JP2023021455A - Converter lens, interchangeable lens, and image capturing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a converter lens which is designed to be placed on the image side of a master lens to allow an entire system to provide superior optical performance.

SOLUTION: A converter lens RCL of the present invention comprises three negative lenses and is designed to increase a focal length of an entire system. An average refractive index Ndave of materials of the three negative lenses of the converter lens RCL for the d-ray (587.56 nm wavelength) is appropriately set.

SELECTED DRAWING: Figure 1

COPYRIGHT: (C)2023,JPO&INPIT

Description

The present invention relates to a converter lens, an interchangeable lens, and an imaging device.

A rear converter lens (hereinafter referred to as a converter lens) is known that can extend the focal length of the entire system (lengthen the focal length) by being placed between an interchangeable lens and an imaging device.

Patent Document 1 discloses a converter lens having five negative lenses and a focal length magnification of 2.0.

JP 2017-173692 A

Generally, a converter lens has a negative refractive power, and the negative refractive power tends to increase as the magnification of the focal length increases. It is also known that if the curvature of the negative lens in the converter lens is increased in order to increase the negative refractive power, various aberrations such as coma due to the off-axis light flux are likely to occur.

Furthermore, since the converter lens does not have an aperture stop, off-axis rays that have passed through the master lens in the interchangeable lens are incident on the image plane without their principal rays intersecting the optical axis of the converter lens. Therefore, it is likely to be difficult to perform aberration correction with lenses arranged before and after the aperture stop like an interchangeable lens.

In view of such problems, an object of the present invention is to provide a converter lens capable of obtaining high optical characteristics in the entire system when arranged on the image side of the master lens.

A converter lens that is arranged on the image side of the master lens, has negative refractive power as a whole, and lengthens the focal length of the entire system, wherein the converter lens has three positive lenses, and the converter lens is When there are three negative lenses, and the average refractive index of the material of the three negative lenses at the d-line is Ndave,
1.92<Ndave<2.10
It is characterized by satisfying the following conditional expression.

According to the converter lens of the present invention, high optical characteristics can be obtained in the entire system even when arranged on the image side of the master lens.

4 is a cross-sectional view of the converter lens of Example 1. FIG. FIG. 4 is a longitudinal aberration diagram when focusing on an object at infinity when the converter lens of Example 1 is arranged on the image side of the master lens; FIG. 4 is a lateral aberration diagram when focusing on an infinite distance object when the converter lens of Example 1 is arranged on the image side of the master lens; FIG. 10 is a cross-sectional view of a converter lens of Example 2; FIG. 10 is a longitudinal aberration diagram when focusing on an object at infinity when the converter lens of Example 2 is arranged on the image side of the master lens; FIG. 10 is a lateral aberration diagram when focusing on an object at infinity when the converter lens of Example 2 is arranged on the image side of the master lens; FIG. 11 is a cross-sectional view of a converter lens of Example 3; FIG. 11 is a longitudinal aberration diagram when focusing on an infinite distance object when the converter lens of Example 3 is arranged on the image side of the master lens; FIG. 11 is a lateral aberration diagram when focusing on an infinite distance object when the converter lens of Example 3 is arranged on the image side of the master lens; FIG. 11 is a cross-sectional view of a converter lens of Example 4; FIG. 11 is a longitudinal aberration diagram when focusing on an infinite distance object when the converter lens of Example 4 is arranged on the image side of the master lens; FIG. 11 is a lateral aberration diagram when focusing on an object at infinity when the converter lens of Example 4 is arranged on the image side of the master lens; FIG. 11 is a cross-sectional view of a converter lens of Example 5; FIG. 12 is a longitudinal aberration diagram when focusing on an infinite distance object when the converter lens of Example 5 is arranged on the image side of the master lens; FIG. 11 is a lateral aberration diagram when focusing on an object at infinity when the converter lens of Example 5 is arranged on the image side of the master lens; FIG. 11 is a cross-sectional view of a converter lens of Example 6; FIG. 11 is a longitudinal aberration diagram when focusing on an infinite distance object when the converter lens of Example 6 is arranged on the image side of the master lens; FIG. 11 is a lateral aberration diagram when focusing on an infinite distance object when the converter lens of Example 6 is arranged on the image side of the master lens; 4 is a cross-sectional view of a master lens; FIG. FIG. 4 is a longitudinal aberration diagram of the master lens when focusing on an object at infinity; FIG. 4 is a lateral aberration diagram of the master lens when focusing on an infinite object; It is a figure which shows the structure of an imaging device.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a converter lens and an imaging device according to embodiments of the present invention will be described in detail with reference to the accompanying drawings.

