U.S. patent application number 11/513748 was filed with the patent office on 2007-03-22 for back-light module for image scanning device and method for calibrating illumination with the back-light module.
Invention is credited to Tsung-Yin Chen, Che-Kuei Mai.
Application Number | 20070064287 11/513748 |
Document ID | / |
Family ID | 25413210 |
Filed Date | 2007-03-22 |
United States Patent
Application |
20070064287 |
Kind Code |
A1 |
Mai; Che-Kuei ; et
al. |
March 22, 2007 |
Back-light module for image scanning device and method for
calibrating illumination with the back-light module
Abstract
A back-light module for an image scanning device includes a
casing, a pair of tubular lamps, a light guide plate, and a frosted
transparent plate. The image scanning device includes a document
supporting plate and an optical scanning module movable in a
longitudinal direction. A calibration of illumination with the
back-light module is done by (1) activating the back-light module
to project light onto the optical scanning module, (2) driving the
optical scanning module in the longitudinal direction, (3)
obtaining illumination signals associated with selected pixels of a
longitudinally-extending calibration zone formed on the document
supporting plate, (4) comparing each illumination signal with a
reference to obtain a result and manipulating the result to obtain
a calibration parameter, and (5) calibrating the illumination of
pixels of an image with the corresponding calibration parameters in
scanning a transmissive original document.
Inventors: |
Mai; Che-Kuei; (Hsinchu
City, TW) ; Chen; Tsung-Yin; (Hsinchu City,
TW) |
Correspondence
Address: |
BERKELEY LAW & TECHNOLOGY GROUP
1700NW 167TH PLACE
SUITE 240
BEAVERTON
OR
97006
US
|
Family ID: |
25413210 |
Appl. No.: |
11/513748 |
Filed: |
August 30, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11301805 |
Dec 12, 2005 |
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11513748 |
Aug 30, 2006 |
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09900865 |
Jul 10, 2001 |
6999212 |
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11301805 |
Dec 12, 2005 |
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Current U.S.
Class: |
358/504 ;
358/474 |
Current CPC
Class: |
G02B 6/0081 20130101;
H04N 1/401 20130101; G02B 6/0051 20130101; G02B 27/024
20130101 |
Class at
Publication: |
358/504 ;
358/474 |
International
Class: |
H04N 1/46 20060101
H04N001/46 |
Claims
1-8. (canceled)
9. A scanning system comprising an image scanning device capable of
calibrating illumination in a first direction and calibrating
illumination in a second direction.
10. The scanning system of claim 9, wherein the image scanning
device further comprises: an optical scanning module comprising at
least one image sensing element, the at least one image sensing
element capable of sensing an image signal of at least one selected
pixel; a back-light module capable of illuminating the optical
scanning module; and at least one processing module capable of
obtaining an image signal of at least one selected pixel, wherein
said processing module is further capable of obtaining at least one
calibration parameter.
11. The system of claim 10, wherein the image signal is associated
with red, green or blue colors, or combinations thereof.
12. The system of claim 10, wherein the at least one calibration
parameter comprises parameters for red, green or blue colors, or
combinations thereof.
13. The system of claim 10, wherein said processing module is
further capable of determining said at least one calibration
parameter with respect to the image signal and a reference.
14. The system of claim 13, further comprising a memory unit
capable of storing the reference.
15. A system comprising: an image scanning device capable of
calibrating illumination in a first direction and calibrating
illumination in a second direction, the image scanning device
comprising a calibration zone extending in the first direction and
a calibration zone extending in a second direction, the image
scanning device further comprising: an optical scanning module; at
least one image sensing element disposed within the optical
scanning module capable of detecting a first image signal of a
first selected pixel and a second image signal of a second selected
pixel of the calibration zone extending in the second direction; at
least one processing unit capable of: comparing the first image
signal with a reference to obtain a first comparison result;
comparing the first image signal with the second image signal to
obtain a second comparison result; manipulating the first
comparison result and the second comparison result to determine at
least one calibration parameter; and calibrating an illumination of
an image based, at least in part, on the at least one calibration
parameter.
