Note: Descriptions are shown in the official language in which they were submitted.
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TITLE: METHOD AND SYSTEM FOR PERFORMING X-RAY INSPECTION OF A
LIQUID PRODUCT AT A SECURITY CHECKPOINT
FIELD OF THE INVENTION
The present invention relates to technologies for assessing the threat status
of liquid
products by means of penetrating radiation such as X-rays. The invention has
numerous
applications; in particular it can be used for scanning bottles holding liquid
substances at
airport security check points.
BACKGROUND
Some liquid or combinations of liquid and other compounds may cause enough
damage to
bring down an aircraft. As no reliable technology-based solution currently
exists to
adequately address this threat, authorities have implemented a ban of most
liquids, gels and
aerosols in cabin baggage.
As a result, there have been disruptions in operations (e.g., a longer
screening process; a
change of focus for screeners; additional line-ups), major inconveniences for
passengers (as
well as potential health hazards for some) and economic concerns (e.g.,
increased screening
costs; lost revenues for airlines and duty free shops; large quantities of
confiscated -
including hazardous - merchandise to dispose of), and so on.
In light of the above, there is a need to provide a technology-based solution
to assess the
threat status of liquid products.
SUMMARY
This patent application focuses on the processing of partially filled bottles
of liquid at
security check points.
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According to a broad aspect, the level of fill of a bottle is used as a factor
in the
determination of the threat status of the bottle. For example, if the level of
fill of the
bottle is below a certain threshold level of fill, (e.g. 25% full) then a
decision can be
made to reject that bottle irrespective of its content. It will be appreciated
that deriving
the precise level of fill of a bottle, for example 25%, is not critical to the
present
invention. More specifically, the level of fill may be derived so that it is
within a certain
tolerance, for example 25% full 10%. Consequently, the level of fill of the
bottle can
be an approximate measure of the level of fill of the bottle rather than an
exact
measurement.
In specific examples of implementation, the level of fill of a bottle may be
derived based
on a visual inspection of the bottle by a security screening and/or based on
an x-ray
image of the bottle.
According to a specific example of implementation, the level of fill is
derived from an x-
ray image of the bottle at least in part by extracting from the x-ray image
characteristics
of the meniscus formed by the liquid held in the bottle. Characteristic of the
meniscus
may include for example, the shape and position of the meniscus. Any suitable
technique
for obtaining characteristics pertaining to the meniscus formed by the liquid
held in the
bottle may be used.
According to another specific example of implementation, the length of a path
travelled
by X-rays through a liquid held by a bottle is determined from the x-ray image
of the
bottle, where the bottle is only partially filled with liquid. In accordance
with this
implementation, location information associated with a meniscus formed by the
liquid in
the bottle is obtained from the X-ray image. The location information
associated with the
meniscus is used in combination with geometric information associated with the
bottle in
the computation of the length of the path travelled by X-rays through the
liquid held by
the bottle. The determined length of the patent is then used in combination
with
attenuation information from an x-ray image of the bottle holding the liquid
to determine
the threat status of the bottle holding the liquid.
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In specific implementations, the bottle may be positioned at a known angle
(e.g. by
means of a tray having an inclined bottom surface), or may be positioned
horizontally
while it is being scanned by the X-ray machine.
In specific implementations, the X-ray machine used to perform the X-ray
inspection
may be a single-view machine or a multi-view machine.
In accordance with yet another broad aspect, the present invention provides a
method for
assessing a threat status of a liquid product at a security checkpoint. The
liquid product is
comprised of a bottle holding a liquid, wherein the bottle is at least
partially filled with
liquid. The method comprises receiving X-ray image data associated with the
liquid
product, the X-ray image data being derived by performing an X-ray scan of the
liquid
product using an X-ray imaging apparatus. The method also comprises processing
the X-
ray image data to derive information conveying a level of fill of the bottle
and
determining the threat status of the liquid product at least in part based on
the level of fill
of the bottle. The method further comprises releasing information conveying
the
determined threat status of the liquid product.
In a specific example of implementation, the method comprises processing the X-
ray
image data to derive information conveying the level of fill of the bottle
wherein the
processing comprises locating a meniscus formed by the liquid in the bottle.
In a specific example of implementation, the method comprises processing the X-
ray
image data to derive geometric information associated with the bottle and
processing the
X-ray image data to derive location information associated with a meniscus
formed by
the liquid in the bottle. The method also comprises deriving the level of fill
of the bottle
at least in part based on the location information associated with the
meniscus and on the
geometric information associated with the bottle.
In a specific example of implementation, the method comprises deriving path
length data
at least in part based on the location information associated with the
meniscus and the
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geometric information associated with the bottle. The path length data conveys
an
estimated length of a path followed by X-rays through the liquid held in the
bottle. The
method also comprises processing the X-ray image data to determine the threat
status of
the liquid product based in part on the path length data and X-ray attenuation
information
obtained from the X-ray image data.
In yet another specific example of implementation, the method comprises
processing the
X-ray image data to derive geometric information associated with the bottle at
least in
part based on an angle made between a longitudinal axis of the bottle and a
horizontal
plane and processing the X-ray image data to derive location information
associated with
a meniscus formed by the liquid in the bottle at least in part based on the
angle made
between the longitudinal axis of the bottle and the horizontal plane.
In a specific example of implementation, the liquid product is supported by a
tray while
the liquid product is subjected to an X-ray inspection at a security
checkpoint to
determine the threat status of the bottle filled with liquid. The bottle has a
top extremity
and a bottom extremity and the tray is configured to hold the bottle in an
inclined position
such that a meniscus in the bottle filled with liquid has a tendency to
migrate toward one
of the extremities of the bottle filled with liquid. Alternatively, the tray
may be a
conventional tray with a flat bottom surface.
In yet a further specific example of implementation, the method comprises
receiving the
X-ray image data associated with the liquid product, wherein the X-ray image
data is
obtained using a multi-view X-ray machine. The X-ray image data conveys a
first X-ray
image of the liquid product taken by subjecting the liquid product to X-rays
in a first
orientation and a second X-ray image of the liquid product taken by subjecting
the liquid
product to X-rays in a second orientation. The method also comprises
processing the X-
ray image data corresponding to the first X-ray image of the liquid product to
derive
information conveying an estimated level of fill of the bottle and processing
the X-ray
image data corresponding to the second X-ray image of the liquid product and
the
estimated level of fill of the bottle obtained based on the X-ray image data
corresponding
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to the first X-ray image to derive an adjusted level of fill of the bottle.
The method
further comprises determining the threat status of the liquid product at least
in part based
on the adjusted level of fill of the bottle and releasing information
conveying the
determined threat status of liquid product.
In accordance with another broad aspect, the invention provides a computer
readable
storage medium storing a program element suitable for execution by a computing
apparatus for assessing a threat status of a liquid product at a security
checkpoint, the
liquid product being comprised of a bottle holding a liquid, wherein the
bottle is at least
partially filled with liquid. The computing apparatus comprises a memory unit
and a
processor operatively connected to the memory unit. The program element, when
executing on the processor, is operative for assessing the threat status of a
liquid product
in accordance with the above-described method.
In accordance with yet another broad aspect, the invention provides an
apparatus for
assessing a threat status of a liquid product at a security checkpoint, where
the liquid
product is comprised of a bottle holding a liquid and wherein the bottle is at
least partially
filled with liquid. The apparatus comprises an input, a processing unit and an
output and
is operative for assessing the threat status of a liquid product in accordance
with the
above-described method.
In accordance with a further broad aspect, the invention provides a system
suitable for
assessing a threat status of a liquid product at a security checkpoint. The
liquid product is
comprised of a bottle holding a liquid, wherein the bottle is at least
partially filled with
liquid. The system comprises an inspection device for performing an X-ray
inspection on
the liquid product using penetrating radiation to generate an X-ray image of
the liquid
product. The system also comprises an apparatus for assessing the threat
status of the
liquid product. The apparatus comprises an input, a processing unit and an
output and is
operative for assessing the threat status of a liquid product in accordance
with the above-
described method. The system further comprises a display screen in
communication with
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the output of the apparatus for visually conveying to an operator the assessed
threat status
of the liquid product based on information released by the apparatus.
In accordance with another broad aspect, the present invention provides a
method for
assessing a threat status of a liquid product at a security checkpoint. The
liquid product is
comprised of a bottle holding a liquid, wherein the bottle is at least
partially filled with
liquid. The method comprises performing an X-ray scan of the liquid product
using an
X-ray imaging apparatus to obtain X-ray image data associated with the liquid
product.
The method also comprises processing the X-ray image data to derive
information
conveying a level of fill of the bottle and determining the threat status of
the liquid
product at least in part based on the level of fill of the bottle. The method
further
comprises releasing information conveying the determined threat status of
liquid product.
In accordance with another broad aspect, the present invention provides a
method for
assessing a threat status of a liquid product at a security checkpoint. The
liquid product is
comprised of a bottle holding a liquid, wherein the bottle is at least
partially filled with
liquid. The method comprises receiving X-ray image data associated with the
liquid
product, the X-ray image data being derived by performing an X-ray scan of the
liquid
product using an X-ray imaging apparatus. The method also comprises processing
the X-
ray image data to derive location information associated with a meniscus
formed by the
liquid in the bottle and processing the X-ray image data in combination with
the location
information associated with the meniscus formed by the liquid in the bottle to
derive path
length data. The path length data conveys an estimated length of a path
followed by X-
rays through the liquid held in the bottle. The method further comprises
processing the
X-ray image data in combination with the path length data to determine the
threat status
of the liquid product and releasing information conveying the determined
threat status of
the liquid product.
