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Description  |
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TECHNICAL FIELD
The invention relates to optical information storage.
BACKGROUND ART
Dil, in U.S. Pat. No. 4,209,804, teaches a reflective information recording
structure which contains prepressed V-shaped grooves in which data may be
recorded by local melting of the reflective metal coating by a laser. The
data on the media is read by means of optical phase shift effects. Since
the preformed grooves are at an optical phase depth of 95.degree. to
140.degree., the reading laser must be of the precise wavelength
corresponding to the groove depth. The information area has a width of
approximately 0.6 microns, so a thick protective substrate, usually 1200
microns deep is used to ensure that one micron surface dust particles are
out-of-focus for the read beam.
Such thick protective materials cannot be used for wallet cards which have
a total thickness of only 800 microns under ISO (International Standards
Organization) standards and further it would be uncomfortable to carry a
rigid card in trouser pockets or wallets. Also, it is difficult to bond a
phase sensitive recording/reading surface to a protective laminating
material with an adhesive without introducing a varying phase shift across
the surface. It is also impractical to melt large holes since a large lip
would be formed around the hole causing a great distortion of the phase
shift. Edge transition of the hole is the phase shift which is measured,
and since the height of the lip is directly proportional to the square
root of the hole diameter, phase shift reading is only practical for small
holes. For example, a 25 micron diameter hole creates a lip with one
micron height, which is much larger than the wavelength of the reading
beam. Thus for large holes and bonded protective materials it is desirable
to have a recording/reading structure that does not rely on phase shifts.
Lahr in U.S. Pat. No. 3,873,813 teaches a debit card in which use is
indicated by alteration of a spot of heat sensitive coating in a selected
area thereby permanently changing the reflective characteristics of that
area. A reflective heat sensitive material becomes transparent on heating,
thereby exposing an underlying strip of black paper which then absorbs the
light energy. Recording requires exposure to a high intensity light beam
for 0.7 second to raise the temperature of the material to 175.degree. F.
and an additional 5 milliseconds above 175.degree. F. This type of credit
card system permits recording of less than two data bits per second.
Because of the retained, diffused liquid, the sizes of the data spots are
large and difficult to regulate. This card requires a blue read beam,
therefore scratches and surface dust will cause a large number of data
errors unless very large data spots are used that reduce capacity to under
10,000 bits. While this data capacity is satisfactory for some debit and
credit cards, it is unsuitable for detailed recording of financial,
insurance, medical and personal records. Also, the recording rate of less
than two bits per second would make it unacceptable for use in most
applications. Another disadvantage of this card is that all of the data is
destroyed if its temperature reaches 175.degree. C., for example on the
dashboard of a car or if passed through a household washer and dryer.
Nagata in U.S. Pat. No. 4,197,986, Girard in U.S. Pat. No. 4,224,666 and
Atalla in U.S. Pat. No. 4,304,990 teach updating of data cards. Nagata
teaches the updating of maximum limits and balance on a card in which the
complete data file is in an auxiliary memory circuit such as a magnetic
disc or drum. A sales slip containing the transaction is recorded
separately from the card. Giraud teaches a data-processing machine-access
card containing an integrated circuit chip with a memory bank. The memory
stores predetermined items of confidential data intended to authorize or
prevent access to the machine. Only the balance is updated.
Atalla teaches a card in which only the balance is recorded and updated.
This card can only be used where the transaction system is connected to a
central computer. None of these cards has the memory storage capacity
needed to accumulate records of past transactions.
Various recording media have been developed for use on a rotating disc
format. Because the disc is spinning rapidly, short laser pulse times (on
the order of 500 nanoseconds) are necessary to confine the heating to
small spots. The media have been developed to increase the sensitivity to
the beam by varying the parameter of media absorptivity. Spong in U.S.
