Facsimile and static presentation processing – Facsimile – Specific signal processing circuitry
Reexamination Certificate
1998-07-02
2001-02-27
Grant, II, Jerome (Department: 2722)
Facsimile and static presentation processing
Facsimile
Specific signal processing circuitry
C358S406000, C358S474000
Reexamination Certificate
active
06195179
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image reading device such as an image scanner.
2. Description of the Related Art
Recently, a multifunction peripheral device has been developed. The single multifunction peripheral device can perform many functions, such as a printer function, a facsimile function, a scanner function, and a copy function. The multifunction peripheral device is therefore convenient to be used as a peripheral device for a computer.
The multifunction peripheral device is provided with an image scanner. The image scanner includes: a lamp (scanner light source) for irradiating an original document with light; and a charge coupled device (CCD) for picking up light reflected from the original document. The CCD has a plurality of light conversion elements aligned in a line. Each light conversion element in the CCD outputs a voltage with its value corresponding to the intensity of the received light. The value of the voltage therefore represents a corresponding pixel on the original document. The voltage value (voltage data) is then converted into numeric data representing an image read from the original document.
SUMMARY OF THE INVENTION
The voltage data outputted from the CCD for each pixel may be converted into hexadecimal numeric data of “00h” to “FFh” based on the following formula (1):
(
numeric
data
)
=
(
voltage
data
)
-
(
lower
reference
voltage
)
(
upper
reference
voltage
)
-
(
lower
reference
voltage
)
×
256
(
1
)
It is noted that when the voltage data is higher than the upper reference voltage, the numeric data is set to “FFh.” When voltage data is lower than the lower reference voltage, the numeric data is set to “00h.” That is, if (voltage data)>(upper reference voltage), (numeric data)=FFh, and if (voltage data)<(lower reference voltage), (numeric data)=00h.
Thus, values of the lower reference voltage and the upper reference voltage have to be determined prior to the voltage data conversion process.
For this reason, the image scanner may be designed to set the values of the upper and lower reference voltages before reading images from an original document. The values of the upper and lower reference voltages may be set in a manner described below.
It is now assumed that the value of the upper reference voltage should be set in a range between two (2) and four (4) volts and that the value of the lower reference voltage should be set in another range between zero (0) and one (1) volts.
First, the lamp is turned ON. A white reference plate provided in the image scanner is irradiated with light from the lamp. Receiving light reflected from the white reference plate, all the light conversion elements in the CCD generate the same input voltage
101
shown in FIG.
1
(
a
). Simultaneously, a temporary reference voltage
102
is set to have a value of two (2) volts which is equal to the minimum value in the upper reference voltage range of 2 to 4 volts. Then, the amount of the temporary reference voltage
102
is increased one level (=(4-2)/256 volts) at a time until the temporary reference voltage
102
becomes higher than the CCD's generating input voltage
101
. It is noted that when the input voltage
101
is greater than the temporary reference voltage
102
, the input voltage
101
is detected as “overflow.” Accordingly, the amount of the temporary reference voltage
102
is increased one level at a time until no overflow is detected. Once overflow is eliminated, the temporary reference voltage
102
is decreased one level at a time until overflow is again detected. When overflow is again detected, the temporary reference voltage
102
is increased one more level, and the resultant temporary voltage value, which is now substantially equal to the CCD's generating input voltage
101
, is set as the upper reference voltage
103
as shown in FIG.
1
(
b
).
The value of the lower reference voltage is set in the manner similar to that described above.
First, the lamp is turned OFF. The CCD is controlled to receive light reflected from the white reference plate in the dark condition. All the light conversion elements in the CCD generate the same input voltage. This input voltage is different from that generated by the CCD in the light-illuminated condition. Simultaneously, a temporary reference voltage is set to have a value of one (1) volt which is equal to the maximum value in the lower reference voltage range of zero (0) to one (1) volts. The temporary reference voltage is decreased one level ((1-0)/256 volts) at a time until the temporary reference voltage becomes lower than the input voltage. It is noted that when the input voltage is lower than the temporary reference voltage, the input voltage is detected as “underflow.” Accordingly, the temporary reference voltage is decreased one level at a time until no underflow is detected. Once underflow is eliminated, the temporary reference voltage is increased one level at a time until underflow is again detected. When underflow is again detected, the temporary reference voltage is decreased one more level, and the resultant temporary reference voltage value, which is now substantially equal to the CCD's generating input voltage, is set as the lower reference voltage.
Thus, the upper reference voltage is determined by repeatedly changing the amount of the temporary reference voltage one level at a time from the minimum value of the upper reference voltage range. The lower reference voltage is determined by repeatedly changing the amount of the temporary reference voltage one level at a time from the maximum value of the lower reference voltage range. Therefore, a great deal of time is required to set each of the upper and lower reference voltages.
In addition, each time the temporary reference voltage is increased or decreased, a certain amount of time is required before the condition stabilizes. Therefore, it is impossible to detect overflow or underflow immediately after the temporary reference voltage is changed. Accordingly, it takes a certain amount of time before detecting existence of overflow or underflow.
Accordingly, in order to detect existence of overflow or underflow in a stable condition, it is conceivable to periodically execute an interrupt routine, wherein the temporary reference voltage is changed one level and overflow or underflow is detected. In this case, however, the interrupt routine has to be repeatedly performed a great number of times until the temporary reference voltage becomes substantially equal to the CCD's generating input voltage. It takes a long period of time until finally determining each of the upper and lower reference voltages.
It is therefore an objective of the present invention to overcome the above-described problems and to provide an improved image reading device that is capable of setting, within a short period of time, the reference voltage to be used for converting voltage data read from an original image into numeric data.
In order to attain the above and other objects, the present invention provides an image reading device comprising: reading means capable of reading an original image through converting the original image into voltage data; reference voltage supply means capable of supplying a reference voltage; conversion means capable of receiving the voltage data and the reference voltage and converting the voltage data into numeric data with referring to the reference voltage; and image reading control means for performing successively-executed image reading processes through repeatedly controlling the reading means to convert the original image into voltage data, the reference voltage supply means to supply the reference voltage, and the conversion means to convert the voltage data into the numeric data with referring to the reference voltage, the image reading control means setting a value of
Brother Kogyo Kabushiki Kaisha
Grant II Jerome
Kianni Kevin C.
Oliff & Berridge PLC.
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