In a specific example of implementation, the method comprises receiving X-ray
image
data associated with the liquid product, wherein the X-ray image data is
obtained using a
multi-view X-ray machine. The X-ray image data conveys a first X-ray image of
the
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liquid product taken by subjecting the liquid product to X-rays in a first
orientation and a
second X-ray image of the liquid product taken by subjecting the liquid
product to X-rays
in a second orientation. The method comprises processing the X-ray image data
corresponding to the first X-ray image of the liquid product to derive
estimated location
information associated with the meniscus formed by the liquid in the bottle.
The method
also comprises processing the X-ray image data corresponding to the second X-
ray image
of the liquid product and the estimated location information associated with
the meniscus
obtained based on the X-ray image data corresponding to the first X-ray image
to derive
adjusted location information associated with the meniscus. The method further
comprises deriving the path length data at least in part based on the adjusted
location
information associated with the meniscus formed by the liquid in the bottle.
In accordance with another broad aspect, the invention provides a computer
readable
storage medium storing a program element suitable for execution by a computing
apparatus for assessing a threat status of a liquid product at a security
checkpoint. The
liquid product is comprised of a bottle holding a liquid, wherein the bottle
is at least
partially filled with liquid. The computing apparatus comprises a memory unit,
a
processor operatively connected to the memory unit. The program element, when
executing on the processor, is operative for assessing the threat status of a
liquid product
in accordance with the above-described method.
In accordance with yet another broad aspect, the invention provides an
apparatus for
assessing a threat status of a liquid product at a security checkpoint. The
liquid product is
comprised of a bottle holding a liquid, wherein the bottle is at least
partially filled with
liquid. The apparatus comprises an input, a processing unit and an output and
is
operative for assessing the threat status of a liquid product in accordance
with the above-
described method.
In accordance with a further broad aspect, the invention provides a system
suitable for
assessing a threat status of a liquid product at a security checkpoint. The
liquid product is
comprised of a bottle holding a liquid, wherein the bottle is at least
partially filled with
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liquid. The system comprises an inspection device for performing an X-ray
inspection on
the liquid product using penetrating radiation to generate an X-ray image of
the liquid
product. The system also comprises an apparatus for assessing the threat
status of the
liquid product. The apparatus comprises an input, a processing unit and an
output and is
operative for assessing the threat status of a liquid product in accordance
with the above-
described method. The system further comprises a display screen in
communication with
the output of the apparatus for visually conveying to an operator the assessed
threat status
of the liquid product based on information released by the apparatus.
In accordance with yet a further broad aspect, the invention provides an
apparatus for
assessing a threat status of a liquid product at a security checkpoint. The
liquid product is
comprised of a bottle holding a liquid, wherein the bottle is at least
partially filled with
liquid. The apparatus comprises means for receiving X-ray image data
associated with
the liquid product, the X-ray image data being obtained by performing an X-ray
scan of
the liquid product using an X-ray imaging apparatus. The apparatus also
comprises
means for processing the X-ray image data to derive information conveying a
level of fill
of the bottle and means for determining the threat status of the liquid
product at least in
part based on the level of fill of the bottle. The apparatus further comprises
means for
releasing information conveying the determined threat status of liquid
product.
In accordance with another broad aspect, the invention provides a method for
assessing a
threat status of a liquid product at a security checkpoint, the liquid product
being
comprised of a bottle holding a liquid, wherein the bottle is at least
partially filled with
liquid. The method comprises determining if the bottle holding the liquid has
a level of
fill below a threshold level of fill. In response to the level of fill of the
bottle falling
below the threshold level of fill, the method includes rejecting the liquid
product as a
being a potential threat. In response to the level of fill of the bottle being
at least at the
threshold level of fill, the liquid product is screened using an X-ray machine
to derive the
threat status of the liquid product.
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Other aspects and features of the present invention will become apparent to
those ordinarily
skilled in the art upon review of the following description of specific
embodiments of the
invention in conjunction with the accompanying Figures.
BRIEF DESCRIPTION OF THE DRAWINGS
A detailed description of examples of implementation of the present invention
is provided
herein below with reference to the following drawings, in which:
Figure 1 shows a system for assessing the threat status of a liquid product at
a security
checkpoint in accordance with a specific example of implementation of the
invention;
Figure 2 is a diagrammatic representation of an inspection device suitable for
use in the
system depicted in Figure 1 in accordance with a specific example of
implementation of
the invention;
Figure 3 is a block diagram of a processing module for assessing the threat
status of a
liquid product suitable for use in the system depicted in Figure 1 in
accordance with a
specific example of implementation of the invention;
Figures 4a and 4b are flow diagrams of a process implemented by the system
depicted in
Figure 1 in accordance with a specific example of implementation of the
invention;
Figure 5a is a cutaway side view of a bottle partially filled with liquid up
to a first level
of fill and maintained in an inclined position in accordance with a non-
limiting example
of implementation of the invention;
Figure 5b is a cutaway side view of the bottle shown in figure 5a filled with
liquid up to a
second level of fill different from the first level of fill and maintained in
an inclined
position in accordance with a non-limiting example of implementation of the
invention;
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Figure 6 is a top perspective view of a tray for positioning a bottle in an
inclined position
during X-ray inspection according to a non-limiting example of implementation
of the
invention.
Figure 7 is a diagrammatic representation of bottles partially filled with
liquid and
depicting different location meniscus;
Figure 8 depicts a relationship between different coordinate spaces according
to a non-
limiting example of implementation of the invention;
Figure 9a is an X-ray image of three (3) bottles each at least partially
filled with liquid in
accordance with a specific example of implementation of the invention;
Figure 9b shows visual representations of reconstructed 3-D images of the
three (3)
bottles depicted in the X-ray image of figure 9a in accordance with a specific
example of
implementation of the invention;
Figure 10 is a 3-D map of surface normals derived based on an X-ray intensity
image of
one of the bottles shows in figure 9a in accordance with a non-limiting
example of
implementation of the invention;
Figures 11 a 11 b and 11 c are projections in the x-y, y-z and x-z planes
respectively of the
3-D intensity map depicted in figure 10 in accordance with a non-limiting
example of of
implementation of the invention;
Figure 12 shows a graphical representation of a scene reconstructed in 3-D
from the x-ray
image depicted in figure 9a in accordance with a specific example of
implementation of
the invention;
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Figure 13 is a block diagram of a computing apparatus suitable for use in
connection with
the apparatus illustrated in Figure 3 in accordance with a specific example of
implementation of the invention;
Figure 14 is a block diagram of a computing apparatus suitable for use in
connection with
the apparatus illustrated in Figure 3 in accordance with an alternative
specific example of
implementation of the invention;
Figure 15 shows a functional block diagram of a client-server system suitable
for
implementing for assessing the threat status of a liquid product at a security
checkpoint in
accordance with an alternative specific example of implementation of the
present
invention;
Figure 16a shows a process for determining location information associated
with a
meniscus formed by liquid held in a bottle according to a first specific
example of
implementation of the invention;
Figure 16b shows a process for determining location information associated
with a
meniscus formed by liquid held in a bottle according to a second specific
example of
implementation of the invention;
Figure 16c shows a process for determining location information associated
with a
meniscus formed by liquid held in a bottle according to a third specific
example of
implementation of the invention.
In the drawings, embodiments of the invention are illustrated by way of
example. It is to
be expressly understood that the description and drawings are only for
purposes of
illustration and as an aid to understanding, and are not intended to be a
definition of the
limits of the invention.
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DETAILED DESCRIPTION
Specific examples of implementation of the invention will now be described
with
reference to the figures. For the purpose of this description, the objects for
which the
threat status is to be assessed include liquid products comprised of a bottle
holding a
liquid, wherein the bottle is at least partially filled with liquid. It will
be appreciated that,
in addition to inspecting liquid products to assess their threat status, other
embodiments
of the invention may further be configured to assess the threat status of
other types of
objects. For example, embodiments of the invention may be configured to detect
the
presence of weapons or prohibited objects based on shape. Such additional
functionality
may be implemented in accordance with any suitable methods known in the art
and will
not be described further here.
For the purpose of the present description, a "bottle holding a liquid" refers
to the
combination of a body of liquid and the container in which the liquid is
contained. For
the purposes of this specification, "liquid" refers to a state of matter that
is neither gas nor
solid, that generally takes the shape of the container in which it is put and
has a
characteristic readiness to flow. Heterogeneous liquids would also be
encompassed by
such a definition.
In addition, a "bottle" refers to the container in which the liquid is
contained. Although
the term "bottle" typically refers to a cylindrical container that is used to
contain liquids
(namely beverages), a bottle in this specification refers to any enclosing
structure that is
made from a material that is suitable to hold the liquid contained within.
Such containers
include but are not limited to rigid containers, such as a glass bottle or
metal (e.g.
Aluminum) containers, as well as semi-rigid containers, such as a bottle made
of
polyvinyl chloride (PVC), polyethylene or of similar flexible materials. The
bottle may
be of any shape including generally cylindrical bottles, such as those used
for beverages
(e.g. a wine bottle or a can of a soft drink), square bottles used for
beverage and non-
beverage liquids (e.g. a carton of milk or fruit juice), elliptical bottles,
rectangular bottles
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as well as bottles of any other suitable shapes. Each bottle has a transverse
dimension
and a longitudinal dimension that defines an overall size suitable to be
carried in hand-
carried luggage that is allowed onboard a commercial aircraft. In the case of
cylindrical
bottles, the transverse dimension is defined by the diameter of the bottle,
which may
differ between a bottom end and a tapered top end of the bottle. For example,
bottles
containing wine traditionally have a larger circumference at their bottom end
that narrows
as the bottle tapers at the top end. Without intent of being bound by any
specific
definition, bottles filled with liquid of an overall size suitable for
transport in hand-
carried luggage allowed onboard a commercial aircraft are those that have a
transverse
dimension that is less than 5 inches, preferably less than 4 inches, and most
preferably
less than 3 inches. However, these dimensions are merely guidelines and may
vary
depending on the rules and regulations enforced for such articles by local,
national and
international transportation organizations.
