Illuminating device, image reading device, and image forming apparatus with multiple light sources
An illuminating device, an image reading device, and an image forming apparatus. The illuminating device includes a plurality of first light sources arrayed on a circuit board, the first light sources having a plurality of first light emitting surfaces through which light is emitted, and a second light source disposed on an upstream side of the first light sources in an irradiation direction of the light. In the illuminating device, the second light source has a second light emitting surface through which light is emitted, and the second light source has a directivity angle different from a directivity angle of each one of the first light sources. The image reading device includes the illuminating device, and an imaging device to receive the light reflected by a document to capture an image of the document.
1. An illuminating device comprising:
a plurality of first light sources of a side-view type arrayed on a circuit board having an implementation surface, the plurality of first light sources having a plurality of first light emitting surfaces configured to emit light, the plurality of first light emitting surfaces being vertically on the implementation surface of the circuit board-; and
a second light source of the side-view type on an upstream side of the plurality of first light sources in an irradiation direction of the light, the second light source having a second light emitting surface configured to emit, the second light emitting surface being vertically on the implementation surface of the circuit board,
wherein the second light source has a directivity angle different from a directivity angle of each one of the plurality of first light sources.
2. The illuminating device according to claim 1 ,
wherein the directivity angle of the second light source is narrower than the directivity angle of each one of the plurality of first light sources.
3. The illuminating device according to claim 1 , wherein
the second light source having the directivity angle smaller than the directivity angle of each one of the plurality of first light sources,
wherein a≤A is satisfied, wherein
a is a distance between an object and each one of the plurality of first light emitting surfaces of the plurality of first light sources, and
A is a distance between the object and the second light emitting surface of the second light source.
4. The illuminating device according to claim 1 , wherein the directivity angle is a half-value angle.
5. The illuminating device according to claim 1 , wherein
the second light source is between a pair of the plurality of first light sources in a longer-side direction of the circuit board, and
based on the illuminating device being viewed from a light-source mount surface of the circuit board in a vertical direction,
B≤X / tan θ is satisfied, wherein
B is a distance between the second light emitting surface of the second light source and neighboring one of the plurality of first light emitting surfaces of the plurality of first light sources in the longer-side direction,
θ is a half-value angle of the second light source, and
X is a distance between a center of light emission of the second light source and an edge of the neighboring one of the plurality of first light emitting surfaces of the plurality of first light sources on a side of the second light source.
6. The illuminating device according to claim 1 , wherein the directivity angle is a half-value angle in a longer-side direction of the circuit board.
7. The illuminating device according to claim 1 , wherein the plurality of first light emitting surfaces of the plurality of first light sources and the second light emitting surface of the second light source are vertical to a light-source mount surface of the circuit board.
8. The illuminating device according to claim 7 , wherein a half-value angle of the second light source in a vertical direction to the light-source mount surface of the circuit board is narrower than a half-value angle of each one of the plurality of first light sources in the vertical direction.
9. The illuminating device according to claim 7 , wherein the plurality of first light emitting surfaces of the plurality of first light sources are coplanar to an edge face of the circuit board.
10. The illuminating device according to claim 1 , wherein an array pitch of the plurality of first light sources on an edge side of the circuit board in a longer-side direction of the circuit board is narrower than an array pitch of the plurality of first light sources on a central side of the circuit board in the longer-side direction.
11. The illuminating device according to claim 1 , wherein
the plurality of first light sources are a plurality of infrared light sources based on the second light source being a white light source, and
the plurality of first light sources are a plurality of white light sources based on the second light source being an infrared light source.
12. The illuminating device according to claim 1 , wherein the plurality of first light emitting surfaces of the plurality of first light sources are disposed in a straight line.
13. An image reading device comprising:
the illuminating device according to claim 1 ; and
an imaging device configured to receive the light reflected by a document to capture an image of the document,
wherein the illuminating device is configured to irradiate the document with light.
14. An image forming apparatus comprising:
the image reading device according to claim 13 , the image reading device being configured to read an image on a document; and
an image forming device configured to form an image on a recording material based on data of the image read by the image reading device.