U.S. patent application number 14/591985 was filed with the patent office on 2015-07-16 for image reading apparatus.
This patent application is currently assigned to BROTHER KOGYO KABUSHIKI KAISHA. The applicant listed for this patent is BROTHER KOGYO KABUSHIKI KAISHA. Invention is credited to Takahiro IKENO, Hidenobu KONDO, Isao KUBO, Kyoichi MORITA.
Application Number | 20150201098 14/591985 |
Document ID | / |
Family ID | 53492119 |
Filed Date | 2015-07-16 |
United States Patent
Application |
20150201098 |
Kind Code |
A1 |
MORITA; Kyoichi ; et
al. |
July 16, 2015 |
IMAGE READING APPARATUS
Abstract
An image reading apparatus includes: a command unit which
generates a command signal periodically; a reading unit which reads
an original in accordance with the command signal every time the
command signal is generated; a conveying unit which conveys at
least one of the reading unit and the original so as to change a
relative position between the reading unit and the original; a
signal output unit which outputs a displacement signal every time
the relative position is changed by a predetermined amount
corresponding to a reading interval; and a control unit which
controls a generation timing of the command signal by the command
unit. A generation period of the command signal is less than an
output time interval of the displacement signal.
Inventors: |
MORITA; Kyoichi; (Anjo-shi,
JP) ; KUBO; Isao; (Tokoname-shi, JP) ; KONDO;
Hidenobu; (Tokoname-shi, JP) ; IKENO; Takahiro;
(Seto-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
BROTHER KOGYO KABUSHIKI KAISHA |
Nagoya-shi |
|
JP |
|
|
Assignee: |
BROTHER KOGYO KABUSHIKI
KAISHA
Nagoya-shi
JP
|
Family ID: |
53492119 |
Appl. No.: |
14/591985 |
Filed: |
January 8, 2015 |
Current U.S.
Class: |
358/406 |
Current CPC
Class: |
H04N 1/00063 20130101;
H04N 1/00034 20130101; H04N 1/00055 20130101; H04N 1/00082
20130101; H04N 1/0005 20130101; H04N 2201/0081 20130101; H04N
1/00013 20130101; H04N 1/00798 20130101; H04N 1/10 20130101 |
International
Class: |
H04N 1/00 20060101
H04N001/00; H04N 1/10 20060101 H04N001/10 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 10, 2014 |
JP |
2014-003411 |
Claims
1. An image reading apparatus comprising: a command unit configured
to generate a command signal periodically; a reading unit
configured to read an original in a main scanning direction in
accordance with the command signal every time the command signal is
generated; a conveying unit configured to perform a conveying
process for conveying at least one of the reading unit and the
original so as to change a relative position between the reading
unit and the original in a sub scanning direction; a signal output
unit configured to output a displacement signal every time the
relative position is changed by a predetermined reading interval;
and a control unit configured to control a generation timing at
which the command signal is generated by the command unit, wherein
a generation period of the command signal is less than an output
time interval at which the displacement signal is outputted by the
signal output unit in the conveying process, the control unit is
configured to determine, with respect to the command signal
periodically generated, an elapsed time elapsed from an output
timing at which the displacement signal has been outputted by the
signal output unit until a generation timing at which the command
signal is generated by the command unit after the displacement
signal has been outputted, and under a condition that the elapsed
time is less than a reference value, the control unit delays
generating the command signal until the elapsed time is not less
than the reference value.
2. The image reading apparatus according to claim 1, wherein under
a condition that the elapsed time is less than the reference value,
the control unit controls the command unit to generate the command
signal at a timing when the elapsed time is greater than the
reference value.
3. The image reading apparatus according to claim 1, wherein under
a condition that the elapsed time is less than the reference value,
the control unit controls the command unit to delay the generation
timing of the command signal, by a predetermined time, from the
generation timing adopted under a condition that the command signal
is generated periodically.
4. The image reading apparatus according to claim 1, wherein the
control unit delays generating the command signal under a condition
that the elapsed time is less than the reference value in a
high-velocity conveyance segment included in the conveying process,
the output time interval of the displacement signal being less than
twice the generation period of the command signal in the
high-velocity conveyance segment.
5. The image reading apparatus according to claim 1, wherein the
conveying process includes an acceleration segment in which
relative velocity between the original and the reading unit is
accelerated to a predetermined velocity, a constant velocity
segment in which the relative velocity is controlled to be the
predetermined velocity, and a deceleration segment in which the
relative velocity is decelerated from the predetermined velocity,
and the control unit delays generating the command signal under a
condition that the elapsed time is less than the reference value in
the constant velocity segment.
6. The image reading apparatus according to claim 5, wherein the
reference value is determined to be not more than difference
between the output time interval of the displacement signal and the
generation period of the command signal in the constant velocity
segment.
7. The image reading apparatus according to claim 6, wherein under
a condition that the elapsed time is less than the reference value,
the control unit delays generating the command signal until the
elapsed time is not less than the reference value and is more than
twice the difference between the output time interval of the
displacement signal and the generation period of the command signal
in the constant velocity segment.
8. The image reading apparatus according to claim 5, wherein under
a condition that the elapsed time is less than the reference value,
the control unit delays generating the command signal until the
elapsed time is not less than the reference value and is not more
than 1/2 times the output time interval of the displacement signal
in the constant velocity segment.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] The present application claims priority from Japanese Patent
Application No. 2014-003411 filed on Jan. 10, 2014 the disclosure
of which is incorporated herein by reference in its entirety.
BACKGROUND
[0002] 1. Field of the Invention
[0003] The present invention relates to an image reading
apparatus.
[0004] 2. Description of the Related Art
[0005] There is known a conventional image reading apparatus which
conveys an image sensor at an area located below an original so as
to read the original. For example, there is known an image
recording apparatus which generates a transfer timing signal at a
predetermined time interval while conveying the image sensor (see
Japanese Patent Application Laid-open No. 2009-246636). The
transfer timing signal is a signal for transferring an image signal
generated by the image sensor. The image sensor executes a reading
operation every time the transfer timing signal is inputted to the
image sensor.
[0006] It may happen in this image reading apparatus that the
transfer timing signal is generated at a deviated position from an
appropriate original-reading position (timing) at which the
original is to be read, depending on the velocity of the image
sensor. Thus, the transfer timing signal is corrected based on the
count number of pulse edge of an encoder signal which is generated
and outputted in accordance with a rotation of a motor which
conveys the image sensor. Specifically, an error between a target
control value and the count number indicating the position of the
image sensor is detected each time interval corresponding to the
generation cycle (generation period) of the transfer timing signal,
and in a case that the error exceeds an allowable range, the
transfer timing signal is generated at a shifted timing.
SUMMARY
[0007] In the conventional technique described above, however, it
is necessary that the number of pulse edge of the encoder signal is
counted since the reading has started, and that the value of
counting is stored as the positional information of the image
sensor. Further, in a case that the transfer timing signal is
generated at a shifted timing, the control target value needs to be
updated.
