JP6435635B2 - Optical system, optical device - Google Patents

Description

  The present invention relates to an optical system, an optical device, and a method for manufacturing the optical system.

  Conventionally, in photo cameras, electronic still cameras, and the like, telephoto type and inner focus type optical systems are often used as optical systems having a large focal length (see, for example, Patent Document 1). In recent years, not only aberration performance but also ghost and flare, which are one of the factors that impair optical performance, are becoming more demanding for such optical systems. Therefore, higher performance is also required for the antireflection film applied to the lens surface of the optical system, and multilayer film design technology and film formation technology continue to advance to meet such requirements (for example, Patent Document 2). See).

JP 2008-164997 A JP 2000-356704 A

  However, the conventional optical system as described above has a problem that miniaturization and high performance are not sufficiently achieved. At the same time, the lens surface in the conventional optical system also has a problem that reflected light that becomes ghost or flare is likely to be generated.

  Therefore, the present invention has been made in view of the above problems, and an object thereof is to provide an optical system, an optical device, and a method for manufacturing the optical system, which further reduce ghosts and flares and are small and have good optical performance. And

In order to solve the above problems, the present invention
In order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a third lens group having a positive refractive power,
An antireflection film is provided on at least one of the optical surfaces of the first lens group, the second lens group, and the third lens group, and the antireflection film is a layer formed using a wet process. At least one layer,
The second lens group has two negative lens components;
By moving the second lens group along the optical axis, focusing from an object at infinity to an object at a short distance,
The following conditional expression is satisfied:
0.30 <f / f12 <0.55
However,
f: focal length of the optical system f12: combined focal length of the first lens group and the second lens group at the time of focusing on an object at infinity The first lens group has a plurality of positive lenses,
Among the plurality of positive lenses, the biconvex positive lens arranged closest to the object side satisfies the following conditional expression :
85 <νd1pf <110
However,
νd1pf: Abbe number with respect to d-line of the glass material of the positive lens arranged closest to the object side among the plurality of positive lenses in the first lens group
The first lens group is composed of a 1a lens group and a 1b lens group in order from the object side,
An air space between the first lens group and the first lens group is the largest of the air spaces in the first lens group;
An optical system characterized by satisfying the following conditional expression is provided.
0.30 <TL1a / TL1 <0.50
However,
TL1a: length along the optical axis of the first lens group
TL1: The length along the optical axis of the first lens group, or the present invention,
In order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a third lens group having a positive refractive power,
An antireflection film is provided on at least one of the optical surfaces of the first lens group, the second lens group, and the third lens group, and the antireflection film is a layer formed using a wet process. At least one layer,
By moving the second lens group along the optical axis, focusing from an object at infinity to an object at a short distance,
The second lens group has at least three lenses;
The following conditional expression is satisfied:
0.30 <f / f12 <0.85
However,
f: focal length of the optical system f12: combined focal length of the first lens group and the second lens group at the time of focusing on an object at infinity The first lens group has a plurality of positive lenses,
Among the plurality of positive lenses, the biconvex positive lens arranged closest to the object side satisfies the following conditional expression :
85 <νd1pf <110
However,
νd1pf: Abbe number with respect to d-line of the glass material of the positive lens arranged closest to the object side among the plurality of positive lenses in the first lens group
The first lens group is composed of a 1a lens group and a 1b lens group in order from the object side,
An air space between the first lens group and the first lens group is the largest of the air spaces in the first lens group;
An optical system characterized by satisfying the following conditional expression is provided.
0.30 <TL1a / TL1 <0.50
However,
TL1a: length along the optical axis of the first lens group
TL1: Length along the optical axis of the first lens group

In addition, the present onset Ming,
An optical apparatus comprising the optical system is provided.

  ADVANTAGE OF THE INVENTION According to this invention, a ghost and a flare can be reduced more and the manufacturing method of the optical system, the optical apparatus, and the optical system which were small and provided with the favorable optical performance can be provided.

FIG. 1 is a cross-sectional view showing a lens arrangement at the time of focusing on an object at infinity of the optical system according to the first embodiment of the first and second inventions of the present application. FIGS. 2A and 2B are graphs showing various aberrations when the optical system according to the first embodiment of the first and second inventions of the present application is focused on an object at infinity and focused on a short distance object, respectively. It is. FIG. 3 is a sectional view showing the lens arrangement at the time of focusing on an object at infinity of the optical system according to the second embodiment of the first and second inventions of the present application. FIGS. 4A and 4B are diagrams showing various aberrations when the optical system according to the second embodiment of the first and second inventions of the present application is focused on an object at infinity and focused on a short distance object, respectively. It is. FIG. 5 is a cross-sectional view showing the lens arrangement at the time of focusing on an object at infinity of the optical system according to the third embodiment of the first and second inventions of the present application. FIGS. 6A and 6B are graphs showing various aberrations when the optical system according to the third embodiment of the first and second inventions of the present application is focused on an object at infinity and focused on a short distance object, respectively. It is. FIG. 7 is a sectional view showing the lens arrangement at the time of focusing on an object at infinity of the optical system according to the fourth example of the first and second inventions of the present application. FIGS. 8A and 8B are diagrams showing various aberrations when the optical system according to the fourth example of the first and second inventions of the present application is focused on an object at infinity and focused on a short distance object, respectively. It is. FIG. 9 is a sectional view showing the lens arrangement at the time of focusing on an object at infinity of the optical system according to the fifth embodiment of the first and second inventions of the present application. FIGS. 10A and 10B are diagrams showing various aberrations when the optical system according to the fifth example of the first and second inventions of the present application is focused on an object at infinity and focused on a short distance object, respectively. It is. FIG. 11 is a sectional view showing the lens arrangement at the time of focusing on an object at infinity of the optical system according to the sixth example of the first and second inventions of the present application. FIGS. 12A and 12B are graphs showing various aberrations when the optical system according to the sixth example of the first and second inventions of the present application is focused on an object at infinity and focused on a short distance object, respectively. It is. FIG. 13 is a diagram showing a configuration of a camera provided with the optical system of the first or second invention of the present application. FIG. 14 is a diagram showing an outline of the method of manufacturing the optical system according to the first invention of the present application. FIG. 15 shows that a light ray incident on the optical system according to the first embodiment of the first and second inventions of the present application is reflected by the first reflecting surface and the second reflecting surface to form a ghost or flare on the image surface. It is a figure which shows an example of a mode to do. FIG. 16 is an explanatory view showing an example of the layer structure of the first and second invention antireflection films. FIG. 17 is a graph showing the spectral characteristics of the first and second invention antireflection films. FIG. 18 is a graph showing the spectral characteristics of the antireflection film according to the first and second invention modifications. FIG. 19 is a graph showing the incident angle dependence of the spectral characteristics of the antireflection films according to the first and second invention modifications. FIG. 20 is a graph showing the spectral characteristics of the antireflection film prepared by the prior art. FIG. 21 is a graph showing the incident angle dependence of the spectral characteristics of the antireflection film prepared by the prior art. FIG. 22 is a diagram showing an outline of the method of manufacturing the optical system of the second invention of the present application.

Hereinafter, the optical system, the optical device, and the method for manufacturing the optical system according to the first invention of the present application will be described.
The optical system of the first invention of this application includes, in order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a third 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, the second lens group, and the third lens group, and the antireflection film is formed using a wet process. At least one layer, and the second lens group is moved along the optical axis to focus from an infinite object to a close object, and the following conditional expression (1-1) It is characterized by satisfaction.
(1-1) 0.10 <f / f12 <0.55
However,
f: Focal length of the optical system f12: Composite focal length of the first lens group and the second lens group at the time of focusing on an object at infinity

  As described above, the optical system of the first invention of the present application, in order from the object side, the first lens group having a positive refractive power, the second lens group having a negative refractive power, and the third lens having a positive refractive power. And a lens group. With this configuration, the optical system of the first invention of the present application can achieve both miniaturization and high performance while having a large focal length.

  In addition, as described above, the optical system of the first invention of the present application performs focusing from an object at infinity to a near object by moving the second lens group along the optical axis. With this configuration, the second lens group can be driven by a relatively small motor unit.

  Conditional expression (1-1) defines the combined refractive power of the first lens group and the second lens group. The optical system of the present application can satisfactorily correct lateral chromatic aberration by satisfying conditional expression (1-1). Further, the light emitted from the second lens group becomes convergent light. For this reason, since the second lens group can be arranged on the image side, and the first lens group can be arranged on the image side accordingly, the overall length of the optical system of the present application can be reduced. . In addition, the lateral chromatic aberration can be corrected satisfactorily.

  If the corresponding value of the conditional expression (1-1) of the optical system according to the first invention of the present application exceeds the upper limit value, it will be difficult to correct lateral chromatic aberration. In order to secure the effect of the present application, it is more preferable to set the upper limit of conditional expression (1-1) to 0.54. In order to further secure the effect of the present application, it is more preferable to set the upper limit of conditional expression (1-1) to 0.53.

On the other hand, when the corresponding value of the conditional expression (1-1) of the optical system of the first invention of the present application is less than the lower limit value, the light emitted from the second lens group becomes parallel light, and therefore the optical system of the first invention of the present application. The total length of becomes larger. Therefore, if it is attempted to shorten the overall length of the optical system according to the first invention of the present application, it becomes difficult to correct coma. In order to secure the effect of the present application, it is more preferable to set the lower limit of conditional expression (1-1) to 0.20. In order to secure the effect of the present application, it is more preferable to set the lower limit of conditional expression (1-1) to 0.30.
With the above configuration, an optical system having a small size and good optical performance can be realized.

  In the optical system of the first invention of the present application, an antireflection film is provided on at least one of the optical surfaces of the first lens group, the second lens group, and the third lens group, and the antireflection film is provided. The film includes at least one layer formed by using a wet process. With this configuration, the optical system of the first invention of the present application can further reduce ghosts and flares caused by reflection of light from an object on an optical surface, and can achieve high imaging performance.

  Further, in the optical system of the first invention of the present application, the antireflection film is a multilayer film, and the layer formed by using the wet process is the most surface layer among the layers constituting the multilayer film. It 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. Can do.

  Further, in the optical system of the first invention of the present application, when the refractive index for the d-line (wavelength λ = 587.6 nm) of the layer formed by using 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. Can do.

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

  In the optical system according to the first aspect of the present invention, it is preferable that the concave lens surface when viewed from the image surface side is an image surface side lens surface of a 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 image surface side. For this reason, a ghost and flare can be effectively reduced by forming an antireflection film on such a lens surface.

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

  In the optical system according to the first aspect of the present invention, it is desirable that the concave lens surface when viewed from the image surface side is an object side lens surface of a 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 image surface side. For this reason, a ghost and flare can be effectively reduced by forming an antireflection film on such a lens surface.

  In the optical system according to the first aspect of the present invention, it is desirable that the concave lens surface when viewed from the image surface side is an image surface side lens surface of a 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 image surface side. For this reason, a ghost and flare can be effectively reduced by forming an antireflection film on such a lens surface.

  In the optical system according to the first aspect of the present invention, it is desirable that the concave lens surface when viewed from the image surface side is the image surface side lens surface of the fourth lens from the object side 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 image surface side. For this reason, a ghost and flare can be effectively reduced by forming an antireflection film on such a lens surface.

  In the optical system of the first invention of the present application, it is desirable 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 first lens group and the second 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 optical system according to the first aspect of 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 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 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 optical system according to the first aspect of the present invention, it is preferable that the concave lens surface when viewed from the object side is an image surface side lens surface of a 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 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 optical system according to the first aspect of 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 second lens group. Of the optical surfaces in the second 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.

  The antireflection film in the optical system of the first invention of the present application is not limited to a 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 the antireflection film is formed by a wet process can be obtained. Note that the layer having a refractive index of 1.30 or less is preferably the outermost layer among the layers constituting the multilayer film.

In the optical system of the first invention of the present application, it is desirable that the first lens group has at least one positive lens that satisfies the following conditional expression (1-2).
(1-2) 80 <νd1p <110
However,
νd1p: Abbe number with respect to d-line (wavelength 587.6 nm) of the glass material of the positive lens in the first lens group

  Conditional expression (1-2) defines the Abbe number of the glass material of the positive lens in the first lens group. The optical system of the first invention of the present application can satisfactorily correct axial chromatic aberration and lateral chromatic aberration by satisfying conditional expression (1-2).

