JP6780758B2 - Optical system and optical equipment having this optical system - Google Patents

Description

The present invention relates to an optical system and an optical device having this optical system.

Conventionally, optical systems suitable for photographic cameras, electronic still cameras, video cameras and the like have been proposed (see, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2013-033178

With the recent increase in the number of pixels of image pickup devices, an optical system in which various aberrations such as chromatic aberration are satisfactorily corrected is desired.

In the present invention
Substantially 3 of 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 in order from the object side along the optical axis. Consists of a group of lenses
Upon focusing, the distance between the first lens group and the second lens group changes, and the distance between the second lens group and the third lens group changes.
When focusing from an infinite object to a short-distance object, the second lens group moves along the optical axis, and the lens group moves along the optical axis.
The first lens group has at least one bonded lens, and the bonded lens is composed of a positive lens and a negative lens in order from the object side.
An optical system satisfying the following conditional expression was used.
1.00 <f / (-f2) <2.40
0.80 <f1 / (-f2) <1.45
1.40 <TL / f1 <2.05
However,
f: Focal length when the optical system is in focus at infinity f2: Focal length of the second lens group f1: Focal length of the first lens group TL: Overall length of the optical system

Further, in the present invention,
Substantially 3 of 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 in order from the object side along the optical axis. Consists of a group of lenses
Upon focusing, the distance between the first lens group and the second lens group changes, and the distance between the second lens group and the third lens group changes.
When focusing from an infinite object to a short-distance object, the second lens group moves along the optical axis, and the lens group moves along the optical axis.
The third lens group has a positive lens and a negative lens arranged next to each other in order from the object side.
An optical system satisfying the following conditional expression was used.
1.00 <f / (-f2) <2.40
0.80 <f1 / (-f2) <1.45
1.11 <f1 / f3 <1.40
However,
f: Focal length at infinity focusing of the optical system f2: Focal length of the second lens group f1: Focal length of the first lens group f3: Focal length of the third lens group

Further, in the present invention,
Substantially 3 of 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 in order from the object side along the optical axis. Consists of a group of lenses
Upon focusing, the distance between the first lens group and the second lens group changes, and the distance between the second lens group and the third lens group changes.
When focusing from an infinite object to a short-distance object, the second lens group moves along the optical axis, and the lens group moves along the optical axis.
The lens surface having an aperture diaphragm and adjacent to the object side of the aperture diaphragm is a lens surface having a convex shape toward the object side, and the lens surface adjacent to the image side of the aperture diaphragm has a convex shape toward the image side. It is the lens surface
An optical system satisfying the following conditional expression was used.
1.00 <f / (-f2) <2.40
70.00 <νp
However,
f: Focal length at infinity focusing of the optical system f2: Focal length νp of the second lens group: Mean value of Abbe numbers of all positive lenses included in the first lens group

Further, in the present invention,
Substantially 3 of 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 in order from the object side along the optical axis. Consists of a group of lenses
Upon focusing, the distance between the first lens group and the second lens group changes, and the distance between the second lens group and the third lens group changes.
When focusing from an infinite object to a short-distance object, the second lens group moves along the optical axis, and the lens group moves along the optical axis.
The first lens group has at least one bonded lens, and the bonded lens is composed of a positive lens and a negative lens in order from the object side.
An optical system satisfying the following conditional expression was used.
0.80 <f / f1 <1.60
0.80 <f1 / (-f2) <1.45
1.40 <TL / f <2.05
However,
f: Focal length when the optical system is in focus at infinity f1: Focal length of the first lens group f2: Focal length of the second lens group TL: Overall length of the optical system Further, in the present invention,
Substantially 3 of 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 in order from the object side along the optical axis. Consists of a group of lenses
Upon focusing, the distance between the first lens group and the second lens group changes, and the distance between the second lens group and the third lens group changes.
When focusing from an infinite object to a short-distance object, the second lens group moves along the optical axis, and the lens group moves along the optical axis.
The third lens group has a positive lens and a negative lens arranged next to each other in order from the object side.
An optical system that satisfies the following conditional expression.
0.80 <f / f1 <1.60
0.80 <f1 / (-f2) <1.45
1.11 <f1 / f3 <1.40
However,
f: Focal length at infinity focusing of the optical system f1: Focal length of the first lens group f2: Focal length of the second lens group f3: Focal length of the third lens group Further, in the present invention. ,
Substantially 3 of 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 in order from the object side along the optical axis. Consists of a group of lenses
Upon focusing, the distance between the first lens group and the second lens group changes, and the distance between the second lens group and the third lens group changes.
When focusing from an infinite object to a short-distance object, the second lens group moves along the optical axis, and the lens group moves along the optical axis.
The lens surface having an aperture diaphragm and adjacent to the object side of the aperture diaphragm is a lens surface having a convex shape toward the object side, and the lens surface adjacent to the image side of the aperture diaphragm has a convex shape toward the image side. It is the lens surface
An optical system satisfying the following conditional expression was used.
0.80 <f / f1 <1.60
70.00 <νp
However,
f: Focal length at infinity focusing of the optical system f1: Focal length νp of the first lens group: Mean value of Abbe numbers of all positive lenses included in the first lens group

Further, in the present invention, an optical device provided with the above optical system is used.

It is sectional drawing which shows the lens structure of the optical system which concerns on 1st Example of this application. It is a diagram of various aberrations in the infinity focusing state of the optical system according to the first embodiment of the present application. It is a diagram of various aberrations in a close-up shooting distance state of the optical system according to the first embodiment of the present application. It is sectional drawing which shows the lens structure of the optical system which concerns on 2nd Example of this application. It is a diagram of various aberrations in the infinity in-focus state of the optical system according to the second embodiment of the present application. It is a diagram of various aberrations in a close-up shooting distance state of the optical system according to the second embodiment of the present application. It is sectional drawing which shows the lens structure of the optical system which concerns on 3rd Example of this application. It is a diagram of various aberrations in the infinity in-focus state of the optical system according to the third embodiment of the present application. It is a diagram of various aberrations in a close-up shooting distance state of the optical system according to the third embodiment of the present application. It is sectional drawing of the single-lens reflex camera equipped with the optical system of this application. It is a flowchart for demonstrating the manufacturing method of the optical system of this application. It is a flowchart for demonstrating another manufacturing method of the optical system of this application. It is explanatory drawing which shows an example of the layer structure of the antireflection film. It is a graph which shows the spectral characteristic of the antireflection film. It is a graph which shows the spectral characteristic of the antireflection film which concerns on the modification. It is a graph which shows the incident angle dependence of the spectral characteristic of the antireflection film which concerns on a modification. It is a graph which shows the spectral characteristic of the antireflection film produced by the prior art. It is a graph which shows the incident angle dependence of the spectral characteristic of the antireflection film created by the prior art.

Hereinafter, an optical system, an optical device, and a method for manufacturing the optical system according to the embodiment of the present application will be described. The optical system of the present embodiment is 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 in order from the object side along the optical axis. It has a group, and the second lens group moves along the optical axis when focusing from an infinity object to a short-range object.

As described above, in the optical system of the present embodiment, the second lens group is used as a focusing lens group and is moved in the optical axis direction to focus from an infinity object to a short-range object, thereby causing aberration during focusing. Fluctuations can be reduced. In addition, the weight of the focusing lens group can be reduced, which enables high-speed focusing.

It is desirable that the optical system of this embodiment satisfies the following conditional expression (1).
1.00 <f / (-f2) <2.40 (1)
However,
f: Focal length when the optical system is in focus at infinity f2: Focal length of the second lens group

The conditional expression (1) defines the focal length of the optical system of the present embodiment when in focus at infinity and the focal length of the second lens group. By satisfying the conditional expression (1), the optical system of the present embodiment can satisfactorily correct spherical aberration and curvature of field, and prevent the overall length of the optical system from becoming large.

