U.S. patent number 3,582,623 [Application Number 04/790,270] was granted by the patent office on 1971-06-01 for detection of mixtures of narrow band photoluminescers.
This patent grant is currently assigned to American Cyanamid Company. Invention is credited to Walter John Greene, John L. Rothery.
United States Patent |
3,582,623 |
Rothery , et al. |
June 1, 1971 |
**Please see images for:
( Certificate of Correction ) ** |
DETECTION OF MIXTURES OF NARROW BAND PHOTOLUMINESCERS
Abstract
Readout process and apparatus for reading coded symbols in a
code in which the components are narrow band photoluminescent
compositions. The symbols, on suitable substrates such as paper
tape, labels on cans, bottles and the like, are illuminated by
flashes from a xenon tube with an ultraviolet transmitting filter.
The flashing tube is aimable so that it can be directed either on a
window in front of which tape containing the symbols is passed or
through another window onto containers with labels and the like.
Suitable optics are moved into position so that the different
locations of the substrate do not change the image path length.
When the symbols are illuminated with successive ultraviolet
flashes, they luminesce in the visible in the different narrow band
colors corresponding to the different components and this is imaged
on a filter wheel having the same number of filters as there are
components: four for numerical work or six for alphanumeric work.
After passing through the filter wheel, the visible beam is imaged
on the cathode of a photomultiplier tube. The filter wheel also is
provided with magnets which open switches connecting the
photomultiplier tube to different circuits for each filter and also
generate a trigger pulse which triggers the flashes of the xenon
tube in synchronism with the positioning of each filter by the
rotation of the wheel. The signal from the photomultiplier tube
passes through amplifiers, one for each filter, and into logic
circuits which provide for gates to select the particular signal
from a particular filtered beam and also start readout at the
beginning of a symbol and reset after the filter wheel has made a
second full revolution during which no signals are received.
Response of each amplifier is delayed about 20 .mu.sec. so that the
extremely short-persistence fluorescence from such compounds as
optical brighteners and the like has died out and response is only
from the slower decaying photoluminescence of the narrow band code
components. The logic circuits send out coded signals corresponding
to the code to display mechanisms, such as Nixie tubes, or a
permanent recording, such as a solenoid driven typewriter of the
computer readout type, or both, or to a solenoid driven diverter
for deflection from a conveyor system.
Inventors: |
Rothery; John L. (Marblehead,
MA), Greene; Walter John (Reading, MA) |
Assignee: |
American Cyanamid Company
(Stamford, CT)
|
Family
ID: |
25150164 |
Appl.
No.: |
04/790,270 |
Filed: |
January 10, 1969 |
Current U.S.
Class: |
235/468;
250/271 |
Current CPC
Class: |
G06K
7/12 (20130101); C09D 5/22 (20130101) |
Current International
Class: |
C09D
5/22 (20060101); G06K 7/12 (20060101); G06k
007/12 (); G01n 021/30 (); G01n 021/38 () |
Field of
Search: |
;235/61.11,61.115
;250/219L,DC,D,71,71.5 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Cook; Daryl W.
Claims
We claim:
1. A process for the readout of coded symbols, the code being
represented by the absence or presence in at least one level of
photoluminescent materials which luminesce under ultraviolet
illumination and which therefore permit a choice of symbols
represented by X.sup.n -1, where X is one more than the levels at
which the components may be present, which comprises,
a. illuminating a marking area containing the coded symbol with
brief flashes of short wave radiation,
b. optically imaging photoluminescence from the marking area onto
at least one detector, transforming radiation striking the detector
into an electrical signal,
c. sequentially limiting radiation to the detector to that of a
single code component,
d. starting electrical readout by the occurrence of two signals,
one in synchronism with sequential limitation of the whole number
of different components and the second the first electrical signal
from the detector above a predetermined low level,
e. amplifying the signals from the detector in separate channels
sequentially, the channel amplifying only the signals corresponding
to its component,
f. temporarily storing the amplified signals from each channel,
and
g. decoding the stored signals after a full sequence into forms
corresponding to the symbols represented by the code and of
suitable nature for initiating at least one operation selected from
the group consisting of visual display, printout, and other logical
operations requiring the same type of electrical signal.
2. A process according to claim 1 in which the code is represented
by the presence or absence of a photoluminescent component and the
choice of symbols is, therefore, 2.sup.n -1.
3. A process according to claim 2 in which the components of the
code have multimicrosecond decay half-lives and storage of the
signals from the detectors takes place after a delay less than the
decay half-life of the component but much longer than the decay
half-life of organic fluorescers which have decay half-lives of a
small fraction of a microsecond.