  If the corresponding value of the conditional expression (1-2) of the optical system according to the first invention of the present application exceeds the upper limit value, the axial chromatic aberration and the lateral chromatic aberration are excessively corrected, which is not preferable. In order to secure the effect of the present application, it is more preferable to set the upper limit of conditional expression (1-2) to 105. In order to further secure the effect of the present application, it is more preferable to set the upper limit of conditional expression (1-2) to 100.

  On the other hand, if the corresponding value of the conditional expression (1-2) of the optical system of the first invention of the present application is below the lower limit value, it will be difficult to correct axial chromatic aberration and lateral chromatic aberration. In order to secure the effect of the present application, it is more preferable to set the lower limit of conditional expression (1-2) to 85. In order to further secure the effect of the present application, it is more preferable to set the lower limit of conditional expression (1-2) to 90.

In the optical system of the first invention of the present application, the first lens group has a plurality of positive lenses, and the positive lens arranged closest to the object among the plurality of positive lenses is defined by the following conditional expression (1- It is desirable to satisfy 3).
(1-3) 80 <νd1pf <110
However,
νd1pf: Abbe number with respect to the d-line (wavelength 587.6 nm) of the glass material of the positive lens arranged closest to the object side among the plurality of positive lenses in the first lens group

  Conditional expression (1-3) defines the Abbe number of the glass material of the positive lens arranged closest to the object among the plurality of positive lenses in the first lens group. The optical system of the present application can satisfactorily correct axial chromatic aberration and lateral chromatic aberration by satisfying conditional expression (1-3).

  If the corresponding value of the conditional expression (1-3) of the optical system according to the first invention of the present application exceeds the upper limit value, the axial chromatic aberration and the lateral chromatic aberration are excessively corrected, which is not preferable. In order to secure the effect of the present application, it is more preferable to set the upper limit of conditional expression (1-3) to 105. In order to further secure the effect of the present application, it is more preferable to set the upper limit of conditional expression (1-3) to 100.

  On the other hand, if the corresponding value of the conditional expression (1-3) of the optical system of the first invention of the present application is below the lower limit value, it will be difficult to correct axial chromatic aberration and lateral chromatic aberration. In order to secure the effect of the present application, it is more preferable to set the lower limit of conditional expression (1-3) to 85. In order to further secure the effect of the present application, it is more preferable to set the lower limit of conditional expression (1-3) to 90.

In the optical system of the first invention of the present application, it is desirable that the first lens group has at least one negative lens that satisfies the following conditional expression (1-4).
(1-4) 1.50 <nd1n <1.75
However,
nd1n: refractive index with respect to d-line (wavelength 587.6 nm) of the glass material of the negative lens in the first lens group

  Conditional expression (1-4) defines the refractive index of the glass material of the negative lens in the first lens group. By satisfying conditional expression (1-4), the optical system of the first invention of the present application can correct coma and curvature of field favorably while reducing the weight.

  When the corresponding value of the conditional expression (1-4) of the optical system according to the first invention of the present application exceeds the upper limit value, the specific gravity of the glass material of the negative lens in the first lens group increases. Therefore, if the specific gravity of the other lenses in the first lens group is reduced in order to reduce the weight of the optical system of the present application, it becomes difficult to correct coma. In order to secure the effect of the present application, it is more preferable to set the upper limit of conditional expression (1-4) to 1.70. In order to further secure the effect of the present application, it is more preferable to set the upper limit of conditional expression (1-4) to 1.65.

  On the other hand, when the corresponding value of the conditional expression (1-4) of the optical system according to the first invention of the present application is less than the lower limit value, it becomes difficult to correct the curvature of field. In order to secure the effect of the present application, it is more preferable to set the lower limit of conditional expression (1-4) to 1.55. In order to secure the effect of the present application, it is more preferable to set the lower limit of conditional expression (1-4) to 1.60.

  In the optical system of the first invention of the present application, it is desirable that at least a part of the third lens group moves so as to include a component in a direction orthogonal to the optical axis. With this configuration, image blur due to camera shake or the like can be corrected, that is, image stabilization can be performed, and the occurrence of decentration aberrations during image stabilization can be suppressed to a level where there is no problem.

  In the optical system according to the first invention of the present application, the third lens group includes, in order from the object side, a 3a lens group having positive refractive power, a 3b lens group having negative refractive power, and positive refraction. It is desirable that the third lens group is configured to include a component in a direction orthogonal to the optical axis. With this configuration, image blur due to camera shake or the like can be corrected, that is, image stabilization can be performed, and the occurrence of decentration aberrations during image stabilization can be suppressed to a level where there is no problem. In addition, since the diameter of the 3b lens group can be reduced, the mechanical unit for driving the 3b lens group during vibration isolation can be reduced in size.

  In the optical system of the first invention of the present application, it is desirable that the first lens group has a cemented lens of a negative lens and a positive lens in order from the object side. With this configuration, the decentration aberration can be corrected satisfactorily. The cemented lens is more preferably arranged on the most image side in the first lens group.

In the optical system according to the first aspect of the present invention, the first lens group includes a 1a lens group and a 1b lens group in order from the object side, and the 1a lens group and the 1b lens group Is the largest among the air intervals in the first lens group, and it is preferable that the following conditional expression (1-5) is satisfied.
(1-5) 0.30 <TL1a / TL1 <0.70
However,
TL1a: length along the optical axis of the first lens group TL1: length along the optical axis of the first lens group

  Conditional expression (1-5) defines the length of the first lens group with respect to the length of the first lens group. By satisfying conditional expression (1-5), the optical system of the first invention of the present application can correct coma well while reducing the weight.

  When the corresponding value of the conditional expression (1-5) of the optical system according to the first invention of the present application exceeds the upper limit value, the weight of the first lens group increases. Therefore, for example, if a glass material having a small refractive index is used for the negative lens in the first lens group in order to reduce the weight, it becomes difficult to correct curvature of field. In order to secure the effect of the present application, it is more preferable to set the upper limit of conditional expression (1-5) to 0.60. In order to secure the effect of the present application, it is more preferable to set the upper limit of conditional expression (1-5) to 0.50.

  On the other hand, when the corresponding value of the conditional expression (1-5) of the optical system according to the first invention of the present application is lower than the lower limit value, it becomes difficult to correct the coma aberration. In order to secure the effect of the present application, it is more preferable to set the lower limit of conditional expression (1-5) to 0.35. In order to secure the effect of the present application, it is more preferable to set the lower limit of conditional expression (1-5) to 0.40.

In the optical system of the first invention of the present application, it is preferable that the 1a lens group includes a positive lens, a positive lens, and a negative lens in order from the object side. With this configuration, the weight of the optical system of the present application can be reduced.
In the optical system of the first invention of the present application, it is preferable that the first lens group has a protective filter glass on the most object side. The protective filter glass is a lens having substantially no refractive power, and its focal length is preferably 10 times or more of the focal length of the optical system of the present application. In particular, the optical system of the first invention of the present application preferably has a negative meniscus shape in which the protective filter glass has a convex surface facing the object side. With this configuration, the ghost can be cut well.
In the optical system of the first invention of the present application, it is desirable that the first lens group b includes a negative lens and a positive lens in order from the object side. With this configuration, it is possible to satisfactorily correct variations in spherical aberration when focusing on a short-distance object. In particular, in the optical system of the first invention of the present application, it is preferable that the 1b lens group includes only a cemented lens of a negative lens and a positive lens in order from the object side. With this configuration, it is possible to reduce the weight of the optical system according to the first aspect of the present invention.

In the optical system according to the first aspect of the present invention, the first lens group includes a 1a lens group and a 1b lens group in order from the object side, and the 1a lens group and the 1b lens group Is the largest of the air intervals in the first lens group, and the 1b lens group preferably includes a positive lens that satisfies the following conditional expression (1-6).
(1-6) 70 <νd1bp <110
However,
νd1bp: Abbe number with respect to d-line (wavelength 587.6 nm) of the glass material of the positive lens in the 1b lens group

  Conditional expression (1-6) defines the Abbe number of the glass material of the positive lens in the 1b lens group. The optical system of the first invention of the present application can satisfactorily correct axial chromatic aberration and lateral chromatic aberration by satisfying conditional expression (1-6).

  If the corresponding value of the conditional expression (1-6) of the optical system according to the first invention of the present application exceeds the upper limit value, the axial chromatic aberration and the lateral chromatic aberration are excessively corrected, which is not preferable. In order to secure the effect of the present application, it is more preferable to set the upper limit of conditional expression (1-6) to 105. In order to secure the effect of the present application, it is more preferable to set the upper limit of conditional expression (1-6) to 100.

  On the other hand, if the corresponding value of the conditional expression (1-6) of the optical system of the first invention of the present application is less than the lower limit value, it will be difficult to correct axial chromatic aberration and lateral chromatic aberration. In order to secure the effect of the present application, it is more preferable to set the lower limit of conditional expression (1-6) to 75. In order to secure the effect of the present application, it is more preferable to set the lower limit of conditional expression (1-6) to 80.

In the optical system of the first invention of the present application, it is desirable that the second lens group has two negative lens components. With this configuration, coma can be corrected well. Here, in the first invention of the present application, the “lens component” refers to a cemented lens or a single lens formed by cementing two or more lenses.
In the optical system of the first invention of the present application, the second lens group may include a negative lens, a positive lens, and a negative lens in order from the object side. The second lens group may include a positive lens, a negative lens, and a negative lens in order from the object side. With these configurations, coma can be corrected well.

In the optical system of the first invention of the present application, it is desirable that the second lens group has a positive lens that satisfies the following conditional expression (1-7).
(1-7) 15 <νd2p <30
However,
νd2p: Abbe number with respect to d-line (wavelength 587.6 nm) of the glass material of the positive lens in the second lens group

  Conditional expression (1-7) defines the Abbe number of the glass material of the positive lens in the second lens group. The optical system of the first invention of the present application can satisfactorily correct lateral chromatic aberration and axial chromatic aberration by satisfying conditional expression (1-7).

  If the corresponding value of conditional expression (1-7) of the optical system according to the first invention of the present application exceeds the upper limit value, it will be difficult to correct lateral chromatic aberration. In order to secure the effect of the present application, it is more preferable to set the upper limit of conditional expression (1-7) to 27. In order to further secure the effect of the present application, it is more preferable to set the upper limit of conditional expression (1-7) to 25.

  On the other hand, when the corresponding value of the conditional expression (1-7) of the optical system according to the first invention of the present application is less than the lower limit value, in order to prevent the transmittance of light having a short wavelength from decreasing, Therefore, it becomes impossible to use a lens made of a glass material having a large dispersion in the lens group located in the position. This makes it difficult to correct axial chromatic aberration. In order to secure the effect of the present application, it is more preferable to set the lower limit of conditional expression (1-7) to 16. In order to further secure the effect of the present application, it is more preferable to set the lower limit of conditional expression (1-7) to 17.

  The optical device according to the first invention of the present application has the optical system having the above-described configuration. Thereby, an optical device having a small size and good optical performance can be realized.

The manufacturing method of the optical system according to the first invention of the present application includes, in order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a third lens having a positive refractive power. And an antireflection film provided on at least one of the optical surfaces of the first lens group, the second lens group, and the third lens group, and the antireflection film. Includes at least one layer formed using a wet process, the optical system satisfies the following conditional expression (1-1), and the second lens group is moved along the optical axis: In this way, focusing from an object at infinity to an object at a short distance is performed. Thereby, an optical system having a small size and good optical performance can be manufactured.
(1-1) 0.10 <f / f12 <0.55
However,
f: Focal length of the optical system f12: Composite focal length of the first lens group and the second lens group at the time of focusing on an object at infinity

Next, the optical system, the optical device, and the method for manufacturing the optical system according to the second invention of the present application will be described.
The optical system of the second invention of this application includes, in order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a third 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, the second lens group, and the third lens group, and the antireflection film is formed using a wet process. At least one layer, the second lens group is moved along the optical axis to focus from an infinite object to a near object, and the second lens group includes at least three lenses. And the following conditional expression (2-1) is satisfied.
(2-1) 0.10 <f / f12 <0.85
However,
f: Focal length of the optical system f12: Composite focal length of the first lens group and the second lens group at the time of focusing on an object at infinity

  As described above, the optical system of the second invention of the present application, in order from the object side, the first lens group having a positive refractive power, the second lens group having a negative refractive power, and the third lens having a positive refractive power. And a lens group. With this configuration, the optical system of the second invention of the present application can achieve both miniaturization and high performance while having a large focal length.