If it is less than the lower limit of the conditional expression (1), the refractive power of the second lens group becomes small, so that the spherical aberration becomes insufficiently corrected, and it becomes difficult to sufficiently correct the curvature of field, which is not preferable. Further, the movement amount of the second lens group, which is the focusing lens group, at the time of focusing becomes large, and the total length of the optical system becomes large, which is not preferable. By setting the lower limit value of the conditional expression (1) to 1.15, the effect of the present embodiment can be made more reliable. Further, by setting the lower limit value of the conditional expression (1) to 1.30, the effect of the present application can be further ensured.

On the other hand, if the upper limit of the conditional expression (1) is exceeded, the refractive power of the second lens group becomes large, so that spherical aberration becomes excessively corrected and it becomes difficult to correct curvature of field, which is not preferable. By setting the upper limit value of the conditional expression (1) to 2.20, the effect of the present embodiment can be made more reliable. Further, by setting the upper limit value of the conditional expression (1) to 2.00, the effect of the present embodiment can be further ensured.

With the above configuration, it is possible to realize excellent optical performance from infinity to short-distance object points in an optical system having a relatively long focal length and a small F number.

Further, it is desirable that the optical system of the present embodiment satisfies the following conditional expression (2).
0.80 <f / f1 <1.60 (2)
However,
f: Focal length when the optical system is in focus at infinity f1: Focal length of the first lens group

The conditional expression (2) defines the focal length of the entire optical system and the focal length of the first lens group of the present embodiment. By satisfying the conditional expression (2), the optical system of the present embodiment can prevent the overall length of the optical system from becoming large, and can satisfactorily correct curvature of field and coma.

If it is less than the lower limit of the conditional expression (2), the refractive power of the first lens group becomes small, so that the total length of the optical system increases, and it becomes difficult to secure the peripheral illumination, which is not preferable. Further, if the refractive power of the third lens group is increased in order to shorten the overall length of the optical system, it becomes difficult to correct spherical aberration and curvature of field, which is not preferable. By setting the lower limit value of the conditional expression (2) to 0.90, the effect of the present embodiment can be made more reliable. Further, by setting the lower limit value of the conditional expression (2) to 1.00, the effect of the present embodiment can be further ensured.

On the other hand, if the upper limit of the conditional equation (2) is exceeded, the refractive power of the first lens group becomes large, which makes it difficult to correct spherical aberration, coma, and curvature of field, which is not preferable. By setting the upper limit value of the conditional expression (2) to 1.50, the effect of the present embodiment can be made more reliable. Further, by setting the upper limit value of the conditional expression (2) to 1.35, the effect of the present application can be further ensured.

Further, it is desirable that the optical system of the present embodiment satisfies the following conditional expression (3).
0.80 <f1 / (-f2) <1.45 (3)
However,
f1: Focal length of the first lens group f2: Focal length of the second lens group

The above conditional expression (3) defines the focal length of the first lens group and the focal length of the second lens group of the present embodiment. By satisfying the conditional expression (3), the optical system of the present embodiment can satisfactorily correct spherical aberration and curvature of field, and can prevent the overall length of the optical system from becoming large.

If it is less than the lower limit of the conditional expression (3), the refractive power of the second lens group becomes small, so that the spherical aberration becomes insufficiently corrected, and it becomes difficult to sufficiently correct the curvature of field, which is not preferable. Further, the amount of movement of the second lens group, which is the focusing lens group, at the time of focusing becomes large, and the total length of the optical system becomes large, which is not preferable. By setting the lower limit value of the conditional expression (3) to 0.90, the effect of the present embodiment can be made more reliable. Further, by setting the lower limit value of the conditional expression (3) to 1.00, the effect of the present embodiment can be further ensured.

On the other hand, if the upper limit of the conditional expression (3) is exceeded, the refractive power of the second lens group becomes large, so that spherical aberration becomes excessively corrected and it becomes difficult to correct curvature of field, which is not preferable. By setting the upper limit value of the conditional expression (3) to 1.44, the effect of the present embodiment can be made more reliable. Further, by setting the upper limit value of the conditional expression (3) to 1.42, the effect of the present embodiment can be further ensured.

Further, it is desirable that the optical system of the present embodiment satisfies the following conditional expression (4).
1.11 <f1 / f3 <1.50 (4)
However,
f1: Focal length of the first lens group f3: Focal length of the third lens group

The conditional expression (4) defines the focal length of the first lens group and the focal length of the third lens group of the present embodiment. By satisfying the conditional expression (4), the optical system of the present embodiment can prevent the overall length of the optical system from becoming large, and can satisfactorily correct curvature of field and coma.

If the upper limit of the conditional expression (4) is exceeded, the refractive power of the first lens group becomes small, so that the total length of the optical system increases and it becomes difficult to secure the peripheral light amount, which is not preferable. Further, if the refractive power of the third lens group is increased in order to shorten the overall length of the optical system, it becomes difficult to correct spherical aberration and curvature of field, which is not preferable. By setting the upper limit value of the conditional expression (4) to 1.40, the effect of the present embodiment can be made more reliable. Further, by setting the upper limit value of the conditional expression (4) to 1.30, the effect of the present embodiment can be further ensured.

If it is less than the lower limit of the conditional equation (4), the refractive power of the first lens group becomes large, which makes it difficult to correct spherical aberration, coma, and curvature of field, which is not preferable. By setting the lower limit of the conditional expression (4) to 1.115, the effect of the present application can be made more reliable.

Further, it is desirable that the optical system of the present embodiment satisfies the following conditional expression (5).
0.70 <(-f2) /f3 <1.50 (5)
However,
f2: Focal length of the second lens group f3: Focal length of the third lens group

The above conditional expression (5) defines the focal length of the second lens group and the focal length of the third lens group of the present application. By satisfying the conditional expression (5), the optical system of the present embodiment can satisfactorily correct spherical aberration and curvature of field, and can prevent the overall length of the optical system from becoming large.

If the upper limit of the conditional expression (5) is exceeded, the refractive power of the second lens group becomes small, so that the spherical aberration becomes insufficiently corrected, and it becomes difficult to sufficiently correct the curvature of field, which is not preferable. Further, the amount of movement of the second lens group, which is the focusing lens group, at the time of focusing becomes large, and the total length of the optical system becomes large, which is not preferable. By setting the upper limit value of the conditional expression (5) to 1.35, the effect of the present embodiment can be made more reliable. Further, by setting the upper limit value of the conditional expression (5) to 1.20, the effect of the present embodiment can be further ensured.

On the other hand, if it is less than the lower limit of the conditional expression (5), the refractive power of the second lens group becomes large, so that the spherical aberration becomes excessively corrected and it becomes difficult to correct the curvature of field, which is not preferable. By setting the lower limit value of the conditional expression (5) to 0.75, the effect of the present embodiment can be made more reliable. Further, by setting the lower limit value of the conditional expression (5) to 0.80, the effect of the present embodiment can be further ensured.

Further, it is desirable that the optical system of the present embodiment satisfies the following conditional expression (6).
1.20 <TL / f1 <2.05 (6)
However,
TL: Overall length of the optical system f1: Focal length of the first lens group

The conditional expression (6) defines the total length of the optical system of the present embodiment and the focal length of the first lens group. By satisfying the conditional expression (6), the optical system of the present embodiment can prevent the overall length of the optical system from becoming large, and can satisfactorily correct curvature of field and coma.

