Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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MICROWAVE READABLE DIELECTRIC BARCODE
FIELD OF THE INVENTION
The present invention relates to barcodes, to the methods and materials to
fabricate
such barcodes, as well as to the methods of how to write and read the
information
represented by barcodes. In particular, the invention relates to barcodes that
are composed
of dielectric materials.
BACKGROUND OF THE INVENTION
Today uniform product.code (UPC) labels are on practically every product
produced
in the world. Optical barcodes have become so widely accepted because of their
low
production costs, device complexity, and high durability. These same
properties which
caused their success now limit their usefulness in commercial applications.
The simple
design has low production costs, but is severely limited in the amount of data
it can
represent. The design also allows for simple and cheap detection through
optical reading
systems. However, optical reading systems require a direct, unobstructed path
for light to
be emitted onto the barcode and then reflected back to the sensor. This
unobstructed (i.e.,
"line-of-sight") property of optical read barcodes limits their usefulness.
For example, to
conduct inventory management, objects must be placed in a specific physical
location for
their identification information to be read.
To combat the "line-of-sight" problem posed by traditional barcodes, radio-
frequency identification solutions have been developed. Radio-Frequency
Identification
(RFID) tags store and transmit identification information that is similar to
the information
stored in barcodes. A RFID system consists of an interrogation device that
broadcasts a
radio signal and a RFID tag which receives said radio signal. With a passive
RFID tag, the
radio signal power itself is used to power-up a small microchip within the
tag, which then
transmits its unique identification code back to the interrogation device. The
radio waves
used to interrogate RFID tags for can pass through many materials, therefore
solving the
"line-of-sight" issue present in optically read barcodes.
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RFID technology does, however, have its own problems. RFID tags can be divided
into two major categories: active and passive. Active RFID tags contain their
own power
source which increases the distance in which it can provide identification
information.
Problems with this type of tag include cost of production due to the
complexity of such a
device as well as maintenance issues, physical size and weight constraints,
and power
consumption. Passive tags overcome cost and complexity issues, but in turn
have greatly
restricted operability and flexibility. Because a microchip is embedded in an
RFID tag,
along with radio frequency receivers, front ends, and transmitters, the device
complexity
and associated cost is much higher than that of optical barcodes.
Because of economic issues industry has been tentative in its adoption of
RFID.
Wal-Mart Corporation recently rolled out an initiative to have all of their
suppliers utilize
RFID tagging to aid in their inventory management and supply chain. While this
program
has benefits, it raises a new problem of data redundancy. Not only will each
product now
have barcode identification information on it, but it will also have RFID
Identification. The
use of two identification methods for different purposes is costly and
unneeded. Another
problem with RFID technology is the separation between an object and its
identification
information. An object is not directly identifiable as it was when a barcode
was embedded
directly on the object itself. A tag is affixed to the object, therefore
causing all relevant
data to be associated with not the object itself, but with a tag on the
object. If a tag
becomes separated from the object the identity of that object is lost.
One example of the problems associated with data separation caused by RFID
technology can be seen in the field of livestock tracking. Since the advent of
RFID
solutions; the agriculture industry has been attempting to utilize this
technology for means
of animal identification in the form of a RFID tag affixed to an ear tag
placed on the
animal. (See U.S. Animal Identification Plan - National Identification
Development
Team, available on the Internet at the U.S. AIP website information page,
hereby
incorporated by reference in its entirety.) Studies have shown that
approximately 10% of
ear tags become separated from the animal throughout its life cycle either by
accidental
separation, or through human removal. If data relative to an animal is
associated with a
RFID tag, and the tag becomes separated from the animal all data associated
with that
animal is also lost. Thus, with RFID technology, information is related not to
the object
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itself, but to a tag which is then associated with the object. This three
party identification
solution is more complex than a direct identification solution, and is
therefore less reliable
and less permanent.
One solution to all the aforementioned problems with the above identification
technologies is proposed in European Patent No. EP1065623A26 to J. F. P.
Marchand,
titled "Microwave Readable Barcode" (the EP '623 Patent"), which is hereby
incorporated
by reference in its entirety. The EP '623 Patent describes a microwave
readable barcode
that consists of conductive bars made from a conductive ink or conductive
foil. Barcode
information can be encoded using conductive bars of different lengths,
different angles, or
different positions. When the device is illuminated by a microwave signal, the
encoded
information can be read through the attenuation, or non-attenuation, of the
signal by the
conductive bars, and/or the scattering, or the non-scattering, of the
microwave signal by the
bars. A complete microwave readable barcode system includes conductive
barcodes, a
transmitter that radiates a microwave signal onto the barcode, and a detector
that senses the
microwave signal reflected from the conductive bars. Barcode systems can use
multiple
microwave signals that differ in one or more respects, such as polarization or
wavelength.
