Title: Image processing apparatus, image processing method and recording medium
Abstract: An image processing apparatus easily and reliably realizes complicated 1-line processing by a simple method, and controls accumulation period for respective colors without any particular function such as shutters on the line sensor side. One line period is divided into a reading section for reading valid image data, a dummy section for sweeping electric charge accumulated in the reading section and for synchronization, and a section for setting accumulation periods for the respective colors. In the reading section, the line sensor is driven by a necessary transfer frequency, and in the other sections, the sensor is driven at a high speed.
Patent Number: 7,009,740 Issued on 03/07/2006 to Sakai
| Inventors:
|
Sakai; Takashi (Kanagawa, JP)
|
| Assignee:
|
Canon Kabushiki Kaisha (Tokyo, JP)
|
| Appl. No.:
|
915598 |
| Filed:
|
July 26, 2001 |
Foreign Application Priority Data
| Jul 28, 2000[JP] | 2000-229492 |
| Current U.S. Class: |
358/514; 358/513; 358/512 |
| Current Intern'l Class: |
H04N 1/46 (20060101) |
| Field of Search: |
358/514,513,512,482,483,474,497,494,505,506
250/208.1
348/294,297,298,241,243,242,245,250,96,97
382/312,318,319
|
References Cited [Referenced By]
U.S. Patent Documents
| 5771070 | Jun., 1998 | Ohzu et al.
| |
| 6507365 | Jan., 2003 | Nakamura et al.
| |
| 6747699 | Jun., 2004 | Ohzu et al.
| |
| Foreign Patent Documents |
| A 6-233054 | Aug., 1994 | JP.
| |
| A 11-55509 | Feb., 1999 | JP.
| |
Other References
English Translation of an extract of Japanese Patent Application Laid-Open No. 11-55509.
|
Primary Examiner: Lee; Cheukfan
Attorney, Agent or Firm: Morgan & Finnegan, LLP
Claims
What is claimed is:
1. An image processing apparatus comprising:
a line sensor which photoelectric-converts light into a signal then accumulates
the signal, and outputs the signal as a 1-line electric signal; and
a drive circuit which drives said line sensor such that one line period is divided
into a first section for reading valid image data, a second section for storing
dummy image data, and a third section for storing valid image data,
wherein said line sensor includes a first line sensor and a second line sensor
for storing different color signals, and wherein said drive circuit sets different
accumulation periods for the respective colors by setting different second sections
in said first line sensor and said second line sensor.
2. The image processing apparatus according to claim 1, wherein said drive circuit
reads said dummy image data during said third section.
3. The image processing apparatus according to claim 1, wherein a transfer frequency
for electric charge transfer in said first section is different from that in said
second and third sections.
4. The image processing apparatus according to claim 3, wherein a product of
duration of said second section and the transfer frequency of said second section
is greater than that of duration of said first section and the transfer frequency
of said first section.
5. The image processing apparatus according to claim 1, wherein accumulated electric
charge is periodically read out during said second section.
6. An image processing apparatus comprising:
plural photoreception accumulation portions which respectively perform photoelectric
conversion and accumulate different color signals; and
drive circuit which starts accumulation of new signal by reading signals accumulated
in said photoreception accumulation portions, and sets accumulation periods for
respective colors by changing timings of reading signals from said photoreception
accumulation portions for the respective colors,
wherein said drive circuit reads valid image data from said photoreception accumulation
portions and then sets different dummy signal accumulation periods for each of
the respective colors.
7. The image processing apparatus according to claim 6, wherein said drive circuit
transfers dummy data at a speed higher than that for transferring said valid image data.
8. An image processing method comprising the steps of:
photoelectric-converting light into a signal then
accumulating the signal, and outputting the signal as a 1-line electric signal,
by a line sensor; and
driving said line sensor such that one line period is divided into a first section
for reading valid image data, a second section for storing dummy image data, and
a third section for storing the valid image data,
wherein said line sensor includes a first line sensor and a second line sensor
for storing different color signals, and wherein said drive circuit sets different
accumulation periods for the respective colors by setting different second sections
in said first line sensor and said second line sensor.
9. The image processing method according to claim 8, wherein said dummy image
data is read during said third section.
10. The image processing method according to claim 8, wherein a transfer frequency
for electric charge transfer in said first section is different from that in said
second and third sections.
