U.S. patent application number 12/962228 was filed with the patent office on 2011-03-31 for method and apparatus for processing images using black character substitution.
This patent application is currently assigned to KABUSHIKI KAISHA TOSHIBA. Invention is credited to Naoyuki MISAKA, Hirokazu Shoda.
Application Number | 20110075004 12/962228 |
Document ID | / |
Family ID | 34911509 |
Filed Date | 2011-03-31 |
United States Patent
Application |
20110075004 |
Kind Code |
A1 |
MISAKA; Naoyuki ; et
al. |
March 31, 2011 |
METHOD AND APPARATUS FOR PROCESSING IMAGES USING BLACK CHARACTER
SUBSTITUTION
Abstract
An image correction section in an image processing section
performs a resolution-enhancing process for an input R signal from
a RED photodiode array 9R1, an input G signal from a GREEN
photodiode array 9G1 and an input B signal from a BLUE photodiode
array 9B1, using an input K signal from a BLACK photodiode array
9K1. The image correction section outputs four signals: an Rc1
signal, a Gc1 signal and a Bc1 signal, which are subjected to the
resolution-enhancing process, and the K signal that is used for the
resolution-enhancing process.
Inventors: |
MISAKA; Naoyuki; (Sunto-gun,
JP) ; Shoda; Hirokazu; (Yokohama-shi, JP) |
Assignee: |
KABUSHIKI KAISHA TOSHIBA
TOSHIBA TEC KABUSHIKI KAISHA
|
Family ID: |
34911509 |
Appl. No.: |
12/962228 |
Filed: |
December 7, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11966217 |
Dec 28, 2007 |
7873230 |
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12962228 |
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10790009 |
Mar 2, 2004 |
7336846 |
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11966217 |
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Current U.S.
Class: |
348/311 ;
348/E5.091 |
Current CPC
Class: |
H04N 1/40068 20130101;
H04N 5/3692 20130101 |
Class at
Publication: |
348/311 ;
348/E05.091 |
International
Class: |
H04N 5/335 20110101
H04N005/335 |
Claims
1. An image input apparatus that inputs an image of an original,
comprising: photoelectric conversion means including a first line
sensor and a second line sensor, the first line sensor being
composed of a plurality of line sensors having different color
filters on light receiving surfaces thereof, and the second line
sensor having no color filter on a light receiving surface thereof;
and correction means for correcting output signals from the plural
line sensors of the first line sensor of the photoelectric
conversion means, using an output signal from the second line
sensor of the photoelectric conversion means.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application is a continuation of U.S.
application Ser. No. 11/966,217, filed Dec. 28, 2007 which is a
continuation of U.S. application Ser. No. 10/790,009, filed Mar. 2,
2004, now U.S. Pat. No. 7,336,846, the entire contents of which is
incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to an image input apparatus
that inputs image information using a 4-line CCD sensor, and an
image processing method.
[0004] 2. Description of the Related Art
[0005] A conventional 3-line CCD sensor having three line sensors
for RED, GREEN and BLUE has been used to read a color image. The
3-line CCD sensor is configured such that color filters of RED,
GREEN and BLUE are disposed on light-receiving surfaces of the
respective three line sensors, and the three line sensors are
arranged in a one-dimensional fashion. Thus, one location on an
original cannot be read at the same time by all the line sensors. A
resultant displacement in the original scan direction is corrected
by performing position correction for image signals read by the
respective line sensors, with use of a memory circuit comprising,
e.g. a line memory.
[0006] Recently, a 4-line CCD sensor having a 4-line architecture
has been marketed as a product. The 4-line CCD sensor is configured
such that a monochromatic line sensor for reading a monochromatic
image, which has no color filter on its light-receiving surface, is
added to the aforementioned 3-line CCD sensor for reading a color
image.
[0007] Jpn. Pat. Appln. KOKAI Publication No. 2003-87556 discloses
a technique wherein a monochromatic original is read with a high
resolution and a color original is read with a high sensitivity. In
this technique, the light receiving areas of pixels are made
different between a line sensor for reading a monochromatic image
and three line sensors for reading a color image.
[0008] However, this CCD line sensor comprises the line sensor for
reading a monochromatic image and the three line sensors for
reading a color image and, compared to the line sensor for reading
a monochromatic image, the three line sensors for reading a color
image are unable to read one location on the original at the same
time, as mentioned above. Consequently, color overlapping of a
black character becomes difficult when the magnification for
reading is changed or non-uniformity occurs in reading speed.
[0009] When the color original is read with high sensitivity by
making the light receiving areas of pixels different between the
line sensor for reading a monochromatic image and the line sensors
for reading a color image, the resolution of the color original
lowers. Although the resolution can be increased by simple linear
interpolation, reproduction of a fine character is degraded by
linear interpolation in the prior art.
BRIEF SUMMARY OF THE INVENTION
[0010] The object of an aspect of the present invention is to
provide an image input apparatus and an image processing method,
which can enhance the quality of image information that is input
using a 4-line CCD sensor.
[0011] According to an aspect of the present invention, there is
provided an image input apparatus that inputs an image of an
original, comprising: photoelectric conversion means including a
first line sensor and a second line sensor, the first line sensor
being composed of a plurality of line sensors having different
color filters on light receiving surfaces thereof, and the second
line sensor having no color filter on a light receiving surface
thereof; and correction means for correcting output signals from
the plural line sensors of the first line sensor of the
photoelectric conversion means, using an output signal from the
second line sensor of the photoelectric conversion means.
