Communications – electrical: acoustic wave systems and devices – Echo systems
Reexamination Certificate
2001-02-26
2003-04-08
Pihulic, Daniel T. (Department: 3662)
Communications, electrical: acoustic wave systems and devices
Echo systems
C367S135000, C342S022000
Reexamination Certificate
active
06545945
ABSTRACT:
The present invention relates to the field of substance identification from a remote location. More particularly, the invention provides significant improvements over previous U.S. Pat. No. 4,922,467, issued on May 1, 1990. The original patent disclosed an acoustic detection apparatus for characterization of an object within an enclosure, or buried beneath the ground. For this purpose, U.S. Pat. No. 4,922,467 disclosed an apparatus that transmits acoustic energy towards the object, and subsequently detects and analyzes the energy reflected and refracted/transmitted by the object. By comparing the transmitted, reflected, and refracted/transmitted energy, the apparatus can assign a signature to the object, and compare the signature with a database of signatures of known objects, thus identifying the object.
The apparatus of the present application provides significant improvements over the original patent, by allowing highly accurate characterization of a substance that is enclosed within a container. The improved material classification technique involves application of acoustic or electromagnetic (EM) energy to the container, and detection of both the reflected and refracted/transmitted energy therefrom. Subsequent analysis of the time and energy content of the detected signals allows computation of acoustic/EM energy impedance, acoustic/EM energy absorption, and acoustic/EM wave velocity changes that are conferred on the reflected and transmitted/refracted signals by the presence of the substance. These values allow sound predictions to be made regarding the mechanical properties of the substance, thus providing the substance with a specific signature. Comparison of the signature with a database of known signatures permits identification of the substance. The present invention can also analyze the absorption characteristics of the substance over a range of frequencies. In this way, the apparatus allows computation of additional parameters involving absorption as a function of frequency. These additional parameters allow the formulation of a highly detailed signature for each substance. The improvements over U.S. Pat. No. 4,922,467 therefore permit the apparatus to identify a considerably wider range of substances with increased accuracy. For specific classes of substances, analysis of the absorption/frequency characteristics alone can be sufficient for accurate substance identification.
Analysis of reflected acoustic energy is well known in the art to facilitate identification of a substance concealed beneath an outer layer. For example, U.S. Pat. No. 5,979,240 issued Nov. 9, 1999, discloses a device for detecting recyclable plastic and metal items within solid waste. Acoustic energy of a fixed wavelength is transmitted into the waste causing specific substances to resonate. Detection of the resonating energy allows the recyclable items to be located. Other such devices are directed towards medical uses. For example U.S. Pat. No. 4,855,911 issued Aug. 8, 1989, provides a device for transmitting ultrasound into tissues and detecting the back-scatter energy reflected from buried anomalies within the tissue. Still further devices, such as those disclosed by U.S. Pat. No. 5,563,848 issued Oct. 8, 1996, and U.S. Pat. No. 5,974,881 issued Nov. 2, 1999, detect the presence of objects buried within the ground. Sound waves are transmitted into the ground, and the nature of the energy reflected by the buried object is detected and analyzed.
It is important to note that the devices disclosed by the cited references specifically involve detection of reflected acoustic energy. By limiting analysis to reflected energy, the parameters for substance determination are limited. For this reason, U.S. Pat. No. 4,922,467, which is incorporated herein by reference, provides a preliminary means for material classification by simultaneous analysis of both reflected and refracted/transmitted acoustic energy, thus providing each substance with a unique and characteristic signature. The present application further expands and refines the accuracy and flexibility of the apparatus disclosed by U.S. Pat. No. 4,922,467. The improved apparatus therefore provides both rapid and highly accurate substance determination.
SUMMARY OF THE INVENTION
In accordance with the present invention, “enclosure” is defined as being a hollow box-like structure containing an object to be detected and identified with respect to its constituents. The apparatus disclosed permits reliable, accurate and non-invasive identification of enclosed materials, and can have a number of important applications.
In a first embodiment, the present invention provides a means for detecting illegal substances such as drugs and explosives within suitcases and baggage, without the need for time-consuming human intervention. Current systems for analyzing the contents of a suitcase include X-ray scanning machines and animals trained for chemical sniffing. However, these systems are labor intensive. Moreover, visual scanning of X-ray images is prone to human error, since illegal substances may appear similar to those which are legal. Animals can be trained to detect the scent of specific chemicals, but the number and range of substances may be restricted, and such substances may be masked by other smells to prevent their detection. It is therefore desirable to develop more accurate, automated techniques for the detection of illegal substances within suitcases and other baggage. In particular, by using a wider frequency range of energy input (including EM radiation), and by analyzing energy absorption properties over a range of frequencies, the present invention permits highly accurate identification of substances within an enclosure. The devices of the present invention may be arranged as an array over a conveyor, thus mapping the contents of the suitcases as they are transported horizontally along the conveyor. In addition, the present apparatus does not require shielding from the operator or public, since harmless acoustic or electromagnetic energy may be used by the device. This contrasts with the X-ray devices presently used for luggage analysis, which require shielding and potentially dangerous radiation.
In a second embodiment, the invention may be used to detect the presence of substances buried beneath the surface of the earth. For example, the apparatus of the present invention can determine the location of pipelines or other enclosures containing oil, gas or chemicals. Importantly, once the enclosure or pipeline has been located, the present invention may be used to quickly and accurately characterize the nature of the substance contained within the enclosure or pipeline. In this regard, it is well known in the art that acoustic waves may be bounced off the ocean floor, in order to determine the nature of the material from which sediment layers are comprised. The present invention provides for significant additions and enhancements to these previous techniques, permitting the formulation of detailed signatures for different types of substances.
In a third embodiment, the invention may be used to detect the presence of explosives buried beneath the ground. For example, a potentially explosive land mine may be differentiated from spent shrapnel or other scrap metal by the detection of explosive substances enclosed within the body of the mine. The invention presents a significant advantage in that the mine may be detected and characterized whilst still underground, without the need for disturbing the mine and risking detonation.
The apparatus of the present invention comprises a transmitter device for directing a pulse of EM or acoustic energy towards the enclosure that contains the unknown substance. The energy may be in the form of a specific pulse, or may be random noise. The energy is reflected from any intercepted interface, which may include the surface of the enclosure, and the surface of the substance to be detected within. The duration and intensity of the reflected energy can be detected by a first receiver (EM or acoustic). A propor
Ocean Data Equipment Corporation
Pihulic Daniel T.
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