JP6168761B2 - Teleconversion lens and imaging apparatus using the same - Google Patents

Description

  The present invention relates to a teleconversion lens mounted between a master lens and a camera body, a photographing optical system using the same, and an imaging device, and more particularly to an imaging device such as a single-lens reflex camera.

  A single-lens reflex camera is required to be small in size to facilitate carrying. In addition, high-speed and high-accuracy autofocus (automatic focusing) is required in order to perform comfortable shooting.

  As an autofocus method, a contrast method is known in which focusing is performed based on the contrast of an image obtained from an image sensor.

  In the contrast method, the shift direction with respect to the in-focus position can be detected from the change in contrast when the focusing lens group is moved in the optical axis direction. In addition, the signal component of a specific frequency band in the image area is detected from the output signal of the image sensor, the optimum position of the focusing lens group that is in focus is calculated, and the focusing lens group is moved to the optimum position for alignment. Complete the focusing operation.

  In a single-lens reflex camera, the focal length of the entire system may be changed to the telephoto side by mounting a teleconversion lens having a negative refractive power between the interchangeable lens (master lens) and the camera body.

JP 2000-89101 A Japanese Patent Publication No. 6-60970 JP 2011-175054 A

  In many cases, the master lens to which the teleconversion lens is attached is a telephoto lens having a relatively long focal length, and the weight of the focusing lens group tends to increase (Patent Document 1).

  For this reason, during autofocusing using the contrast method, it takes time to move the focusing lens group back and forth in the optical axis direction (wobbling operation), and it is difficult to realize high-speed autofocusing. Alternatively, a large driving device is required to move the focusing lens group having a large weight to the light flux.

  On the other hand, a teleconversion lens having a focusing function has been proposed (Patent Document 2). Since the teleconversion lens of Patent Document 2 performs focusing by driving the entire teleconversion lens, the weight of the focusing lens group is relatively large.

  The attachment lens of Patent Document 3 includes, in order from the object side, an object-side lens group having a negative refractive power, a wobbling lens group having a positive refractive power, and an image-side lens group having a negative refractive power. Since it is about 1 time, it does not have a teleconversion function. In addition, since the image side lens unit has a negative refractive power, the off-axis light beam emitted from the image side lens unit is incident on the image sensor at a large angle, so that the peripheral light amount is likely to decrease.

  An object of the present invention is to provide a teleconversion lens capable of high-speed wobbling operation and having good telecentric characteristics.

The teleconversion lens of the present invention is a teleconversion lens that is mounted between a master lens and a camera body and has a negative refractive power as a whole, and is arranged in order from the object side to the image side, and includes a front group Lf, focusing The lens unit Ln has a negative refractive power that reciprocates in the direction of the optical axis to perform a wobbling operation, and a rear group Lr with a positive refractive power, and during focusing, the distance between the front group Lf and the lens group Ln, A teleconversion lens in which the distance between the lens unit Ln and the rear unit Lr changes, and when the focal length of the rear unit Lr is fr and the focal length of the lens unit Ln is fn,
1.30 <| fr / fn | <1.80
The following conditional expression is satisfied.

  According to the present invention, it is possible to provide a teleconversion lens capable of high-speed wobbling operation and having good telecentric characteristics.

Sectional drawing when the teleconversion lens of Numerical Example 1 of the present invention is attached to a master lens Sectional view of a teleconversion lens of Numerical Example 1 of the present invention Aberration diagram when the teleconversion lens of Numerical Example 1 of the present invention is attached to a master lens. Sectional view of the teleconversion lens of Reference Example 2 of the present invention Aberration diagram when the teleconversion lens of Reference Example 2 of the present invention is attached to a master lens Sectional drawing of the teleconversion lens of the numerical Example 3 of this invention Aberration diagram when the teleconversion lens of Numerical Example 3 of the present invention is attached to a master lens. Sectional drawing of the teleconversion lens of Numerical Example 4 of this invention Aberration diagram when the teleconversion lens of Numerical Example 4 of the present invention is mounted on a master lens Schematic diagram of imaging device of the present invention

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a cross-sectional view when the teleconversion lens of Numerical Example 1 of the present invention is attached to a master lens.

