Platform for item sensing and identification

• US 20010035815A1
• Filed: 12/27/2000
• Published: 11/01/2001
• Est. Priority Date: 12/29/1999
• Status: Active Grant

• Current Assignee: Massachusetts Institute of Technology
• Original Assignee: Massachusetts Institute of Technology
• Inventors: Neil, Gershenfeld, Ishii, Hiroshi, Fletcher, Richard, Yarin, Paul
• Granted Patent: US 6,791,452 B2
• Time in Patent Office: Days
• US Class Current: 340/10.6
• CPC Class Codes: G01B 7/004 for measuring coordinates of points
• 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

The response of an object to a single time-varying magnetic field is sensed to determine object position and/or manipulation on a horizontal or vertical surface. A time-varying interrogation signal, which interacts with tags disposed on the surface, is read by an array of sensing coils. Control circuitry receives signals from the sensing coils representing this interaction and, based thereon, determines the identity, position, and manipulation of each of the objects based on the sensed signals and the known positions of the sensing coils. Feedback to the user can be provided in the form of a localized output (e.g. light, sound, heat, etc.) physically coincident with the object.

Claims

1. A platform for sensing physical objects having electromagnetically actuable tags associated therewith, the platform comprising:

a. a sensing surface having a sensing area;

b. beneath the sensing surface, an array of coils;

c. control circuitry for (i) causing at least one of the coils to generate a time-varying interrogation signal, the interrogation signal interacting with tags disposed on the surface within the sensing area, (ii) receiving a signal indicative of the interrogation signal as affected by the tags and their proximities to the various coils, and (iii) based on the received signal, determining positions for each of the objects within the sensing area; and

d. a display generator for creating displays relating to the sensed objects derived from the tags associated therewith, the displays remaining in proximity to the sensed objects notwithstanding movement thereof on the sensing surface.

2. The platform of

claim 1

wherein the control circuitry is further configured to determine, for each of the objects, a height of the object above the surface.

3. The platform of

claim 1

wherein the coils include an excitation coil and a series of sensing coils, the excitation coil generating the interrogation signal, the received signal comprising sensing signals received from the sensing coils, the sensing signals representing the interrogation signal as affected by the tags and their proximities to the sensing coils.

4. The platform of

claim 3

wherein the coils are affixed to a planar surface, the excitation coil surrounding the sensing coils.

5. The platform of

claim 3

wherein the control circuitry is configured to (a) cause continuous generation of the interrogation signal and (b) determine the positions by measuring an average signal strength at a center point of each sensing coil and interpolating between the average signal strengths.

6. The platform of

claim 1

wherein the control circuitry is further configured to track the positions of the objects over time.

7. The platform of

claim 1

wherein the coils are sequentially caused to generate the interrogation signal, the received signal comprising a field strength sensed by the coil generating the interrogation signal, the sensed field strength being affected by the tags and their proximities to said coil.

8. A platform for sensing physical objects having electromagnetically actuable tags associated therewith, the platform comprising:

a. a sensing surface having a sensing area;

b. beneath the sensing surface, a series of coils;

c. control circuitry for (i) causing at least one of the coils to generate a time-varying interrogation signal, the interrogation signal interacting with tags disposed on the surface within the sensing area, the tags being configured to respond to the interrogation signal based on a physical condition of the object, (ii) receiving a signal indicative of the interrogation signal as affected by the tags and their proximities to the various coils, and (iii) based on the received signal, determining the physical condition for each of the objects within the sensing area.

9. The platform of

claim 8

wherein each of the coils is part of an LC circuit having a measurable electrical characteristic altered by an external condition, the control circuitry being further configured to sense the characteristic in order to determine the condition.

10. The platform of

claim 8

wherein the physical condition is at least one of applied force, temperature, humidity, and light.

11. The platform of

claim 10

wherein the electrical characteristic is at least one of resonant frequency, harmonic spectra, and Q factor.

12. The platform of

claim 8

further comprising a display generator for creating displays indicating the physical condition of the sensed objects, the displays remaining in proximity to the sensed objects notwithstanding movement thereof on the sensing surface.

13. A method of sensing physical objects having electromagnetically actuable tags associated therewith, the method comprising the steps of:

a. providing a sensing surface having a sensing area;

b. causing generation of at least one time-varying interrogation signal within the sensing area, the at least one interrogation signal interacting with tags disposed on the surface within the sensing area;

c. receiving a signal indicative of the at least one interrogation signal as affected by the tags;

d. based on the received signal, determining positions for each of the objects within the sensing area; and

e. displaying information relevant to the sensed objects and derived from the tags associated therewith, the display remaining in proximity to the sensed objects notwithstanding movement thereof on the sensing surface

14. The method of

claim 13

further comprising the step of determining, for each of the objects, a height of the object above the surface.

15. The method of

claim 14

further comprising the step of providing a plurality of coils including an excitation coil and a series of sensing coils, the excitation coil generating an interrogation signal, the received signal comprising sensing signals received from the sensing coils, the sensing signals representing the interrogation signal as affected by the tags and their proximities to the sensing coils.

16. The method of

claim 15

wherein the coils are located beneath the surface, the excitation coil surrounding the sensing coils.

17. The method of

claim 16

further comprising the steps of (a) causing continuous generation of the excitation signal and (b) determining the positions by measuring an average signal strength at a center point of each sensing coil and interpolating between the average signal strengths.

18. The method of

claim 13

further comprising the step of providing a plurality of coils proximate to the sensing area, the coils being sequentially caused to generate the interrogation signal, the received signal comprising a field strength sensed by the coil generating the interrogation signal, the sensed field strength being affected by the tags and their proximities to said coil.

19. The method of

claim 13

wherein the display imparts at least one of a visual indication, heat, and sound.

20. A method of sensing physical objects having electromagnetically actuable tags associated therewith, the method comprising the steps of:

a. providing a sensing surface having a sensing area;

b. causing generation of at least one time-varying interrogation signal within the sensing area, the at least one interrogation signal interacting with tags disposed on the surface within the sensing area, the tags being configured to respond to the interrogation signal based on a physical condition of the object;

c. receiving a signal indicative of the at least one interrogation signal as affected by the tags; and

d. based on the received signal, determining the physical condition for each of the objects within the sensing area.

21. The method of

claim 20

wherein each of the coils is part of an LC circuit having a measurable electrical characteristic altered by external condition, and further comprising the step of sensing the characteristic in order to determine the condition.

22. The method of

claim 21

wherein the external condition is at least one of applied force, temperature, humidity, and light.

23. The method of

claim 21

wherein the electrical characteristic is at least one of resonant frequency, harmonic spectra, and Q factor.

24. The method of

claim 20

further comprising the step of creating displays indicating the physical condition of the sensed objects, the displays remaining in proximity to the sensed objects notwithstanding movement thereof on the sensing surface.