[0012] According to another aspect of the present invention, there
is provided an image processing method for an image input apparatus
that inputs an image of an original, comprising: scanning the
original using photoelectric conversion means including a first
line sensor and a second line sensor, the first line sensor being
composed of a plurality of line sensors having different color
filters on light receiving surfaces thereof, and the second line
sensor having no color filter on a light receiving surface thereof;
and correcting output signals from the plural line sensors of the
first line sensor, using an output signal that is produced from the
second line sensor of the photoelectric conversion means by the
scanning of the original.
[0013] Additional objects and advantages of an aspect of the
invention will be set forth in the description which follows, and
in part will be obvious from the description, or may be learned by
practice of the invention. The objects and advantages of an aspect
of the invention may be realized and obtained by means of the
instrumentalities and combinations particularly pointed out
hereinafter.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING
[0014] The accompanying drawings, which are incorporated in and
constitute a part of the specification, illustrate presently
preferred embodiments of the invention, and together with the
general description given above and the detailed description of the
embodiments given below, serve to explain the principles of an
aspect of the invention.
[0015] FIG. 1 schematically shows the structure of an image input
apparatus according to the present invention;
[0016] FIG. 2 schematically shows the structure of a control
board;
[0017] FIG. 3 schematically shows the structure of CCD line
sensors;
[0018] FIG. 4 illustrates processing performed successively by the
CCD sensor, a various analog processing circuit and an image
processing section;
[0019] FIG. 5 shows an example of arrangement of the CCD
sensor;
[0020] FIG. 6 is a view for explaining the pixel size of each line
sensor;
[0021] FIG. 7 is a block diagram schematically showing the
structure of an image processing section in a first embodiment of
the invention;
[0022] FIG. 8 shows structures of respective signals that are input
to an image correction section;
[0023] FIG. 9 shows structures of respective signals that are
subjected to a resolution-enhancing process in the image correction
section and are output;
[0024] FIG. 10 is a block diagram schematically showing the
structure of an image processing section in a modification of the
first embodiment of the invention;
[0025] FIG. 11 shows structures of respective signals that are
subjected to a resolution-enhancing process in the image correction
section and are output;
[0026] FIG. 12 shows a high-resolution BLACK output signal;
[0027] FIG. 13 shows an example of a low-resolution color output
signal, which is read at the same time as the high-resolution BLACK
signal;
[0028] FIG. 14 illustrates an example of the resolution-enhancing
process;
[0029] FIG. 15 shows an example in which the resolution of the
low-resolution color signal is enhanced by simple linear
interpolation;
[0030] FIG. 16 shows an example of arrangement of a CCD sensor
according to a second embodiment of the invention;
[0031] FIG. 17 is a view for explaining the pixel size of each line
sensor;
[0032] FIG. 18 is a block diagram schematically showing the
structure of an image processing section in the second embodiment
of the invention;
[0033] FIG. 19 shows structures of respective signals that are
input to an image correction section;
[0034] FIG. 20 shows structures of respective signals that are
subjected to a correction process in the image correction section
and are output;
[0035] FIG. 21 is a block diagram schematically showing the
structure of an image processing section in a modification of the
second embodiment of the invention;
[0036] FIG. 22 shows structures of respective signals that are
subjected to a correction process in the image correction section
and are output;
[0037] FIG. 23 shows an example in which black lines with the same
density and thickness are arranged;
[0038] FIG. 24 shows an example of color output signals in a case
where luminance values are calculated; and
[0039] FIG. 25 shows a BLACK output signal at the same position as
in the example of the color output signals.
DETAILED DESCRIPTION OF THE INVENTION
[0040] Embodiments of the present invention will now be described
with reference to the accompanying drawings.
[0041] FIG. 1 schematically shows the structure of an image input
apparatus using a CCD line sensor. The image input apparatus, which
is a general scanner, comprises a first carriage 4 including a
light source 1, a reflector 2 for correcting the light distribution
of the light source 1, and a first mirror 3; a second carriage 7
including a second mirror 5 and a third mirror 6; a converging lens
8; a CCD sensor board 10 on which a CCD sensor 9 is mounted; a
control board 11 for controlling the CCD sensor 9 and performing
various processings; a white reference plate 12 serving as a
reference of white color; an original glass 13 on which an original
org is placed; an original hold cover 14 for holding the original
org; and a scanner casing 15 in which all the structural components
are disposed.
[0042] The present invention relates to the CCD sensor 9 and
control board 11.
[0043] The operation of the image input apparatus is described in
brief with reference to FIG. 1.
[0044] Light radiated from the light source 1 passes through the
original glass 13 and illuminates the original org. Distribution of
light radiated from the light source 1 is not uniform, and
non-uniformity in illuminance occurs on the original org. To solve
the problem, reflective light from the reflector 2 is also radiated
on the original org, thereby uniformizing light distribution on the
original org.
[0045] The reflective light from the original org is reflected by
the first mirror 3, second mirror 5 and third mirror 6. Light
coming from the third mirror 6 passes through the converging lens 8
and is focused on the light receiving surface of the CCD sensor 9.
The CCD sensor 9 is mounted on the CCD sensor board 10 and is
controlled by a control signal input from the control board 11.
[0046] The original hold cover 14 serves to bring the to-be-read
surface of the original org, which is placed on the original glass
13, into close contact with the original glass 13.
[0047] An analog signal that is output from the CCD sensor 9
includes a high-frequency distortion due to a conversion efficiency
variance among photoelectric converters, and a low-frequency
distortion due to an aberration resulting from the use of a
reduction-type optical system that includes the converging lens
8.
