Radiant energy – Photocells; circuits and apparatus – Optical or pre-photocell system
Reexamination Certificate
2000-11-21
2002-07-09
Allen, Stephone B. (Department: 2878)
Radiant energy
Photocells; circuits and apparatus
Optical or pre-photocell system
C358S296000
Reexamination Certificate
active
06417508
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image reading apparatus suitably used as an image sensor in a scanner, a copying machine, or the like.
2. Related Background Art
FIGS. 26
to
28
show an image sensor according to a related art. As shown in
FIGS. 26
to
28
, this sensor is constituted by a sensor unit
1
, a sensor board
2
on which the sensor unit
1
is mounted, a lens array
3
, an illumination device
4
, a transparent glass plate
5
, and a frame
6
for positioning/holding these components. The illumination device
4
includes lead frame type LEDs
7
and a light guide
8
. An output from the sensor unit
1
is supplied to an external system through a connector
13
mounted on the sensor board
2
. Note that halogen or xenon lamps or the like may be used as light sources in place of the LEDs.
The LEDs
7
are electrically connected to the external system through connector cables
16
constituted by lead portions
11
and LED connectors
12
. As shown in
FIG. 27
, since the two LEDs
7
are arranged on both sides of the light guide
8
, two connector cables
16
are required. In addition, since the LEDs
7
emit light onto the two ends of the light guide
8
, the overall image sensor tends to increase in size in the longitudinal direction.
As shown in
FIG. 28
, light L emitted from the LED
7
is incident on an incident surface
8
a
of the light guide
8
. The light having reached a diffusion portion
8
d
emerges from the light guide
8
through an exit surface
8
c
(FIG.
26
). The light that is incident at an incident angle &thgr; of 49° or less (when the light guide is made of an acrylic resin and has a refractive index n=1.5) satisfies the total reflection angle, condition and propagates in a desired direction.
When an original (not shown) is placed on the glass plate
5
, the light emerging from the exit surface
8
c
passes through the glass plate
5
and is reflected by the original. The reflected light then reaches the sensor unit
1
through the lens array
3
. The sensor unit
1
is a line sensor constituted by many photoelectric conversion elements arranged in a line, and serves to read an original image while scanning it. The read image signal is sent to the external system through the connector
13
and a lead wire.
A color image sensor according to the related art will be described next.
A light source switching type color image sensor has been known. This sensor includes LEDs respectively having the properties of emitting light beams of three colors, i.e., R, G, and B light beams. The sensor emits R, G, and B light beams at the same position on an original, and outputs signals by reading the reflected light beams. A color image signal corresponding to the original is then obtained in accordance with the output signals.
FIGS. 29
to
33
show an example of the light source switching type color image sensor. This image sensor includes an LED array constituted by R, G, and B LEDs arranged in a line, a short-focus imaging element lens array, and a sensor array constituted by a plurality of line sensors arranged in a line.
Referring to
FIGS. 29 and 30
, a transparent glass plate
201
on which an original is to be placed is mounted on the upper portion of a frame
200
. Light beams emitted form R, G, and B LEDs
230
R
1
,
230
G
1
,
230
B
1
,
230
R
2
,
230
G
2
,
230
B
2
, . . . , which are alternately arranged in a line on an LED board
210
mounted in the frame
200
as shown in
FIG. 31
, are reflected by the original placed on the upper surface of the glass plate
201
. Reflected light beams
213
are read by a sensor array
10
on a board
19
through an optical system
209
. As the optical system
209
, the above short-focus image element lens array represented by, e.g., “SELFOC lens array” (available from Nippon Sheet Glass Co., Ltd.) is used.
As shown in
FIG. 31
, the LEDs
230
R
1
,
230
G
1
,
230
B
1
,
230
R
2
,
230
G
2
,
230
B
2
, . . . are mounted on the LED board
210
.
FIG. 32
shows the structure of each of these LEDs, and more specifically, the LED
230
R
1
as an example. An LED chip
211
R
1
is mounted on an LED base
216
. The emission surface side of the LED chip
211
R
1
is covered with a transparent resin
215
. On the LED board
210
, these LEDs
230
R
1
,
230
G
1
,
230
B
1
,
230
R
2
,
230
G
2
,
230
B
2
, . . . can be ON/OFF-controlled at independent timings respectively set for R, G, and B.
As shown in
FIG. 33
, the sensor array
10
is constituted by a plurality of line sensors
10
1
,
10
2
,
10
3
, . . . arranged in a line on the board
19
, and a protective film
206
covering the line sensors. In principle, the contact multichip image sensor is designed to form reflected light from an original into a one-to-one image on the sensor array
10
and read it. For this reason, the sensor array
10
needs to have a length equal to the width of an original to be read. Therefore, as the size of an original to be read changes, the required length of the sensor array
10
changes, and the number of line sensors constituting the sensor array
10
changes. Assume that an A3-size original is to be read. In this case, if one line sensor is 20 mm long, it suffices if the sensor array
10
is constituted by 15 line sensors
10
1
to
10
15
.
The board
19
is supported by a bottom plate
205
engaged with the frame
200
as shown in
FIG. 30
, and connected to a flexible board
203
through a flexible interconnection
208
as shown in
FIG. 33. A
connector
202
for power, control signals, and the like is mounted on the flexible board
203
. The flexible board
203
is fastened to the frame
200
with screws
207
.
A color original read operation of the color image sensor having the above arrangement is started from loading of data for correction shading caused by variations in sensitivity of the respective line sensors or irregularities in light irradiated from the light sources. The shading correction data is loaded as follows. Light beams are sequentially emitted from the R LEDs
230
R
1
,
230
R
2
, . . . , the G LEDs
230
G
1
,
230
G
2
, . . . , and the B LEDs
230
B
1
,
230
B
2
, . . . in units of colors to read a white reference set in the image sensor. The resultant output signals from the image sensor are temporarily stored in a memory. Shading correction is performed by using the obtained R, G, and B shading correction signals obtained in such a manner that when the white reference is read again, the R, G, and B signals are uniform on one line, and an output signal r obtained when the R LEDs
211
R
1
,
211
R
2
, . . . are turned on, an output signal g obtained when the G LEDs
211
G
1
,
211
G
2
, . . . are turned on, and an output signal b obtained when the B LEDs
211
B
1
,
211
B
2
, . . . are turned on are set to r=g=b.
In an actual original read operation of the light source switching type color image sensor, to obtain R, G, and B signals at one point on the original to be read, R, G, and B light beams must be separately irradiated on the original. In this case, the operation of subscanning the image sensor over the entire original with one of the R, G, and B LEDs being turned on may be repeated three times while the type of LED turned on is changed. That is, the original may be read by the so-called field sequential scheme. Alternatively, the image sensor may be subscanned over the entire original while the R, G, and B LEDs are sequentially turned on in units of lines to be read, thereby obtaining R, G, and B signals. That is, the original may be read by the so-called line sequential scheme. By either of these methods, R, G, and B signals can be obtained from the entire original surface, and a color image can be reproduced by using the signals.
In the apparatus described with reference to
FIGS. 26
to
28
, however, the LEDs
7
are electrically connected to the external system through the connector cables
16
, and the main irradiation direction of the LEDs
7
coincides with the longitudinal direction of the light guide
8
Ogura Makoto
Yushiya Akihiko
Allen Stephone B.
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
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