Systems and methods useful for detecting presence and / or location of various materials

• US 7,705,598 B2
• Filed: 02/25/2008
• Issued: 04/27/2010
• Est. Priority Date: 05/09/2000
• Status: Expired due to Fees

• Current Assignee: Admiralty Corporation (Admiralty Holding Co.)
• Original Assignee: Admiralty Corporation (Admiralty Holding Co.)
• Inventors: Larsen, James Wagner
• Primary Examiner(s): LeDynh; Bot L
• Application Number:
  US12/072,248
• Publication Number:
  US 20080309344A1
• Time in Patent Office: 792 Days
• Field of Search: 324232-233, 324/326, 324/329, 324/335, 324/337, 342/22, 342/83, 342/102
• US Class Current: 324/326
• CPC Class Codes: G01V 3/08 operating with magnetic or electric fields produced or modified by objects or geological structures or by detecting devices with electromagnetic waves G01V3/12
• CPC Class Codes: G01V 3/104 using several coupled or uncoupled coils G01V3/101 takes precedence

Abstract

The present invention provides systems and methods which can be employed to locate or detect presence of various materials, including nonferrous metals. These systems include new and useful sensors, circuits, systems and devices which power and/or interoperate with the sensors, and methods of making, operating and using such systems. Any or all of the systems, devices or processes can be combined with other systems, devices or processes disclosed.

Claims

1. Apparatus for determining presence of an object, comprising:

a. an emitter adapted to produce and propagate a time varying primary electromagnetic field, the primary electromagnetic field including a plurality of primary electric field cycles, the emitter including a clock circuit;

b. at least one sensor, the sensor adapted to receive a secondary electromagnetic field, the secondary electromagnetic field produced by the object as a function of the primary electromagnetic field and containing a plurality of secondary field cycles;

c. the sensor coupled to a receiver, the receiver adapted to determine differences in phase between the primary electromagnetic field and the secondary electromagnetic field at a plurality of points in the primary field cycles and the secondary field cycles and to provide information corresponding to identification of the material forming the object as a function of said phase differences; and

d. in which the emitter is adapted to pulse width modulate the emitter at a high frequency in order to generate at least one smooth lower frequency waveform in the primary electromagnetic field;

e. in which the at least one sensor uses the emitter clock circuit.

2. Apparatus for determining presence of an object, comprising:

a. an emitter adapted to produce and propagate a time varying primary electromagnetic field, the primary electromagnetic field including a plurality of primary electric field cycles, the emitter including a clock circuit;

b. at least one sensor, the sensor adapted to receive a secondary electromagnetic field, the secondary electromagnetic field produced by the object as a function of the primary electromagnetic field and containing a plurality of secondary field cycles;

c. the sensor coupled to a receiver, the receiver adapted to determine differences in phase between the primary electromagnetic field and the secondary electromagnetic field at a plurality of points in the primary field cycles and the secondary field cycles and to provide information corresponding to identification of the material forming the object as a function of said phase differences; and

d. in which the emitter is adapted to pulse width modulate the emitter at a high frequency in order to generate at least one smooth lower frequency waveform in the primary electromagnetic field;

e. in which the at least one sensor is synchronized with the emitter clock circuit.

3. A detection system for detecting, locating and classifying an object selected from the group of magnetic and conducting objects, the detection system adapted to detect a secondary magnetic field generated by the object in response to a primary magnetic field transmitted by the detection system, the detection system including an active subsystem for generating an alternating current magnetic field of simultaneous multiple frequencies and a synchronous detection subsystem for accurately measuring the amplitude and phase of the secondary magnetic field;

in which the synchronous detection subsystem includes a plurality of sensors, and the active subsystem is adapted to shape the transmitted field in the vicinity of the sensors in order to reduce the sensors'"'"' sensitivity to the transmitted field and to desensitize the sensors to movement with respect to the active subsystem;

in which the active subsystem includes at least one transmitter coil having windings that are shaped to reduce the primary magnetic field or primary magnetic field gradient sensed by the sensors in order to desensitize the sensors to movement with respect to the primary magnetic field.

