U.S. patent application number 09/898015 was filed with the patent office on 2001-11-01 for image reading device, method and program.
Invention is credited to Nakamura, Shoei, Ochiai, Toru.
Application Number | 20010035491 09/898015 |
Document ID | / |
Family ID | 27299791 |
Filed Date | 2001-11-01 |
United States Patent
Application |
20010035491 |
Kind Code |
A1 |
Ochiai, Toru ; et
al. |
November 1, 2001 |
Image reading device, method and program
Abstract
An image can be read during main scanning under an optimized
image reading condition even if dust is attached to a document such
as a photographic film or the like, or if there are scratches. A
scanner irradiates visible light and infrared light from a light
source, and an image of the document is separated into infrared and
visible components. These components are detected for pixels of the
image by an image sensor. A controller, e.g., of the scanner
recognizes defective pixels based on the infrared component.
Furthermore, the controller corrects a visible component level in
the defective pixel based on the infrared component level of the
defective pixel and a reference level obtained where there is no
defect, in order to create a histogram. The controller determines
image reading conditions such as, for example, an exposure amount
(exposure time) for use during main scanning and an LUT gradation
conversion characteristic based on this histogram.
Inventors: |
Ochiai, Toru; (Tokyo,
JP) ; Nakamura, Shoei; (Tokyo, JP) |
Correspondence
Address: |
OLIFF & BERRIDGE, PLC
P.O. Box 19928
Alexandria
VA
22320
US
|
Family ID: |
27299791 |
Appl. No.: |
09/898015 |
Filed: |
July 5, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
09898015 |
Jul 5, 2001 |
|
|
|
09525761 |
Mar 14, 2000 |
|
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Current U.S.
Class: |
250/208.1 ;
250/340 |
Current CPC
Class: |
H04N 1/4097
20130101 |
Class at
Publication: |
250/208.1 ;
250/340 |
International
Class: |
G01J 005/02 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 15, 1999 |
JP |
11-068597 |
Apr 7, 2000 |
JP |
2000-202600 |
Claims
What is claimed is:
1. An image reading device comprising: infrared component forming
means for forming an infrared component of an image of a document;
infrared component detecting means for detecting an infrared
component level of the infrared component for pixels of the image;
defective infrared component detecting means for detecting a
defective infrared component level of a defective pixel for which
the detected infrared component level is less than a reference
level; visible component forming means for forming a visible
component of the image of the document; visible component detecting
means for detecting a visible component level for the pixels of the
image; correcting means for correcting the visible component level
of the defective pixel to obtain a corrected visible component
level for the defective pixel based on the reference level and the
detected defective infrared component level for the defective
pixel; visible image data obtaining means for outputting visible
image data based on the detected visible component level of pixels
other than the defective pixel and based on the corrected visible
component level of the defective pixel; and reading condition
determining means for determining a reading condition of the image
of the document based on the visible image data.
2. The image reading device of claim 1, further comprising: minimum
brightness level detecting means for detecting a minimum brightness
level of the visible image data; gradation conversion
characteristic setting means for setting a gradation conversion
characteristic with respect to the visible image data based on the
detected minimum brightness level; and gradation characteristic
conversion means for converting a gradation characteristic of the
visible image data based on the set gradation conversion
characteristic.
3. The image reading device of claim 2, wherein the correcting
means calculates the corrected visible component level by
multiplying a detected visible component level of the defective
pixel by a correction coefficient that is equal to the reference
level divided by the defective infrared component level.
4. The image reading device of claim 3, wherein the minimum
brightness level detecting means detects the minimum brightness
level while excluding the detected visible component level of the
defective pixel in which the detected infrared component level is
less than a predetermined level that is lower than the reference
level.
5. The image reading device of claim 2, wherein the minimum
brightness level detecting means detects the minimum brightness
level while excluding the detected visible component level of the
defective pixel in which the detected infrared component level is
less than a predetermined level that is lower than the reference
level.
6. The image reading device of claim 2, wherein: the visible
component forming means forms a plurality of visible wavelength
components of the image; the visible image data obtaining means
outputs visible image data for each of the plurality of visible
wavelength components; the defective infrared component detecting
means detects the defective pixel from the visible image data for
each of the plurality of visible wavelength components; the minimum
brightness level detecting means detects the minimum brightness
level of the visible image data for each of the plurality of
visible wavelength components; the gradation conversion
characteristic setting means sets the gradation conversion
characteristic for the visible image data for each of the plurality
of visible wavelength components based on the minimum brightness
level for each of the visible wavelength components; and the
gradation characteristic converting means converts the gradation
characteristic of the visible image data for each of the plurality
of visible wavelength components based on the set gradation
conversion characteristic for each of the visible wavelength
components.
7. An image reading device comprising: an illumination system that
irradiates a document with visible light and infrared light; an
image detection system that detects an infrared component of an
image of the document and a visible light component of the image of
the document; and a controller that: determines an infrared
component level for pixels of the infrared component of the image;
detects a defective infrared component level of a defective pixel
for which the determined infrared component level is less than a
reference level; determines a visible component level of the pixels
of the visible light component of the image; corrects the visible
component level of the defective pixel to obtain a corrected
visible component level for the defective pixel based on the
reference level and the detected defective infrared component level
for the defective pixel; outputs visible image data based on the
detected visible component level of pixels other than the defective
pixel and based on the corrected visible component level of the
defective pixel; and determines a reading condition of the image of
the document based on the visible image data.
8. The image reading device of claim 7, wherein the controller:
determines a minimum brightness level of the visible image data;
sets a gradation conversion characteristic with respect to the
visible image data based on the detected minimum brightness level;
and converts a gradation characteristic of the visible image data
based on the set gradation conversion characteristic.