  FIG. 2 is a cross-sectional view of the teleconversion lens according to Numerical Example 1 of the present invention. FIG. 3 is an aberration diagram when the teleconversion lens of Numerical Example 1 of the present invention is attached to a master lens. Numerical Example 1 is a teleconversion lens with a magnification of 1.41.

FIG. 4 is a cross-sectional view of the teleconversion lens of Reference Example 2 of the present invention. FIG. 5 is an aberration diagram when the teleconversion lens of Reference Example 2 of the present invention is attached to a master lens. Reference Example 2 is a teleconversion lens with a magnification of 1.41.

  FIG. 6 is a cross-sectional view of a teleconversion lens according to Numerical Example 3 of the present invention. FIG. 7 is an aberration diagram when the teleconversion lens according to Numerical Example 3 of the present invention is attached to the master lens. Numerical Example 3 is a teleconversion lens with a magnification of 1.41.

  FIG. 8 is a cross-sectional view of a teleconversion lens according to Numerical Example 3 of the present invention. FIG. 9 is an aberration diagram when the teleconversion lens according to Numerical Example 3 of the present invention is attached to a master lens. Numerical Example 3 is a teleconversion lens with a magnification of 1.41.

  FIG. 10 is a schematic diagram of the imaging apparatus 100 of the present invention.

  In the lens cross-sectional view, Lf is a front group, Ln is a focusing lens group (lens group Ln) having a negative refractive power, and Lr is a rear group (lens group Lr) having a positive refractive power.

  SP is an F number determining member (hereinafter also referred to as “aperture stop”) that functions as an aperture stop that determines (limits) an open F number (Fno) light beam. IP is an image plane, and when used as a photographing optical system of a video camera or a digital still camera, an imaging plane of a solid-state imaging device (photoelectric conversion device) such as a CCD sensor or a CMOS sensor is placed.

  In the aberration diagram, the solid line in spherical aberration is the d line, the two-dot chain line is the g line, and the broken line is the sine condition S.D. C. Represents. The broken line in astigmatism represents the d-line meridional image plane, and the solid line represents the d-line sagittal image plane. Distortion aberration represents distortion at the d-line. Lateral chromatic aberration is represented by the g-line. Fno is an F number, and ω is a half angle of view (degrees).

  The teleconversion lens 10 is attached between the master lens 20 and the camera body 40. An optical image of a subject is formed on the image sensor 42 of the camera body 40 by the photographing optical system 30 constituted by the teleconversion lens 10 and the master lens 20. The image sensor 42 photoelectrically converts the optical image formed by the photographing optical system 30. A plurality of tele conversion lenses 10 can be mounted between the master lens 20 and the camera body 40. By mounting the teleconversion lens 10 on the image side of the master lens 20, the teleconversion lens 10 can be made compact. The tele conversion lens is a conversion lens having a magnification of 1.3 or more.

  The teleconversion lens 10 includes, in order from the object side to the image side, a front group Lf, a lens group Ln having a negative refractive power, and a rear group Lr having a positive refractive power. The lens unit Ln is driven by a driving unit (not shown) in order to perform a wobbling operation that reciprocates in the optical axis direction for autofocusing.

  By disposing the rear lens unit Lr having a positive refractive power on the image side of the lens unit Ln having a negative refractive power, the negative refractive power of the lens unit Ln can be made relatively large. Thereby, it becomes easy to obtain a contrast change due to the wobbling operation, and the moving range of the reciprocating movement of the lens unit Ln can be reduced.

  Further, by disposing the rear lens unit Lr having a positive refractive power on the image side of the lens unit Ln having a negative refractive power, good telecentric characteristics can be obtained even with a short back focus. That is, since the rear group Lr having a positive refractive power converges with respect to the off-axis light beam emitted from the lens unit Ln having a negative refractive power, the off-axis light beam emitted from the rear group Lr at a relatively small angle. The light can be incident on the image sensor, and the amount of peripheral light can be easily secured. Further, it becomes easy to suppress a change in the shooting angle of view due to the wobbling operation.

