Technical Field of the Invention

This invention relates to the field of security screening, in particular to apparatus and methods for screening cargo or people.

Background to the Invention

The term 'cargo' refers to goods, equipment, baggage or luggage that is loaded onto a vehicle for transport. The term is generally used to refer to the entirety of the goods being transported by a vehicle, but it may also be used in the singular, to refer to a single item of baggage, for instance. Both cargo and people require transport, and the vehicle performing the transport of cargo or people may be airborne (aircraft), sea based (boats) or land based (cars, vans, trucks and trains).

For security reasons it is necessary to screen the cargo a particular vehicle is transporting to and from a location. This may be because particular types of cargo are prohibited from a certain form of transport. For instance, explosives cannot be transported on commercial passenger aircraft. Whilst permitted and non-permitted cargo may be well advertised, there remains the threat of non-permitted cargo being loaded onto vehicles with the intent to cause damage or harm to the vehicle itself, or other cargo or passengers on board the vehicle. People may also conceal items which are desirable to detect on (or in) their body, and it is therefore necessary to screen people for similar reasons, when travelling on different modes of transport, or for access to controlled areas or events.

To mitigate the risk of harm, cargo that is being transported is typically screened prior to loading onto a vehicle. The screening process may comprise manual checking of cargo or automated screening of cargo, for instance using X-ray scanners. Automated screening processes are intended to reveal the contents of cargo without the requirement to open the container or vessel holding the cargo. Regularly used automated screening apparatus are the X-ray scanners used in airports to scan luggage and freight, and millimetre wave scanners used to screen people.

Automated cargo scanners, and people screening systems, operate according to a receiver operating characteristic curve that is an attribute of the detector system, typically a function of hardware and software. The receiver operating characteristic describes the diagnostic ability of a binary classifier system as its discrimination threshold is varied. For security screening, the receiver operating characteristic curve describes the probability of detection (detection rate) of the scanner system as a function of probability of false alarm (false alarm rate). Owing to the high throughput of cargo and passengers where automated scanners are routinely used, such as in airport security, the automated scanners are set to operate with a minimum detection standard that balances the likelihood of detecting a threat with an acceptable throughput of passengers or cargo, resulting in uniform false alarm rates across the population of screened cargo or people, but lower detection rates for smaller threat masses compared to higher threat masses.

Therefore it is an aim of the present invention to provide an alternative screening apparatus and method that mitigates these issues.

Summary of the Invention

According to a first aspect of the invention there is provided screening apparatus comprising means for screening, and means for processing data, wherein the means for processing data is configured to be capable of operating the means for screening at a plurality of detection points for each of a plurality of threat quantity values, wherein each detection point comprises a probability of detection and respective false alarm rate, such that in use an item of cargo or a person can be adaptively scanned in a respective screening event.

A means for screening refers to apparatus that is used to scan an item of cargo or a person with the aim of revealing information regarding the contents of that cargo or person. The means for screening will operate according to a receiver operating characteristic i.e. it will have a probability of detection that can be expressed as a function of false alarm rate. The receiver operating characteristic will be different for different threat quantity values. By way of example a basic means for screening is a metal detector. The aim of the metal detector is to identify whether an object being scanned contains metal. The metal detector will have a probability of detection for a given size and shape of metal, and corresponding false alarm rate. Decreasing the false alarm rate would mean decreasing the probability of detection, in accordance with a receiver operating characteristic curve. With a decreased probability of false alarm therefore, the risk of not detecting a metallic device such as a knife, is more substantial. A further example of a means for screening is an X-ray scanner. The aim of an x- ray scanner may be to generate an image of the contents of an item of cargo, or measure the density and spatial disposition of the contents. The resultant output may be manually inspected (with the assistance of computer algorithms) or automatically inspected using computer software, e.g. in computed tomography X-Ray screening. An example of a computed tomography X-ray screening system used in airports is the Smiths Detection Hl- SCAN 10080 XCT. An X-ray scanner suitable for use in screening postal items is the WG X15 mail scanner. An example of a person-screening system is the L3 Provision 2.