The Abbe number νd of a certain material is defined by Nd and NF , NC, Ng,
νd = (Nd-1)/(NF-NC)
is represented by

The converter lens of each embodiment is arranged, for example, between an imaging device and an interchangeable lens detachable from the imaging device. The converter lens of each embodiment can make the focal length of the photographic optical system (whole system) consisting of the optical system of the interchangeable lens and the converter lens longer than when only the interchangeable lens is used as the photographic optical system. .

In the sectional views of the converter lenses shown in FIGS. 1, 4, 7, 10, 13, and 16 and the sectional view of the master lens shown in FIG. 19, the left side is the object side (front) and the right side is the image side (rear). is. In each cross-sectional view, Li indicates the i-th lens group, where i is the order of the lens groups from the object side to the image side. The aperture stop SP determines (limits) the light flux at the open F-number (Fno). FP is a flare cut diaphragm that cuts unnecessary light.

When the imaging device is a digital video camera, a digital camera, or the like, the image plane IP corresponds to an imaging element (photoelectric conversion element) such as a CCD sensor or a CMOS sensor. If the imaging device is a silver halide film camera, the image plane IP corresponds to the film plane.

FIGS. 2, 5, 8, 11, 14, and 17 are longitudinal aberration diagrams of converter lenses of respective examples described later, and FIG. 20 is a longitudinal aberration diagram of a master lens. In the spherical aberration diagrams, the solid line indicates the d-line, and the two-dot chain line indicates the g-line. In the astigmatism diagrams, the dashed line M is the meridional image plane, and the solid line S is the sagittal image plane. Distortion is shown for the d-line. Lateral chromatic aberration is shown for the g-line. ω is the half angle of view (degrees), and Fno is the F-number.

3, 6, 9, 12, 15, and 18 are lateral aberration diagrams of converter lenses of respective examples described later, and FIG. 21 is a lateral aberration diagram of a master lens. In the lateral aberration diagrams, the dashed line M is the meridional image plane, and the solid line S is the sagittal image plane.

As described above, in a converter lens having negative refractive power as a whole, various aberrations such as coma are likely to occur due to off-axis light beams, and correction is likely to be difficult.

Therefore, the converter lens according to the embodiment has negative refractive power as a whole and has three or more negative lenses. By increasing the average refractive index of the negative lens material contained in the converter lens, the curvature of the surface of each lens is reduced, thereby reducing the occurrence of various aberrations such as coma caused by off-axis light beams. .

Specifically, when the average refractive index of the material of the three negative lenses included in the converter lens at the d-line (wavelength 587.56 nm) is Ndave,
1.92<Ndave<2.10 (1)
satisfies the following conditional expression.

When the lower limit of conditional expression (1) is exceeded and the average refractive index of the lens material becomes small, the Petzval sum can be easily configured to be small, making it easy to correct curvature of field and the like. However, this is not preferable because the curvature of the lens surface becomes large, making it difficult to correct various aberrations such as coma.

The greater the average refractive index of the material, the greater the material dispersion of the glass, in general. Therefore, if the average refractive index of the negative lens material exceeds the upper limit of conditional expression (1), it becomes difficult to correct the chromatic aberration of magnification, which is not preferable.

As described above, the converter lens of the example satisfies the above-described lens configuration and conditional expression (1), so that it can satisfactorily correct aberrations caused by off-axis light beams such as coma, even when attached to the master lens. High optical performance can be obtained.