11. The image processing method according to claim 10, wherein a product of duration
of said second section and the transfer frequency of said second section is greater
than that of duration of said first section and the transfer frequency of said
first section.
12. The image processing method according to claim 8, wherein accumulated electric
charge is periodically read out during said second section.
13. A computer program embodied in a computer readable medium for executing the
image processing method in claim 8.
14. A computer readable recording medium encoded with the program in claim 13.
Description
FIELD OF THE INVENTION
The present invention relates to an image processing apparatus having a sensor
which photoelectric-converts light from an original or the like then accumulates
the obtained signal and outputs the signal, and an image processing method for
the apparatus.
BACKGROUND OF THE INVENTION
An image processing apparatus which reads an original on a glass plate and sends
image data to a host computer or the like is known. As the original, a document
type original such as an article of magazine or the like, and a film type original
such as a photographic film are used. In use of the former original, light reflected
from the original is read, and in use of the latter original, light transmitted
through the original is read. Image processings respectively characteristic of
these original types are performed.
As the image sensor of the image processing apparatus, a line sensor such as a
CCD is used. Especially, as a sensor for reading a color original, a 3-line color
sensor with 3 arrays of line sensors, having color filters formed on photoelectric
conversion devices, is often employed. In the image reading apparatus, two-dimensional
image data is read by moving the above-described line sensor orthogonally to a
direction along the array of photoreception devices.
FIG. 8 is a schematic view showing the structure of the CCD line sensor.
Numeral 802 denotes shift gates which are closed during a storage
period. A photoreception device portion 801 accumulates electric charge
while performing photoelectric conversion during a photoreception period. When
the shift gates 802 are opened, the accumulated electric charge is moved
to shift registers 803. At this time, electric charge at odd-numbered photoreception
devices and electric charge at even-numbered photoreception devices, in one line,
are respectively moved to separate registers on both sides. The moved electric
charge are transferred via the shift registers.
FIG. 9 is a timing chart showing a drive pulse and 1-line data processing.
Symbol Hsync denotes a period required for moving the sensor in a subscanning
direction to read one line of image, i.e., a period for image processing for one
line in the system. Symbol SH denotes a signal supplied to the shift gates of the
sensor. When the signal is at a LOW level, the shift gates are closed, on the other
hand, when the signal is at a HIGH level, the shift gates are open and accumulated
electric charge is transferred to the shift registers. The period of the signal
corresponds to the storage period of the line. Numerals φ1 and φ2
denote drive signals for the shift registers. The transfer frequency of the pulses
corresponds to the transfer speed. In this manner, all the pixels are transferred
as image data within the storage period.
Generally, the image processing apparatus performs various image processings
to obtain an ideal output image. Color balance adjustment performed upon color
image reading is one of those processings. Generally, in the image sensor, the
color balance is not completely adjusted among R, G and B of output signal due
to influence of light source lamp and/or color filters.
Further, when a transmission-type original such as a positive film or a
negative film is read by the same system, the color balance must be adjusted in
consideration of film density or the like as well as the above factors. Especially,
when a negative film is read, tonality must be adjusted for each original.
As to these requirements, gain control of analog signal, processing on AD-converted
digital data and the like can be made. Further, a color sensor may be supplied
with a shutter function to control exposure for each color. In this sensor, photoreception
and storage portions are connected to shutter drains. Pulses are supplied to shutter
gates to arbitrarily control actual storage periods.
FIG. 10 is a timing chart showing a driving method for the color sensor with
the shutter function.
Storage periods SH_R, SH_G and SH_B of 3 color photoreception portions are
the same, however, drive signals supplied to shutter gates are different for respective
colors. When these signals are at a HIGH level, the gates are opened and electric
charge is discharged to the shutter drains, while when the signals are at a LOW
level, storage is started. In this manner, the actual electric-charge storage period
can be changed for respective colors while synchronizing the 3 color lines. However,
this function added to the sensor increases the costs, and further, widens the
distance between the lines.
SUMMARY OF THE INVENTION
The present invention provides image processing apparatus and method which control
storage period for respective colors without any particular function such as electronic
shutters on the sensor side, and arbitrarily set storage periods without consideration
of blooming or the limit of hardware processing speed in the subsequent stage.
To solve the above-described problem and attain the foregoing object, according
to a first aspect of the present invention, the image processing apparatus has
the following construction.
