state, the intermediate position state, and the telephoto end state, respectively. It is.

  From the various aberration diagrams, it can be seen that the zoom lens ZL (2) according to the second example has excellent imaging performance by properly correcting various aberrations from the wide-angle end state to the telephoto end state.

(Third embodiment)
A third embodiment will be described with reference to FIGS. 5 and 6 and Table 3. FIG. FIG. 5 is a diagram illustrating a lens configuration of a zoom lens according to Example 3 of the present embodiment. The zoom lens ZL (3) according to the third example includes a first lens group G1 having negative refractive power, a second lens group G2 having positive refractive power, and negative refraction, which are arranged in order from the object side. The third lens group G3 having power and the fourth lens group G4 having positive refractive power are configured. A flare cut FC is provided on the most object side of the second lens group G2, an aperture stop S is provided therein, and an image plane I is provided on the image plane side of the fourth lens group G4. A filter FL and a cover glass CG (protective glass for the image plane I) are provided in the vicinity of the image plane I on the image side of the fourth lens group G4. The filter FL includes a low-pass filter, an infrared cut filter, and the like.

  The first lens group G1 is composed of a negative meniscus L11 having a convex surface facing the object side, a biconcave negative lens L12, and a positive meniscus lens L13 having a convex surface facing the object side, which are arranged in order from the object side. As a whole, it has a negative refractive power.

  The second lens group G2 includes, in order from the object side, a positive meniscus lens L21 having a convex surface facing the object side, a negative meniscus lens L22 having a convex surface facing the object side, a biconcave negative lens L23, and a biconvex lens. This positive lens L24 and a biconvex positive lens L25 have a positive refractive power as a whole. The negative lens L23 and the positive lens L24 are cemented to form a cemented lens. The image side surface of the positive lens L21 has an aspherical shape.

  The third lens group G3 includes a positive meniscus lens L31 having a convex surface directed toward the object side, and a negative meniscus lens L32 having a convex surface directed toward the object side, and has a negative refracting power as a whole. Both lenses L31 and L32 are cemented to form a cemented lens.

  The fourth lens group G4 includes a biconvex positive lens L41 and a biconcave negative lens L42, and has a positive refractive power as a whole. Both lenses L41 and L42 are cemented to form a cemented lens. The object side surface of the positive lens L41 has an aspheric shape.

  In the zoom lens ZL (3), the third lens group G3 is moved in the image plane direction, thereby focusing from an infinite distance (a long distance object) to a short distance object.

  Furthermore, at least a part of the second lens group G2 (the entire second lens group G2 or any of the lenses L21 to L25 constituting the second lens group G2 or a combination thereof) is perpendicular to the optical axis. An anti-vibration lens group having a directional displacement component is formed, and image blur correction (anti-vibration, camera shake correction) on the image plane I is performed.

  Table 3 below lists values of specifications of the optical system according to the third example.

(Table 3) Third Example
[Lens specifications]
Surface number RD nd νd
1 3.1617 0.0728 1.72916 54.61
2 1.099 0.481
3 -3.8044 0.0607 1.6968 55.52
4 3.2708 0.0121
5 1.8237 0.1804 1.80518 25.45
6 4.6117 (variable)
7 (FC) ∞ 0.0303
8 1.5619 0.3034 1.72903 54.04
* 9 209.5984 0.4278
10 (Aperture S) ∞ 0.0121
11 2.7616 0.0364 1.69895 30.13
12 1.3473 0.0982
13 11.4013 0.0364 1.72825 28.38
14 1.1268 0.2033 1.603 65.44
15 -6.665 0.0913
16 1.947 0.1866 1.816 46.59
17 -3.4748 (variable)
18 2.1426 0.0903 1.846663 23.78
19 3.3842 0.0364 1.60342 38.03
20 0.8437 (variable)
* 21 2.1942 0.2495 1.72903 54.04
22 -55.1888 0.0485 1.8044 39.61
23 5.9502 (variable)
24 ∞ 0.0425 1.516798 64.2
25 ∞ 0.091
26 ∞ 0.0425 1.516798 64.2
27 ∞

[Overall specifications]
Zoom ratio 1.77
Wide angle end Intermediate position Telephoto end f 1 1.27 1.77
Fno 2.06 2.22 2.54
ω 41.3 34.6 26.5
Y 0.765 0.821 0.88
BF 0.5919 0.5875 0.5862
BF (air equivalent) 0.5629 0.5585 0.5573
TL 6.0419 5.5042 5.1419
TL (Air conversion) 6.0129 5.4752 5.1130

