Non-contact system for sensing and signalling by externally induced intra-body currents

• US 5,914,701 A
• Filed: 08/06/1997
• Issued: 06/22/1999
• Est. Priority Date: 05/08/1995
• Status: Expired due to Term

• Current Assignee: Massachusetts Institute of Technology
• Original Assignee: Massachusetts Institute of Technology
• Inventors: Zimmerman, Thomas, Allport, David, Gersheneld, Neil
• Primary Examiner(s): Peng, John K.
• Assistant Examiner(s): LO, LINUS H
• Application Number:
  US08/907,062
• Time in Patent Office: 685 Days
• Field of Search: 345/156, 345/158, 345/157, 345/174, 340/562, 340/561, 340/407.1, 340/870.37, 340/563, 340/564, 340/825.71, 341/21, 341/31, 341/32, 341/33, 434/12, 455/41, 455/100
• US Class Current: 345/156
• CPC Class Codes: G06F 3/017 Gesture based interaction, e.g. based on a set of recognized hand gestures interaction based on gestures traced on a digitiser G06F3/04883
• CPC Class Codes: G06F 3/0346 with detection of the device orientation or free movement in a 3D space, e.g. 3D mice, 6-DOF [six degrees of freedom] pointers using gyroscopes, accelerometers or tilt-sensors
• CPC Class Codes: G06F 3/04162 for exchanging data with external devices, e.g. smart pens, via the digitiser sensing hardware
• CPC Class Codes: G06F 3/044 by capacitive means
• CPC Class Codes: G06F 3/046 by electromagnetic means
• CPC Class Codes: G06K 19/041 Constructional details G06K19/06 takes precedence
• CPC Class Codes: G06K 19/07749 the record carrier being capable of non-contact communication, e.g. constructional details of the antenna of a non-contact smart card
• CPC Class Codes: G06K 19/07758 arrangements for adhering the record carrier to further objects or living beings, functioning as an identification tag
• CPC Class Codes: G06K 19/07788 the antenna being of the capacitive type
• CPC Class Codes: G06K 7/10326 the antenna being of the very-near field type, e.g. capacitive
• CPC Class Codes: H04B 13/005 Transmission systems in which the medium consists of the human body
• CPC Class Codes: H04B 5/00 Near-field transmission systems, e.g. inductive or capacitive transmission systems
• CPC Class Codes: H04B 5/22 Capacitive coupling
• CPC Class Codes: H04B 5/48 Transceivers
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

A wireless system includes one or more transmitters and one or more remote receivers that are respectively coupled through one or more users and room ground. The transmitters each produce low-frequency, low power signals that, through capacitive coupling, pass as displacement currents into and from the body of the user, which acts as a conductive node. A receiver that couples capacitively to the user responds to the displacement currents and reproduces the signals. The transmitter includes a signal generator and a pair of electrodes. The signal generator produces modulated signals that vary the voltage between the electrodes, a first one of which is closely coupled capacitively to the user'"'"'s body such that the "quasi-electrostatic" field resulting from the electrode potential causes a displacement current to pass to the user'"'"'s body. The second electrode is oriented so that its coupling to the room ground is stronger than that of the first electrode, such that room ground acts as a return path for the current from the receiver. The signal generator may modulate the information to be transmitted using, for example, a pseudorandom code, to produce spread spectrum signals. This increases noise immunity and allows multiple transmitters, each using a different modulation code, to operate at the same time. The receivers each include a detector/demodulator that acquires and tracks the signals from the one or more transmitters.

Claims

1. A wireless communication system including:

A. a transmitter for producing low frequency signals that include data, the transmitter being capacitively coupled to a user and to ground, the transmitter passing to the user a current that is associated with the low frequency signals; and

B. a receiver that is displaced from the user and is coupled to ground for receiving when capacitively coupled to the user a current that is associated with the signals produced by the transmitter, the receiver reproducing the transmitted signals and recovering the data.

2. The wireless communication system of claim 1, wherein the transmitter includes:

i. a pair of electrodes; and

ii. a signal generator connected between the electrodes, the signal generator generating the low frequency signals that result in an associated displacement current between the electrodes and the user.

3. The wireless communication system of claim 2, wherein the receiver includes:

i. a pair of electrodes; and

ii. a signal detector connected between the electrodes, the signal detector reproducing the low frequency signals from a displacement current developed between the electrodes and the user.

4. The wireless communication system of claim 1 wherein the system further includes

a. a plurality of receivers;

and

b. a processor for determining from the signals reproduced by the receivers the position of the user relative to one or more of the receivers.

5. The wireless communication system of claim 4 wherein:

the receivers are mounted on the periphery of a computer screen; and

the processor moves a cursor to a position on the screen that is associated with the position of the user relative to one or more of the receivers.

6. The wireless communication system of claim 2 wherein the transmitter further includes a signal modulator for spread spectrum modulating the signals with a predetermined pseudorandom code.