9. The image reading device of claim 8, wherein the controller
calculates the corrected visible component level by multiplying a
detected visible component level of the defective pixel by a
correction coefficient that is equal to the reference level divided
by the defective infrared component level.
10. The image reading device of claim 9, wherein the controller
determines the minimum brightness level while excluding the
detected visible component level of the defective pixel in which
the detected infrared component level is less than a predetermined
level that is lower than the reference level.
11. The image reading device of claim 8, wherein the controller
determines the minimum brightness level while excluding the
detected visible component level of the defective pixel in which
the detected infrared component level is less than a predetermined
level that is lower than the reference level.
12. A computer readable storage medium that stores a control
program to control an image reading device having an illumination
system that irradiates a document with visible light and infrared
light, and an image detection system that detects an infrared
component of an image of the document and a visible light component
of the image of the document, the control program comprising: an
infrared component procedure that determines an infrared component
level for pixels of the infrared component of the image; a
defective infrared component detecting procedure that detects a
defective infrared component level of a defective pixel for which
the determined infrared component level is less than a reference
level; a visible component procedure that determines a visible
component level of the pixels of the visible light component of the
image; a correcting procedure that corrects the visible component
level of the defective pixel based on the reference level and the
defective infrared component level to obtain a corrected visible
component level; a visible image data obtaining procedure that
outputs visible image data according to the visible component level
of pixels other than the defective pixel and the corrected visible
component level of the defective pixel; and a reading condition
determining procedure that determines a reading condition of the
image of the document based on the visible image data.
13. A computer data signal, embodied in a carrier wave, and
representing a control program to control an image reading device
having an illumination system that irradiates a document with
visible light and infrared light, and an image detection system
that detects an infrared component of an image of the document and
a visible light component of the image of the document, the control
program comprising: an infrared component procedure that determines
an infrared component level for pixels of the infrared component of
the image; a defective infrared component detecting procedure that
detects a defective infrared component level of a defective pixel
for which the determined infrared component level is less than a
reference level; a visible component procedure that determines a
visible component level of the pixels of the visible light
component of the image; a correcting procedure that corrects the
visible component level of the defective pixel based on the
reference level and the defective infrared component level to
obtain a corrected visible component level; a visible image data
obtaining procedure that outputs visible image data according to
the visible component level of pixels other than the defective
pixel and the corrected visible component level of the defective
pixel; and a reading condition determining procedure that
determines a reading condition of the image of the document based
on the visible image data.
14. A method of controlling an image reading device that reads an
image from a document, the method comprising the steps of: forming
an infrared component of the image of the document; detecting an
infrared component level of the infrared component for pixels of
the image; detecting a defective infrared component level of a
defective pixel for which the detected infrared component level is
less than a reference level; forming a visible component of the
image of the document; detecting a visible component level for the
pixels of the image; correcting the visible component level of the
defective pixel to obtain a corrected visible component level for
the defective pixel based on the reference level and the detected
defective infrared component level for the defective pixel;
outputting visible image data based on the detected visible
component level of pixels other than the defective pixel and based
on the corrected visible component level of the defective pixel;
and determining a reading condition of the image of the document
based on the visible image data.
15. The method of claim 14, further comprising: detecting a minimum
brightness level of the visible image data; setting a gradation
conversion characteristic with respect to the visible image data
based on the detected minimum brightness level; and converting a
gradation characteristic of the visible image data based on the set
gradation conversion characteristic.
16. The method of claim 15, wherein the corrected visible component
level is calculated by multiplying a detected visible component
level of the defective pixel by a correction coefficient that is
equal to the reference level divided by the defective infrared
component level.
17. The method of claim 16, wherein the minimum brightness level is
detected while excluding the detected visible component level of
the defective pixel in which the detected infrared component level
is less than a predetermined level that is lower than the reference
level.
18. The method of claim 15, wherein the minimum brightness level is
detected while excluding the detected visible component level of
the defective pixel in which the detected infrared component level
is less than a predetermined level that is lower than the reference
level.
19. The method of claim 15, wherein: the visible component forming
step forms a plurality of visible wavelength components of the
image; the visible image data obtaining step outputs visible image
data for each of the plurality of visible wavelength components;
the defective infrared component detecting step detects the
defective pixel from the visible image data for each of the
plurality of visible wavelength components; the minimum brightness
level detecting step detects the minimum brightness level of the
visible image data for each of the plurality of visible wavelength
components; the gradation conversion characteristic setting step
sets the gradation conversion characteristic for the visible image
data for each of the plurality of visible wavelength components
based on the minimum brightness level for each of the visible
wavelength components; and the gradation characteristic converting
step converts the gradation characteristic of the visible image
data for each of the plurality of visible wavelength components
based on the set gradation conversion characteristic for each of
the visible wavelength components.
Description
INCORPORATION BY REFERENCE
[0001] This is a Continuation-in-Part of U.S. patent application
Ser. No. 09/525,761, filed Mar. 14, 2000, the entire disclosure of
which is incorporated herein by reference. In addition, the
disclosures of the following priority applications are herein
incorporated by reference in their entireties: Japanese Patent
Application No. 11-068597, filed Mar. 15, 1999 and Japanese Patent
Application No. 2000-202600, filed Jul. 4, 2000. Furthermore, the
disclosure of U.S. patent application No. 09/024,124, filed Feb.
17, 1998 is incorporated herein by reference in its entirety.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] This invention relates to an image reading device, method
and program for reading an image of a transparent document such as
a photographic film.
