JP2015212822A - Optical system, image capturing device having the same, and manufacturing method for such optical system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide: an optical system that offers a wide view angle, compactness, and high optical performance; an image capturing device having the same; and a manufacturing method for such an optical system.SOLUTION: An optical system comprises a first lens group, and a second lens group having positive refractive power arranged in order from the object side along an optical axis, where the first lens group includes, in order from the object side along the optical axis, two negative lens components and a positive lens component located on the image side from the two negative lens components, and where the second lens group comprises a first lens subgroup comprising a positive lens and negative lens and having positive refractive power as a whole and a second lens subgroup which includes a cemented lens, a cemented negative lens located on the image side from the cemented lens and having a convex surface on the object side, and another cemented lens located on the image side from the cemented negative lens and comprising positive lenses or positive and negative lenses cemented together. An air gap distance between the first lens group and the second lens group changes while shifting focus from an object at infinity to an object at a short distance. The optical system satisfies a predetermined condition.

Description

  The present invention relates to an optical system suitable for a photographic camera, an electronic still camera, a video camera, and the like, an imaging device including the optical system, and a method for manufacturing the optical system.

  Conventionally, a retrofocus type optical system has been proposed (see, for example, Patent Document 1).

Japanese Patent Publication No. 60-32852

  The conventional retrofocus type optical system has a problem that when the angle of view is increased, it becomes larger and difficult to handle, and correction of aberration is not sufficient.

In order to solve the above problems, the present invention includes, in order from the object side along the optical axis, a first lens group and a second lens group having a positive refractive power, and the first lens group includes: It has two negative lens components in order from the object side along the optical axis, has a positive lens component closer to the image side than the two negative lens components, and the second lens group includes a positive lens and a negative lens. A first partial lens group having a positive refractive power as a whole, and a second partial lens group, the second partial lens group having a cemented lens, closer to the image side than the cemented lens, It has a cemented negative lens with a convex surface facing the object side, and has a cemented negative lens on the image side of the cemented negative lens or another cemented lens composed of a cemented positive lens and negative lens, and is close to an object at infinity When focusing on an object, the air spacing between the first lens group and the second lens group changes, To provide an optical system that satisfies the conditional expression below.
1.0 <| fF | / fR <50.0
However,
fF: focal length of the first lens group fR: focal length of the second lens group

The present invention is also a method of manufacturing an optical system having a first lens group and a second lens group having a positive refractive power in order from the object side along the optical axis. And having two negative lens components in order from the object side along the optical axis, and having a positive lens component closer to the image side than the two negative lens components, and the second lens group is a positive lens A first partial lens group having a negative lens and having a positive refractive power as a whole, and a second partial lens group, the second partial lens group having a cemented lens, and the cemented lens A cemented negative lens having a convex surface facing the object side closer to the image side than the lens, and another cemented lens formed by cementing a positive lens or a positive lens and a negative lens on the image side of the cemented negative lens When focusing from an object at infinity to a near object, the first Air space lens group and said second lens group is configured to change, to provide a manufacturing method of an optical system configured to satisfy the following condition.
1.0 <| fF | / fR <50.0
However,
fF: focal length of the first lens group fR: focal length of the second lens group

It is sectional drawing which shows the structure in the infinite object focusing state of the optical system which concerns on 1st Example. FIG. 6 is a diagram illustrating various aberrations of the optical system according to Example 1 in the state of focusing on an object at infinity. It is sectional drawing which shows the structure in the infinite object focusing state of the optical system which concerns on 2nd Example. FIG. 12 is a diagram illustrating various aberrations of the optical system according to Example 2 in the state of focusing on an object at infinity. It is sectional drawing which shows the structure in the infinite object focusing state of the optical system which concerns on 3rd Example. FIG. 11 is a diagram illustrating various aberrations of the optical system according to Example 3 in the state of focusing on an object at infinity. It is sectional drawing which shows the structure in the infinite object focusing state of the optical system which concerns on 4th Example. FIG. 10 is a diagram illustrating various aberrations of the optical system according to Example 4 in the state of focusing on an object at infinity. It is sectional drawing which shows the structure in the infinite object focusing state of the optical system which concerns on 5th Example. FIG. 10 is a diagram illustrating various aberrations of the optical system according to Example 5 in the state of focusing on an object at infinity. It is sectional drawing which shows the structure in the infinite object focusing state of the optical system which concerns on 6th Example. It is an aberration diagram in the infinite object focusing state of the optical system which concerns on 6th Example. It is sectional drawing of the imaging device provided with the optical system of this application. It is a flowchart which shows the outline of the manufacturing method of the optical system of this application. It is a figure which shows an example of a mode that the light ray which injected into the optical system which concerns on 1st Example of this application reflects on the 1st reflective surface and the 2nd reflective surface, and forms a ghost and a flare on an image surface. It is explanatory drawing which shows an example of the layer structure of an antireflection film. It is a graph which shows the spectral characteristic of an antireflection film. It is a graph which shows the spectral characteristics of the antireflection film concerning a modification. It is a graph which shows the incident angle dependence of the spectral characteristic of the antireflection film concerning a modification. It is a graph which shows the spectral characteristic of the anti-reflective film produced with the prior art. It is a graph which shows the incident angle dependence of the spectral characteristic of the anti-reflective film produced with the prior art.

  Hereinafter, an optical system, an imaging device, and an optical system manufacturing method according to the embodiment of the present application will be described. First, the optical system of the present application will be described.

The optical system of the present application includes, in order from the object side along the optical axis, a first lens group and a second lens group having a positive refractive power, and the first lens group includes an object along the optical axis. Two negative lens components in order from the side, and a positive lens component on the image side of the two negative lens components. The second lens group includes a positive lens and a negative lens, and is positive as a whole. A first partial lens group having a refractive power; and a second partial lens group. The second partial lens group includes a cemented lens, and a convex surface is directed to the image side and the object side of the cemented lens. A positive lens or another cemented lens composed of a positive lens and a negative lens on the image side of the cemented negative lens, for focusing from an object at infinity to a near object. At this time, the air gap between the first lens group and the second lens group changes.
With such a configuration, it is possible to realize a large angle of view, a small size, and a small diameter. The lens component refers to a single lens or a cemented lens.

In addition, the optical system of the present application satisfies the following conditional expression (1) under such a configuration.
(1) 1.0 <| fF | / fR <50.0
However,
fF: focal length of the first lens group fR: focal length of the second lens group

  Conditional expression (1) is a conditional expression that defines an appropriate ratio between the absolute value of the focal length of the first lens group and the focal length of the second lens group. In other words, it is a conditional expression that prescribes the optimum value of the magnitude relationship of the refractive power between the first lens group and the second lens group. By satisfying conditional expression (1), it is possible to realize a large angle of view and a small size while maintaining high optical performance.

  When the corresponding value of conditional expression (1) exceeds the upper limit value, the refractive power of the second lens group becomes stronger than that of the first lens group. In this case, the refractive power of the second lens group, which is the master lens of the optical system of the present application, is remarkably increased, which makes it difficult to correct coma, field curvature, and astigmatism, which is not preferable.

  In order to secure the effect of the present application, it is preferable to set the upper limit of conditional expression (1) to 45.0. In order to further secure the effect of the present application, it is preferable to set the upper limit of conditional expression (1) to 40.0. In order to further secure the effect of the present application, it is more preferable to set the upper limit of conditional expression (1) to 30.0.

  When the corresponding value of conditional expression (1) is lower than the lower limit value, the refractive power of the first lens group becomes stronger than that of the second lens group. In this case, the refractive power of the first lens group, which is the converter section of the optical system of the present application, is remarkably increased, which is not preferable because distortion, field curvature, and astigmatism deteriorate. Further, the number of components of the optical system is increased, that is, the size of the optical system is increased, which is not preferable.

  In order to secure the effect of the present application, it is preferable to set the lower limit of conditional expression (1) to 1.2. In order to further secure the effect of the present application, it is preferable to set the lower limit of conditional expression (1) to 1.8. In order to further secure the effect of the present application, it is more preferable to set the lower limit of conditional expression (1) to 2.0.

  With the above configuration, an optical system having a large angle of view, a small size, and high optical performance can be realized.

In the optical system of the present application, it is preferable that the first lens group has at least one negative lens that satisfies the following conditional expression (2).
(2) 65 <νdn
However,
νdn: Abbe number with respect to d-line (wavelength λ = 587.6 nm)

  Conditional expression (2) defines the Abbe number of at least one negative lens among the negative lenses constituting the first lens group. When at least one negative lens among the negative lenses constituting the first lens group satisfies the conditional expression (2), the longitudinal chromatic aberration can be corrected well. Further, it is possible to satisfactorily correct the secondary dispersion component of the lateral chromatic aberration and the chromatic aberration of coma, which are difficult to correct at a wide angle and an ultra wide angle.

Therefore, when the conditional expression (2) is not satisfied, the secondary dispersion component of the lateral chromatic aberration and the chromatic aberration of the coma deteriorate, which is not preferable.
In order to secure the effect of the present application, it is preferable to set the lower limit of conditional expression (2) to 69. In order to further secure the effect of the present application, it is preferable to set the lower limit of conditional expression (2) to 80. In order to further secure the effect of the present application, it is more preferable to set the lower limit of conditional expression (2) to 90.

