# US 9,521,287 B2 · Light guide, illuminating device for image reading, and image reading apparatus

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- Number: US 9,521,287 B2
- Document ID: US9521287B2
- Status: Granted
- Kind: B2
- Application number: 14/597,668
- Filed: 2015-01-15
- Published: 2015-07-16
- Granted: 2016-12-13
- Earliest claimed: 2014-01-15
- Assignees: Konica Minolta, Inc.
- Applicants: Konica Minolta, Inc.
- Inventors: Akira Yamamura; Masahiko Tanaka
- Web page: https://patentgrep.com/patent/US9521287B2

## CPC

- H04N 1/02835: {in combination with a light guide, e.g. optical fibre, glass plate (light-guides per se G02B6/00)}
- G02B 6/0006: {Coupling light into the fibre (in general G02B6/4298)}
- G02B 6/001: {the light being emitted along at least a portion of the lateral surface of the fibre}
- G02B 6/0038: {Linear indentations or grooves, e.g. arc-shaped grooves or meandering grooves, extending over the full length or width of the light guide}
- H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS

## Abstract

A light guide for use in an image reading apparatus. The light guide extends in a predetermined direction. The light guide comprises an emitting surface, through which light rays entering the light guide are emitted, and a reflecting surface configured to reflect the light rays to the emitting surface. A cross-sectional surface of the light guide, which is a sectional surface of the light guide along a plane orthogonal to the predetermined direction in which the light guide extends, has a shape including a combination of an ellipse and a parabola. The parabola on the cross-sectional surface of the light guide defines the reflecting surface. A focal point of the parabola is located on a first focal point of the ellipse that is closer to the reflecting surface.

## Claims

### Claim 1

An image reading apparatus comprising:
a light guide comprising:
an emitting surface, through which light rays entering the light guide are emitted;
a reflecting surface configured to reflect the light rays to the emitting surface;
a cross-sectional surface of the light guide, which is a sectional surface of the light guide along a plane orthogonal to a predetermined direction in which the light guide extends, the cross-sectional surface having a shape comprising a combination of an ellipse and a parabola that is convex outward with respect to the light guide;
wherein the parabola on the cross-sectional surface of the light guide defines the reflecting surface; and
a focal point of the parabola is located in the light guide, on a first focal point of the ellipse that is closer to the reflecting surface
wherein an image reading point is located on a line passing two focal points of the ellipse on the cross-sectional surface.

### Claim 2 (depends on 1)

The light guide according to claim 1, wherein the emitting surface of the light guide has a non-elliptic shape on the cross-sectional surface.

### Claim 3 (depends on 1)

The light guide according to claim 1, comprising a tapered end portion near an entrance surface through which the light rays enter the light guide.

### Claim 4 (depends on 3)

The light guide according to claim 3, wherein the tapered end portion is in such a shape that an angle of incidence of a light ray to the thin end portion is greater than a critical angle.

### Claim 5 (depends on 1)

An illuminating device for image reading, the illuminating device comprising:
the light guide according to claim 1, and
a light source provided at an end of the light guide,
wherein the light source is located such that the light source overlaps with the first focal point when viewed from the predetermined direction in which the light guide extends.

### Claim 6 (depends on 5)

An image reading apparatus comprising: the illuminating device according to claim 5.

### Claim 7 (depends on 1)

An illuminating device for image reading, the illuminating device comprising:
the light guide according to claim 1; and
a reflective mirror configured to reflect light rays emitted from the light guide to an image reading point.

### Claim 8 (depends on 1)

An image reading apparatus comprising:
the light guide according to claim 1,
wherein a document supporting surface is located at a position on which light rays emitted from the light guide through the emitting surface are focused.

### Claim 9

A light guide for use in an image reading apparatus, the light guide comprising:
an emitting surface, through which light rays entering the light guide are emitted;
a reflecting surface configured to reflect the light rays to the emitting surface;
a cross-sectional surface of the light guide, which is a sectional surface of the light guide along a plane orthogonal to a predetermined direction in which the light guide extends, the cross-sectional surface having a shape comprising a combination of an ellipse and a parabola that is convex outward with respect to the light guide; and
a tapered end portion near an entrance surface through which the light rays enter the light guide
wherein the parabola on the cross-sectional surface of the light guide defines the reflecting surface;
a focal point of the parabola is located in the light guide, on a first focal point of the ellipse that is closer to the reflecting surface; and
the tapered end portion is in such a shape that an angle of incidence of a light ray to the thin end portion is greater than a critical angle.

### Claim 10 (depends on 9)

An illuminating device for image reading, the illuminating device comprising:
the light guide according to claim 9, and
a light source provided at an end of the light guide,
wherein the light source is located such that the light source overlaps with the first focal point when viewed from the predetermined direction in which the light guide extends.

### Claim 11 (depends on 9)

An illuminating device for image reading, the illuminating device comprising:
the light guide according to claim 9; and
a reflective mirror configured to reflect light rays emitted from the light guide to an image reading point.

### Claim 12 (depends on 11)

An image reading apparatus comprising: the illuminating device according to claim 11.

### Claim 13 (depends on 9)

An image reading apparatus comprising:
the light guide according to claim 9,
wherein a document supporting surface is located at a position on which light rays emitted from the light guide through the emitting surface are focused.