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BACKGROUND AND SUMMARY OF THE INVENTION
For a period of several years, continuing efforts have been maintained to
safeguard valuable documents and other objects against counterfeits and
misuse. One such effort has involved producing specific forms of objects
that are exceedingly difficult or impractical to duplicate. As a related
cosideration, such objects must be recognizable for their identifiable
characteristic. In that regard, it has been proposed to sense the
identifying characteristic of an object, reduce the characteristic to a
manageable data format and record such data on the object as a so-called
"escort memory". For example, U.S. Pat. No. 4,423,415 (Goldman) discloses
utilizing the inherent random characteristic of bond paper to identify
individual documents. In another arrangement, U.S. Pat. No. 4,114,032
(Brosow et al.) discloses embedding magnetizable particles, e.g. fibers,
in documents to accomplish an identifiable characteristic. Various other
schemes for characterizing objects including documents have been proposed.
However, a continuing need exists for alternative and improved forms of
such systems to accommodate the needs of economy and expediency.
Magnetic materials have been developed as effective mediums to record data.
Magnetics are generally inexpensive and relatively immune from dirt and
small scratches. In general, the present invention is based on recognizing
certain random characteristics of magnetic medium and utilizing such
characteristics as a basis for identification. For example, magnetic
medium may be printed or otherwise disposed on a base or substrate sheet
of paper or paper-like medium, to impart random magnetic characteristics
that may be repeatably sensed to identify an object. An effective form of
document identification is disclosed herein utilizing a repeatably
sensible, random characteristic of a magnetic substrate deposited on a
document. The document also carries data indicative of the characteristic
that may be used for verification by comparison.
In accordance with one technique of the present invention, a base member,
e.g. paper, provides a support substrate surface on which a layer of
magnetic substance is disposed to possess a repeatably sensible, random
characteristic. The magnetic substance may vary as a result of:
nonuniformity of the paper surface, nonuniformities in printing or other
deposition process, or variations in the dispersion of magnetic particles.
Thus, density variations are randomly created that uniquely characterize
an individual document and furthermore are fixed and repeatable. The
random characteristic is sensed and may be recorded on the document as
with a magnetic stripe as well known in the prior art. Of course, other
machine-readable indicia as optical codes may also be utilized. In any
event, such a document may be verified or authenticated by freshly sensing
the random magnetic characteristic, reducing it to a data format as
before, and comparing the result with the recorded data format. In
accordance herewith, various production and verification systems are
disclosed and in that regard specific sensing techniques are set out.
As disclosed in detail below, the system hereof may be variously
implemented using different forms of magnetic medium, different support
substances and different production and utilization techniques. For
example, the random magnetic characteristic may be accomplished by
printing a document with varying magnetic materials. Also, various
techniques may be employed to precondition and sense the magnetic layer
for comparison.
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings, which constitute a part of this specification, exemplary
embodiments of the invention are set forth as follows:
FIG. 1 is a plan view of a document according to the present invention
illustrated as a stock certificate;
FIG. 2 is an enlarged fragmentary sectional view take through a portion of
the document along a magnetic characteristic of FIG. 1;
FIG. 3 is a view similar to FIG. 2 illustrating a magnetic characteristic
of a medium;
FIG. 4 is a block diagram of a document production system in accordance
with the present invention;
FIG. 5 is a block diagram of a document verification system in accordance
with the present invention;
FIG. 6 is a schematic diagram illustrating sensory operations for use in
the systems of FIGS. 4 and 5; and
FIG. 7 is a diagram illustrating a sensor arrangement to accomplish the
operations illustrated in FIG. 1.
DESCRIPTION OF THE ILLUSTRATIVE EMBODIMENTS
As indicated above, detailed illustrative embodiments of the present
invention are disclosed herein. However, physical identification media,
magnetic substances, data formats and operating systems structured in
accordance with the present invention may be embodied in a wide variety of
forms, some of which may be quite different from those of the disclosed
embodiments. Consequently, the specific structural and functional details
disclosed herein are merely representative; yet in that regard they are
deemed to afford the best embodiments for purposes of disclosure and to
afford a basis for the claims herein which define the scope of the present
invention.
