U.S. patent number 3,566,120 [Application Number 04/777,538] was granted by the patent office on 1971-02-23 for method of coded data storage by means of coded inks in which the code components have particular absorption bands in the infrared.
This patent grant is currently assigned to American Cyanamid Company, Stamford, CT. Invention is credited to Leslie C. Lane, Jr..
United States Patent |
3,566,120 |
|
February 23, 1971 |
METHOD OF CODED DATA STORAGE BY MEANS OF CODED INKS IN WHICH THE
CODE COMPONENTS HAVE PARTICULAR ABSORPTION BANDS IN THE
INFRARED
Abstract
A data storage method is described in which inks with code
components of compounds having narrow absorption bands in the
infrared are impressed on a substrate which is transparent to the
infrared in the regions of the absorption bands of the code
components. Decoding is effected by passing infrared radiation
through the areas of the substrate where the symbols have been
placed in the coded inks and the infrared radiation detected in the
particular bands of the coded components to produce electrical
signals which are then analyzed to produce a readout corresponding
to the particular symbol.
Inventors: |
Leslie C. Lane, Jr. (Stamford,
CT) |
Assignee: |
American Cyanamid Company,
Stamford, CT (N/A)
|
Family
ID: |
25110522 |
Appl.
No.: |
04/777,538 |
Filed: |
September 25, 1968 |
Current U.S.
Class: |
250/271; 250/226;
250/341.1 |
Current CPC
Class: |
G01N
21/255 (20130101); G06K 7/12 (20130101) |
Current International
Class: |
G06K
7/12 (20060101); G01N 21/25 (20060101); G01j
003/34 () |
Field of
Search: |
;250/83.3(IR),226 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Archie R. Borchelt
Attorney, Agent or Firm: Samual Branch Walker
Parent Case Text
REALTED APPLICATIONS
This application is a continuation-in-part of my earlier
application, Ser. No. 526,183, filed Feb. 9, 1966, and now
abandoned.
Claims
1. In a process for encoding and retrieval of information in which
the encoding is with coded inks having various components, the code
constituting the absence of presence of particular components to
represent a symbol, the improvement which comprises: a. applying to
a substrate transparent to infrared radiation symbols encoded in
inks having various components with narrow absorption bands within
the wavelength range in the infrared in which the substrate is
transparent; b. shining infrared radiation in the wavelength range
containing the narrow absorption bands through the substrate,
detecting radiation encountering the coding components by infrared
detectors, each detector being responsive to wavelength in the
infrared including the absorption band of a coding component and
being unresponsive to wavelengths in the range of absorption of the
other components, the detectors transforming infrared radiations
into an electrical signal; and c. transforming said signal into a
readout of a coded symbol represented by
2. A process according to claim 1 comprising focusing the infrared
radiation passing through the ink component on the substrate
corresponding to a symbol onto a fixed plane and conducting said
radiation to each
3. A process according to claim 2 in which the individual detectors
are in the plane and receive infrared radiation directly.
Description
In the patent of Freeman and Halverson, U.S. Pat. No. 3,473,027,
Oct. 14, 1969, there is described a method and apparatus for
recording and retrieving information by means of photoluminescent
materials. In the patent so-called coded inks are utilized in which
various symbols, such as numbers, are represented by the presence
or absence of particular photoluminescent material rather than
representing the symbols by particular shapes which are
distinguishable either visually, magnetically or by other
characteristics. When dealing with numbers, for example, four
different photoluminescent materials may be used, and this gives
the possibility of 15 different codes, the general formula being
2.sup.n - l. Larger numbers of coded materials permit representing
still larger numbers of different symbols. For example, with six
different photoluminescent materials 63 symbols are
distinguishable. The different coded inks contained the necessary
mixtures of materials which fluoresced under ultraviolet
illumination in definite colors.
The present invention provides symbols which have one or more
components having sharp absorption bands in the infrared. The
choice of materials is wide, as most transparent organic compounds
have one or more sharp absorption bands in the infrared. The
substrate on which the symbols are written or printed must, of
course, transmit infrared at least in the ranges in which the
absorption bands of the components are located. This is, however,
no problem as there are plastics, such as for example polyethylene,
which are transparent to the infrared through a wide range. As most
of the infrared absorbers are colorless or transparent, the symbols
are not visible to the eye, and therefore any message is secret. Of
course the same advantages as with fluorescent materials are
shared, namely that the symbol can be read regardless of its shape
and is, therefore, machine readable even if somewhat mutilated.