[0048] This requires data that is to be used as a reference for
normalization correction. In the present embodiment, the reference
data is image data that is obtained by reading the white reference
plate 12.
[0049] FIG. 2 schematically shows the structure of the control
board 11.
[0050] The control board 11 comprises a process IC (CPU) 11A, a
various timing generating circuit 11B, a various analog processing
circuit 11C, a line memory circuit 11D, and an image processing
section 11E.
[0051] The process IC (CPU) 11 performs various processes.
[0052] The various timing generating circuit 11B generates various
timings.
[0053] The various analog processing circuit 11C performs various
processings that range from the processing of analog signals input
from the CCD sensor 9 to the conversion of the analog signals to
digital signals.
[0054] The image processing section 11E performs image correction
such as shading correction for correcting high-frequency and
low-frequency distortions in digital signals produced from the
various analog processing circuit 11C, and inter-line correction
for correcting an inter-line displacement between a plurality of
line sensors.
[0055] The line memory circuit 11D delays image data in units of a
line when the inter-line correction process is carried out.
[0056] The process IC (CPU) 11A controls a CCD sensor control
circuit 19A that is mounted on the CCD sensor board 10, a light
source control circuit 16 that controls light emission of the light
source 1, and a drive system control circuit 17 that controls a
motor 18 for driving the first carriage 4 and second carriage
7.
[0057] The CCD sensor board 10 comprises the CCD sensor 9, the CCD
sensor control circuit 10A for driving the CCD sensor 9, and a CCD
driver 10B that receives an output from the CCD sensor control
circuit 10A and generates proper driving conditions for the CCD
sensor 9.
[0058] FIG. 3 schematically shows the structure of the CCD sensor
9.
[0059] The CCD sensor 9 is a 4-line CCD sensor and comprises a RED
line sensor 9R, a GREEN line sensor 9G, a BLUE line sensor 9B and a
BLACK line sensor 9K.
[0060] The RED line sensor 9R comprises a RED photodiode array 9R1,
a shift gate 9R2, an analog shift register 9R3, and an output
amplifier 9R4. A RED color filter (not shown) is disposed on the
light receiving surface of the RED photodiode array 9R1. The RED
photodiode array 9R1 converts (photoelectric conversion) incident
light to a charge corresponding to the amount of light, and
accumulates the charge in the respective photodiodes. The
accumulated charge is transferred to the analog shift register 9R3
via the shift gate 9R2 by a control signal SH1 that is applied to
the shift gate 9R2. The charge that has been transferred to the
analog shift register 9R3 is successively delivered to the
rear-stage output amplifier 9R4 by control signals .phi.1 and
.phi.2. The output amplifier 9R4 outputs the charge as an output
signal OUT1.
[0061] The GREEN line sensor 9G comprises a GREEN photodiode array
9G1, a shift gate 9G2, an analog shift register 9G3, and an output
amplifier 9G4 A GREEN color filter (not shown) is disposed on the
light receiving surface of the GREEN photodiode array 9G1. The
GREEN photodiode array 9G1 converts (photoelectric conversion)
incident light to a charge corresponding to the amount of light,
and accumulates the charge in the respective photodiodes. The
accumulated charge is transferred to the analog shift register 9G3
via the shift gate 9G2 by a control signal SH2 that is applied to
the shift gate 9G2. The charge that has been transferred to the
analog shift register 9G3 is successively delivered to the
rear-stage output amplifier 9G4 by control signals .phi.1 and
.phi.2. The output amplifier 9G4 outputs the charge as an output
signal OUT2.
[0062] The BLUE line sensor 9B comprises a BLUE photodiode array
9B1, a shift gate 9B2, an analog shift register 9B3, and an output
amplifier 9B4. A BLUE color filter (not shown) is disposed on the
light receiving surface of the BLUE photodiode array 9B1. The BLUE
photodiode array 9B1 converts (photoelectric conversion) incident
light to a charge corresponding to the amount of light, and
accumulates the charge in the respective photodiodes. The
accumulated charge is transferred to the analog shift register 9B3
via the shift gate 9B2 by a control signal SH3 that is applied to
the shift gate 9B2. The charge that has been transferred to the
analog shift register 9B3 is successively delivered to the
rear-stage output amplifier 9B4 by control signals .phi.1 and
.phi.2. The output amplifier 9B4 outputs the charge as an output
signal OUT3.
[0063] The BLACK line sensor 9K comprises a BLACK photodiode array
9K1, a shift gate 9K2, an analog shift register 9K3, and an output
amplifier 9K4. No color filter is disposed on the light receiving
surface of the BLACK photodiode array 9K1. The BLACK photodiode
array 9K1 converts (photoelectric conversion) incident light to a
charge corresponding to the amount of light, and accumulates the
charge in the respective photodiodes. The accumulated charge is
transferred to the analog shift register 9K3 via the shift gate 9K2
by a control signal SH4 that is applied to the shift gate 9K2. The
charge that has been transferred to the analog shift register 9K3
is successively delivered to the rear-stage output amplifier 9K4 by
control signals .phi.1 and .phi.2. The output amplifier 9K4 outputs
the charge as an output signal OUT4.
[0064] In the CCD sensor 9, the above-described photodiode arrays,
shift gates, analog shift registers and output amplifiers are
disposed at predetermined positions.
[0065] FIG. 4 illustrates processing that is performed successively
by the CCD sensor 9, the various analog processing circuit 11C and
the image processing section 11E. In FIG. 4, depiction of the
above-described structure of the various analog processing circuit
11C is partly omitted.
