Facsimile and static presentation processing – Facsimile – Picture signal generator
Reexamination Certificate
2000-02-22
2004-04-20
Lee, Cheukfan (Department: 2622)
Facsimile and static presentation processing
Facsimile
Picture signal generator
C358S475000, C358S482000, C250S208100
Reexamination Certificate
active
06724503
ABSTRACT:
TECHNICAL FIELD
The present invention relates to an image sensor board as a component for various kinds of image sensors such as a flat-bed type image sensor. Further, the present invention relates to an image sensor incorporating such an image sensor board.
BACKGROUND ART
A typical prior art contact-type image sensor has a structure shown in FIG.
14
. The illustrated image sensor comprises a light source
2
e
, a casing
4
e
for accommodating the light source
2
e
, an image sensor board
6
e
mounted at the bottom of the casing
4
e
, a document supporting panel
70
e
mounted in an upper portion of the casing
4
e
, a focus lens unit
51
e
disposed between the document supporting panel
70
e
and the image sensor board
6
e
and a platen
90
e
for transmitting a document K held in contact with the document supporting panel
70
e
. The image sensor board
6
e
is provided with a plurality of light receiving elements
52
e
disposed in an array extending in the primary scanning direction. The document supporting panel
70
e
is made of a transparent glass material and is held in contact with the platen
90
e
at a portion, which serves as an image-reading line P.
In reading an image of the document, the light source
2
e
emits light toward the image-reading line P while the platen
90
e
transmits the document K in the secondary scanning direction. The light reflected by the document K is focused on the array of light receiving elements
52
e
by the focus lens unit
51
e
. As a result, each of the light receiving elements
52
e
generates an image signal corresponding to the received amount of light. The image sensor board
6
e
may be, for example, a white plate made of a ceramic material. The image sensor board is disposed so as to close a bottom opening of the casing
4
e
so that disturbing external light is prevented from entering the inner space
46
e
located below the focus lens
51
e.
However, with such a conventional image sensor, depending on the conditions of the use, noises are included in reading out the image of the document, which leads to degradation of the quality of the obtained image. The inventors have experimentally found the following to be one cause.
The image sensor board
6
e
, though having a white surface, does not reflect all the received light, but allows a certain amount of light to pass through the image sensor board. Accordingly, if another light source exists outside the casing
4
e
, a certain amount of light (including visible rays as well as ultraviolet rays and infrared rays) emitted from such an outer light source passes through the image sensor board
6
e
to enter the inner space
46
e
of the casing
4
e
.
On the other hand, the light receiving element
52
e
, which may be a phototransistor capable of photoelectric conversion, generates a signal upon receiving visible rays as well as ultraviolet rays and infrared rays. Thus, in the prior art, the light entering the inner space
46
through the image sensor board
6
e
is unfavorably detected by the light receiving element
52
e
, which generates an improper signal, thereby causing noises.
This problem occurs even when the image sensor board
6
e
is made of a synthetic resin such as glass-fiber-reinforced epoxy resin instead of a ceramic material.
DISCLOSURE OF THE INVENTION
It is, therefore, an object of the present invention to prevent disturbing external light from passing through an image sensor board to be received by light receiving elements, thereby enhancing the image reading quality provided by an image sensor.
In accordance with a first aspect of the present invention, there is provided an image sensor board comprising a substrate having an obverse surface provided with a plurality of light receiving elements for generating image signals upon receiving light, and a light shielding layer for covering a reverse surface of the substrate at least entirely over a portion of the obverse surface where the plurality of light receiving elements are mounted.
According to a preferred embodiment of the present invention, the light shielding layer may be black. Specifically, it is advantageous that the shielding layer comprises a black glass material containing a first Fe—Cr—Co based black pigment and a second Cu—Cr based black pigment in a total amount of 13-25 wt %.
The light shielding layer may cover the entire reverse surface of the substrate. Moreover, the light shielding layer may further extend beyond the substrate.
According to another preferred embodiment of the present invention, the light shielding layer may comprise a light-shielding tape bonded to the reverse surface of the substrate.
According to still another preferred embodiment of the present invention, the light shielding layer may be formed by applying, to the reverse surface of the substrate, a coating material containing a black pigment.
In accordance with a second aspect of the present invention, there is provided an image sensor comprising: a casing; a light source disposed in the casing for emitting light toward an object to be read; an image sensor board having on an obverse surface provided with a plurality of light receiving elements for generating image signals upon receiving light reflected by the object, the image sensor board being disposed so that the obverse surface thereof directed inwardly of the casing; wherein the substrate is covered with a light shielding layer for covering a reverse surface of the substrate at least entirely over a portion of the obverse surface where the plurality of light receiving elements are mounted.
REFERENCES:
patent: 5569390 (1996-10-01), Endo
patent: 6169317 (2001-01-01), Sawada et al.
patent: 6343162 (2002-01-01), Saito et al.
patent: 63-165976 (1988-11-01), None
patent: 63-288560 (1988-11-01), None
patent: 64-5062 (1989-01-01), None
patent: 64-65522 (1989-03-01), None
patent: 4-061546 (1992-02-01), None
patent: 5-335539 (1993-12-01), None
Hayashi Hiroaki
Sako Teruhisa
Yokoyama Eiji
Lee Cheukfan
Merchant & Gould P.C.
Rohm & Co., Ltd.
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