U.S. patent application number 09/196112 was filed with the patent office on 2002-06-27 for color image reading apparatus.
Invention is credited to HOSHUYAMA, HIDEO, KAWAHARA, ATSUSHI.
Application Number | 20020080432 09/196112 |
Document ID | / |
Family ID | 18112183 |
Filed Date | 2002-06-27 |
United States Patent
Application |
20020080432 |
Kind Code |
A1 |
KAWAHARA, ATSUSHI ; et
al. |
June 27, 2002 |
COLOR IMAGE READING APPARATUS
Abstract
A color image reading apparatus includes a color separation unit
to separate a color of an image of an object into more than three
visible color wavelength components in a visible wavelength range
and an image sensing unit to read the image of the object whose
color is separated by the color separation unit and outputting
image signals of the respective colors. The apparatus also has a
color calculation circuit to calculate image data of not less than
three colors from the image signals corresponding to the colors
separated by said color separation unit.
Inventors: |
KAWAHARA, ATSUSHI;
(MELVILLE, NY) ; HOSHUYAMA, HIDEO; (KAWASAKI-SHI,
JP) |
Correspondence
Address: |
DAVID M PITCHER
STAAS & HALSEY
700 11TH ST NW
SUITE 500
WASHINGTON
DC
20001
|
Family ID: |
18112183 |
Appl. No.: |
09/196112 |
Filed: |
November 20, 1998 |
Current U.S.
Class: |
358/515 |
Current CPC
Class: |
H04N 1/484 20130101;
H04N 1/488 20130101 |
Class at
Publication: |
358/515 |
International
Class: |
H04N 001/46 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 20, 1997 |
JP |
9-319608 |
Claims
What is claimed is:
1. A color image reading apparatus comprising: a color separation
unit to separate a color of an image of an object into more than
three visible color wavelength components in a visible wavelength
range; an image sensing unit to read the image of the object whose
color is separated by said color separation unit and outputting
image signals of the respective colors; and a color calculation
circuit to calculate image data of not less than three colors from
the image signals corresponding to the colors separated by said
color separation unit.
2. An apparatus according to claim 1, further comprising a reading
mode setting unit for setting any one of a first mode in which the
color of the image of the object is separated into three visible
color wavelength components by said color separation unit and a
second mode in which the color of the image of the object is
separated into more than three visible color wavelength components
by said color separation unit, and wherein said color separation
unit separates the color of the image of the object in accordance
with setting by said reading mode setting unit.
3. An apparatus according to claim 2, wherein said color
calculation circuit calculates the image data of not less than
three colors from the image signals of three colors when the first
mode is set by said reading mode setting unit, and calculates the
image data of not less than three colors from the image signals of
not less than four colors when the second mode is set by said
reading mode setting unit.
4. An apparatus according to claim 1, wherein said color separation
unit comprises a light source for emitting light components of more
than three different colors, and a color selection circuit for
causing said light source to emit light while selecting one or some
of the colors.
5. An apparatus according to claim 4, further comprising multiple
color simultaneous emission mode setting means for setting a
multiple color simultaneous emission mode, and wherein in
separating a specific color, said color selection circuit causes
said light source to emit at least two colors simultaneously on the
basis of setting by said multiple color simultaneous emission mode
setting means.
Description
[0001] The entire disclosure of Japanese Patent Application No.
9-319608 including specifications, claims, drawings, and summaries
is incorporated herein by reference in their entirety.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a color image reading
apparatus.
[0004] 2. Related Background Art
[0005] A color image reading apparatus for switching illumination
light generally uses three light sources for emitting red (R),
green (G), and blue (B) light components, respectively. The
wavelength of illumination light is switched by sequentially
switching the light source to be turned on.
[0006] A color image is reproduced on the basis of R, G, and B
image componentswhich have been read using an R, G, and B light
sources, respectively.
[0007] The conventional color image reading apparatus uses a
fluorescent lamp or the like as a light source. Some recent
apparatuses use a light-emitting diode as a light source.
[0008] Recent light-emitting diodes are quite useful as
illumination light sources because of high luminance. In addition,
various light-emitting diodes having different emission wavelengths
are available.
[0009] When light-emitting diodes are used as light sources, three
light-emitting diodes, i.e., a red light-emitting diode having a
peak emission wavelength in the range longer than 600 [nm], a green
light-emitting diode having a peak emission wavelength near 550
[nm], and a blue light-emitting diode having a peak emission
wavelength in the range shorter than 500 [nm] are used.
[0010] Popular color image reading apparatuses directly output the
data of read R (red), G (green), and B (blue) color components. On
the other hand, some color image reading apparatuses execute color
correction calculation to improve color reproducibility. As the
color correction calculation, for example, 3.times.3 matrix
calculation is performed.
[0011] The conventional color image reading apparatuses cannot
obtain sufficient color reproduction performance when an image is
read from an original such as a color reversal film with a wide
color gamut. That is, the color image reading apparatuses fail to
provide satisfactory color reproduction capability. Especially,
when a film having four photosensitive layers is used as an
original, the color development characteristics of the film are
more complex than the color reproduction capability of the color
image reading apparatus. For this reason, the color difference
between the actual original image and the read image becomes more
conspicuous.
[0012] The color reproducibility is somewhat improved by executing
color correction calculation. However, the color reproducibility is
still poor. Especially, when a film having four photosensitive
layers is used as an original, further improvement of color
reproducibility is required.
[0013] Color image reading apparatuses sequentially read images of
the R, G, and B color components. This prolongs the image reading
time as compared to monochrome reading.
[0014] When the emission intensity of the illumination light source
is low, the illuminance of the illuminated original surface is low.
To read the image at a sufficient brightness, the exposure time
(charging time) of the image sensing device must be made longer. As
the exposure time becomes longer, the image reading time also
becomes longer.
SUMMARY OF THE INVENTION
[0015] It is an object of the present invention to improve the
color reproducibility of a color image reading apparatus without
largely increasing cost. It is another object of the present
invention to provide a color image reading apparatus capable of
shortening the image reading time.
[0016] According to the present invention, there is provided a
color image reading apparatus comprising:
[0017] a color separation unit to separate a color of an image of
an object into not less than four visible color wavelength
components in a visible wavelength range;
[0018] an image sensing unit to read the image of the object whose
color is separated by the color separation unit and outputting
image signals of the respective colors; and
[0019] a color calculation circuit to calculate image data of not
less than three colors from the image signals corresponding to the
colors separated by the color separation unit.
[0020] The color image reading apparatus according to one mode of
the present invention has a light source having four or more types
of light emitters which have different peak emission wavelengths in
the visible light range, an illumination optical system for
illuminating an original with light from the light source, an image
forming optical system for forming the image of the original
illuminated by the illumination optical system, a one-dimensional
image sensing unit for reading the image formed by the image
forming optical system as a one-dimensional image, a subscan unit
for moving the position of the original relative to the
one-dimensional image sensing unit in an axial direction crossing
the axial direction of the one-dimensional image, an emission color
switching unit for controlling the state of each of the four or
more types of light emitters to switch the emission color of the
light source, and color calculation means for obtaining three or
more color-converted data on the basis of a plurality of color data
obtained from the image sensing unit.