4. A process according to claim 3 in which there is a single
detector and the sequential irradiation in the wavelength ranges of
the photoluminescence of the different components is effected by
filtering out luminescence in wavelength ranges outside that of the
particular detector components the luminescence from which is to
irradiate the detector.
5. A process according to claim 4 in which the photoluminescent
components of the code are complexes containing different
lanthanide ions having an atomic number greater than 57.
6. An apparatus for carrying out the process of claim 4 comprising
in combination,
a. a short-duration, intense, gaseous-discharge flash tube provided
with a filter passing ultraviolet light but substantially opaque to
visible light,
b. means for imaging flashes from the flash tube onto the plane of
a marking area containing a coded symbol,
c. a single detector responsive to longer wave radiation at least
through the visible range,
d. means for imaging radiation from the marking area corresponding
to coded components therein onto the detector,
e. a filter wheel and means for rotating it, the wheel being
located to interpose successive filters in the luminescent
radiation, each filter passing a wavelength band including the
wavelength range of only a single component,
f. means driven in synchronism with the filter wheel to trigger
flashes from the flash tube each time a filter is interposed in the
luminescence beam,
g. a plurality of electronic amplifying and processing circuits
receiving inputs from the photodetector, the number of channels
being equal to the number of components,
h. means operated in synchronism with the filter wheel to open the
electronic circuits for a single channel only each time a
particular filter is interposed in the luminescence radiation,
i. a plurality of temporary electronic signal storage means equal
in number to the channels and responsive to input signals of at
least one level, means for connecting the output of each channel to
one of the electronic signal storage means,
j. electronic decoding means for transforming stored signals into
separate signals corresponding to particular coded symbols
represented by one or more photoluminescent components, and
k. means for initiating actuation of a full sequence of channels
representing a full revolution of the filter wheel, said means
being operated in synchronism with the filter wheel and including
means controlled by the first filter receiving luminescence
radiation to produce a signal from the photodetector of
predetermined level and means for resetting the electronic circuits
actuated by a full revolution of the filter wheel during which no
signals of predetermined level are produced from any component.
7. An apparatus according to claim 6 in which the electronic
processing circuits include an electronic time delay less than the
half-life decay of photoluminescence from any components but more
than a microsecond whereby very short life luminescence from
organic fluorescent material, such as optical brighteners, do not
reach the electronic signal storage.
8. An apparatus according to claim 7 in which the flash tube is
movable to one of at least two positions and optical means moved by
the same movement to image the flashes from the flash tube onto
substrates at different distances and to image luminescent
radiation from these different distances onto the
photodetector.
9. An apparatus according to claim 8 in which the photodetector is
a photomultiplier tube.
10. An apparatus according to claim 7 in which the photodetector is
a photomultiplier tube.
Description
BACKGROUND OF THE INVENTION
Photoluminescent coded inks have been described and claimed in the
Freeman and Halverson U.S. Pat. No. 3,473,027, Oct. 14, 1969 and a
modification in which some of the symbols are short-life
fluorescers, and these are distinguished from the longer-decay-time
photoluminescent materials of the other components, are described
and claimed in the U.S. Pat. No. 3,412,245 of Halverson, Nov. 19,
1968.
Various readout mechanisms involving illumination of the coded
symbol are described in the above patents. There is, however, a
demand for automatic apparatus and process for the rapid readout of
symbols on various substrates, such as paper tapes, labels on
containers, and the like.
The Freeman and Halverson and Halverson patents above referred to
describe the use of narrow band fluorescent components in the
coding, such as chelates of lanthanide ions having an atomic number
greater than 57, lanthanide-doped inorganic fluorescers, such as
vanadates, and the like. All of these narrow band fluorescers have
time constants of the multimicrosecond range, such as 10 to some
hundreds of .mu. seconds as contrasted to the extremely short
half-life or time constant of the fluorescence of certain organic
compounds, such as optical brighteners, which have a time constant
of the order of a small fraction of a microsecond. As described in
the Freeman and Halverson patent, codes which depend on the
presence or absence of a particular photoluminescent component
provide a choice of symbols represented by 2.sup.n -1, where n is
the number of components. This provides 15 symbols for straight
numeric work with four components, 63 symbols for alpha numeric
operations with six components, and the like.