Referring now to the figures, shown in Figure 1 is a screening system 100
suitable for
assessing the threat status of a liquid product at a security checkpoint in
accordance with
a specific example of implementation of the present invention.
As depicted, the system 100 includes an inspection device 102 for scanning
objects, a
processing module 112 for processing data generated by the inspection device
102 and a
display device 150 for visually conveying information to a security operator,
the
information being derived by the processing module 112 and pertaining to the
objects
being scanned by the inspection device 102.
More specifically, the inspection device 102 is adapted for scanning a liquid
product
using penetrating radiation to generate X-ray data conveying an X-ray image of
the liquid
product. The processing module 112 receives the X-ray data from the inspection
device
102 and processes that data to derive information related to the threat status
of that liquid
product. In accordance with a first approach, the processing module 112
processes the X-
ray image data to derive information conveying a level of fill of the bottle
and to
determine the threat status of the liquid product at least in part based on
the level of fill of
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the bottle. In accordance with a second approach, which may be used
concurrently with
or independently from the first approach, the processing module 112 processes
the X-ray
image data to derive location information associated with a meniscus formed by
the
liquid in the bottle. The processing module 112 then processes the X-ray image
data in
combination with the location information associated with the meniscus formed
by the
liquid in the bottle to derive path length data, the path length data
conveying an estimated
length of a path followed by X-rays through the liquid held in the bottle. The
processing
module then processes the X-ray image data in combination with the path length
data to
determine the threat status of the liquid product. Specific examples of the
manner in
which the threat status of the liquid product can be determined will be
described later on
in the specification.
Once the threat status of the liquid product has been determined, the
processing module
112 then releases information conveying the determined threat status. The
display device
150, shown in the figure as a display screen, visually conveys to an operator
the
determined threat status of the liquid product based on the information
released by the
processing module 112.
Advantageously, the system 100 provides assistance to the human security
personnel in
assessing the threat status of a liquid product, including full bottles and
partially filled
bottles, during security screening.
The components of the system 100 depicted in figure 1 will now be described in
greater
detail.
Display device 150
The display device 150 may be any device suitable for visually conveying
information to
a user of the system 100. The display device 150 may be part of a computing
station, as
shown in figure 1, may be part of a centralized security station and located
remotely from
the inspection device 102 or may be integrated into a hand-held portable
device (not
shown) for example. In another specific example of implementation, the display
device
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150 includes a printer adapted for displaying in printed format information
related to the
determined threat status of the liquid product under inspection. The person
skilled in the
art will readily appreciate, in light of the present specification, that other
suitable types of
output devices may be used in alternative examples of implementation of the
present
invention.
In a specific example of implementation, the display device 150 displays to a
user of the
system 100 a graphical user interface conveying the determined threat status
of the liquid
product based on the information released by the processing module 112. The
graphical
user interface (GUI) may also provide functionality for permitting interaction
with a user.
The specific manner in which the information is visually conveyed to a human
operator
may vary from one implementation to the other.
In a first example of implementation, the information conveying the determined
threat
status of the liquid product conveys the threat status in terms of a level of
threat. The
level of threat may be represented as an alpha-numeric character
(SAFE/UNSAFE/UNKNOWN), a color indicator (e.g. RED for unsafe; GREEN for safe
and YELLOW for UNKOWN) and/or using any other suitable manner of conveying a
level of threat.
In a second example of implementation, the information conveying the
determined threat
status of the liquid product provides information as to the nature of the
liquid product
being screened. For example, the GUI may indicate that the liquid product may
be water,
orange juice, hydrogen peroxide and so on. Optionally, when indicating the
nature of the
liquid product, a level of confidence in the determination may be displayed.
For
example, the GUI may indicate that the liquid product is likely to be water
with a level of
confidence of 80%.
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In a third example of implementation, the information conveying the determined
threat
status of the liquid product provides information as to the level of fill of
the liquid
product. For example, the information may convey that the bottle is X% full.
In
situations where X% is less then a threshold level of fill, the information
displayed to the
user may further convey that since X% is less then the threshold filled level,
the bottle
has been classified as UNSAFE irrespective of its content.
It will be readily apparent to the person skilled in the art that other types
of information
may be displayed by display device and that the examples provide above were
provided
for the purpose of illustration only.
Inspection device 102
In a specific example of implementation, the inspection device 102 is in the
form of an
X-ray machine typical of the type of device used to scan luggage at security
checkpoints
within airports and other transportation locations. The X-ray machine may be a
single
view x-ray machine or a multi-view x-ray machine. For the purpose of
simplicity, the
present description will primarily focus on implementations in which the X-ray
machine
is of a single-view type. Variants of the invention taking advantage of the
multiple X-ray
images generated by multi-view X-ray machines will also be presented.
The inspection device 102 will now be described in greater detail with
reference to figure
2. As depicted, the inspection device 102 includes a scanning area 104, a
conveyor belt
106, an X-ray source 108 and an array of X-ray detectors 110. The inspection
device 102
performs an X-ray inspection on a liquid product using penetrating radiation
in the form
of X-rays to generate X-ray image data associated with the liquid product.
The scanning area 104 (also referred to as scanning tunnel) is defined by an
enclosed
void between the X-ray source 108 and the array of X-ray detectors 110, in
which the
objects to be scanned are subjected to penetrating radiation, such as X-rays.
The
scanning area 104 is typically horizontally oriented and is dimensioned both
vertically
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and horizontally to accommodate the types of objects to be scanned, including
articles of
hand-carried luggage allowed onboard a commercial aircraft, such as handbags,
backpacks, briefcases and shopping bags, among others. The scanning area 104
is
centrally traversed by a conveyor belt 106 that is used to convey objects to
be scanned
both into and out of the scanning area 104 and is described below.
The articles to be scanned can be placed either directly on the conveyor belt
106 or in one
or more trays that are then placed on the conveyor belt 106.
The conveyor belt 106 is a horizontally-oriented continuous belt of material
arranged in
an endless loop between two terminal rollers. The belt 106 has an exterior
surface on
which objects or trays containing the objects to be scanned are placed, as
well as an
interior surface within which the terminal rollers (as well as other guide
rollers and/or
supports) lie.
The width of the conveyor belt 106 is sufficient to accommodate the placement
of trays
within which the objects to be scanned are placed, while its overall length is
sufficient to
create an endless loop whose length includes:
- A pre-scanning area that lies before the scanning area 104, where the
objects to be
scanned are placed on the belt 106;
- The scanning area 104, where the objects being scanned are subjected to
penetrating radiation (i.e. X-rays); and
- A post-scanning area that lies after the scanning area 104, where the
objects that
have been scanned emerge after being subjected to penetrating radiation. It is
in
that area that a user can pick up his or her objects after the security
screening
operation is completed.
It is worth noting that the terminal rollers constituting the end points of
the conveyor belt
106 at the pre-scanning and post-scanning areas may be connected to motors
(not shown)
that allow an operator to move the belt 106 forwards or backwards to displace
the objects
to be scanned between different areas of the X-ray inspection device 102.
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The X-ray source 108 is the source of penetrating radiation (in this case, X-
ray radiation).
The X-ray source 108 is located opposite to the array of X-ray detectors 110
so that X-
rays emitted by the source 108 pass through the objects that are located on
the conveyor
belt 106 and are detected by the array of X-ray detectors 110 as a result. In
a non-
limiting example, the inspection device 102 is a dual-energy X-ray scanner and
the x-ray
source 108 emits x-rays at two distinct photon energy levels, either
simultaneously or in
sequence. Example energy levels include 50 keV (50 thousand electron-volts)
and 150
keV, although persons skilled in the art will appreciate that other energy
levels are
possible.
The array of X-ray detectors 110 detects the penetrating radiation (i.e. X-
rays) that was
emitted by the X-ray source 108 and that penetrated the objects to be scanned.
The array
of X-ray detectors 110 is located opposite to the X-ray source 108 so that X-
rays that are
emitted by the source 108 pass through the objects that are located on the
conveyor belt
106 and are detected by the array 110.
Processing module 112
The processing module 112 is in communication with the inspection device 102
and
receives the X-ray image data output by the array of X-ray detectors 110. In
the example
depicted in figures 1 and 2, the processing module 112 is shown as a component
external
to the inspection device 102. It will be appreciated that, in alternate
example of
implementation of the system 100, the functionality of processing module 112
may be
integrated within the inspection device 102.
The processing module 112 uses the X-ray data output by the array of X-ray
detectors
110 of the inspection device 102 to generate an X-ray image of the contents
being
scanned. The generated X-ray image is then processed and/or analyzed further
by human
or automated means, as will be shown below. In a non-limiting example of
implementation, attenuation information conveyed by the X-ray image data
generated by
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the inspection device 102 is processed to generate an X-ray image in which
different
shades of gray are used to convey different levels of attenuation of the X-
rays.
A specific example of implementation of the processing module 112 is depicted
in figure
3 of the drawings. As shown, the processing module 112 includes an input 300
in
communication with the inspection device 102 for receiving there from X-ray
data, a
processor 302 in communication with the input 300, a memory 306 storing data
for use
by the processor 302 and an output 304 in communication with the display
device 150
(shown in figure 1) for releasing information derived by the processor 302.
The processor 302 implements a process for assessing the threat status of a
liquid product
unit based on the X-ray data received at input 300 from the inspection device
102.
Results of the threat status assessment are then released at output 304.
Specific examples
of processes for assessing the threat status of a liquid product that may be
implemented
by processor 302 will be described later on in the present specification.
