JP2019113575A - Optical system, optical device, and method of manufacturing optical system - Google Patents

Abstract

To provide an optical system which is suitable for mirrorless cameras and offers reduced weight of a focusing group, minimized variations in aberrations when focused, and good optical performance, and to provide an optical device having the same and method of manufacturing such optical system.SOLUTION: An optical system comprises a front group GF having positive refractive power, an aperture stop S, and a rear group GR having positive refractive power arranged in order from the object side. The front group GF comprises, in order from the object side, a positive lens group GFA having positive refractive power and a front focusing group GFF having positive refractive power, while the rear group GR comprises, in order from the object side, a rear focusing group GRF having positive refractive power and a negative lens group GRB having negative refractive power. The front focusing group GFF and the rear focusing group GRF move along an optical axis while focusing. A lens L1 located on the most object side has negative refractive power.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an optical system, an optical apparatus, and a method of manufacturing an optical system.

  Conventionally, as a focusing method of an optical system, a rear focusing method of moving a lens group on the image side of the optical system and an inner focusing method of moving an intermediate lens group of the optical system are known (for example, Patent Document 1) reference.). However, in the case of a large aperture lens having a small open F-number and which is likely to cause various aberrations, there is a problem that the aberration fluctuation due to the movement of the lens unit is large.

JP, 2014-123018, A

The first aspect of the present invention is
From the object side, it consists of a front group having positive refractive power, an aperture stop, and a rear group having positive refractive power,
The front group includes, in order from the object side, a positive lens group having positive refractive power and a front focusing group having positive refractive power.
The rear group includes, in order from the object side, a rear focusing group having positive refractive power and a negative lens group having negative refractive power.
At the time of focusing, the front focusing group and the rear focusing group move in the optical axis direction,
A lens located closest to the object side provides an optical system having negative refractive power.

The second aspect of the present invention is
A method of manufacturing an optical system comprising, in order from an object side, a front group having positive refractive power, an aperture stop, and a rear group having positive refractive power,
The front group includes, in order from the object side, a positive lens group having positive refractive power and a front focusing group having positive refractive power.
The rear group includes, in order from the object side, a rear focusing group having positive refractive power and a negative lens group having negative refractive power.
At the time of focusing, the front focusing group and the rear focusing group are moved in the optical axis direction,
Provided is a method of manufacturing an optical system in which a lens located closest to the object side has negative refractive power.

It is sectional drawing of the optical system which concerns on 1st Example. FIG. 5 shows various aberrations of the optical system according to the first example. It is sectional drawing of the optical system concerning 2nd Example. FIG. 7 shows various aberrations of the optical system according to the second example. It is sectional drawing of the optical system which concerns on 3rd Example. FIG. 7 shows various aberrations of the optical system according to the third example. It is sectional drawing of the optical system which concerns on 4th Example. FIG. 7 shows various aberrations of the optical system according to the fourth example. It is sectional drawing of the optical system which concerns on 5th Example. FIG. 7 shows various aberrations of the optical system according to the fifth example. It is sectional drawing of the optical system which concerns on 6th Example. FIG. 16 shows various aberrations of the optical system according to the sixth example. It is sectional drawing of the optical system which concerns on 7th Example. FIG. 21 shows various aberrations of the optical system according to the seventh example. It is sectional drawing of the optical system which concerns on 8th Example. FIG. 21 shows various aberrations of the optical system according to the eighth example. It is sectional drawing of the optical system concerning 9th Example. FIG. 21 shows various aberrations of the optical system according to the ninth example. It is a figure which shows the structure of the camera provided with the optical system. It is a figure which shows the outline of the manufacturing method of an optical system.

Hereinafter, an optical system, an optical apparatus, and a method of manufacturing the optical system according to the embodiment will be described.
The optical system of the present embodiment comprises, in order from the object side, a front group having positive refractive power, an aperture stop, and a rear group having positive refractive power, and the front group is positive in order from the object side. And a rear lens group having a positive refractive power and a front focusing group having a positive refractive power, and the rear lens group includes, in order from the object side, a rear focusing group having a positive refractive power, and a negative lens group. The front focusing group and the rear focusing group move in the optical axis direction at the time of focusing at least part of an object at infinity to a near object, with a negative lens group having a refractive power. The lens located on the object side has negative refractive power.

In the conventional retrofocus type wide-angle lens, when the lens unit positioned on the image side of the aperture stop is used as the focusing unit, the focusing unit has to be largely moved to the object side to suppress the image plane fluctuation.
The optical system of this embodiment is configured to move the object side of the aperture stop on the object side and the positive lens group on the image side of the aperture stop as the focusing group to perform focusing. It is possible to suppress fluctuations of various aberrations at the time of focusing, and in particular to correct spherical aberration and field curvature aberration well. Further, by setting the number of focusing groups to two, it is possible to reduce the weight of each focusing group and to speed up the focusing operation.

Further, in the optical system of the present embodiment, the refractive power of the entire front group is positive while the lens located closest to the object side has a negative refractive power. As a result, it is possible to reduce the diameter of the lens group closest to the object while securing a large angle of view, and it is also possible to shorten the total length while securing an appropriate back focus.
With the above-described configuration, it is possible to realize an optical system having good optical performance, which is suitable for a mirrorless camera, suppresses the fluctuation of various aberrations at the time of focusing while reducing the weight of the focusing group.

  Moreover, as for the optical system of this embodiment, it is desirable that the position of the said aperture stop is fixed at the time of focusing. Thereby, various aberrations such as spherical aberration and curvature of field aberration can be corrected well, and fluctuations of the various aberrations at the time of focusing can be suppressed.

Moreover, as for the optical system of this embodiment, it is desirable to satisfy the following conditional expressions (1).
(1) 0.010 <fRF / fFF <0.900
However,
fFF: focal length of the front focusing group fRF: focal length of the rear focusing group

  The above conditional expression (1) describes the appropriate distribution of refractive power of the two focusing groups by the ratio of focal lengths.

  When the corresponding value of the conditional expression (1) of the optical system of the present embodiment falls below the lower limit value, the refractive power of the front focusing group becomes too small. For this reason, the front focusing group has an excessively large stroke at the time of focusing and interferes with the positive lens group. Alternatively, field curvature aberration can not be corrected sufficiently. In order to secure the effect of the present embodiment, it is more preferable to set the lower limit value of the conditional expression (1) to 0.015, further 0.020, and 0.024.

  On the other hand, when the corresponding value of the conditional expression (1) of the optical system of the present embodiment exceeds the upper limit, the refractive power of the rear focusing group becomes too large. For this reason, it becomes difficult to correct spherical aberration and the like. In order to secure the effect of the present embodiment, it is more preferable to set the upper limit value of conditional expression (1) to 0.700, further 0.500, 0.400, 0.300, and 0.250.

Moreover, as for the optical system of this embodiment, it is desirable to satisfy the following conditional expressions (2).
(2) 0.400 <Bf / f <2.000
However,
Bf: The distance from the image-side lens surface of the lens closest to the image side when focusing on an infinite distance object to the image plane, ie back focus f: focal length of the optical system when focusing on an infinite distance object

  The conditional expression (2) is a conditional expression which defines an appropriate range of the back focus and the focal length of the entire optical system. When Bf in the conditional expression (2) is a parallel flat plate such as a filter in the optical system, a value calculated by replacing this with air is used. The same applies to ST, TL and Bf in conditional expressions (3) and (9) described later.

  When the corresponding value of the conditional expression (2) of the optical system of the present embodiment exceeds the upper limit value, the back focus becomes large, and although the telecentricity is maintained, the entire optical system becomes large. In addition, it is difficult to correct distortion and the like if it is attempted to suppress an increase in the diameter of the front group due to the increase in size. In order to secure the effect of the present embodiment, the upper limit value of conditional expression (2) is set to 1.900, further 1.800, 1.700, 1.600, 1.500, 1.400, and 1. More preferably, 300, 1.200, and 1.100.

  On the other hand, when the corresponding value of the conditional expression (2) of the optical system of the present embodiment falls below the lower limit value, the position of the exit pupil is displaced to the image side. For this reason, the shading becomes remarkable, and in particular the resolution around the screen is lowered. In order to secure the effect of the present embodiment, it is more preferable to set the lower limit value of conditional expression (2) to 0.450, further 0.500, 0.550, 0.600 and 0.700.

Moreover, as for the optical system of this embodiment, it is desirable to satisfy the following conditional expressions (3).
(3) 0.100 <ST / TL <0.600
However,
ST: Distance TL from the aperture stop to the image plane when focusing on an infinite object: Distance from the object-side lens surface of the lens closest to the object side to the image surface when focusing on an infinite object, ie, an optical system Total length of

  The conditional expression (3) defines the appropriate range of the distance from the aperture stop to the image plane and the total length of the optical system, and estimates the position of the exit pupil from the position of the aperture stop in the optical system. .

  When the corresponding value of the conditional expression (3) of the optical system of the present embodiment exceeds the upper limit value, although the telecentricity is maintained, the total length of the optical system becomes large and downsizing can not be achieved. If the diameter of the front group is to be reduced in the state where the overall length of the optical system is increased, it becomes difficult to sufficiently correct distortion and the like. In order to secure the effect of the present embodiment, the upper limit value of the conditional expression (3) should be 0.570, 0.550, 0.530, 0.500, 0.480, and 0.460. Is more preferred.

  On the other hand, when the corresponding value of the conditional expression (3) of the optical system of the present embodiment falls below the lower limit value, the aperture stop is disposed closer to the object than the appropriate position. For this reason, the light beam can not be blocked equally by the aperture stop, distortion occurs in the point image when the aperture is narrowed, and peripheral light reduction is deteriorated. Further, it also becomes difficult to correct magnification chromatic aberration. In order to secure the effect of the present embodiment, the lower limit value of conditional expression (3) is 0.120, 0.140, 0.170, 0.200, 0.250, 0.300, 0.1. It is more preferable to set it as 350.

Moreover, as for the optical system of this embodiment, it is desirable to satisfy the following conditional expressions (4).
(4) 0.200 <βRF / βFF <1.100
However,
βFF: Magnification of the front focusing group at the time of infinity focusing on the object βRF: Magnification of the rear focusing group at the infinity of objects focusing

  The conditional expression (4) is a conditional expression which defines an appropriate magnification ratio of the front focusing group and the rear focusing group.

  When the corresponding value of the conditional expression (4) of the optical system of the present embodiment exceeds the upper limit value, the refractive power of the rear focusing group becomes too large, and spherical aberration, coma aberration and the like can be sufficiently corrected. It will be gone. In order to secure the effect of the present embodiment, the upper limit value of conditional expression (4) is set to 1.000, 0.950, 0.900, 0.850, 0.800, 0.750, 0.1, and so on. It is more preferable to set it as 700.

  On the other hand, if the corresponding value of the conditional expression (4) of the optical system of the present embodiment falls below the lower limit value, the refractive power of the rear focusing group becomes too small, and the magnification necessary for focusing can not be obtained. For this reason, sufficient performance can not be secured at the time of focusing on an object at close distance, and the curvature of field aberration is not sufficiently corrected. In order to secure the effect of the present embodiment, the lower limit value of conditional expression (4) may be 0.220, 0.240, 0.260, 0.280, 0.300, 0.320, 0.1. It is more preferable to set it as 350 and 0.370.

  Further, in the optical system of the present embodiment, it is desirable that the position of the positive lens unit be fixed at the time of focusing. As a result, it is possible to obtain a good image with a small change in image magnification at the time of focusing, and it is possible to simplify the mechanical configuration of the optical system of the present embodiment.

  Further, in the optical system according to the present embodiment, it is desirable that the position of the lens unit located closest to the image side at the time of focusing be fixed. As a result, it is possible to ensure a back focus of an appropriate size and a sufficient exit pupil distance, and it is possible to simplify the mechanical configuration of the optical system of the present embodiment.

  In the optical system according to this embodiment, it is preferable that the front focusing group have at least one positive lens and at least one negative lens. Thereby, various aberrations such as lateral chromatic aberration can be corrected well.