The optical system of the present application preferably satisfies the following conditional expression (3).
(3) 0.2 <fR1 / fR <5.0
However,
fR1: focal length of the first lens group fR: focal length of the second lens group

  Conditional expression (3) is a conditional expression that defines the ratio of the focal lengths of the first partial lens group and the second lens group in the second lens group. In other words, it is a conditional expression that prescribes the optimum value of the magnitude relationship between the refractive powers of the first partial lens group and the second lens group. By satisfying conditional expression (3), high optical performance can be realized.

When the corresponding value of conditional expression (3) exceeds the upper limit value, the refractive power of the second lens group becomes strong. In this case, coma aberration, astigmatism, and field curvature are deteriorated, which is not preferable.
In order to secure the effect of the present application, it is preferable to set the upper limit of conditional expression (3) to 4.0. In order to further secure the effect of the present application, it is preferable to set the upper limit of conditional expression (3) to 3.0. In order to further secure the effect of the present application, it is more preferable to set the upper limit of conditional expression (3) to 2.0.

When the corresponding value of conditional expression (3) is lower than the lower limit value, the refractive power of the first partial lens group in the second lens group becomes strong. In this case, spherical aberration and coma are deteriorated, which is not preferable.
In order to secure the effect of the present application, it is preferable to set the lower limit of conditional expression (3) to 0.3. In order to further secure the effect of the present application, it is preferable to set the lower limit of conditional expression (3) to 0.5. In order to further secure the effect of the present application, it is more preferable to set the lower limit of conditional expression (3) to 0.7.

The optical system of the present application preferably satisfies the following conditional expression (4).
(4) 0.2 <| fR2 | / fR <80.0
However,
fR2: focal length of the second lens group fR: focal length of the second lens group

  Conditional expression (4) is a conditional expression that defines the ratio of the focal lengths of the second partial lens group and the second lens group in the second lens group. In other words, this is a conditional expression that defines the optimum value of the magnitude relationship between the refractive powers of the second partial lens group and the second lens group. By satisfying conditional expression (4), high optical performance can be realized.

When the corresponding value of conditional expression (4) exceeds the upper limit value, the refractive power of the second lens group becomes strong. In this case, coma aberration, astigmatism, and field curvature are deteriorated, which is not preferable.
In order to secure the effect of the present application, it is preferable to set the upper limit of conditional expression (4) to 75.0. In order to further secure the effect of the present application, it is preferable to set the upper limit of conditional expression (4) to 70.0. In order to further secure the effect of the present application, it is more preferable to set the upper limit of conditional expression (4) to 68.0.

When the corresponding value of conditional expression (4) is below the lower limit value, the refractive power of the second partial lens group in the second lens group becomes strong. Also in this case, coma aberration, astigmatism, and field curvature of off-axis aberrations deteriorate, which is not preferable.
In order to secure the effect of the present application, it is preferable to set the lower limit of conditional expression (4) to 2.5. In order to further secure the effect of the present application, it is preferable to set the lower limit of conditional expression (4) to 3.0. In order to further secure the effect of the present application, it is more preferable to set the lower limit of conditional expression (4) to 4.0.

Moreover, it is preferable that the optical system of the present application satisfies the following conditional expression (5).
(5) 0.3 <| fR21 | / fR1 <200.0
However,
fR21: focal length of the cemented lens in the second partial lens group fR1: focal length of the first partial lens group

  Conditional expression (5) is a conditional expression that defines the ratio between the absolute value of the focal length of the cemented lens in the second partial lens group and the focal length of the first partial lens group. In other words, this is a conditional expression that prescribes the optimum value of the refractive power magnitude relationship between the cemented lens in the second partial lens group and the first partial lens group. By satisfying conditional expression (5), spherical aberration and coma can be corrected well.

When the corresponding value of conditional expression (5) exceeds the upper limit value, the refractive power of the first partial lens group becomes strong. In this case, correction of spherical aberration and coma aberration deteriorates, which is not preferable.
In order to secure the effect of the present application, it is preferable to set the upper limit of conditional expression (5) to 190.0. In order to further secure the effect of the present application, it is preferable to set the upper limit of conditional expression (5) to 180.0. In order to further secure the effect of the present application, it is more preferable to set the upper limit of conditional expression (5) to 170.0.

When the corresponding value of conditional expression (5) is below the lower limit value, the refractive power of the cemented lens in the second partial lens group becomes strong. Also in this case, spherical aberration and coma are deteriorated, which is not preferable.
In order to secure the effect of the present application, it is preferable to set the lower limit of conditional expression (5) to 0.35. In order to further secure the effect of the present application, it is preferable to set the lower limit of conditional expression (5) to 0.40. In order to further secure the effect of the present application, it is more preferable to set the lower limit of conditional expression (5) to 0.45.

The optical system of the present application preferably satisfies the following conditional expression (6).
(6) 0.3 <−fR22 / fR1 <5.0
However,
fR22: focal length of the cemented negative lens in the second partial lens group fR1: focal length of the first partial lens group

  Conditional expression (6) is a conditional expression that defines the ratio of the focal lengths of the cemented negative lens in the second partial lens group and the first partial lens group. In other words, this is a conditional expression that prescribes the optimum value of the refractive power magnitude relationship between the cemented negative lens in the second partial lens group and the first partial lens group. By satisfying conditional expression (6), high optical performance can be realized.

When the corresponding value of conditional expression (6) exceeds the upper limit value, the refractive power of the first partial lens group becomes strong. In this case, spherical aberration and coma are deteriorated, which is not preferable.
In order to secure the effect of the present application, it is preferable to set the upper limit of conditional expression (6) to 4.0. In order to further secure the effect of the present application, it is preferable to set the upper limit of conditional expression (6) to 3.5. In order to further secure the effect of the present application, it is more preferable to set the upper limit of conditional expression (6) to 3.0.

When the corresponding value of conditional expression (6) is below the lower limit value, the refractive power of the cemented negative lens in the second partial lens group becomes strong. In this case, off-axis aberrations, particularly coma, curvature of field, astigmatism, and distortion are deteriorated, which is not preferable.
In order to secure the effect of the present application, it is preferable to set the lower limit of conditional expression (6) to 0.35. In order to further secure the effect of the present application, it is preferable to set the lower limit of conditional expression (6) to 0.40. In order to further secure the effect of the present application, it is more preferable to set the lower limit of conditional expression (6) to 0.45.

In the optical system of the present application, it is preferable that the first lens group and the second lens group are moved from the infinity object to the near object by moving the first lens group and the second lens group to the object side with different movement amounts.
With such a configuration, astigmatism and curvature of field can be favorably corrected when focusing from an object at infinity to an object at a short distance.

Moreover, it is preferable that the optical system of the present application satisfies the following conditional expression (7).
(7) 1.0 <X2 / X1 <3.5
However,
X1: Amount of movement of the first lens group when focusing from an object at infinity to a short distance object X2: Amount of movement of the second lens group when focusing from an object at infinity to a short distance object

  Conditional expression (7) is a conditional expression that prescribes an optimal movement amount ratio between the first lens group and the second lens group when focusing from an object at infinity to an object at a short distance. By satisfying conditional expression (7), high optical performance can be realized.

When the corresponding value of the conditional expression (7) exceeds the upper limit value, the movement amount for focusing the second lens group becomes significantly larger than the movement amount for focusing the first lens group, and the short-range aberration is increased. This is not preferable because the fluctuation increases, and in particular, astigmatism and field curvature greatly change and worsen in the negative direction.
In order to secure the effect of the present application, it is preferable to set the upper limit of conditional expression (7) to 3.0. In order to further secure the effect of the present application, it is preferable to set the upper limit of conditional expression (7) to 2.5. In order to further secure the effect of the present application, it is more preferable to set the upper limit of conditional expression (7) to 2.0.

When the corresponding value of conditional expression (7) is below the lower limit value, the amount of movement for focusing the first lens group is significantly greater than the amount of movement for focusing the second lens group, and short-range aberration. This is not preferable because the effect of correction is reduced, and in particular, astigmatism and field curvature are greatly changed and deteriorated in the positive direction.
In order to secure the effect of the present application, it is preferable to set the lower limit of conditional expression (7) to 1.1. In order to further secure the effect of the present application, it is preferable to set the lower limit of conditional expression (7) to 1.2. In order to further secure the effect of the present application, it is more preferable to set the lower limit of conditional expression (7) to 1.3.

In the optical system of the present application, it is preferable that the first lens group has at least one aspheric surface whose curvature decreases from the center toward the periphery.
With such a configuration, distortion and coma can be corrected well.

In the optical system of the present application, it is preferable that the first lens group has a meniscus aspherical lens having a convex surface facing the object side and satisfying the following conditional expression.
(8) 0.000 <| (r2-r1) / (r2 + r1) | <0.100
However,
r1: radius of curvature of the object-side lens surface of the aspheric lens r2: radius of curvature of the image-side lens surface of the aspheric lens

  Conditional expression (8) is a conditional expression for defining the reciprocal of the form factor of the aspherical lens in the first lens group. This condition is greatly related to correction of distortion, coma, astigmatism, and field curvature.