[0021] In this apparatus, the light source for illuminating the
original has four or more types of light emitters which have
different peak emission wavelengths in the visible light range. The
emission color switching device controls the state of each of the
four or more types of light emitters to switch the emission color
of the light source. The original is illuminated with light from
the light source through the illumination light system. The image
of the illuminated original is formed on the one-dimensional image
sensing device by the image forming optical system. The
one-dimensional image sensing device reads the image formed by the
image forming optical system as a one-dimensional image. Since the
subscan means moves the position of the original relative to the
one-dimensional image sensing means in the axial direction crossing
the axial direction of the one-dimensional image, the
two-dimensional image of the original can be read.
[0022] The color calculation means obtains three or more
color-converted data on the basis of a plurality of color data
obtained from the image sensing means. For example, when five types
of light emitters of R (red), Y (yellow), G (green), C (cyan), and
B (blue) are used, the image of each of the R, Y, G, C, and B color
components can be sequentially read.
[0023] To output color image data having three color components of
R, G, and B, which are generally used, image data of three color
components of R, G, and B are generated from image data of each of
the color components of R, Y, G, C, and B by calculation
(conversion) by the color calculation means. The color data of the
image generated on the basis of the image data of four or more
color components has good color reproducibility as compared to
color data obtained by the conventional image reading apparatus.
Therefore, even when a film having four photosensitive layers is
used as an original, the color image reading apparatus of the
present invention can reproduce the color of the original image
more accurately.
[0024] In this color image reading apparatus, the emission color
switching means may have, as a reading mode, a first mode in which
the emission color of the light source is sequentially switched to
any one of three colors, and a second mode in which the emission
color of the light source is sequentially switched to any one of N
colors (N.gtoreq.4). More preferably, the color calculation means
automatically may switch the contents of formulas representing the
correlation between the input color data of three or more colors
and output color data of three or more colors in accordance with
the reading mode of the emission color switching means.
[0025] When images of four or more color components are to be
sequentially read, in some cases, the reading time may become
longer than that in reading images of three color components due to
more complicated image processing etc. When a film having four
photosensitive layers is used as an original, high color
reproducibility is required for the color image reading apparatus.
However, when the original has a relatively narrow color gamut, it
is sometimes more preferable to shorten the reading time rather
than to increase the color reproducibility. When the first mode in
which the emission color of the light source is sequentially
switched to any one of three colors and the second mode in which
the emission color of the light source is sequentially switched to
any one of N colors (N.gtoreq.4), the color reproducibility is
relatively low while the reading time is relatively short in the
first mode. In the second mode, the color reproducibility is
improved while the reading time becomes longer.
[0026] The color components of input image data change between the
first and second modes. The color calculation means automatically
switches the contents of formulas representing the correlation
between the input color data of three or more colors and output
color data of three or more colors in accordance with the reading
mode.
[0027] In this color image reading apparatus, when the emission
color switching means selects a specific color as the color to be
emitted by the light source in a specific reading mode, a plurality
of light emitters having different peak emission wavelengths may be
simultaneously driven to emit light. For example, B (blue) and C
(cyan) have a small wavelength difference. For this reason, B and C
can be regarded as one color (B). In this case, when the B and C
light emitters are simultaneously turned on, the emission intensity
of the light source increases as compared to a case wherein only
the B light emitter emits light. Similarly, G (green) and Y
(yellow) have a small wavelength difference. For this reason, G and
Y can be regarded as one color (G). In this case, when the G and Y
light emitters are simultaneously turned on, the emission intensity
of the light source increases as compared to a case wherein only
the G light emitter emits light. As the emission intensity of the
light source increases, the illuminance of the original increases.
For this reason, even when the exposure time of the image sensing
device is shortened, a bright image can be read. That is, the image
reading time can be shortened.
BRIEF DESCRIPTION OF THE DRAWINGS
[0028] FIG. 1 is a partially cutaway front view of an image reading
apparatus;
[0029] FIG. 2 is a longitudinal sectional view showing the light
source unit of the image reading apparatus shown in FIG. 1;
[0030] FIG. 3 is a plan view of the light source unit;
[0031] FIG. 4 is a graph showing the characteristics of five
light-emitting elements used in the light source unit;
[0032] FIG. 5 is a perspective view showing the illumination unit
of the image reading apparatus shown in FIG. 1;
[0033] FIG. 6 is a schematic exploded view showing the optical path
from the light source unit to a linear image sensor;
[0034] FIG. 7 is a schematic exploded view showing the optical path
from the light source unit to the linear image sensor;
[0035] FIG. 8 is a block diagram showing the electrical circuit in
the image reading apparatus 60 shown in FIG. 1;
[0036] FIG. 9 is a flow chart showing operation of a main control
unit shown in FIG. 8;
[0037] FIG. 10 is a flow chart showing contents of step S11 in FIG.
9;
[0038] FIG. 11 is a flow chart showing contents of step S12 in FIG.
9;
[0039] FIG. 12 is a flow chart showing contents of step S13 in FIG.
9;
[0040] FIG. 13 is a flow chart showing contents of step S14 in FIG.
9;
[0041] FIG. 14 is a flow chart showing contents of step S15 in FIG.
9; and
[0042] FIG. 15 is a flow chart showing contents of step S16 in FIG.
9.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0043] An embodiment of the present invention will be described
below with reference to FIGS. 1 to 15.
[0044] The schematic arrangement of an image reading apparatus 60
will be described first with reference to FIG. 1. This image
reading apparatus 60 uses, as an original, a negative film or
reversal (or positive) film photographed with a camera. The
original is held inside a holder 62 and loaded in the image reading
apparatus 60. The holder 62 is supported to freely move in an axial
direction indicated by an arrow X by a driving mechanism (not
shown). When an electrical motor M1 (to be described later) is
driven, the holder 62 moves in the X-axis direction.
[0045] The image reading apparatus 60 has an illumination unit 50
incorporating a light source unit 20. FIG. 5 shows the outer
appearance of the illumination unit 50. As shown in FIG. 1, the
original in the holder 62 is illuminated from the lower side by the
illumination unit 50. Light transmitted through the original is
reflected by a mirror 63 inserted above the original and is
incident on the image sensing surface of a linear image sensor 61
through a lens 64.
[0046] FIGS. 6 and 7 show the optical path from the light source
unit 20 to the image sensing surface of the linear image sensor 61.
To accommodate the illumination optical system in a limited space,
the optical path is converted in the illumination unit 50. More
specifically, as shown in FIG. 5, light emitted by the light source
unit 20 is reflected by a toric mirror 51 and then by a mirror 52
toward the original. To guide the light reflected by the toric
mirror 51 to the mirror 52, the axis of light emitted by the light
source unit 20 is slightly tilted downward. As shown in FIG. 7, the
optical path is adjusted by a curved surface R2 of the toric mirror
51 to illuminate only a small area at the original position in the
direction of original movement. As shown in FIG. 6, the optical
path is also adjusted by a curved surface R1 of the toric mirror 51
to illuminate a region corresponding to a full line width at the
original position.
[0047] To read a color image, the light source unit 20 of the image
reading apparatus 60 can emit a plurality of illumination light
components having different wavelengths. More specifically, the R,
G, and B color components of the original image can be read using
R, G, and B illumination light components, respectively.
Especially, in this example, to improve the color reproducibility
of an image, the light source unit 20 capable of emitting five
illumination light components, i.e., R (red), Y (yellow), G
(green), C (cyon), and B (blue) light components is used.