[Aspherical data]
Surface number κ A4 A6 A8 A10
9 1 8.22518E-02 -6.73715E-03 0.00000E + 00 0.00000E + 00
21 1 -1.76844E-02 4.58251E-02 -2.36183E-02 3.39188E-02

[Variable interval data]
Wide angle end Intermediate position Telephoto end
D6 1.7306 1.0198 0.3230
D17 0.2731 0.4506 0.7282
D20 0.7888 0.7888 0.8470
D23 0.4159 0.4115 0.4102

[Lens group data]
Group number Group first surface Focal length G1 1 -1.715
G2 7 1.449
G3 18 -2.692
G4 21 4.915

[Conditional expression values]
Conditional expression (1) T2 / fw 1.396
Conditional expression (2) T2 / T1 1.729
Conditional expression (3) f3 / fw 2.692
Conditional expression (4) (-f1) / fw 1.715
Conditional expression (5) f3 / (− f1) 1.570
Conditional expression (6) ωw 41.3

  As shown in the table of [Conditional Expression Corresponding Values], the zoom lens ZL (3) according to the third example shown in FIG. 5 satisfies all the conditional expressions (1) to (6).

  FIGS. 6A, 6B, and 6C are graphs showing various aberrations when the zoom lens ZL (3) according to the third example is focused at infinity in the wide-angle end state, the intermediate position state, and the telephoto end state, respectively. It is.

  From the various aberration diagrams, it can be seen that the zoom lens ZL (3) according to Example 3 has excellent imaging performance by correcting various aberrations well from the wide-angle end state to the telephoto end state.

(Fourth embodiment)
A fourth embodiment will be described with reference to FIGS. 7 and 8 and Table 4. FIG. FIG. 7 is a diagram showing a lens configuration of a zoom lens according to Example 4 of the present embodiment. The zoom lens ZL (4) according to the fourth example includes a first lens group G1 having negative refractive power, a second lens group G2 having positive refractive power, and negative refraction, which are arranged in order from the object side. The third lens group G3 having power and the fourth lens group G4 having positive refractive power are configured. A flare cut FC is provided on the most object side of the second lens group G2, an aperture stop S is provided therein, and an image plane I is provided on the image plane side of the fourth lens group G4. A filter FL and a cover glass CG (protective glass for the image plane I) are provided in the vicinity of the image plane I on the image side of the fourth lens group G4. The filter FL includes a low-pass filter, an infrared cut filter, and the like.

  The first lens group G1 is composed of a negative meniscus L11 having a convex surface facing the object side, a biconcave negative lens L12, and a positive meniscus lens L13 having a convex surface facing the object side, which are arranged in order from the object side. As a whole, it has a negative refractive power.

  The second lens group G2 includes, in order from the object side, a positive meniscus lens L21 having a convex surface facing the object side, a negative meniscus lens L22 having a convex surface facing the object side, a biconcave negative lens L23, and a biconvex lens. This positive lens L24 and a biconvex positive lens L25 have a positive refractive power as a whole. The negative lens L23 and the positive lens L24 are cemented to form a cemented lens. The image side surface of the positive lens L21 has an aspherical shape.

  The third lens group G3 includes a positive meniscus lens L31 having a convex surface directed toward the object side, and a negative meniscus lens L32 having a convex surface directed toward the object side, and has a negative refracting power as a whole. Both lenses L31 and L32 are cemented to form a cemented lens.

  The fourth lens group G4 includes a biconvex positive lens L41 and a biconcave negative lens L42, and has a positive refractive power as a whole. Both lenses L41 and L42 are cemented to form a cemented lens. The object side surface of the positive lens L41 has an aspheric shape.

  In the zoom lens ZL (1), the third lens group G3 is moved in the image plane direction, thereby focusing from an infinite distance (a long distance object) to a short distance object.

  Furthermore, at least a part of the second lens group G2 (the entire second lens group G2 or any of the lenses L21 to L25 constituting the second lens group G2 or a combination thereof) is perpendicular to the optical axis. An anti-vibration lens group having a directional displacement component is formed, and image blur correction (anti-vibration, camera shake correction) on the image plane I is performed.