When the corresponding value of the conditional expression (8) exceeds the upper limit value, the aspherical lens is greatly changed from a meniscus shape having a convex surface facing the object side, exceeding a plano-convex shape or plano-concave shape, and a biconvex shape. Or it becomes a biconcave shape. As a result, coma and astigmatism are deteriorated, which is not preferable.
In order to secure the effect of the present application, it is preferable to set the upper limit of conditional expression (8) to 0.090. In order to further secure the effect of the present application, it is preferable to set the upper limit of conditional expression (8) to 0.080. In order to further secure the effect of the present application, it is more preferable to set the upper limit of conditional expression (8) to 0.070.

  In order to secure the effect of the present application, it is preferable to set the lower limit of conditional expression (8) to 0.001. In order to further secure the effect of the present application, it is preferable to set the lower limit of conditional expression (8) to 0.002. In order to further secure the effect of the present application, it is more preferable to set the lower limit of conditional expression (8) to 0.003.

In the optical system of the present application, it is preferable that the first lens group has at least two aspheric surfaces.
With such a configuration, distortion and coma can be corrected well.

In the optical system of the present application, it is preferable that at least one positive lens among the lens components constituting the optical system uses a Kurzflint glass material having abnormal partial dispersion.
With such a configuration, axial chromatic aberration can be favorably corrected. Furthermore, it is possible to satisfactorily correct the secondary dispersion of lateral chromatic aberration.

In the optical system of the present application, an antireflection film is provided on at least one of the optical surfaces of the first lens group and the second lens group, and the antireflection film is formed using a wet process. It is preferable that at least one layer is included.
In recent years, with respect to a retrofocus optical system as shown in Patent Document 1, not only aberration performance but also ghost and flare, which are one of the factors that impair optical performance, are becoming more severe. Therefore, higher performance is also required for the antireflection film applied to the lens surface of the optical system, and multilayer film design technology and film formation technology continue to advance in order to meet such requirements.
With the above 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 achieve high imaging performance.

  In the optical system of the present application, it is desirable that the antireflection film is a multilayer film, and the layer formed using the wet process is the most surface layer among the layers constituting the multilayer film. . 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 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 desirably 1.30 or less. 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.

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

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

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

  In the optical system of the present application, it is preferable that the concave lens surface when viewed from the aperture stop 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 concave lens surfaces as viewed from the aperture stop. For this reason, a ghost and flare can be effectively reduced by forming an antireflection film on such a lens surface.

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

  In the optical system of the present application, it is preferable that the optical surface provided with the antireflection film is a concave lens surface when viewed from the object. 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. 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 present application, it is preferable that the concave lens surface when viewed from the object is an image 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. 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 present application, it is preferable that the optical surface provided with the antireflection film is a concave lens surface when viewed from the image side. Of the optical surfaces in the second lens group (and the first lens group), reflected light tends to be generated on a concave lens surface as viewed from the image 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 present application, it is preferable that the concave lens surface as viewed from the image side is an 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 image 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 present application, it is desirable that the concave lens surface when viewed from the image side is an image 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 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 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.

  The imaging apparatus of the present application includes the optical system having the above-described configuration. As a result, it is possible to realize an imaging apparatus having a large angle of view, a small size, and high optical performance.

The optical system manufacturing method of the present application is a manufacturing method of an optical system having a first lens group and a second lens group having a positive refractive power in order from the object side along the optical axis, The first lens group includes two negative lens components in order from the object side along the optical axis, and has a positive lens component closer to the image side than the two negative lens components, and the second lens group Is configured to include a first partial lens group having a positive lens and a negative lens and having a positive refractive power as a whole, and a second partial lens group, and the second partial lens group includes a cemented lens. And having a cemented negative lens having a convex surface facing the object side on the image side relative to the cemented lens, and another image formed by cementing a positive lens or a positive lens and a negative lens on the image side of the cemented negative lens. Constructed to have a cemented lens, so that When, constructed as air gap between the second lens group and the third lens group varies, and constitutes so as to satisfy the following conditional expression (1).
(1) 1.0 <| fF | / fR <50.0
However,
fF: focal length of the first lens group fR: focal length of the second lens group

  By such an optical system manufacturing method, a photographing lens having a large angle of view, a small size, and high optical performance can be manufactured.

(Numerical example)
Hereinafter, a variable magnification optical system according to numerical examples of the present application will be described with reference to the accompanying drawings.

(First embodiment)
FIG. 1 is a cross-sectional view showing the configuration of the optical system OS1 according to the first example in an infinitely focused state.
As shown in FIG. 1, the optical system OS1 according to the present embodiment includes a first lens group GF having a negative refractive power and a second lens group having a positive refractive power in order from the object side along the optical axis. It is composed of GR.

  The first lens group GF has, in order from the object side along the optical axis, a negative meniscus lens L11 having a convex surface directed toward the object side, a negative meniscus lens L12 having a convex surface directed toward the object side, and a convex surface directed toward the object side. It is composed of a positive meniscus lens L13 and a biconvex positive lens L14. The negative meniscus lens L11 is an aspheric lens in which the image side lens surface has an aspheric shape with a curvature that decreases from the center toward the periphery. The positive meniscus lens L13 is an aspheric lens having an aspheric lens surface on the image side.

The second lens group GR includes, in order from the object side along the optical axis, a first partial lens group GR1 having a positive refractive power, an aperture stop S, and a second partial lens group GR2 having a negative refractive power. It is configured.
The first partial lens group GR1 includes, in order from the object side along the optical axis, a negative meniscus lens L21 having a convex surface directed toward the object side, and a biconvex positive lens L22.
The second partial lens group GR2 includes a cemented positive lens GR21 of a biconvex positive lens L23 and a negative meniscus lens L24 having a convex surface facing the image side, a biconvex positive lens L25, and a convex surface facing the object side. A negative negative meniscus lens L26 having a convex surface facing the object side, a positive meniscus lens L28 having a convex surface facing the image side, and a negative meniscus lens L29 having a convex surface facing the image side. It is composed of

  The optical system according to this example includes the image side lens surface (surface number 2) of the negative meniscus lens L11 of the first lens group GF and the object side lens surface (surface number 3) of the negative meniscus lens L12 of the first lens group GF. ) Is formed with an antireflection film to be described later.

  On the image plane I, an image sensor (not shown) made up of a CCD, a CMOS, or the like is disposed.

  The photographic lens OS1 according to the present embodiment focuses from an infinitely distant object to a close object by extending the entire short distance correction method (all groups). That is, the first lens group GF and the second lens group GR are focused on an object at infinity from a short distance object by moving the first lens group GF and the second lens group GR to the object side along the optical axis with different movement amounts.

  In addition, the photographing lens OS1 according to the present embodiment uses J-KZFH1 (optical glass) which is a Kurzflint glass type having an abnormal partial dispersion for the positive lens L14 in the first lens group GF.

Table 1 below lists specifications of the photographing lens OS1 according to the first example of the present application.
In [Surface data] in Table 1, the surface number is the order of the lens surfaces counted from the object side, r is the radius of curvature of the lens surfaces, d is the distance between the lens surfaces, and nd is the d-line (wavelength λ = 587.6 nm). And νd represents the Abbe number for the d-line (wavelength λ = 587.6 nm). The object plane indicates the object plane, (aperture S) indicates the aperture stop S, and the image plane indicates the image plane I. The radius of curvature r = ∞ indicates a plane, and the description of the refractive index nd of air = 1.000 is omitted. When the lens surface is an aspheric surface, the surface number is marked with * and the paraxial radius of curvature is shown in the column of the radius of curvature r.

[Aspherical data] shows the conical coefficient and aspherical coefficient when the shape of the aspherical surface shown in [Surface data] is expressed by the following equation.
^{X (y) = (y 2} / r) / [1+ {1-κ (y 2 / r 2)} 1/2] + A4y 4 + A6y 6 + A8y 8 + A10y 10 + A12y 12 + A14y 14 + A16y 16 + A18y 18
Here, the height in the direction perpendicular to the optical axis is y, the amount of displacement in the optical axis direction at height y is X (y), the radius of curvature of the reference sphere (paraxial radius of curvature) is r, the cone coefficient is κ, Let the n-th order aspheric coefficient be An. The secondary aspheric coefficient A2 is 0 (zero), and is not shown. “E−n” indicates “× 10 ⁻ⁿ ”, for example, “1.23456E-07” indicates “1.23456 × 10 ⁻⁷ ”.

  In [various data], f is a focal length, FNO is an F number, ω is a half angle of view (unit is “° (degree)”), Y is an image height, TL is an optical total length, and BF is a back focus. . These values are those when focusing on an object at infinity. Here, the optical total length TL is the distance on the optical axis from the lens surface closest to the object side of the optical system to the image plane I, and BF is the light from the lens surface closest to the image side of the optical system to the image plane I. The distance on the axis.

  In [variable interval data], f is the focal length of the entire optical system, β is the photographing magnification, d0 is the distance from the object to the lens surface closest to the object, and di (i is an integer) is the i-th surface. BF represents the back focus, and the distance between the (i + 1) th plane and the BF. 1-POS indicates when an object at infinity is in focus, 2-POS indicates when an intermediate distance is in focus, and 3-POS indicates when an object at close distance is in focus.

[Lens Group Data] indicates the start surface number and focal length of each lens group.
[Conditional Expression Corresponding Value] indicates the corresponding value of each conditional expression.

