JP2015043040A - Variable power optical system, optical apparatus, and method for manufacturing variable power optical system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a variable power optical system achieving a reduction in size and an increase in autofocusing speed, reducing ghost and flare and having high optical performance.SOLUTION: The variable power optical system includes, in order from the object side along the optical axis; a first lens group having positive refractive power; a second lens group having negative refractive power; a third lens group having positive refractive power; and a fourth lens group having positive refractive power. A reflection preventing film is provided on at least one of optical surfaces in the first to fourth lens groups, and the reflection preventing film comprises at least one layer formed by using a wet process. When varying power from the wide angle end state to the telephoto end state, the distance between the first lens group and the second lens group is changed, the distance between the second lens group and the third lens group is changed, and the distance between the third lens group and the fourth lens group is changed. The third lens group consists of one positive lens. The third lens group is moved in the optical axis direction to perform focusing from an infinite distance object to a short distance object.

Description

  The present invention relates to a variable magnification optical system suitable for an interchangeable lens for a camera, a digital camera, a video camera, and the like, an optical apparatus having the same, and a method for manufacturing the variable magnification optical system.

  Conventionally, as a variable power optical system used for an interchangeable lens for an interchangeable lens camera, an optical system in which the lens unit closest to the object side has a positive refractive power has been proposed (for example, see Patent Document 1). Further, in recent years, for such a variable magnification optical system, not only aberration performance but also ghost and flare, which are one of the factors that impair optical performance, are becoming more severe. Therefore, higher performance is also required for the antireflection film applied to the lens surface, and multilayer film design technology and multilayer film formation technology continue to advance to meet such requirements (for example, see Patent Document 2).

JP 2009-86535 A JP 2000-356704 A

  However, in the conventional variable power optical system, it has been difficult to ensure sufficiently high optical performance while realizing miniaturization and high speed autofocus. At the same time, there has also been a problem that reflected light that becomes ghost or flare is likely to be generated from the optical surface in the conventional variable magnification optical system.

  The present invention has been made in view of such a situation, while realizing miniaturization and high speed autofocus, reducing ghosts and flares, a variable power optical system having sufficiently high optical performance, It is an object of the present invention to provide an optical device including the variable magnification optical system and a method for manufacturing the variable magnification optical system.

  In order to achieve the above object, a zoom optical system according to the present invention includes a first lens group having a positive refractive power and a second lens group having a negative refractive power in order from the object side along the optical axis. And a third lens group having a positive refractive power and a fourth lens group having a positive refractive power, and reflected from at least one of the optical surfaces of the fourth lens group from the first lens group. An anti-reflection film is provided, and the anti-reflection film includes at least one layer formed using a wet process, and the first lens group and the second lens at the time of zooming from the wide-angle end state to the telephoto end state The distance between the second lens group and the third lens group changes, the distance between the third lens group and the fourth lens group changes, and the third lens group Consists of a single positive lens, and moves the third lens group in the optical axis direction. And performing focusing from infinity to a close object by the.

  An optical apparatus according to the present invention includes the above-described variable magnification optical system.

  The variable magnification optical system manufacturing method according to the present invention includes a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a positive lens in order from the object side along the optical axis. A variable magnification optical system having a third lens group having a refractive power of 4 and a fourth lens group having a positive refractive power, the optical surface of the fourth lens group from the first lens group. An antireflection film is provided on at least one surface, and the antireflection film is configured to include at least one layer formed using a wet process, and at the time of zooming from the wide-angle end state to the telephoto end state, The distance between the first lens group and the second lens group changes, the distance between the second lens group and the third lens group changes, and the distance between the third lens group and the fourth lens group The third lens group is composed of a single positive lens. Characterized by configured to perform focusing from infinity to a close object by moving the third lens group in the optical axis direction.

  According to the present invention, a variable magnification optical system having sufficiently high optical performance and an optical apparatus including the variable magnification optical system while reducing ghosts and flares while realizing miniaturization and high speed autofocus. , And a method of manufacturing a variable magnification optical system can be provided.

It is sectional drawing which shows the lens structure of the variable magnification optical system which concerns on 1st Example of this invention. FIG. 4 is a diagram illustrating various aberrations of the variable magnification optical system according to Example 1 during focusing at infinity, where (a) shows a wide-angle end state, (b) shows an intermediate focal length state, and (c) shows a telephoto end state. ing. It is sectional drawing which shows the lens structure of the variable magnification optical system which concerns on 2nd Example of this invention. FIG. 7 is a diagram illustrating various aberrations of the variable magnification optical system according to Example 2 during focusing at infinity, where (a) shows the wide-angle end state, (b) shows the intermediate focal length state, and (c) shows the telephoto end state. ing. It is sectional drawing which shows the lens structure of the variable magnification optical system which concerns on 3rd Example of this invention. FIG. 7 is a diagram illustrating various aberrations of the variable magnification optical system according to Example 3 when focusing on infinity, where (a) shows a wide-angle end state, (b) shows an intermediate focal length state, and (c) shows a telephoto end state. ing. It is sectional drawing which shows the lens structure of the variable magnification optical system which concerns on 4th Example of this invention. FIG. 10 is a diagram illustrating various aberrations of the variable magnification optical system according to Example 4 at the time of focusing on infinity, where (a) shows a wide-angle end state, (b) shows an intermediate focal length state, and (c) shows a telephoto end state. ing. It is sectional drawing which shows the outline of the camera provided with the variable magnification optical system of this invention. It is a figure which shows the outline of the manufacturing method of the variable magnification optical system which concerns on this invention. The figure which shows an example of a mode that the light ray which injected into the variable magnification optical system which concerns on 1st Example of this invention reflects in the 1st reflective surface and the 2nd reflective surface, and forms a ghost and a flare in an image surface. It is. It is a figure which shows an example of the layer structure of an antireflection film. It is a graph which shows the spectral characteristic of an antireflection film. It is a graph which shows the spectral characteristics of the antireflection film concerning a modification. It is a graph which shows the incident angle dependence of the spectral characteristic of the antireflection film concerning a modification. It is a graph which shows the spectral characteristic of the anti-reflective film produced with the prior art. It is a graph which shows the incident angle dependence of the spectral characteristic of the anti-reflective film produced with the prior art.

  Hereinafter, a variable magnification optical system, an optical apparatus, and a method for manufacturing the variable magnification optical system according to the present invention will be described.

  First, the variable magnification optical system according to the present invention will be described. A variable magnification optical system according to the present invention has a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a positive refractive power in order from the object side along the optical axis. A third lens group and a fourth lens group having a positive refractive power, and an antireflection film is provided on at least one of the optical surfaces of the first lens group to the fourth lens group; The prevention film includes at least one layer formed by using a wet process, and the distance between the first lens group and the second lens group changes when zooming from the wide-angle end state to the telephoto end state. The distance between the lens group and the third lens group is changed, the distance between the third lens group and the fourth lens group is changed, the third lens group is composed of one positive lens, and the third lens group is irradiated with light. Focusing from an infinite object to a near object by moving in the axial direction And butterflies.

 As described above, the variable magnification optical system according to the present invention includes, in order from the object side along the optical axis, a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a positive lens group. And a fourth lens group having a positive refractive power, and an antireflection film is provided on at least one of the optical surfaces of the fourth lens group from the first lens group. The antireflection film includes at least one layer formed by using a wet process, and changes a distance between the first lens group and the second lens group upon zooming from the wide-angle end state to the telephoto end state. The distance between the second lens group and the third lens group is changed, and the distance between the third lens group and the fourth lens group is changed. With this configuration, an optical system capable of zooming is realized, and fluctuations in curvature of field due to zooming can be suppressed to achieve high optical performance.

  In the variable magnification optical system according to the present invention, an antireflection film is provided on at least one of the optical surfaces of the first lens group to the fourth lens group, and the antireflection film is formed using a wet process. It contains at least one layer. With this configuration, the variable magnification optical system according to this embodiment can further reduce ghosts and flares caused by reflection of light from an object on an optical surface, and can achieve high imaging performance. .

  In the variable magnification optical system according to the present invention, the antireflection film is a multilayer film, and the layer formed by using the wet process is the most surface layer of the films constituting the multilayer film. Is desirable. With this configuration, the refractive index difference between the layer formed using the wet process and air can be reduced, so that the reflection of light can be further reduced, and ghosts and flares can be further reduced. .

  In the variable magnification optical system according to the present invention, when the refractive index with respect to the d-line (wavelength λ = 587.6 nm) of the layer formed by the wet process is nd, nd is 1.30 or less. Is desirable. With this configuration, the refractive index difference between the layer formed using the wet process and air can be reduced, so that the reflection of light can be further reduced, and ghosts and flares can be further reduced. .

