Method and system for locating objects

• US 7,049,960 B2
• Filed: 12/29/2003
• Issued: 05/23/2006
• Est. Priority Date: 12/29/2003
• Status: Expired due to Fees

• Current Assignee: Lenovo Singapore Pte Limited (Lenovo Group Ltd.)
• Original Assignee: Lenovo Singapore Pte Limited (Lenovo Group Ltd.)
• Inventors: Waltermann, Rod David
• Primary Examiner(s): Mullen, Jr., Thomas J.
• Assistant Examiner(s): Hunnings, Travis R.
• Application Number:
  US10/747,568
• Publication Number:
  US 20050146433A1
• Time in Patent Office: 876 Days
• Field of Search: 340/568.1, 340/572.1, 367/93, 367/95, 367/99
• US Class Current: 340/568.1
• CPC Class Codes: G01S 15/74 Systems using reradiation of acoustic waves, e.g. IFF, i.e. identification of friend or foe
• CPC Class Codes: G01S 15/87 Combinations of sonar systems
• CPC Class Codes: G08B 13/2462 Asset location systems combined with EAS inventory, tracking, logistic G06Q10/00; entrance control systems G07C9/00
• CPC Class Codes: G08B 21/0261 System arrangements wherein the object is to detect trespassing over a fixed physical boundary, e.g. the end of a garden

Abstract

An area is established by positioning a string of boundary objects that are reflective to a range of ultrasonic frequencies. Tracking objects may be placed inside the area which also are reflective to the range of ultrasonic frequencies. An array of transducers insonify the area and the reflected signals are received by each transducer, digitized and stored as digital data. The digital data is read out in time reverse order and time reversal signals are generated that are coupled to each corresponding transducer. The time reversed signals focus energy on the reflective sources. The reflected signals resulting from the time reversed signals are analyzed to generate a reference signature indicating relative locations of boundary and tracking objects. The time reversed signals are sent intervals to generate new signatures which are compared to the reference signature to determine if tracking objects have been moved outside the area.

Claims

1. A method for determining if a tracking object is within a selected area comprising the steps of:

a) transmitting a first acoustic signal simultaneously from an array of transducers proximate to the selected area;

b) receiving first reflected signals, generated in response to the first acoustic signal, in each transducer in the array of transducers, the first reflected signals reflected from boundary objects defining a boundary of the selected area and from one or more tracking objects within the selected area;

c) storing digital data corresponding to the first reflected signals in a memory associated with each transducers in the array of transducers generating stored digital data;

d) generating second acoustic signals from each transducer in the array of transducers in response to time reversing a read out of the stored digital data;

e) receiving second reflected signals in response to the second acoustic signals and generating second digital data;

f) analyzing the second digital data and generating and storing a first signature pattern indicating relative locations of the boundary objects and the one or more tracking objects;

g) transmitting the second acoustic signals at time intervals and generating a second signature pattern;

h) comparing a second signature pattern to the first signature pattern; and

i) determining if a tracking object has moved from the selected area in response to the step of comparing the new signature pattern to the reference signature pattern.

2. The method of claim 1, wherein the boundary objects are shaped to reflect the first acoustic signals in a particular frequency range.

3. The method of claim 1, wherein the tracking objects incorporate a tag that is reflective to the first acoustic signals in a particular frequency range.

4. The method of claim 3, wherein the tag is removable or capable of being disabled after completion of a sale of a tracking object authorizing the tracking object to be moved outside an area defined by the boundary objects.

5. A method for determining if an object is removed from a selected area comprising the steps of:

a) transmitting a first acoustic signal simultaneously from an array of transducers;

b) receiving first reflected signals in each transducer in the array of transducers in response to a first reflected signal from boundary objects defining a boundary of the selected area and from one or more tracking objects within the selected area;

c) storing digital data corresponding to the first reflected signals in a memory associated with each transducers in the array of transducers generating stored digital data;

d) generating second acoustic signals from each transducer of the array of transducers in response to time reversing the stored digital data in each transducer of the array of transducers;

e) receiving an identification signal generated by the one or more tracking object in response to the one or more tracking objects receiving a second acoustic signal;

f) repeating steps a)–

d) if a tracking object does not generate an identification signal; and

g) generating an alarm signal if a tracking object continues to not generate an identification signal after step f).

