阅读说明：本技术 用于人群预筛查的多传感器盗窃/威胁检测系统 (Multi-sensor theft/threat detection system for people pre-screening ) 是由 陈鸿群 唐志鸿 于 2018-06-29 设计创作，主要内容包括：一种用于人群监视设备的系统和方法,所述人群监视设备包括连接到处理设备(13)的多传感器系统,其中所述处理设备(13)包括：图像融合模块(14),用于从所述多传感器系统接收图像,将图像变换并融合成融合图像；图像分析模块(15),用于提取每个个体目标并识别所述个体目标上的任何隐藏对象；警报触发模块(16),用于在识别出所述个体目标上的隐藏对象的情况下触发警报。(A system and method for a crowd monitoring device comprising a multi-sensor system connected to a processing device (13), wherein the processing device (13) comprises: an image fusion module (14) for receiving images from the multi-sensor system, transforming and fusing the images into a fused image; an image analysis module (15) for extracting each individual target and identifying any hidden objects on said individual target; an alert triggering module (16) for triggering an alert if a hidden object on the individual target is identified.)

1. A crowd monitoring device comprising:

a multi-sensor system connected to the processing device,

wherein the processing device comprises:

the image fusion module is used for receiving the images from the multi-sensor system, and transforming and fusing the images into a fused image;

an image analysis module for extracting each individual target and identifying any hidden objects on the individual target;

an alert triggering module to trigger an alert if a hidden object on the individual target is identified.

2. The crowd monitoring device of claim 1, wherein the multi-sensor system comprises a passive millimeter wave sensor.

3. The crowd monitoring device of claim 2, wherein the multi-sensor system further comprises an RGB imaging device, a depth sensor, and a thermal sensor.

4. The crowd monitoring device of claim 3, wherein the multi-sensor system is connected to the processing device by a wired connection.

5. The crowd monitoring device of claim 3, wherein the multi-sensor system is connected to the processing device through a wireless connection.

6. The crowd monitoring device of claim 3, wherein the image analysis module is adapted to analyze a series of time-shifted fused images produced by the image fusion module to track the individual target and identify any hidden objects on the individual target.

7. The crowd monitoring device of claim 6, wherein the alarm trigger module is adapted to store the alarm, the image, and related information to a database server connected to the processing device.

8. The crowd monitoring device of claim 7, wherein the processing device is adapted to connect to an alarm visualization device that displays an alarm, an image, and the information.

9. The crowd monitoring device of claim 8, wherein the image fusion module comprises: a hardware or software module adapted to transform the received images and find mutual alignment by solving said corresponding problem in computer vision.

10. The crowd monitoring device of claim 9, wherein the image analysis module is adapted to process the fused image by performing the steps of:

extracting each individual from a plurality of targets on the fused image;

finding and associating any suspected contraband from the passive millimeter wave sensor and thermal sensor with the extracted individual; and

true hidden objects are distinguished by comparing images generated from the passive millimeter wave sensor and thermal sensor.

11. The crowd monitoring device of claim 10, wherein the alarm triggering module is adapted to analyze the suspicious object and hidden objects identified from the image analysis module across a plurality of frames.

12. The crowd monitoring device of claim 11, wherein the processing device is associated with a database server for storing and retrieving image data.

13. The crowd monitoring device of claim 12, wherein the database server is connected to an alarm visualization device.

14. The crowd monitoring device of claim 13, wherein the database server is adapted to collect and store information of suspicious objects once there is an alarm asserted by the processing device.

15. The crowd monitoring device of claim 14, wherein the visualization device is adapted to receive or retrieve alerts and their corresponding information from the database.

16. The crowd monitoring device of claim 15, wherein the visualization device comprises a display for displaying the information.

17. A method for pre-screening of a population using multi-sensor theft/threat detection, the method comprising the steps of:

transforming images obtained from the multi-sensor system;

fusing the transformed images;

extracting each individual target with a depth sensor and a thermal sensor and tracking the target across a plurality of frames;

analyzing each extracted passive millimetre wave image of an individual target on the image across a plurality of frames and identifying any hidden objects on the individual target.

18. The method of claim 17, further comprising the steps of:

triggering an alarm and storing the image and related information to the database.

19. The method of claim 18, further comprising the steps of: displaying the alarm, the image, and the information on a display device.

20. The method of claim 19, wherein the multi-sensor system comprises a passive millimeter wave sensor.

21. The method of claim 20, wherein the multi-sensor system further comprises an RGB imaging device, a depth sensor, and a thermal sensor.