  Further, in the optical system of the present embodiment, it is desirable that the rear side focusing group has at least one positive lens and at least one negative lens. Thereby, various aberrations such as lateral chromatic aberration can be corrected well.

Moreover, as for the optical system of this embodiment, it is desirable to satisfy the following conditional expressions (5).
(5) 0.300 <fF / fR <1.300
However,
fF: focal length of the front group when focusing on an infinite object fR: focal length of the rear group when focusing on an infinite object

  The conditional expression (5) is a conditional expression which defines an appropriate distribution of refractive power between the front group and the rear group.

  When the corresponding value of the conditional expression (5) of the optical system of the present embodiment exceeds the upper limit, the refractive power of the rear group becomes too large, and it becomes impossible to sufficiently correct spherical aberration, coma and the like. . In order to secure the effect of the present embodiment, the upper limit value of conditional expression (5) is set to 1.200, 1.150, 1.100, 1.050, 1.000, 0.950, 0.1. It is more preferable to set it as 900, 0.850, and 0.800.

  On the other hand, when the corresponding value of the conditional expression (5) of the optical system of the present embodiment falls below the lower limit, the refractive power of the rear group becomes too small to obtain the magnification necessary for focusing. For this reason, sufficient performance can not be secured at the time of focusing on an object at close distance, and the curvature of field aberration is not sufficiently corrected. In order to secure the effect of the present embodiment, the lower limit value of the conditional expression (5) may be 0.330, 0.350, 0.380, 0.400, 0.430, 0.450, 0.1. It is more preferable to set it to 480, 0.500.

  Further, in the optical system of the present embodiment, it is desirable that the front focusing group move to the object side at the time of focusing. Thereby, various aberrations such as spherical aberration and curvature of field aberration can be corrected well, and fluctuations of the various aberrations at the time of focusing can be suppressed.

  In the optical system according to the present embodiment, it is desirable that the rear focusing group move to the object side at the time of focusing. Thereby, various aberrations such as spherical aberration and curvature of field aberration can be corrected well, and fluctuations of the various aberrations at the time of focusing can be suppressed.

Moreover, as for the optical system of this embodiment, it is desirable to satisfy the following conditional expressions (6).
(6) 0.010 <fFA / fFF <0.750
However,
fFA: focal length of the positive lens group fFF: focal length of the front focusing group

  The conditional expression (6) defines the focal length of the front focusing group and the focal length of the positive lens group.

  If the corresponding value of the conditional expression (6) of the optical system of the present embodiment exceeds the upper limit value, the refractive power of the front focusing group becomes too large, which makes it difficult to correct lateral chromatic aberration and the like. In order to secure the effect of the present embodiment, the upper limit value of conditional expression (6) is set to 0.700, further 0.650, 0.600, 0.550, 0.500, 0.450, 0.1. It is more preferable to set it as 400, 0.350, 0.300, and 0.250.

  On the other hand, if the corresponding value of the conditional expression (6) of the optical system of the present embodiment falls below the lower limit value, the refractive power of the front focusing group becomes too small, making it difficult to correct field curvature aberration etc. I will. In order to secure the effect of the present embodiment, the lower limit value of the conditional expression (6) is set to 0.015, further 0.020, 0.025, 0.030, 0.035, 0.040, 0.1. It is more preferable to set it as 045, 0.050, 0.060, 0.070, and 0.080.

Moreover, as for the optical system of this embodiment, it is desirable to satisfy the following conditional expressions (7).
(7) 0.010 <f / fFF <0.300
However,
f: Focal length of the optical system when focusing on an infinite object fFF: Focal length of the front focusing group

  The conditional expression (7) defines the focal length of the front focusing group and the focal length of the entire optical system.

  If the corresponding value of the conditional expression (7) of the optical system of the present embodiment exceeds the upper limit value, the refractive power of the front focusing group becomes too large, which makes it difficult to correct lateral chromatic aberration and the like. In order to secure the effect of the present embodiment, the upper limit value of conditional expression (7) may be 0.280, 0.250, 0.230, 0.200, 0.180, 0.160, 0. It is more preferable to set it as 140, 0.120, 0.100, and 0.080.

  On the other hand, if the corresponding value of the conditional expression (7) of the optical system of the present embodiment falls below the lower limit value, the refractive power of the front focusing group becomes too small, making it difficult to correct field curvature aberration etc. I will. In order to secure the effect of the present embodiment, the lower limit value of conditional expression (7) is set to 0.012, further 0.014, 0.016, 0.017, 0.020, 0.025, 0.1. More preferably, 030 and 0.035.

Moreover, as for the optical system of this embodiment, it is desirable to satisfy the following conditional expressions (8).
(8) 0.300 <f / fRF <1.100
However,
f: Focal length of the optical system when focusing on an infinite object fRF: Focal length of the back focusing group

  The conditional expression (8) defines the focal length of the rear focusing group and the focal length of the entire optical system.

  When the corresponding value of the conditional expression (8) of the optical system of the present embodiment exceeds the upper limit value, the refractive power of the rear focusing group becomes too small. For this reason, the stroke of the rear side focusing group at the time of focusing becomes large, and the optical system becomes large. Alternatively, field curvature aberration can not be corrected sufficiently. In order to secure the effect of the present embodiment, it is more preferable to set the upper limit value of conditional expression (8) to 1.050, more preferably 1.000, 0.950, 0.900, and 0.850.

  On the other hand, if the corresponding value of the conditional expression (8) of the optical system of the present embodiment falls below the lower limit value, the refractive power of the rear focusing group becomes too large, which makes it difficult to correct spherical aberration etc. . In order to secure the effect of the present embodiment, the lower limit value of conditional expression (8) should be set to 0.350, further 0.400, 0.450, 0.500, 0.550 and 0.600. Is more preferred.

Moreover, as for the optical system of this embodiment, it is desirable to satisfy the following conditional expressions (9).
(9) 0.800 <TL / (Fno · Bf) <6.000
However,
TL: Distance from the object-side lens surface of the lens closest to the object side to the image plane when focusing on an infinite distance object Fno: Open f-number of the optical system Bf: Most on the image side when focusing on an infinite distance object Distance from the image-side lens surface of the lens to the image plane

  The conditional expression (9) is a conditional expression showing an optimal balance between the total length of the optical system and the back focus in order to make the optical system a bright wide-angle lens.

  When the corresponding value of the conditional expression (9) of the optical system of the present embodiment exceeds the upper limit value, the total length of the optical system increases and the optical system becomes large. Alternatively, since the F number decreases, it becomes difficult to correct spherical aberration. In order to secure the effect of the present embodiment, the upper limit value of conditional expression (9) is set to 5.500, further 5.000, 4.500, 4.300, 4.100, 4.000, 3. It is more preferable to set it as 800 and 3.600.

  On the other hand, when the corresponding value of the conditional expression (9) of the optical system of the present embodiment falls below the lower limit value, the total length of the optical system becomes too small, and it becomes difficult to correct coma and the like. In order to secure the effect of the present embodiment, the lower limit value of conditional expression (9) is 0.900, and further 1.000, 1.100, 1.300, 1.500, 1.800, 2. It is more preferable to set it as 000, 2.200, 2.500.

Moreover, as for the optical system of this embodiment, it is desirable to satisfy the following conditional expressions (10).
(10) | Ainf-Amod | / f <0.070
However,
Ainf: Half angle of view of the optical system when focusing on an infinite object (unit: "°")
Amod: Half angle of view of the optical system when the closest object is in focus (the unit is "°")

  The conditional expression (10) is a conditional expression that defines the ratio of the incident light beam angle at the time of focusing on an infinite distance object to the incident light beam angle at the time of focusing on the nearest object. It is.

  When the corresponding value of the conditional expression (10) of the optical system of the present embodiment exceeds the upper limit value, the image magnification changes during focusing, which makes it impossible to obtain a good image. In order to secure the effect of the present embodiment, the upper limit value of conditional expression (10) should be set to 0.065, further 0.060, 0.055, 0.050, 0.045, 0.040. Is more preferred.

In the optical system of the present embodiment, the front focusing group is composed of one positive lens and one negative lens, and it is preferable that the following conditional expression (11) be satisfied.
(11) 30.00 <νFFp-νFFn <75.00
However,
FFFFp: Abbe number FFFFn for the d-line (λ = 587.6 nm) of the positive lens in the front focusing group: Abbe number for the d-line (λ = 587.6 nm) of the negative lens in the front focusing group

  The conditional expression (11) is a relational expression of dispersion of the positive lens and the negative lens included in the front focusing group. By satisfying the conditional expression (11), the optical system of the present embodiment can correct chromatic aberration well.

  In order to secure the effect of the present embodiment, it is more preferable to set the upper limit value of conditional expression (11) to 70.00, further 65.00, 61.00, 58.00, 56.00.

  In order to secure the effect of the present embodiment, it is more preferable to set the lower limit value of the conditional expression (11) to 35.00, further 40.00, 45.00, 50.00.

Moreover, as for the optical system of this embodiment, it is desirable to satisfy the following conditional expressions (12).
(12) -1.000 <(FFr2 + FFr1) / (FFr2-FFr1) <2.000
However,
FFr1: Radius of curvature FFr2 of the object-side lens surface of the positive lens closest to the image side in the front focus group: Curvature radius of the image-side lens surface of the positive lens closest to the image side in the front focus group

  The conditional expression (12) defines the shape factor of the positive lens located closest to the image side in the front focusing group.

  If the corresponding value of the conditional expression (12) of the optical system of the present embodiment exceeds the upper limit value, the curvature of the object-side lens surface of the positive lens becomes large, and it becomes difficult to correct spherical aberration. In order to secure the effect of the present embodiment, the upper limit value of conditional expression (12) is set to 1.500, 1.300, 1.000, 0.900, 0.800, 0.700, 0.1. It is more preferable to set it as 600.

  On the other hand, when the corresponding value of the conditional expression (12) of the optical system of the present embodiment falls below the lower limit value, it becomes difficult to correct coma and the like. In order to secure the effect of the present embodiment, the lower limit value of conditional expression (12) should be −0.800, further −0.600, −0.400, −0.200, and 0.000. Is more preferred.

  Further, in the optical system of the present embodiment, it is desirable that the front focusing group be composed of two or three lenses. As a result, weight reduction of the front focusing group can be achieved, and speeding up of autofocus can be achieved.

  In the optical system according to the present embodiment, it is desirable that the rear focusing group be formed of four or less lenses. Thus, the weight of the rear focusing group can be reduced, and speeding up of autofocus can be achieved.

Moreover, as for the optical system of this embodiment, it is desirable to satisfy the following conditional expressions (13).
(13) 0.800 <(-fRB) / f <10.000
However,
fRB: focal length of the negative lens group f: focal length of the optical system when focusing on an infinite object

  The conditional expression (13) defines the focal length of the negative lens unit and the focal length of the entire optical system.

  When the corresponding value of the conditional expression (13) of the optical system of the present embodiment exceeds the upper limit value, the refractive power of the negative lens unit becomes too small. For this reason, the back focus becomes large, and the optical system becomes large. In addition, coma and the like can not be sufficiently corrected. In order to secure the effect of the present embodiment, it is more preferable to set the upper limit value of conditional expression (13) to 9.000, and further, 8.000, 7.000, 6.000, and 5.000.

  On the other hand, when the corresponding value of the conditional expression (13) of the optical system of the present embodiment falls below the lower limit value, the refractive power of the negative lens group becomes too large. Therefore, the exit pupil distance can not be sufficiently secured. In addition, distortion and the like can not be sufficiently corrected. In order to secure the effect of the present embodiment, the lower limit value of the conditional expression (13) should be 1.000, and further 1.200, 1.400, 1.600, 1.800, 2.000. Is more preferred.

  Further, in the optical system of the present embodiment, it is desirable that the lens group located closest to the image side have a positive lens and a negative lens in order from the image side. As a result, it is possible to ensure a back focus of an appropriate size and a sufficient exit pupil distance.