SUMMARY OF THE INVENTION
The present invention involves an improved automatic process and
apparatus for the readout of photoluminescent coded symbols, such
as those described in the two applications above referred to. The
components to be used are the ones having a moderate half-life.
This is for the reason that many substrates, such as papers,
contain blue fluorescent materials which have the extremely short
time constants of from 10.sup..sup.- 7 to 10.sup..sup.- 8 sec.
Under certain types of nomenclature the moderately long half-life
materials might be referred to as phosphorescers instead of
fluorescers, but throughout the remainder of this application the
more general term "photoluminescers" or "photoluminescence" will be
used.
As it will appear from the more detailed description below, a wide
variety of apparatus elements may be used in practicing the present
invention, so that the invention may be considered both as a
process for readout and as a broad apparatus. In general, from the
apparatus aspect it will appear that the present invention is a
combination of elements which are not individually new things.
Essentially in the present invention a substrate having a series of
coded symbols, such as a paper tape or sheet or labels on
containers, such as bottles or cans with labels, or printing of the
photoluminescent coded symbols directly on their surfaces are
passed in front of the reading mechanism, either continuously or
semicontinuously. In the case of labels on containers, such as
bottles and cans, the container may move intermittently and then be
rotated for reasons which will appear below.
A flash tube of short-wave radiation, such as a xenon tube with an
ultraviolet transmitting filter which does not transmit the visible
is triggered to flash at predetermined short intervals. The flash
is directed to illuminate successive small marking areas on the
particular substrate from which the symbol is to be read, a marking
area being defined as a small area in which a symbol in the
different photoluminescent components is imprinted. A symbol may be
in the shape of a number, letter or a small area of no special
shape having the coded components. Each flash, which is of short
duration, for example of the order of 2 or 3 .mu. sec., is quite
intense and causes the components of the symbol in the marking area
to photoluminesce in their particular different wavelengths, which
can be in the visible or in some cases in the near infrared. Since
the components have half-lives of a number of .mu. sec., they
continue to luminesce for a number of .mu. secs. after illumination
has ceased. The photoluminescence is optically imaged in a beam
passing through successive filters, preferably on a filter wheel
rotating at reasonable speed, for example of the order of 1,000
r.p.m. or a few thousand r.p.m. There is provided one filter for
each component which passes only the photoluminescence from that
particular component. The preferred components which contain
lanthanide ions of atomic number greater than 57 are all relatively
narrow band photoluminescers and, therefore, the filters can be
quite narrow in their wavelength band response, interference
filters being a useful type. After passing through the filter, the
radiation is imaged on the cathode of a photomultiplier tube or
other sensitive detector of radiation in the visible and/or the
near infrared.
The filter wheel carries magnets which perform two functions: one
is to produce a signal pulse which, if necessary after suitable
amplification, triggers a flash from the xenon tube when a
particular filter associated with the magnet is in the light beam
from the substrate back to the photodetector; the magnets also
perform an additional function in the preferred form of the
invention, that is to say, they switch in amplifiers for a number
of channels corresponding to the number of components.
Alternatively inputs can be switched into a single amplifier or a
smaller number of amplifiers. The magnets also produce signals for
timing and initiating readout. Another magnet which actuates a
switch only once during a revolution of the filter wheel starts the
readout cycle so that it makes no difference which particular
filter first receives visible photoluminescence. The actuation of
these devices or those performing a similar function need not be
from elements physically mounted on the filter wheel, as they can
be from any source which is synchronously driven therewith.
However, because of the great simplicity of magnets and magnet
operated switches associated with the filter wheel itself, this
modification is preferred and presents many practical operating and
constructional advantages.
The output from the anode of the photomultiplier tube or other
photodetector contains the information from some one of the
components. The cutting in of a single channel when a particular
filter is in the beam demultiplexes the signal due to that
particular component. This is preferably effected by suitable gate
circuits which receive timing pulses.
A very suitable form of gate circuits which lends itself to compact
integrated circuit structure, involves disabling the circuit output
until the gating pulse is received. These types of gates will be
referred to as disabling gates, abbreviated DG. These are only
typical ways of cutting in a particular channel when a
corresponding filter is in place. Following the gating, a symbol is
examined for its threshold level to eliminate spurious responses
and this circuitry also preferably shapes the resulting pulses.
