Note: Descriptions are shown in the official language in which they were submitted.
CA 02188386 1996-10-21
2~~8.~86
Coded Items fog Labelling Objects - - --
This invention relates to coded items for labelling objects such as vehicles,
credit cards and jewellery, and is particularly useful for the invisible
labelling of such
objects with security marks to enable the objects to be identified or their
origin to be
identified.
Many methods are employed to protect merchantable items from theft or
forgery. Car chassis and engines have serial numbers, credit cards have
holographic
icons, etc. Ultimately, all these devices can be defeated by either removal or
replication. Ideally, an item would be marked with a security device which was
impossible to remove or replicate, or where the effort required to remove or
replicate
it exceeded the value of the item itself.
There have been several methods devised for the production of particles
which carry some form of information in such a way as to allow the particles
to
potentially be used as a method of marking or identifying an object. These
constitute
the prior art to the invention. Dillon, for example (US-A-4 243 734) describes
microdots carrying indicia identifying the owner of an article. The microdots
are small
pieces of foil which carry the printed indicia and which are mechanically cut
from a
larger sheet of foil. Because of the nature of the cutting process, the
microdots are
restricted to one of several polygonal shapes, the preference being square of
side
typically from 0.003 inches (76 micrometres) to 0.125 inches (3100
micrometres).
LaPerre (US-A-4 329 393) describes particles carrying information by way of
visually
distinguishable coloured layers. The particles are produced by the random
comminution of brittle laminates, and have therefore irregular and
uncontrolled shape,
with typical sizes along the broadest dimension of between 15 and 1000
micrometres
across the coloured layers. Stevens (US-A-4 390 452) describes similar
particles
1
AMENGEG ~HEE~
CA 02188386 1996-10-21
which carry information by way of one or a number of identifying features such
as
coloured layers, fluorescent or phosphorescent material layers, or the
presence of
trace elements. Again, the particles are produced by the shattering of brittle
laminates into irregular broken pieces, with typical sizes along the broadest
dimension
of between 15 and 1000 micrometres. In all of these methods, the shape of
individual
particles is either uncontrolled or is restricted to one of several simple
polygonal
geometries. The information carried on these microparticles is either alpha-
numeric
or colour codes.
The invention provides a microparticle which is invisible to the naked eye and
is marked with a machine readable code.
The invention also provides a tagging compound comprising a powder, fluid
or gas when mixed wim one or more set or sets of microparticles or which each
has a
predetermined shape representative of a unique code selected from a
multiplicity of
such codes, such that the presence of the microparticles is undetectable to
the naked
eye.
The invention also provides a method of marking an object invisibly with a
machine-readable code, comprising applying to the object a set of
microparticles of
the above type.
By applying such microparticles to an item, the item
1A
~~iwl'll::.t.' JI'iv .~
,~. , ..... , .,....:.. .. .a..,.., .. ~ . . ..~_ riN. ~w-~.~" w." ~,~~., .,
,~,.,,., ~~ ,. ~~ ,..,. ~..W ... . . ..
CA 02188386 1996-10-21
WO 95/29473 2 ~ 8 g ~ ~ ~ PCT/GB95/00756
can be marked extensively or even covered without detracting
from its aesthetic or practical purpose.
Preferably, the microparticle is in the form of a wafer
whose thickness is from O.l~u. to 5~.c.. and whose width and
length are both in the range of 0.5~,.~ to 50~ ; preferably,
the microparticle is of silicon or silicon dioxide. Such
particles can be made by micromachining.
Silicon micromachining is a process developed from the
electronics industry. The processes and techniques used in
silicon micromachining are based largely upon the highly
refined fabrication technology used in semiconductor
manufacture - with the objective in micromachining being the
creation of microscopic physical or mechanical structures on
silicon wafer substrates as opposed to electronic circuitry.