Pat. Nos. 4,190,843 and 4,305,081 puts an absorptive dye layer over a
reflective aluminum layer. Spots are recorded by ablation of the dye layer
exposing the underlying reflective layer. Bell in U.S. Pat. No. 4,300,143,
teaches a similar technique. Bartolini in U.S. Pat. No. 4,313,188 adds a
protective layer between the dye layer and the reflective layer. Wilkinson
in U.S. Pat. No. 4,345,261 uses a light absorptive silica dielectric layer
in place of the dye layer. Terao teaches an inorganic absorptive layer
over an organic recording film layer. Holes are formed in the film layer
by heat generated in the absorptive layer. Suzuki in U.S. Pat. No.
4,202,491 uses a fluorescent ink layer on which data spots emit infrared
radiation. Improved sensitivity is obtained in these media at the expense
of extra layers which increase complexity and cost. This increased
sensitivity is not necessary for a card format.
DISCLOSURE OF INVENTION
It is the object of the present invention to devise a wallet-size plastic
data card containing a laser recordable strip and a system for sequential
recording transaction data on the data card with a laser where the data on
the card optically contrasts with the surrounding unrecorded field. It is
also an object of the invention to perform related sequential laser
recording of transactions and events related to the fields of insurance,
personal medical records, personal information, banking and related data
records.
It is a further object of the invention to devise a wallet-size card,
containing a laser recordable strip, that meets the ISO dimensions for
plastic credit cards, has a capacity of at least 250,000 bits, can record
data at thousands of bits per second and contains prerecorded information
such as reference position on the strip, and would not degrade at
temperatures of 175.degree. F. or higher.
These objects were met with a wallet-size sealed plastic card only 800
microns thick containing a laser recordable strip using data spots up to
25 microns in size to minimize reading errors and which also contains
prerecorded information on the strip such as reference position
information. The data system of the present invention relies on reading of
optical contrast ratios. The card is formed by photographically
prerecording information on the strip, adhering the strip on the card
base, bonding protective, transparent material over the strip and then
recording transaction information with a laser.
One of the chief advantages of the present invention is the high
information capacity of laser recording media strips. Typically, high
resolution laser recording materials record spots of altered reflectivity
optically contrasting with the surrounding reflective field and having
dimensions less than 25 microns. A high capacity laser recording material
strip enables a credit card to carry the equivalent of scores of pages of
text, more than ample for most applications. The transaction card of the
present invention is suitable for accumulating sequentially recorded data
involving financial transactions, insurance transactions, medical
information and events, and personal information and identification.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 is a plan view of one side of a data card in accord with the present
invention.
FIG. 2 is a partial side sectional view taken along lines 2--2 in FIG. 1.
FIG. 3 is a detail of laser writing on a portion of the laser recording
strip illustrated by dashed lines in FIG. 1.
FIG. 4 is a plan view of an apparatus for reading and writing on the
optical recording media strip illustrated in FIG. 1.
BEST MODE FOR CARRYING OUT THE INVENTION
With reference to FIGS. 1 and 2, a data card 11 is illustrated having a
size common to most credit cards. The width dimension of such a card is
approximately 54 mm and the length dimension is approximately 85 mm. These
dimensions are not critical, but preferred because such a size easily fits
into a wallet and has historically been adopted as a convenient size for
automatic teller machines and the like. The card's base 13 is a
dielectric, usually a plastic material such as polyvinyl chloride or
similar material. Polycarbonate plastic is preferred. The surface finish
of the base should have low specular reflectivity, preferably less than
10%. Base 13 carries strip 15. The strip is about 15 millimeters wide and
extends the length of the card. Alternatively, the strip may have other
sizes and orientations. The strip is relatively thin, approximately
100-500 microns, although this is not critical. The strip may be applied
to the card by any convenient method which achieves flatness. The strip is
adhered to the card with an adhesive and covered by a transparent
laminating sheet 19 which serves to keep strip 15 flat, as well as
protecting the strip from dust and scratches. Sheet 19 is a thin,
transparent plastic sheet laminating material or a coating, such as a
transparent lacquer. The material is preferably made of polycarbonate
plastic.
The opposite side of base 13 may have user identification indicia embossed
on the surface of the card. Other indicia such as card expiration data,
card number and the like may be optionally provided.