The level of fill of a bottle and the meniscus
Prior to describing the process by which the threat status of a liquid
product, a short
description on impacts of the level of fill of a bottle on the determination
of the
characteristics of the liquid held by the bottle based on an X-ray image will
be described
for the purpose of facilitating the reader's understanding.
Generally speaking, the threat status of a bottle filled with liquid is based
in part on X-ray
attenuation information extracted from the X-ray image data and an estimated
length of a
path travelled by X-ray through the liquid in the bottle. The closer the
estimate path
length is to the actual length of the path travelled by X-rays through the
body of liquid in
the bottle, the more accurate the nature of the liquid in the bottle can be
derived and
therefore a more accurate assessment of its threat status can be made.
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Since bottles are typically not filled to their full capacity, there is
usually a meniscus that
can interfere with the X-ray scanning. In situations in which the bottle being
screened is
completely full, or nearly completely full, the meniscus formed by liquid in
the bottle
being screened will be very small and will have minimal impact on the
determination of
the characteristics of the liquid held by the bottle (e.g. the effective
atomic number (Zeff
number), the density and/or linear attenuation coefficient) and the ensuing
assessment of
the threat status of the liquid product under inspection. However as the level
of fill of the
bottle diminishes, the impact of meniscus on the determination of the
characteristics of
the liquid held by the bottle, and hence the assessment of the threat status
of the liquid
product under inspection, increases and taking the meniscus into account will
increase the
accuracy of the threat assessment.
As can be observed, when a bottle is placed horizontally on the tray, the
meniscus is
likely to spread, and (depending on the size of the meniscus) an air layer may
be created.
The size of such an air layer is determined by the degree to which the bottle
has been
filled: a full bottle will have a smaller meniscus while a bottle filled
partially will have a
larger meniscus. In certain cases, the air layer created by the meniscus can
extend above
the entire body of liquid, which can lead to an inaccurate path length being
obtained if the
characteristics of the meniscus are not taken into account. For example, due
to the
presence of an air layer, the path length through the liquid body may be
shorter than the
distance between the bottle walls (the transverse dimension of the void space
within the
bottle).
It can also be observed that by setting a bottle holding liquid in an inclined
position, the
meniscus will tend to migrate toward one of the extremities of the bottle.
For the purpose of simplicity, examples presented in the present application
will describe
embodiments in which the bottle holding liquid is in an inclined position.
Embodiments
in which the bottles are placed horizontally during inspection will become
readily
apparent to the person skilled in the art in light of the present description.
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Figures 5a and 5b show a side cutaway view of a bottle 500 partially filled
with liquid in
an inclined position. With respect to these figures, the bottle 500 is
generally inclined at
an angle 501 relative to a generally horizontal plane. For the purpose of this
example, the
angle 501 is achieved by positioning the bottle on a tray having an inclined
bottom
surface and an angle of 501.
Figures 5a and 5b also show a path taken by a ray of penetrating radiation
(i.e. an X-ray)
through the bottle. The X-ray enters the bottle 500 at location 502, travels
through the
bottle walls and the bottle contents, and emerges from the bottle at location
514. The
angle between the X-ray and the longitudinal axis of the bottle of liquid can
be derived
using simple trigonometry since the angle 501 is known and the orientation of
the X-ray
is also known.
As can be seen, as the X-ray travels from the X-ray source to the X-ray
detectors (not
shows), the X-ray is attenuated by not only the liquid in the bottle but by a
supporting
structure (such as a tray and/or conveyor belt) holding the bottle and the
side walls of the
bottle as well. Segment 510 between the locations 502 and 514, herein referred
to as the
combined segment 510, is a combination of the following segments:
- segment 504 through the supporting structure (for example a tray);
- segments 506 and 508 through the side walls of the bottle; and
- segment 512 through the inside portion of the bottle 500.
The lengths of segments 504, 506 and 508 may be derived based on the thickness
of the
supporting structure (tray material) and the bottle side walls, both of which
may be
known or may be derived using other image analysis techniques known in the
art.
Similarly, the length of the combined segment 510 may be obtained based on
geometrical
information associated with the bottle obtained based on the X-ray image
and/or based on
certain geometrical assumptions as to the shape of the bottle and obtained
(symmetry,
shape of the bottom of the bottle, reference database of bottle shapes,
etc...). As a result,
the length of the segment 512 may be determined by subtracting the lengths
504, 506 and
508 from the length of combined segment 510.
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As can be observed in figure 5a, the position of the meniscus 520 is such that
the length
of the path segment 512, which is the length of the path through the inside
portion of the
bottle 500, corresponds to the length of the path taken by the X-ray passing
entirely
through the liquid within the bottle. As such, the length of the path segment
512 can be
used with other information, such as X-ray attenuation information obtained
from an X-
ray image of the bottle holding the liquid, to derive characteristics of the
liquid in the
bottle including, for example, density, the effective atomic number (Zell
number) and/or
linear attenuation coefficient according to well known methods. Known
attenuation
information, such as the attenuation attributed to the tray, conveyor belt and
optionally
the walls of the bottle 500 can also be taken into account to compensate the
attenuation
information in the X-ray image data when deriving characteristics of the
liquid in the
bottle.
If we now consider figure 5b, we note that the position of the meniscus 520'
is such that
the length of the path segment 512 includes a first component 592
corresponding to the
length of the path taken by the X-ray passing through the liquid within the
bottle but also
includes a second component 590 corresponding to the length of a path taken by
the X-
ray in a layer of air above the meniscus. As a result, the determination of
the length of
the path taken by the X-ray through the body of liquid (in other words
component 592),
should take into account the location and characteristics of the meniscus.
As can be observed from figure 5a and 5b, since the meniscus is a generally
horizontal
flat surface aligned with the surface of the conveyor belt, the level of
meniscus 520 520'
can be determined by identifying the location of the point (594 in figure 5a
and 594' in
figure 5b) at which the meniscus is in contact with the wall of the bottle.
Once of the
location of the meniscus is known, it can be used in determining a more
accurate path
length taken by x-ray through the liquid, in particular in situations where
the level of fill
of the bottle is such that there is a layer of air above the meniscus (as in
figure 5b).
The location information associated with the meniscus may include various
components
such as:
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- The height of the meniscus relative to the conveyor belt of the inspection
device 102;
- The location of the point (594 in figure 5a and 594' in figure 5b) at which
the
meniscus is in contact with the wall of the bottle
- Distance 590 in figure 5b
It is to be appreciated that any method suitable for determining the location
of the
meniscus, including the level (height) of the meniscus and/or the location of
the point
(594 in figure 5a and 594' in figure 5b) at which the meniscus is in contact
with the wall
of the bottle may be used. Specific approaches for determining the approximate
location
of the point (594 in figure 5a and 594' in figure 5b) and the level of the
meniscus based
on an x-ray image of the bottle will be described later on in the
specification with
reference to figures 16a,16b and 16c.
As can be observed from figure 5a and 5b, having knowledge of location
information
associated with the meniscus and information pertaining to the geometry of the
bottle
under inspection, the level of fill of the bottle 500 can be derived using
well-known
methods.
As can also be observed from figure 5a and 5b, having knowledge of location
information associated with the meniscus and information pertaining to the
geometry of
the bottle under inspection, the length of the path of an X-ray through a
continuous body
of liquid (segment 512 in figure 5a and segment 592 in figure 5b) can be
obtained and
used according to well-known methods to derive characteristics of the liquid
held by the
bottle (e.g. density, effective atomic number (Zell number) and/or linear
attenuation
coefficient) and the ensuing assessment of the threat status of the liquid
product under
inspection.
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Process implemented by system 100
A specific example of a process implemented by the system 100 (shown in figure
1) will
now be described with reference to figure 4A.
As shown, at step 400 an X-ray scan of a liquid product to be screened is
performed by
the inspection device 102 (shown in figure 1) to obtain X-ray image data
associated with
the liquid product.
In a first non-limiting example, the liquid product is placed directly on the
conveyor belt
of the inspection device 102 or is placed on a tray which is then placed on
the conveyor
belt of the inspection device 102.
In a second non-limiting example, the liquid product is placed on a tray
having an
inclined bottom surface and including retaining member for preventing the
liquid product
from being displaced during inspection. For example, a tray of the type
depicted in
figure 6 may be used for that purpose. In a specific example of
implementation, the
bottom surface of the tray longitudinal axis forms an angle to the horizontal
plane in the
range from about 5 to about 40 , preferably in the range from about 5 to
about 30 , and
preferably in the range from about 10 to about 20 . In a specific non-
limiting practical
implementation, the angle is between about 10 and about 15 .
The person skilled in the art will appreciate that it is desirable to maintain
the stability of
the liquid product during the scanning operation in order to improve the
accuracy of the
threat detection process. Should the liquid product be allowed to roll or
otherwise move
on the surface of the tray or the conveyor belt, (especially when the bottle
is of a circular
cross-sectional shape, which would promote such movement) the X-ray image may
be
taken while the bottle is in motion. This motion may produce corrupted X-ray
image data
that may lead to a false identification (i.e. a non-threatening liquid being
assessed as a
threat and vice versa) or require that another X-ray image be taken before any
analysis is
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performed. As such, mechanisms for positioning the liquid product and
preventing it
from being displaced during inspection may be used when scanning the liquid
product.
The reader is invited to refer to the following document for examples of
mechanisms for
positioning a liquid product:
- PCT International Patent Application serial number PCT/CA2008/002025
filed in the Canadian Receiving Office on November 17, 2008 by Michel
Roux et al. and presently pending.
The liquid product having been placed either directly on the conveyor belt or
on a tray is
then displaced toward the scanning area 104 of the inspection device 102
(shown in
figure 2). X-ray image data is then generated by the inspection device 102 by
subjecting
the liquid product to penetrating radiation. Figure 9a is an X-ray image of
three (3)
bottles each at least partially filled with liquid derived from data generated
by an
inspection device in accordance with a specific example of implementation of
the
invention. In this figures, the meniscus for each bottle has been emphasized
in this image
for the purpose of illustration only.
