Variable focal length lens, optical apparatus, and adjustment method for variable focal length lens

Patent metadata

Field	Value
Publication number	US-2016170228-A1
Application number	US-201615049038-A
Country	US
Kind code	A1
Filing date	Feb 20, 2016
Priority date	Aug 20, 2013
Publication date	Jun 16, 2016
Grant date	—

Abstract

Provided are a variable focal length imaging lens, an optical apparatus having the imaging lens and a method for adjusting the imaging lens, whereby it is possible to achieve satisfactory optical performance and reduce a cost. The imaging lens comprises, in order from an object side, a first lens group G 1 having negative refractive power and a second lens group G 2 having positive refractive power. A focal length of the imaging lens is varied by changing an air space between the first lens group and the second lens group. The imaging lens further comprises an adjustment mechanism 20, 30 which performs a position adjustment for making shift decentering or tilt decentering of a whole or a partial lens group of the first lens group and a partial lens group of the second lens group, after assembling the first lens group and the second lens group.

First claim

What is claimed is:

1 . A variable focal length lens comprising, in order from an object side, a first lens group having negative refractive power and a second lens group having positive refractive power;
a focal length being varied by changing an air space between the first lens group and the second lens group; and an adjustment mechanism being provided, the adjustment mechanism performing a position adjustment for making shift decentering or tilt decentering of a whole or a partial lens group of the first lens group and a partial lens group of the second lens group, after assembling the first lens group and the second lens group.

2 . A variable focal length lens according to claim 1 , wherein the following conditional expressions are satisfied:
2.0< MAt/MAw MBt/MBw< 2.0 where MAt denotes a composite imaging magnification of a lens group positioned between the whole or the partial lens group of the first lens group subjected to the shift decentering or the tilt decentering and an image surface, in a telephoto end state of the variable focal length lens, MAw denotes a composite imaging magnification of a lens group positioned between the whole or the partial lens group of the first lens group subjected to the shift decentering or the tilt decentering and the image surface, in a wide angle end state of the variable focal length lens, MBt denotes a composite imaging magnification of a lens group positioned between the partial lens group of the second lens group subjected to the shift decentering or the tilt decentering and the image surface, in the telephoto end state of the variable focal length lens, MBw denotes a composite imaging magnification of a lens group positioned between the partial lens group of the second lens group subjected to the shift decentering or the tilt decentering and the image surface, in the wide angle end state of the variable focal length lens, and MBt=MBw=1 is set on condition that no lens group exists between the partial lens group of the second lens group and the image surface.

3 . A variable focal length lens according to claim 1 , wherein the second lens group comprises a vibration reduction lens group to be moved so as to include a component in a direction orthogonal to an optical axis.

4 . A variable focal length lens according to claim 1 , wherein
the first lens group comprises a positive lens on the most image side, and the adjustment mechanism performs a position adjustment for making shift decentering of the positive lens and a position adjustment for making tilt decentering of a lens group on the most object side in the second lens group.

5 . A variable focal length lens according to claim 4 , wherein the following conditional expressions are satisfied:
2.0< MAt/MAw MBt/MBw<− 3.0 where MAt denotes a composite imaging magnification of a lens group positioned between the positive lens and an image surface, in a telephoto end state of the variable focal length lens, MAw denotes a composite imaging magnification of the lens group positioned between the positive lens and the image surface, in a wide angle end state of the variable focal length lens, MBt denotes a composite imaging magnification of a lens group positioned between the lens group on the most object side in the second lens group and the image surface, in the telephoto end state of the variable focal length lens, and MBw denotes a composite imaging magnification of the lens group positioned between the lens group on the most object side in the second lens group and the image surface, in the wide angle end state of the variable focal length lens.

6 . A variable focal length lens according to claim 1 , wherein
a positive lens is provided on the most image side in the first lens group, the second lens group comprises a vibration reduction lens group to be moved so as to include a component in a direction orthogonal to an optical axis, the adjustment mechanism performs a position adjustment for making shift decentering of the positive lens and a position adjustment for making tilt decentering of the partial lens group of the second lens group, and the vibration reduction lens group performs vibration reduction by making shift decentering of the partial lens group of the second lens group.

7 . A variable focal length lens according to claim 6 , wherein the following conditional expressions are satisfied:
2.0< MAt/MAw MBt/MBw< 2.0 where MAt denotes a composite imaging magnification of a lens group positioned between the positive lens and an image surface, in a telephoto end state of the variable focal length lens, MAw denotes a composite imaging magnification of the lens group positioned between the positive lens and the image surface, in a wide angle end state of the variable focal length lens, MBt denotes a composite imaging magnification of a lens group positioned between the vibration reduction lens group and the image surface, in the telephoto end state of the variable focal length lens, MBw denotes a composite imaging magnification of the lens group positioned between the vibration reduction lens group and the image surface, in the wide angle end state of the variable focal length lens, and MBt=MBw=1 is set on condition that no lens group exists between the vibration reduction lens group and the image surface.

8 . A variable focal length lens according to claim 1 , wherein
a positive lens is provided on the most image side in the first lens group, the second lens group comprises a vibration reduction lens group to be moved so as to include a component in a direction orthogonal to an optical axis, and includes a negative lens group positioned on an image side of the vibration reduction lens group, and the adjustment mechanism performs a position adjustment for making shift decentering of the positive lens and a position adjustment for making shift decentering of the negative lens group.

9 . A variable focal length lens according to claim 8 , wherein the following conditional expressions are satisfied:
2.0< MAt/MAw MBt/MBw< 2.0 where MAt denotes a composite imaging magnification of a lens group positioned between the positive lens and an image surface, in a telephoto end state of the variable focal length lens, MAw denotes a composite imaging magnification of the lens group positioned between the positive lens and the image surface, in a wide angle end state of the variable focal length lens, MBt denotes a composite imaging magnification of a lens group positioned between the negative lens group and the image surface, in the telephoto end state of the variable focal length lens, MBw denotes a composite imaging magnification of the lens group positioned between the negative lens group and the image surface, in the wide angle end state of the variable focal length lens, and MBt=MBw=1 is set on condition that no lens group exists between the negative lens group and the image surface.

10 . A variable focal length lens according to claim 1 , wherein
a positive lens is provided on the most image side in the first lens group and a positive lens is provided on the most image side in the second lens group, and the adjustment mechanism performs a position adjustment for making shift decentering of the positive lens of the first lens group and a position adjustment for making shift decentering of the positive lens of the second lens group.

11 . A variable focal length lens according to claim 10 , wherein the following conditional expression is satisfied:
2.0< MAt/MAw where MAt denotes a composite imaging magnification of a lens group positioned between the positive lens of the first lens group an

Assignees

• Nikon Corp

Inventors

• Yamagami Akira

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

• G02B27/0025

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

• G02B7/10

  by relative axial movement of several lenses, e.g. of varifocal objective lens · CPC title

• G02B7/023

  permitting adjustment · CPC title

• G02B9/64

  having more than six components · CPC title