If it is less than the lower limit of the conditional expression (6), the refractive power of the first lens group becomes small, so that the total length of the optical system increases, and it becomes difficult to secure the peripheral illumination, which is not preferable. Further, if the refractive power of the third lens group is increased in order to shorten the overall length of the optical system, it becomes difficult to correct spherical aberration and curvature of field, which is not preferable. By setting the lower limit value of the conditional expression (6) to 1.40, the effect of the present embodiment can be made more reliable. Further, by setting the lower limit value of the conditional expression (6) to 1.60, the effect of the present embodiment can be further ensured.

On the other hand, if the upper limit of the conditional equation (6) is exceeded, the refractive power of the first lens group becomes large, which makes it difficult to correct spherical aberration, coma, and curvature of field, which is not preferable. By setting the upper limit value of the conditional expression (6) to 2.03, the effect of the present application can be made more reliable. Further, by setting the upper limit value of the conditional expression (6) to 2.00, the effect of the present application can be further ensured.

Further, it is desirable that the optical system of the present embodiment satisfies the following conditional expression (7).
1.50 <TL / (-f2) <3.10 (7)
However,
TL: Overall length f2 of the optical system: Focal length of the second lens group

The conditional expression (7) defines the total length of the optical system of the present embodiment and the focal length of the second lens group. By satisfying the conditional expression (7), the optical system of the present embodiment can prevent the overall length of the optical system from becoming large, and can satisfactorily correct curvature of field and coma.

If it is less than the lower limit of the conditional expression (7), the refractive power of the second lens group becomes small, so that the total length of the optical system increases and it becomes difficult to secure the peripheral illumination, which is not preferable. Further, if the refractive power of the third lens group is increased in order to shorten the overall length of the optical system, it becomes difficult to correct spherical aberration and curvature of field, which is not preferable. By setting the lower limit value of the conditional expression (7) to 1.70, the effect of the present embodiment can be made more reliable. Further, by setting the lower limit value of the conditional expression (7) to 1.90, the effect of the present application can be further ensured.

On the other hand, if the upper limit of the conditional expression (7) is exceeded, the refractive power of the second lens group becomes large, which makes it difficult to correct spherical aberration, coma, and curvature of field, which is not preferable. By setting the upper limit value of the conditional expression (7) to 3.00, the effect of the present embodiment can be made more reliable. Further, by setting the upper limit value of the conditional expression (7) to 2.90, the effect of the present embodiment can be further ensured.

Further, it is desirable that the optical system of the present embodiment satisfies the following conditional expression (8).
63.00 <νp (8)
However,
νp: Average value of Abbe numbers of all positive lenses included in the first lens group

The conditional expression (8) defines the average value of the Abbe numbers of all the positive lenses included in the first lens group of the present embodiment. The optical system of the present embodiment can satisfactorily correct axial chromatic aberration by satisfying the conditional expression (8).

If it is less than the lower limit of the conditional expression (8), it becomes difficult to satisfactorily correct the axial chromatic aberration, which is not preferable. By setting the lower limit value of the conditional expression (8) to 65.00, the effect of the present embodiment can be made more reliable. Further, by setting the lower limit value of the conditional expression (8) to 70.0, the effect of the present embodiment can be further ensured.

Further, in the optical system of the present embodiment, it is desirable that the first lens group is fixed when focusing from an infinite object to a short-distance object. With this configuration, the in-focus lens group can be miniaturized as compared with the case where both the first lens group and the second lens group move, and coma aberration caused by an error when many in-focus lens groups move. It is possible to reduce the occurrence of various aberrations such as.

Further, in the optical system of the present embodiment, it is desirable that the third lens group is fixed when focusing from an infinite object to a short-distance object. With this configuration, the in-focus lens group can be miniaturized as compared with the case where both the second lens group and the third lens group move, and coma aberration caused by an error when many in-focus lens groups move. It is possible to reduce the occurrence of various aberrations such as.

Further, in the optical system of the present embodiment, it is desirable that the first lens group has a bonded lens, and the bonded lens is composed of a positive lens and a negative lens in order from the object side. With this configuration, spherical aberration and axial chromatic aberration can be satisfactorily corrected.

Further, it is desirable that the optical system of the present embodiment has an aperture diaphragm in the third lens group. With this configuration, curvature of field and astigmatism can be satisfactorily corrected.

Further, the optical system of the present embodiment has an aperture diaphragm, and the lens surface adjacent to the object side of the aperture diaphragm is a lens surface having a convex shape toward the object side, and is adjacent to the image side of the aperture diaphragm. It is desirable that the lens surface is a lens surface having a convex shape on the image side. With this configuration, spherical aberration, curvature of field, and astigmatism can be satisfactorily corrected.

Further, in the optical system of the present embodiment, it is desirable that the third lens group has a positive lens and a negative lens arranged adjacent to each other in order from the object side. With this configuration, spherical aberration can be satisfactorily corrected.

Further, in the optical system of the present embodiment, the second lens group has a bonded lens, the bonded lens is composed of a positive lens and a negative lens in order from the object side, and the second lens group is the bonded lens. It is desirable that it is composed of a lens, or is composed of a negative lens and the junction lens in order from the object side. With this configuration, it is possible to realize an optical system that is compact and has satisfactorily corrected axial chromatic aberration. In addition, with this configuration, fluctuations in spherical aberration during focusing can be reduced.

Further, in the optical system of the present embodiment, it is desirable that the third lens group has at least one aspherical surface. With this configuration, coma aberration can be satisfactorily corrected.

Further, it is desirable that the optical system of the present embodiment 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, it is possible to correct (vibration-proof) image blur caused by camera shake or the like. Then, the aberration fluctuation at the time of image blur correction can be reduced.

Further, in the optical system of the present embodiment, an antireflection film is provided on at least one of the optical surfaces in the first lens group to the third lens group, and the antireflection film uses a wet process. It is desirable to include at least one layer formed. With this configuration, the optical system of the present embodiment can further reduce ghosts and flares caused by reflection of light from an object on an optical surface, and can achieve high imaging performance.

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

The antireflection film in the optical system of the present embodiment is not limited to the wet process, and may be formed by a dry process or the like. In this case, it is preferable that the antireflection film contains 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. The layer having a refractive index of 1.30 or less is preferably the most surface-side layer among the layers constituting the multilayer film.

The optical device of this embodiment includes an optical system having the above-described configuration. As a result, it is possible to realize an optical device in which ghosts and flares are further reduced and aberration fluctuations during image blur correction are satisfactorily suppressed.

In the method for manufacturing an optical system of the present embodiment, a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a positive refractive power are sequentially applied from the object side along the optical axis. A method for manufacturing an optical system having a third lens group having the lens.
When focusing from an infinity object to a short-distance object, the second lens group is moved along the optical axis.
The following conditional expression (1) is satisfied.
1.00 <f / (-f2) <2.40 (1)
However,
f: Focal length when the optical system is in focus at infinity f2: Focal length of the second lens group

By the method of manufacturing the optical system of the present embodiment, it is possible to manufacture an optical system having excellent optical performance from a point at infinity to a point at infinity.

Further, in the method for manufacturing an optical system according to another embodiment of the present application, a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a second lens group having a negative refractive power are sequentially arranged from the object side along the optical axis. A method for manufacturing an optical system having a third lens group having a positive refractive power.
When focusing from an infinity object to a short-distance object, the second lens group is moved along the optical axis.
Satisfy the following conditional expression (2).
0.80 <f / f1 <1.60 (2)
However,
f: Focal length when the optical system is in focus at infinity f1: Focal length of the first lens group

By the method of manufacturing the optical system of the present embodiment, it is possible to manufacture an optical system having excellent optical performance from a point at infinity to a point at infinity.