[0008] Namely, in a case of executing a periodic reading operation
by inputting a periodic signal to the image sensor in the
conventional technique, the correction of the transfer timing
signal and the suppression of any lowering in image quality due to
the above-described phenomenon, in which the original-reading
position is deviated from the appropriate position, cannot be
realized without performing any complicated processing such as the
storage of counting value as the positional information of the
image sensor, updating the control target value, etc.
[0009] The present teaching is made in view of such a problem, and
an object of the present teaching is to provide a technique capable
of efficiently adjusting a generation timing of a reading command
signal in an image reading apparatus in which the reading command
signal is periodically inputted to a reading unit, such that the
original-reading position of the reading unit, that is determined
based on the reading command signal, is an appropriate
position.
[0010] According to an aspect of the present teaching, there is
provided an image reading apparatus including: a command unit
configured to generate a command signal periodically; a reading
unit configured to read an original in a main scanning direction in
accordance with the command signal every time the command signal is
generated; a conveying unit configured to perform a conveying
process for conveying at least one of the reading unit and the
original so as to change a relative position between the reading
unit and the original in a sub scanning direction; a signal output
unit configured to output a displacement signal every time the
relative position is changed by a predetermined reading interval;
and a control unit configured to control a generation timing at
which the command signal is generated by the command unit, wherein
a generation period of the command signal is less than an output
time interval at which the displacement signal is outputted by the
signal output unit in the conveying process, the control unit is
configured to determine, with respect to the command signal
periodically generated, an elapsed time elapsed from an output
timing at which the displacement signal has been outputted by the
signal output unit until a generation timing at which the command
signal is generated by the command unit after the displacement
signal has been outputted, and under a condition that the elapsed
time is less than a reference value, the control unit delays
generating the command signal until the elapsed time is not less
than the reference value.
[0011] In the image reading apparatus, the generation period of the
command signal is shorter than the output time interval of the
displacement signal outputted from the signal output unit, in the
conveying process executed by the conveying unit. In a case that
the generation period of the command signal is shorter than the
output time interval of the displacement signal corresponding to
the reading interval, it is possible to cause the reading unit to
execute the reading operation at least one time during a period of
time (time period) in which the relative position is changed by the
amount corresponding to the reading interval. In a case that the
reading unit can be made to execute the reading operation a
plurality of times during the time period in which the relative
position is changed by the amount corresponding to the reading
interval, it is possible to determine one image data for each
reading interval as a valid data from the plural line image data
generated by the plural reading operations executed by the reading
unit respectively, and to discard remaining image data among the
plural line image data and different from the one image data,
thereby making it possible to generate read- image data composed of
line image data aggregation of plural line image data generated by
reading the original substantially at an equal interval.
[0012] However, in such a case that the generation period of the
command signal is shorter only to a little extent than the output
time interval of the displacement signal, it is difficult to
generate a high-quality read-image data for the following reason.
Namely, in a case of thinning (curtailing) a part or portion of
plural line image data generated by the respective reading
operations by the reading unit so as to generate the read-image
data of the original, the reading positions of two line image data
located before and after the curtailed line image data are greatly
apart.
[0013] In view of the above situation, the present teaching adjusts
the original-reading position, at which the reading of the original
is performed by the reading unit and which is gradually deviated
(shifted) from the original-reading position corresponding to the
normal (appropriate) reading interval, due to the difference
between the generation period of the command signal and the reading
interval (output time interval of the displacement signal), by
delaying the generation timing of the command signal with the
above-described technique.
[0014] According to the present teaching, the generation operation
of the command signal is delayed, with the time length between the
time point (output time point) at which the displacement signal is
outputted and a time point (generation time point) which is after
the output time point and at which the command signal is generated
next time, as an indicator, thereby adjusting the original-reading
position by the reading unit. Accordingly, the generation timing of
the command signal can be adjusted more easily and more efficiently
than the conventional technique.
[0015] Namely, according to the present teaching, the generation
timing of the command signal can be adjusted such that the
original-reading position of the reading unit is an appropriate
position, without successively storing the position of the
conveyance target and/or updating the control target value for the
purpose of evaluating the error between the position of the
conveyance target and the control target value as in the
conventional technique. Therefore, according to the present
teaching, the generation timing of the command signal can be
adjusted more efficiently than the conventional technique, thereby
making it possible to generate a read-image data with high image
quality.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 is a block diagram depicting a schematic
configuration of an image reading apparatus.
[0017] FIG. 2 is a cross-sectional view of the image reading
apparatus, depicting a line sensor and a conveying mechanism which
conveys an original.
[0018] FIG. 3 is a block diagram depicting an inner configuration
of an ASIC (Application Specific Integrated Circuit).
[0019] FIGS. 4A and 4B indicate a flow chart indicating a
processing executed by a motor control section.
[0020] FIG. 5 is a graph indicating a velocity locus of a
conveyance target.
[0021] FIG. 6 is a block diagram depicting a configuration of a
timing control section.
[0022] FIG. 7 is a time chart indicating a waveform of a TG signal
from an acceleration segment to a constant velocity segment.
[0023] FIG. 8 is a time chart indicating a waveform of the TG
signal from the constant velocity segment to a deceleration
segment.
[0024] FIG. 9 is a block diagram depicting a configuration of a
timing control section of a modification.
[0025] FIG. 10 is a time chart indicating a waveform of a TG signal
in a case of performing a color image reading operation.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0026] An embodiment of the present teaching will be explained as
follows, with reference to the drawings. An image reading apparatus
1 of the embodiment and depicted in FIG. 1 includes a CPU 11, a ROM
13, a RAM 15, an interface 17, a FB (flatbed) reading device 20, an
ADF (auto document feeder) device 30, and an ASIC 40.
[0027] The CPU 11 controls the image reading apparatus 1 as a whole
by executing a processing according to a program stored in the ROM
13. The RAM 15 is used as a workspace when the CPU 11 executes the
program. The interface 17 is configured to be capable of
communicating with an external personal computer 5.
[0028] The CPU 11 supplies a read-image data of an original Q
generated by using the FB reading device 20 to the external
personal computer 5 via the interface 17. The FB reading device 20
is configured to read the original Q as an object to be read, by
transporting (conveying) the line sensor 21. The ADF device 30 is
configured to convey the original Q to a reading position at which
the original Q is to be read by the line sensor 21. The ASIC 40
controls the FB reading device 20 and the ADF reading device 30 in
accordance with an instruction from the CPU 11.
[0029] In the image reading apparatus 1, the CPU 11 sets an
operation parameter for the ASIC 40 and activates the ASIC 40. The
operation parameter can be exemplified by an operation parameter
indicating a reading mode, a reading area, etc. The reading mode
can be exemplified by an ADF reading mode, in which the line sensor
21 is arranged in a fixed manner and the original Q is read by the
line sensor 21 while conveying the original Q so as to change the
relative position between the line sensor 21 and the original Q;
and a FB reading mode, in which the line sensor 21 is conveyed to
read the original Q placed on a platen glass member 103A.
[0030] The ASIC 40 controls the FB reading device 20 and the ADF
device 30 in accordance with the operation parameter, and causes
the line sensor 21 to execute the reading operation for each line,
while changing the relative position between the original Q and the
line sensor 21. The line sensor 21 generates, for each of the
reading operations, a line image data indicating a result of
reading for one line of the original Q. The ASIC 40 executes the
shading correction, etc. for each of the line image data generated
in such a manner. Each of the corrected line image data generated
by the ASIC 40 is stored in the RAM 15.