Here, “mm” is generally used as the unit of the focal length f, the radius of curvature r, and other lengths described in Table 1. However, the optical system is not limited to this because an equivalent optical performance can be obtained even when proportionally enlarged or proportionally reduced.
In addition, the code | symbol of Table 1 described above shall be similarly used also in the table | surface of each Example mentioned later.

(Table 1) First Example [Surface Data]
Surface number r d nd νd
Object ∞
1) 66.6250 3.0000 1.744429 49.52
* 2) 14.8549 12.6167
3) 46.5757 1.8000 1.437000 95.00
4) 17.3124 1.0000
5) 17.7032 3.5000 1.516800 63.88
* 6) 17.3948 9.1024
7) 57.2461 18.3659 1.612660 44.46
8) -41.4712 d8
9) 148.1451 1.0000 1.516800 63.88
10) 20.3104 0.1000
11) 14.5141 4.3987 1.497820 82.57
12) -48.3678 4.0321
13) (Aperture S) 2.6600
14) 919.7853 3.6000 1.497820 82.57
15) -9.5380 1.0000 1.755000 52.34
16) -28.5600 0.1000
17) 153.5363 2.0000 1.772500 49.62
18) -60.0537 0.1000
19) 148.9845 1.0000 1.834810 42.73
20) 16.3267 3.0000 1.497820 82.57
21) 101.4528 1.5000
22) -282.4539 5.5000 1.497820 82.57
23) -19.7828 1.0000
24) -16.1321 1.5000 1.772500 49.62
25) -38.5557 (BF)
Image plane ∞

[Aspherical data]
Surface number: 2
κ = 0.1353
A4 = 8.93430E−09
A6 = -8.08589E−09
A8 = 7.45499E-11
A10 = -8.82104E-14
A12 = -0.22473E-15
A14 = 0.72213E-18
A16 = -0.11800E-21
A18 = 0.23404E−24

Surface number: 6
κ = -5.2120
A4 = 1.76375E−04
A6 = -6.64114E-07
A8 = 3.86859E−09
A10 = -7.93950E-12
A12 = 0.00000E−00
A14 = 0.00000E−00
A16 = 0.00000E−00
A18 = 0.00000E−00

[Various data]
f 19.50
FNO 4.1
ω 59.257
Y 33.000
TL 113.370
BF 26.495

[Variable interval data]
1-POS 2-POS 3-POS
forβ 19.49991 -0.02500 -0.13453
d0 ∞ 770.1533 135.2685
d8 5.00000 4.76493 3.73424
BF 26.49466 26.98249 29.12146

[Lens group data]
Start surface Focal length
GF 1 -593.07402
GR 9 49.78447

[Values for each conditional expression]
(1) | fF | /fR=11.913
(2) νdn = 95.00
(3) fR1 / fR = 0.002
(4) | fR2 | /fR=4.367
(5) | fR21 | /fR1=54.236
(6) -fR22 / fR1 = 1.115
(7) X2 / X1 = 1.930
(8) | (r2-r1) / (r2 + r1) | = 0.008787

FIG. 2 is a diagram illustrating various aberrations of the optical system OS1 according to the first example in the infinite focus state.
In each aberration diagram, FNO indicates an F number, and A indicates a half angle of view (unit: “° (degree)”). D represents the d-line (λ = 587.6 nm), and g represents the g-line (λ = 435.8 nm). In the astigmatism diagrams, the solid line indicates the sagittal image plane, and the broken line indicates the meridional image plane. In the coma aberration diagram, the solid line represents the meridional coma aberration with respect to the d-line and the g-line. In the following examples, the same symbols are used, and the following description is omitted.

  It can be seen from the respective aberration diagrams that the optical system OS1 according to the first example has excellent optical performance with various aberrations corrected well.

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 3, ghost or flare) of the negative meniscus lens L12 in the first lens group GF. Is reflected by the first reflecting surface on which the reflected light becomes, and the image side lens surface of the negative meniscus lens L11 in the first lens group GF (surface number 2, second reflected light causing the ghost or flare is generated). The reflection surface is reflected again, and finally reaches the image plane I to cause ghost and flare. The first reflecting surface is a concave lens surface when viewed from the aperture stop S, and the second reflecting surface is a concave lens surface when viewed from the aperture stop S.
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)
FIG. 3 is a cross-sectional view showing the configuration of the optical system OS2 according to the second example in the infinitely focused state.
As shown in FIG. 3, the optical system OS2 according to the present embodiment includes a first lens group GF having a negative refractive power and a second lens group having a positive refractive power in order from the object side along the optical axis. It is composed of GR.

  The first lens group GF has, in order from the object side along the optical axis, a negative meniscus lens L11 having a convex surface directed toward the object side, a negative meniscus lens L12 having a convex surface directed toward the object side, and a convex surface directed toward the object side. It is composed of a positive meniscus lens L13 and a biconvex positive lens L14. The negative meniscus lens L11 is an aspheric lens in which the image side lens surface has an aspheric shape with a curvature that decreases from the center toward the periphery. The positive meniscus lens L13 is an aspheric lens having an aspheric lens surface on the image side.

The second lens group GR includes, in order from the object side along the optical axis, a first partial lens group GR1 having a positive refractive power, an aperture stop S, and a second partial lens group GR2 having a negative refractive power. It is configured.
The first partial lens group GR1 includes, in order from the object side along the optical axis, a negative meniscus lens L21 having a convex surface directed toward the object side, and a biconvex positive lens L22.
The second partial lens group GR2 includes a cemented negative lens GR21 of a biconvex positive lens L23 and a biconcave negative lens L24, a biconvex positive lens L25, and a negative meniscus lens having a convex surface facing the object side. The lens includes a cemented negative lens GR22 composed of a positive meniscus lens L27 having a convex surface facing the object side, and a cemented negative lens composed of a biconvex positive lens L28 and a negative meniscus lens L29 having a convex surface facing the image side. Yes.

  The optical system according to this example includes the image side lens surface (surface number 21) of the positive meniscus lens L27 of the second lens group GR and the object side lens surface of the biconvex positive lens L28 of the second lens group GR ( An antireflection film to be described later is formed on the surface number 22).

  On the image plane I, an image sensor (not shown) made up of a CCD, a CMOS, or the like is disposed.

  The photographic lens OS2 according to the present embodiment focuses from an infinitely distant object to a close object by extending the entire short distance correction method (all groups). That is, the first lens group GF and the second lens group GR are focused on an object at infinity from a short distance object by moving the first lens group GF and the second lens group GR to the object side along the optical axis with different movement amounts.

  In addition, the photographing lens OS2 according to the present example uses J-KZFH1 (optical glass) that is a Kurzflint glass type having an abnormal partial dispersion for the positive lens L14 in the first lens group GF.

  Table 2 below provides specification values of the photographing lens OS2 according to the second example of the present application.

(Table 2) Second Example [Surface Data]
Surface number r d nd νd
Object ∞
1) 69.1532 3.0000 1.744429 49.52
* 2) 14.4843 10.5256
3) 41.8295 1.8000 1.437000 95.00
4) 17.2042 1.0000
5) 17.6171 3.5000 1.516800 63.88
* 6) 17.2451 8.4825
7) 53.8161 21.5619 1.612660 44.46
8) -41.4508 d8
9) 99.8218 1.0000 1.516800 63.88
10) 16.8232 0.1000
11) 13.3744 4.5053 1.497820 82.57
12) -45.6872 2.9082
13) (Aperture S) 2.6600
14) 74.3832 3.5000 1.497820 82.57
15) -9.4419 1.0000 1.755000 52.34
16) 35.2359 0.4477
17) 37.9522 3.0000 1.816000 46.59
18) -23.7734 0.1000
19) 45.8082 1.0000 1.834810 42.73
20) 15.2838 3.0000 1.497820 82.57
21) 33.4928 1.0000
22) 60.7512 7.5000 1.437000 95.00
23) -13.9770 1.5000 1.772500 49.62
24) -54.1571 (BF)
Image plane ∞

[Aspherical data]
Surface number: 2
κ = 0.1129
A4 = -1.22640E-06
A6 = -6.46195E−09
A8 = 6.97941E-11
A10 = -9.13447E-14
A12 = -0.21976E-15
A14 = 0.86642E-18
A16 = -0.71294E-22
A18 = 0.14727E−24

Surface number: 6
κ = -5.1519
A4 = 1.78378E−04
A6 = -6.89424E-07
A8 = 4.01216E−09
A10 = -8.48888E-12
A12 = 0.00000E−00
A14 = 0.00000E−00
A16 = 0.00000E−00
A18 = 0.00000E−00

[Various data]
f 19.44
FNO 4.23
ω 59.298
Y 33.000
TL 114.571
BF 26.480

[Variable interval data]
1-POS 2-POS 3-POS
forβ 19.44321 -0.02509 -0.13284
d0 ∞ 765.3938 137.0910
d8 5.00000 4.78438 3.86102
BF 26.47989 26.96804 26.47989

[Lens group data]
Start surface Focal length
GF 1 -687.59558
GR 9 49.34171

[Values for each conditional expression]
(1) | fF | /fR=13.935
(2) νdn = 95.00
(3) fR1 / fR = 0.9107
(4) | fR2 | /fR=4.787
(5) | fR21 | /fR1=0.5368
(6) -fR22 / fR1 = 1.2075
(7) X2 / X1 = 1.787
(8) | (r2-r1) / (r2 + r1) | = 0.01067

FIG. 4 is a diagram illustrating various aberrations of the optical system OS2 according to the second example in the infinite focus state.
It can be seen from the respective aberration diagrams that the optical system OS2 according to the second example has excellent optical performance with various aberrations corrected satisfactorily.