[0048] As shown in FIG. 3, eight light-emitting diode chips 11 to
18 are set on a board 21 constituting the main portion of the light
source unit 20. The light-emitting diode chips 11, 12, 13, 14, 15,
16, 17, and 18 emit Y, G, R, G, Y, C, B, and C light components,
respectively. The light-emitting diode chips 11 and 15 have the
same emission characteristics. The light-emitting diode chips 12
and 14 have the same emission characteristics. The light-emitting
diode chips 16 and 18 have the same emission characteristics. The
emission characteristics of the five light-emitting diode chips 17,
16, 12, 11, and 13 are shown in FIG. 4 as characteristics P1, P2,
P3, P4, and P5, respectively.
[0049] As shown in FIGS. 2 and 3, the light-emitting diode chips
11, 12, 13, 14, 15, 16, 17, and 18 are mounted on the bottoms of
recesses 21a, 21b, 21c, 21d, 21e, 21f, 21g, and 21h formed in the
board 21, respectively. The inner walls of the recesses 21a to 21h
of the board 21 reflect transverse light emitted by the
light-emitting diode chips 11 to 18 in a direction indicated by an
arrow Y.
[0050] C illumination light emitted by the light-emitting diode
chips 16 and 18 and B illumination light emitted by the
light-emitting diode chip 17 are reflected by a surface 23b of a
spectral filter 23 to travel almost in a direction indicated by an
arrow X, as shown in FIG. 2. Y illumination light emitted by the
light-emitting diode chips 11 and 15, G illumination light emitted
by the light-emitting diode chips 12 and 14, and R illumination
light emitted by the light-emitting diode chip 13 are reflected by
a total reflection mirror 22, refracted by a surface 23a of the
spectral filter 23, transmitted through the spectral filter 23, and
refracted by the surface 23b to travel almost in the direction
indicated by the arrow X, as shown in FIG. 2. That is, all the R,
Y, G, C, and B illumination light components emitted by the light
source unit 20 travel in the X direction. Therefore, as shown in
FIGS. 1 and 5, the original supported by the holder 62 can be
illuminated with the light emitted by the light source unit 20.
[0051] As shown in FIG. 8, the electrical circuit in the image
reading apparatus 60 comprises a main control unit 100, a sampling
unit 110, an A/D converter 120, a memory unit 130, an interface
unit 140, a timing control unit 150, a digital signal processing
unit 160, a light source control unit 170, and a subscan control
unit 180. The main control unit 100 controls the entire operation
of the image reading apparatus 60. The main control unit 100
incorporates a microcomputer.
[0052] To read an image, the timing control unit 150 supplies
various timing signals (pulse signals) necessary for image reading
to the linear image sensor 61. The linear image sensor 61 reads the
image in units of lines in synchronism with the timing signal. Line
images read by the linear image sensor 61 are sequentially output
in units of pixels as an analog image signal.
[0053] The sampling unit 110 samples the analog image signal output
from the linear image sensor 61 in synchronism with the timing
signal supplied from the timing control unit 150. More
specifically, the sampling unit 110 extracts the signal level in
units of pixels. The analog image signal sampled by the sampling
unit 110 is converted into a digital signal by the A/D converter
120 and input to the memory unit 130. The memory unit 130 has a
storage capacity which allows storage of color image data of at
least one frame separated into five color components of R, Y, G, C,
and B in this example.
[0054] When the five color components of R, Y, G, C, and B of the
image are converted into three color components of R, G, and B in
units of lines, i.e., color conversion is always performed before
the completion of reading one frame image, the storage capacity of
the memory unit 130 can be reduced.
[0055] The digital signal processing unit 160 performs
predetermined image processing for the image data held by the
memory unit 130 in accordance with an instruction from the main
control unit 100. For example, the five color components of R, Y,
G, C, and B are converted into three color components of R, G, and
B.
[0056] The color image data held by the memory unit 130 is output
to the interface unit 140 in response to a request from the host
computer connected to the image reading apparatus 60 through the
interface unit 140.
[0057] The light source control unit 170 turns on/off, i.e.,
ON/OFF-controls the light-emitting diode chips 11 to 18 of the
light source unit 20 in accordance with an instruction from the
main control unit 100. Instead of the ON/OFF control, the light
source control unit 170 may control the magnitude of an
energization current for each light-emitting diode. In either case,
the magnitude of the energization current for each light-emitting
diode is controlled in accordance with a desired light emission
luminance.
[0058] The subscan control unit 180 controls drive of the
electrical motor M1 in accordance with an instruction from the main
control unit 100. The driving shaft of the electrical motor M1 is
coupled to a subscan mechanism (not shown) for moving the holder 62
in the direction indicated by the arrow X.
[0059] FIG. 9 schematically shows the operation of the main control
unit 100. The contents of the respective steps will be described
with reference to FIG. 9. In the following description, processing
is executed by the microcomputer incorporated in the main control
unit 100 unless otherwise specified.
[0060] In step S1, the entire system is initialized. More
specifically, the main control unit 100, and the interface unit
140, timing control unit 150, digital signal processing unit 160,
light source control unit 170, and subscan control unit 180
connected to the main control unit 100 are initialized. With this
processing, the electrical motor M1 is stopped, and all the
light-emitting diode chips 11 to 18 of the light source unit 20 are
turned off. The main control unit 100 can communicate with a
predetermined host computer connected through the interface unit
140.
[0061] In step S2, it is determined whether a predetermined mode
designation has been inputted from the host computer. In this
example, the image reading apparatus 60 has six reading modes. One
of the reading modes is selected in accordance with the designation
from the host computer. If YES in step S2, the flow advances from
step S2 to step S3.
[0062] In step S3, the value of the reading mode designated by the
host computer is set in a mode register M allocated in the internal
memory.
[0063] In step S4, it is determined whether predetermined image
reading has been ordered by the host computer. If YES in step S4,
the flow advances from step S4 to step S5.
[0064] In step S5, the value held by the mode register M is
compared with 1. That is, it is determined whether reading mode "1"
has been set. If YES in step S5, the flow advances to step S11. If
NO in step S5, the flow advances to step S6.
[0065] In step S6, the value held by the mode register M is
compared with 2. That is, it is determined whether reading mode "2"
has been set. If YES in step S6, the flow advances to step S12. If
NO in step S6, the flow advances to step S7.
[0066] In step S7, the value held by the mode register M is
compared with 3. That is, it is determined whether reading mode "3"
has been set. If YES in step S7, the flow advances to step S13. If
NO in step S7, the flow advances to step S8.
[0067] In step S8, the value held by the mode register M is
compared with 4. That is, it is determined whether reading mode "4"
has been set. If YES in step S8, the flow advances to step S14. If
NO in step S8, the flow advances to step S9.
[0068] In step S9, the value held by the mode register M is
compared with 5. That is, it is determined whether reading mode "5"
has been set. If YES in step S9, the flow advances to step S15. If
NO in step S9, the flow advances to step S10.
[0069] In step S10, the value held by the mode register M is
compared with 6. That is, it is determined whether reading mode "6"
has been set. If YES in step S10, the flow advances to step S16. If
NO in step S10, the flow returns to step S2.