  Table 4 below provides values of specifications of the optical system according to the fourth example.

(Table 4) Fourth Example
[Lens specifications]
Surface number RD nd νd
1 2.8876 0.0728 1.72916 54.61
2 1.0914 0.5169
3 -3.0657 0.0607 1.6968 55.52
4 4.4581 0.0121
5 1.9908 0.1872 1.84666 23.8
6 4.799 (variable)
7 (FC) ∞ 0.0303
8 1.4783 0.3337 1.72903 54.04
* 9 20.1734 0.4311
10 (Aperture S) ∞ 0.0121
11 2.6347 0.0364 1.76182 26.58
12 1.2888 0.1047
13 6.7332 0.0364 1.76182 26.58
14 1.192 0.2066 1.62299 58.12
15 -6.5462 0.0985
16 1.8886 0.2306 1.816 46.59
17 -3.6254 (variable)
18 2.2798 0.1005 1.84666 23.8
19 4.9181 0.0364 1.60342 38.03
20 0.8455 (variable)
* 21 2.3532 0.2356 1.72903 54.04
22 -35.1929 0.0485 1.8044 39.61
23 6.3397 (variable)
24 ∞ 0.0425 1.516798 64.2
25 ∞ 0.091
26 ∞ 0.0425 1.516798 64.2
27 ∞

[Overall specifications]
Zoom ratio 1.77
Wide angle end Intermediate position Telephoto end f 1 1.27 1.77
Fno 1.88 2.12 2.54
ω 41.3 34.6 26.5
Y 0.761 0.822 0.88
BF 0.6464 0.5662 0.5392
BF (air equivalent) 0.6174 0.5372 0.5103
TL 5.9230 5.4719 5.1495
TL (Air conversion) 5.8940 5.4429 5.1206

[Aspherical data]
Surface number κ A4 A6 A8 A10
9 1 8.54634E-02 -6.35507E-03 0.00000E + 00 0.00000E + 00
21 1 -1.34845E-02 2.91361E-02 0.00000E + 00 2.40121E-02

[Variable interval data]
Wide angle end Intermediate position Telephoto end
D6 1.6056 0.9539 0.2803
D17 0.3034 0.4601 0.6978
D20 0.5765 0.7006 0.8411
D23 0.4704 0.3902 0.3632

[Lens group data]
Group number Group first surface Focal length G1 1 -1.750
G2 7 1.458
G3 18 -2.695
G4 21 5.340

[Conditional expression values]
Conditional expression (1) T2 / fw 1.490
Conditional expression (2) T2 / T1 1.754
Conditional expression (3) f3 / fw 2.695
Conditional expression (4) (-f1) / fw 1.750
Conditional expression (5) f3 / (-f1) 1.540
Conditional expression (6) ωw 41.3

  As shown in the table of [Conditional Expression Corresponding Values], the zoom lens ZL (4) according to Example 4 shown in FIG. 7 satisfies all of the conditional expressions (1) to (6).

  FIGS. 8A, 8B, and 8C are graphs showing various aberrations when the zoom lens ZL (4) according to the fourth example is in focus at infinity in the wide-angle end state, the intermediate position state, and the telephoto end state, respectively. It is.

  From the various aberration diagrams, it can be seen that the zoom lens ZL (4) according to the fourth example has excellent imaging performance by properly correcting various aberrations from the wide-angle end state to the telephoto end state.

  Here, each said Example has shown one specific example of this invention, and this invention is not limited to these.

  The following contents can be appropriately adopted as long as the optical performance of the zoom lens of the present embodiment is not impaired.

  As an example of the zoom lens according to the present embodiment, a four-group configuration is shown. However, the present application is not limited to this, and a zoom lens having another group configuration (for example, five groups, six groups, etc.) can also be configured. . Specifically, a configuration in which a lens or a lens group is added to the most object side or the most image plane side of the zoom lens of the present embodiment may be used. The lens group refers to a portion having at least one lens separated by an air interval that changes during zooming.

  A single lens group, a plurality of lens groups, or a partial lens group may be moved in the optical axis direction to be a focusing lens group that performs focusing from an object at infinity to a near object. This focusing lens group can be applied to autofocus, and is also suitable for driving a motor for autofocus (using an ultrasonic motor or the like). In particular, it is preferable that at least a part of the third lens group is a focusing lens group.