  The front group Lf may have a positive refractive power, a negative refractive power, or a refractive power of zero. By disposing the lens group Ln between the front group Lf and the rear group Lr, it is possible to prevent a large force from being applied to the lens group Ln from the outside, and thus the drive mechanism connected to the lens group Ln is protected. be able to. In addition, the axial chromatic aberration and the spherical aberration can be easily corrected by disposing the front group Lf on the most object side passing through the position where the peripheral ray of the axial light beam is high.

  As described above, it is possible to obtain a teleconversion lens capable of high-speed wobbling and having good telecentric characteristics. By satisfying at least one of the conditional expressions and configurations described below, the effects corresponding to each of them can be obtained, and a more preferable teleconversion lens can be realized.

  In order to detect the shift direction with respect to the in-focus position, it is necessary to sufficiently change the contrast when the focusing lens group is driven. In the case of a lens having a small F-number, the depth of focus is shallow, so that the contrast changes greatly with a small drive amount.

  On the other hand, when the lens with a large F number or the aperture stop of the lens is narrowed, the depth of focus is deep. Therefore, in order to change the contrast by the same amount, it is necessary to increase the driving amount of the focusing lens group.

  However, when the driving amount of the focusing lens group is increased, it becomes difficult to detect the deviation direction from the in-focus direction at high speed.

  When the amount of movement of the image plane in the optical axis direction when the focusing lens group is driven in the optical axis direction by a minute amount Δxf is Δxp, the focus sensitivity is expressed as Δxp / Δxf.

  By increasing the focus sensitivity, it becomes easy to detect the deviation direction from the in-focus direction at high speed even when the depth of focus is deep.

  On the other hand, if the focus sensitivity is increased too much, the positioning accuracy of the focusing lens group becomes high, and the required processing accuracy becomes too high.

The focus sensitivity is obtained by using the lateral magnification βf of the focusing lens group and the combined lateral magnification βR of the lens group existing on the image side of the focusing lens group.
Δxp / Δxf = | βf ² −1 | × βR ²
Can be expressed as However, βR is 1 when there is no lens on the image side of the focusing lens group.

  In order to set the focus sensitivity to an appropriate value, it is important to select an appropriate refractive power arrangement and focusing lens group.

In the teleconversion lens 10, when the lateral magnification of the lens group Ln is βn and the lateral magnification of the rear group Lr is βr,
1.0 <| βn ² −1 | × βr ² <3.5 (1)
It is desirable to satisfy the following conditions.

  Conditional expression (1) relates to the focus sensitivity of the lens unit Ln. Exceeding the lower limit of conditional expression (1) is not preferable because the moving range of the lens unit Ln during the wobbling operation becomes too large.

  Exceeding the upper limit of conditional expression (1) is not preferable because the positioning accuracy of the lens unit Ln becomes too high.

More preferably, the following conditions are satisfied.
1.2 <| βn ² −1 | × βr ² <3.0 (1a)

When the radius of curvature of the lens surface closest to the object side of the lens unit Ln is Rnf and the radius of curvature of the lens surface closest to the image side of the lens unit Ln is Rnr,
0.30 <(Rnr−Rnf) / (Rnr + Rnf) <0.94 (2)
It is desirable to satisfy the following conditions.

  Conditional expression (2) relates to the lens shape of the lens unit Ln. In the wobbling operation of the lens unit Ln, it is desirable to reduce the change in contrast that is not caused by the movement of the image plane as much as possible. Therefore, it is desirable that the lens unit Ln as a whole has a meniscus shape with a convex surface facing the image side so that the principal ray of the off-axis light beam is incident on the lens surface of the lens unit Ln at a small angle. By making the lens unit Ln into a meniscus shape with a convex surface facing the image side, it becomes easy to correct the aberration of the axial ray.

  If the lower limit of conditional expression (2) is exceeded, it is difficult to ensure the focus sensitivity of the lens unit Ln, which is not preferable.

  Exceeding the upper limit of conditional expression (2) is not preferable because it makes it difficult to correct field curvature well.