In addition, as described above, the optical system of the second invention of the present application performs focusing from an object at infinity to an object at a short distance by moving the second lens group along the optical axis. With this configuration, the second lens group can be driven by a relatively small motor unit.
Further, as described above, in the optical system of the second invention of the present application, the second lens group has at least three lenses. With this configuration, coma can be corrected well.

  Conditional expression (2-1) defines the combined refractive power of the first lens group and the second lens group. The optical system of the second invention of the present application can satisfactorily correct lateral chromatic aberration by satisfying conditional expression (2-1). Further, the light emitted from the second lens group becomes convergent light. For this reason, since the second lens group can be arranged on the image side and the first lens group can be arranged on the image side accordingly, the overall length of the optical system of the second invention of the present application is reduced. be able to. In addition, the lateral chromatic aberration can be corrected satisfactorily.

  If the corresponding value of conditional expression (2-1) of the optical system of the second invention of the present application exceeds the upper limit value, it will be difficult to correct lateral chromatic aberration. In order to secure the effect of the present application, it is more preferable to set the upper limit of conditional expression (2-1) to 0.80. In order to further secure the effect of the present application, it is more preferable to set the upper limit of conditional expression (2-1) to 0.75.

On the other hand, when the corresponding value of the conditional expression (2-1) of the optical system of the second invention of the present application is below the lower limit value, the light emitted from the second lens group becomes parallel light, and therefore the optical system of the second invention of the present application. The total length of becomes larger. Therefore, if it is attempted to shorten the overall length of the optical system according to the second invention of the present application, it becomes difficult to correct coma. In order to secure the effect of the present application, it is more preferable to set the lower limit of conditional expression (2-1) to 0.20. In order to secure the effect of the present application, it is more preferable to set the lower limit of conditional expression (2-1) to 0.30.
With the above configuration, an optical system having a small size and good optical performance can be realized.

  In the optical system of the second invention of the present application, an antireflection film is provided on at least one of the optical surfaces of the first lens group, the second lens group, and the third lens group, and the antireflection film is provided. The film includes at least one layer formed by using a wet process. With this configuration, the optical system of the present application can further reduce ghosts and flares caused by reflection of light from an object on an optical surface, and can achieve high imaging performance.

  Further, in the optical system of the second invention of the present application, the antireflection film is a multilayer film, and the layer formed by using the wet process is the most surface layer among the layers constituting the multilayer film. It 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. Can do.

  Further, in the optical system of the second invention of the present application, when the refractive index with respect to the d-line (wavelength λ = 587.6 nm) of the layer formed using 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. Can do.

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

  In the optical system according to the second aspect of the present invention, it is preferable that the concave lens surface when viewed from the image surface side is an image surface side lens surface of a 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 image surface side. For this reason, a ghost and flare can be effectively reduced by forming an antireflection film on such a lens surface.

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

  In the optical system according to the second aspect of the present invention, it is desirable that the concave lens surface as viewed from the image surface side is an 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 image surface side. For this reason, a ghost and flare can be effectively reduced by forming an antireflection film on such a lens surface.

  In the optical system of the second invention of this application, it is desirable that the concave lens surface as viewed from the image surface side is an image surface side lens surface of a 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 image surface side. For this reason, a ghost and flare can be effectively reduced by forming an antireflection film on such a lens surface.

  In the optical system of the second invention of the present application, it is desirable that the concave lens surface when viewed from the image surface side is the image surface side lens surface of the fourth lens from the object side 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 image surface side. For this reason, a ghost and flare can be effectively reduced by forming an antireflection film on such a lens surface.

  In the optical system of the second invention of the present application, the optical surface provided with the antireflection film is preferably a concave lens surface when viewed from the object side. Of the optical surfaces in the first lens group and the second 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 optical system of the second invention of the present application, 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 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 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 optical system according to the second aspect of the present invention, it is preferable that the concave lens surface when viewed from the object side is an image surface side lens surface of a 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 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 optical system of the second invention of the present application, 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 second lens group. Of the optical surfaces in the second 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.

  The antireflection film in the optical system of the second invention of the present application is not limited to a 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 the antireflection film is formed by a wet process can be obtained. Note that the layer having a refractive index of 1.30 or less is preferably the outermost layer among the layers constituting the multilayer film.

In the optical system of the second invention of the present application, it is desirable that at least two of the at least three lenses in the second lens group are negative lenses. With this configuration, coma can be corrected well.
In the optical system of the second invention of the present application, the second lens group includes a negative lens, a positive lens, and a negative lens in order from the object side, or a positive lens and a negative lens in order from the object side. More preferably, the lens has a lens and a negative lens. In these configurations, it is most preferable to join a positive lens and a negative lens. With the above configuration, coma aberration can be corrected more favorably.

In the optical system of the second invention of the present application, it is desirable that the second lens group has at least one negative lens satisfying the following conditional expression (2-2).
(2-2) 1.45 <nd2n <1.65
However,
nd2n: refractive index with respect to d-line (wavelength 587.6 nm) of the glass material of the negative lens in the second lens group

  Conditional expression (2-2) defines the refractive index of the glass material of the negative lens in the second lens group. The optical system of the second invention of the present application satisfactorily corrects coma and curvature of field while reducing the weight of the second lens group, which is the focusing lens group, by satisfying conditional expression (2-2). be able to.

  When the corresponding value of the conditional expression (2-2) of the optical system of the second invention of the present application exceeds the upper limit value, the specific gravity of the glass material of the negative lens in the second lens group increases. Therefore, if the specific gravity of other lenses in the second lens group is reduced in order to reduce the weight of the optical system of the second invention of the present application, it will be difficult to correct coma. In order to secure the effect of the present application, it is more preferable to set the upper limit of conditional expression (2-2) to 1.64. In order to secure the effect of the present application, it is more preferable to set the upper limit value of conditional expression (2-2) to 1.63.

  On the other hand, if the corresponding value of the conditional expression (2-2) of the optical system of the second invention of the present application is less than the lower limit value, it becomes difficult to correct the curvature of field. In order to secure the effect of the present application, it is more preferable to set the lower limit of conditional expression (2-2) to 1.48. In order to further secure the effect of the present application, it is more preferable to set the lower limit of conditional expression (2-2) to 1.50.

In the optical system of the second invention of the present application, it is desirable that the second lens group has a positive lens that satisfies the following conditional expression (2-3).
(2-3) 15 <νd2p <30
However,
νd2p: Abbe number with respect to d-line (wavelength 587.6 nm) of the glass material of the positive lens in the second lens group

  Conditional expression (2-3) defines the Abbe number of the glass material of the positive lens in the second lens group. The optical system of the second invention of the present application can satisfactorily correct lateral chromatic aberration and axial chromatic aberration by satisfying conditional expression (2-3).

  If the corresponding value of the conditional expression (2-3) of the optical system according to the second invention of the present application exceeds the upper limit value, it will be difficult to correct lateral chromatic aberration. In order to secure the effect of the present application, it is more preferable to set the upper limit of conditional expression (2-3) to 27. In order to secure the effect of the present application, it is more preferable to set the upper limit of conditional expression (2-3) to 25.

  On the other hand, when the corresponding value of the conditional expression (2-3) of the optical system according to the second invention of the present application is less than the lower limit value, in order to prevent the transmittance of light having a short wavelength from decreasing, the image side is more than the second lens group. Therefore, it becomes impossible to use a lens made of a glass material having a large dispersion in the lens group located in the position. This makes it difficult to correct axial chromatic aberration. In order to secure the effect of the present application, it is more preferable to set the lower limit of conditional expression (2-3) to 16. In order to secure the effect of the present application, it is more preferable to set the lower limit of conditional expression (2-3) to 17.

In the optical system of the second invention of the present application, it is desirable that the first lens group has at least one positive lens that satisfies the following conditional expression (2-4).
(2-4) 80 <νd1p <110
However,
νd1p: Abbe number with respect to d-line (wavelength 587.6 nm) of the glass material of the positive lens in the first lens group

  Conditional expression (2-4) defines the Abbe number of the glass material of the positive lens in the first lens group. The optical system of the second invention of the present application can satisfactorily correct axial chromatic aberration and lateral chromatic aberration by satisfying conditional expression (2-4).

  If the corresponding value of the conditional expression (2-4) of the optical system of the second invention of the present application exceeds the upper limit value, the axial chromatic aberration and the lateral chromatic aberration are excessively corrected, which is not preferable. In order to secure the effect of the present application, it is more preferable to set the upper limit of conditional expression (2-4) to 105. In order to further secure the effect of the present application, it is more preferable to set the upper limit of conditional expression (2-4) to 100.

  On the other hand, if the corresponding value of the conditional expression (2-4) of the optical system of the second invention of the present application is below the lower limit value, it will be difficult to correct axial chromatic aberration and lateral chromatic aberration. In order to secure the effect of the present application, it is more preferable to set the lower limit of conditional expression (2-4) to 85. In order to further secure the effect of the present application, it is more preferable to set the lower limit of conditional expression (2-4) to 90.

In the optical system of the second invention of the present application, the first lens group has a plurality of positive lenses, and the positive lens arranged closest to the object among the plurality of positive lenses is defined by the following conditional expression (2- It is desirable to satisfy 5).
(2-5) 80 <νd1pf <110
However,
νd1pf: Abbe number with respect to the d-line (wavelength 587.6 nm) of the glass material of the positive lens arranged closest to the object side among the plurality of positive lenses in the first lens group

  Conditional expression (2-5) defines the Abbe number of the glass material of the positive lens disposed closest to the object side among the plurality of positive lenses in the first lens group. The optical system of the second invention of the present application can satisfactorily correct axial chromatic aberration and lateral chromatic aberration by satisfying conditional expression (2-5).

  If the corresponding value of the conditional expression (2-5) of the optical system according to the second invention of the present application exceeds the upper limit value, the axial chromatic aberration and the lateral chromatic aberration are excessively corrected, which is not preferable. In order to secure the effect of the present application, it is more preferable to set the upper limit of conditional expression (2-5) to 105. In order to secure the effect of the present application, it is more preferable to set the upper limit of conditional expression (2-5) to 100.

  On the other hand, when the corresponding value of the conditional expression (2-5) of the optical system according to the second invention of the present application is below the lower limit value, it becomes difficult to correct axial chromatic aberration and lateral chromatic aberration. In order to secure the effect of the present application, it is more preferable to set the lower limit of conditional expression (2-5) to 85. In order to further secure the effect of the present application, it is more preferable to set the lower limit of conditional expression (2-5) to 90.

In the optical system of the second invention of the present application, it is desirable that the first lens group has at least one negative lens satisfying the following conditional expression (2-6).
(2-6) 1.50 <nd1n <1.75
However,
nd1n: refractive index with respect to d-line (wavelength 587.6 nm) of the glass material of the negative lens in the first lens group

  Conditional expression (2-6) defines the refractive index of the glass material of the negative lens in the first lens group. By satisfying conditional expression (2-6), the optical system according to the second aspect of the present invention can favorably correct coma and curvature of field while reducing the weight.

  When the corresponding value of the conditional expression (2-6) of the optical system of the second invention of the present application exceeds the upper limit value, the specific gravity of the glass material of the negative lens in the first lens group increases. Accordingly, if the specific gravity of the other lenses in the first lens group is reduced in order to reduce the weight of the optical system according to the second invention of the present application, it becomes difficult to correct coma. In order to secure the effect of the present application, it is more preferable to set the upper limit of conditional expression (2-6) to 1.70. In order to secure the effect of the present application, it is more preferable to set the upper limit of conditional expression (2-6) to 1.65.

  On the other hand, if the corresponding value of the conditional expression (2-6) of the optical system according to the second invention of the present application is less than the lower limit value, it becomes difficult to correct the curvature of field. In order to secure the effect of the present application, it is more preferable to set the lower limit of conditional expression (2-6) to 1.55. In order to secure the effect of the present application, it is more preferable to set the lower limit of conditional expression (2-6) to 1.60.

