Johns Hopkins University

Carl V Nelson

Harvey Wayne Ko

Yanping Guo

David M White

Dexter G Smith

Bryan C Jacobs

Paul R Schuster

Charles B Cooperman

Matthew G Bevan

Mary R Keller

Henry A Kues

An expendable tamper evident seal system for monitoring a mechanism to which physical access is required in order to open or close an access-way, comprising: an embedding material moldable into a shape conforming to the mechanism and adapted to be applied to the mechanism; circuit components randomly embedded in the embedding material so as to be arranged in positions and orientations corresponding to the shape, whereby physical access to the mechanism that alters the shape of the embedding material correspondingly alters the positions and orientations of the circuit components in the material; and an electronic interrogation device (EID) including components that induce in the circuit components an electromagnetic spectral response indicative of the position of the EID relative to the positions and orientations of the circuit components in the material, and measure the spectral response.

Expendable tamper evident security seal

A vehicle includes a motorized belt track directly or indirectly connected to a frame. The belt track frictionally contacts a drive surface on which the vehicle moves, such as any form of road or off-road surface. The belt track moves forward and backward in a direction parallel to a centerline of the belt track to move the vehicle backward and forward along the drive surface. A steering appendage is also directly or indirectly connected to the frame. The steering appendage is also adapted to frictionally contact the drive surface. The steering appendage is off the centerline of the belt track. The steering appendage causes the vehicle to turn from the centerline of the belt track when in contact with the drive surface.

Mono-track vehicle

An expendable metal detector system for facilitating the detection of improved explosive devices (IED) where the metal detector is launched toward the suspected IED and using either magnetic field sensors in a passive mode to detect magnetic anomalies or current pulses through a loop antenna in an active mode to detect eddy currents, or using both modes sequentially, detects the ferrous material in the IED. In the active mode, the loop antenna is deployed automatically after launch and impact. The signals are transmitted from the metal detector to the operator who can then take appropriate steps to neutralize the IED.

Expendable metal detector

A pulse induction metal detector includes a pulse transmitter coil for generating and transmitting a first electromagnetic signal and a receiver coil for detecting and amplifying a second electromagnetic signal emitted by a nearby metal target due to eddy currents generated in response to the first electromagnetic signal. The receiver coil is a coil of wire having multiple loops. At least one switch is coupled with the coil of wire such that when the switch is in its open position, the coil of wire is a broken circuit. In this condition, the inductive properties of the receiver coil are minimized during abrupt transmitter coil turn off. The number of switches per coil loop can be varied to achieve varying levels of sensitivity.

Switched coil receiver antenna for metal detector

A device in which the receiver coil of a pulse inductive metal detector is capable of switching between a differential configuration (i.e., gradiometer configuration) to a non-differential or summing configuration under control of the operator or computer.

Re-configurable induction coil for metal detection

A device and method to improve pulse inductive metal detector (MD) sensitivity uses multiple, current steps to reduce the voltage rating of electronic components. Current reduction in one implementation is done with multiple switched resistors coupled to a voltage source and connected to the transmitter coil. The current reduction in another implementation is done with multiple switched current sources that are connected to the transmitter coil and are switched inactive one by one to reduce the total current to the transmitter coil. The current is stepped down in rapid secession with a time delay between current transitions less than the time constant of the metal target under investigation.

Step current inductive antenna for pulse inductive metal detector

A detection system is provided which is configured to have a transmitter capable of interacting with an object by generating a field, and a multiplicity of receivers operative to measure changes in the environment caused by the object's response to the generated field and mounted to a closed-looped belt, which is displaceable in a proximity to the object.

Moving belt sensor

A method for identifying a buried metal object using a three-dimensional steerable magnetic field (3DSMF) system. The method comprises generating a magnetic field vector (MFV) at a first MFV position above the buried metal object; measuring a time decay response at the first MFV position; generating a MFV at a next MFV position above the buried metal object; measuring a time decay response at the next MFV position; repeating the above steps until a complete 360-degree measurement of time decay responses of the buried metal object is completed; processing all measured time decay responses with a target search algorithm to determine a magnetic polarizability tensor of the buried metal object; and identifying the buried metal object by matching the magnetic polarizability tensor of the buried metal object to a known magnetic polarizability tensor of an object.