Further, by using the converter lens of the present invention, even when a master lens for an imaging device having an imaging device with a low maximum image height is used in an imaging device having an imaging device with a high maximum image height, aberration can be reduced. From this point of view, the user can use it without a sense of incongruity.

It is preferable to set the numerical range of conditional expression (1) as follows.
1.95<Ndave<2.08 (1a)

Furthermore, it is preferable to set the numerical range of conditional expression (1) as follows.
1.98<Ndave<2.05 (1b)

Also, the converter lens preferably has three or more negative lenses, more preferably four or more negative lenses in the second lens group.

Furthermore, the converter lens preferably satisfies one or more of the following conditional expressions.
1.30<(R1+R2)/(R1-R2)<2.50 (2)
0.10<sk/TD<0.50 (3)
-2.30<f1/f2<-0.95 (4)
-1.40<f1/f<-0.30 (5)

However, the radius of curvature of the object-side surface of the lens located closest to the image side is R1, and the radius of curvature of the image-side surface of the lens is R2. Let sk be the air conversion length from the most image side surface of the converter lens to the image plane, and TD be the distance on the optical axis from the most object side surface to the most image side surface of the converter lens. Let f1 be the focal length of the first lens group, f2 be the focal length of the second lens group, and f be the focal length of the converter lens. Here, the first lens group is composed of a cemented lens obtained by cementing a negative lens and a positive lens.

Conditional expression (2) defines the shape of the positive lens located closest to the image side of the converter lens. It is preferable to make the radius of curvature of one surface larger than that of the other surface in order to suppress the occurrence of aberration while refracting off-axis light beams. This makes it possible to refract the off-axis light flux more than the on-axis light flux while suppressing the occurrence of aberration, making it easier to correct the aberration caused by the off-axis light flux.

Conditional expression (2) is determined in view of this. If the lower limit of conditional expression (2) is not reached and the difference between the curvature of the image-side surface and the curvature of the object-side surface becomes large, the curvature of field becomes under, which is not preferable. If the upper limit of conditional expression (2) is exceeded and the difference between the curvature of the image-side surface and the curvature of the object-side surface becomes small, the curvature of field becomes excessive, which is not preferable.

Conditional expression (3) is the back focus of the converter lens and the distance from the object-side surface of the lens closest to the object to the image-side surface of the lens closest to the image (lens configuration length ) ratio. If the conditional expression (3) is not satisfied, the lens configuration length becomes long, which is not preferable. If the lens configuration length becomes shorter than conditional expression (3), the refractive power of each lens increases, making it difficult to correct spherical aberration, which is not preferable.

Conditional expression (4) defines the ratio of the focal length of the first lens group to the focal length of the second lens group. If the lower limit of conditional expression (4) is not reached, a large amount of spherical aberration occurs on the over side, making it difficult to correct. Exceeding the upper limit of conditional expression (4) is not preferable because a large amount of spherical aberration occurs on the under side and correction becomes difficult.

Conditional expression (5) defines the ratio between the focal length of the first lens group and the focal length of the converter lens. If the lower limit of conditional expression (5) is not reached, the absolute value of the focal length of the first lens group becomes large and the refractive power becomes weak. If the upper limit of conditional expression (5) is exceeded and the absolute value of the focal length of the first lens group becomes small and the refractive power becomes strong, spherical aberration will occur on the underside, which is not preferable.

Furthermore, it is preferable to set the numerical ranges of conditional expressions (2) to (5) as follows.
1.40<(R1+R2)/(R1-R2)<2.30 (2a)
0.15<sk/TD<0.40 (3a)
-2.10<f1/f2<-1.00 (4a)
−1.20<f1/f<−0.32 (5a)

Furthermore, it is preferable to set the numerical ranges of conditional expressions (2) to (5) as follows.
1.50<(R1+R2)/(R1-R2)<2.10 (2b)
0.25<sk/TD<0.35 (3b)
-1.90<f1/f2<-1.10 (4b)
-1.10<f1/f<-0.34 (5b)

Satisfying at least one of the above conditional expressions makes it possible to obtain higher optical characteristics in the entire system even when arranged on the image side of the master lens.

