Image reading apparatus

Facsimile and static presentation processing – Natural color facsimile – Scanning

Reexamination Certificate

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Details

C358S505000, C358S475000, C358S513000

Reexamination Certificate

active

06320681

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to an image reading apparatus for reading an original image in an image scanner, a facsimile apparatus, or the like. More particularly, the invention is suitable for use in an image reading apparatus with a construction such that an original is irradiated by an irradiation light of an LED (light emitting diode) and an image of the original is photographed by a CCD (charge coupled device) one-dimensional image sensor.
2. Related Background Art
As a conventional color image reading apparatus, there is known a color image sensor of a light source switching type such that LEDs having light emitting characteristics of three colors of R, G, and B are used and signals are extracted from image sensors each time the same position of an original is irradiated by lights of R, G, and B, thereby obtaining a color signal corresponding to the original.
FIGS. 17
to
19
show an example of such a color image sensor of the light source switching type. The color image sensor is constructed by: a light source
53
for allowing LED lights of three colors of R, G, and B to enter from an edge surface of an optical guide member and irradiating the uniform light from a side surface to an original; an image pickup device array
29
of a short focal point; and a sensor array
1
in which a plurality of line sensors are arranged in a line.
A main portion of the color image sensor as mentioned above has a construction such that a transparent glass plate
61
which is in contact with the original surface is attached to an upper surface of a frame
60
, an emission light
12
of the optical guide light source
53
provided in the frame
60
is reflected by the original surface which is in contact with an upper surface of the transparent glass plate
61
, and a reflection light
13
enters the sensor array
1
provided on a board
19
through the optical system
29
in correspondence to the optical system
29
. As an optical system, a short focal point image pickup device array represented by, for example, a trade name “SELFOC lens array” (made by Nippon Sheet Glass Co., Ltd.) is used.
As shown in
FIG. 19
, the sensor array
1
serving as photoelectric converting means is a multichip type line sensor in which a plurality of line sensors
2
-
1
,
2
-
2
, . . . , and
2
-
15
are arranged in a line on the board
19
. The whole sensor array
1
is covered by a protecting film
26
. Like a SELFOC lens array as mentioned above, when the reflection light from the original is formed as an image onto the sensor array
1
at an equal magnification and the image is read out, a length of sensor array
1
corresponding to only a width of original to be read is needed. Therefore, the length of sensor array
1
which is necessary changes in dependence on a size of original to be read. The number of line sensors constructing the sensor array
1
also changes.
For example, in case of the sensor unit which can read an original of the A3 size, now assuming that a length of one line sensor is equal to 20 mm, it is sufficient to construct the sensor array of 15 line sensors. The board
19
on which such a sensor array
1
is installed is supported onto a bottom plate
65
which is in engagement with the frame
60
. The board
19
is connected to a flexible board
23
through a flexible wiring
28
. A connector
22
for inputting/outputting a power source, a control signal, and the like is provided on the flexible board
23
. The flexible board
23
is attached to the frame
60
.
FIG. 20
shows a shape in the longitudinal direction of the image sensor of the optical guide light source
53
and a positional relation between the optical guide and LED boards
42
and
43
. The LED boards
42
and
43
are attached to incident surfaces
54
at both edges.
FIGS. 21 and 22
show an arrangement of LED packages
71
to
74
,
77
and
78
on the LED boards
42
and
43
and an arrangement of LED chips
31
to
34
,
37
, and
38
in LED packages
71
to
74
,
77
, and
78
. One LED chip is enclosed in one LED package. One LED chip is included in each LED board every light emitting color of R, G, and B. There are the LED chips
31
and
32
each having a light emitting color of R, the LED chips
33
and
34
each having a light emitting color of G, and the LED chips
37
and
38
each having a light emitting color of B. On the LED boards
42
and
43
, the light on/off operations of the LED chips
31
to
34
,
37
, and
38
can be controlled at independent timings for every light emitting color of R, G, and B.
FIG. 23
shows a cross sectional view of the optical guide light source
53
and a positional relation between the light source
53
and the LED packages
71
to
74
,
77
, and
78
on the LED boards
42
and
43
. Rectangles shown by broken lines indicate positions of the LED packages
71
to
74
,
77
, and
78
on the LED boards
42
and
43
shown in
FIGS. 20 and 21
.
The apparatus is designed in a manner such that the lights emitted from the LED chips
31
to
34
,
37
, and
38
on the LED boards
42
and
43
don't directly enter a reflecting portion
56
provided in the lower portion of the optical guide light source
53
and an optical guide portion
55
is set to an angle such that the LED lights are totally reflected at both edges in the transversal direction of the optical guide portion
55
. Therefore, the internal reflection is repeated many times in the optical guide light source
53
and the light is transmitted in the longitudinal direction of the optical guide portion
55
with a very small loss of light amount. After completion of a few times of internal reflection, when the light enters the reflecting portion
56
, the light is diffused and reflected in the original direction and is further converged by a light converging portion
57
, thereby irradiating only a region near the reading surface of the original. In this instance, the light beam entering the reflecting portion
56
is an indirect light reflected in the optical guide light source
53
. An opening is adjusted in the longitudinal direction so that the irradiation light to the original becomes uniform. Therefore, a uniformity of the illuminance on the original surface is good.
When a color original is read by the image sensor with such a construction, first, data to correct a shading which is caused by a variation in sensitivity of the line sensor or a variation in irradiation light of the light source is fetched. When the data for correcting the shading is fetched, the LEDs
31
and
32
of R, the LEDs
33
and
34
of G, and the LEDs
37
and
38
of B are respectively sequentially driven so as to emit the light every kind and every color, a white reference provided in the original reading apparatus is read, and output signals of the image sensor in this instance are respectively temporarily stored into the memory. A correction is performed in a manner such that when the white reference is again read by signals for correcting the shading of R, G, and B obtained as mentioned above, the signals of R, G, and B are uniform on one line, and there is a relation of (r=g=b) among a sensor output signal r when the LEDs
31
and
32
of R emit the lights, a sensor output signal g when the LEDs
33
and
34
of G emit the lights, and a sensor output signal b when the LEDs
35
and
36
of B emit the lights.
When the original is actually read, in case of the color image sensor of the light source switching type, as mentioned above, in order to obtain the three signals of R, G, and B at one point on the original to be read, it is necessary to individually irradiate the lights of R, G, and B to the original. As a method for this purpose, the original can be read by what is called an area-sequential method such that the operation to sub-scan the image sensor for the whole original in a light-on state of the LED of one of the three colors of R, G, and B is repeated three times while changing the kind of LED to be lit on. Or, the original can be read by what is call

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