  The zoom optical system according to the present invention preferably has an aperture stop, and the optical surface provided with the antireflection film is preferably a concave lens surface when viewed from the aperture stop. Of the optical surfaces in the first lens group to the fourth lens group, reflected light tends to be generated on a concave lens surface as viewed from the aperture stop. For this reason, a ghost and flare can be effectively reduced by forming an antireflection film on such a lens surface.

  In the zoom optical system according to the present invention, it is desirable that the concave lens surface as viewed from the aperture stop is the object side lens surface of the lens in the first lens group. Of the optical surfaces in the first lens group, reflected light tends to be generated on a concave lens surface as viewed from the aperture stop. For this reason, a ghost and flare can be effectively reduced by forming an antireflection film on such a lens surface.

  In the zoom optical system according to the present invention, it is preferable that the concave lens surface as viewed from the aperture stop is an image surface side lens surface of the lens in the second lens group. Of the optical surfaces in the second lens group, reflected light tends to be generated on concave lens surfaces as viewed from the aperture stop. For this reason, a ghost and flare can be effectively reduced by forming an antireflection film on such a lens surface.

  In the zoom optical system according to the present invention, it is desirable that the concave lens surface when viewed from the aperture stop is the object side lens surface of the lens in the third lens group. Of the optical surfaces in the third lens group, reflected light tends to be generated on a concave lens surface as viewed from the aperture stop. For this reason, a ghost and flare can be effectively reduced by forming an antireflection film on such a lens surface.

  In the zoom optical system according to the present invention, it is preferable that the concave lens surface as viewed from the aperture stop is an image surface side lens surface of the lens in the fourth lens group. Of the optical surfaces in the fourth lens group, reflected light tends to be generated on concave lens surfaces as viewed from the aperture stop. For this reason, a ghost and flare can be effectively reduced by forming an antireflection film on such a lens surface.

  In the variable magnification optical system according to the present invention, it is preferable that the optical surface provided with the antireflection film is a concave lens surface when viewed from the object side. Of the optical surfaces in the third lens group and the fourth lens group, reflected light tends to be generated on a concave lens surface as viewed from the object side. For this reason, a ghost and flare can be effectively reduced by forming an antireflection film on such a lens surface.

  In the zoom optical system according to the present invention, it is preferable that the concave lens surface as viewed from the object side is an image surface side lens surface of the lens in the third lens group. Of the optical surfaces in the third lens group, reflected light tends to be generated on a concave lens surface as viewed from the object side. For this reason, a ghost and flare can be effectively reduced by forming an antireflection film on such a lens surface.

  In the zoom optical system according to the present invention, it is desirable that the concave lens surface when viewed from the object side is the object side lens surface of the lens in the fourth lens group. Of the optical surfaces in the fourth lens group, reflected light tends to be generated on a concave lens surface as viewed from the object side. For this reason, a ghost and flare can be effectively reduced by forming an antireflection film on such a lens surface.

  In the zoom optical system according to the present invention, the antireflection film is not limited to the wet process, and may be formed by a dry process or the like. In this case, the antireflection film preferably includes at least one layer having a refractive index of 1.30 or less. With this configuration, even when the antireflection film is formed by a dry process or the like, the same effect as when formed by using a wet process can be obtained. The layer having a refractive index of 1.30 or less is preferably the most surface layer among the layers constituting the multilayer film.

  Further, in the variable magnification optical system according to the present invention, the third lens group is composed of one positive lens under such a configuration, and the third lens group is moved to infinity by moving the third lens group in the optical axis direction. Focus from an object to a close object. With this configuration, the focus lens is reduced in weight, and high-speed autofocus is possible even with a small actuator. Furthermore, the variable magnification optical system can be reduced in size, and the outer diameter of the lens barrel can be reduced. As a result, it is possible to realize a variable magnification optical system having high optical performance while realizing miniaturization and high speed autofocus.

  In the variable magnification optical system according to the present invention, it is desirable that the positive lens of the third lens group has a biconvex shape. With this configuration, it is possible to realize high optical performance by suppressing the variation of spherical aberration due to focusing.

  In the variable magnification optical system according to the present invention, it is desirable that the positive lens of the third lens group has a spherical lens surface. With this configuration, it is possible to achieve higher optical performance by suppressing the variation of spherical aberration due to focusing.

Moreover, it is desirable that the variable magnification optical system according to the present invention satisfies the following conditional expression (1).
(1) 1.00 <R31A / (-R31B) <3.00
However,
R31A: radius of curvature of the object side surface of the positive lens of the third lens group R31B: radius of curvature of the image side surface of the positive lens of the third lens group

  Conditional expression (1) defines an appropriate ratio between the radius of curvature of the object side surface of the positive lens of the third lens group and the radius of curvature of the image side surface. By satisfying conditional expression (1), it is possible to appropriately correct spherical aberration generated in the positive lens of the third lens group, and to realize high optical performance.

  When the corresponding value of conditional expression (1) is below the lower limit, it is difficult to correct negative spherical aberration that occurs in the positive lens of the third lens group. As a result, high optical performance cannot be realized, which is not preferable. In order to secure the effect of the present invention, it is desirable to set the lower limit of conditional expression (1) to 1.20.

  When the corresponding value of conditional expression (1) exceeds the upper limit value, it is difficult to correct positive spherical aberration that occurs in the positive lens of the third lens group. As a result, high optical performance cannot be realized, which is not preferable. In order to secure the effect of the present invention, it is desirable to set the upper limit of conditional expression (1) to 2.50.

Moreover, it is desirable that the variable magnification optical system according to the present invention satisfies the following conditional expression (2).
(2) 3.50 <ft / f3 <5.00
However,
ft: focal length of the entire variable magnification optical system in the telephoto end state f3: focal length of the third lens unit

  Conditional expression (2) defines an appropriate ratio between the focal length of the entire variable magnification optical system in the telephoto end state and the focal length of the third lens group. By satisfying conditional expression (2), it is possible to achieve high optical performance by suppressing aberration variation during focusing while reducing the size.

  When the corresponding value of the conditional expression (2) is below the lower limit value, the amount of movement of the third lens group at the time of focusing increases. As a result, the total length of the optical system becomes long, which makes it difficult to reduce the size. In order to secure the effect of the present invention, it is desirable to set the lower limit of conditional expression (2) to 3.70.

  When the corresponding value of the conditional expression (2) exceeds the upper limit value, the power of the third lens group becomes strong, and the aberration fluctuation at the time of focusing becomes large. As a result, high optical performance cannot be realized, which is not preferable. In order to secure the effect of the present invention, it is desirable to set the upper limit of conditional expression (2) to 4.70.

Moreover, it is desirable that the variable magnification optical system according to the present invention satisfies the following conditional expression (3).
(3) 1.00 <f1 / fw <2.00
However,
f1: Focal length of the first lens unit fw: Focal length of the entire variable magnification optical system in the wide-angle end state

  Conditional expression (3) defines an appropriate range of the focal length of the first lens group. In the following description, “the refractive power is strong or weak” means that the absolute value of the refractive power is large or small.

  When the corresponding value of conditional expression (3) is lower than the lower limit, the refractive power of the first lens group becomes strong, and it becomes difficult to correct spherical aberration and axial chromatic aberration. As a result, high optical performance cannot be realized, which is not preferable. In order to secure the effect of the present invention, it is desirable to set the lower limit of conditional expression (3) to 1.20.

  When the corresponding value of conditional expression (3) exceeds the upper limit value, the refractive power of the first lens group becomes weak, and the total length of the variable magnification optical system becomes long. As a result, downsizing becomes difficult, which is not preferable. In addition, it becomes difficult to correct astigmatism. As a result, high optical performance cannot be realized, which is not preferable. In order to secure the effect of the present invention, it is desirable to set the upper limit of conditional expression (3) to 1.80.

Moreover, it is desirable that the variable magnification optical system according to the present invention satisfies the following conditional expression (4).
(4) 0.300 <(− f2) / fw <0.500
However,
f2: Focal length of the second lens unit fw: Focal length of the entire variable magnification optical system in the wide-angle end state

  Conditional expression (4) defines an appropriate range of the focal length of the second lens group.

  When the corresponding value of conditional expression (4) is below the lower limit, the negative refractive power of the second lens group becomes strong, and it becomes difficult to correct spherical aberration and coma. As a result, high optical performance cannot be realized, which is not preferable. In order to secure the effect of the present invention, it is desirable to set the lower limit of conditional expression (4) to 0.330.