(Third embodiment)
FIG. 5 is a cross-sectional view illustrating the configuration of the optical system OS3 according to the third example in an infinitely focused state.
As shown in FIG. 5, the optical system OS3 according to the present embodiment includes a first lens group GF having a positive refractive power and a second lens group having a positive refractive power in order from the object side along the optical axis. It is composed of GR.

  The first lens group GF has, in order from the object side along the optical axis, a negative meniscus lens L11 having a convex surface directed toward the object side, a negative meniscus lens L12 having a convex surface directed toward the object side, and a convex surface directed toward the object side. It is composed of a positive meniscus lens L13 and a biconvex positive lens L14. The negative meniscus lens L11 is an aspheric lens in which the image side lens surface has an aspheric shape with a curvature that decreases from the center toward the periphery. The positive meniscus lens L13 is an aspheric lens having an aspheric lens surface on the image side.

The second lens group GR includes, in order from the object side along the optical axis, a first partial lens group GR1 having a positive refractive power, an aperture stop S, and a second partial lens group GR2 having a negative refractive power. It is configured.
The first partial lens group GR1 includes, in order from the object side along the optical axis, a negative meniscus lens L21 having a convex surface directed toward the object side, and a biconvex positive lens L22.
The second partial lens group GR2 includes a cemented negative lens GR21 including a positive meniscus lens L23 having a convex surface facing the image side and a negative meniscus lens L24 having a convex surface facing the image side, a biconvex positive lens L25, and an object side. A cemented negative lens GR22 of a negative meniscus lens L26 having a convex surface toward the object side and a positive meniscus lens L27 having a convex surface toward the object side, a positive lens L28 having a biconvex shape, and a negative meniscus lens L29 having a convex surface facing the image side It is composed of

  The optical system according to this example includes the image side lens surface (surface number 23) of the biconvex positive lens L28 of the second lens group GR and the object side lens surface of the negative meniscus lens L29 of the second lens group GR (surface number 23). An antireflection film described later is formed on the surface number 24).

  On the image plane I, an image sensor (not shown) made up of a CCD, a CMOS, or the like is disposed.

  The photographic lens OS3 according to the present embodiment focuses from an infinitely distant object to a close object by extending the entire short distance correction method (all groups). That is, the first lens group GF and the second lens group GR are focused on an object at infinity from a short distance object by moving the first lens group GF and the second lens group GR to the object side along the optical axis with different movement amounts.

  In addition, the photographing lens OS3 according to the present example uses J-KZFH1 (optical glass) which is a Kurzflint glass type having an abnormal partial dispersion for the positive lens L14 in the first lens group GF.

  Table 3 below lists specifications of the taking lens OS3 according to the third example of the present application.

(Table 3) Third Example [Surface Data]
Surface number r d nd νd
Object ∞
1) 66.6250 3.0000 1.744429 49.52
* 2) 14.8549 12.6167
3) 46.5757 1.8000 1.437000 95.00
4) 17.3124 1.0000
5) 17.7032 3.5000 1.516800 63.88
* 6) 17.3948 9.1024
7) 45.4326 18.3659 1.612660 44.46
8) -40.4473 d8
9) 8352.8003 1.0000 1.516800 63.88
10) 17.4856 0.1000
11) 13.6265 3.0000 1.497820 82.57
12) -46.7219 4.2830
13) (Aperture S) 2.6600
14) -809.2210 3.6000 1.497820 82.57
15) -9.1262 1.0000 1.755000 52.34
16) -26.7471 0.1000
17) 45.7726 2.0000 1.772500 49.62
18) -57.5916 0.1000
19) 468.8086 1.0000 1.834810 42.73
20) 16.2687 2.0000 1.497820 82.57
21) 32.4966 1.0000
22) 125.2460 7.0000 1.437000 95.00
23) -19.5638 1.3000
24) -16.4334 1.5000 1.772500 49.62
25) -34.1977 (BF)
Image plane ∞

[Aspherical data]
Surface number: 2
κ = 0.1353
A4 = 8.93430E−09
A6 = -8.08589E−09
A8 = 7.45499E-11
A10 = -8.82104E-14
A12 = -0.22473E-15
A14 = 0.72213E-18
A16 = -0.11800E-21
A18 = 0.23404E−24

Surface number: 6
κ = -5.2120
A4 = 1.76375E−04
A6 = -6.64114E-07
A8 = 3.86859E−09
A10 = -7.93950E-12
A12 = 0.00000E−00
A14 = 0.00000E−00
A16 = 0.00000E−00
A18 = 0.00000E−00

[Various data]
f 19.52
FNO 4.12
ω 59.1373
Y 33.000
TL 112.524
BF 26.496

[Variable interval data]
1-POS 2-POS 3-POS
forβ 19.52134 -0.02470 -0.13527
d0 ∞ 779.7990 134.0515
d8 5.00000 4.76200 3.69203
BF 26.49601 26.97977 29.14050

[Lens group data]
Start surface Focal length
GF 1 232.58048
GR 9 54.26369

[Values for each conditional expression]
(1) | fF | /fR=4.284
(2) νdn = 95.00
(3) fR1 / fR = 1.0417
(4) | fR2 | /fR=67.8386
(5) | fR21 | /fR1=169.246
(6) -fR22 / fR1 = 0.5109
(7) X2 / X1 = 1.9786
(8) | (r2-r1) / (r2 + r1) | = 0.008787

FIG. 6 is a diagram illustrating various aberrations of the optical system OS3 according to the third example in the infinite focus state.
From each aberration diagram, it can be seen that the optical system OS3 according to the third example has excellent optical performance with various aberrations corrected well.

(Fourth embodiment)
FIG. 7 is a cross-sectional view illustrating the configuration of the optical system OS4 according to the fourth example in an infinitely focused state.
As shown in FIG. 7, the optical system OS4 according to the present embodiment includes a first lens group GF having a negative refractive power and a second lens group having a positive refractive power in order from the object side along the optical axis. It is composed of GR.

  The first lens group GF includes, in order from the object side along the optical axis, a negative meniscus lens L11 having a convex surface directed toward the object side, a negative meniscus lens L12 having a convex surface directed toward the object side, and a positive meniscus having a convex surface directed toward the object side. It consists of a cemented negative lens with a meniscus lens L13 and a biconvex positive lens L14. The negative meniscus lens L11 is an aspheric lens in which the image side lens surface has an aspheric shape with a curvature that decreases from the center toward the periphery. The positive meniscus lens L13 is an aspheric lens having an aspheric lens surface on the image side.

The second lens group GR includes, in order from the object side along the optical axis, a first partial lens group GR1 having a positive refractive power, an aperture stop S, and a second partial lens group GR2 having a negative refractive power. It is configured.
The first partial lens group GR1 includes, in order from the object side along the optical axis, a negative meniscus lens L21 having a convex surface directed toward the object side, and a biconvex positive lens L22.
The second partial lens group GR2 includes a cemented negative lens GR21 including a positive meniscus lens L23 having a convex surface facing the image side and a negative meniscus lens L24 having a convex surface facing the image side, a biconvex positive lens L25, and an object side. A negative meniscus lens L22 composed of a negative meniscus lens L26 having a convex surface and a biconvex positive lens L27, a positive meniscus lens L28 having a convex surface on the image side, and a negative meniscus lens L29 having a convex surface on the image side It is composed of

  In the optical system according to the present example, an antireflection film described later is formed on the image side lens surface (surface number 7) of the biconvex positive lens L14 of the first lens group GF.

  On the image plane I, an image sensor (not shown) made up of a CCD, a CMOS, or the like is disposed.

  The photographic lens OS4 according to the present embodiment focuses from an object at infinity to a near object by extending the entire short distance correction method (all groups). That is, the first lens group GF and the second lens group GR are focused on an object at infinity from a short distance object by moving the first lens group GF and the second lens group GR to the object side along the optical axis with different movement amounts.

  In addition, the photographing lens OS4 according to the present example uses J-KZFH1 (optical glass) that is a Kurzflint glass type having abnormal partial dispersion for the positive lens L14 in the first lens group GF.

  Table 4 below provides specification values of the photographing lens OS4 according to the fourth example of the present application.

