Method and system for performing X-ray inspection of a liquid product at a security checkpoint

A method, an apparatus and a system are provided for assessing at a security checkpoint the threat status of a liquid product, where the liquid product is comprised of a bottle at least partially filled with liquid. In accordance with a broad aspect, the level of fill is used as a factor in the determination of the threat status of the liquid product. In accordance with another broad aspect, an X-ray image of the liquid product is obtained and processed to derive a level of fill of the bottle and the threat status of the liquid product is determined at least in part based on the level of fill of the bottle. In accordance with yet another broad aspect, an X-ray image of the liquid product is processed to derive location information associated with a meniscus formed by the liquid in the bottle. An estimated length of a path followed by X-rays through the liquid held in the bottle is derived in part based on the location information and is used to determine the threat status of the liquid product.

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.

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 traveled 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 traveled 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.

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 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 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 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 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 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.

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.

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 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 inFIG. 1is a screening system100suitable 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 system100includes an inspection device102for scanning objects, a processing module112for processing data generated by the inspection device102and a display device150for visually conveying information to a security operator, the information being derived by the processing module112and pertaining to the objects being scanned by the inspection device102.

More specifically, the inspection device102is 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 module112receives the X-ray data from the inspection device102and processes that data to derive information related to the threat status of that liquid product. In accordance with a first approach, the processing module112processes 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 module112processes the X-ray image data to derive location information associated with a meniscus formed by the liquid in the bottle. The processing module112then 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 module112then releases information conveying the determined threat status. The display device150, 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 module112.

Advantageously, the system100provides 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 system100depicted inFIG. 1will now be described in greater detail.

The display device150may be any device suitable for visually conveying information to a user of the system100. The display device150may be part of a computing station, as shown inFIG. 1, may be part of a centralized security station and located remotely from the inspection device102or may be integrated into a hand-held portable device (not shown) for example. In another specific example of implementation, the display device150includes 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 device150displays to a user of the system100a graphical user interface conveying the determined threat status of the liquid product based on the information released by the processing module112. 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%.

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.

In a specific example of implementation, the inspection device102is 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 device102will now be described in greater detail with reference toFIG. 2. As depicted, the inspection device102includes a scanning area104, a conveyor belt106, an X-ray source108and an array of X-ray detectors110. The inspection device102performs 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 area104(also referred to as scanning tunnel) is defined by an enclosed void between the X-ray source108and the array of X-ray detectors110, in which the objects to be scanned are subjected to penetrating radiation, such as X-rays. The scanning area104is typically horizontally oriented and is dimensioned both vertically 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 area104is centrally traversed by a conveyor belt106that is used to convey objects to be scanned both into and out of the scanning area104and is described below.

The articles to be scanned can be placed either directly on the conveyor belt106or in one or more trays that are then placed on the conveyor belt106.

The conveyor belt106is a horizontally-oriented continuous belt of material arranged in an endless loop between two terminal rollers. The belt106has 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 belt106is 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 area104, where the objects to be scanned are placed on the belt106;The scanning area104, where the objects being scanned are subjected to penetrating radiation (i.e. X-rays); andA post-scanning area that lies after the scanning area104, 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 belt106at the pre-scanning and post-scanning areas may be connected to motors (not shown) that allow an operator to move the belt106forwards or backwards to displace the objects to be scanned between different areas of the X-ray inspection device102.

The X-ray source108is the source of penetrating radiation (in this case, X-ray radiation). The X-ray source108is located opposite to the array of X-ray detectors110so that X-rays emitted by the source108pass through the objects that are located on the conveyor belt106and are detected by the array of X-ray detectors110as a result. In a non-limiting example, the inspection device102is a dual-energy X-ray scanner and the x-ray source108emits 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 detectors110detects the penetrating radiation (i.e. X-rays) that was emitted by the X-ray source108and that penetrated the objects to be scanned. The array of X-ray detectors110is located opposite to the X-ray source108so that X-rays that are emitted by the source108pass through the objects that are located on the conveyor belt106and are detected by the array110.

The processing module112is in communication with the inspection device102and receives the X-ray image data output by the array of X-ray detectors110. In the example depicted inFIGS. 1 and 2, the processing module112is shown as a component external to the inspection device102. It will be appreciated that, in alternate example of implementation of the system100, the functionality of processing module112may be integrated within the inspection device102.

The processing module112uses the X-ray data output by the array of X-ray detectors110of the inspection device102to 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 the inspection device102is 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 module112is depicted inFIG. 3of the drawings. As shown, the processing module112includes an input300in communication with the inspection device102for receiving there from X-ray data, a processor302in communication with the input300, a memory306storing data for use by the processor302and an output304in communication with the display device150(shown inFIG. 1) for releasing information derived by the processor302.