Next, the master lens of Examples and the converter lens of each Example will be described.

[Converter lens]
Next, converter lenses of Examples 1 to 6 will be described.

[Example 1]
FIG. 1(a) is a cross-sectional view of the converter lens RCL of Example 1. FIG. FIG. 1B is a cross-sectional view of the master lens ML and the converter lens RCL of Example 1 arranged on the image side of the master lens ML. 2 and 3 are longitudinal and lateral aberration diagrams when focusing on an object at infinity when the converter lens RCL of Example 1 is arranged on the image side of the master lens ML. The magnification of the converter lens RCL is 1.61 times.

The first lens group is composed of a cemented lens of a negative lens G1 and a positive lens G2.

The second lens group consists of a cemented lens composed of a negative lens, a positive lens, and a negative lens, and a positive lens arranged on the image side of the cemented lens. That is, the converter lens RCL has three negative lenses.

[Example 2]
FIG. 4A is a cross-sectional view of the converter lens RCL of Example 2. FIG. FIG. 4B is a cross-sectional view of the master lens ML and the converter lens RCL of Example 2 arranged on the image side of the master lens ML. 5 and 6 are longitudinal and lateral aberration diagrams when focusing on an object at infinity when the converter lens RCL of Example 2 is arranged on the image side of the master lens ML. The magnification of the converter lens RCL is 1.60 times.

The first lens group is composed of a cemented lens of a negative lens G1 and a positive lens G2.

The second lens group is composed of a cemented lens composed of a negative lens and a positive lens, a negative lens, a positive lens, a negative lens, and a positive lens, which are arranged in order from the object side to the image side. That is, the converter lens RCL has four negative lenses.

[Example 3]
FIG. 7A is a cross-sectional view of the converter lens RCL of Example 3. FIG. FIG. 7B is a sectional view of the master lens ML and the converter lens RCL of Example 3 arranged on the image side of the master lens ML. 8 and 9 are longitudinal and lateral aberration diagrams when focusing on an object at infinity when the converter lens RCL of Example 3 is arranged on the image side of the master lens ML. The magnification of the converter lens RCL is 2.01 times.

The first lens group is composed of a cemented lens of a negative lens G1 and a positive lens G2.

The second lens group is composed of a cemented lens composed of a negative lens and a positive lens, a negative lens, a positive lens, a negative lens, and a positive lens, which are arranged in order from the object side to the image side. That is, the converter lens RCL has four negative lenses.

[Example 4]
FIG. 10A is a cross-sectional view of the converter lens RCL of Example 4. FIG. FIG. 10B is a cross-sectional view of the master lens ML and the converter lens RCL of Example 4 arranged on the image side of the master lens ML. 11 and 12 are longitudinal and lateral aberration diagrams when focusing on an object at infinity when the converter lens RCL of Example 4 is arranged on the image side of the master lens ML. The magnification of the converter lens RCL is 2.02 times.

The first lens group is composed of a cemented lens of a negative lens G1 and a positive lens G2.

The second lens group is composed of a cemented lens composed of a negative lens and a positive lens, a negative lens, a negative lens, a positive lens, a negative lens, and a positive lens, which are arranged in order from the object side to the image side. That is, the converter lens RCL has five negative lenses.

[Example 5]
FIG. 13A is a cross-sectional view of the converter lens RCL of Example 5. FIG. FIG. 13B is a cross-sectional view of the master lens ML and the converter lens RCL of Example 5 arranged on the image side of the master lens ML. 14 and 15 are longitudinal and lateral aberration diagrams when focusing on an object at infinity when the converter lens of Example 5 is arranged on the image side of the master lens ML. The magnification of the converter lens RCL is 1.61 times.

The first lens group is composed of a cemented lens of a negative lens G1 and a positive lens G2.

The second lens group consists of a cemented lens composed of a negative lens, a positive lens, and a negative lens, and a positive lens arranged on the image side of the cemented lens. That is, the converter lens RCL has three negative lenses.

