# US 12,007,538 B2 · Optical system, image pickup apparatus, and image pickup system

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- Number: US 12,007,538 B2
- Document ID: US12007538B2
- Status: Granted
- Kind: B2
- Application number: 17/032,506
- Filed: 2020-09-25
- Published: 2021-04-22
- Granted: 2024-06-11
- Earliest claimed: 2019-10-17
- Assignees: Canon Kabushiki Kaisha
- Applicants: Canon Kabushiki Kaisha
- Inventors: Shuichi Mogi
- Web page: https://patentgrep.com/patent/US12007538B2

## CPC

- G02B 15/1421: {the first group being positive}
- G02B 13/18: with lenses having one or more non-spherical faces, e.g. for reducing geometrical aberration {(G02B13/002 takes precedence)}
- G02B 3/04: with continuous faces that are rotationally symmetrical but deviate from a true sphere {, e.g. so called "aspheric" lenses}
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS

## Abstract

An optical system includes a first lens unit having a positive refractive power disposed closest to an object, a first focus lens unit having a positive refractive power disposed on an image side of the first lens unit, and a second focus lens unit having a negative refractive power disposed on the image side of the first focus lens unit. The first lens unit is fixed during focusing. The first focus lens unit and the second focus lens unit are movable during focusing so that a distance between the first focus lens unit and the second focus lens unit changes. The first lens unit includes a single negative lens disposed closest to the object. A predetermined condition is satisfied.

## Claims

### Claim 1

An optical system comprising a first lens unit having a positive refractive power disposed closest to an object, a first focus lens unit having a positive refractive power disposed on an image side of the first lens unit, and a second focus lens unit having a negative refractive power disposed on the image side of the first focus lens unit, the first lens unit being fixed for focusing, and the first focus lens unit and the second focus lens unit being movable during focusing so that a distance between the first focus lens unit and the second focus lens unit changes,
wherein the first lens unit includes a single negative lens disposed closest to the object,
wherein the first lens unit includes an aperture stop and a plurality of positive lenses which are disposed on the image side of the aperture stop, and
wherein the following inequalities are satisfied:
−5.0<fp2/fn1<−0.1
−0.290<n1gt/fn1<−0.095
where fp2 is a focal length of the first focus lens unit, fn1 is a focal length of the second focus lens unit, and n1gt is a distance on an optical axis from a surface closest to the object of the second focus lens unit to a surface closest to an image plane of the second focus lens unit.

### Claim 2 (depends on 1)

The optical system according to claim 1, wherein the following inequality is satisfied:
1<|f/Mn2|<15000
where Mn2 is a moving amount of the second focus lens unit relative to the image plane during focusing from infinity to a shortest distance, and f is a focal length of the optical system.

### Claim 3 (depends on 1)

The optical system according to claim 1, wherein the following inequality is satisfied:
−15.00<fnr/f<−0.20
where fnr is a combined focal length from the surface closest to the object of the second focus lens unit to the image plane when focused on the object at infinity and f is a focal length of the optical system.

### Claim 4 (depends on 1)

The optical system according to claim 1, further comprising a diaphragm,
wherein the following inequality is satisfied:
0.05<f/X1<3.00
where X1 is a distance from the diaphragm to the image plane when focused on the object at infinity, and f is a focal length of the optical system.

### Claim 5 (depends on 1)

The optical system according to claim 1, wherein the following inequality is satisfied:
−10.00<SFn1<−0.05
where SFn is a shape factor of a negative lens having a strongest negative refractive power among negative lenses included in the second focus lens unit.

### Claim 6 (depends on 1)

The optical system according to claim 1, wherein the following inequality is satisfied:
0.05<Dp/f<2.00
where Dp is a distance on the optical axis from a surface closest to the image plane of the first lens unit to a surface closest to the object of the first focus lens unit when focused on the object at infinity, and f is a focal length of the optical system.

### Claim 7 (depends on 1)

The optical system according to claim 1, wherein the following inequality is satisfied:
0.20<βfn1<6.00
where βfn1 is a lateral magnification of the second focus lens unit when focused on the object at infinity.

### Claim 8 (depends on 1)

The optical system according to claim 1, wherein the following inequality is satisfied:
0.20<f/y<10.00
where y is a radius of an image circle, and f is a focal length of the optical system.

### Claim 9 (depends on 1)

The optical system according to claim 1, wherein the following inequality is satisfied:
0.01<Dfp/f<0.50
where Dfp is a distance on the optical axis from a surface closest to the image plane of the first focus lens unit to the surface closest to the object of the second focus lens unit when focused on the object at infinity, and f is a focal length of the optical system.