6. The method of claim 5, wherein each of the boundary objects has a transmitter that is stimulated to transmit an identification signal when the boundary object receives a second signal of greater than a predetermined level.

7. The method of claim 5, wherein one or more tracking objects have a transmitter that is stimulated to transmit an identification signal when the tracking object receives a second signal of greater than a predetermined level.

8. The method of claim 7, further comprising the step of regenerating the reference pattern in response to determining that a tracking object did not transmit an identification signal in response to broadcast of the second signals.

9. A system for determining if a tracking object is removed from a selected area comprising:

an array of transducers distributed in proximity to the selected area, wherein each transducer in the array of transducers generates output acoustic energy in response to an electrical input signal and generates an electrical output signal in response to received input acoustic energy;

a multiplicity of boundary objects defining the selected area, wherein each of the boundary objects has features for selectively reflecting acoustic energy in a particular acoustic frequency band;

signal processing circuitry coupled to the array of transducers for converting the electrical output signal from each transducer in the array of transducers into digital receive data and converting digital transmit data into the electrical input signal for each transducer in the array of transducers;

a processor coupled to the signal processing circuitry for generating the digital transmit data and analyzing the digital receive data to determine signature patterns defining relative locations of the boundary objects and one or more tracking objects placed in the selected area, wherein the one or more tracking objects have features for selectively reflecting acoustic energy in a particular frequency band;

compare circuitry coupled to the processor for comparing the signature patterns to a predetermined reference signature pattern defining desired relative locations of the boundary objects and the one or more tracking objects; and

a memory system for storing the digital receive data and the reference signature pattern.

10. The system of claim 9, wherein the multiplicity of boundary objects and one or more tracking objects comprise transmitter circuitry for generating a first output acoustic signal in response to detecting a first input acoustic signal transmitted from the array of transducers.

11. The system of claim 10, wherein each of the multiplicity of boundary objects and one or more tracking objects generates an acoustic identification signal in response to receiving a second acoustic signal transmitted by the array of transducers.

12. The system of claim 11, wherein the second input acoustic signal is generated by time reversing digital data generated in response to the first output acoustic signal.

13. The system of claim 12, wherein the acoustic identification signal is generated if a level of the second acoustic signal received by a boundary object or a tracking object exceeds a predetermined value.

14. The system of claim 12, wherein the first acoustic signal is simultaneously transmitted by the array of transducers if one or more of the tracking objects fails to generate an identification signal in response to transmission of the second acoustic signal.

15. The system of claim 9, wherein the boundary objects have features to reflect the first signals in a particular frequency range.

16. The system of claim 13, wherein the one or more tracking objects each incorporate a tag that is reflective to the first signals in a particular frequency range.

17. The system of claim 14, wherein tag is removable after completion of a sale of a tracking object.

18. The system of claim 9, wherein the memory system is coupled to the processor and comprises a memory array coupled to a memory controller, the memory controller for controlling read and write operations to the memory array.

19. A method of locating an object comprising:

a) transmitting a first acoustic signal;

b) receiving first reflected signals comprising first acoustic signal energy reflected from the object;

c) transmitting a second acoustic signal comprising a time-reversed version of said first reflected signal;

d) receiving second reflected signals comprising second acoustic signal energy reflected from the object;

e) storing said second reflected signals as a first signature signal indicating the location of the object;

f) periodically transmitting said second acoustic signal;

g) receiving third reflected signals comprising acoustic signal energy reflected from the object as a result of each said periodic transmission;

h) storing each said third reflected signals as a second signature signal indicating the location of the object; and

i) comparing said second signature signal to said first signature signal to determine if the object has moved.