[Example 6]
FIG. 16A is a cross-sectional view of the converter lens RCL of Example 6. FIG. FIG. 16B is a cross-sectional view of the master lens ML and the converter lens RCL of Example 6 arranged on the image side of the master lens ML. 17 and 18 are longitudinal and lateral aberration diagrams when focusing on an object at infinity when the converter lens RCL of Example 6 is arranged on the image side of the master lens ML. The magnification of the converter lens RCL is 1.59 times.

The first lens group is composed of a cemented lens of a negative lens G1 and a positive lens G2.

The second lens group consists of a cemented lens composed of a negative lens, a positive lens, and a negative lens, and a positive lens arranged on the image side of the cemented lens. That is, the converter lens RCL has three negative lenses.

[Master lens]
FIG. 19 is a cross-sectional view of the master lens ML when focusing on an infinite object. FIG. 20 is a longitudinal aberration diagram of the master lens ML when focusing on an object at infinity. FIG. 21 is a lateral aberration diagram of the master lens ML when focusing on an object at infinity.

The master lens ML is a single focus lens composed of an aperture stop SP, a front group Lf arranged on the object side of the aperture stop SP, and a rear group Lr arranged on the image side of the aperture stop SP. The master lens ML has an F number of 2.88 and a half angle of view of 29 degrees. Note that the master lens ML given as an example is merely an example, and other optical systems may be used as long as they are capable of forming an image on the image plane.

[Numerical example]
Numerical examples 1 to 6 corresponding to numerical examples of the master lens ML and converter lenses RCL of examples 1 to 6 are shown.

Also, in each numerical example, the surface numbers indicate the order of the optical surfaces from the object side. r is the radius of curvature of the optical surface (mm), d in the surface number i is the distance (mm) between the i-th optical surface and the i+1-th optical surface, nd is the refractive index of the material of the optical member on the d line, νd is the Abbe number of the material of the optical member with respect to the d-line, and is defined as described above.

BF indicates back focus. It should be noted that the back focus is the distance on the optical axis from the surface closest to the image side to the paraxial image plane, expressed in air conversion length.

The total lens length of the master lens ML is the distance on the optical axis from the surface closest to the object (first lens surface) of the master lens ML to the surface closest to the image (final lens surface) of the master lens ML plus the back focus. length. When the converter lens RCL is arranged on the image side of the master lens ML, the total lens length is the distance on the optical axis from the surface of the master lens ML closest to the object side to the surface of the converter lens RCL closest to the image side. is the length plus the back focus of .

The distance between the master lens and the converter is the distance on the optical axis from the most image side surface of the master lens to the most object side surface of the converter lens. The distance between the master lens and the converter lens is represented by the air conversion length. Magnification is the ratio of the focal length of the entire system with the master lens and converter to the focal length of the master lens.

The lens configuration length of the converter lens is the distance on the optical axis from the most object side surface of the converter lens to the most image side surface of the converter lens.

The effective diameter is the diameter of the range through which the on-axis light flux and the off-axis light flux pass. The entrance pupil position is the distance from the most object side surface to the entrance pupil, and the exit pupil position is the distance from the most image side surface to the exit pupil. The front principal point position is the distance from the most object side surface to the front principal point, and the rear principal point position is the distance from the most image side surface to the rear principal point. Each numerical value for the front principal point position and the rear principal point position is a paraxial amount, and the sign is positive in the direction from the object side to the image side.

Moreover, when the optical surface is an aspherical surface, an asterisk (*) is attached to the right side of the surface number. The aspheric shape has x as the displacement amount from the surface vertex in the optical axis direction, h as the height from the optical axis in the direction perpendicular to the optical axis, R as the paraxial radius of curvature, k as the conic constant, A4, A6, When A8, A10, and A12 are aspheric coefficients of each order,
x=(h ² /R)/[1+{1−(1+k)(h/R) ² } ^1/2 +A4×h ⁴ +A6×h ⁶ +A8×h ⁸ +A10×h ¹⁰ +A12×h ¹²
is represented by "e±XX" in each aspheric coefficient means "×10± ^XX ". [Table 1] shows the physical quantities used in the above conditional expressions in each of Numerical Examples 1 to 6, and [Table 2] shows the values corresponding to the above conditional expressions.