[0066] The output signal OUT1 from the RED line sensor 9R of the
CCD sensor 9 is subjected to amplitude adjustment in a gain
amplifier circuit (PGA-R) 22R. An ADC section 25R converts the
amplitude-adjusted analog signal to a digital signal, and outputs
the digital signal to the image processing section 11E.
[0067] Similarly, the output signal OUT2 from the GREEN line sensor
9G of the CCD sensor 9 is subjected to amplitude adjustment in a
gain amplifier circuit (PGA-G) 22G. An ADC section 25G converts the
amplitude-adjusted analog signal to a digital signal, and outputs
the digital signal to the image processing section 11E.
[0068] Similarly, the output signal OUT3 from the BLUE line sensor
9B of the CCD sensor 9 is subjected to amplitude adjustment in a
gain amplifier circuit (PGA-B) 22B. An ADC section 25B converts the
amplitude-adjusted analog signal to a digital signal, and outputs
the digital signal to the image processing section 11E.
[0069] Similarly, the output signal OUT4 from the BLACK line sensor
9K of the CCD sensor 9 is subjected to amplitude adjustment in a
gain amplifier circuit (PGA-BLACK) 22K. An ADC section 25K converts
the amplitude-adjusted analog signal to a digital signal, and
outputs the digital signal to the image processing section 11E.
[0070] The image processing section 11E performs, for instance,
shading correction, inter-line correction, and a process for
correcting the RED, GREEN and BLUE output signals on the basis of
the BLACK output signal. The processed signals are output to the
rear-stage image processing system (engine section).
[0071] According to the present invention, in the 4-line CCD sensor
that outputs RED, GREEN, BLUE and BLACK signals, the image
processing section 11E shown in FIG. 4 performs an image process
for correcting the RED, GREEN and BLUE output signals by using the
BLACK output signal, thereby producing corrected RED, GREEN and
BLUE signals.
[0072] Next, a first embodiment of the invention with the
above-described structure will be described.
[0073] The first embodiment is associated with a process in a case
where the resolution of each of the output signals from the RED
line sensor 9R, GREEN line sensor 9G and BLUE line sensor 9B
differs from the resolution of the output signal from the BLACK
line sensor 9K.
[0074] FIG. 5 shows an example of arrangement of the CCD sensor 9.
In this example of arrangement, the RED photodiode array 9R1 is
disposed as a first array in the original scan direction. Next, the
GREEN photodiode array 9G1 is disposed. Then, the BLUE photodiode
array 9B1 is disposed. At last, the BLACK photodiode array 9K1 is
disposed.
[0075] The size of each photodiode (hereinafter referred to as
"pixel size") in each of the RED photodiode array 9R1, GREEN
photodiode array 9G1 and BLUE photodiode array 9B1 is larger than
the pixel size of the BLACK photodiode array 9K1. Accordingly, the
number of pixels in each of the RED photodiode array 9R1, GREEN
photodiode array 9G1 and BLUE photodiode array 9B1 is less than the
number of pixels in the BLACK photodiode array 9K1.
[0076] In the first embodiment, as shown in FIG. 6, the pixel size
of the BLACK photodiode array is set at a.times.a, and the pixel
size of each of the RED photodiode array 9R1, GREEN photodiode
array 9G1 and BLUE photodiode array 9B1 is set at (a.times.2)
.times.(a.times.2).
[0077] Since each photodiode array has the same longitudinal
length, the number of pixels of each of the RED photodiode array
9R1, GREEN photodiode array 9G1 and BLUE photodiode array 9B1 is
half the number of pixels of the BLACK photodiode array 9K1.
[0078] When an A4-size paper sheet with a longitudinal length of
297 mm is read with a resolution of 600 dpi, the number of pixels
that is required is 600 dpi/25.4 mm.times.297 mm=7015.7. Thus, the
BLACK photodiode array 9K1 needs to have at least 7016 pixels.
[0079] If an error in attachment of the CCD sensor 9 or an error in
placing the original org is taken into account, the BLACK
photodiode array 9K1 needs to have (7016+a) pixels. Assume that the
number of pixels of the BLACK photodiode array 9K1 is 7500.
[0080] In this case, the number of pixels in each of the RED
photodiode array 9R1, GREEN photodiode array 9G1 and BLUE
photodiode array 9B1 is 3750 (1/2 of 7500).
[0081] When an image is read by using the CCD sensor 9 of the first
embodiment, the resolution of each of the output signals from the
RED photodiode array 9R1, GREEN photodiode array 9G1 and BLUE
photodiode array 9B1 is lower than the resolution of the output
signal from the BLACK photodiode array 9K1.
[0082] In this case, in the first embodiment, the output signals
from the RED photodiode array 9R1, GREEN photodiode array 9G1 and
BLUE photodiode array 9B1 are corrected on the basis of the output
signal from the BLACK photodiode array 9K1 (hereinafter referred to
as "resolution-enhancing process"). The resolution-enhancing
process is carried out to produce RED, GREEN and BLUE signals each
having a resolution substantially equal to the resolution of the
output signal from the BLACK photodiode array 9K1.
[0083] Next, image processes including the resolution-enhancing
process in the image processing section 11E of the first embodiment
are described.
[0084] FIG. 7 schematically shows the structure of the image
processing section 11E. The image processing section 11E comprises
a shading correction section 31, an inter-line correction section
32, an image correction section 33, a filter process section 34, an
image region discrimination section 35 and a color conversion
section 36.
