Facsimile and static presentation processing – Facsimile – Picture signal generator
Reexamination Certificate
1998-09-14
2002-02-12
Lee, Cheukfan (Department: 2722)
Facsimile and static presentation processing
Facsimile
Picture signal generator
C358S475000
Reexamination Certificate
active
06346997
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an illumination device, an image reading apparatus having the illumination device and an information processing system having the image reading apparatus, and more particularly to an information processing system such as copying apparatus, facsimile apparatus, scanner and electronic blackboard, an image reading apparatus used therein and an illumination device suitably used-in the reading apparatus.
2. Related Background Art
In a prior art the reading apparatus of an information processing system such as a facsimile machine or an electronic copying machine, a discharge lamp such as a fluorescent lamp or an LED array having a number of LED chips in an array has been used as an illumination device. Recently, as the facsimile machine is used even in a home, a compact and low cost product is required and many products use the LED arrays.
In order to improve an output image quality, a function capable of outputting a multitone image which images a color document read information without drop while using monotone image has been replacing a conventional binary image system, and an improvement of color discrimination ability for color image read information in an image reading apparatuses required to cope with the future colorization.
A light source of an image reading apparatus to improve the color discrimination ability of the color document uses a plurality of LED's having a predetermined wavelength range and it is desired to emit a linear light beam from each of the LED light sources. An example of the image reading apparatus having the illumination device which uses such LED light sources is shown in
FIGS. 1A
to
1
C.
FIG. 1A
shows a sectional view of a photoelectric conversion element array of the image reading apparatus as viewed along a main scan direction, and
FIG. 1B
shows a side elevational view of the image reading apparatus as viewed along arrow A shown in FIG.
1
A.
In
FIGS. 1A
to
1
C, numeral
10
denotes a light transmissive sensor substrate on which a plurality of photoelectric conversion elements formed by using a thin film semiconductor layer such as amorphous silicon or polycrystalline silicon are arranged in one dimension. A protective layer, not shown, is provided on the light transmissive sensor substrate
10
to protect the photoelectric conversion elements, not shown, from damage due of relative movement to an original.
The light transmissive sensor substrate
10
is packaged on a light transmissive packaging substrate
15
by bonding and is electrically connected with a drive circuit, not shown, which is also packaged, by wire bonding.
Numeral
30
denotes an illumination means (light source) which comprises LED light sources
41
R and
41
G. Numeral
3
denotes a light transmissive member such as a silica rod having a circular cross-section, numeral
4
denotes an incident plane through which a light beam emitted from the illumination means
30
is applied to the light transmissive member
3
, and numeral
5
denotes a scatter and reflection area for scattering and reflecting the light beam propagated-through the light transmissive member
3
to take out of the light transmissive member
3
. The scatter and reflection area
5
is formed by roughening a portion of the surface of the light transmissive member
3
or applying light diffusion reflective paint. Numeral
6
denotes a reflection plane formed at an end plane opposite to the illumination means
30
of the light transmissive member
3
. The reflection plane may be formed by vapor depositing a metal such as aluminum on the surface of the end of the light transmissive member
3
, or applying a light diffusion reflective paint, or it may be a separate member. A sectional shape of the light transmissive member
3
is commonly square or rectangular.
A read position of an original
100
, an arrangement position of an illumination window of the light transmissive sensor substrate
10
and an optical axis along the array of the scatter and reflection area
5
of the light transmissive member
3
are set such that they are in a vertical plane passing through a read position of the document sheet
100
.
A light beam L emitted from the LED light sources
41
G and
41
R of the respective light emission wavelengths of the illumination means
30
and directed into the light transmissive member
3
from the incident plane
4
of the light transmissive member
3
repeats the reflection at an inner surface of the light transmissive member
3
and propagates therein, and reaches the opposite plane to the incident plane
4
, where it is again reflected and propagates in the light transmissive member
3
. While it repeats the reflection, it reaches the scatter and reflection area
5
where it is diffused and a portion I
1
thereof is emitted from an exit plane located to oppose the area
5
and it passes through the light transmissive packaging substrate
15
and the illumination window in the light transmissive sensor substrate
10
and irradiates the document sheet
100
. Another portion I
2
of the diffused light beam is directed to the exit plane obliquely so that it is totally reflected and propagates in the light transmissive member. It repeats the propagation and finally reaches the incident plane
4
where it is emitted.
The light beam which irradiates the document sheet
100
is reflected by the original
100
and directed to the photoelectric conversion elements on the light transmissive sensor substrate
10
where it is photo-electrically converted to produce an image read signal which is outputted to an external device.
FIG. 1C
shows distributions G and R of document plane illumination in a main scan direction of the photo-electric conversion element array of the light sources
41
G and
41
R having the respective light emitting wavelength ranges when the image reading apparatus shown in
FIGS. 1A and 1B
is used.
In the foregoing example, as described above, the LED light sources
41
G and
41
R having a plurality of light emission wavelength ranges are used as the illumination means
30
.
There are various sorts of LED light sources and they cannot be generally discussed, but an LED chip of a surface packaging type which attains further compaction and is convenient for packaging has been developed recently.
FIG. 2
shows a surface packaging type LED light source. In
FIG. 2
, numeral
81
denotes an LED chip, numeral
82
denotes a substrate, numeral
83
denotes a reflection frame, numeral
84
denotes a light transmissive resin, and numerals
85
and
86
denote electrodes formed on a surface of the substrate
82
. The size of the LED light source is less than 2 to 3 mm in length and less than 2 mm in height. Since the electrodes
85
and
86
are taken out via a side of the substrate
82
, it can be packaged by merely placing creamy solder on the printed packaging substrate and heating (reflowing) it by a reflow oven. Thus, efficient packaging is attained. Accordingly, it is desirable to use such LED light source as a linear light source.
Since such an LED light source has a light emission directivity as shown in
FIG. 2
, when a document sheet is to be illuminated by conducting, reflecting and diffusing the light by the light transmissive member
3
as shown in
FIGS. 1A and 1B
, the illumination distribution is not uniform, that is, the illumination is high in the area closer to the light source
30
and low in other areas. Thus, it poses a problem in the uniformity of the illumination distribution.
This is due to the fact that the light beam obliquely emitted from the LED light source
30
is directly applied to the area
5
of the light transmissive member
3
, scattered there and taken out of the light transmissive member
3
.
Another problem arises in that the illumination to the document sheet of different light emission wavelength ranges has different factors depending on the longitudinal position of the document sheet. This is due to the difference in the ratios of incident light beams, that is
Kaifu Noriyuki
Kobayashi Isao
Mizutani Hidemasa
Takeda Shinichi
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Lee Cheukfan
LandOfFree
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