More preferably, the following conditions are satisfied.
0.45 <(Rnr−Rnf) / (Rnr + Rnf) <0.92 (2a)

  Further, it is preferable to form the lens unit Ln with a single negative lens, because the focusing lens unit can be reduced in weight and a high-speed wobbling operation is facilitated. However, the lens group Ln can be, for example, a cemented lens of a negative lens and a positive lens, and can be configured using a plurality of lenses.

When the focal length of the lens unit Ln is fn and the focal length of the entire teleconversion lens system is f,
0.06 <fn / f <0.35 (3)
It is desirable to satisfy the following conditions.

  Conditional expression (3) relates to the refractive power of the lens unit Ln. Exceeding the lower limit of conditional expression (3) is not preferable because the absolute value of the refractive power of the lens unit Ln becomes too large and aberration fluctuations and field angle changes during wobbling operation become large.

  Exceeding the upper limit of conditional expression (3) is not preferable because the absolute value of the refractive power of the lens unit Ln becomes too small to make it difficult to ensure focus sensitivity.

More preferably, the following conditions are satisfied.
0.08 <fn / f <0.31 (3a)

Further, when the focal length of the rear group Lr is fr and the focal length of the lens group Ln is fn,
1.30 <| fr / fn | <1.80 (4)
It is desirable to satisfy the following conditions.

  Conditional expression (4) relates to the ratio of the refractive powers of the lens unit Ln and the rear unit Lr. Exceeding the lower limit of conditional expression (4) is not preferable because the absolute value of the refractive power of the lens unit Ln becomes too small to make it difficult to ensure focus sensitivity.

  If the upper limit of conditional expression (4) is exceeded, the refractive power of the rear group Lr becomes too small, making it difficult to obtain good telecentric characteristics, which is not preferable.

More preferably, the following conditions are satisfied.
1.35 <| fr / fn | <1.77 (4a)

The distance on the optical axis from the lens surface closest to the object side to the lens surface closest to the image side of the teleconversion lens is TD, and the distance on the optical axis from the lens surface closest to the image side of the teleconversion lens to the image plane is When BFc,
2.0 <TD / BFc <4.5 ( 5 )
It is good to satisfy the condition.

Conditional expression ( 5 ) relates to the ratio of the lens configuration length of the teleconversion lens to the back focus.

Exceeding the lower limit of conditional expression ( 5 ) is not preferable because the back focus becomes too long and the entire length of the imaging optical system 30 when the teleconversion lens 10 is attached to the master lens 20 becomes long.

Exceeding the upper limit of conditional expression ( 5 ) is not preferable because the back focus becomes too short and interferes with the camera body 40.

More preferably, the following conditions are satisfied.
2.2 <TD / BFc <4.3 ··· (5 a)

  In addition, it is preferable to arrange an aspherical surface in the rear group Lr with good separation of off-axis rays because aberrations can be corrected well.

  As shown in FIG. 10, it is preferable that the teleconverter CPU (control means) 11 communicates with at least one of the master lens CPU 21 and the camera body CPU 41 via the master lens side communication means 12 and the camera body side communication means 13.

Using the communication means 12 and 13, the teleconversion lens 10 communicates with at least one of the master lens 20 and the camera body 40, thereby acquiring information on whether or not the camera body 40 is compatible with contrast autofocus. can do.
When the camera body 40 is compatible with contrast autofocus, the wobbling operation of the lens group Ln of the teleconversion lens 10 can be used for autofocus during live view or movie shooting.

  During movie shooting, the aperture stop SP of the lens may be stopped. As the F number increases, the depth of focus increases, so it is preferable to increase the driving amount of the lens unit Ln according to the F number of the photographing optical system 30. It is preferable that the driving amount of the lens group Ln is determined by at least one of the teleconverter CPU11, the master lens CPU21, and the camera body CPU41 based on optical information at the time of photographing such as the F number of the photographing optical system 30.