(Table 4) Fourth Example [Surface Data]
Surface number r d nd νd
Object ∞
1) 66.6250 3.0000 1.744429 49.52
* 2) 14.8549 12.6167
3) 42.5449 1.8000 1.437000 95.00
4) 16.0452 3.5000 1.516800 63.88
* 5) 16.3088 9.1024
6) 57.2461 18.3659 1.612660 44.46
7) -41.4712 d7
8) 315.2506 1.0000 1.516800 63.88
9) 23.4072 0.1000
10) 14.7244 4.3987 1.497820 82.57
11) -44.0855 4.0321
12) (Aperture S) 2.6600
13) -104.0205 3.6000 1.497820 82.57
14) -9.2425 1.0000 1.755000 52.34
15) -29.9152 0.1000
16) 120.5513 2.0000 1.772500 49.62
17) -68.1248 0.1000
18) 138.6150 1.0000 1.834810 42.73
19) 17.1959 3.0000 1.497820 82.57
20) -306.4005 1.5000
21) -225.9079 5.5000 1.497820 82.57
22) -18.8197 1.0000
23) -15.6017 1.5000 1.772500 49.62
24) -38.5557 (BF)
Image plane ∞

[Aspherical data]
Surface number: 2
κ = 0.1353
A4 = 8.93430E−09
A6 = -8.08589E−09
A8 = 7.45499E-11
A10 = -8.82104E-14
A12 = -0.22473E-15
A14 = 0.72213E-18
A16 = -0.11800E-21
A18 = 0.23404E−24

Surface number: 5
κ = -4.5672
A4 = 1.88839E−04
A6 = -6.76905E-07
A8 = 3.92896E−09
A10 = -6.97871E-12
A12 = 0.00000E−00
A14 = 0.00000E−00
A16 = 0.00000E−00
A18 = 0.00000E−00

[Various data]
f 19.50
FNO 4.10
ω 58.988
Y 33.000
TL 112.372
BF 26.496

[Variable interval data]
1-POS 2-POS 3-POS
forβ 19.50140 -0.02500 -0.13457
d0 ∞ 770.1533 135.2685
d7 5.00000 4.76493 3.73424
BF 26.49628 26.98498 29.13028

[Lens group data]
Start surface Focal length
GF 1 -305.11204
GR 8 47.45853

[Values for each conditional expression]
(1) | fF | /fR=6.429
(2) νdn = 95.00
(3) fR1 / fR = 0.8677
(4) | fR2 | /fR=4.2103
(5) | fR21 | /fR1=3.5043
(6) -fR22 / fR1 = 2.0498
(7) X2 / X1 = 1.9251
(8) | (r2-r1) / (r2 + r1) | = 0.008148

FIG. 8 is a diagram illustrating various aberrations of the optical system OS4 according to the fourth example in the infinitely focused state.
It can be seen from the respective aberration diagrams that the optical system OS4 according to the fourth example has excellent optical performance with various aberrations corrected well.

(5th Example)
FIG. 9 is a cross-sectional view illustrating the configuration of the optical system OS5 according to the fifth example in the infinitely focused state.
As shown in FIG. 9, the optical system OS5 according to the present embodiment includes, in order from the object side along the optical axis, a first lens group GF having a positive refractive power and a second lens group having a positive refractive power. It is composed of GR.

  The first lens group GF includes, in order from the object side along the optical axis, a negative meniscus lens L11 having a convex surface facing the object side, a negative meniscus lens L12 having a convex surface facing the object side, and a biconvex positive lens L13. And a cemented positive lens with a negative meniscus lens L14 having a convex surface facing the image side. The negative meniscus lens L11 is an aspheric lens in which the image side lens surface has an aspheric shape with a curvature that decreases from the center toward the periphery. The negative meniscus lens L12 is an aspherical lens having an aspherical lens surface on the image side.

The second lens group GR includes, in order from the object side along the optical axis, a first partial lens group GR1 having a positive refractive power, an aperture stop S, and a second partial lens group GR2 having a positive refractive power. It is configured.
The first partial lens group GR1 includes, in order from the object side along the optical axis, a biconcave negative lens L21 and a biconvex positive lens L22.
The second partial lens group GR2 includes a cemented positive lens GR21 including a positive meniscus lens L23 having a convex surface facing the image side and a negative meniscus lens L24 having a convex surface facing the image side, a biconvex positive lens L25, and a biconvex lens. It comprises a cemented negative lens GR22 formed of a positive lens L26 having a shape and a negative lens L27 having a biconcave shape, and a positive meniscus lens L28 having a convex surface facing the image side.

  In the optical system according to the present example, an antireflection film described later is formed on the image side lens surface (surface number 7) of the negative meniscus lens L14 of the first lens group GF.

  On the image plane I, an image sensor (not shown) made up of a CCD, a CMOS, or the like is disposed.

  The photographic lens OS5 according to the present embodiment focuses from an object at infinity to a near object by extending the entire short distance correction method (all groups). That is, the first lens group GF and the second lens group GR are focused on an object at infinity from a short distance object by moving the first lens group GF and the second lens group GR to the object side along the optical axis with different movement amounts.

  In addition, the photographing lens OS5 according to the present example uses J-KZFH1 (optical glass) which is a Kurzflint glass type having an abnormal partial dispersion for the positive lens L13 in the first lens group GF.

  Table 5 below provides specification values of the photographing lens OS5 according to the fifth example of the present application.

(Table 5) Fifth Example [Surface data]
Surface number r d nd νd
Object ∞
1) 66.6250 3.0000 1.744429 49.52
* 2) 14.8549 12.6167
3) 28.5344 3.5000 1.437000 95.00
* 4) 17.8236 9.1024
5) 57.2461 18.3659 1.612660 44.46
6) -30.2739 3.0000 1.816000 46.59
7) -41.1842 d7
8) -115.5888 1.0000 1.516800 63.88
9) 26.5588 0.1000
10) 15.2035 4.3987 1.497820 82.57
11) -61.1646 1.0321
12) (Aperture S) 5.6600
13) -54.9902 3.6000 1.497820 82.57
14) -8.8484 1.0000 1.755000 52.34
15) -18.3426 0.1000
16) 439.0320 2.0000 1.772500 49.62
17) -39.5291 0.1000
18) 59.8387 5.0000 1.497820 82.57
19) -14.9944 1.0000 1.834810 42.73
20) 65.2873 3.0000
21) -42.9769 3.0000 1.497820 82.57
22) -38.5557 (BF)
Image plane ∞

[Aspherical data]
Surface number: 2
κ = 0.1353
A4 = 8.93430E−09
A6 = -8.08589E−09
A8 = 7.45499E-11
A10 = -8.82104E-14
A12 = -0.22473E-15
A14 = 0.72213E-18
A16 = -0.11800E-21
A18 = 0.23404E−24

Surface number: 4
κ = -6.2186
A4 = 1.75637E−04
A6 = -6.43868E-07
A8 = 3.31561E−09
A10 = -5.26124E-12
A12 = 0.00000E−00
A14 = 0.00000E−00
A16 = 0.00000E−00
A18 = 0.00000E−00

[Various data]
f 19.55
FNO 4.23
ω 59.121
Y 33.000
TL 112.076
BF 26.500

[Variable interval data]
1-POS 2-POS 3-POS
forβ 19.55006 -0.02504 -0.13409
d0 ∞ 770.1533 135.2685
d7 5.00000 4.76493 3.73424
BF 26.50006 26.98955 29.12070

[Lens group data]
Start surface Focal length
GF 1 1199.57392
GR 8 47.71946

[Values for each conditional expression]
(1) | fF | /fR=25.138
(2) νdn = 95.00
(3) fR1 / fR = 1.254
(4) | fR2 | /fR=5.162
(5) | fR21 | /fR1=4.010
(6) -fR22 / fR1 = 0.6486
(7) X2 / X1 = 1.934

FIG. 10 is a diagram illustrating various aberrations of the optical system OS5 according to Example 5 in the infinitely focused state.
It can be seen from the respective aberration diagrams that the optical system OS5 according to Example 5 has various aberrations corrected well and has excellent optical performance.

(Sixth embodiment)
FIG. 11 is a cross-sectional view illustrating the configuration of the optical system OS6 according to the sixth example in an infinitely focused state.
As shown in FIG. 11, the optical system OS6 according to the present embodiment includes a first lens group GF having a negative refractive power and a second lens group having a positive refractive power in order from the object side along the optical axis. It is composed of GR.

  The first lens group GF has, in order from the object side along the optical axis, a negative meniscus lens L11 having a convex surface directed toward the object side, a negative meniscus lens L12 having a convex surface directed toward the object side, and a convex surface directed toward the object side. It is composed of a positive meniscus lens L13 and a biconvex positive lens L14. The negative meniscus lens L11 is an aspheric lens in which the image side lens surface has an aspheric shape with a curvature that decreases from the center toward the periphery. The positive meniscus lens L13 is an aspheric lens having an aspheric lens surface on the image side.

The second lens group GR includes, in order from the object side along the optical axis, a first partial lens group GR1 having a positive refractive power, an aperture stop S, and a second partial lens group GR2 having a negative refractive power. It is configured.
The first partial lens group GR1 includes, in order from the object side along the optical axis, a biconvex positive lens L21 and a negative meniscus lens L22 having a convex surface facing the object side.
The second partial lens group GR2 includes a cemented positive lens GR21 including a biconvex positive lens L23 and a negative meniscus lens L24 having a convex surface facing the image side, a biconvex positive lens L25, and a biconcave negative lens L26. And a negative meniscus lens L29 having a convex surface facing the object side, and a negative meniscus lens L29 having a convex surface facing the image side. Yes.

  The optical system according to this example includes the image side lens surface (surface number 2) of the negative meniscus lens L11 of the first lens group GF and the object side lens surface (surface number 3) of the negative meniscus lens L12 of the first lens group GF. ) Is formed with an antireflection film to be described later.

  On the image plane I, an image sensor (not shown) made up of a CCD, a CMOS, or the like is disposed.