That is, provided is an image processing apparatus comprising: a line sensor
which photoelectric-converts light into a signal then accumulates the signal, and
outputs the signal as a 1-line electric signal; and a drive circuit which drives
the line sensor such that one line period is divided into a first section for reading
valid image data, a second section for storing dummy image data, and a third section
for storing valid image data.
Further, according to a second aspect of the present invention, the image
processing apparatus has the following construction.
That is, provided is an image processing apparatus comprising: plural photoreception
storage portions which respectively perform photoelectric conversion and accumulate
different color signals; and drive circuit which starts storage of new signal by
reading signals accumulated in the photoreception storage portions, and sets storage
periods for respective colors by changing timings of reading signals from the photoreception
storage portions for the respective colors.
Further, according to a third aspect of the present invention, the image
processing method has the following construction.
That is, provided is an image processing method comprising the steps of: photoelectric-converting
light into a signal then accumulates the signal, and outputting the signal as a
1-line electric signal, by a line sensor; and driving the line sensor such that
one line period is divided into a first section for reading valid image data, a
second section for storing dummy image data, and a third section for storing the
valid image data.
Further, according to a fourth aspect of the present invention, the image
processing method has the following construction.
That is, provided is an image processing method for an image processing apparatus
having plural photoreception storage portions which respectively perform photoelectric
conversion and accumulate different color signals, wherein storage of new signal
is started by reading signals accumulated in the photoreception storage portions,
and storage periods are set for respective colors by changing timings of reading
signals from the photoreception storage portions for the respective colors.
Further, a control program of the present invention has the following construction.
That is, the above image processing method is executed by a computer.
Further, a recording medium of the present invention has the following construction.
That is, the above control program is accumulated in a computer-readable recording medium.
Other objects and advantages besides those discussed above shall be apparent
to those skilled in the art from the description of a preferred embodiment of the
invention which follows. In the description, reference is made to accompanying
drawings, which form a part thereof, and which illustrate an example of the invention.
Such example, however, is not exhaustive of the various embodiments of the invention,
and therefore reference is made to the claims which follow the description for
determining the scope of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawings, which are incorporated in and constitute a part of
the specification, illustrate embodiments of the invention and, together with the
description, serve to explain the principles of the invention.
FIG. 1 is a cross-sectional view of an image processing apparatus main body
according to the present invention;
FIG. 2 is a block diagram of the image processing apparatus;
FIG. 3 is a schematic view of the inside of a 3-line color line sensor;
FIG. 4 is a timing chart explaining a driving method for the line sensor;
FIG. 5 is a timing chart showing signals φ1, φ2, RS
and CP during a reading section;
FIG. 6 is a timing chart showing signals in a dummy section and a storage section;
FIG. 7 is a timing chart showing a driving method for the image processing apparatus
according to a third embodiment of the present invention;
FIG. 8 is a schematic view of the structure of the conventional line sensor;
FIG. 9 is a timing chart showing the drive pulse and 1-line data processing
in the conventional line sensor; and
FIG. 10 is a timing chart showing the driving method for the color sensor with
shutter function.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Preferred embodiments of the present invention will now be described in
detail in accordance with the accompanying drawings.
<First Embodiment>
FIG. 1 is a cross-sectional view of an image processing apparatus main body
according to the present embodiment, cut at the center of a lens
108.
Numeral
101 denotes an image processing apparatus to read an original
placed on a platen glass
102, by scanning, convert the read image information
into digital information, and send the image information to a computer;
103,
a first mirror which scan-reads the original placed on the platen glass
102
of the image processing apparatus
101;
104, a second mirror which
moves at a speed ½ of that of the first mirror
103;
105, a fluorescent
lamp which irradiates the original;
106, a reflector which collects light
from the lamp to a reading position;
107, a carriage to which the lamp,
the first mirror, the reflector and the like are fixed;
108, a image formation
lens; and
109, a line sensor which converts the optical image information
into an electric signal. As the first mirror
103 and the second mirror
104
move at speeds in the ratio of 1:0.5, a constant optical distance is maintained
between the original on the platen glass
102 and the line sensor
109.
FIG. 2 is a block diagram of the image processing apparatus.
A lamp inverter
209 turns on a fluorescent lamp
201 based on a
light-source
ON/OFF control signal from a CPU
210. The light from the light source irradiates
the original, and further, reflected light from the original enters the image sensor
203 through a image forming lens
202. The image sensor photoelectric-converts
the reflected light and outputs an electric signal to an analog circuit
204.