The means for processing data may be a computer system that is a standalone computer forming part of the apparatus of the invention, or equally can refer to computational functionality achieved through a field programmable gate array (FPGA) or electronics processing unit (such as a CPU). The means for processing data has the function of operating the means for screening. The means for processing data may comprise on board memory for containing software (for instance to operate the means for screening and apply detection algorithms), and/or for containing other data. The means for processing data may comprise one or more input/output interfaces, for instance to access a network or input/output device.

The means for processing data is configured to be capable of operating the means for screening at a plurality of detection points (probability of detection and respective false alarm rate), for each of a plurality of threat quantity values. A threat quantity may be a variable which embodies the mass, disposition, shape, or combination thereof, of an explosive or other non-permitted substance, which is sufficient to cause catastrophic damage to an aircraft, ship or other vehicle. For instance in aviation security it can refer to the mass of explosive which, if it detonates, is sufficient to cause the aircraft to disintegrate resulting in the death of all passengers. Where transport security is regulated, for example in aviation security, the regulator typically defines a minimum acceptable detection rate for a single minimum threat quantity. The regulator may also set a maximum acceptable false alarm rate. Therefore, current aviation cargo scanners are configured to detect the specified minimum threat quantity with the specified probability of detection, irrespective of the specific vulnerability of the transport scenario (type of passenger; vehicle (e.g. aircraft) type; travel route; location of cargo within vehicle). The inventor has recognised that the specific transport scenario within which an item of cargo or indeed a person is being transported can be used to determine adaptively the appropriate threat quantity needing to be detected in a given screening event, based on the vulnerability of that transport scenario. For instance different construction materials and designs of aircraft (or other vehicles) may have different resistance to explosive forces. A weaker airframe may be more susceptible to a smaller explosive blast, and therefore a cargo scanner may be configured to scan for a smaller threat quantity value than that used for a stronger airframe. For a given probability of detection (e.g. that specified by a regulator), screening for a lower threat quantity will result in a larger false alarm rate than would occur when screening for a higher threat quantity. However there are two primary benefits of this approach. Firstly if the probability of detection remains at the current mandated level, there would be a reduction in overall false alarms (compared to current screening systems) because screening passengers or cargo travelling on more resilient aircraft (as an example of a vehicle) will generate fewer false alarms, and this will reduce airport operator costs and inconvenience to the travelling public. Secondly if regulators mandate an increase in the probability of detection of for instance explosives threats, this approach will enable improved security (compared to current screening systems) without increasing the overall false alarm rate, because screening for higher threat quantities will generate fewer false alarms which will balance the increase in false alarms that would be observed for lower threat quantities. The threat quantity values for specific scenarios (for instance particular airframe types) may be predetermined and stored within or accessible by, the means for processing data.

The configurability of the cargo or person screening apparatus is such that the detection point (probability of detection and respective false alarm rate) can be altered in accordance with a selected receiver operating characteristic curve. Each threat quantity value will have a different receiver operating characteristic curve, and so the same probability of detection (for instance 0.95) will have a different false alarm rate for different threat quantities. Both probability of detection and false alarm rate are determined by hardware specifications and data processing methodologies. By selecting a threat quantity value the detection point can be selected by adjusting a detection algorithm for a means for screening.

In some embodiments of the invention the means for processing data is configured to receive a threat quantity value from an input device for each screening event. A user may know a quantity of items of cargo are to be transported by a vehicle of a particular construction, and therefore may input directly to the means for processing data, a threat quantity value. The data processing means may then operate the means for screening at a detection point on a receiver operating characteristic curve corresponding to the threat quantity value.

In other embodiments the means for processing data contains threat information and is configured for each screening event to calculate a threat quantity value from a subset of the threat information using a threat quantity function. Threat information is information used to determine the risk of damage or harm to a transport vehicle or its contents (cargo and/or passengers). Threat information may in some applications of the invention comprise passenger profiles i.e. details on passenger travel history; transport information for instance the travel route, start location and destination; vehicle construction information such as airframe type; the location of cargo within a vehicle; the container within which the cargo will be placed; or any combination thereof. Threat information may be provided as a database or searchable repository of information in, for instance, the means for processing data. Alternatively, such information may be available remotely through a computer network. Threat information is intended to be a wider repository of information from which a subset of information can be selected that is specific to the cargo (or person) being scanned. The subset of threat information is that used to calculate a threat quantity value using the threat quantity function. A threat quantity function may be a lookup table stored within the means for processing data. The lookup table may comprise a list of airframe types and their associated threat quantity values. The look up table may be a two dimensional array of threat quantity values corresponding to combinations of airframe type and seat row, for instance. The look up table may be a three dimensional array of threat quantity values corresponding to combinations of airframe type, seat row and passenger score, where the passenger score may be a 'risk' rating based on flight history or other information. By providing threat information each item of cargo or person can be considered as having its own unique scenario, and the screening process can be very precisely tailored to that specific scenario.

