# US 8,542,444 B2 · Image pickup optical system for capsule endoscope

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- Number: US 8,542,444 B2
- Document ID: US8542444B2
- Status: Granted
- Kind: B2
- Application number: 13/257,518
- Filed: 2010-03-24
- Published: 2012-01-19
- Granted: 2013-09-24
- Earliest claimed: 2009-03-24
- Assignees: FUJIFILM Corporation
- Applicants: Tomoyuki Baba; Hitoshi Miyano
- Inventors: Tomoyuki Baba; Hitoshi Miyano
- Web page: https://patentgrep.com/patent/US8542444B2

## CPC

- A61B 1/0625: {for multiple fixed illumination angles}
- G02B 3/00: Simple or compound lenses
- A61B 1/00096: {Optical elements}
- A61B 1/00188: {with focusing or zooming features}
- A61B 1/041: {Capsule endoscopes for imaging}
- A61B 1/0607: {for annular illumination}
- G02B 13/06: Panoramic objectives; So-called "sky lenses" {including panoramic objectives having reflecting surfaces}
- G02B 23/243: {Objectives for endoscopes}
- A61B 1/05: characterised by the image sensor, e.g. camera, being in the distal end portion
- A61B 1/0676: {at distal tip of an endoscope}
- A61B 1/0684: {using light emitting diodes [LED]}
- A61M 2039/0279: {for introducing medical instruments into the body, e.g. endoscope, surgical tools}
- A61B: DIAGNOSIS; SURGERY; IDENTIFICATION (usefulness limited to only animals A61D)
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- A61M: DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY (introducing media into or onto the bodies of animals A61D7/00; means for inserting tampons A61F13/26; devices for administering food or medicines orally A61J; containers for collecting, storing or administering blood or medical fluids A61J1/05); DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY (surgery A61B; chemical aspects of surgical articles A61L); DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR {(Electrotherapy, e.g. producing anaesthesia by the use of alternating or intermittent currents A61N1/36021)}

## Abstract

A capsule endoscope includes an image pickup optical system for imaging an object. The image pickup optical system satisfies a condition expressed by −5≦ΔZr/ΔZp≦5. Assuming ωmax is a maximum half angle of view, ΔZr is a difference between a position of a real image surface with respect to light flux of 2ωmax and that with respect to light flux of ωmax, and ΔZp is a difference between a paraxial image forming position of a first virtual object plane surface and that of a second virtual object plane surface. The first virtual object plane surface passes through an intersection point P1 of the object and principal rays of 2ωmax. The second virtual object plane surface passes through an intersection point of the object and principal rays of ωmax. The first and second virtual object planes are vertical to the optical axis.

## Claims

### Claim 1

An image pickup optical system for use in a capsule endoscope, which is accommodated in a capsule to be swallowed into a body and used to capture an image inside a body cavity through a dome-shaped powerless transparent cover constituting part of said capsule, said image pickup optical system satisfying a condition expressed by:
−5.0≦ΔZr/ΔZp≦5.0
when said image pickup optical system is disposed in front of an object in the shape of concave curved surface and image capturing is performed,
wherein said ΔZr denotes a difference between a position of a real image surface with respect to light flux of a maximum angle of view 2ωmax and a position of said real image surface with respect to light flux of a half angle of view ωmax, and A ΔZp denotes a difference between a paraxial image forming position of a virtual object plane surface passing through an intersection point of said object and principal rays of 2ωmax and being vertical to an optical axis and a paraxial image forming position of a virtual object plane surface passing through an intersection point of said object and principal rays of ωmax and being vertical to said optical axis.

### Claim 2 (depends on 1)

The image pickup optical system for use in a capsule endoscope described in claim 1, wherein said maximum angle of view 2ωmax is at least 135°.

### Claim 3 (depends on 1)

The image pickup optical system for use in a capsule endoscope described in claim 1, wherein said maximum angle of view 2ωmax is at least 120° and a condition expressed by −0.5≦ΔZr/ΔZp≦0.5 is satisfied.

### Claim 4 (depends on 2)

The image pickup optical system for use in a capsule endoscope described in claim 2, wherein a condition expressed by:
0.7<(Y(ω+Δω)−Y(ω))/Y(Δω)
is satisfied, wherein Y(Δω) denotes an image height at an arbitrary angle of view ω, and Δω denotes an amount of slight change in said arbitrary angle of view ω.

### Claim 5 (depends on 1)

The image pickup optical system for use in a capsule endoscope described in claim 1, wherein a negative lens which is convex toward said object is disposed at a position nearest to said object, a positive lens is disposed at a position nearest to an image surface, and at least a surface of said negative lens at a side nearer to said image surface and one of surfaces of said positive lens are aspherical.

### Claim 6 (depends on 5)

The image pickup optical system for use in a capsule endoscope described in claim 5, wherein a positive lens group constituted by a plurality of lenses and having a positive power as a whole is disposed at a side nearer to said image surface than said negative lens, and a lens located at a position nearest to said object and a lens located at a position nearest to said image surface among said positive lens group are positive lenses.