Zoom lens and image pickup apparatus including the same

Patent metadata

Field	Value
Publication number	US-9946065-B2
Application number	US-201615232109-A
Country	US
Kind code	B2
Filing date	Aug 9, 2016
Priority date	Aug 21, 2015
Publication date	Apr 17, 2018
Grant date	Apr 17, 2018

Abstract

Provided is an optical system, including, in order from an object side to an image side, a first lens unit having a positive refractive power, a second lens unit having a negative refractive power, which is configured to move during focusing, and a third lens unit having a positive or negative refractive power, the first lens unit consisting of, in order from the object side to the image side, a positive lens (Gp 1 ), a positive lens (Gp 2 ), and a subunit including a plurality of lenses, the subunit including at least one negative lens, in which an Abbe number νdGp 1 of a material of the positive lens (Gp 1 ), an Abbe number νdGn 1 of a material of a negative lens (Gn 1 ) closest to the object side among the negative lenses of the subunit, and a partial dispersion ratio θgFGn 1 of the material of the negative lens (Gn 1 ) are each appropriately set.

First claim

What is claimed is:

1. An optical system comprising, in order from an object side to an image side:
a first lens unit having a positive refractive power;
a second lens unit having a negative refractive power, which is configured to move during focusing; and
a third lens unit having one of a positive refractive power or a negative refractive power,
wherein the first lens unit consists of, in order from the object side to the image side:
a positive lens Gp 1 ;
a positive lens Gp 2 ; and
a subunit comprising a plurality of lenses, including at least one negative lens,

wherein the following conditional expressions are satisfied:
18≤ vdGp 1≤45.0;

18≤ vdGn 1≤40.0;and

−0.004<θ gFGn 1−0.6438+0.001682× vdGn 1<0.012,

where:
vdGp 1 represents an Abbe number of a material of the positive lens Gp 1 ,
vdGn 1 represents an Abbe number of a material of a negative lens Gn 1 closest to the object side among the at least one negative lens of the subunit, and
θgFGn 1 represents a partial dispersion ratio of the material of the negative lens Gn 1 .

2. An optical system according to claim 1 , wherein the following conditional expression is satisfied:
0.000<θ gFGp 1−0.6438+0.001682× vdGp 1<0.020,

where θgFGp 1 represents a partial dispersion ratio of the material of the positive lens Gp 1 .

3. An optical system according to claim 1 , wherein the following conditional expression is satisfied:
2.00≤ dGp 1≤3.006933× ndGp 1−2.01278,

where ndGp 1 represents a refractive index of the material of the positive lens Gp 1 , and dGp 1 represents a specific gravity of the material of the positive lens Gp 1 , the specific gravity dGp 1 of the material being a ratio of a mass of the material at 20° C., which is used for the positive lens Gp 1 , to a mass of pure water with the same volume as the material, under a pressure of 101.325 kPa, which is a normal atmospheric pressure, at 4° C.

4. An optical system according to claim 1 , wherein the following conditional expression is satisfied:
1.50< ndGp 1<1.71,
where ndGp 1 represents a refractive index of the material of the positive lens Gp 1 .

5. An optical system according to claim 1 , wherein the following conditional expression is satisfied:
0.08< L 12/ fGp 1<0.25,
where fGp 1 represents a focal length of the positive lens Gp 1 , and L 12 represents an interval on an optical axis between the positive lens Gp 1 and the positive lens Gp 2 .

6. An optical system according to claim 1 , wherein the subunit comprises, in order from the object side to the image side, a negative lens, a positive lens, and a negative lens.

7. An optical system according to claim 1 , wherein the second lens unit comprises a cemented lens comprising a positive lens and a negative lens.

8. An image pickup apparatus comprising:
an optical system according to claim 1 ; and
an image pickup element configured to receive an image formed by the optical system.

