Electricity: measuring and testing – Of geophysical surface or subsurface in situ – For small object detection or location
Reexamination Certificate
2001-10-30
2003-05-06
Lefkowitz, Edward (Department: 2862)
Electricity: measuring and testing
Of geophysical surface or subsurface in situ
For small object detection or location
C324S233000
Reexamination Certificate
active
06559645
ABSTRACT:
ORIGIN OF THE INVENTION
The invention described herein was made in the performance of work under a NASA contract and is subject to the provisions of Section 305 of the National Aeronautics and Space Act of 1958, Public Law 85-568 (72 Stat. 435; 42 U.S.C. 2457).
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to detecting metal subterranean anomalies such as land mines and, more particularly, to the use of a digitally configured system for processing complex system transfer data utilizing one or more transmitter and receiver sets.
2. Description of Prior Art
On average, every twenty minutes someone in the world loses a limb to a landmine. Landmines may be made of plastic or metal. In just the Sinai desert and the West Bank of the Nile River, approximately 10,000,000 metal mines remain from World War II. Shifting sands and the like result in mines being widely displaced from their original locations. Thus, it is desirable that a mine detector be highly sensitive to permit location of small metal objects such as miniature mines at various depths. In fact, it would be desirable to provide a metal detector that is able to locate underground mines four or more times deeper than is believed now possible utilizing the most widely used prior art metal detector.
Moreover, it would be desirable to provide a landmine detector that may be utilized for detecting either plastic or metal land mines. U.S. application Ser. No. 09/056,363, filed Apr. 7, 1998, discloses an exemplary plastic mine detector. The present application discloses a very high sensitivity metal detector that may be utilized in conjunction with the exemplary plastic mine detector mentioned above or with other plastic detectors with little or no interference problems. Such interference problems may be produced by additional electronic components, antennas, metal connectors, or other metal objects, in the immediate vicinity of the metal detector, such as between transmitter/receiver coils, that otherwise result in transmitter and/or receiver noise and variations that create false signals.
Patent applications that show attempts to solve problems related to the above include the following:
U.S. Pat. No. 5,786,696, issued Jul. 28, 1998, to Weaver et al., discloses a metal detector which utilizes digital signal processing and a microprocessor to process buffers of information which is received at a periodic rate. Both high and low gain phase quadrature and in-phase signals are provided via a multiplexer to an analog-to-digital converter from a first receive antenna. A second receive antenna provides phase quadrature and in-phase signals also through the multiplexer to the analog-to-digital converter. The received signals are averaged, decimated and low pass filtered to eliminate noise and reduce the quantity of data which must be processed. A threshold (triggering) processing operation is performed to determine whether a valid target signal is present in the data. If not, no further processing is performed. The in-phase and quadrature components are processed using Fourier transforms to select a frequency band which includes the energy for the target signal. The energy in this frequency band is utilized to determine the identification of the target. The depth of the target is determined by comparing the quadrature phase components received from the first and second receive antennas. The size of the target is determined by reference to a look-up table based on the depth factor and the signal amplitude determined for the target object A display screen has a plurality of horizontal depth symbols, each of which has a plurality of size indicators and upon determining the depth and size of a target, one depth symbol is activated together with one of the size indicators to concurrently display this information to an operator.
U.S. Pat. No. 5,729,143, issued Mar. 17, 1998, to Tavernetti et al., discloses a metal detector which includes a receive coil and a transmit coil connected in an inductive bridge. To overcome imbalances in the bridge due for instance to misalignment of the coils or the presence of mineralization in the medium which is being examined, the metal detector automatically produces a nulling (bucking) signal to cancel out the effects of any unwanted receive coil signals detected during calibration. This nulling signal is a nulling current both in terms of level and phase, and its level and phase are determined during a calibration process prior to actual metal detection. By inclusion in the metal detector of a microprocessor (microcontroller) operating at a much higher frequency than the variations in the magnetic field used to detect metal, the nulling signal generation is performed with a high degree of time resolution, resulting a precision metal detector which adaptively ignores any unwanted signals.
U.S. Pat. No. 6,163,292, issued Dec. 19, 2000, to Liedtke et al., discloses a method of determining the ability of a medium to absorb electromagnetic waves including placing an antenna unit having spaced transmitting and receiving antennas on a limiting surface of a medium, emitting, with the transmitting antenna, a radar wave into the medium which is detected as a cross-signal by the receiving antenna, pre-processing and digitizing the cross-signal, and, thereafter, analyzing the cross-signal with an algorithm for determining the ability of the medium to absorb electromagnetic waves and, thereby, a type of the medium; and an electromagnetic sensor the operation of which is based on the method.
U.S. Pat. No. 6,150,810, issued Nov. 21, 2000, to Lyle G. Roybal, discloses a method for detecting a presence or an absence of a ferromagnetic object within a sensing area which may comprise the steps of sensing, during a sample time, a magnetic field adjacent the sensing area; producing surveillance data representative of the sensed magnetic field; determining an absolute value difference between a maximum datum and a minimum datum comprising the surveillance data; and determining whether the absolute value difference has a positive or negative sign. The absolute value difference and the corresponding positive or negative sign thereof forms a representative surveillance datum that is indicative of the presence or absence in the sensing area of the ferromagnetic material.
U.S. Pat. No. 5,969,528, issued Nov. 19, 1999, to Brent C. Weaver, discloses a metal detector which has multiple transmit and receive coils for producing multiple detection fields. In one embodiment, a transmit coil is combined with two receive coils in a configuration that enables the detector to generate two detection fields, one being substantially narrower than the other. The transmit coil is inductively balanced with the receive coils such that the transmit coil induces minimum signals in each of the two receive coils. A metal target lying within a detection field changes the coupling between transit and receive coils and produces signals in the receive coils. The received signals are utilized to identify the target's presence within one or both of the detection fields. The use of two detection fields, substantially different in size, enables the metal detector to search over a broad area for object detection and then narrow the search to more precisely locate the detected object. A further embodiment has two transit coils and one receive coil and likewise produces a broad and a narrow detection field.
U.S. Pat. No. 5,790,685, issued Aug. 4, 1998, to Bradley T. Sallee, discloses an invention which relates to the field of metal detectors. More particularly, it relates to an imaging metal detector for imaging the metal on subjects passing through a spatial plane providing the specific location, shape and mass of the metal object. This invention makes use of an array of active sensors to transmit and receive magnetic beams and a computer for generating an image of the metal object based upon the data received from the sensors. Through the use of this invention it is possible to scan several subjects at the same
Arndt G. Dickey
Byerly Kent A.
Carl James R.
Dusl John
Ngo Phong H.
Cate James M.
Lefkowitz Edward
The United States of America as represented by the Administrator
Zaveri Subhash
LandOfFree
Detector apparatus and method does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Detector apparatus and method, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Detector apparatus and method will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3003320