Referring initially to FIG. 1, a document 10, symbolized as a stock
certificate, is illustrated embodying the present invention. Specifically,
in addition to considerable printed indicia 12, the document 10 carries a
conventional magnetic recording stripe 14 and a magnetic characteristic
layer 16 also in the configuration of a narrow strip.
The layer 16 has a magnetic characteristic as described in detail below,
which can be sensed and reduced to a convenient data format to identify
the document 10. Specifically, as illustrated in FIG. 1, the magnetic
characteristic of the layer 16 is sensed and reduced to a digital format
which is recorded on the magnetic stripe 14. Accordingly, the document 10
can be effectively authenticated by freshly sensing the magnetic
characteristic of the layer 16, processing the sensed signal according to
a predetermined format, and comparing the result with data from the
magnetic stripe 14. Of course, a variety of correlation and signal
processing techniques may be employed along with a variety of sensing
techniques; however in any event, a favorable comparison verifies the
authenticity of the document 10.
Some consideration of the relationship between the magnetic stripe 14 and
the layer 16 is appropriate with respect to understanding the disclosed
system embodying the present invention. The magnetic data stripe 14
involves techniques of the magnetic recording industry wherein the media
of the magnetic stripe is an integral part of a magnetic read-write
system. Accordingly, the media of the magnetic stripe 14 is tightly
specified and highly controlled in accordance with well known standards of
the art. Conversely, the media of the layer 16 varies significantly and in
fact it is such variation that affords the characteristic for identifying
the document 10. The density along the magnetic layer 16 varies for three
primary reasons, i.e. the nonuniformity of the paper in the document 10,
the process of depositing the layer 16 on the document 10 and the
dispersion of magnetic particles in the layer 10. The density variations
are randomly created to afford a unique document and are fixed and
repeatable to identify the document. In that regard, as used herein,
density and remanent magnetization are equivalents. Of course, in some
cases, the remanent magnetization may vary in a fixed, repeatable pattern
for a given magnetic layer while the density remains relatively constant.
Such a fixed, repeatable pattern is a form of the characteristic as
described and utilized by the present invention for object identification.
At this point it may be helpful to discuss methods of creating random
magnetic characteristic manifestations or "noise" attendant sensing the
layer 16. Forms of "noise" can be defined as follows. First, DC noise
results when a magnetic media has been magnetized by a DC field.
Modulation noise is defined as variations in the reproduced amplitude
which occur when an AC signal of constant amplitude is recorded. Bias
noise occurs when an AC bias is applied to a recording head with
substantially no signal current, e.g. no signal riding on the AC bias.
Bulk-erased noise results when a media has been demagnetized by a cyclic
field. Note that bulk-erased noise occurs because a media is composed of
numerous magnetic domains which always remain magnetized. That is, only
the polarity changes. Demagnetization on a large scale causes
substantially equal numbers of particles to be magnetized in opposing
directions with a net difference of substantially zero. Accordingly, in a
perfectly dispersed media (magnetic particles equal) that is magnetized
longitudinally in a perfectly uniform manner, flux emanates only at the
ends. As a result, the noise would be the same as if the media was in a
state of zero net magnetic flux. Any change will cause flux, that is,
variance from the state of zero net magnetic flux is caused by
nonuniformity.
Essentially, nonuniformity of magnetization can be attributed to three
major causes, specifically: (1) variation in the amount of magnetic
material per unit of volume along the media (produced by the printing
process or nonuniformities in the substrate surface as paper); (2)
variations in the magnetic material; and (3) fluctuations in the applied
recording current.
Each of the sources of nonuniformity will be considered independently as
related to the present development. However, preliminarily reference will
be made to the enlarged sectional view of FIG. 2 illustrating
nonlinearities of the magnetic layer 16. Specifically, the layer 16 is
deposited on a sheet 18 providing a support substrate. The sheet 18 may
comprise a multitude of different papers or paper-like materials as a
product comprising a collection of plastic fibers known as "Premoid".