16. The system of claim 15, wherein the first selected pixel is
associated with red, green or blue colors, or combinations
thereof.
17. The system of claim 15, further comprising a memory unit
capable of storing the reference.
18. An image scanning device capable of calibrating illumination in
a first direction and calibrating illumination in a second
direction.
19. The image scanning device of claim 18, further comprising: an
optical scanning module comprising at least one image sensing
element, the at least one image sensing element capable of sensing
an image signal of at least one selected pixel; a back-light module
capable of illuminating the optical scanning module; and at least
one processing module capable of obtaining an image signal of at
least one selected pixel, wherein said processing module is further
capable of obtaining at least one calibration parameter.
20. A scanning method comprising: illuminating a document; and
calibrating illumination in a first direction and calibrating
illumination in a second direction.
21. An apparatus for scanning comprising: means for illuminating a
document; and means for calibrating illumination in a first
direction and calibrating illumination in a second direction.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention generally relates to a back-light
module of image scanning devices for transmissive original
documents, and in particular to a method for calibration of
illumination in order to obtain a substantially uniform
illumination over an original document.
[0003] 2. Description of the Prior Art
[0004] Document scanners are generally classified in two types for
respectively handling a reflective original document which
comprises an opaque substrate and a transmissive original document
which comprises a transparent substrate. A transmissive original
document scanner comprises a back-light module for generating light
projecting the image formed on an original onto an image sensor
system of the document scanner.
[0005] A conventional back-light module comprises a movable
line-type light source which is moved in a given direction from one
end of the original document to an opposite end. A driving system
is required to move the light source which complicates the overall
structure of the back-light module.
[0006] Another conventional back-light module comprises a
surface-type light source which requires no movement of any parts
of the back-light module. FIG. 1 of the attached drawings shows an
image scanning device having a back-light module comprising a
surface-type light source and FIG. 2 shows an exploded view of the
back-light module.
[0007] As shown in FIG. 1, a conventional scanner for transmissive
original documents, designated with reference numeral 1, comprises
a housing (not labeled) having a transparent document supporting
plate 10 for supporting an original document (not shown) containing
an original and a back-light module 3 in the form of a flip cover
for selectively covering the document supporting plate 10. An
optical scanning module 11 comprising a sensor system is movably
supported inside the housing by guide rails 12, 13 for moving in a
longitudinal direction (Y direction) under the control of a control
unit 14. The sensor system comprises a line of sensing elements,
such as an array of CCD (Charge Coupling Device), arranged in a
lateral direction (X direction) onto which a "scan line" of the
original is projected by light generated by the back-light module
3. The sensing elements convert the optical signal caused by the
scan line into electrical representation of the scan line. By
moving the optical scanning module in the longitudinal direction
line by line or step by step and scanning the original one scan
line at a time, the original or a portion of the original document
may be scanned.
[0008] As shown in FIG. 2, the back-light module 3 comprises a
casing 31 having an open bottom closed by a bottom plate 32. An
opening 32a is defined in a central area of the bottom plate 32
receiving and retaining a transparent plate 37. Two tubular lamps
41, 42, such as cold cathode fluorescent lamps, are arranged inside
the casing 31 and spaced from each other with a light guide plate
34 disposed therebetween. Two diffusion boards 35, 36 are arranged
between the light guide plate 34 and the transparent plate 37.
Light from the tubular lamps 41, 42 are guided by the light guide
plate 34 for spreading over and projecting from the light guide
plate 34 onto the diffusion boards 35, 36. The light is further
distributed by the diffusion boards 35, 36 to uniformly project
toward and through the transparent plate 37. A reflective sheet 33
is arranged between the light guide plate 34 and a top of the
casing 31 for directing light back to the transparent plate 37.