Each pulse is then divided into a positive and an inverted or a
negative pulse, one polarity being used for selection of a
particular mark and the other for character storage. In the
circuitry there is also included a suitable delay so that sampling
of the photomultiplier output occurs only after a certain time
interval from illumination has passed such that short time constant
photoluminescence, such as for example from optical brighteners in
paper, has died out. Delays may be of the order of around 20 .mu.
sec. and can provide for the channel being kept open for a suitable
readout time, for example of the order of 50 .mu. sec. The delay
mechanism can be a one-shot, (monostable multivibrator), which will
be abbreviated OS, and this is preferred.
When there has been a full revolution of the filter wheel after the
start of readout, the pulses in the various channels, depending on
whether there was a component present or not, are stored, for
example using flip-flop circuits, which will be abbreviated FF.
After a full revolution a gate pulse causes the flip-flops to
transmit their stored signals, after suitable manipulation if
desired in buffer amplifiers, to a decoding matrix of conventional
design which can put out outputs corresponding to the number of
symbols, for example 15 in the case of a four component code or 63
in the case of a six component code. These outputs can then be
displayed, for example by means of Nixie tubes, or may operate
solenoids on an electric typewriter to produce printout in the
conventional manner used with printout typewriters for computers.
Both modes can, of course, be used at the same time depending on
the selection by suitable switching.
After a full rotation of the filter wheel at a blank location
between inked areas where there is no symbol and therefore no
signals in any of the channels, a reset pulse is generated which
resets the flip-flops and the other circuits for the readout of the
next marking area. It will be noted that while a single full
revolution of the filter wheel will have sampled all of the
channels corresponding to the number of components, it is by no
means necessary that this should be limited to a single revolution.
Thus, for example, if the filter wheel makes more than one
revolution, it simply repeats the character storage, making
possible redundancy with increased reliability at the expense,
however, of the number of symbols in the marking areas which can be
read in unit time. For most purposes the increased reliability
provided by redundance is not essential, and in such preferred
cases a single revolution or a single symbol storage is
preferred.
In the case of paper substrates, such as tape, it will be noted
that the spacing between symbols is what produces resetting,
because in the space, which must be of a size comparable to the
dimensions of a symbol marking area or at least as large as the
geometrical area sensed by the optical system, there are no
components, and this is what actuates resetting. If printout is
chosen, the typewriter may print continuously on tape or, if it is
desired to print on an ordinary sheet, an additional suitable
symbol for carriage return may actuate the corresponding
solenoid.
Where a series of labeled containers are moved, the container is
generally rotated after being brought into position in the image
plane of the flashes. At this setting of the apparatus, there will
be a different readout and/or display if there is a wrong label.
The present invention really ceases with readout, but of course
where a wrong response is given, conventional comparator circuits
can give a signal, such as an alarm, for throwing a container out
of the normal path of the properly labeled containers or for any
other purpose. The design of such operations is not changed by the
present invention and therefore forms no part thereof and will not
be described in detail below. However, it should be pointed out
here that the nature of the reader which can be used to produce
such additional results is an advantageous additional factor of
versatility or flexibility. Needless to say, other functions may
also be preformed by the signals where desired.
The speed of operation of the present invention depends both on the
time constants of the components and on the reliable operating
speeds of the elements used. In general the mechanical elements,
such as the rotating filter wheel, will prove to be the limiting
factors as the electronic circuitry is capable of responses orders
of magnitude more rapid. With reasonable operating speeds, for
example a filter wheel turning at 1,200 r.p.m., symbols can be read
at the rate of 10 per second, and if it is desired to have visual
display, this is sufficiently fast so that the persistence of
vision permits a satisfactory visual readout. In the case of
labels, for example a label having a 12 -symbol message, which is
frequently encountered in pharmaceutical labels, it is possible to
read labels in 1 or 2 seconds, which permits quite rapid
examination of labeled containers. The operation is entirely
automatic and the reliability is high.
It should be noted that a rapid readout of purely photoluminescent
coded symbols is obtained and the symbols can be entirely secret as
the photoluminescent components are colorless under visible light.
This has a number of advantages in the case of labeling. However,
for certain purposes, for example for bank checks, there is an
advantage in being able to read specially shaped symbols visually
as well as by photoluminescence. In such a case the symbols may be
imprinted in inks which contain a pigment so that the symbol can be
read visually as well as under ultraviolet illumination. This added
advantage, where it is desired, is not unique with the present
invention but is fully described in the applications above referred
to. It is, however, an advantage of the present invention that the
rapid automatic readouts and/or printouts can be obtained without
any sacrifice in the advantageous versatility of photoluminescent
coding.