While the approach disclosed in the EP '623 Patent solves two problems (the
"line-
of-sight" readability restrictions associated with optical barcode systems,
and the data
separation problem associated with RFID technology), the disclosed microwave
readable
barcodes have limitations and problems. The complexity of a device consisting
of either
conductive bars of conductive foil causes economic hurdles in the production
of the
precursor material and in the fabrication of the conductive barcode.
Therefore, embedding
of a conductive barcode in an object is difficult and costly. The
oxidation/corrosion
processes limit the reliability of the conductive barcode. High cost of
biocompatible metals
makes conductive barcodes non-feasible for animal labeling. Also, it is
impossible to make
an invisible conductive barcode.
Missing from the art is a barcode system that has increased commercial
application
with increased data representation, and overcomes the problems of data
separation, "line-
of-sight" issues, and production problems. The present invention can satisfy
one or more
of these and other needs.
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SUMMARY OF THE INVENTION
The present invention relates to a dielectric barcode which is a pattern
fabricated
from a dielectric material, and a system for interrogating the dielectric
barcode. In
accordance with one aspect of the invention, a plurality of dielectric bars
are arranged on or
within a substrate. The dielectric bars are arranged in a spatial manner to
encode
information.
In another aspect of the invention, the dielectric bars are formed from a
dielectric
material having a suspension of a metallic material in a density insufficient
to provide
conductivity at an operating frequency of a remote interrogator.
In accordance with another aspect of the invention, a barcode interrogation
system
comprises a dielectric barcode formed from a plurality of dielectric bars
arranged on or
within a substrate in a spatial manner to encode information, a signal
transmitter connected
to a first antenna so as to radiate an interrogation signal on the dielectric
barcode, a signal
receiver connected to an antenna so as to receive a return signal from the
dielectric
barcode, and a processor connected to the receive signal and operable to
decode the
encoded information.
In yet another aspect of the invention, the interrogation system is operable
to scan
the interrogation signal through space to read the dielectric barcode. The
system is capable
to scan the signal by rotating the transmitting antenna, frequency shifting or
phase shifting
of the transmitted signal.
These and other aspects, features, steps and advantages can be further
appreciated
from the accompanying figures and description of certain illustrative
embodiments.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention together with further objects and advantages thereof, may best
be
understood by making reference to the following description taken together
with the
accompanying drawings in which:
Fig. 1 illustrates a schematic rendition of a dielectric barcode system
embodying the
present invention;
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Figs. 2a-2e illustrate several classes of microwave readable dielectric
elements; and
Figs. 3a-3c illustrate time variant reading of dielectric elements.
Throughout the drawings, the same reference characters will be used for
corresponding or similar elements.
DETAILED DESCRIPTION OF THE ILLUSTRATIVE EMBODIMENTS
By way of overview and introduction, presented and described are embodiments
of a
dielectric barcode which is a pattern fabricated from a dielectric material.
The dielectric
barcode is readable by a microwave device. A dielectric barcode formed from
any
dielectric material in any form is within the contemplation of this invention.
For instance
the dielectric barcode material can be in the form of an ink, a powder, or a
solid material.
An interrogating microwave signal propagates through the surrounding media
where it is
effectively reflected and/or absorbed by the dielectric barcode. Similar to an
x-ray
"shadow image" the pattern made from the dielectric material barcode can be
visualized by
the transmitted or reflected microwave radiation.
In an embodiment of the invention, the dielectric barcode is formed from a
dielectric
material with a suspension of a ferroelectric material, having a high
dielectric permittivity,
within the dielectric material. The high dielectric permittivity of the
ferroelectric material
creates a strong microwave contrast with the media surrounding the
ferroelectric barcode at
particular operating frequencies.
In another embodiment of the invention, the dielectric barcode is formed from
a
dielectric material provided with a fine powder suspension synthesized by
chemical
methods, and dispersed in suitable fluidic system to obtain a dielectric ink.
A pattern is
made from the dielectric ink by inkjet printing, injection, spraying, drawing
or any other
technique. Injection can be done by an impetus injection mechanism where the
dielectric
material with the fine powder suspension is deposited beneath a device's
plastic subsurface
or beneath the skin layer of an animal to form a dielectric barcode. A non-
inclusive list of
suitable materials for suspension within the dielectric material to form the
dielectric inks
includes, but is not limited to, heavy metals, heavy metal salts, piezo-
electric ceramics,
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barium titanate (BaTiO3), sodium potassium niobate (NaKNbO3), and lead
zirconium
titanate (PbZrTiO3 aka "PZT"). Metallic nano-particles (e.g., titanium nano-
particles) are
also suitable for suspension within dielectric materials to form the
dielectric barcode. As is
readily understood by a person of skill in the art, at different operating
bands across the
spectrum a particular dielectric material's perturbation to an electric field
changes. For
example, a dielectric material that is transparent at one operating band may
become very
lossy at another operating band. Thus, the suspension of particles within the
dielectric
material forming the dielectric barcodes optimizes performance at the
particular operating
band of interest. The density of these suspensions are enough to sufficiently
alter the
refractive and reflection properties of the dielectric material, but not dense
enough to
render the dielectric material conductive in the operating band.