7. The wireless communication system of claim 6 wherein the system further includes a plurality of transmitters, each of the transmitters being associated with a predetermined code that differs from the codes associated with the other transmitters in the system, the receiver using the codes to distinguish between the signals passed from each of the transmitters in the plurality of transmitters.

8. The wireless communication system of claim 7 wherein each of the transmitters in the plurality of transmitters is capacitively coupled to a different user, and the receiver receives signals respectively from the individual transmitters when the receiver is capacitively coupled to the individual transmitters.

9. The wireless communication system of claim 8 wherein the system further includes:

a. a plurality of receivers; and

b. a processor for determining from the signals reproduced by the receivers the relative positions of the users.

10. The wireless communication system of claim 9 wherein:

the receivers are mounted on the periphery of a computer screen; and

the processor moves one or more objects to positions on the screen that are associated with the positions of one or more of the users relative to one or more of the receivers.

21. The wireless communication system of claim 1 wherein the receiver is mounted on an object.

22. The wireless communication system of claim 1 wherein the receiver is coupled to another user.

23. The wireless communication system of claim 1 wherein the system further includes:

a. a plurality of transmitters that are capacitively coupled to one or more users;

b. a plurality of receivers that are displaced from the users; and

c. a processor for determining from the signals reproduced by the receivers the positions of the one or more users relative to one or more of the receivers.

24. The wireless communication system of claim 23 wherein:

i. the transmitters also receive signals; and

ii. the receivers also transmit signals.

25. The wireless communication system of claim 1 wherein:

i. the transmitter also receives signals; and

ii. the receiver also transmits signals.

11. A computer system including:

A. a screen for displaying on-screen objects;

B. a keyboard for data entry to the system;

C. a transmitter for producing low frequency signals, the transmitter being capacitively coupled to a user to pass to the user a current that is associated with the low frequency signals;

D. a plurality of receivers mounted on the periphery of the screen, each of the receivers in the plurality receiving from the user, through capacitive coupling to the user, a current that is associated with the signals produced by the transmitter, the receivers determining the position of the closest extremity of the user'"'"'s body relative to one or more of the receivers; and

E. a processor for controlling the screen display, the processor directing the screen to display the objects in positions that correspond to the position of the user'"'"'s extremity as determined by the receivers.

12. The computer system of claim 11 wherein the transmitter is incorporated into the keyboard.

13. The computer system of claim 11 further including a receiver that is mounted on the keyboard, the receiver determining, based on the strength of the received signals if the user is selecting the information that is displayed below the cursor, the system determining that the user is selecting the information if the strength of the signals received by the receiver mounted on the keyboard is above a predetermined threshold.

14. A wireless communication system including:

A. a plurality of transmitters for producing low frequency signals, the transmitters being capacitively coupled to one or more users and to ground and, respectively, including a pair of electrodes and connected between the electrodes a signal generator that generates low frequency signals, each transmitter passing to the associated user a current that is associated with the low frequency signals; and

B. a plurality of receivers coupled to ground for receiving, respectively, from the one or more users to which they capacitively couple one or more currents associated with the signals produced by the transmitters, the receivers reproducing the transmitted signals; and

C. a processor for determining from the signals reproduced by the receivers the respective positions of the users relative to one or more of the receivers.

15. The wireless communication system of claim 14 wherein:

i. the transmitters each, respectively, transmit signals associated with a different predetermined code; and

ii. the receivers distinguish between the signals produced by the individual transmitters based on the codes.

16. The wireless communication system of claim 14 wherein the receivers distinguish between the signals produced by the individual transmitters based on the times the signals are transmitted.

17. The wireless communication system of claim 14 wherein:

i. the transmitters each, respectively, transmit signals at different predetermined frequencies; and

ii. the receivers distinguish between the signals produced by the individual transmitters based on the frequencies.

18. A system including:

A. a screen for displaying one or more on-screen objects including a cursor;

B. a keyboard for data entry to the system;

C. a transmitter for producing low frequency signals, the transmitter being capacitively coupled to a user to pass to the user a current that is associated with the low frequency signals;

D. a plurality of receivers mounted on the periphery of the screen, each of the receivers in the plurality receiving from the user, through capacitive coupling to the user, a current that is associated with the signals produced by the transmitter, the receivers determining the position of the closest extremity of the user'"'"'s body relative to one or more of the receivers;

E. a selection receiver mounted on the system for determining, based on the strength of the received signals, if the user is selecting the information that is displayed below the cursor, the system determining that the user is selecting the information if the strength of the signals received by the selection receiver is above a predetermined threshold; and

F. a processor for controlling the screen display, the processor directing the screen to display one or more of the objects in positions that correspond to the position of the user'"'"'s extremity as determined by one or more of the plurality of the receivers.

19. The system of claim 18 wherein the selection receiver is mounted on the keyboard.

20. The system of claim 19 wherein the system further includes a plurality of selection receivers.