At step 402, the X-ray image data generated by the inspection device 102 is
received by
the processing module 112.
At step 404, the processing module 112 processes the X-ray image data to
determine the
threat status of the liquid product scanned at step 400. Many different
approaches may
be taken for determining the threat status of the liquid product.
In accordance with a first approach, the processing module 112 processes the X-
ray
image data to derive information conveying a level of fill of the bottle and
to determine
the threat status of the liquid product at least in part based on the level of
fill of the bottle.
In accordance with a second approach, which may be used concurrently with or
independently from the first approach, the processing module 112 processes the
X-ray
image data to derive location information associated with a meniscus formed by
the
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liquid in the bottle. The processing module 112 then processes the X-ray image
data in
combination with the location information associated with the meniscus formed
by the
liquid in the bottle to derive path length data, the path length data
conveying an estimated
length of a path followed by X-rays through the liquid held in the bottle. The
processing
module 112 then processes the X-ray image data in combination with the path
length data
to determine the threat status of the liquid product.
In accordance with a third approach, which may be used concurrently with or
independently from the first and second approaches, the processing module 112
may
implement a method for assessing the characteristics of liquids from the X-ray
images of
bottles of liquid of the types described in international patent application
no.
PCT/CA2007/001658, "Method and Apparatus for Assessing the Characteristics of
Liquids", which was filed by Optosecurity Inc. et al. with the Canadian
Receiving Office
on September 17, 2007 and was published on March 27, 2008 under publication
no.
W02008034232. Amongst others, the above referenced PCT application describes a
method that can be implemented as software and/or hardware and that can be
used in
order to perform an analysis of X-ray image data in order to determine a
threat status of a
container. In particular, the method described makes use of X-ray attenuation
information extracted from the X-ray image, which was obtained by subjecting
the
bottles filled with liquid to X-ray radiation, to determine if a bottle filled
with liquid
presents a threat or not.
Specific examples of the manner in which step 404 may be implemented will be
described in greater detail below.
At step 408, the processing module 112 releases information conveying the
threat status
of the liquid product determined at step 404.
Following this, at step 410, the display device 150 (shown in figure 1)
receives the
information released by the processing modules and conveys this information in
visual
format, and optionally in audio format, to an operator.
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Step 404
A specific approach for determining the threat status of the liquid product at
step 404 will
now be described with reference to figure 4B. It will be readily appreciated
that other
suitable approaches may be contemplated in alternative examples of
implementation of
the invention. Such alternative approaches will become apparent to the person
skilled in
the art in light of the present description.
As depicted, at step 440 the X-ray image data received from the inspection
device 102
(shown in figure 1) is processed to derive geometric information associated
with the
bottle of the liquid product. The derived geometric information associated
with the bottle
may include one or more of the following elements:
- Approximation of the bottle height;
- Approximation of the bottle width;
- Approximation of the bottle length;
- Approximation of the profile of the bottle;
- Presence or absence of certain surface features such as:
o Annular recesses on the body of the bottle and position
of those annular recesses;
o Presence or absence of cap
- Approximation of the position of the bottle in the tray
- Three-dimensional representation of the bottle
The image processing performed to extract the features described above can be
done
using any suitable image processing technique known in the art.
In implementations in which the inspection device 102 (shown in figure 1) is a
"single-
view" type X-ray machine generating a two-dimensional image of the liquid
product,
image processing techniques allowing deriving three-dimensional information
based on a
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two-dimensional image are used. In implementation in which the liquid product
is
positioned on a tray having a bottom surface with a known inclination, the
angle made
between a longitudinal axis of the bottle and a horizontal plane is used to
derive the
geometric information associated with the bottle. Assumptions based on the
symmetry of
the bottle holding the liquid as well as assumption regarding the inclination
of the bottle
(for example in cases where the bottles are positioned at a known angle of
inclination
using a tray) may be used in order to assist in the extraction of geometric
information
associated with the bottle. More specifically, the person skilled in the art
will appreciate
that, although there may be some exceptions, most bottles have shapes
exhibiting
symmetrical properties. For instance, several bottles exhibit some level of
rotational
symmetry along their longitudinal axis. For example, the general three-
dimensional
shape of a bottle can be approximated by:
deriving the location and orientation of its longitudinal axis;
deriving the extent (extremities of the bottle);
- deriving the shape of the profile of the bottle along one side of the
longitudinal axis; and
extrapolating all other points on the bottle by effecting a rotation of the
profile of the bottle around the longitudinal axis.
Although the above approach assumes that the bottle has a generally circular
cross-
section, the person skilled in the art will readily appreciated that
adaptations to account
for bottles having generally elliptical, generally square and generally
rectangular cross-
section can also be made. In implementations in which the inspection device
102 (shown
in figure 1) is a "multi-view" type X-ray machine generating multiple two-
dimensional
image of the liquid product, the multiple images may be used to obtain
additional
information as to the size, shape and positioning of the bottle. Several
suitable methods
for extracting geometric information from an image are known in the art of
computer
vision and as such will not be described in further detail here.
In a non-limiting example of implementation, a three-dimensional mathematical
representation of the bottle under inspection is generated at step 440 based
on the X-ray
image data generated by the inspection device 102 (shown in figure 1). Figure
9B of the
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drawings shows graphical three-dimensional mathematical representations 950
952 954,
corresponding respectively to bottles 900 902 and 904 depicted in the X-ray
images
shown in figure 9A.
Once geometric information associated with the bottle of the liquid product
has been
obtained, the process proceeds to step 442.
At step 442, the X-ray image data is processed to derive location information
associated
with a meniscus formed by liquid in the bottle being screened. As described
above,
location information associated with the meniscus may include various
components
including but not limited to:
- The height of the meniscus relative to the conveyor belt of the inspection
device 102
- The location of the point (594 in figure 5a and 594' in figure 5b) at which
the
meniscus is in contact with the wall of the bottle
Any method suitable for determining location information associated with the
meniscus
may be used. Specific approaches for determining location information
associated with
the meniscus will be described later on in the specification with reference to
figures 16a,
16b and 16c.
Once of the location of the meniscus is known, it can be used in determining
the level of
fill of the bottle and/or a path length taken by x-ray through the liquid, in
particular in
situations where the level of fill of the bottle is such that there is a layer
of air above the
meniscus.
Therefore, following step 442, the process proceeds to steps 444 and 446
and/or 450 452
and 460.
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At step 444, the level of fill of the bottle is derived at least in part based
on the geometric
information associated with the bottle, which was derived in step 440, and
based on the
location information associated with the meniscus, which was derived in step
442.
Any suitable method for deriving the level of fill of the bottle may be used
without
detracting from the spirit of the invention. In a non-limiting example, the
volume of the
bottle is derived based on the geometric information associated with the
bottle according
to well known methods. Similarly, the volume of the liquid in the bottle may
be derived
based on a combination of the geometric information associated with the bottle
and the
location information associated with the meniscus. Using the derived volume of
the
bottle and volume of liquid, the level of fill of the bottle may be derived by
taking a ratio
of the two volumes.
It will be appreciated that deriving the precise level of fill of a bottle,
for example 25%, is
not critical to the present invention. More specifically, the level of fill
may be derived so
that it is within a certain tolerance, for example 25% full 10%.
Consequently, the level
of fill of the bottle can be an approximate measure of the level of fill of
the bottle rather
than an exact measurement.
It will be appreciated that, in alternative embodiments, the derived level of
fill of a bottle
can simply indicate that the bottle has a level of fill above one or more
certain pre-
determined levels. For example, the derived level of fill may indicate that
the bottle has
a level of fill above 20%. This would encompass situations where the level of
fill is 80%
as well as cases where the level of fill is 30%.
At step 446, the level of fill of the bottle derived at step 444 is used as a
factor to
determine the threat status of the liquid product.
In a specific example of implementation, the level of fill of the bottle
derived at step 444
is compared to a threshold level of fill. If the level of fill of the bottle
is below the
threshold level of fill, then a decision can be made to identify the liquid
product as a
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threat irrespective of its content. The specific threshold level of fill used
may vary from
one implementation to the other and will generally depend on the amount of
liquid
necessary to be present in the bottle in order to perform a threat assessment
having a
sufficiently high rate of accuracy.
Generally speaking, the determined level of fill alone is not sufficient to
identify a liquid
product as "safe" and additional information will be used to complete the
assessment
such as for example the assessment performed in steps 450 452 and 460 in
figure 4B.
Consequently, in a specific example of implementation after step 446, the
liquid product
will have been identified either as a being a "threat" or as being
"undetermined and
requiring further assessment". In cases where the liquid product has been
identified as a
threat based on the level of fill, steps 450 452 and 460 may be omitted.
In cases where the liquid product has been identified as being undetermined
and requiring
further assessment, the process continue with steps 450 452 and 460.
At step 450, the X-image data is processed to extract X-ray attenuation
information
associated with the liquid in the bottle. The X-ray attenuation information in
the X-ray
image may be processed to compensate it for an attenuation attributed to
elements
extraneous to the liquid in the bottle, such as for example, the conveyor belt
of the
inspection device that generated the X-ray image data, the tray (if any) on
which the
bottle was placed during the screen and/or the walls of the bottle holding the
liquid.
At step 452, the location information associated with the meniscus derived at
step 442
and the geometric information associated with the bottle derived at step 440
are
processed in order to derive path length information, wherein the path length
information
convey an estimated length of a path followed by X-rays through the liquid
held in the
bottle. Methods for deriving the path length information based on the location
information associated with the meniscus derived and the geometric information
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associated with the bottle will be readily apparent to the person skilled in
art in light of
the present description and as such will not be described further here.