  Further, when the teleconversion lens 10 communicates with at least one of the master lens 20 and the camera body 40, it is possible to acquire information regarding whether or not the master lens 20 has a focusing lens group capable of wobbling operation. When the master lens 20 has a focusing lens group capable of wobbling, the teleconverter CPU 11, the master lens CPU 21, and the camera body CPU 41 communicate with each other so that the master lens 20, the teleconversion lens 10 or both focusing lens groups can be selected. Control can be performed so as to determine the optimum driving amount used.

  For example, when the aperture stop SP is stopped, the depth of focus becomes deep, so that the wobbling is performed using the focusing lens group having the higher focus sensitivity among the focusing lens groups of the master lens 20 and the teleconversion lens 10. It is good to operate. Thereby, it is possible to prevent the driving amount of the focusing lens group from becoming too large.

  On the other hand, when the aperture of the aperture stop SP is large, the depth of focus becomes shallow. Therefore, among the focusing lens groups of the master lens 20 and the teleconversion lens 10, the wobbling operation is performed using the focusing lens group having the lower focus sensitivity. It is good to let it. By using the focusing lens group whose focus sensitivity is not too high, the wobbling operation of the focus lens group can be easily controlled.

  The teleconversion lens of the present invention may be a mount adapter that is mounted between the camera body and the master lens having a shorter flange back than the master lens flange back. Thus, teleconversion for changing the focal length of the master lens to the telephoto side and extension of the flange back can be achieved at the same time. Furthermore, the optical system portion of the teleconversion lens may be detachable from the lens barrel portion of the mount adapter for extending the flange back.

  Next, numerical examples of the master lens 20 to which the teleconversion lens 10 of the present invention is attached and numerical examples 1 to 4 of the teleconversion lens 10 of the present invention will be described below. In these numerical examples, the surface number i indicates the order from the object side, ri is the radius of curvature of the i-th surface in order from the object side, and di is between the i-th and i + 1-th in order from the object side. Lens thickness or air spacing. d0 is an air space from the final surface of the master lens to the first surface of the teleconversion lens. nd and νd are respectively the refractive index and Abbe number at the d-line of the i-th optical member in order from the object side. The aspherical shape is the X axis in the optical axis direction, the H axis in the direction perpendicular to the optical axis, the light traveling direction is positive, R is the paraxial radius of curvature, K is the conic constant, and A4, A6, A8, and A10 are aspherical surfaces. As a coefficient

It is expressed by the following formula. [E + X] means [× 10 ^x ], and [e−X] means [× 10 ^−x ]. BF is an air-converted distance (back focus) from the lens surface closest to the image side of the master lens to the image surface when no teleconversion lens is attached. The total lens length is obtained by adding BF to the distance from the lens surface closest to the object side of the master lens to the lens surface closest to the image side of the master lens. An aspherical surface is indicated by adding * after the surface number.

  Table 1 shows the correspondence between each numerical example of the present invention and each conditional expression.

(Master lens)
Unit mm

Surface data surface number rd nd νd
1 270.270 14.50 1.48749 70.4
2 -835.232 31.14
3 138.907 20.35 1.43387 95.1
4 -523.327 0.19
5 -499.366 4.30 1.72047 34.7
6 310.896 27.04
7 96.687 14.92 1.43387 95.1
8 664.543 0.24
9 63.598 6.00 1.51633 64.1
10 51.493 24.99
11 461.177 5.35 1.80809 22.8
12 -178.181 3.20 1.83400 37.2
13 117.578 73.69
14 (Aperture) ∞ 10.03
15 285.718 7.19 1.72916 54.7
16 -69.727 2.18 1.84666 23.8
17 -247.741 0.84
18 81.104 5.31 1.84666 23.8
19 -151.144 2.00 1.69680 55.5
20 41.763 5.33
21 -163.217 1.70 1.88300 40.8
22 95.192 2.18
23 93.284 5.74 1.83400 37.2
24 -356.898 8.32
25 63.599 9.04 1.74950 35.3
26 -95.263 1.87 1.80809 22.8
27 101.811 11.05
28 ∞ 2.20 1.48749 70.2
29 ∞ 27.79
30 ∞ BF
Image plane ∞

Various data

Focal length 390.09
F number 2.90
Angle of View 2.01
Statue height 13.66
Total lens length 367.66
BF 44.00