22. The method of claim 20, wherein the multi-sensor system is connected to the processing device by a wired connection.

23. The method of claim 20, wherein the multi-sensor system is connected to the processing device through a wireless connection.

24. The method of claim 20, further comprising the steps of:

analyzing a series of time-shifted fused images generated by the image fusion module for tracking the individual target and identifying any hidden objects on the individual target.

25. The method of claim 24, further comprising the steps of: storing the alert, the image, and related information to a database server.

26. The method of claim 25, further comprising the steps of: is connected to an alarm visualization device for displaying an alarm, an image and said information.

27. The method of claim 26, wherein the step of transforming the image comprises the steps of: transforming images received from the multi-sensor system and finding mutual alignment by solving the corresponding problem in computer vision.

28. The method of claim 27, wherein the analyzing step further comprises the steps of:

extracting each individual from a plurality of targets on the fused image;

finding and associating any suspected contraband from the passive millimeter wave sensor and thermal sensor with the extracted individual; and

true hidden objects are distinguished by comparing images generated from the passive millimeter wave sensor and thermal sensor.

29. The method of claim 28, further comprising the steps of:

analyzing the suspicious object and hidden objects identified from the image analysis module across a plurality of frames.

30. The method of claim 29, further comprising the steps of: confirming suspicious contraband of the individual and generating an alert by accumulating the positive detection results from the image analysis module across a plurality of time-shifted frames.

31. The method of claim 30, wherein the database server is adapted to store and retrieve image data and is associated with a processing device connected to the multi-sensor system.

32. The method of claim 31, wherein the database server is connected to an alarm visualization device.

33. The method of claim 32, wherein the database server is adapted to collect and store information of suspicious objects once there is an alarm asserted by the processing device.

34. The method according to claim 33, wherein the visualization device is adapted to receive or retrieve alerts and their corresponding information from the database.

35. The method of claim 34, wherein the visualization device comprises a display for displaying the information.

Technical Field

The present invention relates generally to an apparatus, system, or method for a multi-mode sensor image data processing method and system. In particular, although not exclusively, the invention relates to a multi-sensor theft/threat detection system for pre-screening of people using image fusion techniques.

Background

Image Fusion (IF) is a technique that integrates complementary multi-mode, multi-temporal, and/or multi-view information into a new image. The new image will contain information whose quality is not otherwise available.

Has wide application in IF technology. In astronomy, multi-sensor fusion is used to achieve high spatial and spectral resolution by combining images from two or more sensors: high spatial resolution sensors, IR sensors and X-ray sensors. Medical imaging uses IF on simultaneous evaluation of CT, MRI and/or PET images. Military, security, and surveillance applications use multimodal image fusion of visible and infrared images. With these techniques, a security system for theft or threat detection may be implemented.

Disclosure of Invention

The present invention provides an apparatus, system or method for a multi-mode sensor image data processing method and system that can be used in a multi-sensor theft/threat detection system for people pre-screening using image fusion techniques. Advantageously, the present invention may provide a new and novel method of computer vision monitoring.

According to a first aspect of the present invention there is provided a crowd monitoring device comprising: a multi-sensor system connected to a processing device, wherein the processing device comprises: an image fusion module for receiving the transformed images from the multi-sensor system and fusing them into a fused image; an image analysis module for extracting each individual target and identifying any hidden objects on the individual target; and an alert triggering module for triggering an alert if a hidden object on the individual target is identified.

In an embodiment of the first aspect, the multi-sensor system comprises a passive millimeter wave sensor.

In an embodiment of the first aspect, the multi-sensor system further comprises an RGB imaging device, a depth sensor, and a thermal sensor.

In an embodiment of the first aspect, the multi-sensor system is connected to the processing device by a wired connection.

In an embodiment of the first aspect, the multi-sensor system is connected to the processing device by a wireless connection.

In an embodiment of the first aspect, the image analysis module is adapted to analyze a series of time-shifted (time lapse) fused images generated by the image fusion module in order to track the individual target and to identify any hidden objects on the individual target.

In an embodiment of the first aspect, the alarm triggering module is adapted to store the alarm, the image and the related information to a database server connected to the processing device.

In an embodiment of the first aspect, the processing device is adapted to be connected to an alarm visualization device displaying alarms, images and information.

In an embodiment of the first aspect, the image fusion module comprises a hardware or software module adapted to transform the received images and find the mutual alignment by solving a corresponding problem in computer vision.