The sheet 18 has a surface 20 indicated as an irregular boundary which
receives and supports the magnetic layer 16 and a protective coating 17.
The irregularity of the surface 20 along with irregularities in the
surface 22 of the layer 16 are illustrated in FIG. 2 and constitute a
source of nonuniformity, i.e. variation in the amount of magnetic material
per unit of volume along the media. The nonuniformity affords a
characteristic that is enhanced by the layer 17 of lacquer, enamel or
other nonmagnetic coating that may vary the spacing of a sensor head from
the layer 16.
The nonlinearity is illustrated graphically in FIG. 3. Specifically, an
idealized section of the support substrate 24 is illustrated carrying a
similarly represented section 26 of magnetic media. That is, for purposes
of explanation, and rather than to illustrate the irregularities and voids
of substrate as paper, in FIG. 3, solid lines are shown to depict perfect
or uniform dispersion of magnetic material 26 on a perfect or uniform
support substrate 24.
In FIG. 3, the dashed lines 28 and 30 illustrate variations from the
idealized structure which result from printing process variations
(asperity) and substrate variations (nonuniformity). That is, the asperity
or roughness indicated by the dashed line 28 is attributed to the printing
process for depositing the section 26. Variations in the substrate
illustrated by the dashed line 30 are caused by variations at the surface
of the substrate 24, e.g. the paper.
The variations illustrated in FIG. 3 provide the basis for individual
characteristics which enable identifying objects in accordance herewith.
That is, variations in the magnetic material thickness as illustrated in
FIGS. 2 and 3 afford a characteristic that can be repeatedly measured for
identifying an object.
Referring to FIG. 3, it is to be noted that the irregularities illustrated
by the line 28 (asperity) may change as the surface defined by the line 28
is abraded as with use of the document. However, the variations
represented by the line 30 are less susceptible to change. These
considerations are significant in implementing systems for individual
documents and applications where the documents may or may not be subject
to wear, as described in detail below.
As indicated above, magnetic character also may result from varying the
magnetic material in the layer 16 (FIG. 1). Specifically, character may be
obtained by using an ink mixture to print the layer 16 which carries
magnetic particles of varying size, or like magnetic particles that are
variably dispersed. Such a technique may be employed to provide the
magnetic character or to enhance the character of a magnetic layer.
Similar structures can be accomplished by heat transfer, slurrying or
gluing.
As indicated above, character may be sensed as a result of variations in
the recording current. Generally, such variations are accounted for in
implementations of the present invention by subjecting the magnetic layer
to a standardized treatment, e.g. erasing and recording to a standard.
In view of the above considerations, techniques for producing the document
10 may now be considered in a more meaningful context. Surface
nonuniformity is a well known characteristic of various paper forms.
Accordingly, the character of the document 10 can be enhanced by selecting
a paper or other substrate possessing a particularly nonuniform or
irregular surface. Somewhat similarly, various forms of ink and printing
techniques are known to deposit coatings or layers which are smooth to
varying degrees. Accordingly, enhanced asperity can be attained.
With the considerations of paper and printing in view, a substrate is
selected, cut to the desired document size and printed with the layer 16
as illustrated in FIG. 1. As a part of the operation, the printed indicia
12 may also be deposited. To complete the physical form of the document
10, the magnetic stripe 14 may be adhesively affixed. Such a "raw"
document form is then processed to accomplish the document 10 in
accordance herewith. Such processing involves apparatus as represented in
FIG. 4 and will now be considered in detail.
A raw form of the document 10 is received by a transport mechanism 32 (FIG.
4, right central) the physical relationship being symbolically represented
by a dashed line 34. A wide variety of transport mechanisms for dynamic
magnetic recording are well known in the prior art and may be implemented
for use as the mechanism 32 for processing the document 10. Essentially,
such mechanisms detect the presence of a document then move the document
or other sheet form to facilitate dynamic sensing and recording. As
represented in FIG. 4, the mechanism 32 moves the document 10 to the right
as represented by an arrow (upper right).