  The photographic lens OS6 according to the present embodiment focuses from an infinite object to a near object by extending the entire short distance correction method (all groups). That is, the first lens group GF and the second lens group GR are focused on an object at infinity from a short distance object by moving the first lens group GF and the second lens group GR to the object side along the optical axis with different movement amounts.

  In addition, the photographing lens OS6 according to the present example uses J-KZFH1 (optical glass) that is a Kurzflint glass type having an abnormal partial dispersion for the positive lens L14 in the first lens group GF.

  Table 6 below provides specification values of the photographing lens OS6 according to the sixth example of the present application.

(Table 6) Sixth Example [Surface data]
Surface number r d nd νd
Object ∞
1) 66.6250 3.0000 1.744429 49.52
* 2) 14.8549 12.6167
3) 46.5757 1.8000 1.437000 95.00
4) 17.3124 1.0000
5) 17.7032 3.5000 1.516800 63.88
* 6) 17.3948 9.1024
7) 50.2315 18.3659 1.612660 44.46
8) -57.9228 d8
9) 18.9058 2.5000 1.497820 82.57
10) -67.8944 0.5000
11) 19.6898 1.0000 1.516800 63.88
12) 13.1908 4.2973
13) (Aperture S) 1.6000
14) 266.5360 3.0000 1.497820 82.57
15) -9.7793 1.0000 1.755000 52.34
16) -18.1524 0.1000
17) 757.4227 2.0000 1.497820 82.57
18) -106.9527 1.0000 1.834810 42.73
19) 18.4322 5.5000 1.497820 82.57
20) -44.2830 0.5000
21) -126.0087 3.6000 1.497820 82.57
22) -30.6255 1.4000
23) -20.5159 1.5000 1.772500 49.62
24) -50.9526 (BF)
Image plane ∞

[Aspherical data]
Surface number: 2
κ = 0.1353
A4 = 8.93430E−09
A6 = -8.08589E−09
A8 = 7.45499E-11
A10 = -8.82104E-14
A12 = -0.22473E-15
A14 = 0.72213E-18
A16 = -0.11800E-21
A18 = 0.23404E−24

Surface number: 6
κ = -5.2120
A4 = 1.76375E−04
A6 = -6.64114E-07
A8 = 3.86859E−09
A10 = -7.93950E-12
A12 = 0.00000E−00
A14 = 0.00000E−00
A16 = 0.00000E−00
A18 = 0.00000E−00

[Various data]
f 19.49
FNO 4.17
ω 59.5598
Y 33.000
TL 110.383
BF 26.501

[Variable interval data]
1-POS 2-POS 3-POS
forβ 19.48942 -0.02502 -0.13541
d0 ∞ 770.1533 135.2685
d8 5.00000 4.76493 3.73424
BF 26.50056 26.99739 29.20206

[Lens group data]
Start surface Focal length
GF 1 -101.17826
GR 9 42.53115

[Values for each conditional expression]
(1) | fF | /fR=2.379
(2) νdn = 95.00
(3) fR1 / fR = 1.0362
(4) | fR2 | /fR=38.740
(5) | fR21 | /fR1=1.2834
(6) -fR22 / fR1 = 2.6151
(7) X2 / X1 = 1.882
(8) | (r2-r1) / (r2 + r1) | = 0.008787

FIG. 12 is a diagram illustrating various aberrations of the optical system OS6 according to Example 6 in the infinitely focused state.
It can be seen from the respective aberration diagrams that the optical system OS6 according to the sixth example has excellent optical performance with various aberrations corrected well.

  Here, an antireflection film (also referred to as a multilayer broadband antireflection film) used in the optical system according to the embodiment 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 this embodiment 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. 20 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 this embodiment shown in FIGS. 17 to 19 are compared with the spectral characteristics of the conventional example shown in FIGS. 20 and 21, the antireflection film according to this embodiment is compared. It can be seen that has a lower reflectivity at any angle of incidence and a lower reflectivity over a wider band.

  Next, application examples of the above-described antireflection film of the present application (antireflection film of Table 7) and its modified examples (antireflection film of Table 8) to the optical systems according to the above embodiments will be described.

In the optical system according to the first example, as shown in Table 1,
The refractive index of the negative meniscus lens L11 of the first lens group GF is 1.744429,
The refractive index of the negative meniscus lens L12 of the first lens group GF is 1.437000.
Therefore, an antireflection film corresponding to a substrate having a refractive index of 1.74 shown in Table 7 is used on the image side lens surface of the negative meniscus lens L11.
An antireflection film corresponding to a substrate having a refractive index of 1.46 shown in Table 8 is used on the object side lens surface of the negative meniscus lens L12.
Thereby, the optical system according to the first example can reduce the reflected light from each lens surface using the antireflection film, and can reduce ghost and flare.

In the optical system according to the second example, as shown in Table 2,
The refractive index of the positive meniscus lens L27 of the second lens group GR is 1.497820,
The refractive index of the biconvex positive lens L28 of the second lens group GR is 1.437000.
Therefore, an antireflection film corresponding to a substrate having a refractive index of 1.52 shown in Table 8 is used on the image side lens surface of the positive meniscus lens L27.
An antireflection film corresponding to a substrate having a refractive index of 1.46 shown in Table 8 is used on the object side lens surface of the biconvex positive lens L28.
Thereby, the optical system according to the second example can reduce the reflected light from each lens surface using the antireflection film, and can reduce ghost and flare.

In the optical system according to the third example, as shown in Table 3,
The refractive index of the biconvex positive lens L28 of the second lens group GR is 1.437000,
The refractive index of the negative meniscus lens L29 of the second lens group GR is 1.772500.
Therefore, an antireflection film corresponding to a substrate having a refractive index of 1.46 shown in Table 8 is used on the image side lens surface of the biconvex positive lens L28.
An antireflection film corresponding to a substrate having a refractive index of 1.74 shown in Table 7 is used on the object side lens surface of the negative meniscus lens L29.
Thereby, the optical system according to the third example can reduce the reflected light from each lens surface using the antireflection film, and can reduce ghost and flare.

In the optical system according to the fourth example, as shown in Table 4,
The refractive index of the biconvex positive lens L14 of the first lens group GF is 1.612660.
Therefore, an antireflection film corresponding to a substrate having a refractive index of 1.62 shown in Table 7 is used on the image side lens surface of the biconvex positive lens L14.
Thereby, the optical system according to the fourth example can reduce reflected light from each lens surface using the antireflection film, and can reduce ghost and flare.

In the optical system according to Example 5, as shown in Table 5,
The refractive index of the negative meniscus lens L14 in the first lens group GF is 1.816000.
Therefore, an antireflection film corresponding to a substrate having a refractive index of 1.85 shown in Table 7 is used on the image side lens surface of the negative meniscus lens L14.
Thereby, the optical system according to the fifth example can reduce the reflected light from each lens surface using the antireflection film, and can reduce ghost and flare.

In the optical system according to the sixth example, as shown in Table 6,
The refractive index of the negative meniscus lens L11 of the first lens group GF is 1.744429,
The refractive index of the negative meniscus lens L12 of the first lens group GF is 1.437000.
Therefore, an antireflection film corresponding to a substrate having a refractive index of 1.74 shown in Table 7 is used on the image side lens surface of the negative meniscus lens L11.
An antireflection film corresponding to a substrate having a refractive index of 1.46 shown in Table 8 is used on the object side lens surface of the negative meniscus lens L12.
Thereby, the optical system according to the sixth example can reduce the reflected light from each lens surface using the antireflection film, and can reduce ghost and flare.

As described above, according to each of the above embodiments, an optical system having a large angle of view, a small size, and high optical performance can be realized. In particular, an optical system that can satisfactorily correct coma, curvature of field, astigmatism, and distortion can be realized. Moreover, ghost and flare can be further reduced. The contents described below can be appropriately adopted as long as the optical performance is not impaired.
In the above embodiment, a configuration having two groups is shown, but the present invention can be applied to other group configurations such as having three groups and four groups. Further, a configuration in which a lens or a lens group is added to the most object side, or a configuration in which a lens or a lens group is added to the most image side may be used.

  The optical system of the present application focuses from an object at infinity to a near object by extending the entire short distance correction method (all groups). The focusing lens group may be moved in the optical axis direction. The focusing lens group can be applied to autofocus, and is also suitable for driving by an autofocus motor such as an ultrasonic motor. The lens group refers to a portion having at least one lens separated by an air interval.

  Further, in the optical system of the present application, a blur detection system for detecting blur of the optical system due to camera shake or the like and a driving unit are combined, and one lens group or partial lens group has a component in a direction perpendicular to the optical axis. It is possible to function as an anti-vibration lens that corrects image blur caused by camera shake by moving in such a manner as described above or by rotating (swinging) in the in-plane direction including the optical axis. In the above embodiment, it is preferable that the lens group in the vicinity of the aperture stop is the 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 facilitated, and deterioration of optical performance due to errors in lens processing and assembly adjustment can be prevented. Further, even when the image plane is deviated, it is preferable because there is little deterioration in drawing performance. When the lens surface is aspheric, any of aspherical surfaces by grinding, a glass mold aspherical surface formed by molding glass into an aspherical surface, or a composite aspherical surface formed by forming resin on the glass surface into an aspherical surface An aspherical surface may be used. The lens surface may be a diffractive surface, and the lens may be a gradient index lens (GRIN lens) or a plastic lens.