Moreover, as for the optical system of this embodiment, it is desirable to satisfy the following conditional expressions (14).
(14) 0.030 <nRBp-nRBn
However,
nRBp: refractive index nRBn relative to the d-line (λ = 587.6 nm) of the positive lens in the lens group located closest to the image side: d-line (λ = 587.6 nm) of the negative lens in the lens group located closest to the image Index of refraction for)

The conditional expression (14) defines the refractive index difference between the positive lens and the negative lens in the lens unit located closest to the image side.
If the corresponding value of the conditional expression (14) of the optical system of the present embodiment falls below the lower limit value, the Petzval sum can not be corrected, and an appropriate exit pupil distance and back focus can not be maintained. In order to secure the effect of the present embodiment, the lower limit value of conditional expression (14) should be 0.040, further 0.050, 0.060, 0.070, 0.080, 0.090, 0. It is more preferable to set it to 100.

  Further, in the optical system of the present embodiment, it is desirable that the image-side lens surface of the lens positioned closest to the image side in the lens group positioned closest to the image side be convex on the image side. This makes it possible to secure an appropriate exit pupil distance and back focus.

Moreover, as for the optical system of this embodiment, it is desirable to satisfy the following conditional expressions (15) and (16).
(15) 1.000 <nRBp + 0.005νRBp <2.500
(16) 1.000 <nRBn + 0.005νRBn <2.500
However,
nRBp: refractive index nRBn relative to the d-line (λ = 587.6 nm) of the positive lens in the lens group located closest to the image side: d-line (λ = 587.6 nm) of the negative lens in the lens group located closest to the image ), The Abbe number RBRBn for the d-line (λ = 587.6 nm) of the positive lens in the lens group located closest to the image side: the d-line (λ for the negative lens in the lens group located closest to the image side) Abbe number for (= 587.6 nm)

  The conditional expression (15) defines the relationship between the refractive index and the dispersion of the positive lens included in the lens unit positioned closest to the image side. By satisfying the conditional expression (15), the optical system of the present embodiment can correct chromatic aberration well.

  In order to secure the effect of the present embodiment, it is more preferable to set the upper limit value of conditional expression (15) to 2.400, more preferably 2.300, 2.200, and 2.100.

  In order to secure the effect of the present embodiment, it is more preferable to set the lower limit value of conditional expression (15) to 1.200, further 1.400, 1.600, and 1.800.

  The conditional expression (16) defines the relationship between the refractive index and the dispersion of the negative lens included in the lens unit positioned closest to the image side. By satisfying the conditional expression (16), the optical system of the present embodiment can correct chromatic aberration well.

  In order to secure the effect of the present embodiment, it is more preferable to set the upper limit value of conditional expression (16) to 2.400, further 2.300, 2.200, and 2.100.

  In order to secure the effect of the present embodiment, it is more preferable to set the lower limit value of conditional expression (16) to 1.200, more preferably 1.400, 1.600, and 1.800.

  In the optical system according to this embodiment, it is desirable that the front focusing group and the aperture stop be adjacent to each other. Thereby, various aberrations such as spherical aberration and curvature of field aberration can be corrected well, and fluctuations of the various aberrations at the time of focusing can be suppressed.

  In the optical system according to this embodiment, it is desirable that the aperture stop and the rear focusing group be adjacent to each other. Thereby, various aberrations such as spherical aberration and curvature of field aberration can be corrected well, and fluctuations of the various aberrations at the time of focusing can be suppressed.

  In the optical system according to this embodiment, it is preferable that the front group further includes a lens group whose position is fixed at the time of focusing, between the front focusing group and the aperture stop. Thereby, various aberrations such as spherical aberration and curvature of field aberration can be corrected well, and fluctuations of the various aberrations at the time of focusing can be suppressed.

  In the optical system according to this embodiment, it is preferable that the rear group further includes a lens group whose position is fixed at the time of focusing, between the aperture stop and the rear focusing group. Thereby, various aberrations such as spherical aberration and curvature of field aberration can be corrected well, and fluctuations of the various aberrations at the time of focusing can be suppressed.

  The optical apparatus of the embodiment includes the optical system having the above-described configuration. Thus, it is possible to realize an optical apparatus having good optical performance, which is suitable for a mirrorless camera, suppresses the fluctuation of various aberrations at the time of focusing while achieving weight reduction of the focusing group.

  The method of manufacturing an optical system according to the embodiment is a method of manufacturing an optical system including a front group having positive refractive power, an aperture stop, and a rear group having positive refractive power, and the front group is an object. In order from the side, a positive lens group having a positive refractive power and a front focusing group having a positive refractive power are arranged, and the rear group is arranged in order from the object side, a rear focusing surface having a positive refractive power. It is arranged to have a focusing group and a negative lens group having negative refractive power, and the front focusing group and the rear focusing group are light when focusing at least part of an object at infinity to a near object. It is made to move in the axial direction so that the lens closest to the object side has negative refractive power. Accordingly, it is possible to manufacture an optical system having good optical performance, which is suitable for a mirrorless camera, suppresses variation of various aberrations at the time of focusing while achieving weight reduction of the focusing group.

Hereinafter, the example concerning the optical system of an embodiment is described based on an accompanying drawing.
(First embodiment)
FIGS. 1A and 1B are cross-sectional views of an optical system according to the first embodiment when focusing on an infinite object and when focusing on a near object, respectively.
The optical system according to the first embodiment includes, in order from the object side, a front group GF having positive refractive power, an aperture stop S, and a rear group GR having positive refractive power. A filter F is disposed in the vicinity of the object side of the image plane I.

The front group GF comprises, in order from the object side, a positive lens group GFA having positive refractive power and a front focusing group GFF having positive refractive power.
The positive lens group GFA includes, in order from the object side, a negative meniscus lens L1 having a convex surface on the object side, a negative meniscus lens L2 having a convex surface on the object side, a biconvex positive lens L3, and a biconcave shape It consists of a cemented lens of a negative lens L4 and a biconvex positive lens L5, and a biconvex positive lens L6.
The front focusing group GFF is a cemented lens of a biconvex positive lens L7 and a biconcave negative lens L8 in this order from the object side.

The rear group GR includes, in order from the object side, a rear focusing group GRF having positive refractive power and a negative lens group GRB having negative refractive power.
The rear focusing group GRF includes, in order from the object side, a negative meniscus lens L9 having a convex surface facing the image side, and a biconvex positive lens L10.
The negative lens group GRB is composed of, in order from the object side, a biconcave negative lens L11 and a plano-convex positive lens L12 having a convex surface facing the object side.

  In the optical system according to the first embodiment, focusing from an infinite distance object to a near distance object is performed by moving the front focusing group GFF and the rear focusing group GRF to the object side along the optical axis. At the time of focusing, the positions of the positive lens unit GFA, the aperture stop S, and the negative lens unit GRB are fixed.

Table 1 below provides values of specifications of the optical system according to the first example.
In Table 1, f indicates the focal length, and Bf indicates the back focus (the distance between the lens surface closest to the image and the image plane I on the optical axis).
In [Surface Data], the surface number is the order of the optical surface counted from the object side, r is the radius of curvature, d is the surface distance (the distance between the nth surface (n is an integer) and the n + 1th surface), nd is The refractive index for the d-line (wavelength 587.6 nm) and ν d indicate the Abbe number for the d-line (wavelength 587.6 nm). The object plane indicates the object plane, the variable plane spacing is variable, the stop S indicates the aperture stop S, and the image plane indicates the image plane I. The radius of curvature r = ∞ indicates a plane. In the aspheric surface, the surface number is attached with “*”, and the value of paraxial radius of curvature is shown in the column of radius of curvature r.

[Spherical surface data] shows the aspheric surface coefficient and the conical constant when the shape of the aspheric surface shown in [Surface data] is expressed by the following equation.
x = (h ² / r) / [1+ {1-κ (h / r) ² } ^1/2 ] + A4h ⁴ + A6h ⁶ + A8h ⁸
Here, h is the height in the direction perpendicular to the optical axis, x is the distance along the optical axis direction from the tangent plane of the apex of the aspheric surface at height h to the aspheric surface (sag amount), and κ is the conical constant , A4, A6 and A8 are aspheric coefficients, and r is a radius of curvature (paraxial radius of curvature) of the reference spherical surface. Incidentally, "E-n" (n is an integer) indicates "× 10 ^-n", for example "1.23456E-07" represents "1.23456 × 10 ^-7". The second-order aspheric coefficient A2 is 0, and the description is omitted.

In [Various data], Fno is F number, 2ω is angle of view (unit is “°”), ω is half angle of view (unit is “°”), Ymax is maximum image height, β is close-up shooting magnification, TL is The total length (the distance on the optical axis from the first surface to the image plane I) of the optical system according to the first embodiment, and dn indicate the variable distance between the nth surface and the (n + 1) th surface. The air conversion Bf and the air conversion TL respectively indicate Bf and TL obtained by converting the thickness of the filter F into air. Ainf indicates a half angle of view at the time of focusing on an infinite object, and Amod indicates a half angle of view at the time of focusing on the closest object (both in the unit of “°”). In addition, infinity indicates the time of focusing on an infinite distance object, and the near distance indicates the time of focusing on a short distance object.
[Lens group data] indicates the starting surface of each lens group and the focal length.
[Conditional Expression Correspondence Value] indicates the correspondence values of the conditional expressions of the optical system according to the first example.

Here, the unit of focal length f, radius of curvature r and other lengths listed in Table 1 is generally “mm”. However, the optical system is not limited to this because the same optical performance can be obtained by proportional enlargement or reduction.
In addition, the code | symbol of Table 1 described above shall be similarly used also in the table | surface of each Example mentioned later.

(Table 1) First embodiment
[Plane data]
Face number r d nd d d
Object ∞ 1.000000
1) 85.0000 2.7000 1.744000 44.80
2) 25.0533 9.4391 1.000000
3) 54.7416 2.0000 1.588870 61.13
* 4) 18.4256 10.7081 1.000000
5) 516.8640 3.7787 1.903658 31.31
6) -114.1419 3.5370 1.000000
7) -50.2377 2.0000 1.620040 36.40
8) 30.6947 10.4006 1.851500 40.78
9) -261.5465 0.2000 1.000000
10) 41.0143 5.7649 1.851500 40.78
11) -317.4121 variable 1.000000
12) (virtual surface) 0.000 0.0000 1.000000
13) 56.941 4.1550 1.497820 82.57
14) -64.4398 1.2000 1.808090 22.74
15) 364.1222 Variable 1.000000
16) (F-stop S) 可 変 Variable 1.000000
* 17) -38.5516 1.4869 1.860999 37.10
* 18) -43.3477 1.3930 1.000000
19) 54.9022 6.5932 1.497820 82.57
20) -18.1086 Variable 1.000000
* 21) -26.4619 1.4000 1.689480 31.02
22) 48.9165 2.3305 1.000000
* 23) 39.3225 3.4184 1.832199 40.10
24) 17. 17.1751 1.000000
25) ∞ 1.6000 1.516800 64.13
26) ∞ 0.9931 1.000000
Image plane ∞
[Aspheric surface data]
Face number κ A4 A6 A8 A10 A12
4 0.0000 8.15384E-06 -6.41018E-09 3.11521E-11 -7.69764E-14 0.67523E-16
17 0.0000 -3.75535E-05 4.12683E-08 9.77350E-10 -1.51945E-11 0.24817E-13
18 1.0000 7.81937E-06 1.19209E-07 1.46234E-09 -1.69623E-11 0.50939E-13
21 1.5918 1.17009E-04-7.89 622E-07 5.72645E-09 -2.68019E-11 0.55035E-13
23 1.0000 -7.49387E-05 4.05516E-07 -2.44584E-09 8.81114E-12 -0.14105E-13
[Various data]
f 20.1396
Fno 1.85813
2 ω 96.9415
Ymax 21.60
TL 113.97307
Air conversion TL 113.42787
Bf 19.7682
Air conversion Bf 19.223
Ainf 49.11334
Amod 48.15531
Infinite distance short distance f 20.1396
β -0.1886
d0 ∞ 86.0518
d11 6.6882 3.2619
d15 4.1566 7.5829
d16 7.3258 5.5189
d20 3.5287 5.3356
2 ω 96.9415
ω 48.4707
[Lens group data]
Group front f
GF 1 41.6168
GR 17 56.1686
GFA 1 50.6422
GFF 12 519.7498
GRF 17 29.1224
GRB 21 -59. 3852
[Conditional expression corresponding value]
(1) fRF / fFF = 0.0560
(2) Bf / f = 0.9545
(3) ST / TL = 0.4500
(4) βRF / βFF = 0. 3989
(5) fF / fR = 0.7409
(6) fFA / fFF = 0.0971
(7) f / fFF = 0.0387
(8) f / fRF = 0.6916
(9) TL / (Fno · Bf) = 3.1756
(10) | Ainf-Amod | / f = 0.0476
(11) FFFFp-FFFFn = 59.8300
(12) (FFr2 + FFr1) / (FFr2-FFr1) = 0.0639
(13) (-fRB) / f = 2.9486
(14) nRBp-nRBn = 0.1427
(15) nRBp + 0.005 RB RBp = 2.0327
(16) nRBn + 0.005 RB RBn = 1.8446

  FIG. 2A and FIG. 2B are various aberration diagrams, respectively, at the time of focusing on an infinite distance object and during focusing on a near distance object of the optical system according to the first embodiment.