[0070] In step S11, "image reading 1" is executed. Details of this
processing are shown in FIG. 10. In "image reading 1", the color of
light emitted by the light source unit 20 is sequentially changed
to B, C, G, Y, and R to read the images of color components of B,
C, G, Y, and R, respectively. Every time one line of the image is
read, the color of light emitted by the light source unit 20 is
switched. This processing will be described later in detail.
[0071] In step S12, "image reading 2" is executed. Details of this
processing are shown in FIG. 11. In "image reading 2", the color of
light emitted by the light source unit 20 is sequentially switched
to B, G, and R to read the images of color components B, G, and R,
respectively. Every time one line of the image is read, the color
of light emitted by the light source unit 20 is switched. This
processing will be described later in detail.
[0072] In step S13, "image reading 3" is executed. Details of this
processing are shown in FIG. 12. In "image reading 3", the color of
light emitted by the light source unit 20 is sequentially switched
to B, G, and R to read the images of color components B, G, and R,
respectively. Especially, to cause the light source unit 20 to emit
B light, not only the light-emitting diode chip 17 for emitting B
light but also the light-emitting diode chips 16 and 18 for
emitting C light are simultaneously turned on. To cause the light
source unit 20 to emit R light, not only the light-emitting diode
chip 13 for emitting R light but also the light-emitting diode
chips 11 and 15 for emitting Y light are simultaneously turned on.
The color of light emitted by the light source unit 20 is switched
every time one line of the image is read. Details of this
processing will be described later in detail.
[0073] In step S14, "image reading 4" is executed. Details of this
processing are shown in FIG. 13. In "image reading 4", the color of
light emitted by the light source unit 20 is sequentially switched
to B, C, G, Y, and R to read the images of color components B, C,
G, Y, and R, respectively. The color of light emitted by the light
source unit 20 is switched every time one frame of the image is
read. Details of this processing will be described later in
detail.
[0074] In step S15, "image reading 5" is executed. Details of this
processing are shown in FIG. 14. In "image reading 5", the color of
light emitted by the light source unit 20 is sequentially switched
to B, G, and R to read the images of color components B, G, and R,
respectively. The color of light emitted by the light source unit
20 is switched every time one frame of the image is read. Details
of this processing will be described later in detail.
[0075] In step S16, "image reading 6" is executed. Details of this
processing are shown in FIG. 15. In "image reading 6", the color of
light emitted by the light source unit 20 is sequentially switched
to B, G, and R to read the images of color components B, G, and R,
respectively. Especially, to cause the light source unit 20 to emit
B light, not only the light-emitting diode chip 17 for emitting B
light but also the light-emitting diode chips 16 and 18 for
emitting C light are simultaneously turned on. To cause the light
source unit 20 to emit R light, not only the light-emitting diode
chip 13 for emitting R light but also the light-emitting diode
chips 11 and 15 for emitting Y light are simultaneously turned on.
The color of light emitted by the light source unit 20 is switched
every time one frame of the image is read. Details of this
processing will be described later in detail.
[0076] FIG. 9 shows only processing associated with image reading.
However, for example, when an image data transfer request is issued
from the host computer, image data is output from the memory unit
130 to the interface unit 140 in response to the request. This
processing is omitted in FIG. 9. "Image reading 1" executed in
reading mode "1"
[0077] will be described in detail with reference to FIG. 10.
[0078] In step S20, the contents of counters NC and NL allocated in
the internal memory are initialized. The value of the counter NC
represents a number assigned to the color of illumination. In this
case, the values "0", "1", "2", "3", and "4" of the counter NC
correspond to the B, C, G, Y, and R color components of light
emitted by the light source unit 20, respectively. The value of the
counter NL represents the scanning position in the subscan
direction (X direction). Every time the images of all color
components of one line are read, the value of the counter NL is
updated.
[0079] In step S21, an instruction is issued to the subscan control
unit 180 to start subscan drive. The electrical motor Ml is driven
to move the holder 62 for supporting the original in the direction
indicated by the arrow X at a predetermined speed. When the holder
62 moves, the relative positional relationship between the image
reading position and the original supported by the holder 62
changes.
[0080] In step S22, it is determined whether image reading has been
completed for one frame. More specifically, the value of the
counter NL is compared with a predetermined threshold value to
determine whether the scanning position in the subscan direction
has moved by a distance corresponding to one frame.
[0081] If NO in step S22, the flow advances to step S23. If YES in
step S22, the flow advances to step S36.
[0082] In step S23, the state of a line synchronizing signal which
periodically appears every time one line image is read is monitored
to determine whether a predetermined line synchronization timing is
detected. If YES in step S23, the flow advances from step S23 to
step S24.
[0083] In step S24, the next processing is selected in accordance
with the value of the counter NC. When the value of the counter NC
is "0", "1", "2", "3", or "4", the flow advances to step S25, S26,
S27, S28, or S29, respectively.
[0084] In step S25, the light source control unit 170 is controlled
to turn on the light-emitting diode chip 17 of the light source
unit 20. All the remaining light-emitting diode chips 11, 12, 13,
14, 15, 16, and 18 are turned off. That is, B light is emitted as
illumination light.
[0085] In step S26, the light source control unit 170 is controlled
to turn on the light-emitting diode chips 16 and 18 of the light
source unit 20. All the remaining light-emitting diode chips 11,
12, 13, 14, 15, and 17 are turned off. That is, C light is emitted
as illumination light.
[0086] In step S27, the light source control unit 170 is controlled
to turn on the light-emitting diode chip 12 and 14 of the light
source unit 20. All the remaining light-emitting diode chips 11,
13, 15, 16, 17, and 18 are turned off. That is, G light is emitted
as illumination light.
[0087] In step S28, the light source control unit 170 is controlled
to turn on the light-emitting diode chips 11 and 15 of the light
source unit 20. All the remaining light-emitting diode chips 12,
13, 14, 16, 17, and 18 are turned off. That is, Y light is emitted
as illumination light.
[0088] In step S29, the light source control unit 170 is controlled
to turn on the light-emitting diode chip 13 of the light source
unit 20. All the remaining light-emitting diode chips 11, 12, 14,
15, 16, 17, and 18 are turned off. That is, R light is emitted as
illumination light.
[0089] In step S30, an image is read for one line. More
specifically, transmission light from the original illuminated with
any one of the B, C, G, Y, and R light components is read by the
linear image sensor 61 for one line.
[0090] The signal output from the linear image sensor 61 is input
to the memory unit 130 through the sampling unit 110 and A/D
converter 120. The signal input to the memory unit 130 is one of
color signal components obtained by separating the image into five
colors: B, C, G, Y, and R. The memory unit 130 holds the input
color signal for one line in a line buffer allocated in the
internal memory. The color signal components of B, C, G, Y, and R
are held by different line buffers.
[0091] In step S31, the value of the counter NC is updated. Every
time step S31 is executed, the value of the counter NC is
incremented by one.
[0092] In step S32, the value of the counter NC is compared with a
predetermined maximum value "4". If the value of the counter NC is
not more than 4, the flow returns to step S22 to repeatedly execute
the above processing. That is, the image for one line is read again
in step S30.
[0093] Every time step S31 is executed, the value of the counter NC
changes. For this reason, processing to be executed in steps S25 to
S29 is switched. That is, the color of light emitted by the light
source unit 20 is sequentially switched, so the image of each of
the color components of B, C, G, Y, and R for one line is
sequentially read.