In an embodiment of the first aspect, the image analysis module is adapted to process the fused image by performing the steps of:

each individual is extracted from a plurality of objects on the fused image,

finding and associating any suspected contraband from the passive millimeter wave sensor and thermal sensor with the extracted individual, an

Truly hidden objects are distinguished by comparing images generated from the passive millimeter wave sensor and thermal sensor.

In an embodiment of the first aspect, the alert triggering module is adapted to analyze the suspicious object and the hidden object identified from the image analysis module across a plurality of frames.

In an embodiment of the first aspect, the alarm triggering module is adapted to confirm suspicious contraband of the individual and to generate the alarm by accumulating positive detection results from the image analysis module across a plurality of delay frames.

In an embodiment of the first aspect, the processing device is associated with a database server for storing and retrieving image data.

In an embodiment of the first aspect, the database server is connected to the alarm visualization device.

In an embodiment of the first aspect, the database server is adapted to collect and store information of the suspicious object once there is an alarm asserted by the processing device.

In an embodiment of the first aspect, the visualization device is adapted to receive or retrieve the alert and its corresponding information from a database.

In an embodiment of the first aspect, the visualization device comprises a display for displaying information.

According to a second aspect of the present invention there is provided a method of pre-screening a population using multi-sensor theft/threat detection, the method comprising the steps of:

transforming images obtained from a multi-sensor system;

fusing the transformed images;

extracting each individual target with a depth sensor and a thermal sensor and tracking the target across a plurality of frames;

the passive millimetre-wave image of each extracted individual target on the image is analyzed across a plurality of frames and any hidden objects on the individual target are identified.

In an embodiment of the second aspect, the method further comprises the steps of: triggering an alarm and storing the image and related information to a database.

In an embodiment of the second aspect, the method further comprises the steps of: displaying alarms, images and information on a display device.

In an embodiment of the second aspect, the multi-sensor system comprises a passive millimeter wave sensor.

In an embodiment of the second aspect, the multi-sensor system further comprises an RGB imaging device, a depth sensor and a thermal sensor.

In an embodiment of the second aspect, the multi-sensor system is connected to the processing device by a wired connection.

In an embodiment of the second aspect, the multi-sensor system is connected to the processing device by a wireless connection.

In an embodiment of the second aspect, the method further comprises the steps of: a series of time-shifted fused images generated by the image fusion module are analyzed to track individual targets and identify any hidden objects on the individual targets.

In an embodiment of the second aspect, the method further comprises the steps of: the alerts, images and related information are stored to a database server.

In an embodiment of the second aspect, the method further comprises the steps of: connected to the alarm visualization device to display alarms, images and information.

In an embodiment of the second aspect, the transforming the image step comprises the steps of: the images received from the multi-sensor system are transformed and the mutual alignment is found by solving the corresponding problem in computer vision.

In an embodiment of the second aspect, the analyzing step further comprises the steps of:

each individual is extracted from a plurality of objects on the fused image,

finding and associating any suspected contraband from the passive millimeter wave sensor and thermal sensor with the extracted individual, an

Truly hidden objects are distinguished by comparing images generated from the passive millimeter wave sensor and thermal sensor.

In an embodiment of the second aspect, the method further comprises the steps of: suspicious objects and hidden objects identified from the image analysis module are analyzed across multiple frames.

In an embodiment of the second aspect, the method further comprises the steps of: an individual's suspicious contraband is confirmed and an alert is generated by accumulating positive detection results from the image analysis module across a plurality of delay frames.

In an embodiment of the second aspect, the database server is adapted to store and retrieve image data and is associated with a processing device connected to the multi-sensor system.

In an embodiment of the second aspect, the database server is connected to the alarm visualization device.

In an embodiment of the second aspect, the database server is adapted to collect and store information of the suspicious object once there is an alarm asserted by the processing device.

In an embodiment of the second aspect, the visualization device is adapted to receive or retrieve the alarms and their respective information from the database.

In an embodiment of the second aspect, the visualization device comprises a display for displaying information.

Drawings

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

FIG. 1 illustrates a schematic diagram of a crowd monitoring device according to an embodiment of the invention;

FIG. 2 shows two image fusion results obtained with or without transformation; and

fig. 3 shows the overall image fusion result based on the respective images obtained by the plurality of image sensors, and the result of locating a hidden object hidden by two different recognized persons.