  The optical system of the second invention of the present application preferably moves so that at least a part of the third lens group includes a component in a direction orthogonal to the optical axis. With this configuration, image blur due to camera shake or the like can be corrected, that is, image stabilization can be performed, and the occurrence of decentration aberrations during image stabilization can be suppressed to a level where there is no problem.

  In the optical system according to the second aspect of the present invention, the third lens group includes, in order from the object side, a 3a lens group having a positive refractive power, a 3b lens group having a negative refractive power, and a positive refraction. It is desirable that the third lens group is configured to include a component in a direction orthogonal to the optical axis. With this configuration, image blur due to camera shake or the like can be corrected, that is, image stabilization can be performed, and the occurrence of decentration aberrations during image stabilization can be suppressed to a level where there is no problem. In addition, since the diameter of the 3b lens group can be reduced, the mechanical unit for driving the 3b lens group during vibration isolation can be reduced in size.

  In the optical system of the second invention of the present application, it is desirable that the first lens group includes a cemented lens of a negative lens and a positive lens in order from the object side. With this configuration, the decentration aberration can be corrected satisfactorily. The cemented lens is more preferably arranged on the most image side in the first lens group.

In the optical system of the second invention of the present application, the first lens group is composed of a 1a lens group and a 1b lens group in order from the object side, and the 1a lens group and the 1b lens group Is the largest among the air intervals in the first lens group, and it is preferable that the following conditional expression (2-7) is satisfied.
(2-7) 0.30 <TL1a / TL1 <0.70
However,
TL1a: length along the optical axis of the first lens group TL1: length along the optical axis of the first lens group

  Conditional expression (2-7) defines the length of the first lens group with respect to the length of the first lens group. By satisfying conditional expression (2-7), the optical system of the second invention of the present application can correct coma well while reducing the weight.

  When the corresponding value of the conditional expression (2-7) of the optical system according to the second invention of the present application exceeds the upper limit value, the weight of the first lens group increases. Therefore, for example, if a glass material having a small refractive index is used for the negative lens in the first lens group in order to reduce the weight, it becomes difficult to correct curvature of field. In order to secure the effect of the present application, it is more preferable to set the upper limit of conditional expression (2-7) to 0.60. In order to secure the effect of the present application, it is more preferable to set the upper limit of conditional expression (2-7) to 0.50.

  On the other hand, if the corresponding value of the conditional expression (2-7) of the optical system according to the second invention of the present application is less than the lower limit value, it becomes difficult to correct coma. In order to secure the effect of the present application, it is more preferable to set the lower limit of conditional expression (2-7) to 0.35. In order to secure the effect of the present application, it is more preferable to set the lower limit of conditional expression (2-7) to 0.40.

  In the optical system of the second invention of the present application, it is preferable that the 1a lens group includes a positive lens, a positive lens, and a negative lens in order from the object side. With this configuration, it is possible to reduce the weight of the optical system according to the second aspect of the present invention.

  In the optical system of the second invention of the present application, it is preferable that the 1a lens group has a protective filter glass on the most object side. The protective filter glass is a lens having substantially no refractive power, and its focal length is preferably 10 times or more of the focal length of the optical system of the present application. In particular, the optical system of the second invention of the present application preferably has a negative meniscus shape in which the protective filter glass has a convex surface facing the object side. With this configuration, the ghost can be cut well.

  In the optical system according to the second aspect of the present invention, it is preferable that the first lens group includes a negative lens and a positive lens in order from the object side. With this configuration, it is possible to satisfactorily correct variations in spherical aberration when focusing on a short-distance object. In particular, in the optical system of the second invention of the present application, it is preferable that the 1b lens group includes only a cemented lens of a negative lens and a positive lens in order from the object side. With this configuration, it is possible to reduce the weight of the optical system according to the second aspect of the present invention.

In the optical system of the second invention of the present application, the first lens group is composed of a 1a lens group and a 1b lens group in order from the object side, and the 1a lens group and the 1b lens group Is the largest of the air intervals in the first lens group, and the first b lens group preferably has a positive lens that satisfies the following conditional expression (2-8).
(2-8) 70 <νd1bp <110
However,
νd1bp: Abbe number with respect to d-line (wavelength 587.6 nm) of the glass material of the positive lens in the 1b lens group

  Conditional expression (2-8) defines the Abbe number of the glass material of the positive lens in the 1b lens group. The optical system of the second invention of the present application can satisfactorily correct axial chromatic aberration and lateral chromatic aberration by satisfying conditional expression (2-8).

  If the corresponding value of the conditional expression (2-8) of the optical system according to the second invention of the present application exceeds the upper limit value, the axial chromatic aberration and the lateral chromatic aberration are excessively corrected, which is not preferable. In order to secure the effect of the present application, it is more preferable to set the upper limit of conditional expression (2-8) to 105. In order to secure the effect of the present application, it is more preferable to set the upper limit of conditional expression (2-8) to 100.

  On the other hand, if the corresponding value of conditional expression (2-8) of the optical system of the second invention of the present application is below the lower limit value, it will be difficult to correct axial chromatic aberration and lateral chromatic aberration. In order to secure the effect of the present application, it is more preferable to set the lower limit of conditional expression (2-8) to 75. In order to secure the effect of the present application, it is more preferable to set the lower limit of conditional expression (2-8) to 80.

  The optical device of the second invention of the present application is characterized by having the optical system having the above-described configuration. Thereby, an optical device having a small size and good optical performance can be realized.

The optical system manufacturing method according to the second invention of the present application includes, in order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a third lens having a positive refractive power. And an antireflection film provided on at least one of the optical surfaces of the first lens group, the second lens group, and the third lens group, and the antireflection film. Includes at least one layer formed using a wet process, the second lens group includes at least three lenses, and the optical system satisfies the following conditional expression (2-1): In this case, the second lens group is moved along the optical axis to focus from an object at infinity to an object at short distance. Thereby, an optical system having a small size and good optical performance can be manufactured.
(2-1) 0.10 <f / f12 <0.85
However,
f: Focal length of the optical system f12: Composite focal length of the first lens group and the second lens group at the time of focusing on an object at infinity

Hereinafter, an optical system according to numerical examples of the first and second inventions of the present application will be described with reference to the accompanying drawings.
(First embodiment of the first and second inventions)
FIG. 1 is a cross-sectional view showing a lens arrangement at the time of focusing on an object at infinity of the optical system according to the first embodiment of the first and second inventions of the present application.
The optical system according to this example includes, in order from the object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, and a third lens group having a positive refractive power. And G3. An aperture stop S is provided between the second lens group G2 and the third lens group G3, and a filter FL is provided between the third lens group G3 and the image plane I.

The first lens group G1 includes, in order from the object side, a first a lens group G1a having a positive refractive power and a first b lens group G1b having a positive refractive power.
The first-a lens group G1a includes, in order from the object side, a protective filter glass FLG, a biconvex positive lens L11, a biconvex positive lens L12, and a biconcave negative lens L13. The protective filter glass FLG has a negative meniscus shape with a convex surface facing the object side, and has substantially no refractive power.
The first-b lens group G1b includes, in order from the object side, a cemented lens of a negative meniscus lens L14 having a convex surface facing the object side and a positive meniscus lens L15 having a convex surface facing the object side.

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

The third lens group G3 includes, in order from the object side, a third a lens group G3a having a positive refractive power, a third b lens group G3b having a negative refractive power, and a third c lens group G3c having a positive refractive power. It is composed of
The third-a lens group G3a is composed of, in order from the object side, a biconvex positive lens L31 and a negative meniscus lens L32 having a concave surface facing the object side.
The third-b lens group G3b includes, in order from the object side, a cemented lens of a biconvex positive lens L33 and a biconcave negative lens L34, and a biconcave negative lens L35.
The third c lens group G3c includes, in order from the object side, a biconvex positive lens L36, and a cemented lens of a biconvex positive lens L37 and a biconcave negative lens L38.

  The optical system according to this example includes an object of the image side lens surface (surface number 24) of the biconcave negative lens L34 of the third lens group G3 and the biconvex positive lens L36 of the third lens group G3. An antireflection film described later is formed on the side lens surface (surface number 27).

Under the above configuration, in the optical system according to the present embodiment, the second lens group G2 is moved to the image side along the optical axis, thereby focusing from an object at infinity to a near object.
In the optical system according to the present example, the third lens group G3 in the third lens group G3 is moved as a vibration proof lens group so as to include a component in a direction orthogonal to the optical axis, thereby performing vibration proofing.

Table 1 below lists values of specifications of the optical system according to the present example.
In Table 1, f represents the focal length, and Bf represents the back focus (distance on the optical axis between the filter FL and the image plane I).
In [Surface data], the surface number is the order of the optical surfaces counted from the object side, r is the radius of curvature, d is the surface interval (the interval between the nth surface (n is an integer) and the n + 1th surface), and nd is The refractive index for d-line (wavelength 587.6 nm) and νd indicate the Abbe number for d-line (wavelength 587.6 nm), respectively. Further, the object plane indicates the object plane, the variable indicates the variable plane spacing, the stop S indicates the aperture stop S, and the image plane indicates the image plane I. The radius of curvature r = ∞ indicates a plane. Further, the description of the refractive index nd of air = 1.0000 is omitted.

In [various data], FNO is the F number, 2ω is the angle of view (unit is “°”), Y is the image height, TL is the total length of the optical system according to the present embodiment (light from the first surface to the image surface I). (Distance on the axis), dn indicates a variable distance between the nth surface and the (n + 1) th surface, respectively. Here, β represents the photographing magnification, and d0 represents the distance from the object to the first surface.
[Lens Group Data] indicates the start surface and focal length of each lens group.
In [Conditional Expression Corresponding Value], the corresponding value of each conditional expression of the optical system according to this embodiment of the first and second inventions is shown.

Here, the focal length f, the radius of curvature r, and other length units listed in Table 1 are generally “mm”. 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 embodiment of the first and second inventions
[Surface data]
Surface number r d nd νd
Object ∞ ∞

1 1200.3704 5.00 1.51680 63.88
2 1199.7897 1.00
3 208.5821 17.50 1.43385 95.25
4 -1176.6338 45.00
5 180.4147 18.00 1.43385 95.25
6 -380.1711 3.00
7 -348.9527 6.00 1.61266 44.46
8 384.9936 90.00
9 67.5463 4.00 1.79500 45.31
10 46.6351 15.00 1.49782 82.57
11 1089.9704 Variable

12 -1616.0869 2.50 1.77250 49.62
13 118.0496 3.35
14 -285.3999 3.50 1.84666 23.80
15 -87.3702 2.40 1.51823 58.82
16 63.6357 Variable

17 (Aperture S) ∞ 2.00

18 84.6009 8.00 1.48749 70.31
19 -63.3175 0.60
20 -66.2548 1.90 1.84666 23.80
21 -116.1778 5.00
22 433.7902 3.50 1.84666 23.80
23 -123.0826 1.90 1.59319 67.90
24 51.3275 3.60
25 -293.4310 1.90 1.75500 52.34
26 110.9976 4.00
27 130.2260 3.50 1.77250 49.62
28 -326.0207 0.10
29 67.6197 4.50 1.64000 60.20
30 -391.1361 1.90 1.84666 23.80
31 276.0025 9.00

32 ∞ 2.00 1.51680 63.88
33 ∞ Bf

Image plane ∞

[Various data]
f 392.00
FNO 2.88
2ω 6.27
Y 21.60
TL 396.95
Bf 71.551

When focusing on an object at infinity When focusing on a near object f or β 392.003 -0.173
d0 ∞ 2201.931
d11 19.530 34.930
d16 36.219 20.820
Bf 71.551 71.575

[Lens group data]
Group start surface f
1 1 179.9884
2 12 -67.9431
3 18 163.6612

[Conditional expression values]
(First invention)
(1-1) f / f12 = 0.38
(1-2) νd1p = 95.25 (L11), 95.25 (L12), 82.57 (L15)
(1-3) νd1pf = 95.25
(1-4) nd1n = 1.61
(1-5) TL1a / TL1 = 0.47
(1-6) νd1bp = 82.57
(1-7) νd2p = 23.80

(Second invention)
(2-1) f / f12 = 0.38
(2-2) nd2n = 1.52
(2-3) νd2p = 23.80
(2-4) νd1p = 95.25 (L11), 95.25 (L12), 82.57 (L15)
(2-5) νd1pf = 95.25
(2-6) nd1n = 1.61
(2-7) TL1a / TL1 = 0.47
(2-8) νd1bp = 82.57

FIGS. 2A and 2B are graphs showing various aberrations when the optical system according to the first embodiment of the first and second inventions of the present application is focused on an object at infinity and focused on a short distance object, respectively. It is.
In each aberration diagram, FNO represents an F number, and Y represents an image height. d indicates the aberration at the d-line (wavelength 587.6 nm), and g indicates the aberration at the g-line (wavelength 435.8 nm). In the astigmatism diagram, the solid line indicates the sagittal image plane, and the broken line indicates the meridional image plane. The coma aberration diagram shows coma aberration at each image height Y. Note that the same reference numerals as in this embodiment are used in the aberration diagrams of each embodiment described later.
From each aberration diagram, it can be seen that the optical system according to the present example corrects various aberrations well and has excellent imaging performance.