Hereinafter, the optical system according to the numerical embodiment of the present application will be described with reference to the accompanying drawings.

(First Example)
FIG. 1 is a diagram showing a lens configuration of an optical system according to a first embodiment of the present application.

The optical system according to this embodiment has a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, and a positive refractive power in order from the object side along the optical axis. It is composed of a third lens group G3 having.

The first lens group G1 having a positive refractive power includes a biconvex positive lens L11, a biconvex positive lens L12, a biconvex positive lens L13, and a biconcave negative lens in order from the object side. It is composed of a bonded lens formed by bonding L14.

The second lens group G2 having a negative refractive power is composed of a bonded lens formed by joining a positive meniscus lens L21 having a concave surface facing the object side and a biconcave negative lens L22 in order from the object side.

The third lens group G3 having a positive refractive force includes a biconvex positive lens L31, a negative meniscus lens L32 with a convex surface facing the object side, an aperture aperture S, and a biconcave negative in order from the object side. A junction made by joining a lens L33 and a positive meniscus lens L34 with a convex surface facing the object side, a biconvex positive lens L35, a biconcave negative lens L36, and a biconvex positive lens L37. It consists of a lens.

In the optical system according to this embodiment, the most image side surface (plane number 22) of the third lens group G3 is an aspherical surface.

In the optical system according to the present embodiment, the first lens group G1 and the third lens group G3 are fixed to the image plane, and the entire second lens group G2 moves toward the image side along the optical axis, thereby infinitely. Focusing is performed from a distant object to a short-range object.

In the optical system according to the present embodiment, a junction lens composed of a negative lens L33 and a positive meniscus lens L34 and arranged adjacent to the image side of the aperture diaphragm S is a component in a direction orthogonal to the optical axis as a vibration-proof lens group. It is possible to correct the image blur by moving so as to include.

In the optical system according to the present embodiment, a wet process is used on the most object-side lens surface (plane number 19) of the bonded lenses composed of the positive lens L35, the negative lens L36, and the positive lens L37 and arranged on the image side. An antireflection film is formed so as to include at least one formed layer.

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

In the [Overall specifications] of Table 1, "f" is the focal length, "FNO" is the F number, "2ω" is the angle of view (unit: "°"), "Y" is the image height, and "TL" is. The total length of the optical system, "Bf", represents the back focus. The total length TL indicates the distance on the optical axis from the lens surface (first surface) on the most object side of this optical system to the image surface, and the back focus Bf is the lens surface (first surface) on the most image side of this optical system. It represents the distance on the optical axis from the 22nd plane) to the image plane.

In [plane data], "plane number" is the order of optical planes counted from the object side along the optical axis, "r" is the radius of curvature of each optical plane, and "d" is the plane spacing (nth plane (nth plane (nth plane)). N is an integer) and the distance between the n + 1 planes), “nd” is the refractive index for the d line, and “νd” is the number of abbreviations for the d line (wavelength λ = 587.6 nm). Further, "object surface" indicates an object surface, "(aperture S)" indicates an aperture aperture S, and "variable" indicates a variable surface spacing. The radius of curvature r = ∞ indicates a plane, and the refractive index nd = 1.00000 of air is omitted. "*" Is attached to the right side of the surface number on the aspherical surface.

In addition, [lens group focal length] indicates the surface number (starting surface) of the surface closest to the object in each lens group and the focal length of each lens group.

[Aspherical data] shows the conical constant and the aspherical coefficient when the shape of the aspherical surface shown in [Surface data] is expressed by the following equation. In addition, "En" indicates "x10- ⁿ ", for example, "1.234E-05" indicates "1.234 × ^10-5 ". The second-order aspherical coefficient A2 is 0.
X (y) = (y ² / r) / [1 + [1-κ (y ² / r ² )] ^1/2 ]
+ A4 x y ⁴ + A6 x y ⁶ + A8 x y ⁸ + A10 x y ¹⁰
Here, the height in the direction perpendicular to the optical axis is defined as "y", and the distance (sag amount) along the optical axis from the tangent plane of the apex of each aspherical surface to each aspherical surface at the height y is "S (sag amount). y) ”, the radius of curvature of the reference sphere (paraxial radius of curvature) is“ r ”, the conical constant is“ κ ”, and the nth-order aspherical coefficient is“ An ”.

In [variable interval data], "f" is the focal length of the entire system, "β" is the imaging magnification between the object and the image, and "Di" (where i is an integer) is the variable of the i-th plane. Indicates the surface spacing. Further, "infinity" indicates an infinity in-focus state, and "close" indicates a close-up shooting distance state. Note that D0 indicates the distance from the object to the first surface.

Here, "mm" is generally used as the unit of the focal length f, the radius of curvature r, the surface spacing d, and other lengths listed in all the following specification values, but the optical system is proportionally expanded or proportional. It is not limited to this because the same optical performance can be obtained even if the reduction is performed. Further, the description of these symbols and the description of the specification table are the same in the following examples.

(Table 1)
[Overall specifications]
f = 102.128
FNO = 1.449
2ω = 23.891
Y = 21.60
TL = 146.818
Bf = 41.301

[Surface data]
Surface number r d nd ν d
Paraboloid ∞ ∞
1 176.41170 7.081 1.59349 67.00
2 -997.05190 0.100
3 96.85690 9.766 1.49782 82.57
4 -2499.53100 0.100
5 64.16290 13.758 1.49782 82.57
6 -222.06850 3.500 1.73800 32.26
7 171.04680 Variable
8-136.08080 4.000 1.80809 22.74
9 -85.91600 2.500 1.48749 70.32
10 40.41360 Variable
11 121.43430 5.687 1.72916 54.61
12 -106.55980 0.100
13 97.96380 1.800 1.61505 35.73
14 33.61330 6.326
15 (Aperture S) ∞ 6.526
16 -52.40880 1.600 1.59238 35.86
17 71.14860 3.733 1.72916 54.61
18 478.61380 0.100
19 80.79100 8.330 1.75596 49.76
20 -33.83920 1.600 1.58128 37.40
21 61.41580 4.724 1.89799 34.84
22 * -225.35840 BF
Image plane ∞

[Lens group focal length]
Focal length
1 1 81.118
2 8 -69.336
3 11 72.558

[Aspherical data]
κ A4 A6 A8 A10
Side 22 1 9.931E-07 -1.978E-09 8.134E-12 -1.116E-14

[Variable interval data]
Near infinity
f or β 102.128 -0.136 times
D7 8.522 18.522
D10 15.664 5.664

[Conditional expression correspondence value]
(1) f / (-f2) = 1.47
(2) f / f1 = 1.26
(3) f1 / (-f2) = 1.17
(4) f1 / f3 = 1.12
(5) (-f2) /f3=0.96
(6) TL / f1 = 1.81
(7) TL / (-f2) = 2.12
(8) νP = 77.38

As described above, the optical system according to the first embodiment satisfies all of the above conditional expressions (1) to (8).

FIG. 2 shows various aberration diagrams of spherical aberration, astigmatism, distortion, chromatic aberration of magnification, and coma in the infinity focusing state of the optical system according to the first embodiment. Further, FIG. 3 shows various aberration diagrams of spherical aberration, astigmatism, distortion, chromatic aberration of magnification, and coma in a state of focusing at a short distance at a shooting magnification β = −0.136. In each aberration diagram, "FNO" indicates an F number and "Y" indicates an image height. Further, in each aberration diagram, "d" represents an aberration with respect to the d line (wavelength λ = 587.6 nm), and "g" represents an aberration with respect to the g line (wavelength λ = 435.8 nm). Further, in the astigmatism diagram, the solid line indicates the sagittal image plane, and the broken line indicates the meridional image plane. The description of this aberration diagram is the same in the following examples.