In the Freeman and Halverson patent referred to above, it is
brought out that in order to get the maximum of reliability, the
quantum efficiency of the photoluminescent components should be
high so that a strong, narrow band signal is produced that
minimizes interference due to other fluorescent or phosphorescent
materials in the substrate. In the Freeman and Halverson patent the
choice of particular photoluminescent materials is given in terms
of a figure of merit. The same considerations apply when the
present invention is used, but it is noted that the intensity of
the ultraviolet flash from the xenon tube is very high and,
therefore, there is usually available sufficient energy so that in
some cases photoluminescent components may be used which are not
quite as efficient as might be needed in the Freeman and Halverson
code, where lower energy ultraviolet readouts may sometimes be
encountered. Nevertheless, there is still an advantage in choosing
photoluminescent components having good efficiencies or figures of
merit.
It will be noted that since readout is by flashes with only one
filter interposed at a time, only a single detector is used, and a
highly sensitive photomultiplier tube can economically be employed.
This is a distinct advantage as any system involving digital
electronic circuits always operates with maximum effectiveness when
it has strong inputs, and this is true of the amplifiers and their
electronic elements that are used in the present invention and
which operate with great reliability as a result of the relatively
strong electrical signal produced by the highly sensitive
photomultiplier tube. It is, of course, possible to use other
photodetectors, provided they have the required sensitivity and low
noise, but since there is plenty of room for photomultiplier tubes,
the compactness of other photodetectors, such as solid-state
photodetectors, is not required; and, therefore, the use of highly
sensitive photomultiplier tubes constitutes a preferred
modification of the present invention. In this connection, it
should be pointed out that there are certain narrow band
photoluminescent compositions which luminesce in the near infrared
and for which some of the modern special infrared-sensitive
photomultiplier tubes, such as those employing cesium in the
cathodes, are desirable. The infrared photomultiplier tube is no
better than one which only responds to the visible or ultraviolet,
but the possibility of having a wider choice of coding components
is a very real advantage, especially where six or more are used, as
are needed in alphanumeric systems.
In the Freeman and Halverson patent it is pointed out that it is
possible to have the code represented by absence or presence in
more than one different signal level. The formula for the number of
symbols would then be represented by X.sup.n -1, where X is one
more than the number of levels of coded component; in the case of
two levels, this is, of course, 3.sup.n -1. The precision and
accuracy are not as high as when there is a presence and absence
situation, and for most purposes, where sufficient components are
available, this is preferred. Exactly the same situation, of
course, applies in the present invention. It can be used for
reading out more than one level. In the case of two levels, this
would mean that in the storage part of the memory there would have
to be a pair of signal amplitude responsive elements with different
thresholds adjusted for the anticipated levels of response of each
component in the symbols.
Throughout this specification and claims the term "time constant"
or "decay half-life" will be used in a strict sense as meaning the
time between points of one-half the peak luminescence. These points
are passed, of course, in the rise of luminescence after
illumination and then in its decay. The terms will be used in no
other sense.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a horizontal section through the optics of a typical
readout mechanism;
FIG. 2 is an elevation of a filter wheel;
FIG. 3 is a cross section along the line 3-3 of FIG. 2;
FIG. 4A is a side view of the mask and mounting plate for reed
switches;
FIG. 4B is a pair section along the line 4B-4B of FIG. 4A;
FIG. 5 is a pair of curves of luminescent intensities of a
short-time constant fluorescer, such as an optical brightener, and
a longer time constant, narrow band photoluminescer corresponding
to a component of the code;
FIG. 6 is a block diagram showing production of positive and
negative pulses from the readout;
FIG. 7 is a block diagram of mark selection, character storage,
display and printout utilizing the pulses from FIG. 6;
FIG. 8 is a schematic of an integrated circuit;
FIG. 9 is a plan view looking up at the integrated circuit;
FIG. 10 shows connections of FIG. 9 as a DG;
FIG. 11 shows connections of FIG. 9 as a FF;
FIG. 12 shows connections of FIG. 9 as an OS or delay element;
FIG. 13 is a schematic of an inverter stage;
FIG. 14 is a schematic of connections to the flash tube;
FIG. 15 is a schematic of a trigger pulse generator;
FIG. 16 is a block diagram with a partial schematic, constituting
the timing pulse generator portion of the circuits of FIG. 6;
FIG. 17 is a schematic of one of a series of channel
amplifiers;
FIG. 18 is a schematic of character storage reading gate
circuits;
FIG. 19 is a schematic of one of the threshold level and pulse
shapers for the channels;
FIG. 20 is a block diagram in more detail of a portion of the
circuits of FIG. 6;
FIG. 21 is a block diagram of a sequence timer;
FIG. 22 is a block diagram in more detail of the character storage
and buffer amplifiers of FIG. 6.