The processor302implements a process for assessing the threat status of a liquid product unit based on the X-ray data received at input300from the inspection device102. Results of the threat status assessment are then released at output304. Specific examples of processes for assessing the threat status of a liquid product that may be implemented by processor302will 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 traveled by X-ray through the liquid in the bottle. The closer the estimate path length is to the actual length of the path traveled 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.

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 (Zeffnumber), 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.

FIGS. 5aand5bshow a side cutaway view of a bottle500partially filled with liquid in an inclined position. With respect to these figures, the bottle500is generally inclined at an angle501relative to a generally horizontal plane. For the purpose of this example, the angle501is achieved by positioning the bottle on a tray having an inclined bottom surface and an angle of501.

FIGS. 5aand5balso show a path taken by a ray of penetrating radiation (i.e. an X-ray) through the bottle. The X-ray enters the bottle500at location502, travels through the bottle walls and the bottle contents, and emerges from the bottle at location514. The angle between the X-ray and the longitudinal axis of the bottle of liquid can be derived using simple trigonometry since the angle501is 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. Segment510between the locations502and514, herein referred to as the combined segment510, is a combination of the following segments:segment504through the supporting structure (for example a tray);segments506and508through the side walls of the bottle; andsegment512through the inside portion of the bottle500.

The lengths of segments504,506and508may 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 segment510may 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 segment512may be determined by subtracting the lengths504,506and508from the length of combined segment510.

As can be observed inFIG. 5a, the position of the meniscus520is such that the length of the path segment512, which is the length of the path through the inside portion of the bottle500, 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 segment512can 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 (Zeffnumber) 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 bottle500can 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 considerFIG. 5b, we note that the position of the meniscus520′ is such that the length of the path segment512includes a first component592corresponding to the length of the path taken by the X-ray passing through the liquid within the bottle but also includes a second component590corresponding 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 component592), should take into account the location and characteristics of the meniscus.

As can be observed fromFIGS. 5aand5b, since the meniscus is a generally horizontal flat surface aligned with the surface of the conveyor belt, the level of meniscus520520′ can be determined by identifying the location of the point (594inFIG. 5aand594′ inFIG. 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 inFIG. 5b).

The location information associated with the meniscus may include various components such as:The height of the meniscus relative to the conveyor belt of the inspection device102;The location of the point (594inFIG. 5aand594′ inFIG. 5b) at which the meniscus is in contact with the wall of the bottleDistance590inFIG. 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 (594inFIG. 5aand594′ inFIG. 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 (594inFIG. 5aand594′ inFIG. 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 toFIGS. 16a,16band16c.

As can be observed fromFIGS. 5aand5b, 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 bottle500can be derived using well-known methods.

As can also be observed fromFIGS. 5aand5b, 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 (segment512inFIG. 5aand segment592inFIG. 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 (Zeffnumber) and/or linear attenuation coefficient) and the ensuing assessment of the threat status of the liquid product under inspection.

Process Implemented by System100

A specific example of a process implemented by the system100(shown inFIG. 1) will now be described with reference toFIG. 4A.

As shown, at step400an X-ray scan of a liquid product to be screened is performed by the inspection device102(shown inFIG. 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 device102or is placed on a tray which is then placed on the conveyor belt of the inspection device102.

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 inFIG. 6may 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 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 Nov. 17, 2008 by Michel Roux et al. and presently pending.

The contents of the above mentioned document are incorporated herein by reference.

The liquid product having been placed either directly on the conveyor belt or on a tray is then displaced toward the scanning area104of the inspection device102(shown inFIG. 2). X-ray image data is then generated by the inspection device102by subjecting the liquid product to penetrating radiation.FIG. 9ais 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 step402, the X-ray image data generated by the inspection device102is received by the processing module112.

At step404, the processing module112processes the X-ray image data to determine the threat status of the liquid product scanned at step400. Many different approaches may be taken for determining the threat status of the liquid product.

In accordance with a first approach, the processing module112processes 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 module112processes the X-ray image data to derive location information associated with a meniscus formed by the liquid in the bottle. The processing module112then 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 module112then 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 module112may 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 Sep. 17, 2007 and was published on Mar. 27, 2008 under publication no. WO2008034232. The contents of the aforementioned document are incorporated herein by reference. 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 step404may be implemented will be described in greater detail below.

At step408, the processing module112releases information conveying the threat status of the liquid product determined at step404.

Following this, at step410, the display device150(shown inFIG. 1) receives the information released by the processing modules and conveys this information in visual format, and optionally in audio format, to an operator.