At step 460, the path length information derived at step 452 and the
attenuation
information derived at step 450 are processed to assess the threat status
associated with
the liquid product.
In a specific example of implementation, the path length information derived
at step 452
and the attenuation information derived at step 450 are processed to derived
characteristics associated with the liquid product (e.g. the density, the
effective atomic
number (Zeff number) and/or the linear attenuation coefficient). Methods for
deriving
such characteristics based on path length and attenuation information are well-
known in
the art and as such will not be described further here. The characteristics
associated with
the liquid product can then be compared to entries in a database stored in a
memory to
determine the threat status of the liquid in the bottle. The database provides
information
mapping characteristics associated with liquids (e.g. density, effective
atomic number
(Zell number) and/or linear attenuation coefficient) with addition information
such as for
example, the nature of the liquid and/or the threat status. It will be
appreciated that the
above approach for assessing the threat status associated with the liquid
product has been
presented for the purpose of illustration only and that other approaches
making use of
path length information and attenuation information to assess the threat
status associated
with the liquid product without detracting from the spirit of invention.
As will be appreciated in light of the above, the first path of the process,
including step
444 and step 446, is associated to an assessment of the threat status of the
liquid product
using a determined level of fill of the bottle as a factor in the
determination of the threat
status of the bottle. The second path, including steps 450 452 and 460, is
associated to an
assessment of the threat status of the liquid product based in part on the
length of the path
travelled by X-rays through the liquid held by the bottle. Specific examples
of
implementation may perform the first and second paths either in parallel or in
series.
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Optionally, the steps in the second path may be performed on a conditional
basis
depending on the results obtained by the steps in the first path.
At step 462, the threat status determined at step 446 based on the level of
fill as well as
the threat status derived based on the path length data and attenuation
information in the
X-ray image data derived at step 460 are considered in combination to obtain a
level of
threat associated with the liquid product.
In a non-limiting example of implementation, if either step 446 or 460 result
in the liquid
product being classified as a "threat", step 462 will classify the liquid
product as a threat.
Once step 462 is completed, the process proceeds to step 408 (shown in figure
4a) in
which information conveying the threat status is released by the processing
module 112.
Deriving Location Information Associated with the Meniscus (step 442)
As described above with reference to figure 4B, at step 442, the x-ray image
data
associated with the liquid product being screened is processed to derive
characteristics of
a meniscus formed by the liquid in the bottle. The derived characteristics of
the meniscus
may generally include location information associated with the meniscus and
optionally
information related to the shape of the meniscus. It will be appreciated that
specific
derived characteristics of the meniscus may vary from one implementation to
the other.
For example, in a non-limiting example of implementation, the curvature of the
meniscus
as would be present where the liquid has a certain viscosity may also be part
of the
characteristics of the meniscus that could be derived.
In the present section, specific examples of methods for deriving
characteristics of the
meniscus associated with the meniscus will be presented. It will be readily
appreciated by
the person skilled in the art that other methods for deriving such
characteristics may also
be used without detracting from the spirit of the invention.
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In a first specific example of implementation, the liquid products are
positioned at a
known angle (e.g. by means of a tray having an inclined bottom surface) while
it is being
scanned by the X-ray machine. By setting a bottle filled with liquid in an
inclined
position, the meniscus will tend to migrate toward one of the extremities of
the bottle. In
a specific and non-limiting example of implementation, the liquid products are
inclined at
a 15 angle from the horizontal plane. It can be appreciated that, in other
specific
examples of implementation, the angle of incline relative to the horizontal
plane can be in
the range from about 5 to about 30 and preferably in the range from about 10
to about
20 . In a further specific and non-limiting example of implementation, the
angle of
incline is in the range from about 10 to about 15 . This may be achieved
through the use
of a tray having an included bottom surface, of the type depicted in figure 6
for example.
For specific examples of trays allowing positioning liquids products in
inclined positions
during screening, the reader is invited to refer to PCT International Patent
Application
serial number PCT/CA2008/002025 filed in the Canadian Receiving Office on
November
17, 2008 by Michel Roux et al..
As will be observed, based on the level of fill of the bottle, the meniscus
formed by the
liquid in the bottle will vary in shape and size. For instance, depending on
the level of fill
of the bottle, the meniscus will end along either the upper wall of the bottle
or along the
lower wall of the bottle.
Figures 7a an 7b of the drawings show in very simplified form a bottle 700
holding liquid
and positioned at an inclined angle of a. As shown, the bottle has an upper
wall 704 and
a lower wall 710. In the example shown in figure 7b, the level of fill of the
bottle 700 is
such that the meniscus appears as an air bubble in the upper end of the bottle
and ends
along the upper wall 704 of the bottle 700 at point 720 that is along the axis
of the bottle.
As will be observed, in such circumstances, the lower portion of the meniscus
will appear
as an upward-facing parabola in the X-ray image of the bottle. For the purpose
of the
present description, in such circumstances the meniscus will be referred to as
a positive
meniscus. As will be observed, for a relatively full commercial bottle, the
meniscus will
typically be a positive meniscus and will end along the upper wall of the
bottle.
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In the example shown in figure 7a, the level of fill of the bottle 700 is such
that the
meniscus ends along the lower wall 710 of the bottle 700 at point 708 that is
along the
axis of the bottle. As will be observed, in such circumstances, the upper
portion of the
meniscus is in contact with the lower wall of the bottle and appears as a
downward-facing
parabola in the X-ray image of the bottle. For the purpose of the present
description, in
such circumstances the meniscus will be referred to as a negative meniscus.
In accordance with a specific example of implementation of the invention, the
level of fill
of a bottle is determined at least in part based on geometric information
related to the
bottle holding the liquid and on the point (720 or 708 in figures 7a and 7b)
at which the
meniscus is in contact with the upper/lower wall of the bottle. In addition,
the shape of
the meniscus can also be used to validate and/or adapt the geometric
information
associated with the bottle that was derived in prior steps (step 440 shown in
figure 4B).
In a non-limiting example of implementation, different approaches may be used
for
determining the location of the point (708 or 720 in figures 7a and 7b) at
which the
meniscus is in contact with the upper/lower wall of the bottle depending on
whether we
have a positive or negative meniscus. In the section below, examples of
different
approaches will be described. It will be readily appreciated by the person
skilled in the
art in light of the present description that other suitable approaches may be
contemplated.
As such, the approaches presented here are being presented for the purpose of
illustration
only.
In a specific example of implementation, the detection and characterisation of
the
meniscus is based at least in part by tracking the changes in the intensity of
the gray-
shaded areas in an X-ray image as obtained from the X-ray image data generated
by the
inspection device 102 (shown in figure 1).
More specifically, the X-ray image data generated by the inspection device 102
(shown in
figure 1) provides attenuation information for each {x,y} coordinate in a two-
dimensional
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plane. This attenuation information is typically represented in the form of a
greyscale
level in an X-ray image. By tracking the change in intensity of the gray scale
levels in
the X-ray image, a general indication of the surface of the objects depicted
in the X-ray
image can be obtained.
It can be observed that, for most liquids, the meniscus formed by the liquid
in a bottle
will be a generally flat surface. Although some minor variations in the
surface caused by
the viscosity/surface tension of the liquid in the bottle may be present, for
most liquids of
interest, the assumption that the liquid in the bottle will be a generally
flat surface has
been found to be a reasonable one. By tracking the change in intensity of the
gray scale
levels in the X-ray image depicting areas inside the bottle, information
pertaining to
characteristics of the meniscus' surface as well as the shape of the meniscus
can be
obtained.
Positive meniscus
One mechanism that can be used in order to track the change in intensity of
the gray scale
levels in the X-ray image is the use of surface normals.
Generally speaking, a surface normal, or simply normal, to a flat surface is a
vector
which is perpendicular to that surface. A normal to a non-flat surface at a
point P on the
surface is a vector perpendicular to the tangent plane to that surface at P.
In the case of a
two-dimensional image, such as for example an X-ray image, the intensity
information
conveyed by the X-ray image data is used to represent the third dimension of
the objects
being represented.
Another mechanism that can be used in order to track the change in intensity
of the gray
scale levels in the X-ray image is the use of gradients. In vector calculus,
the gradient of
a scalar field (e.g. the intensity values represented by the grayscale levels
in the X-ray
image) is a vector field which points in the direction of the greatest rate of
increase of the
scalar field, and whose magnitude is the greatest rate of change. In Cartesian
coordinates, the gradient may be expressed as follows:
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r of of
Vf`x, y) = adx , ady
Where f() is the intensity function and "x" and "y" represent the 2-D
coordinate space in
the X-ray image. The gradients can then been used to obtain information on the
shape of
the meniscus, including identifying the coordinates of the lowest point of the
meniscus.
Other mechanisms for tracking such changes may be used and will become readily
apparent to the person skilled in the art in light of the present description.
Although surface normals and gradients could be used in situations where the
meniscus
formed by the liquid in the bottle is either positive or negative, it has been
found that the
use surface normals and gradients yields more consistent and reliable results
in cases
where the meniscus is positive.
An exemplary process for using surface normals to detect and characterise a
positive
meniscus based on X-ray image data will now be described with reference to
figure 16a.
At step 1600, the X-ray image is processed to locate areas of the image
associated to the
liquid product. Following this, the computations of the surface normals and
subsequent
assessments are performed on the identified areas. Advantageously, this allows
reducing
the number of computations compared to processing to X-ray image as a whole.
It will
be readily appreciated that step 1600 may be omitted in some implementations.
