# US 11,307,400 B2 · Zoom lens and image pickup apparatus

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- Number: US 11,307,400 B2
- Document ID: US11307400B2
- Status: Granted
- Kind: B2
- Application number: 16/507,482
- Filed: 2019-07-10
- Published: 2020-01-16
- Granted: 2022-04-19
- Earliest claimed: 2018-07-13
- Assignees: Canon Kabushiki Kaisha
- Applicants: Canon Kabushiki Kaisha
- Inventors: Shoichi Takemoto; Tomoya Yamada
- Web page: https://patentgrep.com/patent/US11307400B2

## CPC

- G02B 15/145125: {arranged +--++}
- G02B 23/145: {Zoom viewfinders}
- G02B 3/14: of variable focal length
- G02B 7/10: by relative axial movement of several lenses, e.g. of varifocal objective lens
- G02B 15/10: by adding a part, e.g. close-up attachment
- G02B 15/14: by axial movement of one or more lenses or groups of lenses relative to the image plane for continuously varying the equivalent focal length of the objective
- G03B 13/10: adjusting viewfinders field
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G03B: APPARATUS OR ARRANGEMENTS FOR TAKING PHOTOGRAPHS OR FOR PROJECTING OR VIEWING THEM; APPARATUS OR ARRANGEMENTS EMPLOYING ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ACCESSORIES THEREFOR (optical parts of such apparatus G02B; photosensitive materials or processes for photographic purposes G03C; apparatus for processing exposed photographic materials G03D)

## Abstract

A zoom lens includes: a master lens including in order from an object side: a positive first lens unit configured not to move for zooming; a negative second lens unit configured to move for zooming; at least one lens unit configured to move for zooming; and a positive relay lens unit arranged closest to the image side; and an extender lens unit configured to change a focal length range of the zoom lens by one of: being inserted in place of a lens unit arranged adjacent to the relay lens unit on the object side; and being inserted into a space adjacent to the positive relay lens unit on the object side, wherein the extender lens unit includes a positive lens Gp, and an Abbe number and a partial dispersion ratio of the positive lens Gp are suitably set.

## Claims

### Claim 1

A zoom lens comprising:
a master lens including in order from an object side to an image side:
a first lens unit having a positive refractive power and configured not to move for zooming;
a second lens unit having a negative refractive power and configured to move for zooming;
at least one lens unit configured to move for zooming; and
a relay lens unit having a positive refractive power and arranged closest to the image side; and
an extender lens unit configured to be insertable into or removable from an optical path of the zoom lens between the at least one lens unit and the relay lens unit to extend a focal length of the zoom lens by one of: being inserted in place of a lens unit arranged adjacent to the relay lens unit and being inserted into a space adjacent to the relay lens unit,
wherein the extender lens unit includes a positive lens Gp, and the positive lens Gp satisfies conditional expressions
θgF−(−1.6650×10−7·νd3+5.2130×10−5·νd2−5.6560×10−3·νd+0.7370)>0;
0.5450<θgF; and
50.0<νd<85.0,
where νd and θgF represent an Abbe number and a partial dispersion ratio of the positive lens Gp, respectively, and
wherein an Abbe number νd and a partial dispersion ratio θgF of a material are expressed by expressions
νd=(Nd−1)/(NF−NC); and
θgF=(Ng−NF)/(NF−NC),respectively,
where Ng, NF, NC, and Nd represent refractive indices of the material with respect to a g-line (wavelength of 435.8 nm), an F-line (wavelength of 486.1 nm), a C-line (wavelength of 656.3 nm), and a d-line (wavelength of 587.6 nm), respectively.

### Claim 2 (depends on 1)

The zoom lens according to claim 1, wherein the zoom lens satisfies a conditional expression
1.3<fiew/fw<3.0,
where fw represents a focal length of the master lens at a wide angle end, and fiew represents a focal length of the zoom lens at the wide angle end in a state in which the extender lens unit is inserted.

### Claim 3 (depends on 1)

The zoom lens according to claim 1, wherein the zoom lens satisfies a conditional expression
0<LGp1/Lie<0.4,
where Lie represents a distance from an apex of a surface of the extender lens unit closest to the object side to an apex of a surface of the extender lens unit closest to the image side, and LGp1 represents a distance from the apex of the surface closest to the object side to an apex of a surface on the object side of a positive lens Gp1, which is arranged closest to the object side of the positive lens Gp.

### Claim 4 (depends on 1)

The zoom lens according to claim 1, wherein the extender lens unit consists of, in order from the object side to the image side, a positive lens and three cemented lenses.

### Claim 5 (depends on 1)

The zoom lens according to claim 1, wherein the extender lens unit consists of, in order from the object side to the image side, at least one positive lens and two cemented lenses.

### Claim 6 (depends on 1)

The zoom lens according to claim 1, wherein the extender lens unit consists of, in order from the object side to the image side, one positive lens, two cemented lenses, and one negative lens.