Here, the cause of the occurrence of ghost and flare in the optical system according to the present embodiment will be described.
FIG. 15 is a diagram illustrating an example of a state in which light rays incident on the optical system according to the present embodiment are reflected by the first reflecting surface and the second reflecting surface to form ghosts and flares on the image plane I. is there.
In FIG. 15, when a light beam BM from the object side enters the optical system as shown, a part of the light beam BM is an object side lens surface (surface number 27, 27) of the biconvex positive lens L36 in the third lens group G3. It is reflected by the first reflecting surface where the reflected light that becomes ghost or flare is generated, and further the image side lens surface (surface number 24, ghost or flare) of the biconcave negative lens L34 in the third lens group G3. 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 is a concave lens surface when viewed from the image surface side, and the second reflecting surface is a concave lens surface when viewed from the image surface side.
Therefore, the optical system according to the present embodiment suppresses the generation of reflected light by effectively forming ghosts and flares by forming an antireflection film corresponding to light rays having a wide incident angle in a wide wavelength range on the lens surface. Can be reduced.

(Second embodiment of the first and second inventions)
FIG. 3 is a sectional view showing the lens arrangement at the time of focusing on an object at infinity of the optical system according to the second embodiment of the first and second inventions of the present application.
The optical system according to this example includes, in order from the object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, and a third lens group having a positive refractive power. And G3. An aperture stop S is provided between the second lens group G2 and the third lens group G3, and a filter FL is provided between the third lens group G3 and the image plane I.

The first lens group G1 includes, in order from the object side, a first a lens group G1a having a positive refractive power and a first b lens group G1b having a positive refractive power.
The first-a lens group G1a includes, in order from the object side, a protective filter glass FLG, a biconvex positive lens L11, a biconvex positive lens L12, and a biconcave negative lens L13. The protective filter glass FLG has a negative meniscus shape with a convex surface facing the object side, and has substantially no refractive power.
The first-b lens group G1b includes, in order from the object side, a cemented lens of a negative meniscus lens L14 having a convex surface facing the object side and a positive meniscus lens L15 having a convex surface facing the object side.

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

The third lens group G3 includes, in order from the object side, a third a lens group G3a having a positive refractive power, a third b lens group G3b having a negative refractive power, and a third c lens group G3c having a positive refractive power. It is composed of
The third-a lens group G3a is composed of, in order from the object side, a biconvex positive lens L31 and a negative meniscus lens L32 having a concave surface facing the object side.
The third-b lens group G3b includes, in order from the object side, a cemented lens of a biconvex positive lens L33 and a biconcave negative lens L34, and a biconcave negative lens L35.
The third c lens group G3c includes, in order from the object side, a biconvex positive lens L36, and a cemented lens of a biconvex positive lens L37 and a biconcave negative lens L38.

  In the optical system according to the present example, an antireflection film described later is formed on the image surface side lens surface (surface number 24) of the biconcave negative lens L34 of the third lens group G3.

Under the above configuration, in the optical system according to the present embodiment, the second lens group G2 is moved to the image side along the optical axis, thereby focusing from an object at infinity to a near object.
In the optical system according to the present example, the third lens group G3 in the third lens group G3 is moved as a vibration proof lens group so as to include a component in a direction orthogonal to the optical axis, thereby performing vibration proofing.
Table 2 below lists values of specifications of the optical system according to the present example.

(Table 2) Second embodiment of the first and second inventions
[Surface data]
Surface number r d nd νd
Object ∞ ∞

1 1200.3704 5.00 1.51680 63.88
2 1199.7897 1.00
3 205.7091 17.50 1.43385 95.25
4 -1134.8251 45.00
5 173.6014 18.00 1.43385 95.25
6 -417.4854 3.07
7 -374.6983 6.00 1.61266 44.46
8 347.6771 90.00
9 66.1559 4.00 1.79500 45.31
10 45.7808 15.00 1.49782 82.57
11 874.9561 Variable

12 -2545.8867 2.50 1.77250 49.62
13 114.9779 3.35
14 -271.4306 3.50 1.84666 23.80
15 -87.3926 2.40 1.51823 58.82
16 63.5469 Variable

17 (Aperture S) ∞ 2.00

18 87.7161 7.60 1.48749 70.31
19 -64.5076 1.20
20 -66.7841 1.90 1.84666 23.80
21 -116.0392 5.00
22 325.4187 3.50 1.84666 23.80
23 -134.7294 1.90 1.59319 67.90
24 52.9625 3.60
25 -331.8219 1.90 1.75500 52.34
26 98.9972 4.00
27 117.6253 3.50 1.77250 49.62
28 -402.3365 0.10
29 67.6197 4.50 1.64000 60.20
30 -391.1361 1.90 1.84666 23.80
31 264.8450 9.00

32 ∞ 2.00 1.51680 63.88
33 ∞ Bf

Image plane ∞

[Various data]
f 391.99
FNO 2.88
2ω 6.29
Y 21.63
TL 397.00
Bf 71.300

When focusing on an object at infinity When focusing on a near object f or β 391.991 -0.174
d0 ∞ 2203.000
d11 18.344 33.670
d16 37.438 22.112
Bf 71.300 71.300

[Lens group data]
Group start surface f
1 1 179.8867
2 12 -67.1696
3 18 160.1914

[Conditional expression values]
(First invention)
(1-1) f / f12 = 0.36
(1-2) νd1p = 95.25 (L11), 95.25 (L12), 82.57 (L15)
(1-3) νd1pf = 95.25
(1-4) nd1n = 1.61
(1-5) TL1a / TL1 = 0.47
(1-6) νd1bp = 82.57
(1-7) νd2p = 23.80

(Second invention)
(2-1) f / f12 = 0.36
(2-2) nd2n = 1.52
(2-3) νd2p = 23.80
(2-4) νd1p = 95.25 (L11), 95.25 (L12), 82.57 (L15)
(2-5) νd1pf = 95.25
(2-6) nd1n = 1.61
(2-7) TL1a / TL1 = 0.47
(2-8) νd1bp = 82.57

FIGS. 4A and 4B are diagrams showing various aberrations when the optical system according to the second embodiment of the first and second inventions of the present application is focused on an object at infinity and focused on a short distance object, respectively. It is.
From each aberration diagram, it can be seen that the optical system according to the present example corrects various aberrations well and has excellent imaging performance.

(Third embodiment of the first and second inventions)
FIG. 5 is a cross-sectional view showing the lens arrangement at the time of focusing on an object at infinity of the optical system according to the third embodiment of the first and second inventions of the present application.
The optical system according to this example includes, in order from the object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, and a third lens group having a positive refractive power. And G3. An aperture stop S is provided between the second lens group G2 and the third lens group G3, and a filter FL is provided between the third lens group G3 and the image plane I.

The first lens group G1 includes, in order from the object side, a first a lens group G1a having a positive refractive power and a first b lens group G1b having a positive refractive power.
The first-a lens group G1a includes, in order from the object side, a protective filter glass FLG, a biconvex positive lens L11, a biconvex positive lens L12, and a biconcave negative lens L13. The protective filter glass FLG has a negative meniscus shape with a convex surface facing the object side, and has substantially no refractive power.
The first-b lens group G1b includes, in order from the object side, a cemented lens of a negative meniscus lens L14 having a convex surface facing the object side and a positive meniscus lens L15 having a convex surface facing the object side.

  The second lens group G2 includes, in order from the object side, a negative meniscus lens L21 having a convex surface directed toward the object side, and a cemented negative lens composed of a positive meniscus lens L22 having a concave surface directed toward the object side and a biconcave negative lens L23. Consists of.

The third lens group G3 includes, in order from the object side, a third a lens group G3a having a positive refractive power, a third b lens group G3b having a negative refractive power, and a third c lens group G3c having a positive refractive power. It is composed of
The third-a lens group G3a is composed of, in order from the object side, a biconvex positive lens L31 and a negative meniscus lens L32 having a concave surface facing the object side.
The third-b lens group G3b includes, in order from the object side, a cemented lens of a biconvex positive lens L33 and a biconcave negative lens L34, and a biconcave negative lens L35.
The third c lens group G3c includes, in order from the object side, a biconvex positive lens L36, and a cemented lens of a biconvex positive lens L37 and a biconcave negative lens L38.

  In the optical system according to the present example, an antireflection film described later is formed on the image surface side lens surface (surface number 11) of the positive meniscus lens L15 of the first lens group G1.

Under the above configuration, in the optical system according to the present embodiment, the second lens group G2 is moved to the image side along the optical axis, thereby focusing from an object at infinity to a near object.
In the optical system according to the present example, the third lens group G3 in the third lens group G3 is moved as a vibration proof lens group so as to include a component in a direction orthogonal to the optical axis, thereby performing vibration proofing.
Table 3 below lists values of specifications of the optical system according to the present example.

(Table 3) Third embodiment of the first and second inventions
[Surface data]
Surface number r d nd νd
Object ∞ ∞

1 1200.3704 5.00 1.51680 63.88
2 1199.7897 1.00
3 207.0795 17.50 1.43384 95.26
4 -1127.5309 44.90
5 175.9698 18.00 1.43384 95.26
6 -397.2708 3.07
7 -360.2396 6.00 1.61266 44.46
8 353.1837 90.00
9 66.4844 4.00 1.79500 45.32
10 45.9182 15.00 1.49782 82.54
11 1114.1067 Variable

12 2992.5492 2.50 1.75500 52.34
13 118.0399 3.35
14 -241.6942 3.50 1.84668 23.83
15 -86.4136 2.40 1.53996 59.52
16 64.2643 Variable

17 (Aperture S) ∞ 1.50

18 90.0336 7.60 1.48749 70.43
19 -63.8039 1.20
20 -65.9768 1.90 1.84668 23.83
21 -114.8763 5.00
22 300.3587 3.50 1.84668 23.83
23 -128.0558 1.90 1.59319 67.94
24 53.9004 3.10
25 -347.5421 1.90 1.75500 52.33
26 94.5337 4.19
27 118.3533 3.50 1.77250 49.68
28 -384.3825 0.10
29 67.4622 4.50 1.64000 60.14
30 -340.4206 1.90 1.84668 23.83
31 246.6417 6.50

32 ∞ 1.50 1.51680 63.88
33 ∞ Bf

Image plane ∞

[Various data]
f 392.00
FNO 2.89
2ω 6.28
Y 21.63
TL 396.91
Bf 74.220

When focusing on an object at infinity When focusing on a near object f or β 392.000 -0.173
d0 ∞ 2203.010
d11 18.503 33.773
d16 38.179 22.909
Bf 74.220 73.906

[Lens group data]
Group start surface f
1 1 179.1160
2 12 -67.4099
3 18 162.8784

[Conditional expression values]
(First invention)
(1-1) f / f12 = 0.37
(1-2) νd1p = 95.26 (L11), 95.26 (L12), 82.54 (L15)
(1-3) νd1pf = 95.26
(1-4) nd1n = 1.61
(1-5) TL1a / TL1 = 0.47
(1-6) νd1bp = 82.54
(1-7) νd2p = 23.83

(Second invention)
(2-1) f / f12 = 0.37
(2-2) nd2n = 1.54
(2-3) νd2p = 23.83
(2-4) νd1p = 95.26 (L11), 95.26 (L12), 82.54 (L15)
(2-5) νd1pf = 95.26
(2-6) nd1n = 1.61
(2-7) TL1a / TL1 = 0.47
(2-8) νd1bp = 82.54

FIGS. 6A and 6B are graphs showing various aberrations when the optical system according to the third embodiment of the first and second inventions of the present application is focused on an object at infinity and focused on a short distance object, respectively. It is.
From each aberration diagram, it can be seen that the optical system according to the present example corrects various aberrations well and has excellent imaging performance.