[0085] Assume that an output signal from the BLACK photodiode array
9K1 is a K signal, an output signal from the RED photodiode array
9R1 is an R signal, an output signal from the GREEN photodiode
array 9G1 is a G signal, and an output signal from the BLUE
photodiode array 9B1 is a B signal.
[0086] The K signal, R signal, G signal and B signal are subjected
to shading correction in the shading correction section 31. The
shading-corrected signals are subjected to inter-line correction
for positioning in the inter-line correction section 32. The K
signal, R signal, G signal and B signal, which have been subjected
to inter-line correction, are input to the image correction section
33.
[0087] Using the input K signal, the image correction section 33
subjects the R signal, G signal and B signal to the
resolution-enhancing process. The image correction section 33
outputs four signals: an Rc1 signal, a Gc1 signal and a Bc1 signal,
which are produced by the resolution-enhancing process, and the K
signal that is used for the resolution-enhancing process.
[0088] The resolution-enhancing process in the image correction
section 33 is described in greater detail.
[0089] The pixel size of RED, GREEN and BLUE is double the pixel
size of BLACK. Thus, if the K signal that is input to the image
correction section 33 comprises components K01, K02, K03 and K04,
the R signal comprises components R01 and R02, the G signal
comprises components G01 and G02, and the B signal comprises
components B01 and B02.
[0090] FIG. 8 shows the configuration of the K signal (K01, K02,
K03, K04), the R signal (R01, R02), the G signal (G01, G02) and the
B signal (B01, B02).
[0091] The image correction section 33 subjects the R signal to the
resolution-enhancing process so that it may have a pixel size that
is equal to the pixel size of the K signal (BLACK). Thus, the image
correction section 33 outputs a RED correction signal comprising
Rc01, Rc02, Rc03 and Rc04. Similarly, the image correction section
33 subjects the G signal to the resolution-enhancing process and
outputs a GREEN correction signal comprising Gc01, Gc02, Gc03 and
Gc04. The image correction section 33 subjects the B signal to the
resolution-enhancing process and outputs a BLUE correction signal
comprising Bc01, Bc02, Bc03 and Bc04. In addition, the image
correction section 33 outputs K01, K02, K03 and K04 of the K
signal, which have been used for the resolution-enhancing
process.
[0092] FIG. 9 shows the configuration of the K signal (K01, K02,
K03, K04), the R signal (Rc01, Rc02, Rc03, Rc04), the G signal
(Gc01, Gc02, Gc03, Gc04) and the B signal (Bc01, Bc02, Bc03, Bc04),
which are produced by the resolution-enhancing process in the image
correction section 33.
[0093] In FIG. 7, these four signals are output from the image
correction section 33 as the K signal, Rc1 signal, Gc1 signal and
Bc1 signal.
[0094] The K signal, Rc1 signal Gc1 signal and Bc1 signal are
successively subjected to a filter process in the filter process
section 34, an image region discrimination process in the image
region discrimination section 35, and a color conversion process in
the color conversion section 36.
[0095] In the image process section 11E, a Kc1 signal, a Cc1 signal
(CYAN), an Mc1 signal (MAGENTA) and a Yc1 signal (YELLOW), which
are output from the color conversion section 36, are delivered to
the rear-stage image processing system.
[0096] FIG. 10 schematically shows the structure of an image
processing section 11E according to a modification of the first
embodiment shown in FIG. 7. The image processing section 11E
comprises a shading correction section 31, an inter-line correction
section 32, an image correction section 43, a filter process
section 34, an image region discrimination section 35 and a color
conversion section 36. The parts common to those in the first
embodiment are denoted by like reference numerals, and a
description thereof is omitted.
[0097] The K signal, R signal, G signal and B signal are subjected
to shading correction in the shading correction section 31. The
shading-corrected signals are subjected to inter-line correction
for positioning in the inter-line correction section 32. The K
signal, R signal, G signal and B signal, which have been subjected
to inter-line correction, are input to the image correction section
43.
[0098] Using the input K signal, the image correction section 43
subjects the R signal, G signal and B signal to the
resolution-enhancing process. The image correction section 43
outputs an Rc2 signal, a Gc2 signal and a Bc2 signal, which are
produced by the resolution-enhancing process.
[0099] The resolution-enhancing process in the image correction
section 43 is described in greater detail.
[0100] The pixel size of RED, GREEN and BLUE is double the pixel
size of BLACK. Thus, if the K signal that is input to the image
correction section 43 comprises components K01, K02, K03 and K04,
the R signal comprises components R01 and R02, the G signal
comprises components G01 and G02, and the B signal comprises
components B01 and B02. This is the same as in the structure shown
in FIG. 8.
[0101] The image correction section 43 subjects the R signal to the
resolution-enhancing process so that it may have a pixel size that
is equal to the pixel size of the K signal (BLACK). Thus, the image
correction section 43 outputs a RED correction signal comprising
Rc11, Rc12, Rc13 and Rc14. Similarly, the image correction section
43 subjects the G signal to the resolution-enhancing process and
outputs a GREEN correction signal comprising Gc11, Gc12, Gc13 and
Gc14. The image correction section 43 subjects the B signal to the
resolution-enhancing process and outputs a RED correction signal
comprising Bc11, Bc12, Bc13 and Bc14.
[0102] FIG. 11 shows the configuration of the R signal (Rc11, Rc12,
Rc13, Rc14), the G signal (Gc11, Gc12, Gc13, Gc14) and the B signal
(Bc11, Bc12, Bc13, Bc14), which are produced by the
resolution-enhancing process in the image correction section
43.