For certain purposes it is desirable that the symbols be readable
under visible light. This can be effected in the present invention
by introducing a small amount of a suitable dyestuff in the coded
inks. Of course the colorant used must be on which has reasonable
transmission in the ranges of infrared in which the absorption
bands of the symbol components are located and does not have itself
sharp absorption bands in these ranges which would interfere with
recognition of the symbols themselves.
In readout out or retrieving the information according to the
present invention, an infrared source shines on the transparent or
translucent substrate containing the symbols, the source radiating
over a sufficiently wide infrared band to include all of the strong
absorption bands of the different components of the symbols. On the
other side of the transparent substrate are located a series of
light pipes, which may be suitable plastic rods, glass fiber
bundles, and the like. The end of each light pipe carries the
radiation through a narrow band filter to a radiation detector, one
for each component. The filter corresponds to the absorption band
of the particular component and is preferably narrow band, but this
presents no problem with modern narrow band filters, such as
interference filters. It goes without saying that the light pipes
must be capable of transmitting radiation in the proper wavelengths
in the infrared where the components have strong absorption bands.
It will be found that there are a large number of compounds, such
as organic plastics, with bands located in the near infrared, for
example wavelengths shorter than 3.mu., so that glass fiber light
pipes can be employed. If components having absorption bands in the
further infrared are used, the light pipes must of course be
modified accordingly. Fibers or rods of different plastics or even
a hollow pipe with its inner surfaces in the form of a good
infrared mirror can be used. When fiber or rod light pipes are used
of particular plastics, these may be the same plastics as the
substrate or a different component.
Typical materials are polymethylmethacrylate, polyacrylamide,
polyvinyl alcohol; various amides and polyamides, such as
N,N-dialkyl amides; super polyamides, such as for example nylon-6,
which is a polymer of .omega.-amino caproic acid, and the like.
Many of these components are not readily soluble in solvents such
as benzene, toluene, cyclohexane, and the like which do not exhibit
bands that conflict with the absorption bands of the components. In
such cases finely divided powders may be dispersed in inks having a
film-forming substance which also does not have absorption bands in
the infrared which conflict with the bands of the components. Such
inks normally require a film-forming substance, for which
polyolefins are suitable, for example solid polyisobutylene. Of
course all of the various components can be distributed in inks in
this form even through some of them, such as
polymethylmethacrylate, are readily soluble in suitable
solvents.
The amounts of the components are not critical, but they must be
sufficient in the residue form when the volatile solvents of the
inks evaporate so that the components are represented by a layer of
at least 20 to 50 microns.
Radiation detectors may be of conventional types for use in
infrared. For example, if all of the components or some of them are
in the very near infrared, it is possible to use special
photomultiplier tubes, and where this is feasible it constitutes an
advantage, as the sensitivity of the photomultiplier tube is so
great that amplification of the signal from the tube can often be
dispensed with. In other ranges in the infrared, it is necessary to
use a different type of radiation detector, which may be either
photoresistive or photovoltaic. For example, a lead sulfide or lead
selenide cell.
Some of the typical components, such as polymethylmethacrylate;
nylon-6; or N,N-dialkyl amides, such as N,N-dibutylpropionamide;
and polyacrylonitrile have infrared absorption bands at wavelengths
longer than 4.mu. and ranging up to slightly over 6.mu. for some of
the amides, such as nylon-6. In such cases it is possible to use a
photoresistive detector, such as indium antimonide.
It is also possible to use thermal detectors, such as thermocouples
or thermopiles, thermistors and the like, which are of course
responsive through very wide ranges of the infrared. In the case of
these detectors which are less sensitive, it is normal to provide
signal amplification and standard preamplifiers, such as for
example solid state preamplifiers, are used. As the nature of the
detector and/or the amplification of its signal are not changed by
the present invention, it is not desired to limit it to any
particular design.
The signals from the various radiation detectors are then read out
in standard readout circuits, which also are not changed by the
present invention and which can be the same as are used in the
readout of the Freeman and Halverson patent above referred to. One
may consider that the novelty of the present invention ceases when
signals are produced from the various radiation detectors, and it
is an advantage of the invention that no new design of detectors,
amplifiers or readout circuitry is required.
