Converter lens device and photographing system including the same

Patent metadata

Field	Value
Publication number	US-9885852-B2
Application number	US-201615073753-A
Country	US
Kind code	B2
Filing date	Mar 18, 2016
Priority date	Mar 19, 2015
Publication date	Feb 6, 2018
Grant date	Feb 6, 2018

Abstract

The present disclosure is directed to a converter lens device that includes a first mount to which a master lens device is capable of being attached, a second mount to which a camera body is capable of being attached and a converter lens having a negative refractive power, wherein, an optical system comprising the converter lens device and the master lens device has a focal length longer than a focal length of an optical system of the master lens device, the converter lens comprises sequentially from an object side, a first lens unit of a positive refractive power, a second lens unit of a negative refractive power, and a third lens unit.

First claim

What is claimed is:

1. A converter lens device comprising:
a first mount to which a master lens device is attached;
a second mount to which a camera body is attached; and
a converter lens having a negative refractive power, wherein,
a focal length, in which the converter lens and the master lens are combined, is longer than a focal length of the master lens,
the converter lens comprises sequentially from an object side,
a first lens unit of a positive refractive power,
a second lens unit of a negative refractive power, and
a third lens unit, and

wherein
the converter lens device satisfies conditional expression (1):
0.1≦| f |/(β× D )≦0.87  (1)

where
an object side of the converter lens device is a side closer to the first mount, an image side of the converter lens device is a side closer to the second mount,
f is a focal length of the converter lens,
β is a magnification of the converter lens, and
D is a thickness of the converter lens on an optical axis, wherein the second lens unit comprises sequentially from the object side, an object side lens sub-unit having a negative refractive power, and an image side lens sub-unit.

2. The converter lens device according to claim 1 , wherein the converter lens satisfies conditional expression (3):
0.3≦ f 23 /f≦ 0.9  (3)

wherein
f 23 is a composite focal length of the second lens unit and the third lens unit, and
f is a focal length of the converter lens.

3. The converter lens device according to claim 1 , wherein and the converter lens device satisfies conditional expression (4):
−2.0≦( r 21f +r 21r )/( r 21f −r 21r )≦2.0  (4)

wherein
r 21f is a radius of curvature of a surface of the object side lens sub-unit closer to the object side, and
r 21r is a radius of curvature of a surface of the object side lens sub-unit closer to the image side.

4. The converter lens device according to claim 1 , wherein the second lens unit comprises an image side lens sub-unit having a negative refractive power, and the converter lens device satisfies conditional expression (5):
−2.0≦( r 22f +r 22r )/( r 22f −r 22r )≦0  (5)

wherein
r 22f is a radius of curvature of a surface of the image side lens sub-unit closer to the object side, and
r 22r is a radius of curvature of a surface of the image side lens sub-unit closer to the image side.

5. The converter lens device according to claim 4 , wherein the second lens unit comprises an image side lens sub-unit having a negative refractive power, and the converter lens device satisfies conditional expression (7):
25≦ν d 22N ≦50  (7)

wherein
νd 22N is an average value of Abbe numbers with respect to a d line of a negative lens included in the image side lens sub-unit.

6. The converter lens device according to claim 1 , wherein the second lens unit comprises an image side lens sub-unit having a negative refractive power, and the converter lens device satisfies conditional expression (6):
1.75 ≦nd 22N ≦2.00  (6)

wherein
nd 22N is an average value of refractive indexes on a d line in a negative lens included in the image side lens sub-unit.

7. The converter lens device according to claim 1 , wherein the second lens unit comprises sequentially from the object side, wherein the image side lens sub-unit has a negative refractive power.

8. The converter lens device according to claim 1 , wherein the second lens unit comprises sequentially from the object side, wherein the image side lens sub-unit has a negative refractive power, and the converter lens device satisfies conditional expression (2′):
0.6≦ f 21 /f 22 ≦10  (2′)

wherein
f 21 is a focal length of the object side lens sub-unit, and
f 22 is a focal length of the image side lens sub-unit.

9. The converter lens device according to claim 1 , wherein the third lens unit has a positive refractive power.

10. A photographing system comprising:
a master lens device;
a camera body including an image pickup sensor; and
the converter lens device according to claim 1 attachable between the master lens device and the camera body, wherein
an optical system constituted by the master lens device and the converter lens device forms an image of an object, and
the image pickup sensor is disposed at an image position of the object and converts an image of the object into an electric signal.

11. A converter lens device according to claim 1 , wherein
the first lens unit comprises a positive lens convex to an image side, wherein a total number of positive lenses included in the first lens unit is one,
the second lens unit comprises a cemented triplet lens and a cemented doublet lens, wherein the cemented triplet lens has a bi-concave negative lens, a bi-convex positive lens and a negative lens, and wherein the cemented doublet lens has a positive lens and a negative lens, wherein a total number of lenses in the second lens unit is five, and
the third lens unit comprises a negative lens and a positive lens, wherein a total number of lenses in the third lens unit is two.

12. A converter lens device comprising:
a first mount to which a master lens device is attached;
a second mount to which a camera body is attached; and
a converter lens having a negative refractive power, wherein,
a focal length, in which the converter lens and the master lens are combined, is longer than a focal length of the master lens,
the converter lens comprises sequentially from an object side,
a first lens unit of a positive refractive power,
a second lens unit of a negative refractive power, and
a third lens unit, and
the second lens unit comprises sequentially from the object side, an object side lens sub-unit having a negative refractive power, and an image side lens sub-unit having a negative refractive power, and
the converter lens device satisfies conditional expression (2):
1.7≦ f 21 /f 22 ≦18  (2)

where
the object side is a side closer to the first part, an image side is a side closer to the second mount,
f 21 is a focal length of the object side lens sub-unit, and
f 22 is a focal length of the image side lens sub-unit.

13. The converter lens device according to claim 12 , wherein the converter lens device satisfies conditional expression (1):
0.1≦| f |/(β× D )≦0.87  (1)

wherein
f is a focal length of the converter lens,
β is a magnification of the converter lens, and
D is a thickness of the converter lens on an optical axis.

14. A converter lens device comprising:
a first mount to which a master lens device is attached;
a second mount to which a camera body is attached; and
a converter lens having a negative refractive power, wherein,
a focal length, in which the converter lens and the master lens are combined, is longer than a focal length of the master lens,
the converter lens comprises sequentially from an object side,
a first lens unit of a positive refractive power,
a second lens unit of a negative refractive power, and
a third lens unit, and
the second lens unit comprises sequentially from an object side, an object side lens sub-unit having a negative refractive power, and an image side lens sub-unit having a negative refractive power,
each of the object side lens sub-unit and the image side lens sub-unit comprises a cemented lens, and
the converter lens device satisfies conditional expression (2′):
0.6≦ f 21 /f 22 ≦10  (2′)

where
the object side is a side closer to the first mount, an image side is a side closer to the second mount,
f 21 is a focal length of the object side lens sub-unit, and
f 22 is a focal length

Assignees

• Olympus Corp

Inventors

• Ogata Yasuji

Classifications

• G02B9/12 Primary

  having three components only · CPC title

• G02B13/00 Primary

  Optical objectives specially designed for the purposes specified below (with variable magnification {in general} G02B15/00) · CPC title

• G02B15/10

  by adding a part, e.g. close-up attachment · CPC title

• G02B7/021

  for more than one lens · CPC title

• G03B17/565

  Optical accessories, e.g. converters for close-up photography, tele-convertors, wide-angle convertors · CPC title