(Fourth embodiment of the first and second inventions)
FIG. 7 is a sectional view showing the lens arrangement at the time of focusing on an object at infinity of the optical system according to the fourth example of the first and second inventions of the present application.
The optical system according to this example includes, in order from the object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, and a third lens group having a positive refractive power. And G3. An aperture stop S is provided between the second lens group G2 and the third lens group G3, and a filter FL is provided between the third lens group G3 and the image plane I.

The first lens group G1 includes, in order from the object side, a first a lens group G1a having a positive refractive power and a first b lens group G1b having a positive refractive power.
The first-a lens group G1a includes, in order from the object side, a protective filter glass FLG, a biconvex positive lens L11, a biconvex positive lens L12, and a biconcave negative lens L13. The protective filter glass FLG has a negative meniscus shape with a convex surface facing the object side, and has substantially no refractive power.
The first-b lens group G1b includes, in order from the object side, a cemented lens of a negative meniscus lens L14 having a convex surface facing the object side and a positive meniscus lens L15 having a convex surface facing the object side.

  The second lens group G2 includes, in order from the object side, a negative meniscus lens L21 having a convex surface directed toward the object side, and a cemented negative lens composed of a positive meniscus lens L22 having a concave surface directed toward the object side and a biconcave negative lens L23. Consists of.

The third lens group G3 includes, in order from the object side, a third a lens group G3a having a positive refractive power, a third b lens group G3b having a negative refractive power, and a third c lens group G3c having a positive refractive power. It is composed of
The third-a lens group G3a is composed of, in order from the object side, a biconvex positive lens L31 and a negative meniscus lens L32 having a concave surface facing the object side.
The third-b lens group G3b includes, in order from the object side, a cemented lens of a biconvex positive lens L33 and a biconcave negative lens L34, and a biconcave negative lens L35.
The third c lens group G3c includes, in order from the object side, a biconvex positive lens L36, and a cemented lens of a biconvex positive lens L37 and a biconcave negative lens L38.

  In the optical system according to the present example, an antireflection film described later is formed on the image surface side lens surface (surface number 13) of the negative meniscus lens L21 of the second lens group G2.

Under the above configuration, in the optical system according to the present embodiment, the second lens group G2 is moved to the image side along the optical axis, thereby focusing from an object at infinity to a near object.
In the optical system according to the present example, the third lens group G3 in the third lens group G3 is moved as a vibration proof lens group so as to include a component in a direction orthogonal to the optical axis, thereby performing vibration proofing.
Table 4 below lists values of specifications of the optical system according to the present example.

(Table 4) Fourth embodiment of the first and second inventions
[Surface data]
Surface number r d nd νd
Object ∞ ∞

1 1200.3704 5.00 1.51680 63.88
2 1199.7897 1.00
3 210.9074 17.50 1.43384 95.26
4 -1135.2477 44.90
5 173.4175 18.00 1.43384 95.26
6 -413.8140 3.07
7 -375.4223 6.00 1.61266 44.46
8 358.4435 90.00
9 66.9574 4.00 1.79500 45.32
10 46.1708 15.00 1.49782 82.54
11 1030.2823 Variable

12 10236.2589 2.50 1.77250 49.68
13 110.7581 3.35
14 -289.4383 3.50 1.84668 23.83
15 -96.1712 2.40 1.51680 63.88
16 65.0724 Variable

17 (Aperture S) ∞ 1.50

18 86.8540 7.60 1.48749 70.43
19 -62.9408 1.20
20 -65.5511 1.90 1.84668 23.83
21 -118.4244 5.00
22 300.3217 3.50 1.84668 23.83
23 -128.4546 1.90 1.59319 67.94
24 53.9974 3.10
25 -348.7023 1.90 1.75500 52.33
26 93.3844 4.19
27 119.2828 3.50 1.77250 49.68
28 -375.3153 0.10
29 68.1234 4.50 1.64000 60.14
30 -426.6037 1.90 1.84668 23.83
31 243.3294 6.50

32 ∞ 1.50 1.51680 63.88
33 ∞ Bf

Image plane ∞

[Various data]
f 392.00
FNO 2.89
2ω 6.28
Y 21.63
TL 396.91
Bf 74.220

When focusing on an object at infinity When focusing on a near object f or β 392.000 -0.174
d0 ∞ 2203.010
d11 18.503 33.773
d16 38.179 22.909
Bf 74.220 74.374

[Lens group data]
Group start surface f
1 1 179.5793
2 12 -68.1638
3 18 164.8495

[Conditional expression values]
(First invention)
(1-1) f / f12 = 0.37
(1-2) νd1p = 95.26 (L11), 95.26 (L12), 82.54 (L15)
(1-3) νd1pf = 95.26
(1-4) nd1n = 1.61
(1-5) TL1a / TL1 = 0.47
(1-6) νd1bp = 82.54
(1-7) νd2p = 23.83

(Second invention)
(2-1) f / f12 = 0.37
(2-2) nd2n = 1.52
(2-3) νd2p = 23.83
(2-4) νd1p = 95.26 (L11), 95.26 (L12), 82.54 (L15)
(2-5) νd1pf = 95.26
(2-6) nd1n = 1.61
(2-7) TL1a / TL1 = 0.47
(2-8) νd1bp = 82.54

FIGS. 8A and 8B are diagrams showing various aberrations when the optical system according to the fourth example of the first and second inventions of the present application is focused on an object at infinity and focused on a short distance object, respectively. It is.
From each aberration diagram, it can be seen that the optical system according to the present example corrects various aberrations well and has excellent imaging performance.

(Fifth embodiment of the first and second inventions)
FIG. 9 is a sectional view showing the lens arrangement at the time of focusing on an object at infinity of the optical system according to the fifth embodiment of the first and second inventions of the present application.
The optical system according to this example includes, in order from the object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, and a third lens group having a positive refractive power. And G3. An aperture stop S is provided between the second lens group G2 and the third lens group G3, and a filter FL is provided between the third lens group G3 and the image plane I.

The first lens group G1 includes, in order from the object side, a first a lens group G1a having a positive refractive power and a first b lens group G1b having a positive refractive power.
The first-a lens group G1a includes, in order from the object side, a protective filter glass FLG, a biconvex positive lens L11, a biconvex positive lens L12, and a biconcave negative lens L13. The protective filter glass FLG has a negative meniscus shape with a convex surface facing the object side, and has substantially no refractive power.
The first-b lens group G1b includes, in order from the object side, a cemented lens of a negative meniscus lens L14 having a convex surface facing the object side and a positive meniscus lens L15 having a convex surface facing the object side.

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

The third lens group G3 includes, in order from the object side, a third a lens group G3a having a positive refractive power, a third b lens group G3b having a negative refractive power, and a third c lens group G3c having a positive refractive power. It is composed of
The third-a lens group G3a is composed of, in order from the object side, a biconvex positive lens L31 and a negative meniscus lens L32 having a concave surface facing the object side.
The third-b lens group G3b includes, in order from the object side, a cemented lens of a biconvex positive lens L33 and a biconcave negative lens L34, and a biconcave negative lens L35.
The third c lens group G3c includes, in order from the object side, a biconvex positive lens L36, and a cemented lens of a biconvex positive lens L37 and a biconcave negative lens L38.

  The optical system according to this example includes an object of the image side lens surface (surface number 6) of the biconvex positive lens L12 of the first lens group G1 and the biconcave negative lens L13 of the first lens group G1. An antireflection film described later is formed on the side lens surface (surface number 7).

Under the above configuration, in the optical system according to the present embodiment, the second lens group G2 is moved to the image side along the optical axis, thereby focusing from an object at infinity to a near object.
In the optical system according to the present example, the third lens group G3 in the third lens group G3 is moved as a vibration proof lens group so as to include a component in a direction orthogonal to the optical axis, thereby performing vibration proofing.
Table 5 below lists values of specifications of the optical system according to the present example.

(Table 5) Fifth embodiment of the first and second inventions
[Surface data]
Surface number r d nd νd
Object ∞ ∞

1 1200.3704 5.00 1.51680 63.88
2 1199.7897 1.00
3 237.4785 15.50 1.43385 95.25
4 -1507.8850 45.00
5 198.3323 19.00 1.43385 95.25
6 -342.1796 3.00
7 -327.8324 6.00 1.61266 44.46
8 772.9939 93.00
9 70.7391 5.40 1.79952 42.09
10 47.9832 16.00 1.49782 82.57
11 1681.9346 Variable

12 -2709.1390 3.00 1.77250 49.62
13 136.3998 3.50
14 -487.1729 4.00 1.84666 23.80
15 -108.0510 2.50 1.51742 52.20
16 59.4298 Variable

17 (Aperture S) ∞ 2.00

18 228.1074 5.25 1.59319 67.90
19 -85.4981 0.60
20 -124.4314 1.90 2.00069 25.46
21 -295.5719 3.85
22 294.4912 3.30 1.84666 23.80
23 -171.7558 1.90 1.59319 67.90
24 54.4393 4.05
25 -281.8305 1.90 1.69680 55.52
26 152.6451 2.94
27 104.2002 3.00 1.77250 49.62
28 -1538.2155 0.10
29 71.9218 4.80 1.57957 53.74
30 -155.3605 1.90 1.84666 23.80
31 1092.5548 11.00

32 ∞ 2.00 1.51680 63.88
33 ∞ Bf

Image plane ∞

[Various data]
f 391.99
FNO 2.88
2ω 6.27
Y 21.60
TL 399.38
Bf 70.081

When focusing on an object at infinity When focusing on a near object f or β 391.990 -0.172
d0 ∞ 2203.007
d11 16.500 31.900
d16 40.401 25.001
Bf 70.081 70.033

[Lens group data]
Group start surface f
1 1 177.7760
2 12 -73.1720
3 18 187.9179

[Conditional expression values]
(First invention)
(1-1) f / f12 = 0.51
(1-2) νd1p = 95.25 (L11), 95.25 (L12), 82.57 (L15)
(1-3) νd1pf = 95.25
(1-4) nd1n = 1.61
(1-5) TL1a / TL1 = 0.45
(1-6) νd1bp = 82.57
(1-7) νd2p = 23.80

(Second invention)
(2-1) f / f12 = 0.51
(2-2) nd2n = 1.52
(2-3) νd2p = 23.80
(2-4) νd1p = 95.25 (L11), 95.25 (L12), 82.57 (L15)
(2-5) νd1pf = 95.25
(2-6) nd1n = 1.61
(2-7) TL1a / TL1 = 0.45
(2-8) νd1bp = 82.57

FIGS. 10A and 10B are diagrams showing various aberrations when the optical system according to the fifth example of the first and second inventions of the present application is focused on an object at infinity and focused on a short distance object, respectively. It is.
From each aberration diagram, it can be seen that the optical system according to the present example corrects various aberrations well and has excellent imaging performance.

(Sixth embodiment of the first and second inventions)
FIG. 11 is a sectional view showing the lens arrangement at the time of focusing on an object at infinity of the optical system according to the sixth example of the first and second inventions of the present application.
The optical system according to this example includes, in order from the object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, and a third lens group having a positive refractive power. And G3. An aperture stop S is provided between the second lens group G2 and the third lens group G3, and a filter FL is provided between the third lens group G3 and the image plane I.

The first lens group G1 includes, in order from the object side, a first a lens group G1a having a positive refractive power and a first b lens group G1b having a positive refractive power.
The first-a lens group G1a includes, in order from the object side, a protective filter glass FLG, a biconvex positive lens L11, a biconvex positive lens L12, and a biconcave negative lens L13. The protective filter glass FLG has a negative meniscus shape with a convex surface facing the object side, and has substantially no refractive power.
The first-b lens group G1b includes, in order from the object side, a cemented lens of a negative meniscus lens L14 having a convex surface facing the object side and a positive meniscus lens L15 having a convex surface facing the object side.

  The second lens group G2 includes, in order from the object side, a negative meniscus lens L21 having a convex surface facing the object side, a positive meniscus lens L22 having a concave surface facing the object side, and a negative meniscus lens L23 having a concave surface facing the object side. It consists of a cemented negative lens.