  In addition, the aperture stop of the optical system of the present application is preferably arranged in the vicinity of the approximate center of the entire system, but 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 contrast optical performance can be achieved.

  Next, an imaging apparatus provided with the optical system of the present application will be described.

  FIG. 13 is a diagram illustrating a configuration of a camera including the optical system of the present application. As shown in FIG. 13, the camera 1 is a so-called mirrorless camera of an interchangeable lens provided with the optical system OS <b> 1 according to the first embodiment as the photographing lens 2. In the camera 1, light from an object (not shown) (not shown) is collected by the photographing lens 2 and forms a subject image on the imaging surface of the imaging unit 3 via an optical low-pass filter (not shown). Then, the subject image is photoelectrically converted by the photoelectric conversion element provided in the imaging unit 3 to generate an image of the subject. This image is displayed on the electronic viewfinder 4 provided in the camera 1. Thus, the photographer can observe the subject through the electronic viewfinder 4.

  When a release button (not shown) is pressed by the photographer, an image photoelectrically converted by the imaging unit 3 is stored in a memory (not shown). In this way, the photographer can shoot the subject with the camera 1.

  Here, the optical system OS1 according to the first embodiment mounted as the photographing lens 2 on the camera 1 is an optical system having a large angle of view, a small size, and high optical performance. Therefore, the camera 1 having high optical performance can be realized.

  In addition, even if it comprises the camera which mounts optical system OS2-OS6 which concerns on the said 2nd Example-6th Example as the taking lens 2, the same effect as the said camera 1 can be show | played. In this embodiment, an example of a mirrorless camera has been described. However, the photographic lens according to each of the above embodiments is mounted on a single-lens reflex camera that has a quick return mirror in the camera body and observes a subject with a finder optical system. Even in this case, the same effect as the camera 1 can be obtained.

  Next, a method for manufacturing the optical system of the present application will be described. FIG. 14 is a diagram showing an outline of the manufacturing method of the optical system of the present application.

The optical system manufacturing method of the present application is a manufacturing method of an optical system having a first lens group and a second lens group having a positive refractive power in order from the object side along the optical axis. As shown, the following steps S1 to S5 are included.
Step S1: The first lens unit is configured to have two negative lens components in order from the object side along the optical axis, and to have a positive lens component closer to the image side than the two negative lens components.
Step S2: The second lens group is configured to have a first partial lens group having a positive lens and a negative lens and having a positive refractive power as a whole, and a second partial lens group.
Step S3: The second partial lens group includes a cemented lens, a cemented negative lens having a convex surface directed toward the object side on the image side of the cemented lens, and a positive lens on the image side of the cemented negative lens. Or it comprises so that it may have another junction lens which consists of junction of a positive lens and a negative lens.
Step S4: When focusing from an object at infinity to an object at a short distance, the air gap between the first lens group and the second lens group is changed.
Step S5: The optical system is configured to satisfy the following conditional expression (1).
(1) 1.0 <| fF | / fR <50.0
However,
fF: focal length of the first lens group fR: focal length of the second lens group

  According to such an optical system manufacturing method of the present application, an optical system having a large angle of view, a small size, and high optical performance can be manufactured.

OS1 to OS6 Optical system GF Front group GR Rear group S Aperture stop I Image plane 1 Camera 2 Shooting lens 3 Shooting unit 4 Electronic viewfinder 101 Antireflection film 101a First layer 101b Second layer 101c Third layer 101d Fourth layer 101e 5th layer 101f 6th layer 101g 7th layer 102 Optical member

Claims (27)

In order from the object side along the optical axis, the first lens group and a second lens group having a positive refractive power,
The first lens group has two negative lens components in order from the object side along the optical axis, and has a positive lens component closer to the image side than the two negative lens components,
The second lens group includes a first partial lens group having a positive lens and a negative lens and having a positive refractive power as a whole, and a second partial lens group,
The second partial lens group has a cemented lens, has a cemented negative lens with a convex surface facing the object side, closer to the image side than the cemented lens, and a positive lens or a positive lens on the image side of the cemented negative lens. Having another cemented lens consisting of a cemented lens and negative lens,
When focusing from an object at infinity to an object at a short distance, the air interval between the first lens group and the second lens group changes,
An optical system that satisfies the following conditional expression.
1.0 <| fF | / fR <50.0
However,
fF: focal length of the first lens group fR: focal length of the second lens group The optical system according to claim 1, wherein the first lens group includes at least one negative lens that satisfies the following conditional expression.
65 <νdn
However,
νdn: Abbe number with respect to d-line (wavelength λ = 587.6 nm) The optical system according to claim 1, wherein the following conditional expression is satisfied.
0.2 <fR1 / fR <5.0
However,
fR1: focal length of the first lens group fR: focal length of the second lens group The optical system according to claim 1, wherein the following conditional expression is satisfied.
0.2 <| fR2 | / fR <80.0
However,
fR2: focal length of the second lens group fR: focal length of the second lens group The optical system according to claim 1, wherein the following conditional expression is satisfied.
0.3 <| fR21 | / fR1 <200.0
However,
fR21: focal length of the cemented lens in the second partial lens group fR1: focal length of the first partial lens group The optical system according to claim 1, wherein the following conditional expression is satisfied.
0.3 <−fR22 / fR1 <5.0
However,
fR22: focal length of the cemented negative lens in the second partial lens group fR1: focal length of the first partial lens group   The optical system according to any one of claims 1 to 6, wherein the first lens group and the second lens group are moved from the infinity object to the near distance object by moving the first lens group and the second lens group toward the object side with different movement amounts. system. The optical system according to claim 1, wherein the following conditional expression is satisfied.
1.0 <X2 / X1 <3.5
However,
X1: Amount of movement of the first lens group when focusing from an object at infinity to a short distance object X2: Amount of movement of the second lens group when focusing from an object at infinity to a short distance object   9. The optical system according to claim 1, wherein the first lens group has at least one aspheric surface whose curvature decreases from the center toward the periphery. 10. The optical system according to claim 1, wherein the first lens group includes a meniscus aspheric lens that has a convex surface directed toward the object side and satisfies the following conditional expression. 10.
0.000 <| (r2-r1) / (r2 + r1) | <0.100
However,
r1: radius of curvature of the object-side lens surface of the aspheric lens r2: radius of curvature of the image-side lens surface of the aspheric lens   The optical system according to claim 1, wherein the first lens group has at least two aspheric surfaces.   The optical system according to any one of claims 1 to 11, wherein, among the lens components constituting the optical system, at least one positive lens uses a Kurzflint glass material having anomalous partial dispersion.   An antireflection film is provided on at least one of the optical surfaces of the first lens group and the second lens group, and the antireflection film includes at least one layer formed using a wet process. The optical system according to any one of claims 1 to 12. The antireflection film is a multilayer film,
The optical system according to claim 13, wherein the layer formed by using the wet process is a layer on a most surface side among layers constituting the multilayer film.   The optical system according to claim 13 or 14, wherein nd is 1.30 or less, where nd is a refractive index with respect to d-line (wavelength λ = 587.6 nm) of a layer formed by the wet process. Having an aperture stop,
The optical system according to claim 13, wherein the optical surface provided with the antireflection film is a concave lens surface when viewed from the aperture stop.   The optical system according to claim 16, wherein the concave lens surface viewed from the aperture stop is an object side lens surface of a lens in the first lens group.   The optical system according to claim 16, wherein the concave lens surface viewed from the aperture stop is an image-side lens surface of a lens in the first lens group.   The optical system according to claim 16, wherein the concave lens surface viewed from the aperture stop is an object side lens surface of a lens in the second lens group.   The optical system according to claim 16, wherein the concave lens surface viewed from the aperture stop is an image side lens surface of a lens in the second lens group.   The optical system according to any one of claims 13 to 15, wherein the optical surface provided with the antireflection film is a concave lens surface when viewed from the object side.   The optical system according to claim 21, wherein the concave lens surface as viewed from the object side is an image side lens surface of a lens in the first lens group.   The optical system according to claim 13, wherein the optical surface provided with the antireflection film is a concave lens surface when viewed from the image side.   The optical system according to claim 23, wherein the lens surface having a concave shape when viewed from the image side is an object side lens surface of a lens in the second lens group.   The optical system according to claim 23, wherein the concave lens surface as viewed from the image side is an image side lens surface of a lens in the second lens group.   An imaging apparatus comprising the optical system according to any one of claims 1 to 25. A method for manufacturing an optical system having a first lens group and a second lens group having a positive refractive power in order from the object side along the optical axis,
The first lens group has two negative lens components in order from the object side along the optical axis, and has a positive lens component closer to the image side than the two negative lens components,
The second lens group is configured to have a first partial lens group having a positive lens and a negative lens and having a positive refractive power as a whole, and a second partial lens group,
The second partial lens group includes a cemented lens, a cemented negative lens having a convex surface facing the object side, closer to the image side than the cemented lens, and a positive lens or a positive lens on the image side of the cemented negative lens. It is configured to have another cemented lens composed of a lens and a negative lens.
When focusing from an object at infinity to an object at a short distance, the air gap between the first lens group and the second lens group is changed,
A method of manufacturing an optical system configured to satisfy the following conditional expression.
1.0 <| fF | / fR <50.0
However,
fF: focal length of the first lens group fR: focal length of the second lens group

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