The analog circuit
204 performs analog processing such as amplification
on the image signal from the sensor, and sends the signal to the A/D converter
205. The A/D converter
205 converts the analog signal received from
the analog circuit
204 to a digital signal and outputs the signal to a digital
circuit
207. Numeral
206 denotes a memory for temporarily storing
shading data and work data for the CPU
210. In a digital processing block,
necessary processing is performed on the digital image signal outputted from the
A/D converter
205, and the data is sent to a subsequent-stage interface
circuit
208. The interface circuit
208 transmits the processed image
data to a host computer
211 in correspondence with a communication protocol.
A drive circuit
212 outputs various pulses necessary for driving the image
sensor
203, thereby controls the image sensor. The CPU
210 controls
the digital circuit
207, the interface circuit
208, the lamp inverter
209, the drive circuit
212 and the like.
FIG. 3 is a schematic view of the inside of 3-line color line sensor.
Numeral
301 denotes a photoreception storage portion of the color
line sensor which photoelectric-converts light received by photodiodes and stores
electric charge;
302, a shift gate which is closed while the electric charge
is accumulated, and opened when the electric charge accumulated in the storage
portion is moved to a transfer register; and
303, the transfer register
which transfers the electric charge moved from the storage portion to an output
stage, pixel by pixel. In this embodiment, two signals φ
1 and φ
2
are alternately inputted into the transfer register. The electric charge is transferred
by the signals of mutually opposite phases. Numeral
304 denotes a capacitor
temporarily storing the electric charge, which resets the electric charge by a
reset pulse (RS). Numeral
305 denotes a clamp circuit with a voltage clamped
by a clamp pulse (CP) to a reference voltage. The transferred electric charge is
outputted as image data electric signal through an output buffer.
Note that a red color filter is provided in the photoreception storage portion
301 of the line sensor
300a, a green color filter is provided
in the photoreception storage portion
301 of the line sensor
300b,
and a blue color filter is provided in the photoreception accumulation portion
301 of the line sensor
300c, respectively for storing and
transmitting different color signals.
FIG. 4 is a timing chart for explaining a driving method for the line sensor
controlled by a drive circuit, showing processing in 1-line period. Symbol Hsync
denotes a horizontal synchronizing signal of a period required for reading one
image line during which the sensor moves for one line in the subscanning direction.
Symbols SH_R, SH_G and SH_B denote signals respectively supplied to the shift gates
of the sensor. When the signals are at a LOW level, the shift gates are closed,
and when the signals are at a HIGH level, the shift gate is opened, and the electric
charge in the accumulation portion is transferred to the transfer resisters. Symbols
φ
1 and φ
2 denote drive signals for the transfer register.
The electric charge in the transfer register is transferred in correspondence with
frequencies of these signals.
In FIG. 4, the period for one line is divided into three sections. First, immediately
after the first section Hsync, valid image data is read out. All the shift gates
of three line sensors
300a,
300b and
300c
are opened with the Hsync, and electric charge accumulated in a previous line
accumulation section is transferred, and processed as valid image data. In the
previous line, different accumulation periods are set for the respective colors.
The second section is provided for reading the electric charge accumulated in the
photoreception accumulation portion
301 in the first section (B in FIG.
4), and for storing dummy electric charge for setting the third section to be described
later to periods for the respective colors. That is, the timing of transferring
dummy electric charge from the photoreception accumulation portion
301 to
the transfer register
303 is shifted for the respective colors. In the third
section, the accumulation periods are changed in accordance with settings. The
accumulation data in this section are processed in the next line. Further, in the
third section, the dummy electric charge accumulated in the second section is read
(in FIG. 4, C indicates a pulse for reading the dummy electric charge from the
line sensor
300a; D, a pulse for reading the dummy electric charge
from the line sensor
300b; and E, a pulse for reading the dummy electric
charge from the line sensor
300c). In this manner, one line, divided
into a section for electric charge accumulation and sections for data reading,
can be easily controlled. Further, signals to drive the sensor in the reading section
is different from that in the other sections.
FIG. 5 shows the signals φ
1, φ
2, RS and CP in the
reading section. FIG. 6 shows the signals in the dummy section and the accumulation
section. In the present embodiment, in FIG. 6, the electric charge in the register
is transferred at a speed
4 times that in FIG. 5. In this manner, in the
sections other than the reading section, the electric charge is transferred at
a high speed, thereby all the electric charge can be sent even if the electric
charge accumulated in the accumulation period overflows the transfer register
203.