In the numerical examples shown below, the unit of length is mm, and the unit of angle is degree. It is also possible to use units of length.

[Master Lens] - Common to Numerical Examples 1 to 6 of Converter Lenses -
unit mm

Surface data Surface number rd nd vd Effective diameter
1 23.706 2.83 1.91082 35.3 16.13
2 63.184 0.25 14.42
3 22.266 0.90 1.48749 70.2 12.89
4 7.213 4.00 10.11
5 ∞ 3.26 8.13 (flare cut aperture)
6 (Aperture) ∞ 3.24 8.78
7 -16.321 4.82 1.69680 55.5 9.30
8 -8.400 0.80 1.80610 33.3 11.37
9 -36.438 0.20 13.67
10 227.537 4.39 1.59522 67.7 15.23
11 -15.547 0.90 16.72
12* -34.842 3.55 1.58313 59.4 17.76
13 -15.035 35.68 18.94
Image plane ∞

Aspheric data 12th surface
K = 0.00000e+000 A 4=-5.24174e-005 A 6= 5.25723e-008 A 8=-3.53661e-009 A10= 3.36031e-011 A12=-1.48386e-013

Various data focal length of master lens 24.50
F number 2.88
Half angle of view (degrees) 29.14
Image height 13.66
Total lens length 64.83
BF 35.68

Entrance pupil position 10.34
Exit pupil position -35.77
Front principal point position 26.44
Rear principal point position 11.18

Single lens data lens of master lens Starting surface Focal length
1 1 40.28
2 3 -22.32
3 7 19.87
4 8 -13.72
5 10 24.62
6 12 42.54

[Converter lens]
[Numerical Example 1]
unit mm

Surface data Surface number rd nd vd Effective diameter
1 141.314 1.20 1.95375 32.3 25.80
2 20.811 8.90 1.80518 25.4 25.40
3 -50.545 4.45 25.60
4 -36.637 1.20 2.00100 29.1 24.10
5 62.836 8.70 1.62588 35.7 25.00
6 -19.857 1.30 2.00100 29.1 25.80
7 -424.225 7.20 29.00
8 -74.271 9.35 1.59551 39.2 35.20
9 -25.409 13.96 37.90
Image plane ∞

Distance between master lens and converter lens 4.19

Various data focal length when the converter lens is placed on the image side of the master lens 39.54
F number 4.65
Half angle of view (degrees) 28.68
Image height 21.64
Lens length 89.59
BF 13.96

Various data focal length of converter lens -148.00
Lens length 42.30
Front principal point position -24.78
Rear principal point position -76.86
Magnification 1.61

Single lens data lens of converter lens Starting surface Focal length
1 1 -25.71
2 2 19.39
3 4 -22.98
4 5 25.13

5 6 -20.84
6 8 60.53

[Numerical Example 2]
unit mm

Surface data Surface number rd nd vd Effective diameter
1 108.446 1.20 2.00100 29.1 25.90
2 18.934 8.60 1.85478 24.8 25.40
3 -62.820 4.00 25.40
4 -49.683 1.20 2.05090 26.9 24.30
5 27.755 6.00 1.80810 22.8 24.90
6 -109.942 1.30 25.50
7 -45.352 1.20 2.05090 26.9 25.60
8 144.322 0.10 27.30
9 49.805 5.00 1.53172 48.8 29.50
10 -100.714 1.30 30.30
11 -52.534 1.60 2.00 100 29.1 30.40
12 -149.361 2.90 32.10
13 -86.192 8.00 1.54072 47.2 34.30
14 -27.523 13.08 36.50
Image plane ∞

Distance between master lens and converter lens 4.19

Various data focal length when the converter lens is placed on the image side of the master lens 39.21
F number 4.61
Half angle of view (degrees) 28.89
Image height 21.64
Lens length 88.80
BF 13.08

Various data focal length of converter lens -83.09
Lens length 42.40
Front principal point position 0.34
Rear principal point position -36.78
Magnification 1.60