  When the corresponding value of conditional expression (4) exceeds the upper limit value, the negative refractive power of the second lens group becomes weak, and it is difficult to correct astigmatism and field curvature. As a result, high optical performance cannot be realized, which is not preferable. In order to secure the effect of the present invention, it is desirable to set the upper limit of conditional expression (4) to 0.470.

  In the variable magnification optical system according to the present invention, the fourth lens group includes, in order from the object side along the optical axis, a fourth A lens group having a positive refractive power and a fourth B lens group having a negative refractive power. And a fourth C lens group having a positive refractive power, and moving the fourth B lens group so as to have a component in a direction substantially orthogonal to the optical axis, thereby correcting image blur due to camera shake, that is, image stabilization. It is desirable to do. With such a configuration, it is possible to prevent vibration with a small-diameter lens group, and it is possible to reduce the size and weight of the camera shake correction mechanism and the size of the lens barrel. In addition, the movement having a component in a substantially orthogonal direction is a movement in a direction perpendicular to the optical axis, a movement in an oblique direction with respect to the optical axis, or a swing on one point on the optical axis. To include.

  In the zoom optical system according to the present invention, it is desirable that the first lens unit moves toward the object side with respect to the image plane along the optical axis when zooming from the wide-angle end state to the telephoto end state. With this configuration, the refractive power of the first lens group can be weakened, the refractive power of each lens group can be made appropriate, and a predetermined zoom ratio can be ensured. If the refractive power of each lens group becomes too strong, correction of aberrations becomes difficult. In particular, if the refractive power of the second lens group becomes too strong, the field curvature becomes large, which makes it difficult to correct and is not preferable. Also, if the refractive power of the third lens group becomes too strong, it is difficult to correct aberrations during focusing, which is not preferable.

  An optical apparatus according to the present invention includes the variable magnification optical system having the above-described configuration. Thereby, an optical apparatus having high optical performance can be realized.

  The variable magnification optical system manufacturing method according to the present invention includes a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a positive lens in order from the object side along the optical axis. A variable magnification optical system having a third lens group having a refractive power of 4 and a fourth lens group having a positive refractive power, the optical surface of the fourth lens group from the first lens group. An antireflection film is provided on at least one surface, and the antireflection film is configured to include at least one layer formed using a wet process, and at the time of zooming from the wide-angle end state to the telephoto end state, The distance between the first lens group and the second lens group changes, the distance between the second lens group and the third lens group changes, and the distance between the third lens group and the fourth lens group The third lens group is composed of a single positive lens. Characterized by configured to perform focusing from infinity to a close object by moving the third lens group in the optical axis direction.

  With such a variable magnification optical system manufacturing method, a variable magnification optical system having high optical performance can be manufactured.

(Numerical example)
A variable magnification optical system according to numerical examples of the present invention will be described below with reference to the accompanying drawings.

(First embodiment)
FIG. 1 is a sectional view showing the lens configuration of a variable magnification optical system ZL1 according to the first example of the present invention.

  As shown in FIG. 1, the variable magnification optical system ZL1 according to this example includes a first lens group G1 having a positive refractive power and a second lens having a negative refractive power in order from the object side along the optical axis. The lens group G2 includes a third lens group G3 having a positive refractive power and a fourth lens group G4 having a positive refractive power.

  In the zoom optical system ZL1 according to the present embodiment, when zooming from the wide-angle end state W to the telephoto end state T, the distance between the first lens group G1 and the second lens group G2 increases, and the second lens group G2 And the third lens group G3 are decreased, and the distance between the third lens group G3 and the fourth lens group G4 is increased. The first lens group G1 moves monotonously toward the object side with respect to the image plane I, the second lens group G2 moves to the convex shape on the image plane I side, and the third lens group G3 and the fourth lens group G4. Moves to the object side monotonously. Focusing from an infinite object to a close object is performed by moving the third lens group G3 to the image plane I side.

  The fourth lens group G4 includes, in order from the object side along the optical axis, a fourth A lens group G4A having a positive refractive power, a fourth B lens group G4B having a negative refractive power, and a first lens having a positive refractive power. 4C lens group G4C. By moving the fourth lens group G4B so as to have a component in a direction substantially orthogonal to the optical axis, image blur correction due to camera shake, that is, image stabilization is performed. The aperture stop S is disposed inside the fourth lens group G4, and is configured to move integrally with the fourth lens group G4 at the time of zooming from the wide-angle end to the telephoto end.

  The first lens group G1 includes, in order from the object side along the optical axis, a positive meniscus lens L11 having a convex surface facing the object side, a negative meniscus lens L12 having a convex surface facing the object side, and a biconvex positive lens L13. And a cemented lens.

  The second lens group G2 includes, in order from the object side along the optical axis, a cemented lens of a biconcave negative lens L21 and a positive meniscus lens L22 having a convex surface facing the object side, and a biconcave negative lens L23. Consists of

  The third lens group G3 includes a biconvex positive lens L31.

  The fourth A lens group G4A includes, in order from the object side along the optical axis, a positive meniscus lens L41 having a convex surface directed toward the object side, and a cemented lens of a biconvex positive lens L42 and a biconcave negative lens L43. And a biconvex positive lens L44.

  The fourth lens group G4B is composed of, in order from the object side along the optical axis, a cemented lens of a biconcave negative lens L45 and a positive meniscus lens L46 having a convex surface directed toward the object side.

  The fourth C lens group G4C includes, in order from the object side along the optical axis, a positive meniscus lens L47 having a convex surface directed toward the object side, and a cemented lens of a biconvex positive lens L48 and a biconcave negative lens L49. The light beam emitted from the L49 lens forms an image on the image plane I.

  The variable magnification optical system ZL1 according to this example includes an image surface side lens surface (surface number 10) of the biconcave negative lens L23 of the second lens group G2 and an image of the positive meniscus lens L41 of the fourth lens group G4. An antireflection film to be described later is formed on the surface side lens surface (surface number 14).

Table 1 below lists specifications of the variable magnification optical system ZL1 according to the first example of the present invention.
In [Overall specifications] in Table 1, f is the focal length of the entire variable magnification optical system, FNO is the F number, 2ω is the angle of view (unit: degree), Y is the image height, and TL is in the infinitely focused state. The entire lens length from the most object-side surface of the first lens group G1 to the image plane I is shown. W indicates a wide angle end state, M indicates an intermediate focal length state, and T indicates a focal length state in a telephoto end state.

  In [Surface Data], the surface number is the order of the lens surfaces counted from the object side, r is the radius of curvature of the lens surfaces, d is the distance between the lens surfaces, nd is the refractive index with respect to the d-line (wavelength λ = 587.6 nm), νd represents the Abbe number for the d-line (wavelength λ = 587.6 nm). The object plane indicates the object plane, (aperture) indicates the aperture stop S, and the image plane indicates the image plane I. Note that the radius of curvature r = ∞ indicates a plane, and the description of the refractive index of air d = 1.00000 is omitted.

[Variable interval data] indicates values of the focal length f, the variable interval, and the aperture stop diameter φ.
[Lens Group Data] indicates the start surface number and focal length of each lens group.
[Conditional Expression Corresponding Value] indicates the corresponding value of each conditional expression.

  Here, “mm” is generally used as the unit of the focal length f, the radius of curvature r, and other lengths described in Table 1. However, the optical system is not limited to this because an equivalent optical performance can be obtained even when proportionally enlarged or proportionally reduced.

  In addition, the code | symbol of Table 1 described above shall be similarly used also in the table | surface of each Example mentioned later.

