Communications: electrical – Selective – Interrogation response
Reexamination Certificate
2000-12-27
2004-09-14
Horabik, Michael (Department: 2635)
Communications: electrical
Selective
Interrogation response
C340S010100, C340S010510, C340S505000, C340S517000, C340S524000, C340S572100
Reexamination Certificate
active
06791452
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to remote sensing and identification, and in particular to sensing based on inexpensive electromagnetically actuable “tags.”
BACKGROUND OF THE INVENTION
Many human tasks involve the manipulation of items disposed on a surface, such as a desk, kitchen counter/stove, a liquor-bar countertop, white drawing board, retail display rack, game board, or assembly surface. The items themselves may simply be moved around on the surface, or may instead undergo some type of manipulation (such as rotation, bending, opening, stretching, or squeezing). Frequently it would be useful to track the positions and identity of the items, as well as monitor the physical manipulations they undergo. Sensing the object manipulations would, for example, allow the objects themselves (or portions of the objects) to be used as controllers for an external process or control of displayed information.
Unfortunately, current approaches to these tasks tend to be very expensive and/or limited in capability. For example, computer-vision techniques have been employed to identify objects and observe object manipulations, but these techniques involve elaborate equipment and specialized interpretive software for particular applications. Moreover, computer vision requires continuous line-of-sight visual access to the objects and is significantly affected by changes in lighting, placing limitations on system robustness and the allowable range of monitorable user-item interactions. Accordingly, such systems are frequently unsuitable for real-world applications.
DESCRIPTION OF THE INVENTION
Brief Summary of the Invention
The present invention monitors objects that have been equipped with “tags” that impart information by electromagnetic coupling. One well-known type of tag is the radio frequency identification (RFID) device, which has been employed for some time to remotely sense parameters of interest in people or objects. An RFID tag receives a wireless signal from an externally located “reader,” which determines the identity (or other parameter of interest) of the item based on the response of the RFID device to the transmitted signal. Other types of tags do not contain electronic circuitry, instead relying on the unique electromagnetic response of certain material structures. Anti-theft tags utilized in department stores represent an example of this approach.
In accordance with the present invention, an object's response to a single time-varying magnetic field is sensed and analyzed to determine object position and/or manipulation on a work surface. This may be accomplished by means of coils disposed underneath the surface on which the objects reside. An array of sensing coils (e.g., in a linear sequence or two-dimensional matrix), and optionally larger excitation coil—which may surround the sensing coils—generates a time-varying interrogation signal. The interrogation signal interacts with electromagnetic (e.g., RFID or materials-based) tags disposed on the surface, and each sensing coil is capable of independently sensing electromagnetic signals from tagged objects in its vicinity. Control circuitry receives signals from the sensing coils representing this interaction. These signals represent the interrogation signal as affected by the tags themselves as well as by their proximities to the sensing coils. Alternatively, the same coils may be used for interrogation and sensing. In this case, the coils are sequentially energized, and the electromagnetic response of the tag identifies it.
The control circuitry is further configured to determine positions for each of the objects based on the sensed signals and the known positions of the sensing coils; object position may include not only the two-dimensional location of the object on the surface, but also a spatial component representing the height of the object thereabove.
Preferably, the system includes a display device that facilitates “coincident feedback” concerning an object-that is, object information is presented proximate to or “co-located” with the object itself, even as its position changes. For example, the surface upon which the objects are manipulated may contain a matrix of individually actuable display elements or pixels responsive to object identity and position, such that only those devices in proximity to objects are active at any time. For example, coincident illumination feedback may appear as a halo of light or graphical icon that follows the tagged object as it is moved around by the user (in the manner of an optical shadow). In addition to light patterns, other forms of coincident feedback are possible, for example, localized sound or heat generated by a suitable array of sound elements or heating elements. As used herein, the term “display” refers generally to all such forms of coincident feedback.
REFERENCES:
patent: 4988837 (1991-01-01), Murakami et al.
patent: 5815091 (1998-09-01), Dames et al.
patent: 5936523 (1999-08-01), West
patent: 6563417 (2003-05-01), Shaw
Fletcher Richard
Ishii Hiroshi
Neil Gershenfeld
Yarin Paul
Brown Vernal
Horabik Michael
Massachusetts Institute of Technology
Testa Hurwitz & Thibeault LLP
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