Data processing: measuring – calibrating – or testing – Measurement system – Orientation or position
Reexamination Certificate
2001-12-06
2004-12-21
Barlow, John (Department: 2863)
Data processing: measuring, calibrating, or testing
Measurement system
Orientation or position
C314S025000, C314S025000, C314S005000, C340S572800, C340S398100, C340S286080, C340S572100, C340S572700, C343S850000, C342S445000, C318S685000
Reexamination Certificate
active
06834251
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to improvements in identifying, sensing, and tracking of objects in predefined spaces by electromagnetic means.
2. Background and Prior Art
There exists a great and increasing need to identify and to automatically detect the presence, orientation and movement of objects in a predefined area. Such objects can include a wide range of animate and inanimate things, such as people's hands, pill bottles, tools, packages, toys, and many more. The applications for such automatic object detection and identification are numerous, including detecting a person's activity over a work surface or interactive display; monitoring the inventory or theft of products on a retail store shelf; locating and aligning parts for robotic assembly in manufacture; and recreational games or toys relying upon placement and movement of objects, to name a few.
One common method of identifying and tracking objects employs a visible “tag” or target marking that is affixed to the desired object and uses a computer vision tracking system to monitor the object. U.S. Pat. Nos. 6,301,763, 5,828,770, and 4,672,562, incorporated herein by reference, disclose various machine vision methods for identifying and tracking the 3D movement of objects. While the low cost of such optical tags and markers is an attractive feature, the cost of the camera and vision system is not sufficiently low for many consumer applications. Additionally, vision-based systems require line-of-sight access between the visible marker and the detector, which is difficult to employ in non-controlled environments and lighting conditions, such as for home or retail applications.
Another method of detecting and tracking objects employs an “active” electronic tag affixed to the object, which contains circuitry for transmitting a radio frequency signal that can be used by the host unit to determine the object's identity, presence, orientation or movement. As an example, U.S. Pat. No. 6,204,764, incorporated herein by reference, discloses a method for identifying and tracking objects such as key cards and folders inside a filing cabinet drawers. Although radio-frequency tagging methods are robust and do not require line-of-sight, the expense of the electronic circuitry inside these tag makes this approach prohibitive for low-cost applications.
As a means of reducing cost, it is also possible to tag an object with an electromagnetically resonant structure, such as an “LC” resonator having an identifiable and detectable resonant frequency and Q factor. U.S. Pat. Nos. 6,020,849 and 5,386,219, incorporated herein by reference, provide a method for tracking such tagged objects over a surface using an electronic sensing array of coils or electrodes. This technology is commonly used in digitizing pen tablets and computer automated design (CAD) stylus input devices. While the electromagnetic tags employed in such systems are relatively low cost, the electronic switching circuitry and wiring required to multiplex the signals throughout the sensing array make these systems too costly for simple mass market products such as retail store displays, a home medicine cabinet shelf, or children's toys.
Other methods for identifying objects have also been invented in the field of anti-counterfeiting and authentication. U.S. Pat. Nos. 5,434,917 and 3,878,367, incorporated herein by reference, disclose methods for identifying and authenticating credit cards through the use of randomly dispersed embedded magnetic particles that are detected as the credit card is swiped past a specialized scanner. U.S. Pat. No. 3,519,802, incorporated herein by reference, describes a method for electromagnetically marking a credit card through the use of embedded conducting plates; detection circuitry for this invention is not described. U.S. Pat. No. 5,992,601, incorporated herein by reference, discloses an apparatus for identifying and sorting currency that has been tagged with specific patterns of magnetic ink. While such anti-counterfeiting and authentication technologies provide a rudimentary means of identifying objects, the detection means is generally limited to specialized scanning and sorting apparatus with fixed geometries, and not adaptable or scalable to surfaces such as table tops, desks, shelves, retail display fixtures, or game boards. Additionally, these inventions do not provide a means for tracking the position or orientation of objects over a surface.
SUMMARY OF THE INVENTION
The present invention provides a method of identifying objects over a surface and a means for determining the position and orientation of the specified objects with respect to the sensing surface. The present invention combines the low-cost advantage of using vision-based tags (e.g. barcodes) with the versatility and security of electronic tagging methods. Furthermore, the present invention can be easily implemented with a conventional manufacturing process, such as printing or attaching a label, and still achieve the ability to operate via non-optical means, such as through a table-top or through packaging material such as an envelope, plastic casing, or product label.
The present invention entails the use of a reference surface, comprised of an array of electrodes or coils generating electromagnetic radiation having a characteristic frequency of oscillation, typically in the range 1-50 MHz. The objects in proximity to the sensing surface couple electromagnetically to the array of electrodes and coils, which then alters the characteristic frequency of one or more elements in the array. The resulting frequency shifts are thus an indirect measure of the electromagnetic response of the object. By monitoring the individual frequency shifts among the array elements, one or more objects in proximity to the surface can be sensed.
Changes in the characteristic frequencies of the elements are measured using a threshold detector and frequency counter, both of which can be easily implemented using a low-cost microcontroller, for example. Although changes in the sensing field induced by the object can also be monitored by other standard methods, such as measuring changes in the amplitude or phase of the sensing voltage, the technique of frequency-counting is much more inexpensive, requiring a minimal number of electronic components.
For most applications of this invention, the area of each sensing element (electrode or coil) in the sensing array would typically be in the range of 0.1 square centimeters to 100 square centimeters. A densely-spaced array of small sensing elements provides better lateral resolution; however, larger sensing elements provide a greater detection distance, since they produce probing fields that extend a further distance perpendicular to the array surface. In a given application, a combination of large and small sensing elements can also be used.
In the first embodiment of the present invention, rudimentary identification and detection of each object is accomplished by noting the intrinsic electromagnetic response of the material comprising the object (for example, distinguishing between a plastic box, a metal box, or container of milk). The characteristic electromagnetic properties of the objects can be intrinsic to the object or can be engineered, such as through the use of electrically conductive, magnetic, or dielectric materials applied to the object.
More significantly, for the case of a plurality of objects having similar electromagnetic properties, such as a stack of magnetic-ink-coated paper, this embodiment enables the ability to estimate the quantity of objects present. This ability is particularly relevant for inventory-monitoring applications, such as counting the number of greeting cards in each pocket of a display rack, or counting the number of magazines in a vending machine row.
In a preferred embodiment of the present invention, a quantifiable method of object identification is further achieved through the use of electromagnetic markers, such as electricall
Barlow John
Bhat Aditya
Testa Hurwitz & Thibeault LLP
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