(Table 1) First Example [Overall Specifications]
W M T
f 72.00125 134.89858 291.55642
FNO 4.49 5.00 5.87
2ω 13.27 7.04 3.26
Y 8.35 8.35 8.35
TL 174.82320 192.82728 205.27212

[Surface data]
Surface number r d nd νd
Object ∞
1) 76.45460 4.70390 1.618000 63.34
2) 256.81660 0.10000
3) 83.48100 2.00000 1.795040 28.69
4) 52.02470 7.82340 1.437000 95.00
5) −2180.58150 (D5)
6) −157.69770 1.10000 1.696800 55.52
7) 24.58730 4.85060 1.846660 23.80
8) 63.50810 2.55870
9) −56.90330 1.10000 1.772500 49.62
10) 132.70460 (D10)
11) 116.40050 3.30690 1.618000 63.34
12) −74.88570 (D12)
13) 46.27990 3.11080 1.593190 67.90
14) 690.26650 2.83790
15) 36.41800 4.52180 1.603000 65.44
16) −121.73140 1.59630 1.950000 29.37
17) 27.66160 0.72790
18) 26.84000 3.88680 1.593190 67.90
19) −1460.77280 2.00000
20) −255.28680 0.90000 1.696800 55.52
21) 20.15450 2.79110 1.902650 35.73
22) 36.13630 14.30890
23) (Aperture) ∞ 1.00000
24) 53.33500 2.00000 1.805180 25.45
25) 14779.41800 18.48370
26) 216.36190 2.89740 1.603420 38.03
27) −18.15210 1.00000 1.834810 42.73
28) 86.81180 (BF)
Image plane ∞

[Variable interval data]
W M T
f 72.00125 134.89858 291.55642
D5 10.53320 37.13510 45.64880
D10 40.49600 25.95820 3.84220
D12 4.75360 10.25890 11.38910
BF 29.43430 29.86898 54.78592
φ 14.60 13.20 17.40

[Lens group data]
Start surface Focal length
G1 1 116.15003
G2 6 −31.59403
G3 11 74.22647
G4 13 202.33188
G4A 13 65.90638
G4B 20 −57.99956
G4C 23 471.52911

[Values for each conditional expression]
R31A = 116.40050
R31B = −74.88570
ft = 291.55642
fw = 72.00125
f1 = 116.15003
f2 = −31.59403
f3 = 74.22647
(1) R31A / (-R31B) = 1.554
(2) ft / f3 = 3.928
(3) f1 / fw = 1.613
(4) (−f2) /fw=0.4388

  2A and 2B are graphs showing various aberrations of the variable magnification optical system ZL1 according to the first example when focusing on infinity. FIG. 2A is a wide-angle end state, FIG. 2B is an intermediate focal length state, and FIG. Each end state is shown.

  In each aberration diagram, FNO indicates an F number, and A indicates a half angle of view (unit: degree). In the figure, d indicates an aberration curve at the d-line (wavelength λ = 587.6 nm), g indicates an aberration curve at the g-line (wavelength λ = 435.8 nm), and those not described are d-line The aberration curve at is shown. In the aberration diagram showing astigmatism, the solid line indicates the sagittal image plane, and the broken line indicates the meridional image plane. The aberration diagram showing coma represents the meridional coma with respect to the d-line and the g-line at each half angle of view. In addition, in the various aberration diagrams of the following examples, the same reference numerals as those of the present example are used.

  As is apparent from each aberration diagram, it is understood that the variable magnification optical system ZL1 according to the first example has excellent optical performance with various aberrations corrected well from the wide-angle end state to the telephoto end state.

  Here, the cause of the occurrence of ghost and flare in the variable magnification optical system ZL1 according to the present embodiment will be described.

  FIG. 11 shows an example of how a light beam incident on the variable magnification optical system ZL1 according to the present embodiment is reflected by the first reflecting surface and the second reflecting surface to form a ghost or flare on the image plane I. FIG.

  In FIG. 11, when a light beam BM from the object side enters the zoom optical system ZL1 as shown, a part of the light beam BM is an image surface side lens surface (surface number 14) of the positive meniscus lens L41 in the fourth lens group G4. , Reflected on the first reflecting surface where reflected light that becomes a ghost or flare is generated, and further the image side lens surface (surface number 10, ghost or flare) of the biconcave negative lens L23 in the second lens group G2. The second reflected surface where the reflected light is generated) is reflected again and finally reaches the image plane I to generate ghost and flare. The first reflecting surface and the second reflecting surface are concave lens surfaces when viewed from the aperture stop S. Therefore, the variable magnification optical system according to the present embodiment suppresses the generation of reflected light and forms ghosts and flares by forming an antireflection film corresponding to light beams having a wide incident angle in a wide wavelength range on such a lens surface. Can be reduced.

(Second embodiment)
FIG. 3 is a sectional view showing the lens configuration of the variable magnification optical system ZL2 according to the second example of the present invention.

  As shown in FIG. 3, the variable magnification optical system ZL2 according to the present embodiment includes a first lens group G1 having a positive refractive power and a second lens having a negative refractive power in order from the object side along the optical axis. The lens group G2 includes a third lens group G3 having a positive refractive power and a fourth lens group G4 having a positive refractive power.

  In the zoom optical system ZL2 according to the present embodiment, when zooming from the wide-angle end state W to the telephoto end state T, the distance between the first lens group G1 and the second lens group G2 increases, and the second lens group G2 And the third lens group G3 are decreased, and the distance between the third lens group G3 and the fourth lens group G4 is increased. The first lens group G1 moves monotonously toward the object side with respect to the image plane I, the second lens group G2 moves to the convex shape on the image plane I side, and the third lens group G3 and the fourth lens group G4. Moves to the object side monotonously. Focusing from an infinite object to a close object is performed by moving the third lens group G3 to the image plane I side.

  The fourth lens group G4 includes, in order from the object side along the optical axis, a fourth A lens group G4A having a positive refractive power, a fourth B lens group G4B having a negative refractive power, and a first lens having a positive refractive power. 4C lens group G4C. By moving the fourth lens group G4B so as to have a component in a direction substantially orthogonal to the optical axis, image blur correction due to camera shake, that is, image stabilization is performed. The aperture stop S is disposed inside the fourth lens group G4, and is configured to move integrally with the fourth lens group G4 at the time of zooming from the wide-angle end to the telephoto end.

  The first lens group G1 includes, in order from the object side along the optical axis, a positive meniscus lens L11 having a convex surface facing the object side, a negative meniscus lens L12 having a convex surface facing the object side, and a biconvex positive lens L13. And a cemented lens.

  The second lens group G2 includes, in order from the object side along the optical axis, a cemented lens of a biconcave negative lens L21 and a positive meniscus lens L22 having a convex surface facing the object side, and a biconcave negative lens L23. Consists of

  The third lens group G3 includes a biconvex positive lens L31.

  The fourth A lens group G4A includes, in order from the object side along the optical axis, a positive meniscus lens L41 having a convex surface directed toward the object side, a biconvex positive lens L42, a biconcave negative lens L43, and a biconvex shape. It consists of a cemented lens with a positive lens L44.

  The fourth lens group G4B is composed of, in order from the object side along the optical axis, a cemented lens of a biconcave negative lens L45 and a positive meniscus lens L46 having a convex surface directed toward the object side.

  The fourth C lens group G4C includes, in order from the object side along the optical axis, a positive meniscus lens L47 having a convex surface directed toward the object side, and a cemented lens of a biconvex positive lens L48 and a biconcave negative lens L49. The light beam emitted from the L49 lens forms an image on the image plane I.

  In the zoom optical system ZL2 according to the present example, an antireflection film described later is formed on the image surface side lens surface (surface number 14) of the positive lens L41 of the fourth lens group G4.

Table 2 below lists specifications of the variable magnification optical system ZL2 according to the second example of the present invention.
(Table 2) Second embodiment [Overall specifications]
W M T
f 72.00407 134.90005 291.56827
FNO 4.55 5.34 5.87
2ω 13.30 7.05 3.26
Y 8.35 8.35 8.35
TL 174.74594 189.28266 203.71361

[Surface data]
Surface number r d nd νd
Object ∞
1) 70.10870 5.23050 1.618000 63.34
2) 268.66420 0.12210
3) 76.54770 2.00000 1.795040 28.69
4) 47.28020 8.25010 1.437000 95.00
5) −24087.04000 (D5)
6) −183.21520 1.12770 1.696800 55.52
7) 23.23900 5.01110 1.846660 23.80
8) 57.06550 2.79090
9) −52.66330 1.10000 1.772500 49.62
10) 120.63120 (D10)
11) 103.55650 3.40050 1.618000 63.34
12) −74.96490 (D12)
13) 44.07140 3.24670 1.593190 67.90
14) 1062.48610 3.54580
15) 34.82560 4.03550 1.603000 65.44
16) −137.84300 1.28180 1.950000 29.37
17) 27.29790 3.83840 1.593190 67.90
18) −368.78740 2.00000
19) −161.60230 1.10000 1.696800 55.52
20) 18.28860 2.78580 1.902650 35.73
21) 31.91770 16.09810
22) (Aperture) ∞ 1.00000
23) 41.98930 2.00000 1.805180 25.45
24) 148.51900 12.76000
25) 38.57320 3.28950 1.603420 38.03
26) −25.68470 1.00000 1.834810 42.73
27) 37.72480 (BF)
Image plane ∞

[Variable interval data]
W M T
f 72.00407 134.90005 291.56827
D5 8.03140 31.60210 38.95920
D10 40.23810 25.83910 3.62640
D12 4.70750 9.88860 11.68210
BF 34.75444 34.93836 62.43141
φ 13.60 11.60 16.60

[Lens group data]
Start surface Focal length
G1 1 105.61803
G2 6 −29.4996
G3 11 70.88067
G4 13 207.1073
G4A 13 58.25003
G4B 19 −47.40352
G4C 22 296.63183

[Values for each conditional expression]
R31A = 103.55650
R31B = −74.96490
ft = 291.56827
fw = 72.00407
f1 = 105.61803
f2 = -29.4996
f3 = 70.88067
(1) R31A / (− R31B) = 1.382
(2) ft / f3 = 4.114
(3) f1 / fw = 1.467
(4) (−f2) /fw=0.4097

  4A and 4B are graphs showing various aberrations of the variable magnification optical system ZL2 according to the second example when focusing on infinity, where FIG. 4A is a wide-angle end state, FIG. 4B is an intermediate focal length state, and FIG. 4C is telephoto. Each end state is shown.