Detailed Description

The inventors have designed, through their own studies, experiments and experiments, that the millimeter wave is in a frequency band that can penetrate most garment materials, which makes it a widely used imaging device for security applications. These imaging devices can be classified as either active or passive devices.

The active device emits millimeter waves and analyzes the reflected waves for scanning. This enables a clearer image to be formed, but it violates the privacy of the scanned object. On the other hand, the passive device receives only the millimeter waves radiated from the human body to generate an image, but since the energy received by the device is low, it always results in a blurred image.

Passive devices may suffer from several limitations. Due to the low energy received by the device, the object is required to be stationary in front of the device to obtain a sharp image. Furthermore, it can only scan a single target at a time.

Without wishing to be bound by theory, these limitations may prevent the use of passive millimeter waves in busy passenger traffic environments. Therefore, it is always a challenge to balance between effective traffic and security management of passenger traffic. Thus, no existing system has been proposed to use passive millimeter waves for population pre-screening purposes.

Multi-view fusion techniques refer to a set of images of the same scene taken by the same sensor but from different viewpoints, which are fused to obtain an image with a higher resolution than the one typically provided by the sensor or to cover a wider area than the one typically provided by the sensor or to restore a 3D representation of the scene. A typical application of this technique has been for the production of 3D movies.

The multi-time IF technique recognizes two different purposes. Images of the same scene are acquired at different times to discover and evaluate changes in the scene or to obtain images of the scene that are less degraded. The former target is common in medical imaging, in particular in the detection of changes in organs and tumours, and in remote sensing for monitoring land or forest mining. The acquisition period is typically months or years. The latter objective requires that different measurements be closer to each other, typically in seconds, and possibly under different conditions.

Multi-mode cameras take advantage of the sensing capabilities of various cameras and integrate their information in order to provide a more comprehensive understanding of the real world environment. Image fusion is a typical solution to integrate information from different cameras. This needs to solve the corresponding problem in computer vision, i.e. finding a set of points in one image that can be identified as the same points in another image.

Multimodal or multi-sensor image fusion is the process of combining relevant information from several images into one image. The final output image may provide more information than any single image and reduce the signal-to-noise ratio. The user can gather useful information without looking at and comparing images from multiple sensors.

One imported image fusion technique is a pixel-level method, which works in the spatial or transform domain. The averaging method, the maximization method, the brooey method, the Principal Component Analysis (PCA), the wavelet transform, and the intensity-hue-saturation (HIS) based methods belong to the pixel level fusion method.

A prerequisite for performing pixel-level fusion is that the images have been acquired by homogeneous sensors, where the sensors are in a stereo setting, same modality, same or similar field of view (FOV) and resolution.

In one example, an apparatus for detecting contraband includes at least one two-dimensional array of spatially distributed point sources of millimeter wave radiation arranged to illuminate a field of view. A point source includes, but is not limited to, an oscillator that oscillates at the same frequency, means for focusing millimeter wave radiation from a field of view onto a focal plane, and a two-dimensional array of detectors disposed in the focal plane, each of the detectors generating an output signal in response to millimeter wave radiation from a particular portion of the field of view. The output signals may be provided to a means for displaying an image of the field of view, the pixels of the displayed image corresponding to the output signals generated by the elements of the array.

The detection means is an example of an active millimeter wave device. However, since this system relies on a millimeter wave source to focus on the target, it is not suitable for use in crowded environments.

In an alternative example, a contraband detection system is provided that includes a first camera having a first field of view, a second camera having a second field of view, and a display station coupled to the first camera and the second camera. The first camera has an output that provides first image data representing radiation in a first frequency band from the item in the first field of view. The second field of view at least partially overlaps the first field of view. The second camera has an output providing second image data representing radiation in a second frequency band different from the first frequency band, representing the item in the second field of view. The display station is adapted to receive first image data and second image data. The display station includes at least one computer programmed to present a display of items in the first field of view using the first image data selectively overlaid with an indication of at least one item derived from the second image data. However, such devices are not suitable for use in crowded environments.

In yet another example embodiment, an apparatus for detecting contraband is provided. The apparatus comprises at least one spatially distributed array of point sources of millimeter wave radiation. The distributed point sources are arranged to illuminate a field of view. The apparatus also has means for focusing millimeter wave radiation from the field of view onto a focal plane, and a detector array disposed in the focal plane. Each detector is adapted to produce an output signal in response to millimetre wave radiation from a particular portion of the field of view. The output signals may be provided to a means for displaying an image of the field of view, the pixels of the displayed image corresponding to the output signals generated by the elements of the array. However, such devices are not suitable for use in crowded environments.