(Numerical example 1)
Unit mm

Surface data surface number rd nd νd
1 -1799.466 2.56 1.72825 28.5
2 -37.195 0.15
3 -190.736 0.67 1.83481 42.7
4 15.769 2.72 1.72825 28.5
5 89.570 6.21
6 -14.103 1.50 2.00069 25.5
7 -42.328 3.35
8 * 534.515 6.50 1.51823 58.9
9 -18.019

Aspheric data 8th surface
K = 0.00000e + 000 A 4 = 8.30447e-006 A 6 = -9.02224e-008 A 8 = 2.22742e-010 A10 = -3.23884e-013

Focal length -226.69
Magnification 1.41
d0 22.83

Front principal point position -44.82
Rear principal point position -83.57

Single lens Data lens Start surface Focal length
1 1 52.12
2 3 -17.42
3 4 25.88
4 6 -21.71
5 8 33.77

( Reference Example 2)
Unit mm

Surface data surface number rd nd νd
1 -256.923 1.46 1.72151 29.2
2 -36.298 1.06
3 -45.290 0.67 1.83481 42.7
4 17.884 5.50 1.69895 30.1
5 -27.816 3.26
6 -15.067 1.20 2.00069 25.5
7 -286.282 3.95
8 * 766.576 6.66 1.61340 44.3
9 -17.345 1.82
10 -59.190 1.00 2.00330 28.3
11 -145.569

Aspheric data 8th surface
K = 0.00000e + 000 A 4 = 8.85530e-006 A 6 = -9.04161e-008 A 8 = 1.98493e-010 A10 = -2.24647e-013

Focal length -118.38
Magnification 1.41
d0 21.91

Front principal point position -12.36
Rear principal point position -39.10

Single lens Data lens Start surface Focal length
1 1 58.42
2 3 -15.29
3 4 16.39
4 6 -15.93
5 8 27.74
6 10 -100.00

(Numerical Example 3)
Unit mm

Surface data surface number rd nd νd
1 14.358 0.90 1.80000 29.8
2 12.357 0.15
3 11.427 2.17 1.48749 70.4
4 * 22.120 11.53
5 -39.361 1.66 1.69895 30.1
6 -13.092 0.34
7 -11.815 0.67 1.88 300 40.8
8 18.720 0.15
9 18.695 2.00 1.75520 27.5
10 -95.590 6.29
11 -11.235 0.90 2.00330 28.3
12 -48.650 1.55
13 * 36.082 5.77 1.62588 35.7
14 -22.236

Aspheric data 4th surface
K = 0.00000e + 000 A 4 = -1.43926e-005 A 6 = 6.42189e-008 A 8 = -1.65290e-009 A10 = 1.18681e-011

Side 13
K = 0.00000e + 000 A 4 = -1.83270e-005 A 6 = -9.86530e-008 A 8 = 8.80640e-010 A10 = -2.41944e-012

Focal length -49.30
Magnification 1.41
d0 0.15

Front principal point position 29.50
Rear principal point position -10.52

Single lens Data lens Start surface Focal length
1 1 -138.45
2 3 45.46
3 5 27.36
4 7 -8.12
5 9 20.86
6 11 -14.74
7 13 22.85

(Numerical example 4)
Unit mm

Surface data surface number rd nd νd
1 15.247 2.02 1.51742 52.4
2 * 42.313 1.50
3 35.649 0.90 1.83481 42.7
4 19.099 13.86
5 -24.723 0.59 1.83481 42.7
6 66.919 0.15
7 24.692 3.83 1.67270 32.1
8 -21.848 0.90 1.83481 42.7
9 -65.161 4.49
10 -14.017 0.90 2.00330 28.3
11 -76.924 3.89
12 * 37.546 7.16 1.64769 33.8
13 -26.934

Aspheric data 2nd surface
K = 0.00000e + 000 A 4 = -6.91885e-006 A 6 = -2.67402e-009 A 8 = -1.07989e-010 A10 = 8.56404e-013 A12 = -3.37999e-025

