# US 11,307,394 B2 · Optical system and image pickup apparatus

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- Number: US 11,307,394 B2
- Document ID: US11307394B2
- Status: Granted
- Kind: B2
- Application number: 16/393,826
- Filed: 2019-04-24
- Published: 2019-11-07
- Granted: 2022-04-19
- Earliest claimed: 2018-05-01
- Assignees: Canon Kabushiki Kaisha
- Applicants: Canon Kabushiki Kaisha
- Inventors: Yuichi Gyoda
- Web page: https://patentgrep.com/patent/US11307394B2

## CPC

- G02B 13/24: for reproducing or copying at short object distances
- G02B 15/167: having an additional fixed front lens or group of lenses
- G02B 13/0045: {having five or more lenses}
- G02B 13/009: {having zoom function}
- G02B 13/02: 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
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS

## 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 first focus lens unit having a positive refractive power and configured to move toward the object side for focusing from infinity to a closest object distance; and a second focus lens unit having a negative refractive power and configured to move toward the image side during focusing from infinity to the closest object distance, and an interval between each pair of adjacent lens units is changed during focusing. Further, a focal length of the first focus lens unit, a movement amount of the first focus lens unit during focusing from infinity to the closest object distance, a focal length of the optical system, and a total lens length of the optical system are each appropriately set.

## Claims

### Claim 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 first focus lens unit having a positive refractive power and configured to move toward the object side for focusing from infinity to a closest object distance; and
a second focus lens unit having a negative refractive power and configured to move toward the image side for focusing from infinity to the closest object distance,
wherein an interval between each pair of adjacent lens units is changed during focusing,
wherein conditional expressions:
−5.00<DA/fA<−0.18;
D/f<1.00, and
0.735≤f1/f<1.20,
are satisfied where fA is a focal length of the first focus lens unit, DA is a movement amount of the first focus lens unit for focusing from infinity to the closest object distance, f is a focal length of the optical system, D is a total lens length of the optical system, and f1 is a focal length of the first lens unit.

### Claim 2 (depends on 1)

The optical system according to claim 1, wherein a conditional expression:
−5.00<DB/fB<−0.05,
is satisfied where fB is a focal length of the second focus lens unit, and DB is a movement amount of the second focus lens unit for focusing from infinity to the closest object distance.

### Claim 3 (depends on 1)

The optical system according to claim 1, wherein the first lens unit includes a first positive lens arranged closest to the object side in the first lens unit, and a second positive lens arranged on the image side of and adjacent to the first positive lens.

### Claim 4 (depends on 1)

The optical system according to claim 1, wherein the second focus lens unit includes a positive lens, and a negative lens.

### Claim 5 (depends on 1)

The optical system according to claim 1, wherein the first focus lens unit includes a positive lens, and a negative lens.

### Claim 6 (depends on 1)

The optical system according to claim 1, wherein a conditional expression:
|β|>0.3,
is satisfied where β is an imaging magnification of the optical system at a time when the optical system is focused on the closest object distance.

### Claim 7 (depends on 1)

The optical system according to claim 1, wherein the first lens unit includes an aperture stop arranged closest to the image side in the first lens unit.

### Claim 8 (depends on 1)

The optical system according to claim 1, wherein the first lens unit is configured not to move for focusing.

### Claim 9 (depends on 1)

The optical system according to claim 1, wherein the optical system consists of the first lens unit, the first focus lens unit, the second focus lens unit, and a lens unit having a positive refractive power and configured not to move for focusing.

### Claim 10 (depends on 1)

The optical system according to claim 1, wherein the first focus lens unit consists of a cemented lens formed by cementing a negative lens and a positive lens.

### Claim 11 (depends on 1)

The optical system according to claim 1, wherein the first focus lens unit consists of one positive lens.

### Claim 12 (depends on 1)

The optical system according to claim 1, wherein the second focus lens unit consists of, in order from the object side to the image side, a cemented lens formed by cementing a positive lens and a negative lens, and a negative lens.

### Claim 13 (depends on 1)

The optical system according to claim 1, wherein the second focus lens unit consists of a cemented lens formed by cementing a negative lens and a positive lens.

### Claim 14

An image pickup apparatus comprising:
an optical system;
an image pickup element configured to receive an image formed by the optical system,
wherein the optical system includes, in order from an object side to an image side:
a first lens unit having a positive refractive power;
a first focus lens unit having a positive refractive power and configured to move toward the object side for focusing from infinity to a closest object distance; and
a second focus lens unit having a negative refractive power and configured to move toward the image side for focusing from infinity to the closest object distance,
wherein an interval between each pair of adjacent lens units is changed during focusing, and
wherein conditional expressions:
−5.00<DA/fA<−0.18;
D/f<1.00, and
0.735≤f1/f<1.20,
are satisfied where fA is a focal length of the first focus lens unit, DA is a movement amount of the first focus lens unit for focusing from infinity to the closest object distance, “f” is a focal length of the optical system, D is a total lens length of the optical system, and f1 is a focal length of the first lens unit.

### Claim 15 (depends on 14)

The image pickup apparatus according to claim 14, wherein a conditional expression:
−5.00<DB/fB<−0.05,
is satisfied where fB is a focal length of the second focus lens unit, and DB is a movement amount of the second focus lens unit for focusing from infinity to the closest object distance.

### Claim 16 (depends on 14)

The image pickup apparatus according to claim 14, wherein the first lens unit includes a first positive lens arranged closest to the object side in the first lens unit, and a second positive lens arranged on the image side of and adjacent to the first positive lens.

### Claim 17 (depends on 14)

The image pickup apparatus according to claim 14, wherein the second focus lens unit includes a positive lens, and a negative lens.

### Claim 18 (depends on 14)

The image pickup apparatus according to claim 14, wherein the first focus lens unit includes a positive lens, and a negative lens.

### Claim 19 (depends on 14)

The image pickup apparatus according to claim 14, wherein a conditional expression:
|β|>0.3,
is satisfied where β is an imaging magnification of the optical system at a time when the optical system is focused on the closest object distance.