In association with the transport mechanism 32, several magnetic heads are
mounted in transducing relationship with the magnetic data stripe 14 and
the magnetic characteristic layer 16. Specifically, a magnetic record head
36 (right) is supported in transducing relationship with the magstripe 14.
The head 36 receives recording signals from a data compiler 38 which is
connected to receive signals from a data source 40 and a signal processor
42.
The signal processor 42 receives signals from a sense head 44 disposed at
the left as illustrated, in transducing relationship with the layer 16.
Essentially, the head 44 senses the characteristic of the layer 16 in the
form of an electrical signal which is applied to a processor 42 to provide
a digital format that is combined with other digital data from the source
40 by the compiler 38 and recorded on the magstripe 14.
In considering the relationship between the heads 36 and 44, as indicated
above, the transport mechanism 32 transports the document 10 from left to
right as depicted. Consequently, the head 44 substantially completes a
scansion of the document 10 before the head 36 begins to scan the document
10. Thus, the head 44 reads the characteristic from the layer 16 and
thereafter the head 36 records signals representative of the
characteristic in the stripe 14. Preceding the head 44 are conditioning
heads, specifically an erase head 46 and a record head 48. The erase head
46 is driven by an erase circuit 50 and the record head 48 is driven by a
record circuit 52.
Considering the operation of the system of FIG. 4 to complete the document
10 from a raw form, assume the placement of such a form in the transport
mechanism 32 for transducing action in cooperative relationship with the
magnetic heads 36, 44, 46 and 48. As the raw form of the document 10 is
initially propelled under the head 46 (moving from left to right) the
layer 16 is erased or cleared of spurious magnetic content. The layer 16
next passes under the head 48 which is driven by a circuit 52 to
accomplish a standard recording on the layer 16. For example as explained
above, the head might be driven with a linear DC signal to accomplish DC
noise, by a linear AC signal to accomplish modulation noise or by a linear
bias signal to accomplish bias noise. A nonlinear recording also might be
employed. In any event, a standard record is thus accomplished.
As the document continues to move, the layer 16 next encounters the head 44
which senses the magnetic characteristic of the preconditioned layer 16.
Consequently, an analog signal manifesting the characteristic is supplied
from the head 44 to the characteristic signal processor 42. A portion or
portions of the analog signal may be selected to manifest select areas of
the layer 16 as by well known sampling techniques and apparatus in the
processor 42 to provide specific values for reduction to digital
representations. Note that techniques for selecting and processing area
representative analog signals are disclosed in the above-referenced to
Goldman, U.S. Pat. No. 4,423,415.
The processor 42 also incorporates an analog-digital converter as well
known in the art for converting the selected analog samples. Accordingly,
a format of select digital signals representative of the magnetic
characteristic are supplied from the processor 42 to the compiler 38.
As suggested above, the compiler 38 also receives other data which may be
representative of information concerning the document 10 and the
techniques employed for sensing the characteristic of the layer 16. In the
disclosed embodiment, the data specifies the location of the
characteristic features of concern. Such data is instrumental in
selectively sampling the analog signal representative of the
characteristic to obtain the specified signals to be digitized.
The compiler 38 assembles the digital data and accordingly drives the
record head 36 to accomplish the desired record in the magnetic stripe 14.
With the completion of such recording, the document 10 is complete and may
be subsequently processed for verification as genuine.
Documents produced in accordance herewith may be subject to a wide variety
of different applications and uses. In the exemplary form of a stock
certificate, the document 10 may be released to the owner and with
reasonable safety may be placed in the hands of a bailee, for example as a
pledge. Usually, after periods of random custody, it is important to
verify such a document as genuine. The system of the present invention
contemplates such verification and confirmation of the document 10 as
genuine. A system of verification is illustrated in FIG. 5 and will now be
considered in detail. The system of FIG. 5 receives the document 10 in a
transport mechanism 60 somewhat as the mechanism described above with
reference to FIG. 4. However, the mechanism 60 is physically associated
with a set of transducer heads in an arrangement distinctly different from
that described above with respect to FIG. 4. Specifically, as the
transport mechanism 60 propels the document 10 from left to right (as
indicated), initial transducing relationship is established between the
magnetic stripe 14 and a sensing head 62. Note that in accordance with the
prior art, the transport mechanism 60 senses the presence of the document
10 and supplies a signal. In the system of FIG. 5 that signal is manifest
in a line 64.