  In each aberration diagram, FNO denotes an F number, Y denotes an image height, and NA denotes a numerical aperture. Specifically, in the spherical aberration diagram, the value of the F number FNO or the numerical aperture NA corresponding to the maximum aperture is shown, and in the astigmatism diagram and the distortion diagram, the maximum value of the image height Y is shown respectively. Indicates the value of. Further, in each aberration diagram, d indicates an aberration at d-line (wavelength 587.6 nm) and g indicates an aberration at g-line (wavelength 435.8 nm). In astigmatism diagrams, a solid line indicates a sagittal image plane, and a broken line indicates a meridional image plane. The coma aberration diagram shows coma aberration at each image height Y. The same reference numerals as in this example are used also in the aberration charts of the examples which will be described later.

  From the aberration diagrams, it is understood that the optical system according to the present embodiment has excellent imaging performance by satisfactorily correcting various aberrations from focusing on an infinite distance object to focusing on a close distance object.

Second Embodiment
FIGS. 3A and 3B are cross-sectional views of an optical system according to the second embodiment when focusing on an infinite object and when focusing on a near object, respectively.
The optical system according to the second embodiment includes, in order from the object side, a front group GF having positive refractive power, an aperture stop S, and a rear group GR having positive refractive power. A filter F is disposed in the vicinity of the object side of the image plane I.

The front group GF comprises, in order from the object side, a positive lens group GFA having positive refractive power and a front focusing group GFF having positive refractive power.
The positive lens group GFA includes, in order from the object side, a negative meniscus lens L1 having a convex surface on the object side, a negative meniscus lens L2 having a convex surface on the object side, a biconvex positive lens L3, and a biconcave shape It consists of a cemented lens of a negative lens L4 and a positive meniscus lens L5 with a convex surface facing the object side, and a biconvex positive lens L6.
The front focusing group GFF is a cemented lens of a biconvex positive lens L7 and a biconcave negative lens L8 in this order from the object side.

The rear group GR is composed of, in order from the object side, a negative lens group GRA having a negative refractive power, a rear focusing group GRF having a positive refractive power, and a negative lens group GRB having a negative refractive power.
The negative lens group GRA is composed of a negative meniscus lens L9 having a convex surface facing the object side.
The rear focusing group GRF is composed of, in order from the object side, a positive meniscus lens L10 having a convex surface facing the image side, and a biconvex positive lens L11.
The negative lens group GRB is composed of, in order from the object side, a biconcave negative lens L12 and a plano-convex positive lens L13 having a convex surface facing the object side.

In the optical system according to the second embodiment, focusing from an infinite distance object to a near distance object is performed by moving the front focusing group GFF and the rear focusing group GRF to the object side along the optical axis. At the time of focusing, the positions of the positive lens group GFA, the aperture stop S, the negative lens group GRA, and the negative lens group GRB are fixed.
Table 2 below presents values of specifications of the optical system according to the second example.

(Table 2) Second embodiment
[Plane data]
Face number r d nd d d
Object ∞ 1.000000
1) 89.6637 2.3000 1.744000 44.80
2) 29.1933 8.8855 1.000000
3) 80.9611 2.0000 1.588870 61.13
* 4) 18.6119 11.2072 1.000000
5) 363.7622 4.9254 1.903658 31.31
6) -101.1501 2.7468 1.000000
7) -54.6987 5.0000 1.620040 36.40
8) 32.2537 8.4862 1.851500 40.78
9) 1296.4983 0.2000 1.000000
10) 45.2794 5.9980 1.851500 40.78
11) -141.1734 variable
12) (virtual surface) 0.000 0.0000 1.000000
13) 41.5816 4.4074 1.497820 82.57
14) -76.5015 1.2000 1.808090 22.74
15) 129.2012 variable
16) (F-stop S) 2. 2.0000 1.000000
17) 340.8668 1.2000 1.48790 70.32
18) 102.2210 Variable
* 19) -96.2233 2.0483 1.860999 37.10
20) -78.6357 1.3930 1.000000
21) 60.1667 7.9457 1.497820 82.57
22) -18.5027 variable
* 23) -27.6858 1.3000 1.689480 31.02
24) 44.6169 1.9137 1.000000
* 25) 37.7956 2.4912 1.832199 40.10
26) ∞ 16.6751 1.000000
27) ∞ 1.6000 1.516800 63.88
28) ∞ 1.0000 1.000000
Image plane ∞
[Aspheric surface data]
Face number κ A4 A6 A8 A10 A12
4 0.0000 8.02959E-06 2.44201E-09 1.15819E-11 -5.28374E-15 0.20308E-16
19 0.0000-3.96 671 E-05-9.87 679 E-08 2. 895 585 E-11-4. 2 3597 E-12-0.1 7 965 E-15
23 1.5084 1.22824E-04 -8.31232E-07 5.29431E-09 -2.14010E-11 0.35630E-13
25 1.0000 -8.30036E-05 4.42223E-07 -2.362224E-09 7.62005E-12 -0.96482E-14
[Various data]
f 20.4000
Fno 1.86668
2 ω 96.1606
Ymax 21.60
TL 117.00851
Air conversion TL 116.64331
Bf 19.27514
Air conversion Bf 18.72994
Ainf 18.75122
Amod 47.95116
Infinite distance short distance f 20.4000
β -0.1896
d0 ∞ 86.3709
d11 5.7481 2.6300
d15 4.1550 7.2731
d18 6.4768 4.6001
d22 3.7053 5.5821
2 ω 96.1606
ω 48.0803
[Lens group data]
Group front f
GF 1 41.2883
GR 19 54. 7498
GFA 1 51.4084
GFF 12 485.7773
GRA 16 -300.0000
GRF 19 27.7405
GRB 23 -60.6065
[Conditional expression corresponding value]
(1) fRF / fFF = 0.0571
(2) Bf / f = 0.9181
(3) ST / TL = 0.4225
(4) βRF / βFF = 0.3322
(5) fF / fR = 0.7451
(6) fFA / fFF = 0.1058
(7) f / fFF = 0.0420
(8) f / fRF = 0.7354
(9) TL / (Fno · Bf) = 3.3311
(10) | Ainf-Amod | / f = 0.0392
(11) FFFFp-FFFFn = 59.8300
(12) (FFr2 + FFr1) / (FFr2-FFr1) = 0.2957
(13) (−fRB) /f=2.9709
(14) nRBp-nRBn = 0.1427
(15) nRBp + 0.005 RB RBp = 2.0327
(16) nRBn + 0.005 RB RBn = 1.8446

FIG. 4A and FIG. 4B are various aberration diagrams, respectively, at the time of focusing on an infinite distance object and during focusing on a near distance object of the optical system according to the second example.
From the aberration diagrams, it is understood that the optical system according to the present embodiment has excellent imaging performance by satisfactorily correcting various aberrations from focusing on an infinite distance object to focusing on a close distance object.

Third Embodiment
FIGS. 5A and 5B are cross-sectional views of an optical system according to a third embodiment when focusing on an infinite object and when focusing on a near object, respectively.
The optical system according to the third embodiment includes, in order from the object side, a front group GF having positive refractive power, an aperture stop S, and a rear group GR having positive refractive power. A filter F is disposed in the vicinity of the object side of the image plane I.

The front group GF includes, in order from the object side, a positive lens group GFA having positive refractive power, a front focusing group GFF having positive refractive power, and a positive lens group GFB having positive refractive power.
The positive lens group GFA includes, in order from the object side, a negative meniscus lens L1 having a convex surface on the object side, a negative meniscus lens L2 having a convex surface on the object side, and a positive meniscus lens L3 having a convex surface on the image side. It comprises a cemented lens of a biconcave negative lens L4 and a biconvex positive lens L5, and a biconvex positive lens L6.
The front focusing group GFF is a cemented lens of a biconvex positive lens L7 and a biconcave negative lens L8 in this order from the object side.
The positive lens group GFB is composed of a plano-convex positive lens L9 having a convex surface facing the object side.

The rear group GR includes, in order from the object side, a rear focusing group GRF having positive refractive power and a negative lens group GRB having negative refractive power.
The rear focusing group GRF includes, in order from the object side, a negative meniscus lens L10 having a convex surface facing the image side, and a positive biconvex lens L11.
The negative lens group GRB is composed of, in order from the object side, a biconcave negative lens L12 and a plano-convex positive lens L13 having a convex surface facing the object side.

In the optical system according to the third embodiment, focusing from an infinite distance object to a near distance object is performed by moving the front focusing group GFF and the rear focusing group GRF to the object side along the optical axis. At the time of focusing, the positions of the positive lens group GFA, the positive lens group GFB, the aperture stop S, and the negative lens group GRB are fixed.
Table 3 below presents values of specifications of the optical system according to the third example.

(Table 3) Third embodiment
[Plane data]
Face number r d nd d d
Object ∞ 1.000000
1) 97.1220 2.5000 1.744000 44.80
2) 25.5141 8.5243 1.000000
3) 54.3787 2.0000 1.588870 61.13
* 4) 19.3078 12.0516 1.000000
5) -2541.0384 4.4832 1.903658 31.31
6) -89.4461 3.2029 1.000000
7) -55.7529 4.8378 1.620040 36.40
8) 31.5163 8.0322 1.851500 40.78
9) -603.1050 0.2000 1.000000
10) 44.5738 5.5569 1.851500 40.78
11) -295.5770 variable 1.000000
12) (virtual surface) 0.000 0.0000 1.000000
13) 56.3391 4.1355 1.497820 82.57
14) -77.0418 2.0843 1.808090 22.74
15) 274.8271 Variable 1.000000
16) 150.0000 1.6000 1.48790 70.32
17) ∞ 2.0000 1.000000
18) (F-stop S) 可 変 Variable 1.000000
* 19) -43.8243 1.2000 1.860999 37.10
20) -57.8611 1.3930 1.000000
21) 70.5507 6.94.44 1.497820 82.57
22) -17.1866 Variable 1.000000
* 23) -32.2891 1.3000 1.689480 31.02
24) 34.1671 2.2422 1.000000
25) 37.1466 3.3825 1.832199 40.10
26) ∞ 16.2621 1.000000
27) ∞ 1.6000 1.516800 63.88
28) ∞ 1.0000 1.000000
Image plane ∞
[Aspheric surface data]
Face number κ A4 A6 A8 A10 A12
4 0.0000 6.01620E-06 6.79387E-09 -4.02993E-11 1.2032E-13 -0.15113E-15
19 0.0000 -4.87007E-05 -8.95876E-08 -3.14165E-10 -2.43481E-12 -0.23860E-13
23 5.5636 1.08484E-04 -7.41132E-07 6.01375E-09 -3.07989E-11 0.79304E-13
25 1.0000 -6.01745E-05 3.38304E-07 -1.58920E-09 5.05882E-12 -0.65680E-14
[Various data]
f 20.2698
Fno 1.84435
2ω 96.5219
Ymax 21.60
TL 116.60345
Air conversion TL 116.05825
Bf 18.86209
Air conversion Bf 18.31689
Ainf 48.94839
Amod 48.37479
Infinite distance short distance f 20.2698
β -0.1902
d0 ∞ 85.4430
d11 5.6165 2.4956
d15 2.2463 5.3672
d18 8.5521 6.5490
d22 3.6056 5.6088
2ω 96.5219
ω 48.2609
[Lens group data]
Group front f
GF 1 34.2040
GR 17 66.9283
GFA 1 54.0606
GFF 12 486.5933
GFB 16 307.6986
GRF 19 31.4696
GRB 23-58.8568
[Conditional expression corresponding value]
(1) fRF / fFF = 0.0647
(2) Bf / f = 0.9037
(3) ST / TL = 0.4049
(4) βRF / βFF = 0.5105
(5) fF / fR = 0.5111
(6) fFA / fFF = 0.1111
(7) f / fFF = 0.0417
(8) f / fRF = 0.6441
(9) TL / (Fno · Bf) = 3.4354
(10) | Ainf-Amod | / f = 0.0283
(11) FFFFp-FFFFn = 59.8300
(12) (FFr2 + FFr1) / (FFr2-FFr1) = 0.1552
(13) (−fRB) /f=2.9037
(14) nRBp-nRBn = 0.1427
(15) nRBp + 0.005 RB RBp = 2.0327
(16) nRBn + 0.005 RB RBn = 1.8446