A specific approach for determining the threat status of the liquid product at step404will now be described with reference toFIG. 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 step440the X-ray image data received from the inspection device102(shown inFIG. 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:Annular recesses on the body of the bottle and position of those annular recesses;Presence or absence of capApproximation of the position of the bottle in the trayThree-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 device102(shown inFIG. 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 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; andextrapolating 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 device102(shown inFIG. 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 step440based on the X-ray image data generated by the inspection device102(shown inFIG. 1).FIG. 9Bof the drawings shows graphical three-dimensional mathematical representations950952954, corresponding respectively to bottles900902and904depicted in the X-ray images shown inFIG. 9A.

Once geometric information associated with the bottle of the liquid product has been obtained, the process proceeds to step442.

At step442, 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 device102The location of the point (594inFIG. 5aand594′ inFIG. 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 toFIGS. 16a,16band16c.

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 step442, the process proceeds to steps444and446and/or450452and460.

At step444, 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 step440, and based on the location information associated with the meniscus, which was derived in step442.

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 step446, the level of fill of the bottle derived at step444is 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 step444is 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 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 steps450452and460inFIG. 4B.

Consequently, in a specific example of implementation after step446, 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, steps450452and460may be omitted.

In cases where the liquid product has been identified as being undetermined and requiring further assessment, the process continue with steps450452and460.

At step450, 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 step452, the location information associated with the meniscus derived at step442and the geometric information associated with the bottle derived at step440are 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 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 step460, the path length information derived at step452and the attenuation information derived at step450are processed to assess the threat status associated with the liquid product.

In a specific example of implementation, the path length information derived at step452and the attenuation information derived at step450are processed to derived characteristics associated with the liquid product (e.g. the density, the effective atomic number (Zeffnumber) 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 (Zeffnumber) 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 step444and step446, 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 steps450452and460, is associated to an assessment of the threat status of the liquid product based in part on the length of the path traveled 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. 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 step462, the threat status determined at step446based 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 step460are considered in combination to obtain a level of threat associated with the liquid product.

In a non-limiting example of implementation, if either step446or460result in the liquid product being classified as a “threat”, step462will classify the liquid product as a threat.

Once step462is completed, the process proceeds to step408(shown inFIG. 4a) in which information conveying the threat status is released by the processing module112.

Deriving Location Information Associated with the Meniscus (Step442)

As described above with reference toFIG. 4B, at step442, 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.

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 inFIG. 6for 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 Nov. 17, 2008 by Michel Roux et al. and presently pending. The contents of the aforementioned documents are incorporated herein by reference.

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.

FIGS. 7aan7bof the drawings show in very simplified form a bottle700holding liquid and positioned at an inclined angle of α. As shown, the bottle has an upper wall704and a lower wall710. In the example shown inFIG. 7b, the level of fill of the bottle700is such that the meniscus appears as an air bubble in the upper end of the bottle and ends along the upper wall704of the bottle700at point720that 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.

In the example shown inFIG. 7a, the level of fill of the bottle700is such that the meniscus ends along the lower wall710of the bottle700at point708that 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 (720or708inFIGS. 7aand7b) 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 (step440shown inFIG. 4B).

In a non-limiting example of implementation, different approaches may be used for determining the location of the point (708or720inFIGS. 7aand7b) 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 device102(shown inFIG. 1).

More specifically, the X-ray image data generated by the inspection device102(shown inFIG. 1) provides attenuation information for each {x,y} coordinate in a two-dimensional 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:

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 toFIG. 16a.

At step1600, 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 step1600may be omitted in some implementations.

At step1602, the X-ray image data generated by the inspection device102(or the portion of the X-ray image data identified at step1600as 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 step1602may be omitted in some implementations.

At step1604, 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 step1600, surface normals may be computed for all (x,y) coordinates in the X-ray image.

FIG. 10of the drawings depicts in graphical form surface normals derived based on the portion of the X-ray image shown inFIG. 9Acorresponding to bottle900.

Once the surface normals are computed at step1604, the process proceeds to step1606.

At step1606, 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.

FIGS. 11a,11band11cof the drawings depict in graphical form projections of the surface normals depicted inFIG. 10in 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 inFIG. 11a) 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 parabola. The projections on the (x,z) and (y,z) planes (shown inFIGS. 11band11c) 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 step1600as corresponding to a liquid product.

At step1608, the location of the point (720inFIG. 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 (720inFIG. 7b) at which the meniscus is in contact with the upper wall of the bottle is determined the process proceeds to step1610.

At step1610, position information pertaining to the meniscus in the bottle is derived based in part on the location of the point (720inFIG. 7b) at which the meniscus is in contact with the upper wall of the bottle determine at step1608and on the geometric information associated with the bottle derived at step440(shown inFIG. 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 step440(shown inFIG. 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 (720inFIG. 7b) at which the meniscus is in contact with the upper wall of the bottle and the 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.

FIG. 8provides 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 θ and H variables may be estimated in situ using any suitable calibration method.

FIG. 12shows a graphical representation of a scene reconstructed in three-dimensional from the X-ray image depicted inFIG. 9ain 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.