As the document 10 moves to substantially complete the scansion of the
stripe 14 by the head 62 (as illustrated), the layer 16 encounters a
sequence of heads 66, 68 and 70. Accordingly, the magnetic stripe 14 is
sensed by the head 62 well ahead of the heads 66, 68 and 70 sensing the
layer 16.
In sensing the magnetic stripe 14, the head 62 supplies digital data to a
decoding circuit 72 which is in turn connected to a register 74.
Accordingly, the magstripe 14 is sensed, the contents is decoded and set
in the register 74. Specifically, the decoded data specifies the
characteristic data of interest, the location of that data and any desired
ancillary information, all in a digital format.
As the register 74 is being loaded, scanning of the layer 16 begins. The
head 66 is connected to an erase circuit 76 while the record head 68 is
connected to a record circuit 68. Accordingly, the heads 66 and 68
precondition the layer 16. The preconditioned layer 16 is then sensed by
the sense head 70, connected to a characteristic signal processor 80. Note
that the function of the heads 66, 68 and 70 is similar to that of the
heads 44, 46 and 48 as described with respect to FIG. 4. That is, the head
66 clears the layer 16, the head 68 imposes a predetermined recording
pattern and the head 70 senses the layer to provide the characteristic
signal as described in detail above. The resulting characteristic signal
is supplied to a processor 80.
The data decoding circuit 72 (upper left) supplies information to the
processor 80 to specify the selection or sampling of values in the
characteristic signal. That is, the characteristic signal processor 80
samples the same predetermined portions of the received signal to derive
sets of digital values for comparison and may be as described in the
above-referenced U.S. Pat. No. 4,423,415.
The sampled values are digitized then supplied from the processor 80 to a
correlation circuit 82 which is also coupled to the register 74.
Functionally, if appropriate, the correlation circuit 82 actuates an
output device 84 to manifest predetermined degrees of similarity between
the freshly observed characteristic data and the previously recorded
characteristic data from the same locations. The correlation circuit 82
may take various well known forms. Peak values exceeding a threshold can
be tested, various sampled values can be used or correlation algorithms
may be implemented. Various forms of signal devices might be employed in
the output device 84 as well known in the prior art.
To consider a verification operation by the system as illustrated in FIG.
5, assume the placement of the document 10 in cooperative relationship
with the transport mechanism 60. Accordingly, the transport mechanism 60
senses the presence of the document 10 and provides a signal through the
line 64 to initiate the operation of the processor 80 and the circuit 72
to perform transducing operations. As suggested above, the signal
indicating the presence of a document may be provided by an optical sensor
in accordance with well known and widely used techniques of magnetic
stripe card readers.
The initial transducing relationship occurs when the magstripe 14 of the
document 10 encounters the head 62. As a consequence, digital values
representative of the document characteristic (layer 16) are sensed from
the stripe 14 along with certain information to indicate the specific
location of values for comparison within the layer 16. Other data may also
be provided. The data relating to identification of the characteristic is
supplied to the processor 80 while signals representative of the actual
select characteristic are set in the register 74.
When the head 62 has substantially completed its scan of the stripe 14, the
layer 16 encounters the heads 66, 68 and 70 in that sequence. The head 66
clears the layer of any spurious signals after which the head 68 records
the layer with a predetermined test signal. Thereafter, with the layer
preconditioned, the head 70 senses the recorded signal (along with other
noise) for processing by the processor 80 to develop the select
characteristic values in a digital format.