As is clear from the aberration diagrams shown in FIGS. 2 and 3, various aberrations are satisfactorily corrected in the optical system according to the first embodiment, and it can be seen that the optical system has high optical performance.

(Second Example)
FIG. 4 is a diagram showing a lens configuration of an optical system according to a second embodiment of the present application.

The optical system according to this embodiment has a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, and a positive refractive power in order from the object side along the optical axis. It is composed of a third lens group G3 having.

The first lens group G1 having a positive refractive power includes a biconvex positive lens L11, a biconvex positive lens L12, a biconvex positive lens L13, and a biconcave negative lens in order from the object side. It is composed of a bonded lens formed by bonding L14.

The second lens group G2 having a negative refractive power is composed of a bonded lens formed by joining a positive meniscus lens L21 having a concave surface facing the object side and a biconcave negative lens L22 in order from the object side.

The third lens group G3 having a positive refractive force includes a biconvex positive lens L31, a negative meniscus lens L32 with a convex surface facing the object side, an aperture aperture S, and a biconcave negative in order from the object side. A junction lens formed by joining a lens L33 and a biconvex positive lens L34, a junction lens formed by joining a biconvex positive lens L35 and a biconcave negative lens, and a biconvex positive lens. It consists of L37.

In the optical system according to this embodiment, the most image side surface (plane number 23) of the third lens group G3 is an aspherical surface.

In the optical system according to the present embodiment, the first lens group G1 and the third lens group G3 are fixed to the image plane, and the entire second lens group G2 moves toward the image side along the optical axis, thereby infinitely. Focusing is performed from a distant object to a short-range object.

In the optical system according to the present embodiment, a junction lens composed of a negative lens L33 and a positive lens L34 and arranged adjacent to the image side of the aperture diaphragm S provides a component in a direction orthogonal to the optical axis as a vibration-proof lens group. It can be moved so as to include, thereby correcting the image blur.

In the optical system according to the present embodiment, the image-side lens surface (plane number 22) of the positive lens L37 on the image side and the image-side lens surface (plane) of the negative lens L36 arranged adjacent to the object side of the positive lens L37. An antireflection film configured to include at least one layer formed by using a wet process is formed in No. 21).

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

(Table 2)
[Overall specifications]
f = 102.643
FNO = 1.441
2ω = 23.836
Y = 21.60
TL = 156.819
Bf = 44.626

[Surface data]
Surface number rd nd νd
Paraboloid ∞ ∞
1 232.74460 5.460 1.59349 67.00
2 -941.72040 0.100
3 99.95980 9.402 1.49782 82.57
4 -635.59410 0.100
5 67.81170 13.106 1.49782 82.57
6 -170.83160 3.500 1.64769 33.72
7 136.65740 Variable
8-132.42720 4.400 1.80809 22.74
9 -82.87930 2.500 1.48749 70.32
10 43.90050 Variable
11 76.67630 6.700 1.74397 44.85
12 -145.75050 0.100
13 365.29930 1.800 1.51742 52.20
14 35.15610 7.500
15 (Aperture S) ∞ 5.022
16 -52.41160 1.800 1.60482 34.33
17 48.32170 8.500 1.76457 48.44
18 -99.22310 0.100
19 302.91470 7.000 1.72916 54.61
20 -46.57540 1.800 1.61532 33.18
21 63.20750 2.000
22 63.50280 6.000 1.90265 35.72
23 * -264.53160 BF
Image plane ∞

[Lens group focal length]
Focal length
1 1 87.792
2 8 -74.149
3 11 72.509

[Aspherical data]
κ A4 A6 A8 A10
Side 23 1 2.199E-07 -4.073E-11 -2.713E-13 4.702E-16

[Variable interval data]
Near infinity
f or β 102.643 -0.141 times
D7 8.654 20.317
D10 16.649 4.986

[Conditional expression correspondence value]
(1) f / (-f2) = 1.38
(2) f / f1 = 1.17
(3) f1 / (-f2) = 1.18
(4) f1 / f3 = 1.21
(5) (-f2) /f3=1.02
(6) TL / f1 = 1.79
(7) TL / (-f2) = 2.11
(8) νP = 77.38

As described above, the optical system according to the second embodiment satisfies all of the above conditional expressions (1) to (8).

FIG. 5 shows various aberration diagrams of spherical aberration, astigmatism, distortion, chromatic aberration of magnification, and coma in the infinity focusing state of the optical system according to the second embodiment. Further, FIG. 6 shows various aberration diagrams of spherical aberration, astigmatism, distortion, chromatic aberration of magnification, and coma in a state of focusing at a short distance at a shooting magnification of β = −0.141. As is clear from the aberration diagrams shown in FIGS. 5 and 6, it can be seen that in the optical system according to the second embodiment, various aberrations are satisfactorily corrected and the optical performance is high.

(Third Example)
FIG. 7 is a diagram showing a lens configuration of an optical system according to a third embodiment of the present application.

The optical system according to this embodiment has a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, and a positive refractive power in order from the object side along the optical axis. It is composed of a third lens group G3 having.

The first lens group G1 having a positive refractive power is a junction lens formed by joining a biconvex positive lens L11, a biconvex positive lens L12, and a biconcave negative lens L13 in order from the object side. It is composed of a positive meniscus lens L14 having a convex surface facing the object side.

The second lens group G2 having a negative refractive power joins a biconcave negative lens L21, a positive meniscus lens L22 with a concave surface facing the object side, and a biconcave negative lens L23 in order from the object side. It consists of a bonded lens.

The third lens group G3 having a positive refractive force includes a junction lens formed by joining a biconvex positive lens L31 and a biconcave negative lens L32, an aperture aperture S, and a biconcave in order from the object side. A bonding lens formed by joining a negative lens L33 having a shape and a positive lens L34 having a biconvex shape, and a bonding lens formed by joining a negative meniscus lens L35 having a convex surface facing the object side and a positive lens L36 having a biconvex shape. Consists of.

In the optical system according to this embodiment, the most image side surface (plane number 22) of the third lens group G3 is an aspherical surface.

In the optical system according to the present embodiment, the first lens group G1 and the third lens group G3 are fixed to the image plane, and the entire second lens group G2 moves toward the image side along the optical axis, thereby infinitely. Focusing is performed from a distant object to a short-range object.

In the optical system according to the present embodiment, the optical system is composed of a negative lens L33 and a positive lens L34, and a junction lens arranged adjacent to the image side of the aperture diaphragm S includes a component in a direction orthogonal to the optical axis as a vibration-proof lens group. It is possible to correct the image blur by moving in the same manner.

In the optical system according to the present embodiment, a layer composed of a negative lens L35 and a positive lens L36 and formed on the most object-side lens surface (plane number 20) of the bonded lens arranged on the most image side by a wet process is formed. An antireflection film configured to include at least one layer is formed.