  Move the lens group or partial lens group so that it has a displacement component in the direction perpendicular to the optical axis, or rotate (sway) it in the in-plane direction including the optical axis to correct image blur caused by camera shake. An anti-vibration lens group may be used. In particular, it is preferable that at least a part of the second lens group is an anti-vibration lens group.

  The lens surface may be formed as a spherical surface, a flat surface, or an aspheric surface. When the lens surface is a spherical surface or a flat surface, lens processing and assembly adjustment are facilitated, and optical performance deterioration due to errors in processing and assembly adjustment can be prevented. Further, even when the image plane is deviated, it is preferable because there is little deterioration in drawing performance.

  When the lens surface is an aspheric surface, the aspheric surface is an aspheric surface by grinding, a glass mold aspheric surface made of glass with an aspheric shape, or a composite aspheric surface made of resin with an aspheric shape on the glass surface. Either is fine. The lens surface may be a diffractive surface, and the lens may be a gradient index lens (GRIN lens) or a plastic lens.

  The aperture stop is preferably arranged in the vicinity of or in the second lens group, but the role of the aperture stop may be substituted by a lens frame without providing a member as the aperture stop.

  Each lens surface may be provided with an antireflection film having a high transmittance in a wide wavelength region in order to reduce flare and ghost and achieve high contrast optical performance.

G1 First lens group G2 Second lens group G3 Third lens group G4 Fourth lens group I Image plane S Aperture stop
FC flare-cut diaphragm

Claims (13)

A first lens group having negative refractive power, a second lens group having positive refractive power, a third lens group having negative refractive power, arranged in order from the object side along the optical axis, and positive A fourth lens group having refractive power,
During zooming, the distance between all adjacent lens groups changes,
The second lens group includes a positive lens and a negative lens arranged in order from the object side and has five lenses.
A zoom lens satisfying the following conditional expression:
1.15 <T2 / fw <1.65
Where T2: thickness of the second lens group on the optical axis fw: focal length of the entire zoom lens in the wide-angle end state   2. The zoom lens according to claim 1, wherein the fourth lens group moves toward the image plane side during zooming from the wide-angle end state to the telephoto end state. The zoom lens according to claim 1, wherein the following conditional expression is satisfied.
1.00 <T2 / T1 <2.50
T1: Thickness of the first lens group on the optical axis The zoom lens according to claim 1, wherein the following conditional expression is satisfied.
2.40 <f3 / fw <5.50
Where f3: focal length of the third lens group The zoom lens according to claim 1, wherein the following conditional expression is satisfied.
1.60 <(− f1) / fw <2.50
Where f1: focal length of the first lens group The zoom lens according to claim 1, wherein the following conditional expression is satisfied.
1.20 <f3 / (− f1) <3.00
Where f1: focal length of the first lens group f3: focal length of the third lens group The zoom lens according to claim 1, wherein the following conditional expression is satisfied.
35.0 <ωw <65.0
Where ωw is the half angle of view of the entire zoom lens in the wide-angle end state (unit: degree)   The second lens group includes the positive lens, the negative lens, a cemented lens of a negative lens and a positive lens, and a positive lens arranged in order from the object side. The zoom lens according to Crab.   The zoom lens according to claim 1, wherein the first lens group includes a negative lens, a negative lens, and a positive lens arranged in order on the object side.   10. The zoom lens according to claim 1, wherein at least a part of the third lens group constitutes a focusing lens group that moves in an optical axis direction during focusing.   The zoom lens according to claim 1, wherein at least a part of the second lens group constitutes an anti-vibration lens group having a displacement component in a direction perpendicular to the optical axis.   An optical apparatus comprising the zoom lens according to claim 1. A first lens group having negative refractive power, a second lens group having positive refractive power, a third lens group having negative refractive power, arranged in order from the object side along the optical axis, and positive A method of manufacturing a zoom lens having a fourth lens group having refractive power,
During zooming, the distance between all adjacent lens groups changes,
The second lens group includes a positive lens and a negative lens arranged in order from the object side and has five lenses.
A zoom lens manufacturing method, wherein the first to fourth lens groups are arranged in a lens barrel so as to satisfy the following conditional expression.
1.15 <T2 / fw <1.65
Where T2: thickness of the second lens group on the optical axis fw: focal length of the entire zoom lens in the wide-angle end state

Images