[0031] The CPU 11 transmits each of the line image data stored in
the RAM 15 to the personal computer 5 via the interface 17. By
doing so, the CPU 11 provide read-image data of the original Q
composed of plural line image data. As another example, in a case
that the image reading apparatus 1 is a digital multi-function
peripheral having a copying function, the read-image data stored in
the RAM 15 is subjected to a print processing. With this, a copied
image of the original Q is formed on a paper sheet.
[0032] Next, the detailed configuration of the FB reading device 20
will be explained. The FB reading device 20 includes the line
sensor 21, a line sensor conveying mechanism 23, a FB motor 25, a
driving circuit 27 and a FB encoder 29.
[0033] The line sensor 21 is configured, for example, as a contact
image sensor (CIS). The line sensor 21 is configured to be
elongated in a main scanning direction, and to read the original Q
in the main scanning direction. The line sensor conveying mechanism
23 receives the driving force from the FB motor constructed of a
direct current motor and conveys the line sensor 21 in a sub
scanning direction orthogonal to the main scanning direction.
[0034] As depicted in FIG. 2, the line sensor conveying mechanism
23 is provided inside a lower case 101 of the image recording
apparatus 1. The lower case 101 provided on the image reading
apparatus 1 includes transparent platen glass members 103A and 103B
which are arranged on the upper surface of the lower case 101. The
original Q is placed on the upper surface of the platen glass
member 103A manually by a user in the FB reading mode. On the other
hand, the platen glass member 103B is used in the ADF reading mode.
In the ADF reading mode, the line sensor 21 is arranged in fixed
manner in an area located below the platen glass member 103B.
[0035] The line sensor conveying mechanism 23 is configured to be
capable of conveying the line sensor 21 in the sub scanning
direction at an area located below the platen glass members 103A
and 103B. In the line sensor conveying mechanism 23, a carriage 231
in which the line sensor 21 is placed is attached to a belt 235
wound around and stretched between a driving pulley 233 and a
driven pulley 234. The FB motor 25 is connected to the driving
pulley 233 via a gear.
[0036] Namely, in the line sensor conveying mechanism 23, the
driving pulley 233 is rotated by receiving the driving force from
the FB motor 25, and the belt 235 and the driven pulley 234 are
rotated in accordance with the rotation of the driving pulley 233,
thereby transmitting the driving force to the carriage 231 attached
to the belt 235. The carriage 231 receiving the driving force moves
in the sub scanning direction while the movement of the carriage
231 is regulated by a guide axis 237. By such an operation, the
line sensor conveying mechanism 23 conveys the line sensor 21 in
the sub scanning direction.
[0037] The driving circuit 27 drives the FB motor 25 in accordance
with a control signal from the ASIC 40. The FB encoder 29 is
attached to a driving force-transmitting path from the FB motor 25
to the line sensor 21, and outputs pulse signals (ENC1a, ENC1b) in
accordance with the movement (conveyance) of the line sensor 21 in
the sub scanning direction. Each of the pulse signals (ENC1a,
ENC1b) is outputted every time the line sensor 21 is conveyed in
the sub scanning direction by a predetermined distance.
[0038] For example, the FB encoder 29 is constructed of a rotary
encoder provided on the rotation axis of the FB motor 25. The pulse
signals (ENC1a, ENC1b) correspond to an A-phase signal (ENC1a) and
a B-phase signal (ENC1b), which are different in the phase by
.pi./2, respectively. In the following, the pulse signals (ENC1a,
ENC1b) are also referred to as encoder signals (ENC1a, ENC1b).
[0039] On the other hand, the ADF device 30 is provided with an
original-conveying mechanism 31, an ADF motor 35, a driving circuit
37 and an ADF encoder 39. The original-conveyance mechanism 31 is
provided on an upper case 111 of the image reading apparatus 1, as
depicted in FIG. 2. The upper case 111 is provided to be pivotable
relative to the lower case 101 of the image recording apparatus 1.
The upper case 111 functions as a cover body covering the upper
surface of the lower case 101 including the platen glass members
103A and 103B.
[0040] The original-conveying mechanism 31 is disposed in the upper
case 111 and includes a separation roller 311, a separation pad
312, an intake roller 313, a main roller 315, a pinch roller 316,
an original-pressing member 317 and a paper sheet-discharge roller
318.
[0041] The separation pad 312 is arranged to face the separation
roller 311 and imparts a predetermined conveying resistance to the
original Q. The intake roller 313 feeds the original Q (plurality
of pieces of the original Q stacked) on an original tray 113
provided on the upper case 111 toward the separation roller 311.
The separation roller 311 conveys the original Q toward the main
roller 315.
[0042] The main roller 315 conveys the original Q conveyed from the
separation roller 311 to the downstream in the conveyance path
while invering the conveyance direction of the original Q toward
the platen glass member 103B. In this situation, the pinch roller
316 presses the original Q toward the main roller 315. The
original-pressing member 317 presses the original Q, conveyed from
the side of the main roller 315, against the platen glass member
103B. The paper sheet-discharge roller 318 conveys the original Q
which is being conveyed while passing a space underneath the
original-pressing member 317, toward a paper sheet- discharge tray
115.
[0043] The ADF motor 35 is constructed of a direct current motor
and imparts the driving force to the original-conveying mechanism
31. The driving circuit 37 drives the ADF motor 35 in accordance
with a control signal from the ASIC 40. The rollers 311, 313, 315
and 318 constructing the original-conveying mechanism 31 receive
the driving force from the ADF motor 35 and rotate in mutually
cooperative manner.
[0044] By causing the rollers 311, 313, 315 and 318 to rotate, the
original-conveying mechanism 31 conveys the original Q in the sub
scanning direction only by an amount in accordance with the
rotation amounts of the rollers 311, 313, 315 and 318 from the
original tray 113 to the paper sheet-discharge tray 115 via the
original-pressing member 317. In the ADF reading mode, the line
sensor 21 is arranged at a location below the original-pressing
member 317 and reads the original Q when the original Q passes this
location.
[0045] The ADF encoder 39 outputs pulse signals (ENC2a, ENC2b) in
accordance with the conveyance amount of the original Q by the
original-conveying mechanism 31. The ADF encoder 39 is constructed,
for example, of a rotary encoder. The ADF encoder 39 is provided,
for example, on the rotation axis of the ADF motor 35 and outputs
the pulse signals (ENC2a, ENC2b) in accordance with the rotation of
the ADF motor 35. Each of the pulse signals (ENC2a, ENC2b) is
outputted every time the ADF motor 35 is rotated by a predetermined
amount, in other words, every time the original Q is conveyed by a
predetermined amount. The pulse signals (ENC2a, ENC2b) correspond
to an A-phase signal (ENC2a) and a B-phase signal (ENC2b) which are
different in the phase by .pi./2, respectively. In the following,
the pulse signals (ENC2a, ENC2b) are also referred to as encoder
signals (ENC2a, ENC2b).