Table 3 below lists the specifications of the optical system according to the third embodiment.
(Table 3)
[Overall specifications]
f = 102.618
FNO = 1.440
2ω = 23.596
Y = 21.60
TL = 164.819
Bf = 47.774

[Surface data]
Surface number rd nd νd
Paraboloid ∞ ∞
1 198.29690 7.671 1.59349 67.00
2 -268.67610 0.100
3 91.70170 13.288 1.49782 82.57
4-128.83920 3.500 1.64769 33.72
5 203.55460 0.100
6 79.79810 8.164 1.49782 82.57
7 1937.33200 Variable
8 -194.71540 2.500 1.71999 50.27
9 117.67630 3.032
10 -1433.39560 5.200 1.80809 22.74
11 -76.31750 2.500 1.51742 52.20
12 53.75550 Variable
13 49.94100 11.096 1.88462 36.82
14 -83.51650 1.800 1.63199 34.05
15 37.73780 7.500
16 (Aperture S) ∞ 7.600
17 -40.81280 1.800 1.69044 27.44
18 99.54650 8.500 1.72916 54.61
19 -55.04360 0.100
20 285.10750 1.800 1.55390 42.19
21 41.90420 8.500 1.80733 43.13
22 * -158.99830 BF
Image plane ∞

[Lens group focal length]
Focal length
1 1 83.797
2 8 -59.773
3 11 69.892

[Aspherical data]
κ A4 A6 A8 A10
Side 22 1 9.463E-07 3.760E-10 -7.363E-13 1.038E-15

[Variable interval data]
Near infinity
f or β 102.643 -0.144 times
D7 7.857 17.857
D12 14.437 4.437

[Conditional expression correspondence value]
(1) f / (-f2) = 1.72
(2) f / f1 = 1.22
(3) f1 / (-f2) = 1.40
(4) f1 / f3 = 1.20
(5) (-f2) /f3=0.86
(6) TL / f1 = 1.97
(7) TL / (-f2) = 2.76
(8) νP = 77.38

As described above, the optical system according to the third embodiment satisfies all of the above conditional expressions (1) to (8).

FIG. 8 shows various aberration diagrams of spherical aberration, astigmatism, distortion, chromatic aberration of magnification, and coma in the infinity focusing state of the optical system according to the third embodiment. Further, FIG. 9 shows various aberration diagrams of spherical aberration, astigmatism, distortion, chromatic aberration of magnification, and coma in a state of focusing at a short distance at a shooting magnification of β = −0.144. As is clear from the aberration diagrams shown in FIGS. 8 and 9, it can be seen that in the optical system according to the third embodiment, various aberrations are satisfactorily corrected and the optical performance is high.

The values corresponding to the conditional expressions of each of the first to third embodiments shown above are shown in Table 4 below for reference.

(Table 4)
Conditional expression 1st Example 2nd Example 3rd Example (1) f / (-f2) 1.47 1.38 1.72
(2) f / f1 1.26 1.17 1.22
(3) f1 / (-f2) 1.17 1.18 1.40
(4) f1 / f3 1.12 1.21 1.20
(5) (-f2) /f3 0.96 1.02 0.86
(6) TL / f1 1.81 1.79 1.97
(7) TL / (-f2) 2.12 2.11 2.76
(8) νP 77.38 77.38 77.38

Here, an antireflection film (also referred to as a multilayer wideband antireflection film) used in the optical system according to the embodiment of the present application will be described. FIG. 13 is a diagram showing an example of the film configuration of the antireflection film. The antireflection film 101 is composed of seven layers and is formed on the optical surface of an optical member 102 such as a lens. The first layer 101a is made of aluminum oxide vapor-deposited by a vacuum vapor deposition method. Further, a second layer 101b made of a mixture of titanium oxide and zirconium oxide vapor-deposited by a vacuum vapor deposition method is further formed on the first layer 101a. Further, a third layer 101c made of aluminum oxide vapor-deposited by a vacuum vapor deposition method is formed on the second layer 101b, and titanium oxide and zirconium oxide vapor-deposited on the third layer 101c by a vacuum vapor deposition method are formed. A fourth layer 101d made of the mixture is formed. Furthermore, a fifth layer 101e made of aluminum oxide vapor-deposited by a vacuum vapor deposition method is formed on the fourth layer 101d, and titanium oxide and zirconium oxide vapor-deposited on the fifth layer 101e by a vacuum vapor deposition method. The sixth layer 101f composed of the mixture of the above is formed.

Then, on the sixth layer 101f thus formed, a seventh layer 101g made of a mixture of magnesium fluoride and silica is formed by a wet process to form the antireflection film 101 of the present embodiment. A sol-gel method, which is a kind of wet process, is used to form 101 g of the seventh layer. The sol-gel method is a method in which a sol obtained by mixing raw materials is made into a non-fluid gel by a hydrolysis / polycondensation reaction or the like, and this gel is heated / 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 for obtaining a solid film without going through a gel state may be used.

As described above, the first layer 101a to the sixth layer 101f of the antireflection film 101 are formed by electron beam vapor deposition, which is a dry process, and the uppermost layer, the seventh layer 101g, is prepared by the hydrofluoric acid / magnesium acetate method. It is formed by the following procedure by a wet process using the 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, and a third layer are formed in advance on the lens film-forming surface (the optical surface of the above-mentioned optical member 102) by 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. Then, after taking out the optical member 102 from the vapor deposition apparatus, a sol solution prepared by the hydrofluoric acid / magnesium acetate method to which silicon alkoxide is added is applied by the spin coating method to obtain 101 g of magnesium fluoride as the seventh layer. A layer consisting of a mixture of and silica is formed. The reaction formula when prepared by the hydrofluoric acid / magnesium acetate method is shown in the following formula (b).
2HF + Mg (CH3COO) 2 → MgF2 + 2CH3COOH (b)
The sol solution used for this film formation is used for film formation after being mixed with raw materials and then subjected to a high temperature pressure aging treatment at 140 ° C. for 24 hours in an autoclave. The optical member 102 is completed by heat treatment at 160 ° C. for 1 hour in the air after the film formation of 101 g of the 7th layer is completed. By using such a sol-gel method, particles having a size of several nm to several tens of nm are deposited leaving voids to form 101 g of the seventh layer.

The optical performance of the optical member having the antireflection film 101 thus formed will be described with reference to the spectral characteristics shown in FIG.

The optical member (lens) having the antireflection film according to the present embodiment is formed under the conditions shown in Table 5 below. Here, in Table 5, the reference wavelength is λ, and the refractive indexes of the substrate (optical member) are 1.62, 1.74, and 1.85, and each layer 101a (first layer) of the antireflection film 101 is 101 g (7th layer). The optical film thickness of each layer) was obtained. In Table 5, aluminum oxide is represented as Al2O3, a mixture of titanium oxide and zirconium oxide is represented as ZrO2 + TiO2, and a mixture of magnesium fluoride and silica is represented as MgF2 + SiO2.

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

FIG. 14 shows the spectral characteristics when a light beam is vertically incident on an optical member whose optical film thickness of each layer of the antireflection film 101 is designed with a reference wavelength λ of 550 nm in Table 5.

From FIG. 14, it can be seen that the optical member having the antireflection film 101 designed with the reference wavelength λ at 550 nm can suppress the reflectance to 0.2% or less in the entire range of the wavelength of light rays of 420 nm to 720 nm. Further, even an optical member having an antireflection film 101 whose optical film thickness is designed with the reference wavelength λ as the d line (wavelength 587.6 nm) in Table 5 has almost no effect on the spectral characteristics, and the reference shown in FIG. It has substantially the same spectral characteristics as when the wavelength λ is 550 nm.

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

(Table 6)
Material Refractive index Optical film thickness Optical film thickness Medium Air 1
Layer 5 MgF2 + SiO2 1.26 0.275λ 0.269λ
4th layer ZrO2 ＋ TiO2 2.12 0.045λ 0.043λ
Layer 3 Al2O3 1.65 0.212λ 0.217λ
Second layer ZrO2 ＋ TiO2 2.12 0.077λ 0.066λ
Layer 1 Al2O3 1.65 0.288λ 0.290λ
Refractive index of substrate 1.46 1.52

FIG. 15 shows the spectral characteristics when a light beam is vertically incident on an optical member having an antireflection film whose 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 6. There is. From FIG. 15, it can be seen that the antireflection film of this modified example has a reflectance of 0.2% or less in the entire range of the wavelength of light rays of 420 nm to 720 nm. In Table 6, 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) has almost no effect on the spectral characteristics, and the spectral characteristics shown in FIG. Has almost the same characteristics as.