### Claim 7

An image pickup apparatus comprising:
a zoom lens; and
an image pickup element configured to receive an image formed by the zoom lens,
wherein the zoom lens comprising:
a master lens including in order from an object side to an image side:
a first lens unit having a positive refractive power and configured not to move for zooming;
a second lens unit having a negative refractive power and configured to move for zooming;
at least one lens unit configured to move for zooming; and
a relay lens unit having a positive refractive power and arranged closest to the image side; and
an extender lens unit configured to be insertable into or removable from an optical path of the zoom lens between the at least one lens unit and the relay lens unit to extend a focal length of the zoom lens by one of: being inserted in place of a lens unit arranged adjacent to the relay lens unit; and being inserted into a space adjacent to the relay lens unit,
wherein the extender lens unit includes a positive lens Gp, and the positive lens Gp satisfies conditional expressions
θgF−(−1.6650×10−7·νd3+5.2130×10−5·νd2−5.6560×10−3·νd+0.7370)>0;
0.5450<θgF; and
50.0<νd<85.0,
where νd and θgF represent an Abbe number and a partial dispersion ratio of the positive lens (Gp), respectively, and
wherein an Abbe number νd and a partial dispersion ratio θgF of a material are expressed by expressions
νd=(Nd−1)/(NF−NC); and
θgF=(Ng−NF)/(NF−NC),respectively,
where Ng, NF, NC, and Nd represent refractive indices of the material with respect to a g-line (wavelength of 435.8 nm), an F-line (wavelength of 486.1 nm), a C-line (wavelength of 656.3 nm), and a d-line (wavelength of 587.6 nm), respectively.

### Claim 8

An extender lens unit configured to be insertable into or removable from an optical path of an image pickup apparatus to extend a focal length of the image pickup apparatus,
wherein the extender lens unit includes a positive lens Gp, and the positive lens Gp satisfies conditional expressions
θgF−(−1.6650×10−7·νd3+5.2130×10−5·νd2−5.6560×10−3·νd+0.7370)>0;
0.5450<θgF; and
50.0<νd<85.0,
where νd and θgF represent an Abbe number and a partial dispersion ratio of the positive lens Gp, respectively, and
wherein an Abbe number νd and a partial dispersion ratio θgF of a material are expressed by expressions
νd=(Nd−1)/(NF−NC); and
θgF=(Ng−NF)/(NF−NC), respectively,
where Ng, NF, NC, and Nd represent refractive indices of the material with respect to a g-line (wavelength of 435.8 nm), an F-line (wavelength of 486.1 nm), a C-line (wavelength of 656.3 nm), and a d-line (wavelength of 587.6 nm), respectively.

### Claim 9 (depends on 8)

The extender lens unit according to claim 8, wherein the extender lens unit satisfies a conditional expression
1.3<fiew/fw<3.0,
where fw represents a focal length of a master lens, and fiew represents a focal length of the image pickup apparatus in a state in which the extender lens unit is inserted into the optical path.

### Claim 10 (depends on 8)

The extender lens unit according to claim 8, wherein the extender lens unit satisfies a conditional expression
0<LGp1/Lie<0.4,
where Lie represents a distance from an apex of a surface of the extender lens unit closest to an object side to an apex of a surface of the extender lens unit closest to an image side, and LGp1 represents a distance from the apex of the surface closest to the object side to an apex of a surface on the object side of a positive lens Gp1, which is arranged closest to the object side of the positive lens Gp.

### Claim 11 (depends on 8)

The extender lens unit according to claim 8, wherein the extender lens unit consists of, in order from an object side to an image side, a positive lens and three cemented lenses.

### Claim 12 (depends on 1)

The extender lens unit according to claim 1, wherein the extender lens unit consists of, in order from the object side to the image side, at least one positive lens and two cemented lenses.

### Claim 13 (depends on 1)

The extender lens unit according to claim 1, wherein the extender lens unit consists of, in order from the object side to the image side, one positive lens, two cemented lenses, and one negative lens.

### Claim 14

An image pickup apparatus comprising:
an extender lens unit; and
an image pickup element configured to receive an image formed via the extender lens unit,
wherein the extender lens unit includes a positive lens Gp, and the positive lens Gp satisfies conditional expressions
θgF−(−1.6650×10−7·νd3+5.2130×10−5·νd2−5.6560×10−3·νd+0.7370)>0;
0.5450<θgF; and
50.0<νd<85.0,
where νd and θgF represent an Abbe number and a partial dispersion ratio of the positive lens Gp, respectively, and
wherein an Abbe number νd and a partial dispersion ratio θgF of a material are expressed by expressions
νd=(Nd−1)/(NF−NC); and
θgF=(Ng−NF)/(NF−NC), respectively,
where Ng, NF, NC, and Nd represent refractive indices of the material with respect to a g-line (wavelength of 435.8 nm), an F-line (wavelength of 486.1 nm), a C-line (wavelength of 656.3 nm), and a d-line (wavelength of 587.6 nm), respectively.