FIGS. 6 (a) and 6 (b) are various aberration diagrams, respectively, at the time of focusing on an infinite distance object and during focusing on a near distance object of the optical system according to the third example.
From the aberration diagrams, it is understood that the optical system according to the present embodiment has excellent imaging performance by satisfactorily correcting various aberrations from focusing on an infinite distance object to focusing on a close distance object.

Fourth Embodiment
FIGS. 7A and 7B are cross-sectional views of an optical system according to a fourth embodiment when focusing on an infinite object and when focusing on a near object, respectively.
The optical system according to the fourth embodiment comprises, in order from the object side, a front group GF having positive refractive power, an aperture stop S, and a rear group GR having positive refractive power. A filter F is disposed in the vicinity of the object side of the image plane I.

The front group GF comprises, in order from the object side, a positive lens group GFA having positive refractive power and a front focusing group GFF having positive refractive power.
The positive lens group GFA includes, in order from the object side, a negative meniscus lens L1 having a convex surface on the object side, a negative meniscus lens L2 having a convex surface on the object side, and a positive meniscus lens L3 having a convex surface on the image side. It comprises a cemented lens of a biconcave negative lens L4 and a biconvex positive lens L5, and a biconvex positive lens L6.
The front focusing group GFF is a cemented lens of a biconvex positive lens L7 and a biconcave negative lens L8 in this order from the object side.

The rear group GR includes, in order from the object side, a rear focusing group GRF having positive refractive power and a negative lens group GRB having negative refractive power.
The rear focusing group GRF includes, in order from the object side, a positive meniscus lens L9 having a convex surface facing the image side, and a biconvex positive lens L10.
The negative lens group GRB is composed of, in order from the object side, a biconcave negative lens L11 and a plano-convex positive lens L12 having a convex surface facing the object side.

In the optical system according to the fourth embodiment, focusing from an infinite distance object to a near distance object is performed by moving the front focusing group GFF and the rear focusing group GRF to the object side along the optical axis. At the time of focusing, the positions of the positive lens unit GFA, the aperture stop S, and the negative lens unit GRB are fixed.
Table 4 below presents values of specifications of the optical system according to the fourth example.

(Table 4) Fourth embodiment
[Plane data]
Face number r d nd d d
Object ∞ 1.000000
1) 105.1730 2.5000 1.717000 47.97
2) 28.0761 6.9819 1.000000
3) 54.1318 2.0000 1.568830 56.00
* 4) 19.1358 12.2439 1.000000
5) -1386.9567 3.2295 1.903658 31.31
6) -106.4455 2.3599 1.000000
7) -63.4529 3.3027 1.620040 36.40
8) 29.5793 7.1269 1.851500 40.78
9) -2671.7190 2.3092 1.000000
10) 42.2306 5.3571 1.851500 40.78
11)-303.1326 Variable 1.000000
12) (virtual surface) 0.000 0.0000 1.000000
13) 58.1267 4.5140 1.497820 82.57
14) -67.7518 2.5150 1.808090 22.74
15) 464.6438 Variable 1.000000
16) (F-stop S) 可 変 Variable 1.000000
* 17) -58.9498 2.0443 1.860999 37.10
18) -56.5635 1.3930 1.000000
19) 119.9079 7.3545 1.497820 82.57
20) -17.3792 Variable 1.000000
* 21)-27.6859 1.3000 1.689480 31.02
22) 41.8186 1.7994 1.000000
* 23) 39.3203 3.4174 1.808350 40.55
24) 18. 18.4523 1.000000
25) ∞ 1.6000 1.516800 64.13
26) 0.9 0.9866 1.000000
Image plane ∞
[Aspheric surface data]
Face number κ A4 A6 A8 A10 A12
4 0.0000 1.01451E-05 3.09662E-10 2.61797E-11-5.26695E-14 0.49110E-16
17 0.0000 -4.44232E-05 -7.92259E-08 -9.22854E-10 6.75991E-12 -0.57395E-13
21 2.0933 1.10413E-04 -7.62492E-07 5.30334E-09 -2.25140E-11 0.40859E-13
23 1.0000 -7.16079E-05 4.39983E-07 -2.36885E-09 7.66187E-12 -0.10235E-13
[Various data]
f 23.0000
Fno 1.85172
2ω 90.6552
Ymax 21.60
TL 114.98658
Air conversion TL 114.44138
Bf 21.03884
Air conversion Bf 20.49364
Ainf 45.31854
Amod 44.51854
Infinite distance short distance f 23.0000
β -0.1828
d0 ∞ 104.9388
d11 5.9052 2.4996
d15 4.0403 7.4460
d16 8.5116 6.667
d20 3.7419 5.5858
2ω 90.6552
ω 45.3276
[Lens group data]
Group front f
GF 1 44.7746
GR 17 64.6935
GFA 1 57.4905
GFF 12 413.4387
GRF 17 29.9133
GRB 21-52.0504
[Conditional expression corresponding value]
(1) fRF / fFF = 0.0724
(2) Bf / f = 0.8910
(3) ST / TL = 0.4374
(4) βRF / βFF = 0.4327
(5) fF / fR = 0.6921
(6) fFA / fFF = 0.1391
(7) f / fFF = 0.0556
(8) f / fRF = 0.7689
(9) TL / (Fno · Bf) = 3.0157
(10) | Ainf-Amod | / f = 0.0348
(11) FFFFp-FFFFn = 59.8300
(12) (FFr2 + FFr1) / (FFr2-FFr1) = 0.0765
(13) (-fRB) / f = 2.2631
(14) nRBp-nRBn = 0.1189
(15) nRBp + 0.005 RB RBp = 2.0111
(16) nRBn + 0.005 RB RBn = 1.8446

FIGS. 8 (a) and 8 (b) are various aberration diagrams, respectively, at the time of focusing on an infinite distance object and during focusing on a near distance object of the optical system according to the fourth example.
From the aberration diagrams, it is understood that the optical system according to the present embodiment has excellent imaging performance by satisfactorily correcting various aberrations from focusing on an infinite distance object to focusing on a close distance object.

Fifth Embodiment
FIGS. 9A and 9B are cross-sectional views of an optical system according to the fifth embodiment when focusing on an infinite distance object and when focusing on a near distance object, respectively.
The optical system according to the fifth example includes, in order from the object side, a front group GF having positive refractive power, an aperture stop S, and a rear group GR having positive refractive power. A filter F is disposed in the vicinity of the object side of the image plane I.

The front group GF comprises, in order from the object side, a positive lens group GFA having positive refractive power and a front focusing group GFF having positive refractive power.
The positive lens group GFA includes, in order from the object side, a negative meniscus lens L1 having a convex surface on the object side, a negative meniscus lens L2 having a convex surface on the object side, and a positive meniscus lens L3 having a convex surface on the image side. It comprises a cemented lens of a biconcave negative lens L4 and a biconvex positive lens L5, and a biconvex positive lens L6.
The front focusing group GFF is a cemented lens of a biconvex positive lens L7 and a biconcave negative lens L8 in this order from the object side.

The rear group GR includes, in order from the object side, a rear focusing group GRF having positive refractive power and a negative lens group GRB having negative refractive power.
The rear focusing group GRF includes, in order from the object side, a positive meniscus lens L9 having a convex surface facing the image side, and a biconvex positive lens L10.
The negative lens group GRB is composed of, in order from the object side, a biconcave negative lens L11 and a plano-convex positive lens L12 having a convex surface facing the object side.

In the optical system according to the fifth embodiment, focusing from an infinite distance object to a near distance object is performed by moving the front focusing group GFF and the rear focusing group GRF to the object side along the optical axis. At the time of focusing, the positions of the positive lens unit GFA, the aperture stop S, and the negative lens unit GRB are fixed.
Table 5 below presents values of specifications of the optical system according to the fifth example.

(Table 5) fifth embodiment
[Plane data]
Face number r d nd d d
Object ∞ 1.000000
1) 397.0808 2.5000 1.655234 44.96
2) 41.1626 4.3963 1.000000
3) 63.8851 2.0000 1.556354 55.30
* 4) 19.8504 11.8696 1.000000
5) -335.9120 3.4498 1.891325 32.78
6) -92.502 2.6562 1.000000
7) -66.8872 1.9012 1.620040 36.40
8) 29.5548 8.8222 1.851500 40.78
9) -2141.5083 1.8071 1.000000
10) 44.7902 5.3588 1.851500 40.78
11)-299.4337 Variable 1.000000
12) (virtual surface) 0.000 0.0000 1.000000
13) 44.5714 5.4239 1.497820 82.57
14) -78.9223 2.8047 1.805180 25.45
15) 160.0738 Variable 1.000000
16) (F-stop S) 可 変 Variable 1.000000
* 17) -46.7376 2.0809 1.860999 37.10
18) -42.7565 1.3930 1.000000
19) 262.5587 7.2654 1.497820 82.57
20)-18.8498 Variable 1.000000
* 21) -30.1253 1.3000 1.689480 31.02
22) 40.4709 1.9883 1.000000
* 23) 37.2836 3.3332 1.808350 40.55
24) 19. 19.7825 1.000000
25) ∞ 1.6000 1.516800 64.13
26) ∞ 1.0059 1.000000
Image plane ∞
[Aspheric surface data]
Face number κ A4 A6 A8 A10 A12
4 0.0000 9.77757E-06-1.86856E-10 3.61428E-11 -7.97773E-14 0.95711E-16
17 0.0000 -3.98939E-05 -3.97571E-08 -4.94760E-10 2.83561E-12 -0.20949E-13
21 2.6936 1.03810E-04 -7.47656E-07 5.22059E-09-2.32930E-11 0.46411E-13
23 1.0000 -6.38484E-05 4.30545E-07 -2.33889E-09 8.08344E-12 -0.12063E-13
[Various data]
f 27.0000
Fno 1.8511
2ω 80.1035
Ymax 21.60
TL 115.00586
Air conversion TL 114.40606
Bf 22.38833
Air conversion Bf 21.84313
Ainf 40.75144
Amod 39.9517
Infinite distance short distance f 27.0000
β -0.1432
d0 168 168.6086
d11 5.9402 2.4572
d15 4.0055 7.4884
d16 8.4916 6.7346
d20 3.8298 5.5867
2ω 80.1035
ω 40.0518
[Lens group data]
Group front f
GF 1 50.0572
GR 17 68.9718
GFA 1 67.4727
GFF 12 375.4378
GRF 17 32.8785
GRB 21 -60.8771
[Conditional expression corresponding value]
(1) fRF / fFF = 0.0876
(2) Bf / f = 0.8090
(3) ST / TL = 0.4502
(4) βRF / βFF = 0.4980
(5) fF / fR = 0.7258
(6) fFA / fFF = 0.1797
(7) f / fFF = 0.0719
(8) f / fRF = 0.8212
(9) TL / (Fno · Bf) = 2.8308
(10) | Ainf-Amod | / f = 0.0296
(11) FFFFp-νFFn = 57.3000
(12) (FFr2 + FFr1) / (FFr2-FFr1) = 0.2782
(13) (−fRB) /f=2.2547
(14) nRBp-nRBn = 0.1189
(15) nRBp + 0.005 RB RBp = 2.0111
(16) nRBn + 0.005 RB RBn = 1.8446

FIGS. 10 (a) and 10 (b) are various aberration diagrams, respectively, at the time of focusing on an infinite distance object and during focusing on a near distance object of the optical system according to the fifth example.
From the aberration diagrams, it is understood that the optical system according to the present embodiment has excellent imaging performance by satisfactorily correcting various aberrations from focusing on an infinite distance object to focusing on a close distance object.