[0094] Since the holder 62 holding the original moves in the
direction indicated by the arrow X at a predetermined speed, the
position at which the original is to be read moves every time step
S30 is executed. However, the moving amount during image reading
for five lines is very small. Therefore, when step S30 is
repeatedly executed five times, color component data of B, C, G, Y,
and R can be obtained substantially at the same position on the
original.
[0095] In this example, the holder is continuously driven in the
subscan direction. Alternatively, subscan drive may be performed
while repeating movement and stop in units of lines. In this case,
the image for five lines is read while the holder 62 is at a stand
still, so the color component data at the same position can be
obtained.
[0096] When the value of the counter NC exceeds 4, the flow
advances to step S33. That is, when all color component data of B,
C, G, Y, and R are acquired, the flow advances to step S33.
[0097] In step S33, color calculation for one line image data is
executed. A color image signal processed by a device such as a
color display or a color printer generally comprises three color
signals of R, G, and B, which represent the levels of color
components having prescribed wavelengths of R, G, and B,
respectively. On the other hand, the signal obtained by processing
in step S30 has five color components of B, C, G, Y, and R. In some
cases, the wavelengths of B, G, and R light components emitted by
the light source unit 20 do not accurately match the prescribed
wavelengths of R, G, and B. Therefore, to generate a color image
signal to be processed by a device such as a color display or a
color printer, the color signals must be converted. This conversion
is executed in step S33.
[0098] For the descriptive convenience, B, C, G, Y, and R color
components obtained by processing in step S30 are defined as B1,
C1, G1, Y1, and R1, respectively. In addition, signals of the B1,
C1, G1, Y1 and R1 color components are defined as DB1, DC1, DG1,
DY1, and DR1, respectively.
[0099] In step S33, prescribed color components of R, G, and B are
obtained from the signals DB1, DC1, DG1, DY1, and DR1 using
following formula (1). 1 [ R G B ] = [ K11 K12 K13 K14 K15 K21 K22
K23 K24 K25 K31 K32 K33 K34 K35 ] [ DR1 DY1 DG1 DC1 DB1 ] ( 1 )
[0100] where K11 to K15, K21 to K25, and K31 to K35 are
constants.
[0101] In step S33, calculation or operation for a large quantity
of data must be repeated. Actual calculation is executed at a high
speed using the digital signal processing unit 160.
[0102] In step S34, one line image data of R, G, and B generated in
step S33 are stored in a frame memory area allocated in the memory
unit 130. The write address is determined in accordance with the
position in the subscan direction, i.e., the contents of the
counter NL.
[0103] In step S35, the value of the counter NC is cleared to 0. In
addition, the value of the counter NL representing the subscan
position is updated. The value of the counter NL is incremented
every time step S35 is executed.
[0104] In step S36, all the light-emitting diode chips 11 to 18 of
the light source unit 20 are turned off. Subscan drive is also
stopped.
[0105] When "image reading 1" shown in FIG. 10 is to be executed,
the color of image data is reproduced on the basis of the five
color components of B1, C1, G1, Y1, and R1 of the read image, so a
color image with high color reproducibility can be obtained.
[0106] Color reproducibility in a case wherein the color of image
data was reproduced on the basis of four or more color components
and that in a case wherein the color of image data was reproduced
on the basis of three color components were compared by a computer
simulation. As a result, we confirmed that, when the color of image
data was reproduced on the basis of four or more color components,
the color reproducibility largely improved as compared to the case
in which only three colors are used.
[0107] In "image reading 1" shown in FIG. 10, image data is read
for each of the five color components.
[0108] However, for example, only four color components of B1, C1,
G1, and R1 or B1, G1, Y1, and R1 may be read. Even when the image
is read for each of the four color components, the color
reproducibility sufficiently improves as compared to the prior art.
Especially, when a film having four photosensitive layers is used
as an original, high color reproducibility can be obtained by
reading the image while appropriately selecting the wavelengths of
four color components.
[0109] "Image reading 2" executed in reading mode "2" will be
described next in detail with reference to FIG. 11. The same
numerals as in FIG. 10 denote the same steps in FIG. 11. In FIG.
11, steps S21B, S32B, S33B, S37, S38, and S39 are different from
FIG. 10. Processing operations different from FIG. 10 will be
described below.
[0110] In "image reading 2" shown in FIG. 11, only three colors of
R, G, and B are used as illumination colors. Hence, the three color
components of R, G, and B of the original image are sequentially
read.
[0111] When the value of the counter NC is 0, step S37 is executed.
In step S37, the light source control unit 170 is controlled to
turn on the light-emitting diode chip 17 of the light source unit
20. All the remaining light-emitting diode chips 11, 12, 13, 14,
15, 16, and 18 are turned off. That is, the B light is emitted as
illumination light.
[0112] When the value of the counter NC is 1, step S38 is executed.
In step S38, the light source control unit 170 is controlled to
turn on the light-emitting diode chips 12 and 14 of the light
source unit 20. All the remaining light-emitting diode chips 11,
13, 15, 16, 17, and 18 are turned off. That is, the G light is
emitted as illumination light.
[0113] When the value of the counter NC is 2, step S39 is executed.
In step S39, the light source control unit 170 is controlled to
turn on the light-emitting diode chip 13 of the light source unit
20. All the remaining light-emitting diode chips 11, 12, 14, 15,
16, 17, and 18 are turned off. That is, the R light is emitted as
illumination light.
[0114] In step S32B, the value of the counter NC is compared with a
predetermined maximum value "2". If the value of the counter NC is
not more than 2, the flow returns to step S22 to repeat step S30.
That is, image reading for one line is repeated.
[0115] When step S31 is executed, the value of the counter NC
changes, so processing to be executed in steps S37 to S39 is
switched. That is, the color of light emitted by the light source
unit 20 is sequentially switched, so the image of each of the color
components of B, G, and R for one line is sequentially read.
[0116] Since the holder 62 holding the original moves in the
direction indicated by the arrow X at a predetermined speed, the
position at which the original is to be read moves every time step
S30 is executed. However, the moving amount during image reading
for three lines is very small. Therefore, when step S30 is repeated
three times, color component data of B, G, and R can be obtained
substantially at the same position on the original.
[0117] The subscan speed determined in step S21B is larger than
that in step S21 in FIG. 10. In "image reading 1" in FIG. 10, the
image is read five times per line of the output image. In "image
reading 2" in FIG. 11, the image is read three times per line of
the output image. Hence, when processing shown in FIG. 11 is
executed, the reading time per line of the image is shorter than
that in processing shown in FIG. 10.
[0118] In step S21B, the subscan speed is determined on the basis
of the reading time per line of the image. Since the reading time
per line of the image is shorter, the subscan speed in step S21B is
higher than that in step S21.
[0119] When the value of the counter NC exceeds 2, the flow
advances to step S33B. That is, when all color component data of B,
G, and R are acquired for one line, the flow advances to step
S33B.
[0120] In step S33B, color calculation for one line image data is
executed. Step S33B is different from step S33 only in the contents
of calculation.
[0121] The signal obtained by processing in step S30 has three
color components of B, G, and R. In some cases, the wavelengths of
B, G, and R light components emitted by the light source unit 20 do
not accurately match the prescribed wavelengths of R, G, and B.