[0004] 2. Description of Related Art
[0005] A photograph is taken under various environments of the
natural world. Therefore, there are various kinds of images to be
recorded to a transparent document such as a photographic film,
ranging from those whose range from the brightest point to the
darkest point is wide to those whose range from the brightest point
to the darkest point is narrow.
[0006] Because of this, when an image that has been actually
recorded on a photographic film (e.g., a negative film) is read by
a film scanner, prescanning is performed prior to main
scanning.
[0007] The darkest point and the brightest point of the image can
be pre-detected by this prescanning. Additionally, during main
scanning, based on the darkest and brightest points of the image
that have been detected by this prescanning, image reading
conditions are determined, such as exposure amount (exposure time)
when image data is read and LUT (Look Up Table) gradation
conversion characteristics.
[0008] However, when foreign matter such as dust is attached to the
film surface, or when there is a scratch, etc., this can be
considered as an image during prescanning. This causes problems,
particularly in the case of a transparent document such as a
negative film. That is, foreign matter such as dust usually shields
visible light and deteriorates a visible component level of image
data. Because of this, an image of foreign matter may be determined
to be the darkest point (the lowest point of the range) of an image
(negative image) that has been recorded on the film. Thus, when the
darkest point is erroneously recognized, the most appropriate value
cannot be obtained for the exposure amount (exposure time), for the
LUT gradation conversion characteristic, or the like, when the
image is read during main scanning.
[0009] The same can be said for the case in which there is a
scratch on a photographic film.
SUMMARY OF THE INVENTION
[0010] This invention addresses the above-mentioned problems. One
object of this invention is to provide an image reading device that
can read an image by main scanning using optimal image reading
conditions even when foreign matter is attached to a transparent
document such as a photographic film and/or there is damage to the
document.
[0011] In order to accomplish the above and/or other objects,
according to one aspect of the invention, an image reading device
having an illumination system that irradiates a document with
visible light and infrared light and an image detection system that
detects an infrared component of an image of the document and a
visible light component of the image of the document includes a
controller that:
[0012] determines an infrared component level for pixels of the
infrared component of the image;
[0013] detects a defective infrared component level of a defective
pixel for which the determined infrared component level is less
than a reference level;
[0014] determines a visible component level of the pixels of the
visible light component of the image;
[0015] corrects the visible component level of the defective pixel
to obtain a corrected visible component level for the defective
pixel based on the reference level and the detected defective
infrared component level for the defective pixel;
[0016] outputs visible image data based on the detected visible
component level of pixels other than the defective pixel and based
on the corrected visible component level of the defective pixel;
and
[0017] determines a reading condition of the image of the document
based on the visible image data. The visible component level of the
defective pixel is corrected, so effects of the defective pixel can
be eliminated in determination of the reading condition of the
document by using the corrected visible component level.
[0018] According to another aspect of the invention, the controller
of the image reading device also: (a) determines a minimum
brightness level of the visible image data; (b) sets a gradation
conversion characteristic with respect to the visible image data
based on the detected minimum brightness level; and (c) converts a
gradation characteristic of the visible image data based on the set
gradation conversion characteristic. Thus, even if the brightness
level of the defective pixel is the minimum brightness level, the
brightness level is corrected. Therefore, the defective pixel does
not affect conversion of gradation characteristics of the visible
image date based on the gradation conversion characteristic in
addition to setting of the gradation conversion
characteristics.
[0019] According to another aspect of the invention, the controller
of the image reading device calculates the corrected visible
component level by multiplying a detected visible component level
of the defective pixel by a correction coefficient that is equal to
the reference level divided by the defective infrared component
level. Therefore, correction of the visible component level in the
defective pixel can be performed by a simplified method.
[0020] According to another aspect of the invention, the controller
of the image reading device determines the minimum brightness level
while excluding the detected visible component level of the
defective pixel in which the detected infrared component level is
less than a predetermined level that is lower than the reference
level. Therefore, effects of the defective pixel which are
unrecoverable can be eliminated in determination of the reading
condition of the document.
[0021] According to another aspect of the invention, the controller
of the image reading device performs the above-described functions
for a plurality of color components of the visible image of the
document. Because of this, correction of the defective pixel can be
performed for the respective visible wavelength components, and the
gradation characteristic of the visible image data can be made to
be optimum which eliminates effects of the defective pixel for each
respective visible wavelength component.
[0022] According to other aspects of the invention, a control
program for controlling an image reading device to perform the
above-described functions/operations a plurality of procedures can
be stored in a recording medium, or represented as a data signal
embodied in a carrier wave. The control program can, for example,
be recorded in a recording device of an image processing device by
downloading or the like via the Internet. Therefore, this image
processing device can eliminate effects of the defective pixel in
determination of the reading condition of the document
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] The invention will be described in conjunction with the
following drawings in which like reference numerals designate like
elements and wherein:
[0024] FIG. 1 is an overall structural diagram of an image
processing system to which this invention is applied;
[0025] FIG. 2 is a block diagram showing a schematic structure of a
host computer;
[0026] FIG. 3 is a block diagram showing a structure of a film
scanner;
[0027] FIG. 4 is an explanatory diagram showing a main scanning
direction and a subscanning direction during scanning of a
photographic film;
[0028] FIG. 5 is a diagram showing a reading region of a
photographic film;
[0029] FIG. 6 is a flowchart showing a prescanning program
according to an embodiment of the invention;
[0030] FIG. 7 is an explanatory view showing defective pixels with
hatching;
[0031] FIG. 8 is a graph showing an infrared component level of
each pixel of an image having defect pixels;
[0032] FIG. 9 is a diagram explaining a principle of infrared
correction according to an embodiment of the invention;
[0033] FIGS. 10A and 10B are graphs showing histograms that can be
obtained during prescanning;
[0034] FIG. 11 is a graph showing a LUT gradation table; and
[0035] FIG. 12 is a graph showing a LUT gradation table used when a
positive-type film is read.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0036] The following explains embodiments of this invention with
reference to FIGS. 1-12. First, an overall structure of an image
processing system 1 to which this invention is applied is explained
with reference to FIG. 1.