[0046] Next, the detailed configuration of the ASIC 40 will be
explained. The ASIC 40 includes a motor control section 41, an
encoder process section 42, a timing control section 43, a reading
control section 45, a read-data process section 47 and a buffer 49,
as depicted in FIG. 3.
[0047] The encoder process section 42 detects the position and
velocity of the line sensor 21 based on the encoder signals (ENC1a,
ENC1b) inputted from the FB encoder 29 and inputs these detected
values to the motor control section 41. Further, the encoder
process section 42 detects the rotational position and velocity of
the ADF motor 35, which corresponds to the position and velocity of
the original Q, based on the encoder signals (ENC2a, ENC2b)
inputted from the ADF encoder 39, and inputs these detected values
to the motor control section 41.
[0048] Furthermore, the encoder process section 42 inputs a
displacement signal (EN) corresponding to the reading mode to the
timing control section 43. In the FB reading mode, every time the
position of the line sensor 21 is changed in the sub scanning
direction by a predetermined amount, the encoder process section 42
inputs a pulse signal as the above-described displacement signal
(EN) to the timing control section 43 based on the encoder signals
(ENC1a, ENC1b) inputted from the FB encoder 29. For example, the
encoder process section 42 is capable of inputting any one of the
A-phase signal (ENC1a) and the B-phase signal (ENC1b), inputted
from the FB encoder 29, to the timing control section 43 as the
displacement signal (EN) in the FB reading mode.
[0049] On the other hand, in the ADF reading mode, every time the
original Q is conveyed by a predetermined amount, the encoder
process section 42 inputs a pulse signal as the above-described
displacement signal (EN) to the timing control section 43 based on
the encoder signals (ENC2a, ENC2b) inputted from the ADF encoder
39. For example, the encoder process section 42 is capable of
inputting any one of the A-phase signal (ENC2a) and the B-phase
signal (ENC2b), inputted from the ADF encoder 39, to the timing
control section 43 as the displacement signal (EN) in the ADF
reading mode.
[0050] The motor control section 41 controls driving of the FB
motor 25 and the ADF motor 35 in accordance with an instruction
from the CPU 11. Specifically, in the FB reading mode, the motor
control section 41 inputs a PWM signal corresponding to a driving
current to be applied to the FB motor 25, to the driving circuit
27, to thereby control the driving of the FB motor 25. The motor
control section 41 controls the conveyance velocity of the line
sensor 21 in the sub scanning direction by performing a feedback
control based on the detected values of the position and velocity
of the line sensor 21 inputted from the encoder process section
42.
[0051] Further, in the ADF reading mode, the motor control section
41 inputs a PWM signal corresponding to a driving current to be
applied to the ADF motor 35, to the driving circuit 37, to thereby
control the driving of the ADF motor 35. The motor control section
41 controls the conveyance velocity of the original Q by performing
a feedback control based on the detected values of the rotational
position and velocity of the ADF motor 35 inputted from the encoder
process section 42.
[0052] On the other hand, the timing control section 43 controls
the reading timing, at which the original Q is read by the line
sensor 21, in the FB reading mode and the ADF reading mode.
Basically, the timing control section 43 generates a TG signal that
is a pulse signal for designating the reading timing of the line
sensor 21 periodically at a predetermined time interval and inputs
the TG signal to the reading control section 45. Here, the period
of the TG signal is represented as "T0". Note that, however, the
timing control section 43 adjusts, as necessary, the generation
timing of the TG signal to be inputted to the reading control
section 45, based on the displacement signal (EN) inputted from the
encoder process section 42, thereby adjusting the input timing at
which the TG signal is inputted to the reading control section
45.
[0053] The reading control section 45 generates a control signal
for the line sensor 21 based on the TG signal inputted from the
timing control section 43, and inputs the control signal to the
line sensor 21. The control signal includes a line start signal
(SG1), a lighting control signal (SG2) and a transfer control
signal (SG3).
[0054] Every time the reading control section 45 detects the rising
edge of the TG signal, the reading control section 45 inputs the
line start signal (SG1) to the line sensor 21. When the line start
signal (SG1) is inputted, the electric charge accumulated in a
light-receiving element group 211 provided on the line sensor 21 is
transmitted to an analog shift resistor 213. With this, the
electric charge, that is generated by the photoelectric effect
during a time period from a time point at which the line start
signal (SG1) has been inputted to the line sensor 21 last time
until a time point at which the line start signal (SG1) is inputted
to the line sensor 21 this time, is transmitted to the analog shift
resistor 213.
[0055] As depicted in FIG. 3, the line sensor 21 includes
light-receiving elements each provided for every pixel
(light-receiving element group 211), the analog shift resistor 213
having a size corresponding to the number of the light-receiving
elements, and a light source 215. The information of electric
charge per each of the light-receiving elements, that is
transmitted to the analog shift resistor 213 by the input of the
line start signal (SG1), corresponds to a pixel data. Namely, the
information aggregation of electric charge stored to the analog
shift resistor 213 corresponds to the pixel data aggregation
representing a result of reading of one line of the original Q, and
corresponds to the line image data.
[0056] Due to the transmittance of the accumulated electric charge
of the light-receiving element group 211 to the analog shift
resistor 213, the accumulated electric charge in each of the
light-receiving elements is initialized, and in the light-receiving
element group 211, a new reading operation utilizing the
photoelectric effect is started.
[0057] The lighting control signal (SG2) is a signal for
controlling the lighting ON and lighting OFF of the light source
215. The reading control section 45 inputs the lighting control
signal (SG2) for lighting ON the light source 215 synchronizing
with the input of the line start signal (SG1), to the line sensor
21. Specifically, the reading control section 45 inputs the
lighting controlling signal (SG2) to the line sensor 21 so that the
light source 215 is switched ON for a predetermined time period
from a time point at which the line start signal (SG1) has been
inputted. The light source 215 is lighted ON in accordance with the
lighting control signal (SG2) and irradiates a light onto the
original Q.
[0058] The transfer control signal (SG3) is a signal for
controlling an operation of transferring the electric charge
information, which is stored in the analog shift resistor 213, from
the line sensor 21 to the read-data process section 47. When a
certain TG signal is inputted to the reading control section 45,
the reading control section 45 inputs the transfer control signal
(SG3) to the line sensor 21 so that the electric charge information
(line image data), that is transferred to the analog shift resistor
213 at a time point at which the line start signal (SG1)
corresponding to the certain TG signal has been inputted, is
transferred to the read-data process section 47 before next time
point at which next line start signal (SG1) will be inputted to the
line sensor 21.
[0059] The read-data process section 47 converts the electric
charge information inputted from the line sensor 21 to digital line
image data. Further, the read-data process section 47 performs
image processing such as the shading correction, gamma correction,
etc. to the line image data, and causes the RAM 15 to store the
corrected line image data corrected by such image processing. Among
the line image data inputted from the line sensor 21 to the
read-data process section 47, the line image data before being
corrected and the line image data after being corrected and before
being stored to the RAM 15 are temporarily stored in the buffer
49.