9. An optical system comprising, in order from an object side to an image side:
a first lens unit having a positive refractive power;
a second lens unit having a negative refractive power, which is configured to move during focusing; and
a third lens unit having one of a positive refractive power or a negative refractive power,
wherein the first lens unit consists of, in order from the object side to the image side:
a positive lens Gp 1 ;
a positive lens Gp 2 ; and
a subunit comprising a plurality of lenses, including at least one negative lens,

wherein the following conditional expressions are satisfied:
18≤ vdGp 1≤50.0;

18≤ vdGn 1≤40.0;

−0.004<θ gFGn 1−0.6438+0.001682× vdGn 1<0.012; and

2.00≤ dGp 1≤3.006933× ndGp 1−2.01278,

where:
vdGp 1 represents an Abbe number of a material of the positive lens Gp 1 ,
vdGn 1 represents an Abbe number of a material of a negative lens Gn 1 closest to the object side among the at least one negative lens of the subunit,
θgFGn 1 represents a partial dispersion ratio of the material of the negative lens Gn 1 ,
ndGp 1 represents a refractive index of the material of the positive lens Gp 1 , and
dGp 1 represents a specific gravity of the material of the positive lens Gp 1 , the specific gravity dGp 1 of the material being a ratio of a mass of the material at 20° C., which is used for the positive lens Gp 1 , to a mass of pure water with the same volume as the material, under a pressure of 101.325 kPa, which is a normal atmospheric pressure, at 4° C.

10. An image pickup apparatus comprising:
an optical system according to claim 9 ; and
an image pickup element configured to receive an image formed by the optical system.

11. An optical system comprising, in order from an object side to an image side:
a first lens unit having a positive refractive power;
a second lens unit having a negative refractive power, which is configured to move during focusing; and
a third lens unit having one of a positive refractive power or a negative refractive power,
wherein the first lens unit consists of, in order from the object side to the image side:
a positive lens Gp 1 ;
a positive lens Gp 2 ; and
a subunit comprising a plurality of lenses, including at least one negative lens,

wherein the following conditional expressions are satisfied:
18≤ vdGp 1≤50.0;

18≤ vdGn 1≤40.0;

−0.004<θ gFGn 1−0.6438+0.001682× vdGn 1<0.012; and

0.08< L 12/ fGp 1<0.25,

where:
vdGp 1 represents an Abbe number of a material of the positive lens Gp 1 ,
vdGn 1 represents an Abbe number of a material of a negative lens Gn 1 closest to the object side among the at least one negative lens of the subunit,
θgFGn 1 represents a partial dispersion ratio of the material of the negative lens Gn 1 , and
fGp 1 represents a focal length of the positive lens Gp 1 , and L 12 represents an interval on an optical axis between the positive lens Gp 1 and the positive lens Gp 2 .

12. An image pickup apparatus comprising:
an optical system according to claim 11 ; and
an image pickup element configured to receive an image formed by the optical system.

13. An optical system comprising, in order from an object side to an image side:
a first lens unit having a positive refractive power;
a second lens unit having a negative refractive power, which is configured to move during focusing; and
a third lens unit having one of a positive refractive power or a negative refractive power,
wherein the first lens unit consists of, in order from the object side to the image side:
a positive lens Gp 1 ;
a positive lens Gp 2 ; and
a subunit comprising, in order from the object side to the image side, a negative lens, a positive lens, and a negative lens,

wherein the following conditional expressions are satisfied:
18≤ vdGp 1≤50.0;

18≤ vdGn 1≤40.0;and

−0.004<θ gFGn 1−0.6438+0.001682× vdGn 1<0.012,

where:
vdGp 1 represents an Abbe number of a material of the positive lens Gp 1 ,
vdGn 1 represents an Abbe number of a material of a negative lens Gn 1 closest to the object side among the at least one negative lens of the subunit, and
θgFGn 1 represents a partial dispersion ratio of the material of the negative lens Gn 1 .

14. An image pickup apparatus comprising:
an optical system according to claim 13 ; and
an image pickup element configured to receive an image formed by the optical system.

Assignees

• Canon Kk

Inventors

• Okumura Tetsuichiro

Classifications

• G02B27/0062 Primary

  by controlling the dispersion of a lens material, e.g. adapting the relative partial dispersion · CPC title

• G02B13/02

  Telephoto objectives, i.e. systems of the type + - in which the distance from the front vertex to the image plane is less than the equivalent focal length · CPC title

• G02B13/16

  for use in conjunction with image converters or intensifiers {, or for use with projectors, e.g. objectives for projection TV} · CPC title