Studies that enable millimeter wave tracking target imaging stay in active mode and allow only single target screening. The inventors have devised that passive millimeter wave imaging devices may be used for large scale pre-screening for theft/threat detection. For example, methods or devices utilizing passive millimeter waves may be used to scan multiple moving targets or provide a fully automatic theft/threat alert system based on the multi-sensor system.

The system may utilize passive millimeter waves via a multi-sensor system to overcome the limitations of passive millimeter waves in pre-screening of people for theft/threat detection. In a preferred embodiment of the present invention, a multi-sensor system is provided that includes a plurality of imaging sensors and a passive millimeter wave imaging device for scanning a plurality of moving objects within the field of view of the sensors. This can be used for surveillance tracking and theft/threat detection.

In a preferred embodiment of the invention, the multi-sensor system uses a multi-frame analysis technique in which the system analyzes a plurality of successive frames to eliminate noise caused by moving objects so that the objects do not need to stand still for scanning.

In another embodiment of the present invention, a multi-sensor system uses multiple sensors with various capabilities to segment and detect any suspicious hidden objects for each individual in a population.

In this specification, a passive millimeter wave sensor or imaging device is a sensor or device adapted to receive millimeter waves directly emitted or radiated from a body or object, rather than receiving millimeter waves reflected from the body or object. It is different from an active millimeter wave sensor or imaging device adapted to receive millimeter waves emitted from an illumination source to a body and reflected back from the body.

A multimode sensor or multimode imaging device is a sensor or imaging device for sensing or capturing images of non-millimeter wave electromagnetic waves. In one embodiment, the multimodal sensor or multimodal imaging apparatus is any one of an RGB camera, a depth camera, a thermal camera, or an infrared sensor.

In one embodiment of the present invention, as shown in FIG. 1, there is provided a crowd monitoring device 10 comprising: a multi-sensor system connected to the processing device 13.

In this embodiment, the multi-sensor system should include at least one passive millimeter wave imaging device 11 and one or more multimode sensors 12, such as the RGB camera, depth camera, and thermal camera shown in FIG. 1.

The processing device 13 comprises an image fusion module 14, an image analysis module 15, an alarm triggering module 16. The processing device 13 is adapted to obtain image signals from the multi-sensor system and to process the images with different software modules. In one embodiment, the multi-sensor system is wired directly to the processing device 13 by a data cable. In another embodiment, the multi-sensor system is remotely connected to the processing device 13 via a wireless protocol such as WiFi or Bluetooth.

Referring to fig. 1, the image fusion module 14 comprises a hardware or software module that can transform images and find mutual alignment by solving corresponding problems in computer vision.

The image analysis module 15 is a hardware or software module that processes the fused image to perform the following operations: 1) extracting each individual from a plurality of targets, 2) discovering and associating suspicious contraband with the extracted individual, and 3) differentiating truly hidden objects to enhance passive millimeter wave detection capabilities.

The alarm triggering module 16 is a hardware or software module that analyzes suspicious objects and hidden objects identified from the image analysis module across multiple frames. By analyzing a series of time-shifted frames, the module can trigger a more accurate alarm.

The processing device 13 is associated with a database server 17 for storing and retrieving image data. The database server 17 is connected to an alarm visualization device 18.

Once the processing device 13 has raised the alarm, the database server 17 will collect and store detailed information of the suspect from the processing device. The visualization device 18 is adapted to receive or retrieve the alerts and their corresponding detailed information from the database and display the information on a display (e.g., screen, tablet …) of the visualization device.

In one embodiment of the present invention, a method for pre-screening a population using multi-sensor theft/threat detection is provided, the method comprising the steps of:

transforming images obtained from a multi-sensor system;

fusing the transformed images;

extracting each individual target with a depth sensor and a thermal sensor and tracking the target across a plurality of frames;

analyzing a series of time-shifted passive millimeter wave images generated by the passive millimeter wave sensor to identify any concealed objects on the individual target;

triggering an alarm and storing the image and related information to the database; and

displaying the alarm, the image, and the information on a display device.

In one embodiment, the multi-sensor system includes a passive millimeter wave sensor 11, an RGB imaging device 12, a depth sensor 12, and a thermal sensor 12.