[0060] In some cases, the available storage capacity of the buffer
49 is reduced by any delay in the processing after the line image
data has been corrected in the read-data process section 47 until
the corrected line image data is stored in the RAM 15. In a case
that the available storage capacity of the buffer 49 is less than a
threshold value, the read-data process section 47 inputs a memory
full signal to the motor control section 41 so as to temporarily
interrupt (pause) the conveying operation of the original Q or the
line sensor 21 executed by the motor control section 41.
[0061] The processing operation by the motor control section 41 is
executed in accordance with a flow chart indicated in FIGS. 4A and
4B. In the FB reading mode, the motor control section 41 sets the
line sensor 21 as a conveyance target, and executes the processing
indicated in FIGS. 4A and 4B. In the ADF reading mode, the motor
control section 41 sets the original Q as the conveyance target,
and executes the processing indicated in FIGS. 4A and 4B. This
processing is started by an instruction from the CPU 11 triggered,
for example, by a pressing operation by a user made on a
non-illustrated operation section.
[0062] In a case that the processing is started, the motor control
section 41 starts a motor control for accelerating the conveyance
target (S110). This motor control is executed until velocity V of
the conveyance target reaches a predetermined constant target
velocity Vc. In the FB reading mode, the motor control section 41
determines the driving current to be applied to the FB motor 25 as
a motor to be driven, based on the velocity V of the line sensor 21
detected by the encoder process section 42, and inputs a PWM signal
corresponding to the determined driving current to the driving
circuit 27.
[0063] On the other hand, in the ADF reading mode, the motor
control section 41 determines the driving current to be applied to
the ADF motor 35 as a motor to be driven, based on the rotational
velocity of the ADF motor 35 detected by the encoder process
section 42 and corresponding to the velocity V of the original Q,
and inputs a PWM signal corresponding to the determined driving
current to the driving circuit 37. With this, the velocity of the
conveyance target is accelerated up to the target velocity Vc in
the acceleration segment after the start of conveyance. The term
"acceleration segment" described in the embodiment means a
conveyance segment until the velocity V of the conveyance target
reaches the target velocity Vc.
[0064] The motor control section 41 judges whether or not the
velocity V of the conveyance target is a value which is not less
than a predetermined threshold value during the acceleration of the
conveyance target by the motor control (S120). At a time point at
which the velocity V of the conveyance target reaches a value not
less than the threshold value (S120: YES), the motor control
section 41 inputs an instruction (adjustment-start instruction) to
the timing control section 43 so as to start adjustment of the TG
signal (S125). The details about the adjustment of the TG signal
will be described later on. In a case that the adjustment-start
instruction is inputted to the timing control section 43, the
timing control section 43 starts a processing for adjusting, as
necessary, the input timing at which the TG signal is inputted to
the reading control section 45, based on the displacement signal
(EN).
[0065] In a case that the velocity V of the conveyance target has
reached the target velocity Vc, the motor control section 41 starts
a constant velocity-conveyance processing (S130). In the constant
velocity-conveyance processing, the motor control section 41
determines the driving current to be applied to the motor (FB motor
25 or ADF motor 35) so that the conveyance target is conveyed at a
constant velocity that is the target velocity Vc, and the motor
control section 41 inputs a PWM signal corresponding to the
determined driving current to the driving circuit 27 or 37
corresponding to the conveyance target. With this, in the constant
velocity segment following the acceleration segment, the conveyance
target is conveyed at the target velocity Vc. The term "constant
velocity segment" described in the embodiment means a segment in
which the velocity V of the conveyance target is maintained at a
constant velocity (target velocity Vc).
[0066] After that, the motor control section 41 judges whether or
not the conveyance target has reached a deceleration start point
(S140). The deceleration start point is set as follows. Namely, at
first, a reading completion point is determined as a position of
the conveyance target at a time point when the reading operation
for the last line of the original Q is completed. Then, the
deceleration start point is set as a same point with the reading
completion point, or a point around the reading completion
point.
[0067] In a case that the motor control section 41 judges that the
conveyance target has reached the deceleration start point (S140:
YES), the process proceeds to S200 and performs a motor control for
decelerating and stopping the conveyance target. With this motor
control, the conveyance target is decelerated and stopped in the
deceleration segment following the constant velocity segment. The
term "decelerating segment" described in the embodiment means a
conveyance segment in which the velocity V of the conveyance target
is decelerated from the target velocity Vc until the conveyance
target is stopped.
[0068] In a case that the deceleration start point is set at a
point upstream of the reading completion point, the line sensor 21
executes the reading operation for each of the lines, even in the
deceleration segment, in accordance with the control signal from
the reading control section 45 until the conveyance target has
passed through the reading completion point.
[0069] In S200, the motor control section 41 inputs an instruction
for stopping the adjustment (adjustment-stop instruction) of the TG
signal to the timing control section 43 at a time point at which
the conveyance velocity V becomes a value less than the threshold
value. When this adjustment-stop instruction is inputted to the
timing control section 43, the timing control section 43 stops the
processing for adjusting the input timing of the TG signal to the
reading control section 45.
[0070] According to such a processing executed by the motor control
section 41, the adjustment of the input timing of the TG signal is
executed, as depicted in FIG. 5, in the constant velocity segment
and in each of the acceleration and deceleration segments only in
an area (region) thereof in which the velocity V has a value not
less than the threshold value. A time-velocity graph indicated in
FIG. 5 indicates, as an example, the locus of velocity V of the
conveyance target from the acceleration to the deceleration.
[0071] In the ADF reading mode, when the reading operation up to
the last line is completed, a judgment is made in S140 that the
original Q as the conveyance target has reached the deceleration
start point. In S200, the original Q as the conveyance target is
conveyed, without decreasing the velocity V of the original Q,
until the original Q is discharged to the paper sheet-discharge
tray 115. Afterward, the motor control section 41 ends the
processing indicated in FIGS. 4A and 4B.
[0072] On the other hand, in a case that the motor control section
41 judges that the conveyance target has not reached the
deceleration start point (S140: NO), the motor control section 41
judges whether or not any interruption factor for the motor control
has occurred. The motor control section 41 judges that the
interruption factor has occurred, under a condition that the memory
full signal is inputted to the motor control section 41 from the
read-data process section 47 (S150).
[0073] In a case that the motor control section 41 judges that any
interruption factor has not occurred (S150: NO), the process
proceeds to S140. In a case that the motor control section 140
judges that the interruption factor has occurred (S150: YES), the
process proceeds to S160. After proceeding to S160, the motor
control section 41 starts the motor control for decelerating and
stopping the conveyance target. The TG signal is inputted to the
reading control section 45 also during the deceleration and
stopping of the conveyance target by this motor control, and the
reading operation by the line sensor 21 is executed continuously
and repeatedly.
[0074] During the deceleration, the motor control section 41 judges
whether or not the conveyance velocity V has become a value less
than the threshold value (S170). Further at a time point at which
the conveyance velocity V has become the value less than the
threshold value (S170: YES), the motor control section 41 inputs
the adjustment-stop instruction to the timing control section 43
(S175).
[0075] Then, the motor control section 41 stands by in a state that
the conveyance target is stopped, until the interruption factor is
dissolved (S180). For example, the motor control section 41 stands
by until the interruption factor is dissolved by such a situation
that the available storage capacity of the buffer 49 has become a
value not less than the threshold value.
