# US 8,570,671 B2 · Single focus lens system and photographing apparatus including the same

> Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt

- Number: US 8,570,671 B2
- Document ID: US8570671B2
- Status: Granted
- Kind: B2
- Application number: 13/556,444
- Filed: 2012-07-24
- Published: 2013-03-07
- Granted: 2013-10-29
- Earliest claimed: 2011-09-02
- Assignees: Samsung Electronics Co., Ltd.
- Applicants: Tae-kun Lee
- Inventors: Tae-kun Lee
- Web page: https://patentgrep.com/patent/US8570671B2

## CPC

- G02B 13/04: Reversed telephoto objectives
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS

## Abstract

A single focus lens system and a photographing apparatus including the single focus lens system are disclosed. A single focus lens system is provided that includes a first lens group having a negative refractive power, a stop, and a second lens group having a positive refractive power, sequentially arranged in order from an object side, wherein the first lens group comprises first and second air lenses having a negative refractive power, a meniscus shape and a convex surface toward the object side, and the second lens group comprises a lens that has a positive refractive power, is disposed closest to the object side, and has a convex surface toward the object side.

## Claims

### Claim 1

A single focus lens system comprising a first lens group having a negative refractive power, a stop, and a second lens group having a positive refractive power, sequentially arranged in order from an object side,
wherein the first lens group comprises first and second air lenses having a negative refractive power, a meniscus shape and a convex surface toward the object side, and the second lens group comprises a lens that has a positive refractive power, is disposed closest to the object side, and has a convex surface toward the object side,
wherein the single focus lens system satisfies the following expressions,
−10<Fair1/F<−2.5
−6<Fair2/F<−1
0.6<Fp2/F<1.5,
where F denotes an overall focal length, Fair1 denotes a focal length of the first air lens of the first lens group, Fair2 denotes a focal length of the second air lens of the first lens group, and Fp2 denotes a focal length of the lens of the second lens group.

### Claim 2 (depends on 1)

The single focus lens system of claim 1, wherein the first lens group comprises at least one first lens having a negative refractive power,
wherein the at least one first lens satisfies the following expressions,
Ndn1<1.65
Vdn1>55,
where Ndn1 denotes a refractive index of the at least one first lens, and Vdn1 denotes an Abbe number of the at least one first lens.

### Claim 3 (depends on 2)

The single focus lens system of claim 2, wherein the first lens group comprises a second lens having a positive refractive power,
wherein the second lens satisfies the following expression,
Ndp1<1.75,
where Ndp1 denotes a refractive index of the second lens.

### Claim 4 (depends on 3)

The single focus lens system of claim 3, wherein the single focus lens system satisfies the following expression,
0.4<Fp1/F<2.0,
wherein F denotes an overall focal length of the single focus lens system, and Fp1 denotes a focal length of the second lens.

### Claim 5 (depends on 1)

The single focus lens system of claim 1, wherein the first and second air lenses of the first lens group comprise at least one aspherical surface and satisfy the following expression,
1.5<Haph*F/ID<4.0,
wherein Haph denotes a distance from a point where a ray passing through a center of an aperture among light fluxes, which are formed as an image at the highest image height of a diagonal line of an image plane, meets the aspherical surface to an optical axis, F denotes an overall focal length, and ID denotes a diagonal length of the image plane.

### Claim 6 (depends on 1)

The single focus lens system of claim 1, wherein the first lens group satisfies the following expressions,
−0.5<(R1air1−R2air1)/(R1air1+R2air1)<−0.1
−1.0<(R1air2−R2air2)/(R1air2+R2air2)<−0.3,
where R1air1 denotes a curvature radius of the first air lens at the object side, R2air1 denotes a curvature radius of the first air lens at an image side, R1air2 denotes a curvature radius of the second air lens at the object side, and R2air2 denotes a curvature radius of the second air lens at the image side.