[0103] In FIG. 10, these three signals are output from the image
correction section 43 as the Rc2 signal, Gc2 signal and Bc2
signal.
[0104] The Rc2 signal Gc2 signal and Bc2 signal are successively
subjected to a filter process in the filter process section 34, an
image region discrimination process in the image region
discrimination section 35, and a color conversion process in the
color conversion section 36.
[0105] In the image process section 11E, a Cc2 signal (CYAN), an
Mc2 signal (MAGENTA) and a Yc2 signal (YELLOW), which are output
from the color conversion section 36, are delivered to the
rear-stage image processing system.
[0106] The details of the resolution-enhancing process are
described below.
[0107] In an example of the resolution-enhancing process, RED,
GREEN and BLUE output signals are corrected with reference to a
high-resolution BLACK output signal.
[0108] FIG. 12 shows a high-resolution BLACK output signal.
[0109] FIG. 13 shows an example of a low-resolution color output
signal, which is read at the same time as the high-resolution BLACK
signal shown in FIG. 12.
[0110] The ordinate indicates an output signal luminance value, and
the abscissa indicates the number of pixels. Broken lines indicate
division lines in units of 300 dpi. If the reading by a
high-resolution sensor and the reading by a low-resolution sensor
are compared, it is understood that high-luminance portions and
low-luminance portions of the output signal are rounded in the case
of the low-resolution reading. In the resolution-enhancing process,
the above two output signals are used to obtain a high-resolution
color signal.
[0111] FIG. 14 illustrates an example of the resolution-enhancing
process. The ordinate indicates an output signal luminance value,
and the abscissa indicates the number of pixels. Broken lines
indicate division lines in units of 300 dpi. A thick solid line
indicates an output signal after the resolution-enhancing process,
and a thick broken line indicates an input low-resolution color
signal. Arrows indicate directions of correction.
[0112] The high-resolution BLACK signal and low-resolution color
signal are superimposed on each other. Referring to the BLACK
output signal, the low-resolution signal is corrected so as to
conform to the BLACK signal. By carrying out this
resolution-enhancing process, a high-resolution color image can be
obtained.
[0113] FIG. 15 shows an example in which the resolution of the
low-resolution color signal shown in FIG. 13 is enhanced by simple
linear interpolation. If FIG. 14 and FIG. 15 are compared, it is
understood that in FIG. 14 high-luminance portions and
low-luminance portions of the output signal are clearly
reproduced.
[0114] As illustrated in the first embodiment and the modification
thereof, each of the low-resolution RED, GREEN and BLUE output
signals can be made to conform to the resolution of the BLACK
output signal by the above-described resolution-enhancing process.
Thus, high-resolution RED, GREEN and BLUE correction signals are
obtained.
[0115] A second embodiment of the present-invention will now be
described.
[0116] The second embodiment is associated with a process in a case
where the resolution of each of the output signals from the RED,
GREEN and BLUE sensors is equal to the resolution of the output
signal from the BLACK sensor.
[0117] FIG. 16 shows an example of arrangement of the CCD sensor 9
according to the second embodiment. In this example of arrangement,
a RED photodiode array 9R1-2 is disposed as a first array in the
original scan direction. A GREEN photodiode array 9G1-2 is then
disposed. Subsequently, a BLUE photodiode array 9B1-2 is disposed.
At last, a BLACK photodiode array 9K1-2 is disposed.
[0118] The size of each photodiode (hereinafter referred to as
"pixel size") in each of the RED photodiode array 9R1-2, GREEN
photodiode array 9G1-2 and BLUE photodiode array 9B1-2 is equal to
the pixel size of the BLACK photodiode array 9K1-2.
[0119] In the second embodiment, as shown in FIG. 17, the pixel
size of the BLACK photodiode array 9K1-2 is set at a.times.a, and
the pixel size of each of the RED photodiode array 9R1-2, GREEN
photodiode array 9G1-2 and BLUE photodiode array 9B1-2 is set at
a.times.a. Since each photodiode array has the same longitudinal
length, the number of pixels of each of the RED photodiode array
9R1-2, GREEN photodiode array 9G1-2 and BLUE photodiode array 9B1-2
is equal to the number of pixels of the BLACK photodiode array
9K1-2.
[0120] When an A4-size paper sheet with a longitudinal length of
297 mm is read with a resolution, of 600 dpi, the number of pixels
that is required is 600 dpi/25.4 mm.times.297 mm=7015.7. Thus, the
BLACK photodiode array 9K1-2 needs to have at least 7016
pixels.
[0121] If an error in attachment of the CCD sensor 9 or an error in
placing the original org is taken into account, the BLACK
photodiode array 9K1-2 needs to have (7016+a) pixels. Assume that
the number of pixels of the BLACK photodiode array 9K1-2 is
7500.
[0122] In this case, the number of pixels in each of the RED
photodiode array 9R1-2, GREEN photodiode array 9G1-2 and BLUE
photodiode array 9B1-2 is 7500, which is equal to the number of
pixels in the BLACK photodiode array 9K1-2.
[0123] When an image is read by using the CCD sensor 9 of the
second embodiment, the output signals from the RED photodiode array
9R1-2, GREEN photodiode array 9G1-2, BLUE photodiode array 9B1-2
and the BLACK photodiode array 9K1-2 have the same resolution.
[0124] In this case, in the second embodiment, a black character
substitution process is performed for the output signals from the
RED photodiode array 9R1-2, GREEN photodiode array 9G1-2 and BLUE
photodiode array 9B1-2 on the basis of the output signal from the
BLACK photodiode array 9K1-2. The details of the black character
substitution process will be described later.