Sixth Embodiment
FIGS. 11 (a) and 11 (b) are cross-sectional views of an optical system according to a sixth embodiment when focusing on an infinite object and when focusing on a near object, respectively.
The optical system according to the sixth embodiment includes, in order from the object side, a front group GF having positive refractive power, an aperture stop S, and a rear group GR having positive refractive power. A filter F is disposed in the vicinity of the object side of the image plane I.

The front group GF comprises, in order from the object side, a positive lens group GFA having positive refractive power and a front focusing group GFF having positive refractive power.
The positive lens group GFA includes, in order from the object side, a negative meniscus lens L1 having a convex surface facing the object side, a positive meniscus lens L2 having a convex surface facing the image side, a biconcave negative lens L3, and a biconvex positive lens. It consists of a cemented lens with the lens L4, and a cemented lens of a biconvex positive lens L5 and a biconcave negative lens L6.
The front focusing group GFF includes, in order from the object side, a cemented lens of a plano-convex positive lens L7 having a convex surface facing the object side and a plano-concave negative lens L8 having a concave surface facing the image side.

The rear group GR includes, in order from the object side, a rear focusing group GRF having positive refractive power and a negative lens group GRB having negative refractive power.
The rear focusing group GRF includes, in order from the object side, a negative meniscus lens L9 having a convex surface facing the image side, and a biconvex positive lens L10.
The negative lens group GRB is composed of, in order from the object side, a biconcave negative lens L11 and a biconvex positive lens L12.

In the optical system according to the sixth embodiment, focusing from an infinite distance object to a near distance object is performed by moving the front focusing group GFF and the rear focusing group GRF to the object side along the optical axis. At the time of focusing, the positions of the positive lens unit GFA, the aperture stop S, and the negative lens unit GRB are fixed.
Table 6 below presents values of specifications of the optical system according to the sixth example.

(Table 6) Sixth embodiment
[Plane data]
Face number r d nd d d
Object ∞ 1.000000
1) 348.4574 2.4000 1.504120 59.90
* 2) 21.4609 13.4041 1.000000
3) -105.0871 4.5427 1.922860 20.88
4) -64.8044 3.8789 1.000000
5) -34.8938 2.0000 1.632947 34.71
6) 40.3703 11.1 155 1.834810 42.73
7) -48.0907 0.2187 1.000000
8) 31.3856 7.6538 1.834810 42.73
9) -144.1208 1.6000 1.657414 32.27
10) 31.7227 Variable 1.000000
11) 28.8127 5.3410 1.497820 82.57
12) ∞ 1.2002 1.713322 30.66
13) 55.4010 Variable 1.000000
14) (F-stop S) 可 変 Variable 1.000000
* 15) -46.5696 1.8000 1.728267 45.36
16) -592.3084 0.2365 1.000000
17) 51.5274 10.3228 1.497820 82.57
* 18) -18.0668 variable 1.000000
19) -48.0041 1.4000 1.593929 38.23
20) 55.8143 2.2498 1.000000
* 21) 102. 4799 3.8639 1. 906998 28. 77
22) -1000.0000 17.2535 1.000000
23) ∞ 1.6000 1.516800 64.13
24) 0.9 0.9835 1.000000
Image plane ∞
[Aspheric surface data]
Face number κ A4 A6 A8 A10 A12
2 0.0000 1.12877E-05 7.54278E-09 3.77786E-11-8.64032E-14 0.22683E-15
15 0.0000 -3.875799E-05 -9.55276E-08 2.02210E-10 -5.21627E-12 0.22387E-13
18 1.0000 1.16752E-05 -2.00823E-08 2.86154E-10 -7.78259E-13 0.34805E-14
21 1.0000 3.63716E-06 -5.43228E-09 2.25434E-11 -7.54064E-14 0.77846E-16
[Various data]
f 34.0000
Fno 1.84694
2ω 68.7634
Ymax 21.60
TL 114.98352
Air conversion TL 114.43832
Bf 19.83701
Air conversion Bf 19.29181
Ainf 34.37218
Amod 33.44787
Infinite distance short distance f 34.0000
β -0.1434
d0 ∞ 216.6806
d10 5.4302 2.1248
d13 4.0990 7.4045
d14 9.0459 6.1458
d18 3.3432 6.2432
2ω 68.7634
ω 34.3817
[Lens group data]
Group front f
GF 1 47.9103
GR 15 86.8580
GFA 1 78.4519
GFF 11 186.8714
GRF 15 40.9478
GRB 19-78.5376
[Conditional expression corresponding value]
(1) fRF / fFF = 0.2191
(2) Bf / f = 0.5674
(3) ST / TL = 0.4505
(4) βRF / βFF = 0.8696
(5) fF / fR = 0.5516
(6) fFA / fFF = 0.4198
(7) f / fFF = 0.1819
(8) f / fRF = 0.8303
(9) TL / (Fno · Bf) = 3.2118
(10) | Ainf-Amod | / f = 0.0272
(11) FFFFp-FFFFn = 51.9700
(12) (FFr2 + FFr1) / (FFr2-FFr1) = 1.0000
(13) (−fRB) /f=2.3099
(14) nRBp-nRBn = 0.3130
(15) nRBp + 0.005 RB RBp = 2.0508
(16) nRBn + 0.005 ν RBn = 1.7851

FIGS. 12 (a) and 12 (b) are various aberration diagrams, respectively, at the time of focusing on an infinite distance object and during focusing on a near distance object of the optical system according to the sixth embodiment.
From the aberration diagrams, it is understood that the optical system according to the present embodiment has excellent imaging performance by satisfactorily correcting various aberrations from focusing on an infinite distance object to focusing on a close distance object.

Seventh Embodiment
FIGS. 13A and 13B are cross-sectional views of an optical system according to a seventh embodiment when focusing on an infinite object and when focusing on a near object, respectively.
The optical system according to the seventh embodiment is composed of, in order from the object side, a front group GF having positive refractive power, an aperture stop S, and a rear group GR having positive refractive power. A filter F is disposed in the vicinity of the object side of the image plane I.

The front group GF comprises, in order from the object side, a positive lens group GFA having positive refractive power and a front focusing group GFF having positive refractive power.
The positive lens group GFA includes, in order from the object side, a negative meniscus lens L1 having a convex surface on the object side, a negative meniscus lens L2 having a convex surface on the image side, a biconvex positive lens L3, and a biconcave shape. It consists of a cemented lens of a negative lens L4 and a biconvex positive lens L5, and a biconvex positive lens L6. The negative meniscus lens L2 is a composite aspheric lens in which a resin is disposed on the image side lens surface to form an aspheric shape.
The front focusing group GFF is a cemented lens of a biconvex positive lens L7 and a biconcave negative lens L8 in this order from the object side.

The rear group GR includes, in order from the object side, a rear focusing group GRF having positive refractive power and a negative lens group GRB having negative refractive power.
The rear focusing group GRF includes, in order from the object side, a negative meniscus lens L9 having a convex surface facing the image side, and a biconvex positive lens L10.
The negative lens group GRB is composed of, in order from the object side, a positive meniscus lens L11 having a convex surface facing the object side, a biconcave negative lens L12, and a plano-convex positive lens L13 having a convex surface facing the object side .

In the optical system according to the seventh embodiment, focusing from an infinite distance object to a near distance object is performed by moving the front focusing group GFF and the rear focusing group GRF to the object side along the optical axis. At the time of focusing, the positions of the positive lens unit GFA, the aperture stop S, and the negative lens unit GRB are fixed.
Table 7 below presents values of specifications of the optical system according to the seventh example.

(Table 7) Seventh embodiment
[Plane data]
Face number r d nd d d
Object ∞ 1.000000
1) 97.4192 2.2000 1.768494 44.86
2) 25.3748 9.4393 1.000000
3) 73.0366 1.6500 1.611353 59.10
4) 28.1065 0.1500 1.513800 52.97
* 5) 23.3508 8.7999 1.000000
6) 314.3211 3.3152 1.922860 20.88
7) -230.9882 3.9581 1.000000
8) -54.6239 2.1432 1.620040 36.40
9) 34.0933 10.71.70 1.834810 42.73
10) -93.8515 0.2008 1.000000
11) 45.4462 5.5158 1.834810 42.73
12) -76941.34500 Variable 1.000000
13) 40.48.893 4.1495 1.497820 82.57
14) -135.4706 1.2000 1.808090 22.74
15) 126.4048 Variable 1.000000
16) (F-stop S) 可 変 Variable 1.000000
* 17) -20.6195 1.7865 1.860999 37.10
* 18) -32.1327 1.4206 1.000000
19) 102.6671 7.8877 1.497820 82.57
20) -16.3909 Variable 1.000000
21) 57.0592 2.6167 1.710936 47.27
22) 304.2075 4.1090 1.000000
* 23) -22.4255 1.3000 1.689480 31.02
24) 61.5136 2.0782 1.000000
* 25) 36.1918 2.6262 1.820980 42.50
26) ∞ 12.6819 1.000000
27) ∞ 1.6000 1.516800 63.88
28) ∞ 1.0000 1.000000
Image plane ∞
[Aspheric surface data]
Face number κ A4 A6 A8 A10 A12
5 0.0000 4.47584E-07 -6.22190E-09 1.22365E-11 -3.40101E-14 0.32669E-16
17 0.0000 9.62834E-05-4.19153E-07-3.28271E-09 2.90182E-11-0.13502E-12
18 1.0000 1.33216E-04-1.90915E-07 -3.36920E-09 2.71394E-11 -0.83703E-13
23 1.9124 1.43602E-04 -8.35674E-07 5.32507E-09 -1.97434E-11 0.34513E-13
25 1.0000 -8.47161E-05 4.39056E-07 -2.13972E-09 6.18894E-12 -0.71916E-14
[Various data]
f 20.4000
Fno 1.85009
2 ω 96.1353
Ymax 21.60
TL 115.02541
Air conversion TL 114.48021
Bf 15.28192
Air conversion Bf 14.73672
Ainf 48.67662
Amod 48.15648
Infinite distance short distance f 20.4000
β -0.1972
d0 ∞ 84.0279
d12 6.0921 2.2355
d15 4.3398 8.1964
d16 9.0834 5.6834
d20 2.9645 6.3646
2 ω 96.1353
ω 48.0677
[Lens group data]
Group front f
GF 1 40.2194
GR 17 51.7452
GFA 1 59. 587
GFF 13 253.1359
GRF 17 40.2592
GRB 21 -156.7545
[Conditional expression corresponding value]
(1) fRF / fFF = 0.1590
(2) Bf / f = 0.7224
(3) ST / TL = 0.4421
(4) βRF / βFF = 0.6742
(5) fF / fR = 0.7773
(6) fFA / fFF = 0.2361
(7) f / fFF = 0.0806
(8) f / fRF = 0.5067
(9) TL / (Fno · Bf) = 4.1989
(10) | Ainf-Amod | / f = 0.0300
(11) FFFFp-FFFFn = 59.8300
(12) (FFr2 + FFr1) / (FFr2-FFr1) = 0.5398
(13) (-fRB) / f = 7.684
(14) nRBp-nRBn = 0.0765
(15) nRBp + 0.005 RB RBp = 1.9904
(16) nRBn + 0.005 RB RBn = 1.8446

FIGS. 14 (a) and 14 (b) are various aberration diagrams, respectively, at the time of focusing on an infinite distance object and during focusing on a near distance object of the optical system according to the seventh embodiment.
From the aberration diagrams, it is understood that the optical system according to the present embodiment has excellent imaging performance by satisfactorily correcting various aberrations from focusing on an infinite distance object to focusing on a close distance object.