  As is apparent from each aberration diagram, it is understood that the variable magnification optical system ZL2 according to the second example has high optical performance with various aberrations corrected well from the wide-angle end state to the telephoto end state.

(Third embodiment)
FIG. 5 is a sectional view showing the lens configuration of the variable magnification optical system ZL3 according to the third example of the present invention.

  As shown in FIG. 5, the variable magnification optical system ZL3 according to the present embodiment includes a first lens group G1 having a positive refractive power and a second lens having a negative refractive power in order from the object side along the optical axis. The lens group G2 includes a third lens group G3 having a positive refractive power and a fourth lens group G4 having a positive refractive power.

  In the variable magnification optical system ZL3 according to the present example, when the magnification is changed from the wide-angle end state W to the telephoto end state T, the distance between the first lens group G1 and the second lens group G2 increases, and the second lens group G2 And the third lens group G3 are decreased, and the distance between the third lens group G3 and the fourth lens group G4 is increased. The first lens group G1 moves monotonously toward the object side with respect to the image plane I, the second lens group G2 moves to the convex shape on the image plane I side, and the third lens group G3 and the fourth lens group G4. Moves to the object side monotonously. Focusing from an infinite object to a close object is performed by moving the third lens group G3 to the image plane I side.

  The fourth lens group G4 includes, in order from the object side along the optical axis, a fourth A lens group G4A having a positive refractive power, a fourth B lens group G4B having a negative refractive power, and a first lens having a positive refractive power. 4C lens group G4C. By moving the fourth lens group G4B so as to have a component in a direction substantially orthogonal to the optical axis, image blur correction due to camera shake, that is, image stabilization is performed. The aperture stop S is disposed inside the fourth lens group G4, and is configured to move integrally with the fourth lens group G4 at the time of zooming from the wide-angle end to the telephoto end.

  The first lens group G1 includes, in order from the object side along the optical axis, a positive meniscus lens L11 having a convex surface facing the object side, a negative meniscus lens L12 having a convex surface facing the object side, and a biconvex positive lens L13. And a cemented lens.

  The second lens group G2 includes, in order from the object side along the optical axis, a cemented lens of a biconcave negative lens L21 and a positive meniscus lens L22 having a convex surface facing the object side, and a biconcave negative lens L23. Consists of

  The third lens group G3 includes a biconvex positive lens L31.

  The fourth A lens group G4A includes, in order from the object side along the optical axis, a positive meniscus lens L41 having a convex surface directed toward the object side, a biconvex positive lens L42, a biconcave negative lens L43, and a convex surface toward the object side. And a cemented lens with a positive meniscus lens L44.

  The fourth lens group G4B is composed of, in order from the object side along the optical axis, a cemented lens of a biconcave negative lens L45 and a positive meniscus lens L46 having a convex surface directed toward the object side.

  The fourth C lens group G4C includes, in order from the object side along the optical axis, a biconvex positive lens L47, and a cemented lens of a biconvex positive lens L48 and a biconcave negative lens L49. The light beam emitted from the L49 lens forms an image on the image plane I.

  The variable magnification optical system ZL3 according to this example includes an image surface side lens surface (surface number 12) of the biconvex positive lens L31 of the third lens group G3 and a biconcave negative lens of the fourth lens group G4. An antireflection film described later is formed on the object side lens surface (surface number 19) of L45.

Table 3 below lists specifications of the variable magnification optical system ZL3 according to the third example of the present invention.
(Table 3) Third Example [Overall Specifications]
W M T
f 72.00160 134.90047 291.52685
FNO 4.57 5.23 5.88
2ω 13.32 7.04 3.26
Y 8.35 8.35 8.35
TL 175.31110 187.01799 201.23981

[Surface data]
Surface number r d nd νd
Object ∞
1) 70.57290 4.93910 1.618000 63.34
2) 242.25150 0.10000
3) 68.52880 2.00000 1.795040 28.69
4) 43.51940 8.96140 1.437000 95.00
5) −923.91020 (D5)
6) −119.38590 1.10000 1.772500 49.62
7) 19.58400 4.52140 2.000690 25.46
8) 57.05290 2.23580
9) −62.25060 1.10000 1.816000 46.59
10) 66.25170 (D10)
11) 104.75140 3.25500 1.603000 65.44
12) −65.16700 (D12)
13) 28.76740 4.34410 1.487490 70.31
14) −817.13650 0.10000
15) 30.79330 4.33220 1.603000 65.44
16) −102.29120 2.74200 1.902650 35.73
17) 17.49490 5.22550 1.487490 70.31
18) 152.53090 2.00000
19) −175.94560 0.90000 1.696800 55.52
20) 19.08870 2.32080 1.902650 35.73
21) 34.38970 14.77920
22) (Aperture) ∞ 1.00000
23) 46.00240 2.25290 1.834000 37.18
24) −262.68650 10.32110
25) 35.86780 5.06690 1.603420 38.03
26) −34.36720 1.00000 1.883000 40.66
27) 31.82930 (BF)
Image plane ∞

[Variable interval data]
W M T
f 72.00160 134.90047 291.52685
D5 13.85170 32.83900 39.17860
D10 37.69540 24.12950 3.55890
D12 4.37180 9.08570 10.13310
BF 34.79480 36.36639 63.77181
φ 13.40 12.10 16.90

[Lens group data]
Start surface Focal length
G1 1 98.62711
G2 6 −26.12048
G3 11 67.10744
G4 13 161.32694
G4A 13 82.33786
G4B 19 −51.98201
G4C 22 90.43851

[Values for each conditional expression]
R31A = 104.75140
R31B = −65.16700
ft = 291.52685
fw = 72.00160
f1 = 98.62711
f2 = -26.12048
f3 = 67.10744
(1) R31A / (-R31B) = 1.607
(2) ft / f3 = 4.344
(3) f1 / fw = 1.370
(4) (−f2) /fw=0.3628

  6A and 6B are graphs showing various aberrations of the variable magnification optical system ZL3 according to the third example when focusing on infinity, where FIG. 6A is a wide-angle end state, FIG. 6B is an intermediate focal length state, and FIG. Each end state is shown.

  As is apparent from each aberration diagram, it is understood that the variable magnification optical system ZL3 according to the third example has high optical performance with various aberrations corrected well from the wide-angle end state to the telephoto end state.

(Fourth embodiment)
FIG. 7 is a sectional view showing the lens configuration of the variable magnification optical system ZL4 according to the fourth example of the present invention.

  As shown in FIG. 7, the variable magnification optical system ZL4 according to the present embodiment includes a first lens group G1 having a positive refractive power and a second lens having a negative refractive power in order from the object side along the optical axis. The lens group G2 includes a third lens group G3 having a positive refractive power and a fourth lens group G4 having a positive refractive power.

  In the variable magnification optical system ZL4 according to the present example, when the magnification is changed from the wide-angle end state W to the telephoto end state T, the distance between the first lens group G1 and the second lens group G2 increases, and the second lens group G2 And the third lens group G3 are decreased, and the distance between the third lens group G3 and the fourth lens group G4 is increased. The first lens group G1 moves monotonously toward the object side with respect to the image plane I, the second lens group G2 moves to the convex shape on the image plane I side, and the third lens group G3 and the fourth lens group G4. Moves to the object side monotonously. Focusing from an infinite object to a close object is performed by moving the third lens group G3 to the image plane I side.