[0037] The image processing system 1 is constituted by a film
scanner (image reading device) 100, a host computer (e.g., a
personal computer) 20, a display 30, an input device 40 (e.g., a
keyboard 40A, a mouse 40B), and/or the like as shown in FIG. 1.
Here, an interface board (e.g., a SCSI board) 25 is housed in the
host computer 20. This interface board 25 is connected to the film
scanner 100 via an interface cable 26.
[0038] The image processing system 1 is operated in accordance with
software that is installed in the host computer 20. A user can
operate a keyboard 40A and a mouse 40B by looking at the display
30. In response to the operation content, an instruction signal is
output to the film scanner 100 from the host computer 20.
[0039] The film scanner 100 receives the above-mentioned
instruction signal and prescans and main-scans a photographic film
(e.g., a transparent document) 2.
[0040] Here, prescanning is performed prior to main scanning. As
described in detail later, main scanning is performed under image
reading conditions (exposure amount, LUT gradation conversion
characteristics, and/or the like) that have been determined by
prescanning. During prescanning, visible light (three channels of
R, G, and B) and infrared light are selectively irradiated onto the
photographic film 2 (four channels in total). The irradiation of
the three types of visible light is for separating the color
components of the image of the transparent document into a
plurality of visible components (visible wavelength components).
The irradiation of infrared light is to separate the color
components of the image of the transparent document into infrared
components. Here, performing prescanning by irradiating infrared
light is only performed to detect dust (foreign matter) or
scratches on the document surface that does not relate to the image
of the photographic film 2. This is based on the fact that the dye
of the photographic film (negative film is used here) 2 generally
transmits infrared light at substantially 100%. That is, with
respect to an image obtained by irradiation of infrared light,
luminescence lowers due to elements (defects such as a foreign
matter) other than color elements. This reduced amount of
transmitted infrared light is used to identify a defective
pixel(s). Furthermore, the wavelength of the infrared light during
prescanning can be determined according to the wavelength
characteristics of the dye of the photographic film 2.
[0041] Main scanning is performed under the image reading
conditions (exposure amount, LUT gradation conversion
characteristics, and/or the like) that have been determined by this
prescanning. During main scanning, visible light (three channels of
R, G, and B) is selectively irradiated onto the photographic film
2. By so doing, the color components of the image of the
transparent document can be separated into a plurality of visible
components (visible wavelength components).
[0042] The image data that has been obtained by main scanning is
transferred to the host computer 20. This image data is stored in a
hard disk 23 or the like within the host computer 20. As shown in
FIG. 2, the host computer 20 includes a CPU 21, a memory 22, a hard
disk 23, and a CD-ROM drive 24.
[0043] The CPU 21 executes control programs stored in the hard disk
23, a CD-ROM (storage medium) 3, or the like in accordance with an
instruction that has been input from the input device 40. The CPU
21 performs processing of the image data that has been obtained,
provides instructions for image reading to the film scanner 100,
and the like in accordance with this program.
[0044] As shown in FIG. 3, the film scanner 100 is constituted by a
scanner block 110, a lens driving part 100D, and a controller 100E.
In the scanner block 110, a light source 111, a holder (film
holder) 112, a lens 113 that forms an image optical system, an
image sensor (e.g., a CCD) 114, and mirrors 115, 115 which together
form a shooting optical system are arranged.
[0045] The light source 111 can be formed of a plurality of light
emitting diodes that emit three types of visible light (e.g., R, G
and B) with different visible wavelength components, and infrared
light. The three types of visible light and infrared light from the
light source 111 are selectively irradiated at a predetermined
timing onto the photographic film 2. This irradiation is performed
in response to a control signal output from a control circuit 136
described hereafter. By so doing, the light source 111 functions as
a visible component separation means and an infrared component
separation means.
[0046] In the holder 112, a transparent document is held. Here, the
transparent document is a photographic film (negative film) 2 (see
FIG. 4).
[0047] The image sensor 1 14 reads one line of an image in a main
scanning direction X of the photographic film 2 held in the holder
112 (reading of the image along a line L1 in FIG. 4). In other
words, when any of the three types of visible light or the infrared
light is selectively irradiated, the image sensor 114 transfers a
charge signal showing luminescence to the controller 100E
(specifically, to the analog processing circuit 131) pixel-by-pixel
for every line. A charge signal from the image sensor 114 is
transferred to the controller 100E and is used in order to
recognize an image that was separated into the respective visible
components (visible wavelength components) and an infrared
component.
[0048] The lens driving part 100D is constituted by a lead screw
121 to drive the scanning block 110 and a scanning motor 122. The
scanning motor 122 is, e.g., a stepping motor. Additionally, an
axis of the scanning motor 122 is coupled to and drives the lead
screw. The lead screw 121 that is connected to the scanning motor
122 is engaged to a through hole (undepicted) of the scanning block
110.
[0049] The scanning motor 122 is rotated at a predetermined angle
in response to the number of pulses of a driving signal output from
the controller 100E. At this time, the scanning block 110 is
step-moved (moved in the subscanning direction shown by arrow Y in
FIGS. 4 and 5) at a predetermined interval (e.g., Pp1 of FIG. 5)
relative to the photographic film 2 in response to the number of
pulses.
