Zoom lens and image pickup apparatus including the same

Patent metadata

Field	Value
Publication number	US-9715092-B2
Application number	US-201615170432-A
Country	US
Kind code	B2
Filing date	Jun 1, 2016
Priority date	Jun 5, 2015
Publication date	Jul 25, 2017
Grant date	Jul 25, 2017

Abstract

A zoom lens includes: a first lens unit having a negative refractive power; and a rear group having a positive refractive power, in which, when a focal length of the zoom lens is a shortest focal length, a maximum image height is lower than a half of a diagonal length of an image pickup region, and when a focal length of the zoom lens at which the maximum image height becomes a half of the diagonal length of the image pickup region is defined as an intermediate focal length, a focal length of the zoom lens at a longest focal length, a half angle of field of the zoom lens at the longest focal length, and other such factors are appropriately set so that the maximum image height is increased continuously from the shortest focal length to the intermediate focal length.

First claim

What is claimed is:

1. A zoom lens, which is configured to form a subject image on an image pickup element, comprising, in order from an object side to an image side:
a first lens unit having a negative refractive power; and
a rear group including a plurality of lens units,
wherein the rear group comprises a lens unit having a positive refractive power,
wherein an interval between each pair of adjacent lens units is changed during zooming from a shortest focal length to a longest focal length,
wherein the image pickup element has a rectangular image pickup region, and when a focal length of the zoom lens is the shortest focal length, a maximum image height is lower than a half of a diagonal length of the rectangular image pickup region, and there are regions in which the subject image is not formed in the image pickup region,
wherein, when a focal length of the zoom lens at which the maximum image height becomes a half of the diagonal length of the image pickup region is defined as an intermediate focal length, the maximum image height is increased during zooming from the shortest focal length to the intermediate focal length, and
wherein the following conditional expressions are satisfied:
0.75< D /( ft ×tan(ω t ))<1.10; and

1.4< D/Yw< 2.6,

where ft represents a focal length of the zoom lens at the longest focal length, ωt represents a half angle of field of the zoom lens at the longest focal length, Yw represents an image height at the shortest focal length, and D represents a length that is a half of the diagonal length of the image pickup element.

2. The zoom lens according to claim 1 , wherein the following conditional expressions are satisfied:
0.9<ω m/ωw< 1.1; and

80°<ω w< 115°,

where ωw represents a half angle of field of the zoom lens at the shortest focal length in degrees, and ωm represents a half angle of field of the zoom lens at the intermediate focal length in degrees.

3. The zoom lens according to claim 1 , wherein the lens unit having the positive refractive power included in the rear group is configured to move monotonously toward the object side during zooming from the shortest focal length to the longest focal length, and to satisfy the following conditional expression:
1.0<| mp/fp|< 4.0,

where fp represents a focal length of the lens unit having the positive refractive power included in the rear group, and mp represents a movement amount of the lens unit having the positive refractive power included in the rear group during zooming from the shortest focal length to the longest focal length.

4. The zoom lens according to claim 1 , wherein the first lens unit comprises, in order from the object side to the image side, a first negative lens having a meniscus shape with a convex surface thereof facing the object side, and a second negative lens having a meniscus shape with a convex surface thereof facing the object side.

5. The zoom lens according to claim 4 , wherein the following conditional expressions are satisfied:
1.0<( R 1 a+R 1 b )/( R 1 a−R 1 b )<4.5; and
0.5<( R 2 a+R 2 b )/( R 2 a−R 2 b )<3.5,

where R 1 a and R 1 b represent curvature radii of lens surfaces on the object side and the image side of the first negative lens, respectively, and R 2 a and R 2 b represent curvature radii of lens surfaces on the object side and the image side of the second negative lens, respectively.

6. The zoom lens according to claim 1 , wherein the first lens unit includes three negative lenses successively arranged closest to the object side and in order toward the image side, and satisfies the following conditional expressions:
0.8< fG 1/ fG 2<4.0; and
0.3< fG 2/ fG 3<1.5,

where fG 1 , fG 2 , and fG 3 represent focal lengths of the three negative lenses in order from the object side to the image side, respectively.

7. The zoom lens according to claim 1 , wherein the following conditional expression is satisfied:
0.2<| f 1/ fp|< 0.7,

where f 1 represents a focal length of the first lens unit, and fp represents a focal length of the lens unit having the positive refractive power included in the rear group.

8. The zoom lens according to claim 1 , wherein the following conditional expression is satisfied:
0.4<| fp/ft|< 3.0,

where fp represents a focal length of the lens unit having the positive refractive power included in the rear group.

9. The zoom lens according to claim 1 , wherein the lens unit having the positive refractive power included in the rear group includes a lens having a lens surface having an aspherical shape, and a cemented lens obtained by cementing a positive lens and a negative lens.

10. The zoom lens according to claim 1 ,
wherein the first lens unit is configured to move during zooming, and
wherein the rear group consists of a second lens unit having a positive refractive power, which is configured to move during zooming, a third lens unit having a negative refractive power, which is configured to move during zooming, and a fourth lens unit having a positive refractive power, the second lens unit, the third lens unit, and the fourth lens unit being arranged in the stated order from the object side to the image side.

11. The zoom lens according to claim 1 ,
wherein the first lens unit is configured to move during zooming, and
wherein the rear group consists of a second lens unit having a positive refractive power, which is configured to move during zooming, a third lens unit having a positive refractive power, which is configured to move during zooming, a fourth lens unit having a negative refractive power, which is configured to move during zooming, and a fifth lens unit having a positive refractive power, the second lens unit, the third lens unit, the fourth lens unit, and the fifth lens unit being arranged in the stated order from the object side to the image side.

12. The zoom lens according to claim 1 ,
wherein the first lens unit is configured to move during zooming, and
wherein the rear group consists of a second lens unit having a positive refractive power, which is configured to move during zooming, and a third lens unit having a positive refractive power, which is configured to move during zooming, the second lens unit and the third lens unit being arranged in the stated order from the object side to the image side.

13. The zoom lens according to claim 1 ,
wherein the first lens unit is configured to move during zooming, and
wherein the rear group consists of a second lens unit having a positive refractive power, which is configured to move during zooming, and a third lens unit having a negative refractive power, which is configured to move during zooming, the second lens unit and the third lens unit being arranged in the stated order from the object side to the image side.

14. An image pickup apparatus, comprising:
a zoom lens; and
an image pickup element configured to receive an image formed by the zoom lens,
the zoom lens comprising, in order from an object side to an image side:
a first lens unit having a negative refractive power; and
a rear group including a plurality of lens units,
wherein the rear group comprises a lens unit having a positive refractive power,
wherein an interval between each pair of adjacent lens units is changed during zooming from a shortest focal length to a longest focal length,
wherein the image pickup element has a rectangular image pickup region, and when a focal length of the zoom lens is the shortest focal length, a maximum image height is lower than a half of a diagonal length of the rectangular image pickup region, and there

Assignees

• Canon Kk

Inventors

• Inomoto Yu

Classifications

• H04N23/698

  for achieving an enlarged field of view, e.g. panoramic image capture · 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

• G02B13/18

  with lenses having one or more non-spherical faces, e.g. for reducing geometrical aberration {(G02B13/002 takes precedence)} · CPC title

• G02B13/06

  Panoramic objectives; So-called "sky lenses" {including panoramic objectives having reflecting surfaces} · CPC title

• H04N5/23238

  Electricity · mapped topic