Metal detector having target characterization and search classification

• US 5,148,151 A
• Filed: 06/20/1990
• Issued: 09/15/1992
• Est. Priority Date: 06/20/1990
• Status: Expired due to Term

• Current Assignee: Garrett Electronics Incorporated
• Original Assignee: Garrett Electronics Incorporated
• Inventors: Podhrasky, Robert J.
• Primary Examiner(s): Ng, Jin F.
• Assistant Examiner(s): MULLEN, THOMAS J
• Application Number:
  US07/541,151
• Time in Patent Office: 818 Days
• Field of Search: 340/572, 340/525, 340/691, 340/658, 340/825.7, 324/329, 364/516, 446/129
• US Class Current: 324/329
• CPC Class Codes: G01V 3/105 forming directly coupled primary and secondary coils or loops
• CPC Class Codes: G01V 3/15 specially adapted for use during transport, e.g. by a person, vehicle or boat
• CPC Class Codes: G06V 10/255 Detecting or recognising potential candidate objects based on visual cues, e.g. shapes

Abstract

A metal detector is provided with circuitry for producing a plurality of vector signals derived from a target signal. Each of these vector signals corresponds to a phase characteristic of target signals. These vector signals define phase ranges which correspond to classifications of targets. Upon detection of a target signal, the metal detector generates first and second phase detected signals which in turn generate a plurality of vector signals. These vector signals are digitized and within a microprocessor a determination is made through slope analysis to determine which range includes the principal phase of the detected target signal. The vector signals which define the identified range are then utilized in algebraic calculations to define one of a plurality of subphase ranges within each range. This identified subphase range identifies a segment in a linear display which is illuminated to show the determined characteristic for the detected object. An operator can program the detector to select or reject target objects having certain electrical characteristics and this is likewise displayed to the operator. When the detector determines that a target signal has the same characteristics as selected by the operator, an audio output is generated. The display provided to the operator enables the operator to easily select or reject specific signal characteristics pertaining to certain types of targets.

Claims

1. A target characterization display for a metal detector which produces a detection signal for objects in a region of the detector, comprising:

a first set of arrayed display segments each having first and second display states,

a discrimination memory having respective storage locations therein corresponding to each of said display segments in said first set, each discrimination memory storage location corresponding to a unique signal parameter for metal detector targets and wherein the value stored in each of said discrimination memory storage locations controls the display state for the corresponding display segment,

a second set of arrayed display segments each having first and second display states, said second set of display segments positioned proximate said first set of display segments and having a correspondence between the segments of said first set and said second set, and

a target memory having respective storage locations therein for each of said display segments in said second set, wherein the values in said target memory storage locations are derived from phase detected signals and wherein the value in each of said target memory storage locations controls the display state for the corresponding display segment.

2. A target characterization display for a metal detector as recited in claim, further including:

means for detecting when corresponding ones of said storage locations in said discrimination and target memories have been set to values for driving the corresponding display segments to an active display state, and for generating a control signal upon said detecting, and

an audio output circuit connected to receive said control signal and for producing an audio output upon receipt of said control signal.

3. A target characterization display for a metal detector which produces a detection signal for objects in a region of the detector, comprising:

a first set of linearly arrayed display segments each having first and second display states,

a discrimination memory having respective storage locations therein corresponding to each of said display segments in said first set, each discrimination memory storage location corresponding to a unique signal parameter for metal detector targets and wherein the value stored in each of said discrimination memory storage locations controls the display state for the corresponding display segment,

a second set of linearly arrayed display segments each having first and second display states, said second set of display segments positioned essentially in parallel with said first set of display segments and having a one-to-one correspondence between the segments of said first set and said second set, and

a target memory having respective storage locations therein for each of said display segments in said second set, wherein the values in said target memory storage locations are derived from phase detected signals and wherein the value in each of said target memory storage locations controls the display state for the corresponding display segment.

4. A target characterization display for a metal detector as recited in claim 3, further including:

means for detecting when corresponding ones of said storage locations in said discrimination and target memories have been set to values for driving the corresponding display segments to an active display state, and for generating a control signal upon said detecting, and

an audio output circuit connected to receive said control signal and for producing an audio output upon receipt of said control signal.

5. A target characterization display for a metal detector which has transmit and receive coils for producing a detection signal and phase detection circuits for producing phase detected target signals from said detection signal, comprising:

a first set of linearly arrayed display segments, each having first and second display states,

a discrimination memory having respective storage locations therein corresponding to each of said display segments in said first set, each discrimination memory storage location corresponding to a unique signal parameter for metal detector targets and wherein the value stored in each of said discrimination memory storage locations controls the display state for the corresponding display segment,

a second set of linearly arrayed display segments each having first and second display states, said second set of display segments positioned essentially in parallel with said first set of display segments and having a one-to-one correspondence between the segments of said first set and said second set, and

a target memory having respective storage locations therein for each of said display segments in said second set, wherein the values in said target memory storage locations are derived from said phase detected signals and wherein the value in each of said target memory storage locations controls the display state for the corresponding display segment.

6. A target characterization display for a metal detector as recited in claim 5, further including:

means for detecting when corresponding ones of said storage locations in said discrimination and target memories have been set to values for driving the corresponding display segments to an active display state, and for generating a control signal upon said detecting, and

an audio output circuit connected to receive said control signal and for producing an audio output upon receipt of said control signal.

7. A method of operation for a signal processing circuit used in conjunction with a metal detector circuit which produces multiple detection signals that represent a target vector signal related to target object composition, the method comprising the steps of:

producing first and second vector signals which are related to target composition,

producing a plurality of vector signals which are algebraic combinations of said first and second vector signals,

examining each of said vector signals to determine a pair of said vector signals which encompasses the target vector signal,

algebraically combining the pair of vector signals to produce a target identification value, and

determining within which one of a plurality of predefined subphase ranges, which are between said pair of vector signals, said target identification value is present, thereby indicating a characteristic of the target object.