[0076] In a case that the motor control section 41 judges that the
interruption factor has been dissolved (S180: YES), the motor
control section 41 controls the motor, and starts the motor control
for accelerating the conveyance target up to the target velocity Vc
(S190).
[0077] Then, the process proceeds to S120, and at a time point at
which the velocity V of the conveyance target has become a value
not less than the threshold value (S120: YES), the motor control
section 41 inputs the adjustment-start instruction for adjusting
the TG signal again to the timing control section 43 (S125).
Further, when the velocity V of the conveyance target has reached
the target velocity Vc, the motor control section 41 starts the
control for performing constant velocity-conveyance (S130).
[0078] Next, the detailed configuration of the timing control
section 43 will be explained with reference to FIGS. 6 to 8. As
depicted in FIG. 6, the timing control section 43 includes a
frequency divider 431, a reference signal-generating section 432, a
counter 433, a comparator 434, a first TG signal-generating section
435, a second TG signal-generating section 436, a TG selecting
section 438 and a valid data-judging section 439.
[0079] The frequency divider 431 divides the displacement signal
(EN) inputted from the encoder process section 42 and inputs a
divided displacement signal (EN_D) to the counter 433, the second
TG signal-generating section 436 and the valid data-judging section
439. The division ratio is determined so that the displacement
amount of the conveyance target corresponding to the appearance
time interval of the rising edge of the divided displacement signal
(EN_D, hereinafter referred also to as "displacement signal (EN_D)
as appropriate) is a distance corresponding to the width of one
line of the original Q in the sub scanning direction.
[0080] The period T0 of the TG signal inputted to the reading
control section 45 is set to be shorter only to a little extent
than an appearance (occurrence) time interval TE of the rising edge
of the displacement signal (EN_D) when the conveyance target is
conveyed at the target velocity VC in the constant velocity
segment. For example, assuming there is such a possibility that the
velocity V of the conveyance target might become greater than the
target velocity Vc due to any control error when the conveyance
target is conveyed at the constant velocity, the period T0 may be
set to be shorter than the appearance time interval TE in view of
such a possibility. The ratio of the period T0 to the appearance
time interval TE is, for example, T0:TE=7:8.
[0081] On the other hand, the reference signal-generating section
432 inputs a periodic pulse signal, which corresponds to the period
T0 of the TG signal, to the counter 433 and the first TG
signal-generating section 435, as a reference signal defining the
input timing of the TG signal to the reading control section 45.
Specifically, the reference signal-generating section 432 inputs
the pulse signal to the counter 433 and the first TG
signal-generating section 435, at a time point at which a time
corresponding to the period T0 has elapsed from a generation time
point at which the TG signal has been generated last time as the
input signal to the reading control section 45.
[0082] The counter 433 measures, for each displacement signal
(EN_D), an elapsed time Tc elapsed from a certain time point of
appearance (occurrence) of the rising edge of the displacement
signal (EN_D) inputted from the frequency divider 431 until another
time point of appearance of the rising edge of the reference signal
inputted after the certain time point, and the counter 433 inputs
the elapsed time Tc to the comparator 434 for each displacement
signal (EN_D).
[0083] In a case that the elapsed time Tc has a value not less than
a reference value Tref, the comparator 434 inputs a first TG signal
(TG1) generation instruction for generating the first TG signal
(TG1) to the first TG signal-generating section 435, and inputs an
instruction for selecting the first TG signal (TG1) to the TG
selecting section 438. On the other hand, in a case that the
elapsed time Tc has a value less than the reference value Tref, the
comparator 434 inputs a second TG signal (TG2) generation
instruction for generating the second TG signal (TG2) to the second
TG signal-generating section 436, and inputs an instruction for
selecting the second TG signal (TG2) to the TG selecting section
438.
[0084] Note that, however, the comparator 434 executes the
above-described processing only during a time period from the
adjustment-start instruction has been inputted until the
adjustment-stop instruction is inputted. In any other time
period(s) different from this time period, the comparator 434
inputs the first TG signal generation instruction to the first TG
signal-generating section 435, regardless of whether or not the
elapsed time Tc has a value not less than the reference value Tref.
With this input, the first TG signal (TG1) among the first and
second TG signals (TG1, TG2) is inputted to the reading control
section 45, as the TG signal.
[0085] Further, the comparator 434 controls the second TG
signal-generating section 436 and the TG selecting section 438 so
that the second TG signal (TG2) is inputted to the reading control
section 45 as the TG signal, immediately after a time point P1 at
which the adjustment-start instruction has been inputted.
[0086] When the first TG signal-generating section 435 receives the
first TG signal generation instruction, the first TG
signal-generating section 435 generates the first TG signal (TG1)
that is a TG signal in accordance with the reference signal, and
inputs the first TG signal (TG1) to the TG selecting section 438.
For example, when the first TG signal-generating section 435
receives the first TG signal generation instruction, the first TG
signal-generating section 435 may be configured to allow the
reference signal as it is to be inputted to the TG selecting
section 438, as the first TG signal (TG1). As another example, the
first TG signal-generating section 435 may be configured to input a
pulse signal, rising at a timing at which the first TG signal
generation instruction is inputted, to the TG selecting section 438
as the first TG signal (TG1).
[0087] On the other hand, when the second TG signal-generating
section 436 receives the second TG signal generation instruction,
the second TG signal-generating section 436 generates a pulse
signal of which rising is delayed by a predetermined time Td from
the rising edge of the displacement signal (EN_D), as the second TG
signal (TG2), and inputs the second TG signal (TG2) to the TG
selecting section 438.
[0088] The TG selecting section 438 inputs one of the first TG
signal (TG1) and the second TG signal (TG2), in accordance with a
selection instruction inputted from the comparator 434, to the
reading control section 45 as the TG signal. The timing control
section 43 generates the TG signal to be inputted to the reading
control section 45, in such a manner.
[0089] According to the timing control section 43 configured in
this manner, the TG signal is inputted to the reading control
section 45 with patterns as depicted in FIGS. 7 and 8, and the
reading operation corresponding thereto is executed by the line
sensor 21.
[0090] Based on the TG signal inputted to the reading control
section 45 and the displacement signal (EN_D) inputted from the
frequency divider 431 to the valid data judging section 439, the
valid data-judging section 439 judges, at each appearance
(occurrence) of the rising edge of the displacement signal (EN_D),
a line image data corresponding to an electric charge information
transmitted to the analog shift resistor 213 by a TG signal which
is generated secondly after the time point of appearance of the
rising edge, as a valid data. Then, the valid data-judging section
439 inputs a result of this judgment to the read data-process
section 47.
[0091] The line image data judged as the valid data is a line image
data based on the electric charge accumulated in the
light-receiving element group 211 during a time period that is
after appearance of the rising edge of the displacement signal
(EN_D) and ranging from first generation time point of the TG
signal until second generation time point of the TG signal.
