# US 2018/0024320 A1 · Imaging lens and imaging apparatus

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- Number: US 2018/0024320 A1
- Document ID: US20180024320A1
- Status: Published application
- Kind: A1
- Application number: 15/622,894
- Filed: 2017-06-14
- Published: 2018-01-25
- Earliest claimed: 2016-07-20
- Assignees: FUJIFILM Corporation
- Applicants: FUJIFILM Corporation
- Inventors: Taro ASAMI; Takeshi KAMIYA
- Web page: https://patentgrep.com/patent/US20180024320A1

## CPC

- G02B 13/004: {having four lenses}
- G02B 9/34: having four components only
- G02B 13/14: for use with infrared or ultraviolet radiation ({G02B13/008, } G02B13/16 take precedence)
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS

## Abstract

Disclosed are an imaging lens having satisfactory performance in a region of near infrared light, and an imaging apparatus including the imaging lens. The imaging lens includes, in order from an object side, as lenses having refractive power, only four lenses including a positive first lens L1, a negative second lens L2, a positive third lens L3, and a positive fourth lens L4. A conditional expression relating to a focal length fs1 of the first lens L1 with respect to s-line and a focal length fs of the entire system with respect to s-line: 0.5<fs1/fs<2.5 is satisfied.

## Claims

### Claim 1

An imaging lens comprising, in order from an object side, as lenses having refractive power:
only four lenses including a first lens having positive refractive power, a second lens having negative refractive power, a third lens having positive refractive power, and a fourth lens having positive refractive power,
wherein the following conditional expression (1) is satisfied;
0.5<fs1/fs<2.5 (1)
where
fs1: a focal length of the first lens with respect to s-line
fs: a focal length of an entire system with respect to s-line.

### Claim 2 (depends on 1)

The imaging lens according to claim 1,
wherein the following conditional expression (1-1) is satisfied.
0.7<fs1/fs<2.3 (1-1)

### Claim 3 (depends on 1)

The imaging lens according to claim 1,
wherein the following conditional expression (2) is satisfied;
1.7<Ns1 (2)
where
Ns1: a refractive index of the first lens with respect to s-line.

### Claim 4 (depends on 2)

The imaging lens according to claim 2,
wherein the following conditional expression (2) is satisfied;
1.7<Ns1 (2)
where
Ns1: a refractive index of the first lens with respect to s-line.

### Claim 5 (depends on 3)

The imaging lens according to claim 3,
wherein the following conditional expression (2-1) is satisfied.
1.75<Ns1 (2-1)

### Claim 6 (depends on 4)

The imaging lens according to claim 4,
wherein the following conditional expression (2-1) is satisfied.
1.75<Ns1 (2-1)

### Claim 7 (depends on 1)

The imaging lens according to claim 1,
wherein the following conditional expression (3) is satisfied;
−2.0<fs2/fs<−0.2 (3)
where
fs2: a focal length of the second lens with respect to s-line.

### Claim 8 (depends on 2)

The imaging lens according to claim 2,
wherein the following conditional expression (3) is satisfied;
−2.0<fs2/fs<−0.2 (3)
where
fs2: a focal length of the second lens with respect to s-line.

### Claim 9 (depends on 3)

The imaging lens according to claim 3,
wherein the following conditional expression (3) is satisfied;
−2.0<fs2/fs<−0.2 (3)
where
fs2: a focal length of the second lens with respect to s-line.

### Claim 10 (depends on 4)

The imaging lens according to claim 4,
wherein the following conditional expression (3) is satisfied;
−2.0<fs2/fs<−0.2 (3)
where
fs2: a focal length of the second lens with respect to s-line.

### Claim 11 (depends on 5)

The imaging lens according to claim 5,
wherein the following conditional expression (3) is satisfied;
−2.0<fs2/fs<−0.2 (3)
where
fs2: a focal length of the second lens with respect to s-line.

### Claim 12 (depends on 6)

The imaging lens according to claim 6,
wherein the following conditional expression (3) is satisfied;
−2.0<fs2/fs<−0.2 (3)
where
fs2: a focal length of the second lens with respect to s-line.

### Claim 13 (depends on 1)

The imaging lens according to claim 1,
wherein the following conditional expression (4) is satisfied;
1.6<Ns2 (4)
where
Ns2: a refractive index of the second lens with respect to s-line.

### Claim 14 (depends on 2)

The imaging lens according to claim 2,
wherein the following conditional expression (4) is satisfied;
1.6<Ns2 (4)
where
Ns2: a refractive index of the second lens with respect to s-line.

### Claim 15 (depends on 3)

The imaging lens according to claim 3,
wherein the following conditional expression (4) is satisfied;
1.6<Ns2 (4)
where
Ns2: a refractive index of the second lens with respect to s-line.

### Claim 16 (depends on 4)

The imaging lens according to claim 4,
wherein the following conditional expression (4) is satisfied;
1.6<Ns2 (4)
where
Ns2: a refractive index of the second lens with respect to s-line.

### Claim 17 (depends on 5)

The imaging lens according to claim 5,
wherein the following conditional expression (4) is satisfied;
1.6<Ns2 (4)
where
Ns2: a refractive index of the second lens with respect to s-line.

### Claim 18 (depends on 6)

The imaging lens according to claim 6,
wherein the following conditional expression (4) is satisfied;
1.6<Ns2 (4)
where
Ns2: a refractive index of the second lens with respect to s-line.

### Claim 19 (depends on 1)

The imaging lens according to claim 1, further comprising:
a wavelength selection member which selectively transmits light in a near-infrared wavelength range on an image side of the fourth lens.

### Claim 20 (depends on 1)

An imaging apparatus comprising:
the imaging lens according to claim 1.