Even more preferred embodiments of the invention further comprise a cargo tag reader, the means for processing data being further configured to receive from the cargo tag reader a cargo ID for each screening event, and to select the subset of the threat information associated with the cargo ID. The cargo ID is a unique identifier for a specific item of cargo that links that item of cargo to the subset of threat information, for instance a transport vehicle and the owner of that cargo item (which may be a passenger). The cargo ID itself may have such information encoded within it (for instance through use of a barcode). This down-selection may be automated upon the means for processing data receiving a cargo ID from an input device, such as a keyboard, but the preferred embodiments use a cargo tag reader. The subset of threat information can then be used in a threat quantity function (for instance a lookup table) to obtain a threat quantity value. The threat quantity value may then be used to select a detection point on an appropriate receiver operating characteristic curve, for the operation of the means for screening.

A cargo tag itself may be a sticker having a barcode that is attached to an item of cargo. In this example the cargo tag reader would be a barcode scanner. Alternatively a cargo tag may be an RFID tag, and the cargo tag reader being an RFID reader. The cargo tag reader may provide the cargo ID to the data processing means wirelessly or via cable. The cargo tag reader may provide more than the cargo ID to the data processing system (for instance any information encoded within the tag itself may also be provided).

Some embodiments of the invention comprise a scanner as the means for screening. An x- ray scanner may be used for instance, or a millimetre wave scanner, as they have proven utility in high throughput cargo screening applications, such as baggage, freight and person screening at airports.

In some embodiments the means for processing data contains a predetermined probability of detection and is configured to operate the means for screening at the predetermined probability of detection for any threat quantity value. A probability of detection may be specified by a transport authority regulator. This predetermined probability of detection may be stored inside the means for processing data (for instance in computer memory). Whilst the predetermined probability of detection may be constant for all threat quantity values, the false alarm rate will vary according to the threat quantity value. Therefore for a fixed probability of detection, smaller threat quantities will have a higher false alarm rate than larger threat quantities.

According to a second aspect of the invention there is provided a method of adaptively screening a person or an item of cargo, the method comprising the steps of: providing screening apparatus comprising means for screening, and means for processing data, wherein the means for processing data is configured to be capable of operating the means for screening at a plurality of detection points for each of a plurality of threat quantity values, wherein each detection point comprises a probability of detection and respective false alarm rate; providing a person or an item of cargo to be screened; providing a threat quantity value associated with the person or item of cargo within the means for processing data; providing a predetermined probability of detection within the means for processing data; and then operating the screening apparatus using the threat quantity value and predetermined probability of detection, such that the person or item of cargo is adaptively screened.

Operating the screening apparatus includes the means for processing data using the threat quantity value to operate the means for screening at a detection point on a receiver operating characteristic curve associated with the threat quantity value. This detection point will be the predetermined probability of detection and corresponding false alarm rate on that curve. This detection point may be configured by adjusting a detection algorithm within the means for processing data or means for screening. In preferred embodiments of the second aspect of the invention the step of providing a threat quantity value within the means for processing data comprises the steps of: providing threat information within the means for processing data; and calculating a threat quantity value from a subset of the threat information using a threat quantity function. In even more preferred embodiments the threat information comprises vehicle construction information.

In some embodiments of the second aspect of the invention the cargo screening apparatus further comprises a cargo tag reader, and the step of calculating a threat quantity value comprises the steps of: receiving with the cargo tag reader a cargo ID; selecting the subset of threat information associated with the cargo ID; and then operating the threat quantity function on the subset of threat information to obtain a threat quantity value.