In one embodiment, the multi-sensor system is adapted to perform a calibration procedure on an imaging sensor of the multi-sensor system. This is done by first calibrating the multi-sensor system to obtain a pixel mapping relationship between the images. This is an off-line process and need only be done once before the system is set up.

All images are transformed based on the pixel mapping relationship. This transformation allows them to be aligned in the same camera plane to facilitate image fusion.

In a preferred embodiment, the step of fusing images is performed by feature point matching. In another embodiment, the step of fusing the images is performed by accounting for parallax by means of a depth sensor. If there are feature points common to all images, the fusion step can be done by feature point matching. If there are no common feature points, the fusion step can be done by modeling the disparity between the cameras and translating the images in real time based on the depth information.

Fig. 2 shows the difference between image fusion with or without image transformation. Translation vectors, which may be obtained from matching feature points or modeling differences between imaging sensors, are used to align the transformed images.

In the step of extracting the respective objects on the image, the processing device 13 is adapted to analyze the images from the depth sensor and the thermal sensor. The processing device 13 extracts or identifies objects from the depth sensors by analyzing images from the depth sensors in different depth layers.

The fusion module 14 of the processing device 13 then fuses the images from the depth sensor and the thermal sensor. By fusing the depth and thermal images, the processing device 13 is adapted to determine whether the object extracted from the depth sensor is a human being (individual target). This is based on the assumption that the human body has a constant temperature, which is usually distinguishable from other objects.

After setting the bandwidth of the thermal detection zone, the non-human subject may be further filtered out for further processing.

In this specification, a hidden object is an object that is positioned and covered by one or more layers of material without any covering object (e.g. a bag) in front of the material. The material must be a material that is transparent to millimeter waves. In other applications, the passive millimeter wave sensor may be replaced with an X-ray sensor, such that the material may be thicker and a different type of material, such as plastic or fresh people.

Once the respective targets are recognized, the images are passed to the image analysis module 15 to execute an automatic hidden object detection method based on the images from the passive millimeter wave sensor 11.

The above extraction method can segment each individual object. Combining this result with automatic hidden object detection on the passive millimetric-wave image, the processing device 13 is able to detect each individual in the crowd one by one.

Fig. 3 illustrates a hidden object detection method according to an embodiment of the present invention.

The analysis module 15 is adapted to analyze the passive millimetre-wave image to indicate that the hidden object is detected in two cases: 1) only hidden objects hidden under clothing, and 2) clothing with covering objects in front of the clothing, but clothing with covering objects in front of the clothing is less interesting. One embodiment of the invention is to detect a protrusion of a hidden object hidden under clothing without any covering in front of the clothing.

In one embodiment, the analysis module 15 is adapted to distinguish between the thermal image and the passive millimeter wave image by analyzing the two. In the case where the covering is found in front of the garment, the surface temperature is typically lower than the surface temperature of the garment. Thus, the thermal image will show a sudden change in temperature on the surface of the garment. In case the hidden object is hidden under the clothing, the surface temperature is distributed relatively more constantly over the surface of the clothing.

In a preferred embodiment, the analysis module 15 is adapted to distinguish between these two events by analyzing the temperature distribution and the steepness of the temperature change on the surface of the garment.

In one embodiment, the processing device 13 is adapted to track each individual target and its motion with a computer vision algorithm (e.g., a Kalman filter).

The processing device 13 is adapted to save all positive alarms in an alarm record associated with each tracked individual in a plurality of consecutive frames. The processing device 13 may store the alarm record in its own storage device, such as a hard disk drive, solid state drive, RAM, or the like. In other embodiments, the processing device 13 may store the alert record in the database server 17.

In the case of hidden objects being found, the processing device 13 is adapted to issue an alarm and to store data in the database server 17 when there is at least more than one alarm within each alarm record found for a particular tracked individual.

In one embodiment the processing device 13 is associated with an alarm visualization device 18, the visualization device 18 being adapted to periodically query the database server 17 and pop up any new alarms and display details of the suspect on the device.

It will also be appreciated that any suitable computing system architecture may be utilized where the method and system of the present invention are implemented, in whole or in part, by a computing system. This would include stand-alone computers, network computers and dedicated hardware devices. Where the terms "computing system" and "computing device" are used, these terms are intended to cover any suitable arrangement of computer hardware capable of implementing the described functionality.

It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the invention as shown in the specific embodiments without departing from the spirit or scope of the invention as broadly described. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.

Any reference to prior art contained herein is not to be taken as an admission that the information is common general knowledge, unless otherwise indicated.