1. Field
This system relates, generally, to surveillance. More particularly, it relates to the detection of concealed person-borne objects including, but not limited to, Improvised Explosive Devices (“IEDs”).
2. Description of Related Art
A wide variety of security systems are employed for consumer, commercial, industrial, government and military applications. Security systems can utilize a variety of technologies, including mechanical, electrical, electromechanical, optical, laser and other techniques. Additionally, security systems can generally be separated into two classes: active and passive.
Active security systems detect disturbances in the absorption and/or reflection of a transmitted signal. Thus active security systems require a transmitter and a receiver to function. Some active security systems utilize a transceiver to accomplish both functions, while others use a possibly disparate “illuminator” separate from the receiver. A common example of an active security system is one based on radar, which uses transmitted energy or sound to illuminate an area or subject and then detect disturbances in the reflected energy or sound. In this example, sound has been explicitly mentioned since sound is debatably not a form of radiated energy but is a vibration of molecules in surrounding medium, such as water or atmosphere. Hence, sound does not propagate in a vacuum whereas typical transmitted energy does.
Passive security systems do not emit radiation or signals but simply observe/image the existing energy contained within a scene. Since there is no transmitter involved, passive security systems are particularly adept at long stand-off surveillance where the sensor and operator can be located a safe distance away from danger or at a distance amenable to interdiction. In the presently described invention, the infrared sensor element of the concealed object detection system can detect the presence of a concealed suicide bomb vest at distances exceeding 100 meters.
Typical passive security systems include visual, infrared, millimeter wave and/or terahertz imaging systems. These passive systems image different frequencies of energy in the electromagnetic spectrum.
Infrared, millimeter wave and terahertz based security systems have the benefit of being able to image concealed objects under the clothing of subjects if properly designed. Imaging and detection of concealed objects is essential for detecting terrorist threats as well as enabling less lethal applications such as detecting contraband or stolen objects. These systems image the contrast between the human body and the concealed object that may block or otherwise attenuate the body's natural energy.
While the human body emits, absorbs and reflects infrared, millimeter wave and terahertz energy in a sensor-observable fashion, concealed objects such as explosives, weapons, contraband and the like block, absorb, reflect or otherwise attenuate the body's energy providing the imaging system with a contrasting signal or image. When considering an imaging system, these contrasts may appear as areas either darker or lighter than the body.
Most clothing is transparent to radiation in the millimeter wave and terahertz spectra, and conductive of body heat in the infrared spectrum. Objects (weapons or bomb devices) that are worn beneath one's apparel will block or attenuate the body's natural radiation and results in a signature that can be detected much as a lamp shade blocks the light from a light bulb. Under most circumstances, large objects such as bomb devices or protective vests worn under clothing present a detectable thermal signature which can be additionally detected using infrared, or thermal, sensors.
The aforementioned capability is effective for imaging suicide bombers, smugglers, and persons with concealed objects such as firearms, contraband, currency, hazardous liquids and gels, and the like. This is especially significant since some threats like plastic explosives, powders, liquids and gels cannot be detected using other forms of security devices such as metal detectors.
Contemporary sensor technology provides individual solutions for imaging in the spectra most favorable for concealed object detection. Infrared sensors produced by FLIR Systems, Inc., millimeter wave sensors produced by Brijot Imaging Systems, Inc., and terahertz sensors produced by Thruvision, Ltd. are available for imaging their respective spectra. Occasionally, these classes of sensors offer a degree of concealed object detection capability within their disparate spectra.
One disadvantage of these passive security systems, and security systems in general, is they typically image using a select subset of the electromagnetic spectrum as defined by their respective sensor/receiver. Many such passive systems employ a single sensor imaging in the infrared, millimeter wave, terahertz or x-ray band, resulting in a reduction the effectiveness of the detection. Detection capability is reduced since a concealed object may be less observable in one spectrum versus another. Passive infrared systems may offer significant standoff distances but image thermal conduction through the clothes instead of penetrating the clothing. Passive millimeter wave systems excel at detecting metal objects but perform worse detecting liquids. Passive terahertz sensors image through clothing more readily than millimeter wave but suffer greater effects of solar loading outdoors. Here the use of a plurality of sensors imaging disparate spectra is desirable.
A second disadvantage of typical passive security systems is the lack of computer-assisted or automated detection capability. Prior art concealed object imaging and detection systems typically lack computer-assisted or automated detection, or confine such computer-assisted or automated detection to a single frequency in the electromagnetic spectrum.
A third disadvantage of typical passive security systems is they are typically engineered for a particular environment, location or use case, making these systems costly in terms of application-specific engineering, training and support. These systems typically require support infrastructure such as inspection areas/lanes, backdrops and the like to improve the “limited visibility” nature of imaging a singular spectrum, thereby limiting or eliminating their “ad hoc” or “on demand” responsiveness and capabilities.