FIG. 23 is a block diagram of a decoding matrix.
FIG. 24 is a block diagram of display circuits, and
FIG. 25 is a schematic of typewriter printout circuits.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIGS. 1 to 5 illustrate the optics of the present invention. In the
illustrative example a four-component code is shown, which permits
15 different symbols and is sufficient for numerical readout. For
many purposes an alphanumeric system is more desirable with six
components and 63 symbols, but as the additional components merely
multiply elements in the drawings, the simpler four-component
system will be described in order to avoid confusion and
unnecessary repetition.
FIG. 5 represents curves of a fast decaying photoluminescent
material, such as an optical brightener, which is in solid lines,
and a component which has a typical longer time constant, in dashed
lines. This corresponds to a component having terbium as the
lanthanide ion determining the green photoluminescence.
FIG. 1 is a cross section through the optical readout box. A xenon
strobe light 11 provided with a focusing lens 61 and a filter 12,
both of which pass ultraviolet light but the filter does not pass
visible light, is mounted on a bracket 13 which is hinged to turn
into either of two positions. The bracket has an extension 14 on
which is mounted an auxiliary lens 10. Beam imaging lenses are
present 15. The bracket 13 can be turned to either of two
positions, one of which, shown in full lines on FIG. 1, directs the
beam out through a window 60 adjacent to which can be mounted a
tape transporting mechanism to move a printed tape. As the device
is of simple well-known construction, the details of which, as
such, form no part of the present invention, it is not shown, but a
piece of the tape is shown at 62 which is struck by the beam from
the flash of the tube 11 whenever it occurs. When the bracket 13 is
moved into its left-hand position, the beam is projected out
through window 59, the beam imaging lens shown in dashed lines 15
being used. At the same time, the auxiliary lens 10 is brought into
the beam coming through the window 60. This lens compensates for
the change of path length, because when the beam goes out through
the window 59 it impinges on a container, (not shown), which is
moved past it at a considerable distance, for example 8 to 10
inches. The position of the container is such that the
photoluminescence from its coded symbols passes through the window
60. Since this path is considerably longer the auxiliary lens 10 is
thrown into the beam and compensates for the change in path
length.
The photoluminescence coming through window 60, regardless of
whether originating from the substrate 62, or in the other position
of the bracket 13 coming in from a container at some distance and
passing through the auxiliary lens 10, then passes through an
imaging lens 18 and another 9, the beam going on through a window
29 in a mask 17 and thence through a filter wheel 25. In the
position shown in the cross section in FIG. 1, this is a portion of
the filter wheel which is solid, as will be described in
conjunction with FIG. 2. The filter wheel is turned at 1,200 r.p.m.
by the motor 28 and successively brings in data relating to
.alpha., .beta., .gamma., and .delta. to correspond with the code
in which the four components are similarly labeled. This code is
represented by the following diagram, where P represents presence
and-- represents absence of the indicated components: ##SPC1##
The four components are the following compounds:
.alpha. dysprosium (dipivaloylmethide).sub.3 (trioctylphosphine
oxide).sub.2
.beta. terbium (trifluoracetylacetonate).sub.3 (trioctylphosphine
oxide).sub.2
.gamma. samarium (trifluoracetylacetonate).sub.3 (trioctylphosphine
oxide).sub.2
.delta. europium (trifluoroacetylacetonate).sub.3
(trioctylphosphine oxide).sub.2
It will be noted that for the 10 digits only 10 of the available
symbols are used, those corresponding to 11 to 15 being used for
various other functions, such as a carriage return in the case of a
typewriter printing out on a page, X, hyphen, period, and equal
mark.
The filter wheel 25 carries four magnets 30 which are spaced around
the periphery in particular spatial relations to the filters. There
is also provided another magnet 31 on the face of the wheel. These
are more clearly shown in FIG. 3. Let us assume that the filter
.alpha. in front of the window 29 of the mask 17. It will be noted
that as the cross section line in FIG. 2 goes through the filter
wheel at its center in the relative position where it is in FIG. 2,
no filter shows. However, when the wheel has turned so that filter
.alpha. is in the beam from the lens 9, as is shown in FIG. 1,
luminescence corresponding to component .alpha. passes through, and
is reflected by the mirror 27 onto the cathode of the
photomultiplier tube 26. Accordingly, the output of the
photomultiplier tube will contain a signal corresponding to this
component. If the bracket 13 had been turned into the left-hand
position the same result would have occurred, but the
photoluminescent beam would have come from a more distant container
instead of from the substrate 62.