The high resolution laser recording material which forms strip 15 may be
any of the reflective recording material which have been developed for use
as direct read-after-write (DRAW) optical disks, so long as the materials
can be formed on thin substrates. An advantage of reflective materials
over transmissive materials is that the read/write equipment is all on one
side of the card and automatic focus is easier. For example, the high
resolution material described in U.S. Pat. No. 4,230,939 issued to de
Bont, et al. teaches a thin metallic recording layer of reflective metals
such as Bi, Te, Ind, Sn, Cu , Al, Pt, Au, Rh, As, Sb, Ge, Se, Ga.
Materials which are preferred are those having high reflectivity and low
melting point, particularly Cd, Sn, Tl, Ind, Bi and amalgams. Suspensions
of reflective metal particles in organic colloids also form low melting
temperature laser recording media. Silver is one such metal. Typical
recording media are described in U.S. Pat. Nos. 4,314,260, 4,298,684,
4,278,758, 4,278,758, 4,278,756 and 4,269,917, all assigned to the
assignee of the present invention. The laser recording material which is
selected should be compatible with the laser which is used for writing on
it. Some materials are more sensitive than others at certain wavelengths.
Good sensitivity to infrared light is preferred because infrared is
affected least by scratches and dirt on the transparent laminating sheet.
The selected recording material should have a favorable signal-to-noise
ratio and form high contrast data bits with the read/write system with
which it is used. The material should not lose data when subjected to
temperatures of about 180.degree. F. (82.degree. C.) for long periods. The
material should also be capable of recording at speeds of at least several
thousand bits/sec. This generally precludes the use of materials that
require long heating times or that rely on slow chemical reactions in the
presence of heat, which may permit recording of only a few bits/sec. A
large number of highly reflective laser recording materials have been used
for optical data disk applications. Data is recorded by forming spots in
the surrounding field of the reflective layer itself, thereby altering the
reflectivity in the data spot. Data is read by detecting the optical
reflective contrast between the surrounding reflective field of unrecorded
areas and the recorded spots. Spot reflectivity of less than half the
reflectivity of the surrounding field produces a contrast ratio of at
least two to one, which is sufficient contrast for reading. Greater
contrast is preferred. Reflectivity of the strip field of about 50% is
preferred with reflectivity of a spot in the reflective field being less
than 10%, thus creating a contrast ratio of greater than five to one.
Alternatively, data may also be recorded by increasing the reflectivity of
the strip. For example, the recording laser can melt a field of dull
microscopic spikes on the strip to create flat shiny spots. This method is
described in SPIE, Vol. 329, Optical Disk Technology (1982), p. 202. A
spot reflectivity of more than twice the surrounding spiked field
reflectivity produces a contrast ratio of at least two to one, which is
sufficient contrast for reading.
With reference to FIG. 3, a magnified view of laser writing on the laser
recording material strip 15 may be seen. The dashed line 33, corresponds
to the dashed line 33 in FIG. 1. The oblong spots 35 are aligned in a path
and have generally similar dimensions. The spots are generally circular or
oval in shape with the axis of the oval perpendicular to the lengthwise
dimension of the strip. A second group of spots 37 is shown aligned in a
second path. The spots 37 have similar dimensions to the spots 35. The
spacing between paths is not critical, except that the optics of the
readback system should be able to easily distinguish between paths.
Presently, in optical disk technology, tracks which are separated by only a
few microns may be resolved. The spacing and pattern of the spots along
each path is selected for easy decoding. For example, oval spots of the
type shown can be clustered and spaced in accord with self-clocking bar
codes. If variations in the dimensions of a spot are required, such
dimensions can be achieved by clustering spots, such as the double spot
39. Such variations are used in the ETAB bar code which is described in
U.S. Pat. No. 4,245,152. While the American Banker's Association has not
yet adopted any particular code, the strip material is such that many
machine and eye readable codes can be accommodated. Some optical codes
such as the Universal Product Code are both machine and eye readable. Such
codes could also be accommodated, although a great deal more laser writing
would be required than with circular or oval spots, and a much lower
information density would be achieved. The spots illustrated in FIG. 3
have a recommended size of approximately 5 microns by 20 microns, or
circular spots 5 microns or 10 microns in diameter. Generally, the
smallest dimension of a spot should be less than 50 microns. In the
preferred embodiment the largest dimension would also be less than 50
microns. Of course, to offset lower densities from larger spots, the size
of the strip 15 could be expanded to the point where it covers a large
extent of the card. In FIG. 1, the laser recording strip 15 could
completely cover a single side of the card. A minimum information capacity
of 250,000 bits is indicated and a storage capacity of over one million
bits is preferable.
