Tag interrogation with observable response signal

• US 20040061612A1
• Filed: 09/26/2002
• Published: 04/01/2004
• Est. Priority Date: 09/26/2002
• Status: Active Grant

• Current Assignee: Massachusetts Institute of Technology
• Original Assignee: Massachusetts Institute of Technology
• Inventors: Lippman, Andrew Benjamin, Ma, Hongshen, Paradiso, Joseph A.
• Granted Patent: US 7,109,865 B2
• Time in Patent Office: Days
• US Class Current: 340/572.1
• CPC Class Codes: G06K 7/0008 General problems related to the reading of electronic memory record carriers, independent of its reading method, e.g. power transfer
• CPC Class Codes: G06K 7/10079 the collision being resolved in the spatial domain, e.g. temporary shields for blindfolding the interrogator in specific directions

Abstract

An identification tag identifies a unique item from among a plurality of items with a similar appearance. Tagged items are searched by scanning the items with an interrogation signal. The tag emits an observable signal to indicate when it receives an identification that matches the identification contained in the tag. When the reader'"'"'s interrogation is not present, the tag either sleeps at a very low power level or is passively unpowered.

Claims

1. A method of discriminating among similar items, the method comprising the steps of:

a. associating each of the items with a device responsive to a unique stimulus; and

b. exposing the items to a stimulus corresponding to a selected one of the items, the exposure causing the corresponding item, but not the other items, to impart an observable signal.

2. The method of claim 1 wherein each of the devices responds to a differently modulated light beam.

3. The method of claim 2 wherein the light beam is modulated by an AM frequency, each of the devices responding to modulation by a different AM frequency.

4. The method of claim 1 wherein the device comprises a processor that is maintained in a low-power shutdown mode until the unique stimulus is detected.

5. The method of claim 1 wherein the observable signal is a light signal.

6. The method of claim 1 wherein, upon exposure to the stimulus, the device emits the observable signal.

7. The method of claim 1 wherein, upon exposure to the stimulus, the device causes the observable signal to be emitted by the selected item.

8. The method of claim 1 wherein the signal is emitted by an external source and is blocked from observation by all items except, upon exposure, the selected item.

9. The method of claim 1 wherein the observable signal is a directly observable signal.

10. An identification system, the system comprising:

a transmitter for transmitting an interrogation signal comprising a transmitted identification associated with a selected tag;

a plurality of tags each containing a tag identification uniquely identifying the tag, the tag being responsive to an interrogation signal whose transmitted identification matches the tag identification; and

associated with each of the tags, a transducer, in communication with the tag identification, for imparting an observable signal upon response of the tag identification to the interrogation signal.

11. The identification system of claim 10 wherein the tag comprises a transducer for emitting a different signal if the transmitted identification does not match the tag identification.

12. The identification system of claim 10 wherein the transmitter is integrated within a wireless handheld device.

13. The identification system of claim 12 wherein the handheld device is a personal digital assistant.

14. The identification system of claim 10 wherein the observable signal is directly observable in the vicinity of the tag.

15. The identification system as claimed in claim 10 wherein the transmitted identification is incorporated in a light beam by modulation thereof.

16. The identification system of claim 10 wherein each tag responds to a differently modulated light beam.

17. The identification system of claim 15 wherein the light beam is modulated by an AM frequency, each of the tags responding to modulation by a different AM frequency.

18. The identification system of claim 10 wherein the tags are maintained in a low-power shutdown mode until the interrogation signal is detected.

19. The identification system of claim 10 wherein the observable signal is a light signal.

20. The identification system of claim 10 wherein, upon exposure to the interrogation signal, the tag emits the observable signal.

21. The identification system of claim 10 wherein, upon exposure to the stimulus, the tag causes the observable signal to be emitted by an item.

22. The identification system of claim 21 wherein the item is an electronic storage medium.

23. The identification system of claim 10 wherein the tag comprises a power source that supplies an operating current for the tag.

24. The identification system of claim 23 wherein the tag operates in a sleep mode when not processing the interrogation signal.

25. The identification system of claim 24 wherein the power source supplies an operating current less than or equal to 500 nanoamps when the tag is in the sleep mode.

26. The identification system of claim 10 wherein the observable signal is audible.

27. The identification system of claim 10 wherein the observable signal is visible.

28. An identification tag that identifies a unique object having a generic appearance, the tag comprising:

a receiver for receiving an interrogation signal comprising an object identification;

a memory for storing a tag identification uniquely identifying the tag; and

a device for emitting an observable signal in response to the interrogation signal when the object identification matches the tag identification, wherein the object identification uniquely identifies the object from among a plurality of objects having a similar appearance.

29. The identification tag of claim 28 further comprising a power source that supplies an operating current for the tag.

30. The identification tag of claim 29 wherein the tag operates in a sleep mode when not processing the interrogation signal.

31. The identification tag of claim 30 wherein the power source supplies an operating current less than or equal to 500 nanoamps when the tag is in the sleep mode.

32. The identification tag of claim 28 wherein the tag is configured for integration within a media item, the memory receiving the tag identification when information is transferred to the media item.

33. The identification tag of claim 32 wherein the tag identification is read when data is transferred to the media item.

34. The identification tag of claim 28 wherein the interrogation signal is a modulated light beam.

35. The identification tag of claim 28 wherein the observable signal is audible.

36. The identification tag of claim 28 wherein the observable signal is visible.