[0092] In accordance with such a result of judgment by the valid
data-judging section 439, the read-data process section 47 selects
one line image data at each rising edge of the displacement signal
(EN_D) (in other words, at each conveyance, of the conveyance
target, corresponding to one line of the original), the one line
image being included in plural line image data generated by the
reading operations executed by the line sensor 21 a plurality times
respectively. The read-data process section 47 transmits the
selected one line image data to the RAM 15 and discards remaining
line image data among the plural line image data and different from
the selected one image data.
[0093] FIG. 7 is a time chart indicating the waveform of the
divided displacement signal (EN_D) in the first stage, indicating
the waveform of the TG signal in the second stage, and indicating
ON/OFF of the light source 215 in the third stage. FIG. 8 is a time
chart, after the time point P1 indicated in FIG. 7, indicating the
waveform of the displacement signal (EN_D), the waveform of the TG
signal, and the ON/OFF of the light source 215 in the first stage
to the third stage, respectively.
[0094] In the third stage of each of FIGS. 7 and 8, a hatched area
depicted with diagonal lines indicates that a line image data
corresponding to the electric charge accumulated in the light-
receiving element group 211 during the lighted-ON period of the
light source 215 is judged as a non-valid data. On the other hand,
a hatched area depicted with mesh lines indicates that a line image
data corresponding to the electric charge accumulated in the
light-receiving element group 211 during the lighted-ON period of
the light source 215 is judged as a valid data.
[0095] The time point P1 indicated in FIG. 7 is a time point at
which the adjustment-start instruction of the TG signal is inputted
by a situation that the velocity V of the conveyance target has
become a value not less than the threshold value. A time point P2
is a time point elapsed by the predetermined time Td from the
rising edge of the displacement signal (EN_D) appeared at the time
point P1. Immediately after the input of the adjustment-start
instruction, at the time point (time point P2) elapsed by the
predetermined time Td from the time point of appearance of the
rising edge of the displacement signal (EN_D), the second TG signal
(TG2) from the second TG signal-generating section 436 is inputted
to the reading control section 45.
[0096] As appreciated from FIG. 7, the threshold value defining the
input timing of the adjustment-start instruction (the threshold
value which is referred to in S120) is set to be such a velocity V
of the conveyance target that the appearance time interval of the
rising edge of the displacement signal (EN_D) is less than twice
the period T0 of the TG signal.
[0097] The adjustment processing of the input timing of the TG
signal is started at the time point P1 at which the velocity V of
the conveyance target has a value not less than the threshold
value, immediately before the conveyance target proceeds to (enters
to) the constant velocity segment from the acceleration segment.
During the time period before the time point P1, the TG signal is
regularly inputted to the reading control section 45 at the period
T0, without any adjustment being made to the input timing of the TG
signal, and the reading operation is executed in the line sensor 21
with the period T0.
[0098] Even after the adjustment start-instruction has been
generated, the TG signal is basically inputted to the reading
control section 45 with the period T0. Note that, however, the
timing control section 45 identifies the elapsed time Tc elapsed
from a time point of appearance of the rising edge of the
displacement signal (EN_D) until another time point at which the TG
signal is inputted to the reading control unit 45. In a case that
the elapsed time Tc has a value less than the reference value Tref
(corresponding to the elapsed time Tc indicated in FIG. 8), the
timing control section 43 controls the second TG signal-generating
section 436 and the TG selecting section 438, so that the second TG
signal (SG2) is inputted from the second TG signal-generating
section 436 to the reading control section 45 at a time point
(corresponding to a time point P4 indicated in FIG. 8) elapsed by
the predetermined time Td from a time point P3 at which the rising
edge of the displacement signal (EN_D) has appeared.
[0099] The configuration of the image reading apparatus 1 of the
embodiment has been described as above. According to the method for
adjusting the generation and input timing of the TG signal of the
embodiment, it is possible to appropriately adjust the
original-reading position by the line sensor 21 which is gradually
deviated (shifted) from the original-reading position corresponding
to the normal (appropriate) reading interval, due to the difference
between the period T0 of the TG signal and the normal reading
interval (the appearance time interval TE of the rising edge of the
displacement signal (EN_D)).
[0100] In such a case that the period T0 of the TG signal is
shorter only to a little extent than the output time interval TE of
the displacement signal (EN_D), it is difficult to generate a
high-quality read-image data for the following reason. Namely, in a
case of thinning (curtailing) a part or portion of plural line
image data generated by the respective reading operations so as to
generate the read-image data of the original, the reading positions
of two line images located before and after the curtailed line
image are greatly apart.
[0101] In view of the above situation, the present embodiment
adjusts the original-reading position by the line sensor 21, by
delaying the input operation of the TG signal from the TG selecting
section 438 to the reading control section 45 at an appropriate
timing, based on the length (value) of the time length (elapsed
time Tc) from the rising edge of the displacement signal (EN_D)
until the generation time point at which the TG signal is generated
next to the rising edge. Thus, according to the present embodiment,
the reading timing by which the original is read by the line sensor
21 can be adjusted appropriately.
[0102] Further, according to the present embodiment, the input
timing of the TG signal can be adjusted such that the
original-reading position is an appropriate position, without
successively storing the position of the conveyance target and/or
updating the control target value for the purpose of evaluating the
error between the position of the conveyance target and the control
target value as in the conventional technique. Therefore, according
to the present teaching, the reading timing can be adjusted more
easily and more efficiently than the conventional technique,
thereby making it possible to generate a read-image data with high
image quality.
[0103] Furthermore, according to the embodiment, the input timing
of the TG signal is adjusted only in the high-velocity conveyance
segment in which the appearance time interval of the rising edge of
the displacement signal (EN_D) is less than twice the period T0 of
the TG signal. In other words, the present embodiment is configured
such that under a condition that the appearance time interval TE is
not less than twice the period T0 of the TG signal and that the
line sensor 21 can be made to execute the reading operation a
plurality of times during a conveyance time period corresponding to
one line of the original, the input timing of the TG signal is not
adjusted. Thus, according to the embodiment, the reading timing can
be efficiently adjusted, without needing to perform any unnecessary
timing adjustment.
[0104] Note that the above-described reference value Tref can be
determined to be not more than difference between the appearance
time interval TE of the displacement signal (EN_D) in the constant
velocity segment (namely, the output time interval TE in a case
that the conveyance target is conveyed at the target velocity Vc)
and the period T0 of the TG signal (TE-T0). Specifically, the
reference value Tref can be determined to a value same as the
difference.
[0105] In the constant velocity segment, the input timing of the TG
signal is deviated relative to the appearance timing of the rising
edge of the displacement signal (EN_D) by a time corresponding to
the above-described difference. Accordingly, by delaying the input
timing of a TG signal which is to be inputted within a time period
starting from the rising edge of the displacement signal (EN_D) and
corresponding to the length of the difference (TE-T0), it is
possible to suppress such a phenomenon that the input timing of a
TG signal to be inputted next is before (precedes) the appearance
time point of the rising edge of a displacement signal (EN_D) to be
outputted next.