  The fourth lens group G4 includes, in order from the object side along the optical axis, a fourth A lens group G4A having a positive refractive power, a fourth B lens group G4B having a negative refractive power, and a first lens having a positive refractive power. 4C lens group G4C. By moving the fourth lens group G4B so as to have a component in a direction substantially orthogonal to the optical axis, image blur correction due to camera shake, that is, image stabilization is performed. The aperture stop S is disposed inside the fourth lens group G4, and is configured to move integrally with the fourth lens group G4 at the time of zooming from the wide-angle end to the telephoto end.

  The first lens group G1 includes, in order from the object side along the optical axis, a positive meniscus lens L11 having a convex surface facing the object side, a negative meniscus lens L12 having a convex surface facing the object side, and a positive meniscus having a convex surface facing the object side. It comprises a cemented lens with a meniscus lens L13.

  The second lens group G2 includes, in order from the object side along the optical axis, a cemented lens of a biconcave negative lens L21 and a positive meniscus lens L22 having a convex surface facing the object side, and a biconcave negative lens L23. Consists of

  The third lens group G3 includes a biconvex positive lens L31.

  The fourth A lens group G4A includes, in order from the object side along the optical axis, a biconvex positive lens L41, a biconvex positive lens L42, a biconcave negative lens L43, and a biconvex positive lens L44. And a cemented lens.

  The fourth lens group G4B is composed of, in order from the object side along the optical axis, a cemented lens of a biconcave negative lens L45 and a positive meniscus lens L46 having a convex surface directed toward the object side.

  The fourth C lens group G4C is composed of, in order from the object side along the optical axis, a biconvex positive lens L47, and a cemented lens of a biconcave negative lens L48 and a biconvex positive lens L49. The light beam emitted from the L49 lens forms an image on the image plane I.

  The variable magnification optical system ZL4 according to the present example includes the object side lens surface (surface number 3) of the negative meniscus lens L12 of the first lens group G1 and the object side of the biconvex positive lens L31 of the third lens group G3. An antireflection film described later is formed on the lens surface (surface number 11).

Table 4 below lists specifications of the variable magnification optical system ZL4 according to the fourth example of the present invention.
(Table 4) Fourth Example [Overall Specifications]
W M T
f 72.00198 134.90087 291.56400
FNO 4.53 5.17 5.89
2ω 13.31 7.05 3.26
Y 8.35 8.35 8.35
TL 174.11210 185.42109 200.30283

[Surface data]
Surface number r d nd νd
Object ∞
1) 54.92170 6.29800 1.603000 65.44
2) 199.31210 0.10000
3) 61.80160 2.00000 1.834000 37.18
4) 34.33480 10.49620 1.437000 95.00
5) 16937.45500 (D5)
6) −156.57000 1.22310 1.618000 63.34
7) 20.34000 4.24490 1.846660 23.80
8) 33.04330 3.78250
9) −36.70970 1.10000 1.593190 67.90
10) 193.98970 (D10)
11) 122.80240 3.24640 1.603000 65.44
12) −60.94980 (D12)
13) 32.71430 4.15430 1.487490 70.31
14) -266.57680 0.10000
15) 32.58110 4.70130 1.548140 45.51
16) −62.05980 1.13330 1.902650 35.73
17) 16.57230 5.51490 1.593190 67.90
18) −229.10060 2.00000
19) −186.61440 0.90000 1.772500 49.62
20) 19.26900 2.92390 1.902650 35.73
21) 44.24910 13.47910
22) (Aperture) ∞ 1.00000
23) 78.39800 3.47240 1.517420 52.20
24) -28.49740 12.23000
25) −26.06210 1.00000 1.804000 46.60
26) 27.95010 2.09780 1.688930 31.16
27) −80.50700 (BF)
Image plane ∞

[Variable interval data]
W M T
f 72.00198 134.90087 291.56400
D5 10.32410 28.70590 35.09120
D10 37.61910 23.80120 3.05980
D12 4.45650 9.12770 11.45850
BF 34.51430 36.58819 63.49523
φ 14.20 12.90 17.70

[Lens group data]
Start surface Focal length
G1 1 98.28877
G2 6 −26.13187
G3 11 68.00255
G4 13 165.0289
G4A 13 70.31244
G4B 19 −56.39926
G4C 22 157.08603

[Values for each conditional expression]
R31A = 122.80240
R31B = −60.94980
ft = 291.56400
fw = 72.00198
f1 = 98.28877
f2 = −26.13187
f3 = 68.00255
(1) R31A / (− R31B) = 2.0 15
(2) ft / f3 = 4.288
(3) f1 / fw = 1.365
(4) (−f2) /fw=0.3629

  FIGS. 8A and 8B are graphs showing various aberrations of the variable magnification optical system ZL4 according to the fourth example at the time of focusing on infinity. FIG. 8A is a wide-angle end state, FIG. 8B is an intermediate focal length state, and FIG. Each end state is shown.

  As is apparent from the respective aberration diagrams, it is understood that the variable magnification optical system ZL4 according to the fourth example has excellent optical performance with various aberrations corrected well from the wide-angle end state to the telephoto end state.

  Here, an antireflection film (also referred to as a multilayer broadband antireflection film) used in the variable magnification optical system according to the embodiment of the present invention will be described. FIG. 12 is a diagram illustrating an example of a film configuration of the antireflection film. The antireflection film 101 is composed of seven layers and is formed on the optical surface of the optical member 102 such as a lens. The first layer 101a is formed of aluminum oxide deposited by a vacuum deposition method. Further, a second layer 101b made of a mixture of titanium oxide and zirconium oxide deposited by a vacuum deposition method is formed on the first layer 101a. Further, a third layer 101c made of aluminum oxide deposited by vacuum deposition is formed on the second layer 101b, and titanium oxide and zirconium oxide deposited by vacuum deposition on the third layer 101c. A fourth layer 101d made of the mixture is formed. Furthermore, a fifth layer 101e made of aluminum oxide deposited by vacuum deposition is formed on the fourth layer 101d, and titanium oxide and zirconium oxide deposited by vacuum deposition on the fifth layer 101e. The sixth layer 101f made of the mixture of is formed.

  Then, on the sixth layer 101f formed in this way, a seventh layer 101g made of a mixture of magnesium fluoride and silica is formed by a wet process to form the antireflection film 101 of this embodiment. For the formation of the seventh layer 101g, a sol-gel method which is a kind of wet process is used. The sol-gel method is a method in which a sol obtained by mixing raw materials is made into a non-flowable gel by hydrolysis / polycondensation reaction, etc., and this gel is heated and decomposed to obtain a product, In the production of an optical thin film, a film can be formed by applying an optical thin film material sol on the optical surface of an optical member and forming a gel film by drying and solidifying. The wet process is not limited to the sol-gel method, and a method of obtaining a solid film without going through a gel state may be used.

Thus, the first layer 101a to the sixth layer 101f of the antireflection film 101 are formed by electron beam evaporation which is a dry process, and the seventh layer 101g which is the uppermost layer is prepared by a hydrofluoric acid / magnesium acetate method. It is formed by the following procedure by a wet process using a sol solution. First, an aluminum oxide layer to be the first layer 101a, a titanium oxide-zirconium oxide mixed layer to be the second layer 101b, a third layer on the lens film formation surface (the optical surface of the optical member 102 described above) in advance using a vacuum deposition apparatus, An aluminum oxide layer to be the layer 101c, a titanium oxide-zirconium oxide mixed layer to be the fourth layer 101d, an aluminum oxide layer to be the fifth layer 101e, and a titanium oxide-zirconium oxide mixed layer to be the sixth layer 101f are formed in this order. And after taking out the optical member 102 from a vapor deposition apparatus, the thing which added the silicon alkoxide to the sol liquid prepared by the hydrofluoric acid / magnesium acetate method is apply | coated by the spin coat method, The magnesium fluoride used as the 7th layer 101g A layer made of a mixture of silica and silica is formed. The reaction formula when prepared by the hydrofluoric acid / magnesium acetate method is shown in the following formula (a).
(A) 2HF + Mg (CH3COO) 2 → MgF2 + 2 + CH3COOH
The sol solution used for the film formation is used for film formation after mixing raw materials and subjecting to an autoclave at 140 ° C. for 24 hours at a high temperature and pressure. The optical member 102 is completed by heat treatment at 160 ° C. for 1 hour in the air after the seventh layer 101g is formed. By using such a sol-gel method, the seventh layer 101g is formed by depositing particles having a size of several nm to several tens of nm leaving a void.

  The optical performance of the optical member having the antireflection film 101 formed in this way will be described using the spectral characteristics shown in FIG.