Single lens data lens of converter lens Starting surface Focal length
1 1 -23.07
2 2 17.89
3 4 -16.81
4 5 27.97
5 7 -32.73
6 9 63.41
7 11 -81.63
8 13 71.36

[Numerical Example 3]
unit mm

Surface data Surface number rd nd vd Effective diameter
1 71.603 1.20 2.05090 26.9 25.50
2 17.334 9.10 1.85478 24.8 24.20
3 -55.856 0.45 24.00
4 -83.837 1.20 2.00100 29.1 23.40
5 15.257 8.15 1.80810 22.8 22.50
6 -109.942 3.45 22.80
7 -36.477 1.20 2.05090 26.9 22.80
8 53.517 0.20 24.30
9 38.586 4.70 1.53172 48.8 26.20
10 -174.517 6.95 27.20
11 -127.684 1.60 2.00100 29.1 32.50
12 424.763 4.65 33.50
13 -73.668 10.00 1.51742 52.4 35.20
14 -24.017 11.00 37.90
Image plane ∞

Distance between master lens and converter lens 4.19

Various data focal length when the converter lens is placed on the image side of the master lens 49.27
F number 5.79
Half angle of view (degrees) 23.71
Image height 21.64
Lens length 97.18
BF 11.00

Various data focal length of converter lens -81.18
Lens length 52.85
Front principal point position -9.30
Rear principal point position -71.02
Magnification 2.01

Single lens data lens of converter lens Starting surface Focal length
1 1 -22.01
2 2 16.42
3 4 -12.82
4 5 17.08
5 7 -20.50
6 9 59.89
7 11 -97.93
8 13 64.44

[Numerical Example 4]
unit mm

Surface data Surface number rd nd vd Effective diameter
1 81.547 1.20 2.05090 26.9 25.60
2 17.175 8.90 1.85478 24.8 24.40
3 -74.877 0.40 24.10
4 -800.041 1.20 2.00 100 29.1 23.60
5 15.215 8.10 1.80810 22.8 22.40
6 -109.942 1.35 22.50
7 -59.136 1.20 2.00 100 29.1 22.40
8 800.004 3.95 22.80
9 -35.142 1.20 2.05090 26.9 23.40
10 309.433 0.15 25.30
11 50.320 5.10 1.53172 48.8 28.20
12 -77.229 0.60 29.10
13 -79.630 1.60 2.00 100 29.1 29.20
14 387.478 6.50 30.70
15 -116.685 10.00 1.51742 52.4 35.50
16 -25.328 13.96 37.90
Image plane ∞

Distance between master lens and converter lens 4.19

Various data focal length when the converter lens is placed on the image side of the master lens 49.40
F number 5.81
Half angle of view (degrees) 23.65
Image height 21.64
Lens length 98.73
BF 13.96

Various data focal length of converter lens -75.46
Lens length 51.45
Front principal point position -6.52
Rear principal point position -62.68
Magnification 2.02

Single lens data lens of converter lens Starting surface Focal length
1 1 -20.90
2 2 17.11
3 4 -14.91
4 5 17.03
5 7 -54.97
6 9 -29.98
7 11 58.11
8 13 -65.88
9 15 60.27

[Numerical Example 5]
unit mm

Surface data Surface number rd nd vd Effective diameter
1 105.372 1.10 1.90525 35.0 25.80
2 20.274 9.30 1.74077 27.8 25.40
3 -43.036 3.30 25.50
4 -34.856 1.20 1.85150 40.8 24.20
5 50.808 9.00 1.54072 47.2 24.90
6 -19.532 1.30 2.00330 28.3 25.60
7 -612.486 7.20 28.90
8 -70.239 9.60 1.61293 37.0 35.20
9 -24.676 13.95 37.90
Image plane ∞

Distance between master lens and converter lens 4.19

Various data focal length when the converter lens is placed on the image side of the master lens 39.45
F number 4.64
Half angle of view (degrees) 28.74
Image height 21.64
Lens length 89.28
BF 13.95

Various data focal length of converter lens -162.19
Lens length 42.00
Front principal point position -29.93
Rear principal point position -84.93
Magnification 1.61