[0125] Next, image processes including the correction process in
the image processing section 11E of the second embodiment are
described.
[0126] FIG. 18 schematically shows the structure of the image
processing section 11E according to the second embodiment. The
image processing section 11E comprises a shading correction section
51, an inter-line correction section 52, an image correction
section 53, a filter process section 54, an image region
discrimination section 55, a color conversion section 56, and an
image region discrimination section 57.
[0127] Assume that an output signal from the BLACK photodiode array
9K1-2 is a K signal, an output signal from the RED photodiode array
9R1-2 is an R signal, an output signal from the GREEN photodiode
array 9G1-2 is a G signal, and an output signal from the BLUE
photodiode array 9B1-2 is a B signal.
[0128] The K signal, R signal, G signal and B signal are subjected
to shading correction in the shading correction section 51. The
shading-corrected signals are subjected to inter-line correction
for positioning in the inter-line correction section 52. The K
signal, R signal, G signal and B signal, which have been subjected
to inter-line correction, are input to the image correction section
53. At the same time, the R signal, G signal and B signal are input
to the image region discrimination section 57.
[0129] The image region discrimination section 57 determines
(discriminates) the position of a black part, such as a black
character or a black line, on the basis of the input R signal, G
signal and B signal, and delivers the discrimination information to
the image correction section 53.
[0130] Based on the information from the image region
discrimination section 57, the image correction section 53 performs
the black character substitution process for the R signal, G signal
and B signal by using the K signal. The image correction section 53
outputs four signals: an Rc3 signal, a Gc3 signal and a Bc3 signal,
which have been subjected to the black character substitution
process, and the K signal that has been used for the black
character substitution process.
[0131] The pixel size of RED, GREEN and BLUE is equal. Thus, if the
K signal that is input to the image correction section 53 comprises
components K21, K22, K23 and K24, the R signal comprises components
R21, R22, R23 and R24, the G signal comprises components G21, G22,
G23 and G24, and the B signal comprises components B21, B22, B23
and B24.
[0132] FIG. 19 shows the configuration of the K signal (K21, K22,
K23 and K24), the R signal (R21, R22, R23 and R24), the G signal
(G21, G22, G23 and G24) and the B signal (B21, B22, B23 and
B24).
[0133] The image correction section 53 subjects the R signal, G
signal and B signal to the black character substitution process by
using K21, K22, K23 and K24 of the K signal, on the basis of the
information from the image region discrimination section 57. Thus,
the image correction section 53 outputs a RED correction signal
comprising Rc21, Rc22, Rc23 and Rc24, a GREEN correction signal
comprising Gc21, Gc22, Gc23 and Gc24, a BLUE correction signal
comprising Bc21, Bc22, Bc23 and Bc24. Each of the RED correction
signal, GREEN correction signal and BLUE correction signal has the
same pixel size as the K signal. In addition, the image correction
section 53 outputs K21, K22, K23 and K24 of the K signal, which
have been used for the correction process.
[0134] FIG. 20 shows the configuration of the K signal (K21, K22,
K23, K24), the R signal (Rc21, Rc22, Rc23, Rc24), the G signal
(Gc21, Gc22, Gc23, Gc24) and the B signal (Bc21, Bc22, Bc23, Bc24),
which are produced by the correction process in the image
correction section 53.
[0135] In FIG. 18, these four signals are output as the K signal,
Rc3 signal, Gc3 signal and Bc3 signal.
[0136] The K signal, Rc3 signal Gc3 signal and Bc3 signal are
successively subjected to a filter process in the filter process
section 54, an image region discrimination process in the image
region discrimination section 55, and a color conversion process in
the color conversion section 56.
[0137] In the image process section 11E, a Kc3 signal, a Cc3 signal
(CYAN), an Mc3 signal (MAGENTA) and a Yc3 signal (YELLOW), which
are output from the color conversion section 56, are delivered to
the rear-stage image processing system.
[0138] FIG. 21 schematically shows the structure of an image
processing section 11E according to a modification of the second
embodiment shown in FIG. 18. The image processing section 11E
according to the modification of the second embodiment comprises a
shading correction section 51, an inter-line correction section 52,
an image correction section 63, a filter process section 54, an
image region discrimination section 55, a color conversion section
56 and an image region discrimination section 57. The parts common
to those in the second embodiment are denoted by like reference
numerals, and a description thereof is omitted.
[0139] The K signal, R signal, G signal and B signal are subjected
to shading correction in the shading correction section 51. The
shading-corrected signals are subjected to inter-line correction
for positioning in the inter-line correction section 52. In
addition, the R signal, G signal and B signal are input to the
image region discrimination section 57.
[0140] The image region discrimination section 57 discriminates the
position of a black part, such as a black character or a black
line, on the basis of the input R signal, G signal and B signal,
and delivers the discrimination information to the image correction
section 63.
[0141] Based on the information from the image region
discrimination section 57, the image correction section 63 performs
the black character substitution process for the R signal, G signal
and B signal by using the K signal. The image correction section 63
outputs an Rc4 signal, a Gc4 signal and a Bc4 signal, which have
been subjected to the black character substitution process.
[0142] The correction process in the image correction section 63 is
described in greater detail.
[0143] The pixel size of RED, GREEN and BLUE is equal. Thus, if the
K signal that is input to the image correction section 63 comprises
components K21, K22, K23 and K24, the R signal comprises components
R21, R22, R23 and R24, the G signal comprises components G21, G22,
G23 and G24, and the B signal comprises components B21, B22, B23
and B24. This is the same as in the structure shown in FIG. 19.