It has been shown in The Production of Precision
Silicon Micromachined Non-spherical Particles for Aerosol
Studies - Kaye, P.H., Micheli, F., Tracey, M., Hirst, E.,
and Gundlach, A.M. Journal of Aerosol Science. Vol. 23,
Supplement 1, pp 201-204, 1992, that extremely uniform
microscopic particles of silicon or silicon dioxide (glass)
or a metal such as aluminium, silver, or gold, can be made
using the process of silicon micromachining. These
particles may be of dimensions from about 0.5u to 50~m or
more across, and from about 0.1 to 5~m thick. (A printed
Period mark by comparison is typically SOO~m across). The
shapes of the particles are designed using a
computer-aided-design (CAD) programme and may be of
virtually any desired form within the limitations mentioned
- 2 -
_~n~
CA 02188386 1996-10-21~
WO 95129473 p~~Gg95/pp~~
above. A single silicon wafer of normally 7.5cm (3 inch) or
20cm (8 inch) diameter is used as the substrate on to which
the desired particle shapes are projected using-an optical
mask or directly drawn using so-called e-beam writing. The
particles are subsequently formed on the wafer using the
deposition and etching processes of silicon micromachining.
Typically 200 million particles can be formed on a 7.5cm (3
inch) wafer, each of the particles accurately defined in
size and shape. Normally all the particles on one wafer are
designed to be of identical size and shape so that when the
particles are freed from the wafer substrate (using a
further etching process) one is left with a suspension
containing a single particle type.
Because the particles can be made to a uniform and
predetermined shape they can be used as identifying markers.
Thus their shape alone can be the unique identification.
However, in the preferred example, apart from the shape of
each particle being defined, each particle is marked with
pits, holes, notches, or other marks so that it is
2p characterised by a unique mark. The marks may form a binary
code or some other encrypted coding which only the designer
of the particle may have access to. Each particle could then
carry a code of typically several hundred binary 'bits' of
information.
. In order unambiguously to optically image a unique
binary number etched in the form of pits, holes, etc.
forming a pattern on~the microparticle, it is necessary for
each constituent mark which represents a binary bit of the
- 3 -
CA 02188386 1996-10-21
wo 9sn9a~3 G~ ~ $ $ 3 ~ ~ rcncs~sroo~s6
number to satisfy Abbe's Condition for the microscopic
imaging system in question. With white light illumination
and a microscope objective of Numerical Aperture 0.5 the bit
spacing should typically exceed approximately 1.2
micrometres. Such an objective, in reflector form, can
display a working distance of approximately l6mm and a
usable depth of field of approximately 5 micrometres. Such
a microscope would be suitable for the analysis of objects
such as credit cards or identity cards. Microscopic
analysis of larger objects would either require a sample to
be removed for analysis (for instance a paint sample from an
automobile) or would require the design of a microscope
mounting specific to that application (for instance a
magnetic mounting or precisely defined objective to base
distance such that when held on a plane it is in focus).
An alternative to microscopic analysis would be offered
by the employment of a scanning system ( analogous to a very
high resolution 'bar code reader') employing a laser beam
and appropriate optics to produce a narrow, collimated beam
in conjunction with electronics to control the beam and
interpret the interaction between the beam and the object
under scrutiny. Such a system could offer a focused working
distance range sufficient to allow hand-held scrutinisation
instruments to be employed.
25- Additionally the particles should be patterned in such
a manner as to ensure that ambiguous pattern interpretation
cannot occur in the case of 90, 180 or 270 degree rotation
from the intended viewing orientation; ambiguous
- 4 -
CA 02188386 1996-10-21
wo 9sn9a~3
PGT/GB95/00756
interpretation due to imaging the microparticle's incorrect
face should also be precluded. The addition of unique
corner patterns could be employed to achieve this.
A particle meeting this design constraint, when imaged
* 5 by a microscope, will form an image on the imaging element
of a video camera. This image, in electronic form, can be
digitised and processed by a computer using image processing
software. Numerous conventional algorithms can be emp3~oyed
by this software to uniquely identify the morphology of the
lp imaged microparticle. Their operation would typically
involve:
(i) Delineating the object image from its background. This
operation could be performed by a general purpose commercial
image processing package such as Optimas or Visilog.