### Claim 10 (depends on 1)

The optical system according to claim 1, wherein the following inequality is satisfied:
0.20<|fa/f|<1000
where fa is a combined focal length of optical elements between a surface closest to the object of the first focus lens unit and the surface closest to the image plane of the second focus lens unit when focused the object at infinity, and f is a focal length of the optical system.

### Claim 11 (depends on 1)

The optical system according to claim 1, wherein the following inequality is satisfied:
0.20<di/f<10.00
where di is a distance on the optical axis from a surface closest to the image plane of the first lens unit to the image plane when focused on the object at infinity, and f is a focal length of the optical system.

### Claim 12 (depends on 1)

The optical system according to claim 1, wherein the optical system includes, in order from an object side to the image side, the first lens unit, the first focus lens unit serving as a second lens unit, and the second focus lens unit serving as a third lens unit.

### Claim 13 (depends on 1)

The optical system according to claim 1, wherein the optical system includes, in order from an object side to the image side, the first lens unit, the first focus lens unit serving as a second lens unit, the second focus lens unit serving as a third lens unit, and a fourth lens unit having a positive or negative refractive power, the fourth lens unit being fixed during focusing.

### Claim 14 (depends on 1)

The optical system according to claim 1, wherein the optical system includes, in order from an object side to the image side, the first lens unit, the first focus lens unit serving as a second lens unit, a third lens unit having a positive refractive power, the second focus lens unit serving as a fourth lens unit, and a fifth lens unit having a negative refractive power, the third lens and the fifth lens unit being fixed during focusing.

### Claim 15 (depends on 1)

The optical system according to claim 1, wherein the second focus lens unit includes a positive lens disposed closest to the object in the second focus lens unit, and a negative lens adjacently disposed on the image side of the positive lens.

### Claim 16 (depends on 1)

The optical system according to claim 1, wherein the first focus lens unit includes a negative lens disposed closest to the object in the first focus lens unit and having a concave lens surface on an object side.

### Claim 17 (depends on 1)

The optical system according to claim 1, wherein lenses arranged adjacent to the aperture stop on an object side and the image side of the aperture stop are positive lenses.

### Claim 18 (depends on 1)

The optical system according to claim 1, wherein the first lens unit has a positive lens, a positive lens, and a negative lens which are arranged in order from the aperture stop to the image side.

### Claim 19 (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 20 (depends on 1)

The optical system according to claim 1, wherein the first lens unit includes a negative lens disposed on the image side of the aperture stop and having a concave surface on the image side.

### Claim 21 (depends on 1)

The optical system according to claim 1, wherein the following inequality is satisfied:
−2.027≤fnr/f<−0.790
where fnr is a combined focal length from the surface closest to the object of the second focus lens unit to the image plane when focused on the object at infinity and f is a focal length of the optical system.

### Claim 22 (depends on 1)

The optical system according to claim 1, wherein the following inequality is satisfied: −5.000<fp2/fn1<−0.820.

### Claim 23 (depends on 1)

The optical system according to claim 1, wherein the following inequality is satisfied: −2.720<fp2/fn1<−0.820.

### Claim 24 (depends on 1)

The optical system according to claim 1,
wherein the first lens unit includes a cemented lens constituted of a negative lens and a positive lens adjacently disposed on an image side of the negative lens, and
wherein the cemented lens is adjacently disposed on an object side of the aperture stop.

### Claim 25 (depends on 1)

The optical system according to claim 1, wherein the first lens unit includes three biconcave lenses.

### Claim 26

An image pickup apparatus comprising:
an optical system comprising a first lens unit having a positive refractive power disposed closest to an object, a first focus lens unit having a positive refractive power disposed on an image side of the first lens unit, and a second focus lens unit having a negative refractive power disposed on the image side of the first focus lens unit, the first lens unit being fixed for focusing, and the first focus lens unit and the second focus lens unit being movable during focusing so that a distance between the first focus lens unit and the second focus lens unit changes; and
an image sensor configured to receive light of an image formed by the optical system,
wherein the first lens unit includes a single negative lens disposed closest to the object,
wherein the first lens unit includes an aperture stop and a plurality of positive lenses which are disposed on the image side of the aperture stop, and
wherein the following inequalities are satisfied:
−5.0<fp2/fn1<−0.1
−0.290<n1gt/fn1<−0.095
where fp2 is a focal length of the first focus lens unit, fn1 is a focal length of the second focus lens unit, and n1gt is a distance on an optical axis from a surface closest to the object of the second focus lens unit to a surface closest to an image plane of the second focus lens unit.