[0050] The controller 100E is constituted by an analog processing
circuit 131, an A/D converter 132, a LUT circuit 133, a memory 134,
an interface circuit 135, a control circuit 136, a microprocessor
unit (MPU) 137, and a program memory 138. Furthermore, in this
embodiment, the controller 100E functions as an infrared component
detecting means, a defective infrared component detecting means, a
visible component detecting means, a correcting means, a visible
image data obtaining means, a reading condition determining means,
a minimum brightness level detecting means, a gradation conversion
characteristic setting means, and a gradation characteristic
conversion means.
[0051] The analog processing circuit 131 is constituted by a sample
and hold circuit, a clamp circuit, an offset circuit, and/or the
like. This analog processing circuit 131 performs signal processing
to the charge signal transferred from the image sensor 114
(pixel-by-pixel). That is, the sample and hold circuit performs
signal processing such as removal of unnecessary signal components.
The clamp circuit improves stabilization by clamping part of the
signal. The offset circuit adjusts the signal level to a
predetermined level.
[0052] The A/D converter 132 converts the analog signal from the
analog processing circuit 131 to a digital signal (image data). The
LUT circuit 133 performs gradation conversion processing, in
accordance with a LUT gradation table (FIG. 11), to the digital
signal output from the A/D converter 132. The memory 134
temporarily stores image data for one line detected by the main
scanning direction of the image sensor 114.
[0053] The control circuit 136 outputs a control signal to control
lighting of the light source 111. Additionally, the control circuit
136 outputs a control signal, such as a clock signal/reading gate
signal, for the image sensor 114. Furthermore, the control circuit
136 outputs a control signal instructing a conversion start timing
to the A/D converter 132. In addition, the control circuit 136
outputs a control signal such as a memory address signal/memory
writing signal. Here, the memory address signal/memory writing
signal are signals to gradation-convert the signal in the LUT
circuit 133 and successively write to the memory 134.
[0054] MPU 137 determines the type of light (any of R, G, B, and
infrared light) irradiated from the light source 111. Furthermore,
the MPU 13 7 determines the lighting time (exposure time) of the
light source 111. The charge amount (corresponding to the light
amount) that is accumulated during the accumulation time
(accumulation of the signal charge) of the image sensor 114 is
adjusted by the control of the lighting time of the light source
111.
[0055] Additionally, the MPU 137 determines the timing of
accumulation/transfer of the charge by the image sensor 114 in
relation to the lighting time of the light source 111. Various
instruction signals that indicate instructions that have been thus
determined are converted to the above-mentioned specific control
signals by the control circuit 136. These control signals are
output to the light source 111, the image sensor 114, and the like
by the control circuit 136.
[0056] Meanwhile, the MPU 137 recognizes a total of four channels
of image data (visible image data, infrared image data) of the
respective color components of visible light (R, G, and B) and
infrared light, based on the charge signal from the image sensor
114. Furthermore, after the MPU 137 recognizes that one line of
image data has been performed by the image sensor 114 with respect
to four types of light (R, G, B, and infrared light), a
predetermined number of driving signals (pulse signals) is output
to the scanning motor 122, which then moves the scanning block 110
one step at a predetermined interval Pp1.
[0057] Additionally, the MPU 137 determines the exposure amount
(exposure time) during main scanning, the LUT gradation conversion
characteristics, and the like based on image data (visible image
data, infrared data) generated by the operation of the image sensor
114, the analog processing circuit 131, and the like during
prescanning. In addition, a main scanning program (undepicted) and
a prescanning program (FIG. 6) executed by MPU 137 are stored in
the program memory 138.
[0058] Next, prescanning that determines the exposure amount
(exposure time) during main scanning and the LUT gradation
conversion characteristics is explained in accordance with the
prescanning program of FIG. 6. Prescanning is performed to broaden
a dynamic range of an output image (final output image) from the
film scanner 100. The exposure amount (exposure time) during main
scanning and the LUT gradation conversion characteristics can be
optimized by this prescanning. As a result, the quality of the
image that has been read during main scanning is improved.
[0059] When this prescanning program (FIG. 6) begins, first, in
step S1, the lighting time (light-ON time) during prescanning is
set to a predetermined value. In the following step S2, the
scanning motor 122 is rotated by a predetermined angle, and the
scanning block 110 is moved (it is moved to a prescanning start
position (Yp1 of FIG. 5) immediately after the program starts).
[0060] In step S3, four channels of light (i.e., three channels of
visible light (R, G, and B) and one channel of infrared light) are
sequentially irradiated from the light source 111. Based on the
charge signal obtained from this image sensor 114, image data for
one line is obtained.
[0061] In step S4, three types (R, G, and B) of image data are
recognized in one pixel (ith image data) among image data for one
line that was obtained. In the following step S5, image data for
the infrared component is recognized.
[0062] In the following step S6, it is determined whether the
infrared component level of the recognized infrared image data is
larger than a predetermined threshold Lth. If this determination
result is "Yes", in step S7, with respect to the pixels in which
the infrared component level is larger than the threshold Lth,
"infrared correction" using the infrared component level is
performed (a correction visible component level is obtained).
[0063] In the following step S8, based on the image data after this
"infrared correction," a histogram (visible image data) is created.
As shown in FIG. 7, a case in which defective pixels (shown by
hatching in the figure) exist on the photographic film (transparent
document) 2 is considered.
[0064] If image reading using infrared light is performed with
respect to this transparent document, FIG. 8 shows a state of
infrared component data of (1-A), (1-B), . . . (5-D), and (5-E).
