Method and apparatus for touch-activated identification and information transfer

• US 6,642,837 B1
• Filed: 10/19/1999
• Issued: 11/04/2003
• Est. Priority Date: 10/19/1999
• Status: Expired due to Term

• Current Assignee: Massachusetts Institute of Technology
• Original Assignee: Massachusetts Institute of Technology
• Inventors: Gershenfeld, Neil, Vigoda, Benjamin
• Primary Examiner(s): Crosland, Donnie L.
• Application Number:
  US09/420,829
• Time in Patent Office: 1,477 Days
• Field of Search: 340/10.1, 340/10.51, 340/562, 340/5.9, 340/825.72, 340/5.92, 340/5.91, 341/20, 341/33, 200/600, 200/DIG.2, 235/385
• US Class Current: 340/10.1
• CPC Class Codes: G06K 19/0723 the record carrier comprising an arrangement for non-contact communication, e.g. wireless communication circuits on transponder cards, non-contact smart cards or RFIDs
• CPC Class Codes: Y10S 200/02 Body attached switches

Abstract

Physical structures respond to proximity or touch, conveying to a reader information such as the identity of the structure or some data associated therewith. In its simplest form, the structure comprises an electrical load and a pair of electrodes connected thereto. The electrodes are spaced apart (by air or other dielectric medium). A signal generator, which acts as a “reader,” is connected to a larger electrode that may be embedded in an environmental surface. When the structure is placed in proximity to the reader electrode, application of the signal results in capacitive coupling between the reader and the electrodes of the structure. The structure is not detected by the reader, however, because the capacitive coupling is comparable for both electrodes, so the load experiences only a small electrical gradient. But if one of the electrodes is grounded, this symmetry is broken and current is drawn through the load. In general, grounding occurs when a person, coupled (even weakly) to environmental ground—e.g., by virtue of standing on the floor—touches one of the electrodes. The resulting loading, which may be varied over time by the structure, is detected by the signal generator.

Claims

1. A method of wirelessly imparting information, the method comprising:

a. providing a tag unit comprising an electrical load and a pair of electrodes spaced apart by a dielectric medium, the load bridging the electrodes;

b. capacitively coupling a signal source to the electrodes without creating a detectable potential difference therebetween;

c. selectively coupling one of the electrodes to ground, thereby creating a detectable potential difference across the electrodes and drawing current from the signal source through the load; and

d. sensing the load and deriving information therefrom.

2. The method of claim 1 wherein a plurality of tag units, all capacitively coupled to the signal source and each having a different load, are provided, the information comprising identification of a tag touched by a user, the user'"'"'s touch coupling the selected ground.

3. The method of claim 1 wherein the electrical load is a variable-impedance circuit powered by the potential difference and drawn current, powering of the circuit producing temporal variations in impedance corresponding to information and causing, in the signal source, corresponding variations in loading, the variations being sensed to derive the information.

4. The method of claim 3 wherein the variable-impedance circuit varies a Q-factor of the receiver.

5. The method of claim 3 wherein the variable-impedance circuit varies a resonant frequency of the receiver.

6. The method of claim 1 wherein the signal source is capacitively coupled to the electrodes by means of a transmitting electrode connected to the signal source and within a read range of the tag-unit electrodes.

7. The method of claim 6 wherein the transmitting electrode is part of an item of furniture.

8. The method of claim 6 wherein the transmitting electrode is embedded within an architectural surface or fixture.

9. The method of claim 6 wherein the transmitting electrode is embedded in a game board and the tag unit serves as a game token.

10. The method of claim 1 wherein the derived information causes an action to be taken by a computer.

11. The method of claim 10 wherein the action is selection of a web page.

12. The apparatus of claim 11 further comprising a transmitting electrode connected to the signal source and capacitively coupling the signal source to the electrodes within a read range of the tag-unit electrodes.

13. The apparatus of claim 12 wherein the transmitting electrode is part of an item of furniture.

14. The apparatus of claim 12 wherein the transmitting electrode is embedded within an architectural surface or fixture.

15. The apparatus of claim 12 wherein the transmitting electrode is embedded in a game board and the tag unit serves as a game token.

16. The apparatus of claim 10 further comprising means for causing the derived information to cause an action to be taken by a computer.

17. The apparatus of claim 16 wherein the action is selection of a web page.

18. Apparatus for wirelessly imparting information, the apparatus comprising:

a. a tag unit comprising an electrical load and a pair of electrodes spaced apart by a dielectric medium, the load bridging the electrodes; and

b. a signal source capacitively coupled to the electrodes without creating a detectable potential difference therebetween, the signal source being configured to detect the load and derive information therefrom when current is drawn therethrough as a result of selective coupling of one of the electrodes to ground, thereby creating a potential difference across the electrodes.

19. The apparatus of claim 18 wherein the electrical load is a variable-impedance circuit powered by the potential difference and drawn current, powering of the circuit producing temporal variations in impedance corresponding to information and causing, in the signal source, corresponding variations in loading, the variations being detected to derive the information.

20. The apparatus of claim 19 wherein the variable-impedance circuit varies a Q-factor of the receiver.

21. The apparatus of claim 19 wherein the variable-impedance circuit varies a resonant frequency of the receiver.