  The optical member, that is, the lens having the antireflection film according to this embodiment is formed under the conditions shown in Table 5 below. Here, Table 5 shows that the reference wavelength is λ, and the layers 101a (first layer) to 101g (seventh layer) of the antireflection film 101 when the refractive index of the substrate (optical member) is 1.62, 1.74, and 1.85. The optical film thickness of each layer is determined. In Table 5, aluminum oxide is represented by Al203, a mixture of titanium oxide and zirconium oxide is represented by Zr02 + Ti02, and a mixture of magnesium fluoride and silica is represented by MgF2 + Si02.

(Table 5)
Substance Refractive index Optical film thickness Optical film thickness Optical film thickness Medium Air 1
7th layer MgF2 + Si02 1.26 0.268λ 0.271λ 0.269λ
6th layer Zr02 + Ti02 2.12 0.057λ 0.054λ 0.059λ
5th layer Al203 1.65 0.171λ 0.178λ 0.162λ
4th layer Zr02 + Ti02 2.12 0.127λ 0.13λ 0.158λ
3rd layer Al203 1.65 0.122λ 0.107λ 0.08λ
Second layer Zr02 + Ti02 2.12 0.059λ 0.075λ 0.105λ
1st layer Al203 1.65 0.257λ 0.03λ 0.03λ
Refractive index of substrate 1.62 1.74 1.85

  FIG. 13 shows spectral characteristics when light rays are perpendicularly incident on an optical member in which the reference wavelength λ is 550 nm in Table 5 and the optical film thickness of each layer of the antireflection film 101 is designed.

  From FIG. 13, it can be seen that the optical member having the antireflection film 101 designed with the reference wavelength λ of 550 nm can suppress the reflectance to 0.2% or less over the entire wavelength range of 420 nm to 720 nm. Further, even in the optical member having the antireflection film 101 in which each optical film thickness is designed with the reference wavelength λ as the d-line (wavelength 587.6 nm) in Table 5, the spectral characteristics are hardly affected, and the reference shown in FIG. Spectral characteristics substantially equivalent to those when the wavelength λ is 550 nm.

  Next, a modified example of the antireflection film will be described. This antireflection film consists of five layers, and similarly to Table 5, the optical film thickness of each layer with respect to the reference wavelength λ is designed under the conditions shown in Table 6 below. In this modification, the above-described sol-gel method is used for forming the fifth layer.

(Table 6)
Material Refractive index Optical film thickness Optical film thickness Medium Air 1
5th layer MgF2 + Si02 1.26 0.275λ 0.269λ
4th layer Zr02 + Ti02 2.12 0.045λ 0.043λ
3rd layer Al203 1.65 0.212λ 0.217λ
Second layer Zr02 + Ti02 2.12 0.077λ 0.066λ
1st layer Al203 1.65 0.288λ 0.290λ
Refractive index of substrate 1.46 1.52

  FIG. 14 shows spectral characteristics in Table 6 when light rays are perpendicularly incident on an optical member having an antireflection film having a refractive index of 1.52 and a reference wavelength λ of 550 nm and each optical film thickness designed. Yes. From FIG. 14, it can be seen that the antireflection film of this modification has a reflectivity of 0.2% or less over the entire wavelength range of 420 nm to 720 nm. In Table 6, even an optical member having an antireflection film in which each optical film thickness is designed with the reference wavelength λ as d-line (587.6 nm) hardly affects the spectral characteristics, and the spectral characteristics shown in FIG. It has almost the same characteristics.

  FIG. 15 shows the spectral characteristics when the incident angles of the light rays to the optical member having the spectral characteristics shown in FIG. 14 are 30, 45, and 60 degrees, respectively. 14 and 15 do not show the spectral characteristics of the optical member having the antireflection film with the refractive index of 1.46 shown in Table 6, but the refractive index of the substrate is almost equal to 1.52. Needless to say, it has the following spectral characteristics.

  For comparison, FIG. 16 shows an example of an antireflection film formed only by a dry process such as a conventional vacuum deposition method. FIG. 16 shows the spectral characteristics when a light beam is perpendicularly incident on an optical member designed with an antireflection film configured under the conditions shown in Table 7 below at a refractive index of 1.52 of the same substrate as in Table 6. FIG. 17 shows the spectral characteristics when the incident angles of the light rays to the optical member having the spectral characteristics shown in FIG. 16 are 30, 45, and 60 degrees, respectively.

(Table 7)
Material Refractive index Optical film thickness Medium Air 1
7th layer MgF2 1.39 0.243λ
6th layer Zr02 + Ti02 2.12 0.119λ
5th layer Al203 1.65 0.057λ
4th layer Zr02 + Ti02 2.12 0.220λ
3rd layer Al203 1.65 0.064λ
Second layer Zr02 + Ti02 2.12 0.057λ
1st layer Al203 1.65 0.193λ
Refractive index of substrate 1.52

  When the spectral characteristics of the optical member having the antireflection film according to this embodiment shown in FIGS. 13 to 15 are compared with the spectral characteristics of the conventional example shown in FIGS. 16 and 17, the antireflection film according to this embodiment is compared. Shows a lower reflectivity at any incident angle and has a lower reflectivity over a wider band.

  Next, examples in which the antireflection films shown in Tables 5 and 6 are applied to the first to fourth examples of the present application will be described.

  In the zoom optical system of the first example, the refractive index of the biconcave negative lens L23 of the second lens group G2 is nd = 1.772500 as shown in Table 1, and the fourth lens group G4 Since the refractive index of the positive meniscus lens L41 is nd = 1.593190, the antireflective film 101 (with the refractive index of the substrate corresponding to 1.74 on the image side lens surface of the biconcave negative lens L23) The reflection light from each lens surface is obtained by using an antireflection film (see Table 5) corresponding to a refractive index of the substrate of 1.62 on the lens surface on the image surface side of the positive meniscus lens L41. , And ghost and flare can be reduced.

  In the variable magnification optical system of the second example, the refractive index of the positive meniscus lens L41 of the fourth lens group G4 is nd = 1.593190 as shown in Table 2, so that the image plane of the positive meniscus lens L41 is By using the antireflection film 101 (see Table 5) corresponding to the refractive index of the substrate of 1.62 on the side lens surface, the reflected light from each lens surface can be reduced, and ghosts and flares can be reduced.

  In the variable magnification optical system of the third example, the refractive index of the biconvex positive lens L31 of the third lens group G3 is nd = 1.603000, as shown in Table 3, and the fourth lens group G4 Since the refractive index of the biconcave negative lens L45 is nd = 1.696800, the antireflective function corresponding to the refractive index of the substrate corresponding to 1.62 on the image surface side lens surface of the biconvex positive lens L31. Using the film 101 (see Table 5), an antireflection film (see Table 5) corresponding to a refractive index of the substrate of 1.74 is used on the object-side lens surface of the biconcave negative lens L45. Light reflected from the surface can be reduced, and ghost and flare can be reduced.

  In the variable magnification optical system of the fourth example, the refractive index of the negative meniscus lens L12 of the first lens group G1 is nd = 1.844000 as shown in Table 4, and the biconvexity of the third lens group G3. Since the refractive index of the positive lens L31 having a shape is nd = 1.603000, the antireflective film 101 corresponding to the refractive index of the substrate on the lens surface on the object side in the negative meniscus lens L12 is 1.85 (see Table 5). And using an antireflection film (see Table 5) corresponding to a refractive index of the substrate of 1.62 on the object-side lens surface of the biconvex positive lens L31, the reflected light from each lens surface is reduced. Ghost and flare can be reduced.

  Here, each said Example has shown the specific example of this invention, and this invention is not limited to these. The contents described below can be appropriately adopted as long as the optical performance is not impaired.

  Although four groups are shown as numerical examples of the variable magnification optical system of the present invention, the present invention is not limited to this, and it is also possible to configure variable magnification optical systems of other group configurations (for example, five groups). It is. Specifically, a configuration in which a lens or a lens group is added to the most object side of the variable magnification optical system of the present invention, or a configuration in which a lens or a lens group is added to the most image side may be used. The lens group indicates a portion having at least one lens separated by an air interval.

  The focusing lens group of the variable magnification optical system of the present invention is also suitable for driving by an ultrasonic motor or the like as an autofocus motor.

  Further, in the variable magnification optical system of the present invention, either the entire lens group or a part thereof is moved as an anti-vibration lens group so as to include a component in a direction orthogonal to the optical axis, or in an in-plane including the optical axis. It is also possible to adopt a configuration in which image blur caused by camera shake is corrected by rotationally moving (swinging) in the direction. In particular, it is preferable that at least a part of the fourth lens group is an anti-vibration lens group.