Due to dielectric permittivity (g), the electromagnetic length in a dielectric
material
is ,fe shorter than in a vacuum. This phenomenon allows for the dielectric
barcodes to be
significantly miniaturized. For example, a resonant barcode composed of
dielectric
material with the dielectric permittivity e- 1000 for 10 GHz (3 cm wavelength)
operation
will be only a millimeter in size. Dielectric barcodes can be
transparent/translucent in the
visible light spectrum, though highly contrasting for microwaves. In one
embodiment to be
used, as an example, for animal labeling, a biocompatible NaxKl_,,NbO3 ceramic
could be
the candidate material from which to make dielectric barcodes. Biocompatible
ferroelectric
ceramics can be injected under the skin remaining there as a non-degradable
tattoo for the
entire life of the animal. U.S. Patent No. 6,526,984 to Nilsoon et al., issued
March 4,
2003, and titled "Biocompatible Material for Implants" discloses the
biocompatible ceramic
Na,Ki_,,NbO3, and is hereby incorporated by reference in its entirety.
Figure 1 illustrates a schematic rendition of one embodiment of a dielectric
barcode
system 10. The system 10 includes a microwave transmitter 11 which emits a
signal 12
that radiates outwards and towards a substance 15 having a readable dielectric
element 16.
The microwave signal 12 has a wavelength 13 and is polarized such that the E-
field is in the
vertical direction 14. However, the wavelength and field polarization are not
limited to any
one value or orientation, as would be understood by a person of ordinary skill
in the art.
The frequencies of interest range from around 100 kHz to over 100 GHz, and
further up to
and including the TeraHertz (1012 Hz) frequency band. A range just above the
operation of
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satellite dishes and mobile phones (about 90 - 100 GHz) through to adjacent to
infrared
frequencies used in remote controllers (about 30 THz), and more particularly,
operating
frequencies of about several Terahertz are believed to be beneficial.
In one embodiment, the readable element 16 is a ferroelectric bar formed from
the
biocompatible ceramic NaKl_,NbO3. So as to make the barcode resonance and
polarization
sensitive to the interrogating electromagnetic wave of signal 12, the readable
element 16
has a length that is one-half the wave-length 13, and an axis that is parallel
to the direction
14. Using the formula of wavelength equals the speed of light over frequency,
the
wavelength necessary to read various sizes of dielectric barcode elements can
be calculated.
Thus,
k=c/v where: Eq. 1
k= wavelength (microns)
v = frequency (Hertz), and
c=3*10"14 m /sec (speed of light).
The required wavelength necessary to read a dielectric barcode element of a
specific
size can be calculated. For an embodiment operating in the TeraHertz operating
band, a
frequency of 1.0 THz has a wavelength of 300 m, requiring a readable element
16 to have
a length of 150 m. For multiple readable elements in a single barcode, the
readable
elements would be spaced apart one-half the wavelength. From this information
it is
possible to calculate the overall width of this embodiment of a microwave
readable barcode
from the following equation:
W = NQ,J2) +(N-1)(W) m where: Eq. 2
W is the barcode width in microns,
N is the number of readable elements forming the barcode, and
a,=wavelength (microns).
Thus, applying Equation 2, the width of a barcode tag having 96 bits would be
96 * 150 (the elements) + 95 * 150 (spaces between elements) = 14400 + 14250 =
28650
m = 28.65 mm long.
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With reference to Figs. 3a-3c, a time variant reading of the microwave
readable
barcode is illustrated. To resolve a tag of more than one dimension (i. e. , a
tag utilizing a
2-dimensional encoding scheme) a spatial relationship (e.g., an interstitial
gap) must be
established between elements. To accomplish this, a single microwave source'
can scan the
tag area relative to the time constant to achieve a 2-D "image" of the tag,
which can then
be processed to extract the information therein. Thus, by collecting the
readings relative to
time and position an image of the barcode can be reconstructed and its
information
extracted.
There are many schemes known to a person of ordinary skill in the art to
achieve a
scan of the tag area. For example, an antenna (not shown) connected to the
microwave
transmitter 11 can be physically rotated in at least one degree of freedom
(e.g., azimuth,
vertical, roll, pitch and yaw) to move the peak of the transmitted signal 12
across a group
of dielectric elements 16 which form a barcode. Alternatively, the phase or
the frequency
of the transmitted signal 12 can be varied to cause the beam collimation to
move in spatial
relation to the location of the dielectric elements. The antenna can be
composed of an array
of elements, where the inter-element phasing is controlled to adjust the
beam's spatial
location. These and other implementations and methods of scanning a
transmitted signal
through space are within the contemplation of the present invention.