As described above, according to the present embodiment, the complicated 1-line
processing in the line sensor
109 is easily and reliably realized by a simple
method. Further, the accumulation periods can be controlled for respective colors
without providing any particular function such as electronic shutters on the line
sensor side. Further, the accumulation periods can be freely set for the respective
colors without consideration of blooming and/or the limit of hardware processing
speed in the subsequent stage.
<Second Embodiment>
In the above-described first embodiment, one line period is divided into three
sections having independent functions, thereby the accumulation periods can be
controlled for the respective colors. Further, the sensor drive signals used in
the valid data reading section are different from those in other sections. In FIG.
4, the period of dummy section "B" is much shorter than that of reading section
"A". In the present embodiment, the transfer frequency of the sensor for electric
charge transfer is increased such that a product of the duration of the dummy section
and the transfer frequency of the section is greater than the product of the duration
of the reading section and the transfer frequency of the section, i.e., the number
of cycles of the dummy section is greater than that of the reading section.
In this arrangement, in addition to the advantages in the first embodiment, obtained
is an advantage that even if a short dummy section is set, all the electric charge
in the register can be transferred.
<Third Embodiment>
FIG. 7 is a timing chart showing the driving method for the image processing
apparatus according to a third embodiment of the present invention.
In this embodiment, the SH pulses (SH_R, SH_G and SH_B) are periodically applied
during the dummy section, so as to periodically read the accumulated electric charge.
In this arrangement, in addition to the advantages in the first embodiment, obtained
is an advantage that the accumulation period of the dummy section can be prevented
from becoming extremely long.
Note that the present invention also includes a case where, to operate various
devices to realize the functions according to the embodiments, software program
code is provided to a computer in an apparatus or a system connected to the various
devices, and the computer of the system or apparatus (CPU or MPU) operates in accordance
with the accumulated program.
In this case, the above software program code itself realizes the functions according
to the above-described embodiments, and the program code itself, and means for
providing the program code to the computer, e.g., an accumulation medium storing
the program code, constitute the invention. As the accumulation medium storing
the program code, a floppy disk, a hard disk, an optical disk, a magneto-optical
disk, a CD-ROM, a magnetic tape, a non-volatile type memory card, a ROM and the
like can be used.
Furthermore, besides aforesaid functions according to the above embodiments
are realized by executing the program code which is read by a computer, the present
invention includes a case where an OS (operating system) or the like working on
the computer performs a part or entire processes in accordance with designations
of the program code and realizes functions according to the above embodiments.
Furthermore, the present invention also includes a case where, after
the program code read from the accumulation medium is written in a function expansion
card which is inserted into the computer or in a memory provided in a function
expansion unit which is connected to the computer, a CPU or the like contained
in the function expansion card or unit performs a part or entire process in accordance
with designations of the program code and realizes functions of the above embodiments.
In the image processing apparatus according to the present embodiment, in the
first section, valid image data is read, in the third section, the electric charge
accumulation periods are variable for the respective colors, and in the second
section as a dummy section, the function of the third section is complemented.
In this manner, as one line period is divided into first to third sections having
different functions, the line sensor can be easily controlled, and valid electric
charge accumulation period can be easily controlled for the respective colors without
providing any particular mechanism such as shutters to the image sensor.
Further, as the transfer frequency for electric charge transfer in the first
section is different from that in the second and third sections, unnecessary electric
charge can be idle-transferred during a short accumulation period by selecting
a line sensor drive pulse for a normal reading mode or a pulse for a high-speed
mode only for transfer from the register, in one line.
Further, as the second section as a dummy section has a part where accumulated
electric charge is periodically read out, electric charge remaining in the photo
diodes can be removed.
In the above-described embodiments, the accumulation periods can be easily and
reliably controlled for the respective colors by a simple method, and the freedom
of color matching design can be increased in the entire image processing apparatus.
Further, the lengths of the accumulation periods can be freely set for the respective
colors without consideration of blooming and/or the limit of hardware processing
speed in the subsequent stage.
The present invention is not limited to the above embodiments and various changes
and modifications can be made within the spirit and scope of the present invention.
Therefore, to appraise the public of the scope of the present invention, the following
claims are made.
*
