Zoom lens and image pickup apparatus including the same

Patent metadata

Field	Value
Publication number	US-9739988-B2
Application number	US-201514836389-A
Country	US
Kind code	B2
Filing date	Aug 26, 2015
Priority date	Aug 28, 2014
Publication date	Aug 22, 2017
Grant date	Aug 22, 2017

Abstract

A zoom lens including, in order from an object side: a positive first lens unit that does not move for zooming; a negative second lens unit that moves during the zooming; a negative third lens unit that moves along a locus convex to the object side during the zooming; an aperture stop; and a positive fourth lens unit that does not move for the zooming. The third lens unit includes a cemented lens formed by cementing a single negative lens and a single positive lens and a single negative lens. A focal length (fn 1 ) of the single negative lens included in the cemented lens, a focal length (fp) of the single positive lens included in the cemented lens, and a lateral magnification (β3w) of the third lens unit at a wide angle end are each appropriately set.

First claim

What is claimed is:

1. A zoom lens, comprising, in order from an object side to an image side:
a first lens unit having a positive refractive power that does not move for zooming;
a second lens unit having a negative refractive power that moves during the zooming;
a third lens unit having a negative refractive power that moves during the zooming;
a fourth lens unit having a positive refractive power that moves during the zooming;
an aperture stop; and
a fifth lens unit having a positive refractive power that does not move for zooming,
the third lens unit comprising:
a cemented lens formed by cementing a single negative lens and a single positive lens; and
a single negative lens,

wherein the following conditional expressions are satisfied:
0.60 <|fn 1 x/fpx |<3.5; and
0.24<β3 wx< 0.53,

where fn 1 x represents a focal length of the single negative lens included in the cemented lens, fpx represents a focal length of the single positive lens included in the cemented lens, and β3wx represents a lateral magnification of the third lens unit at a wide angle end.

2. A zoom lens according to claim 1 , wherein the following conditional expression is satisfied:
2.5< f 3 x/f 2 x< 7.5,
where f2x represents a focal length of the second lens unit, and f3x represents a focal length of the third lens unit.

3. A zoom lens according to claim 1 , wherein the following conditional expression is satisfied:
3.7<| f 1 x/f 2 x |<7.0,
where f1x represents a focal length of the first lens unit, and f2x represents a focal length of the second lens unit.

4. A zoom lens according to claim 1 , wherein the cemented lens of the third lens unit has a cementing surface convex to the object side.

5. A zoom lens according to claim 1 , wherein the following conditional expression is satisfied:
3.5 <|f 3 x/fwx |<11.0,
where f3x represents a focal length of the third lens unit, and fwx represents a focal length of an entire system of the zoom lens at the wide angle end.

6. A zoom lens according to claim 1 , wherein the following conditional expression is satisfied:
0.4 <fn 1 x/fn 2 x <8.0,
where fn2x represents a focal length of one of the negative lenses of the third lens unit, which is not included in the cemented lens.

7. A zoom lens according to claim 1 , wherein the following conditional expressions are satisfied:
0.65 <Nn 1 x/Npx <1.20; and
1.4 <νn 1 x/νpx <4.2,
where Nn1x and νn1x respectively represent a refractive index and an Abbe number of a material of the single negative lens included in the cemented lens, and Npx and vpx respectively represent a refractive index and an Abbe number of a material of the single positive lens included in the cemented lens.

8. An image pickup apparatus comprising:
a zoom lens comprising, in order from an object side to an image side:
a first lens unit having a positive refractive power that does not move for zooming;
a second lens unit having a negative refractive power that moves during the zooming;
a third lens unit having a negative refractive power that moves during the zooming;
a fourth lens unit having a positive refractive power that moves during the zooming;
an aperture stop; and
a fifth lens unit having a positive refractive power that does not move for zooming,

the third lens unit comprising:
a cemented lens formed by cementing a single negative lens and a single positive lens; and
a single negative lens,
wherein the following conditional expressions are satisfied:
0.60 <|fn 1 x/fpx <3.5; and
0.24<β3 wx <0.53,

where fn 1 x represents a focal length of the single negative lens included in the cemented lens, fpx represents a focal length of the single positive lens included in the cemented lens, and β3wx represents a lateral magnification of the third lens unit at a wide angle end; and
an image pickup element receiving an optical image formed by the zoom lens.

Assignees

• Canon Kk

Inventors

• Sakamoto Masaru

Classifications

• H04N23/69

  Control of means for changing angle of the field of view, e.g. optical zoom objectives or electronic zooming · CPC title

• H04N5/23296

  Electricity · mapped topic

• G02B27/0025

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

• G02B15/17 Primary

  arranged +-- · CPC title

• G02B15/24

  having a front fixed lens or lens group and two movable lenses or lens groups in front of a fixed lens or lens group · CPC title