Image analysis – Image sensing – Optical
Reexamination Certificate
1996-02-23
2003-03-25
Johns, Andrew W. (Department: 2621)
Image analysis
Image sensing
Optical
C382S312000, C358S505000
Reexamination Certificate
active
06539129
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to an image reading apparatus which is used for, for example, a scanner, a facsimile, or the like.
2. Related Background Art
Hitherto, as one of image reading apparatuses, a contact type multi-chip image sensor constructed by a light source, a short focal point image pickup element array, and a plurality of line sensors is known.
FIGS. 1
to
3
show an example of such an image reading apparatus. A transparent glass plate
201
which is in contact with an original surface is attached onto the upper surface of a frame
200
. An emission light
212
of an LED
211
attached onto an LED board
210
provided in the frame
200
is reflected by the original surface which is in contact with the upper surface of the transparent glass plate
201
. An optical system
209
for transmitting a reflection light
213
from the original surface to be read and a sensor array
1
provided on a board
19
in correspondence to the optical system
209
are provided in the frame
200
. As an optical system, the foregoing short focal point image pickup element array represented by, for example, “Cellhock lens array (trade name)” (made by Nippon Sheet Glass Co., Ltd.) is used.
As shown in
FIG. 3
, the sensor array
1
is constructed by arranging a plurality of line sensors
2
-
1
,
2
-
2
, . . . , and
2
-
15
in a line on the board
19
and is covered with a protecting film
206
. In the contact type multi-chip image sensor, since the reflection light from the original is formed as an image onto the sensor array at an equal magnification and is read in principle, a length of sensor array
1
needs to be set to a value corresponding to only the width of original to be read.
Therefore, the necessary length of sensor array
1
changes depending on the size of original to be read and the number of line sensors constructing the sensor array
1
also changes. The case of reading the original of the A3 size will now be considered as an example. Assuming that a length of one line sensor is equal to 20 mm, it is sufficient to construct the sensor array by 15 line sensors.
The board
19
is supported onto a bottom plate
205
which is in engagement with the frame
200
and is connected to a flexible board
203
through a flexible wiring
208
. A connector
202
for input and output of a power source, a control signal, and the like is provided on the flexible board
203
and is attached to the frame
200
by a screw
207
.
The operation of the contact type multi-chip image sensor will now be described with reference to
FIG. 4
showing wirings on the board and
FIG. 5
showing a timing chart. The operations of the plurality of line sensors
2
-
1
,
2
-
2
, . . . , and
2
-
15
arranged in a line on the board
19
are started by a start pulse &phgr;SP and a shift register
36
-
1
starts the operation. Now, assuming that the number of photosensitive (pixel) elements arranged in each line sensor is equal to
316
, the shift register
36
-
1
which started the operation generates signals for sequentially making switches
32
-
1
-
1
,
32
-
1
-
2
, . . . , and
32
-
1
-
316
conductive, thereby allowing the signals accumulated in photosensitive elements
31
-
1
-
1
,
31
-
1
-
2
, . . . , and
31
-
1
-
316
to be transferred to an output line
33
-
1
. While the reading operation of the line sensor
2
-
1
is being performed, a switch
35
-
1
is conducting by a control signal &phgr;sw
1
, so that the signals transferred to the output line
33
-
1
are transmitted through a buffer amplifier
34
-
1
to a common output terminal Vout on the board
19
.
An output signal &phgr;end
1
at the final stage of the shift register
36
-
1
in the line sensor
2
-
1
is connected by the wiring on the board
19
and becomes a start pulse &phgr;st
2
of the line sensor
2
-
2
. After completion of the reading of the signal of the line sensor
2
-
1
, the reading operation of the line sensor
2
-
2
is started. In a manner similar to the line sensor
2
-
1
, a shift register
36
-
2
starts the operation and sequentially makes switches
32
-
2
-
1
,
32
-
2
-
2
, . . . , and
32
-
2
-
316
conductive, thereby allowing signals accumulated in photosensitive elements
31
-
2
-
1
,
31
-
2
-
2
, . . . , and
31
-
2
-
316
to be transferred to an output line
33
-
2
.
While the reading operation of the line sensor
2
-
2
is being performed, a switch
35
-
2
is conducting by a control signal &phgr;sw
2
, thereby allowing the signals transferred to the output line
33
-
2
to be transmitted to the common output terminal Vout through a buffer amplifier
34
-
2
.
Similarly, an output signal &phgr;end
2
at the final stage of the shift register
36
-
2
in the line sensor
2
-
2
is connected by the wiring on the board
19
and becomes a start pulse &phgr;st
3
of the line sensor
2
-
3
. The reading operation of the line sensor
2
-
3
is executed subsequent to the line sensor
2
-
2
. In a manner similar to the above, signals of the line sensors
2
-
4
to
2
-
15
are also sequentially read out by a similar procedure.
As mentioned above, the sensor array
1
constructed by a plurality of line sensors
2
-
1
,
2
-
2
, . . . , and
2
-
15
functions as one image sensor and sequentially generates the signals of all of the photosensitive elements to the common output terminal Vout.
After completion of the reading of the image data of one line, the contact type multi-chip image sensor is moved in the sub scanning direction (direction perpendicular to the arranging direction of the plurality of line sensors) by a distance corresponding to one line and reads the next line. By repeating the above operation a number of times corresponding to the original size, an image of the entire original is completely read out by using the contact type multi-chip image sensor.
In the above conventional apparatus, however, since the signals of all of the sensor chips are sequentially outputted to one output line, it takes a time to obtain the signals of one line. Although a request such that the user wants to read the original in a short time is increasing more and more in recent years, if the user tries to output the signal at a high speed in such a construction, the circuit to read out the signals from the photosensitive elements, buffer amplifiers, and the like have to be constructed so as to cope with a further higher band, thereby causing complication of a circuit construction and a manufacturing process. This inevitably results in an increase in costs and becomes a large problem, on the other hand, since the reduction of the costs is also an important object. Further, the realization of the high output speed in the conventional apparatus also causes a problem such that not only does the complexity of the circuit design increase but the number of development elements, such as analog signal processes of the generated signals and the like, increase also so that development time increases.
SUMMARY OF THE INVENTION
An object of the invention is to provide an image reading apparatus which can read an image at a high quality in a short time.
Another object of the invention is to provide an image reading apparatus which can read an image at a high quality and at a high speed.
Still another object of the invention is to provide an image reading apparatus which can read an image at a high quality by means of a simple construction.
Yet another object of the invention is to provide an image reading apparatus which can read an image at a high quality and with low cost.
To accomplish the above objects, according to an embodiment of the invention, there is provided an image reading apparatus in which a plurality of line sensors each for converting an image pickup light into an electric signal are arranged in the longitudinal direction, comprising: driving means for driving the plurality of line sensors; and switching means for switching a first operation to simultaneously drive the plurality of line sensors by the driving means and to output signals of the line sensors in parallel and
Dang Duy M
Johns Andrew W.
LandOfFree
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