Variable magnification optical system, and image pickup apparatus and image pickup optical system using the same

Patent metadata

Field	Value
Publication number	US-10274708-B2
Application number	US-201615177050-A
Country	US
Kind code	B2
Filing date	Jun 8, 2016
Priority date	Dec 11, 2013
Publication date	Apr 30, 2019
Grant date	Apr 30, 2019

Abstract

A variable magnification optical system is an optical system in which, a magnification ratio varies from a lower magnification end to a high magnification end, and includes at least a first lens unit having a positive refractive power, which is disposed nearest to an object, and a second lens unit having a positive refractive power, which is disposed on an image side of the first lens unit. At the time of varying magnification, a distance between the first lens unit and the second lens unit changes, and the following conditional expression (1) is satisfied:

0<1/β HG1 <1  (1),
where, β HG1 denotes an imaging magnification of the first lens unit at the high magnification end.

First claim

What is claimed is:

1. A variable magnification optical system in which, a magnification ratio varies from a low magnification end to a high magnification end, comprising:
a first lens unit having a positive refractive power, which is disposed nearest to an object; and
a second lens unit having a positive refractive power, which is disposed on an image side of the first lens unit, wherein
at a time of varying magnification, a distance between the first lens unit and the second lens unit changes, and
a stop is disposed on the image side of the second lens unit, and
a predetermined positive lens unit is disposed on the image side of the stop, and
the predetermined positive lens unit has a positive refractive power, and is a lens unit of which, a distance from the stop at the high magnification end is smaller than a distance from the stop at the low magnification end, and
the following conditional expression (1) is satisfied:
0<1/β HG1 <1  (1),

where,
β HG1 denotes an imaging magnification of the first lens unit at the high magnification end.

2. The variable magnification optical system according to claim 1 , wherein the following conditional expression (2) is satisfied:
0<BF L /Y≤ 4.3  (2),

where,
BF L denotes a back focus at the low magnification end, and
Y denotes a maximum image height of the overall variable magnification optical system.

3. The variable magnification optical system according to claim 1 , wherein the predetermined positive lens unit includes at least two or more than two positive lenses and one or more than one negative lens.

4. The variable magnification optical system according to claim 1 , wherein
a plurality of predetermined positive lens units is disposed on the image side of the stop, and
a first predetermined positive lens unit from among the plurality of predetermined positive lens units, is disposed nearest to an object, and
the following conditional expression (3) is satisfied:
0<Δ Gpmax /Δ Gpobj ≤0.6  (3),

where,
Δ Gpmax denotes a maximum amount of change from among amounts of change in a distance on an optical axis between any two predetermined positive lens units, and
Δ Gpobj denotes a maximum amount of movement from among amounts of movement on the optical axis of the first predetermined positive lens unit, and
here, Δ Gpmax is the maximum of the amount of change in distance on the optical axis between the positive lens units from among all combinations of two lens units selected from three or more than three lens unit in a case in which, the predetermined positive lens units includes three or more than three lens units.

5. The variable magnification optical system according to claim 1 , wherein the following conditional expression (4) is satisfied:
0.1≤ f G1 /f G2 ≤5  (4),

where,
f G1 denotes a focal length of the first lens unit, and
f G2 denotes a focal length of the second lens unit.

6. The variable magnification optical system according to claim 1 , wherein at the time of varying magnification from the low magnification end to the high magnification end, the stop moves from the image side to the object side.

7. The variable magnification optical system according to claim 1 , wherein the following conditional expression (5) is satisfied:
0.2≤ f G1 /f LGp ≤10  (5),

where,
f G1 denotes a focal length of the first lens unit, and
f LGp denotes a focal length of the predetermined positive lens unit at the low magnification end.

8. The variable magnification optical system according to claim 1 , wherein
one or more than one predetermined positive lens is included, and
a high-dispersion glass material with Abbe number not more than 30 is used for the predetermined positive lens.

9. The variable magnification optical system according to claim 1 , wherein the following conditional expression (6) is satisfied:
−1≤ D HGpop /D HGpoi ≤0.65  (6),

where,
D HGpop denotes a distance on the optical axis from a lens surface nearest to the object up to a principal plane on the object side in the predetermined positive lens unit at the high magnification end, and
D HGpoi denotes a distance on the optical axis from a lens surface nearest to the object up to a lens surface nearest to the image in the predetermined positive lens unit at the high magnification end.

10. The variable magnification optical system according to claim 1 , wherein
the stop and a predetermined negative lens unit are included, and
the predetermined negative lens unit has a negative refractive power, and is disposed to be adjacent to the stop, and
the following conditional expression (7) is satisfied:
| D sGno /ϕ Hs |≤1  (7),

where,
D sGno denotes a distance on the optical axis from the stop up to a lens surface nearest to the stop in the predetermined negative lens unit, and
ϕ Hs denotes a diameter of the stop at the high magnification end.

11. The variable magnification optical system according to claim 10 , wherein
the predetermined negative lens unit includes at least one or more than one positive lens and one or more than one negative lens, and
a glass material having a dispersion higher than a dispersion of the negative lens is used for the positive lens.

12. The variable magnification optical system according to claim 11 , wherein the positive lens and the negative lens are cemented.

13. A variable magnification optical system in which, a magnification ratio varies from a low magnification end to a high magnification end, comprising:
a first lens unit having a positive refractive power, which is disposed nearest to an object; and
a second lens unit having a negative refractive power, which is disposed on an image side of the first lens unit; wherein
a stop which is disposed on the object side of the second lens unit is included; and
at a time of varying magnification, the second lens unit moves, and a distance between the first lens unit and the second lens unit changes, and
a third lens unit is disposed on an image side of the second lens unit, and
the following conditional expression (8) is satisfied:
0.15≤Δ G2max /D HIGi ≤2  (8),

where,
Δ G2max denotes a maximum amount of movement from among amounts of movement of the second lens unit on the optical axis, and
D HIGi denotes a distance on the optical axis from a lens surface nearest to the object in the third lens unit up to an image plane, at the high magnification end.

14. The variable magnification optical system according to claim 13 , wherein the following conditional expression (2) is satisfied:
0<BF L /Y≤ 4.3  (2),

where,
BF L denotes a back focus at the low magnification end, and
Y denotes a maximum image height of the overall variable magnification optical system.

15. The variable magnification optical system according to claim 13 , wherein
one or more than one predetermined positive lens is included, and
a high-dispersion glass material with Abbe number not more than 30 is used for the predetermined positive lens.

16. The variable magnification optical system according to claim 13 , wherein the following conditional expression (4-1) is satisfied:
−2.5≤ f G1 /f G2 ≤−0.2  (4-1),

where,
f G1 denotes a focal length of the first lens unit, and
f G2 denotes a focal length of the second lens unit.

17. The variable magnification optical system according to claim 13 , wherein
the third lens unit has a positive refractive power, and is disposed on the image side of the second lens unit, to be adjacent to the second lens unit, and
at th

Assignees

• Olympus Corp

Inventors

• Abe Kenichiro
• Amanai Takahiro

Classifications

• G02B15/167

  having an additional fixed front lens or group of lenses · CPC title

• G02B15/163

  having a first movable lens or lens group and a second movable lens or lens group, both in front of a fixed lens or lens group (G02B15/177 takes precedence) · CPC title

• G02B21/361

  Optical details, e.g. image relay to the camera or image sensor (G02B21/364 takes precedence; illumination details G02B21/06 and subgroups) · CPC title

• G02B13/0045

  having five or more lenses · CPC title

• G02B21/26

  Stages; Adjusting means therefor · CPC title