Facsimile and static presentation processing – Facsimile – Specific signal processing circuitry
Reissue Patent
1998-08-19
2001-09-18
Rogers, Scott (Department: 2724)
Facsimile and static presentation processing
Facsimile
Specific signal processing circuitry
C358S474000, C358S483000
Reissue Patent
active
RE037378
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a reader and more particularly, to a reader having a high-resolution mode and a high-speed mode using a CCD sensor.
2. Description of the Related Art
Recently, as means for inputting a document and drawing data or input means for digital copiers and facsimile, there has been widely used a reader using a CCD sensor.
A CCD sensor used in this reader will be described by referring to FIG.
5
.
Analog shift registers arranged in odd rows and analog shift register arranged in even rows are finally combined into an output signal CCD
OUT
through buffers. Symbols S
1
, S
2
, . . . S
N
denote light receiving means. OSR
1
, OSR
2
, . . . OSR
N/2
denote odd-row shift registers for shifting out the analog outputs of light receiving means on the odd side (light receiving means arranged in odd rows) an ESR
1
, ESR
2
, . . . ESR
N/2
denote even-row shift registers for shifting out the analog outputs of light receiving means on the even side (light receiving means arranged in even rows). Furthermore, symbol SH denote a start pulse for the shift operation of the shift registers, symbols &phgr;
1
and &phgr;
2
denote transfer pulses, and symbol &phgr;
R
denotes a reset pulse.
Then, referring to
FIG. 3
, the positional relationship between a line-shaped fluorescent lamp
33
and a CCD sensor
37
in a reader will be described.
A manuscript
31
is laid on a glass table
32
. In
FIG. 3
, the glass table
32
and the manuscript
31
are spaced from each other but actually are closely in contact with each other. The manuscript
31
is illuminated through the glass table
32
with a ray of light emitted from the fluorescent lamp
33
with the longitudinal direction placed vertically to the surface of a paper. The ray of light reflected from the manuscript passes again through the glass table and is reflected from the mirror
35
. The ray of light reflected from the mirror
35
is focussed at a lens
36
and illuminated to the light receiving surface of the CCD sensor
37
. Numeral
34
denotes an optical unit including the mirror
35
, the lens
36
and the CCD sensor
37
, while numerals
38
and
39
denote a pulse motor and a cabinet, respectively.
As shown in
FIG. 4
, a conventional reader incorporates a CCD sensor
40
for converting a received light into an electrical signal and the CCD sensor
40
is connected via a capacitor C to an input of a buffer
41
. The input of the buffer
41
is connected to a 5 V electric power source via an analog switch. The output of the buffer
41
is connected to the input of an AD converter
42
. The outputs D
0
-D
7
of the AD converter
42
are connected to a control circuit
43
. The output FLON of the control circuit
43
is connected to the input of a lighting device
48
. The output of the lighting device
48
is connected to the input of a fluorescent lamp
33
. When the FLON turns to “1”, the fluorescent lamp
33
turns on. The outputs T
STEP
and FORWARD of the control circuit
43
are connected to the input of a pulse motor drive circuit
46
. The input of the pulse motor drive circuit
46
is connected to the input of a pulse motor
38
. If “FORWARD” is “1” the pulse motor
38
is rotated by the pulse motor drive circuit
46
so as to forward the optical unit
34
and the fluorescent lamp
33
by one step, when the pulse motor receives one time of T
STEP
pulse. Similarly, if “FORWARD” IS “0”, the pulse motor
38
is rotated so as to reverse the optical unit
34
and the fluorescent lamp
33
, when the pulse motor receives the T
STEP
pulse.
The control circuit
43
comprises an oscillator
44
and a clock generating circuit
45
connected thereto. A basic clock t
0
is oscillated by the oscillator
44
and divided in frequency by the clock generating circuit
45
to generate various control pulses SH, &phgr;
1
, &phgr;
2
, &phgr;
R
and T
CLAMP
. Control pulses SH, &phgr;
1
, &phgr;
2
and &phgr;
R
are supplied to the CCD sensor
40
and a control pulse T
CLAMP
is supplied to the analog switch.
FIG. 2
shows drive signals SH, &phgr;
1
, &phgr;
2
, &phgr;
R
to the CCD sensor
40
, a CCD output CCD
out
a clamp signal T
CLAMP
for clamping the CCD
out
a timing of ADIN which is an input signal to the AD converter
42
.
Then, the operation of an analog switch and C shown in
FIG. 4
will be described.
Ordinarily, the CCD output CCD
out
is not defined as a DC signal, for example, outputted in the negative direction from a standard voltage of 4 V, as shown in FIG.
2
. This standard varies between 3.5 V and 4.5 V according to each CCD sensors. However, since the AD convertor will digitalize an analog voltage of 5 V or less, it is necessary to shift the DC level in such a manner that a value of output voltage from the capacitor C and the analog switch may be 5 V or less. Thus, the capacitor C comes to be always charged to 1 V.
Here, the CCD
out
has a load of long transmission path and is usually amplified in use, and accordingly noises in the relevant amplifier are randomly superimposed onto the CCD
out
. For example, the DC level of the CCD
out
is normally 4 V but is assumed to become 3.8 V due to the random noises mentioned above. At this time, C has to be rapidly charged to 1.2 V that is 0.2 V higher than a normal 1 V. Thus, setting the clamp time to t=300 nsec and the ON resistance of the analog switch to 50 &OHgr;, The capacitance C becomes as follows:
C&OHgr;R<<t
C≦300 nsec/50 &OHgr;=6000 pF.
In conventional scanners, a value of 1000 pF or less is selected. By secure clamping of the DC level of each individual CCD signal outputs in this way, an image with reduced random noise is obtained as a reader.
On the other hand, Japanese Patent Application Laying Open No. 5-48460 discloses a three-dimensional integrated circuit comprising an AD converter for executing a digital to analog conversion with high-speed and high-resolution.
However, in a reader described by referring to
FIGS. 2
to
5
, through an image with reduced random noise is obtained as a reader, by secure clamping of the DC level of each individual CCD signal outputs, the stable period of the CCD
out
is further needed before and after the clamp signal T
CLAMP
, thereby the operating speed becomes slower. In addition, a three-dimensional integrated circuit disclosed in Japanese Patent Application Laying Open No. 5-48460 comprises a complicated circuit and becomes slower in the rate of AD conversion than ordinary AD converter.
In order to solve these problems, as shown in Japanese Patent application Laying Open No. 6-253091, the applicant of the present invention proposes a reader comprising: a CCD sensor for individually outputting an output of the light receiving section arranged in odd rows and an output of that arranged in even rows; a first AD converter corresponding to either one of the outputs of odd rows or even rows; a second AD convertor corresponding to the other of the outputs of odd rows or even rows; and means for supplying the other of the outputs of odd rows or even rows to the first AD convertor when a high-resolution mode is selected.
However, in the reader of Japanese Patent Application Laying Open No. 6-253091, the quality in the high-resolution mode is equal to the quality of ordinary reader though the device becomes complicated.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a reader capable of selecting either the high-resolution mode or the high-speed mode and further enabling the read to be performed at higher speed in the high-speed mode and/or at higher quality in the high-resolution mode.
According to the present invention, the above object is achieved by a reader having a high-resolution mode and a high-speed mode comprising: a CCD sensor for converting a received light into an electrical signal; a first AD convertor for converting the output signal of said CCD sensor into a digital signal; a second AD converter for converting the output signal of said CCD sensor into a digital signal with fewer b
Conlin David G.
Dike Bronstein, Roberts & Cushman LLP
Rogers Scott
Sharp Kabushiki Kaisha
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