Zoom lens and image pickup apparatus including the same

Patent metadata

Field	Value
Publication number	US-10095010-B2
Application number	US-201715647849-A
Country	US
Kind code	B2
Filing date	Jul 12, 2017
Priority date	Aug 9, 2016
Publication date	Oct 9, 2018
Grant date	Oct 9, 2018

Abstract

A zoom lens includes, in order from object-side, a fixed positive first group including three-or-more lenses, a negative second group including a unit moving toward image-side during zooming toward telephoto-end, a positive third group including a unit moving toward object-side during zooming from wide-end to telephoto-end, a negative fourth group moving during zooming and focusing, and a rear group. Focal lengths of the first group and the zoom lens at wide-end, a movement amount of a unit moving by largest amount during zooming toward telephoto-end in the second group, a largest value of position change between wide-end and telephoto-end of units moving toward an object side during zooming from wide-end to telephoto-end, refractive index for d-line of a positive lens closest to image-side in the first group, and average refractive index for d-line of positive lenses of the first group other than the positive lens are 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 group which is not moved for zooming and is composed of a single lens unit having a positive refractive power;
a second lens group which has a negative refractive power and comprises at least one lens unit each of which is moved toward an image side during zooming from a wide angle end to a telephoto end;
a third lens group which has a positive refractive power and comprises at least one lens unit each of which is moved toward the object side during zooming from the wide angle end to the telephoto end;
a fourth lens group which is configured to move during zooming and focusing and is composed of a single lens unit having a negative refractive power; and
a rear lens group which is composed of at least one lens unit,
wherein intervals between adjacent lens units are changed during zooming,
wherein the first lens group comprises at least three lenses, and
wherein the following conditional expressions are satisfied:
4.80< f 1/ fw< 8.00;
−5.00< M 2/ Mv<− 1.50;

−3.50< Mv/fw<− 0.77; and

0.99< Nd 1 pr/Nd 1 pf< 1.40,

where f1 represents a focal length of the first lens group, fw represents a focal length of the zoom lens at the wide angle end, M2 represents an amount of movement of a lens unit which is moved by a largest amount during zooming from the wide angle end to the telephoto end in the second lens group, Mv represents an amount of movement of a lens unit which is moved by a largest amount during zooming from the wide angle end to the telephoto end among lens units which are moved toward an object side during zooming from the wide angle end to the telephoto end, Nd1pr represents a refractive index with respect to a d-line of a material of a positive lens G1pr arranged closest to the image side in the first lens group, Nd1pf represents an average of refractive indices with respect to the d-line of materials of positive lenses included in the first lens group other than the positive lens G1pr, and a sign of an amount of movement of a lens unit is defined as positive when the lens unit is located closer to the image side at the telephoto end than at the wide angle end.

2. The zoom lens according to claim 1 , wherein the following conditional expression is satisfied:
−7.00< f 1/ f 2<−4.50,

where f1 represents the focal length of the first lens group, and f2 represents a combined focal length of the lens units of the second lens group at the wide angle end in which focus is at infinity.

3. The zoom lens according to claim 1 , wherein the following conditional expression is satisfied:
1.50< f 3/ fw< 3.50,

where f3 represents a combined focal length of the lens units of the third lens group at the wide angle end in which focus is at infinity, and fw represents the focal length of the zoom lens at the wide angle end.

4. The zoom lens according to claim 1 , wherein the following conditional expression is satisfied:
−4.00< f 4/ fw<− 1.00,

where f4 represents a focal length of the fourth lens group, and fw represents the focal length of the zoom lens at the wide angle end.

5. The zoom lens according to claim 1 , wherein the third lens group comprises a negative lens.

6. The zoom lens according to claim 1 , wherein the following conditional expression is satisfied:
−4.50< M 2/ f 2<−2.50,

where M2 represents the amount of movement of the lens unit which is moved by the largest amount during zooming from the wide angle end to the telephoto end among the at least one lens unit included in the second lens group, and f2 represents a combined focal length of the lens units of the second lens group at the wide angle end in which focus is at infinity.

7. The zoom lens according to claim 1 , wherein the following conditional expression is satisfied:
−4.00<(1−β4 w 2 )×β Rw 2 <−1.40,

where β4w represents a lateral magnification of the fourth lens group at the wide angle end, and βRw represents a lateral magnification of the rear lens group at the wide angle end.

8. The zoom lens according to claim 1 , further comprising an aperture stop arranged between the second lens group and the third lens group.

9. The zoom lens according to claim 8 , wherein the aperture stop is not moved in an optical axis direction for zooming.

10. An image pickup apparatus, comprising:
a zoom lens, comprising, in order from an object side to an image side:
a first lens group which is not moved for zooming and is composed of a single lens unit having a positive refractive power;
a second lens group which has a negative refractive power and comprises at least one lens unit each of which is moved toward an image side during zooming from a wide angle end to a telephoto end;
a third lens group which has a positive refractive power and comprises at least one lens unit each of which is moved toward the object side during zooming from the wide angle end to the telephoto end;
a fourth lens group which is configured to move during zooming and focusing and is composed of a single lens unit having a negative refractive power; and
a rear lens group which is composed of at least one lens unit,
wherein intervals between adjacent lens units are changed during zooming,
wherein the first lens group comprises at least three lenses, and
wherein the following conditional expressions are satisfied:
4.80< f 1/ fw< 8.00;
−5.00< M 2/ Mv<− 1.50;

−3.50< Mv/fw<− 0.77; and

0.99< Nd 1 pr/Nd 1 pf< 1.40,

where f1 represents a focal length of the first lens group, fw represents a focal length of the zoom lens at the wide angle end, M2 represents an amount of movement of a lens unit which is moved by a largest amount during zooming from the wide angle end to the telephoto end among the at least one lens unit included in the second lens group, Mv represents an amount of movement of a lens unit which is moved by a largest amount during zooming from the wide angle end to the telephoto end among lens units which are moved toward an object side during zooming from the wide angle end to the telephoto end, Nd1pr represents a refractive index with respect to a d-line of a material of a positive lens G1pr arranged closest to the image side in the first lens group, Nd1pf represents an average of refractive indices with respect to the d-line of materials of positive lenses included in the first lens group other than the positive lens G1pr, and a sign of an amount of movement of a lens unit is defined as positive when the lens unit is located closer to the image side at the telephoto end than at the wide angle end; and
an image pickup element configured to receive light of an image formed by the zoom lens.

Assignees

• Canon Kk

Inventors

• Takemoto Shoichi

Classifications

• G02B15/28

  arranged +-+ · CPC title

• G02B15/167 Primary

  having an additional fixed front lens or group of lenses · CPC title

• G02B15/145121 Primary

  arranged +-+-+ · CPC title

• G02B15/145117

  arranged +---+ · CPC title

• G02B15/173

  arranged +-+ · CPC title