Single lens data lens of converter lens Starting surface Focal length
1 1 -27.90
2 2 19.84
3 4 -24.12
4 5 27.32
5 6 -20.13
6 8 57.46

[Numerical Example 6]
unit mm

Surface data Surface number rd nd vd Effective diameter
1 258.268 1.00 2.00 100 29.1 25.80
2 23.518 7.70 1.85478 24.8 25.70
3 -54.781 6.10 25.90
4 -30.390 1.00 2.05090 26.9 24.40
5 31.048 7.40 1.89286 20.4 26.30
6 -48.829 1.00 2.24163 16.9 27.30
7 -1396.349 8.60 28.70
8 -130.600 9.80 1.51742 52.4 36.30
9 -26.447 13.65 38.60
Image plane ∞

Distance between master lens and converter lens 4.19

Various data focal length when the converter lens is placed on the image side of the master lens 39.02
F number 4.59
Half angle of view (degrees) 29.00
Image height 21.64
Lens length 89.58
BF 13.65

Various data focal length of converter lens -194.07
Lens length 42.60
Front principal point position -40.70
Rear principal point position -101.32
Magnification 1.59

Single lens data lens of converter lens Starting surface Focal length
1 1 -25.90
2 2 20.16
3 4 -14.49
4 5 22.23
5 6 -40.77
6 8 62.10

[Embodiment of Imaging Device]
FIG. 22 is a diagram showing the configuration of the imaging device (digital camera) 10. As shown in FIG. FIG. 22(a) is a perspective view, and FIG. 22(b) is a side view. The imaging device 10 photoelectrically converts an image formed by the camera body 13, the master lens ML, the converter lens RCL which is the same as in any of the first to sixth embodiments, and the master lens ML and the converter lens RCL. A light receiving element (imaging element) 12 is provided. As the light receiving element 12, an imaging element such as a CCD sensor or a CMOS sensor can be used. The master lens ML and the converter lens RCL may be integrated with the camera body 13 or may be detachable from the camera body 13 .

When the master lens ML and the converter lens RCL are configured integrally with the camera body 13, the converter lens RCL is configured to be removable on the optical axis.

[Example of Interchangeable Lens]
The present invention can also be applied to an interchangeable lens in which the master lens ML and the converter lens RCL are configured in the same lens barrel and which can be attached to and detached from the imaging apparatus. The interchangeable lens may be a single focus lens with a fixed focal length, or a zoom lens with a variable focal length. In this case, the converter lens RCL is configured to be insertable and removable on the optical axis. The converter lens RCL is arranged on or off the optical axis according to instructions from the user via the operation member or the user interface.

Although preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments and examples, and various combinations, modifications, and changes are possible within the scope of the gist thereof.

RCL Converter lens ML Master lens

Claims (6)

A converter lens arranged on the image side of the master lens, having negative refractive power as a whole, and increasing the focal length of the entire system,
The converter lens has three positive lenses,
The converter lens has three negative lenses,
When the average refractive index for the d-line of the material of the three negative lenses is Ndave,
1.92<Ndave<2.10
A converter lens characterized by satisfying the following conditional expression: When the converter lens has a positive lens located closest to the image side, and the radius of curvature of the object-side surface of the positive lens is R1, and the radius of curvature of the image-side surface of the positive lens is R2,
1.30<(R1+R2)/(R1-R2)<2.50
2. The converter lens according to claim 1, which satisfies the following conditional expression: When sk is the converted air length from the most image side surface of the converter lens to the image plane, and TD is the distance on the optical axis from the most object side surface to the most image side surface of the converter lens,
0.10<sk/TD<0.50
3. The converter lens according to claim 1, wherein the following conditional expression is satisfied. 4. The converter lens according to any one of claims 1 to 3, wherein the converter lens has four or more positive lenses. An interchangeable lens comprising a master lens and the converter lens according to any one of claims 1 to 4. An imaging apparatus comprising: a master lens; the converter lens according to any one of claims 1 to 5; and an imaging device that receives an image formed by the master lens and the converter lens.

Images