15 (ii) Interpreting the morphology of the object in order to
ascertain the pattern of marks and hence the unique binary
number. This operation would probably employ custom-written
software to interpret the data produced by (i).
A suspension of particles, all having identical code
2~ markings, may then be used to uniquely identify an object
and thus act as a security tag. Examination of the
particles on the object can be achieved for example With an
optical reader similar to (though of higher resolution) than
a bar-code reader found in supermarkets, and the code
25 contained on the particles then identifies the rightful
ownership of the object.
For example, an item of jewellery such as a gold
necklace could be coated in part or whole with a transparent
- 5 -
CA 02188386 1996-10-21
88~38~
WO 95/Z9473 PGT/GB95100756
lacquer containing a suspension of particles. The lacquer
would dry to become invisible, and the particles contained,
though invisible to the human eye, could nevertheless be
viewed using a suitable magnifying device so as to reveal
the hidden identity code. To avoid the possibility of the
lacquer being removed by a solvent (thus removing the
particles as well), the particles could be stamped into the
jewellery at the time of hallmarking, thus becoming
essentially part of the item itself, resilient to removal
without totally removing the hallmarks (which would normally
significantly reduce the value of the item).
Another example could be the unique marking of credit
cards and similar 'plastic' devices for electronic financial
transactions, or paper currency or security bonds etc. The
cards could be marked at some points) with an 'ink'
containing the particles. Again the particles would each
carry a copy of a unique coding tag which could be traceable
to the rightful owner of the card. An imaging system, again
like a bar-code reader, could be used to 'read' the data on
the particles and ascertain the authority of ownership.
Removal of the ink and particles would render the card
invalid.
Another example would be to apply the particles (all
having the same code) with the top layer of paint or varnish
onto a motor car. The particles, invisible to the naked
eye, would not detract from the appearance of the vehicle.
By coating the whole vehicle, inner facing panels included,
with this coded paint, a potential thief would have to
- 6 -
CA 02188386 1996-10-21
WO 95129473 ~ PCTIGB95/00756
remove all the paint from the vehicle to remove all the
particles in order to prevent its true identification
becoming known. Such a process, and subsequent repainting,
would involve so much labour as to render the original theft
non-profitable. Typically, one particle per square
millimetre of surface area would be required to coat the
vehicle. This may amount to 20 million particles per
vehicle, i.e. corresponding to approximately one-tenth of a
7.Scm (3 inch) wafer's worth.
A further example would be to incorporate the particles
in so-called security smoke devices. These devices are
found for example in hole-in-the-wall cash machines and
armoured vehicles. They release automatically a smoke dye
to cover the currency and possibly the thief when disturbed.
The particles would also cover the currency and thief and,
because they would carry a unique code, would provide a
means of linking a specific item of currency or person to
the specific incident.
Any item could in theory be marked in this way to
provide identifying security marks. The particles have many
advantages including that (i) they can be made identically
and in huge numbers by the process of micromachining - they
can be made if desired in silicon dioxide, i.e. glass
(coloured if required) and as such be impervious to most
acids etc., (ii) their production, e.g. through the process
of micromachining, is non-trivial and requires highly
specialist equipment and skills, thus unauthorised
replication of the particles would be very difficult to
CA 02188386 1996-10-21
WO 95129473 ~ ~ ~ ~ PCT/GB95/00756
achieve, and (iii) they are essentially invisible to the
naked eye.
If more information is required to identify .an article,
a mixture of two or more sets of differently-coded particles
could be applied, at the cost of longer read-time by the
optical scanning device.
Although in many examples it is appropriate to coat
outer surf aces of the objects with the identifying
particles, it is envisaged that liquids and other fluid
materials such as drinks, fuels and perfumes could be marked
by mixing with the microparticles. Even solid objects could
be impregnated internally with the microparticles, or the
microparticles could be mixed with fluid materials during
the manufacture of the solid objects, e.g. in a mould.
20
_ g _