With reference to Figure 1, when the transmitted signal 12 strikes the
dielectric
element 16, the signal is partially scattered and partially attenuated. The
scattered portion
18 of the signal 12 can be sensed by a sensor 20. Sensor 20 itself can be the
same antenna
connected to the transmitter 11, or a different sensor implementing the same
or different
technology as the antenna. The sensor further includes a processor capable of
decoding the
encoded information present in the dielectric barcode. As is readily
understood, sensor 20
can be implemented by separate components of an antenna, a processor, and an
output
interface.
If the sensor 20 receives a scattered signal it determines that a dielectric
readable
element exists. In that case the sensor 20 produces a predetermined output
signal. In a
binary information system, the predetermined output signal indicates the
presence of a
readable element and could be a one or a zero. Figure 1 also shows a
dielectric bar 17 that
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is much thinner than the readable element 16. The dielectric bar 17 would only
slightly
scatter the signal 12. The sensor 20 would then produce another output signal,
say a zero,
based upon a missing (low scattered) signal. Of course, the dielectric bar 17
might be
missing altogether.
While the foregoing discusses the use of binary information (zeros and ones),
the
present invention is not limited to only one type of encoding scheme. In
another
embodiment, a first ferroelectric bar of one length and/or orientation can
represent any
member of a set (such as a letter or a number). Further, a second dielectric
bar of another
length and/or orientation can represent another member of the set, and a third
and other
dielectric bars of other lengths and/or orientations might represent other
members, and so
on. By varying the wavelength and/or polarization of transmitted signal 12
these differing
lengths and orientations can be sensed and the corresponding set members
identified.
Inkjet printing technique can be applied to deposit dielectric layers and
structures
consisting of nano-sized dielectric particles. These dielectric particles can
be synthesized
by chemical methods and suspended in a suitable fluidic system. The
rheological
parameters of the fluids can be adjusted for inkjet printing. The resulting
micron-scale
patterns can be obtained with a high reproducibility and structure control.
The dielectric
local structure of the patterns can be studied by using a local dielectric
probe technique as
well as at nano-scale atomic force microscopy with a local capacitance probe
can be
employed. The deposited structures will have a chain-like self-alignment of
the dielectric
particles. Potential applications of this fast and versatile process are the
production of low-
and medium density dielectric mass storage patterns on almost any kind of
substrate and for
dielectric character recognition purposes. Printed patterns with minimal
structure
dimensions in the range of 50-100 m are easy to achieve.
The illustrated embodiments of the present invention attempt to overcome the
problems associated with the conventional identification methods discussed
above.
Dielectric barcodes solve the readability problem through utilizing microwaves
as the
method of extracting information from the tag. A dielectric barcode also
solves the
problem of data redundancy associated with the use of optical barcodes in
conjunction with
RFID technology. Dielectric barcodes can be constructed to utilize not only
optical reading
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systems, but also quasi-optical systems (i.e., systems operating at millimeter
wavelength
bands) similar to that of RFID technology to be remotely identified as well.
Dielectric
barcodes overcome the problem of data separation as well. Since dielectric
barcodes can be
directly embedded or printed on an object in a similar fashion to optical
barcodes instead of
embodied in a tag which is affixed to an object, the identification
information comes
directly from the object itself instead of from a tag placed on the object.
In particular, a non-exhaustive list of advantages offered over the prior art
by the
various embodiments of the present invention includes:
= providing cheap and reliable material for radio-frequency identification
tags;
= reducing the number of extra elements and eliminating power consuming units
connected to the device, thereby allowing a small overall device size and
complexity;
= providing advanced encoding of the identification information in the form of
spatial and temporal dispersion of the reflected/transmitted interrogating
microwave signal;
= allowing biocompatible barcode labeling of creatures;
= providing invisible barcode patterns and/or a barcode pattern deposited
beneath
the surface of the coded sample.
Thus, while there have been shown, described, and pointed out fundamental
novel
features of the invention as applied to several embodiments, it will be
understood that
various omissions, substitutions, and changes in the form and details of the
devices
illustrated, and in their operation, may be made by those skilled in the art
without departing
from the spirit and scope of the invention. Substitutions of elements from one
embodiment
to another are also fully intended and contemplated. It is also to be
understood that the
drawings are not necessarily drawn to scale, but that they are merely
conceptual in nature.
The invention is defined solely with regard to the claims appended hereto, and
equivalents.
of the recitations therein.