Negative 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 toFIG. 16b.

At step1700, which is analogous to step1600shown inFIG. 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 step1700may be omitted in some implementations.

At step1702, which is analogous to step1702shown inFIG. 16a, the X-ray image data generated by the inspection device102(or the portion of the X-ray image data identified at step1700as corresponding to the liquid product) is filtered to remove noise in the X-ray image.

At step1704, 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 step1706the location of the point (708inFIG. 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)|∇T(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. The content of the aforementioned document are incorporated herein by reference. Another approach is described in “Perception-based 3D Triangle Mesh Segmentation Using Fast Matching Watersheds”, by D. L. Page et al., Proc. Intl. Conf. on Computer Vision and Pattern Recognition, Vol. II, pp. 27032, Madison, Wis., June 2008. The content of the aforementioned document are incorporated herein by reference.

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 (708inFIG. 7a) at which the meniscus is in contact with the upper wall of the bottle is determined the process proceeds to step1708.

At step1708, which is analogous to step1610shown inFIG. 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 step1706and on the geometric information associated with the bottle derived at step440(shown inFIG. 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.

Another Example for Deriving Location Information Associated with the Meniscus (Step442)

Another example for deriving location information associated with the meniscus (step442) is illustrated in the flowchart shown inFIG. 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 step1800where geometric information associated with the bottle, of the type derived at step440shown inFIG. 4B, is received.

Once the geometric information associated with the bottle is available, we proceed to step1802where 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 module112(shown inFIG. 1) and the desired degree of precision to be attained.

In a second specific example of implementation (shown inFIG. 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 device102(shows inFIGS. 1 and 2). Alternatively, the specific initial height is selected based in part on the geometric information associated with the bottle under inspection and received at step1800to 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 step1804.

At step1804, the response of the inspection device102(shown inFIG. 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 device102and aims deriving the likely X-ray attenuation data that would be obtained when a liquid product having geometric characteristics corresponding to those received at step1800, 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 device102.

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 step1800and 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 device102is 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 device102. 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 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 step1804is data conveying estimated X-ray attenuation information.

At step1806, the attenuation information obtained at step1804via 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 device102(shown inFIGS. 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 step1808, the error distribution obtained at step1806is 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 step1810a 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 step1810is answered in the negative, the currently estimated height of the meniscus is set to a new estimated height at step1814. 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 step1806will be minimized. Steps180418061808and1810are then repeated for the new estimated height.

If condition at step1810is 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 module112(shown inFIGS. 1 and 3) may be implemented on a general purpose digital computer1300, of the type depicted inFIG. 13, including a processing unit1302and a memory1304connected by a communication bus. The memory1304stores data1308and program instructions1306. The processing unit1302is adapted to process the data1308and the program instructions1306in order to implement the functions described in the specification and depicted in the drawings. The digital computer1300may also comprise an I/O interface1310for receiving or sending data elements to external devices, such as the for example the inspection device102and the display device150(both shown inFIG. 1).

Alternatively, the above-described processing module112can 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 module112can be implemented as a combination of dedicated hardware and software, of the type depicted inFIG. 14and generally designated by reference numeral1400. Such an implementation comprises a dedicated image processing hardware module1408and a general purpose computing unit1406including a CPU1412and a memory1414connected by a communication bus. The memory1414stores data1418and program instructions1416. The CPU1412is adapted to process the data1418and the program instructions1416in 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 interfaces14041402for receiving or sending data elements to external devices such as, for example, inspection and display devices of the type depicted inFIG. 1.

It will also be appreciated that the screening system100that is depicted inFIG. 1may 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 module112described 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.

FIG. 15illustrates a network-based client-server system1500for screening objects in accordance with a specific example of implementation of the invention. The client-server system1500includes a plurality of client systems1502,1504,1506and1508and inspections devices1560A1560B connected to a server system1510through network1512. The communication links1514between the client systems1502,1504,1506,1508, the inspections devices1560A1560B and the server system1510can be metallic conductors, optical fibers or wireless, without departing from the spirit of the invention. The network1512may 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 server1510may be adapted to process information received from the inspections devices1560A1560B and issue signals conveying screening results to the client systems1502,1504,1506,1508using suitable methods known in the computer related arts.

The server system1510includes a program element1516for execution by a CPU (not shown). Program element1516includes functionality to implement the functionality of processing module112(shown inFIGS. 1 and 3) described above. Program element1516also includes the necessary networking functionality to allow the server system1510to communicate with the client systems1502,1504,1506,1508and inspections devices1560A1560B over network1512. In a specific implementation, the client systems1502,1504,1506and1508include display devices responsive to signals received from the server system1510for displaying screening results derived by the server system1510.

Although the above embodiments have been described with reference to an inspection device102(shows inFIGS. 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 device102is 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 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.