The select characteristic values are supplied to the correlation circuit 82
which also receives previously sensed similar-format values from the
register 74. Accordingly, the correlation circuit 82 determines the degree
of correlation and in accordance with predetermined standards actuates the
output device 84 accordingly. Thus, depending on the degree of correlation
or similarity between the fresh characteristic values and the previously
recorded characteristic values, the document 10 is authenticated as
genuine.
As indicated above, the use of a magnetic layer to provide an identifying
characteristic affords different possibilities which account for random
characteristics in a magnetic medium. As explained, the characteristic
might result from variations in the gross amount of magnetic material,
variations in the individual quantity of magnetic material or variations
in the recording signal. Any of such variations might be sensed, refined
and converted to a digital format using signal processing circuits as well
known in the prior art. As an additional consideration, signal selectivity
may be exercised in the interests of the nature of the document 10 or its
intended use.
As indicated above, the character resulting from variations in the gross
amount of magnetic material per unit of volume along the layer 16 are
attributed both to the printing process and nonuniformities of the
substrate surface, see FIGS. 2 and 3. As explained with respect to FIG. 3,
the character relating to irregularities indicated by the dashed line 28
(asperity) may change somewhat with use of the document 10 in which the
surface of the layer 16 is abraded. In the event that anticipated wear is
negligent, a magnetic characteristic may be sensed by providing a
recording current in the magnetic record head to a level so that the
effective recording field is nearly uniform throughout the magnetic
material depth. For example, referring to FIG. 6, the idealized substrate
section 24 and the magnetic section 26 (similarly idealized) are
illustrated in relation to a magnetic recording head 88. Note that a
dashed line 90 indicates an effective recording field that approaches
uniformity through the depth of the section 26.
A sensing of the section 26 that has reached maximum remanent magnitization
yields a waveform that is directly related to the amount of magnetic
material along the substrate which is fixed and repeatable relative to
specific locations along the magnetic layer. Such a waveform represents a
raw form of an observed characteristic. However, in some instances wear of
the magnetic layer 16 (FIG. 1) will not be expected to be negligible and
as a result, compensation may be provided. For such an application, a
select magnetic characteristic is obtained by deriving the waveform
described above along with another waveform that indicates the asperity
variations as illustrated with respect to a head 92. Note that the dashed
line 94 involves a magnetic field which is limited to a space near the
surface of the section 26.
While the head 92 senses the surface (asperity), the head 88 senses the
total substrate section 26. Accordingly, the heads sense at different
depths and a characteristic that is somewhat immune from surface wear in
the magnetic layer may involve the subtractive combination of a deep field
minus a shallow field. As a result, the asperity signal is eliminated from
the total sensed signal. Essentially, the asperity waveform is the
component which is susceptible to modification with wear of the document.
Note that the asperity waveform may be derived by passing a DC current
through the recording head adjusted to produce minimum noise. The
effective field penetrates to a level above the substrate nonuniformities.
For example, a remanent magnitization of fifty percent of the maximum
remanent magnitization accomplishes such an operation. A read-back of the
magnetic stripe then generates the asperity waveform.
To illustrate the selective-depth sensing operation, a magnetic layer 16 is
illustrated in FIG. 7 which is being sensed by heads 102 and 104 similar
to the heads 88 and 92 of FIG. 6. The characteristic signals from the
heads 102 and 104 are processed respectively by the processors 106 and
108. The signal from the processor 108 is delayed by a delay circuit 110
to be in space-time coincidence with the signal from the processor 106.
The delayed signal from the circuit 110, and with the signal from the
processor 106 are applied to a difference circuit 112 which essentially
subtracts the asperity waveform from the total characteristic waveform. As
a result, a characteristic analog signal is provided at an output 114
which is somewhat immune to changes in the surface of the magnetic layer
16. The structure of FIG. 7 may replace either of the single heads 46 or
70 to provide a select characteristic somewhat immune to surface
variations of the chracteristic magnetic layer.
As will be readily appreciated from the above illustrative embodiments, the
system hereof is susceptible to a great number of modificat | | |