FIG. 16 shows the spectral characteristics when the incident angles of the light rays on the optical member having the spectral characteristics shown in FIG. 15 are 30, 45, and 60 degrees, respectively. Although the spectral characteristics of the optical member having the antireflection film having a refractive index of 1.46 on the substrate shown in Table 6 are not shown in FIGS. 15 and 16, the refractive index of the substrate is almost the same as 1.52. Needless to say, it has the spectral characteristics of.

For comparison, FIG. 17 shows an example of an antireflection film formed only by a dry process such as a conventional vacuum vapor deposition method. FIG. 17 shows the spectral characteristics when a light beam is vertically incident on an optical member designed with an antireflection film having a refractive index of 1.52 on the same substrate as in Table 6 and having the conditions shown in Table 7 below. Further, FIG. 18 shows the spectral characteristics when the incident angles of the light rays on the optical member having the spectral characteristics shown in FIG. 17 are 30, 45, and 60 degrees, respectively.

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

Comparing the spectral characteristics of the optical member having the antireflection film according to the present embodiment shown in FIGS. 14 to 16 with the spectral characteristics of the conventional example shown in FIGS. 17 and 18, the antireflection film according to the present embodiment is compared. It can be clearly seen that has a lower reflectance at any angle of incidence and a lower reflectance over a wider band.

Next, an example in which the antireflection film shown in Tables 5 and 6 is applied to the first to third examples of the present application will be described.

In the optical system of the first embodiment, the refractive index of the positive lens L35 of the third lens group G3 is nd = 1.75596 as shown in Table 1, so that the lens surface on the object side of the positive lens L35 By using the antireflection film 101 (see Table 5) having a refractive index of 1.74 on the substrate, the reflected light from the lens surface can be reduced, and ghosts and flares can be reduced.

In the optical system of the second embodiment, the refractive index of the negative lens L36 of the third lens group G3 is nd = 1.61532 as shown in Table 1, and the refraction of the positive lens L37 of the third lens group G3. Since the ratio is nd = 1.90265, an antireflection film 101 (see Table 5) corresponding to a refractive index of 1.62 on the substrate is used for the lens surface on the image plane side of the negative lens L36, and an object in the positive lens L37. By using an antireflection film 101 (see Table 5) corresponding to a refractive index of 1.85 on the lens surface on the side, the reflected light from each lens surface can be reduced, and ghosts and flares can be reduced. ..

In the optical system of the third embodiment, the refractive index of the negative meniscus lens L35 of the third lens group G3 is nd = 1.55390 as shown in Table 7, so that the lens on the object side in the negative meniscus lens L35. By using an antireflection film (see Table 6) having a refractive index of 1.52 on the surface, the reflected light from the lens surface can be reduced, and ghosts and flares can be reduced.

The contents described below can be appropriately adopted as long as the optical performance is not impaired.

In the examples, the optical system having a three-group configuration is shown, but it can be applied to other group configurations such as four groups. Further, a configuration in which a lens or a lens group is added on the most object side or a configuration in which a lens or a lens group is added on the most image side may be used. Further, the lens group refers to a portion having at least one lens separated by an air interval that changes at the time of focusing.

A single lens group, a plurality of lens groups, or a partial lens group may be moved in the optical axis direction to focus on a short-range object from an infinity object. The focusing lens group can also be applied to autofocus, and is also suitable for driving a motor for autofocus (using an ultrasonic motor or the like). In particular, it is preferable that the second lens group is the focusing lens group.

The aperture diaphragm is preferably arranged in the third lens group, but the role may be substituted by the frame of the lens without providing the member as the aperture diaphragm.

Prevents image blur caused by camera shake by moving the lens group or partial lens group so that it has a component in the direction perpendicular to the optical axis, or by rotating (swinging) in the in-plane direction including the optical axis. It may be a swing lens group. In particular, it is preferable that at least a part of the third lens group is an anti-vibration lens group. Further, it is preferable that the lens components arranged adjacent to each other on the image side of the aperture diaphragm are the anti-vibration lens group.

The lens surface may be spherical or flat, or may be aspherical. When the lens surface is spherical or flat, lens processing and assembly adjustment are facilitated, and deterioration of optical performance due to processing and assembly adjustment errors can be prevented, which is preferable. Further, even if the image plane is deviated, the depiction performance is less deteriorated, which is preferable. When the lens surface is an aspherical surface, the aspherical surface is an aspherical surface formed by grinding, a glass mold aspherical surface formed by forming glass into an aspherical shape, or a composite formed by forming a resin provided on the surface of the glass into an aspherical shape. It may be a type aspherical surface. Further, the lens surface may be a diffraction surface, and the lens may be a refractive index distribution type lens (GRIN lens) or a plastic lens.

An antireflection film having a high transmittance in a wide wavelength range may be applied to each lens surface in order to reduce flare and ghost and achieve high contrast optical performance.

FIG. 10 shows a schematic cross-sectional view of a single-lens reflex camera 1 (hereinafter, simply referred to as a camera) as an example of an optical device provided with the above-mentioned optical system. In the camera 1, the light from an object (subject) (not shown) is focused by the photographing lens 2 (optical system) and imaged on the focal plate 4 via the quick return mirror 3. Then, the light formed on the focal plate 4 is reflected a plurality of times in the pentaprism 5 and guided to the eyepiece lens 6. As a result, the photographer can observe the object (subject) image as an upright image through the eyepiece lens 6.

When the photographer presses the release button (not shown), the quick return mirror 3 retracts out of the optical path, and the light of the object (subject) (subject) collected by the photographing lens 2 (not shown) is the subject on the image sensor 7. Form an image. As a result, the light from the object (subject) is captured by the image sensor 7 and recorded as an object (subject) image in a memory (not shown). In this way, the photographer can photograph an object (subject) with the camera 1. The camera 1 shown in FIG. 10 may hold the photographing lens 2 detachably, or may be integrally molded with the photographing lens 2. Further, the camera 1 may be a so-called single-lens reflex camera, a compact camera without a quick return mirror or the like, or a mirrorless single-lens reflex camera.

Here, the optical system described above as the photographing lens 2 of the present camera 1 further reduces ghosts and flares due to its characteristic lens configuration, and satisfactorily suppresses aberration fluctuations during image blur correction. As a result, the present camera 1 further reduces ghosts and flares, and realizes shooting in which aberration fluctuations during image blur correction are satisfactorily suppressed.

Hereinafter, an outline of the method for manufacturing the optical system of the present embodiment will be described with reference to FIG. The method for manufacturing this optical system is as follows, in order from the object side along the optical axis, a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a third lens group having a positive refractive power. It is a method for manufacturing an optical system having a lens group, and includes the following steps S1 and S2.

When focusing from an infinity object to a short-distance object, the second lens group moves along the optical axis (step S1).

The following conditional expression (1) is satisfied (step S2).
1.00 <f / (-f2) <2.40 (1)
However,
f: Focal length when the optical system is in focus at infinity f2: Focal length of the second lens group

According to the above manufacturing method, it is possible to manufacture an optical system having excellent optical performance from a point at infinity to a point at infinity.

Hereinafter, an outline of another manufacturing method of the optical system according to the present embodiment will be described with reference to FIG. The method for manufacturing this optical system is as follows, in order from the object side along the optical axis, a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a third lens group having a positive refractive power. It is a method for manufacturing an optical system having a lens group, and includes the following steps S1 and S2.

When focusing from an infinity object to a short-distance object, the second lens group moves along the optical axis (step S1).