Here, with respect to the data of (1-B), (2-C), (3-E), (4-D) and
(5-A), the infrared component level is less than a predetermined
threshold Lth (predetermined level lower than the reference level
IL), so it cannot be saved by "infrared correction". Because of
this, the data of pixels (1-B), (2-C), (3-E), (4-D) and (5-A) will
be ignored with respect to creation of a histogram.
[0065] Meanwhile, "infrared correction" is performed in accordance
with the following procedure with respect to other pixels. FIG. 9
is a diagram explaining a principle of "infrared correction".
Furthermore, here, in order to simplify the explanation, "infrared
correction" of the red components is explained; however, with
respect to the G and B components, "infrared correction" is
performed in the same procedure.
[0066] When dust, scratches, or the like can be seen on the
photographic film 2, the illumination light is shielded by the
dust, scratches, or the like, so the light amount that transmits
through the photographic film 2 and reaches the image sensor 114
decreases. That is, the data with dust, scratches, or the like
becomes data that is darker than the image that is actually
recorded on the photographic film 2. Here, the photographic film 2
transmits a predetermined wavelength of infrared light according to
the wave characteristics of the color elements at substantially
100%. Therefore, the irradiated predetermined wavelength of
infrared light is not affected by the image that is recorded on the
photographic film 2. That is, when a predetermined wavelength of
infrared light is irradiated, the data that was obtained by the
image sensor 114 shows only a light amount that is decreased by
dust, scratches, or the like.
[0067] When there is no defect on the photographic film 2, a
transmittance level of the infrared light shows a constant value
(maximum value IR) as shown in the left side of FIG. 9. When there
is a defect, the transmittance level of the infrared light shows a
smaller value (e.g., the decreased value IR') for the level which
is decreased by a defect (dust, scratches, or the like) from the
constant value (maximum value IR).
[0068] Therefore, prior to reading the image data of the
photographic film 2, the maximum value IR is obtained by using
other photographic film without any defect. Alternatively, if this
maximum value (IR) is already known, the value is stored in the
memory in advance.
[0069] Additionally, with respect to the photographic film 2, the
transmittance level (decreased value IR') of the infrared light is
obtained. Furthermore, a correction coefficient k (=IR/IR') showing
the decrease of the infrared light due to dust, scratches, or the
like in the photographic film 2 is obtained by these two values
(maximum value IR, decreased value IR').
[0070] Next, a transmittance level (R) is obtained by irradiating
visible light (in this example, red light is used) onto the
photographic film 2. The transmittance level (R) that was obtained
at this time includes both the image data of the recorded image and
a decreased light amount due to scratches or the like.
[0071] Then, by multiplying the above-mentioned correction
coefficient k by the transmittance level (R), with respect to the
transmittance level (R) including the decreased amount, the
transmittance level (R') that excludes any effect (decrease) due to
dust, scratches, or the like can be obtained.
[0072] However, effectiveness of this infrared correction is
limited to the case when the data stored in the photographic film 2
includes data (R) of the color component (red is used here) of the
visible light that received a limited amount of decrease due to
defects. That is, when the level of IR' which determines the ratio
(IR/IR') is lower than a predetermined value (Lth), a decreased
amount (of the detected visible light) due to dust, scratches, or
the like is too large. Therefore, reliability of data due to
illumination light of the visible light is low. In such a
situation, even if infrared correction is performed, accurate image
data of the image recorded in the photographic film 2 cannot be
obtained. As will be described later, the image data of such
excessively defective pixels is not corrected and is not used to
prepare the histogram.
[0073] Image data in which defect correction (infrared correction)
was performed in steps S6 and S7 is used in order to create a
histogram (FIG. 10A) (step S8). In the following step S9, it is
determined whether the pixel in which "infrared correction" was
performed was the last pixel (nth) of the image data of the one
line. If this determination result is "No", the program returns to
step S4, and "infrared correction" is repeated for the next pixel
in the line.
[0074] Meanwhile, if the determination result in step S9 is "Yes",
the program moves to step S10 and determines whether the pixel in
which "infrared correction" was performed in this loop was the last
line. When this determination result is "No", processing proceeds
to step S2, and then the next line is scanned and processed as
described above.
[0075] When the determination result of step S10 becomes "Yes", the
program moves to step S11, and the brightest point (MXR) and the
darkest point (MNR) are calculated from the created histogram (FIG.
10A). The brightest point (MXR) and the darkest point (MNR), which
were thus obtained, are used in order to determine the most
appropriate value of the exposure amount (exposure time) and the
LUT gradation conversion characteristics.
[0076] In the following step S12, the exposure time during main
scanning is calculated so that the above-mentioned brightest point
(MXR) becomes a full scale (a maximum value that does not result in
over-saturation of the image sensor). The calculated exposure time
is set as an exposure time during main scanning.
[0077] Here, by focusing on the brightest point (MXR), the exposure
amount (E1) is determined based on the following equation (1) so
that this becomes a full scale (FS).
E1=Ep.times.FS/MXR (1)
[0078] Here, Ep is the exposure amount obtained during prescanning.
Based on this E1, the exposure time (the visible light exposure
time of the light source 111) is determined. As a result, even when
there is a transmitted light amount distribution during prescanning
as shown in FIG. 10A, the transmitted light amount distribution is
obtained during main scanning as shown in FIG. 10B. That is, the
brightest point MXR of the transparent document is matched with the
full scale value FS.
[0079] In step S13, the LUT gradation conversion characteristics
are determined so that the darkest point (MNR) by the
above-determined exposure time matches the end point of the
gradation table (FIG. 11). In this step, MPU 137 functions as a
gradation conversion characteristic means. The LUT gradation
conversion characteristics are set so that the darkest point (MNR)
level of the input side during irradiation by E1 becomes the
highest output (the end point of the LUT gradation conversion
characteristics) after being converted.