[0009] Since uniform distribution of light is required in obtaining
good result of scanning transparent original documents, the
diffusion boards 35, 36 are important parts for the conventional
scanner. Although an illumination calibration zone 2 extending in
the direction of the CCD array, namely the X direction (or the
lateral direction as defined above), for calibration of
illumination of the back-light source, there is no way in the
conventional design to calibrate illumination in the Y direction
(or the longitudinal direction as defined above). Uniformity of
illumination in the Y direction is in generally achieved by the
diffusion boards 35, 36. However, using diffusion boards to
uniformly distribute light complicates the overall structure of the
back-light module and increases costs.
[0010] Thus, it is desired to provide a back-light module of an
image scanning device for overcoming the above discussed
problems.
SUMMARY OF THE INVENTION
[0011] Accordingly, an object of the present invention is to
provide a back-light module of an image scanning device having a
simple structure and thus low costs.
[0012] Another object of the present invention is to provide a
method for operating the back-light module to achieve an excellent
scanning result of a transparent original document.
[0013] According to the present invention, a back-light module of
an image scanning device comprises a casing having an open bottom,
a pair of tubular lamps mounted inside the casing with a light
guide plate arranged between the lamps and a frosted transparent
plate attached to the open bottom of the casing. The image scanning
device includes a document supporting plate for supporting a
transmissive original document and an optical scanning module
containing sensing elements arranged in a line in a lateral
direction and movable in a longitudinal direction in a scan line by
scan line fashion. The back-light module is selectively positioned
on the document supporting plate with the frosted plate facing the
document. Light is projected from the back-light module through the
document and toward the sensing elements. The frosted plate
functions to more uniformly distribute the light over the document
supporting plate.
[0014] A method for calibrating illumination of a surface type
back-light source is also provided in the present invention. The
calibration of illumination is done by (1) activating the
back-light module to project light onto the sensing elements, (2)
driving the optical scanning module in the longitudinal direction,
(3) obtaining illumination signals associated with selected pixels
of a longitudinally-extending calibration zone formed on the
document supporting plate, (4) comparing each illumination signal
with a reference to obtain a result and manipulating the result to
obtain a calibration parameter, and (5) calibrating illumination of
pixels of an image with the corresponding calibration parameters in
scanning a transmissive original document on which the image is
formed to obtain an excellent scanning result of the document.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] The present invention will be apparent to those skilled in
the art by reading the following description of a preferred
embodiment and the best mode of operation thereof with reference to
the attached drawings, in which:
[0016] FIG. 1 is a perspective view of a conventional flat bed
image scanning device having a back-light module thereon;
[0017] FIG. 2 is an exploded view of the back-light module of the
conventional image scanning device of FIG. 1;
[0018] FIG. 3 is an exploded view of a back-light module
constructed in accordance with the present invention;
[0019] FIG. 4 is a perspective view of an image scanning device
constructed in accordance with the present invention; and
[0020] FIG. 5 is a flow chart of a method for calibrating
illumination of the back-light module of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0021] With reference to the drawings and in particular to FIG. 3,
a back-light module constructed in accordance with the present
invention, generally designated with reference numeral 3', is
shown. It is to be noted that, for simplicity, similar elements
through the drawings will be designated with same or like reference
numerals.
[0022] The back-light module 3' comprises a casing 31 inside which
two spaced tubular lamps 41, 42, such as cold cathode fluorescent
lamps. A light guide plate 34 is arranged between the tubular lamps
41, 42. A reflective sheet 33 is located between the light guide
plate 34 and the casing 31. A frosted light-transmissive plate 38,
such as a frosted transparent acrylic board, is attached to a
bottom opening (not labeled) of the casing 31 opposing the light
guide plate 34 for distributing light from the light guide plate
34. The frosted light-transmissive plate 38 also protects the light
guide plate 34 and prevents debris and other contamination from
entering the casing 31.