Method for metal object identification using a three-dimensional steerable magnetic field antenna

Provided herein is a method and system for detecting hidden dense objects in cargo containers including at least a cargo container platform with two-dimensional sensor arrays in juxtaposition therewith. The system further includes a process that estimates a weight and mass distribution data from a cargo manifest for the cargo container and available historical information about the cargo container. The historical weight and mass distribution is compared to the actual weight and mass distribution measured by the sensor arrays to detect discrepancies which will identify the tested cargo container as suspect and in need for further investigation.

Dense object detection system and method

A metal detector capable of operating in both a time-domain mode and a frequency-domain mode includes a transmitter component and a receiver component. The transmitter component includes a transmitter coil that can receive both an AC and DC current source for frequency-and time-domain operation respectively. The AC signal is impressed on the DC signal such that while the transmitter coil is charging, frequency-domain sensing is occurring and when the transmitter coil is switched off, time-domain sensing is occurring. The receiver component uses a primary field bucking method to ensure that both time-and frequency-domain modes can operate with the receiver coil.

Simultaneous time-domain and frequency-domain metal detector

A pulse inductive metal detector that includes a variable resistor for controlling coil characteristics for both transmitter and receiver modes of operation. A coil coupled with an electronic switch is charged with current from the power source in a transmitter mode such that when the electronic switch is abruptly switched closed the coil emits a magnetic field that induces eddy currents in a metal target. Once the transmitter magnetic fields have decayed enough, the coil can be operated in a receiver mode to detect a magnetic field resulting from eddy currents in the metal target. The variable resistor is coupled across the coil for varying the resistance across the coil to optimize the pulse inductive metal detector sensitivity to the metal target.

Variable damping induction coil for metal detection

A steerable electromagnetic induction (EMI) sensor system for measuring the magnetic polarizability tensor of a metal target. Instead of creating a vertical magnetic field from a horizontal loop transmitter configuration used by most prior art EMI metal detectors, the transmitter geometry of the sensor system's antenna is designed especially for creating multiple horizontal and vertical magnetic fields and for steering the same in all directions. The horizontal magnetic field (HMF) antenna has the potential advantage of a relatively uniform magnetic field over a large volume. A second potential advantage of the HMF antenna is that compared to a conventional loop antenna, the magnetic field intensity falls off slowly with distance from the plane of the antenna. Combining two HMF sensor systems creates a steerable two-dimensional magnetic field sensor. Combining the steerable HMF sensor with a vertical magnetic field antenna forms a three-dimensional steerable magnetic field sensor system.

Steerable three-dimensional magnetic field sensor system for detection and classification of metal targets

A Wide Area Metal Detection (WAMD) system and method for security screening a crowd of people is provided. The system comprises at least one Magnetic Field Generator (MFG), e.g., a Horizontal Magnetic Field Generator (HMFG) buried below a walking surface for generating a magnetic field, a plurality of magnetic field sensors located within the sensing area of the MFG for sensing a metallic object, based on eddy currents in the magnetic field, and a location indicator for indicating a location of an individual with the metallic object at a position corresponding to that of one of the plurality of magnetic field sensors that sensed the metallic object. At least one video camera is included for identifying the individual at the location indicated by the location indicator and tracking further movements of the individual.

Wide area metal detection (WAMD) system and method for security screening crowds

A multi-mode electromagnetic target discrimination sensor system for transmitting an electromagnetic signal and receiving a reflected signal from at least one target is disclosed having a variable inductance antenna having a variable inductance transmitter and a variable inductance receiver for varying at least one of operating bandwidth, sensitivity and size of the antenna, a processor for alternating between a time domain operating mode and a frequency domain operating mode, and controlling the variation of the inductance of the variable inductance antenna based on a current operating mode, and at least one processing algorithm for receiving signals from the receiver, discriminating targets from the received signals, and outputting the discrimination results is disclosed.

Multi-mode electromagnetic target discriminator sensor system and method of operation thereof

A method of improving pulse inductive metal detector sensitivity by minimizing adverse ground responses and transmitter coil transients is disclosed. The method provides a calibration mode for a typical pulsed EMI metal detector. The purpose of the calibration mode is to determine and record a nulling signal representative of the transmitter coil coupling to the receiver coil and a ground response that has no metal. The nulling signal is then used during normal operation of the metal detector by combining it with the instant receiver coil signal in a difference amplifier. The difference amplifier effectively subtracts the nulling signal from the instant signal yielding a response signal that has removed the ground response that may be present in the instant signal. The metal detector can be periodically re-calibrated. It may also be re-calibrated upon discovery of a metal target to provide the most up to date nulling signal for the ground around the metal target.

Growing community of inventors

Derwood, MD, United States of America

Carl V Nelson