[0106] Further, the time Td can be determined to be greater than
the reference value Tref. Specifically, the time Td can be
determined to be greater than twice the difference (TE-T0) between
the appearance time interval TE of the rising edge of the
displacement signal (EN_D) in the constant velocity segment and the
period T0 of the TG signal. Also in the constant velocity segment,
the velocity V of the conveyance target varies due to any control
error. When considering this situation, the time Td can be
determined to be greater than twice the difference (TE-T0), by
using an appearance time interval TE adopted when the velocity V is
lowest in the constant velocity segment.
[0107] By setting the time Td in such a manner, the frequency of
occurrence of the phenomenon, that the elapsed time Tc is less than
the reference value Tref, can be suppressed to be smaller than in a
case that the time Td is set to be less than twice the difference
(TE-T0). In a case that the input timing of the TG signal is
adjusted highly frequently, the period of the TG signal is likely
to vary (fluctuate) by the above-described adjustment. However, by
suppressing the frequency of occurrence of the above-described
phenomenon, the variation in the period can be suppressed, thereby
making it possible to increase the quality of read-image.
[0108] Other than this, the time Td can be determined, with the
appearance time interval TE of the rising edge of the displacement
signal (EN_D) in the constant velocity segment as the reference, so
that the time Td is not more than 1/2 times the appearance time
interval TE. Considering any fluctuation (variation) in the
velocity in the constant velocity segment, the time Td can be
determined to be not more than 1/2 times an appearance time
interval TE adopted when the velocity V is highest in the constant
velocity segment.
[0109] In a case that the time Td is set to be a great value, the
adjustment amount of the TG signal becomes great, as a result. On
the other hand, in a case that the time Td is set to be a value
within the above-described range, the adjustment amount of the
input timing of the TG signal can be set within a value not more
than half the reading interval. Accordingly, it is possible to
suppress any effect to the image quality of the read image caused
by the change in the reading position brought about by the
adjustment.
[0110] Next, a modification of the present teaching will be
explained. A timing control section 44 depicted in FIG. 9 is used
in the image reading apparatus 1 of the above-described embodiment,
instead of the timing control section 43 depicted in FIG. 6. In the
timing control section 44 of the modification, the constitutive
parts or elements, designated with the same reference numerals as
those in the embodiment, are configured in a similar manner as in
the embodiment.
[0111] The timing control section 44 of the modification is
different from the timing control section 43 of the embodiment in
that the configuration of a second TG signal-generating section 446
is different from the second TG signal-generating section 436 of
the embodiment. Rather than generating (outputting) the
displacement signal (EN_D), the second TG signal-generating section
446 generates a second TG signal (TG2), based on a reference signal
from a reference signal-generating section 432. The second TG
signal (TG2) has a rising edge delayed by a predetermined time Te
from the rising edge of a first TG signal (TG1) outputted by the
first TG signal generating section 435. The time Te is set to be a
value greater than the reference value Tref.
[0112] Namely, in a case that the elapsed time Tc is less than the
reference value Tref, the timing control section 44 delays the
input timing of the TG signal to a time point at which the time T0
is elapsed from the previous input point of time of the TG signal
inputted last time. In other words, the timing control section 44
delays the input timing of the TG signal from the input time point
of the first TG signal (TG1) by the predetermined time Te, and
inputs the second TG signal (TG2) to the reading control section 45
at this delayed timing. With this method, the generation of the TG
signal and the delaying of the inputting operation can be performed
easily and appropriately, thereby making it possible to
appropriately adjust the original-reading position by the line
sensor 21.
[0113] Additionally, according to the modification, it is possible
to prevent the deviation in the input period of the TG signal from
exceeding the time Te, as compared with a case of delaying the
input timing of the TG signal with the rising edge of the
displacement signal (EN_D) as the reference. Accordingly, the
period of the TG signal can be made stable, as compared with the
above-described embodiment. In the modification, the elapsed time
Td elapsed from the time point at which the rising edge of the
displacement signal (EN_D) has appeared until the TG signal is
generated and inputted corresponds to a time obtained by adding the
elapsed time Tc of the embodiment with the time Te.
[0114] Further, the present teaching is not limited to the
embodiment and modification described above, and may be modified to
have a variety of kinds of aspects. For example, the line sensor 21
may be any of a monochrome image sensor and a color image sensor.
In a case that a color image sensor is adopted as the line sensor
21, the reading control section 45 may be configured to input, to
the line sensor 21, a control signal based on TG signals for
generating line image data of three colors (red, green, blue).
[0115] In a case of adopting the color image sensor as the line
sensor 21, as another example, the image reading apparatus 1 may be
configured as follows. Namely, the period T0 of the TG signal is
set to be a value which is shorter to a little extent than a value
that is 1/3 times the appearance time interval TE of the rising
edge of the displacement signal (EN_D) corresponding to the
constant target velocity Vc. Further, every time the TG signal is
inputted, the reading control unit 45 inputs a lighting control
signal (SG2) corresponding to one of the red, green and blue colors
to the line sensor 21 so that the respective light sources of red,
green and blue colors are successively lighted ON.
[0116] On the other hand, regarding the three TG signals by which
the reading operations for the red, green and blue colors are
started, the timing control section 43 performs adjustment for a TG
signal, by which the reading operation for a first color (red
color) is started, so that the input timing of this TG signal for
the first color is adjusted as depicted in FIG. 10, in a similar
manner as in the embodiment described above. In the third stage of
FIG. 10, reference sign "R" indicates that the red light source is
lighted ON, reference sign "G" indicates that the green light
source is lighted ON, and reference sign "B" indicates that the
blue light source is lighted ON. According to this adjustment, even
in an image recording apparatus provided with the color image
sensor as the line sensor, read-image data with an excellent image
quality can be generated.
[0117] In addition, the embodiment has been explained with the
example in which the line sensor 21 is conveyed in a state that the
original Q is fixed to thereby change the relative position between
the line sensor 21 and the original Q in the sub scanning
direction, and another example in which the original Q is conveyed
in a state that the line sensor 21 is fixed to thereby change the
relative position between the original Q and the line sensor 21 in
the sub scanning direction. However, the technical idea of the
embodiment is applicable also to an image reading apparatus which
conveys both of the line sensor and the original to thereby change
the relative position between the original Q and the line sensor in
the sub scanning direction.
[0118] Further, the processing executed by the timing control
section 43 for generating the TG signal, and for adjusting the
input timing of the TG signal and the processing executed by the
motor control section 41, etc. may be realized by a hardware or by
a software, or a combination of the hardware and software.
[0119] Finally, the correspondence in the present teaching is
provided as follows. The line sensor 21 corresponds to an example
of the reading unit. The line sensor conveying mechanism 23, the
original-conveying mechanism 31, the FB motor 25, the ADF motor 35,
the driving circuit 27, 37 and the motor control section 41
correspond to an example of the conveying unit.
[0120] In addition, the FB encoder 29, the ADF encoder 39, the
encoder process section 42 and the frequency divider 431 correspond
to an example of the signal output unit. The reference
signal-generating section 432 and the first TG signal-generating
section 435 correspond to an example of the command unit, the
counter 433, the comparator 434, the second TG signal-generating
section 436, 446 and the TG selecting section 438 (and the reading
control section 45) correspond to an example of the control unit.
The TG signal and the line start signal (SG1) correspond to an
example of the command signal.
* * * * *