Eighth embodiment
FIGS. 15 (a) and 15 (b) are cross-sectional views of an optical system according to an eighth embodiment when focusing on an infinite object and when focusing on a near object, respectively.
The optical system according to the eighth embodiment is composed of, in order from the object side, a front group GF having positive refractive power, an aperture stop S, and a rear group GR having positive refractive power. A filter F is disposed in the vicinity of the object side of the image plane I.

The front group GF comprises, in order from the object side, a positive lens group GFA having positive refractive power and a front focusing group GFF having positive refractive power.
The positive lens group GFA includes, in order from the object side, a biconcave negative lens L1, a cemented lens of a biconcave negative lens L2 and a biconvex positive lens L3, and a biconvex positive lens L4 and both And a cemented lens with a concave negative lens L5.
The front focusing group GFF is a cemented lens of a biconvex positive lens L6 and a biconcave negative lens L7 in this order from the object side.

The rear group GR includes, in order from the object side, a rear focusing group GRF having positive refractive power and a negative lens group GRB having negative refractive power.
The rear focusing group GRF is composed of, in order from the object side, a biconcave negative lens L8 and a biconvex positive lens L9.
The negative lens group GRB is composed of, in order from the object side, a negative meniscus lens L10 having a convex surface facing the image side, and a negative meniscus lens L11 having a convex surface facing the image side.

In the optical system according to the eighth embodiment, focusing from an infinite distance object to a near distance object is performed by moving the front focusing group GFF and the rear focusing group GRF to the object side along the optical axis. At the time of focusing, the positions of the positive lens unit GFA, the aperture stop S, and the negative lens unit GRB are fixed.
Table 8 below presents values of specifications of the optical system according to the eighth example.

(Table 8) Eighth Example
[Plane data]
Face number r d nd d d
Object ∞ 1.000000
1) -1384.5606 2.4000 1.518230 58.82
* 2) 22.7521 19.5726 1.000000
3) -210.4727 2.0000 1.603420 38.03
4) 34.8221 11.0013 1.834810 42.73
5) -98.9663 0.2000 1.000000
6) 41.5127 8.8597 1.834810 42.73
7) -70.1358 1.6000 1.647690 33.72
8) 41.7744 Variable 1.000000
9) 30.8554 5.2069 1.497820 82.57
10) -344.99897 1.2000 1.672700 32.18
11) 59.4370 Variable 1.000000
12) (F-stop S) 可 変 Variable 1.000000
* 13) -128.3993 1.8000 1.834810 42.73
14) 316.2495 1.3930 1.000000
15) 98.6994 10.2289 1.497820 82.57
* 16) -18.9378 Variable 1.000000
17) -47.2364 3.0654 1.902650 35.72
18) -35.8672 5.9831 1.000000
19) -30.0877 1.4000 1.688931 31.07
20) -1077.5863 14.3679 1.000000
21) ∞ 1.6000 1.516800 64.13
22) 0.9 0.9778 1.000000
Image plane ∞
[Aspheric surface data]
Face number κ A4 A6 A8 A10 A12
2 0.0000 8.60806E-06 -2.33850E-09 3.59347E-11 -7.01381E-14 0.61254E-16
13 0.0000 -3.09776E-05 -8.13151E-08 -2.38297E-10 2.73111E-14 -0.12604E-13
16 1.0000 4.53043E-07 -2.70015E-08 4.55831E-11 -6.17207E-13 0.12765E-14
[Various data]
f 34. 1413
Fno 1.85683
2ω 65.0328
Ymax 21.60
TL 114.97777
Air conversion TL 114.43257
Bf 53.1934
Air conversion Bf 54.6482
Ainf 33.09508
Amod 32.1484
Infinite distance short distance f 34.1413
β -0.1418
d0 ∞ 221.3238
d8 5.743 9 2.0995
d11 4.0000 7.6445
d12 9.1921 6.0059
d16 3.1853 6.3715
2ω 65.0328
ω 32.5164
[Lens group data]
Group front f
GF 1 57.9019
GR 13 86.1509
GFA 1 102.0669
GFF 9 196.0962
GRF 13 42.5650
GRB 17 -65.8197
[Conditional expression corresponding value]
(1) fRF / fFF = 0.2171
(2) Bf / f = 1.5421
(3) ST / TL = 0.1433
(4) βRF / βFF = 0.8301
(5) fF / fR = 0.6721
(6) fFA / fFF = 0.5205
(7) f / fFF = 0.1741
(8) f / fRF = 0.8021
(9) TL / (Fno · Bf) = 1.1706
(10) | Ainf-Amod | / f = 0.0277
(11) FFFFp-FFFFn = 50.3900
(12) (FFr2 + FFr1) / (FFr2-FFr1) = 0.8358
(13) (-fRB) / f = 1.9279
(14) nRBp-nRBn = 0.2137
(15) nRBp + 0.005 RB RBp = 2.0813
(16) nRBn + 0.005 RB RBn = 1.8443

16 (a) and 16 (b) are various aberration diagrams, respectively, at the time of focusing on an infinite distance object and during focusing on a near distance object of the optical system according to the eighth example.
From the aberration diagrams, it is understood that the optical system according to the present embodiment has excellent imaging performance by satisfactorily correcting various aberrations from focusing on an infinite distance object to focusing on a close distance object.

(9th embodiment)
FIGS. 17A and 17B are cross-sectional views of an optical system according to a ninth embodiment at focusing on an infinite object and focusing on a near object, respectively.
The optical system according to the ninth embodiment is composed of, in order from the object side, a front group GF having positive refractive power, an aperture stop S, and a rear group GR having positive refractive power. A filter F is disposed in the vicinity of the object side of the image plane I.

The front group GF comprises, in order from the object side, a positive lens group GFA having positive refractive power and a front focusing group GFF having positive refractive power.
The positive lens group GFA includes, in order from the object side, a negative meniscus lens L1 having a convex surface on the object side, a negative meniscus lens L2 having a convex surface on the object side, a biconcave negative lens L3, and a convex surface on the object side And a positive meniscus lens L6 having a convex surface facing the object side.
The front focusing group GFF is a cemented lens of a biconvex positive lens L7 and a biconcave negative lens L8 in this order from the object side.

The rear group GR includes, in order from the object side, a rear focusing group GRF having positive refractive power and a negative lens group GRB having negative refractive power.
The rear focusing group GRF includes, in order from the object side, a negative meniscus lens L9 having a convex surface facing the image side, and a biconvex positive lens L10.
The negative lens group GRB is composed of, in order from the object side, a biconcave negative lens L11 and a biconvex positive lens L12.

In the optical system according to the ninth embodiment, focusing from an infinite distance object to a near distance object is performed by moving the front focusing group GFF and the rear focusing group GRF to the object side along the optical axis. At the time of focusing, the positions of the positive lens unit GFA, the aperture stop S, and the negative lens unit GRB are fixed.
Table 9 below presents values of specifications of the optical system according to the ninth example.

Table 9 ninth embodiment
[Plane data]
Face number r d nd d d
Object ∞ 1.000000
1) 90.1539 2.0000 1.658440 50.83
2) 35.0000 1.0023 1.000000
3) 38.0000 1.8000 1.622910 58.30
* 4) 17.5155 13.7363 1.000000
5) -135.7140 1.6000 1.593190 67.90
6) 48.9808 6.5355 1.000000
7) 861.6049 2.4809 1.620040 36.40
8) 31.3689 9.0000 1.851500 40.78
9) -150.1624 3.1783 1.000000
10) 40.3712 5.2632 1.851500 40.78
11) 1025.5030 Variable 1.000000
12) 32.7343 4.0000 1.497820 82.57
13) -155.0414 1.2000 1.808090 22.74
14) 62.0187 Variable 1.000000
15) (F-stop S) 可 変 Variable 1.000000
* 16) -45.5353 2.0000 1.860999 37.10
* 17) -52.3373 1.5881 1.000000
18) 60.0000 7.3310 1.497820 82.57
19) -19.2015 Variable 1.000000
* 20) -27.0655 1.2000 1.689480 31.02
21) 81.9849 1.4246 1.000000
* 22) 43.0859 4.0000 1.882023 37.22
23) -1000.0000 17.7393 1.000000
24) ∞ 1.6000 1.516800 63.88
25) ∞ 1.0000 1.000000
Image plane ∞
[Aspheric surface data]
Face number κ A4 A6 A8 A10 A12
4 0.0000 1.52130E-05-1.37943E-09 1.13792E-10-3.10899E-13 0.49329E-15
16 0.0000 -3.46585E-05 1.35812E-08 1.68641E-09 -1.95052E-11 0.59812E-13
17 1.0000 2.60772E-06 8.97314E-08 1.14490E-09 -1.26537E-11 0.35190E-13
20 1.5918 1.23579E-04 -8.07461E-07 5.37616E-09 -2.11181E-11 0.34821E-13
22 1.0000 -8.27671E-05 4.88811E-07 -2.91586E-09 9.85401E-12 -0.14168E-13
[Various data]
f 20.0000
Fno 1.854
2ω 97.6294
Ymax 21.60
TL 114.09
Air conversion TL 113.5448
Bf 20.33935
Air conversion Bf 19.79415
Ainf 48.68147
Amod 47.75113
Infinite distance short distance f 20.0000
β -0.1987
d0 ∞ 80.548
d11 8.0031 5.1763
d14 5.0918 7.9186
d15 7.1424 4.7424
d19 4.1730 6.5730
2ω 97.6294
ω 48.8147
[Lens group data]
Group front f
GF 1 51.8791
GR 16 47.3528
GFA 1 59.9544
GFF 12 1108.3235
GRF 16 31.1504
GRB 20-88.9793
[Conditional expression corresponding value]
(1) fRF / fFF = 0.0281
(2) Bf / f = 0.9897
(3) ST / TL = 0.4285
(4) βRF / βFF = 0.3388
(5) fF / fR = 1.0956
(6) fFA / fFF = 0.0541
(7) f / fFF = 0.0180
(8) f / fRF = 0.6420
(9) TL / (Fno · Bf) = 3.0940
(10) | Ainf-Amod | / f = 0.0465
(11) FFFFp-FFFFn = 59.8300
(12) (FFr2 + FFr1) / (FFr2-FFr1) = 0.6513
(13) (−fRB) /f=4.4490
(14) nRBp-nRBn = 0.1925
(15) nRBp + 0.005 RB RBp = 1.6719
(16) nRBn + 0.005 RB RBn = 2.0681

18 (a) and 18 (b) are various aberration diagrams, respectively, at the time of focusing on an infinite distance object and during focusing on a near distance object of the optical system according to the ninth example.
From the aberration diagrams, it is understood that the optical system according to the present embodiment has excellent imaging performance by satisfactorily correcting various aberrations from focusing on an infinite distance object to focusing on a close distance object.

  According to each of the above embodiments, it is suitable for a mirrorless camera, and it is possible to realize an optical system having good optical performance by suppressing fluctuations of various aberrations during focusing while achieving weight reduction of the focusing group. .

  The above-described embodiments show one specific example of the present invention, and the present invention is not limited thereto. The following contents can be adopted appropriately as long as the optical performance of the optical system of the present embodiment is not impaired.