FIGS. 4a, b, show a detail of the mask 17. It will be seen that
there are mounted on this mask at 90.degree. angles four pairs of
reed switches 20 to 23, A and B. Each pair is actuated only when
the magnet 31 approaches them, which occurs only when the
particular filter is in the luminescence beam. In addition, there
is a single reed switch 63 at the top which is actuated by each of
the magnets 30 in turn; in other words, it is closed 4 times during
a revolution of the filter wheel or every time a filter is thrown
into the beam, regardless of which filter it is. This single reed
switch is used to produce triggering pulses which trigger off
flashes of the xenon tube. The other switches 20 to 23 are
connected into separate channels, as will be described below, and
are only actuated during the time a particular filter is in the
beam. In other words, as the filter wheel turns, each time a filter
is in position a flash is triggered off and the two particular
switches of a pair 20 to 23 corresponding to that filter are
closed. As these switches act as commutators, they will sometimes
be referred to in further description and on the drawings as
commutating switches.
It is necessary that each time a symbol is to be read from a
particular marking area on the substrate 62, or on a label on a
container if the bracket 13 is thrown into its left-hand position,
there must be a full revolution of the filter wheel. If the symbol
has a single component there will only be a signal from the
photomultiplier tube when the filter corresponding to the component
is in the beam. On the other hand, if a particular symbol, such as
the symbol corresponding to the equal mark or 15, has all four
components, there will, of course, be four signals in the
photomultiplier tube as each of the filters successively comes into
play.
Turning now to FIG. 6, which shows a trigger pulse generator 58,
that will be described in greater detail below, it will be seen
that the filter wheel generates four signals in a revolution, which
cause the trigger pulse generator 58 to trigger four flashes in the
flash lamp 11. Also, there is an output to a timing pulse generator
50. The schematic of the trigger pulse generator 58 is shown in
FIG. 15 and is self-explanatory, the values for voltages and other
components being as given. It will be noticed that there are two
transistors 64 and 65 which amplify the input signals in the
customary manner.
The timing pulse generator 50 is shown in partial schematic in FIG.
16, which also shows a series of circuit elements, some of them
being triggered pulse generators, marked OS, and others being
inverters, INV. The inverters are conventional transistor circuits
shown in schematic in FIG. 13 with their particular output waves.
The triggered pulse generators, OS, are one-shot multivibrators and
are integrated circuits, the schematic of one of which is shown in
FIG. 8 with the pin connections in FIG. 9. To produce the required
delays, the pulse lengths are set by RC circuits which are provided
as shown in FIG. 12. The amount of delay depends on the values of
these components, and these values are shown for the various
one-shot multivibrators in FIG. 16 to give the particular delays.
It will be seen that the first one-shot multivibrator triggers the
second, which in turn triggers the third after a delay of 20 .mu.
sec. The fourth is triggered 50 .mu. sec later, and provides a 25
.mu. sec. inverted timing pulse which goes to the switches 20A to
23A. In other words, these switches can only be turned on after the
delay set forth, and of course only one switch at a time is turned
on when the magnet 31 on the filter wheel 25 closes the particular
reed switch, as has been described above.
Somewhat before the pulse to the commutating switches A, there is a
gate pulse to the gate circuit 40, which will be described below.
In the meantime, the photomultiplier 26 has been receiving signals
each time a filter came into the beam and the flash tube fired
provided there was present the corresponding component. The output,
of course, is multiplexed for all four channels and is fed through
the other commutating switches 20B to 23B of the pairs. This
results in demultiplexing, and the demultiplexed signals are
amplified by amplifiers 56.
The schematic of one amplifier is shown in FIG. 17 for the channel
corresponding to the .alpha. component, and as indicated this is
duplicated in the other three. The amplifier input signal wave
appears at the left of the figure, and it will be seen that it is a
negative going signal which rises rapidly to a peak when the lamp
flash occurs and then gradually dies off exponentially. It will be
noted that the response of the switches 20B to 23B and their
respective amplifiers are not delayed, in other words, the signal
comes through as soon as the flash occurs. If there were present
photoluminescent materials in the marking area of very short time
constant, for example optical brighteners with time constants of
the order of 10.sup..sup.-7 or 10.sup..sup.-8 sec., these signals
would also come through. However, it is desired that there should
be no final response until sufficient delay has been introduced,
and this is effected by the gate pulse, shown in FIG. 16.