In FIG. 4, a side view of the lengthwise dimension of a card 41 is shown.
The card is usually received in a movable holder 42 which brings the card
into the beam trajectory. A laser light source 43, preferably a pulsed
semiconductor laser of near infrared wavelength emits a beam 45 which
passes through collimating and focussing optics 47. The beam is sampled by
a beam splitter 49 which transmits a portion of the beam through a
focusing lens 51 to a photodetector 53. The detector 53 confirms laser
writing and is not essential. The beam is then directed to a first servo
controlled mirror 55 which is mounted for rotation along the axis 57 in
the direction indicated by the arrows A. The purpose of the mirror 55 is
to find the lateral edges of the laser recording material in a coarse mode
of operation and then in a fine mode of operation identify data paths
which exist predetermined distances from the edges.
From mirror 55, the beam is directed toward mirror 61. This mirror is
mounted for rotation at pivot 63. The purpose of mirror 55 is for fine
control of motion of the beam along the length of the card. Coarse control
of the lengthwise position of the card relative to the beam is achieved by
motion of movable holder 42. The position of the holder may be established
by a linear motor adjusted by a closed loop position servo system of the
type used in magnetic disk drives. During its manufacture the card may be
prerecorded with a preinscribed pattern containing servo tracks, timing
marks, program instructions, and related functions. These positioning
marks can be used as a reference for the laser recording system to record
or read data at particular locations. Each of the various industries, that
is, financial, insurance, medical, and personal, has formats specific to
its particular needs. U.S. Pat. No. 4,304,848 describes how formatting may
be done photographically. Formatting may also be done using laser
recording of the servo tracks, having marks, programming and related
functions. Reference position information may be prerecorded on the card
so that position error signals may be generated and used as feedback in
motor control. Upon reading one data path, the mirror 55 is slightly
rotated. The motor moves holder 41 lengthwise so that the path can be
read, and so on. Light scattered and reflected from the spots contrasts
with the surrounding field where no spots exist. The beam should deliver
sufficient laser pulse energy to the surface of the recording material to
create spots. Typically, 5-20 milliwatts is required, depending on the
recording material. A 20 milliwatt semiconductor laser, focussed to a five
micron beam size, records at temperatures of about 200.degree. C. and is
capable of creating spots in less than 25 microseconds. The wavelength of
the laser should be compatible with the recording material. In the read
mode, power is lowered to about 5% of the record power.
Optical contrast between a spot and surrounding field are detected by light
detector 65 which may be a photodiode. Light is focussed onto detector 65
by beam splitter 67 and focusing lens 69. Servo motors, not shown, control
the positions of the mirrors and drive the mirrors in accord with
instructions received from control circuits, as well as from feedback
devices. The detector 65 produces electrical signals corresponding to
spots. These signals are processed and recorded for subsequent display as
useful information regarding the transaction recorded on the card.
In operation, the card of the present invention is used to record
sequentially accumulated data, as medical records, insurance records,
personal information, or financial transactions. For example, it could be
used just like a passbook. First the card is read to determine previously
recorded information. Next, a user enters his transaction and if validated
by an ATM, the ATM then causes data to be written on the first strip by
means of the laser. The data represents a passbook entry with a new
account status. Operating in this mode, a user may use the card of the
present invention in free standing ATMs in isolated locations. While it is
necessary for the ATM to make a record of each transaction, there is no
need to transmit transaction data using telecommunication links to a CPU
at a distant location.
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Description |
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