  The lens surface of the lens constituting the variable magnification optical system of the present invention may be a spherical surface, a flat surface, or an aspheric surface. When the lens surface is a spherical surface or a flat surface, it is preferable because lens processing and assembly adjustment are facilitated, and deterioration of optical performance due to errors in lens 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 aspheric, any of aspherical surfaces by grinding, a glass mold aspherical surface formed by molding glass into an aspherical surface, or a composite aspherical surface formed by forming resin on the glass surface into an aspherical surface An aspherical surface may be used. The lens surface may be a diffractive surface, and the lens may be a gradient index lens (GRIN lens) or a plastic lens.

  In addition, the aperture stop S of the zoom optical system according to the present invention is preferably disposed in the vicinity of the fourth lens group. However, the role may be substituted by a lens frame without providing a member as the aperture stop.

  Next, an optical apparatus including the variable magnification optical system ZL according to the present invention will be described using a digital single lens reflex camera as an example.

  FIG. 9 is a cross-sectional view showing an outline of a digital single-lens reflex camera provided with the variable magnification optical system of the present invention. In the digital single-lens reflex camera 1 shown in FIG. 9, light from an object (subject) (not shown) is collected by the variable magnification optical system ZL and is focused on the focusing plate 5 via the quick return mirror 3. The light imaged on the collecting plate 5 is reflected a plurality of times in the pentaprism 7 and guided to the eyepiece lens 9. Thus, the photographer can observe the object (subject) image as an erect image through the eyepiece 9.

  When a release button (not shown) is pressed by the photographer, the quick return mirror 3 is retracted out of the optical path, and the light of the object (subject) collected by the zoom optical system ZL forms an object image on the image sensor 11. Form. Thereby, the light from the object is picked up by the image pickup device 11 and stored in a memory (not shown) as an object image. In this way, the photographer can photograph an object with the camera 1.

  With the above configuration, the digital single-lens reflex camera 1 equipped with the variable magnification optical system ZL according to the present invention realizes downsizing and high-speed autofocus, and corrects various aberrations satisfactorily to achieve high optical performance. can do. Note that the camera 1 in FIG. 9 may hold the photographic lens in a detachable manner, or may be formed integrally with the photographic lens. The camera may be a single-lens reflex camera or a camera that does not have a quick return mirror or the like.

Next, a method for manufacturing the variable magnification optical system ZL of the present invention will be described.
FIG. 10 is a diagram showing an outline of a method for manufacturing the variable magnification optical system ZL according to the present invention.

The method of manufacturing the variable magnification optical system ZL according to the present invention includes, in order from the object side along the optical axis, a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a positive refraction. A variable magnification optical system manufacturing method having a third lens group having power and a fourth lens group having positive refractive power, and includes the following steps S1 to S4 as shown in FIG. .
Step S1: An antireflection film is provided on at least one of the optical surfaces in the first lens group to the fourth lens group, and the antireflection film is configured to include at least one layer formed using a wet process.
Step S2: During zooming from the wide-angle end state to the telephoto end state, the distance between the first lens group and the second lens group changes, the distance between the second lens group and the third lens group changes, and the third The distance between the lens group and the fourth lens group is configured to change.
Step S3: The third lens group is composed of one positive lens.
Step S4: The third lens group is moved in the optical axis direction so as to perform focusing from an object at infinity to an object at a short distance.

  According to the method for manufacturing a variable magnification optical system of the present invention, it is possible to realize a variable magnification optical system that achieves downsizing and high speed autofocus and further has high optical performance.

ZL variable magnification optical system G1 1st lens group G2 2nd lens group G3 3rd lens group G4 4th lens group G4A 4A lens group G4B 4B lens group G4C 4C lens group S Aperture stop I Image plane 1 Optical device 3 Quick return mirror 5 Gathering plate 7 Penta prism 9 Eyepiece 11 Imaging element 101 Antireflection film 101a First layer 101b Second layer 101c Third layer 101d Fourth layer 101e Fifth layer 101f Sixth layer 101g Seventh layer 102 Optical Element

Claims (21)

A first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a positive refractive power in order from the object side along the optical axis. A fourth lens group having
An antireflection film is provided on at least one of the optical surfaces of the first lens group to the fourth lens group, and the antireflection film includes at least one layer formed using a wet process,
During zooming from the wide-angle end state to the telephoto end state, the distance between the first lens group and the second lens group changes, and the distance between the second lens group and the third lens group changes, The distance between the third lens group and the fourth lens group changes,
The third lens group is composed of one positive lens,
A variable magnification optical system characterized in that focusing from an object at infinity to a near object is performed by moving the third lens group in the optical axis direction.   The antireflection film is a multilayer film, and the layer formed by using the wet process is a layer on the most surface side of the films constituting the multilayer film. Variable magnification optical system.   The nd is 1.30 or less, where nd is a refractive index with respect to d-line (wavelength λ = 587.6 nm) of a layer formed by the wet process. Variable magnification optical system. Having an aperture stop,
4. The zoom optical system according to claim 1, wherein the optical surface provided with the antireflection film is a concave lens surface when viewed from the aperture stop. 5.   5. The variable magnification optical system according to claim 4, wherein the lens surface having a concave shape when viewed from the aperture stop is an object side lens surface of a lens in the first lens group.   5. The variable magnification optical system according to claim 4, wherein the lens surface having a concave shape when viewed from the aperture stop is an image surface side lens surface of a lens in the second lens group.   5. The variable magnification optical system according to claim 4, wherein the lens surface that is concave when viewed from the aperture stop is an object side lens surface of a lens in the third lens group.   5. The variable magnification optical system according to claim 4, wherein the lens surface having a concave shape when viewed from the aperture stop is an image surface side lens surface of a lens in the fourth lens group.   4. The zoom optical system according to claim 1, wherein the optical surface provided with the antireflection film is a concave lens surface when viewed from the object side. 5.   10. The variable magnification optical system according to claim 9, wherein the lens surface having a concave shape when viewed from the object side is an image surface side lens surface of a lens in the third lens group.   10. The variable magnification optical system according to claim 9, wherein the lens surface having a concave shape when viewed from the object side is an object side lens surface of a lens in the fourth lens group.   The variable magnification optical system according to any one of claims 1 to 11, wherein the positive lens of the third lens group has a biconvex shape.   The variable magnification optical system according to any one of claims 1 to 12, wherein a lens surface of the positive lens of the third lens group is a spherical surface. The variable power optical system according to claim 1, wherein a condition of the following formula is satisfied.
1.00 <R31A / (-R31B) <3.00
However,
R31A: radius of curvature of object side surface of positive lens of third lens group R31B: radius of curvature of image side surface of positive lens of third lens group 15. The variable magnification optical system according to claim 1, wherein a condition of the following formula is satisfied.
3.50 <ft / f3 <5.00
However,
ft: focal length of the entire variable magnification optical system in the telephoto end state f3: focal length of the third lens group 16. The variable magnification optical system according to claim 1, wherein a condition of the following formula is satisfied.
1.00 <f1 / fw <2.00
However,
f1: Focal length of the first lens group fw: Focal length of the entire variable magnification optical system in the wide-angle end state The variable power optical system according to any one of claims 1 to 16, wherein a condition of the following formula is satisfied.
0.300 <(-f2) / fw <0.500
However,
f2: Focal length of the second lens group fw: Focal length of the entire variable magnification optical system in the wide-angle end state The fourth lens group includes, in order from the object side along the optical axis, a fourth A lens group having a positive refractive power, a fourth B lens group having a negative refractive power, and a fourth C lens having a positive refractive power. And having a group
18. The image blur correction due to camera shake is performed by moving the fourth B lens group so as to have a component in a direction substantially orthogonal to the optical axis. 18. Variable magnification optical system.   19. When zooming from a wide-angle end state to a telephoto end state, the first lens group moves toward the object side with respect to the image plane along the optical axis. The zoom optical system according to 1.   An optical apparatus comprising the variable magnification optical system according to any one of claims 1 to 19. A first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a positive refractive power in order from the object side along the optical axis. A variable magnification optical system having a fourth lens group having:
An antireflection film is provided on at least one of the optical surfaces of the first lens group to the fourth lens group, and the antireflection film includes at least one layer formed using a wet process,
During zooming from the wide-angle end state to the telephoto end state, the distance between the first lens group and the second lens group changes, and the distance between the second lens group and the third lens group changes, The distance between the third lens group and the fourth lens group is configured to change,
The third lens group is composed of one positive lens,
A method of manufacturing a variable magnification optical system, wherein the third lens group is configured to perform focusing from an object at infinity to an object at a short distance by moving the third lens group in the optical axis direction.

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