Therefore, to generate a color image signal to be processed by a
device such as a color display or a color printer, the color
signals are converted in step S33B. For the descriptive
convenience, B, G, and R color components obtained by processing in
step S30 are defined as B1, G1, and R1, respectively. In addition,
signals of the B1, G1, and R1 color components are defined as DB1,
DG1, and DR1, respectively.
[0122] In step S33B, prescribed color components of R, G, and B are
obtained from the signals DB1, DG1, and DR1 using following formula
(2). 2 [ R G B ] = [ K11B K12B K13B K21B K22B K23B K31B K32B K33B ]
[ DR1 DG1 DB1 ] ( 2 )
[0123] where K11B to K13B, K21B to K23B, and K31B to K33B are
constants.
[0124] In step S33B, calculation for a large quantity of data must
be repeated. Actual calculation is executed at a high speed using
the digital signal processing unit 160.
[0125] The operation realized by "image reading 2" shown in FIG. 11
is basically the same as that of the conventional operation. That
is, when reading mode "2" is designated, the same operation as that
of the conventional apparatus is executed. For example, when an
image on an original having relatively low image quality is read,
particularly high color reproducibility is unnecessary. For this
reason, "image reading 2" shown in FIG. 11 may be performed. Since
the subscan speed of processing shown in FIG. 11 is higher than
that of processing in FIG. 10, the entire image of the original can
be read in a short time. "Image reading 3" executed in reading mode
"3"
[0126] will be described next in detail with reference to FIG. 12.
The same numerals as in FIG. 10 denote the same steps in FIG.
12.
[0127] In FIG. 12, steps S21C, S32B, S33C, S41, S38, and S42 are
different from FIG. 10. Processing operations different from FIG.
10 will be described below.
[0128] In "image reading 3" shown in FIG. 12, only three colors of
R, G, and B are used as illumination colors. Hence, the three color
components of R, G, and B of the original image are sequentially
read. However, the illumination colors of R and B in FIG. 12 are
slightly different from those in FIG. 10.
[0129] When the value of the counter NC is 0, step S41 is executed.
In step S41, the light source control unit 170 is controlled to
turn on the light-emitting diode chips 16, 17, and 18 of the light
source unit 20. All the remaining light-emitting diode chips 11,
12, 13, 14, and 15 are turned off.
[0130] As shown in FIG. 4, the wavelength of C is relatively close
to the wavelength of B. When the two types of light-emitting diode
chips 16, 17, and 18 are simultaneously turned on, illumination
light having a wavelength which can substantially be classified
into B can be obtained. When the two types of light-emitting diode
chips 16, 17, and 18 are turned on, the emission intensity becomes
higher than that in a case wherein only one type of light-emitting
diode chip 17 is turned on.
[0131] When the value of the counter NC is 1, step S38 is executed.
In step S38, the light source control unit 170 is controlled to
turn on the light-emitting diode chips 12 and 14 of the light
source unit 20. All the remaining light-emitting diode chips 11,
13, 15, 16, 17, and 18 are turned off. That is, G light is emitted
as illumination light.
[0132] When the value of the counter NC is 2, step S42 is executed.
In step S42, the light source control unit 170 is controlled to
turn on the light-emitting diode chips 11, 13, and 15 of the light
source unit 20. All the remaining light-emitting diode chips 12,
14, 16, 17, and 18 are turned off.
[0133] As shown in FIG. 4, the wavelength of Y is relatively close
to the wavelength of R. When the two types of light-emitting diode
chips 11, 13, and 15 are simultaneously turned on, illumination
light having a wavelength which can substantially be classified
into R can be obtained. When the two types of light-emitting diode
chips 11, 13, and 15 are turned on, the emission intensity becomes
higher than that in a case wherein only one type of light-emitting
diode chip 13 is turned on.
[0134] In step S32B, the value of the counter NC is compared with a
predetermined maximum value "2". If the value of the counter NC is
not more than 2, the flow returns to step S22 to repeat step S30.
That is, image reading for one line is repeated.
[0135] When step S31 is executed, the value of the counter NC
changes, so processing to be executed in steps S41, S38, and S42 is
switched. That is, the color of light emitted by the light source
unit 20 is sequentially switched, so the image of each of the color
components of B, G, and R for one line is sequentially read.
[0136] Since the holder 62 holding the original moves in the
direction indicated by the arrow X at a predetermined speed, the
position at which the original is to be read moves every time step
S30 is executed. However, the moving amount during image reading
for three lines is very small. Therefore, when step S30 is repeated
three times, color component data of B, G, and R can be obtained
essentially at the same position on the original.
[0137] The subscan speed determined in step S21C is much larger
than that in step S21 or S21B. In "image reading 2" in FIG. 11 and
"image reading 3" in FIG. 12, the image is read three times per
line of the output image. However, in "image reading 3" in FIG. 12,
a plurality of types of light-emitting diode chips are
simultaneously turned on to obtain the B and G illumination light
components. For this reason, the illumination intensity of
processing in FIG. 12 is higher than that of processing in FIG. 11.
When the illumination intensity is high, the original exposure time
(charging time of the linear image sensor 61) can be shortened. The
reading time per line of the image is also shortened.
[0138] In step S21C, the subscan speed is determined on the basis
of the reading time per line of the image. Since the reading time
per line of the image is shorter, the subscan speed in step S21C is
higher than that in step S21B.
[0139] When YES in step S32B, i.e., the value of the counter NC
exceeds 2, the flow advances to step S33C. That is, when all color
component data of B, G, and R are acquired for one line, the flow
advances to step S33C.
[0140] In step S33C, color calculation for one line image data is
executed. Step S33C, S33, and S33B are different only in the
contents of calculation.
[0141] The signal obtained by processing in step S30 has three
color components of B, G, and R. In some cases, the wavelengths of
B, G, and R light components emitted by the light source unit 20 do
not accurately match the prescribed wavelengths of R, G, and B.
Therefore, to generate a color image signal to be processed by a
device such as a color display or a color printer, the color
signals are converted in step S33C. For the descriptive
convenience, B, G, and R color components obtained by processing in
step S30 are defined as B2, G1, and R2, respectively. In addition,
signals of the B2, G1, and R2 color components are defined as DB2,
DG1, and DR2, respectively.
[0142] In step S33C, prescribed color components of R, G, and B are
obtained from the signals DB2, DG1, and DR2 by following formula
(3). 3 [ R G B ] = [ K11C K12C K13C K21C K22C K23C K31C K32C K33C ]
[ DR2 DG2 DB2 ] ( 3 )
[0143] where K11C to K13C, K21C to K23C, and K31C to K33C are
constants.
[0144] In step S33C, calculation for a large quantity of data must
be repeated. Actual calculation is executed at a high speed using
the digital signal processing unit 160.
[0145] When "image reading 3" shown in FIG. 12 is executed, the
entire image of the original can be read in a time shorter than in
"image reading 2" shown in FIG. 11. However, the color
reproducibility of the image is slightly lower in "image reading 3"
than in "image reading 2". However, when an image or an original
having relatively low image quality is read, particularly high
color reproducibility is unnecessary. For this reason, "image
reading 3" shown in FIG. 12 may be performed in accordance with
user's intention.