[0080] Here, the darkest point (MNR) level also changes and becomes
the darkest point (MNR') level. This is because the exposure amount
(exposure time) changes at the same ratio when the exposure amount
is changed as described above. The darkest point (MNR') after being
changed is obtained by the following equation (2).
MNR'=MNR.times.FS/MXR (2)
[0081] Based on this darkest point (MNR'), the LUT gradation
conversion characteristics are determined (solid line of FIG. 11).
Here, the ratio of the entire LUT gradation conversion
characteristics (broken lines in FIG. 11) in which "0" is a
reference point is corrected with the full scale side (right side)
as the origin (dotted lines .fwdarw. solid line in FIG. 11). FIG.
11 shows a LUT gradation table when a negative film is used. The
LUT gradation conversion characteristics vary depending on the type
of film (e.g., manufacturer, ISO value, or the like), the
transmitted light amount distribution, and the like.
[0082] Furthermore, when the LUT gradation conversion
characteristics are determined based on the darkest point (=MNdR0)
using the defective pixels, a curved line can be seen which is
shown by the two-dotted line of FIG. 11. Because the actual darkest
point of the image is MNR', a full scale output cannot be obtained
by this curved line. If the defective pixels are not removed, the
dynamic range becomes too narrow by this amount.
[0083] Thus, by creating the histogram (FIG. 10A) by the image data
in which defect correction was performed by infrared correction and
using the darkest point MNR and the brightest point MXR of the
histogram, the exposure amount (exposure time) during main scanning
and the LUT gradation conversion characteristics can be
optimized.
[0084] The following briefly explains main scanning that is
executed by using the exposure amount and the LUT gradation
conversion characteristics determined by the prescanning. Main
scanning is executed after prescanning when a user inputs a signal
that starts main scanning from the input device 40 to the host
computer 20. In the film scanner 100 that has received the
instruction signal, the MPU 137 executes the above-mentioned
prescanning, and then the main scanning begins.
[0085] According to the main scanning program (not depicted), the
MPU 137 first outputs a control signal (driving signal) to the
scanning motor 122. By so doing, the scanning block 110 is moved to
a reading start position (main scanning start position). This main
scanning start position is the same as the above-mentioned
prescanning start position (the reading line L1 is Yp1 of FIG.
5).
[0086] Furthermore, the main scanning and subscanning of the image
sensor 114 are from points Xp1 to Xp2 and from points Yp1 to Yp2 of
FIG. 5, respectively, in the same manner as in prescanning.
Additionally, the reading pitch is set at a desired pitch each time
according to the reading condition of main scanning.
[0087] When the scanning block 110 is moved to the main scanning
start position, specified light (R, G, and B) is sequentially
irradiated from the light source 111, with respect to the one line
(L1), and the image for one line is read by the image sensor 114
(main scanning). The read image is processed by the analog
processing circuit 131 as a plurality of charge signals for the
respective pixels. Then, the plurality of charge signals are
sequentially A/D converted by the A/D converter 132 and become
digital signals (pixel data).
[0088] Based on an instruction from the MPU 137, the LUT circuit
133 sequentially LUT-gradation converts the pixel data (i.e., MPU
137 functions as a gradation characteristic converting means). The
LUT gradation conversion is performed in accordance with the LUT
converting table (FIG. 11). The converted image data for one line
is temporarily stored in the memory 134. The image data for one
line stored in the memory 134 is later transferred to the host
computer 20 (the memory 22 and/or the hard disk 23, etc.).
[0089] When the charge signal that shows the image for one line is
output from the image sensor 114, the scanning motor 122 is
rotated. Along with this rotation, the image scanner 114 is again
step-moved in the subscanning direction at a specified pitch. At
this time, the visible light (R, G, B) is irradiated from the light
source 111, and the image of the following line is read. This
processing is performed with respect to the subscanning direction
(Yp1-Yp2).
[0090] As described above, the LUT gradation conversion
characteristics by the LUT circuit 133 and the irradiation time
(exposure time) of the light source 111 are determined based on the
brightest point (MXR or MXR') and the darkest point (MNR or MNR')
of the corrected histogram (FIG. 10B) in which defective pixels
caused by dust (foreign matter) and/or scratches are corrected when
main scanning is performed. As a result, the LUT gradation
conversion characteristics and the exposure amount (exposure time)
during main scanning can be optimized without having any effect of
defective pixels caused by dust (foreign matter) and/or
scratches.
[0091] Furthermore, in the above-mentioned embodiment, an example
was explained using a negative film as a transparent document, but
the invention is not limited to negative films. This invention can
also be applied to the case where a positive film is used as a
transparent document. At this time, instead of the LUT converting
table (negative film) shown in FIG. 11, the LUT conversion can be
executed by using a LUT converting table (for a positive film) as
shown in FIG. 12. In this case, in the LUT converting table for the
positive film as well, based on the darkest point MNR'
(=MNR.times.FS/MXR), which was obtained by the above-mentioned
procedure, the LUT gradation conversion characteristics during main
scanning can be determined (solid line of FIG. 12).
[0092] Additionally, in the above-mentioned embodiment, the MPU 137
of the film scanner controls an image for prescanning; however, the
CPU 21 of the host computer 20 can also control the image for
prescanning. In this case, the prescanning program can be stored in
the hard disk 23, for example.
[0093] In addition, by recording the prescanning program to a
CD-ROM (recording medium) 3, these programs can be executed by the
CPU 21 or MPU 137 of existing machines as long as they can
irradiate with (or be modified to irradiate with) IR light.