The third lens group G3 includes, in order from the object side, a third a lens group G3a having a positive refractive power, a third b lens group G3b having a negative refractive power, and a third c lens group G3c having a positive refractive power. It is composed of
The third-a lens group G3a is composed of, in order from the object side, a biconvex positive lens L31 and a negative meniscus lens L32 having a concave surface facing the object side.
The third lens group G3b includes, in order from the object side, a cemented lens of a positive meniscus lens L33 having a concave surface directed toward the object side and a biconcave negative lens L34, and a negative meniscus lens L35 having a convex surface directed toward the object side. Become.
The third c lens group G3c includes, in order from the object side, a biconvex positive lens L36, and a cemented lens of a biconvex positive lens L37 and a biconcave negative lens L38.

  In the optical system according to the present example, an antireflection film described later is formed on the object side lens surface (surface number 14) of the positive meniscus lens L22 of the second lens group G2.

Under the above configuration, in the optical system according to the present embodiment, the second lens group G2 is moved to the image side along the optical axis, thereby focusing from an object at infinity to a near object.
In the optical system according to the present example, the third lens group G3 in the third lens group G3 is moved as a vibration proof lens group so as to include a component in a direction orthogonal to the optical axis, thereby performing vibration proofing.
Table 6 below lists values of specifications of the optical system according to the present example.

(Table 6) Sixth embodiment of the first and second inventions
[Surface data]
Surface number r d nd νd
Object ∞ ∞

1 1200.3704 5.00 1.51680 63.88
2 1199.7897 1.50
3 217.9147 15.50 1.43385 95.25
4 -2272.2650 45.00
5 191.4672 18.50 1.43385 95.25
6 -388.7337 3.24
7 -366.9736 6.00 1.61266 44.46
8 692.0557 90.02
9 65.4296 5.20 1.80610 40.97
10 45.0727 15.00 1.49782 82.57
11 760.0090 Variable

12 2386.5723 2.50 1.81600 46.59
13 64.7944 6.50
14 -159.3202 4.50 1.80809 22.74
15 -67.3666 2.00 1.61772 49.81
16 -4529.1486 Variable

17 (Aperture S) ∞ 2.00

18 128.3829 8.00 1.59319 67.90
19 -58.5025 0.60
20 -58.7397 1.90 1.79504 28.69
21 -122.7539 5.79
22 -216.6393 3.30 1.84666 23.80
23 -61.9303 1.90 1.59319 67.90
24 59.0225 3.00
25 728.9238 1.90 1.81600 46.59
26 93.0674 4.00
27 141.2086 3.00 1.77250 49.62
28 -1505.6719 0.15
29 69.4894 4.80 1.74320 49.26
30 -136.7089 1.90 1.84666 23.80
31 672.4408 9.00

32 ∞ 2.00 1.51680 63.88
33 ∞ Bf

Image plane ∞

[Various data]
f 392.00
FNO 2.88
2ω 6.27
Y 21.60
TL 400.00
Bf 71.300

When focusing on an object at infinity When focusing on a near object f or β 392.000 -0.173
d0 ∞ 2200.000
d11 17.463 31.763
d16 37.536 23.236
Bf 71.300 71.260

[Lens group data]
Group start surface f
1 1 172.5113
2 12 -69.4949
3 18 175.8293

[Conditional expression values]
(First invention)
(1-1) f / f12 = 0.46
(1-2) νd1p = 95.25 (L11), 95.25 (L12), 82.57 (L15)
(1-3) νd1pf = 95.25
(1-4) nd1n = 1.61
(1-5) TL1a / TL1 = 0.46
(1-6) νd1bp = 82.57
(1-7) νd2p = 22.74

(Second invention)
(2-1) f / f12 = 0.46
(2-2) nd2n = 1.62
(2-3) νd2p = 22.74
(2-4) νd1p = 95.25 (L11), 95.25 (L12), 82.57 (L15)
(2-5) νd1pf = 95.25
(2-6) nd1n = 1.61
(2-7) TL1a / TL1 = 0.46
(2-8) νd1bp = 82.57

FIGS. 12A and 12B are graphs showing various aberrations when the optical system according to the sixth example of the first and second inventions of the present application is focused on an object at infinity and focused on a short distance object, respectively. It is.
From each aberration diagram, it can be seen that the optical system according to the present example corrects various aberrations well and has excellent imaging performance.

  Here, an antireflection film (also referred to as a multilayer broadband antireflection film) used in the optical system according to the embodiments of the first and second inventions of the present application will be described. FIG. 16 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 further formed on the first layer 101a. Further, a third layer 101c made of aluminum oxide deposited by a vacuum deposition method is formed on the second layer 101b, and titanium oxide and zirconium oxide deposited by a vacuum deposition method are formed 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. A sixth layer 101f made of the mixture is formed.

  Then, a seventh layer 101g made of a mixture of magnesium fluoride and silica is formed on the sixth layer 101f formed in this way by a wet process, and the antireflection film 101 of this embodiment is formed. 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 the prepared 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 as described above will be described with reference to spectral characteristics shown in FIG.

  The optical member (lens) having the antireflection film according to the first and second embodiments of the present application is formed under the conditions shown in Table 7 below. Here, Table 7 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 7, aluminum oxide is represented by Al2O3, a mixture of titanium oxide and zirconium oxide is represented by ZrO2 + TiO2, and a mixture of magnesium fluoride and silica is represented by MgF2 + SiO2.

(Table 7)
Substance Refractive index Optical film thickness Optical film thickness Optical film thickness
Medium air 1
7th layer MgF2 + SiO2 1.26 0.268λ 0.271λ 0.269λ
6th layer ZrO2 + TiO2 2.12 0.057λ 0.054λ 0.059λ
5th layer Al2O3 1.65 0.171λ 0.178λ 0.162λ
4th layer ZrO2 + TiO2 2.12 0.127λ 0.13λ 0.158λ
3rd layer Al2O3 1.65 0.122λ 0.107λ 0.08λ
Second layer ZrO2 + TiO2 2.12 0.059λ 0.075λ 0.105λ
1st layer Al2O3 1.65 0.257λ 0.03λ 0.03λ
Refractive index of substrate 1.62 1.74 1.85

  FIG. 17 shows the spectral characteristics when light rays are perpendicularly incident on an optical member in which the reference wavelength λ is 550 nm in Table 7 and the optical film thickness of each layer of the antireflection film 101 is designed.

  From FIG. 17, 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 d line (wavelength 587.6 nm) in Table 7, 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 7, the optical film thickness of each layer with respect to the reference wavelength λ is designed under the conditions shown in Table 8 below. In this modification, the above-described sol-gel method is used for forming the fifth layer.

(Table 8)
Material Refractive index Optical film thickness Optical film thickness Medium Air 1
5th layer MgF2 + SiO2 1.26 0.275λ 0.269λ
4th layer ZrO2 + TiO2 2.12 0.045λ 0.043λ
3rd layer Al2O3 1.65 0.212λ 0.217λ
Second layer ZrO2 + TiO2 2.12 0.077λ 0.066λ
1st layer Al2O3 1.65 0.288λ 0.290λ
Refractive index of substrate 1.46 1.52

  FIG. 18 shows spectral characteristics when light rays are vertically incident on an optical member having an antireflection film in which the optical film thickness is designed with the refractive index of the substrate being 1.52 and the reference wavelength λ being 550 nm in Table 8. Yes. From FIG. 18, it can be seen that the antireflection film of this modification has a reflectance of 0.2% or less over the entire wavelength range of 420 nm to 720 nm. In Table 8, even an optical member having an antireflection film whose optical film thickness is designed with the reference wavelength λ as the d-line (wavelength 587.6 nm) hardly affects the spectral characteristics, and the spectral characteristics shown in FIG. Has almost the same characteristics.

  FIG. 19 shows the spectral characteristics when the incident angles of the light rays to the optical member having the spectral characteristics shown in FIG. 18 are 30, 45, and 60 degrees, respectively. 18 and 19 do not show the spectral characteristics of the optical member having the antireflection film with the refractive index of 1.46 shown in Table 8, 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. 20 shows an example of an antireflection film formed only by a dry process such as a conventional vacuum deposition method. FIG. 21 shows 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 9 below with a refractive index of 1.52 of the same substrate as in Table 8. FIG. 21 shows spectral characteristics when the incident angles of light rays to the optical member having the spectral characteristics shown in FIG. 20 are 30, 45, and 60 degrees, respectively.

(Table 9)
Material Refractive index Optical film thickness Medium Air 1
7th layer MgF2 1.39 0.243λ
6th layer ZrO2 + TiO2 2.12 0.119λ
5th layer Al2O3 1.65 0.057λ
4th layer ZrO2 + TiO2 2.12 0.220λ
3rd layer Al2O3 1.65 0.064λ
Second layer ZrO2 + TiO2 2.12 0.057λ
1st layer Al2O3 1.65 0.193λ
Refractive index of substrate 1.52

  When the spectral characteristics of the optical member having the antireflection film according to the first and second embodiments of the present invention shown in FIGS. 17 to 19 are compared with the spectral characteristics of the conventional example shown in FIGS. It can be seen that the antireflection film according to the embodiment has a lower reflectance at any incident angle and has a lower reflectance in a wider band.

  Next, an example in which the antireflection film shown in Table 7 and Table 8 is applied to the first to sixth embodiments of the first and second inventions of the present application will be described.

In the optical system of the first embodiment of the first and second inventions of the present application,
The refractive index of the biconcave negative lens L34 of the third lens group G3 is
As shown in Table 1,
nd = 1.59319,
The refractive index of the biconvex positive lens L36 of the third lens group G3 is
Since nd = 1.77250,
An antireflection film 101 (see Table 8) having a refractive index of the substrate of 1.62 is used on the image surface side lens surface of the biconcave negative lens L34.
On the object side lens surface of the biconvex positive lens L36,
By using an antireflection film (see Table 8) corresponding to a refractive index of the substrate of 1.74, reflected light from each lens surface can be reduced, and ghost and flare can be reduced.

In the optical system of the second embodiment of the first and second inventions of the present application,
The refractive index of the biconcave negative lens L34 of the third lens group G3 is
As shown in Table 2,
Since nd = 1.59319,
By using an antireflection film 101 (see Table 8) corresponding to a refractive index of the substrate of 1.62 on the image surface side lens surface of the biconcave negative lens L34, reflected light from each lens surface can be reduced, Ghost and flare can be reduced.

In the optical system of the third embodiment of the first and second inventions of the present application,
The refractive index of the positive meniscus lens L15 of the first lens group G1 is
As shown in Table 3,
Since nd = 1.49782,
By using an antireflection film 101 (see Table 7) whose refractive index of the substrate corresponds to 1.52 on the image surface side lens surface of the positive meniscus lens L15, reflected light from each lens surface can be reduced, and ghost and flare Can be reduced.

In the optical system of the fourth embodiment of the first and second inventions of the present application,
The refractive index of the negative meniscus lens L21 of the second lens group G2 is
As shown in Table 4,
Since nd = 1.77250,
By using an antireflection film 101 (see Table 8) whose refractive index of the substrate corresponds to 1.74 on the image surface side lens surface of the negative meniscus lens L21, reflected light from each lens surface can be reduced, and ghost and flare. Can be reduced.

In the optical system of the fifth embodiment of the first and second inventions of the present application,
The refractive index of the biconvex positive lens L12 of the first lens group G1 is
As shown in Table 5,
nd = 1.43385,
The refractive index of the biconcave negative lens L13 of the first lens group G1 is
Since nd = 1.61266,
Using an antireflection film 101 (see Table 7) corresponding to a refractive index of the substrate of 1.46 on the image surface side lens surface of the biconvex positive lens L12,
On the object-side lens surface of the biconcave negative lens L13
By using an antireflection film (see Table 8) corresponding to a refractive index of the substrate of 1.62, reflected light from each lens surface can be reduced, and ghost and flare can be reduced.

In the optical system of the sixth embodiment of the first and second inventions of the present application,
The refractive index of the positive meniscus lens L22 of the second lens group G2 is
As shown in Table 6,
Since nd = 1.80809,
By using an antireflection film 101 (see Table 8) having a refractive index of 1.85 on the object-side lens surface of the positive meniscus lens L22, reflected light from each lens surface can be reduced, and ghost and flare can be reduced. Can be reduced.