[0146] When "image reading 1", "image reading 2", or "image reading
3" is executed, the color component to be read is sequentially
switched every time one line of the image is scanned. On the other
hand, when "image reading 4" shown in FIG. 13, "image reading 5"
shown in FIG. 14, or "image reading 6" shown in FIG. 15 is
executed, the color component to be read is sequentially switched
every time one frame of the image is scanned.
[0147] "Image reading 4" executed in reading mode "4" will be
described in detail with reference to FIG. 13.
[0148] In step S50, the contents of the counters NC and NL
allocated in the internal memory are initialized. The value of the
counter NC represents the number assigned to the color of
illumination. Actually, the value "0", "1", "2", "3", and "4" of
the counter NC correspond to the B, C, G, Y, and R color components
of light emitted by the light source unit 20, respectively. The
value of the counter NL represents the scanning position in the
subscan direction (X direction). Actually, every time one line
image is read, the value of the counter NL is updated.
[0149] In step S51, an instruction is issued to the subscan control
unit 180 to start subscan drive. The electrical motor M1 is driven
to move the holder 62 for supporting the original in the direction
indicated by the arrow X at a predetermined speed. The holder 62
may be driven stepwise using a stepping motor as the electrical
motor M1.
[0150] When the holder 62 moves, the relative positional
relationship between the image reading position and the original
supported by the holder 62 changes.
[0151] In step S52, the next processing is selected in accordance
with the value of the counter NC. When the value of the counter NC
is "0", "1", "2", "3", or "4", the flow advances to step S53, S54,
S55, S56, or S57, respectively.
[0152] In step S53, the light source control unit 170 is controlled
to turn on the light-emitting diode chip 17 of the light source
unit 20. All the remaining light-emitting diode chips 11, 12, 13,
14, 15, 16, and 18 are turned off. That is, B light is emitted as
illumination light.
[0153] In step S54, the light source control unit 170 is controlled
to turn on the light-emitting diode chips 16 and 18 of the light
source unit 20. All the remaining light-emitting diode chips 11,
12, 13, 14, 15, and 17 are turned off. That is, C light is emitted
as illumination light.
[0154] In step S55, the light source control unit 170 is controlled
to turn on the light-emitting diode chip 12 and 14 of the light
source unit 20. All the remaining light-emitting diode chips 11,
13, 15, 16, 17, and 18 are turned off. That is, G light is emitted
as illumination light.
[0155] In step S56, the light source control unit 170 is controlled
to turn on the light-emitting diode chips 11 and 15 of the light
source unit 20. All the remaining light-emitting diode chips 12,
13, 14, 16, 17, and 18 are turned off. That is, Y light is emitted
as illumination light.
[0156] In step S57, the light source control unit 170 is controlled
to turn on the light-emitting diode chip 13 of the light source
unit 20. All the remaining light-emitting diode chips 11, 12, 14,
15, 16, 17, and 18 are turned off. That is, R light is emitted as
illumination light.
[0157] In step S58, it is determined whether image reading has been
completed for one frame. More specifically, the value of the
counter NL is compared with a predetermined threshold value to
determine whether the scanning position in the subscan direction
has moved by one frame. If NO in step S58, the flow advances to
step S59. If YES in step S58, the flow advances to step S62.
[0158] In step S59, the state of a line synchronizing signal which
periodically appears every time one line image is read is monitored
to determine whether a predetermined line synchronization timing is
detected. If YES in step S59, the flow advances from step S59 to
step S60.
[0159] In step S60, an image is read for one line. More
specifically, transmission light from the original illuminated with
any one of the B, C, G, Y, and R light components is read by the
linear image sensor 61 for one line.
[0160] The signal output from the linear image sensor 61 is input
to the memory unit 130 through the sampling unit 110 and A/D
converter 120. The signal input to the memory unit 130 is one of
color signal components obtained by separating the image into five
colors: B, C, G, Y, and R.
[0161] The memory unit 130 holds the input color signal for one
line in a frame memory area allocated in the internal memory. The
write address is determined in accordance with the counter NL. The
color signal components of B, C, G, Y, and R are held by different
frame memories.
[0162] In step S61, the value of the counter NC is updated. Every
time step S61 is executed, the value of the counter NC is
incremented by one.
[0163] Processing in step S60 is repeated until the completion of
image reading for one frame is detected in step S58. Therefore, an
image signal of one frame associated with any one of colors B, C,
G, Y, and R is stored in one frame memory area of the memory unit
130.
[0164] When image reading for one frame associated with one color
is completed the flow advances from step S58 to step S62.
[0165] In step S62, the value of the counter NL is initialized to
0. In addition, the value of the counter NC is updated. The value
of the counter NC is incremented by one every time step S62 is
executed.
[0166] In step S63, the value of the counter NC is compared with a
predetermined maximum value "4". If the value of the counter NC is
not more than 4, the flow advances to step S64. When the value of
the counter NC exceeds 4, the flow advances to step S65.
[0167] In step S64, the electrical motor Ml is controlled through
the subscan control unit 180 to return the subscan position to the
reading start position. More specifically, the driving direction of
the electrical motor Ml is reversed to move the holder 62 to the
position at which step S51 has been executed. After this, the
driving direction of the electrical motor M1 is reversed again to
return the moving direction of the holder 62 to the forward
direction of subscan. That is, the holder 62 is reciprocally driven
in the direction indicated by the arrow X every time one frame
image associated with one color is read. After step S64 is
executed, the flow returns to step S52. Image reading for one frame
and one color is executed again by processing in steps S58 to
S61.
[0168] When step S62 is executed, the value of the counter NC
changes, so processing to be executed in steps S53 to S57 is
switched. That is, the color of light emitted by the light source
unit 20 is sequentially switched, so the image of each of the color
components of B, C, G, Y, and R for one frame is sequentially
read.
[0169] When the value of the counter NC exceeds 4, the flow
advances from step S63 to step S65. That is, when all color
component data of B, C, G, Y, and R for one frame image have been
acquired, the flow advances to step S65.
[0170] In step S65, all the light-emitting diode chips 11 to 18 of
the light source unit 20 are turned off. Subscan drive is also
stopped.
[0171] In step S66, color calculation is executed for all image
data of one frame. The contents of processing are the same as in
step S33 except that the data to be processed is data of one
frame.
[0172] More specifically, prescribed color components of R, G, and
B are obtained from the signals DB1, DC1, DG1, DY1, and DR1 using
formula (1) above. The R, G, and B image data for one frame, which
are generated in step S66, are stored in frame memory areas
allocated in the memory unit 130.
[0173] "Image reading 5" executed in reading mode "5" will be
described next in detail with reference to FIG. 14. The same
numerals as in FIG. 13 denote the same steps in FIG. 14.
[0174] In FIG. 14, steps S63B, S66B, S71, S72, and S73 are
different from FIG. 13. Processing operations different from FIG.
13 will be described below.
[0175] In "image reading 5" shown in FIG. 14, only three colors of
R, G, and B are used as illumination colors. Hence, the three color
components of R, G, and B of the original image are sequentially
read.
[0176] When the value of the counter NC is 0, step S71 is executed.
In step S71, the light source control unit 170 is controlled to
turn on the light-emitting diode chip 17 of the light source unit
20. All the remaining light-emitting diode chips 11, 12, 13, 14,
15, 16, and 18 are turned off. That is, B light is emitted as
illumination light.