According to a third aspect of the invention there is provided a computer implemented method of operating a means for screening to adaptively screen a person or item of cargo, comprising the steps of: receiving a threat quantity value associated with a person or item of cargo; receiving a predetermined probability of detection; and then operating a means for screening using the threat quantity value and predetermined probability of detection, thereby adaptively screening a person or item of cargo. The threat quantity value and predetermined probability of detection may be received by a user input device such as a keyboard or mouse, or may be received by a barcode or RFID scanner for instance. The threat quantity value and predetermined probability of detection may be received across a computer network or by using a look-up operation in non-volatile computer memory. The means for screening may be electrically or wirelessly connected to a computer operating the computer implemented method.

According to a fourth aspect of the invention there is provided a computer program comprising code which when executed performs the steps of the third aspect of the invention. This allows the computer implemented method to be installed onto some pre existing screening systems. According to a fifth aspect of the invention there is provided computer readable storage media comprising the computer program of the fourth aspect of the invention. This allows the computer implemented method to be operated by some means for screening that do not themselves comprise non-volatile memory for installing computer program software, for instance.

Brief Description of the Drawings

Embodiments of the invention will now be described by way of example only and with reference to the accompanying drawings, in which:

Figure 1 provides an illustration of the functionality of an embodiment of a cargo screening apparatus;

Figure 2 provides an illustration of an embodiment of a cargo screening apparatus; and Figure 3 provides an illustration of example receiver operating characteristic curves.

Detailed Description

Figure 1 shows an illustration of the functionality of an embodiment of cargo screening apparatus 10. The figure shows cargo screening apparatus 10 comprising a means for screening that is a luggage x-ray scanner 11, an item of luggage 12 having an RFID tag, an RFID tag reader 13, and a means for processing data as a computer system 14 containing software 15 and threat information 16. The RFID tag on luggage 12 contains a cargo ID reference. The computer software 15 is stored in memory internal to the computer system 14 and instructs RFID reader 13 to read RFID tag on luggage 12 via a wired interface Com_2. RFID reader 13 reads the data comprising the cargo ID from the RFID tag on luggage 12 (as indicated by Com_4) and communicates via Com_2 the data to the software 15. The threat information 16 is stored within computer memory as two databases. The threat information 16 comprises passenger profile information and vehicle structural information. The passenger profile information comprises a passenger profile score for each of a plurality of passengers. The structural information comprises an airframe type threat score for each of a plurality of aircraft types. The cargo ID is a unique identifier linking a passenger to a particular flight. The software 15 obtains from threat information 16 a subset of information comprising the passenger profile threat score and airframe threat score as indicated by Com_5. The software 15 uses a threat quantity function to determine a threat quantity value. The threat quantity function is an array of threat quantity values corresponding to each passenger profile score and airframe score combination. The software 15 configures scanner 11 via a wired link Com_l to operate using a predetermined probability of detection for the determined threat quantity value. Software 15 then requests scanner 11 to begin screening cargo 12 via link Com_l. The scanner 11 scans the cargo 12 as indicated by Com_3. The screening results are communicated back to software 15 via link Com_l.

Figure 2 shows an illustration of an embodiment of cargo screening apparatus 20. The cargo screening apparatus 20 comprises a luggage X-ray scanner 21 with conveyor 22. The figure shows cargo item 23 entering luggage scanner 21. The luggage scanner 21 is controlled by computer 24 via interface 26. Also shown is a display means 25 for displaying a scan image.

Figure 3 shows an illustration of example receiver operating characteristic curves 30 for a plurality of threat quantity values. The receiver operating characteristic 30 provides probability of detection 'Pd' as a function of false alarm rate 'Pfa'. The figure shows that for a fixed probability of detection, as the threat quantity value decreases (from 1 TQ to 0.1 TQ), the false alarm rate increases. The figure also shows that configuring a means for screening based purely on an aspiration to identify a single threat quantity value at a predetermined probability of detection, will not result in the same probability of detection for a different threat quantity value. A weaker aircraft structure may be susceptible to catastrophic damage from a much lower threat quantity value than a stronger aircraft structure. Therefore providing means for screening that is configurable according to the threat quantity value associated with a particular aircraft structure, enables a tailored screening of cargo (or indeed a person) for each screening event.