### Claim 7 (depends on 1)

The single focus lens system of claim 1, wherein the single focus lens system satisfies the following expressions,
−8.0<F1/F<−1.0
0.8<F2/F<1.4,
wherein F denotes an overall focal length of the single focus lens system, F1 denotes a focal length of the first lens group, and F2 denotes a focal length of the second lens group.

### Claim 8 (depends on 1)

The single focus lens system of claim 1, wherein the second lens group further comprises a third lens having a negative refractive power and a fourth lens having a positive refractive power, arranged in order from the lens that is closest to the object side toward an image side.

### Claim 9 (depends on 8)

The single focus lens system of claim 8, wherein the fourth lens has a convex, aspherical surface toward the image side.

### Claim 10 (depends on 1)

The single focus lens system of claim 1, wherein the lens of the second lens group that is closest to the object side has an aspherical surface.

### Claim 11 (depends on 1)

The single focus lens system of claim 1, wherein the second lens group comprises a positive-negative doublet lens or a negative-positive doublet lens disposed closest to an image side.

### Claim 12 (depends on 1)

The single focus lens system of claim 1, wherein the first lens group and the second lens group move in parallel along an optical axis to perform focusing.

### Claim 13 (depends on 1)

The single focus lens system of claim 1, wherein the first lens group and the second lens group move in parallel with respect to an optical axis with different loci to perform focusing.

### Claim 14 (depends on 1)

The single focus lens system of claim 1, wherein the lens of the second lens group closest to the object side performs focusing.

### Claim 15 (depends on 1)

The single focus lens system of claim 1, wherein a half-viewing angle of the single focus lens system is in a range from 40 to 45 degrees.

### Claim 16 (depends on 1)

The single focus lens system of claim 1, wherein an F-number of the single focus lens system is in a range from 2 to 2.8.

### Claim 17

A photographing apparatus comprising:
a single focus lens system; and
an imaging device receiving an image formed by the single focus lens system,
wherein the single focus lens system comprises a first lens group having a negative refractive power, a stop, and a second lens group having a positive refractive power, sequentially arranged in order from an object side,
wherein the first lens group comprises first and second air lenses having a negative refractive power, a meniscus shape and a convex surface toward the object side, and the second lens group comprises a lens that has a positive refractive power, is disposed closest to the object side, and has a convex surface toward the object side,
wherein the single focus lens system satisfies the following expression,
−10<Fair1/F<−2.5
−6<Fair2/F<−1
0.6<Fp2/F<1.5,
where F denotes an overall focal length, Fair1 denotes a focal length of the first air lens of the first lens group, Fair2 denotes a focal length of the second air lens of the first lens group, and Fp2 denotes a focal length of the lens of the second lens group.

### Claim 18 (depends on 17)

The photographing apparatus of claim 17, wherein the first lens group comprises at least one first lens having a negative refractive power,
wherein the at least one first lens satisfies the following expressions,
Ndn1<1.65
Vdn1>55,
where Ndn1 denotes a refractive index of the at least one first lens, and Vdn1 denotes an Abbe number of the at least one first lens.

### Claim 19 (depends on 18)

The photographing apparatus of claim 18, wherein the first lens group comprises a second lens having a positive refractive power,
wherein the second lens satisfies the following expression,
Ndp1<1.75,
where Ndp1 denotes a refractive index of the second lens.

### Claim 20 (depends on 19)

The photographing apparatus of claim 19, wherein the single focus lens system satisfies the following expression,
0.4<Fp1/F<2.0,
wherein F denotes an overall focal length of the single focus lens system, and Fp1 denotes a focal length of the second lens.

### Claim 21 (depends on 17)

The photographing apparatus of claim 17, wherein the first and second air lenses of the first lens group comprise at least one aspherical surface and satisfy the following expression,
1.5<Haph*F/ID<4.0,
wherein Haph denotes a distance from a point where a ray passing through a center of an aperture among light fluxes, which are formed as an image at the highest image height of a diagonal line of an image plane, meets the aspherical surface to an optical axis, F denotes an overall focal length, and ID denotes a diagonal length of the image plane.