At step 1602, the X-ray image data generated by the inspection device 102 (or
the portion
of the X-ray image data identified at step 1600 as corresponding to the liquid
product) is
filtered to remove noise in the X-ray image. This may be achieved by any
suitable
mechanism known in the art of image processing. In a non-limiting example of
implementation, a low-pass filter designed to remove higher frequency noise in
the X-ray
image may be used to filter the X-ray image. It will be readily appreciated
that step 1602
may be omitted in some implementations.
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At step 1604, the X-ray image data is processed to derive an associated
pattern of surface
normals, where the intensity information of each pixel in the image to
designate the third
dimension of the X-ray image. Deriving surface normals is well known in the
field of
computer graphics and as such will not be described in greater detail here.
The surface normals are computed for each (x,y) coordinates in the X-ray image
associated with the liquid product under inspection. It will be readily
appreciated that, in
alternative examples of implementation that omit step 1600, surface normals
may be
computed for all (x,y) coordinates in the X-ray image.
Figure 10 of the drawings depicts in graphical form surface normals derived
based on the
portion of the X-ray image shown in figure 9A corresponding to bottle 900.
Once the surface normals are computed at step 1604, the process proceeds to
step 1606.
At step 1606, projections of the surface normals are computed. In a specific
example of
implementation, projections of the surface normals are obtained in the (x,y)
plane, the
(y,z) plane and/or the (x,z) plane in order to extract various characteristics
pertaining to
the shape of the meniscus. Computing projections of surface normals is well-
known in
the art and as such will not be described in greater detail here.
Figures 1la, lib and 11c of the drawings depict in graphical form projections
of the
surface normals depicted in figure 10 in the (x,y) plane, the (y,z) plane and
the (x,z) plane
respectively.
The projection of the surface normals on the (x,y) plane (shown in figure l
la) provides
the main characteristic of the meniscus' surface based on the mapping of the
normal of
the intensity profile inside the bottles. As can be observed from the
projection of the
surface normals on the (x,y) plane, the meniscus appears in the form of an
upward-facing
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parabola. The projections on the (x,z) and (y,z) planes (shown in figures 11 b
and 11 c)
can be used to filter the main image and to provide information for image
segmentation.
In addition, the projections on the (x,z) and (y,z) planes can be used to
confirm the
accuracy of the portion of the X-ray image identified at step 1600 as
corresponding to a
liquid product.
At step 1608, the location of the point (720 in figure 7b) at which the
meniscus is in
contact with the upper wall of the bottle is determined based on the
projection of the
surface normals on the (x,y) plane. Amongst others, image-segmentation
techniques such
as threshold calculation, morphology and label analysis may be used in order
to isolate
the information relative to the meniscus in the projected (x,y) plane . Once
the meniscus
is isolated, the position corresponding to the lowest point of the parabola
can be
identified using any suitable image processing method. Such methods are well-
known in
the art of computer graphics and computer vision and as such will not be
described in
further detail here.
Once the location of the point (720 in figure 7b) at which the meniscus is in
contact with
the upper wall of the bottle is determined the process proceeds to step 1610.
At step 1610, position information pertaining to the meniscus in the bottle is
derived
based in part on the location of the point (720 in figure 7b) at which the
meniscus is in
contact with the upper wall of the bottle determine at step 1608 and on the
geometric
information associated with the bottle derived at step 440 (shown in figure
4B). The
position information of the meniscus includes, amongst others, information
related to the
height of the meniscus (in mm) in the bottle. In a non-limiting specific
example of
implementation, a mathematical 3-D reconstruction of the bottle under
inspection will
have been generated at step 440 (shown in figure 4B) wherein coordinates of
the bottle in
the X-ray image will have been mapped into a new coordinate space. In such an
implementation, the coordinates of the meniscus, including location of the
point (720 in
figure 7b) at which the meniscus is in contact with the upper wall of the
bottle and the
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level of the meniscus in the bottle are also mapped into the same coordinate
space as the
reconstructed bottle using mapping techniques known in the art of computer
graphics.
Figure 8 provides an example of a coordinate system that may be used for the
purpose of
positioning the meniscus into a mathematical 3-D reconstruction of the bottle
under
inspection. The 0 and H variables may be estimated in situ using any suitable
calibration
method.
Figure 12 shows a graphical representation of a scene reconstructed in three-
dimensional
from the X-ray image depicted in figure 9a in accordance with a specific
example of
implementation of the invention. It is to be appreciated that this three-
dimensional
reconstruction is being presented for the purpose of illustration only.
dative meniscus
Another mechanism that can be used in order to track the change in intensity
of the gray
scale levels in the X-ray image is the use of potentials from which a distance
map can be
calculated. Although potentials and distance maps can be used in situations
where the
meniscus formed by the liquid in the bottle is either positive or negative, it
has been
found that this approach yields more consistent and reliable results in cases
where the
meniscus is negative.
An exemplary process for using potentials and distance maps to detect and
characterise a
meniscus based on X-ray image data will now be described with reference to
figure 16b.
At step 1700, which is analogous to step 1600 shown in figure 16a, the X-ray
image is
processed to locate areas of the image associated to the liquid product.
Following this,
the subsequent computations/assessments are performed on the identified areas.
Advantageously, this allows reducing the number of computations compared to
processing to X-ray image as a whole. It will be readily appreciated that step
1700 may
be omitted in some implementations.
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At step 1702, which is analogous to step 1702 shown in figure 16a, the X-ray
image data
generated by the inspection device 102 (or the portion of the X-ray image data
identified
at step 1700 as corresponding to the liquid product) is filtered to remove
noise in the X-
ray image.
At step 1704, the X-ray image data is processed to derive an associated
pattern of
potentials and a corresponding distance map. More specifically, the intensity
information
of each pixel in the image is used to designate the potential levels. Deriving
potentials is
well known in the field of computer graphics and as such will not be described
in greater
detail here.
Following this, at step 1706 the location of the point (708 in figure 7a) at
which the
meniscus is in contact with the lower wall of the bottle is performed based at
least in part
on the minimization of the distance between two (2) points (a start point and
an end
point). In a non-limiting example of implementation, the "Fast Marching"
method (J.A.
Sethian) is used in order to minimize of the distance between two (2) points
and derive
the location of the point at which the meniscus is in contact with the lower
wall of the
bottle. The fast marching method is introduced by James A. Sethian as a
numerical
method for solving boundary value problems of the form:
F(x) VT(x) = 1.
Typically, such a problem describes the evolution of a closed curve as a
function of time
T with speed F(x) in the normal direction at a point x on the curve. The speed
function is
specified, and the time at which the contour crosses a point x is obtained by
solving the
equation. For additional information pertaining to the "Fast Marching" method,
the
reader is invited to refer to "Level Set Methods and Fast Marching Methods,
Evolving
Interfaces in Computational Geometry, Fluid Mechanics, Computer Vision, and
Materials
Science", J.A. Sethian, Cambridge University Press, 1999, Cambridge Monograph
on
Applied and Computational Mathematics. Another approach is described in
"Perception-
based 3D Triangle Mesh Segmentation Using Fast Matching Watersheds", by D. L.
Page
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et al., Proc. Intl. Conf on Computer Vision and Pattern Recognition, Vol. II,
pp. 27032,
Madison, WI, June 2008.
In specific example of implementation, in instances where the above described
approach
yields a solution indicating a positive meniscus, the result is discarded and
methods better
suited for identifying characteristics for a positive meniscus are used
instead, such as a
surface normals and/or gradient described above.
Once the location of the point (708 in figure 7a) at which the meniscus is in
contact with
the upper wall of the bottle is determined the process proceeds to step 1708.
At step 1708, which is analogous to step 1610 shown in figure 16a, position
information
pertaining to the meniscus in the bottle is derived based in part on the
location of the
point at which the meniscus is in contact with the lower wall of the bottle
determine at
step 1706 and on the geometric information associated with the bottle derived
at step 440
(shown in figure 4B). The position information of the meniscus includes,
amongst
others, information related to the height of the meniscus (in mm) in the
bottle.
The person skilled in the art will appreciated that since in typically usage
of the system
depicted in figures, it will generally not be know a priori whether the
meniscus formed by
liquid in a bottle is positive or negative, it may be appropriate to perform
both a first
approach suitable for a negative meniscus and a second approach suitable for a
positive
meniscus on a same bottle. In a first example of implementation, approaches
suitable for
positive and negative meniscus are performed sequentially so that if a first
one of the
approaches yields a results that is unexpected, for example an approach that
is more
suitable for a positive meniscus yields a results that indicates a negative
meniscus or vice
versa, then the other approach may be initiated. In a second example of
implementation,
approaches suitable for positive and negative meniscus are performed in
parallel.
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Another Example for Deriving Location Information Associated with the Meniscus
(step 442)
Another example for deriving location information associated with the meniscus
(step
442) is illustrated in the flowchart shown in figure 16c.
In this example, the logic works on the basis of an assumption as to the
height of the
meniscus. The assumption is then subjected to a validation procedure, the
results of
which are used to modify and or refine the assumption. Optionally, this
process may be
performed iteratively until a certain condition is met. The condition may be,
for example,
that a pre-determined number of iterations has been made or that the
validation procedure
indicates a satisfactory result.
More specifically, the process starts at step 1800 where geometric information
associated
with the bottle, of the type derived at step 440 shown in figure 4B, is
received.
Once the geometric information associated with the bottle is available, we
proceed to step
1802 where an assumption as to the height of the meniscus is made. In a first
specific
example of implementation (not shown in the figures), multiple assumptions as
to the
height of meniscus are made concurrently and processed in parallel in order to
identify
the most likely height of the meniscus. In this first specific example of
implementation
the number of assumptions is not limiting and depends on the processing
capability of the
processing module 112 (shown in figure 1) and the desired degree of precision
to be
attained.