[0177] When the value of the counter NC is 1, step S72 is executed.
In step S72, the light source control unit 170 is controlled to
turn on the light-emitting diode chips 12 and 14 of the light
source unit 20. All the remaining light-emitting diode chips 11,
13, 15, 16, 17, and 18 are turned off. That is, G light is emitted
as illumination light.
[0178] When the value of the counter NC is 2, step S73 is executed.
In step S73, the light source control unit 170 is controlled to
turn on the light-emitting diode chip 13 of the light source unit
20. All the remaining light-emitting diode chips 11, 12, 14, 15,
16, 17, and 18 are turned off. That is, R light is emitted as
illumination light.
[0179] In step S63B, the value of the counter NC is compared with a
predetermined maximum value "2". If the value of the counter NC is
not more than 2, the flow returns to step S52 via step S64 to
repeat steps S58 to S61. That is, image reading for one frame and
one color is repeated.
[0180] When the value of the counter NC exceeds 2, the flow
advances to step S66B via step S65. That is, when all color
component data of B, G, and R for one frame image are acquired, the
flow advances to step S66B.
[0181] In step S66B, color calculation is executed for all image
data of one frame. Steps S66B and S66 are different only in the
contents of processing. That is, the contents of processing are the
same as in step S33B except that the data to be processed is data
of one frame. More specifically, prescribed color components of R,
G, and B are obtained from the signals DB1, DG1, and DR1 using
formula (2) above. The R, G, and B image data for one frame, which
are generated in step S66B, are stored in frame memory areas
assigned on the memory unit 130.
[0182] The operation realized by "image reading 5" shown in FIG. 14
is basically the same as that of the conventional operation. That
is, when reading mode "5" is designated, the same operation as that
of the conventional apparatus is executed. For example, when an
image on an original having relatively low image quality is to be
read, particularly high color reproducibility is unnecessary. For
this reason, "image reading 5" shown in FIG. 14 may be performed.
Since the number of times of frame scanning for image reading is
smaller in processing shown in FIG. 14 than that in processing in
FIG. 13, the entire image of the original can be read in a short
time.
[0183] "Image reading 6" executed in reading mode "6" will be
described next in detail with reference to FIG. 15. The same
numerals as in FIG. 13 denote the same steps in FIG. 15.
[0184] In FIG. 15, steps S51C, S63B, S66C, S74, S75, and S76 are
different from FIG. 13. Processing operations different from FIG.
13 will be described below.
[0185] In "image reading 6" shown in FIG. 15, only three colors of
R, G, and B are used as illumination Colors. Hence, the three color
components of R, G, and B of the original image are sequentially
read. However, the illumination colors of R and B in FIG. 15 are
slightly different from those in FIG. 13.
[0186] When the value of the counter NC is 0, step S74 is executed.
In step S74, the light source control unit 170 is controlled to
turn on the light-emitting diode chips 16, 17, and 18 of the light
source unit 20. All the remaining light-emitting diode chips 11,
12, 13, 14, and 15 are turned off.
[0187] As shown in FIG. 4, the wavelength of C is reatively close
to the wavelength of B. When the two types of light-emitting diode
chips 16, 17, and 18 are simultaneously turned on, illumination
light having a wavelength which can substantially be classified
into B can be obtained. When the two types of light-emitting diode
chips 16, 17, and 18 are turned on, the emission intensity becomes
higher than that in a case wherein only one type of light-emitting
diode chip 17 is turned on.
[0188] When the value of the counter NC is 1, step S75 is executed.
In step S75, the light source control unit 170 is controlled to
turn on the light-emitting diode chips 12 and 14 of the light
source unit 20. All the remaining light-emitting diode chips 11,
13, 15, 16, 17, and 18 are turned off. That is, G light is emitted
as illumination light.
[0189] When the value of the counter NC is 2, step S76 is executed.
In step S76, the light source control unit 170 is controlled to
turn on the light-emitting diode chips 11, 13, and 15 of the light
source unit 20. All the remaining light-emitting diode chips 12,
14, 16, 17, and 18 are turned off.
[0190] As shown in FIG. 4, the wavelength of Y is relatively close
to the wavelength of R. When the two types of light-emitting diode
chips 11, 13, and 15 are simultaneously turned on, illumination
light having a wavelength which can substantially be classified
into R can be obtained. When the two types of light-emitting diode
chips 11, 13, and 15 are turned on, the emission intensity becomes
higher than that in a case wherein only one type of light-emitting
diode chip 13 is turned on.
[0191] In step S63B, the value of the counter NC is compared with a
predetermined maximum value "2". If the value of the counter NC is
not more than 2, the flow returns to step S52 via step S64 to
repeat steps S58 to S61. That is, image reading for one frame and
one color is repeated.
[0192] The subscan speed determined in step S51C is much higher
than that in step S51.
[0193] In "image reading 6" in FIG. 15, a plurality of types of
light-emitting diode chips are simultaneously turned on to obtain
the B and G illumination light components. For this reason, the
illumination intensity is higher in processing shown in FIG. 15
than that in processing in FIG. 13 or 14.
[0194] When the illumination intensity is high, the original
exposure time (charging time) of the linear image sensor 61 can be
shortened. The reading time per frame of the image is also
shortened.
[0195] In step S51C, the subscan speed is determined on the basis
of the charging time per line of the image. Since the reading time
per frame of the image is shorter, the subscan speed in step S51C
is higher than that in step S51.
[0196] When the value of the counter NC exceeds 2, the flow
advances to step S66C via step S65. That is, when all color
component data of B, G, and R for one frame image have been
acquired, the flow advances to step S66C.
[0197] In step S66C, color calculation is executed for all image
data of one frame. Step S66C is different from step S66 or S66b
only in the contents of processing. That is, the contents of
processing are the same as in step S33C except that the data to be
processed is data of one frame. More specifically, prescribed color
components of R, G, and B are obtained from the signals DB2, DG1,
and DR2 using formula (3) above. The R, G, and B image data for one
frame, which are generated in step S66C, are stored in frame memory
areas assigned on the memory unit 130.
[0198] When "image reading 6" shown in FIG. 15 is executed, the
entire image of the original can be read in a time shorter than in
"image reading 5" shown in FIG. 14. However, the color
reproducibility of the image is slightly lower in "image reading 6"
than in "image reading 5". However, when an image reading on an
original having relatively low image quality is to be read,
particularly high color reproducibility is unnecessary. For this
reason, "image reading 6" shown in FIG. 15 may be performed in
accordance with the user's intention.
[0199] In this embodiment, the image reading apparatus 60 for
reading a film-shaped original has been described. However, the
present invention can also be practiced for a general image
scanner.
[0200] In the above embodiment, the light source unit 20 uses five
types of light-emitting devices having different peak emission
wavelengths in the visible light range. However, four types of
light-emitting devices may be used. Alternatively, the number of
types of light-emitting devices may be increased to six or
more.
[0201] In the above embodiment, the output color image data has R,
G, and B color components. However, only by changing the contents
of formulas (1), (2), and (3), data of the XYZ color system or Lab
calorimetric system can also be output.
[0202] In the above embodiment, color conversion using formulas
(1), (2), and (3) is executed inside the image reading apparatus
60. However, this color conversion may be omitted, and instead,
color conversion may be executed on the host computer side.
* * * * *