ZOOM LENS AND IMAGE PICKUP APPARATUS HAVING THE SAME

• US 20130271849A1
• Filed: 04/09/2013
• Published: 10/17/2013
• Est. Priority Date: 04/13/2012
• Status: Active Grant

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Hori, Masao
• Granted Patent: US 8,879,164 B2
• Time in Patent Office: Days
• US Class Current: 359/687
• CPC Class Codes: G02B 15/144113 arranged +-++
• CPC Class Codes: G02B 15/173 arranged +-+

Abstract

A zoom lens includes, in order from an object side to an image side: a positive first lens unit; a negative second lens unit; a positive third lens unit; and a positive fourth lens unit, wherein the first lens unit includes a positive first lens subunit, which does not move for focusing, a positive second lens subunit, which moves during the focus adjustment, and a positive third lens subunit, which does not move for focusing; and focal lengths of the first lens unit, the second lens unit, the third lens unit, a magnification of the third lens unit U3 at a wide angle end, focal lengths of the first lens subunit, the second lens subunit appropriately satisfy certain relations.

Claims

1. A zoom lens comprising, in order from an object side:

a first lens unit having a positive refractive power, which does not move for zooming;

a second lens unit having a negative refractive power, which moves during varying magnification;

a third lens unit having a positive refractive power, which moves during varying magnification; and

a fourth lens unit having a positive refractive power, which does not move for varying magnification, wherein

the first lens unit comprises, in order from the object side, a first lens subunit having a negative refractive power, which does not move for focusing, a second lens subunit having a positive refractive power, which moves during focusing, and a third lens subunit having a positive refractive power, which does not move for focusing;

the third lens unit forms such a locus as to move toward an image side during varying magnification toward a telephoto end from a wide angle end and then move toward the object side; and

the following expressions are satisfied;

−

2.2<

f1/f2<

−

0.8,

−

0.7<

1/β

3w<

0.5,

−

0.55<

f2/f3<

−

0.25, and

−

6.0<

f12/f11<

−

2.5,

where f1 represents a focal length of the first lens unit, f2 represents a focal length of the second lens unit, f3 represents a focal length of the third lens unit, β

3w represents a magnification of the third lens unit at the wide angle end, f11 represents a focal length of the first lens subunit and f12 represents a focal length of the second lens subunit.

2. The zoom lens according to claim 1, wherein the following expression is satisfied:

−

1.5<

f11/f1<

−

0.8.

3. The zoom lens according to claim 1, wherein the following expression is satisfied:

1.4<

f13/f1<

2.6,

where f13 represents a focal length of the third lens subunit.

4. The zoom lens according to claim 1, wherein the first lens subunit has one or more lenses having a positive refractive power and one or more lenses having a negative refractive power, and the following expressions are satisfied:

0.50<

f11n/f11<

0.85, and

−

6.0<

f11p/f11<

−

1.5,

where f11n represents a combined focal length of the lenses having the negative refractive power in the first lens subunit, f11p represents a combined focal length of the lenses having the positive refractive power in the first lens subunit.

5. The zoom lens according to claim 1, wherein the following expressions are satisfied:

3.0<

f12/f1<

7.0, and

60<

ν

12,

where f12 represents the focal length of the second lens subunit and ν

12 represents an average Abbe constant of an optical material to be used in the second lens subunit.

6. The zoom lens according to claim 1, wherein the following expressions are satisfied:

1.0<

ft/f1<

2.2, and

20.0<

ν

fn−

ν

fp<

45.0,

where ft represents a focal length of the whole system of the zoom lens at a telephoto end, ν

fn represents an average value of an Abbe constant of a glass material of the lens having the negative refractive power, which is included in the first lens subunit, and ν

fp represents an average value of an Abbe constant of a glass material of the lens having the positive refractive power, which is included in the first lens subunit.

7. The zoom lens according to claim 1, wherein the following expressions are satisfied:

35.0<

ν

vn−

ν

vp<

75.0, and

−

2.2×

10<sup>−

3</sup><

(θ

vp−

θ

vn)/(ν

vn−

ν

vp)<

−

1.0×

10<sup>−

3</sup>,

where ν

vn represents the maximum value of an Abbe constant of glass materials of negative lenses included in the second lens unit U2 of the zoom lens, θ

vn represents a partial dispersion ratio of the glass material of negative lenses included in the second lens unit U2 of the zoom lens, ν

vp represents the minimum value of an Abbe constant of glass materials of positive lenses included in the second lens unit, and θ

vp represents a partial dispersion ratio of the glass materials of positive lenses included in the second lens unit.

8. The zoom lens according to claim 1, wherein the third lens unit of the zoom lens comprises, in order from the object side:

a lens having a negative refractive power;

a lens having a positive refractive power; and

a lens having a positive refractive power.

9. The zoom lens according to claim 1, wherein

the first lens subunit or the second lens subunit of the zoom lens has a lens having an aspherical surface on one or more surfaces of the lens.

11. The image pickup apparatus according to claim 9, wherein the following expressions are satisfied:

1.5<

ft/fw<

5.0, and

37.0<

ω

w<

50.0,

where ω

w represents a photographing angle of field of the zoom lens at the wide angle end, fw represents a focal length of the whole system at the wide angle end, and ft represents a focal length of the whole system at the telephoto end.

10. An image pickup apparatus comprising a zoom lens and a solid-state image pickup element which receives light of an image formed by the zoom lens,

wherein the zoom lens comprising, in order from an object side:

a first lens unit having a positive refractive power, which does not move for zooming;

a second lens unit having a negative refractive power, which moves during varying magnification;

a third lens unit having a positive refractive power, which moves during varying magnification; and

a fourth lens unit having a positive refractive power, which does not move for varying magnification, wherein

the first lens unit comprises, in order from the object side, a first lens subunit having a negative refractive power, which does not move for focusing, a second lens subunit having a positive refractive power, which moves during focusing, and a third lens subunit having a positive refractive power, which does not move for focusing;

the third lens unit forms such a locus as to move toward an image side during varying magnification toward a telephoto end from a wide angle end and then move toward the object side; and

the following expressions are satisfied;

−

2.2<

f1/f2<

−

0.8,

−

0.7<

1/β

3w<

0.5,

−

0.55<

f2/f3<

−

0.25, and

−

6.0<

f12/f11<

−

2.5,

where f1 represents a focal length of the first lens unit, f2 represents a focal length of the second lens unit, f3 represents a focal length of the third lens unit, β

3w represents a magnification of the third lens unit at the wide angle end, f11 represents a focal length of the first lens subunit and f12 represents a focal length of the second lens subunit.