[0023] FIG. 4 shows an image scanning device, generally designated
with reference numeral 1, incorporating the back-light module 3' of
the present invention. The image scanning device I comprises a
housing having a top surface, providing a document supporting plate
10. The back-light module 3' is pivotally attached to the housing
for selectively positioning on the document supporting plate 10 or
covering an original document placed on the document supporting
plate 10. A pair of guide rails 12, 13 extending in a longitudinal
direction (Y direction) is arranged inside the image scanning
device for movably supporting an optical scanning module 11 whereby
the optical scanning module 11 is controlled by a control unit 14
to move in the longitudinal direction Y.
[0024] The image scanning device 1 comprises a line of image
sensing elements (not shown), such as a CCD array, extending in a
lateral direction (X direction) for detecting a scan line of the
original document when light is generated by and projected from the
back-light module 3', through the transmissive original document,
onto the optical scanning module 11.
[0025] A first calibration zone or X-directional calibration zone 2
extending in the X direction (lateral direction) is attached to the
bottom surface of the document supporting plate 10 for calibration
of illumination in the lateral direction, namely the X direction. A
second calibration zone or Y-directional calibration zone 4
extending in the Y direction (longitudinal direction) is attached
to the bottom surface of the document supporting plate 10 for
calibration of illumination in the Y direction. By means of the
provision of the second calibration zone 4, a calibration of
illumination of the light projected from the frosted plate 38 can
be performed to obtain an excellent scanning result without using
diffusion boards employed in the conventional scanner.
[0026] FIG. 5 shows a flow chart of illumination calibration
carried out in accordance with the present invention. The
calibration of illumination in the lateral direction is known to
those skilled in the art and no further discussion will be given
herein. The operation of illumination calibration performed by the
flow chart of FIG. 5 is mainly for calibration of illumination in
the longitudinal direction (Y direction). The operation begins at
step 101. The back-light module 3' is provided and activated to
generate and project light onto the optical scanning module 11
(step 102). The optical scanning module 11 is then driven to
sequentially move from one scan line to the next one in the Y
direction or longitudinal direction (step 103). The image sensing
elements of the scanning device 1 detect an image signal of each
pixel of the second calibration zone 4 when moving in the Y
direction and convert and store the optical signal into an
electrical representation corresponding to illumination of the
pixel (step 104). The storage of the electrical signals can be done
with memory means provided in the scanner. If desired, the
electrical representation may be taken at a given number of scan
lines, such as every five scan lines. That is the optic signal of
the pixels is taken every five successive pixels in the
longitudinal direction. In case of color scanners, different
electrical representation for red, green and blue colors can be
taken separately.
[0027] In step 105, a preset illumination reference signal is
provided, which may be stored in a memory unit of the scanner.
Then, the electrical representation of the illumination of selected
pixel is compared with the preset illumination reference signal in
step 106. The comparison result is then used to evaluate the
difference of illumination between two successively-taken pixels
that belong to different scan lines and a calibration parameter
indicating the difference is obtained based on the difference of
illumination (step 106). The parameters are then stored. In case of
color scanners, different parameters are obtained for red, green
and blue colors of each image pixel.
[0028] The stored parameters may be retrieved later to calibrate
the illumination of pixels of an image obtained from a transmissive
original document. When an original document is scanned, the
illumination of each pixel is obtained through the sensing elements
of the image scanning device. The illumination of each pixel is
then calibrated with the corresponding parameter that is obtained
previously and stored in the memory means (step 107). After each
pixel is calibrated with the corresponding parameter, the whole
image may then output through suitable output means (step 108).
[0029] In brief, the scanner in accordance with the present
invention employs a frosted plate to replace the diffusion boards
adapted in the conventional scanner. This simplifies the overall
structure and reduces the costs. The illumination of each pixel of
an image that is being scanned is then calibrated with the
corresponding calibration parameter previously obtained to
alleviate and even overcome the possible non-uniform distribution
of illumination in the longitudinal direction. An excellent quality
of image can thus be obtained.
[0030] Although the present invention has been described with
reference to the preferred embodiment and the best mode of
operation thereof, it is apparent to those skilled in the art that
a variety of modifications and changes may be made without
departing from the scope of the present invention which is intended
to be defined by the appended claims.
* * * * *