A fourth disadvantage of typical passive concealed object detection security systems is the fixed-range imaging capability of typical infrared, millimeter wave and terahertz sensors deployed in those systems. The infrared imagers typically do not include zoom optics and millimeter wave and terahertz imagers must be custom designed for a particular narrow operating range by virtue of the aperture, feed horn and antenna design selected during their design and construction phases.
Therefore, a need exists in the art for a concealed object detection security system that employs a plurality of disparate sensors imaging a scene using complimentary spectra. Such a system would leverage the spectral resolving power of each sensor cumulatively offering a “best of all worlds” solution to concealed object detection, by reinforcing the benefits and capability of each sensor while minimizing any one sensor's deficiencies. For example, the outdoor deployment deficiencies inherent in terahertz sensors can be offset by the presence of the infrared and millimeter wave sensors.
Another need exists in the art for a concealed object detection security system for concealed object detection that includes computer-assisted or automated detection capability applied in a holistic system-of-systems methodology. While this capability exists within the spectrum of some individual sensors, true multi-spectral computer-assisted or automated detection capability does not currently exist.
Another need exists in the art for automated sensor fusion capability, reducing the level of effort required by the operator in assessing the imagery of a plurality of disparate sensors. As an example, the imagery of an infrared sensor may depict brighter pixels as areas of greater thermal content while the imagery of a millimeter wave sensor may depict brighter pixels as areas of lower millimeter wave content and the imagery of a terahertz sensor may eschew bright or dark pixels in favor of a false color image. Thus requiring an operator to assess these disparate images in real time and continually is disadvantageous versus employment of automated sensor fusion.
Another need exists in the art for a concealed object detection security system that can be deployed ad hoc into multiple situations by virtue of the magnification of capability provided by a plurality of disparate spectrum sensors. This reduces or eliminates the potential incompatibility of a single sensor system operating in an environment where its efficacy is ill suited to that environment (e.g., a terahertz imager operating under a sunny sky).
Another need exists in the art for a concealed object detection security system of maximized Probability of Detection (Pd) and minimized Probability of False Alarm (Pfa) as can be achieved by imaging multiple disparate spectra and then algorithmically and holistically evaluating the results.
Another need exists in the art for a concealed object detection security system utilizing a plurality of disparate spectrum sensors to include a voting or weighting algorithm, maximizing Pd and minimizing Pfa. Such a voting or weighting algorithm would empathize detection presence when a majority of sensors detect a concealed object and de-empathize detection presence when an isolated (or no) sensor detects a concealed object.
Another need exists in the art for a concealed object detection security system that leverages multi-spectral sensor fusion and multi-sensor voting or weighting algorithms where results from one or more sensors can provide negative feedback to the voting or weighting algorithms on detection of an innocuous concealed object, thusly minimizing Pfa.
Another need exists in the art for a concealed object detection security system that leverages multi-spectral sensor fusion and multi-sensor voting or weighting algorithms to simplify operation for the operator, test and support staff, thereby reducing operator fatigue, training and operator sustaining costs.
Another need exists in the art for a concealed object detection security system that has a deep range imaging capability exceeding the imaging ranges of its individual sensors. The combination of short range millimeter wave imaging, medium range terahertz imaging and long range infrared imaging described in the current system, provides maximal coverage of a variety of ranges heretofore not obtainable from a single sensor solution.
Another need exists in the art for a concealed object detection security system that cohesively combines multi-spectral detection in a single system, providing holistic procurement, deployment, operation, training and support of the homogeneous system versus a multitude of separate systems, each with their own requirements for procurement, setup, environment, operation, training and support.
Another need exists in the art for a concealed object detection security system that is flexible enough to be employed in a wide variety of applications, locations and environments without additional engineering, site preparation, operator training or unit modifications. The system would be quickly deployable for indoor or outdoor conditions, daytime or nighttime conditions, humid or arid conditions, and the like, and exhibit a large advantage over systems that are custom tailored for a particular deployment location or use case, and thereby reduce or eliminate the costs involved in engineering and personnel training for each specific deployment.
However, in view of the prior art at the time the present system was made, it was not obvious to those of ordinary skill in the pertinent art how the identified needs could be fulfilled.
While certain aspects of conventional technologies have been discussed to facilitate disclosure of the system, Applicants in no way disclaim these technical aspects, and it is contemplated that the claimed system may encompass one or more of the conventional technical aspects discussed herein.
The present invention may address one or more of the problems and deficiencies of the related art discussed above. However, it is contemplated that the system may prove useful in addressing other problems and deficiencies in a number of technical areas. Therefore, the claimed system should not necessarily be construed as limited to addressing any of the particular problems or deficiencies discussed herein.
In this specification, where a document, act or item of knowledge is referred to or discussed, this reference or discussion is not an admission that the document, act or item of knowledge or any combination thereof was at the priority date, publicly available, known to the public, part of common general knowledge, or otherwise constitutes prior art under the applicable statutory provisions; or is known to be relevant to an attempt to solve any problem with which this specification is concerned.