BRIEF DESCRIPTION OF THE DRAWING
The drawing shows in diagrammatic form an apparatus for reading a
code containing four components.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
In the drawing an infrared lamp of conventional design 1, which
radiates infrared in the range in which all of the components have
absorption bands, shines infrared onto a substrate 2 which is
transparent to infrared and may, for example, be polyethylene. On
this substrate there are printed various symbols: A, B, C, and D,
which for simplicity are shown as containing a single component
only, though of course any particular symbol may have two, three or
four components. The thickness of the symbols is enormously
exaggerated for clearness and in actual fact they are no thicker
than ordinary printing.
As a typical illustration, component A is polymethylmethacrylate
with an infrared absorption band at 5.8.mu., B is nylon-6 or N,N-
dibutylpropionamide with an infrared absorption band at about
6.1.mu., C is polyacrylonitrile with an absorption band at 4.4.mu.,
and D is polyvinyl alcohol with an absorption band at 2.96.mu.. If
separate inks are used for each component, component A can be a
benzene solution of the polymer, but the other three components are
not readily soluble in suitable solvents and therefore in the form
of very finely divided powder uniformly dispersed in an ink which
is a solution of solid polyisobutylene in cyclohexane. Of course if
inks are used with a number of components mixed in them, it is
preferable to have the polymethylmethacrylate also in the form of a
fine powder. While the thickness of the symbols is exaggerated, the
layer of the component material should be at least 20.mu. to 50.mu.
in thickness.
The entrance pupil of the infrared source after the radiation has
passed through the substrate 2 passes through a field lens 3 which
focuses the entrance pupil onto a plane in which four light pipes
4A, 4B, 4C, and 4D are located. The light pipes are capable of
transmitting infrared radiation in the range including the strong
absorption band of the particular components respectively. The
entrance of the light pipes is shown with the pipes quite widely
separated for clarity. In an actual device they are of course quite
closely adjacent, which is made possible by the fact that the pipes
can be bent to bring the radiation out into a wider area. The
radiation from each light pipe passes through a sharp cutting
infrared filter 5A, 5B, 5C, and 5D respectively, each filter
passing only the wavelength range corresponding to the absorption
band of a particular component or a little beyond, the filters
being arranged so that there is no overlap in transmission. Back of
the filters 5A to 5D are four radiation detectors shown
diagrammatically as 6A, 6B, 6C, and 6D. The detectors may be of
indium antimonide or of course thermopiles or thermistor bolometers
with suitable amplification to make up for the lower sensitivity of
these detectors. With components which have absorption bands in the
sufficiently short wave infrared, infrared sensitive
photomultiplier tubes may be used as the detectors and have the
advantage of enormously enhanced sensitivity.
Each radiation detector produces an electrical signal if its
particular component is absent but produces no signal if it is
present, although the reverse effect can be achieved by changing
the electronics. The electrical signals from the detectors pass
into an amplifier and readout circuitry 7 of the conventional
design which reads out the particular symbols. This element is of
conventional design and may be a multichannel analyzer, an
oscilloscope with timing so that each signal appears at a
particular point of the horizontal sweep, or any other standard
form of readout circuit. Since it is an advantage of the present
invention that any known circuit may be used and the invention is
not limited to any particular design, this element is shown in the
drawings as a block.
The preferred modification of the invention using light pipes and
spatially separated filtering means and detector is not the only
form in which the present invention can be developed. Where solid
state infrared detectors are used, such as indium antimonide, these
can be very tiny and provided with equally small filters, the
detectors being arranged in the form of a mosaic on which the field
lens images the infrared beam after passing through any particular
coded symbol. The signals from the different detectors pass to
preamplifiers and the readout circuit in the conventional manner.
Very small apparatus is thus made possible and for certain uses
this compactness is of primary importance. However, the
modification described in the drawing using light pipes and more
widely separated filters and radiation detectors permits using a
wider choice of detectors, including some of higher efficiency,
such as for example photomultiplier tubes, where the absorption
band of a particular component is the sufficiently short wave
infrared. Therefore, the modification described in the drawing
using light pipes is preferred, but the invention is in no sense
limited thereto.
* * * * *