The gate circuit 40 is shown in schematic in FIG. 18. Whenever the
gate opens in any particular circuit, the signal in this channel
goes to a threshold level and pulse shaper 57, the schematic for
one channel being shown in FIG. 19 and of course duplicated for the
other channels. The purpose of the threshold level is to prevent
signals coming out below a certain intensity. These signals in each
channel are then fed to inverters so that, as will be seen from
FIG. 6, there are pairs of signals, one positive and one negative,
for each channel.
FIG. 7 shows that the positive pulses from FIG. 6 go into a mark
selector, shown in FIG. 20. The positive signals pass through 200
.mu.s one-shot multivibrators into dual AND gates which also
receive the positive timing pulses. The mark selector develops an
output pulse only after four contiguous zero signal level inputs.
The output from the mark selector starts the sequence timer 34,
shown in FIG. 21.
The negative signal pulses from FIG. 6 go into a set of four AND
gates in the character storage section 33, which is shown in more
detail in FIG. 22. The gates are only opened when there is both an
inverted signal and a gate pulse from the sequence timer. Each
opened gate sets a storage flip-flop 33. The mark selector output
also resets the storage which takes place at the time the sequence
timer is started, (FIG. 7). As soon as the sequence timer output
has conditioned the gates, the flip-flops 33 receive and store any
signals present. These signals are fed through buffer amplifiers 37
to the decoding matrix 36, as is shown in FIG. 7.
The mark selector operates when there has been a complete
revolution of the filter wheel after the first pulse from the
photomultiplier tube which is high enough to pass through the
threshold level circuit 57. There is a delay in the first OS, shown
on FIG. 21, of 50 .mu.s. The second OS of FIG. 21 causes a gate
pulse to feed to the gates of the character storage 33 and the
gates remain conditioned for 50ms. at least a full revolution of
the filter wheel 25. The signals on all four flip-flops are
amplified in buffer amplifiers 37. The amplified signals from the
storage flip-flops then enter the decoding matrix 36, which is
shown in FIG. 23. Depending on the particular settings of the
flip-flops which have been fed on through the buffer amplifiers 37,
this results in decoding. It will be noticed that there are 15 AND
gates, which are labeled DUG on FIG. 23. This figure merely shows
the gates for the symbols 1, 14 and 15, but of course there are 12
additional ones. The 15 outputs then go to Nixie drivers 38 and a
Nixie display 39. The block diagram for this portion of the
electronics is shown in FIG. 24, and the result is that the Nixie
tubes for 10's and 1's display in the conventional manner.
It will be noted on FIG. 21 that an 80ms. gating pulse enables the
solenoid drivers 35 of a typewriter 66 which are operated from the
outputs of the decoding matrix in the normal manner. This is shown
for one solenoid and driver in FIG. 25. It will be noted that in
FIG. 7 the output from the decoding matrix passes through a
switching device 67 which permits directing either to the Nixie
tubes alone, the solenoid drivers alone, or both. This is a
three-position switch of conventional design and, therefore, the
details are not shown.
When the mark selector has received four negative responses, that
is to say, the kind of signal when there is no luminescence on any
of the four channels, it resets everything and there will be no
further readout until another marking area comes into position.
Then magnet 31 starts the sequence at a definite position of the
filter wheel and the sequence above referred to is repeated. It
will be noted that this requires a total of two revolutions of the
filter wheel.
The specific description has been in conjunction with a typical set
of circuits which can carry out the process of the present
invention. Needless to say, any equivalent mechanisms may be used.
All that is necessary is that the proper sequence of operations
takes place. To recapitulate in process language, this means that
there must be a flash of ultraviolet light on a particular marking
area for each component; the multiplexed signal from the radiation
detector must then pass signals in each channel, after a delay
which prevents response from very short time constant fluorescers
such as optical brighteners, into a storage device which stores the
signals from each of the channels corresponding to the different
components. Then the stored information must be decoded to produce
an output which can be displayed as by means of Nixie tubes and/or
printed out, or which can actuate other logical operations, such as
selected counters or deflection gates. In order to prevent spurious
responses, a signal, after the delay to allow extinction of short
time constant fluorescers, must be above a sufficient level so that
the readout is not started by a spurious signal of low level. So
long as these functions are performed, the process phase of the
present invention is not concerned with the particular mechanisms
which produce the results; and therefore, from a process standpoint
the invention is not limited to particular apparatus.
* * * * *