In a second specific example of implementation (shown in figure 16c), a
currently
estimated height of the meniscus is set to an initial meniscus height. The
specific initial
meniscus height selected may vary from one implementation to the other. In a
first
example, the initial height may be selected based on a default height
(distance) of the
meniscus from the conveyor belt of the inspection device 102 (shows in figure
1 and 2).
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Alternatively, the specific initial height is selected based in part on the
geometric
information associated with the bottle under inspection and received at step
1800 to
correspond to a certain height within the bottle. In a non-limiting
implementation, the
initial height of the meniscus is set to generally correspond to the middle of
the bottle.
Following this the process proceeds to step 1804.
At step 1804, the response of the inspection device 102 (shown in figure 1)
obtained by
subjecting the liquid product to X-rays is simulated using a computer
implemented
simulation engine. The simulation process implemented by the computer
implemented
simulation engine is a coarse modelling of the operation of the X-ray
inspection device
102 and aims deriving the likely X-ray attenuation data that would be obtained
when a
liquid product having geometric characteristics corresponding to those
received at step
1800, filled with a reference liquid, such as water for example, and having a
meniscus
positioned at the currently estimated height of the meniscus is screened by
the X-ray
inspection device 102.
The simulation is generally a multi-step process, although it may vary in
different
implementations. During a first step, a virtual model of the bottle is
generated using
geometric characteristics received at step 1800 and the currently estimated
height of the
meniscus according to any suitable method known in the field of computer
vision.
During a second step, a virtual model of the inspection device 102 is
generated and the
virtual model of the bottle placed in that model, such as to match the
position of the real
liquid product in the real inspection device 102. Given those simulated
conditions, a
model which simulates the interaction of X-rays with the reference liquid is
executed to
determine what likely attenuation information would be produced. Different
types of
models can be used without departing from the spirit of the invention.
One example of a model that can be used is one which determines the
attenuation to
which the X-rays would be subjected, at different locations throughout the
liquid product
on the basis of theoretical equations that map attenuation with path length,
liquid
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characteristics and X-ray characteristics. Since the X-ray characteristics are
known, the
liquid characteristics are also known, and the path length can be derived
based on the
virtual model, an estimate of the attenuation information can be derived.
The result of step 1804 is data conveying estimated X-ray attenuation
information.
At step 1806, the attenuation information obtained at step 1804 via the
virtual model is
compared with the attenuation information in the X-ray image data obtained by
scanning
the liquid product using the real inspection device 102 (shown in figure 1 and
2). The
purpose of the comparison is to determine the error distribution between the
two. The
attenuation information generated by the model will likely be different from
the
attenuation information in the X-ray image data since the liquids are likely
different.
Recall that the model uses a reference liquid, such as water, while the real
liquid product
is filled most likely with something else. However, if the currently estimated
height of
the meniscus is generally correct, the attenuation error distribution will be
generally
uniform. On the other hand, if the currently estimated height of the meniscus
is far from
the actual height, then the error distribution will not be uniform.
At the validation step 1808, the error distribution obtained at step 1806 is
evaluated to
determine whether the currently estimated height of the meniscus is likely to
be correct.
This evaluation may be effected by comparing the error distribution to a
reference and/or
to an error distribution associated with a different estimated height of the
meniscus.
At step 1810 a decision is made as to whether to currently estimated height of
the
meniscus is satisfactory or whether a new estimated height should be selected.
If
condition at step 1810 is answered in the negative, the currently estimated
height of the
meniscus is set to a new estimated height at step 1814. The selection of the
new
estimated height is made in order to converge to a meniscus height where the
variances in
the error distribution obtained at step 1806 will be minimized. Steps 1804
1806 1808 and
1810 are then repeated for the new estimated height.
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If condition at step 1810 is answered in the positive, the estimated height of
the meniscus
is set to correspond to the currently estimated height.
Specific Practical Implementation
Certain portions of the processing module 112 (shown in figures 1 and 3) may
be
implemented on a general purpose digital computer 1300, of the type depicted
in Figure
13, including a processing unit 1302 and a memory 1304 connected by a
communication
bus. The memory 1304 stores data 1308 and program instructions 1306. The
processing
unit 1302 is adapted to process the data 1308 and the program instructions
1306 in order
to implement the functions described in the specification and depicted in the
drawings.
The digital computer 1300 may also comprise an I/O interface 1310 for
receiving or
sending data elements to external devices, such as the for example the
inspection device
102 and the display device 150 (both shown in figure 1).
Alternatively, the above-described processing module 112 can be implemented on
a
dedicated hardware platform where electrical/optical components implement the
functions described in the specification and depicted in the drawings.
Specific
implementations may be realized using ICs, ASICs, DSPs, FPGA, an optical
correlator,
digital correlator or other suitable hardware platform.
Other alternative implementations of the processing module 112 can be
implemented as a
combination of dedicated hardware and software, of the type depicted in figure
14 and
generally designated by reference numeral 1400. Such an implementation
comprises a
dedicated image processing hardware module 1408 and a general purpose
computing unit
1406 including a CPU 1412 and a memory 1414 connected by a communication bus.
The memory 1414 stores data 1418 and program instructions 1416. The CPU 1412
is
adapted to process the data 1418 and the program instructions 1416 in order to
implement
the functions described in the specification and depicted in the drawings. As
depicted,
this specific implementation also comprise one or more I/O interfaces 1404
1402 for
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receiving or sending data elements to external devices such as, for example,
inspection
and display devices of the type depicted in figure 1.
It will also be appreciated that the screening system 100 that is depicted in
Figure 1 may also
be of a distributed nature where the X-ray images are obtained by an
inspection device in
one location (or more than one location) and transmitted over a network to
another entity
implementing the functionality of the processing module 112 described above.
Another unit
may then transmit a signal for causing one or more display devices to display
information to
the user, such as the X-ray image of the objects being scanned. The display
device may be
located in the same location where the X-ray images of objects were obtained
or in an
alternate location. In a non-limiting implementation, the display device may
be part of a
centralized screening facility.
Figure 15 illustrates a network-based client-server system 1500 for screening
objects in
accordance with a specific example of implementation of the invention. The
client-server
system 1500 includes a plurality of client systems 1502, 1504, 1506 and 1508
and
inspections devices 1560A 1560B connected to a server system 1510 through
network 1512.
The communication links 1514 between the client systems 1502, 1504, 1506,
1508, the
inspections devices 1560A 1560B and the server system 1510 can be metallic
conductors,
optical fibers or wireless, without departing from the spirit of the
invention. The network
1512 may be any suitable network including but not limited to a global public
network such
as the Internet, a private network and a wireless network. The server 1510
maybe adapted
to process information received from the inspections devices 1560A 1560B and
issue
signals conveying screening results to the client systems 1502, 1504, 1506,
1508 using
suitable methods known in the computer related arts.
The server system 1510 includes a program element 1516 for execution by a CPU
(not
shown). Program element 1516 includes functionality to implement the
functionality of
processing module 112 (shown in figures 1 and 3) described above. Program
element 1516
also includes the necessary networking functionality to allow the server
system 1510 to
communicate with the client systems 1502, 1504, 1506, 1508 and inspections
devices
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1560A 1560B over network 1512. In a specific implementation, the client
systems 1502,
1504, 1506 and 1508 include display devices responsive to signals received
from the server
system 1510 for displaying screening results derived by the server system
1510.
Although the above embodiments have been described with reference to an
inspection
device 102 (shows in figures 1 and 2) embodied single view X-ray imaging
apparatus, it is
to be appreciated that embodiments of the invention may be used in connection
with any
suitable type of inspection device including multi-view X-ray imaging
apparatus.
As such, in an alternative example of implementation, the inspection device
102 is
embodied as a multi-view X-ray machine. The multi-view X-ray machine generates
X-
ray image data associated with the liquid product conveying a first X-ray
image of the
liquid product taken by subjecting the liquid product to X-rays in a first
orientation and a
second X-ray image of the liquid product taken by subjecting the liquid
product to X-rays
in a second orientation. The first and second orientations are different from
one another
and will frequently be orthogonal to one another, although that may vary
depending on
the X-ray machine being used. In such an alternative implementation, the X-ray
image
data corresponding to the first X-ray image of the liquid product may be
processed to
derive information associated with the location of the meniscus, information
conveying
an estimated level of fill of the bottle and/or information pertaining to the
threat status of
the liquid product according to the methods described above. The X-ray image
data
corresponding to the second X-ray image of the liquid product is then
processed to
validate and/or adjust the information derived based on the X-ray image of the
liquid
product. For example, the X-ray image data corresponding to the second X-ray
image
and the location information associated with the meniscus obtained based on
the X-ray
image data corresponding to the first X-ray image may be processed to derive
adjusted
location information associated with the meniscus. In a non-limiting example
of
implementation, the adjusted location information associated with the meniscus
may be
set to the mean between the location information associated with the meniscus
derived
based on the first X-ray image and that derived based on the second X-ray
image. IN
another example, the X-ray image data corresponding to the second X-ray image
and the
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level of fill of the bottle obtained based on the X-ray image data
corresponding to the first
X-ray image may be processed to derive an adjusted level of fill. The threat
status of the
liquid product may be derived based on the adjusted level of fill of the
bottle and/or
adjusted location information associated with the meniscus for example.
An advantage of using a multi-view X-ray imaging apparatus, compared to the
use of a
single view X-ray imaging apparatus, is that the additional view provide three-
dimensional information that is unavailable from single two-dimensional view.
It will also be appreciated that the multi-view X-ray machine may generate X-
ray image
data conveying X-ray images of the liquid taken by subjecting the liquid
product to X-
rays more that two orientations there by generated three of more X-ray images.
It will therefore be appreciated that other various modifications will become
apparent to
those skilled in the art and are within the scope of this invention, which is
defined more
particularly by the attached claims.