Satisfy the following conditional expression (2) (step S2).
0.80 <f / f1 <1.60 (2)
However,
f: Focal length when the optical system is in focus at infinity f1: Focal length of the first lens group

According to the above manufacturing method, it is possible to manufacture an optical system having excellent optical performance from infinity to short-distance object points.

G1 1st lens group G2 2nd lens group G3 3rd lens group S Aperture aperture I Image plane 1 Single-lens reflex camera 2 Shooting lens 3 Quick return mirror 4 Focus plate 5 Pentaprism 6 Eyepiece 7 Imaging element

Claims (22)

Substantially 3 of 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 in order from the object side along the optical axis. Consists of a group of lenses
Upon focusing, the distance between the first lens group and the second lens group changes, and the distance between the second lens group and the third lens group changes.
When focusing from an infinite object to a short-distance object, the second lens group moves along the optical axis, and the lens group moves along the optical axis.
The first lens group has at least one bonded lens, and the bonded lens is composed of a positive lens and a negative lens in order from the object side.
An optical system that satisfies the following conditional expression.
1.00 <f / (-f2) <2.40
0.80 <f1 / (-f2) <1.45
1.40 <TL / f1 <2.05
However,
f: Focal length when the optical system is in focus at infinity f2: Focal length of the second lens group f1: Focal length of the first lens group TL: Overall length of the optical system Substantially 3 of 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 in order from the object side along the optical axis. Consists of a group of lenses
Upon focusing, the distance between the first lens group and the second lens group changes, and the distance between the second lens group and the third lens group changes.
When focusing from an infinite object to a short-distance object, the second lens group moves along the optical axis, and the lens group moves along the optical axis.
The third lens group has a positive lens and a negative lens arranged next to each other in order from the object side.
An optical system that satisfies the following conditional expression.
1.00 <f / (-f2) <2.40
0.80 <f1 / (-f2) <1.45
1.11 <f1 / f3 <1.40
However,
f: Focal length at infinity focusing of the optical system f2: Focal length of the second lens group f1: Focal length of the first lens group f3: Focal length of the third lens group Substantially 3 of 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 in order from the object side along the optical axis. Consists of a group of lenses
Upon focusing, the distance between the first lens group and the second lens group changes, and the distance between the second lens group and the third lens group changes.
When focusing from an infinite object to a short-distance object, the second lens group moves along the optical axis, and the lens group moves along the optical axis.
The lens surface having an aperture diaphragm and adjacent to the object side of the aperture diaphragm is a lens surface having a convex shape toward the object side, and the lens surface adjacent to the image side of the aperture diaphragm has a convex shape toward the image side. It is the lens surface
An optical system that satisfies the following conditional expression.
1.00 <f / (-f2) <2.40
70.00 <νp
However,
f: Focal length at infinity focusing of the optical system f2: Focal length νp of the second lens group: Mean value of Abbe numbers of all positive lenses included in the first lens group The optical system according to any one of claims 1 to 3, which satisfies the following conditional expression.
0.80 <f / f1 <1.60
However,
f: Focal length when the optical system is in focus at infinity f1: Focal length of the first lens group Substantially 3 of 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 in order from the object side along the optical axis. Consists of a group of lenses
Upon focusing, the distance between the first lens group and the second lens group changes, and the distance between the second lens group and the third lens group changes.
When focusing from an infinite object to a short-distance object, the second lens group moves along the optical axis, and the lens group moves along the optical axis.
The first lens group has at least one bonded lens, and the bonded lens is composed of a positive lens and a negative lens in order from the object side.
An optical system that satisfies the following conditional expression.
0.80 <f / f1 <1.60
0.80 <f1 / (-f2) <1.45
1.40 <TL / f <2.05
However,
f: Focal length when the optical system is in focus at infinity f1: Focal length of the first lens group f2: Focal length of the second lens group TL: Overall length of the optical system Substantially 3 of 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 in order from the object side along the optical axis. Consists of a group of lenses
Upon focusing, the distance between the first lens group and the second lens group changes, and the distance between the second lens group and the third lens group changes.
When focusing from an infinite object to a short-distance object, the second lens group moves along the optical axis, and the lens group moves along the optical axis.
The third lens group has a positive lens and a negative lens arranged next to each other in order from the object side.
An optical system that satisfies the following conditional expression.
0.80 <f / f1 <1.60
0.80 <f1 / (-f2) <1.45
1.11 <f1 / f3 <1.40
However,
f: Focal length at infinity focusing of the optical system f1: Focal length of the first lens group f2: Focal length of the second lens group f3: Focal length of the third lens group Substantially 3 of 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 in order from the object side along the optical axis. Consists of a group of lenses
Upon focusing, the distance between the first lens group and the second lens group changes, and the distance between the second lens group and the third lens group changes.
When focusing from an infinite object to a short-distance object, the second lens group moves along the optical axis, and the lens group moves along the optical axis.
The lens surface having an aperture diaphragm and adjacent to the object side of the aperture diaphragm is a lens surface having a convex shape toward the object side, and the lens surface adjacent to the image side of the aperture diaphragm has a convex shape toward the image side. It is the lens surface
An optical system that satisfies the following conditional expression.
0.80 <f / f1 <1.60
70.00 <νp
However,
f: Focal length at infinity focusing of the optical system f1: Focal length νp of the first lens group: Mean value of Abbe numbers of all positive lenses included in the first lens group The optical system according to any one of claims 1, 2, 5, and 6, which satisfies the following conditional expression.
63.00 <νp
However,
νp: Average value of Abbe numbers of all positive lenses included in the first lens group The lens surface having an aperture diaphragm and adjacent to the object side of the aperture diaphragm is a lens surface having a convex shape toward the object side, and the lens surface adjacent to the image side of the aperture diaphragm has a convex shape toward the image side. The optical system according to any one of claims 1, 2, 5, and 6, which is a lens surface. The optical system according to any one of claims 2, 3, 6, and 7, wherein the first lens group includes a bonded lens, and the bonded lens is composed of a positive lens and a negative lens in order from the object side. .. The optical system according to any one of claims 1, 3, 5, and 7, wherein the third lens group has a positive lens and a negative lens arranged next to each other in order from the object side. The optical system according to any one of claims 1 to 11, which satisfies the following conditional expression.
0.70 <(-f2) /f3 <1.50
However,
f2: Focal length of the second lens group f3: Focal length of the third lens group The optical system according to any one of claims 1 to 12, which satisfies the following conditional expression.
1.50 <TL / (-f2) <3.10
However,
TL: Overall length f2 of the optical system: Focal length of the second lens group The optical system according to any one of claims 1 to 13, wherein the first lens group is fixed when focusing from an infinity object to a short-distance object. The optical system according to any one of claims 1 to 14, wherein the third lens group is fixed when focusing from an infinity object to a short-distance object. The optical system according to any one of claims 1 to 15, which has an aperture diaphragm in the third lens group. The second lens group has a bonded lens, the bonded lens is composed of a positive lens and a negative lens in order from the object side, and the second lens group is composed of the bonded lens or an object. The optical system according to any one of claims 1 to 16, which is composed of a negative lens and the bonded lens in order from the side. The optical system according to any one of claims 1 to 17, wherein the third lens group has at least one aspherical surface. 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. An antireflection film is provided on at least one of the optical surfaces in the first lens group to the third lens group, and the antireflection film includes at least one layer formed by a wet process. The optical system according to any one of items 1 to 19. The optical system according to claim 20, wherein the nd is 1.30 or less, where nd is the refractive index of the layer formed by using the wet process with respect to the d line (wavelength λ = 587.6 nm). An optical device comprising the optical system according to any one of claims 1 to 21.

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