Zoom optical system, imaging device and method for manufacturing the zoom optical system

Patent metadata

Field	Value
Publication number	US-2020041772-A1
Application number	US-201916599107-A
Country	US
Kind code	A1
Filing date	Oct 10, 2019
Priority date	Mar 27, 2014
Publication date	Feb 6, 2020
Grant date	—

Abstract

A zoom optical system includes, disposed in order from an object, a first lens group having positive refractive power, a second lens group having negative refractive power, and a third lens group having positive refractive power, wherein at least a part of the third lens group is arranged to be movable along an optical axis as a focusing lens group, the focusing lens group is moved toward an image when a focusing state on a long-distance object is changed to a focusing state on a short-distance object, and the following conditional expression is satisfied:
0.90< f 3/ fw <1.50
where f3 denotes a focal length of the third lens group, and fw denotes a focal length of the zoom optical system in a wide-angle end state.

First claim

1 . A zoom optical system, comprising:
in order from an object, a first lens group having positive refractive power; a second lens group having negative refractive power; and a third lens group having positive refractive power, wherein focusing is effected by moving, as a focusing lens group, at least a part of the third lens group along an optical axis, the focusing lens group is moved toward an image when a focusing state on a long-distance object is changed to a focusing state on a short-distance object, and the following conditional expression is satisfied:
0.90< f 3/ fw< 1.50
where f3 denotes a focal length of the third lens group, and fw denotes a focal length of the zoom optical system in a wide-angle end state.

2 . The zoom optical system according to claim 1 , wherein zooming is effected by varying an air distance between the first lens group and the second lens group and an air distance between the second lens group and the third lens group.

3 . The zoom optical system according to claim 1 , wherein, upon zooming from the wide-angle end state to a telephoto end state, an air distance between the first lens group and the second lens group is increased, and an air distance between the second lens group and the third lens group is decreased.

4 . The zoom optical system according to claim 1 , further comprising:
an aperture stop, and wherein the aperture stop is disposed between the second lens group and an image surface.

5 . The zoom optical system according to claim 1 , wherein the following conditional expression is satisfied:
30.00°<ω w< 80.00°
where ωw denotes a half angle of view in the wide-angle end state.

6 . The zoom optical system according to claim 1 , wherein the following conditional expression is satisfied:
2.00< ft/fw< 15.00 where ft denotes a focal length of the zoom optical system in a telephoto end state.

7 . The zoom optical system according to claim 1 , wherein the first lens group comprises, in an order from the object, a cemented lens of a negative lens and a positive lens.

8 . The zoom optical system according to claim 1 , wherein the first lens group is moved toward the object upon zooming from the wide-angle end state to a telephoto end state.

9 . The zoom optical system according to claim 1 , wherein the focusing lens group has positive refractive power.

10 . The zoom optical system according to claim 1 , including a vibration-proofing lens group on an image side of the second lens group for correcting image blur.

11 . The zoom optical system according to claim 1 , including a vibration-proofing lens group on an image side of the focusing lens group for correcting image blur.

12 . The zoom optical system according to claim 1 , including a vibration-proofing lens group for correcting image blur, the vibration-proofing lens group having negative refractive power.

13 . The zoom optical system according to claim 1 , wherein the second lens group comprises at least two negative lenses and a positive lens.

14 . The zoom optical system according to claim 1 , wherein the second lens group comprises, in an order from the object, a negative lens, a negative lens and a positive lens.

15 . An imaging device, comprising the zoom optical system according to claim 1 .

16 . A method for manufacturing a zoom optical system, comprising:
disposing, in order from an object, a first lens group having positive refractive power, a second lens group having negative refractive power, and a third lens group having positive refractive power, wherein the lens groups are arranged within a lens barrel in such a manner that focusing is effected by moving, as a focusing lens group, at least a part of the third lens group along an optical axis, and the focusing lens group is moved toward an image when a focusing state on a long-distance object is changed to a focusing state on a short-distance object, and the following conditional expression is satisfied:
0.90< f 3/ fw< 1.50
where f3 denotes a focal length of the third lens group, and fw denotes a focal length of the zoom optical system in a wide-angle end state.

Assignees

• Nikon Corp

Inventors

• Ito Tomoki
• Yamamoto Hiroshi

Classifications

• G02B27/646 Primary

  compensating for small deviations, e.g. due to vibration or shake (movement of one or more optical elements for control of motion blur in cameras, projectors or printers G03B2205/0007; image stabilisation in cameras peculiar to the presence or use of an electronic image sensor H04N23/68) · CPC title

• G02B5/005

  Diaphragms (for cameras G03B9/02) · CPC title

• G02B27/0025

  for optical correction, e.g. distorsion, aberration · CPC title

• G02B15/173 Primary

  arranged +-+ · CPC title

• G02B15/144113 Primary

  arranged +-++ · CPC title