  According to each of the above embodiments, it is possible to realize an optical system having an angle of view of 4 to 9 degrees, being small and light, correcting various aberrations satisfactorily, and suppressing deterioration of optical performance during image stabilization. it can. In addition, 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 optical system of the present application is not impaired.

  Although a three-group configuration is shown as a numerical example of the optical system of the present application, the present application is not limited to this, and an optical system of another group configuration (for example, the fourth group or the fifth group) 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 side of the optical system of the present application may be used. In addition, although the optical system according to each of the above embodiments includes the protective filter glass on the most object side in the first lens group, the optical system may be configured without this.

  Further, the optical system of the present application uses a part of a lens group, an entire lens group, or a plurality of lens groups as a focusing lens group in order to perform focusing from an object at infinity to a near object in the optical axis direction. It is good also as a structure moved to. In particular, it is preferable that at least a part of the second lens group is a focusing lens group. Such a focusing lens group can be applied to autofocus, and is also suitable for driving by an autofocus motor such as an ultrasonic motor.

  Further, in the optical system of the present application, 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 perpendicular to the optical axis, or an in-plane direction including the optical axis It can also be set as the structure which carries out anti-vibration by carrying out rotational movement (oscillation) to (F). In particular, in the optical system of the present application, it is preferable that at least a part of the third lens group is an anti-vibration lens group.

  The lens surface of the lens constituting the optical system of the present application 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 easy, 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 aspherical, any of aspherical surface by grinding, glass mold aspherical surface in which glass is molded into an aspherical shape, or composite aspherical surface in which resin provided on the glass surface is formed in an aspherical shape Good. The lens surface may be a diffractive surface, and the lens may be a gradient index lens (GRIN lens) or a plastic lens.

  In the optical system of the present application, the aperture stop is preferably arranged in the vicinity of the object side of the third lens group, and the role may be substituted by a lens frame without providing a member as the aperture stop.

  Further, an antireflection film having a high transmittance in a wide wavelength range may be applied to the lens surface of the lens constituting the optical system of the present application. Thereby, flare and ghost can be reduced, and high optical performance with high contrast can be achieved.

Next, a camera provided with the optical system of the first or second invention of the present application will be described with reference to FIG.
FIG. 13 is a diagram showing a configuration of a camera provided with the optical system of the first or second invention of the present application.
The camera 1 is a lens-interchangeable digital single-lens reflex camera provided with the optical system according to the first embodiment as the photographing lens 2.
In the present camera 1, light from an object (not shown) that is a subject is collected by the photographing lens 2 and imaged on the focusing screen 4 via the quick return mirror 3. The light imaged on the focusing screen 4 is reflected in the pentaprism 5 a plurality of times and guided to the eyepiece lens 6. Thus, the photographer can observe the subject image as an erect image through the eyepiece 6.

  When the release button (not shown) is pressed by the photographer, the quick return mirror 3 is retracted out of the optical path, and light from the subject (not shown) reaches the image sensor 7. Thereby, the light from the subject is picked up by the image pickup device 7 and recorded as a subject image in a memory (not shown). In this way, the photographer can shoot the subject with the camera 1.

  Here, the optical system according to the first embodiment mounted on the camera 1 as the photographing lens 2 is small and has good optical performance as described above. That is, the camera 1 can achieve downsizing and good optical performance. In addition, even if the camera which mounts the optical system which concerns on the said 2nd-6th Example as the taking lens 2 is comprised, there can exist an effect similar to the said camera 1. FIG. Further, even when the optical system according to each of the above embodiments is mounted on a camera having a configuration that does not include the quick return mirror 3, the same effect as the camera 1 can be obtained.

Next, the outline of the manufacturing method of the optical system of the first invention will be described with reference to FIG.
FIG. 14 is a diagram showing an outline of the method of manufacturing the optical system according to the first invention of the present application.
The optical system manufacturing method according to the first aspect of the present invention shown in FIG. 14 includes, in order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a positive refractive power. A method for manufacturing an optical system having a third lens group, which includes the following steps S1 to S3.

  Step S1: An antireflection film is provided on at least one of the optical surfaces in the first lens group, the second lens group, and the third lens group, and the antireflection film has at least one layer formed by a wet process. Each lens group is arranged in the lens barrel in order from the object side.

Step S2: First to third lens groups are prepared so that the optical system satisfies the following conditional expression (1-1).
(1-1) 0.10 <f / f12 <0.55
However,
f: Focal length of optical system f12: Composite focal length of first lens group and second lens group at the time of focusing on an object at infinity

  Step S3: By providing a known moving mechanism, the second lens group is moved along the optical axis, thereby focusing from an object at infinity to an object at short distance.

  According to the method of manufacturing the optical system of the first invention of the present application, it is possible to manufacture an optical system having a small size and good optical performance.

Finally, the outline of the optical system manufacturing method of the second invention of the present application will be described with reference to FIG.
FIG. 22 is a diagram showing an outline of the method of manufacturing the optical system of the second invention of the present application.
The optical system manufacturing method according to the second aspect of the present invention shown in FIG. 22 has, in order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a positive refractive power. A method of manufacturing an optical system having a third lens group, which includes the following steps S1 to S4.

  Step S1: An antireflection film is provided on at least one of the optical surfaces in the first lens group, the second lens group, and the third lens group, and the antireflection film has at least one layer formed by a wet process. Each lens group is arranged in the lens barrel in order from the object side.

Step S2: The second lens group has at least three lenses.
Step S3: First to third lens groups are prepared so that the optical system satisfies the following conditional expression (2-1):
(2-1) 0.10 <f / f12 <0.85
However,
f: Focal length of optical system f12: Composite focal length of first lens group and second lens group at the time of focusing on an object at infinity

  Step S4: By providing a known moving mechanism, the second lens group is moved along the optical axis so that focusing from an object at infinity to an object at short distance is performed.

  According to such an optical system manufacturing method of the second invention of the present application, an optical system having a small size and good optical performance can be manufactured.

G1 1st lens group G1a 1a lens group G1b 1b lens group G2 2nd lens group G3 3rd lens group G3a 3a lens group G3b 3b lens group G3c 3c lens group FLG Protective filter glass S Aperture stop I Image surface 101 Antireflection film 101a 1st layer 101b 2nd layer 101c 3rd layer 101d 4th layer 101e 5th layer 101f 6th layer 101g 7th layer 102 Optical member

Claims (23)

In order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a third lens group having a positive refractive power,
An antireflection film is provided on at least one of the optical surfaces of the first lens group, the second lens group, and the third lens group, and the antireflection film is a layer formed using a wet process. At least one layer,
The second lens group has two negative lens components;
By moving the second lens group along the optical axis, focusing from an object at infinity to an object at a short distance,
The following conditional expression is satisfied:
0.30 <f / f12 <0.55
However,
f: focal length of the optical system f12: combined focal length of the first lens group and the second lens group at the time of focusing on an object at infinity The first lens group has a plurality of positive lenses,
Among the plurality of positive lenses, the biconvex positive lens arranged closest to the object side satisfies the following conditional expression :
85 <νd1pf <110
However,
νd1pf: Abbe number with respect to d-line of the glass material of the positive lens arranged closest to the object side among the plurality of positive lenses in the first lens group
The first lens group is composed of a 1a lens group and a 1b lens group in order from the object side,
An air space between the first lens group and the first lens group is the largest of the air spaces in the first lens group;
An optical system satisfying the following conditional expression:
0.30 <TL1a / TL1 <0.50
However,
TL1a: length along the optical axis of the first lens group
TL1: Length along the optical axis of the first lens group In order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a third lens group having a positive refractive power,
An antireflection film is provided on at least one of the optical surfaces of the first lens group, the second lens group, and the third lens group, and the antireflection film is a layer formed using a wet process. At least one layer,
By moving the second lens group along the optical axis, focusing from an object at infinity to an object at a short distance,
The second lens group has at least three lenses;
The following conditional expression is satisfied:
0.30 <f / f12 <0.85
However,
f: focal length of the optical system f12: combined focal length of the first lens group and the second lens group at the time of focusing on an object at infinity The first lens group has a plurality of positive lenses,
Among the plurality of positive lenses, the biconvex positive lens arranged closest to the object side satisfies the following conditional expression :
85 <νd1pf <110
However,
νd1pf: Abbe number with respect to d-line of the glass material of the positive lens arranged closest to the object side among the plurality of positive lenses in the first lens group
The first lens group is composed of a 1a lens group and a 1b lens group in order from the object side,
An air space between the first lens group and the first lens group is the largest of the air spaces in the first lens group;
An optical system satisfying the following conditional expression:
0.30 <TL1a / TL1 <0.50
However,
TL1a: length along the optical axis of the first lens group
TL1: Length along the optical axis of the first lens group The optical system according to claim 2, wherein the second lens group includes at least one negative lens that satisfies the following conditional expression.
1.45 <nd2n <1.65
However,
nd2n: refractive index with respect to d-line of the glass material of the negative lens in the second lens group The antireflection film is a multilayer film,
Wherein the layer formed using a wet process, the optical according to any one of claims 1 to 3, wherein the a layer of the most surface side of the layers constituting the multilayer film system. Wherein when the refractive index was nd at the d-line of a layer formed using a wet process (wavelength lambda = 587.6 nm), nd is claims 1 to 4, characterized in that 1.30 or less The optical system according to any one of the above. Wherein the optical surface of the antireflection film is provided, an optical system as claimed in any one of claims 5, characterized in that when viewed from the image side is a concave lens surface. The optical system according to claim 6 , wherein the concave lens surface when viewed from the image surface side is an image surface side lens surface of a lens in the first lens group. The optical system according to claim 6 , wherein the lens surface having a concave shape when viewed from the image surface side is an image surface side lens surface of a lens in the second lens group. The optical system according to claim 6 , wherein the lens surface having a concave shape when viewed from the image surface side is an object-side lens surface of a lens in the third lens group. The optical system according to claim 6 , wherein the lens surface having a concave shape when viewed from the image surface side is an image surface side lens surface of a lens in the third lens group. The optical system according to claim 6 , wherein the concave lens surface when viewed from the image surface side is an image surface side lens surface of a fourth lens from the object side in the third lens group. Wherein the optical surface of the antireflection film is provided, an optical system as claimed in any one of claims 5, characterized in that a concave lens surface as viewed from the object side. The optical system according to claim 12 , wherein the concave lens surface when viewed from the object side is an object-side lens surface of a lens in the first lens group. The optical system according to claim 12 , 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 first lens group. The optical system according to claim 12 , wherein the concave lens surface as viewed from the object side is an object side lens surface of a lens in the second lens group. The optical system according to any one of claims 1 to 15 , wherein the second lens group includes a positive lens that satisfies the following conditional expression.
15 <νd2p <30
However,
νd2p: Abbe number with respect to d-line of the glass material of the positive lens in the second lens group The optical system according to any one of claims 1 to 16 , wherein the first lens group includes at least one positive lens that satisfies the following conditional expression.
80 <νd1p <110
However,
νd1p: Abbe number with respect to d-line of the glass material of the positive lens in the first lens group The optical system according to any one of claims 1 to 17 , wherein the first lens group includes at least one negative lens that satisfies the following conditional expression.
1.50 <nd1n <1.75
However,
nd1n: Refractive index with respect to d-line of the glass material of the negative lens in the first lens group The optical system according to any one of claims 1 to 18 , wherein at least a part of the third lens group moves so as to include a component in a direction orthogonal to the optical axis. The third lens group includes, in order from the object side, a 3a lens group having a positive refractive power, a 3b lens group having a negative refractive power, and a third c lens group having a positive refractive power. ,
The optical system according to any one of claims 1 to 19 , wherein the third lens group group moves so as to include a component in a direction orthogonal to the optical axis. The optical system according to any one of claims 1 to 20 , wherein the first lens group includes a cemented lens of a negative lens and a positive lens in order from the object side. Before Symbol the 1b lens group, an optical system as claimed in any one of claims 21, characterized in that it comprises a positive lens that satisfies a conditional expression.
70 <νd1bp <110
However,
νd1bp: Abbe number with respect to d-line of the glass material of the positive lens in the 1b lens group An optical device comprising the optical system according to any one of claims 1 to 22 .

Images