12th page
K = 0.00000e + 000 A 4 = -2.42802e-005 A 6 = -1.45674e-009 A 8 = 4.61608e-010 A10 = -3.10605e-012 A12 = 6.92587e-015

Focal length -149.54
Magnification 1.41
d0 0.15

Front principal point position 0.33
Rear principal point position -51.76

Single lens Data lens Start surface Focal length
1 1 44.92
2 3 -50.53
3 5 -21.56
4 7 17.82
5 8 -39.75
6 10 -17.21
7 12 25.32

  As mentioned above, although preferable embodiment of this invention was described, this invention is not limited to these embodiment, A various deformation | transformation and change are possible within the range of the summary. For example, the master lens 20 to which the teleconversion lens 10 of the present invention is attached is not limited to this, and the teleconversion lens 10 can be attached to various master lenses 20.

10 Tele conversion lens 11 Tele converter CPU
12 Master lens side communication means 13 Camera body side communication means 20 Master lens 21 Master lens CPU
30 Photonic optical system 40 Camera body 41 Camera body CPU
42 Imaging device 100 Imaging device Lf Front group Ln Focusing lens group Lr Rear group SP Aperture IP image surface S Sagittal image surface M Meridional image surface dd line g g line

Claims (12)

A teleconversion lens that is mounted between the master lens and the camera body and has negative refractive power as a whole, and is arranged in order from the object side to the image side, and moves back and forth in the optical axis direction during focusing. A lens unit Ln having a negative refractive power that performs a wobbling operation and a rear group Lr having a positive refractive power, and during focusing, the distance between the front group Lf and the lens group Ln, and the lens group Ln and the rear group Lr. Is a teleconversion lens in which the distance between the rear group Lr and the focal length of the rear lens group Lr is fr and fn, respectively.
1.30 <| fr / fn | <1.80
A teleconversion lens characterized by satisfying the following conditional expression: When the lateral magnification of the lens group Ln is βn and the lateral magnification of the rear group Lr is βr,
1.0 <| βn ² −1 | × βr ² <3.5
The teleconversion lens according to claim 1, wherein the following conditional expression is satisfied. When the radius of curvature of the lens surface closest to the object side of the lens unit Ln is Rnf and the radius of curvature of the lens surface closest to the image side of the lens unit Ln is Rnr,
0.30 <(Rnr-Rnf) / (Rnr + Rnf) <0.94
The teleconversion lens according to claim 1, wherein the following conditional expression is satisfied.   The teleconversion lens according to any one of claims 1 to 3, wherein the lens group Ln includes one negative lens. When the focal length of the entire system of the teleconversion lens is f,
0.06 <fn / f <0.35
The teleconversion lens according to claim 1, wherein the following conditional expression is satisfied. The distance on the optical axis from the lens surface closest to the object side to the lens surface closest to the image side of the teleconversion lens is TD, and the distance on the optical axis from the lens surface closest to the image side of the teleconversion lens to the image plane is When BFc,
2.0 <TD / BFc <4.5
The teleconversion lens according to claim 1, wherein the following conditional expression is satisfied.   7. The flange back of the master lens is longer than the flange back of the camera body, and the teleconversion lens extends the focal length of the master lens to the telephoto side. The teleconversion lens described in 1.   2. The communication device according to claim 1, further comprising a communication unit configured to acquire information on whether or not the camera body is compatible with autofocus by a contrast method by communicating with at least one of the master lens and the camera body. 8. The teleconversion lens according to any one of 7 above.   2. A communication unit that acquires information on whether or not the master lens has a focusing lens group capable of a wobbling operation by communicating with at least one of the master lens and the camera body. 9. The teleconversion lens according to any one of 8 above.   10. The teleconversion lens according to claim 9, further comprising a control unit configured to control driving of the lens group Ln and the focusing lens group during wobbling when the master lens includes the focusing lens group.   An imaging optical system comprising the teleconversion lens according to any one of claims 1 to 10, and a master lens to which the teleconversion lens is attached.   An imaging apparatus comprising: the imaging optical system according to claim 11; and a camera body including an imaging element that photoelectrically converts an optical image formed by the imaging optical system.

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