  Although an example of the optical system according to the present embodiment has been described as having a two-group configuration, the present invention is not limited to this, and an optical system having another group configuration (for example, three-group etc.) may be configured. Specifically, a lens or a lens group may be added to the most object side or the most image side of the optical system of each of the above embodiments. Moreover, although the front group and the rear group showed the thing of 2 group or 3 group structure, this application is not restricted to this, It is also possible to set it as other group structures (for example, 4 groups etc.). Specifically, the most object side or the most image side of the front group in each embodiment, between the positive lens group and the front focusing group, the most object side or the most image side of the rear group, the back focusing group and the negative A lens or a lens group may be added between the lens groups or the like.

  The optical system of each of the above embodiments uses the front focusing group and the rear focusing group as focusing lens groups. Such a focusing lens group can also be applied to auto focusing, and is also suitable for driving by a motor for auto focusing, such as an ultrasonic motor, a stepping motor, a VCM motor, etc. Quietness at the time of focusing can be achieved well.

Further, in the optical system of each of the above embodiments, the whole or a part of any lens group is moved as a vibration reduction lens group so as to include a component in a direction perpendicular to the optical axis or an in-plane including the optical axis It is also possible to adopt a configuration in which vibration isolation is performed by rotational movement (rocking) in the direction.
Further, the aperture stop in the optical system of each of the above embodiments may be configured such that the lens frame substitutes for the role without providing a member as the aperture stop.

  Further, the lens surface of the lens constituting the optical system of each of the above embodiments may be a spherical surface, a flat surface, or an aspheric surface. Each lens may be formed of a glass material, a resin material, or a composite of a glass material and a resin material. When the lens surface is spherical or flat, it is preferable because lens processing and assembly adjustment can be facilitated, and deterioration of optical performance due to lens processing and assembly adjustment errors can be prevented. In addition, even when the image plane shifts, it is preferable because the deterioration of the imaging performance is small. When the lens surface is aspheric, any of aspheric aspheric surfaces by grinding, a glass mold aspheric surface formed by shaping a glass into aspheric surface shape, or a composite aspheric surface formed by forming a resin on a glass surface into an aspheric surface shape Good. The lens surface may be a diffractive surface, and the lens may be a gradient index lens (GRIN lens) or a plastic lens.

  Further, an antireflective film may be provided on the lens surface of the lens constituting the optical system of each of the above embodiments. This can reduce flare and ghost and achieve high contrast and high optical performance. In particular, it is preferable to apply an anti-reflection film to the lens surface on the object side of the second lens counted from the object side in the optical system of each of the above embodiments.

Next, a camera provided with the optical system of the present embodiment will be described based on FIG.
FIG. 19 is a diagram showing a configuration of a camera provided with the optical system of the present embodiment.
As shown in FIG. 19, the camera 1 is an interchangeable lens mirrorless camera provided with the optical system according to the first embodiment as the photographing lens 2.

In the present camera 1, light from an object (not shown) from the object (not shown) is collected by the photographing lens 2 and passes through an OLPF (Optical Low Pass Filter) (not shown) on the imaging surface of the imaging unit 3 Form an image of the subject. Then, the subject image is photoelectrically converted by the photoelectric conversion element provided in the imaging unit 3 to generate the image of the subject. This image is displayed on an EVF (Electronic view finder) 4 provided in the camera 1. Thereby, the photographer can observe the subject via the EVF 4.
When the photographer presses a release button (not shown), the image of the subject generated by the imaging unit 3 is stored in a memory (not shown). In this way, the photographer can shoot a subject with the main camera 1.

  By mounting the optical system according to the first embodiment as the photographing lens 2, the present camera 1 achieves favorable optical performance by suppressing fluctuations of various aberrations during focusing while achieving weight reduction of the focusing group. can do.

  Even if a camera is mounted with the optical system according to the second to ninth examples as the photographing lens 2, the same effect as the camera 1 can be obtained. Even when the optical system according to each of the above-described embodiments is mounted on a single-lens reflex camera having a quick return mirror and observing a subject by a finder optical system, the same effect as that of the camera 1 can be obtained.

Finally, an outline of a method of manufacturing an optical system of the present embodiment will be described based on FIG.
FIG. 20 is a view showing an outline of a method of manufacturing an optical system according to the present embodiment.
The method of manufacturing an optical system according to the present embodiment shown in FIG. 20 includes, in order from the object side, a method of manufacturing an optical system including a front group having positive refractive power, an aperture stop, and a rear group having positive refractive power. And includes the following steps S1 to S5.

Step S1: Prepare the front group, the aperture stop and the rear group, and arrange them in order from the object side in the lens barrel.
Step S2: The front group is made to have a positive lens group having positive refractive power and a front focusing group having positive refractive power in order from the object side.
Step S3: The rear group is made to have, in order from the object side, a rear focusing group having positive refractive power and a negative lens group having negative refractive power.
Step S4: By providing a known moving mechanism on the lens barrel, the front focusing group and the rear focusing group are moved in the optical axis direction at the time of focusing.
Step S5: A lens located closest to the object side is made to have negative refractive power.

  According to the manufacturing method of the optical system of the present embodiment, it is suitable for a mirrorless camera, and an optical system having good optical performance by suppressing fluctuation of various aberrations at the time of focusing while achieving weight reduction of the focusing group. The system can be manufactured.

GFA: positive lens group, GFF: front focusing group, GRF: rear focusing group, GRB: negative lens group, S: aperture stop, I: image plane

Claims (33)

From the object side, it consists of a front group having positive refractive power, an aperture stop, and a rear group having positive refractive power,
The front group includes, in order from the object side, a positive lens group having positive refractive power and a front focusing group having positive refractive power.
The rear group includes, in order from the object side, a rear focusing group having positive refractive power and a negative lens group having negative refractive power.
At the time of focusing, the front focusing group and the rear focusing group move in the optical axis direction,
An optical system in which the lens located closest to the object side has negative refractive power.   The optical system according to claim 1, wherein the position of the aperture stop is fixed at the time of focusing. The optical system according to claim 1, wherein the following conditional expression is satisfied.
0.010 <fRF / fFF <0.900
However,
fFF: focal length of the front focusing group fRF: focal length of the rear focusing group The optical system according to any one of claims 1 to 3, which satisfies the following conditional expression.
0.400 <Bf / f <2.000
However,
Bf: Distance from the image-side lens surface of the lens closest to the image side when focusing on an infinite distance object to the image plane f: Focal length of the optical system when focusing on an infinite distance object The optical system according to any one of claims 1 to 4, which satisfies the following conditional expression.
0.100 <ST / TL <0.600
However,
ST: The distance from the aperture stop to the image plane when focusing on an infinite object TL: The distance from the object-side lens surface of the lens closest to the object side to the image plane when focusing on an infinite object The optical system according to any one of claims 1 to 5, which satisfies the following conditional expression.
0.200 <βRF / βFF <1.100
However,
βFF: magnification of the front focusing group βRF: magnification of the rear focusing group   The optical system according to any one of claims 1 to 6, wherein the position of the positive lens group is fixed at the time of focusing.   The optical system according to any one of claims 1 to 7, wherein the position of the lens unit located closest to the image side at the time of focusing is fixed.   The optical system according to any one of claims 1 to 8, wherein the front focusing group has at least one positive lens and at least one negative lens.   The optical system according to any one of claims 1 to 9, wherein the rear focusing group has at least one positive lens and at least one negative lens. The optical system according to any one of claims 1 to 10, which satisfies the following conditional expression.
0.300 <fF / fR <1.300
However,
fF: focal length of the front group when focusing on an infinite object fR: focal length of the rear group when focusing on an infinite object   The optical system according to any one of claims 1 to 11, wherein the front focusing group moves to the object side at the time of focusing.   The optical system according to any one of claims 1 to 12, wherein the rear focusing group moves to the object side at the time of focusing. The optical system according to any one of claims 1 to 13, which satisfies the following conditional expression.
0.010 <fFA / fFF <0.750
However,
fFA: focal length of the positive lens group fFF: focal length of the front focusing group The optical system according to any one of claims 1 to 14, which satisfies the following conditional expression.
0.010 <f / fFF <0.300
However,
f: Focal length of the optical system when focusing on an infinite object fFF: Focal length of the front focusing group The optical system according to any one of claims 1 to 15, which satisfies the following conditional expression.
0.300 <f / fRF <1.100
However,
f: Focal length of the optical system when focusing on an infinite object fRF: Focal length of the back focusing group The optical system according to any one of claims 1 to 16, which satisfies the following conditional expression.
0.800 <TL / (Fno · Bf) <6.000
However,
TL: Distance from the object-side lens surface of the lens closest to the object side to the image plane when focusing on an infinite distance object Fno: Open f-number of the optical system Bf: Most on the image side when focusing on an infinite distance object Distance from the image-side lens surface of the lens to the image plane The optical system according to any one of claims 1 to 17, which satisfies the following conditional expression.
| Ainf-Amod | / f <0.070
However,
Ainf: half angle of view of the optical system at the time of infinity object focusing Amod: half angle of the optical system at the time of closest object focusing The front focusing group consists of one positive lens and one negative lens.
The optical system according to any one of claims 1 to 18, which satisfies the following conditional expression.
30.00 <νFFp-νFFn <75.00
However,
FFFFp: Abbe number of the positive lens in the front focusing group FFFFn: Abbe number of the negative lens in the front focusing group The optical system according to any one of claims 1 to 19, which satisfies the following conditional expression.
−1.000 <(FFr2 + FFr1) / (FFr2-FFr1) <2.000
However,
FFr1: Radius of curvature FFr2 of the object-side lens surface of the positive lens closest to the image side in the front focus group: Curvature radius of the image-side lens surface of the positive lens closest to the image side in the front focus group   The optical system according to any one of claims 1 to 20, wherein the front focusing group comprises two or three lenses.   The optical system according to any one of claims 1 to 21, wherein the rear focusing group comprises four or less lenses. The optical system according to any one of claims 1 to 22, which satisfies the following conditional expression.
0.800 <(− fRB) / f <10.000
However,
fRB: focal length of the negative lens group f: focal length of the optical system when focusing on an infinite object   The optical system according to any one of claims 1 to 23, wherein the lens unit located closest to the image side has, in order from the image side, a positive lens and a negative lens. The optical system according to any one of claims 1 to 24, which satisfies the following conditional expression.
0.030 <nRBp-nRBn
However,
nRBp: refractive index of the positive lens in the lens unit located closest to the image side nRBn: refractive index of the negative lens in the lens unit located closest to the image side   The optical system according to any one of claims 1 to 25, wherein an image-side lens surface of a lens positioned closest to the image side in the lens group positioned closest to the image side is convex toward the image side. The optical system according to any one of claims 1 to 26, which satisfies the following conditional expression.
1.000 <nRBp + 0.005νRBp <2.500
1.000 <nRBn + 0.005νRBn <2.500
However,
nRBp: The refractive index nRBn of the positive lens in the lens unit positioned closest to the image side: The refractive index RBRBp of the negative lens in the lens unit positioned closest to the image: Abbe of the positive lens in the lens unit positioned closest to the image Number RB RBn: Abbe number of the negative lens in the lens unit located closest to the image side   The optical system according to any one of claims 1 to 27, wherein the front focusing group and the aperture stop are adjacent to each other.   The optical system according to any one of claims 1 to 28, wherein the aperture stop and the rear focusing group are adjacent to each other.   The optical system according to any one of claims 1 to 27, wherein the front group further includes a lens group whose position is fixed at the time of focusing, between the front focusing group and the aperture stop.   The optical system according to any one of claims 1 to 28, wherein the rear group further includes a lens group fixed in position at the time of focusing, between the aperture stop and the rear focusing group.   An optical apparatus comprising the optical system according to any one of claims 1 to 31. A method of manufacturing an optical system comprising, in order from an object side, a front group having positive refractive power, an aperture stop, and a rear group having positive refractive power,
The front group includes, in order from the object side, a positive lens group having positive refractive power and a front focusing group having positive refractive power.
The rear group includes, in order from the object side, a rear focusing group having positive refractive power and a negative lens group having negative refractive power.
At the time of focusing, the front focusing group and the rear focusing group are moved in the optical axis direction,
A method of manufacturing an optical system, wherein a lens located closest to the object side has negative refractive power.

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