[0144] The image correction section 63 subjects the R signal, G
signal and B signal to the correction process by using K21, K22,
K23 and K24 of the K signal, on the basis of the information from
the image region discrimination section 57. Thus, the image
correction section 63 outputs a RED correction signal comprising
Rc31, Rc32, Rc33 and Rc34, a GREEN correction signal comprising
Gc31, Gc32, Gc33 and Gc34, a BLUE correction signal comprising
Bc31, Bc32, Bc33 and Bc34. Each of the RED correction signal, GREEN
correction signal and BLUE correction signal has the same pixel
size as the K signal.
[0145] FIG. 22 shows the configuration of the R signal (Rc31, Rc32,
Rc33, Rc34), the G signal (Gc31, Gc32, Gc33, Gc34) and the B signal
(Bc31, Bc32, Bc33, Bc34), which are produced by the correction
process in the image correction section 63.
[0146] In FIG. 21, these three signals are output from the image
correction section 63 as the Rc4 signal, Gc4 signal and Bc4
signal.
[0147] The Rc4 signal Gc4 signal and Bc4 signal are successively
subjected to a filter process in the filter process section 54, an
image region discrimination process in the image region
discrimination section 55, and a color conversion process in the
color conversion section 56.
[0148] In the image process section 11E, a Cc4 signal (CYAN), an
Mc4 signal (MAGENTA) and a Yc4 signal (YELLOW), which are output
from the color conversion section 56, are delivered to the
rear-stage image processing system.
[0149] The details of the black character substitution are
described below.
[0150] In the prior-art 3-line sensor that outputs RED, GREEN and
BLUE signals, when a black character is read, the black character
is expressed by overlapping three colors. In this case, color
misregistration may occur due to aberration of the lens or
non-uniformity in rotation of the motor. Because of a failure in
color overlapping, a black character with a uniform density may not
be read with a uniform density, resulting in a non-uniform output
signal. Further, color overlapping becomes more difficult, for
example, when the magnification for reading is changed.
[0151] In the image processing according to the second embodiment,
an image region discrimination is performed based on the RED, GREEN
and BLUE output signals. If a black character is determined, the
BLACK output signal is substituted for the RED, GREEN and BLUE
output signals.
[0152] When a black character is read by the BLACK sensor, only one
output is obtained. Hence, no color misregistration occurs due to
aberration of the lens or non-uniformity in rotation of the motor.
It is less possible that the output signal value varies when the
black character with the same density is read. By executing this
process, it becomes possible to decrease the non-uniformity in
density of the black character or in line width, which results from
aberration of the lens or non-uniform rotation of the motor.
[0153] FIG. 24 shows an example of color output signals that are
obtained when luminance values of a region including black lines
with the same density and thickness, which are arranged as shown in
FIG. 23, are calculated in a direction indicated by a broken line
in FIG. 23.
[0154] FIG. 25 shows a BLACK output signal at the same position as
in the example of the color output signals shown in FIG. 23.
[0155] In FIG. 24, the ordinate indicates an output signal
luminance value, and the abscissa indicates the number of pixels. A
solid line indicates a RED output signal, a dot-and-dash line
indicates a GREEN output signal, and a broken line indicates a BLUE
output signal. As is understood from FIG. 24, high-luminance
portions and low-luminance portions appear with variations due to
slight differences in sensitivity of sensors. If a black signal is
produced from these color signals, it is possible that the density
varies from line to line. Moreover, the line width that is
represented by each output signal may vary due to non-uniform
rotation of the motor or aberration of the lens. If a black signal
is produced from these color signals, it is also possible that the
line thickness varies from line to line.
[0156] By contrast, in the second embodiment, the black character
substitution process is executed using a single-color line (BLACK
output signal) as shown in FIG. 25. It is thus possible to reduce
the non-uniformity in density or line width.
[0157] As has been described above, according to the embodiments of
the present invention, there is provided an image input apparatus
that has a plurality of lines sensors, which have different numbers
of, or the same number of, pixels, and synthesizes output signals
of the line sensors, thereby to form image information. Using the
output signal of the line sensor having no color filter on its
light receiving surface, the output of the line sensor having a
color filter on its light receiving surface is corrected. Thereby,
the following advantages are obtained.
[0158] In a case where the number of pixels of the line sensor
having the color filter on its light receiving surface is less than
the number of pixels of the line sensor having no color filter on
its light receiving surface, a BLACK output signal with a larger
number of pixels is used to perform a resolution conversion process
for RED, GREEN and BLUE output signals with less numbers of pixels.
Thereby, a high image quality is obtained.
[0159] In a case where the number of pixels of the line sensor
having the color filter on its light receiving surface is equal to
the number of pixels of the line sensor having no color filter on
its light receiving surface, image information that is obtained by
synthesizing RED, GREEN and BLUE output signals is subjected to an
image region discrimination process. If the image information is
determined to be a black character or a black part, a BLACK output
signal is substituted. Thereby, it becomes possible to reduce
non-uniformity in density of a black character or non-uniformity in
line width associated with the RED, GREEN and BLUE output signals,
which results from aberration in the black character or black part
or non-uniform rotation of the motor. Thus, a high image quality
can be obtained.
[0160] Additional advantages and modifications will readily occur
to those skilled in the art. Therefore, the invention in its
broader aspects is not limited to the specific details and
representative embodiments shown and described herein. Accordingly,
various modifications may be made without departing from the spirit
or scope of the general inventive concept as defined by the
appended claims and their equivalents.
* * * * *