4. A detection system for detecting, locating and classifying an object selected from the group of magnetic and conducting objects, the detection system adapted to detect a secondary magnetic field generated by the object in response to a primary magnetic field transmitted by the detection system, the detection system including an active subsystem for generating an alternating current magnetic field of simultaneous multiple frequencies and a synchronous detection subsystem for accurately measuring the amplitude and phase of the secondary magnetic field;

in which the synchronous detection subsystem includes a plurality of sensors, and the active subsystem is adapted to shape the transmitted field in the vicinity of the sensors in order to reduce the sensors'"'"' sensitivity to the transmitted field and to desensitize the sensors to movement with respect to the active subsystem;

further comprising a magnetically permeable material that is shaped and positioned in the vicinity of the sensors to desensitize the sensors to movement with respect to the transmitted field.

5. A detection system for detecting, locating and classifying an object selected from the group of magnetic and conducting objects, the detection system adapted to detect a secondary magnetic field generated by the object in response to a primary magnetic field transmitted by the detection system, the detection system including an active subsystem for generating an alternating current magnetic field of simultaneous multiple frequencies and a synchronous detection subsystem for accurately measuring the amplitude and phase of the secondary magnetic field;

in which the synchronous detection subsystem includes a plurality of sensors, and the active subsystem is adapted to shape the transmitted field in the vicinity of the sensors in order to reduce the sensors'"'"' sensitivity to the transmitted field and to desensitize the sensors to movement with respect to the active subsystem;

further comprising an electrically conductive material that is shaped and positioned in the vicinity of the sensors to desensitize the sensors to movement with respect to the transmitted field.

6. Apparatus for determining presence of an object, comprising:

a. an emitter adapted to produce and propagate a time varying primary electromagnetic field, the emitter including a clock circuit;

the primary electromagnetic field including a plurality of primary electromagnetic field cycles;

b. at least one sensor, the sensor adapted to receive a secondary electromagnetic field, the secondary electromagnetic field produced by the object as a function of the primary electromagnetic field, the secondary electromagnetic field including a plurality of secondary electromagnetic field cycles;

c. the at least one sensor coupled to a receiver, the receiver adapted to determine differences in phase between the primary electromagnetic field and the secondary electromagnetic field at a plurality of points in the primary electromagnetic field cycles and the secondary electromagnetic field cycles, and to provide information corresponding to identification of the material forming the object as a function of said phase differences;

d. wherein the emitter is adapted to pulse width modulate the primary electromagnetic field and

e. wherein the emitter uses switched capacitors in order to pulse width modulate the primary electromagnetic field;

f. wherein the at least one sensor uses the clock circuit of the emitter.

7. Apparatus for determining presence of an object, comprising:

a. an emitter adapted to produce and propagate a time varying primary electromagnetic field, the emitter including a clock circuit;

the primary electromagnetic field including a plurality of primary electromagnetic field cycles;

b. at least one sensor, the sensor adapted to receive a secondary electromagnetic field, the secondary electromagnetic field produced by the object as a function of the primary electromagnetic field, the secondary electromagnetic field including a plurality of secondary electromagnetic field cycles;

c. the at least one sensor coupled to a receiver, the receiver adapted to determine differences in phase between the primary electromagnetic field and the secondary electromagnetic field at a plurality of points in the primary electromagnetic field cycles and the secondary electromagnetic field cycles, and to provide information corresponding to identification of the material forming the object as a function of said phase differences;

d. wherein the emitter is adapted to pulse width modulate the primary electromagnetic field and

e. wherein the emitter uses switched capacitors in order to pulse width modulate the primary electromagnetic field;

f. wherein the at least one sensor is synchronized to the clock circuit of the emitter.

8. A detection system for detecting, locating and classifying an object selected from the group of magnetic and conducting objects, the detection system adapted to detect a secondary magnetic field generated by the object in response to a primary magnetic field transmitted by the detection system, the detection system including an active subsystem for generating an alternating current magnetic field of simultaneous multiple frequencies and a synchronous detection subsystem for accurately measuring the amplitude and phase of the secondary magnetic field;

in which the synchronous detection subsystem includes a plurality of sensors, and the active subsystem is adapted to shape the transmitted field in the vicinity of the sensors in order to reduce the sensors'"'"' sensitivity to the transmitted field and to desensitize the sensors to movement with respect to the active subsystem;

said system further comprising a nulling circuit that reduces the primary electromagnetic field sensed by the sensors.

9. A system according to claim 8 in which the nulling circuit is capable of being adjusted.

10. A system according to claim 8 in which the nulling circuit is a nulling transmitter that generates a nulling field.

11. A system according to claim 8 in which the nulling circuit comprises a voltage null circuit in the synchronous detection subsystem.

12. A system according to claim 8 in which the nulling circuit is passive.