[0094] Furthermore, in the above-mentioned embodiment, the LUT
gradation conversion characteristics are determined for the
respective histograms by creating three histograms, corresponding
to the three types of visible wavelength components. However, the
LUT gradation conversion characteristics can also be determined by
focusing on one visible wavelength component only. The LUT
gradation conversion characteristics that were obtained at this
time can also be used for other visible wavelength components.
[0095] Additionally, in the above-mentioned embodiment, three types
of visible light R, G, and B are used as visible wavelength
components, but needless to say, other visible wavelength
components can also be used. Furthermore, needless to say, the
gradation conversion characteristics are not limited to the
examples shown in the above-mentioned embodiment.
[0096] Additionally, in the above-mentioned embodiment, the example
was explained showing the LUT conversion for an image signal that
has been digitally converted by the A/D converter, but LUT
conversion can also be performed by the analog circuit to the
analog signal prior to A/ID conversion.
[0097] Furthermore, in the above-mentioned embodiment, an example
was explained in which a light source 111 is used that can
irradiate three types of visible light R, G, and B and infrared
light, but the image data of the respective color components R, G,
and B and the infrared light can also be obtained by arranging a
filter(s) in the image sensor.
[0098] Furthermore, in the above-mentioned embodiment, an example
was explained in which, every time one image is read, by using the
infrared histogram and the image histograms that had been obtained
during prescanning, the exposure amount/LUT conversion
characteristics during main scanning were determined. However,
prescanning may be performed only once, the visible histogram and
the infrared histogram may be obtained, and then the exposure
amount/LUT conversion characteristics during main scanning that
uses these histograms can be determined for a plurality of images
that are read.
[0099] Furthermore, the image reading program may be accessed from
a predetermined home page via the Internet and can be downloaded to
the host computer 20 as driver software or firmware.
[0100] For example, in a state in which the image reading program
can be accessed from a predetermined home page by the host computer
20, this type of downloading can be performed by selecting a film
scanner which is one of the image reading devices from the product
display on the screen and selecting driver software or firmware
that matches the office service environment of the host computer
20.
[0101] Additionally, the following dial up connection can be
applied as a state connecting the host computer 20 to the Internet.
That is, the host computer 20 is connected to telephone lines via a
modem or a terminal adapter and is connected to a modem or a
terminal adapter of a provider, which is an Internet connection
service company, by the telephone lines. The modem or terminal
adapter of the provider is connected to a server, and the server is
connected to the Internet via a rooter which sets a relay route.
Thus, the host computer 20 can be connected to the Internet (home
page) via a server of the provider through telephone lines.
[0102] According to one aspect of the invention, even if foreign
matter is attached to a transparent document or if the document is
scratched, when the reading condition of the transparent document
is determined, quality can be optimized without receiving any
adverse effect due to foreign matter or the like, and image quality
of the read image can be improved.
[0103] Furthermore, according to another aspect of the invention,
even if foreign matter is attached to a transparent document or
when there is a scratch, the gradation conversion characteristic
based on the visible image data is determined after the effects due
to foreign matter or the like are removed by correction. Because of
this, the gradation conversion characteristic can be optimized for
an image, and image quality can be improved.
[0104] In addition, according to another aspect of the invention,
even if foreign matter is attached to a transparent document or
when there is a scratch, compensation for the effects given to the
visible component by foreign matter or the like can be easily
effected. A reading condition can be optimized for an image, and
image quality of the read image can be improved.
[0105] Additionally, according to another aspect of the invention,
if there is a situation in which a visible component is
unrecoverable due to foreign matter attached to a transparent
document or due to a scratch, by ignoring the defective pixel in
the determination of the reading condition, effects due to foreign
matter can be removed as much as possible, and image quality can be
improve.
[0106] Furthermore, according to another aspect of the invention,
with respect to all the visible image data with different color
components, by correcting effects due to foreign matter, scratches,
etc. in the defective pixel(s), a fine gradation conversion
characteristic can be set for each respective color component. As a
result, without having any effects of the defective pixel, an
appropriate color image can be obtained.
[0107] Additionally, according to another aspect of the invention,
a program that optimally avoids the affects of foreign matter or
the like even if attached foreign matter or scratches exist when
the reading condition of the transparent document is determined
improves image quality of the read image, and can be written in a
recording device within the image processing device, for example,
via the Internet.
[0108] In the illustrated embodiment, the controller 100E is
implemented as a programmed general purpose computer. It will be
appreciated by those skilled in the art that the controller can be
implemented using a single special purpose integrated circuit
(e.g., ASIC) having a main or central processor section for
overall, system-level control, and separate sections dedicated to
performing various different specific computations, functions and
other processes under control of the central processor section. The
controller can be a plurality of separate dedicated or programmable
integrated or other electronic circuits or devices (e.g., hardwired
electronic or logic circuits such as discrete element circuits, or
programmable logic devices such as PLDs, PLAs, PALs or the like).
The controller can be implemented using a suitably programmed
general purpose computer, e.g., a microprocessor, microcontroller
or other processor device (CPU or MPU), either alone or in
conjunction with one or more peripheral (e.g., integrated circuit)
data and signal processing devices. In general, any device or
assembly of devices on which a finite state machine capable of
implementing the procedures described herein can be used as the
controller. A distributed processing architecture can be used for
maximum data/signal processing capability and speed.
[0109] While the invention has been described with reference to
preferred embodiments thereof, it is to be understood that the
invention is not limited to the preferred embodiments or
constructions. To the contrary, the invention is intended to cover
various modifications and equivalent arrangements. In addition,
while the various elements of the preferred embodiments are shown
in various combinations and configurations, which are exemplary,
other combinations and configurations, including more, less or only
a single element, are also within the spirit and scope of the
invention.
* * * * *